Investigation of micromixing by acoustically oscillated sharp-edges.

PubMed

Nama, Nitesh; Huang, Po-Hsun; Huang, Tony Jun; Costanzo, Francesco

2016-03-01

Recently, acoustically oscillated sharp-edges have been utilized to achieve rapid and homogeneous mixing in microchannels. Here, we present a numerical model to investigate acoustic mixing inside a sharp-edge-based micromixer in the presence of a background flow. We extend our previously reported numerical model to include the mixing phenomena by using perturbation analysis and the Generalized Lagrangian Mean (GLM) theory in conjunction with the convection-diffusion equation. We divide the flow variables into zeroth-order, first-order, and second-order variables. This results in three sets of equations representing the background flow, acoustic response, and the time-averaged streaming flow, respectively. These equations are then solved successively to obtain the mean Lagrangian velocity which is combined with the convection-diffusion equation to predict the concentration profile. We validate our numerical model via a comparison of the numerical results with the experimentally obtained values of the mixing index for different flow rates. Further, we employ our model to study the effect of the applied input power and the background flow on the mixing performance of the sharp-edge-based micromixer. We also suggest potential design changes to the previously reported sharp-edge-based micromixer to improve its performance. Finally, we investigate the generation of a tunable concentration gradient by a linear arrangement of the sharp-edge structures inside the microchannel.

Pinning down high-performance Cu-chalcogenides as thin-film solar cell absorbers: A successive screening approach

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

Zhang, Yubo; Zhang, Wenqing, E-mail: wqzhang@mail.sic.ac.cn, E-mail: pzhang3@buffalo.edu; State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050

2016-05-21

Photovoltaic performances of Cu-chalcogenides solar cells are strongly correlated with the absorber fundamental properties such as optimal bandgap, desired band alignment with window material, and high photon absorption ability. According to these criteria, we carry out a successive screening for 90 Cu-chalcogenides using efficient theoretical approaches. Besides the well-recognized CuInSe{sub 2} and Cu{sub 2}ZnSnSe{sub 4} materials, several novel candidates are identified to have optimal bandgaps of around 1.0–1.5 eV, spike-like band alignments with CdS window layer, sharp photon absorption edges, and high absorption coefficients. These new systems have great potential to be superior absorbers for photovolatic applications if their carrriermore » transport and defect properties are properly optimized.« less

Analysis of sharpness increase by image noise

NASA Astrophysics Data System (ADS)

Kurihara, Takehito; Aoki, Naokazu; Kobayashi, Hiroyuki

2009-02-01

Motivated by the reported increase in sharpness by image noise, we investigated how noise affects sharpness perception. We first used natural images of tree bark with different amounts of noise to see whether noise enhances sharpness. Although the result showed sharpness decreased as noise amount increased, some observers seemed to perceive more sharpness with increasing noise, while the others did not. We next used 1D and 2D uni-frequency patterns as stimuli in an attempt to reduce such variability in the judgment. The result showed, for higher frequency stimuli, sharpness decreased as the noise amount increased, while sharpness of the lower frequency stimuli increased at a certain noise level. From this result, we thought image noise might reduce sharpness at edges, but be able to improve sharpness of lower frequency component or texture in image. To prove this prediction, we experimented again with the natural image used in the first experiment. Stimuli were made by applying noise separately to edge or to texture part of the image. The result showed noise, when added to edge region, only decreased sharpness, whereas when added to texture, could improve sharpness. We think it is the interaction between noise and texture that sharpens image.

Novel Laser-Based Technique for Measurements of Primary Atomization Characteristics of Liquid Jets

DTIC Science & Technology

2012-08-22

worth noting that round supercavitating nozzles were used that had sharp edged inlets and exits, with length-to-diameter ratios smaller than 3. This...noting that round supercavitating nozzles were used that had sharp edged inlets and exits, with length-to-diameter ratios smaller than 3. This...breakup. It is worth noting that round supercavitating nozzles were used that had sharp edged inlets and exits, with length-to-diameter ratios

Adding to the Mercury Speciation Toolbox

NASA Astrophysics Data System (ADS)

Fitts, J. P.; Northrup, P. A.; Chidambaram, D.; Kalb, P. D.

2007-12-01

Mercury was used to separate lithium-6 isotope for weapons production at the Y-12 Plant in Oak Ridge, TN in the 1950s and 1960s. A large portion of the waste Hg entered the environment and continues to move throughout the sub-surface and surface waters in the area. Environmental management of Hg contamination within this complex hydrologic system, where Hg speciation and the mobile fraction have been found to vary widely, will require ongoing characterization and predictive modeling of Hg speciation. State-of-the-art spectroscopic tools that can directly probe Hg speciation in preserved aqueous and sediment samples with greater sensitivity, however, are required to determine rates and mechanisms of biogeochemical reactions. We will present the first results demonstrating the use of x-ray absorption spectroscopy (XAS) at the Hg M5 edge (2295 eV) to fingerprint Hg species. Heavy-metal M5 absorption edges can have very sharp features due to local electron transitions, and therefore, we are developing this edge as a tool for quantitative measurement of Hg species. In addition, sulfur speciation using the sulfur K absorption edge, which is at a similar energy (2472 eV), can be measured in the same scan as the Hg M5 edge. Potentially important organic and inorganic sulfur species (sulfide, disulfide, elemental sulfur, sulfite and sulfate) are readily differentiated, and thereby, provides an independent method for monitoring the redox state of the system along with changes in S-Hg bonding. We will also present x-ray microprobe 2-D concentration maps of Hg and other elements at the grain and pore scales to identify its microscopic distribution and chemical associations. When used in combination with established sequential extraction and direct spectroscopic methods, the addition of XAS at the Hg M5 edge should provide a significant advancement in the determination of Hg speciation in complex biogeochemical environments.

Molybdenum X-Ray Absorption Edges from 200 – 20,000 eV, The Benefits of Soft X-Ray Spectroscopy for Chemical Speciation

PubMed Central

George, Simon J.; Drury, Owen B.; Fu, Juxia; Friedrich, Stephan; Doonan, Christian J.; George, Graham N.; White, Jonathan M.; Young, Charles G.; Cramer, Stephen P.

2009-01-01

We have surveyed the chemical utility of the near-edge structure of molybdenum x-ray absorption edges from the hard x-ray K-edge at 20,000 eV down to the soft x-ray M4,5-edges at ~230 eV. We compared, for each edge, the spectra of two tetrahedral anions, MoO4 and MoS42-. We used three criteria for assessing near-edge structure of each edge: (i) the ratio of the observed chemical shift between MoO42- and MoS42- and the linewidth, (ii) the chemical information from analysis of the near-edge structure and (iii) the ease of measurement using fluorescence detection. Not surprisingly, the K-edge was by far the easiest to measure, but it contained the least information. The L2,3-edges, although harder to measure, had benefits with regard to selection rules and chemical speciation in that they had both a greater chemical shift as well as detailed lineshapes which could be theoretically analyzed in terms of Mo ligand field, symmetry, and covalency. The soft x-ray M2,3-edges were perhaps the least useful, in that they were difficult to measure using fluorescence detection and had very similar information content to the corresponding L2,3-edges. Interestingly, the soft x-ray, low energy (~230 eV) M4,5-edges had greatest potential chemical sensitivity and using our high resolution superconducting tunnel junction (STJ) fluorescence detector they appear to be straightforward to measure. The spectra were amenable to analysis using both the TT-multiplet approach and FEFF. The results using FEFF indicate that the sharp near-edge peaks arise from 3d → 5p transitions, while the broad edge structure has predominately 3d → 4f character. A proper understanding of the dependence of these soft x-ray spectra on ligand field and site geometry is necessary before a complete assessment of the utility of the Mo M4,5-edges can be made. This work includes crystallographic characterization of sodium tetrathiomolybdate. PMID:19041140

Resolving the Cygnus X-3 iron K line

NASA Technical Reports Server (NTRS)

Kitamoto, Shunji; Kawashima, Kenji; Negoro, Hitoshi; Miyamoto, Sigenori; White, N. E.; Nagase, Fumiaki

1994-01-01

An Advanced Satellite for Cosmology and Astrophysics (ASCA) observation of Cygnus X-3 on 1993 June 11, in its X-ray high intensity state, has for the first time resolved the broad iron K line emission into three components: a He-like line at 6.67 +/- 0.01 keV, a H-like line at 6.96 +/- 0.02 keV, and a neutral line at 6.37 +/- 0.03 keV. The line intensities of the 6.67 keV and 6.96 keV lines are modulated with the 4.8 hr orbital period and are maximum when the continuum intensity is minimum. There is a sharp minimum of the line intensity on the rising phase of the continuum intensity. An iron absorption edge is observed at 7.19 +/- 0.02 keV. The optical depth of the absorption edge varies from 0.3 to 0.5 and is in anti-phase with the overall X-ray continuum modulation. The observed complexity of the iron K line region is greater than that had been assumed in previous spectral modeling based on observations with lower resolution detectors.

Hollow structure formation of intense ion beams with sharp edge in background plasmas

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

Hu, Zhang-Hu; Wang, You-Nian, E-mail: ynwang@dlut.edu.cn

The transport of intense ion beams with sharp radial beam edge in plasmas has been studied with two-dimensional electromagnetic particle simulations. The initial solid beam evolves into a hollow beam due to the nonlinear sharp transverse force peak in the regions of beam edge. The magnitude and nonlinearity of this peak are enhanced as the ion beam travels further into the plasma, due to the self-consistent interactions between the beam ions and the plasma electrons. This structure formation is shown to be independent on the beam radius.

Europa in the Far-UV: Spatial and Spectral Analysis from HST Observations

NASA Astrophysics Data System (ADS)

Becker, Tracy M.; Retherford, Kurt D.; Roth, Lorenz; Hendrix, Amanda R.; McGrath, Melissa; Alday, Juan; Saur, Joachim; Molyneux, Philippa M.; Raut, Ujjwal; Teolis, Benjamin

2017-10-01

We present a spatial and spectral analysis of Europa using far-UV observations from 1999 - 2015 made by the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST). Disk-integrated observations show that the far-UV spectrum from ~130 nm - 170 nm is blue (increasing albedo with decreasing wavelength) for the studied hemispheres: the leading, trailing, and anti-Jovian hemispheres. At Lyman-alpha (121.6 nm), the albedo of the trailing hemisphere continues the blue trend, but it reddens for the leading hemisphere. At wavelengths shorter than 133.5 nm, the leading hemisphere, which is brighter than the trailing hemisphere at near-UV and visible wavelengths, becomes darker than the trailing hemisphere. We find no evidence of a sharp water-ice absorption edge at 165 nm on any hemisphere of Europa, which is intriguing since such an absorption feature has been observed on most icy moons. This suggests the possibility that radiolytic alteration by Jovian magnetospheric plasma has made the surface more strongly absorbing, masking the absorption edge. We will also present a spatial map of Lyman-alpha across the entire surface of Europa. This map can then be used to distinguish variable H emissions in the atmosphere from surface reflectance, improving our ability to detect potential plumes occurring on the disk of Europa during an observation.

Transformation-optics description of plasmonic nanostructures containing blunt edges/corners: from symmetric to asymmetric edge rounding.

PubMed

Luo, Yu; Lei, Dang Yuan; Maier, Stefan A; Pendry, John B

2012-07-24

The sharpness of corners/edges can have a large effect on the optical responses of metallic nanostructures. Here we deploy the theory of transformation optics to analytically investigate a variety of blunt plasmonic structures, including overlapping nanowire dimers and crescent-shaped nanocylinders. These systems are shown to support several discrete optical modes, whose energy and line width can be controlled by tuning the nanoparticle geometry. In particular, the necessary conditions are highlighted respectively for the broadband light absorption effect and the invisibility dips that appear in the radiative spectrum. More detailed discussions are provided especially with respect to the structures with asymmetric edge rounding. These structures can support additional subradiant modes, whose interference with the neighboring dipolar modes results in a rapid change of the scattering cross-section, similar to the phenomenon observed in plasmonic Fano resonances. Finite element numerical calculations are also performed to validate the analytical predictions. The physical insights into blunt nanostructures presented in this work may be of great interest for the design of broadband light-harvesting devices, invisible and noninvasive biosensors, and slowing-light devices.

Flow-field in a vortex with breakdown above sharp edged delta wings

NASA Technical Reports Server (NTRS)

Hayashi, Y.; Nakaya, T.

1978-01-01

The behavior of vortex-flow, accompanied with breakdown, formed above sharp-edged delta wings, was studied experimentally as well as theoretically. Emphasis is placed particularly on the criterion for the breakdown at sufficiently large Reynolds numbers

Spectrally selective solar absorber with sharp and temperature dependent cut-off based on semiconductor nanowire arrays

NASA Astrophysics Data System (ADS)

Wang, Yang; Zhou, Lin; Zheng, Qinghui; Lu, Hong; Gan, Qiaoqiang; Yu, Zongfu; Zhu, Jia

2017-05-01

Spectrally selective absorbers (SSA) with high selectivity of absorption and sharp cut-off between high absorptivity and low emissivity are critical for efficient solar energy conversion. Here, we report the semiconductor nanowire enabled SSA with not only high absorption selectivity but also temperature dependent sharp absorption cut-off. By taking advantage of the temperature dependent bandgap of semiconductors, we systematically demonstrate that the absorption cut-off profile of the semiconductor-nanowire-based SSA can be flexibly tuned, which is quite different from most of the other SSA reported so far. As an example, silicon nanowire based selective absorbers are fabricated, with the measured absorption efficiency above (below) bandgap ˜97% (15%) combined with an extremely sharp absorption cut-off (transition region ˜200 nm), the sharpest SSA demonstrated so far. The demonstrated semiconductor-nanowire-based SSA can enable a high solar thermal efficiency of ≳86% under a wide range of operating conditions, which would be competitive candidates for the concentrated solar energy utilizations.

16 CFR 1500.49 - Technical requirements for determining a sharp metal or glass edge in toys and other articles...

Code of Federal Regulations, 2014 CFR

2014-01-01

... intended for use by children under 8 years of age. (a) Objective. The sharp edge test method prescribed by... and articles, present a potential risk of injury by laceration or avulsion under section 2(s) of the... articles with edges that are identified as presenting a potential risk of laceration or avulsion injury to...

16 CFR 1500.49 - Technical requirements for determining a sharp metal or glass edge in toys and other articles...

Code of Federal Regulations, 2011 CFR

2011-01-01

... intended for use by children under 8 years of age. (a) Objective. The sharp edge test method prescribed by... and articles, present a potential risk of injury by laceration or avulsion under section 2(s) of the... articles with edges that are identified as presenting a potential risk of laceration or avulsion injury to...

16 CFR 1500.49 - Technical requirements for determining a sharp metal or glass edge in toys and other articles...

Code of Federal Regulations, 2010 CFR

2010-01-01

... intended for use by children under 8 years of age. (a) Objective. The sharp edge test method prescribed by... and articles, present a potential risk of injury by laceration or avulsion under section 2(s) of the... articles with edges that are identified as presenting a potential risk of laceration or avulsion injury to...

16 CFR § 1500.49 - Technical requirements for determining a sharp metal or glass edge in toys and other articles...

Code of Federal Regulations, 2013 CFR

2013-01-01

... articles intended for use by children under 8 years of age. (a) Objective. The sharp edge test method... such toys and articles, present a potential risk of injury by laceration or avulsion under section 2(s... toys and other articles with edges that are identified as presenting a potential risk of laceration or...

16 CFR 1500.49 - Technical requirements for determining a sharp metal or glass edge in toys and other articles...

Code of Federal Regulations, 2012 CFR

2012-01-01

... intended for use by children under 8 years of age. (a) Objective. The sharp edge test method prescribed by... and articles, present a potential risk of injury by laceration or avulsion under section 2(s) of the... articles with edges that are identified as presenting a potential risk of laceration or avulsion injury to...

Sharp Refractory Composite Leading Edges on Hypersonic Vehicles

NASA Technical Reports Server (NTRS)

Walker, Sandra P.; Sullivan, Brian J.

2003-01-01

On-going research of advanced sharp refractory composite leading edges for use on hypersonic air-breathing vehicles is presented in this paper. Intense magnitudes of heating and of heating gradients on the leading edge lead to thermal stresses that challenge the survivability of current material systems. A fundamental understanding of the problem is needed to further design development. Methodology for furthering the technology along with the use of advanced fiber architectures to improve the thermal-structural response is explored in the current work. Thermal and structural finite element analyses are conducted for several advanced fiber architectures of interest. A tailored thermal shock parameter for sharp orthotropic leading edges is identified for evaluating composite material systems. The use of the tailored thermal shock parameter has the potential to eliminate the need for detailed thermal-structural finite element analyses for initial screening of material systems being considered for a leading edge component.

[Perceptual sharpness metric for visible and infrared color fusion images].

PubMed

Gao, Shao-Shu; Jin, Wei-Qi; Wang, Xia; Wang, Ling-Xue; Luo, Yuan

2012-12-01

For visible and infrared color fusion images, objective sharpness assessment model is proposed to measure the clarity of detail and edge definition of the fusion image. Firstly, the contrast sensitivity functions (CSF) of the human visual system is used to reduce insensitive frequency components under certain viewing conditions. Secondly, perceptual contrast model, which takes human luminance masking effect into account, is proposed based on local band-limited contrast model. Finally, the perceptual contrast is calculated in the region of interest (contains image details and edges) in the fusion image to evaluate image perceptual sharpness. Experimental results show that the proposed perceptual sharpness metrics provides better predictions, which are more closely matched to human perceptual evaluations, than five existing sharpness (blur) metrics for color images. The proposed perceptual sharpness metrics can evaluate the perceptual sharpness for color fusion images effectively.

