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The Conducting System of the Heart

Original Author(s): Sophie White Last updated: April 24, 2023 Revisions: 31

• 1 Overview of Heart Conduction
• 2.1 Sinoatrial Node
• 2.2 Atrioventricular Node
• 2.3 Atrioventricular Bundle
• 2.4 Purkinje Fibres
• 3 Clinical Relevance: Artificial Pacemaker

The cardiac conduction system is a collection of nodes and specialised conduction cells that initiate and co-ordinate contraction of the heart muscle. It consists of:

• Sinoatrial node
• Atrioventricular node
• Atrioventricular bundle (bundle of His)
• Purkinje fibres

In this article, we shall look at the anatomy of the cardiac conduction system – its structure, function and clinical correlations.

Overview of Heart Conduction

The following sequence of electrical events occurs during one full contraction of the heart muscle:

• An excitation signal (an action potential) is created by the sinoatrial (SA) node .
• The wave of excitation spreads across the atria, causing them to contract.
• Upon reaching the atrioventricular (AV) node , the signal is delayed.
• It is then conducted into the bundle of His , down the interventricular septum.
• The bundle of His and the Purkinje fibres  spread the wave impulses along the ventricles, causing them to contract.

We will now discuss the anatomy of the individual components involved in the conducting system.

Fig 1 – Animation of the spread of conduction through the heart

Components of the Cardiac Conduction System

Sinoatrial node.

The  sinoatrial (SA) node is a collection of specialised cells (pacemaker cells), and is located in the upper wall of the right atrium, at the junction where the superior vena cava enters.

These pacemaker cells can spontaneously generate electrical impulses . The wave of excitation created by the SA node spreads via gap junctions across both atria, resulting in atrial contraction (atrial systole) – with blood moving from the atria into the ventricles.

The rate at which the SA node generates impulses is influenced by the autonomic nervous system:

• Sympathetic nervous system – increases firing rate of the SA node, and thus increases heart rate.
• Parasympathetic nervous system – decreases firing rate of the SA node, and thus decreases heart rate.

Atrioventricular Node

After the electrical impulses spread across the atria, they converge at the  atrioventricular node  – located within the atrioventricular septum, near the opening of the coronary sinus.

The AV node acts to delay the impulses by approximately  120ms , to ensure the atria have enough time to fully eject blood into the ventricles before ventricular systole.

The wave of excitation then passes from the atrioventricular node into the atrioventricular bundle.

Atrioventricular Bundle

The atrioventricular bundle (bundle of His) is a continuation of the specialised tissue of the AV node, and serves to transmit the electrical impulse from the AV node to the Purkinje fibres of the ventricles.

It descends down the membranous part of the interventricular septum, before dividing into two main bundles:

• Right bundle branch – conducts the impulse to the Purkinje fibres of the right ventricle
• Left bundle branch – conducts the impulse to the Purkinje fibres of the left ventricle.

Fig 2 – Overview of the individual components of the heart conduction pathway

Purkinje Fibres

The Purkinje fibres (sub-endocardial plexus of conduction cells) are a network of specialised cells. They are abundant with glycogen and have extensive gap junctions.

These cells are located in the subendocardial surface of the ventricular walls, and are able to rapidly transmit cardiac action potentials from the atrioventricular bundle to the myocardium of the ventricles.

This rapid conduction allows coordinated ventricular contraction (ventricular systole) and blood is moved from the right and left ventricles to the pulmonary artery and aorta respectively.

Clinical Relevance: Artificial Pacemaker

An artificial pacemaker is a small electrical device commonly fitted to monitor and correct heart rate and rhythm. It is inserted into the chest under the left clavicle, with wires connected to the heart via the venous system.

The most common indication for a pacemaker is bradycardia . Once inserted, the pacemaker monitors the heart rate, and only fires if the rate becomes too slow. Pacemakers can also be used to treat some tachycardias, certain types of heart block and other rhythm abnormalities.

Fig 3 – There are various types of pacemakers; the most common are dual-chamber and single-chamber.

In this article, we shall look at the anatomy of the cardiac conduction system - its structure, function and clinical correlations.

These pacemaker cells can spontaneously generate electrical impulses . The wave of excitation created by the SA node spreads via gap junctions across both atria, resulting in atrial contraction (atrial systole) - with blood moving from the atria into the ventricles.

• Sympathetic nervous system - increases firing rate of the SA node, and thus increases heart rate.
• Parasympathetic nervous system - decreases firing rate of the SA node, and thus decreases heart rate.

After the electrical impulses spread across the atria, they converge at the  atrioventricular node  - located within the atrioventricular septum, near the opening of the coronary sinus.

• Right bundle branch - conducts the impulse to the Purkinje fibres of the right ventricle
• Left bundle branch - conducts the impulse to the Purkinje fibres of the left ventricle.

[start-clinical]

[end-clinical]

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Data Analysis in Qualitative Research: A Brief Guide to Using Nvivo

MSc, PhD, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia

Qualitative data is often subjective, rich, and consists of in-depth information normally presented in the form of words. Analysing qualitative data entails reading a large amount of transcripts looking for similarities or differences, and subsequently finding themes and developing categories. Traditionally, researchers ‘cut and paste’ and use coloured pens to categorise data. Recently, the use of software specifically designed for qualitative data management greatly reduces technical sophistication and eases the laborious task, thus making the process relatively easier. A number of computer software packages has been developed to mechanise this ‘coding’ process as well as to search and retrieve data. This paper illustrates the ways in which NVivo can be used in the qualitative data analysis process. The basic features and primary tools of NVivo which assist qualitative researchers in managing and analysing their data are described.

QUALITATIVE RESEARCH IN MEDICINE

Qualitative research has seen an increased popularity in the last two decades and is becoming widely accepted across a wide range of medical and health disciplines, including health services research, health technology assessment, nursing, and allied health. 1 There has also been a corresponding rise in the reporting of qualitative research studies in medical and health related journals. 2

The increasing popularity of qualitative methods is a result of failure of quantitative methods to provide insight into in-depth information about the attitudes, beliefs, motives, or behaviours of people, for example in understanding the emotions, perceptions and actions of people who suffer from a medical condition. Qualitative methods explore the perspective and meaning of experiences, seek insight and identify the social structures or processes that explain people”s behavioural meaning. 1 , 3 Most importantly, qualitative research relies on extensive interaction with the people being studied, and often allows researchers to uncover unexpected or unanticipated information, which is not possible in the quantitative methods. In medical research, it is particularly useful, for example, in a health behaviour study whereby health or education policies can be effectively developed if reasons for behaviours are clearly understood when observed or investigated using qualitative methods. 4

ANALYSING QUALITATIVE DATA

Qualitative research yields mainly unstructured text-based data. These textual data could be interview transcripts, observation notes, diary entries, or medical and nursing records. In some cases, qualitative data can also include pictorial display, audio or video clips (e.g. audio and visual recordings of patients, radiology film, and surgery videos), or other multimedia materials. Data analysis is the part of qualitative research that most distinctively differentiates from quantitative research methods. It is not a technical exercise as in quantitative methods, but more of a dynamic, intuitive and creative process of inductive reasoning, thinking and theorising. 5 In contrast to quantitative research, which uses statistical methods, qualitative research focuses on the exploration of values, meanings, beliefs, thoughts, experiences, and feelings characteristic of the phenomenon under investigation. 6

Data analysis in qualitative research is defined as the process of systematically searching and arranging the interview transcripts, observation notes, or other non-textual materials that the researcher accumulates to increase the understanding of the phenomenon. 7 The process of analysing qualitative data predominantly involves coding or categorising the data. Basically it involves making sense of huge amounts of data by reducing the volume of raw information, followed by identifying significant patterns, and finally drawing meaning from data and subsequently building a logical chain of evidence. 8

Coding or categorising the data is the most important stage in the qualitative data analysis process. Coding and data analysis are not synonymous, though coding is a crucial aspect of the qualitative data analysis process. Coding merely involves subdividing the huge amount of raw information or data, and subsequently assigning them into categories. 9 In simple terms, codes are tags or labels for allocating identified themes or topics from the data compiled in the study. Traditionally, coding was done manually, with the use of coloured pens to categorise data, and subsequently cutting and sorting the data. Given the advancement of software technology, electronic methods of coding data are increasingly used by qualitative researchers.

Nevertheless, the computer does not do the analysis for the researchers. Users still have to create the categories, code, decide what to collate, identify the patterns and draw meaning from the data. The use of computer software in qualitative data analysis is limited due to the nature of qualitative research itself in terms of the complexity of its unstructured data, the richness of the data and the way in which findings and theories emerge from the data. 10 The programme merely takes over the marking, cutting, and sorting tasks that qualitative researchers used to do with a pair of scissors, paper and note cards. It helps to maximise efficiency and speed up the process of grouping data according to categories and retrieving coded themes. Ultimately, the researcher still has to synthesise the data and interpret the meanings that were extracted from the data. Therefore, the use of computers in qualitative analysis merely made organisation, reduction and storage of data more efficient and manageable. The qualitative data analysis process is illustrated in Figure 1 .

Qualitative data analysis flowchart

USING NVIVO IN QUALITATIVE DATA ANALYSIS

NVivo is one of the computer-assisted qualitative data analysis softwares (CAQDAS) developed by QSR International (Melbourne, Australia), the world’s largest qualitative research software developer. This software allows for qualitative inquiry beyond coding, sorting and retrieval of data. It was also designed to integrate coding with qualitative linking, shaping and modelling. The following sections discuss the fundamentals of the NVivo software (version 2.0) and illustrates the primary tools in NVivo which assist qualitative researchers in managing their data.

Key features of NVivo

To work with NVivo, first and foremost, the researcher has to create a Project to hold the data or study information. Once a project is created, the Project pad appears ( Figure 2 ). The project pad of NVivo has two main menus: Document browser and Node browser . In any project in NVivo, the researcher can create and explore documents and nodes, when the data is browsed, linked and coded. Both document and node browsers have an Attribute feature, which helps researchers to refer the characteristics of the data such as age, gender, marital status, ethnicity, etc.

