Non-Gaussian Geostatistical Modeling using (skew) t Processes

We propose a new model for regression and dependence analysis when addressing spatial data with possibly heavy tails and an asymmetric marginal distribution. We first propose a stationary process with $t$ marginals obtained through scale mixing of a Gaussian process with an inverse square root process with Gamma marginals. We then generalize this construction by considering a skew-Gaussian process, thus obtaining a process with skew-t marginal distributions. For the proposed (skew) $t$ process we study the second-order and geometrical properties and in the $t$ case, we provide analytic expressions for the bivariate distribution. In an extensive simulation study, we investigate the use of the weighted pairwise likelihood as a method of estimation for the $t$ process. Moreover we compare the performance of the optimal linear predictor of the $t$ process versus the optimal Gaussian predictor. Finally, the effectiveness of our methodology is illustrated by analyzing a georeferenced dataset on maximum temperatures in Australi

Detection and quantification of geosmin and other fungal metabolites in grape juice by HS-SPME coupled with GC/MS

(-)-Geosmin (GEO) (Figure 1) is an aromatic volatile metabolite the presence of which in grapes is associated with an earthy smell of crucial importance in grape products (e.g. grape juice). Two fungi are involved in the accumulation of geosmin in grapes: Botrytis cinerea and Penicillium expansum (La Guerche et al., 2005). Other compounds of fungal origin such as fenchone, fenchol, anisoles and methyl isoborneol (MIB) can also transmit undesirable aromas (Boutou and Chatonnet, 2007) According to literature (Boutou and Chatonnet, 2007; Baghery et al., 2007; Salto et al., 2008 and Prat et al., 2008), Head Space Solid-Phase Microextraction (HS-SPME) coupled with Gas Chromatography/Mass Spectrometry (GC/MS) methodology was used to detect and quantify GEO. The fiber used was divinilbenzene/carboxen/polidimetilsiloxane (DVB/CAR/PDMS). Grape juice spiked with standards of the analytes was analyzed to validate the method. Optimization of the method was performed by determining the efficiency of GEO extraction. The influence of the ionization of the analytes was tested by extracting at different pH (from ca. 3.5 to 7.0) and/or addition of NaCl (from none to saturation). Also, the optimal ethanol concentration in the sample was assessed (from none to 6% v/v). Time of extraction (from 20 to 65 min) and temperature of extraction (from 30 to 70 ºC) were assayed as was the position of the Head Space fiber. The results underwent ANOVA tests to evaluate the significance of the differences in geosmin extraction. Graphics of extraction of GEO as a function of the factors tested were plotted to choose those conditions that maximized the detection of GEO and permitted the detection of the other analytes. Finally, internal standards were tested (4- Nonanol; Methyl-4-pentan-2-ol and 2,3,4-Trichloroanisole) to obtain calibration curves. The calibration curves of GEO were linear with high correlation coefficients. Geosmin, MIB and most of the other metabolites were detected. Quantification of GEO was possible in the range of concentrations in naturally contaminated grape juice

Microextraction and gas chromatography/mass spectrometry for improved analysis of geosmin and other fungal "off" volatiles in grape juice

Geosmin is a volatile fungal metabolite with an earthy aroma produced in grape products from rotten grapes. The accumulation of geosmin in grapes is caused by the interaction of Botrytis cinerea and Penicillium expansum. Solid Phase Microextraction (SPME) has great utility for collecting volatile compounds in wine. However, contamination with earthy odours may have occurred previously in the must and novel methods are required for this commodity. In the present report, several parameters of the SPME were evaluated to optimize geosmin extraction. The method permitted quantification of geosmin and other fungal volatiles by Gas Chromatography–Mass Spectrometer (GC–MS) at very low concentrations. Limits of detection and quantification (LD and LQ) for geosmin were 4.7 ng L−1 and 15.6 ng L−1 respectively. The RSD was 4.1% and the recovery rates ranged from 115% to 134%. Uniquely, haloanisoles were analyzed by using only one internal standard (2,3,6-trichloroanisole) thus avoiding the synthesis of deuterated anisole analogues that are used as internal standard in other methods. The method was used for the analysis of grape juice samples inoculated with B. cinerea and P. expansum. Geosmin and methylisoborneol were the compounds that appeared to contribute most to earthy odours, although other fungal compounds which are claimed to cause earthy or mouldy off-odours were detected (e.g. 1-octen-3-ol and fenchol).Fundação para a Ciência e a Tenoplogia (FCT

Incidence of Botrytis cinerea and Penicillium spp. and other fungi in the regions of “Vinho Verde” (Portugal) and “Alvariño” (Spain)

Fundação para a Ciência e a Tecnologia (FCT

Presión arterial : ¿esfigmomanómetro manual o digital?

