7,452 research outputs found
Topological defect formation in quenched ferromagnetic Bose-Einstein condensates
We study the dynamics of the quantum phase transition of a ferromagnetic
spin-1 Bose-Einstein condensate from the polar phase to the broken-axisymmetry
phase by changing magnetic field, and find the spontaneous formation of spinor
domain walls followed by the creation of polar-core spin vortices. We also find
that the spin textures depend very sensitively on the initial noise
distribution, and that an anisotropic and colored initial noise is needed to
reproduce the Berkeley experiment [Sadler et al., Nature 443, 312 (2006)]. The
dynamics of vortex nucleation and the number of created vortices depend also on
the manner in which the magnetic field is changed. We point out an analogy
between the formation of spin vortices from domain walls in a spinor BEC and
that of vortex-antivortex pairs from dark solitons in a scalar BEC.Comment: 10 pages, 11 figure
Thermo-mechanical analysis of dental silicone polymers
Soft lining materials are used to replace the inner surface of a conventional complete denture, especially for weak elderly patients, with delicate health who cannot tolerate the hard acrylic denture base. Most of these patients have fragile supporting mucosa, excessive residual ridge resorption, particularly on the mandibular arch. The application of a soft liner to the mandibular denture allows absorbing impact forces during mastication and relieving oral mucosa. Actually, the silicone rubbers constitute the main family of commercialised soft lining materials. This study was conducted to understand the relationships between the mechanical properties and the physical structure of polysiloxanes. For this purpose, a series of polysiloxanes of various chemical compositions have been investigated. The evolution of their physical structure as a function of temperature has been followed by differential scanning calorimetry (DSC). In order to facilitate comparisons, the mechanical modulus has been analysed upon the same heating rate using dynamic mechanical analysis (DMA). Polysiloxanes actually commercialised as soft denture liners are three-dimensional networks: the flexibility of chains allows a crystalline organisation in an amorphous phase leading to the low value of the shear modulus. The dynamic mechanical analysis shows that they are used in the rubbery state. So, polysiloxanes have steady mechanical properties during physiological utilisation
First Meeting of the joint IOC-ICES Study Group on Nutrient Standards (SGONS)
A meeting of the joint IOC-ICES Study Group on Nutrient Standards (SGONS) was held in Paris, France on 23-24 March 2010. It focused on the ongoing activities of the SGONS and plans for extended international collaborations to establish global comparability of the nutrient data from the world’s ocean. Thirty two scientists and experts from 11 countries and 2 delegates from IOC attended the meeting. The discussions followed the Terms of References of SGONS established in July 2009. Development of the reference materials for nutrients in seawater (RMNS) were also discussed in collaboration with the producers. The background and history of SGONS and an international nutrients scale system INSS and the progress with the production of RMNS materials and their current availability were reported. The production of RMNS and the latest status of the RMNS production facility, current status on the certification of RMNS for nitrate, nitrite, phosphate and silicate at the National Metrology Institute of Japan were also reported. The revised nutrients analysis manual which is being undertaken by the SGONS hopefully would be completed by 1 August 2010, and it will be published on line at the Go-Ship website. Results obtained with RMNS solutions used on the P6 reoccupation cruise in 2009-2010 by SIO (Scripps Institute of Oceanography, USA) showed that considerable improvement could be made in the internal comparability of the data by referencing it to the RMNS results and related good comparability with the previous P6 cruise in 2003 by JAMSTEC when RMNS were also used. The meeting strongly endorsed the idea of a ship board workshop in 2013/14 during which major groups would carry out a full inter-comparison of all procedures including analytical methods on board a research ship. The global stability test of RMNS by ten core laboratories of SGONS which started in 2009 will continue for more two years. It also was agreed to set up an international steering committee to plan the next inter-laboratory comparison study which will extend the study to about 70 laboratories working globally on deep sea hydrography. This will happen in early 2011. Future arrangements were considered for the collection of more batches of seawater for the preparation of RMNS waters suitable for use in all major water masses, and a list of candidate cruises in 2010/2011 was prepared. The related point of the extension of the use of RMNS for work in shelf sea water was also discussed, this followed on from discussions at the ICES Marine Chemistry Working Group (MCWG) meeting in 2010. The ICES MCWG considered that the use of suitable RMNS solutions would be valuable for improving the inter comparability of shelf sea data and be a valuable complement to work with the existing QUASIMEME proficiency testing scheme
