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Short-Lived Positron Emitting Radionuclides
Published in Frank Helus, Lelio G. Colombetti, Radionuclides Production, 2019
From hot atom investigations in the earlier 1960s emerged11,12 that when cyclopropane is bombarded with protons, 11C-acetylene is formed through the same nuclear reaction. Because of the chemical difference between target and product, very high specific activities can be obtained.91 Alternatively methane, ethane, or propane can be used as target. Because of the low radiation stability of the alkanes resulting in polymerization, only low beam currents can be used. For routine production of useful amounts of 11C-acetylene this method is not very suitable.92 Recently Crouzel93 prepared 11C-acetylene by pyrolysis of 11CH4 in an inductive argon plasma. The 11CH4 is produced by bombarding a mixture of N2 and 5% H2 with protons. The conditions are the same as described for the production of H11CN. The 11CH4 produced is trapped and introduced batch-wise together with some carrier methane into the base of an argon plasma. The plasma is generated with a high frequency generator using a flow of argon as the plasmagenic gas. Under these circumstances 60% of the 11CH4 can be converted momentarily into 11C-acetylene while 40% remains unconverted. After separation, H11C≡CH with a purity of 98% and a specific activity of 150 Ci/mmol can be obtained. Of course the specific activity which can be achieved depends upon the available proton beam current.
Oxidation Numbers
Published in Patrick E. McMahon, Rosemary F. McMahon, Bohdan B. Khomtchouk, Survival Guide to General Chemistry, 2019
Patrick E. McMahon, Rosemary F. McMahon, Bohdan B. Khomtchouk
Use the given equation or write the correct balanced equation; then analyze the redox reaction using steps (1) through (4). Calcium metal reacts with water to produce calcium hydroxide solid plus hydrogen gas.Lead metal reacts with aqueous sulfuric acid to form lead (IV) sulfate solid plus hydrogen gas.Iron metal reacts with oxygen gas to form iron (III) oxide.Acetylene gas (C2H2) burns in oxygen gas to form carbon dioxide plus water.Iron metal reacts with aqueous silver nitrate to form aqueous iron (II) nitrate plus silver metal.
Nitrate Inhibition of Nodulation in Legumes
Published in Peter M. Gresshoff, Molecular Biology of Symbiotic Nitrogen Fixation, 2018
Bernard J. Carroll, Anne Mathews
Much of the research discussed above has been based on the acetylene reduction assay, and recently it was shown that acetylene often induces a rapid decline in nitrogenase activity.145,146 This decline is due to an increased diffusive resistance to oxygen and may lead to erroneous interpretation when quantitative comparisons, such as those reported above, are being made. The implications and applications of the phenomenon have been thoroughly reviewed,147 but it is important to emphasize that this research demonstrated that legume nodules have the capacity to rapidly adjust the supply of oxygen to the nitrogen-fixing bacteroids.148 Earlier, it was shown that the oxygen delivery in soybean nodules is subject to regulation in that the nodules adjust to changes in rhizosphere pO2, such that the pO2 inside the nodule is optimal for nitrogen fixation.149,150
Arrested Acetylene-Induced Pulmonary and Testicular Toxicity in Rats Through Treatment With Polyphenols
Published in Drug and Chemical Toxicology, 2023
Tanitoluwa O. Oluwabayo, Afolabi C. Akinmoladun, Afolabi A. Akindahunsi
Acetylene (molecular formula: C2H2) is a colorless, extremely flammable gas used in combination with oxygen to generate oxyacetylene, a fuel for making hot flame that can weld and cut metals in industries. Acetylene is odorless when made from the hydrolysis of 100% pure calcium carbide, but it has a stifling garlic stench when it is made from impure calcium carbide which is the type mainly utilized in the Nigerian welding industry (Ibeh et al. 2016). Impurities such as arsenic, phosphorus, and sulfur are often found in commercial-grade calcium carbide, and on reaction with water yield arsine, phosphine, ammonia, hydrogen sulfide, and other compounds which are known to be carcinogenic and genotoxic (Onwukwe et al. 2018). Exposure to this flame for an extended period has been linked to hemolysis and oxidative stress, and noncompliance of many workers to safety measures like the use of personal protective equipment results in an increased level of exposure to the gas. The problem is exacerbated by a lack of data on the toxic profile of this industrial gas which limits the search for appropriate measures to ameliorate its toxic effects.