385 research outputs found
Magnetic Non-Potentiality of Solar Active Regions and Peak X-Ray Flux of the Associated Flares
Predicting the severity of the solar eruptive phenomena like flares and
Coronal Mass Ejections (CMEs) remains a great challenge despite concerted
efforts for several decades. The advent of high quality vector magnetograms
obtained from Hinode (SOT/SP) has increased the possibility of meeting this
challenge. In particular, the Spatially Averaged Signed Shear Angle (SASSA)
seems to be an unique parameter to quantify the non-potentiality of the active
regions. We demonstrate the usefulness of SASSA for predicting the flare
severity. For this purpose we present case studies of the evolution of magnetic
non-potentiality using 115 vector magnetograms of four active regions namely
ARs NOAA 10930, 10960, 10961 and 10963 during December 08-15, 2006, June 03-10,
2007, June 28-July 5, 2007 and July 10-17, 2007 respectively. The NOAA ARs
10930 and 10960 were very active and produced X and M class flares
respectively, along with many smaller X-ray flares. On the other hand, the NOAA
ARs 10961 and 10963 were relatively less active and produced only very small
(mostly A and B-class) flares. For this study we have used a large number of
high resolution vector magnetograms obtained from Hinode (SOT/SP). The analysis
shows that the peak X-ray flux of the most intense solar flare emanating from
the active regions depends on the magnitude of the SASSA at the time of the
flare. This finding of the existence of a lower limit of SASSA for a given
class of X-ray flare will be very useful for space weather forecasting. We have
also studied another non-potentiality parameter called mean weighted shear
angle (MWSA) of the vector magnetograms along with SASSA. We find that the MWSA
does not show such distinction as the SASSA for upper limits of GOES X-Ray flux
of solar flares, however both the quantities show similar trends during the
evolution of all active regions studied.Comment: 25 pages, 5 figures, accepted for publication in the Astrophysical
Journa
Pluto: A Monte Carlo Simulation Tool for Hadronic Physics
Pluto is a Monte-Carlo event generator designed for hadronic interactions
from Pion production threshold to intermediate energies of a few GeV per
nucleon, as well as for studies of heavy ion reactions. This report gives an
overview of the design of the package, the included models and the user
interface.Comment: XI International Workshop on Advanced Computing and Analysis
Techniques in Physics Research, April 23-27 2007, Amsterdam, the Netherland
Effective conductivity in association with model structure and spatial inhomogeneity of polymer/carbon black composites
The relationship between effective conductivity and cell structure of
polyethylene/carbon composites as well as between effective conductivity and
spatial distribution of carbon black are discussed. Following Yoshida's model
both structures can, in a way, be said to be intermediate between the well
known Maxwell-Garnett (MG) and Bruggeman (BR) limiting structures. Using TEM
photographs on composites with various carbon blacks we have observed that the
larger is Garncarek's inhomogeneity measure H of two-dimensional (2D)
representative distribution of the carbon black, the smaller is the effective
conductivity of the composite.Comment: 7 pages, 9 figure
Agave negatively regulates YAP and TAZ transcriptionally and post-translationally in osteosarcoma cell lines
Osteosarcoma (OS) is the most aggressive type of primary solid tumor that develops in bone. Whilst conventional chemotherapy can improve survival rates, the outcome for patients with metastatic or recurrent OS remains poor, so novel treatment agents and strategies are required. Research into new anticancer therapies has paved the way for the utilisation of natural compounds as they are typically less expensive and less toxic compared to conventional chemotherapeutics. Previously published works indicate that Agave exhibits anticancer properties, however potential molecular mechanisms remain poorly understood. In the present study, we investigate the anticancer effects of Agave leaf extract in OS cells suggesting that Agave inhibits cell viability, colony formation, and cell migration, and can induce apoptosis in OS cell lines. Moreover, Agave sensitizes OS cells to cisplatin (CDDP) and radiation, to overcome chemo- and radio-resistance. We demonstrate that Agave extract induces a marked decrease of Yes Associated Protein (YAP) and Tafazzin (TAZ) mRNA and protein expression upon treatment. We propose an initial mechanism of action in which Agave induces YAP/TAZ protein degradation, followed by a secondary event whereby Agave inhibits YAP/TAZ transcription, effectively deregulating the Nuclear Factor kappa B (NF-\u3baB) p65:p50 heterodimers responsible for transcriptional induction of YAP and TAZ
