Tunneling current-controlled spin states in few-layer van der Waals magnets.

Effective control of magnetic phases in two-dimensional magnets would constitute crucial progress in spintronics, holding great potential for future computing technologies. Here, we report a new approach of leveraging tunneling current as a tool for controlling spin states in CrI3. We reveal that a tunneling current can deterministically switch between spin-parallel and spin-antiparallel states in few-layer CrI3, depending on the polarity and amplitude of the current. We propose a mechanism involving nonequilibrium spin accumulation in the graphene electrodes in contact with the CrI3 layers. We further demonstrate tunneling current-tunable stochastic switching between multiple spin states of the CrI3 tunnel devices, which goes beyond conventional bi-stable stochastic magnetic tunnel junctions and has not been documented in two-dimensional magnets. Our findings not only address the existing knowledge gap concerning the influence of tunneling currents in controlling the magnetism in two-dimensional magnets, but also unlock possibilities for energy-efficient probabilistic and neuromorphic computing.

Ultraviolet Excitation of M-O2 (M = Phenalenone, Fluorenone, Pyridine, & Acridine) Complexes Resulting in 1O2.

In our experiment, a trace amount of an organic molecule (M = 1H-phenalen-1-one, 9-fluorenone, pyridine, or acridine) was seeded into a gas mix consisting of 3% O2 with a rare gas buffer (He or Ar) and then supersonically expanded. We excited the resulting molecular beam with ultraviolet light at either 355 nm (1H-phenalen-1-one, 9-fluorenone, or acridine) or 266 nm (pyridine) and used resonance enhanced multiphoton ionization (REMPI) spectroscopy to probe for the formation of O2 in the a-1Δg state, 1O2. For all systems, the REMPI spectra demonstrate that ultraviolet excitation results in the formation of 1O2 and the oxygen product is confirmed to be in the ground vibrational state and with an effective rotational temperature below 80 K. We then recorded the velocity map ion image of the 1O2 product. From the ion images, we determined the center-of-mass translational energy distribution, P(ET), assuming photodissociation of a bimolecular M-O2 complex. We also report results from electronic structure calculations that allow for a determination of the M-O2 ground state binding energy. We use the complex binding energy, the energy to form 1O2, and the adiabatic triplet energy for each organic molecule to determine the available energy following photodissociation. For dissociation of a bimolecular complex, this available energy may be partitioned into either center-of-mass recoil or internal degrees of freedom of the organic moiety. We use the available energy to generate a Prior distribution, which predicts statistical energy partitioning during dissociation. For low available energies, less than 0.2 eV, we find that the statistical prediction is in reasonable agreement with the experimental observations. However, at higher available energies, the experimental distribution is biased to lower center-of-mass kinetic energies compared with the statistical prediction, which suggests the complex undergoes vibrational predissociation.

Nonvolatile Memristive Effect in Few-Layer CrI3 Driven by Electrostatic Gating.

The potential of memristive devices for applications in nonvolatile memory and neuromorphic computing has sparked considerable interest, particularly in exploring memristive effects in two-dimensional (2D) magnetic materials. However, the progress in developing nonvolatile, magnetic field-free memristive devices using 2D magnets has been limited. In this work, we report an electrostatic-gating-induced nonvolatile memristive effect in CrI3-based tunnel junctions. The few-layer CrI3-based tunnel junction manifests notable hysteresis in its tunneling resistance as a function of gate voltage. We further engineered a nonvolatile memristor using the CrI3 tunneling junction with low writing power and at zero magnetic field. We show that the hysteretic transport observed is not a result of trivial effects or inherent magnetic properties of CrI3. We propose a potential association between the memristive effect and the newly predicted ferroelectricity in CrI3 via gating-induced Jahn-Teller distortion. Our work illuminates the potential of 2D magnets in developing next-generation advanced computing technologies.

Screening and Assessing Suicide Risk in Medical Settings: Feasible Strategies for Early Detection.

