共查询到20条相似文献,搜索用时 15 毫秒
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Yu. P. Raizer 《Plasma Physics Reports》2011,37(3):276-277
A new voluminous book on gas-discharge physics is reviewed. It is emphasized that the authors consistently follow a nontraditional approach based on the electron distribution function with allowance for its nonlocal character. This opens new, sometimes unexpected, issues of the well-known phenomena, which is illustrated by the reviewer by using the positive column of a low-pressure glow discharge as an example. 相似文献
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It seems self-evident that changes in the cellular synaptic function of the brain must underlie the formation and storage of cognitive memories. Because it has been identified as a brain area important in the formation of memory, the hippocampus has been a focus in the study of such synaptic changes. An activity-induced increase in hippocampal synaptic efficacy, known as long-term potentiation (LTP), has been widely studied as a potential substrate for memory. This paper briefly reviews some of the significant progress that has been made in understanding the cellular mechanisms that underlie LTP, including recent experiments dealing with its synaptic locus, or the question of whether the mechanism regulating LTP is pre- or postsynaptic. 相似文献
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J. P. Fonseca A. Levy R. Henriques J. C. Costa C. Neto J. Robalo 《Plant biosystems》2016,150(4):787-798
In this paper, we analyzed the phylogeny of the section Bulbocodii (genus Narcissus; Amarillydaceae) using the matK and trnL-F fragments of cpDNA in order to review the validity of the recognized taxa. Our results indicate that Narcissus obesus should be considered a valid species, and that N. blancoi is a distinct taxon. In addition, seven previously recognized species, N. juressianus, N. subnivalis, N. graellsii, N. conspicuus, N. citrinus, N. nivalis, and N. quintanilhae, should be assigned to an infraspecific rank under N. bulbocodium, as they are not valid species. In addition, we analyzed the distribution of the three morphological characters widely used in the systematics of this section and found that their variation does not agree with the phylogenetic results, rendering these characters limited taxonomical utility. This result suggests that the section Bulbocodii shows high morphological lability, which can explain the proliferation of nominal species. 相似文献
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In this paper cremated human remains from an urn field dating from the final phase of the Bronze age (Guidonia, Rome, Central
Italy) were studied. The aim of this study was to identify the minimal number of individuals for grave and cremation patterns.
The results show as the ways in which the cremations were carried out were archaic in all the elements that made them up. 相似文献
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The nucleotide dependence of PKC priming phosphorylations has provided compelling evidence for an ATP-induced conformational change to the kinase domain. This has various implications for the manner in which kinase inactive dominant negative PKC mutants work and also predicts that those inactivating mutations that do not lead to loss of priming may provide a more selective route to dominant negative mutants. It might be argued that this is also the case for other kinases and that caution should be employed in considering the dominant properties of the lysine mutant forms. In fact this pattern of behaviour is shared to some extent, with very clear examples of nucleotide pocket directed inhibitors triggering related phosphorylations and responses in other kinases. Alongside these cautionary tales, the functional implications for pseudokinases are clear, so that ATP binding within a suitably conserved nucleotide pocket can trigger conformational change and impact on the scaffolding function of that pseudokinase – here the kinase itself is simply an “ATP effector”. 相似文献
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At risk or not at risk? A meta‐analysis of the prognostic accuracy of psychometric interviews for psychosis prediction 下载免费PDF全文
Paolo Fusar‐Poli Marco Cappucciati Grazia Rutigliano Frauke Schultze‐Lutter Ilaria Bonoldi Stefan Borgwardt Anita Riecher‐Rössler Jean Addington Diana Perkins Scott W. Woods Thomas H. McGlashan Jimmy Lee Joachim Klosterkötter Alison R. Yung Philip McGuire 《World psychiatry》2015,14(3):322-332
An accurate detection of individuals at clinical high risk (CHR) for psychosis is a prerequisite for effective preventive interventions. Several psychometric interviews are available, but their prognostic accuracy is unknown. We conducted a prognostic accuracy meta‐analysis of psychometric interviews used to examine referrals to high risk services. The index test was an established CHR psychometric instrument used to identify subjects with and without CHR (CHR+ and CHR?). The reference index was psychosis onset over time in both CHR+ and CHR? subjects. Data were analyzed with MIDAS (STATA13). Area under the curve (AUC), summary receiver operating characteristic curves, quality assessment, likelihood ratios, Fagan's nomogram and probability modified plots were computed. Eleven independent studies were included, with a total of 2,519 help‐seeking, predominately adult subjects (CHR+: