962 research outputs found

    Neutrino neutral reaction on 4He, effects of final state interaction and realistic NN force

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    The inelastic neutral reaction of neutrino on 4He is calculated microscopically, including full final state interaction among the four nucleons. The calculation is performed using the Lorentz integral transform (LIT) method and the hyperspherical-harmonic effective interaction approach (EIHH), with a realistic nucleon-nucleon interaction. A detailed energy dependent calculation is given in the impulse approximation. With respect to previous calculations, this work predicts an increased reaction cross-section by 10%-30% for neutrino temperature up to 15 MeV.Comment: 4 pages, 2 fig

    The X-ray spectrum of Fe XVII revisited with a multi-ion model

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    The theoretical intensities of the soft X-ray Fe XVII lines arising from 2l-3l' transitions are reexamined using a three-ion collisional-radiative model that includes the contributions to line formation of radiative recombination (RR), dielectronic recombination (DR), resonant excitation (RE), and inner-shell collisional ionization (CI), in addition to the usual contribution of collisional excitation (CE). These additional processes enhance mostly the 2p-3s lines and not the 2p-3d lines. Under coronal equilibrium conditions, in the electron temperature range of 400 to 600 eV where the Fe XVII line emissivities peak, the combined effect of the additional processes is to enhance the 2p-3s lines at 16.78, 17.05, and 17.10 A, by ~ 25%, 30%, and 55%, respectively, compared with their traditional, single-ion CE values. The weak 2p-3d line at 15.45 A is also enhanced by up to 20%, while the other 2p-3d lines are almost unaffected. The effects of DR and RE are found to be dominant in this temperature range (400 - 600 eV), while that of CI is 3% at the most, and the contribution of RR is less than 1%. At lower temperatures, where the Fe XVII / Fe XVIII abundance ratio is high, the RE effect dominates. However, as the temperature rises and the Fe XVIII abundance increases, the DR effect takes over. The newly calculated line powers can reproduce most of the often observed high values of the (I17.05 + I17.10) / I15.01 intensity ratio. The importance of ionization and recombination processes to the line strengths also helps to explain why laboratory measurements in which CE is essentially the sole mechanism agree well with single-ion calculations, but do not reproduce the astrophysically observed ratios.Comment: Submitted to Ap

    Evaluating Smoking Cessation Interventions and Cessation Rates in Cancer Patients: A Systematic Review and Meta-Analysis

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    Background. Tobacco smoking cessation interventions in the oncology population are an important part of comprehensive treatment plan. Objectives. To evaluate through a systematic review smoking cessation interventions and cessation rates in cancer patients. Search Strategy. The literature was searched using Medline, EMBASE, and the Cochrane Library (inception to November 2010) by three independent review authors. Selection Criteria. Studies were included if tobacco smoking cessation interventions were evaluated and patients were randomized to usual care or an intervention. The primary outcome measure was cessation rates. Data Collection and Analysis. Two authors extracted data independently for each paper, with disagreements resolved by consensus. Main Results. The systematic review found eight RCTs investigating smoking cessation interventions in the oncology patient population. Pooled relative risks were calculated from two groups of RCTs of smoking cessation interventions based on followup duration. In both groups, the pooled relative risk did not suggest a statistically significant improvement in tobacco cessation compared to usual care. Conclusions. Our review demonstrates that recent interventions in the last decade which are a combination of non-pharmacological and pharmacological approaches yield a statistically significant improvement in smoking cessation rates compared to usual care

    Quantal Brownian Motion - Dephasing and Dissipation

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    We analyze quantal Brownian motion in dd dimensions using the unified model for diffusion localization and dissipation, and Feynman-Vernon formalism. At high temperatures the propagator possess a Markovian property and we can write down an equivalent Master equation. Unlike the case of the Zwanzig-Caldeira-Leggett model, genuine quantum mechanical effects manifest themselves due to the disordered nature of the environment. Using Wigner picture of the dynamics we distinguish between two different mechanisms for destruction of coherence. The analysis of dephasing is extended to the low temperature regime by using a semiclassical strategy. Various results are derived for ballistic, chaotic, diffusive, both ergodic and non-ergodic motion. We also analyze loss of coherence at the limit of zero temperature and clarify the limitations of the semiclassical approach. The condition for having coherent effect due to scattering by low-frequency fluctuations is also pointed out. It is interesting that the dephasing rate can be either larger or smaller than the dissipation rate, depending on the physical circumstances.Comment: LaTex, 23 pages, 4 figures, published vesio

