Photoinduced doping in heterostructures of graphene and boron nitride

The design of stacks of layered materials in which adjacent layers interact by van der Waals forces has enabled the combination of various two-dimensional crystals with different electrical, optical and mechanical properties as well as the emergence of novel physical phenomena and device functionality. Here, we report photoinduced doping in van der Waals heterostructures consisting of graphene and boron nitride layers. It enables flexible and repeatable writing and erasing of charge doping in graphene with visible light. We demonstrate that this photoinduced doping maintains the high carrier mobility of the graphene/boron nitride heterostructure, thus resembling the modulation doping technique used in semiconductor heterojunctions, and can be used to generate spatially varying doping profiles such as p-n junctions. We show that this photoinduced doping arises from microscopically coupled optical and electrical responses of graphene/boron nitride heterostructures, including optical excitation of defect transitions in boron nitride, electrical transport in graphene, and charge transfer between boron nitride and graphene.

Optimal Rectangle Packing: An Absolute Placement Approach

We consider the problem of finding all enclosing rectangles of minimum area that can contain a given set of rectangles without overlap. Our rectangle packer chooses the x-coordinates of all the rectangles before any of the y-coordinates. We then transform the problem into a perfect-packing problem with no empty space by adding additional rectangles. To determine the y-coordinates, we branch on the different rectangles that can be placed in each empty position. Our packer allows us to extend the known solutions for a consecutive-square benchmark from 27 to 32 squares. We also introduce three new benchmarks, avoiding properties that make a benchmark easy, such as rectangles with shared dimensions. Our third benchmark consists of rectangles of increasingly high precision. To pack them efficiently, we limit the rectangles' coordinates and the bounding box dimensions to the set of subset sums of the rectangles' dimensions. Overall, our algorithms represent the current state-of-the-art for this problem, outperforming other algorithms by orders of magnitude, depending on the benchmark.

Satisfaction with continuous glucose monitoring in adults and youths with Type 1 diabetes

AIMS

To describe satisfaction with continuous glucose monitoring in Type 1 diabetes; to correlate continuous glucose monitoring satisfaction scores with usage; and to identify common themes in perceived benefits and barriers of monitoring reported by adults, youths and the parents of youths in the Juvenile Diabetes Research Foundation continuous glucose monitoring trials.

METHODS

The Continuous Glucose Monitoring Satisfaction Scale questionnaire was completed after 6 months of monitoring. Participants also answered open-ended queries of positive and negative attributes of continuous glucose monitoring.

RESULTS

More frequent monitoring was associated with higher satisfaction for adults (n = 224), youths (n = 208) and parents of youths (n = 192) (all P < 0.001) in both the 'benefits' and 'hassles' sub-scales of the Continuous Glucose Monitoring Satisfaction Scale, but the greatest differences between the two groups involved scores on hassle items. Common barriers to monitoring use included insertion pain, system alarms and body issues; while common benefits included glucose trend data, opportunities to self-correct out-of-range glucose levels and to detect hypoglycaemia.

CONCLUSIONS

As frequent use of continuous glucose monitoring is associated with improved glycaemic control without increased hypoglycaemia it is important to overcome barriers, reinforce benefits and set realistic expectations for this technology in order to promote its more consistent and frequent use in individuals with Type 1 diabetes.