Preparation of Glutaraldehyde Cross-Linked Chitosan Beads Under Microwave Irradiation and Properties of Urease Immobilized onto the Beads

The glutaraldehyde cross-linked chitosan beads were prepared under microwave irradiation and urease was immobilized onto the beads. The activity and the yield of enzyme activity of the immobilized urease were 10.83 U/g carrier and 47.7%, respectively. The optimum conditions of immobilization were 1% of glutaraldehyde volume fraction, 10 mg/g of urease/beads weight ratio, 24 h of the processing time and pH 6.5 of the reaction medium for immobilization. The properties of the immobilized urease were investigated and compared with those of the free enzyme. The optimum pH values were 6.5 and 7.0 for the immobilized and free urease, respectively. The optimum temperature was 60℃ for the free urease, while it shifted to 65 ℃ for the immobilized enzyme. The Michaelis constant Kr, was 9.1 mmol/L for the immobilized and 12.5 mmol/L for the free urease. The immobilized urease retained 40% of its initial enzyme activity even after 10 repeated uses. The immobilized urease stored at 4 ℃ retained 46% of its initial activity even after 35 d.     

《多元统计分析及程序》

多元统计分析方法虽然属于数理统计学的范畴,但随着电子计算机的日益普及和软件开发技术的不断推陈出新、研究者素质的逐步提高,现已广泛应用于自然科学、社会科学、经济科学等各个领域,成为具有相当实用价值的数据处理及分析方法。目前,介绍此方法的书籍有多种版本,...     

语篇衔接理论在大学生英语写作中的应用研究

本文以韩礼德和哈桑的衔接理论为框架,通过非英语专业大学一年级学生的教学实验研究:(1)中国大学生在英语写作中出现的衔接问题及其原因;(2)有意识的衔接手段的教学能否提高学生的英文写作水平。结果表明:(1)中国学生在衔接手段的使用方面存在许多问题,尤其是指称衔接、连接衔接和词汇衔接手段。误用的原因主要有三个方面:语言迁移、文化差异和有限的语言水平。(2)英语教学中教授衔接手段的使用是提高大学生英语写作水平的一个行之有效的方法。     

导评结合，授之以渔——已叙文中场面描写写作指导

场面是生活的横断面。生活像一条长河,场面是一朵浪花,要学会描写生活,首先得学会写生活片断,所以,对记叙文中场面描写的指导非常重要。     

节约生命

我们注意节约用水，因为水资源贫乏；我们提倡节约用电，以减少能源消耗；我们呼吁节约纸张，以减少时森林的砍伐量。有多少人想到节约生命呢？生命对每个人来说犹如一堆煤、一块炭，燃烧过后只刺下一堆灰烬。不能像海水取之不尽，不能像空气用之不竭，生命如此短暂，浪费生命使生命更加短暂。节约用水固然重要，节约生命要是人生必修的重要课程。     

略论"三个代表"思想蕴涵的辩证唯物主义及历史唯物主义思想

江泽民同志提出的“三个代表”重要思想与马克思列宁主义、毛泽东思想和邓小平理论一脉相承。正确理解和把握其运涵的哲学思想,是新时期进一步贯彻“三个代表”思想精神,永葆中国共产党的先进地位的哲学基础和力量源泉。     

名字的由来

天真烂漫的小学低年级孩子,在家都是“独苗苗”、“小太阳”,怎样让孩子与父母建立起平等、和谐的互爱关系呢?我们在对孩子们进行创爱情感培养的过程中,发现孩子们对父母的爱只是一种肤浅的认识,认为父母给自己吃好、穿好、玩好就是对自己的爱,无法感受父母殷殷期盼的拳拳之心,怎样解决这一难题呢?编写情意课教材时,我们就     

Synthesis of 3-O-Benzoyl-1 ,2-O-isopropylidene-a-D-allofuranose and Its Dimesylated Derivative

Diisopropylidenated a-D-glucofuranose (1) was oxidated with CrO;-Pyridine complex. Oxidated product and its hydrate were separated and were reduced together to synthesize diisopro-pylidenated a-D-allofuranose (3 ). The yield of 3 increased by 8% than that with only oxidated prod-uct as reduction substrate. Benzoylated derivative of 3 was selectively hydrolyzed and dimesylated to synthesize 3-O-benzoyl-l ,2-O-isopropylidene-a-D-allofuranose (5) and its dimesylated deriva-tive respectively. The overall yield of 5 from 1 was 36%. Each step and final products were analyzed by 'H-NMR spectra and other methods. The experiments showed that the influence of acetic acid concentration on selective hydrolysis was obvious. The hydrolysis yield was 81. 8%. Oxidation, re-duction and other procedures were practical and had application potential.     

在听课中提升

听课、评课过程，是教师在互动中获取经验、自我提高的过程：听课过程中，不能为了记录而记录，听课教师不是“摄像机”，不可能也没必要对整个教学活动过程作一翻录；也不可能像专业速记那样，一字不漏地记录。听课者应讲究听课技巧，记录时做到有所选择，要学会“去粗存精”，让自己真正从听课中受益。     

让学生爱上数学日记

数学日记伴随着新课改应运而生,它给学生提供了一个用语言表达数学情感、交流数学思想的平台。不过,由于数学日记是在新课程下产生的新事物,许多教师和学生缺乏对数学日记的认识,片面认为数学日记就是在语文日记中出现了一些数字、一些加减法而已。使原本丰富多彩的数学日记失去了其应有的价值,走