Early detection of risk is a key suicide prevention strategy. Given that most individuals who die by suicide visit a health care provider in the year leading up to their death, medical settings are ideal venues for identifying those at elevated risk and bridging them to life-saving care. Clinicians are presented with an opportunity to engage in proactive suicide prevention efforts through practical and adaptable suicide risk screening, assessment, and management processes. Psychiatrists and mental health clinicians are well positioned to assist nonpsychiatric clinicians on the frontlines of this public health problem. This article discusses the importance of identifying people at elevated suicide risk through screening, differentiates screening from assessment procedures, and presents practical strategies for implementing evidence-based screening and assessment tools into practice as part of a three-tiered clinical pathway. Specifically, this article discusses key components that guide embedding suicide prevention strategies into the workflows of busy medical settings.

Suicide in young people: screening, risk assessment, and intervention.

Suicide is the fourth leading cause of death among young people worldwide and the third leading cause of death among those in the US. This review outlines the epidemiology of suicide and suicidal behavior in young people. It discusses intersectionality as an emerging framework to guide research on prevention of suicide in young people and highlights several clinical and community settings that are prime targets for implementation of effective treatment programs and interventions aimed at rapidly reducing the suicide rate in young people. It provides an overview of current approaches to screening and assessment of suicide risk in young people and the commonly used screening tools and assessment measures. It discusses universal, selective, and indicated evidence based suicide focused interventions and highlights components of psychosocial interventions with the strongest evidence for reducing risk. Finally, the review discusses suicide prevention strategies in community settings and considers future research directions and questions challenging the field.

The impact of peer influencing on adolescent suicidal ideation and suicide attempts.

OBJECTIVE: The purpose of this study was to examine the role of peer influence on adolescent suicidal ideation and attempts within youth seeking emergency care or outpatient mental health services. We examined whether affiliation with peers reporting suicidal thoughts/behaviors was associated with an adolescent's own suicidal ideation and/or suicide attempt beyond individual risk factors. METHODS: One hundred and eighteen adolescents, ages 13-18, were recruited from the emergency department and outpatient mental health clinics at a large, metropolitan children's hospital. Adolescents with suicidal ideation in the past six months (ideators, n=19) and with a suicide attempt in the past year (attempters, n=40) were matched with controls with no history of ideation or attempt on age (±1 year), sex, and race. Adolescents and parents completed semi-structured interviews and self-report questionnaires to examine individual and peer associated risk factors. RESULTS: Both ideators and attempters were more likely to affiliate with peers with suicidal behavior compared to their matched controls. However, affiliation with suicidal peers was only associated with attempter group status after controlling for individual risk factors. CONCLUSION: Affiliation with peers reporting suicidal thoughts/behaviors was linked to an adolescent's own history of suicide attempt. Through understanding peer affiliation, peers may be an important resource for both identifying and preventing youth suicidal behavior. Evidence-based programs that focus and utilize peer influence may be invaluable for prevention efforts.

Time-Dependent Mechanical Response of Ice Adhesion on Aluminum Substrates.

Ice adhesion on aerospace-relevant materials is both complex and not well understood. Measuring such adhesion and understanding the underlying physics involved require reliable testing techniques that can yield multifaceted data sets. The latter includes the surface morphology, that is, roughness, and its spatial correlation structure, resolving substrate-induced strain, and direct mechanical testing of adhesion. As part of a continuing investigation of ice adhesion on a relevant surface, we performed time-dependent stress ramps on aluminum surfaces. The temperature range explored, from -20 to -7 °C, allowed spontaneous icing and ice morphologies, namely, below or above -15 °C. Additionally, we characterized the spatial correlation surface roughness maps of the specimens. Our novel test protocol yields reproducible and high-precision results when compared with alternative methods reported throughout the literature. The stress-ramp test data using the proposed protocol show that the apparent average critical stress (proportional to the adhesion strength) depends on both stress-ramp rate and temperature. More specifically, the adhesion strength is higher for higher stress rates and increases with decreasing temperature. The stress-ramp test yields the full span of the time-dependent adhesive behavior of ice and particularly the upper bound. Additional stress-concentration analysis is needed to correct for this effect and thereby yield the critical stress rather than the average value produced by our procedure. The results in this work should aid to improve our understanding of ice adhesion mechanisms.

Two-Dimensional 2M-WS2 Nanolayers for Superconductivity.

