1,199 research outputs found
A new primal-dual path-following interior-point algorithm for semidefinite optimization
AbstractIn this paper we present a new primal-dual path-following interior-point algorithm for semidefinite optimization. The algorithm is based on a new technique for finding the search direction and the strategy of the central path. At each iteration, we use only full NesterovâTodd step. Moreover, we obtain the currently best known iteration bound for the algorithm with small-update method, namely, O(nlognÏ”), which is as good as the linear analogue
Predicting bioavailability of PAHs in field-contaminated soils by passive sampling with triolein embedded cellulose acetate membranes
Triolein embedded cellulose acetate membrane (TECAM) was used for passive sampling of the fraction of naphthalene, phenanthrene, pyrene and benzo[a]pyrene in 18 field -contaminated soils. The sampling process of PAHs by TECAM fitted well with a first-order kinetics model and PAHs reached 95% of equilibrium in TECAM within 20 h. Concentrations of PAHs in TECAM (C-TECAM) correlated well with the concentrations in soils (r(2) = 0.693-0.962, p < 0.001). Furthermore. concentrations of PAHs determined in the soil solution were very close to the values estimated by C-TECAM and the partition coefficient between TECAM and water (KTECAM-W). After lipid normalization nearly 1:1 relationships were observed between PAH concentrations in TECAMs and earthworms exposed to the soils (r(2) = 0.591-0.824, n = 18, p < 0.01). These results suggest that TECAM can be a useful tool to predict bioavailability of PAHs in field-contaminated soils. (C) 2008 Elsevier Ltd. All rights reserved
Intertwined Order and Holography: The Case of Parity Breaking Pair Density Waves
Article / Letter to editorLeids Instituut Onderzoek Natuurkund
Intertwined Order and Holography: The Case of Parity Breaking Pair Density Waves
Article / Letter to editorLeids Instituut Onderzoek Natuurkund
Magnetic phase diagrams of the Kagome staircase compound Co3V2O8
At zero magnetic field, a series of five phase transitions occur in Co3V2O8.
The Neel temperature, TN=11.4 K, is followed by four additional phase changes
at T1=8.9 K, T2=7.0 K, T3=6.9 K, and T4=6.2 K. The different phases are
distinguished by the commensurability of the b-component of its spin density
wave vector. We investigate the stability of these various phases under
magnetic fields through dielectric constant and magnetic susceptibility
anomalies. The field-temperature phase diagram of Co3V2O8 is completely
resolved. The complexity of the phase diagram results from the competition of
different magnetic states with almost equal ground state energies due to
competing exchange interactions and frustration.Comment: Proceedings of the 2007 Conference on Strongly Correlated Electron
Systems, 2 pages, 2 figure
A tunable radiation source by coupling laser-plasma-generated electrons to a periodic structure
Near-infrared radiation around 1000 nm generated from the interaction of a high-density MeV electron beam, obtained by impinging an intense ultrashort laser pulse on a solid target, with a metal grating is observed experimentally. Theoretical modeling and particle-in-cell simulation suggest that the radiation is caused by the Smith-Purcell mechanism. The results here indicate that tunable terahertz radiation with tens GV=m ïŹeld strength can be achieved by using appropriate grating parameter
Effects of chitosan addition on growth performance, diarrhoea, anti-oxidative function and serum immune parameters of weaned piglets
The present experiment was designed to determine the efficacy of a commercial source of chitosan (CS) to enhance performance, anti-oxidative function, and immune response in weaned pigs. A total of 60 crossbreed piglets (Duroc Ă Landrace Ă Yorkshire), with average live bodyweight of 8.85 ± 1.52 kg, were weaned at 28 ± 2 days and randomly assigned to five treatment groups, which were fed maize-soybean meal diets containing 0 (basal diet, control) and 250, 500, 1000, and 2000 mg/kg CS. The experiment lasted for two weeks. Body weight was recorded and daily feed intake was calculated. Faecal consistency was monitored for the overall period. After two weeks, blood