Weak Localization Thickness Measurements of Si:P Delta-Layers

We report on our results for the characterization of Si:P delta-layers grown by low temperature molecular beam epitaxy. Our data shows that the effective thickness of a delta-layer can be obtained through a weak localization analysis of electrical transport measurements performed in perpendicular and parallel magnetic fields. An estimate of the diffusivity of phosphorous in silicon is obtained by applying this method to several samples annealed at 850 Celsius for intervals of zero to 15 minutes. With further refinements, this may prove to be the most precise method of measuring delta-layer widths developed to date, including that of Secondary Ion Mass Spectrometry analysis

Three steps to data quality

The quality of data in general practice clinical information systems varies enormously. This variability jeopardizes the proposed national strategy for an integrated care records service and the capacity of primary care organisations to respond coherently to the demands of clinical governance and the proposed quality-based general practice contract. This is apparent in the difficulty in automating the audit process and in comparing aggregated data from different practices. In an attempt to provide data of adequate quality to support such operational needs, increasing emphasis is being placed on the standardisation of data recording

Far Infrared and Raman Spectroscopic Investigations of the Lattice:Modes of Crystalline Thiophene

Vibrational spectroscopic measurements combined with the lattice statics and lattice mod es calculations have been applied in order to derive the most probable structure of the low temperature (stable) phase V of thiophene (below 112 K). The far infrared spectrum has been recorded from 135 to 30 cm? of this phase of thiophene at 20 K. The low frequency Raman spectrum from 150 to 10 cm" has also been record ed for the phase V at 35 K. From the fact that there is coincidence between lattice mode frequencies observed in the infrared and Raman spectra, one can exclude centrosymmetric space groups. The observations of 20 lattice modes in the Raman spectrum and 14 modes in the FIR spectrum eliminate the possibility of tetragonal symmetry, but the data are consistent with orthorhombic symmetry with the unit cell containing 4 molecules on Cl sites. In spite of the glassy-like transition observed for this phase at 42 K, both spectra bear striking resemblance to the typical low frequency spectra of molecular crystals. Therefore, it is assumed, for the purposes of the static and dynamic studies, that the thiophene in phase V can be considered as an ideally ordered crystal. Calculations of the lattice energy and lattice mode frequencies, based on the atom-atom potential, appear to be most consistent with space group Pca2l (C2v5) which is in agreement with most of the earlier predictions made for the structure of the thiophene phase V. The Raman spectrum of the metastable phase II2 is also given

Far Infrared and Raman Spectroscopic Investigations of the Lattice:Modes of Crystalline Thiophene

Vibrational spectroscopic measurements combined with the lattice statics and lattice mod es calculations have been applied in order to derive the most probable structure of the low temperature (stable) phase V of thiophene (below 112 K). The far infrared spectrum has been recorded from 135 to 30 cm? of this phase of thiophene at 20 K. The low frequency Raman spectrum from 150 to 10 cm" has also been record ed for the phase V at 35 K. From the fact that there is coincidence between lattice mode frequencies observed in the infrared and Raman spectra, one can exclude centrosymmetric space groups. The observations of 20 lattice modes in the Raman spectrum and 14 modes in the FIR spectrum eliminate the possibility of tetragonal symmetry, but the data are consistent with orthorhombic symmetry with the unit cell containing 4 molecules on Cl sites. In spite of the glassy-like transition observed for this phase at 42 K, both spectra bear striking resemblance to the typical low frequency spectra of molecular crystals. Therefore, it is assumed, for the purposes of the static and dynamic studies, that the thiophene in phase V can be considered as an ideally ordered crystal. Calculations of the lattice energy and lattice mode frequencies, based on the atom-atom potential, appear to be most consistent with space group Pca2l (C2v5) which is in agreement with most of the earlier predictions made for the structure of the thiophene phase V. The Raman spectrum of the metastable phase II2 is also given

Simulations of Galactic Cosmic Ray Impacts on the Herschel/PACS bolometer Arrays with Geant4 Code

The effects of the in-flight behaviour of the bolometer arrays of the Herschel/PACS instrument under impacts of Galactic cosmic rays are explored. This instrument is part of the ESA-Herschel payload, which will be launched at the end of 2008 and will operate at the Lagrangian L2 point of the Sun-Earth system. We find that the components external to the detectors (the spacecraft, the cryostat, the PACS box, collectively referred to as the `shield') are the major source of secondary events affecting the detector behaviour. The impacts deposit energy on the bolometer chips and influence the behaviour of nearby pixels. 25% of hits affect the adjacent pixels. The energy deposited raises the bolometer temperature by a factor ranging from 1 to 6 percent of the nominal value. We discuss the effects on the observations and compare simulations with laboratory tests.Comment: Experimental Astronomy, 2008, in pres

Genetics of Tinnitus: Time to Biobank Phantom Sounds

Tinnitus is a common phantom sensation resulting most often from sensory deprivation, and for which little knowledge on the molecular mechanisms exists. While the existing evidence for a genetic influence on the condition has been until now sparse and underpowered, recent data suggest that specific forms of tinnitus have a strong genetic component revealing that not all tinnitus percepts are alike, at least in how they are genetically driven. These new findings pave the way for a better understanding on how phantom sensations are molecularly driven and call for international biobanking efforts

