Orbital Optimization in the Density Matrix Renormalization Group, with applications to polyenes and \beta-carotene

In previous work we have shown that the Density Matrix Renormalization Group (DMRG) enables near-exact calculations in active spaces much larger than are possible with traditional Complete Active Space algorithms. Here, we implement orbital optimisation with the Density Matrix Renormalization Group to further allow the self-consistent improvement of the active orbitals, as is done in the Complete Active Space Self-Consistent Field (CASSCF) method. We use our resulting DMRGCASSCF method to study the low-lying excited states of the all-trans polyenes up to C24H26 as well as \beta-carotene, correlating with near-exact accuracy the optimised complete \pi-valence space with up to 24 active electrons and orbitals, and analyse our results in the light of the recent discovery from Resonance Raman experiments of new optically dark states in the spectrum.Comment: 16 pages, 8 figure

Reexamination of Mocs and Tauti chondritic meteorites: Classification with shock degree

The Mocs meteorite, which fell on February 3,1882,in Transylvania over a large area (15km by 3km) has been reclassified from a L6 to a L5-6 chondrite in this study. Six fragments of the Mocs chondrite were observed by optical microscopy and measured using electron microprobe analyses and standard wet chemical analysis. Although the petrologic type of the 6 samples is almost the same, 2 fragments : Mocs-1 and Mocs-3 show heterogeneous features (opaque shock veins and melt pockets) due to different shock degrees (S-5 and S-4,respectively). Therefore the mean shock degree of the Mocs chondrite was found to be S3-5. The Tauti meteorite which fell in 1937 in Transylvania was previously classified as L6 chondrite using the bulk chemical analyses of H. SAVU (St. Cerc. Geol., 2 (IV), 272,1959) (A. L. GRAHAM; Meteoritics, 14,1,1979; A. L. GRAHAM et al.; Catalogue of Meteorites, London, British Museum, Natural History, 1985). The chemical compositions of olivines and orthopyroxenes determined by electron microprobe analysis, the bulk chemical analysis, along with textural characteristics classify Tauti shower as L6 chondrite with a shock degree of S-3

Bulk composition and classification of the Tahara meteorite fell in Central Japan on March 1991

The Tahara meteorite which fell on March 26,1991 on a ship\u27s deck anchored at Tahara, Aichi-ken, Japan was found at Matsue-shi, Shimaneken on December 28,1992. It has been classified as an H4-5 chondrite using optical and electron microscopy and bulk chemical analysis. This equilibrated chondrite is completely different from the Mihonoseki L chondrite which fell on December 10,1992 in the same area of Japan, Shimane-ken. The retrieval process of new Japanese meteorites is similar to Antarctic meteorites of different origins which are collected in the same area

Correct quantum chemistry in a minimal basis from effective Hamiltonians

We describe how to create ab-initio effective Hamiltonians that qualitatively describe correct chemistry even when used with a minimal basis. The Hamiltonians are obtained by folding correlation down from a large parent basis into a small, or minimal, target basis, using the machinery of canonical transformations. We demonstrate the quality of these effective Hamiltonians to correctly capture a wide range of excited states in water, nitrogen, and ethylene, and to describe ground and excited state bond-breaking in nitrogen and the chromium dimer, all in small or minimal basis sets

Population density, water supply, and the risk of dengue fever in Vietnam: cohort study and spatial analysis.

BACKGROUND: Aedes aegypti, the major vector of dengue viruses, often breeds in water storage containers used by households without tap water supply, and occurs in high numbers even in dense urban areas. We analysed the interaction between human population density and lack of tap water as a cause of dengue fever outbreaks with the aim of identifying geographic areas at highest risk. METHODS AND FINDINGS: We conducted an individual-level cohort study in a population of 75,000 geo-referenced households in Vietnam over the course of two epidemics, on the basis of dengue hospital admissions (n = 3,013). We applied space-time scan statistics and mathematical models to confirm the findings. We identified a surprisingly narrow range of critical human population densities between around 3,000 to 7,000 people/km² prone to dengue outbreaks. In the study area, this population density was typical of villages and some peri-urban areas. Scan statistics showed that areas with a high population density or adequate water supply did not experience severe outbreaks. The risk of dengue was higher in rural than in urban areas, largely explained by lack of piped water supply, and in human population densities more often falling within the critical range. Mathematical modeling suggests that simple assumptions regarding area-level vector/host ratios may explain the occurrence of outbreaks. CONCLUSIONS: Rural areas may contribute at least as much to the dissemination of dengue fever as cities. Improving water supply and vector control in areas with a human population density critical for dengue transmission could increase the efficiency of control efforts. Please see later in the article for the Editors' Summary

Constraining the source regions of lunar meteorites using orbital geochemical data

Lunar meteorites provide important new samples of the Moon remote from regions visited by the Apollo and Luna sample return missions. Petrologic and geochemical analysis of these meteorites, combined with orbital remote-sensing measurements have enabled additional discoveries about the composition and age of the lunar surface on a global scale. However, the interpretation of these samples is limited by the fact that we do not know the source region of any individual lunar meteorite. Here we investigate the link between meteorite and source region on the Moon using the Lunar Prospector Gamma Ray Spectrometer remote sensing dataset for the elements Fe, Ti and Th. The approach has been validated using Apollo and Luna bulk regolith samples and we have applied it to 48 meteorites excluding paired stones. Our approach is able broadly to differentiate the best compositional matches as potential regions of origin for the various classes of lunar meteorites. Basaltic and intermediate-Fe regolith breccia meteorites are found to have the best constrained potential launch sites, with some impact breccias and pristine mare basalts also having reasonably well defined potential source regions. Launch areas for highland feldspathic meteorites are much less well constrained and the addition of another element, such as Mg, will probably be required to identify potential source regions for these