Electrolytic reduction of U(VI) to U(IV) in acidic chloride and acidic sulfate solutions

In order to examine the applicability of the electrolytic reduction process of U(VI) (originally developed for the chloride system by PNC) to the sulfate solution system, a fundamental study was made. In this study, the concentrations of various chemical species in the catholytes were calculated at 298 K at various percentages of uranium reduction, taking the chloro-complex and sulfato-complex formation reactions of uranium into consideration. The polarization characteristics of the electrolytic reduction of uranyl chloride and uranyl sulfate were determined, using titanium and platinum cathodes, respectively, at 303 ± 1 K. In conjunction with this process, the electrical conductivity of the catholyte, the electrical resistivity of the cation exchange membrane, and the diffusion coefficient of uranyl sulfate were also determined.     

Fundamental studies on the continuous electrolytic reduction of uranyl sulfate

With the aim of developing a process for continuous electrolytic reduction of uranyl sulfate, the effects of temperature and HF concentration on the electrolytic reduction were investigated using both a rectangular cell and a bipolar cell. Some tests on the semicontinuous-type elec-trolytic reduction of U(VI) and the continuous monitoring of U(VI) in a catholyte were carried out to examine the feasibility of a process for continuous electrolytic reduction. The reduction rate and current efficiency of the electrolysis were increased with increasing temperature up to 333 K, due to an increase in the diffusion coefficient of uranyl sulfate. The presence of a small amount of HF in the catholyte improved the polarization characteristics of the electrolysis. The precipitation of uranous sulfate occurring in electrolysis above 323 K was eliminated by the addition of HF of 2.3 g dm^-3. However, the addition of the excess amount of HF causes the precipitation of UF₄ on the cathode surface during electrolysis. Increase in electric current was not effective in the semicontinuous electrolytic reduction of U(VI) for catholytes with high reduction ratios, and a catholyte with a composition of around 50 pct reduction ratio is pref-erable for continuous operation. The concentration of U(VI) in a catholyte can be monitored continuously either in the absence or in the presence of HF by using a device consisting of three small electrodes. Formerly Graduate Student in the Department of Metallurgy, Kyoto University Formerly Director, Mining and Ore Processing Division, Ningyo-toge Works, PNC Japan     

The measurement of the diffusion coefficient of U(VI) in aqueous uranyl sulfate solutions

The diffusion coefficients of U(VI) in aqueous uranyl solutions were determined between 293.5 and 311.0 K by comparing the limiting current densities between the copper electrodeposition and the electrolytic reduction of uranyl sulfate under the same hydrodynamic condition. The diffusion coefficients thus determined were almost constant despite the change in agitation speed of electrolyte solutions, which suggests the appropriateness of the method employed in this study. On the other hand, the diffusion coefficients of U(VI) showed a slightly decreasing trend with increase in uranyl sulfate concentration, but when total uranium concentration was kept constant the diffusion coefficient appeared to be almost constant. The activation energies of diffusion coefficients of U(VI) were found to be 21 to 22 kJ mol⁻¹ for the solution studied. KOJI SATO formerly Graduate Student, Department of Metallurgy, Kyoto University, Kyoto, Japan     

Therapeutic efficiency of lipoprotein(a) reduction by low-density lipoprotein immunoapheresis

This study was performed to investigate the effect of low-density lipoprotein (LDL) immunoapheresis on lipoprotein(a) [Lp(a)] reduction in patients with heterozygous and homozygous familial hyperlipidemia (N=16) and insufficient response to lipid-lowering agents. By desorption of approximately 5,700+/-500 mL of plasma, a mean reduction in total cholesterol of 62% (P < .001) and in LDL-cholesterol of 70% (P < .001) was achieved. Lp(a), which was elevated at study entry in seven of these patients (82.1+/-34.3 mg/dL; range, 48 to 148 mg/dL), was reduced during the initial LDL-apheresis procedure by 74.8%+/-14.1% (P < .001). Long-term apheresis treatment performed at weekly intervals resulted in an mean reduction in Lp(a) pretreatment values to 39.1+/-28.5 mg/dL (-54%; P < .001). Desorbed Lp(a) was measured at the waste of the columns for 31 apheresis treatments. Lp(a) concentration of the column waste was higher in patients with elevated serum Lp(a) pretreatment values as compared with those with Lp(a) serum values within the normal range (elevated Lp(a), 1,420+/-380 mg; without elevated Lp(a), 235+/-190 mg; P < .001). The rate of return of Lp(a) following apheresis treatment scheduled at weekly intervals was comparable to that of LDL-cholesterol.     

Determination of metal inventory and current efficiency in commercial aluminum reduction cells

A method for the determination of the metal inventory in commercial aluminum reduction cells, based on radioisotope dilution, has been developed, employing a¹⁹⁸Au tracer. By taking a large number of samples from the cells, the current efficiency is evaluated from the slope of the cumulative metal inventory vs time data. The method allows a determination of the current efficiency over a period of 2 to 3 days with a relative precision of approximately 1 pct. The paper gives a thorough discussion of the sources of error inherent in the procedure suggested. Formerly Research Associate at the same University.     

