7,239 research outputs found
A Proposal to Localize Fermi GBM GRBs Through Coordinated Scanning of the GBM Error Circle via Optical Telescopes
We investigate the feasibility of implementing a system that will coordinate
ground-based optical telescopes to cover the Fermi GBM Error Circle (EC). The
aim of the system is to localize GBM detected GRBs and facilitate
multi-wavelength follow-up from space and ground. This system will optimize the
observing locations in the GBM EC based on individual telescope location, Field
of View (FoV) and sensitivity. The proposed system will coordinate GBM EC
scanning by professional as well as amateur astronomers around the world. The
results of a Monte Carlo simulation to investigate the feasibility of the
project are presented.Comment: 2011 Fermi Symposium proceedings - eConf C11050
A CLEAN-based Method for Deconvolving Interstellar Pulse Broadening from Radio Pulses
Multipath propagation in the interstellar medium distorts radio pulses, an
effect predominant for distant pulsars observed at low frequencies. Typically,
broadened pulses are analyzed to determine the amount of propagation-induced
pulse broadening, but with little interest in determining the undistorted pulse
shapes. In this paper we develop and apply a method that recovers both the
intrinsic pulse shape and the pulse broadening function that describes the
scattering of an impulse. The method resembles the CLEAN algorithm used in
synthesis imaging applications, although we search for the best pulse
broadening function, and perform a true deconvolution to recover intrinsic
pulse structre. As figures of merit to optimize the deconvolution, we use the
positivity and symmetry of the deconvolved result along with the mean square
residual and the number of points below a given threshold. Our method makes no
prior assumptions about the intrinsic pulse shape and can be used for a range
of scattering functions for the interstellar medium. It can therefore be
applied to a wider variety of measured pulse shapes and degrees of scattering
than the previous approaches. We apply the technique to both simulated data and
data from Arecibo observations.Comment: 9 pages, 6 figures, Accepted for publication in the Astrophysical
Journa
The effect of network structure on phase transitions in queuing networks
Recently, De Martino et al have presented a general framework for the study
of transportation phenomena on complex networks. One of their most significant
achievements was a deeper understanding of the phase transition from the
uncongested to the congested phase at a critical traffic load. In this paper,
we also study phase transition in transportation networks using a discrete time
random walk model. Our aim is to establish a direct connection between the
structure of the graph and the value of the critical traffic load. Applying
spectral graph theory, we show that the original results of De Martino et al
showing that the critical loading depends only on the degree sequence of the
graph -- suggesting that different graphs with the same degree sequence have
the same critical loading if all other circumstances are fixed -- is valid only
if the graph is dense enough. For sparse graphs, higher order corrections,
related to the local structure of the network, appear.Comment: 12 pages, 7 figure
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Inhibition of acetyl-CoA carboxylase suppresses fatty acid synthesis and tumor growth of non-small-cell lung cancer in preclinical models.
