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Pulse Wave Velocity
Pulse wave velocity (PWV) is the velocity at which the blood pressure pulse propagates through the circulatory system, usually an artery or a combined length of arteries. PWV is used clinically as a measure of arterial stiffness and can be readily measured non-invasively in humans, with measurement of carotid to femoral PWV (cfPWV) being the recommended method. cfPWV is highly reproducible, and predicts future cardiovascular events and all-cause mortality independent of conventional cardiovascular risk factors. It has been recognized by thEuropean Society of Hypertensionas an indicator of target organ damage and a useful additional test in the investigation of hypertension. Relationship with arterial stiffness The theory of the velocity of the transmission of the pulse through the circulation dates back to 1808 with the work of Thomas Young. The relationship between pulse wave velocity (PWV) and arterial wall stiffness can be derived from Newton's second law of motion (F=m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Velocity
Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of bodies. Velocity is a physical vector quantity; both magnitude and direction are needed to define it. The scalar absolute value (magnitude) of velocity is called , being a coherent derived unit whose quantity is measured in the SI (metric system) as metres per second (m/s or m⋅s−1). For example, "5 metres per second" is a scalar, whereas "5 metres per second east" is a vector. If there is a change in speed, direction or both, then the object is said to be undergoing an ''acceleration''. Constant velocity vs acceleration To have a ''constant velocity'', an object must have a constant speed in a constant direction. Constant directi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmosphere Of Earth
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation). By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude. Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diederik Korteweg
Diederik Johannes Korteweg (31 March 1848 – 10 May 1941) was a Dutch mathematician. He is now best remembered for his work on the Korteweg–de Vries equation, together with Gustav de Vries. Early life and education Diederik Korteweg's father was a judge in 's-Hertogenbosch, Netherlands. Korteweg received his schooling there, studying at a special academy which prepared students for a military career. However, he decided against a military career and, making the first of his changes of direction, he began his studies at the Polytechnical School of Delft. Korteweg originally intended to become an engineer but, although he maintained an interest in mechanics and other applications of mathematics throughout his life, his love of mathematics made him change direction for the second time when he was not enjoying the technical courses at Delft. He decided to terminate his course and pull out of his studies so that he could concentrate on mathematics. He then enrolled in mathematics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adriaan Isebree Moens
Adriaan Isebree Moens (15 November 1846 – 24 June 1891) was a Dutch physician and physiologist. He is known for his work on arterial stiffness and the propagation of waves in elastic tubes. Life and family Adriaan Isebree Moens was the son of Jan Isebree Moens (1793–1865) and Susanna Cornelia De Kater (1805–1862). He was born on November 15, 1846, in Zierikzee, Netherlands. He married Hermine Gertrude Constance Marie Kolff van Oosterwijk (1848–1878) in 1877 and after her death, Caroline Frederika Wilhelmina Kolff Van Oosterwijk (1854–1937) in 1880. He had three children, Gertrude Hermina Moens, Suzanna Cornelia Moens and Neeltje Isebree Moens. He died on 1891 after a chronic illness. Career In 1872 after completing a course in engineering at Ghent University, Moens began to study medicine at Leiden University. He became a pathology assistant in 1874 and in 1875 (probably) he took up an appointment as assistant to Adriaan Heynsius, Professor of Physiology at Leiden. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moens–Korteweg Equation
In biomechanics, the Moens–Korteweg equation models the relationship between wave speed or pulse wave velocity (PWV) and the incremental elastic modulus of the arterial wall or its distensibility. The equation was derived independently by Adriaan Isebree Moens and Diederik Korteweg Diederik Johannes Korteweg (31 March 1848 – 10 May 1941) was a Dutch mathematician. He is now best remembered for his work on the Korteweg–de Vries equation, together with Gustav de Vries. Early life and education Diederik Korteweg's father .... It is derived from Newton's second law of motion, using some simplifying assumptions, and reads: :PWV = \sqrt The Moens–Korteweg equation states that PWV is proportional to the square root of the incremental elastic modulus, (''E''inc), of the vessel wall given constant ratio of wall thickness, ''h'', to vessel radius, ''r'', and blood density, ρ, assuming that the artery wall is isotropic and experiences isovolumetric change with pulse pressure. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distensibility
Distensibility is a metric of the stiffness of blood vessels. It is defined as D = \frac, where d_ and d_ are the diameter of the vessel in systole and diastole, and p_and p_are the systolic and diastolic blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure ....{{Wikidata redirect References Human physiology ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radius
