Collision probabilities in the rarefaction fan of asymmetric exclusion processes

We consider the one-dimensional asymmetric simple exclusion process (ASEP) in which particles jump to the right at rate p is an element of (1/2, 1.] and to the left at rate 1 - p, interacting by exclusion. In the initial state there is a finite region such that to the left of this region all sites are occupied and to the right of it all sites are empty. Under this initial state, the hydrodynamical limit of the process converges to the rarefaction fan of the associated Burgers equation. In particular suppose that the initial state has first-class particles to the left of the origin, second-class particles at sites 0 and I, and holes to the right of site I. We show that the probability that the two second-class particles eventually collide is (1 + p)/(3p), where a collision occurs when one of the particles attempts to jump over the other. This also corresponds to the probability that two ASEP processes. started from appropriate initial states and coupled using the so-called ""basic coupling,"" eventually reach the same state. We give various other results about the behaviour of second-class particles in the ASEP. In the totally asymmetric case (p = 1) we explain a further representation in terms of a multi-type particle system, and also use the collision result to derive the probability of coexistence of both clusters in a two-type version of the corner growth model.

Conceito, classificação e quantificação da fiabilidade humana na relação homem-máquina

O estudo da fiabilidade é um tema imprescindível para qualquer sistema homem-máquina que pretenda adquirir os melhores índices de segurança e rendimento. Se a fiabilidade dos equipamentos é um campo onde já muito foi estudado, debatido e provado no terreno e onde os novos desenvolvimentos irão apenas acontecer devido aos avanços tecnológicos que permitam melhor predizer as potenciais falhas dos equipamentos, já a fiabilidade humana é uma área de estudo relativamente nova e onde muito há a desenvolver, particularmente devido ás características inatas do ser humano. Ao contrário da evolução tecnológica, onde a melhoria dos materiais e processos obedece a um aperfeiçoamento relativamente gradual e crescente e que pode ser avaliado e melhorado, o comportamento e o aperfeiçoamento do ser humano apresentam dificuldades e complexidades variadas porque o mesmo é único e sofre influências adversas e imprevisíveis do meio em que vive, as quais têm influência directa no seu comportamento. Assim este trabalho académico propõe-se estudar e identificar as principais causas de erros humanos, através do conhecimento adquirido acerca dos processos cognitivos mais comuns do Homem, bem como definir os conceitos e procedimentos adjacentes à fiabilidade humana e às suas principais ferramentas de avaliação.

A Hopping Mechanism for Cargo Transport by Molecular Motors on Crowded Microtubules

Most models designed to study the bidirectional movement of cargos as they are driven by molecular motors rely on the idea that motors of different polarities can be coordinated by external agents if arranged into a motor-cargo complex to perform the necessary work Gross, Hither and yon: a review of bidirectional microtubule-based transport (Gross in Phys. Biol. 1:R1-R11, 2004). Although these models have provided us with important insights into these phenomena, there are still many unanswered questions regarding the mechanisms through which the movement of the complex takes place on crowded microtubules. For example (i) how does cargo-binding affect motor motility? and in connection with that-(ii) how does the presence of other motors (and also other cargos) on the microtubule affect the motility of the motor-cargo complex? We discuss these questions from a different perspective. The movement of a cargo is conceived here as a hopping process resulting from the transference of cargo between neighboring motors. In the light of this, we examine the conditions under which cargo might display bidirectional movement even if directed by motors of a single polarity. The global properties of the model in the long-time regime are obtained by mapping the dynamics of the collection of interacting motors and cargos into an asymmetric simple exclusion process (ASEP) which can be resolved using the matrix ansatz introduced by Derrida (Derrida and Evans in Nonequilibrium Statistical Mechanics in One Dimension, pp. 277-304, 1997; Derrida et al. in J. Phys. A 26: 1493-1517, 1993).

The dynamics of cargo driven by molecular motors in the context of asymmetric simple exclusion processes

We consider the dynamics of cargo driven by a collection of interacting molecular motors in the context of ail asymmetric simple exclusion process (ASEP). The model is formulated to account for (i) excluded-volume interactions, (ii) the observed asymmetry of the stochastic movement of individual motors and (iii) interactions between motors and cargo. Items (i) and (ii) form the basis of ASEP models and have already been considered to study the behavior of motor density profile [A. Parmeggiani. T. Franosch, E. Frey, Phase Coexistence in driven one-dimensional transport, Phys. Rev. Lett. 90 (2003) 086601-1-086601-4]. Item (iii) is new. It is introduced here as an attempt to describe explicitly the dependence of cargo movement on the dynamics of motors in this context. The steady-state Solutions Of the model indicate that the system undergoes a phase transition of condensation type as the motor density varies. We study the consequences of this transition to the behavior of the average cargo velocity. (C) 2009 Elsevier B.V. All rights reserved.