Recently, a newly discovered VIB group transition metal dichalcogenide (TMD) material, 2M-WS2, has attracted extensive attention due to its interesting physical properties such as topological superconductivity, nodeless superconductivity, and anisotropic Majorana bound states. However, the techniques to grow high-quality 2M-WS2 bulk crystals and the study of their physical properties at the nanometer scale are still limited. In this work, we report a new route to grow high-quality 2M-WS2 single crystals and the observation of superconductivity in its thin layers. The crystal structure of the as-grown 2M-WS2 crystals was determined by X-ray diffraction (XRD) and scanning tunneling microscopy (STM). The chemical composition of the 2M-WS2 crystals was determined by energy dispersive X-ray spectroscopy (EDS) analysis. At 77 K, we observed the spatial variation of the local tunneling conductance (dI/dV) of the 2M-WS2 thin flakes by scanning tunneling spectroscopy (STS). Our low temperature transport measurements demonstrate clear signatures of superconductivity of a 25 nm-thick 2M-WS2 flake with a critical temperature (T C) of ∼8.5 K and an upper critical field of ∼2.5 T at T = 1.5 K. Our work may pave new opportunities in studying the topological superconductivity at the atomic scale in simple 2D TMD materials.

Spectroscopic Determination of Ice-Induced Interfacial Strain on Single-Layer Graphene.

Reliably determining the physical properties of ice (e.g., crystal structure, adhesion strength, interfacial state, and molecular orientation) has proven to be both challenging and highly dependent on experiment-specific conditions, including surface roughness, ice formation, water purity, and measurement method. Here, non-destructive measurements of single-layer graphene (SLG) interfaced with bulk ice are used to determine temperature-dependent, ice-induced strain and estimate ice-created strain elastic density in SLG. The use of SLG enables the precise study of interfacial strain by monitoring the 2D Raman mode. Upon ice formation, a clear, ≈2 cm-1 decrease in the 2D mode frequency is observed, which is ascribed to a 0.012% biaxial tensile shear strain at the ice-SLG interface. From this shear strain value, the ice-created SLG elastic strain energy density is estimated to be 2.4 µJ m-2 . In addition to these Raman strain measurements, intentionally ionized water is used to show that water-mediated charging of the SLG surface manifests itself in a distinctly different manner than ice-induced strain. Finally, the localized nature of the Raman probe is used to map SLG regions with and without ice, suggesting that this method cannot only determine ice-induced interfacial strain, but also correlate ice adhesion properties with surface roughness and topology.

Neurocognitive vulnerability to youth suicidal behavior.

Neurocognitive deficits have been associated with suicidal behavior in adults with major depressive disorder (MDD), but it is unclear if similar impairments are linked to youth suicidal behavior. This study compared neurocognitive functioning in suicidal and non-suicidal youth with a lifetime history of MDD and explored whether neurocognitive functioning predicted future suicide attempts. Neurocognition was examined using the Cambridge Neuropsychological Test Automated Battery (CANTAB) and Iowa Gambling Task (IGT) in 309 youths ages 12-15 (117 suicide attempters; 132 suicidal ideators; 60 never-suicidal). Prospective analyses included 284 youths (41 youth with a future attempt; 243 without a future attempt). Multivariate analysis of variance (MANOVA) yielded a significant group-by-sex interaction effect [Wilks' Λ = 0.901, F (16, 560) = 1.87, p = .021] for the primary neurocognitive outcomes, guiding the decision to stratify the sample by sex. Female suicide attempters and ideators were slower to respond correctly to both positive and negative emotion words than never-suicidal controls on tests of affective bias. Male suicide attempters and ideators made significantly more total and between errors than never-suicidal subjects. Exploratory analyses found that total commission errors on the Affective Go/No-Go (AGN) test significantly predicted future suicide attempts in females, and that higher strategy scores on Spatial Working Memory (SWM) tests predicted future male attempts. Study findings identified sex-specific neurocognitive deficits that differentiate suicidal and non-suicidal youth with histories of MDD. Extended longitudinal studies are needed to elucidate the temporal association between neurocognitive impairments and suicidal behavior and frame targets for early preventive interventions.

Association Between the Release of Netflix's 13 Reasons Why and Suicide Rates in the United States: An Interrupted Time Series Analysis.

