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Agnes Pockels
Agnes Luise Wilhelmine Pockels (14 February 1862 – 21 November 1935) was a German chemist whose research was fundamental in establishing the modern discipline known as surface science, which describes the properties of liquid and solid surfaces and interfaces. Pockels became interested in fundamental research in surface science through observations of soaps and soapy water in her own home while washing dishes. She devised a surface film balance technique to study the behavior of molecules such as soaps and surfactants at air-liquid interfaces. From these studies, Pockels defined the "Pockels Point" which is the minimum area that a single molecule can occupy in monomolecular films. Pockels was an autodidact. She was not a paid, professional scientist and had no institutional affiliation and so is an example of a citizen scientist. Early life and education Pockels was born in Venice, Italy, in 1862. At the time, Venice was under Austrian rule, and Pockels' father served ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Venice
Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy and the capital of the Veneto Regions of Italy, region. It is built on a group of 118 small islands that are separated by canals and linked by over 400 bridges. The islands are in the shallow Venetian Lagoon, an enclosed bay lying between the mouths of the Po River, Po and the Piave River, Piave rivers (more exactly between the Brenta (river), Brenta and the Sile (river), Sile). In 2020, around 258,685 people resided in greater Venice or the ''Comune di Venezia'', of whom around 55,000 live in the historical island city of Venice (''centro storico'') and the rest on the mainland (''terraferma''). Together with the cities of Padua, Italy, Padua and Treviso, Italy, Treviso, Venice is included in the Padua-Treviso-Venice Metropolitan Area (PATREVE), which is considered a statistical metropolitan area, with a total population of 2.6 million. The name is derived from the ancient Adri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friedrich Carl Alwin Pockels
Friedrich Carl Alwin Pockels (18 June 1865 – 29 August 1913) was a German physicist. He was born in Italy to Captain Theodore Pockels and Alwine Becker. He obtained a doctorate from the University of Göttingen in 1888, and from 1900 to 1913 he was professor of theoretical physics at the University of Heidelberg. In 1893 he discovered that a steady electric field applied to certain birefringent materials causes the refractive index to vary, approximately in proportion to the strength of the field. The coefficient of proportionality is of the order of to . This phenomenon is now called the Pockels effect. His sister Agnes Pockels (1862–1935) was a pioneer in chemistry. See also *Photoelasticity Photoelasticity describes changes in the optical properties of a material under mechanical deformation. It is a property of all dielectric media and is often used to experimentally determine the stress distribution in a material, where it gives ... 19th-century German phys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophilic
A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press. In contrast, hydrophobes are not attracted to water and may seem to be repelled by it. Hygroscopics ''are'' attracted to water, but are not dissolved by water. Molecules A hydrophilic molecule or portion of a molecule is one whose interactions with water and other polar substances are more thermodynamically favorable than their interactions with oil or other hydrophobic solvents. They are typically charge-polarized and capable of hydrogen bonding. This makes these molecules soluble not only in water but also in other polar solvents. Hydrophilic molecules (and portions of molecules) can be contrasted with hydrophobic molecules (and portions of molecules). In some cases, both hydrophilic and hydrophobic properties occur in a single molecule. An example of these amphiph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surfactant
Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, or dispersants. The word "surfactant" is a blend of ''surface-active agent'', coined . Agents that increase surface tension are "surface active" in the literal sense but are not called surfactants as their effect is opposite to the common meaning. A common example of surface tension increase is salting out: by adding an inorganic salt to an aqueous solution of a weakly polar substance, the substance will precipitate. The substance may itself be a surfactant – this is one of the reasons why many surfactants are ineffective in sea water. Composition and structure Surfactants are usually organic compounds that are amphiphilic, meaning each molecule contains both a hydrophilic "water-seeking" group (the ''head''), and a hydro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wilhelmy Plate
A Wilhelmy plate is a thin plate that is used to measure equilibrium surface or interfacial tension at an air–liquid or liquid–liquid interface. In this method, the plate is oriented perpendicular to the interface, and the force exerted on it is measured. Based on the work of Ludwig Wilhelmy, this method finds wide use in the preparation and monitoring of Langmuir films. Detailed description The Wilhelmy plate consists of a thin plate usually on the order of a few square centimeters in area. The plate is often made from filter paper, glass or platinum which may be roughened to ensure complete wetting. In fact, the results of the experiment do not depend on the material used, as long as the material is wetted by the liquid. The plate is cleaned thoroughly and attached to a balance with a thin metal wire. The force on the plate due to wetting is measured using a tensiometer or microbalance and used to calculate the surface tension (\gamma) using the Wilhelmy equation: :\ga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ludwig Wilhelmy
