Construction and evaluation of an ultrahigh-vacuum-compatible sputter deposition source

NASA Astrophysics Data System (ADS)

Lackner, Peter; Choi, Joong Il Jake; Diebold, Ulrike; Schmid, Michael

2017-10-01

A sputter deposition source for the use in ultrahigh vacuum (UHV) is described, and some properties of the source are analyzed. The operating principle is based on the design developed by Mayr et al. [Rev. Sci. Instrum. 84, 094103 (2013)], where electrons emitted from a filament ionize argon gas and the Ar+ ions are accelerated to the target. In contrast to the original design, two grids are used to direct a large fraction of the Ar+ ions to the target, and the source has a housing cooled by liquid nitrogen to reduce contaminations. The source has been used for the deposition of zirconium, a material that is difficult to evaporate in standard UHV evaporators. At an Ar pressure of 9 ×1 0-6 mbar in the UHV chamber and moderate emission current, a highly reproducible deposition rate of ≈1 ML in 250 s was achieved at the substrate (at a distance of ≈50 mm from the target). Higher deposition rates are easily possible. X-ray photoelectron spectroscopy shows a high purity of the deposited films. Depending on the grid voltages, the substrate gets mildly sputtered by Ar+ ions; in addition, the substrate is also reached by electrons from the negatively biased sputter target.

Enhancement of thickness uniformity of thin films grown by pulsed laser deposition

NASA Technical Reports Server (NTRS)

Fernandez, Felix E.

1995-01-01

A peculiarity of the pulsed laser deposition technique of thin-film growth which limits its applicability is the very rapid drop of resulting film thickness as a function of distance from the deposition axis. This is due to the narrow forward peaking of the emission plume characteristic of the laser ablation process. The plume is usually modeled by a cos(sup n) theta function with n greater, and in some cases, much higher, than 1. Based on this behavior, a method is presented to substantially enhance coverage uniformity in substrate zones of the order of the target-substrate distance h, and to within a specified thickness tolerance. Essentially, target irradiation is caused to form an annular emission source instead of the usual spot. By calculating the resulting thickness profiles, an optimum radius s is found for the annular source, corresponding to a given power in the emission characteristic and a given value of h. The radius of this annulus scales with h. Calculated numerical results for optimal s/h ratios corresponding to a wide range of values for n are provided for the case of +/- 1% tolerance in deviation from the thickness at deposition axis. Manners of producing annular illumination of the target by means of conic optics are presented for the case of a laser beam with radially symmetric profile. The region of uniform coverage at the substrate can be further augmented by extension of the method to multiple concentric annular sources. By using a conic optic of novel design, it is shown also how a single-laser beam can be focused onto a target in the required manner. Applicability of the method would be limited in practice by the available laser power. On the other hand, the effective emitting area can be large, which favors extremely high growth rates, and since growth can occur uniformly over the whole substrate for each laser pulse, single-shot depositions with substantial thicknesses are possible. In addition, the simultaneity of growth over the complete substrate is desirable when monitoring the growth in situ.

Convective flow reversal in self-powered enzyme micropumps.

PubMed

Ortiz-Rivera, Isamar; Shum, Henry; Agrawal, Arjun; Sen, Ayusman; Balazs, Anna C

2016-03-08

Surface-bound enzymes can act as pumps that drive large-scale fluid flows in the presence of their substrates or promoters. Thus, enzymatic catalysis can be harnessed for “on demand” pumping in nano- and microfluidic devices powered by an intrinsic energy source. The mechanisms controlling the pumping have not, however, been completely elucidated. Herein, we combine theory and experiments to demonstrate a previously unreported spatiotemporal variation in pumping behavior in urease-based pumps and uncover the mechanisms behind these dynamics. We developed a theoretical model for the transduction of chemical energy into mechanical fluid flow in these systems, capturing buoyancy effects due to the solution containing nonuniform concentrations of substrate and product. We find that the qualitative features of the flow depend on the ratios of diffusivities δ=D(P)/D(S) and expansion coefficients β=β(P)/β(S) of the reaction substrate (S) and product (P). If δ>1 and δ>β (or if δ<1 and δ<β ), an unexpected phenomenon arises: the flow direction reverses with time and distance from the pump. Our experimental results are in qualitative agreement with the model and show that both the speed and direction of fluid pumping (i) depend on the enzyme activity and coverage, (ii) vary with the distance from the pump, and (iii) evolve with time. These findings permit the rational design of enzymatic pumps that accurately control the direction and speed of fluid flow without external power sources, enabling effective, self-powered fluidic devices.

Convective flow reversal in self-powered enzyme micropumps

PubMed Central

Ortiz-Rivera, Isamar; Shum, Henry; Agrawal, Arjun; Sen, Ayusman; Balazs, Anna C.

2016-01-01

Surface-bound enzymes can act as pumps that drive large-scale fluid flows in the presence of their substrates or promoters. Thus, enzymatic catalysis can be harnessed for “on demand” pumping in nano- and microfluidic devices powered by an intrinsic energy source. The mechanisms controlling the pumping have not, however, been completely elucidated. Herein, we combine theory and experiments to demonstrate a previously unreported spatiotemporal variation in pumping behavior in urease-based pumps and uncover the mechanisms behind these dynamics. We developed a theoretical model for the transduction of chemical energy into mechanical fluid flow in these systems, capturing buoyancy effects due to the solution containing nonuniform concentrations of substrate and product. We find that the qualitative features of the flow depend on the ratios of diffusivities δ=DP/DS and expansion coefficients β=βP/βS of the reaction substrate (S) and product (P). If δ>1 and δ>β (or if δ<1 and δ<β), an unexpected phenomenon arises: the flow direction reverses with time and distance from the pump. Our experimental results are in qualitative agreement with the model and show that both the speed and direction of fluid pumping (i) depend on the enzyme activity and coverage, (ii) vary with the distance from the pump, and (iii) evolve with time. These findings permit the rational design of enzymatic pumps that accurately control the direction and speed of fluid flow without external power sources, enabling effective, self-powered fluidic devices. PMID:26903618

Modelling of low-temperature/large-area distributed antenna array microwave-plasma reactor used for nanocrystalline diamond deposition

NASA Astrophysics Data System (ADS)

Bénédic, Fabien; Baudrillart, Benoit; Achard, Jocelyn

2018-02-01

In this paper we investigate a distributed antenna array Plasma Enhanced Chemical Vapor Deposition system, composed of 16 microwave plasma sources arranged in a 2D matrix, which enables the growth of 4-in. diamond films at low pressure and low substrate temperature by using H2/CH4/CO2 gas chemistry. A self-consistent two-dimensional plasma model developed for hydrogen discharges is used to study the discharge behavior. Especially, the gas temperature is estimated close to 350 K at a position corresponding to the substrate location during the growth, which is suitable for low temperature deposition. Multi-source discharge modeling evidences that the uniformity of the plasma sheet formed by the individual plasmas ignited around each elementary microwave source strongly depends on the distance to the antennas. The radial profile of the film thickness homogeneity may be thus linked to the local variations of species density. Contribution to the topical issue "Plasma Sources and Plasma Processes (PSPP)", edited by Luis Lemos Alves, Thierry Belmonte and Tibeinea Minea.

Non-imaging Optics of multi-LED light source for hyperspectral imaging

NASA Astrophysics Data System (ADS)

Islam, Kashif; Gosnell, Martin E.; Ploschner, Martin; Anwer, Ayad G.; Goldys, Ewa M.

2016-12-01

The main objective of our work was to design a light source which should be capable to collect and illuminate light of LEDs at the smaller aperture of cone (9mm) which could be either coupled with secondary optics of a microscope or utilized independently for hyperspectral studies. Optimized performance of cone was assessed for different substrates (diffused glass silica, Alumina, Zerodur glass, acrylic plastic) and coating surfaces (white diffused, flat white paint, standard mirror) using a simulation software. The parameters optimized for truncated cone include slanting length and Top Major R (Larger diameter of cone) which were also varied from 10 to 350 mm and 10 to 80 mm respectively. In order to see affect of LED positions on cone efficiency, the positions of LED were varied from central axis to off-axis. Similarly, interLED distance was varied from 2 mm to 6 mm to reckon its effect on the performance of cone. The optimized Slant length (80 mm) and Top Major R (50 mm) were determined for substrates (glass zerodur or acrylic plastic) and coating surface (standard mirror). The output profile of truncated source was found non uniform, which is a typical presentation of non imaging optics problem. The maximum efficiency of cone has been found for LED at the centre and it was found decreasing as LED moves away from the central axis. Moreover, shorter the interLED distance, better is the performance of cone. The primary optics of cone shaped light source is capable to lit visible and UV LEDs in practical design. The optimum parameters obtained through simulations could be implemented in the fabrication procedure if the reflectance of source would have been maintained upto finish level of a standard mirror.

Effect of sputtering parameters on optical and electrical properties of ITO films on PET substrates

NASA Astrophysics Data System (ADS)

Tseng, Kun-San; Lo, Yu-Lung

2013-11-01

The optical and electrical properties of indium tin oxide (ITO) thin films deposited on flexible polyethylene terephthalate (PET) substrates using a DC magnetron sputtering technique are investigated as a function of the deposition time, the argon flow rate and the target-substrate distance. It is found that all of the ITO films contain a high fraction of amorphous phase. The volume fraction of crystallite precipitates in the amorphous host increases with an increasing deposition time or a reducing argon flow rate. The deposition time and argon flow rate have higher effects on the optical transparency of the ITO films than the target-substrate distance has. Increasing film thickness is not the only reason for the transmittance reduced. It is found that an increase of the extinction coefficient by increasing deposition time or an increase of the refractive index by decreasing argon flow rate also reduces the transmittance of thin film. For a constant deposition time, the resistivity of the ITO films reduces with a reducing argon flow rate or a reducing target-substrate distance. For a constant argon flow rate, a critical value of the deposition time exists at which both the resistivity and the effect of the target-substrate distance are minimized. Finally, it is concluded that the film resistivity has low sensitivity to the target-substrate distance if the best deposition conditions which mostly attain the lowest resistivity are matched.

Monte Carlo simulation of the influence of pressure and target-substrate distance on the sputtering process for metal and semiconductor layers

NASA Astrophysics Data System (ADS)

Bouazza, Abdelkader; Settaouti, Abderrahmane

2016-07-01

The energy and the number of particles arriving at the substrate during physical vapor deposition (PVD) are in close relation with divers parameters. In this work, we present the influence of the distance between the target and substrate and the gas pressure in the sputtering process of deposited layers of metals (Cu, Al and Ag) and semiconductors (Ge, Te and Si) for substrate diameter of 40 cm and target diameter of 5 cm. The nascent sputter flux, the flux of the atoms and their energy arriving at the substrate have been simulated by Monte Carlo codes. A good agreement between previous works of other groups and our simulations for sputter pressures (0.3-1 Pa) and target-substrate distances (8-20 cm) is obtained.

Self-catalytic crystal growth, formation mechanism, and optical properties of indium tin oxide nanostructures

NASA Astrophysics Data System (ADS)

Liang, Yuan-Chang; Zhong, Hua

2013-08-01

In-Sn-O nanostructures with rectangular cross-sectional rod-like, sword-like, and bowling pin-like morphologies were successfully synthesized through self-catalytic growth. Mixed metallic In and Sn powders were used as source materials, and no catalyst layer was pre-coated on the substrates. The distance between the substrate and the source materials affected the size of the Sn-rich alloy particles during crystal growth in a quartz tube. This caused In-Sn-O nanostructures with various morphologies to form. An X-ray photoelectron spectroscope and a transmittance electron microscope with an energy-dispersive X-ray spectrometer were used to investigate the elemental binding states and compositions of the as-synthesized nanostructures. The Sn doping and oxygen vacancies in the In2O3 crystals corresponded to the blue-green and yellow-orange emission bands of the nanostructures, respectively.

Emplacement of rock avalanche material across saturated sediments, Southern Alp, New Zealand

NASA Astrophysics Data System (ADS)

Dufresne, A.; Davies, T. R.; McSaveney, M. J.

2012-04-01

The spreading of material from slope failure events is not only influenced by the volume and nature of the source material and the local topography, but also by the materials encountered in the runout path. In this study, evidence of complex interactions between rock avalanche and sedimentary runout path material were investigated at the 45 x 106 m3 long-runout (L: 4.8 km) Round Top rock avalanche deposit, New Zealand. It was sourced within myolinitic schists of the active strike-slip Alpine Fault. The narrow and in-failure-direction elongate source scarp is deep-seated, indicating slope failure was triggered by strong seismic activity. The most striking morphological deposit features are longitudinal ridges aligned radially to source. Trenching and geophysical surveys show bulldozed and sheared substrate material at ridge termini and laterally displaced sedimentary strata. The substrate failed at a minimum depth of 3 m indicating a ploughing motion of the ridges into the saturated material below. Internal avalanche compression features suggest deceleration behind the bulldozed substrate obstacle. Contorted fabric in material ahead of the ridge document substrate disruption by the overriding avalanche material deposited as the next down-motion hummock. Comparison with rock avalanches of similar volume but different emplacement environments places Round Top between longer runout avalanches emplaced over e.g. playa lake sediments and those with shorter travel distances, whose runout was apparently retarded by topographic obstacles or that entrained high-friction debris. These empirical observations indicate the importance of runout path materials on tentative trends in rock avalanche emplacement dynamics and runout behaviour.

Insights into the glycyl radical enzyme active site of benzylsuccinate synthase: a computational study.

PubMed

Bharadwaj, Vivek S; Dean, Anthony M; Maupin, C Mark

2013-08-21

The fumarate addition reaction, catalyzed by the enzyme benzylsuccinate synthase (BSS), is considered to be one of the most intriguing and energetically challenging reactions in biology. BSS belongs to the glycyl radical enzyme family and catalyzes the fumarate addition reaction, which enables microorganisms to utilize hydrocarbons as an energy source under anaerobic conditions. Unfortunately, the extreme sensitivity of the glycyl radical to oxygen has hampered the structural and kinetic characterization of BSS, thereby limiting our knowledge on this enzyme. To enhance our molecular-level understanding of BSS, a computational approach involving homology modeling, docking studies, and molecular dynamics (MD) simulations has been used to deduce the structure of BSS's catalytic subunit (BSSα) and illuminate the molecular basis for the fumarate addition reaction. We have identified two conserved and distinct binding pockets at the BSSα active site: a hydrophobic pocket for toluene binding and a polar pocket for fumaric acid binding. Subsequent dynamical and energetic evaluations have identified Glu509, Ser827, Leu390, and Phe384 as active site residues critical for substrate binding. The orientation of substrates at the active site observed in MD simulations is consistent with experimental observations of the syn addition of toluene to fumaric acid. It is also found that substrate binding tightens the active site and restricts the conformational flexibility of the thiyl radical, leading to hydrogen transfer distances conducive to the proposed reaction mechanism. The stability of substrates at the active site and the occurrence of feasible radical transfer distances between the thiyl radical, substrates, and the active site glycine indicate a substrate-assisted radical transfer pathway governing fumarate addition.

Composition variations in pulsed-laser-deposited Y-Ba-Cu-O thin films as a function of deposition parameters

NASA Technical Reports Server (NTRS)

Foote, M. C.; Jones, B. B.; Hunt, B. D.; Barner, J. B.; Vasquez, R. P.; Bajuk, L. J.

1992-01-01

The composition of pulsed-ultraviolet-laser-deposited Y-Ba-Cu-O films was examined as a function of position across the substrate, laser fluence, laser spot size, substrate temperature, target conditioning, oxygen pressure and target-substrate distance. Laser fluence, laser spot size, and substrate temperature were found to have little effect on composition within the range investigated. Ablation from a fresh target surface results in films enriched in copper and barium, both of which decrease in concentration until a steady state condition is achieved. Oxygen pressure and target-substrate distance have a significant effect on film composition. In vacuum, copper and barium are slightly concentrated at the center of deposition. With the introduction of an oxygen background pressure, scattering results in copper and barium depletion in the deposition center, an effect which increases with increasing target-substrate distance. A balancing of these two effects results in stoichiometric deposition.

Functionalization of nanotextured substrates for enhanced identification of metastatic breast cancer cells

NASA Astrophysics Data System (ADS)

Mansur, Nuzhat; Raziul Hasan, Mohammad; Kim, Young-tae; Iqbal, Samir M.

2017-09-01

Metastasis is the major cause of low survival rates among cancer patients. Once cancer cells metastasize, it is extremely difficult to contain the disease. We report on a nanotextured platform for enhanced detection of metastatic cells. We captured metastatic (MDA-MDB-231) and non-metastatic (MCF-7) breast cancer cells on anti-EGFR aptamer modified plane and nanotextured substrates. Metastatic cells were seen to change their morphology at higher rates when captured on nanotextured substrates than on plane substrates. Analysis showed statistically different morphological behaviors of metastatic cells that were very pronounced on the nanotextured substrates. Several distance matrices were calculated to quantify the dissimilarity of cell shape change. Nanotexturing increased the dissimilarity of the metastatic cells and as a result the contrast between metastatic and non-metastatic cells increased. Jaccard distance measurements found that the shape change ratio of the non-metastatic and metastatic cells was enhanced from 1:1.01 to 1:1.81, going from plane to nanotextured substrates. The shape change ratio of the non-metastatic to metastatic cells improved from 1:1.48 to 1:2.19 for the Hausdorff distance and from 1:1.87 to 1:4.69 for the Mahalanobis distance after introducing nanotexture. Distance matrix analysis showed that nanotexture increased the shape change ratios of non-metastatic and metastatic cells. Hence, the detectability of metastatic cells increased. These calculated matrices provided clear and explicit measures to discriminate single cells for their metastatic state on functional nanotextured substrates.

Projection parameters for zirconia-alumina-ceria coatings made by flame spraying from results of numerical simulation

NASA Astrophysics Data System (ADS)

Rodríguez, L.; Ferrer, M.; Vargas, F.; Peña, G.

2017-12-01

A numerical simulation was performed with the software Jets et Poudres, the results let choose the parameters to deposit zirconia-alumina-ceria coatings of different composition on substrates of red clay, by thermal spraying with the oxyacetylene flame to obtain homogeneous coatings with good adhesion to the substrate. The effect of the projection distance (7, 10 and 12cm) between the substrate and the torch, the fusion percentage of particles and the K-Sommerfeld number was determined. This number is dimensionless and is affected by the projection distance and by the chemical composition of the particles. For a projection distance of 9cm, the fusion percentage of the particles varies between 83.8% and 100%, and the K-Sommerfeld number between 47.3 and 50 for the different compounds. This makes possible to obtain uniform coatings with good wettability, therefore, good adhesion to the substrate, while for the distance of 7cm the fusion percentage varies between 22% and 38%, due to the short time of the particles in the flame which causes low adhesion, when the projection distance is 12cm the particles do not have sufficient kinetic energy to reach the substrate and therefore the coating is not deposited.

Overlay coating degradation by simultaneous oxidation and coating/substrate interdiffusion. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Nesbitt, J. A.

1983-01-01

Degradation of NiCrAlZr overlay coatings on various NiCrAl substrates was examined after cyclic oxidation. Concentration/distance profiles were measured in the coating and substrate after various oxidation exposures at 1150 C. For each stubstrate, the Al content in the coating decreased rapidly. The concentration/distance profiles, and particularly that for Al, reflected the oxide spalling resistance of each coated substrate. A numerical model was developed to simulate diffusion associated with overlay-coating degradation by oxidation and coating/substrate interdiffusion. Input to the numerical model consisted of the Cr and Al content of the coating and substrate, ternary diffusivities, and various oxide spalling parameters. The model predicts the Cr and Al concentrations in the coating and substrate after any number of oxidation/thermal cycles. The numerical model also predicts coating failure based on the ability of the coating to supply sufficient Al to the oxide scale. The validity of the model was confirmed by comparison of the predicted and measured concentration/distance profiles. The model was subsequently used to identify the most critical system parameters affecting coating life.

Advances in low-defect multilayers for EUVL mask blanks

NASA Astrophysics Data System (ADS)

Folta, James A.; Davidson, J. Courtney; Larson, Cindy C.; Walton, Christopher C.; Kearney, Patrick A.

2002-07-01

Low-defect multilayer coatings are required to fabricate mask blanks for Extreme Ultraviolet Lithography (EUVL). The mask blanks consist of high reflectance EUV multilayers on low thermal expansion substrates. A defect density of 0.0025 printable defects/cm2 for both the mask substrate and the multilayer is required to provide a mask blank yield of 60 percent. Current low defect multilayer coating technology allows repeated coating-added defect levels of 0.05/cm2 for defects greater than 90 nm polystyrene latex sphere (PSL) equivalent size for lots of 20 substrates. Extended clean operation of the coating system at levels below 0.08/cm2 for 3 months of operation has also been achieved. Two substrates with zero added defects in the quality area have been fabricated, providing an existence proof that ultra low defect coatings are possible. Increasing the ion source-to-target distance from 410 to 560 mm to reduce undesired coating of the ion source caused the defect density to increase to 0.2/cm2. Deposition and etching diagnostic witness substrates and deposition pinhole cameras showed a much higher level of ion beam spillover (ions missing the sputter target) than expected. Future work will quantify beam spillover, and test designs to reduce spillover, if it is confirmed to be the cause of the increased defect level. The LDD system will also be upgraded to allow clean coating of standard format mask substrates. The upgrade will confirm that the low defect process developed on Si wafers is compatible with the standard mask format 152 mm square substrates, and will provide a clean supply of EUVL mask blanks needed to support development of EUVL mask patterning processes and clean mask handling technologies.

Three-dimensional architecture for solid state radiation detectors

DOEpatents

Parker, S.

1999-03-30

A radiation-damage resistant radiation detector is formed on a substrate formed of a material doped with a first conductivity type dopant. The detector includes at least one first electrode formed of first conductivity type dopant, and at least one second electrode that is spaced-apart from the first electrode and formed of a second conductivity type dopant. Each first and second electrode penetrates into the substrate from a substrate surface, and one or more electrodes may penetrate entirely through the substrate, that is traversing from one surface to the other surface. Particulate and/or electromagnetic radiation penetrating at least a surface of the substrate releases electrons and holes in substrate regions. Because the electrodes may be formed entirely through the substrate thickness, the released charges will be a relatively small distance from at least a portion of such an electrode, e.g., a distance less than the substrate thickness. The electrons and/or holes traverse the small distance and are collected by said electrodes, thus promoting rapid detection of the radiation. By providing one or more electrodes with a dopant profile radially graded in a direction parallel to a substrate surface, an electric field results that promotes rapid collection of released electrons and said holes. Monolithic combinations of such detectors may be fabricated including CMOS electronics to process radiation signals. 45 figs.

Three-dimensional architecture for solid state radiation detectors

DOEpatents

Parker, Sherwood

1999-01-01

A radiation-damage resistant radiation detector is formed on a substrate formed of a material doped with a first conductivity type dopant. The detector includes at least one first electrode formed of first conductivity type dopant, and at least one second electrode that is spaced-apart from the first electrode and formed of a second conductivity type dopant. Each first and second electrode penetrates into the substrate from a substrate surface, and one or more electrodes may penetrate entirely through the substrate, that is traversing from one surface to the other surface. Particulate and/or electromagnetic radiation penetrating at least a surface of the substrate releases electrons and holes in substrate regions. Because the electrodes may be formed entirely through the substrate thickness, the released charges will be a relatively small distance from at least a portion of such an electrode, e.g., a distance less than the substrate thickness. The electrons and/or holes traverse the small distance and are collected by said electrodes, thus promoting rapid detection of the radiation. By providing one or more electrodes with a dopant profile radially graded in a direction parallel to a substrate surface, an electric field results that promotes rapid collection of released electrons and said holes. Monolithic combinations of such detectors may be fabricated including CMOS electronics to process radiation signals.

Ultrahigh-yield growth of GaN via halogen-free vapor-phase epitaxy

NASA Astrophysics Data System (ADS)

Nakamura, Daisuke; Kimura, Taishi

2018-06-01

The material yield of Ga during GaN growth via halogen-free vapor-phase epitaxy (HF-VPE) was systematically investigated and found to be much higher than that obtained using conventional hydride VPE. This is attributed to the much lower process pressure and shorter seed-to-source distance, owing to the inherent chemical reactions and corresponding reactor design used for HF-VPE growth. Ultrahigh-yield GaN growth was demonstrated on a 4-in.-diameter sapphire seed substrate.

Energy shift and Casimir-Polder force for an atom out of thermal equilibrium near a dielectric substrate

NASA Astrophysics Data System (ADS)

Zhou, Wenting; Yu, Hongwei

2014-09-01

We study the energy shift and the Casimir-Polder force of an atom out of thermal equilibrium near the surface of a dielectric substrate. We first generalize, adopting the local source hypothesis, the formalism proposed by Dalibard, Dupont-Roc, and Cohen-Tannoudji [J. Phys. (Paris) 43, 1617 (1982), 10.1051/jphys:0198200430110161700; J. Phys. (Paris) 45, 637 (1984), 10.1051/jphys:01984004504063700], which separates the contributions of thermal fluctuations and radiation reaction to the energy shift and allows a distinct treatment of atoms in the ground and excited states, to the case out of thermal equilibrium, and then we use the generalized formalism to calculate the energy shift and the Casimir-Polder force of an isotropically polarizable neutral atom. We identify the effects of the thermal fluctuations that originate from the substrate and the environment and discuss in detail how the Casimir-Polder force out of thermal equilibrium behaves in three different distance regions in both the low-temperature limit and the high-temperature limit for both the ground-state and excited-state atoms, with special attention devoted to the distinctive features as opposed to thermal equilibrium. In particular, we recover the distinctive behavior of the atom-wall force out of thermal equilibrium at large distances in the low-temperature limit recently found in a different theoretical framework, and furthermore we give a concrete region where this behavior holds.

Effect of Spray Distance on Microstructure and Tribological Performance of Suspension Plasma-Sprayed Hydroxyapatite-Titania Composite Coatings

NASA Astrophysics Data System (ADS)

Zhang, Chao; Xu, Haifeng; Geng, Xin; Wang, Jingjing; Xiao, Jinkun; Zhu, Peizhi

2016-10-01

Hydroxyapatite (HA)-titania (TiO2) composite coatings prepared on Ti6Al4V alloy surface can combine the excellent mechanical property of the alloy substrate and the good biocompatibility of the coating material. In this paper, HA-TiO2 composite coatings were deposited on Ti6Al4V substrates using suspension plasma spray (SPS). X-ray diffraction, scanning electron microscopy, Fourier infrared absorption spectrometry and friction tests were used to analyze the microstructure and tribological properties of the obtained coatings. The results showed that the spray distance had an important influence on coating microstructure and tribological performance. The amount of decomposition phases decreased as the spray distance increased. The increase in spray distance from 80 to 110 mm improved the crystalline HA content and decreased the wear performance of the SPS coatings. In addition, the spray distance had a big effect on the coating morphology due to different substrate temperature resulting from different spray distance. Furthermore, a significant presence of OH- and CO3 2- was observed, which was favorable for the biomedical applications.

Optimization of vertical and lateral distances between target and substrate in deposition process of CuGaSe 2 thin films using one-step sputtering

DOE PAGES

Park, Jae -Cheol; Al-Jassim, Mowafak; Kim, Tae -Won

2017-02-01

Here, copper gallium selenide (CGS) thin films were fabricated using a combinatorial one-step sputtering process without an additional selenization process. The sample libraries as a function of vertical and lateral distance from the sputtering target were synthesized on a single soda-lime glass substrate at the substrate temperature of 500 °C employing a stoichiometric CGS single target. As we increased the vertical distance between the target and substrate, the CGS thin films had more stable and uniform characteristics in structural and chemical properties. Under the optimized conditions of the vertical distance (150 mm), the CGS thin films showed densely packed grainsmore » and large grain sizes up to 1 μm in scale with decreasing lateral distances. The composition ratio of Ga/[Cu+Ga] and Se/[Cu+Ga] showed 0.50 and 0.93, respectively, in nearly the same composition as the sputtering target. X-ray diffraction and Raman spectroscopy revealed that the CGS thin films had a pure chalcopyrite phase without any secondary phases such as Cu–Se or ordered vacancy compounds, respectively. In addition, we found that the optical bandgap energies of the CGS thin films are shifted from 1.650 to 1.664 eV with decreasing lateral distance, showing a near-stoichiometric region with chalcopyrite characteristics.« less

Determining the virtual surface in the thermal evaporation process of magnesium fluoride from a tungsten boat for different deposition rates, to be used in precision optical components

NASA Astrophysics Data System (ADS)

Tejada Esteves, A.; Gálvez de la Puente, G.

2013-11-01

Vacuum thermal evaporation has, for some time now, been the principal method for the deposition of thin films, given, among other aspects, its simplicity, flexibility, and relatively low cost. Therefore, the development of models attempting to predict the deposition patterns of given thin film materials in different locations of a vacuum evaporation chamber are arguably important. With this in mind, we have designed one of such models for the thermal evaporation process of magnesium fluoride (MgF2), a common material used in optical thin films, originating from a tungsten boat source. For this we took several deposition samples in glass slide substrates at different locations in the vacuum chamber, considering as independent variables the mean deposition rate, and the axial and vertical distances of the source to the substrate. After a careful analysis by matrix method from the spectral transmittance data of the samples, while providing as output data the spectral transmittance, as well as the physical thickness of the films, both as functions of the aforementioned variables, the virtual surface of the source was determined.

Single Neurons in the Avian Auditory Cortex Encode Individual Identity and Propagation Distance in Naturally Degraded Communication Calls.

PubMed

Mouterde, Solveig C; Elie, Julie E; Mathevon, Nicolas; Theunissen, Frédéric E

2017-03-29

One of the most complex tasks performed by sensory systems is "scene analysis": the interpretation of complex signals as behaviorally relevant objects. The study of this problem, universal to species and sensory modalities, is particularly challenging in audition, where sounds from various sources and localizations, degraded by propagation through the environment, sum to form a single acoustical signal. Here we investigated in a songbird model, the zebra finch, the neural substrate for ranging and identifying a single source. We relied on ecologically and behaviorally relevant stimuli, contact calls, to investigate the neural discrimination of individual vocal signature as well as sound source distance when calls have been degraded through propagation in a natural environment. Performing electrophysiological recordings in anesthetized birds, we found neurons in the auditory forebrain that discriminate individual vocal signatures despite long-range degradation, as well as neurons discriminating propagation distance, with varying degrees of multiplexing between both information types. Moreover, the neural discrimination performance of individual identity was not affected by propagation-induced degradation beyond what was induced by the decreased intensity. For the first time, neurons with distance-invariant identity discrimination properties as well as distance-discriminant neurons are revealed in the avian auditory cortex. Because these neurons were recorded in animals that had prior experience neither with the vocalizers of the stimuli nor with long-range propagation of calls, we suggest that this neural population is part of a general-purpose system for vocalizer discrimination and ranging. SIGNIFICANCE STATEMENT Understanding how the brain makes sense of the multitude of stimuli that it continually receives in natural conditions is a challenge for scientists. Here we provide a new understanding of how the auditory system extracts behaviorally relevant information, the vocalizer identity and its distance to the listener, from acoustic signals that have been degraded by long-range propagation in natural conditions. We show, for the first time, that single neurons, in the auditory cortex of zebra finches, are capable of discriminating the individual identity and sound source distance in conspecific communication calls. The discrimination of identity in propagated calls relies on a neural coding that is robust to intensity changes, signals' quality, and decreases in the signal-to-noise ratio. Copyright © 2017 Mouterde et al.

Modeling degradation and failure of Ni-Cr-Al overlay coatings

NASA Technical Reports Server (NTRS)

Nesbitt, J. A.; Heckel, R. W.

1984-01-01

Degradation of a Ni-16Cr-25Al-0.06Zr overlay coating on a Ni-22Cr substrate was examined after oxidation accompanied by thermal cycling. Concentration/distance profiles were measured in the coating and substrate after various one-hour cycles at 1150 C. A numerical model was developed to simulate coating degradation by simultaneous oxidation and coating/substrate interdiffusion. The validity of the model was confirmed by comparison of predicted and measured concentration/distance profiles. The ability of the model to identify critical system parameters was demonstrated for the case of the initial Al and Cr content of the coating and substrate.

Modeling of enhanced catalysis in multienzyme nanostructures: effect of molecular scaffolds, spatial organization, and concentration.

PubMed

Roberts, Christopher C; Chang, Chia-en A

2015-01-13

Colocalized multistep enzymatic reaction pathways within biological catabolic and metabolic processes occur with high yield and specificity. Spatial organization on membranes or surfaces may be associated with increased efficiency of intermediate substrate transfer. Using a new Brownian dynamics package, GeomBD, we explored the geometric features of a surface-anchored enzyme system by parallel coarse-grained Brownian dynamics simulations of substrate diffusion over microsecond (μs) to millisecond (ms) time scales. We focused on a recently developed glucose oxidase (GOx), horseradish peroxidase (HRP), and DNA origami-scaffold enzyme system, where the H2O2 substrate of HRP is produced by GOx. The results revealed and explained a significant advantage in catalytic enhancement by optimizing interenzyme distance and orientation in the presence of the scaffold model. The planar scaffold colocalized the enzymes and provided a diffusive barrier that enhanced substrate transfer probability, becoming more relevant with increasing interenzyme distance. The results highlight the importance of protein geometry in the proper assessment of distance and orientation dependence on the probability of substrate transfer. They shed light on strategies for engineering multienzyme complexes and further investigation of enhanced catalytic efficiency for substrate diffusion between membrane-anchoring proteins.

Critical Casimir effect for colloids close to chemically patterned substrates.

PubMed

Tröndle, M; Kondrat, S; Gambassi, A; Harnau, L; Dietrich, S

2010-08-21

Colloids immersed in a critical or near-critical binary liquid mixture and close to a chemically patterned substrate are subject to normal and lateral critical Casimir forces of dominating strength. For a single colloid, we calculate these attractive or repulsive forces and the corresponding critical Casimir potentials within mean-field theory. Within this approach we also discuss the quality of the Derjaguin approximation and apply it to Monte Carlo simulation data available for the system under study. We find that the range of validity of the Derjaguin approximation is rather large and that it fails only for surface structures which are very small compared to the geometric mean of the size of the colloid and its distance from the substrate. For certain chemical structures of the substrate, the critical Casimir force acting on the colloid can change sign as a function of the distance between the particle and the substrate; this provides a mechanism for stable levitation at a certain distance which can be strongly tuned by temperature, i.e., with a sensitivity of more than 200 nm/K.

Preparation and Characterization of RF Sputtered BARIUM(2) SILICON(2) Titanium OXYGEN(8) Thin Films

NASA Astrophysics Data System (ADS)

Li, Yi.

Thin films of barium titanium silicate ( Ba_2Si_2TiO_8) are grown on crystalline (100) Si at substrate temperatures raging from 750 to 955^circC by the radio-frequency triode sputtering technique. The chemical composition, microstructure, physical properties, and growth conditions of the deposited films are investigated by dc and high-frequency dielectric measurements, wavelength dispersive and energy dispersive x-ray spectrometries, x-ray diffraction spectrometry, and optical and scanning electron microscopies. The results of the x-ray diffraction analysis show that the Ba_2Si_2TiO _8 films deposited at the optimum condition of substrate temperature of 845^circ C, 4 cm source-substance distance, 50 W rf power, and 1.2 times 10^ {-3} torr pressure of Ar, are highly c -axis oriented. The as-deposited films are smooth, glossy, polycrystalline films, exhibiting a bulk resistivity range of 10^6 Omegacdotcm, and an isotropic surface resistivity of 1.5 times 10^3 Omegacdot cm. The relative dielectric constant is 0.05, and the dielectric loss is lower than 1.0, in the frequency band 9 ~ 1000 MHz. The high-frequency impedance of BST films, which is typical for piezoelectric materials, gives a minimum impedance frequency of 9.0 MHz and a series resonant frequency of 9.5 MHz. Optical and SEM observations show that the film texture is dependent on the substrate conditions. The non-liquid-like grain coalescence of the Ba_2Si_2TiO _8 grains is characteristic of a strong film -substrate interaction. The grain growth kinetics obtained from "short-time" sputtering gives an initial lateral grain growth rate of 770 nm/min at 845^circ C, which decreases with the grain size. The initial film growth rate in the direction of thickness, measured from SEM micrographs, is 1.95 nm/min, and decreases with sputtering time. The activation free energy for grain growth is 359 +/- 30 KJ/mol for the initial stage, decreasing to 148 +/- 20 KJ/mol for the final stage. The variation of the grain growth rate and the activation energy with grain size is the result of a combined nucleation and growth mechanism in the initial stage of the film growth, and a coalescence -dominated growth mechanism at longer sputtering time and at higher temperature. Film orientation is sensitive to the supersaturation adjacent to the film surface, which depends on the source-substrate distance and substrate temperature. The effect of the substrate temperature on the orientation of the film is investigated over a wide temperature range using (100) and (111) Si substrates. Several orientations for the BST films, including an amorphous state, are obtained with increasing substrate temperature. This is discussed in relation to the atomic plane density and the energetics for the deposition process.

Optimization of process parameters for RF sputter deposition of tin-nitride thin-films

NASA Astrophysics Data System (ADS)

Jangid, Teena; Rao, G. Mohan

2018-05-01

Radio frequency Magnetron sputtering technique was employed to deposit Tin-nitride thin films on Si and glass substrate at different process parameters. Influence of varying parameters like substrate temperature, target-substrate distance and RF power is studied in detail. X-ray diffraction method is used as a key technique for analyzing the changes in the stoichiometric and structural properties of the deposited films. Depending on the combination of deposition parameters, crystalline as well as amorphous films were obtained. Pure tin-nitride thin films were deposited at 15W RF power and 600°C substrate temperature with target-substrate distance fixed at 10cm. Bandgap value of 1.6 eV calculated for the film deposited at optimum process conditions matches well with reported values.

Pathogen alarm behavior in a termite: A new form of communication in social insects

PubMed

Rosengaus; Jordan; Lefebvre; Traniello

1999-11-01

Dampwood termites, Zootermopsis angusticollis, show an alarm response after detecting the presence of spores of the pathogenic fungus Metarhizium anisopliae. Termites in direct contact with a high concentration of spores (10(7) spores/ml) show a striking vibratory display which appears to convey information about the presence of pathogens to nearby unexposed nestmates through substrate vibration. Nestmates not directly in contact with spores that perceive the vibrational signal increase significantly their distance from the spore-exposed vibrating termites, apparently to escape from the source of infection. The fleeing response is not induced by the presence of the spores alone or by pheromones, and requires the perception of the vibrations propagated through the substrate. This "pathogen alarm behavior" appears to be a previously unrecognized communication mechanism that allows termites to reduce disease risks within the nest.

Pathogen Alarm Behavior in a Termite: A New Form of Communication in Social Insects

NASA Astrophysics Data System (ADS)

Rosengaus, R. B.; Jordan, C.; Lefebvre, M. L.; Traniello, J. F. A.

Dampwood termites, Zootermopsis angusticollis, show an alarm response after detecting the presence of spores of the pathogenic fungus Metarhizium anisopliae. Termites in direct contact with a high concentration of spores (107 spores/ml) show a striking vibratory display which appears to convey information about the presence of pathogens to nearby unexposed nestmates through substrate vibration. Nestmates not directly in contact with spores that perceive the vibrational signal increase significantly their distance from the spore-exposed vibrating termites, apparently to escape from the source of infection. The fleeing response is not induced by the presence of the spores alone or by pheromones, and requires the perception of the vibrations propagated through the substrate. This "pathogen alarm behavior" appears to be a previously unrecognized communication mechanism that allows termites to reduce disease risks within the nest.

Role of target-substrate distance on the growth of CuInSe{sub 2} thin films by pulsed laser ablation technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rawat, Kusum; Dhruvashi; Department of Electronic Science, University of Delhi South Campus, Delhi 110021

2016-05-06

CuInSe{sub 2} thin films have been deposited on corning glass substrates by pulsed laser ablation technique. The chamber pressure and substrate temperature was maintained at 1 × 10{sup −6} torr and 550°C respectively during deposition of the films. The influence of target to substrate (T-S) distance on the structural and optical properties of thin films have been investigated by grazing incidence x-ray diffraction, Raman spectroscopy, scanning electron microscope and UV-Vis-NIR spectroscopy. The study reveals that thin films crystallized in a chalcopyrite structure with highly preferential orientation along (112) plane. Optimum T-S distance has been attained for the growth of thinmore » films with large grain size. An intense Raman peak at 174 cm{sup −1} corresponding to dominant A{sub 1} vibration mode is gradually shifted to smaller wavenumber with the increase in T-S distance. The optical bandgap energy of the films was evaluated and found to vary with the T-S distance. The bandgap tailing was observed to obey the Urbach rule and the Urbach energy was also calculated for the films. Scanning electron micrographs depicts uniform densely packed grains and EDAX studies revealed the elemental composition of CuInSe{sub 2} thin films.« less

Pulsed laser deposition of transparent conductive oxide thin films on flexible substrates

NASA Astrophysics Data System (ADS)

Socol, G.; Socol, M.; Stefan, N.; Axente, E.; Popescu-Pelin, G.; Craciun, D.; Duta, L.; Mihailescu, C. N.; Mihailescu, I. N.; Stanculescu, A.; Visan, D.; Sava, V.; Galca, A. C.; Luculescu, C. R.; Craciun, V.

2012-11-01

The influence of target-substrate distance during pulsed laser deposition of indium zinc oxide (IZO), indium tin oxide (ITO) and aluminium-doped zinc oxide (AZO) thin films grown on polyethylene terephthalate (PET) substrates was investigated. It was found that the properties of such flexible transparent conductive oxide (TCO)/PET electrodes critically depend on this parameter. The TCO films that were deposited at distances of 6 and 8 cm exhibited an optical transmittance higher than 90% in the visible range and electrical resistivities around 5 × 10-4 Ω cm. In addition to these excellent electrical and optical characteristics the films grown at 8 cm distance were homogenous, smooth, adherent, and without cracks or any other extended defects, being suitable for opto-electronic device applications.

Computational Investigation of the Interplay of Substrate Positioning and Reactivity in Catechol O-Methyltransferase

PubMed Central

Patra, Niladri; Ioannidis, Efthymios I.

2016-01-01

Catechol O-methyltransferase (COMT) is a SAM- and Mg2+-dependent methyltransferase that regulates neurotransmitters through methylation. Simulations and experiments have identified divergent catecholamine substrate orientations in the COMT active site: molecular dynamics simulations have favored a monodentate coordination of catecholate substrates to the active site Mg2+, and crystal structures instead preserve bidentate coordination along with short (2.65 Å) methyl donor-acceptor distances. We carry out longer dynamics (up to 350 ns) to quantify interconversion between bidentate and monodentate binding poses. We provide a systematic determination of the relative free energy of the monodentate and bidentate structures in order to identify whether structural differences alter the nature of the methyl transfer mechanism and source of enzymatic rate enhancement. We demonstrate that the bidentate and monodentate binding modes are close in energy but separated by a 7 kcal/mol free energy barrier. Analysis of interactions in the two binding modes reveals that the driving force for monodentate catecholate orientations in classical molecular dynamics simulations is derived from stronger electrostatic stabilization afforded by alternate Mg2+ coordination with strongly charged active site carboxylates. Mixed semi-empirical-classical (SQM/MM) substrate C-O distances (2.7 Å) for the bidentate case are in excellent agreement with COMT X-ray crystal structures, as long as charge transfer between the substrates, Mg2+, and surrounding ligands is permitted. SQM/MM free energy barriers for methyl transfer from bidentate and monodentate catecholate configurations are comparable at around 21–22 kcal/mol, in good agreement with experiment (18–19 kcal/mol). Overall, the work suggests that both binding poses are viable for methyl transfer, and accurate descriptions of charge transfer and electrostatics are needed to provide balanced relative barriers when multiple binding poses are accessible, for example in other transferases. PMID:27564542

Graphene-on-paper sound source devices.

PubMed

Tian, He; Ren, Tian-Ling; Xie, Dan; Wang, Yu-Feng; Zhou, Chang-Jian; Feng, Ting-Ting; Fu, Di; Yang, Yi; Peng, Ping-Gang; Wang, Li-Gang; Liu, Li-Tian

2011-06-28

We demonstrate an interesting phenomenon that graphene can emit sound. The application of graphene can be expanded in the acoustic field. Graphene-on-paper sound source devices are made by patterning graphene on paper substrates. Three graphene sheet samples with the thickness of 100, 60, and 20 nm were fabricated. Sound emission from graphene is measured as a function of power, distance, angle, and frequency in the far-field. The theoretical model of air/graphene/paper/PCB board multilayer structure is established to analyze the sound directivity, frequency response, and efficiency. Measured sound pressure level (SPL) and efficiency are in good agreement with theoretical results. It is found that graphene has a significant flat frequency response in the wide ultrasound range 20-50 kHz. In addition, the thinner graphene sheets can produce higher SPL due to its lower heat capacity per unit area (HCPUA). The infrared thermal images reveal that a thermoacoustic effect is the working principle. We find that the sound performance mainly depends on the HCPUA of the conductor and the thermal properties of the substrate. The paper-based graphene sound source devices have highly reliable, flexible, no mechanical vibration, simple structure and high performance characteristics. It could open wide applications in multimedia, consumer electronics, biological, medical, and many other areas.

Narrowband infrared emitters for combat ID

NASA Astrophysics Data System (ADS)

Pralle, Martin U.; Puscasu, Irina; Daly, James; Fallon, Keith; Loges, Peter; Greenwald, Anton; Johnson, Edward

2007-04-01

There is a strong desire to create narrowband infrared light sources as personnel beacons for application in infrared Identify Friend or Foe (IFF) systems. This demand has augmented dramatically in recent years with the reports of friendly fire casualties in Afghanistan and Iraq. ICx Photonics' photonic crystal enhanced TM (PCE TM) infrared emitter technology affords the possibility of creating narrowband IR light sources tuned to specific IR wavebands (near 1-2 microns, mid 3-5 microns, and long 8-12 microns) making it the ideal solution for infrared IFF. This technology is based on a metal coated 2D photonic crystal of air holes in a silicon substrate. Upon thermal excitation the photonic crystal modifies the emitted yielding narrowband IR light with center wavelength commensurate with the periodicity of the lattice. We have integrated this technology with microhotplate MEMS devices to yield 15mW IR light sources in the 3-5 micron waveband with wall plug efficiencies in excess of 10%, 2 orders of magnitude more efficient that conventional IR LEDs. We have further extended this technology into the LWIR with a light source that produces 9 mW of 8-12 micron light at an efficiency of 8%. Viewing distances >500 meters were observed with fielded camera technologies, ideal for ground to ground troop identification. When grouped into an emitter panel, the viewing distances were extended to 5 miles, ideal for ground to air identification.

Basis for substrate recognition and distinction by matrix metalloproteinases

PubMed Central

Ratnikov, Boris I.; Cieplak, Piotr; Gramatikoff, Kosi; Pierce, James; Eroshkin, Alexey; Igarashi, Yoshinobu; Kazanov, Marat; Sun, Qing; Godzik, Adam; Osterman, Andrei; Stec, Boguslaw; Strongin, Alex; Smith, Jeffrey W.

2014-01-01

Genomic sequencing and structural genomics produced a vast amount of sequence and structural data, creating an opportunity for structure–function analysis in silico [Radivojac P, et al. (2013) Nat Methods 10(3):221–227]. Unfortunately, only a few large experimental datasets exist to serve as benchmarks for function-related predictions. Furthermore, currently there are no reliable means to predict the extent of functional similarity among proteins. Here, we quantify structure–function relationships among three phylogenetic branches of the matrix metalloproteinase (MMP) family by comparing their cleavage efficiencies toward an extended set of phage peptide substrates that were selected from ∼64 million peptide sequences (i.e., a large unbiased representation of substrate space). The observed second-order rate constants [k(obs)] across the substrate space provide a distance measure of functional similarity among the MMPs. These functional distances directly correlate with MMP phylogenetic distance. There is also a remarkable and near-perfect correlation between the MMP substrate preference and sequence identity of 50–57 discontinuous residues surrounding the catalytic groove. We conclude that these residues represent the specificity-determining positions (SDPs) that allowed for the expansion of MMP proteolytic function during evolution. A transmutation of only a few selected SDPs proximal to the bound substrate peptide, and contributing the most to selectivity among the MMPs, is sufficient to enact a global change in the substrate preference of one MMP to that of another, indicating the potential for the rational and focused redesign of cleavage specificity in MMPs. PMID:25246591

Controllable synthesis and optical properties of novel ZnO cone arrays via vapor transport at low temperature.

PubMed

Han, Xinhai; Wang, Guanzhong; Jie, Jiansheng; Choy, Wallace C H; Luo, Yi; Yuk, T I; Hou, J G

2005-02-24

Novel ZnO cone arrays with controllable morphologies have been synthesized on silicon (100) substrates by thermal evaporation of metal Zn powder at a low temperature of 570 degrees C without a metal catalyst. Clear structure evolutions were observed using scanning electron microscopy: well-aligned ZnO nanocones, double-cones with growing head cones attached by stem cones, and cones with straight hexagonal pillar were obtained as the distance between the source and the substrates was increased. X-ray diffraction shows that all cone arrays grow along the c-axis. Raman and photoluminescence spectra reveal that the optical properties of the buffer layer between the ZnO cone arrays and the silicon substrates are better than those of the ZnO cone arrays due to high concentration of Zn in the heads of the ZnO cone arrays and higher growth temperature of the buffer layer. The growth of ZnO arrays reveals that the cone arrays are synthesized through a self-catalyzed vapor-liquid-solid (VLS) process.

Permeability and Microstructure of Suspension Plasma-Sprayed YSZ Electrolytes for SOFCs on Various Substrates

NASA Astrophysics Data System (ADS)

Marr, Michael; Kesler, Olivera

2012-12-01

Yttria-stabilized zirconia electrolyte coatings for solid oxide fuel cells were deposited by suspension plasma spraying using a range of spray conditions and a variety of substrates, including finely structured porous stainless steel disks and cathode layers on stainless steel supports. Electrolyte permeability values and trends were found to be highly dependent on which substrate was used. The most gas-tight electrolyte coatings were those deposited directly on the porous metal disks. With this substrate, permeability was reduced by increasing the torch power and reducing the stand-off distance to produce dense coating microstructures. On the substrates with cathodes, electrolyte permeability was reduced by increasing the stand-off distance, which reduced the formation of segmentation cracks and regions of aligned and concentrated porosity. The formation mechanisms of the various permeability-related coating features are discussed and strategies for reducing permeability are presented. The dependences of electrolyte deposition efficiency and surface roughness on process conditions and substrate properties are also presented.

FT-IR standoff detection of thermally excited emissions of trinitrotoluene (TNT) deposited on aluminum substrates.

PubMed

Castro-Suarez, John R; Pacheco-Londoño, Leonardo C; Vélez-Reyes, Miguel; Diem, Max; Tague, Thomas J; Hernandez-Rivera, Samuel P

2013-02-01

A standoff detection system was assembled by coupling a reflecting telescope to a Fourier transform infrared spectrometer equipped with a cryo-cooled mercury cadmium telluride detector and used for detection of solid-phase samples deposited on substrates. Samples of highly energetic materials were deposited on aluminum substrates and detected at several collector-target distances by performing passive-mode, remote, infrared detection measurements on the heated analytes. Aluminum plates were used as support material, and 2,4,6-Trinitrotoluene (TNT) was used as the target. For standoff detection experiments, the samples were placed at different distances (4 to 55 m). Several target surface temperatures were investigated. Partial least squares regression analysis was applied to the analysis of the intensities of the spectra obtained. Overall, standoff detection in passive mode was useful for quantifying TNT deposited on the aluminum plates with high confidence up to target-collector distances of 55 m.

Turbine bucket for use in gas turbine engines and methods for fabricating the same

DOEpatents

Garcia-Crespo, Andres

2014-06-03

A turbine bucket for use with a turbine engine. The turbine bucket includes an airfoil that extends between a root end and a tip end. The airfoil includes an outer wall that defines a cavity that extends from the root end to the tip end. The outer wall includes a first ceramic matrix composite (CMC) substrate that extends a first distance from the root end to the tip end. An inner wall is positioned within the cavity. The inner wall includes a second CMC substrate that extends a second distance from the root end towards the tip end that is different than the first distance.

Photoluminescence enhancement of silicon quantum dot monolayer by plasmonic substrate fabricated by nano-imprint lithography

NASA Astrophysics Data System (ADS)

Yanagawa, Hiroto; Inoue, Asuka; Sugimoto, Hiroshi; Shioi, Masahiko; Fujii, Minoru

2017-12-01

Near-field coupling between a silicon quantum dot (Si-QD) monolayer and a plasmonic substrate fabricated by nano-imprint lithography and having broad multiple resonances in the near-infrared (NIR) window of biological substances was studied by precisely controlling the QDs-substrate distance. A strong enhancement of the NIR photoluminescence (PL) of Si-QDs was observed. Detailed analyses of the PL and PL excitation spectra, the PL decay dynamics, and the reflectance spectra revealed that both the excitation cross-sections and the emission rates are enhanced by the surface plasmon resonances, thanks to the broad multiple resonances of the plasmonic substrate, and that the relative contribution of the two enhancement processes depends strongly on the excitation wavelength. Under excitation by short wavelength photons (405 nm), where enhancement of the excitation cross-section is not expected, the maximum enhancement was obtained when the QDs-substrate distance was around 30 nm. On the other hand, under long wavelength excitation (641 nm), where strong excitation cross-section enhancement is expected, the largest enhancement was obtained when the distance was minimum (around 1 nm). The achievement of efficient excitation of NIR luminescence of Si-QDs by long wavelength photons paves the way for the development of Si-QD-based fluorescence bio-sensing devices with a high bound-to-free ratio.

Quasi-steady-state voltammetry of rapid electron transfer reactions at the macroscopic substrate of the scanning electrochemical microscope.

PubMed

Nioradze, Nikoloz; Kim, Jiyeon; Amemiya, Shigeru

2011-02-01

We report on a novel theory and experiment for scanning electrochemical microscopy (SECM) to enable quasi-steady-state voltammetry of rapid electron transfer (ET) reactions at macroscopic substrates. With this powerful approach, the substrate potential is cycled widely across the formal potential of a redox couple while the reactant or product of a substrate reaction is amperometrically detected at the tip in the feedback or substrate generation/tip collection mode, respectively. The plot of tip current versus substrate potential features the retraceable sigmoidal shape of a quasi-steady-state voltammogram although a transient voltammogram is obtained at the macroscopic substrate. Finite element simulations reveal that a short tip-substrate distance and a reversible substrate reaction (except under the tip) are required for quasi-steady-state voltammetry. Advantageously, a pair of quasi-steady-state voltammograms is obtained by employing both operation modes to reliably determine all transport, thermodynamic, and kinetic parameters as confirmed experimentally for rapid ET reactions of ferrocenemethanol and 7,7,8,8-tetracyanoquinodimethane at a Pt substrate with ∼0.5 μm-radius Pt tips positioned at 90 nm-1 μm distances. Standard ET rate constants of ∼7 cm/s were obtained for the latter mediator as the largest determined for a substrate reaction by SECM. Various potential applications of quasi-steady-state voltammetry are also proposed.

Vacuum vapor deposition

NASA Technical Reports Server (NTRS)

Poorman, Richard M. (Inventor); Weeks, Jack L. (Inventor)

1995-01-01

A method and apparatus is described for vapor deposition of a thin metallic film utilizing an ionized gas arc directed onto a source material spaced from a substrate to be coated in a substantial vacuum while providing a pressure differential between the source and the substrate so that, as a portion of the source is vaporized, the vapors are carried to the substrate. The apparatus includes a modified tungsten arc welding torch having a hollow electrode through which a gas, preferably inert, flows and an arc is struck between the electrode and the source. The torch, source, and substrate are confined within a chamber within which a vacuum is drawn. When the arc is struck, a portion of the source is vaporized and the vapors flow rapidly toward the substrate. A reflecting shield is positioned about the torch above the electrode and the source to ensure that the arc is struck between the electrode and the source at startup. The electrode and the source may be confined within a vapor guide housing having a duct opening toward the substrate for directing the vapors onto the substrate.

Vapor bridges between solid substrates in the presence of the contact line pinning effect: Stability and capillary force

NASA Astrophysics Data System (ADS)

Liu, Yawei; Zhang, Xianren

2016-12-01

In this work, we focus on investigating how nanobubbles mediate long-range interaction between neighboring solid substrates in the presence of the contact line pinning effect caused by surface heterogeneities. Using the constrained lattice density functional theory (LDFT), we prove that the nanobubbles, which take the form of vapor bridges here, are stabilized by the pinning effect if the separation between two substrates is less than a critical distance. The critical distance strongly depends on the chemical potential (i.e., the degree of saturation) and could become extremely long at a special chemical potential. Moreover, under the pinning effect, the substrate chemistry only determines the stability of the vapor bridges and the range of the capillary force, but has less influences on the magnitude of the capillary force, indicating that the substrate chemistry or the apparent contact angle for droplets or bubbles on the substrates is no longer a direct parameter to determine the magnitude of capillary force. A qualitative analysis for the two dimensional vapor bridges by considering the feedback mechanism can explain the results from the LDFT calculations.

In-situ spectrophotometric probe

DOEpatents

Prather, William S.

1992-01-01

A spectrophotometric probe for in situ absorption spectra measurements comprising a first optical fiber carrying light from a remote light source, a second optical fiber carrying light to a remote spectrophotometer, the proximal ends of the first and second optical fibers parallel and coterminal, a planoconvex lens to collimate light from the first optical fiber, a reflecting grid positioned a short distance from the lens to reflect the collimated light back to the lens for focussing on the second optical fiber. The lens is positioned with the convex side toward the optical fibers. A substrate for absorbing analyte or an analyte and reagent mixture may be positioned between the lens and the reflecting grid.

Transport properties of bilayer graphene due to charged impurity scattering: Temperature-dependent screening and substrate effects

NASA Astrophysics Data System (ADS)

Linh, Dang Khanh; Khanh, Nguyen Quoc

2018-03-01

We calculate the zero-temperature conductivity of bilayer graphene (BLG) impacted by Coulomb impurity scattering using four different screening models: unscreened, Thomas-Fermi (TF), overscreened and random phase approximation (RPA). We also calculate the conductivity and thermal conductance of BLG using TF, zero- and finite-temperature RPA screening functions. We find large differences between the results of the models and show that TF and finite-temperature RPA give similar results for diffusion thermopower Sd. Using the finite-temperature RPA, we calculate temperature and density dependence of Sd in BLG on SiO2, HfO2 substrates and suspended BLG for different values of interlayer distance c and distance between the first layer and the substrate d.

Probe-Substrate Distance Control in Desorption Electrospray Ionization

NASA Astrophysics Data System (ADS)

Yarger, Tyler J.; Yuill, Elizabeth M.; Baker, Lane A.

2018-03-01

We introduce probe-substrate distance (Dps)-control to desorption electrospray ionization (DESI) and report a systematic investigation of key experimental parameters. Examination of voltage, flow rate, and nebulizing gas pressure suggests as Dps decreases, the distance-dependent spray current increases, until a critical point. At the critical point the relationship inverts, and the spray current decreases as the probe moves closer to the surface due to constriction of solution flow by the nebulizing gas. Dps control was used to explore the use of spray current as a signal for feedback positioning, while mass spectrometry imaging was performed simultaneously. Further development of this technique is expected to find application in study of structure-function relationships for clinical diagnostics, biological investigation, and materials characterization. [Figure not available: see fulltext.

Terahertz radiation in graphene hyperbolic medium excited by an electric dipole.

PubMed

Feng, Xiaodong; Gong, Sen; Zhong, Renbin; Zhao, Tao; Hu, Min; Zhang, Chao; Liu, Shenggang

2018-03-01

In this Letter, the enhanced and directional radiation in a wide terahertz (THz) frequency range in a graphene hyperbolic medium excited by an electric dipole is presented. The numerical simulations and theoretical analyses indicate that the enhanced radiation comes from the strong surface plasmon couplings in the graphene hyperbolic medium, consisting of alternative graphene and dielectric substrate layers. The simulation results also show that the peak power flow of the enhanced THz radiation in the graphene hyperbolic medium is dramatically enhanced by more than 1 order of magnitude over that in a general medium within a certain distance from the dipole, and the electromagnetic fields are strongly concentrated in a narrow angle. Also, the radiation fields can be manipulated, and the fields' angular distributions can be tuned by adjusting the dielectric permittivity and thickness of the substrates, and the chemical potential of graphene. Accordingly, it provides a good opportunity for developing miniature, integratable, high-power-density, and tunable radiation sources in the THz band at room temperature.

Substrate comprising a nanometer-scale projection array

DOEpatents

Cui, Yi; Zhu, Jia; Hsu, Ching-Mei; Connor, Stephen T; Yu, Zongfu; Fan, Shanhui; Burkhard, George

2012-11-27

A method for forming a substrate comprising nanometer-scale pillars or cones that project from the surface of the substrate is disclosed. The method enables control over physical characteristics of the projections including diameter, sidewall angle, and tip shape. The method further enables control over the arrangement of the projections including characteristics such as center-to-center spacing and separation distance.

Effect of Warm-Up on Plasma Free Fatty Acid Response and Substrate Utilization During Submaximal Exercise.

ERIC Educational Resources Information Center

Hetzler, Ronald K.; And Others

1986-01-01

This study examined the effect of preliminary walking on free fatty acid responses and substrate utilization during a 40-minute treadmill run by experienced male distance runners. Conclusions are presented. (Author/MT)

Process optimization of ultrasonic spray coating of polymer films.

PubMed

Bose, Sanjukta; Keller, Stephan S; Alstrøm, Tommy S; Boisen, Anja; Almdal, Kristoffer

2013-06-11

In this work we have performed a detailed study of the influence of various parameters on spray coating of polymer films. Our aim is to produce polymer films of uniform thickness (500 nm to 1 μm) and low roughness compared to the film thickness. The coatings are characterized with respect to thickness, roughness (profilometer), and morphology (optical microscopy). Polyvinylpyrrolidone (PVP) is used to do a full factorial design of experiments with selected process parameters such as temperature, distance between spray nozzle and substrate, and speed of the spray nozzle. A mathematical model is developed for statistical analysis which identifies the distance between nozzle and substrate as the most significant parameter. Depending on the drying of the sprayed droplets on the substrate, we define two broad regimes, "dry" and "wet". The optimum condition of spraying lies in a narrow window between these two regimes, where we obtain a film of desired quality. Both with increasing nozzle-substrate distance and temperature, the deposition moves from a wet state to a dry regime. Similar results are also achieved for solvents with low boiling points. Finally, we study film formation during spray coating with poly (D,L-lactide) (PDLLA). The results confirm the processing knowledge obtained with PVP and indicate that the observed trends are identical for spraying of other polymer films.

Physical adsorption at the nanoscale: Towards controllable scaling of the substrate-adsorbate van der Waals interaction

NASA Astrophysics Data System (ADS)

Ambrosetti, Alberto; Silvestrelli, Pier Luigi; Tkatchenko, Alexandre

2017-06-01

The Lifshitz-Zaremba-Kohn (LZK) theory is commonly considered as the correct large-distance limit for the van der Waals (vdW) interaction of adsorbates (atoms, molecules, or nanoparticles) with solid substrates. In the standard approximate form, implicitly based on local dielectric functions, the LZK approach predicts universal power laws for vdW interactions depending only on the dimensionality of the interacting objects. However, recent experimental findings are challenging the universality of this theoretical approach at finite distances of relevance for nanoscale assembly. Here, we present a combined analytical and numerical many-body study demonstrating that physical adsorption can be significantly enhanced at the nanoscale. Regardless of the band gap or the nature of the adsorbate specie, we find deviations from conventional LZK power laws that extend to separation distances of up to 10-20 nm. Comparison with recent experimental observations of ultra-long-ranged vdW interactions in the delamination of graphene from a silicon substrate reveals qualitative agreement with the present theory. The sensitivity of vdW interactions to the substrate response and to the adsorbate characteristic excitation frequency also suggests that adsorption strength can be effectively tuned in experiments, paving the way to an improved control of physical adsorption at the nanoscale.

Experimental Investigation of Terminal Fans Prograding on a Salt Substrate: 3-d Physical Experiments

NASA Astrophysics Data System (ADS)

Chatmas, E.; Kim, W.

2015-12-01

Interactions between geologic features and a mobile substrate layer are present in several passive margin locations throughout the world. Deformation of a substrate layer is primarily due to differential loading of sediment and results in complexities within the morphology and subsequently the stratigraphic record. By using simplified scaled tank experiments, we investigated the relationship between substrate deformation and fan evolution in a fluvial-dump-wind-redistribution setting. In this system, sediment is being eroded from a mountain range and creating terminal fans; fluvial channels form off of the fan body and the deposited fluvial sediment is the source for an aeolian dune field. Several past experimental studies have focused on how deltas and dunes are affected on when deposited on a salt substrate, however terminal fans and channel formation off of fans have not been thoroughly investigated. The current experiments focused on which variables are the most significant in controlling fan growth, channel initiation and channel behavior on the salt substrate. Our experimental basin is 120 cm long, 60 cm wide and 30 cm tall. The materials used for a suite of five experiments involved a polymer polydimethylsiloxane (PDMS) as the deformable substrate analog and 100-μm quartz sand. By isolating certain variables such as substrate thickness, basin slope and sediment discharge we are able to see how terminal fans and channels are affected in different settings. The experimental results show that 1) increase in substrate thickness increased the amount of subsidence around the fan body, limiting sediment transport to channels off of the toe of the fan, 2) a higher basin slope increased the number of channels formed and increased sinuosity and width variations of channels over distance, and 3) a higher sediment discharge rate on a thin substrate allowed for the farthest downstream fan deposits. Preliminary results show that channel behavior and fan morphology is strongly dependent on substrate thickness and basin slope directly influences channel geometry. These findings will also be compared to the Mojave River Wash located in southern California off the San Bernardino Mountains near Zzyzx, CA to further understand the dynamics of terminal fans on a mobile substrate.

Rotatable crucible for rapid solidification process

NASA Technical Reports Server (NTRS)

Gaspar, Thomas (Inventor)

1990-01-01

This invention relates to an apparatus for producing filament, fiber, ribbon or film from a molten material, comprising a preferably heat extracting crucible which contains a pool of molten material at a selected horizontal level in the pool. The crucible has an opening extending from above the free surface level to a bottom edge of the opening, the bottom edge being sufficiently below the free surface level so that the molten material cannot form and hold a meniscus by surface tension between the edge and the level of the free surface and further comprises a heat extracting substrate laterally disposed with respect to the crucible and which rotates about an axis of rotation. The substrate is positioned adjacent the edge of the opening which confines the molten material and prevents it from overflowing downwardly out of the crucible. The invention features rotating means which includes a first drive means for tiltably rotating the crucible about an axis of rotation which is coaxial with the axis of rotation of the substrate, so the crucible edge can be maintained a predetermined constant distance from the substrate. The distance chosen is suitable for depositing molten material on the substrate and the apparatus also has a second drive means which is drivingly connected to the substrate for continuously moving the surface of the substrate upwardly past the edge and a melt front formed at the interface of the molten material and the substrate surface.

Origin and spatial distribution of metals in moss samples in Albania: A hotspot of heavy metal contamination in Europe.

PubMed

Lazo, Pranvera; Steinnes, Eiliv; Qarri, Flora; Allajbeu, Shaniko; Kane, Sonila; Stafilov, Trajce; Frontasyeva, Marina V; Harmens, Harry

2018-01-01

This study presents the spatial distribution of 37 elements in 48 moss samples collected over the whole territory of Albania and provides information on sources and factors controlling the concentrations of elements in the moss. High variations of trace metals indicate that the concentrations of elements are affected by different factors. Relations between the elements in moss, geochemical interpretation of the data, and secondary effects such as redox conditions generated from local soil and/or long distance atmospheric transport of the pollutants are discussed. Zr normalized data, and the ratios of different elements are calculated to assess the origin of elements present in the current moss samples with respect to different geogenic and anthropogenic inputs. Factor analysis (FA) is used to identify the most probable sources of the elements. Four dominant factors are identified, i.e. natural contamination; dust emission from local mining operations; atmospheric transport of contaminants from local and long distance sources; and contributions from air borne marine salts. Mineral particle dust from local emission sources is classified as the most important factor affecting the atmospheric deposition of elements accumulated in the current moss samples. The open slag dumps of mining operation in Albania is probably the main factor contributing to high contents of Cr, Ni, Fe, Ti and Al in the moss. Enrichment factors (EF) were calculated to clarify whether the elements in the present moss samples mainly originate from atmospheric deposition and/or local substrate materials. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nitrogen regulation of transpiration controls mass-flow acquisition of nutrients.

