3,298 research outputs found
BAT AGN spectroscopic survey - XV: the high frequency radio cores of ultra-hard X-ray selected AGN
We have conducted 22 GHz radio imaging at 1 arcsec resolution of 100 low-redshift AGN selected at 14–195 keV by the Swift-BAT. We find a radio core detection fraction of 96 per cent, much higher than lower frequency radio surveys. Of the 96 radio-detected AGN, 55 have compact morphologies, 30 have morphologies consistent with nuclear star formation, and 11 have sub-kpc to kpc-scale jets. We find that the total radio power does not distinguish between nuclear star formation and jets as the origin of the radio emission. For 87 objects, we use optical spectroscopy to test whether AGN physical parameters are distinct between radio morphological types. We find that X-ray luminosities tend to be higher if the 22 GHz morphology is jet-like, but find no significant difference in other physical parameters. We find that the relationship between the X-ray and core radio luminosities is consistent with the L_R/L_X ∼ 10⁻⁵ of coronally active stars. We further find that the canonical fundamental planes of black hole activity systematically overpredict our radio luminosities, particularly for objects with star formation morphologies
AC susceptibility and V NMR study of MnVO
We report V zero-field NMR of manganese vanadate spinel of
MnVO, together with both ac and dc magnetization measurements. The
field and temperature dependence of ac susceptibilities show a
reentrant-spin-glass-like behavior below the ferrimagnetic(FEM) ordering
temperature. The zero-field NMR spectrum consists of multiple lines ranging
from 240 MHz to 320 MHz. Its temperature dependence reveals that the ground
state is given by the simultaneous formation of a long-range FEM order and a
short-range order component. We attribute the spin-glass-like anomalies to
freezing and fluctuations of the short-range ordered state caused by the
competition between spin and orbital ordering of the V site
Modulation of Mitochondrial Function and Autophagy Mediates Carnosine Neuroprotection Against Ischemic Brain Damage
Background and Purpose—Despite the rapidly increasing global burden of ischemic stroke, no therapeutic options for neuroprotection against stroke currently exist. Recent studies have shown that autophagy plays a key role in ischemic neuronal death, and treatments that target autophagy may represent a novel strategy in neuroprotection. We investigated whether autophagy is regulated by carnosine, an endogenous pleiotropic dipeptide that has robust neuroprotective activity against ischemic brain damage.
Methods—We examined the effect of carnosine on mitochondrial dysfunction and autophagic processes in rat focal ischemia and in neuronal cultures.
Results—Autophagic pathways such as reduction of phosphorylated mammalian target of rapamycin (mTOR)/p70S6K and the conversion of microtubule-associated protein 1 light chain 3 (LC3)-I to LC3-II were enhanced in the ischemic brain. However, treatment with carnosine significantly attenuated autophagic signaling in the ischemic brain, with improvement of brain mitochondrial function and mitophagy signaling. The protective effect of carnosine against autophagy was also confirmed in primary cortical neurons.
Conclusions—Taken together, our data suggest that the neuroprotective effect of carnosine is at least partially mediated by mitochondrial protection and attenuation of deleterious autophagic processes. Our findings shed new light on the mechanistic pathways that this exciting neuroprotective agent influences
Controlled growth and characterization of epitaxially-laterally-overgrown InGaN/GaN quantum heterostructures
Crystal material quality is fundamentally important for optoelectronic devices including laser diodes and light emitting diodes. To this end epitaxial lateral overgrowth (ELO) has proven to be a powerful technique for reducing dislocation density in GaN and its alloys [1,2]. Implementation and design of ELO process is, however, critical for obtaining high-quality material with high-efficiency quantum structures for light emitters [3]. ©2010 IEEE
Nemo: a computational tool for analyzing nematode locomotion
The nematode Caenorhabditis elegans responds to an impressive range of
chemical, mechanical and thermal stimuli and is extensively used to investigate
the molecular mechanisms that mediate chemosensation, mechanotransduction and
thermosensation. The main behavioral output of these responses is manifested as
alterations in animal locomotion. Monitoring and examination of such
alterations requires tools to capture and quantify features of nematode
movement. In this paper, we introduce Nemo (nematode movement), a
computationally efficient and robust two-dimensional object tracking algorithm
for automated detection and analysis of C. elegans locomotion. This algorithm
enables precise measurement and feature extraction of nematode movement
components. In addition, we develop a Graphical User Interface designed to
facilitate processing and interpretation of movement data. While, in this
study, we focus on the simple sinusoidal locomotion of C. elegans, our approach
can be readily adapted to handle complicated locomotory behaviour patterns by
