Dielectric relaxation and Charge trapping characteristics study in Germanium based MOS devices with HfO2 /Dy2O3 gate stacks

In the present work we investigate the dielectric relaxation effects and charge trapping characteristics of HfO2 /Dy2O3 gate stacks grown on Ge substrates. The MOS devices have been subjected to constant voltage stress (CVS) conditions at accumulation and show relaxation effects in the whole range of applied stress voltages. Applied voltage polarities as well as thickness dependence of the relaxation effects have been investigated. Charge trapping is negligible at low stress fields while at higher fields (>4MV/cm) it becomes significant. In addition, we give experimental evidence that in tandem with the dielectric relaxation effect another mechanism- the so-called Maxwell-Wagner instability- is present and affects the transient current during the application of a CVS pulse. This instability is also found to be field dependent thus resulting in a trapped charge which is negative at low stress fields but changes to positive at higher fields.Comment: 27pages, 10 figures, 3 tables, regular journal contribution (accepted in IEEE TED, Vol.50, issue 10

What makes a successful transition from primary to secondary school?

This report presents the findings of a sub-study on transitions undertaken as part of the Effective Pre-school, Primary and Secondary Education 3-14 (EPPSE 3-14 project) a major longitudinal study investigating the influence of pre-school, primary and secondary school on children’s cognitive and social/behavioural development in England. The transitions sub-study of more than 500 children and families sheds light on current transition practices and highlights what helps and hinders a successful transition. It takes into account the influence of child and family background characteristics such as socio-economic status (SES) and gender. It suggests how the transition experience could be improved to enhance the smooth continuity between primary and secondary school. By adopting a mixed methods approach, the study investigated the issues related to transition for four distinctive groups: Local Authorities, children, parents and schools. Officers in six Local Authorities were asked about the way transition was dealt with in their Authority. Children in their first term at secondary school completed a questionnaire on their thoughts and experiences of transition, and the study also sought their parents’ opinions in order to illustrate the whole family’s experience. Finally, there were twelve case studies selected from the respondents of the questionnaire because of their positive experiences of transition. These involved interviews with the children and their primary and secondary teachers. This provided further details of the systems in place that support the transition processes between school phases. The sample was drawn from children and families in the wider EPPSE project. 1190 children from the EPPSE sample made a transition at the end of the 2005-06 academic year. Responses were received from 550 children (a 46% response rate) and 569 parents (a 48% response rate) from across England drawn from 6 Local Authorities (Shire County, Inner London borough, Midlands/Metropolitan region, East Anglia area, and two authorities in the North East). Children were recruited to the case studies using stratified selection to get a balanced mix by region, gender, socio-economic status (SES) and ethnicity. A wide range of data, already available from the main EPPSE study was used to complement the analyses

Gate Stack Dielectric Degradation of Rare-Earth Oxides Grown on High Mobility Ge Substrates

We report on the dielectric degradation of Rare-Earth Oxides (REOs), when used as interfacial buffer layers together with HfO2 high-k films (REOs/HfO2) on high mobility Ge substrates. Metal-Oxide-Semiconductor (MOS) devices with these stacks,show dissimilar charge trapping phenomena under varying levels of Constant- Voltage-Stress (CVS) conditions, which also influences the measured densities of the interface (Nit) and border (NBT) traps. In the present study we also report on C-Vg hysteresis curves related to Nit and NBT. We also propose a new model based on Maxwell-Wagner instabilities mechanism that explains the dielectric degradations (current decay transient behavior) of the gate stack devices grown on high mobility substrates under CVS bias from low to higher fields, and which is unlike to those used for other MOS devices. Finally, the time dependent degradation of the corresponding devices revealed an initial current decay due to relaxation, followed by charge trapping and generation of stress-induced leakage which eventually lead to hard breakdown after long CVS stressing.Comment: 19pages (double space), 7 figures, original research article, Submitted to JAP (AIP

Two Interacting Electrons in a Quasiperiodic Chain

We study numerically the effect of on-site Hubbard interaction U between two electrons in the quasiperiodic Harper's equation. In the periodic chain limit by mapping the problem to that of one electron in two dimensions with a diagonal line of impurities of strength U we demonstrate a band of resonance two particle pairing states starting from E=U. In the ballistic (metallic) regime we show explicitly interaction-assisted extended pairing states and multifractal pairing states in the diffusive (critical) regime. We also obtain localized pairing states in the gaps and the created subband due to U, whose number increases when going to the localized regime, which are responsible for reducing the velocity and the diffusion coefficient in the qualitatively similar to the non-interacting case ballistic and diffusive dynamics. In the localized regime we find propagation enhancement for small U and stronger localization for larger U, as in disordered systems.Comment: 14 pages Revtex file, 8 figures (split into 19 jpg figures). (postscript versions of the jpg figures are also available upon request) submitted to PR

