Gas permeation through a polymer network

We study the diffusion of gas molecules through a two-dimensional network of polymers with the help of Monte Carlo simulations. The polymers are modeled as non-interacting random walks on the bonds of a two-dimensional square lattice, while the gas particles occupy the lattice cells. When a particle attempts to jump to a nearest-neighbor empty cell, it has to overcome an energy barrier which is determined by the number of polymer segments on the bond separating the two cells. We investigate the gas current $J$ as a function of the mean segment density $\rho$, the polymer length $\ell$ and the probability $q^{m}$ for hopping across $m$ segments. Whereas $J$ decreases monotonically with $\rho$ for fixed $\ell$, its behavior for fixed $\rho$ and increasing $\ell$ depends strongly on $q$. For small, non-zero $q$, $J$ appears to increase slowly with $\ell$. In contrast, for $q=0$, it is dominated by the underlying percolation problem and can be non-monotonic. We provide heuristic arguments to put these interesting phenomena into context.Comment: Dedicated to Lothar Schaefer on the occasion of his 60th birthday. 11 pages, 3 figure

Autonomous detection and anticipation of jam fronts from messages propagated by inter-vehicle communication

In this paper, a minimalist, completely distributed freeway traffic information system is introduced. It involves an autonomous, vehicle-based jam front detection, the information transmission via inter-vehicle communication, and the forecast of the spatial position of jam fronts by reconstructing the spatiotemporal traffic situation based on the transmitted information. The whole system is simulated with an integrated traffic simulator, that is based on a realistic microscopic traffic model for longitudinal movements and lane changes. The function of its communication module has been explicitly validated by comparing the simulation results with analytical calculations. By means of simulations, we show that the algorithms for a congestion-front recognition, message transmission, and processing predict reliably the existence and position of jam fronts for vehicle equipment rates as low as 3%. A reliable mode of operation already for small market penetrations is crucial for the successful introduction of inter-vehicle communication. The short-term prediction of jam fronts is not only useful for the driver, but is essential for enhancing road safety and road capacity by intelligent adaptive cruise control systems.Comment: Published in the Proceedings of the Annual Meeting of the Transportation Research Board 200

Reducing congestion in obstructed highways with traffic data dissemination using adhoc vehicular networks

Vehicle-to-vehicle communications can be used effectively for intelligent transport systems (ITSs) and location-aware services. The ability to disseminate information in an ad hoc fashion allows pertinent information to propagate faster through a network. In the realm of ITS, the ability to spread warning information faster and further is of great advantage to receivers. In this paper we propose and present a message-dissemination procedure that uses vehicular wireless protocols to influence vehicular flow, reducing congestion in road networks. The computational experiments we present show how a car-following model and lane-change algorithm can be adapted to “react” to the reception of information. This model also illustrates the advantages of coupling together with vehicular flow modelling tools and network simulation tools

Simple and selective spectrophotometric assay of diethylcarbamazine citrate using 2,3-dichloro-5,6-dicyano-p-benzoquinone and 2,4-dinitro phenol

Two simple, rapid and inexpensive spectrophotometric methods are described for the determination of diethylcarbamazine citrate (DEC) in bulk drug and formulations. The methods are based on the charge-transfer (CT) complexation reaction involving DEC as the n- donor and 2,3-dichloro-5,6-dicyano-p-benzoquinone DDQ] (method A) and 2,4-dinitro phenol DNP] (method B) as pi-acceptors in chloroform. The absorbance of CT complexes was measured at 480 nm for method A, and 420 nm for method B. Under optimum conditions, Beer's law was obeyed over the concentration ranges 4-90 and 4-100 mu g mL(-1) for methods A and B, respectively

