共查询到20条相似文献,搜索用时 31 毫秒
1.
Richard C. Harris 《Brittonia》1988,40(2):172-179
Winona Welch's contributions to lichenology are reviewed. An index of the collectors of lichens represented in the DePauw University Herbarium (DPU), now at the New York Botanical Garden (NY), and lists of the Indiana lichen records included are presented. The gift of a few lichens from Wabash, College (WAB) is noted. 相似文献
2.
The distinctive morphological and karyological features of the two new species, collected from freshwater habitats in North India, are presented and compared with those of related taxa of the generaWoloszynskia andGymnodinium. Asexual reproduction takes place through zoospore formation and sexual reproduction through planozygotes inWoloszynskia stoschii. 相似文献
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《Mathematical biosciences》1987,84(1):85-118
Deterministic models are presented for epidemics which occur quickly and for long-term endemic diseases where births and deaths must be considered. Contact-rate matrices are formulated in terms of activity levels and subpopulation sizes by using a proportionate-mixing assumption. Methods are presented for estimating epidemic and endemic parameters in both homogeneous and heterogeneous populations. Other authors' approaches to contact-rate matrices and spatial heterogeneity are described. Three immunization programs are analyzed for a model of a spatially heterogeneous population and are compared in a “city and villages” example. 相似文献
5.
A single strain representing the fusiform group of caulobacters first described by Henrici and Johnson has been isolated from a freshwater pond. Like the genusCaulobacter this is a chemo-organotrophic bacterium that has one polar prostheca, a stalk in the sense that its apical holdfast permits the cell to attach to solid substrates. Fine structure studies reveal, however, that the prostheca of this organism contains typical cellular constituents, not the membranous material found in the stalks ofCaulobacter andAsticcacaulis. The organism also differs from the other caulobacters in having no motile stage and no dimorphic life cycle (both daughter cells are stalked at the time of division). Because only one strain has been isolated no nomenclatural proposals are made, but sufficient evidence is presented to indicate that this is a representative of a new genus of the Schizomycetes. 相似文献
6.
A new classification, using the Zürich-Montpellier procedures, is presented for the grassland, thicket and forest vegetation of the Accra Plains, Ghana. Newly described syntaxa comprise 1 class (Vetiverietea), 4 orders, 9 alliances, 16 associations and 16 subassociations. Altogether 350 species of vascular plants were recorded in 140 relevés. Correlations are made between syntaxa and climatic, edaphic and anthropogenic factors. The floristic distinctness of the area is assessed: 4 endemic species and about 40 widely disjunct species occur. Although the majority of species are of Guinean affinity, the plant communities of the Accra Plains are unique in the context of African tropical vegetation. 相似文献
7.
Ben Berkhout 《Retrovirology》2005,2(1):1-2
In this editorial, Retrovirology's choice for best basic science "retrovirus paper of the year" and a perspective on challenges and responsibilities facing HIV-1 and HTLV-I research are presented. 相似文献
8.
Rupert C. Barneby 《Brittonia》1985,37(1):85-87
Acacia guilandinae DC. is recognized asMimosa guilandinae (DC.) Barneby, endemic to French Guiana and adjoining Amapá, Brazil;M. pseudo-obovata is subordinated as a Brazilian var.pseudo-obovata (Taub.) Barneby to CaribbeanM. ceratonia L.; andM. laticifera is found synonymous withM. obovata Benth. Diagnostic morphological characters of each taxon are presented in key form. 相似文献
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AbstractSurvivorship curves and life tables for the 1971-75 generations of currant clearwing in an unsprayed blackcurrant (cv. 'Cotswold Cross') plantation and for the 1972-74 generations in a sprayed blackcurrant plantation (cvs 'Cotswold Cross' and 'Magnus') are presented. The key element in the life cycle is identified as adult survival, and the density dependence of the various mortalities is identified by various indices. The possible effects on population levels of currant clearwing of the proposed pruning management for mechanically harvested blackcurrants is discussed. 相似文献
11.
Experiments have been carried out on the duration of larval development of the spider crabHyas araneus L., in relation to temperature, food quality, and individual variation. A graphical model is presented which predicts larval occurrence and settlement in the field (Helgoland waters, North Sea). Preliminary observations are reported on predator-prey interactions with larvae of the spionid polychaetePolydora ciliata. Cannibalism and necrophagy during starvation experiments with zooplankton are considered: In larvae which are not kept in individual confinement, maximum survival time doubles due to feeding on living or dead sibling larvae. Analyses are presented revealing elemental and biochemical composition of starved and fed larvae as well as energy equivalents calculated from these data. During starvation, early larvae lose carbon, nitrogen, and hydrogen. Their main metabolic substrate is protein; lipid is utilized to a much lesser extent. Exoskeleton formation is, apparently, independent of nutrition: Zoea-1 larvae starved for 8 days contain the same amount of chitin as larvae fed well over this period of time. Energy calculations suggest an extremely low respiration rate and a very effective reconstruction of body material in starved larvae. 相似文献
12.
