D-990 离子交换树脂吸附铂和铼性能的研究

研究了在酸性介质中Ｄ－９９０离子交换树脂吸附铂和铼的性能。在较低酸度下,该树脂对铂和铼有良好的吸附性能,吸附容量分别达到铂１０２ｍｇ／ｇ干树脂和铼１６２ｍｇ／ｇ干树脂。在较高酸度下,铼很容易解吸,而铂不解吸仍留在树脂上,此特性有利于铂和铼的分离。     

YCo_5和 NdCo_5从4.2K到450K磁各向异性的热变化

长期以来就已知道 RCo_5中 Co 的磁能各向异性很高。最近,高场测量观察到了迄今被忽略的磁化强度各向异性,其值达到4.2K 时自发磁化强度的4%研究了4.2K 到450K 之间这两种磁各向异性随温度的变化。当温度升高时,各向异性常数 K 的下降比     

K接板连铸坯的生产和轧制

综述了 K 接板连铸坯的浇铸和轧制工艺.K 接板连铸坯的中心疏松可轧合,用其生产的鱼尾板各项性能符合有关标准,基本上达到初轧坯鱼尾板质量水平.     

试验机K值的含义和测定方法及结果

一在万能试验机上进行拉力(或压力)试验时,验验机的受力部件如主体支架、应变机构、测力机构以及夹持试样的夹头和夹头本身的附件如拉杆等所组成的力学系统,将     

双波长K系数法同时测定钯和铁

本文提出应用亚硝基R盐(NRS)作显色剂,双波长K系数法在同一份显色溶液中同时测定钯和铁。 在pH5±1;Fe(Ⅱ)与NRS生成绿色配合物,最大吸收波长在720nm,Pd与NRS生成红色配合物在720nm波长无吸收,因此可以直接测定铁。Pd-NRS配合物最大吸收波长在460nm,在此波长Fe-NRS配合物也有吸收,故采用K系数校正其影响。本方法对常见的10多种离子干扰做过实验,除Co、Cu、Ni外多数元素无干扰,可用于催化剂、合金中微量铁和钯的测定,方法简单快速,重现性好,相对误差<10％。     

D-290大孔阴离子交换树脂吸附金的机理和应用

本文报道了D—290大孔强碱性阴离子交换树脂吸附金的机理、酸度曲线、吸附速率、平衡时吸附的容量及吸附反应活化能。通过柱色谱试验,拟定了用D—290树脂分离、原子吸收法测定阳极泥中微量金的方法,取得较好结果。     

N型热电偶和K型热电偶的性能比对

热电偶问世已有160年多年的历史了。N型热电偶是最近20年发展起来的一种镍基热电偶,亦称为NiCrSil/NiSil热电偶。由于调整合金成份,添加稀土金属镧、铈、钇和钙(La、Ce、y和Ca)等,使这种热电偶材料具有很好的高温抗氧化性,因而高温稳定性好,寿命长。N型偶与K型偶比对结果,前者优于后者,因此,N型偶成为用于-50～1300℃的最好的廉价金属热电偶材料。     

SWRCH35K钢冷镦开裂分析和工艺优化

φ6.5~20mm SWRCH35K冷镦钢盘条的生产流程为120 t LD-LF-180 mm×180 mm方坯连铸-轧制。分析了SWRCH35K钢(/%:0.35~0.37C,0.11~0.14Si,0.71~0.72Mn,0.016~0.023P,0.005~0.007S,0.023~0.030Alt)的成分、组织、铸坯表面质量、钢中夹杂物、轧制工艺对该钢冷镦性能的影响,得出冷镦钢盘条裂纹等表面缺陷和近表面大型夹杂物是引起冷镦开裂的主要原因。通过LD出钢预脱氧铝块从120~150 kg增加至160~180kg,LF终渣碱度从3.0提高至3.5,(FeO+MnO)从≤1.5%降至≤1.2%,过热度从20~40℃降至20~35℃,精轧温度和终轧温度分别从940℃和860℃提高至950℃和880℃等工艺措施,使该钢冷镦开裂率由18.60%降至5.80%。     

Glucose-induced positive cooperativity of fructose phosphorylation by human B-cell glucokinase

