Bootstrap methods for capture-recapture sampling

Lo scopo del presente lavoro \ue8 quello di estendere al caso del campionamento per cattura-ricattura il metodo bootstrap per la stima della varianza di stimatori costruiti su campioni da popolazioni finite. Nel campionamento da popolazioni di animali, non \ue8 raro il caso in cui alcuni animali, gi\ue0 catturati una volta, mostrino una accresciuta familiarit\ue0 nei confronti del contatto umano, mentre altri tendano a nascondersi. In questi casi, le probabilit\ue0 di inclusione possono risultare modificate. In questo lavoro si presentano due applicazioni dell\u2019algoritmo bootstrap per il campionamento PS \u3c0 proposto da Mecatti (2000) adattate al caso del campionamento per cattura-ricattura. La prima riguarda la stima della varianza dell\u2019usuale stimatore di Petersen della numerosit\ue0 della popolazione. La seconda utilizza la stessa stima come numerosit\ue0 delle popolazioni empiriche bootstrap su cui si basa l\u2019algoritmo di Mecatti. Il lavoro si conclude con due simulazioni su dati real

Bootstrap algorithms for risk models with auxiliary variable and complex samples

Resampling methods are often invoked in risk modelling when the stability of estimators of model parameters has to be assessed. The accuracy of variance estimates is crucial since the operational risk management affects strategies, decisions and policies. However, auxiliary variables and the complexity of the sampling design are seldom taken into proper account in variance estimation. In this paper bootstrap algorithms for finite population sampling are proposed in presence of an auxiliary variable and of complex samples. Results from a simulation study exploring the empirical performance of some bootstrap algorithms are presente

Bootstrap methods for capture-recapture sampling

Lo scopo del presente lavoro \ue8 quello di estendere al caso del campionamento per cattura-ricattura il metodo bootstrap per la stima della varianza di stimatori costruiti su campioni da popolazioni finite. Nel campionamento da popolazioni di animali, non \ue8 raro il caso in cui alcuni animali, gi\ue0 catturati una volta, mostrino una accresciuta familiarit\ue0 nei confronti del contatto umano, mentre altri tendano a nascondersi. In questi casi, le probabilit\ue0 di inclusione possono risultare modificate. In questo lavoro si presentano due applicazioni dell\u2019algoritmo bootstrap per il campionamento PS \u3c0 proposto da Mecatti (2000) adattate al caso del campionamento per cattura-ricattura. La prima riguarda la stima della varianza dell\u2019usuale stimatore di Petersen della numerosit\ue0 della popolazione. La seconda utilizza la stessa stima come numerosit\ue0 delle popolazioni empiriche bootstrap su cui si basa l\u2019algoritmo di Mecatti. Il lavoro si conclude con due simulazioni su dati real

Preliminary approach on early post mortem stress and quality indexes changes in large size bluefin tuna (Thunnus thynnus)

Bluefin tuna (Thunnus thynnus) is very appreciated on Japan and USA market for the preparation of sushi and sahimi. The market price of the fresh product can vary from 8 to 33 Euro/kg (gate farm/producers prices) according to size, shape, fat level, meat colour, consistency and freshness (absence of "hyake"), all parameters strictly connected to feeding quality and quantity, rearing and killing stress factors and refrigeration times and conditions after death. Excessive levels of stress during the slaughtering can affect meat quality, contributing to significantly decrease of tuna's price. The present trial was carried out to evaluate the possible harvesting/slaughtering stress effect on reared bluefin tuna meat quality, starting from the examination of the most important stress and quality parameters changes during the early post mortem period

Welfare and quality of farmed trout fed high plant protein diets. 2 innovative killing method effect on stress and quality indicators

AbstractThe fish stunning/slaughtering procedure has an important role both for the ethical aspect related to animal welfare and for the potential quality of the final products. Stressful harvest procedure and killing methods can negatively influence the post mortem biochemical processes with a consequent faster fish freshness loss. In particular, killing procedures causing a long agony are not humane and can shorten fish shelf life; others, more humane, can have risks for the consumers health (anaesthetics or chemical substances) or are not feasible in small/medium size fish industry (spiking and knocking). The aim of this study was to compare the traditional killing method (asphyxia - A) used for rainbow trout (Onchorynchus mykiss) with an innovative stunning/slaughtering method (two-stage electric stun: 2s at a 500Hz electric field of 2.5V/cm and then 58s at a 50Hz electric field of 0.75V/cm - E), through the study of their effects on stress and quality indicators in fish fed with traditional fish meal..