PubMed

Matimati, Ignatious; Verboom, G Anthony; Cramer, Michael D

2014-01-01

Transpiration may enhance mass-flow of nutrients to roots, especially in low-nutrient soils or where the root system is not extensively developed. Previous work suggested that nitrogen (N) may regulate mass-flow of nutrients. Experiments were conducted to determine whether N regulates water fluxes, and whether this regulation has a functional role in controlling the mass-flow of nutrients to roots. Phaseolus vulgaris were grown in troughs designed to create an N availability gradient by restricting roots from intercepting a slow-release N source, which was placed at one of six distances behind a 25 μm mesh from which nutrients could move by diffusion or mass-flow (termed 'mass-flow' treatment). Control plants had the N source supplied directly to their root zone so that N was available through interception, mass-flow, and diffusion (termed 'interception' treatment). 'Mass-flow' plants closest to the N source exhibited 2.9-fold higher transpiration (E), 2.6-fold higher stomatal conductance (gs), 1.2-fold higher intercellular [CO2] (Ci), and 3.4-fold lower water use efficiency than 'interception' plants, despite comparable values of photosynthetic rate (A). E, gs, and Ci first increased and then decreased with increasing distance from the N source to values even lower than those of 'interception' plants. 'Mass-flow' plants accumulated phosphorus and potassium, and had maximum concentrations at 10mm from the N source. Overall, N availability regulated transpiration-driven mass-flow of nutrients from substrate zones that were inaccessible to roots. Thus when water is available, mass-flow may partially substitute for root density in providing access to nutrients without incurring the costs of root extension, although the efficacy of mass-flow also depends on soil nutrient retention and hydraulic properties.

Nitrogen regulation of transpiration controls mass-flow acquisition of nutrients

PubMed Central

Matimati, Ignatious

2014-01-01

Transpiration may enhance mass-flow of nutrients to roots, especially in low-nutrient soils or where the root system is not extensively developed. Previous work suggested that nitrogen (N) may regulate mass-flow of nutrients. Experiments were conducted to determine whether N regulates water fluxes, and whether this regulation has a functional role in controlling the mass-flow of nutrients to roots. Phaseolus vulgaris were grown in troughs designed to create an N availability gradient by restricting roots from intercepting a slow-release N source, which was placed at one of six distances behind a 25 μm mesh from which nutrients could move by diffusion or mass-flow (termed ‘mass-flow’ treatment). Control plants had the N source supplied directly to their root zone so that N was available through interception, mass-flow, and diffusion (termed ‘interception’ treatment). ‘Mass-flow’ plants closest to the N source exhibited 2.9-fold higher transpiration (E), 2.6-fold higher stomatal conductance (g s), 1.2-fold higher intercellular [CO2] (C i), and 3.4-fold lower water use efficiency than ‘interception’ plants, despite comparable values of photosynthetic rate (A). E, g s, and C i first increased and then decreased with increasing distance from the N source to values even lower than those of ‘interception’ plants. ‘Mass-flow’ plants accumulated phosphorus and potassium, and had maximum concentrations at 10mm from the N source. Overall, N availability regulated transpiration-driven mass-flow of nutrients from substrate zones that were inaccessible to roots. Thus when water is available, mass-flow may partially substitute for root density in providing access to nutrients without incurring the costs of root extension, although the efficacy of mass-flow also depends on soil nutrient retention and hydraulic properties. PMID:24231035

Piezoelectric substrate effect on electron-acoustic phonon scattering in bilayer graphene

NASA Astrophysics Data System (ADS)

Ansari, Mohd Meenhaz; Ashraf, SSZ

2018-05-01

We have studied the effect of piezoelectric scattering as a function of electron temperature and distance between the sample and the substrate on electron-acoustic phonon scattering rate in Bilayer Graphene sitting on a piezoelectric substrate. We obtain approximate analytical result by neglecting the chiral nature of carriers and then proceed to obtain unapproximated numerical results for the scattering rate incorporating chirality of charge carriers. We find that on the incorporation of full numerical computation the magnitude as well as the power exponent both is affected with the power exponent changed from T3 to T3.31 in the low temperature range and to T6.98 dependence in the temperature range (>5K). We also find that the distance between the sample and substrate begins to strongly affect the scattering rate at temperatures above 10K. These calculation not only suggest the influencing effect of piezoelectric substrate on the transport properties of Dirac Fermions at very low temperatures but also open a channel to study low dimension structures by probing piezoelectric acoustical phonons.

Experimental investigation into the initiation and intensity of erosion in granular flows and its effect on flow dynamics with applications to pyroclastic density currents

NASA Astrophysics Data System (ADS)

Pollock, N. M.; Brand, B. D.; Roche, O.

2017-12-01

The macroscopic processes that control the behavior of pyroclastic density currents (PDCs) include the transportation and deposition of flow particles, entrainment of air, and interaction with topography. However, recent field studies demonstrate that substrate erosion by PDCs is also pervasive. Furthermore, analogue experiments suggest that erosion can increase flow runout distance up to 50%. We present the results from a series of analogue flume experiments on both non-fluidized and initially gas fluidized (i.e. high pore fluid pressure) granular flows. The experiments are designed to explore the controls on erosion initiation and intensity, and how erosion affects flow dynamics. A range of initial conditions allow us to explore how the angle of the bed (0°-20°) and diameter of substrate particles (40 to 700 μm) affect the onset of erosion. The experiments also explore how erosion, once initiated, affects the behavior of the flow in terms of velocity and runout distance. We observe that fluidized flows have increased runout distances of 50-300% relative to non-fluidized flows with the same initial conditions. Fluidized flows that travel over substrates composed of 40 μm particles consistently experience the largest increase in runout distance relative to non-fluidized flows, while flows over substrates of 80 μm particles experience the lowest increase. Erosion occurs for all experimental configurations in both non-fluidized and fluidized flows; however, the intensity of erosion varies widely, from small, millimeter-scale erosional features to decimeter sized wave-like features. Fluidized flows consistently show more intense erosion than non-fluidized flows, suggesting that the fluid-like behavior of these flows allows for efficient mixing between flow and substrate particles. These experiments demonstrate that erosion is a pervasive process for fluidized granular flows and that intense erosion is associated with increased flow runout distances. These results improve our understanding of the role of fluidization in erosion processes, what controls when PDCs become erosional, and how that erosion can alter flow behavior. To accurately model and predict hazards associated with PDCs, we must better understand erosional processes as they relate to these dangerous volcanic phenomena.

Adhesion of living cells revealed by variable-angle total internal reflection fluorescence microscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Cardoso Dos Santos, Marcelina; Vézy, Cyrille; Jaffiol, Rodolphe

2016-02-01

Total Internal Reflection Fluorescence Microscopy (TIRFM) is a widespread technique to study cellular process occurring near the contact region with the glass substrate. In this field, determination of the accurate distance from the surface to the plasma membrane constitutes a crucial issue to investigate the physical basis of cellular adhesion process. However, quantitative interpretation of TIRF pictures regarding the distance z between a labeled membrane and the substrate is not trivial. Indeed, the contrast of TIRF images depends on several parameters more and less well known (local concentration of dyes, absorption cross section, angular emission pattern…). The strategy to get around this problem is to exploit a series of TIRF pictures recorded at different incident angles in evanescent regime. This technique called variable-angle TIRF microscopy (vaTIRFM), allowing to map the membrane-substrate separation distance with a nanometric resolution (10-20 nm). vaTIRFM was developed by Burmeister, Truskey and Reichert in the early 1990s with a prism-based TIRF setup [Journal of Microscopy 173, 39-51 (1994)]. We propose a more convenient prismless setup, which uses only a rotatable mirror to adjust precisely the laser beam on the back focal plane of the oil immersion objective (no azimuthal scanning is needed). The series of TIRF images permit us to calculate accurately membrane-surface distances in each pixel. We demonstrate that vaTIRFM are useful to quantify the adhesion of living cells for specific and unspecific membrane-surface interactions, achieved on various functionalized substrates with polymers (BSA, poly-L-lysin) or extracellular matrix proteins (collagen and fibronectin).

Conditions for extreme sensitivity of protein diffusion in membranes to cell environments

PubMed Central

Tserkovnyak, Yaroslav; Nelson, David R.

2006-01-01

We study protein diffusion in multicomponent lipid membranes close to a rigid substrate separated by a layer of viscous fluid. The large-distance, long-time asymptotics for Brownian motion are calculated by using a nonlinear stochastic Navier–Stokes equation including the effect of friction with the substrate. The advective nonlinearity, neglected in previous treatments, gives only a small correction to the renormalized viscosity and diffusion coefficient at room temperature. We find, however, that in realistic multicomponent lipid mixtures, close to a critical point for phase separation, protein diffusion acquires a strong power-law dependence on temperature and the distance to the substrate H, making it much more sensitive to cell environment, unlike the logarithmic dependence on H and very small thermal correction away from the critical point. PMID:17008402

Innovative microchannel plate with reformulation of composition and modification of microstructure

NASA Astrophysics Data System (ADS)

Pan, Jingsheng; Lv, Jingwen; Kesaev, S. A.; Liu, Shulin; Liu, Zhanying; Li, Junguo; Chong, Xiaoqin; Shu, Detan

2009-07-01

The signal-to-noise ratio (SNR) and mean time to failure (MTTF) are two important attributes to describe the performance and operation life of an image intensifier. The presents of the ion barrier film (IBF) in Gen. III image intensifier, which used to suppress MCP's ion feedback, while dramatically improve the MTTF but significantly reduce the SNR, so more completely diminishing the ion poisoning source within the channels of MCP are crucial for improved Gen. III; image intensifier to thinned thickness IBF and achieving this two conflicting attributes promotion simultaneously. This research was originally initiated to develop a MCP with glass composition redesigned specially for GaAs photocathode image intensifier, proved which can be imposed an exceedingly intensive electron bombard degassing but without suffering a fatal gain degrade, and had achieved significantly improved SNR of Gen. III image intensifier but with a short distance to meet the lifetime success, so that our research work step forward to intent upon the restriction of ion poisoning source formation within the MCP substrate, we reformulated the MCP glass composition, and modified the microstructure of this MCP glass substrate though a glass-crystal phase transition during the MCP fabricate heating process, we present an innovative MCP based on a glass-ceramic substrate, with reformulated composition and close-linked network microstructure mix with many of nanometer size crystal grains, provide this MCP with sustainable high gain, lower ion feedback and less outgasing performance, this glass-ceramic MCPs are assembled to Gen. III image intensifiers which results showing promoting both the MTTF and SNR of Gen. III image intensifier.

Metabolic and hormonal changes during aerobic exercise in distance runners.

PubMed

Fernández-Pastor, V J; Ruiz, M; Diego-Acosta, A M; Avila, C; García, J C; Pérez, F; Guirado, F; Noguer, N

1999-03-01

A group of long-distance runners is studied in order to clarify aspects concerning neuroendocrine mechanisms regulating organic adaptation to maximum effort, with special interest in the function of the growth hormone in fat metabolism and the possible use of ketone bodies as an alternative source of energy. A test is designed on a treadmill with a gradient of 3% and progressive increases in speed of 2 Km/h every 10 min, starting at 6 Km/h, and continuing until exhaustion. Masks are worn to enable the breath by breath measurement of expired gases and the subjects are monitored electrocardiographically using V5. For blood sample collection an antecubital vein is catheterized with a system enabling the replacement of the blood volume extracted by means of perfusion with physiological saline solution, and the increasing concentration of hormones in the blood is evaluated. The results obtained, indicate that epinephrine as well as GH hormones increase significatively from 20 min of exercise in runners promoting changes from carbohydrates to lipids as fuels to carry out exercise. The concomitant variations in energy substrates support the former hypothesis of work. Moreover, the muscle could employ acetylCoA originating from acetoacetate as an alternative metabolic source of fuel during maximum effort.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabah, Fayroz A., E-mail: fayroz-arif@yahoo.com; Department of Electrical Engineering, College of Engineering, Al-Mustansiriya University, Baghdad; Ahmed, Naser M., E-mail: naser@usm.my

The copper sulphide (CuS) thin films were grown with good adhesion by spray pyrolysis deposition (SPD) on Ti, ITO and glass substrates at 200 °C. The distance between nozzle and substrate is 30 cm. The composition was prepared by mixing copper chloride CuCl{sub 2}.2H{sub 2}O as a source of Cu{sup 2+} and sodium thiosulfate Na{sub 2}S{sub 2}O{sub 3}.5H{sub 2}O as a source of and S{sup 2−}. Two concentrations (0.2 and 0.4 M) were used for each CuCl{sub 2} and Na{sub 2}S{sub 2}O{sub 3} to be prepared and then sprayed (20 ml). The process was started by spraying the solution formore » 3 seconds and after 10 seconds the cycle was repeated until the solution was sprayed completely on the hot substrates. The structural characteristics were studied using X-ray diffraction; they showed covellite CuS hexagonal crystal structure for 0.2 M concentration, and covellite CuS hexagonal crystal structure with two small peaks of chalcocite Cu{sub 2}S hexagonal crystal structure for 0.4 M concentration. Also the surface and electrical characteristics were investigated using Field Emission Scanning Electron Microscopy (FESEM) and current source device, respectively. The surface study for the CuS thin films showed nanorods to be established for 0.2 M concentration and mix of nanorods and nanoplates for 0.4 M concentration. The electrical study showed ohmic behavior and low resistivity for these films. Hall Effect was measured for these thin films, it showed that all samples of CuS are p- type thin films and ensured that the resistivity for thin films of 0.2 M concentration was lower than that of 0.4 M concentration; and for the two concentrations CuS thin film deposited on ITO had the lowest resistivity. This leads to the result that the conductivity was high for CuS thin film deposited on ITO substrate, and the conductivity of the three thin films of 0.2 M concentration was higher than that of 0.4 M concentration.« less

In-situ spectrophotometric probe

DOEpatents

Prather, W.S.

1992-12-15

A spectrophotometric probe is described for in situ absorption spectra measurements comprising a first optical fiber carrying light from a remote light source, a second optical fiber carrying light to a remote spectrophotometer, the proximal ends of the first and second optical fibers parallel and co-terminal, a planoconvex lens to collimate light from the first optical fiber, a reflecting grid positioned a short distance from the lens to reflect the collimated light back to the lens for focusing on the second optical fiber. The lens is positioned with the convex side toward the optical fibers. A substrate for absorbing analyte or an analyte and reagent mixture may be positioned between the lens and the reflecting grid. 5 figs.

Signals and cues in the recruitment behavior of stingless bees (Meliponini).

PubMed

Barth, Friedrich G; Hrncir, Michael; Jarau, Stefan

2008-04-01

Since the seminal work of Lindauer and Kerr (1958), many stingless bees have been known to effectively recruit nestmates to food sources. Recent research clarified properties of several signals and cues used by stingless bees when exploiting food sources. Thus, the main source of the trail pheromone in Trigona are the labial, not however the mandibular glands. In T. recursa and T. spinipes, the first stingless bee trail pheromones were identified as hexyl decanoate and octyl decanoate, respectively. The attractant footprints left by foragers at the food source are secreted by glandular epithelia of the claw retractor tendon, not however by the tarsal gland. Regarding intranidal communication, the correlation between a forager's jostling rate and recruitment success stresses the importance of agitated running and jostling. There is no evidence for a "dance" indicating food source location, however, whereas the jostling rate depends on food quality. Thoracic vibrations, another intranidal signal well known in Melipona, were analyzed using modern technology and distinguishing substrate vibrations from airborne sound. Quantitative data now permit estimates of signal and potential communication ranges. Airflow jets as described for the honeybee were not found, and thoracic vibrations do not "symbolically" encode visually measured distance in M. seminigra.

Direct observation of small cluster mobility and ripening. [during annealing of metal films on amorphous substrates

NASA Technical Reports Server (NTRS)

Heinemann, K.; Poppa, H.

1975-01-01

Direct evidence is reported for the simultaneous occurrence of Ostwald ripening and short-distance cluster mobility during annealing of discontinuous metal films on clean amorphous substrates. The annealing characteristics of very thin particulate deposits of silver on amorphized clean surfaces of single crystalline thin graphite substrates were studied by in-situ transmission electron microscopy (TEM) under controlled environmental conditions (residual gas pressure of 10 to the minus 9th power torr) in the temperature range from 25 to 450 C. Sputter cleaning of the substrate surface, metal deposition, and annealing were monitored by TEM observation. Pseudostereographic presentation of micrographs in different annealing stages, the observation of the annealing behavior at cast shadow edges, and measurements with an electronic image analyzing system were employed to aid the visual perception and the analysis of changes in deposit structure recorded during annealing. Slow Ostwald ripening was found to occur in the entire temperature range, but the overriding surface transport mechanism was short-distance cluster mobility.

Estimating rupture distances without a rupture

USGS Publications Warehouse

Thompson, Eric M.; Worden, Charles

2017-01-01

Most ground motion prediction equations (GMPEs) require distances that are defined relative to a rupture model, such as the distance to the surface projection of the rupture (RJB) or the closest distance to the rupture plane (RRUP). There are a number of situations in which GMPEs are used where it is either necessary or advantageous to derive rupture distances from point-source distance metrics, such as hypocentral (RHYP) or epicentral (REPI) distance. For ShakeMap, it is necessary to provide an estimate of the shaking levels for events without rupture models, and before rupture models are available for events that eventually do have rupture models. In probabilistic seismic hazard analysis, it is often convenient to use point-source distances for gridded seismicity sources, particularly if a preferred orientation is unknown. This avoids the computationally cumbersome task of computing rupture-based distances for virtual rupture planes across all strikes and dips for each source. We derive average rupture distances conditioned on REPI, magnitude, and (optionally) back azimuth, for a variety of assumed seismological constraints. Additionally, we derive adjustment factors for GMPE standard deviations that reflect the added uncertainty in the ground motion estimation when point-source distances are used to estimate rupture distances.

Creating "hotels" for cells by electrospinning honeycomb-like polymeric structures.

PubMed

Liang, T; Mahalingam, S; Edirisinghe, M

2013-10-01

It is well established that three-dimensional honeycomb-like nanofibrous structures enhance cell activity. In this work, we report that electrospun polymer nanofibres self-assemble into three-dimensional honeycomb-like structures. The underlying mechanism is studied by varying the polymer solution concentration, collecting substrates and working distance. The polymer solution concentration has a significant effect on the size of the electrospun nanofibres. The collection substrate and working distance affect the electric field strength, the evaporation of solvent and the discharging of nanofibres and consequently these two had a significant influence on the self-assembly of nanofibres. © 2013.

Analog laboratory experiments on the influence of substrate roughness on the run out distance of pyroclastic flows

NASA Astrophysics Data System (ADS)

Roche, O.; Chedevile, C.

2012-12-01

We carried out scaled experiments on gas-particles flows propagating on a rough substrate in order to investigate the emplacement of pyroclastic flows. The flows were generated from the release of non-fluidized or gas-fluidized columns of fine (80 μm) glass beads of height of 30 cm into a 3 m-long horizontal channel. The base of the channel was either smooth or was made rough by gluing a monodisperse layer of spherical particles of diameter of 80 μm to 3 mm. We defined the substrate roughness as the size of the glued particles, which corresponded to up to several tens of centimeters when scaled to the natural system. The flow front kinematics and the detailed interactions between the base of the flow and the rough substrate were investigated from high speed videos. We measured systematically the run out distance of the flows, and experiments were repeated 8-10 times for each configuration to obtain a mean value. The run out distance increased with the substrate roughness for both initially non-fluidized and fluidized flows. The run out had a minimum value for a smooth base and was about twice that value for the highest roughness of 3 mm. Analysis of the flow kinematics revealed that the increase in run out was caused by higher front velocities essentially at late stages of emplacement, during which the head of the flows stretched considerably. High speed videos made at the base of the flows showed that their head first slid over the substrate before aggregates of particles fell into the interstices between the particles forming the rough substrate, at a mean speed of several centimeters per second. In contrast, complementary experiments on flows of coarse beads of 350 μm showed that the substrate roughness did not influence their run out, and at the flow base their particles bumped into those of the substrate before falling individually into the interstices. These observations suggest that the positive correlation between the flow run out and the substrate roughness for flows of fine particles could result from two mechanisms. The first was the reduction of the contact area between the flow base and the substrate as the roughness increased because of the reduced number of particles per unit length. The second, main mechanism was auto-fluidization generated as the fine particles falling into the interstices expulsed the air upward at a velocity much larger than the minimum fluidization velocity. This promoted at least partial fluidization or additional pore pressure in case of initially non-fluidized or fluidized flows, respectively. This experimental investigation provides some counterintuitive results and has implication for hazards assessment. Other things being equal, the run out distance of fines-rich pyroclastic flows is expected to increase with the roughness of the terrain on which they propagate.

Coupling between apical tension and basal adhesion allow epithelia to collectively sense and respond to substrate topography over long distances.

PubMed

Broaders, Kyle E; Cerchiari, Alec E; Gartner, Zev J

2015-12-01

Epithelial sheets fold into complex topographies that contribute to their function in vivo. Cells can sense and respond to substrate topography in their immediate vicinity by modulating their interfacial mechanics, but the extent to which these mechanical properties contribute to their ability to sense substrate topography across length scales larger than a single cell has not been explored in detail. To study the relationship between the interfacial mechanics of single cells and their collective behavior as tissues, we grew cell-sheets on substrates engraved with surface features spanning macroscopic length-scales. We found that many epithelial cell-types sense and respond to substrate topography, even when it is locally nearly planar. Cells clear or detach from regions of local negative curvature, but not from regions with positive or no curvature. We investigated this phenomenon using a finite element model where substrate topography is coupled to epithelial response through a balance of tissue contractility and adhesive forces. The model correctly predicts the focal sites of cell-clearing and epithelial detachment. Furthermore, the model predicts that local tissue response to substrate curvature is a function of the surrounding topography of the substrate across long distances. Analysis of cell-cell and cell-substrate contact angles suggests a relationship between these single-cell interfacial properties, epithelial interfacial properties, and collective epithelial response to substrate topography. Finally, we show that contact angles change upon activation of oncogenes or inhibition of cell-contractility, and that these changes correlate with collective epithelial response. Our results demonstrate that in mechanically integrated epithelial sheets, cell contractility can be transmitted through multiple cells and focused by substrate topography to affect a behavioral response at distant sites.

Improvement of adhesion properties of low density polyethylene (LDPE) substrate using atmospheric plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanchez-Nacher, L.; Garcia-Sanoguera, D.; Fenollar, O.

2010-06-02

In this work we have used atmospheric plasma technology on polyethylene surface with different treatment conditions. These modify surface pre-treatments on polyethylene, thus having a positive effect on overall surface activity of polymer surface and, consequently, adhesion properties can be remarkably improved. We have evaluated the influence of the nozzle/substrate distance and atmospheric plasma speed on wettability changes and adhesion properties. Wettability changes have been studied by contact angle measurements and subsequent surface energy calculation. Mechanical characterization of adhesion joints has been carried out in two different ways: peel and shear tensile test. The overall results show a remarkable increasemore » in mechanical properties of adhesion joints for low nozzle/substrate distances and low speed. So plasma atmospheric technology is highly useful to increase adhesion properties of polypropylene.« less

The neural substrates of driving at a safe distance: a functional MRI study.

PubMed

Uchiyama, Yuji; Ebe, Kazutoshi; Kozato, Akio; Okada, Tomohisa; Sadato, Norihiro

2003-12-11

An important driving skill is the ability to maintain a safe distance from a preceding car. To determine the neural substrates of this skill we performed functional magnetic resonance imaging of simulated driving in 21 subjects. Subjects used a joystick to adjust their own driving speed in order to maintain a constant distance from a preceding car traveling at varying speeds. The task activated multiple brain regions. Activation of the cerebellum may reflect visual feedback during smooth tracking of the preceding car. Co-activation of the basal ganglia, thalamus and premotor cortex is related to movement selection. Activation of a premotor-parietal network is related to visuo-motor co-ordination. Task performance was negatively correlated with anterior cingulate activity, consistent with the role of this region in error detection and response selection.

Single-step synthesis of crystalline h-BN quantum- and nanodots embedded in boron carbon nitride films

NASA Astrophysics Data System (ADS)

Matsoso, Boitumelo J.; Ranganathan, Kamalakannan; Mutuma, Bridget K.; Lerotholi, Tsenolo; Jones, Glenn; Coville, Neil J.

2017-03-01

Herein we report on the synthesis and characterization of novel crystalline hexagonal boron nitride (h-BN) quantum- and nanodots embedded in large-area boron carbon nitride (BCN) films. The films were grown on a Cu substrate by an atmospheric pressure chemical vapour deposition technique. Methane, ammonia, and boric acid were used as precursors for C, N and B to grow these few atomic layer thick uniform films. We observed that both the size of the h-BN quantum/nanodots and thickness of the BCN films were influenced by the vaporization temperature of boric acid as well as the H3BO3 (g) flux over the Cu substrate. These growth conditions were easily achieved by changing the position of the solid boric acid in the reactor with respect to the Cu substrate. Atomic force microscope (AFM) and TEM analyses show a variation in the h-BN dot size distribution, ranging from nanodots (˜224 nm) to quantum dots (˜11 nm) as the B-source is placed further away from the Cu foil. The distance between the B-source and the Cu foil gave an increase in the C atomic composition (42 at% C-65 at% C) and a decrease in both B and N contents (18 at% B and 14 at% N to 8 at% B and 7 at% N). UV-vis absorption spectra showed a higher band gap energy for the quantum dots (5.90 eV) in comparison with the nanodots (5.68 eV) due to a quantum confinement effect. The results indicated that the position of the B-source and its reaction with ammonia plays a significant role in controlling the nucleation of the h-BN quantum- and nanodots. The films are proposed to be used in solar cells. A mechanism to explain the growth of h-BN quantum/nanodots in BCN films is reported.

Carbon Nanotube Patterning on a Metal Substrate

NASA Technical Reports Server (NTRS)

Nguyen, Cattien V. (Inventor)

2016-01-01

A CNT electron source, a method of manufacturing a CNT electron source, and a solar cell utilizing a CNT patterned sculptured substrate are disclosed. Embodiments utilize a metal substrate which enables CNTs to be grown directly from the substrate. An inhibitor may be applied to the metal substrate to inhibit growth of CNTs from the metal substrate. The inhibitor may be precisely applied to the metal substrate in any pattern, thereby enabling the positioning of the CNT groupings to be more precisely controlled. The surface roughness of the metal substrate may be varied to control the density of the CNTs within each CNT grouping. Further, an absorber layer and an acceptor layer may be applied to the CNT electron source to form a solar cell, where a voltage potential may be generated between the acceptor layer and the metal substrate in response to sunlight exposure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elhadj, Selim; Bass, Isaac Louis; Guss, Gabriel Mark

Techniques for removing material from a substrate are provided. A laser beam is focused at a distance from the surface to be treated. A gas is provided at the focus point. The gas is dissociated using the laser energy to generate gas plasma. The substrate is then brought in contact with the gas plasma to enable material removal.

Method for electrostatic deposition of graphene on a substrate

NASA Technical Reports Server (NTRS)

Sumanasekera, Gamini (Inventor); Sidorov, Anton N. (Inventor); Ouseph, P. John (Inventor); Yazdanpanah, Mehdi M. (Inventor); Cohn, Robert W. (Inventor); Jalilian, Romaneh (Inventor)

2010-01-01

A method for electrostatic deposition of graphene on a substrate comprises the steps of securing a graphite sample to a first electrode; electrically connecting the first electrode to a positive terminal of a power source; electrically connecting a second electrode to a ground terminal of the power source; placing the substrate over the second electrode; and using the power source to apply a voltage, such that graphene is removed from the graphite sample and deposited on the substrate.

Molecular dynamics simulations reveal a new role for a conserved active site asparagine in a ubiquitin-conjugating enzyme.

PubMed

Wilson, R Hunter; Zamfir, Serban; Sumner, Isaiah

2017-09-01

The role of a highly conserved active site asparagine (N79) in the ubiquitin conjugating enzyme, Ubc13, is probed using molecular dynamics simulations. Both wild type and mutant enzymes (N79A and N79D) are studied. Contrary to a popular hypothesis, we show that it is unlikely that N79 stabilizes a reaction intermediate, but instead preferentially hydrogen bonds to a loop near the active site. This keeps the sidechain carboxylate of an aspartate in the loop (D119) near the sidechain amine of the substrate lysine. Our simulations show that this distance increases in the mutants. D119 has been hypothesized to play a variety of roles in the enzyme, including deprotonating the substrate lysine, so changing this distance can have an effect on the enzyme's efficiency. Finally, we show that it is possible for the aspartate to deprotonate the substrate even across long distances if short water wires form that connect the proton donor and acceptor. Short water wires form with greater probability in the wild type than in mutant enzymes. Copyright © 2017 Elsevier Inc. All rights reserved.

Method for materials deposition by ablation transfer processing

DOEpatents

Weiner, Kurt H.

1996-01-01

A method in which a thin layer of semiconducting, insulating, or metallic material is transferred by ablation from a source substrate, coated uniformly with a thin layer of said material, to a target substrate, where said material is desired, with a pulsed, high intensity, patternable beam of energy. The use of a patternable beam allows area-selective ablation from the source substrate resulting in additive deposition of the material onto the target substrate which may require a very low percentage of the area to be covered. Since material is placed only where it is required, material waste can be minimized by reusing the source substrate for depositions on multiple target substrates. Due to the use of a pulsed, high intensity energy source the target substrate remains at low temperature during the process, and thus low-temperature, low cost transparent glass or plastic can be used as the target substrate. The method can be carried out atmospheric pressures and at room temperatures, thus eliminating vacuum systems normally required in materials deposition processes. This invention has particular application in the flat panel display industry, as well as minimizing materials waste and associated costs.

Primary Beam Air Kerma Dependence on Distance from Cargo and People Scanners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strom, Daniel J.; Cerra, Frank

The distance dependence of air kerma or dose rate of the primary radiation beam is not obvious for security scanners of cargo and people in which there is relative motion between a collimated source and the person or object being imaged. To study this problem, one fixed line source and three moving-source scan-geometry cases are considered, each characterized by radiation emanating perpendicular to an axis. The cases are 1) a stationary line source of radioactive material, e.g., contaminated solution in a pipe; 2) a moving, uncollimated point source of radiation that is shuttered or off when it is stationary; 3)more » a moving, collimated point source of radiation that is shuttered or off when it is stationary; and 4) a translating, narrow “pencil” beam emanating in a flying-spot, raster pattern. Each case is considered for short and long distances compared to the line source length or path traversed by a moving source. The short distance model pertains mostly to dose to objects being scanned and personnel associated with the screening operation. The long distance model pertains mostly to potential dose to bystanders. For radionuclide sources, the number of nuclear transitions that occur a) per unit length of a line source, or b) during the traversal of a point source, is a unifying concept. The “universal source strength” of air kerma rate at a meter from the source can be used to describe x-ray machine or radionuclide sources. For many cargo and people scanners with highly collimated fan or pencil beams, dose varies as the inverse of the distance from the source in the near field and with the inverse square of the distance beyond a critical radius. Ignoring the inverse square dependence and using inverse distance dependence is conservative in the sense of tending to overestimate dose.« less

Primary Beam Air Kerma Dependence on Distance from Cargo and People Scanners.

PubMed

Strom, Daniel J; Cerra, Frank

2016-06-01

The distance dependence of air kerma or dose rate of the primary radiation beam is not obvious for security scanners of cargo and people in which there is relative motion between a collimated source and the person or object being imaged. To study this problem, one fixed line source and three moving-source scan-geometry cases are considered, each characterized by radiation emanating perpendicular to an axis. The cases are 1) a stationary line source of radioactive material, e.g., contaminated solution in a pipe; 2) a moving, uncollimated point source of radiation that is shuttered or off when it is stationary; 3) a moving, collimated point source of radiation that is shuttered or off when it is stationary; and 4) a translating, narrow "pencil" beam emanating in a flying-spot, raster pattern. Each case is considered for short and long distances compared to the line source length or path traversed by a moving source. The short distance model pertains mostly to dose to objects being scanned and personnel associated with the screening operation. The long distance model pertains mostly to potential dose to bystanders. For radionuclide sources, the number of nuclear transitions that occur a) per unit length of a line source or b) during the traversal of a point source is a unifying concept. The "universal source strength" of air kerma rate at 1 m from the source can be used to describe x-ray machine or radionuclide sources. For many cargo and people scanners with highly collimated fan or pencil beams, dose varies as the inverse of the distance from the source in the near field and with the inverse square of the distance beyond a critical radius. Ignoring the inverse square dependence and using inverse distance dependence is conservative in the sense of tending to overestimate dose.

High conductivity a-C:N thin films prepared by electron gun evaporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rebollo-Plata, B.; Lozada-Morales, R.; Palomino-Merino, R.

2007-08-15

By employing electron beam evaporation, amorphous carbon nitride (a-C:N) thin films, with a low nitrogen content ({approx} 1%), were prepared on Si(110) and glass substrates at about 150 deg. C. The source was a graphite target and an ambient of N{sub 2} was introduced into the growing chamber. The source-substrate distance (SSD) was the main parameter that was intentionally varied. Electron dispersion spectroscopy measurements indicate the nitrogen concentration in the layer as {approx} 1%. The dark electrical conductivity ({sigma}) of layers was very sensitive to SSD variation, changing up to six orders of magnitude when this parameter was varied frommore » 10.5 to 23.5 cm. A maximum value of {sigma} = 1 x 10{sup 3} {omega}{sup -1} cm{sup -1} at room temperature was obtained when the SSD was equal to 15.5 cm. We have deduced that, in accordance with the Ferrari-Robertson model (FRM), our samples are localized in the second stage of the amorphization trajectory of FRM. When the SSD increases the C atoms have more probability to collide with N{sub 2} molecules, and the content of nitrogen in the a-C film increases. The amorphization trajectory followed by the films with an SSD increase is from nanocrystalline graphite to amorphous carbon. The changes in the amorphization are due to the nitrogen content in the layers.« less

Ferromagnetism and Ru-Ru distance in SrRuO3 thin film grown on SrTiO3 (111) substrate

PubMed Central

2014-01-01

Epitaxial SrRuO3 thin films were grown on both (100) and (111) SrTiO3 substrates with atomically flat surfaces that are required to grow high-quality films of materials under debate. The following notable differences were observed in the (111)-oriented SrRuO3 films: (1) slightly different growth mode, (2) approximately 10 K higher ferromagnetic transition temperature, and (3) better conducting behavior with higher relative resistivity ratio, than (100)c-oriented SrRuO3 films. Together with the reported results on SrRuO3 thin films grown on (110) SrTiO3 substrate, the different physical properties were discussed newly in terms of the Ru-Ru nearest neighbor distance instead of the famous tolerance factor. PACS 75.70.Ak; 75.60.Ej; 81.15.Fg PMID:24393495

Highly patterned growth of SnO2 nanowires using a sub-atmospheric vapor-liquid-solid deposition

NASA Astrophysics Data System (ADS)

Akbari, M.; Mohajerzadeh, S.

2017-08-01

We report the realization of tin-oxide nanowires on patterned structures using a vapor-liquid-solid (VLS) process. While gold acts as the catalyst for the growth of wires, a tin-oxide containing sol-gel solution is spin coated on silicon substrate to act as the source for SnO vapor. The growth of tin-oxide nano-structures occurs mostly at the vicinity of the pre-deposited solution. By patterning the gold as the catalyst material, one is able to observe the growth at desired places. The growth of nanowires is highly dense within 100 µm away from such in situ source and their length is of the order of 5 µm. By further distancing from the source, the growth becomes more limited and nanowires become shorter and more sparsely distributed. The growth of nanowires has been studied using scanning and transmission electron microscopy tools while their composition has been investigated using XRD and EDS analyses. As a novel application, we have employed the grown nanowires as electron detection elements to measure the emitted electrons from electron sources. This configuration can be further used as electron detectors for scanning electron microscopes.

Ion-beam treatment to prepare surfaces of p-CdTe films

DOEpatents

Gessert, Timothy A.

2001-01-01

A method of making a low-resistance electrical contact between a p-CdTe layer and outer contact layers by ion beam processing comprising: a) placing a CdS/CdTe device into a chamber and evacuating the chamber; b) orienting the p-CdTe side of the CdS/CdTe layer so that it faces apparatus capable of generating Ar atoms and ions of preferred energy and directionality; c) introducing Ar and igniting the area of apparatus capable of generating Ar atoms and ions of preferred energy and directionality in a manner so that during ion exposure, the source-to-substrate distance is maintained such that it is less than the mean-free path or diffusion length of the Ar atoms and ions at the vacuum pressure; d) allowing exposure of the p-CdTe side of the device to said ion beam for a period less than about 5 minutes; and e) imparting movement to the substrate to control the real uniformity of the ion-beam exposure on the p-CdTe side of the device.

Non-imaging ray-tracing for sputtering simulation with apodization

NASA Astrophysics Data System (ADS)

Ou, Chung-Jen

2018-04-01

Although apodization patterns have been adopted for the analysis of sputtering sources, the analytical solutions for the film thickness equations are yet limited to only simple conditions. Empirical formulations for thin film sputtering lacking the flexibility in dealing with multi-substrate conditions, a suitable cost-effective procedure is required to estimate the film thickness distribution. This study reports a cross-discipline simulation program, which is based on discrete particle Monte-Carlo methods and has been successfully applied to a non-imaging design to solve problems associated with sputtering uniformity. Robustness of the present method is first proved by comparing it with a typical analytical solution. Further, this report also investigates the overall all effects cause by the sizes of the deposited substrate, such that the determination of the distance between the target surface and the apodization index can be complete. This verifies the capability of the proposed method for solving the sputtering film thickness problems. The benefit is that an optical thin film engineer can, using the same optical software, design a specific optical component and consider the possible coating qualities with thickness tolerance, during the design stage.

Non-imaging ray-tracing for sputtering simulation with apodization

NASA Astrophysics Data System (ADS)

Ou, Chung-Jen

2018-06-01

Although apodization patterns have been adopted for the analysis of sputtering sources, the analytical solutions for the film thickness equations are yet limited to only simple conditions. Empirical formulations for thin film sputtering lacking the flexibility in dealing with multi-substrate conditions, a suitable cost-effective procedure is required to estimate the film thickness distribution. This study reports a cross-discipline simulation program, which is based on discrete particle Monte-Carlo methods and has been successfully applied to a non-imaging design to solve problems associated with sputtering uniformity. Robustness of the present method is first proved by comparing it with a typical analytical solution. Further, this report also investigates the overall all effects cause by the sizes of the deposited substrate, such that the determination of the distance between the target surface and the apodization index can be complete. This verifies the capability of the proposed method for solving the sputtering film thickness problems. The benefit is that an optical thin film engineer can, using the same optical software, design a specific optical component and consider the possible coating qualities with thickness tolerance, during the design stage.

Long-Term Enrichment on Cellulose or Xylan Causes Functional and Taxonomic Convergence of Microbial Communities from Anaerobic Digesters

PubMed Central

Jia, Yangyang; Wilkins, David; Lu, Hongyuan; Cai, Mingwei

2015-01-01

Cellulose and xylan are two major components of lignocellulosic biomass, which represents a potentially important energy source, as it is abundant and can be converted to methane by microbial action. However, it is recalcitrant to hydrolysis, and the establishment of a complete anaerobic digestion system requires a specific repertoire of microbial functions. In this study, we maintained 2-year enrichment cultures of anaerobic digestion sludge amended with cellulose or xylan to investigate whether a cellulose- or xylan-digesting microbial system could be assembled from sludge previously used to treat neither of them. While efficient methane-producing communities developed under mesophilic (35°C) incubation, they did not under thermophilic (55°C) conditions. Illumina amplicon sequencing results of the archaeal and bacterial 16S rRNA genes revealed that the mature cultures were much lower in richness than the inocula and were dominated by single archaeal (genus Methanobacterium) and bacterial (order Clostridiales) groups, although at finer taxonomic levels the bacteria were differentiated by substrates. Methanogenesis was primarily via the hydrogenotrophic pathway under all conditions, although the identity and growth requirements of syntrophic acetate-oxidizing bacteria were unclear. Incubation conditions (substrate and temperature) had a much greater effect than inoculum source in shaping the mature microbial community, although analysis based on unweighted UniFrac distance found that the inoculum still determined the pool from which microbes could be enriched. Overall, this study confirmed that anaerobic digestion sludge treating nonlignocellulosic material is a potential source of microbial cellulose- and xylan-digesting functions given appropriate enrichment conditions. PMID:26712547

Comparison of Genetic Structure of Epixylic Liverwort Crossocalyx hellerianus between Central European and Fennoscandian Populations.

PubMed

Holá, Eva; Košnar, Jiří; Kučera, Jan

2015-01-01

Patterns of genetic variation and spatial genetic structure (SGS) were investigated in Crossocalyx hellerianus, a strictly epixylic dioicous liverwort (Scapaniaceae s.l., Marchantiophyta). Studied populations were located in Fennoscandia and Central Europe, with localities differing in availability of substrate and the population connectivity, and their populations consequently different in size, density, and prevailing reproductive mode. A set of nine polymorphic microsatellites was successfully developed and used. Identical individuals were only found within populations. Especially in large populations, the majority of the individuals were genetically unique. Resampled number of genotypes, mean number of observed alleles per locus after rarefaction, and Nei's gene diversity in large populations reached high values and ranged between 4.41-4.97, 3.13-4.45, and 0.94-0.99, respectively. On the contrary, the values in small populations were lower and ranged between 1.00-4.42, 1.00-2.73, and 0.00-0.95, respectively. As expected, large populations were found to be more genetically diverse than small populations but relatively big diversity of genotypes was also found in small populations. This indicated that even small populations are important sources of genetic variation in bryophytes and processes causing loss of genetic variation might be compensated by other sources of variability, of which somatic mutations might play an important role. The presence of SGS was discovered in all populations. Large populations possessed less SGS, with individuals showing a pronounced decrease in kinship over 50 cm of distance. Apparent SGS of small populations even at distances up to 16 meters suggests the aggregation of similar genotypes, caused predominantly by the deposition of asexually formed gemmae. Although no strong kinship was detectable at the distances over 16 meters in both small and large populations, identical genotypes were occasionally detected at longer distances (20-80 m), suggesting effective dispersal of asexual propagules.

Comparison of Genetic Structure of Epixylic Liverwort Crossocalyx hellerianus between Central European and Fennoscandian Populations

PubMed Central

Holá, Eva; Košnar, Jiří; Kučera, Jan

2015-01-01

Patterns of genetic variation and spatial genetic structure (SGS) were investigated in Crossocalyx hellerianus, a strictly epixylic dioicous liverwort (Scapaniaceae s.l., Marchantiophyta). Studied populations were located in Fennoscandia and Central Europe, with localities differing in availability of substrate and the population connectivity, and their populations consequently different in size, density, and prevailing reproductive mode. A set of nine polymorphic microsatellites was successfully developed and used. Identical individuals were only found within populations. Especially in large populations, the majority of the individuals were genetically unique. Resampled number of genotypes, mean number of observed alleles per locus after rarefaction, and Nei’s gene diversity in large populations reached high values and ranged between 4.41–4.97, 3.13–4.45, and 0.94–0.99, respectively. On the contrary, the values in small populations were lower and ranged between 1.00–4.42, 1.00–2.73, and 0.00–0.95, respectively. As expected, large populations were found to be more genetically diverse than small populations but relatively big diversity of genotypes was also found in small populations. This indicated that even small populations are important sources of genetic variation in bryophytes and processes causing loss of genetic variation might be compensated by other sources of variability, of which somatic mutations might play an important role. The presence of SGS was discovered in all populations. Large populations possessed less SGS, with individuals showing a pronounced decrease in kinship over 50 cm of distance. Apparent SGS of small populations even at distances up to 16 meters suggests the aggregation of similar genotypes, caused predominantly by the deposition of asexually formed gemmae. Although no strong kinship was detectable at the distances over 16 meters in both small and large populations, identical genotypes were occasionally detected at longer distances (20–80 m), suggesting effective dispersal of asexual propagules. PMID:26186214

Numerical Study of Suspension HVOF Spray and Particle Behavior Near Flat and Cylindrical Substrates

NASA Astrophysics Data System (ADS)

Jadidi, M.; Yeganeh, A. Zabihi; Dolatabadi, A.

2018-01-01

In thermal spray processes, it is demonstrated that substrate shape and location have significant effects on particle in-flight behavior and coatings quality. In the present work, the suspension high-velocity oxygen fuel (HVOF) spraying process is modeled using a three-dimensional two-way coupled Eulerian-Lagrangian approach. Flat and cylindrical substrates are placed at different standoff distances, and particles characteristics near the substrates and upon impact are studied. Suspension is a mixture of ethanol, ethylene glycol, and mullite solid powder (3Al2O3·2SiO2) in this study. Suspension droplets with predefined size distribution are injected into the combustion chamber, and the droplet breakup phenomenon is simulated using Taylor analogy breakup model. Furthermore, the eddy dissipation model is used to model the premixed combustion of oxygen-propylene, and non-premixed combustion of oxygen-ethanol and oxygen-ethylene glycol. To simulate the gas phase turbulence, the realizable k-ɛ model is applied. In addition, as soon as the breakup and combustion phenomena are completed, the solid/molten mullite particles are tracked through the domain. It is shown that as the standoff distance increases the particle temperature and velocity decrease and the particle trajectory deviation becomes more significant. The effect of stagnation region on the particle velocity and temperature is also discussed in detail. The catch rate, which is defined as the ratio of the mass of landed particles to injected particles, is calculated for different substrate shapes and standoff distances in this study. The numerical results presented here is consistent with the experimental data in the literature for the same operating conditions.

A novel molecular index for secondary oil migration distance

PubMed Central

Zhang, Liuping; Li, Maowen; Wang, Yang; Yin, Qing-Zhu; Zhang, Wenzheng

2013-01-01

Determining oil migration distances from source rocks to reservoirs can greatly help in the search for new petroleum accumulations. Concentrations and ratios of polar organic compounds are known to change due to preferential sorption of these compounds in migrating oils onto immobile mineral surfaces. However, these compounds cannot be directly used as proxies for oil migration distances because of the influence of source variability. Here we show that for each source facies, the ratio of the concentration of a select polar organic compound to its initial concentration at a reference point is independent of source variability and correlates solely with migration distance from source rock to reservoir. Case studies serve to demonstrate that this new index provides a valid solution for determining source-reservoir distance and could lead to many applications in fundamental and applied petroleum geoscience studies. PMID:23965930

Method to Create Arbitrary Sidewall Geometries in 3-Dimensions Using Liga with a Stochastic Optimization Framework

NASA Technical Reports Server (NTRS)

Eyre, Francis B. (Inventor); Fink, Wolfgang (Inventor)

2011-01-01

Disclosed herein is a method of making a three dimensional mold comprising the steps of providing a mold substrate; exposing the substrate with an electromagnetic radiation source for a period of time sufficient to render the portion of the mold substrate susceptible to a developer to produce a modified mold substrate; and developing the modified mold with one or more developing reagents to remove the portion of the mold substrate rendered susceptible to the developer from the mold substrate, to produce the mold having a desired mold shape, wherein the electromagnetic radiation source has a fixed position, and wherein during the exposing step, the mold substrate is manipulated according to a manipulation algorithm in one or more dimensions relative to the electromagnetic radiation source; and wherein the manipulation algorithm is determined using stochastic optimization computations.

Efficient growth of HTS films with volatile elements

DOEpatents

Siegal, M.P.; Overmyer, D.L.; Dominguez, F.

1998-12-22

A system is disclosed for applying a volatile element-HTS layer, such as Tl-HTS, to a substrate in a multiple zone furnace, said method includes heating at higher temperature, in one zone of the furnace, a substrate and adjacent first source of Tl-HTS material, to sublimate Tl-oxide from the source to the substrate; and heating at lower temperature, in a separate zone of the furnace, a second source of Tl-oxide to replenish the first source of Tl-oxide from the second source. 3 figs.

Dynamic wetting on a thin film of soluble polymer: effects of nonlinearities in the sorption isotherm.

PubMed

Dupas, Julien; Verneuil, Emilie; Ramaioli, Marco; Forny, Laurent; Talini, Laurence; Lequeux, Francois

2013-10-08

The wetting dynamics of a solvent on a soluble substrate interestingly results from the rates of the solvent transfers into the substrate. When a supported film of a hydrosoluble polymer with thickness e is wet by a spreading droplet of water with instantaneous velocity U, the contact angle is measured to be inversely proportionate to the product of thickness and velocity, eU, over two decades. As for many hydrosoluble polymers, the polymer we used (a polysaccharide) has a strongly nonlinear sorption isotherm φ(a(w)), where φ is the volume fraction of water in the polymer and aw is the activity of water. For the first time, this nonlinearity is accounted for in the dynamics of water uptake by the substrate. Indeed, by measuring the water content in the polymer around the droplet φ at distances as small as 5 μm, we find that the hydration profile exhibits (i) a strongly distorted shape that results directly from the nonlinearities of the sorption isotherm and (ii) a cutoff length ξ below which the water content in the substrate varies very slowly. The nonlinearities in the sorption isotherm and the hydration at small distances from the line were not accounted for by Tay et al., Soft Matter 2011, 7, 6953. Here, we develop a comprehensive description of the hydration of the substrate ahead of the contact line that encompasses the two water transfers at stake: (i) the evaporation-condensation process by which water transfers into the substrate through the atmosphere by the condensation of the vapor phase, which is fed by the evaporation from the droplet itself, and (ii) the diffusion of liquid water along the polymer film. We find that the eU rescaling of the contact angle arises from the evaporation-condensation process at small distances. We demonstrate why it is not modified by the second process.

Compact ion accelerator source

DOEpatents

Schenkel, Thomas; Persaud, Arun; Kapadia, Rehan; Javey, Ali

2014-04-29

An ion source includes a conductive substrate, the substrate including a plurality of conductive nanostructures with free-standing tips formed on the substrate. A conductive catalytic coating is formed on the nanostructures and substrate for dissociation of a molecular species into an atomic species, the molecular species being brought in contact with the catalytic coating. A target electrode placed apart from the substrate, the target electrode being biased relative to the substrate with a first bias voltage to ionize the atomic species in proximity to the free-standing tips and attract the ionized atomic species from the substrate in the direction of the target electrode.

Method for materials deposition by ablation transfer processing

DOEpatents

Weiner, K.H.

1996-04-16

A method in which a thin layer of semiconducting, insulating, or metallic material is transferred by ablation from a source substrate, coated uniformly with a thin layer of said material, to a target substrate, where said material is desired, with a pulsed, high intensity, patternable beam of energy. The use of a patternable beam allows area-selective ablation from the source substrate resulting in additive deposition of the material onto the target substrate which may require a very low percentage of the area to be covered. Since material is placed only where it is required, material waste can be minimized by reusing the source substrate for depositions on multiple target substrates. Due to the use of a pulsed, high intensity energy source the target substrate remains at low temperature during the process, and thus low-temperature, low cost transparent glass or plastic can be used as the target substrate. The method can be carried out atmospheric pressures and at room temperatures, thus eliminating vacuum systems normally required in materials deposition processes. This invention has particular application in the flat panel display industry, as well as minimizing materials waste and associated costs. 1 fig.

A distance-controlled nanoparticle array using PEGylated ferritin

NASA Astrophysics Data System (ADS)

He, Chao; Uenuma, Mutsunori; Okamoto, Naofumi; Kamitake, Hiroki; Ishikawa, Yasuaki; Yamashita, Ichiro; Uraoka, Yukiharu

2014-12-01

A distance-controlled nanoparticle (NP) array was investigated using a simple spin coating process. It was found that the separation distance of NPs was controlled at the nanoscale by using polyethylene glycols (PEGs). Ferritin was used to synthesize NPs and carry them to a substrate by using the different molecular weight of PEGs. In order to control the distance of the NPs, PEGs with molecular weights of 2k, 5k, 10k and 20k were modified on ferritin with 10 mM ion strength and 0.01 mg ml-1 ferritin concentration. The separated distances of NPs increased along with increase in PEG molecular weight.

High throughput optical scanner

DOEpatents

Basiji, David A.; van den Engh, Gerrit J.

2001-01-01

A scanning apparatus is provided to obtain automated, rapid and sensitive scanning of substrate fluorescence, optical density or phosphorescence. The scanner uses a constant path length optical train, which enables the combination of a moving beam for high speed scanning with phase-sensitive detection for noise reduction, comprising a light source, a scanning mirror to receive light from the light source and sweep it across a steering mirror, a steering mirror to receive light from the scanning mirror and reflect it to the substrate, whereby it is swept across the substrate along a scan arc, and a photodetector to receive emitted or scattered light from the substrate, wherein the optical path length from the light source to the photodetector is substantially constant throughout the sweep across the substrate. The optical train can further include a waveguide or mirror to collect emitted or scattered light from the substrate and direct it to the photodetector. For phase-sensitive detection the light source is intensity modulated and the detector is connected to phase-sensitive detection electronics. A scanner using a substrate translator is also provided. For two dimensional imaging the substrate is translated in one dimension while the scanning mirror scans the beam in a second dimension. For a high throughput scanner, stacks of substrates are loaded onto a conveyor belt from a tray feeder.

Highly porous micro-roughened structures developed on aluminum surface using the jet of rotating arc discharges at atmospheric pressure

NASA Astrophysics Data System (ADS)

Asadollahi, Siavash; Farzaneh, Masoud; Stafford, Luc

2018-02-01

Aluminum 6061 samples were exposed to the jet of an atmospheric pressure rotating arc discharge operated in either nitrogen or air. After multiple passes of treatment with an air-based plasma jet at very short source-to-substrate distances, scanning electron microscopy combined with x-ray photoelectron spectroscopy revealed a highly porous micro-roughened alumina-based structure on the surface of aluminum. Based on optical emission spectroscopy and high-speed optical imaging of the jet interacting with aluminum samples, it was found that the process is mainly driven by the energy transfer from the plasma source to the surface through transient plasma-transferred arcs. The occurrence of multiple arc discharges over very short time scales can induce rapid phase transformations of aluminum with characteristics similar to the ones usually observed during laser ablation of materials with femto- to nanosecond laser pulses or during the formation of cathode spots on the surface of metals.

Germanene on single-layer ZnSe substrate: novel electronic and optical properties.

PubMed

Ye, H Y; Hu, F F; Tang, H Y; Yang, L W; Chen, X P; Wang, L G; Zhang, G Q

2018-06-01

In this work, the structural, electronic and optical properties of germanene and ZnSe substrate nanocomposites have been investigated using first-principles calculations. We found that the large direct-gap ZnSe semiconductors and zero-gap germanene form a typical orbital hybridization heterostructure with a strong binding energy, which shows a moderate direct band gap of 0.503 eV in the most stable pattern. Furthermore, the heterostructure undergoes semiconductor-to-metal band gap transition when subjected to external out-of-plane electric field. We also found that applying external strain and compressing the interlayer distance are two simple ways of tuning the electronic structure. An unexpected indirect-direct band gap transition is also observed in the AAII pattern via adjusting the interlayer distance. Quite interestingly, the calculated results exhibit that the germanene/ZnSe heterobilayer structure has perfect optical absorption in the solar spectrum as well as the infrared and UV light zones, which is superior to that of the individual ZnSe substrate and germanene. The staggered interfacial gap and tunability of the energy band structure via interlayer distance and external electric field and strain thus make the germanene/ZnSe heterostructure a promising candidate for field effect transistors (FETs) and nanoelectronic applications.

Molecular aspect ratio and anchoring strength effects in a confined Gay-Berne liquid crystal

NASA Astrophysics Data System (ADS)

Cañeda-Guzmán, E.; Moreno-Razo, J. A.; Díaz-Herrera, E.; Sambriski, E. J.

2014-04-01

Phase diagrams for Gay-Berne (GB) fluids were obtained from molecular dynamics simulations for GB(2, 5, 1, 2) (i.e. short mesogens) and GB(3, 5, 1, 2) (i.e. long mesogens), which yield isotropic, nematic, and smectic-B phases. The long-mesogen fluid also yields the smectic-A phase. Ordered phases of the long-mesogen fluid form at higher temperatures and lower densities when compared to those of the short-mesogen fluid. The effect of confinement under weak and strong substrate couplings in slab geometry was investigated. Compared to the bulk, the isotropic-nematic transition does not shift in temprature significantly for the weakly coupled substrate in either mesogen fluid. However, the strongly coupled substrate shifts the transition to lower temperature. Confinement induces marked stratification in the short-mesogen fluid. This effect diminishes with distance from the substrate, yielding bulk-like behaviour in the slab central region. Fluid stratification is very weak for the long-mesogen fluid, but the strongly coupled substrate induces 'smectisation', an ordering effect that decays with distance. Orientation of the fluid on the substrate depends on the mesogen. There is no preferred orientation in a plane parallel to the substrate for the weakly coupled case. In the strongly coupled case, the mesogen orientation mimics that of adjacent fluid layers. Planar anchoring is observed with a broad distribution of orientations in the weakly coupled case. In the strongly coupled case, the distribution leans toward planar orientations for the short-mesogen fluid, while a marginal preference for tilting persists in the long-mesogen fluid.

Synergistic effects of semiconductor substrate and noble metal nano-particles on SERS effect both theoretical and experimental aspects

NASA Astrophysics Data System (ADS)

Yang, Chen; Liang, Pei; Tang, Lisha; Zhou, Yongfeng; Cao, Yanting; Wu, Yanxiong; Zhang, De; Dong, Qianmin; Huang, Jie; He, Peng

2018-04-01

As a means of chemical identification and analysis, Surface enhanced Raman spectroscopy (SERS), with the advantages of high sensitivity and selectivity, non-destructive, high repeatability and in situ detection etc., has important significance in the field of composition detection, environmental science, biological medicine etc. Physical model of coupling effect between different semiconductor substrates and noble metal particles were investigated by using 3D-FDTD method. Mechanism and the effects of excitation wavelength, particle spacing and semiconductor substrate types on the SERS effect were discussed. The results showed that the optimal excitation wavelengths of three noble metals of Ag, Au, Cu, were located at 510, 600 and 630 nm, respectively; SERS effect of Ag, Au, Cu increases with the decreasing of the inter distance of particles, while the distance of the NPs reaches the critical value of 3 nm, the strength of SERS effect will be greatly enhanced. For the four different types of substrate of Ge, Si, SiO2 (glass) and Al2O3, the SERS effect of Ag on SiO2 > Ge > Al2O3 > Si. For Au and Cu nanoparticles, the SERS effect of them on oxide substrate is stronger than that on non-oxide substrate. In order to verify FDTD simulations, taking silver nanoparticles as an example, and silver nanoparticles prepared by chemical method were spinning coating on the four different substrates with R6G as probe molecules. The results show that the experimental results are consistent with FDTD theoretical simulations, and the SERS enhancement effect of Ag-SiO2 substrate is best. The results of this study have important theoretical significance to explain the variations of SERS enhancement on different noble metals, which is also an important guide for the preparation of SERS substrates, especially for the microfluidics. The better Raman effect can be realized by choosing proper substrate type, particle spacing and excitation wavelength, result in expanding the depth and width of SERS application.

Edge coating apparatus with movable roller applicator for solar cell substrates

DOEpatents

Pavani, Luca; Abas, Emmanuel

2012-12-04

A non-contact edge coating apparatus includes an applicator for applying a coating material on an edge of a solar cell substrate and a control system configured to drive the applicator. The control system may drive the applicator along an axis to maintain a distance with an edge of the substrate as the substrate is rotated to have the edge coated with a coating material. The applicator may include a recessed portion into which the edge of the substrate is received for edge coating. For example, the applicator may be a roller with a groove. Coating material may be introduced into the groove for application onto the edge of the substrate. A variety of coating materials may be employed with the apparatus including hot melt ink and UV curable plating resist.

The effect of spraying parameters on micro-structural properties of WC-12%Co coating deposited on copper substrate by HVOF process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sathwara, Nishit, E-mail: nishit-25@live.in; Metallurgical & Materials Engineering Department, Indus University, Ahmedabad-382115; Jariwala, C., E-mail: chetanjari@yahoo.com

High Velocity Oxy-Fuel (HVOF) thermal sprayed coatingmade from Tungsten Carbide (WC) isconsidered as one of the most durable materials as wear resistance for industrial applications at room temperature. WC coating offers high wear resistance due to its high hardness and tough matrix imparts. The coating properties strongly depend on thermal spray processing parameters, surface preparation and surface finish. In this investigation, the effect of variousHVOF process parameters was studied on WC coating properties. The WC-12%Co coating was produced on Copper substrate. Prior to coating, theCopper substrate surface was prepared by grit blasting. WC-12%Co coatings were deposited on Coppersubstrates with varyingmore » process parameters such as Oxygen gas pressure, Air pressure, and spraying distance. Microstructure of coating was examined using Scanning Electron Microscope (SEM) and characterization of phasespresentin the coating was examined by X-Ray Diffraction (XRD). Microhardness of all coatingswas measured by VickerMicrohardness tester. At low Oxygen Pressure(10.00 bar), high Air pressure (7bar) and short nozzle to substrate distance of 170mm, best coating adhesion and porosity less structure isachieved on Coppersubstrate.« less

The effect of spraying parameters on micro-structural properties of WC-12%Co coating deposited on copper substrate by HVOF process

NASA Astrophysics Data System (ADS)

Sathwara, Nishit; Jariwala, C.; Chauhan, N.; Raole, P. M.; Basa, D. K.

2015-08-01

High Velocity Oxy-Fuel (HVOF) thermal sprayed coatingmade from Tungsten Carbide (WC) isconsidered as one of the most durable materials as wear resistance for industrial applications at room temperature. WC coating offers high wear resistance due to its high hardness and tough matrix imparts. The coating properties strongly depend on thermal spray processing parameters, surface preparation and surface finish. In this investigation, the effect of variousHVOF process parameters was studied on WC coating properties. The WC-12%Co coating was produced on Copper substrate. Prior to coating, theCopper substrate surface was prepared by grit blasting. WC-12%Co coatings were deposited on Coppersubstrates with varying process parameters such as Oxygen gas pressure, Air pressure, and spraying distance. Microstructure of coating was examined using Scanning Electron Microscope (SEM) and characterization of phasespresentin the coating was examined by X-Ray Diffraction (XRD). Microhardness of all coatingswas measured by VickerMicrohardness tester. At low Oxygen Pressure(10.00 bar), high Air pressure (7bar) and short nozzle to substrate distance of 170mm, best coating adhesion and porosity less structure isachieved on Coppersubstrate.

Directed Magnetic Particle Transport above Artificial Magnetic Domains Due to Dynamic Magnetic Potential Energy Landscape Transformation.

PubMed

Holzinger, Dennis; Koch, Iris; Burgard, Stefan; Ehresmann, Arno

2015-07-28

An approach for a remotely controllable transport of magnetic micro- and/or nanoparticles above a topographically flat exchange-bias (EB) thin film system, magnetically patterned into parallel stripe domains, is presented where the particle manipulation is achieved by sub-mT external magnetic field pulses. Superparamagnetic core-shell particles are moved stepwise by the dynamic transformation of the particles' magnetic potential energy landscape due to the external magnetic field pulses without affecting the magnetic state of the thin film system. The magnetic particle velocity is adjustable in the range of 1-100 μm/s by the design of the substrate's magnetic field landscape (MFL), the particle-substrate distance, and the magnitude of the applied external magnetic field pulses. The agglomeration of magnetic particles is avoided by the intrinsic magnetostatic repulsion of particles due to the parallel alignment of the particles' magnetic moments perpendicular to the transport direction and parallel to the surface normal of the substrate during the particle motion. The transport mechanism is modeled by a quantitative theory based on the precise knowledge of the sample's MFL and the particle-substrate distance.

Formation of CuAlO2 Film by Ultrasonic Spray Pyrolysis

NASA Astrophysics Data System (ADS)

Iping, S.; Lockman, Zainovia; Hutagalung, S. D.; Kamsul, A.; Matsuda, Atsunori

2011-10-01

Smooth, crack free and homogenous CuAlO2 film was produced by chemical solution deposition process via spray pyrolysis technique on a cleaned Si substrate. The precursor solution used was comprised of a mixture of 45.87 mmol Cu(NO3)2.3H2O and 90 mmol Al(NO3)3.9H2O at ratio of Cu:Al = 1.2:1. The precursor solution was placed in a mist chamber and was atomized by a nebulizer to produce precursor mist. The precursor mist was then carried out by Ar gas and was sprayed onto a heated Si. Two main parameters were studied: the distance between the nozzle of the precursor mist chamber and the Si and the temperature of the Si substrate. It appears that from the XRD data, CuAlO2 can be detected for samples prepared by spraying the precursor mist at temperature of > 550 °C with distance between the nozzle and the substrate of 3cm. Reaction of the Cu and Al ions in the mist near the substrate may have promoted the crystallisation of CuAlO2.

Effect of grit-blasting on substrate roughness and coating adhesion

NASA Astrophysics Data System (ADS)

Varacalle, Dominic J.; Guillen, Donna Post; Deason, Douglas M.; Rhodaberger, William; Sampson, Elliott

2006-09-01

Statistically designed experiments were performed to compare the surface roughness produced by grit blasting A36/1020 steel using different abrasives. Grit blast media, blast pressure, and working distance were varied using a Box-type statistical design of experiment (SDE) approach. The surface textures produced by four metal grits (HG16, HG18, HG25, and HG40) and three conventional grits (copper slag, coal slag, and chilled iron) were compared. Substrate roughness was measured using surface profilometry and correlated with operating parameters. The HG16 grit produced the highest surface roughness of all the grits tested. Aluminum and zinc-aluminum coatings were deposited on the grit-blasted substrates using the twin-wire electric are (TWEA) process. Bond strength of the coatings was measured with a portable adhesion tester in accordance with ASTM standard D 4541. The coatings on substrates roughened with steel grit exhibit superior bond strength to those prepared with conventional grit. For aluminum coatings sprayed onto surfaces prepared with the HG16 grit, the bond strength was most influenced by current, spray distance, and spray gun pressure (in that order). The highest bond strength for the zinc-aluminum coatings was attained on surfaces prepared using the metal grits.

Diameter Tuning of β-Ga2O3 Nanowires Using Chemical Vapor Deposition Technique.

PubMed

Kumar, Mukesh; Kumar, Vikram; Singh, R

2017-12-01

Diameter tuning of [Formula: see text]-Ga 2 O 3 nanowires using chemical vapor deposition technique have been investigated under various experimental conditions. Diameter of root grown [Formula: see text]-Ga 2 O 3 nanowires having monoclinic crystal structure is tuned by varying separation distance between metal source and substrate. Effect of gas flow rate and mixer ratio on the morphology and diameter of nanowires has been studied. Nanowire diameter depends on growth temperature, and it is independent of catalyst nanoparticle size at higher growth temperature (850-900 °C) as compared to lower growth temperature (800 °C). These nanowires show changes in structural strain value with change in diameter. Band-gap of nanowires increases with decrease in the diameter.

Role of the source to building lateral separation distance in petroleum vapor intrusion.

PubMed

Verginelli, Iason; Capobianco, Oriana; Baciocchi, Renato

2016-06-01

The adoption of source to building separation distances to screen sites that need further field investigation is becoming a common practice for the evaluation of the vapor intrusion pathway at sites contaminated by petroleum hydrocarbons. Namely, for the source to building vertical distance, the screening criteria for petroleum vapor intrusion have been deeply investigated in the recent literature and fully addressed in the recent guidelines issued by ITRC and U.S.EPA. Conversely, due to the lack of field and modeling studies, the source to building lateral distance received relatively low attention. To address this issue, in this work we present a steady-state vapor intrusion analytical model incorporating a piecewise first-order aerobic biodegradation limited by oxygen availability that accounts for lateral source to building separation. The developed model can be used to evaluate the role and relevance of lateral vapor attenuation as well as to provide a site-specific assessment of the lateral screening distances needed to attenuate vapor concentrations to risk-based values. The simulation outcomes showed to be consistent with field data and 3-D numerical modeling results reported in previous studies and, for shallow sources, with the screening criteria recommended by U.S.EPA for the vertical separation distance. Indeed, although petroleum vapors can cover maximum lateral distances up to 25-30m, as highlighted by the comparison of model outputs with field evidences of vapor migration in the subsurface, simulation results by this new model indicated that, regardless of the source concentration and depth, 6m and 7m lateral distances are sufficient to attenuate petroleum vapors below risk-based values for groundwater and soil sources, respectively. However, for deep sources (>5m) and for low to moderate source concentrations (benzene concentrations lower than 5mg/L in groundwater and 0.5mg/kg in soil) the above criteria were found extremely conservative as the model results indicated that for such scenarios the lateral screening distance may be set equal to zero. Copyright © 2016 Elsevier B.V. All rights reserved.

Structure having spatially separated photo-excitable electron-hole pairs and method of manufacturing same

DOEpatents

Liang, Yong [Richland, WA; Daschbach, John L [Richland, WA; Su, Yali [Richland, WA; Chambers, Scott A [Kennewick, WA

2006-08-22

A method for producing quantum dots. The method includes cleaning an oxide substrate and separately cleaning a metal source. The substrate is then heated and exposed to the source in an oxygen environment. This causes metal oxide quantum dots to form on the surface of the substrate.

Structure having spatially separated photo-excitable electron-hole pairs and method of manufacturing same

DOEpatents

Liang, Yong [Richland, WA; Daschbach, John L [Richland, WA; Su, Yali [Richland, WA; Chambers, Scott A [Kennewick, WA

2003-03-18

A method for producing quantum dots. The method includes cleaning an oxide substrate and separately cleaning a metal source. The substrate is then heated and exposed to the source in an oxygen environment. This causes metal oxide quantum dots to form on the surface of the substrate.

