Four Dimensionality in Non-compact Kaluza-Klein Model

Five dimensional model with extended dimensions investigated. It is shown that four dimensionality of our world is the result of stability requirement. Extra component of Einstein equations giving trapping solution for matter fields coincides with the one of conditions of stability.Comment: 6 pages, LaTEX file, no figures, no macro

Exact reconstruction of ocean bottom velocity profiles from monochromatic scattering data

Submitted in partial fulfillment of the requirements for the degree of Doctor of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution January 1987This thesis presents the theoretical and computational underpinnings of a novel approach to the determination of the acoustic parameters of the ocean bottom using a monochromatic source. The problem is shown to be equivalent to that of the reconstruction of the potential in a Schrodinger equation from the knowledge of the plane-wave reflection coefficient as a function of vertical wavenumber, r(kz) for all real positive k z. First, the reflection coefficient is shown to decay asymptotically at least as fast as (1/kz2) for large kz and is therefore inteqrable. The Gelfand-Levitan inversion procedure is extended to include the case of basement velocity higher than the velocity of sound in water. The neglect of bound states is shown to be justified in both clayey silt and silty clay at the 220 Hz frequency of operation. Three methods for the numerical solution of the integral equation are investigated. The first one is an "Improved Born approximation" wherein the solution is given as a series expansion the first term of which is the Born approximation while the second term represents a substantial and yet easy to implement improvement over Born. The two other methods are based on a discretization of the Gelfand-Levitan integral equation, and both avoid a matrix inversion: one by employing a recursive procedure, and the other by coupling the Gelfand-Levitan equation with a partial differential equation. Bounds are obtained on errors in the solution due either to discretization or to data inaccuracy. These methods are tested on synthetic data obtained from known geoacoustic models of the ocean bottom. Results are found to be very accurate particularly at the top of the sediment layer with resolution of less than the wavelength of the acoustic source in the water. Several effects are investigated, such as sampling, attenuation, and noise. Also examined is the gradual restriction of the reflection coefficient to a finite range of vertical wave numbers and the consequent progressive deterioration of the reconstruction. The analysis shows how to reconstruct velocity profiles in the presence of density variation when the experiment is conducted at two frequencies. Our results provide a good understanding of the issues involved in conducting a monochromatic deep ocean bottom experiment and constitute a promising technique for processing the experimental data when it becomes available.Support for this thesis was provided in part by the education office at WHOI and by the Office of Naval Research

Gravitational Field of Spherical Branes

The warped solution of Einstein's equations corresponding to the spherical brane in five-dimensional AdS is considered. This metric represents interiors of black holes on both sides of the brane and can provide gravitational trapping of physical fields on the shell. It is found the analytic form of the coordinate transformations from the Schwartschild to co-moving frame that exists only in five dimensions. It is shown that in the static coordinates active gravitational mass of the spherical brane, in agreement with Tolman's formula, is negative, i.e. such objects are gravitationally repulsive.Comment: Minor corrections, 8 pages, the version accepted by Mod. Phys. Lett.

Changing Trends in Dreamboat Children’s Theatre, Calabar, Nigeria

In the last twenty eight years DreamBoat Children’s theatre has gained prominence in South-South Nigeria. Its operations have become more professional and have received more attention within the school system. But this was not so in the beginning. The study set out to find out what factors led to this development. Qualitative method was used to gather data from children, teachers and practitioners as well as observation of many DreamBoat’s children’s theatre productions across two states of Cross River and Akwa Ibom. Data was gathered from over 500 children and two hundred teachers in four towns. The principal question the study sought to answer was: How can the DreamBoat children’s theatre performances help the child perceive patterns, relations feelings and produce an inner meaning? Or how do children experience theatre aesthetically? The research findings revealed that the type of stories enacted were the principal framework of transmitting meanings to young persons, the play is the heart of production and another aesthetics medium is the style of production. This is the icing on the cake it adds colours, sparkle and glamour. Conclusively as Children’s theatre producers work to stir the souls of young people by bringing them universal themes, feeding their imagination and giving beauty and fantasy enshrined in theatre which embodies all arts, then and only then will valuable contributions be made to the growth of creative individuals who will hold the baton for generations yet unborn