Spectrometric analysis of different fluorophosphate glasses doped with Sm{sup 3+} ions for reddish-orange laser emission

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

Babu, S., E-mail: ratnakaramsvu@gmail.com; Balakrishna, A., E-mail: ratnakaramsvu@gmail.com; Ratnakaram, Y. C., E-mail: ratnakaramsvu@gmail.com

2014-04-24

Optical properties of Sm{sup 3+} doped different fluorophosphate glasses have been synthesized and discussed. The J- O intensity parameters Ω{sub λ} (λ= 2, 4, 6) from absorption spectra have been evaluated. No sharp edges are found in the absorption spectra, which confirm amorphous nature of present glass matrices. Various radiative parameters have been obtained from luminescence spectra for excited states to corresponding {sup 4}G{sub 5/2}→{sup 6}H{sub 5/2}, {sup 6}H{sub 7/2}, {sup 6}H{sub 9/2} and {sup 6}H{sub 11/2} transitions. The nature of decay curve analysis was performed for the {sup 4}G{sub 5/2} level. These glasses are expected to give interesting applicationmore » in field of optical devices.« less

46 CFR 163.002-13 - Construction.

Code of Federal Regulations, 2013 CFR

2013-10-01

... sharp edges and projections of excessive length. A pilot hoist must not have nonfunctional sharp edges... vessel's side rails for support; and (3) Unobstructed passage between the ladder or lift platform of the... between the vessel's compressed air source and the pneumatic motor. (l) Hoist control lever. Each pilot...

46 CFR 163.002-13 - Construction.

Code of Federal Regulations, 2014 CFR

2014-10-01

... sharp edges and projections of excessive length. A pilot hoist must not have nonfunctional sharp edges... vessel's side rails for support; and (3) Unobstructed passage between the ladder or lift platform of the... between the vessel's compressed air source and the pneumatic motor. (l) Hoist control lever. Each pilot...

46 CFR 163.002-13 - Construction.

Code of Federal Regulations, 2012 CFR

2012-10-01

... sharp edges and projections of excessive length. A pilot hoist must not have nonfunctional sharp edges... vessel's side rails for support; and (3) Unobstructed passage between the ladder or lift platform of the... between the vessel's compressed air source and the pneumatic motor. (l) Hoist control lever. Each pilot...

Optical absorption of carbon-gold core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Zhaolong; Quan, Xiaojun; Zhang, Zhuomin; Cheng, Ping

2018-01-01

In order to enhance the solar thermal energy conversion efficiency, we propose to use carbon-gold core-shell nanoparticles dispersed in liquid water. This work demonstrates theoretically that an absorbing carbon (C) core enclosed in a plasmonic gold (Au) nanoshell can enhance the absorption peak while broadening the absorption band; giving rise to a much higher solar absorption than most previously studied core-shell combinations. The exact Mie solution is used to evaluate the absorption efficiency factor of spherical nanoparticles in the wavelength region from 300 nm to 1100 nm as well as the electric field and power dissipation profiles inside the nanoparticles at specified wavelengths (mostly at the localized surface plasmon resonance wavelength). The field enhancement by the localized plasmons at the gold surfaces boosts the absorption of the carbon particle, resulting in a redshift of the absorption peak with increased peak height and bandwidth. In addition to spherical nanoparticles, we use the finite-difference time-domain method to calculate the absorption of cubic core-shell nanoparticles. Even stronger enhancement can be achieved with cubic C-Au core-shell structures due to the localized plasmonic resonances at the sharp edges of the Au shell. The solar absorption efficiency factor can exceed 1.5 in the spherical case and reach 2.3 in the cubic case with a shell thickness of 10 nm. Such broadband absorption enhancement is in great demand for solar thermal applications including steam generation.

A novel green approach for reduction of free standing graphene oxide: electrical and electronic structural investigations.

PubMed

Saravanan, K; Panigrahi, B K; Suresh, K; Sundaravel, B; Magudapathy, P; Gupta, Mukul

2018-08-24

Ion beam irradiation technique has been proposed, for efficient, fast and eco-friendly reduction of graphene oxide (GO), as an alternative to the conventional methods. 5 MeV, Au + ion beam has been used to reduce the free standing GO flake. Both electronic and nuclear energy loss mechanisms of the irradiation process play a major role in removal of oxygen moieties and recovery of graphene network. Atomic resolution scanning tunnelling microscopy analysis of the irradiated GO flake shows the characteristic honeycomb structure of graphene. X-ray absorption near edge structure analysis at C K-edge reveals that the features of the irradiated GO flake resemble the few layer graphene. Resonant Rutherford backscattering spectrometry analysis evidenced an enhanced C/O ratio of ∼23 in the irradiated GO. In situ sheet resistance measurements exhibit a sharp decrease of resistance (few 100 s of Ω) at a fluence of 6.5 × 10 14 ions cm -2 . Photoluminescence spectroscopic analysis of irradiated GO shows a sharp blue emission, while pristine GO exhibits a broad emission in the visible-near IR region. Region selective reduction, tunable electrical and optical properties by controlling C/O ratio makes ion irradiation as a versatile tool for the green reduction of GO for diverse applications.

Tunable Non-Thermal Distribution of Hot Electrons in a Semiconductor Injected from a Plasmonic Gold Nanostructure.

PubMed

Cushing, Scott Kevin; Chen, Chih-Jung; Dong, Chung Li; Kong, Xiang-Tian; Govorov, Alexander O; Liu, Ru-Shi; Wu, Nianqiang

2018-06-26

For semiconductors photosensitized with organic dyes or quantum dots, transferred electrons are usually considered thermalized at the conduction band edge. This study suggests that the electrons injected from a plasmonic metal into a thin semiconductor shell can be non-thermal with energy up to the plasmon frequency. In other words, the electrons injected into the semiconductor are still hot carriers. Photomodulated x-ray absorption measurements of the Ti L 2,3 edge are compared before and after excitation of the plasmon in Au@TiO 2 core shell nanoparticles. Comparison with theoretical predictions of the x-ray absorption, which include the heating and state-filling effects from injected hot carriers, suggest that the electrons transferred from the plasmon remain non-thermal in the ~10 nm TiO 2 shell, due in part to a slow trapping in defect states. By repeating the measurements for spherical, rod-like, and star-like metal nanoparticles, the magnitude of the non-thermal distribution, peak energy, and number of injected hot electrons are confirmed to be tuned by the plasmon frequency and the sharp corners of the plasmonic nanostructure. The results suggest that plasmonic photosensitizers can not only extend the sunlight absorption spectral range of semiconductor-based devices, but could also result in increased open circuit voltages and elevated thermodynamic driving forces for solar fuel generation in photoelectrochemical cells.

K-Shell Photoionization of Nickel Ions Using R-Matrix

NASA Technical Reports Server (NTRS)

Witthoeft, M. C.; Bautista, M. A.; Garcia, J.; Kallman, T. R.; Mendoza, C.; Palmeri, P.; Quinet, P.

2011-01-01

We present R-matrix calculations of photoabsorption and photoionization cross sections across the K edge of the Li-like to Ca-like ions stages of Ni. Level-resolved, Breit-Pauli calculations were performed for the Li-like to Na-like stages. Term-resolved calculations, which include the mass-velocity and Darwin relativistic corrections, were performed for the Mg-like to Ca-like ion stages. This data set is extended up to Fe-like Ni using the distorted wave approximation as implemented by AUTOSTRUCTURE. The R-matrix calculations include the effects of radiative and Auger dampings by means of an optical potential. The damping processes affect the absorption resonances converging to the K thresholds causing them to display symmetric profiles of constant width that smear the otherwise sharp edge at the K-shell photoionization threshold. These data are important for the modeling of features found in photoionized plasmas.

The formation of sharp edges in planetary rings by nearby satellites

NASA Astrophysics Data System (ADS)

Borderies, N.; Goldreich, P.; Tremaine, S.

1989-08-01

Equations are derived which govern the shapes of the perturbed streamlines near the 'sharp edge' boundaries between regions of high and low planetary ring optical depth; these are maintained by the shepherd satellites, which transfer angular momentum to and from ring particles. The results obtained by these equations' solution with a simple numerical model, whose parameters resemble those of the Encke division, are found to faithfully reproduce the sharp edges bounding the division; they imply that the ring thickness in the unperturbed regions far from the edges is of the order of 10 m, and that the angle-averaged surface density varies on a much shorter radial length scale than that over which the satellite torque is applied. This feature's relationship to the local reversal of angular momentum viscous transport, in the most strongly perturbed regions, is demonstrated.

The formation of sharp edges in planetary rings by nearby satellites

NASA Technical Reports Server (NTRS)

Borderies, Nicole; Goldreich, Peter; Tremaine, Scott

1989-01-01

Equations are derived which govern the shapes of the perturbed streamlines near the 'sharp edge' boundaries between regions of high and low planetary ring optical depth; these are maintained by the shepherd satellites, which transfer angular momentum to and from ring particles. The results obtained by these equations' solution with a simple numerical model, whose parameters resemble those of the Encke division, are found to faithfully reproduce the sharp edges bounding the division; they imply that the ring thickness in the unperturbed regions far from the edges is of the order of 10 m, and that the angle-averaged surface density varies on a much shorter radial length scale than that over which the satellite torque is applied. This feature's relationship to the local reversal of angular momentum viscous transport, in the most strongly perturbed regions, is demonstrated.

Haemothorax following bullectomy caused by a sharp edge of the Endoloop.

PubMed

Otsuka, Hajime; Hata, Yoshinobu; Takagi, Keigo; Sato, Fumitomo

2013-05-01

A 22-year old man presented with a massive haemothorax 25 days after bullectomy for a spontaneous pneumothorax. Thoracoscopic surgery revealed ongoing bleeding from the chest wall caused by a sharp edge of the Endoloop Ligature (Ethicon Endo-Surgery) used to resect the remaining small part of the lung at the earlier staple bullectomy. The point where bleeding was occurring was clipped and covered using a collagen patch coated with human fibrinogen and thrombin. The protruding sharp edge of the Endoloop was excised together with the surrounding lung tissue, using a stapler. Although prevention of this type of complication is difficult, awareness of the potential problem may help in managing such extremely rare events.

Haemothorax following bullectomy caused by a sharp edge of the Endoloop

PubMed Central

Otsuka, Hajime; Hata, Yoshinobu; Takagi, Keigo; Sato, Fumitomo

2013-01-01

A 22-year old man presented with a massive haemothorax 25 days after bullectomy for a spontaneous pneumothorax. Thoracoscopic surgery revealed ongoing bleeding from the chest wall caused by a sharp edge of the Endoloop Ligature (Ethicon Endo-Surgery) used to resect the remaining small part of the lung at the earlier staple bullectomy. The point where bleeding was occurring was clipped and covered using a collagen patch coated with human fibrinogen and thrombin. The protruding sharp edge of the Endoloop was excised together with the surrounding lung tissue, using a stapler. Although prevention of this type of complication is difficult, awareness of the potential problem may help in managing such extremely rare events. PMID:23407693

Fracture Mechanical Analysis of Open Cell Ceramic Foams Under Thermal Shock Loading

NASA Astrophysics Data System (ADS)

Settgast, C.; Abendroth, M.; Kuna, M.

2016-11-01

Ceramic foams made by replica techniques containing sharp-edged cavities, which are potential crack initiators and therefore have to be analyzed using fracture mechanical methods. The ceramic foams made of novel carbon bonded alumina are used as filters in metal melt filtration applications, where the filters are exposed to a thermal shock. During the casting process the filters experience a complex thermo-mechanical loading, which is difficult to measure. Modern numerical methods allow the simulation of such complex processes. As a simplified foam structure an open Kelvin cell is used as a representative volume element. A three-dimensional finite element model containing realistic sharp-edged cavities and three-dimensional sub-models along these sharp edges are used to compute the transient temperature, stress and strain fields at the Kelvin foam. The sharp edges are evaluated using fracture mechanical methods like the J-integral technique. The results of this study describe the influence of the pore size, relative density of the ceramic foam, the heat transfer and selected material parameters on the fracture mechanical behaviour.

Focusing optical waves with a rotationally symmetric sharp-edge aperture

NASA Astrophysics Data System (ADS)

Hu, Yanwen; Fu, Shenhe; Li, Zhen; Yin, Hao; Zhou, Jianying; Chen, Zhenqiang

2018-04-01

While there has been various kinds of patterned structures proposed for wave focusing, these patterned structures usually involve complicated lithographic techniques since the element size of the patterned structures should be precisely controlled in microscale or even nanoscale. Here we propose a new and straightforward method for focusing an optical plane wave in free space with a rotationally symmetric sharp-edge aperture. The focusing phenomenon of wave is realized by superposition of a portion of the higher-order symmetric plane waves generated from the sharp edges of the apertures, in contrast to previously focusing techniques which usually depend on a curved phase. We demonstrate both experimentally and theoretically the focusing effect with a series of apertures having different rotational symmetry, and find that the intensity of the hotspots could be controlled by the symmetric strength of the sharp-edge apertures. The presented results would advance the conventional wisdom that light would diffract in all directions and become expanding when it propagates through an aperture. The proposed method is easy to be processed, and might open potential applications in interferometry, image, and superresolution.

On the aeroacoustic tonal noise generation mechanism of a sharp-edged plate.

PubMed

Moreau, Danielle J; Brooks, Laura A; Doolan, Con J

2011-04-01

This letter presents an experimental study on the tonal noise generated by a sharp-edged flat plate at low-to-moderate Reynolds number. Flow and far-field noise data reveal that, in this particular case, the tonal noise appears to be governed by vortex shedding processes. Also related to the existence of the tonal noise is a region of separated flow slightly upstream of the trailing edge. Hydrodynamic fluctuations at selected vortex shedding frequencies are strongly amplified by the inflectional mean velocity profile in the separated shear layer. The amplified hydrodynamic fluctuations are diffracted by the trailing edge, producing strong tonal noise.

Lithium K(1s) synchrotron NEXAFS spectra of lithium-ion battery cathode, anode and electrolyte materials

NASA Astrophysics Data System (ADS)

Braun, Artur; Wang, Hongxin; Shim, Joongpyo; Lee, Steven S.; Cairns, Elton J.

The lithium(1s) K-edge X-ray absorption spectra of lithium-ion battery relevant materials (Li metal, Li 3N, LiPF 6, LiC 6, and LiMn 1.90Ni 0.10O 4) are presented. The Li and LiC 6 spectra are discussed and compared with literature data. The Li in lithium-intercalated carbon LiC 6, typically used as anode battery electrode material, could be clearly identified in the spectrum, and a presumed purely metallic character of the Li can be ruled out based on the chemical shift observed. The Li in corresponding cathode electrode materials, LiMn 1.90Ni 0.10O 4, could be detected with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, but the strong (self-) absorption of the spinel lattice provides an obstacle for quantitative analysis. Owing to its ionic bonding, the spectrum of the electrolyte salt LiPF 6 contains a sharp π-resonance at 61.8 eV, suggesting a distinct charge transfer between Li and the hexafluorophosphate anion. In addition, LiPF 6 resembles many spectral features of LiF, making it difficult to discriminate both from each other. Residual electrolyte on anodes or cathodes poses a problem for the spectroscopic analysis of the electrodes, because its Li spectrum overshadows the spectral features of the Li in the anode or cathode. The electrolyte must be removed from electrodes prior to spectroscopic analysis.

Calculating corner singularities by boundary integral equations.

PubMed

Shi, Hualiang; Lu, Ya Yan; Du, Qiang

2017-06-01

Accurate numerical solutions for electromagnetic fields near sharp corners and edges are important for nanophotonics applications that rely on strong near fields to enhance light-matter interactions. For cylindrical structures, the singularity exponents of electromagnetic fields near sharp edges can be solved analytically, but in general the actual fields can only be calculated numerically. In this paper, we use a boundary integral equation method to compute electromagnetic fields near sharp edges, and construct the leading terms in asymptotic expansions based on numerical solutions. Our integral equations are formulated for rescaled unknown functions to avoid unbounded field components, and are discretized with a graded mesh and properly chosen quadrature schemes. The numerically found singularity exponents agree well with the exact values in all the test cases presented here, indicating that the numerical solutions are accurate.

Adhesion of osteoblasts to a nanorough titanium implant surface

PubMed Central

Gongadze, Ekaterina; Kabaso, Doron; Bauer, Sebastian; Slivnik, Tomaž; Schmuki, Patrik; van Rienen, Ursula; Iglič, Aleš

2011-01-01

This work considers the adhesion of cells to a nanorough titanium implant surface with sharp edges. The basic assumption was that the attraction between the negatively charged titanium surface and a negatively charged osteoblast is mediated by charged proteins with a distinctive quadrupolar internal charge distribution. Similarly, cation-mediated attraction between fibronectin molecules and the titanium surface is expected to be more efficient for a high surface charge density, resulting in facilitated integrin mediated osteoblast adhesion. We suggest that osteoblasts are most strongly bound along the sharp convex edges or spikes of nanorough titanium surfaces where the magnitude of the negative surface charge density is the highest. It is therefore plausible that nanorough regions of titanium surfaces with sharp edges and spikes promote the adhesion of osteoblasts. PMID:21931478

The epitaxial growth of wurtzite ZnO films on LiNbO 3 (0 0 0 1) substrates

NASA Astrophysics Data System (ADS)

Yin, J.; Liu, Z. G.; Liu, H.; Wang, X. S.; Zhu, T.; Liu, J. M.

2000-12-01

ZnO epitaxial films were deposited on LiNbO 3 (0 0 0 1) substrates by pulsed laser deposition. The smaller lattice misfit (-8.5%) between ZnO along <1 0 1¯ 0>- direction and LiNbO 3 (0 0 0 1) along <1 1 2¯ 0>- direction, as compared with that in the case of normally used sapphire (0 0 0 1) substrates, favored the epitaxial growth of ZnO films. The transmittance spectra of ZnO films deposited in vacuum after annealed in pure oxygen show a sharp absorption edge at 375.6 nm (E g=3.31 eV) .