Capturing of FePt nanoparticles in a stream of a liquid
This study considers capturing of FePt nanoparticle in a magnetic field when the particles are injected into a stream of flowing liquid. A roller pump is used to induce a flow of water at several flow rates to assess the growth of FePt aggregation near magnetic field source. The particles are injected into the system using a micro syringe pump at different flow rates. The aggregations are observed with a microscope. Subsequently some estimation is performed with respect to a magnetic hyperthermia, which is a part of a method for treating undesirable biological entities in blood vessels
Winding Number in String Field Theory
Motivated by the similarity between cubic string field theory (CSFT) and the
Chern-Simons theory in three dimensions, we study the possibility of
interpreting N=(\pi^2/3)\int(U Q_B U^{-1})^3 as a kind of winding number in
CSFT taking quantized values. In particular, we focus on the expression of N as
the integration of a BRST-exact quantity, N=\int Q_B A, which vanishes
identically in naive treatments. For realizing non-trivial N, we need a
regularization for divergences from the zero eigenvalue of the operator K in
the KBc algebra. This regularization must at same time violate the
BRST-exactness of the integrand of N. By adopting the regularization of
shifting K by a positive infinitesimal, we obtain the desired value
N[(U_tv)^{\pm 1}]=\mp 1 for U_tv corresponding to the tachyon vacuum. However,
we find that N[(U_tv)^{\pm 2}] differs from \mp 2, the value expected from the
additive law of N. This result may be understood from the fact that \Psi=U Q_B
U^{-1} with U=(U_tv)^{\pm 2} does not satisfy the CSFT EOM in the strong sense
and hence is not truly a pure-gauge in our regularization.Comment: 20 pages, no figures; v2: references added, minor change
Melting Spectral Functions of the Scalar and Vector Mesons in a Holographic QCD Model
We investigate the finite-temperature spectral functions of heavy quarkonia
by using the soft-wall AdS/QCD model. We discuss the scalar, the pseudo-scalar,
the vector, and the axial-vector mesons and compare their qualitative features
of the melting temperature and growing width. We find that the axial-vector
meson melts earlier than the vector meson, while there appears only a slight
difference between the scalar and pseudo-scalar mesons which also melt earlier
than the vector meson.Comment: 27 pages, 10 figure
AKARI/IRC Broadband Mid-infrared data as an indicator of Star Formation Rate
AKARI/Infrared Camera (IRC) Point Source Catalog provides a large amount of
flux data at {\it S9W} () and {\it L18W} ()
bands. With the goal of constructing Star-Formation Rate(SFR) calculations
using IRC data, we analyzed an IR selected
GALEX-SDSS-2MASS-AKARI(IRC/Far-Infrared Surveyor) sample of 153 nearby
galaxies. The far-infrared fluxes were obtained from AKARI diffuse maps to
correct the underestimation for extended sources raised by the point-spread
function photometry. SFRs of these galaxies were derived by the spectral energy
distribution fitting program CIGALE. In spite of complicated features contained
in these bands, both the {\it S9W} and {\it L18W} emission correlate with the
SFR of galaxies. The SFR calibrations using {\it S9W} and {\it L18W} are
presented for the first time. These calibrations agree well with previous works
based on Spitzer data within the scatters, and should be applicable to
dust-rich galaxies.Comment: PASJ, in pres
Chiral currents and static properties of nucleons in holographic QCD
We analyze static properties of nucleons in the two flavor holographic QCD
model of Sakai and Sugimoto described effectively by a five-dimensional U(2)
Yang-Mills theory with the Chern-Simons term on a curved background. The
baryons are represented in this model as a soliton, which at a time slice is
approximately the BPST instanton with a fixed size. First, we construct a
chiral current in four dimensions from the Noether current of local gauge
transformations which are non-vanishing on the boundaries of the extra
dimension. We examine this chiral current for nucleons with quantized
collective coordinates to compute their charge distribution, charge radii,
magnetic moments and axial vector coupling. Most of the results are better
close to the experimental values than in the Skyrme model. We discuss the
problems of our chiral current; non-uniqueness of the local gauge
transformation for defining the current, and its gauge-noninvariance.Comment: 30 pages, 1 figure; a footnote added in sec. 4.4, minor correction
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