A Body Shape Index (ABSI), hip index and risk of cancer in the UK Biobank cohort

Abdominal size is associated positively with the risk of some cancers but the influence of body mass index (BMI) and gluteofemoral size is unclear because waist and hip circumference are strongly correlated with BMI. We examined associations of 33 cancers with A Body Shape Index (ABSI) and hip index (HI), which are independent of BMI by design, and compared these with waist and hip circumference, using multivariable Cox proportional hazards models in UK Biobank. During a mean follow up of seven years, 14,682 incident cancers were ascertained in 200,289 men and 12,965 cancers in 230,326 women. In men, ABSI was associated positively with cancers of the head and neck (hazard ratio HR=1.14; 95% confidence interval 1.03-1.26 per one standard deviation increment), oesophagus (adenocarcinoma, HR=1.27; 1.12-1.44), gastric cardia (HR=1.31; 1.07-1.61), colon (HR=1.18; 1.10-1.26), rectum (HR=1.13; 1.04-1.22), lung (adenocarcinoma, HR=1.16; 1.03-1.30; squamous-cell carcinoma (SCC), HR=1.33; 1.17-1.52), and bladder (HR=1.15; 1.04-1.27), while HI was associated inversely with cancers of the oesophagus (adenocarcinoma, HR=0.89; 0.79-1.00), gastric cardia (HR=0.79; 0.65-0.96), colon (HR=0.92; 0.86-0.98), liver (HR=0.86; 0.75-0.98), and multiple myeloma (HR=0.86; 0.75-1.00). In women, ABSI was associated positively with cancers of the head and neck (HR=1.27; 1.10-1.48), oesophagus (SCC, HR=1.37; 1.07-1.76), colon (HR=1.08; 1.01-1.16), lung (adenocarcinoma, HR=1.17; 1.06-1.29; SCC, HR=1.40; 1.20-1.63; small-cell, HR=1.39; 1.14-1.69), kidney (clear-cell, HR=1.25; 1.03-1.50), and post-menopausal endometrium (HR=1.11; 1.02-1.20), while HI was associated inversely with skin SCC (HR=0.91; 0.83-0.99), post-menopausal kidney cancer (HR=0.77; 0.67-0.88) and post-menopausal melanoma (HR=0.90; 0.83-0.98). Unusually, ABSI was associated inversely with melanoma in men (HR=0.89; 0.82-0.96) and pre-menopausal women (HR=0.77; 0.65-0.91). Waist and hip circumference reflected associations with BMI, when examined individually, and provided biased risk estimates, when combined with BMI. In conclusion, preferential positive associations of ABSI or inverse of HI with several major cancers indicate an important role of factors determining body shape in cancer development

Associations of body shape phenotypes with sex steroids and their binding proteins in the UK Biobank cohort

Associations of sex steroids and their binding proteins with body shape are unclear, because waist and hip circumference are correlated strongly with body size. We defined body shape using “a body shape index” (ABSI) and hip index (HI), which are independent of weight and height by design, and examined associations in multivariable generalised linear models for the UK Biobank cohort (179,902 men, 207,444 women). Total testosterone was associated inversely with ABSI, especially in men. Free testosterone was lowest for large-ABSI-large-HI (“wide”) and highest for small-ABSI-small-HI (“slim”) in men, but lowest for small-ABSI-large-HI (“pear”) and highest for large-ABSI-small-HI (“apple”) in women. Oestradiol was associated inversely with ABSI in obese pre-menopausal women but positively with HI in obese men and post-menopausal women not using hormone replacement therapy. Sex-hormone binding globulin (SHBG) was associated inversely with ABSI but positively with HI and was lowest for “apple” and highest for “pear” phenotype in both sexes. Albumin was associated inversely with HI in women, but matched the pattern of free testosterone in obese men (lowest for “wide”, highest for “slim” phenotype). In conclusion, sex steroids and their binding proteins are associated with body shape, including hip as well as waist size, independent of body size

Interactions of platelets with obesity in relation to lung cancer risk in the UK Biobank cohort

