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281.
Richard L. Wallace J. S. Griffith Jr. D. M. Daley Patrick J. Connolly G. B. Beckham 《西北部美国博物学家》2011,44(2)
Cottus greenei, a potentially threatened species endemic to Idaho, was collected from 49 localities in 25 springs/streams in south central Idaho. Most localities were along the north bank of the Snake River in waters of the Thousand Springs formation, Gooding County. One population was found in a spring in the main Snake River. Another sculpin, Cottus bairdi, was collected with C. greenei at 23 locations in 16 springs/streams. Confusion concerning the type locality of Cottus greenei is discussed. 相似文献
282.
L. Vanderkelen J. M. Van Herreweghe K. G. A. Vanoirbeek G. Baggerman B. Myrnes P. J. Declerck I. W. Nilsen C. W. Michiels L. Callewaert 《Cellular and molecular life sciences : CMLS》2011,68(6):1053-1064
Lysozymes are antibacterial effectors of the innate immune system in animals that hydrolyze peptidoglycan. Bacteria have evolved
protective mechanisms that contribute to lysozyme tolerance such as the production of lysozyme inhibitors, but only inhibitors
of chicken (c-) and invertebrate (i-) type lysozyme have been identified. We here report the discovery of a novel Escherichia coli inhibitor specific for goose (g-) type lysozymes, which we designate PliG (periplasmic lysozyme inhibitor of g-type lysozyme).
Although it does not inhibit c- or i-type lysozymes, PliG shares a structural sequence motif with the previously described
PliI and MliC/PliC lysozyme inhibitor families, suggesting a common ancestry and mode of action. Deletion of pliG increased the sensitivity of E. coli to g-type lysozyme. The existence of inhibitors against all major types of animal lysozyme and their contribution to lysozyme
tolerance suggest that lysozyme inhibitors may play a role in bacterial interactions with animal hosts. 相似文献
283.
Along shore sediment transport that is driven by waves is generally assumed to smooth a coastline. This assumption is valid for small angles between the wave crest lines and the shore, as has been demonstrated in shoreline models. But when the angle between the waves and the shoreline is sufficiently large, small perturbations to a straight shoreline will grow. Here we use a numerical model to investigate the implications of this instability mechanism for large-scale morphology over long timescales. Our simulations show growth of coastline perturbations that interact with each other to produce large-scale features that resemble various kinds of natural landforms, including the capes and cuspate forelands observed along the Carolina coast of southeastern North America. Wind and wave data from this area support our hypothesis that such an instability mechanism could be responsible for the formation of shoreline features at spatial scales up to hundreds of kilometres and temporal scales up to millennia. 相似文献
284.
An inflammatory drug prospect. 总被引:2,自引:0,他引:2
285.
Tylobolus utahensis Chamberlin, the only representative of the genus occurring in the southwestern deserts, ranges from central Inyo County, California, to the western periphery of Kane County, Utah. This distribution roughly corresponds to the northern limit of the Mojave Desert ecosystem and is also shown by the millipede Piedolus utus Chamberlin. (Spirobolida: Atopetholidae) and the centipede Theatops posticus (Say) (Scolopendromorpha: Cryptopidae). Tylobolus fredericksoni Causey, ostensibly from Douglas County, Kansas, is designated "" nomen dubium "" and disregarded pending collection of fresh material; Narceus gordanus (Chamberlin) is deleted from South Carolina and Tennessee. Tyobolus uncigerus (Wood) occurs north of the Columbia River in Klickitat County, Washington, and Hiltonius thebanus Chamberlin is referable to Onychelus Cook in the family Atopetholidae. 相似文献
286.
The diatom flora of selected sites in the Animas River Watershed, San Juan County, Colorado, was studied. Eighty diatom taxa were identified from 10 sites: 8 sites on the Animas River and 1 site each on the Cement and Cascade tributaries. The sample diatom abundance was dominated by Achnanthidium minutissimum , Encyonema silesiacum , Aulacoseira distans , Hannaea arcus , and Diatoma mesodon . The presence of teratologic specimens of Fragilaria and Achnanthidium in the samples indicated the possibility of metals contamination. Diatom diversity was low and Lange-Bertalot pollution index scores indicated little organic pollution evidenced from diatom composition. There was evidence that diatom composition at the sites was differentially affected by pH and possibly by the concentrations of Zn alone or in combination with Cd, Cu, and Fe. 相似文献
287.
Streambed surveys were conducted along the upper Colorado River, Colorado, to describe the distributions of Claassenia sabulosa larvae in relation to current speed and to determine their diets. We also addressed diel feeding periodicity by sampling during both day and night. Claassenia sabulosa was more abundant in riffle habitats than in runs. A positive relationship existed between C. sabulosa abundance and stream current, with larval size increasing with current speed. Chironomidae, Baetidae, and Simulidae collectively accounted for 93% of the prey found in stonefly guts; however, these categories were not consumed equally by all C. sabulosa . Smaller C. sabulosa primarily ate chironomids, and larger individuals consumed more baetids. Only a slight difference existed in the percentage of empty guts between night- and day-collected stoneflies, and ranges of prey per gut at night were higher than those in the day, suggesting that these stoneflies may forage more intensively at night. 相似文献
288.
Richard B. Watson 《Systemic Practice and Action Research》2012,25(5):441-456
Soft systems methodology (SSM) is now 40?years old. Another decade has passed since Checkland??s thirty year retrospective on the methodology, published in 2000. It can now be described as an old methodology. But it has adapted and changed over the years and is still very much alive, although the days are long gone when it was mainly developed and practised by its founders at the University of Lancaster. Interestingly, considering that many applications of SSM over the years have been to information systems, it was developed before the age of personal computers and the Internet. The way SSM is viewed has changed over the years as it has been applied to various types of problem situation. Every use of SSM will potentially hold methodological lessons in addition to those about the situation of concern; these may include SSMs framework of ideas, processes and way of use. How is SSM going to change in the future? This will depend in part on the types of problem situation to which it is applied. This paper examines some problem situations associated with emerging technologies in the information age to which SSM has not yet been much applied. These include computer simulation and virtual reality, ubiquitous computing and the design of cities, Information Technology Service Management and the design of enterprise information architectures. Some of the different worldviews associated with these problem situations which could be explored using SSM are noted. 相似文献
289.
There is substantial evidence that the martian volatile inventory and climate have changed markedly throughout the planet's history. Clues come from areas as disparate as the history and properties of the deep interior, the composition of the crust and regolith, the morphology of the surface, composition of the present-day atmosphere, and the nature of the interactions between the upper atmosphere and the solar wind. We piece together the relevant observations into a coherent view of the evolution of the martian climate, focusing in particular on the observations that provide the strongest constraints. 相似文献
290.
A large fraction of the mass of the interstellar medium in our Galaxy is in the form of warm (103-104 K) and cool (50-100 K) atomic hydrogen (H i) gas. Cold (10-30 K) regions are thought to be dominated by dense clouds of molecular hydrogen. Cold H i is difficult to observe, and therefore our knowledge of its abundance and distribution in the interstellar medium is poor. The few known clouds of cold H i are much smaller in size and mass than typical molecular clouds. Here we report the discovery that the H i supershell GSH139-03-69 is very cold (10 K). It is about 2 kiloparsecs in size and as massive as the largest molecular complexes. The existence of such an immense structure composed of cold atomic hydrogen in the interstellar medium runs counter to the prevailing view that cold gas resides almost exclusively in clouds dominated by molecular hydrogen. 相似文献