Valley-optical absorption in planar transition metal dichalcogenide superlattices

In this study, we investigate the optical absorption of a planar superlattice comprising alternatively arranged two-dimensional Transition Metal DiChalcogenide semiconductors. Within a semi-classical model and using the Dirac-like equation in the presence of light interaction as a perturbation, we obtained the governing Hamiltonian. Using this Hamiltonian, we derived a fully analytical relationship for the absorption coefficient of the structure. By calculating the effective mass for different bands and using the Drude-Lorentz model, our approach is able to determine the oscillator strength and the effective refractive index of the structure. We found that the spin-orbit coupling has important effect on the absorption coefficient and energy bands where it reduces the absorption coefficient of the structure from typical value of [Formula: see text]-[Formula: see text], also the valence band experiences a significant blue shift, while the conduction band shows minor changes due to spin orbit coupling. Moreover, the role of incident light angle and light polarization were studied in details at different valleys of [Formula: see text] and [Formula: see text]. The most important finding is that by changing the polarization of incident light, it is possible to increase the absorption coefficients of [Formula: see text] and [Formula: see text] valleys by up to 30 times. For light propagation direction close to perpendicular to the plane of the superlattice, the right-circular polarization is absorbed only by [Formula: see text] valley in contrast to the left-circular polarization, which is absorbed by the [Formula: see text] valley. Our model might be used to design newly developed 2D optovalleytronic devices.

Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

Doppler broadening thermometry of acetylene and accurate measurement of the Boltzmann constant

In this paper, we present accurate measurements of the fundamental Boltzmann constant based on a line-shape analysis of acetylene spectra in the ν1 + ν3 band recorded using a tunable diode laser. Experimental spectra recorded at low pressures (0.25 - 9 Torr), have been analyzed using a Speed Dependent Voigt model that takes into account the molecular speed dependence effects. This line-shape model reproduces the experimental data with good accuracy and allows us to determine precise line-shape parameters for the P(25) transition of the ν1 + ν3 band. From the recorded spectra we obtained the Doppler-width and then determined the Boltzmann constant, k(B).

Epidemiological survey on pandemic influenza A (H1N1) virus infection in Kurdistan province, Islamic Republic of Iran, 2009

This study evaluated the epidemiology of suspected cases of pandemic influenza A (H1N1) virus infection in 2009-2010 in Kurdistan province, a frontier province of the Islamic Republic of Iran. A questionnaire covering demographic characteristics, clinical presentation and outcome, and history of exposure and travel was completed by patients attending health centres and hospitals in the province. Nasal and throat swabs were analysed by RT-PCR. A total of 1059 suspected cases were assessed; H1N1 influenza A was confirmed in 157 (14.8%). The highest proportion of confirmed cases was 30.0%, among children aged < 1 year. In multivariate analysis, previous contact with symptomatic influenza patients (OR = 2.17) and hospitalization (OR = 3.88) were the only significant risk factors for confirmed H1N1 infection. Age, sex, residency, presenting symptoms and history of national or international travel were not significant. Influenza A (H1N1) virus has spread in Islamic Republic of Iran; probably transmitted by travellers to Kurdistan.

Lipoic acid prevents hepatic and intestinal damage induced by obstruction of the common bile duct in rats

INTRODUCTION

Cholestatic liver diseases are characterized by impaired hepatocellular secretion of bile, resulting in intracellular accumulation of bile acids which result in a shift in the oxidant/prooxidant balance in favor of increased free radical activity and injury of different tissues including liver and intestine. The aim of this research was to study protective effect of lipoic acid (LA) as a potent antioxidant in cholestsis induced hepatic and intestinal injury in rats.

MATERIALS AND METHODS

Forty five adult male Wistar rats were randomly assigned to four groups each containing fifteen rats as follows: sham operation (SO) (control), bile duct ligating (BDL), and BDL+LA (25 mg/kg). After fourteen days hepatic and intestinal tissue sampled and blood serum sampled for pathologic and biochemical studies.

RESULTS

Levels of SOD and GPx antioxidant enzymes were higher in BDL+LA group comparing to BDL group, levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and γ-glutamyltranspeptidase (GGT), and pathologic scores in liver and intestine were lower in BDL+LA group comparing to BDL group significantly, but there is no significant difference in concentrations of total bilirubin between groups.

