1,328 research outputs found
Distribution and density of the partition function zeros for the diamond-decorated Ising model
Exact renormalization map of temperature between two successive decorated
lattices is given, and the distribution of the partition function zeros in the
complex temperature plane is obtained for any decoration-level. The rule
governing the variation of the distribution pattern as the decoration-level
changes is given. The densities of the zeros for the first two
decoration-levels are calculated explicitly, and the qualitative features about
the densities of higher decoration-levels are given by conjecture. The Julia
set associated with the renormalization map is contained in the distribution of
the zeros in the limit of infinite decoration level, and the formation of the
Julia set in the course of increasing the decoration-level is given in terms of
the variations of the zero density.Comment: 8 pages,8figure
Quasi-particle Lifetimes in a d_{x^2-y^2} Superconductor
We consider the lifetime of quasi-particles in a d-wave superconductor due to
scattering from antiferromagnetic spin-fluctuations, and explicitly separate
the contribution from Umklapp processes which determines the electrical
conductivity. Results for the temperature dependence of the total scattering
rate and the Umklapp scattering rate are compared with relaxation rates
obtained from thermal and microwave conductivity measurements, respectively.Comment: 14 pages, 4 figure
The relative efficacy of different strain combinations of lactic acid bacteria in the reduction of populations of Salmonella enterica Typhimurium in the livers and spleens of mice
Multispecies probiotics have been reported to be more effective than monostrain probiotics in health promoting for the host. In this study, 12 lactic acid bacteria (LAB) strains were selected based on the level of induction of tumor necrosis factor (TNF)-alpha in RAW 264.7 macrophage cells. Their adherence to Caco-2 cells and inhibitory effects on Salmonella invasion of Caco-2 cells were compared. Strains with different probiotic properties were then combined and BALB/c mice were fed with LAB strains for 63 days; then the mice were challenged with Salmonella on day 64. For Salmonella-unchallenged mice that received a multistrain combination of LAB strains that have greater TNF-alpha production in macrophages, greater adherence and inhibit Salmonella invasion of Caco-2 cells to a greater extent, their peritoneal macrophages had greater phagocytic activity. For Salmonella-challenged mice, a significant reduction of Salmonella cells in the livers and spleens of the mice was observed 8 days post challenge. The addition of 12% skim milk powder together with LAB strain combinations significantly enhanced the reduction of Salmonella cells in the mice livers and spleens. In conclusion, we have shown that LAB strain combinations with particular probiotic properties when fed to mice can inhibit Salmonella invasion of the liver and spleen
Kondo effect in systems with dynamical symmetries
This paper is devoted to a systematic exposure of the Kondo physics in
quantum dots for which the low energy spin excitations consist of a few
different spin multiplets . Under certain conditions (to be
explained below) some of the lowest energy levels are nearly
degenerate. The dot in its ground state cannot then be regarded as a simple
quantum top in the sense that beside its spin operator other dot (vector)
operators are needed (in order to fully determine its quantum
states), which have non-zero matrix elements between states of different spin
multiplets . These "Runge-Lenz"
operators do not appear in the isolated dot-Hamiltonian (so in some sense they
are "hidden"). Yet, they are exposed when tunneling between dot and leads is
switched on. The effective spin Hamiltonian which couples the metallic electron
spin with the operators of the dot then contains new exchange terms,
beside the ubiquitous ones . The operators and generate a
dynamical group (usually SO(n)). Remarkably, the value of can be controlled
by gate voltages, indicating that abstract concepts such as dynamical symmetry
groups are experimentally realizable. Moreover, when an external magnetic field
is applied then, under favorable circumstances, the exchange interaction
involves solely the Runge-Lenz operators and the corresponding
dynamical symmetry group is SU(n). For example, the celebrated group SU(3) is
realized in triple quantum dot with four electrons.Comment: 24 two-column page
Knowledge-based energy functions for computational studies of proteins
This chapter discusses theoretical framework and methods for developing
knowledge-based potential functions essential for protein structure prediction,
protein-protein interaction, and protein sequence design. We discuss in some
details about the Miyazawa-Jernigan contact statistical potential,
distance-dependent statistical potentials, as well as geometric statistical
potentials. We also describe a geometric model for developing both linear and
non-linear potential functions by optimization. Applications of knowledge-based
potential functions in protein-decoy discrimination, in protein-protein
interactions, and in protein design are then described. Several issues of
knowledge-based potential functions are finally discussed.Comment: 57 pages, 6 figures. To be published in a book by Springe
Kondo effect in coupled quantum dots: a Non-crossing approximation study
The out-of-equilibrium transport properties of a double quantum dot system in
the Kondo regime are studied theoretically by means of a two-impurity Anderson
Hamiltonian with inter-impurity hopping. The Hamiltonian, formulated in
slave-boson language, is solved by means of a generalization of the
non-crossing approximation (NCA) to the present problem. We provide benchmark
calculations of the predictions of the NCA for the linear and nonlinear
transport properties of coupled quantum dots in the Kondo regime. We give a
series of predictions that can be observed experimentally in linear and
nonlinear transport measurements through coupled quantum dots. Importantly, it
is demonstrated that measurements of the differential conductance , for the appropriate values of voltages and inter-dot tunneling
couplings, can give a direct observation of the coherent superposition between
the many-body Kondo states of each dot. This coherence can be also detected in
the linear transport through the system: the curve linear conductance vs
temperature is non-monotonic, with a maximum at a temperature
characterizing quantum coherence between both Kondo states.Comment: 20 pages, 17 figure
Migration of dissolved organic carbon in biochars and biochar-mineral complexes
The objective of this work was to determine the contribution of dissolved organic carbon (DOC) from a biochar mineral complex (BMC), so as to better understand the interactions between DOC, biochar, clay, and minerals during thermal treatment, and the effects of BMC on amended soils. The BMC was prepared by heating a mixture of a H3PO4-treated saligna biochar from Acacia saligna, clays, other minerals, and chicken manure. The BMC was applied to a sandy loam soil in Western Australia, where wheat was grown. Liquid chromatography-organic carbon detection (LC-OCD) tests were carried out on water extracts from the untreated biochar, the BMC, the BMC-amended soil, and on a control soil to measure the DOC concentration. LC-OCD tests provide a fingerprint of the DOC, which allows the fractions of DOC to be determined. Thermal processing enhanced the reaction of the A. saligna biochar with manure, clays and minerals, and affected the distribution of the DOC fractions. Notably, the process leads to immobilization of hydrophobic DOC and to an increase in the concentration of low-molecular-weight neutrals in the BMC. The application of the BMC to soil increases the DOC in the amended soil, especially the biopolymer fraction
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