1,097 research outputs found
Catching NGC4051 in the low state with XMM-Newton
The Narrow Line Seyfert 1 galaxy NGC4051 shows unusual low flux states,
lasting several months, when the 2-10 keV X-ray spectrum becomes unusually hard
(photon index<1) while the spectrum at lower X-ray energies is dominated by a
large soft excess. A Chandra TOO of the low state has shown that the soft
excess and hard components are variable and well-correlated. The variability of
the hard component rules out an origin in a distant reflector. Here we present
results from a recent XMM-Newton TOO of NGC4051 in the low state, which allows
a much more detailed examination of the nature of the hard and soft spectral
components in the low state. We demonstrate that the spectral shape in the low
state is consistent with the extrapolation of the spectral pivoting observed at
higher fluxes. The XMM-Newton data also reveals the warm absorbing gas in
emission, as the drop in the primary continuum flux unmasks prominent emission
lines from a range of ion species.Comment: 4 pages, 4 figures. Proc. of the meeting: "The Restless High-Energy
Universe" (Amsterdam, The Netherlands), E.P.J. van den Heuvel, J.J.M. in 't
Zand, and R.A.M.J. Wijers Ed
Chemostratigraphy of Neoproterozoic carbonates: implications for 'blind dating'
The delta C-13(carb) and Sr-87/Sr-86 secular variations in Neoproteozoic seawater have been used for the purpose of 'isotope stratigraphy' but there are a number of problems that can preclude its routine use. In particular, it cannot be used with confidence for 'blind dating'. The compilation of isotopic data on carbonate rocks reveals a high level of inconsistency between various carbon isotope age curves constructed for Neoproteozoic seawater, caused by a relatively high frequency of both global and local delta C-13(carb) fluctuations combined with few reliable age determinations. Further complication is caused by the unresolved problem as to whether two or four glaciations, and associated negative delta C-13(carb) excursions, can be reliably documented. Carbon isotope stratigraphy cannot be used alone for geological correlation and 'blind dating'. Strontium isotope stratigraphy is a more reliable and precise tool for stratigraphic correlations and indirect age determinations. Combining strontium and carbon isotope stratigraphy, several discrete ages within the 590-544 Myr interval, and two age-groups at 660-610 and 740-690 Myr can be resolved
Detecting new microRNAs in human osteoarthritic chondrocytes identifies miR-3085 as a human, chondrocyte-selective, microRNA
Objective: To use deep sequencing to identify novel microRNAs in human osteoarthritic cartilage which have a functional role in chondrocyte phenotype or function. Design: A small RNA library was prepared from human osteoarthritic primary chondrocytes using in-house adaptors and analysed by Illumina sequencing. Novel candidate microRNAs were validated by northern blot and qRT-PCR. Expression was measured in cartilage models. Targets of novel candidates were identified by microarray and computational analysis, validated using 3’-UTR-luciferase reporter plasmids. Protein levels were assessed by western blot and functional analysis by cell adhesion. Results: We identified 990 known microRNAs and 1621 potential novel microRNAs in human osteoarthritic chondrocytes, 60 of the latter were expressed in all samples assayed. MicroRNA-140-3p was the most highly expressed microRNA in osteoarthritic cartilage. Sixteen novel candidate microRNAs were analysed further, of which 6 remained after northern blot analysis. Three novel microRNAs were regulated across models of chondrogenesis, chondrocyte differentiation or cartilage injury. One sequence (novel #11), annotated in rodents as microRNA-3085-3p, was preferentially expressed in cartilage, dependent on chondrocyte differentiation and, in man, is located in an intron of the cartilage-expressed gene CRTAC-1. This microRNA was shown to target the ITGA5 gene directly (which encodes integrin alpha5) and inhibited adhesion to fibronectin (dependent on alpha5beta1 integrin). Conclusion: Deep sequencing has uncovered many potential microRNA candidates expressed in human cartilage. At least three of these show potential functional interest in cartilage homeostasis and osteoarthritis. Particularly, novel #11 (microRNA-3085-3p) which has been identified for the first time in man
The effect of culture preservation techniques on patulin and citrinin production by Penicillium expansum Link
Aims: To study the influence of culture preservation methods and culture conditions on the
production of the mycotoxins patulin and citrinin by Penicillium expansum.
Methods and results: Ten strains of Penicillium expansum were preserved using subculture
and maintenance at 4 ºC, mineral oil, drying on silica gel and freeze-drying. Patulin and
citrinin production was assessed on yeast extract sucrose agar (YES) and grape juice agar (GJ),
using TLC before and after 0.5, 2–3, 6 and 12 months preservation. Citrinin was detected in all
cultures for all preservation techniques on YES. The patulin profiles obtained differed with
strain and culture media used.
Conclusions: Citrinin production seems to be a stable character for the tested strains. There is
a tendency for patulin detection with time apparently more consistent for silica gel storage and
freeze-drying, especially when the strains are grown on GJ.
Significance and Impact of the Study: Variability in the profiles of the mycotoxins tested
seems to be more strain-specific than dependent on the preservation technique used
Impurity-induced transition and impurity-enhanced thermopower in the thermoelectric oxide NaCo_{2-x}Cu_x$O_4
Various physical quantities are measured and analysed for the Cu-substituted
thermoelectric oxide NaCo_{2-x}Cu_xO_4. As was previously known, the
substituted Cu enhances the thermoelectric power, while it does not increase
the resistivity significantly. The susceptibility and the electron
specific-heat are substantially decreased with increasing x, which implies that
the substituted Cu decreases the effective-mass enhancement. Through a
quantitative comparison with the heavy fermion compounds and the valence
fluctuation systems, we have found that the Cu substitution effectively
increases the coupling between the conduction electron and the magnetic
fluctuation. The Cu substitution induces a phase transition at 22 K that is
very similar to a spin-density-wave transition.Comment: 8 pages, 7 figures, submitted to Phys. Rev.
