Nickel — cobalt monitor

Frequently the nuclear reaction Ni (n,p) Co is used for determination of the fast neutron fluence, but it has two severe drawbacks when compared to the Fe-Mn reaction described above The rather short halflife of Co of 71.3 days limits the application of this reaction to irradiation times of less than 150 days, even when the irradiation history of the sample is taken into account. In addition, the complex nature of the nuclear reaction requires expensive calculations when accurate results are required. On the other hand, the intense y ray of Co at 0.81 MeV (transition probability 99.5%) can be easily measured using a Ge detector, in most cases making chemical separation work unnecessary. 

The effective threshold energy of the reaction is about 3 MeV, which means it is very similar to that of the Fe (n,p) Mn reaction. The total cross section values 

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In the search for battery materials with better performance characteristics, the parent nickel hydroxide system has been modified by the inclusion of other metal ions. The EQCM has been used to monitor redox-driven ion and solvent transfers in sol-gel derived nickel-cobalt oxide films [79] and, through the solvent-transfer signature shown in Fig. 12, phase changes in electroprecipitated Co-Ni(OH)2 films [78]. An as-prepared Co-Ni(OH)2... 

Analysis of zinc solutions at the purification stage before electrolysis is critical and several metals present in low concentrations are monitored carefully. Methods vary from plant to plant but are highly specific and usually capable of detecting 0.1 ppm or less. Colorimetric process-control methods are used for cobalt, antimony, and germanium, turbidimetric methods for cadmium and copper. Alternatively, cadmium, cobalt, and copper are determined polarographicaHy, arsenic and antimony by a modified Gutzeit test, and nickel with a dimethylglyoxime spot test. 

Bencko V, Wagner V, Wagnerova M, et al. 1986. Human exposure to nickel and cobalt Biological monitoring and immunobiological response. Environ Res 40 399-410. 

Furthermore, qdt can be used for the simultaneous determination of cobalt, nickel, and copper in acidic ethanol solutions by monitoring the absorbance maxima (Xmax) at 510, 656, and 625 nm, and solving the simultaneous equations at each wavelength (Scheme 2) (9). In this method, thiourea is added to generate Cu(I), the reactive form of copper. At pH 6, in the absence of thiourea, nickel and cobalt can be determined without interference from copper. 

In a search for a suitable catalyst we started with lanthanide iodides, monitoring by 1 B NMR analysis the stability of 1 M catecholborane solutions in tetrahydrofliran containing 10 molar % of SmL, f-BuOSmL, and Lat. Unfortunately, in the presence of these iodides a signal corresponding to borane-tetrahydrofiiran, and other signals, appeared in less than 1 h. In contrast, catecholborane in tetrahydrofliran was stable in the presence of nickel(II), cobalt(II) and iron(H) chloride complexes with dppe. 

Chemical vapor deposition (CVD) was applied to produce homogeneous thin films of pure and doped spinel cobalt oxide with similar morphology on the surface of planar and monolithic supports. The planar substrates were used to investigate the thermal stability and the redox properties of the spinel using temperature-programmed methods monitored by emission-FTIR spectroscopy, while the monolithic substrates were used to test the catalytic performance of the deposited films toward the deep oxidation of methane and to evaluate its durability. The high performance of cobalt oxide to oxidize methane in diluted streams was demonstrated at 500 °C. Furthermore, controlled doping of cobalt oxide layers with suitable cations was demonstrated for nickel as an example, which resulted in substantial increase of electric conductivity. 

Steering Group on Food Surveillance (1985) The Working Party on the Monitoring of Foodstuffs for Heavy Metals. Survey of Aluminium, Antimony, Chromium, Cobalt, Indium, Nickel, Thallium, and Tin in Food, pp. 1-76. Ministry of Agriculture, Fisheries and Food Surveillance Paper No. 15, HMSO, London, UK. 

Very promising is the application of micelles for differential reaction rate methods. Micelles can alter the rate constant ratio of two or more species that interact with a common reagent. Simultaneous kinetic determination of nickel and cobalt based on the complex formation with 5-octyloxymethyl-8-quinolinol in the nonionic micellar medium of Triton X-100 is effective as this surfactant decreases the rates of formation of both complexes compared with an aqueous medium, so permitting their spectropho-tometric monitoring. In the micellar medium the formation of the Co complex is 44 times faster than that of Ni, and determinations of both ions in the lO moll range are possible. 

Other Studies.— The kinetics and mechanisms of reactions of tptz (5) complexes of cobalt(ii), copper(ii), and nickel(u) with water and with hydroxide have been established and compared. Covalent hydrates are believed to be important intermediates in aquation of the [M(tptz)(OH2)3] + complexes. Kinetics of aquation of the anions [M(acac)a] (M = Co, Cr, or Ru) have been studied in pulse radiolysis experiments. All three steps were monitored for the cobalt(n) complex, but the first step for the chromium(ii) complex was too fast to follow and, predictably, all steps for the ruthenium(ir) complex were too slow to follow by this technique. The mechanism of acac loss is thought to involve equilibrium... 

In 900MWe units, the capsules are irradiated along the outer surface of the thermal shield assembly. In 1300 and 1450 MWe units, the capsules are directly attached to the core barrel. In the case of Chooz-A, the thermal shield assembly was removed in 1970 and the surveillance capsules were then located under the core. The capsules are equipped with neutron dosimeters and thermal monitors, with some variations according to the reactor series. In all cases, activation dosimeters of nickel, copper and cobalt, as well as fissile dosimeters of uranium-238 and neptunium-237 are used. This instrumentation is complemented by iron and cadmium-shielded cobalt dosimeters in most cases and, in the most recent plants, also by niobium dosimeters. Each capsule contains temperature detectors based on eutectic alloys with melting points generally of 304 and 310 °C. 

Three sets of flux spectrum monitors are included in each capsule assembly. Each detector is placed inside a sheath which identifies the material and facilitates handling. Cadmium covers are used for those materials (e.g., uranium, nickel, copper, cobalt and neptunium) which have competing neutron capture activities. 

Other DC methods that are quite simple to use and provide important information to the corrosion scientist include polarization resistance (ASTM G 59, Practice for Conducting Potentiodynamic Polarization Resistance Measurements), potentiostatic and potentiodynamic polarization measurements (ASTM G 5, Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements), cyclic polarization measurements (ASTM G 61, Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron-, Nickel-, or Cobalt-based Alloys), and galvanic current monitoring. These DC techniques can be used to estimate the reactivity of a mateiieJ in a peurticular environment, to determine the corrosion rate of a materieJ in a particular environment, and/or to determine the susceptibility of a material to localized corrosion. 

The intracellular localization of stress proteins is problematic for the evaluation of the response in humans. Because the cells for the assay of stress proteins are not readily available through noninvasive procedures, the application of this response to human monitoring is limited. Recently, however, enhanced synthesis of stress proteins was demonstrated in primary cultures of human lymphocytes exposed to several metals (Yamada and Koizumi 1993). The specificity of the response was dependent on the metal to which the cultures were exposed. For example, cadmium and zinc induced both hsp70 and MT, while cobalt and triphenyltin induced only hsp70. Conversely, copper, mercury, nickel, and silver all induced synthesis of MT, but not of hsp70. Enhanced synthesis of stress proteins has also been demonstrated in vivo in lymphocytes and spleen cells excised from mice exposed to hyperthermia (Rodenhiser et al. 1985). 

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