Antikaon production in nucleon-nucleon reactions near threshold

The antikaon production cross section from nucleon-nucleon reactions near threshold is studied in a meson exchange model. We include both pion and kaon exchange, but neglect the interference between the amplitudes. In case of pion exchange the antikaon production cross section can be expressed in terms of the antikaon production cross section from a pion-nucleon interaction, which we take from the experimental data if available. Otherwise, a $K^*$-resonance exchange model is introduced to relate the different reaction cross sections. In case of kaon exchange the antikaon production cross section is related to the elastic $KN$ and $\bar KN$ cross sections, which are again taken from experimental measurements. We find that the one-meson exchange model gives a satisfactory fit to the available data for the $NN\to NNK\bar K$ cross section at high energies. We compare our predictions for the cross section near threshold with an earlier empirical parameterization and that from phase space models.Comment: 16 pages, LaTeX, 5 postscript figures included, submitted to Z. Phys.

Mechanical Systems with Symmetry, Variational Principles, and Integration Algorithms

This paper studies variational principles for mechanical systems with symmetry and their applications to integration algorithms. We recall some general features of how to reduce variational principles in the presence of a symmetry group along with general features of integration algorithms for mechanical systems. Then we describe some integration algorithms based directly on variational principles using a discretization technique of Veselov. The general idea for these variational integrators is to directly discretize Hamilton’s principle rather than the equations of motion in a way that preserves the original systems invariants, notably the symplectic form and, via a discrete version of Noether’s theorem, the momentum map. The resulting mechanical integrators are second-order accurate, implicit, symplectic-momentum algorithms. We apply these integrators to the rigid body and the double spherical pendulum to show that the techniques are competitive with existing integrators

The impact of deregulation and re-regulation on bank efficiency: evidence from Asia

Following the 1997 crisis, banking sector reforms in Asia have been characterised by the emphasis on prudential regulation, associated with increased financial liberalisation. Using a panel data set of commercial banks from eight major Asian economies over the period 2001-2010, this study explores how the coexistence of liberalisation and prudential regulation affects banks’ cost characteristics. Given the presence of heterogeneity of technologies across countries, we use a stochastic frontier approach followed by the estimation of a deterministic meta-frontier to provide ‘true’ estimates of bank cost efficiency measures. Our results show that the liberalization of bank interest rates and the increase in foreign banks' presence have had a positive and significant impact on technological progress and cost efficiency. On the other hand, we find that prudential regulation might adversely affect bank cost performance. When designing an optimal regulatory framework, policy makers should combine policies which aim to foster financial stability without hindering financial intermediation

High energy emission from microquasars

The microquasar phenomenon is associated with the production of jets by X-ray binaries and, as such, may be associated with the majority of such systems. In this chapter we briefly outline the associations, definite, probable, possible, and speculative, between such jets and X-ray, gamma-ray and particle emission.Comment: Contributing chapter to the book Cosmic Gamma-Ray Sources, K.S. Cheng and G.E. Romero (eds.), to be published by Kluwer Academic Publishers, Dordrecht, 2004. (19 pages

TMFoldRec: a statistical potential-based transmembrane protein fold recognition tool.

BACKGROUND: Transmembrane proteins (TMPs) are the key components of signal transduction, cell-cell adhesion and energy and material transport into and out from the cells. For the deep understanding of these processes, structure determination of transmembrane proteins is indispensable. However, due to technical difficulties, only a few transmembrane protein structures have been determined experimentally. Large-scale genomic sequencing provides increasing amounts of sequence information on the proteins and whole proteomes of living organisms resulting in the challenge of bioinformatics; how the structural information should be gained from a sequence. RESULTS: Here, we present a novel method, TMFoldRec, for fold prediction of membrane segments in transmembrane proteins. TMFoldRec based on statistical potentials was tested on a benchmark set containing 124 TMP chains from the PDBTM database. Using a 10-fold jackknife method, the native folds were correctly identified in 77 % of the cases. This accuracy overcomes the state-of-the-art methods. In addition, a key feature of TMFoldRec algorithm is the ability to estimate the reliability of the prediction and to decide with an accuracy of 70 %, whether the obtained, lowest energy structure is the native one. CONCLUSION: These results imply that the membrane embedded parts of TMPs dictate the TM structures rather than the soluble parts. Moreover, predictions with reliability scores make in this way our algorithm applicable for proteome-wide analyses. AVAILABILITY: The program is available upon request for academic use

Decreased brain venous vasculature visibility on susceptibility-weighted imaging venography in patients with multiple sclerosis is related to chronic cerebrospinal venous insufficiency.