Project pad with documents tab selected

The document browser is the main work space for coding documents ( Figure 3 ). Documents in NVivo can be created inside the NVivo project or imported from MS Word or WordPad in a rich text (.rtf) format into the project. It can also be imported as a plain text file (.txt) from any word processor. Transcripts of interview data and observation notes are examples of documents that can be saved as individual documents in NVivo. In the document browser all the documents can be viewed in a database with short descriptions of each document.

Document browser with coder and coding stripe activated

NVivo is also designed to allow the researcher to place a Hyperlink to other files (for example audio, video and image files, web pages, etc.) in the documents to capture conceptual links which are observed during the analysis. The readers can click on it and be taken to another part of the same document, or a separate file. A hyperlink is very much like a footnote.

The second menu is Node explorer ( Figure 4 ), which represents categories throughout the data. The codes are saved within the NVivo database as nodes. Nodes created in NVivo are equivalent to sticky notes that the researcher places on the document to indicate that a particular passage belongs to a certain theme or topic. Unlike sticky notes, the nodes in NVivo are retrievable, easily organised, and give flexibility to the researcher to either create, delete, alter or merge at any stage. There are two most common types of node: tree nodes (codes that are organised in a hierarchical structure) and free nodes (free standing and not associated with a structured framework of themes or concepts). Once the coding process is complete, the researcher can browse the nodes. To view all the quotes on a particular Node, select the particular node on the Node Explorer and click the Browse button ( Figure 5 ).

Node explorer with a tree node highlighted

Browsing a node

Coding in NVivo using Coder

Coding is done in the document browser. Coding involves the desegregation of textual data into segments, examining the data similarities and differences, and grouping together conceptually similar data in the respective nodes. 11 The organised list of nodes will appear with a click on the Coder button at the bottom of document browser window.

To code a segment of the text in a project document under a particular node, highlight the particular segment and drag the highlighted text to the desired node in the coder window ( Figure 3 ). The segments that have been coded to a particular node are highlighted in colours and nodes that have attached to a document turns bold. Multiple codes can be assigned to the same segment of text using the same process. Coding Stripes can be activated to view the quotes that are associated with the particular nodes. With the guide of highlighted text and coding stripes, the researcher can return to the data to do further coding or refine the coding.

Coding can be done with pre-constructed coding schemes where the nodes are first created using the Node explorer followed by coding using the coder. Alternatively, a bottom-up approach can be used where the researcher reads the documents and creates nodes when themes arise from the data as he or she codes.

Making and using memos

In analysing qualitative data, pieces of reflective thinking, ideas, theories, and concepts often emerge as the researcher reads through the data. NVivo allows the user the flexibility to record ideas about the research as they emerge in the Memos . Memos can be seen as add-on documents, treated as full status data and coded like any other documents. 12 Memos can be placed in a document or at a node. A memo itself can have memos (e.g. documents or nodes) linked to it, using DocLinks and NodeLinks .

Creating attributes

Attributes are characteristics (e.g. age, marital status, ethnicity, educational level, etc.) that the researcher associates with a document or node. Attributes have different values (for example, the values of the attribute for ethnicity are ‘Malay’, ‘Chinese’ and ‘Indian’). NVivo makes it possible to assign attributes to either document or node. Items in attributes can be added, removed or rearranged to help the researcher in making comparisons. Attributes are also integrated with the searching process; for example, linking the attributes to documents will enable the researcher to conduct searches pertaining to documents with specified characteristics ( Figure 6 ).

Document attribute explorer

Search operation

The three most useful types of searches in NVivo are Single item (text, node, or attribute value), Boolean and Proximity searches. Single item search is particularly important, for example, if researchers want to ensure that every mention of the word ‘cure’ has been coded under the ‘Curability of cervical cancer’ tree node. Every paragraph in which this word is used can be viewed. The results of the search can also be compiled into a single document in the node browser and by viewing the coding stripe. The researcher can check whether each of the resulting passages has been coded under a particular node. This is particularly useful for the researcher to further determine whether conducting further coding is necessary.

Boolean searches combine codes using the logical terms like ‘and’, ‘or’ and ‘not’. Common Boolean searches are ‘or’ (also referred to as ‘combination’ or ‘union’) and ‘and’ (also called ‘intersection’). For example, the researcher may wish to search for a node and an attributed value, such as ‘ever screened for cervical cancer’ and ‘primary educated’. Search results can be displayed in matrix form and it is possible for the researcher to perform quantitative interpretations or simple counts to provide useful summaries of some aspects of the analysis. 13 Proximity searches are used to find places where two items (e.g. text patterns, attribute values, nodes) appear near each other in the text.

Using models to show relationships

Models or visualisations are an essential way to describe and explore relationships in qualitative research. NVivo provides a Modeler designated for visual exploration and explanation of relationships between various nodes and documents. In Model Explorer, the researcher can create, label and connect ideas or concepts. NVivo allows the user to create a model over time and have any number of layers to track the progress of theory development to enable the researcher to examine the stages in the model-building over time ( Figure 7 ). Any documents, nodes or attributes can be placed in a model and clicking on the item will enable the researcher to inspect its properties.

Model explorer showing the perceived risk factors of cervical cancer

NVivo has clear advantages and can greatly enhance research quality as outlined above. It can ease the laborious task of data analysis which would otherwise be performed manually. The software certainly removes the tremendous amount of manual tasks and allows more time for the researcher to explore trends, identify themes, and make conclusions. Ultimately, analysis of qualitative data is now more systematic and much easier. In addition, NVivo is ideal for researchers working in a team as the software has a Merge tool that enables researchers that work in separate teams to bring their work together into one project.

The NVivo software has been revolutionised and enhanced recently. The newly released NVivo 7 (released March 2006) and NVivo 8 (released March 2008) are even more sophisticated, flexible, and enable more fluid analysis. These new softwares come with a more user-friendly interface that resembles the Microsoft Windows XP applications. Furthermore, they have new data handling capacities such as to enable tables or images embedded in rich text files to be imported and coded as well. In addition, the user can also import and work on rich text files in character based languages such as Chinese or Arabic.

To sum up, qualitative research undoubtedly has been advanced greatly by the development of CAQDAS. The use of qualitative methods in medical and health care research is postulated to grow exponentially in years to come with the further development of CAQDAS.

More information about the NVivo software

Detailed information about NVivo’s functionality is available at http://www.qsrinternational.com . The website also carries information about the latest versions of NVivo. Free demonstrations and tutorials are available for download.

ACKNOWLEDGEMENT

The examples in this paper were adapted from the data of the study funded by the Ministry of Science, Technology and Environment, Malaysia under the Intensification of Research in Priority Areas (IRPA) 06-02-1032 PR0024/09-06.

TERMINOLOGY

Attributes : An attribute is a property of a node, case or document. It is equivalent to a variable in quantitative analysis. An attribute (e.g. ethnicity) may have several values (e.g. Malay, Chinese, Indian, etc.). Any particular node, case or document may be assigned one value for each attribute. Similarities within or differences between groups can be identified using attributes. Attribute Explorer displays a table of all attributes assigned to a document, node or set.

CAQDAS : Computer Aided Qualitative Data Analysis. The CAQDAS programme assists data management and supports coding processes. The software does not really analyse data, but rather supports the qualitative analysis process. NVivo is one of the CAQDAS programmes; others include NUDIST, ATLAS-ti, AQUAD, ETHNOGRAPH and MAXQDA.

Code : A term that represents an idea, theme, theory, dimension, characteristic, etc., of the data.

Coder : A tool used to code a passage of text in a document under a particular node. The coder can be accessed from the Document or Node Browser .

Coding : The action of identifying a passage of text in a document that exemplifies ideas or concepts and connecting it to a node that represents that idea or concept. Multiple codes can be assigned to the same segment of text in a document.

Coding stripes : Coloured vertical lines displayed at the right-hand pane of a Document ; each is named with title of the node at which the text is coded.

DataLinks : A tool for linking the information in a document or node to the information outside the project, or between project documents. DocLinks , NodeLinks and DataBite Links are all forms of DataLink .

Document : A document in an NVivo project is an editable rich text or plain text file. It may be a transcription of project data or it may be a summary of such data or memos, notes or passages written by the researcher. The text in a document can be coded, may be given values of document attributes and may be linked (via DataLinks ) to other related documents, annotations, or external computer files. The Document Explorer shows the list of all project documents.

Memo : A document containing the researcher”s commentary flagged (linked) on any text in a Document or Node. Any files (text, audio or video, or picture data) can be linked via MemoLink .

Model : NVivo models are made up of symbols, usually representing items in the project, which are joined by lines or arrows, designed to represent the relationship between key elements in a field of study. Models are constructed in the Modeller .

Node : Relevant passages in the project”s documents are coded at nodes. A Node represents a code, theme, or idea about the data in a project. Nodes can be kept as Free Nodes (without organisation) or may be organised hierarchically in Trees (of categories and subcategories). Free nodes are free-standing and are not associated to themes or concepts. Early on in the project, tentative ideas may be stored in the Free Nodes area. Free nodes can be kept in a simple list and can be moved to a logical place in the Tree Node when higher levels of categories are discovered. Nodes can be given values of attributes according to the features of what they represent, and can be grouped in sets. Nodes can be organised (created, edited) in Node Explorer (a window listing all the project nodes and node sets). The Node Browser displays the node”s coding and allow the researcher to change the coding.

Project : Collection of all the files, documents, codes, nodes, attributes, etc. associated with a research project. The Project pad is a window in NVivo when a project is open which gives access to all the main functions of the programme.

Sets : Sets in NVivo hold shortcuts to any nodes or documents, as a way of holding those items together without actually combining them. Sets are used primarily as a way of indicating items that in some way are related conceptually or theoretically. It provides different ways of sorting and managing data.