Transport of a helicon plasma by a convergent magnetic field for high speed and compact plasma etching

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Motomura, Taisei; Ando, Akira; Kasashima, Yuji; Kikunaga, Kazuya; Uesugi, Fumihiko; Hara, Shiro

2014-10-01

A high density argon plasma produced in a compact helicon source is transported by a convergent magnetic field to the central region of a substrate located downstream of the source. The magnetic field converging near the source exit is applied by a solenoid and further converged by installing a permanent magnet (PM) behind the substrate, which is located downstream of the source exit. Then a higher plasma density above 5 × 1012 cm-3 can be obtained in 0.2 Pa argon near the substrate, compared with the case without the PM. As no noticeable changes in the radially integrated density near the substrate and the power transfer efficiency are detected when testing the source with and without the PM, it can be deduced that the convergent field provided by the PM plays a role in constricting the plasma rather than in improving the plasma production. Furthermore it is applied to physical ion etching of silicon and aluminum substrates; then high etching rates of 6.5 µm min-1 and 8 µm min-1 are obtained, respectively.

Motor scaling by viewing distance of early visual motion signals during smooth pursuit

NASA Technical Reports Server (NTRS)

Zhou, Hui-Hui; Wei, Min; Angelaki, Dora E.

2002-01-01

The geometry of gaze stabilization during head translation requires eye movements to scale proportionally to the inverse of target distance. Such a scaling has indeed been demonstrated to exist for the translational vestibuloocular reflex (TVOR), as well as optic flow-selective translational visuomotor reflexes (e.g., ocular following, OFR). The similarities in this scaling by a neural estimate of target distance for both the TVOR and the OFR have been interpreted to suggest that the two reflexes share common premotor processing. Because the neural substrates of OFR are partly shared by those for the generation of pursuit eye movements, we wanted to know if the site of gain modulation for TVOR and OFR is also part of a major pathway for pursuit. Thus, in the present studies, we investigated in rhesus monkeys whether initial eye velocity and acceleration during the open-loop portion of step ramp pursuit scales with target distance. Specifically, with visual motion identical on the retina during tracking at different distances (12, 24, and 60 cm), we compared the first 80 ms of horizontal pursuit. We report that initial eye velocity and acceleration exhibits either no or a very small dependence on vergence angle that is at least an order of magnitude less than the corresponding dependence of the TVOR and OFR. The results suggest that the neural substrates for motor scaling by target distance remain largely distinct from the main pathway for pursuit.

Particle transport patterns of short-distance soil erosion by wind-driven rain, rain and wind

NASA Astrophysics Data System (ADS)

Marzen, Miriam; Iserloh, Thomas; de Lima, João L. M. P.; Ries, Johannes B.

2015-04-01

Short distance erosion of soil surface material is one of the big question marks in soil erosion studies. The exact measurement of short-distance transported soil particles, prior to the occurrence of overland flow, is a challenge to soil erosion science due to the particular requirements of the experimental setup and test procedure. To approach a quantification of amount and distance of each type of transport, we applied an especially developed multiple-gutter system installed inside the Trier Portable Wind and Rainfall Simulator (PWRS). We measured the amount and travel distance of soil particles detached and transported by raindrops (splash), wind-driven rain (splash-saltation and splash-drift) and wind (saltation). The test setup included three different erosion agents (rain/ wind-driven rain/ wind), two substrates (sandy/ loamy), three surface structures (grain roughness/ rills lengthwise/ rills transversal) and three slope angles (0°/+7°/-7°). The results present detailed transport patterns of the three erosion agents under the varying soil and surface conditions up to a distance of 1.6 m. Under the applied rain intensity and wind velocity, wind-driven rain splash generates the highest erosion. The erodibility and travel distance of the two substrates depend on the erosion agent. The total erosion is slightly higher for the slope angle -7° (downslope), but for wind-driven rain splash, the inclination is not a relevant factor. The effect of surface structures (rills) changes with traveling distance. The wind driven rain splash generates a much higher amount of erosion and a further travel distance of the particles due to the combined action of wind and rain. The wind-driven rain factor appears to be much more significant than the other factors. The study highlights the effects of different erosion agents and surface parameters on short-distance particle transport and the powerful impact of wind-driven rain on soil erosion.

Effect of V2O5 concentration on structural and optical properties of WO3 thin films prepared by RF magnetron sputtering

NASA Astrophysics Data System (ADS)

Meenakshi, M.; Gowthami, V.; Perumal, P.; Sanjeeviraja, C.

2014-10-01

Thin films of WO3 and V2O5 doped WO3 were coated on glass substrates using sputtering targets of diameter 50mm and thickness 5mm with RF power of 100 W and source to substrate distance of 60mm at room temperature for various V2O5 compositions (1, 2, 4, 6 and 10 %). XRD studies revealed that as deposited films were amorphous for all compositions. Morphological studies like Laser Raman and SEM too confirmed this amorphous nature of films. Refractive index (n) and the extinction coefficient (k) were calculated from the optical spectra such as transmittance and absorbance measured over the wavelength range of 200 to 2500nm. The films exhibited transmittance in the range of 80 to 90% in the UV-Vis-NIR region. Optical band gaps were calculated for both direct and indirect transitions. The optical parameters such as optical dispersion energies Eo and Ed, the average dielectric constant (ɛ), average values of the oscillator strength (So), wavelength of single oscillator (λo), and plasma frequency (ωp) were also calculated.

The structural properties of Sn-doped zinc oxide synthesized by hot-tube thermal evaporation

NASA Astrophysics Data System (ADS)

Suhaimi, Syahida; Sakrani, Samsudi; Yatim, Nadhrah Md.; Hashim, Mohd Azman

2018-06-01

The growth of Sn:ZnO nanowires on a silicon substrate using a low thermal evaporation method is reported. A horizontal quartz tube with controlled supply of O2 gas were used to fabricate the samples where Zn and Sn metal powders were previously mixed and heated at 500°C. This allows the reactant vapours to deposit onto the substrate, which placed at a certain distance from the source materials. The samples were characterized using FESEM, EDX and HRTEM measurements. Randomly oriented nanowires were formed with varying dopant concentrations from 3 to 15 at%. It was observed that from FESEM images, when the dopant concentrations were increased, a hexagonal rod with a wire extended at its end was clearly formed and the best images of nanowires were shown at the highest concentration of 15 at% measuring between 26 to 35 nm and roughly 500 nm in diameter and length respectively. The doping process played an important role in order to alter the morphological properties of Sn:ZnO nanowires. Sn:ZnO nanowires have large potential in many applications such as in selected sensor technology including gaseous sensors, liquid sensors and others.

Intrinsic and extrinsic parameters for controlling the growth of organic single-crystalline nanopillars in photovoltaics.

PubMed

Zhang, Yue; Diao, Ying; Lee, Hyunbok; Mirabito, Timothy J; Johnson, Richard W; Puodziukynaite, Egle; John, Jacob; Carter, Kenneth R; Emrick, Todd; Mannsfeld, Stefan C B; Briseno, Alejandro L

2014-10-08

The most efficient architecture for achieving high donor/acceptor interfacial area in organic photovoltaics (OPVs) would employ arrays of vertically interdigitated p- and n- type semiconductor nanopillars (NPs). Such morphology could have an advantage in bulk heterojunction systems; however, precise control of the dimension morphology in a crystalline, interpenetrating architecture has not yet been realized. Here we present a simple, yet facile, crystallization technique for the growth of vertically oriented NPs utilizing a modified thermal evaporation technique that hinges on a fast deposition rate, short substrate-source distance, and ballistic mass transport. A broad range of organic semiconductor materials is beneficial from the technique to generate NP geometries. Moreover, this technique can also be generalized to various substrates, namely, graphene, PEDOT-PSS, ZnO, CuI, MoO3, and MoS2. The advantage of the NP architecture over the conventional thin film counterpart is demonstrated with an increase of power conversion efficiency of 32% in photovoltaics. This technique will advance the knowledge of organic semiconductor crystallization and create opportunities for the fabrication and processing of NPs for applications that include solar cells, charge storage devices, sensors, and vertical transistors.

Understanding auditory distance estimation by humpback whales: a computational approach.

PubMed

Mercado, E; Green, S R; Schneider, J N

2008-02-01

Ranging, the ability to judge the distance to a sound source, depends on the presence of predictable patterns of attenuation. We measured long-range sound propagation in coastal waters to assess whether humpback whales might use frequency degradation cues to range singing whales. Two types of neural networks, a multi-layer and a single-layer perceptron, were trained to classify recorded sounds by distance traveled based on their frequency content. The multi-layer network successfully classified received sounds, demonstrating that the distorting effects of underwater propagation on frequency content provide sufficient cues to estimate source distance. Normalizing received sounds with respect to ambient noise levels increased the accuracy of distance estimates by single-layer perceptrons, indicating that familiarity with background noise can potentially improve a listening whale's ability to range. To assess whether frequency patterns predictive of source distance were likely to be perceived by whales, recordings were pre-processed using a computational model of the humpback whale's peripheral auditory system. Although signals processed with this model contained less information than the original recordings, neural networks trained with these physiologically based representations estimated source distance more accurately, suggesting that listening whales should be able to range singers using distance-dependent changes in frequency content.

Perceptual constancy in auditory perception of distance to railway tracks.

PubMed

De Coensel, Bert; Nilsson, Mats E; Berglund, Birgitta; Brown, A L

2013-07-01

Distance to a sound source can be accurately estimated solely from auditory information. With a sound source such as a train that is passing by at a relatively large distance, the most important auditory information for the listener for estimating its distance consists of the intensity of the sound, spectral changes in the sound caused by air absorption, and the motion-induced rate of change of intensity. However, these cues are relative because prior information/experience of the sound source-its source power, its spectrum and the typical speed at which it moves-is required for such distance estimates. This paper describes two listening experiments that allow investigation of further prior contextual information taken into account by listeners-viz., whether they are indoors or outdoors. Asked to estimate the distance to the track of a railway, it is shown that listeners assessing sounds heard inside the dwelling based their distance estimates on the expected train passby sound level outdoors rather than on the passby sound level actually experienced indoors. This form of perceptual constancy may have consequences for the assessment of annoyance caused by railway noise.

Auditory spatial representations of the world are compressed in blind humans.

PubMed

Kolarik, Andrew J; Pardhan, Shahina; Cirstea, Silvia; Moore, Brian C J

2017-02-01

Compared to sighted listeners, blind listeners often display enhanced auditory spatial abilities such as localization in azimuth. However, less is known about whether blind humans can accurately judge distance in extrapersonal space using auditory cues alone. Using virtualization techniques, we show that auditory spatial representations of the world beyond the peripersonal space of blind listeners are compressed compared to those for normally sighted controls. Blind participants overestimated the distance to nearby sources and underestimated the distance to remote sound sources, in both reverberant and anechoic environments, and for speech, music, and noise signals. Functions relating judged and actual virtual distance were well fitted by compressive power functions, indicating that the absence of visual information regarding the distance of sound sources may prevent accurate calibration of the distance information provided by auditory signals.

Nanoconfinement platform for nanostructure quantification via grazing-transmission X-ray scattering

DOEpatents

Black, Charles T.; Yager, Kevin G.

2017-01-31

A nano-confinement platform that may allow improved quantification of the structural order of nanometer-scale systems. Sample-holder `chips` are designed for the GTSAXS experimental geometry. The platform involves fabricated nanostructured sample holders on and in one or more corners of a substrate support where the sample material of interest is positioned at the corner of the substrate support. In an embodiment, the substrate material making up the substrate support beneath the sample-holding area is removed. A scattering x-ray sample platform includes a substrate support arranged in a parallelepiped form, having a substantially flat base and a substantially flat top surface, the top surface being substantially parallel with the base, the parallelepiped having a plurality of corners. At least one corner of the substrate support has a sample holding area formed in the top surface of the substrate support and within a predetermined distance from the corner. The sample holding area includes a regular array of nano-wells formed in the top surface of the substrate support.

Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

DOEpatents

Lowden, Richard A.

1994-01-01

A process for chemical vapor deposition of crystalline silicon nitride which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide.

Near-field polarization distribution of Si nanoparticles near substrate

NASA Astrophysics Data System (ADS)

Reshetov, S. A.; Vladimirova, Yu. V.; Gevorkian, L. P.; Zadkov, V. N.

2017-01-01

Structure of the near-field intensity and polarization distributions, the latter is described with the generalized 3D Stokes parameters, of a spherical Si subwavelength nanoparticle in a non-magnetic and non-absorbing media near a dielectric substrate has been studied in detail with the help of the Mie theory and an extension of the Weyl's method for the calculation of the reflection of dipole radiation by a flat surface. It is shown that for the nanoparticle near the substrate the interference effects due to the scattering by the nanoparticle and interaction with the substrate play an essential role. We also demonstrate how these effects depend on the dielectric properties of the nanoparticle, its size, distance to the substrate as well as on the polarization, wavelength and incident angle of the external light field.

Roll-to-roll light directed electrophoretic deposition system and method

DOEpatents

Pascall, Andrew J.; Kuntz, Joshua

2017-06-06

A roll-to-roll light directed electrophoretic deposition system and method advances a roll of a flexible electrode web substrate along a roll-to-roll process path, where a material source is positioned to provide on the flexible electrode web substrate a thin film colloidal dispersion of electrically charged colloidal material dispersed in a fluid. A counter electrode is also positioned to come in contact with the thin film colloidal dispersion opposite the flexible electrode web substrate, where one of the counter electrode and the flexible electrode web substrate is a photoconductive electrode. A voltage source is connected to produce an electric potential between the counter electrode and the flexible electrode web substrate to induce electrophoretic deposition on the flexible electrode web substrate when the photoconductive electrode is rendered conductive, and a patterned light source is arranged to illuminate the photoconductive electrode with a light pattern and render conductive illuminated areas of the photoconductive electrode so that a patterned deposit of the electrically charged colloidal material is formed on the flexible electrode web substrate.

Visualization and quantification of magnetic nanoparticles into vesicular systems by combined atomic and magnetic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, C.; Department of Physics, SAPIENZA University of Rome, Piazzale A. Moro 5, 00185, Rome; Corsetti, S.

2015-06-23

We report a phenomenological approach for the quantification of the diameter of magnetic nanoparticles (MNPs) incorporated in non-ionic surfactant vesicles (niosomes) using magnetic force microscopy (MFM). After a simple specimen preparation, i.e., by putting a drop of solution containing MNPs-loaded niosomes on flat substrates, topography and MFM phase images are collected. To attempt the quantification of the diameter of entrapped MNPs, the method is calibrated on the sole MNPs deposited on the same substrates by analyzing the MFM signal as a function of the MNP diameter (at fixed tip-sample distance) and of the tip-sample distance (for selected MNPs). After calibration,more » the effective diameter of the MNPs entrapped in some niosomes is quantitatively deduced from MFM images.« less

Near field Rayleigh wave on soft porous layers.

PubMed

Geebelen, N; Boeckx, L; Vermeir, G; Lauriks, W; Allard, J F; Dazel, O

2008-03-01

Simulations performed for a typical semi-infinite reticulated plastic foam saturated by air show that, at distances less than three Rayleigh wavelengths from the area of mechanical excitation by a circular source, the normal frame velocity is close to the Rayleigh pole contribution. Simulated measurements show that a good order of magnitude estimate of the phase speed and damping can be obtained at small distances from the source. Simulations are also performed for layers of finite thickness, where the phase velocity and damping depend on frequency. They indicate that the normal frame velocity at small distances from the source is always close to the Rayleigh pole contribution and that a good order of magnitude estimate of the phase speed of the Rayleigh wave can be obtained at small distances from the source. Furthermore, simulations show that precise measurements of the damping of the Rayleigh wave need larger distances. Measurements performed on a layer of finite thickness confirm these trends.

Method and system using power modulation and velocity modulation producing sputtered thin films with sub-angstrom thickness uniformity or custom thickness gradients

DOEpatents

Montcalm, Claude [Livermore, CA; Folta, James Allen [Livermore, CA; Walton, Christopher Charles [Berkeley, CA

2003-12-23

A method and system for determining a source flux modulation recipe for achieving a selected thickness profile of a film to be deposited (e.g., with highly uniform or highly accurate custom graded thickness) over a flat or curved substrate (such as concave or convex optics) by exposing the substrate to a vapor deposition source operated with time-varying flux distribution as a function of time. Preferably, the source is operated with time-varying power applied thereto during each sweep of the substrate to achieve the time-varying flux distribution as a function of time. Preferably, the method includes the steps of measuring the source flux distribution (using a test piece held stationary while exposed to the source with the source operated at each of a number of different applied power levels), calculating a set of predicted film thickness profiles, each film thickness profile assuming the measured flux distribution and a different one of a set of source flux modulation recipes, and determining from the predicted film thickness profiles a source flux modulation recipe which is adequate to achieve a predetermined thickness profile. Aspects of the invention include a computer-implemented method employing a graphical user interface to facilitate convenient selection of an optimal or nearly optimal source flux modulation recipe to achieve a desired thickness profile on a substrate. The method enables precise modulation of the deposition flux to which a substrate is exposed to provide a desired coating thickness distribution.

Two odometers in honeybees?

PubMed

Dacke, M; Srinivasan, M V

2008-10-01

Although several studies have examined how honeybees gauge and report the distance and direction of a food source to their nestmates, relatively little is known about how this information is combined to obtain a representation of the position of the food source. In this study we manipulate the amount of celestial compass information available to the bee during flight, and analyse the encoding of spatial information in the waggle dance as well as in the navigation of the foraging bee. We find that the waggle dance encodes information about the total distance flown to the food source, even when celestial compass cues are available only for a part of the journey. This stands in contrast to how a bee gauges distance flown when it navigates back to a food source that it already knows. When bees were trained to find a feeder placed at a fixed distance in a tunnel in which celestial cues were partially occluded and then tested in a tunnel that was fully open to the sky, they searched for the feeder at a distance that corresponds closely to the distance that was flown under the open sky during the training. Thus, when navigating back to a food source, information about distance travelled is disregarded when there is no concurrent input from the celestial compass. We suggest that bees may possess two different odometers - a 'community' odometer that is used to provide information to nestmates via the dance, and a 'personal' odometer that is used by an experienced individual to return to a previously visited source.

Deposition of device quality, low hydrogen content, hydrogenated amorphous silicon at high deposition rates

DOEpatents

Mahan, Archie Harvin; Molenbroek, Edith C.; Gallagher, Alan C.; Nelson, Brent P.; Iwaniczko, Eugene; Xu, Yueqin

2002-01-01

A method of fabricating device quality, thin-film a-Si:H for use as semiconductor material in photovoltaic and other devices, comprising in any order; positioning a substrate in a vacuum chamber adjacent a plurality of heatable filaments with a spacing distance L between the substrate and the filaments; heating the filaments to a temperature that is high enough to obtain complete decomposition of silicohydride molecules that impinge said filaments into Si and H atomic species; providing a flow of silicohydride gas, or a mixture of silicohydride gas containing Si and H, in said vacuum chamber while maintaining a pressure P of said gas in said chamber, which, in combination with said spacing distance L, provides a P.times.L product in a range of 10-300 mT-cm to ensure that most of the Si atomic species react with silicohydride molecules in the gas before reaching the substrate, to thereby grow a a-Si:H film at a rate of at least 50 .ANG./sec.; and maintaining the substrate at a temperature that balances out-diffusion of H from the growing a-Si:H film with time needed for radical species containing Si and H to migrate to preferred bonding sites.

Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

DOEpatents

Lowden, R.A.

1994-04-05

A process for chemical vapor deposition of crystalline silicon nitride is described which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide. 5 figures.

Effects of detector-source distance and detector bias voltage variations on time resolution of general purpose plastic scintillation detectors.

PubMed

Ermis, E E; Celiktas, C

2012-12-01

Effects of source-detector distance and the detector bias voltage variations on time resolution of a general purpose plastic scintillation detector such as BC400 were investigated. (133)Ba and (207)Bi calibration sources with and without collimator were used in the present work. Optimum source-detector distance and bias voltage values were determined for the best time resolution by using leading edge timing method. Effect of the collimator usage on time resolution was also investigated. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effects of near-bed turbulence and micro-topography on macroinvertebrate movements across contrasting gravel-bed surfaces (Invited)

NASA Astrophysics Data System (ADS)

Buffin-Belanger, T. K.; Rice, S. P.; Reid, I.; Lancaster, J.

2009-12-01

Fluvial habitats can be described from a series of physical variables but to adequately address the habitat quality it becomes necessary to develop an understanding that combines the physical variables with the behaviour of the inhabitating organisms. The hypothesis of flow refugia provide a rational that can explain the persistence of macroinvertebrate communities in gravel-bed rivers when spates occur. The movement behaviour of macroinvertebrates is a key element to the flow refugia hypothesis, but little is known about how local near-bed turbulence and bed microtopography may affect macroinvertebrate movements. We reproduced natural gravel-bed substrates with contrasting gravel bed textures in a large flume where we were able to document the movement behaviour of the cased caddisfly Potamophylax latipennis for a specific discharge. The crawling paths and drift events of animals were analysed from video recordings. Characteristics of movements differ from one substrate to another. The crawling speed is higher for the small grain-size substrates but the mean travel distance remains approximately the same between substrates. For each substrate, the animals tended to follow consistent paths across the surface. The number of drift events and mean distance drifted is higher for the small grain-size substrate. ADV measurements close to the boundary allow detailed characterisation of near-bed hydraulic variables, including : skewness coefficients, TKE, UV correlation coefficients and integral time scales from autocorrelation analysis. For these variables, the vertical patterns of turbulence parameters are similar between the substrates but the amplitude of the average values and standard errors vary significantly. The spatial distribution of this variability is considered in relation to the crawling paths. It appears that the animals tend to crawl within areas of the substrate where low flow velocities and low turbulent kinetic energies are found, while sites that insects avoided were characterised by higher elevations, velocities and turbulence.

The Inverse-Square Law with Data Loggers

ERIC Educational Resources Information Center

Bates, Alan

2013-01-01

The inverse-square law for the intensity of light received at a distance from a light source has been verified using various experimental techniques. Typical measurements involve a manual variation of the distance between a light source and a light sensor, usually by sliding the sensor or source along a bench, measuring the source-sensor distance…

Laser device

DOEpatents

Scott, Jill R [Idaho Falls, ID; Tremblay, Paul L [Idaho Falls, ID

2007-07-10

A laser device includes a target position, an optical component separated a distance J from the target position, and a laser energy source separated a distance H from the optical component, distance H being greater than distance J. A laser source manipulation mechanism exhibits a mechanical resolution of positioning the laser source. The mechanical resolution is less than a spatial resolution of laser energy at the target position as directed through the optical component. A vertical and a lateral index that intersect at an origin can be defined for the optical component. The manipulation mechanism can auto align laser aim through the origin during laser source motion. The laser source manipulation mechanism can include a mechanical index. The mechanical index can include a pivot point for laser source lateral motion and a reference point for laser source vertical motion. The target position can be located within an adverse environment including at least one of a high magnetic field, a vacuum system, a high pressure system, and a hazardous zone. The laser source and an electro-mechanical part of the manipulation mechanism can be located outside the adverse environment. The manipulation mechanism can include a Peaucellier linkage.

Laser device

DOEpatents

Scott, Jill R.; Tremblay, Paul L.

2004-11-23

A laser device includes a target position, an optical component separated a distance J from the target position, and a laser energy source separated a distance H from the optical component, distance H being greater than distance J. A laser source manipulation mechanism exhibits a mechanical resolution of positioning the laser source. The mechanical resolution is less than a spatial resolution of laser energy at the target position as directed through the optical component. A vertical and a lateral index that intersect at an origin can be defined for the optical component. The manipulation mechanism can auto align laser aim through the origin during laser source motion. The laser source manipulation mechanism can include a mechanical index. The mechanical index can include a pivot point for laser source lateral motion and a reference point for laser source vertical motion. The target position can be located within an adverse environment including at least one of a high magnetic field, a vacuum system, a high pressure system, and a hazardous zone. The laser source and an electro-mechanical part of the manipulation mechanism can be located outside the adverse environment. The manipulation mechanism can include a Peaucellier linkage.

Mechanical Cell-Cell Communication in Fibrous Networks: The Importance of Network Geometry.

PubMed

Humphries, D L; Grogan, J A; Gaffney, E A

2017-03-01

Cells contracting in extracellular matrix (ECM) can transmit stress over long distances, communicating their position and orientation to cells many tens of micrometres away. Such phenomena are not observed when cells are seeded on substrates with linear elastic properties, such as polyacrylamide (PA) gel. The ability for fibrous substrates to support far reaching stress and strain fields has implications for many physiological processes, while the mechanical properties of ECM are central to several pathological processes, including tumour invasion and fibrosis. Theoretical models have investigated the properties of ECM in a variety of network geometries. However, the effects of network architecture on mechanical cell-cell communication have received little attention. This work investigates the effects of geometry on network mechanics, and thus the ability for cells to communicate mechanically through different networks. Cell-derived displacement fields are quantified for various network geometries while controlling for network topology, cross-link density and micromechanical properties. We find that the heterogeneity of response, fibre alignment, and substrate displacement fields are sensitive to network choice. Further, we show that certain geometries support mechanical communication over longer distances than others. As such, we predict that the choice of network geometry is important in fundamental modelling of cell-cell interactions in fibrous substrates, as well as in experimental settings, where mechanical signalling at the cellular scale plays an important role. This work thus informs the construction of theoretical models for substrate mechanics and experimental explorations of mechanical cell-cell communication.

Deposition of Electrically Conductive Coatings on Castable Polyurethane Elastomers by the Flame Spraying Process

NASA Astrophysics Data System (ADS)

Ashrafizadeh, H.; McDonald, A.; Mertiny, P.

2016-02-01

Deposition of metallic coatings on elastomeric polymers is a challenging task due to the heat sensitivity and soft nature of these materials and the high temperatures in thermal spraying processes. In this study, a flame spraying process was employed to deposit conductive coatings of aluminum-12silicon on polyurethane elastomers. The effect of process parameters, i.e., stand-off distance and air added to the flame spray torch, on temperature distribution and corresponding effects on coating characteristics, including electrical resistivity, were investigated. An analytical model based on a Green's function approach was employed to determine the temperature distribution within the substrate. It was found that the coating porosity and electrical resistance decreased by increasing the pressure of the air injected into the flame spray torch during deposition. The latter also allowed for a reduction of the stand-off distance of the flame spray torch. Dynamic mechanical analysis was performed to investigate the effect of the increase in temperature within the substrate on its dynamic mechanical properties. It was found that the spraying process did not significantly change the storage modulus of the polyurethane substrate material.

Multi-enzyme complexes on DNA scaffolds capable of substrate channelling with an artificial swinging arm

NASA Astrophysics Data System (ADS)

Fu, Jinglin; Yang, Yuhe Renee; Johnson-Buck, Alexander; Liu, Minghui; Liu, Yan; Walter, Nils G.; Woodbury, Neal W.; Yan, Hao

2014-07-01

Swinging arms are a key functional component of multistep catalytic transformations in many naturally occurring multi-enzyme complexes. This arm is typically a prosthetic chemical group that is covalently attached to the enzyme complex via a flexible linker, allowing the direct transfer of substrate molecules between multiple active sites within the complex. Mimicking this method of substrate channelling outside the cellular environment requires precise control over the spatial parameters of the individual components within the assembled complex. DNA nanostructures can be used to organize functional molecules with nanoscale precision and can also provide nanomechanical control. Until now, protein-DNA assemblies have been used to organize cascades of enzymatic reactions by controlling the relative distance and orientation of enzymatic components or by facilitating the interface between enzymes/cofactors and electrode surfaces. Here, we show that a DNA nanostructure can be used to create a multi-enzyme complex in which an artificial swinging arm facilitates hydride transfer between two coupled dehydrogenases. By exploiting the programmability of DNA nanostructures, key parameters including position, stoichiometry and inter-enzyme distance can be manipulated for optimal activity.

Multi-enzyme complexes on DNA scaffolds capable of substrate channelling with an artificial swinging arm.

PubMed

Fu, Jinglin; Yang, Yuhe Renee; Johnson-Buck, Alexander; Liu, Minghui; Liu, Yan; Walter, Nils G; Woodbury, Neal W; Yan, Hao

2014-07-01

Swinging arms are a key functional component of multistep catalytic transformations in many naturally occurring multi-enzyme complexes. This arm is typically a prosthetic chemical group that is covalently attached to the enzyme complex via a flexible linker, allowing the direct transfer of substrate molecules between multiple active sites within the complex. Mimicking this method of substrate channelling outside the cellular environment requires precise control over the spatial parameters of the individual components within the assembled complex. DNA nanostructures can be used to organize functional molecules with nanoscale precision and can also provide nanomechanical control. Until now, protein-DNA assemblies have been used to organize cascades of enzymatic reactions by controlling the relative distance and orientation of enzymatic components or by facilitating the interface between enzymes/cofactors and electrode surfaces. Here, we show that a DNA nanostructure can be used to create a multi-enzyme complex in which an artificial swinging arm facilitates hydride transfer between two coupled dehydrogenases. By exploiting the programmability of DNA nanostructures, key parameters including position, stoichiometry and inter-enzyme distance can be manipulated for optimal activity.

Diffractive phase-shift lithography photomask operating in proximity printing mode.

PubMed

Cirino, Giuseppe A; Mansano, Ronaldo D; Verdonck, Patrick; Cescato, Lucila; Neto, Luiz G

2010-08-02

A phase shift proximity printing lithographic mask is designed, manufactured and tested. Its design is based on a Fresnel computer-generated hologram, employing the scalar diffraction theory. The obtained amplitude and phase distributions were mapped into discrete levels. In addition, a coding scheme using sub-cells structure was employed in order to increase the number of discrete levels, thus increasing the degree of freedom in the resulting mask. The mask is fabricated on a fused silica substrate and an amorphous hydrogenated carbon (a:C-H) thin film which act as amplitude modulation agent. The lithographic image is projected onto a resist coated silicon wafer, placed at a distance of 50 microm behind the mask. The results show a improvement of the achieved resolution--linewidth as good as 1.5 microm--what is impossible to obtain with traditional binary masks in proximity printing mode. Such achieved dimensions can be used in the fabrication of MEMS and MOEMS devices. These results are obtained with a UV laser but also with a small arc lamp light source exploring the partial coherence of this source.

Process for depositing I-125 onto a substrate used to manufacture I-125 sources

DOEpatents

McGovern, James J.; Olynyk, Joseph M.

1988-01-01

The invention relates to a process for depositing I-125 on a substrate which comprises contacting a predetermined surface area of substrate with Xe-125 gas, whereby the Xe-125 decays to I-125 and the I-125 in turn deposits as a solid on the surface of the substrate, the contact being for a time sufficient to deposit at least about 1 microcurie of I-125. I-125 is thereby deposited in a relatively uniform amount over the surface area of the substrate. The substrate is then assayed to determine how much I-125 has been deposited. The substrate is then divided into pieces of measured surface area, each piece therefore containing a measured amount of deposited I-125, and each piece can then be used in the manufacture of an I-125 source.

The Confirmation of the Inverse Square Law Using Diffraction Gratings

ERIC Educational Resources Information Center

Papacosta, Pangratios; Linscheid, Nathan

2014-01-01

Understanding the inverse square law, how for example the intensity of light or sound varies with distance, presents conceptual and mathematical challenges. Students know intuitively that intensity decreases with distance. A light source appears dimmer and sound gets fainter as the distance from the source increases. The difficulty is in…

Method of forming emitters for a back-contact solar cell

DOEpatents

Li, Bo; Cousins, Peter J.; Smith, David D.

2015-09-29

Methods of forming emitters for back-contact solar cells are described. In one embodiment, a method includes forming a first solid-state dopant source above a substrate. The first solid-state dopant source includes a plurality of regions separated by gaps. Regions of a second solid-state dopant source are formed above the substrate by printing.

Method of forming emitters for a back-contact solar cell

DOEpatents

Li, Bo; Cousins, Peter J; Smith, David D

2014-12-16

Methods of forming emitters for back-contact solar cells are described. In one embodiment, a method includes forming a first solid-state dopant source above a substrate. The first solid-state dopant source includes a plurality of regions separated by gaps. Regions of a second solid-state dopant source are formed above the substrate by printing.

Method or forming emitters for a back-contact solar cell

DOEpatents

Li, Bo; Cousins, Peter J.; Smith, David D.

2014-08-12

Methods of forming emitters for back-contact solar cells are described. In one embodiment, a method includes forming a first solid-state dopant source above a substrate. The first solid-state dopant source includes a plurality of regions separated by gaps. Regions of a second solid-state dopant source are formed above the substrate by printing.

A Conceptual Model of the Cognitive Processing of Environmental Distance Information

NASA Astrophysics Data System (ADS)

Montello, Daniel R.

I review theories and research on the cognitive processing of environmental distance information by humans, particularly that acquired via direct experience in the environment. The cognitive processes I consider for acquiring and thinking about environmental distance information include working-memory, nonmediated, hybrid, and simple-retrieval processes. Based on my review of the research literature, and additional considerations about the sources of distance information and the situations in which it is used, I propose an integrative conceptual model to explain the cognitive processing of distance information that takes account of the plurality of possible processes and information sources, and describes conditions under which particular processes and sources are likely to operate. The mechanism of summing vista distances is identified as widely important in situations with good visual access to the environment. Heuristics based on time, effort, or other information are likely to play their most important role when sensory access is restricted.

Comparative study of probability distribution distances to define a metric for the stability of multi-source biomedical research data.

PubMed

Sáez, Carlos; Robles, Montserrat; García-Gómez, Juan Miguel

2013-01-01

Research biobanks are often composed by data from multiple sources. In some cases, these different subsets of data may present dissimilarities among their probability density functions (PDF) due to spatial shifts. This, may lead to wrong hypothesis when treating the data as a whole. Also, the overall quality of the data is diminished. With the purpose of developing a generic and comparable metric to assess the stability of multi-source datasets, we have studied the applicability and behaviour of several PDF distances over shifts on different conditions (such as uni- and multivariate, different types of variable, and multi-modality) which may appear in real biomedical data. From the studied distances, we found information-theoretic based and Earth Mover's Distance to be the most practical distances for most conditions. We discuss the properties and usefulness of each distance according to the possible requirements of a general stability metric.

Substrates of Peltigera Lichens as a Potential Source of Cyanobionts.

PubMed

Zúñiga, Catalina; Leiva, Diego; Carú, Margarita; Orlando, Julieta

2017-10-01

Photobiont availability is one of the main factors determining the success of the lichenization process. Although multiple sources of photobionts have been proposed, there is no substantial evidence confirming that the substrates on which lichens grow are one of them. In this work, we obtained cyanobacterial 16S ribosomal RNA gene sequences from the substrates underlying 186 terricolous Peltigera cyanolichens from localities in Southern Chile and maritime Antarctica and compared them with the sequences of the cyanobionts of these lichens, in order to determine if cyanobacteria potentially available for lichenization were present in the substrates. A phylogenetic analysis of the sequences showed that Nostoc phylotypes dominated the cyanobacterial communities of the substrates in all sites. Among them, an overlap was observed between the phylotypes of the lichen cyanobionts and those of the cyanobacteria present in their substrates, suggesting that they could be a possible source of lichen photobionts. Also, in most cases, higher Nostoc diversity was observed in the lichens than in the substrates from each site. A better understanding of cyanobacterial diversity in lichen substrates and their relatives in the lichens would bring insights into mycobiont selection and the distribution patterns of lichens, providing a background for hypothesis testing and theory development for future studies of the lichenization process.

Rapid low-temperature epitaxial growth using a hot-element assisted chemical vapor deposition process

DOEpatents

Iwancizko, Eugene; Jones, Kim M.; Crandall, Richard S.; Nelson, Brent P.; Mahan, Archie Harvin

2001-01-01

The invention provides a process for depositing an epitaxial layer on a crystalline substrate, comprising the steps of providing a chamber having an element capable of heating, introducing the substrate into the chamber, heating the element at a temperature sufficient to decompose a source gas, passing the source gas in contact with the element; and forming an epitaxial layer on the substrate.

Skyshine at neutron energies less than or equal to 400 MeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alsmiller, A.G. Jr.; Barish, J.; Childs, R.L.

1980-10-01

The dose equivalent at an air-ground interface as a function of distance from an assumed azimuthally symmetric point source of neutrons can be calculated as a double integral. The integration is over the source strength as a function of energy and polar angle weighted by an importance function that depends on the source variables and on the distance from the source to the filed point. The neutron importance function for a source 15 m above the ground emitting only into the upper hemisphere has been calculated using the two-dimensional discrete ordinates code, DOT, and the first collision source code, GRTUNCL,more » in the adjoint mode. This importance function is presented for neutron energies less than or equal to 400 MeV, for source cosine intervals of 1 to .8, .8 to .6 to .4, .4 to .2 and .2 to 0, and for various distances from the source to the field point. As part of the adjoint calculations a photon importance function is also obtained. This importance function for photon energies less than or equal to 14 MEV and for various source cosine intervals and source-to-field point distances is also presented. These importance functions may be used to obtain skyshine dose equivalent estimates for any known source energy-angle distribution.« less

[Study of the effect of heat source separation distance on plasma physical properties in laser-pulsed GMAW hybrid welding based on spectral diagnosis technique].

PubMed

Liao, Wei; Hua, Xue-Ming; Zhang, Wang; Li, Fang

2014-05-01

In the present paper, the authors calculated the plasma's peak electron temperatures under different heat source separation distance in laser- pulse GMAW hybrid welding based on Boltzmann spectrometry. Plasma's peak electron densities under the corresponding conditions were also calculated by using the Stark width of the plasma spectrum. Combined with high-speed photography, the effect of heat source separation distance on electron temperature and electron density was studied. The results show that with the increase in heat source separation distance, the electron temperatures and electron densities of laser plasma did not changed significantly. However, the electron temperatures of are plasma decreased, and the electron densities of are plasma first increased and then decreased.

Space use of a dominant Arctic vertebrate: Effects of prey, sea ice, and land on Pacific walrus resource selection

USGS Publications Warehouse

Beatty, William; Jay, Chadwick V.; Fischbach, Anthony S.; Grebmeier, Jacqueline M.; Taylor, Rebecca L.; Blanchard, Arny L.; Jewett, Stephen C.

2016-01-01

Sea ice dominates marine ecosystems in the Arctic, and recent reductions in sea ice may alter food webs throughout the region. Sea ice loss may also stress Pacific walruses (Odobenus rosmarus divergens), which feed on benthic macroinvertebrates in the Bering and Chukchi seas. However, no studies have examined the effects of sea ice on foraging Pacific walrus space use patterns. We tested a series of hypotheses that examined walrus foraging resource selection as a function of proximity to resting substrates and prey biomass. We quantified walrus prey biomass with 17 benthic invertebrate families, which included bivalves, polychaetes, amphipods, tunicates, and sipunculids. We included covariates for distance to sea ice and distance to land, and systematically developed a series of candidate models to examine interactions among benthic prey biomass and resting substrates. We ranked candidate models with Bayesian Information Criterion and made inferences on walrus resource selection based on the top-ranked model. Based on the top model, biomass of the bivalve family Tellinidae, distance to ice, distance to land, and the interaction of distances to ice and land all positively influenced walrus foraging resource selection. Standardized model coefficients indicated that distance to ice explained the most variation in walrus foraging resource selection followed by Tellinidae biomass. Distance to land and the interaction of distances to ice and land accounted for similar levels of variation. Tellinidae biomass likely represented an index of overall bivalve biomass, indicating walruses focused foraging in areas with elevated levels of bivalve and tellinid biomass. Our results also emphasize the importance of sea ice to walruses. Projected sea ice loss will increase the duration of the open water season in the Chukchi Sea, altering the spatial distribution of resting sites relative to current foraging areas and possibly affecting the spatial structure of benthic communities.

Fundamental Insights into Proton-Coupled Electron Transfer in Soybean Lipoxygenase from Quantum Mechanical/Molecular Mechanical Free Energy Simulations.

PubMed

Li, Pengfei; Soudackov, Alexander V; Hammes-Schiffer, Sharon

2018-02-28

The proton-coupled electron transfer (PCET) reaction catalyzed by soybean lipoxygenase has served as a prototype for understanding hydrogen tunneling in enzymes. Herein this PCET reaction is studied with mixed quantum mechanical/molecular mechanical (QM/MM) free energy simulations. The free energy surfaces are computed as functions of the proton donor-acceptor (C-O) distance and the proton coordinate, and the potential of mean force is computed as a function of the C-O distance, inherently including anharmonicity. The simulation results are used to calculate the kinetic isotope effects for the wild-type enzyme (WT) and the L546A/L754A double mutant (DM), which have been measured experimentally to be ∼80 and ∼700, respectively. The PCET reaction is found to be exoergic for WT and slightly endoergic for the DM, and the equilibrium C-O distance for the reactant is found to be ∼0.2 Å greater for the DM than for WT. The larger equilibrium distance for the DM, which is due mainly to less optimal substrate binding in the expanded binding cavity, is primarily responsible for its higher kinetic isotope effect. The calculated potentials of mean force are anharmonic and relatively soft at shorter C-O distances, allowing efficient thermal sampling of the shorter distances required for effective hydrogen tunneling. The primarily local electrostatic field at the transferring hydrogen is ∼100 MV/cm in the direction to facilitate proton transfer and increases dramatically as the C-O distance decreases. These simulations suggest that the overall protein environment is important for conformational sampling of active substrate configurations aligned for proton transfer, but the PCET reaction is influenced primarily by local electrostatic effects that facilitate conformational sampling of shorter proton donor-acceptor distances required for effective hydrogen tunneling.

An integrated system for dynamic control of auditory perspective in a multichannel sound field

NASA Astrophysics Data System (ADS)

Corey, Jason Andrew

An integrated system providing dynamic control of sound source azimuth, distance and proximity to a room boundary within a simulated acoustic space is proposed for use in multichannel music and film sound production. The system has been investigated, implemented, and psychoacoustically tested within the ITU-R BS.775 recommended five-channel (3/2) loudspeaker layout. The work brings together physical and perceptual models of room simulation to allow dynamic placement of virtual sound sources at any location of a simulated space within the horizontal plane. The control system incorporates a number of modules including simulated room modes, "fuzzy" sources, and tracking early reflections, whose parameters are dynamically changed according to sound source location within the simulated space. The control functions of the basic elements, derived from theories of perception of a source in a real room, have been carefully tuned to provide efficient, effective, and intuitive control of a sound source's perceived location. Seven formal listening tests were conducted to evaluate the effectiveness of the algorithm design choices. The tests evaluated: (1) loudness calibration of multichannel sound images; (2) the effectiveness of distance control; (3) the resolution of distance control provided by the system; (4) the effectiveness of the proposed system when compared to a commercially available multichannel room simulation system in terms of control of source distance and proximity to a room boundary; (5) the role of tracking early reflection patterns on the perception of sound source distance; (6) the role of tracking early reflection patterns on the perception of lateral phantom images. The listening tests confirm the effectiveness of the system for control of perceived sound source distance, proximity to room boundaries, and azimuth, through fine, dynamic adjustment of parameters according to source location. All of the parameters are grouped and controlled together to create a perceptually strong impression of source location and movement within a simulated space.

Direct observation of small cluster mobility and ripening

NASA Technical Reports Server (NTRS)

Heinemann, K.; Poppa, H.

1976-01-01

Direct evidence is reported for the simultaneous occurrence of Ostwald ripening and short-distance cluster mobility during annealing of discontinuous metal films on clean amorphous substrates. The annealing characteristics of very thin particulate deposits of silver on amorphized clean surfaces of single-crystalline thin graphite substrates have been studied by in situ transmission electron microscopy (TEM) under controlled environmental conditions in the temperature range from 25 to 450 C. It was possible to monitor all stages of the experiments by TEM observation of the same specimen area. Slow Ostwald ripening was found to occur over the entire temperature range, but the overriding surface transport mechanism was short-distance cluster mobility. This was concluded from in situ observations of individual particles during annealing and from measurements of cluster size distributions, cluster number densities, area coverages, and mean cluster diameters.

Nanostructure iron-silicon thin film deposition using plasma focus device

NASA Astrophysics Data System (ADS)

Kotb, M.; Saudy, A. H.; Hassaballa, S.; Eloker, M. M.

2013-03-01

The presented study in this paper reports the deposition of nano-structure iron-silicon thin film on a glass substrate using 3.3 KJ Mather-type plasma focus device. The iron-silicon powder was put on the top of hollow copper anode electrode. The deposition was done under different experimental conditions such as numbers of electric discharge shots and angular position of substrate. The film samples were exposed to energetic argon ions generated by plasma focus device at different distances from the top of the central electrode. The exposed samples were then analyzed for their structure and optical properties using X-ray diffraction (XRD) and UV-visible spectroscopy. The structure of iron-silicon thin films deposited using plasma focus device depends on the distance from the anode, the number of focus deposition shots and the angular position of the sample

Biogeomorphic relationships between slope processes and globular Grimmia mosses in Haleakala's Crater (Maui, Hawai’i)

NASA Astrophysics Data System (ADS)

Pérez, Francisco L.

2010-04-01

Globular mosses were found in Haleakala's crater (Maui) at five locations between 2175 and 2725 m; the highest-altitude site, with abundant epilithic mosses growing on alkali-olivine basalt outcrops and a large mossball population, was studied. Mossballs form when moss cushions are dislodged from rocks but continue growing unattached to substrate; detachment agents include rainsplash, desiccation, wind, frost, and disturbance by birds (dark-rumped petrels) that burrow nests under outcrops, or by goats. When loosened, moss polsters are transported down steep (26-34°) slopes by different geomorphic processes, including frost—mainly needle ice—activity, runoff, and wind. Mossballs contained two species, Grimmia trichophylla Grev. and Grimmia torquata Drumm., growing separately or commingled. Weight, size, and various shape indices were determined for 260 specimens. Shape and size were correlated; larger mosses become less spheroidal because heavier specimens are less disturbed by needle ice, remaining immobile for increasingly longer time periods, thus becoming flattened. Distance of downslope transport from source rockwalls was measured for 330 specimens; 83% shifted ≤ 100 cm, but only ˜ 5% had moved > 200-839 cm. Heavier mossballs moved short distances, thus ˜ 88% of all biomass remained within 200 cm from outcrops. Substrate soils were compared with those within globoids; surface site soils were much coarser than mossball grains. Twelve substrate samples had, on average, 21.3% gravel (≥ 2 mm), 6.1% fines (≤ 0.063 mm) and 2.1% organic matter; in contrast, 12 mossballs contained < 0.1% gravel, 47.9% fines, and 34.1% organic matter. G. torquata polsters had slightly finer soil (53.2%) than G. trichophylla (43.5%). This significant fine-grain concentration results as mosses trap aeolian dust among stems and leaves; ˜ 91% of moss grains were ≤ 0.25 mm, but only ˜ 30% of substrate particles measured ≤ 0.25 mm. Such fine texture, along with abundant organic matter contributed by moss growth, generates greater water-storage capacity in globoids (˜ 310%) than in site soils (16.8%); this is ecologically significant for mossball development and survival during drought periods. This area is frequently subjected to freezing temperatures, while fog interception from incoming tradewinds contributes significant moisture amounts to precipitation. Ground disturbance by frost activity seemed significant. Needle ice grows frequently on this slope, as evidenced by widespread presence of miniature sorted stripes, striated soils, fine-earth flags below stones, gaps around stones, and fine-soil raised patches, observed during multiple visits. Biogeomorphic interactions between mossballs and substrate at Haleakala are briefly discussed from the perspective of self-organized criticality, and interpreted to represent a self-replicating moss-dispersal system dependent on slope geomorphic processes.

Universal aspects of adhesion and atomic force microscopy

NASA Technical Reports Server (NTRS)

Banerjea, Amitava; Smith, John R.; Ferrante, John

1990-01-01

Adhesive energies are computed for flat and atomically sharp tips as a function of the normal distance to the substrate. The dependence of binding energies on tip shape is investigated. The magnitudes of the binding energies for the atomic force microscope are found to depend sensitively on tip material, tip shape and the sample site being probed. The form of the energy-distance curve, however, is universal and independent of these variables, including tip shape.

Fully depleted back illuminated CCD

DOEpatents

Holland, Stephen Edward

2001-01-01

A backside illuminated charge coupled device (CCD) is formed of a relatively thick high resistivity photon sensitive silicon substrate, with frontside electronic circuitry, and an optically transparent backside ohmic contact for applying a backside voltage which is at least sufficient to substantially fully deplete the substrate. A greater bias voltage which overdepletes the substrate may also be applied. One way of applying the bias voltage to the substrate is by physically connecting the voltage source to the ohmic contact. An alternate way of applying the bias voltage to the substrate is to physically connect the voltage source to the frontside of the substrate, at a point outside the depletion region. Thus both frontside and backside contacts can be used for backside biasing to fully deplete the substrate. Also, high resistivity gaps around the CCD channels and electrically floating channel stop regions can be provided in the CCD array around the CCD channels. The CCD array forms an imaging sensor useful in astronomy.

Charge-free method of forming nanostructures on a substrate

DOEpatents

Hoffbauer; Mark , Akhadov; Elshan

2010-07-20

A charge-free method of forming a nanostructure at low temperatures on a substrate. A substrate that is reactive with one of atomic oxygen and nitrogen is provided. A flux of neutral atoms of least one of oxygen and nitrogen is generated within a laser-sustained-discharge plasma source and a collimated beam of energetic neutral atoms and molecules is directed from the plasma source onto a surface of the substrate to form the nanostructure. The energetic neutral atoms and molecules in the beam have an average kinetic energy in a range from about 1 eV to about 5 eV.

Deconvolution for three-dimensional acoustic source identification based on spherical harmonics beamforming

NASA Astrophysics Data System (ADS)

Chu, Zhigang; Yang, Yang; He, Yansong

2015-05-01

Spherical Harmonics Beamforming (SHB) with solid spherical arrays has become a particularly attractive tool for doing acoustic sources identification in cabin environments. However, it presents some intrinsic limitations, specifically poor spatial resolution and severe sidelobe contaminations. This paper focuses on overcoming these limitations effectively by deconvolution. First and foremost, a new formulation is proposed, which expresses SHB's output as a convolution of the true source strength distribution and the point spread function (PSF) defined as SHB's response to a unit-strength point source. Additionally, the typical deconvolution methods initially suggested for planar arrays, deconvolution approach for the mapping of acoustic sources (DAMAS), nonnegative least-squares (NNLS), Richardson-Lucy (RL) and CLEAN, are adapted to SHB successfully, which are capable of giving rise to highly resolved and deblurred maps. Finally, the merits of the deconvolution methods are validated and the relationships of source strength and pressure contribution reconstructed by the deconvolution methods vs. focus distance are explored both with computer simulations and experimentally. Several interesting results have emerged from this study: (1) compared with SHB, DAMAS, NNLS, RL and CLEAN all can not only improve the spatial resolution dramatically but also reduce or even eliminate the sidelobes effectively, allowing clear and unambiguous identification of single source or incoherent sources. (2) The availability of RL for coherent sources is highest, then DAMAS and NNLS, and that of CLEAN is lowest due to its failure in suppressing sidelobes. (3) Whether or not the real distance from the source to the array center equals the assumed one that is referred to as focus distance, the previous two results hold. (4) The true source strength can be recovered by dividing the reconstructed one by a coefficient that is the square of the focus distance divided by the real distance from the source to the array center. (5) The reconstructed pressure contribution is almost not affected by the focus distance, always approximating to the true one. This study will be of great significance to the accurate localization and quantification of acoustic sources in cabin environments.

Foraging location and site fidelity of the Double-crested Cormorant on Oneida Lake, New York

USGS Publications Warehouse

Coleman, J.T.H.; Richmond, M.E.; Rudstam, L. G.; Mattison, P.M.

2005-01-01

We studied the foraging behavior of the Double-crested Cormorant (Phalacrocorax auritus) on Oneida Lake, New York, by monitoring the activities of 27 radio-tagged birds in July and August of 1999 and 2000. A total of 224 locations were obtained of cormorants actively diving, and presumed foraging, at the time of detection. A geographic information system was used to examine foraging distances from the nesting island, the water depth and type of substrate at preferred foraging sites, and to estimate kernel home ranges for analysis of individual foraging site fidelity. An explanatory model was developed to determine parameters affecting the distance to cormorant foraging sites. The mean distance to foraging locations of tagged cormorants from the colony site was 2,920 m (SE ?? 180 m, max = 14,190 m), and 52% of the locations were within 2,000 m of the nesting island. No cormorant was observed making daily foraging trips to outside water bodies. Mean foraging distance was greater during morning than in the afternoon, and there was a significant effect of the time of day on distance. There was no significant effect of sex date, a seasonal measure on distance to foraging location. Individual cormorants exhibited fidelity to specific foraging sites. Most cormorants foraged in close proximity to the nesting island much of the time, while those detected further from the island tended to return repeatedly to the same locations. Ninety percent of the foraging locations were in water depths ???7.5 m, and most were in water 2.5-5 m deep. Compositional analysis of habitat use revealed a preference for these depths, along with substrates of cobble with rubble, and silt with clay.

Investigation of the relationship between radon anomalıes in deep water resources near Akşehir fault zone and the radial distances of the sources to an earthquake center

NASA Astrophysics Data System (ADS)

Gümüş, Ayla; Yalım, Hüseyin Ali

2018-02-01

Radon emanation occurs all the rocks and earth containing uranium element. Anomalies in radon concentrations before earthquakes are observed in fault lines, geothermal sources, uranium deposits, volcanic movements. The aim of this study is to investigate the relationship between the radon anomalies in water resources and the radial distances of the sources to the earthquake center. For this purpose, radon concentrations of 9 different deep water sources near Akşehir fault line were determined by taking samples with monthly periods for two years. The relationship between the radon anomalies and the radial distances of the sources to the earthquake center was obtained for the sources.

Fan-beam densitometry of the growing skeleton: are we measuring what we think we are?

PubMed

Cole, Jacqueline H; Scerpella, Tamara A; van der Meulen, Marjolein C H

2005-01-01

Magnification error in fan-beam densitometers varies with distance from the X-ray source to the bone measured and might obscure bone mineral changes in the growing skeleton. Magnification was examined by scanning aluminum rods of different shapes (square, rectangular, solid round, and hollow round) at four distances above the X-ray source in two orientations, with rods aligned parallel (SI) and perpendicular (ML) to the longitudinal axis of the scanning table. Measured area (cm(2)) decreased linearly with distance above the X-ray source for all rods in the SI orientation (p < 0.005). Measured mineral content (g) decreased linearly with distance but only for SI round rods (p < 0.0001) and for ML hollow round rods (p < 0.005). Area and mineral content decreased 1.6-1.8% per centimeter above the source for round rods. Measured mineral density (g/cm(2)) decreased linearly with distance from the source only for ML hollow round rods (p < 0.005). Variation in area, mineral content, and mineral density measurements was 6.6-6.9%, 6.9-7.5%, and 1.9-2.3%, respectively, for SI round rods. Magnification errors of this magnitude are problematic for clinical studies using fan-beam densitometry. Particularly in pediatric subjects, increases in soft tissue during normal growth could increase a bone's distance from the fan-beam source and result in apparent reductions in area and bone mineral content.

Numerical study on the mechanisms of the SERS of gold-coated pyramidal tip substrates.

PubMed

Li, Rui; Wang, Qiao; Li, Hong; Liu, Kun; Pan, Shi; Zhan, Weishen; Chen, Maodu

2016-06-29

In this paper, the physical enhancement mechanisms of the surface-enhanced Raman scattering (SERS) of pyramidal tip substrates are studied theoretically. We structure the periodic square-based arrays of adjacent nanometer pyramidal gold-coated tips on silicon. In order to determine the contribution of plasmonic or diffraction effects on the SERS, three-dimensional (3D) numerical simulations are implemented by taking into account the substrate coated with a gold thin film or a perfect electrical conductor thin film. The tip distance, metal coating thickness and incident light polarization angle are also optimized to investigate whether the further SERS signal can be enhanced.

Correction of the exciton Bohr radius in monolayer transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Li, Run-Ze; Dong, Xi-Ying; Li, Zhi-Qing; Wang, Zi-Wu

2018-07-01

We theoretically investigate the correction of exciton Bohr radius in monolayer transition metal dichalcogenides (TMDCs) on different polar substrates arising from the exciton-optical phonon coupling, in which both the intrinsic longitudinal optical phonon and surface optical phonon modes couple with the exciton are taken into account. We find that the exciton Bohr radius is enlarged markedly due to these coupling. Moreover, it can be changed on a large scale by modulating the polarizability of polar substrate and the internal distance between the monolayer TMDCs and polar substrate. Theoretical result provides a potential explanation for the variation of the exciton Bohr radius in experimental measurement.

Monte Carlo dose calculations of beta-emitting sources for intravascular brachytherapy: a comparison between EGS4, EGSnrc, and MCNP.

PubMed

Wang, R; Li, X A

2001-02-01

The dose parameters for the beta-particle emitting 90Sr/90Y source for intravascular brachytherapy (IVBT) have been calculated by different investigators. At a distant distance from the source, noticeable differences are seen in these parameters calculated using different Monte Carlo codes. The purpose of this work is to quantify as well as to understand these differences. We have compared a series of calculations using an EGS4, an EGSnrc, and the MCNP Monte Carlo codes. Data calculated and compared include the depth dose curve for a broad parallel beam of electrons, and radial dose distributions for point electron sources (monoenergetic or polyenergetic) and for a real 90Sr/90Y source. For the 90Sr/90Y source, the doses at the reference position (2 mm radial distance) calculated by the three code agree within 2%. However, the differences between the dose calculated by the three codes can be over 20% in the radial distance range interested in IVBT. The difference increases with radial distance from source, and reaches 30% at the tail of dose curve. These differences may be partially attributed to the different multiple scattering theories and Monte Carlo models for electron transport adopted in these three codes. Doses calculated by the EGSnrc code are more accurate than those by the EGS4. The two calculations agree within 5% for radial distance <6 mm.

Photo-ionization and modification of nanoparticles on transparent substrates by ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly; Komolov, Vladimir; Li, Hao; Yu, Qingsong; Przhibel'skii, Sergey; Smirnov, Dmitry

2011-02-01

The objective of this combined experimental and theoretical research is to study the dynamics and mechanisms of nanoparticle interaction with ultrashort laser pulses and related modifications of substrate surface. For the experimental effort, metal (gold), dielectric (SiO2) and dielectric with metal coating (about 30 nm thick) spherical nanoparticles deposited on glass substrate are utilized. Size of the particles varies from 20 to 200 nm. Density of the particles varies from low (mean inter-particle distance 100 nm) to high (mean inter-particle distance less than 1 nm). The nanoparticle assemblies and the corresponding empty substrate surfaces are irradiated with single 130-fs laser pulses at wavelength 775 nm and different levels of laser fluence. Large diameter of laser spot (0.5-2 mm) provides gradient variations of laser intensity over the spot and allows observing different laser-nanoparticle interactions. The interactions vary from total removal of the nanoparticles in the center of laser spot to gentle modification of their size and shape and totally non-destructive interaction. The removed particles frequently form specific sub-micrometer-size pits on the substrate surface at their locations. The experimental effort is supported by simulations of the nanoparticle interactions with high-intensity ultrashort laser pulse. The simulation employs specific modification of the molecular dynamics approach applied to model the processes of non-thermal particle ablation following laser-induced electron emission. This technique delivers various characteristics of the ablation plume from a single nanoparticle including energy and speed distribution of emitted ions, variations of particle size and overall dynamics of its ablation. The considered geometry includes single isolated particle as well a single particle on a flat substrate that corresponds to the experimental conditions. The simulations confirm existence of the different regimes of laser-nanoparticle interactions depending on laser intensity and wavelength. In particular, implantation of ions departing from the nanoparticles towards the substrate is predicted.

The distances of the Galactic Novae

NASA Astrophysics Data System (ADS)

Ozdonmez, Aykut; Guver, Tolga; Cabrera-Lavers, Antonio; Ak, Tansel

2016-07-01

Using location of the RC stars on the CMDs obtained from the UKIDSS, VISTA and 2MASS photometry, we have derived the reddening-distance relations towards each Galactic nova for which at least one independent reddening measurement exists. We were able to determine the distances of 72 Galactic novae and set lower limits on the distances of 45 systems. The reddening curves of the systems are presented. These curves can be also used to estimate reddening or the distance of any source, whose location is close to the position of the nova in our sample. The distance measurement method in our study can be easily applicable to any source, especially for ones that concentrated along the Galactic plane.

An active-site phenylalanine directs substrate binding and C-H cleavage in the alpha-ketoglutarate-dependent dioxygenase TauD.

PubMed

McCusker, Kevin P; Klinman, Judith P

2010-04-14

Enzymes that cleave C-H bonds are often found to depend on well-packed hydrophobic cores that influence the distance between the hydrogen donor and acceptor. Residue F159 in taurine alpha-ketoglutarate dioxygenase (TauD) is demonstrated to play an important role in the binding and orientation of its substrate, which undergoes a hydrogen atom transfer to the active site Fe(IV)=O. Mutation of F159 to smaller hydrophobic side chains (L, V, A) leads to substantially reduced rates for substrate binding and for C-H bond cleavage, as well as increased contribution of the chemical step to k(cat) under steady-state turnover conditions. The greater sensitivity of these substrate-dependent processes to mutation at position 159 than observed for the oxygen activation process supports a previous conclusion of modularity of function within the active site of TauD (McCusker, K. P.; Klinman, J. P. Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 19791-19795). Extraction of intrinsic deuterium kinetic isotope effects (KIEs) using single turnover transients shows 2- to 4-fold increase in the size of the KIE for F159V in relation to wild-type and F159L. It appears that there is a break in behavior following removal of a single methylene from the side chain of F159L to generate F159V, whereby the protein active site loses its ability to restore the internuclear distance between substrate and Fe(IV)=O that supports optimal hydrogenic wave function overlap.

Time reversal for localization of sources of infrasound signals in a windy stratified atmosphere.

PubMed

Lonzaga, Joel B

2016-06-01

Time reversal is used for localizing sources of recorded infrasound signals propagating in a windy, stratified atmosphere. Due to the convective effect of the background flow, the back-azimuths of the recorded signals can be substantially different from the source back-azimuth, posing a significant difficulty in source localization. The back-propagated signals are characterized by negative group velocities from which the source back-azimuth and source-to-receiver (STR) distance can be estimated using the apparent back-azimuths and trace velocities of the signals. The method is applied to several distinct infrasound arrivals recorded by two arrays in the Netherlands. The infrasound signals were generated by the Buncefield oil depot explosion in the U.K. in December 2005. Analyses show that the method can be used to substantially enhance estimates of the source back-azimuth and the STR distance. In one of the arrays, for instance, the deviations between the measured back-azimuths of the signals and the known source back-azimuth are quite large (-1° to -7°), whereas the deviations between the predicted and known source back-azimuths are small with an absolute mean value of <1°. Furthermore, the predicted STR distance is off only by <5% of the known STR distance.

Auditory performance in an open sound field

NASA Astrophysics Data System (ADS)

Fluitt, Kim F.; Letowski, Tomasz; Mermagen, Timothy

2003-04-01

Detection and recognition of acoustic sources in an open field are important elements of situational awareness on the battlefield. They are affected by many technical and environmental conditions such as type of sound, distance to a sound source, terrain configuration, meteorological conditions, hearing capabilities of the listener, level of background noise, and the listener's familiarity with the sound source. A limited body of knowledge about auditory perception of sources located over long distances makes it difficult to develop models predicting auditory behavior on the battlefield. The purpose of the present study was to determine the listener's abilities to detect, recognize, localize, and estimate distances to sound sources from 25 to 800 m from the listing position. Data were also collected for meteorological conditions (wind direction and strength, temperature, atmospheric pressure, humidity) and background noise level for each experimental trial. Forty subjects (men and women, ages 18 to 25) participated in the study. Nine types of sounds were presented from six loudspeakers in random order; each series was presented four times. Partial results indicate that both detection and recognition declined at distances greater than approximately 200 m and distance estimation was grossly underestimated by listeners. Specific results will be presented.

Effects of MAR-M247 substrate (modified) composition on coating oxidation coating/substrate interdiffusion. M.S. Thesis. Final Report; [protective coatings for hot section components of gas turbine engines

NASA Technical Reports Server (NTRS)

Pilsner, B. H.

1985-01-01

The effects of gamma+gamma' Mar-M247 substrate composition on gamma+beta Ni-Cr-Al-Zr coating oxidation and coating/substrate interdiffusion were evaluated. These results were also compared to a prior study for a Ni-Cr-Al-Zr coated gamma Ni-Cr-Al substrate with equivalent Al and Cr atomic percentages. Cyclic oxidation behavior at 1130 C was investigated using change in weight curves. Concentration/distance profiles were measured for Al, Cr, Co, W, and Ta. The surface oxides were examined by X-ray diffraction and scanning electron microscopy. The results indicate that variations of Ta and C concentrations in the substrate do not affect oxidation resistance, while additions of grain boundary strengthening elements (Zr, Hf, B) increase oxidation resistance. In addition, the results indicate that oxidation phenomena in gamma+beta/gamma+gamma' Mar-M247 systems have similar characteristics to the l gamma+beta/gamma Ni-Cr-Al system.

On the construction of a time base and the elimination of averaging errors in proxy records

NASA Astrophysics Data System (ADS)

Beelaerts, V.; De Ridder, F.; Bauwens, M.; Schmitz, N.; Pintelon, R.

2009-04-01

Proxies are sources of climate information which are stored in natural archives (e.g. ice-cores, sediment layers on ocean floors and animals with calcareous marine skeletons). Measuring these proxies produces very short records and mostly involves sampling solid substrates, which is subject to the following two problems: Problem 1: Natural archives are equidistantly sampled at a distance grid along their accretion axis. Starting from these distance series, a time series needs to be constructed, as comparison of different data records is only meaningful on a time grid. The time series will be non-equidistant, as the accretion rate is non-constant. Problem 2: A typical example of sampling solid substrates is drilling. Because of the dimensions of the drill, the holes drilled will not be infinitesimally small. Consequently, samples are not taken at a point in distance, but rather over a volume in distance. This holds for most sampling methods in solid substrates. As a consequence, when the continuous proxy signal is sampled, it will be averaged over the volume of the sample, resulting in an underestimation of the amplitude. Whether this averaging effect is significant, depends on the volume of the sample and the variations of interest of the proxy signal. Starting from the measured signal, the continuous signal needs to be reconstructed in order eliminate these averaging errors. The aim is to provide an efficient identification algorithm to identify the non-linearities in the distance-time relationship, called time base distortions, and to correct for the averaging effects. Because this is a parametric method, an assumption about the proxy signal needs to be made: the proxy record on a time base is assumed to be harmonic, this is an obvious assumption because natural archives often exhibit a seasonal cycle. In a first approach the averaging effects are assumed to be in one direction only, i.e. the direction of the axis on which the measurements were performed. The measured averaged proxy signal is modeled by following signal model: -- Δ ∫ n+12Δδ- y(n,θ) = δ- 1Δ- y(m,θ)dm n-2 δ where m is the position, x(m) = Δm; θ are the unknown parameters and y(m,θ) is the proxy signal we want to identify (the proxy signal as found in the natural archive), which we model as: y(m, θ) = A +∑H [A sin(kωt(m ))+ A cos(kωt(m ))] 0 k=1 k k+H With t(m): t(m) = mTS + g(m )TS Here TS = 1/fS is the sampling period, fS the sampling frequency, and g(m) the unknown time base distortion (TBD). In this work a splines approximation of the TBD is chosen: ∑ g(m ) = b blφl(m ) l=1 where, b is a vector of unknown time base distortion parameters, and φ is a set of splines. The estimates of the unknown parameters were obtained with a nonlinear least squares algorithm. The vessel density measured in the mangrove tree R mucronata was used to illustrate the method. The vessel density is a proxy for the rain fall in tropical regions. The proxy data on the newly constructed time base showed a yearly periodicity, this is what we expected and the correction for the averaging effect increased the amplitude by 11.18%.

Method and system using power modulation for maskless vapor deposition of spatially graded thin film and multilayer coatings with atomic-level precision and accuracy

DOEpatents

Montcalm, Claude [Livermore, CA; Folta, James Allen [Livermore, CA; Tan, Swie-In [San Jose, CA; Reiss, Ira [New City, NY

2002-07-30

A method and system for producing a film (preferably a thin film with highly uniform or highly accurate custom graded thickness) on a flat or graded substrate (such as concave or convex optics), by sweeping the substrate across a vapor deposition source operated with time-varying flux distribution. In preferred embodiments, the source is operated with time-varying power applied thereto during each sweep of the substrate to achieve the time-varying flux distribution as a function of time. A user selects a source flux modulation recipe for achieving a predetermined desired thickness profile of the deposited film. The method relies on precise modulation of the deposition flux to which a substrate is exposed to provide a desired coating thickness distribution.

Pulsed laser deposition of lithium niobate thin films

NASA Astrophysics Data System (ADS)

Canale, L.; Girault-Di Bin, C.; Cosset, F.; Bessaudou, A.; Celerier, A.; Decossas, J.-Louis; Vareille, J.-C.

