Vibrations of Short Span Railway Bridges for High Speed Lines

The physical model based on moving constant loads is widely used for the analysis of railway bridges. Nevertheless, this model is not well-suited for the study of short span bridges (L<=15-20 m), and the results it produces (displacements and accelerations) are much greater than those obtained experimentally. In this paper two factors are analysed which are believed to have an influence in the dynamic behaviour of short bridges. These two factors are not accounted for by the moving loads model and are the following: the distribution of the loads due to the presence of the sleepers and ballast layer, and the train-bridge interaction. Several numerical simulations have been performed in order to decide on their influence, and the results are presented and discussed herein

Ionic calcium content of light dense human red cells separated by percoll density gradients

AbstractIn this paper we have compared the adequacy of two methods using Percoll density gradients to separate light and dense erythrocytes from fresh human blood. After measuring the distribution of some classical age-markers such as haemoglobin, potassium and creatine contents, it was found that preformed gradients generated more stringent conditions for age-related density separations. Employing such gradients, the free Ca2+ content of above sub-populations was assessed with Fura-2, under conditions where the viscosity effect was abolished. In five experiments, the free Ca2+ content (mean value±1 S.D.) was 8.4±2.82 nM and 31.2±13.0 nM for the 7–10% lightest and densest cells, respectively. These results are discussed in connection to red cell senescence

Markovianization with approximate unitary designs

Memoryless processes are ubiquitous in nature, in contrast with the mathematics of open systems theory, which states that non-Markovian processes should be the norm. This discrepancy is usually addressed by subjectively making the environment forgetful. Here we prove that there are physical non-Markovian processes that with high probability look highly Markovian for all orders of correlations; we call this phenomenon Markovianization. Formally, we show that when a quantum process has dynamics given by an approximate unitary design, a large deviation bound on the size of non-Markovian memory is implied. We exemplify our result employing an efficient construction of an approximate unitary circuit design using two-qubit interactions only, showing how seemingly simple systems can speedily become forgetful. Conversely, since the process is closed, it should be possible to detect the underlying non-Markovian effects. However, for these processes, observing non-Markovian signatures would require highly entangling resources and hence be a difficult task.Comment: 6+9 pages, 5 figures. Published version, only presentation change

Almost Markovian processes from closed dynamics

It is common, when dealing with quantum processes involving a subsystem of a much larger composite closed system, to treat them as effectively memory-less (Markovian). While open systems theory tells us that non-Markovian processes should be the norm, the ubiquity of Markovian processes is undeniable. Here, without resorting to the Born-Markov assumption of weak coupling or making any approximations, we formally prove that processes are close to Markovian ones, when the subsystem is sufficiently small compared to the remainder of the composite, with a probability that tends to unity exponentially in the size of the latter. We also show that, for a fixed global system size, it may not be possible to neglect non-Markovian effects when the process is allowed to continue for long enough. However, detecting non-Markovianity for such processes would usually require non-trivial entangling resources. Our results have foundational importance, as they give birth to almost Markovian processes from composite closed dynamics, and to obtain them we introduce a new notion of equilibration that is far stronger than the conventional one and show that this stronger equilibration is attained.Comment: 9 pages, 13 pages of appendices, 5 figures, numerical example. Replaced with journal version and fixed hyperlink

Regretting fatherhood in Spain

Objective: In this first study of its kind in Spain, we analyse the scope of and reasons underlying paternal regret. Background: Research on parental regret, a subject only recently broached by analysts, tends to focus on motherhood. Regretting fatherhood has been only scantly researched. In this study we test the effects of intensive fathering, the use of different care resources, economic and employment conditions, and satisfaction with respondents’ partnership on their regret for having children. Method: The analysis is based on an online survey of parents of children under 7 years old (QUIDAN Survey) A total of 3100 parents were interviewed, with the sample evenly distributed by sex and youngest child’s age, and proportional by parents’ highest level of schooling and place of residence. The weighted subsample used in this article included 1374 fathers. The hypotheses are tested with logistic regression. Results: The social factors associated with a greater likelihood of regret include circumstances that challenge men’s role as primary breadwinner, a negative impact of fatherhood on job career, a high dependence on grandparents for balancing working and private lives and partnership dissatisfaction. A relationship between intensive fathering and regret could not be observed. Conclusion: The findings show the extent of paternal regret to be fairly limited, similar to the proportion reported for maternal regret. Paternal regret is mainly associated with family and working circumstancesThe research was funded by the Spanish Research Agency under the project ‘Childcare practices among Spanish families with children less than seven years old: Agents, practices and satisfaction’, grant number CSO2017-84634-

Is Spanish parental leave 'traditionalising' the gender distribution of childcare and housework?

Objective: The question addressed in this study is the possible effect of mothers' use of parental leave on the share of childcare and housework assumed by each parent. Background: Whilst the length of parental leave is greater in Spain than in other European countries, as it is unpaid, take-up rates are low. Such leaves are taken more frequently and for longer periods by women than men. Method: To determine the answer, two multivariate regression models were applied to National Statistics Institute 2018 Fertility Survey data. The main independent variables were fathers' and mothers' use of parental leave. The models also controlled for the effects of family and socio-economic variables on the share of childcare and housework assumed by each parent. Results: The findings showed that mothers' use of unpaid full-time parental leave traditionalises the distribution of domestic chores only when the leave extends beyond one year, whereas part-time leave-taking has no effect whatsoever. That such reversion to tradition can be neutralised when fathers take leaves attests to the advisability of encouraging paternal use. The effects apply to childcare only, however, for other household chores are still distributed along very traditional lines. Conclusion: Unpaid parental leave use by mothers "traditionalizes" the allocation of childcare within the couple, but only when it takes longer than a yearThis study was funded by the Agencia Estatal de Investigación under Grant CSO2017-84634-

Effect of soil properties on the dynamic response of simply-supported bridges under railway traffic through coupled boundary element-finite element analyses

Railway induced vibrations on short-to-medium span simply-supported (SS) bridges is addressed in this contribution. Such structures may experience high levels of vertical acceleration at the platform, leading to adverse consequences such as a premature degradation of the ballast layer and passenger discomfort. In the present study, the evolution of the bridge dynamic response when soil-structure interaction (SSI) is taken into account is investigated. To this end a coupled three-dimensional (3D) Boundary Element-Finite Element model (BEM-FEM) formulated in the time domain is implemented to reproduce the soil and structural behaviour, respectively. First, a set of soil-bridge systems of interest is defined, covering a wide range of lengths and natural frequencies for the structures, and an interval of expectable elastic properties and damping levels for the soil. Then, different types of analyses are performed on the soil-bridge systems extracting conclusions regarding the effect of including SSI in numerical models for predicting the bridge behaviour under railway traffic. In particular natural frequencies and modal damping levels are identified, and the structure amplification after the passage of a moving load in free vibration is investigated. Conclusions regarding how resonance and cancellation conditions may be affected by soil properties are extracted. Finally, the dynamic response of a real bridge, belonging to the Spanish railway network, is evaluated under the circulation of trains that induce second and third resonances of the bridge fundamental mode. The effect of the soil flexibility, soil material damping and the bridge resonance order are evaluated. Conclusions regarding the appropriateness of the results provided by common models which do not include SSI effects are extractedMinisterio de Economía y Competitividad BIA2013-43085-PMinisterio de Economía y Competitividad BIA2016-75042-C2Centro Informático Científico de Andalucía (CICA