Control of etch pit formation for epitaxial growth of graphene on germanium

Graphene epitaxy on germanium by chemical vapor deposition is a promising approach to integrate graphene into microelectronics, but the synthesis is still accompanied by several challenges such as the high process temperature, the reproducibility of growth, and the formation of etch pits during the process. We show that the substrate cleaning by preannealing in molecular hydrogen, which is crucial to successful and reproducible graphene growth, requires a high temperature and dose. During both substrate cleaning and graphene growth, etch pits can develop under certain conditions and disrupt the synthesis process. We explain the mechanisms how these etch pits may form by preferential evaporation of substrate, how substrate topography is related to the state of the cleaning process, and how etch pit formation during graphene growth can be controlled by choice of a sufficiently high precursor flow. Our study explains how graphene can be grown reliably on germanium at high temperature and thereby lays the foundation for further optimization of the growth process. © 2019 Author(s)

A Triarylamine-Triarylborane Dyad with a Photochromic Dithienylethene Bridge

A molecular triad composed of a triarylamine donor, a triarylborane acceptor, and a photoisomerizable dithienylethene bridge has been synthesized and explored by cyclic voltammetry, UV–vis, and luminescence spectroscopy. The effects of irradiation with UV light and fluoride addition on the electrochemical and optical spectroscopic properties of the donor–bridge–acceptor molecule were investigated. Photoisomerization of the dithienylethene bridge affects the triarylboron reduction potential, but not the triarylamine oxidation potential. UV–vis experiments reveal that the association constant for fluoride binding at the triarylborane site is independent of the isomerization state of the bridge. Irradiation of a THF solution of our donor–bridge–acceptor molecule with UV light, followed by F– addition, leads to a different color of the sample than UV irradiation alone or F– addition alone

Catalytic diesel particulate filters reduce the in vitro estrogenic activity of diesel exhaust

An in vitro reporter gene assay based on human breast cancer T47D cells (ER-CALUX®) was applied to examine the ability of diesel exhaust to induce or inhibit estrogen receptor (ER)-mediated gene expression. Exhaust from a heavy-duty diesel engine was either treated by iron- or copper/iron-catalyzed diesel particulate filters (DPFs) or studied as unfiltered exhaust. Collected samples included particle-bound and semivolatile constituents of diesel exhaust. Our findings show that all of the samples contained compounds that were able to induce ER-mediated gene expression as well as compounds that suppressed the activity of the endogenous hormone 17β-estradiol (E2). Estrogenic activity prevailed over antiestrogenic activity. We found an overall ER-mediated activity of 1.63 ± 0.31ng E2 CALUX equivalents (E2-CEQs) per m3 of unfiltered exhaust. In filtered exhaust, we measured 0.74 ± 0.07 (iron-catalyzed DPF) and 0.55 ± 0.09ng E2-CEQ m−3 (copper/iron-catalyzed DPF), corresponding to reductions in estrogenic activity of 55 and 66%, respectively. Our study demonstrates that both catalytic DPFs lowered the ER-mediated endocrine-disrupting potential of diesel exhaus

A Mobile Phone–Based Life-Skills Training Program for Substance Use Prevention Among Adolescents: Cluster-Randomized Controlled Trial