Maximal lactate steady state in running rats

The higher concentration during exercise at which lactate entry in blood equals its removal is known as maximal lactate steady state (MLSS) and is considered an important indicator of endurance exercise capacity. The aim of the present study was to determine MLSS in running rats. Adult male Wistar sedentary rats, which were selected and adapted to treadmill running for three weeks, were used. After becoming familiarized with treadmill running, the rats were submitted to five exercise tests at 15, 20, 25, 30 and 35 m/min velocities. The velocity sequence was distributed at random. Each test consisted of continuous running for 25 min at one velocity or until the exhaustion. Blood lactate was determined at rest and each 5 min of exercise to find the MLSS. The running rats presented MLSS at the 20 m/min velocity, with blood lactate of 3.9±1.1 mmol/L. At the 15 m/min velocity, the blood lactate also stabilized, but at a lower concentration (3.2±1.1 mmol/L). There was a progressive increase in blood lactate concentration at higher velocities, and some animals reached exhaustion between the 10 th and 25 th minute of exercise. These results indicate that the protocol of MLSS can be used for determination of the maximal aerobic intensity in running rats.

Determination of critical velocity and anaerobic capacity of running rats

The aim of this study was to validate a non-invasive protocol to determine aerobic and anaerobic capacity of treadmill running rats. Thirteen male Wistar rats (90 days old) were submitted to 4 exercise tests, consisting of running at 25, 30, 35 and 40 m min-1, continuously until exhaustion. For the critical velocity (CV) and anaerobic running capacity (ARC) estimations, the hyperbolic curve (velocity versus time to exhaustion (tlim)) was linearized to V= CV+ARC/tlim, where the CV and ARC were linear and slope coefficients, respectively. In order to verify if the CV was the maximal aerobic intensity, the rats were submitted to the maximal lactate steady state test (MLSS) composed of three 25-minute tests of continuous running trials at 15, 20 and 25 m min-1, with blood collection every 5 minutes. The CV was obtained at 22.8±0.7 m min-1 and the ARC, at 26.80±2.77 m. The MLSS was observed at 20m min-1, with blood lactate 3.84 ± 0.31 mmol L-1. There was a progressive increase in lactate concentration at 25 m min-1. The CV and MLSS were different, but presented a high and significant correlation (r=0.81). These results indicate that the non-invasive protocol can be used for physical evaluation of aerobic running rats, but the ARC should still be further investigated.

Effects of physical exercise and cinnamon extract on blood chemistry of type 1 diabetic rats

The present study was designed to analyze the effects of the association between cinnamon extract and aerobic exercise on the glycemic control and serum lipid profile of diabetic rats. Fifty Wistar male rats divided into five groups: control (C), sedentary nondiabetic rats; diabetic (D), sedentary diabetic rats; diabetic cinnamon (DC), sedentary diabetic rats that received cinnamon extract; diabetic exercise (DE), sedentary diabetic rats subjected to physical training; and diabetic cinnamon exercise (DCE), diabetic rats that received cinnamon extract and were subjected to physical training. For the induction of diabetes, the rats received alloxan. The cinnamon was administered to once a day for four weeks. The groups performed swimming exercises for one hour each day with lead overloads (3% - 5% of b.w) for five days a week for four weeks. Body weight loss was lower in the DE group compared to the other diabetic groups. The basal serum glucose of all the diabetic groups was higher compared to the control group. Group D had higher serum cholesterol concentrations compared to the DE and DCE groups. The resting blood lactate in group D was higher than the resting blood lactate in the DC and DE groups. Aerobic exercise partially counteracted the diabetic effects on body weight, serum cholesterol and blood lactate concentrations. No additional beneficial effects of cinnamon extract and aerobic exercise were observed on the parameters studied.

