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51.
The authors propose a simple version of the dot-plot scheme to be used in the case when the distances between sequence elements may take more than two values. The method is applicable, in particular, to the case of the sequences of large-length windows when the sets of distance values are continuous. The proposed technique is simple to implement and the results can produce readable maps for further analysis. To illustrate its potentialities, the method has been applied to the comparison of genomic sequences. The asymmetry in the number of direct and reverse tracks for the Homo sapience genome has been discovered.  相似文献   
52.
Several transportation networks in living systems are pulsatile branching trees. Due to the alternating character of the flow, these trees have to simultaneously satisfy two constraints: they have to deliver the carried products in a limited time and they must exhibit a satisfactory hydrodynamic performance in both directions of the flow. We report here that introducing a systematic branching asymmetry into a distribution tree improves performance and robustness, both at inhalation and exhalation. Moreover, optimizing the asymmetry level for both phases leads to a value very close to the one measured in the human lung.  相似文献   
53.
本文以上海为研究对象,分析了上海作为一个特大型城市所存在的产业结构与劳动力就业结构不对称的现象及其成因,认为这种现象是由传统的经济发展思路造成的。要改变现状,就必须改变经济发展的思路,变注重产业发展为注重城市区域经济的整体发展,而重新城市化是落实新发展思路,从而矫正经济结构的不对称的具体途径。文章最后认为从五个方面来看上海已经具备了重新城市化的条件,并且简要论述了上海重新城市化的前景。  相似文献   
54.
从工程建设监理制的实际出发,分析了工程建设监理制中存在的问题,并给出了解决问题的想法和建议。此外,还从信息经济学的角度,提出了业主、监理单位之间的委托-代理关系,提出了监理在消除业主、承包商之间信息不对称时的作用。  相似文献   
55.
滤波电路电容器联接方法对滤波效果影响的分析   总被引:1,自引:0,他引:1  
文章对滤波电路电容器的联接方法进行分析,得出联接方法对谐波效果有很大影响的结论。尤其是零序谐波,采用角型连接的电容器,没有滤波作用。目前大部分厂商采用角型连接电容器串接14.5%电抗器滤除3次谐波,其实作用甚微。提出了解决方法和需注意事项。  相似文献   
56.
Persistent organic pollutants (POPs) encompass an array of anthropogenic organic and elemental substances and their degradation and metabolic byproducts that have been found in the tissues of exposed animals, especially POPs categorized as organohalogen contaminants (OHCs). OHCs have been of concern in the circumpolar arctic for decades. For example, as a consequence of bioaccumulation and in some cases biomagnification of legacy (e.g., chlorinated PCBs, DDTs and CHLs) and emerging (e.g., brominated flame retardants (BFRs) and in particular polybrominated diphenyl ethers (PBDEs) and perfluorinated compounds (PFCs) including perfluorooctane sulfonate (PFOS) and perfluorooctanic acid (PFOA) found in Arctic biota and humans. Of high concern are the potential biological effects of these contaminants in exposed Arctic wildlife and fish. As concluded in the last review in 2004 for the Arctic Monitoring and Assessment Program (AMAP) on the effects of POPs in Arctic wildlife, prior to 1997, biological effects data were minimal and insufficient at any level of biological organization. The present review summarizes recent studies on biological effects in relation to OHC exposure, and attempts to assess known tissue/body compartment concentration data in the context of possible threshold levels of effects to evaluate the risks. This review concentrates mainly on post-2002, new OHC effects data in Arctic wildlife and fish, and is largely based on recently available effects data for populations of several top trophic level species, including seabirds (e.g., glaucous gull (Larus hyperboreus)), polar bears (Ursus maritimus), polar (Arctic) fox (Vulpes lagopus), and Arctic charr (Salvelinus alpinus), as well as semi-captive studies on sled dogs (Canis familiaris). Regardless, there remains a dearth of data on true contaminant exposure, cause-effect relationships with respect to these contaminant exposures in Arctic wildlife and fish. Indications of exposure effects are largely based on correlations between biomarker endpoints (e.g., biochemical processes related to the immune and endocrine system, pathological changes in tissues and reproduction and development) and tissue residue levels of OHCs (e.g., PCBs, DDTs, CHLs, PBDEs and in a few cases perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonates (PFSAs)). Some exceptions include semi-field studies on comparative contaminant effects of control and exposed cohorts of captive Greenland sled dogs, and performance studies mimicking environmentally relevant PCB concentrations in Arctic charr. Recent tissue concentrations in several arctic marine mammal species and populations exceed a general threshold level of concern of 1 part-per-million (ppm), but a clear evidence of a POP/OHC-related stress in these populations remains to be confirmed. There remains minimal evidence that OHCs are having widespread effects on the health of Arctic organisms, with the possible exception of East Greenland and Svalbard polar bears and Svalbard glaucous gulls. However, the true (if any real) effects of POPs in Arctic wildlife have to be put into the context of other environmental, ecological and physiological stressors (both anthropogenic and natural) that render an overall complex picture. For instance, seasonal changes in food intake and corresponding cycles of fattening and emaciation seen in Arctic animals can modify contaminant tissue distribution and toxicokinetics (contaminant deposition, metabolism and depuration). Also, other factors, including impact of climate change (seasonal ice and temperature changes, and connection to food web changes, nutrition, etc. in exposed biota), disease, species invasion and the connection to disease resistance will impact toxicant exposure. Overall, further research and better understanding of POP/OHC impact on animal performance in Arctic biota are recommended. Regardless, it could be argued that Arctic wildlife and fish at the highest potential risk of POP/OHC exposure and mediated effects are East Greenland, Svalbard and (West and South) Hudson Bay polar bears, Alaskan and Northern Norway killer whales, several species of gulls and other seabirds from the Svalbard area, Northern Norway, East Greenland, the Kara Sea and/or the Canadian central high Arctic, East Greenland ringed seal and a few populations of Arctic charr and Greenland shark.  相似文献   
57.
