There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.

A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)

Heterogeneous photocatalyst materials for water splitting

Preparation and Structure of Platinum Group Metal Colloids: Without Solvent.

A series of monometallic dihydrogen complexes of the type M(OEP)(L)(H{sub 2}) (M = Ru, Os; L = THF, *Im) was synthesized and characterized by {sup 1}H NMR. The H-H bond length was found to increase when Os was replaced by Ru or when *Im was replaced by THF. The bond distances (as determined by T{sub 1}) range from 0.92 to 1.18 {angstrom}. The first example of a bimetallic bridging dihydrogen complex, Ru{sub 2}(DPB)(*IM){sub 2}(H{sub 2}), was also prepared. The H{sub 2} ligand is simultaneously bound to both Ru-metal centers. High-field {sup 1}H NMR experiments (620 MHz) revealed a -7.37 Hz dipolar splitting of the H{sub 2} ligand for this complex. Analysis of this splitting suggests that the H{sub 2} ligand is bound with the H-H axis perpendicular to the Ru-Ru axis. These complexes were examined as possible catalysts for the oxidation of dihydrogen through prior heterolytic activation of H{sub 2}. Only Ru(OEP)(THF)(H{sub 2}) can be conveniently deprotonated. Ru(OEP)(THF)(H{sub 2}) is also implicated in the Ru-(OEP)((THF){sub 2}) catalyzed isotopic exchange between H{sub 2} and D{sub 2}O in THF solution. Each step for this mechanism has been elucidated. We have also achieved catalytic dihydrogen oxidation using [Ru(OEP)]{sub 2} adsorbed onto graphite. Twomore » mechanisms for this ruthenium porphyrin catalyzed dihydrogen oxidation are presented and compared. 54 refs., 12 figs., 5 tabs.« less

Dihydrogen Complexes of Metalloporphyrins: Characterization and Catalytic Hydrogen Oxidation Activity.

Flash kinetic spectroscopic studies of dinuclear rhodium(i) complexes

Response data were collected for a carbon black-polymer composite electronic nose array during expo- sure to homologous series of alkanes and alcohols. The mean response intensity of the electronic nose detectors and the response intensity of the most strongly driven set of electronic nose detectors were essentially constant for members of a chemically homologous odorant series when the concentration of each odorant in the gas phase was maintained at a constant fraction of the odorant's vapor pressure. A similar trend is observed in human odor detection threshold values for these same homologous series of odorants. Because the thermody- namic activity of an odorant at equilibrium in a sorbent phase is equal to the partial pressure of the odorant in the gas phase divided by the vapor pressure of the odorant and because the activity coefficients are similar within these homologous series of odorants for sorption of the vapors into specific polymer films, the data imply that the trends in detector response can be understood based on the thermodynamic tendency to establish a relatively constant concentration of sorbed odorant into each of the polymeric films of the electronic nose at a constant fraction of the odorant's vapor pressure. Similarly, the data are consistent with the hypoth- esis that the odor detection thresholds observed in human psychophysical experiments for the odorants studied herein are driven predominantly by the similarity in odorant con- centrations sorbed into the olfactory epithelium at a constant fraction of the odorant's vapor pressure. Numerous attempts have been made to understand the trends in odor detection thresholds that are displayed by the human olfactory sense. High odor detection thresholds are observed for most odorants that are gases under standard pressure and temperature conditions, whereas odorants with low vapor pressures generally have low odor detection thresholds (1). Quantitative structure-activity relationships have been for- mulated in an attempt to correlate trends in olfactory odor intensity with specific microscopic and macroscopic properties of various odorants. For example, many workers have pro- posed that trends in odor detection thresholds arise from the presence of important steric and functional group features in certain olfactory receptors (2, 3). Such receptors could then primarily respond to chemically specific features such as odorant molecular length and polarity (3-6). Other workers have empirically correlated trends in human odor detection thresholds with macroscopic properties of the odorant, such as the boiling point of the liquid phase of the odorant species (7-9). Some workers have noted the correlation between odor thresholds and the vapor pressure of the odorant (10-14). In this work, we have measured the response intensities of an electronic nose (15), based on an array of carbon black- polymer composite detectors, to straight chain alkanes and alcohols. We propose a fundamental first-order explanation for the observed trends in response intensity of the detectors in the electronic nose, based on the thermodynamic tendency for odorants to partition into sorbent phases as a function of the odorant's vapor pressure. A striking resemblance has been observed in the odor intensity trends for the human and electronic olfactory systems for these series of odorants. This similarity in odor intensity behavior occurs even though the detectors in the electronic nose array have no specific receptor sites and even though the electronic nose array is not a structural model for the human olfactory system.

Trends in odor intensity for human and electronic noses: Relative roles of odorant vapor pressure vs. molecularly specific odorant binding (carbon black compositesyolfactionyvapor sensoryodor threshold)

Introduction Solar irradiation is the most abundant energy source available but it is distributed and intermittent, thereby necessitating its storage via conversion to a fuel (e.g., hydrogen). One possible route for direct solar-hydrogen production is through an integrated electrochemical device that uses light-capturing semiconductors in contact with electrodes to generate oxygen and hydrogen [1,2]. Key in such a device is balancing product crossover with Ohmic losses in the solution which necessitate higher photovoltages. Often these requirements are accomplished using a polymer-electrolyte separator [3], yet the exact material-property design targets are not definitively known. In this presentation, a validated multi-physics numerical model of an electrochemical solar-hydrogen generator is used to study its performance. Advantages and limitations concerning current efficiency, required photovoltage, and safety are investigated as a function of separator transport parameters which leads to general design guidelines. Systems including both porous and nonporous photoactive components are examined.

Nathan S. Lewis

Papers

Preparation and Structure of Platinum Group Metal Colloids: Without Solvent.

Dihydrogen Complexes of Metalloporphyrins: Characterization and Catalytic Hydrogen Oxidation Activity.

Flash kinetic spectroscopic studies of dinuclear rhodium(i) complexes

Trends in odor intensity for human and electronic noses: Relative roles of odorant vapor pressure vs. molecularly specific odorant binding (carbon black compositesyolfactionyvapor sensoryodor threshold)

Separator design criteria for a solar-hydrogen electrochemical generator