Human B-cell glucokinase displays sigmoidal kinetics towards D-glucose or D-mannose, but fails to do so towards D-fructose. Yet, D-glucose, D-mannose and 2-deoxy-D-glucose confer to the enzyme positive cooperativity towards D-fructose. For instance, in the presence of 5 mM D-[U-14C]fructose, its rate of phosphorylation is increased to 214.3 +/- 11.0%, 134.0 +/- 4.3% and 116.5 +/- 3.0% of paired control value by D-glucose, D-mannose and 2-deoxy-D-glucose (each 6 mM), respectively. D-glucose and, to a lesser extent, D-mannose also display reciprocal kinetic cooperativity. D-fructose, however, fails to affect D-glucose or D-mannose phosphorylation under conditions in which positive cooperativity is otherwise observed. These findings are relevant to the reciprocal effects of distinct hexoses upon their phosphorylation by B-cell glucokinase and, as such, to the metabolic and functional response evoked in pancreatic islet B-cells by these sugars, when tested either separately or in combination.     

Effects of the self-administration of ethanol and ethanol/sucrose on rates of local cerebral glucose utilization in rats

In a previous study, the voluntary ingestion of ethanol by rats was found to be associated with a discrete pattern of changes in functional activity that included the nucleus accumbens, medial prefrontal cortex, basolateral and central nuclei of the amygdala, as well as the ventral midbrain. Rats in this study, however, consumed a combination of ethanol in a sucrose vehicle. The purpose of the present experiment was to characterize the role of sucrose in determining the effects of orally self-administered ethanol using the quantitative autoradiographic 2-[14C]deoxyglucose (2DG) method for measurement of rates of local cerebral glucose utilization. A modified sucrose-substitution procedure was employed to train three groups of Wistar rats to self-administer either water, 10% ethanol (10E), or a 10% ethanol/2% sucrose solution (10E/2S) in daily sessions. An additional group of rats was trained using a modified acclimation procedure (home cage) in order to determine if any exposure to sucrose would alter rates of glucose utilization. Once stable rates of consumption were established, the 2DG method was applied immediately following completion of the final test session. Rats received a dose of ethanol equivalent to 0.5 g kg-1 on the day of the procedure or a comparable volume of water. Rates of energy metabolism were significantly increased in all three groups of rats that consumed ethanol (10E/2S, 10E, and home cage), as compared to rates in rats that consumed water. The areas of significant change included the rostral pole and posterior shell of the nucleus accumbens, medial prefrontal cortex, the basolateral and central nuclei of the amygdala, the ventral tegmental area, and the substantia nigra pars compacta. Thus, the pattern of changes in functional brain activity that accompanies voluntary ingestion of ethanol is independent of the vehicle in which the ethanol is presented or the procedures used to initiate consumption. Furthermore, these data demonstrate that it is the simultaneous activation of an interrelated network of limbic brain regions that serves as the substrate of the effects of ethanol self-administration.     

Benzodiazepine-GABA modulation of concurrent ethanol and sucrose reinforcement in the rat.

These experiments examined the role of the benzodiazepine (BZ)-GABA receptor complex in modulating ethanol consumption in rats. Lever presses were reinforced with concurrently available, isocaloric solutions: 10% ethanol-10% sucrose and 24% sucrose. Both reinforcers were available on independent, variable-interval 5-s schedules of reinforcement. In baseline sessions, rats earned approximately 110 sucrose reinforcers and 131 ethanol-sucrose reinforcers, equivalent to about 2 g ethanol per kilogram of body weight. Before experimental sessions, rats received injections of Ro 15-4513, Ro 15-1788, and Ro 15-4513 in combination with Ro 15-4513, chlordiazepoxide, picrotoxin, baclofen, and muscimol. Responding for the ethanol solution was significantly and selectively reduced by the BZ inverse agonist Ro 15-4513, and this effect was blocked by administration of the BZ antagonist Ro 15-1788. Conversely, responding for the ethanol solution increased following a low dose of the BZ agonist chlordiazepoxide. A low dose of baclofen significantly decreased responding for sucrose and increased consumption of ethanol. Picrotoxin and muscimol selectively reduced responding for the ethanol solution. These results are discussed in terms of the relationship between the BZ-GABA receptor complex and ethanol consumption. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The impact of HIV on infectiousness of pulmonary tuberculosis: a community study in Zambia

