71 research outputs found
Magnetic-Field-Driven Superconductor-Insulator-Type Transition in Graphite
A magnetic-field-driven transition from metallic- to semiconducting-type
behavior in the basal-plane resistance takes place in highly oriented pyrolytic
graphite at a field kOe applied along the hexagonal c-axis. The
analysis of the data reveals a striking similarity between this transition and
that measured in thin-film superconductors and Si MOSFET's. However, in
contrast to those materials, the transition in graphite is observable at almost
two orders of magnitude higher temperatures.Comment: 4 Figure
Electron Glass in Ultrathin Granular Al Films at Low Temperatures
Quench-condensed granular Al films, with normal-state sheet resistance close
to 10 k, display strong hysteresis and ultraslow, non-exponential
relaxation in the resistance when temperature is varied below 300 mK. The
hysteresis is nonlinear and can be suppressed by a dc bias voltage. The
relaxation time does not obey the Arrhenius form, indicating the existence of a
broad distribution of low energy barriers. Furthermore, large resistance
fluctuations, having a 1/f-type power spectrum with a low-frequency cut-off,
are observed at low temperatures. With decreasing temperature, the amplitude of
the fluctuation increases and the cut-off frequency decreases. These
observations combine to provide a coherent picture that there exists a new
glassy electron state in ultrathin granular Al films, with a growing
correlation length at low temperatures.Comment: RevTeX 3.1, 4 pages, 4 figures (EPS files) (Minor Additions
Strong Association of 677 C>T Substitution in the MTHFR Gene with Male Infertility - A Study on an Indian Population and a Meta-Analysis
Methylenetetrahydrofolate reductase (MTHFR) is an important enzyme of folate and methionine metabolism, making it crucial for DNA synthesis and methylation. The objective of this study was to analyze MTHFR gene 677C>T polymorphism in infertile male individuals from North India, followed by a meta-analysis on our data and published studies.We undertook genotyping on a total of 837 individuals including well characterized infertile (N = 522) and confirmed fertile (N = 315) individuals. The SNP was typed by direct DNA sequencing. Chi square test was done for statistical analysis. Published studies were searched using appropriate keywords. Source of data collection for meta-analysis included 'Pubmed', 'Ovid' and 'Google Scholar'. Those studies analyzing 677C>T polymorphism in male infertility and presenting all relevant data were included in meta-analysis. The genotype data for infertile subjects and fertile controls was extracted from each study. Chi square test was done to obtain odds ratio (OR) and p-value. Meta-analysis was performed using Comprehensive Meta-analysis software (Version 2). The frequency of mutant (T) allele (p = 0.0025) and genotypes (CT+TT) (p = 0.0187) was significantly higher in infertile individuals in comparison to fertile controls in our case-control study. The overall summary estimate (OR) for allele and genotype meta-analysis were 1.304 (p = 0.000), 1.310 (p = 0.000), respectively, establishing significant association of 677C>T polymorphism with male infertility.677C>T substitution associated strongly with male infertility in Indian population. Allele and genotype meta-analysis also supported its strong correlation with male infertility, thus establishing it as a risk factor
Efficacy of pegylated interferon α-2a and α-2b in patients with genotype 1 chronic hepatitis C: a meta-analysis
Systematic review and meta-analysis of Transurethral Needle Ablation in symptomatic Benign Prostatic Hyperplasia
BACKGROUND: Benign prostatic hyperplasia (BPH) constitutes a major clinical problem. Minimally invasive therapies for the treatment of symptomatic BPH include Transurethral Needle Ablation (TUNA), but it is unclear what impact this technique has on the disease and its role among other currently available therapeutic options. The objective of this study is to ascertain the efficacy and safety of TUNA in the treatment of BPH. METHODS: Systematic review of the literature until January 2005 and meta-analysis of clinical studies assessing TUNA in symptomatic BPH. Studies were critically appraised. Estimates of effect were calculated according to the random-effects model. RESULTS: 35 studies (9 comparative, 26 non-comparative) were included. Although evidence was limited by methodological issues, the analysis of relevant outcomes indicates that while TUNA significantly improves BPH parameters with respect to baseline, it does not reach the same level of efficacy as TURP in respect to all subjective and objective variables. Further, its efficacy declines in the long-term with a rate of secondary-treatment significantly higher than of TURP [OR: 7.44 (2.47, 22.43)]. Conversely, TUNA seems to be a relatively safe technique and shows a lower rate of complications than TURP [OR:0.14 (0.05, 0.14)] with differences being particularly noteworthy in terms of postoperative bleeding and sexual disorders. Likewise, TUNA has fewer anesthetic requirements and generates a shorter hospital stay than TURP [WMD: -1.9 days (-2.75, -1.05)]. Scarce data and lack of replication of comparisons hinder the assessment of TUNA vs. other local therapies. No comparisons with medical treatment were found. CONCLUSION: The body of evidence on which TUNA has been introduced into clinical practice is of only moderate-low quality. Available evidence suggest that TUNA is a relatively effective and safe technique that may eventually prove to have a role in selected patients with symptomatic BPH. TUNA significantly improves BPH parameters with respect to baseline values, but it does not reach the same level of efficacy and long-lasting success as TURP. On the other hand, TUNA seems to be superior to TURP in terms of associated morbidity, anesthetic requirements and length of hospital stay. With respect to the role of TUNA vis-à-vis other minimally invasive therapies, the results of this review indicate that there are insufficient data to define this with any degree of accuracy. Overall cost-effectiveness and the role of TUNA versus medical treatment need further evaluation
Radial distribution of dust, stars, gas, and star-formation rate in DustPedia face-on galaxies
Aims. The purpose of this work is the characterization of the radial distribution of dust, stars, gas, and star-formation rate (SFR) in a sub-sample of 18 face-on spiral galaxies extracted from the DustPedia sample.