BACKGROUND: The potential pathogenesis between the presence and severity of chronic cerebrospinal venous insufficiency (CCSVI) and its relation to clinical and imaging outcomes in brain parenchyma of multiple sclerosis (MS) patients has not yet been elucidated. The aim of the study was to investigate the relationship between CCSVI, and altered brain parenchyma venous vasculature visibility (VVV) on susceptibility-weighted imaging (SWI) in patients with MS and in sex- and age-matched healthy controls (HC). METHODS: 59 MS patients, 41 relapsing-remitting and 18 secondary-progressive, and 33 HC were imaged on a 3T GE scanner using pre- and post-contrast SWI venography. The presence and severity of CCSVI was determined using extra-cranial and trans-cranial Doppler criteria. Apparent total venous volume (ATVV), venous intracranial fraction (VIF) and average distance-from-vein (DFV) were calculated for various vein mean diameter categories: .9 mm. RESULTS: CCSVI criteria were fulfilled in 79.7% of MS patients and 18.2% of HC (p < .0001). Patients with MS showed decreased overall ATVV, ATVV of veins with a diameter < .3 mm, and increased DFV compared to HC (all p < .0001). Subjects diagnosed with CCSVI had significantly increased DFV (p < .0001), decreased overall ATVV and ATVV of veins with a diameter < .3 mm (p < .003) compared to subjects without CCSVI. The severity of CCSVI was significantly related to decreased VVV in MS (p < .0001) on pre- and post-contrast SWI, but not in HC. CONCLUSIONS: MS patients with higher number of venous stenoses, indicative of CCSVI severity, showed significantly decreased venous vasculature in the brain parenchyma. The pathogenesis of these findings has to be further investigated, but they suggest that reduced metabolism and morphological changes of venous vasculature may be taking place in patients with MS

Assessment of Genetic Diversity of Bermudagrass (Cynodon dactylon) Using ISSR Markers

Bermudagrass (Cynodon spp.) is a major turfgrass for home lawns, public parks, golf courses and sport fields and is known to have originated in the Middle East. Morphological and physiological characteristics are not sufficient to differentiate some bermudagrass genotypes because the differences between them are often subtle and subjected to environmental influences. In this study, twenty seven bermudagrass accessions and introductions, mostly from different parts of Iran, were assayed by inter-simple sequence repeat (ISSR) markers to differentiate and explore their genetic relationships. Fourteen ISSR primers amplified 389 fragments of which 313 (80.5%) were polymorphic. The average polymorphism information content (PIC) was 0.328, which shows that the majority of primers are informative. Cluster analysis using the un-weighted paired group method with arithmetic average (UPGMA) method and Jaccard’s similarity coefficient (r = 0.828) grouped the accessions into six main clusters according to some degree to geographical origin, their chromosome number and some morphological characteristics. It can be concluded that there exists a wide genetic base of bermudograss in Iran and that ISSR markers are effective in determining genetic diversity and relationships among them

Physical distress is associated with cardiovascular events in a high risk population of elderly men

Background Self-reported health perceptions such as physical distress and quality of life are suggested independent predictors of mortality and morbidity in patients with established cardiovascular disease. This study examined the associations between these factors and three years incidence of cardiovascular events in a population of elderly men with long term hyperlipidemia. Methods We studied observational data in a cohort of 433 men aged 64–76 years from a prospective, 2 × 2 factorial designed, three-year interventional trial. Information of classical risk factors was obtained and the following questionnaires were administered at baseline: Hospital Anxiety and Depression Scale, Physical Symptom Distress Index and Life Satisfaction Index. The occurrence of cardiovascular death, myocardial infarction, cerebrovascular incidences and peripheral arterial disease were registered throughout the study period. Continuous data with skewed distribution was split into tertiles. Hazard ratios (HR) were calculated from Cox regression analyses to assess the associations between physical distress, quality of life and cardiovascular events. Results After three years, 49 cardiovascular events were registered, with similar incidence among subjects with and without established cardiovascular disease. In multivariate analyses adjusted for age, smoking, systolic blood pressure, serum glucose, HADS-anxiety and treatment-intervention, physical distress was positively associated (HR 3.1, 95% CI 1.2 – 7.9 for 3rd versus 1st tertile) and quality of life negatively associated (HR 2.6, 95% CI 1.1–5.8 for 3rd versus 1st tertile) with cardiovascular events. The association remained statistically significant only for physical distress (hazard ratio 2.8 95% CI 1.2 – 6.8, p < 0.05) when both variables were evaluated in the same model. Conclusion Physical distress, but not quality of life, was independently associated with increased risk of cardiovascular events in an observational study of elderly men predominantly without established cardiovascular disease. Trial Registration Trial registration: NCT0076401

Circadian Consequence of Socio-Sexual Interactions in Fruit Flies Drosophila melanogaster

In fruit flies Drosophila melanogaster, courtship is an elaborate ritual comprising chasing, dancing and singing by males to lure females for mating. Courtship interactions peak in the night and heterosexual couples display enhanced nighttime activity. What we do not know is if such socio-sexual interactions (SSI) leave long-lasting after-effects on circadian clock(s). Here we report the results of our study aimed at examining the after-effects of SSI (as a result of co-habitation of males and females in groups) between males and females on their circadian locomotor activity rhythm. Males undergo reduction in the evening activity peak and lengthening of circadian period, while females show a decrease in overall activity. Such after-effects, at least in males, require functional circadian clocks during SSI as loss-of-function clock mutants and wild type flies interacting under continuous light (LL), do not display them. Interestingly, males with electrically silenced Pigment Dispersing Factor (PDF)-positive ventral lateral (LNv) clock neurons continue to show SSI mediated reduction in evening activity peak, suggesting that the LNv clock neurons are dispensable for SSI mediated after-effects on locomotor activity rhythm. Such after-effects in females may not be clock-dependent because clock manipulated females with prior exposure to males show decrease in overall activity, more or less similar to rhythmic wild type females. The expression of SSI mediated after-effects requires a functional olfactory system in males because males with compromised olfactory ability do not display them. These results suggest that SSI causes male-specific, long-lasting changes in the circadian clocks of Drosophila, which requires the presence of functional clocks and intact olfactory ability in males