Nucleation and growth of platelets in hydrogen-ion-implanted silicon

H ion implantation into crystalline Si is known to result in the precipitation of planar defects in the form of platelets. Hydrogen-platelet formation is critical to the process that allows controlled cleavage of Si along the plane of the platelets and subsequent transfer and integration of thinly sliced Si with other substrates. Here we show that H-platelet formation is controlled by the depth of the radiation-induced damage and then develop a model that considers the influence of stress to correctly predict platelet orientation and the depth at which platelet nucleation density is a maximum. © 2005 American Institute of Physics

In package inactivation of Bacillus atrophaeus spores using high voltage atmospheric cold plasma

Introduction: Hospital acquired infections are of a great concern, considering a large number of infections reported every year. Sterilization is an important step in healthcare industry that is attained by utilizing conventional sterilization approaches. It includes heat treatment, use of chemicals like ethylene oxide, hydrogen peroxide, and gamma radiation. These methods have drawbacks such as material properties of medical devices could be altered or damaged. Therefore, it is necessary to investigate cheap alternative approaches to achieve sterilization without generating toxic residues. Nonthermal atmospheric plasma is a fourth state of matter that consists of charged particles, positive and negative ions and number of reactive species. This plasma mixture has greater microbicidal effects on number of food products and wide range of surfaces. Novel nonthermal plasma technology has number of applications in food and medical industries. Methods: The objective of this study was to investigate the effect of plasma parameters on inactivation of resistant biological forms of Bacillus atrophaeus inside a sealed package. Bacillus atrophaeus spore strip (spore population 6.36 log10/strip) was placed in a petri dish, sealed in a polypropylene container, and was subjected to high voltage atmospheric cold plasma treatment (HVACP). HVACP system was operated at 70 kVRMS and at a frequency of 50 Hz. The two 15-cm diameter aluminum disk electrodes were separated by a rigid polypropylene container which served as a sample holder and as a dielectric barrier. The distance between the two electrodes was equal to the height of the container (22 mm). The top electrode served as a high voltage electrode and bottom electrode was grounded. The discharge was monitored using electrical probes and an Agilent InfiniVision 2000 X-Series Oscilloscope. Influence of different process parameters on spore inactivation including treatment time, mode of exposure (direct/indirect), and working gas types were mainly evaluated. Effect of relative humidity on HVACP inactivation efficacy was also assessed. The inactivation efficacy was determined using standard colony count method. To assess gas composition following HVACP exposure, optical absorption spectroscopy was used. Results: A strong effect of process parameters on inactivation was observed. Direct exposure to plasma was very effective for spore inactivation, achieving ≥6 log cycle reduction of spores in all gas types tested, in only 60 s of treatment time. However, a strong influence of gas type was noted on spore reductions where indirect mode of plasma exposure was utilized. The relative humidity also noted as a critical factor in bacterial spore inactivation by HVACP, where a major role of plasma generated species other than ozone was noted. Conclusion: Overall, a strong influence of process parameters on spore inactivation was noted. Effective in-package bacterial spore inactivation within 30‑60 s demonstrates the promising potential application of HVACP for sterilization of medical devices and heat sensitive materials

Moduli Redefinitions and Moduli Stabilisation

Field redefinitions occur in string compactifications at the one loop level. We review arguments for why such redefinitions occur and study their effect on moduli stabilisation and supersymmetry breaking in the LARGE volume scenario. For small moduli, although the effect of such redefinitions can be larger than that of the $\alpha'$ corrections in both the K\"ahler and scalar potentials, they do not alter the structure of the scalar potential. For the less well motivated case of large moduli, the redefinitions can dominate all other terms in the scalar potential. We also study the effect of redefinitions on the structure of supersymmetry breaking and soft terms.Comment: 21 pages, 3 figures; v2. references adde

Moduli Stabilization and Inflationary Cosmology with Poly-Instantons in Type IIB Orientifolds

Equipped with concrete examples of Type IIB orientifolds featuring poly-instanton corrections to the superpotential, the effects on moduli stabilization and inflationary cosmology are analyzed. Working in the framework of the LARGE volume scenario, the Kaehler modulus related to the size of the four-cycle supporting the poly-instanton contributes sub-dominantly to the scalar potential. It is shown that this Kaehler modulus gets stabilized and, by displacing it from its minimum, can play the role of an inflaton. Subsequent cosmological implications are discussed and compared to experimental data.Comment: 38 pages, 7 figures, Reference added, Typo fixed, Published versio

