3,561 research outputs found
NLO predictions for the growth of at small and comparison with experimental data
We present parametrizations for the proton structure function in the
next to leading order in perturbative QCD. The calculations show that the
dominant term to should grow as x^{-\ls} for small values,
with the exponent \ls being essentially independent of . Comparisons
with the most recent H1 and ZEUS data confirm the value \ls \sim 0.35
obtained previously from fits to low energy data.Comment: 18 page
A Bayesian approach to filter design: detection of compact sources
We consider filters for the detection and extraction of compact sources on a
background. We make a one-dimensional treatment (though a generalization to two
or more dimensions is possible) assuming that the sources have a Gaussian
profile whereas the background is modeled by an homogeneous and isotropic
Gaussian random field, characterized by a scale-free power spectrum. Local peak
detection is used after filtering. Then, a Bayesian Generalized Neyman-Pearson
test is used to define the region of acceptance that includes not only the
amplification but also the curvature of the sources and the a priori
probability distribution function of the sources. We search for an optimal
filter between a family of Matched-type filters (MTF) modifying the filtering
scale such that it gives the maximum number of real detections once fixed the
number density of spurious sources. We have performed numerical simulations to
test theoretical ideas.Comment: 10 pages, 2 figures. SPIE Proceedings "Electronic Imaging II", San
Jose, CA. January 200
An identification procedure for woolly soft-flesh peaches by instrumental assessment
Woolliness in peaches, a negative attribute of sensory texture characterized by the lack of crispness and juiciness, also known as mealiness in other fruits, has been identified fruit-by fruit by instrumental means. The use of a non-supervised clustering data analysis procedure, studying crispness and juiciness, enables four instrumental degrees of texture degradation to be defined, of which woolliness appears to be the last stage. This procedure also provides some information on several experimental factors (ripeness stages, storage time and storage temperature) with regard to the onset of woolliness. It is confirmed through this study that, in Maycrest peaches, woolliness starts to appear after 2 weeks of storage at 5°C. Fruits classified at harvest in 'first' and 'second' ripeness stages are more susceptible to woolliness than those in the third ripeness stage. This clustering procedure may also be effective for studying other species, varieties and quality attributes of fruit
Mining microsatellite markers from public expressed sequence tags databases for the study of threatened plants
Background: Simple Sequence Repeats (SSRs) are widely used in population genetic studies but their classical development is costly and time-consuming. The ever-increasing available DNA datasets generated by high-throughput techniques offer an inexpensive alternative for SSRs discovery. Expressed Sequence Tags (ESTs) have been widely used as SSR source for plants of economic relevance but their application to non-model species is still modest. Methods: Here, we explored the use of publicly available ESTs (GenBank at the National Center for Biotechnology Information-NCBI) for SSRs development in non-model plants, focusing on genera listed by the International Union for the Conservation of Nature (IUCN). We also search two model genera with fully annotated genomes for EST-SSRs, Arabidopsis and Oryza, and used them as controls for genome distribution analyses. Overall, we downloaded 16 031 555 sequences for 258 plant genera which were mined for SSRsand their primers with the help of QDD1. Genome distribution analyses in Oryza and Arabidopsis were done by blasting the sequences with SSR against the Oryza sativa and Arabidopsis thaliana reference genomes implemented in the Basal Local Alignment Tool (BLAST) of the NCBI website. Finally, we performed an empirical test to determine the performance of our EST-SSRs in a few individuals from four species of two eudicot genera, Trifolium and Centaurea. Results: We explored a total of 14 498 726 EST sequences from the dbEST database (NCBI) in 257 plant genera from the IUCN Red List. We identify a very large number (17 102) of ready-to-test EST-SSRs in most plant genera (193) at no cost. Overall, dinucleotide and trinucleotide repeats were the prevalent types but the abundance of the various types of repeat differed between taxonomic groups. Control genomes revealed that trinucleotide repeats were mostly located in coding regions while dinucleotide repeats were largely associated with untranslated regions. Our results from the empirical test revealed considerable amplification success and transferability between congenerics. Conclusions: The present work represents the first large-scale study developing SSRs by utilizing publicly accessible EST databases in threatened plants. Here we provide a very large number of ready-to-test EST-SSR (17 102) for 193 genera. The cross-species transferability suggests that the number of possible target species would be large. Since trinucleotide repeats are abundant and mainly linked to exons they might be useful in evolutionary and conservation studies. Altogether, our study highly supports the use of EST databases as an extremely affordable and fast alternative for SSR developing in threatened plants
Interest groups’ incentives to cooperate in the production of information in the context of the EU policy-making
The literature on information economics serves the European Commission to justify the participation of interest groups in response to problems of asymmetric information in the European Union (EU) policy-making processes.