Isolated ventral and dorsal rat spinal roots incubated in normal (2.5 mM) or high glucose (25 mM) concentrations or in high concentrations of other hexoses were exposed transiently to hypoxia (30 min) in a solution of low buffering power. Compound nerve action potentials, extracellular direct current potentials, and interstitial pH were continuously recorded before, during, and after hypoxia. Ventral roots incubated in 25 mM D-glucose showed resistance to hypoxia. Dorsal roots, on the other hand, revealed electrophysiological damage by hyperglycemic hypoxia as indicated by a lack of posthypoxic recovery. In both types of spinal roots, interstitial acidification was most pronounced during hyperglycemic hypoxia. The changes in the sensitivity to hypoxia induced by high concentrations of D-glucose were imitated by high concentrations of D-mannose. In contrast, D-galactose, L-glucose, D-fructose, and L-fucose did not have such effects. Resistance to hypoxia, hypoxia-generated interstitial acidification, and hypoxia-induced electrophysiological damage were absent after pharmacological inhibition of nerve glycolysis with iodoacetate. These observations indicate 1) that enhanced anaerobic glycolysis produces resistance to hypoxia in hyperglycemic peripheral nerves and 2) that acidification may impair the function of peripheral axons when anaerobic glycolysis proceeds in a tissue with reduced buffering power.     

Sucrose, ethanol, and sucrose/ethanol reinforced responding under variable-interval schedules of reinforcement

Adding sweeteners to ethanol solutions is a common method of inducing rats to consume ethanol. However, it has usually been assumed that it is the sweet taste and/or the calories contained in the sweet solution that controls consumption. The present experiment examined the role of ethanol in controlling responding reinforced by ethanol or an ethanol/sucrose mixture compared with sucrose solutions of various concentrations. After initiation to self-administer 10% (v/v) ethanol using the sucrose-substitution method, rats were trained to respond under a concurrent VI 5" VI 5" schedule. During one condition, responding on one lever was reinforced by the presentation of 10% ethanol, and responding on a second lever was reinforced by water or one of the following sucrose solutions: 1% (w/v), 1.5%, 2%, 2.5%, 3%, and 5%. During a subsequent condition, responding reinforced by a 10% ethanol/2% sucrose mixture was compared under the concurrent schedule with responding reinforced by water, 2%, 2.5%, 3%, 5%, or 10% sucrose (w/v). The results indicated that the ethanol or ethanol/sucrose mixture maintained more responding than did sucrose solutions that were sweeter. Data support the conclusion that, after initiation, the taste and/or pharmacological effects of ethanol had become an important component of the reinforcing stimulus independent of the sweetener.     

Experimental investigation of the thermodynamics of Fe-Nb-C austenite and nonstoichiometric niobium and titanium carbides (T = 1273 to 1473 K)

The thermodynamics of Fe-Nb-C austenite and nonstoichiometric binary niobium carbide and titanium carbide in the temperature range of 1273 to 1473 K has been investigated using a dynamic gas equilibration technique. Methane-hydrogen mixtures have been used for fixing carbon potentials, and the carbon contents have been determined as dynamic weight changesvia a sensitive Cahn microbalance. The niobium-carbon interactions, similar to the titaniumcarbon interactions, are manifested as a minimum in the niobium carbide solubility in austenite, as increased amounts of dissolved carbon with niobium additions, and as the variation of solubility limit of the carbide with carbon content at high carbon levels. The results on the isoactivity measurements in the ternary Fe-Nb-C have been analyzed using the modified Wagner formalism, and the ternary interaction parameter ε _C ^Nb has been evaluated. The solubility of niobium carbide in Fe-Nb-C in austenite has been determined as the deflection in the variation of carbon content with Nb additions at constant carbon activity. The dissolution free energy of body-centered cubic (bcc) Nb in face-centered cubic (fcc) Fe has also been determined from the solubility data. Rational correlation between the dissolution free energies of transition metal solutes in fcc Fe and the group number in the Periodic Table has been shown to exist. A correlational relationship between the ternary interaction parameter and the free energy of formation of carbides has been established. These relationships are utilized in the assessment, as well as the systematization of thermodynamic data. The results on the activity-composition relationship in the binary niobium and titanium carbides have been analyzed using the sublattice-subregular model proposed by Hillert and Staffansson, [2] and the interaction parameters in the model were determined. The thermodynamic calculations based on this model and our experimental results were carried out, and very good agreement between experimental and calculated results was obtained. K. BALASUBRAMANIAN, Formerly with McMaster University,     

Isolation and in vitro translation of zein messenger ribonucleic acid

Zein messenger RNA was isolated from membrane-bound polyribosomes of developing maize kernels by oligo(dT)-cellulose chromatography. Translation of the mRNA in vitro yielded protein similar to native zein in amino acid content, ethanol solubility, and mobility on sodium dodecyl sulfate- polyacrylamide gels. The zein mRNA sedimented as a homogeneous peak on sucrose gradients and contained a poly(A)-rich region based upon hybridization to [3H]poly(U). The mRNA had an apparent molecular weight of 540 000 on agarose-acrylamide gels. It synthesized both 21 800 and 19 000 molecular weight zein components in the wheat-germ cell-free protein synthesis system. The possibility of a polycistronic mRNA or two mRNAs of similar molecular weight is considered.     

