1,842 research outputs found
Shot noise in the chaotic-to-regular crossover regime
We investigate the shot noise for phase-coherent quantum transport in the
chaotic-to-regular crossover regime. Employing the Modular Recursive Green's
Function Method for both ballistic and disordered two-dimensional cavities we
find the Fano factor and the transmission eigenvalue distribution for regular
systems to be surprisingly similar to those for chaotic systems. We argue that
in the case of regular dynamics in the cavity, diffraction at the lead openings
is the dominant source of shot noise. We also explore the onset of the
crossover from quantum to classical transport and develop a quasi-classical
transport model for shot noise suppression which agrees with the numerical
quantum data.Comment: 4 pages, 3 figures, submitted to Phys.Rev.Let
PCDAmpl, a new antigen at the interface of the embryonic collecting duct epithelium and the nephrogenic mesenchyme
P CDAmpl, a new antigen at the interface of the embryonic collecting duct epithelium and the nephrogenic mesenchyme. In the neonatal rabbit kidney nephrogenesis is not yet terminated. The ampullar collecting duct epithelium acts as an inducer that generates the nephron anlagen, however, to date the morphogenic mechanisms involved are unknown. A presupposition for successful nephron induction is the close tissue interaction between the basal aspect of the ampullar collecting duct epithelium and the surrounding mesenchyme. To gain new insights in this area we raised monoclonal antibodies (mabs), to identify specific structures localized at the tissue interface. With the generated mab CDAmpl we found an intensive immunohistochemical reaction between the basal aspect of the ampullar collecting duct epithelium and the mesenchyme. The label was most concentrated at the ampullar tip and continuously decreased in the shaft region. In the maturing collecting duct of the neonatal kidney and in the adult renal collecting duct no immunohistochemical reaction was found. The binding pattern of mab CDAmpl is different from that of all known collecting duct cell markers and from antibodies against known basement membrane compounds such as laminin or collagen type IV. Under in vitro conditions immunoreactivity with mab CDAmpl was obtained using embryonic collecting duct epithelia and perfusion culture. The antigen was present in specimens treated with Iscove's modified Dulbecco's Medium (IMDM) containing 10% fetal bovine serum. Omittance of serum or hormonal treatment with aldosterone, insulin or vitamin D3 led to the disappearance of the newly detected antigen, while characteristics of the differentiated collecting duct cells were up-regulated. We conclude that the expression of P CDAmpl is a characteristic feature of the embryonic parts of the collecting duct epithelium. It may play a pivotal role during nephron induction
Uniform generation in trace monoids
We consider the problem of random uniform generation of traces (the elements
of a free partially commutative monoid) in light of the uniform measure on the
boundary at infinity of the associated monoid. We obtain a product
decomposition of the uniform measure at infinity if the trace monoid has
several irreducible components-a case where other notions such as Parry
measures, are not defined. Random generation algorithms are then examined.Comment: Full version of the paper in MFCS 2015 with the same titl
Quantum Hall transitions: An exact theory based on conformal restriction
We revisit the problem of the plateau transition in the integer quantum Hall
effect. Here we develop an analytical approach for this transition, based on
the theory of conformal restriction. This is a mathematical theory that was
recently developed within the context of the Schramm-Loewner evolution which
describes the stochastic geometry of fractal curves and other stochastic
geometrical fractal objects in 2D space. Observables elucidating the connection
with the plateau transition include the so-called point-contact conductances
(PCCs) between points on the boundary of the sample, described within the
language of the Chalker-Coddington network model. We show that the
disorder-averaged PCCs are characterized by classical probabilities for certain
geometric objects in the plane (pictures), occurring with positive statistical
weights, that satisfy the crucial restriction property with respect to changes
in the shape of the sample with absorbing boundaries. Upon combining this
restriction property with the expected conformal invariance at the transition
point, we employ the mathematical theory of conformal restriction measures to
relate the disorder-averaged PCCs to correlation functions of primary operators
in a conformal field theory (of central charge ). We show how this can be
used to calculate these functions in a number of geometries with various
boundary conditions. Since our results employ only the conformal restriction
property, they are equally applicable to a number of other critical disordered
electronic systems in 2D. For most of these systems, we also predict exact
values of critical exponents related to the spatial behavior of various
disorder-averaged PCCs.Comment: Published versio
RNA-binding protein CPEB1 remodels host and viral RNA landscapes.
Host and virus interactions occurring at the post-transcriptional level are critical for infection but remain poorly understood. Here, we performed comprehensive transcriptome-wide analyses revealing that human cytomegalovirus (HCMV) infection results in widespread alternative splicing (AS), shortening of 3' untranslated regions (3' UTRs) and lengthening of poly(A)-tails in host gene transcripts. We found that the host RNA-binding protein CPEB1 was highly induced after infection, and ectopic expression of CPEB1 in noninfected cells recapitulated infection-related post-transcriptional changes. CPEB1 was also required for poly(A)-tail lengthening of viral RNAs important for productive infection. Strikingly, depletion of CPEB1 reversed infection-related cytopathology and post-transcriptional changes, and decreased productive HCMV titers. Host RNA processing was also altered in herpes simplex virus-2 (HSV-2)-infected cells, thereby indicating that this phenomenon might be a common occurrence during herpesvirus infections. We anticipate that our work may serve as a starting point for therapeutic targeting of host RNA-binding proteins in herpesvirus infections
Single-crossover dynamics: finite versus infinite populations
Populations evolving under the joint influence of recombination and
resampling (traditionally known as genetic drift) are investigated. First, we
summarise and adapt a deterministic approach, as valid for infinite
populations, which assumes continuous time and single crossover events. The
corresponding nonlinear system of differential equations permits a closed
solution, both in terms of the type frequencies and via linkage disequilibria
of all orders. To include stochastic effects, we then consider the
corresponding finite-population model, the Moran model with single crossovers,
and examine it both analytically and by means of simulations. Particular
emphasis is on the connection with the deterministic solution. If there is only
recombination and every pair of recombined offspring replaces their pair of
parents (i.e., there is no resampling), then the {\em expected} type
frequencies in the finite population, of arbitrary size, equal the type
frequencies in the infinite population. If resampling is included, the
stochastic process converges, in the infinite-population limit, to the
deterministic dynamics, which turns out to be a good approximation already for
populations of moderate size.Comment: 21 pages, 4 figure
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