Competition between electron and phonon excitations in the scattering of nitrogen atoms and molecules off tungsten and silver surfaces

We investigate the role played by electron-hole pair and phonon excitations in the interaction of reactive gas molecules and atoms with metal surfaces. We present a theoretical framework that allows us to evaluate within a full-dimensional dynamics the combined contribution of both excitation mechanisms while the gas particle-surface interaction is described by an ab-initio potential energy surface. The model is applied to study energy dissipation in the scattering of N$_2$ on W(110) and N on Ag(111). Our results show that phonon excitation is the dominant energy loss channel whereas electron-hole pair excitations represent a minor contribution. We substantiate that, even when the energy dissipated is quantitatively significant, important aspects of the scattering dynamics are well captured by the adiabatic approximation.Comment: 4pages and 3 figure

Non-equilibrium Anisotropic Phases, Nucleation and Critical Behavior in a Driven Lennard-Jones Fluid

We describe short-time kinetic and steady-state properties of the non--equilibrium phases, namely, solid, liquid and gas anisotropic phases in a driven Lennard-Jones fluid. This is a computationally-convenient two-dimensional model which exhibits a net current and striped structures at low temperature, thus resembling many situations in nature. We here focus on both critical behavior and details of the nucleation process. In spite of the anisotropy of the late--time spinodal decomposition process, earlier nucleation seems to proceed by Smoluchowski coagulation and Ostwald ripening, which are known to account for nucleation in equilibrium, isotropic lattice systems and actual fluids. On the other hand, a detailed analysis of the system critical behavior rises some intriguing questions on the role of symmetries; this concerns the computer and field-theoretical modeling of non-equilibrium fluids.Comment: 7 pages, 9 ps figures, to appear in PR

Long-term acute infections during a bovine viral diarrhea virus (BVDV) outbreak in dairy farm from Galicia (NW Spain)

An observational study describes an outbreak of bovine viral diarrhea virus (BVDV) in a dairy herd in Spain. The herd was subjected to a voluntary control program. In a sampling carried out in June 2020, bulk tank milk antibody levels increased compared to the previous sampling. Additionally, serum samples from 4 young heifers also tested positive for antibodies. Since the results were consistent with a recent infection, we proceeded to detect possible persistently infected (PI) animals using antigen ELISA (on serum/ear-notch samples), following the program guidelines. From this moment on, 42 animals tested positive for BVDV antigen, of which 17 were under typical acute infection (AI), 13 were deemed as PI, and eight died early on the farm before having information to determine their status. The remaining 4 showed intriguing test results consistent with a long-term AI since they tested BVDV positive in at least two antigen tests more than 3 weeks apart. Thus, one animal was positive until 80 days of age in serum, and others even for longer periods in ear-notch samples, until they finally tested negative for BVDV. Based on these results, longer follow-up may be necessary in BVDV positive animals to accurately confirm persistent infectionS

Influence of salt level, starter culture, fermentable carbohydrates, and temperature on the behaviour of L. monocytogenes in sliced chouriço during storage

Sliced ready-to-eat traditional meat products presented in individual packaging with more convenience to the consumer is the way that food industry tries to adapt to the new consumer tendencies. The current work assessed the survival of Listeria monocytogenes in a contaminated sliced vacuum packed chouriço with different sugar concentrations, two salt levels, and presence/absence of Lactobacillus sakei as starter culture along the storage period at two temperatures (8 °C and 22 °C). Neither the inoculation with L. sakei, nor the addition of carbohydrates influenced the survival of the pathogen. Higher amount of salt resulted in a significant reduction of L. monocytogenes, and storage at the higher temperature displayed a safer product. After 7 days, L. monocytogenes was not detected in any samples. The study of the association of the factors contributing for L. monocytogenes survival by logistic regression showed that increasing the level of salt addition from 1.5% to 3% reduces the odds of survival of L. monocytogenes to about one fifth (0.174). Worthy of attention is the significant reduction in the odds (OR=0.028) of finding viable L. monocytogenes when the samples are stored at room temperature (22 °C), when compared to low temperature (8 °C). The general and indiscriminate use of refrigeration for meat products might increase the risk of presence of L. monocytogenes. The competitive advantage that L. monocytogenes has at low temperatures, as the potential inhibition of LAB activity, is probably the reason of the observed behaviour. The amount of salt was an important hurdle to control L. monocytogenes growth, so, manufacturing meat products with lower salt contents to meet the demands of healthy products might represent a risk for safety, since high levels of salt together with low aw are the keys for their conservation

Interactions of Ar(9+) and metastable Ar(8+) with a Si(100) surface at velocities near the image acceleration limit

Auger LMM spectra and preliminary model simulations of Ar(9+) and metastable Ar(8+) ions interacting with a clean monocrystalline n-doped Si(100) surface are presented. By varying the experimental parameters, several yet undiscovered spectroscopic features have been observed providing valuable hints for the development of an adequate interaction model. On our apparatus the ion beam energy can be lowered to almost mere image charge attraction. High data acquisition rates could still be maintained yielding an unprecedented statistical quality of the Auger spectra.Comment: 34 pages, 11 figures, http://pikp28.uni-muenster.de/~ducree

