Context. The optical light curve of Type Ia supernovae (SNIa) is powered by thermalized gamma-rays produced by the decay of 56Ni and 56Co, the main radioactive isotopes synthesized by the ...thermonuclear explosion of a C/O white dwarf. Aims. Gamma-rays escaping the ejecta can be used as a diagnostic tool for studying the characteristics of the explosion. In particular, it is expected that the analysis of the early gamma emission, near the maximum of the optical light curve, could provide information about the distribution of the radioactive elements in the debris. Methods. The gamma data obtained from SN2014J in M 82 by the instruments on board INTEGRAL were analysed paying special attention to the effect that the detailed spectral response has on the measurements of the intensity of the lines. Results. The 158 keV emission of 56Ni has been detected in SN2014J at ~5σ at low energy with both ISGRI and SPI around the maximum of the optical light curve. After correcting the spectral response of the detector, the fluxes in the lines suggest that, in addition to the bulk of radioactive elements buried in the central layers of the debris, there is a plume of 56Ni, with a significance of ~3σ, moving at high velocity and receding from the observer. The mass of the plume is in the range of ~0.03−0.08 M⊙. Conclusions. No SNIa explosion model has ever predicted the mass and geometrical distribution of 56Ni suggested here. According to its optical properties, SN2014J looks like a normal SNIa, so it is extremely important to discern whether it is also representative in the gamma-ray band.
Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory ...together record GRBs over a broad energy range spanning about 7 decades of gamma-ray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.
Context. The detection of GeV photons from gamma-ray bursts (GRBs) has important consequences for the interpretation and modelling of these most-energetic cosmological explosions. The full ...exploitation of the high-energy measurements relies, however, on accurate knowledge of the distance to the events. Aims. Here we report on the discovery of the afterglow and subsequent redshift determination of GRB 080916C, the first GRB detected by the Fermi Gamma-Ray Space Telescope with high significance detection of photons at energies >0.1 GeV. Methods. Observations were done with the 7-channel “Gamma-Ray Optical and Near-infrared Detector” (GROND) at the 2.2 m MPI/ESO telescope, the SIRIUS instrument at the Nagoya-SAAO 1.4 m telescope in South Africa, and the GMOS instrument at Gemini-S. Results. The afterglow photometric redshift of $z = 4.35 \pm 0.15$, based on simultaneous 7-filter observations with GROND, places GRB 080916C among the top 5% most distant GRBs and makes it the most energetic GRB known to date. The detection of GeV photons from such a distant event is unexpected because of the predicted opacity due to interaction with the extragalactic background light. The observed gamma-ray variability in the prompt emission, together with the redshift, suggests a lower limit for the Lorentz factor of the ultra-relativistic ejecta of $\Gamma > 1090$. This value rivals any previous measurements of Γ in GRBs and strengthens the extreme nature of GRB 080916C.
SPI: The spectrometer aboard INTEGRAL Vedrenne, G.; Roques, J.-P.; Schönfelder, V. ...
Astronomy and astrophysics (Berlin),
11/2003, Letnik:
411, Številka:
1
Journal Article
Recenzirano
Odprti dostop
SPI is a high spectral resolution gamma-ray telescope on board the ESA mission INTEGRAL (International Gamma Ray Astrophysics Laboratory). It consists of an array of 19 closely packed germanium ...detectors surrounded by an active anticoincidence shield of BGO. The imaging capabilities of the instrument are obtained with a tungsten coded aperture mask located 1.7 m from the Ge array. The fully coded field-of-view is $16\deg$, the partially coded field of view amounts to $31\deg$, and the angular resolution is $2.5\deg$. The energy range extends from 20 keV to 8 MeV with a typical energy resolution of 2.5 keV at 1.3 MeV. Here we present the general concept of the instrument followed by a brief description of each of the main subsystems. INTEGRAL was successfully launched in October 2002 and SPI is functioning extremely well.
