Study of the evolution of the seismic cycle of stress and strain associated to the El Salvador Fault Zone

• Central America: – Regional studies in Central America (Seismic Hazard). – El Salvador Fault Zone (ESFZ). – Aguacaliente‐Navarro Fault Zone (ANFZ), Central Valley of Costa Rica. – Haiti (seismic hazard) • Spain: – Regional‐Nacional studies of seismic hazards (applications to building codes, eurocode, emergency plans, etc.) – Betic range zone, south of Spain. – Ibero‐Maghrebi region (collision zone)

Implications of the mesophyll conductance to CO2 for photosynthesis and water-use efficiency during long-term water stress and recovery in two contrasting Eucalyptu species

Water stress (WS) slows growth and photosynthesis (An), but most knowledge comes from short-time studies that do not account for longer term acclimation processes that are especially relevant in tree species. Using two Eucalyptus species that contrast in drought tolerance, we induced moderate and severe water deficits by withholding water until stomatal conductance (gsw) decreased to two pre-defined values for 24 d, WS was maintained at the target gsw for 29 d and then plants were re-watered. Additionally, we developed new equations to simulate the effect on mesophyll conductance (gm) of accounting for the resistance to refixation of CO2. The diffusive limitations to CO2, dominated by the stomata, were the most important constraints to An. Full recovery of An was reached after re-watering, characterized by quick recovery of gm and even higher biochemical capacity, in contrast to the slower recovery of gsw. The acclimation to long-term WS led to decreased mesophyll and biochemical limitations, in contrast to studies in which stress was imposed more rapidly. Finally, we provide evidence that higher gm under WS contributes to higher intrinsic water-use efficiency (iWUE) and reduces the leaf oxidative stress, highlighting the importance of gm as a target for breeding/genetic engineering.

Social stress and the reactivation of latent herpes simplex virus type 1

Psychological stress is thought to contribute to reactivation of latent herpes simplex virus (HSV). Although several animal models have been developed in an effort to reproduce different pathogenic aspects of HSV keratitis or labialis, until now, no good animal model existed in which application of a psychological laboratory stressor results in reliable reactivation of the virus. Reported herein, disruption of the social hierarchy within colonies of mice increased aggression among cohorts, activated the hypothalamic-pituitary-adrenal axis, and caused reactivation of latent HSV type 1 in greater than 40% of latently infected animals. However, activation of the hypothalamic-pituitary-adrenal axis using restraint stress did not activate the latent virus. Thus, the use of social stress in mice provides a good model in which to investigate the neuroendocrine mechanisms that underlie behaviorally mediated reactivation of latent herpesviruses.

Physical stress and diversity-productivity relationships: The role of positive interactions

If environmental stress provides conditions under which positive relationships between plant species richness and productivity become apparent, then species that seem functionally redundant under constant conditions may add to community functioning under variable conditions. Using naturally co-occurring mosses and liverworts, we constructed bryophyte communities to test relationships between species diversity (1, 2, 4, 8, 16, 24, or 32 species) and productivity under constant conditions and when exposed to experimental drought. We found no relationship between species richness and biomass under constant conditions. However, when communities were exposed to experimental drought, biomass increased with species richness. Responses of individual species demonstrated that facilitative interactions rather than sampling effects or niche complementarity best explained results—survivorship increased for almost all species, and those species least resistant to drought in monoculture had the greatest increase in biomass. Positive interactions may be an important but previously underemphasized mechanism linking high diversity to high productivity under stressful environmental conditions.

Regulation of K+ Channels in Maize Roots by Water Stress and Abscisic Acid1

Root cortical and stelar protoplasts were isolated from maize (Zea mays L.) plants that were either well watered or water stressed, and the patch-clamp technique was used to investigate their plasma membrane K+ channel activity. In the root cortex water stress did not significantly affect inward- or outward-rectifying K+ conductances relative to those observed in well-watered plants. In contrast, water stress significantly reduced the magnitude of the outward-rectifying K+ current in the root stele but had little effect on the inward-rectifying K+ current. Pretreating well-watered plants with abscisic acid also significantly affected K+ currents in a way that was consistent with abscisic acid mediating, at least in part, the response of roots to water stress. It is proposed that the K+ channels underlying the K+ currents in the root stelar cells represent pathways that allow K+ exchange between the root symplasm and xylem apoplast. It is suggested that the regulation of K+ channel activity in the root in response to water stress could be part of an important adaptation of the plant to survive drying soils.

Cellular oxidative stress and the control of apoptosis by wild-type p53, cytotoxic compounds, and cytokines.

Apoptosis induced by wild-type p53 or cytotoxic compounds in myeloid leukemic cells can be inhibited by the cytokines interleukin 6, interleukin 3, granulocyte-macrophage colony-stimulating factor, and interferon gamma and by antioxidants. The antioxidants and cytokines showed a cooperative protective effect against induction of apoptosis. Cells with a higher intrinsic level of peroxide production showed a higher sensitivity to induction of apoptosis and required a higher cytokine concentration to inhibit apoptosis. Decreasing the intrinsic oxidative stress in cells by antioxidants thus inhibited apoptosis, whereas increasing this intrinsic stress by adding H2O2 enhanced apoptosis. Induction of apoptosis by wild-type p53 was not preceded by increased peroxide production or lipid peroxidation and the protective effect of cytokines was not associated with a decrease in these properties. The results indicate that the intrinsic degree of oxidative stress can regulate cell susceptibility to wild-type p53-dependent and p53-independent induction of apoptosis and the ability of cytokines to protect cells against apoptosis.

