135 research outputs found
Structure Constant of the Yang-Lee Edge Singularity
This paper studies the Yang-Lee singularity of the 2-dimensional Ising model
on the cylinder via transfer matrix and finite-size scaling techniques. These
techniques enable a measurement of the 2-point and 3-point correlations and a
comparison of a measurement of a corresponding universal amplitude with a
prediction for the amplitude from the (A4,A1) minimal conformal field theory.Comment: 1 figur
Excitation Spectrum at the Yang-Lee Edge Singularity of 2D Ising Model on the Strip
At the Yang-Lee edge singularity, finite-size scaling behavior is used to
measure the low-lying excitation spectrum of the Ising quantum spin chain for
free boundary conditions. The measured spectrum is used to identify the CFT
that describes the Yang-Lee edge singularity of the 2D Ising model for free
boundary conditions.Comment: 7 pages, 1 figur
Critical Excitation Spectrum of Quantum Chain With A Local 3-Spin Coupling
This article reports a measurement of the low-energy excitation spectrum
along the critical line for a quantum spin chain having a local interaction
between three Ising spins and longitudinal and transverse magnetic fields. The
measured excitation spectrum agrees with that predicted by the (D, A)
conformal minimal model under a nontrivial correspondence between translations
at the critical line and discrete lattice translations. Under this
correspondence, the measurements confirm a prediction that the critical line of
this quantum spin chain and the critical point of the 2D 3-state Potts model
are in the same universality class.Comment: 7 pages, 2 figure
Chiral Symmetry Breaking in Bent-Core Liquid Crystals
By molecular modeling we demonstrate that the nematic long-range order
discovered in bent-core liquid crystal systems should reveal further spatially
homogeneous phases. Two of them are identified as a tetrahedratic nematic
() phase with symmetry and a chiral tetrahedratic nematic
() phase with symmetry. These new phases were found for a lattice
model with quadrupolar and octupolar anisotropic interactions using Mean Field
theory and Monte Carlo simulations. The phase diagrams exhibit tetrahedratic
(), and phases, in addition to ordinary isotropic (),
uniaxial nematic () and biaxial nematic () phases. To our knowledge,
this is the first molecular model with spontaneous chiral symmetry breaking in
non-layered systems.Comment: 12 pages, 4 figures, submitted for publicatio
Oxysterols Versus Cholesterol in Model Neuronal Membrane. I. The Case of 7-Ketocholesterol. The Langmuir Monolayer Study
On the connection of the generalized nonlinear sigma model with constrained stochastic dynamics
The dynamics of a freely jointed chain in the continuous limit is described
by a field theory which closely resembles the nonlinear sigma model. The
generating functional of this field theory contains nonholonomic
constraints, which are imposed by inserting in the path integral expressing
a suitable product of delta functions. The same procedure is commonly
applied in statistical mechanics in order to enforce topological conditions on
a system of linked polymers. The disadvantage of this method is that the
contact with the stochastic process governing the diffusion of the chain is
apparently lost. The main goal of this work is to reestablish this contact. To
this purpose, it is shown here that the generating functional
coincides with the generating functional of the correlation functions of the
solutions of a constrained Langevin equation. In the discrete case, this
Langevin equation describes as expected the Brownian motion of beads connected
together by links of fixed length.Comment: LaTeX+RevTeX, 12 pages, no figure
Hypersensitive to Red and Blue 1 and Its Modification by Protein Phosphatase 7 Are Implicated in the Control of Arabidopsis Stomatal Aperture
The stomatal pores are located on the plant leaf epidermis and regulate CO2 uptake for photosynthesis and the loss of water by transpiration. Their stomatal aperture therefore affects photosynthesis, water use efficiency, and agricultural crop yields. Blue light, one of the environmental signals that regulates the plant stomatal aperture, is perceived by the blue/UV-A light-absorbing cryptochromes and phototropins. The signal transduction cascades that link the perception of light to the stomatal opening response are still largely unknown. Here, we report two new players, Hypersensitive to Red and Blue 1 (HRB1) and Protein Phosphatase 7 (PP7), and their genetic and biochemical interactions