El presente es un estudio prospectivo y comparativo entre la medición de la presión arterial obtenida de manera manual con esfigmomanómetro aneroide y la obtenida mediante monitor automático. El desarrollo de la práctica se realizó sobre un grupo de 100 pacientes hospitalizados en el servicio de Neurocirugía y Otorrinolaringología del Consorcio Hospital General de Valencia durante el primer trimestre del año 2007, mediante mediciones secuenciales y efectuadas por el mismo observador con ambos aparatos bien calibrados. Se observó mediante el método de correlación bivariada de Pearson que no existen diferencias estadísticamente significativas entre las presiones tomadas por ambos aparatos determinando así la fiabilidad del aparato automático utilizado en esta sala para el registro de la tensión arterial.This is a prospective and comparative work between arterial pressure obtained through manual measurement with aneroid sphygmomanometer and the arterial pressure obtained through automatic monitor. The practice was carried out in a group of 100 inpatients in the Neurosurgery and Otolaryngology Service in the Consortium of the General Hospital of Valencia during the first term of 2007. The development of this hospital training was made on each individual through sequential measurements and executed by the same observer with both well-calibrated machines. It was observed that through the method of Pearson's bivaried correlation there are not statistically significant differences between the pressures taken by both machines. As regards this fact, both automatic machines of arterial pressure register are [email protected] [email protected]

Food mycology : from the fork to the farm

Filamentous fungi are ubiquitous in nature and are responsible for producing mycotoxins in agricultural crops. Fungi and mycotoxins are considered generally as being natural and unavoidable [1]. The control and detection of mycotoxins is a continuous process in commodity production. Since mycotoxins can become established and remain within the commodity anywhere throughout the production, storage, transportation and processing chain, there is a need to study all the food chain: from the fork to the farm. The control over the presence of mycotoxins involves several competencies, such as taxonomy skills, ability to evaluate mycotoxins production by fungi, and ability to quantify mycotoxins in commodities. The prevention of mycotoxin formation is achieved by influencing environmental conditions through management of agricultural practices prior to harvest. After harvest, two overriding factors for storage are water activity (aw) and temperature. Control over these parameters may lead to the prevention of fungi growth and of mycotoxins accumulation. Strategies followed to have control over the presence of mycotoxins in commodities will be illustrated by presenting case studies: (i) ochratoxin A in wine; and (ii) aflatoxins in maize and in nuts

Diversity of Botrytis cinerea from vineyards in the north west Iberian peninsula

Botrytis cinerea is associated with a fungal gray rot in the concomitant regions of north west Spain and northern Portugal, where it is the most damaging pathogen and results in severe economic losses. Also, the physiological interactions of B. cinerea with Penicillium expansum are responsible for the production of geosmin, a volatile metabolite that transmit undesirable earthy odours to must and thus to wine. B. cinerea is not a homogeneous species and may be divided into several sub-species groupings. Some previous studies indicated two groups or cryptic species (I and II). Other work revealed that spore size and vegetative compatibility are characteristic features of these groups. In the present work a survey was taken of the population of B. cinerea from the above mentioned regions. The spore size and compatibility tests allowed characterisation of most isolates of B. cinerea into Group I or Group II taxa. Interestingly, some isolates could not be characterised according to their spore size and also presented ambiguous vegetative compatibility features. Furthermore, the influence of other factors on the spore size and grouping were studied. Grape variety, vineyard, country, sanitary state of the bunch and whether the isolates were obtained from the exterior or the interior of the bunch were compared with spore size and vegetative compatibility. Characterization of strains was affected by whether isolates were obtained from a particular grape variety. Also, isolates from Group II were obtained exclusively from a particular vineyard. The results suggest that there is considerable genetic diversity within the species which may explain patterns of gray rot within grapes.Fundação para a Ciência e a Tecnologia (FCT