University of Pennsylvania

About: University of Pennsylvania is a education organization based out in Philadelphia, Pennsylvania, United States. It is known for research contribution in the topics: Population & Medicine. The organization has 109318 authors who have published 257688 publications receiving 14150562 citations. The organization is also known as: UPenn & Penn.

Suppression of the coffee-ring effect by shape-dependent capillary interactions

Abstract: When a drop of liquid dries on a solid surface, its suspended particulate matter is deposited in ring-like fashion. This phenomenon, known as the coffee-ring effect, is familiar to anyone who has observed a drop of coffee dry. During the drying process, drop edges become pinned to the substrate, and capillary flow outward from the centre of the drop brings suspended particles to the edge as evaporation proceeds. After evaporation, suspended particles are left highly concentrated along the original drop edge. The coffee-ring effect is manifested in systems with diverse constituents, ranging from large colloids to nanoparticles and individual molecules. In fact--despite the many practical applications for uniform coatings in printing, biology and complex assembly-the ubiquitous nature of the effect has made it difficult to avoid. Here we show experimentally that the shape of the suspended particles is important and can be used to eliminate the coffee-ring effect: ellipsoidal particles are deposited uniformly during evaporation. The anisotropic shape of the particles significantly deforms interfaces, producing strong interparticle capillary interactions. Thus, after the ellipsoids are carried to the air-water interface by the same outward flow that causes the coffee-ring effect for spheres, strong long-ranged interparticle attractions between ellipsoids lead to the formation of loosely packed or arrested structures on the air-water interface. These structures prevent the suspended particles from reaching the drop edge and ensure uniform deposition. Interestingly, under appropriate conditions, suspensions of spheres mixed with a small number of ellipsoids also produce uniform deposition. Thus, particle shape provides a convenient parameter to control the deposition of particles, without modification of particle or solvent chemistry.

What Are the Effects of Induction and Mentoring on Beginning Teacher Turnover

Abstract: In recent years there has been an increase in the number of programs offering support, guidance, and orientation for beginning teachers during the transition into their first teaching job. This study examines whether such programs—collectively known as induction—have a positive effect on the retention of beginning teachers. The data used in the analysis are from the nationally representative 1999–2000 Schools and Staffing Survey. The results indicate that beginning teachers who were provided with mentors from the same subject field and who participated in collective induction activities, such as planning and collaboration with other teachers, were less likely to move to other schools and less likely to leave the teaching occupation after their first year of teaching.

Large-scale genome-wide association analysis of bipolar disorder identifies a new susceptibility locus near ODZ4

Abstract: We conducted a combined genome-wide association study (GWAS) of 7,481 individuals with bipolar disorder (cases) and 9,250 controls as part of the Psychiatric GWAS Consortium. Our replication study tested 34 SNPs in 4,496 independent cases with bipolar disorder and 42,422 independent controls and found that 18 of 34 SNPs had P < 0.05, with 31 of 34 SNPs having signals with the same direction of effect (P = 3.8 × 10−7). An analysis of all 11,974 bipolar disorder cases and 51,792 controls confirmed genome-wide significant evidence of association for CACNA1C and identified a new intronic variant in ODZ4. We identified a pathway comprised of subunits of calcium channels enriched in bipolar disorder association intervals. Finally, a combined GWAS analysis of schizophrenia and bipolar disorder yielded strong association evidence for SNPs in CACNA1C and in the region of NEK4-ITIH1-ITIH3-ITIH4. Our replication results imply that increasing sample sizes in bipolar disorder will confirm many additional loci.