Continuous de novo fatty acid synthesis is a common feature of cancer that is required to meet the biosynthetic demands of a growing tumor. This process is controlled by the rate-limiting enzyme acetyl-CoA carboxylase (ACC), an attractive but traditionally intractable drug target. Here we provide genetic and pharmacological evidence that in preclinical models ACC is required to maintain the de novo fatty acid synthesis needed for growth and viability of non-small-cell lung cancer (NSCLC) cells. We describe the ability of ND-646-an allosteric inhibitor of the ACC enzymes ACC1 and ACC2 that prevents ACC subunit dimerization-to suppress fatty acid synthesis in vitro and in vivo. Chronic ND-646 treatment of xenograft and genetically engineered mouse models of NSCLC inhibited tumor growth. When administered as a single agent or in combination with the standard-of-care drug carboplatin, ND-646 markedly suppressed lung tumor growth in the Kras;Trp53-/- (also known as KRAS p53) and Kras;Stk11-/- (also known as KRAS Lkb1) mouse models of NSCLC. These findings demonstrate that ACC mediates a metabolic liability of NSCLC and that ACC inhibition by ND-646 is detrimental to NSCLC growth, supporting further examination of the use of ACC inhibitors in oncology
The Lag-Luminosity Relation in the GRB Source Frame: An Investigation with Swift BAT Bursts
Spectral lag. which is defined as the difference in time of arrival of high- and low-energy photons. is a common feature in gamma-ray bursts (GRBs). Previous investigations have shown a correlation between this lag and the isotropic peak luminosity for long duration bursts. However. most of the previous investigations used lags extracted in the observer frame only. In this work (based on a sample of 43 Swift long GRBs with known redshifts). we present an analysis of the lag-luminosity relation in the GRB source frame. Our analysis indicates a higher degree of correlation -0.82 +/- 0.05 (chance probability of approx. 5.5 x 10(exp -5) between the spectral lag and the isotropic peak luminosity, L(sub iso). with a best-fitting power-law index of -1.2 +/- 0.2. In addition, there is an anticorrelation between the source-frame spectral lag and the source-frame peak energy of the burst spectrum
Low Temperature Transport and Specific Heat Studies of Nd_{1-x}Pb_{x}MnO_{3} Single Crystals
Electrical transport and specific heat properties of Nd_{1-x}Pb_{x}MnO_{3}
single crystals for 0.15 < x 0.5 have been studied in low temperature regime.
The resistivity in the ferromagnetic insulating (FMI) phase for x < 0.3 has an
activated character. The dependence of the activation gap Delta on doping x has
been determined and the critical concentration for the zero-temperature
metal-insulator transition was determined as x_{c} ~ 0.33. For a metallic
sample with x=0.42, a conventional electron-electron (e-e) scattering term
proportional T^{2} is found in the low-temperature electrical resistivity,
although the Kadowaki-Woods ratio is found to be much larger for this manganite
than for a normal metal. For a metallic sample with x=0.5, a resistivity
minimum is observed for x= 0.5. The effect is attributed to weak localization
and can be described by a negative T^{1/2} weak-localization contribution to
resistivity for a disordered three-dimensional electron system. The specific
heat data have been fitted to contributions from free electrons (gamma), spin
excitations (beta_{3/2}), lattice and a Schottky-like anomaly related to the
rare-earth magnetism of the Nd ions. The value of gamma is larger than for
normal metals, which is ascribed to magnetic ordering effects involving Nd.
Also, the Schottky-like anomaly appears broadened and weakened suggesting
inhomogeneous molecular fields at the Nd-sites.Comment: 14 pages, 8 figure
Bioactive Compounds of Rambutan (Nephelium lappaceum L.)
Rambutan, a widely popular tropical fruit encompasses rich amount of bioactive compounds.
All parts of this plant (leaves, bark, root, fruits, fruit skin, pulp and seeds) finds traditional
usage, and are linked with high therapeutic values. Rambutan fruits parts like that of peel, pulp
and seeds have been scientifically investigated in-depth and is reported to encompass high
amounts of bioactive compounds (such as polyphenol, flavonoid, alkaloid, essential mineral,
dietary fiber). These compounds contribute towards antioxidant, antimicrobial, anticancer,
antidiabetic and anti-obesity activities. However, literature pertaining towards potential
industrial applications (food, cosmetics, pharmaceutical) of rambutan fruits are limited. In the
present chapter, it is intended to document some of the interesting research themes published
on rambutan fruits, and identify the existing gaps to open up arena for future research work.This chapter theme is based on our ongoing project—VALORTECH,
which has received funding from the European Union’s Horizon 2020 research and innovation
program under grant agreement No 810630
Pharmacokinetic parameters of meloxicam after its oral administration in goat
Aim: The objective of the present study was to find out the levels of analgesic drug meloxicam in the blood plasma of young goats. The drug was given to them through oral route. Data was used to elucidate the Pharmacokinetic determinants of the drug which were employed to arrive at the dose schedule and frequency of the drug in goats.