including additional movement characteristics and parameters subject to
quantification. Our software tool offers the capacity to extract, analyze and
measure nematode locomotion features by processing simple video files. By
allowing precise and quantitative assessment of behavioral traits, this tool
will assist the genetic dissection and elucidation of the molecular mechanisms
underlying specific behavioral responses.Comment: 12 pages, 2 figures. accepted by BMC Neuroscience 2007, 8:8
Implications of the 125 GeV Higgs boson for scalar dark matter and for the CMSSM phenomenology
We study phenomenological implications of the ATLAS and CMS hint of a GeV Higgs boson for the singlet, and singlet plus doublet non-supersymmetric
dark matter models, and for the phenomenology of the CMSSM. We show that in
scalar dark matter models the vacuum stability bound on Higgs boson mass is
lower than in the standard model and the 125 GeV Higgs boson is consistent with
the models being valid up the GUT or Planck scale. We perform a detailed study
of the full CMSSM parameter space keeping the Higgs boson mass fixed to GeV, and study in detail the freeze-out processes that imply the observed
amount of dark matter. After imposing all phenomenological constraints except
for the muon we show that the CMSSM parameter space is divided
into well separated regions with distinctive but in general heavy sparticle
mass spectra. Imposing the constraint introduces severe tension
between the high SUSY scale and the experimental measurements -- only the
slepton co-annihilation region survives with potentially testable sparticle
masses at the LHC. In the latter case the spin-independent DM-nucleon
scattering cross section is predicted to be below detectable limit at the
XENON100 but might be of measurable magnitude in the general case of light dark
matter with large bino-higgsino mixing and unobservably large scalar masses.Comment: 17 pages, 7 figures. v3: same as published versio
On the possibility of a very light A^0 at low \tan\beta
The searches at LEP II for the processes e^+e^-\to h^0Z and e^+e^-\to h^0A^0
in the Minimal Supersymmetric Standard Model (MSSM) fail to exclude regions of
the m_h,m_A plane where \tan\beta <1, thus allowing a very light A^0 (m_A< 20
GeV). Such a parameter choice would predict a light H^\pm with m_{H^\pm}< m_W.
Although the potentially large branching ratio for H^\pm \to A^0 W^* would
ensure that H^\pm also escaped detection in direct searches at LEP II and the
Tevatron Run I, we show that this elusive parameter space is overwhelmingly
disfavoured by electroweak precision measurements.Comment: 11 pages, 2 figures, Revtex, references added, minor additions to
tex
Spin dynamics in molecular ring nanomagnets: Significant effect of acoustic phonons and magnetic anisotropies
The nuclear spin-lattice relaxation rate 1/T_1_ is calculated for magnetic
ring clusters by fully diagonalizing their microscopic spin Hamiltonians.
Whether the nearest-neighbor exchange interaction J is ferromagnetic or
antiferromagnetic, 1/T_1_ versus temperature T in ring nanomagnets may be
peaked at around k_B_T=|J| provided the lifetime broadening of discrete energy
levels is in proportion to T^3^. Experimental findings for ferromagnetic and
antiferromagnetic Cu^II^ rings are reproduced with crucial contributions of
magnetic anisotropies as well as acoustic phonons.Comment: 5 pages with 5 figures embedded, to be published in J. Phys. Soc.
Jpn. 75, No. 10 (2006
Comparative cerebroprotective potential of d- and l-carnosine following ischemic stroke in mice
l-carnosine is an attractive therapeutic agent for acute ischemic stroke based on its robust preclinical cerebroprotective properties and wide therapeutic time window. However, large doses are needed for efficacy because carnosine is rapidly degraded in serum by carnosinases. The need for large doses could be particularly problematic when translating to human studies, as humans have much higher levels of serum carnosinases. We hypothesized that d-carnosine, which is not a substrate for carnosinases, may have a better pharmacological profile and may be more efficacious at lower doses than l-carnosine. To test our hypothesis, we explored the comparative pharmacokinetics and neuroprotective properties of d- and L-carnosine in acute ischaemic stroke in mice. We initially investigated the pharmacokinetics of d- and L-carnosine in serum and brain after intravenous (IV) injection in mice. We then investigated the comparative efficacy of d- and l-carnosine in a mouse model of transient focal cerebral ischemia followed by in vitro testing against excitotoxicity and free radical generation using primary neuronal cultures. The pharmacokinetics of d- and l-carnosine were similar in serum and brain after IV injection in mice. Both d- and l-carnosine exhibited similar efficacy against mouse focal cerebral ischemia. In vitro studies in neurons showed protection against excitotoxicity and the accumulation of free radicals. d- and l-carnosine exhibit similar pharmacokinetics and have similar efficacy against experimental stroke in mice. Since humans have far higher levels of carnosinases, d-carnosine may have more favorable pharmacokinetics in future human studies
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