Ludwig Ferdinand Wilhelmy (25 December 1812, Stargard in Pommern – 18 February 1864, Berlin) was a German scientist who is usually credited with publishing the first quantitative study in chemical kinetics. Scientific work Wilhelmy studied at Heidelberg, earning a doctorate in 1846. He worked as a Privatdozent from 1849 to 1854 before moving to Berlin. Wilhelmy's work in chemical kinetics concerned the acid-catalyzed conversion of a sucrose solution into a 1:1 mixture of fructose and glucose, a reaction that he followed with a polarimeter. He wrote a differential equation to describe the reaction, integrated it, and used it to interpret his experimental results. Wilhelmy found that the reaction's rate was proportional to the concentrations of sucrose and of acid present. He also examined the influence of temperature on the reaction. According to Moore, Wilhelmy received little credit from his contemporaries for his early investigations in the field of chemical ki ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weight
In science and engineering, the weight of an object is the force acting on the object due to gravity. Some standard textbooks define weight as a Euclidean vector, vector quantity, the gravitational force acting on the object. Others define weight as a scalar quantity, the magnitude of the gravitational force. Yet others define it as the magnitude of the reaction (physics), reaction force exerted on a body by mechanisms that counteract the effects of gravity: the weight is the quantity that is measured by, for example, a spring scale. Thus, in a state of free fall, the weight would be zero. In this sense of weight, terrestrial objects can be weightless: ignoring Drag (physics), air resistance, the famous apple falling from the tree, on its way to meet the ground near Isaac Newton, would be weightless. The unit of measurement for weight is that of force, which in the International System of Units (SI) is the newton (unit), newton. For example, an object with a mass of one kilogram ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apothecary
''Apothecary'' () is a mostly archaic term for a medical professional who formulates and dispenses '' materia medica'' (medicine) to physicians, surgeons, and patients. The modern chemist (British English) or pharmacist (British and North American English) now perform this role. In some languages and regions, the word "apothecary" is still used to refer to a retail pharmacy or a pharmacist who owns one. Apothecaries' investigation of herbal and chemical ingredients was a precursor to the modern sciences of chemistry and pharmacology. In addition to dispensing herbs and medicine, apothecaries offered general medical advice and a range of services that are now performed by other specialist practitioners, such as surgeons and obstetricians. Apothecary shops sold ingredients and the medicines they prepared wholesale to other medical practitioners, as well as dispensing them to patients. In 17th-century England, they also controlled the trade in tobacco which was imported as a me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weighing Scale
A scale or balance is a device used to measure weight or mass. These are also known as mass scales, weight scales, mass balances, and weight balances. The traditional scale consists of two plates or bowls suspended at equal distances from a fulcrum. One plate holds an object of unknown mass (or weight), while known masses are added to the other plate until static equilibrium is achieved and the plates level off, which happens when the masses on the two plates are equal. The perfect scale rests at neutral. A spring scale will make use of a spring of known stiffness to determine mass (or weight). Suspending a certain mass will extend the spring by a certain amount depending on the spring's stiffness (or spring constant). The heavier the object, the more the spring stretches, as described in Hooke's law. Other types of scales making use of different physical principles also exist. Some scales can be calibrated to read in units of force (weight) such as newtons instead of unit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Button
A button is a fastener that joins two pieces of fabric together by slipping through a loop or by sliding through a buttonhole. In modern clothing and fashion design, buttons are commonly made of plastic but also may be made of metal, wood, or seashell. Buttons can also be used on containers such as wallets and bags. Buttons may be sewn onto garments and similar items exclusively for purposes of ornamentation. In the applied arts and craft, a button can be an example of folk art, studio craft, or even a miniature work of art. In archaeology, a button can be a significant artifact. History Buttons and button-like objects used as ornaments or seals rather than fasteners have been discovered in the Indian Indus Valley civilization during its Kot Diji phase (c. 2800–2600 BC), at the Tomb of the Eagles, Scotland (2200-1800 BC), and at Bronze Age sites in China (c. 2000–1500 BC) and Ancient Rome. Buttons made from seashell were used in the Indus Valley Civilization for ornam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Area
The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc length of one-dimensional curves, or of the surface area for polyhedra (i.e., objects with flat polygonal faces), for which the surface area is the sum of the areas of its faces. Smooth surfaces, such as a sphere, are assigned surface area using their representation as parametric surfaces. This definition of surface area is based on methods of infinitesimal calculus and involves partial derivatives and double integration. A general definition of surface area was sought by Henri Lebesgue and Hermann Minkowski at the turn of the twentieth century. Their work led to the development of geometric measure theory, which studies various notions of surface area for irregular objects of any dimension. An important example is the Minkowski cont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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