1,200 research outputs found
Hydrogen production by photoelectrolytic decomposition of H2O using solar energy
Photoelectrochemical systems for the efficient decomposition of water are discussed. Semiconducting d band oxides which would yield the combination of stability, low electron affinity, and moderate band gap essential for an efficient photoanode are sought. The materials PdO and Fe-xRhxO3 appear most likely. Oxygen evolution yields may also be improved by mediation of high energy oxidizing agents, such as CO3(-). Examination of several p type semiconductors as photocathodes revealed remarkable stability for p-GaAs, and also indicated p-CdTe as a stable H2 photoelectrode. Several potentially economical schemes for photoelectrochemical decomposition of water were examined, including photoelectrochemical diodes and two stage, four photon processes
Impact of BPRS interview length on ratings reliability in a schizophrenia trial
AbstractSignal detection in clinical trials relies on ratings reliability. We conducted a reliability analysis of site-independent rater scores derived from audio-digital recordings of site-based rater interviews of the structured Brief Psychiatric Rating Scale (BPRS) in a schizophrenia study. “Dual” ratings assessments were conducted as part of a quality assurance program in a 12-week, double-blind, parallel-group study of PF-02545920 compared to placebo in patients with sub-optimally controlled symptoms of schizophrenia (ClinicalTrials.gov identifier NCT01939548). Blinded, site-independent raters scored the recorded site-based BPRS interviews that were administered in relatively stable patients during two visits prior to the randomization visit. We analyzed the impact of BPRS interview length on “dual” scoring variance and discordance between trained and certified site-based raters and the paired scores of the independent raters.Mean total BPRS scores for 392 interviews conducted at the screen and stabilization visits were 50.4±7.2 (SD) for site-based raters and 49.2±7.2 for site-independent raters (t=2.34; p=0.025). “Dual” rated total BPRS scores were highly correlated (r=0.812). Mean BPRS interview length was 21:05±7:47min ranging from 7 to 59min. 89 interviews (23%) were conducted in less than 15min. These shorter interviews had significantly greater “dual” scoring variability (p=0.0016) and absolute discordance (p=0.0037) between site-based and site-independent raters than longer interviews.In-study ratings reliability cannot be guaranteed by pre-study rater certification. Our findings reveal marked variability of BPRS interview length and that shorter interviews are often incomplete yielding greater “dual” scoring discordance that may affect ratings precision
A modified version of the Bayley Scales of Infant Development-II for cognitive matching of infants with and without Down syndrome
Background Many measures of infants' early cognitive development, including the BSID-II (The Bayley Scales of Infant Development), mix together test items that assess a number of different developmental domains including language, attention, motor functioning and social abilities, and some items contribute to the assessment of more than one domain. Consequently, the scales may lead to under- or over-estimates of cognitive abilities in some clinical samples and may not be the best measure to use for matching purposes.
Method To address this issue we created a modified form of the BSID-II (the BSID-M) to provide a ‘purer’ assessment of the general cognitive capacities in infants with Down syndrome (DS) from 6 to 18 months of age. We excluded a number of items that implicated language, motor, attentional and social functioning from the original measure. This modified form was administered to 17 infants with Down syndrome when 6, 12 and 18 months old and to 41 typically developing infants at 4, 7 and 10 months old.
Results The results suggested that the modified form continued to provide a meaningful and stable measure of cognitive functioning and revealed that DS infants may score marginally higher in terms of general cognitive abilities when using this modified form than they might when using the standard BSID-II scales.
