752 research outputs found
Discrete logarithms in quasi-polynomial time in finite fields of fixed characteristic
We prove that the discrete logarithm problem can be solved in quasi-polynomial expected time in the multiplicative group of finite fields of fixed characteristic. More generally, we prove that it can be solved in the field of cardinality pn in expected time (pn)2log2(n)+O(1)
Multiscale simulations in simple metals: a density-functional based methodology
We present a formalism for coupling a density functional theory-based quantum
simulation to a classical simulation for the treatment of simple metallic
systems. The formalism is applicable to multiscale simulations in which the
part of the system requiring quantum-mechanical treatment is spatially confined
to a small region. Such situations often arise in physical systems where
chemical interactions in a small region can affect the macroscopic mechanical
properties of a metal. We describe how this coupled treatment can be
accomplished efficiently, and we present a coupled simulation for a bulk
aluminum system.Comment: 15 pages, 7 figure
Dynamical Generation of Fermion Mass and Magnetic Field in Three-Dimensional QED with Chern-Simons Term
We study dynamical symmetry breaking in three-dimensional QED with a
Chern-Simons (CS) term, considering the screening effect of flavor
fermions. We find a new phase of the vacuum, in which both the fermion mass and
a magnetic field are dynamically generated, when the coefficient of the CS term
equals . The resultant vacuum becomes the finite-density
state half-filled by fermions. For , we find the fermion
remains massless and only the magnetic field is induced. For ,
spontaneous magnetization does not occur and should be regarded as an external
field.Comment: 8 pages, no figure, to be published in Phys. Rev. Let
Elevated CO2 did not stimulate stem growth in 11 provenances of a globally important hardwood plantation species
Elevated atmospheric carbon dioxide (eCO2) often enhances rates of photosynthesis leading to increased productivity in trees. In their native habitats in Australia, eucalypts display considerable phenotypic plasticity in response to changes in environmental conditions. Little is known whether this plasticity can be harnessed effectively under future atmospheric eCO2 conditions and be used to identify provenances with superior growth. Here, we report two experiments that assessed the physiological and growth responses of Eucalyptus grandis—one of the world's most important hardwood plantation species—to eCO2. We used 11 provenances from contrasting climates. Our selection was based on site-specific information of long-term temperature and water availability. In Experiment 1, four provenances exhibited significant variation in light-saturated photosynthetic rates (Asat), stomatal conductance (gs), and concentrations of non-structural carbohydrates in leaves, stems and roots when grown under ambient CO2 (aCO2). Biomass of leaves, stems and roots varied significantly and were negatively correlated with mean annual temperature (MAT) at seed origin, indicating that provenances from cooler, wetter climates generally produced greater biomass. Yet, stem growth of these provenances was not stimulated by eCO2. Given the vast environmental gradient covered by provenances of E. grandis, we expanded the selection from four to nine provenances in Experiment 2. This allowed us to validate results from Experiment 1 with its small selection and detailed measurements of various physiological parameters by focusing on growth responses to eCO2 across a wider environmental gradient in Experiment 2. In Experiment 2, nine provenances also exhibited intraspecific differences in growth, but these were not related to climate of origin, and eCO2 had little effect on growth traits. Growth responses under eCO2 varied widely across provenances in both experiments, confirming phenotypic plasticity in E. grandis, though responses were not systematically correlated with climate of origin. These results indicate that selection of provenances for improved stem growth of E. grandis under future eCO2 cannot be based solely on climate of origin, as is common practice for other planted tree species
Higher Derivative CP(N) Model and Quantization of the Induced Chern-Simons Term
We consider higher derivative CP(N) model in 2+1 dimensions with the
Wess-Zumino-Witten term and the topological current density squared term. We
quantize the theory by using the auxiliary gauge field formulation in the path
integral method and prove that the extended model remains renormalizable in the
large N limit. We find that the Maxwell-Chern-Simons theory is dynamically
induced in the large N effective action at a nontrivial UV fixed point. The
quantization of the Chern-Simons term is also discussed.Comment: 8 pages, no figure, a minor change in abstract, added Comments on the
quantization of the Chern-Simons term whose coefficient is also corrected,
and some references are added. Some typos are corrected. Added a new
paragraph checking the equivalence between (3) and (5), and a related
referenc
Detailed Analysis of Transverse Emittance of the FLUTE Electron Bunch