Enzymatic reduction of chromium(VI) by human hepatic microsomes

The reduction of chromium(VI) by human hepatic microsomes was investigated. The reduction rates were proportional to the amount of microsomes added and reduction was mediated by an NADPH-dependent enzymatic system which exhibited a Km for chromate of 1.04 +/- 0.18 microM and a Vmax of 5.03 +/- 0.49 nmol/min/mg protein. Relative to incubation under 0% O2, 21% O2 inhibited microsomal Cr(VI) reduction in three individuals by 53, 36 and 37%. Cr(VI) reduction was not inhibited by metyrapone, carbon monoxide, aminopyrine, piperonyl butoxide or chloroform, suggesting that cytochrome P450s did not play a major role. Thallium trichloride (0.13 and 0.26 mM), a known flavoprotein inhibitor, caused a complete inhibition of both Cr(VI) reduction and NADPH:cytochrome P450 (c) reductase activity. A partial inhibition of Cr(VI) reduction was seen in the presence of n-octylamine, which may suggest a possible role for flavin-containing monooxygenase (FMO). Overall, human microsomal Cr(VI) reduction is very different from the P450-mediated microsomal reduction observed in rodents. Specifically, the human system is much less oxygen-sensitive, has a much greater affinity for chromate and is apparently mediated by flavoproteins.     

Chemical conversions of osmium (VI) sulfite complexes in ammonia–sulfate solutions

It has been found that osmium (VI) sulfite complexes having composition [OsO₂(SO₃)₂(H₂O)₂]²⁻ in ammonia and sulfuric acid solutions enter into reaction of intrasphere substitution resulting in the formation of new complexes of osmium (VI). The rate of their formation depends on the concentration of constituents in the system and the temperature of solutions. Water-soluble ammonia–sulfite complexes of osmium (VI) (final form is [OsO₂(SO₃)₂(NH₃)₂]²⁻) are formed in ammonia-sulfate solutions. These complexes are converted into sulfate derivatives—water-soluble ([OsO₂(SO₃)(SO₄)(NH₃)₂]²⁻) and insoluble ([OsO₂(SO₄)₂(NH₃)₂]²⁻) in solutions containing (NH₄)₂SO₄ and H₂SO₄.     

纳米零价镍去除溶液中U(VI)的研究

采用液相还原法制备纳米零价镍,并用来去除溶液中的U(VI)。通过SEM、EDS技术表征反应前后材料的形貌,从微观角度分析纳米零价镍去除溶液中U(VI)的机理,并进行了热力学分析。结果表明,纳米零价镍对溶液中U(VI)有良好的去除效果,在室温下,pH=4.0、接触时间60min、固液比0.3g/L和初始浓度50mg/L时,U(VI)的去除率和去除量分别达到了98.44%和182.372mg/g。新制备的纳米零价镍呈明显的球状,颗粒较为分散且粒径较均匀,反应后,材料表面形貌发生变化,呈不规则碎片堆积、粒径变大,且材料中出现了铀元素。热力学研究结果表明,该反应是自发吸热反应,同时也是不可逆的熵增反应。     

Equine dyschondroplasia (osteochondrosis)--histological findings and type VI collagen localization

Platelets are small, disc-shaped, anucleated cells formed by fragmentation of megakaryocytes in the bone marrow. They circulate in blood with a lifespan of 7 to 10 days and, together with fibrin, form hemostatic plugs at sites of vessel injury. Abnormalities of platelets, either quantitative or qualitative, may cause clinically significant bleeding with resultant morbidity and, on occasion, mortality. This review will focus on platelet disorders in neonates, defined as infants of up to 4 months of age. Special emphasis will be given to the physiology of platelet function in healthy and sick newborn infants. The review will be divided into sections as follows: role of platelets in hemostasis, platelet function in newborn infants, quantitative platelet disorders, qualitative platelet disorders, and platelet transfusion therapy.     

Structure and multiple conformations of the kunitz-type domain from human type VI collagen alpha3(VI) chain in solution

BACKGROUND: The Kunitz-type inhibitor motif is found at the C terminus of the human collagen alpha3(VI) chain. This 76-residue module (domain C5) was prepared in recombinant form and showed high stability against proteases; however, it lacked any inhibitory activity against trypsin, thrombin, kallikrein and several other proteases. We have undertaken the determination of the three-dimensional (3D) structure of domain C5 in solution, by nuclear magnetic resonance (NMR), in order to establish the structural basis for the properties of this protein. RESULTS: The 7 N-terminal and 12 C-terminal residues of domain C5 are disordered in the solution structure. The 55-residue core, which shows high homology to bovine pancreatic trypsin inhibitor, retains the characteristic fold of all members of the Kunitz-type inhibitor family. 24 residues of this main structural body show more than one resonance, symptomatic of multiple conformations slowly exchanging on the NMR time scale. In addition, significant proton chemical exchange line broadening is observed for residues in the vicinity of the disulfide bridge between residues 20 and 44: this indicates interconversion, on the micro- to millisecond time scale, between multiple conformations. CONCLUSION: The NMR study demonstrates that domain C5 is a highly dynamic molecule at temperatures studied (between 10 and 30 degrees C). Indeed, some 44% of the main body structure of C5 showed multiple conformations. The existence of multiple conformations was not necessarily expected in view of the conformational constraints imposed by the 3D structure of proteins as rigid as C5; it should therefore be considered in the interpretation of its structural and dynamical properties. The accessibility of the inhibitory binding loop (Gly18 [P4] to Leu25 [P4']) should be relatively unaffected by this conformational exchange and thus would not explain the unusual specificity of C5. Most serine proteinase inhibitors that, like C5, have an arginine at the P1 position inhibit trypsin; the lack of trypsin inhibition of C5 must therefore arise from the amino-acid side-chain composition of the adjoining positions in the binding loop.     

