Intrinsic Metastabilities in the Charge Configuration of a Double Quantum Dot

We report a thermally activated metastability in a GaAs double quantum dot exhibiting real-time charge switching in diamond shaped regions of the charge stability diagram. Accidental charge traps and sensor back action are excluded as the origin of the switching. We present an extension of the canonical double dot theory based on an intrinsic, thermal electron exchange process through the reservoirs, giving excellent agreement with the experiment. The electron spin is randomized by the exchange process, thus facilitating fast, gate-controlled spin initialization. At the same time, this process sets an intrinsic upper limit to the spin relaxation time.Comment: 4 pages, 5 figures (color

Self-Regulation in a Web-Based Course: A Case Study

Little is known about how successful students in Web-based courses self-regulate their learning. This descriptive case study used a social cognitive model of self-regulated learning (SRL) to investigate how six graduate students used and adapted traditional SRL strategies to complete tasks and cope with challenges in a Web-based technology course; it also explored motivational and environmental influences on strategy use. Primary data sources were three transcribed interviews with each of the students over the course of the semester, a transcribed interview with the course instructor, and the students’ reflective journals. Archived course documents, including transcripts of threaded discussions and student Web pages, were secondary data sources. Content analysis of the data indicated that these students used many traditional SRL strategies, but they also adapted planning, organization, environmental structuring, help seeking, monitoring, record keeping, and self-reflection strategies in ways that were unique to the Web-based learning environment. The data also suggested that important motivational influences on SRL strategy use—self-efficacy, goal orientation, interest, and attributions—were shaped largely by student successes in managing the technical and social environment of the course. Important environmental influences on SRL strategy use included instructor support, peer support, and course design. Implications for online course instructors and designers, and suggestions for future research are offered

Empowerment theory, research, and application

This introduction to the special issue briefly reviews the meaning and significance of the empowerment concept and problems associated with the proliferation of interest in empowerment. We identify some of the topics not included in this issue and relate those to the many broad and diverse areas of psychological empowerment theory and community‐based research and intervention that are covered. We present synopses of each article along with some of the themes and lessons cutting across the frameworks, studies, and applications. These include a wide diversity of settings, fairly representative of empowerment interventions, and, at the same time, improved clarity (if not unanimity) of definitions and measurement, which has been a problem in much empowerment research and intervention.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117200/1/ajcpbf02506982.pd

Investigation of Bubble Size Distributions in Oscillatory Flow at Various Flow Rates

The demand for eco-friendly technologies for industrial processes is increasing. Various factors such as labour costs, exploitation and waste management influence the production costs and hence the profit generated. The water treatment industry is one example of a well-developed sector which is facing these concerns. Microbubble techniques exhibit many benefits which make them applicable to heterogeneous processes, such as longer contact time and greater surface area giving higher mass transfer rates. The Fluidic Oscillator (FO) is a relatively new device which enhances the efficacy of microbubble generation. The FO produces smaller bubbles by applying oscillatory flow through a diffuser to generate microbubbles. This paper aims to study the influence of steady and oscillatory flow to bubble size distribution. The experimentation was carried out with a ceramic diffuser to produce microbubbles in water. A High Speed Camera was used for bubble imaging. Data on bubble distributions at various flow rates was obtained by image post-processing. It was observed that the application of the FO at selected operational conditions gave narrower bubble size distributions in a range of flow rates compared to continuous flow. The range of applications of this technology is continuously populating

GaAs Quantum Dot Thermometry Using Direct Transport and Charge Sensing

We present measurements of the electron temperature using gate defined quantum dots formed in a GaAs 2D electron gas in both direct transport and charge sensing mode. Decent agreement with the refrigerator temperature was observed over a broad range of temperatures down to 10 mK. Upon cooling nuclear demagnetization stages integrated into the sample wires below 1 mK, the device electron temperature saturates, remaining close to 10 mK. The extreme sensitivity of the thermometer to its environment as well as electronic noise complicates temperature measurements but could potentially provide further insight into the device characteristics. We discuss thermal coupling mechanisms, address possible reasons for the temperature saturation and delineate the prospects of further reducing the device electron temperature.Comment: 8 pages, 3 (color) figure