    Assessing natural variations in gene expression in humans by comparing with monozygotic twins using microarrays

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    Quantitative variation in gene expression in humans is the outcome of various factors, including differences in genetic background, gender, age, and environment. However, the extent of the influence of these factors on gene expression is not clear. We attempted to address this issue by carrying out gene expression profiling in blood leukocytes with 13 individuals (including 5 pairs of monozygotic twins) on 10,000 genes using HG-U95Av2 oligonucleotide microarrays. The proportion of differentially expressed genes between monozygotic twins was low (up to 1.76%). Most of the variations belonged to the least variable category. These genes, exhibiting "random variations," did not show clear preference to any functional class, although "signaling and communication" and "immune and related functions" generally topped the list. The extent of variation in gene expression increased in comparisons between unrelated individuals (up to 14.13%). Most of the genes (89%) exhibiting random variations in twins also varied in expression in unrelated individuals. As with twins, signaling and communication topped the list, and substantial variations were observed in all three categories: least variable, moderately variable, and most variable. An important outcome of this study was that the housekeeping genes were nearly insensitive to random variations but appeared to be more susceptible to genetic differences. However, the highly expressed housekeeping genes exhibited low variation and appeared to be insensitive to all known factors. Gene expression profiling in monozygotic twins can provide useful data for the assessment of natural variation in gene expression in humans

    Electric fields in plasmas under pulsed currents

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    Electric fields in a plasma that conducts a high-current pulse are measured as a function of time and space. The experiment is performed using a coaxial configuration, in which a current rising to 160 kA in 100 ns is conducted through a plasma that prefills the region between two coaxial electrodes. The electric field is determined using laser spectroscopy and line-shape analysis. Plasma doping allows for 3D spatially resolved measurements. The measured peak magnitude and propagation velocity of the electric field is found to match those of the Hall electric field, inferred from the magnetic-field front propagation measured previously.Comment: 13 pages, 13 figures, submitted to PR

    Sialendoscopy for the management of obstructive salivary gland disease: A systematic review and meta-analysis

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    Objective: To conduct a systematic review with metaanalysis to determine the efficacy and safety of sialendoscopy in the treatment of obstructive diseases of the salivary glands in adults. Data Sources: MEDLINE, EMBASE, and the Cochrane Library (no lower limit to October 2010). Reference lists were searched for identification of relevant studies. Study Selection: Prospective or retrospective studies of adult patients treated with interventional sialendoscopy for the management of salivary gland obstruction were selected. Outcome measures included rates of success (symptom-free and absence of residual obstruction), sialadenectomy, and complications. Non-English publications were excluded. Data Extraction: Two independent review authors screened eligible studies, extracted relevant data, and resolved discrepancies by consensus when applicable. Weighted pooled proportion, 95% confidence intervals, and test results for heterogeneity are reported. Data Synthesis: Twenty-nine studies were included in the analysis. The weighted pooled proportion of success rates were 0.86 (95% CI, 0.83-0.89) for studies involving 1213 patients undergoing sialendoscopy alone and 0.93 (95% CI, 0.89-0.96) for the 374 patients undergoing sialendoscopy with a combined surgical approach. Outcomes following interventional sialendoscopy for radioiodine-induced sialadenitis were reported in 3 studies, and success rates were variable. Rates of sialadenectomy were low, and few major complications were reported. Conclusion: Findings from the present systematic review and meta-analysis suggest that sialendoscopy is efficacious, safe, and gland preserving for the treatment of obstructive major salivary gland disease
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