1,115 research outputs found
Direct observation of molecular cooperativity near the glass transition
We describe direct observations of molecular cooperativity near the glass
transition in poly-vinyl-acetate (PVAc), through nanometer-scale probing of
dielectric fluctuations. Molecular clusters switched spontaneously between two
to four distinct configurations, producing complex random-telegraph-signals
(RTS). Analysis of the RTS and their power spectra shows that individual
clusters exhibit both transient dynamical heterogeneity and non-exponential
kinetics.Comment: 14 pages pdf, need Acrobat Reade
VLBI imaging of a flare in the Crab Nebula: More than just a spot
We report on very long baseline interferometry (VLBI) observations of the
radio emission from the inner region of the Crab Nebula, made at 1.6 GHz and 5
GHz after a recent high-energy flare in this object. The 5 GHz data have
provided only upper limits of 0.4 milli-Jansky (mJy) on the flux density of the
pulsar and 0.4 mJy/beam on the brightness of the putative flaring region. The
1.6 GHz data have enabled imaging the inner regions of the nebula on scales of
up to ~40". The emission from the inner "wisps" is detected for the first time
with VLBI observations. A likely radio counterpart (designated "C1") of the
putative flaring region observed with Chandra and HST is detected in the radio
image, with an estimated flux density of \,mJy and a size of
0.2-0.6". Another compact feature ("C2") is also detected in the VLBI image
closer to the pulsar, with an estimated flux density of 0.4 +- 0.2 mJy and a
size smaller than 0{\farcs}2. Combined with the broad-band SED of the flare,
the radio properties of C1 yield a lower limit of ~0.5 mG for the magnetic
field and a total minimum energy of 1.2*10^41 ergs vested in the flare
(corresponding to using about 0.2% of the pulsar spin-down power). The 1.6 GHz
observations provide upper limits for the brightness (0.2 mJy/beam) and total
flux density (0.4 mJy) of the optical Knot 1 located at 0.6" from the pulsar.
The absolute position of the Crab pulsar is determined, and an estimate of the
pulsar proper motion is obtained.Comment: Astronomy & Astrophysics; accepted; 10 pages, 8 figure
The Role of the SMA and the Contingent Negative Variation in Interval Timing
Over the last decades, many studies have been published that have been interpreted in favour of the view that the Contingent Negative Variation (CNV) reflects the subjective experience of time. However, a number of papers have recently appeared that question this direct link, but at the same time new studies using new methodologies have solidified the original claims. In this symposium, both views will be presented. Frank Vidal and Laurence Casini will present the original literature and link the EEG findings to more recent fMRI data. Martin Wiener will discuss new data that demonstrates that supplementary motor area (SMA) activity reflects both the experience of the current trial and the perceived difference between the current and previous trials. Trevor Penney and Kwun Kei Ng will discuss the extend to which duration bisection tasks support and question the view that the CNV reflects the accumulator. Finally, Hedderik van Rijn and Tadeusz Kononowicz will present data that question the prominent role of the CNV in the subjective temporal experience. The titles and abstracts of the four talks are given below
Thermodynamic Concepts in the Study of Microbial Populations: Age Structure in Plasmodium falciparum Infected Red Blood Cells
Variability is a hallmark of microbial systems. On the one hand, microbes are subject to environmental heterogeneity and undergo changeable conditions in their immediate surroundings. On the other hand, microbial populations exhibit high cellular diversity. The relation between microbial diversity and variability of population dynamics is difficult to assess. This connection can be quantitatively studied from a perspective that combines in silico models and thermodynamic methods and interpretations. The infection process of Plasmodium falciparum parasitizing human red blood cells under laboratory cultivation conditions is used to illustrate the potential of Individual-based models in the context of predictive microbiology and parasitology. Experimental data from several in vitro cultures are compared to the outcome of an individual-based model and analysed from a thermodynamic perspective. This approach allows distinguishing between intrinsic and external constraints that give rise to the diversity in the infection forms, and it provides a criterion to quantitatively define transient and stationary regimes in the culture. Increasing the ability of models to discriminate between different states of microbial populations enhances their predictive capability which finally leads to a better the control over culture systems. The strategy here presented is of general application and it can substantially improve modelling of other types of microbial communities
Spectral and morphological analysis of the remnant of Supernova 1987A with ALMA & ATCA
We present a comprehensive spectral and morphological analysis of the remnant
of Supernova (SN) 1987A with the Australia Telescope Compact Array (ATCA) and
the Atacama Large Millimeter/submillimeter Array (ALMA). The non-thermal and
thermal components of the radio emission are investigated in images from 94 to
672 GHz ( 3.2 mm to 450 m), with the assistance of a
high-resolution 44 GHz synchrotron template from the ATCA, and a dust template
from ALMA observations at 672 GHz. An analysis of the emission distribution
over the equatorial ring in images from 44 to 345 GHz highlights a gradual
decrease of the east-to-west asymmetry ratio with frequency. We attribute this
to the shorter synchrotron lifetime at high frequencies. Across the transition
from radio to far infrared, both the synchrotron/dust-subtracted images and the
spectral energy distribution (SED) suggest additional emission beside the main
synchrotron component () and the thermal component
originating from dust grains at K. This excess could be due to
free-free flux or emission from grains of colder dust. However, a second
flat-spectrum synchrotron component appears to better fit the SED, implying
that the emission could be attributed to a pulsar wind nebula (PWN). The
residual emission is mainly localised west of the SN site, as the spectral
analysis yields across the western regions,
with around the central region. If there is a PWN in the remnant
interior, these data suggest that the pulsar may be offset westward from the SN
position.Comment: ApJ accepted. 21 pages, emulateapj. References update
Dust Production and Particle Acceleration in Supernova 1987A Revealed with ALMA
Supernova (SN) explosions are crucial engines driving the evolution of
galaxies by shock heating gas, increasing the metallicity, creating dust, and
accelerating energetic particles. In 2012 we used the Atacama Large
Millimeter/Submillimeter Array to observe SN 1987A, one of the best-observed
supernovae since the invention of the telescope. We present spatially resolved
images at 450um, 870um, 1.4mm, and 2.8mm, an important transition wavelength
range. Longer wavelength emission is dominated by synchrotron radiation from
shock-accelerated particles, shorter wavelengths by emission from the largest
mass of dust measured in a supernova remnant (>0.2Msun). For the first time we
show unambiguously that this dust has formed in the inner ejecta (the cold
remnants of the exploded star's core). The dust emission is concentrated to the
center of the remnant, so the dust has not yet been affected by the shocks. If
a significant fraction survives, and if SN 1987A is typical, supernovae are
important cosmological dust producers.Comment: ApJL accepte
1,3-Dihydroxy-2-methoxymethyl-9,10-anthraquinone from Rennellia elliptica Korth.
