超声波在生物工程中的应用

研究发现在酶和细胞催化的生物反应过程中,较低强度的超声作用可提高酶的催化活性或加速细胞的代谢过程。本文主要简述超声波作用的物理机制并对其在生物工程中的应用前景进行讨论。     

秦岭川金丝猴下地活动的初步调查

川金丝猴(Ｒｈｉｎｏｐｉｔｈｅｃｕｓｒｏｘｅｌｌａｎａ)是以树栖为主的灵长类动物。近年来,人类在秦岭地区的森林砍伐对金丝猴的行为生态产生一定影响,我们就此问题对行进中的金丝猴下地行为和森林植被类型间的关系进行定量研究,以探讨森林砍伐是否为导致川金丝猴下地?..     

气候变化对雪豹全球潜在适生区分布的影响与评估

气候变化不仅是人类正在面临的挑战,也是野生动物需要应对的危机。雪豹(Panthera uncia)作为亚洲中部高原和山脉的旗舰种,它的生存和繁衍可以反映青藏高原等地区生态系统的健康状况。青藏高原等地区的气候变暖速度远快于全球平均水平,研究气候变化对雪豹的生境的影响对于高原物种的保护有重要意义。以雪豹为研究对象,采用第六次国际耦合模式比较计划(CMIP6)气候模式下四种共享社会经济路径(SSPs)对应的未来21世纪中期和21世纪末期的环境数据,并基于最大熵模型(MaxEnt),结合ENMTool、SDMTool、ArcGIS和R等工具对当前和未来全球不同发展模式引起的气候变化对雪豹适宜生境的影响进行了模拟预测和分析评估。研究发现：(1)影响雪豹分布的主要环境因素包括：两种气候变量(年平均气温和最冷月最低温度),两种地形变量(海拔和坡度)和一种水文变量(距离最近河流的距离)。(2)当前气候模式下雪豹的全球潜在适宜分布区的总面积约为1122.05万km²,其中低适生区面积为534.5万km²,中适生区面积为386.15万km²...     

浅山区乡镇社会-生态系统脆弱性演化与模拟——以北京平谷为例

浅山区乡镇社会-生态系统相比于平原区受地形环境等因素制约更为脆弱，在国土空间开发与保护中更需要权衡。使用显式空间脆弱性(SERV)模型，从暴露度、敏感性、适应能力3个维度构建评价体系评估平谷浅山区12个乡镇社会-生态系统脆弱性，并使用有序加权平均算法(OWA)模拟多种决策风险下脆弱性情景。研究表明：(1)平谷浅山区2007-2017年总体脆弱性呈现中度脆弱水平，局部呈现上升态势，10年间中等以上脆弱乡镇面积比重由73.09%上升到80.74%。空间上呈现"东南高，西北低"的格局。(2)处于高脆弱水平乡镇应进行严格控制，增加水土保持林面积等提高适应能力；同时注重低脆弱乡镇的高暴露风险源及时进行生态修复。(3)通过设定不同决策风险系数预测不同发展导向下区域系统脆弱性差异，在倾向于可持续发展导向下优先生态环境治理，在经济发展导向下应推动绿色基础设施建设。评价结果可满足不同决策思路下指导区域发展实践。     

Testing for the presence of magnetite in the upper-beak skin of homing pigeons

We carried out magnetic and nonmagnetic experiments on fresh, upper-beak skin tissue samples isolated from six pairs of homing pigeons to test whether the tissue contains magnetite particles. Results of (1) room-temperature isothermal remanent magnetization (IRM) acquisition and alternating field (AF) demagnetization, (2) low-temperature demagnetization of saturation IRM acquired at 5 K in a field of 5 tesla (T) (SIRM_{5 K}) after zero-field cooled (ZFC) and field cooled (FC) treatments, and (3) cycling of the saturation IRM acquired at 300 K in a field of 5 T (SIRM_{300 K}) between 5 and 300 K, indicate the presence of magnetite in the measured samples. A significant loss of SIRM_{5 K} below 20 K suggests the dominance of superparamagnetic (SPM) particles. The SIRM acquisition capacity of the female pigeon is stronger than that of the male pigeon in all four measured pairs, suggesting for the first time that the magnetite concentration is probably sex dependent. Light microscopic observation on the histological sections stained with Prussian Blue detected the presence of some tiny, dotted, dark-blue staining Fe³⁺ aggregates (size 1–4 μm) located directly beneath the subcutis within strands of connective tissue, nearby the rim of the regions full of red nuclei. The results of this study support the idea that homing pigeons may have a magnetite-based receptor, which potentially could be used for sensing the Earth’s magnetic field during navigation.     