Cost analysis of a vaccination startegy for respiratory syncytial virus (RSV) in a network model

[EN] In this paper an age-structured mathematical model for respiratory syncytial virus (RSV) is proposed where children younger than one year old, who are the most affected by this illness, are specially considered. Real data of hospitalized children in the Spanish region of Valencia are used in order to determine some seasonal parameters of the model. Once the parameters are determined, we propose a complete stochastic network model to study the seasonal evolution of the respiratory syncytial virus (RSV) epidemics. In this model every susceptible individual can acquire the disease after a random encounter with any infected individual in the social network. The edges of a complete graph connecting every pair of individuals in the network simulate these encounters and a season dependent probability, beta(t), determines whether the healthy susceptible individual becomes infected or not. We show that the prediction of this model is compatible with the above mentioned age-structured model based upon differential equations, but sharper peaks are obtained in the case of the network. Then, on the network model, we propose the vaccination of children at 2 months, 4 months and 1 year old, and we study the cost of this vaccination strategy, which is emerging as the most plausible one to be applied when the vaccine hits the market. It is worth to note that this vaccination strategy is simulated in the network model because to implement it in the continuous model is very difficult and increases its complexity. (C) 2010 Elsevier Ltd. All rights reserved.Acedo Rodríguez, L.; Moraño Fernández, JA.; Diez-Domingo, J. (2010). Cost analysis of a vaccination startegy for respiratory syncytial virus (RSV) in a network model. Mathematical and Computer Modelling. 52(7):1016-1022. doi:10.1016/j.mcm.2010.02.041S1016102252

Postpartum impairment of pelvic floor muscle function: factors involved and association with prolapse

Esta publicación refleja el estudio realizado para identificar los factores implicados en el deterioro de la musculatura del suelo pélvico (MSP) tras el parto vaginal. También se evalúa la asociación de dicho deterioro con el prolapso de los órganos pélvicos (POP). Nuestra hipótesis principal del trabajo fue que el parto instrumental podría asociarse a un empeoramiento de la función de la MSP tras el parto. Se trata de un estudio prospectivo que incluyo 319 primigrávidas que dieron a luz por vía vaginal en el año 2007 en el Hospital Universitario Donostia. La capacidad contráctil de la MSP se valoró en las gestantes a término y seis meses después del parto mediante la palpación y perineometria a través de la vagina. El prolapso se evaluó utilizando el sistema “Pelvic Organ Prolapse Quantification” (POPQ) validado por la International Continence Society (ICS). La identificación de los factores asociados al deterioro de la función de la MSP se realizó a través de un análisis multivariante. El parto vaginal fue espontaneo en 220 (69,0%) mujeres, asistido por fórceps en 84 (26,3%) y con ventosa en 15 (4,7%). El parto instrumental, el perímetro cefálico del recién nacido ≥36 cm y la edad ≥30 fueron factores de riesgo independientes para el deterioro de la función de la MSP después del parto. Estas asociaciones se establecieron considerando otros factores obstétricos como la duración del segundo periodo del parto, la utilización de oxitocina o anestesia epidural, la episiotomía y los desgarros de 3º y 4º grado. La evaluación del POP a los seis meses del parto indicó que 69 (21,6%) mujeres tenían un grado de POP-Q ≥ II. Este grupo de mujeres tuvieron una disminución significativa de la capacidad contráctil de la MSP después del parto en comparación con los valores del embarazo. También presentaron menor capacidad contráctil al compararlas con el grupo de mujeres sin POP. Con estos resultados confirmamos nuestra hipótesis de que el parto instrumental se asocia a un empeoramiento de la función de la MSP. También identificamos el perímetro cefálico ≥36 cm como otro factor asociado al deterioro, que comparte con el parto instrumental una mayor distención de la MSP durante el parto. El perímetro cefálico no es modificable y el parto instrumental puede ser imprescindible en determinados casos, por lo que la prevención primaria está limitada. Sin embargo, como se ha visto en publicaciones posteriores sobre la materia, una rehabilitación precoz de las mujeres que han sufrido un mayor daño de la MSP puede ser útil para la recuperación de su funcionalidad. Por tanto, el haber identificado pacientes con mayor posibilidad de lesión, puede ayudar a implementar medidas precoces para su recuperación.Fondo de Investigación Sanitaria del Instituto Carlos III, Departamento de Salud de España (PI070261

Auto-adaptative Robot-aided Therapy based in 3D Virtual Tasks controlled by a Supervised and Dynamic Neuro-Fuzzy System

This paper presents an application formed by a classification method based on the architecture of ART neural network (Adaptive Resonance Theory) and the Fuzzy Set Theory to classify physiological reactions in order to automatically and dynamically adapt a robot-assisted rehabilitation therapy to the patient needs, using a three-dimensional task in a virtual reality system. Firstly, the mathematical and structural model of the neuro-fuzzy classification method is described together with the signal and training data acquisition. Then, the virtual designed task with physics behavior and its development procedure are explained. Finally, the general architecture of the experimentation for the auto-adaptive therapy is presented using the classification method with the virtual reality exercise