The plasmoelectric effect: optically induced electrochemical potentials in resonant metallic structures

We describe a strategy for conversion of optical power into DC electrical power using resonant absorption in plasmonic nanostructures. A thermodynamic analysis of the underlying mechanism motivates our description of the phenomenon, which we term the plasmoelectric effect. Power conversion results from the dependence of optically generated heat on shifts of the plasmon resonance frequency that occur with changes of electron density. We model an all-metal device constructed from 10 nm radius silver spheres and predict a characteristic conversion efficiency of 14.3% under 1 kW m-2 intensity, single-frequency radiation. We discuss strategies for enhanced efficiency, broadband power conversion, and further applications of this new class of optoelectronic device.Comment: 24 pages with supplemental include

A comparison of leaf crystal macropatterns in the two sister genera Piper and Peperomia (Piperaceae)

Premise of the study: This is the first large-scale study comparing leaf crystal macropatterns of the species-rich sister genera Piper and Peperomia. It focuses on identifying types of calcium oxalate crystals and their macropatterns in leaves of both genera. The Piper results are placed in a phylogenetic context to show evolutionary patterns. This information will expand knowledge about crystals and provide specific examples to help study their form and function. One example is the first-time observation of Piper crystal sand tumbling in chlorenchyma vacuoles. Methods: Herbarium and fresh leaves were cleared of cytoplasmic content and examined with polarizing microscopy to identify types of crystals and their macropatterns. Selected hydrated herbarium and fresh leaf punches were processed for scanning electron microscopy and x-ray elemental analysis. Vibratome sections of living Piper and Peperomia leaves were observed for anatomical features and crystal movement. Key results: Both genera have different leaf anatomies. Piper displays four crystal types in chlorenchyma-crystal sand, raphides, styloids, and druses, whereas Peperomia displays three types-druses, raphides, and prisms. Because of different leaf anatomies and crystal types between the genera, macropatterns are completely different. Crystal macropattern evolution in both is characterized by increasing complexity, and both may use their crystals for light gathering and reflection for efficient photosynthesis under low-intensity light environments. Conclusions: Both genera have different leaf anatomies, types of crystals and crystal macropatterns. Based on Piper crystals associated with photosynthetic tissues and low-intensity light, further study of their function and association with surrounding chloroplasts is warranted, especially active crystal movement

A system overview of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

The AVIRIS instrument has been designed to do high spectral resolution remote sensing of the Earth. Utilizing both silicon and indium antimonide line array detectors, AVIRIS covers the spectral region from 0.41 to 2.45 microns in 10-nm bands. It was designed to fly aboard NASA's U-2 and ER-2 aircraft, where it will simulate the performance of future spacecraft instrumentation. Flying at an altitude of 20 km, it has an instantaneous field of view of 20 m and views a swath over 10 km wide. With an ability to record 40 minutes of data, it can, during a single flight, capture 500 km of flight line

Improved silicon nitride for advanced heat engines

The results of a four year program to improve the strength and reliability of injection-molded silicon nitride are summarized. Statistically designed processing experiments were performed to identify and optimize critical processing parameters and compositions. Process improvements were monitored by strength testing at room and elevated temperatures, and microstructural characterization by optical, scanning electron microscopes, and scanning transmission electron microscope. Processing modifications resulted in a 20 percent strength and 72 percent Weibull slope improvement of the baseline material. Additional sintering aids screening and optimization experiments succeeded in developing a new composition (GN-10) capable of 581.2 MPa at 1399 C. A SiC whisker toughened composite using this material as a matrix achieved a room temperature toughness of 6.9 MPa m(exp .5) by the Chevron notched bar technique. Exploratory experiments were conducted on injection molding of turbocharger rotors

Comparative study of evolution of residual stress state by local mechanical tensioning and laser processing of ferritic and austenitic structural steel welds.

Complex thermal stresses generated in welded structures are undesirable but inevitable in fusion welding. The presence of residual stresses can be detrimental to the integrity of a welded joint. In this research, redistribution of residual stress magnitude and profile was studied and compared in two multi-pass welded structural alloys (API X100 and 304L stainless steel) after cold rolling and laser processing. The residual stress field was studied by neutron diffraction using the SALSA strain scanner at their reactor neutron source at ILL, Grenoble. In addition to a complex distribution of residual stress state, multi-pass welds also forms dendritic grain structure, which are repeatedly heated, resulting in segregation of alloying elements. Dendritic grain structure is weaker and segregation of alloying elements may result in formation of corrosion microcells as well as reduction in overall corrosion prevention due to depletion of alloying elements in certain areas. The modification of as-welded residual stress state was done by cold rolling which was followed by laser processing to create a recrystallized microstructure to minimise segregation. The main objective of this study is to understand the suitability of this novel manufacturing technique to create a stress free weldment with recrystallised grain structure. Hardness evolution in the welded structures was scanned following welding, post weld cold rolling and cold rolling followed by laser processing. Hardness distribution in both the structural alloys showed a significant evidence of plastic deformation near the cap pass of the weld metal. Residual stress redistribution was observed up to 4 mm from the capping pass for ferritic steel, while in austenitic steel weld, post weld cold rolling was effective in modifying the residual stress redistribution throughout the entire thickness. Laser processing in both cases reinstated the as-welded residual stress distribution and resulted in softening of the strained area

Innovative Stormwater Treatment Technologies: Best Management Practices Manual

Urban stormwater carries a number of pathogens, nutrients, heavy metals, sediment, and other contaminants as surface runoff flows over land. The increase in impervious or paved surfaces associated with development in urban areas reduces the natural infiltration of precipitation into the ground. With impervious cover, precipitation collects and carries contaminants before draining into nearby surface waters. Stormwater runoff from paved surfaces in developed areas can degrade downstream waters with both contaminants and increased volumes of water. This publication aims to make information on innovative stormwater treatment technologies more available to New Hampshire’s urban planners, developers, and communities. Traditional runoff management techniques such as detention basins and infiltration swales may be preferable, but are not always practical for treating urban stormwater. Lack of space for natural solutions is often a problem in existing developed areas, making innovative treatment technologies an attractive alternative. Mostly designed for subsurface installation, urban “retrofits” use less space than conventional methods to treat stormwater. This manual provides information on the innovative stormwater “retrofit” technologies currently available for use in developed areas in New Hampshire

Reflection high-energy electron diffraction analysis of polycrystalline films with grain size and orientation distributions

We report a computationally efficient algorithm to calculate reflection high-energy electron diffraction (RHEED) intensities from well-textured, small-grained polycrystalline films in the kinematic limit. We also show how the intensity maps of the spots in a RHEED pattern from such a film can be quantitatively analyzed to determine the film's average grain size, as well as its in-plane orientation and texture distributions. We find that the in-plane orientation and texture distribution widths of these films can be determined to within 1 degree and that the average lateral grain size can be measured to within a fraction of a nanometer after suitable calibration of our technique