3,030 research outputs found
A photoluminescence study of indium implanted silicon
The results of a photolummescence (PL) study of indium implanted silicon are presented. When silicon implanted with indium is annealed in the temperature range 400°C to 700°C a sharp no-phonon line at 1096 6 ± 0 1 meV with an associated phonon sideband is produced in the PL spectra Usmg uniaxial stress perturbation techniques the no-phonon line is identified as an A to A transition at a centre with trigonal symmetry. The shift rates for the lme under stress are found to be nonlinear, indicating that some mteraction with a nearby excited state is occurring. Transitions from this state are not directly observed Evidence suggests that the luminescence arises from the recombmation of excitons bound to an electrically neutral indium-implantation damage related centre, and that these exciton states are conduction band associated or donor-like in nature. This centre is shown to be similar to one of three defects observed by Wichert et al [1], usmg the perturbed angular correlation (PAC) spectroscopy technique, in silicon implanted with the radioactive indium isotope, indium-111.
The benefits of PL as a complementary technique to PAC and other nuclear techniques, and of radioactive implants to PL spectroscopy, are briefly outlined
Israel Charny’s attack on the Journal of Genocide Research and its authors: a response
Israel Charny has published an article, “Holocaust Minimization, Anti-Israel Themes, and Antisemitism: Bias at the Journal of Genocide Research” (JGR) in the Journal for the Study of Antisemitism. His specific allegations are bundled together in a single sentence: “minimization of the Holocaust, delegitimization of the State of Israel, and repeat[ing] common themes of contemporary antisemitism”. We write as the authors of articles and contributors to the JGR attacked by Charny. His allegations are false and we reject them. This article shows how they are based on distortions, misquotations, and falsifications of our work
Dynamical evolution of the inner asteroid belt
A determination of the dynamical evolution of the asteroid belt is difficult
because the asteroid belt has evolved since the time of asteroid formation
through mechanisms that include: (1) catastrophic collisions, (2) rotational
disruption, (3) chaotic orbital evolution and (4) orbital evolution driven by
Yarkovsky radiation forces. The timescales of these loss mechanisms are
uncertain and there is a need for more observational constraints. In the inner
main belt, the mean size of the non-family asteroids increases with increasing
inclination. Here, we use that observation to show that all inner main belt
asteroids originate from either the known families or from ghost families, that
is, old families with dispersed orbital elements. We estimate that the average
age of the asteroids in the ghost families is a factor of 1/3 less than the
Yarkovsky orbital evolution timescale. However, this orbital evolution
timescale is a long-term average that must allow for the collisional evolution
of the asteroids and for stochastic changes in their spin directions. By
applying these constraints on the orbital evolution timescales to the evolution
of the size-frequency distribution of the Vesta asteroid family, we estimate
that the age of this family is greater than 1.3 and could be comparable
with the age of the solar system. By estimating the number of ghost families,
we calculate that the number of asteroids that are the root sources of the
meteorites and the near-Earth asteroids that originate from the inner main belt
is about 20.Comment: 23 pages, 25 figures, submitted to MNRAS (to replace an old version
of the paper titled "A new observational constraint on the Yarkovsky-driven
mobility of main belt") asteroid
Syndecan 4 is Required for Endothelial Alignment in Flow and Atheroprotective Signaling
Atherosclerotic plaque localization correlates with regions of disturbed flow in which endothelial cells (ECs) align poorly, whereas sustained laminar flow correlates with cell alignment in the direction of flow and resistance to atherosclerosis. We now report that in hypercholesterolemic mice, deletion of syndecan 4 (S4−/−) drastically increased atherosclerotic plaque burden with the appearance of plaque in normally resistant locations. Strikingly, ECs from the thoracic aortas of S4−/− mice were poorly aligned in the direction of the flow. Depletion of S4 in human umbilical vein endothelial cells (HUVECs) using shRNA also inhibited flow-induced alignment in vitro, which was rescued by re-expression of S4. This effect was highly specific, as flow activation of VEGF receptor 2 and NF-κB was normal. S4-depleted ECs aligned in cyclic stretch and even elongated under flow, although nondirectionally. EC alignment was previously found to have a causal role in modulating activation of inflammatory versus antiinflammatory pathways by flow. Consistent with these results, S4-depleted HUVECs in long-term laminar flow showed increased activation of proinflammatory NF-κB and decreased induction of antiinflammatory kruppel-like factor (KLF) 2 and KLF4. Thus, S4 plays a critical role in sensing flow direction to promote cell alignment and inhibit atherosclerosis
