1,144 research outputs found
The Multiphase Intracluster Medium in Galaxy Groups Probed by the Lyman Alpha Forest
The case is made that the intracluster medium (ICM) in spiral-rich galaxy
groups today probably has undergone much slower evolution than that in
elliptical-rich groups and clusters. The environments of proto-clusters and
proto-groups at z > 2 are likely similar to spiral-rich group environments at
lower redshift. Therefore, like the ICM in spiral-rich groups today, the ICM in
proto-groups and proto-clusters at z > 2 is predicted to be significantly
multiphased. The QSO Lyman alpha forest in the vicinity of galaxies is an
effective probe of the ICM at a wide range of redshift. Two recent observations
of Lyman alpha absorption around galaxies by Adelberger et al. and by
Pascarelle et al are reconciled, and it is shown that observations support the
multiphase ICM scenario. Galaxy redshifts must be very accurate for such
studies to succeed. This scenario can also explain the lower metallicity and
lower hot gas fraction in groups.Comment: 4 pages, 1 figure, replaced with the version after proo
Mirroring everyday clinical practice in clinical trial design: a new concept to improve the external validity of randomized double-blind placebo-controlled trials in the pharmacological treatment of major depression
Background: Randomized, double-blind, placebo-controlled trials constitute the gold standard in clinical research when testing the efficacy of new psychopharmacological interventions in the treatment of major depression. However, the blinded use of placebo has been found to influence clinical trial outcomes and may bias patient
selection.
Discussion: To improve clinical trial design in major depression so as to reflect clinical practice more closely we propose to present patients with a balanced view of the benefits of study participation irrespective of their assignment to placebo or active treatment. In addition every participant should be given the option to finally
receive the active medication. A research agenda is outlined to evaluate the impact of the proposed changes on the efficacy of the drug to be evaluated and on the demographic and clinical characteristics of the enrollment fraction with regard to its representativeness of the eligible population.
Summary: We propose a list of measures to be taken to improve the external validity of double-blind, placebocontrolled trials in major depression. The recommended changes to clinical trial design may also be relevant for other psychiatric as well as medical disorders in which expectations regarding treatment outcome may affect the
outcome itself
Quantifying Lipid Contents in Enveloped Virus Particles with Plasmonic Nanoparticles
Phosphatidylserine (PS) and monosialotetrahexosylganglioside (GM1) are examples of two host-derived lipids in the membrane of enveloped virus particles that are known to contribute to virus attachment, uptake, and ultimately dissemination. A quantitative characterization of their contribution to the functionality of the virus requires information about their relative concentrations in the viral membrane. Here, a gold nanoparticle (NP) binding assay for probing relative PS and GM1 lipid concentrations in the outer leaflet of different HIV-1 and Ebola virus-like particles (VLPs) using sample sizes of less than 3 × 106 particles is introduced. The assay evaluates both scattering intensity and resonance wavelength, and determines relative NP densities through plasmon coupling as a measure for the target lipid concentrations in the NP-labeled VLP membrane. A correlation of the optical observables with absolute lipid contents is achieved by calibration of the plasmon coupling-based methodology with unilamellar liposomes of known PS or GM1 concentration. The performed studies reveal significant differences in the membrane of VLPs that assemble at different intracellular sites and pave the way to an optical quantification of lipid concentration in virus particles at physiological titers.NIH grants RO1CA138509 (B.M.R.), RO1A1064099 (S. G., and 1R56Al104393 (B.M.R. and S. G.; Ethan Edmonds support (CHE 1156666
Nonlinear interaction of charged particles with a free electron gas beyond the random-phase approximation
A nonlinear description of the interaction of charged particles penetrating a
solid has become of basic importance in the interpretation of a variety of
physical phenomena. Here we develop a many-body theoretical approach to the
quadratic decay rate, energy loss, and wake potential of charged particles
moving in an interacting free electron gas. Explicit expressions for these
quantities are obtained either within the random-phase approximation (RPA) or
with full inclusion of short-range exchange and correlation effects. The Z^3
correction to the energy loss of ions is evaluated beyond RPA, in the limit of
low velocities.Comment: 5 pages, 2 figures To appear in Phys. Rev.