Endurance swimming periodized training in rats

The aim of this study was to develop an experimental protocol for endurance swimming periodization training in rats similar to high performance training in humans, and compare it to continuous training. Three groups of male Wistar rats (90 days old) were allocated to Sedentary Control (SC); Continuous Training (CT); and Periodized Experimental Training (PET) groups. PET and CT trained 5 days/week, over five weeks, CT: continuous training supporting a 5% body mass (bm) load for 40 min/day; PET: training subdivided into basic, specific, and taper periods, with overload changed daily (volume-intensity, continuous, and interval training). Total training overload was quantified (% bm X exercise time in training session) and equalized for the two trained groups. Glucose ([ 3H]2-deoxyglucose) uptake, incorporation to glycogen (synthesis), glucose oxidation (CO 2 production), and lactate production from [U- 14C]glucose by soleus muscle strips incubated in presence of insulin (100μU/mL) were evaluated 48h after the last training session. The load equivalent at 5.5mM blood lactate concentration ([La-5.5]) was determined in the incremental test. Lactate production was similar in all groups. PET presented higher glucose uptake (59%) than SC, and higher glycogen synthesis (51 and 22%) and glucose oxidation (147 and 178%) than SC and CT, respectively. CT presented higher glycogen synthesis rates (23%) than SC. Load [La-5.5] was similar between trained groups and higher than SC. PET presented higher values for glucose metabolism than CT and SC. These results open up new perspectives for studying training methods used in high performance sport through swimming exercise in rats.

Responses of blood lactate concentration in aerobic and anaerobic training protocols at different swimming exercise intensities in rats

A swimming periodized experimental training model in rats in which different training protocols (TP) were classified in aerobic (A) and anaerobic (AN) intensity levels. The purpose of the present study was to verify if the classification of the TP used in the periodized training experimental model presented the blood lactate concentration [La] response adequate to the aerobic and anaerobic intensities levels. Twenty three male Wistar rats were divided into three groups. Two groups of swimming training (continuous, CT, n = 7, and periodized training, PET, n = 7) rats were evaluated during 5 weeks in eight different TP (TP-1 to TP-8) through the analysis of the [La] response. The third group was the sedentary control (SC, n = 9). The TP were classified in five intensity levels, three aerobic (A-1, A-2, A-3) and two anaerobic (AN-1, AN-2). Analysis of variance (ANOVA one-way, P<0.05) indicated significant differences in the [La] among the TP and among the five intensity levels. All TP of the A-2 and A-3 intensity levels differed from the A-1 and AN-1. The A-1 and AN-1 also differed among them. These findings demonstrate that the TP were classified properly at different levels of aerobic and anaerobic intensities, as based on the [La] response in a way similar to that of high performance swimming with humans. The results offer new perspectives for the study of exercise training in swimming rats at different levels intensity for performance or for health.

Glucose homeostasis in type 1 diabetic rats after acute physical activity

Physical activity is considered an extremely effective therapy in cases of type 1 diabetes (DM-1), as it promotes glucose uptake independent of insulin action. However, there are few studies on the effect of a single session of exercise on glucose uptake in DM-1 (i.e., in the absence of insulin). Therefore, the purpose of this study was to assess the effect of a single exercise session on glucose homeostasis in DM-1 rats. For this purpose, 30 male rats were divided into three groups: sedentary control (SC), sedentary diabetic (SD), and exercise diabetic (ED). DM was induced by administration of alloxan and identified by the value of fasting glucose. The physical activity consisted of a single swimming session at the anaerobic threshold intensity for diabetic rats (3.5% body weight overload) for 30 min. The oral glucose tolerance test (OGTT) was performed immediately after the physical activity. The animals were sacrificed 48 hr after the OGTT, and samples were taken from the blood, liver, gastrocnemius, and mesenteric and subcutaneous adipose tissue. We observed that DM caused significant reduction in body weight. A single session of physical activity did not modify the response to the OGTT or glucose. However, it resulted in increased HDL cholesterol and hepatic glycogen content. These results suggest that, despite not having an effect on glucose homeostasis, acute physical activity performed at anaerobic threshold intensity leads to beneficial changes in the context of type 1 diabetes.

Energy expenditure during multiple sets of leg press and bench press

The purpose of this study was to quantify energy expenditure (EE) during multiple sets of leg press (LP) and bench press (BP) exercises in 10 males with at least 1 yr of resistance training (RT). The subjects underwent two sessions to determine 1 repetition maximum (1RM) on the BP and LP and one protocol consisting of a warm up and 4 sets for 10 repetitions at 70% 1RM with a 3-min rest period between sets for each exercise. Energy expenditure was calculated as the sum of oxygen uptake (aerobic component), EPOC, and lactate production (anaerobic component). There were no significant differences in EE between exercises for sets 1 to 4 and the total energy expended. However, statistical analysis revealed a significant difference (P<0.05) between exercises in RT economy (BP, 0.0206 ± 0.0044 kcal·kg-1 vs. LP, 0.0051 ± 0.0015 kcal·kg-1). Within exercise comparison showed set 4 was significantly different from sets 1 and 3 for BP, and for LP a significant difference was found between set 4 and sets 1, 2 and 3. Our results point to an increase in EE during multiple sets at 70% 1RM and show that in spite of the difference in muscle mass involved and total work done during each type of exercise, EE was not different due to greater economy during the LP.

