1,285 research outputs found
A Field-Theoretic Approach to Connes' Gauge Theory on
Connes' gauge theory on is reformulated in the Lagrangian
level. It is pointed out that the field strength in Connes' gauge theory is not
unique. We explicitly construct a field strength different from Connes' one and
prove that our definition leads to the generation-number independent Higgs
potential. It is also shown that the nonuniqueness is related to the assumption
that two different extensions of the differential geometry are possible when
the extra one-form basis is introduced to define the differential
geometry on . Our reformulation is applied to the standard model
based on Connes' color-flavor algebra. A connection between the unimodularity
condition and the electric charge quantization is then discussed in the
presence or absence of .Comment: LaTeX file, 16 page
Level spectroscopy of the square-lattice three-state Potts model with a ferromagnetic next-nearest-neighbor coupling
We study the square-lattice three-state Potts model with the ferromagnetic
next-nearest-neighbor coupling at finite temperature. Using the
level-spectroscopy method, we numerically analyze the excitation spectrum of
the transfer matrices and precisely determine the global phase diagram. Then we
find that, contrary to a previous result based on the finite-size scaling, the
massless region continues up to the decoupling point with criticality in the antiferromagnetic region. We also check the universal
relations among excitation levels to provide the reliability of our result.Comment: 4 pages, 2 figure
An improved method for the in vitro differentiation of Plasmodium falciparum gametocytes into ookinetes
<p>Abstract</p> <p>Background</p> <p>Ookinete is the form of the malaria parasite that invades the mosquito midgut epithelium to initiate sporogony. Differentiation of ingested gametocytes into ookinetes in the mosquito midgut lumen and subsequent interaction with the lumenal surface of the midgut epithelium in preparation for invasion is a complex and multi-stepped process. To facilitate the study of these events in detail it is necessary to produce sufficient numbers of pure, fully mature and functional ookinetes. However, production of even a small number of <it>Plasmodium </it><it>falciparum </it>ookinetes <it>in vitro </it>has proven to be a daunting task. Consequently, over the past four decades our collective understanding of the biology of this parasite form remains sorely deficient. This article reports on investigations of five different ookinete media, in an effort to improve the <it>in vitro </it>transformation efficiency of <it>P. falciparum </it>gametocytes into mature ookinetes and their infectivity of the mosquito midgut.</p> <p>Methods</p> <p>Five different ookinete media were evaluated for their ability to support the differentiation of gametocytes into gametes and further into mature stage V ookinetes. Moreover, infectivity of the <it>in vitro</it>-transformed ookinetes was evaluated by feeding them to vector mosquitoes and measuring their ability to traverse the midgut and form oocysts.</p> <p>Results</p> <p>One of the five media (medium E) was clearly superior in that the cultured ookinetes produced the largest number of oocysts when fed to mosquitoes. Key components were additions of human serum, human red blood cell lysate and mosquito pupal extract, resulting in the production of larger numbers of ookinetes able to develop into oocysts when fed to mosquitoes.</p> <p>Conclusion</p> <p>This simple and practical improvement over the prevailing methodology will facilitate the investigation of how this important human malaria parasite initiates its development in the mosquito and will contribute to the understanding of its transmission biology.</p
Global phase diagram and six-state clock universality behavior in the triangular antiferromagnetic Ising model with anisotropic next-nearest-neighbor coupling: Level-spectroscopy approach
We investigate the triangular-lattice antiferromagnetic Ising model with a
spatially anisotropic next-nearest-neighbor ferromagnetic coupling, which was
first discussed by Kitatani and Oguchi. By employing the effective geometric
factor, we analyze the scaling dimensions of the operators around the
Berezinskii-Kosterlitz-Thouless (BKT) transition lines, and determine the
global phase diagram. Our numerical data exhibit that two types of
BKT-transition lines separate the intermediate critical region from the ordered
and disordered phases, and they do not merge into a single curve in the
antiferromagnetic region. We also estimate the central charge and perform some
consistency checks among scaling dimensions in order to provide the evidence of
the six-state clock universality. Further, we provide an analysis of the shapes
of boundaries based on the crossover argument.Comment: 8 pages, 5 figure
OsYSL16 plays a role in the allocation of iron