2000-12-01

Pulsed laser deposition of Lithium Niobate thin films onto sapphire (0001) substrates is reported. Thin films composition and structure have been determined using Rutherford Backscattermg Spectroscopy (RBS) and X-ray diffraction ( XRD) experiments. The influe:nce of deposition parameters such as substrate temperature, oxygen pressure and target to substrate distance on the composition and the structure of the films has been studied. Deposition temperature is found to be an important parameter which enables us to grow LiNbO3 films without the Li deficient phase LiNb3O8. Nearly stoichiometric thin fihns have been obtained for an oxygen pressure of 0. 1 Ton and a substrate temperature of 800°C. Under optimized conditions the (001) preferential orientation of growth, suitable for most optical applications, has been obtained.

The Role of Work Function and Band Gap in Resistive Switching Behaviour of ZnTe Thin Films

NASA Astrophysics Data System (ADS)

Rowtu, Srinu; Sangani, L. D. Varma; Krishna, M. Ghanashyam

2018-02-01

Resistive switching behavior by engineering the electrode work function and band gap of ZnTe thin films is demonstrated. The device structures Au/ZnTe/Au, Au/ZnTe/Ag, Al/ZnTe/Ag and Pt/ZnTe/Ag were fabricated. ZnTe was deposited by thermal evaporation and the stoichiometry and band gap were controlled by varying the source-substrate distance. Band gap could be varied between 1.0 eV to approximately 4.0 eV with the larger band gap being attributed to the partial oxidation of ZnTe. The transport characteristics reveal that the low-resistance state is ohmic in nature which makes a transition to Poole-Frenkel defect-mediated conductivity in the high-resistance states. The highest R off-to- R on ratio achieved is 109. Interestingly, depending on stoichiometry, both unipolar and bipolar switching can be realized.

Cell adhesion and proliferation on poly(tetrafluoroethylene) with plasma-metal and plasma-metal-carbon interfaces

NASA Astrophysics Data System (ADS)

Reznickova, Alena; Kvitek, Ondrej; Kolarova, Katerina; Smejkalova, Zuzana; Svorcik, Vaclav

2017-06-01

The aim of this article is to investigate the effect of the interface between plasma activated, gold and carbon coated poly(tetrafluoroethylene) (PTFE) on in vitro adhesion and spreading of mouse fibroblasts (L929). Surface properties of pristine and modified PTFE were studied by several experimental techniques. The thickness of a deposited gold film is an increasing function of the sputtering time, conversely thickness of carbon layer decreases with increasing distance between carbon source and the substrate. Because all the used surface modification techniques take place in inert Ar plasma, oxidized degradation products are formed on the PTFE surface, which affects wettability of the polymer surface. Cytocompatibility tests indicate that on samples with Au/C interface, the cells accumulate on the part of sample with evaporated carbon. Number of L929 cells proliferated on the studied samples is comparable to tissue culture polystyrene standard.

Structural and Mechanistic Insights into C-P Bond Hydrolysis by Phosphonoacetate Hydrolase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agarwal, Vinayak; Borisova, Svetlana A.; Metcalf, William W.

2011-12-22

Bacteria have evolved pathways to metabolize phosphonates as a nutrient source for phosphorus. In Sinorhizobium meliloti 1021, 2-aminoethylphosphonate is catabolized to phosphonoacetate, which is converted to acetate and inorganic phosphate by phosphonoacetate hydrolase (PhnA). Here we present detailed biochemical and structural characterization of PhnA that provides insights into the mechanism of C-P bond cleavage. The 1.35 {angstrom} resolution crystal structure reveals a catalytic core similar to those of alkaline phosphatases and nucleotide pyrophosphatases but with notable differences, such as a longer metal-metal distance. Detailed structure-guided analysis of active site residues and four additional cocrystal structures with phosphonoacetate substrate, acetate, phosphonoformatemore » inhibitor, and a covalently bound transition state mimic provide insight into active site features that may facilitate cleavage of the C-P bond. These studies expand upon the array of reactions that can be catalyzed by enzymes of the alkaline phosphatase superfamily.« less

Stability of an optically contacted etalon to cosmic radiation. [aboard Dynamics Explorer satellite

NASA Technical Reports Server (NTRS)

Killeen, T. L.; Dettman, D. L.; Hays, P. B.

1980-01-01

An investigation has been completed to determine the effects of prolonged exposure to cosmic radiation on Zerodur spacing elements used between two dielectric reflectors on silica substrates in the plane Fabry-Perot etalon selected for flight in the Dynamics Explorer satellite. The measured radiation expansion coefficient for Zerodur is approximately -4.0 x 10 to the -12th/rad. In addition to the overall change in gap dimension, test data indicate a degradation in etalon parallelism, which is ascribed to the different doses received by the three spacers due to their differing distances from a Co-60 source. The effect is considered to be of practical use in the tuning and parallelism adjustment of fixed gap etalons. The variation is small enough not to pose a problem for the satellite instrument where expected radiation doses are less than 10,000 rads.

Effect of Cultural Distance on Translation of Culture-Bound Texts

ERIC Educational Resources Information Center

Rafieyan, Vahid

2016-01-01

Sociolinguistic and sociocultural features of the source language can be ideally transferred to the target language when the translator's cultural background knowledge has a high overlap with the source language culture. This signifies the crucial role of national cultural distance from the source language society in the quality of translation of…

A Citation Analysis of Psychology Students' Use of Sources in Online Distance Learning

ERIC Educational Resources Information Center

Weaver, Nancy Evans; Barnard, Estelle

2015-01-01

Reference lists from two assignments of psychology students in university-level online distance learning (ODL) were analyzed for number and type of sources and mark achieved. Most referenced were resources relevant to the assignment and provided by instructors. Use changed across assignments: Instructor sources were used more on the first…

Methodology to set up nozzle-to-substrate gap for high resolution electrohydrodynamic jet printing

NASA Astrophysics Data System (ADS)

Park, Jaehong; Park, Ji-Woon; Nasrabadi, Ali Mohamadi; Hwang, Jungho

2016-09-01

Several efforts have been made for the prediction of jet diameter in electrohydrodynamic jet printing; however, not much attention has been paid to the jet length, which is the distance from the cone apex to the location where the jet is unstable and is broken into atomized droplets. In this study, we measured both the cone length and the jet length using a high-speed camera, and measured the line pattern width with an optical microscope to investigate the effects of cone length and jet length on the pattern quality. Measurements were carried out with variations in nozzle diameter, flow rate, and applied voltage. The pattern width was theoretically predicted for the case when the nozzle-to-substrate distance was more than the cone length, and smaller than the summation of the cone and jet lengths (which is the case when there is no jet breakup).

Long distance spin communication in chemical vapour deposited graphene

NASA Astrophysics Data System (ADS)

Kamalakar, M. Venkata; Groenveld, Christiaan; Dankert, André; Dash, Saroj P.

2015-04-01

Graphene is an ideal medium for long-distance spin communication in future spintronic technologies. So far, the prospect is limited by the smaller sizes of exfoliated graphene flakes and lower spin transport properties of large-area chemical vapour-deposited (CVD) graphene. Here we demonstrate a high spintronic performance in CVD graphene on SiO2/Si substrate at room temperature. We show pure spin transport and precession over long channel lengths extending up to 16 μm with a spin lifetime of 1.2 ns and a spin diffusion length ~6 μm at room temperature. These spin parameters are up to six times higher than previous reports and highest at room temperature for any form of pristine graphene on industrial standard SiO2/Si substrates. Our detailed investigation reinforces the observed performance in CVD graphene over wafer scale and opens up new prospects for the development of lateral spin-based memory and logic applications.

Modular injector integrated linear apparatus with motion profile optimization for spatial atomic layer deposition.

PubMed

Wang, Xiaolei; Li, Yun; Lin, Jilong; Shan, Bin; Chen, Rong

2017-11-01

A spatial atomic layer deposition apparatus integrated with a modular injector and a linear motor has been designed. It consists of four parts: a precursor delivery manifold, a modular injector, a reaction zone, and a driving unit. An injector with multi-layer structured channels is designed to help improve precursor distribution homogeneity. During the back and forth movement of the substrate at high speed, the inertial impact caused by jerk and sudden changes of acceleration will degrade the film deposition quality. Such residual vibration caused by inertial impact will aggravate the fluctuation of the gap distance between the injector and the substrate in the deposition process. Thus, an S-curve motion profile is implemented to reduce the large inertial impact, and the maximum position error could be reduced by 84%. The microstructure of the film under the S-curve motion profile shows smaller root-mean-square and scanning voltage amplitude under an atomic force microscope, which verifies the effectiveness of the S-curve motion profile in reducing the residual vibration and stabilizing the gap distance between the injector and the substrate. The film deposition rate could reach 100 nm/min while maintaining good uniformity without obvious periodic patterns on the surface.

Modular injector integrated linear apparatus with motion profile optimization for spatial atomic layer deposition

NASA Astrophysics Data System (ADS)

Wang, Xiaolei; Li, Yun; Lin, Jilong; Shan, Bin; Chen, Rong

2017-11-01

A spatial atomic layer deposition apparatus integrated with a modular injector and a linear motor has been designed. It consists of four parts: a precursor delivery manifold, a modular injector, a reaction zone, and a driving unit. An injector with multi-layer structured channels is designed to help improve precursor distribution homogeneity. During the back and forth movement of the substrate at high speed, the inertial impact caused by jerk and sudden changes of acceleration will degrade the film deposition quality. Such residual vibration caused by inertial impact will aggravate the fluctuation of the gap distance between the injector and the substrate in the deposition process. Thus, an S-curve motion profile is implemented to reduce the large inertial impact, and the maximum position error could be reduced by 84%. The microstructure of the film under the S-curve motion profile shows smaller root-mean-square and scanning voltage amplitude under an atomic force microscope, which verifies the effectiveness of the S-curve motion profile in reducing the residual vibration and stabilizing the gap distance between the injector and the substrate. The film deposition rate could reach 100 nm/min while maintaining good uniformity without obvious periodic patterns on the surface.

Seasonal movement and mesohabitat usage of adult and juvenile lake sturgeon in the Grasse River, New York

USGS Publications Warehouse

Trested, D.G.; Chan, Matthew D.; Bridges, W.C.; Isely, J.J.

2011-01-01

Long-term restoration efforts for lake sturgeon Acipenser fulvescens populations will benefit from better understanding of this species' movements and habitat use in riverine systems. Radio transmitters were implanted in both juvenile and adult lake sturgeon in the Grasse River, New York, and individuals were relocated over a 2-year period. Adult lake sturgeon demonstrated greater minimum daily distance moved, absolute distance moved, and mean home range size than juvenile lake sturgeon during the spring. During the course of the study, both adult and juvenile lake sturgeon exhibited movements upstream and downstream through a breached low-head weir, and individuals did not necessarily remain resident on an annual basis in the Grasse River. Mesohabitat and substrate use patterns were determined based on comparisons of frequency distributions for relocated lake sturgeon and quantified mesohabitat and substrate over a 15-km river reach. Lake sturgeon used pool mesohabitat and limited their use of run mesohabitat under both low- and mid-flow conditions. During most of the year, adult and juvenile lake sturgeon were detected over silt substrate. This study illustrates behavioral differences and similarities between the movements and habitat use of adult and juvenile lake sturgeon in a riverine system.

Optimal properties for coated titanium implants with the hydroxyapatite layer formed by the pulsed laser deposition technique

NASA Astrophysics Data System (ADS)

Himmlova, Lucia; Dostalova, Tatjana; Jelinek, Miroslav; Bartova, Jirina; Pesakova, V.; Adam, M.

1999-02-01

Pulsed laser deposition technique allow to 'tailor' bioceramic coat for metal implants by the change of deposition conditions. Each attribute is influenced by the several deposition parameters and each parameter change several various properties. Problem caused that many parameters has an opposite function and improvement of one property is followed by deterioration of other attribute. This study monitor influence of each single deposition parameter and evaluate its importance form the point of view of coat properties. For deposition KrF excimer laser in stainless-steel deposition chamber was used. Deposition conditions (ambient composition and pressures, metallic substrate temperature, energy density and target-substrate distance) were changed according to the film properties. A non-coated titanium implant was used as a control. Films with promising mechanical quality underwent an in vitro biological tests -- measurement of proliferation activity, observing cell interactions with macrophages, fibroblasts, testing toxicity of percolates, observing a solubility of hydroxyapatite (HA) coat. Deposition conditions corresponding with the optimal mechanical and biochemical properties are: metal temperature 490 degrees Celsius, ambient-mixture of argon and water vapor, energy density 3 Jcm-2, target-substrate distance 7.5 cm.

Heat Flux Analysis of a Reacting Thermite Spray Impingent on a Substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eric S. Collins; Michelle L. Pantoya; Michael A. Daniels

2012-03-01

Spray combustion from a thermite reaction is a new area of research relevant to localized energy generation applications, such as welding or cutting. In this study, we characterized the heat flux of combustion spray impinging on a target from a nozzle for three thermite mixtures. The reactions studied include aluminum (Al) with iron oxide (Fe2O3), Al with copper oxide (CuO), and Al with molybdenum oxide (MoO3). Several standoff distances (i.e., distance from the nozzle exit to the target) were analyzed. A fast response heat flux sensor was engineered for this purpose and is discussed in detail. Results correlated substrate damagemore » to a threshold heat flux of 4550 W/cm2 for a fixed-nozzle configuration. Also, higher gas-generating thermites were shown to produce a widely dispersed spray and be less effective at imparting kinetic energy damage to a target. These results provide an understanding of the role of thermal and physical properties (i.e., such as heat of combustion, gas generation, and particle size) on thermite spray combustion performance measured by damaging a target substrate.« less

Nanofork for single cells adhesion measurement via ESEM-nanomanipulator system.

PubMed

Ahmad, Mohd Ridzuan; Nakajima, Masahiro; Kojima, Masaru; Kojima, Seiji; Homma, Michio; Fukuda, Toshio

2012-03-01

In this paper, single cells adhesion force was measured using a nanofork. The nanofork was used to pick up a single cell on a line array substrate inside an environmental scanning electron microscope (ESEM). The line array substrate was used to provide small gaps between the single cells and the substrate. Therefore, the nanofork could be inserted through these gaps in order to successfully pick up a single cell. Adhesion force was measured during the cell pick-up process from the deflection of the cantilever beam. The nanofork was fabricated using focused ion beam (FIB) etching process while the line array substrate was fabricated using nanoimprinting technology. As to investigate the effect of contact area on the strength of the adhesion force, two sizes of gap distance of line array substrate were used, i.e., 1 μm and 2 μm. Results showed that cells attached on the 1 μm gap line array substrate required more force to be released as compared to the cells attached on the 1 μm gap line array substrate.

Development and evaluation of a boat-mounted RFID antenna for monitoring freshwater mussels

USGS Publications Warehouse

Fischer, Jesse R.; Neebling, Travis E.; Quist, Michael C.

2012-01-01

Development of radio frequency identification (RFID) technology and passive integrated transponder (PIT) tags has substantially increased the ability of researchers and managers to monitor populations of aquatic organisms. However, use of transportable RFID antenna systems (i.e., backpack-mounted) is currently limited to wadeable aquatic environments (<1.4 m water depth). We describe the design, construction, and evaluation of a boat-mounted RFID antenna to detect individually PIT-tagged benthic aquatic organisms (mussels). We evaluated the effects of tag orientation on detection distances in water with a 32-mm half-duplex PIT tag. Detection distances up to 50 cm from the antenna coils were obtained, but detection distance was dependent on tag orientation. We also evaluated detection distance of PIT tags beneath the sediment to simulate detection of burrowing mussels with 23- and 32-mm tags. In sand substrate, the maximum detection distance varied from 3.5 cm and 4.5 cm (vertical tag orientation) to 24.7 cm and 39.4 cm (45° tag orientation) for the 23- and 32-mm PIT tags, respectively. Our results suggest a 1.4-m total detection width for tagged mussels on the substrate surface by the boat-mounted antenna system regardless of tag orientation. However, burrowed mussels may require multiple passes to increase detection that would be influenced by depth, tag orientation, and tag size. Construction of the boat-mounted antenna was relatively low in cost (<500 USD) and had several advantages (less labor and time intensive, increased safety) over traditional mussel sampling techniques (diving, snorkeling) in nonwadeable habitats.

Adaption of a microwave plasma source for low temperature diamond deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulczynski, M.; Reinhard, D.K.; Asmussen, J.

1996-12-31

This report describes the adaption of a microwave plasma reactor for low temperature diamond deposition. The reactor is of a resonant cavity design. Three approaches have been taken to establish plasma conditions for diamond deposition on substrates which are in the range of 450 C to 550 C. In the first, the substrate is heated only by the plasma and the source is operated at pressures on the order of 10 torr, such that the volumetric power density is sufficiently low to achieve these temperatures. In the second, the plasma pressure and microwave input power were reduced and a substratemore » heater was used to maintain the desired deposition temperatures. In the third approach, the plasma pressure and microwave power were increased and a substrate cooler was used to keep the substrate temperature in the desired range. Reactor performance and deposition results will be described for the three configurations. For the plasma heated substrate assembly, substrate dimensions were up to 10 cm diameter. For the heated and cooled substrate assemblies, substrate dimensions were up to 7.5 cm diameter. Deposition results on a variety of substrates will be reported including low-temperature substrates such as borosilicate glass.« less

Multilevel assessment of fish species traits to evaluate habitat degradation in streams of the upper midwest

USGS Publications Warehouse

Goldstein, R.M.; Meador, M.R.

2005-01-01

We used species traits to examine the variation in fish assemblages for 21 streams in the Northern Lakes and Forests Ecoregion along a gradient of habitat disturbance. Fish species were classified based on five species trait-classes (trophic ecology, substrate preference, geomorphic preference, locomotion morphology, and reproductive strategy) and 29 categories within those classes. We used a habitat quality index to define a reference stream and then calculated Euclidean distances between the reference and each of the other sites for the five traits. Three levels of species trait analyses were conducted: (1) a composite measure (the sum of Euclidean distances across all five species traits), (2) Euclidean distances for the five individual species trait-classes, and (3) frequencies of occurrence of individual trait categories. The composite Euclidean distance was significantly correlated to the habitat index (r = -0.81; P = 0.001), as were the Euclidean distances for four of the five individual species traits (substrate preference: r = -0.70, P = 0.001; geomorphic preference: r = -0.69, P = 0.001; trophic ecology: r = -0.73, P = 0.001; and reproductive strategy: r = -0.64, P = 0.002). Although Euclidean distances for locomotion morphology were not significantly correlated to habitat index scores (r = -0.21; P = 0.368), analysis of variance and principal components analysis indicated that Euclidean distances for locomotion morphology contributed to significant variation in the fish assemblages among sites. Examination of trait categories indicated that low habitat index scores (degraded streams) were associated with changes in frequency of occurrence within the categories of all five of the species traits. Though the objectives and spatial scale of a study will dictate the level of species trait information required, our results suggest that species traits can provide critical information at multiple levels of data analysis. ?? Copyright by the American Fisheries Society 2005.

An iterative method for the localization of a neutron source in a large box (container)

NASA Astrophysics Data System (ADS)

Dubinski, S.; Presler, O.; Alfassi, Z. B.

2007-12-01

The localization of an unknown neutron source in a bulky box was studied. This can be used for the inspection of cargo, to prevent the smuggling of neutron and α emitters. It is important to localize the source from the outside for safety reasons. Source localization is necessary in order to determine its activity. A previous study showed that, by using six detectors, three on each parallel face of the box (460×420×200 mm 3), the location of the source can be found with an average distance of 4.73 cm between the real source position and the calculated one and a maximal distance of about 9 cm. Accuracy was improved in this work by applying an iteration method based on four fixed detectors and the successive iteration of positioning of an external calibrating source. The initial positioning of the calibrating source is the plane of detectors 1 and 2. This method finds the unknown source location with an average distance of 0.78 cm between the real source position and the calculated one and a maximum distance of 3.66 cm for the same box. For larger boxes, localization without iterations requires an increase in the number of detectors, while localization with iterations requires only an increase in the number of iteration steps. In addition to source localization, two methods for determining the activity of the unknown source were also studied.

Masks For Deposition Of Aspherical Optical Surfaces

NASA Technical Reports Server (NTRS)

Rogers, John R.; Martin, John D.

1992-01-01

Masks of improved design developed for use in fabrication of aspherical, rotationally symmetrical surfaces of mirrors, lenses, and lens molds by evaporative deposition onto rotating substrates. In deposition chamber, source and mask aligned with axis of rotation of substrate. Mask shadows source of rotating substrate. Azimuthal opening (as function of radius) in mask proportional to desired thickness (as function of radius) to which material deposited on substrate. Combination of improved masks and modern coating chambers provides optical surfaces comparable or superior to those produced by conventional polishing, computer-controlled polishing, replication from polished molds, and diamond turning, at less cost in material, labor, and capital expense.

Drop Impact Dynamics with Sessile Drops and Geometries: Spreading, Jetting, and Fragmentation

NASA Astrophysics Data System (ADS)

Tilger, Christopher F.

The tendency of surface tension to cause small parcels of fluid to form into drops allows convenient packaging, transport, dispersal of liquid phase matter. Liquid drop impacts with solids, liquids, and other drops have realized and additional future applications in biological, manufacturing, heat transfer, and combustion systems. Experiments were conducted to investigate the dynamics of multiple drop collisions, rather than the most-studied phenomenon of single drop impacts. Additional drop impacts were performed on rigid hemispheres representing sessile drops, angled substrates, and into the vertex of two tilted surfaces arranged into a vee shape. A qualitative inspection of drop-sessile drop impacts shows distinct post-impact shapes depending on the offset distance between the drops. At intermediate offset distances, distinct jets issue from the overlap region between the two drops projected areas. These jets are observed to reach their maximum extent at a critical offset distance ratio, epsilon epsilon ˜ 0.75-0.80, with substrate contact angle and W e having a lesser effect. Capillary waves that traverse the sessile drop after collision cause a lower aspect ratio liquid column to emanate from the sessile drop opposite the impact. In order to better understand the jetting phenomenon seen in the offset drop-sessile drop impacts, simpler solid geometries are investigated that elicit a similar behavior. Solid hemispheres do not show the singular jetting observed in the fluidic case, however, a simple vee formed by two intersection planar substrates do jet in a similar fashion to the fluidic case. A geometric model with partnered experiments is developed to describe the bisymmetric spread of an impacting drop on an angled substrate. This geometric model is used to guide a time of arrival based model for various features of the drop impact, which is used to predict jetting in various vee channel experiments.

THE BOLOCAM GALACTIC PLANE SURVEY. XII. DISTANCE CATALOG EXPANSION USING KINEMATIC ISOLATION OF DENSE MOLECULAR CLOUD STRUCTURES WITH {sup 13}CO(1-0)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ellsworth-Bowers, Timothy P.; Glenn, Jason; Rosolowsky, Erik

2015-01-20

We present an expanded distance catalog for 1710 molecular cloud structures identified in the Bolocam Galactic Plane Survey (BGPS) version 2, representing a nearly threefold increase over the previous BGPS distance catalog. We additionally present a new method for incorporating extant data sets into our Bayesian distance probability density function (DPDF) methodology. To augment the dense-gas tracers (e.g., HCO{sup +}(3-2), NH{sub 3}(1,1)) used to derive line-of-sight velocities for kinematic distances, we utilize the Galactic Ring Survey (GRS) {sup 13}CO(1-0) data to morphologically extract velocities for BGPS sources. The outline of a BGPS source is used to select a region ofmore » the GRS {sup 13}CO data, along with a reference region to subtract enveloping diffuse emission, to produce a line profile of {sup 13}CO matched to the BGPS source. For objects with a HCO{sup +}(3-2) velocity, ≈95% of the new {sup 13}CO(1-0) velocities agree with that of the dense gas. A new prior DPDF for kinematic distance ambiguity (KDA) resolution, based on a validated formalism for associating molecular cloud structures with known objects from the literature, is presented. We demonstrate this prior using catalogs of masers with trigonometric parallaxes and H II regions with robust KDA resolutions. The distance catalog presented here contains well-constrained distance estimates for 20% of BGPS V2 sources, with typical distance uncertainties ≲ 0.5 kpc. Approximately 75% of the well-constrained sources lie within 6 kpc of the Sun, concentrated in the Scutum-Centaurus arm. Galactocentric positions of objects additionally trace out portions of the Sagittarius, Perseus, and Outer arms in the first and second Galactic quadrants, and we also find evidence for significant regions of interarm dense gas.« less

Compact ion source neutron generator

DOEpatents

Schenkel, Thomas; Persaud, Arun; Kapadia, Rehan; Javey, Ali; Chang-Hasnain, Constance; Rangelow, Ivo; Kwan, Joe

2015-10-13

A neutron generator includes a conductive substrate comprising a plurality of conductive nanostructures with free-standing tips and a source of an atomic species to introduce the atomic species in proximity to the free-standing tips. A target placed apart from the substrate is voltage biased relative to the substrate to ionize and accelerate the ionized atomic species toward the target. The target includes an element capable of a nuclear fusion reaction with the ionized atomic species to produce a one or more neutrons as a reaction by-product.

Substrate strain induced interaction of adatoms on W (110)

NASA Astrophysics Data System (ADS)

Kappus, W.

1980-09-01

The interaction of adatoms due to elastic strains created in an elastically isotropic substrate is investigated. For cases where the adatoms occupy sites with low symmetry, an angular dependent interaction results which falls off as s-3 at large distances. An exact expression is given for the long range interaction in terms of an anisotropy parameter of the force dipole tensor. The short range interaction is calculated by introducing a smooth cutoff. Interactions of adatoms on near neighbour sites on W (110) are given.

Vacuum Head Checks Foam/Substrate Bonds

NASA Technical Reports Server (NTRS)

Lloyd, James F.

1989-01-01

Electromechanical inspection system quickly gives measurements indicating adhesion, or lack thereof, between rigid polyurethane foam and aluminum substrate. Does not damage inspected article, easy to operate, and used to perform "go/no-go" evaluations or as supplement to conventional destructive pull-plug testing. Applies vacuum to small area of foam panel and measures distance through which foam pulled into vacuum. Probe head applied to specimen and evacuated through hose to controller/monitor unit. Digital voltmeter in unit reads deflection of LVDT probe head.

Vortex dynamics of collapsing bubbles: Impact on the boundary layer measured by chronoamperometry.

PubMed

Reuter, Fabian; Cairós, Carlos; Mettin, Robert

2016-11-01

Cavitation bubbles collapsing in the vicinity to a solid substrate induce intense micro-convection at the solid. Here we study the transient near-wall flows generated by single collapsing bubbles by chronoamperometric measurements synchronously coupled with high-speed imaging. The individual bubbles are created at confined positions by a focused laser pulse. They reach a maximum expansion radius of approximately 425μm. Several stand-off distances to the flat solid boundary are investigated and all distances are chosen sufficiently large that no gas phase of the expanding and collapsing bubble touches the solid directly. With a microelectrode embedded into the substrate, the time-resolved perturbations in the liquid shear layer are probed by means of a chronoamperometric technique. The measurements of electric current are synchronized with high-speed imaging of the bubble dynamics. The perturbations of the near-wall layer are found to result mainly from ring vortices created by the jetting bubble. Other bubble induced flows, such as the jet and flows following the radial bubble oscillations are perceptible with this technique, but show a minor influence at the stand-off distances investigated. Copyright © 2016 Elsevier B.V. All rights reserved.

DEER distance measurement between a spin label and a native FAD semiquinone in electron transfer flavoprotein.

PubMed

Swanson, Michael A; Kathirvelu, Velavan; Majtan, Tomas; Frerman, Frank E; Eaton, Gareth R; Eaton, Sandra S

2009-11-11

The human mitochondrial electron transfer flavoprotein (ETF) accepts electrons from at least 10 different flavoprotein dehydrogenases and transfers electrons to a single electron acceptor in the inner membrane. Paracoccus denitrificans ETF has the identical function, shares the same three-dimensional structure and functional domains, and exhibits the same conformational mobility. It has been proposed that the mobility of the alphaII domain permits the promiscuous behavior of ETF with respect to a variety of redox partners. Double electron-electron resonance (DEER) measurements between a spin label and an enzymatically reduced flavin adenine dinucleotide (FAD) cofactor in P. denitrificans ETF gave two distributions of distances: a major component centered at 4.2 +/- 0.1 nm and a minor component centered at 5.1 +/- 0.2 nm. Both components had widths of approximately 0.3 nm. A distance of 4.1 nm was calculated using the crystal structure of P. denitrificans ETF, which agrees with the major component obtained from the DEER measurement. The observation of a second distribution suggests that ETF, in the absence of substrate, adopts some conformations that are intermediate between the predominant free and substrate-bound states.

DEER Distance Measurement Between a Spin Label and a Native FAD Semiquinone in Electron Transfer Flavoprotein

PubMed Central

Swanson, Michael A.; Kathirvelu, Velavan; Majtan, Tomas; Frerman, Frank E.; Eaton, Gareth R.; Eaton, Sandra S.

2009-01-01

The human mitochondrial electron transfer flavoprotein (ETF) accepts electrons from at least 10 different flavoprotein dehydrogenases and transfers electrons to a single electron acceptor in the inner membrane. Paracoccus denitrificans ETF has the identical function, shares the same three dimensional structure and functional domains, and exhibits the same conformational mobility. It has been proposed that the mobility of the αII domain permits the promiscuous behavior of ETF with respect to a variety of redox partners. Double electron-electron resonance (DEER) measurements between a spin label and an enzymatically reduced flavin adenine dinucleotide (FAD) cofactor in P. denitrificans ETF gave two distributions of distances: a major component centered at 4.2 ± 0.1 nm and a minor component centered at 5.1 ± 0.2 nm. Both components had widths of approximately 0.3 nm. A distance of 4.1 nm was calculated using the crystal structure of P. denitrificans ETF, which agrees with the major component obtained from the DEER measurement. The observation of a second distribution suggests that ETF, in the absence of substrate, adopts some conformations that are intermediate between the predominant free and substrate-bound states. PMID:19886689

Visual and semantic processing of living things and artifacts: an FMRI study.

PubMed

Zannino, Gian Daniele; Buccione, Ivana; Perri, Roberta; Macaluso, Emiliano; Lo Gerfo, Emanuele; Caltagirone, Carlo; Carlesimo, Giovanni A

2010-03-01

We carried out an fMRI study with a twofold purpose: to investigate the relationship between networks dedicated to semantic and visual processing and to address the issue of whether semantic memory is subserved by a unique network or by different subsystems, according to semantic category or feature type. To achieve our goals, we administered a word-picture matching task, with within-category foils, to 15 healthy subjects during scanning. Semantic distance between the target and the foil and semantic domain of the target-foil pairs were varied orthogonally. Our results suggest that an amodal, undifferentiated network for the semantic processing of living things and artifacts is located in the anterolateral aspects of the temporal lobes; in fact, activity in this substrate was driven by semantic distance, not by semantic category. By contrast, activity in ventral occipito-temporal cortex was driven by category, not by semantic distance. We interpret the latter finding as the effect exerted by systematic differences between living things and artifacts at the level of their structural representations and possibly of their lower-level visual features. Finally, we attempt to reconcile contrasting data in the neuropsychological and functional imaging literature on semantic substrate and category specificity.

Probing the probe: AFM tip-profiling via nanotemplates to determine Hamaker constants from phase-distance curves.

PubMed

Rodriguez, Raul D; Lacaze, Emmanuelle; Jupille, Jacques

2012-10-01

A method to determine the van der Waals forces from phase-distance curves recorded by atomic force microscopy (AFM) in tapping mode is presented. The relationship between the phase shift and the tip-sample distance is expressed as a function of the product of the Hamaker constant by tip radius. Silica-covered silicon tips are used to probe silica-covered silicon substrate in dry conditions to avoid capillary effects. Tips being assumed spherical, radii are determined in situ by averaging profiles recorded in different directions on hematite nanocrystals acting as nanotemplates, thus accounting for tip anisotropy. Through a series of reproducible measurements performed with tips of various radii (including the in-situ characterization of a damaged tip), a value of (6.3±0.4)×10(-20) J is found for the Hamaker constant of interacting silica surfaces in air, in good agreement with tabulated data. The results demonstrate that the onset of the tip-surface interaction is dominated by the van der Waals forces and that the total force can be modeled in the framework of the harmonic approximation. Based on the tip radius and the Hamaker constant associated to the tip-substrate system, the model is quite flexible. Once the Hamaker constant is known, a direct estimate of the tip size can be achieved whereas when the tip size is known, a quantitative evaluation of the van der Waals force becomes possible on different substrates with a spatial resolution at the nanoscale. Copyright © 2012 Elsevier B.V. All rights reserved.

Nanocrystal powered nanomotor

DOEpatents

Regan, Brian C [Los Angeles, CA; Zettl, Alexander K [Kensington, CA; Aloni, Shaul [Albany, CA

2011-01-04

A nanoscale nanocrystal which may be used as a reciprocating motor is provided, comprising a substrate having an energy differential across it, e.g. an electrical connection to a voltage source at a proximal end; an atom reservoir on the substrate distal to the electrical connection; a nanoparticle ram on the substrate distal to the atom reservoir; a nanolever contacting the nanoparticle ram and having an electrical connection to a voltage source, whereby a voltage applied between the electrical connections on the substrate and the nanolever causes movement of atoms between the reservoir and the ram. Movement of the ram causes movement of the nanolever relative to the substrate. The substrate and nanolever preferably comprise multiwalled carbon nanotubes (MWNTs) and the atom reservoir and nanoparticle ram are preferably metal (e.g. indium) deposited as small particles on the MWNTs. The substrate may comprise a silicon chip that has been fabricated to provide the necessary electrodes and other electromechanical structures, and further supports an atomic track, which may comprise an MWNT.

Clast comminution during pyroclastic density current transport: Mt St Helens

NASA Astrophysics Data System (ADS)

Dawson, B.; Brand, B. D.; Dufek, J.

2011-12-01

Volcanic clasts within pyroclastic density currents (PDCs) tend to be more rounded than those in fall deposits. This rounding reflects degrees of comminution during transport, which produces an increase in fine-grained ash with distance from source (Manga, M., Patel, A., Dufek., J. 2011. Bull Volcanol 73: 321-333). The amount of ash produced due to comminution can potentially affect runout distance, deposit sorting, the volume of ash lofted into the upper atmosphere, and increase internal pore pressure (e.g., Wohletz, K., Sheridan, M. F., Brown, W.K. 1989. J Geophy Res, 94, 15703-15721). For example, increased pore pressure has been shown to produce longer runout distances than non-comminuted PDC flows (e.g., Dufek, J., and M. Manga, 2008. J. Geophy Res, 113). We build on the work of Manga et al., (2011) by completing a pumice abrasion study for two well-exposed flow units from the May 18th, 1980 eruption of Mt St Helens (MSH). To quantify differences in comminution from source, sampling and the image analysis technique developed in Manga et al., 2010 was completed at distances proximal, medial, and distal from source. Within the units observed, data was taken from the base, middle, and pumice lobes within the outcrops. Our study is unique in that in addition to quantifying the degree of pumice rounding with distance from source, we also determine the possible range of ash sizes produced during comminution by analyzing bubble wall thickness of the pumice through petrographic and SEM analysis. The proportion of this ash size is then measured relative to the grain size of larger ash with distance from source. This allows us to correlate ash production with degree of rounding with distance from source, and determine the fraction of the fine ash produced due to comminution versus vent-fragmentation mechanisms. In addition we test the error in 2D analysis by completing a 3D image analysis of selected pumice samples using a Camsizer. We find that the roundness of PDC pumice at MSH increases with distance from source, as does the quantity of fine-grained ash. In addition, we have made the first steps towards determining the proportion of fine ash produced by comminution with distance from source. These results are being tested by numerical methods to understand the effect of an increase in fine ash on overall flow dynamics of the PDCs in which they were produced.

Thin films of mixed metal compounds

DOEpatents

Mickelsen, R.A.; Chen, W.S.

1985-06-11

Disclosed is a thin film heterojunction solar cell, said heterojunction comprising a p-type I-III-IV[sub 2] chalcopyrite substrate and an overlying layer of an n-type ternary mixed metal compound wherein said ternary mixed metal compound is applied to said substrate by introducing the vapor of a first metal compound to a vessel containing said substrate from a first vapor source while simultaneously introducing a vapor of a second metal compound from a second vapor source of said vessel, said first and second metals comprising the metal components of said mixed metal compound; independently controlling the vaporization rate of said first and second vapor sources; reducing the mean free path between vapor particles in said vessel, said gas being present in an amount sufficient to induce homogeneity of said vapor mixture; and depositing said mixed metal compound on said substrate in the form of a uniform composition polycrystalline mixed metal compound. 5 figs.

Influence of surface morphology on adsorption of potassium stearate molecules on diamond-like carbon substrate: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Guo, Shusen; Cao, Yongzhi; Sun, Tao; Zhang, Junjie; Gu, Le; Zhang, Chuanwei; Xu, Zhiqiang

2018-05-01

Molecular dynamics (MD) simulations were used to provide insights into the influence of nano-scale surface morphology on adsorptive behavior of Potassium stearate molecules on diamond-like carbon (DLC) substrates. Particular focus was given to explain that how the distinctive geometric properties of different surface morphologies affect the equilibrium structures and substrate-molecules interactions of monolayers, which was achieved through adsorptive analysis methods including adsorptive process, density profile, density distribution and surface potential energy. Analysis on surface potential energy demonstrated that the adsorptivity of amorphous smooth substrate is uniformly distributed over the surface, while DLC substrates with different surface morphologies appear to be more potentially corrugated, which improves the adsorptivity significantly. Because of the large distance of molecules from carbon atoms located at the square groove bottom, substrate-molecules interactions vanish significantly, and thus potassium stearate molecules cannot penetrate completely into the square groove. It can be observed that the equilibrium substrate-molecules interactions of triangle groove and semi-circle groove are much more powerful than that of square groove due to geometrically advantageous properties. These findings provided key information of optimally design of solid substrates with controllable adsorptivity.

Solid-state radiation-emitting compositions and devices

DOEpatents

Ashley, Carol S.; Brinker, C. Jeffrey; Reed, Scott; Shepodd, Timothy J.; Leonard, Leroy E.; Ellefson, Robert E.; Gill, John T.; Walko, Robert J.; Renschler, Clifford L.

1992-01-01

The invention relates to a composition for the volumetric generation of radiation, wherein a first substance functions as a source of exciting radiation, and a second substance interacts with the exciting radiation to provide a second radiation. The compositions comprise a porous substrate which is loaded with: a source of exciting radiation, a component capable of emitting radiation upon interaction with the exciting radiation, or both. In the composition, a composite is formed from a carrier material and at least one of the source of the exciting radiation or the component which is capable of interacting with the exciting radiation. The composite is then employed for loading a porous substrate, preferably an aerogel substrate.

Reaching nearby sources: comparison between real and virtual sound and visual targets

PubMed Central

Parseihian, Gaëtan; Jouffrais, Christophe; Katz, Brian F. G.

2014-01-01

Sound localization studies over the past century have predominantly been concerned with directional accuracy for far-field sources. Few studies have examined the condition of near-field sources and distance perception. The current study concerns localization and pointing accuracy by examining source positions in the peripersonal space, specifically those associated with a typical tabletop surface. Accuracy is studied with respect to the reporting hand (dominant or secondary) for auditory sources. Results show no effect on the reporting hand with azimuthal errors increasing equally for the most extreme source positions. Distance errors show a consistent compression toward the center of the reporting area. A second evaluation is carried out comparing auditory and visual stimuli to examine any bias in reporting protocol or biomechanical difficulties. No common bias error was observed between auditory and visual stimuli indicating that reporting errors were not due to biomechanical limitations in the pointing task. A final evaluation compares real auditory sources and anechoic condition virtual sources created using binaural rendering. Results showed increased azimuthal errors, with virtual source positions being consistently overestimated to more lateral positions, while no significant distance perception was observed, indicating a deficiency in the binaural rendering condition relative to the real stimuli situation. Various potential reasons for this discrepancy are discussed with several proposals for improving distance perception in peripersonal virtual environments. PMID:25228855

An Overview of Distance Education at Boise State University. Research Report.

ERIC Educational Resources Information Center

Belcheir, Marcia J.; Atkinson, Janet

This study, first in a three-part series, looked at distance education at Boise State University, Idaho, to explore the current distance education delivery methods, the growth in distance education, enrollment, and teaching in distance education. Data from various university sources show that in the past 5 years, the numbers of distance education…

Microfluidic hubs, systems, and methods for interface fluidic modules

DOEpatents

Bartsch, Michael S; Claudnic, Mark R; Kim, Hanyoup; Patel, Kamlesh D; Renzi, Ronald F; Van De Vreugde, James L

2015-01-27

Embodiments of microfluidic hubs and systems are described that may be used to connect fluidic modules. A space between surfaces may be set by fixtures described herein. In some examples a fixture may set substrate-to-substrate spacing based on a distance between registration surfaces on which the respective substrates rest. Fluidic interfaces are described, including examples where fluid conduits (e.g. capillaries) extend into the fixture to the space between surfaces. Droplets of fluid may be introduced to and/or removed from microfluidic hubs described herein, and fluid actuators may be used to move droplets within the space between surfaces. Continuous flow modules may be integrated with the hubs in some examples.

Experience, but not distance, influences the recruitment precision in the stingless bee Scaptotrigona mexicana

NASA Astrophysics Data System (ADS)

Sánchez, Daniel; Kraus, F. Bernhard; Hernández, Manuel De Jesús; Vandame, Rémy

2007-07-01

Recruitment precision, i.e. the proportion of recruits that reach an advertised food source, is a crucial adaptation of social bees to their environment. Studies with honeybees showed that recruitment precision is not a fixed feature, but it may be enhanced by factors like experience and distance. However, little is known regarding the recruitment precision of stingless bees. Hence, in this study, we examined the effects of experience and spatial distance on the precision of the food communication system of the stingless bee Scaptotrigona mexicana. We conducted the experiments by training bees to a three-dimensional artificial patch at several distances from the colony. We recorded the choices of individual recruited foragers, either being newcomers (foragers without experience with the advertised food source) or experienced (foragers that had previously visited the feeder). We found that the average precision of newcomers (95.6 ± 2.61%) was significantly higher than that of experienced bees (80.2 ± 1.12%). While this might seem counter-intuitive on first sight, this “loss” of precision can be explained by the tendency of experienced recruits to explore nearby areas to find new rewarding food sources after they had initially learned the exact location of the food source. Increasing the distance from the colony had no significant effect on the precision of the foraging bees. Thus, our data show that experience, but not the distance of the food source, affected the patch precision of S. mexicana foragers.

Far field focusing for a microwave patch antenna with composite substrate

NASA Astrophysics Data System (ADS)

Wan, Jian; Rybin, Oleg; Shulga, Sergey

2018-03-01

Modeling for a compact microwave antenna structure on base of a miniaturized rectangular patch antenna with composite substrate and magnetic superstrates is made in this study by using FDTD simulations. The resonant frequency of the antenna structure is supposed to be 15 GHz. The design of the antenna with composite substrate and without superstrate is made up by using the microwave miniaturization concept for rectangular patch antennas created by first author of this study. The optimal distance between the superstrate and antenna surface is found by using Fabry-Perot cavity theory as maximum values of power directivity and efficiency of the antenna is achieved. The comparative analysis with regard to some far and near field parameters of the above antenna structures and the antenna with dielectric substrate having same value of the relative permittivity is performed.

Morphology and topography study of graphene synthesized from plant oil

NASA Astrophysics Data System (ADS)

Robaiah, M.; Rusop, M.; Abdullah, S.; Khusaimi, Z.; Azhan, H.; Laila, M. O.; Salifairus, M. J.; Asli, N. A.

2018-05-01

The graphene is material consists of bonded atom carbon atoms in sheet form one atom thick. The different types of carbon sources which are refined corn oil, palm oil and waste cooking palm oil were used as carbon feedstock to supply carbon atom for synthesizing graphene on the nickel substrate by thermal chemical vapour deposition. The substrate and carbon sources were placed in double zone furnaces. The carbon sources and the substrate were heated at 300 °C and 900 °C respectively. The both furnaces were switched off after synthesis time for cooling process finish. The formation of the graphene on the Ni surface appears due to segregation and precipitation of a high amount of carbon from the source material during the cooling process. FESEM, AFM, UV-VIS Spectroscopy and Raman Spectroscopy were used to characterize and synthesized graphene.

Low cost batch fabrication of microdevices using ultraviolet light-emitting diode photolithography technique

NASA Astrophysics Data System (ADS)

Lee, Neam Heng; Swamy, Varghese; Ramakrishnan, Narayanan

2016-01-01

Solid-state technology has enabled the use of light-emitting diodes (LEDs) in lithography systems due to their low cost, low power requirement, and higher efficiency relative to the traditional mercury lamp. Uniform irradiance distribution is essential for photolithography to ensure the critical dimension (CD) of the feature fabricated. However, light illuminated from arrays of LEDs can have nonuniform irradiance distribution, which can be a problem when using LED arrays as a source to batch-fabricate multiple devices on a large wafer piece. In this study, the irradiance distribution of an UV LED array was analyzed, and the separation distance between light source and mask optimized to obtain maximum irradiance uniformity without the use of a complex lens. Further, employing a diffuser glass enhanced the fabrication process and the CD loss was minimized to an average of 300 nm. To assess the performance of the proposed technology, batch fabrication of surface acoustic wave devices on lithium niobate substrate was carried out, and all the devices exhibited identical insertion loss of -18 dB at a resonance frequency of 39.33 MHz. The proposed low-cost UV lithography setup can be adapted in academic laboratories for research and teaching on microdevices.

Mirror-field confined compact plasma source using permanent magnet for plasma processings.

PubMed

Goto, Tetsuya; Sato, Kei-Ichiro; Yabuta, Yuki; Sugawa, Shigetoshi

2016-12-01

A mirror-field confined compact electron cyclotron resonance (ECR) plasma source using permanent magnets was developed, aiming for the realization of high-quality plasma processings where high-density reactive species are supplied to a substrate with minimizing the ion bombardment damages. The ECR position was located between a microwave transmissive window and a quartz limiter, and plasmas were transported from the ECR position to a midplane of the magnetic mirror field through the quartz limiter. Thus, a radius of core plasma could be determined by the limiter, which was 15 mm in this study. Plasma parameters were investigated by the Langmuir probe measurement. High-density plasma larger than 10 11 cm -3 could be produced by applying 5.85-GHz microwave power of 10 W or more. For the outside region of the core plasma where a wafer for plasma processings will be set at, the ion current density was decreased dramatically with distance from the core plasma and became smaller by approximately two orders of magnitude that in the core plasma region for the radial position of 40 mm, suggesting the realization of reduction in ion bombardment damages.

Study of magnetism in Ni-Cr hardface alloy deposit on 316LN stainless steel using magnetic force microscopy

NASA Astrophysics Data System (ADS)

Kishore, G. V. K.; Kumar, Anish; Chakraborty, Gopa; Albert, S. K.; Rao, B. Purna Chandra; Bhaduri, A. K.; Jayakumar, T.

2015-07-01

Nickel base Ni-Cr alloy variants are extensively used for hardfacing of austenitic stainless steel components in sodium cooled fast reactors (SFRs) to avoid self-welding and galling. Considerable difference in the compositions and melting points of the substrate and the Ni-Cr alloy results in significant dilution of the hardface deposit from the substrate. Even though, both the deposit and the substrate are non-magnetic, the diluted region exhibits ferromagnetic behavior. The present paper reports a systematic study carried out on the variations in microstructures and magnetic behavior of American Welding Society (AWS) Ni Cr-C deposited layers on 316 LN austenitic stainless steels, using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The phase variations of the oscillations of a Co-Cr alloy coated magnetic field sensitive cantilever is used to quantitatively study the magnetic strength of the evolved microstructure in the diluted region as a function of the distance from the deposit/substrate interface, with the spatial resolution of about 100 nm. The acquired AFM/MFM images and the magnetic property profiles have been correlated with the variations in the chemical compositions in the diluted layers obtained by the energy dispersive spectroscopy (EDS). The study indicates that both the volume fraction of the ferromagnetic phase and its ferromagnetic strength decrease with increasing distance from the deposit/substrate interface. A distinct difference is observed in the ferromagnetic strength in the first few layers and the ferromagnetism is observed only near to the precipitates in the fifth layer. The study provides a better insight of the evolution of ferromagnetism in the diluted layers of Ni-Cr alloy deposits on stainless steel.

Tunable terahertz radiation source

DOEpatents

Boulaevskii, Lev; Feldmann, David M; Jia, Quanxi; Koshelev, Alexei; Moody, Nathan A

2014-01-21

Terahertz radiation source and method of producing terahertz radiation, said source comprising a junction stack, said junction stack comprising a crystalline material comprising a plurality of self-synchronized intrinsic Josephson junctions; an electrically conductive material in contact with two opposing sides of said crystalline material; and a substrate layer disposed upon at least a portion of both the crystalline material and the electrically-conductive material, wherein the crystalline material has a c-axis which is parallel to the substrate layer, and wherein the source emits at least 1 mW of power.

A new approach to geographic partitioning of probabilistic seismic hazard using seismic source distance with earthquake extreme and perceptibility statistics: an application to the southern Balkan region

NASA Astrophysics Data System (ADS)

Bayliss, T. J.

2016-02-01

The southeastern European cities of Sofia and Thessaloniki are explored as example site-specific scenarios by geographically zoning their individual localized seismic sources based on the highest probabilities of magnitude exceedance. This is with the aim of determining the major components contributing to each city's seismic hazard. Discrete contributions from the selected input earthquake catalogue are investigated to determine those areas that dominate each city's prevailing seismic hazard with respect to magnitude and source-to-site distance. This work is based on an earthquake catalogue developed and described in a previously published paper by the author and components of a magnitude probability density function. Binned magnitude and distance classes are defined using a joint magnitude-distance distribution. The prevailing seismicity to each city-as defined by a child data set extracted from the parent earthquake catalogue for each city considered-is divided into distinct constrained data bins of small discrete magnitude and source-to-site distance intervals. These are then used to describe seismic hazard in terms of uni-variate modal values; that is, M* and D* which are the modal magnitude and modal source-to-site distance in each city's local historical seismicity. This work highlights that Sofia's dominating seismic hazard-that is, the modal magnitudes possessing the highest probabilities of occurrence-is located in zones confined to two regions at 60-80 km and 170-180 km from this city, for magnitude intervals of 5.75-6.00 Mw and 6.00-6.25 Mw respectively. Similarly, Thessaloniki appears prone to highest levels of hazard over a wider epicentral distance interval, from 80 to 200 km in the moment magnitude range 6.00-6.25 Mw.

Conformational Dynamics of a Y-Family DNA Polymerase during Substrate Binding and Catalysis As Revealed by Interdomain Förster Resonance Energy Transfer

PubMed Central

2015-01-01

Numerous kinetic, structural, and theoretical studies have established that DNA polymerases adjust their domain structures to enclose nucleotides in their active sites and then rearrange critical active site residues and substrates for catalysis, with the latter conformational change acting to kinetically limit the correct nucleotide incorporation rate. Additionally, structural studies have revealed a large conformational change between the apoprotein and the DNA–protein binary state for Y-family DNA polymerases. In previous studies [Xu, C., Maxwell, B. A., Brown, J. A., Zhang, L., and Suo, Z. (2009) PLoS Biol.7, e1000225], a real-time Förster resonance energy transfer (FRET) method was developed to monitor the global conformational transitions of DNA polymerase IV from Sulfolobus solfataricus (Dpo4), a prototype Y-family enzyme, during nucleotide binding and incorporation by measuring changes in distance between locations on the enzyme and the DNA substrate. To elucidate further details of the conformational transitions of Dpo4 during substrate binding and catalysis, in this study, the real-time FRET technique was used to monitor changes in distance between various pairs of locations in the protein itself. In addition to providing new insight into the conformational changes as revealed in previous studies, the results here show that the previously described conformational change between the apo and DNA-bound states of Dpo4 occurs in a mechanistic step distinct from initial formation or dissociation of the binary complex of Dpo4 and DNA. PMID:24568554

An empirical formula to calculate the full energy peak efficiency of scintillation detectors.

PubMed

Badawi, Mohamed S; Abd-Elzaher, Mohamed; Thabet, Abouzeid A; El-khatib, Ahmed M

2013-04-01

This work provides an empirical formula to calculate the FEPE for different detectors using the effective solid angle ratio derived from experimental measurements. The full energy peak efficiency (FEPE) curves of the (2″(*)2″) NaI(Tl) detector at different seven axial distances from the detector were depicted in a wide energy range from 59.53 to 1408keV using standard point sources. The distinction was based on the effects of the source energy and the source-to-detector distance. A good agreement was noticed between the measured and calculated efficiency values for the source-to-detector distances at 20, 25, 30, 35, 40, 45 and 50cm. Copyright © 2012 Elsevier Ltd. All rights reserved.

Optical study of plasma sprayed hydroxyapatite coatings deposited at different spray distance

NASA Astrophysics Data System (ADS)

Belka, R.; Kowalski, S.; Żórawski, W.

2017-08-01

Series of hydroxyapatite (HA) coatings deposited on titanium substrate at different spray (plasma gun to workpiece) distance were investigated. The optical methods as dark field confocal microscopy, Raman/PL and UV-VIS spectroscopy were used for study the influence of deposition process on structural degradation of HA precursor. The hydroxyl group concentration was investigated by study the OH mode intensity in the Raman spectra. Optical absorption coefficients at near UV region were analyzed by Diffuse Reflectance Spectroscopy. PL intensity observed during Raman measurement was also considered as relation to defects concentration and degradation level. It was confirmed the different gunsubstrate distance has a great impact on structure of deposited HA ceramics.

Optical Distance Measurement Device And Method Thereof

DOEpatents

Bowers, Mark W.

2004-06-15

A system and method of efficiently obtaining distance measurements of a target by scanning the target. An optical beam is provided by a light source and modulated by a frequency source. The modulated optical beam is transmitted to an acousto-optical deflector capable of changing the angle of the optical beam in a predetermined manner to produce an output for scanning the target. In operation, reflected or diffused light from the target may be received by a detector and transmitted to a controller configured to calculate the distance to the target as well as the measurement uncertainty in calculating the distance to the target.

Si substrates texturing and vapor-solid-solid Si nanowhiskers growth using pure hydrogen as source gas

NASA Astrophysics Data System (ADS)

Nordmark, H.; Nagayoshi, H.; Matsumoto, N.; Nishimura, S.; Terashima, K.; Marioara, C. D.; Walmsley, J. C.; Holmestad, R.; Ulyashin, A.

2009-02-01

Scanning and transmission electron microscopies have been used to study silicon substrate texturing and whisker growth on Si substrates using pure hydrogen source gas in a tungsten hot filament reactor. Substrate texturing, in the nanometer to micrometer range of mono- and as-cut multicrystalline silicon, was observed after deposition of WSi2 particles that acted as a mask for subsequent hydrogen radical etching. Simultaneous Si whisker growth was observed for long residence time of the source gas and low H2 flow rate with high pressure. The whiskers formed via vapor-solid-solid growth, in which the deposited WSi2 particles acted as catalysts for a subsequent metal-induced layer exchange process well below the eutectic temperature. In this process, SiHx species, formed by substrate etching by the H radicals, diffuse through the metal particles. This leads to growth of crystalline Si whiskers via metal-induced solid-phase crystallization. Transmission electron microscopy, electron diffraction, and x-ray energy dispersive spectroscopy were used to study the WSi2 particles and the structure of the Si substrates in detail. It has been established that the whiskers are partly crystalline and partly amorphous, consisting of pure Si with WSi2 particles on their tips as well as sometimes being incorporated into their structure.

Measurements and modeling of the impact of weak magnetic fields on the plasma properties of a planar slot antenna driven plasma source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshikawa, Jun, E-mail: jun.yoshikawa@tel.com; Susa, Yoshio; Ventzek, Peter L. G.

The radial line slot antenna plasma source is a type of surface wave plasma source driven by a planar slot antenna. Microwave power is transmitted through a slot antenna structure and dielectric window to a plasma characterized by a generation zone adjacent to the window and a diffusion zone that contacts a substrate. The diffusion zone is characterized by a very low electron temperature. This renders the source useful for soft etch applications and thin film deposition processes requiring low ion energy. Another property of the diffusion zone is that the plasma density tends to decrease from the axis tomore » the walls under the action of ambipolar diffusion at distances far from where the plasma is generated. A previous simulation study [Yoshikawa and. Ventzek, J. Vac. Sci. Technol. A 31, 031306 (2013)] predicted that the anisotropy in transport parameters due to weak static magnetic fields less than 50 G could be leveraged to manipulate the plasma profile in the radial direction. These simulations motivated experimental tests in which weak magnetic fields were applied to a radial line slot antenna source. Plasma absorption probe measurements of electron density and etch rate showed that the magnetic fields remote from the wafer were able to manipulate both parameters. A summary of these results is presented in this paper. Argon plasma simulation trends are compared with experimental plasma and etch rate measurements. A test of the impact of magnetic fields on charge up damage showed no perceptible negative effect.« less

Method and apparatus for coating a patterned thin film on a substrate from a fluid source with continuous feed capability

DOEpatents

Burrows, Paul E [Kennewick, WA; Sapochak, Linda S [Kennewick, WA

2009-09-22

A method and apparatus for forming patterned coatings of thin film, non-polymerizable compounds on a substrate. A mixture of the non-polymerizable compound and a liquid carrier is pumped into the interior of a heated evaporation box having an internal temperature sufficient to convert substantially all of the non-polymerizable compound and liquid carrier to a gaseous form. The non-polymerizable compound and liquid carrier are then removed from the evaporation box via exit slit in the evaporation box. Adjacent to the exit slit, and maintained in a vacuum, is a first substrate upon which the non-polymerizable compound condenses. The first substrate is in motion, for example on a web roller, thereby allowing a continuous coating of the non-polymerizable compound to be applied to the first substrate. Once the non-polymerizable compound is applied to one side of the first substrate, an energy source is then directed toward the opposite side of the first substrate. In this manner, a portion of the non-polymerizable compound is removed from the first substrate. A second substrate is then provided adjacent to the first substrate, and the non-polymerizable compound is thereby transferred from the first substrate onto the second substrate. By repeatedly transferring portions of the non-polymerizable material from the first substrate to the second substrate in this manner, the thin film, non-polymerizable materials can be formed onto the second substrate in a predetermined pattern, and in a continuous and highly efficient process.

Formation of graphene on BN substrate by vapor deposition method and size effects on its structure

NASA Astrophysics Data System (ADS)

Giang, Nguyen Hoang; Hanh, Tran Thi Thu; Ngoc, Le Nhu; Nga, Nguyen To; Van Hoang, Vo

2018-04-01

We report MD simulation of the growth of graphene by the vapor deposition on a two-dimensional hBN substrate. The systems (containing carbon vapor and hBN substrate) are relaxed at high temperature (1500 K), and then it is cooled down to room one (300 K). Carbon atoms interact with the substrate via the Lennard-Jones potential while the interaction between carbon atoms is computed via the Tersoff potential. Depending on the size of the model, different crystalline honeycomb structures have been found. Structural properties of the graphene obtained at 300 K are studied by analyzing radial distribution functions (RDFs), coordination numbers, ring statistics, interatomic distances, bond-angle distributions and 2D visualization of atomic configurations. We find that the models containing various numbers of atoms have a honeycomb structure. Besides, differences in structural properties of graphene formed by the vapor deposition on the substrate and free standing one are found. Moreover, the size effect on the structure is significant.

Influence of FeEDDS, FeEDTA, FeDTPA, FeEDDHA, and FeSO4 on Marigold Growth and Nutrition, and Substrate and Runoff Chemistry

USDA-ARS?s Scientific Manuscript database

Objectives of the study were to determine effects of Fe source on plant growth, plant nutrition, substrate chemistry and runoff chemistry. Iron source (FS) treatments consisted of Fe-aminopolycarboxylic acid (APCA) complexones iron ethylenediaminetetraacetic acid (FeEDTA), iron [S, S']-ethylenediam...

Treatment and prevention systems for acid mine drainage and halogenated contaminants

DOEpatents

Jin, Song [Fort Collins, CO; Fallgren, Paul H [Laramie, WY; Morris, Jeffrey M [Laramie, WY

2012-01-31

Embodiments include treatments for acid mine drainage generation sources (10 perhaps by injection of at least one substrate (11) and biologically constructing a protective biofilm (13) on acid mine drainage generation source materials (14). Further embodiments include treatments for degradation of contaminated water environments (17) with substrates such as returned milk and the like.

Long Distance Dispersal Potential of Two Seagrasses Thalassia hemprichii and Halophila ovalis

PubMed Central

Wu, Kuoyan; Chen, Ching-Nen Nathan; Soong, Keryea

2016-01-01

The wide distribution of many seagrasses may be attributable to exploitation of currents. However, many species have seeds heavier than seawater, limiting surface floating, and thus, deep water becomes a potential barrier between suitable habitats. In this investigation, we studied the dispersal potential of various life history stages of two species of seagrasses, Thalassia hemprichii and Halophila ovalis, at Dongsha Atoll and Penghu Islands in Taiwan Strait, west Pacific. The adult plants of both species, often dislodged naturally from substrate by waves, could float, but only that of T. hemprichii could float for months and still remain alive and potentially able to colonize new territories. The seedlings of T. hemprichii could also float for about a month once failing to anchor to substrate of coral sand, but that of H. ovalis could not. The fruits and seeds of T. hemprichii could both float, but for too short a duration to enable long distance travel; those seeds released from long floating fruits had low germination rates in our tests. Obviously, their seeds are not adaptive for long distance dispersal. Fruits and seeds of H. ovalis do not float. The potential of animals as vectors was tested by feeding fruits and seeds of both species to a goose, a duck, and two fish in the laboratory. The fruits and seeds of T. hemprichii were digested and could no longer germinate; those of H. ovalis could pass through the digestive tracts and have a much higher germination rates than uningested controls. Therefore, birds could be important vectors for long distance dispersal of H. ovalis. The two seagrasses adopted very different dispersal mechanisms for long distance travel, and both exploited traits originally adaptive for other purposes. PMID:27248695

Long Distance Dispersal Potential of Two Seagrasses Thalassia hemprichii and Halophila ovalis.

PubMed

Wu, Kuoyan; Chen, Ching-Nen Nathan; Soong, Keryea

2016-01-01

The wide distribution of many seagrasses may be attributable to exploitation of currents. However, many species have seeds heavier than seawater, limiting surface floating, and thus, deep water becomes a potential barrier between suitable habitats. In this investigation, we studied the dispersal potential of various life history stages of two species of seagrasses, Thalassia hemprichii and Halophila ovalis, at Dongsha Atoll and Penghu Islands in Taiwan Strait, west Pacific. The adult plants of both species, often dislodged naturally from substrate by waves, could float, but only that of T. hemprichii could float for months and still remain alive and potentially able to colonize new territories. The seedlings of T. hemprichii could also float for about a month once failing to anchor to substrate of coral sand, but that of H. ovalis could not. The fruits and seeds of T. hemprichii could both float, but for too short a duration to enable long distance travel; those seeds released from long floating fruits had low germination rates in our tests. Obviously, their seeds are not adaptive for long distance dispersal. Fruits and seeds of H. ovalis do not float. The potential of animals as vectors was tested by feeding fruits and seeds of both species to a goose, a duck, and two fish in the laboratory. The fruits and seeds of T. hemprichii were digested and could no longer germinate; those of H. ovalis could pass through the digestive tracts and have a much higher germination rates than uningested controls. Therefore, birds could be important vectors for long distance dispersal of H. ovalis. The two seagrasses adopted very different dispersal mechanisms for long distance travel, and both exploited traits originally adaptive for other purposes.

Nanostructured Ti-Ta thin films synthesized by combinatorial glancing angle sputter deposition

NASA Astrophysics Data System (ADS)

Motemani, Yahya; Khare, Chinmay; Savan, Alan; Hans, Michael; Paulsen, Alexander; Frenzel, Jan; Somsen, Christoph; Mücklich, Frank; Eggeler, Gunther; Ludwig, Alfred

2016-12-01

Ti-Ta alloys are attractive materials for applications in actuators as well as biomedical implants. When fabricated as thin films, these alloys can potentially be employed as microactuators, components for micro-implantable devices and coatings on surgical implants. In this study, Ti100-x Ta x (x = 21, 30) nanocolumnar thin films are fabricated by glancing angle deposition (GLAD) at room temperature using Ti73Ta27 and Ta sputter targets. Crystal structure, morphology and microstructure of the nanostructured thin films are systematically investigated by XRD, SEM and TEM, respectively. Nanocolumns of ˜150-160 nm in width are oriented perpendicular to the substrate for both Ti79Ta21 and Ti70Ta30 compositions. The disordered α″ martensite phase with orthorhombic structure is formed in room temperature as-deposited thin films. The columns are found to be elongated small single crystals which are aligned perpendicular to the (20\\bar{4}) and (204) planes of α″ martensite, indicating that the films’ growth orientation is mainly dominated by these crystallographic planes. Laser pre-patterned substrates are utilized to obtain periodic nanocolumnar arrays. The differences in seed pattern, and inter-seed distances lead to growth of multi-level porous nanostructures. Using a unique sputter deposition geometry consisting of Ti73Ta27 and Ta sputter sources, a nanocolumnar Ti-Ta materials library was fabricated on a static substrate by a co-deposition process (combinatorial-GLAD approach). In this library, a composition spread developed between Ti72.8Ta27.2 and Ti64.4Ta35.6, as confirmed by high-throughput EDX analysis. The morphology over the materials library varies from well-isolated nanocolumns to fan-like nanocolumnar structures. The influence of two sputter sources is investigated by studying the resulting column angle on the materials library. The presented nanostructuring methods including the use of the GLAD technique along with pre-patterning and a combinatorial materials library fabrication strategy offer a promising technological approach for investigating Ti-Ta thin films for a range of applications. The proposed approaches can be similarly implemented for other materials systems which can benefit from the formation of a nanocolumnar morphology.

Morphogenesis of nanostructures in glancing angle deposition of metal thin film coatings

NASA Astrophysics Data System (ADS)

Brown, Timothy James

Atomic vapors condensed onto solid surfaces form a remarkable category of condensed matter materials, the so-called thin films, with a myriad of compositions, morphological structures, and properties. The dynamic process of atomic condensation exhibits self-assembled pattern formation, producing morphologies with atomic-scale three- dimensional structures of seemingly limitless variety. This study attempts to shed new light on the dynamical growth processes of thin film deposition by analyzing in detail a previously unreported specific distinct emergent structure, a crystalline triangular-shaped spike that grows within copper and silver thin films. I explored the deposition parameters that lead to the growth of these unique structures, referred to as "nanospikes", fabricating approximately 55 thin films and used scanning electron microscopy and x-ray diffraction analysis. The variation of parameters include: vapor incidence angle, film thickness, substrate temperature, deposition rate, deposition material, substrate, and source-to-substrate distance. Microscopy analysis reveals that the silver and copper films deposited at glancing vapor incidence angles, 80 degrees and greater, have a high degree of branching interconnectivity between adjacent inclined nanorods. Diffraction analysis reveals that the vapor incidence angle influences the sub-populations of crystallites in the films, producing two different [110] crystal texture orientations. I hypothesize that the growth of nanospikes from nanorods is initiated by the stochastic arrival of vapor atoms and photons emitted from the deposition source at small diameter nanorods, and then driven by localized heating from vapor condensation and photon absorption. Restricted heat flow due to nanoscale thermal conduction maintains an elevated local temperature at the nanorod, enhancing adatom diffusion and enabling fast epitaxial crystal growth, leading to the formation and growth of nanospikes. Electron microscopy and x-ray diffraction analysis, and comparisons to related scientific literature, support this hypothesis. I also designed a highly modular ultrahigh vacuum deposition chamber, capable of concurrently mounting several different pieces of deposition equipment, that allows for a high degree of control of the growth dynamics of deposited thin films. I used the newly designed chamber to fabricate tailor-made nanostructured tantalum films for use in ultracapacitors, for the Cabot Corporation.

Near-chip compliant layer for reducing perimeter stress during assembly process

DOEpatents

Schultz, Mark D.; Takken, Todd E.; Tian, Shurong; Yao, Yuan

2018-03-20

A heat source (single semiconductor chip or group of closely spaced semiconductor chips of similar height) is provided on a first side of a substrate, which substrate has on said first side a support member comprising a compressible material. A heat removal component, oriented at an angle to said heat source, is brought into proximity of said heat source such that said heat removal component contacts said support member prior to contacting said heat source. Said heat removal component is assembled to said heat source such that said support member at least partially absorbs global inequality of force that would otherwise be applied to said heat source, absent said support member comprising said compressible material.

Near-chip compliant layer for reducing perimeter stress during assembly process

DOEpatents

Schultz, Mark D.; Takken, Todd E.; Tian, Shurong; Yao, Yuan

2017-02-14

A heat source (single semiconductor chip or group of closely spaced semiconductor chips of similar height) is provided on a first side of a substrate, which substrate has on said first side a support member comprising a compressible material. A heat removal component, oriented at an angle to said heat source, is brought into proximity of said heat source such that said heat removal component contacts said support member prior to contacting said heat source. Said heat removal component is assembled to said heat source such that said support member at least partially absorbs global inequality of force that would otherwise be applied to said heat source, absent said support member comprising said compressible material.