Unexpected solvent effects on the UV/Vis absorption spectra of o-cresol in toluene and benzene: in contrast with non-aromatic solvents

PubMed Central

Zheng, Dong; Yuan, Xiang-Ai; Ma, Haibo; Li, Xiaoxiong; Wang, Xizhang; Liu, Ziteng

2018-01-01

Cresol is a prototype molecule in understanding intermolecular interactions in material and biological systems, because it offers different binding sites with various solvents and protonation states under different pH values. It is found that the UV/Vis absorption spectra of o-cresol in aromatic solvents (benzene, toluene) are characterized by a sharp peak, unlike the broad double-peaks in 11 non-aromatic solvents. Both molecular dynamics simulations and electronic structure calculations revealed the formation of intermolecular π-complexation between o-cresol and aromatic solvents. The thermal movements of solvent and solute molecules render the conformations of o-cresol changing between trans and cis isomers. The π-interaction makes the cis configuration a dominant isomer, hence leading to the single keen-edged UV/Vis absorption peak at approximately 283 nm. The free conformation changes between trans and cis in aqueous solution rationalize the broader absorption peaks in the range of 260–280 nm. The pH dependence of the UV/Vis absorption spectra in aqueous solutions is also rationalized by different protonation states of o-cresol. The explicit solvent model with long-ranged interactions is vital to describe the effects of π-complexation and electrostatic interaction on the UV/Vis absorption spectra of o-cresol in toluene and alkaline aqueous (pH > 10.3) solutions, respectively. PMID:29657794

Unexpected solvent effects on the UV/Vis absorption spectra of o-cresol in toluene and benzene: in contrast with non-aromatic solvents.

PubMed

Zheng, Dong; Yuan, Xiang-Ai; Ma, Haibo; Li, Xiaoxiong; Wang, Xizhang; Liu, Ziteng; Ma, Jing

2018-03-01

Cresol is a prototype molecule in understanding intermolecular interactions in material and biological systems, because it offers different binding sites with various solvents and protonation states under different pH values. It is found that the UV/Vis absorption spectra of o -cresol in aromatic solvents (benzene, toluene) are characterized by a sharp peak, unlike the broad double-peaks in 11 non-aromatic solvents. Both molecular dynamics simulations and electronic structure calculations revealed the formation of intermolecular π-complexation between o -cresol and aromatic solvents. The thermal movements of solvent and solute molecules render the conformations of o -cresol changing between trans and cis isomers. The π-interaction makes the cis configuration a dominant isomer, hence leading to the single keen-edged UV/Vis absorption peak at approximately 283 nm. The free conformation changes between trans and cis in aqueous solution rationalize the broader absorption peaks in the range of 260-280 nm. The pH dependence of the UV/Vis absorption spectra in aqueous solutions is also rationalized by different protonation states of o -cresol. The explicit solvent model with long-ranged interactions is vital to describe the effects of π-complexation and electrostatic interaction on the UV/Vis absorption spectra of o -cresol in toluene and alkaline aqueous (pH > 10.3) solutions, respectively.

Determination of Scattering and Absorption Coefficients for Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings at Elevated Temperatures

NASA Technical Reports Server (NTRS)

Eldridge, Jeffrey I.; Spuckler, Charles M.; Markham, James R.

2009-01-01

The temperature dependence of the scattering and absorption coefficients for a set of freestanding plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) was determined at temperatures up to 1360 C in a wavelength range from 1.2 micrometers up to the 8YSZ absorption edge. The scattering and absorption coefficients were determined by fitting the directional-hemispherical reflectance and transmittance values calculated by a four-flux Kubelka Munk method to the experimentally measured hemispherical-directional reflectance and transmittance values obtained for five 8YSZ thicknesses. The scattering coefficient exhibited a continuous decrease with increasing wavelength and showed no significant temperature dependence. The scattering is primarily attributed to the relatively temperature-insensitive refractive index mismatch between the 8YSZ and its internal voids. The absorption coefficient was very low (less than 1 per centimeter) at wavelengths between 2 micrometers and the absorption edge and showed a definite temperature dependence that consisted of a shift of the absorption edge to shorter wavelengths and an increase in the weak absorption below the absorption edge with increasing temperature. The shift in the absorption edge with temperature is attributed to strongly temperature-dependent multiphonon absorption. While TBC hemispherical transmittance beyond the absorption edge can be predicted by a simple exponential decrease with thickness, below the absorption edge, typical TBC thicknesses are well below the thickness range where a simple exponential decrease in hemispherical transmittance with TBC thickness is expected. [Correction added after online publication August 11, 2009: "edge to a shorter wavelengths" has been updated as edge to shorter wavelengths."

Unsteady aerodynamic analysis of space shuttle vehicles. Part 2: Steady and unsteady aerodynamics of sharp-edged delta wings

NASA Technical Reports Server (NTRS)

Ericsson, L. E.; Reding, J. P.

1973-01-01

An analysis of the steady and unsteady aerodynamics of sharp-edged slender wings has been performed. The results show that slender wing theory can be modified to give the potential flow static and dynamic characteristics in incompressible flow. A semiempirical approximation is developed for the vortex-induced loads, and it is shown that the analytic approximation for sharp-edged slender wings gives good prediction of experimentally determined steady and unsteady aerodynamics at M = 0 and M = 1. The predictions are good not only for delta wings but also for so-called arrow and diamond wings. The results indicate that the effects of delta planform lifting surfaces can be included in a simple manner when determining elastic launch vehicle dynamic characteristics. For Part 1 see (N73-32763).

Vegetation's red edge: a possible spectroscopic biosignature of extraterrestrial plants.

PubMed

Seager, S; Turner, E L; Schafer, J; Ford, E B

2005-06-01

Earth's deciduous plants have a sharp order-of-magnitude increase in leaf reflectance between approximately 700 and 750 nm wavelength. This strong reflectance of Earth's vegetation suggests that surface biosignatures with sharp spectral features might be detectable in the spectrum of scattered light from a spatially unresolved extrasolar terrestrial planet. We assess the potential of Earth's step-function-like spectroscopic feature, referred to as the "red edge," as a tool for astrobiology. We review the basic characteristics and physical origin of the red edge and summarize its use in astronomy: early spectroscopic efforts to search for vegetation on Mars and recent reports of detection of the red edge in the spectrum of Earthshine (i.e., the spatially integrated scattered light spectrum of Earth). We present Earthshine observations from Apache Point Observatory (New Mexico) to emphasize that time variability is key to detecting weak surface biosignatures such as the vegetation red edge. We briefly discuss the evolutionary advantages of vegetation's red edge reflectance, and speculate that while extraterrestrial "light-harvesting organisms" have no compelling reason to display the exact same red edge feature as terrestrial vegetation, they might have similar spectroscopic features at different wavelengths than terrestrial vegetation. This implies that future terrestrial-planet-characterizing space missions should obtain data that allow time-varying, sharp spectral features at unknown wavelengths to be identified. We caution that some mineral reflectance edges are similar in slope and strength to vegetation's red edge (albeit at different wavelengths); if an extrasolar planet reflectance edge is detected care must be taken with its interpretation.

Impact of L/D on 90 Degree Sharp-Edge Orifice Flow with Manifold Passage Cross Flow (Preprint)

DTIC Science & Technology

2007-04-30

that are observed by measurement as the flow transitions from non-cavitation to cavitation (turbulent flow), supercavitation , and finally separation in...include inception of cavitation, supercavitation , and separation. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...cavitation to cavitation (turbulent flow), supercavitation , and finally separation in sharp-edge 90 degree orifices. This study includes orifice L/D from

Numerical investigation of rarefaction effects in the vicinity of a sharp leading edge

NASA Astrophysics Data System (ADS)

Pan, Shaowu; Gao, Zhenxun; Lee, Chunhian

2014-12-01

This paper presents a study of rarefaction effect on hypersonic flow over a sharp leading edge. Both continuum approach and kinetic method: a widely spread commercial Computational Fluid Dynamics-Navior-Stokes-Fourier (CFD-NSF) software - Fluent together with a direct simulation Monte Carlo (DSMC) code developed by the authors are employed for simulation of transition regime with Knudsen number ranging from 0.005 to 0.2. It is found that Fluent can predict the wall fluxes in the case of hypersonic argon flow over the sharp leading edge for the lowest Kn case (Kn = 0.005) in current paper while for other cases it also has a good agreement with DSMC except at the location near the sharp leading edge. Among all of the wall fluxes, it is found that coefficient of pressure is the most sensitive to rarefaction while heat transfer is the least one. A parameter based on translational nonequilibrium and a cut-off value of 0.34 is proposed for continuum breakdown in this paper. The structure of entropy and velocity profile in boundary layer is analyzed. Also, it is found that the ratio of heat transfer coefficient to skin friction coefficient remains uniform along the surface for the four cases in this paper.

Distribution of contact loads over the flank-land of the cutter with a rounded cutting edge

NASA Astrophysics Data System (ADS)

Kozlov, V.; Gerasimov, A.; Kim, A.

2016-04-01

In this paper, contact conditions between a tool and a workpiece material for wear-simulating turning by a cutter with a sharp-cornered edge and with a rounded cutting edge are analysed. The results of the experimental study of specific contact load distribution over the artificial flank wear-land of the cutter in free orthogonal turning of the disk from titanium alloy (Ti6Al2Mo2Cr), ductile (63Cu) and brittle (57Cu1Al3Mn) brasses are described. Investigations were carried out by the method of ‘split cutter’ and by the method of the artificial flank-land of variable width. The experiments with a variable feed rate and a cutting speed show that in titanium alloy machining with a sharp-cornered cutting edge the highest normal contact load (σh max = 3400…2200 MPa) is observed immediately at the cutting edge, and the curve has a horizontal region with the length of 0.2… 0.6 mm. At a distance from the cutting edge, the value of specific normal contact load is dramatically reduced to 1100…500 MPa. The character of normal contact load for a rounded cutting edge is different -it is uniform, and its value is approximately 2 times smaller compared to machining with a sharp-cornered cutting edge. In author’s opinion it is connected with generation of a seizure zone in a chip formation region and explains the capacity of highly worn-out cutting tools for titanium alloys machining. The paper analyses the distribution of tangential contact loads over the flank land, which pattern differs considerably for machining with a sharp-cornered edge and with a rounded cutting edge. Abbreviation and symbols: m/s - meter per second (cutting speed v); mm/r - millimeter per revolution (feed rate f); MPa - mega Pascal (specific contact load as a stress σ or τ) hf - the width of the flank wear land (chamfer) of the cutting tool, flank wear land can be natural or artificial like the one in this paper [mm]; xh - distance from the cutting edge on the surface of the flank-land [mm]; σh - normal specific contact load on the flank land [MPa]; τh - tangential (shear) specific contact load on the flank land [MPa]; HSS - high speed steel (material of cutting tool); Py - radial component of cutting force [N]; Py r - radial component of cutting force on the rake face [N]; Pz - tangential component of cutting force [N]; γ - rake angle of the cutting tool [°] α - clearance angle of the sharp cutting tool [°] αh - clearance angle of the flank wear land [°] ρ - rounding off radius of the cutting edge [mm]; b - width of the machined disk [mm].

Wrinkled substrate and Indium Tin Oxide-free transparent electrode making organic solar cells thinner in active layer

NASA Astrophysics Data System (ADS)

Liu, Kong; Lu, Shudi; Yue, Shizhong; Ren, Kuankuan; Azam, Muhammad; Tan, Furui; Wang, Zhijie; Qu, Shengchun; Wang, Zhanguo

2016-11-01

To enable organic solar cells with a competent charge transport efficiency, reducing the thickness of active layer without sacrificing light absorption efficiency turns out to be of high feasibility. Herein, organic solar cells on wrinkled metal surface are designed. The purposely wrinkled Al/Au film with a smooth surface provides a unique scaffold for constructing thin organic photovoltaic devices by avoiding pinholes and defects around sharp edges in conventional nanostructures. The corresponding surface light trapping effect enables the thin active layer (PTB7-Th:PC71BM) with a high absorption efficiency. With the innovative MoO3/Ag/ZnS film as the top transparent electrode, the resulting Indium Tin Oxide-free wrinkled devices show a power conversion efficiency as 7.57% (50 nm active layer), higher than the planner counterparts. Thus, this paper provides a new methodology to improve the performance of organic solar cells by balancing the mutual restraint factors to a high level.

The Physical Nature of the Sharp Spectral Feature at 7 keV Detected in 1H0707-495

NASA Technical Reports Server (NTRS)

Brandt, Niel

2005-01-01

XMM-Newton acquired data on the accepted target, 1H0707-495, on 2002 October 13 during revolution 0521. The observation was successful, with only about 5% data loss due to background flaring. We compared the data from this observation with earlier data taken on this Narrow-Line Seyfert 1 about two years before, performing interpretation studies in the context of the partial-covering model. Our second longer observation once again displays a sharp (< 200 eV) spectral drop above 7 keV. However, in comparison to the first observation, the edge depth and energy have changed significantly. In addition to changes in the edge parameters, the high-energy spectrum appears steeper. The changes in the high-energy spectrum can be adequately explained in terms of a partial-covering absorber out-flowing from the central region. The low-energy spectrum also shows significant long-term spectral variability, including (1) a substantial increase in the disk temperature, (2) detection of an approx. 0.9 keV emission feature, and (3) the presence of ionized absorption that was detected during the ASCA mission. The large increase in disk temperature, and the more modest rise in luminosity, can be understood if we consider a slim-disk model for 1H0707-495. In addition, the higher disk luminosity could be the driving force behind the outflow and the re-appearance of an ionized medium during the second XMM-Newton observation.

Thermal, optical and vibrational studies of tyrosine doped LaF3:Ce nanoparticles for bioimaging and biotagging

NASA Astrophysics Data System (ADS)

Singh, Amit T.

2018-05-01

Upconversion quantum dots of tyrosine doped LaF3:Ce nanoparticles have been synthesized by wet chemical route. The thermal studies (TGA/DTA) confirm the crystallinity and stability of different phases of synthesized nanoparticles. The UV-Visible spectra show multiple absorption edges at 215.60 nm and 243.10 nm indicating quantum dot nature of the synthesized nanoparticles. The PL spectra showed upconversion with sharp emission peak at 615 nm (red colour). The FT-RAMAN spectra of the synthesized nanoparticles show the modification of the surface of the nanoparticles in the form of functional groups and skeletal groups. Upconversion nature of the synthesized nanoparticles indicates their potential application in bioimaging and biotagging.

Unsteady aerodynamics and vortex-sheet formation of a two-dimensional airfoil

NASA Astrophysics Data System (ADS)

Xia, X.; Mohseni, K.

2017-11-01

Unsteady inviscid flow models of wings and airfoils have been developed to study the aerodynamics of natural and man-made flyers. Vortex methods have been extensively applied to reduce the dimensionality of these aerodynamic models, based on the proper estimation of the strength and distribution of the vortices in the wake. In such modeling approaches, one of the most fundamental questions is how the vortex sheets are generated and released from sharp edges. To determine the formation of the trailing-edge vortex sheet, the classical Kutta condition can be extended to unsteady situations by realizing that a flow cannot turn abruptly around a sharp edge. This condition can be readily applied to a flat plate or an airfoil with cusped trailing edge since the direction of the forming vortex sheet is known to be tangential to the trailing edge. However, for a finite-angle trailing edge, or in the case of flow separation away from a sharp corner, the direction of the forming vortex sheet is ambiguous. To remove any ad-hoc implementation, the unsteady Kutta condition, the conservation of circulation, as well as the conservation laws of mass and momentum are coupled to analytically solve for the angle, strength, and relative velocity of the trailing-edge vortex sheet. The two-dimensional aerodynamic model together with the proposed vortex-sheet formation condition is verified by comparing flow structures and force calculations with experimental results for airfoils in steady and unsteady background flows.

Studies on absorption coefficient near edge of multi elements

NASA Astrophysics Data System (ADS)

Eisa, M. H.; Shen, H.; Yao, H. Y.; Mi, Y.; Zhou, Z. Y.; Hu, T. D.; Xie, Y. N.

2005-12-01

X-ray absorption near edge structure (XANES) was used to study the near edge mass-absorption coefficients of seven elements, such as, Ti, V, Fe, Co, Ni, Cu and Zn. It is well known that, on the near edge absorption of element, when incident X-ray a few eV change can make the absorption coefficient an order magnitude alteration. So that, there are only a few points mass-absorption coefficient at the near edge absorption and that always average value in published table. Our results showed a wide range of data, the total measured data of mass-absorption coefficient of the seven elements was about 505. The investigation confirmed that XANES is useful technique for multi-element absorption coefficient measurement. Details of experimental methods and results are given and discussed. The experimental work has been performed at Beijing Synchrotron Radiation Facility. The measured values were compared with the published data. Good agreement between experimental results and published data is obtained.

Catastrophe optics of sharp-edge diffraction.

PubMed

Borghi, Riccardo

2016-07-01

A classical problem of diffraction theory, namely plane wave diffraction by sharp-edge apertures, is here reformulated from the viewpoint of the fairly new subject of catastrophe optics. On using purely geometrical arguments, properly embedded into a wave optics context, uniform analytical estimates of the diffracted wavefield at points close to fold caustics are obtained, within paraxial approximation, in terms of the Airy function and its first derivative. Diffraction from parabolic apertures is proposed to test reliability and accuracy of our theoretical predictions.

Flow Control Over Sharp-Edged Wings

DTIC Science & Technology

2007-07-01

Gad-el-Hak (2001) as the ability to actively or passively manipulate a flow field to effect a desired change. The challenge is to achieve that change...combinations. Been able to independently control both is a great challenge . These requirements may appear too stringent for the sharp- edged airfoils...06 0𔄁 08 09 lic Vlc Figure 22: Pressure distributions for Model B at a=13 °. Stations I (left); 2 (right) 1 , -2 1 F - [12 1 -6a -16 08 -08 06 -06

Lock-in of elastically mounted airfoils at a 90° angle of attack

NASA Astrophysics Data System (ADS)

Ehrmann, R. S.; Loftin, K. M.; Johnson, S.; White, E. B.

