Use of antibiotics by the poultry industry has the potential to produce residues in edible tissues. In order to protect consumers, the U.S. federal government performs extensive evaluations to ...quantify residues in edible tissues to ensure that concentrations do not exceed the tolerance level. However, in the case of muscle tissue, the regulatory process does not differentiate between different edible muscle types in poultry. Previous studies performed by our laboratory determined higher fluoroquinolone residue concentrations in breast versus thigh muscle. Thus, if thigh tissues were used for residue monitoring, it would not accurately depict the higher concentrations. It is also possible that residue concentrations vary within tissues. To evaluate this possibility, fluoroquinolone antibiotic residues were determined for different breast sections. One hundred sixty chickens were randomly divided into four groups and dosed at 33 days of age with the fluoroquinolone antibiotic, enrofloxacin (Baytril), at either 25 ppm for 3 days, 25 ppm for 7 days, 50 ppm for 3 days, or 50 ppm for 7 days. Breast fillets were collected from each bird (n = 5 birds per day per group) during the dosing and withdrawal period. Each breast was divided into four sections (upper left, upper right, lower left, and lower right) that were analyzed as individual samples for determination of fluoroquinolone concentration. Our results indicated no significant difference (P > 0.05) in the levels of enrofloxacin residues between breast sections during the dosing or withdrawal periods. Consequently, samples can be collected from any breast section to evaluate fluoroquinolone residue concentrations during the regulatory monitoring process.
We consider the problem of automatic generation of control strategies for robotic vehicles given a set of high-level mission specifications, such as "Vehicle x must eventually visit a target region ...and then return to a base," "Regions A and B must be periodically surveyed," or "None of the vehicles can enter an unsafe region." We focus on instances when all of the given specifications cannot be reached simultaneously due to their incompatibility and/or environmental constraints. We aim to find the least-violating control strategy while considering different priorities of satisfying different parts of the mission. Formally, we consider the missions given in the form of linear temporal logic formulas, each of which is assigned a reward that is earned when the formula is satisfied. Leveraging ideas from the automata-based model checking, we propose an algorithm for finding an optimal control strategy that maximizes the sum of rewards earned if this control strategy is applied. We demonstrate the proposed algorithm on an illustrative case study.
Sterols isolated from Tubifex tubifex Perez Gutierrez, Rosa Martha; Reyes, Ivan Cordova
Natural product research,
11/2006, Letnik:
20, Številka:
13
Journal Article
Recenzirano
Four 3β-hydroxysterols isolated from chloroform extract from Tubifex tubifex were shown to have the structures stigmast-23-en-3-ol, stigmast-7,14-dien-3-ol, 22-dehydrocholesterol, and 24 ...methylenecholesterol based on spectroscopic methods. Stigmasterol and β-sitosterol were also investigated on the basis of mass spectral analyses and compared with known compounds.
Teachers' adoption of a new teaching practice is related to their investment in staff development and the degree to which they consider it worthwhile. We conducted an interactive staff development, ...which involved teachers in the analysis, practice, and refinement of new instructional activities. Data from teaching observations, interviews and surveys indicate that the interactive nature of the staff development assisted the teachers to adapt the featured instructional practices in ways that both mirrored and challenged their personal beliefs and knowledge about teaching and learning. The sustained interactive staff development process helped the teachers re-consider the efficacy of their current approaches to teaching while integrating new instructional practices.
We study experimentally gravity-driven granular discharges of laboratory scale silos, during the initial instants of the discharge. We investigate deformable wall silos around their critical collapse ...height, as well as rigid wall silos. We propose a criterion to determine a maximum time for the onset of the collapse and find that the onset of collapse always occurs before the grains adjacent to the wall are sliding down. We conclude that the evolution of the static friction toward a state of maximum mobilization plays a crucial role in the collapse of the silo.
This paper studies the problem of control strategy synthesis for dynamical systems with differential constraints to fulfill a given reachability goal while satisfying a set of safety rules. ...Particular attention is devoted to goals that become feasible only if a subset of the safety rules are violated. The proposed algorithm computes a control law, that minimizes the level of unsafety while the desired goal is guaranteed to be reached. This problem is motivated by an autonomous car navigating an urban environment while following rules of the road such as "always travel in right lane'' and "do not change lanes frequently''. Ideas behind sampling based motion-planning algorithms, such as Probabilistic Road Maps (PRMs) and Rapidly-exploring Random Trees (RRTs), are employed to incrementally construct a finite concretization of the dynamics as a durational Kripke structure. In conjunction with this, a weighted finite automaton that captures the safety rules is used in order to find an optimal trajectory that minimizes the violation of safety rules. We prove that the proposed algorithm guarantees asymptotic optimality, i.e., almost-sure convergence to optimal solutions. We present results of simulation experiments and an implementation on an autonomous urban mobility-on-demand system.
We find by Monte Carlo simulations that the distribution of Voronoï cell sizes for the parking lot model follows a gamma distribution with shape parameter k approximately 2 for high enough packing ...fractions varphi . A gamma distribution of Voronoï cells sizes was found recently by Aste Europhys. Lett. 79, 24003 (2007) in experiments of static packings of monodisperse spheres. This statistic implies that, for high varphi , Edwards' compactivity of the parking lot model depends linearly on the average volume per cell, as predicted by the statistical mechanics calculation of Tarjus and Viot, which explicitly counted the blocked configurations of this model Phys. Rev. E 69, 011307 (2004).
Este documento trata la descripción de un proyecto para conseguir un recurso vital, el agua. El agua es el recurso más importante en la vida diaria de la humanidad. Este proyecto intenta compensar la ...falta de acceso a este recurso mediante condensación de vapor presente en el aire. Se vio la necesidad de hacer este trabajo, dado que, por terremotos, zonas costeras se vieron afectadas, destruyendo edificaciones y tuberías de distribución de este producto vital; lo cual dejó en muy precarias condiciones las zonas afectadas. El objetivo de este trabajo es mostrar cómo condensar agua, limpia y de calidad para el consumo humano, mediante un dispositivo de condensación, para cubrir las necesidades más vitales, que son hidratación diaria, prevención de enfermedades y preparación de alimentos. De esta manera, el diferencial de temperatura entre el aire y el suelo, es el factor clave en el diseño, ya que se da de manera natural sin ningún aporte energético extra. En la historia se han generado distintos mecanismos de condensación, los más eficientes no toman en cuenta la humedad relativa del aire, sino alcanzar el punto de rocío cambiando la temperatura. Este es el mecanismo de funcionamiento del proyecto. Este trabajo fue diseñado para la zona serrana del país, y a partir de este, se puede extrapolar el trabajo para una zona más cálida.
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