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1.
Stochastic models of some endemic infections   总被引:3,自引:0,他引:3  
Stochastic models are established and studied for several endemic infections with demography. Approximations of quasi-stationary distributions and of times to extinction are derived for stochastic versions of SI, SIS, SIR, and SIRS models. The approximations are valid for sufficiently large population sizes. Conditions for validity of the approximations are given for each of the models. These are also conditions for validity of the corresponding deterministic model. It is noted that some deterministic models are unacceptable approximations of the stochastic models for a large range of realistic parameter values.  相似文献   

2.
Thirty-eight species of Aleocharinae are newly reported from New Brunswick, bringing the total number of species known from the province to 216. Thirty-one of these species are newly recorded for the Maritime provinces, and four of them, Phloeopora oregona Casey, Gyrophaena michigana Seevers, Gyrophaena wisconsinica Seevers, and Tomoglossa decora (Casey), are newly recorded for Canada. Tomoglossa constitutes a new generic record for Canada. Collection and habitat data for all these species are presented and discussed. Color habitus, median lobe of the aedeagus, and male tergite and sternite 8 images are presented for the first time for Phloeopora oregona, and references to illustrations are provided for all other species included in this paper. A color habitus image is presented for Tomoglossa decora.  相似文献   

3.
Summary Mathematical procedures are given to estimate infestation totals and daily life stage arrivals, departures, and mortality ofDendroctonus frontalis Zimmermann for an infested tree in the field. These estimates are based on minimal sample data and are designed to utilize all available information. Daily arrival estimates for larvae, pupae, and callow adults are obtained by indirect analysis without direct observation of these stages. The procedures are applied to 147 infested trees, and the results are transformed to a common time basis to obtain daily expectations by life stage for an “average” tree. These expectations suggest optimal times for field sampling or relative times of sampling when optimal times are missed. Expected daily arrival distributions by life stage for a single egg and a single attacking adult are given. Procedures are given for utilizing collateral information to obtain an infestation total and daily arrival estimates for a boundary life stage. The results of this study are applicable to anyD. frontalis field study, and the procedures given are applicable to any bark inhabiting insect having similar habits.  相似文献   

4.
Formulas for the variance of direct standardized rates are given for three different sampling models. The three models are product multinomial models when population totals are fixed by design, or strata totals are fixed by design, or cell (each population—each stratum) totals are fixed by design. Asymptotic distributions are derived for each model. A discussion on the relevance and use of standardized rates and the need for distribution theory is also provided.  相似文献   

5.
6.
Method agreement analysis: A review of correct methodology   总被引:2,自引:0,他引:2  
P.F. Watson  A. Petrie 《Theriogenology》2010,73(9):1167-1179
The correct approach to analyzing method agreement is discussed. Whether we are considering agreement between two measurements on the same samples (repeatability) or two individuals using identical methodology on identical samples (reproducibility) or comparing two methods, appropriate procedures are described, and worked examples are shown. The correct approaches for both categorical and numerical variables are explained. More complex analyses involving a comparison of more than two pairs of data are mentioned and guidance for these analyses given. Simple formulae for calculating the approximate sample size needed for agreement analysis are also given. Examples of good practice from the reproduction literature are cited, and common errors of methodology are indicated.  相似文献   

7.
中国秋海棠属植物的传统利用   总被引:2,自引:0,他引:2  
秋海棠属植物除了具有较高的观赏价值外,在中国还作为药用、食用、饮料和饲料等被利用。本文应用民族植物学研究方法,通过野外调查、文献和标本收集整理和研究,共记载了中国产26种秋海棠属植物被作为药用、食用、饮料和饲料加以利用。在所记载的26种国产秋海棠属植物中,有24种作药用,8种作食用(蔬菜)或饮料,5种作饲料。3种作饮料的种类在其自然分布地被广泛利用。9种秋海棠作为多种用途加以利用,其中8种既被作为药用、食用和饮料,也被作为饲料加以利用。本研究还表明,国产秋海棠属植物中,有些种类由于过度采集利用或其它因素已变得稀有或濒危。由此提出,合理开发利用和有效保护应成为今后中国秋海棠属植物研究的重要内容。  相似文献   

