Block copolymer self-assembly for nanophotonics

The ability to control and modulate the interaction of light with matter is crucial to achieve desired optical properties including reflection, transmission, and selective polarization. Photonic materials rely upon precise control over the composition and morphology to establish periodic interactions with light on the wavelength and sub-wavelength length scales. Supramolecular assembly provides a natural solution allowing the encoding of a desired 3D architecture into the chemical building blocks and assembly conditions. The compatibility with solution processing and low-overhead manufacturing is a significant advantage over more complex approaches such as lithography or colloidal assembly. Here we review recent advances on photonic architectures derived from block copolymers and highlight the influence and complexity of processing pathways. Notable examples that have emerged from this unique synthesis platform include Bragg reflectors, antireflective coatings, and chiral metamaterials. We further predict expanded photonic capabilities and limits of these approaches in light of future developments of the field

Elastic Interactions of Cells

Biological cells in soft materials can be modeled as anisotropic force contraction dipoles. The corresponding elastic interaction potentials are long-ranged ($\sim 1/r^3$ with distance $r$) and depend sensitively on elastic constants, geometry and cellular orientations. On elastic substrates, the elastic interaction is similar to that of electric quadrupoles in two dimensions and for dense systems leads to aggregation with herringbone order on a cellular scale. Free and clamped surfaces of samples of finite size introduce attractive and repulsive corrections, respectively, which vary on the macroscopic scale. Our theory predicts cell reorientation on stretched elastic substrates.Comment: Revtex, 6 pages, 2 Postscript files included, to appear in Phys. Rev. Let

Interplex modulation and a suppressed-carrier tracking loop for coherent communications systems

Simple addition to hardware and new mode of operation of transmitter and receiver in coherent, PCM/PSK/PM configuration greatly improves channel efficiency. Procedure reduces amount of power lost to intermodulation products

Sooty blotch of apple: Efficacy of different application strategies

Sooty blotch causes heavy losses in Lake Constance organic apple production. In the last five years research has been done at the research station for fruit growing (Kompetenzzentrum Obstbau – Bodensee) on strategies to control Sooty blotch on organic grown pome fruit. Different control strategies with lime sulphur, coconut soap and potassium bicarbonate with different application rates, application times were tested in several trials on the cultivar ‘Topaz’. Over the years the results show that lime sulphur has significant effects in controlling Sooty blotch. In a first trial potassium bicarbonate showed a promising efficacy against Sooty blotch. Concerning the right application times we need further investigations. The problem is that Sooty blotch is a disease complex caused by several fungi and it is likely that the fungi that are a part of the complex differ from area to area

CO oxidation on a single Pd atom supported on magnesia

The oxidation of CO on single Pd atoms anchored to MgO(100) surface oxygen vacancies is studied with temperature-programmed-reaction mass-spectrometry and infrared spectroscopy. In one-heating-cycle experiments CO$_2$, formed from O$_2$ and CO preadsorbed at 90 K, is detected at 260 K and 500 K. Ab-initio simulations suggest two reaction routes, with Pd(CO)$_2$O$_2$ and Pd(CO$_3$)CO found as precursors for the low and high temperature channels, respectively. Both reactions result in annealing of the vacancy and induce migration and coalescence of the remaining Pd-CO to form larger clusters.Comment: 4 pages, 3 figures, scheduled for publication in PRL 18 June 200

Mollusk species at a Pliocene shelf whale fall (Orciano Pisano, Tuscany)

The recovery of an intact, 10 m long fossil baleen whale from the Pliocene of Tuscany (Italy) offers the first opportunity to study the paleoecology of a fully developed, natural whale-fall community at outer shelf depth. Quantitative data on mollusk species from the whale fall have been compared with data from the sediments below and around the bones, representing the fauna living in the muddy bottom before and during the sinking of the carcass, but at a distance from it. Although the bulk of the fauna associated with the fossil bones is dominated by the same heterotrophs as found in the surrounding community, whale-fall samples are distinguishable primarily by the presence of chemosymbiotic bivalves and a greater species richness of carnivores and parasites. Large lucinid clams (Megaxinus incrassatus) and very rare small mussels (Idas sp.) testify to the occurrence of a sulphophilic stage, but specialized, chemosymbiotic vesicomyid clams common at deep-sea whale falls are absent. The whale-fall community is at the threshold between the nutrient-poor deep sea and the shallow-water shelf, where communities are shaped around photosynthetic trophic pathways and chemosymbiotic specialists are excluded by competition. © SEPM (Society for Sedimentary Geology)

Measuring electron energy distribution by current fluctuations

A recent concept of local noise sensor is extended to measure the energy resolved electronic energy distribution $f(\varepsilon)$ at a given location inside a non-equilibrium normal metal interconnect. A quantitative analysis of $f(\varepsilon)$ is complicated because of a nonlinear differential resistance of the noise sensor, represented by a diffusive InAs nanowire. Nevertheless, by comparing the non-equilibrium results with reference equilibrium measurements, we conclude that $f(\varepsilon)$ is indistinguishable from the Fermi distribution

Acute toxicity of synyhetic resin effluent to African Catfish, Clarias gariepinus [BURCHELL, 1822].

Aquatic pollution as a field has gained a lot of attention over the decades majorly because of the vital role the aquatic environment plays in the human lifecycle. Indusrial wastewaters are often generated and discharged into the environment without treatment. Toxicity of effluents from Synythetic Resin production plant were evaluated in this study. Acute toxicity (96-h LC50) was evaluated using 0.23, 0.31, 0.35 and 0.39 mg/L of the effluent in a renewal bioassay procedure. Physicochemical parameters of the effluent were also evaluated, the values obtained for lead, cyanide, total suspened solid, total hadness, total dissolved solids and alkalinity were higher than the Federal Environmental Protection Agency standard specification for effluent discharge into aquatic environment and as such contributed to the effluent's toxicity. Mortality increased as the concentrations of the effluent increases and 0.355mg/L was obtained as LC50. The research eventually revealed that the synthetic resin effluent has a high level of toxicity to catfish. Deleterious effects such as biomagnification and other abberations may occur in man if exposed to substantial concentration of the effluent

Bose-Einstein Correlations and Sonoluminescence

Sonoluminescence may be studied in detail by intensity correlations among the emitted photons. As an example, we discuss an experiment to measure the size of the light-emitting region by the Hanbury Brown-Twiss effect. We show that single bubble sonoluminescence is almost ideally suited for study by this method and that plausible values for the physical parameters are within easy experimental reach. A sequence of two and higher order photon correlation experiments is outlined.Comment: Latex File, 8 pages, Postscript file with 2 figs. attache

CPP- Giant Magnetoresistance and Thermo-Electric Power of multilayers

Oscillations of magnetoresistance and thermo-electric power (TEP) vs. both nonmagnetic spacer as well as ferromagnetic slab thicknesses are studied in the current-perpendicular-to-plane (CPP) geometry, in terms of a single-band tight-binding model. The spin-dependent conductance has been calculated from the Kubo formula by means of a recursion Green's function technique, and the $TEP$ directly from the well-known Onsager relations. In general, the observed oscillations may have either just one or two periods. In the latter case the long period of oscillations, related to spectacular beats, is apparently of non-RKKY type. The relative TEP oscillations are strongly enhanced in comparison with those of the giant magnetoresistance, have the same periods, but different phases and a negative bias.Comment: Latex (4 pages); 2 figures included; to appear in Proc. of 'Physics of Magn. 1996', Acta Physica Polonic