Graminaceous plants acquire iron by secreting mugineic acid family phytosiderophores into the rhizosphere and taking up complexes of iron and phytosiderophores through YSL (yellow stripe 1-like) transporters. Rice OsYSL15 is a transporter of the iron(III)-2′-deoxymugineic acid complex. OsYSL16 has 85 % similarity to both OsYSL15 and the iron(II)-nicotianamine transporter OsYSL2. In the present study, we show that OsYSL16 functionally complemented a yeast mutant defective in iron uptake when grown on medium containing iron(III)-deoxymugineic acid, but not when grown on medium containing iron(II)-nicotianamine. OsYSL16-knockdown seedlings were smaller than wild-type seedlings when only iron(III)chloride was supplied as an iron source. The iron concentration in shoots of OsYSL16-knockdown plants was similar to that of the wild type; however, they showed more severe chlorosis than wild-type plants under iron-deficient conditions. Furthermore, OsYSL16-knockdown plants accumulated more iron in the vascular bundles of the leaves. Expression of the OsYSL16 promoter fused to the β-glucuronidase gene showed that OsYSL16 is expressed in the root epidermis and vascular bundles of whole plants. The expression was typically observed around the xylem. In the vascular bundles of unelongated nodes, it was detected in the xylem of old leaves and the phloem of new leaves. Graminaceous plants translocate iron from the roots to old leaves mainly via the xylem and to new leaves mainly via the phloem. Our results suggest that OsYSL16 plays a role in the allocation of iron(III)-deoxymugineic acid via the vascular bundles. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11103-012-9930-1) contains supplementary material, which is available to authorized users
Magnetic Field-Induced Superconductor-Insulator-Metal Transition in an Organic Conductor: An Infrared Magneto-Optical Imaging Spectroscopy
The magnetic field-induced superconductor-insulator-metal transition (SIMT)
in partially deuterated -(BEDT-TTF)Cu[N(CN)]Br, which is just
on the Mott boundary, has been observed using the infrared magneto-optical
imaging spectroscopy. The infrared reflectivity image on the sample surface
revealed that the metallic (or superconducting) and insulating phases coexist
and they have different magnetic field dependences. One of the magnetic field
dependence is SIMT that appeared on part of the sample surface. The SIMT was
concluded to originate from the balance of the inhomogenity in the sample
itself and the disorder of the ethylene end groups resulting from fast cooling.Comment: 5 pages, 5 figures, to appear in Phys. Rev.
Black holes and a scalar field in an expanding universe
We consider a model of an inhomogeneous universe including a massless scalar
field, where the inhomogeneity is assumed to consist of many black holes. This
model can be constructed by following Lindquist and Wheeler, which has already
been investigated without including scalar field to show that an averaged scale
factor coincides with that of the Friedmann model. In this work we construct
the inhomogeneous universe with an massless scalar field, where we assume that
the averaged scale factor and scalar field are given by those of the Friedmann
model including a scalar field. All of our calculations are carried out in the
framework of Brans-Dicke gravity. In constructing the model of an inhomogeneous
universe, we define the mass of a black hole in the Brans-Dicke expanding
universe which is equivalent to ADM mass if the mass evolves adiabatically, and
obtain an equation relating our mass to the averaged scalar field and scale
factor. As the results we find that the mass has an adiabatic time dependence
in a sufficiently late stage of the expansion of the universe, and that the
time dependence is qualitatively diffenrent according to the sign of the
curvature of the universe: the mass increases decelerating in the closed
universe case, is constant in the flat case and decreases decelerating in the
open case. It is also noted that the mass in the Einstein frame depends on
time. Our results that the mass has a time dependence should be retained even
in the general scalar-tensor gravitiy with a scalar field potential.
Furthermore, we discuss the relation of our results to the uniqueness theorem
of black hole spacetime and gravitational memory effect.Comment: 16 pages, 3 tables, 5 figure
On the Limits of Analogy Between Self-Avoidance and Topology-Driven Swelling of Polymer Loops
The work addresses the analogy between trivial knotting and excluded volume
in looped polymer chains of moderate length, , where the effects of
knotting are small. A simple expression for the swelling seen in trivially
knotted loops is described and shown to agree with simulation data. Contrast
between this expression and the well known expression for excluded volume
polymers leads to a graphical mapping of excluded volume to trivial knots,
which may be useful for understanding where the analogy between the two
physical forms is valid. The work also includes description of a new method for
the computational generation of polymer loops via conditional probability.
Although computationally intensive, this method generates loops without
statistical bias, and thus is preferable to other loop generation routines in
the region .Comment: 10 pages, 5 figures, supplementary tex file and datafil
Monte Carlo study of the antiferromagnetic three-state Potts model with staggered polarization field on the square lattice
Using the Wang-Landau Monte Carlo method, we study the antiferromagnetic (AF)
three-state Potts model with a staggered polarization field on the square
lattice. We obtain two phase transitions; one belongs to the ferromagnetic
three-state Potts universality class, and the other to the Ising universality
class. The phase diagram obtained is quantitatively consistent with the
transfer matrix calculation. The Ising transition in the large nearest-neighbor
interaction limit has been made clear by the detailed analysis of the energy
density of states.Comment: accepted for publication in J. Phys.
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