Kaehler Manifolds of Quasi-Constant Holomorphic Sectional Curvatures

The Kaehler manifolds of quasi-constant holomorphic sectional curvatures are introduced as Kaehler manifolds with complex distribution of codimension two, whose holomorphic sectional curvature only depends on the corresponding point and the geometric angle, associated with the section. A curvature identity characterizing such manifolds is found. The biconformal group of transformations whose elements transform Kaehler metrics into Kaehler ones is introduced and biconformal tensor invariants are obtained. This makes it possible to classify the manifolds under consideration locally. The class of locally biconformal flat Kaehler metrics is shown to be exactly the class of Kaehler metrics whose potential function is only a function of the distance from the origin in complex Euclidean space. Finally we show that any rotational even dimensional hypersurface carries locally a natural Kaehler structure, which is of quasi-constant holomorphic sectional curvatures.Comment: 36 page

Crystal Structure of Methanobacterium thermoautotrophicum Phosphoribosyl-AMP Cyclohydrolase HisI

NRC publication: Ye

A structural genomics pilot project based on gene targets selected from Escherichia coli

A pilot project based on gene targets selected from the genome of E. coli has been initiated with 38 genes for initial cloning. Of these, 18 proteins have been purified to date and some crystals were obtained for twelve of them. Of these, four proteins yielded crystals diffracting to a sufficiently high resolution to warrant structural investigation. We have determined 3-D structures of three of these proteins using Se-Met labeling and MAD methods, while the structure of the fourth one was simultaneously determined by another group. To manage the parallel work on many proteins by several researchers it became necessary to create a searchable database containing the pertinent information about every stage of the work.NRC publication: Ye

Synergistically Enhanced Performance of Ultrathin Nanostructured Silicon Solar Cells Embedded in Plasmonically Assisted, Multispectral Luminescent Waveguides

Ultrathin silicon solar cells fabricated by anisotropic wet chemical etching of single-crystalline wafer materials represent an attractive materials platform that could provide many advantages for realizing high-performance, low-cost photovoltaics. However, their intrinsically limited photovoltaic performance arising from insufficient absorption of low-energy photons demands careful design of light management to maximize the efficiency and preserve the cost-effectiveness of solar cells. Herein we present an integrated flexible solar module of ultrathin, nanostructured silicon solar cells capable of simultaneously exploiting spectral upconversion and downshifting in conjunction with multispectral luminescent waveguides and a nanostructured plasmonic reflector to compensate for their weak optical absorption and enhance their performance. The 8 μm-thick silicon solar cells incorporating a hexagonally periodic nanostructured surface relief are surface-embedded in layered multispectral luminescent media containing organic dyes and NaYF₄:Yb³⁺,Er³⁺ nanocrystals as downshifting and upconverting luminophores, respectively, <i>via</i> printing-enabled deterministic materials assembly. The ultrathin nanostructured silicon microcells in the composite luminescent waveguide exhibit strongly augmented photocurrent (∼40.1 mA/cm²) and energy conversion efficiency (∼12.8%) than devices with only a single type of luminescent species, owing to the synergistic contributions from optical downshifting, plasmonically enhanced upconversion, and waveguided photon flux for optical concentration, where the short-circuit current density increased by ∼13.6 mA/cm² compared with microcells in a nonluminescent medium on a plain silver reflector under a confined illumination