CONCLUSIONS

Our results showed the protective potential of LA with liver and intestine damage. Despite improvements in operative technique and the development of potent, broad-spectrum antibiotics, biliary tract surgery in patients with obstructive jaundice is still associated with high morbidity and mortality rates In summary, our results show that BDL induced hepatic and intestinal injury were significantly attenuated by LA administration and the administration of LA could effectively diminish this damage.

A latent process model for joint modeling of events and marker

The paper formulates joint modeling of a counting process and a sequence of longitudinal measurements, governed by a common latent stochastic process. The latent process is modeled as a function of explanatory variables and a Brownian motion process. The conditional likelihood given values of the latent process at the measurement times, has been drawn using Brownian bridge properties; then integrating over all possible values of the latent process at the measurement times leads to the desired joint likelihood. An estimation procedure using joint likelihood and a numerical optimization is described. The method is applied to the study of cognitive decline and Alzheimer's disease.

Analysis of Fgf15 expression pattern in the mouse neural tube

The dynamic process of neural tube regionalization in vertebrates is regulated by the expression of developmental genes which appear in characteristic patterns at neuroepithelial transversal domains, which are called secondary organizers. The molecular code present in these neuroepithelial organizers controls the generation of morphogenetic signals that induce and maintain regional characteristics in the surrounding neuroepithelium. The product of the Fgf8 gene is a secreted protein that has been demonstrated to be the key molecule for the isthmic organizer and is also expressed in two other organizer regions: the zona limitans and the anterior neural ridge. Here we analyze the expression of Fgf15 at different stages of mouse development in relation to Fgf8 and Otx2 expression patterns.

Depolarisation induces rapid and transient formation of intracellular sphingosine-1-phosphate

Formation of sphingosine-1-phosphate (SPP) by sphingosine kinase serves as a signalling pathway for various membrane receptors. Here, we show that membrane depolarisation is another mechanism by which this pathway can be activated. Formation of [(3)H]SPP as well as levels of endogenous SPP were rapidly and transiently increased in PC12 pheochromocytoma cells depolarised with high KCl. Time course and maximum were similar to those induced by bradykinin. Depolarisation-induced SPP production was also observed in RINm5F insulinoma cells, dependent on extracellular Ca(2+) and fully suppressed by verapamil, thus apparently caused by Ca(2+) influx via voltage-gated Ca(2+) channels. Studies with sphingosine kinase inhibitors and overexpression of sphingosine kinase revealed a partial contribution of this pathway to depolarisation-induced noradrenaline release and Ca(2+) increase.

Type IV pilus genes pilA and pilC of Pseudomonas stutzeri are required for natural genetic transformation, and pilA can be replaced by corresponding genes from nontransformable species

Pseudomonas stutzeri lives in terrestrial and aquatic habitats and is capable of natural genetic transformation. After transposon mutagenesis, transformation-deficient mutants were isolated from a P. stutzeri JM300 strain. In one of them a gene which coded for a protein with 75% amino acid sequence identity to PilC of Pseudomonas aeruginosa, an accessory protein for type IV pilus biogenesis, was inactivated. The presence of type IV pili was demonstrated by susceptibility to the type IV pilus-dependent phage PO4, by occurrence of twitching motility, and by electron microscopy. The pilC mutant had no pili and was defective in twitching motility. Further sequencing revealed that pilC is clustered in an operon with genes homologous to pilB and pilD of P. aeruginosa, which are also involved in pilus formation. Next to these genes but transcribed in the opposite orientation a pilA gene encoding a protein with high amino acid sequence identity to pilin, the structural component of type IV pili, was identified. Insertional inactivation of pilA abolished pilus formation, PO4 plating, twitching motility, and natural transformation. The amounts of (3)H-labeled P. stutzeri DNA that were bound to competent parental cells and taken up were strongly reduced in the pilC and pilA mutants. Remarkably, the cloned pilA genes from nontransformable organisms like Dichelobacter nodosus and the PAK and PAO strains of P. aeruginosa fully restored pilus formation and transformability of the P. stutzeri pilA mutant (along with PO4 plating and twitching motility). It is concluded that the type IV pili of the soil bacterium P. stutzeri function in DNA uptake for transformation and that their role in this process is not confined to the species-specific pilin.