Stochastic modeling of soil salinity

A minimalist stochastic model of primary soil salinity is proposed, in which the rate of soil salinization is determined by the balance between dry and wet salt deposition and the intermittent leaching events caused by rainfall events. The long term probability density functions of salt mass and concentration are found by reducing the coupled soil moisture and salt mass balance equation to a single stochastic differential equation driven by multiplicative Poisson noise. The novel analytical solutions provide insight on the interplay of the main soil, plant and climate parameters responsible for long-term soil salinization. In particular, they show the existence of two distinct regimes, one where the mean salt mass remains nearly constant (or decreases) with increasing rainfall frequency, and another where mean salt content increases markedly with increasing rainfall frequency. As a result, relatively small reductions of rainfall in drier climates may entail dramatic shifts in long-term soil salinization trends, with significant consequences e.g. for climate change impacts on rain-fed agricultur

The neglected C of intercultural relations. Cross-cultural adaptation shapes sojourner representations of locals

We investigated, by means of the Reverse Correlation Task (RCT), visual representations of the culturally dominating group of local people held by sojourners as a function of their degree of cross-cultural adaptation. In three studies, using three different methods (reduced RCT, full RCT, conceptual replication) with three independent samples of sojourners and seven independent samples of Portuguese and US-American raters, we gathered clear evidence that poor adaptation goes along with more negative representations of locals. This indicates that sojourner adaptation is reflected, at a social-cognitive level, in the valence of outgroup representationsinfo:eu-repo/semantics/publishedVersio

Protective or harmful? Exploring the ambivalent role of social identification as a moderator of intergroup stress in sojourners

Living outside one's home country may be stressful, and having strong social ties should help deal with this stress. However, social ties may be protective or harmful depending on whether the social group they evoke belongs to the host- or the home country context. The current study examines how social identification with different groups may either buffer or aggravate the negative effects of two stressors (perceived discrimination and symbolic threat) on sojourner adaptation. Two hundred and twenty international students sojourning in nine different countries responded to an online questionnaire. As expected, adaptation was negatively predicted by both stressors. Moreover, high identification with the group of international students attenuated the negative effects of perceived discrimination on psychological adaptation, while home country identification aggravated the negative effects of symbolic threat on sociocultural adaptation.info:eu-repo/semantics/acceptedVersio

Acculturation strategies among ethnic minority workers and the role of intercultural personality traits

International audienceIn an increasingly diverse work context minority employees strive to place and define themselves in terms of work and cultural identities. Based on Berry's acculturation model (1990), we defined and tested preferred acculturation strategies at work. It was predicted that , reflecting strong cultural identity maintenance combined with strong team identity adoption, is the most preferred strategy at work. The present study among non-Dutch employees working in The Netherlands ( = 108) showed that the dual identity is indeed preferred over strong team identity adoption, but solely among minority members who are emotionally stable. It is argued that these people are competent in dealing with the extra conflict and diversity-related stress that this acculturation strategy produces

Flux evaluation in primal and dual boundary-coupled problems

A crucial aspect in boundary-coupled problems such as fluid-structure interaction pertains to the evaluation of fluxes. In boundary-coupled problems, the flux evaluation appears implicitly in the formulation and, consequently, improper flux evaluation can lead to instability. Finite-element approximations of primal and dual problems corresponding to improper formulations can therefore be non-convergent or display suboptimal convergence rates. In this paper, we consider the main aspects of flux evaluation in finite-element approximations of boundary-coupled problems. Based on a model problem, we consider various formulations and illustrate the implications for corresponding primal and dual problems. In addition, we discuss the extension to free-boundary problems, fluid-structure interaction, and electro-osmosis applications

Acute effects of winter air pollution on respiratory health

In this thesis, acute respiratory health effects of exposure to winter air pollution are investigated in panels of children (7-11 yr) and adults (50-70 yr) with and without chronic respiratory symptoms, living in urban and non-urban areas in the Netherlands. The study was performed during three consecutive winters starting in 1992/1993. Each winter, subjects performed twice daily measurements of Peak Expiratory Flow (PEF) and registered the occurrence of respiratory symptoms and medication use in a diary. Air pollution concentrations were measured daily in both areas.The contrast in the concentrations of particulate air pollutants (PM 10 , Black Smoke and sulfate) between urban andnon-urban areas was small, but there was more contrast in the concentrations of the gaseous pollutants SO 2 and NO 2 .In symptomatic children from both areas, significant associations were observed between PM 10 , Black Smoke (BS) and sulfate concentrations and the prevalence of lower respiratory symptoms (LRS) and PEF decrements. Particle concentrations were also associated with bronchodilator use in the urban areas, but not in the non-urban areas. However, differences in use of maintenace medication might be responsible for this. In non-symptomatic children, significant associations were observed between PM 10 and BS concentration and the prevalence of PEF decrements, but of smaller magnitude than for symptomatic children. No associations with respiratory symptoms were observed.In symptomatic adults living in urban areas, PM 10 , BS, sulfate and SO 2 concentrations were associated with the prevalence of decrements in morning PEF, but not in evening PEF. Although especially BS was also associated with upper respiratory symptoms, particle concentrations were not associated with LRS or bronchodilator use. In symptomatic subjects living in non-urban areas, and in non-symptomatic adults from both urban and non-urban areas, no consistent associations between air pollution concentrations and indicators of respiratory health iwere found.Separate analyses in children, based on the presence/absence of objective medical characteristics showed that PM 10 was most cocnsistently associated with respiratory health indicators in symptomatic children who had either high total serum IgE level or a positive skin prick test.In conclusion, low levels of particulate air pollution were associated with adverse effects on respiratory health in 7-11 yr children, while in 50-70 year old symptomatic adults only a weak effect was found. Although there was a tendency of more consistent particle effects in the urban panels, the differences with the non-urban panels were small and might reflect differences in asthma medication use.</p

Memory retention in wild-type and tau mutant Syrian hamsters

Rats are known to display a temporary deficit in memory function 6 h after training on a learning task, a phenomenon known as the ‘Kamin effect’. Later studies showed that maximal retrieval recurs in 24 h intervals after a single training and implied the role of the circadian clock in the suppression of memory retrieval at non-24 h intervals. This study aimed to investigate this further by analysing retention deficits following passive avoidance training in the Syrian hamster. The availability of hamsters carrying the tau mutation was exploited to address the role of the circadian system in periodic retention deficits. It was expected that tau mutant hamsters with an endogenous circadian period of approximately 20 h would have a high retention score at 20 h after training. Surprisingly, deficits in retention were found at 12, 18, 24, and 36 h after training in wild-type hamsters with best performance at 30 h after training. Tau mutant hamsters had significant deficits in memory retention at 20, 24, and 30 h, and no clear periodicity in retention could be observed. Step-through latency scores for mutant hamsters were low at all times except training-testing intervals of 0.25 and 6 h. These results demonstrate the absence of clear memory deficit oscillations in both wild-type and mutant hamsters, and may suggest in particular a long-termmemory deficit in tau mutant hamsters.

A High-Efficiency 4x45W Car Audio Power Amplifier using Load Current Sharing

A 4x45W (EIAJ) monolithic car audio power amplifier is presented that achieves a power dissipation decrease of nearly 2x over standard class AB operation by sharing load currents between loudspeakers. Output signals are conditioned using a common-mode control loop to allow switch placement between loads with minimal THD increase. A prototype is realized in a SOI bipolar-CMOS-DMOS process with 0.5μm feature size. Die area is 7.5x4.6mm2. THD+N @(1kHz,10W) is 0.05%