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Willem Einthoven
Willem Einthoven (21 May 1860 – 29 September 1927) was a Dutch doctor and physiologist. He invented the first practical electrocardiograph (ECG or EKG) in 1895 and received the Nobel Prize in Physiology or Medicine in 1924 for it ("for the discovery of the mechanism of the electrocardiogram"). original URL now redirects to https://ethw.org/Willem_Einthoven Background Willem Einthoven was born in Semarang on Java in the Dutch East Indies (now Indonesia), the son of Louise Marie Mathilde Caroline de Vogel and Jacob Einthoven. His father, a doctor, died when Willem was a child. His mother returned to the Netherlands with her children in 1870 and settled in Utrecht. His father was of Jewish and Dutch descent, and his mother's ancestry was Dutch and Swiss. In 1885, Einthoven received a medical degree from the University of Utrecht. He became a professor at the University of Leiden in 1886. He married his first cousin Frédérique Jeanne Louise de Vogel (7 September 1861 31 J ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semarang
Semarang ( jv, ꦏꦸꦛꦯꦼꦩꦫꦁ , Pegon: سماراڠ) is the capital and largest city of Central Java province in Indonesia. It was a major port during the Dutch colonial era, and is still an important regional center and port today. The city has been named as the cleanest tourist destination in Southeast Asia by the ASEAN Clean Tourist City Standard (ACTCS) for 2020–2022. It has an area of and is located at . The population of the city was 1,555,984 at the 2010 censusBiro Pusat Statistik, Jakarta, 2011. and 1,653,524 at the 2020 census,Badan Pusat Statistik, Jakarta, 2021. making it Indonesia's ninth most populous city after Jakarta, Surabaya, Bekasi, Bandung, Medan, Depok, Tangerang and Palembang. The built-up urban area had 3,183,516 inhabitants at the 2010 census spread over two cities and 26 districts. The Semarang metropolitan area (a.k.a. ''Kedungsepur'') has a population of over 6 million in 2020 (''see Greater Semarang section''). The population of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Utrecht (city)
Utrecht ( , , ) is the fourth-largest city and a municipality of the Netherlands, capital and most populous city of the province of Utrecht. It is located in the eastern corner of the Randstad conurbation, in the very centre of mainland Netherlands, about 35 km south east of the capital Amsterdam and 45 km north east of Rotterdam. It has a population of 361,966 as of 1 December 2021. Utrecht's ancient city centre features many buildings and structures, several dating as far back as the High Middle Ages. It has been the religious centre of the Netherlands since the 8th century. It was the most important city in the Netherlands until the Dutch Golden Age, when it was surpassed by Amsterdam as the country's cultural centre and most populous city. Utrecht is home to Utrecht University, the largest university in the Netherlands, as well as several other institutions of higher education. Due to its central position within the country, it is an important hub for both rail and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Google Doodle
A Google Doodle is a special, temporary alteration of the logo on Google's homepages intended to commemorate holidays, events, achievements, and notable historical figures. The first Google Doodle honored the 1998 edition of the long-running annual Burning Man event in Black Rock City, Nevada, and was designed by co-founders Larry Page and Sergey Brin to notify users of their absence in case the servers crashed. Early Marketing employee Susan Wojcicki then spearheaded subsequent Doodles, including an alien landing on Google and additional custom logos for major holidays. Google Doodles were designed by an outside contractor until 2000, when Page and Brin asked public relations officer Dennis Hwang to design a logo for Bastille Day. Since then, a team of employees called "Doodlers" have organized and published the Doodles. Initially, Doodles were neither animated nor hyperlinked—they were simply images with tooltips describing the subject or expressing a holiday greeting. Doo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound
In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the brain. Only acoustic waves that have frequencies lying between about 20 Hz and 20 kHz, the audio frequency range, elicit an auditory percept in humans. In air at atmospheric pressure, these represent sound waves with wavelengths of to . Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges. Acoustics Acoustics is the interdisciplinary science that deals with the study of mechanical waves in gasses, liquids, and solids including vibration, sound, ultrasound, and infrasound. A scientist who works in the field of acoustics is an ''acoustician'', while someone working in the field of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heart Disease
Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, heart failure, hypertensive heart disease, rheumatic heart disease, cardiomyopathy, abnormal heart rhythms, congenital heart disease, valvular heart disease, carditis, aortic aneurysms, peripheral artery disease, thromboembolic disease, and venous thrombosis. The underlying mechanisms vary depending on the disease. It is estimated that dietary risk factors are associated with 53% of CVD deaths. Coronary artery disease, stroke, and peripheral artery disease involve atherosclerosis. This may be caused by high blood pressure, smoking, diabetes mellitus, lack of exercise, obesity, high blood cholesterol, poor diet, excessive alcohol consumption, and poor sleep, among other things. High blood pressure is estimated to account for approximate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equilateral Triangle
