7,835 research outputs found
Spectral properties and magneto-optical excitations in semiconductor double-rings under Rashba spin-orbit interaction
We have numerically solved the Hamiltonian of an electron in a semiconductor
double ring subjected to the magnetic flux and Rashba spin-orbit interaction.
It is found that the Aharonov-Bohm energy spectrum reveals multi-zigzag
periodic structures. The investigations of spin-dependent electron dynamics via
Rabi oscillations in two-level and three-level systems demonstrate the
possibility of manipulating quantum states. Our results show that the optimal
control of photon-assisted inter-ring transitions can be achieved by employing
cascade-type and -type transition mechanisms. Under chirped pulse
impulsions, a robust and complete transfer of an electron to the final state is
shown to coincide with the estimation of the Landau-Zener formula.Comment: RevTex, 9 pages, 5 figure
The quantum mechanical geometric phase of a particle in a resonant vibrating cavity
We study the general-setting quantum geometric phase acquired by a particle
in a vibrating cavity. Solving the two-level theory with the rotating-wave
approximation and the SU(2) method, we obtain analytic formulae that give
excellent descriptions of the geometric phase, energy, and wavefunction of the
resonating system. In particular, we observe a sudden -jump in the
geometric phase when the system is in resonance. We found similar behaviors in
the geometric phase of a spin-1/2 particle in a rotating magnetic field, for
which we developed a geometrical model to help visualize its evolution.Comment: 15pages,6figure
Derivation of therapeutic lung spheroid cells from minimally invasive transbronchial pulmonary biopsies
BACKGROUND: Resident stem and progenitor cells have been identified in the lung over the last decade, but isolation and culture of these cells remains a challenge. Thus, although these lung stem and progenitor cells provide an ideal source for stem-cell based therapy, mesenchymal stem cells (MSCs) remain the most popular cell therapy product for the treatment of lung diseases. Surgical lung biopsies can be the tissue source but such procedures carry a high risk of mortality.
METHODS: In this study we demonstrate that therapeutic lung cells, termed "lung spheroid cells" (LSCs) can be generated from minimally invasive transbronchial lung biopsies using a three-dimensional culture technique. The cells were then characterized by flow cytometry and immunohistochemistry. Angiogenic potential was tested by in-vitro HUVEC tube formation assay. In-vivo bio- distribution of LSCs was examined in athymic nude mice after intravenous delivery.
RESULTS: From one lung biopsy, we are able to derive >50 million LSC cells at Passage 2. These cells were characterized by flow cytometry and immunohistochemistry and were shown to represent a mixture of lung stem cells and supporting cells. When introduced systemically into nude mice, LSCs were retained primarily in the lungs for up to 21 days.
CONCLUSION: Here, for the first time, we demonstrated that direct culture and expansion of human lung progenitor cells from pulmonary tissues, acquired through a minimally invasive biopsy, is possible and straightforward with a three-dimensional culture technique. These cells could be utilized in long-term expansion of lung progenitor cells and as part of the development of cell-based therapies for the treatment of lung diseases such as chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF)
Influenza Vaccine Effectiveness against Hospitalisation with Confirmed Influenza in the 2010-11 Seasons: A Test-negative Observational Study
Immunisation programs are designed to reduce serious morbidity and mortality from influenza, but most evidence supporting the effectiveness of this intervention has focused on disease in the community or in primary care settings. We aimed to examine the effectiveness of influenza vaccination against hospitalisation with confirmed influenza. We compared influenza vaccination status in patients hospitalised with PCR-confirmed influenza with patients hospitalised with influenza-negative respiratory infections in an Australian sentinel surveillance system. Vaccine effectiveness was estimated from the odds ratio of vaccination in cases and controls. We performed both simple multivariate regression and a stratified analysis based on propensity score of vaccination. Vaccination status was ascertained in 333 of 598 patients with confirmed influenza and 785 of 1384 test-negative patients. Overall estimated crude vaccine effectiveness was 57% (41%, 68%). After adjusting for age, chronic comorbidities and pregnancy status, the estimated vaccine effectiveness was 37% (95% CI: 12%, 55%). In an analysis accounting for a propensity score for vaccination, the estimated vaccine effectiveness was 48.3% (95% CI: 30.0, 61.8%). Influenza vaccination was moderately protective against hospitalisation with influenza in the 2010 and 2011 seasons
Cosmic microwave background polarization, Faraday rotation and stochastic gravity-waves backgrounds
A magnetic field, coherent over the horizon size at the decoupling and strong
enough to rotate the polarization plane of the CMBR, can be generated from the
electromagnetic vacuum fluctuations amplified by the space-time evolution of
the dilaton coupling. The possible relevance of this result for superstring
inspired cosmological models is discussed. Particular attention will be paid to
the connection between Faraday rotation signals and stochastic gravity-wave
backgrounds.Comment: 24 A4 pages in Latex style plus two figures combined into an eps
file, accepted for publication in Physical Review
Wetting transitions of Ne
We report studies of the wetting behavior of Ne on very weakly attractive
surfaces, carried out with the Grand Canonical Monte Carlo method. The Ne-Ne
interaction was taken to be of Lennard-Jones form, while the Ne-surface
interaction was derived from an ab initio calculation of Chizmeshya et al.