in the control of stomatal aperture. Mutations in either HRB1 or PP7 lead to the misregulation of the stomatal aperture and reduce water loss under blue light. Both HRB1 and PP7 are expressed in the guard cells in response to a light-to-dark or dark-to-light transition. HRB1 interacts with PP7 through its N-terminal ZZ-type zinc finger motif and requires a functional PP7 for its stomatal opening response. HRB1 is phosphorylated in vivo, and PP7 can dephosphorylate HRB1. HRB1 is mostly dephosphorylated in a protein complex of 193 kDa in the dark, and blue light increases complex size to 285 kDa. In the pp7 mutant, this size shift is impaired, and HRB1 is predominately phosphorylated. We propose that a modification of HRB1 by PP7 under blue light is essential to acquire a proper conformation or to bring in new components for the assembly of a functional HRB1 protein complex. Guard cells control stomatal opening in response to multiple environmental or biotic stimuli. This study may furnish strategies that allow plants to enjoy the advantages of both constitutive and ABA-induced protection under water-limiting conditions
Prebiotic Effects of Wheat Arabinoxylan Related to the Increase in Bifidobacteria, Roseburia and Bacteroides/Prevotella in Diet-Induced Obese Mice
BACKGROUND: Alterations in the composition of gut microbiota--known as dysbiosis--has been proposed to contribute to the development of obesity, thereby supporting the potential interest of nutrients targeting the gut with beneficial effect for host adiposity. We test the ability of a specific concentrate of water-extractable high molecular weight arabinoxylans (AX) from wheat to modulate both the gut microbiota and lipid metabolism in high-fat (HF) diet-induced obese mice. METHODOLOGY/PRINCIPAL FINDINGS: Mice were fed either a control diet (CT) or a HF diet, or a HF diet supplemented with AX (10% w/w) during 4 weeks. AX supplementation restored the number of bacteria that were decreased upon HF feeding, i.e. Bacteroides-Prevotella spp. and Roseburia spp. Importantly, AX treatment markedly increased caecal bifidobacteria content, in particular Bifidobacterium animalis lactis. This effect was accompanied by improvement of gut barrier function and by a lower circulating inflammatory marker. Interestingly, rumenic acid (C18:2 c9,t11) was increased in white adipose tissue due to AX treatment, suggesting the influence of gut bacterial metabolism on host tissue. In parallel, AX treatment decreased adipocyte size and HF diet-induced expression of genes mediating differentiation, fatty acid uptake, fatty acid oxidation and inflammation, and decreased a key lipogenic enzyme activity in the subcutaneous adipose tissue. Furthermore, AX treatment significantly decreased HF-induced adiposity, body weight gain, serum and hepatic cholesterol accumulation and insulin resistance. Correlation analysis reveals that Roseburia spp. and Bacteroides/Prevotella levels inversely correlate with these host metabolic parameters. CONCLUSIONS/SIGNIFICANCE: Supplementation of a concentrate of water-extractable high molecular weight AX in the diet counteracted HF-induced gut dysbiosis together with an improvement of obesity and lipid-lowering effects. We postulate that hypocholesterolemic, anti-inflammatory and anti-obesity effects are related to changes in gut microbiota. These data support a role for wheat AX as interesting nutrients with prebiotic properties related to obesity prevention
Biology of moderately halophilic aerobic bacteria
The moderately halophilic heterotrophic aerobic bacteria form a diverse group of microorganisms. The property of halophilism is widespread within the bacterial domain. Bacterial halophiles are abundant in environments such as salt lakes, saline soils, and salted food products. Most species keep their intracellular ionic concentrations at low levels while synthesizing or accumulating organic solutes to provide osmotic equilibrium of the cytoplasm with the surrounding medium. Complex mechanisms of adjustment of the intracellular environments and the properties of the cytoplasmic membrane enable rapid adaptation to changes in the salt concentration of the environment. Approaches to the study of genetic processes have recently been developed for several moderate halophiles, opening the way toward an understanding of haloadaptation at the molecular level. The new information obtained is also expected to contribute to the development of novel biotechnological uses for these organisms
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