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Evaluation of Performance of WL Fe-Based Spin-LEDs

A study was performed to evaluate the performance of a recently developed type of Fe-based spin-light-emitting diodes (spin-LEDs) that incorporate wetting layers (WLs). [The term "wetting layer" has two slightly different meanings as explained below.] Light beams emitted by the WL Febased spin-LEDs were found to exhibit the same high degree of circular polarization as do those of previously developed Fe-based spin-LEDs, but differ in one very important aspect: they are an order of magnitude brighter than those emitted by their previously developed counterparts. As a consequence, the WL Fe-based spin-LEDs function reliably at room temperature, whereas their previously developed counterparts do not.

Posted in: Briefs, Photonics
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Advances Toward Affordable High-Energy Laser Modules

A multidisciplinary research project entitled “Affordable High-Energy Lasers” has made numerous contributions to the development of several types of advanced laser modules, including not only lasers but also coupling optics and integral laser/ coupling-optic combinations. There are numerous potential applications for such modules, including weaponry, lidar, high-data-rate optical communications, interferometry, spectroscopy, remote sensing, and processing of materials. The devices developed in this project include novel fiber lasers, novel vertical-external-cavity surface emitting lasers (VECSELs), and a radially emitting photonic-bandgap (PBG) polymer fiber laser. Somewhat more specifically, the contributions are summarized as follows:

Posted in: Briefs, Photonics, Design processes, Lasers, Product development, Research and development
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Lasing Consequences of Silicon Nanostructures

While silicon electronics has been a success in modem technologies, silicon photonics is still in development and in need of a laser source. Many approaches have been explored, from anodized silicon luminescence, to generating direct emissions by quantum-confinement, and to indirect down-conversion of a shorter wavelength laser light via silicon's nonlinear dielectric responses. One approach that was developed has led to the demonstration of laser emission in silicon-on-insulator at cryogenic temperatures (<85K).

Posted in: Briefs, Photonics
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Software Optimizes Multi-Core Platforms

Perseus is a suite of tools that allows existing x86-based software (in binary form) to be optimized for commodity multi-core platforms. Optimizations are made with respect to both performance (e.g., by avoiding undesirable cache effects) and power consumption (e.g., by modulating frequency and voltage of cores according to necessary workloads). The Perseus solution works by using dynamic binary instrumentation to both insert probes and modify deployed code, and by using genetic-algorithm-based searches to determine optimal deployments within the potential design space.

Posted in: Briefs, Software
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Fluidic Flexible Matrix Composites for Autonomous Structural Tailoring

In previous research, a high-mechanical- advantage actuator system inspired by the fibrillar networks in plant cell walls was developed. One of the basic elements in the actuator system is a composite tube consisting of a flexible matrix and multiple layers of oriented, high-performance fibers such as carbon. By tailoring the properties of the fibers and matrix of the flexible matrix composite (FMC) tube, one can create a material that is flexible in certain directions, yet compliant in others. For example, the ratio of Young's moduli in the directions parallel and transverse to the fibers can range from 102 to 104. Strands of such FMC material can be wound into a tube at selected angles relative to the winding axis (a process called filament winding) such that the tube can contract or elongate axially via internal pressurization. It was previously shown that large strain and large force can be achieved with individual, pressurized FMC tubes, and that parallel arrays of tubular elements can be integrated to form 2D adaptive structures (e.g., skins and plates with multiple tubes).

Posted in: Briefs, Materials
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Macromolecular Carriers for Nanomedicine and Nano Devices

Tailoring the surface properties of biodegradable nanospheres and microspheres for in-vivo blood-contacting applications includes defining relationships among chemical composition, processing parameters, nanosphere sizes and size distributions, and surface structure. Developments include: 1) a facile method for achieving magnetite-polylactide nanospheres that can be dispersed in aqueous media; 2) methods for functionalizing the termini of the hydrophilic brushes on the nanospheres in order to conjugate targeting moieties; 3) development of a nanosphere processing approach that yields nanospheres in the desired size range with a narrow distribution of sizes; and 4) maintainence of all of these characteristics with up to approximately 60 weight percent of magnetite incorporated into the nanospheres.

Posted in: Briefs, Medical
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Genetic Studies of Responses of Bones to Mechanical Stresses

Progress has been reported in a continuing program of molecular genetic studies of the responses of bones to mechanical stresses. Prior studies in mice and humans had provided evidence that mechanical loading stimulates bone formation and that immobilization or loss of mechanical stimulation leads to decreasing bone formation and increasing bone loss. Other prior studies in humans and mice had demonstrated that bone anabolic response differs widely among individuals subjected to the same degree of mechanical loading. The initiation of the present studies was motivated by the conjecture that variations in bone anabolic response among individuals are attributable to differences in the transcription levels of genes; that is, they are genetically controlled.

Posted in: Briefs, Medical
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Characterization of a MEMS Directional Sound Sensor

There is a wide range of potential military applications in which ambiguity in bearing occurs with respect to sound. For example, autonomous unmanned aerial vehicles (UAVs) could employ a sensor to determine the bearing of an explosion and conduct battle damage assessment (BDA) on it. With existing sensors this is difficult to do because the explosion is too short in duration to use the Doppler effect to determine the bearing. Also, an autonomous underwater vehicle (AUV) acting as a quiet platform to tow a short, omni-directional hydrophone array must contend with bearing ambiguity.

Posted in: Briefs, Physical Sciences
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Two-Camera Imaging System for Kinematic Measurements

A high-speed imaging system has been devised as a noninvasive means of collecting data on the kinematics of working models of developmental underwater or aerial vehicles that would utilize flapping fins or flapping wings for propulsion. The system includes two high-speed digital electronic cameras aimed along orthogonal axes that acquire snapshots of a model simultaneously in rapid succession. The data from successive images are postprocessed to obtain three-dimensional coordinates of points of interest on the model as functions of time. In the case of a flapping appendage, the points of interest are tips on the appendage, and the temporal evolution of the tip coordinates through multiple flapping cycles is utilized, in conjunction with computational fluid dynamics and other analytical tools, in an iterative process of testing and design directed toward improving the swimming or flying performance of the model. The system can, of course, be used as a noninvasive means of kinematic testing of models other than those of vehicles utilizing flapping appendages.

Posted in: Briefs, Physical Sciences
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Synthesizing Pseudo-Finer-Resolution MODIS Data Products

A document discusses a methodology for synthesizing finerresolution data products from outputs of the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard NASA's Terra and Aqua satellites. Typical MODIS ocean color data have 1-km resolution, but those in five wavelength bands have 500-m resolution and those in two wavelength bands have 250-m resolution. Finer-resolution bio-optical-property data products improve our capability for monitoring coastal ocean and estuarine processes.

Posted in: Briefs, Physical Sciences
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