307 research outputs found
Controlled DNA compaction within chromatin: the tail-bridging effect
We study the mechanism underlying the attraction between nucleosomes, the
fundamental packaging units of DNA inside the chromatin complex. We introduce a
simple model of the nucleosome, the eight-tail colloid, consisting of a charged
sphere with eight oppositely charged, flexible, grafted chains that represent
the terminal histone tails. We demonstrate that our complexes are attracted via
the formation of chain bridges and that this attraction can be tuned by
changing the fraction of charged monomers on the tails. This suggests a
physical mechanism of chromatin compaction where the degree of DNA condensation
can be controlled via biochemical means, namely the acetylation and
deacetylation of lysines in the histone tails.Comment: 4 pages, 5 figures, submitte
Anderson impurity model in nonequilibrium: analytical results versus quantum Monte Carlo data
We analyze the spectral function of the single-impurity two-terminal Anderson
model at finite voltage using the recently developed diagrammatic quantum Monte
Carlo technique as well as perturbation theory. In the
(particle-hole-)symmetric case we find an excellent agreement of the numerical
data with the perturbative results of second order up to interaction strengths
, where is the transparency of the
impurity-electrode interface. The analytical results are obtained in form of
the nonequilibrium self-energy for which we present explicit formulas in the
closed form at arbitrary bias voltage. We observe an increase of the spectral
density around zero energy brought about by the Kondo effect. Our analysis
suggests that a finite applied voltage acts as an effective temperature of
the system. We conclude that at voltages significantly larger than the
equilibrium Kondo temperature there is a complete suppression of the Kondo
effect and no resonance splitting can be observed. We confirm this scenario by
comparison of the numerical data with the perturbative results.Comment: 8 pages, 6 figure
Early prediction of pulmonary outcomes in preterm infants using electrical impedance tomography
INTRODUCTION
Electrical impedance tomography (EIT) allows assessment of ventilation and aeration homogeneity which may be associated with respiratory outcomes in preterm infants.
METHODS
This was a secondary analysis to a recent randomized controlled trial in very preterm infants in the delivery room (DR). The predictive value of various EIT parameters assessed 30 min after birth on important respiratory outcomes (early intubation <24 h after birth, oxygen dependency at 28 days after birth, and moderate/severe bronchopulmonary dysplasia; BPD) was assessed.
RESULTS
Thirty-two infants were analyzed. A lower percentage of aerated lung volume [OR (95% CI) = 0.8 (0.66-0.98), p = 0.027] as well as a higher aeration homogeneity ratio (i.e., more aeration in the non-gravity-dependent lung) predicted the need for supplemental oxygen at 28 days after birth [9.58 (5.16-17.78), p = 0.0028]. Both variables together had a similar predictive value to a model using known clinical contributors. There was no association with intubation or BPD, where numbers were small.
DISCUSSION
In very preterm infants, EIT markers of aeration at 30 min after birth accurately predicted the need for supplemental oxygen at 28 days after birth but not BPD. EIT-guided individualized optimization of respiratory support in the DR may be possible
Object-Oriented Business Solutions
This report summarises the presentations, discussions, and main results of the ECOOP’01 Workshop on Object-Oriented Business Solutions (WOOBS).
It was not a pure scientific meeting, but a mixed gathering where people from the industry and the academia met to exchange ideas, experiences and build a network of relationships with others committed to the emergence of object-oriented business solutions. WOOBS had an invited talk on quality of service, twelve presentations and lively discussions during and after them. The main conclusions were on the importance of Multi-Organisational Web-Based Systems in today’s e-commerce world, which justifies the study of a new multidisciplinary paradigm called Web-Oriented Programming
Wilson chains are not thermal reservoirs
Wilson chains, based on a logarithmic discretization of a continuous
spectrum, are widely used to model an electronic (or bosonic) bath for Kondo
spins and other quantum impurities within the numerical renormalization group
method and other numerical approaches. In this short note we point out that
Wilson chains can not serve as thermal reservoirs as their temperature changes
by a number of order Delta E when a finite amount of energy Delta E is added.
This proves that for a large class of non-equilibrium problems they cannot be
used to predict the long-time behavior.Comment: 2 page
Heisenberg's Uncertainty Relation and Bell Inequalities in High Energy Physics
An effective formalism is developed to handle decaying two-state systems.
Herewith, observables of such systems can be described by a single operator in
the Heisenberg picture. This allows for using the usual framework in quantum
information theory and, hence, to enlighten the quantum feature of such systems
compared to non-decaying systems. We apply it to systems in high energy
physics, i.e. to oscillating meson-antimeson systems. In particular, we discuss
the entropic Heisenberg uncertainty relation for observables measured at
different times at accelerator facilities including the effect of CP violation,
i.e. the imbalance of matter and antimatter. An operator-form of Bell
inequalities for systems in high energy physics is presented, i.e. a
Bell-witness operator, which allows for simple analysis of unstable systems.Comment: 17 page
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