Method and system for producing sputtered thin films with sub-angstrom thickness uniformity or custom thickness gradients

DOEpatents

Folta, James A.; Montcalm, Claude; Walton, Christopher

2003-01-01

A method and system for producing a thin film with highly uniform (or highly accurate custom graded) thickness on a flat or graded substrate (such as concave or convex optics), by sweeping the substrate across a vapor deposition source with controlled (and generally, time-varying) velocity. In preferred embodiments, the method includes the steps of measuring the source flux distribution (using a test piece that is held stationary while exposed to the source), calculating a set of predicted film thickness profiles, each film thickness profile assuming the measured flux distribution and a different one of a set of sweep velocity modulation recipes, and determining from the predicted film thickness profiles a sweep velocity modulation recipe which is adequate to achieve a predetermined thickness profile. Aspects of the invention include a practical method of accurately measuring source flux distribution, and a computer-implemented method employing a graphical user interface to facilitate convenient selection of an optimal or nearly optimal sweep velocity modulation recipe to achieve a desired thickness profile on a substrate. Preferably, the computer implements an algorithm in which many sweep velocity function parameters (for example, the speed at which each substrate spins about its center as it sweeps across the source) can be varied or set to zero.

35 GHz ENDOR characterization of the "very rapid" signal of xanthine oxidase reacted with 2-hydroxy-6-methylpurine (13C8): evidence against direct Mo-C8 interaction.

PubMed

Manikandan, P; Choi, E Y; Hille, R; Hoffman, B M

2001-03-21

Xanthine oxidase is a molybdenum-containing enzyme that catalyzes the hydroxylation of xanthine and a wide variety of other aromatic heterocycles. In the course of the reaction with xanthine and substrates such as 2-hydroxy-6-methylpurine (HMP), the enzyme gives rise to a Mo(V) EPR signal, denoted "very rapid", that arises from an authentic catalytic intermediate. The two alternative catalytic mechanisms proposed for this enzyme differ critically in whether the distance between Mo and C8 of the purine nucleus in this intermediate is short enough to admit a direct bonding interaction. To examine this distance, we have performed 13C ENDOR measurements of the "very rapid" EPR signal generated by xanthine oxidase during reaction with 13C8-HMP. The resulting (13)C8 hyperfine tensor, A = [10.2(1), 7.0(1), 6.5(1)] MHz, is discussed in the framework of a detailed consideration of factors involved in extracting metrical parameters from an anisotropic hyperfine interaction composed of contributions from multiple sources, in particular, the effect of the local contributions from spin density on (13)C8. The analysis presented here gives a Mo...C distance whose value is expected to be ca. 2.7-2.9 A in the "very rapid" intermediates formed with both xanthine and HMP, consistent with plausible bond lengths for a Mo-O-C8 fragment where C8 is a trigonal-planar aromatic carbon. The difference from earlier conclusions is explained. The data thus do not support the existence of a direct Mo-C bond in the signal-giving species. This conclusion supports a mechanism that does not involve such an interaction and which begins with base-assisted nucleophilic attack of the Mo(VI)-OH group on the C-8 of substrate, with concomitant hydride transfer to the Mo=S group to give Mo(IV)-SH; the EPR-active "very rapid" species then forms by one-electron oxidation and deprotonation to yield the EPR-detectable Mo(V)OS(OR) species. We further discuss the complexities and limitations of the semiempirical method used to arrive at these conclusions.

Dosimetry of 192Ir sources used for endovascular brachytherapy

NASA Astrophysics Data System (ADS)

Reynaert, N.; Van Eijkeren, M.; Taeymans, Y.; Thierens, H.

2001-02-01

An in-phantom calibration technique for 192Ir sources used for endovascular brachytherapy is presented. Three different source lengths were investigated. The calibration was performed in a solid phantom using a Farmer-type ionization chamber at source to detector distances ranging from 1 cm to 5 cm. The dosimetry protocol for medium-energy x-rays extended with a volume-averaging correction factor was used to convert the chamber reading to dose to water. The air kerma strength of the sources was determined as well. EGS4 Monte Carlo calculations were performed to determine the depth dose distribution at distances ranging from 0.6 mm to 10 cm from the source centre. In this way we were able to convert the absolute dose rate at 1 cm distance to the reference point chosen at 2 mm distance. The Monte Carlo results were confirmed by radiochromic film measurements, performed with a double-exposure technique. The dwell times to deliver a dose of 14 Gy at the reference point were determined and compared with results given by the source supplier (CORDIS). They determined the dwell times from a Sievert integration technique based on the source activity. The results from both methods agreed to within 2% for the 12 sources that were evaluated. A Visual Basic routine that superimposes dose distributions, based on the Monte Carlo calculations and the in-phantom calibration, onto intravascular ultrasound images is presented. This routine can be used as an online treatment planning program.

Rectification of Ion Current in Nanopipettes by External Substrates

PubMed Central

Shi, Wenqing; Baker, Lane A.

2014-01-01

We describe ion distribution and the current-voltage (i-V) response of nanopipettes at different probe-to-substrate distances (Dps) as simulated by finite-element methods. Results suggest electrostatic interactions between a charged substrate and the nanopipette dominate electrophoretic ion transport through the nanopipette when Dps is within one order of magnitude of the Debye length (~10 nm for a 1 mM solution as employed in the simulation). Ion current rectification (ICR) and permselectivity associated with a neutral or charged nanopipette can be reversibly enhanced or reduced dependent on Dps, charge polarity and charge density (σ) of the substrate. Regulation of nanopipette current is a consequence of the enrichment or depletion of ions within the nanopipette interior which influences conductivity of the nanopipette. When the external substrate is less negatively charged than the nanopipette, the substrate first reduces, and then enhances the ICR as Dps decreases. Surprisingly, both experimental and simulated data show that a neutral substrate was also able to reduce and reverse the ICR of a slightly negatively charged nanopipette. Simulated results ascribe such effects to the elimination of ion depletion within the nanopipette at positive potentials. PMID:24200344

Rectification of ion current in nanopipettes by external substrates.

PubMed

Sa, Niya; Lan, Wen-Jie; Shi, Wenqing; Baker, Lane A

2013-12-23

We describe ion distribution and the current-voltage (i-V) response of nanopipettes at different probe-to-substrate distances (Dps) as simulated by finite-element methods. Results suggest electrostatic interactions between a charged substrate and the nanopipette dominate electrophoretic ion transport through the nanopipette when Dps is within 1 order of magnitude of the Debye length (∼10 nm for a 1 mM solution as employed in the simulation). Ion current rectification (ICR) and permselectivity associated with a neutral or charged nanopipette can be reversibly enhanced or reduced dependent on Dps, charge polarity, and charge density (σ) of the substrate. Regulation of nanopipette current is a consequence of the enrichment or depletion of ions within the nanopipette interior, which influences conductivity of the nanopipette. When the external substrate is less negatively charged than the nanopipette, the substrate first reduces, and then enhances the ICR as Dps decreases. Surprisingly, both experimental and simulated data show that a neutral substrate was also able to reduce and reverse the ICR of a slightly negatively charged nanopipette. Simulated results ascribe such effects to the elimination of ion depletion within the nanopipette at positive potentials.

Determination of psychostimulants and their metabolites by electrochemistry linked on-line to flowing atmospheric pressure afterglow mass spectrometry.

PubMed

Smoluch, Marek; Mielczarek, Przemyslaw; Reszke, Edward; Hieftje, Gary M; Silberring, Jerzy

2014-09-07

The flowing atmospheric pressure afterglow (FAPA) ion source operates in the ambient atmosphere and has been proven to be a promising tool for direct and rapid determination of numerous compounds. Here we linked a FAPA-MS system to an electrochemical flow cell for the identification of drug metabolites generated electrochemically in order to study simulated metabolic pathways. Psychostimulants and their metabolites produced by electrochemistry (EC) were detected on-line by FAPA-MS. The FAPA source has never been used before for an on-line connection with liquid flow, neither for identification of products generated in an electrochemical flow cell. The system was optimized to achieve the highest ionization efficiency by adjusting several parameters, including distances and angles between the ion source and the outlet of the EC system, the high voltage for plasma generation, flow-rates, and EC parameters. Simulated metabolites from tested compounds [methamphetamine (MAF), para-methoxy-N-methylamphetamine (PMMA), dextromethorphan (DXM), and benzydamine (BAM)] were formed in the EC cell at various pH levels. In all cases the main products were oxidized substrates and compounds after N-demethylation. Generation of such products and their thorough on-line identification confirm that the cytochrome P450 - driven metabolism of pharmaceuticals can be efficiently simulated in an electrochemical cell; this approach may serve as a step towards predictive pharmacology using a fast and robust design.

The role of vision in auditory distance perception.

PubMed

Calcagno, Esteban R; Abregú, Ezequiel L; Eguía, Manuel C; Vergara, Ramiro

2012-01-01

In humans, multisensory interaction is an important strategy for improving the detection of stimuli of different nature and reducing the variability of response. It is known that the presence of visual information affects the auditory perception in the horizontal plane (azimuth), but there are few researches that study the influence of vision in the auditory distance perception. In general, the data obtained from these studies are contradictory and do not completely define the way in which visual cues affect the apparent distance of a sound source. Here psychophysical experiments on auditory distance perception in humans are performed, including and excluding visual cues. The results show that the apparent distance from the source is affected by the presence of visual information and that subjects can store in their memory a representation of the environment that later improves the perception of distance.

Direct-location versus verbal report methods for measuring auditory distance perception in the far field.

PubMed

Etchemendy, Pablo E; Spiousas, Ignacio; Calcagno, Esteban R; Abregú, Ezequiel; Eguia, Manuel C; Vergara, Ramiro O

2018-06-01

In this study we evaluated whether a method of direct location is an appropriate response method for measuring auditory distance perception of far-field sound sources. We designed an experimental set-up that allows participants to indicate the distance at which they perceive the sound source by moving a visual marker. We termed this method Cross-Modal Direct Location (CMDL) since the response procedure involves the visual modality while the stimulus is presented through the auditory modality. Three experiments were conducted with sound sources located from 1 to 6 m. The first one compared the perceived distances obtained using either the CMDL device or verbal report (VR), which is the response method more frequently used for reporting auditory distance in the far field, and found differences on response compression and bias. In Experiment 2, participants reported visual distance estimates to the visual marker that were found highly accurate. Then, we asked the same group of participants to report VR estimates of auditory distance and found that the spatial visual information, obtained from the previous task, did not influence their reports. Finally, Experiment 3 compared the same responses that Experiment 1 but interleaving the methods, showing a weak, but complex, mutual influence. However, the estimates obtained with each method remained statistically different. Our results show that the auditory distance psychophysical functions obtained with the CMDL method are less susceptible to previously reported underestimation for distances over 2 m.

Distance biases in the estimation of the physical properties of Hi-GAL compact sources - I. Clump properties and the identification of high-mass star-forming candidates

NASA Astrophysics Data System (ADS)

Baldeschi, Adriano; Elia, D.; Molinari, S.; Pezzuto, S.; Schisano, E.; Gatti, M.; Serra, A.; Merello, M.; Benedettini, M.; Di Giorgio, A. M.; Liu, J. S.

2017-04-01

The degradation of spatial resolution in star-forming regions, observed at large distances (d ≳ 1 kpc) with Herschel, can lead to estimates of the physical parameters of the detected compact sources (clumps), which do not necessarily mirror the properties of the original population of cores. This paper aims at quantifying the bias introduced in the estimation of these parameters by the distance effect. To do so, we consider Herschel maps of nearby star-forming regions taken from the Herschel Gould Belt survey, and simulate the effect of increased distance to understand what amount of information is lost when a distant star-forming region is observed with Herschel resolution. In the maps displaced to different distances we extract compact sources, and we derive their physical parameters as if they were original Herschel infrared Galactic Plane Survey maps of the extracted source samples. In this way, we are able to discuss how the main physical properties change with distance. In particular, we discuss the ability of clumps to form massive stars: we estimate the fraction of distant sources that are classified as high-mass stars-forming objects due to their position in the mass versus radius diagram, that are only 'false positives'. We also give a threshold for high-mass star formation M>1282 (r/ [pc])^{1.42} M_{⊙}. In conclusion, this paper provides the astronomer dealing with Herschel maps of distant star-forming regions with a set of prescriptions to partially recover the character of the core population in unresolved clumps.

Sound Spectrum Influences Auditory Distance Perception of Sound Sources Located in a Room Environment

PubMed Central

Spiousas, Ignacio; Etchemendy, Pablo E.; Eguia, Manuel C.; Calcagno, Esteban R.; Abregú, Ezequiel; Vergara, Ramiro O.

2017-01-01

Previous studies on the effect of spectral content on auditory distance perception (ADP) focused on the physically measurable cues occurring either in the near field (low-pass filtering due to head diffraction) or when the sound travels distances >15 m (high-frequency energy losses due to air absorption). Here, we study how the spectrum of a sound arriving from a source located in a reverberant room at intermediate distances (1–6 m) influences the perception of the distance to the source. First, we conducted an ADP experiment using pure tones (the simplest possible spectrum) of frequencies 0.5, 1, 2, and 4 kHz. Then, we performed a second ADP experiment with stimuli consisting of continuous broadband and bandpass-filtered (with center frequencies of 0.5, 1.5, and 4 kHz and bandwidths of 1/12, 1/3, and 1.5 octave) pink-noise clips. Our results showed an effect of the stimulus frequency on the perceived distance both for pure tones and filtered noise bands: ADP was less accurate for stimuli containing energy only in the low-frequency range. Analysis of the frequency response of the room showed that the low accuracy observed for low-frequency stimuli can be explained by the presence of sparse modal resonances in the low-frequency region of the spectrum, which induced a non-monotonic relationship between binaural intensity and source distance. The results obtained in the second experiment suggest that ADP can also be affected by stimulus bandwidth but in a less straightforward way (i.e., depending on the center frequency, increasing stimulus bandwidth could have different effects). Finally, the analysis of the acoustical cues suggests that listeners judged source distance using mainly changes in the overall intensity of the auditory stimulus with distance rather than the direct-to-reverberant energy ratio, even for low-frequency noise bands (which typically induce high amount of reverberation). The results obtained in this study show that, depending on the spectrum of the auditory stimulus, reverberation can degrade ADP rather than improve it. PMID:28690556

Sound Spectrum Influences Auditory Distance Perception of Sound Sources Located in a Room Environment.

PubMed

Spiousas, Ignacio; Etchemendy, Pablo E; Eguia, Manuel C; Calcagno, Esteban R; Abregú, Ezequiel; Vergara, Ramiro O

2017-01-01

Previous studies on the effect of spectral content on auditory distance perception (ADP) focused on the physically measurable cues occurring either in the near field (low-pass filtering due to head diffraction) or when the sound travels distances >15 m (high-frequency energy losses due to air absorption). Here, we study how the spectrum of a sound arriving from a source located in a reverberant room at intermediate distances (1-6 m) influences the perception of the distance to the source. First, we conducted an ADP experiment using pure tones (the simplest possible spectrum) of frequencies 0.5, 1, 2, and 4 kHz. Then, we performed a second ADP experiment with stimuli consisting of continuous broadband and bandpass-filtered (with center frequencies of 0.5, 1.5, and 4 kHz and bandwidths of 1/12, 1/3, and 1.5 octave) pink-noise clips. Our results showed an effect of the stimulus frequency on the perceived distance both for pure tones and filtered noise bands: ADP was less accurate for stimuli containing energy only in the low-frequency range. Analysis of the frequency response of the room showed that the low accuracy observed for low-frequency stimuli can be explained by the presence of sparse modal resonances in the low-frequency region of the spectrum, which induced a non-monotonic relationship between binaural intensity and source distance. The results obtained in the second experiment suggest that ADP can also be affected by stimulus bandwidth but in a less straightforward way (i.e., depending on the center frequency, increasing stimulus bandwidth could have different effects). Finally, the analysis of the acoustical cues suggests that listeners judged source distance using mainly changes in the overall intensity of the auditory stimulus with distance rather than the direct-to-reverberant energy ratio, even for low-frequency noise bands (which typically induce high amount of reverberation). The results obtained in this study show that, depending on the spectrum of the auditory stimulus, reverberation can degrade ADP rather than improve it.

An innovative wood-chip-framework substrate used as slow-release carbon source to treat high-strength nitrogen wastewater.

PubMed

Li, Huai; Chi, Zifang; Yan, Baixing; Cheng, Long; Li, Jianzheng

2017-01-01

Removal of nitrogen in wastewater before discharge into receiving water courses is an important consideration in treatment systems. However, nitrogen removal efficiency is usually limited due to the low carbon/nitrogen (C/N) ratio. A common solution is to add external carbon sources, but amount of liquid is difficult to determine. Therefore, a combined wood-chip-framework substrate (with wood, slag and gravel) as a slow-release carbon source was constructed in baffled subsurface-flow constructed wetlands to overcome the problem. Results show that the removal rate of ammonia nitrogen (NH 4 + -N), total nitrogen (TN) and chemical oxygen demand (COD) could reach 37.5%-85%, 57.4%-86%, 32.4%-78%, respectively, indicating the combined substrate could diffuse sufficient oxygen for the nitrification process (slag and gravel zone) and provide carbon source for denitrification process (wood-chip zone). The nitrification and denitrification were determined according to the location of slag/gravel and wood-chip, respectively. Nitrogen removal was efficient at the steady phase before a shock loading using slag-wood-gravel combined substrate because of nitrification-denitrification process, while nitrogen removal was efficient under a shock loading with wood-slag-gravel combined substrate because of ANAMMOX process. This study provides a new idea for wetland treatment of high-strength nitrogen wastewater. Copyright © 2016. Published by Elsevier B.V.

Strontium source and depth of uptake shifts with substrate age in semiarid ecosystems

NASA Astrophysics Data System (ADS)

Coble, Ashley A.; Hart, Stephen C.; Ketterer, Michael E.; Newman, Gregory S.; Kowler, Andrew L.

2015-06-01

Without exogenous rock-derived nutrient sources, terrestrial ecosystems may eventually regress or reach a terminal steady state, but the degree to which exogenous nutrient sources buffer or slow to a theoretical terminal steady state remains unclear. We used strontium isotope ratios (87Sr/86Sr) as a tracer and measured 87Sr/86Sr values in aeolian dust, soils, and vegetation across a well-constrained 3 Myr semiarid substrate age gradient to determine (1) whether the contribution of atmospheric sources of rock-derived nutrients to soil and vegetation pools varied with substrate age and (2) to determine if the depth of uptake varied with substrate age. We found that aeolian-derived nutrients became increasingly important, contributing as much as 71% to plant-available soil pools and tree (Pinus edulis) growth during the latter stages of ecosystem development in a semiarid climate. The depth of nutrient uptake increased on older substrates, demonstrating that trees in arid regions can acquire nutrients from greater depths as ecosystem development progresses presumably in response to nutrient depletion in the more weathered surface soils. Our results demonstrate that global and regional aeolian transport of nutrients to local ecosystems is a vital process for ecosystem development in arid regions. Furthermore, these aeolian nutrient inputs contribute to deep soil nutrient pools, which become increasingly important for maintaining plant productivity over long time scales.

Giant Dirac point shift of graphene phototransistors by doped silicon substrate current

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimatani, Masaaki; Ogawa, Shinpei, E-mail: Ogawa.Shimpei@eb.MitsubishiElectric.co.jp; Fujisawa, Daisuke

2016-03-15

Graphene is a promising new material for photodetectors due to its excellent optical properties and high-speed response. However, graphene-based phototransistors have low responsivity due to the weak light absorption of graphene. We have observed a giant Dirac point shift upon white light illumination in graphene-based phototransistors with n-doped Si substrates, but not those with p-doped substrates. The source-drain current and substrate current were investigated with and without illumination for both p-type and n-type Si substrates. The decay time of the drain-source current indicates that the Si substrate, SiO{sub 2} layer, and metal electrode comprise a metal-oxide-semiconductor (MOS) capacitor due tomore » the presence of defects at the interface between the Si substrate and SiO{sub 2} layer. The difference in the diffusion time of the intrinsic major carriers (electrons) and the photogenerated electron-hole pairs to the depletion layer delays the application of the gate voltage to the graphene channel. Therefore, the giant Dirac point shift is attributed to the n-type Si substrate current. This phenomenon can be exploited to realize high-performance graphene-based phototransistors.« less

Ultra-hard AlMgB14 coatings fabricated by RF magnetron sputtering from a stoichiometric target

NASA Astrophysics Data System (ADS)

Grishin, A. M.; Khartsev, S. I.; Böhlmark, J.; Ahlgren, M.

2015-01-01

For the first time hard aluminum magnesium boride films were fabricated by RF magnetron sputtering from a single stoichiometric ceramic AlMgB14 target. Optimized processing conditions (substrate temperature, target sputtering power and target-to-substrate distance) enable fabrication of stoichiometric in-depth compositionally homogeneous films with the peak values of nanohardness 88 GPa and Young's modulus 517 GPa at the penetration depth of 26 nm and, respectively, 35 and 275 GPa at 200 nm depth in 2 μm thick film.

Tuning the adhesion between polyimide substrate and MWCNTs/epoxy nanocomposite by surface treatment

NASA Astrophysics Data System (ADS)

Bouhamed, Ayda; Kia, Alireza Mohammadian; Naifar, Slim; Dzhagan, Volodymyr; Müller, Christian; Zahn, Dietrich R. T.; Choura, Slim; Kanoun, Olfa

2017-11-01

MWCNTs/epoxy nanocomposite thin films are coated on the polyimide (PI) flexible substrate, to be used as a strain sensor. Previous studies showed that the adhesion between polyimide and other materials are very poor. In this work, two approaches, oxygen plasma cleaning and simple solvent cleaning are performed for activation of the polyimide surface. In order to understand the impact of both cleaning techniques, the physicochemical properties of PI are measured and characterized using contact angle measurements (CAMs), X-ray photoelectron spectroscopy(XPS), and atomic force microscopy (AFM). In addition, the adhesion properties of PI/[MWCNTs/epoxy] systems by varying surface treatment time are investigated and evaluated using force-distance measurements by AFM. The results illustrate that the activated surface exhibits higher surface energy for oxygen plasma cleaning in comparison with the solvent cleaning method. The improvement can be related to the increase of oxygen concentration, which is accompanied by the enhancement of the polar component to 53.79 mN/m due to the formation of functional groups on the surface and the change of the substrate surface roughness from 1.72 nm to 15.5 nm. As a result, improved adhesion was observed from force-distance measurement between PI/[MWCNTs/epoxy] systems due to oxygen plasma effects.

Influence of host anemone (Stichodactyla haddoni, saville-kent, 1893) locomotion on its resident anemonefish reproduction.

PubMed

Balamurugan, R J; Kumar, T T Ajith; Balasubramanian, T

2013-07-01

Anemonefish are found commonly in reef habitats and they select only limited anemone species to exist their life. This study describes the movement of anemone, Stichodactyla haddoni and its impact on the reproduction of anemonefishes in captivity. The anemone movement was found to be creeping and in straight-line between successive positions (based on overlay mapping). The distance traveled by the host with (60%) and without substrate (20%) varied significantly (P<0.05) at a random direction. Spawning interval of the resident fish (3-4 days) increased significantly to 8-12 days (P<0.001) because of anemone mobility. Furthermore, host locomotion affected the embryonic development of harbored fish clutches. Percentage of egg maturity (3.5-35.3%) showed an exponential decrease with increase in the distance of substrate from the clutches, from 98 to 100% in the absence of host mobility to 3.5-35% with movement of >60cm. This study concludes that the sedentary habitat would enhance the reproduction value of the harbored fish. Further, in captivity providing with a substrate, supplying regular feed and good light intensity could prevent anemone migration and its implications on the reproductive success of the anemonefish. Copyright © 2013 Elsevier B.V. All rights reserved.

Investigation of stand-off distance effect on structure, adhesion and hardness of copper coatings obtained by the APS technique

NASA Astrophysics Data System (ADS)

Masoumeh, Goudarzi; Shahrooz, Saviz; Mahmood, Ghoranneviss; Ahmad, Salar Elahi

2018-03-01

The outbreak of the disease and infection in the hospital environment and medical equipment is one of the concerns of modern life. One of the effective ways for preventing and reducing the complications of infections is modification of the surface. Here, the handmade atmospheric plasma spray system is used for accumulating copper as an antibacterial agent on the 316L stainless steel substrate, which applies to hospital environment and medical equipment. As a durable coating with proper adhesion is needed on the substrate, the effect of stand-off distance (SOD) which is an important parameter of the spray on the microstructure, the hardness and adhesion of the copper coating on the 316L stainless steel were investigated. The structure and phase composition of copper depositions were investigated using scanning electron microscopy and X-ray diffraction. The adhesion and hardness of depositions are evidenced using the cross cut tester and Vickers hardness tester, respectively. The findings confirm that the voids in the coatings increase with increasing SOD, which leads to decreasing the hardness of coatings and also the adhesion strength between depositions and substrate. In addition, by increasing the SOD, the oxygen content and the size of grains in the lamellae (fine structure) of coatings also increase.

Long-range wetting transparency on top of layered metal-dielectric substrates

NASA Astrophysics Data System (ADS)

Noginov, M. A.; Barnakov, Yuri A.; Liberman, Vladimir; Prayakarao, Srujana; Bonner, Carl E.; Narimanov, Evgenii E.

2016-06-01

It has been recently shown that scores of physical and chemical phenomena (including spontaneous emission, scattering and Förster energy transfer) can be controlled by nonlocal dielectric environments provided by metamaterials with hyperbolic dispersion and simpler metal/dielectric structures. At this time, we have researched van der Waals interactions and experimentally studied wetting of several metallic, dielectric and composite multilayered substrates. We have found that the wetting angle of water on top of MgF2 is highly sensitive to the thickness of the MgF2 layer and the nature of the underlying substrate that could be positioned as far as ~100 nm beneath the water/MgF2 interface. We refer to this phenomenon as long range wetting transparency. The latter effect cannot be described in terms of the most basic model of dispersion van der Waals-London forces based on pair-wise summation of dipole-dipole interactions across an interface or a gap separating the two media. We infer that the experimentally observed gradual change of the wetting angle with increase of the thickness of the MgF2 layer can possibly be explained by the distance dependence of the Hamaker function (describing the strength of interaction), which originates from retardation of electromagnetic waves at the distances comparable to a wavelength.

Long-range wetting transparency on top of layered metal-dielectric substrates.

PubMed

Noginov, M A; Barnakov, Yuri A; Liberman, Vladimir; Prayakarao, Srujana; Bonner, Carl E; Narimanov, Evgenii E

2016-06-21

It has been recently shown that scores of physical and chemical phenomena (including spontaneous emission, scattering and Förster energy transfer) can be controlled by nonlocal dielectric environments provided by metamaterials with hyperbolic dispersion and simpler metal/dielectric structures. At this time, we have researched van der Waals interactions and experimentally studied wetting of several metallic, dielectric and composite multilayered substrates. We have found that the wetting angle of water on top of MgF2 is highly sensitive to the thickness of the MgF2 layer and the nature of the underlying substrate that could be positioned as far as ~100 nm beneath the water/MgF2 interface. We refer to this phenomenon as long range wetting transparency. The latter effect cannot be described in terms of the most basic model of dispersion van der Waals-London forces based on pair-wise summation of dipole-dipole interactions across an interface or a gap separating the two media. We infer that the experimentally observed gradual change of the wetting angle with increase of the thickness of the MgF2 layer can possibly be explained by the distance dependence of the Hamaker function (describing the strength of interaction), which originates from retardation of electromagnetic waves at the distances comparable to a wavelength.

Long-range wetting transparency on top of layered metal-dielectric substrates

PubMed Central

Noginov, M. A.; Barnakov, Yuri A.; Liberman, Vladimir; Prayakarao, Srujana; Bonner, Carl E.; Narimanov, Evgenii E.

2016-01-01

It has been recently shown that scores of physical and chemical phenomena (including spontaneous emission, scattering and Förster energy transfer) can be controlled by nonlocal dielectric environments provided by metamaterials with hyperbolic dispersion and simpler metal/dielectric structures. At this time, we have researched van der Waals interactions and experimentally studied wetting of several metallic, dielectric and composite multilayered substrates. We have found that the wetting angle of water on top of MgF2 is highly sensitive to the thickness of the MgF2 layer and the nature of the underlying substrate that could be positioned as far as ~100 nm beneath the water/MgF2 interface. We refer to this phenomenon as long range wetting transparency. The latter effect cannot be described in terms of the most basic model of dispersion van der Waals-London forces based on pair-wise summation of dipole-dipole interactions across an interface or a gap separating the two media. We infer that the experimentally observed gradual change of the wetting angle with increase of the thickness of the MgF2 layer can possibly be explained by the distance dependence of the Hamaker function (describing the strength of interaction), which originates from retardation of electromagnetic waves at the distances comparable to a wavelength. PMID:27324650

Refractive Index Imaging of Cells with Variable-Angle Near-Total Internal Reflection (TIR) Microscopy.

PubMed

Bohannon, Kevin P; Holz, Ronald W; Axelrod, Daniel

2017-10-01

The refractive index in the interior of single cells affects the evanescent field depth in quantitative studies using total internal reflection (TIR) fluorescence, but often that index is not well known. We here present method to measure and spatially map the absolute index of refraction in a microscopic sample, by imaging a collimated light beam reflected from the substrate/buffer/cell interference at variable angles of incidence. Above the TIR critical angle (which is a strong function of refractive index), the reflection is 100%, but in the immediate sub-critical angle zone, the reflection intensity is a very strong ascending function of incidence angle. By analyzing the angular position of that edge at each location in the field of view, the local refractive index can be estimated. In addition, by analyzing the steepness of the edge, the distance-to-substrate can be determined. We apply the technique to liquid calibration samples, silica beads, cultured Chinese hamster ovary cells, and primary culture chromaffin cells. The optical technique suffers from decremented lateral resolution, scattering, and interference artifacts. However, it still provides reasonable results for both refractive index (~1.38) and for distance-to-substrate (~150 nm) for the cells, as well as a lateral resolution to about 1 µm.

Effect of Substrate and Process Parameters on the Gas-Substrate Convective Heat Transfer Coefficient During Cold Spraying

NASA Astrophysics Data System (ADS)

Mahdavi, Amirhossein; McDonald, André

2018-02-01

The final quality of cold-sprayed coatings can be significantly influenced by gas-substrate heat exchange, due to the dependence of the deposition efficiency of the particles on the substrate temperature distribution. In this study, the effect of the air temperature and pressure, as process parameters, and surface roughness and thickness, as substrate parameters, on the convective heat transfer coefficient of the impinging air jet was investigated. A low-pressure cold spraying unit was used to generate a compressed air jet that impinged on a flat substrate. A comprehensive mathematical model was developed and coupled with experimental data to estimate the heat transfer coefficient and the surface temperature of the substrate. The effect of the air total temperature and pressure on the heat transfer coefficient was studied. It was found that increasing the total pressure would increase the Nusselt number of the impinging air jet, while total temperature of the air jet had negligible effect on the Nusslet number. It was further found that increasing the roughness of the substrate enhanced the heat exchange between the impinging air jet and the substrate. As a result, higher surface temperatures on the rough substrate were measured. The study of the effect of the substrate thickness on the heat transfer coefficient showed that the Nusselt number that was predicted by the model was independent of the thickness of the substrate. The surface temperature profile, however, decreased in increasing radial distances from the stagnation point of the impinging jet as the thickness of the substrate increased. The results of the current study were aimed to inform on the influence and effect of substrate and process parameters on the gas-substrate heat exchange and the surface temperature of the substrate on the final quality of cold-sprayed coatings.

13C ENDOR Spectroscopy of Lipoxygenase-Substrate Complexes Reveals the Structural Basis for C-H Activation by Tunneling.

PubMed

Horitani, Masaki; Offenbacher, Adam R; Carr, Cody A Marcus; Yu, Tao; Hoeke, Veronika; Cutsail, George E; Hammes-Schiffer, Sharon; Klinman, Judith P; Hoffman, Brian M

2017-02-08

In enzymatic C-H activation by hydrogen tunneling, reduced barrier width is important for efficient hydrogen wave function overlap during catalysis. For native enzymes displaying nonadiabatic tunneling, the dominant reactive hydrogen donor-acceptor distance (DAD) is typically ca. 2.7 Å, considerably shorter than normal van der Waals distances. Without a ground state substrate-bound structure for the prototypical nonadiabatic tunneling system, soybean lipoxygenase (SLO), it has remained unclear whether the requisite close tunneling distance occurs through an unusual ground state active site arrangement or by thermally sampling conformational substates. Herein, we introduce Mn 2+ as a spin-probe surrogate for the SLO Fe ion; X-ray diffraction shows Mn-SLO is structurally faithful to the native enzyme. 13 C ENDOR then reveals the locations of 13 C10 and reactive 13 C11 of linoleic acid relative to the metal; 1 H ENDOR and molecular dynamics simulations of the fully solvated SLO model using ENDOR-derived restraints give additional metrical information. The resulting three-dimensional representation of the SLO active site ground state contains a reactive (a) conformer with hydrogen DAD of ∼3.1 Å, approximately van der Waals contact, plus an inactive (b) conformer with even longer DAD, establishing that stochastic conformational sampling is required to achieve reactive tunneling geometries. Tunneling-impaired SLO variants show increased DADs and variations in substrate positioning and rigidity, confirming previous kinetic and theoretical predictions of such behavior. Overall, this investigation highlights the (i) predictive power of nonadiabatic quantum treatments of proton-coupled electron transfer in SLO and (ii) sensitivity of ENDOR probes to test, detect, and corroborate kinetically predicted trends in active site reactivity and to reveal unexpected features of active site architecture.

Vacuum-insulated catalytic converter

DOEpatents

Benson, David K.

2001-01-01

A catalytic converter has an inner canister that contains catalyst-coated substrates and an outer canister that encloses an annular, variable vacuum insulation chamber surrounding the inner canister. An annular tank containing phase-change material for heat storage and release is positioned in the variable vacuum insulation chamber a distance spaced part from the inner canister. A reversible hydrogen getter in the variable vacuum insulation chamber, preferably on a surface of the heat storage tank, releases hydrogen into the variable vacuum insulation chamber to conduct heat when the phase-change material is hot and absorbs the hydrogen to limit heat transfer to radiation when the phase-change material is cool. A porous zeolite trap in the inner canister absorbs and retains hydrocarbons from the exhaust gases when the catalyst-coated substrates and zeolite trap are cold and releases the hydrocarbons for reaction on the catalyst-coated substrate when the zeolite trap and catalyst-coated substrate get hot.

Propagation of misfit dislocations from buffer/Si interface into Si

DOEpatents

Liliental-Weber, Zuzanna [El Sobrante, CA; Maltez, Rogerio Luis [Porto Alegre, BR; Morkoc, Hadis [Richmond, VA; Xie, Jinqiao [Raleigh, VA

2011-08-30

Misfit dislocations are redirected from the buffer/Si interface and propagated to the Si substrate due to the formation of bubbles in the substrate. The buffer layer growth process is generally a thermal process that also accomplishes annealing of the Si substrate so that bubbles of the implanted ion species are formed in the Si at an appropriate distance from the buffer/Si interface so that the bubbles will not migrate to the Si surface during annealing, but are close enough to the interface so that a strain field around the bubbles will be sensed by dislocations at the buffer/Si interface and dislocations are attracted by the strain field caused by the bubbles and move into the Si substrate instead of into the buffer epi-layer. Fabrication of improved integrated devices based on GaN and Si, such as continuous wave (CW) lasers and light emitting diodes, at reduced cost is thereby enabled.

Fabrication of micro/nano optical fiber by mechano-electrospinning

NASA Astrophysics Data System (ADS)

Chen, Qinnan; Wu, Dezhi; Yu, Zhe; Mei, Xuecui; Fang, Ke; Sun, Daoheng

2017-10-01

We study a novel fabrication method of micro/nano optical fiber by mechano-electrospinning (MES) direct-written technology. MES process is able to precisely manipulate the position and diameter of the electro-spun micro/nano fiber by adjusting the mechanical drawing force, which through changing the speed of motion stage (substrate). By adjusting the substrate speed, the nozzle-to-substrate distance and the applied voltage, the poly(methyl methacrylate) (PMMA) micro/nano optical fibers (MNOF) with controlled diameter are obtained and the tapered MNOF are fabricated by continuously changing the substrate speed. The transmission characteristics of PMMA micro/nano fiber is experimentally demonstrated, and a PMMA micro/nano fiber based refractive index sensor is designed. Our works shows the new fabrication method of MNOF by MES has the potential in the field of light mode conversion, optical waveguide coupling, refractive index detection and new micro/nano optical fiber components.

Increase in dance imprecision with decreasing foraging distance in the honey bee Apis mellifera L. is partly explained by physical constraints.

PubMed

Beekman, Madeleine; Doyen, Laurent; Oldroyd, Benjamin P

2005-12-01

Honey bee foragers communicate the direction and distance of both food sources and new nest sites to nest mates by means of a symbolic dance language. Interestingly, the precision by which dancers transfer directional information is negatively correlated with the distance to the advertised food source. The 'tuned-error' hypothesis suggests that colonies benefit from this imprecision as it spreads recruits out over a patch of constant size irrespective of the distance to the advertised site. An alternative to the tuned-error hypothesis is that dancers are physically incapable of dancing with great precision for nearby sources. Here we revisit the tuned-error hypothesis by studying the change in dance precision with increasing foraging distance over relatively short distances while controlling for environmental influences. We show that bees indeed increase their dance precision with the increase in foraging distance. However, we also show that dance performed by swarm-scouts for a nearby (30 m) nest site, where there could be no benefit to imprecision, are either without or with only limited directional information. This result suggests that imprecision in dance communication is caused primarily by physical constraints in the ability of dancers to turn around quickly enough when the advertised site is nearby.

Apparatus to collect, classify, concentrate, and characterize gas-borne particles

DOEpatents

Rader, Daniel J.; Torczynski, John R.; Wally, Karl; Brockmann, John E.

2003-12-16

An aerosol lab-on-a-chip (ALOC) integrates one or more of a variety of particle collection, classification, concentration (enrichment), an characterization processes onto a single substrate or layered stack of such substrates. By mounting a UV laser diode laser light source on the substrate, or substrates tack, so that it is located down-stream of the sample inlet port and at right angle the sample particle stream, the UV light source can illuminate individual particles in the stream to induce a fluorescence response in those particles having a fluorescent signature such as biological particles, some of said particles. An illuminated particle having a fluorescent signal above a threshold signal would trigger a sorter module that would separate that particle from the particle stream.

Acoustic localization of triggered lightning

NASA Astrophysics Data System (ADS)

Arechiga, Rene O.; Johnson, Jeffrey B.; Edens, Harald E.; Thomas, Ronald J.; Rison, William

2011-05-01

We use acoustic (3.3-500 Hz) arrays to locate local (<20 km) thunder produced by triggered lightning in the Magdalena Mountains of central New Mexico. The locations of the thunder sources are determined by the array back azimuth and the elapsed time since discharge of the lightning flash. We compare the acoustic source locations with those obtained by the Lightning Mapping Array (LMA) from Langmuir Laboratory, which is capable of accurately locating the lightning channels. To estimate the location accuracy of the acoustic array we performed Monte Carlo simulations and measured the distance (nearest neighbors) between acoustic and LMA sources. For close sources (<5 km) the mean nearest-neighbors distance was 185 m compared to 100 m predicted by the Monte Carlo analysis. For far distances (>6 km) the error increases to 800 m for the nearest neighbors and 650 m for the Monte Carlo analysis. This work shows that thunder sources can be accurately located using acoustic signals.

Sputtered silicon nitride coatings for wear protection

NASA Technical Reports Server (NTRS)

Grill, A.; Aron, P. R.

1982-01-01

Silicon nitride films were deposited by RF sputtering on 304 stainless steel substrates in a planar RF sputtering apparatus. The sputtering was performed from a Si3N4 target in a sputtering atmosphere of argon and nitrogen. The rate of deposition, the composition of the coatings, the surface microhardness and the adhesion of the coatings to the substrates were investigated as a function of the process parameters, such as: substrate target distance, fraction nitrogen in the sputtering atmosphere and sputtering pressure. Silicon rich coating was obtained for fraction nitrogen below 0.2. The rate of deposition decreases continuously with increasing fraction nitrogen and decreasing sputtering pressure. It was found that the adherence of the coatings improves with decreasing sputtering pressure, almost independently of their composition.

Correlation of plume dynamics and oxygen pressure with VO2 stoichiometry during pulsed laser deposition

NASA Astrophysics Data System (ADS)

Lafane, S.; Kerdja, T.; Abdelli-Messaci, S.; Khereddine, Y.; Kechouane, M.; Nemraoui, O.

2013-07-01

Vanadium dioxide thin films have been deposited on Corning glass substrates by a KrF laser ablation of V2O5 target at the laser fluence of 2 J cm-2. The substrate temperature and the target-substrate distance were set to 500 ∘C and 4 cm, respectively. X-ray diffraction analysis showed that pure VO2 is only obtained at an oxygen pressure range of 4×10-3-2×10-2 mbar. A higher optical switching contrast was obtained for the VO2 films deposited at 4×10-3-10-2 mbar. The films properties were correlated to the plume-oxygen gas interaction monitored by fast imaging of the plume.

Dry season distribution of land crabs, Gecarcinus quadratus (Crustacea: Gecarcinidae), in Corcovado National Park, Costa Rica.

PubMed

Griffiths, Megan E; Mohammad, Basma A; Vega, Andres

2007-03-01

The land crab Gecarcinus quadratus is an engineering species that controls nutrient cycling in tropical forests. Factors regulating their coastal distribution are not fully understood. We quantified land crab distribution during the dry season at Sirena Field Station in Corcovado National Park, Costa Rica, and found that land crab burrow density decreases with increasing distance from the ocean. Leaf litter depth and tree seedling density are negatively correlated with land crab burrow density. Burrows are strongly associated with sand substrate and burrow density is comparatively low in clay substrate. Results suggest that G. quadratus is limited to a narrow coastal zone with sand substrate, and this distribution could have profound effects on plant community structure.

Polaron effect on the bandgap modulation in monolayer transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Xiao, Yao; Li, Zhi-Qing; Wang, Zi-Wu

2017-12-01

We theoretically study the bandgap modulation in monolayer transition metal dichalcogenides (TMDs) originating from the carrier-optical phonon coupling in the Fröhlich polaron model, in which both of the surface optical phonons modes induced by the polar substrate and the intrinsic longitudinal optical phonons modes have been taken into account. We find that the modulated magnitude of the bandgap is in the range of 100-500 meV by altering different polar substrates and tuning the internal distance between TMDs and polar substrate. The large tunability of the bandgap not only provides a possible explanation for the experimental measurements regarding the dielectric environmental sensitivity of the bandgap, but also holds promise for potential applications in optoelectronics and photovoltaics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Rabindar K., E-mail: rkrksharma6@gmail.com; Reddy, G. B., E-mail: rkrksharma6@gmail.com

In this report, we synthesize vertically aligned molybdenum trioxide (α−MoO{sub 3}) nanoflakes (NFs) with high aspect ratio (height/thickness >15) on the cobalt coated glass substrates by the plasma assisted sublimation process, employing Mo metal strip as a sublimation source. The effect of substrate temperature, nature of substrate as well as the geometry of the sublimation source (Mo-strip) have been investigated on the morphological, structural and optical properties of the grown NFs, keeping plasma parameters as fixed. The surface morphology, crystalline structure and optical properties of MoO{sub 3} NFs have been studied systematically by using scanning electron microscope (SEM), transmission electronmore » microscope (TEM) with selected area electron diffraction (SAED), X-ray diffractometer, and IR- spectroscopy. The experimental observations endorse that the characteristics of MoO{sub 3} NFs are strongly depend on substrate temperature, substrate nature as well as geometry of Mo-strip. All the observed results are well in consonance with each other.« less

Influence of laser power on the penetration depth and geometry of scanning tracks in selective laser melting

NASA Astrophysics Data System (ADS)

Stopyra, Wojciech; Kurzac, Jarosław; Gruber, Konrad; Kurzynowski, Tomasz; Chlebus, Edward

2016-12-01

SLM technology allows production of a fully functional objects from metal and ceramic powders, with true density of more than 99,9%. The quality of manufactured items in SLM method affects more than 100 parameters, which can be divided into fixed and variable. Fixed parameters are those whose value before the process should be defined and maintained in an appropriate range during the process, e.g. chemical composition and morphology of the powder, oxygen level in working chamber, heating temperature of the substrate plate. In SLM technology, five parameters are variables that optimal set allows to produce parts without defects (pores, cracks) and with an acceptable speed. These parameters are: laser power, distance between points, time of exposure, distance between lines and layer thickness. To develop optimal parameters thin walls or single track experiments are performed, to select the best sets narrowed to three parameters: laser power, exposure time and distance between points. In this paper, the effect of laser power on the penetration depth and geometry of scanned single track was shown. In this experiment, titanium (grade 2) substrate plate was used and scanned by fibre laser of 1064 nm wavelength. For each track width, height and penetration depth of laser beam was measured.

Power density measurements to optimize AC plasma jet operation in blood coagulation.

PubMed

Ahmed, Kamal M; Eldeighdye, Shaimaa M; Allam, Tarek M; Hassanin, Walaa F

2018-06-14

In this paper, the plasma power density and corresponding plasma dose of a low-cost air non-thermal plasma jet (ANPJ) device are estimated at different axial distances from the nozzle. This estimation is achieved by measuring the voltage and current at the substrate using diagnostic techniques that can be easily made in laboratory; thin wire and dielectric probe, respectively. This device uses a compressed air as input gas instead of the relatively-expensive, large-sized and heavy weighed tanks of Ar or He gases. The calculated plasma dose is found to be very low and allows the presented device to be used in biomedical applications (especially blood coagulation). While plasma active species and charged-particles are found to be the most effective on blood coagulation formation, both air flow and UV, individually, do not have any effect. Moreover, optimal conditions for accelerating blood coagulation are studied. Results showed that, the power density at the substrate is shown to be decreased with increasing the distance from the nozzle. In addition, both distances from nozzle and air flow rate play an important role in accelerating blood coagulation process. Finally, this device is efficient, small-sized, safe enough, of low cost and, hence, has its chances to be wide spread as a first aid and in ambulance.

Distance Education Programs in Social Work: Current and Emerging Trends

ERIC Educational Resources Information Center

Vernon, Robert; Vakalahi, Halaevalu; Pierce, Dean; Pittman-Munke, Peggy; Adkins, Lynn Frantz

2009-01-01

This article reports on current and emerging trends in the use of distance education technologies in social work education. Areas studied include the extent of distance education programs, curricular areas covered, technologies used, pedagogical approaches, intentions for degree-program development, sources of pressure to adopt distance education…

Ultraluminous X-ray sources: new distance indicators?

NASA Astrophysics Data System (ADS)

Różańska, A.; Bresler, K.; Bełdycki, B.; Madej, J.; Adhikari, T. P.

2018-05-01

Aims: In this paper we fit the NuSTAR and XMM-Newton data of three sources: NGC 7793 P13, NGC5907 ULX1, and Circinus ULX5. Methods: Our single model contains emission from a non-spherical system: a neutron star plus an accretion disk directed towards the observer. Results: We obtained a very good fit with the reduced χ2 per degree of freedom equal to 1.08 for P13, 1.01 for ULX1, and 1.14 for ULX5. The normalization of our model constrains the distance to the source. The resulting distances are D = 3.41-0.10+0.11, 6.55-0.81+0.69, and 2.60-0.03+0.05 Mpc for P13, ULX1, and ULX5 respectively. The distances to P13 and ULX5 are in perfect agreement with previous distance measurements to their host galaxies. Conclusions: Our results confirm that P13, ULX1, and ULX5 may contain central hot neutron stars. When the outgoing emission is computed by integration over the emitting surface and successfully fitted to the data, then the resulting model normalization is the direct distance indicator.

Photo-vibrational sensing of trace chemicals and explosives by long-distance differential laser Doppler vibrometer

NASA Astrophysics Data System (ADS)

Fu, Yu; Liu, Huan; Hu, Qi; Xie, Jiecheng

2017-05-01

Photoacoustic/photothermal spectroscopy is an established technique for trace detection of chemicals and explosives. Normally high-sensitive microphone or PZT sensor is used to detect the signal in photoacoustic cell. In recent years, laser Doppler vibrometer (LDV) is proposed to remote-sense photoacoustic signal on various substrates. It is a highsensitivity sensor with a displacement resolution of <10pm. In this research, the photoacoustic effect of various chemicals and explosives is excited by a quantum cascade laser (QCL) at their absorbance peak. A home-developed differential LDV at 1550nm wavelength is applied to detect the vibration signal at 100m. A differential configuration is applied to minimize the environment factors, such as environment noise and vibration, air turbulence, etc. and increase the detection sensitivity. The photo-vibrational signal of chemicals and explosives on different substrates are detected. The results show the potential of the proposed technique on detection of trace chemicals and explosives at long standoff distance.

Analysis and Design of a Long Range PTFE Substrate UHF RFID Tag for Cargo Container Identification

NASA Astrophysics Data System (ADS)

Petrariu, Adrian-Ioan; Popa, Valentin

2016-01-01

In this paper, a high-performances microstrip antenna for UHF (ultra high frequency) RFID (radio frequency identification) tag is designed, prototyped and tested. The antenna consists of two main components: a 1.52 mm RT/duroid 5880 laminate substrate on which the antenna is designed and a 10 mm polytetrafluoroethylene (PTFE) dielectric material placed as a separator between the antenna and the reference ground plane for the microstrip antenna. With this structure, the RFID tag can reach a maximum reading distance of 19 m, although the antenna has a compact size of 80 mm × 50 mm. The long reading distance is obtained by attaching to the antenna an RFID chip that can provide a reading sensitivity of -20.5 dBm. The high bandwidth from 677 MHz to 947 MHz measured at -10 dB, makes the tag being usable worldwide especially for cargo container identification, the main purpose of this research.

An investigation on physical properties of SiOx nanowires deposited by chemical vapor deposition method: The effect of substrate to boat distance

NASA Astrophysics Data System (ADS)

Heidaryan, Narges; Eshghi, Hosein

2017-09-01

Large-scale silicon oxide nanowires (SiOx NWs) with a diameter about 250 nm on silicon wafers were synthesized by thermal evaporation of silicon monoxide (SiO) powder. In order to investigate the role of distance on the physical properties of SiOx NWs, Si substrates were positioned at 5 cm and 10 cm apart from the boat position set at 1150∘C. The local temperatues of the samples were 1100∘C and 1050∘C, respectively. The SEM images and EDS spectra showed interweaved networks of SiOx NWs with x = 0.62 and 0.65 in these layers. The XRD patterns showed S1 has a polycrystalline structure (cristobalite), while S2 has amorphous nature. The PL spectra showed an intense blue peak at 468 nm in S1, and a violet peak at 427 nm in S2 that could be related to the differences in the crystallite structures and oxygen vacancies in these samples.

LPG sensing characteristics of electrospray deposited SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Gürbüz, Mevlüt; Günkaya, Göktuğ; Doğan, Aydın

2014-11-01

In this study, SnO2 films were fabricated on conductive substrate such as aluminum and platinum coated alumina using electro-spray deposition (ESD) method for gas sensor applications. Solution flow rate, coating time, substrate-nozzle distance and solid/alcohol ratio were studied to optimize SnO2 film structure. The morphology of the deposited films was characterized by stereo and scanning electron microscopy (SEM). The gas sensing properties of tin oxide films were investigated using liquid petroleum gas (LPG) for various lower explosive limit (LEL). The results obtained from microscopic analyses show that optimum SnO2 films were evaluated at flow rate of 0.05 ml/min, at distance of 6 cm, for 10 min deposition time, for 20 gSnO2/Lethanol ratio and at 7 kV DC electric field. By the results obtained from the gas sensing behavior, the sensitivity of the films was increased with operating temperature. The films showed better sensitivity for 20 LEL LPG concentration at 450 °C operating temperature.

Some factors affecting efficiency of the ultrasound-aided enzymatic hydrolysis of cotton cellulose.

PubMed

Szabo, Orsolya Erzsebet; Csiszar, Emilia

2017-01-20

The efficiency of the enzymatic hydrolysis of cellulose with low frequency ultrasound (horn-type reactor) was investigated and characterized by the concentration of reducing sugars liberated. Small squares of bleached cotton fabric were used for comparing the efficiency of different agitation methods (i.e. magnetic stirring, horizontal and vertical mechanical agitation) and ultrasound. At the same enzyme dosage and substrate level, sonication at 40, 60 and 80% amplitudes (I diss : 16.2, 32.2 and 43.4W/cm 2 , respectively) intensified the hydrolysis over the most efficient mechanical agitation (i.e. magnetic stirring) alone by 15%, 24% and 54%, respectively. For mapping the ultrasonicated field, fabric layers positioned perpendicularly to the ultrasonic probe at different distances were hydrolysed. The optimal operating conditions were reached at 60% amplitude and 9mm The yield depended mainly on important factors such as amplitude, the presence of a reflector, distance from horn and form of substrate. Copyright © 2016 Elsevier Ltd. All rights reserved.

Examination of P/S Spectral Ratios for Small Explosions at Local Distances and Interpretation of Moment Tensors Estimated from Near-Source Data

DTIC Science & Technology

2010-09-01

EXAMINATION OF P/S SPECTRAL RATIOS FOR SMALL EXPLOSIONS AT LOCAL DISTANCES AND INTERPRETATION OF MOMENT TENSORS ESTIMATED FROM NEAR-SOURCE DATA...and particle motion. We then estimated smoothed spectra for the P- and S-waves and formed P/S spectral ratios. The signal quality and difficulty in...4. TITLE AND SUBTITLE Examination of P/S Spectral Ratios for Small Explosions at Local Distances and Interpretation of Moment Tensors Estimated from

A study on the evaporation process with multiple point-sources

NASA Astrophysics Data System (ADS)

Jun, Sunghoon; Kim, Minseok; Kim, Suk Han; Lee, Moon Yong; Lee, Eung Ki

2013-10-01

In Organic Light Emitting Display (OLED) manufacturing processes, there is a need to enlarge the mother glass substrate to raise its productivity and enable OLED TV. The larger the size of the glass substrate, the more difficult it is to establish a uniform thickness profile of the organic thin-film layer in the vacuum evaporation process. In this paper, a multiple point-source evaporation process is proposed to deposit a uniform organic layer uniformly. Using this method, a uniformity of 3.75% was achieved along a 1,300 mm length of Gen. 5.5 glass substrate (1300 × 1500 mm2).

HOW FAR AWAY ARE THE SOURCES OF ICECUBE NEUTRINOS? CONSTRAINTS FROM THE DIFFUSE TERAELECTRONVOLT GAMMA-RAY BACKGROUND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Xiao-Chuan; Liu, Ruo-Yu; Wang, Xiang-Yu, E-mail: xywang@nju.edu.cn

The nearly isotropic distribution of teraelectronvolt to petaelectronvolt neutrinos recently detected by the IceCube Collaboration suggests that they come from sources at a distance beyond our Galaxy, but how far away they are is largely unknown because of a lack of any associations with known sources. In this paper, we propose that the cumulative TeV gamma-ray emission accompanying the production of neutrinos can be used to constrain the distance of these neutrino sources, since the opacity of TeV gamma rays due to absorption by the extragalactic background light depends on the distance these TeV gamma rays have traveled. As themore » diffuse extragalactic TeV background measured by Fermi is much weaker than the expected cumulative flux associated with IceCube neutrinos, the majority of IceCube neutrinos, if their sources are transparent to TeV gamma rays, must come from distances larger than the horizon of TeV gamma rays. We find that above 80% of the IceCube neutrinos should come from sources at redshift z > 0.5. Thus, the chance of finding nearby sources correlated with IceCube neutrinos would be small. We also find that, to explain the flux of neutrinos under the TeV gamma-ray emission constraint, the redshift evolution of neutrino source density must be at least as fast as the cosmic star formation rate.« less

Radiation characteristics of a source in a thin substrate mounted over a dielectric medium

NASA Technical Reports Server (NTRS)

Engheta, Nader; Elachi, Charles

1988-01-01

The radiation pattern of a line source is calculated for the case in which the source is lying on the top or the bottom surface of a lossless dielectric substrate that is mounted on the top of semiinfinite dielectric medium. It is found that in both cases the pattern along the interfaces has a null; that the pattern in the upper semiinfinite medium has a single lobe; and that the pattern in the lower semiinfinite medium has many lobes, the number of which varies with the substrate thickness. In both cases, the power radiated into the lower medium is more than that radiated into the upper medium. Applications of this calculation to remote sensing, microstrip antenna technology, and antenna arrays are discussed.

THE BOLOCAM GALACTIC PLANE SURVEY. VIII. A MID-INFRARED KINEMATIC DISTANCE DISCRIMINATION METHOD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ellsworth-Bowers, Timothy P.; Glenn, Jason; Battersby, Cara

2013-06-10

We present a new distance estimation method for dust-continuum-identified molecular cloud clumps. Recent (sub-)millimeter Galactic plane surveys have cataloged tens of thousands of these objects, plausible precursors to stellar clusters, but detailed study of their physical properties requires robust distance determinations. We derive Bayesian distance probability density functions (DPDFs) for 770 objects from the Bolocam Galactic Plane Survey in the Galactic longitude range 7. Degree-Sign 5 {<=} l {<=} 65 Degree-Sign . The DPDF formalism is based on kinematic distances, and uses any number of external data sets to place prior distance probabilities to resolve the kinematic distance ambiguity (KDA)more » for objects in the inner Galaxy. We present here priors related to the mid-infrared absorption of dust in dense molecular regions and the distribution of molecular gas in the Galactic disk. By assuming a numerical model of Galactic mid-infrared emission and simple radiative transfer, we match the morphology of (sub-)millimeter thermal dust emission with mid-infrared absorption to compute a prior DPDF for distance discrimination. Selecting objects first from (sub-)millimeter source catalogs avoids a bias towards the darkest infrared dark clouds (IRDCs) and extends the range of heliocentric distance probed by mid-infrared extinction and includes lower-contrast sources. We derive well-constrained KDA resolutions for 618 molecular cloud clumps, with approximately 15% placed at or beyond the tangent distance. Objects with mid-infrared contrast sufficient to be cataloged as IRDCs are generally placed at the near kinematic distance. Distance comparisons with Galactic Ring Survey KDA resolutions yield a 92% agreement. A face-on view of the Milky Way using resolved distances reveals sections of the Sagittarius and Scutum-Centaurus Arms. This KDA-resolution method for large catalogs of sources through the combination of (sub-)millimeter and mid-infrared observations of molecular cloud clumps is generally applicable to other dust-continuum Galactic plane surveys.« less

Effect of tissue composition on dose distribution in brachytherapy with various photon emitting sources

PubMed Central

Ghorbani, Mahdi; Salahshour, Fateme; Haghparast, Abbas; Knaup, Courtney

2014-01-01

Purpose The aim of this study is to compare the dose in various soft tissues in brachytherapy with photon emitting sources. Material and methods 103Pd, 125I, 169Yb, 192Ir brachytherapy sources were simulated with MCNPX Monte Carlo code, and their dose rate constant and radial dose function were compared with the published data. A spherical phantom with 50 cm radius was simulated and the dose at various radial distances in adipose tissue, breast tissue, 4-component soft tissue, brain (grey/white matter), muscle (skeletal), lung tissue, blood (whole), 9-component soft tissue, and water were calculated. The absolute dose and relative dose difference with respect to 9-component soft tissue was obtained for various materials, sources, and distances. Results There was good agreement between the dosimetric parameters of the sources and the published data. Adipose tissue, breast tissue, 4-component soft tissue, and water showed the greatest difference in dose relative to the dose to the 9-component soft tissue. The other soft tissues showed lower dose differences. The dose difference was also higher for 103Pd source than for 125I, 169Yb, and 192Ir sources. Furthermore, greater distances from the source had higher relative dose differences and the effect can be justified due to the change in photon spectrum (softening or hardening) as photons traverse the phantom material. Conclusions The ignorance of soft tissue characteristics (density, composition, etc.) by treatment planning systems incorporates a significant error in dose delivery to the patient in brachytherapy with photon sources. The error depends on the type of soft tissue, brachytherapy source, as well as the distance from the source. PMID:24790623

Comparison of pelletized biochar derived from two source materials as replacements for peat in potting substrates

USDA-ARS?s Scientific Manuscript database

Soilless substrates are primarily used in the production of containerized greenhouse and nursery crops, with sphagnum peat moss being a primary constituent of most substrates. We are examining biochars for several horticultural applications, including as peat moss replacements. Biochar was prepared ...

The Gould’s Belt Distances Survey (GOBELINS). III. The Distance to the Serpens/Aquila Molecular Complex

NASA Astrophysics Data System (ADS)

Ortiz-León, Gisela N.; Dzib, Sergio A.; Kounkel, Marina A.; Loinard, Laurent; Mioduszewski, Amy J.; Rodríguez, Luis F.; Torres, Rosa M.; Pech, Gerardo; Rivera, Juana L.; Hartmann, Lee; Boden, Andrew F.; Evans, Neal J., II; Briceño, Cesar; Tobin, John J.; Galli, Phillip A. B.

2017-01-01

We report on new distances and proper motions to seven stars across the Serpens/Aquila complex. The observations were obtained as part of the Gould’s Belt Distances Survey (GOBELINS) project between 2013 September and 2016 April with the Very Long Baseline Array (VLBA). One of our targets is the proto-Herbig AeBe object EC 95, which is a binary system embedded in the Serpens Core. For this system, we combined the GOBELINS observations with previous VLBA data to cover a total period of 8 years, and derive the orbital elements and an updated source distance. The individual distances to sources in the complex are fully consistent with each other, and the mean value corresponds to a distance of 436.0 ± 9.2 pc for the Serpens/W40 complex. Given this new evidence, we argue that Serpens Main, W40, and Serpens South are physically associated and form a single cloud structure.

Detection of Optical Ghost in the HST ACS Solar Blind Channel Filter 122M

NASA Astrophysics Data System (ADS)

Collins, K. A.; Grady, C. A.; Woodgate, B. E.; Williger, G. M.

2007-06-01

We report the detection of an optical ghost in the Advanced Camera for Surveys (ACS) Solar Blind Channel (SBC). The ghost was first detected in deep imagery of two Herbig Ae stars, HD 169142 and HD 100453, using filter F122M in April and June of 2006, respectively. The ghost was then verified in two different epochs (June 2002 and March 2003) of archival calibration imaging of the reference white dwarf star HS 2027+0651, which is a known single source. After detailed analysis of the above data, we show that the ghost has a consistent offset and position angle for the four sets of images and does not depend on spacecraft orientation. The mean energy of the ghost is about 0.82% of the energy of the primary target and is located 19° to the left of the positive y-axis of the geometrically corrected detector frame at a distance of about 4 to 4.5 arcsec (160-180 pixels) from the peak of the primary target. The ghost is consistent with a reflection between the back and front sides of the F122M filter. The variation in the distance to the nearest edge and the elongation of the ghost is consistent with the variation in refractive index of the filter substrate over its passband.

Deformation behavior of coherently strained InAs/GaAs(111)A heteroepitaxial systems: Theoretical calculations and experimental measurements

NASA Astrophysics Data System (ADS)

Zepeda-Ruiz, Luis A.; Pelzel, Rodney I.; Nosho, Brett Z.; Weinberg, W. Henry; Maroudas, Dimitrios

2001-09-01

A comprehensive, quantitative analysis is presented of the deformation behavior of coherently strained InAs/GaAs(111)A heteroepitaxial systems. The analysis combines a hierarchical theoretical approach with experimental measurements. Continuum linear elasticity theory is linked with atomic-scale calculations of structural relaxation for detailed theoretical studies of deformation in systems consisting of InAs thin films on thin GaAs(111)A substrates that are mechanically unconstrained at their bases. Molecular-beam epitaxy is used to grow very thin InAs films on both thick and thin GaAs buffer layers on epi-ready GaAs(111)A substrates. The deformation state of these samples is characterized by x-ray diffraction (XRD). The interplanar distances of thin GaAs buffer layers along the [220] and [111] crystallographic directions obtained from the corresponding XRD spectra indicate clearly that thin buffer layers deform parallel to the InAs/GaAs(111)A interfacial plane, thus aiding in the accommodation of the strain induced by lattice mismatch. The experimental measurements are in excellent agreement with the calculated lattice interplanar distances and the corresponding strain fields in the thin mechanically unconstrained substrates considered in the theoretical analysis. Therefore, this work contributes direct evidence in support of our earlier proposal that thin buffer layers in layer-by-layer semiconductor heteroepitaxy exhibit mechanical behavior similar to that of compliant substrates [see, e.g., B. Z. Nosho, L. A. Zepeda-Ruiz, R. I. Pelzel, W. H. Weinberg, and D. Maroudas, Appl. Phys. Lett. 75, 829 (1999)].

An interpolation method for stream habitat assessments

USGS Publications Warehouse

Sheehan, Kenneth R.; Welsh, Stuart A.

2015-01-01

Interpolation of stream habitat can be very useful for habitat assessment. Using a small number of habitat samples to predict the habitat of larger areas can reduce time and labor costs as long as it provides accurate estimates of habitat. The spatial correlation of stream habitat variables such as substrate and depth improves the accuracy of interpolated data. Several geographical information system interpolation methods (natural neighbor, inverse distance weighted, ordinary kriging, spline, and universal kriging) were used to predict substrate and depth within a 210.7-m2 section of a second-order stream based on 2.5% and 5.0% sampling of the total area. Depth and substrate were recorded for the entire study site and compared with the interpolated values to determine the accuracy of the predictions. In all instances, the 5% interpolations were more accurate for both depth and substrate than the 2.5% interpolations, which achieved accuracies up to 95% and 92%, respectively. Interpolations of depth based on 2.5% sampling attained accuracies of 49–92%, whereas those based on 5% percent sampling attained accuracies of 57–95%. Natural neighbor interpolation was more accurate than that using the inverse distance weighted, ordinary kriging, spline, and universal kriging approaches. Our findings demonstrate the effective use of minimal amounts of small-scale data for the interpolation of habitat over large areas of a stream channel. Use of this method will provide time and cost savings in the assessment of large sections of rivers as well as functional maps to aid the habitat-based management of aquatic species.

SU-E-T-254: Development of a HDR-BT QA Tool for Verification of Source Position with Oncentra Applicator Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumazaki, Y; Miyaura, K; Hirai, R

2015-06-15

Purpose: To develop a High Dose Rate Brachytherapy (HDR-BT) quality assurance (QA) tool for verification of source position with Oncentra applicator modeling, and to report the results of radiation source positions with this tool. Methods: We developed a HDR-BT QA phantom and automated analysis software for verification of source position with Oncentra applicator modeling for the Fletcher applicator used in the MicroSelectron HDR system. This tool is intended for end-to-end tests that mimic the clinical 3D image-guided brachytherapy (3D-IGBT) workflow. The phantom is a 30x30x3 cm cuboid phantom with radiopaque markers, which are inserted into the phantom to evaluate applicatormore » tips and reference source positions; positions are laterally shifted 10 mm from the applicator axis. The markers are lead-based and scatter radiation to expose the films. Gafchromic RTQA2 films are placed on the applicators. The phantom includes spaces to embed the applicators. The source position is determined as the distance between the exposed source position and center position of two pairs of the first radiopaque markers. We generated a 3D-IGBT plan with applicator modeling. The first source position was 6 mm from the applicator tips, and the second source position was 10 mm from the first source position. Results: All source positions were consistent with the exposed positions within 1 mm for all Fletcher applicators using in-house software. Moreover, the distance between source positions was in good agreement with the reference distance. Applicator offset, determined as the distance from the applicator tips at the first source position in the treatment planning system, was accurate. Conclusion: Source position accuracy of applicator modeling used in 3D-IGBT was acceptable. This phantom and software will be useful as a HDR-BT QA tool for verification of source position with Oncentra applicator modeling.« less

Benefits of Atrial Substrate Modification Guided by Electrogram Similarity and Phase Mapping Techniques to Eliminate Rotors and Focal Sources Versus Conventional Defragmentation in Persistent Atrial Fibrillation.

