Medical Genetics in Clinical Practice

Two hundred and fifty-four patients were seen in the Genetic Clinics during 1973, the first full year of activity of the Department of Human Genetics, University of Cape Town. The current role of medical genetics in clinical practice is exemplified by an analysis and discussion of the problems presented by these individuals.S. Afr. Med. J., 48, 1759 (1974

Models of Ultraluminous X-Ray Sources with Intermediate-Mass Black Holes

We have computed models for ultraluminous X-ray sources ("ULXs") consisting of a black-hole accretor of intermediate mass ("IMBH"; e.g., ~1000 Msun) and a captured donor star. For each of four different sets of initial donor masses and orbital separations, we computed 30,000 binary evolution models using a full Henyey stellar evolution code. To our knowledge this is the first time that a population of X-ray binaries this large has been carried out with other than approximation methods, and it serves to demonstrate the feasibility of this approach to large-scale population studies of mass-transfer binaries. In the present study, we find that in order to have a plausible efficiency for producing active ULX systems with IMBHs having luminosities > 10^{40} ergs/sec, there are two basic requirements for the capture of companion/donor stars. First, the donor stars should be massive, i.e., > 8 Msun. Second, the initial orbital separations, after circularization, should be close, i.e., < 6-30 times the radius of the donor star when on the main sequence. Even under these optimistic conditions, we show that the production rate of IMBH-ULX systems may fall short of the observed values by factors of 10-100.Comment: 5 pages, 2 figures, submitted to Ap

Models for the Observable System Parameters of Ultraluminous X-ray Sources

We investigate the evolution of the properties of model populations of ultraluminous X-ray sources (ULXs) consisting of a black-hole accretor in a binary with a donor star. We have computed models corresponding to three different populations of black-hole binaries; two invoke stellar-mass (~10 Msun) black hole accretors, and the third utilizes intermediate-mass (~1000 Msun) black holes (IMBHs). For each of the three populations, we computed 30,000 binary evolution sequences using a full Henyey stellar evolution code. The optical flux from the model ULXs includes contributions from the accretion disk, due to x-ray irradiation as well as intrinsic viscous heating, and that due to the donor star. We present "probability images" for the ULX systems in planes of color-magnitude, orbital period vs. X-ray luminosity, and luminosity vs. evolution time. Estimates of the numbers of ULXs in a typical galaxy as functions of time and of X-ray luminosity are also presented. Our model CMDs are compared with six ULX counterparts that have been discussed in the literature. Overall, the observed systems seem more closely related to model systems with very high-mass donors (> ~25 Msun) in binaries with IMBH accretors. However, significant difficulties remain with both the IMBH and stellar-mass black hole models.Comment: 15 pages, 8 figures, submitted to ApJ on Oct 05, 200

The Past and Future History of Regulus

We show how the recent discovery of a likely close white dwarf companion to the well known star Regulus, one of the brightest stars in the sky, leads to considerable insight into the prior evolutionary history of this star, including the cause of its current rapid rotation. We infer a relatively narrow range for the initial masses of the progenitor system: M_{10} = 2.3 +/- 0.2 M_sun and M_{20} = 1.7 +/- 0.2 M_sun, where M_{10} and M_{20} are the initial masses of the progenitors of the white dwarf and Regulus, respectively. In this scenario, the age of the Regulus system would exceed 1 Gyr. We also show that Regulus, with a current orbital period of 40 days, has an interesting future ahead of it. This includes (i) a common envelope phase, and, quite possibly, (ii) an sdB phase, followed by (iii) an AM CVn phase with orbital periods < 1 hr. Binary evolution calculations are presented in support of this scenario. We also discuss alternative possibilities, emphasizing the present uncertainties in binary evolution theory. Thus, this one particular star system illustrates many different aspects of binary stellar evolution.Comment: PDFLaTeX, 9 pages with 8 figure

Random Walks Along the Streets and Canals in Compact Cities: Spectral analysis, Dynamical Modularity, Information, and Statistical Mechanics

Different models of random walks on the dual graphs of compact urban structures are considered. Analysis of access times between streets helps to detect the city modularity. The statistical mechanics approach to the ensembles of lazy random walkers is developed. The complexity of city modularity can be measured by an information-like parameter which plays the role of an individual fingerprint of {\it Genius loci}. Global structural properties of a city can be characterized by the thermodynamical parameters calculated in the random walks problem.Comment: 44 pages, 22 figures, 2 table

