4,679 research outputs found
Normal mode analysis for scalar fields in BTZ black hole background
We analyze the possibility of inequivalent boundary conditions for a scalar
field propagating in the BTZ black hole space-time. We find that for certain
ranges of the black hole parameters, the Klein-Gordon operator admits a
one-parameter family of self-adjoint extensions. For this range, the BTZ
space-time is not quantum mechanically complete. We suggest a physically
motivated method for determining the spectra of the Klein-Gordon operator.Comment: 6 pages, no figure, late
Perspectives for analyzing non-linear photo-ionization spectra with deep neural networks trained with synthetic Hamilton matrices
We have constructed deep neural networks, which can map fluctuating photo-electron spectra obtained from noisy pulses to spectra from noise-free pulses. The network is trained on spectra from noisy pulses in combination with random Hamilton matrices, representing systems which could exist but do not necessarily exist. In [Giri et al., Phys. Rev. Lett., 2020, 124, 113201] we performed a purification of fluctuating spectra, that is, mapping them to those from Fourier-limited Gaussian pulses. Here, we investigate the performance of such neural-network-based maps for predicting spectra of double pulses, pulses with a chirp and even partially-coherent pulses from fluctuating spectra generated by noisy pulses. Secondly, we demonstrate that along with purification of a fluctuating double-pulse spectrum, one can estimate the time-delay of the underlying double pulse, an attractive feature for single-shot spectra from SASE FELs. We demonstrate our approach with resonant two-photon ionization, a non-linear process, sensitive to details of the laser pulse
A model-based multithreshold method for subgroup identification
Thresholding variable plays a crucial role in subgroup identification for personalizedmedicine. Most existing partitioning methods split the sample basedon one predictor variable. In this paper, we consider setting the splitting rulefrom a combination of multivariate predictors, such as the latent factors, principlecomponents, and weighted sum of predictors. Such a subgrouping methodmay lead to more meaningful partitioning of the population than using a singlevariable. In addition, our method is based on a change point regression modeland thus yields straight forward model-based prediction results. After choosinga particular thresholding variable form, we apply a two-stage multiple changepoint detection method to determine the subgroups and estimate the regressionparameters. We show that our approach can produce two or more subgroupsfrom the multiple change points and identify the true grouping with high probability.In addition, our estimation results enjoy oracle properties. We design asimulation study to compare performances of our proposed and existing methodsand apply them to analyze data sets from a Scleroderma trial and a breastcancer study
Self-Adjointness of Generalized MIC-Kepler System
We have studied the self-adjointness of generalized MIC-Kepler Hamiltonian,
obtained from the formally self-adjoint generalized MIC-Kepler Hamiltonian. We
have shown that for \tilde l=0, the system admits a 1-parameter family of
self-adjoint extensions and for \tilde l \neq 0 but \tilde l <{1/2}, it has
also a 1-parameter family of self-adjoint extensions.Comment: 11 pages, Latex, no figur
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Prevalence and correlates of vitamin D status in African American men
Background: Few studies have examined vitamin D insufficiency in African American men although they are at very high risk. We examined the prevalence and correlates of vitamin D insufficiency among African American men in Philadelphia. Methods: Participants in this cross-sectional analysis were 194 African American men in the Philadelphia region who were enrolled in a risk assessment program for prostate cancer from 10/96–10/07. All participants completed diet and health history questionnaires and provided plasma samples, which were assessed for 25-hydroxyvitamin D (25(OH)D) concentrations. We used linear regression models to examine associations with 25(OH)D concentrations and logistic regression to estimate odds ratios (OR) for having 25(OH)D ≥ 15 ng/mL. Results: Mean 25(OH)D was 13.7 ng/mL, and 61% of men were classified as having vitamin D insufficiency (25(OH)D 400 vs. 0 IU/day), milk consumption (OR 5.9, 95% CI 2.2, 16.0 for ≥ 3.5 vs. <1 time per week), and blood collection in the summer. Additionally, 25(OH)D concentrations increased with more recreational physical activity (OR 1.3, 95% CI 1.1, 1.6 per hour). A significant inverse association of body mass index with 25(OH)D concentrations in bivariate analyses was attenuated with adjustment for season of blood collection. Conclusion: The problem of low vitamin D status in African American men may be more severe than previously reported. Future efforts to increase vitamin D recommendations and intake, such as through supplementation, are warranted to improve vitamin D status in this particularly vulnerable population
Type II endometrial cancers: original research on a series
Background: Endometrial carcinoma, which ranks 3rd in India amongst the gynecological malignancies, is of two histological types: I and II. These differ in molecular as well as in clinical and histopathological profiles. Type II is estrogen independent, nonendometrioid, with higher grade histologies, more aggressive and carries an adverse prognosis.Methods: Endometrial carcinomas diagnosed from endometrial biopsies and hysterectomy specimens in the Dept of Gynaec-oncology, AHRCC, Cuttack from November 2009 to January 2015 were included in the study. All specimens were fixed in 10% neutral buffered formalin and paraffin embedded for histological examination with hematoxylin and eosin staining. The clinicopathological analysis of the cases of EC was done with an emphasis on morphology.Results: Of a total of 150 cases of EC reported, 20 cases were classified as type II EC (13.33%) as per histology. The age of the patients ranged from 36 to 73 years, with mean age is 61 years. In 11 cases (55%), the myometrial invasion was more than half. the histological type was a clear cell adenocarcinoma in 50% of the cases. All were treated with hysterectomy and chemotherapy.Conclusions: Of the type II EC, serous carcinoma is the most common type. Clinical presentation and prognosis differs in comparison to type I EC, thus the recognition of this type of EC is pivotal
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