221 research outputs found
Stripes Disorder and Correlation lengths in doped antiferromagnets
For stripes in doped antiferromagnets, we find that the ratio of spin and
charge correlation lenghts, , provide a sharp criterion for
determining the dominant form of disorder in the system. If stripes disorder is
controlled by topological defects then . In contast,
if stripes correlations are disordered primarily by non-topological elastic
deformations (i.e., a Bragg-Glass type of disorder) then is expected. Therefore, the observation of in and in invariably implies that the stripes
are in a Bragg glass type state, and topological defects are much less relevant
than commonly assumed. Expected spectral properties are discussed. Thus, we
establish the basis for any theoretical analysis of the experimentally
obsereved glassy state in these material.Comment: 4 pages, 2 figure
Insertion Loss Estimation of EMI Filters in Unmatched Input/Output Impedance System
One of the problems in the design of powerline EMI filters is the uncertainty and ambiguity of their source/load impedances which results in breach of expected filter parameters in a real installation. The paper presents a simple technique for prediction of insertion loss limit values of EMI filters working in arbitrary unmatched mains line impedance systems
Exact Results for 1D Kondo Lattice from Bosonization
We find a solvable limit to the problem of the 1D electron gas interacting
with a lattice of Kondo scattering centers. In this limit, we present exact
results for the problems of incommensurate filling, commensurate filling,
impurity vacancy states, and the commensurate-incommensurate transition.Comment: 4 pages, two columns, Latex fil
Hypoxia Enhances Differentiation of Adipose Tissue-Derived Stem Cells toward the Smooth Muscle Phenotype.
Smooth muscle differentiated adipose tissue-derived stem cells are a valuable resource for regeneration of gastrointestinal tissues, such as the gut and sphincters. Hypoxia has been shown to promote adipose tissue-derived stem cells proliferation and maintenance of pluripotency, but the influence of hypoxia on their smooth myogenic differentiation remains unexplored. This study investigated the phenotype and contractility of adipose-derived stem cells differentiated toward the smooth myogenic lineage under hypoxic conditions. Oxygen concentrations of 2%, 5%, 10%, and 20% were used during differentiation of adipose tissue-derived stem cells. Real time reverse transcription polymerase chain reaction and immunofluorescence staining were used to detect the expression of smooth muscle cells-specific markers, including early marker smooth muscle alpha actin, middle markers calponin, caldesmon, and late marker smooth muscle myosin heavy chain. The specific contractile properties of cells were verified with both a single cell contraction assay and a gel contraction assay. Five percent oxygen concentration significantly increased the expression levels of α-smooth muscle actin, calponin, and myosin heavy chain in adipose-derived stem cell cultures after 2 weeks of induction (p < 0.01). Cells differentiated in 5% oxygen conditions showed greater contraction effect (p < 0.01). Hypoxia influences differentiation of smooth muscle cells from adipose stem cells and 5% oxygen was the optimal condition to generate smooth muscle cells that contract from adipose stem cells
Localized charged states and phase separation near second order phase transition
Localized charged states and phase segregation are described in the framework
of the phenomenological Ginzburg-Landau theory of phase transitions. The
Coulomb interactions determines the charge distribution and the characteristic
length of the phase separated states. The phase separation with charge
segregation becomes possible because of the large dielectric constant and the
small density of extra charge in the range of charge localization. The phase
diagram is calculated and the energy gain of the phase separated state is
estimated. The role of the Coulomb interaction is elucidated
Stripes: Why hole rich lines are antiphase domain walls?
For stripes of hole rich lines in doped antiferromagnets, we investigate the
competition between anti-phase and in-phase domain wall ground state
configurations. We argue that a phase transition must occure as a function of
the electron/hole filling fraction of the domain wall. Due to {\em transverse}
kinetic hole fluctuations, empty domain walls are always anti-phase. At
arbitrary electron filling fraction () of the domain wall (and in
particular for as in LaNdSrCuO), it is essential to
account also for the transverse magnetic interactions of the electrons and
their mobility {\em along} the domain wall.
