Lohmannstevenson0748

A layer dependent (532 nm) micro-Raman study has been carried out down to two layers with no detectable spectral shifts as a function of the layer number and with respect to the bulk. © 2020 IOP Publishing Ltd.We theoretically investigate the electronic structure and optical absorption spectrum of armchair-edged black phosphorene nanoribbons (APNRs) with and without uniaxial strain based on the tight-binding Hamiltonian and Kubo formula. We analytically obtain the energy spectrum and wavefunction, and reveal the band gap scaling law as $1/(N+1)^2$ for APNRs in the presence and absence of uniaxial strain, where $N$ is the number of armchair dimer across the ribbon. We find the band gap of APNRs linearly increases (decreases) with increasing in-plane uniaxial tensile (compressive) strain $\varepsilon_x/y$, but shows contrary dependence on the out-of-plane uniaxial strain $\varepsilon_z$. The effective mass versus strain exhibits the same behavior to that of band gap but with nonlinear dependence. Under an incident light linearly-polarized along the ribbon, we demonstrate that the inter-band optical transitions obey the selection rule $\Delta n=n-n^\prime$=0, but the intra-band transitions are forbidden for both pristine and strained APNRs originating from the orthogonality between the transverse wavefunctions of the sublattices belonging to different subbands. Importantly, the transverse electric field or impurities can release the optical selection rules by breaking the wavefunction orthogonality, which results in that the optical transitions between any subbands are all possible. Our findings provide further understanding on the electronic and optical properties of APNRs, which may pave the way for designing optoelectronic devices based on phosphorene. © 2020 IOP Publishing Ltd.The measurement of fluorescence spectra and the determination of fluorescence quantum yields in transparent samples are conceptually simple tasks, but these procedures are subject to several pitfalls that can lead to significant errors. Available technical reports and protocols often assume that the reader possesses a solid theoretical background in spectroscopy and has ample experience with fluorescence instrumentation, but this is often not the case given the many applications of fluorescence in diverse fields of science. The goal of this tutorial is to provide a didactic treatment of the topic that will hopefully be accessible to readers without extensive expertise in the field of fluorescence. The article covers the theoretical background needed to understand the origins of the most common artifacts researchers can expect. Possible artifacts are illustrated with examples to help readers avoid them or identify them if present. A step-by-step example of a fluorescence quantum yield determination in solution is provided with detailed experimental information to help readers understand how to design and analyze experiments. © 2020 IOP Publishing Ltd.Inducing electrostatic doping in 2D materials by laser exposure (photodoping effect) is an exciting route to tune optoelectronic phenomena. However, there is a lack of investigation concerning in what respect the action of photodoping in optoelectronic devices is local. Here, we employ scanning photocurrent microscopy (SPCM) techniques to investigate how a permanent photodoping modulates the photocurrent generation in MoS2 transistors locally. We claim that the photodoping fills the electronic states in MoS2 conduction band, preventing the photon-absorption and the photocurrent generation by the MoS2 sheet. Moreover, by comparing the persistent photocurrent (PPC) generation of MoS2 on top of different substrates, we elucidate that the interface between the material used for the gate and the insulator (gate-insulator interface) is essential for the photodoping generation. Our work gives a step forward to the understanding of the photodoping effect in MoS2 transistors and the implementation of such an effect in integrated devices. © 2020 IOP Publishing Ltd.Single molecule localization microscopy (SMLM) allows the imaging of cellular structures with resolutions five to ten times below the diffraction limit of optical microscopy. It was originally introduced as a two-dimensional technique based on the localization of single emitters as projection onto the x-y imaging plane. The determination of the axial position of a fluorescent emitter is only possible by additional information. Here we report a method (spatial filter SMLM (SFSMLM)) that allows to determine the axial positions of fluorescent molecules and nanoparticles on the nanometer scale by the usage of two spatial filters, which are placed in two otherwise identical emission detection channels. SFSMLM allows axial localization in a range of ca. 1.5 μm with a localization precision of 15 - 30 nm in axial direction. The technique was utilized for localizing and imaging small cellular structures - e.g. actin filaments, vesicles and mitochondria - in three dimensions.PURPOSE This study examined the association between self-perceived actual and ideal body sizes and objectively assessed moderate-to-vigorous physical activity (MVPA) among adolescents, controlling for puberty, fat mass index, and sex. A secondary objective was to explore the association between objectively assessed fat mass index and MVPA. METHODS Participants were 438 early adolescents (Mage = 11.61, SD = 0.92). Participants selected body sizes that represented their self-perceived actual and ideal bodies. Participants then wore an accelerometer for 1 week to assess MVPA. Polynomial regression analysis with response surface methods was used