2014-01-01

Reducing vortex-induced vibration (VIV) of elastically mounted cylinders has applications to petroleum, nuclear, and civil engineering. One simple method is streamlining the cylinder into an airfoil shape. However, if flow direction changes, an elastic airfoil could experience similar oscillations with even more drag. To better understand a general airfoil's response, three elastically mounted airfoil shapes are tested at a 90° angle of attack in a 3 ft by 4 ft wind tunnel. The shapes are a NACA 0018, a sharp leading- and trailing-edge (sharp-sharp) model, and a round leading- and trailing-edge (round-round) model. Mass-damping ranges from 0.96 to 1.44. For comparison to canonical VIV research, a cylinder is also tested. Since lock-in occurs near Rec=125×103, the models are also tested with a trip strip. The NACA 0018 and sharp-sharp configuration show nearly identical responses. The cylinder and round-round airfoil have responses five to eight times larger. Thus, the existence of a single sharp edge is sufficient to greatly reduce VIV at 90° angle of attack. Whereas the cylinder and round-round maximum response amplitudes are similar, cylinder lock-in occurs over a velocity range three times larger than the round-round. The tripped cylinder and round-round models' response is attenuated by 70% compared to their respective clean configurations. Hysteresis is only observed in the circular cylinder and round-round models. Hotwire data indicates the clean cylinder has a unique vortex pattern compared to the other configurations.

Unexpected Patterns in Snow and Dirt

NASA Astrophysics Data System (ADS)

Ackerson, Bruce J.

2018-01-01

For more than 30 years, Albert A. Bartlett published "Thermal patterns in the snow" in this journal. These are patterns produced by heat sources underneath the snow. Bartlett's articles encouraged me to pay attention to patterns in snow and to understanding them. At winter's end the last snow becomes dirty and is heaped into piles. This snow comes from the final clearing of sidewalks and driveways. The patterns observed in these piles defied my intuition. This melting snow develops edges where dirt accumulates, in contrast to ice cubes, which lose sharp edges and become more spherical upon melting. Furthermore, dirt absorbs more radiation than snow and yet doesn't melt and round the sharp edges of snow, where dirt accumulates.

Investigation of the Hydraulic Characteristics of Capillary Elements of the Injector Head of Jet Engines under Conditions of Isothermal Flow of A Liquid

NASA Astrophysics Data System (ADS)

Nigodjuk, V. E.; Sulinov, A. V.

2018-01-01

The article presents the results of an experimental study of the hydraulic characteristics of capillary elements of the injector head of jet engines in isothermal fluid flow and the proposed method of their calculation. The main geometric dimensions of the capillaries in the experiment were changed in the following range: Inner diameter from 0.16 to 0.36 mm, length from 4.3 to 158 mm and relative length from 25 to 614 and the inlet edge of the capillaries: sharp or smooth the leading edge. As the working fluid during the tests were distilled water, acetone and ethyl alcohol. Based on the results of a study of the dependences for calculation of ultimate losses in laminar and turbulent flow regimes in capillary tubes with smooth and sharp edges input. The influence of surface tension forces on loss of input on a sharp cutting edge. Experimentally confirmed the possibility of calculating the linear coefficient of hydraulic resistance of capillary tubes with a diameter of 0.16-0.36 mm in isothermal stable during the known dependencies that are valid for hydrodynamically smooth round tube.

How Sharp Does a "Knife Edge" Have to Be?

ERIC Educational Resources Information Center

Dietz, Eric R.; Gash, Philip W.

1994-01-01

Describes an experiment designed to help understand the effect of the curvature of the laboratory equipment support (cylindrical rod instead of knife-edge) on the frequency of oscillation of pendula. (ZWH)

Fundamental aerodynamic characteristics of delta wings with leading-edge vortex flows

NASA Technical Reports Server (NTRS)

Wood, R. M.; Miller, D. S.

1985-01-01

An investigation of the aerodynamics of sharp leading-edge delta wings at supersonic speeds has been conducted. The supporting experimental data for this investigation were taken from published force, pressure, and flow-visualization data in which the Mach number normal to the wing leading edge is always less than 1.0. The individual upper- and lower-surface nonlinear characteristics for uncambered delta wings are determined and presented in three charts. The upper-surface data show that both the normal-force coefficient and minimum pressure coefficient increase nonlinearly with a decreasing slope with increasing angle of attack. The lower-surface normal-force coefficient was shown to be independent of Mach number and to increase nonlinearly, with an increasing slope, with increasing angle of attack. These charts are then used to define a wing-design space for sharp leading-edge delta wings.

Sharp Absorption Peaks in THz Spectra Valuable for Crystal Quality Evaluation of Middle Molecular Weight Pharmaceuticals

NASA Astrophysics Data System (ADS)

Sasaki, Tetsuo; Sakamoto, Tomoaki; Otsuka, Makoto

2018-05-01

Middle molecular weight (MMW) pharmaceuticals (MW 400 4000) are attracting attention for their possible use in new medications. Sharp absorption peaks were observed in MMW pharmaceuticals at low temperatures by measuring with a high-resolution terahertz (THz) spectrometer. As examples, high-resolution THz spectra for amoxicillin trihydrate, atorvastatin calcium trihydrate, probucol, and α,β,γ,δ-tetrakis(1-methylpyridinium-4-yl)porphyrin p-toluenesulfonate (TMPyP) were obtained at 10 K. Typically observed as peaks with full width at half-height (FWHM) values as low as 5.639 GHz at 0.96492 THz in amoxicillin trihydrate and 8.857 GHz at 1.07974 THz for probucol, many sharp peaks of MMW pharmaceuticals could be observed. Such narrow absorption peaks enable evaluation of the crystal quality of MMW pharmaceuticals and afford sensitive detection of impurities.

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

Dixon, William V.; Chayer, Pierre, E-mail: dixon@stsci.edu, E-mail: chayer@stsci.edu

The far-ultraviolet spectrum of the Bright Star (B8 III) in 47 Tuc (NGC 104) shows a remarkable pattern: it is well fit by local thermodynamic equilibrium models at wavelengths longer than Ly{beta}, but at shorter wavelengths it is fainter than the models by a factor of two. A spectrum of this star obtained with the Far Ultraviolet Spectroscopic Explorer shows broad absorption troughs with sharp edges at 995 and 1010 A and a deep absorption feature at 1072 A; none of which are predicted by the models. We find that these features are caused by resonances in the photoionization crossmore » sections of the first and second excited states of atomic nitrogen (2s {sup 2} 2p {sup 3} {sup 2} D {sup 0} and {sup 2} P {sup 0}). Using cross sections from the Opacity Project, we can reproduce these features, but only if we use the cross sections at their full resolution, rather than the resonance-averaged cross sections usually employed to model stellar atmospheres. These resonances are strongest in stellar atmospheres with enhanced nitrogen and depleted carbon abundances, a pattern typical of post-asymptotic giant branch stars.« less

Simulation of Acoustic Scattering from a Trailing Edge

NASA Technical Reports Server (NTRS)

Singer, Bart A.; Brentner, Kenneth S.; Lockard, David P.; Lilley, Geoffrey M.

1999-01-01

Three model problems were examined to assess the difficulties involved in using a hybrid scheme coupling flow computation with the the Ffowcs Williams and Hawkings equation to predict noise generated by vortices passing over a sharp edge. The results indicate that the Ffowcs Williams and Hawkings equation correctly propagates the acoustic signals when provided with accurate flow information on the integration surface. The most difficult of the model problems investigated inviscid flow over a two-dimensional thin NACA airfoil with a blunt-body vortex generator positioned at 98 percent chord. Vortices rolled up downstream of the blunt body. The shed vortices possessed similarities to large coherent eddies in boundary layers. They interacted and occasionally paired as they convected past the sharp trailing edge of the airfoil. The calculations showed acoustic waves emanating from the airfoil trailing edge. Acoustic directivity and Mach number scaling are shown.

Ripples Beside Pahrump Hills Outcrop at Base of Mount Sharp

NASA Image and Video Library

2014-11-18

This northeast-facing view from the lower edge of the pale Pahrump Hills outcrop at the base of Mount Sharp includes wind-sculpted ripples of sand and dust in the middle ground. It was taken by Curiosity Navcam on Nov. 13, 2014.

The red edge in arid region vegetation: 340-1060 nm spectra

NASA Technical Reports Server (NTRS)

Ray, Terrill W.; Murray, Bruce C.; Chehbouni, A.; Njoku, Eni

1993-01-01

The remote sensing study of vegetated regions of the world has typically been focused on the use of broad-band vegetation indices such as NDVI. Various modifications of these indices have been developed in attempts to minimize the effect of soil background, e.g., SAVI, or to reduce the effect of the atmosphere, e.g., ARVI. Most of these indices depend on the so-called 'red edge,' the sharp transition between the strong absorption of chlorophyll pigment in visible wavelengths and the strong scattering in the near-infrared from the cellular structure of leaves. These broadband indices tend to become highly inaccurate as the green canopy cover becomes sparse. The advent of high spectral resolution remote sensing instrument such as the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) has allowed the detection of narrow spectral features in vegetation and there are reports of detection of the red edge even for pixels with very low levels of green vegetation cover by Vane et al. and Elvidge et al., and to characterize algal biomass in coastal areas. Spectral mixing approaches similar to those of Smith et al. can be extended into the high spectral resolution domain allowing for the analysis of more endmembers, and potentially, discrimination between material with narrow spectral differences. Vegetation in arid regions tends to be sparse, often with small leaves such as the creosote bush. Many types of arid region vegetation spend much of the year with their leaves in a senescent state, i.e., yellow, with lowered chlorophyll pigmentation. The sparseness of the leaves of many arid region plants has the dual effect of lowering the green leaf area which can be observed and of allowing more of the sub-shrub soil to be visible which further complicates the spectrum of a region covered with arid region vegetation. Elvidge examined the spectral characteristics of dry plant materials showing significant differences in the region of the red edge and the diagnostic ligno-cellulose absorptions at 2090 nm and 2300 nm. Ray et al. detected absorption at 2100 nm in AVIRIS spectra of an abandoned field known to be covered by a great deal of dead plant litter. In order to better study arid region vegetation remote sensing data, it is necessary to better characterize the reflectance spectra of in situ, living, arid region plants.

Toward understanding as photosynthetic biosignatures: light harvesting and energy transfer calculation

NASA Astrophysics Data System (ADS)

Komatsu, Y.; Umemura, M.; Shoji, M.; Shiraishi, K.; Kayanuma, M.; Yabana, K.

2014-03-01

Among several proposed biosignatures, red edge is a direct evidence of photosynthetic life if it is detected (Kiang et al 2007). Red edge is a sharp change in reflectance spectra of vegetation in NIR region (about 700-750 nm). The sign of red edge is observed by Earthshine or remote sensing (Wolstencroft & Raven 2002, Woolf et al 2002). But, why around 700-750 nm? The photosynthetic organisms on Earth have evolved to optimize the sunlight condition. However, if we consider about photosynthetic organism on extrasolar planets, they should have developed to utilize the spectra of its principal star. Thus, it is not strange even if it shows different vegetation spectra. In this study, we focused on the light absorption mechanism of photosynthetic organisms on Earth and investigated the fundamental properties of the light harvesting mechanisms, which is the first stage for the light absorption. Light harvesting complexes contain photosynthetic pigments like chlorophylls. Effective light absorption and the energy transfer are accomplished by the electronic excitations of collective photosynthetic pigments. In order to investigate this mechanism, we constructed an energy transfer model by using a dipole-dipole approximation for the interactions between electronic excitations. Transition moments and transition energies of each pigment are calculated at the time-dependent density functional theory (TDDFT) level (Marques & Gross 2004). Quantum dynamics simulation for the excitation energy transfer was calculated by the Liouvelle's equation. We adopted the model to purple bacteria, which has been studied experimentally and known to absorb lower energy. It is meaningful to focus on the mechanism of this bacteria, since in the future mission, M planets will become a important target. We calculated the oscillator strengths in one light harvesting complex and confirmed the validity by comparing to the experimental data. This complex is made of an inner and an outer ring. The energy transfer from the outer to the inner ring can be reproduced. To deal with a realistic system, we calculated at a macro structural model. The energy transfer between light harvesting complexes is accomplished rapidly via inner rings. By exchange the original pigment to a pigment absorb lower energy, faster energy transfer occurs and the density was trapped in pigment having lower energy. We will compare the result of purple bacteria, which is considered to show longer red edge, cyanobacteria and plants.

Improved liquid-film electron stripper

DOEpatents

Gavin, B.F.

1984-11-01

An improved liquid-film electron stripper particularly for high intensity heavy ion beams which produces constant regenerated, stable, free-standing liquid films having an adjustable thickness between 0.3 to 0.05 microns. The improved electron stripper is basically composed of at least one high speed, rotating disc with a very sharp, precision-like, ground edge on one side of the disc's periphery and with highly polished, flat, radial surface adjacent the sharp edge. A fine stream of liquid, such as oil, impinges at a 90/sup 0/ angle adjacent the disc's sharp outer edge. Film terminators, located at a selected distance from the disc perimeter are positioned approximately perpendicular to the film. The terminators support, shape, and stretch the film and are arranged to assist in the prevention of liquid droplet formation by directing the collected film to a reservoir below without breaking or interfering with the film. One embodiment utilizes two rotating discs and associated terminators, with the discs rotating so as to form films in opposite directions, and with the second disc being located down beam-line relative to the first disc.

Liquid-film electron stripper

DOEpatents

Gavin, Basil F.

1986-01-01

An improved liquid-film electron stripper particularly for high intensity heavy ion beams which produces constant regenerated, stable, free-standing liquid films having an adjustable thickness between 0.3 to 0.05 microns. The improved electron stripper is basically composed of at least one high speed, rotating disc with a very sharp, precision-like, ground edge on one said of the disc's periphery and with a highly polished, flat, radial surface adjacent the sharp edge. A fine stream of liquid, such as oil, impinges at a 90.degree. angle adjacent the disc's sharp outer edge. Film terminators, located at a selected distance from the disc perimeter are positioned approximately perpendicular to the film. The terminators support, shape, and stretch the film and are arranged to assist in the prevention of liquid droplet formation by directing the collected film to a reservoir below without breaking or interfering with the film. One embodiment utilizes two rotating discs and associated terminators, with the discs rotating so as to form films in opposite directions, and with the second disc being located down beam-line relative to the first disc.

Fatal Injuries of Law Enforcement/Correctional Officers Attacked with Sharp-Edged Weapons.

PubMed

Chenpanas, Patsy; Bir, Cynthia

2017-05-01

According to the National Law Enforcement Memorial Fund, there were 117 law enforcement fatalities in the United States in 2015. Assaults with sharp-edged weapons have resulted in a total of over 400 fatalities in the United States. The goal of the current research was to examine sharp-edged weapon assaults against law enforcement and correctional agents that resulted in a fatal outcome. A total of twelve autopsy reports were reviewed from across the United States. Four cases involved law enforcement officers, seven involved correctional officers, and one was an off-duty border officer. The male-to-female ratio was 11:1. A total of 70.2% of the wounds analyzed were stab wounds (n = 85), and 29.8% of the wounds were slash wounds (n = 36). Based on this review, the neck, shoulder, and chest regions were the most vulnerable to single fatal stab/slash wounds. Multiple stab/slash wounds often resulted in exsanguination. The use of body armor was only noted in one case. © 2016 American Academy of Forensic Sciences.

Supersonic Leading Edge Receptivity

NASA Technical Reports Server (NTRS)

Maslov, Anatoly A.

1998-01-01

This paper describes experimental studies of leading edge boundary layer receptivity for imposed stream disturbances. Studies were conducted in the supersonic T-325 facility at ITAM and include data for both sharp and blunt leading edges. The data are in agreement with existing theory and should provide guidance for the development of more complete theories and numerical computations of this phenomena.

Measurements of Thermal Effects on Acoustic Screech in a Choked Circular Jet Emanating from a Sharp-Edged Orifice

NASA Technical Reports Server (NTRS)

Kandula, Max

2012-01-01

Experiments are performed in a 24.4 mm diameter choked circular hot and cold jets issuing from a sharp-edged orifice at a fully expanded jet Mach number of 1.85. The stagnation temperature of the hot and the cold jets are 319 K and 299 K respectively. The results suggest that temperature effects on the screech amplitude and frequency are manifested for the fundamental, with a reduced amplitude and increased frequency for hot jet relative to the cold jet. Temperature effects on the second harmonic are also observed.

Fundamental edge broadening effects during focused electron beam induced nanosynthesis

DOE PAGES

Schmied, Roland; Fowlkes, Jason Davidson; Winkler, Robert; ...

2015-02-16

In this study, we explore lateral broadening effects of 3D structures fabricated through focused electron beam induced deposition using MeCpPt(IV)Me 3 precursor. In particular, the scaling behavior of proximity effects as a function of the primary electron energy and the deposit height is investigated through experiments and validated through simulations. Correlated Kelvin force microscopy and conductive atomic force microscopy measurements identified conductive and non-conductive proximity regions. It was determined that the highest primary electron energies enable the highest edge sharpness while lower energies contain a complex convolution of broadening effects. In addition, it is demonstrated that intermediate energies lead tomore » even more complex proximity effects that significantly reduce lateral edge sharpness and thus should be avoided if desiring high lateral resolution.« less

Modeling of Electron Transpiration Cooling for Leading Edges of Hypersonic Vehicles

NASA Astrophysics Data System (ADS)

Hanquist, Kyle Matthew

The development of aeronautics has been largely driven by the passion to fly faster. From the flight of the Wright Flyer that flew 48 km/hr to the recent advances in hypersonic flight, most notably NASA's X-43A that flew at over 3 km/s, the velocity of flight has steadily increased. However, as these hypersonic speeds are reached and increased, contradicting aerothermodynamic design requirements present themselves. For example, a hypersonic cruise vehicle requires sharp leading edges to decrease the drag in order to maximize the range. However, the aerodynamic performance gains obtained by having a sharp leading edge come at the cost of very high, localized heating rates. There is currently no ideal way to manage these heating loads for sustained hypersonic flight, especially as flight velocities continue to increase. An approach that has been recently proposed involves using thermo-electric materials on these sharp leading edges to manage the heating loads. When exposed to high convective heating rates, these materials emit a current of electrons that leads to a cooling effect of the surface of the vehicle called electron transpiration cooling (ETC). This dissertation focuses on developing a modeling approach to investigate this phenomenon. The research includes developing and implementing an approach for ETC into a computational fluid dynamics code for simulation of hypersonic flow that accounts for electron emission from the surface. Models for space-charge-limited emission are also developed and implemented in order to accurately determine the level of emission from the surface. This work involves developing analytic models and assessing them using a direct-kinetic plasma sheath solver. Electric field effects are also implemented in the modeling approach, which accounts for forced diffusion and Joule heating. Finally, the modeling approach is coupled to a material response code in order to model the heat transfer into the material surface. Using this modeling approach, ETC is investigated as a viable technology for a wide range of hypersonic operating conditions. This includes altitudes between 30 and 60 km, freestream velocities between 4 and 8 km/s, and leading edge radii between 1 mm and 10 cm. The results presented in this study show that ETC can reduce the leading edge temperature significantly for certain conditions, most notably from 3120 to 1660 K for Mach 26 flight for a sharp leading edge (1 cm). However, at lower velocities, the cooling effect can be diminished by space-charge limits in the plasma sheath. ETC is shown to be most effective at cooling hotter surfaces (e.g. high freestream velocities and sharp leading edges) and the level of ionization in the flowfield can help the emission overcome space-charge limits. The modeling approach is assessed using experiments from the 1960s where thermionic emission was investigated as a mode of power generation for reentry vehicles. The computational results produce a wide range of emitted current due to the uncertainty in the freestream conditions and material properties, but they still agree well with the experiments. Overall, this work indicates that ETC is a viable method of managing the immense heat loads on sharp leading edges during hypersonic flight for certain conditions and motivates future work in the area both computationally and experimentally.

