Overshoot mechanism in transient excitation of THz and Gunn oscillations in wide-bandgap semiconductors

A detailed study of high-field transient and direct-current (DC) transport in GaN-based Gunn diode oscillators is carried out using the commercial simulator Sentaurus Device. Applicability of drift-diffusion (DD) and hydrodynamic (HD) models to high-speed, highfrequency devices is discussed in depth, and the results of the simulations from these models are compared. It is shown, for a highly homogeneous device based on a short (2 μm) supercritically doped (1017 cm-3) GaN specimen, that the DD model is unable to correctly take into account some essential physical effects which determine the operation mode of the device. At the same time, the HD model is ideally suited to solve such problems due to its ability to incorporate non-local effects. We show that the velocity overshoot near the device contacts and space charge injection and extraction play a crucial role in defining the operation mode of highly homogeneous short diodes in both the transient regime and the voltagecontrolled oscillation regime. The transient conduction current responses are fundamentally different in the DD and HD models. The DD current simply repeats the velocity-field (v-F) characteristics, and the sample remains in a completely homogeneous state. In the HD model, the transient current pulse with a full width at half maximum of approximately 0.2 ps is increased about twofold due to the carrier injection (extraction) into (from) the active region and the velocity overshoot. The electron gas is characterized by highly inhomogeneous distributions of the carrier density, the electric field and the electron temperature. The simulation of the DC steady states of the diodes also shows very different results for the two models. The HD model shows the trapped stable anodic domain in the device, while the DD model completely retains all features of the v-F characteristics in a homogeneous gas. Simulation of the voltage-controlled oscillator shows that it operates in the accumulation layer mode generating microwave signals at 0.3 to 0.7 THz. In spite of the fact that the known criterion of a Gunn domain mode n0L > (n0L)0 was satisfied, no Gunn domains were observed. The explanation of this phenomenon is given. © 2012 Momox et al

Evolution and lineage dynamics of a transmissible cancer in Tasmanian devils.

Devil facial tumour 1 (DFT1) is a transmissible cancer clone endangering the Tasmanian devil. The expansion of DFT1 across Tasmania has been documented, but little is known of its evolutionary history. We analysed genomes of 648 DFT1 tumours collected throughout the disease range between 2003 and 2018. DFT1 diverged early into five clades, three spreading widely and two failing to persist. One clade has replaced others at several sites, and rates of DFT1 co-infection are high. DFT1 gradually accumulates copy number variants (CNVs) and its telomere lengths are short but constant. Recurrent CNVs reveal genes under positive selection, sites of genome instability and repeated loss of a small derived chromosome. Cultured DFT1 cell lines have increased CNV frequency and undergo highly reproducible convergent evolution. Overall, DFT1 is a remarkably stable lineage whose genome illustrates how cancer cells adapt to diverse environments and persist in a parasitic niche.This work was supported by grants from Wellcome (102942/Z/13/A), the National Science Foundation (DEB-1316549), the University of Tasmania Foundation (Eric Guiler Tasmanian Devil Research Grants), the Australian Research Council (DE 170101116) and a Philip Leverhulme Prize from the Leverhulme Trust. YMK was supported by a Herchel Smith Postgraduate Fellowship

Younger adult type 2 diabetic patients have poorer glycaemic control: A cross-sectional study in a primary care setting in Singapore

10.1186/1472-6823-13-18BMC Endocrine Disorders13-BEDM

Low-carbohydrate diet in type 2 diabetes: stable improvement of bodyweight and glycemic control during 44 months follow-up

<p>Abstract</p> <p>Background</p> <p>Low-carbohydrate diets, due to their potent antihyperglycemic effect, are an intuitively attractive approach to the management of obese patients with type 2 diabetes. We previously reported that a 20% carbohydrate diet was significantly superior to a 55–60% carbohydrate diet with regard to bodyweight and glycemic control in 2 groups of obese diabetes patients observed closely over 6 months (intervention group, n = 16; controls, n = 15) and we reported maintenance of these gains after 22 months. The present study documents the degree to which these changes were preserved in the low-carbohydrate group after 44 months observation time, without close follow-up. In addition, we assessed the performance of the two thirds of control patients from the high-carbohydrate diet group that had changed to a low-carbohydrate diet after the initial 6 month observation period. We report cardiovascular outcome for the low-carbohydrate group as well as the control patients who did not change to a low-carbohydrate diet.</p> <p>Method</p> <p>Retrospective follow-up of previously studied subjects on a low carbohydrate diet.</p> <p>Results</p> <p>The mean bodyweight at the start of the initial study was 100.6 ± 14.7 kg. At six months it was 89.2 ± 14.3 kg. From 6 to 22 months, mean bodyweight had increased by 2.7 ± 4.2 kg to an average of 92.0 ± 14.0 kg. At 44 months average weight has increased from baseline g to 93.1 ± 14.5 kg. Of the sixteen patients, five have retained or reduced bodyweight since the 22 month point and all but one have lower weight at 44 months than at start. The initial mean HbA1c was 8.0 ± 1.5%. After 6, 12 and 22 months, HbA1c was 6.1 ± 1.0%, 7.0 ± 1.3% and 6.9 ± 1.1% respectively. After 44 months mean HbA1c is 6.8 ± 1.3%.</p> <p>Of the 23 patients who have used a low-carbohydrate diet and for whom we have long-term data, two have suffered a cardiovascular event while four of the six controls who never changed diet have suffered several cardiovascular events.</p> <p>Conclusion</p> <p>Advice to obese patients with type 2 diabetes to follow a 20% carbohydrate diet with some caloric restriction has lasting effects on bodyweight and glycemic control.</p