WW Domains of the Yes-Kinase-Associated-Protein (YAP) Transcriptional Regulator Behave as Independent Units with Different Binding Preferences for PPxY Motif-Containing Ligands
YAP is a WW domain-containing effector of the Hippo tumor suppressor pathway, and the object of heightened interest as a potent oncogene and stemness factor. YAP has two major isoforms that differ in the number of WW domains they harbor. Elucidating the degree of co-operation between these WW domains is important for a full understanding of the molecular function of YAP. We present here a detailed biophysical study of the structural stability and binding properties of the two YAP WW domains aimed at investigating the relationship between both domains in terms of structural stability and partner recognition. We have carried out a calorimetric study of the structural stability of the two YAP WW domains, both isolated and in a tandem configuration, and their interaction with a set of functionally relevant ligands derived from PTCH1 and LATS kinases. We find that the two YAP WW domains behave as independent units with different binding preferences, suggesting that the presence of the second WW domain might contribute to modulate target recognition between the two YAP isoforms. Analysis of structural models and phage-display studies indicate that electrostatic interactions play a critical role in binding specificity. Together, these results are relevant to understand of YAP function and open the door to the design of highly specific ligands of interest to delineate the functional role of each WW domain in YAP signaling.This work was supported by the Spanish Ministry of Education and Science [grant BIO2009-13261-CO2], the Spanish Ministry of Economy and Competitivity [grant BIO2012-39922-CO2] including FEDER (European Funds for Regional Development) funds and the Governement of Andalusia [grant CVI-5915]. Marius Sudol was supported by PA Breast Cancer Coalition Grants (#60707 and #920093) plus the Geisinger Clinic
Caveolin-3 Directly Interacts with the C-terminal Tail of β-Dystroglycan IDENTIFICATION OF A CENTRAL WW-LIKE DOMAIN WITHIN CAVEOLIN FAMILY MEMBERS
Caveolin-3, the most recently recognized member of the caveolin gene family, is muscle-specific and is found in both cardiac and skeletal muscle, as well as smooth muscle cells. Several independent lines of evidence indicate that caveolin-3 is localized to the sarcolemma, where it associates with the dystrophin-glycoprotein complex. However, it remains unknown which component of the dystrophin complex interacts with caveolin-3. Here, we demonstrate that caveolin-3 directly interacts with b-dystroglycan, an integral membrane component of the dystrophin complex. Our results indicate that caveolin-3 co-localizes, co-fractionates, and coimmunoprecipitates with a fusion protein containing the cytoplasmic tail of b-dystroglycan. In addition, we show that a novel WW-like domain within caveolin-3 directly recognizes the extreme C terminus of b-dystroglycan that contains a PPXY motif. As the WW domain of dystrophin recognizes the same site within b-dystroglycan, we also demonstrate that caveolin-3 can effectively block the interaction of dystrophin with b-dystroglycan. In this regard, interaction of caveolin-3 with b-dystroglycan may competitively regulate the recruitment of dystrophin to the sarcolemma. We discuss the possible implications of our findings in the context of Duchenne muscular dystrophy
Imaging Spectroscopy of a White-Light Solar Flare
We report observations of a white-light solar flare (SOL2010-06-12T00:57,
M2.0) observed by the Helioseismic Magnetic Imager (HMI) on the Solar Dynamics
Observatory (SDO) and the Reuven Ramaty High-Energy Solar Spectroscopic Imager
(RHESSI). The HMI data give us the first space-based high-resolution imaging
spectroscopy of a white-light flare, including continuum, Doppler, and magnetic