Validation of the lactate minimum test as a specific aerobic evaluation protocol for table tennis players

The purpose of this study was to validate the lactate minimum test as a specific aerobic evaluation protocol for table tennis players. Using the frequency of 72 balls·min-1 for 90 sec, an exercise-induced metabolic acidosis was determined in 8 male table tennis players. The evaluation protocol began with a frequency of 40 balls·min-1 followed by an increase of 8 balls·min-1 every 3 min until exhaustion. The mean values that corresponded to the subjects' lactate minimum (Lacmin) were equal to 53.1 ± 1.5 balls·min-1 [adjusted for the time test (Lacmin_time)] and 51.6 ± 1.6 balls·min-1 [adjusted for the frequency of balls (Lacmin_Freq)], which resulted in a high correlation between the two forms of adjustment (r = 0.96 and (P = 0.01). The mean maximum lactate steady state (MLSS) was 52.6 ± 1.6 balls·min-1. Pearson's correlations between Lacmin_time vs. MLSS and Lacmin_freq vs. MLSS were statistically significant (P = 0.03 and r = 0.86, P = 0.03 and r = 0.85, respectively). These findings indicate that the Lacmin test predicts MLSS. Therefore, it is an excellent method to obtain the athletes' anaerobic threshold. Also, there is the advantage that it can be performed in 1 day in the game area. However, the Lacmin value does not depend on the Lacpeak value.

Six-month evaluation of a resin/dentin interface created by methacrylate and silorane-based materials

Objectives: This study aimed to compare the micro-tensile bond strength of methacrylate resin systems to a silorane-based restorative system on dentin after 24 hours and six months water storage. Material and Methods: The restorative systems Adper Single Bond 2/Filtek Z350 (ASB), Clearfil SE Bond/Z350 (CF), Adper SE Plus/Z350 (ASEP) and P90 Adhesive System/Filtek P90 (P90) were applied on flat dentin surfaces of 20 third molars (n=5). The restored teeth were sectioned perpendicularly to the bonding interface to obtain sticks (0.8 mm2) to be tested after 24 hours (24 h) and 6 months (6 m) of water storage, in a universal testing machine at 0.5 mm/min. The data was analyzed via two-way Analysis of Variance/Bonferroni post hoc tests at 5% global significance. Results: Overall outcomes did not indicate a statistical difference for the resin systems (p=0.26) nor time (p=0.62). No interaction between material × time was detected (p=0.28). Mean standard-deviation in MPa at 24 h and 6 m were: ASB 31.38 (4.53) and 30.06 (1.95), CF 34.26 (3.47) and 32.75 (4.18), ASEP 29.54 (4.14) and 33.47 (2.47), P90 30.27 (2.03) and 31.34 (2.19). Conclusions: The silorane-based system showed a similar performance to methacrylate-based materials on dentin. All systems were stable in terms of bond strength up to 6 month of water storage.

Narraciones de frontera. Las formas del relato de la vida cotidiana en los umbrales escolares de la alfabetización en Misiones. 16H316