to explore MVPA in relation to the discrepancy and agreement (ie, no discrepancy) between self-perceived actual and ideal body sizes. RESULTS When self-perceived actual and ideal body sizes were in agreement and represented smaller and larger bodies, MVPA was low. Participants with similar self-perceived actual and ideal bodies in the middle of the body-size spectrum demonstrated the highest levels of MVPA. The direction and degree of the discrepancy between self-perceived actual and ideal bodies were not significantly associated with MVPA. Fat mass index was significantly and negatively associated with MVPA. CONCLUSIONS These findings may inform physical activity promotion programs and provide methodological contributions to the study of how body image and MVPA are related.BACKGROUND Children and adolescents with disabilities often report low levels of physical activity (PA). Estimating the magnitude of PA disparities has been previously challenged by underreporting and variability in subsampling of disability. Using the National Survey of Children's Health, this study estimated the population-level PA disparities experienced and the association between disability status and PA engagement. METHODS Weighted prevalence of PA engagement (National Physical Activity Guidelines for Americans (2nd edition) and sports participation) was compared across disability groups for children (n = 20,867, 6-11 y) and adolescents (n = 28,651, 12-17 y) and found to be 12%. Age-stratified multivariable logistic regressions estimated the likelihood of PA engagement as a function of disability status and type, after adjusting for child and household factors. RESULTS Children, but not adolescents, with disabilities had significantly lower odds of being sufficiently active compared with peers without disabilities (adjusted odds ratio = 0.75; 95% confidence interval, 0.60-0.94). Across age groups, the lowest prevalence rates were observed among those experiencing function and mobility disabilities. Children and adolescents were significantly less likely to participate in sports compared with peers. CONCLUSION Children with function and mobility disabilities were identified as priority subpopulations least likely to be sufficiently active. The disparity in sports participation highlights a critical intervention point for increasing PA among children with disabilities.Wearable physical activity (PA) monitors are widely promoted as a means to motivate people to be more active, but the motivational profile of users has never been assessed. This study's purpose was to classify adult users by their motivational regulation scores and examine how these profiles were associated with moderate to vigorous PA (MVPA). Current users (N = 320) recruited across the United States completed a Web-based survey. Motivational regulations were measured using the Behavioral Regulation in Exercise Questionnaire, and associations with MVPA were explored using bivariate correlations. MVPA was more highly correlated with autonomous rather than controlling regulations. A cluster analysis was conducted using the respondents' motivational regulation scores. Five motivational profiles emerged from this analysis, and they differed significantly across motivation and MVPA scores. PA monitor users characterized by more autonomous motives presented with higher MVPA. As technology use increases, assessing the multidimensionality of PA monitor users' motivation may add value when researching PA behaviors.This study examined the relationships among cognitive acceptance, behavioral commitment, psychological need satisfaction, autonomous extrinsic motivation (EM) for physical activity (PA), and PA behavior. Participants (N = 456, Mage = 40.7 years) completed online measures of these variables, and data were analyzed using structural equation modeling. selleck Results indicated a direct pathway from behavioral commitment to autonomous EM, plus indirect effects via autonomy, competence, and relatedness. There was no direct pathway from cognitive acceptance to autonomous EM, but there were indirect effects via competence and autonomy satisfaction. There was a direct pathway from cognitive acceptance to self-reported PA plus indirect effects via autonomous EM. There was no direct pathway from behavioral commitment to self-reported PA, but there were indirect effects via autonomous EM. Cognitive acceptance and behavioral commitment potentially support the development of autonomous EM for PA. Future research using longitudinal and intervention-based research designs is required to determine the causal relationships among these variables.OBJECTIVE To (1) compare the 1-repetition-maximum (1RM) performance between the push press, push jerk, and split jerk and (2) explore these differences between weightlifters, CrossFit athletes, and a mixed group of athletes. METHODS Forty-six resistance-trained males (age 28.8 [6.4] y; height 180.0 [6.0] cm; body mass 84.1 [10.2] kg; weightlifting training experience 3.64 [3.14] y) participated in this study. The 1RM performance of the push press, push jerk, and split jerk was assessed during the same session in a sequential order (ie, combined 1RM assessment method). Thirty-six participants were retested to determine between-sessions reliability of the 1RM values. RESULTS Intraclass correlation coefficients (ICCs) and associated 95% confidence intervals (CIs) showed a high between-sessions reliability for the push press (ICC = .98; 95% CI, .95-.99), push jerk (ICC = .99; 95% CI, .98-1.00), and split jerk (ICC = .99; 95% CI, .98-1.00). There was a significant main effect of exercise (η2 = .101) and exercise × group interaction (η2 = .