samples were collected and anti-oxidative and immune parameters were determined. The results showed that CS improved average daily gain and daily gain: daily feed intake during the experiment. Mean faecal score values for the second week were improved by CS, which showed decreased values compared with the control diet. The CS increased the total antioxidant capacity and the activities of superoxide dismutase, catalase and glutathione peroxidase and the content of reduced glutathione in serum, and decreased the malondialdehyde and cortisol contents of serum. Furthermore, CS increased the levels of serum IL-1ÎČïŒIL-2 and IgG. These findings suggested that the use of CS improved performance and anti-oxidative function, and regulated the immune response of weaned pigs.Keywords: Anti-oxidative capability, chitosan, immunity, performance, piglet
Thermal expansion and pressure effect in MnWO4
MnWO4 has attracted attention because of its ferroelectric property induced
by frustrated helical spin order. Strong spin-lattice interaction is necessary
to explain ferroelectricity associated with this type of magnetic order.We have
conducted thermal expansion measurements along the a, b, c axes revealing the
existence of strong anisotropic lattice anomalies at T1=7.8 K, the temperature
of the magnetic lock-in transition into a commensurate low-temperature
(reentrant paraelectric) phase. The effect of hydrostatic pressure up to 1.8
GPa on the FE phase is investigated by measuring the dielectric constant and
the FE polarization. The low- temperature commensurate and paraelectric phase
is stabilized and the stability range of the ferroelectric phase is diminished
under pressure.Comment: 2 pages, 3 figures. SCES conference proceedings, houston, TX, 2007.
to be published in Physica
Superconductivity in MgB_2 doped with Ti and C
Measurements of the superconducting upper critical field, H_{c2}, and
critical current density, J_c, have been carried out for MgB_2 doped with Ti
and/or C in order to explore the problems encountered if these dopants are used
to enhance the superconducting performance. Carbon replaces boron in the MgB_2
lattice and apparently shortens the electronic mean free path thereby raising
H_c2. Titanium forms precipitates of either TiB or TiB_2 that enhance the flux
pinning and raise J_c. Most of these precipitates are intra-granular in the
MgB_2 phase. If approximately 0.5% Ti and approximately 2% C are co-deposited
with B to form doped boron fibers and these fibers are in turn reacted in Mg
vapor to form MgB_2, the resulting superconductor has H_{c2}(T=0) ~ 25 T and
J_c ~ 10,000 A/cm**2 at 5 K and 2.2 T.Comment: 11 pages, 10 figure
Identification of a candidate gene for Rc-D1, a locus controlling red coleoptile colour in wheat
Red coleoptile is an easily observed agronomic trait of wheat and has been extensively studied. However, the molecular mechanism of this trait has not yet been revealed. In this study, the MYB gene TaMYB-D1 was isolated from the wheat cultivar âGy115â, which possesses red coleoptiles. This gene resided at the short arm of the homoelogous group 7 chromosomes. TaMYB-D1 was the only gene expressed in the coleoptiles of âGy115â and was not expressed in âOpataâ and âCSâ, which have uncoloured coleoptiles. Phylogenetic analysis placed TaMYB-D1 very close to ZmC1 and other MYB proteins regulating anthocyanin biosynthesis. The encoded protein of TaMYB-D1 had an integrated DNA binding domain of 102 amino acids and a transcription domain with 42 amino acids, similar to the structure of ZmC1. Transient expression analysis in onion epidermal cells showed that TaMYB-D1 was located at the plant nucleus, which suggested its role as a transcription factor. The expression of TaMYB-D1 was accompanied with the expression of TaDFR and anthocyanin biosynthesis in the development of the coleoptile of âGy115â. Transient expression analysis showed that only TaMYB-D1 induced a few âOpataâ coleoptile cells to synthesize anthocyanin in light, and the gene also induced a colour change to red in many cells with the help of ZmR. All of these results suggested TaMYB-D1 as the candidate gene for the red coleoptile trait of âGy115â
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