Local inhomogeneities resolved by scanning probe techniques and their impact on local 2DEG formation in oxide heterostructures.

Lateral inhomogeneities in the formation of two-dimensional electron gases (2DEG) directly influence their electronic properties. Understanding their origin is an important factor for fundamental interpretations, as well as high quality devices. Here, we studied the local formation of the buried 2DEG at LaAlO3/SrTiO3 (LAO/STO) interfaces grown on STO (100) single crystals with partial TiO2 termination, utilizing in situ conductive atomic force microscopy (c-AFM) and scattering-type scanning near-field optical microscopy (s-SNOM). Using substrates with different degrees of chemical surface termination, we can link the resulting interface chemistry to an inhomogeneous 2DEG formation. In conductivity maps recorded by c-AFM, a significant lack of conductivity is observed at topographic features, indicative of a local SrO/AlO2 interface stacking order, while significant local conductivity can be probed in regions showing TiO2/LaO interface stacking order. These results could be corroborated by s-SNOM, showing a similar contrast distribution in the optical signal which can be linked to the local electronic properties of the material. The results are further complemented by low-temperature conductivity measurements, which show an increasing residual resistance at 5 K with increasing portion of insulating SrO-terminated areas. Therefore, we can correlate the macroscopic electrical behavior of our samples to their nanoscopic structure. Using proper parameters, 2DEG mapping can be carried out without any visible alteration of sample properties, proving c-AFM and s-SNOM to be viable and destruction-free techniques for the identification of local 2DEG formation. Furthermore, applying c-AFM and s-SNOM in this manner opens the exciting prospect to link macroscopic low-temperature transport to its nanoscopic origin.

Overt and relational aggression in adolescents: social-psychological adjustment of aggressors and victims.

Examined the relative and combined associations among relational and overt forms of aggression and victimization and adolescents' concurrent depression symptoms, loneliness, self-esteem, and externalizing behavior. An ethnically diverse sample of 566 adolescents (55% girls) in Grades 9 to 12 participated. Results replicated prior work on relational aggression and victimization as distinct forms of peer behavior that are uniquely associated with concurrent social-psychological adjustment. Victimization was associated most closely with internalizing symptoms, and peer aggression was related to symptoms of disruptive behavior disorder. Findings also supported the hypothesis that victims of multiple forms of aggression are at greater risk for adjustment difficulties than victims of one or no form of aggression. Social support from close friends appeared to buffer the effects of victimization on adjustment.

Self-mutilative behavior in adolescents who attempt suicide by overdose.

OBJECTIVE: To examine the cognitive/affective and behavioral symptoms of adolescent suicide attempters with self-mutilative behavior (SMB). METHOD: Adolescents evaluated after a suicide attempt that occurred between 1996 and 2000 were divided into two groups: suicide attempters with a history of SMB (n = 52) and suicide attempters without SMB (n = 43). The groups were then compared on psychiatric diagnosis, suicide intent, depression, hopelessness, loneliness, anger, reckless behavior, substance use, and family functioning. RESULTS: Carving on the skin and picking at a wound were the most commonly reported SMBs, occurring in about one third of the sample. The SMB group was significantly more likely to be diagnosed with oppositional defiant disorder, major depression, and dysthymia and had higher scores on measures of hopelessness, loneliness, anger, risk taking, reckless behavior, and alcohol use than did the non-SMB group. Loneliness increased the odds of SMB almost 6-fold. CONCLUSIONS: Adolescent suicide attempts with SMB are associated with greater cognitive/affective and behavioral symptoms. Adolescent suicide attempters should be routinely screened for SMB.

Adolescents' and their friends' health-risk behavior: factors that alter or add to peer influence.

OBJECTIVE: To examine models of risk for adolescent health-risk behavior, including family dysfunction, social acceptance, and depression as factors that may compound or mitigate the associations between adolescents' and peers' risk behavior. METHODS: Participants were 527 adolescents in grades 9-12. Adolescents reported on their substance use (cigarette and marijuana use, heavy episodic drinking), violent behavior (weapon carrying, physical fighting), suicidality (suicidal ideation and attempts), and the health-risk behavior of their friends. RESULTS: Adolescents' substance use, violence, and suicidal behavior were related to their friends' substance use, deviance, and suicidal behaviors, respectively. Friends' prosocial behavior was negatively associated with adolescent violence and substance use. Family dysfunction, social acceptance, and depression altered the magnitude of association between peers' and adolescents' risk behavior. In cumulative risk factor models, rates of adolescent health-risk behavior increased twofold with each added risk factor. CONCLUSIONS: Results supported both additive and multiplicative models of risk. Implications for intervention and primary prevention are discussed.

