Free vibrations of simply-supported beam bridges under moving loads: Maximum resonance, cancellation and resonant vertical acceleration

The advent of high-speed railways has raised many concerns regarding the behaviour of bridges. Particularly, the analysis of the free vibrations generated by each load is of great interest because they can possibly accumulate and create resonance phenomena. Regarding simply supported beams, earlier contributions showed that the free vibrations created by a single moving force are of maximum or zero amplitude (cancellation) for certain speeds. In the present paper new closed-form expressions are given for the cancellation speeds of a generic mode, as well as for the most representative points of maximum amplitude. Similar new results are provided for elastically supported beams as well. A simpler, closed-form approximate expression of the cancellation condition for an elastically supported beam is also derived from the analysis of a single passing load; this approximate formula is in good agreement with the exact results. Knowing a priori the speeds of maximum free vibrations or cancellation is of great interest for experimental tests on bridges, particularly as regards the evaluation of amplitude-dependent magnitudes such as structural damping. Regarding the resonance phenomena, if the resonance speeds coincide with either a maximum free vibration or a cancellation speed, then a maximum resonance or a cancellation of resonance will occur. The most relevant cases thereof have been investigated, and new expressions which allow predicting them for a generic mode are given. Finally, a new approximate formula is proposed for estimating the maximum acceleration of simply supported bridges caused by resonances of the fundamental mode. After extensive numerical testing, the formula has proved to be a useful tool for a first assessment of simply supported bridges according to building codes such as Eurocodes. (C) 2012 Elsevier Ltd. All rights reserved.The authors acknowledge the financial support of the State Secretariat for Research of the Spanish Ministry of Science and Innovation (Secretaria de Estado de Investigacion, Ministerio de Ciencia e Innovacion, MICINN) in the framework of the Research Project BIA2008-04111.Museros Romero, P.; Moliner, E.; Martinez-Rodrigo, M. (2013). Free vibrations of simply-supported beam bridges under moving loads: Maximum resonance, cancellation and resonant vertical acceleration. Journal of Sound and Vibration. 332(2):326-345. https://doi.org/10.1016/j.jsv.2012.08.008326345332

Short-term adaptations following Complex Training in team-sports: A meta-analysis

Objective. The purpose of this meta-analysis was to study the short-term adaptations on sprint and vertical jump (VJ) performance following Complex Training (CT) in team-sports. CT is a resistance training method aimed at developing both strength and power, which has a direct effect on sprint and VJ. It consists on alternating heavy resistance training exercises with plyometric/power ones, set for set, on the same workout. Methods. A search of electronic databases up to July 2016 (PubMed-MEDLINE, SPORTDiscus, Web of Knowledge) was conducted. Inclusion criteria: 1) at least one CT intervention group; 2) training protocols ≥4-wks; 3) sample of team-sport players; 4) sprint or VJ as an outcome variable. Effect sizes (ES) of each intervention were calculated and subgroup analyses were performed. Results. A total of 9 studies (13 CT groups) met the inclusion criteria. Medium effect sizes (ES) (ES = 0.73) were obtained for pre-post improvements in sprint, and small (ES = 0.41) in VJ, following CT. Experimental-groups presented better post-intervention sprint (ES = 1.01) and VJ (ES = 0.63) performance than control-groups. Sprint. Large ESs were exhibited in younger athletes (12 total sessions (ES = 0.74). VJ. Large ESs in programs with >12 total sessions (ES = 0.81). Medium ESs obtained for under-Division I individuals (ES = 0.56); protocols with intracomplex rest intervals ≥2 min (ES = 0.55); conditioning activities with intensities ≤85% 1RM (ES = 0.64); basketball/volleyball players (ES = 0.55). Small ESs were found for younger athletes (ES = 0.42); interventions ≥6 weeks (ES = 0.45). Conclusions. CT interventions have positive medium effects on sprint performance and small effects on VJ in team-sport athletes. This training method is a suitable option to include in the season planning

Does major depressive disorder cause osteoporosis in a young man?

We recently reviewed the literature about major depressive disorder (MDD) as an additional risk factor for osteoporosis (1, 2). Most of the studies examining the association between depression and osteoporosis have been conducted in women whereas the few existing studies on depression and osteoporosis conducted in men have been limited to the elderly (3, 4). An association between depression and lower BMD has been reported in elderly Asian men (4), however, the same association was not observed in community-dwelling, elderly Caucasian men (3). Very little is known about osteoporosis in young men (5, 6). Results from the Third National Health and Nutrition Examination Survey (NHANES III) show that major depressive episode (MDE) is associated with 2% lower BMD at the total proximal femoral level in multivariate models in young men but not in women (5). The existence of a relationship between depression and osteoporosis in young men remains controversial

Mutualism effectiveness and vertical transmission of symbiotic fungal endophytes in response to host genetic backround

