The Spectrum and Dips of RE 0751+14: A joint evaluation of ROSAT and ASCA Archival Data

Using archival ASCA and ROSAT observations of RE 0751+14, X-ray energy spectra, pulse profiles and the results of pulse timing analysis are presented. The energy spectra are well-fitted by a blackbody model at low energy and a Raymond-Smith model at high energy, together with a partial covering absorber. A fluorescence emission line at 6.4 keV with an equivalent width $\sim 220$ eV was resolved for the first time.Comment: To appear on Astrophysics and Space Science, vol 259, pages 191-203, January 199

State of Information Technology in Small Retail and Service Businesses: An Exploratory Study

During the recent years, there have been major changes in the availability and use of information technology by large businesses to gain efficiencies and competitive advantage over rivals. Some of the earlier research shows that this is not necessarily the case in small businesses. This study tries to identify the degree and the type of information technologies currently accepted and used by the small retail and service businesses

AB Dor: A Single Star with RSCVn Like Activity in X-ray Band

Using the archival ROSAT PSPC observations, AB Dor is found to be variable in X-rays. The periodic variations are consistent with previously reported rotational period of 0.514 days. The average spectrum of AB Dor is best represented with two-temperature Raymond-Smith model with kT values of 0.19+/-0.07 and 1.17+/-0.02 keV. The quiescent luminosity of the system is found to be 4.36+/-0.6 10^30 ergs/s. A flare with a rise time of about 350 seconds is detected during which X-ray luminosity rises from 5.8+/-1.6 10^30 to 15.8+/-4.9 10^30 ergs/s. We conclude that AB Dor is very similar to the active components of RS CVn binaries and other active classes. In view of the wide separation from the binary companion Rst 137B, this activity must be intrinsic to the active star.Comment: 11 pages in PostScript including figures, accepted for publication in Astrophysics and Space Science, available at http://astroa.physics.metu.edu.tr/preprints.htm

Expression profiling of circulating non-red blood cells in embryonic blood

<p>Abstract</p> <p>Background</p> <p>In addition to erythrocytes, embryonic blood contains other differentiated cell lineages and potential progenitor or stem cells homed to changing niches as the embryo develops. Using chicken as a model system, we have isolated an enriched pool of circulating non red blood cells (nRBCs) from E4 and E6 embryos; a transition period when definitive hematopoietic lineages are being specified in the peri-aortic region.</p> <p>Results</p> <p>Transcriptome analysis of both nRBC and RBC enriched populations was performed using chicken Affymetrix gene expression arrays. Comparison of transcript profiles of these two populations, with verification by RT-PCR, reveals in nRBCs an expression signature indicative of hematopoietic stem cells (HSCs) and progenitor cells of myeloid and lymphoid lineages, as well as a number of previously undescribed genes possibly involved in progenitor and stem cell maintenance.</p> <p>Conclusion</p> <p>This data indicates that early circulating embryonic blood contains a full array of hematopoietic progenitors and stem cells. Future studies on their heterogeneity and differentiation potentials may provide a useful alternative to ES cells and perinatal blood.</p

Modular Lie algebras and the Gelfand-Kirillov conjecture

Let g be a finite dimensional simple Lie algebra over an algebraically closed field of characteristic zero. We show that if the Gelfand-Kirillov conjecture holds for g, then g has type A_n, C_n or G_2.Comment: 20 page

Smile Arc in Palestinian Adolesants

Smile Arc is good indicator of dentolabial harmony and attractiveness. The number of teeth displayed has an impact on smiling. Smiles which show first molar to first molar are judged the most attractive. Thus the aim of our study was to assess the smile arc in Palestinian adolescents and the number of teeth displayed in smiling so that to determine the attractiveness of Palestinian smile. This study was conducted on Palestinian adolescents with a total of 851 subjects (446 males and 405 females) aged between 12 and 17 years. They were examined for the smile arc using computer software program. (Adobe Photoshop CS3, Japan) The results showed that 75.8% of the Palestinian adolescents examined had consonant smile arc. Flat Smile Arc was present in 19.2% and reverse smile arc was present in 5% of the population examined. Statistically significant difference was present between males and females considering the smile arc and teeth displayed during smiling (p<0.05). The only insignificance was for consonant smile arc and smile that displays first premolars. The results also showed the percentage of people displayed canines during smiling was 5.1%, first premolars was 16.9%, second premolars was 35.5%, first molars was 40.3% and second molars was 2.2%. Palestinian adolescents generally show an attractive smile considering the impact of the number of teeth displayed on smiling and percentage of population having consonant smile arc

Poisson-de Rham homology of hypertoric varieties and nilpotent cones

We prove a conjecture of Etingof and the second author for hypertoric varieties, that the Poisson-de Rham homology of a unimodular hypertoric cone is isomorphic to the de Rham cohomology of its hypertoric resolution. More generally, we prove that this conjecture holds for an arbitrary conical variety admitting a symplectic resolution if and only if it holds in degree zero for all normal slices to symplectic leaves. The Poisson-de Rham homology of a Poisson cone inherits a second grading. In the hypertoric case, we compute the resulting 2-variable Poisson-de Rham-Poincare polynomial, and prove that it is equal to a specialization of an enrichment of the Tutte polynomial of a matroid that was introduced by Denham. We also compute this polynomial for S3-varieties of type A in terms of Kostka polynomials, modulo a previous conjecture of the first author, and we give a conjectural answer for nilpotent cones in arbitrary type, which we prove in rank less than or equal to 2.Comment: 25 page

Automorphisms of associative algebras and noncommutative geometry

A class of differential calculi is explored which is determined by a set of automorphisms of the underlying associative algebra. Several examples are presented. In particular, differential calculi on the quantum plane, the $h$-deformed plane and the quantum group GLpq(2) are recovered in this way. Geometric structures like metrics and compatible linear connections are introduced.Comment: 28 pages, some references added, several amendments of minor importance, remark on modular group in section 8 omitted, to appear in J. Phys.