Discreet element modeling of under sleeper pads using a box test

It has recently been reported that under sleeper pads (USPs) could improve ballasted rail track by decreasing the sleeper settlement and reducing particle breakage. In order to find out what happens at the particle-pad interface, discrete element modelling (DEM) is used to provide micro mechanical insight. The same positive effects of USP are found in the DEM simulations. The evidence provided by DEM shows that application of a USP allows more particles to be in contact with the pad, and causes these particles to transfer a larger lateral load to the adjacent ballast but a smaller vertical load beneath the sleeper. This could be used to explain why the USP helps to reduce the track settlement. In terms of particle breakage, it is found that most breakage occurs at the particle-sleeper interface and along the main contact force chains between particles under the sleeper. The use of USPs could effectively reduce particle abrasion that occurs in both of these regions

Effect of intraoperative fluid optimisation on renal function in patients undergoing emergency abdominal surgery; a randomised controlled pilot study (ISRCTN 11799696) Fluid optimisation for emergency surgery

<b>Background:</b> Emergency abdominal surgery carries a high risk of postoperative morbidity and mortality. Goal directed therapy has been advocated to improve outcome in high-risk surgery. The aim of the present pilot study was to examine the effect of goal directed therapy using fluid alone on postoperative renal function and organ failure score in patients undergoing emergency abdominal surgery. <b>Methods:</b> This prospective randomised pilot study included patients over the age of 50 undergoing emergency abdominal surgery. In the intervention group pulse pressure variation measurements were used to guide fluid boluses of 6% Hydroxyethylstarch 130/0.4. The control group received standard care. Serum urea, creatinine and cystatin C levels were measured prior to and at the end of surgery and postoperatively on day 1, day 3 and day 5. <b>Results:</b> Thirty patients were recruited. One patient died prior to surgery and was excluded from the analysis. The intervention group received a median of 750ml of hydroxyethylstarch. The peak values of postoperative urea were 6.9 (2.7–31.8) vs. 6.4 (3.5–11.5)mmol/l (p=0.425), creatinine 100 (60–300) vs. 85 (65–150) μmol/l (p=0.085) and cystatin C 1.09 (0.66–4.94) vs. 1.01 (0.33–2.29)mg/dl (p=0.352) in the control and intervention group, respectively. <b>Conclusions:</b> In the present pilot study replacing the identified fluid deficit was not associated with a change in renal function. These results do not preclude that goal directed therapy using fluid alone may have an effect on renal function but they would suggest that the effect size of fluid optimisation alone on renal function is small

VOLUMEN 16, NÚMERO 30 (1983-1984)

PROYECTO GEOTÉRMICO CHILES - CERRO NEGRO. Lozano, E.; Cruz, L.ZONAS HIDROGEOLÓGICAS DE COLOMBIA. Lobo-Guerrero, A.ESTUDIO GEOQUÍMICO Y PETROGRÁFICO DE ROCAS SUBVOLCÁNICAS ENTRE LA QUEBRADA CHIRAPOTO Y EL RÍO ARQUÍA (DEPARTAMENTO DE ANTIOQUIA Y CALDAS). Sánchez, L. H.; Parra, R. A.; Ortíz, F.GEOLOGÍA Y EXPERIENCIAS CONSTRUCTIVAS EN EL TÚNEL TUNJITA. Tejada, S. E.CONTRIBUCIÓN AL CONOCIMIENTO DEL PALEOZOICO SUPERIOR EN LA SECCIÓN QUETAME - VILLAVICENCIO. Cortés, R.; De La Espriella, R.TECTÓNICA GRAVITACIONAL EN LA CORDILLERA ORIENTAL AL ESTE DE LA FALLA DE BOYACÁ (DEPARTAMENTO DE BOYACÁ). Reyes, Ch. I.AMBIENTES GEOLÓGICOS URANÍFEROS EN COLOMBIA. Ortega Montero, C

VOLUMEN 16, NÚMERO 30 (1983-1984)

PROYECTO GEOTÉRMICO CHILES - CERRO NEGRO. Lozano, E.; Cruz, L.ZONAS HIDROGEOLÓGICAS DE COLOMBIA. Lobo-Guerrero, A.ESTUDIO GEOQUÍMICO Y PETROGRÁFICO DE ROCAS SUBVOLCÁNICAS ENTRE LA QUEBRADA CHIRAPOTO Y EL RÍO ARQUÍA (DEPARTAMENTO DE ANTIOQUIA Y CALDAS). Sánchez, L. H.; Parra, R. A.; Ortíz, F.GEOLOGÍA Y EXPERIENCIAS CONSTRUCTIVAS EN EL TÚNEL TUNJITA. Tejada, S. E.CONTRIBUCIÓN AL CONOCIMIENTO DEL PALEOZOICO SUPERIOR EN LA SECCIÓN QUETAME - VILLAVICENCIO. Cortés, R.; De La Espriella, R.TECTÓNICA GRAVITACIONAL EN LA CORDILLERA ORIENTAL AL ESTE DE LA FALLA DE BOYACÁ (DEPARTAMENTO DE BOYACÁ). Reyes, Ch. I.AMBIENTES GEOLÓGICOS URANÍFEROS EN COLOMBIA. Ortega Montero, C

