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121.
Paul W. Weber Laurens E. Howle Mark M. Murray Joseph M. Corless 《Biophysical journal》2011,100(3):525
When radiolabeled precursors and autoradiography are used to investigate turnover of protein components in photoreceptive cone outer segments (COSs), the labeled components—primarily visual pigment molecules (opsins)—are diffusely distributed along the COS. To further assess this COS labeling pattern, we derive a simplified mass-transfer model for quantifying the contributions of advective and diffusive mechanisms to the distribution of opsins within COSs of the frog retina. Two opsin-containing regions of the COS are evaluated: the core axial array of disks and the plasmalemma. Numerical solutions of the mass-transfer model indicate three distinct stages of system evolution. In the first stage, plasmalemma diffusion is dominant. In the second stage, the plasmalemma density reaches a metastable state and transfer between the plasmalemma and disk region occurs, which is followed by an increase in density that is qualitatively similar for both regions. The final stage consists of both regions slowly evolving to the steady-state solution. Our results indicate that autoradiographic and cognate approaches for tracking labeled opsins in the COS cannot be effective methodologies for assessing new disk formation at the base of the COS. 相似文献
122.
A Practicable Li/Na‐Ion Hybrid Full Battery Assembled by a High‐Voltage Cathode and Commercial Graphite Anode: Superior Energy Storage Performance and Working Mechanism 下载免费PDF全文
Jin‐Zhi Guo Yang Yang Dao‐Sheng Liu Xing‐Long Wu Bao‐Hua Hou Wei‐Lin Pang Ke‐Cheng Huang Jing‐Ping Zhang Zhong‐Min Su 《Liver Transplantation》2018,8(10)
With the rapidly growing demand for low‐cost and safe energy storage, the advanced battery concepts have triggered strong interests beyond the state‐of‐the‐art Li‐ion batteries (LIBs). Herein, a novel hybrid Li/Na‐ion full battery (HLNIB) composed of the high‐energy and lithium‐free Na3V2(PO4)2O2F (NVPOF) cathode and commercial graphite anode mesophase carbon micro beads is for the first time designed. The assembled HLNIBs exhibit two high working voltage at about 4.05 and 3.69 V with a specific capacity of 112.7 mA h g?1. Its energy density can reach up to 328 W h kg?1 calculated from the total mass of both cathode and anode materials. Moreover, the HLNIBs show outstanding high‐rate capability, long‐term cycle life, and excellent low‐temperature performance. In addition, the reaction kinetics and Li/Na‐insertion/extraction mechanism into/out NVPOF is preliminarily investigated by the galvanostatic intermittent titration technique and ex situ X‐ray diffraction. This work provides a new and profound direction to develop advanced hybrid batteries. 相似文献
123.
在人工气候室内比较研究了灰飞虱和褐飞虱在汕优63和秀水11上的种内和种间密度效应对其主要生物学参数的影响,结果表明两种稻飞虱均存在显著的种内竞争,主要表现为随着密度增加,若虫发育历期延长、若虫羽化率下降、雌成虫寿命缩短、每雌产卵量下降。种内密度效应与稻飞虱种类和寄主品种有显著互作关系,灰飞虱种内竞争较褐飞虱明显,二者在适宜寄主上种内竞争更为明显。同时,两种稻飞虱存在着显著的种间密度效应,主要表现为异种存在时的促进作用,即异种共存时若虫历期缩短、若虫羽化率提高、雌虫寿命延长、每雌产卵量增加。种间密度效应也与稻飞虱种类和寄主品种有显著互作关系,两种共存对灰飞虱的有利作用显著大于对褐飞虱的有利作用,在欠适宜寄主上种间互利效应更为明显。最后,本文对稻飞虱种内和种间密度效应的机制和进化意义进行了讨论。 相似文献
124.
Nonidentifiability of population size from capture-recapture data with heterogeneous detection probabilities 总被引:2,自引:0,他引:2
Link WA 《Biometrics》2003,59(4):1123-1130
Heterogeneity in detection probabilities has long been recognized as problematic in mark-recapture studies, and numerous models developed to accommodate its effects. Individual heterogeneity is especially problematic, in that reasonable alternative models may predict essentially identical observations from populations of substantially different sizes. Thus even with very large samples, the analyst will not be able to distinguish among reasonable models of heterogeneity, even though these yield quite distinct inferences about population size. The problem is illustrated with models for closed and open populations. 相似文献
125.
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127.
