Counting statistics of single electron transport in a quantum dot.

We have measured the full counting statistics of current fluctuations in a semiconductor quantum dot (QD) by real-time detection of single electron tunneling with a quantum point contact. This method gives direct access to the distribution function of current fluctuations. Suppression of the second moment (related to the shot noise) and the third moment (related to the asymmetry of the distribution) in a tunable semiconductor QD is demonstrated experimentally. With this method we demonstrate the ability to measure very low current and noise levels.

Cotunneling-mediated transport through excited states in the Coulomb-blockade regime.

We present finite-bias transport measurements on a few-electron quantum dot. In the Coulomb-blockade regime, strong signatures of inelastic cotunneling occur which can directly be assigned to excited states observed in the nonblockaded regime. In addition, we observe structures related to sequential tunneling through the dot, occurring after it has been excited by an inelastic cotunneling process. We explain our findings using transport calculations within the real-time Green's function approach, including diagrams up to fourth order in the tunneling matrix elements.

Thought disorder and psychosocial functioning in schizophrenia: the concurrent and predictive relationships.

Recent findings have linked impairments in social performance among individuals with schizophrenia to deficits in cognition. However, one component of cognition, thought disorder (TD), has received little attention in its association with social functioning. The current investigation examined the cross-sectional and predictive relationships between bizarre-idiosyncratic thought and psychosocial functioning throughout the early course of schizophrenia and compared these relationships to those observed among individuals with affective disorders (i.e., bipolar disorder, manic type, and major depression without psychotic features). Participants were assessed on TD, work, and social functioning using standardized procedures across three follow-ups over an 8-year period. The cross-sectional relationships between TD and impairment in work performance were generally significant. TD also significantly predicted subsequent work functioning years later. Less support was found for the relationship between TD and social functioning. Finally, the relationship between TD and work performance appeared to be more consistent over time for the subjects with schizophrenia compared to those with affective disorders. The results suggest that techniques which minimize TD may have implications for occupational functioning among persons with chronic psychiatric disorders.

Piagetian conservation and response to cognitive therapy in attention deficit disordered children.

Cognitive therapy is often used in treating attention-deficit-disordered (ADD) children because of its purported ability to address this population's attentional deficits and behavioral difficulties and to create durable therapeutic effects. Nonetheless, research findings on these treatments have been inconsistent. This study sought to explain these inconsistencies by examining the influence of cognitive development on children's ability to benefit from such treatment. The ability to conserve number and substance was shown to influence treatment outcome, as measured by laboratory tasks of cognitive style and impulsivity. No effects were found on standardized academic achievement measures or on behavioral ratings by teachers or parents. Further study of individual development will be important in understanding the outcomes of cognitive therapy.

Methylphenidate and cognitive therapy with ADD children: a methodological reconsideration.

The present double-blind study examined the effects of methylphenidate, cognitive therapy, and their combination in attention deficit-disordered (ADD) children. Four treatment groups were compared on measures of attentional deployment and cognitive style, tests of academic achievement, and behavioral rating scales. In contrast to a previous study conducted in this laboratory, children in this study were not receiving medication during post-testing. Results were interpreted to suggest that measurable effects of stimulant medication dissipate rapidly upon discontinuation of pharmacotherapy. The combination of methylphenidate and cognitive therapy was not found to be any more efficacious than either of the treatments studied alone. Discussion suggests that medication status at follow-up is an essential feature of research design.

A comparison of recruiting strategies for increasing older adults' initial entry and compliance in a memory training program.

Older adults in highrise buildings were recruited for memory training using positive ("build your memory power"), neutral ("learn memory skills"), or negative ("avoid memory failures") content approaches which were: printed on a poster mounted in a prominent place (CSA), presented orally at a building meeting (PC), and, finally, printed on flyers distributed to the residents (DC). There were more volunteers after PC with neutral or positive content, but the CSA respondents were more likely to complete the training. Negative content was most likely to attract persons concerned about age-related memory decline. The discussion focused on the appropriate recruitment methods for particular intervention programs.

The performance of attention-deficit-disordered and normal children on conservation tasks.

The present study was designed to investigate whether a specific subgroup of learning-disabled children (attention-deficit-disordered, ADD) differed from their normal counterparts on Piagetian tasks of conservation. The subjects were 34 third-and fourth-grade children. Seventeen children had been diagnosed as ADD; the remaining half were designated as normal. The two groups were equivalent in chronological age, mental age, and intelligence. The results indicated significant differences between the two groups on tasks tapping conservation of substance and number. These results may support the theory of a lag in the development of conservation in children with specific learning disabilities (ADD). Implications of the present research for therapeutic and remedial programs that serve ADD children are also discussed.

The role of student volunteers in door-to-door hypertension screening.

This study was part of a continuing effort to develop a community-based approach to health care. Student volunteers in seventh- and ninth-grade health classes were trained to take blood pressure measurements and then conduct door-to-door screening for hypertension. One group of student volunteers within each grade level screened households surrounding the school they attended (low-convenience condition), while another group of volunteers screened households adjacent to their own homes (high-convenience condition). The results from these screening methods were compared with the results obtained from a central-site neighborhood screening center. Chi-square tests on the proportion of households screened indicated that the high convenience door-to-door screening method was significantly more effective than either the low-convenience door-to-door method or the central-site screening method. The latter two methods were not statistically different from each other. Both seventh and ninth graders screened significantly more households in the high-convenience condition than in the low-convenience condition. Ninth graders were superior to seventh graders in the high-convenience, but not in the low-convenience, condition.

The link between memory performance, self-assessment, and affective status.

To investigate the relationship between memory performance, self-assessment of memory, and affective status, 67 elderly females were administered a self-assessment memory questionnaire and multiple measures of affect and laboratory memory tet performance. Canonical correlations indicated that the memory performance scores were not related to the affective measures nor to the scales of self-assessed memory ability. Affective status and self-assessment of memory skill were related, suggesting that investigations of memory performance which rely on self-assessment should also measure affective status.