Angular Forces Around Transition Metals in Biomolecules

Quantum-mechanical analysis based on an exact sum rule is used to extract an semiclassical angle-dependent energy function for transition metal ions in biomolecules. The angular dependence is simple but different from existing classical potentials. Comparison of predicted energies with a computer-generated database shows that the semiclassical energy function is remarkably accurate, and that its angular dependence is optimal.Comment: Tex file plus 4 postscript figure

Cyclometalated iridium(III)-sensitized titanium dioxide solar cells

Ir(III) dyes used as sensitizers in dye-sensitized solar cells produced quantum yields approaching unity for conversion of absorbed photons to current under simulated air mass 1.0 sunlight, with current production resulting from ligand-to-ligand charge-transfer states, rather than the typical metal-to-ligand charge-transfer states in ruthenium-based cells

Self force on particle in orbit around a black hole

We study the self force acting on a scalar charge in uniform circular motion around a Schwarzschild black hole. The analysis is based on a direct calculation of the self force via mode decomposition, and on a regularization procedure based on Ori's mode-sum regularization prescription. We find the four self-force at arbitrary radii and angular velocities (both geodesic and non-geodesic), in particular near the black hole, where general-relativistic effects are strongest, and for fast motion. We find the radial component of the self force to be repulsive or attractive, depending on the orbit.Comment: RevTeX, 4 pages, 4 Encapsulated PostScript figures. Submitted to Phys. Rev. Let

Charge carrier solvation and large polaron formation on a polymer chain revealed in model ab initio computations

When an excess charge carrier is added to a semiconducting polymer chain, it is well known that the carrier may self-trap into a polaronic state accompanied by a bond length adjustment pattern. A different mechanism of self-localization is the solvation of charge carriers expected to take place when the polymer chain is immersed in polar media such as common solvents. We use state-of-the-art ab initio computations in conjunction with the Polarizable Continuum Model to unequivocally demonstrate solvation-induced self-consistent charge localization into large-radius one-dimensional (1D) polarons on long $C_{N}H_{2}$ carbon chains with the polyynic structure. Within the framework used, the solvation results in a much more pronounced charge localization. We believe this mechanism of polaron formation to be of relevance for various 1D semiconductors in polar environments

Criterios ambientales para la selección de un Sistema de Información Geográfica en la evaluación de impacto ambiental de infraestructuras lineales

Geographic Information Systems can be consider as one of the most powerful tools for the Environmental Impact Assessment in the long distance railways and highways infrastructures. The evaluation process begin with the analysis of the activity and the physical and ecological geography. One of the most common bottlenecks is the use of environmental criteria for the discrimination of different evaluation proposals. A methodotogical approach is presented with seven diverse environmental criteria involved. The use of this multilevel methodology can help to physical planner sand decision makers in the selection of the best environmental proposal.Los Sistemas de Información Geográfica (SIG) son una herramienta muy poderosa para la evaluación de los impactos ambientales de grandes infraestructuras lineales. El proceso de evaluación comienza con el análisis de la actividad y de los factores físicos y ecológicos del medio. En la mayoría de los métodos, la selección de los criterios ambientales usados para la discriminación de alternativas se convierte en el cuello de botella del proceso de evaluación. En este artículo se presenta una metodología de trabajo en la que se proponen varios criterios medioambientales para la selección de alternativas de trazado de infraestructuras lineales. El uso de esta metodología multinivel puede ayudar a los profesionales involucrados en la planificación del medio físico en la toma de decisiones para la selección de la mejor alternativa de trazado de infraestructuras lineales

Hyalotekite, (Ba,Pb,K)(4)(Ca,Y)(2)Si-8(B,Be)(2)(Si,B)(2)O28F, a Tectosilicate Related to Scapolite: New Structure Refinement, Phase Transitions and a Short-Range Ordered 3B Superstructure