Rhodopsin Molecular Evolution in Mammals Inhabiting Low Light Environments

The ecological radiation of mammals to inhabit a variety of light environments is largely attributed to adaptive changes in their visual systems. Visual capabilities are conferred by anatomical features of the eyes as well as the combination and properties of their constituent light sensitive pigments. To test whether evolutionary switches to different niches characterized by dim-light conditions coincided with molecular adaptation of the rod pigment rhodopsin, we sequenced the rhodopsin gene in twenty-two mammals including several bats and subterranean mole-rats. We compared these to thirty-seven published mammal rhodopsin sequences, from species with divergent visual ecologies, including nocturnal, diurnal and aquatic groups. All taxa possessed an intact functional rhodopsin; however, phylogenetic tree reconstruction recovered a gene tree in which rodents were not monophyletic, and also in which echolocating bats formed a monophyletic group. These conflicts with the species tree appear to stem from accelerated evolution in these groups, both of which inhabit low light environments. Selection tests confirmed divergent selection pressures in the clades of subterranean rodents and bats, as well as in marine mammals that live in turbid conditions. We also found evidence of divergent selection pressures among groups of bats with different sensory modalities based on vision and echolocation. Sliding window analyses suggest most changes occur in transmembrane domains, particularly obvious within the pinnipeds; however, we found no obvious pattern between photopic niche and predicted spectral sensitivity based on known critical amino acids. This study indicates that the independent evolution of rhodopsin vision in ecologically specialised groups of mammals has involved molecular evolution at the sequence level, though such changes might not mediate spectral sensitivity directly.     

Loss of cytoskeletal transport during egress critically attenuates ectromelia virus infection in vivo

Egress of wrapped virus (WV) to the cell periphery following vaccinia virus (VACV) replication is dependent on interactions with the microtubule motor complex kinesin-1 and is mediated by the viral envelope protein A36. Here we report that ectromelia virus (ECTV), a related orthopoxvirus and the causative agent of mousepox, encodes an A36 homologue (ECTV-Mos-142) that is highly conserved despite a large truncation at the C terminus. Deleting the ECTV A36R gene leads to a reduction in the number of extracellular viruses formed and to a reduced plaque size, consistent with a role in microtubule transport. We also observed a complete loss of virus-associated actin comets, another phenotype dependent on A36 expression during VACV infection. ECTV ΔA36R was severely attenuated when used to infect the normally susceptible BALB/c mouse strain. ECTV ΔA36R replication and spread from the draining lymph nodes to the liver and spleen were significantly reduced in BALB/c mice and in Rag-1-deficient mice, which lack T and B lymphocytes. The dramatic reduction in ECTV ΔA36R titers early during the course of infection was not associated with an augmented immune response. Taken together, these findings demonstrate the critical role that subcellular transport pathways play not only in orthopoxvirus infection in an in vitro context but also during orthopoxvirus pathogenesis in a natural host. Furthermore, despite the attenuation of the mutant virus, we found that infection nonetheless induced protective immunity in mice, suggesting that orthopoxvirus vectors with A36 deletions may be considered another safe vaccine alternative.     

Genetic source tracking of human plague cases in Inner Mongolia-Beijing, 2019

On 12 November 2019, one couple from the Sonid Left Qi (County) in the Inner Mongolia Autonomous Region was diagnosed with pneumonic plague in Beijing. The wife acquired the infection from her husband. Thereafter, two bubonic plague cases were identified in Inner Mongolia on November 16^th and 24^th. In this study, genome-wide single nucleotide polymorphism (SNP) analysis was used to identify the phylogenetic relationship of Yersinia pestis strains isolated in Inner Mongolia. Strains isolated from reservoirs in 2018 and 2019 in Inner Mongolia, together with the strain isolated from Patient C, were further clustered into 2.MED3m, and two novel lineages (2.MED3q, 2.MED3r) in the 2.MED3 population. According to the analysis of PCR-based molecular subtyping methods, such as the MLVA 14 scheme and seven SNP allele sequencing, Patients A/B and D were classified as 2.MED3m. In addition, strains from rodents living near the patients’ residences were clustered into the same lineage as patients. Such observations indicated that human plague cases originated from local reservoirs. Corresponding phylogenetic analysis also indicated that rodent plague strains in different areas in Inner Mongolia belong to different epizootics rather than being caused by spreading from the same epizootic in Meriones unguiculatus in 2019.     

Is There Any Overtrading in Stock Markets? The Moderating Role of Big Five Personality Traits and Gender in a Unilateral Trend Stock Market

Overtrading is a common anomaly among stock investors. This study examines the relationship between overtrading and investment returns and the impact of the Big Five traits and gender on overtrading in a unilateral trend stock market using a simulated stock investment system. The data were derived from a sample of undergraduates from six universities who performed in a simulated stock investment situation and had their personality traits measured by the Big Five Personality Questionnaire. The results indicate that: (1) Overtrading was significant in rising stock markets, but not significant in falling markets. (2) The degree of female investors who overtraded was significant in rising markets. (3) The degree of overtrading investors who were high in extroversion or agreeableness was significant in rising markets. The implications of these results for more effective investment strategies are discussed.