On considere une variable aleatoire (X,Z) dans #7B-R P ×#7B-R q . On construit un estimateur generalisant l'estimateur des moindres carres ordinaires en inserant des estimateurs non parametriques de la regression dans la projection orthogonale non lineaire sur Z

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Root-n-consistent semiparametric regression

Quantitative fisheries stock assessment : , Quantitative fisheries stock assessment : , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Quantitative fisheries stock assessment

Fish lengths have been measured in many different ways The differences arise from choosing different reference points near the anterior end and near the posterior end of the fish, and from using different methods of making the measurement Methods of making the measurement include using calipers; using a tape held along the curve of the body; laying the fish on a measuring board with the front end pressed against an upright piece; laying the fish on a board with a movable cross hair above it, attached to an indicator running along a scale In theory, any combination of reference points and methods might be used, but practice is considerably more restricted Some of the commoner combinations have special names; these are provided in the chapter, together with the reference points used In addition to these methodological differences, length varies with the condition of the fish—for example, whether it is alive, recently killed, after rigor mortis has set in, or at different intervals of time after preservation in formalin or alcohol

11 – Growth Rates and Models

Although Escherichia coli can be an innocuous resident of the gastrointestinal tract, it also has the pathogenic capacity to cause significant diarrheal and extraintestinal diseases. Pathogenic variants of E. coli (pathovars or pathotypes) cause much morbidity and mortality worldwide. Consequently, pathogenic E. coli is widely studied in humans, animals, food, and the environment. While there are many common features that these pathotypes employ to colonize the intestinal mucosa and cause disease, the course, onset, and complications vary significantly. Outbreaks are common in developed and developing countries, and they sometimes have fatal consequences. Many of these pathotypes are a major public health concern as they have low infectious doses and are transmitted through ubiquitous mediums, including food and water. The seriousness of pathogenic E. coli is exemplified by dedicated national and international surveillance programs that monitor and track outbreaks; unfortunately, this surveillance is often lacking in developing countries. While not all pathotypes carry the same public health profile, they all carry an enormous potential to cause disease and continue to present challenges to human health. This comprehensive review highlights recent advances in our understanding of the intestinal pathotypes of E. coli.

Recent Advances in Understanding Enteric Pathogenic Escherichia coli

Book reviewFishes of the North-eastern Atlantic and the Mediterranean: Volume II. P.J.P. Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen, E. Tortonese (Editors). UNESCO Press, Paris, 1986, pp. 510–1007, FF 250, Dfl 105.00, ISBN 92-3-002308-6

For estimating age-group parameters from size-frequency data, conventional efficient statistical methods, such as maximum likelihood, can be more effective than the commonly used graphical methods ...

Age-Groups from Size-Frequency Data: A Versatile and Efficient Method of Analyzing Distribution Mixtures

Escherichia coli O157 infections are the cause of sporadic or epidemic cases of often bloody diarrhea that can progress to hemolytic uremic syndrome (HUS), a systematic microvascular syndrome with predominately renal and neurological complications. HUS is responsible for most deaths associated with E. coli O157 infection. From March 2002 to February 2004, approximately 13,000 fecal pat samples from 481 farms with finishing/store cattle throughout Scotland were examined for the presence of E. coli O157. A total of 441 fecal pats from 91 farms tested positive for E. coli O157. From the positive samples, a point estimate for high-level shedders was identified using mixture distribution analysis on counts of E. coli O157. Models were developed based on the confidence interval surrounding this point estimate (high-level shedder, greater than 103 or greater than 104 CFU g−1 feces). The mean prevalence on high-level-shedding farms was higher than that on low-level-shedding farms. The presence of a high-level shedder on a farm was found to be associated with a high proportion of low-level shedding, consistent with the possibility of a higher level of transmission. Analysis of risk factors associated with the presence of a high-level shedder on a farm suggested the importance of the pathogen and individual host rather than the farm environment. The proportion of high-level shedders of phage 21/28 was higher than expected by chance. Management-related risk factors that were identified included the type of cattle (female breeding cattle) and cattle stress (movement and weaning), as opposed to environmental factors, such as water supply and feed.

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Risk factors for the presence of high-level shedders of Escherichia coli O157 on Scottish farms.

Two Models for Seasonal Growth in Fishes

Summary An extension of Barrett and Marshall's model expressing fecundability as a function of coital pattern is proposed. In particular, this extension includes the probability that the ovum remains alive. The extended model has been applied to Barrett and Marshall's data, a series of cycles for which basal body temperature curves and the date of coitus have been recorded. It was thus possible to estimate the daily probabilities of fertilization and, under certain assumptions, the proportion of lost ova. This proportion was estimated to be above 50 per cent, and increases with age. The increase of fecundability with frequency of intercourse is more moderate than that predicted by Barrett and Marshall's model.

P. D. M. Macdonald

Papers

Age-Groups from Size-Frequency Data: A Versatile and Efficient Method of Analyzing Distribution Mixtures

Risk factors for the presence of high-level shedders of Escherichia coli O157 on Scottish farms.

Two Models for Seasonal Growth in Fishes

Fecundability coital frequency and the viability of ova.

Demography and substrate affinity of the round goby (Neogobius melanostomus) in Hamilton Harbour.