The biology and chemistry of fertilization

Fertilization of eggs by sperm, the means by which sexual reproduction takes place in nearly all multicellular organisms, is fundamental to the maintenance of life. In both mammals and nonmammals, the pathway that leads to fusion of an egg with a single sperm consists of many steps that occur in a compulsory order. These steps include species-specific cellular recognition, intracellular and intercellular membrane fusions, and enzyme-catalyzed modifications of cellular investments. In several instances, the molecular mechanisms that underlie these events during mammalian fertilization are beginning to be revealed.     

化学CAI课件制作实例

本从化学CAI课件的实例入手，详细介绍了课件的设计流程图、特点、制作中的体会和值得注意的问题。为更好的制作化学CAI教学课件提供借鉴。     

Supramolecular chemistry: receptors, catalysts, and carriers

Supramolecular chemistry is the study of the structures and functions of the supermolecules that result from binding substrates to molecular receptors. Macropolycyclic receptors and coreceptors have been designed that form cryptate inclusion complexes and display molecular recognition towards spherical, tetrahedral, and linear substrates of various kinds (metal cations, inorganic anions, and organic or biological cations or anions). Anion binding has led to the development of anion coordination chemistry. Metalloreceptors simultaneously bind organic molecules and metal ions; speleands combine polar and nonpolar binding subunits. Receptors bearing reactive functional groups may act as molecular reagents or catalysts, performing a chemical transformation on the bound substrates (by such reactions as hydrogen transfer, ester cleavage, and protoadenosinetriphosphatase and protokinase activities). Receptors fitted with lipophilic groups can operate as molecular carriers, translocating bound species through a membrane; this transport can be coupled to chemical potentials (proton and redox gradients).     

西湖底泥中酶活性与养分释放的关系

采用实验室厌氧恒温培育方法，分析了西湖底泥中酶的活性与有机质分解和养分释放的关系．结果表明，蛋白酶的活性与有机氮的分解和氮的释放相关性较好；磷酸酶活性与有机磷的分解有一定的关系，但磷的形态转化可能是制约磷释放的因素之一；纤维素酶的活性与有机碳的分解没有必然的联系，这可能与西湖底泥有机碳的组成中低含量的纤维素有关     

论长白山生态旅游与资源保护的关系

资源保护是建设长白山生态旅游的关键，本文阐述了生态旅游与环境、旅游开发与自然保护、旅游景区与保护区的功能区、旅游与科研四个方面关系。     

Gulf stream cold-core rings: their physics, chemistry, and biology

Cyclonic Gulf Stream rings are energetic eddies in the warm Sargasso Sea consisting of a ring of Gulf Stream water surrounding a core of cold Slope Water. Initially a ring core has the characteristics of the Slope Water; it is rich in plants, animals, and nutrients. As a ring decays the Slope Water properties of its core are gradually replaced by those of the Sargasso Sea, where standing crops of plants, animals, and nutrients generally are low. Although the decay rate suggests a rather long lifetime (2 to 4 years), the usual death of a ring comes when it rejoins the Gulf Stream after 6 to 12 months.     

河北主要土壤中重金属镉、铅形态与土壤酶活性的关系

采用网室盆栽试验，运用连续提取方法，研究了河北平原潮土、潮褐土2种土类上Cd、Pb的化学形态特征与4种土壤酶活性（脲酶、H2O2酶、转化酶、碱性磷酸酶）间的关系。结果表明：用Cd、Pb的化学形态研究重金属对土壤酶活性的影响明显好于总量Cd、Pb。交换态和有机结合态Cd、Pb对土壤酶活性的抑制作用贡献最大。在石灰性土壤中，把交换态Cd、有机结合态Cd和4种土壤酶活性共同作为评价土壤Cd污染程度的主要生化指标是可行的。     

植物根际土壤中铅形态与土壤酶活性的关系

采用根袋法进行盆栽试验,研究了黄壤中添加不同浓度的铅后,外源铅总量对4种土壤酶(脲酶、过氧化氢酶、中性磷酸酶、淀粉酶)活性的影响,以及黄壤中不同植物根际土壤中铅的化学形态特征及其与土壤酶活性的关系,结果表明,在0～3000mg·kg-1的铅浓度下,淀粉酶活性被抑制;过氧化氢酶活性总体趋势上被激活,在0～1000mg ·kg-1的铅浓度范围内,脲酶、中性磷酸酶活性被激活,大于1000mg·kg-1的铅浓度抑制其活性;用Pb的化学形态研究重金属对土壤酶活性的影响明显好于总量铅,碳酸盐结合态和铁锰氧化物结合态铅对淀粉酶活性有显著抑制作用,呈显著负相关(R=-0.998),因此可以把碳酸盐结合态和铁锰氧化物结合态铅与淀粉酶活性总体共同作用作为评价黄壤铅污染程度的主要生物学指标.     

The newest synthesis: understanding the interplay of evolutionary and ecological dynamics

The effect of ecological change on evolution has long been a focus of scientific research. The reverse--how evolutionary dynamics affect ecological traits--has only recently captured our attention, however, with the realization that evolution can occur over ecological time scales. This newly highlighted causal direction and the implied feedback loop--eco-evolutionary dynamics--is invigorating both ecologists and evolutionists and blurring the distinction between them. Despite some recent relevant studies, the importance of the evolution-to-ecology pathway across systems is still unknown. Only an extensive research effort involving multiple experimental approaches-particularly long-term field experiments--over a variety of ecological communities will provide the answer.     

传统民间美术与现代艺术设计的差异及融合

传统民间美术是我国民间文化的一个重要载体,集中表现出人民群众的审美情趣,对于许多艺术形式来讲是较为重要的创作基础,也是较为主要的创作根源。现代艺术设计是现代工业文明的必然产物,它与传统民间美术定然存在某种联系。因此,两者间存在差异性的同时,也具有较多共通之处,两者在差异性基础上存在有机融合,使得现代艺术设计具有更为特别的艺术魅力。