Quantum measurement in a family of hidden-variable theories

The measurement process for hidden-configuration formulations of quantum mechanics is analysed. It is shown how a satisfactory description of quantum measurement can be given in this framework. The unified treatment of hidden-configuration theories, including Bohmian mechanics and Nelson's stochastic mechanics, helps in understanding the true reasons why the problem of quantum measurement can succesfully be solved within such theories.Comment: 16 pages, LaTeX; all special macros are included in the file; a figure is there, but it is processed by LaTe

Acute gastroenteritis in Hong Kong: A population-based telephone survey

A population-based telephone survey of acute gastroenteritis (AG) was conducted in Hong Kong from August 2006 to July 2007. Study subjects were recruited through random digit-dialling with recruitments evenly distributed weekly over the 1-year period. In total, 3743 completed questionnaires were obtained. An AG episode is defined as diarrhoea 3 times or any vomiting in a 24-h period during the 4 weeks prior to interview, in the absence of known non-infectious causes. The prevalence of AG reporting was 7%. An overall rate of 091 (95% CI 081-101) episodes per person-year was observed with women having a slightly higher rate (094, 95% CI 079-108) than men (088, 95% CI 073-104). The mean duration of illness was 36 days (s.d.=552). Thirty-nine percent consulted a physician, 19% submitted a stool sample for testing, and 26% were admitted to hospital. Of the subjects aged 15 ≥ years, significantly more of those with AG reported eating raw oysters (OR 24, 95% CI 13-44), buffet meals (OR 18, 95% CI 13-25), and partially cooked beef (OR 18, 95% CI 12-27) in the previous 4 weeks compared to the subjects who did not report AG. AG subjects were also more likely to have had hot pot, salad, partially cooked or raw egg or fish, sushi, sashimi, and snacks bought at roadside in the previous 4 weeks. This first population-based study on the disease burden of AG in Asia showed that the prevalence of AG in Hong Kong is comparable to that experienced in the West. The study also revealed some risky eating practices that are more prevalent in those affected with AG. Copyright © 2009 Cambridge University Press.published_or_final_versio

L\'evy-Schr\"odinger wave packets

We analyze the time--dependent solutions of the pseudo--differential L\'evy--Schr\"odinger wave equation in the free case, and we compare them with the associated L\'evy processes. We list the principal laws used to describe the time evolutions of both the L\'evy process densities, and the L\'evy--Schr\"odinger wave packets. To have self--adjoint generators and unitary evolutions we will consider only absolutely continuous, infinitely divisible L\'evy noises with laws symmetric under change of sign of the independent variable. We then show several examples of the characteristic behavior of the L\'evy--Schr\"odinger wave packets, and in particular of the bi-modality arising in their evolutions: a feature at variance with the typical diffusive uni--modality of both the L\'evy process densities, and the usual Schr\"odinger wave functions.Comment: 41 pages, 13 figures; paper substantially shortened, while keeping intact examples and results; changed format from "report" to "article"; eliminated Appendices B, C, F (old names); shifted Chapters 4 and 5 (old numbers) from text to Appendices C, D (new names); introduced connection between Relativistic q.m. laws and Generalized Hyperbolic law

Decays of metastable vacua in SQCD

The decay rates of metastable SQCD vacua in ISS-type models, both towards supersymmetric vacua as well as towards other nonsupersymmetric configurations arising in theories with elementary spectators, are estimated numerically in the semiclassical approximation by computing the corresponding multifield bounce configurations. The scaling of the bounce action with respect to the most relevant dimensionless couplings and ratios of scales is analyzed. In the case of the decays towards the susy vacua generated by nonperturbative effects, the results confirm previous analytical estimations of this scaling, obtained by assuming a triangular potential barrier. The decay rates towards susy vacua generated by R-symmetry breaking interactions turn out to be more than sufficiently suppressed for the phenomenologically relevant parameter range, and their behavior in this regime differs from analytic estimations valid for parametrically small scale ratios. It is also shown that in models with spectator fields, even though the decays towards vacua involving nonzero spectator VEVs don't have a strong parametric dependence on the scale ratios, the ISS vacuum can still be made long-lived in the presence of R-symmetry breaking interactions.Comment: 22 pages, 7 figure