Methods. This study is performed by exploiting the multi-wavelength DustPedia database, from ultraviolet (UV) to sub-millimeter bands, in addition to molecular (12CO) and atomic (Hi) gas maps and metallicity abundance information available in the literature. We fitted the surface-brightness profiles of the tracers of dust and stars, the mass surface-density profiles of dust, stars, molecular gas, and total gas, and the SFR surface-density profiles with an exponential curve and derived their scale-lengths. We also developed a method to solve for the CO-to-H2 conversion factor (αCO) per galaxy by using dust- and gas-mass profiles.
Results. Although each galaxy has its own peculiar behavior, we identified a common trend of the exponential scale-lengths versus wavelength. On average, the scale-lengths normalized to the B-band 25 mag/arcsec2 radius decrease from UV to 70 μm, from 0.4 to 0.2, and then increase back up to ~0.3 at 500 microns. The main result is that, on average, the dust-mass surface-density scale-length is about 1.8 times the stellar one derived from IRAC data and the 3.6 μm surface brightness, and close to that in the UV. We found a mild dependence of the scale-lengths on the Hubble stage T: the scale-lengths of the Herschel bands and the 3.6 μm scale-length tend to increase from earlier to later types, the scale-length at 70 μm tends to be smaller than that at longer sub-mm wavelength with ratios between longer sub-mm wavelengths and 70 μm that decrease with increasing T. The scale-length ratio of SFR and stars shows a weak increasing trend towards later types. Our αCO determinations are in the range (0.3−9) M⊙ pc-2 (K km s-1)-1, almost invariant by using a fixed dust-to-gas ratio mass (DGR) or a DGR depending on metallicity gradient
Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases
The production of peroxide and superoxide is an inevitable consequence of
aerobic metabolism, and while these particular "reactive oxygen species" (ROSs)
can exhibit a number of biological effects, they are not of themselves
excessively reactive and thus they are not especially damaging at physiological
concentrations. However, their reactions with poorly liganded iron species can
lead to the catalytic production of the very reactive and dangerous hydroxyl
radical, which is exceptionally damaging, and a major cause of chronic
inflammation. We review the considerable and wide-ranging evidence for the
involvement of this combination of (su)peroxide and poorly liganded iron in a
large number of physiological and indeed pathological processes and
inflammatory disorders, especially those involving the progressive degradation
of cellular and organismal performance. These diseases share a great many
similarities and thus might be considered to have a common cause (i.e.
iron-catalysed free radical and especially hydroxyl radical generation). The
studies reviewed include those focused on a series of cardiovascular, metabolic
and neurological diseases, where iron can be found at the sites of plaques and
lesions, as well as studies showing the significance of iron to aging and
longevity. The effective chelation of iron by natural or synthetic ligands is
thus of major physiological (and potentially therapeutic) importance. As
systems properties, we need to recognise that physiological observables have
multiple molecular causes, and studying them in isolation leads to inconsistent
patterns of apparent causality when it is the simultaneous combination of
multiple factors that is responsible. This explains, for instance, the
decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference
The prevalence of depression and anxiety among Chinese adults with cancer: a systematic review and meta-analysis
Fluctuating estrogen and progesterone receptor expression in brainstem norepinephrine neurons through the rat estrous cycle
Norepinephrine (NE) neurons within the nucleus tractus solitarii (NTS; A2 neurons) and ventrolateral medulla (A1 neurons) represent gonadal steroid-dependent components of several neural networks regulating reproduction. Previous studies have shown that both A1 and A2 neurons express estrogen receptors (ERs). Using double labeling immunocytochemistry we report here that substantial numbers of NE neurons located within the NTS express progesterone receptor (PR) immunoreactivity, whereas few PRs are found in ventrolateral medulla. The evaluation of ERα and PR immunoreactivity in NE neurons through the estrous cycle revealed a fluctuating pattern of expression for both receptors within the NTS. The percentage of A2 neurons expressing PR immunoreactivity was low on metestrus and diestrus (3-7%), but increased significantly to approximately 24% on proestrous morning and remained at intermediate levels until estrus. The pattern of ERα immunoreactivity in A2 neurons was more variable, but a similar increment from 11% to 40% of NE neurons expressing ERα was found from diestrus to proestrus. Experiments in ovariectomized, estrogen-treated and estrogen-plus progesterone-treated rats revealed that PR immunoreactivity in A2 neurons was induced strongly by estrogen treatment, whereas progesterone had no significant effect. The numbers of ERα-positive NE neurons were not influenced by steroid treatment. These observations provide direct evidence for PRs in NE neurons of the brainstem and show that cyclical patterns of gonadal steroid receptor expression exist in A2, but not A1, neurons through the rat estrous cycle. The expression of PR in A2 neurons appears to be driven principally by circulating estrogen concentrations. The fluctuating levels of ERα and PR expression in these brainstem NE neurons may help generate cyclical patterns of biosynthetic and electrical activity within reproductive neural networks
Efficacy of antioxidant therapy on sperm quality measurements after varicocelectomy: A systematic review and meta‐analysis
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