9,719 research outputs found
Helstrom Theorem by No-Signaling Condition
We prove a special case of Helstrom theorem by using no-signaling condition
in the special theory of relativity that faster-than-light communication is
impossible.Comment: Minor corrections (A reference added, discussion part deleted, typos
in equations corrected), 2 pages, RevTe
Using Virtual Observatory techniques to search for Adaptive Optics suitable AGN
Until recently, it has been possible only for nearby galaxies to study the
scaling relations between central black hole and host galaxy in detail. Because
of the small number densities at low redshift, (luminous) AGN are
underrepresented in such detailed studies. The advent of adaptive optics (AO)
at large telescopes helps overcoming this hurdle, allowing to reach small
linear scales over a wide range in redshift. Finding AO-suitable targets, i.e.,
AGN having a nearby reference star, and carrying out an initial multiwavelength
classification is an excellent use case for the Virtual Observatory. We present
our Virtual-Observatory approach to select an AO-suitable catalog of
X-ray-emitting AGN at redshifts 0.1<z<1.Comment: 4 pages, 5 figures, submitted to "EURO-VO AIDA workshop:
Multiwavelength astronomy and Virtual Observatory", ESAC, Spain, 1-3 Dec.
200
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Comparing carbon sequestration in an oil reservoir to sequestration in a brine formation-field study
Geologic sequestration of CO2 in an oil reservoir is generally considered a different class than sequestration in
formations which contain only brine. In this paper, the significance and validity of this conceptualization is
examined by comparing the performance of CO2 injected into a depleted oil reservoir with the performance of
similar injection into non-oil bearing sandstones using a field test at Cranfield Field, Mississippi as a case study. The
differences considered are:
(1)Residual oil in the reservoir slightly reduces the CO2 breakthrough time and rate of pressure build up as
compared to a reservoir containing only brine, because under miscible conditions, more CO2 dissolves into oil
than in to brine.
(2)Dense wells provide improved assessment of the oil reservoir quality leading to improved prediction as well as
verification of CO2 movement in this reservoir as compared to the sparsely characterized brine leg. The value of
this information exceeds the risk of leakage.
Assessment of the difference made by the presence of residual oil requires a good understanding reservoir properties
to predict oil and gas distribution. Stratal slicing, attribute analysis and petrographic analyses are used to define the
reservoir architecture. Real-time pressure response at a dedicated observation well and episodic pressure mapping
has been conducted in the reservoir under flood since mid-2008; comparison measurements are planned for 2009 in
down-dip environments lacking hydrocarbons. Model results using GEM compositional simulator compare well in
general to measured reservoir response under CO2 flood; imperfections in model match of flood history document
uncertainties Time laps RST logging is underway to validate fluid composition and migration models. Monitoring
assessing the performance of the wells during the injection of CO2 suggests that the value of wells to provide field
data for characterization exceeds the risk of leakage.Bureau of Economic Geolog
Threshold electric field in unconventional density waves
As it is well known most of charge density wave (CDW) and spin density wave
(SDW) exhibit the nonlinear transport with well defined threshold electric
field E_T. Here we study theoretically the threshold electric field of
unconventional density waves. We find that the threshold field increases
monotonically with temperature without divergent behaviour at T_c, unlike the
one in conventional CDW. The present result in the 3D weak pinning limit
appears to describe rather well the threshold electric field observed recently
in the low-temperature phase (LTP) of alpha-(BEDT-TTF)_2KHg(SCN)_4.Comment: 4 pages, 2 figure
Variations in porcine colostrum oligosaccharide composition between breeds and in association with sow maternal performance
Background: Oligosaccharides (OS) are indigestible carbohydrates naturally found in milk. The composition of porcine colostrum OS may influence the growth and the health of the neonate and consuming optimal concentrations of OS may reduce piglet susceptibility to illness. In this manner, targeted supplementation of animal feed with OS is being explored as a health management tool in the livestock industry. The variation in OS composition between different breeds of pig and its association with the litter performance is currently unknown. The aim of this study was to characterize the colostrum OS composition from sows of different breed and parity and correlate this data with sow maternal traits. Methods: Eighty-three colostrum samples from parities 1 to 8 were gathered from 3 different breeds of sow: 44 Large White sows, 27 Landrace sows and 12 Duroc sows. Samples were taken between the birth of the first and the last piglet from sows that were not pharmacologically induced to farrow. OS were purified from the samples and analysed by MALDI-ToF mass spectrometry (21 OS compositions detected). The farrowing season and the maternal data were recorded for each sow, including the number of live piglets and the litter body weight at birth, at day (d) 3 and at weaning. Results: Five OS compositions, including isomers of the bifidogenic Sialyllactose, Lacto-N-Tetraose and Lacto-N-Hexaose series, were detected in all the samples. Twelve other OS were identified in at least 50% of samples, and their abundances were affected by breed (P < 0.05; 6 of 12), marginally affected by season (P < 0.10; 3 of 12) and never by parity number. The abundances of each OS component were standardized by Z-score scaling (\u3bc = 0 and SD = 1), transformed by principal component analysis, and four similarity clusters were generated. Cluster membership was associated with litter weight gain within 3 days (P = 0.063) and at weaning (P < 0.05), but not with piglet mortality within 3 days. Conclusions: OS composition of colostrum may partially explain the variability in maternal performance within and between different breeds of sow. The obtained OS data can provide useful information for the development of novel prebiotic food supplements for suckling and weaning pigs
