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Catches of whales show a historically cyclical pattern, with catches declining as stocks of the financially most attractive species fell, but expanding as substitute species were caught. Total combined catch peaked in the early 1960s and fell thereafter to the current regulated levels. While it is widely thought that international whaling agreements account for the current stable stock levels, economic analysis reveals that market forces leading to reduced catch were already in place well before the agreements took hold. To some extent, therefore, catches were destined to decline as whale products ceased to be commercially attractive on a large scale. Using econometric analysis, the paper shows the various forces at work: declining stocks, the rise of substitute products, internationally increasing environmentalism, and rising incomes. Of these forces, stock decreases, which resulted in high unit catch costs, and income growth, which reduced rather than increased demand, were the most important factors, with regulation following, rather than leading, catch changes.  相似文献   

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The common factors have a long history in the field of psychotherapy theory, research and practice. To understand the evidence supporting them as important therapeutic elements, the contextual model of psychotherapy is outlined. Then the evidence, primarily from meta‐analyses, is presented for particular common factors, including alliance, empathy, expectations, cultural adaptation, and therapist differences. Then the evidence for four factors related to specificity, including treatment differences, specific ingredients, adherence, and competence, is presented. The evidence supports the conclusion that the common factors are important for producing the benefits of psychotherapy.  相似文献   

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Microgravity or simulated microgravity induces acute and chronic cardiovascular responses, whose mechanism is pivotal for understanding of physiological adaptation and pathophysiological consequences. We investigated hemodynamic responses of conscious Wistar rats to 45? head-down tilt (HDT) for 7 days. Arterial blood pressure (BP) was recorded by telemetry. Heart rate (HR), spectral properties and the spontaneous baroreflex sensitivity (sBRS) were calculated. Head-up tilt (HUT) was applied for 2 h before and after HDT to assess the degree of any possible cardiovascular deconditioning. Horizontal control BP and HR were 112.5+/-2.8 mmHg and 344.7+/-10 bpm, respectively. HDT elicited an elevation in BP and HR by 8.3 % and 8.8 %, respectively, in less than 1 h. These elevations in BP and HR were maintained for 2 and 3 days, respectively, and then normalized. Heart rate variability was unchanged, while sBRS was permanently reduced from the beginning of HDT (1.01+/-0.08 vs. 0.74+/-0.05 ms/mmHg). HUT tests before and after HDT resulted in BP elevations (6.9 vs. 11.6 %) and sBRS reduction (0.44 vs. 0.37 ms/mmHg), respectively. The pressor response during the post-HDT HUT test was accompanied by tachycardia (13.7 %). In conclusion, chronic HDT does not lead to symptoms of cardiovascular deconditioning. However the depressed sBRS and tachycardic response seen during the post-HDT HUT test may indicate disturbances in cardiovascular control.  相似文献   

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P Joliot  A Joliot 《Biochemistry》1999,38(34):11130-11136
Electron transfer within PS I reaction centers has been analyzed in vivo in a mutant of Chlorella sorokiniana which lacks most of the PS II and of the peripheric antennae, using a new spectrophotometric technique with a time resolution of approximately 5 ns. Absorption changes associated with the oxidation of semiphylloquinone (acceptor A(1)(-)) have been characterized in the 371-545 nm spectral range. The oxidation of A(1)(-) and the reduction of an iron-sulfur cluster (F(X), F(A)F(B)) is monitored by an absorption decrease at 377 nm (semiphylloquinone absorption band) and by the decrease of two positive absorption bands around 480 and 515 nm, respectively, very likely associated with a local electrochromic shift induced by A(1)(-) on a carotenoid molecule localized in its vicinity. A(1)(-) undergoes a two-phase oxidation of about equal amplitude with half-times of approximately 18 and approximately 160 ns, respectively. Two hypotheses are proposed to interpret these data: (1) Photosystem I reaction centers are present under two conformational states which differ by the reoxidation rate of A(1)(-). (2) The two phylloquinones corresponding to the two branches of the PS I heterodimer are involved in the electron transfer. The similar amplitude of the two phases implies that the rates of electron transfer from P700 to each of the phylloquinones are about equal. The two different rate constants measured for A(1)(-) oxidation suggests some asymmetry in the relative position of the two phylloquinones with respect to F(X).  相似文献   