We find that the transition from anti-phase to in-phase stripe domain wall
occurs at a critical filling fraction , for any value of
. We further use our model to estimate the spin-wave
velocity in a stripe system. Finally, relate the results of our microscopic
model to previous Landau theory approach to stripes.Comment: 11 pages, 3 figure
Local Moments in an Interacting Environment
We discuss how local moment physics is modified by the presence of
interactions in the conduction sea. Interactions in the conduction sea are
shown to open up new symmetry channels for the exchange of spin with the
localized moment. We illustrate this conclusion in the strong-coupling limit by
carrying out a Schrieffer Wolff transformation for a local moment in an
interacting electron sea, and show that these corrections become very severe in
the approach to a Mott transition. As an example, we show how the Zhang Rice
reduction of a two-band model is modified by these new effects.Comment: Latex file with two postscript figures. Revised version, with more
fully detailed calculation
Transcriptional activation of immediate-early gene ETR101 by human T-cell leukaemia virus type I Tax
Human T-cell leukaemia virus type I (HTLV-I) Tax regulates viral and cellular gene expression through interactions with multiple cellular transcription pathways. This study describes the finding of immediate-early gene ETR101 expression in HTLV-I-infected cells and its regulation by Tax. ETR101 was persistently expressed in HTLV-I-infected cells but not in HTLV-I uninfected cells. Expression of ETR101 was dependent upon Tax expression in the inducible Tax-expressing cell line JPX-9 and also in Jurkat cells transiently transfected with Tax-expressing vectors. Tax transactivated the ETR101 gene promoter in a transient transfection assay. A series of deletion and mutation analyses of the ETR101 gene promoter indicated that a 35 bp region immediately upstream of the TATA-box sequence, which contains a consensus cAMP response element (CRE) and a G+C-rich sequence, is the critical responsive element for Tax activation. Site-directed mutagenesis analysis of the 35 bp region suggested that both the consensus CRE motif and its upstream G+C-rich sequence were critical for Tax transactivation. Electrophoretic mobility shift analysis (EMSA) using the 35 bp sequence as probe showed the formation of a specific protein-DNA complex in HTLV-I-infected cell lines. EMSA with specific antibodies confirmed that the CREB transcription factor was responsible for formation of this specific protein-DNA complex. These results suggested that Tax directly transactivated ETR101 gene expression, mainly through a CRE sequence via the CREB transcription pathway.published_or_final_versio
Topological Excitations of One-Dimensional Correlated Electron Systems
Properties of low-energy excitations in one-dimensional superconductors and
density-wave systems are examined by the bosonization technique. In addition to
the usual spin and charge quantum numbers, a new, independently measurable
attribute is introduced to describe elementary, low-energy excitations. It can
be defined as a number w which determines, in multiple of , how many times
the phase of the order parameter winds as an excitation is transposed from far
left to far right. The winding number is zero for electrons and holes with
conventional quantum numbers, but it acquires a nontrivial value w=1 for
neutral spin-1/2 excitations and for spinless excitations with a unit electron
charge. It may even be irrational, if the charge is irrational. Thus, these
excitations are topological, and they can be viewed as composite particles made
of spin or charge degrees of freedom and dressed by kinks in the order
parameter.Comment: 5 pages. And we are not only splitting point
Classification and Stability of Phases of the Multicomponent One-Dimensional Electron Gas
The classification of the ground-state phases of complex one-dimensional
electronic systems is considered in the context of a fixed-point strategy.
Examples are multichain Hubbard models, the Kondo-Heisenberg model, and the
one-dimensional electron gas in an active environment. It is shown that, in
order to characterize the low-energy physics, it is necessary to analyze the
perturbative stability of the possible fixed points, to identify all discrete
broken symmetries, and to specify the quantum numbers and elementary wave
vectors of the gapless excitations. Many previously-proposed exotic phases of
multichain Hubbard models are shown to be unstable because of the ``spin-gap
proximity effect.'' A useful tool in this analysis is a new generalization of
Luttinger's theorem, which shows that there is a gapless even-charge mode in
any incommensurate N-component system.Comment: 15 pages revtex. Final version as publishe
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