Statistical Inference for Truncated Dirichlet Distribution and Its Application in Misclassification

This paper is concerned with the statistical inference of a truncated Dirichlet distribution (TDD) arising in the general context of misclassified multinomial models (such as medical screening or diagnostic tests) and experimental design with mixtures. By employing the conditional distribution method, we offer a generating procedure for the TDD. Alternatively, a sampling‐based approach using the Gibbs sampler was provided as a means for developing the posterior moments of interest. Finding the mode of a TDD is equivalent to extracting the constrained maximum likelihood estimate (MLE) of parameter vector in a multinomial model. Based upon a theoretic result, we propose an algorithm to calculate the constrained MLE. Applications in misclassification are presented.     

A new adhesive for airborne pollen sampling in Spain

The use of a double-sided self-adhesive tapefor pollen trapping could offer some advantagesover traditional adhesives, manually applied tothe Melinex tape of a Hirst-type spore trap,since variation in terms of adhesiveapplication is nil and additional effort inapplying the adhesive is avoided. Nevertheless,its efficiency with respect to the standardadhesives must be tested. In Cordoba (southwestSpain), the Spanish Aerobiology Network Centreperformed a series of comparative studies andrecommended the use of a silicone fluid as anadhesive. This paper compares the efficiency ofa double-sided self-adhesive tape (3M) withsilicone fluid as adhesive. Sampling wascarried out using a Hirst type 7-day spore traplocated 15 m above ground level. A Melinex tapecoated with silicone fluid covered one half ofthe weekly drum; the other half was coveredwith 3M tape that included the adhesive. It iswidely reported that the physicalcharacteristics of silicone fluid do not varywith temperature (Galán andDomínguez-Vilches, 1997), but this studyshowed that 3M efficiency did vary withtemperature. The results revealed that 3M tapewas less efficacious at low temperatures, whileat high temperatures it becomes stickier. Incontrast, silicone fluid does not vary withtemperature. The efficiency of 3M tape alsoseems to be negatively influenced by rain.     

Bayesian estimation in animal breeding using the Dirichlet process prior for correlated random effects

In the case of the mixed linear model the random effects are usually assumed to be normally distributed in both the Bayesian and classical frameworks. In this paper, the Dirichlet process prior was used to provide nonparametric Bayesian estimates for correlated random effects. This goal was achieved by providing a Gibbs sampler algorithm that allows these correlated random effects to have a nonparametric prior distribution. A sampling based method is illustrated. This method which is employed by transforming the genetic covariance matrix to an identity matrix so that the random effects are uncorrelated, is an extension of the theory and the results of previous researchers. Also by using Gibbs sampling and data augmentation a simulation procedure was derived for estimating the precision parameter M associated with the Dirichlet process prior. All needed conditional posterior distributions are given. To illustrate the application, data from the Elsenburg Dormer sheep stud were analysed. A total of 3325 weaning weight records from the progeny of 101 sires were used.     

An in-situ mobile interstitial water and sediment sampler (MISS)

An inexpensive, easily constructed sampler for collecting interstitial water and sediment, seperately or combined is presented. The instrument has been developed for use in wetlands and shallow water as a tool for taxonomical and ecological investigations. Different to other samplers, our sampling depth is down to more than one meter at defined depths. Sampling showed highly reproducable sampling results for both, hydrophysical-chemical and biological analysis, which will be shown in the article.     

A new transparent handy sampler for collecting water from lakes,rivers and seas

A handy sampler for collecting water from lakes, rivers and seas is described. The sampler consists of an exchangeable sample tube and a new sample-holding system. The system comprises an upper disk, a lower disk, a pair of arms with a guide pin and a semicircular arm guide with a groove. The water sample collected into the acryl tube is held without flow by a tight tube-closing system. Contamination of the sample by chemical and biological materials from the sample tube is minimized by exchanging the tube with a clean one at each sampling station. This new sampler is light, simple and useful for sampling of water from surface to bottom.     

A method of collecting water samples from immediately below an ice cover

A plexiglas box with cellular neoprene gaskets in two opposite faces which can be frozen in situ in a developing ice cover on a lake is described along with a water sampling system using evacuated glass tubes (Vacutainers) and blood collecting needles. This system allows collecting of water samples from directly beneath the ice without disturbing the ice cover. The box may be removed in an ice block at the end of the sampling period.     

Palynological characterization of honeys from the Andean Patagonia (Chubut,Argentina)

The pollen content of 58 honey samples of Apis mellifera L. from the Andean region of Chubut (Argentinian Patagonia) was analyzed. The samples were provided by beekeepers between 1999 and 2004. Eighty‐eight pollen types were identified, 30 of them are not reported in Argentinian honeys. Identified types belong to 47 families, of which the most diverse were Asteraceae (15 pollen types), Fabaceae (13 pollen types), and Rosaceae (four pollen types). From the samples analyzed, 47% were monofloral and corresponded to the following taxa: Trifolium spp. (16%), Rosaceae (10%), Aristotelia chilensis (Molina) Stuntz (7%), Discaria‐Colletia (5%), Escallonia spp. (3%), Schinus patagonica (Phil.) I. M. Johnst. (2%), Phacelia secunda J. F. Gmel. (2%), Myrtaceae (2%). The results of this study show a high level of utilization of native flora by Apis mellifera. Four new types of monofloral honey were recognized: Aristotelia chilensis, Discaria‐Colletia, Phacelia secunda, and Schinus patagonica. The high representation of native flora distinguishes these honeys geographically.     

Sampling performance of Ekman grabs — in situ observations and design improvements

The performance of five types of Ekman grab: the Birge-Ekman, the Kebo Lab-Ekman, the Hydro-Bios-Ekman, the Winnipeg-Ekmanand the Håkanson-Ekman, were examined in situ by SCUBA diving. Trials and observations are presented, and photographic documentation provided. Each type of grab often produced unrepresentative samples due to operation deficiencies. Tilting, brimming, and entry of sediment from outside the sample chamber, as well as redistribution, resuspension and loss of enclosed matter are the main biasing factors. Since the grabs under study are models in general use, these findings suggest that caution must be exercised when evaluating studies based on Ekman grabs of the usual design. Sampling reliability can be significantly improved by furnishing the grabs with a supporting stand and a mechanism which secures the lids during ascent. Tested designs for such devices are presented. A properly operated Ekman grab of adequate design is a suitable instrument for collecting certain types of samples such as benthic macrofauna, and infauna in particular.     

The efficiency of a new lightweight suction sampler for sampling aphids and their predators in arable land

A petrol driven machine, normally used to collect leaf litter, was modified to be used as a suction sampler for polyphagous predators in cereals and grassy habitats and aphids in cereals. Recovery efficiency of Araneae, Carabidae and Staphylinidae did not differ significantly between winter sampling from Agrostis stolonifera, Dactylis glomerata, Festuca rubra, Holcus lanatus or Lolium perenne although the structure of these grasses was very different. Summer sampling of aphids and their predators in winter wheat showed that the new sampler captured significantly more target organisms per unit area than did a traditional suction sampler. The machine was also lighter, cheaper and much easier to use than a traditional machine.