Allometric scaling of resource acquisition by ruminants in dynamic and heterogeneous environments

We present a mechanistic formulation of the intake response of ruminants to vegetation biomass based solely on physiological and morphological parameters that scale allometrically with the animal's body mass. The model is applied to describe herbivore-vegetation interactions in dynamic and heterogeneous landscapes with low quality but abundant “tall grass” and high quality but sparsely available “short grass”, under two conditions: “uncoupled” (such that the effect of food intake on vegetation biomass can be neglected), or “coupled” (such that the vegetation biomass is determined by herbivore feeding). The results show that under uncoupled conditions, the minimum acceptance (proportion of vegetation consumed by the herbivore) at which the herbivore can leave its current patch without reducing its intake rate is when it has depleted the current patch by the energetic cost required to travel to another patch. The maximum acceptance at which the herbivore should leave its patch is when it has depleted the current patch by the cumulative energetic cost of traveling, handling, cropping, and digesting. Under coupled conditions, the optimal acceptance equals half the relative growth rate of the vegetation. Analytical solutions are obtained for equilibrium values for utilization of the vegetation, and for the densities of vegetation and ruminants, expressed in physiological and morphological herbivore parameters.     

氯酚与乙酰胆碱酯酶相互作用的光谱研究

采用荧光光谱法和紫外-可见光谱法研究了2,4,6-三氯酚(2,4,6-TCP)及五氯酚(PCP)与乙酰胆碱酯酶(AChE)的相互作用,获得了相互作用的Stern-Volmer猝灭常数、结合常数、热力学参数和作用距离.结果表明, 2,4,6-TCP及PCP均可以使AChE内源荧光有规律地猝灭,温度小于303K时,其猝灭机制为静态猝灭. 2,4,6-TCP及PCP与AChE的结合过程是受熵驱动的自发过程,作用力为典型的疏水作用力. 2,4,6-TCP及PCP与AChE分子中酪氨酸残基的作用距离分别为1.91,2.00nm, 2,4,6-TCP及PCP与AChE分子的结合常数为104~105L/mol,表明2种氯酚与AChE之间发生了非辐射能量转移,两者形成了稳定的复合物.2,4,6-TCP与AChE的结合作用比PCP与AChE的结合作用强,氯酚分子向AChE分子疏水空腔的结合过程是疏水性效应和空间位阻效应彼此竞争的结果.     

电化学方法研究小分子与核酸相互作用的进展(Recent Electrochemical Investigation on the Interaction of Small Molecules with Nucleic Acids)

研究小分子与核酸的相互作用,对了解分子对DNA体内复制和转录的影响、探索疾病的发病机理和寻找新型药物设计等具有重要意义.电化学方法是一种重要的研究小分子与核酸相互作用的方法,而这方面的综述较少.论文首先论述了小分子与核酸相互作用的结合方式,并对采用电化学方法考察无机金属离子、金属配合物、有机药物分子、有机环境污染物与DNA相互作用的研究进展进行了归纳和评述,其中对有机小分子与核酸的相互作用进行了较详细介绍.最后,对该领域研究趋势进行了讨论.     

Tolerating castration by hiding flowers in plain sight

A key challenge in the study of inter-specific cooperation, or mutualisms, is to understand the mechanisms that prevent cheating. However, many mutualisms are still invaded by parasites, and we propose that plant ‘tolerance strategies’, which allow an individual to re-grow and/or reproduce after damage, might have evolved to recover some of the fitness lost to parasitism. We focus on the ant plant Cordia nodosa and its protecting ant symbionts Allomerus octoarticulatus and Azteca spp. Allomerus is a castration parasite, destroying host flowers. However, some flowers are produced on new branch shoots, where they escape castration. Here, we ask whether C. nodosa tolerates castration by directing floral growth to new shoots. We find that C. nodosa produces four times more floral buds on the new shoots of Allomerus-inhabited plants, compared to Azteca-inhabited plants. Additionally, on Allomerus-inhabited plants, the production of floral buds is three times greater on new than on mature shoots, and more floral buds are grown on plants with new shoots than on those without. We conclude therefore that C. nodosa tolerates castration by re-allocating floral resources to new shoots. We also test whether tolerance exploits behavioural differences between the brood-tending ‘nurse’ ant worker caste, which is active on mature shoots, and the new shoot-protecting ‘patroller’ caste. Behavioural assay experiments reveal that nurse ants are strongly attracted to extracts of flowers, whereas patrollers are not, suggesting that nurses are the primary castrating caste. Thus, producing flowers on new shoots avoids the castrating caste. We finish by proposing that tolerance strategies can promote the evolution and maintenance of mutualism.     