Background: Life skills are abilities for adaptive and positive behavior that enable individuals to deal effectively with the demands and challenges of everyday life. Life-skills training programs conducted within the school curriculum are effective in preventing the onset and escalation of substance use among adolescents. However, their dissemination is impeded due to their large resource requirements. Life-skills training provided via mobile phones may provide a more economic and scalable approach. Objective: The goal of this study was to test the appropriateness (ie, acceptance, use, and evaluation) and short-term efficacy of a mobile phone–based life-skills training program to prevent substance use among adolescents within a controlled trial. Methods: The study design was a two-arm, parallel-group, cluster-randomized controlled trial with assessments at baseline and follow-up assessments after 6 and 18 months. This report includes outcomes measured up to the 6-month follow-up. The efficacy of the intervention was tested in comparison to an assessment-only control group. The automated intervention program SmartCoach included online feedback and individually tailored text messages provided over 22 weeks. The contents were based on social cognitive theory and addressed self-management skills, social skills, and substance use resistance skills. Linear mixed models and generalized linear mixed models, as well as logistic or linear regressions, were used to investigate changes between baseline and 6-month follow-up in the following outcomes: 30-day prevalence rates of problem drinking, tobacco use, and cannabis use as well as quantity of alcohol use, quantity of cigarettes smoked, cannabis use days, perceived stress, well-being, and social skills. Results: A total of 1759 students from 89 Swiss secondary and upper secondary school classes were invited to participate in the study. Of these, 1473 (83.7%) students participated in the study; the mean age was 15.4 years (SD 1.0) and 55.2% (813/1473) were female. Follow-up assessments at 6 months were completed by 1233 (83.7%) study participants. On average, program participants responded to half (23.6 out of 50) of the prompted activities. Program evaluations underlined its appropriateness for the target group of secondary school students, with the majority rating the program as helpful and individually tailored. The results concerning the initial effectiveness of this program based on 6-month follow-up data are promising, with three of nine outcomes of the intention-to-treat analyses showing beneficial developments of statistical significance (ie, quantity of alcohol use, quantity of tobacco use, and perceived stress; P<.05) and another three outcomes (ie, problem drinking prevalence, cannabis use days, and social skills) showing beneficial developments of borderline significance (P<.10). Conclusions: The results showed good acceptance of this intervention program that could be easily and economically implemented in school classes. Initial results on program efficacy indicate that it might be effective in both preventing or reducing substance use and fostering life skills; however, data from the final 18-month follow-up assessments will be more conclusive. Trial Registration: ISRCTN Registry ISRCTN41347061; https://doi.org/10.1186/ISRCTN4134706

Longer-Term Efficacy of a Digital Life-Skills Training for Substance Use Prevention

Introduction: The main objective of this study was to test the longer-term and differential efficacy of a mobile phone‒based life-skills training program designed to prevent substance use among adolescents. Study design: A 2-arm, parallel-group, cluster RCT with assessments at baseline and follow-up after 6 and 18 months was conducted. The efficacy of the intervention was compared with that of an assessment-only control condition. Setting/participants: A total of 1,473 students with a mean age of 15.4 years were recruited in 2019/2020 within 89 Swiss secondary and upper secondary school classes. Intervention: The automated intervention program included online feedback and individually tailored text messages provided over 22 weeks. The contents were based on social cognitive theory and addressed self-management, social, and substance use resistance skills. Main outcome measures: Primary outcomes included 30-day prevalence rates for problem drinking and tobacco use. Results: The 18-month follow-up assessments were completed by 1,232 study (83.6%) participants. Those in the intervention group reported lower tobacco-smoking prevalence than the controls (OR=0.67; 95% CI=0.47, 0.96), but no significant difference in problem drinking (OR=0.84; 95% CI=0.61, 1.17) was observed. Among secondary outcomes, the intervention was effective at reducing cannabis-smoking prevalence (OR=0.55; 95% CI=0.39, 0.76) and cannabis use days (Cohen's d= -0.19; 95% CI= -0.29, -0.09), whereas no effects were observed for quantity of alcohol use, quantity of cigarettes smoked, well-being, or social skills. No significant moderators of the primary outcomes were observed. Conclusions: An automated mobile phone‒based life-skills training program produced longer-term effectiveness in preventing tobacco smoking and cannabis use, whereas no effects were observed for problem drinking. These results suggest that digitally delivered life-skills training programs are similarly effective and are an easy-to-implement alternative to training conducted within a school curriculum

Blended smartphone intervention for patients in opioid maintenance treatment in Iran: protocol for a randomized controlled trial

Background The pattern of substance use in Iran is characterized by a high prevalence of opioid use and opioid use disorder (OUD). Although opioid maintenance therapy (OMT) has been introduced in Iran, approximately 50% of people with opioid use disorder remain unreached. Moreover, psychosocial treatment of OUD and common mental health symptoms during OMT is limited. Digital interventions have been shown to improve psychological distress, depression, anxiety, and post-traumatic stress disorder symptoms. In addition, providing psychoeducation and risk reduction counseling to prevent communicable diseases like HIV and infectious hepatitis is common via the Internet. However, despite these promising advances, no smartphone intervention in OMT has been investigated for the treatment of OUD and common comorbid mental health symptoms. Objective We examine the effectiveness of adding a blended smartphone intervention based on community reinforcement approach, motivational interviewing- and cognitive behavioral therapy compared to OMT as usual that aims to improve OMT outcomes and addresses common mental health symptoms in OMT patients in Iran. Method Adults with opioid dependence entering 8 treatment centers in Tehran, Iran will be randomly assigned to receive either OMT plus a smartphone intervention or OMT as usual. The primary outcomes will be the percentage of negative urine tests for illicit, non-prescribed use of opioids (opium, heroin, tramadol) and treatment retention. Secondary outcomes will include the longest period of abstinence from the illicit, non-prescribed use of opioids (opium, heroin, and tramadol) confirmed by urine samples, changes in communicable disease risk-taking behaviors, changes in stress and common mental health symptoms, and client satisfaction. Data analysis will follow the intention-to-treat principle and employ (generalized) linear mixed models. Discussion This study will provide substantial knowledge for designing effective blended interventions for OUD. Moreover, it will investigate if treatment retention and OMT-related outcomes and common mental health symptoms can be improved by adding a smartphone intervention to OMT. Trial Registration https://en.irct.ir/trial/53578