PubMed

Lin, Yenn-Jiang; Lo, Men-Tzung; Chang, Shih-Lin; Lo, Li-Wei; Hu, Yu-Feng; Chao, Tze-Fan; Chung, Fa-Po; Liao, Jo-Nan; Lin, Chin-Yu; Kuo, Huan-Yu; Chang, Yi-Chung; Lin, Chen; Tuan, Ta-Chuan; Vincent Young, Hsu-Wen; Suenari, Kazuyoshi; Dan Do, Van Buu; Raharjo, Suunu Budhi; Huang, Norden E; Chen, Shih-Ann

2016-11-01

This prospective study compared the efficacy of atrial substrate modification guided by a nonlinear phase mapping technique with that of conventional substrate ablation. The optimal ablation strategy for persistent atrial fibrillation (AF) was unknown. In phase 1 study, we applied a cellular automation technique to simulate the electrical wave propagation to improve the phase mapping algorithm, involving analysis of high-similarity electrogram regions. In addition, we defined rotors and focal AF sources, using the physical parameters of the divergence and curvature forces. In phase 2 study, we enrolled 68 patients with persistent AF undergoing substrate modification into 2 groups, group-1 (n = 34) underwent similarity index (SI) and phase mapping techniques; group-2 (n = 34) received complex fractionated atrial electrogram ablation with commercially available software. Group-1 received real-time waveform similarity measurements in which a phase mapping algorithm was applied to localize the sources. We evaluated the single-procedure freedom from AF. In group-1, we identified an average of 2.6 ± 0.89 SI regions per chamber. These regions involved rotors and focal sources in 65% and 77% of patients in group-1, respectively. Group-1 patients had shorter ablation procedure times, higher termination rates, and significant reduction in AF recurrence compared to group-2 and a trend toward benefit for all atrial arrhythmias. Multivariate analysis showed that substrate mapping using nonlinear similarity and phase mapping was the independent predictor of freedom from AF recurrence (hazard ratio: 0.26; 95% confidence interval: 0.09 to 0.74; p = 0.01). Our study showed that for persistent AF ablation, a specified substrate modification guided by nonlinear phase mapping could eliminate localized re-entry and non-pulmonary focal sources after pulmonary vein isolation. Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

A Dust-scattering Halo of 4U 1630–47 Observed with Chandra and Swift: New Constraints on the Source Distance

NASA Astrophysics Data System (ADS)

Kalemci, E.; Maccarone, T. J.; Tomsick, J. A.

2018-06-01

We have observed the Galactic black hole transient 4U 1630‑47 during the decay of its 2016 outburst with Chandra and Swift to investigate the properties of the dust-scattering halo created by the source. The scattering halo shows a structure that includes a bright ring between 80″ and 240″ surrounding the source, and a continuous distribution beyond 250″. An analysis of the 12CO J = 1–0 map and spectrum in the line of sight to the source indicates that a molecular cloud with a radial velocity of ‑79 km s‑1 (denoted MC ‑79) is the main scattering body that creates the bright ring. We found additional clouds in the line of sight, calculated their kinematic distances, and resolved the well known “near” and “far” distance ambiguity for most of the clouds. At the favored far-distance estimate of MC ‑79, the modeling of the surface brightness profile results in a distance to 4U 1630‑47 of 11.5 ± 0.3 kpc. If MC ‑79 is at the near distance, then 4U 1630‑47 is at 4.7 ± 0.3 kpc. Future Chandra, Swift, and submillimeter radio observations not only can resolve this ambiguity, but also would provide information regarding properties of dust and the distribution of all molecular clouds along the line of sight. Using the results of this study we also discuss the nature of this source and the reasons for the observation of an anomalously low soft state during the 2010 decay.

Optimization of water absorbing exopolysaccharide production on local cheap substrates by Bacillus strain CMG1403 using one variable at a time approach.

PubMed

Muhammadi; Afzal, Muhammad

2014-01-01

Optimum culture conditions, and carbon and nitrogen sources for production of water absorbing exopolysaccharide by Bacillus strain CMG1403 on local cheap substrates were determined using one variable at a time approach. Carbon source was found to be sole substrate for EPS biosynthesis in the presence of yeast extract that supported the growth only and hence, indirectly enhanced the EPS yield. Whereas, urea only coupled with carbon source could enhance the EPS production but no effect on growth. The maximum yield of EPS was obtained when Bacillus strain CMG1403 was grown statically in neutral minimal medium with 25% volumetric aeration at 30°C for 10 days. Under these optimum conditions, a maximum yield of 2.71±0.024, 3.82±0.005, 4.33±0.021, 4.73±0.021, 4.85±0.024, and 5.52±0.016 g/L culture medium was obtained with 20 g (sugar) of sweet whey, glucose, fructose, sucrose, cane molasses and sugar beet the most efficient one respectively as carbon sources. Thus, the present study showed that under optimum culture conditions, the local cheap substrates could be superior and efficient alternatives to synthetic carbon sources providing way for an economical production of water absorbing EPS by indigenous soil bacterium Bacillus strain CMG1403.

Accreditation and Assuring Quality in Distance Learning. CHEA Monograph Series, 2002.

ERIC Educational Resources Information Center

Council for Higher Education Accreditation, Washington, DC.

This report describes the scope and impact of distance learning on higher education and identifies the primary challenges that distance learning poses for accreditation. The responses of the accrediting community designed to assure quality in distance learning are outlined. Data from a variety of sources show that 5,655 institutions are accredited…

Synthetic substrate-borne vibrational signals that elicit Asian citrus psyllid communicatory and search responses

USDA-ARS?s Scientific Manuscript database

The Asian Citrus Psyllid (ACP), Diaphorina citri Kuwayama, vectors a harmful bacterium, Candidatus Liberibacter asiaticus, that causes huanglongbing, an economically devastating disease of citrus. Adult male and female ACP transmit vibratory communication signals over 10-50-cm distances within their...

Determining the Depth of Infinite Horizontal Cylindrical Sources from Spontaneous Polarization Data

NASA Astrophysics Data System (ADS)

Cooper, G. R. J.; Stettler, E. H.

2017-03-01

Previously published semi-automatic interpretation methods that use ratios of analytic signal amplitudes of orders that differ by one to determine the distance to potential field sources are shown also to apply to self-potential (S.P.) data when the source is a horizontal cylinder. Local minima of the distance (when it becomes closest to zero) give the source depth. The method was applied to an S.P. anomaly from the Bourkes Luck potholes district in Mpumalanga Province, South Africa, and gave results that were confirmed by drilling.

Influence of nitrogen substrates and substrate C:N ratios on the nitrogen isotopic composition of amino acids from the marine bacterium Vibrio harveyi

NASA Astrophysics Data System (ADS)

Maki, K.; Ohkouchi, N.; Chikaraishi, Y.; Fukuda, H.; Miyajima, T.; Nagata, T.

2014-09-01

Nitrogen (N) isotopic compositions of individual hydrolysable amino acids (δ15NAAs) in N pools have been increasingly used for trophic position assessment and evaluation of sources and transformation processes of organic matter in marine environments. However, there are limited data about variability in δ15NAAs patterns and how this variability influences marine bacteria, an important mediator of trophic transfer and organic matter transformation. We explored whether marine bacterial δ15NAAs profiles change depending on the type and C:N ratio of the substrate. The δ15NAAs profile of a marine bacterium, Vibrio harveyi, was examined using medium containing either glutamate, alanine or ammonium as the N source [substrate C:N ratios (range, 3 to 20) were adjusted with glucose]. The data were interpreted as a reflection of isotope fractionations associated with de novo synthesis of amino acids by bacteria. Principal component analysis (PCA) using the δ15N offset values normalized to glutamate + glutamine δ15N revealed that δ15NAAs profiles differed depending on the N source and C:N ratio of the substrate. High variability in the δ15N offset of alanine and valine largely explained this bacterial δ15NAAs profile variability. PCA was also conducted using bacterial and phytoplankton (cyanobacteria and eukaryotic algae) δ15NAAs profile data reported previously. The results revealed that bacterial δ15NAAs patterns were distinct from those of phytoplankton. Therefore, the δ15NAAs profile is a useful indicator of biochemical responses of bacteria to changes in substrate conditions, serving as a potentially useful method for identifying organic matter sources in marine environments.

Nanoengineered Polystyrene Surfaces with Nanopore Array Pattern Alters Cytoskeleton Organization and Enhances Induction of Neural Differentiation of Human Adipose-Derived Stem Cells.

PubMed

Jung, Ae Ryang; Kim, Richard Y; Kim, Hyung Woo; Shrestha, Kshitiz Raj; Jeon, Seung Hwan; Cha, Kyoung Je; Park, Yong Hyun; Kim, Dong Sung; Lee, Ji Youl

2015-07-01

Human adipose-derived stem cells (hADSCs) can differentiate into various cell types depending on chemical and topographical cues. One topographical cue recently noted to be successful in inducing differentiation is the nanoengineered polystyrene surface containing nanopore array-patterned substrate (NP substrate), which is designed to mimic the nanoscale topographical features of the extracellular matrix. In this study, efficacies of NP and flat substrates in inducing neural differentiation of hADSCs were examined by comparing their substrate-cell adhesion rates, filopodia growth, nuclei elongation, and expression of neural-specific markers. The polystyrene nano Petri dishes containing NP substrates were fabricated by a nano injection molding process using a nickel electroformed nano-mold insert (Diameter: 200 nm. Depth of pore: 500 nm. Center-to-center distance: 500 nm). Cytoskeleton and filopodia structures were observed by scanning electron microscopy and F-actin staining, while cell adhesion was tested by vinculin staining after 24 and 48 h of seeding. Expression of neural specific markers was examined by real-time quantitative polymerase chain reaction and immunocytochemistry. Results showed that NP substrates lead to greater substrate-cell adhesion, filopodia growth, nuclei elongation, and expression of neural specific markers compared to flat substrates. These results not only show the advantages of NP substrates, but they also suggest that further study into cell-substrate interactions may yield great benefits for biomaterial engineering.

Investigation of antenna-coupled Nb5N6 microbolometer THz detector with substrate resonant cavity.

PubMed

Tu, Xuecou; Jiang, Chengtao; Xiao, Peng; Kang, Lin; Zhai, Shimin; Jiang, Zhou; Feng Su, Run; Jia, Xiaoqing; Zhang, Labao; Chen, Jian; Wu, Peiheng

2018-04-02

Fabricating resonant cavities with conventional methods to improve the coupling efficiency of a detector in the terahertz (THz) region is difficult for the wavelength is too long. Here, we propose a solution by using the substrate cavity effect given that the substrate wavelength and thickness of the preparation device are in the same order. The planar dipole antenna-coupled Nb 5 N 6 microbolometers with different substrate thicknesses were fabricated. The interference effect of the substrate cavity on the optical voltage response of the detector is analyzed experimentally and theoretically. The experimental results show that the optical response of the detector is determined by the length of the substrate cavity. Thus, the THz devices with different detection frequencies can be designed by changing the substrate cavity length. Furthermore, on the basis of this substrate cavity effect, an asymmetric coupled Fabry-Pérot (FP) cavity is constituted by simply placing a movable metallic planar mirror at the backside of the Si substrate. The incident THz radiation on the Nb 5 N 6 microbolometer can be effectively manipulated by changing the substrate-mirror distance to modulate the phase relation between the reflect wave and the incident wave. The distinct radiation control can be observed, and the experiments can be well explained by numerically analyzing the responsivity dynamics that highlights the role of the FP cavity effect during radiation. All of the results discussed here can be extended to a broad range of frequency and other type of THz detectors.

Carbon nanotube network thin-film transistors on flexible/stretchable substrates

DOEpatents

Takei, Kuniharu; Takahashi, Toshitake; Javey, Ali

2016-03-29

This disclosure provides systems, methods, and apparatus for flexible thin-film transistors. In one aspect, a device includes a polymer substrate, a gate electrode disposed on the polymer substrate, a dielectric layer disposed on the gate electrode and on exposed portions of the polymer substrate, a carbon nanotube network disposed on the dielectric layer, and a source electrode and a drain electrode disposed on the carbon nanotube network.

Method of forming contacts for a back-contact solar cell

DOEpatents

Manning, Jane

2015-10-20

Methods of forming contacts for solar cells are described. In one embodiment, a method includes forming a silicon layer above a substrate, forming and patterning a solid-state p-type dopant source on the silicon layer, forming an n-type dopant source layer over exposed regions of the silicon layer and over a plurality of regions of the solid-state p-type dopant source, and heating the substrate to provide a plurality of n-type doped silicon regions among a plurality of p-type doped silicon regions.

Method of forming contacts for a back-contact solar cell

DOEpatents

Manning, Jane

2014-07-15

Methods of forming contacts for solar cells are described. In one embodiment, a method includes forming a silicon layer above a substrate, forming and patterning a solid-state p-type dopant source on the silicon layer, forming an n-type dopant source layer over exposed regions of the silicon layer and over a plurality of regions of the solid-state p-type dopant source, and heating the substrate to provide a plurality of n-type doped silicon regions among a plurality of p-type doped silicon regions.

Electro-optic device with gap-coupled electrode

DOEpatents

Deri, Robert J.; Rhodes, Mark A.; Bayramian, Andrew J.; Caird, John A.; Henesian, Mark A.; Ebbers, Christopher A.

2013-08-20

An electro-optic device includes an electro-optic crystal having a predetermined thickness, a first face and a second face. The electro-optic device also includes a first electrode substrate disposed opposing the first face. The first electrode substrate includes a first substrate material having a first thickness and a first electrode coating coupled to the first substrate material. The electro-optic device further includes a second electrode substrate disposed opposing the second face. The second electrode substrate includes a second substrate material having a second thickness and a second electrode coating coupled to the second substrate material. The electro-optic device additionally includes a voltage source electrically coupled to the first electrode coating and the second electrode coating.

Evidence for enhanced discrimination of virtual auditory distance among blind listeners using level and direct-to-reverberant cues.

PubMed

Kolarik, Andrew J; Cirstea, Silvia; Pardhan, Shahina

2013-02-01

Totally blind listeners often demonstrate better than normal capabilities when performing spatial hearing tasks. Accurate representation of three-dimensional auditory space requires the processing of available distance information between the listener and the sound source; however, auditory distance cues vary greatly depending upon the acoustic properties of the environment, and it is not known which distance cues are important to totally blind listeners. Our data show that totally blind listeners display better performance compared to sighted age-matched controls for distance discrimination tasks in anechoic and reverberant virtual rooms simulated using a room-image procedure. Totally blind listeners use two major auditory distance cues to stationary sound sources, level and direct-to-reverberant ratio, more effectively than sighted controls for many of the virtual distances tested. These results show that significant compensation among totally blind listeners for virtual auditory spatial distance leads to benefits across a range of simulated acoustic environments. No significant differences in performance were observed between listeners with partial non-correctable visual losses and sighted controls, suggesting that sensory compensation for virtual distance does not occur for listeners with partial vision loss.

The range and intensity of backscattered electrons for use in the creation of high fidelity electron beam lithography patterns.

PubMed

Czaplewski, David A; Holt, Martin V; Ocola, Leonidas E

2013-08-02

We present a set of universal curves that predict the range and intensity of backscattered electrons which can be used in conjunction with electron beam lithography to create high fidelity nanoscale patterns. The experimental method combines direct write dose, backscattered dose, and a self-reinforcing pattern geometry to measure the dose provided by backscattered electrons to a nanoscale volume on the substrate surface at various distances from the electron source. Electron beam lithography is used to precisely control the number and position of incident electrons on the surface of the material. Atomic force microscopy is used to measure the height of the negative electron beam lithography resist. Our data shows that the range and the intensity of backscattered electrons can be predicted using the density and the atomic number of any solid material, respectively. The data agrees with two independent Monte Carlo simulations without any fitting parameters. These measurements are the most accurate electron range measurements to date.

Effect of Substrate Bias on Friction Coefficient, Adhesion Strength and Hardness of TiN-COATED Tool Steel

NASA Astrophysics Data System (ADS)

Hamzah, Esah; Ali, Mubarak; Toff, Mohd Radzi Hj. Mohd

In the present study, TiN coatings have been deposited on D2 tool steel substrates by using cathodic arc physical vapor deposition technique. The objective of this research work is to determine the usefulness of TiN coatings in order to improve the micro-Vickers hardness and friction coefficient of TiN coating deposited on D2 tool steel, which is widely used in tooling applications. A Pin-on-Disc test was carried out to study the coefficient of friction versus sliding distance of TiN coating deposited at various substrate biases. The standard deviation parameter during tribo-test result showed that the coating deposited at substrate bias of -75 V was the most stable coating. A significant increase in micro-Vickers hardness was recorded, when substrate bias was reduced from -150 V to zero. Scratch tester was used to compare the critical loads for coatings deposited at different bias voltages and the adhesion achievable was demonstrated with relevance to the various modes, scratch macroscopic analysis, critical load, acoustic emission and penetration depth. A considerable improvement in TiN coatings was observed as a function of various substrate bias voltages.

Single-mode plasmonic waveguiding properties of metal nanowires with dielectric substrates.

PubMed

Wang, Yipei; Ma, Yaoguang; Guo, Xin; Tong, Limin

2012-08-13

Single-mode plasmonic waveguiding properties of metal nanowires with dielectric substrates are investigated using a finite-element method. Au and Ag are selected as plasmonic materials for nanowire waveguides with diameters down to 5-nm-level. Typical dielectric materials with relatively low to high refractive indices, including magnesium fluoride (MgF2), silica (SiO2), indium tin oxide (ITO) and titanium dioxide (TiO2), are used as supporting substrates. Basic waveguiding properties, including propagation constants, power distributions, effective mode areas, propagation distances and losses are obtained at the typical plasmonic resonance wavelength of 660 nm. Compared to that of a freestanding nanowire, the mode area of a substrate-supported nanowire could be much smaller while maintaining an acceptable propagation length. For example, the mode area and propagation length of a 100-nm-diameter Ag nanowire with a MgF2 substrate are about 0.004 μm2 and 3.4 μm, respectively. The dependences of waveguiding properties on geometric and material parameters of the nanowire-substrate system are also provided. Our results may provide valuable references for waveguiding dielectric-supported metal nanowires for practical applications.

Enhancement of Ti-containing hydrogenated carbon (Tisbnd C:H) films by high-power plasma-sputtering

NASA Astrophysics Data System (ADS)

Gwo, Jyh; Chu, Chun-Lin; Tsai, Ming-Jui; Lee, Shyong

2012-02-01

Ti-containing amorphous hydrogenated carbon (Tisbnd C:H) thin films were deposited on stainless steel SS304 substrates by high-power pulsed magnetron sputtering (HPPMS) in an atmosphere of mixed Ar and C2H2 gases using titanium metal as the cathodic material. The multilayer structure of the deposited film had a Tisbnd TiCsbnd DLC gradient to improve adhesion and reduce residual stress. This study investigates the effects of substrate bias and target-to-substrate distance on the mechanical properties of Tisbnd C:H films. Film properties, including composition, morphology, microstructure, mechanical, and tribology, were examined by glow discharge spectroscopy (GDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and a nanoindenter and a pin-on-disk tribometer. Experiments revealed impressive results.

A theoretical analysis of steady-state photocurrents in simple silicon diodes

NASA Technical Reports Server (NTRS)

Edmonds, L.

1995-01-01

A theoretical analysis solves for the steady-state photocurrents produced by a given photo-generation rate function with negligible recombination in simple silicon diodes, consisting of a uniformly doped quasi-neutral region (called 'substrate' below) adjacent to a p-n junction depletion region (DR). Special attention is given to conditions that produce 'funneling' (a term used by the single-eventeffects community) under steady-state conditions. Funneling occurs when carriers are generated so fast that the DR becomes flooded and partially or completely collapses. Some or nearly all of the applied voltage, plus built-in potential normally across the DR, is now across the substrate. This substrate voltage drop affects substrate currents. The steady-state problem can provide some qualitative insights into the more difficult transient problem. First, it was found that funneling can be induced from a distance, i.e., from carriers generated at locations outside of the DR. Secondly, it was found that the substrate can divide into two subregions, with one controlling substrate resistance and the other characterized by ambipolar diffusion. Finally, funneling was found to be more difficult to induce in the p(sup +)/n diode than in the n(sup +)/p diode. The carrier density exceeding the doping density in the substrate and at the DR boundary is not a sufficient condition to collapse a DR.

Method for in-situ cleaning of carbon contaminated surfaces

DOEpatents

Klebanoff, Leonard E.; Grunow, Philip; Graham, Jr., Samuel

2006-12-12

Activated gaseous species generated adjacent a carbon contaminated surface affords in-situ cleaning. A device for removing carbon contamination from a surface of the substrate includes (a) a housing defining a vacuum chamber in which the substrate is located; (b) a source of gaseous species; and (c) a source of electrons that are emitted to activate the gaseous species into activated gaseous species. The source of electrons preferably includes (i) a filament made of a material that generates thermionic electron emissions; (ii) a source of energy that is connected to the filament; and (iii) an electrode to which the emitted electrons are attracted. The device is particularly suited for photolithography systems with optic surfaces, e.g., mirrors, that are otherwise inaccessible unless the system is dismantled. A method of removing carbon contaminants from a substrate surface that is housed within a vacuum chamber is also disclosed. The method employs activated gaseous species that react with the carbon contaminants to form carbon containing gaseous byproducts.

Excitation of Love waves in a thin film layer by a line source.

NASA Technical Reports Server (NTRS)

Tuan, H.-S.; Ponamgi, S. R.

1972-01-01

The excitation of a Love surface wave guided by a thin film layer deposited on a semiinfinite substrate is studied in this paper. Both the thin film and the substrate are considered to be elastically isotropic. Amplitudes of the surface wave in the thin film region and the substrate are found in terms of the strength of a line source vibrating in a direction transverse to the propagating wave. In addition to the surface wave, the bulk shear wave excited by the source is also studied. Analytical expressions for the bulk wave amplitude as a function of the direction of propagation, the acoustic powers transported by the surface and bulk waves, and the efficiency of surface wave excitation are obtained. A numerical example is given to show how the bulk wave radiation pattern depends upon the source frequency, the film thickness and other important parameters of the problem. The efficiency of surface wave excitation is also calculated for various parameter values.

Thermodynamic analysis of vapor-phase epitaxial growth of GaAsN on Ge

NASA Astrophysics Data System (ADS)

Kawano, Jun; Kangawa, Yoshihiro; Ito, Tomonori; Kakimoto, Koichi; Koukitu, Akinori

2012-03-01

In this paper, we use thermodynamic analysis to determine how the nitrogen (N) ratio in the source gases affects the solid composition of coherently grown GaAs1-xNx(x˜0.03). The source gases for Ga, As, and N are trimethylgallium ((CH3)3Ga), arsine (AsH3), and ammonia (NH3), respectively. The growth occurs on a Ge substrate, and the analysis includes the stress from the substrate-crystal lattice mismatch. Calculation results indicate that to have just a few percent N incorporation into the grown solid, the V/III ratio in the source gases should be several thousands and the input-gas partial-pressure ratio NH3/(NH3+AsH3) should exceed 0.99. We also find that the lattice mismatch stress from the Ge substrate increases the V/III source-gas ratio required for stable growth, whereas an increase in input Ga partial pressure ratio has the opposite effect.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberson, G P; Logan, C M

We have estimated interference from external background radiation for a computed tomography (CT) scanner. Our intention is to estimate the interference that would be expected for the high-resolution SkyScan 1072 desk-top x-ray microtomography system. The SkyScan system uses a Microfocus x-ray source capable of a 10-{micro}m focal spot at a maximum current of 0.1 mA and a maximum energy of 130 kVp. All predictions made in this report assume using the x-ray source at the smallest spot size, maximum energy, and operating at the maximum current. Some of the systems basic geometry that is used for these estimates are: (1)more » Source-to-detector distance: 250 mm, (2) Minimum object-to-detector distance: 40 mm, and (3) Maximum object-to-detector distance: 230 mm. This is a first-order, rough estimate of the quantity of interference expected at the system detector caused by background radiation. The amount of interference is expressed by using the ratio of exposure expected at the detector of the CT system. The exposure values for the SkyScan system are determined by scaling the measured values of an x-ray source and the background radiation adjusting for the difference in source-to-detector distance and current. The x-ray source that was used for these measurements was not the SkyScan Microfocus x-ray tube. Measurements were made using an x-ray source that was operated at the same applied voltage but higher current for better statistics.« less

Bremsstrahlung versus Monoenergetic Photon Dose and Photonuclear Stimulation Comparisons at Long Standoff Distances

NASA Astrophysics Data System (ADS)

Jones, J. L.; Sterbentz, J. W.; Yoon, W. Y.; Norman, D. R.

2009-12-01

Energetic photon sources with energies greater than 6 MeV continue to be recognized as viable source for various types of inspection applications, especially those related to nuclear and/or explosive material detection. These energetic photons can be produced as a continuum of energies (i.e., bremsstrahlung) or as a set of one or more discrete photon energies (i.e., monoenergetic). This paper will provide a follow-on extension of the photon dose comparison presented at the 9th International Conference on Applications of Nuclear Techniques (June 2008). Our previous paper showed the comparative advantages and disadvantages of the photon doses provided by these two energetic interrogation sources and highlighted the higher energy advantage of the bremsstrahlung source, especially at long standoff distances (i.e., distance from source to the inspected object). This paper will pursue higher energy photon inspection advantage (up to 100 MeV) by providing dose and stimulated photonuclear interaction predictions in air and for an infinitely dilute interrogated material (used for comparative interaction rate assessments since it excludes material self-shielding) as the interrogation object positioned forward on the inspection beam axis at increasing standoff distances. In addition to the direct energetic photon-induced stimulation, the predictions will identify the importance of secondary downscattered/attenuated source-term effects arising from the photon transport in the intervening air environment.

Analysis of factors affecting the accuracy, reproducibility, and interpretation of microbial community carbon source utilization patterns

USGS Publications Warehouse

Haack, S.K.; Garchow, H.; Klug, M.J.; Forney, L.J.

1995-01-01

We determined factors that affect responses of bacterial isolates and model bacterial communities to the 95 carbon substrates in Biolog microliter plates. For isolates and communities of three to six bacterial strains, substrate oxidation rates were typically nonlinear and were delayed by dilution of the inoculum. When inoculum density was controlled, patterns of positive and negative responses exhibited by microbial communities to each of the carbon sources were reproducible. Rates and extents of substrate oxidation by the communities were also reproducible but were not simply the sum of those exhibited by community members when tested separately. Replicates of the same model community clustered when analyzed by principal- components analysis (PCA), and model communities with different compositions were clearly separated un the first PCA axis, which accounted for >60% of the dataset variation. PCA discrimination among different model communities depended on the extent to which specific substrates were oxidized. However, the substrates interpreted by PCA to be most significant in distinguishing the communities changed with reading time, reflecting the nonlinearity of substrate oxidation rates. Although whole-community substrate utilization profiles were reproducible signatures for a given community, the extent of oxidation of specific substrates and the numbers or activities of microorganisms using those substrates in a given community were not correlated. Replicate soil samples varied significantly in the rate and extent of oxidation of seven tested substrates, suggesting microscale heterogeneity in composition of the soil microbial community.

Particle-Film Plasmons on Periodic Silver Film over Nanosphere (AgFON): A Hybrid Plasmonic Nanoarchitecture for Surface-Enhanced Raman Spectroscopy.

PubMed

Lee, Jiwon; Zhang, Qianpeng; Park, Seungyoung; Choe, Ayoung; Fan, Zhiyong; Ko, Hyunhyub

2016-01-13

Plasmonic systems based on particle-film plasmonic couplings have recently attracted great attention because of the significantly enhanced electric field at the particle-film gaps. Here, we introduce a hybrid plasmonic architecture utilizing combined plasmonic effects of particle-film gap plasmons and silver film over nanosphere (AgFON) substrates. When gold nanoparticles (AuNPs) are assembled on AgFON substrates with controllable particle-film gap distances, the AuNP-AgFON system supports multiple plasmonic couplings from interparticle, particle-film, and crevice gaps, resulting in a huge surface-enhanced Raman spectroscopy (SERS) effect. We show that the periodicity of AgFON substrates and the particle-film gaps greatly affects the surface plasmon resonances, and thus, the SERS effects due to the interplay between multiple plasmonic couplings. The optimally designed AuNP-AgFON substrate shows a SERS enhancement of 233 times compared to the bare AgFON substrate. The ultrasensitive SERS sensing capability is also demonstrated by detecting glutathione, a neurochemical molecule that is an important antioxidant, down to the 10 pM level.

Substrate attributes determine gait in a terrestrial gastropod.

PubMed

McKee, Amberle; Voltzow, Janice; Pernet, Bruno

2013-02-01

Some terrestrial gastropods are able to move using two gaits: adhesive crawling, where the entire foot is separated from the substrate only by a thin layer of mucus and the snail leaves a continuous mucus trail; and loping, where regions of the foot arch above the substrate and the snail leaves a discontinuous mucus trail. Loping has been interpreted as a means of rapidly escaping predators. We found that the pulmonate Cornu aspersum moved using adhesive crawling on dry acrylic or glass substrates, but loped on dry concrete or wood. Loping snails did not move more rapidly than snails using adhesive crawling. Snails moving on concrete secreted a greater volume of pedal mucus per area of trail than those moving on acrylic; locomotion on concrete thus requires greater expenditure of mucus than does locomotion on acrylic. Because loping snails deposit a smaller area of mucus per distance traveled than do snails using adhesive crawling, loping may conserve mucus when moving on porous, absorbent substrates. Members of several other terrestrial pulmonate taxa can also lope on concrete, suggesting that this plasticity in gait is widespread among terrestrial snails.

Charge-free low-temperature method of forming thin film-based nanoscale materials and structures on a substrate

DOEpatents

Hoffbauer, Mark [Los Alamos, NM; Mueller, Alex [Santa Fe, NM

2008-07-01

A method of forming a nanostructure at low temperatures. A substrate that is reactive with one of atomic oxygen and nitrogen is provided. A flux of neutral atoms of at least one of nitrogen and oxygen is generated within a laser-sustained-discharge plasma source and a collimated beam of energetic neutral atoms and molecules is directed from the plasma source onto a surface of the substrate to form the nanostructure. The energetic neutral atoms and molecules in the plasma have an average kinetic energy in a range from about 1 eV to about 5 eV.

Substrate vibrations during acoustic signalling in the cicada Okanagana rimosa

PubMed Central

Stölting, Heiko; Moore, Thomas E.; Lakes-Harlan, Reinhard

2002-01-01

Males of the North American cicada Okanagana rimosa (Homoptera: Cicadidae, Tibicininae) emit loud airborne acoustic signals for intraspecific communication. Specialised vibratory signals could not be detected; however, the airborne signal induced substrate vibrations. Both auditory and vibratory spectra peak in the range from 7–10 kHz. Thus, the vibrations show similar frequency components to the sound spectrum within biologically relevant distances. These vibratory signals could be important as signals involved in mate localization and perhaps even as the context for the evolution of the ear in a group of parasitoid flies. PMID:15455036

Critical Issues for Cu(InGa)Se2 Solar Cells on Flexible Polymer Web

NASA Technical Reports Server (NTRS)

Eser, Erten; Fields, Shannon; Shafarman, William; Birkmire, Robert

2007-01-01

Elemental in-line evaporation on glass substrates has been a viable process for the large-area manufacture of CuInSe2-based photovoltaics, with module efficiencies as high as 12.7% [1]. However, lightweight, flexible CuInSe2-based modules are attractive in a number of applications, such as space power sources. In addition, flexible substrates have an inherent advantage in manufacturability in that they can be deposited in a roll-to-roll configuration allowing continuous, high yield, and ultimately lower cost production. As a result, high-temperature polymers have been used as substrates in depositing CuInSe2 films [2]. Recently, efficiency of 14.1% has been reported for a Cu(InGa)Se2-based solar cell on a polyimide substrate [3]. Both metal foil and polymer webs have been used as substrates for Cu(InGa)Se2-based photovoltaics in a roll-to-roll configuration with reasonable success [4,5]. Both of these substrates do not allow, readily, the incorporation of Na into the Cu(InGa)Se2 film which is necessary for high efficiency devices [3]. In addition, polymer substrates, can not be used at temperatures that are optimum for Cu(InGa)Se2 deposition. However, unlike metal foils, they are electrically insulating, simplifying monolithically-integrated module fabrication and are not a source of impurities diffusing into the growing film. The Institute of Energy Conversion (IEC) has modified its in-line evaporation system [6] from deposition onto glass substrates to roll-to-roll deposition onto polyimide (PI) film in order to investigate key issues in the deposition of large-area Cu(InGa)Se2 films on flexible polymer substrates. This transition presented unexpected challenges that had to be resolved. In this paper, two major problems, spitting from the Cu source and the cracking of Mo back contact film, will be discussed and the solution to each will be presented.

Arrays of size and distance controlled platinum nanoparticles fabricated by a colloidal method

NASA Astrophysics Data System (ADS)

Manzke, Achim; Vogel, Nicolas; Weiss, Clemens K.; Ziener, Ulrich; Plettl, Alfred; Landfester, Katharina; Ziemann, Paul

2011-06-01

Based on emulsion polymerization in the presence of a Pt complex, polystyrene (PS) particles were prepared exhibiting a well defined average diameter with narrow size-distribution. Furthermore, the colloids contain a controlled concentration of the Pt precursor complex. Optimized coating of Si substrates with such colloids leads to extended areas of hexagonally ordered close-packed PS particles. Subsequent application of plasma etching and annealing steps allows complete removal of the PS carriers and in parallel nucleation and growth of Pt nanoparticles (NPs) which are located at the original center of the PS colloids. In this way, hexagonally arranged spherical Pt NPs are obtained with controlled size and interparticle distances demonstrating variability and precision with so far unknown parameter scalability. This control is demonstrated by the fabrication of Pt NP arrays at a fixed particle distance of 185 nm while systematically varying the diameters between 8 and 15 nm. Further progress could be achieved by seeded emulsion polymerization. Here, Pt loaded PS colloids of 130 nm were used as seeds for a subsequent additional emulsion polymerization, systematically enlarging the diameter of the PS particles. Applying the plasma and annealing steps as above, in this way hexagonally ordered arrays of 9 nm Pt NPs could be obtained at distances up to 260 nm. To demonstrate their stability, such Pt particles were used as etching masks during reactive ion etching thereby transferring their hexagonal pattern into the Si substrate resulting in corresponding arrays of nanopillars.Based on emulsion polymerization in the presence of a Pt complex, polystyrene (PS) particles were prepared exhibiting a well defined average diameter with narrow size-distribution. Furthermore, the colloids contain a controlled concentration of the Pt precursor complex. Optimized coating of Si substrates with such colloids leads to extended areas of hexagonally ordered close-packed PS particles. Subsequent application of plasma etching and annealing steps allows complete removal of the PS carriers and in parallel nucleation and growth of Pt nanoparticles (NPs) which are located at the original center of the PS colloids. In this way, hexagonally arranged spherical Pt NPs are obtained with controlled size and interparticle distances demonstrating variability and precision with so far unknown parameter scalability. This control is demonstrated by the fabrication of Pt NP arrays at a fixed particle distance of 185 nm while systematically varying the diameters between 8 and 15 nm. Further progress could be achieved by seeded emulsion polymerization. Here, Pt loaded PS colloids of 130 nm were used as seeds for a subsequent additional emulsion polymerization, systematically enlarging the diameter of the PS particles. Applying the plasma and annealing steps as above, in this way hexagonally ordered arrays of 9 nm Pt NPs could be obtained at distances up to 260 nm. To demonstrate their stability, such Pt particles were used as etching masks during reactive ion etching thereby transferring their hexagonal pattern into the Si substrate resulting in corresponding arrays of nanopillars. Electronic supplementary information (ESI) available: Detailed description of the experimental part (S1-S4) platinum concentration inside the polymer particles synthesized by a seeded polymerization from the same seed particles measured by ICP-OES (Fig. S1 and S5); SEM image of Pt complex containing PS particles after oxygen plasma treatment (Fig. S2 and S6); effect of hydrofluoric acid treatment on silicon oxide elevation under Pt NPs (Fig. S3 and S6); SEM images demonstrating the variability of Pt NP distance while keeping the diameter constant (Fig. S4 and S8); results of experimental determination of Pt content by ICP-OES (Tables S1 and S9); diameter of the particles at different fabrication states (Tables S2 and S10). See DOI: 10.1039/c1nr10169b

Process diagnostics and monitoring using the multipole resonance probe in an inhomogeneous plasma for ion-assisted deposition of optical coatings

NASA Astrophysics Data System (ADS)

Styrnoll, T.; Harhausen, J.; Lapke, M.; Storch, R.; Brinkmann, R. P.; Foest, R.; Ohl, A.; Awakowicz, P.

2013-08-01

The application of a multipole resonance probe (MRP) for diagnostic and monitoring purposes in a plasma ion-assisted deposition (PIAD) process is reported. Recently, the MRP was proposed as an economical and industry compatible plasma diagnostic device (Lapke et al 2011 Plasma Sources Sci. Technol. 20 042001). The major advantages of the MRP are its robustness against dielectric coating and its high sensitivity to measure the electron density. The PIAD process investigated is driven by the advanced plasma source (APS), which generates an ion beam in the deposition chamber for the production of high performance optical coatings. With a background neutral pressure of p0 ˜ 20 mPa the plasma expands from the source region into the recipient, leading to an inhomogeneous spatial distribution. Electron density and electron temperature vary over the distance from substrate (ne ˜ 109 cm-3 and Te,eff ˜ 2 eV) to the APS (ne ≳ 1012 cm-3 and Te,eff ˜ 20 eV) (Harhausen et al 2012 Plasma Sources Sci. Technol. 21 035012). This huge variation of the plasma parameters represents a big challenge for plasma diagnostics to operate precisely for all plasma conditions. The results obtained by the MRP are compared to those from a Langmuir probe chosen as reference diagnostics. It is demonstrated that the MRP is suited for the characterization of the PIAD plasma as well as for electron density monitoring. The latter aspect offers the possibility to develop new control schemes for complex industrial plasma environments.

The RMS survey: galactic distribution of massive star formation

NASA Astrophysics Data System (ADS)

Urquhart, J. S.; Figura, C. C.; Moore, T. J. T.; Hoare, M. G.; Lumsden, S. L.; Mottram, J. C.; Thompson, M. A.; Oudmaijer, R. D.

2014-01-01

We have used the well-selected sample of ˜1750 embedded, young, massive stars identified by the Red MSX Source (RMS) survey to investigate the Galactic distribution of recent massive star formation. We present molecular line observations for ˜800 sources without existing radial velocities. We describe the various methods used to assign distances extracted from the literature and solve the distance ambiguities towards approximately 200 sources located within the solar circle using archival H I data. These distances are used to calculate bolometric luminosities and estimate the survey completeness (˜2 × 104 L⊙). In total, we calculate the distance and luminosity of ˜1650 sources, one third of which are above the survey's completeness threshold. Examination of the sample's longitude, latitude, radial velocities and mid-infrared images has identified ˜120 small groups of sources, many of which are associated with well-known star formation complexes, such as G305, G333, W31, W43, W49 and W51. We compare the positional distribution of the sample with the expected locations of the spiral arms, assuming a model of the Galaxy consisting of four gaseous arms. The distribution of young massive stars in the Milky Way is spatially correlated with the spiral arms, with strong peaks in the source position and luminosity distributions at the arms' Galactocentric radii. The overall source and luminosity surface densities are both well correlated with the surface density of the molecular gas, which suggests that the massive star formation rate per unit molecular mass is approximately constant across the Galaxy. A comparison of the distribution of molecular gas and the young massive stars to that in other nearby spiral galaxies shows similar radial dependences. We estimate the total luminosity of the embedded massive star population to be ˜0.76 × 108 L⊙, 30 per cent of which is associated with the 10 most active star-forming complexes. We measure the scaleheight as a function of the Galactocentric distance and find that it increases only modestly from ˜20-30 pc between 4 and 8 kpc, but much more rapidly at larger distances.

Seasonal associations and atmospheric transport distances of fungi in the genus Fusarium collected with unmanned aerial vehicles and ground-based sampling devices

NASA Astrophysics Data System (ADS)

Lin, Binbin; Ross, Shane D.; Prussin, Aaron J.; Schmale, David G.

2014-09-01

Spores of fungi in the genus Fusarium may be transported through the atmosphere over long distances. New information is needed to characterize seasonal trends in atmospheric loads of Fusarium and to pinpoint the source(s) of inoculum at both local (farm) and regional (state or country) scales. We hypothesized that (1) atmospheric concentrations of Fusarium spores in an agricultural ecosystem vary with height and season and (2) transport distances from potential inoculum source(s) vary with season. To test these hypotheses, spores of Fusarium were collected from the atmosphere in an agricultural ecosystem in Blacksburg, VA, USA using a Burkard volumetric sampler (BVS) 1 m above ground level and autonomous unmanned aerial vehicles (UAVs) 100 m above ground level. More than 2200 colony forming units (CFUs) of Fusarium were collected during 104 BVS sampling periods and 180 UAV sampling periods over four calendar years (2009-2012). Spore concentrations ranged from 0 to 13 and 0 to 23 spores m-3 for the BVS and the UAVs, respectively. Spore concentrations were generally higher in the fall, spring, and summer, and lower in the winter. Spore concentrations from the BVS were generally higher than those from the UAVs for both seasonal and hourly collections. A Gaussian plume transport model was used to estimate distances to the potential inoculum source(s) by season, and produced mean transport distances of 1.4 km for the spring, 1.7 km for the summer, 1.2 km for the fall, and 4.1 km for the winter. Environmental signatures that predict atmospheric loads of Fusarium could inform disease spread, air pollution, and climate change.

An iterative method for obtaining the optimum lightning location on a spherical surface

NASA Technical Reports Server (NTRS)

Chao, Gao; Qiming, MA

1991-01-01

A brief introduction to the basic principles of an eigen method used to obtain the optimum source location of lightning is presented. The location of the optimum source is obtained by using multiple direction finders (DF's) on a spherical surface. An improvement of this method, which takes the distance of source-DF's as a constant, is presented. It is pointed out that using a weight factor of signal strength is not the most ideal method because of the inexact inverse signal strength-distance relation and the inaccurate signal amplitude. An iterative calculation method is presented using the distance from the source to the DF as a weight factor. This improved method has higher accuracy and needs only a little more calculation time. Some computer simulations for a 4DF system are presented to show the improvement of location through use of the iterative method.

Conversion of fullerenes to diamond

DOEpatents

Gruen, Dieter M.

1993-01-01

A method of forming synthetic diamond on a substrate is disclosed. The method involves providing a substrate surface covered with a fullerene or diamond coating, positioning a fullerene in an ionization source, creating a fullerene vapor, ionizing fullerene molecules, accelerating the fullerene ions to energies above 250 eV to form a fullerene ion beam, impinging the fullerene ion beam on the substrate surface and continuing these steps to obtain a diamond thickness on the substrate.

Conversion of fullerenes to diamond

DOEpatents

Gruen, Dieter M.

1994-01-01

A method of forming synthetic diamond on a substrate. The method involves providing a substrate surface covered with a fullerene or diamond coating, positioning a fullerene in an ionization source, creating a fullerene vapor, ionizing fullerene molecules, accelerating the fullerene ions to energies above 250 eV to form a fullerene ion beam, impinging the fullerene ion beam on the substrate surface and continuing these steps to obtain a diamond film thickness on the substrate.

High resolution ion chamber array delivery quality assurance for robotic radiosurgery: Commissioning and validation.

PubMed

Blanck, Oliver; Masi, Laura; Chan, Mark K H; Adamczyk, Sebastian; Albrecht, Christian; Damme, Marie-Christin; Loutfi-Krauss, Britta; Alraun, Manfred; Fehr, Roman; Ramm, Ulla; Siebert, Frank-Andre; Stelljes, Tenzin Sonam; Poppinga, Daniela; Poppe, Björn

2016-06-01

High precision radiosurgery demands comprehensive delivery-quality-assurance techniques. The use of a liquid-filled ion-chamber-array for robotic-radiosurgery delivery-quality-assurance was investigated and validated using several test scenarios and routine patient plans. Preliminary evaluation consisted of beam profile validation and analysis of source-detector-distance and beam-incidence-angle response dependence. The delivery-quality-assurance analysis is performed in four steps: (1) Array-to-plan registration, (2) Evaluation with standard Gamma-Index criteria (local-dose-difference⩽2%, distance-to-agreement⩽2mm, pass-rate⩾90%), (3) Dose profile alignment and dose distribution shift until maximum pass-rate is found, and (4) Final evaluation with 1mm distance-to-agreement criterion. Test scenarios consisted of intended phantom misalignments, dose miscalibrations, and undelivered Monitor Units. Preliminary method validation was performed on 55 clinical plans in five institutions. The 1000SRS profile measurements showed sufficient agreement compared with a microDiamond detector for all collimator sizes. The relative response changes can be up to 2.2% per 10cm source-detector-distance change, but remains within 1% for the clinically relevant source-detector-distance range. Planned and measured dose under different beam-incidence-angles showed deviations below 1% for angles between 0° and 80°. Small-intended errors were detected by 1mm distance-to-agreement criterion while 2mm criteria failed to reveal some of these deviations. All analyzed delivery-quality-assurance clinical patient plans were within our tight tolerance criteria. We demonstrated that a high-resolution liquid-filled ion-chamber-array can be suitable for robotic radiosurgery delivery-quality-assurance and that small errors can be detected with tight distance-to-agreement criterion. Further improvement may come from beam specific correction for incidence angle and source-detector-distance response. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Cluster pattern analysis of energy deposition sites for the brachytherapy sources 103Pd, 125I, 192Ir, 137Cs, and 60Co.

PubMed

Villegas, Fernanda; Tilly, Nina; Bäckström, Gloria; Ahnesjö, Anders

2014-09-21

Analysing the pattern of energy depositions may help elucidate differences in the severity of radiation-induced DNA strand breakage for different radiation qualities. It is often claimed that energy deposition (ED) sites from photon radiation form a uniform random pattern, but there is indication of differences in RBE values among different photon sources used in brachytherapy. The aim of this work is to analyse the spatial patterns of EDs from 103Pd, 125I, 192Ir, 137Cs sources commonly used in brachytherapy and a 60Co source as a reference radiation. The results suggest that there is both a non-uniform and a uniform random component to the frequency distribution of distances to the nearest neighbour ED. The closest neighbouring EDs show high spatial correlation for all investigated radiation qualities, whilst the uniform random component dominates for neighbours with longer distances for the three higher mean photon energy sources (192Ir, 137Cs, and 60Co). The two lower energy photon emitters (103Pd and 125I) present a very small uniform random component. The ratio of frequencies of clusters with respect to 60Co differs up to 15% for the lower energy sources and less than 2% for the higher energy sources when the maximum distance between each pair of EDs is 2 nm. At distances relevant to DNA damage, cluster patterns can be differentiated between the lower and higher energy sources. This may be part of the explanation to the reported difference in RBE values with initial DSB yields as an endpoint for these brachytherapy sources.

Cluster pattern analysis of energy deposition sites for the brachytherapy sources 103Pd, 125I, 192Ir, 137Cs, and 60Co

NASA Astrophysics Data System (ADS)

Villegas, Fernanda; Tilly, Nina; Bäckström, Gloria; Ahnesjö, Anders

2014-09-01

Analysing the pattern of energy depositions may help elucidate differences in the severity of radiation-induced DNA strand breakage for different radiation qualities. It is often claimed that energy deposition (ED) sites from photon radiation form a uniform random pattern, but there is indication of differences in RBE values among different photon sources used in brachytherapy. The aim of this work is to analyse the spatial patterns of EDs from 103Pd, 125I, 192Ir, 137Cs sources commonly used in brachytherapy and a 60Co source as a reference radiation. The results suggest that there is both a non-uniform and a uniform random component to the frequency distribution of distances to the nearest neighbour ED. The closest neighbouring EDs show high spatial correlation for all investigated radiation qualities, whilst the uniform random component dominates for neighbours with longer distances for the three higher mean photon energy sources (192Ir, 137Cs, and 60Co). The two lower energy photon emitters (103Pd and 125I) present a very small uniform random component. The ratio of frequencies of clusters with respect to 60Co differs up to 15% for the lower energy sources and less than 2% for the higher energy sources when the maximum distance between each pair of EDs is 2 nm. At distances relevant to DNA damage, cluster patterns can be differentiated between the lower and higher energy sources. This may be part of the explanation to the reported difference in RBE values with initial DSB yields as an endpoint for these brachytherapy sources.

Optimization of High-Throughput Sequencing Kinetics for determining enzymatic rate constants of thousands of RNA substrates

PubMed Central

Niland, Courtney N.; Jankowsky, Eckhard; Harris, Michael E.

2016-01-01

Quantification of the specificity of RNA binding proteins and RNA processing enzymes is essential to understanding their fundamental roles in biological processes. High Throughput Sequencing Kinetics (HTS-Kin) uses high throughput sequencing and internal competition kinetics to simultaneously monitor the processing rate constants of thousands of substrates by RNA processing enzymes. This technique has provided unprecedented insight into the substrate specificity of the tRNA processing endonuclease ribonuclease P. Here, we investigate the accuracy and robustness of measurements associated with each step of the HTS-Kin procedure. We examine the effect of substrate concentration on the observed rate constant, determine the optimal kinetic parameters, and provide guidelines for reducing error in amplification of the substrate population. Importantly, we find that high-throughput sequencing, and experimental reproducibility contribute their own sources of error, and these are the main sources of imprecision in the quantified results when otherwise optimized guidelines are followed. PMID:27296633

Separation of mycotoxin-containing sources in grain dust and determination of their mycotoxin potential.

PubMed Central

Palmgren, M S; Lee, L S

1986-01-01

Two distinct reservoirs of mycotoxins exist in fungal-infected cereal grains--the fungal spores and the spore-free mycelium-substrate matrix. Many fungal spores are of respirable size and the mycelium-substrate matrix can be pulverized to form particles of respirable size during routine handling of grain. In order to determine the contribution of each source to the level of mycotoxin contamination of dust, we developed techniques to harvest and separate mycelium-substrate matrices from spores of fungi. Conventional quantitative chromatographic analyses of separated materials indicated that aflatoxin from Aspergillus parasiticus, norsolorinic acid from a mutant of A. parasiticus, and secalonic acid D from Penicillium oxalicum were concentrated in the mycelium-substrate matrices and not in the spores. In contrast, spores of Aspergillus niger and Aspergillus fumigatus contained significant concentrations of aurasperone C and fumigaclavine C, respectively; only negligible amounts of the toxins were detected in the mycelium-substrate matrices of these two fungi. PMID:3709472

The hydrolysis and biogas production of complex cellulosic substrates using three anaerobic biomass sources.

PubMed

Keating, C; Cysneiros, D; Mahony, T; O'Flaherty, V

2013-01-01

In this study, the ability of various sludges to digest a diverse range of cellulose and cellulose-derived substrates was assessed at different temperatures to elucidate the factors affecting hydrolysis. For this purpose, the biogas production was monitored and the specific biogas activity (SBA) of the sludges was employed to compare the performance of three anaerobic sludges on the degradation of a variety of complex cellulose sources, across a range of temperatures. The sludge with the highest performance on complex substrates was derived from a full-scale bioreactor treating sewage at 37 °C. Hydrolysis was the rate-limiting step during the degradation of complex substrates. No activity was recorded for the synthetic cellulose compound carboxymethylcellulose (CMC) using any of the sludges tested. Increased temperature led to an increase in hydrolysis rates and thus SBA values. The non-granular nature of the mesophilic sludge played a positive role in the hydrolysis of solid substrates, while the granular sludges proved more effective on the degradation of soluble compounds.

Auditory Distance Coding in Rabbit Midbrain Neurons and Human Perception: Monaural Amplitude Modulation Depth as a Cue

PubMed Central

Zahorik, Pavel; Carney, Laurel H.; Bishop, Brian B.; Kuwada, Shigeyuki

2015-01-01

Mechanisms underlying sound source distance localization are not well understood. Here we tested the hypothesis that a novel mechanism can create monaural distance sensitivity: a combination of auditory midbrain neurons' sensitivity to amplitude modulation (AM) depth and distance-dependent loss of AM in reverberation. We used virtual auditory space (VAS) methods for sounds at various distances in anechoic and reverberant environments. Stimulus level was constant across distance. With increasing modulation depth, some rabbit inferior colliculus neurons increased firing rates whereas others decreased. These neurons exhibited monotonic relationships between firing rates and distance for monaurally presented noise when two conditions were met: (1) the sound had AM, and (2) the environment was reverberant. The firing rates as a function of distance remained approximately constant without AM in either environment and, in an anechoic condition, even with AM. We corroborated this finding by reproducing the distance sensitivity using a neural model. We also conducted a human psychophysical study using similar methods. Normal-hearing listeners reported perceived distance in response to monaural 1 octave 4 kHz noise source sounds presented at distances of 35–200 cm. We found parallels between the rabbit neural and human responses. In both, sound distance could be discriminated only if the monaural sound in reverberation had AM. These observations support the hypothesis. When other cues are available (e.g., in binaural hearing), how much the auditory system actually uses the AM as a distance cue remains to be determined. PMID:25834060

Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation

NASA Astrophysics Data System (ADS)

Bedekar, M. M.; Safari, A.; Wilber, W.

1992-11-01

Superconducting thin films of Bi-Sr-Ca-Cu-O have been deposited by KrF excimer laser ablation. The best in situ films showed a Tc onset of 110 K and a Tc(0) of 76 K. A study of the laser plume revealed the presence of two distinct regimes. The forward directed component increased with fluence and the film composition was stoichiometric in this region. This is in agreement with the results on the 123 system by Venkatesan et al. [1]. The film properties were found to be critically dependent on the substrate temperature and temperatures close to melting gave rise to 2212 and 2223 phases. At lower temperatures, 2201 and amorphous phases were obtained. The film morphology and superconducting properties were a function of the target to substrate distance and the oxygen pressure during deposition and cooling. An increase in the target to substrate distance led to a deterioration of the properties due to the energy consideration for the formation of 2212 and 2223 phases. The best films were obtained using cooling pressures of 700 Torr. The microwave surface resistance of the films measured at 35 GHz dropped below that of copper at 30 K. Film growth was studied using X-ray diffraction and STM/AFM. This work is a discussion of the role of the different variables on the film properties.

Influence of air humidity and the distance from the source on negative air ion concentration in indoor air.

PubMed

Wu, Chih Cheng; Lee, Grace W M; Yang, Shinhao; Yu, Kuo-Pin; Lou, Chia Ling

2006-10-15

Although negative air ionizer is commonly used for indoor air cleaning, few studies examine the concentration gradient of negative air ion (NAI) in indoor environments. This study investigated the concentration gradient of NAI at various relative humidities and distances form the source in indoor air. The NAI was generated by single-electrode negative electric discharge; the discharge was kept at dark discharge and 30.0 kV. The NAI concentrations were measured at various distances (10-900 cm) from the discharge electrode in order to identify the distribution of NAI in an indoor environment. The profile of NAI concentration was monitored at different relative humidities (38.1-73.6% RH) and room temperatures (25.2+/-1.4 degrees C). Experimental results indicate that the influence of relative humidity on the concentration gradient of NAI was complicated. There were four trends for the relationship between NAI concentration and relative humidity at different distances from the discharge electrode. The changes of NAI concentration with an increase in relative humidity at different distances were quite steady (10-30 cm), strongly declining (70-360 cm), approaching stability (420-450 cm) and moderately increasing (560-900 cm). Additionally, the regression analysis of NAI concentrations and distances from the discharge electrode indicated a logarithmic linear (log-linear) relationship; the distance of log-linear tendency (lambda) decreased with an increase in relative humidity such that the log-linear distance of 38.1% RH was 2.9 times that of 73.6% RH. Moreover, an empirical curve fit based on this study for the concentration gradient of NAI generated by negative electric discharge in indoor air was developed for estimating the NAI concentration at different relative humidities and distances from the source of electric discharge.

Hybrid III-V/silicon lasers

NASA Astrophysics Data System (ADS)

Kaspar, P.; Jany, C.; Le Liepvre, A.; Accard, A.; Lamponi, M.; Make, D.; Levaufre, G.; Girard, N.; Lelarge, F.; Shen, A.; Charbonnier, P.; Mallecot, F.; Duan, G.-H.; Gentner, J.-.; Fedeli, J.-M.; Olivier, S.; Descos, A.; Ben Bakir, B.; Messaoudene, S.; Bordel, D.; Malhouitre, S.; Kopp, C.; Menezo, S.

2014-05-01

The lack of potent integrated light emitters is one of the bottlenecks that have so far hindered the silicon photonics platform from revolutionizing the communication market. Photonic circuits with integrated light sources have the potential to address a wide range of applications from short-distance data communication to long-haul optical transmission. Notably, the integration of lasers would allow saving large assembly costs and reduce the footprint of optoelectronic products by combining photonic and microelectronic functionalities on a single chip. Since silicon and germanium-based sources are still in their infancy, hybrid approaches using III-V semiconductor materials are currently pursued by several research laboratories in academia as well as in industry. In this paper we review recent developments of hybrid III-V/silicon lasers and discuss the advantages and drawbacks of several integration schemes. The integration approach followed in our laboratory makes use of wafer-bonded III-V material on structured silicon-on-insulator substrates and is based on adiabatic mode transfers between silicon and III-V waveguides. We will highlight some of the most interesting results from devices such as wavelength-tunable lasers and AWG lasers. The good performance demonstrates that an efficient mode transfer can be achieved between III-V and silicon waveguides and encourages further research efforts in this direction.

Graphene array antenna for 5G applications

NASA Astrophysics Data System (ADS)

Sa'don, Siti Nor Hafizah; Kamarudin, Muhammad Ramlee; Ahmad, Fauzan; Jusoh, Muzammil; Majid, Huda A.

2017-02-01

Fifth generation (5G) needs to provide better coverage than the previous generation. However, high frequency and millimeter wave experience penetration loss, propagation loss and even more loss in energy for long distance. Hence, a graphene array antenna is proposed for high gain to cover a long distance communications since array antenna enables in providing more directive beams. The investigation is conducted on three types of substrates with gain achieved is more than 7 dBi. The gain obtained is good since it is comparable with other studies. In addition, these antennas consume small numbers of elements to achieve high gain.

Use of Very Weak Radiation Sources to Determine Aircraft Runway Position

NASA Technical Reports Server (NTRS)

Drinkwater, Fred J., III; Kibort, Bernard R.

1965-01-01

Various methods of providing runway information in the cockpit during the take-off and landing roll have been proposed. The most reliable method has been to use runway distance markers when visible. Flight tests were used to evaluate the feasibility of using weak radio-active sources to trigger a runway distance counter in the cockpit. The results of these tests indicate that a weak radioactive source would provide a reliable signal by which this indicator could be operated.

Method for preparing high temperature superconductor

DOEpatents

Balachandran, Uthamalingam; Chudzik, Michael P.

2002-01-01

A method of depositing a biaxially textured metal oxide on a substrate defining a plane in which metal oxide atoms are vaporized from a source to form a plume of metal oxide atoms. Atoms in the plume disposed at a selected angle in a predetermined range of angles to the plane of the substrate are allowed to contact the substrate while preventing atoms outside a selected angle from reaching the substrate. The preferred range of angles is 40.degree.-70.degree. and the preferred angle is 60.degree..+-.5.degree.. A moving substrate is disclosed.

Increased Alignment in Carbon Nanotube Growth

NASA Technical Reports Server (NTRS)

Delzeit, Lance D. (Inventor)

2007-01-01

Method and system for fabricating an array of two or more carbon nanotube (CNT) structures on a coated substrate surface, the structures having substantially the same orientation with respect to a substrate surface. A single electrode, having an associated voltage source with a selected voltage, is connected to a substrate surface after the substrate is coated and before growth of the CNT structures, for a selected voltage application time interval. The CNT structures are then grown on a coated substrate surface with the desired orientation. Optionally, the electrode can be disconnected before the CNT structures are grown.

Epitaxial Growth of Cadmium Telluride Films on Silicon and Indium Antimonide Substrates Using a Closed Hot Wall Epitaxy System

NASA Astrophysics Data System (ADS)

Kuo, Tien-Chuan

For many applications, such as infrared detector and high speed devices, we need high quality cadmium telluride (CdTe) films. To fabricate CdTe films we are using a home -built Closed Hot Wall Epitaxy system (CHWE). This system consists of two growth chambers, preheat chamber, substrate exchange load lock and ultra-high vacuum system. It can exchange the substrates without disturbing the vacuum environment and prevents the source materials from contamination. Two different substrate materials, Si and InSb, are used in this work. Deposition parameters were varied in order to determine the growth condition for obtaining good quality CdTe films. The characteristics of the films were investigated by Scanning Electron Microscope, X-ray diffractormeter and Auger Electron Spectroscope. The electrical properties of Al/CdTe/InSb MIS diodes are also examined. Experimental results show that the quality of the CdTe films on these two substrates are functions of the source and substrate temperatures. The surface of CdTe films grown on Si substrate are rougher than CdTe films grown on InSb substrate. X -ray patterns show that the crystal orientations of the CdTe films are, (100) and (111), similar to those of the substrates under optimum growth conditions. The CdTe film are stoichiometric based on the results of Auger survey. Electrical measurement also indicates that CdTe films grown on InSb substrates have very high purity and are insulator. The induced stresses due to the differences of lattice constant and thermal expansion coefficient between CdTe films and substrates were observed in CdTe films. The critical thickness of CdTe films on InSb substrates are measured by X-ray diffraction to be 2.63 um.

Method and system for nanoscale plasma processing of objects

DOEpatents

Oehrlein, Gottlieb S [Clarksville, MD; Hua, Xuefeng [Hyattsville, MD; Stolz, Christian [Baden-Wuerttemberg, DE

2008-12-30

A plasma processing system includes a source of plasma, a substrate and a shutter positioned in close proximity to the substrate. The substrate/shutter relative disposition is changed for precise control of substrate/plasma interaction. This way, the substrate interacts only with a fully established, stable plasma for short times required for nanoscale processing of materials. The shutter includes an opening of a predetermined width, and preferably is patterned to form an array of slits with dimensions that are smaller than the Debye screening length. This enables control of the substrate/plasma interaction time while avoiding the ion bombardment of the substrate in an undesirable fashion. The relative disposition between the shutter and the substrate can be made either by moving the shutter or by moving the substrate.

The geochemical controls on vent fluids from the Lucky Strike vent field, Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Von Damm, K. L.; Bray, A. M.; Buttermore, L. G.; Oosting, S. E.

1998-08-01

Hydrothermal vent fluids were collected from the Lucky Strike site at 37°17'N on the Mid-Atlantic Ridge in both 1993 and 1996. Seven vents were sampled with the DSV Alvin in 1993 and six vents were sampled in 1996 using the ROV Jason during the LUSTRE '96 Cruise. As three of the vents were sampled in both 1993 and in 1996, a time series of vent fluid chemistry is also reported. Measured temperatures ranged from 202 to 333°C at the 1618-1726 m depth of the vent field, which is located on Lucky Strike Seamount. These fluids are either equal to or less than the local bottom seawater in chlorinity. While the range in fluid compositions at Lucky Strike is generally within that observed elsewhere, the unusual aspects of the fluid chemistries are the relatively high pH and low Fe, Mn, Li and Zn. We attribute this, as well as an usually low Sr/Ca ratio, to reaction with a highly altered substrate. The high Si and Cu contents suggest a deep, as well as hot, source for these fluids. The fluid compositions therefore suggest formation by super-critical phase separation at a depth not less than 1300 m below the seafloor, and reaction with a relatively oxic, and previously altered, substrate. There is temporal variability in some of the vent fluid compositions as Li, K, Ca and Fe concentrations have increased in some of the vents, as has the Fe/Mn (molar) ratio, although the chlorinities have remained essentially constant from 1993 to 1996. While there is not a simple relationship between vent fluid compositions (or temperatures) and distance from the lava lake at the summit of the seamount, the vent fluids from many of the vents can be shown to be related to others, often at distances >200 m. The most southeasterly vents (Eiffel Tower and the Marker/Mounds vents) are distinct in chlorinity and other chemical parameters from the rest of the vents, although closely related to each other within the southeastern area. Similarly all of the vents not in this one area, appear closely related to each other. This suggests one or two source fluids for many of the vents, as is also inferred to be the case at TAG, but which is in contrast to observations on faster spreading ridges. This may suggest inherently different plumbing for hydrothermal systems at slower versus faster spreading ridges.

Pollen flow of wheat under natural conditions in the Huanghuai River Wheat Region, China

PubMed Central

Sun, Ai-Qing; Zhang, Chun-Qing; Wu, Cheng-Lai; Gao, Qing-Rong

2015-01-01

abstract The transgenic pollen spread is the main pathway of transgenic plant gene flow. The maximum distance of pollen dispersal (horizontal), the spatial dynamics of pollen movement (vertical), and the patterns of pollen dispersal are important considerations in biosafety assessments of genetically modified crops. To evaluate wheat (Triticum aestivum) pollen dispersal, we measured the pollen suspension velocity and analyzed pollen dispersal patterns under natural conditions in the Huanghuai River wheat-growing region in 2009. The pollen suspension velocity was 0.3–0.4 m/s. The highest pollen densities were detected in the north, northwest, and south of the pollen source. Pollen was dispersed over distances greater than 245 m in the northwest and northeast directions. At the pollen source center, pollen density decreased with increasing vertical height. In the north of the pollen source, the pollen density from 65 m to 225 m showed a wave-mode decrease with increasing height. The horizontal transport of pollen over longer distances fitted polynomial equations. In the north, the pollen density was highest at 45 m from the pollen source, and decreased with increasing distance. In the northwest, the pollen density showed a double-peak trend. In the northeast, pollen density was highest from 45 m to 125 m from the source. Wind speeds greater than the pollen suspension velocity and the duration of continuous gusts were the main factors affecting pollen dispersal. This information will be useful for determining the spatial isolation distances for hybrid seed production and for the commercial production of transgenic wheat. PMID:25658025

Preparation of a micropatterned rigid-soft composite substrate for probing cellular rigidity sensing.

PubMed

Wong, Stephanie; Guo, Wei-hui; Hoffecker, Ian; Wang, Yu-li

2014-01-01

Substrate rigidity has been recognized as an important property that affects cellular physiology and functions. While the phenomenon has been well recognized, understanding the underlying mechanism may be greatly facilitated by creating a microenvironment with designed rigidity patterns. This chapter describes in detail an optimized method for preparing substrates with micropatterned rigidity, taking advantage of the ability to dehydrate polyacrylamide gels for micropatterning with photolithography, and subsequently rehydrate the gel to regain the original elastic state. While a wide range of micropatterns may be prepared, typical composite substrates consist of micron-sized islands of rigid photoresist grafted on the surface of polyacrylamide hydrogels of defined rigidity. These islands are displaced by cellular traction forces, for a distance determined by the size of the island, the rigidity of the underlying hydrogel, and the magnitude of traction forces. Domains of rigidity may be created using this composite material to allow systematic investigations of rigidity sensing and durotaxis. Copyright © 2014 Elsevier Inc. All rights reserved.

One-step femtosecond laser welding and internal machining of three glass substrates

NASA Astrophysics Data System (ADS)

Tan, Hua; Duan, Ji'an

2017-05-01

In this paper, it demonstrated one-step femtosecond laser welding and internal machining of three fused silica substrates in the optical- and non-optical-contact regimes by focusing 1030-nm laser pulses at the middle of the second substrate. Focusing laser pulses within the second glass in optical-contact and non-optical-contact samples induces permanent internal structural modification, leading to the three glass substrates bonding together simultaneously. The bonding mechanism is based on the internal modification of glass, and this mechanism is different from that of ordinary glass welding at the interface. Welding-spot size is affected by not only the gap distance (ablation effect) and heat transmission, but also by gravity through examining the sizes of the welding spots on the four contact welding surfaces. The maximum bonding strength of the lower interface (56.2 MPa) in the optical-contact regime is more than double that (27.6 MPa) in the non-optical-contact regime.

Effect of substrate rotation speed and off-center deposition on the structural, optical, and electrical properties of AZO thin films fabricated by DC magnetron sputtering

NASA Astrophysics Data System (ADS)

Turkoglu, F.; Koseoglu, H.; Zeybek, S.; Ozdemir, M.; Aygun, G.; Ozyuzer, L.

2018-04-01

In this study, aluminum-doped zinc oxide (AZO) thin films were deposited by DC magnetron sputtering at room temperature. The distance between the substrate and target axis, and substrate rotation speed were varied to get high quality AZO thin films. The influences of these deposition parameters on the structural, optical, and electrical properties of the fabricated films were investigated by X-ray diffraction (XRD), Raman spectroscopy, spectrophotometry, and four-point probe techniques. The overall analysis revealed that both sample position and substrate rotation speed are effective in changing the optical, structural, and electrical properties of the AZO thin films. We further observed that stress in the films can be significantly reduced by off-center deposition and rotating the sample holder during the deposition. An average transmittance above 85% in the visible range and a resistivity of 2.02 × 10-3 Ω cm were obtained for the AZO films.

Self-energy effect and Coulomb potential modulation of the exciton in monolayer MoS2 on polar substrate

NASA Astrophysics Data System (ADS)

Wang, Zi-Wu; Xiao, Yao; Li, Run-Ze; Li, Wei-Ping; Li, Zhi-Qing

2017-11-01

We theoretically investigate the correction of exciton binding energy in monolayer MoS2 resulting from the exciton couples with surface optical (SO) phonons induced by polar substrate. The total correction of binding energy can be divided into the self-energy effect and modification of Coulomb potential using the unitary transformation method. We find that both the self-energy and Coulomb potential vary from tens of meV to several hundreds of meV depending on the cut-off wave vector of SO phonon modes, polarizability of substrate materials and internal distance between the monolayer MoS2 and polar substrate. An effective Coulomb potential is obtained by combining the modified term into the Coulomb potential. This potentially could be widely used in various two-dimensional materials. Our theoretical results not only propose the ways to externally control the exciton binding energy in experiment, but also enrich the understanding of the exciton properties in the dielectric environment.

Technology Learning Activities. Design Brief--Measuring Inaccessible Distances. Alternative Energy Sources: Designing a Wind Powered Generator. Alternative Energy Sources: Designing a Hot Dog Heater Using Solar Energy.