Alzheimer’s disease is a devastating cureless neurodegenerative disorder affecting >35 million people worldwide. The disease is caused by toxic oligomers and aggregates of amyloid β protein and the ...microtubule-associated protein tau. Recently, the Lys-specific molecular tweezer CLR01 has been shown to inhibit aggregation and toxicity of multiple amyloidogenic proteins, including amyloid β protein and tau, by disrupting key interactions involved in the assembly process. Following up on these encouraging findings, here, we asked whether CLR01 could protect primary neurons from Alzheimer’s disease-associated synaptotoxicity and reduce Alzheimer’s disease–like pathology in vivo. Using cell culture and brain slices, we found that CLR01 effectively inhibited synaptotoxicity induced by the 42-residue isoform of amyloid β protein, including ∼80% inhibition of changes in dendritic spines density and long-term potentiation and complete inhibition of changes in basal synaptic activity. Using a radiolabelled version of the compound, we found that CLR01 crossed the mouse blood–brain barrier at ∼2% of blood levels. Treatment of 15-month-old triple-transgenic mice for 1 month with CLR01 resulted in a decrease in brain amyloid β protein aggregates, hyperphosphorylated tau and microglia load as observed by immunohistochemistry. Importantly, no signs of toxicity were observed in the treated mice, and CLR01 treatment did not affect the amyloidogenic processing of amyloid β protein precursor. Examining induction or inhibition of the cytochrome P450 metabolism system by CLR01 revealed minimal interaction. Together, these data suggest that CLR01 is safe for use at concentrations well above those showing efficacy in mice. The efficacy and toxicity results support a process-specific mechanism of action of molecular tweezers and suggest that these are promising compounds for developing disease-modifying therapy for Alzheimer’s disease and related disorders.
We present the sample of gamma-ray bursts detected with the anti-coincidence shield ACS of the spectrometer SPI on-board INTEGRAL for the first 26.5 months of mission operation (up to Jan. 2005). ...SPI-ACS works as a nearly omnidirectional gamma-ray burst detector above ~80 keV but lacks spatial and spectral information. In this catalogue, the properties derived from the 50 ms light curves (e.g., T90, $C_{\max}$, Cint, variability, $V/V_{\max}$) are given for each candidate burst in the sample. A strong excess of very short events with durations <0.25 s is found. This population is shown to be significantly different from the short- and long-duration burst sample by means of the intensity distribution and $V/V_{\max}$ test and is certainly connected with cosmic ray hits in the detector. A rate of 0.3 true gamma-ray bursts per day is observed.
Cognitive impairment in humans with Alzheimer's disease (AD) and in animal models of Aβ-pathology can be ameliorated by treatments with the nuclear receptor peroxisome proliferator-activated ...receptor-gamma (PPARγ) agonists, such as rosiglitazone (RSG). Previously, we demonstrated that in the Tg2576 animal model of AD, RSG treatment rescued cognitive deficits and reduced aberrant activity of granule neurons in the dentate gyrus (DG), an area critical for memory formation.
We used a combination of mass spectrometry, confocal imaging, electrophysiology and split-luciferase assay and in vitro phosphorylation and Ingenuity Pathway Analysis.
Using an unbiased, quantitative nano-LC-MS/MS screening, we searched for potential molecular targets of the RSG-dependent rescue of DG granule neurons. We found that S226 phosphorylation of fibroblast growth factor 14 (FGF14), an accessory protein of the voltage-gated Na+ (Nav) channels required for neuronal firing, was reduced in Tg2576 mice upon treatment with RSG. Using confocal microscopy, we confirmed that the Tg2576 condition decreased PanNav channels at the AIS of the DG, and that RSG treatment of Tg2576 mice reversed the reduction in PanNav channels. Analysis from previously published data sets identified correlative changes in action potential kinetics in RSG-treated T2576 compared to untreated and wildtype controls. In vitro phosphorylation and mass spectrometry confirmed that the multifunctional kinase GSK–3β, a downstream target of insulin signaling highly implicated in AD, phosphorylated FGF14 at S226. Assembly of the FGF14:Nav1.6 channel complex and functional regulation of Nav1.6-mediated currents by FGF14 was impaired by a phosphosilent S226A mutation. Bioinformatics pathway analysis of mass spectrometry and biochemistry data revealed a highly interconnected network encompassing PPARγ, FGF14, SCN8A (Nav 1.6), and the kinases GSK–3 β, casein kinase 2β, and ERK1/2.
