发酵液中植酸酶活性测定方法的研究

以钒钼法对发酵液中植酸酶活性进行了测定,并对影响酶活性测定结果的因素进行了研究.实验结果表明,钒钒法测磷的灵敏度和线性范围分别为0.025mmol/L和0.025mmol/L～0.6mmol/L;为减小植酸酶活性的测定误差,结果测定必须在颜色反应结束后的4h以内完成.研究中同时发现,发酵液含有的无机磷远远大于酶活测定产生的无机磷含量,直接用发酵液测得的植酸酶酶活是不可靠的.通过对透析2h的发酵液进行植酸酶酶活的测定,实验结果的最大相对偏差仅为7.1%.     

Performance of dairy cows fed roasted sunflower seed

The objectives of this study were to determine the effects on milk yield, milk composition, ruminal fermentation and total tract nutrient utilization of feeding roasted whole sunflower seed to dairy cows. Three diets were formulated: a control diet with no sunflower seed (NSF), a raw sunflower seed diet (USF) and a roasted sunflower seed diet (RSF). The level of sunflower seed in USF and RSF was 78 g kg^?1 of dry matter (DM). The effects of dietary treatments on yield and composition of milk were determined using nine Holstein cows in three 3 × 3 Latin squares. Three ruminally fistulated cows were used to determine the effects of dietary treatments on ruminal fermentation and total tract nutrient digestibilities. Cows fed sunflower seed diets consumed 8% less (P < 0.05) DM but produced similar amounts of milk as cows fed NSF. However, milk fat content (30.7 vs 33.5 g kg^?1) and yield (1.33 vs 1.47 kg day^?1) were lower (P < 0.05) for cows fed USF and RSF than for those fed NSF. Supplemental sunflower seed had no effect on concentrations and yields of other milk components. The concentrations of short‐chain (C_4:0 to C_12:0) and medium‐chain (C_14:0 to C_16:0) fatty acids were, respectively, 27% and 29% lower (P < 0.05) while those of long‐chain fatty acids (C_18:0 to C_18:3) were 51% higher (P < 0.05) in the milk of cows fed USF and RSF than for cows fed NSF. Ruminal pH, ammonia N and total volatile fatty acids were not affected by dietary treatments. Feeding sunflower seed (USF or RSF) reduced (P < 0.05) the concentration of acetate and increased (P < 0.05) the concentration of propionate. Total tract nutrient digestibilities were not affected by sunflower seed supplementation or by heat treatment. Supplementing dairy cow diets with unheated or roasted sunflower seed improved the efficiency of milk production and increased concentrations of long‐chain and polyunsaturated fatty acids. Feeding sunflower seed at up to 78 g kg^?1 of diet DM had no adverse effects on nutrient utilization. Roasting had no additional benefits on milk yield or milk fatty acid composition. Copyright © 2004 Society of Chemical Industry     

The effect of sowing date and growth stage on the essential oil composition of three types of parsley (Petroselinum crispum)

Essential oils obtained by simultaneous distillation–extraction (SDE) from leaves, petioles and roots of three types of parsley (turnip‐rooted, plain leaf and curly leaf type), sown on three different dates, were analysed by GC‐MS (gas chromatography–mass spectrometry) analysis. Parsley plants were found to produce mainly β‐phellandrene, 1,3,8‐p‐menthatriene, α‐,p‐dimethylstyrene, myristicin, β‐myrcene and apiole. In some cases α‐ and β‐pinene were also found, whereas β‐elemene was detected, especially in the curly leaf type. The growth stage, plant tissue and date of sowing, as well as the climate conditions, all had a significant effect on the essential oil composition by altering the ratio of the above substances. Copyright © 2004 Society of Chemical Industry     

