Hydrolysis of Fe(OH)SO4 in the presence of metallic iron

Hydrolysis of Fe(OH)SO₄ was carried out in the presence of metallic iron in order to prevent the formation of iron(III) oxides with strongly bonded sulphate. Under the conditions of the experiment, the products were found to be mixtures of ?-Fe₂O₃ and α-FeOOH. The occluded sulphate, if any, could be easily washed out with water. The hydrolysis reaction passes through an equilibrium state before coming to completion. The entropy with enthalpy of the hydrolysis corresponding to the equilibrium state were found to be 4 e.u. and 0·5 kJ/mol, respectively. The activation energy of the hydrolysis reaction was found to be 21 kJ/mol.     

Application of functionalised carbon nanotubes immobilised into chitosan films in amperometric enzyme biosensors

A new approach for building a bio-conductive interface for enzyme immobilisation is described. This strategy permits very simple preparation of the enzyme biosensor and also reveals direct electron transfer features. A graphite-epoxy resin composite (GrEC) electrode modified with functionalised multi-wall carbon nanotubes (MWCNTs) immobilised by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide together with N-hydroxysuccinimide (EDC–NHS) in a chitosan (Chit) matrix was prepared and characterised by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in the presence of hexaammineruthenium (III) chloride. It was then used as a base for glucose oxidase (GOx) immobilisation by the simple method of crosslinking with glutaraldehyde (GA) with bovine serum albumin (BSA) as carrier protein. The resulting mediator-free biosensor was applied to the determination of glucose in amperometric mode at different applied potentials and the mechanism of reaction was also investigated by cyclic voltammetry, with and without dissolved oxygen in solution. Analytical parameters, as well as reproducibility, repeatability and stability were determined. Interferences were assessed using different compounds usually present in natural samples, such as wines, juices or blood, in order to evaluate the selectivity of the developed biosensor. The novel combination of carbon nanotubes immobilised with chitosan crosslinked with EDC–NHS and glucose oxidase immobilised by crosslinking with glutaraldehyde offers an excellent, easy to make biosensor for glucose determination without interferences.     

Morphology of porous n-GaP anodically formed in different mineral acids

n-type GaP(100) was anodized in H₂SO₄, HF, HCl, HBr, HI, HNO₃ and H₃PO₄ in order to obtain porous structures. Remarkable differences in the morphology were found when anodisation was carried out under comparable electrochemical conditions. Etching in HF led to a statistically porous structure, but no evidence for higher ordering was obtained. Etching in HCl solutions caused a localized attack of the surface leading to porous insular areas. In HBr highly defined rectangular pores grow perpendicular to the (100)-surface forming several μm thick well defined porous layers. In HI pores are aligned parallel to equipotential lines along defects. Pore formation in H₃PO₄ and HNO₃ can lead to highly complex ordered structures. Clearly the work shows that the formation of porous n-GaP is strongly dependent on the anion present in the electrolyte.     

High temperature piezoelectric materials: Defect chemistry and electro-mechanical properties

Langasite (La₃Ga₅SiO₁₄, LGS) and gallium orthophosphate (GaPO₄) resonators exhibit piezoelectrically exited bulk acoustic waves at temperatures of up to at least 1400^∘C and 900^∘C, respectively. Their mass sensitivity at elevated temperatures has been found to be about as high as that of quartz at room temperature. Within its operation temperature range, GaPO₄ shows significantly lower losses than LGS. Factors restricting application relevant properties of LGS at elevated temperatures, such as the mass resolution, include excessive viscous damping. Therefore, the effective viscosity is determined as a function of the temperature by fitting the calculated complex impedance to the experimental data in the vicinity of the resonance frequency. The viscosity shows an Arrhenius-like behavior if a temperature independent contribution is subtracted. The activation energies of the viscosity for LGS and GaPO₄ correspond to those of the bulk electrical conductivity for each material. Viscosity and conductivity are obviously correlated. Therefore, it is highly likely that the predominant conductivity mechanism also controls the mechanical damping. First attempts to minimize the viscosity of LGS by doping are undertaken. Very light doping does, however, not change the conductivity and viscosity of LGS. Higher doping levels have to be applied and tested. Based on the electromechanical properties given for undoped LGS, the applicability of this material as resonant gas sensor at 600^∘C is demonstrated.     