Absorption-Edge-Modulated Transmission Spectra for Water Contaminant Monitoring

DTIC Science & Technology

2016-03-31

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--16-9675 Absorption-Edge-Modulated Transmission Spectra for Water Contaminant ...ABSTRACT c. THIS PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Absorption-Edge-Modulated Transmission Spectra for Water Contaminant Monitoring...Unlimited Unclassified Unlimited 35 Samuel G. Lambrakos (202) 767-2601 Monitoring of contaminants associated with specific water resources using

The development of a tunable, single-frequency ultraviolet laser source for UV filtered Rayleigh scattering

NASA Technical Reports Server (NTRS)

Finkelstein, N.; Gambogi, J.; Lempert, Walter R.; Miles, Richard B.; Rines, G. A.; Finch, A.; Schwarz, R. A.

1995-01-01

We present the development of a flexible, high power, narrow line width, tunable ultraviolet source for diagnostic application. By frequency tripling the output of a pulsed titanium-sapphire laser, we achieve broadly tunable (227-360 nm) ultraviolet light with high quality spatial and spectral resolution. We also present the characterization of a mercury vapor cell which provides a narrow band, sharp edge absorption filter at 253.7 nm. These two components form the basis for the extension of the Filtered Rayleigh Scattering technique into the ultraviolet. The UV-FRS system is comprised of four pieces: a single frequency, cw tunable Ti:Sapphire seeding source; a high-powered pulsed Ti:Sapphire oscillator; a third harmonic generator system; and an atomic mercury vapor filter. In this paper we discuss the development and characterization of each of these elements.

Atomic multiplets at the L2,3 edge of 3d transition metals and the ligand K edge in x-ray absorption spectroscopy of ionic systems

NASA Astrophysics Data System (ADS)

Olalde-Velasco, P.; Jiménez-Mier, J.; Denlinger, J.; Yang, W.-L.

2013-06-01

Experimental X-ray absorption spectra at the fluorine K and transition metal L2,3 absorption edges of the MF2 (M=Cr-Ni) family are presented. Ligand field calculations in D4h symmetry show very good agreement with the transition metal L2,3 XAS spectra. To successfully explain nominal Cr2+ L2,3 XAS spectrum in CrF2, the inclusion of Cr+ and Cr3+ was needed implying the presence of a disproportionation reaction. The multiplet calculations were then modified to remove the structure of the 2p hole in the calculated M 2p→3d absorption spectra. These results for the 3dn+1 states are in one to one correspondence with the leading edge structures found at the fluorine K edge. A direct comparison with the metal L2,3 edges also indicates that there is evidence of the metal multiplet at the fluorine K pre-edge structures.

The risk of capsular breakage from phacoemulsification needle contact with the lens capsule: a laboratory study.

PubMed

Meyer, Jay J; Kuo, Annie F; Olson, Randall J

2010-06-01

To determine capsular breakage risk from contact by phacoemulsification needles by machine and tip type. Experimental laboratory investigation. Infiniti (Alcon, Inc.) with Intrepid cartridges and Signature (Abbott Medical Optics, Inc.) phacoemulsification machines were tested using 19- and 20-gauge sharp and rounded tips. Actual and unoccluded flow vacuum were determined at 550 mm Hg, bottle height of 75 cm, and machine-indicated flow rate of 60 mL/minute. Breakage from brief tip contact with a capsular surrogate and human cadaveric lenses was calculated. Nineteen-gauge tips had more flow and less unoccluded flow vacuum than 20-gauge tips for both machines, with highest unoccluded flow vacuum in the Infiniti. The 19-gauge sharp tip was more likely than the 20-gauge sharp tip to cause surrogate breakage for Signature with micropulse and Ellips (Abbott Medical Optics, Inc.) ultrasound at 100% power. For Infiniti using OZil (Alcon, Inc.) ultrasound, 20-gauge sharp tips were more likely than 19-gauge sharp tips to break the membrane. For cadaveric lenses, using rounded 20-gauge tips at 100% power, breakage rates were micropulse (2.3%), Ellips (2.3%), OZil (5.3%). Breakage rates for sharp 20-gauge Ellips tips were higher than for rounded tips. Factors influencing capsular breakage may include active vacuum at the tip, flow rate, needle gauge, and sharpness. Nineteen-gauge sharp tips were more likely than 20-gauge tips to cause breakage in lower vacuum methods. For higher-vacuum methods, breakage is more likely with 20-gauge than with 19-gauge tips. Rounded-edge tips are less likely than sharp-edged tips to cause breakage. Copyright 2010 Elsevier Inc. All rights reserved.

Si K EDGE STRUCTURE AND VARIABILITY IN GALACTIC X-RAY BINARIES

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

Schulz, Norbert S.; Corrales, Lia; Canizares, Claude R.

2016-08-10

We survey the Si K edge structure in various absorbed Galactic low-mass X-ray binaries (LMXBs) to study states of silicon in the inter- and circum-stellar medium. The bulk of these LMXBs lie toward the Galactic bulge region and all have column densities above 10{sup 22} cm{sup −2}. The observations were performed using the Chandra High Energy Transmission Grating Spectrometer. The Si K edge in all sources appears at an energy value of 1844 ± 0.001 eV. The edge exhibits significant substructure that can be described by a near edge absorption feature at 1849 ± 0.002 eV and a far edgemore » absorption feature at 1865 ± 0.002 eV. Both of these absorption features appear variable with equivalent widths up to several mÅ. We can describe the edge structure using several components: multiple edge functions, near edge absorption excesses from silicates in dust form, signatures from X-ray scattering optical depths, and a variable warm absorber from ionized atomic silicon. The measured optical depths of the edges indicate much higher values than expected from atomic silicon cross sections and interstellar medium abundances, and they appear consistent with predictions from silicate X-ray absorption and scattering. A comparison with models also indicates a preference for larger dust grain sizes. In many cases, we identify Si xiii resonance absorption and determine ionization parameters between log ξ = 1.8 and 2.8 and turbulent velocities between 300 and 1000 km s{sup −1}. This places the warm absorber in close vicinity of the X-ray binaries. In some data, we observe a weak edge at 1.840 keV, potentially from a lesser contribution of neutral atomic silicon.« less

Enhancement of broadband optical absorption in photovoltaic devices by band-edge effect of photonic crystals.

PubMed

Tanaka, Yoshinori; Kawamoto, Yosuke; Fujita, Masayuki; Noda, Susumu

2013-08-26

We numerically investigate broadband optical absorption enhancement in thin, 400-nm thick microcrystalline silicon (µc-Si) photovoltaic devices by photonic crystals (PCs). We realize absorption enhancement by coupling the light from the free space to the large area resonant modes at the photonic band-edge induced by the photonic crystals. We show that multiple photonic band-edge modes can be produced by higher order modes in the vertical direction of the Si photovoltaic layer, which can enhance the absorption on multiple wavelengths. Moreover, we reveal that the photonic superlattice structure can produce more photonic band-edge modes that lead to further optical absorption. The absorption average in wavelengths of 500-1000 nm weighted to the solar spectrum (AM 1.5) increases almost twice: from 33% without photonic crystal to 58% with a 4 × 4 period superlattice photonic crystal; our result outperforms the Lambertian textured structure.

Two-photon absorption of soft X-ray free electron laser radiation by graphite near the carbon K-absorption edge

NASA Astrophysics Data System (ADS)

Lam, Royce K.; Raj, Sumana L.; Pascal, Tod A.; Pemmaraju, C. D.; Foglia, Laura; Simoncig, Alberto; Fabris, Nicola; Miotti, Paolo; Hull, Christopher J.; Rizzuto, Anthony M.; Smith, Jacob W.; Mincigrucci, Riccardo; Masciovecchio, Claudio; Gessini, Alessandro; De Ninno, Giovanni; Diviacco, Bruno; Roussel, Eleonore; Spampinati, Simone; Penco, Giuseppe; Di Mitri, Simone; Trovò, Mauro; Danailov, Miltcho B.; Christensen, Steven T.; Sokaras, Dimosthenis; Weng, Tsu-Chien; Coreno, Marcello; Poletto, Luca; Drisdell, Walter S.; Prendergast, David; Giannessi, Luca; Principi, Emiliano; Nordlund, Dennis; Saykally, Richard J.; Schwartz, Craig P.

2018-07-01

We have examined the transmission of soft X-ray pulses from the FERMI free electron laser through carbon films of varying thickness, quantifying nonlinear effects of pulses above and below the carbon K-edge. At typical of soft X-ray free electron laser intensities, pulses exhibit linear absorption at photon energies above and below the K-edge, ∼308 and ∼260 eV, respectively; whereas two-photon absorption becomes significant slightly below the K-edge, ∼284.2 eV. The measured two-photon absorption cross section at 284.18 eV (∼6 × 10-48 cm4 s) is 7 orders of magnitude above what is expected from a simple theory based on hydrogen-like atoms - a result of resonance effects.

Operando Soft X-ray Absorption Spectroscopic Study on a Solid Oxide Fuel Cell Cathode during Electrochemical Oxygen Reduction.

PubMed

Nakamura, Takashi; Oike, Ryo; Kimura, Yuta; Tamenori, Yusuke; Kawada, Tatsuya; Amezawa, Koji

2017-05-09

An operando soft X-ray absorption spectroscopic technique, which enabled the analysis of the electronic structures of the electrode materials at elevated temperature in a controlled atmosphere and electrochemical polarization, was established and its availability was demonstrated by investigating the electronic structural changes of an La 2 NiO 4+δ dense-film electrode during an electrochemical oxygen reduction reaction. Clear O K-edge and Ni L-edge X-ray absorption spectra could be obtained below 773 K under an atmospheric pressure of 100 ppm O 2 /He, 0.1 % O 2 /He, and 1 % O 2 /He gas mixtures. Considerable spectral changes were observed in the O K-edge X-ray absorption spectra upon changing the PO2 and application of electrical potential, whereas only small spectral changes were observed in Ni L-edge X-ray absorption spectra. A pre-edge peak of the O K-edge X-ray absorption spectra, which reflects the unoccupied partial density of states of Ni 3d-O 2p hybridization, increased or decreased with cathodic or anodic polarization, respectively. The electronic structural changes of the outermost orbital of the electrode material due to electrochemical polarization were successfully confirmed by the operando X-ray absorption spectroscopic technique developed in this study. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

29 CFR 1910.145 - Specifications for accident prevention signs and tags.

Code of Federal Regulations, 2014 CFR

2014-07-01

... from sharp edges, burrs, splinters, or other sharp projections. The ends or heads of bolts or other... portion of a tag's inscription that is more specific than the signal word and that indicates the specific... convey a safety instruction. Signal word means that portion of a tag's inscription that contains the word...

Force Modelling in Orthogonal Cutting Considering Flank Wear Effect

NASA Astrophysics Data System (ADS)

Rathod, Kanti Bhikhubhai; Lalwani, Devdas I.

2017-05-01

In the present work, an attempt has been made to provide a predictive cutting force model during orthogonal cutting by combining two different force models, that is, a force model for a perfectly sharp tool plus considering the effect of edge radius and a force model for a worn tool. The first force model is for a perfectly sharp tool that is based on Oxley's predictive machining theory for orthogonal cutting as the Oxley's model is for perfectly sharp tool, the effect of cutting edge radius (hone radius) is added and improve model is presented. The second force model is based on worn tool (flank wear) that was proposed by Waldorf. Further, the developed combined force model is also used to predict flank wear width using inverse approach. The performance of the developed combined total force model is compared with the previously published results for AISI 1045 and AISI 4142 materials and found reasonably good agreement.

Two-Photon Absorption of Soft X-Ray Free Electron Laser Radiation by Graphite Near the Carbon K-Absorption Edge

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

Christensen, Steven T; Lam, Royce K.; Raj, Sumana L.

We have examined the transmission of soft X-ray pulses from the FERMI free electron laser through carbon films of varying thickness, quantifying nonlinear effects of pulses above and below the carbon K-edge. At typical of soft X-ray free electron laser intensities, pulses exhibit linear absorption at photon energies above and below the K-edge, ~308 and ~260 eV, respectively; whereas two-photon absorption becomes significant slightly below the K-edge, ~284.2 eV. The measured two-photon absorption cross section at 284.18 eV (~6 x 10-48 cm4 s) is 7 orders of magnitude above what is expected from a simple theory based on hydrogen-like atomsmore » - a result of resonance effects.« less

Nanoporous structures on ZnO thin films

NASA Astrophysics Data System (ADS)

Gür, Emre; Kılıç, Bayram; Coşkun, C.; Tüzemen, S.; Bayrakçeken, Fatma

2010-01-01

Porous structures were formed on ZnO thin films which were grown by an electrochemical deposition (ECD) method. The growth processes were carried out in a solution of dimethylsulfoxide (DMSO) zinc perchlorate, Zn(ClO 4) 2, at 120 ∘C on indium tin oxide (ITO) substrates. Optical and structural characterizations of electrochemically grown ZnO thin films have shown that the films possess high (0002) c-axis orientation, high nucleation, high intensity and low FWHM of UV emission at the band edge region and a sharp UV absorption edge. Nanoporous structures were formed via self-assembled monolayers (SAMs) of hexanethiol (C 6SH) and dodecanethiol (C 12SH). Scanning electron microscope (SEM) measurements showed that while a nanoporous structure (pore radius 20 nm) is formed on the ZnO thin films by hexanathiol solution, a macroporous structure (pore radius 360 nm) is formed by dodecanethiol solution. No significant variation is observed in X-ray diffraction (XRD) measurements on the ZnO thin films after pore formation. However, photoluminescence (PL) measurements showed that green emission is observed as the dominant emission for the macroporous structures, while no variation is observed for the thin film nanoporous ZnO sample.

Surface-Pressure and Flow-Visualization Data at Mach Number of 1.60 for Three 65 deg Delta Wings Varying in Leading-Edge Radius and Camber

NASA Technical Reports Server (NTRS)

McMillin, S. Naomi; Bryd, James E.; Parmar, Devendra S.; Bezos-OConnor, Gaudy M.; Forrest, Dana K.; Bowen, Susan

1996-01-01

An experimental investigation of the effect of leading-edge radius, camber, Reynolds number, and boundary-layer state on the incipient separation of a delta wing at supersonic speeds was conducted at the Langley Unitary Plan Wind Tunnel at Mach number of 1.60 over a free-stream Reynolds number range of 1 x 106 to 5 x 106 ft-1. The three delta wing models examined had a 65 deg swept leading edge and varied in cross-sectional shape: a sharp wedge, a 20:1 ellipse, and a 20:1 ellipse with a -9.750 circular camber imposed across the span. The wings were tested with and without transition grit applied. Surface-pressure coefficient data and flow-visualization data indicated that by rounding the wing leading edge or cambering the wing in the spanwise direction, the onset of leading-edge separation on a delta wing can be raised to a higher angle of attack than that observed on a sharp-edged delta wing. The data also showed that the onset of leading-edge separation can be raised to a higher angle of attack by forcing boundary-layer transition to occur closer to the wing leading edge by the application of grit or the increase in free-stream Reynolds number.

Addressing challenges of modulation transfer function measurement with fisheye lens cameras

NASA Astrophysics Data System (ADS)

Deegan, Brian M.; Denny, Patrick E.; Zlokolica, Vladimir; Dever, Barry; Russell, Laura

2015-03-01

Modulation transfer function (MTF) is a well defined and accepted method of measuring image sharpness. The slanted edge test, as defined in ISO12233 is a standard method of calculating MTF, and is widely used for lens alignment and auto-focus algorithm verification. However, there are a number of challenges which should be considered when measuring MTF in cameras with fisheye lenses. Due to trade-offs related Petzval curvature, planarity of the optical plane is difficult to achieve in fisheye lenses. It is therefore critical to have the ability to accurately measure sharpness throughout the entire image, particularly for lens alignment. One challenge for fisheye lenses is that, because of the radial distortion, the slanted edges will have different angles, depending on the location within the image and on the distortion profile of the lens. Previous work in the literature indicates that MTF measurements are robust for angles between 2 and 10 degrees. Outside of this range, MTF measurements become unreliable. Also, the slanted edge itself will be curved by the lens distortion, causing further measurement problems. This study summarises the difficulties in the use of MTF for sharpness measurement in fisheye lens cameras, and proposes mitigations and alternative methods.

X-Ray Absorption near Edge Structure Spectroscopy of Nanodiamonds from the Allende Meteorite

NASA Technical Reports Server (NTRS)

Flynn, G. J.; Keller, L. P.; Hill, H.; Jacobsen, C.; Wirick, S.