Background: Platelet count (PLT) is associated positively with lung cancer risk but has a more complex association with body mass index (BMI), positive only in women (mainly never smokers) and inverse in men (mainly ever smokers), raising the question whether platelets interact with obesity in relation to lung cancer risk. Prospective associations of platelet size (an index of platelet maturity and activity) with lung cancer risk are unclear. Methods: We examined the associations of PLT, mean platelet volume (MPV), and platelet distribution width (PDW) (each individually, per one standard deviation increase) with lung cancer risk in UK Biobank men and women using multivariable Cox proportional hazards models adjusted for BMI and covariates. We calculated Relative Excess Risk from Interaction (RERI) with obese (BMI ≥30 kg/m2), dichotomising platelet parameters at ≥median (sex-specific), and multiplicative interactions with BMI (continuous scale). We examined heterogeneity according to smoking status (never, former, current smoker) and antiaggregant/anticoagulant use (no/yes). Results: During a mean follow-up of 10.4 years, 1620 lung cancers were ascertained in 192,355 men and 1495 lung cancers in 218,761 women. PLT was associated positively with lung cancer risk in men (hazard ratio HR=1.14; 95% confidence interval (CI): 1.09–1.20) and women (HR=1.09; 95%CI: 1.03–1.15) but interacted inversely with BMI only in men (RERI=-0.53; 95%CI: -0.80 to -0.26 for high-PLT-obese; HR=0.92; 95%CI=0.88–0.96 for PLTBMI). Only in men, MPV was associated inversely with lung cancer risk (HR=0.95; 95%CI: 0.90–0.99) and interacted positively with BMI (RERI=0.27; 95%CI=0.09–0.45 for high-MPV-obese; HR=1.08; 95%CI=1.04–1.13 for MPVBMI), while PDW was associated positively (HR=1.05; 95%CI: 1.00–1.10), with no evidence for interactions. The associations with PLT were consistent by smoking status, but MPV was associated inversely only in current smokers and PDW positively only in never/former smokers. The interactions with BMI were retained for at least eight years of follow-up and were consistent by smoking status but were attenuated in antiaggregant/anticoagulant users. Conclusions: In men, PLT was associated positively and MPV inversely with lung cancer risk and these associations appeared hindered by obesity. In women, only PLT was associated positively, with little evidence for interaction with obesity

Associations of body shape index (ABSI) and hip index with liver, metabolic, and inflammatory biomarkers in the UK Biobank cohort

Associations of liver, metabolic, and inflammatory biomarkers in blood with body shape are unclear, because waist circumference (WC) and hip circumference (HC) are dependent on overall body size, resulting in bias. We have used the allometric “a body shape index” (ABSI = WC(mm)∗Weight(kg)-2/3∗Height(m)5/6) and hip index (HIwomen = HC(cm)∗Weight(kg)-0.482∗Height(cm)0.310, HImen = HC(cm)∗Weight(kg)-2/5∗Height(cm)1/5), which are independent of body mass index (BMI) by design, in multivariable linear regression models for 121,879 UK Biobank men and 135,559 women. Glucose, glycated haemoglobin (HbA1c), triglycerides, low-density-lipoprotein cholesterol, apolipoprotein-B, alanine aminotransferase (ALT), gamma-glutamyltransferase, and lymphocytes were associated positively with BMI and ABSI but inversely with HI. High-density-lipoprotein cholesterol and apolipoprotein-A1 were associated inversely with BMI and ABSI but positively with HI. Lipid-related biomarkers and ALT were associated only with HI in obese men. C-reactive protein, neutrophils, monocytes, and alkaline phosphatase were associated positively, while bilirubin was associated inversely, with BMI and ABSI but not with HI. Associations were consistent within the clinical reference ranges but were lost or changed direction for low or high biomarker levels. Our study confirms associations with waist and hip size, independent of BMI, for metabolic biomarkers but only with waist size for inflammatory biomarkers, suggesting different contribution of the mechanistic pathways related to body shape

Localization-delocalization transition in the quasi-one-dimensional ladder chain with correlated disorder

The generalization of the dimer model on a two-leg ladder is defined and investigated both, analytically and numerically. For the closed system we calculate the Landauer resistance analytically and found the presence of the point of delocalization at the band center which is confirmed by the numerical calculations of the Lyapunov exponent. We calculate also analytically the localization length index and present the numerical investigations of the density of states (DOS). For the open counterpart of this model the distribution of the Wigner delay times is calculated numerically. It is shown how the localization-delocalization transition manifest itself in the behavior of the distribution.Comment: 9 pages, 10 figures, Revte

The struggle of a good friend getting old:cellular senescence in viral responses and therapy

Cellular senescence is a state of stable cell cycle arrest associated with macromolecular alterations and secretion of pro-inflammatory cytokines and molecules. Senescence-associated phenotypes restrict damage propagation and activate immune responses, two essential processes involved in response to viral infections. However, excessive accumulation and persistence of senescent cells can become detrimental and promote pathology and dysfunctions. Various pharmacological interventions, including antiviral therapies, lead to aberrant and premature senescence. Here, we review the molecular mechanisms by which viral infections and antiviral therapy induce senescence. We highlight the importance of these processes in attenuating viral dissemination and damage propagation, but also how prematurely induced senescent cells can promote detrimental adverse effects in humans. We describe which sequelae due to viral infections and treatment can be partly due to excessive and aberrant senescence. Finally, we propose that pharmacological strategies which eliminate senescent cells or suppress their secretory phenotype could mitigate side effects and alleviate the onset of additional morbidities. These strategies can become extremely beneficial in patients recovering from viral infections or undergoing antiviral therapy