Idalis Villanueva Maria Valladares Wade Goodridge 《Journal of visualized experiments : JoVE》2016,(108)
Typically, self-reports are used in educational research to assess student response and performance to a classroom activity. Yet, addition of biological and physiological measures such as salivary biomarkers and galvanic skin responses are rarely included, limiting the wealth of information that can be obtained to better understand student performance. A laboratory protocol to study undergraduate students'' responses to classroom events (e.g., exams) is presented. Participants were asked to complete a representative exam for their degree. Before and after the laboratory exam session, students completed an academic achievement emotions self-report and an interview that paralleled these questions when participants wore a galvanic skin sensor and salivary biomarkers were collected. Data collected from the three methods resulted in greater depth of information about students'' performance when compared to the self-report. The work can expand educational research capabilities through more comprehensive methods for obtaining nearer to real-time student responses to an examination activity. 相似文献
13.
Ma Shu Yun 《Ethnic and racial studies》2013,36(4):527-541
Some terms have been coined to highlight the important relation between nationalism and ethnicity. However, there has been much confusion as to the meaning of such concepts as ‘ethnonationalism’, ‘ethnic nationalism’ and ‘mini‐nationalism’. This article compares the three terms, as used respectively in the works of Walker Connor, Anthony Smith and Louis Snyder. These scholars are selected not only because of their well‐respected position in the study of nationalism but also because their works are representative of each of the three concepts. The comparison finds that since both Connor and Smith emphasized the ethnic dimension of nationalism, their ideas can be presented in one analytical framework. In fact, Connor's ‘ethnonationalism’ and Smith's ‘ethnic nationalism’ overlap with each other. However, Smith's theory of nationalism is comprehensive enough to take care of the fact that the nationalisms of many new states of today's world have no ethnic base at all, whereas Connor's analysis makes no mention of this. In this respect, Smith's model is preferred to that of Connor. Finally, Snyder's ‘mini‐nationalism’ is seen as the least useful concept, since the use of size rather than ethnicity to classify nationalisms does not increase our understanding of the concept. 相似文献
14.
M Harrison A Kilby J A Walker-Smith N E France C B Wood 《BMJ (Clinical research ed.)》1976,1(6024):1501-1504
Twenty-five children with cows'' milk protein intolerance were studied. Twenty had presented with an illness clinically indistinguishable from infantile gastroenteritis; an enteropathogenic Escherichia coli was isolated from the stools in two children, and in six another member of the family simultaneously developed acute diarrhoea and vomiting. Twenty-three children had lactose intolerance secondary to cows'' milk protein intolerance. Eight out of 20 children were found to be partially IgA deficient. An acute attack of gastroenteritis, in damaging the small mucosa, may act as a triggering mechanism in cows'' milk protein intolerance, and a deficiency in IgA may be a predisposing factor in so far as it allows the patient to become sensitised to foreign protein. 相似文献
15.
David J Hele 《Respiratory research》2001,2(5):E003-4
The 97th American Thoracic Society meeting proved to be an excellent meeting, providing a wealth of new information on inflammatory diseases of the airways. Once again there appeared to be an increased emphasis on chronic obstructive pulmonary disease (COPD) with most of the major drug companies concentrating a large part of their efforts in this field. An assessment of the new British Thoracic Society guidelines, which are designed to promote better management of COPD, was also presented at the meeting. Potential new treatments for inflammatory diseases of the airways including COPD were described, ranging from phase III trial data with GlaxoSmithKline's PDE4 inhibitor, Cilomilast (Ariflo®) to the development of AstraZeneca's novel dual dopamine D2-receptor/β2-adrenoreceptor agonist, Viozan?. Of particular interest was Byk Gulden's Ciclesonide, a new corticosteroid with equivalent efficacy to the market leaders but with an improved safety profile. The same company also presented data on their PDE4 inhibitor, Roflumilast, which is now in phase II/III. Bayer presented data on their PDE4 inhibitor, BAY 19-8004, in a smoking animal model and claimed greater anti-inflammatory efficacy than with a steroid. Asta Medica (now known as Elbion) also described a new potent PDE4 inhibitor, AWD 12-281, with anti-inflammatory activity. In the bronchodilator field, an analysis of data from a one-year trial with Boehringer Ingelheim's Tiotropium revealed a possible improvement in lung function in COPD patients; this needs to be confirmed in a specifically designed study. Inhibitors of p38 (c-Jun NH2-terminal kinase and syk kinase) were also discussed as anti-inflammatory agents with potential in the treatment of COPD and asthma. GlaxoSmithKline's p38 kinase inhibitor, SB 239063, appeared to be the most advanced of these with clinical data expected in two to three years. Lyn kinase was also discussed as a novel target for inflammatory airway diseases. 相似文献
16.