Materials and Methods: Elaborate pharmacokinetic research of the drug meloxicam was done on 18 to 24 months old, five adult male local goats (Capra hircus) of Assam weighing 20 to 25 kg.The drug was given orally at the dose rate of 0.35 mg/kg at the Goat Rearing farm, Guwahati, Assam. Analysis of blood was done by high performance liquid chromatography (HPLC) system.
Results: The mean values of area under curve (AUC) and mean area under curve (AUMC) were 3137.488 ± 125.3749 µg.min/ml and 4650460 ± 380892.4744 µg.min2/ml respectively .The mean peak plasma level of meloxicam was 1.972 ± 0.0477 µg/ml at 600 min. The mean values of elimination half life (t1/2β) and absorption half life (t1/2Ka) were 693±0.00 min and 170.6 ± 17.0076 min respectively. The mean values of volume of distribution (Vd) and mean residence time (MRT) were 0.114 ± 0.0156 L/kg and 1472.264 ± 63.336 min respectively. The mean value of Tmax was found to be 497 ± 19.8040 min. Following single oral administration the minimum effective therapeutic concentration or minimum effective plasma concentration of meloxicam was detectable up to 1200 min. The bioavailibity (F) of the drug was 80.5 ± 10.0150%.
Conclusion: These pharmacokinetic determinants were used to determine the frequency and dose schedule of meloxicam in goats. The minimum effective concentration of the drug is 0.7 µg/ml in plasma. To maintain this, an initial loading dose of 0.5 mg/kg body weight should be followed by a maintenance dose of 0.4 mg/kg body weight/10 hour
Multiwavelength Intraday Variability of the BL Lac S5 0716+714
We report results from a 1 week multi-wavelength campaign to monitor the BL
Lac object S5 0716+714 (on December 9-16, 2009). In the radio bands the source
shows rapid (~ (0.5-1.5) day) intra-day variability with peak amplitudes of up
to ~ 10 %. The variability at 2.8 cm leads by about 1 day the variability at 6
cm and 11 cm. This time lag and more rapid variations suggests an intrinsic
contribution to the source's intraday variability at 2.8 cm, while at 6 cm and
11 cm interstellar scintillation (ISS) seems to predominate. Large and
quasi-sinusoidal variations of ~ 0.8 mag were detected in the V, R and I-bands.
The X-ray data (0.2-10 keV) do not reveal significant variability on a 4 day
time scale, favoring reprocessed inverse-Compton over synchrotron radiation in
this band. The characteristic variability time scales in radio and optical
bands are similar. A quasi-periodic variation (QPO) of 0.9 - 1.1 days in the
optical data may be present, but if so it is marginal and limited to 2.2
cycles. Cross-correlations between radio and optical are discussed. The lack of
a strong radio-optical correlation indicates different physical causes of
variability (ISS at long radio wavelengths, source intrinsic origin in the
optical), and is consistent with a high jet opacity and a compact synchrotron
component peaking at ~= 100 GHz in an ongoing very prominent flux density
outburst. For the campaign period, we construct a quasi-simultaneous spectral
energy distribution (SED), including gamma-ray data from the FERMI satellite.
We obtain lower limits for the relativistic Doppler-boosting of delta >= 12-26,
which for a BL\,Lac type object, is remarkably high.Comment: 16 pages, 15 figures, table 2; Accepted for Publication in MNRA
Search for associated Higgs boson production using like charge dilepton events in p(p)over-bar collisions at root s=1.96 TeV
We present a search for associated Higgs boson production in the process p (p) over bar -> W/ZH -> l(+/-)l'(+/-) + X in ee, e mu, and mu mu final states. The search is based on data collected by the D0 experiment at the Fermilab Tevatron Collider at root s = 1.96 TeV corresponding to 5.3 fb(-1) of integrated luminosity. We require two isolated leptons (electrons or muons) with the same electric charge and additional kinematic requirements. No significant excess above background is observed, and we set 95% C. L. observed (expected) upper limits on ratio of the production cross section to the standard model prediction of 6.4 (7.3) for a Higgs boson mass of 165 GeV and 13.5 (19.8) for a mass of 115 GeV
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