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the spoke of a chariot wheel. as a function of axial position ../nowiki>" Spherical coordinates In a spherical coordinate system, the radius describes the distance of a point from a fixed origin. Its position if further defined by the polar angle measured between the radial direction and a fixed zenith direction, and the azimuth angle, the angle between the orthogonal projection of the radial direction on a reference plane that passes through the origin and is orthogonal to the zenith, and a fixed reference direction in that plane. See also *Bend radius *Filling radius in Riemannian geometry *Radius of convergence *Radius of convexity * Radius of curvature *Radius of gyration ''Radius of gyration'' or gyradius of a body about the axis of ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archibald Hill
Archibald Vivian Hill (26 September 1886 – 3 June 1977), known as A. V. Hill, was a British physiologist, one of the founders of the diverse disciplines of biophysics and operations research. He shared the 1922 Nobel Prize in Physiology or Medicine for his elucidation of the production of heat and mechanical work in muscles. Biography Born in Bristol, he was educated at Blundell's School and graduated from Trinity College, Cambridge as third wrangler in the mathematics tripos before turning to physiology. While still an undergraduate at Trinity College, he derived in 1909 what came to be known as the Langmuir equation. This is closely related to Michaelis-Menten kinetics. In this paper, Hill's first publication, he derived both the equilibrium form of the Langmuir equation, and also the exponential approach to equilibrium. The paper, written under the supervision of John Newport Langley, is a landmark in the history of receptor theory, because the context for the deri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Otto Frank (physiologist)
Otto Frank (21 June 1865 – 12 November 1944) was a German born doctor and physiologist who made contributions to cardiac physiology and cardiology. The Frank–Starling law of the heart is named after him and Ernest Starling. Family and early life (Friedrich Wilhelm Ferdinand) Otto Frank was born in Groß-Umstadt and was the son of Georg Frank (1838–1907), a doctor of medicine and a practicing physician, and Mathilde Lindenborn (1841–1906). Otto Frank was married to Theres Schuster in a Catholic wedding in Munich. Training and Work Otto Frank studied medicine in Munich and Kiel between 1884 and 1889 (approbation in Munich 1889). During 1889 to 1891 he undertook training in mathematics, chemistry, physics, anatomy and zoology in Heidelberg, Glasgow, Munich and Straßburg. He then worked until 1894 as an assistant to Carl Friedrich Wilhelm Ludwig in the ''Physiologisches Institut'' in Leipzig. There in 1892 he completed his doctoral studies (''Promotion''). Subsequently, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equation
In mathematics, an equation is a formula that expresses the equality of two expressions, by connecting them with the equals sign . The word ''equation'' and its cognates in other languages may have subtly different meanings; for example, in French an ''équation'' is defined as containing one or more variables, while in English, any well-formed formula consisting of two expressions related with an equals sign is an equation. ''Solving'' an equation containing variables consists of determining which values of the variables make the equality true. The variables for which the equation has to be solved are also called unknowns, and the values of the unknowns that satisfy the equality are called solutions of the equation. There are two kinds of equations: identities and conditional equations. An identity is true for all values of the variables. A conditional equation is only true for particular values of the variables. An equation is written as two expressions, connected by a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and even by industry. Further, both spellings are often used ''within'' a particular industry or country. Industries in British English-speaking countries typically use the "gauge" spelling. is the pressure relative to the ambient pressure. Various #Units, units are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the International System of Units, SI unit of pressure, the Pascal (unit), pascal (Pa), for example, is one newton (unit), newton per square metre (N/m2); similarly, the Pound (force), pound-force per square inch (Pounds per square inch, psi) is the traditional unit of pressure in the imperial units, imperial and United States customary units, U.S. customary systems. Pressure may also be e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Length
Length is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance. In most systems of measurement a base unit for length is chosen, from which all other units are derived. In the International System of Units (SI) system the base unit for length is the metre. Length is commonly understood to mean the most extended dimension of a fixed object. However, this is not always the case and may depend on the position the object is in. Various terms for the length of a fixed object are used, and these include height, which is vertical length or vertical extent, and width, breadth or depth. Height is used when there is a base from which vertical measurements can be taken. Width or breadth usually refer to a shorter dimension when length is the longest one. Depth is used for the third dimension of a three dimensional object. Length is the measure of one spatial dimension, whereas area is a measure of two dimensions (length squ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