Tree Node : Nodes organised hierarchically into trees to catalogue categories and subcategories.

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Home » Science » Biology » Human Anatomy » Difference Between SA Node and AV Node

Difference Between SA Node and AV Node

The main difference between SA node and AV node is that the SA node generates cardiac impulses whereas the AV node relays and intensifies cardiac impulses . Furthermore, SA node is located in the right atrium , close to the point of entry of the superior vena cava while AV node is located in the right atrium, close to the opening of the coronary sinus.

SA node and AV node are two elements of the cardiac conduction system that controls the heart rate .

Key Areas Covered

1. What is SA Node      – Definition, Location, Role 2. What is AV Node      – Definition, Location, Role 3. What are the Similarities Between SA Node and AV Node      – Outline of Common Features 4. What is the Difference Between SA Node and AV Node      – Comparison of Key Differences

AV (Atrioventricular) Node, Pacemaker, Pacesetter, Right Atrium, SA (Sinoatrial) Node

What is SA Node

SA ( sinoatrial ) node is the group of cells that generate electrical impulses in the heart. It sends sparks electrical impulses within a set of intervals, establishing the rate of the heart as 60-80 beats per minute (bpm). The beats generated by the SA node are called the rhythm of the heart. When the body requires more oxygen while doing power-intensive physical activities, SA node increases the rate of the heart, pumping more blood to the tissues.

Figure 1: Electrical Conduction System of the Heart

SA node is made up of pacemaker cells surrounded by paranodal cells. The cells of the SA node are smaller than the cells that make up the atrium. Also, they encompass fewer mitochondria. Sympathetic nervous system slows down the rate of the impulses while parasympathetic nervous system accelerates the rate of impulses.  

What is AV Node

AV ( atrioventricular ) node is the group of cells located in the border between the right atrium and the right ventricle , which serves as the secondary contractile system of the heart. It is primarily induced by SA node. It relays on signals of the SA node and holds them for 0.09 seconds, which is the time required by the ventricles to be filled with the atrial blood. 

Figure 2: Cardiac Contraction

Then the cardiac impulses from the SA node are transmitted to the ventricles, contracting them. This chiefly means SA node sets the rhythm of the heartbeat while AV node sets the rhythm of the heart contraction. 

Similarities Between SA Node and AV Node

• SA node and AV node are two elements of the contractile system of the heart.
• They are located in the wall of the right atrium.
• Both are involved in maintaining the heart rate by inducing contraction.

SA (sinoatrial) node refers to a small mass of tissue in the right atrium functioning as pacemaker of the heart by giving rise to the electric impulses that initiate heart contractions while AV (atrioventricular) node refers to a small mass of tissue that is situated in the wall of the right atrium and passes impulses received from the SA node to the ventricles.

SA node is located in the superior lateral wall of the right atrium, close to the opening of the superior vena cava while AV node is located in the posterior septal wall of the right atrium, close to the opening of the coronary sinus.

Size and Shape

When comparing the size and shape, SA node is longer, flattened, and ellipsoidal while AV node is short and half-oval.

While SA node generates cardiac impulses, AV node relays the cardiac impulses generated by SA node and intensifies them. This is the main difference between SA node and AV node.

Firing Rate

The firing rate of the SA node is 60-100 bpm while the intrinsic firing rate of the AV node is 40-60 bpm.

Transmission of the Impulses

SA node transmits cardiac impulses directly to the right and left atrium while AV node transmits cardiac impulses the right and left ventricles through the branches and the terminal strands of the bundle of His.

Significance

Whereas SA node serves as the pacemaker of the heart, AV node serves as the pacesetter of the heart.

The autonomic nervous system regulates SA node while AV node is regulated by the SA node.

SA node is the primary element of the heart that produces cardiac impulses. Therefore, it is called the pacemaker of the heart. On the other hand, AV node is the secondary element of the heart, which relays on the signals of the SA node, intensifying them and transmitting them to the ventricles. The main difference between SA node and AV node is the function.

1. Kashou AH, Kashou HE. Physiology, Sinoatrial Node (SA Node) [Updated 2017 Oct 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2018 Jan-. Available Here   2. Klabunde, Richard E. “Normal Impulse Conduction.” Cardiovascular Physiology Concepts, Available Here  

Image Courtesy:

1. “ConductionsystemoftheheartwithouttheHeart-en” By Madhero88 (original files); Angelito7 (this SVG version); – ConductionsystemoftheheartwithouttheHeart.png & ConductionsystemoftheheartwithoutHeart.svg ( CC BY-SA 3.0 ) via Commons Wikimedia    2. “2019 Cardiac ConductionN” By OpenStax College – Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013. ( CC BY 3.0 ) via Commons Wikimedia  

About the Author: Lakna

Lakna, a graduate in Molecular Biology and Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things. She has a keen interest in writing articles regarding science.

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Nodal Anatomy of Angiosperms: Unilacunar, Trilacunar and Multilacunar Node

Nodal anatomy refers to the study of the structure and function of nodes of plants, which are the points on a stem where leaves, branches, and buds arise. This includes the examination of the internal and external features of nodes, such as the vascular tissue, meristems, leaf gaps and leaf traces. Understanding nodal anatomy is important for comprehending the growth and development of angiosperms and for identifying their different parts and structures. The present articles discusses the features of Nodal Anatomy in flowering plants with suitable examples.

Nodal Anatomy

Anatomy of nodal and inter-nodal region are different.

The stem of plants is differentiated into nodes and internodes. The anatomical features of the nodal region are quite different from that of the inter-nodal region. This anatomical difference is due to the presence of Vascular Supply to the leaves and branches from the main vascular cylinder of the stem.

Nodal Region of Higher Plants Posses Leaf Gaps and Leaf Traces

Each leaf that originates from the node, of higher plants possesses vascular tissue and these vascular tissues of the leaves are connected to that of the stem. A vascular strand that extends between the vascular cylinder of stem and the base of the leaf is called Leaf Trace or Foliar Trace .

Even if the leaf trace possesses both xylem and phloem , the relative amount of xylem will be more in the leaf trace than phloem. Moreover, the proximal portion, (portion near the vascular cylinder of the stem) contains only the xylem. Whereas, the distal end of the leaf trace (near to the leaf base) contains both xylem and phloem.

Leaf trace helps to transport water and minerals from the xylem to the leaf lamina for photosynthesis. The circulation of photosynthetic products from the leaf lamina to the phloem of the stem is also facilitated by the phloem strands in the leaf traces.

Even though the leaf trace is an extension of the vascular cylinder to the leaf, they are not a continuous supply from the main vascular cylinder. In the vascular cylinder just above the point of departure of the leaf trace, a small parenchymatous patch occurs. This parenchymatous region between the main vascular cylinder and the leaf trace is called Leaf Gap or Lacuna .

The leaf gap is situated on the upper side of the leaf trace. In a cross-section through the leaf gap region, it is visualized as a zone of parenchyma inside the vascular cylinder. Due to the presence of leaf gap, the cortical parenchyma becomes continuous with that of pith during the early stages of secondary growth .

Nodes are classified on the basis of Number of Leaf Gaps and Leaf Traces

The number and nature of leaf gaps and leaf traces varies in different plants. On the basis of the number of leaf gaps and leaf traces, THREE main nodes are described in Angiosperms.

(1). Unilacunar

(2). Trilacunar

(3). Multilacunar

(1). Unilacunar Node

A unilacunar node possesses only a single leaf gap to a leaf. Each leaf may possess one or two or three leaf traces.

Example: Nerium, Lantana camara, Justicia (with one gap and one trace); Clerodendron splendens (two traces); Chenopodium album and Withania somnifera (with one gap and three traces).

(2). Trilacunar Node

A trilacunar node possesses three leaf gaps and three leaf traces. Among these three leaf traces, the middle one (median) will be larger and the other two laterals will be smaller.

Example: Azadirachta

(3). Multilacunar Node

A multilacunar node possesses many leaf gaps and many leaf traces. Among the many traces, the median one (middle) will be larger and all others will be smaller.

Example: Polygonum plebeium, Coriandrum sativum, Aralium

Nodal Anatomy shows the Phylogenetic Primitiveness or Advancements

A unilacular node with two traces is considered to be the most primitive type of node among Angiosperms. One trace unilacunar node and trilacunar node is considered to be evolved from a trilacunar condition. During the evolution of nodal region, fusion, deletion and additions of leaf traces have occurred in the remote past. Apart from the phylogenetic significance, the nodal anatomy is a good taxonomic character used in the systematics of higher plants.

Key questions

1.  What is leaf trace? What is its significance?

2.  What is Leaf gap? Explain the structure of leaf gap.

3.  Explain unilacunar node with examples and diagram.

4.  Explain the anatomy of trilacunar node with examples and diagram

5.  Describe the structure of a multilacunar node in plants.

6.  With suitable diagrams and examples, write an essay on the anatomy of the nodal region in higher plants. What are the evolutionary significances of nodal anatomy?

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326.Worknets (20%, 20 points)

Worknets in ENGL326 involve you in bringing to light four distinct research webs: semantic, bibliographic, affinity-based, and choral. Begin by choosing a key (e.g., known, influential) academic article in your field of study since 1980. You will need a copy of the article, and you should make arrangements early in the semester to retrieve it. Each of the worknets will consist of a network-like visual representation (sketched in Google Docs/Drawing) and a brief inventory or synthesis (300-500 words) that accounts for associations illuminated in the net.

Worknets provide an inventive method for composing, through the tracing of associations, linkages and connections manifest in researched writing, many of which are elusive. Attending to these dimensions of research activity should prove generative: it will allow us to more richly explore and develop written research along related lines of inquiry. That is, while these worknets offer us criteria for tracing associations, the routes we follow shall in many cases lead us back through our own in-progress researched projects (e.g., P2).