OBJECTIVE: To estimate the association between the release of the Netflix series 13 Reasons Why and suicide rates in the United States. METHOD: Using segmented quasi-Poisson regression and Holt-Winters forecasting models, we assessed monthly rates of suicide among individuals aged 10 to 64 years grouped into 3 age categories (10-17, 18-29, and 30-64 years) between January 1, 2013, and December 31, 2017, before and after the release of 13 Reasons Why on March 31, 2017. We also assessed the impact of the show's release on a control outcome, homicide deaths. RESULTS: After accounting for seasonal effects and an underlying increasing trend in monthly suicide rates, the overall suicide rate among 10- to 17-year-olds increased significantly in the month immediately following the release of 13 Reasons Why (incidence rate ratio [IRR], 1.29; 95% CI, 1.09-1.53); Holt-Winters forecasting revealed elevated observed suicide rates in the month after release and in two subsequent months, relative to corresponding forecasted rates. Contrary to expectations, these associations were restricted to boys. Among 18- to 29-year-olds and 30- to 64-year-olds, we found no significant change in level or trend of suicide after the show's release, both overall and by sex. The show's release had no apparent impact in the control analyses of homicide deaths within any age group. CONCLUSION: The release of 13 Reasons Why was associated with a significant increase in monthly suicide rates among US youth aged 10 to 17 years. Caution regarding the exposure of children and adolescents to the series is warranted.

Suicide attempts by self-poisoning in the United States among 10-25 year olds from 2000 to 2018: substances used, temporal changes and demographics.

Objective: To evaluate the substances used, outcomes, temporal and demographics associated with suicide attempts by self-poisoning in children and young adults aged 10-25 years old from 2000 to 2018.Methods: This is a retrospective review of suspected-suicide self-poisoning cases reported to the National Poison Data System (NPDS) from US Poison Centers from 2000 to 2018 for patients 10-25 years old. For comparison of annual rates, we obtained population data by year of age from the US Census Bureau. We evaluated changes in: monthly and annual incidence/rate per 100,000 population, substances used and outcome by patient age and demographics.Results: There were 1,677,435 cases of suicide attempt by self-poisoning among individuals 10-25 years old reported to US PCCs from 2000 to 2018. There were 410,940 self-poisoning cases (24.5%) with a serious medical outcome, and the proportion of exposures that resulted in a serious medical outcome increased with increasing age group. For the age groups of 10-12, 13-15 and 16-18 years of age, there was a significant increase after 2011, which was influenced primarily by females. The substance groups with the greatest number of serious medical outcomes were OTC analgesics, antidepressants, antihistamines and antipsychotics. ADHD medications were common in the younger age groups of 10-15 years, while the sedative/hypnotics occurred more commonly in the older age groups. The groups with the greatest increase in serious medical outcomes after 2011 were antidepressants, OTC analgesics, antihistamines and ADHD medications. Opiates were less commonly involved (7.4%) in cases with serious medical outcomes and decreased significantly in the 19-25 year-old age groups after 2012. States with a lower population per square mile had a greater number of reported cases with serious medical outcomes. There was a significant decrease in the number of cases in the age groups of 10-18 years during the traditional non-school months of June-August compared with September-May. This seasonal trend occurred among cases with all outcomes and among cases with serious medical outcomes. This decrease did not occur in the age group of 19-21 years, and there was an increase during summer months in the age group 22-25 years.Conclusions: The substances used during self-poisoning varies by age group but appears to include substances available to that age group, with a significant increase after 2011, increased rates in more rural states, and a seasonal variation of increased rates during school months among adolescents but not among young adults. Two of the top substances, OTC analgesics and antihistamines, in all age groups, comprising more than a third of all substances used, are widely available over-the-counter with no restrictions regarding access. Of additional concern, ADHD medications had the highest risk of a serious medical outcome.

Sex- and Age-specific Increases in Suicide Attempts by Self-Poisoning in the United States among Youth and Young Adults from 2000 to 2018.