On Minc's sheltered middle path

This paper shows that a construction, which was introduced by Piotr Minc in connection with a problem that came from Helly type theorems and that allows to replace three PL-arcs with a "sheltered middle path", can in the case of general (non-PL) paths result in the topologist's sine curve.Comment: 18 pages, 3 figure

Predictors of Youth Accessibility for a Mobile Phone-Based Life Skills Training Program for Addiction Prevention

Background: Digital interventions are an emerging and promising avenue for addiction prevention and mental health promotion, but their reach and use are often limited, and little is known about the factors associated with youth accessibility. SmartCoach is a life skills training program for addiction prevention where adolescents are proactively invited for program participation in secondary school classes. The mobile phone-based program provides individualized coaching for a period of 4 months and addresses self-management skills, social skills, and substance use resistance skills. This study examined sociodemographic and other predictors of program participation and program use. Methods: A total of 476 adolescents in 28 secondary and upper secondary school classes in the German-speaking part of Switzerland were proactively invited for participation in the SmartCoach program. Using generalized linear mixed models (GLMMs), we examined predictors of both program participation and program use at the individual and school class levels. Results: In total, 315 (66.2%) of the present 476 adolescents gave their active consent and provided the necessary information to be included in the program. None of the individual sociodemographic characteristics significantly predicted program participation, however, the participation rate was significantly higher in upper secondary school classes (84%) than secondary school classes (59%). The mean number of interactions with the program was 15.9, i.e., participants took part in almost half of the 34 possible interactions with the SmartCoach program. None of the baseline characteristics on the level of the school class significantly predicted program use. On the level of the individual, the univariate models showed that, compared to the reference category of 14-year-old students, program use was significantly lower for students who were 16 or older. Furthermore, participants with a migration background or an origin from a non-German-speaking country showed significantly lower program use. Finally, students with a medium level of perceived stress showed higher program use compared to those with a low level of stress. Within the final multivariate model for program use, only the variable “origin from a non-German-speaking country” remained significant. Conclusions: SmartCoach is an attractive offer for young people, in which two out of three young people who are invited in the classroom to participate do so. Among the program participants, the use of the program is acceptable, with an average of almost half of the content being worked on. There is potential for improvement in terms of recruitment, especially in school classes with a lower level of education. The most important starting point for improving program use lies in taking greater account of needs and wishes of students with non-German-speaking countries of origin

Towards the Growth of Hexagonal Boron Nitride on Ge(001)/Si Substrates by Chemical Vapor Deposition

The growth of hexagonal boron nitride (hBN) on epitaxial Ge(001)/Si substrates via high-vacuum chemical vapor deposition from borazine is investigated for the first time in a systematic manner. The influences of the process pressure and growth temperature in the range of 10−7–10−3 mbar and 900–980 °C, respectively, are evaluated with respect to morphology, growth rate, and crystalline quality of the hBN films. At 900 °C, nanocrystalline hBN films with a lateral crystallite size of ~2–3 nm are obtained and confirmed by high-resolution transmission electron microscopy images. X-ray photoelectron spectroscopy confirms an atomic N:B ratio of 1 ± 0.1. A three-dimensional growth mode is observed by atomic force microscopy. Increasing the process pressure in the reactor mainly affects the growth rate, with only slight effects on crystalline quality and none on the principle growth mode. Growth of hBN at 980 °C increases the average crystallite size and leads to the formation of 3–10 well-oriented, vertically stacked layers of hBN on the Ge surface. Exploratory ab initio density functional theory simulations indicate that hBN edges are saturated by hydrogen, and it is proposed that partial de-saturation by H radicals produced on hot parts of the set-up is responsible for the growth