Conclusions This modified form may be useful for researchers who need a ‘purer’ measure with which to match infants with DS and other infants with intellectual disabilities on cognitive functioning
Direct detection and characterization of foot-and-mouth disease virus in East Africa using a field-ready real-time PCR platform
Effective control and monitoring of foot-and-mouth disease (FMD) relies upon rapid and accurate disease confirmation. Currently, clinical samples are usually tested in reference laboratories using standardized assays recommended by The World Organisation for Animal Health (OIE). However, the requirements for prompt and serotype-specific diagnosis during FMD outbreaks, and the need to establish robust laboratory testing capacity in FMD-endemic countries have motivated the development of simple diagnostic platforms to support local decision-making. Using a portable thermocycler, the T-COR™ 8, this study describes the laboratory and field evaluation of a commercially available, lyophilized pan-serotype-specific real-time RT-PCR (rRT-PCR) assay and a newly available FMD virus (FMDV) typing assay (East Africa-specific for serotypes: O, A, Southern African Territories [SAT] 1 and 2). Analytical sensitivity, diagnostic sensitivity and specificity of the pan-serotype-specific lyophilized assay were comparable to that of an OIE-recommended laboratory-based rRT-PCR (determined using a panel of 57 FMDV-positive samples and six non-FMDV vesicular disease samples for differential diagnosis). The FMDV-typing assay was able to correctly identify the serotype of 33/36 FMDV-positive samples (no cross-reactivity between serotypes was evident). Furthermore, the assays were able to accurately detect and type FMDV RNA in multiple sample types, including epithelial tissue suspensions, serum, oesophageal–pharyngeal (OP) fluid and oral swabs, both with and without the use of nucleic acid extraction. When deployed in laboratory and field settings in Tanzania, Kenya and Ethiopia, both assays reliably detected and serotyped FMDV RNA in samples (n = 144) collected from pre-clinical, clinical and clinically recovered cattle. These data support the use of field-ready rRT-PCR platforms in endemic settings for simple, highly sensitive and rapid detection and/or characterization of FMDV
Bloch Electrons in a Magnetic Field - Why Does Chaos Send Electrons the Hard Way?
We find that a 2D periodic potential with different modulation amplitudes in
x- and y-direction and a perpendicular magnetic field may lead to a transition
to electron transport along the direction of stronger modulation and to
localization in the direction of weaker modulation. In the experimentally
accessible regime we relate this new quantum transport phenomenon to avoided
band crossing due to classical chaos.Comment: 4 pages, 3 figures, minor modifications, PRL to appea
Fractal Stability Border in Plane Couette Flow
We study the dynamics of localised perturbations in plane Couette flow with
periodic lateral boundary conditions. For small Reynolds number and small
amplitude of the initial state the perturbation decays on a viscous time scale
. For Reynolds number larger than about 200, chaotic transients
appear with life times longer than the viscous one. Depending on the type of
the perturbation isolated initial conditions with infinite life time appear for
Reynolds numbers larger than about 270--320. In this third regime, the life
time as a function of Reynolds number and amplitude is fractal. These results
suggest that in the transition region the turbulent dynamics is characterised
by a chaotic repeller rather than an attractor.Comment: 4 pages, Latex, 4 eps-figures, submitted to Phys. Rev. Le
Hall conductance of Bloch electrons in a magnetic field
We study the energy spectrum and the quantized Hall conductance of electrons
in a two-dimensional periodic potential with perpendicular magnetic field
WITHOUT neglecting the coupling of the Landau bands. Remarkably, even for weak
Landau band coupling significant changes in the Hall conductance compared to
the one-band approximation of Hofstadter's butterfly are found. The principal
deviations are the rearrangement of subbands and unexpected subband
contributions to the Hall conductance.Comment: to appear in PRB; Revtex, 9 pages, 5 postscript figures; figures with
better resolution may be obtained from http://www.chaos.gwdg.d
Triangle Diagram with Off-Shell Coulomb T-Matrix for (In-)Elastic Atomic and Nuclear Three-Body Processes
The driving terms in three-body theories of elastic and inelastic scattering
of a charged particle off a bound state of two other charged particles contain
the fully off-shell two-body Coulomb T-matrix describing the intermediate-state
Coulomb scattering of the projectile with each of the charged target particles.
Up to now the latter is usually replaced by the Coulomb potential, either when
using the multiple-scattering approach or when solving three-body integral
equations. General properties of the exact and the approximate on-shell driving
terms are discussed, and the accuracy of this approximation is investigated
numerically, both for atomic and nuclear processes including bound-state
excitation, for energies below and above the corresponding three-body
dissociation threshold, over the whole range of scattering angles.Comment: 22 pages, 11 figures, figures can be obtained upon request from the
Authors, revte
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