How Will I Represent Each Worknet? After you select a scholarly article to work with, you will produce four worknets. I recommend you use Google Docs/Drawing to produce a visual representation of each worknet because its drawing tools are simple; however, you are welcome to try out other software options, such as CMap Tools (free; download required; available for Mac or PC). In addition to the visual representation, you will write an account of the worknet that explores and/or synthesizes your choices and digs into their suggestiveness for the research you are currently pursuing in ENGL326.

What Are These Worknets Building Toward? I have described worknets as an inventive method, but they also enlarge the context within which you are conducting research. As researchers read (in whatever field of study), they frequently trace associations in these (and many other) ways. For some, the worknets you create in ENGL326 will directly influence the developmental buildup of P2, the researched project. For others, the worknets will establish parallel pathways, perhaps not as directly giving shape to your research, but nevertheless providing you with invaluable first-hand experience with these practices.

An Example I have sketched for you a series of worknets extending from Marylin Cooper's 1986 College English article, "The Ecology of Writing." This is an important scholarly essay—a key precursor to ecological thinking about writing practices that has continued to take hold in the 24 years since it was published.

1. Semantic Worknet The sematic worknet concerns vocabulary —words and phrases that appear in the article itself and whose reference and meaning can be traced to peripheral ideas suited to further exploration. A written account accompanying this semantic worknet would carefully examine selected phrases. For instance, it might dig more deeply into "process model," a phrase that appears eight times in Cooper's article. What exactly is a "process model" in the context of the article? In what other ways has "process model" figured into scholarship about writing? Similar questions could be asked of other words and phrases included here: textual forms, solitary author, cognitive process, and ecological model. The written account might also work through definitional groundwork drawn from the Oxford English Dictionary. What is the etymology (historical and linguistic development) of a term? What other words are similar to it? How does studying these words and phrases enrich your understanding of the article and identifiable lines of inquiry related to it?

2. Bibliographic Worknet Cooper's essay cites 32 sources. Certainly collecting and reading all of them would be a formidable undertaking. Nevertheless, taking some interest in them will prove worthwhile for your research. For the bibliographic worknet, you will identify 3-5 of the sources cited in an article and explore them more fully, examining the original source in light of how it is used in the article. For example, having tracked down a copy of Burke's A Grammar of Motives , next you might ask, What pieces of Burke's work does Cooper use? What other sections of the book might, at a glance, extend the idea of an ecology of writing? If you track down article-length sources, you should take the time to read them all the way through. For books, it is adequate, for the purposes of the account accompanying the bibliographic worknet, for you to read more selectively. Again, the idea here is to enlarge the context: to explore bibliographies as a method for enriching inquiry.

3. Affinity Worknet Affinity worknets focus on an author's working relationships: collaborations, professional appointments and associations, graduate program of study, and identifiable intellectual influences. Whereas the semantic and bibliographic worknets take root in the text itself, affinity worknets are extra-textual. Based on what we know or what we can find out, can we pinpoint particular affinities for Marylin Cooper? Inevitably this will be a speculative and imprecise pursuit, but it may nevertheless prove inventive. Particular affinities are shown in the worknet model above: 1) Cooper collaborated with Cynthia Selfe on an article in 1990; in 1980, her dissertation research at the University of Minnesota, "Implicatures in Dramatic Conversation," focused on H. Paul Grice; she worked with Dennis Lynch and Diana George on an award-winning article in 1997. As with the bibliographic worknet, the account of affinities will require you to gather materials, read them, and speculate about linkages between the work in the focal article and these ties based on affinity. Yet another approach to affinities, when such information is available, would be to identify people who attended a graduate program at the same time (e.g., cohorts, schools of thought), or to search the Proquest UMI Dissertation Abstracts Online database for information about dissertation committee members whose work you could then look into.

4. Choral Worknet Choral worknets explore time-place coincidences as an inventive technique. Like the affinity worknet above, a choral worknet is not explicitly identifiable in the text of the article. Rather than attend to scholarly and intellectual ties as the affinity worknet does, it explores coincident objects and events from popular culture in the interest of enlarging context. Cooper's article was published in 1986, the same year Ferris Bueller's Day Off played in theaters, Chinese economist Deng Xiaoping was celebrated as Time 's Man of the Year, Al Capone's vault was opened, Bill Buckner missed the ground ball, and Da Yoopers released their first album, "Yoopanese." The choral worknet instigates surprising, accidental insights through juxtaposition. These disparate elements may or may not prove, ultimately, to be inventive. Identifying this particular worknet (3-5 pop cultural coincidences), however, can lead to possible projects, as follows: How do ideas of process and ecology generalize to the economic theories embraced by Deng Xiapong? Or how does an ecological approach to writing change the ways we might think about school movies from 1986, such as Ferris Bueller's Day Off or Back to School ?

Assignment Details You will produce four worknets, each consisting of 1) a visual representation of linkages and 2) a written account of the investigations such linkages have generated. Each visual representation should include 3-5 nodes; each account should be between 300-500 words.

Your first worknet—either semantic or bibliographic—is due on Monday, October 18 . Turn in a second worknet with your draft of P2 on Wednesday, November 5 . The remaining two worknets are due on Monday, November 8 .

Contact Information

"Really, we should say 'worknet' instead of 'network'. It's the work, and the movement, and the flow, and the changes that should be stressed." —Bruno Latour, "A Dialogue on ANT" joie de vivre . And we then wonder, as de Tocqueville prophesied we would, why life has lost its savor" (19). —Richard Lanham, Style: An Anti-textbook "Let us collectively raise the level of discourse online. What starts as a relentless tide of simple-minded chatter resembles the most perfect wave of literary turbulence under the right conditions" (89). —Dom Sagolla, 140 Characters: A Style Guide for the Short Form -->

What Exactly is Node.js? Explained for Beginners

Node.js allows developers to create both front-end and back-end applications using JavaScript. It was released in 2009 by Ryan Dahl.

In this article, you will learn about Node.js. You will learn the following:

What is Node.js?

• How the Node.js environment differs from the browser.
• Why you should learn Node.js.
• How to get started with Node.js.
• Resources to help you learn Node.js.

"Node.js is an open-source and cross-platform JavaScript runtime environment." - Nodejs.dev Docs

This sounds like a cool, straightforward answer. But for a beginner, this definition might raise further questions. So let's break it down and understand what it means.

Node.js is open-source: This means that the source code for Node.js is publicly available. And it's maintained by contributors from all over the world. The Node.js contribution guide shows you how to contribute.

Node.js is cross-platform: Node.js is not dependent on any operating system software. It can work on Linux, macOS, or Windows.

Node.js is a JavaScript runtime environment: When you write JavaScript code in your text editor, that code cannot perform any task unless you execute (or run) it. And to run your code, you need a runtime environment.

Browsers like Chrome and Firefox have runtime environments. That is why they can run JavaScript code. Before Node.js was created, JavaScript could only run in a browser. And it was used to build only front-end applications.

Node.js provides a runtime environment outside of the browser. It's also built on the Chrome V8 JavaScript engine . This makes it possible to build back-end applications using the same JavaScript programming language you may be familiar with.

Differences Between the Browser and Node.js Runtime Environments

Both the browser and Node.js are capable of executing JavaScript programs. But there are some key differences that you need to know. They include the following.

Access to the DOM APIs

With the browser runtime, you can access the Document Object Model (DOM). And you can perform all the DOM operations. But Node.js does not have access to the DOM.

Node.js exposes almost all the system resources to your programs. This means you can interact with the operating system, access the file systems, and read and write to the files. But, you do not have access to operating systems and file systems from the browser.

Window vs Global object

JavaScript has a built-in global object. The JavaScript global object for the browser is called the window object. In Node.js, the global object goes by the name global .

The window object contains methods and properties available only in the browser environment.

Control over runtime versions

With Node.js, you can choose which version to run your server-side application on. As a result, you can use modern JavaScript features without worrying about any version-specific inconsistencies.

Contrast this to the browser runtime environment. As a developer, you have no control over the version of browsers your clients use to access your app.

Loading modules ( import vs require keywords)

Node.js offers out-of-the-box support for CommonJS and ES modules. You can load modules using the require keyword (CommonJS syntax) and the import keyword (ES syntax).

Some modern browsers support ES modules. This means you can use import ES modules. But you will still need to create bundles to cater to older browsers that do not support ES modules.

How Much JavaScript Do You Need to Get Started with Node?

If you are an absolute beginner to JavaScript, I recommend that you start with the basics.

Become familiar with basic JavaScript concepts first. Then, you can move on to learning to build server-side applications with Node.js.

There's no way you'll ever exhaust all there is to learn about JavaScript. So, how to determine when you know enough JavaScript to get started with Node.js?

The Nodejs.dev documentation provides a list of JavaScript topics to learn before diving deep with Node.js.

Once you have a grasp of JavaScript basics, then you can get started with Node.js

How to Get Started with Node.js

Let's see how you can create your first Node.js application. This section will show you how to run Node.js scripts from the command line.

How to download and install Node.js

First, you need to download and install Node.js. There are different ways you can do that. If you are a beginner, I would suggest that you download Node.js from the official website .

Official packages are available on the website for all major platforms (Windows, macOS, and Linux). Download and install the appropriate package for your system.

How to check the Node.js version

To check the Node.js version, run the command node --version in your terminal. If the installation was successful, you will see the version of Node.js you installed. You should get a response like the screenshot below.

How to run Node.js from the command line

Let's build a simple Hello World app.

Create a new project folder. You can call it my-project. Open the project in your code editor. Inside the folder, create an app.js file.

Add the following code to app.js

As you can see, this is JavaScript code.

You can run the script in the command line by running the command node <fileName> . In this case, the file name is app.js .

Run the following command in your terminal to execute the Hello world. program:

You should see the string "Hello world." logged in your terminal like so.

Congratulations! You just ran your first Node.js application.

Should You Learn Node.js?

