Disappearing Arctic lakes

Historical archived satellite images were compared with contemporary satellite data to track ongoing changes in more than 10,000 large lakes in rapidly warming Siberia. A widespread decline in lake abundance and area has occurred since 1973, despite slight precipitation increases to the region. The spatial pattern of lake disappearance suggests (i) that thaw and "breaching" of permafrost is driving the observed losses, by enabling rapid lake draining into the subsurface; and (ii) a conceptual model in which high-latitude warming of permafrost triggers an initial but transitory phase of lake and wetland expansion, followed by their widespread disappearance.     

Ecology. Can science rescue salmon?

At a press conference on 27 July, the National Marine Fisheries Service (NMFS) released a long-awaited plan to save the Columbia River's endangered salmon by restoring fish habitat, overhauling hatcheries, limiting harvest, and improving river flow. What the plan did not do, however, was call for immediate breaching of four dams on the Snake River, the Columbia's major tributary--an option that has been the subject of a nationwide environmental crusade. The NMFS will hold that option in abeyance while it sees whether the less drastic measures will do the trick. Responses from both sides were immediate and outraged.     

浅析东北地区砼板大坝护坡损害的预防

本文着重论述了我国东北地区如何预防砼板大坝护坡损害的方法。通过增加坡长、改善土持和坝面结构、重点加固等措施，可有铲地减少砼板的损害，延长大坝的使用寿命。     

促乳中草药对泌乳大鼠内分泌功能的影响

试验主要目的是探讨促乳中草药对泌乳母鼠内分泌功能的影响.选用妊娠18d大鼠96只,分成4组,每组24只.对照组饲喂基础饲粮,试验组分别在基础饲粮的基础上添加1％中草药(分别为王不留行、黄芪、益母草).母鼠分娩后当日将每窝仔鼠一律调整为8只.在3,11,22日龄屠宰母鼠取血清测定各激素水平.结果表明,与对照组相比,分别添...     

坝地淤积物干容重分布规律及其在层泥沙还原中的应用

针对淤地坝减水减沙效益计算中以1.35 g/cm3作为转换值求层泥沙淤积量时存在较大差异的问题,选取典型坝挖取剖面进行剖面分析,并提取每层淤积物的土样进行土样干容重测定,分析了典型坝坝地淤积物的干容重分布情况。结果表明,对同一座典型坝,其坝地淤积物的干容重值并不是沿深度方向保持不变,而是沿纵向有一定的波动趋势,但波动幅度不大;对于淤积程度相似的典型坝,其干容重值接近,干容重变化幅度类似;以实测每层淤积物干容重还原层泥沙淤积量,可以较精确地对应层淤积量与次侵蚀性降雨,以此对淤积过程机理进行分析将更加科学合理。     

土石坝老化病害评价的量化分析法

土石坝由于受自然和人为因素的破坏，许多大坝都程度不同的存在裂缝、渗漏、滑坡、护坡破坏等隐患，成为病险库坝。准确、及时地诊断出土石坝的隐患和病害，及时采取处理和加固措施，对土石坝安全具有重大意义。本文在调查分析的基础上，依据土石坝监测资料，研究建立了土石坝老化病害程度评价的指标，应用多因素分析法对土石坝老化病害进行量化评价分级，从而为准确地评价土石坝老化程度，及时采取相应的预防、维修、加固、改造措施提供了科学依据。     

The effect of the prepartum diet of the cow on the vitamin A reserves of her newborn offspring

Feeding vitamin A at the rate of a million U.S.P. units daily to individual dairy cows in the latter stages of gestation augmented significantly the vitamin A concentration in the blood and the livers of their newborn calves, but pasture grazing, providing an abundance of carotene in the prepartum diet of the dams, failed to effect an increase over that observed in calves from dams restricted to a standard winter ration. The explanation for these divergent results is obscure, but it is suggested that the placental membrane may be more permeable to the ester form of vitamin A than to the alcohol form. This high initial vitamin A reserve in the newborn calf should have practical value in the maintenance of its postnatal health.     