The title compound, C16H12O5, common name: lucidin ω-methyl ether, exists as a planar molecule (r.m.s. deviation = 0.04 Å). Within the molecule, the 1-hydroxy group forms a hydrogen bond to the adjacent carbonyl O atom, and the 3-hydroxy group forms a hydrogen bond to the adjacent methoxy O atom. The methoxy O atom is disordered over two positions of equal occupancy
Heredity of type 2 diabetes confers increased susceptibility to oxidative stress and inflammation.
INTRODUCTION AND OBJECTIVE: Heredity of type 2 diabetes mellitus (T2DM) is associated with greater risk for developing T2DM. Thus, individuals who have a first-degree relative with T2DM (FDRT) provide a natural model to study factors of susceptibility towards development of T2DM, which are poorly understood. Emerging key players in T2DM pathophysiology such as adverse oxidative stress and inflammatory responses could be among possible mechanisms that predispose FDRTs to develop T2DM. Here, we aimed to examine the role of oxidative stress and inflammatory responses as mediators of this excess risk by studying dynamic postprandial responses in FDRTs. RESEARCH DESIGN AND METHODS: In this open-label case-control study, we recruited normoglycemic men with (n=9) or without (n=9) a family history of T2DM. We assessed plasma glucose, insulin, lipid profile, cytokines and F2-isoprostanes, expression levels of oxidative and inflammatory genes/proteins in circulating mononuclear cells (MNC), myotubes and adipocytes at baseline (fasting state), and after consumption of a carbohydrate-rich liquid meal or insulin stimulation. RESULTS: Postprandial glucose and insulin responses were not different between groups. Expression of oxidant transcription factor NRF2 protein (p<0.05 for myotubes) and gene (pgroup=0.002, ptime×group=0.016), along with its target genes TXNRD1 (pgroup=0.004, ptime×group=0.007), GPX3 (pgroup=0.011, ptime×group=0.019) and SOD-1 (pgroup=0.046 and ptime×group=0.191) was upregulated in FDRT-derived MNC after meal ingestion or insulin stimulation. Synergistically, expression of target genes of inflammatory transcription factor nuclear factor kappa B such as tumor necrosis factor alpha (pgroup=0.001, ptime×group=0.007) was greater in FDRT-derived MNC than in non-FDRT-derived MNC after meal ingestion or insulin stimulation. CONCLUSIONS: Our findings shed light on how heredity of T2DM confers increased susceptibility to oxidative stress and inflammation. This could provide early insights into the underlying mechanisms and future risk of FDRTs for developing T2DM and its associated complications
Entanglement Perturbation Theory for Antiferromagnetic Heisenberg Spin Chains
A recently developed numerical method, entanglement perturbation theory
(EPT), is used to study the antiferromagnetic Heisenberg spin chains with
z-axis anisotropy and magnetic field B. To demonstrate the accuracy,
we first apply EPT to the isotropic spin-1/2 antiferromagnetic Heisenberg
model, and find that EPT successfully reproduces the exact Bethe Ansatz results
for the ground state energy, the local magnetization, and the spin correlation
functions (Bethe ansatz result is available for the first 7 lattice
separations). In particular, EPT confirms for the first time the asymptotic
behavior of the spin correlation functions predicted by the conformal field
theory, which realizes only for lattice separations larger than 1000. Next,
turning on the z-axis anisotropy and the magnetic field, the 2-spin and 4-spin
correlation functions are calculated, and the results are compared with those
obtained by Bosonization and density matrix renormalization group methods.
Finally, for the spin-1 antiferromagnetic Heisenberg model, the ground state
phase diagram in space is determined with help of the Roomany-Wyld RG
finite-size-scaling. The results are in good agreement with those obtained by
the level-spectroscopy method.Comment: 12 pages, 14 figure
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