OBJECTIVE: To evaluate the incidence and outcomes from intentional suspected-suicide self-poisoning in children and young adults ages 10-24 years old from 2000 to 2018. STUDY DESIGN: Retrospective review of intentional suspected-suicide self-poisoning cases reported to the National Poison Data System from US poison centers from 2000 to 2018 for patients 10-24 years old. For comparison of annual rates, population data by year of age were obtained from the US Census Bureau. We evaluated changes in the annual incidence, the annual rate per 100 000 population, and the medical outcome by patient age and sex. RESULTS: There were 1 627 825 intentional suspected-suicide self-poisoning cases, of which 1 162 147 (71%) were female. In children 10-15 years old from 2000 to 2010, there was a decrease in number and rate per 100 000 population followed by a significant increase (from 125% to 299%) from 2011 to 2018. In children 10-18 years old, the increase from 2011 to 2018 was driven predominantly by females. In 19-24 years old age groups, there was a temporal delay and reduced increase in slope compared with the younger groups. There were 340 563 moderate outcomes, 45 857 major outcomes, and 1404 deaths. The percentage of cases with a serious outcome, major effect, or death increased over time and with age. CONCLUSIONS: The incidence and rate of suicide attempts using self-poisoning in children less than 19 years old increased significantly after 2011, occurring predominantly in young girls. There has been an increase in the severity of outcomes independent of age or sex.

Adaptation of Multi-Family Psychoeducational Psychotherapy (MF-PEP) for Adolescents with Mood Disorders: Preliminary Findings.

Adolescent mood disorders are a major public health concern. Clinical need for services outstrips availability in many communities. Group psychotherapy is an efficient means to provide service to a larger number of clientele and can offer certain clinical advantages. Multi-Family Psychoeducational Psychotherapy (MF-PEP), an adjunctive group psychosocial treatment, has been shown to improve children's mood symptoms, increase parents' knowledge of mood disorder symptoms, improve family interactions and improve use of behavioral health services. In this study, an adaptation of MF-PEP for adolescents with mood disorders is described and preliminary data are presented. Among the 19 adolescents with mood disorders and 22 parents who completed the study, improvements in adolescents' depressive symptoms, quality of life, families' understanding of mood disorders, and overall satisfaction with treatment were reported. Results have informed ongoing pilot testing of Teen-MF-PEP.

Decision-making in adolescents with suicidal ideation: A case-control study.

Decision-making deficits have been associated with attempted suicide in adolescents and adults. This study examined Iowa Gambling Task performance in 19 youths with suicidal ideation and 19 never-suicidal comparison subjects. Group differences in decision-making did not persist after controlling for current affective problems and psychotropic medication use. Future research should determine the contribution of decision-making in predicting the transition from suicidal thoughts to suicide attempts.

Impulsive aggression, delay discounting, and adolescent suicide attempts: effects of current psychotropic medication use and family history of suicidal behavior.

OBJECTIVE: Impulsive-aggressive behaviors have been consistently implicated in the phenomenology, neurobiology, and familial aggregation of suicidal behavior. The purpose of this study was to extend previous work by examining laboratory behavioral measures of delayed reward impulsivity and impulsive aggression in adolescent suicide attempters and never-suicidal comparison subjects. METHODS: Using the Point Subtraction Aggression Paradigm (PSAP) and the Delay Discounting Task (DDQ), the authors examined delay discounting and impulsive aggression in 40 adolescent suicide attempters, ages 13-18, and 40 never-suicidal, demographically matched psychiatric comparison subjects. RESULTS: Overall, suicide attempters and comparison subjects performed similarly on the PSAP and DDQ. There was a significant group by current psychotropic medication use interaction (p=0.013) for mean aggressive responses on the PSAP. Group comparisons revealed that attempters emitted more aggressive responses per provocation than comparison subjects, only in those not on psychotropic medication (p=0.049), whereas for those currently treated with psychotropic medication, there were no group differences (p>0.05). This interaction effect was specific to current antidepressant use. Among all subjects, family history of suicidal behavior (suicide or suicide attempt) in first degree relatives was significantly correlated with both delay discounting (r=-0.22, p=0.049), and aggressive responding (r=0.27, p=0.015). Family history of suicidal behavior was associated with delay discounting, but not with aggressive responding on the PSAP, after controlling for relevant covariates. CONCLUSIONS: In this study, impulsive-aggressive responding was associated with suicide attempt only in those not being treated with antidepressants. Future work to replicate and extend these findings could have important therapeutic implications for the treatment of depressed suicide attempters, many of whom are affected by impulsive aggression.

