Traversable wormholes: minimum violation of null energy condition revisited

It was argued in literature that traversable wormholes can exist with arbitrarily small violation of null energy conditions. We show that if the amount of exotic material near the wormhole throat tends to zero, either this leads to a horn instead of a wormhole or the throat approaches the horizon in such a way that infnitely large stresses develop on the throat.Comment: 12 pages. To appear in PR

On the Transfer of Metric Fluctuations when Extra Dimensions Bounce or Stabilize

In this report, we study within the context of general relativity with one extra dimension compactified either on a circle or an orbifold, how radion fluctuations interact with metric fluctuations in the three non-compact directions. The background is non-singular and can either describe an extra dimension on its way to stabilization, or immediately before and after a series of non-singular bounces. We find that the metric fluctuations transfer undisturbed through the bounces or through the transients of the pre-stabilization epoch. Our background is obtained by considering the effects of a gas of massless string modes in the context of a consistent 'massless background' (or low energy effective theory) limit of string theory. We discuss applications to various approaches to early universe cosmology, including the ekpyrotic/cyclic universe scenario and string gas cosmology.Comment: V2. Minor Clarifications V3. appendix and 2 figures added, typos corrected, conclusions unchanged 12 pages, 6 figure

High-energy effective theory for matter on close Randall Sundrum branes

Extending the analysis of hep-th/0504128, we obtain a formal expression for the coupling between brane matter and the radion in a Randall-Sundrum braneworld. This effective theory is correct to all orders in derivatives of the radion in the limit of small brane separation, and, in particular, contains no higher than second derivatives. In the case of cosmological symmetry the theory can be obtained in closed form and reproduces the five-dimensional behaviour. Perturbations in the tensor and scalar sectors are then studied. When the branes are moving, the effective Newtonian constant on the brane is shown to depend both on the distance between the branes and on their velocity. In the small distance limit, we compute the exact dependence between the four-dimensional and the five-dimensional Newtonian constants.Comment: Updated version as published in PR

Parental satisfaction with quality of health care of children with sickle cell disease at the University of Benin Teaching Hospital, Benin City

Background: Parents play a major role in determining where and when to access care for their children. Assessing parental satisfaction with the health system will be a pointer to attitude towards health institutions compliance with treatment and achievement of better treatment outcome, especially in the care of children with chronic diseases such as sickle cell disease (SCD). This study determined parental satisfaction with quality of health care of their children with SCD at the University of Benin Teaching Hospital (UBTH), Benin City.Methods: The study was a descriptive survey. A structured questionnaire with a five point Likert scale was used for data collection from parents of children with SCD. A mean score of 3.0 and above was used as an acceptable response for high level of satisfaction. The maximum allowable score was 5.Results: Parents of children with SCD had a good perception of the health facility with a high mean score of 4.35 ± 0.43. Parental satisfaction was high (mean score ranged from 3.49 ± 0.68 to 4.31 ± 0.50) across the entire construct. The highest and lowest levels of satisfaction was found in the domain “visit to the doctors (mean score was 4.31 ± 0.50) and “staff communication” (mean score 3.49 ± 0.68) respectively. Socio-demographic and economic factors did not significantly affect parental satisfaction with quality of health care.Conclusion: Parental satisfaction with quality of health care was high in this study. Areas with least level of satisfaction such as “communication with staff” and “care from the laboratory” should be reviewed for improvement.Keywords: Parental Satisfaction, Quality, Healthcare, Children, Sickle Cell Disease

Brane Cosmology in an Arbitrary Number of Dimensions

We derive the effective cosmological equations for a non-$\mathbb{Z}_2$ symmetric codimension one brane embedded in an arbitrary D-dimensional bulk spacetime, generalizing the $D=5,6$ cases much studied previously. As a particular case, this may be considered as a regularized codimension (D-4) brane avoiding the problem of curvature divergence on the brane. We apply our results to the case of spherical symmetry around the brane and to partly compactified AdS-Schwarzschild bulks.Comment: 23 page

