Determination of nitrite and nitrate levels in meat and vegetable products by high performance liquid chromatography

A range of fresh and processed meat and vegetable products was analysed by h.p.l.c. for nitrite and nitrate contents. Satisfactory results were obtained for vegetable products and most meats, but some meat products were subject to matrix interference. Sucrose, sulphate and phosphate did not affect results. Added sodium chloride decreased retention time of nitrite and increased apparent levels of both nitrite and nitrate. Ascorbic and erythorbic acids decreased apparent nitrite levels and correspondingly increased apparent nitrate levels.     

Activation of Polycyclic Aromatic Compounds by cDNA-Expressed Phase I and Phase II Enzymes

A large number of human and other mammalian xenobiotic-metabolizing enzymes have been expressed in target cells of standard mutagenicity tests, such as Ames's Salmonella typhimurium strains and Chinese hamster V79 cells. These recombinant cells are useful for determining the ability of individual enzymes to activate (or inactivate) a given compound. In contrast to standard S9-mediated test systems, they also allow the detection of mutagenic metabolites that do not penetrate cell membranes--a situation often found with reactive phase II metabolites. We present mutagenicity data for benzo[ a ]pyrene and dibenzo[ a,l ]pyrene in V79-derived cells expressing human cytochrome P450 (CYP) 1A1, 1A2, and 1B1, and for 1-hydroxymethylpyrene, R - and S -1-( f -hydroxyethyl) pyrene, 4-hydroxycyclopenta[ def ]chrysene and N -hydroxy-2-acetylaminofluorene in V79-derived cells and/or Salmonella strains expressing the 11 human sulfotransferases (SULTs) identified. In some cases, allelic variants and orthologous enzymes from other mammalian species were also investigated. The data indicate that mutagenicity of many compounds is detected in the appropriate recombinant systems at extremely low substrate concentrations, that the activation of various promutagens is mediated with high specificity by only one or few enzyme forms, and that substantial differences may occur between alloenzymes from the same species and orthologous enzymes from different species. Such information could be important for understanding differences in susceptibility between tissues, species, individual genetic traits, and physiological states.     

环氧乙烷羰基合成1,3—丙二醇的催化剂配方研究（下）

介绍了环氧乙烷羰基合成１，３－丙二醇过程中的化学特性；考察了不同催化剂组合物配方对反应结果的影响，并对反应产物作了较尽尽的定性分析。     

Responses of Human Cells to PAH-Induced DNA Damage

Benzo[ a ]pyrene (B[ a ]P) and dibenzo[ a,l ]pyrene (DB[ a,l ]P) induce cytochrome P450 (CYP) CYP1A1 and CYP1B1, which metabolize these polycyclic aromatic hydrocarbons (PAHs) into DNA-binding species. In order to detail roles of CYP1A1 and CYP1B1 in activation of DB[ a,l ]P to the diol epoxide, we here report the inhibition of CYP1A1 in human MCF-7 cells with phosphorodiamidate morpholino antisense oligomers (morpholinos). PAH-DNA adduct formation was also determined after treatment with morpholinos and B[ a ]P or DB[ a,l ]P. p53 is involved in DNA repair, cell cycle arrest, and apoptosis. Cells with normal p53 protein arrest in the G1 phase of the cell cycle on exposure to DNA-damaging agents (presumably allowing the cell sufficient time to repair damaged DNA prior to replication). Previous studies in human MCF-7 cells indicate that cells with PAH-DNA adducts escape cell cycle arrest and accumulate in the S phase. In the present study the effect of PAH-DNA adducts on the cell cycle were observed in human diploid fibroblasts (HDF). We found that treatment of HDF with the diol epoxide of DB[ a,l ]P causes cell cycle arrest in G 1 . An increase in DNA adduct formation with increase in concentration of dibenzo[ a,l ]pyrene diol epoxide {( m )- anti -DB[ a,l ]PDE} was also observed.     

Impact of the condition of storage of tartaric acid solutions on the production and stability of glyoxylic acid

The production and stability of glyoxylic acid was followed during the storage of tartaric acid solutions under various conditions. The solutions were prepared both with and without ethanol. Quantification of glyoxylic acid and other oxidation products, including hydrogen peroxide and formic acid, were performed using ion exclusion chromatography. Glyoxylic acid was only detected in tartaric acid samples that had been stored outdoors and sunlight was identified as the critical component of outdoor storage that allowed its formation. The hydrogen peroxide and glyoxylic acid generated under these conditions were of limited stability due to their reaction with each other to produce formic acid. The concentration of the glyoxylic acid was greatly increased when ethanol was omitted from the sample matrix. Copper(II) enhanced the stability of glyoxylic acid but slowed its production. The reaction pathway responsible for the sunlight-induced production and subsequent stability of glyoxylic acid is discussed.     

Catalytic fluorination of HCFC-133a (1,1,1-trifluoro-2-chloroethane)

Catalytic fluorination of HCFC-133a was performed over metal oxide catalysts. Chromium oxide showed the best catalytic activity among several metal oxides tested. An increase in the crystallinity with decreased surface area resulted in a decrease of catalytic activity for the fluorination reaction. Active phase of chromia is Cr-O-F-OH having a proper ratio of O/F and a high hydroxyl content. The hydroxyl content on the catalyst is strongly dependent on support material. The selectivity to HFC-134a is independent of the O/F ratio on the Cr surface.     

洗尽铅华看“WAP”

在过去的3年中，WAP（无线应用协议）曾经红极一时，又很快被冷落一旁。喧嚣过后，一切归于沉寂。很多业内人士认为，WAP失败的命运似乎已经无法避免，然而，这是否是关于WAP结局的定论？本文通过回顾WAP在我国的发展及对WAP协议集进行详尽的分析，力图以客观求实的观点论述WAP发展的未来。     

Entwicklung eines Universal Tractor Transmission Oil (UTTO) auf Basis nachwachsender Rohstoffe

Development of a Universal Tractor Transmission Oil (UTTO) based on renewable raw materials The 2<sup>nd</sup> generation of an environmentally friendly fluid for vehicles with a common oil tank for transmission and hydraulics was developed in a governmentally funded research project. The fluid consists to about 75 % of native rapeseed oil. The boundary conditions as well as the intentions and goals of this new development will be explained as well as the reasons which led to this unique lubricant conception. The fluids properties will be illustrated by experimental investigations and their results. The discussion based on the comparison of results achieved with BIO‐HY‐GARD II and parallel tests with reference fluids enables the validation of different lubricants technology performance as well as the verification of the achieved progress with this new development.     

基于DSP的信号单边带调制的实现

首先分析了常规的单边带调制方法,然后根据数字信号的内插原理及其频谱特性,提出了一种简单的、易于DSP编程实现的单边带调制方法。并将这种方法和传统的方法进行了比较,最后经过计算机仿真和DSP试验表明,该方法具有推广应用的价值。