Using the framework of the agency theory, the role of interest groups as information producers is incorporated into a model where the types of conditions in which they would have the incentive to cooperate in the production of information are examined.
The results of the model show that the interest group’s expected utility when acting independently is equal to the reserve utility, while it increases when acting cooperatively. It can therefore be concluded that incentives for cooperation in the production of information among interest groups exist.
One potential policy implication for the EU is that the EC could decrease the conditions of the contracts, thereby diminishing the costs of obtaining information.peer-reviewe
Harinosidad en manzana y melocotón: sondeo a los consumidores de Madrid
La harinosidad, tanto en manzana como en melocotón, es una característica sobre la cual el consumidor muestra un completo desconocimiento, como se demuestra en la encuesta realizada a un total de 768 consumidores de Madrid; en la muestra se seleccionaron distintos barrios de la ciudad, varios lugares de compra y personas de diferente sexo y edad para ver cómo influyen estos factores en su comportamiento y en sus preferencias. En general, se observa que el comportamiento del consumidor está guiado por las características sensoriales de una determinada fruta y por su capacidad para identificar visualmente determinadas variedades que gustativamente han resultado de su agrado
Detection of point sources on two-dimensional images based on peaks
This article considers the detection of point sources in two dimensional
astronomical images. The detection scheme we propose is based on peak
statistics. We discuss the example of the detection of far galaxies in Cosmic
Microwave Background experiments throughout the paper, although the method we
present is totally general and can be used in many other fields of data
analysis. We assume sources with a Gaussian profile --that is a fair
approximation of the profile of a point source convolved with the detector beam
in microwave experiments-- on a background modeled by a homogeneous and
isotropic Gaussian random field characterized by a scale-free power spectrum.
Point sources are enhanced with respect to the background by means of linear
filters. After filtering, we identify local maxima and apply our detection
scheme, a Neyman-Pearson detector that defines our region of acceptance based
on the a priori pdf of the sources and the ratio of number densities. We study
the different performances of some linear filters that have been used in this
context in the literature: the Mexican Hat wavelet, the matched filter and the
scale-adaptive filter. We consider as well an extension to two dimensions of
the biparametric scale adaptive filter (BSAF). The BSAF depends on two
parameters which are determined by maximizing the number density of real
detections while fixing the number density of spurious detections. For our
detection criterion the BSAF outperforms the other filters in the interesting
case of white noise.Comment: 21 pages, 3 figures, version accepted for publication on EURASIP
Journal on Applied Signal Processing: Applications of Signal Processing in
Astrophysics and Cosmolog
Calibración de una nariz electrónica tipo QCM y relación con las especificaciones para la calidad de la pera.
Las microbalanzas de cristal de cuarzo (QCM), son mecanismos piezoeléctricos, para transformarlos en sensores químicos es necesario recubrirlos con una capa de material capaz de capturar las moléculas del ambiente. Cuando una masa es adsorbida sobre la superficie del cristal, la frecuencia de oscilación cambia en proporción a la cantidad de masa (Di Natale et al. 1997). La respuesta de los sensores depende de numerosos factores que pueden ser difíciles de controlar, tales como la temperatura y la humedad del gas portador. Todos estos factores producen cambios en la selectividad de los sensores que afectan a la reproducibilidad de las medidas. A pesar de la existencia de numerosos estudios no existe ningún procedimiento establecido para la calibración de las QCM en relación con la sensibilidad necesaria en los sensores para el aseguramiento de la calidad en pera o en otras frutas
Isocurvature Fluctuations in Tracker Quintessence Models
We consider effects of the isocurvature perturbation in the framework of the
tracker-type quintessence models. During the inflation, fluctuations in the
amplitude of the quintessence field are generated, which provide isocurvature
component of the cosmic density perturbation. Contrary to the conventional
notion, it is shown that effects of the isocurvature fluctuation may become
sizable in some cases, and in particular, the cosmic microwave background
angular power spectrum may be significantly enhanced due to the effect of the
isocurvature mode. Such an enhancement may be detectable in on-going and future
experiments.Comment: 15 pages, 5 figures. Discussion on the scale dependence of the
isocurvature mode is changed. Figures are revise
- …