Sustainable construction: a web-based performance assessment tool

The quest towards sustainable development, both nationally and globally, puts the construction industry in the foreground as the main consumer of natural resources. The industry has profound economic, social and environmental impacts. Sustainable construction is one of the most important challenges faced by the construction industry today. In the UK, sustainability is being driven and enforced by the government through stringent fiscal policies and regulations, voluntary initiatives combined with naming and shaming strategies. Stakeholders are becoming more aware of the global challenges and are using their power to exert pressure on companies. Increasingly, construction clients are demanding that their business partners submit: their corporate sustainability policies with tender packages to demonstrate their performance in dealing with opportunities and risks stemming from economic, environmental and social aspect of sustainability. However, the lack of understanding of the concept and its practical application has been a recurrent problem. The conceptual confusion; its vagueness and ambiguity, the complexity of the myriad of challenges and fluidity of the sustainability concept, compounded with the myopic attitude of the industry, lack of clear-cut and practical framework are causing frustration in the construction industry. Consequently, a number of sustainability management frameworks have been proposed. There are probably more than one hundred frameworks for sustainable business strategy. However, the majority of these are either complicated to implement or lack sound theoretical base, effective change management and completeness. These, therefore, do not make the situation any easier. Many are still baffled as to what they should do and how they should go about affecting change. Corporate sustainability in the construction industry is a challenge to many companies. The industry is still under-performing in each of the key themes of sustainable construction and this has lead to a 'blame culture’ where each sector of the industry allocates responsibility for its current failings to others (CIRIA C563, 2001). Such a situation poses a need for a comprehensive, practical and easy to use tool that would aid the implementation and management of sustainability at the core of business process. The tool will complement the existing frameworks, which breaks down the strategic and management issues into manageable components. This will enable companies to focus on individual areas and identify actions needed to facilitate change. The problem is that such a tool is virtually non-existent. The main focal point of this research is the development of a tool to facilitate the implementation, management and integration of sustainability issues at the strategic level and promote wider uptake of the concept in the construction industry. This requires a thorough understanding of the concepts of sustainable development, sustainable construction and related issues as well as drivers, benefits, barriers and enablers for achieving corporate sustainability. It also demands an examination of existing management frameworks and collation of case studies from the early adopters to establish critical factors for strategic and management issues involved in achieving corporate sustainability. Through, diverse research epistemologies (quantitative, qualitative and triangulation methods), the research established four main critical factors and thirty-six sub-critical factors for achieving corporate sustainability. These factors underpinned the development of a web-based prototype software (ConPass). This thesis presents the development and evaluation ConPass Model and the prototype software

Critical current density and ac harmonic voltage generation in YBa2Cu3O7−δYBa_2Cu_3O_{7-\delta} thin films by the screening technique

The temperature and field dependence of harmonics in voltage $V_n=V'_n-iV"_n$ using the screening technique have been measured for $\mathrm{Y}\mathrm{Ba}_{2}\mathrm{Cu}_3\mathrm{O}_{7-\delta}$ superconducting thin films. Using the Sun model we obtained the curves for the temperature-dependent critical current density $J_c(T)$. In addition, we applied the criterion proposed by Acosta et al. to compute $J_c(T)$. Also, we made used of the empirical law $J_c \propto (1-T/T_c)^n$ as an input in our calculations to reproduce experimental harmonic generation up to the fifth harmonic. We found that most models fit well the fundamental voltage but higher harmonics are poorly reproduced. Such behavior suggests the idea that higher harmonics contain information concerning complex processes like flux creep or thermally assisted flux flow.Comment: 2 pages, 2 figure

Measuring the Welfare Impact of Public Expenditure on Primary Healthcare Services in Rural Nigeria: A Benefit-Incidence Approach

In this study, attempt has been made to measure the welfare impact of government expenditure on primary healthcare services in rural Nigeria employing the benefit-incidence approach. To do this data were generated from the various healthcare centres located in Ika South Local Government Area from a combination of primary and secondary sources. On the basis of the sample selected, households were decomposed into non-poor, moderately poor and core poor. An analysis of the data generated depicts that the non-poor benefited more from the public primary healthcare services. The low benefit accruing to the poor group is attributable to their relative inaccessibility to access public healthcare in terms of drugs and consultatison. There is therefore the need for proper implementation of primary healthcare policies to make them more pro-poor. In this regard, this paper recommends that local governments should collaborate with community for drug revolving scheme. This is to enable the poor in the rural areas have more  access to genuine drug at affordable price. Most importantly, there should be restructuring in public health expenditure pattern, focusing more on primary healthcare since this will benefit more of the poor and vulnerable in the society. By so doing, their welfare would be greatly improved. Keywords: Public expenditure on healthcare services, welfare impact, benefit-incidence analysis JEL classification: C2; C3; E

Chern-Simons theory of multi-component quantum Hall systems

The Chern-Simons approach has been widely used to explain fractional quantum Hall states in the framework of trial wave functions. In the present paper, we generalise the concept of Chern-Simons transformations to systems with any number of components (spin or pseudospin degrees of freedom), extending earlier results for systems with one or two components. We treat the density fluctuations by adding auxiliary gauge fields and appropriate constraints. The Hamiltonian is quadratic in these fields and hence can be treated as a harmonic oscillator Hamiltonian, with a ground state that is connected to the Halperin wave functions through the plasma analogy. We investigate several conditions on the coefficients of the Chern-Simons transformation and on the filling factors under which our model is valid. Furthermore, we discuss several singular cases, associated with symmetric states.Comment: 11 pages, shortened version, accepted for publication in Phys. Rev.