Role of galactic gaseous halos in recycling enriched winds from bulges to disks: A new bulge-disk chemical connection

We demonstrate for the first time that gaseous halos of disk galaxies can play a vital role in recycling metal-rich gas ejected from the bulges and thus in promoting chemical evolution of disks. Our numerical simulations show that metal-rich stellar winds from bulges in disk galaxies can be accreted onto the thin disks owing to hydrodynamical interaction between the gaseous ejecta and the gaseous halos, if the mean densities of the halos (rho_ hg) are as high as 10^{-5} cm^{-3}. The total amount of gas that is ejected from a bulge through a stellar wind and then accreted onto the disk depends mainly on rho_ hg and the initial velocity of the stellar wind. About ~ 1% of gaseous ejecta from bulges in disk galaxies of scale length a_d can be accreted onto disks around R ~ 2.5 a_ d for a reasonable set of model parameters. We discuss these results in the context of the origin of the surprisingly high metallicities of the solar neighborhood disk stars in the Galaxy. We also discuss some implications of the present results in terms of chemical evolution of disk galaxies with possibly different rho_ hg in different galaxy environments.Comment: 13 pages, 4 figures (1 color), accepted by ApJ

Influence of Light Intensity on Surface Free Energy and Dentin Bond Strength of Core Build-up Resins

Objective: We examined the influence of light intensity on surface free energy characteristics and dentin bond strength of dual-cure direct core build-up resin systems. Methods: Two commercially available dual-cure direct core build-up resin systems, Clearfil DC Core Automix with Clearfil Bond SE One and UniFil Core EM with Self-Etching Bond, were studied. Bovine mandibular incisors were mounted in acrylic resin and the facial dentin surfaces were wet ground on 600-grit silicon carbide paper. Adhesives were applied to dentin surfaces and cured with light intensities of 0 (no irradiation), 200, 400, and 600 mW/cm2. The surface free energy of the adhesives (five samples per group) was determined by measuring the contact angles of three test liquids placed on the cured adhesives. To determine the strength of the dentin bond, the core build-up resin pastes were condensed into the mold on the adhesive-treated dentin surfaces according to the methods described for the surface free energy measurement. The resin pastes were cured with the same light intensities as those used for the adhesives. Ten specimens per group were stored in water maintained at 37°C for 24 hours, after which they were shear tested at a crosshead speed of 1.0 mm/minute in a universal testing machine. Two-way analysis of variance (ANOVA) and a Tukey-Kramer test were performed, with the significance level set at 0.05. Results: The surface free energies of the adhesive-treated dentin surfaces decreased with an increase in the light intensity of the curing unit. Two-way ANOVA revealed that the type of core build-up system and the light intensity significantly influence the bond strength, although there was no significant interaction between the two factors. The highest bond strengths were achieved when the resin pastes were cured with the strongest light intensity for all the core build-up systems. When polymerized with a light intensity of 200 mW/cm2 or less, significantly lower bond strengths were observed. Conclusions: The data suggest that the dentin bond strength of core build-up systems are still affected by the light intensity of the curing unit, which is based on the surface free energy of the adhesives. On the basis of the results and limitations of the test conditions used in this study, it appears that a light intensity of >400 mW/cm2 may be required for achieving the optimal dentin bond strength

Exercise can improve sleep quality: a systematic review and meta-analysis

Background Insomnia is common. However, no systematic reviews have examined the effect of exercise on patients with primary and secondary insomnia, defined as both sleep disruption and daytime impairment. This systematic review and meta-analysis aimed to examine the effectiveness/efficacy of exercise in patients with insomnia. Methods We searched the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, PsycINFO, World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov to identify all randomized controlled trials that examined the effects of exercise on various sleep parameters in patients with insomnia. All participants were diagnosed with insomnia, using standard diagnostic criteria or predetermined criteria and standard measures. Data on outcome measures were subjected to meta-analyses using random-effects models. The Cochrane Risk of Bias Tool and Grading of Recommendations, Assessment, Development, and Evaluation approach were used to assess the quality of the individual studies and the body of evidence, respectively. Results We included nine studies with a total of 557 participants. According to the Pittsburgh Sleep Quality Index (mean difference [MD], 2.87 points lower in the intervention group; 95% confidence interval [CI], 3.95 points lower to 1.79 points lower; low-quality evidence) and the Insomnia Severity Index (MD, 3.22 points lower in the intervention group; 95% CI, 5.36 points lower to 1.07 points lower; very low-quality evidence), exercise was beneficial. However, exercise interventions were not associated with improved sleep efficiency (MD, 0.56% lower in the intervention group; 95% CI, 3.42% lower to 2.31% higher; moderate-quality evidence). Only four studies noted adverse effects. Most studies had a high or unclear risk of selection bias. Discussion Our findings suggest that exercise can improve sleep quality without notable adverse effects. Most trials had a high risk of selection bias. Higher quality research is needed

Broadly Tunable Sub-terahertz Emission from Internal Branches of the Current-voltage Characteristics of Superconducting Bi2Sr2CaCu2O8+d Single Crystals

Continuous, coherent sub-terahertz radiation arises when a dc voltage is applied across a stack of the many intrinsic Josephson junctions in a Bi2Sr2CaCu2O8+d single crystal. The active junctions produce an equal number of I-V characteristic branches. Each branch radiates at a slightly tunable frequency obeying the ac Josephson relation. The overall output is broadly tunable and nearly independent of heating effects and internal cavity frequencies. Amplification by a surrounding external cavity to allow for the development of a useful high-power source is proposed.Comment: 4 pages, 4 figures, accepted for publication in PR

Chemical Compositions of Kinematically Selected Outer Halo Stars

Chemical abundances of 26 metal-poor dwarfs and giants are determined from high-resolution and high signal-to-noise ratio spectra obtained with Subaru/HDS. The sample is selected so that most of the objects have outer-halo kinematics. Self-consistent atmospheric parameters were determined by an iterative procedure based on spectroscopic analysis. Abundances of 13 elements, including $\alpha$-elements (Mg, Si, Ca, Ti), odd-Z light elements (Na, Sc), iron-peak elements (Cr, Mn, Fe, Ni, Zn) and neutron-capture elements (Y, Ba), are determined by two independent data reduction and LTE analysis procedures, confirming the consistency of the stellar parameters and abundances results. We find a decreasing trend of [$\alpha$/Fe] with increasing [Fe/H] for the range of $-3.5 <$ [Fe/H]$< -1$, as found by Stephens and Boesgaard (2002). [Zn/Fe] values of most objects in our sample are slightly lower than the bulk of halo stars previously studied. These results are discussed as possible chemical properties of the outer halo in the Galaxy.Comment: 50 pages, 15 figures, Accepted for publication by Ap