2000-01-01

Carbon X-ray Absorption Near Edge Structure Spectroscopy shows Allende DM nanodiamonds have two pre-edge peaks, consistent with other small diamonds, but fail to show a diamond exciton which is seen in 3.6 nm diamond thin films.

PbS nanosculptured thin film for phase retarder, anti-reflective, excellent absorber, polarizer and sensor applications

NASA Astrophysics Data System (ADS)

Chaudhary, Ashok; Klebanov, Matvey; Abdulhalim, Ibrahim

2015-11-01

Lead-sulphide (PbS) nanosculptured thin film (nSTF) is prepared using a glancing angle deposition (GLAD) technique and the physical vapour deposition (PVD) process. The morphology of the GLAD films clearly shows that an anisotropic structure is obtained and is composed of micro-sheets with sharp top edges (a few tens of nanometres tip width). Due to this anisotropy, optical birefringence is induced in the nSTF as well as linear dichroism. The structural and optical properties of the PbS nSTF have been characterized by scanning electron microscopy, atomic force microscopy, Raman spectroscopy and transmission measurements. The Raman spectra of PbS nSTF exhibit sharp peaks representative of vibrations in nano-crystalline PbS. Due to the absorption of PbS the nSTF is found to act as a linear polarizer with good extinction and contrast in the near infra-red range. Due to its porosity this nSTF also has the ability to sense fluids, which we demonstrate using ethanol-water solution at different concentrations. The combination of these effects in PbS nSTF is believed to constitute a prime candidate for many desirable device applications in different aspects with the low cost of production in large areas.

Pb0.65Mn2.85Ga3S8 and Pb0.72Mn2.84Ga2.95Se8: Two Quaternary Metal Chalcognides with Open-Tunnel-Framework Structures Displaying Intense Second Harmonic Generation Responses and Interesting Magnetic Properties.

PubMed

Zhou, Molin; Jiang, Xingxing; Guo, Yangwu; Lin, Zheshuai; Yao, Jiyong; Wu, Yicheng

2017-07-17

By combining different nonlinear optical-active structural chromophores with transition metal Mn into a crystal structure, two novel quaternary metal chalcogenides Pb 0.65 Mn 2.85 Ga 3 S 8 (1) and Pb 0.72 Mn 2.84 Ga 2.95 Se 8 (2) were successfully synthesized. Compounds 1 and 2 are isostructural, and they represent a new structure type that crystallizes in the space group P6̅ (No. 174) in the hexagonal system. Their structures feature an interesting three-dimensional open-tunnel framework composed of bridged infinite chains with Pb 2+ cations filling in the biggest tunnels. Interestingly, both 1 and 2 demonstrate intense second harmonic generation responses at 2.09 μm that is about 1.5 and 4.4 times, respectively, of that of the benchmark material AgGaS 2 . However, 1 and 2 possess different optical diffuse reflectance spectra: 1 displays an evident multiband absorption characteristic with two distinguishing absorption edges of 738 and 551 nm, corresponding to two band gaps of 1.68 and 2.25 eV, respectively, while 2 exhibits only one sharp edge, and the corresponding band gap was estimated to be 1.65 eV. Moreover, apart from the considerable structural similarity between 1 and 2, the dc temperature dependent susceptibility measurements indicate that compound 1 is paramagnetic, while compound 2 exhibits spin-glass-like behavior.

Experimental investigation of leading-edge thrust at supersonic speeds

NASA Technical Reports Server (NTRS)

Wood, R. M.; Miller, D. S.

1983-01-01

Wings, designed for leading edge thrust at supersonic speeds, were investigated in the Unitary Plan Wind Tunnel at Mach numbers of 1.60, 1.80, 2.00, 2.16, and 2.36. Experimental data were obtained on a uncambered wing which had three interchangeable leading edges that varied from sharp to blunt. The leading edge thrust concept was evaluated. Results from the investigation showed that leading edge flow separation characteristics of all wings tested agree well with theoretical predictions. The experimental data showed that significant changes in wing leading edge bluntness did not affect the zero lift drag of the uncambered wings.

Photoionization of the Fe lons: Structure of the K-Edge

NASA Technical Reports Server (NTRS)

Palmeri, P.; Mendoza, C.; Kallman, T.; Bautista, M.; White, Nicholas E. (Technical Monitor)

2002-01-01

X-ray absorption and emission features arising from the inner-shell transitions in iron are of practical importance in astrophysics due to the Fe cosmic abundance and to the absence of traits from other elements in the nearby spectrum. As a result, the strengths and energies of such features can constrain the ionization stage, elemental abundance, and column density of the gas in the vicinity of the exotic cosmic objects, e.g. active galactic nuclei (AGN) and galactic black hole candidates. Although the observational technology in X-ray astronomy is still evolving and currently lacks high spectroscopic resolution, the astrophysical models have been based on atomic calculations that predict a sudden and high step-like increase of the cross section at the K-shell threshold (see for instance. New Breit-Pauli R-matrix calculations of the photoionization cross section of the ground states of Fe XVII in the region near the K threshold are presented. They strongly support the view that the previously assumed sharp edge behaviour is not correct. The latter has been caused by the neglect of spectator Auger channels in the decay of the resonances converging to the K threshold. These decay channels include the dominant KLL channels and give rise to constant widths (independent of n). As a consequence, these series display damped Lorentzian components that rapidly blend to impose continuity at threshold, thus reformatting the previously held picture of the edge. Apparent broadened iron edges detected in the spectra of AGN and galactic black hole candidates seem to indicate that these quantum effects may be at least partially responsible for the observed broadening.

29 CFR 1910.145 - Specifications for accident prevention signs and tags.

Code of Federal Regulations, 2013 CFR

2013-07-01

... from sharp edges, burrs, splinters, or other sharp projections. The ends or heads of bolts or other... presenting a risk of death, injury or illness to employees. Major message means that portion of a tag's... instruction. Signal word means that portion of a tag's inscription that contains the word or words that are...

29 CFR 1910.145 - Specifications for accident prevention signs and tags.

Code of Federal Regulations, 2012 CFR

2012-07-01

... from sharp edges, burrs, splinters, or other sharp projections. The ends or heads of bolts or other... presenting a risk of death, injury or illness to employees. Major message means that portion of a tag's... instruction. Signal word means that portion of a tag's inscription that contains the word or words that are...

Resonances in the Photoionization Cross Sections of Atomic Nitrogen Shape the Far-ultraviolet Spectrum of the Bright Star in 47 Tucanae

NASA Astrophysics Data System (ADS)

Dixon, William V.; Chayer, Pierre

2013-08-01

The far-ultraviolet spectrum of the Bright Star (B8 III) in 47 Tuc (NGC 104) shows a remarkable pattern: it is well fit by local thermodynamic equilibrium models at wavelengths longer than Lyβ, but at shorter wavelengths it is fainter than the models by a factor of two. A spectrum of this star obtained with the Far Ultraviolet Spectroscopic Explorer shows broad absorption troughs with sharp edges at 995 and 1010 Å and a deep absorption feature at 1072 Å none of which are predicted by the models. We find that these features are caused by resonances in the photoionization cross sections of the first and second excited states of atomic nitrogen (2s 2 2p 3 2 D 0 and 2 P 0). Using cross sections from the Opacity Project, we can reproduce these features, but only if we use the cross sections at their full resolution, rather than the resonance-averaged cross sections usually employed to model stellar atmospheres. These resonances are strongest in stellar atmospheres with enhanced nitrogen and depleted carbon abundances, a pattern typical of post-asymptotic giant branch stars.

Evidence of three-body correlation functions in Rb+ and Sr2+ acetonitrile solutions

NASA Astrophysics Data System (ADS)

D'Angelo, P.; Pavel, N. V.

1999-09-01

The local structure of Sr2+ and Rb+ ions in acetonitrile has been investigated by x-ray absorption spectroscopy (XAS) and molecular dynamics simulations. The extended x-ray absorption fine structure above the Sr and Rb K edges has been interpreted in the framework of multiple scattering (MS) formalism and, for the first time, clear evidence of MS contributions has been found in noncomplexing ion solutions. Molecular dynamics has been used to generate the partial pair and triangular distribution functions from which model χ(k) signals have been constructed. The Sr2+ and Rb+ acetonitrile pair distribution functions show very sharp and well-defined first peaks indicating the presence of a well organized first solvation shell. Most of the linear acetonitrile molecules have been found to be distributed like hedgehog spines around the Sr2+ and Rb+ ions. The presence of three-body correlations has been singled out by the existence of well-defined peaks in the triangular configurations. Excellent agreement has been found between the theoretical and experimental data enforcing the reliability of the interatomic potentials used in the simulations. These results demonstrate the ability of the XAS technique in probing the higher-order correlation functions in solution.

Fabrication of cerium-doped β-Ga2O3 epitaxial thin films and deep ultraviolet photodetectors.

PubMed

Li, Wenhao; Zhao, Xiaolong; Zhi, Yusong; Zhang, Xuhui; Chen, Zhengwei; Chu, Xulong; Yang, Hujiang; Wu, Zhenping; Tang, Weihua

2018-01-20

High-quality cerium-doped β-Ga 2 O 3 (Ga 2 O 3 :Ce) thin films could be achieved on (0001)α-Al 2 O 3 substrates using a pulsed-laser deposition method. The impact of dopant contents concentration on crystal structure, optical absorption, photoluminescence, and photoelectric properties has been intensively studied. X-ray diffraction analysis results have shown that Ga 2 O 3 :Ce films are highly (2¯01) oriented, and the lattice spacing of the (4¯02) planes is sensitive to the Ce doping level. The prepared Ga 2 O 3 :Ce films show a sharp absorption edge at about 250 nm, meaning a high transparency to deep ultraviolet (DUV) light. The photoluminescence results revealed that the emissions were in the violet-blue-green region, which are associated with the donor-acceptor transitions with the Ce 3+ and oxygen vacancies related defects. A simple DUV photodetector device with a metal-semiconductor-metal structure has also been fabricated based on Ga 2 O 3 :Ce thin film. A distinct DUV photoresponse was obtained, suggesting a potential application in DUV photodetector devices.

Perovskite Solar Cells: From the Atomic Level to Film Quality and Device Performance.

PubMed

Saliba, Michael; Correa-Baena, Juan-Pablo; Grätzel, Michael; Hagfeldt, Anders; Abate, Antonio

2018-03-01

Organic-inorganic perovskites have made tremendous progress in recent years due to exceptional material properties such as high panchromatic absorption, charge carrier diffusion lengths, and a sharp optical band edge. The combination of high-quality semiconductor performance with low-cost deposition techniques seems to be a match made in heaven, creating great excitement far beyond academic ivory towers. This is particularly true for perovskite solar cells (PSCs) that have shown unprecedented gains in efficiency and stability over a time span of just five years. Now there are serious efforts for commercialization with the hope that PSCs can make a major impact in generating inexpensive, sustainable solar electricity. In this Review, we will focus on perovskite material properties as well as on devices from the atomic to the thin film level to highlight the remaining challenges and to anticipate the future developments of PSCs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fundamental absorption edge of NiO nanocrystals

NASA Astrophysics Data System (ADS)

Sokolov, V. I.; Druzhinin, A. V.; Kim, G. A.; Gruzdev, N. B.; Yermakov, A. Ye.; Uimin, M. A.; Byzov, I. V.; Shchegoleva, N. N.; Vykhodets, V. B.; Kurennykh, T. E.

2013-12-01

NiO nanocrystals with the average size of 5, 10 and 25 nm were synthesized by gas-condensation method. The well-defined increase of the optical density D near the fundamental absorption edge of NiO nanocrystals in the range of 3.5-4.0 eV observed after the annealing in air is caused by the oxygen content growth. It is the direct experimental evidence of the fact that p-d charge transfer transitions form the fundamental absorption edge.

Analysis of the separated boundary layer flow on the surface and in the wake of blunt trailing edge airfoils

NASA Technical Reports Server (NTRS)

Goradia, S. H.; Mehta, J. M.; Shrewsbury, G. S.

1977-01-01

The viscous flow phenomena associated with sharp and blunt trailing edge airfoils were investigated. Experimental measurements were obtained for a 17 percent thick, high performance GAW-1 airfoil. Experimental measurements consist of velocity and static pressure profiles which were obtained by the use of forward and reverse total pressure probes and disc type static pressure probes over the surface and in the wake of sharp and blunt trailing edge airfoils. Measurements of the upper surface boundary layer were obtained in both the attached and separated flow regions. In addition, static pressure data were acquired, and skin friction on the airfoil upper surface was measured with a specially constructed device. Comparison of the viscous flow data with data previously obtained elsewhere indicates reasonable agreement in the attached flow region. In the separated flow region, considerable differences exist between these two sets of measurements.

Change Observed in Martian Sand Dune

NASA Image and Video Library

2015-11-16

This animation flips back and forth between views taken in 2010 and 2014 of a Martian sand dune at the edge of Mount Sharp, documenting dune activity. The images are from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. They cover an area about 740 feet (about 225 meters) wide, showing a site called "Dune 2" in the "Bagnold Dunes" dune field. NASA's Curiosity Mars rover will observe this dune up close on the rover's route up Mount Sharp. North is toward the top. The edge of the dune at the crescent-shaped slip face on the south edge advances slightly during the four-year period between the dates of the images. Figure A is an annotated version with an arrow indicating the location of this change. The lighting angle is different in the two images, resulting in numerous changes in shadows. http://photojournal.jpl.nasa.gov/catalog/PIA20161

Design and Analysis of Bionic Cutting Blades Using Finite Element Method.

PubMed

Li, Mo; Yang, Yuwang; Guo, Li; Chen, Donghui; Sun, Hongliang; Tong, Jin

2015-01-01

Praying mantis is one of the most efficient predators in insect world, which has a pair of powerful tools, two sharp and strong forelegs. Its femur and tibia are both armed with a double row of strong spines along their posterior edges which can firmly grasp the prey, when the femur and tibia fold on each other in capturing. These spines are so sharp that they can easily and quickly cut into the prey. The geometrical characteristic of the praying mantis's foreleg, especially its tibia, has important reference value for the design of agricultural soil-cutting tools. Learning from the profile and arrangement of these spines, cutting blades with tooth profile were designed in this work. Two different sizes of tooth structure and arrangement were utilized in the design on the cutting edge. A conventional smooth-edge blade was used to compare with the bionic serrate-edge blades. To compare the working efficiency of conventional blade and bionic blades, 3D finite element simulation analysis and experimental measurement were operated in present work. Both the simulation and experimental results indicated that the bionic serrate-edge blades showed better performance in cutting efficiency.

Design and Analysis of Bionic Cutting Blades Using Finite Element Method

PubMed Central

Li, Mo; Yang, Yuwang; Guo, Li; Chen, Donghui; Sun, Hongliang; Tong, Jin

2015-01-01

Praying mantis is one of the most efficient predators in insect world, which has a pair of powerful tools, two sharp and strong forelegs. Its femur and tibia are both armed with a double row of strong spines along their posterior edges which can firmly grasp the prey, when the femur and tibia fold on each other in capturing. These spines are so sharp that they can easily and quickly cut into the prey. The geometrical characteristic of the praying mantis's foreleg, especially its tibia, has important reference value for the design of agricultural soil-cutting tools. Learning from the profile and arrangement of these spines, cutting blades with tooth profile were designed in this work. Two different sizes of tooth structure and arrangement were utilized in the design on the cutting edge. A conventional smooth-edge blade was used to compare with the bionic serrate-edge blades. To compare the working efficiency of conventional blade and bionic blades, 3D finite element simulation analysis and experimental measurement were operated in present work. Both the simulation and experimental results indicated that the bionic serrate-edge blades showed better performance in cutting efficiency. PMID:27019583

Studies by Near Edge X-ray Absorption Spectroscopies of Bonding Dynamics at the Graphene/Guanine Interface - A Proposal for High Mobility, Organic Graphene Field Effect Transistors

DTIC Science & Technology

2015-07-01

AFRL-AFOSR-UK-TR-2015-0034 Studies by Near Edge X-ray Absorption Spectroscopies of Bonding Dynamics at the Graphene /Guanine...Interface – A Proposal for High Mobility, Organic Graphene Field Effect Transistors Eva Campo BANGOR UNIVERSITY COLLEGE ROAD BANGOR...April 2015 4. TITLE AND SUBTITLE Studies by Near Edge X-ray Absorption Spectroscopies of Bonding Dynamics at the Graphene /Guanine Interface - A

Experimental And Numerical Study Of CMC Leading Edges In Hypersonic Flows

NASA Astrophysics Data System (ADS)

Kuhn, Markus; Esser, Burkard; Gulhan, Ali; Dalenbring, Mats; Cavagna, Luca

2011-05-01

Future transportation concepts aim at high supersonic or hypersonic speeds, where the formerly sharp boundaries between aeronautic and aerospace applications become blurred. One of the major issues involved to high speed flight are extremely high aerothermal loads, which especially appear at the leading edges of the plane’s wings and at sharp edged air intake components of the propulsion system. As classical materials like metals or simple ceramics would thermally and structurally fail here, new materials have to be applied. In this context, lightweight ceramic matrix composites (CMC) seem to be prospective candidates as they are high-temperature resistant and offer low thermal expansion along with high specific strength at elevated temperature levels. A generic leading edge model with a ceramic wing assembly with a sweep back angle of 53° was designed, which allowed for easy leading edge sample integration of different CMC materials. The samples consisted of the materials C/C-SiC (non-oxide), OXIPOL and WHIPOX (both oxide) with a nose radius of 2 mm. In addition, a sharp edged C/C-SiC sample was prepared to investigate the nose radius influence. Overall, 13 thermocouples were installed inside the entire model to measure the temperature evolution at specific locations, whereby 5 thermocouples were placed inside the leading edge sample itself. In addition, non-intrusive techniques were applied for surface temperature measurements: An infrared camera was used to measure the surface temperature distribution and at specific spots, the surface temperature was also measured by pyrometers. Following, the model was investigated in DLR’s arc-heated facility L3K at a total enthalpy of 8.5 MJ/kg, Mach number of 7.8, different angles of attack and varying wing inclination angles. These experiments provide a sound basis for the simulation of aerothermally loaded CMC leading edge structures. Such fluid-structure coupled approaches have been performed by FOI, basing on a modal approach for the conduction model. Results show, that the temperature profiles are correctly depicted dependent on the model’s angle of attack.

