University of Rochester

About: University of Rochester is a education organization based out in Rochester, New York, United States. It is known for research contribution in the topics: Population & Laser. The organization has 63915 authors who have published 112762 publications receiving 5484122 citations. The organization is also known as: Rochester University.

Cation and anion immobilization through chemical bonding enhancement with fluorides for stable halide perovskite solar cells

Abstract: Defects play an important role in the degradation processes of hybrid halide perovskite absorbers, impeding their application for solar cells. Among all defects, halide anion and organic cation vacancies are ubiquitous, promoting ion diffusion and leading to thin-film decomposition at surfaces and grain boundaries. Here, we employ fluoride to simultaneously passivate both anion and cation vacancies, by taking advantage of the extremely high electronegativity of fluoride. We obtain a power conversion efficiency of 21.46% (and a certified 21.3%-efficient cell) in a device based on the caesium, methylammonium (MA) and formamidinium (FA) triple-cation perovskite (Cs0.05FA0.54MA0.41)Pb(I0.98Br0.02)3 treated with sodium fluoride. The device retains 90% of its original power conversion efficiency after 1,000 h of operation at the maximum power point. With the help of first-principles density functional theory calculations, we argue that the fluoride ions suppress the formation of halide anion and organic cation vacancies, through a unique strengthening of the chemical bonds with the surrounding lead and organic cations. Defects and defect migration are detrimental for perovskite solar cell efficiency and long-term stability. Li et al. show that fluoride is able to suppress the formation of halide anion and organic cation vacancy defects by restraining the relative ions via ionic and hydrogen bonds.

Conservatism in Accounting Part II: Evidence and Research Opportunities

Abstract: This paper is Part II in a two‐part series on conservatism in accounting. Part I examined alternative explanations for conservatism in accounting and their implications for accounting regulators (SEC and FASB). Part II summarizes the empirical evidence on the existence of conservatism, conservatism's increase over time, and conservatism's alternative explanations. It also discusses opportunities for future research on conservatism. The empirical literature uses a variety of conservatism measures in time‐series and cross‐sectional tests of contracting, shareholder litigation, taxation, and accounting regulation explanations for conservatism. The tests' results suggest the importance of all four explanations. Two non‐conservatism explanations—earnings management and the abandonment option—cannot individually or jointly explain the observed systematic understatement of net assets that is the hallmark of conservatism. Researchers should note that accounting's effects on managerial behavior play a central role...

New evidence pyramid

Abstract: A pyramid has expressed the idea of hierarchy of medical evidence for so long, that not all evidence is the same. Systematic reviews and meta-analyses have been placed at the top of this pyramid for several good reasons. However, there are several counterarguments to this placement. We suggest another way of looking at the evidence-based medicine pyramid and explain how systematic reviews and meta-analyses are tools for consuming evidence—that is, appraising, synthesising and applying evidence.

Influence of the Genotype on the Clinical Course of the Long-QT Syndrome

Abstract: Background The congenital long-QT syndrome, caused by mutations in cardiac potassium-channel genes (KVLQT1 at the LQT1 locus and HERG at the LQT2 locus) and the sodium-channel gene (SCN5A at the LQT3 locus), has distinct repolarization patterns on electrocardiography, but it is not known whether the genotype influences the clinical course of the disease. Methods We determined the genotypes of 541 of 1378 members of 38 families enrolled in the International Long-QT Syndrome Registry: 112 had mutations at the LQT1 locus, 72 had mutations at the LQT2 locus, and 62 had mutations at the LQT3 locus. We determined the cumulative probability and lethality of cardiac events (syncope, aborted cardiac arrest, or sudden death) occurring from birth through the age of 40 years according to genotype in the 246 gene carriers and in all 1378 members of the families studied. Results The frequency of cardiac events was higher among subjects with mutations at the LQT1 locus (63 percent) or the LQT2 locus (46 percent) than am...