A Small Cosmological Constant and Backreaction of Non-Finetuned Parameters

We include the backreaction on the warped geometry induced by non-finetuned parameters in a two domain-wall set-up to obtain an exponentially small Cosmological Constant $\Lambda_4$. The mechanism to suppress the Cosmological Constant involves one classical fine-tuning as compared to an infinity of finetunings at the quantum level in standard D=4 field theory.Comment: 13 pages, minor corrections and references adde

On cross-beam monitoring of atmospheric winds and turbulence with two orbiting telescopes

Crossed beam monitoring of atmospheric winds and turbulence with two orbiting astronomical telescopes mounted on single spacecraf

The evidence of quasi-free positronium state in GiPS-AMOC spectra of glycerol

We present the results of processing of Age-Momentum Correlation (AMOC) spectra that were measured for glycerol by the Gamma-induced positron spectroscopy (GiPS) facility. Our research has shown that the shape of experimental s(t) curve cannot be explained without introduction of the intermediate state of positronium (Ps), called quasi-free Ps. This state yields the wide Doppler line near zero lifetimes. We discuss the possible properties of this intermediate Ps state from the viewpoint of developed model. The amount of annihilation events produced by quasi-free Ps is estimated to be less than 5% of total annihilations. In the proposed model, quasi-free Ps serves as a precursor for trapped Ps of para- and ortho-states

Uptake of genetic counselling services by patients with cystic fibrosis and their families

Background: Although cystic fibrosis (CF) is a common genetic condition, genetic counselling services appear to be underutilised by affected families. The aim of this study was to determine the uptake of genetic counselling and mutation testing for CF by relatives of affected individuals, and the impact of introducing hospital-based genetic counselling services.Method: The files of 153 families seen for genetic counselling for CF by staff of the Division of Human Genetics, School of Pathology, University of the Witwatersrand, and the National Health Laboratory Service (NHLS) in Johannesburg, were retrospectively reviewed from 1990 to 2006, the year when hospital-based genetic counselling services were introduced.Results: Parents of CF probands were the largest single group (35%) of counsellees. Most individuals (66%) attended genetic counselling to gather information. Most had been referred by medical specialists (56%). Only 10% of referrals originated from general practitioners. On average, from 1990-2005, six families received genetic counselling annually, whereas in 2006, 58 families were seen. In 140 unrelated families, 1 991 relatives with carrier risks of . 25% were identified. Only 11% of these relatives underwent mutation testing, and eight per cent received genetic counselling through our division over the review period.Conclusion: Overall, referrals of family members (of affected CF  individuals) to genetic counselling, by general practitioners, are poor. Uptake of genetic counselling services is greater when such services are integrated into hospital-based CF management clinics, than when offered elsewhere. The low uptake of mutation testing and genetic counselling by at-risk relatives is a concern, since these relatives are at high risk of having affected children, if their partners are CF carriers. Education of affected individuals, their close relatives, and medical practitioners, should be prioritised. This will ensure referral to genetic counselling for discussion about the risks of and available testing for CF, and other genetic conditions

Scanning Photo-Induced Impedance Microscopy - Resolution studies and polymer characterization

Scanning Photo-Induced Impedance Microscopy (SPIM) is an impedance imaging technique that is based on photocurrent measurements at field-effect structures. The material under investigation is deposited onto a semiconductor-insulator substrate. A thin metal film or an electrolyte solution with an immersed electrode serves as the gate contact. A modulated light beam focused into the space charge region of the semiconductor produces a photocurrent, which is directly related to the local impedance of the material. The absolute impedance of a polymer film can be measured by calibrating photocurrents using a known impedance in series with the sample. Depending on the wavelength of light used, charge carriers are not only generated in the focus but also throughout the bulk of the semiconductor. This can have adverse effects on the lateral resolution. Two-photon experiments were carried out to confine charge carrier generation to the spacecharge layer. The lateral resolution of SPIM is also limited by the lateral diffusion of charge carriers in the semiconductor. This problem can be solved by using thin silicon layers as semiconductor substrates. A resolution of better than 1 mu m was achieved using silicon on sapphire (SOS) substrates with a I l.Lm thick silicon layer

Aspects of Nucleon Chiral Perturbation Theory

I review recent progress made in the calculation of nucleon properties in the framework of heavy baryon CHPT. Topics include: Compton scattering, $\pi N$ scattering, the anatomy of a low-energy constant and the induced pseudoscalar form factor.Comment: plain TeX (macro included), 12pp, lecture delivered at the workshop on "Chiral Dynamics: Theory and Experiments", MIT, July 25-29, 199

Advanced nickel-cadmium batteries for geosynchronous spacecraft

A nickel cadmium battery was developed that can be operated at 80 percent depth of discharge in excess of 10 years in a geosynchronous orbit application, and has about a 30 percent weight savings per spacecraft over present nickel cadmium batteries when used with a 1000 watts eclipse load. The approach used in the development was to replace nylon separators with inert polymer impregnated zirconia, use electrochemically deposited plates in place of conventional chemically precipitated ones, and use an additive to extend negative plate lifetime. The design has undergone extensive testing using both engineering and protoflight cell configurations