Sum rules for the uniform-background model of an atomic-sharp metal corner

NASA Astrophysics Data System (ADS)

Streitenberger, P.

1994-04-01

Analytical results are derived for the electrostatic potential of an atomic-sharp 90° metal corner in the uniform-background model. The electrostatic potential at a free jellium edge and the jellium corner, respectively, is determined exactly in terms of the energy per electron of the uniform electron gas integrated over the background density. The surface energy, the edge formation energy and the derivative of the corner formation energy with respect to the background density are given as integrals over the electrostatic potential. The present approach represents a novel approach to such sum rules, inclusive of the Budd-Vannimenus sum rules for a free jellium surface, based on general properties of linear response functions.

CHIPPING FRACTURE RESISTANCE OF DENTURE TOOTH MATERIALS

PubMed Central

Quinn, G. D.; Giuseppetti, A. A.; Hoffman, K. H.

2014-01-01

Objective The applicability of the edge chipping method to denture tooth materials was assessed. These are softer materials than those usually tested by edge chipping. The edge chipping fracture resistances of polymethylmethacrylate (PMMA) based and two filled resin composite denture tooth materials were compared. Methods An edge chipping machine was used to chip rectangular blocks and flattened anterior denture teeth. Force versus edge distance data were collected over a broad range of forces and distances. Between 20 and 65 chips were made per condition depending upon the material, the scatter, and the indenter type. Different indenter types were used including Rockwell C, sharp conical 120°, Knoop, and Vickers. The edge toughness, Te, was evaluated for different indenter types. Results The edge chipping data collected on the blocks matched the data collected from flattened teeth. High scatter, particularly at large distances and loads, meant that many tests (up to 64) were necessary to compare the denture tooth materials and to ascertain the appropriate data trends. A linear force – distance trend analysis was adequate for comparing these materials. A power law trend might be more appropriate, but the large scatter obscured the definitive determination of the precise trend. Different indenters produce different linear trends, with the ranking of: sharp conical 120°, Rockwell C, and Knoop, from lowest to highest edge toughness. Vickers indenter data were extremely scattered and a sensible trend could not be obtained. Edge toughness was inversely correlated to hardness. Significance Edge chipping data collected either from simple laboratory scale test blocks or from actual denture teeth may be used to evaluate denture materials. The edge chipping method’s applicability has been extended to another class of restorative materials. PMID:24674342

Non-resonant divertors for stellarators

NASA Astrophysics Data System (ADS)

Boozer, Allen; Punjabi, Alkesh

2017-10-01

The outermost confining magnetic surface in optimized stellarators has sharp edges, which resemble tokamak X-points. The plasma cross section has an even number of edges at the beginning but an odd number half way through the period. Magnetic field lines cannot cross sharp edges, but stellarator edges have a finite length and do not determine the rotational transform on the outermost confining surface. Just outside the last confining surface, surfaces formed by magnetic field lines have splits containing two adjacent magnetic flux tubes: one with entering and the other with an equal existing flux to the walls. The splits become wider with distance outside the outermost confining surface. These flux tubes form natural non-resonant stellarator divertors, which we are studying using maps. This work is supported by the US DOE Grants DE-FG02-95ER54333 to Columbia University and DE-FG02-01ER54624 and DE-FG02-04ER54793 to Hampton University and used resources of the NERSC, supported by the Office of Science, US DOE, under Contract No. DE-AC02-.

Dynamic modeling for rigid rotor bearing systems with a localized defect considering additional deformations at the sharp edges

NASA Astrophysics Data System (ADS)

Liu, Jing; Shao, Yimin

2017-06-01

Rotor bearing systems (RBSs) play a very valuable role for wind turbine gearboxes, aero-engines, high speed spindles, and other rotational machinery. An in-depth understanding of vibrations of the RBSs is very useful for condition monitoring and diagnosis applications of these machines. A new twelve-degree-of-freedom dynamic model for rigid RBSs with a localized defect (LOD) is proposed. This model can formulate the housing support stiffness, interfacial frictional moments including load dependent and load independent components, time-varying displacement excitation caused by a LOD, additional deformations at the sharp edges of the LOD, and lubricating oil film. The time-varying displacement model is determined by a half-sine function. A new method for calculating the additional deformations at the sharp edges of the LOD is analytical derived based on an elastic quarter-space method presented in the literature. The proposed dynamic model is utilized to analyze the influences of the housing support stiffness and LOD sizes on the vibration characteristics of the rigid RBS, which cannot be predicted by the previous dynamic models in the literature. The results show that the presented method can give a new dynamic modeling method for vibration formulation for a rigid RBS with and without the LOD on the races.

Investigation into Behavior of a Steam-Water Mixture Flow Through Holes in a Submerged Perforated Sheet at High Void Fractions

NASA Astrophysics Data System (ADS)

Melikhov, V. I.; Melikhov, O. I.; Nerovnov, A. A.; Nikonov, S. M.

2018-01-01

Processing of experimental data on the pressure difference across a submerged perforated sheet (SPS) revealed that, at sufficiently high void fractions under SPS, the pressure difference across it became less than the pressure difference for the pure steam stream with the same flowrate. To find the cause of this, the effect of a liquid film, which can be formed on the SPS upstream surface as a result of water droplets' impact and can smooth over sharp edges of holes in SDS, was examined. This can decrease the pressure drop across the sharp edges of holes. This assumption was checked through numerical solution to several model problems in the axisymmetric formulation for a steam flow in a round pipe with an orifice. The flow of steam and water was modeled using the viscous incompressible liquid approximation, while the turbulence was described by the k-ɛ model. The evolution of the interfacial area was modeled using the VOF model. The following model problems of steam flow through an orifice were studied: a single-phase flow, a flow through the orifice with a liquid film on its upstream surface, a flow through a chamfered hole, and a flow through the orifice with a liquid film on its upstream surface without liquid supply to the film. The predictions demonstrate that even the approximate account of the liquid film effect on the steam flow yields a considerable decrease in the pressure drop across the hole (from 8 to 24%) due to smoothing its sharp outlet edges over. This makes it possible to make a conclusion that the cause of a decrease in the pressure drop across SPS observed in the experiments at high void fractions is the formation of a liquid film, which smooths the sharp edges of the hole.

Microcutting characteristics on the single crystal diamond tool with edge radius using molecular dynamics

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

Kim, Jeong-Du; Moon, Chan-Hong

1995-12-31

Ultraprecision metal cutting (UPMC) technology which makes possible submicrometer form accuracy and manometer roughness is developed to reach the 1nm nominal (undeformed) thickness of cut. At this thickness level, a few of atom`s layers should be considered. In this paper using the Molecuar Dynamics simulation, the phenomena of microcutting with a subnanometer chip thickness, the cutting mechanism for tool edge configuration to consider the sharp edge and round edge tool, the cut material and cutting speed are evaluated. Cutting mechanism of subnanometer depth of cut is evaluated.

Correction of absorption-edge artifacts in polychromatic X-ray tomography in a scanning electron microscope for 3D microelectronics

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

Laloum, D., E-mail: david.laloum@cea.fr; CEA, LETI, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9; STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles

2015-01-15

X-ray tomography is widely used in materials science. However, X-ray scanners are often based on polychromatic radiation that creates artifacts such as dark streaks. We show this artifact is not always due to beam hardening. It may appear when scanning samples with high-Z elements inside a low-Z matrix because of the high-Z element absorption edge: X-rays whose energy is above this edge are strongly absorbed, violating the exponential decay assumption for reconstruction algorithms and generating dark streaks. A method is proposed to limit the absorption edge effect and is applied on a microelectronic case to suppress dark streaks between interconnections.

Subgap Absorption in Conjugated Polymers

DOE R&D Accomplishments Database

Sinclair, M.; Seager, C. H.; McBranch, D.; Heeger, A. J; Baker, G. L.

1991-01-01

Along with X{sup (3)}, the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of < 10{sup {minus}5}, Photothermal Deflection Spectroscopy (PDS) is ideal for determining the absorption coefficients of thin films of transparent'' materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly(1,4-phenylene-vinylene) (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm{sup {minus}1} to 10 cm{sup {minus}1}. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration of fluorination.

Edge enhancement algorithm for low-dose X-ray fluoroscopic imaging.

PubMed

Lee, Min Seok; Park, Chul Hee; Kang, Moon Gi

2017-12-01

Low-dose X-ray fluoroscopy has continually evolved to reduce radiation risk to patients during clinical diagnosis and surgery. However, the reduction in dose exposure causes quality degradation of the acquired images. In general, an X-ray device has a time-average pre-processor to remove the generated quantum noise. However, this pre-processor causes blurring and artifacts within the moving edge regions, and noise remains in the image. During high-pass filtering (HPF) to enhance edge detail, this noise in the image is amplified. In this study, a 2D edge enhancement algorithm comprising region adaptive HPF with the transient improvement (TI) method, as well as artifacts and noise reduction (ANR), was developed for degraded X-ray fluoroscopic images. The proposed method was applied in a static scene pre-processed by a low-dose X-ray fluoroscopy device. First, the sharpness of the X-ray image was improved using region adaptive HPF with the TI method, which facilitates sharpening of edge details without overshoot problems. Then, an ANR filter that uses an edge directional kernel was developed to remove the artifacts and noise that can occur during sharpening, while preserving edge details. The quantitative and qualitative results obtained by applying the developed method to low-dose X-ray fluoroscopic images and visually and numerically comparing the final images with images improved using conventional edge enhancement techniques indicate that the proposed method outperforms existing edge enhancement methods in terms of objective criteria and subjective visual perception of the actual X-ray fluoroscopic image. The developed edge enhancement algorithm performed well when applied to actual low-dose X-ray fluoroscopic images, not only by improving the sharpness, but also by removing artifacts and noise, including overshoot. Copyright © 2017 Elsevier B.V. All rights reserved.

Photoabsorption study of Bacillus megaterium, DNA and Related Biological Materials in the Phosphorus K-edge Region

NASA Technical Reports Server (NTRS)

Frigo, Sean P.; McNulty,Ian; Richmond, Robert C.; Ehret, Charles F.

2003-01-01

We have measured the x-ray transmission spectra of several biologically related samples in the phosphorus K-edge absorption region. These include red phosphorus, hydrated sodium phosphate (Na3PO4 12 H2O), deoxyribonucleic acid (DNA), adenosinetriphosphate (ATP), diolylphosphatidyl choline (DOPC), and Bacillus megaterium spores. Red phosphorus essentially displays an edge-jump. All other spectra are similar in form and energy position, where each is dominated by a narrower, more intense first peak and a broader but less intense second peak. The corresponding K-edge absorption thresholds are shifted towards higher energy relative to that for red phosphorus, as expected for increasing degrees of phosphorus oxidation. The B.meguterium spectrum has aspects common to both the phosphate and DNA spectra and is therefore interpreted as a composite of spectra arising from DNA/RNA and phosphates within the spore. The B. megaterium spore spectrum provides needed information for resonant radiation damage studies in the phosphorus K-edge absorption region by identifying candidate photoexcitations. In addition, the absorption spectra will be useful in macromolecular crystallography studies employing anomalous dispersion effects at the phosphorus K-edge.

Photoabsorption Study of Bacillus megaterium, DNA and Related Biological Materials in the Phosphorus K-edge Region

NASA Technical Reports Server (NTRS)

Frigo, Sean P.; McNulty, Ian; Richmond, Robert C.; Ehret, Charles F.

2002-01-01

We have measured the x-ray transmission spectra of several biologically related samples in the phosphorus K-edge absorption region. These include elemental red phosphorus, hydrated sodium phosphate (Na3PO4.12H2O), deoxyribonucleic acid (DNA), adenosinetriphosphate (ATP), diolylphosphatidyl choline (DOPC), and Bacillus megaterium spores. Elemental red phosphorus essentially displays an edge-jump. All other spectra are similar in form and energy position. Each spectrum for these substances is dominated by a narrower, more intense first peak and a broader but less intense second peak. The corresponding K-edge absorption thresholds are shifted towards higher energy relative to that for elemental red phosphorus, as expected for increasing degrees of phosphorus oxidation. The B. megaterium spectrum has aspects common to both the phosphate and DNA spectra and is therefore interpreted as a composite of spectra arising from DNA/RNA and phosphates within the spore. The B. megaterium spore spectrum provides needed information for resonant radiation damage studies in the phosphorus K-edge absorption region by identifying candidate photoexcitations. In addition,the absorption spectra will be useful in macromolecular crystallography studies employing anomalous dispersion effects at the phosphorus K-edge.

Apparatus for cutting elastomeric materials

NASA Technical Reports Server (NTRS)

Corbett, A. B.

1974-01-01

Sharp thin cutting edge is held in head of milling machine designed for metal working. Controls of machine are used to position cutting edge in same plane as vibrating specimen. Controls then are operated, making blade come into contact with specimen, to cut it into shapes and sizes desired. Cut surfaces appear mirror-smooth; vibrating mechanism causes no visible striations.

Material/element-dependent fluorescence-yield modes on soft X-ray absorption spectroscopy of cathode materials for Li-ion batteries

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

Asakura, Daisuke; Hosono, Eiji; Nanba, Yusuke

2016-03-07

Here, we evaluate the utilities of fluorescence-yield (FY) modes in soft X-ray absorption spectroscopy (XAS) of several cathodematerials for Li-ion batteries. In the case of total-FY (TFY) XAS for LiNi 0.5Mn 1.5O 4, the line shape of the Mn L 3-edge XAS was largely distorted by the self-absorption and saturation effects, while the distortions were less pronounced at the Ni L 3 edge. The distortions were suppressed for the inverse-partial-FY (IPFY) spectra. We found that, in the cathodematerials, the IPFY XAS is highly effective for the Cr, Mn, and Fe L edges and the TFY and PFY modes are usefulmore » enough for the Ni L edge which is far from the O K edge.« less

Edge physics of the quantum spin Hall insulator from a quantum dot excited by optical absorption.

PubMed

Vasseur, Romain; Moore, Joel E

2014-04-11

The gapless edge modes of the quantum spin Hall insulator form a helical liquid in which the direction of motion along the edge is determined by the spin orientation of the electrons. In order to probe the Luttinger liquid physics of these edge states and their interaction with a magnetic (Kondo) impurity, we consider a setup where the helical liquid is tunnel coupled to a semiconductor quantum dot that is excited by optical absorption, thereby inducing an effective quantum quench of the tunneling. At low energy, the absorption spectrum is dominated by a power-law singularity. The corresponding exponent is directly related to the interaction strength (Luttinger parameter) and can be computed exactly using boundary conformal field theory thanks to the unique nature of the quantum spin Hall edge.

Spectroscopy of Reaction Intermediates in Nitramine Decomposition and Combustion

DTIC Science & Technology

1991-06-20

Dakhis and co-workers, s the very strong absorption of MMN near 1332 cm - 1 did not appear. Unassigned absorptions appeared near 930, 1240, 1460, 2990, and...sharp NO2 absorption. In Table I, the positions of these absorptions are compared with the infrared absorptions of MMN reported by Dakhis and co-workers...Chemistry and Physics of Energetic Materials, S. N. Bulusu, Ed., pp. 51-78 (Kluwer Academic Publishers, Dordrecht, 1990). 56. M. I. Dakhis , V. G. Dashevsky

Spectroscopy of Reaction Intermediates in Nitramine Decomposition and Combustion

DTIC Science & Technology

1991-06-20

absorptions of gas-phase MMN reported by Dakhis and co-workers,5 6 the very strong absorption of MMN near 1332 cm - ’ did not appear. Unassigned...sharp NO 2 absorption. In Table I, the positions of these absorptions are compared with the infrared absorptions of MMN reported by Dakhis and co-workers...Chemistry and Physics of Energetic Materials, S. N. Bulusu, Ed., pp. 51-78 (Kluwer Academic Publishers, Dordrecht, 1990). 56. M. I. Dakhis , V. G

Wild monkeys flake stone tools.

PubMed

Proffitt, Tomos; Luncz, Lydia V; Falótico, Tiago; Ottoni, Eduardo B; de la Torre, Ignacio; Haslam, Michael

2016-11-03

Our understanding of the emergence of technology shapes how we view the origins of humanity. Sharp-edged stone flakes, struck from larger cores, are the primary evidence for the earliest stone technology. Here we show that wild bearded capuchin monkeys (Sapajus libidinosus) in Brazil deliberately break stones, unintentionally producing recurrent, conchoidally fractured, sharp-edged flakes and cores that have the characteristics and morphology of intentionally produced hominin tools. The production of archaeologically visible cores and flakes is therefore no longer unique to the human lineage, providing a comparative perspective on the emergence of lithic technology. This discovery adds an additional dimension to interpretations of the human Palaeolithic record, the possible function of early stone tools, and the cognitive requirements for the emergence of stone flaking.

Two-tint pump-probe measurements using a femtosecond laser oscillator and sharp-edged optical filters.

PubMed

Kang, Kwangu; Koh, Yee Kan; Chiritescu, Catalin; Zheng, Xuan; Cahill, David G

2008-11-01

We describe a simple approach for rejecting unwanted scattered light in two types of time-resolved pump-probe measurements, time-domain thermoreflectance (TDTR) and time-resolved incoherent anti-Stokes Raman scattering (TRIARS). Sharp edged optical filters are used to create spectrally distinct pump and probe beams from the broad spectral output of a femtosecond Ti:sapphire laser oscillator. For TDTR, the diffusely scattered pump light is then blocked by a third optical filter. For TRIARS, depolarized scattering created by the pump is shifted in frequency by approximately 250 cm(-1) relative to the polarized scattering created by the probe; therefore, spectral features created by the pump and probe scattering can be easily distinguished.

[The study of ultra-fine diamond powder used in magnetic head polishing slurry].