QLS motif in transmembrane helix VII of the glucose transporter family interacts with the C-1 position of D-glucose and is involved in substrate selection at the exofacial binding site

The liver-type (GLUT2) and brain-type (GLUT3) human facilitative glucose transporters exhibit distinct kinetics (Km values for deoxyglucose transport of approximately 11 mM and approximately 1.5 mM, respectively) and patterns of substrate transport (GLUT2 is capable of D-fructose transport, while GLUT3 is not). Using a range of chimeric glucose transporters comprised of regions of GLUT2 and GLUT3 studied by expression in Xenopus oocytes after microinjection of cRNA, we have proposed that the seventh putative transmembrane helix is intimately involved in the selection of transported substrate and that this region plays an important role in determining the Km for 2-deoxyglucose [Arbuckle, M. I., Kane, S., Porter, L. M., Seatter, M. J., and Gould, G. W. (1996) Biochemistry 35, 16519-16527]. Inspection of the predicted amino acid sequence of this region reveals that GLUTs 1, 3, and 4 (high-affinity glucose transporters) contain a conserved QLS motif in this helix (residues 277-279 in human GLUT3). In the glucose/fructose transporter (GLUT2) this motif is replaced by HVA. To study the role of the QLS motif in substrate selection, we have engineered substitutions in this region between GLUT2 and GLUT3. GLUT3 (QLS > HVA) exhibits a Km for deoxyglucose transport identical to that of native GLUT3 but increased sensitivity for inhibition of deoxyglucose transport by D-fructose. However, unlike native GLUT3, this species is capable of transporting D-fructose. Compared to wild-type GLUT2, GLUT2 (HVA > QLS) exhibits a lower Km for deoxyglucose transport (approximately 3 mM vs approximately 11 mM), the ability to transport D-fructose is reduced, and D-fructose is a less efficient inhibitor of deoxyglucose transport. Analysis of the ability of a range of glucose epimers and analogues to inhibit transport by these species suggests that the QLS motif interacts with the incoming D-glucose at the C-1 position; this may be a key interaction in the high-affinity recognition of the transported substrate. We further argue that this interaction acts as a molecular filter that is involved in the selection of the transported substrate.     

Intensification of treatment for adults with acute lymphoblastic leukaemia: results of U.K. Medical Research Council randomized trial UKALL XA. Medical Research Council Working Party on Leukaemia in Adults

The effects of short-chain alcohols (methanol, ethanol and n-propanol) on the fast-inactivating, A-type, potassium current of Lymnaea neurons were examined using macroscopic recording techniques. Alcohols produced a blockade of the current and modified its inactivation mechanism. The extracellular concentrations of methanol, ethanol and n-propanol causing 50% suppression of the current were 2970, 830 and 230 mM, respectively. The main effects of alcohols on inactivation were a decrease in the amplitude of the fast component and a simultaneous increase in the amplitude of the slow component of inactivation. In a model, the suppression of the fast component could be reproduced by an increase of the backward rate constant related to the dissociation of the inactivation particle from its binding site. The blockade and modification of inactivation reveal similar dependences on ethanol concentration, indicating that the same type of interaction of ethanol with the channel underlies both of these events. Ethanol was effective only in extracellular applications. The data support an action of alcohols at a hydrophobic site near the extracellular portion of the channel.     

Some physico-chemical properties and structural changes of bovine beta-casein upon glycation

The studies on casein structure modification contribute to better understanding of the role of nonamino acid components in forming casein complexes and improving ways of protein functionality. The objective of the experiments was to explain the influence of bovine milk casein glycation on some physico-chemical properties and structural changes. From the the analysis of glycation rate curve the reaction of the first order range can be assumed during the first 24 h, turning to a mixed type afterwards. The isoelectric point and molecular weight of beta-casein increased after glycation and the electrophoretic mobility was slightly modified. The structural changes were also confirmed by different absorption spectra in UV and a better heat stability of the modified beta-casein. The findings showed higher solubility with modified beta-casein. The glycation caused changes in beta-casein, modifying its susceptibility to the trypsin hydrolysis.