These results identify FGF14 as a potential PPARγ-sensitive target controlling Aβ-induced dysfunctions of neuronal activity in the DG underlying memory loss in early AD.
•Phosphorylation of FGF14 at S226 in Tg2576 animals is reduced by rosiglitazone (RSG).•Tg2576 condition decreases PanNav channels at AIS, which is reversed by RSG.•GSK-3β phosphorylates FGF14 at S226.•Assembly of FGF14:Nav1.6 channel complex is reduced by a S226A mutation•Functional regulation of Nav1.6-mediated currents was impaired by a S226A mutation.
Access to data on quality metrics can better equip palliative care social workers to identify and address gaps in patient care, establish standards and accountability for social work functions on the ...interdisciplinary team, and evaluate the impact of interventions. The objective of this demonstration project was to create and pilot a data collection format in the patient electronic medical record (Epic) for documentation of social work metrics at each inpatient consultation, and to build corresponding pilot reports relevant to quality improvement goals. The successful implementation and initial pilot reports were reviewed for the feasibility of longer-term applications.
Soft-gamma-ray repeaters (SGRs) are galactic X-ray stars that emit numerous short-duration (about 0.1 s) bursts of hard X-rays during sporadic active periods. They are thought to be magnetars: ...strongly magnetized neutron stars with emissions powered by the dissipation of magnetic energy. Here we report the detection of a long (380 s) giant flare from SGR 1806-20, which was much more luminous than any previous transient event observed in our Galaxy. (In the first 0.2 s, the flare released as much energy as the Sun radiates in a quarter of a million years.) Its power can be explained by a catastrophic instability involving global crust failure and magnetic reconnection on a magnetar, with possible large-scale untwisting of magnetic field lines outside the star. From a great distance this event would appear to be a short-duration, hard-spectrum cosmic gamma-ray burst. At least a significant fraction of the mysterious short-duration gamma-ray bursts may therefore come from extragalactic magnetars.
The aryl hydrocarbon receptor (AhR), a regulator of xenobiotic toxicity, is a member of the eukaryotic Per-Arnt-Sim domain protein family of transcription factors. Recent evidence identified a novel ...AhR DNA recognition sequence called the nonconsensus xenobiotic response element (NC-XRE). AhR binding to the NC-XRE in response to activation by the canonical ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin resulted in concomitant recruitment of carbamoyl phosphate synthase 1 (CPS1) to the NC-XRE. Studies presented here demonstrate that CPS1 is a bona fide nuclear protein involved in homocitrullination (hcit), including a key lysine residue on histone H1 (H1K34hcit). H1K34hcit represents a hitherto unknown epigenetic mark implicated in enhanced gene expression of the peptidylarginine deiminase 2 gene, itself a chromatin-modifying protein. Collectively, our data suggest that AhR activation promotes CPS1 recruitment to DNA enhancer sites in the genome, resulting in a specific enzyme-independent post-translational modification of the linker histone H1 protein (H1K34hcit), pivotal in altering local chromatin structure and transcriptional activation.
Characterization of a Nonconsensus xenobiotic response element (NC-XRE), a novel AhR binding site.
AhR binding to the NC-XRE in response to TCDD results in the recruitment of CPS1 and concomitant homocitrullination of histone H1.
CPS1-mediated homocitrullination of histone H1 on lysine 34 is a novel epigenetic mark.
Homocitrulline (hcit) is a novel epigenetic histone mark involved in chromatin remodeling and transcriptional activation.
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