Here are some reasons why you should consider learning Node.js

Node.js allows you to write JavaScript on both client and server.

One of the advantages of Node.js is that it allows you to work on both the front-end and back-end of your application. And you use one programming language – JavaScript – to do so.

This is good news for front-end developers who work with JavaScript. If you want to start working on the server side, it's easier compared to learning a new back-end language from scratch.

Node has a vibrant community.

As I mentioned earlier in the article, Node.js is open-sourced. It is actively maintained by developers from all over the world.

There is a vibrant community surrounding Node.js. You can find  excellent tutorials and solutions to problems when you get stuck.

Node is built on top of Google Chrome's V8 engine.

Node.js is built on top of the Chrome V8 JavaScript engine. This is significant because the V8 engine powers some of Google's in-browser applications like Gmail. As such, Google invests heavily to ensure it offers high performance.

Demand in the market

Many big names like Netflix, Uber, Paypal, and LinkedIn, and others use Node.js. Apart from the big names, many startups also use Node.js in developing their applications.

Learning to work with Node.js will make you a desirable candidate in the job market.

The NPM library

The NPM library is one of the excellent resources that comes with Node.js. The library contains a registry of over a million packages. A package is a reusable piece of code.

You can create a package for a recurring task or problem and share the code with others via the registry.

You can also download packages that others have shared. For many tasks that developers perform regularly, there are packages available for that.

Resources to Learn Node

If you are curious about learning how to build Node.js applications, I recommend the following resources.

• 8-Hour Node.js and Express.js Course on freeCodeCamp YouTube Channel .
• The freeCodeCamp Backend Development and APIs curriculum
• Nodejs.dev Documentation

Also, below is a link to a video of Ryan Dahl when he first presented Node.js.

Ryan Dahl: Original Node.js presentation at JSConf 2009

A single blog post like this is not enough to learn all there is to know about Node.js. The purpose of this article was to give you an overview of what Node.js is.

If you were not sure what Node.js is, I hope this article addressed your concerns and cleared your confusion.

Thanks for reading. And happy coding!

Software Developer | Technical Writer

If you read this far, thank the author to show them you care. Say Thanks

Learn to code for free. freeCodeCamp's open source curriculum has helped more than 40,000 people get jobs as developers. Get started

Frequently asked questions

What is an essay.

An essay is a focused piece of writing that explains, argues, describes, or narrates.

In high school, you may have to write many different types of essays to develop your writing skills.

Academic essays at college level are usually argumentative : you develop a clear thesis about your topic and make a case for your position using evidence, analysis and interpretation.

Frequently asked questions: Writing an essay

For a stronger conclusion paragraph, avoid including:

• Important evidence or analysis that wasn’t mentioned in the main body
• Generic concluding phrases (e.g. “In conclusion…”)
• Weak statements that undermine your argument (e.g. “There are good points on both sides of this issue.”)

Your conclusion should leave the reader with a strong, decisive impression of your work.

Your essay’s conclusion should contain:

• A rephrased version of your overall thesis
• A brief review of the key points you made in the main body
• An indication of why your argument matters

The conclusion may also reflect on the broader implications of your argument, showing how your ideas could applied to other contexts or debates.

The conclusion paragraph of an essay is usually shorter than the introduction . As a rule, it shouldn’t take up more than 10–15% of the text.

The “hook” is the first sentence of your essay introduction . It should lead the reader into your essay, giving a sense of why it’s interesting.

To write a good hook, avoid overly broad statements or long, dense sentences. Try to start with something clear, concise and catchy that will spark your reader’s curiosity.

Your essay introduction should include three main things, in this order:

• An opening hook to catch the reader’s attention.
• Relevant background information that the reader needs to know.
• A thesis statement that presents your main point or argument.

The length of each part depends on the length and complexity of your essay .

Let’s say you’re writing a five-paragraph  essay about the environmental impacts of dietary choices. Here are three examples of topic sentences you could use for each of the three body paragraphs :

• Research has shown that the meat industry has severe environmental impacts.
• However, many plant-based foods are also produced in environmentally damaging ways.
• It’s important to consider not only what type of diet we eat, but where our food comes from and how it is produced.

Each of these sentences expresses one main idea – by listing them in order, we can see the overall structure of the essay at a glance. Each paragraph will expand on the topic sentence with relevant detail, evidence, and arguments.

The topic sentence usually comes at the very start of the paragraph .

However, sometimes you might start with a transition sentence to summarize what was discussed in previous paragraphs, followed by the topic sentence that expresses the focus of the current paragraph.

Topic sentences help keep your writing focused and guide the reader through your argument.

In an essay or paper , each paragraph should focus on a single idea. By stating the main idea in the topic sentence, you clarify what the paragraph is about for both yourself and your reader.

A topic sentence is a sentence that expresses the main point of a paragraph . Everything else in the paragraph should relate to the topic sentence.

The thesis statement is essential in any academic essay or research paper for two main reasons:

• It gives your writing direction and focus.
• It gives the reader a concise summary of your main point.

Without a clear thesis statement, an essay can end up rambling and unfocused, leaving your reader unsure of exactly what you want to say.

The thesis statement should be placed at the end of your essay introduction .

Follow these four steps to come up with a thesis statement :

• Ask a question about your topic .
• Write your initial answer.
• Develop your answer by including reasons.
• Refine your answer, adding more detail and nuance.

A thesis statement is a sentence that sums up the central point of your paper or essay . Everything else you write should relate to this key idea.

An essay isn’t just a loose collection of facts and ideas. Instead, it should be centered on an overarching argument (summarized in your thesis statement ) that every part of the essay relates to.

The way you structure your essay is crucial to presenting your argument coherently. A well-structured essay helps your reader follow the logic of your ideas and understand your overall point.

The structure of an essay is divided into an introduction that presents your topic and thesis statement , a body containing your in-depth analysis and arguments, and a conclusion wrapping up your ideas.

The structure of the body is flexible, but you should always spend some time thinking about how you can organize your essay to best serve your ideas.

The vast majority of essays written at university are some sort of argumentative essay . Almost all academic writing involves building up an argument, though other types of essay might be assigned in composition classes.

Essays can present arguments about all kinds of different topics. For example:

• In a literary analysis essay, you might make an argument for a specific interpretation of a text
• In a history essay, you might present an argument for the importance of a particular event
• In a politics essay, you might argue for the validity of a certain political theory

At high school and in composition classes at university, you’ll often be told to write a specific type of essay , but you might also just be given prompts.

Look for keywords in these prompts that suggest a certain approach: The word “explain” suggests you should write an expository essay , while the word “describe” implies a descriptive essay . An argumentative essay might be prompted with the word “assess” or “argue.”

In rhetorical analysis , a claim is something the author wants the audience to believe. A support is the evidence or appeal they use to convince the reader to believe the claim. A warrant is the (often implicit) assumption that links the support with the claim.

Logos appeals to the audience’s reason, building up logical arguments . Ethos appeals to the speaker’s status or authority, making the audience more likely to trust them. Pathos appeals to the emotions, trying to make the audience feel angry or sympathetic, for example.

Collectively, these three appeals are sometimes called the rhetorical triangle . They are central to rhetorical analysis , though a piece of rhetoric might not necessarily use all of them.

The term “text” in a rhetorical analysis essay refers to whatever object you’re analyzing. It’s frequently a piece of writing or a speech, but it doesn’t have to be. For example, you could also treat an advertisement or political cartoon as a text.

The goal of a rhetorical analysis is to explain the effect a piece of writing or oratory has on its audience, how successful it is, and the devices and appeals it uses to achieve its goals.

Unlike a standard argumentative essay , it’s less about taking a position on the arguments presented, and more about exploring how they are constructed.

You should try to follow your outline as you write your essay . However, if your ideas change or it becomes clear that your structure could be better, it’s okay to depart from your essay outline . Just make sure you know why you’re doing so.

If you have to hand in your essay outline , you may be given specific guidelines stating whether you have to use full sentences. If you’re not sure, ask your supervisor.

When writing an essay outline for yourself, the choice is yours. Some students find it helpful to write out their ideas in full sentences, while others prefer to summarize them in short phrases.

You will sometimes be asked to hand in an essay outline before you start writing your essay . Your supervisor wants to see that you have a clear idea of your structure so that writing will go smoothly.

Even when you do not have to hand it in, writing an essay outline is an important part of the writing process . It’s a good idea to write one (as informally as you like) to clarify your structure for yourself whenever you are working on an essay.

Comparisons in essays are generally structured in one of two ways:

• The alternating method, where you compare your subjects side by side according to one specific aspect at a time.
• The block method, where you cover each subject separately in its entirety.

It’s also possible to combine both methods, for example by writing a full paragraph on each of your topics and then a final paragraph contrasting the two according to a specific metric.

Your subjects might be very different or quite similar, but it’s important that there be meaningful grounds for comparison . You can probably describe many differences between a cat and a bicycle, but there isn’t really any connection between them to justify the comparison.

You’ll have to write a thesis statement explaining the central point you want to make in your essay , so be sure to know in advance what connects your subjects and makes them worth comparing.

Some essay prompts include the keywords “compare” and/or “contrast.” In these cases, an essay structured around comparing and contrasting is the appropriate response.

Comparing and contrasting is also a useful approach in all kinds of academic writing : You might compare different studies in a literature review , weigh up different arguments in an argumentative essay , or consider different theoretical approaches in a theoretical framework .

The key difference is that a narrative essay is designed to tell a complete story, while a descriptive essay is meant to convey an intense description of a particular place, object, or concept.

Narrative and descriptive essays both allow you to write more personally and creatively than other kinds of essays , and similar writing skills can apply to both.

If you’re not given a specific prompt for your descriptive essay , think about places and objects you know well, that you can think of interesting ways to describe, or that have strong personal significance for you.

The best kind of object for a descriptive essay is one specific enough that you can describe its particular features in detail—don’t choose something too vague or general.

