In situ via Contact to hBN-Encapsulated Air-Sensitive Atomically Thin Semiconductors.

Establishing reliable electrical contacts to atomically thin materials is a prerequisite for both fundamental studies and applications yet remains a challenge. In particular, the development of contact techniques for air-sensitive monolayers has lagged behind, despite their unique properties and significant potential for applications. Here, we present a robust method to create contacts to device layers encapsulated within hexagonal boron nitride (hBN). This method uses plasma etching and metal deposition to create 'vias' in the hBN with graphene forming an atomically thin etch-stop. The resulting partially fluorinated graphene (PFG) protects the underlying device layer from air-induced degradation and damage during metal deposition. PFG is resistive in-plane but maintains high out-of-plane conductivity. The work function of the PFG/metal contact is tunable through the degree of fluorination, offering opportunities for contact engineering. Using the in situ via technique, we achieve ambipolar contact to air-sensitive monolayer 2H-molybdenum ditelluride (MoTe2) with more than 1 order of magnitude improvement in on-current density compared to previous literature. The complete encapsulation provides high reproducibility and long-term stability. The technique can be extended to other air-sensitive materials as well as air-stable materials, offering highly competitive device performance.

Identifying Luminescent Boron Vacancies in h-BN Generated Using Controlled He+ Ion Irradiation.

The defect emission from h-BN at 1.55 eV is interesting as it enables optical readout of spins. It is necessary to identify the nature of the relevant point defects for its controlled introduction. However, it is challenging to engineer point defects in h-BN without changing the local atomic structure. Here, we controllably introduce boron vacancies in h-BN using an ultrahigh spatial resolution and low-energy He+ ion beam. By optimizing the He+ ion irradiation conditions, we control the quantity and location of defects spatially and along the depth of h-BN to achieve a robust photoluminescence emission at 1.55 eV from 10 K to room temperature. We show that as-generated defects activate an additional Raman mode at 1295 cm-1. Electron energy loss spectroscopy confirms introduction of boron vacancies without modification of the local h-BN crystal structure. Our results provide a deterministic strategy to create scalable boron vacancy emitters in h-BN for quantum photonics.

A dual-system, machine-learning approach reveals how daily pubertal hormones relate to psychological well-being in everyday life.

The two studies presented in this paper seek to resolve mixed findings in research linking activity of pubertal hormones to daily adolescent outcomes. In study 1 we used a series of Confirmatory Factor Analyses to compare the fit of one and two-factor models of seven steroid hormones (n = 994 participants, 8084 samples) of the HPA and HPG axes, using data from a field study (https://www.icpsr.umich.edu/web/ICPSR/studies/38180) collected over ten consecutive weekdays in a representative sample of teens starting high school. In study 2, we fit a Bayesian model to our large dataset to explore how hormone activity was related to outcomes that have been demonstrated to be linked to mental health and wellbeing (self-reports of daily affect and stress coping). Results reveal, first that a two-factor solution of adolescent hormones showed good fit to our data, and second, that HPG activity, rather than the more often examined HPA activity, was associated with improved daily affect ratios and stress coping. These findings suggest that field research, when it is combined with powerful statistical techniques, may help to improve our understanding of the relationship between adolescent hormones and daily measures of well-being.

Strong and Localized Luminescence from Interface Bubbles Between Stacked hBN Multilayers.

Extraordinary optoelectronic properties of van der Waals (vdW) heterostructures can be tuned via strain caused by mechanical deformation. Here, we demonstrate strong and localized luminescence in the ultraviolet region from interface bubbles between stacked multilayers of hexagonal boron nitride (hBN). Compared to bubbles in stacked monolayers, bubbles formed by stacking vdW multilayers show distinct mechanical behavior. We use this behavior to elucidate radius- and thickness-dependent bubble geometry and the resulting strain across the bubble, from which we establish the thickness-dependent bending rigidity of hBN multilayers. We then utilize the polymeric material confined within the bubbles to modify the bubble geometry under electron beam irradiation, resulting in strong luminescence and formation of optical standing waves. Our results open a route to design and modulate microscopic-scale optical cavities via strain engineering in vdW materials, which we suggest will be relevant to both fundamental mechanical studies and optoelectronic applications.