signatures for the photospheric FeI line at 6173.34{\AA} and its neighboring
continuum. In the impulsive phase of the flare, a bright white-light kernel
appears in each of the two magnetic footpoints. When the flare occurred, the
spectral coverage of the HMI filtergrams (six equidistant samples spanning
\pm172m{\AA} around nominal line center) encompassed the line core and the blue
continuum sufficiently far from the core to eliminate significant Doppler
crosstalk in the latter, which is otherwise a possibility for the extreme
conditions in a white-light flare. RHESSI obtained complete hard X-ray and
\Upsilon-ray spectra (this was the first \Upsilon-ray flare of Cycle 24). The
FeI line appears to be shifted to the blue during the flare but does not go
into emission; the contrast is nearly constant across the line profile. We did
not detect a seismic wave from this event. The HMI data suggest stepwise
changes of the line-of-sight magnetic field in the white-light footpoints.Comment: 14 pages, 7 figures, Accepted by Solar Physic
The HADES Tracking System
The tracking system of the dielectron spectrometer HADES at GSI Darmstadt is
formed out of 24 low-mass, trapezoidal multi-layer drift chambers providing in
total about 30 square meter of active area. Low multiple scattering in the in
total four planes of drift chambers before and after the magnetic field is
ensured by using helium-based gas mixtures and aluminum cathode and field
wires. First in-beam performance results are contrasted with expectations from
simulations. Emphasis is placed on the energy loss information, exploring its
relevance regarding track recognition.Comment: 6 pages, 4 figures, presented at the 10th Vienna Conference on
Instrumentation, Vienna, February 2004, to be published in NIM A (special
issue
From GHz to mHz: A Multiwavelength Study of the Acoustically Active 14 August 2004 M7.4 Solar Flare
We carried out an electromagnetic acoustic analysis of the solar flare of 14
August 2004 in active region AR10656 from the radio to the hard X-ray spectrum.
The flare was a GOES soft X-ray class M7.4 and produced a detectable sun quake,
confirming earlier inferences that relatively low-energy flares may be able to
generate sun quakes. We introduce the hypothesis that the seismicity of the
active region is closely related to the heights of coronal magnetic loops that
conduct high-energy particles from the flare. In the case of relatively short
magnetic loops, chromospheric evaporation populates the loop interior with
ionized gas relatively rapidly, expediting the scattering of remaining trapped
high-energy electrons into the magnetic loss cone and their rapid precipitation
into the chromosphere. This increases both the intensity and suddenness of the
chromospheric heating, satisfying the basic conditions for an acoustic emission
that penetrates into the solar interior.Comment: Accepted in Solar Physic
Amorphous alumina in the extended atmosphere of Alpha Orionis
In this paper we study the extended atmosphere of the late-type supergiant
Alpha Orionis. Infrared spectroscopy of red supergiants reveals strong
molecular bands, some of which do not originate in the photosphere but in a
cooler layer of molecular material above it. Lately, these layers have been
spatially resolved by near and mid-IR interferometry. In this paper, we try to
reconcile the IR interferometric and ISO-SWS spectroscopic results on Alpha
Orionis with a thorough modelling of the photosphere, molecular layer(s) and
dust shell. From the ISO and near-IR interferometric observations, we find that
Alpha Orionis has only a very low density water layer close above the
photosphere. However, mid-IR interferometric observations and a narrow-slit
N-band spectrum suggest much larger extra-photospheric opacity close to the
photosphere at those wavelengths, even when taking into account the detached
dust shell. We argue that this cannot be due to the water layer, and that
another source of mid-IR opacity must be present. We show that this opacity
source is probably neither molecular nor chromospheric. Rather, we present
amorphous alumina (Al2O3) as the best candidate and discuss this hypothesis in
the framework of dust-condensation scenarios.Comment: 15 pages, 18 figures, accepted for publication in A&
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