Bounds on negative energy densities in static space-times

Certain exotic phenomena in general relativity, such as backward time travel, appear to require the presence of matter with negative energy. While quantum fields are a possible source of negative energy densities, there are lower bounds - known as quantum inequalities - that constrain their duration and magnitude. In this paper, we derive new quantum inequalities for scalar fields in static space-times, as measured by static observers with a choice of sampling function. Unlike those previously derived by Pfenning and Ford, our results do not assume any specific sampling function. We then calculate these bounds in static three- and four-dimensional Robertson-Walker universes, the de Sitter universe, and the Schwarzschild black hole. In each case, the new inequality is stronger than that of Pfenning and Ford for their particular choice of sampling function.Comment: 22 pages, 5 figures; LaTeX; minor changes mad

Casimir effect of electromagnetic field in Randall-Sundrum spacetime

We study the finite temperature Casimir effect on a pair of parallel perfectly conducting plates in Randall-Sundrum model without using scalar field analogy. Two different ways of interpreting perfectly conducting conditions are discussed. The conventional way that uses perfectly conducting condition induced from 5D leads to three discrete mode corrections. This is very different from the result obtained from imposing 4D perfectly conducting conditions on the 4D massless and massive vector fields obtained by decomposing the 5D electromagnetic field. The latter only contains two discrete mode corrections, but it has a continuum mode correction that depends on the thicknesses of the plates. It is shown that under both boundary conditions, the corrections to the Casimir force make the Casimir force more attractive. The correction under 4D perfectly conducting condition is always smaller than the correction under the 5D induced perfectly conducting condition. These statements are true at any temperature.Comment: 20 pages, 4 figure

Optimal integral force feedback and structured PI tracking control : application for objective lens positioner

Peer reviewedPostprin

Transcriptional factor PU.1 regulates decidual C1q expression in early pregnancy in human

"Copyright: © 2015 Madhukaran, Kishore, Jamil, Teo, Choolani and Lu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms."C1q is the first recognition subcomponent of the complement classical pathway, which in addition to being synthesized in the liver, is also expressed by macrophages and dendritic cells (DCs). Trophoblast invasion during early placentation results in accumulation of debris that triggers the complement system. Hence, both early and late components of the classical pathway are widely distributed in the placenta and decidua. In addition, C1q has recently been shown to significantly contribute to feto-maternal tolerance, trophoblast migration, and spiral artery remodeling, although the exact mechanism remains unknown. Pregnancy in mice, genetically deficient in C1q, mirrors symptoms similar to that of human preeclampsia. Thus, regulated complement activation has been proposed as an essential requirement for normal successful pregnancy. Little is known about the molecular pathways that regulate C1q expression in pregnancy. PU.1, an Ets-family transcription factor, is required for the development of hematopoietic myeloid lineage immune cells, and its expression is tissue-specific. Recently, PU.1 has been shown to regulate C1q gene expression in DCs and macrophages. Here, we have examined if PU.1 transcription factor regulates decidual C1q expression. We used immune-histochemical analysis, PCR, and immunostaining to localize and study the gene expression of PU.1 transcription factor in early human decidua. PU.1 was highly expressed at gene and protein level in early human decidual cells including trophoblast and stromal cells. Surprisingly, nuclear as well as cytoplasmic PU.1 expression was observed. Decidual cells with predominantly nuclear PU.1 expression had higher C1q expression. It is likely that nuclear and cytoplasmic PU.1 localization has a role to play in early pregnancy via regulating C1q expression in the decidua during implantation

Pacific island economies : some observations on the economic consequences of natural disasters

The many difficult development problems faced by small resource-poor island countries such as those in the South Pacific, are all too familiar. Certainly, with small Pacific island countries the leading constraint is vulnerability to external shocks that can lead to economic collapse. Collapsibility can arise either from a sudden loss of export markets or a sharp decline in the terms of trade, and can lead to a drastic decline in GDP and export earnings and prolonged economic stagnation. Other major disturbances can arise from a political crisis ( e.g., Fiji 1987); the exhaustion of a major non-renewable export product (e.g., Kiribati 1979); crop destruction by insects or viral disease (e.g., Western Samoa 1993). As well, economic collapse can arise from periodic natural disasters such as cyclones and prolonged drought. Valuable insights into the economic collapsibility of small island countries in the Pacific can be found in recent works by Tisdell (1985), Kakazu (1985) and Fairbairn (1987). By means of simple growth models, these authors show that small island countries are incapable of sustainable growth because of vulnerability to external shocks, particularly a collapse in export demand combined with population growth. The analyses come out in favour of development policies that, among other things, encourage subsistence production as a sheet -anchor for these economies. The aim of this paper is to address another potential source of economic collapsibility - natural hazards particularly in the form of highly destructive tropical cyclones. The paper focuses on the recent incidence of tropical cyclones in the South Pacific, the severity of the devastation to these economies, and the impact on growth and policy responses. Particular attention is given to the consequences of a recent cyclone in Western Samoa and a simple theoretical model is presented showing the effects of cyclone devastation. The paper is essentially an exploratory study aimed at highlighting some of the major economic costs to small resource-poor island economies.peer-reviewe

The report of posttraumatic growth in Malaysian cancer patients:relationships with psychological distress and coping strategies

Objective: The challenge of a cancer diagnosis may eventually lead to the experience of positive psychological changes, also referred to as posttraumatic growth. As most research on posttraumatic growth in cancer patients has been conducted in Western countries, little is known about the experience of such positive psychological changes in non-Western countries. Therefore, the purpose of this cross-sectional study was to investigate the prevalence of posttraumatic growth in a Malaysian sample of cancer patients. Secondly, we examined the association of posttraumatic growth with patients' report of psychological distress and their use of coping strategies. Methods: The study was conducted in 113 cancer patients. Posttraumatic growth was measured by the Posttraumatic Growth Inventory, coping strategies by the brief COPE, and psychological distress by the Symptom Check List (SCL-90-R). Results: Results showed that many patients reported posttraumatic growth, mostly in the domain of appreciation of life. As hypothesized, the experience of posttraumatic growth was not significantly related to the level of psychological distress. Findings indicated that greater use of the coping strategies instrumental support, positive reframing, and humor was associated with more posttraumatic growth. Conclusion: Overall, this study suggests that posttraumatic growth is not only a Western phenomenon. Malaysian cancer patients show similar trends in the report of growth as well as in its correlates as their Western counterparts. Copyright (C) 2008 John Wiley & Sons, Ltd

Nonexistence theorems for traversable wormholes

Gauss-Bonnet formula is used to derive a new and simple theorem of nonexistence of vacuum static nonsingular lorentzian wormholes. We also derive simple proofs for the nonexistence of lorentzian wormhole solutions for some classes of static matter such as, for instance, real scalar fields with a generic potential obeying $\phi V'(\phi) \ge 0$ and massless fermions fields