Substituted glycals as probes of glycosidase mechanisms

D-Glucal and a series of substituted derivatives have been tested as substrates, inhibitors and inactivators of the Agrobacterium faecalis beta-glucosidase in order to probe structure/function relationships in this enzyme. D-Glucal is shown to be a substrate (kcat = 2.3 min-1, Km = 0.85 mM) undergoing hydration with stereospecific protonation from the alpha-face to yield 2-deoxy-beta-D-glucose. 1-Methyl-D-glucal surprisingly serves as only a poor substrate (kcat = 0.056 min-1, Km = 57 mM), also undergoing protonation from the alpha-face. 2-Fluoro-D-glucal, however is completely inert, as a result of inductive destabilisation of the oxocarbenium ion-like transition state for protonation, and functions only as a relatively weak (Ki = 24 mM) inhibitor. Similar behaviour was seen with almond beta-glucosidase and yeast alpha-glucosidase and for the interaction of 2-fluoro-D-galactal with Escherichia coli beta-galactosidase. A series of of alpha, beta-unsaturated glucal derivatives was also synthesised and tested as potential substrates, inhibitors or inactivators of A. faecalis beta-glucosidase. Of these only 1-nitro-D-glucal functioned as a time dependent, irreversible inactivator (ki = 0.011 min-1, Ki = 5.5 mM), presumably acting as a Michael acceptor. Electrospray mass spectrometric analysis revealed multiple labeling of the enzyme by this inactivator, lessening its usefulness as an affinity label. Less reactive Michael acceptor glycals which might have been more specific (1-cyano-, 2-cyano-, 1-carboxylic acid, 1-carboxylic acid methyl ester) unfortunately did not function as inactivators or substrates, only as relatively weak reversible inhibitors (Ki = 3-96 mM).     

Improvement of some pharmaceutical properties of drugs by cyclodextrin complexation. 4. Chlorpromazine hydrochloride

This study is a retrospective review of admissions, discharge records and blood culture results of neonates admitted to the Neonatal Intensive Care Unit of Korle Bu Teaching Hospital in Accra, from the first of January 1991 to the 31st of December 1992. During this two year period there were 443 positive blood cultures. Ninety percent of the blood cultures were from babies born in Korle Bu Teaching Hospital, thus making the incidence of neonatal bacteraemia 22.2 per 1000 live births. The overall mortality rate was 37.2%. Gram negative bacteria accounted for 70.9% and Gram positive bacteria for 29.1% of all neonatal bacteraemia. The most common isolates were Enterobacter species 29.6%; Streptococcus faecalis 14.4%; Staphylococcus aureus 10.8%; Acinetobacter species 9.5%; Klebsiella species 9% and Escherichia coli 8.8%. It is concluded that the incidence of neonatal bacterial sepsis is high in our hospital and is associated with a very high mortality rate. There is thus an urgent need to institute appropriate preventive and therapeutic measures.     

Reductions in self-injury produced by transcutaneous electrical nerve stimulation

Transcutaneous electrical nerve stimulation is used to reduce pain but also may be useful for self-injurious behavior (SIB). In the current investigation, a microcurrent electromedical device, classified as a transcutaneous electrical nerve stimulator (TENS), was applied with a man with Down syndrome who displayed SIB that persisted in the absence of social contingencies. Although clinically significant results were not maintained, a clear difference in the rates of SIB during active and inactive TENS was observed.     

基于安全人机学的驾驶作业疲劳评价模型研究

驾驶作业涉及人-汽车-环境,是较复杂的半自动化人机系统,驾驶作业疲劳是由多种因素造成的,对其评价存在不确定性.建立一种多因素多等级的评价模型,对驾驶作业疲劳程度进行总体评价,对致劳因素进行排序,为驾驶疲劳的评价及预防和减轻驾驶疲劳提供一种方法.     

芳纶纤维在轮胎工业中的应用

笔者主要介绍了芳纶纤维(包括长纤维和短纤维)的性能及其在轮胎工业的应用，同时简要叙述了芳纶纤维的分类和发展历史。