8.
We report 21 new species records for the Coleoptera fauna of New Brunswick, Canada, seven of which are new records for the Maritime provinces. Four species of Mycetophagidae (Litargus didesmus Say, Litargus tetrapilotus LeConte, Mycetophagus punctatus Say, and Mycetophagus quadriguttatus Müller) are newly reported for the province of New Brunswick. Litargus didesmus is newly recorded for the Maritime provinces. Seven species of Tetratomidae are added to the faunal list of New Brunswick: Eustrophus tomentosus Say, Penthe obliquata (Fabricius), and Tetratoma tessellata Melsheimer are new to New Brunswick: Hallomenus serricornis LeConte, Pisenus humeralis Kirby, Synstrophus repandus (Horn), and Tetratoma variegata Casey, which are newly recorded for New Brunswick and the Maritime provinces. Ten additional species of Melandryidae are reported from New Brunswick, of which Orchesia cultriformis Laliberté, Orchesia ovata Laliberté, Phloeotrya fusca (LeConte), Scotochroides antennatus Mank, Spilotus quadripustulatus (Melsheimer), Symphora flavicollis (Haldeman), Symphora rugosa (Haldeman), and Zilora hispida LeConte are new for the province, and Microscapha clavicornis LeConte and Zilora nuda Provancher are newly recorded for the Maritime provinces. In addition, we report numerous additional records for three species of Mycetophagidae and one species of Melandryidae previously recorded from New Brunswick that suggest these species are more widely distributed than previously known. Collection, habitat data, and distribution maps are presented for all these species.  相似文献   

9.
Comparative biogeography of mammals on islands   总被引:1,自引:0,他引:1  
Insular faunas of terrestrial mammals and bats are examined on a worldwide basis to test the adequacy of equilibrium and historical legacy models as explanations for species-area relationships. Species numbers of bats on islands conform to predictions from equilibrium theory, whereby recurrent immigrations and extinctions influence species richness. By contrast, species numbers of terrestrial mammals on islands result from a historical legacy of very low immigration rates on oceanic islands (the faunas are colonization-limited) and by the fragmentation of once contiguous continental faunas to form relictual populations, which subsequently undergo extinctions, on landbridge islands (the faunas are extinction-limited). This explanation is supported by several lines of evidence: (1) z values (slopes of species-area curves) are lower for non-volant mammals on oceanic islands than for those on landbridge islands, but are the opposite for bats; (2) z values for non-volant mammals are lower than those for bats on oceanic islands, but are higher than those for bats on landbridge islands; and (3) landbridge island faunas are attenuated mainland faunas, whereas those on oceanic islands are ecologically incomplete. No support is found for alternative hypotheses to explain low species-area slopes for terrestrial mammals on oceanic islands.  相似文献   

10.
Wood, bark and stem anatomy of New World species of Gnetum   总被引:1,自引:0,他引:1  
Quantitative and qualitative data are presented for 11 collections of six species. The wide range of character states for the species is presented in the form of a key to emphasize their potential systematic correlations. Distinctive among these are phcllem characteristics. Fibre-tracheids are newly reported for lianoid Gnetum species. Cells previously thought to be like companion cells in secondary phloem are shown to be uniseriate rays, counterparts to uniseriate xylem rays. Laticifers are abundant in most of the species, and are newly described for secondary tissues of Gnetum. Presence of tyloses in laticifers of two species is apparently a new report for vascular plants. Tori are present in two New World Gnetum species, adding to the report in African species. Perforation plates are simple except near or in primary xylem, where they are simple or foraminate. Torus presence and foraminate perforation plate presence are features more reminiscent of Ephedra and other gymnosperms than of angiosperms. The bark of Gnetum is also very similar to that of Ephedra.  相似文献   

11.
Nondestructive techniques developed by the authors for assessment of chlorophylls, carotenoids, and anthocyanins in higher plant leaves and fruits are presented. The spectral features of leaf reflectance in the visible and near infrared regions are briefly considered. For pigment analysis only reflectance values at several specific wavelengths are required. The chlorophyll (Chl) content over a wide range of its changes can be assessed during leaf ontogeny using reflectance near 700 nm and, in the absence of anthocyanins, at 550 nm. The approaches used for elimination of Chl interference in the analysis of carotenoids (reflectance at 520 nm) and anthocyanins (at 550 nm) are described. The suitability of reflectance spectroscopy for estimates of carotenoid/chlorophyll ratios during leaf senescence and fruit ripening is demonstrated. The algorithms developed for pigment analysis are presented, and the conditions of their applicability are considered. Further perspectives for the application of reflectance spectroscopy including remote sensing for estimation of plant pigment content and physiological states are discussed.  相似文献   

12.
Ritland K 《Molecular ecology》2005,14(10):3157-3165
Estimators for pairwise relatedness designed for dominant markers are derived, based on a genetic model that accounts for the full structure of pairwise relatedness between two individuals at a diploid locus with dominance. They jointly estimate 'relatedness' and 'fraternity', in which case the estimators are inherently multilocus, as at least two loci of differing gene frequency are required. Extensions to cases of zero fraternity and isolation by distance (inbreeding) are also examined. Properties of estimators are examined by simulation and compared to the estimator of Hardy. The most statistical power for pairwise relatedness occurs when roughly half of individuals are the recessive phenotype. Estimation procedures are implemented in the computer program mark.  相似文献   