Molecular Dynamics Simulation Study of Nonconcatenated Ring Polymers in a Melt: I. Statics
Molecular dynamics simulations were conducted to investigate the structural
properties of melts of nonconcatenated ring polymers and compared to melts of
linear polymers. The longest rings were composed of N=1600 monomers per chain
which corresponds to roughly 57 entanglement lengths for comparable linear
polymers. For the rings, the radius of gyration squared was found to scale as N
to the 4/5 power for an intermediate regime and N to the 2/3 power for the
larger rings indicating an overall conformation of a crumpled globule. However,
almost all beads of the rings are "surface beads" interacting with beads of
other rings, a result also in agreement with a primitive path analysis
performed in the following paper (DOI: 10.1063/1.3587138). Details of the
internal conformational properties of the ring and linear polymers as well as
their packing are analyzed and compared to current theoretical models.Comment: 15 pages, 14 figure
Corrugated Silicon Platelet Feed Horn Array for CMB Polarimetry at 150 GHz
Next generation cosmic microwave background (CMB) polarization anisotropy
measurements will feature focal plane arrays with more than 600 millimeter-wave
detectors. We make use of high-resolution photolithography and wafer-scale etch
tools to build planar arrays of corrugated platelet feeds in silicon with
highly symmetric beams, low cross-polarization and low side lobes. A compact
Au-plated corrugated Si feed designed for 150 GHz operation exhibited
performance equivalent to that of electroformed feeds: ~-0.2 dB insertion loss,
<-20 dB return loss from 120 GHz to 170 GHz, <-25 dB side lobes and <-23 dB
cross-polarization. We are currently fabricating a 50 mm diameter array with 84
horns consisting of 33 Si platelets as a prototype for the SPTpol and ACTpol
telescopes. Our fabrication facilities permit arrays up to 150 mm in diameter.Comment: 12 pages; SPIE proceedings for Millimeter, Submillimeter, and
Far-Infrared Detectors and Instrumentation for Astronomy V (Conference 7741,
June 2010, San Diego, CA, USA
Lyman alpha line formation in starbursting galaxies II. Extremely Thick, Dustless, and Static HI Media
The Lya line transfer in an extremely thick medium of neutral hydrogen is
investigated by adopting an accelerating scheme in our Monte Carlo code to skip
a large number of core or resonant scatterings. This scheme reduces computing
time significantly with no sacrifice in the accuracy of the results. We applied
this numerical method to the Lya transfer in a static, uniform, dustless, and
plane-parallel medium. Two types of photon sources have been considered, the
midplane source and the uniformly distributed sources. The emergent profiles
show double peaks and absorption trough at the line-center. We compared our
results with the analytic solutions derived by previous researchers, and
confirmed that both solutions are in good agreement with each other. We
investigated the directionality of the emergent Lya photons and found that limb
brightening is observed in slightly thick media while limb darkening appears in
extremely thick media. The behavior of the directionality is noted to follow
that of the Thomson scattered radiation in electron clouds, because both Lya
wing scattering and Thomson scattering share the same Rayleigh scattering phase
function. The mean number of wing scatterings just before escape is in exact
agreement with the prediction of the diffusion approximation. The Lya photons
constituting the inner part of the emergent profiles follow the relationship
derived from the diffusion approximation. We present a brief discussion on the
application of our results to the formation of Lya broad absorption troughs and
P-Cygni type Lya profiles seen in the UV spectra of starburst galaxies.Comment: 24 papges, 12 figures, The revised version submitted to Ap
Nodal Structure of Unconventional Superconductors Probed by the Angle Resolved Thermal Transport Measurements
Over the past two decades, unconventional superconductivity with gap symmetry
other than s-wave has been found in several classes of materials, including
heavy fermion (HF), high-T_c, and organic superconductors. Unconventional
superconductivity is characterized by anisotropic superconducting gap
functions, which may have zeros (nodes) along certain directions in the
Brillouin zone. The nodal structure is closely related to the pairing
interaction, and it is widely believed that the presence of nodes is a
signature of magnetic or some other exotic, rather than conventional
phonon-mediated, pairing mechanism. Therefore experimental determination of the
gap function is of fundamental importance. However, the detailed gap structure,
especially the direction of the nodes, is an unresolved issue in most
unconventional superconductors. Recently it has been demonstrated that the
thermal conductivity and specific heat measurements under magnetic field
rotated relative to the crystal axes are a powerful method for determining the
shape of the gap and the nodal directions in the bulk. Here we review the
theoretical underpinnings of the method and the results for the nodal structure
of several unconventional superconductors, including borocarbide YNiBC,
heavy fermions UPdAl, CeCoIn, and PrOsSb, organic
superconductor, -(BEDT-TTF)Cu(NCS), and ruthenate
SrRuO, determined by angular variation of the thermal conductivity and
heat capacity.Comment: topical review, 55 pages, 35 figures. Figure quality has been reduced
for submission to cond-mat, higher quality figures available from the authors
or from the publishe
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