4,036 research outputs found
Simultaneous X-ray and optical observations of thermonuclear bursts in the LMXB EXO 0748-676
We report the detection of a large number of optical bursts in the Low Mass
X-ray Binary (LMXB) EXO 0748-676 simultaneous with the thermonuclear X-ray
bursts. The X-ray and the optical bursts are detected in a long observation of
this source with the XMM-Newton observatory. This has increased the number of
thermonuclear X-ray bursts in the LMXBs with simultaneous optical detection by
several factors. The optical bursts are found to have a linear rise followed by
a slow, somewhat exponential decay. Most of the optical bursts have longer rise
and decay timescale compared to the corresponding X-ray bursts. We have
determined the X-ray and optical excess photon counts in the bursts that allow
us to look at the optical to X-ray burst fluence ratio for each burst and the
ratio as a function of the X-ray burst intensity and as a function of the
orbital phase. The delay between the onset of the X-ray bursts and the onset of
the optical bursts have also been measured and is found to have an average
value of 3.25 seconds. We do not find any convincing evidence of orbital phase
dependence of the following parameters: X-ray to optical delay, rise time of
the optical bursts, and optical to X-ray burst intensity ratio as would be
expected if the optical bursts were produced by reprocessing from the surface
of the secondary star that is facing the compact star. On the other hand, if
the optical bursts are produced by reprocessing of the X-rays in the accretion
disk, the onset of the bursts is not expected to have a sharp, linear shape as
is observed in a few of the bursts in EXO 0748-676. We emphasise the fact that
simultaneous optical observations of the X-ray bursts in multiple wavelength
bands will enable further detailed investigations of the reprocessing
phenomena, including any non-linear effect of the X-ray irradiation.Comment: 12 pares, 5 figures (Submitted to the Bulletin of the Astronomical
Society of India
Rates of Short-GRB afterglows in association with Binary Neutron Star mergers
Assuming all binary Neutron Star mergers produce Short Gamma Ray Bursts
(SGRBs), we combine the merger rates of binary Neutron Stars (BNS) from
population synthesis studies, the sensitivities of advanced Gravitational Wave
(GW) interferometer networks, and of the electromagnetic (EM) facilities in
various wave bands, to compute the detection rate of associated afterglows in
these bands. Using the inclination angle measured from GWs as a proxy for the
viewing angle and assuming a uniform distribution of jet opening angle between
3 to 30 degrees, we generate light curves of the counterparts using the open
access afterglow hydrodynamics package BoxFit for X-ray, Optical and Radio
bands. For different EM detectors we obtain the fraction of EM counterparts
detectable in these three bands by imposing appropriate detection thresholds.
In association with BNS mergers detected by five (three) detector network of
advanced GW interferometers, assuming a BNS merger rate of ~\citep{dominik2012double}, we find the afterglow
detection rates (per year) to be (), ()
and () in the X-ray, optical and radio bands respectively.
Our rates represent maximum possible detections for the given BNS rate since we
ignore effects of cadence and field of view in EM follow up observations.Comment: Published in MNRA
Exploring Short-GRB afterglow parameter space for observations in coincidence with gravitational waves
Short duration Gamma Ray Bursts(SGRB) and their afterglows are among the most
promising electro-magnetic (EM) counterparts of Neutron Star (NS) mergers. The
afterglow emission is broadband, visible across the entire electro-magnetic
window from -ray to radio frequencies. The flux evolution in these
frequencies is sensitive to the multi-dimensional afterglow physical parameter
space. Observations of gravitational wave (GW) from BNS mergers in spatial and
temporal coincidence with SGRB and associated afterglows can provide valuable
constraints on afterglow physics. We run simulations of GW-detected BNS events
and assuming all of them are associated with a GRB jet which also produces an
afterglow, investigate how detections or non-detections in X-ray, optical and
radio frequencies can be influenced by the parameter space. We narrow-down the
regions of afterglow parameter space for a uniform top-hat jet model which
would result in different detection scenarios. We list inferences which can be
drawn on the physics of GRB afterglows from multi-messenger astronomy with
coincident GW-EM observations.Comment: Published in MNRA
Association between maternal serum beta human chorionic gonadotropin levels and hypertensive disorders of pregnancy
Background: A major challenge in obstetrics is early identification of hypertensive disorders of pregnancy (HDP). This study was performed to determine the association between elevated maternal serum β-hCG levels and HDP, the correlation between serum β-hCG level and severity of preeclampsia and to determine the value of serum β-hCG level as a diagnostic marker for early diagnosis of HDP.Methods: This was a hospital based observational study conducted in the department of obstetrics and gynecology, Rajendra Institute of Medical Sciences, Ranchi on 375 pregnant women with period of gestation more than 20 weeks, including 250 pregnant women with HDP as study group and 125 normotensive pregnant women as controls. Serum β-hCG concentration was measured and its level was compared between two groups.Results: The maternal mean serum β-hCG levels (51161.08±30038.21 IU/L) of study group of HDP were higher than the normotensive control group (17603.23±16748.21 IU/L). In non-severe preeclampsia, the mean serum levels were 36417.32±23876.74 IU/L while in severe preeclampsia, 60030.34±28771.31 IU/L. There was statistically significant difference (p<0.001) with higher levels in early onset preeclamptic mothers than late onset preeclampsia. The cut-off point of β-hCG for predicting HDP was 32077 IU/L with sensitivity of 65% and specificity of 86%.Conclusions: Serum β-hCG level is higher in HDP when compared to normotensive women. Higher levels of β-hCG are associated with increasing severity of hypertensive disorders of pregnancy. The utility of serum β-hCG as a diagnostic test is limited because of low sensitivity and difficulty in deciding the cut-off value
Non-degenerate, three-wave mixing with the Josephson ring modulator
The Josephson ring modulator (JRM) is a device, based on Josephson tunnel
junctions, capable of performing non-degenerate mixing in the microwave regime
without losses. The generic scattering matrix of the device is calculated by
solving coupled quantum Langevin equations. Its form shows that the device can
achieve quantum-limited noise performance both as an amplifier and a mixer.