If you’re not given much guidance on what your narrative essay should be about, consider the context and scope of the assignment. What kind of story is relevant, interesting, and possible to tell within the word count?

The best kind of story for a narrative essay is one you can use to reflect on a particular theme or lesson, or that takes a surprising turn somewhere along the way.

Don’t worry too much if your topic seems unoriginal. The point of a narrative essay is how you tell the story and the point you make with it, not the subject of the story itself.

Narrative essays are usually assigned as writing exercises at high school or in university composition classes. They may also form part of a university application.

When you are prompted to tell a story about your own life or experiences, a narrative essay is usually the right response.

The majority of the essays written at university are some sort of argumentative essay . Unless otherwise specified, you can assume that the goal of any essay you’re asked to write is argumentative: To convince the reader of your position using evidence and reasoning.

In composition classes you might be given assignments that specifically test your ability to write an argumentative essay. Look out for prompts including instructions like “argue,” “assess,” or “discuss” to see if this is the goal.

At college level, you must properly cite your sources in all essays , research papers , and other academic texts (except exams and in-class exercises).

Add a citation whenever you quote , paraphrase , or summarize information or ideas from a source. You should also give full source details in a bibliography or reference list at the end of your text.

The exact format of your citations depends on which citation style you are instructed to use. The most common styles are APA , MLA , and Chicago .

An argumentative essay tends to be a longer essay involving independent research, and aims to make an original argument about a topic. Its thesis statement makes a contentious claim that must be supported in an objective, evidence-based way.

An expository essay also aims to be objective, but it doesn’t have to make an original argument. Rather, it aims to explain something (e.g., a process or idea) in a clear, concise way. Expository essays are often shorter assignments and rely less on research.

An expository essay is a common assignment in high-school and university composition classes. It might be assigned as coursework, in class, or as part of an exam.

Sometimes you might not be told explicitly to write an expository essay. Look out for prompts containing keywords like “explain” and “define.” An expository essay is usually the right response to these prompts.

An expository essay is a broad form that varies in length according to the scope of the assignment.

Expository essays are often assigned as a writing exercise or as part of an exam, in which case a five-paragraph essay of around 800 words may be appropriate.

You’ll usually be given guidelines regarding length; if you’re not sure, ask.

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Gephi: Analyzing

• Getting Started
• Program Setup
• Visualizing
• Data formats
• Add plugins
• Data management

Tutorial Data

Tutorial Slides

Tutorial Handout

Tutorial Video

Common Procedures

• Degree (when directed, in-degree and out-degree) This is a numerical node variable.  It is the number of edges connected to a particular node. Gephi calculates degree automatically.
• Betweenness Centrality This is a numerical node variable.  It is a measure of how often a node appears on shortest paths between nodes in the network.
• Closeness Centrality This is a numerical node variable.  It is the average distance from a given node to all other nodes in the network.
• Eccentricity This is a numerical node variable.  It is the distance from a given node to the farthest node from it in the network.
• Density This is a property of the whole network.  It is the ratio between the number of edges and the total number of possible edges between the nodes.
• Clustering/Modularity Measures how well a network decomposes into modular communities. This algorithm will calculate an overall modularity score for the network, as well as assign each node to a separate cluster that will appear as a variable suitable for partion coloring.

ProTip: Save output of window for record keeping. Gephi allows you to print, copy, or save the content of the reporting window.

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What is an Essay?

10 May, 2020

11 minutes read

Author:  Tomas White

Well, beyond a jumble of words usually around 2,000 words or so - what is an essay, exactly? Whether you’re taking English, sociology, history, biology, art, or a speech class, it’s likely you’ll have to write an essay or two. So how is an essay different than a research paper or a review? Let’s find out!

Defining the Term – What is an Essay?

The essay is a written piece that is designed to present an idea, propose an argument, express the emotion or initiate debate. It is a tool that is used to present writer’s ideas in a non-fictional way. Multiple applications of this type of writing go way beyond, providing political manifestos and art criticism as well as personal observations and reflections of the author.

An essay can be as short as 500 words, it can also be 5000 words or more.  However, most essays fall somewhere around 1000 to 3000 words ; this word range provides the writer enough space to thoroughly develop an argument and work to convince the reader of the author’s perspective regarding a particular issue.  The topics of essays are boundless: they can range from the best form of government to the benefits of eating peppermint leaves daily. As a professional provider of custom writing, our service has helped thousands of customers to turn in essays in various forms and disciplines.

Origins of the Essay

Over the course of more than six centuries essays were used to question assumptions, argue trivial opinions and to initiate global discussions. Let’s have a closer look into historical progress and various applications of this literary phenomenon to find out exactly what it is.

Today’s modern word “essay” can trace its roots back to the French “essayer” which translates closely to mean “to attempt” .  This is an apt name for this writing form because the essay’s ultimate purpose is to attempt to convince the audience of something.  An essay’s topic can range broadly and include everything from the best of Shakespeare’s plays to the joys of April.

The essay comes in many shapes and sizes; it can focus on a personal experience or a purely academic exploration of a topic.  Essays are classified as a subjective writing form because while they include expository elements, they can rely on personal narratives to support the writer’s viewpoint.  The essay genre includes a diverse array of academic writings ranging from literary criticism to meditations on the natural world.  Most typically, the essay exists as a shorter writing form; essays are rarely the length of a novel.  However, several historic examples, such as John Locke’s seminal work “An Essay Concerning Human Understanding” just shows that a well-organized essay can be as long as a novel.

The Essay in Literature

The essay enjoys a long and renowned history in literature.  They first began gaining in popularity in the early 16 th century, and their popularity has continued today both with original writers and ghost writers.  Many readers prefer this short form in which the writer seems to speak directly to the reader, presenting a particular claim and working to defend it through a variety of means.  Not sure if you’ve ever read a great essay? You wouldn’t believe how many pieces of literature are actually nothing less than essays, or evolved into more complex structures from the essay. Check out this list of literary favorites:

• The Book of My Lives by Aleksandar Hemon
• Notes of a Native Son by James Baldwin
• Against Interpretation by Susan Sontag
• High-Tide in Tucson: Essays from Now and Never by Barbara Kingsolver
• Slouching Toward Bethlehem by Joan Didion
• Naked by David Sedaris
• Walden; or, Life in the Woods by Henry David Thoreau

Pretty much as long as writers have had something to say, they’ve created essays to communicate their viewpoint on pretty much any topic you can think of!

The Essay in Academics

Not only are students required to read a variety of essays during their academic education, but they will likely be required to write several different kinds of essays throughout their scholastic career.  Don’t love to write?  Then consider working with a ghost essay writer !  While all essays require an introduction, body paragraphs in support of the argumentative thesis statement, and a conclusion, academic essays can take several different formats in the way they approach a topic.  Common essays required in high school, college, and post-graduate classes include:

Five paragraph essay

This is the most common type of a formal essay. The type of paper that students are usually exposed to when they first hear about the concept of the essay itself. It follows easy outline structure – an opening introduction paragraph; three body paragraphs to expand the thesis; and conclusion to sum it up.

Argumentative essay

These essays are commonly assigned to explore a controversial issue.  The goal is to identify the major positions on either side and work to support the side the writer agrees with while refuting the opposing side’s potential arguments.

Compare and Contrast essay

This essay compares two items, such as two poems, and works to identify similarities and differences, discussing the strength and weaknesses of each.  This essay can focus on more than just two items, however.  The point of this essay is to reveal new connections the reader may not have considered previously.

Definition essay

This essay has a sole purpose – defining a term or a concept in as much detail as possible. Sounds pretty simple, right? Well, not quite. The most important part of the process is picking up the word. Before zooming it up under the microscope, make sure to choose something roomy so you can define it under multiple angles. The definition essay outline will reflect those angles and scopes.

Descriptive essay

Perhaps the most fun to write, this essay focuses on describing its subject using all five of the senses.  The writer aims to fully describe the topic; for example, a descriptive essay could aim to describe the ocean to someone who’s never seen it or the job of a teacher.  Descriptive essays rely heavily on detail and the paragraphs can be organized by sense.

Illustration essay

The purpose of this essay is to describe an idea, occasion or a concept with the help of clear and vocal examples. “Illustration” itself is handled in the body paragraphs section. Each of the statements, presented in the essay needs to be supported with several examples. Illustration essay helps the author to connect with his audience by breaking the barriers with real-life examples – clear and indisputable.

Informative Essay

Being one the basic essay types, the informative essay is as easy as it sounds from a technical standpoint. High school is where students usually encounter with informative essay first time. The purpose of this paper is to describe an idea, concept or any other abstract subject with the help of proper research and a generous amount of storytelling.

Narrative essay

This type of essay focuses on describing a certain event or experience, most often chronologically.  It could be a historic event or an ordinary day or month in a regular person’s life. Narrative essay proclaims a free approach to writing it, therefore it does not always require conventional attributes, like the outline. The narrative itself typically unfolds through a personal lens, and is thus considered to be a subjective form of writing.

Persuasive essay

The purpose of the persuasive essay is to provide the audience with a 360-view on the concept idea or certain topic – to persuade the reader to adopt a certain viewpoint. The viewpoints can range widely from why visiting the dentist is important to why dogs make the best pets to why blue is the best color.  Strong, persuasive language is a defining characteristic of this essay type.

The Essay in Art

Several other artistic mediums have adopted the essay as a means of communicating with their audience.  In the visual arts, such as painting or sculpting, the rough sketches of the final product are sometimes deemed essays.  Likewise, directors may opt to create a film essay which is similar to a documentary in that it offers a personal reflection on a relevant issue.  Finally, photographers often create photographic essays in which they use a series of photographs to tell a story, similar to a narrative or a descriptive essay.

Drawing the line – question answered

“What is an Essay?” is quite a polarizing question. On one hand, it can easily be answered in a couple of words. On the other, it is surely the most profound and self-established type of content there ever was. Going back through the history of the last five-six centuries helps us understand where did it come from and how it is being applied ever since.