Stress and antidepressants differentially regulate neurotrophin 3 mRNA expression in the locus coeruleus.

The mechanisms by which stress and anti-depressants exert opposite effects on the course of clinical depression are not known. However, potential candidates might include neurotrophic factors that regulate the development, plasticity, and survival of neurons. To explore this hypothesis, we examined the effects of stress and antidepressants on neurotrophin expression in the locus coeruleus (LC), which modulates many of the behavioral and physiological responses to stress and has been implicated in mood disorders. Using in situ hybridization, we demonstrate that neurotrophin 3 (NT-3) is expressed in noradrenergic neurons of the LC. Recurrent, but not acute, immobilization stress increased NT-3 mRNA levels in the LC. In contrast, chronic treatment with antidepressants decreased NT-3 mRNA levels. The effect occurred in response to antidepressants that blocked norepinephrine uptake, whereas serotonin-specific reuptake inhibitors did not alter NT-3 levels. Electroconvulsive seizures also decreased NT-3 expression in the LC as well as the hippocampus. Ntrk3 (neurotrophic tyrosine kinase receptor type 3; formerly TrkC), the receptor for NT-3, is expressed in the LC, but its mRNA levels did not change with stress or antidepressant treatments. Because, NT-3 is known to be trophic for LC neurons, our results raise the possibility that some of the effects of stress and antidepressants on LC function and plasticity could be mediated through NT-3. Moreover, the coexpression of NT-3 and its receptor in the LC suggests the potential for autocrine mechanisms of action.

Interpersonal Trauma, Posttraumatic Stress and Depression

Dating aggression is common among emerging adults, and women who experience aggression from a dating partner are at risk for elevated depression and posttraumatic stress (Dutton et al., 2006). Although some women end their relationships as a result of aggression, other women remain committed to their partner, and aggression tends to escalate over time. The current study explored the role that depression and posttraumatic stress play in ending aggressive dating relationships as well as changes in these symptoms after ending such a relationship. The current study also sought to identify factors predictive of individual differences in emerging adults' commitment to their aggressive dating relationships. A sample of 148 emerging adult women currently in an aggressive dating relationship completed questionnaires about themselves and their relationship; measures of rejection sensitivity, self-worth, and romantic relational style were included as predictors of the Investment Model variables (e.g., investment, satisfaction, quality of alternatives, and commitment; Rusbult, 1980). Two assessments were completed six months apart. Neither depression nor posttraumatic stress predicted ending an aggressive relationship. However, ending an aggressive relationship was associated with experiencing less physical aggression, which mediated reductions in posttraumatic stress. A more avoidant romantic style indirectly predicted commitment through relationship satisfaction and investment. Both commitment and rejection sensitivity significantly predicted continuing an aggressive relationship six months later.

Simultaneous synthesis of heat exchanger networks with pressure recovery: optimal integration between heat and work

The optimal integration between heat and work may significantly reduce the energy demand and consequently the process cost. This paper introduces a new mathematical model for the simultaneous synthesis of heat exchanger networks (HENs) in which the pressure levels of the process streams can be adjusted to enhance the heat integration. A superstructure is proposed for the HEN design with pressure recovery, developed via generalized disjunctive programming (GDP) and mixed-integer nonlinear programming (MINLP) formulation. The process conditions (stream temperature and pressure) must be optimized. Furthermore, the approach allows for coupling of the turbines and compressors and selection of the turbines and valves to minimize the total annualized cost, which consists of the operational and capital expenses. The model is tested for its applicability in three case studies, including a cryogenic application. The results indicate that the energy integration reduces the quantity of utilities required, thus decreasing the overall cost.

MINLP Optimization Algorithm for the Synthesis of Heat and Work Exchange Networks

This paper introduces a new optimization model for the simultaneous synthesis of heat and work exchange networks. The work integration is performed in the work exchange network (WEN), while the heat integration is carried out in the heat exchanger network (HEN). In the WEN synthesis, streams at high-pressure (HP) and low-pressure (LP) are subjected to pressure manipulation stages, via turbines and compressors running on common shafts and stand-alone equipment. The model allows the use of several units of single-shaft-turbine-compressor (SSTC), as well as helper motors and generators to respond to any shortage and/or excess of energy, respectively, in the SSTC axes. The heat integration of the streams occurs in the HEN between each WEN stage. Thus, as the inlet and outlet streams temperatures in the HEN are dependent of the WEN design, they must be considered as optimization variables. The proposed multi-stage superstructure is formulated in mixed-integer nonlinear programming (MINLP), in order to minimize the total annualized cost composed by capital and operational expenses. A case study is conducted to verify the accuracy of the proposed approach. The results indicate that the heat integration between the WEN stages is essential to enhance the work integration, and to reduce the total cost of process due the need of a smaller amount of hot and cold utilities.

Women and work: the economic value of college training

by Helen M. Bennett.