Enhancement of luminescence by pulse laser annealing of ion-implanted europium in sapphire and silica

Sapphire (Al2O3) and silica samples have been implanted with 400 keV europium ions at fluences between 5×1014 and 1×1016 ions cm-2. As-implanted, samples show luminescence at 622 nm, and although the intensity may be increased by furnace anneals up to 1000°C, higher temperatures, to 1200°C, result in less emission, as the impurity ions form precipitate clusters. This problem can be avoided by the use of pulsed laser anneals which dissociate the clusters and quench in atomically dispersed ions. The luminescence intensity has been increased by factors of 95 and 85 for sapphire and silica, respectively, relative to the initial implanted signal. On comparing with furnace anneals at 1200°C, the pulsed laser annealing is more effective, by factors of up to 45 times. Data for pulsed excimer and CO2 lasers are compared. Both types of laser appear to remove the ion-implanted radiation damage, but in the case of silica, higher luminescence performance was obtained with the excimer anneals. There was no evidence for diffusion of the implanted europium, as assessed by Rutherford backscattering spectrometry. © 1995 American Institute of Physics.We thank Barry Farmery for his help with the RBS work, and both the University of Ege in Turkey and the Science and Engineering Research Council for their financial assistance. We appreciate the use of a Lumonics (Hull Op- erations) Ltd. TEA CO, laser.Peer Reviewe

Some Relations between Twisted K-theory and E8 Gauge Theory

Recently, Diaconescu, Moore and Witten provided a nontrivial link between K-theory and M-theory, by deriving the partition function of the Ramond-Ramond fields of Type IIA string theory from an E8 gauge theory in eleven dimensions. We give some relations between twisted K-theory and M-theory by adapting the method of Diaconescu-Moore-Witten and Moore-Saulina. In particular, we construct the twisted K-theory torus which defines the partition function, and also discuss the problem from the E8 loop group picture, in which the Dixmier-Douady class is the Neveu-Schwarz field. In the process of doing this, we encounter some mathematics that is new to the physics literature. In particular, the eta differential form, which is the generalization of the eta invariant, arises naturally in this context. We conclude with several open problems in mathematics and string theory.Comment: 23 pages, latex2e, corrected minor errors and typos in published versio

CMB Imprints of a Pre-Inflationary Climbing Phase

We discuss the implications for cosmic microwave background (CMB) observables, of a class of pre-inflationary dynamics suggested by string models where SUSY is broken due to the presence of D-branes and orientifolds preserving incompatible portions of it. In these models the would-be inflaton is forced to emerge from the initial singularity climbing up a mild exponential potential, until it bounces against a steep exponential potential of "brane SUSY breaking" scenarios, and as a result the ensuing descent gives rise to an inflationary epoch that begins when the system is still well off its eventual attractor. If a pre-inflationary climbing phase of this type had occurred within 6-7 e-folds of the horizon exit for the largest observable wavelengths, displacement off the attractor and initial-state effects would conspire to suppress power in the primordial scalar spectrum, enhancing it in the tensor spectrum and typically superposing oscillations on both. We investigate these imprints on CMB observables over a range of parameters, examine their statistical significance, and provide a semi-analytic rationale for our results. It is tempting to ascribe at least part of the large-angle anomalies in the CMB to pre-inflationary dynamics of this type.Comment: 38 pages, LaTeX, 11 eps figures, references added, matches version to appear in JCA

Observational and genetic associations between cardiorespiratory fitness and cancer: a UK Biobank and international consortia study

Background The association of fitness with cancer risk is not clear. Methods We used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk of lung, colorectal, endometrial, breast, and prostate cancer in a subset of UK Biobank participants who completed a submaximal fitness test in 2009-12 (N = 72,572). We also investigated relationships using two-sample Mendelian randomisation (MR), odds ratios (ORs) were estimated using the inverse-variance weighted method. Results After a median of 11 years of follow-up, 4290 cancers of interest were diagnosed. A 3.5 ml O2⋅min−1⋅kg−1 total-body mass increase in fitness (equivalent to 1 metabolic equivalent of task (MET), approximately 0.5 standard deviation (SD)) was associated with lower risks of endometrial (HR = 0.81, 95% CI: 0.73–0.89), colorectal (0.94, 0.90–0.99), and breast cancer (0.96, 0.92–0.99). In MR analyses, a 0.5 SD increase in genetically predicted O2⋅min−1⋅kg−1 fat-free mass was associated with a lower risk of breast cancer (OR = 0.92, 95% CI: 0.86–0.98). After adjusting for adiposity, both the observational and genetic associations were attenuated. Discussion Higher fitness levels may reduce risks of endometrial, colorectal, and breast cancer, though relationships with adiposity are complex and may mediate these relationships. Increasing fitness, including via changes in body composition, may be an effective strategy for cancer prevention

An integrative multi-omics analysis to identify candidate DNA methylation biomarkers related to prostate cancer risk

It remains elusive whether some of the associations identified in genome-wide association studies of prostate cancer (PrCa) may be due to regulatory effects of genetic variants on CpG sites, which may further influence expression of PrCa target genes. To search for Cp

Identification of multiple risk loci and regulatory mechanisms influencing susceptibility to multiple myeloma

Genome-wide association studies (GWAS) have transformed our understanding of susceptibility to multiple myeloma (MM), but much of the heritability remains unexplained. We report a new GWAS, a meta-analysis with previous GWAS and a replication series, totalling 9974 MM cases and 247,556 controls of European ancestry. Collectively, these data provide evidence for six new MM risk loci, bringing the total number to 23. Integration of information from gene expression, epigenetic profiling and in situ Hi-C data for the 23 risk loci implicate disruption of developmental transcriptional regulators as a basis of MM susceptibility, compatible with altered B-cell differentiation as a key mechanism. Dysregulation of autophagy/apoptosis and cell cycle signalling feature as recurrently perturbed pathways. Our findings provide further insight