Ten-Year Mortality and Cardiovascular Morbidity in the Finnish Diabetes Prevention Study—Secondary Analysis of the Randomized Trial

The Finnish Diabetes Prevention Study (DPS) was a randomized controlled trial, which showed that it is possible to prevent type 2 diabetes by lifestyle changes. The aim of the present study was to examine whether the lifestyle intervention had an effect on the ten-year mortality and cardiovascular morbidity in the DPS participants originally randomized either into an intervention or control group. Furthermore, we compared these results with a population-based cohort comprising individuals of varying glucose tolerance states.Middle-aged, overweight people with IGT (n = 522) were randomized into intensive intervention (including physical activity, weight reduction and dietary counseling), or control "mini-intervention" group. Median length of the intervention period was 4 years and the mean follow-up was 10.6 years. The population-based reference study cohort included 1881 individuals (1570 with normal glucose tolerance, 183 with IGT, 59 with screen-detected type 2 diabetes, 69 with previously known type 2 diabetes) with the mean follow-up of 13.8 years. Mortality and cardiovascular morbidity data were collected from the national Hospital Discharge Register and Causes of Death Register. Among the DPS participants who consented for register linkage (n = 505), total mortality (2.2 vs. 3.8 per 1000 person years, hazard ratio HR = 0.57, 95% CI 0.21-1.58) and cardiovascular morbidity (22.9 vs. 22.0 per 1000 person years, HR = 1.04, 95% CI 0.72-1.51) did not differ significantly between the intervention and control groups. Compared with the population-based cohort with impaired glucose tolerance, adjusted HRs were 0.21 (95% CI 0.09-0.52) and 0.39 (95% CI 0.20-0.79) for total mortality, and 0.89 (95% CI 0.62-1.27) and 0.87 (0.60-1.27) for cardiovascular morbidity in the intervention and control groups of the DPS, respectively. The risk of death in DPS combined cohort was markedly lower than in FINRISK IGT cohort (adjusted HR 0.30, 95% CI 0.17-0.54), but there was no significant difference in the risk of CVD (adjusted HR 0.88, 95% CI 0.64-1.21).Lifestyle intervention among persons with IGT did not decrease cardiovascular morbidity during the first 10 years of follow-up. However, the statistical power may not be sufficient to detect small differences between the intervention and control groups. Low total mortality among participants of the DPS compared with individuals with IGT in the general population could be ascribed to a lower cardiovascular risk profile at baseline and regular follow-up.ClinicalTrials.gov NCT00518167

Risk of malnutrition is associated with mental health symptoms in community living elderly men and women: The Tromsø Study

<p>Abstract</p> <p>Background</p> <p>Little research has been done on the relationship between malnutrition and mental health in community living elderly individuals. In the present study, we aimed to assess the associations between mental health (particularly anxiety and depression) and both the risk of malnutrition and body mass index (BMI, kg/m²) in a large sample of elderly men and women from Tromsø, Norway.</p> <p>Methods</p> <p>In a cross-sectional survey, with 1558 men and 1553 women aged 65 to 87 years, the risk of malnutrition was assessed by the Malnutrition Universal Screening Tool ('MUST'), and mental health was measured by the Symptoms Check List 10 (SCL-10). BMI was categorised into six groups (< 20.0, 20.0-22.4, 22.5-24.9, 25.0-27.4, 27.5-29.9, ≥ 30.0 kg/m²).</p> <p>Results</p> <p>The risk of malnutrition (combining medium and high risk) was found in 5.6% of the men and 8.6% of the women. Significant mental health symptoms were reported by 3.9% of the men and 9.1% of the women. In a model adjusted for age, marital status, smoking and education, significant mental health symptoms (SCL-10 score ≥ 1.85) were positively associated with the risk of malnutrition (odds ratio 3.9 [95% CI 1.7-8.6] in men and 2.5 [95%CI 1.3-4.9] in women), the association was positive also for subthreshold mental health symptoms. For individuals with BMI < 20.0 the adjusted odds ratio for significant mental health symptoms was 2.0 [95% CI 1.0-4.0].</p> <p>Conclusions</p> <p>Impaired mental health was strongly associated with the risk of malnutrition in community living elderly men and women and this association was also significant for subthreshold mental health symptoms.</p

