2,908 research outputs found
Metabolic regulation by p53 family members
The function of p53 is best understood in response to genotoxic stress, but increasing evidence suggests that p53 also plays a key role in the regulation of metabolic homeostasis. p53 and its family members directly influence various metabolic pathways, enabling cells to respond to metabolic stress. These functions are likely to be important for restraining the development of cancer but could also have a profound effect on the development of metabolic diseases, including diabetes. A better understanding of the metabolic functions of p53 family members may aid in the identification of therapeutic targets and reveal novel uses for p53-modulating drugs
Optical Polarization and Spectral Variability in the M87 Jet
During the last decade, M87's jet has been the site of an extraordinary
variability event, with one knot (HST-1) increasing by over a factor 100 in
brightness. Variability was also seen on timescales of months in the nuclear
flux. Here we discuss the optical-UV polarization and spectral variability of
these components, which show vastly different behavior. HST-1 shows a highly
significant correlation between flux and polarization, with P increasing from
at minimum to >40% at maximum, while the orientation of its electric
vector stayed constant. HST-1's optical-UV spectrum is very hard
(, ), and displays "hard lags"
during epochs 2004.9-2005.5, including the peak of the flare, with soft lags at
later epochs. We interpret the behavior of HST-1 as enhanced particle
acceleration in a shock, with cooling from both particle aging and the
relaxation of the compression. We set 2 upper limits of
parsecs and 1.02 on the size and advance speed of the flaring region. The
slight deviation of the electric vector orientation from the jet PA, makes it
likely that on smaller scales the flaring region has either a double or twisted
structure. By contrast, the nucleus displays much more rapid variability, with
a highly variable electric vector orientation and 'looping' in the
plane. The nucleus has a much steeper spectrum () but
does not show UV-optical spectral variability. Its behavior can be interpreted
as either a helical distortion to a steady jet or a shock propagating through a
helical jet.Comment: 14 pages, 7 figures, ApJ, in pres
A two-dimensional risk model with proportional reinsurance
In this paper we consider an extension of the two-dimensional risk model introduced in Avram, Palmowski and Pistorius (2008a). To this end, we assume that there are two insurers. The first insurer is subject to claims arising from two independent compound Poisson processes. The second insurer, which can be viewed as a different line of business of the same insurer or as a reinsurer, covers a proportion of the claims arising from one of these two compound Poisson processes. We derive the Laplace transform of the time until ruin of at least one insurer when the claim sizes follow a general distribution. The surplus level of the first insurer when the second insurer is ruined first is discussed at the end in connection with some open problems. © Applied Probability Trust 2011.postprin
A novel method for measuring the extragalactic background light: Fermi application to the lobes of Fornax A
We describe a new method for measuring the extragalactic background light
(EBL) through the detection of -ray inverse Compton (IC) emission due
to scattering of the EBL photons off relativistic electrons in the lobes of
radio galaxies. Our method has no free physical parameters and is a powerful
tool when the lobes are characterized by a high energy sharp break or cutoff in
their electron energy distribution (EED). We show that such a feature will
produce a high energy IC `imprint' of the EBL spectrum in which the radio lobes
are embedded, and show how this imprint can be used to derive the EBL. We apply
our method to the bright nearby radio galaxy Fornax A, for which we
demonstrate, using WMAP and EGRET observations, that the EED of its lobes is
characterized by a conveniently located cutoff, bringing the IC EBL emission
into the {\sl Fermi} energy range. We show that {\sl Fermi} will set upper
limits to the optical EBL and measure the more elusive infrared EBL.Comment: ApJL, accepte
Perturbative QCD Fragmentation Functions for and Production
The dominant production mechanism for bound states in high
energy processes is the production of a high energy or quark,
followed by its fragmentation into the state. We calculate the
fragmentation functions for the production of the S-wave states and
to leading order in the QCD coupling constant. The fragmentation
probabilities for and
are approximately and , while those
for and are smaller by almost two
orders of magnitude.Comment: Latex, 12 pages, 3 figures available upon request, NUHEP-TH-93-
QCD Radiative Corrections to the Leptonic Decay Rate of the B_c Meson
The QCD radiative corrections to the leptonic decay rate of the meson
are calculated using the formalism of nonrelativistic QCD (NRQCD) to separate
short-distance and long-distance effects. The decay constant is factored
into a sum of NRQCD matrix elements each multiplied by a short-distance
coefficient. The short-distance coefficient for the leading matrix element is
calculated to order by matching a perturbative calculation in full
QCD with the corresponding perturbative calculation in NRQCD. This
short-distance correction decreases the leptonic decay rate by approximately
.Comment: Changed Eq. 2 to read 1/(8 \pi), put in a missing i M_{B_c} in Eq.