Further clinical studies of curdlan sulfate (CRDS)--an anti-HIV agent

Curdlan sulfate (CRDS) is a semi-synthetic sulfated polysaccharide which inhibits the attachment of HIV to T-cells, and also has intracellular anti-HIV activity. In Phase I clinical trials, CRDS was found in 4 hr i.v. infusions, to be well tolerated up to 200 mg/70 kg and unexpectedly to produce marked, dose-related increases in CD4 lymphocytes in HIV-infected patients. Prolongation of bleeding time is expected to be the dose limiting toxicity, but no episodes of bleeding were seen. In one of the studies in this report, CRDS was administered i.v. daily for 7 days to HIV patients at doses of 40, 100, 140 and 180 mg/70 kg/day. At the higher doses, marked increases in CD4 and CD8 lymphocytes were observed. These increases mainly returned to baseline after 24 hr. To further delineate the pharmacokinetics of these changes in CD4 and CD8 lymphocytes, another Phase I study was done in which CRDS was infused i.v. over a 30 min period in HIV patients at single doses of 25, 50, 75, 100, 125, 150, 175 and 200 mg/70 kg/day. The drug was well tolerated in all cases and marked increases in CD4 lymphocytes were again seen at the higher doses, in some cases amounting to increases of 500 cells/mm3 after a single dose. The half-life of CRDS in man was found to be about two hours, as measured by activated partial thromboplastin time (APTT) and by plasma assays.     

Cardiorespiratory and electrolytic changes in status asthmaticus after intravenous administration of magnesium sulfate

The authors studied cardiorespiratory effects of MgSO4 infusion in 30 randomized patients with status asthmaticus. They found, that after having the drug administered, values of VC, FEV1, FIV1, PaO2 and pH increased, the respiratory and heart rate, diastolic blood pressure reduced. Other ventilation, blood gas and ECG parameters were unchanged. Among the electrolytes, serum Ca2+ level has reduced, both plasma and intracellular Mg2+ concentrations increased. It is apparent from the results, that broncholytical ability of MgSO4 given in therapeutical dose i.v. does not reach the level of beta-stimulating agents. However, this completed with the cardioprotective, sedative effect as well as more advantageous ion-distribution, influences favourably the asthmatic dyspnoea.     

纳米铁镍双金属去除溶液中U(VI)的研究

采用同步液相法制备纳米Fe/Ni双金属来去除溶液中的U(VI),通过BET、SEM等方法对双金属材料进行表征分析,用批试验法研究n(Fe)/n(Ni)比、pH、初始铀浓度、反应时间和温度对去除U(VI)的影响。结果表明,铁镍双金属体系去除U(VI)的最佳pH为3.5,反应平衡时间为30 min,25 ℃时的饱和吸附量为161.91 mg/g。     

300kA大型预焙电解槽电流效率影响因素的研究

分析了大型预焙电解槽中电解质温度与电流效率、直流电耗的关系,研究发现电解槽在目标电解温度下可获得最佳的电流效率和最低的直流电耗,高于或低于目标电解温度都将影响生产效率。同时分析了电解质分子比、氧化铝浓度、添加剂以及铝水平、电解质水平等因素对电解质温度及电流效率的影响,并对工艺因素的最佳值进行了探讨。     

中国电解铝行业能源效率初步调查与分析

介绍了中国电解铝行业电力消耗情况及吨铝电耗的分布状况，指出电流密度在160～290kA的电解铝厂其电耗指标较低，总结了影响中国电解铝能源消耗高低的因素。提出了在电解铝指标调查统计分析方面要加强的工作。     

A comparison of the extraction capacity of trioctylamine and its radiolytic products dioctylamine and primary octylamine for the elements U(VI), Mo(VI), Zr(IV) and Sr(II)

The percentage extraction of the elements U(VI), Mo(VI), Zr(IV) and Sr(II) from 1–6 M nitric acid by trioctylamine (TOA) and its radiolytic degradation products dioctylamine (DOA) and primary octylamine (POA) in xylene have been measured. TOA and DOA showed similar extraction capacities for Zr(IV), but DOA was less effective than TOA for U(VI) and Mo(VI), Sr(II) was not extracted by any of these amines. These results suggest that the use of the “Zirconium number” is in itself not sufficient when considering the resistance of TOA to radiation.