If you must write an essay, follow these five important steps to works towards earning the “A” you want:

• Understand and review the kind of essay you must write
• Brainstorm your argument
• Find research from reliable sources to support your perspective
• Cite all sources parenthetically within the paper and on the Works Cited page
• Follow all grammatical rules

Generally speaking, when you must write any type of essay, start sooner rather than later!  Don’t procrastinate – give yourself time to develop your perspective and work on crafting a unique and original approach to the topic.  Remember: it’s always a good idea to have another set of eyes (or three) look over your essay before handing in the final draft to your teacher or professor.  Don’t trust your fellow classmates?  Consider hiring an editor or a ghostwriter to help out!

If you are still unsure on whether you can cope with your task – you are in the right place to get help. HandMadeWriting is the perfect answer to the question “Who can write my essay?”

A life lesson in Romeo and Juliet taught by death

Due to human nature, we draw conclusions only when life gives us a lesson since the experience of others is not so effective and powerful. Therefore, when analyzing and sorting out common problems we face, we may trace a parallel with well-known book characters or real historical figures. Moreover, we often compare our situations with […]

Ethical Research Paper Topics

Writing a research paper on ethics is not an easy task, especially if you do not possess excellent writing skills and do not like to contemplate controversial questions. But an ethics course is obligatory in all higher education institutions, and students have to look for a way out and be creative. When you find an […]

Art Research Paper Topics

Students obtaining degrees in fine art and art & design programs most commonly need to write a paper on art topics. However, this subject is becoming more popular in educational institutions for expanding students’ horizons. Thus, both groups of receivers of education: those who are into arts and those who only get acquainted with art […]

What is SA node and AV node? Where are they located? What are their functions?

Sa node: the sa node (sa stands for sinoatrial) is one of the major elements in the cardiac conduction system, the system that controls the heart rate. location: the sa node consists of a cluster of cells that are situated in the upper part of the wall of the right atrium (the right upper chamber of the heart). location is precisely the upper right auricular wall. function it initiates electric impulses, thus initiating heart beat. the electrical impulses are generated in sa node. the sa node is also called the sinus node. the electrical signal generated by the sa node moves from cell to cell down through the heart until it reaches the atrioventricular node (av node), av node : av node is atrioventricular node. it is a cluster of cells situated in the center of the heart between the atria and ventricles. location: precise location is centre of atrio ventricular septum. function: it causes ventricular contractions. av node collects signals from sa node.the av node serves as a gate that slows the electrical current before the signal is permitted to pass down through to the ventricles. this delay ensures that the atria have a chance to fully contract before the ventricles are stimulated. after passing the av node, the electrical current travels to the ventricles along special fibers embedded in the walls of the lower part of the heart..

The cardiac impulse is initiated and conducted further upto ventricle. The correct sequence of conduction of impulse is ( a ) S A N o d e A V N o d e P u r k i n j e f i b e r A V B u n d l e ( b ) S A N o d e P u r k i n j e f i b e r A V N o d e A V B u n d l e ( c ) S A N o d e A V N o d e A V B u n d l e P u r k i n j e f i b e r ( d ) S A N o d e P u r k i n j e f i b e r A V B u n d l e A V N o d e

The SA node is located in

What is Node.js? A beginner's introduction to JavaScript runtime

To understand why Eddington and Dyson traveled such distances to watch the eclipse, we need to talk about gravity.

Since at least the days of Isaac Newton, who wrote in 1687, scientists thought gravity was a simple force of mutual attraction. Newton proposed that every object in the universe attracts every other object in the universe, and that the strength of this attraction is related to the size of the objects and the distances among them. This is mostly true, actually, but it’s a little more nuanced than that.

On much larger scales, like among black holes or galaxy clusters, Newtonian gravity falls short. It also can’t accurately account for the movement of large objects that are close together, such as how the orbit of Mercury is affected by its proximity the Sun.

Albert Einstein’s most consequential breakthrough solved these problems. General relativity holds that gravity is not really an invisible force of mutual attraction, but a distortion. Rather than some kind of mutual tug-of-war, large objects like the Sun and other stars respond relative to each other because the space they are in has been altered. Their mass is so great that they bend the fabric of space and time around themselves.

Read More: 10 Surprising Facts About the 2024 Solar Eclipse

This was a weird concept, and many scientists thought Einstein’s ideas and equations were ridiculous. But others thought it sounded reasonable. Einstein and others knew that if the theory was correct, and the fabric of reality is bending around large objects, then light itself would have to follow that bend. The light of a star in the great distance, for instance, would seem to curve around a large object in front of it, nearer to us—like our Sun. But normally, it’s impossible to study stars behind the Sun to measure this effect. Enter an eclipse.

Einstein’s theory gives an equation for how much the Sun’s gravity would displace the images of background stars. Newton’s theory predicts only half that amount of displacement.

Eddington and Dyson measured the Hyades cluster because it contains many stars; the more stars to distort, the better the comparison. Both teams of scientists encountered strange political and natural obstacles in making the discovery, which are chronicled beautifully in the book No Shadow of a Doubt: The 1919 Eclipse That Confirmed Einstein's Theory of Relativity , by the physicist Daniel Kennefick. But the confirmation of Einstein’s ideas was worth it. Eddington said as much in a letter to his mother: “The one good plate that I measured gave a result agreeing with Einstein,” he wrote , “and I think I have got a little confirmation from a second plate.”

The Eddington-Dyson experiments were hardly the first time scientists used eclipses to make profound new discoveries. The idea dates to the beginnings of human civilization.

Careful records of lunar and solar eclipses are one of the greatest legacies of ancient Babylon. Astronomers—or astrologers, really, but the goal was the same—were able to predict both lunar and solar eclipses with impressive accuracy. They worked out what we now call the Saros Cycle, a repeating period of 18 years, 11 days, and 8 hours in which eclipses appear to repeat. One Saros cycle is equal to 223 synodic months, which is the time it takes the Moon to return to the same phase as seen from Earth. They also figured out, though may not have understood it completely, the geometry that enables eclipses to happen.

The path we trace around the Sun is called the ecliptic. Our planet’s axis is tilted with respect to the ecliptic plane, which is why we have seasons, and why the other celestial bodies seem to cross the same general path in our sky.

As the Moon goes around Earth, it, too, crosses the plane of the ecliptic twice in a year. The ascending node is where the Moon moves into the northern ecliptic. The descending node is where the Moon enters the southern ecliptic. When the Moon crosses a node, a total solar eclipse can happen. Ancient astronomers were aware of these points in the sky, and by the apex of Babylonian civilization, they were very good at predicting when eclipses would occur.

Two and a half millennia later, in 2016, astronomers used these same ancient records to measure the change in the rate at which Earth’s rotation is slowing—which is to say, the amount by which are days are lengthening, over thousands of years.

By the middle of the 19 th century, scientific discoveries came at a frenetic pace, and eclipses powered many of them. In October 1868, two astronomers, Pierre Jules César Janssen and Joseph Norman Lockyer, separately measured the colors of sunlight during a total eclipse. Each found evidence of an unknown element, indicating a new discovery: Helium, named for the Greek god of the Sun. In another eclipse in 1869, astronomers found convincing evidence of another new element, which they nicknamed coronium—before learning a few decades later that it was not a new element, but highly ionized iron, indicating that the Sun’s atmosphere is exceptionally, bizarrely hot. This oddity led to the prediction, in the 1950s, of a continual outflow that we now call the solar wind.

And during solar eclipses between 1878 and 1908, astronomers searched in vain for a proposed extra planet within the orbit of Mercury. Provisionally named Vulcan, this planet was thought to exist because Newtonian gravity could not fully describe Mercury’s strange orbit. The matter of the innermost planet’s path was settled, finally, in 1915, when Einstein used general relativity equations to explain it.

Many eclipse expeditions were intended to learn something new, or to prove an idea right—or wrong. But many of these discoveries have major practical effects on us. Understanding the Sun, and why its atmosphere gets so hot, can help us predict solar outbursts that could disrupt the power grid and communications satellites. Understanding gravity, at all scales, allows us to know and to navigate the cosmos.

GPS satellites, for instance, provide accurate measurements down to inches on Earth. Relativity equations account for the effects of the Earth’s gravity and the distances between the satellites and their receivers on the ground. Special relativity holds that the clocks on satellites, which experience weaker gravity, seem to run slower than clocks under the stronger force of gravity on Earth. From the point of view of the satellite, Earth clocks seem to run faster. We can use different satellites in different positions, and different ground stations, to accurately triangulate our positions on Earth down to inches. Without those calculations, GPS satellites would be far less precise.

This year, scientists fanned out across North America and in the skies above it will continue the legacy of eclipse science. Scientists from NASA and several universities and other research institutions will study Earth’s atmosphere; the Sun’s atmosphere; the Sun’s magnetic fields; and the Sun’s atmospheric outbursts, called coronal mass ejections.

When you look up at the Sun and Moon on the eclipse , the Moon’s day — or just observe its shadow darkening the ground beneath the clouds, which seems more likely — think about all the discoveries still yet waiting to happen, just behind the shadow of the Moon.

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• Stop Looking for Your Forever Home
• The Sympathizer Counters 50 Years of Hollywood Vietnam War Narratives
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• Want Weekly Recs on What to Watch, Read, and More? Sign Up for Worth Your Time

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Her Arm Was Unbearably Swollen and Painful. What Was Causing It?

A persistent ache had spread throughout her shoulder, down to her elbow. Was her tennis-playing responsible?

By Lisa Sanders, M.D.

“Hell, no!” the man exclaimed as he saw his 49-year-old wife enter the kitchen. Her right arm was huge, swollen. “You have to go to the E.R.,” he said. She was wearing a strapless summer dress, and her bare tanned shoulders made it easy to see that her entire arm, from wrist to clavicle, was much larger than her left, as if somehow it had been pumped full of air.

