Global behavior of a fourth order difference equation

We determine the forbidden set, introduce an explicit formula for the solutions, and discuss the global behavior of solutions of a fourth order difference equation

Covariant Coordinate Transformations on Noncommutative Space

We show how to define gauge-covariant coordinate transformations on a noncommuting space. The construction uses the Seiberg-Witten equation and generalizes similar results for commuting coordinates.Comment: 11 pages, LaTeX; email correspondence to [email protected]

A Chiral Perturbation Expansion for Gravity

A formulation of Einstein gravity, analogous to that for gauge theory arising from the Chalmers-Siegel action, leads to a perturbation theory about an asymmetric weak coupling limit that treats positive and negative helicities differently. We find power counting rules for amplitudes that suggest the theory could find a natural interpretation in terms of a twistor-string theory for gravity with amplitudes supported on holomorphic curves in twistor space.Comment: 11 pages, LaTeX, no figures; v2: one reference adde

On the oscillation of a third order rational difference equation

AbstractIn this paper, we discuss the global asymptotic stability of all solutions of the difference equationxn+1=Axn-2B+Cxnxn-1xn-2,n=0,1,…where A,B,C are positive real numbers and the initial conditions x-2,x-1,x0 are real numbers. Although we have an explicit formula for the solutions of that equation, the oscillation character is worth to be discussed

Identification, abundance and biomass of benthic communities in south east coasts of the Caspian Sea (Golestan Province)

The frequency and distribution of benthic species in the south east coast of Caspian Sea (proposed site for cage and pen culture) were studied. Sampling was carried out in 2 water depths (1, 5) meters and 12 stations were sampled in each depth using VanVeen sampler. Totally, 11 taxa were identified: Pyrgulidae,Ampharetidae, Neritidae, Nereidae, Cardidae, Gammaridae, Naididae, Balanidae, Foraminifera, Ostracoda and Cumaceae. The most abundant taxa were Gastropoda (66.36%), Foraminifera (15.66%), Polychaeta (14.09%) and Bivalvia (1.65%) respectively. The maximum and minimum biomass was 164.1 g/m in summer and 6.56 g/m in spring. Depth, substratum, season, season-depth interaction, season- substratum –depth interaction had significant effects on biomass and had no significant effect on abundance

On the energy-momentum tensor in non-commutative gauge theories

We study the properties of the energy-momentum tensor in non-commutative gauge theories by coupling them to a weak external gravitational field. In particular, we show that the stress tensor of such a theory coincides exactly with that derived from a theory where a Seiberg-Witten map has been implemented (namely, the procedure is commutative). Various other interesting features are also discussed.Comment: 3 page

The prevalence of hepatitis B surface antigen and anti-hepatitis B core antibody in Iran: A population-based study

Background: Hepatitis B virus infection is a very common cause of chronic liver disease worldwide. It is estimated that 3 of Iranians are chronically infected with hepatitis B virus. Current population-based studies on both rural and urban prevalence of hepatitis B virus infection in Iran are sparse with results that do not always agree. We performed this study to find the prevalence of hepatitis B surface antigen, anti-hepatitis B core antibody, and associated factors in the general population of three provinces of Iran. Methods: We randomly selected 6,583 subjects from three provinces in Iran, namely Tehran, Golestan, and Hormozgan. The subjects were aged between 18 and 65 years. Serum samples were tested for hepatitis B surface antigen and anti-hepatitis B core antibody. Various risk factors were recorded and multivariate analysis was performed. Results: The prevalence of hepatitis B surface antigen and anti-hepatitis B core antibody in Iran was 2.6 and 16.4, respectively. Predictors of hepatitis B surface antigen or anti-hepatitis B core antibody in multivariate analysis included older age, not having high-school diploma, living in a rural area, and liver disease in a family member. We did not find any significant differences between males and females. Conclusion: In spite of nationwide vaccination of newborns against hepatitis B virus since 1992, hepatitis B virus infection remains a very common cause of chronic liver disease in Iran which should be dealt with for at least the next 30-50 years

Fetal lung volume and pulmonary artery resistance index for prediction of neonatal respiratory distress syndrome

Background: As gestational age grows, the risk of newborn respiratory distress syndrome (RDS) diminishes because the lungs are the last foetal organs to properly mature. While neonatal RDS does not just occur following preterm births, it is often thought of as a disorder of premature babies. This study sought to determine how prenatal lung capacity and foetal Pulmonary artery resistance index (PARI) affected the probability that newborn RDS would occur. Methods: This prospective observational study was carried out on 200 pregnant women aged 20-35 years, with gestational age between 36-40 weeks and singleton pregnancy. According to neonatal outcome the patients were classified into two groups: group A: 26 cases with noenatal RDS and group B: 174 cases without neonatal RDS. All patients were subjected to 2D ultrasonography and 3D ultrasonography. Results: Fetal lung volume (FLV) is a significant predictor of neonatal RDS (AUC: 0.820, p <0.001), at a cut off value of ≤35, with 88.5% sensitivity and 68.4% specificity. PARI is not a significant predictor of neonatal RDS. 1 and 5 min Apgar score were significantly lower in neonates who developed RDS and those who didn’t (p<0.001). Conclusions: 3D FLV and estimated fetal weight measurement using ultrasonography may be a reliable non-invasive indicator of the incidence of newborn RDS in preterm pregnancies when the risk of RDS progression is present. FLV is a significant predictor for neonatal RDS at a cutoff for ≤35 cm3 with sensitivity 88.5% and specificity 68.4%

Predicting Adverse Outcomes in End Stage Renal Disease: Machine Learning Applied to the United States Renal Data System

We examined machine learning methods to predict death within six months using data derived from the United States Renal Data System (USRDS). We specifically evaluated a generalized linear model, a support vector machine, a decision tree and a random forest evaluated within the context of K-10 fold validation using the CARET package available within the open source architecture R program. We compared these models with the feed forward neural network strategy that we previously reported on with this data set