Calibrating Car-Following Models using Trajectory Data: Methodological Study

The car-following behavior of individual drivers in real city traffic is studied on the basis of (publicly available) trajectory datasets recorded by a vehicle equipped with an radar sensor. By means of a nonlinear optimization procedure based on a genetic algorithm, we calibrate the Intelligent Driver Model and the Velocity Difference Model by minimizing the deviations between the observed driving dynamics and the simulated trajectory when following the same leading vehicle. The reliability and robustness of the nonlinear fits are assessed by applying different optimization criteria, i.e., different measures for the deviations between two trajectories. The obtained errors are in the range between~11% and~29% which is consistent with typical error ranges obtained in previous studies. In addition, we found that the calibrated parameter values of the Velocity Difference Model strongly depend on the optimization criterion, while the Intelligent Driver Model is more robust in this respect. By applying an explicit delay to the model input, we investigated the influence of a reaction time. Remarkably, we found a negligible influence of the reaction time indicating that drivers compensate for their reaction time by anticipation. Furthermore, the parameter sets calibrated to a certain trajectory are applied to the other trajectories allowing for model validation. The results indicate that ``intra-driver variability'' rather than ``inter-driver variability'' accounts for a large part of the calibration errors. The results are used to suggest some criteria towards a benchmarking of car-following models

Idiopathic Adolescent Scoliosis and self-concept

Introducción y objetivos. Esta investigación trata sobre adolescentes que presentan escoliosis idiopática. Queremos estudiar si la manifestación de tal patología tiene efectos psicológicos en el adolescente que la presenta y sobre todo en la imagen que percibe de sí mismo como de su entorno. El objetivo del presente estudio se concreta en conocer la influencia de la escoliosis idiopática en el autoconcepto o imagen de si mismo en el adolescente. Material y métodos. Estudio observacional. Muestra formada por 17 adolescentes de 10-18 años de edad. En primer lugar, al tratarse de menores de edad y con el fin de informar de las características del estudio, como de la participación en el mismo, se le pasó un consentimiento informado a los padres o tutores. Asimismo, se extrajeron una serie de datos biográficos para identificar aspectos como el perfil clínico y personal, diagnóstico, antecedentes familiares, datos personal y de ocio del paciente, a través de un cuestionario de datos biográficos. Finalmente se le pasó el cuestionario de Pierre-Harris que consta de 80 ítems que abarcan las siguientes dimensiones del concepto de si mismo: comportamiento, estatus general y académico, popularidad, felicidad y satisfacción, apariencia física, ansiedad. Tras la recogida de los datos, se realizó un análisis de distribución de frecuencias, mediante el método estadístico SPSS v. 15.0 para Windows, con el cálculo de la media y la desviación típica, de los mismos. Resultados. Las puntuaciones del cuestionario de Pierre-Harris por cada sujeto, están por encima de la media establecida en cada dimensión. Solamente, en la dimensión de ansiedad, hay 5 sujetos por debajo de la media. Conclusiones. No se observó una imagen de sí mismo negativa o por debajo de la media en la muestra estudiada en ninguna dimensión del cuestionario. Solamente una de las dimensiones presentaba algunos individuos por debajo, por lo tanto, en la muestra estudiada con escoliosis idiopática del adolescente, la imagen de sí mismo es buena, por los valores encontrados.Terapia y Rehabilitació

A novel human skin chamber model to study wound infection ex vivo

Wound infections with multi-drug resistant bacteria increase morbidity and mortality and have considerable socioeconomic impact. They can lead to impaired wound healing, resulting in rising treatment costs. The aim of this study was to investigate an ex vivo human wound infection model. Human full-thickness skin from the operating room (OR) was placed into the Bo-Drum® and cultivated for 7 days in an air–liquid interphase. On day 8, the skin was inoculated with either (1) Pseudomonas aeruginosa, (2) Staphylococcus aureus (105 CFU, n = 3) or (3) carrier control. 1, 3 and 7 days after inoculation colony forming units in the tissue/media were determined and cytokine expression was quantified. A reliable and reproducible wound infection could be established for 7 days. At this timepoint, 1.8 × 108 CFU/g tissue of P. aeruginosa and 2 × 107 CFU/g tissue of S. aureus were detected. Immunohistochemical analysis demonstrated bacterial infection and epidermolysis in infected skin. RT-PCR analysis exhibited a significant induction of proinflammatory cytokines after infection. The BO-drum® is a robust, easy-to-use, sterilizable and reusable ex vivo full-skin culture system. For investigation of wound infection, treatment and healing, the BO-drum® presents a convenient model and may help to standardize wound research