ERIC Educational Resources Information Center

Technology Teacher, 1991

1991-01-01

These three learning activities are on measuring accessible distances, designing a wind powered generator, and designing a hot dog heater using solar energy. Each activity includes description of context, objectives, list of materials and equipment, challenge to students, and evaluation questions. (SK)

Academic Essay Writing as Imitative Problem Solving: Examples from Distance Learning

ERIC Educational Resources Information Center

Robertson, Sydney Ian

2014-01-01

Students in tertiary education are often faced with the prospect of writing an essay on a topic they know nothing about in advance. In distance learning institutions, essays are a common method of assessment in the UK, and specified course texts remain the main sources of information the students have. How do students use a source text to…

Functional near-infrared spectroscopy at small source-detector distance by means of high dynamic-range fast-gated SPAD acquisitions: first in-vivo measurements

NASA Astrophysics Data System (ADS)

Di Sieno, L.; Contini, D.; Dalla Mora, A.; Torricelli, A.; Spinelli, L.; Cubeddu, R.; Tosi, A.; Boso, G.; Pifferi, A.

2013-06-01

In this article, we show experimental results of time-resolved optical spectroscopy performed with small distance between launching and detecting fibers. It was already demonstrated that depth discrimination is independent of source-detector separation and that measurements at small source detector distance provide better contrast and spatial resolution. The main disadvantage is represent by the huge increase in early photons (scarcely diffused by tissue) peak that can saturate the dynamic range of most detectors, hiding information carried by late photons. Thanks to a fast-gated Single- Photon Avalanche Diode (SPAD) module, we are able to reject the peak of early photons and to obtain high-dynamic range acquisitions. We exploit fast-gated SPAD module to perform for the first time functional near-infrared spectroscopy (fNIRS) at small source-detector distance for in vivo measurements and we demonstrate the possibility to detect non-invasively the dynamics of oxygenated and deoxygenated haemoglobin occurring in the motor cortex during a motor task. We also show the improvement in terms of signal amplitude and Signal-to-Noise Ratio (SNR) obtained exploiting fast-gated SPAD performances with respect to "non-gated" measurements.

A pH sensor based on electric properties of nanotubes on a glass substrate

PubMed Central

Nakamura, Motonori; Ishii, Atsushi; Subagyo, Agus; Hosoi, Hirotaka; Sueoka, Kazuhisa; Mukasa, Koichi

2007-01-01

We fabricated a pH-sensitive device on a glass substrate based on properties of carbon nanotubes. Nanotubes were immobilized specifically on chemically modified areas on a substrate followed by deposition of metallic source and drain electrodes on the area. Some nanotubes connected the source and drain electrodes. A top gate electrode was fabricated on an insulating layer of silane coupling agent on the nanotube. The device showed properties of ann-type field effect transistor when a potential was applied to the nanotube from the top gate electrode. Before fabrication of the insulating layer, the device showed that thep-type field effect transistor and the current through the source and drain electrodes depend on the buffer pH. The current increases with decreasing pH of the CNT solution. This device, which can detect pH, is applicable for use as a biosensor through modification of the CNT surface. PMID:21806848

Direct growth and patterning of multilayer graphene onto a targeted substrate without an external carbon source.

PubMed

Kang, Dongseok; Kim, Won-Jun; Lim, Jung Ah; Song, Yong-Won

2012-07-25

Using only a simple tube furnace, we demonstrate the synthesis of patterned graphene directly on a designed substrate without the need for an external carbon source. Carbon atoms are absorbed onto Ni evaporator sources as impurities, and incorporated into catalyst layers during the deposition. Heat treatment conditions were optimized so that the atoms diffused out along the grain boundaries to form nanocrystals at the catalyst-substrate interfaces. Graphene patterns were obtained under patterned catalysts, which restricted graphene formation to within patterned areas. The resultant multilayer graphene was characterized by Raman spectroscopy and transmission electron microscopy to verify the high crystallinity and two-dimensional nanomorphology. Finally, a metal-semiconductor diode with a catalyst-graphene contact structure were fabricated and characterized to assess the semiconducting properties of the graphene sheets with respect to the display of asymmetric current-voltage behavior.

Luminescent light source for laser pumping and laser system containing same

DOEpatents

Hamil, Roy A.; Ashley, Carol S.; Brinker, C. Jeffrey; Reed, Scott; Walko, Robert J.

1994-01-01

The invention relates to a pumping lamp for use with lasers comprising a porous substrate loaded with a component capable of emitting light upon interaction of the component with exciting radiation and a source of exciting radiation. Preferably, the pumping lamp comprises a source of exciting radiation, such as an electron beam, and an aerogel or xerogel substrate loaded with a component capable of interacting with the exciting radiation, e.g., a phosphor, to produce light, e.g., visible light, of a suitable band width and of a sufficient intensity to generate a laser beam from a laser material.

Method of forming contacts for a back-contact solar cell

DOEpatents

Manning, Jane

2013-07-23

Methods of forming contacts for back-contact solar cells are described. In one embodiment, a method includes forming a thin dielectric layer on a substrate, forming a polysilicon layer on the thin dielectric layer, forming and patterning a solid-state p-type dopant source on the polysilicon layer, forming an n-type dopant source layer over exposed regions of the polysilicon layer and over a plurality of regions of the solid-state p-type dopant source, and heating the substrate to provide a plurality of n-type doped polysilicon regions among a plurality of p-type doped polysilicon regions.

Detection of CO2•- in the Electrochemical Reduction of Carbon Dioxide in N,N-Dimethylformamide by Scanning Electrochemical Microscopy.

PubMed

Kai, Tianhan; Zhou, Min; Duan, Zhiyao; Henkelman, Graeme A; Bard, Allen J

2017-12-27

The electrocatalytic reduction of CO 2 has been studied extensively and produces a number of products. The initial reaction in the CO 2 reduction is often taken to be the 1e formation of the radical anion, CO 2 •- . However, the electrochemical detection and characterization of CO 2 •- is challenging because of the short lifetime of CO 2 •- , which can dimerize and react with proton donors and even mild oxidants. Here, we report the generation and quantitative determination of CO 2 •- in N,N-dimethylformamide (DMF) with the tip generation/substrate collection (TG/SC) mode of scanning electrochemical microscopy (SECM). CO 2 was reduced at a hemisphere-shaped Hg/Pt ultramicroelectrode (UME) or a Hg/Au film UME, which were utilized as the SECM tips. The CO 2 •- produced can either dimerize to form oxalate within the nanogap between SECM tip and substrate or collected at SECM substrate (e.g., an Au UME). The collection efficiency (CE) for CO 2 •- depends on the distance (d) between the tip and substrate. The dimerization rate (6.0 × 10 8 M -1 s -1 ) and half-life (10 ns) of CO 2 •- can be evaluated by fitting the collection efficiency vs distance curve. The dimerized species of CO 2 •- , oxalate, can also be determined quantitatively. Furthermore, the formal potential (E 0 ') and heterogeneous rate constant (k 0 ) for CO 2 reduction were determined with different quaternary ammonium electrolytes. The significant difference in k 0 is due to a tunneling effect caused by the adsorption of the electrolytes on the electrode surface at negative potentials.

Cation non-stoichiometry in pulsed laser deposited Sr{sub 2+y}Fe{sub 1+x}Mo{sub 1-x}O₆ epitaxial films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meyer, T. L.; Woodward, P. M., E-mail: woodward.55@osu.edu; Dixit, M.

2014-07-07

Sr₂FeMoO₆ (SFMO) films were grown on SrTiO₃ (100)- and (111)-oriented substrates via pulsed laser deposition (PLD). In order to study the fundamental characteristics of deposition, films were grown in two different PLD chambers. In chamber I, the best films were grown with a relatively long substrate-to-target distance (89 mm), high substrate temperature (850 °C), and low pressure (50 mTorr) in a 95% Ar/5% H₂ atmosphere. Although X-ray diffraction (XRD) measurements indicate these films are single phase, Rutherford Backscattering (RBS) measurements reveal considerable non-stoichiometry, corresponding to a Sr₂Fe{sub 1–x}Mo{sub 1+x}O₆ composition with x≅0.2–0.3. This level of non-stoichiometry results in inferior magneticmore » properties. In chamber II, the best films were grown with a much shorter substrate-to-target distance (38 mm), lower temperature (680 °C), and higher pressure (225 mTorr). XRD measurements show that the films are single phase, and RBS measurements indicate that they are nearly stoichiometric. The degree of ordering between Fe and Mo was dependent on both the temperature and pressure used during deposition, reaching a maximum order parameter of 85%. The saturation magnetization increases as the Fe/Mo ordering increases, reaching a maximum of 2.4 μ B/f.u. Based on prior studies of bulk samples, one would expect a higher saturation magnetization for this degree of Fe/Mo order. The presence of extra strontium oxide layers in the form of Ruddlesden-Popper intergrowths appears to be responsible for the lower than expected saturation magnetization of these films.« less

Investigation of the hard x-ray background in backlit pinhole imagers.

PubMed

Fein, J R; Peebles, J L; Keiter, P A; Holloway, J P; Klein, S R; Kuranz, C C; Manuel, M J-E; Drake, R P

2014-11-01

Hard x-rays from laser-produced hot electrons (>10 keV) in backlit pinhole imagers can give rise to a background signal that decreases signal dynamic range in radiographs. Consequently, significant uncertainties are introduced to the measured optical depth of imaged plasmas. Past experiments have demonstrated that hard x-rays are produced when hot electrons interact with the high-Z pinhole substrate used to collimate the softer He-α x-ray source. Results are presented from recent experiments performed on the OMEGA-60 laser to further study the production of hard x-rays in the pinhole substrate and how these x-rays contribute to the background signal in radiographs. Radiographic image plates measured hard x-rays from pinhole imagers with Mo, Sn, and Ta pinhole substrates. The variation in background signal between pinhole substrates provides evidence that much of this background comes from x-rays produced in the pinhole substrate itself. A Monte Carlo electron transport code was used to model x-ray production from hot electrons interacting in the pinhole substrate, as well as to model measurements of x-rays from the irradiated side of the targets, recorded by a bremsstrahlung x-ray spectrometer. Inconsistencies in inferred hot electron distributions between the different pinhole substrate materials demonstrate that additional sources of hot electrons beyond those modeled may produce hard x-rays in the pinhole substrate.

Investigation of the hard x-ray background in backlit pinhole imagers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fein, J. R., E-mail: jrfein@umich.edu; Holloway, J. P.; Peebles, J. L.

Hard x-rays from laser-produced hot electrons (>10 keV) in backlit pinhole imagers can give rise to a background signal that decreases signal dynamic range in radiographs. Consequently, significant uncertainties are introduced to the measured optical depth of imaged plasmas. Past experiments have demonstrated that hard x-rays are produced when hot electrons interact with the high-Z pinhole substrate used to collimate the softer He-α x-ray source. Results are presented from recent experiments performed on the OMEGA-60 laser to further study the production of hard x-rays in the pinhole substrate and how these x-rays contribute to the background signal in radiographs. Radiographicmore » image plates measured hard x-rays from pinhole imagers with Mo, Sn, and Ta pinhole substrates. The variation in background signal between pinhole substrates provides evidence that much of this background comes from x-rays produced in the pinhole substrate itself. A Monte Carlo electron transport code was used to model x-ray production from hot electrons interacting in the pinhole substrate, as well as to model measurements of x-rays from the irradiated side of the targets, recorded by a bremsstrahlung x-ray spectrometer. Inconsistencies in inferred hot electron distributions between the different pinhole substrate materials demonstrate that additional sources of hot electrons beyond those modeled may produce hard x-rays in the pinhole substrate.« less

Time-distance domain transformation for Acoustic Emission source localization in thin metallic plates.

PubMed

Grabowski, Krzysztof; Gawronski, Mateusz; Baran, Ireneusz; Spychalski, Wojciech; Staszewski, Wieslaw J; Uhl, Tadeusz; Kundu, Tribikram; Packo, Pawel

2016-05-01

Acoustic Emission used in Non-Destructive Testing is focused on analysis of elastic waves propagating in mechanical structures. Then any information carried by generated acoustic waves, further recorded by a set of transducers, allow to determine integrity of these structures. It is clear that material properties and geometry strongly impacts the result. In this paper a method for Acoustic Emission source localization in thin plates is presented. The approach is based on the Time-Distance Domain Transform, that is a wavenumber-frequency mapping technique for precise event localization. The major advantage of the technique is dispersion compensation through a phase-shifting of investigated waveforms in order to acquire the most accurate output, allowing for source-sensor distance estimation using a single transducer. The accuracy and robustness of the above process are also investigated. This includes the study of Young's modulus value and numerical parameters influence on damage detection. By merging the Time-Distance Domain Transform with an optimal distance selection technique, an identification-localization algorithm is achieved. The method is investigated analytically, numerically and experimentally. The latter involves both laboratory and large scale industrial tests. Copyright © 2016 Elsevier B.V. All rights reserved.

Connecting long distance: semantic distance in analogical reasoning modulates frontopolar cortex activity.

PubMed

Green, Adam E; Kraemer, David J M; Fugelsang, Jonathan A; Gray, Jeremy R; Dunbar, Kevin N

2010-01-01

Solving problems often requires seeing new connections between concepts or events that seemed unrelated at first. Innovative solutions of this kind depend on analogical reasoning, a relational reasoning process that involves mapping similarities between concepts. Brain-based evidence has implicated the frontal pole of the brain as important for analogical mapping. Separately, cognitive research has identified semantic distance as a key characteristic of the kind of analogical mapping that can support innovation (i.e., identifying similarities across greater semantic distance reveals connections that support more innovative solutions and models). However, the neural substrates of semantically distant analogical mapping are not well understood. Here, we used functional magnetic resonance imaging (fMRI) to measure brain activity during an analogical reasoning task, in which we parametrically varied the semantic distance between the items in the analogies. Semantic distance was derived quantitatively from latent semantic analysis. Across 23 participants, activity in an a priori region of interest (ROI) in left frontopolar cortex covaried parametrically with increasing semantic distance, even after removing effects of task difficulty. This ROI was centered on a functional peak that we previously associated with analogical mapping. To our knowledge, these data represent a first empirical characterization of how the brain mediates semantically distant analogical mapping.

Liquid-phase growth of few-layered graphene on sapphire substrates using SiC micropowder source

NASA Astrophysics Data System (ADS)

Maruyama, Takahiro; Yamashita, Yutaka; Saida, Takahiro; Tanaka, Shin-ichiro; Naritsuka, Shigeya

2017-06-01

We demonstrated direct synthesis of graphene films consisting of a few layers (few-layered graphene) on sapphire substrates by liquid-phase growth (LPG), using liquid Ga as the melt and SiC micropowder as the source material. When the dissolution temperature was above 700 °C, almost all Si atoms of SiC diffused into the Ga melt and only carbon atoms remained at the interface beneath the liquid Ga. Above 800 °C, X-ray photoelectron spectra showed that most of the remaining carbon was graphitized. When the dissolution temperature was 1000 °C, Raman spectra showed that few-layered graphene films grew on the sapphire substrates.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, D.J.; Warner, J.A.; LeBarron, N.

Processes that use energetic ions for large substrates require that the time-averaged erosion effects from the ion flux be uniform across the surface. A numerical model has been developed to determine this flux and its effects on surface etching of a silica/photoresist combination. The geometry of the source and substrate is very similar to a typical deposition geometry with single or planetary substrate rotation. The model was used to tune an inert ion-etching process that used single or multiple Kaufman sources to less than 3% uniformity over a 30-cm aperture after etching 8 {micro}m of material. The same model canmore » be used to predict uniformity for ion-assisted deposition (IAD).« less

Utilization of carbon sources by clinical isolates of Aeromonas.

PubMed

Prediger, Karoline C; Surek, Monica; Dallagassa, Cibelle B; Assis, Flávia E A; Piantavini, Mario S; Souza, Emanuel M; Pedrosa, Fábio O; Farah, Sônia M S S; Alberton, Dayane; Fadel-Picheth, Cyntia M T

2017-04-01

Bacteria in the genus Aeromonas are primarily aquatic organisms; however, some species can cause diseases in humans, ranging from wound infections to septicemia, of which diarrhea is the most common condition. The ability to use a variety of carbon substrates is advantageous for pathogenic bacteria. Therefore, we used Biolog GN2 microplates to analyze the ability of 103 clinical, predominantly diarrheal, isolates of Aeromonas to use various carbon sources, and we verified whether, among the substrates metabolized by these strains, there were some endogenous to the human intestine. The results indicate that Aeromonas present great diversity in the utilization of carbon sources, and that they preferentially use carbohydrates and amino acids as carbon sources. Among the carbon sources metabolized by Aeromonas in vitro, some were found to be components of intestinal mucin, including aspartic acid, glutamic acid, l-serine, galactose, N-acetyl-glucosamine, and glucose, which were used by all strains tested. Additionally, mannose, d-serine, proline, threonine, and N-acetyl-galactosamine were used by several strains. The potential to metabolize substrates endogenous to the intestine may contribute to Aeromonas' capacity to grow in and colonize the intestine. We speculate that this may help explain the ability of Aeromonas to cause diarrhea.

Growth and Properties of Lattice Matched GaAsSbN Epilayer on GaAs for Solar Cell Applications

NASA Technical Reports Server (NTRS)

Bharatan, Sudhakar; Iyer, Shanthi; Matney, Kevin; Collis, Ward J.; Nunna Kalyan; Li, Jia; Wu, Liangjin; McGuire, Kristopher; McNeil, Laurie E.

2006-01-01

The growth and properties of GaAsSbN single quantum wells (SQWs) are investigated in this work. The heterostructures were grown on GaAs substrates in an elemental solid source molecular beam epitaxy (MBE) system assisted with a RF plasma nitrogen source. A systematic study has been carried out to determine the influence of various growth conditions, such as the growth temperature and the source shutter-opening sequence, on the quality of the grown layers and the incorporation of N and Sb. The effects of ex situ and in situ annealing under As overpressure on the optical properties of the layers have also been investigated. Substrate temperature in the range of 450-470 C was found to be optimum. Simultaneous opening of the source shutters was found to yield sharper QW interfaces. N and Sb incorporations were found to depend strongly upon substrate temperatures and source shutter opening sequences. A significant increase in PL intensity with a narrowing of PL line shape and blue shift in emission energy were observed on annealing the GaAsSbN/GaAs SQW, with in situ annealing under As overpressure providing better results, compared to ex situ annealing.

Drying induced upright sliding and reorganization of carbon nanotube arrays

NASA Astrophysics Data System (ADS)

Li, Qingwen; DePaula, Raymond; Zhang, Xiefei; Zheng, Lianxi; Arendt, Paul N.; Mueller, Fred M.; Zhu, Y. T.; Tu, Yi

2006-09-01

Driven by capillary force, wet carbon nanotube (CNT) arrays have been found to reorganize into cellular structures upon drying. During the reorganization process, individual CNTs are firmly attached to the substrate and have to lie down on the substrate at cell bottoms, forming closed cells. Here we demonstrate that by modifying catalyst structures, the adhesion of CNTs to the substrate can be weakened. Upon drying such CNT arrays, CNTs may slide away from their original sites on the surface and self-assemble into cellular patterns with bottoms open. It is also found that the sliding distance of CNTs increases with array height, and drying millimetre tall arrays leads to the sliding of CNTs over a few hundred micrometres and the eventual self-assembly into discrete islands. By introducing regular vacancies in CNT arrays, CNTs may be manipulated into different patterns.

Transversely-illuminated high current photoconductive switches with geometry-constrained conductivity path

DOEpatents

Nelson, Scott D.

2016-05-10

A photoconductive switch having a wide bandgap semiconductor material substrate between opposing electrodes, with one of the electrodes having an aperture or apertures at an electrode-substrate interface for transversely directing radiation therethrough from a radiation source into a triple junction region of the substrate, so as to geometrically constrain the conductivity path to within the triple junction region.

Structured organic materials and devices using low-energy particle beams

DOEpatents

Vardeny, Z. Valy; Li, Sergey; Delong, Matthew C.; Jiang, Xiaomei

2005-09-13

Organic materials exposed to an electron beam for patterning a substrate (1) to make an optoelectronic organic device which includes a source, a drain, gate dielectric layer (4), and a substrate for emitting light.

Structure of Sr-substituted photosystem II at 2.1 A resolution and its implications in the mechanism of water oxidation.

PubMed

Koua, Faisal Hammad Mekky; Umena, Yasufumi; Kawakami, Keisuke; Shen, Jian-Ren

2013-03-05

Oxygen-evolving complex of photosystem II (PSII) is a tetra-manganese calcium penta-oxygenic cluster (Mn4CaO5) catalyzing light-induced water oxidation through several intermediate states (S-states) by a mechanism that is not fully understood. To elucidate the roles of Ca(2+) in this cluster and the possible location of water substrates in this process, we crystallized Sr(2+)-substituted PSII from Thermosynechococcus vulcanus, analyzed its crystal structure at a resolution of 2.1 Å, and compared it with the 1.9 Å structure of native PSII. Our analysis showed that the position of Sr was moved toward the outside of the cubane structure of the Mn4CaO5-cluster relative to that of Ca(2+), resulting in a general elongation of the bond distances between Sr and its surrounding atoms compared with the corresponding distances in the Ca-containing cluster. In particular, we identified an apparent elongation in the bond distance between Sr and one of the two terminal water ligands of Ca(2+), W3, whereas that of the Sr-W4 distance was not much changed. This result may contribute to the decrease of oxygen evolution upon Sr(2+)-substitution, and suggests a weak binding and rather mobile nature of this particular water molecule (W3), which in turn implies the possible involvement of this water molecule as a substrate in the O-O bond formation. In addition, the PsbY subunit, which was absent in the 1.9 Å structure of native PSII, was found in the Sr-PSII structure.

Use of ultrasound in leather processing industry: effect of sonication on substrate and substances--new insights.

PubMed

Sivakumar, Venkatasubramanian; Swaminathan, Gopalaraman; Rao, Paruchuri Gangadhar; Muralidharan, Chellappa; Mandal, Asit Baran; Ramasami, Thirumalachari

2010-08-01

Influence of ultrasound (US) on various unit operations in leather processing has been studied with the aim to improve the process efficiency, quality, reduce process time and achieve near-zero discharge levels in effluent streams as a cleaner option. Effect of US on substrate (skin/leather) matrix as well as substances used in different unit operations have been studied and found to be useful in the processing. Absorption of US energy by leather in process vessel at different distances from US source has been measured and found to be significant. Effect of particle-size of different substances due to sonication indicates positive influence on the diffusion through the matrix. Our experimental results suggest that US effect is better realized for the cases with pronounced diffusion hindrance. Influence of US on bioprocessing of leather has been studied and found beneficial. Attempts have also been made to improve the US aided processing using external aids. Operating US in pulse mode operation could be useful in order to reduce the electrical energy consumption. Use of US has also been studied in the preparation of leather auxiliaries involving mass-transfer resistance. Preliminary cost analysis carried out for ultrasound-assisted leather-dyeing process indicates scale-up possibility. Therefore, US application provide improvement in process efficiency as well as making cleaner production methods feasible. Hence, overall results suggest that use of US in leather industry is imminent and potential viable option in near future. Copyright 2009 Elsevier B.V. All rights reserved.

Erosion by flowing lava: Geochemical evidence in the Cave Basalt, Mount St. Helens, Washington

USGS Publications Warehouse

Williams, D.A.; Kadel, S.D.; Greeley, R.; Lesher, C.M.; Clynne, M.A.

2004-01-01

We sampled basaltic lava flows and underlying dacitic tuff deposits in or near lava tubes of the Cave Basalt, Mount St. Helens, Washington to determine whether the Cave Basalt lavas contain geochemical evidence of substrate contamination by lava erosion. The samples were analyzed using a combination of wavelength-dispersive X-ray fluorescence spectrometry and inductively-coupled plasma mass spectrometry. The results indicate that the oldest, outer lava tube linings in direct contact with the dacitic substrate are contaminated, whereas the younger, inner lava tube linings are uncontaminated and apparently either more evolved or enriched in residual liquid. The most heavily contaminated lavas occur closer to the vent and in steeper parts of the tube system, and the amount of contamination decreases with increasing distance downstream. These results suggest that erosion by lava and contamination were limited to only the initially emplaced flows and that erosion was localized and enhanced by vigorous laminar flow over steeper slopes. After cooling, the initial Cave Basalt lava flows formed an insulating lining within the tubes that prevented further erosion by later flows. This interpretation is consistent with models of lava erosion that predict higher erosion rates closer to sources and over steeper slopes. A greater abundance of xenoliths and xenocrysts relative to xenomelts in hand samples indicates that mechanical erosion rather than thermal erosion was the dominant erosional process in the Cave Basalt, but further sampling and petrographic analyses must be performed to verify this hypothesis. ?? Springer-Verlag 2003.

Lovastatin Production by Aspergillus terreus Using Agro-Biomass as Substrate in Solid State Fermentation

PubMed Central

Faseleh Jahromi, Mohammad; Liang, Juan Boo; Ho, Yin Wan; Mohamad, Rosfarizan; Goh, Yong Meng; Shokryazdan, Parisa

2012-01-01

Ability of two strains of Aspergillus terreus (ATCC 74135 and ATCC 20542) for production of lovastatin in solid state fermentation (SSF) using rice straw (RS) and oil palm frond (OPF) was investigated. Results showed that RS is a better substrate for production of lovastatin in SSF. Maximum production of lovastatin has been obtained using A. terreus ATCC 74135 and RS as substrate without additional nitrogen source (157.07 mg/kg dry matter (DM)). Although additional nitrogen source has no benefit effect on enhancing the lovastatin production using RS substrate, it improved the lovastatin production using OPF with maximum production of 70.17 and 63.76 mg/kg DM for A. terreus ATCC 20542 and A. terreus ATCC 74135, respectively (soybean meal as nitrogen source). Incubation temperature, moisture content, and particle size had shown significant effect on lovastatin production (P < 0.01) and inoculums size and pH had no significant effect on lovastatin production (P > 0.05). Results also have shown that pH 6, 25°C incubation temperature, 1.4 to 2 mm particle size, 50% initial moisture content, and 8 days fermentation time are the best conditions for lovastatin production in SSF. Maximum production of lovastatin using optimized condition was 175.85 and 260.85 mg/kg DM for A. terreus ATCC 20542 and ATCC 74135, respectively, using RS as substrate. PMID:23118499

Dispersive growth and laser-induced rippling of large-area singlelayer MoS2 nanosheets by CVD on c-plane sapphire substrate

PubMed Central

Liu, Hongfei; Chi, Dongzhi

2015-01-01

Vapor-phase growth of large-area two-dimensional (2D) MoS2 nanosheets via reactions of sulfur with MoO3 precursors vaporized and transferred from powder sources onto a target substrate has been rapidly progressing. Recent studies revealed that the growth yield of high quality singlelayer (SL) MoS2 is essentially controlled by quite a few parameters including the temperature, the pressure, the amount/weight of loaded source precursors, and the cleanup of old precursors. Here, we report a dispersive growth method where a shadow mask is encapsulated on the substrate to ‘indirectly’ supply the source precursors onto the laterally advancing growth front at elevated temperatures. With this method, we have grown large-area (up to millimeters) SL-MoS2 nanosheets with a collective in-plane orientation on c-plane sapphire substrates. Regular ripples (~1 nm in height and ~50 nm in period) have been induced by laser scanning into the SL-MoS2 nanosheets. The MoS2 ripples easily initiate at the grain boundaries and extend along the atomic steps of the substrate. Such laser-induced ripple structures can be fundamental materials for studying their effects, which have been predicted to be significant but hitherto not evidenced, on the electronic, mechanical, and transport properties of SL-MoS2. PMID:26119325

Deposition of device quality, low hydrogen content, hydrogenated amorphous silicon at high deposition rates with increased stability using the hot wire filament technique

DOEpatents

Molenbroek, Edith C.; Mahan, Archie Harvin; Gallagher, Alan C.

2000-09-26

A method or producing hydrogenated amorphous silicon on a substrate, comprising the steps of: positioning the substrate in a deposition chamber at a distance of about 0.5 to 3.0 cm from a heatable filament in the deposition chamber; maintaining a pressure in said deposition chamber in the range of about 10 to 100 millitorr and pressure times substrate-filament spacing in the range of about 10 to 100 millitorr-cm, heating the filament to a temperature in the range of about 1,500 to 2,000.degree. C., and heating the substrate to a surface temperature in the range of about 280 to 475.degree. C.; and flowing silicohydride gas into the deposition chamber with said heated filament, decomposing said silicohydride gas into silicon and hydrogen atomic species and allowing products of gas reactions between said atomic species and the silicohydride gas to migrate to and deposit on said substrate while adjusting and maintaining said pressure times substrate-filament spacing in said deposition chamber at a value in said 10 to 100 millitorr range to produce statistically about 3 to 50 atomic collisions between the silicon and hydrogen atomic species migrating to said substrate and undecomposed molecules of the silane or other silicohydride gas in the deposition chamber.

Spread of dwarf mistletoe from discrete seed sources into young stands of ponderosa and Jeffrey pines

Treesearch

J. R. Parmeter Jr.

1972-01-01

The maximum distance of spread of dwarf mistletoes from isolated overstory pines into surrounding reproduction averages 120 feet. The rate of infection in young trees declined as distance from the seed source increased and was generally greatest in the direction of prevailing winds. This pattern of infection was similar to the previously reported pattern of seed...

In situ measurement of low-Z material coating thickness on high Z substrate for tokamaks.

PubMed

Mueller, D; Roquemore, A L; Jaworski, M; Skinner, C H; Miller, J; Creely, A; Raman, P; Ruzic, D

2014-11-01

Rutherford backscattering of energetic particles can be used to determine the thickness of a coating of a low-Z material over a heavier substrate. Simulations indicate that 5 MeV alpha particles from an (241)Am source can be used to measure the thickness of a Li coating on Mo tiles between 0.5 and 15 μm thick. Using a 0.1 mCi source, a thickness measurement can be accomplished in 2 h of counting. This technique could be used to measure any thin, low-Z material coating (up to 1 mg/cm(2) thick) on a high-Z substrate, such as Be on W, B on Mo, or Li on Mo. By inserting a source and detector on a moveable probe, this technique could be used to provide an in situ measurement of the thickness of Li coating on NSTX-U Mo tiles. A test stand with an alpha source and an annular solid-state detector was used to investigate the measurable range of low-Z material thicknesses on Mo tiles.

The effect of dissipation on the resistive admittance of an elastic medium.

PubMed

Photiadis, Douglas M

2012-03-01

The effect of dissipation on the real part of the admittance of an elastic half-space is typically thought to be unimportant if the loss factor ζ of the elastic medium is small. However, dissipation induces losses in the near field of the source and, provided the size of the source is small enough, this phenomenon can be more important than elastic wave radiation. Such losses give rise to a fundamental limit in the quality factor of an oscillator attached to a substrate. Near field losses associated with strains in the elastic substrate can actually be larger than intrinsic losses in the oscillator itself if the internal friction of the substrate is larger than the internal friction of the oscillator. For a uniform stress applied to a disk of radius a, a monopole source, such phenomena become significant for k(L)a<ζ, while for higher order multipole sources of order l, near field losses are important for (k(L)a)(l+1)<ζ, a far less restrictive constraint. © 2012 Acoustical Society of America

Microbial production of rhamnolipids using sugars as carbon sources.

PubMed

Tan, Yun Nian; Li, Qingxin

2018-06-08

Rhamnolipids are a class of biosurfactants with effective surface-active properties. The high cost of microbial production of rhamnolipids largely affects their commercial applications. To reduce the production post, research has been carried out in screening more powerful strains, engineering microbes with higher biosurfactant yields and exploring cheaper substrates to reduce the production cost. Extensive refining is required for biosurfactant production using oils and oil-containing wastes, necessitating the use of complex and expensive biosurfactant recovery methods such as extraction with solvents or acid precipitation. As raw materials normally can account for 10-30% of the overall production cost, sugars have been proven to be an alternative carbon source for microbial production of rhamnolipids due to its lower costs and straightforward processing techniques. Studies have thus been focused on using tropical agroindustrial crop residues as renewable substrates. Herein, we reviewed studies that are using sugar-containing substrates as carbon sources for producing rhamnolipids. We speculate that sugars derived from agricultural wastes rich in cellulose and sugar-containing wastes are potential carbon sources in fermentation while challenges still remain in large scales.

In situ measurement of low-Z material coating thickness on high Z substrate for tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mueller, D., E-mail: dmueller@pppl.gov; Roquemore, A. L.; Jaworski, M.

Rutherford backscattering of energetic particles can be used to determine the thickness of a coating of a low-Z material over a heavier substrate. Simulations indicate that 5 MeV alpha particles from an {sup 241}Am source can be used to measure the thickness of a Li coating on Mo tiles between 0.5 and 15 μm thick. Using a 0.1 mCi source, a thickness measurement can be accomplished in 2 h of counting. This technique could be used to measure any thin, low-Z material coating (up to 1 mg/cm{sup 2} thick) on a high-Z substrate, such as Be on W, B on Mo, or Limore » on Mo. By inserting a source and detector on a moveable probe, this technique could be used to provide an in situ measurement of the thickness of Li coating on NSTX-U Mo tiles. A test stand with an alpha source and an annular solid-state detector was used to investigate the measurable range of low-Z material thicknesses on Mo tiles.« less

Silicon on insulator self-aligned transistors

DOEpatents

McCarthy, Anthony M.

2003-11-18

A method for fabricating thin-film single-crystal silicon-on-insulator (SOI) self-aligned transistors. Standard processing of silicon substrates is used to fabricate the transistors. Physical spaces, between the source and gate, and the drain and gate, introduced by etching the polysilicon gate material, are used to provide connecting implants (bridges) which allow the transistor to perform normally. After completion of the silicon substrate processing, the silicon wafer is bonded to an insulator (glass) substrate, and the silicon substrate is removed leaving the transistors on the insulator (glass) substrate. Transistors fabricated by this method may be utilized, for example, in flat panel displays, etc.

Wear Characteristics of Ni-Based Hardfacing Alloy Deposited on Stainless Steel Substrate by Laser Cladding

NASA Astrophysics Data System (ADS)

Awasthi, Reena; Limaye, P. K.; Kumar, Santosh; Kushwaha, Ram P.; Viswanadham, C. S.; Srivastava, Dinesh; Soni, N. L.; Patel, R. J.; Dey, G. K.

2015-03-01

In this study, dry sliding wear characteristics of the Ni-based hardfacing alloy (Ni-Mo-Cr-Si) deposited on stainless steel SS316L substrate by laser cladding have been presented. Dry sliding wear behavior of the laser clad layer was evaluated against two different counter bodies, AISI 52100 chromium steel (~850 VHN) and tungsten carbide ball (~2200 VHN) to study both adhesive and abrasive wear characteristics, in comparison with the substrate SS316L using ball on plate reciprocating wear tester. The wear resistance was evaluated as a function of load and sliding speed for a constant sliding amplitude and sliding distance. The wear mechanisms were studied on the basis of wear surface morphology and microchemical analysis of the wear track using SEM-EDS. Laser clad layer of Ni-Mo-Cr-Si on SS316L exhibited much higher hardness (~700 VHN) than that of substrate SS316L (~200 VHN). The laser clad layer exhibited higher wear resistance as compared to SS316L substrate while sliding against both the counterparts. However, the improvement in the wear resistance of the clad layer as compared to the substrate was much higher while sliding against AISI 52100 chromium steel than that while sliding against WC, at the same contact stress intensity.

Plasma sputtering robotic device for in-situ thick coatings of long, small diameter vacuum tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hershcovitch, A., E-mail: hershcovitch@bnl.gov; Blaskiewicz, M.; Brennan, J. M.

A novel robotic plasma magnetron mole with a 50 cm long cathode was designed, fabricated, and operated. The reason for this endeavor is to alleviate the problems of unacceptable resistive heating of stainless steel vacuum tubes in the BNL Relativistic Heavy Ion Collider (RHIC). The magnetron mole was successfully operated to copper coat an assembly containing a full-size, stainless steel, cold bore, RHIC magnet tubing connected to two types of RHIC bellows, to which two additional pipes made of RHIC tubing were connected. To increase the cathode lifetime, a movable magnet package was developed, and the thickest possible cathode was made,more » with a rather challenging target to substrate (de facto anode) distance of less than 1.5 cm. Achieving reliable steady state magnetron discharges at such a short cathode to anode gap was rather challenging, when compared to commercial coating equipment, where the target to substrate distance is 10's cm; 6.3 cm is the lowest experimental target to substrate distance found in the literature. Additionally, the magnetron developed during this project provides unique omni-directional uniform coating. The magnetron is mounted on a carriage with spring loaded wheels that successfully crossed bellows and adjusted for variations in vacuum tube diameter, while keeping the magnetron centered. Electrical power and cooling water were fed through a cable bundle. The umbilical cabling system is driven by a motorized spool. Excellent coating adhesion was achieved. Measurements indicated that well-scrubbed copper coating reduced secondary electron yield to 1, i.e., the problem of electron clouds can be eliminated. Room temperature RF resistivity measurement indicated that a 10 μm copper coated stainless steel RHIC tube has a conductivity close to that of pure copper tubing. Excellent coating adhesion was achieved. The device details and experimental results are described.« less

Investigating Information Dynamics in Living Systems through the Structure and Function of Enzymes.

PubMed

Gatenby, Robert; Frieden, B Roy

2016-01-01

Enzymes are proteins that accelerate intracellular chemical reactions often by factors of 105-1012s-1. We propose the structure and function of enzymes represent the thermodynamic expression of heritable information encoded in DNA with post-translational modifications that reflect intra- and extra-cellular environmental inputs. The 3 dimensional shape of the protein, determined by the genetically-specified amino acid sequence and post translational modifications, permits geometric interactions with substrate molecules traditionally described by the key-lock best fit model. Here we apply Kullback-Leibler (K-L) divergence as metric of this geometric "fit" and the information content of the interactions. When the K-L 'distance' between interspersed substrate pn and enzyme rn positions is minimized, the information state, reaction probability, and reaction rate are maximized. The latter obeys the Arrhenius equation, which we show can be derived from the geometrical principle of minimum K-L distance. The derivation is first limited to optimum substrate positions for fixed sets of enzyme positions. However, maximally improving the key/lock fit, called 'induced fit,' requires both sets of positions to be varied optimally. We demonstrate this permits and is maximally efficient if the key and lock particles pn, rn are quantum entangled because the level of entanglement obeys the same minimized value of the Kullback-Leibler distance that occurs when all pn ≈ rn. This implies interchanges pn ⇄ brn randomly taking place during a reaction successively improves key/lock fits, reducing the activation energy Ea and increasing the reaction rate k. Our results demonstrate the summation of heritable and environmental information that determines the enzyme spatial configuration, by decreasing the K-L divergence, is converted to thermodynamic work by reducing Ea and increasing k of intracellular reactions. Macroscopically, enzyme information increases the order in living systems, similar to the Maxwell demon gedanken, by selectively accelerating specific reaction thus generating both spatial and temporal concentration gradients.

Call transmission efficiency in native and invasive anurans: competing hypotheses of divergence in acoustic signals.

PubMed

Llusia, Diego; Gómez, Miguel; Penna, Mario; Márquez, Rafael

2013-01-01

Invasive species are a leading cause of the current biodiversity decline, and hence examining the major traits favouring invasion is a key and long-standing goal of invasion biology. Despite the prominent role of the advertisement calls in sexual selection and reproduction, very little attention has been paid to the features of acoustic communication of invasive species in nonindigenous habitats and their potential impacts on native species. Here we compare for the first time the transmission efficiency of the advertisement calls of native and invasive species, searching for competitive advantages for acoustic communication and reproduction of introduced taxa, and providing insights into competing hypotheses in evolutionary divergence of acoustic signals: acoustic adaptation vs. morphological constraints. Using sound propagation experiments, we measured the attenuation rates of pure tones (0.2-5 kHz) and playback calls (Lithobates catesbeianus and Pelophylax perezi) across four distances (1, 2, 4, and 8 m) and over two substrates (water and soil) in seven Iberian localities. All factors considered (signal type, distance, substrate, and locality) affected transmission efficiency of acoustic signals, which was maximized with lower frequency sounds, shorter distances, and over water surface. Despite being broadcast in nonindigenous habitats, the advertisement calls of invasive L. catesbeianus were propagated more efficiently than those of the native species, in both aquatic and terrestrial substrates, and in most of the study sites. This implies absence of optimal relationship between native environments and propagation of acoustic signals in anurans, in contrast to what predicted by the acoustic adaptation hypothesis, and it might render these vertebrates particularly vulnerable to intrusion of invasive species producing low frequency signals, such as L. catesbeianus. Our findings suggest that mechanisms optimizing sound transmission in native habitat can play a less significant role than other selective forces or biological constraints in evolutionary design of anuran acoustic signals.

Call Transmission Efficiency in Native and Invasive Anurans: Competing Hypotheses of Divergence in Acoustic Signals

PubMed Central

Llusia, Diego; Gómez, Miguel; Penna, Mario; Márquez, Rafael

2013-01-01

Invasive species are a leading cause of the current biodiversity decline, and hence examining the major traits favouring invasion is a key and long-standing goal of invasion biology. Despite the prominent role of the advertisement calls in sexual selection and reproduction, very little attention has been paid to the features of acoustic communication of invasive species in nonindigenous habitats and their potential impacts on native species. Here we compare for the first time the transmission efficiency of the advertisement calls of native and invasive species, searching for competitive advantages for acoustic communication and reproduction of introduced taxa, and providing insights into competing hypotheses in evolutionary divergence of acoustic signals: acoustic adaptation vs. morphological constraints. Using sound propagation experiments, we measured the attenuation rates of pure tones (0.2–5 kHz) and playback calls (Lithobates catesbeianus and Pelophylax perezi) across four distances (1, 2, 4, and 8 m) and over two substrates (water and soil) in seven Iberian localities. All factors considered (signal type, distance, substrate, and locality) affected transmission efficiency of acoustic signals, which was maximized with lower frequency sounds, shorter distances, and over water surface. Despite being broadcast in nonindigenous habitats, the advertisement calls of invasive L. catesbeianus were propagated more efficiently than those of the native species, in both aquatic and terrestrial substrates, and in most of the study sites. This implies absence of optimal relationship between native environments and propagation of acoustic signals in anurans, in contrast to what predicted by the acoustic adaptation hypothesis, and it might render these vertebrates particularly vulnerable to intrusion of invasive species producing low frequency signals, such as L. catesbeianus. Our findings suggest that mechanisms optimizing sound transmission in native habitat can play a less significant role than other selective forces or biological constraints in evolutionary design of anuran acoustic signals. PMID:24155940

Plasma Sputtering Robotic Device for In-Situ Thick Coatings of Long, Small Diameter Vacuum Tubes

NASA Astrophysics Data System (ADS)

Hershcovitch, Ady

2014-10-01

A novel robotic plasma magnetron mole with a 50 cm long cathode was designed fabricated & operated. Reason for this endeavor is to alleviate the problems of unacceptable ohmic heating of stainless steel vacuum tubes and of electron clouds, due to high secondary electron yield (SEY), in the BNL Relativistic Heavy Ion Collider (RHIC). The magnetron mole was successfully operated to copper coat an assembly containing a full-size, stainless steel, cold bore, RHIC magnet tubing connected to two types of RHIC bellows, to which two additional pipes made of RHIC tubing were connected. To increase cathode lifetime, movable magnet package was developed, and thickest possible cathode was made, with a rather challenging target to substrate (de facto anode) distance of less than 1.5 cm. Achieving reliable steady state magnetron discharges at such a short cathode to anode gap was rather challenging, when compared to commercial coating equipment, where the target to substrate distance is 10's cm; 6.3 cm is the lowest experimental target to substrate distance found in the literature. Additionally, the magnetron developed during this project provides unique omni-directional uniform coating. The magnetron is mounted on a carriage with spring loaded wheels that successfully crossed bellows and adjusted for variations in vacuum tube diameter, while keeping the magnetron centered. Electrical power and cooling water were fed through a cable bundle. The umbilical cabling system is driven by a motorized spool. Excellent coating adhesion was achieved. Measurements indicated that well-scrubbed copper coating reduced SEY to 1, i.e., the problem of electron clouds can be eliminated. Room temperature RF resistivity measurement indicated that 10 μm Cu coated stainless steel RHIC tube has conductivity close to that of pure copper tubing. Excellent coating adhesion was achieved. Device detail and experimental results will be presented. Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH1-886 with the US Department of Energy.

Plasma sputtering robotic device for in-situ thick coatings of long, small diameter vacuum tubesa)

NASA Astrophysics Data System (ADS)

Hershcovitch, A.; Blaskiewicz, M.; Brennan, J. M.; Custer, A.; Dingus, A.; Erickson, M.; Fischer, W.; Jamshidi, N.; Laping, R.; Liaw, C.-J.; Meng, W.; Poole, H. J.; Todd, R.

2015-05-01

A novel robotic plasma magnetron mole with a 50 cm long cathode was designed, fabricated, and operated. The reason for this endeavor is to alleviate the problems of unacceptable resistive heating of stainless steel vacuum tubes in the BNL Relativistic Heavy Ion Collider (RHIC). The magnetron mole was successfully operated to copper coat an assembly containing a full-size, stainless steel, cold bore, RHIC magnet tubing connected to two types of RHIC bellows, to which two additional pipes made of RHIC tubing were connected. To increase the cathode lifetime, a movable magnet package was developed, and the thickest possible cathode was made, with a rather challenging target to substrate (de facto anode) distance of less than 1.5 cm. Achieving reliable steady state magnetron discharges at such a short cathode to anode gap was rather challenging, when compared to commercial coating equipment, where the target to substrate distance is 10's cm; 6.3 cm is the lowest experimental target to substrate distance found in the literature. Additionally, the magnetron developed during this project provides unique omni-directional uniform coating. The magnetron is mounted on a carriage with spring loaded wheels that successfully crossed bellows and adjusted for variations in vacuum tube diameter, while keeping the magnetron centered. Electrical power and cooling water were fed through a cable bundle. The umbilical cabling system is driven by a motorized spool. Excellent coating adhesion was achieved. Measurements indicated that well-scrubbed copper coating reduced secondary electron yield to 1, i.e., the problem of electron clouds can be eliminated. Room temperature RF resistivity measurement indicated that a 10 μm copper coated stainless steel RHIC tube has a conductivity close to that of pure copper tubing. Excellent coating adhesion was achieved. The device details and experimental results are described.

Extreme ultraviolet lithography machine

DOEpatents

Tichenor, Daniel A.; Kubiak, Glenn D.; Haney, Steven J.; Sweeney, Donald W.

2000-01-01

An extreme ultraviolet lithography (EUVL) machine or system for producing integrated circuit (IC) components, such as transistors, formed on a substrate. The EUVL machine utilizes a laser plasma point source directed via an optical arrangement onto a mask or reticle which is reflected by a multiple mirror system onto the substrate or target. The EUVL machine operates in the 10-14 nm wavelength soft x-ray photon. Basically the EUV machine includes an evacuated source chamber, an evacuated main or project chamber interconnected by a transport tube arrangement, wherein a laser beam is directed into a plasma generator which produces an illumination beam which is directed by optics from the source chamber through the connecting tube, into the projection chamber, and onto the reticle or mask, from which a patterned beam is reflected by optics in a projection optics (PO) box mounted in the main or projection chamber onto the substrate. In one embodiment of a EUVL machine, nine optical components are utilized, with four of the optical components located in the PO box. The main or projection chamber includes vibration isolators for the PO box and a vibration isolator mounting for the substrate, with the main or projection chamber being mounted on a support structure and being isolated.

Proprioceptive Distance Cues Restore Perfect Size Constancy in Grasping, but Not Perception, When Vision Is Limited.

PubMed

Chen, Juan; Sperandio, Irene; Goodale, Melvyn Alan

2018-03-19

Our brain integrates information from multiple modalities in the control of behavior. When information from one sensory source is compromised, information from another source can compensate for the loss. What is not clear is whether the nature of this multisensory integration and the re-weighting of different sources of sensory information are the same across different control systems. Here, we investigated whether proprioceptive distance information (position sense of body parts) can compensate for the loss of visual distance cues that support size constancy in perception (mediated by the ventral visual stream) [1, 2] versus size constancy in grasping (mediated by the dorsal visual stream) [3-6], in which the real-world size of an object is computed despite changes in viewing distance. We found that there was perfect size constancy in both perception and grasping in a full-viewing condition (lights on, binocular viewing) and that size constancy in both tasks was dramatically disrupted in the restricted-viewing condition (lights off; monocular viewing of the same but luminescent object through a 1-mm pinhole). Importantly, in the restricted-viewing condition, proprioceptive cues about viewing distance originating from the non-grasping limb (experiment 1) or the inclination of the torso and/or the elbow angle of the grasping limb (experiment 2) compensated for the loss of visual distance cues to enable a complete restoration of size constancy in grasping but only a modest improvement of size constancy in perception. This suggests that the weighting of different sources of sensory information varies as a function of the control system being used. Copyright © 2018 Elsevier Ltd. All rights reserved.

Infrasound wave propagation over near-regional and tele-infrasonic distances

NASA Astrophysics Data System (ADS)

McKenna, Sara Mihan House

2005-11-01

Infrasound research is experiencing a renaissance due to advances in acoustic propagation calculations and a deeper understanding of the atmosphere. Uniquely combining observed data and propagation modeling, the three papers presented here quantify the effects of the atmosphere on propagation from a variety of sources at distances from less than 100 km (near-regional distances) to nearly 600 km (tele-infrasonic distances) for sources on the surface and at altitude (63 km). Paper one analyzes infrasound signals recorded at the CHNAR seismo-acoustic array. These sources are predominantly on the surface, result from human activity and occur closer than 250 km away. Propagation for these near-regional distances depends on tropospheric weather patterns and temporally varying, low-altitude ducts. To predict the observed arrivals local meteorological data is necessary; MSIS/HWM (Mass Spectrometer Incoherent Scatter/Horizontal Wind Model) and NRL-G2S (Naval Research Laboratory Ground To Space) did not predict the observed arrivals. Paper two is the first time a waveform from an explosion at height has ever been reproduced; the recorded waveform was from the break-up of the space shuttle Columbia. For the tele-infrasonic normal mode modeling, MSIS/HWM and NRL-G2S yielded identical waveform results. Paper three looks at the tele-infrasonic path between an iron mine in Minnesota and an infrasound array in Manitoba, Canada. Over a four month period, the IS-10 infrasound array provided infrasound data to compare to archived blast statistics. NRL-G2S better reproduced the observed arrival travel times than MSIS/HWM; whether or not arrivals were observed depended on the noise field at the infrasound array. For any distance range or source height, accurate atmospheric parameters from the corresponding propagation paths are necessary to predict observed infrasound.

Holocene loess deposition and soil formation as competing processes, Matanuska Valley, southern Alaska

USGS Publications Warehouse

Muhs, D.R.; McGeehin, J.P.; Beann, J.; Fisher, E.

2004-01-01

Although loess-paleosol sequences are among the most important records of Quaternary climate change and past dust deposition cycles, few modern examples of such sedimentation systems have been studied. Stratigraphic studies and 22 new accelerator mass spectrometry radiocarbon ages from the Matanuska Valley in southern Alaska show that loess deposition there began sometime after ???6500 14C yr B.P. and has continued to the present. The silts are produced through grinding by the Matanuska and Knik glaciers, deposited as outwash, entrained by strong winds, and redeposited as loess. Over a downwind distance of ???40 km, loess thickness, sand content, and sand-plus-coarse-silt content decrease, whereas fine-silt content increases. Loess deposition was episodic, as shown by the presence of paleosols, at distances >10 km from the outwash plain loess source. Stratigraphic complexity is at a maximum (i.e., the greatest number of loesses and paleosols) at intermediate (10-25 km) distances from the loess source. Surface soils increase in degree of development with distance downwind from the source, where sedimentation rates are lower. Proximal soils are Entisols or Inceptisols, whereas distal soils are Spodosols. Ratios of mobile CaO, K2O, and Fe2O3 to immobile TiO2 show decreases in surface horizons with distance from the source. Thus, as in China, where loess deposition also takes place today, eolian sedimentation and soil formation are competing processes. Study of loess and paleosols in southern Alaska shows that particle size can vary over short distances, loess deposition can be episodic over limited time intervals, and soils developed in stabilized loess can show considerable variability under the same vegetation. ?? 2004 University of Washington. All rights reserved.

Astronomical Distance Determination in the Space Age. Secondary Distance Indicators

NASA Astrophysics Data System (ADS)

Czerny, Bożena; Beaton, Rachael; Bejger, Michał; Cackett, Edward; Dall'Ora, Massimo; Holanda, R. F. L.; Jensen, Joseph B.; Jha, Saurabh W.; Lusso, Elisabeta; Minezaki, Takeo; Risaliti, Guido; Salaris, Maurizio; Toonen, Silvia; Yoshii, Yuzuru

2018-02-01

The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations.

Deposition of Lanthanum Strontium Cobalt Ferrite (LSCF) Using Suspension Plasma Spraying for Oxygen Transport Membrane Applications

NASA Astrophysics Data System (ADS)

Fan, E. S. C.; Kesler, O.

2015-08-01

Suspension plasma spray deposition was utilized to fabricate dense lanthanum strontium cobalt ferrite oxygen separation membranes (OSMs) on porous metal substrates for mechanical support. The as-sprayed membranes had negligible and/or reversible material decomposition. At the longer stand-off distance (80 mm), smooth and dense membranes could be manufactured using a plasma with power below approximately 81 kW. Moreover, a membrane of 55 μm was observed to have very low gas leakage rates desirable for OSM applications. This thickness could potentially be decreased further to improve oxygen diffusion by using metal substrates with finer surface pores.

Micro transport machine and methods for using same

DOEpatents

Stalford, Harold

2015-10-13

A micro transport machine may include a substrate and a movable device comprising a drive component responsive to a wireless power source. The movable device is operable to move between a plurality of disparate areas on the substrate.

Apparatus for in situ cleaning of carbon contaminated surfaces

DOEpatents

Klebanoff, Leonard E.; Grunow, Philip; Graham, Jr., Samuel

2004-08-10

Activated gaseous species generated adjacent a carbon contaminated surface affords in-situ cleaning. A device for removing carbon contamination from a surface of the substrate includes (a) a housing defining a vacuum chamber in which the substrate is located; (b) a source of gaseous species; and (c) a source of electrons that are emitted to activate the gaseous species into activated gaseous species. The source of electrons preferably includes (i) a filament made of a material that generates thermionic electron emissions; (ii) a source of energy that is connected to the filament; and (iii) an electrode to which the emitted electrons are attracted. The device is particularly suited for photolithography systems with optic surfaces, e.g., mirrors, that are otherwise inaccessible unless the system is dismantled.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buta, R.; de Vaucouleurs, G.

The diameters d/sub r/ of inner ring structures in disk galaxies are used as geometric distance indicators to derive the distances of 453 spiral and lenticular galaxies, mainly in the distance interval 4<..delta..<63 Mpc. The diameters are weighted means from the catalogs to Kormendy, Pedreros and Madore, and the authors. The distances are calculated by means of the two- and three-parameter formulae of Paper II; the adopted mean distance moduli ..mu../sub 0/(r) have mean errors from all sources of 0.6--0.7 mag for the well-observed galaxies.

Controllable Planar Optical Focusing System

NASA Technical Reports Server (NTRS)

Arbabi, Amir (Inventor); Faraon, Andrei (Inventor)

2016-01-01

An optical device has a first metasurface disposed over a substrate. A high-contrast pattern of the first metasurface is operable for modifying, over a first phase profile, a phase front of an incident light beam. A second metasurface, is disposed over a plane parallel to the first metasurface with a second high-contrast pattern and operable for shaping, over a second phase profile, the modified phase front of the incident light beam into a converging spherical phase front. A spacer layer, in which the modified phase front of the incident light beam diffracts, is disposed in a controllably changeable separation between the first and second metasurfaces. Controllably changing the separation between the first and the second metasurfaces by a first distance correspondingly changes the position of the focus point of the converging spherical phase front by a second distance significantly greater than the first distance.

Trade-off between Photon Management Efficacy and Material Quality in Thin-Film Solar Cells on Nanostructured Substrates of High Aspect Ratio Structures

DOE PAGES

Chin, Alan; Keshavarz, Majid; Wang, Qi

2018-04-13

Although texturing of the transparent electrode of thin-film solar cells has long been used to enhance light absorption via light trapping, such texturing has involved low aspect ratio features. With the recent development of nanotechnology, nanostructured substrates enable improved light trapping and enhanced optical absorption via resonances, a process known as photon management, in thin-film solar cells. Despite the progress made in the development of photon management in thin-film solar cells using nanostructures substrates, the structural integrity of the thin-film solar cells deposited onto such nanostructured substrates is rarely considered. Here, we report the observation of the reduction in themore » open circuit voltage of amorphous silicon solar cells deposited onto a nanostructured substrate with increasing areal number density of high aspect ratio structures. For a nanostructured substrate with the areal number density of such nanostructures increasing in correlation with the distance from one edge of the substrate, a correlation between the open circuit voltage reduction and the increase of the areal number density of high aspect ratio nanostructures of the front electrode of the small-size amorphous silicon solar cells deposited onto different regions of the substrate with graded nanostructure density indicates the effect of the surface morphology on the material quality, i.e., a trade-off between photon management efficacy and material quality. Lastly, this observed trade-off highlights the importance of optimizing the morphology of the nanostructured substrate to ensure conformal deposition of the thin-film solar cell.« less

Trade-off between Photon Management Efficacy and Material Quality in Thin-Film Solar Cells on Nanostructured Substrates of High Aspect Ratio Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chin, Alan; Keshavarz, Majid; Wang, Qi

Although texturing of the transparent electrode of thin-film solar cells has long been used to enhance light absorption via light trapping, such texturing has involved low aspect ratio features. With the recent development of nanotechnology, nanostructured substrates enable improved light trapping and enhanced optical absorption via resonances, a process known as photon management, in thin-film solar cells. Despite the progress made in the development of photon management in thin-film solar cells using nanostructures substrates, the structural integrity of the thin-film solar cells deposited onto such nanostructured substrates is rarely considered. Here, we report the observation of the reduction in themore » open circuit voltage of amorphous silicon solar cells deposited onto a nanostructured substrate with increasing areal number density of high aspect ratio structures. For a nanostructured substrate with the areal number density of such nanostructures increasing in correlation with the distance from one edge of the substrate, a correlation between the open circuit voltage reduction and the increase of the areal number density of high aspect ratio nanostructures of the front electrode of the small-size amorphous silicon solar cells deposited onto different regions of the substrate with graded nanostructure density indicates the effect of the surface morphology on the material quality, i.e., a trade-off between photon management efficacy and material quality. Lastly, this observed trade-off highlights the importance of optimizing the morphology of the nanostructured substrate to ensure conformal deposition of the thin-film solar cell.« less

The Mixed Processing Models Development Of Thermal Fracture And Laser Ablation On Glass Substrate

NASA Astrophysics Data System (ADS)

Huang, Kuo-Cheng; Wu, Wen-Hong; Tseng, Shih-Feng; Hwang, Chi-Hung

2011-01-01

As the industries of cell phone and LCD TV were vigorously flourishing and the manufacturing requirements for LCD glass substrate were getting higher, the thermal fracture cutting technology (TFCT) has progressively become the main technology for LCD glass substrate cutting. Due to using laser as the heat source, the TFCT has many advantages, such as uniform heating, small heat effect zone, and high cutting speed, smooth cutting surface and low residual stress, etc. Moreover, a general laser ablation processing or traditional diamond wheel cutting does not have the last two advantages. The article presents a mixed processing of glass substrate, which consists of TFCT and laser ablation mechanisms, and how to enhance the cutting speed with little ablation laser energy. In this study, a 10W Nd:YAG laser and a 40W CO2 laser are used as the heat source of TFCT and laser ablation processing, respectively. The result indicates that the speed of the mixed processing is more than twice the speed of TFCT. Furthermore, after the mixed processing, the residual stresses in the glass substrates are also smaller.

Psychophysical evidence for auditory motion parallax.

PubMed

Genzel, Daria; Schutte, Michael; Brimijoin, W Owen; MacNeilage, Paul R; Wiegrebe, Lutz

2018-04-17

Distance is important: From an ecological perspective, knowledge about the distance to either prey or predator is vital. However, the distance of an unknown sound source is particularly difficult to assess, especially in anechoic environments. In vision, changes in perspective resulting from observer motion produce a reliable, consistent, and unambiguous impression of depth known as motion parallax. Here we demonstrate with formal psychophysics that humans can exploit auditory motion parallax, i.e., the change in the dynamic binaural cues elicited by self-motion, to assess the relative depths of two sound sources. Our data show that sensitivity to relative depth is best when subjects move actively; performance deteriorates when subjects are moved by a motion platform or when the sound sources themselves move. This is true even though the dynamic binaural cues elicited by these three types of motion are identical. Our data demonstrate a perceptual strategy to segregate intermittent sound sources in depth and highlight the tight interaction between self-motion and binaural processing that allows assessment of the spatial layout of complex acoustic scenes.

Active substrates improving sensitivity in biomedical fluorescence microscopy

NASA Astrophysics Data System (ADS)

Le Moal, E.; Leveque-Fort, S.; Fort, E.; Lacharme, J.-P.; Fontaine-Aupart, M.-P.; Ricolleau, C.

2005-08-01

Fluorescence is widely used as a spectroscopic tool or for biomedical imaging, in particular for DNA chips. In some cases, detection of very low molecular concentrations and precise localization of biomarkers are limited by the weakness of the fluorescence signal. We present a new method based on sample substrates that improve fluorescence detection sensitivity. These active substrates consist in glass slides covered with metal (gold or silver) and dielectric (alumina) films and can directly be used with common microscope set-up. Fluorescence enhancement affects both excitation and decay rates and is strongly dependant on the distance to the metal surface. Furthermore, fluorescence collection is improved since fluorophore emission lobes are advantageously modified close to a reflective surface. Finally, additional improvements are achieved by structuring the metallic layer. Substrates morphology was mapped by Atomic Force Microscopy (AFM). Substrates optical properties were studied using mono- and bi-photonic fluorescence microscopy with time resolution. An original set-up was implemented for spatial radiation pattern's measurement. Detection improvement was then tested on commercial devices. Several biomedical applications are presented. Enhancement by two orders of magnitude are achieved for DNA chips and signal-to-noise ratio is greatly increased for cells imaging.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Surface diffusion of Si, Ge and C adatoms on Si (001) substrate studied by the molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Chen, Zhi-Hui; Yu, Zhong-Yuan; Lu, Peng-Fei; Liu, Yu-Min

2009-10-01

Depositions of Si, Ge and C atoms onto a preliminary Si (001) substrate at different temperatures are investigated by using the molecular dynamics method. The mechanism of atomic self-assembling occurring locally on the flat terraces between steps is suggested. Diffusion and arrangement patterns of adatoms at different temperatures are observed. At 900 K, the deposited atoms are more likely to form dimers in the perpendicular [110] direction due to the more favourable movement along the perpendicular [110] direction. C adatoms are more likely to break or reconstruct the dimers on the substrate surface and have larger diffusion distances than Ge and Si adatoms. Exchange between C adatoms and substrate atoms are obvious and the epitaxial thickness is small. Total potential energies of adatoms and substrate atoms involved in the simulation cell are computed. When a newly arrived adatom reaches the stable position, the potential energy of the system will decrease and the curves turns into a ladder-like shape. It is found that C adatoms can lead to more reduction of the system energy and the potential energy of the system will increase as temperature increases.

On-line Adaptive Radiation Treatment of Prostate Cancer

DTIC Science & Technology

2008-01-01

novel imaging system using a linear x-ray source and a linear detector . This imaging system may significantly improve the quality of online images...yielded the Euclidean voxel distances nside the ROI. The two distance maps were combined with ositive distances outside and negative distances inside...is reduced by 1cm. IMRT is more sensitive to organ motion. Large discrepancies of bladder and rectum doses were observed compared to the actual

Cepheids Geometrical Distances Using Space Interferometry

NASA Astrophysics Data System (ADS)

Marengo, M.; Karovska, M.; Sasselov, D. D.; Sanchez, M.

2004-05-01

A space based interferometer with a sub-milliarcsecond resolution in the UV-optical will provide a new avenue for the calibration of primary distance indicators with unprecedented accuracy, by allowing very accurate and stable measurements of Cepheids pulsation amplitudes at wavelengths not accessible from the ground. Sasselov & Karovska (1994) have shown that interferometers allow very accurate measurements of Cepheids distances by using a ``geometric'' variant of the Baade-Wesselink method. This method has been succesfully applied to derive distances and radii of nearby Cepheids using ground-based near-IR and optical interferometers, within a 15% accuracy level. Our study shows that the main source of error in these measurements is due to the perturbing effects of the Earth atmosphere, which is the limiting factor in the interferometer stability. A space interferometer will not suffer from this intrinsic limitations, and can potentially lead to improve astronomical distance measurements by an order of magnitude in precision. We discuss here the technical requirements that a space based facility will need to carry out this project, allowing distance measurements within a few percent accuracy level. We will finally discuss how a sub-milliarcsecond resolution will allow the direct distance determination for hundreds of galactic sources, and provide a substantial improvement in the zero-point of the Cepheid distance scale.

Supplementation of banana flower powder pellet and plant oil sources on in vitro ruminal fermentation, digestibility, and methane production.

PubMed

Kang, Sungchhang; Wanapat, Metha; Viennasay, Bounnaxay

2016-12-01

The objective of this study was to evaluate the effects of banana flower power pellet (BAFLOP-pellet) and plant oil source on in vitro gas production, fermentation efficiency, and methane (CH 4 ) production. Rumen fluid was collected from two rumen-fistulated dairy steers fed on rice straw-based diet with concentrate supplement to maintain normal rumen ecology. All supplemented feed were added to respective treatments in the 30:70 roughage to concentrate-based substrate. The treatments were arranged according to a 3 × 3 factorial arrangement in a completely randomized design. First factor was different levels of BAFLOP-pellet supplementation (0, 30, and 60 g/kg of dietary substrate) and second factor was plant oil source supplementation [non-supplemented, 20 g/kg krabok seed oil (KSO), and 20 g/kg coconut oil (CO) of dietary substrate, respectively]. Under this investigation, BAFLOP-pellet supplementation increased gas production kinetics and in vitro digestibility (P < 0.05). Ruminal pH was dropped post incubation time in the non-supplemented group but was enhanced in BAFLOP-pellet-supplemented treatments. On the other hand, supplementation of KSO and CO depressed gas production and digestibility, but did not influence ruminal pH. In addition, protozoal population and CH 4 production were decreased by BAFLOP-pellet and plant oil addition (P < 0.05). Based on this study, it could be concluded that supplementation of BAFLOP-pellet and plant oil source could enhance the in vitro fermentation efficiency while reduced protozoal population and CH 4 production. It is suggested that BAFLOP-pellet (60 g/kg of dietary substrate) and KSO/CO (20 g/kg of dietary substrate) could be used to manipulate rumen fermentation characteristics fed on high-concentrate diet.

Method for high specific bioproductivity of .alpha.,.omega.-alkanedicarboxylic acids

DOEpatents

Mobley, David Paul; Shank, Gary Keith

2000-01-01

This invention provides a low-cost method of producing .alpha.,.omega.-alkanedicarboxylic acids. Particular bioconversion conditions result in highly efficient conversion of fatty acid, fatty acid ester, or alkane substrates to diacids. Candida tropicalis AR40 or similar yeast strains are grown in a medium containing a carbon source and a nitrogen source at a temperature of 31.degree. C. to 38.degree. C., while additional carbon source is continuously added, until maximum cell growth is attained. Within 0-3 hours of this point, substrate is added to the culture to initiate conversion. An .alpha.,.omega.-alkanedicarboxylic acid made according to this method is also provided.

Solid-state radiation-emitting compositions and devices

DOEpatents

Ashley, Carol S.; Brinker, C. Jeffrey; Reed, Scott; Walko, Robert J.

1992-01-01

The invention relates to a composition for the volumetric generation of radiation, wherein a first substance functions as a source of exciting radiation, and a second substance interacts with the exciting radiation to provide a second radiation. The compositions comprise a porous substrate which is loaded with: a source of exciting radiation, a component capable of emitting radiation upon interaction with the exciting radiation, or both. Preferably, the composition is an aerogel substrate loaded with both a source of exciting radiation, such as tritium, and a component capable of interacting with the exciting radiation, e.g., a phosphor, to produce radiation of a second energy.

Solid-state radiation-emitting compositions and devices

DOEpatents

Ashley, C.S.; Brinker, C.J.; Reed, S.; Walko, R.J.

1992-08-11

The invention relates to a composition for the volumetric generation of radiation, wherein a first substance functions as a source of exciting radiation, and a second substance interacts with the exciting radiation to provide a second radiation. The compositions comprise a porous substrate which is loaded with: a source of exciting radiation, a component capable of emitting radiation upon interaction with the exciting radiation, or both. Preferably, the composition is an aerogel substrate loaded with both a source of exciting radiation, such as tritium, and a component capable of interacting with the exciting radiation, e.g., a phosphor, to produce radiation of a second energy. 4 figs.

Three extracellular dipeptidyl peptidases found in Aspergillus oryzae show varying substrate specificities.

