近10年塔里木河流域土地利用/土地覆被变化与人口因素关系研究

根据1990年、2000年两期土地利用现状图,运用地理信息系统软件ArcInfo、Arcview以及统计软件,提取、分析塔里木河流域41个县市1990-2000年土地利用/土地覆被的时空变化(LUCC)情况和土地利用程度综合指数。运用SPSS等统计软件,分析并建立土地利用程度人口分异模型,探讨了该研究区LUCC与人口因素的关系。此模型不仅可用于现阶段研究区LUCC分析,还可以根据人口变化趋势进行土地利用程度的变化趋势分析。这对塔河流域土地资源的有效利用和管理具有积极的意义。     

三百年来承德地理环境演变趋势初探

本文通过对三百年来承德干旱灾害的记录和对自1680年以来承德旱涝等级的变化分析,分析出自清朝来,尤其是中华人民共和国成立后,承德地理环境演变的趋势是干旱程度逐渐加强,水土流失、植被减少趋势明显。并分析了造成这种趋势的原因。     

低温胁迫下草坪草Perennial ryegras(cv,Taya)和Meadow bluegrass(cv.Compact)各抗性生理指标的变化

以草坪草多年生黑麦草Ｐｅｒｅｎｎｉａｌｒｙｅｇｒａｓｓ（Ｔａｙａ）和草地早熟禾Ｍｅａｄｏｗｂｌｕｅｇｒａｓｓ（Ｃｏｍ ｐａｃｔ）为材料,通过测定在三种低温胁迫强度和不同的胁迫时间下植物体活性氧清除剂超氧化物歧化酶（ＳＯＤ）、过氧化氢酶（ＣＡＴ）的活性、脯氨酸含量、类胡萝卜素含量和相对电导度等抗性生理指标的变化,以确定其胁变程度,研究两种草坪草抗低温胁迫的形式、途径和大小及其抗性机制问题。结果表明：①草地早熟禾Ｃｏｍｐａｃｔ抗低温胁迫的能力较多年生黑麦草的Ｔａｙａ强。②５℃低温胁迫下两种草坪草的ＳＯＤ、ＣＡＴ活性、类胡萝卜素含量均先升后降,呈现单峰型曲线变化,在三种活性氧清除剂的活性或含量上升时,脯氨酸含量、叶绿素含量和相对电导度没有明显的变化,在三种活性氧清除剂活性或含量下降时,叶绿素含量下降,脯氨酸含量和相对电导度上升。而在０℃与－６℃低温胁迫下ＳＯＤ、ＣＡＴ活性、类胡萝卜素含量随胁迫时间的延长,迅速下降,随后叶绿素含量下降,脯氨酸含量、相对电导度上升。③从５℃到０℃到－６℃,随胁强的增大,一定胁迫时间内各抗性生理指标变化幅度,即胁变程度,随之增大。     

Horizontal resistance: core to a research breakthrough to combat Striga in Africa

The parasltie flowering plants, Striga species, represent the largest biological constraint to cereal and legume crop production in sub-Saharan Africa. Eighty-three percent of Striga worldwide (35 species) occurs in Africa. Among them, Striga hermonthica causes the greatest damage. The IITA's scientists began research on breeding maize for horizontal resistance to Striga in 1982. By 1995 a comprehensive approach to combat Striga on maize had been developed and demonstrated. This included the development of a simple field infestation technique, the discovery of durable resistance genes, genetic studies of resistance genes and the formation of many resistant varieties (hybrids and synthetics) with high grain quality, high grain and stover yields and a combined resistance to major biotic and abiotic stresses. Multilocation testing and subsequent seed multiplication of the resistant varieties was carried out by national programmes in Benin, Burkina Faso, Cameroon, the Ivory Coast, Ethiopia, Ghana, Nigeria, and Togo. Striga-resistant maize varieties show horizontal resistance not only to S. hermonthica, but also to another species, Striga asiatica. Based on the results of a 15 year research, an integrated approach using resistant varieties and cereal-legume intercropping or rotation is recommended as a sustainable and permanent solution to combat Striga in Africa. This horizontal resistance package, with a combined resistance to other biotic stresses, could be applicable not only to Striga problems in other crops such as sorghum, millet, rice and cowpea, but also to other parasitic weeds, such as Orobanche species. This paper reviews and discusses why, approximately a century's research work on parasitic weeds, has not led to a major research breakthrough.     

Surgical treatment of uterine torsion using a ventral midline laparotomy in 19 mares

OBJECTIVE: To report on the outcome of surgical treatment of uterine torsion in preterm mares. DESIGN: Retrospective case series of pregnant mares with uterine torsion presented to the Clinic for Obstetrics, Gynaecology and Andrology of Large and Small Animals. METHODS: Hospital records of all pregnant mares that underwent ventral midline laparotomy for uterine torsion between 1998 and 2004 were reviewed. The signalment, history, clinical signs, results of diagnostic procedures, direction and degree of the uterine twist, treatment and outcome were retrieved from each case record. RESULTS: This study comprised 19 mares between months 5 and 11 of pregnancy (8.7 +/- 1.9) and suffering from uterine torsion. In all cases ventromedian laparotomy was carried out under general anaesthesia. Gastrointestinal disorders were also present in 52.6% of horses. Postoperative complications included subcutaneous seromas (five mares), peritonitis (one mare) and abortion (two mares). In four mares (21%) the operation was unsuccessful (i.e. these mares had to be euthanased intra- or postoperatively). Of the surviving 15 mares, 13 (86.6%) gave birth to viable foals at full term. The foals developed normally. Only two mares aborted. CONCLUSIONS: Because of its versatility the ventral midline approach should be considered for correction of uterine torsion. The approach has many advantages, including rapid and clear access to the abdominal cavity, safety, visual assessment of uterine wall viability, correction of concomitant gastrointestinal tract problems, and performance of hysterotomy or hysterectomy, if indicated. In this study, managing uterine torsion in this way resulted in a high percentage of cases (86.6%) in which pregnancy was maintained, with the birth of a viable, mature foal.     