In geometry, an equilateral triangle is a triangle in which all three sides have the same length. In the familiar Euclidean geometry, an equilateral triangle is also equiangular; that is, all three internal angles are also congruent to each other and are each 60°. It is also a regular polygon, so it is also referred to as a regular triangle. Principal properties Denoting the common length of the sides of the equilateral triangle as a, we can determine using the Pythagorean theorem that: *The area is A=\frac a^2, *The perimeter is p=3a\,\! *The radius of the circumscribed circle is R = \frac *The radius of the inscribed circle is r=\frac a or r=\frac *The geometric center of the triangle is the center of the circumscribed and inscribed circles *The altitude (height) from any side is h=\frac a Denoting the radius of the circumscribed circle as ''R'', we can determine using trigonometry that: *The area of the triangle is \mathrm=\fracR^2 Many of these quantities have simple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Willem Einthoven ECG
Willem () is a Dutch and West FrisianRienk de Haan, ''Fryske Foarnammen'', Leeuwarden, 2002 (Friese Pers Boekerij), , p. 158. masculine given name. The name is Germanic, and can be seen as the Dutch equivalent of the name William in English, Guillaume in French, Guilherme in Portuguese, Guillermo in Spanish and Wilhelm in German. Nicknames that are derived from Willem are Jelle, Pim, Willie, Willy and Wim. Given name *Willem Cody (2007-Present), Active Serbian terrorist, Leader of the Serbian World Republic, Intolerably based * Willem I (1772–1843), King of the Netherlands * Willem II (1792–1849), King of the Netherlands * Willem III (1817–1890), King of the Netherlands * Willem of the Netherlands (1840–1879), Dutch prince *Willem-Alexander (b. 1967), King of the Netherlands * Willem Aantjes (b. 1923), Dutch politician *Willem Adelaar (b. 1948), Dutch linguist *Willem Andriessen (1887–1964), Dutch pianist and composer * Willem Arondeus (1894–1943), Dutch artist an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galvanometer
A galvanometer is an electromechanical measuring instrument for electric current. Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely. A galvanometer works by deflecting a pointer in response to an electric current flowing through a coil in a constant magnetic field. Galvanometers can be thought of as a kind of actuator. Galvanometers came from the observation, first noted by Hans Christian Ørsted in 1820, that a magnetic compass's needle deflects when near a wire having electric current. They were the first instruments used to detect and measure small amounts of current. André-Marie Ampère, who gave mathematical expression to Ørsted's discovery, named the instrument after the Italian electricity researcher Luigi Galvani, who in 1791 discovered the principle of the frog galvanoscope – that electric current would make the legs of a dead frog jerk. Galvanometers have been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field. A permanent magnet's magnetic field pulls on ferromagnetic materials such as iron, and attracts or repels other magnets. In addition, a nonuniform magnetic field exerts minuscule forces on "nonmagnetic" materials by three other magnetic effects: paramagnetism, diamagnetism, and antiferromagnetism, although these forces are usually so small they can only be detected by laboratory equipment. Magnetic fields surround magnetized materials, and are created by electric currents such as those used in electromagnets, and by electric fields varying in time. Since both strength and direction of a magnetic field may vary with location, it is described mathematically by a function assigning a vector to each point of space ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the hole in the center of the coil. The magnetic field disappears when the current is turned off. The wire turns are often wound around a magnetic core made from a ferromagnetic or ferrimagnetic material such as iron; the magnetic core concentrates the magnetic flux and makes a more powerful magnet. The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be quickly changed by controlling the amount of electric current in the winding. However, unlike a permanent magnet that needs no power, an electromagnet requires a continuous supply of current to maintain the magnetic field. Electromagnets are widely used as components of other electrical devices, such as motors, generators, electromechanical s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
String Galvanometer
A string galvanometer is a sensitive fast-responding measuring instrument that uses a single fine filament of wire suspended in a strong magnetic field to measure small currents. In use, a strong light source is used to illuminate the fine filament, and the optical system magnifies the movement of the filament allowing it to be observed or recorded by photography. The principle of the string galvanometer remained in use for electrocardiograms until the advent of electronic vacuum-tube amplifiers in the 1920s. History Submarine cable telegraph systems of the late 19th century used a galvanometer to detect pulses of electric current, which could be observed and transcribed into a message. The speed at which pulses could be detected by the galvanometer was limited by its mechanical inertia, and by the inductance of the multi-turn coil used in the instrument. Clément Adair, a French engineer, replaced the coil with a much faster wire or "string" producing the first string galvanome ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oegstgeest
Oegstgeest () is a town and municipality in the province of South Holland in the western Netherlands. Its population was in . Etymology The portion ''geest'' in the name refers to the geest lands, which were excavated in the seventeenth century for the benefit of the urban expansion of Leiden. There exists more uncertainty about the 'Oegst' part. There are various stories. The name was formerly often spelled Oestgeest or Oostgeest, which could indicate the geographical location of the village: east of the geest lands. However, the oldest spelling found in a copy of a list of goods of the St. Martin's Cathedral in Utrecht from the tenth century states Osgeresgeest. This could indicate an original resident and owner of the territory: Osger. In the Middle Ages they also spoke of the Church of Kerckwerve if one referred to the Oegstgeester parish church (now the Green Church). History Oegstgeest is one of the earliest inhabited places along the coast. Evidence of a Batavian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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