mHealth Series:mHealth project in Zhao County, rural China - Description of objectives, field site and methods
BACKGROUND: We set up a collaboration between researchers in China and the UK that aimed to explore the use of mHealth in China. This is the first paper in a series of papers on a large mHealth project part of this collaboration. This paper included the aims and objectives of the mHealth project, our field site, and the detailed methods of two studies. FIELD SITE: The field site for this mHealth project was Zhao County, which lies 280 km south of Beijing in Hebei Province, China. METHODS: We described the methodology of two studies: (i) a mixed methods study exploring factors influencing sample size calculations for mHealth–based health surveys and (ii) a cross–over study determining validity of an mHealth text messaging data collection tool. The first study used mixed methods, both quantitative and qualitative, including: (i) two surveys with caregivers of young children, (ii) interviews with caregivers, village doctors and participants of the cross–over study, and (iii) researchers’ views. We combined data from caregivers, village doctors and researchers to provide an in–depth understanding of factors influencing sample size calculations for mHealth–based health surveys. The second study, a cross–over study, used a randomised cross–over study design to compare the traditional face–to–face survey method to the new text messaging survey method. We assessed data equivalence (intrarater agreement), the amount of information in responses, reasons for giving different responses, the response rate, characteristics of non–responders, and the error rate. CONCLUSIONS: This paper described the objectives, field site and methods of a large mHealth project part of a collaboration between researchers in China and the UK. The mixed methods study evaluating factors that influence sample size calculations could help future studies with estimating reliable sample sizes. The cross–over study comparing face–to–face and text message survey data collection could help future studies with developing their mHealth tools
The traumagenic neurodevelopmental model of psychosis revisited
Evidence that childhood adversities are risk factors for psychosis has accumulated rapidly. Research into the mechanisms underlying these relationships has focused, productively, on psychological processes, including cognition, attachment and dissociation. In 2001, the traumagenic neurodevelopmental model sought to integrate biological and psychological research by highlighting the similarities between the structural and functional abnormalities in the brains of abused children and adults diagnosed with ‘schizophrenia’. No review of relevant literature has subsequently been published. The aim of this paper, therefore, is to summarize the literature on biological mechanisms underlying the relationship between childhood trauma and psychosis published since 2001. A comprehensive search for relevant papers was undertaken via Medline, PubMed and psycINFO. In total, 125 papers were identified, with a range of methodologies, and provided both indirect support for and direct confirmation of the traumagenic neurodevelopmental model. Integrating our growing understanding of the biological sequelae of early adversity with our knowledge of the psychological processes linking early adversity to psychosis is valuable both theoretically and clinically
Bipolar resistive switching characteristics of poly(3,4-ethylene-dioxythiophene): poly(styrenesulfonate) thin film
We investigated the reversible resistive switching of
poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) thin films
sandwiched between Al electrodes. The J-V sweep curve showed a hysteretic
behavior which depends on the polarity of the applied voltage bias. From the
analysis of I-V curves, it was revealed that the charge transport through the
junction was governed by the bulk space-charge-limited conduction (SCLC) model.
Using transmission electron microscopy (TEM) analysis, it was confirmed that
the initial high resistance state of PEDOT:PSS films is related with the
segregation of PSS- chains induced by redox reaction between a Al metal
electrode and PEDOT:PSS film. Positive space charges present on the top region
of PEDOT:PSS films can be proposed as a possible trap centers of electron
trapping and detrapping process.Comment: 10 pages, 4 figure
Coupling Classical and Quantum Variables using Continuous Quantum Measurement Theory
We propose a system of equations to describe the interaction of a
quasiclassical variable with a set of quantum variables that goes
beyond the usual mean field approximation. The idea is to regard the quantum
system as continuously and imprecisely measured by the classical system. The
effective equations of motion for the classical system therefore consist of
treating the quantum variable as a stochastic c-number \x (t) the
probability distibution for which is given by the theory of continuous quantum
measurements. The resulting theory is similar to the usual mean field equations
(in which is replaced by its quantum expectation value) but with two
differences: a noise term, and more importantly, the state of the quantum
subsystem evolves according to the stochastic non-linear Schrodinger equation
of a continuously measured system. In the case in which the quantum system
starts out in a superposition of well-separated localized states, the classical
system goes into a statistical mixture of trajectories, one trajectory for each
individual localized state.Comment: 11 pages, plain Tex (with revised settings for \vsize and \voffset to
accommodate US paper sizes
Effective Theories of Coupled Classical and Quantum Variables from Decoherent Histories: A New Approach to the Backreaction Problem
We use the decoherent histories approach to quantum theory to derive the form
of an effective theory describing the coupling of classical and quantum
variables. The derivation is carried out for a system consisting of a large
particle coupled to a small particle with the important additional feature that
the large particle is also coupled to a thermal environment producing the
decoherence necessary for classicality. The effective theory is obtained by
tracing out both the environment and the small particle variables. It consists
of a formula for the probabilities of a set of histories of the large particle,
and depends on the dynamics and initial quantum state of the small particle. It
has the form of an almost classical particle coupled to a stochastic variable
whose probabilities are determined by a formula very similar to that given by
quantum measurement theory for continuous measurements of the small particle's
position. The effective theory gives intuitively sensible answers when the
small particle is in a superposition of localized states.Comment: 27 pages, plain Te
Effective Theories of Coupled Classical and Quantum Variables
We address the issue of coupling variables which are essentially classical to
variables that are quantum. Two approaches are discussed. In the first (based
on collaborative work with L.Di\'osi), continuous quantum measurement theory is
used to construct a phenomenological description of the interaction of a
quasiclassical variable with a quantum variable , where the
quasiclassical nature of is assumed to have come about as a result of
decoherence. The state of the quantum subsystem evolves according to the
stochastic non-linear Schr\"odinger equation of a continuously measured system,
and the classical system couples to a stochastic c-number \x (t) representing
the imprecisely measured value of . The theory gives intuitively sensible
results even when the quantum system starts out in a superposition of
well-separated localized states. The second approach involves a derivation of
an effective theory from the underlying quantum theory of the combined
quasiclassical--quantum system, and uses the decoherent histories approach to
quantum theory.Comment: 25 pages, plain Tex. To appear in proceedings of the conference Open
Systems and Measurement in Relativistic Quantum Theory, Naples, April 3-4,
1998, edited by H.P.Breuer and F.Petruccion
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