The clinical presentation of childhood partial arousal parasomnias.

Objectives: The goal of the current study was to compare the sleep characteristics of children diagnosed with a partial arousal parasomnia to a community sample and further, to compare children diagnosed with sleep terrors to those diagnosed with sleepwalking.Background: Many children experience frightened awakenings, with up to 15% meeting criteria for a parasomnia. Despite this, very little empirical data exists examining parasomnias in childhood.Method: The parents of children (between 2 and 12 years of age) referred to a pediatric sleep disorders clinic completed the Children's Sleep Habits Questionnaire (CSH) on their child. The group meeting criteria for partial parasomnia was then matched with a community sample to identify differences in sleep characteristics between children with parasomnias and a normative sample.Results: Children with parasomnias had higher rates of bedtime resistance, sleep onset delay, night waking, and reduced sleep duration than a matched community sample. Sleepwalkers had more sleep onset problems than children with sleep terrors. Almost one quarter of sleepwalkers between 3 and 12 years of age reported nocturnal enuresis.Conclusions: Children with partial arousal parasomnias do have slightly more disturbed sleep than community controls.

Peer functioning, family dysfunction, and psychological symptoms in a risk factor model for adolescent inpatients' suicidal ideation severity.

Examined models of suicidal ideation severity that include two psychosocial risk factors (i.e., peer and family functioning) and four domains of psychological symptoms (i.e., generalized anxiety, depression, conduct problems, and substance abuse/dependence). Participants were 96 psychiatric inpatients (32 boys, 64 girls), ages 12 to 17, who were hospitalized because of concerns of suicidality. Adolescents completed a structured diagnostic interview, measures of suicidal ideation, and several dimensions of family and peer functioning. Results supported a model in which greater levels of perceived peer rejection and lower levels of close friendship support were associated directly with more severe suicidal ideation. In addition, indirect pathways included deviant peer affiliation and global family dysfunction related to suicidal ideation via substance use and depression symptoms. The results are among the first to demonstrate relations between suicidal ideation and several areas of adolescent peer functioning, as well as divergent processes for peer and family predictors of suicidal ideation.

Reasons for adolescent suicide attempts: associations with psychological functioning.

OBJECTIVE: To determine reasons for suicide attempts in adolescents and to examine the relationship between these reasons and psychological functioning. METHOD: Self-reported reasons for suicide attempts and psychological functioning were examined in 120 adolescent suicide attempters who presented to a pediatric general hospital. RESULTS: Consistent with prior research, the most frequently endorsed motives for self-harm were to die, to escape, and to obtain relief. More manipulative reasons for overdose (such as making people sorry) were endorsed less frequently. Adolescents who cited death as a reason for their suicide attempt reported more hopelessness, socially prescribed perfectionism, depression, and anger expression. Discriminant function analyses indicated that high levels of depression and anger expression predicted a self-reported wish to die, and high levels of depression and socially prescribed perfectionism predicted death as the primary reason reported for the suicide attempt. CONCLUSIONS: Systematic assessment of the reasons for a suicide attempt is a useful tool for clinicians in determining recommendations for follow-up treatment.

Dysphoric interpersonal schemata and preadolescents' sensitization to negative events.

Addresses the hypothesis that interpersonal schemata sensitize dysphoric youngsters to negative social information and contribute to the amplification of depressive symptoms. Sensitization was conceptualized as involving multiple components, including heightened anticipation, selective focus, and rapid information processing. Four studies with separate samples of preadolescents and early adolescents were conducted. Results from 3 laboratory-based studies indicated that depressed and dysphoric youngsters evince relatively negative interpersonal schemata, and that these schemata are related to the 3 components of sensitization. A short-term prospective study examined the hypothesis that dysphoric interpersonal schemata moderate the emotional impact of a normative social stressor, the transition to high school. Results indicated that youngsters who entered the transition with relatively negative schema experienced the transition as more stressful than youngsters with relatively positive schema, and that negative interpersonal schema amplified the effects of stress on depressive symptoms.