Population Empirical Likelihood Estimation in Dual Frame Surveys

Dual frame surveys are a device to reduce the costs derived from data collection in surveys and improve coverage for the whole target population. Since their introduction, in the 1960’s, dual frame surveys have gained much attention and several estimators have been formulated based on a number of different approaches. In this work, we propose new dual frame estimators based on the population empirical likelihood method originally proposed by Chen and Kim (2014) and using both the dual and the single frame approach. The extension of the proposed methodology to more than two frame surveys is also sketched. The performance of the proposed estimators in terms of relative bias and relative mean squared error is tested through simulation experiments. These experiments indicate that the proposed estimators yield better results than other likelihood-based estimators proposed in the literature.Ministerio de Economía y Competitividad of Spai

Histomorphometric and immunohistochemical analysis of infectious agents, T-cell subpopulations and inflammatory adhesion molecules in placentas from HIV-seropositive pregnant women

<p>Abstract</p> <p>Background</p> <p>The aim of this study was to compare histomorphometric changes and the results of immunohistochemical tests for VCAM, ICAM-1, CD4 and CD8 in normal placentas from HIV-seropositive pregnant women.</p> <p>Methods</p> <p>Samples of normal placentas were divided into 2 groups: healthy HIV-seronegative pregnant women (control group = C = 60) and HIV-seropositive women (experimental group = E = 57). Conventional histological sections were submitted to morphometric analysis and evaluated in terms of the immunohistochemical expression of ICAM-1, VCAM, CD4 and CD8.</p> <p>Results</p> <p>The villi in group E were smaller than those in group C. The median for the CD8+ T cell count was higher in group E than in group C (p = 0.03). Immunohistochemical expression of ICAM-1 was observed in 57% of the cases in group E, compared with 21% of those in group C (p = 0.001). There was no difference in VCAM expression or CD4+ cell counts between groups and no correlation between the data for antiretroviral therapy and morphometric or immunohistochemical data.</p> <p>Conclusions</p> <p>The morphometric data showed that placentas of HIV-seropositive pregnant women tend to have smaller villi than those of seronegative women. In addition, immunohistochemical testing for infectious agents helped to identify cases that were positive for microorganisms (6/112) that routine pathological examination had failed to detect. The anti-p24 antibody had a limited ability to detect HIV viral protein in this study (2/57). Correlation of immunohistochemical expression of CD8+ T cells and ICAM-1 with the presence of HIV in the placenta revealed that those expressions can act as biomarkers of inflammatory changes. There was no correlation between the data for antiretroviral therapy and morphometric or immunohistochemical data.</p

Kernel-based methods for combining information of several frame surveys

A sample selected from a single sampling frame may not represent adequatly the entire population. Multiple frame surveys are becoming increasingly used and popular among statistical agencies and private organizations, in particular in situations where several sampling frames may provide better coverage or can reduce sampling costs for estimating population quantities of interest. Auxiliary information available at the population level is often categorical in nature, so that incorporating categorical and continuous information can improve the efficiency of the method of estimation. Nonparametric regression methods represent a widely used and flexible estimation approach in the survey context. We propose a kernel regression estimator for dual frame surveys that can handle both continuous and categorical data. This methodology is extended to multiple frame surveys. We derive theoretical properties of the proposed methods and numerical experiments indicate that the proposed estimator perform well in practical settings under different scenarios.Ministerio de Economía y CompetitividadConsejería de Economía, Innovación, Ciencia y Emple

Calibration estimation in dual-frame surveys

Survey statisticians make use of auxiliary information to improve estimates. One important example is calibration estimation, which constructs new weights that match benchmark constraints on auxiliary variables while remaining “close” to the design weights. Multiple-frame surveys are increasingly used by statistical agencies and private organizations to reduce sampling costs and/or avoid frame undercoverage errors. Several ways of combining estimates derived from such frames have been proposed elsewhere; in this paper, we extend the calibration paradigm, previously used for single-frame surveys, to calculate the total value of a variable of interest in a dual-frame survey. Calibration is a general tool that allows to include auxiliary information from two frames. It also incorporates, as a special case, certain dual-frame estimators that have been proposed previously. The theoretical properties of our class of estimators are derived and discussed, and simulation studies conducted to compare the efficiency of the procedure, using different sets of auxiliary variables. Finally, the proposed methodology is applied to real data obtained from the Barometer of Culture of Andalusia survey.Ministerio de Educación y CienciaConsejería de Economía, Innovación, Ciencia y EmpleoPRIN-SURWE