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Soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE) proteins have been at the fore-front of research on biological membrane fusion for some time. The subcellular localization of SNAREs and their ability to form the so-called SNARE complex may be integral to determining the specificity of intracellular fusion (the SNARE hypothesis) and/or serving as the minimal fusion machinery. Both the SNARE hypothesis and the idea of the minimal fusion machinery have been challenged by a number of experimental observations in various model systems, suggesting that SNAREs may have other functions. Considering recent advances in the SNARE literature, it appears that SNAREs may actually function as part of a complex fusion "machine." Their role in the machinery could be any one or a combination of roles, including establishing tight membrane contact, formation of a scaffolding on which to build the machine, binding of lipid surfaces, and many others. It is also possible that complexations other than the classic SNARE complex participate in membrane fusion.  相似文献   

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The recent inclusion of communities of planktonic algae and microbial crusts into the system of European vegetation types is critically discussed. It is argued that formal vegetation classification should be limited to plant taxa represented by macroscopic individuals within a plot, including all vascular plants, bryophytes, lichens, charophyta and macrophytic chlorophyta, rhodophyta or phaeophyta. In the interest of comparability and methodological stringency, all microscopic algae and all prokaryotes, including cyanobacteria, and the habitats dominated by such microorganisms (e.g. plankton, biofilms and crusts), should be excluded from vegetation classification.  相似文献   

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Psychosis is a heterogeneous psychiatric condition for which a multitude of risk and protective factors have been suggested. This umbrella review aimed to classify the strength of evidence for the associations between each factor and psychotic disorders whilst controlling for several biases. The Web of Knowledge database was searched to identify systematic reviews and meta‐analyses of observational studies which examined associations between socio‐demographic, parental, perinatal, later factors or antecedents and psychotic disorders, and which included a comparison group of healthy controls, published from 1965 to January 31, 2017. The literature search and data extraction followed PRISMA and MOOSE guidelines. The association between each factor and ICD or DSM diagnoses of non‐organic psychotic disorders was graded into convincing, highly suggestive, suggestive, weak, or non‐significant according to a standardized classification based on: number of psychotic cases, random‐effects p value, largest study 95% confidence interval, heterogeneity between studies, 95% prediction interval, small study effect, and excess significance bias. In order to assess evidence for temporality of association, we also conducted sensitivity analyses restricted to data from prospective studies. Fifty‐five meta‐analyses or systematic reviews were included in the umbrella review, corresponding to 683 individual studies and 170 putative risk or protective factors for psychotic disorders. Only the ultra‐high‐risk state for psychosis (odds ratio, OR=9.32, 95% CI: 4.91‐17.72) and Black‐Caribbean ethnicity in England (OR=4.87, 95% CI: 3.96‐6.00) showed convincing evidence of association. Six factors were highly suggestive (ethnic minority in low ethnic density area, second generation immigrants, trait anhedonia, premorbid IQ, minor physical anomalies, and olfactory identification ability), and nine were suggestive (urbanicity, ethnic minority in high ethnic density area, first generation immigrants, North‐African immigrants in Europe, winter/spring season of birth in Northern hemisphere, childhood social withdrawal, childhood trauma, Toxoplasma gondii IgG, and non‐right handedness). When only prospective studies were considered, the evidence was convincing for ultra‐high‐risk state and suggestive for urbanicity only. In summary, this umbrella review found several factors to be associated with psychotic disorders with different levels of evidence. These risk or protective factors represent a starting point for further etiopathological research and for the improvement of the prediction of psychosis.  相似文献   

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There is considerable ambiguity around the importance of demographic and socio-economic characteristics that catalyze pro-environmental behaviours. These factors are typically deemed responsible for environmental skepticism, such as the degree of trust in social institutions, fundamental views of the individuals (e.g., religiosity and political ideology), and competing priorities. In this context, the present study analyzed a comprehensive dataset of survey responses to discern the most reliable predictors of environmental attitudes of Canadians related to activism, lifestyle, household practices on air quality, waste disposal, energy and water conservation. To achieve this objective, we capitalize upon the wealth of publicly available data from surveys conducted by Statistics Canada's Households and the Environment Survey. Our analysis suggests that individuals with university-level education and higher income or families with children generally display pro-environmental behaviours. Political conservatism, as expressed by the percentage vote for the Progressive Conservative Party of Canada in a given area, appears to covary with some facets of the documented reluctance to embrace environmentally aligned behaviours (i.e., climate change issues), although we did not find a major “conservative-versus-liberal” divide about the broader spectrum of environmental issues. Our assessment of environmental attitudes in different Canadian provinces suggests an aptitude for more sustainable living in Ontario and British Columbia. Our analysis also provides evidence that the intent to support efforts that reduce emissions from burning fossil fuels or promote clean energy and technology – which has been overwhelmingly communicated in recent national polls – is not necessarily actualized. This established trend of Canadians failing to “walk the talk” and materialize their stated commitment with tangible participation into environmentally supportive behaviours could stem from barriers imposed at the household and societal levels. Notwithstanding the uncertainty regarding the importance of different socio-demographic factors in shaping our predisposition and behaviour towards environmental issues, the findings of our study offer a working model that could allow addressing the roots of environmental skepticism, promote societal trust, and revisit the role of ecopolitics in the social agenda.  相似文献   