Robert C. Koeppen 《Brittonia》1967,19(1):42-61
A combined taxonomic revision and wood anatomical study ofDicorynia, a South American genus of legumes that is unusual in both its floral and wood anatomy, is presented. Two possible evolutionary pathways leading to the unique 8-to 10-thecate anthers are discussed, and it is concluded that apical proliferation of the thecal primordia is the more likely. Gross and microscopic features of this silica-accumulating wood are given in detail and contrasted with other legume woods especially those containing silica. Economic uses of the trees, especially the wood ofD. guianensis, are discussed particularly in regard to marine construction. It is suggested that the high resistance of this wood to marine borers lies not so much in its silica content as to the presence of some other chemical. Based on the similarity of floral and fruit structures, the number of species is reduced from 7 to 2:D. guianensis in the Guianas andD. paraensis in the Amazonian region. Vegetative variations in the Amazonian population, previously given species rank, are reduced to 5 new varieties ofD. paraensis. 相似文献
17.
P M Biggs 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1997,352(1364):1951-1962
There are a number of neoplasias for which a herpesvirus is an essential part of the aetiology. Of these, Marek''s disease is the most common and provides excellent opportunities for the study of a herpesvirus-induced tumour both experimentally and under natural conditions in the field. Marek''s disease is caused by an alpha herpesvirus; it differs from the other oncogenic herpesviruses which are gamma herpesviruses. It is a ubiquitous virus in poultry populations of the world and is highly cell-associated and contagious, yet only a proportion of infected fowl develop tumours. Evidence is presented to suggest that at least one of the reasons for a wide variation in the incidence of the disease is a temporal interplay between virulent viruses and viruses of low or no virulence. The viral genes associated with the oncogenicity of Marek''s disease virus (MDV) are discussed and it is concluded that it is likely that several genes are involved. Finally, a brief history of vaccination to control Marek''s disease is given and mode of action discussed. It is concluded that the mechanism of protection is mainly through an antiviral cell mediated immune response, resulting in a lowered challenge virus burden. Marek''s disease viruses over the past 40 years have been evolving greater oncogenicity, some of which are not adequately controlled by the vaccines that are currently available. It is suggested that for MDV to produce tumours, there is a need for the cytolytic infection phase and that infection must be with an MDV which possesses a functional gC, ICP4 for maintaining latency which allows the expression of at least the 1.8 kb family, pp38, meq, and possibly pp14 genes, for maintaining the tumour state and possibly initiating this state. Intervention in this process reduces the chance of tumour formation and incidence in a population which can occur through natural or man-mediated infection with non-pathogenic MDVs. 相似文献
18.
The aim of this study is to evaluate the reliability of a crowd simulation model developed by the authors by reproducing Dyer et al.''s experiments (published in Philosophical Transactions in 2009) on human leadership and consensus decision making in a computer-based environment. The theoretical crowd model of the simulation environment is presented, and its results are compared and analysed against Dyer et al.''s original experiments. It is concluded that the simulation results are largely consistent with the experiments, which demonstrates the reliability of the crowd model. Furthermore, the simulation data also reveals several additional new findings, namely: 1) the phenomena of sacrificing accuracy to reach a quicker consensus decision found in ants colonies was also discovered in the simulation; 2) the ability of reaching consensus in groups has a direct impact on the time and accuracy of arriving at the target position; 3) the positions of the informed individuals or leaders in the crowd could have significant impact on the overall crowd movement; and 4) the simulation also confirmed Dyer et al.''s anecdotal evidence of the proportion of the leadership in large crowds and its effect on crowd movement. The potential applications of these findings are highlighted in the final discussion of this paper. 相似文献
19.
1. Available evidence on butterfly family-level relationships is re-examined according to the principles of phylogenetic (cladistic) systematics. 2. The assumption of a sister-group relationship between the Hesperioidea and Papilionoidea seems a reasonably substantiated working hypothesis. 3. The Papilionoid families Papilionidae, Pieridae and Lycaenidae sensu Ehrlich (1958) are definable as monophyletic entities; of Ehrlich 's two remaining families, Nymphalidae and Libytheidae, the former is paraphyletic in terms of the latter. 4. The interrelationships between the Papilionoid families may be presented as Papilionidae + (Pieridae + [Lycanidae + Nymphalidae]). 5. In a phylogenetic system any given arrangement of taxa is either correct or not: Contrary to the pheneticists' view (Ehrlich and Ehrlich 1967) phylogenetic systematists cannot accept the existence of a multitude of valid classifications. 相似文献
20.
E. I. Kohorn 《The Yale journal of biology and medicine》1993,66(2):85-105
The persons who directed the academic teaching of women''s health at Yale Medical School are presented by biographical sketches recounting their achievements and some of the difficulties they encountered. Three who provided particular catalysis were Nathan Smith, Herbert Thoms, and Lee Buxton. 相似文献