Hyalotekite, a framework silicate of composition (Ba,Pb,K)(4)(Ca,Y)(2)Si-8(B,Be)(2) (Si,B)(2)O28F, is found in relatively high-temperature(greater than or equal to 500 degrees C) Mn skarns at Langban, Sweden, and peralkaline pegmatites at Dara-i-Pioz, Tajikistan. A new paragenesis at Dara-i-Pioz is pegmatite consisting of the Ba borosilicates leucosphenite and tienshanite, as well as caesium kupletskite, aegirine, pyrochlore, microcline and quartz. Hyalotekite has been partially replaced by barylite and danburite. This hyalotekite contains 1.29-1.78 wt.% Y2O3, equivalent to 0.172-0.238 Y pfu or 8-11% Y on the Ca site; its Pb/(Pb+Ba) ratio ranges 0.36-0.44. Electron microprobe F contents of Langban and Dara-i-Pioz hyalotekite range 1.04-1.45 wt.%, consistent with full occupancy of the F site. A new refinement of the structure factor data used in the original structural determination of a Langban hyalotekite resulted in a structural formula, (Pb1.96Ba1.86K0.18)Ca-2(B1.76Be0.24)(Si1.56B0.44)Si8O28F, consistent with chemical data and all cations with positive-definite thermal parameters, although with a slight excess of positive charge (+57.14 as opposed to the ideal +57.00). An unusual feature of the hyalotekite framework is that 4 of 28 oxygens are non-bridging; by merging these 4 oxygens into two, the framework topology of scapolite is obtained. The triclinic symmetry of hyalotekite observed at room temperature is obtained from a hypothetical tetragonal parent structure via a sequence of displacive phase transitions. Some of these transitions are associated with cation ordering, either Pb-Ba ordering in the large cation sites, or B-Be and Si-B ordering on tetrahedral sites. Others are largely displacive but affect the coordination of the large cations (Pb, Ba, K, Ca). High-resolution electron microscopy suggests that the undulatory extinction characteristic of hyalotekite is due to a fine mosaic microstructure. This suggests that at least one of these transitions occurs in nature during cooling, and that it is first order with a large volume change. A diffuse superstructure observed by electron diffraction implies the existence of a further stage of short-range cation ordering which probably involves both (Pb,K)-Ba and (BeSi,BB)-BSi

Electrostatic self-energy and Bekenstein entropy bound in the massive Schwinger model

We obtain the electrostatic energy of two opposite charges near the horizon of stationary black-holes in the massive Schwinger model. Besides the confining aspects of the model, we discuss the Bekenstein entropy upper bound of a charged object using the generalized second law. We show that despite the massless case, in the massive Schwinger model the entropy of the black hole and consequently the Bekenstein bound are altered by the vacuum polarization.Comment: 14 pages, accepted for publication in "Gen. Rel. Grav. (2005)

A comparison of the healthiness of packaged foods and beverages from 12 countries using the Health Star Rating nutrient profiling system, 2013-2018

We compared the healthiness of packaged foods and beverages between selected countries using the Health Star Rating (HSR) nutrient profiling system. Packaged food and beverage data collected 2013-2018 were obtained for Australia, Canada, Chile, China, India, Hong Kong, Mexico, New Zealand, Slovenia, South Africa, the UK, and USA. Each product was assigned to a food or beverage category and mean HSR was calculated overall by category and by country. Median energy density (kJ/100 g), saturated fat (g/100 g), total sugars (g/100 g) and sodium (mg/100 g) contents were calculated. Countries were ranked by mean HSR and median nutrient levels. Mean HSR for all products (n = 394,815) was 2.73 (SD 1.38) out of 5.0 (healthiest profile). The UK, USA, Australia and Canada ranked highest for overall nutrient profile (HSR 2.74-2.83) and India, Hong Kong, China and Chile ranked lowest (HSR 2.27-2.44). Countries with higher overall HSR generally ranked better with respect to nutrient levels. India ranked consistently in the least healthy third for all measures. There is considerable variability in the healthiness of packaged foods and beverages in different countries. The finding that packaged foods and beverages are less healthy in middle-income countries such as China and India suggests that nutrient profiling is an important tool to enable policymakers and industry actors to reformulate products available in the marketplace to reduce the risk of obesity and NCDs among populations