PubMed

Maeda, Hiroshi; Sakai, Daisuke; Kobayashi, Takuji; Morita, Hiroto; Okamoto, Ayako; Takeuchi, Michio; Kusumoto, Ken-Ichi; Amano, Hitoshi; Ishida, Hiroki; Yamagata, Youhei

2016-06-01

Three extracellular dipeptidyl peptidase genes, dppB, dppE, and dppF, were unveiled by sequence analysis of the Aspergillus oryzae genome. We investigated their differential enzymatic profiles, in order to gain an understanding of the diversity of these genes. The three dipeptidyl peptidases were expressed using Aspergillus nidulans as the host. Each recombinant enzyme was purified and subsequently characterized. The enzymes displayed similar optimum pH values, but optimum temperatures, pH stabilities, and substrate specificities varied. DppB was identified as a Xaa-Prolyl dipeptidyl peptidase, while DppE scissile substrates were similar to the substrates for Aspergillus fumigatus DPPV (AfDPPV). DppF was found to be a novel enzyme that could digest both substrates for A. fumigatus DPPIV and AfDPPV. Semi-quantitative PCR revealed that the transcription of dppB in A. oryzae was induced by protein substrates and repressed by the addition of an inorganic nitrogen source, despite the presence of protein substrates. The transcription of dppE depended on its growth time, while the transcription of dppF was not affected by the type of the nitrogen source in the medium, and it started during the early stage of the fungal growth. Based on these results, we conclude that these enzymes may represent the nutrition acquisition enzymes. Additionally, DppF may be one of the sensor peptidases responsible for the detection of the protein substrates in A. oryzae environment. DppB may be involved in nitrogen assimilation control, since the transcription of dppB was repressed by NaNO3, despite the presence of protein substrates.

Room temperature deposition of sputtered TiN films for superconducting coplanar waveguide resonators

NASA Astrophysics Data System (ADS)

Ohya, S.; Chiaro, B.; Megrant, A.; Neill, C.; Barends, R.; Chen, Y.; Kelly, J.; Low, D.; Mutus, J.; O'Malley, P. J. J.; Roushan, P.; Sank, D.; Vainsencher, A.; Wenner, J.; White, T. C.; Yin, Y.; Schultz, B. D.; Palmstrøm, C. J.; Mazin, B. A.; Cleland, A. N.; Martinis, John M.

2014-01-01

We present a systematic study of the properties of room temperature deposited TiN films by varying the deposition conditions in an ultra-high-vacuum reactive magnetron sputtering chamber. By increasing the deposition pressure from 2 to 9 mTorr while keeping a nearly stoichiometric composition of Ti1-xNx (x = 0.5) without substrate heating, the film resistivity increases, the dominant crystal orientation changes from (100) to (111), grain boundaries become clearer, and the strong compressive in-plane strain changes to weak tensile in-plane strain. The TiN films absorb a high concentration of contaminants including hydrogen, carbon, and oxygen when they are exposed to air after deposition. With the target-substrate distance set to 88 mm the contaminant levels increase from ˜0.1% to ˜10% as the pressure is increased from 2 to 9 mTorr. The contaminant concentrations also correlate with in-plane distance from the center of the substrate and increase by roughly two orders of magnitude as the target-substrate distance is increased from 88 to 266 mm. These contaminants are found to strongly influence the properties of TiN thin films. For instance, the resistivity of stoichiometric films increases by around a factor of 5 as the oxygen content increases from 0.1% to 11%. These results strongly suggest that the energy of the sputtered TiN particles plays a crucial role in determining the TiN film properties, and that it is important to precisely control the energy of these particles to obtain high-quality TiN films. Superconducting coplanar waveguide resonators made from a series of nearly stoichiometric films grown at pressures from 2 to 7 mTorr show a substantial increase in intrinsic quality factor from ˜104 to ˜106 as the magnitude of the compressive strain decreases from nearly 3800 MPa to approximately 150 MPa and the oxygen content increases from 0.1% to 8%. Surprisingly, the films with a higher oxygen content exhibit lower loss, but care must be taken when depositing at room temperature to avoid nonuniform oxygen incorporation, which presents as a radially dependent resistivity and becomes a radially dependent surface inductance in the superconductor.

Halotolerant microbial consortia able to degrade highly recalcitrant plant biomass substrate.

PubMed

Cortes-Tolalpa, Larisa; Norder, Justin; van Elsas, Jan Dirk; Falcao Salles, Joana

2018-03-01

The microbial degradation of plant-derived compounds under salinity stress remains largely underexplored. The pretreatment of lignocellulose material, which is often needed to improve the production of lignocellulose monomers, leads to high salt levels, generating a saline environment that raises technical considerations that influence subsequent downstream processes. Here, we constructed halotolerant lignocellulose degrading microbial consortia by enriching a salt marsh soil microbiome on a recalcitrant carbon and energy source, i.e., wheat straw. The consortia were obtained after six cycles of growth on fresh substrate (adaptation phase), which was followed by four cycles on pre-digested (highly-recalcitrant) substrate (stabilization phase). The data indicated that typical salt-tolerant bacteria made up a large part of the selected consortia. These were "trained" to progressively perform better on fresh substrate, but a shift was observed when highly recalcitrant substrate was used. The most dominant bacteria in the consortia were Joostella marina, Flavobacterium beibuense, Algoriphagus ratkowskyi, Pseudomonas putida, and Halomonas meridiana. Interestingly, fungi were sparsely present and negatively affected by the change in the substrate composition. Sarocladium strictum was the single fungal strain recovered at the end of the adaptation phase, whereas it was deselected by the presence of recalcitrant substrate. Consortia selected in the latter substrate presented higher cellulose and lignin degradation than consortia selected on fresh substrate, indicating a specialization in transforming the recalcitrant regions of the substrate. Moreover, our results indicate that bacteria have a prime role in the degradation of recalcitrant lignocellulose under saline conditions, as compared to fungi. The final consortia constitute an interesting source of lignocellulolytic haloenzymes that can be used to increase the efficiency of the degradation process, while decreasing the associated costs.

Method of processing a substrate

DOEpatents

Babayan, Steven E [Huntington Beach, CA; Hicks, Robert F [Los Angeles, CA

2008-02-12

The invention is embodied in a plasma flow device or reactor having a housing that contains conductive electrodes with openings to allow gas to flow through or around them, where one or more of the electrodes are powered by an RF source and one or more are grounded, and a substrate or work piece is placed in the gas flow downstream of the electrodes, such that said substrate or work piece is substantially uniformly contacted across a large surface area with the reactive gases emanating therefrom. The invention is also embodied in a plasma flow device or reactor having a housing that contains conductive electrodes with openings to allow gas to flow through or around them, where one or more of the electrodes are powered by an RF source and one or more are grounded, and one of the grounded electrodes contains a means of mixing in other chemical precursors to combine with the plasma stream, and a substrate or work piece placed in the gas flow downstream of the electrodes, such that said substrate or work piece is contacted by the reactive gases emanating therefrom. In one embodiment, the plasma flow device removes organic materials from a substrate or work piece, and is a stripping or cleaning device. In another embodiment, the plasma flow device kills biological microorganisms on a substrate or work piece, and is a sterilization device. In another embodiment, the plasma flow device activates the surface of a substrate or work piece, and is a surface activation device. In another embodiment, the plasma flow device etches materials from a substrate or work piece, and is a plasma etcher. In another embodiment, the plasma flow device deposits thin films onto a substrate or work piece, and is a plasma-enhanced chemical vapor deposition device or reactor.

Component characterization and predictive modeling for green roof substrates optimized to adsorb P and improve runoff quality: A review.

PubMed

Jennett, Tyson S; Zheng, Youbin

2018-06-01

This review is a synthesis of the current knowledge regarding the effects of green roof substrate components and their retentive capacity for nutrients, particularly phosphorus (P). Substrates may behave as either sources or sinks of P depending on the components they are formulated from, and to date, the total P-adsorbing capacity of a substrate has not been quantified as the sum of the contributions of its components. Few direct links have been established among substrate components and their physicochemical characteristics that would affect P-retention. A survey of recent literature presented herein highlights the trends within individual component selection (clays and clay-like material, organics, conventional soil and sands, lightweight inorganics, and industrial wastes and synthetics) for those most common during substrate formulation internationally. Component selection will vary with respect to ease of sourcing component materials, cost of components, nutrient-retention capacity, and environmental sustainability. However, the number of distinct components considered for inclusion in green roof substrates continues to expand, as the desires of growers, material suppliers, researchers and industry stakeholders are incorporated into decision-making. Furthermore, current attempts to characterize the most often used substrate components are also presented whereby runoff quality is correlated to entire substrate performance. With the use of well-described characterization (constant capacitance model) and modeling techniques (the soil assemblage model), it is proposed that substrates optimized for P adsorption may be developed through careful selection of components with prior knowledge of their chemical properties, that may increase retention of P in plant-available forms, thereby reducing green roof fertilizer requirements and P losses in roof runoff. Copyright © 2017 Elsevier Ltd. All rights reserved.

Automated Categorization Scheme for Digital Libraries in Distance Learning: A Pattern Recognition Approach

ERIC Educational Resources Information Center

Gunal, Serkan

2008-01-01

Digital libraries play a crucial role in distance learning. Nowadays, they are one of the fundamental information sources for the students enrolled in this learning system. These libraries contain huge amount of instructional data (text, audio and video) offered by the distance learning program. Organization of the digital libraries is…

Leadership in Distance Education: Qualities and Qualifications Sought by Higher Education Institutions

ERIC Educational Resources Information Center

Nworie, John; Haughton, Noela; Oprandi, Stephanie

2012-01-01

This article presents the results of an investigation into the qualities and qualifications sought in distance education leaders by institutions of higher education in the United States. The researchers examined 191 distance education leadership position announcements posted by online sources between 1997 and 2010. Content analysis of these…

Sources of Support for Women Taking Professional Programs by Distance Education

ERIC Educational Resources Information Center

Cragg, C. E. (Betty); Andrusyszyn, Mary-Anne; Fraser, Joy

2005-01-01

Women with multiple roles face many challenges when taking distance education courses in professional programs to achieve credentials or maintain competence. Among these challenges is finding the supports necessary for success as a distance student. As part of a larger study on advantages and stressors identified by such women in distance…

Growth Rate and Relocation Movements of Common Nighthawk (Chordeiles minor) Nestlings in Relation to Age

USGS Publications Warehouse

Kramer, Gunnar R.; Chalfoun, Anna D.

2012-01-01

Relocation by dependent young is a survival strategy that occurs among a wide range of taxa. The Common Nighthawk (Chordeiles minor) lays its eggs on bare substrate and, once hatched, nestlings may relocate to new sites daily. We located and monitored eight Common Nighthawk nests in Grand Teton National Park, Wyoming, quantified inter-use-site distances in relation to nestling age, and calculated a nestling growth rate curve. Common Nighthawk nestlings grow in a nearly linear fashion. Nestlings moved up to 48 m in a single day and larger, older nestlings tended to move greater distances between daily use-sites.

Method and system for evaluating integrity of adherence of a conductor bond to a mating surface of a substrate

DOEpatents

Telschow, K.L.; Siu, B.K.

1996-07-09

A method of evaluating integrity of adherence of a conductor bond to a substrate includes: (a) impinging a plurality of light sources onto a substrate; (b) detecting optical reflective signatures emanating from the substrate from the impinged light; (c) determining location of a selected conductor bond on the substrate from the detected reflective signatures; (d) determining a target site on the selected conductor bond from the detected reflective signatures; (e) optically imparting an elastic wave at the target site through the selected conductor bond and into the substrate; (f) optically detecting an elastic wave signature emanating from the substrate resulting from the optically imparting step; and (g) determining integrity of adherence of the selected conductor bond to the substrate from the detected elastic wave signature emanating from the substrate. A system is disclosed which is capable of conducting the method. 13 figs.

Method and system for evaluating integrity of adherence of a conductor bond to a mating surface of a substrate

DOEpatents

Telschow, Kenneth L.; Siu, Bernard K.

1996-01-01

A method of evaluating integrity of adherence of a conductor bond to a substrate includes: a) impinging a plurality of light sources onto a substrate; b) detecting optical reflective signatures emanating from the substrate from the impinged light; c) determining location of a selected conductor bond on the substrate from the detected reflective signatures; d) determining a target site on the selected conductor bond from the detected reflective signatures; e) optically imparting an elastic wave at the target site through the selected conductor bond and into the substrate; f) optically detecting an elastic wave signature emanating from the substrate resulting from the optically imparting step; and g) determining integrity of adherence of the selected conductor bond to the substrate from the detected elastic wave signature emanating from the substrate. A system is disclosed which is capable of conducting the method.

An empirical method for estimating travel times for wet volcanic mass flows

USGS Publications Warehouse

Pierson, Thomas C.

1998-01-01

Travel times for wet volcanic mass flows (debris avalanches and lahars) can be forecast as a function of distance from source when the approximate flow rate (peak discharge near the source) can be estimated beforehand. The near-source flow rate is primarily a function of initial flow volume, which should be possible to estimate to an order of magnitude on the basis of geologic, geomorphic, and hydrologic factors at a particular volcano. Least-squares best fits to plots of flow-front travel time as a function of distance from source provide predictive second-degree polynomial equations with high coefficients of determination for four broad size classes of flow based on near-source flow rate: extremely large flows (>1 000 000 m3/s), very large flows (10 000–1 000 000 m3/s), large flows (1000–10 000 m3/s), and moderate flows (100–1000 m3/s). A strong nonlinear correlation that exists between initial total flow volume and flow rate for "instantaneously" generated debris flows can be used to estimate near-source flow rates in advance. Differences in geomorphic controlling factors among different flows in the data sets have relatively little effect on the strong nonlinear correlations between travel time and distance from source. Differences in flow type may be important, especially for extremely large flows, but this could not be evaluated here. At a given distance away from a volcano, travel times can vary by approximately an order of magnitude depending on flow rate. The method can provide emergency-management officials a means for estimating time windows for evacuation of communities located in hazard zones downstream from potentially hazardous volcanoes.

Improved process for epitaxial deposition of silicon on prediffused substrates

NASA Technical Reports Server (NTRS)

Clarke, M. G.; Halsor, J. L.; Word, J. C.

1968-01-01

Process for fabricating integrated circuits uniformly deposits silicon epitaxially on prediffused substrates without affecting the sublayer diffusion pattern. Two silicon deposits from different sources, and deposited at different temperatures, protect the sublayer pattern from the silicon tetrachloride reaction.

A novel assay for monoacylglycerol hydrolysis suitable for high-throughput screening.

PubMed

Brengdahl, Johan; Fowler, Christopher J

2006-12-01

A simple assay for monoacylglycerol hydrolysis suitable for high-throughput screening is described. The assay uses [(3)H]2-oleoylglycerol as substrate, with the tritium label in the glycerol part of the molecule and the use of phenyl sepharose gel to separate the hydrolyzed product ([(3)H]glycerol) from substrate. Using cytosolic fractions derived from rat cerebella as a source of hydrolytic activity, the assay gives the appropriate pH profile and sensitivity to inhibition with compounds known to inhibit hydrolysis of this substrate. The assay could also be adapted to a 96-well plate format, using C6 cells as the source of hydrolytic activity. Thus the assay is simple and appropriate for high-throughput screening of inhibitors of monoacylglycerol hydrolysis.

Fabrication of Thin Electrolytes for Second-Generation Solid Oxide Fuel Cells

DTIC Science & Technology

1999-05-05

stabilized zirconia but are equally applicable to components, have been developed. Halogen com- other oxide electrolytes. pounds such as ZrCl4 and YC13...substrates. They used ZrCl4 and an oxygen source reactant. EVD is a two-step YC13 vapor mixtures as the metal compound sources process. The first step...thin zirconia layers on ited film. In this step oxygen ions formed on the porous alumina substrates. ZrCl4 and YC13 vapor water vapor side of the

Thin-film spectroscopic sensor

DOEpatents

Burgess, Jr., Lloyd W.; Goldman, Don S.

1992-01-01

There is disclosed an integrated spectrometer for chemical analysis by evanescent electromagnetic radiation absorption in a reaction volume. The spectrometer comprises a noninteractive waveguide, a substrate, an entrance grating and an exit grating, an electromagnetic radiation source, and an electromagnetic radiation sensing device. There is further disclosed a chemical sensor to determine the pressure and concentration of a chemical species in a mixture comprising an interactive waveguide, a substrate, an entrance grating and an exit grating, an electromagnetic radiation source, and an electromagnetic radiation sensing device.

A New Distance Metric in Ground Motion Prediction Equations Based On Array Back-Projections

NASA Astrophysics Data System (ADS)

Feng, T.; Meng, L.

2017-12-01

Traditional Ground Motion Prediction Equations (GMPEs) measure the distances either relative to the epicenter (Repi) or the hypocenter (Rhyp) assuming point-sources, or relative to the closest point of the fault rupture (Rrup) or its surface projection (Rjb) to account for finite earthquake dimensions. However, it has long been proven that for large megathrust earthquakes (M>8), the over-simplification of the earthquake source characteristics in these distance metrics result in significant bias and uncertainty of the ground motion predictions. Recent advances in earthquake source imaging of major subduction earthquakes highlight the frequency-dependent and depth-varying seismic radiations at the plate interfaces. Low-frequency energy mainly emanated from the shallower portion of the megathrusts while dominant high-frequency energy often radiates from the deeper portion of the megathrust. In the 2011 Tohoku-Oki earthquake, all these distance metrics produce severe biases, underestimating the ground accelerations at short distances (<100km) and overestimating them at long distances (>100km). This phenomenon motivates an alternative distance metric based on the array back-projection (BP) technique that effectively captures regions releasing high-frequency energy. Herein, we define Rbp as the distance between nearest BP radiators and the station sites. We studied five large earthquakes in Japan, and found that Rbp outperforms conventional distance metrics in predicting the Psa (Pseudo Spectral Acceleration) in the high-frequency band (0.5-4 Hz). And at low frequencies (0.1-0.5Hz), we find that Rhyp produces better fits to the Psa spectrum. Thus, we propose to combine Rhyp and Rbp in low-frequency (0.1-0.5Hz) and high-frequency (0.5-4 Hz) range to improve the GMPEs. We consider that Rbp reflects the high-frequency characters of the rupture that are complementary to conventional GMPE distance metrics and a more suitable ground motion predictors in many cases. Based on our new distance metric, we expect to build an automatic system predicting ground motion immediately after the large earthquake (M>7) happens, an alternative to the shakemap.

Evaluation of the Acoustic Measurement Capability of the NASA Langley V/STOL Wind Tunnel Open Test Section with Acoustically Absorbent Ceiling and Floor Treatments

NASA Technical Reports Server (NTRS)

Theobald, M. A.

1978-01-01

The single source location used for helicopter model studies was utilized in a study to determine the distances and directions upstream of the model accurate at which measurements of the direct acoustic field could be obtained. The method used was to measure the decrease of sound pressure levels with distance from a noise source and thereby determine the Hall radius as a function of frequency and direction. Test arrangements and procedures are described. Graphs show the normalized sound pressure level versus distance curves for the glass fiber floor treatment and for the foam floor treatment.

Comparison of methods to estimate water access: a pilot study of a GPS-based approach in low resource settings.

PubMed

Pearson, Amber L

2016-09-20

Most water access studies involve self-reported measures such as time spent or simple spatial measures such as Euclidean distance from home to source. GPS-based measures of access are often considered actual access and have shown little correlation with self-reported measures. One main obstacle to widespread use of GPS-based measurement of access to water has been technological limitations (e.g., battery life). As such, GPS-based measures have been limited by time and in sample size. The aim of this pilot study was to develop and test a novel GPS unit, (≤4-week battery life, waterproof) to measure access to water. The GPS-based method was pilot-tested to estimate number of trips per day, time spent and distance traveled to source for all water collected over a 3-day period in five households in south-western Uganda. This method was then compared to self-reported measures and commonly used spatial measures of access for the same households. Time spent collecting water was significantly overestimated using a self-reported measure, compared to GPS-based (p < 0.05). In contrast, both the GIS Euclidean distances to nearest and actual primary source significantly underestimated distances traveled, compared to the GPS-based measurement of actual travel paths to water source (p < 0.05). Households did not consistently collect water from the source nearest their home. Comparisons between the GPS-based measure and self-reported meters traveled were not made, as respondents did not feel that they could accurately estimate distance. However, there was complete agreement between self-reported primary source and GPS-based. Reliance on cross-sectional self-reported or simple GIS measures leads to misclassification in water access measurement. This new method offers reductions in such errors and may aid in understanding dynamic measures of access to water for health studies.

Approaches to the study of neural coding of sound source location and sound envelope in real environments

PubMed Central

Kuwada, Shigeyuki; Bishop, Brian; Kim, Duck O.

2012-01-01

The major functions of the auditory system are recognition (what is the sound) and localization (where is the sound). Although each of these has received considerable attention, rarely are they studied in combination. Furthermore, the stimuli used in the bulk of studies did not represent sound location in real environments and ignored the effects of reverberation. Another ignored dimension is the distance of a sound source. Finally, there is a scarcity of studies conducted in unanesthetized animals. We illustrate a set of efficient methods that overcome these shortcomings. We use the virtual auditory space method (VAS) to efficiently present sounds at different azimuths, different distances and in different environments. Additionally, this method allows for efficient switching between binaural and monaural stimulation and alteration of acoustic cues singly or in combination to elucidate neural mechanisms underlying localization and recognition. Such procedures cannot be performed with real sound field stimulation. Our research is designed to address the following questions: Are IC neurons specialized to process what and where auditory information? How does reverberation and distance of the sound source affect this processing? How do IC neurons represent sound source distance? Are neural mechanisms underlying envelope processing binaural or monaural? PMID:22754505

Carbohydrate binding sites in a pancreatic alpha-amylase-substrate complex, derived from X-ray structure analysis at 2.1 A resolution.

PubMed Central

Qian, M.; Haser, R.; Payan, F.

1995-01-01

The X-ray structure analysis of a crystal of pig pancreatic alpha-amylase (PPA, EC 3.2.1.1.) that was soaked with the substrate maltopentaose showed electron density corresponding to two independent carbohydrate recognition sites on the surface of the molecule. Both binding sites are distinct from the active site described in detail in our previous high-resolution study of a complex between PPA and a carbohydrate inhibitor (Qian M, Buisson G, Duée E, Haser H, Payan F, 1994, Biochemistry 33:6284-6294). One of the binding sites previously identified in a 5-A-resolution electron density map, lies at a distance of 20 A from the active site cleft and can accommodate two glucose units. The second affinity site for sugar units is located close to the calcium binding site. The crystal structure of the maltopentaose complex was refined at 2.1 A resolution, to an R-factor of 17.5%, with an RMS deviation in bond distances of 0.007 A. The model includes all 496 residues of the enzyme, 1 calcium ion, 1 chloride ion, 425 water molecules, and 3 bound sugar rings. The binding sites are characterized and described in detail. The present complex structure provides the evidence of an increased stability of the structure upon interaction with the substrate and allows identification of an N-terminal pyrrolidonecarboxylic acid in PPA. PMID:7613472

Determination of the optimum-size californium-252 neutron source for borehole capture gamma-ray analysis

USGS Publications Warehouse

Senftle, F.E.; Macy, R.J.; Mikesell, J.L.

1979-01-01

The fast- and thermal-neutron fluence rates from a 3.7 ??g 252Cf neutron source in a simulated borehole have been measured as a function of the source-to-detector distance using air, water, coal, iron ore-concrete mix, and dry sand as borehole media. Gamma-ray intensity measurements were made for specific spectral lines at low and high energies for the same range of source-to-detector distances in the iron ore-concrete mix and in coal. Integral gamma-ray counts across the entire spectrum were also made at each source-to-detector distance. From these data, the specific neutron-damage rate, and the critical count-rate criteria, we show that in an iron ore-concrete mix (low hydrogen concentration), 252Cf neutron sources of 2-40 ??g are suitable. The source size required for optimum gamma-ray sensitivity depends on the energy of the gamma ray being measured. In a hydrogeneous medium such as coal, similar measurements were made. The results show that sources from 2 to 20 ??g are suitable to obtain the highest gamma-ray sensitivity, again depending on the energy of the gamma ray being measured. In a hydrogeneous medium, significant improvement in sensitivity can be achieved by using faster electronics; in iron ore, it cannot. ?? 1979 North-Holland Publishing Co.

An Endohyphal Bacterium (Chitinophaga, Bacteroidetes) Alters Carbon Source Use by Fusarium keratoplasticum (F. solani Species Complex, Nectriaceae)

PubMed Central

Shaffer, Justin P.; U'Ren, Jana M.; Gallery, Rachel E.; Baltrus, David A.; Arnold, A. Elizabeth

2017-01-01

Bacterial endosymbionts occur in diverse fungi, including members of many lineages of Ascomycota that inhabit living plants. These endosymbiotic bacteria (endohyphal bacteria, EHB) often can be removed from living fungi by antibiotic treatment, providing an opportunity to assess their effects on functional traits of their fungal hosts. We examined the effects of an endohyphal bacterium (Chitinophaga sp., Bacteroidetes) on substrate use by its host, a seed-associated strain of the fungus Fusarium keratoplasticum, by comparing growth between naturally infected and cured fungal strains across 95 carbon sources with a Biolog® phenotypic microarray. Across the majority of substrates (62%), the strain harboring the bacterium significantly outperformed the cured strain as measured by respiration and hyphal density. These substrates included many that are important for plant- and seed-fungus interactions, such as D-trehalose, myo-inositol, and sucrose, highlighting the potential influence of EHB on the breadth and efficiency of substrate use by an important Fusarium species. Cases in which the cured strain outperformed the strain harboring the bacterium were observed in only 5% of substrates. We propose that additive or synergistic substrate use by the fungus-bacterium pair enhances fungal growth in this association. More generally, alteration of the breadth or efficiency of substrate use by dispensable EHB may change fungal niches in short timeframes, potentially shaping fungal ecology and the outcomes of fungal-host interactions. PMID:28382021

Spatial Variations in Vitreous Oxygen Consumption

PubMed Central

Murali, Karthik; Kang, Dongyang; Nazari, Hossein; Scianmarello, Nicholas; Cadenas, Enrique; Tai, Yu-Chong; Kashani, Amir; Humayun, Mark

2016-01-01

We investigated the spatial variation of vitreous oxygen consumption in enucleated porcine eyes. A custom made oxygen source was fabricated that could be localized to either the mid or posterior vitreous cavity and steady state vitreous oxygen tension was measured as a function of distance from the source using a commercially available probe. The reaction rate constant of ascorbate oxidation was estimated ex vivo by measuring the change in oxygen tension over time using vitreous harvested from porcine eyes. Vitreous ascorbate from mid and posterior vitreous was measured spectrophotometrically. When the oxygen source was placed in either the mid-vitreous (N = 6) or the posterior vitreous (N = 6), we measured a statistically significant decrease in vitreous oxygen tension as a function of distance from the oxygen source when compared to control experiments without an oxygen source; (p<0.005 for mid-vitreous and p<0.018 for posterior vitreous at all distances). The mid-vitreous oxygen tension change was significantly different from the posterior vitreous oxygen tension change at 2 and 3mm distances from the respective oxygen source (p<0.001). We also found a statistically significant lower concentration of ascorbate in the mid-vitreous as compared to posterior vitreous (p = 0.02). We determined the reaction rate constant, k = 1.61 M-1s-1 ± 0.708 M-1s-1 (SE), of the oxidation of ascorbate which was modeled following a second order rate equation. Our data demonstrates that vitreous oxygen consumption is higher in the posterior vitreous compared to the mid-vitreous. We also show spatial variations in vitreous ascorbate concentration. PMID:26930281

Spatial Variations in Vitreous Oxygen Consumption.

PubMed

Murali, Karthik; Kang, Dongyang; Nazari, Hossein; Scianmarello, Nicholas; Cadenas, Enrique; Tai, Yu-Chong; Kashani, Amir; Humayun, Mark

2016-01-01

We investigated the spatial variation of vitreous oxygen consumption in enucleated porcine eyes. A custom made oxygen source was fabricated that could be localized to either the mid or posterior vitreous cavity and steady state vitreous oxygen tension was measured as a function of distance from the source using a commercially available probe. The reaction rate constant of ascorbate oxidation was estimated ex vivo by measuring the change in oxygen tension over time using vitreous harvested from porcine eyes. Vitreous ascorbate from mid and posterior vitreous was measured spectrophotometrically. When the oxygen source was placed in either the mid-vitreous (N = 6) or the posterior vitreous (N = 6), we measured a statistically significant decrease in vitreous oxygen tension as a function of distance from the oxygen source when compared to control experiments without an oxygen source; (p<0.005 for mid-vitreous and p<0.018 for posterior vitreous at all distances). The mid-vitreous oxygen tension change was significantly different from the posterior vitreous oxygen tension change at 2 and 3mm distances from the respective oxygen source (p<0.001). We also found a statistically significant lower concentration of ascorbate in the mid-vitreous as compared to posterior vitreous (p = 0.02). We determined the reaction rate constant, k = 1.61 M(-1) s(-1) ± 0.708 M(-1) s(-1) (SE), of the oxidation of ascorbate which was modeled following a second order rate equation. Our data demonstrates that vitreous oxygen consumption is higher in the posterior vitreous compared to the mid-vitreous. We also show spatial variations in vitreous ascorbate concentration.

Investigation of high-speed Si photodetectors in standard CMOS technology

NASA Astrophysics Data System (ADS)

Wang, Huaqiang; Guo, Xia

2018-05-01

In this paper, the frequency response characteristics of the photodetector(PD) were studied considering intrinsic and extrinsic effects. Then we designed the interdigitated p-i-n PD on Silicon-on-Insulator (SOI) and epitaxial (EPI) substrates with photosensitive area of 30-μm diameter, fabricated by CMOS process. The 2-μm finger-spacing devices exhibited a 205 MHz bandwidth at a reverse bias of 3 V processed on 2-μm SOI substrates. EPI devices with 1 μm finger spacing exhibited a 131 MHz bandwidth under -3 V. Responsivity of 0.051 A/W and 0.21 A/W were measured at 850 nm on SOI and EPI substrates, respectively. Compared with the bulk silicon PD, the bandwidth is greatly improved. The PD gains the high cost performance ratio, which can be widely used in short distance communication such as visible light communication and free space optical communication.

Molecular dynamics studies of interfacial water at the alumina surface.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Argyris, Dr. Dimitrios; Ho, Thomas; Cole, David

2011-01-01

Interfacial water properties at the alumina surface were investigated via all-atom equilibrium molecular dynamics simulations at ambient temperature. Al-terminated and OH-terminated alumina surfaces were considered to assess the structural and dynamic behavior of the first few hydration layers in contact with the substrates. Density profiles suggest water layering up to {approx}10 {angstrom} from the solid substrate. Planar density distribution data indicate that water molecules in the first interfacial layer are organized in well-defined patterns dictated by the atomic terminations of the alumina surface. Interfacial water exhibits preferential orientation and delayed dynamics compared to bulk water. Water exhibits bulk-like behavior atmore » distances greater than {approx}10 {angstrom} from the substrate. The formation of an extended hydrogen bond network within the first few hydration layers illustrates the significance of water?water interactions on the structural properties at the interface.« less

Energy harvesting devices for harvesting energy from terahertz electromagnetic radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novack, Steven D.; Kotter, Dale K.; Pinhero, Patrick J.

2012-10-09

Methods, devices and systems for harvesting energy from electromagnetic radiation are provided including harvesting energy from electromagnetic radiation. In one embodiment, a device includes a substrate and one or more resonance elements disposed in or on the substrate. The resonance elements are configured to have a resonant frequency, for example, in at least one of the infrared, near-infrared and visible light spectra. A layer of conductive material may be disposed over a portion of the substrate to form a ground plane. An optical resonance gap or stand-off layer may be formed between the resonance elements and the ground plane. Themore » optical resonance gap extends a distance between the resonance elements and the layer of conductive material approximately one-quarter wavelength of a wavelength of the at least one resonance element's resonant frequency. At least one energy transfer element may be associated with the at least one resonance element.« less

Energy harvesting devices for harvesting energy from terahertz electromagnetic radiation

DOEpatents

Novack, Steven D.; Kotter, Dale K.; Pinhero, Patrick J.

2012-10-09

Methods, devices and systems for harvesting energy from electromagnetic radiation are provided including harvesting energy from electromagnetic radiation. In one embodiment, a device includes a substrate and one or more resonance elements disposed in or on the substrate. The resonance elements are configured to have a resonant frequency, for example, in at least one of the infrared, near-infrared and visible light spectra. A layer of conductive material may be disposed over a portion of the substrate to form a ground plane. An optical resonance gap or stand-off layer may be formed between the resonance elements and the ground plane. The optical resonance gap extends a distance between the resonance elements and the layer of conductive material approximately one-quarter wavelength of a wavelength of the at least one resonance element's resonant frequency. At least one energy transfer element may be associated with the at least one resonance element.

Structures, systems and methods for harvesting energy from electromagnetic radiation

DOEpatents

Novack, Steven D [Idaho Falls, ID; Kotter, Dale K [Shelley, ID; Pinhero, Patrick J [Columbia, MO

2011-12-06

Methods, devices and systems for harvesting energy from electromagnetic radiation are provided including harvesting energy from electromagnetic radiation. In one embodiment, a device includes a substrate and one or more resonance elements disposed in or on the substrate. The resonance elements are configured to have a resonant frequency, for example, in at least one of the infrared, near-infrared and visible light spectra. A layer of conductive material may be disposed over a portion of the substrate to form a ground plane. An optical resonance gap or stand-off layer may be formed between the resonance elements and the ground plane. The optical resonance gap extends a distance between the resonance elements and the layer of conductive material approximately one-quarter wavelength of a wavelength of the at least one resonance element's resonant frequency. At least one energy transfer element may be associated with the at least one resonance element.

Resonant surface acoustic wave chemical detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brocato, Robert W.; Brocato, Terisse; Stotts, Larry G.

Apparatus for chemical detection includes a pair of interdigitated transducers (IDTs) formed on a piezoelectric substrate. The apparatus includes a layer of adsorptive material deposited on a surface of the piezoelectric substrate between the IDTs, where each IDT is conformed, and is dimensioned in relation to an operating frequency and an acoustic velocity of the piezoelectric substrate, so as to function as a single-phase uni-directional transducer (SPUDT) at the operating frequency. Additionally, the apparatus includes the pair of IDTs is spaced apart along a propagation axis and mutually aligned relative to said propagation axis so as to define an acousticmore » cavity that is resonant to surface acoustic waves (SAWs) at the operating frequency, where a distance between each IDT of the pair of IDTs ranges from 100 wavelength of the operating frequency to 400 wavelength of the operating frequency.« less

KINEMATIC DISTANCES OF GALACTIC PLANETARY NEBULAE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, A. Y.; Tian, W. W.; Zhu, H.

2016-03-15

We construct H i absorption spectra for 18 planetary nebulae (PNs) and their background sources using data from the International Galactic Plane Survey. We estimate the kinematic distances of these PNs, among which 15 objects’ kinematic distances are obtained for the first time. The distance uncertainties of 13 PNs range from 10% to 50%, which is a significant improvement with uncertainties of a factor of two or three smaller than most previous distance measurements. We confirm that PN G030.2−00.1 is not a PN because of its large distance found here.

The characterization of photographic materials as substrates for surface enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Vaughan, J.; Hortin, N.; Christie, S.; Kvasnik, F.; Scully, P. J.

2005-06-01

In this study, five types of photographic materials were obtained from commercial sources and characterized for use as substrates for surface enhanced Raman spectroscopy. The substrates are photographic emulsions coated on glass or paper support. The emulsions were developed to maximize the amount of metallic silver aggregated into clusters. The test analyte, Cresyl Violet, was deposited directly onto the substrate surface. The permeable nature of the supporting gelatin matrix enables the interaction between the target analyte and the solid silver clusters. The surface enhanced Raman spectra of a 2.75 × 10-7 M concentration of Cresyl Violet in ethanol were obtained using these photographic substrates. The Raman and resonant Raman enhancement of Cresyl Violet varies from substrate to substrate, as does the ratio of Raman to resonant Raman peak heights.

Microbial synthesis of rhamnolipids by Pseudomonas aeruginosa (ATCC 10145) on waste frying oil as low cost carbon source.

PubMed

Wadekar, S D; Kale, S B; Lali, A M; Bhowmick, D N; Pratap, A P

2012-01-01

Vegetable edible oils and fats are mainly used for frying purposes in households and the food industry. The oil undergoes degradation during frying and hence has to be replaced from time to time. Rhamnolipids are produced by microbial cultivation using refined vegetable oils as a carbon source and Pseudomonas aeruginosa (ATCC 10145). The raw material cost accounts for 10-30% of the overall cost of biosurfactant production and can be reduced by using low-cost substrates. In this research, attention was focused on the preparation of rhamnolipids, which are biosurfactants, using potential frying edible oils as a carbon source via a microbial fermentation technique. The use of low-cost substrates as a carbon source was emphasized to tilt the cost of production for rhamnolipids. The yield was 2.8 g/L and 7.5 g/L from waste frying oil before and after activated earth treatment, respectively. The crude product contained mainly dirhamnolipids, confirmed by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), liquid chromatography-mass spectroscopy (LC-MS), and (1)H-nuclear magnetic resonance (NMR). Hence, the treatment can be used to convert waste frying oil as a low-cost substrate into a cost-effective carbon source.

Microscopic Sources of Paramagnetic Noise on α-Al2O3 Substrates for Superconducting Qubits

NASA Astrophysics Data System (ADS)

Dubois, Jonathan; Lee, Donghwa; Lordi, Vince

2014-03-01

Superconducting qubits (SQs) represent a promising route to achieving a scalable quantum computer. However, the coupling between electro-dynamic qubits and (as yet largely unidentified) ambient parasitic noise sources has so far limited the functionality of current SQs by limiting coherence times of the quantum states below a practical threshold for measurement and manipulation. Further improvement can be enabled by a detailed understanding of the various noise sources afflicting SQs. In this work, first principles density functional theory (DFT) calculations are employed to identify the microscopic origins of magnetic noise sources in SQs on an α-Al2O3 substrate. The results indicate that it is unlikely that the existence of intrinsic point defects and defect complexes in the substrate are responsible for low frequency noise in these systems. Rather, a comprehensive analysis of extrinsic defects shows that surface aluminum ions interacting with ambient molecules will form a bath of magnetic moments that can couple to the SQ paramagnetically. The microscopic origin of this magnetic noise source is discussed and strategies for ameliorating the effects of these magnetic defects are proposed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Umbra/penumbra detector

DOEpatents

Carner, Jr., Don C.

1988-01-01

A device which monitors the characteristics of an image cast upon a radiation sensitive substrate. This includes a shadow casting object or mask and at least one source of radiation disposed above the object or mask so that the image cast on the substrate can be analyzed.

VizieR Online Data Catalog: ChaMP. I. First X-ray source catalog (Kim+, 2004)

NASA Astrophysics Data System (ADS)

Kim, D.-W.; Cameron, R. A.; Drake, J. J.; Evans, N. R.; Freeman, P.; Gaetz, T. J.; Ghosh, H.; Green, P. J.; Harnden, F. R. Jr; Karovska, M.; Kashyap, V.; Maksym, P. W.; Ratzlaff, P. W.; Schlegel, E. M.; Silverman, J. D.; Tananbaum, H. D.; Vikhlinin, A. A.; Wilkes, B. J.; Grimes, J. P.

2004-01-01

The Chandra Multiwavelength Project (ChaMP) is a wide-area (~14deg2 < survey of serendipitous Chandra X-ray sources, aiming to establish fair statistical samples covering a wide range of characteristics (such as absorbed active galactic nuclei, high-z clusters of galaxies) at flux levels (fX~10-15 to 10-14erg/s/cm2) ) intermediate between the Chandra deep surveys and previous missions. We present the first ChaMP catalog, which consists of 991 near on-axis, bright X-ray sources obtained from the initial sample of 62 observations. The data have been uniformly reduced and analyzed with techniques specifically developed for the ChaMP and then validated by visual examination. To assess source reliability and positional uncertainty, we perform a series of simulations and also use Chandra data to complement the simulation study. The false source detection rate is found to be as good as or better than expected for a given limiting threshold. On the other hand, the chance of missing a real source is rather complex, depending on the source counts, off-axis distance (or PSF), and background rate. The positional error (95% confidence level) is usually less than 1" for a bright source, regardless of its off-axis distance, while it can be as large as 4" for a weak source (~20counts) at a large off-axis distance (Doff-axis>8'). We have also developed new methods to find spatially extended or temporary variable sources, and those sources are listed in the catalog. (5 data files).

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

PubMed Central

Hazut, Ori; Agarwala, Arunava; Subramani, Thangavel; Waichman, Sharon; Yerushalmi, Roie

2013-01-01

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms. In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station. PMID:24326774

Effect of substrate orientation on CdS homoepitaxy by molecular dynamics

DOE PAGES

Almeida, S.; Chavez, J. J.; Zhou, X. W.; ...

2016-02-10

CdS homoepitaxy growth was performed by molecular dynamics using different substrate orientations and structures in order to analyze the CdS crystallinity. As anticipated from thermodynamics of homoepitaxy, highly crystalline films with only point defects were obtained on substrates with rectangular surface geometries, including View the MathML source[112¯] zinc blende (ZB), [101¯0] wurtzite (WZ), [112¯0] WZ, [110][110] ZB, [010][010] ZB, and View the MathML source[1101110] ZB. In contrast, films grown on substrates with hexagonal surface geometries, corresponding to the [0001][0001] WZ and [111][111] ZB growth directions, showed structures with a large number of defects including; anti-sites, vacancies, stacking faults, twinning, andmore » polytypism. WZ and ZB transitions and grain boundaries are identified using a lattice identification algorithm and represented graphically in a structural map. A dislocation analysis was performed to detect, identify, and quantify linear defects within the atomistic data. Systematic simulations using different temperatures, deposition rates, and substrate polarities were perform to analyze the trends of dislocation densities on [0001][0001] WZ direction and showed persistent polytypism. As a result, the polytypism observed in the films grown on the substrates with hexagonal surface geometry is attributed to the similar formation energies of the WZ and ZB phases.« less

Shear Wave Generation and Modeling Ground Motion From a Source Physics Experiment (SPE) Underground Explosion

NASA Astrophysics Data System (ADS)

Pitarka, Arben; Mellors, Robert; Rodgers, Arthur; Vorobiev, Oleg; Ezzedine, Souheil; Matzel, Eric; Ford, Sean; Walter, Bill; Antoun, Tarabay; Wagoner, Jeffery; Pasyanos, Mike; Petersson, Anders; Sjogreen, Bjorn

2014-05-01

We investigate the excitation and propagation of far-field (epicentral distance larger than 20 m) seismic waves by analyzing and modeling ground motion from an underground chemical explosion recorded during the Source Physics Experiment (SPE), Nevada. The far-field recorded ground motion is characterized by complex features, such as large azimuthal variations in P- and S-wave amplitudes, as well as substantial energy on the tangential component of motion. Shear wave energy is also observed on the tangential component of the near-field motion (epicentral distance smaller than 20 m) suggesting that shear waves were generated at or very near the source. These features become more pronounced as the waves propagate away from the source. We address the shear wave generation during the explosion by modeling ground motion waveforms recorded in the frequency range 0.01-20 Hz, at distances of up to 1 km. We used a physics based approach that combines hydrodynamic modeling of the source with anelastic modeling of wave propagation in order to separate the contributions from the source and near-source wave scattering on shear motion generation. We found that wave propagation scattering caused by the near-source geological environment, including surface topography, contributes to enhancement of shear waves generated from the explosion source. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-06NA25946/ NST11-NCNS-TM-EXP-PD15.

Advanced CIGS Photovoltaic Technology: Annual Technical Report--Phase II, 15 November 2002--14 November 2003

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delahoy, A. E.; Chen, L.

2004-05-01

The objective of this subcontract is to develop and integrate the various pieces of new technology that EPV considers enabling for cost-effective production of CIGS modules. EPV has conducted research to help generate a technology base for production of CIGS PV modules using vacuum deposition of CIGS onto glass. This strategy is consistent with the observation that, despite there being several approaches to forming device-quality CIGS, vacuum deposition has maintained the world record for the highest-efficiency CIGS device. A record thin-film solar cell efficiency of 19.2% (with Ni-Al grid and MgF2 ARC) for a 0.41-cm2 device was achieved by NRELmore » in 2003 using vacuum-deposited CIGS. The deposition employed four point sources and detection of the Cu-poor to Cu-rich transition for process control. To extend this type of processing to the realm of large-area substrates, EPV developed vacuum equipment designed for heating and coating 0.43-m2 moving substrates, with a projected further scale up to 0.79 m2. The substrates are typically low-cost, soda-lime glass, and the materials are supplied to the moving substrates using novel linear-source technology developed by EPV. The use of elemental selenium rather than toxic H2Se gas helps make for a safe manufacturing environment. These choices concerning film deposition, substrates, and source materials help to minimize the processing costs of CIGS.« less

A comparison of the relative biological effectiveness of low energy electronic brachytherapy sources in breast tissue: a Monte Carlo study.

PubMed

White, Shane A; Reniers, Brigitte; de Jong, Evelyn E C; Rusch, Thomas; Verhaegen, Frank

2016-01-07

Electronic brachytherapy sources use low energy photons to treat the tumor bed during or after breast-conserving surgery. The relative biological effectiveness of two electronic brachytherapy sources was explored to determine if spectral differences due to source design influenced radiation quality and if radiation quality decreased with distance in the breast. The RBE was calculated through the number of DNA double strand breaks (RBEDSB) using the Monte Carlo damage simulator (MCDS) in combination with other Monte Carlo electron/photon spectrum calculations. 50kVp photons from the Intrabeam (Carl Zeiss Surgical) and Axxent (Xoft) through 40-mm spherical applicators were simulated to account for applicator and tissue attenuation in a variety of breast tissue compositions. 40kVp Axxent photons were also simulated. Secondary electrons (known to be responsible for most DNA damage) spectra at different distance were inputted into MCDS to calculate the RBEDSB. All RBEDSB used a cobalt-60 reference. RBEDSB data was combined with corresponding average photon spectrum energy for the Axxent and applied to model-based average photon energy distributions to produce an RBEDSB map of an accelerated partial breast irradiation (APBI) patient. Both Axxent and Intrabeam 50kVp spectra were shown to have a comparable RBEDSB of between 1.4 and 1.6 at all distances in spite of progressive beam hardening. The Axxent 40kVp also demonstrated a similar RBEDSB at distances. Most RBEDSB variability was dependent on the tissue type as was seen in rib (RBEDSB  ≈  1.4), gland (≈1.55), adipose (≈1.59), skin (≈1.52) and lung (≈1.50). RBEDSB variability between both sources was within 2%. A correlation was shown between RBEDSB and average photon energy and used to produce an RBEDSB map of a dose distribution in an APBI patient dataset. Radiation quality is very similar between electronic brachytherapy sources studied. No significant reductions in RBEDSB were observed with increasing distance from the source.

Use of Plackett-Burman design for rapid screening of nitrogen and carbon sources for the production of lipase in solid state fermentation by Yarrowia lipolytica from mustard oil cake (Brassica napus).

PubMed

Imandi, Sarat Babu; Karanam, Sita Kumari; Garapati, Hanumantha Rao

2013-01-01

Mustard oil cake (Brassica napus), the residue obtained after extraction of mustard oil from mustard oil seeds, was investigated for the production of lipase under solid state fermentation (SSF) using the marine yeast Yarrowia lipolytica NCIM 3589. Process parameters such as incubation time, biomass concentration, initial moisture content, carbon source concentration and nitrogen source concentration of the medium were optimized. Screening of ten nitrogen and five carbon sources has been accomplished with the help of Plackett-Burman design. The highest lipase activity of 57.89 units per gram of dry fermented substrate (U/gds) was observed with the substrate of mustard oil cake in four days of fermentation.

Virtual Proctoring in Distance Education: An Open-Source Solution

ERIC Educational Resources Information Center

Rose, Chris

2009-01-01

Students will cheat during exams, that is nothing new, but now that the Higher Education Act requires the proctoring of exams, distance education institutions now find that both they and their students have a major problem. Exams have to be proctored, but requiring distance education students to search out a reliable proctor and travel to a…

Study of Cost of Distance Education Institutes with Different Size Classes in India.

ERIC Educational Resources Information Center

Datt, Ruddar

A study of the cost of distance education institutes in India with different size classes involved nine institutions. The sample included 47 percent of total enrollment in distance education institutions in India. The study was restricted to recurring costs and examined the shares of different components of costs and the sources of funding. It…

Monte Carlo modelling of large scale NORM sources using MCNP.

PubMed

Wallace, J D

2013-12-01

The representative Monte Carlo modelling of large scale planar sources (for comparison to external environmental radiation fields) is undertaken using substantial diameter and thin profile planar cylindrical sources. The relative impact of source extent, soil thickness and sky-shine are investigated to guide decisions relating to representative geometries. In addition, the impact of source to detector distance on the nature of the detector response, for a range of source sizes, has been investigated. These investigations, using an MCNP based model, indicate a soil cylinder of greater than 20 m diameter and of no less than 50 cm depth/height, combined with a 20 m deep sky section above the soil cylinder, are needed to representatively model the semi-infinite plane of uniformly distributed NORM sources. Initial investigation of the effect of detector placement indicate that smaller source sizes may be used to achieve a representative response at shorter source to detector distances. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Test method for telescopes using a point source at a finite distance

NASA Technical Reports Server (NTRS)

Griner, D. B.; Zissa, D. E.; Korsch, D.

1985-01-01

A test method for telescopes that makes use of a focused ring formed by an annular aperture when using a point source at a finite distance is evaluated theoretically and experimentally. The results show that the concept can be applied to near-normal, as well as grazing incidence. It is particularly suited for X-ray telescopes because of their intrinsically narrow annular apertures, and because of the largely reduced diffraction effects.

Time resolved small angle X-ray scattering experiments performed on detonating explosives at the advanced photon source: Calculation of the time and distance between the detonation front and the x-ray beam

DOE PAGES

Gustavsen, Richard L.; Dattelbaum, Dana Mcgraw; Watkins, Erik Benjamin; ...

2017-03-10

Time resolved Small Angle X-ray Scattering (SAXS) experiments on detonating explosives have been conducted at Argonne National Laboratory's Advanced Photon Source Dynamic Compression Sector. The purpose of the experiments is to measure the SAXS patterns at tens of ns to a few μs behind the detonation front. Corresponding positions behind the detonation front are of order 0.1–10 mm. From the scattering patterns, properties of the explosive products relative to the time behind the detonation front can be inferred. Lastly, this report describes how the time and distance from the x-ray probe location to the detonation front is calculated, as wellmore » as the uncertainties and sources of uncertainty associated with the calculated times and distances.« less

Long distance education for croatian nurses with open source software.

PubMed

Radenovic, Aleksandar; Kalauz, Sonja

2006-01-01

Croatian Nursing Informatics Association (CNIA) has been established as result of continuing work on promoting nursing informatics in Croatia. Main goals of CNIA are promoting nursing informatics and education of nurses about nursing informatics and using information technology in nursing process. CNIA in start of work is developed three courses from nursing informatics all designed with support of long distance education with open source software. Courses are: A - 'From Data to Wisdom', B - 'Introduction to Nursing Informatics' and C - 'Nursing Informatics I'. Courses A and B are obligatory for C course. Technology used to implement these online courses is based on the open source Learning Management System (LMS), Claroline, free online collaborative learning platform. Courses are divided in two modules/days. First module/day participants have classical approach to education and second day with E-learning from home. These courses represent first courses from nursing informatics' and first long distance education for nurses also.

Method and apparatus for controlling carrier envelope phase

DOEpatents

Chang, Zenghu [Manhattan, KS; Li, Chengquan [Sunnyvale, CA; Moon, Eric [Manhattan, KS

2011-12-06

A chirped pulse amplification laser system. The system generally comprises a laser source, a pulse modification apparatus including first and second pulse modification elements separated by a separation distance, a positioning element, a measurement device, and a feedback controller. The laser source is operable to generate a laser pulse and the pulse modification apparatus operable to modify at least a portion of the laser pulse. The positioning element is operable to reposition at least a portion of the pulse modification apparatus to vary the separation distance. The measurement device is operable to measure the carrier envelope phase of the generated laser pulse and the feedback controller is operable to control the positioning element based on the measured carrier envelope phase to vary the separation distance of the pulse modification elements and control the carrier envelope phase of laser pulses generated by the laser source.

Time resolved small angle X-ray scattering experiments performed on detonating explosives at the advanced photon source: Calculation of the time and distance between the detonation front and the x-ray beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gustavsen, Richard L.; Dattelbaum, Dana Mcgraw; Watkins, Erik Benjamin

Time resolved Small Angle X-ray Scattering (SAXS) experiments on detonating explosives have been conducted at Argonne National Laboratory's Advanced Photon Source Dynamic Compression Sector. The purpose of the experiments is to measure the SAXS patterns at tens of ns to a few μs behind the detonation front. Corresponding positions behind the detonation front are of order 0.1–10 mm. From the scattering patterns, properties of the explosive products relative to the time behind the detonation front can be inferred. Lastly, this report describes how the time and distance from the x-ray probe location to the detonation front is calculated, as wellmore » as the uncertainties and sources of uncertainty associated with the calculated times and distances.« less

Absolute Distance Measurement with the MSTAR Sensor

NASA Technical Reports Server (NTRS)

Lay, Oliver P.; Dubovitsky, Serge; Peters, Robert; Burger, Johan; Ahn, Seh-Won; Steier, William H.; Fetterman, Harrold R.; Chang, Yian

2003-01-01

The MSTAR sensor (Modulation Sideband Technology for Absolute Ranging) is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with sub-nanometer accuracy. The sensor uses a single laser in conjunction with fast phase modulators and low frequency detectors. We describe the design of the system - the principle of operation, the metrology source, beamlaunching optics, and signal processing - and show results for target distances up to 1 meter. We then demonstrate how the system can be scaled to kilometer-scale distances.

Unconventional Behavior of Friction at the Nanoscale beyond Amontons' Law.

PubMed

Chen, Jingrun; Gao, Wang

2017-08-05

By means of a many-body van der Waals (vdW)-corrected density functional theory approach, the atomic-scale friction of a prototypical tip-substrate system consisting of an Si tip and a graphene substrate is studied. In a loading-sliding process, the tip-substrate distance is found to be essential for nanofrictional behavior, through determining the competition between vdW contributions and electronic contributions. As the tip approaches the substrate, this competition results in a smooth transition of normal forces from attraction to repulsion, and the friction coefficient in turn undergoes a sign change from negative to positive with possible giant magnitude and strong anisotropy. The loading-sliding process does not introduce any chemical modification of the underlying system. These findings reveal the boundary of validity of Amontons' law, unify negative and giant friction coefficients, rationalize the experimentally observed anisotropy of nanofriction, and are universal when vdW interactions are crucial, all of which are helpful to establish a comprehensive picture of nanofriction. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of thin film production of ceramic ZrO2 on silicon wafer using second harmonic Nd-Yag laser with pulsed laser deposition technique

NASA Astrophysics Data System (ADS)

Suliyanti, Maria M.; Hidayah, Affi Nur; Kurniawan, K. H.

2012-06-01

Study about thin film production using technique pulsed laser deposition have been done. The Pulsed Laser Deposition (PLD) method has been used for growing thin film of ZrO2 on silicon wafer substrate (111 single crystal, thickness 400μm and diameter 7.5 cm). The target made from Zirconia oxide powder mixing with PVA and press using pressure 100kgN. The laser beam was focused by a lens (f = 100mm) through a quartz window onto the sample surface and the substrate was placed in parallel line with target. The distance between the target and the substrate is about 1 cm. The early results of this synthesis using 75 mJ Nd-YAG second harmonic laser pulse (532 nm Nd-YAG) and low pressure chamber surrounding gas 5 Torr. The irradiation of laser take around 6000 shoots or 10 minutes using frequencies laser 10 Hz. The micro thickness of film can be produced on silicon wafer using this technique. The results of ZrO2 thin film on substrate about 26.92%.

Contact angle of a nanodrop on a nanorough solid surface.

PubMed

Berim, Gersh O; Ruckenstein, Eli

2015-02-21

The contact angle of a cylindrical nanodrop on a nanorough solid surface is calculated, for both hydrophobic and hydrophilic surfaces, using the density functional theory. The emphasis of the paper is on the dependence of the contact angle on roughness. The roughness is modeled by rectangular pillars of infinite length located on the smooth surface of a substrate, with fluid-pillar interactions different in strength from the fluid-substrate ones. It is shown that for hydrophobic substrates the trend of the contact angle to increase with increasing roughness, which was noted in all previous studies, is not universally valid, but depends on the fluid-pillar interactions, pillar height, interpillar distance, as well as on the size of the drop. For hydrophilic substrate, an unusual kink-like dependence of the contact angle on the nanodrop size is found which is caused by the change in the location of the leading edges of the nanodrop on the surface. It is also shown that the Wenzel and Cassie-Baxter equations can not explain all the peculiarities of the contact angle of a nanodrop on a nanorough surface.

Bathymetry, substrate and circulation in Westcott Bay, San Juan Islands, Washington

USGS Publications Warehouse

Grossman, Eric E.; Stevens, Andrew W.; Curran, Chris; Smith, Collin; Schwartz, Andrew

2007-01-01

Nearshore bathymetry, substrate type, and circulation patterns in Westcott Bay, San Juan Islands, Washington, were mapped using two acoustic sonar systems, video and direct sampling of seafloor sediments. The goal of the project was to characterize nearshore habitat and conditions influencing eelgrass (Z. marina) where extensive loss has occurred since 1995. A principal hypothesis for the loss of eelgrass is a recent decrease in light availability for eelgrass growth due to increase in turbidity associated with either an increase in fine sedimentation or biological productivity within the bay. To explore sources for this fine sediment and turbidity, a dual-frequency Biosonics sonar operating at 200 and 430 kHz was used to map seafloor depth, morphology and vegetation along 69 linear kilometers of the bay. The higher frequency 430 kHz system also provided information on particulate concentrations in the water column. A boat-mounted 600 kHz RDI Acoustic Doppler Current Profiler (ADCP) was used to map current velocity and direction and water column backscatter intensity along another 29 km, with select measurements made to characterize variations in circulation with tides. An underwater video camera was deployed to ground-truth acoustic data. Seventy one sediment samples were collected to quantify sediment grain size distributions across Westcott Bay. Sediment samples were analyzed for grain size at the Western Coastal and Marine Geology Team sediment laboratory in Menlo Park, Calif. These data reveal that the seafloor near the entrance to Westcott Bay is rocky with a complex morphology and covered with dense and diverse benthic vegetation. Current velocities were also measured to be highest at the entrance and along a deep channel extending 1 km into the bay. The substrate is increasingly comprised of finer sediments with distance into Westcott Bay where current velocities are lower. This report describes the data collected and preliminary findings of USGS Cruise B-6-07-PS conducted between May 31, 2007 and June 5, 2007.

From the Belly of the Beast: Biogeochemistry and geomicrobiology of a fluid seep at Chimaera [Yanartas], Turkey

NASA Astrophysics Data System (ADS)

Woycheese, K. M.; Yargicoglu, E. N.; Cardace, D.; Meyer-Dombard, D. R.

2012-12-01

Serpentinization is proposed to support chemolithotrophic growth of microorganisms in surface and subsurface environments1. Abiotic CH4 production associated with terrestrial ophiolitic outcrops has been reported in southeastern Turkey2. The Yanartas (Chimaera) seep, located within the Tekirova ophiolite in Çirali, Antalya, Turkey, is one of the largest onshore CH4 seeps documented2-5. The seep consists of dozens of flames erupting from fractures within the ophiolite outcrop that burn continuously on CH4 (80-90% of gas composition2) produced by subsurface serpentinization reactions. Previous studies have focused on gas geochemistry from these seeps2, 4, 5. While past reports have not found active fluid seeps at Yanartas2, in February 2012, a fluid seep (possibly ephemeral) originating from a fracture was identified, which supported microbial mats over an outflow channel several m in length. This is the first investigation of the biogeochemical and geomicrobiological properties of this newly-discovered fluid seep. The fluid seep emits from a fracture that is actively burning, and travels down slope along the ophiolite outcrop for ~10 m. Sediment temperatures under the vent source were 50-60°C, while fluid emitting from the fracture was 18.5°C. The pH of the fluid at the vent source was 11.9, indicative of subterranean serpentinization. Approximately 7.3 m downstream, the pH dropped to 9.4, potentially due to meteoric water mixing. Fluid samples were collected along the outflow channel for major ion analysis, trace element analysis, dissolved inorganic carbon (DIC), and dissolved organic carbon (DOC). Biofilm and biomineralized microbial mats were collected for bulk C and N composition, 13C and 15N isotopes, and microscopy. Weight % total C (CT) in solids generally increases with distance from the source, while weight % organic C (Corg) decreases, reflective of a higher degree of carbonate biomineralization downstream. δ13C of solids indicates a general trend of increased 13C enrichment with distance from the source in both Corg and CT. δ15N becomes more positive with distance from the source, and does not suggest active nitrogen fixation along the outflow channel. Scanning electron microscopy (SEM) equipped with X-ray energy dispersive spectroscopy (XEDS) and X-ray diffraction (XRD) confirms that the biomineralized microbial mats are primarily composed of carbonates. Microbial samples were collected for cultivation, phylogenetic and function-based DNA analysis. Samples will be screened for methanotrophy, C fixation, and N cycling. Successful cultures have been obtained from Yanartas samples, demonstrating growth on a wide variety of carbon substrates (e.g. organic acids, yeast extract, peptone, and sugars). This is the first report of biofilms and surface fluids associated with serpentinization at the Yanartas seep. 1. McCollom, T.M. & W. Bach (2009) GCA. 73(3): 856-875 2. Etiope, G.; Schoell, M. & H. Hosgörmez (2011) EPSL. 310: 96-104 3. de Boer, J.Z.; Chanton, J. & M. Zeitlhöfler (2007) Geowissenshaftliche. 158(4): 997-1003 4. Hosgörmez, H. (2007) J Asian Earth Sci. 30: 131-141

Characterization of a Surface-Flashover Ion Source with 10-250 ns Pulse Widths

NASA Astrophysics Data System (ADS)

Falabella, S.; Guethlein, G.; Kerr, P. L.; Meyer, G. A.; Morse, J. D.; Sampayan, S.; Tang, V.

2009-03-01

As a step towards developing an ultra compact D-D neutron source for various defense and homeland security applications, a compact ion source is needed. Towards that end, we are testing a pulsed, surface flashover source, with deuterated titanium films deposited on alumina substrates as the electrodes. An electrochemically-etched mask was used to define the electrode areas on the substrate during the sputtered deposition of the titanium films. Deuterium loading of the films was performed in an all metal-sealed vacuum chamber containing a heated stage. Deuterium ion current from the source was determined by measuring the neutrons produced when the ions impacted a deuterium-loaded target held at -90 kV. As the duration of the arc current is varied, it was observed that the integrated deuteron current per pulse initially increases rapidly, then reaches a maximum near a pulse length of 100 ns.

Umbra/penumbra detector

DOEpatents

Carner, D.C. Jr.

1988-10-11

A device which monitors the characteristics of an image cast upon a radiation sensitive substrate. This includes a shadow casting object or mask and at least one source of radiation disposed above the object or mask so that the image cast on the substrate can be analyzed. 23 figs.

Flux balance analysis of different carbon source fermentation with hydrogen producing Clostridium butyricum using Cell Net Analyzer.

PubMed

Rafieenia, Razieh; Chaganti, Subba Rao

2015-01-01

A metabolic network model for Clostridium butyricum was developed using six different carbon sources (sucrose, fructose, galactose, mannose, trehalose and ribose) to study the fermentative H2 production. The model was used for investigation of H2 production and the ability of growth on different substrates to predict the maximum abilities for fermentative H2 production that each substrate can support. NADH fluxes were calculated by the model as an important cofactor affecting on H2 production. Butyrate and acetate production were used as model assumptions and biomass formation was chosen as the objective function for flux analysis calculations. Among the substrates selected, sucrose and trehalose supported the maximum growth and H2 yields. The Cell Net Analyzer metabolic network model developed for H2 estimation revealed good correlation with experimental data and could be further used to study the effect of environmental conditions and substrates concentration on H2 yield. Copyright © 2014 Elsevier Ltd. All rights reserved.

Iron translocation in Pleurotus ostreatus basidiocarps: production, bioavailability, and antioxidant activity.

PubMed

Yokota, M E; Frison, P S; Marcante, R C; Jorge, L F; Valle, J S; Dragunski, D C; Colauto, N B; Linde, G A

2016-02-22

Translocation of minerals from substrate to mushrooms can change the medicinal characteristics, commercial value, and biological efficiency of mushroom. In the present study, we demonstrated that addition of iron to the substrate reduces the yield of Pleurotus ostreatus mushroom. The biological efficiency of the mushroom varied from 36.53% on the unsupplemented substrate to 2.08% for the substrate with 500 mg/kg iron added. The maximum iron concentration obtained for mushroom was 478.66 mg/kg (dry basis) and the maximum solubility in vitro was 293.70 mg/kg (dry basis). Iron translocation increased the ash and protein content, reduced antioxidant activity, and enhanced the aroma and flavor characteristics of the mushroom. However mushroom has higher amounts of iron than vegetables like collard greens, it is not feasible to use mushrooms as the only dietary source of iron. The study also indicated that because of more bioaccumulation of iron in mycelium than in the mushroom, mycelium and not mushroom, could be a better alternative as a non-animal iron source.

Molecular dynamics study of the growth of a metal nanoparticle array by solid dewetting

NASA Astrophysics Data System (ADS)

Luan, Yanhua; Li, Yanru; Nie, Tiaoping; Yu, Jun; Meng, Lijun

2018-03-01

We investigated the effect of the substrate and the ambient temperature on the growth of a metal nanoparticle array (nanoarray) on a solid-patterned substrate by dewetting a Au liquid film using an atomic simulation technique. The patterned substrate was constructed by introducing different interaction potentials for two atom groups ( C 1 and C 2) in the graphene-like substrate. The C 1 group had a stronger interaction between the Au film and the substrate and was composed of regularly distributed circular disks with radius R and distance D between the centers of neighboring disks. Our simulation results demonstrate that R and D have a strikingly different influence on the growth of the nanoparticle arrays. The degree of order of the nanoarray increases first before it reaches a peak and then decreases for increasing R at fixed D. However, the degree of order increases monotonously when D is increased and reaches a saturated value beyond a critical value of D for a fixed R. Interestingly, a labyrinth-like structure appeared during the dewetting process of the metal film. The simulation results also indicated that the temperature was an important factor in controlling the properties of the nanoarray. An appropriate temperature leads to an optimized nanoarray with a uniform grain size and well-ordered particle distribution. These results are important for understanding the dewetting behaviors of metal films on solid substrates and understanding the growth of highly ordered metal nanoarrays using a solid-patterned substrate method.

Regional W-Phase Source Inversion for Moderate to Large Earthquakes in China and Neighboring Areas

NASA Astrophysics Data System (ADS)

Zhao, Xu; Duputel, Zacharie; Yao, Zhenxing

2017-12-01

Earthquake source characterization has been significantly speeded up in the last decade with the development of rapid inversion techniques in seismology. Among these techniques, the W-phase source inversion method quickly provides point source parameters of large earthquakes using very long period seismic waves recorded at teleseismic distances. Although the W-phase method was initially developed to work at global scale (within 20 to 30 min after the origin time), faster results can be obtained when seismological data are available at regional distances (i.e., Δ ≤ 12°). In this study, we assess the use and reliability of regional W-phase source estimates in China and neighboring areas. Our implementation uses broadband records from the Chinese network supplemented by global seismological stations installed in the region. Using this data set and minor modifications to the W-phase algorithm, we show that reliable solutions can be retrieved automatically within 4 to 7 min after the earthquake origin time. Moreover, the method yields stable results down to Mw = 5.0 events, which is well below the size of earthquakes that are rapidly characterized using W-phase inversions at teleseismic distances.

Long-range and wide field of view optical coherence tomography for in vivo 3D imaging of large volume object based on akinetic programmable swept source.

PubMed

Song, Shaozhen; Xu, Jingjiang; Wang, Ruikang K

2016-11-01

Current optical coherence tomography (OCT) imaging suffers from short ranging distance and narrow imaging field of view (FOV). There is growing interest in searching for solutions to these limitations in order to expand further in vivo OCT applications. This paper describes a solution where we utilize an akinetic swept source for OCT implementation to enable ~10 cm ranging distance, associated with the use of a wide-angle camera lens in the sample arm to provide a FOV of ~20 x 20 cm 2 . The akinetic swept source operates at 1300 nm central wavelength with a bandwidth of 100 nm. We propose an adaptive calibration procedure to the programmable akinetic light source so that the sensitivity of the OCT system over ~10 cm ranging distance is substantially improved for imaging of large volume samples. We demonstrate the proposed swept source OCT system for in vivo imaging of entire human hands and faces with an unprecedented FOV (up to 400 cm 2 ). The capability of large-volume OCT imaging with ultra-long ranging and ultra-wide FOV is expected to bring new opportunities for in vivo biomedical applications.