Pricing in inflationary times: The penny drops
How does the frequency and magnitude of micro-price rises and falls relate to macroeconomic crisis, as well as moderation? Weekly micropricing behaviour in British groceries was investigated across three leading retailers over the moderation period 2004–7 and the crisis period 2008–10. We find significant price flexibility sharply distinguished from behaviour observed in most previous works. Downward price flexibility increased markedly in 2008. Overall basket prices rise, but significantly more individual prices fall than rise in the latter period. Tests of obfuscation in price setting suggested that large numbers of small price falls were used to disguise the basket price rises
Genetic diversity and recombination between turnip yellows virus strains in Australia
Disease outbreaks caused by turnip yellows virus (TuYV), a member of the genus Polerovirus, family Luteoviridae, regularly occur in canola and pulse crops throughout Australia. To understand the genetic diversity of TuYV for resistance breeding and management, genome sequences of 28 TuYV isolates from different hosts and locations were determined using high-throughput sequencing (HTS). We aimed to identify the parts of the genome that were most variable and clarify the taxonomy of viruses related to TuYV. Poleroviruses contain seven open reading frames (ORFs): ORF 0–2, 3a, and 3–5. Phylogenetic analysis based on the genome sequences, including isolates of TuYV and brassica yellows virus (BrYV) from the GenBank database, showed that most genetic variation among isolates occurred in ORF 5, followed by ORF 0 and ORF 3a. Phylogenetic analysis of ORF 5 revealed three TuYV groups; P5 group 1 and group 3 shared 45–49% amino acid sequence identity, and group 2 is a recombinant between the other two. Phylogenomic analysis of the concatenated ORFs showed that TuYV is paraphyletic with respect to BrYV, and together these taxa form a well-supported monophyletic group. Our results support the hypothesis that TuYV and BrYV belong to the same species and that the phylogenetic topologies of ORF 0, 3a and 5 are incongruent and may not be informative for species demarcation. A number of beet western yellow virus (BWYV)- and TuYV-associated RNAs (aRNA) were also identified by HTS for the first time in Australia
The Rationale and Design of the Reducing Pathology in Alzheimer's Disease through Angiotensin TaRgeting (RADAR) Trial
BACKGROUND: Anti-hypertensives that modify the renin angiotensin system may reduce Alzheimer's disease (AD) pathology and reduce the rate of disease progression. OBJECTIVE: To conduct a phase II, two arm, double-blind, placebo-controlled, randomized trial of losartan to test the efficacy of Reducing pathology in Alzheimer's Disease through Angiotensin TaRgeting (RADAR). METHODS: Men and women aged at least 55 years with mild-to-moderate AD will be randomly allocated 100 mg encapsulated generic losartan or placebo once daily for 12 months after successful completion of a 2-week open-label phase and 2-week placebo washout to establish drug tolerability. 228 participants will provide at least 182 subjects with final assessments to provide 84% power to detect a 25% difference in atrophy rate (therapeutic benefit) change over 12 months at an alpha level of 0.05. We will use intention-to-treat analysis, estimating between-group differences in outcomes derived from appropriate (linear or logistic) multivariable regression models adjusting for minimization variables. RESULTS: The primary outcome will be rate of whole brain atrophy as a surrogate measure of disease progression. Secondary outcomes will include changes to 1) white matter hyperintensity volume and cerebral blood flow; 2) performance on a standard series of assessments of memory, cognitive function, activities of daily living, and quality of life. Major assessments (for all outcomes) and relevant safety monitoring of blood pressure and bloods will be at baseline and 12 months. Additional cognitive assessment will also be conducted at 6 months along with safety blood pressure and blood monitoring. Monitoring of blood pressure, bloods, and self-reported side effects will occur during the open-label phase and during the majority of the post-randomization dispensing visits. CONCLUSION: This study will identify whether losartan is efficacious in the treatment of AD and whether definitive Phase III trials are warranted
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