That arm had been giving her trouble off and on for the past year, but it had never been swollen. The aches and pains she had up to now she attributed to her passion for tennis. She started playing after she and her husband moved from London to the suburban town of Larchmont, N.Y. She saw that many of the women there played, so she took up the game as a way to meet people and make friends. It was a good strategy. Many of her closest friends were among those she met at the court. And while it started as a social strategy, it quickly became an obsession. She played virtually every day, year-round. And in the summer, she could play all day every day and really work on her game.

Everything changed after she took a class to improve her serve. In 30 minutes she must have hit 100 serves, and that familiar pain returned. This time it stayed. She decided to take a break to give her arm a chance to heal, but it was still sore when they traveled to their beach rental in Montauk a week later. By then, the pain seemed different. It was no longer the sore-muscle-and-tendon discomfort she had become used to. This felt deeper: an ache that spread throughout her shoulder, down to her elbow. Even before they went to Montauk, the woman noticed that her shoulder looked a little swollen. The day her husband sent her to the E.R., the swelling had spread down the arm to the wrist.

As she examined her enlarged limb, she took note of a sore she had seen earlier near the crease of her elbow. It had been there a few days. Had she been bitten or stung? She hadn’t felt anything. But beneath her dark tan she could see some red. Was this the hallmark rash of Lyme disease?

That afternoon she went to a local urgent-care center. After hearing her story, the doctor started her on Doxycycline, an antibiotic used to treat tick-borne diseases. She had taken the first dose just a few hours earlier, but her husband was right — her arm was clearly getting worse. So when he suggested that she go to the emergency room, she got in the car and drove herself to Stony Brook Southampton Hospital.

A Mosquito Bite?

In the E.R., Elizabeth Keane was the physician assistant assigned to see the woman. She quickly scanned the patient’s electronic medical record: Swollen painful arm. Insect bite. Normal vital signs. No fever. Keane could see the woman on a stretcher in the E.R. hallway. The patient was slender and tanned. She didn’t look sick but was clearly uncomfortable. Even at a distance it was easy to see why.

Keane walked over and introduced herself. She listened to the patient’s story and then examined the arm. There was a small, healing bite on the inside of the elbow. It looked like a mosquito bite — not a spider or tick bite. The skin wasn’t warm or particularly red, but the arm was tender. She couldn’t feel any enlarged lymph nodes. It didn’t look like an infection. Had there been an injury to the area? There was no bruising visible. Could she move the arm? The woman demonstrated that she could. Finally, Keane asked the patient if she lifted weights. No, she replied; she was a tennis player.

“I think I know what this is,” Keane said. She found a computer and ordered some studies to test her hypothesis and to rule out other possibilities. She thought Lyme disease or another tick-borne illness rather unlikely. The patient could have a ruptured tendon or muscle, but that kind of injury would make movement difficult, and the patient had moved her arm easily. Cellulitis — an infection in the skin — was possible. But those kinds of infections usually make the skin hot and red. After putting in orders for the tests, she hurried on to see the next patient.

Between patients, Keane checked the woman’s results. Her white-blood-cell count was normal. So were the markers of inflammation that usually accompany an infection. The rest of the lab results were equally unremarkable. Same with the chest X-ray. But the most important test, the test that Keane suspected would provide an answer, still hadn’t been done, so she plunged back into the activity of the E.R.

The patient waited restlessly on the stretcher. It was hard to get comfortable. Finally she was taken to a small, recessed area. A technician squirted some cool goo onto the patient’s neck and shoulder, then took a hand-held ultrasound wand and held it to her neck. Grainy images with streaks of blue and red appeared on a screen. The woman moved the device down the patient’s neck to her shoulder and arm, before holstering the device into the machine. “I’ll be right back,” she said. She picked up the phone to let Keane know what she had seen.

A Dark and Murky Line

The thick, dark lines that the technician saw were the veins that carried the patient’s blood from her arm back to her heart. Streaks of blue and red showed the blood moving through the vessels. It was the section of the line where there was no color that caught the technician’s attention. This part of the thick line was dark and murky. The murky line started at the base of the woman’s neck and extended over her shoulder and down her arm halfway to the elbow. There was no blood flow there, and that indicated a clot.

This kind of clot is usually caused by a change in the local anatomy. It’s a condition called thoracic-outlet syndrome. As the vein travels up the arm carrying deoxygenated blood back to the heart and lungs, it must pass between the topmost rib and the clavicle. It’s a tight spot, but the two bones are usually far enough apart so that blood flows easily. The vein is boxed into the space by two muscles: the anterior scalene, a neck muscle that runs from three upper vertebrae to the first rib, and the subclavius muscle that connects that first rib to the clavicle. In those who use their shoulder and arm to work or play, the scalene can get larger, making a tight spot even tighter. Sometimes, the area gets so tight that blood flow is slowed and a clot forms. And this was what happened to the patient.

The tennis player’s ambitious work on her serve may have injured the muscles of her arm and neck, and the resulting inflammation and swelling were sufficient to slow or even stop the flow of blood on its way back to the heart and lungs from the arm. This condition is more likely to occur in serious athletes who stress their arms, like tennis players or baseball pitchers. It can also happen to workers who use their arms over their heads, like painters or teachers who write on blackboards. It’s not just painful; it’s dangerous. If the clot breaks off, it can be carried into the lungs, blocking blood flow there in what’s known as a pulmonary embolism, causing serious injury to the lung and sometimes death.

The patient was started immediately on blood thinners. These medicines stabilize the existing clot and prevent new clots from forming. The following week the patient had surgery to remove the clot. Almost instantly her arm began to deflate. The deep ache disappeared.

A week later, she felt well enough and strong enough to go back to the courts. But the next morning she felt the familiar ache, and she knew the clot was back. Another ultrasound proved her right. Would she ever be able to play tennis again? What would prevent another blood clot the next time she played? She wasn’t willing to give up the game, she told the vascular surgeons. What were her options? When patients with thoracic-outlet syndrome have a recurrence of symptoms, surgeons will often recommend simply removing the structure compressing the vein. Two weeks later the woman had surgery to take out the rib closest to her clavicle.

Recovery from that surgery took more than a month. But when she was able to play again, her game came back as strong as ever. The training that led to her injury clearly paid off on the court. Her U.S. Tennis Association rating improved — an unexpected aftermath of an unexpected ordeal.

Lisa Sanders, M.D. , is a contributing writer for the magazine. Her latest book is “Diagnosis: Solving the Most Baffling Medical Mysteries.” If you have a solved case to share, write to her at [email protected]. More about Lisa Sanders, M.D.

Staying Safe During Tick Season

Thanks to migrating birds and deer vasectomies, new tick species are settling in New York City. Experts are warning that this  could be a particularly bad season .

More ticks mean a higher risk of contracting a Lyme infection. Here is what to do to minimize your exposure .

Lyme isn’t the only tick disease to worry about if you live in the Northeast. Babesiosis, a tick-borne illness that can cause flulike symptoms, is also on the rise .

Think you can outsmart a tick? Test your knowledge with this quiz .

The easiest way to prevent ticks is to look for them. Learn how to do a tick check after spending time outdoors .

Certain products that can help prevent a tick bite. Wirecutter recommends the best options .

INFORMATIONAL: U.S. Postal Service Recommends New Prices for July 2024

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TRAFFIC ADVISORY: 2024 Emancipation Day Celebration

On Sunday, April 14, 2024, the Emancipation Day Celebration will take place in the District of Columbia. In conjunction with this event, there will be parking restrictions and street closures that motorists should take into consideration:

The following streets will be posted as Emergency No Parking on Sunday, April 14, 2024 from 6:00 a.m. to 11:00 p.m.:

• Pennsylvania Avenue from 12th Street to 14th Street, NW
• E Street from 13th Street to 14th Street, NW
• 13th Street from E Street to Pennsylvania Avenue, NW
• The following streets will be closed to vehicle traffic on Sunday, April 14, 2024 from 6:00 a.m. to 11:00 p.m.:

The following streets will be posted as Emergency No Parking and closed to vehicle traffic on Sunday, April 14, 2024 from 10:00 a.m. to 3:00 p.m.:

• 9th Street from E Street to Pennsylvania Avenue, NW
• Pennsylvania Avenue from 9th Street to 12th Street, NW
• 10th Street from E Street to Constitution Avenue, NW
• 11th Street from E Street to Pennsylvania Avenue, NW
• 12th Street from E Street to Constitution Avenue, NW

For timely traffic information, please visit twitter.com/DCPoliceTraffic .

All street closures and listed times are subject to change based upon prevailing or unexpected conditions.

The public should expect parking restrictions along the street and should be guided by the posted emergency no parking signage. All vehicles that are parked in violation of the emergency no parking signs will be ticketed and towed.

Motorists could encounter possible delays if operating in the vicinity of this event and may wish to consider alternative routes. The Metropolitan Police Department and the D.C. Department of Transportation also wishes to remind motorists in the vicinity of this event to proceed with caution as increased pedestrian traffic can be anticipated.

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• 02 April 2024

‘Mini liver’ will grow in person’s own lymph node in bold new trial

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Researchers injected a mouse’s lymph node with liver cells (green), converting the organ into a ‘mini liver’. Credit: Lagasse Lab

A person has received an experimental treatment for the first time that, if successful, will lead them to grow an additional ‘miniature liver’. The procedure, developed by the biotechnology firm LyGenesis, marks the beginning of a clinical trial designed for people whose livers are failing, but who have not received an organ transplant.

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doi: https://doi.org/10.1038/d41586-024-00975-z

Komori, J., Boone, L., DeWard, A., Hoppo, T. & Lagasse, E. Nature Biotechnol . 30 , 976–983 (2012).

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Fontes, P., Komori, J., Lopez, R., Marsh, W. & Lagasse, E. Liver Transplant . 26 , 1629–1643 (2020).

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