Mechanisms of Quasi van der Waals Epitaxy of Three-Dimensional Metallic Nanoislands on Suspended Two-Dimensional Materials.

Understanding structure at the interface between two-dimensional (2D) materials and 3D metals is crucial for designing novel 2D/3D heterostructures and improving the performance of many 2D material devices. Here, we quantify and discuss the 2D/3D interface structure and the 3D morphology in several materials systems. We first deposit faceted Au nanoislands on graphene and transition metal dichalcogenides, using measurements of the equilibrium island shape to determine values for the 2D/Au interface energy and examining the role of surface reconstructions, chemical identity, and defects on the grown structures. We then deposit the technologically relevant metals Ti and Nb under conditions where kinetic rather than thermodynamic factors govern growth. We describe a transition from dendritic to faceted islands as a function of growth temperature and discuss the factors determining island shape in these materials systems. Finally, we show that suspended 2D materials enable the fabrication of a novel type of 3D/2D/3D heterostructure and discuss the growth mechanism. We suggest that emerging nanodevices will utilize versatile fabrication of 2D/3D heterostructures with well-characterized interfaces and morphologies.

Chemiluminescent immunoassay overestimates hormone concentrations and obscures testosterone sex differences relative to LC-MS/MS in a field study of diverse adolescents.

Background: Methodological comparisons of hormone quantification techniques have repeatedly demonstrated that, in adults, enzyme immunoassay (EIA) inflates steroid hormone concentrations relative to mass spectrometry. However, methodological comparisons in adolescent samples remain rare, and few studies have examined how chemiluminescent immunoassay (CLIA), another popular immunoassay, compares to mass spectrometry. Additionally, no studies have examined how differences in analytical techniques may be affecting relationships between steroid hormone levels and outcomes of interest, such as psychopathology. This pre-registered analysis of an existing dataset measured salivary cortisol and testosterone using both CLIA and liquid chromatography dual mass spectrometry (LC-MS/MS) in a repeated measures (516 samples) sample of 207 9th graders. Methods: In aim 1, this study sought to expand on past findings by 1) measuring inflation of testosterone and cortisol by CLIA in a relatively large adolescent sample, and 2) showing that CLIA (like EIA) testosterone inflation was especially true in groups with low 'true' testosterone levels. In aim 2, this study sought to examine the impact of hormone quantification method on relationships between hormone levels and psychopathological measures (the Children's Depression Inventory, the Perceived Social Stress Scale, the UCLA Loneliness Scale, and the Anxious Avoidant and Negative Self Evaluation subscales of the Social Anxiety Scale for Adolescents). Results: We found that CLIA, like EIA, inflated testosterone and cortisol levels and overestimated female testosterone resulting in suppressed sex differences in testosterone. We did not observe these same patterns when examining testosterone in individuals with differing levels of pubertal development. Results of psychopathology analyses demonstrated no significant method differences in hormone-psychopathology relationships. Conclusions: Our findings show that CLIA introduces proportional bias in cortisol and testosterone in a manner that suppresses sex differences in testosterone. Steroid measurement method did not significantly moderate the relationship between hormones and psychopathology in our sample, though more work is needed to investigate this question in larger, clinical samples.

Gonadal and adrenal hormones interact with pubertal maturation to predict depressive symptoms in a group of high-school females.

Adolescent females are at elevated risk for the development of depression. In this study, we addressed two questions: Are pubertal hormones associated with adolescent mental health? Might this association depend on pubertal development? We tested the hypothesis that estradiol, which has been associated with adolescent social sensitivity, might interact with pubertal stage to predict depression risk at three time points in ninth and tenth grade. Hormones and pubertal development were measured ninth-grade females. Linear regression analyses were used to predict fall ninth-grade (N = 79), spring ninth-grade (N = 76), and spring tenth-grade (N = 67) Children's Depression Inventory (CDI) scores. The hypothesized model was not statistically significant, but exploratory analyses revealed that two- and three-way interactions incorporating estradiol, puberty (stage and perceived onset), and cortisol predicted current and future CDI scores. Our exploratory model did not predict changes in CDI but did account for future (spring of ninth grade) CDI scores. Specifically, estradiol was positively correlated with fall and spring ninth-grade depressive symptoms in participants with high cortisol who also reported earlier stages and later perceived onset of pubertal development. These findings suggest that hormones associated with sensitivity to the social environment deserve consideration in models of adolescent depression risk.