Fundamental limitations on simultaneous optimization of performance metrics
like gain, bandwidth and dynamic range (including the effect of pump depletion)
are discussed. We also present three possible integrations of the JRM as the
active medium in a different electromagnetic environment. The resulting
circuits, named Josephson parametric converters (JPC), are discussed in detail,
and experimental data on their dynamic range are found to be in good agreement
with theoretical predictions. We also discuss future prospects and requisite
optimization of JPC as a preamplifier for qubit readout applications.Comment: 21 pages, 16 figures, 4 table
Effect of different potato varieties and tuber sizes on physiological changes under ambient storage performance
The storability and sprouting behavior of three grades (small, medium and large tubers) from four Indian potato cultivars was studied under ambient conditions to assess the quality changes due to physiological losses and sprouting bhaviour of potato tubers. It was found that physiological loss in weight (%), decay loss on number and weight basis (%), sprout loss on number and weight basis (%), total loss (%), general appearance, presence of black or hollow heart were affected significantly by the different varieties as well as by the size. The loss in weight of tubers due to physiological activities, decaying and sprouting increased with the increased in storage period and the loss was more in larger than smaller and medium tubers. Kufri Badshah showed the best control over sprouting, whereas, 100% sprouting was observed in Kufri Bahar with all possible combinations during storage. The maximum value for cumulative physiological loss in weight was observed in variety Kufri Bahar (12.07%), whereas, minimum was in Kufri Pushkar (7.44%). The maximum decay loss was observed in variety Kufri Pushkar (7.89 and 8.72%) and minimum in Kufri Bahar (0.00 and 4.58%) on 80th and 90th day of storage period. Black or hollow heart was absent completely in all the possible treatments. So far general appearance of the tubers was concerned, the larger tubers shrivelled more and earlier than the medium and small sized tubers. Different varieties behaved differently during the entire storage period
Implementation of low-loss superinductances for quantum circuits
The simultaneous suppression of charge fluctuations and offsets is crucial
for preserving quantum coherence in devices exploiting large quantum
fluctuations of the superconducting phase. This requires an environment with
both extremely low DC and high RF impedance. Such an environment is provided by
a superinductance, defined as a zero DC resistance inductance whose impedance
exceeds the resistance quantum at
frequencies of interest (1 - 10 GHz). In addition, the superinductance must
have as little dissipation as possible, and possess a self-resonant frequency
well above frequencies of interest. The kinetic inductance of an array of
Josephson junctions is an ideal candidate to implement the superinductance
provided its phase slip rate is sufficiently low. We successfully implemented
such an array using large Josephson junctions (), and measured
internal losses less than 20 ppm, self-resonant frequencies greater than 10
GHz, and phase slip rates less than 1 mHz
Dental fear in children and its relation to dental caries and gingival condition – a cross sectional study in Bangalore City, India.
Aims and objectives: The aim of this study was to determine the levels of dental fear, and its association with dental caries and gingivitis among 12 – 15 year old government high school children in Bangalore City, India. Methods: Eight government high schools were selected by simple random method from the 2 zones of Bangalore City. All the children who participated in this study were asked the single item Dental Anxiety Question to assess the dental fear and underwent oral examination for dental caries and gingivitis using decayed, missing and filled teeth (DMFT) index and Community Periodontal Index (CPI), respectively. Results: The prevalence of high dental fear among the study population was 23.4%. The mean MT was significantly associated with high fear. Highly significant correlation was found between presence of bleeding on gentle probing and high dental fear. Conclusion: High dental fear plays an important role in the oral health status of 12 to 15 year old children. 
Anterior and Posterior Tongue Regions and Taste Papillae: Distinct Roles and Regulatory Mechanisms with an Emphasis on Hedgehog Signaling and Antagonism.
Sensory receptors across the entire tongue are engaged during eating. However, the tongue has distinctive regions with taste (fungiform and circumvallate) and non-taste (filiform) organs that are composed of specialized epithelia, connective tissues, and innervation. The tissue regions and papillae are adapted in form and function for taste and somatosensation associated with eating. It follows that homeostasis and regeneration of distinctive papillae and taste buds with particular functional roles require tailored molecular pathways. Nonetheless, in the chemosensory field, generalizations are often made between mechanisms that regulate anterior tongue fungiform and posterior circumvallate taste papillae, without a clear distinction that highlights the singular taste cell types and receptors in the papillae. We compare and contrast signaling regulation in the tongue and emphasize the Hedgehog pathway and antagonists as prime examples of signaling differences in anterior and posterior taste and non-taste papillae. Only with more attention to the roles and regulatory signals for different taste cells in distinct tongue regions can optimal treatments for taste dysfunctions be designed. In summary, if tissues are studied from one tongue region only, with associated specialized gustatory and non-gustatory organs, an incomplete and potentially misleading picture will emerge of how lingual sensory systems are involved in eating and altered in disease
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