Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs. An example is the outermost layer of the skin. There are three principal shapes of epithelial cell: squamous and cuboidal; these can be arranged in a single layer of cells as simple epithelium, either squamous, columnar, or cuboidal, or in layers of two or more cells deep as stratified, or compound, either squamous, columnar or cuboidal. In some tissues, a layer of columnar cells may appear to be stratified due to the placement of the nuclei; this sort of tissue is called pseudostratified. All glands are made up of epithelial cells. Functions of epithelial cells include secretion, selective absorption, transcellular transport, sensing. Epithelial layers contain no blood vessels, so they must receive nourishment via diffusion of substances from the underlying connective tissue, through the basement membrane.
Cell junctions are well employed in epithelial tissues. In general, epithelial tissues are classified by the number of their layers and by the shape and function of the cells; the three principal shapes associated with epithelial cells are—squamous and columnar. Squamous epithelium has cells; this is found as the lining of the mouth and including blood vessels and in the alveoli of the lungs. Cuboidal epithelium has cells whose height and width are the same. Columnar epithelium has cells taller. Columnar epithelium can be further classified into ciliated columnar epithelium and glandular columnar epithelium. By layer, epithelium is classed as either simple epithelium, only one cell thick or stratified epithelium having two or more cells in thickness or multi-layered – as stratified squamous epithelium, stratified cuboidal epithelium, stratified columnar epithelium, both types of layering can be made up of any of the cell shapes. However, when taller simple columnar epithelial cells are viewed in cross section showing several nuclei appearing at different heights, they can be confused with stratified epithelia.
This kind of epithelium is therefore described as pseudostratified columnar epithelium. Transitional epithelium has cells that can change from squamous to cuboidal, depending on the amount of tension on the epithelium. Simple epithelium is a single layer of cells with every cell in direct contact with the basement membrane that separates it from the underlying connective tissue. In general, it is found where filtration occur; the thinness of the epithelial barrier facilitates these processes. In general, simple epithelial tissues are classified by the shape of their cells; the four major classes of simple epithelium are: simple squamous. Simple squamous. Simple cuboidal: these cells may have secretory, absorptive, or excretory functions. Examples include small collecting ducts of kidney and salivary gland. Simple columnar. Non-ciliated epithelium can possess microvilli; some tissues are referred to as simple glandular columnar epithelium. These secrete mucus and are found in stomach and rectum. Pseudostratified columnar epithelium.
The ciliated type is called respiratory epithelium as it is exclusively confined to the larger respiratory airways of the nasal cavity and bronchi. Stratified epithelium differs from simple epithelium, it is therefore found where body linings have to withstand mechanical or chemical insult such that layers can be abraded and lost without exposing subepithelial layers. Cells flatten as the layers become more apical, though in their most basal layers the cells can be squamous, cuboidal or columnar. Stratified epithelia can have the following specializations: The basic cell types are squamous and columnar classed by their shape. Epithelial tissue is scutoid shaped packed and form a continuous sheet, it has no intercellular spaces. All epithelia is separated from underlying tissues by an extracellular fibrous basement membrane; the lining of the mouth, lung alveoli and kidney tubules are all made of epithelial tissue. The lining of the blood and lymphatic vessels are of a specialised form of epithelium called endothelium.
Epithelium lines both the outside and the inside cavities and lumina of bodies. The outermost layer of human skin is composed of dead stratified squamous, keratinized epithelial cells. Tissues that line the inside of the mouth, the esophagus, the vagina, part of the rectum are composed of nonkeratinized stratified squamous epithelium. Other surfaces that separate body cavities from the outside environment are lined by simple squamous, columnar, or pseudostratified epithelial cells. Other epithelial cells line the insides of the lungs, the gastrointestinal tract, the reproductive and urinary tracts, make up the exocrine and endocrine glands; the outer surface of the cornea is covered with fast-growing regenerated epithelial cells. A specialised for
Sadratnamala is an astronomical-mathematical treatise in Sanskrit written by Sankara Varman, an astronomer-mathematician of the Kerala school of mathematics, in 1819. Though the book has been written at a time when western mathematics and astronomy had been introduced in India, it is composed purely in the traditional style followed by the mathematicians of the Kerala school. Sankara Varman has written a detailed commentary on the book in Malayalam. Sadratnamala is one of the books cited in C. M. Whish's paper on the achievements of the Kerala school of mathematics; this paper published in the Transactions of the Royal Asiatic Society of Great Britain and Ireland in 1834, was the first attempt to bring the accomplishments of Keralese mathematicians to the attention of Western mathematical scholarship. Whish wrote in his paper thus: "The author of Sadratnamalah is SANCARA VARMA, the younger brother of the present Raja of Cadattanada near Tellicherry, a intelligent man and acute mathematician.
This work, a complete system of Hindu astronomy, is comprehended in two hundred and eleven verses of different measures, abounds with fluxional forms and series, to be found in no work of foreign or other Indian countries." The book contains 212 verses divided into called prakarana-s. Chapter 1: Gives the names of numerals. Chapter 2: Lists the different measures, the measures of time, lunar days and stars, length, grain weight and the directions. Chapter 3: Defines the rule of three and syllabic enumeration. Chapter 4: Deals with arcs and sines and its application in astronomical measurements and computations. Chapter 5: Deals with computations relating to the shadow, vyatipata, retrograde motion of the planets and apses of the moon. Chapter 6: Explains the necessity of periodic revision of astronomical constants. Sankara Varman, author of Sadratnamala, was born as a younger prince in the principality of Katattanad in the North Malabar in Kerala. To the local people he was known as Appu Thampuran.
The date of birth of Sankara Varman is still uncertain. There are some strong arguments in favour of the year 1774 CE. Sankara Varman died in 1839 CE
A cyber PHA is a detailed cybersecurity risk assessment methodology that conforms to ISA 62443-3-2. The name, cyber PHA, was given to this method because it is similar to the Process Hazards Analysis or the hazard and operability study methodology, popular in process safety management in industries that operate hazardous industrial processes; the method is conducted as a workshop that includes a facilitator and a scribe with expertise in the cyber PHA process as well as multiple subject matter experts who are familiar with the industrial process, the industrial automation and control system and related IT systems. For example, the workshop team includes representatives from operations, engineering, IT and health and safety as well as an independent facilitator and scribe. A multidisciplinary team is important in developing realistic threat scenarios, assessing the impact of compromise and achieving consensus on realistic likelihood values given the threat environment, the known vulnerabilities and existing countermeasures.
The facilitator and scribe are responsible for gathering and organizing all of the information required to conduct the workshop and training the workshop team on the method, if necessary. A worksheet is used to document the cyber PHA assessment. Various spreadsheet templates and commercial software tools have been developed to support the cyber PHA method; the organization’s risk matrix is integrated directly into the worksheet to facilitate assessment of severity and likelihood and to look up the resulting risk score. The workshop facilitator guides the team through the process and strives to gather all input, reach consensus and keep the process proceeding smoothly; the workshop proceeds until conduits have been assessed. The results are consolidated and reported to the workshop team and appropriate stakeholders. Safety requires cybersecurity Core Principles of an ICS Cybersecurity Program Security process hazard analysis review Understanding the Risk of Cyber Threats to an Industrial Process with a Cyber PHA Integrating ICS Cybersecurity and Process Safety Management Cyber Security Risk Analysis for Process Control Systems Using Rings of Protection Analysis aeCyberPHA Risk Assessment Methodology