Trait attributions and threat appraisals explain why an entity theory of personality predicts greater internalizing symptoms during adolescence.

Adolescents who hold an entity theory of personality - the belief that people cannot change - are more likely to report internalizing symptoms during the socially stressful transition to high school. It has been puzzling, however, why a cognitive belief about the potential for change predicts symptoms of an affective disorder. The present research integrated three models - implicit theories, hopelessness theories of depression, and the biopsychosocial model of challenge and threat - to shed light on this issue. Study 1 replicated the link between an entity theory and internalizing symptoms by synthesizing multiple datasets (N = 6,910). Study 2 examined potential mechanisms underlying this link using 8-month longitudinal data and 10-day diary reports during the stressful first year of high school (N = 533, 3,199 daily reports). The results showed that an entity theory of personality predicted increases in internalizing symptoms through tendencies to make fixed trait causal attributions about the self and maladaptive (i.e., "threat") stress appraisals. The findings support an integrative model whereby situation-general beliefs accumulate negative consequences for psychopathology via situation-specific attributions and appraisals.

Nanoscale Modification of WS2 Trion Emission by Its Local Electromagnetic Environment.

Structural, electronic, and chemical nanoscale modifications of transition metal dichalcogenide monolayers alter their optical properties. A key missing element for complete control is a direct spatial correlation of optical response to nanoscale modifications due to the large gap in spatial resolution between optical spectroscopy and nanometer-resolved techniques. Here, we bridge this gap by obtaining nanometer-resolved optical properties using electron spectroscopy at cryogenic temperatures, specifically electron energy loss spectroscopy for absorption and cathodoluminescence for emission, which are then directly correlated to chemical and structural information. In an h-BN/WS2/h-BN heterostructure, we observe local modulation of the trion (X-) emission due to tens of nanometer wide dielectric patches. Trion emission also increases in regions where charge accumulation occurs, close to the carbon film supporting the heterostructures. The localized exciton emission (L) detected here is not correlated to strain above 1%, suggesting point defects might be involved in their formation.

Tunable Optical Properties of Thin Films Controlled by the Interface Twist Angle.

Control of materials properties has been the driving force of modern technologies. So far, materials properties have been modulated by their composition, structure, and size. Here, by using cathodoluminescence in a scanning transmission electron microscope, we show that the optical properties of stacked, >100 nm thick hexagonal boron nitride (hBN) films can be continuously tuned by their relative twist angles. Due to the formation of a moiré superlattice between the two interface layers of the twisted films, a new moiré sub-band gap is formed with continuously decreasing magnitude as a function of the twist angle, resulting in tunable luminescence wavelength and intensity increase of >40×. Our results demonstrate that moiré phenomena extend beyond monolayer-based systems and can be preserved in a technologically relevant, bulklike material at room temperature, dominating optical properties of hBN films for applications in medicine, environmental, or information technologies.

Synergistic bactericidal effect of hot water with citric acid against Escherichia coli O157:H7 biofilm formed on stainless steel.

This study investigated the antimicrobial effect of hot water with citric acid against Escherichia coli O157:H7 biofilm on stainless steel (SS). Hot water (50, 60, or 70 °C) with 2% citric acid exhibited a synergistic bactericidal effect on the pathogen biofilm. It was revealed that hot water and citric acid combination induced sub-lethally injured cells. Additionally, mechanisms of the synergistic bactericidal effects of hot water with citric acid were identified through several approaches. In terms of biofilm matrix, hot water removes exopolysaccharides, a major component of extracellular polymeric substances (EPS), thereby increasing contact between surface cells and citric acid, resulting in a synergistic bactericidal effect. In terms of the cell itself, increased permeability of citric acid through cell membranes destructed by hot water promotes the inactivation of superoxide dismutase (SOD) in E. coli O157:H7, which induce synergistic generation of reactive oxygen species (ROS) which promote inactivation of cell by activating lipid peroxidation, resulting in destruction of the cell membrane. Therefore, it is interpreted that when hot water with citric acid is applied to E. coli O157:H7 biofilm, synergy effects on the biofilm matrix and cell itself have a complex interaction with each other, thus causing a dramatic synergistic bactericidal effect.