Experimental studies of the fractional quantum Hall effect in the first excited Landau level

We present a spectrum of experimental data on the fractional quantum Hall effect (FQHE) states in the first excited Landau level, obtained in an ultrahigh mobility two-dimensional electron system (2DES) and at very low temperatures and report the following results: For the even-denominator FQHE states, the sample dependence of the nu=5/2 state clearly shows that disorder plays an important role in determining the energy gap at nu=5/2. For the developing nu=19/8 FQHE state the temperature dependence of the Rxx minimum implies an energy gap of ~5mK.The energy gaps of the odd-denominator FQHE states at nu=7/3 and 8/3 also increase with decreasing disorder, similar to the gap at 5/2 state. Unexpectedly and contrary to earlier data on lower mobility samples, in this ultra-high quality specimen, the nu=13/5 state is missing, while its particle-hole conjugate state, the nu=12/5 state, is a fully developed FQHE state. We speculate that this disappearance might indicate a spin polarization of the nu=13/5 state. Finally, the temperature dependence is studied for the two-reentrant integer quantum Hall states around nu=5/2 and is found to show a very narrow temperature range for the transition from quantized to classical value.Comment: to be publishe

Automorphism groups of polycyclic-by-finite groups and arithmetic groups

We show that the outer automorphism group of a polycyclic-by-finite group is an arithmetic group. This result follows from a detailed structural analysis of the automorphism groups of such groups. We use an extended version of the theory of the algebraic hull functor initiated by Mostow. We thus make applicable refined methods from the theory of algebraic and arithmetic groups. We also construct examples of polycyclic-by-finite groups which have an automorphism group which does not contain an arithmetic group of finite index. Finally we discuss applications of our results to the groups of homotopy self-equivalences of K(\Gamma, 1)-spaces and obtain an extension of arithmeticity results of Sullivan in rational homotopy theory

Developmental toxicity study of sodium molybdate dihydrate administered in the diet to Sprague Dawley rats

AbstractMolybdenum is an essential nutrient for humans and animals and is a constituent of several important oxidase enzymes. It is normally absorbed from the diet and to a lesser extent from drinking water and the typical human intake is around 2μg/kg bodyweight per day. No developmental toxicity studies to contemporary standards have been published and regulatory decisions have been based primarily on older studies where the nature of the test material, or the actual dose levels consumed is uncertain.In the current study the developmental toxicity of sodium molybdate dihydrate as a representative of a broad class of soluble molybdenum(VI) compounds, was given in the diet to Sprague Dawley rats in accordance with OECD Test Guideline 414. Dose levels of 0, 3, 10, 20 and 40mgMo/kgbw/day were administered from GD6 to GD20. No adverse effects were observed at any dose level on the dams, or on embryofetal survival, fetal bodyweight, or development, with no increase in malformations or variations. Significant increases in serum and tissue copper levels were observed but no toxicity related to these was observed. The NOAEL observed in this study was 40mgMo/kgbw/day, the highest dose tested

Neonatal outcomes among twins following assisted reproductive technology: An Australian population-based retrospective cohort study

© 2018 The Author(s). Background: While their incidence is on the rise, twin pregnancies are associated with risks to the mothers and their babies. This study aims to investigate the likelihood of adverse neonatal outcomes of twins following assisted reproductive technology (ART) compared to non-ART twins. Methods: A retrospective population study using the Australian National Perinatal Data Collections (NPDC) which included 19,662 twins of ≥20weeks gestational age or≥400g birthweight in Australia. Maternal outcomes and neonatal outcomes (preterm birth, low birth weight, resuscitation and neonatal death) were compared. Generalized Estimating Equations were used to assess the likelihood of any neonatal outcomes, with adjusted odds ratio (AOR) and 95% confidence intervals (CI) presented. Weinberg's differential rule was used to estimate monozygotic twin rate. Results: ART mothers were 3.3years older than non-ART mothers. The rates of pregnancy-induced hypertension and gestational diabetes were significantly higher for ART mothers than non-ART mothers (12.2% vs. 8.4%, p< 0.01) and (9.7% vs. 7.5%, p< 0.01) respectively. The incidence of monozygotic twins was 2.0% for ART twins and 1.1% for non-ART twins. Compared with non-ART twins, ART twins had higher rates of preterm birth (AOR 1.13, 95% CI: 1.05-1.22), low birth weight (AOR 1.13, 95% CI: 1.05-1.22), and resuscitation (AOR 1.26, 95% CI: 1.17-1.36). Liveborn ART twins had 28% (AOR 1.28, 95% CI 1.09-1.50) increased odds of having any adverse neonatal outcome compared to liveborn non-ART twins, especially for opposite-sex ART twins (AOR 1.42, 95% CI 1.11-1.82). Conclusion: As ART twins had higher rates of adverse outcome, special prenatal care is recommended. Couples accessing ART should be fully informed of the risk of adverse outcome of twin pregnancies