Asteroid flux and impact cratering rate on Venus

By the end of 1990, 65 Venus-crossing asteroids were recognized; these represent 59 percent of the known Earth-crossing asteroids. Further studies, chiefly numerical integrations of orbit evolution, may reveal one or two more Venus crossers among the set of discovered asteroids. A Venus crosser was defined as an asteroid whose orbit can intersect the orbit of Venus as a result of secular (long range) perturbations. Venus crossers revolving on orbits that currently overlap the orbit of Venus are called Venapol asteroids, and those on orbit that don't overlap are called Venamor asteroids; 42 Venapols and 23 Venamors were recognized. Collision probabilities with Venus for 60 of the known Venus crossers were determined

Chemical fractionation of siderophile elements in impactites from Australian meteorite craters

The abundance pattern of siderophile elements in terrestrial and lunar impact melt rocks was used extensively to infer the nature of the impacting projectiles. An implicit assumption made is that the siderophile abundance ratios of the projectiles are approximately preserved during mixing of the projectile constituents with the impact melts. As this mixture occurs during flow of strongly shocked materials at high temperatures, however there are grounds for suspecting that the underlying assumption is not always valid. In particular, fractionation of the melted and partly vaporized material of the projectile might be expected because of differences in volatility, solubility in silicate melts, and other characteristics of the constituent elements. Impactites from craters with associated meteorites offer special opportunities to test the assumptions on which projectile identifications are based and to study chemical fractionation that occurred during the impact process

Research Notes : United States : A possible interaction between cyt-Y3 and y20-k2

Interactions of organelle genomes are a well-documented fact. Interac-tion can take the form of metabolite and energy exchange, co-production of enzyme subunits, and co-production of membrane structural and organizational components (Wallace, 1982). Nucleo-cytoplasmic interaction also has been documented for various traits affecting vegetative and harvest indices (Rob-ertson and Frey, 1984), cytoplasmic male sterility (Levings, 1983), and other agronomic characters (Harvey et al., 1972; Kihara, 1982)

Spin-induced symmetry breaking in orbitally ordered NiCr_2O_4 and CuCr_2O_4

At room temperature, the normal oxide spinels NiCr_2O_4 and CuCr_2O_4 are tetragonally distorted and crystallize in the I4_1/amd space group due to cooperative Jahn-Teller ordering driven by the orbital degeneracy of tetrahedral Ni$^{2+}$ ($t_2^4$) and Cu$^{2+}$ ($t_2^5$). Upon cooling, these compounds undergo magnetic ordering transitions; interactions being somewhat frustrated for NiCr_2O_4 but not for CuCr_2O_4. We employ variable-temperature high-resolution synchrotron X-ray powder diffraction to establish that at the magnetic ordering temperatures there are further structural changes, which result in both compounds distorting to an orthorhombic structure consistent with the Fddd space group. NiCr_2O_4 exhibits additional distortion, likely within the same space group, at a yet-lower transition temperature of $T$ = 30 K. The tetragonal to orthorhombic structural transition in these compounds appears to primarily involve changes in NiO_4 and CuO_4 tetrahedra

Mapping the magic numbers in binary Lennard-Jones clusters

Using a global optimization approach that directly searches for the composition of greatest stability, we have been able to find the particularly stable structures for binary Lennard-Jones clusters with up to 100 atoms for a range of Lennard-Jones parameters. In particular, we have shown that just having atoms of different size leads to a remarkable stabilization of polytetrahedral structures, including both polyicosahedral clusters and at larger sizes structures with disclination lines.Comment: 5 pages, 5 figure

Meeting Report: Soybean Genomics Assessment and Strategy Workshop

http://www.soybiotechcenter.org/archives/?id=195&id2=12On July 19 - 20, 2005, approximately 50 researchers and administrators with expert knowledge of soybean genomics participated in a workshop in St.Louis, MO, which was hosted by the Soybean Genetics Executive Committee and supported by the United Soybean Board. The workshop began with a series of presentations by experts in the topics discussed below. Each presentation was designed to update the audience on the current status of soybean resources and related genomics technologies. Following the presentations the participants divided into discussion groups to assess the status of soybean genomics, identify needs, and identify milestones to achieve objectives. The discussion groups included the general areas of Functional Genomics A (Transcriptome and Proteome), Functional Genomic B (Reverse Genetics), Physical and Genetic Maps, and Bioinformatics. After each discussion section the entire group reconvened to hear group reports and to further discuss each topic. The following is the report from this Workshop. It represents a consensus of the participants of the Workshop and it is structured to integrate with a White Paper generated in 2003 so that progress can be better monitored over time. The results of this report are consistent with those of a National Science Foundation soybean genomics workshop held in 2004 (St. Louis, MO) and a Cross-Legume workshop also held in 2004 (Santa Fe, NM).National Science Foundatio

Nurses\u27 Alumnae Association Bulletin, May 1963

President\u27s Letter Alumnae Meetings, 1962 Building Fund Mediocrity Hospital Report Alumnae Notes Social Committee Student Activities Marriages, New Arrivals and Necrology Annual Giving Fund Driv