227 research outputs found
X-ray Flashes or soft Gamma-ray Bursts? The case of the likely distant XRF 040912
In this work, we present a multi-wavelength study of XRF 040912, aimed at
measuring its distance scale and the intrinsic burst properties. We performed a
detailed spectral and temporal analysis of both the prompt and the afterglow
emission and we estimated the distance scale of the likely host galaxy. We then
used the currently available sample of XRFs with known distance to discuss the
connection between XRFs and classical Gamma-ray Bursts (GRBs). We found that
the prompt emission properties unambiguously identify this burst as an XRF,
with an observed peak energy of E_p=17+/-13 keV and a burst fluence ratio
S(2-30keV)/S(30-400keV)>1. A non-fading optical source with R~24 mag and with
an apparently extended morphology is spatially consistent with the X-ray
afterglow, likely the host galaxy. XRF 040912 is a very dark burst since no
afterglow optical counterpart is detected down to R>25 mag (3 sigma limiting
magnitude) at 13.6 hours after the burst. The host galaxy spectrum detected
from 3800A to 10000A, shows a single emission line at 9552A. The lack of any
other strong emission lines blue-ward of the detected one and the absence of
the Ly alpha cut-off down to 3800A are consistent with the hypothesis of the
[OII] line at redshift z=1.563+/-0.001. The intrinsic spectral properties rank
this XRF among the soft GRBs in the E_peak-E_iso diagram. Similar results were
obtained for most XRFs at known redshift. Only XRF 060218 and XRF 020903
represent a good example of instrinsic XRF(i-XRF) and are possibly associated
with a different progenitor population. This scenario may calls for a new
definition of XRFs.Comment: 10 pages, 7 figures, accepted for publication in Astronomy &
Astrophysic
Apparent Alkyl Transfer and Phenazine Formation via an Aryne Intermediate
Treatment of chlorotriaryl derivatives 3a and 3d or fluorotriaryl derivatives 3b and 3e with potassium diisopropylamide afforded alkyl-shifted phenazine derivatives 5a/5b, rather than the expected 9-membered triazaorthocyclophane 2a. The phenazine derivatives were isolated in 78–98% yield depending on the halogen and alkyl group present. In the absence of the halogen (chloro or fluoro), the apparent alkyl shift proceeds more slowly and cannot proceed via the intermediacy of the aryne intermediate. Mechanistic possibilities include intramolecular nucleophilic attack on an aryne intermediate leading to a zwitterionic intermediate and alkyl transfer via a 5-endo-tet process, or via a Smiles rearrangement
Angiomatoid fibrous histiocytoma: a series of seven cases including genetically confirmed aggressive cases and a literature review
Limbic Justice—Amygdala Involvement in Immediate Rejection in the Ultimatum Game
Imaging studies have revealed a putative neural account of emotional bias in decision making. However, it has been difficult in previous studies to identify the causal role of the different sub-regions involved in decision making. The Ultimatum Game (UG) is a game to study the punishment of norm-violating behavior. In a previous influential paper on UG it was suggested that frontal insular cortex has a pivotal role in the rejection response. This view has not been reconciled with a vast literature that attributes a crucial role in emotional decision making to a subcortical structure (i.e., amygdala). In this study we propose an anatomy-informed model that may join these views. We also present a design that detects the functional anatomical response to unfair proposals in a subcortical network that mediates rapid reactive responses. We used a functional MRI paradigm to study the early components of decision making and challenged our paradigm with the introduction of a pharmacological intervention to perturb the elicited behavioral and neural response. Benzodiazepine treatment decreased the rejection rate (from 37.6% to 19.0%) concomitantly with a diminished amygdala response to unfair proposals, and this in spite of an unchanged feeling of unfairness and unchanged insular response. In the control group, rejection was directly linked to an increase in amygdala activity. These results allow a functional anatomical detection of the early neural components of rejection associated with the initial reactive emotional response. Thus, the act of immediate rejection seems to be mediated by the limbic system and is not solely driven by cortical processes, as previously suggested. Our results also prompt an ethical discussion as we demonstrated that a commonly used drug influences core functions in the human brain that underlie individual autonomy and economic decision making
Involvement of Girdin in the Determination of Cell Polarity during Cell Migration
Cell migration is a critical cellular process that determines embryonic development and the progression of human diseases. Therefore, cell- or context-specific mechanisms by which multiple promigratory proteins differentially regulate cell migration must be analyzed in detail. Girdin (girders of actin filaments) (also termed GIV, Gα-interacting vesicle associated protein) is an actin-binding protein that regulates migration of various cells such as endothelial cells, smooth muscle cells, neuroblasts, and cancer cells. Here we show that Girdin regulates the establishment of cell polarity, the deregulation of which may result in the disruption of directional cell migration. We found that Girdin interacts with Par-3, a scaffolding protein that is a component of the Par protein complex that has an established role in determining cell polarity. RNA interference-mediated depletion of Girdin leads to impaired polarization of fibroblasts and mammary epithelial cells in a way similar to that observed in Par-3-depleted cells. Accordingly, the expression of Par-3 mutants unable to interact with Girdin abrogates cell polarization in fibroblasts. Further biochemical analysis suggests that Girdin is present in the Par protein complex that includes Par-3, Par-6, and atypical protein kinase C. Considering previous reports showing the role of Girdin in the directional migration of neuroblasts, network formation of endothelial cells, and cancer invasion, these data may provide a specific mechanism by which Girdin regulates cell movement in biological contexts that require directional cell movement
Mutation in Archain 1, a Subunit of COPI Coatomer Complex, Causes Diluted Coat Color and Purkinje Cell Degeneration
Intracellular trafficking is critical for delivering molecules and organelles to their proper destinations to carry out normal cellular functions. Disruption of intracellular trafficking has been implicated in the pathogenesis of various neurodegenerative disorders. In addition, a number of genes involved in vesicle/organelle trafficking are also essential for pigmentation, and loss of those genes is often associated with mouse coat-color dilution and human hypopigmentary disorders. Hence, we postulated that screening for mouse mutants with both neurological defects and coat-color dilution will help identify additional factors associated with intracellular trafficking in neuronal cells. In this study, we characterized a mouse mutant with a unique N-ethyl-N-nitrosourea (ENU)–induced mutation, named nur17. nur17 mutant mice exhibit both coat-color dilution and ataxia due to Purkinje cell degeneration in the cerebellum. By positional cloning, we identified that the nur17 mouse carries a T-to-C missense mutation in archain 1 (Arcn1) gene which encodes the δ subunit of the coat protein I (COPI) complex required for intracellular trafficking. Consistent with this function, we found that intracellular trafficking is disrupted in nur17 melanocytes. Moreover, the nur17 mutation leads to common characteristics of neurodegenerative disorders such as abnormal protein accumulation, ER stress, and neurofibrillary tangles. Our study documents for the first time the physiological consequences of the impairment of the ARCN1 function in the whole animal and demonstrates a direct association between ARCN1 and neurodegeneration
Association between neck and shoulder pain, back pain, low back pain and body composition parameters among the Japanese general population
Preparation of a chelating sorbent based on pyridylethylated polyethylenimine for recovering transition metal ions
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