Nonwetting behavior was found for Li, Rb, and Cs in the temperature regime
explored (i.e., T < 42 K). Drying behavior was manifested in a depleted fluid
density near the Cs surface. In contrast, for the case of Mg (a more attractive
potential) a prewetting transition was found near T= 28 K. This temperature was
found to shift slightly when a corrugated potential was used instead of a
uniform potential. The isotherm shape and the density profiles did not differ
qualitatively between these cases.Comment: 22 pages, 12 figures, submitted to Phys. Rev.
Cosmic Microwave Background Anisotropies from Scaling Seeds: Global Defect Models
We investigate the global texture model of structure formation in cosmogonies
with non-zero cosmological constant for different values of the Hubble
parameter. We find that the absence of significant acoustic peaks and little
power on large scales are robust predictions of these models. However, from a
careful comparison with data we conclude that at present we cannot safely
reject the model on the grounds of present CMB data. Exclusion by means of
galaxy correlation data requires assumptions on biasing and statistics. New,
very stringent constraints come from peculiar velocities.
Investigating the large-N limit, we argue that our main conclusions apply to
all global O(N) models of structure formation.Comment: LaTeX file with RevTex, 27 pages, 23 eps figs., submitted to Phys.
Rev. D. A version with higher quality images can be found at
http://mykonos.unige.ch/~kunz/download/lam.tar.gz for the LaTeX archive and
at http://mykonos.unige.ch/~kunz/download/lam.ps.gz for the compiled
PostScript fil
Report on the Third Workshop on Sustainable Software for Science: Practice and Experiences (WSSSPE3)
This report records and discusses the Third Workshop on Sustainable Software
for Science: Practice and Experiences (WSSSPE3). The report includes a
description of the keynote presentation of the workshop, which served as an
overview of sustainable scientific software. It also summarizes a set of
lightning talks in which speakers highlighted to-the-point lessons and
challenges pertaining to sustaining scientific software. The final and main
contribution of the report is a summary of the discussions, future steps, and
future organization for a set of self-organized working groups on topics
including developing pathways to funding scientific software; constructing
useful common metrics for crediting software stakeholders; identifying
principles for sustainable software engineering design; reaching out to
research software organizations around the world; and building communities for
software sustainability. For each group, we include a point of contact and a
landing page that can be used by those who want to join that group's future
activities. The main challenge left by the workshop is to see if the groups
will execute these activities that they have scheduled, and how the WSSSPE
community can encourage this to happen
Thermal Degradation of Adsorbed Bottle-Brush Macromolecules: Molecular Dynamics Simulation
The scission kinetics of bottle-brush molecules in solution and on an
adhesive substrate is modeled by means of Molecular Dynamics simulation with
Langevin thermostat. Our macromolecules comprise a long flexible polymer
backbone with segments, consisting of breakable bonds, along with two side
chains of length , tethered to each segment of the backbone. In agreement
with recent experiments and theoretical predictions, we find that bond cleavage
is significantly enhanced on a strongly attractive substrate even though the
chemical nature of the bonds remains thereby unchanged.
We find that the mean bond life time decreases upon adsorption by
more than an order of magnitude even for brush molecules with comparatively
short side chains $N=1 \div 4$. The distribution of scission probability along
the bonds of the backbone is found to be rather sensitive regarding the
interplay between length and grafting density of side chains. The life time
declines with growing contour length as ,
and with side chain length as . The probability
distribution of fragment lengths at different times agrees well with
experimental observations. The variation of the mean length of the
fragments with elapsed time confirms the notion of the thermal degradation
process as a first order reaction.Comment: 15 pages, 7 figure
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