1,847 research outputs found
Finite Size Scaling and ``perfect'' actions: the three dimensional Ising model
Using Finite-Size Scaling techniques, we numerically show that the first
irrelevant operator of the lattice theory in three dimensions
is (within errors) completely decoupled at . This interesting
result also holds in the Thermodynamical Limit, where the renormalized coupling
constant shows an extraordinary reduction of the scaling-corrections when
compared with the Ising model. It is argued that Finite-Size Scaling analysis
can be a competitive method for finding improved actions.Comment: 13 pages, 3 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
Effects of yeast culture on broiler growth performance, nutrient digestibility and caecal microbiota
This study was conducted to evaluate the effects of yeast culture (YC) supplementation on the growth performance, apparent nutrient digestibility and caecal microflora of broiler chickens. A total of 360 one-day-old Arbor Acres broiler chickens were randomly assigned to six dietary treatments containing 0.2%, 0.4%, 0.6%, 0.8% and 1% YC. The experiment lasted for 42 days. Diet and faecal samples were collected for analysis of dry matter, crude protein, ether extract, calcium and phosphorus. Caecal microbiota on days 21 and 42 were measured using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and real-time PCR. Dietary supplementation with YC did not affect feed intake. On day 42, the 0.8% YC group showed optimal growth and feed efficiency, as well as higher levels of apparent digestibility of ether extract, calcium and phosphorus. On day 21, both 0.8% and 1% YC groups exhibited a significant increase in Ruminococcus, Propionibacterium clostridiales, and Bifidobacterium density. The density of Bacteroides in the YC groups was significantly higher than that of the control group. On day 42, the densities of Bacteroides, Sphingomonas and Bifidobacterium were higher in the 0.8% YC group, whereas a significant decrease was observed in the number of Enterobacteriaceae. These results serve as evidence that dietary supplementation with 0.8% YC not only moderately optimized the feed efficiency and the apparent digestibility of ether extract, calcium and phosphorus, but also positively influenced the caecal bacterial density and diversity in broiler chickens.Keywords: Arbor Acres broiler, caecal microflora, yeast culture supplementatio
Automated 3-D Ultrasound Elastography of the Breast:An In Vivo Validation Study
Objective: Studies have indicated that adding 2-D quasi-static elastography to B-mode ultrasound imaging improved the specificity for malignant lesion detection, as malignant lesions are often stiffer (increased strain ratio) compared with benign lesions. This method is limited by its user dependency and so unsuitable for breast screening. To overcome this limitation, we implemented quasi-static elastography in an automated breast volume scanner (ABVS), which is an operator-independent 3-D ultrasound system and is especially useful for screening women with dense breasts. The study aim was to investigate if 3-D quasi-static elastography implemented in a clinically used ABVS can discriminate between benign and malignant breast lesions. Methods: Volumetric breast ultrasound radiofrequency data sets of 82 patients were acquired before and after automated transducer lifting. Lesions were annotated and strain was calculated using an in-house-developed strain algorithm. Two strain ratio types were calculated per lesion: using axial and maximal principal strain (i.e., strain in dominant direction). Results: Forty-four lesions were detected: 9 carcinomas, 23 cysts and 12 other benign lesions. A significant difference was found between malignant (median: 1.7, range: [1.0â3.2]) and benign (1.0, [0.6â1.9]) using maximal principal strain ratios. Axial strain ratio did not reveal a significant difference between benign (0.6, [â12.7 to 4.9]) and malignant lesions (0.8, [â3.5 to 5.1]). Conclusion: Three-dimensional strain imaging was successfully implemented on a clinically used ABVS to obtain, visualize and analyze in vivo strain images in three dimensions. Results revealed that maximal principal strain ratios are significantly increased in malignant compared with benign lesions.</p
High-precision determination of the critical exponents for the lambda-transition of 4He by improved high-temperature expansion
We determine the critical exponents for the XY universality class in three
dimensions, which is expected to describe the -transition in He.
They are obtained from the analysis of high-temperature series computed for a
two-component model. The parameter is fixed such that
the leading corrections to scaling vanish. We obtain ,
, . These estimates improve previous
theoretical determinations and agree with the more precise experimental results
for liquid Helium.Comment: 8 pages, revte
A Guide to Localized Frames and Applications to Galerkin-like Representations of Operators
This chapter offers a detailed survey on intrinsically localized frames and
the corresponding matrix representation of operators. We re-investigate the
properties of localized frames and the associated Banach spaces in full detail.