秦山三期CANDU-6核电机组技术规格书的修改

描述了制定秦山三期CANDU 6核电机组技术规格书 (TS)的核安全法规依据 ,简要介绍了按照中国核安全法规的要求、参照美国NRC制定的压水堆核电站成熟的标准技术规格书的格式和应用加拿大CANDU机组采用的运行方针和政策所积累的成熟的运行经验 ,对AECL提交的TS进行修改的情况以及对TS中一些重要技术问题的修改内容 ,说明了修改后的TS基本满足了中国核安全法规的要求 ,可以在核电站的运行中使用     

硝酸铀酰光化还原的研究

本文的目的是探讨光化还原制备硝酸钠(Ⅳ)。研制了一个与硝酸钠酰的吸收光谱匹配较好的金属卤化物灯——镓灯作为激发光源,在不另加滤光器的条件下,对几种还原剂的还原能力作了比较,并对乙醇作还原剂时,硝酸浓度、乙醇浓度、初始铀酰离子浓度以及温度等因素对光化还原铀(Ⅵ)到铀(Ⅳ)的还原率的影响进行了研究。     

Chl1, an ATP-Dependent DNA Helicase,Inhibits DNA:RNA Hybrids Formation at DSB Sites to Maintain Genome Stability in S. pombe

As an ATP-dependent DNA helicase, human ChlR1/DDX11 (Chl1 in yeast) can unwind both DNA:RNA and DNA:DNA substrates in vitro. Studies have demonstrated that ChlR1 plays a vital role in preserving genome stability by participating in DNA repair and sister chromatid cohesion, whereas the ways in which the biochemical features of ChlR1 function in DNA metabolism are not well understood. Here, we illustrate that Chl1 localizes to double-strand DNA break (DSB) sites and restrains DNA:RNA hybrid accumulation at these loci. Mutation of Chl1 strongly impairs DSB repair capacity by homologous recombination (HR) and nonhomologous end-joining (NHEJ) pathways, and deleting RNase H further reduces DNA repair efficiency, which indicates that the enzymatic activities of Chl1 are needed in Schizosaccharomyces pombe. In addition, we found that the Rpc37 subunit of RNA polymerase III (RNA Pol III) interacts directly with Chl1 and that deletion of Chl1 has no influence on the localization of Rpc37 at DSB site, implying the role of Rpc37 in the recruitment of Chl1 to this site.     

Synthesis and spectral properties of new tetrakis-2,3-{5,7-bis[(E)-2-(4-methylphenyl)vinyl]pyrazino}porphyrazine metal complexes

The new styryl substituted pyrazinoporphyrazine complex has been synthesised for the first time. The spectral properties of the ytterbium complex have been studied. The introduction of the styryl fragments in the cycle leads to bathochromatic shift of the Q-band. It can be explained by the stabilisation of LUMO.     

Synthesis of acicular α-Bi2O3 microcrystals by microwave-assisted hydrothermal method

ABSTRACT

Materials based on bismuth(III) oxide are candidate to be used in optical and electronic devices because of their properties such as a variable band gap, photoconductivity, photoluminescence, high refractive index, and dielectric permittivity. These properties are dependent of several factors, e.g., present phases and crystal morphology. The microwave-assisted hydrothermal method (MAH) is a fast and efficient approach of synthesis to obtain semiconductor powders. However, the synthesis of monoclinic bismuth oxide (α-Bi₂O₃) with acicular morphology by MAH was not found in literature. In this paper, microcrystals of acicular α-Bi₂O₃ (monophasic) were successfully obtained by MAH using a synthesis temperature of 80°C for 0.5?h. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron, and transmission electron microscopies showed the formation of a monoclinic structure (space group P21/c) with acicular morphology that grew along the [001] direction. The temperature and time necessary to synthetize acicular microcrystals were significantly lower than those found for acicular microcrystals obtained by conventional hydrothermal method.     

DRF-J45型镓单晶炉的开发与设计

当前镓提纯方法大部分采用电解法,电解法生产出的镓晶体纯度不高,常常形成个别杂质元素超标。为了提高其晶体纯度,需采用晶体提拉法来进一步弥补并提升镓晶体提纯工艺方法。从分析镓单晶炉生长的工艺特点出发,简要介绍镓单晶生长设备的设计思想以及新近开发设计的新型镓单晶炉的机械结构及电气控制系统。