Mineral inclusions in diamond: temperature and pressure of equilibration

Two distinct suites of minerals included in natural diamond occur and probably represent different physical and chemical conditions during diamond growth. Minerals of the ultramafic suite appear to have equilibrated in the range 1000 degrees to 1300 degrees C between 45 and 65 kilobars, whereas the temperature range for minerals of the eclogitic suite is 850 degrees to 1250 degrees C. At present, models relating the partitioning of magnesium and iron between coexisting phases are not sufficiently rigorous to determine a value for the pressure of equilibration of these eclogitic suite inclusions.     

Optically active carbon: kinetic resolution of c76 by asymmetric osmylation

The chiral fullerene C(76) was kinetically resolved by asymmetric osmylation providing an example of an optically active allotrope of a pure element. C(76) recovered from the treatment of racemic C(76) with OsO(4) and a chiral alkaloid ligand, showed a specific rotation [alpha](D) of -4000 degrees (> 97 percent enantiomeric excess) and a circular dichroism spectrum corresponding to the ultraviolet spectrum. Regenerated C(76) formed by reducing the asymmetrically osmylated C(76) with SnCl(2) was enriched in the opposite enantiomer. Analysis of the local curvature of the C(76) molecule indicated that OsO(4) should selectively add to 2 of the 30 types of bonds in C(76). This regioselectivity was supported chromatographically and interpreted in terms of the kinetic resolution.     

Ore metals through geologic history

The ores of chromite, nickel, copper, and zinc show a wide distribution over geologic time, but those of iron, titanium, lead, uranium, gold, silver, molybdenum, tungsten, and tin are more restricted. Many of the limitations to specific time intervals are probably imposed by the evolving tectonic history of Earth interacting with the effects of the biomass on the evolution of the earth's s surface chemistry. Photosynthetic generation of free oxygen and "carbon" contributes significantlly to the diversity of redox potentials in both sedimentary and igneous-related processes of ore formation, influencing the selection of metals at the source, during transport, and at the site of ore deposition.     

Wheat Leaf Rust: Control by 4-n-Butyl-1,2,4-triazole, a Systemic Fungicide

Compound 4-n-butyl-1,2,4-triazole was demonstrated as an enduring and selective systemic fungicide for the control of wheat leaf rust by foliar and soil applications. Among several species of rust fungi treated, only wheat leaf rust (Puccinia recondita Rob.) was controlled. Wheat stem rust, for example, was unaffected by either soil or foliar applications.     

Head capsule transmission of long-wavelength light in the curculionidae

The head capsule of many weevils contains a region that transmits only far-red and near-infrared light. In the alfalfa weevil, Hypera postica, this extraocular cutoff filter evidently works in conjunction with the compound eyes, enabling the insect to use visual cues in locating or recognizing its host plant.     

Multi-university research teams: shifting impact, geography, and stratification in science

This paper demonstrates that teamwork in science increasingly spans university boundaries, a dramatic shift in knowledge production that generalizes across virtually all fields of science, engineering, and social science. Moreover, elite universities play a dominant role in this shift. By examining 4.2 million papers published over three decades, we found that multi-university collaborations (i) are the fastest growing type of authorship structure, (ii) produce the highest-impact papers when they include a top-tier university, and (iii) are increasingly stratified by in-group university rank. Despite the rising frequency of research that crosses university boundaries, the intensification of social stratification in multi-university collaborations suggests a concentration of the production of scientific knowledge in fewer rather than more centers of high-impact science.