Regional mitochondrial DNA and cell-type changes in post-mortem brains of non-diabetic Alzheimer’s disease are not present in diabetic Alzheimer’s disease

Background: Mitochondrial dysfunction is implicated in both diabetes and Alzheimer’s disease (AD), and diabetes also increases the risk of AD, however the combined impact of AD and diabetes on brain mitochondria is unknown. The purpose of this study was to test the hypothesis that the combination of both diabetes and AD exacerbates mitochondrial dysfunction. Methods: Post-mortem human brains (n=74), were used to determine mitochondrial DNA (mtDNA) content of cerebellum, frontal cortex and parietal cortex by quantifying absolute mtDNA copy number/cell using real time qPCR. mtDNA content was compared between diabetic and non-diabetic cases representing non-cognitively impaired controls (NCI), mildly cognitively impaired (MCI) and AD. A subset of parietal cortex samples was used to quantify mRNAs corresponding to cell types and mitochondrial function. Immune-staining of parietal cortex sections followed by semi-automated stereological assessment was performed to assess cell types. Results. Using mtDNA as an indicator of mitochondrial content, we observed significant regional variation, being highest in the parietal cortex, and lowest in the cerebellum. In the absence of diabetes, AD cases had decreased parietal cortex mtDNA, reduced MAP2 (neuronal) mRNA and increased GFAP (astrocyte) mRNA, relative to NCI. However, in the presence of both diabetes and AD, we did not observe these changes in the parietal cortex. Irrespective of cognitive status, all 3 brain regions in diabetic cases had significantly higher mtDNA than the non-diabetic cases. Conclusion. Our data show that the parietal cortex has the highest mitochondrial content but is also the most vulnerable to changes in AD, as shown by reduced mtDNA and neurones in this region. In contrast, when patients have both diabetes and AD, the AD associated parietal cortex changes are no longer seen, suggesting that the pathology observed in diabetic AD may be different to that seen in non-diabetic AD. The lack of clear functional changes in mitochondrial parameters in diabetic AD suggest that there may be different mechanisms contributing to cognitive impairment in diabetes and their impact on the respective disease neuro-pathologies remain to be fully understood

Interdisciplinary diabetes care teams operating on the interface between primary and specialty care are associated with improved outcomes of care: findings from the Leuven Diabetes Project

<p>Abstract</p> <p>Background</p> <p>Type 2 diabetes mellitus is a complex, progressive disease which requires a variety of quality improvement strategies. Limited information is available on the feasibility and effectiveness of interdisciplinary diabetes care teams (IDCT) operating on the interface between primary and specialty care. A first study hypothesis was that the implementation of an IDCT is feasible in a health care setting with limited tradition in shared care. A second hypothesis was that patients who make use of an IDCT would have significantly better outcomes compared to non-users of the IDCT after an 18-month intervention period. A third hypothesis was that patients who used the IDCT in an Advanced quality Improvement Program (AQIP) would have significantly better outcomes compared to users of a Usual Quality Improvement Program (UQIP).</p> <p>Methods</p> <p>This investigation comprised a two-arm cluster randomized trial conducted in a primary care setting in Belgium. Primary care physicians (PCPs, n = 120) and their patients with type 2 diabetes mellitus (n = 2495) were included and subjects were randomly assigned to the intervention arms. The IDCT acted as a cornerstone to both the intervention arms, but the number, type and intensity of IDCT related interventions varied depending upon the intervention arm.</p> <p>Results</p> <p>Final registration included 67 PCPs and 1577 patients in the AQIP and 53 PCPs and 918 patients in the UQIP. 84% of the PCPs made use of the IDCT. The expected participation rate in patients (30%) was not attained, with 12,5% of the patients using the IDCT. When comparing users and non-users of the IDCT (irrespective of the intervention arm) and after 18 months of intervention the use of the IDCT was significantly associated with improvements in HbA1c, LDL-cholesterol, an increase in statins and anti-platelet therapy as well as the number of targets that were reached. When comparing users of the IDCT in the two intervention arms no significant differences were noted, except for anti-platelet therapy.</p> <p>Conclusion</p> <p>IDCT's operating on the interface between primary and specialty care are associated with improved outcomes of care. More research is required on what team and program characteristics contribute to improvements in diabetes care.</p> <p>Trial registration</p> <p>NTR 1369.</p