The goals of the current study were to investigate the stability of temperamental exuberance across infancy and toddlerhood and to examine the associations between exuberance and social–emotional outcomes in early childhood. The sample consisted of 291 4-month-olds followed at 9, 24, and 36 months and again at 5 years of age. Behavioral measures of exuberance were collected at 9, 24, and 36 months. At 36 months, frontal electroencephalogram (EEG) asymmetry was assessed. At 5 years, maternal reports of temperament and behavior problems were collected, as were observational measures of social behavior during an interaction with an unfamiliar peer in the laboratory. Latent profile analysis revealed a high, stable exuberance profile that was associated with greater ratings of 5-year externalizing behavior and surgency, as well as observed disruptive behavior and social competence with unfamiliar peers. These associations were particularly true for children who displayed left frontal EEG asymmetry. Multiple factors supported an approach bias for exuberant temperament but did not differentiate between adaptive and maladaptive social–emotional outcomes at 5 years of age. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
58.
The purpose of this study was to evaluate strain-controlled cyclic deformation behavior of an extruded Mg–3Nd–0.2Zn–0.5Zr (NZ30K) magnesium alloy. The microstructure of this alloy consisted of a bimodal microstructure with equiaxed recrystallized grains and unrecrystallized coarse grains along with a large number of smaller second-phase particles present inside the grains and larger particles along the grain boundaries alongside a characteristic precipitate free zone (PFZ). The average grain size was about approximately 5–7 μm. It was observed that unlike the higher RE-containing Mg–10Gd–3Y–0.5Zr (GW103K) magnesium alloy, the NZ30K alloy exhibited asymmetrical hysteresis loops in tension and compression in the fully reversed strain-control tests at a strain ratio of Rε = −1. This was mainly due to the presence of relatively stronger crystallographic texture, PFZ, and the resultant twinning–detwinning activities during cyclic deformation. While this alloy exhibited cyclic softening at lower strain amplitudes and cyclic hardening at higher strain amplitudes, it had an equivalent fatigue life to that of other extruded Mg alloys. Fatigue crack was observed to initiate from the specimen surface with some isolated facets of the cleavage-like planes near the initiation site. Crack propagation was basically characterized by serrated fatigue striations.  相似文献   
59.
随着时代的进步,信息化建设对社会产生了越来越重要的影响,但是其中的信息不对称问题往往被人忽视,对信息化建设产生了很大的影响。本文对信息不对称的概念、产生原因及因而产生的隐患做出了阐述,并且提出了如何解决信息对称问题的方法,对于提高技术水平,防止重复建设,避免信息孤岛有重要意义。  相似文献   
60.
Reports an error in "On the relationship between lateralized brain function and orienting asymmetries" by Christoph Teufel, Asif A. Ghazanfar and Julia Fischer (Behavioral Neuroscience, 2010[Aug], Vol 124[4], 437-445). In the article, we wrote that “the likelihood of obtaining at least one significant result at p n. The probability of obtaining at least one significant result is therefore 1 — (1— α)n. (The following abstract of the original article appeared in record 2010-16138-001.) Hemispheric specializations for language perception constitute one of the classic topic in cognitive neuroscience. Evidence has accumulated to suggest that lateralized acoustic processing is not restricted to humans but is also found in numerous animal species. One of the methods used to track such lateralization is the orienting-asymmetry paradigm, a simple, noninvasive means to study lateralization that has been applied to a range of different species ranging from harpy eagles to humans. Here we summarize and compare the results of studies employing the orienting-asymmetry paradigm, showing that these studies yield largely inconsistent results. We critically discuss the methodology's implicit assumptions and conclude that the empirical inconsistencies produced by the orienting-asymmetry paradigm, and the lack of sufficient evidence supporting the paradigm's underlying assumptions, warrant serious caution when interpreting results obtained by the method. Nontrivial interpretations of orienting-asymmetry results will require a much better understanding of how lateralized brain functions interact with overt behaviors. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
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