v2012okpka ks

Plyometric Training in Female Volleyball Players. Systematic Review

El voleibol femenino se práctica en todo el mundo a nivel profesional y amateur. Los saltos verticales son una parte fundamental para el desarrollo de este deporte, por lo que el entrenamiento pliométrico puede ser eficaz para un aumento del rendimiento. El propósito de estudio fue describir cuáles han sido los métodos y programas de entrenamiento pliométrico en mujeres que practican voleibol, así como el resultado obtenido en función de estos. El proceso de búsqueda en las bases de datos se llevó a cabo desde Marzo hasta Junio de 2016. Las bases de datos consultadas fueron Pubmed, Web of Science, Cochrane y SPORTDiscus. La revisión sistemática fue realizada bajo las recomendaciones de la declaración PRISMA. La calidad metodológica de los estudios fue evaluada mediante la Escala PEDro. Como resultado, se obtuvieron un total de 205 artículos tras eliminar aquellos que estaban por duplicado. Finalmente 7 artículos fueron seleccionados. Los resultados principales fueron que aquellos estudios que utilizan deportistas amateurs obtienen mejores resultados que los realizados con deportistas profesionales cuando se realizan programas de entrenamiento pliométrico. También se indica que un período de entrenamiento pliométrico de baja intensidad puede prevenir una disminución en la altura del salto vertical; así como es necesario programar la pretemporada para evitar pérdida en la capacidad de salto. Todo ello parece indicar, como conclusión, que es necesario una disminución del volumen y un aumento de la intensidad en el entrenamiento pliométrico.Female volleyball is practiced all over the world at a professional and amateur level. Vertical jumps are a fundamental part of the development of this sport. In this sense, plyometric training can be effective for increased performance. The purpose of the study was to describe the methods and programs of plyometric training in women volleyball players, as well as the results obtained from them. The following electronic databases were searched March to June 2016. Electronic databases consulted were Pubmed, Web of Science, Cochrane and SPORTDiscus. This systematic review was performed following PRISMA statement. PEDro scale was used to evaluated the methodological quality of the included studies. As total of 205 articles were obtained after remove duplicates. Finally 7 articles were selected. The main results were that those studies using amateur athletes obtain better results than those performed with professional athletes when performing plyometric training programs. It is also indicated that a period of low intensity plyometric training could prevent a decrease in vertical jump height; As well as it is necessary to schedule the preseason to avoid loss in the ability to jump. All this seems to indicate, in conclusion, that a decrease in volume and an increase in intensity in the training of plyometric training is necessary

Salinity tolerance as a factor controlling spatial patterns in composition and structure of zooplankton in the Guadalquivir estuary

Trabajo presentado en ECSA 56 (Coastal systems in transition: From a 'natural' to an 'anthropogenically-modified' state), celebrado en Bremen del 4 al 7 de septiembre de 2016.N

Factors in the development of secondary hyperparathyroidism during graded renal failure in the rat

Factors in the development of secondary hyperparathyroidism during graded renal failure in the rat. Secondary hyperparathyroidism (2° HPT) develops as a result of renal failure. Hypocalcemia, phosphorus retention, calcitriol deficiency and skeletal resistance to the calcemic action of parathyroid hormone (PTH) are closely interrelated pathogenic factors important for the development of 2° HPT in renal failure. Since previous studies have mainly focused on advanced renal failure, only limited data are available in early renal failure. The goal of the present study was to evaluate how alterations in the dietary calcium and phosphorus composition affect the factors known to contribute to the genesis of 2° HPT in early and more advanced renal failure. To achieve this goal, graded differences in renal function were surgically induced in 453 rats while the dietary content of calcium and phosphorus was varied. Three different diets were used: (1) a high phosphorus diet (HPD), to induce phosphorus retention and stimulate 2° HPT; (2) a high calcium diet (HCaD), to inhibit calcitriol synthesis; and (3) a moderate calcium-moderate phosphorus diet (MCaPD), to separate the effects of high dietary phosphorus and calcium. Based on the serum creatinine (SCr) concentration rats were assigned to one of four different groups: (1) normal renal function (SCr ≤ 0.3 mg/dl); (2) mild renal failure (SCr 0.4 to 0.6 mg/dl); (3) moderate renal failure (SCr 0.7 to 0.8 mg/dl); or (4) advanced renal failure (SCr ≥ 0.9 mg/dl). As the severity of renal failure increased, progressive 2° HPT developed in each of the dietary groups. In the HPD group, the increase in PTH in normals from 47 ± 2 to 135 ± 14 pg/ml in mild renal failure (P < 0.001) was associated with hyperphosphatemia, a decrease in calcitriol and a decreased calcemic response to PTH. In the HCaD group, the increase in PTH in normals from 42 ± 2 to 74 ± 4 pg/ml in mild renal failure (P < 0.001) was associated with a decrease in calcitriol. In the MCaPD group, 2° HPT developed (40 ± 2 vs. 70 ± 4 pg/ml, normals vs. mild renal failure, P < 0.001) despite normal serum calcium, phosphorus and calcitriol levels; however, a decreased calcemic response to PTH was observed. In advanced renal failure, progressive increases of PTH were observed in all groups, but PTH levels were approximately three-fold greater in the HPD than the HCaD and MCaPD groups (410 ± 24, 114 ± 14 and 138 ± 17 pg/ml, respectively; P < 0.001). While serum calcitriol levels were markedly decreased in the HPD and HCaD groups in advanced renal failure, normal calcitriol levels were present in the MCaPD group. In summary, the development and magnitude of 2° HPT in the HPD group could be best explained by the contribution of several additive factors which included: hypocalcemia, phosphorus retention, a calcitriol deficiency and a decreased calcemic response to PTH. In the HCaD group, a calcitriol deficiency appeared to be the most important factor for the development of 2° HPT. In the MCaPD group, a decreased calcemic response to PTH, which may have been due to uremia, was the only factor to which 2° HPT could be attributed

SAVASA project @ TRECVID 2012: interactive surveillance event detection

In this paper we describe our participation in the interactive surveillance event detection task at TRECVid 2012. The system we developed was comprised of individual classifiers brought together behind a simple video search interface that enabled users to select relevant segments based on down~sampled animated gifs. Two types of user -- `experts' and `end users' -- performed the evaluations. Due to time constraints we focussed on three events -- ObjectPut, PersonRuns and Pointing -- and two of the five available cameras (1 and 3). Results from the interactive runs as well as discussion of the performance of the underlying retrospective classifiers are presented