The Release 5.1 annotation of Drosophila melanogaster heterochromatin

The repetitive DNA that constitutes most of the heterochromatic regions of metazoan genomes has hindered the comprehensive analysis of gene content and other functions. We have generated a detailed computational and manual annotation of 24 megabases of heterochromatic sequence in the Release 5 Drosophila melanogaster genome sequence. The heterochromatin contains a minimum of 230 to 254 protein-coding genes, which are conserved in other Drosophilids and more diverged species, as well as 32 pseudogenes and 13 noncoding RNAs. Improved methods revealed that more than 77% of this heterochromatin sequence, including introns and intergenic regions, is composed of fragmented and nested transposable elements and other repeated DNAs. Drosophila heterochromatin contains "islands" of highly conserved genes embedded in these "oceans" of complex repeats, which may require special expression and splicing mechanisms.     

Fragmentation and flow regulation of the world's large river systems

A global overview of dam-based impacts on large river systems shows that over half (172 out of 292) are affected by dams, including the eight most biogeographically diverse. Dam-impacted catchments experience higher irrigation pressure and about 25 times more economic activity per unit of water than do unaffected catchments. In view of projected changes in climate and water resource use, these findings can be used to identify ecological risks associated with further impacts on large river systems.     

我国橡胶树育种面临的问题与对策

结合橡胶树育种特点和我国的实际情况,分析了橡胶树育种中育种材料改良创新、育种手段、突破性杂交种数量、品种抗逆性、品种更新换代等方面出现的问题,提出了相应的对策。     

动物杂交试验设计研究——配测方式和种群组合

因为试验设计对于杂交试验是否科学有效极为关键,所以本文特对它的两大主要问题做了深入研究。其一、配测方式问题。即种畜如何配种、后代如何抽测问题。我们根据客观情况共提出了八种方式。它们要求种畜必须随机地抽自于其所在的亲本种群。在此前提之下,各种方式可以分别表示为：A型（1×11）、B型（1×1n）、C型（m×11）、D型（m×1n）、E型（1×p1）、F型（1×pn）、G型（m×p1）、H型（m×pn）。在此,括号的第一项是每头种用公畜所配的母畜数、等于该公畜所配的每一母本种群的母畜数乘以母本种群数,第二项是每头母畜所产后代被抽测的个体数,m、n都大于1、p为母本种群总数。其二、种群组合问题。即父本种群、母本种群之间如何杂交问题。对此,我们归纳和提出了六类方法,具体为两个组合、两纯一杂、母本唯一、经纬杂交、正反循环和完全双列。这六类种群间的组合方法同八种配测方式相结合可以形成四十余种设计方案。这些方案各有各的功能,但是都不外乎两种：一为效应估计,二为各种决定系数估测。其中后者是新定义的,它们对于亲本种群选择、选配和种畜选择、选配也都有着一定的指导意义。在实际应用中,应采用哪种方案,可视具体情况而定。     

红中牌生物有机肥在棉花上的应用效果

田间试验结果表明,棉花施用红中牌生物有机肥比对照处理(当地施肥模式)的籽棉产量明显增加,增产幅度为2.32%~10.43%,纯收入增长率为6.73%~24.59%。在施用红中肥的3个处理中,单纯施红中肥的方式比施“红中肥+化肥”的方式效果更好。     

A compound ovary with open carpels in winteraceae (magnoliales): evolutionary implications

"Bubbia" perrieri, a primitive angiosperm collected once in 1909 in northwestern Madagascar, differs from all other members of its genus and family (Winteraceae) in its bicarpellate, unilocular ovary. Moreover, its inflorescences are terminal, and its development is partially sympodial. It therefore represents the survivor of a previously undetected evolutionary line that should be accorded at least subfamilial status. If so, Winteraceae might, more likely than previously, be considered as allied to Canellaceae, a group of primitive angiosperms that has an ovary of "Bubbia" perrieri type and is specialized in some other respects.     