Prevalence of Taenia solium cysticercosis in swine from a community-based study in 21 villages of the Eastern Cape Province, South Africa

The pork tapeworm, Taenia solium, causative organism of porcine cysticercosis and human neurocysticercosis is known to occur in areas of South Africa including Eastern Cape Province but, despite increasing reports of its occurrence throughout the subregion, the prevalence is yet to be clearly established. The parasite presents a potentially serious agricultural problem and public health risk in endemic areas. The human populations considered to be at highest risk of infection with this zoonotic helminth are people living in rural areas most of whom earn their livelihood wholly or partially through livestock rearing. Here we report on initial results of a community-based study of pigs owned by resource-poor, emerging pig producers from 21 villages in the Eastern Cape Province. Lingual examination (tongue palpation) in live pigs, two enzyme-linked immunosorbent assays (ELISAs), which detect parasite antigen (B158/B60 Ag-ELISA and HP10 Ag-ELISA) and an enzyme immunotransfer blot (EITB) assay, which detects antiparasite antibody, were used to verify endemicity and estimate apparent prevalence. In the absence of a gold standard true prevalence was obtained, using a Bayesian approach, with a model that uses both available data and prior information. Results indicate that the parasite is indeed present in the study villages and that true prevalence was 64.6%. The apparent prevalences as measured by each of the four tests were: 11.9% for lingual examination, 54.8% for B158/B60 Ag-ELISA, 40.6% for HP10 Ag-ELISA and 33.3% for EITB. This base-line knowledge of the prevalence of T. solium in pigs provides information essential to the design and monitoring of sustainable and appropriate interventions for cysticercosis prevention and control.     

数字图书馆与高校学位论文资源的数字化应用

介绍了数字图书馆的发展及其功能,以及高校图书馆在学位论文资源整合中的数字化应用。     

pH-stat法在测定酶促反应米氏常数中的应用

在pH值为7．2,温度为40C的条件下,As1．398中性蛋白酶水解大豆分离蛋白,采用pH—stat法结合Exeel软件方便准确地求出酶促反应的初始速度,从而根据Lineweaver—Burk双倒数方程计算出该酶的最大反应速度（Vmax）和米氏常数（Km）．实验条件下,As1．398蛋白酶的Km,值为1．46mg／mL．     

Mechanism of molybdenum sorption to iron oxides using pressure‐jump relaxation

It is widely accepted that the fixation of oxyanions is due to diffusion of the ions into the pores and interdomains of iron oxides. Most studies have used batch techniques, which do not allow to clearly differentiate chemisorption from mass transport phenomena. Thus, it is not yet clear, whether strengthening of chemical Mo bonding occurs along with residence time, in addition to diffusion processes. In this study we used pressure jump relaxation (p‐jump), a very fast kinetic technique, to (1) elucidate the Mo/goethite interaction and to (2) analyze the effects of aging the Mo/goethite complex on Mo chemisorption. A synthetic goethite was incubated with Mo solution (1 mM Mo) for 12, 24, and 72 hours at pH 4. At the end of the incubations p‐jump experiments were performed on the suspensions at temperatures ranging from 283 to 303 K. Relaxation kinetics were modelled using a combination of two first order terms. In addition, the amount of Mo sorbed to the goethite after different incubation times was determined by graphite furnace atomic absorption spectroscopy. The MoO₄/goethite systems revealed a fast relaxation time (= reciprocal of rate constant, about 4 ms), that decreased with increasing temperature and a slow one (about 60 ms) that did not depend on temperature. Activation energy of the fast process was 76 kJ mol^—1. We did not observe any effects of incubation time on the fast process. However, the amount of Mo sorbed to the iron oxide increased with increasing incubation time. We conclude that the fast relaxation represents Mo chemisorption to the goethite. Slow relaxation seems to be due to Mo transport within the suspension. The pressure jump results indicate, that the dominant surface species of Mo sorbed to goethite do not change along with residence time.     

不同肥力农田和不同林型林地红壤总硝化特征研究

在3种不同肥力的农田和3种不同林型林地红壤上利用原状土心-15N库稀释技术原位测定了其总硝化率。结果表明:不同肥力农田和不同林地红壤的总硝化速率在N7.29～23.50μg/(g·d)间波动,总体来说,农田土壤的总硝化速率大于林地土壤。在不同肥力的农田间,施肥处理的总硝化率显著高于不施肥处理(p<0.05)。在不同植被类型林地间,湿地松林地的总硝化率比木荷和混交林林地分别提高了24.8%和66.9%。总硝化包括净硝化和NO3--N的消耗部分。本试验农田NO3--N的消耗速率比林地大,与总硝化率的变化趋势类似。在同一利用方式的不同处理中,NO3--N含量的变化趋势与总硝化速率的变化趋势相类似。