13.
The commercial exploitation of seaweeds for use as food and for the production of agar, alginate and carrageenan is outlined. The quantities of seaweed harvested for each purpose are tabulated and discussed. Seaweeds for food are derived chiefly from China, Japan and Korea, with almost 94% obtained by cultivation. Alginophytes are collected in 15 countries but six of these account for more than 80% of the total harvest; all are from natural stocks except for a large quantity of Laminaria cultivated in China. Natural carrageenophytes, from 12 countries, now account for only 20% of the total harvest; the remainder is cultivated Eucheuma species, 99% of which is produced in only two countries, the Philippines and Indonesia. Of the four categories of commercial resources of seaweeds considered, agarophytes are spread more evenly over a greater number of countries; they come from 20 countries and only five of these are minor contributors to the total. Gelidium species are particularly important because of the high quality agar they yield; their distribution and location are discussed.  相似文献   

14.
Summary

Records of fungi occurring in the Hebrides are extended, particularly for Jura and Islay where, respectively, 40 and 47 taxa are recorded for the first time. Twenty taxa are added to the list for Rhum and 89 to that for Colonsay. Additional fungi are also reported for Hirta (St. Kilda) , Bernary, Mingulay, Barra and South Uist in the Outer Hebrides, and Eigg and Canna in the Inner Hebrides.  相似文献   

15.
We present the results of some spider surveys that were conducted in different parts of Iran. Faunistic records for 30 species which are new to Iran are presented here. Biogeographic data are provided for each species. Two families, namely Liocranidae and Mimetidae, are recorded for the first time from the country.  相似文献   

16.
Phycobiliproteins are a group of colored proteins commonly present in cyanobacteria and red algae possessing a spectrum of applications. They are extensively commercialized for fluorescent applications in clinical and immunological analysis. They are also used as a colorant, and their therapeutic value has also been categorically demonstrated. However, a comprehensive knowledge and technological base for augmenting their commercial utilities is lacking. Hence, this work is focused towards this objective by means of analyzing global patents and commercial activities with application oriented research. Strategic mining of patents was performed from global patent databases resulting in the identification of 297 patents on phycobiliproteins. The majority of the patents are from USA, Japan and Europe. Patents are grouped into fluorescent applications, general applications and production aspects of phycobiliproteins and the features of each group are discussed. Commercial and applied research activities are compared in parallel. It revealed that US patents are mostly related to fluorescent applications while Japanese are on the production, purification and application for therapeutic and diagnostic purposes. Fluorescent applications are well represented in research, patents and commercial sectors. Biomedical properties documented in research and patents are not ventured commercially. Several novel applications are reported only in patents. The paper further pinpoints the plethora of techniques used for cell breakage and for extraction and purification of phycobiliproteins. The analysis identifies the lacuna and suggests means for improvements in the application and production of phycobiliproteins.  相似文献   

17.
18.
Fibronectin and its major receptor, integrin α5β1 are required for embryogenesis. These mutants have similar phenotypes, although, defects in integrin α5-deficient mice are milder. In this paper, we examined heart development in those mutants, in which the heart is formed, and discovered that both fibronectin and integrin α5 were required for cardiac morphogenesis, and in particular, for the formation of the cardiac outflow tract. We found that Isl1+ precursors are specified and migrate into the heart in fibronectin- or integrin α5-mutant embryos, however, the hearts in these mutants are of aberrant shape, and the cardiac outflow tracts are short and malformed. We show that these defects are likely due to the requirement for cell adhesion to fibronectin for proliferation of myocardial progenitors and for Fgf8 signaling in the pharyngeal region.  相似文献   

19.
Environmental biosensors and related techniques for monitoring organochlorines, endocrine disrupting chemicals and cyanobacterial toxins are described. The practical requirements for an ideal environmental biosensor are analyzed. Specific case studies for environmental applications are reported for triazines chlorinated phenols, PCBs, microcystins, and endocrine disrupting chemicals. A new promising approach is reported for microcystins and alkylphenols that utilize electrooptical detection.  相似文献   

20.
张丽  张良  刘书成  张义军  韩艺 《遗传》2010,32(6):555-560
随着分子生物学技术的发展, 海洋食品物种鉴定方法由原来的蛋白质水平深入到了DNA水平。目前应用于海洋食品物种鉴定的DNA技术主要是FINS(Forensically informative nucleotide sequencing)、PCR-RFLP和物种特异性PCR标记技术等, 能够实现对新鲜、冰冻、腌制或灌装食品物种进行鉴定, 而对混合样本的鉴定及量化分析是尚待解决的一个问题。基因数据库对物种鉴定的影响也越来越大, 是海洋加工食品物种鉴定可利用的另一种重要信息资源。文章综述了DNA技术在海洋食品物种鉴定中的应用研究进展, 并展望DNA技术在海洋食品检测中的发展趋势。  相似文献   

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