1,341 research outputs found
Renormalization group for the probability distribution of magnetic impurities in a random-field model
Extending the usual Ginzburg-Landau theory for the random-field Ising model,
the possibility of dimensional reduction is reconsidered. A renormalization
group for the probability distribution of magnetic impurities is applied. New
parameters corresponding to the extra coupling constants in the
replica Hamiltonian are introduced. Although they do not affect the critical
phenomena near the upper critical dimension, they can when dimensions are
lowered.Comment: 16 pages, 11 figures, revte
The basic K nuclear cluster K- pp and its enhanced formation in the p + p -> K+ + X reaction
We have studied the structure of K- pp nuclear cluster comprehensively by
solving this three-body system exactly in a variational method starting from
the Ansatz that the Lambda(1405) resonance (Lambda*) is a K-p bound state. We
have found that our original prediction for the presence of K-pp as a compact
bound system with M = 2322 GeV/c), leads to
unusually large self-trapping of Lambda* by the participating proton, since the
Lambda*-p system exists as a compact doorway state propagating to K- pp
(R{Lambda*-p} ~ 1.67 fm).Comment: 18 pages, 14 figures. Phys, Rev. C, in pres
Augmentation of ouabain sensitivity of rat liver Na/K‐ATPase by in vivo adenovirus‐mediated expression of the Na/K‐ATPase α2 subunit
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117011/1/feb2s0014579397000872.pd
State Differentiation by Transient Truncation in Coupled Threshold Dynamics
Dynamics with a threshold input--output relation commonly exist in gene,
signal-transduction, and neural networks. Coupled dynamical systems of such
threshold elements are investigated, in an effort to find differentiation of
elements induced by the interaction. Through global diffusive coupling, novel
states are found to be generated that are not the original attractor of
single-element threshold dynamics, but are sustained through the interaction
with the elements located at the original attractor. This stabilization of the
novel state(s) is not related to symmetry breaking, but is explained as the
truncation of transient trajectories to the original attractor due to the
coupling. Single-element dynamics with winding transient trajectories located
at a low-dimensional manifold and having turning points are shown to be
essential to the generation of such novel state(s) in a coupled system.
Universality of this mechanism for the novel state generation and its relevance
to biological cell differentiation are briefly discussed.Comment: 8 pages. Phys. Rev. E. in pres
Proinflammatory T-cell responses to gut microbiota promote experimental autoimmune encephalomyelitis
Although the effects of commensal bacteria on intestinal immune development seem to be profound, it remains speculative whether the gut microbiota influences extraintestinal biological functions. Multiple sclerosis (MS) is a devastating autoimmune disease leading to progressive deterioration of neurological function. Although the cause of MS is unknown, microorganisms seem to be important for the onset and/or progression of disease. However, it is unclear how microbial colonization, either symbiotic or infectious, affects autoimmunity. Herein, we investigate a role for the microbiota during the induction of experimental autoimmune encephalomyelitis (EAE), an animal model for MS. Mice maintained under germ-free conditions develop significantly attenuated EAE compared with conventionally colonized mice. Germ-free animals, induced for EAE, produce lower levels of the proinflammatory cytokines IFN-γ and IL-17A in both the intestine and spinal cord but display a reciprocal increase in CD4^(+)CD25^(+)Foxp3^+ regulatory T cells (Tregs). Mechanistically, we show that gut dendritic cells from germ-free animals are reduced in the ability to stimulate proinflammatory T cell responses. Intestinal colonization with segmented filamentous bacteria (SFB) is known to promote IL-17 production in the gut; here, we show that SFBs also induced IL-17A–producing CD4^+ T cells (Th17) in the CNS. Remarkably, germ-free animals harboring SFBs alone developed EAE, showing that gut bacteria can affect neurologic inflammation. These findings reveal that the intestinal microbiota profoundly impacts the balance between pro- and antiinflammatory immune responses during EAE and suggest that modulation of gut bacteria may provide therapeutic targets for extraintestinal inflammatory diseases such as MS
Arithmetical properties of Multiple Ramanujan sums
In the present paper, we introduce a multiple Ramanujan sum for arithmetic
functions, which gives a multivariable extension of the generalized Ramanujan
sum studied by D. R. Anderson and T. M. Apostol. We then find fundamental
arithmetic properties of the multiple Ramanujan sum and study several types of
Dirichlet series involving the multiple Ramanujan sum. As an application, we
evaluate higher-dimensional determinants of higher-dimensional matrices, the
entries of which are given by values of the multiple Ramanujan sum.Comment: 19 page
Prebiotic Organic Microstructures
Micro- and sub-micrometer spheres, tubules and fiber-filament soft structures have been synthesized in our experiments conducted with 3 MeV proton irradiations of a mixture of simple inorganic constituents, CO, N2 and H2O. We analysed the irradiation products, with scanning electron microscopy (SEM) and atomic force microscopy (AFM). These laboratory organic structures produced wide variety of proteinous and non-proteinous amino acids after HCl hydrolysis. The enantiomer analysis for D-, L- alanine confirmed that the amino acids were abiotically synthesized during the laboratory experiment. Considering hydrothermal activity, the presence of CO2 and H2, of a ferromagnesian silicate mineral environment, of an Earth magnetic field which was much less intense during Archean times than nowadays and consequently of a proton excitation source which was much more abundant, we propose that our laboratory organic microstructures might be synthesized during Archean times. We show similarities in morphology and in formation with some terrestrial Archean microstructures and we suggest that some of the observed Archean carbon spherical and filamentous microstructures might be composed of abiogenic organic molecules. We further propose a search for such prebiotic organic signatures on Mars. This article has been posted on Nature precedings on 21 July 2010 [1]. Extinct radionuclides as source of excitation have been replaced by cosmic radiations which were much more intense 3.5 Ga ago because of a much less intense Earth magnetic field. The new version of the article has been presented at the ORIGINS conference in Montpellier in july 2011 [2] and has since been published in Origins of Life and Evolution of Biospheres 42 (4) 307-316, 2012. 
DOI: 10.1007/s11084-012-9290-5 


Kagome lattice promotes chiral spin fluctuations
Magnetic materials with tilted electron spins often exhibit conducting
behavior that cannot be explained from semiclassical theories without invoking
fictitious (emergent) electromagnetic fields. Quantum-mechanical models
explaining such phenomena are rooted in the concept of a moving quasiparticle's
Berry phase, driven by a chiral (left- or right-handed) spin-habit. Dynamical
and nearly random spin fluctuations, with a slight bent towards left- or
right-handed chirality, represent a promising route to realizing Berry-phase
phenomena at elevated temperatures, but little is known about the effect of
crystal lattice geometry on the resulting macroscopic observables. Here, we
report thermoelectric and electric transport experiments on two metals with
large magnetic moments on a triangular and on a slightly distorted kagom\'e
lattice, respectively. We show that the impact of chiral spin fluctuations is
strongly enhanced for the kagom\'e lattice. Both these spiral magnets have
similar magnetic phase diagrams including a periodic array of magnetic
skyrmions. However, our modelling shows that the geometry of the kagom\'e
lattice, with corner-sharing spin-trimers, helps to avoid cancellation of
Berry-phase contributions; spin fluctuations are endowed with a net chiral
habit already in the thermally disordered (paramagnetic) state. Hence, our
observations for the kagom\,e material contrast with theoretical models
treating magnetization as a continuous field, and emphasize the role of lattice
geometry on emergent electrodynamic phenomena.Comment: 16 pages, 4 figure
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