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Plant Molecular Biology - The α-Amy1 and α-Amy2 genes of wheat produce distinct subsets of α-amylase isozymes which show different patterns of expression in wheat aleurone cells and...  相似文献   

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Ischemic preconditioning affords the most powerful protection to a heart submitted to a prolonged ischemia-reperfusion. During the past decade, a huge amount of work allowed to better understand the features of this protective effect as well as the molecular mechanisms. Ischemic preconditioning reduces infarct size and improves functional recovery; its effects on arrhythmias remain debated. Triggering of the protection involves cell surface receptors that activate pro-survival pathways including protein kinase C, PI3-kinase, possibly Akt and ERK1/2, whose downstream targets remain to be determined. Much attention has been recently focused on the role of mitochondrial K(+)ATP channels and the permeability transition pore that seem to play a major role in the progression toward irreversible cellular injury. Based on these experimental studies attempts have been made to transfer preconditioning from bench to bedside. Human experimental models of ischemic preconditioning have been set up, including cardiac surgery, coronary angioplasty or treadmill exercise, to perform pathophysiological studies. Yet, protecting the heart of CAD (coronary artery disease) patients requires a pharmacological approach. The IONA trial has been an example of the clinical utility of preconditioning. It helped to demonstrate that chronic administration of nicorandil, a K(+)ATP opener that mimics ischemic preconditioning in experimental preparations, improves the cardiovascular prognosis in CAD patients. Recent experimental studies appear further encouraging. It appears that "postconditioning" the heart (i.e. performing brief episodes of ischemia-reperfusion at the time of reperfusion) is as protective as preconditioning. In other words, a therapeutic intervention performed as late as at the time of reflow can still significantly limit infarct size. Further work is needed to determine whether this may be transferred to the clinical practice.  相似文献   

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Plicatamide is a modified octapeptide from the ascidian Styela plicata having the structure Phe-Phe-His-Leu-His-Phe-His-decarboxyDeltaDOPA (where decarboxyDeltaDOPA = decarboxy-(E)-alpha,beta-dehydro-3, 4-dihydroxyphenylalanine). Edman sequencing, tandem mass spectrometry, and proton NMR have been used to characterize 100 microg of the compound. Plicatamide represents an important link between two classes of biomolecules: the tunichromes which share an oxidatively decarboxylated C-terminus and higher molecular weight DOPA-polypeptides. The 8-residue sequence provides the first opportunity to investigate the biosynthetic origins of the tunichrome family by molecular biological techniques.  相似文献   

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Mammalian Prdm9 has been proposed to be a key determinant of the positioning of chromosome double-strand breaks during meiosis, a contributor to speciation processes, and the most rapidly evolving gene in human, and other animal, genomes. Prdm9 genes often exhibit substantial variation in their numbers of encoded zinc fingers (ZFs), not only between closely related species but also among individuals of a species. The near-identity of these ZF sequences appears to render them very unstable in copy number. The rare sequence differences, however, cluster within ZF sites that determine the DNA-binding specificity of PRDM9, and these substitutions are frequently positively selected. Here, possible drivers of the rapid evolution of Prdm9 are discussed, including selection for efficient pairing of homologous chromosomes or for recombination of deleterious linked alleles, and selection against depletion of recombination hotspots or against disease-associated genome rearrangement.  相似文献   

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What happens when data are fitted to the wrong equation?   总被引:2,自引:0,他引:2       下载免费PDF全文
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In most taxa, owners win fights when defending a territory against intruders. We calculated effect sizes for four factors that potentially contribute to an 'owner advantage'. We studied male fiddler crabs Uca mjoebergi, where owners won 92% of natural fights. Owners were not more successful because they were inherently better fighters (r=0.02). There was a small effect (r=0.18) of the owner's knowledge of territory quality (food availability) and a medium effect (r=0.29) of his having established relations with neighbours (duration of active tenure), but neither was statistically significant. There was, however, a significant effect due to the mechanical advantage the owner gained through access to the burrow during fights (r=0.48, p<0.005).  相似文献   

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