Implications of a revised United States American Indian nadir population and the pattern of decline leading to it are examined. Substituting the new nadir for that used by Dobyns (1966) lowers by several million his estimates of Indian population for the United States (and Canada) area. These estimates then become more compatible with ones currently being suggested by other scholars. The nineteenth century decline leading to this nadir is found to be remarkably linear. Assuming linearity in decline from initial European contact through the eighteenth century, an aboriginal population estimate of 1,845,183 for the United States area may be extrapolated, along with estimates for intervening years. The nineteenth century decline is then graphed with the data extrapolated to 1492. The resulting pattern of population decline is quite different from the ones suggested by Mooney (1928) and Dobyns (1966). 相似文献
128.
The anaerobic ammonium oxidation process is a new process for ammonia removal from wastewater. It is also a new microbial
physiology that was previously believed to be impossible. The identification of Candidatus Brocadia anammoxidans and its relatives as the responsible bacteria was only possible with the development of a new experimental
approach. That approach is the focus of this paper. The approach is a modernisation of the Winogradsky/Beyerinck strategy
of selective enrichment and is based on the introduction of the molecular toolbox and modern bioreactor engineering to microbial
ecology. It consists of five steps: (1) postulation of an ecological niche based on thermodynamic considerations and macro-ecological
field data; (2) engineering of this niche into a laboratory bioreactor for enrichment culture; (3) black-box physiological
characterisation of the enrichment culture as a whole; (4) phylogenetic characterisation of the enriched community using molecular
tools; (5) physical separation of the dominant members of the enrichment culture using gradient centrifugation and the identification
of the species of interest in accordance with Koch's postulates; (6) verification of the in situ importance of these species in the actual ecosystems. The power of this approach is illustrated with a case study: the identification
of the planctomycetes responsible for anaerobic ammonium oxidation. We argue that this was impossible using molecular ecology
or conventional ‘cultivation based techniques’ alone. We suggest that the approach might also be used for the microbiological
study of many interesting microbes such as anaerobic methane oxidisers.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
129.
H. GIBB 《Austral ecology》2012,37(7):789-799
Ecological restoration aims to re‐establish both biodiversity and ecological function in damaged ecosystems. Ants are important drivers of ecological functions and are early colonizers of restored ecosystems. Rates at which ants perform functions are thought to be fuelled by access to plant sugars. In revegetated farmland in south‐eastern Australia, I tested if ant activity on trees, which reflects use of arboreal sugars, follows a predictable trajectory of recovery towards a remnant‐like state. Additionally, I examined whether planting method alters this trajectory by comparing tube stock (TS), which results in low Eucalyptus densities, with direct seeding (DS), which results in high Eucalyptus densities. Replicate sites (n = 5) of young (planted between 1998 and 2001) and old (planted between 1989 and 1994) TS and DS revegetation, pastures and remnants were compared. Activity on trunks was significantly positively correlated with ant tending of Hemiptera in young and old revegetation. In DS plantings, activity and estimated liquid loads on Eucalyptus trees were low and rapidly approached that in remnants, while TS sites remained similar to high values observed in pastures with trees. Patterns for Acacia were less clear, reflecting consistent densities for this species between TS and DS. At the whole‐of‐field scale, planting methods did not differ. Importantly, although trajectories differed, neither TS nor DS sites approached the low activity or estimated liquid loads observed in remnants. Rates of ant use of arboreal sugars and associated sugar‐fuelled processes may thus take considerably longer to recover than the period covered by this study. This finding suggests planting method may affect the trajectory and outcome of revegetation for plant health, as well as sugar‐fuelled ecosystem functions performed by ants. 相似文献
130.
达乌尔黄鼠种群空间分布型研究及其应用 总被引:2,自引:0,他引:2
本文根据1987年在内蒙古东北部低山丘陵区和平原区草原的调查资料,应用频数分布比较法研究了达乌尔黄鼠的空间分布型。结果表明:在抽样单位(样方)大小为1公项(1OO米×100米)时,4个样地内达乌尔黄鼠交尾期和幼鼠分居期的空间分布型均属poisson分布(随机分布)。环境与密度制约因素的影响不明显。并经回归分析得到:种群密度(m)与零样方频率(Po)和有鼠样方频率(Px )的曲线关系分别为m=4.5451-0.96721nPo和m=4.5451-0.96721n(1-Px)。经X2检验与poisson分布理论曲线基本一致(x2《x2 0.05,P>0.05)。为达乌尔黄鼠种群密度估计提供了理论依据. 相似文献