Kahler Moduli Inflation Revisited

We perform a detailed numerical analysis of inflationary solutions in Kahler moduli of type IIB flux compactifications. We show that there are inflationary solutions even when all the fields play an important role in the overall shape of the scalar potential. Moreover, there exists a direction of attraction for the inflationary trajectories that correspond to the constant volume direction. This basin of attraction enables the system to have an island of stability in the set of initial conditions. We provide explicit examples of these trajectories, compute the corresponding tilt of the density perturbations power spectrum and show that they provide a robust prediction of n_s approximately 0.96 for 60 e-folds of inflation.Comment: 27 pages, 9 figure

Prevalence and Predictors of Vitamin D Insufficiency in Children: A Great Britain Population Based Study

Objectives To evaluate the prevalence and predictors of vitamin D insufficiency (VDI) in children In Great Britain. Design A nationally representative cross-sectional study survey of children (1102) aged 4–18 years (999 white, 570 male) living in private households (January 1997–1998). Interventions provided information about dietary habits, physical activity, socio-demographics, and blood sample. Outcome measures were vitamin D insufficiency (<50 nmol/L). Results Vitamin D levels (mean = 62.1 nmol/L, 95%CI 60.4–63.7) were insufficient in 35%, and decreased with age in both sexes (p<0.001). Young People living between 53–59 degrees latitude had lower levels (compared with 50–53 degrees, p = 0.045). Dietary intake and gender had no effect on vitamin D status. A logistic regression model showed increased risk of VDI in the following: adolescents (14–18 years old), odds ratio (OR) = 3.6 (95%CI 1.8–7.2) compared with younger children (4–8 years); non white children (OR = 37 [95%CI 15–90]); blood levels taken December-May (OR = 6.5 [95%CI 4.3–10.1]); on income support (OR = 2.2 [95%CI 1.3–3.9]); not taking vitamin D supplementation (OR = 3.7 [95%CI 1.4–9.8]); being overweight (OR 1.6 [95%CI 1.0–2.5]); <1/2 hour outdoor exercise/day/week (OR = 1.5 [95%CI 1.0–2.3]); watched >2.5 hours of TV/day/week (OR = 1.6[95%CI 1.0–2.4]). Conclusion We confirm a previously under-recognised risk of VDI in adolescents. The marked higher risk for VDI in non-white children suggests they should be targeted in any preventative strategies. The association of higher risk of VDI among children who exercised less outdoors, watched more TV and were overweight highlights potentially modifiable risk factors. Clearer guidelines and an increased awareness especially in adolescents are needed, as there are no recommendations for vitamin D supplementation in older children

Continuous Glucose Monitoring – effects of altitude on glucose and glycaemic variability

Purpose: Exposure to high altitude has been shown to enhance both glucose and lipid utilization depending on experimental protocol. In addition, high and low blood glucose levels have been reported at high altitude. We hypothesized that gradual ascent to high altitude results in changes in glucose levels in healthy young adults. Methods: 25 adult volunteers, split into two teams, took part in the British Services Dhaulagiri Medical Research Expedition completing 14 days of trekking around the Dhaulagiri circuit in Nepal reaching a peak altitude of 5300m on Day 11 of the trek. Participants wore blinded continuous glucose monitors (CGM) throughout. Blood samples for c-peptide, pro-insulin and triacylglycerides were taken at sea level (UK) and in acclimatisation camps at 3600m, 4650m and 5120m. Energy intake was determined from food diaries. Results: There was no difference in time spent in hypoglycemia stratified by altitude. Nocturnal CGM readings (22.00-06.00 hrs) were chosen to reduce the short-term impact of physical activity and food intake and showed a significant (p<0.0001) increase at 3600m (5.53±0.22mmol/L), 4650m (4.77±0.30mmol/L) and 5120m (4.78±0.24mmol/L) compared to baseline altitude 1100m (vs 4.61±0.25mmol/L). Energy intake did not differ by altitude. Insulin resistance and B-cell function, calculated by homeostatic model assessment, was reduced at 3600m compared to sea level. Conclusions: We observed a significant increase in nocturnal CGM glucose at 3600m and above despite gradual ascent from 1100m. Taken with the changes in insulin resistance and B-cell function, it is possible that the stress response to high altitude dominates exercise enhanced insulin sensitivity, resulting in relative hyperglycemia