Climbing up or falling down: Narcissism predicts physiological sensitivity to social status in children and their parents.

Children's narcissism may be rooted in sensitivity to social status (i.e., prominence, respect, and influence in a social group), and this sensitivity might be shared with parents. Testing this idea, a randomized experiment examined how children with high narcissism levels and their parents respond to gains and losses of social status. On a simulated social media platform, children (N = 123, ages 8-13) competed with fictitious peers for status and were randomly assigned to gain or lose status. Unbeknownst to children, parents viewed the course of the task. Children's and parents' affective reactions during the task were measured with facial electromyography, which detects spontaneous facial muscle activity linked to positive affect (i.e., zygomaticus major activity, involved in smiling) and negative affect (i.e., corrugator supercilii activity, involved in frowning). Children with higher narcissism levels showed steeper increases in negative affect during status loss and steeper increases in both positive and negative affect during status gain. Their parents mirrored the steeper increase in positive affect during their child's status gain, but they did not mirror the increase in negative affect. These results suggest that children with high narcissism levels and their parents show intensified affective-motivational responses to children's status-relevant experiences. These responses may be transmitted from one generation to the other (e.g., genetically or through parent-child socialization).

Stress, Sleep, and Coping Self-Efficacy in Adolescents.

Adults are thought to show a sleep-stress spiral in which greater stress worsens sleep quality, which amplifies stress, which leads to worse sleep. This study examined whether adolescents show a similar spiral, and if so, whether coping self-efficacy-believing one can cope with stress-interrupts the spiral. Temporal dynamics of perceived stress, sleep quality, and coping self-efficacy were tracked in 381 9th graders (49% female, mean age 14.43, age range 14-16) using daily surveys across two school weeks (3184 observations). Though expected associations were evident between individuals, only a unidirectional path was found within individuals from sleep quality to perceived stress via coping self-efficacy. This challenges the conventional bidirectional understanding of sleep-stress relations and suggests coping self-efficacy as an intervention target.

Getting Fewer "Likes" Than Others on Social Media Elicits Emotional Distress Among Victimized Adolescents.

Three studies examined the effects of receiving fewer signs of positive feedback than others on social media. In Study 1, adolescents (N = 613, Mage  = 14.3 years) who were randomly assigned to receive few (vs. many) likes during a standardized social media interaction felt more strongly rejected, and reported more negative affect and more negative thoughts about themselves. In Study 2 (N = 145), negative responses to receiving fewer likes were associated with greater depressive symptoms reported day-to-day and at the end of the school year. Study 3 (N = 579) replicated Study 1's main effect of receiving fewer likes and showed that adolescents who already experienced peer victimization at school were the most vulnerable. The findings raise the possibility that technology which makes it easier for adolescents to compare their social status online-even when there is no chance to share explicitly negative comments-could be a risk factor that accelerates the onset of internalizing symptoms among vulnerable youth.

Adolescents with an entity theory of personality are more vigilant to social status and use relational aggression to maintain social status.

The present research proposed that one social-cognitive root of adolescents' willingness to use relational aggression to maintain social status in high school is an entity theory of personality, which is the belief that people's social status-relevant traits are fixed and cannot change. Aggregated data from three studies (N=882) showed that first-year high school adolescents in the U.S. who endorsed more of an entity theory were more likely to show cognitive and motivational vigilance to social status, in terms of judgments on a novel social categorization task and reports of goals related to demonstrating social status to peers. Those with an entity theory then showed a greater willingness to use relational aggression, as measured by retrospective self-reports, responses to a hypothetical scenario, and a behavioral choice task. Discussion centers on theoretical and translational implications of the proposed model and of the novel measures.

How School Contexts Shape the Relations Among Adolescents' Beliefs, Peer Victimization, and Depressive Symptoms.

