Thermal measurements using ultrasonic acoustical pyrometry

Reflections from geometric discontinuities can be used with ultrasonic energy to predict the temperature of an interface where classical temperature measurement techniques are impractical because of physical access limitations or harsh environmental conditions. Additionally, these same ultrasonic measurements can be used with inversion methods commonly applied to ill-posed heat transfer problems to increase the accuracy of the measurement of surface temperature or heat flux at the surface of interest. Both methods for determining surface temperature are presented, along with a comparison of results both from a verification example and using data gathered in a field test of the methods. The results obtained with these two methods are shown to be in good agreement with an empirical relationship used in the design of large caliber guns.     

Solution-grown zinc oxide nanowires

We review two strategies for growing ZnO nanowires from zinc salts in aqueous and organic solvents. Wire arrays with diameters in the nanoscale regime can be grown in an aqueous solution of zinc nitrate and hexamethylenetetramine. With the addition of poly(ethylenimine), the lengths of the wires have been increased to 25 mum with aspect ratios over 125. Additionally, these arrays were made vertical by nucleating the wires from oriented ZnO nanocrystals. ZnO nanowire bundles have been produced by decomposing zinc acetate in trioctylamine. By the addition of a metal salt to the solution, the ZnO wires can be doped with a range of transition metals. Specifically, ZnO nanowires were homogeneously doped with cobalt and showed a marked deviation from paramagnetic behavior. We conclude by highlighting the use of these solution-grown nanowire arrays in dye-sensitized solar cells. The nanowire cells showed an improvement in the charge collection efficiency over traditional nanoparticle cells.     

Biomimetic multifunctional porous chalcogels as solar fuel catalysts

Biological systems that can capture and store solar energy are rich in a variety of chemical functionalities, incorporating light-harvesting components, electron-transfer cofactors, and redox-active catalysts into one supramolecule. Any artificial mimic of such systems designed for solar fuels production will require the integration of complex subunits into a larger architecture. We present porous chalcogenide frameworks that can contain both immobilized redox-active Fe(4)S(4) clusters and light-harvesting photoredox dye molecules in close proximity. These multifunctional gels are shown to electrocatalytically reduce protons and carbon disulfide. In addition, incorporation of a photoredox agent into the chalcogels is shown to photochemically produce hydrogen. The gels have a high degree of synthetic flexibility, which should allow for a wide range of light-driven processes relevant to the production of solar fuels.     

Comparing human and neural network lip readers

Performance in identifying nine vowels from static images of a speaker's mouth was studied experimentally for neural networks and human subjects. Data obtained indicated that they had essentially the same rate of correct identifications overall and vowel by vowel. The estimate of the probability of correct identification and 95% confidence limits were determined for each of the nine vowels.     

Photocatalytic hydrogen evolution from FeMoS-based biomimetic chalcogels

The naturally abundant elements used to catalyze photochemical processes in biology have inspired many research efforts into artificial analogues capable of proton reduction or water oxidation under solar illumination. Most biomimetic systems are isolated molecular units, lacking the protective encapsulation afforded by a protein's tertiary structure. As such, advances in biomimetic catalysis must also be driven by the controlled integration of molecular catalysts into larger superstructures. Here, we present porous chalcogenide framework materials that contain biomimetic catalyst groups immobilized in a chalcogenide network. The chalcogels are formed via metathesis reaction between the clusters [Mo(2)Fe(6)S(8)(SPh)(3)Cl(6)](3-) and [Sn(2)S(6)](4-) in solution, yielding an extended, porous framework structure with strong optical absorption, high surface area (up to 150 m(2)/g), and excellent aqueous stability. Using [Ru(bpy)(3)](2+) as the light-harvesting antenna, the chalcogels are capable of photocatalytically producing hydrogen from mixed aqueous solutions and are stable under constant illumination over a period of at least 3 weeks. We also present improved hydrogen yields in the context of the energy landscape of the chalcogels.     

Enhanced electrocatalytic reduction of CO2 with ternary Ni-Fe4S4 and Co-Fe4S4-based biomimetic chalcogels

Enzymes that catalytically transform small molecules such as CO, formate, or protons are naturally composed of transition metal cluster units bound into a larger superstructure. Artificial biomimetic catalysts are often modeled after the active sites but are typically molecular in nature. We present here a series of fully integrated porous materials containing Fe(4)S(4) clusters, dubbed "biomimetic chalcogels". We examine the effect of third metal cations on the electrochemical and electrocatalytic properties of the chalcogels. We find that ternary biomimetic chalcogels containing Ni or Co show increased effectiveness in transformations of carbon dioxide and can be thought of as solid-state analogues of NiFe or NiFeS reaction centers in enzymes.