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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 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=ma) applied ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Velocity
Velocity is a measurement of speed in a certain direction of motion. It is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of physical objects. Velocity is a vector (geometry), vector Physical quantity, quantity, meaning that both magnitude and direction are needed to define it. The Scalar (physics), scalar absolute value (Magnitude (mathematics), magnitude) of velocity is called , being a coherent derived unit whose quantity is measured in the International System of Units, 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''. Definition Average velocity The average velocity of an object over a period of time is its Displacement (geometry), change in position, \Delta s, divided by the duration of the period, \Delt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmosphere Of Earth
The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weather features such as clouds and hazes), all retained by gravity of Earth, Earth's gravity. The atmosphere serves as a protective buffer between the Earth's surface and outer space, shields the surface from most meteoroids and ultraviolet solar irradiance, solar radiation, keeps it warm and reduces diurnal temperature variation (temperature extremes between daytime, day and night) through heat retention (greenhouse effect), redistributes heat and moisture among different regions via air currents, and provides the atmospheric chemistry, chemical and climate conditions allowing life to exist and evolution, evolve on Earth. By mole fraction (i.e., by quantity of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon ... [...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 th ... [...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. 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 In physics and geometry, isotropy () is uniformity in all orientations. Precise definitions depend on the subject area. Exceptions, or inequalities, are frequently indicated by the prefix ' or ', hence '' anisotropy''. ''Anisotropy'' is also ... 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 Circulatory system, 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 ....{{Cite journal, last=Roccabianca, first=S., last2=Figueroa, first2=C. A., last3=Tellides, first3=G., last4=Humphrey, first4=J. D., date=2014-01-01, title=Quantification of regional differences in aortic stiffness in the aging human, url= , journal=Journal of the Mechanical Behavior of Biomedical Materials, volume=29, pages=618–634, doi=10.1016/j.jmbbm.2013.01.026, issn=1751-6161, pmc=3842391, pmid=23499251 References Human physiology ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radius
In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is the line segment or distance from its center to any of its Vertex (geometry), vertices. The name comes from the Latin ''radius'', meaning ray but also the spoke of a chariot wheel.Definition of Radius at dictionary.reference.com. Accessed on 2009-08-08. The typical abbreviation and mathematical symbol for radius is ''R'' or ''r''. By extension, the diameter ''D'' is defined as twice the radius:Definition of radius at mathwords.com. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archibald Hill
Archibald Vivian Hill (26 September 1886 – 3 June 1977), better known to friends and colleagues 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, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Otto Frank (physiologist)
Otto Frank (21 June 1865 – 12 November 1944) was a German medical 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 mathematical 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. The " =" symbol, which appears in every equati ... [...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 (Pound per square inch, psi, symbol lbf/in2) is the traditional unit of pressure in the imperial units, imperial and United States customary units, US customary systems. Pressure ma ... [...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 (physical quantity), dimension distance. In most systems of measurement a Base unit (measurement), 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 size, 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, width, breadth, and depth. ''Height'' is used when there is a base from which vertical measurements can be taken. ''Width'' and ''breadth'' usually refer to a shorter dimension than ''length''. ''Depth'' is used for the measure of a third dimension. Length is the measure of one spatial dimension, whereas area ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
