Electron transport properties in Al 0.25Ga 0.75N/AlN/ GaN heterostructures with different InGaN back barrier layers and GaN channel thicknesses grown by MOCVD

The electron transport properties in Al 0.25Ga 0.75N/AlN/GaN/In xGa 1-xN/GaN double heterostructures with various indium compositions and GaN channel thicknesses were investigated. Samples were grown on c-plane sapphire substrates by MOCVD and evaluated using variable temperature Hall effect measurements. In order to understand the observed transport properties, various scattering mechanisms, such as acoustic phonon, optical phonon, interface roughness, background impurity, and alloy disorder, were included in the theoretical model that was applied to the temperature-dependent mobility data. It was found that low temperature (T<160K) mobility is limited only by the interface roughness scattering mechanism, while at high temperatures (T>160K), optical phonon scattering is the dominant scattering mechanism for AlGaN/AlN/GaN/InGaN/GaN heterostructures. The higher mobility of the structures with InGaN back barriers was attributed to the large conduction band discontinuity obtained at the channel/buffer interface, which leads to better electron confinement. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

BRD9-containing non-canonical BAF complex maintains somatic cell transcriptome and acts as a barrier to human reprogramming

Epigenetic reprogramming to pluripotency requires extensive remodeling of chromatin landscapes to silence existing cell-type-specific genes and activate pluripotency genes. ATP-dependent chromatin remodeling complexes are important regulators of chromatin structure and gene expression; however, the role of recently identified Bromodomain-containing protein 9 (BRD9) and the associated non-canonical BRG1-associated factors (ncBAF) complex in reprogramming remains unknown. Here, we show that genetic or chemical inhibition of BRD9, as well as ncBAF complex subunit GLTSCR1, but not the closely related BRD7, increase human somatic cell reprogramming efficiency and can replace KLF4 and c-MYC. We find that BRD9 is dispensable for human induced pluripotent stem cells under primed but not under naive conditions. Mechanistically, BRD9 inhibition downregulates fibroblast-related genes and decreases chromatin accessibility at somatic enhancers. BRD9 maintains the expression of transcriptional regulators MN1 and ZBTB38, both of which impede reprogramming. Collectively, these results establish BRD9 as an important safeguarding factor for somatic cell identity whose inhibition lowers chromatin-based barriers to reprogramming

Clinical and demographic features of hidradenitis suppurativa: a multicentre study of 1221 patients with an analysis of risk factors associated with disease severity.

Background Hidradenitis suppurativa (HS) is a chronic, relapsing and debilitating inflammatory disease associated with profound morbidity

Clinical and demographic features of hidradenitis suppurativa: a multicentre study of 1221 patients with an analysis of risk factors associated with disease severity

Background: Hidradenitis suppurativa (HS) is a chronic, relapsing and debilitating inflammatory disease associated with profound morbidity. Aim: In this multicentre study, we investigated the demographic and clinical features of HS, and determined risk factors of disease severity. Methods: In total, 1221 patients diagnosed with HS from 29 centres were enrolled, and the medical records of each patient were reviewed. Results: The mean age of disease onset was 26.2 ± 10.4 years, and almost 70% (n = 849) of patients were current or former smokers. Mean disease duration was 8.9 ± 8.4 years with a delay in diagnosis of 5.8 ± 3.91 years. Just over a fifth (21%; n = 256) of patients had a family history of HS. The axillary, genital and neck regions were more frequently affected in men than in women, and the inframammary region was more frequently affected in women than in men (P < 0.05 for all). Acne (40.8%), pilonidal sinus (23.6%) and diabetes mellitus (12.6%) were the most prevalent associated diseases. Of the various therapies used, antibiotics (76.4%) were most common followed by retinoids (41.7%), surgical interventions (32.0%) and biologic agents (15.4%). Logistic regression analysis revealed that the most important determinants of disease severity were male sex (OR = 2.21) and involvement of the genitals (OR = 3.39) and inguinal region (OR = 2.25). More severe disease was associated with comorbidity, longer disease duration, longer diagnosis delay and a higher number of smoking pack-years. Conclusions: Our nationwide cohort study found demographic and clinical variation in HS, which may help broaden the understanding of HS and factors associated with disease severity. © 2020 British Association of Dermatologist