Goal-directed fluid management based on pulse pressure variation monitoring during high-risk surgery: a pilot randomized controlled trial

Abstract\ud \ud \ud \ud Introduction\ud \ud Several studies have shown that maximizing stroke volume (or increasing it until a plateau is reached) by volume loading during high-risk surgery may improve post-operative outcome. This goal could be achieved simply by minimizing the variation in arterial pulse pressure (ΔPP) induced by mechanical ventilation. We tested this hypothesis in a prospective, randomized, single-centre study. The primary endpoint was the length of postoperative stay in hospital.\ud \ud \ud \ud Methods\ud \ud Thirty-three patients undergoing high-risk surgery were randomized either to a control group (group C, n = 16) or to an intervention group (group I, n = 17). In group I, ΔPP was continuously monitored during surgery by a multiparameter bedside monitor and minimized to 10% or less by volume loading.\ud \ud \ud \ud Results\ud \ud Both groups were comparable in terms of demographic data, American Society of Anesthesiology score, type, and duration of surgery. During surgery, group I received more fluid than group C (4,618 ± 1,557 versus 1,694 ± 705 ml (mean ± SD), P < 0.0001), and ΔPP decreased from 22 ± 75 to 9 ± 1% (P < 0.05) in group I. The median duration of postoperative stay in hospital (7 versus 17 days, P < 0.01) was lower in group I than in group C. The number of postoperative complications per patient (1.4 ± 2.1 versus 3.9 ± 2.8, P < 0.05), as well as the median duration of mechanical ventilation (1 versus 5 days, P < 0.05) and stay in the intensive care unit (3 versus 9 days, P < 0.01) was also lower in group I.\ud \ud \ud \ud Conclusion\ud \ud Monitoring and minimizing ΔPP by volume loading during high-risk surgery improves postoperative outcome and decreases the length of stay in hospital.\ud \ud \ud \ud Trial registration\ud \ud NCT00479011The authors thank Maria De Amorim (Paris, France) and Julia Fukushima (São Paulo, SP, Brazil) for help in data analysis, Dr Julia Wendon (London, UK) for reviewing the manuscript, and Dixtal (Sao Paulo, SP, Brazil) for providing the software for the automatic calculation of ?PP.The authors thank Maria De Amorim (Paris, France) and Julia Fukushima (São Paulo, SP, Brazil) for help in data analysis, Dr Julia Wendon (London, UK) for reviewing the manuscript, and Dixtal (Sao Paulo, SP, Brazil) for providing the software for the automatic calculation of ?PP

Efecto de la perturbación del bosque en la tasa de visitas de murciélagos polinizadores y sus consecuencias sobre el éxito reproductivo y sistema de apareamiento en árboles de la familia Bombacaceae.