Loss of the RNA polymerase III repressor MAF1 confers obesity resistance.
MAF1 is a global repressor of RNA polymerase III transcription that regulates the expression of highly abundant noncoding RNAs in response to nutrient availability and cellular stress. Thus, MAF1 function is thought to be important for metabolic economy. Here we show that a whole-body knockout of Maf1 in mice confers resistance to diet-induced obesity and nonalcoholic fatty liver disease by reducing food intake and increasing metabolic inefficiency. Energy expenditure in Maf1(-/-) mice is increased by several mechanisms. Precursor tRNA synthesis was increased in multiple tissues without significant effects on mature tRNA levels, implying increased turnover in a futile tRNA cycle. Elevated futile cycling of hepatic lipids was also observed. Metabolite profiling of the liver and skeletal muscle revealed elevated levels of many amino acids and spermidine, which links the induction of autophagy in Maf1(-/-) mice with their extended life span. The increase in spermidine was accompanied by reduced levels of nicotinamide N-methyltransferase, which promotes polyamine synthesis, enables nicotinamide salvage to regenerate NAD(+), and is associated with obesity resistance. Consistent with this, NAD(+) levels were increased in muscle. The importance of MAF1 for metabolic economy reveals the potential for MAF1 modulators to protect against obesity and its harmful consequences
Relativistic wave equations for interacting massive particles with arbitrary half-intreger spins
New formulation of relativistic wave equations (RWE) for massive particles
with arbitrary half-integer spins s interacting with external electromagnetic
fields are proposed. They are based on wave functions which are irreducible
tensors of rank n=s-\frac12$) antisymmetric w.r.t. n pairs of indices,
whose components are bispinors. The form of RWE is straightforward and free of
inconsistencies associated with the other approaches to equations describing
interacting higher spin particles
Radio detection of cosmic ray air showers with LOPES
In the last few years, radio detection of cosmic ray air showers has
experienced a true renaissance, becoming manifest in a number of new
experiments and simulation efforts. In particular, the LOPES project has
successfully implemented modern interferometric methods to measure the radio
emission from extensive air showers. LOPES has confirmed that the emission is
coherent and of geomagnetic origin, as expected by the geosynchrotron
mechanism, and has demonstrated that a large scale application of the radio
technique has great potential to complement current measurements of ultra-high
energy cosmic rays. We describe the current status, most recent results and
open questions regarding radio detection of cosmic rays and give an overview of
ongoing research and development for an application of the radio technique in
the framework of the Pierre Auger Observatory.Comment: 8 pages; Proceedings of the CRIS2006 conference, Catania, Italy; to
be published in Nuclear Physics B, Proceedings Supplement
Immersed boundary-finite element model of fluid-structure interaction in the aortic root
It has long been recognized that aortic root elasticity helps to ensure
efficient aortic valve closure, but our understanding of the functional
importance of the elasticity and geometry of the aortic root continues to
evolve as increasingly detailed in vivo imaging data become available. Herein,
we describe fluid-structure interaction models of the aortic root, including
the aortic valve leaflets, the sinuses of Valsalva, the aortic annulus, and the
sinotubular junction, that employ a version of Peskin's immersed boundary (IB)
method with a finite element (FE) description of the structural elasticity. We
develop both an idealized model of the root with three-fold symmetry of the
aortic sinuses and valve leaflets, and a more realistic model that accounts for
the differences in the sizes of the left, right, and noncoronary sinuses and
corresponding valve cusps. As in earlier work, we use fiber-based models of the
valve leaflets, but this study extends earlier IB models of the aortic root by
employing incompressible hyperelastic models of the mechanics of the sinuses
and ascending aorta using a constitutive law fit to experimental data from
human aortic root tissue. In vivo pressure loading is accounted for by a
backwards displacement method that determines the unloaded configurations of
the root models. Our models yield realistic cardiac output at physiological
pressures, with low transvalvular pressure differences during forward flow,
minimal regurgitation during valve closure, and realistic pressure loads when
the valve is closed during diastole. Further, results from high-resolution
computations demonstrate that IB models of the aortic valve are able to produce
essentially grid-converged dynamics at practical grid spacings for the
high-Reynolds number flows of the aortic root
Air Shower Measurements with the LOPES Radio Antenna Array
LOPES is set up at the location of the KASCADE-Grande extensive air shower
experiment in Karlsruhe, Germany and aims to measure and investigate radio
pulses from Extensive Air Showers. Since radio waves suffer very little
attenuation, radio measurements allow the detection of very distant or highly
inclined showers. These waves can be recorded day and night, and provide a
bolometric measure of the leptonic shower component. LOPES is designed as a
digital radio interferometer using high bandwidths and fast data processing and
profits from the reconstructed air shower observables of KASCADE-Grande. The
LOPES antennas are absolutely amplitude calibrated allowing to reconstruct the
electric field strength which can be compared with predictions from detailed
Monte Carlo simulations. We report about the analysis of correlations present
in the radio signals measured by the LOPES 30 antenna array. Additionally,
LOPES operates antennas of a different type (LOPES-STAR) which are optimized
for an application at the Pierre Auger Observatory. Status, recent results of
the data analysis and further perspectives of LOPES and the possible large
scale application of this new detection technique are discussed.Comment: 8 pages, 10 figures, Contribution to the Arena 2008 conference, Rome,
June 200
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