Pieter Zeeman (1865-1943) was a Dutch physicist who discovered the splitting of the spectral lines of a substance when placed in a magnetic field (known as the Zeeman effect). In 1902, Zeeman and Lorentz were jointly awarded the Nobel Prize in Physics, for their, extraordinary service they rendered by their researches into the influence of magnetism upon radiation phenomenon.
Zeeman effect is the splitting of the lines in a spectrum when the source of the spectrum is exposed to a magnetic field. The effect was discovered in 1896 by the Dutch physicist Pieter Zeeman (1865-1943) as a broadening of the yellow D-lines of sodium in a flame held between strong magnetic poles.
The Zeeman effect has helped physicists determine the energy levels in atoms. In astronomy, the Zeeman effect is used in measuring the magnetic field of the Sun and of other stars.
Acheson process is an industrial process to synthesize graphite and silicon carbide (carborundum), named after its inventor the American chemist Edward Goodrich Acheson (1856-1931). In this process, a solid-state reaction between pure silica sand (SiO2) and petroleum coke (C) at very high temperature (more than 2500 °C) leads to the formation of silicon carbide under the general reaction:
While studying the effects of high temperature on carborundum, Acheson had found that silicon vaporizes at about 4150 °C, leaving behind graphitic carbon.
Autocatalysis is a reaction in which its product can act as a catalyst. Oxalate oxidation with permanganate in an acid solution is a slow reaction
Mn2+-ions catalyse this reaction. When enough Mn2+-ions are created, the reaction occurs instantly.
Bronze is an alloy made primarily of copper and tin. It may contain as much as 25 % tin. Bronzes with 10 % or more tin are harder, stronger, and resistant to corrosion. As bronze weathers, a brown or green film forms on the surface. This film inhibits corrosion. Silicon or aluminium is often added to bronze to improve resistance to corrosion. Phosphorus, lead, zinc, and other metals may be added for special purposes. The alloy is hard and easily cast and is extensively used in bearings, valves and other machine parts.
Bronze was one of the first alloys developed by ancient metal workers. The Bronze Age occurred in Europe around 2200 to 700 BC. Bronze was used for weapons such as spearheads, swords, and knives. Since ancient times, bronze has been the most popular metal for casting statues and other art objects.
The term bronze has been adopted commercially for many copper-rich alloys that contain little or no tin but are similar in colour to bronze, including aluminium bronze, manganese bronze, and silicon bronze. Aluminium bronze is used to make tools and, because it will not spark when struck. Manganese bronze is actually a brass that contains manganese. It is often used to make ship propellers because it is strong and resists corrosion by sea water.
Néel temperature (TN) is the critical temperature above which an antiferromagnetic substance becomes paramagnetic. The phenomenon was discovered around 1930 by the French physicist L.E.F. Néel (1904-2000).
Calomel electrode is a type of half cell in which the electrode is mercury coated with calomel (Hg2Cl2) and the electrolyte is a solution of potassium chloride and saturated calomel. In the calomel half cell the overall reaction is
Table: Dependence of potential of calomel electrode upon temperature and concentration of KCl according to standard hydrogen electrode
Potential vs. SHE / V | |||
---|---|---|---|
t / °C | 0.1 mol dm-3 | 3.5 mol dm-3 | sat. solution |
15 | 0.3362 | 0.254 | 0.2511 |
20 | 0.3359 | 0.252 | 0.2479 |
25 | 0.3356 | 0.250 | 0.2444 |
30 | 0.3351 | 0.248 | 0.2411 |
35 | 0.3344 | 0.246 | 0.2376 |
Deoxyribonucleic acid (DNA) is a nucleic acid with 2-deoxy-D-ribose as the sugar in its nucleotides. DNA contains encoded genetic information, specifically templates for the synthesis of all of an organism’s proteins and enzymes.
DNA was first identified in the 1869 by Swiss chemist Friedrich Miescher (1844-1895). In 1953, American biologist James Dewey Watson (1928-) and English physicist Francis Harry Compton Crick (1916–2004) had discovered that DNA occurs in the cell as a double helix, with two long strands of the molecule wound around each other, and further that the chemical structure of the molecule dictates that adenine (A) always aligns or pairs with thymine (T), and cytosine (C) always pairs with guanine (G). It is this base pairing that allows DNA in a cell to copy itself, and transfer its information to a new cell. The diameter of the helix is 2.0 nm and there is a residue on each chain every 0.34 nm in the z direction. The angle between each residue on the same strand is 36°, so that the structure repeats after 10 residues (3.4 nm) on each strand.
The Ecological Footprint is defined as the area of productive land and water ecosystems required to produce the resources that the population consumes (food, fiber, timber, energy, and space for infrastructure) and assimilate the wastes that the population produces (CO2 is the only waste product currently included), wherever on Earth the land and water is located. It compares actual throughput of renewable resources relative to what is annually renewed. Non-renewable resources are not assessed, as by definition their use is not sustainable.
Ecological footprints and biocapacity are expressed in global hectares (gha). Each unit corresponds to one hectare of biologically productive space with world average productivity. In U.S. Footprint results are often presented in global acres (ga). One U.S. acre is equal to 0.405 hectares.
Humanity is currently consuming renewable resources at a faster rate than ecosystems can regenerate them and continuing to release more CO2 than ecosystems can absorb. In 2007, humanity's Footprint was 18 billion gha, or 2.7 gha per person. However, the Earth's biocapacity was only 11.9 billion gha, or 1.8 gha per person. This represents an ecological overshoot of 50 per cent. Put another way, people used the equivalent of 1.5 planets to support their activities (more developed countries generally make higher demands on the Earth's ecosystems than poorer, less developed countries).
The Living Planet Index (LPI) reflects changes in the health of the planet's ecosystems by tracking trends in nearly 8000 populations of vertebrate species. The LPI first calculates the annual rate of change for each species population in the dataset, then calculates the average change across all populations for each year from 1970, when data collection began, to 2007, the latest date for which data is available.
The Global LPI shows a decline of around 30 % from 1970 to 2007, based on 7953 populations of 2544 species of birds, mammals, amphibians, reptiles and fish.
Generalic, Eni. "Zeeman%2C Pieter." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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