The comÂpact and verÂsaÂtile linÂear acÂcelÂerÂaÂtor-based test faÂcilÂity FLUTE (FerÂnÂinÂfrarot Linac- Und Test-ExÂperÂiÂment) is opÂerÂated at KIT. Its priÂmary goal is to serve as a platÂform for a vaÂriÂety of acÂcelÂerÂaÂtor R\&D studÂies like the genÂerÂaÂtion of strong ulÂtra-short terÂaÂhertz pulses. The amÂpliÂtude of the genÂerÂated coÂherÂent THz pulses is proÂporÂtional to the square numÂber of parÂtiÂcles in the bunch. With the transÂverse emitÂtance a meaÂsure for the transÂverse parÂtiÂcle denÂsity can be deÂterÂmined. It is thereÂfore a vital paÂraÂmeÂter in the opÂtiÂmizaÂtion for opÂerÂaÂtion. In a sysÂtemÂatic study, the transÂverse emitÂtance of the elecÂtron beam was meaÂsured in the FLUTE inÂjecÂtor. A deÂtailed analyÂsis conÂsidÂers difÂferÂent inÂfluÂences such as the bunch charge and comÂpares this with parÂtiÂcle trackÂing simÂuÂlaÂtions carÂried out with ASTRA. In this conÂtriÂbuÂtion, the key findÂings of this analyÂsis are disÂcussed
Validation of Tikhonov adaptively regularized gamma variate fitting with 24-h plasma clearance in cirrhotic patients with ascites
PURPOSE: The aim was to compare late-time extrapolation of plasma clearance (CL) from Tikhonov adaptively regularized gamma variate fitting (Tk-GV) and from mono-exponential (E1) fitting. METHODS: Ten (51)Cr-ethylenediaminetetraacetic acid bolus IV studies in adults--8 with ascites--assessed for liver transplantation, with 12-16 plasma samples drawn from 5-min to 24-h, were fit with Tk-GV and E1 models and CL results were compared using Passing-Bablok fitting. RESULTS: The 24-h CL(Tk-GV) values ranged from 11.4 to 79.7 ml/min. Linear regression of 4- versus 24-h CL(Tk-GV) yielded no significant departure from a slope of 1, whereas the 4- versus 24-h CL(E1) slope, 1.56, was significantly increased. For CL(Tk-GV-24-h) versus CL(E1-24-h), there was a biased slope and intercept (0.85, 5.97 ml/min). Moreover, the quality of fitting of 24-h data was significantly better for Tk-GV than for E1, as follows. For 10 logarithm of concentration curves, higher r values were obtained for each Tk-GV fit (median 0.998) than for its corresponding E1 fit (median 0.965), with p < 0.0001 (paired t-test of z-statistics from Fisher r-z transformations). The E1 fit quality degraded with increasing V/W [volume of distribution (l) per kg body weight, p = 0.003]. However, Tk-GV fit quality versus V/W was uncorrelated (p = 0.8). CONCLUSION: CL(E1) values were dependent on sample time and the quality of fit was poor and degraded with increasing ascites, consistent with current opinion that CL(E1) is contraindicated in ascitic patients. CL(Tk-GV) was relatively more accurate and the good quality of fit was unaffected by ascites. CL(Tk-GV) was the preferred method for the accurate calculation of CL and was useful despite liver failure and ascites
Thermodynamic properties of spontaneous magnetization in Chern-Simons QED_3
The spontaneous magnetization in Chern-Simons QED_3 is discussed in a finite
temperature system. The thermodynamical potential is analyzed within the weak
field approximation and in the fermion massless limit. We find that there is a
linear term with respect to the magnetic field with a negative coefficient at
any finite temperature. This implies that the spontaneous magnetic field does
not vanish even at high temperature. In addition, we examine the photon
spectrum in the system. We find that the bare Chern-Simons coefficient is
cancelled by the radiative effects. The photons then become topologically
massless according to the magnetization, though they are massive by finite
temperature effects. Thus the magnetic field is a long-range force without the
screening even at high temperature.Comment: 32 pages, Latex, 4 eps figure
CELL-LINED, NONWOVEN MICROFIBER SCAFFOLDS AS A BLOOD INTERFACE *
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73137/1/j.1749-6632.1977.tb41787.x.pd
False-Positive Human Immunodeficiency Virus Enzyme Immunoassay Results in Pregnant Women
Objective: Examine whether false-positive HIV enzyme immunoassay (EIA) test results occur more frequently among pregnant women than among women who are not pregnant and men (others). Design: To obtain a large number of pregnant women and others tested for HIV, we identified specimens tested at a national laboratory using Genetic Systems HIV-1/HIV-2 Plus O EIA from July 2007 to June 2008. Methods: Specimens with EIA repeatedly reactive and Western blot-negative or indeterminate results were considered EIA false-positive. We compared the false-positive rate among uninfected pregnant women and others, adjusting for HIV prevalence. Among all reactive EIAs, we evaluated the proportion of false-positives, positive predictive value (PPV), and Western blot bands among indeterminates, by pregnancy status. Results: HIV prevalence was 0.06 % among 921,438 pregnant women and 1.34 % among 1,103,961 others. The false-positive rate was lower for pregnant women than others (0.14 % vs. 0.21%, odds ratio 0.65 [95 % confidence interval 0.61, 0.70]). Pregnant women with reactive EIAs were more likely than others (p,0.01) to have Western blot-negative (52.9 % vs. 9.8%) and indeterminate results (17.0 % vs. 3.7%) and lower PPV (30 % vs. 87%). The p24 band was detected more often among pregnant women (p,0.01). Conclusions: False-positive HIV EIA results were rare and occurred less frequently among pregnant women than others
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