野生金头闭壳龟的资源现状调查

笔者于2001-2004年对金头闭壳龟(Cuoraaurocapitata)的野生种群的分布、数量及相关生态学进行了专项调查。结果表明,金头闭壳龟目前仅分布于青弋江源头和上游即北纬30°-30°52′的少数支流中,具体为安徽省泾县的古坝、蔡村和孤峰三地的山涧溪流以及黟县红星乡的清溪河流域。野外种群数量十分稀少,目前已不足400只。金头闭壳龟主要栖息在水质清澈、两侧植被茂密或一侧山脚多石缝的山涧溪流中。经对曾经发现过金头闭壳龟典型地带的各种生态指标的测量表明,泾县古坝乡沈村上沈村段的古坝河段的以及蔡村乡的东园至爱民段的丁溪河段,相比而言仍不失为金头闭壳龟较为理想的栖息地。     

牛体尺影响因素及其应用

牛体尺指标在一定程度上可以评价品种优劣及生产性能的高低。本文对影响牛体尺的因素做一综述,并从体尺与估测体重、屠宰性能、种公牛繁殖性能、奶牛产奶性能4个方面概述牛体尺应用情况,以期为今后生产中评估牛的肉用经济价值、群遗传选育、改善群体繁殖性能和提高生产性能提供一定的借鉴和指导。     

Sex‐dependent responses of perch to changes in water clarity and temperature

Rising temperatures and decreasing water transparency of lakes have strong wide ranging effects on fish. Fish responses to various changes in the environment are usually species‐dependent, but responses may also vary within species. In general, large individuals are considered to be more sensitive to environmental variation due to higher energy demand, than smaller individuals. Similarly, large individuals require more food to maintain bodily functions and are thus more sensitive to resource and food scarcity. These size‐specific responses to environmental gradients are also sex‐dependent in species that exhibit sexual size dimorphism (SSD). We studied in enclosures with short‐term experiments how rising temperatures and decreasing water transparency regulate the feeding rates of female and male European perch (Perca fluviatilis L.). To explore experimental results, we calculated perch SSD in nine lakes with varying environmental conditions using previously collected field data. The results of the experiments revealed that the combined effect of water transparency and temperature on the feeding rate of fish is gender‐dependent: feeding rate of females decreased more than that of males. The experimental results were also supported by field data that revealed a negative relation between water transparency and the magnitude of SSD in perch. Our results suggest that rising temperatures and decreasing water transparency may potentially decrease fish size in a sex‐dependent manner. As female size is one of the main demographic traits determining the reproductive success of a fish population, changing environments may have unexpected and far‐reaching consequences on fish population dynamics.     

Limited effects of land use on soil dissolved organic matter chemistry as assessed by excitation–emission fluorescence spectroscopy and molecular weight fractionation

Dissolved organic matter (DOM) in soil solution represents a complex mixture of organic molecules and plays a central role in carbon and nitrogen cycling in plant–microbial–soil systems. We tested whether excitation–emission matrix (EEM) fluorescence spectroscopy can be used to characterize DOM and support previous findings that the majority of DOM is of high molecular weight (MW). EEM fluorescence spectroscopy was used in conjunction with MW fractionation to characterize DOM in soil solution from a grassland soil land management gradient in North Wales, UK. Data analysis suggested that three distinct fluorescence components could be separated and identified from the EEM data. These components were identified as being of humic‐like or fulvic‐like origin. Contrary to expectations, the majority of the fluorescence signal occurred in the small MW (<1 kDa) fraction, although differences between soils from the differently managed grasslands were more apparent in larger MW fractions. We conclude that following further characterization of the chemical composition of the fluorophores, EEM has potential as a sensitive technique for characterizing the small MW phenolic fraction of DOM in soils.     

利用废弃浸渍纸制造刨花板的试验研究

利用废弃浸渍纸粉末替代部分脲醛树脂胶压制刨花板,采用正交试验方案并考察刨花板的主要理化性能,探讨浸渍纸粉末部分或全部替代脲醛胶的可行性。结果表明:废弃浸渍纸粉末用量为20%、脲醛树脂用量为5%、热压温度为190℃、热压时间为0.4 min/mm时,所压制的刨花板静曲强度为17.97 MPa,内结合强度为0.76 MPa,甲醛释放量为5.69 mg/100g,废弃浸渍纸粉末可部分替代脲醛树脂压制刨花板且性能较佳。     

感应热处理工艺对拖拉机轴类零件扭转强度的影响

对驱动轮工艺轴进行了7种工艺方案的感应热处理表面强化,然后对工艺轴进行扭转破坏试验。通过对驱动轮工艺轴扭转断裂的研究,为驱动轮轴及承受扭力的轴类零件结构设计、工艺流程设计和热处理技术要求提供指导,从而提高其扭转疲劳强度和使用寿命。     

A computer vision system for oocyte counting using images captured by smartphone

This work proposes a computer vision procedure for counting Twospot astyanax (Astyanax bimaculatus) oocytes in Petri dishes using images captured by smartphone. First, the proposed procedure uses simple linear iterative clustering (SLIC) to divide the images into groups of pixels (superpixels). Then, based on their color and space characteristics, the images are classified into light background, dark background, dirt, or oocyte by a machine learning algorithm. Five different types of machine learning algorithms were tested: support vector machines (SVM), decision trees using the algorithm J48 and random forest, k-nearest neighbors (k-NN), and Naive Bayes. To train the algorithms, 8.578 superpixels were classified by an expert into oocyte (n = 354), dirtiness (n = 651), dark background (n = 3.622), and light background (n = 3.951). Of the five learning algorithms, SVM obtained the best result with 97% correct oocyte recognition. Given the wide availability of smartphones, we therefore conclude that the presented procedure can be a valuable tool in future experiments and studies on fertilization and hatching success in Twospot astyanax.     

中国图书馆电子资源联盟采购的实践与思考

[目的/意义]梳理国内图书馆电子资源联盟采购现状,剖析存在问题,提出改进建议。[方法/过程]结合不同类图书馆采购联盟的发展背景、用户需求及客观现实条件,阐述不同类图书馆联盟采购的发展概况,深入分析组织管理架构、采购流程及经费分摊方式等,总结特色亮点,剖析存在的短板或问题。借鉴国内外图书馆联盟采购典型案例和相关研究成果,结合国内图书馆在经费及平台方面的客观实际,分别从6方面提出对策与建议。[结果/结论]建立并完善相关运作机制;优化价格模式、拓展筹资渠道;综合内容、使用和服务等多维数据建立电子资源评价指标体系;深度整合联盟内部资源,构建统一信息交流平台建设;提高法律意识,捍卫长期保存与永久使用权;重视多方合作、灵活组建不同类型联盟、增强竞争实力等,是有效提升图书馆联盟采购效益的良策。