Risk-sensitive decision-making deficit in adolescent suicide attempters.

OBJECTIVE: Suicide among adolescents is a major public health problem. Decision-making deficits may play an important role in vulnerability to suicidal behavior, but few studies have examined decision-making performance in youth at risk for suicide. In this study, we seek to extend recent findings that adolescent suicide attempters process risk evaluations differently than adolescents who have not attempted suicide. METHODS: We assessed decision-making in 14 adolescent suicide attempters and 14 non-attempter comparison subjects, ages 15-19, using the Cambridge Gambling Task (CGT). Each participant was also administered a diagnostic interview (Mini-International Neuropsychiatric Interview [MINI]), structured suicide severity measures, and a brief intelligence quotient (IQ) measure. RESULTS: After controlling for gender and IQ differences, suicide attempters displayed an elevated risk-taking propensity on the CGT relative to comparison subjects, such that they were more willing to take a large risk with their bank of points, a decision-making style that proves disadvantageous over time. No group differences in the latency or accuracy of decision-making were observed. CONCLUSIONS: Adolescents with a history of suicide attempt display increased risk-taking and greater difficulty predicting probable outcomes on the CGT. Such deficits have been associated with dysfunction in the orbitofrontal prefrontal cortex, which supports other studies implicating impaired decision-making among individuals with a history of suicide attempt.

A preliminary study of medial temporal lobe function in youths with a history of caregiver deprivation and emotional neglect.

Previous research findings have linked caregiver deprivation and emotional neglect with sensitivity to threatening cues. The present preliminary study investigated whether dysfunctions of the medial temporal lobe could underlie these associations. Using fMRI, we measured medial temporal lobe responses to emotional faces (angry, fearful, happy, neutral) among 30 youths. Eleven of the youths had a history of caregiver deprivation and emotional neglect. Attention states (i.e., attention to anger, fear, or physical attributes, or passive viewing) were systematically manipulated. Relative to comparison youths, youths with a history of caregiver deprivation and emotional neglect showed significantly greater left amygdala and left anterior hippocampus activation during the processing of threatening information. To our knowledge, these findings are the first to demonstrate altered medial temporal lobe function during the processing of threat cues in youths with a history of caregiver deprivation and emotional neglect.

A review of the effects of prenatal cocaine exposure among school-aged children.

CONTEXT: Studies through 6 years have shown no long-term direct effects of prenatal cocaine exposure (PCE) on children's physical growth, developmental test scores, or language outcomes. Little is known about the effects of PCE among school-aged children aged 6 years and older. OBJECTIVE: We reviewed articles from studies that examined the effects of PCE on growth, cognitive ability, academic functioning, and brain structure and function among school-aged children. METHODS: Articles were obtained by searching PubMed, Medline, TOXNET, and PsycInfo databases from January 1980 to December 2008 with the terms "prenatal cocaine exposure," "cocaine," "drug exposure," "substance exposure," "maternal drug use," "polysubstance," "children," "adolescent," "in utero," "pregnancy," "development," and "behavior." Criteria for inclusion were (1) empirical research on children aged 6 years and older prenatally exposed to cocaine, (2) peer-reviewed English-language journal, (3) comparison group, (4) longitudinal follow-up or historical prospective design, (5) masked assessment, (6) exclusion of subjects with serious medical disabilities, and (7) studies that reported nonredundant findings for samples used in multiple investigations. Thirty-two unique studies met the criteria. Each article was independently abstracted by 2 authors to obtain sample composition, methods of PCE assessment, study design, comparison groups, dependent variables, covariates, and results. RESULTS: Associations between PCE and growth, cognitive ability, academic achievement, and language functioning were small and attenuated by environmental variables. PCE had significant negative associations with sustained attention and behavioral self-regulation, even with covariate control. Although emerging evidence suggests PCE-related alterations in brain structure and function, interpretation is limited by methodologic inconsistencies. CONCLUSIONS: Consistent with findings among preschool-aged children, environmental variables play a key role in moderating and explaining the effects of PCE on school-aged children's functioning. After controlling for these effects, PCE-related impairments are reliably reported in sustained attention and behavioral self-regulation among school-aged children.