La fragmentación y la perturbación del bosque pueden tener efectos deletéreos sobre el éxito reproductivo y el sistema de apareamiento de los árboles tropicales, además de modificar el compartimiento de sus polinizadores. Los objetivos de este capítulo son: (1) evaluar el efecto de la perturbación del bosque sobre la tasa de visita de los murciélagos a cuatro especies de árboles de Bombacaceas; (2) comparar el éxito reproductivo entre árboles en áreas perturbadas y en bosques continuos; (3) determinar las consecuencias de un cambio en la tasa de visitas de los polinizadores sobre el éxito reproductivo de los árboles; y (4) documentar cómo los patrones de visita de los polinizadores pueden afectar el sistema de apareamiento de las plantas que polinizan. Se estudiaron cuatro especies de árboles de la familia Bombacaceae en los bosques tropicales de Jalisco, México, y en las regiones de Guanacaste y la Península de Osa, en Costa Rica. Los murciélagos nectarívoros fueron los únicos polinizadores efectivos para estas cuatro especies. Las flores de Ceiba grandiflora en el bosque recibieron más visitas por parte de Glossophaga soricina; no se observaron diferencias en el número de visitas por parte de Leptonycteris curasoae y Musonycteris harrisoni solo visitó flores dentro del bosque. Ceiba aesculifolia presentó una mayor tasa de visitas en los sitios perturbados, tanto por G.. soricina como por L. curasoae. Ceiba pentandra, en Chamela, no presentó diferencias en la tasa de visitas de G. soricina entre áreas perturbadas y bosque continuo, pero L. curasoae visitó una mayor cantidad de flores en bosque continuo. En Guanacaste, C. pentandra recibió más visitas de Phyllostomus discolor que de G presentó una mayor producción de flores en fragmentos y no hubo diferencias en la proporción de frutos por flor (fruto/flor). Ceiba grandiflora no presentó diferencias en la producción de flores, pero la razón fruto/flor fue mayor en el bosque. Pachira quinata presentó un patrón similar a C. aesculifolia en cuanto a la producción de flores, pero la razón fruto/flor fue mayor en los árboles de bosque continuo. Estas cuatro especies de Bombacaceae son predominantemente autoincompatibles. Los niveles de exocruzamiento fueron independientes del tipo de hábitat para C. aesculifolia, C. grandiflora y C. pentandra en Guanacaste; sin embargo, los árboles C. pentandra, en la Península de Osa, mostraron un sistema de apareamiento mixto. Los efectos de la perturbación del bosque sobre la polinización por murciélagos, la reproducción de plantas y sus patrones de apareamiento varían según la especie de Bombacaceae y su historia de vida.Forest fragmentation and disturbance can have negative effects on the reproductive success and mating systems of tropical trees, in addition to modifying the behavior of the pollinators that pollinate them. The objectives of this study are: (1) to evaluate the effect of forest disturbance on bat pollinator activity for four bombacaceous species; (2) to compare reproductive success between trees found in disturbed habitats and continuous forest; (3) to determine the consequences of a change in bat pollinator activity on plant reproductive success; and (4) to document how bat pollinator activity may affect breeding systems in the plants they pollinate. Four species from the Bombacaceae family were studied in the tropical forests of Jalisco, Mexico, and in the areas of Guanacaste and Peninsula de Osa, in Costa Rica. Nectarivorous bats were the only effective pollinators observed for these four species. Flowers from Ceiba grandiflora in the forest received more visits from Glossophaga soricina. No differences were observed for Leptonycteris curasoae and Musonycteris harrisoni was only observed visiting flowers in the forest. Flowers from C. aesculifolia in fragmented habitats received more visits from both G. soricina and L. curasoae. For C. pentandra in Chamela no differences in visits were observed for G. soricina between disturbed areas and continuous forest, but L. curasoae visited more flowers in continuous forest. In Guanacaste, C. pentandra received more visits from Phyllostoumus discolor than G. soricina, and in Osa no bat visits were observed. Ceiba aesculifolia produced more flowers in disturbed areas but no differences were observed for fruit set. Ceiba grandiflora showed no differences in flower production but fruit set was greater in the forest. Similar to C. grandiflora, Pachira quinata showed no differences in flower production, however, greater fruit set was observed in continuous forest. These four bombacaceous species are predominantly self-incompatible. Out-crossing rates were independent of habitat for C. aesculifolia, C. grandiflora, and C. pentandra en Guanacaste; however, C. pentandra trees from the Osa Peninsula showed a mixed breeding system. Our results show that the effects of forest disturbance on bat pollination, plant reproductive success and breeding system varied depending on the bombacaceous species and its life history characteristics.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

DEM of triaxial tests on crushable sand

This paper presents simulations of high-pressure triaxial shear tests on a crushable sand. The discrete element method is used, featuring a large number of particles and avoiding the use of agglomerates. The triaxial model features a flexible membrane, therefore allowing realistic deformation, and a simple breakage mechanism is implemented using the octahedral shear stress induced in the particles. The simulations show that particle crushing is essential to replicate the realistic behaviour of sand (in particular the volumetric contraction) in high-pressure shear tests. The general effects of crushing during shear are explored, including its effects on critical states, and the influence of particle strength and confining pressure on the degree of crushing are discussed

Prevalence of dementia and Alzheimer's disease in elders of nursing homes and a senior center of Durango City, Mexico

BACKGROUND: Epidemiological reports about dementia and Alzheimer's disease (AD) in elderly people from developing countries are scarce. Therefore, we sought to determine the prevalences of dementia and AD in a population of nursing home residents and senior center attendees of Durango City, Mexico, and to determine whether any socio-demographic characteristics from the subjects associated with dementia or AD exist. METHODS: One hundred and fifty-five residents of two nursing homes and 125 attendees of a senior center were examined for dementia and Alzheimer's disease. All subjects were tested by the mini-mental state examination, and those who scored twenty-four or less underwent psychiatric and neurological evaluations. Diagnosis of dementia, AD and vascular dementia (VaD) was based on the DSM-IV criteria. Socio-demographic characteristics from each participant were also obtained. RESULTS: Residents of nursing homes found to suffer from dementia were 25 out of 155 (16.1%). Eighteen of them (11.6%) had AD, and seven (4.5%) had VaD. None of the attendees of the senior center suffered from dementia. Dementia (pooled AD and VaD cases) correlated with white ethnicity (OR = 3.2; 95%CI = 1.28–8.31), and a history of unemployment (OR = 6.46; 95%CI = 1.42–25.97), while AD correlated with journeymen occupations (OR = 4.55; 95%CI = 1.00–19.29). CONCLUSION: Prevalence of dementia in residents of nursing homes found in this study is much lower than reported from more industrialized countries. AD was more frequent than VaD. Ethnicity and occupation showed effects on the prevalence figures. The prevalence of dementia found has implications for the optimum kind of health care that nursing homes should provide to their residents