虚拟现实技术及其在环境科学中的应用

本文简要介绍了虚拟现实的基本概念和基本特征,重点探讨虚拟现实技术在环境科学领域的应用前景,并结合实例,论述了虚拟现实技术在环境管理、水环境和水资源、大气环境和预报、环境科学研究和教育等方面的应用。     

水岩化学作用对斜坡水文地质及滑坡的影响

在温湿气候区，水岩化学作用对岩质斜坡的水文地质演化及失稳一夷平进程具有重要的控制作用。从地表到新鲜岩体，随着水岩化学作用程度的逐渐减弱，斜坡剖面可依次划分为土层、腐岩带和风化岩带，各带之间多是渐变过渡的。土层多由枯枝落叶层和土壤层组成，有时底部含有残坡积物；腐岩是由岩浆岩、沉积岩或变质岩经等容风化形成的风化软岩；风化岩带是腐岩带的前身，其特征是含有较高数量的核心石。斜坡垂向分带主要是地下水引起的，而这种分带反过来又会强烈影响地下水自身的埋藏与分布。土层可贮存上层滞水，风化岩带则可赋存潜水或承压水。上层滞水是浅层滑坡的主要控制因素。由于形成条件宽松，但规模不大，上层滞水控制的滑坡灾害多具群发性特点，同时，由于其含水介质为松散土体，失稳含水层很容易转化为泥石流。降雨期间，风化岩带内潜水水位上升甚至承压，导致岩体抗剪强度降低并诱发深层滑坡。     

Anaerobic benzene biodegradation by a pure bacterial culture of Bacillus cereus under nitrate reducing conditions

A pure culture using benzene as sole carbon and energy sources was isolated by screening procedure from gasoline contaminated soil. The analysis of the 16S rDNA gene sequence, morphological and physiological characteristics showed that the isolated strain was a member of genus Bacillus cereus. The biodegradation performance of benzene by B. cereus was evaluated, and the results showed that benzene could be e ciently biodegraded when the initial benzene concentration was below 150 mg/L. The metabolites of anaerobic nitrate-dependent benzene oxidation by strain B. cereus were identified as phenol and benzoate. The results of substrate interaction between binary combinations for benzene, phenol and benzoate showed that the simultaneous presence of benzene stimulated the degradation of benzoate, whereas the addition of benzene inhibited the degradation of phenol. Benzene degradation by B. cereus was enhanced by the addition of phenol and benzoate, the enhanced e ects were more pronounced at higher concentration. To our knowledge, this is the first report that the isolated bacterial culture of B. cereus can e ciently degraded benzene under nitrate reducing conditions.     

水热条件与土壤性质对农田土壤硝化作用的影响

水热条件、土壤性质和耕作管理影响了土壤的硝化作用从而影响农田氮素循环和平衡.本试验选择中国东部3个气候带上的主要农田土壤：中温带黑龙江海伦的黑土、暖温带河南封丘的潮土和中亚热带江西鹰潭的红壤,在上述3个地点的生态试验站建立土壤置换试验,对比研究不同水热条件和土壤类型对玉米单作系统中土壤硝化作用的交互影响.2006～2007年的试验结果表明,在玉米抽雄期,从海伦到鹰潭（月均温由22.3℃上升到26.8℃,月降水由100.8 mm增加到199.6 mm）,3种土壤的硝化作用强度均随着月均温和月降水的增加而下降,黑土、潮土和红壤分别下降了64.2％～67.2%、 52.1%～52.5%和41.7%～75.2%,土壤的硝化作用强度与气温（r＝－0.354,p<0.01）和降水（r＝－0.290,p<0.01）均呈极显著负相关.土壤类型也显著影响了土壤硝化细菌的数量和硝化强度,硝化细菌数和硝化强度的大小顺序为：潮土> 黑土> 红壤.土壤pH对土壤硝化强度有显著影响,其相关系数r=0.551（p<0.01）.总体上,在玉米抽雄期,区域水热状况及土壤类型、施肥均影响了土壤的硝化强度,水热×土壤类型、水热×施肥、土壤类型×施肥、水热×土壤类型×施肥等对硝化强度有着极显著的交互作用.     

水稻秸秆生物碳对重金属Pb2+的吸附作用及影响因素

以农业废弃物水稻秸秆为原料,采用限氧裂解法制备了不同温度(350、500和700℃)下的秸秆生物碳(RC350、RC500和RC700),研究了生物碳对Pb2+的吸附性能、作用机制及影响因素,为准确预测生物碳还田固碳对土壤中重金属迁移行为的影响提供理论参考.结果表明,生物碳对Pb2+的吸附行为符合准一级动力学方程,Pb2+在RC350、RC500、RC700上的吸附速率分别为0.167h-1、0.154h-1、0.388h-1;其等温吸附曲线符合Langmuir方程,最大吸附量分别为65.3、85.7和76.3mg·g-1,是原秸秆生物质RC100的5～6倍、活性炭AC的2～3倍.生物碳单位面积上的有效吸附点位比AC高约10倍.经酸化去除表面矿物成分后,RC350和RC700对Pb2+的吸附能力急剧下降,其最大吸附量、吸附亲和力与AC相近;红外光谱分析表明,去灰分后生物碳上有机碳官能团并无明显减少,而无机矿物(如SiO2)含量显著降低.生物碳中的有机碳组分和无机矿物组分对其吸附Pb2+均有重要贡献,其中无机矿物组分的吸附量及亲和力均大于有机碳组分.     

利用等效水力传导系数在地下水与地表水交互影响模拟中的应用

在滨海地区的环境管理工作中,地表水—地下水交互影响的重要性日益凸显。一方面在湿地系统的研究中,交互影响对地下水系统有着巨大的影响;另一方面,在河流——地下水系统中,大尺度管理模型的建立也是一个难题。因此,将等效水力传导系数的概念引入环境管理之中以解决这些问题。等效水力传导系数的推导过程是基于明渠流曼宁公式建立的,完成地表水系统与地下水系统的统一。最后,以抽水井管理为例,对该方法进行了演示。