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Thallium Minerals
Thallium is a chemical element; it has symbol Tl and atomic number 81. It is a silvery-white post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists William Crookes and Claude-Auguste Lamy discovered thallium independently, in 1861, in residues of sulfuric acid production. Both used the newly developed method of flame spectroscopy, in which thallium produces a notable green spectral line. Thallium, from Greek , , meaning "green shoot" or "twig", was named by Crookes. It was isolated by both Lamy and Crookes in 1862, Lamy by electrolysis and Crookes by precipitation and melting of the resultant powder. Crookes exhibited it as a powder precipitated by zinc at the International Exhibition, which opened on 1 May that year. Thallium tends to form the +3 and +1 oxidation states. The +3 state resembles that of the other elements in group 13 (boron, aluminium, gallium, indium). However, the +1 state, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Element
A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its atomic nucleus, nucleus. Atoms of the same element can have different numbers of neutrons in their nuclei, known as isotopes of the element. Two or more atoms can combine to form molecules. Some elements form Homonuclear molecule, molecules of atoms of said element only: e.g. atoms of hydrogen (H) form Diatomic molecule, diatomic molecules (H). Chemical compounds are substances made of atoms of different elements; they can have molecular or non-molecular structure. Mixtures are materials containing different chemical substances; that means (in case of molecular substances) that they contain different types of molecules. Atoms of one element can be transformed into atoms of a different element in nuclear reactions, which change an atom's at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ion Transporter
In biology, an ion transporter is a transmembrane protein that moves ions (or other small molecules) across a biological membrane to accomplish many different biological functions, including cellular communication, maintaining homeostasis, energy production, etc. There are different types of transporters including pumps, uniporters, antiporters, and symporters. Active transporters or ion pumps are transporters that convert energy from various sources—including adenosine triphosphate (ATP), sunlight, and other redox reactions—to potential energy by pumping an ion up its concentration gradient. This potential energy could then be used by secondary transporters, including ion carriers and ion channels, to drive vital cellular processes, such as ATP synthesis. This article is focused mainly on ion transporters acting as pumps, but transporters can also function to move molecules through facilitated diffusion. Facilitated diffusion does not require ATP and allows molecules that ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lead
Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray color when exposed to air. Lead has the highest atomic number of any stable nuclide, stable element and three of its isotopes are endpoints of major nuclear decay chains of heavier elements. Lead is a relatively unreactive post-transition metal. Its weak metallic character is illustrated by its Amphoterism, amphoteric nature; lead and lead oxides react with acids and base (chemistry), bases, and it tends to form covalent bonds. Lead compounds, Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group. Exceptions are mostly limited ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercury (element)
Mercury is a chemical element; it has Symbol (chemistry), symbol Hg and atomic number 80. It is commonly known as quicksilver. A Heavy metal element, heavy, silvery d-block element, mercury is the only metallic element that is known to be liquid at standard temperature and pressure; the only other element that is liquid under these conditions is the halogen bromine, though metals such as caesium, gallium, and rubidium melt just above room temperature. Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide). The red pigment vermilion is obtained by Mill (grinding), grinding natural cinnabar or synthetic mercuric sulfide. Exposure to mercury and mercury-containing organic compounds is toxic to the nervous system, immune system and kidneys of humans and other animals; mercury poisoning can result from exposure to water-soluble forms of mercury (such as mercuric chloride or methylmercury) either directly or through mechanisms of biomagnification. Mercu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inert Pair Effect
The inert-pair effect is the tendency of the two electrons in the outermost atomic ''s''-orbital to remain unshared in compounds of post-transition metals. The term ''inert-pair effect'' is often used in relation to the increasing stability of oxidation states that are two less than the group valency for the heavier elements of groups 13, 14, 15 and 16. The term "inert pair" was first proposed by Nevil Sidgwick in 1927. The name suggests that the outermost ''s'' electron pairs are more tightly bound to the nucleus in these atoms, and therefore more difficult to ionize or share. For example, the p-block elements of the 4th, 5th and 6th period come after d-block elements, but the electrons present in the intervening d- (and f-) orbitals do not effectively shield the s-electrons of the valence shell. As a result, the ''inert pair'' of ''n''s electrons remains more tightly held by the nucleus and hence participates less in bond formation. Description Consider as an example thal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arsenic
Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is notoriously toxic. It occurs naturally in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. It has various Allotropes of arsenic, allotropes, but only the grey form, which has a metallic appearance, is important to industry. The primary use of arsenic is in alloys of lead (for example, in car batteries and ammunition). Arsenic is also a common n-type dopant in semiconductor electronic devices, and a component of the III–V compound semiconductor gallium arsenide. Arsenic and its compounds, especially the trioxide, are used in the production of pesticides, treated wood products, herbicides, and insecticides. These applications are declining with the increasing recognition of the persistent tox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Insecticide
Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, industrial buildings, for vector control, and control of insect parasites of animals and humans. Acaricides, which kill mites and ticks, are not strictly insecticides, but are usually classified together with insecticides. Some insecticides (including common bug sprays) are effective against other non-insect arthropods as well, such as scorpions, spiders, etc. Insecticides are distinct from insect repellents, which repel but do not kill. Sales In 2016 insecticides were estimated to account for 18% of worldwide pesticide sales. Worldwide sales of insecticides in 2018 were estimated as $ 18.4 billion, of which 25% were neonicotinoids, 17% were pyrethroids, 13% were diamides, and the rest were many other classes which sold for less th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rat Poison
Rodenticides are chemicals made and sold for the purpose of killing rodents. While commonly referred to as "rat poison", rodenticides are also used to kill mice, groundhog, woodchucks, chipmunks, porcupines, nutria, beavers, and voles. Some rodenticides are lethal after one exposure while others require more than one. Rodents are disinclined to gorge on an unknown food (perhaps reflecting an adaptation to their inability to emesis, vomit), preferring to sample, wait and observe whether it makes them or other rats sick. This phenomenon of poison shyness is the rationale for poisons that kill only after multiple doses. Besides being directly toxic to the mammals that ingest them, including dogs, cats, and humans, many rodenticides present a secondary poisoning risk to animals that hunt or scavenge the dead corpses of rats. Classes of rodenticides Anticoagulants Anticoagulants are defined as chronic (death occurs one to two weeks after ingestion of the lethal dose, rarely soo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toxic
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell ( cytotoxicity) or an organ such as the liver ( hepatotoxicity). Sometimes the word is more or less synonymous with poisoning in everyday usage. A central concept of toxicology is that the effects of a toxicant are dose-dependent; even water can lead to water intoxication when taken in too high a dose, whereas for even a very toxic substance such as snake venom there is a dose below which there is no detectable toxic effect. Toxicity is species-specific, making cross-species analysis problematic. Newer paradigms and metrics are evolving to bypass animal testing, while maintaining the concept of toxicity endpoints. Etymology In Ancient Greek medical literature, the adjective ''τοξικόν'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cardiac Stress Test
A cardiac stress test is a cardiological examination that evaluates the cardiovascular system's response to external stress within a controlled clinical setting. This stress response can be induced through physical exercise (usually a treadmill) or intravenous pharmacological stimulation of heart rate. As the heart works progressively harder (stressed) it is monitored using an electrocardiogram (ECG) monitor. This measures the heart's electrical rhythms and broader electrophysiology. Pulse rate, blood pressure and symptoms such as chest discomfort or fatigue are simultaneously monitored by attending clinical staff. Clinical staff will question the patient throughout the procedure asking questions that relate to pain and perceived discomfort. Abnormalities in blood pressure, heart rate, ECG or worsening physical symptoms could be indicative of coronary artery disease. Stress testing does not accurately diagnose all cases of coronary artery disease, and can often indicate that it e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Medicine
Nuclear medicine (nuclear radiology, nucleology), is a medical specialty involving the application of radioactivity, radioactive substances in the diagnosis and treatment of disease. Nuclear imaging is, in a sense, ''radiology done inside out'', because it records radiation radiant exitance, emitted from within the body rather than radiation that is transmittance, transmitted through the body from external sources like X-ray generators. In addition, nuclear medicine scans differ from radiology, as the emphasis is not on imaging anatomy, but on the function. For such reason, it is called a Functional imaging, physiological imaging modality. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) scans are the two most common imaging modalities in nuclear medicine. Diagnostic medical imaging Diagnostic In nuclear medicine imaging, radiopharmaceuticals are taken internally, for example, through inhalation, intravenously, or orally. Then, externa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared Detector
An infrared detector is a detector that reacts to infrared (IR) radiation. The two main types of detectors are thermal and photonic (photodetectors). The thermal effects of the incident IR radiation can be followed through many temperature dependent phenomena. Bolometers and microbolometers are based on changes in resistance. Thermocouples and thermopiles use the thermoelectric effect. Golay cells follow thermal expansion. In IR spectrometers the pyroelectric detectors are the most widespread. The response time and sensitivity of photonic detectors can be much higher, but usually these have to be cooled to cut thermal noise. The materials in these are semiconductors with narrow band gaps. Incident IR photons can cause electronic excitations. In photoconductive detectors, the resistivity of the detector element is monitored. Photovoltaic detectors contain a p-n junction on which photoelectric current appears upon illumination. An infrared detector is hybridized by connecting ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