The present research examined how school contexts shape the extent to which beliefs about the potential for change (implicit theories) interact with social adversity to predict depressive symptoms. A preregistered multilevel regression analysis using data from 6,237 ninth-grade adolescents in 25 U.S. high schools showed a three-way interaction: Implicit theories moderated the associations between victimization and depressive symptoms only in schools with high levels of school-level victimization, but not in schools with low victimization levels. In high-victimization schools, adolescents who believed that people cannot change (an entity theory of personality) were more depressed when they were victimized more frequently. Thus, the mental health correlates of adolescents' implicit theories depend on both personal experiences and the norms in the context.

An Entity Theory of Intelligence Predicts Higher Cortisol Levels When High School Grades Are Declining.

Grades often decline during the high school transition, creating stress. The present research integrates the biopsychosocial model of challenge and threat with the implicit theories model to understand who shows maladaptive stress responses. A diary study measured declines in grades in the first few months of high school: salivary cortisol (N = 360 students, N = 3,045 observations) and daily stress appraisals (N = 499 students, N = 3,854 observations). Students who reported an entity theory of intelligence (i.e., the belief that intelligence is fixed) showed higher cortisol when grades were declining. Moreover, daily academic stressors showed a different lingering effect on the next day's cortisol for those with different implicit theories. Findings support a process model through which beliefs affect biological stress responses during difficult adolescent transitions.

Determining optimal parameters of the self-referent encoding task: A large-scale examination of self-referent cognition and depression.

[Correction Notice: An Erratum for this article was reported online in Psychological Assessment on Aug 2 2018 (see record 2018-38659-001). In this article, there was an error in how exclusions for one of the three samples were reported, which resulted in inaccurate reporting of how many participants did not have complete data. This error did not change the primary results of the article or the conclusions. However, in the second paragraph of the Participant Attrition and Data Filtering section, the number of exclusions for the adolescent sample should be 301, not 163. As a result, n=408 should read n=270 in the abstract; in paragraph 3 of the Method section; and in the Figure 1 legend. In addition, the correct values for the Adolescents sample reported in Tables 1 and 2 are provided in the erratum.] Although the self-referent encoding task (SRET) is commonly used to measure self-referent cognition in depression, many different SRET metrics can be obtained. The current study used best subsets regression with cross-validation and independent test samples to identify the SRET metrics most reliably associated with depression symptoms in three large samples: a college student sample (n = 572), a sample of adults from Amazon Mechanical Turk (n = 293), and an adolescent sample from a school field study (n = 408). Across all 3 samples, SRET metrics associated most strongly with depression severity included number of words endorsed as self-descriptive and rate of accumulation of information required to decide whether adjectives were self-descriptive (i.e., drift rate). These metrics had strong intratask and split-half reliability and high test-retest reliability across a 1-week period. Recall of SRET stimuli and traditional reaction time (RT) metrics were not robustly associated with depression severity. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Author Reply: Arousal Reappraisal as an Affect Regulation Strategy.

The biopsychosocial (BPS) model of challenge and threat posits that resource and demand appraisals interact in situations of acute stress to determine affective responses, and concomitant physiological responses, motivation, and decisions/behaviors. Regulatory approaches that alter appraisals to regulate challenge and threat affective states have the potential to facilitate coping. This reply clarifies the conceptualization of one such regulatory approach, arousal (or stress) reappraisal, and suggests avenues for future research. However, it is important to note that arousal reappraisal (or any brief psychological intervention) is not a "silver bullet" for improving stress outcomes, nor should this strategy be expected to positively impact all individuals. More work is needed to better elucidate how psychological and biological stress processes interact to shape health.

Capitalizing on Appraisal Processes to Improve Affective Responses to Social Stress.

Regulating affective responses to acute stress has the potential to improve health, performance, and well-being outcomes. Using the biopsychosocial (BPS) model of challenge and threat as an organizing framework, we review how appraisals inform affective responses and highlight research that demonstrates how appraisals can be used as regulatory tools. Arousal reappraisal, specifically, instructs individuals on the adaptive benefits of stress arousal so that arousal is conceptualized as a coping resource. By reframing the meaning of signs of arousal that accompany stress (e.g., racing heart), it is possible to break the link between stressful situations, and malignant physiological responses and experiences of negative affect. Applications of arousal reappraisal for academic contexts and clinical science, and directions for future research are discussed.