Assessment of Cytotoxic Activity of Five Common Philippine Medicinal Plants Using Brine Shrimp Lethality Assay

A wide variety of plants in the Philippines are used to address several medical ailments; however, many of which have not yet undergone thorough pharmacological studies. The problem on the possible side effects caused by these medicinal preparations has, therefore, increased the interest in validating their safety for human use. The present study was conducted to determine the cytotoxicity of five common local medicinal plants. Annona muricata L., Cymbopogon citratus DC., Graptophyllum pictum (L.) Griff, Jatropha curcas L., and Piper betle L. were selected and subjected to crude aqueous leaf extraction. Extracts were then investigated for cytotoxicity potential using brine shrimp lethality assay. The experiment resulted in median lethal time (LT50) values ranging between 21.23 to 24.06 hours. In addition, all these extracts had median lethal concentrations (LC50) lower than 1.00 mg/mL, suggesting the presence of cytotoxic constituents that could further be investigated both for safety and for anticancer potential

Performance of a Nonelectric Infant Warmer in Rwandan Health Centers.

Background. Neonatal hypothermia remains a challenge in resource-limited settings. Methods. We conducted a prospective mixed-methods cohort study in rural Rwandan health centers to assess the performance of an infant warmer we designed for low-resource settings. All hypothermic infants were eligible for enrollment. Outcomes. Safety: incidence of adverse reactions. Effectiveness: attainment of euthermia, rate of temperature rise. Feasibility: correct use of warmer, signs of wear. Interviews of caregivers and nurses. Findings. Of 102 encounters, there were no adverse reactions. Of 80 encounters for hypothermia when infants on warmer for ≥1 hour, 79 achieved euthermia; 73 in ≤2 hours. Of the 80 encounters, 64 had temperature rise ≥0.5°C/h. Of the 102 encounters, there were no instances of the warmer being prepared, used, or cleaned incorrectly. Five out of the 12 warmers exhibited wear. Interview participants were predominantly positive; some found time for readiness of warmer challenging. Interpretation. The warmer performed well. It is appropriate to study in larger scale

Brane in 6D with increasing gravitational trapping potential

A new solution to Einstein equations in (1+5)-spacetime with an embedded (1+3) brane is given. This solution localizes the zero modes of all kinds of matter fields and 4-gravity on the (1+3) brane by an increasing, transverse gravitational potential. This localization occurs despite the fact that the gravitational potential is not a decreasing exponential, and asymptotically approaches a finite value rather than zero.Comment: Revised paper. 6 pages, revtex 4. to be published in PR

Anti-de-Sitter Island-Universes from 5D Standing Waves

We construct simple standing wave solutions in a 5D space-time with a ghost scalar field. The nodes of these standing waves are 'islands' of 4D Minkowski space-time. For the 5D model with increasing (decreasing) warp factor there are a finite (infinite) number of nodes and thus Minkowski island-universes having different parameters, such as gravitational and cosmological constants. This feature is similar to the assumptions of the landscape models, which postulate a large number of universes with different parameters. This standing wave solution also provides a new localization mechanism - matter fields can reside only on Minkowski 'islands', where the background space-time does not oscillate.Comment: 14 page pre-print format. Discussion about connection to Weyl gravity added and "E&M" localization method added. To be published MPL

Vanishing of cosmological constant in nonfactorizable geometry

We generalize the results of Randall and Sundrum to a wider class of four-dimensional space-times including the four-dimensional Schwarzschild background and de Sitter universe. We solve the equation for graviton propagation in a general four dimensional background and find an explicit solution for a zero mass bound state of the graviton. We find that this zero mass bound state is normalizable only if the cosmological constant is strictly zero, thereby providing a dynamical reason for the vanishing of cosmological constant within the context of this model. We also show that the results of Randall and Sundrum can be generalized without any modification to the Schwarzschild background.Comment: 8 Pages(expanded version), Accepted in Phys. Rev.