Simultaneous effects of hydrostatic pressure and applied electric field on the impurity-related self-polarization in GaAs/Ga1−xAlxAs multiple quantum wells

A detailed theoretical study of the combined effects of hydrostatic pressure and in-growth direction applied electric field on the binding energy and self-polarization of a donor impurity in a system of GaAs-(Ga,Al)As coupled square quantum wells is presented. The study is performed in the framework of the effective mass and parabolic band approximations and using a variational procedure. The electron effective mass, the dielectric constant, the barrier height, the well sizes, all them varying with the hydrostatic pressure are taken into account within the study. The results obtained show that the impurity binding energy and its self-polarization bear strong dependencies with the hydrostatic pressure, the strength of the applied electric field, the width of the confining potential barriers, and the impurity position.     

Rolf Huisgen,Eminent Chemist and Polymath (1920–2020): In His Own Words and In His Publication Metrics

As a compliment to several other publications that present and honor Rolf Huisgen's research achievements, the first part of this paper reveals the human side of this eminent chemist. From excerpts from many of his personal and professional writings, Huisgen's personality and philosophies of life are revealed. Also revealed is Huisgen functioning as a historian of chemistry. The second part of this paper examines the scientometrics of Huisgen's publication history. In the late 1950s and early 1960s, Huisgen's career experienced a major transition in terms of publication metrics and the influence these papers had on the organic chemistry community. This was the result of his research into 1,3‐dipolar cycloadditions. Citations to his scientific contributions are well spread over many of his papers, demonstrating his constant work and the building up of a research topic, which continued after his official retirement in 1988. In fact, 17 % of his more than 600 publications appeared after 1988. The majority of Huisgen's papers were co‐authored with his many graduate and postdoctoral students. Consistent with the trend of that era, Huisgen was the sole author of most of his Review articles, and not just those of his many plenary lectures, and it is those Review articles that proved to be his most cited publications. This demonstrates the power and influence of Review articles—secondary sources, in the vocabulary of historians and sociologists of science. In those Review articles, Huisgen principally described the state of the art of 1,3‐dipolar cycloadditions—his golden offspring.     

Aggregation of sphalerite: role of zinc ions

Sphalerite from six sources is shown to aggregate at ca. pH 7-9, confirmed by different techniques (settling velocity, suspension analysis, and optical microscopy). This does not correlate with the isoelectric point, which is consistently < pH 6. A similar observation was made by Healy and Jellet [J. Colloid Interface Sci. 24 (1967) 41-46] for ZnO (and reconfirmed here), who suggested Zn hydrolysis products were responsible. The hypothesis is tested using chalcopyrite and silica suspensions in the presence of Zn ions. It is found that aggregation occurs over the same pH range, 7-9. Solution and surface analysis (extraction by EDTA) shows sphalerite released sufficient Zn ions to promote aggregation. The pH range 7-9 corresponds to hydroxide formation, suggesting this is the species responsible. Aggregation of sphalerite due to the polymerization/flocculation action of zinc hydroxide is proposed.     

ChemInform Abstract: First-Principles Study of Defective and Nonstoichiometric Sr2FeMoO6.

The influence of disorder and stoichiometry-breaking point defects on the structural and magnetic properties of Sr₂FeMoO₆ is studied by electronic structure calculations within the spin-polarized GGA+U approach.