La historia de las fronteras nacionales que se configuran alrededor de la provincia de Misiones posee un complejo devenir de tensi ones ideológicas y políticas. Desde la colonización española y la instalación de la orden jesuita hasta la actual etapa de “integración regional”, pasando por la constitución del Estado Nacional, la llegada de los colonos europeos y la doctrina de segurida d nacional, la frontera que la provincia mantiene con Paraguay y Brasil se ha constituido como un espacio de tensiones político - ideológicas permanentes. Simultáneamente, la frontera ha sido un tópico continuo en los relatos sustentados por diversas instit uciones, entre las que se destacan la educación, la historiografía oficial y los medios masivos de comunicación. La narración sobre la frontera se desplegó en diversos campos del saber que interrelacionados privilegiaron un relato oficial que justificó la intervención central sobre los devenires fronterizos: la escuela, la academia, los medios de comunicación dispusieron una narrativa de héroes y épicas donde el conflicto de las mixturas quedaba, la mayoría de las veces, solapado por una ética de la armoní a y el crisol de razas o melting pot. El proceso histórico de configuración de la frontera dispone un relato sobre su construcción y su necesidad como también una genealogía del territorio cartografiado, pero también otro tipo de relato, más sutil, que ins erta la necesidad del límite en los imaginarios cotidianos de los sujetos que viven en esta semiosfera . Sin embargo, mientras las políticas del Estado promovieron la fijación de identidades en ciertos objetos y prácticas culturales, en especial en la educa ción, en la vida cotidiana las pertenencias se inscriben en imaginarios heterogéneos y paradójicos: las narraciones de la vida cotidiana en la frontera desarticulan los paradigmas fundantes del relato oficial y los lugares comunes de la cultura massmediáti ca para establecer continuidades entre las vidas de los habitantes del borde político, cultural y semiótico. El locus ubi de los relatos es la frontera, esa estancia desde la cual pensamos la vida cotidiana con extrema paradoja. La narración articula ese universo fronterizo de conexiones heterogéneas donde nada está definido de antemano como explica el relato oficial y donde surgen las aporías de un proyecto político e ideológico, el Estado - Nación, que nunca se puede sentirse seguro y acabado. Ante la asep sia homogénea de las narraciones oficiales, el narrar fronterizo es un contar entre lenguas (Daviña, 2003; Bhabha, 2002), una escenificación de la vida cotidiana - porque ese entre lenguas significa entre mundos : hábitos, creencias, rituales, etc. - , que art icula los sentidos y revitaliza un dialecto de la supervivencia. Por estas circunstancias, nos interesa el multiacentuado relato de la vida cotidiana en la frontera, narración que enfatiza un modo de vivir en el límite, plagado de pasajes y comercios semi óticos y lingüísticos. En este sentido, destacamos dos dimensiones de nuestro problema: la representación de la frontera a través de la producción discursiva de la práctica narrativa y la propia fronteridad de los relatos de la vida cotidiana en el límite. ¿Cómo se configura la fronteridad en esos relatos? ¿Qué procedimientos retóricos o estrategias narrativas características del discurso entre lenguas circulan en esas narraciones? ¿Qué estereotipos de la vida en la frontera se establecen en los relatos o s on explotados por los discursos que los citan e interpretan? ¿Cuáles son los valores semióticos con respecto a la concepción del tiempo, el espacio y los hábitos culturales que circulan en esas narrativas? Estos interrogantes dan cuenta de un dispositivo c omplejo que circula con extrema fluidez en la semiosfera fronteriza misionera y que instala en los umbrales escolares posibles rupturas o continuidades entre los universos semióticos de los niños, caracterizados por mestizajes culturales y lingüísticos, y la dinámica de la vida escolar que propone la enseñanza de una lengua estandarizada y una serie de hábitos culturales en ocasiones reñidos con los procesos semióticos de la vida cotidiana de los sujetos en situación de umbralidad. Teniendo en cuenta las c aracterísticas de esta semiosfera fronteriza y las tensiones que atraviesan su relación con las políticas y los discurso del centro del Estado nacional, nos interesa explorar las narrativas de la vida cotidiana en la frontera y analizar su importancia en el umbral de la alfabetización escolar, espacio de fricción entre una política educativa e institucional que dispone un relato homogéneo y una práctica cultural que despliega una serie heterogénea de narraciones donde el mestizaje semiótico se presenta com o una marca fundacional. Emprender la investigación nos permitirá resaltar que el relato, mediante sus tópicos y recursos retóricos y narrativos constituye un dispositivo (semiótico y cultural) que estructura y semiotiza nuestra cotidianeidad fronteriza . C onsideramos que el juego tensionante entre memoria y olvido produce narraciones que permiten establecer relaciones dialógicas, heterogéneas y políticas en las que emergen representaciones de la identidad y la otredad en la frontera. Existirían múltiples y contradictorios relatos de la experiencia cotidiana de la frontera que destacarían el carácter complejo y paradójico de la vida en el borde . Por otra parte, no podemos soslayar la tensión constante entre los discursos y relatos mediáticos y las redes semió ticas del universo local misionero caracterizado, en muchos casos, por el despliegue de prácticas, hábitos, creencias y modos de relacionarse propios de la ruralidad. En la semiosfera escolar emergen las fricciones entre los discursos mediáticos globales y las experiencias cotidianas de los niños. En las múltiples semiosferas locales - entre ellas la educativa - se presentaría una compleja y tensa fricción entre un modelo narrativo hegemónico, articulado por el discurso mediático, y la heterogeneidad de relat os que los propios protagonistas de la comunidad despliegan. De esta forma, en el umbral escolar alfabetizador, los niños desplegarían relatos de la experiencia cotidiana donde la presencia de lo ficcional, lo mítico y lo fantástico no funcionaría como neg adora del carácter empírico de la experiencia, sino que potenciaría simbólicamente su propia vida.