密云水库上游河流硝态氮含量空间分布格局

为了揭示密云水库上游河流硝态氮含量的空间分布规律,探讨其主要的影响因素。笔者对密云水库上游河流进行了全流域的水样采集,调查和收集了有关人类活动的数据（如人口、土地利用、化肥施用量等）,利用流动注射分析仪测定了河水硝态氮含量。结果表明：密云水库上游东部的潮河水系的硝态氮含量高于西部的白河水系;河流硝态氮含量的空间分布格局与人类活动密切相关,表现在途径畜禽养殖场、居民点和农田时往往升高,而经过水坝、峡谷、森林时又常常降低,其排列次序依次是：畜禽养殖场>居民点>农田>水坝>峡谷>森林。河流硝态氮含量与人口密度、耕地比例和化肥氮施用量呈线性正相关关系。     

土壤重金属污染背景下的任豆修复试验

为寻找适合矿业尾矿坝人工生态恢复的植物,以广西南丹长坡矿堆存50a之久的尾矿坝为背景,通过盆栽模拟,运用室内土培和水培两种试验方法,研究了不同矿土比例(尾矿样与泥土比例分别为5∶0、4∶1、3∶2、2∶3、1∶4、0∶5)以及不同浓度(0、2.5、5、10、25、50、100、150、200、250mg·L-1)Pb2+、Cu2+、Zn2+在任豆苗体内的吸收、积累和分布的动态变化规律。结果表明,任豆对Pb、Cu、Zn都具有一定的吸收能力,任豆幼苗可以在一定的重金属胁迫环境下存活,任豆对重金属Pb的耐性最大,在高浓度下依然可以存活。任豆对不同类型的重金属的吸收及转运能力存在较大差异,从任豆对Pb、Cu、Zn的转运能力来看,任豆并非这3种重金属的超累积植物。试验表明,任豆在矿业尾矿坝的人工生态恢复(植物修复)中有一定的应用价值,但能否大规模采用任豆作为尾矿坝的生态修复物种,尚需进一步研究验证。     

Reticulocyte protein synthesis: response of ribosome fractions to polyuridylic acid

Reticulocyte ribosomes with sedimentation coefficients greater than 100S ("heavy" ribosomes) appear to be considerably more active in hemoglobin synthesis than are 78S ribosomes. When assayed for the ability to synthesize polyphenylalanine in the presence of polyuridylic acid, the 78S ribosomes and "heavy" ribosomes have similar activities. Polyuridylic acid inhibits incorporation by "heavy" ribosomes of amino acids other than phenylalanine.     

Health and safety risk analyses: information for better decisions

Knowing the nature and magnitude of health and safety risks is helpful in setting priorities as well as in making decisions about pursuing recreational activities, foods, jobs, and other aspects of everyday living. "Risk-risk" situations require a choice among risky alternatives. "How safe" situations involve a more general choice as to how much of other desired activities to sacrifice for increased safety. "How safe" situations are inherently more difficult to manage, because they are subject to fuzzy thinking and rhetoric. The large uncertainties of current estimates must be conveyed explicitly to arrive at sensible decisions.     

黄土丘陵第Ⅲ副区典型流域水沙演变过程及其驱动因素分析

流域水沙演变过程是构建区域水土流失模型及评价水土保持措施效益的基础。为探讨气候与下垫面变化对流域水沙变化的影响,以黄土丘陵沟壑区第Ⅲ副区罗玉沟流域为例,采用水文要素累积距平、Mann-Kendall趋势性检验和双累积曲线等方法,分析了1986—2010年间流域水沙关系演变过程及驱动因素,并定量分析了驱动因素的影响。结果表明:1)流域径流量在1993年发生突变,其中1994—2010年(后期)较1986—1993年(前期)不同降水水平年的径流量和输沙量减少率大多超过50%;2)土地利用结构优化可改变流域水沙过程和水沙量,而沟道淤地坝工程的运行改变了水沙搭配关系,使流域单位径流输沙量显著降低;3)降水和土地利用变化对流域径流减少贡献率分别为18.48%和81.52%;降水和土地利用变化对泥沙减少贡献率则分别为27.15%和72.85%。      

堤坝白蚁防治方法比较研究

我国堤坝白蚁防治,提出和使用过多种方法,该文对其中的５种方法加以比较,结果认为要彻底消灭堤坝白蚁,目前最有效的应是“三环节,八程序”的新技术。     

木材过坝方式选择的初步探讨

具有悠久历史、经济有效的木材水运,正面临着产量下降、生产萎缩的严重局面,木材水运事业能否存在和发展,将取决于降低木材流送损失和选择经济合理的过坝方式。本文总结国内部分木材过坝设施的使用情况,从基建投资、过坝成本、使用效果、流送工艺、年过坝量等方面、初步探讨如何选择木材过坝方式。