833 research outputs found
A non-linear resonance model for the black hole and neutron star QPOs: theory supported by observations
Kilohertz Quasi-Periodic Oscillations (QPOs) have been detected in many
accreting X-ray binaries. It has been suggested that the highest QPO
frequencies observed in the modulation of the X-ray flux reflect a non-linear
resonance between two modes of accreting disk oscillation. This hypothesis
implies certain very general predictions, several of which have been borne out
by observations. Some of these follow from properties of non-linear
oscillators, while the others are specific to oscillations of fluid in strong
gravity. A 3:2 resonant ratio of frequencies can be clearly recognized in the
black-hole as well as in the neutron-star QPO data.Comment: 8 pages, 8 figures, to appear in Proceedings of the Albert Einstein
Century International Conferenc
The Kepler view of magnetic chemically peculiar stars
Magnetic chemically peculiar (mCP) stars exhibit complex atmospheres that
allow the investigation of such diverse phenomena as atomic diffusion, magnetic
fields, and stellar rotation. The advent of space-based photometry provides the
opportunity for the first precise characterizations of the photometric
variability properties of these stars. We carried out a search for new mCP
stars in the Kepler field with the ultimate aim of investigating their
photometric variability properties using Kepler data. As an aside, we describe
criteria for selecting mCP star candidates based on light curve properties, and
assess the accuracy of the spectral classifications provided by the MKCLASS
code. As only very few known mCP stars are situated in the Kepler field, we had
to depend largely on alternative (nonspectroscopic) means of identifying
suitable candidates that rely mostly on light curve properties; in particular
we relied on monoperiodic variability and light curve stability. Newly acquired
and archival spectra were used to confirm most of our mCP star candidates.
Linear ephemeris parameters and effective amplitudes were derived from
detrended Kepler data. Our final sample consists of 41 spectroscopically
confirmed mCP stars of which 39 are new discoveries, 5 candidate mCP stars, and
7 stars in which no chemical peculiarities could be established. Our targets
populate the whole age range from zero-age main sequence to terminal-age main
sequence and are distributed in the mass interval from 1.5 M_sun to 4 M_sun.
About 25% of the mCP stars show a hitherto unobserved wealth of detail in their
light curves indicative of complex surface structures. We identified light
curve stability as a primary criterion for identifying mCP star candidates
among early-type stars in large photometric surveys, and prove the reliability
of the spectral classifications provided by the MKCLASS code.Comment: Accepted for publication in Astronomy and Astrophysics. 20 pages, 12
figures, 5 tables. Given above is a slightly shortened version of the
abstract; for the full abstract, please refer to the pape
Menstrual Blood as a Potential Source of Endometrial Derived CD3+ T Cells
Studies of T cell-mediated immunity in the human female genital tract have been problematic due to difficulties associated with the collection of mucosal samples. Consequently, most studies rely on biopsies from the lower female genital tract or remnant tissue from hysterectomies. Availability of samples from healthy women is limited, as most studies are carried out in women with underlying pathologies. Menstruation is the cyclical sloughing off of endometrial tissue, and thus it should be a source of endometrial cells without the need for a biopsy. We isolated and phenotyped T cells from menstrual and peripheral blood and from endometrial biopsy-derived tissue from healthy women to determine the types of T cells present in this compartment. Our data demonstrated that T cells isolated from menstrual blood are a heterogeneous population of cells with markers reminiscent of blood and mucosal cells as well as unique phenotypes not represented in either compartment. T cells isolated from menstrual blood expressed increased levels of HLA-DR, αEβ7 and CXCR4 and reduced levels of CD62L relative to peripheral blood. Menstrual blood CD4+ T cells were enriched for cells expressing both CCR7 and CD45RA, markers identifying naïve T cells and were functional as determined by antigen-specific intracellular cytokine production assays. These data may open new avenues of investigation for cell mediated immune studies involving the female reproductive tract without the need for biopsies
Influence of insulin on glucose metabolism and energy expenditure in septic patients
INTRODUCTION: It is recognized that administration of insulin with glucose decreases catabolic response in sepsis. The aim of the present study was to compare the effects of two levels of insulinaemia on glucose metabolism and energy expenditure in septic patients and volunteers. METHODS: Glucose uptake, oxidation and storage, and energy expenditure were measured, using indirect calorimetry, in 20 stable septic patients and 10 volunteers in a two-step hyperinsulinaemic (serum insulin levels 250 and 1250 mIU/l), euglycaemic (blood glucose concentration 5 mmol/l) clamp. Differences between steps of the clamp (from serum insulin 1250 to 250 mIU/l) for all parameters were calculated for each individual, and compared between septic patients and volunteers using the Wilcoxon nonpaired test. RESULTS: Differences in glucose uptake and storage were significantly less in septic patients. The differences in glucose oxidation between the groups were not statistically significant. Baseline energy expenditure was significantly higher in septic patients, and there was no significant increase in either step of the clamp in this group; when comparing the two groups, the differences between steps were significantly greater in volunteers. CONCLUSION: A hyperdynamic state of sepsis leads to a decrease in glucose uptake and storage in comparison with healthy volunteers. An increase in insulinaemia leads to an increase in all parameters of glucose metabolism, but the increases in glucose uptake and storage are significantly lower in septic patients. A high level of insulinaemia in sepsis increases glucose uptake and oxidation significantly, but not energy expenditure, in comparison with volunteers
Religiosity and Mental Health:A Contribution to Understanding the Heterogeneity of Research Findings
Most studies report positive associations between religiosity and spirituality and aspects of mental health, while a small proportion report mixed or fully negative associations. The aim of this study was to assess the associations of religiosity measured more specifically, with mental health in a secular environment, using a nationally representative sample of Czech adults (n = 1795). We measured religious affiliation, conversion experience, non-religious attitudes and the stability of these attitudes, mental health problems, and anxiety levels. Compared to stable non-religious respondents, unstable non-religious and converted respondents who perceived God as distant were more likely to experience anxiety in close relationships, and had higher risks of worse mental health. Our findings support the idea that the heterogeneity of findings in associations between religiosity/spirituality and mental health could be due to measurement problems and variation in the degree of secularity. A shift towards religiosity could be expected to be seen in a substantial part of non-religious respondents in problematic times
Ultrasound-controlled cryoneurolysis for peripheral mononeuropathies: a retrospective cohort study.
Aim: Cryoneurolysis is a potential therapy for peripheral mononeuropathies, but randomized studies of its effects on the duration of pain reduction are lacking. Methods: This retrospective cohort study evaluated the analgesic effects of cryoneurolysis on patients with refractory peripheral mononeuropathy. We included 24 patients who underwent ultrasound-guided cryoneurolysis between June 2018 and July 2022. The daily maximum pain level was recorded using a numerical rating scale before and 1, 3 and 6Â months after the procedure. Results: At 1Â month, 54.2% of patients reported pain reduction of at least 30%. This percentage was significantly lower at 3 and 6Â months (13.8 and 9.1%, respectively). Conclusion: Our results suggest that repeated cryoneurolysis may be a viable treatment for refractory mononeuropathy. Further investigations are needed
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