We investigate the representation of operators using localized frames in a
Galerkin-type scheme. We show how the boundedness and the invertibility of
matrices and operators are linked and give some sufficient and necessary
conditions for the boundedness of operators between the associated Banach
spaces.Comment: 32 page
Evidence for softening of first-order transition in 3D by quenched disorder
We study by extensive Monte Carlo simulations the effect of random bond
dilution on the phase transition of the three-dimensional 4-state Potts model
which is known to exhibit a strong first-order transition in the pure case. The
phase diagram in the dilution-temperature plane is determined from the peaks of
the susceptibility for sufficiently large system sizes. In the strongly
disordered regime, numerical evidence for softening to a second-order
transition induced by randomness is given. Here a large-scale finite-size
scaling analysis, made difficult due to strong crossover effects presumably
caused by the percolation fixed point, is performed.Comment: LaTeX file with Revtex, 4 pages, 4 eps figure
Confining QCD Strings, Casimir Scaling, and a Euclidean Approach to High-Energy Scattering
We compute the chromo-field distributions of static color-dipoles in the
fundamental and adjoint representation of SU(Nc) in the loop-loop correlation
model and find Casimir scaling in agreement with recent lattice results. Our
model combines perturbative gluon exchange with the non-perturbative stochastic
vacuum model which leads to confinement of the color-charges in the dipole via
a string of color-fields. We compute the energy stored in the confining string
and use low-energy theorems to show consistency with the static quark-antiquark
potential. We generalize Meggiolaro's analytic continuation from parton-parton
to gauge-invariant dipole-dipole scattering and obtain a Euclidean approach to
high-energy scattering that allows us in principle to calculate S-matrix
elements directly in lattice simulations of QCD. We apply this approach and
compute the S-matrix element for high-energy dipole-dipole scattering with the
presented Euclidean loop-loop correlation model. The result confirms the
analytic continuation of the gluon field strength correlator used in all
earlier applications of the stochastic vacuum model to high-energy scattering.Comment: 65 pages, 13 figures, extended and revised version to be published in
Phys. Rev. D (results unchanged, 2 new figures, 1 new table, additional
discussions in Sec.2.3 and Sec.5, new appendix on the non-Abelian Stokes
theorem, old Appendix A -> Sec.3, several references added
Research of Curve Fitting Method on the Measured Settlement of Tanks
AbstractThe settlement data of oil storage tanks made of steel are measured by the measurement points located around the base of the tank wall. The measured settlement data need to be curve fitted in order to reflect the settlement distribution around the whole tank wall base. Considering about the disadvantage of measured settlement data treatment methods on tanks in current standards, an optimization method of curve fitting on the measured settlement data is presented. The Fourier series expansion is used to analyze the measured settlement data, the fitting curves and mean square error according to different order are obtained. The fitting curve with minimum mean square error is selected as the most appropriate one that reflects the actual displacement of the tank base. The optimization method of curve fitting present is applied to analyze the measured settlement data obtained from the floating roof tank and the fixed roof tank. Results show that different effects can be obtained with different order of the fitting curve. Curve fitting referring to different order is necessary to the measured settlement data in actual engineering in order to find the most appropriate one that reflects the real tank base displacement distribution
Method for Measuring the Momentum-Dependent Relative Phase of the Superconducting Gap of High-Temperature Superconductors
The phase variation of the superconducting gap over the (normal) Fermi
surface of the high-temperature superconductors remains a significant
unresolved question. Is the phase of the gap constant, does it change sign, or
is it perhaps complex? A detailed answer to this question would provide
important constraints on various pairing mechanisms. Here we propose a new
method for measuring the relative gap PHASE on the Fermi surface which is
direct, is angle-resolved, and probes the bulk. The required experiments
involve measuring phonon linewidths in the normal and superconducting state,
with resolution available in current facilities. We primarily address the
La_1.85Sr_.15CuO_4 material, but also propose a more detailed study of a
specific phonon in Bi_2Sr_2CaCu_2O_8.Comment: 13 pages (revtex) + 5 figures (postscript-included), NSF-ITP-93-2
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