18, and put in a normalisation factor of 2 M_{B_c} in Eq. 19
Experiments in dynamic control of autonomous marine vehicles using acoustic modems
Marine robots are an increasingly attractive means for observing and monitoring in the ocean, but underwater acoustic communication (“acomms”) remains a major challenge, especially for real-time control. Packet loss occurs widely, bit rates are low, and there are significant delays. We consider here strategies for feedback control with acomms links in either the sensor-controller channel, or the controller-actuator channel. On the controller-actuator side we implement sparse packetized predictive control (S-PPC), which simultaneously addresses packet-loss and the data rate limit. For the sensor-controller channel we study a modified information filter (MIF) in a Linear Quadratic Gaussian (LQG) control scheme. Field experiments were carried out with both approaches, regulating crosstrack error in a robotic kayak using acomms. Outcomes with both the S-PPC and MIF LQG confirm that good performance is achievable.United States. Office of Naval Research (Grant N00014-09-1-0700)National Science Foundation (U.S.) (Contract CNS-1212597)Finmeccanic
Development of an inducible mouse model of iRFP713 to track recombinase activity and tumour development in vivo
While the use of bioluminescent proteins for molecular imaging is a powerful technology to further our understanding of complex processes, fluorescent labeling with visible light fluorescent proteins such as GFP and RFP suffers from poor tissue penetration and high background autofluorescence. To overcome these limitations, we generated an inducible knock-in mouse model of iRFP713. This model was used to assess Cre activity in a Rosa Cre-ER background and quantify Cre activity upon different tamoxifen treatments in several organs. We also show that iRFP can be readily detected in 3D organoid cultures, FACS analysis and in vivo tumour models. Taken together we demonstrate that iRFP713 is a progressive step in in vivo imaging and analysis that widens the optical imaging window to the near-infrared spectrum, thereby allowing deeper tissue penetration, quicker image acquisition without the need to inject substrates and a better signal to background ratio in genetically engineered mouse models (GEMMs)
Rostral medial prefrontal dysfunctions and consummatory pleasure in schizophrenia: A meta-analysis of functional imaging studies
A large number of imaging studies have examined the neural correlates of consummatory pleasure and anticipatory pleasure in schizophrenia, but the brain regions where schizophrenia patients consistently demonstrate dysfunctions remain unclear. We performed a series of meta-analyses on imaging studies to delineate the regions associated with consummatory and anticipatory pleasure dysfunctions in schizophrenia. Nineteen functional magnetic resonance imaging or positron emission tomography studies using whole brain analysis were identified through a literature search (PubMed and EBSCO; januaiy 1990-February 2014). Activation likelihood estimation was performed using the GingerALE software. The clusters identified were obtained after controlling for the false discovery rate at p<0.05 and applying a minimum cluster size of 200 mm(3). It was found that schizophrenia patients exhibited decreased activation mainly in the rostral medial prefrontal cortex (rmPFC), the right parahippocampus/ amygala, and other limbic regions (e.g., the subgenual anterior cingulate cortex, the putamen, and the medial globus pallidus) when consummating pleasure. Task instructions (feeling vs stimuli) were differentially related to medial prefrontal dysfunction in schizophrenia. When patients anticipated pleasure, reduced activation in the left putamen was observed, despite the limited number of studies. Our findings suggest that the medial prefrontal cortex and limbic regions may play an important role in neural dysfunction underlying deficits in consummatory pleasure in schizophrenia. (C) 2015 Elsevier Ireland Ltd. All rights reserved
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