Search results for " rays"
showing 10 items of 520 documents
The flaring afterglow of GRB 050730
2006
We present a detailed spectral and temporal analysis of Swift and XMM-Newton observations of GRB 050730. The X-ray afterglow of GRB 050730 was found to decline with time with intense flaring activity superimposed. Evidence of flaring activity in the early UVOT optical afterglow, simultaneous with that observed in the X-ray band, was found. Strong spectral evolution in the X-ray energy band during the flaring activity was present.
ESR response to gamma-rays of alanine pellets containing B(OH)3 or Gd2O3.
2007
ESR response to gamma-irradiation (1-50 Gy) of blends containing alanine and either B(OH)(3) or Gd(2)O(3) is reported. The sensitivity of the alanine--B(OH)(3) blend is comparable to the sensitivity of pure alanine, although its lowest detectable dose, LDD, is smaller ( approximately 1.3 Gy) than that of pure alanine ( approximately 2.9 Gy). Alanine with Gd(2)O(3) is about two times more sensitive than pure alanine, and its LDD is 0.8 Gy. The better sensitivity and LDD are probably due to the high atomic number (Z=64) of gadolinium, which enhances the interaction probability with photons and, consequently, the radical yield. This study suggests that other high-Z atoms may be useful for incr…
A multifunctional bioconjugate module for versatile photoaffinity labeling and click chemistry of RNA
2011
A multifunctional reagent based on a coumarin scaffold was developed for derivatization of naive RNA. The alkylating agent N3BC [7-azido-4-(bromomethyl)coumarin], obtained by Pechmann condensation, is selective for uridine. N3BC and its RNA conjugates are pre-fluorophores which permits controlled modular and stepwise RNA derivatization. The success of RNA alkylation by N3BC can be monitored by photolysis of the azido moiety, which generates a coumarin fluorophore that can be excited with UV light of 320 nm. The azidocoumarin-modified RNA can be flexibly employed in structure-function studies. Versatile applications include direct use in photo-crosslinking studies to cognate proteins, as dem…
Kinetics of gamma-H2AX focus formation upon treatment of cells with UV light and alkylating agents.
2008
Histone H2AX is rapidly phosphorylated in response to DNA double-strand breaks (DSBs) induced by ionizing radiation (IR). Here we show that DNA damage induced by alkylating agents [methyl methanesulfonate (MMS) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)] and ultraviolet light (UV-C) leads to a dose and time dependent accumulation of phosphorylated H2AX (gamma-H2AX). Time course experiments revealed that the number of gamma-H2AX foci reached peak levels 8 hr after MMS or MNNG treatment and declined to almost control values within 24 hr after exposure. Upon UV-C treatment, a biphasic response was observed with a maximum 12 hr after treatment. In 43-3B cells deficient in nucleotide excisi…
Activation of c-Jun N-terminal kinase 1 by UV irradiation is inhibited by wortmannin without affecting c-iun expression.
1999
Activation of c-Jun N-terminal kinases (JNKs)/stress-activated protein kinases is an early response of cells upon exposure to DNA-damaging agents. JNK-mediated phosphorylation of c-Jun is currently understood to stimulate the transactivating potency of AP-1 (e.g., c-Jun/c-Fos; c-Jun/ATF-2), thereby increasing the expression of AP-1 target genes. Here we show that stimulation of JNK1 activity is not a general early response of cells exposed to genotoxic agents. Treatment of NIH 3T3 cells with UV light (UV-C) as well as with methyl methanesulfonate (MMS) caused activation of JNK1 and an increase in c-Jun protein and AP-1 binding activity, whereas antineoplastic drugs such as mafosfamide, mito…
Primary mouse fibroblasts deficient for c-Fos, p53 or for both proteins are hypersensitive to UV light and alkylating agent-induced chromosomal break…
2000
The important regulatory proteins, c-Fos and p53 are induced by exposure of cells to a variety of DNA damaging agents. To investigate their role in cellular defense against genotoxic compounds, we comparatively analysed chromosomal aberrations and apoptosis induced by ultraviolet (UV-C) light and the potent alkylating agent methyl methanesulfonate (MMS) in primary diploid mouse fibroblasts knockout for either c-Fos or p53, or double knockout for both genes. We show that c-Fos and p53 deficient fibroblasts are more sensitive than the corresponding wild-type cells as to the induction of chromosomal aberrations and apoptosis. Double knockout fibroblasts lacking both c-Fos and p53 are viable an…
Multioctave midinfrared supercontinuum generation in suspended-core chalcogenide fibers
2014
An As2S3 fiber-based supercontinuum source that covers 3500 nm, extending from near visible to the midinfrared, is successfully reported by using a 200-fs-pulsed pump with nJ-level energy at 2.5 μm. The main features of our fiber-based source are two-fold. On the one hand, a low-loss As2S3 microstructured optical fiber has been fabricated, with typical attenuation below 2 dB/m in the 1-4 μm wavelength range. On the other hand, a 20-mm-long microstructured fiber sample is sufficient to enable a spectral broadening, spreading from 0.6 to 4.1 μm in a 40 dB dynamic range.
Microstructured chalcogenide optical fibers from As2S3 glass: towards new IR broadband sources
2010
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A study of the effect of molecular and aerosol conditions in the atmosphere on air fluorescence measurements at the Pierre Auger Observatory
2010
The air fluorescence detector of the Pierre Auger Observatory is designed to perforin calorimetric measurements of extensive air showers created by Cosmic rays of above 10(18) eV. To correct these measurements for the effects introduced by atmospheric fluctuations, the Observatory contains a group Of monitoring instruments to record atmospheric conditions across the detector site, ail area exceeding 3000 km(2). The atmospheric data are used extensively in the reconstruction of air showers, and are particularly important for the correct determination of shower energies and the depths of shower maxima. This paper contains a summary of the molecular and aerosol conditions measured at the Pierr…
Neutrino pair annihilation near accreting, stellar-mass black holes
2006
We investigate the energy-momentum deposition due to neutrino-antineutrino annihilation in the vicinity of axisymmetric, accreting black holes (BHs) by numerically ray-tracing neutrino trajectories in a Kerr space-time. Hyperaccreting stellar-mass BHs are widely considered as energy sources that can drive ultrarelativistic outflows with the potential to produce gamma-ray bursts. In contrast to earlier works, we provide an extensive and detailed parameter study of the influence of general relativistic (GR) effects and of different neutrinosphere geometries. These include idealized thin disks, tori, and spheres, or are constructed as non-selfgravitating equilibrium matter distributions for va…