N=1,359; CHR?: N=1,160) referred to high risk services. The mean follow‐up duration was 38 months. The AUC was excellent (0.90; 95% CI: 0.87‐0.93), and comparable to other tests in preventive medicine, suggesting clinical utility in subjects referred to high risk services. Meta‐regression analyses revealed an effect for exposure to antipsychotics and no effects for type of instrument, age, gender, follow‐up time, sample size, quality assessment, proportion of CHR+ subjects in the total sample. Fagan's nomogram indicated a low positive predictive value (5.74%) in the general non‐help‐seeking population. Albeit the clear need to further improve prediction of psychosis, these findings support the use of psychometric prognostic interviews for CHR as clinical tools for an indicated prevention in subjects seeking help at high risk services worldwide. 相似文献
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A study was made on Fritillaria cirrhosa D.Don and its related species based on both field observation and herbarium material.As a result,four species are recognized and 16 specific names and 18 variety names are reduced as synonyms. 相似文献
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《Biophysical journal》2020,118(4):846-860
Formate/nitrite transporters (FNTs) selectively transport monovalent anions and are found in prokaryotes and lower eukaryotes. They play a significant role in bacterial growth and act against the defense mechanism of infected hosts. Because FNTs do not occur in higher animals, they are attractive drug targets for many bacterial diseases. Phylogenetic analysis revealed that they can be classified into eight subgroups, two of which belong to the uncharacterized YfdC-α and YfdC-β groups. Experimentally determined structures of FNTs belonging to different phylogenetic groups adopt the unique aquaporin-like hourglass helical fold. We considered the formate channel from Vibrio cholerae, the hydrosulphide channel from Clostridium difficile, and the uncharacterized channel from Escherichia coli (EcYfdC) to investigate the mechanism of transport and selectivity. Using equilibrium molecular dynamics and umbrella sampling studies, we determined temporal channel radius profiles, permeation events, and potential of mean force profiles of different substrates with the conserved central histidine residue in protonated or neutral form. Unlike the formate channel from V. cholerae and the hydrosulphide channel from C. difficile, molecular dynamics studies showed that the formate substrate was unable to enter the vestibule region of EcYfdC. Absence of a conserved basic residue and presence of acidic residues in the vestibule regions, conserved only in YfdC-α, were found to be responsible for high energy barriers for the anions to enter EcYfdC. Potential of mean force profiles generated for ammonia and ammonium ion revealed that EcYfdC can transport neutral solutes and could possibly be involved in the transport of cations analogous to the mechanism proposed for ammonium transporters. Although YfdC members belong to the FNT family, our studies strongly suggest that EcYfdC is not an anion channel. Absence or presence of specific charged residues at particular positions makes EcYfdC selective for neutral or possibly cationic substrates. Further experimental studies are needed to get a definitive answer to the question of the substrate selectivity of EcYfdC. This provides an example of membrane proteins from the same family transporting substrates of different chemical nature. 相似文献
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Carel J. van Oss 《Preparative biochemistry & biotechnology》2013,43(2):201-202
The preparative buffer electrofocusing of a variety of thyroid related proteins is described. The study shows that selective electrofocusing of these proteins on granulated gels can be readily achieved with buffer systems of defined chemical composition. Specific proteins were recovered in satisfactory yields (30-70%) with sample loadings in the range 25-500mg. 相似文献
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FIONA A. POWELL DIETER F. HOCHULI CELIA L. SYMONDS GERASIMOS CASSIS 《Austral ecology》2012,37(1):140-148
Secondary extinctions of dependent affiliate species may exceed the numbers of species directly extirpated with habitat loss. We investigated the host specificity, and hence the co‐extinction risk, of multiple psyllid species (Hemiptera: Psylloidea) on the threatened plants Acacia ausfeldii, A. dangarensis and A. gordonii by sampling from these and other sympatric common plants across multiple sites, years and plant phenologies. We found one specialist psyllid species (Psyllidae: Acizzia sp.) on each of the plants A. ausfeldii and A. gordonii but no specialists on A. dangarensis. The A. gordonii specialist only occurred when its host was in flower. Specialist psyllids considered at risk of extinction represented 10% of all psyllid species observed on the three threatened acacias. Potential risks to co‐endangered affiliates need to be considered when implementing threatened plant recovery actions. Conservation of plant populations and plant species diversity is also necessary to maintain high insect diversity. 相似文献
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Maria C. De Korte-Verhoef H. Roeline W. Pasman Bart P. M. Schweitzer Anneke L. Francke Bregje D. Onwuteaka-Philipsen Luc Deliens 《PloS one》2015,10(3)