PubMed

Jin, Hong-Yun; Hou, Shu-En; Pan, Yong; Xiao, Hong-Yan

2008-05-01

In the present paper, atomic absorption spectrometry(AAS), inductively-coupled plasma mass spectrometry (ICP-MS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and laser Raman spectroscopy (RM) were employed to study the commercial ultra-fine diamond powders prepared by the static pressure-catalyst method and used in magnetic head polishing slurry. The results of AAS and ICP-MS indicated that there were silicon oxide, Fe, Ni, Al and some other metal elements in the ultra-fine powders. XRD patterns showed the peaks of SiO2 at 2theta = 35.6 degrees, 39.4 degrees and 59.7 degrees and diamond sharp peaks in agreement with the results above. Diamond sharp peaks implied perfect crystal and high-hardness beneficial to high-efficiency in polishing. The broader Raman band of graphite at 1 592 cm(-1) observed by Raman analysis proved graphite existing in the diamond powders. In the TEM images, the size of ultra-fine powders was estimated between 0.1 and 0.5 microm distributed in a wide scope, however, sharp edges of the powder particles was useful to polish. The ultra-fine diamond powders have many advantages, for example, high-hardness, well abrasion performance, high-polishing efficiency and being useful in magnetic head polishing slurry. But, the impurities influence the polishing efficiency, shortening its service life and the wide distribution reduces the polishing precision. Consequently, before use the powders must be purified and classified. The purity demands is 99.9% and trace silicon oxide under 0.01% should be reached. The classification demands that the particle distribution should be in a narrower scope, with the mean size of 100 nm and the percentage of particles lager than 200 nm not over 2%.

Wisps in the outer edge of the Keeler Gap

NASA Astrophysics Data System (ADS)

Tiscareno, M. S.; Arnault, E. G.

2014-12-01

The outer part of Saturn's A ring contains five sharp edges: the inner and outer edges of the Encke Gap and of the Keeler Gap (which contain the moons Pan and Daphnis, respectively), and the outer edge of the A ring itself. Four of these five edges are characterized by structure at moderate to high spatial frequencies, with amplitudes ranging from 2 to 30 km (Tiscareno et al. 2005, DPS). Only the outer edge of the Keeler Gap is reasonably smooth in appearance (Tiscareno et al. 2005, DPS), with occultations indicating residuals less than 1 km upon a possibly non-zero eccentricity (R.G. French, personal communication, 2014). Superposed upon the relatively smooth outer edge of the Keeler Gap are a system of "wisps," which appear to be ring material protruding inward into the gap, usually with a sharp trailing edge and a smooth gradation back to the background edge location on the leading side (Porco et al. 2005, Science). The radial amplitude of wisps is usually 0.5 to 1 km, and their azimuthal extent is approximately a degree of longitude (~2400 km). Wisps are likely caused by an interplay between Daphnis (and perhaps other moons) and embedded moonlets within the ring, though the details remain unclear. We will present a catalogue of wisp detections in Cassini images. We carry out repeated gaussian fits of the radial edge location in order to characterize edge structure (see Figure, which compares our fitted edge to the figure presented by Porco et al. 2005) and visually scan those fitted edges in order to detect wisps. With extensive coverage in longitude and in time, we will report on how wisps evolve and move, both within an orbit period and on longer timescales. We will also report on the frequency and interpretation of wisps that deviate from the standard morphology. We will discuss the implications of our results for the origin and nature of wisps, and for the larger picture of how masses interact within Saturn's rings.

Comparison of posterior capsule opacification at 360-degree square edge hydrophilic and sharp edge hydrophobic acrylic intraocular lens in diabetic patients

PubMed Central

Bai, Ling; Zhang, Jin; Chen, Ling; Ma, Ting; Liang, Hou-Cheng

2015-01-01

AIM To compare posterior capsule opacification (PCO) degree and visual functions after phacoemulsification in eyes implanted with 360-degree square edge hydrophilic acrylic intraocular lens (IOL) (570C C-flex, Rayner) and sharp edge hydrophobic acrylic IOL (Sensar AR40e, AMO) in diabetic patients. METHODS Sixty diabetic patients underwent uneventful phacoemulsification and randomly implanted one of the two IOLs. The PCO value was measured by retroillumination photographs and Evaluation of Posterior Capsule Opacification (EPCO) 2000 image-analysis software at 1, 6, 12, and 24mo after surgery. Visual acuity, and contrast sensitivity in photopic and mesopic conditions were also examined at each follow up time point. The incidence of eye that required Nd:YAG laser posterior capsulotomy were also compared. RESULTS There was not any statistically significant difference in PCO scores between Rayner C-flex 570C group and Sensar AR40e group at each follow up time point. Visual acuity, Nd:YAG capsulotomy incidence and contrast sensitivity also had no significant difference during the 24mo follow-up. CONCLUSION For diabetic patients, Rayner 570C C-flex and Sensar AR40e IOLs are same effective for prevent PCO. The 360-degree square edge design maybe is a good alternative technique to improve PCO prevention. PMID:26309870

Comparison of posterior capsule opacification at 360-degree square edge hydrophilic and sharp edge hydrophobic acrylic intraocular lens in diabetic patients.

PubMed

Bai, Ling; Zhang, Jin; Chen, Ling; Ma, Ting; Liang, Hou-Cheng

2015-01-01

To compare posterior capsule opacification (PCO) degree and visual functions after phacoemulsification in eyes implanted with 360-degree square edge hydrophilic acrylic intraocular lens (IOL) (570C C-flex, Rayner) and sharp edge hydrophobic acrylic IOL (Sensar AR40e, AMO) in diabetic patients. Sixty diabetic patients underwent uneventful phacoemulsification and randomly implanted one of the two IOLs. The PCO value was measured by retroillumination photographs and Evaluation of Posterior Capsule Opacification (EPCO) 2000 image-analysis software at 1, 6, 12, and 24mo after surgery. Visual acuity, and contrast sensitivity in photopic and mesopic conditions were also examined at each follow up time point. The incidence of eye that required Nd:YAG laser posterior capsulotomy were also compared. There was not any statistically significant difference in PCO scores between Rayner C-flex 570C group and Sensar AR40e group at each follow up time point. Visual acuity, Nd:YAG capsulotomy incidence and contrast sensitivity also had no significant difference during the 24mo follow-up. For diabetic patients, Rayner 570C C-flex and Sensar AR40e IOLs are same effective for prevent PCO. The 360-degree square edge design maybe is a good alternative technique to improve PCO prevention.

Reliable clarity automatic-evaluation method for optical remote sensing images

NASA Astrophysics Data System (ADS)

Qin, Bangyong; Shang, Ren; Li, Shengyang; Hei, Baoqin; Liu, Zhiwen

2015-10-01

Image clarity, which reflects the sharpness degree at the edge of objects in images, is an important quality evaluate index for optical remote sensing images. Scholars at home and abroad have done a lot of work on estimation of image clarity. At present, common clarity-estimation methods for digital images mainly include frequency-domain function methods, statistical parametric methods, gradient function methods and edge acutance methods. Frequency-domain function method is an accurate clarity-measure approach. However, its calculation process is complicate and cannot be carried out automatically. Statistical parametric methods and gradient function methods are both sensitive to clarity of images, while their results are easy to be affected by the complex degree of images. Edge acutance method is an effective approach for clarity estimate, while it needs picking out the edges manually. Due to the limits in accuracy, consistent or automation, these existing methods are not applicable to quality evaluation of optical remote sensing images. In this article, a new clarity-evaluation method, which is based on the principle of edge acutance algorithm, is proposed. In the new method, edge detection algorithm and gradient search algorithm are adopted to automatically search the object edges in images. Moreover, The calculation algorithm for edge sharpness has been improved. The new method has been tested with several groups of optical remote sensing images. Compared with the existing automatic evaluation methods, the new method perform better both in accuracy and consistency. Thus, the new method is an effective clarity evaluation method for optical remote sensing images.

Transition metal atomic multiplets in the ligand K-edge x-ray absorption spectra and multiple oxidation states in the L2,3 emission of strongly correlated compounds

NASA Astrophysics Data System (ADS)

Jiménez-Mier, J.; Olalde-Velasco, P.; Yang, W.-L.; Denlinger, J.

2014-07-01

We present results that show that atomic multiplet ligand field calculations are in very good agreement with experimental x-ray absorption spectra at the L2,3 edge of transition metal (TM) di-fluorides (MF2, MCrCu). For chromium more than one TM oxidation state is needed to achieve such an agreement. We also show that signature of the TM atomic multiplet can be found at the pre-edge of the fluorine K-edge x-ray absorption spectra. TM atomic multiplet ligand field calculations with a structureless core hole show good agreement with the observed pre-edges in the experimental fluorine absorption spectra. Preliminary results for the comparison between calculated and experimental resonant x-ray emission spectra for nominal CrF2 with more than one oxidation state indicate the presence of three chromium oxidation states in the bulk.

Applicability of linearized-theory attached-flow methods to design and analysis of flap systems at low speeds for thin swept wings with sharp leading edges

NASA Technical Reports Server (NTRS)

Carlson, Harry W.; Darden, Christine M.

1987-01-01

Low-speed experimental force and data on a series of thin swept wings with sharp leading edges and leading and trailing-edge flaps are compared with predictions made using a linearized-theory method which includes estimates of vortex forces. These comparisons were made to assess the effectiveness of linearized-theory methods for use in the design and analysis of flap systems in subsonic flow. Results demonstrate that linearized-theory, attached-flow methods (with approximate representation of vortex forces) can form the basis of a rational system for flap design and analysis. Even attached-flow methods that do not take vortex forces into account can be used for the selection of optimized flap-system geometry, but design-point performance levels tend to be underestimated unless vortex forces are included. Illustrative examples of the use of these methods in the design of efficient low-speed flap systems are included.

Graphene-edge dielectrophoretic tweezers for trapping of biomolecules.

PubMed

Barik, Avijit; Zhang, Yao; Grassi, Roberto; Nadappuram, Binoy Paulose; Edel, Joshua B; Low, Tony; Koester, Steven J; Oh, Sang-Hyun

2017-11-30

The many unique properties of graphene, such as the tunable optical, electrical, and plasmonic response make it ideally suited for applications such as biosensing. As with other surface-based biosensors, however, the performance is limited by the diffusive transport of target molecules to the surface. Here we show that atomically sharp edges of monolayer graphene can generate singular electrical field gradients for trapping biomolecules via dielectrophoresis. Graphene-edge dielectrophoresis pushes the physical limit of gradient-force-based trapping by creating atomically sharp tweezers. We have fabricated locally backgated devices with an 8-nm-thick HfO 2 dielectric layer and chemical-vapor-deposited graphene to generate 10× higher gradient forces as compared to metal electrodes. We further demonstrate near-100% position-controlled particle trapping at voltages as low as 0.45 V with nanodiamonds, nanobeads, and DNA from bulk solution within seconds. This trapping scheme can be seamlessly integrated with sensors utilizing graphene as well as other two-dimensional materials.

Three-dimensional vibrations of cylindrical elastic solids with V-notches and sharp radial cracks

NASA Astrophysics Data System (ADS)

McGee, O. G.; Kim, J. W.

2010-02-01

This paper provides free vibration data for cylindrical elastic solids, specifically thick circular plates and cylinders with V-notches and sharp radial cracks, for which no extensive previously published database is known to exist. Bending moment and shear force singularities are known to exist at the sharp reentrant corner of a thick V-notched plate under transverse vibratory motion, and three-dimensional (3-D) normal and transverse shear stresses are known to exist at the sharp reentrant terminus edge of a V-notched cylindrical elastic solid under 3-D free vibration. A theoretical analysis is done in this work utilizing a variational Ritz procedure including these essential singularity effects. The procedure incorporates a complete set of admissible algebraic-trigonometric polynomials in conjunction with an admissible set of " edge functions" that explicitly model the 3-D stress singularities which exist along a reentrant terminus edge (i.e., α>180°) of the V-notch. The first set of polynomials guarantees convergence to exact frequencies, as sufficient terms are retained. The second set of edge functions—in addition to representing the corner stress singularities—substantially accelerates the convergence of frequency solutions. This is demonstrated through extensive convergence studies that have been carried out by the investigators. Numerical analysis has been carried out and the results have been given for cylindrical elastic solids with various V-notch angles and depths. The relative depth of the V-notch is defined as (1- c/ a), and the notch angle is defined as (360°- α). For a very small notch angle (1° or less), the notch may be regarded as a "sharp radial crack." Accurate (four significant figure) frequencies are presented for a wide spectrum of notch angles (360°- α), depths (1- c/ a), and thickness ratios ( a/ h for plates and h/ a for cylinders). An extended database of frequencies for completely free thick sectorial, semi-circular, and segmented plates and cylinders are also reported herein as interesting special cases. A generalization of the elasticity-based Ritz analysis and findings applicable here is an arbitrarily shaped V-notched cylindrical solid, being a surface traced out by a family of generatrix, which pass through the circumference of an arbitrarily shaped V-notched directrix curve, r( θ), several of which are described for future investigations and close extensions of this work.

Contrast-enhanced Magnetic Resonance Imaging of Pelvic Bone Metastases at 3.0 T: Comparison Between 3-dimensional T1-weighted CAIPIRINHA-VIBE Sequence and 2-dimensional T1-weighted Turbo Spin-Echo Sequence.

PubMed

Yoon, Min A; Hong, Suk-Joo; Lee, Kyu-Chong; Lee, Chang Hee

2018-06-12

This study aimed to compare 3-dimensional T1-weighted gradient-echo sequence (CAIPIRINHA-volumetric interpolated breath-hold examination [VIBE]) with 2-dimensional T1-weighted turbo spin-echo sequence for contrast-enhanced magnetic resonance imaging (MRI) of pelvic bone metastases at 3.0 T. Thirty-one contrast-enhanced MRIs of pelvic bone metastases were included. Two contrast-enhanced sequences were evaluated for the following parameters: overall image quality, sharpness of pelvic bone, iliac vessel clarity, artifact severity, and conspicuity and edge sharpness of the smallest metastases. Quantitative analysis was performed by calculating signal-to-noise ratio and contrast-to-noise ratio of the smallest metastases. Significant differences between the 2 sequences were assessed. CAIPIRINHA-VIBE had higher scores for overall image quality, pelvic bone sharpness, iliac vessel clarity, and edge sharpness of the metastatic lesions, and had less artifacts (all P < 0.05). There was no significant difference in conspicuity, signal-to-noise ratio, or contrast-to-noise ratio of the smallest metastases (P > 0.05). Our results suggest that CAIPIRINHA-VIBE may be superior to turbo spin-echo for contrast-enhanced MRI of pelvic bone metastases at 3.0 T.

Absorption edge parameters of the LIII edge for compounds of Hg, Tl, Pb and Bi using EDXRF technique

NASA Astrophysics Data System (ADS)

Singh, Gurinderjeet; Singh, Amrit; Gupta, Manoj Kumar; Dhaliwal, A. S.; Kahlon, K. S.

2018-03-01

The measurement of Absorption edge parameters of the LIII edge of pure elements Hg, Tl, Pb and Bi along with their compounds HgCl2, HgO, HgF2, TlCl, Tl2O3, PbCl2, PbF2, Pb3O4, BiF3, BiCl3 and Bi2O3 has been done using EDXRF technique. In the present measurements 241Am (59.54 keV) radioactive source of activity 100 mCi along with CANBERRA make cryo-cooled Si (Li) detector is used. The measured results are compared with theoretically calculated values from FFAST version 2.1 (Chantler et al., 2005) and shows good agreement with each other within experimental uncertainties within 3.5%. It is observed that the values of absorption edge parameters of the LIII edge depends slightly on the chemical environment and shows almost constant behaviour with effective atomic number (Zeff)

X-ray absorption near-edge spectroscopy in bioinorganic chemistry: Application to M–O2 systems

PubMed Central

Sarangi, Ritimukta

2012-01-01

Metal K-edge X-ray absorption spectroscopy (XAS) has been extensively applied to bioinorganic chemistry to obtain geometric structure information on metalloprotein and biomimetic model complex active sites by analyzing the higher energy extended X-ray absorption fine structure (EXAFS) region of the spectrum. In recent years, focus has been on developing methodologies to interpret the lower energy K-pre-edge and rising-edge regions (XANES) and using it for electronic structure determination in complex bioinorganic systems. In this review, the evolution and progress of 3d-transition metal K-pre-edge and rising-edge methodology development is presented with particular focus on applications to bioinorganic systems. Applications to biomimetic transition metal–O2 intermediates (M = Fe, Co, Ni and Cu) are reviewed, which demonstrate the power of the method as an electronic structure determination technique and its impact in understanding the role of supporting ligands in tuning the electronic configuration of transition metal–O2 systems. PMID:23525635

Experimental observation of the shift and width of the aluminium K absorption edge in laser shock-compressed plasmas

NASA Astrophysics Data System (ADS)

Hall, T. A.; Al-Kuzee, J.; Benuzzi, A.; Koenig, M.; Krishnan, J.; Grandjouan, N.; Batani, D.; Bossi, S.; Nicolella, S.

1998-03-01

Experimental measurements of the shift and width of the aluminium K-absorption edge in laser shock-compressed plasma is presented. The spectrometer used in these experiments allows an accurate wavelength calibration and fiduciary and hence provides precise measurements of both the shift and the width of the absorption edge. Results have been obtained for compressions up to approximately ×2 and temperatures up to about 1.5 eV. The values of shift and width are compared with a new model with which there is very good agreement.

Wisps in the outer edge of the Keeler Gap

NASA Astrophysics Data System (ADS)

Tiscareno, Matthew S.; Arnault, Ethan G.

2015-11-01

Superposed upon the relatively smooth outer edge of the Keeler Gap are a system of "wisps," which appear to be ring material protruding inward into the gap, usually with a sharp trailing edge and a smooth gradation back to the background edge location on the leading side (Porco et al. 2005, Science). The radial amplitude of wisps is usually 0.5 to 1 km, and their azimuthal extent is approximately a degree of longitude (~2400 km). Wisps are likely caused by an interplay between Daphnis (and perhaps other moons) and embedded moonlets within the ring, though the details remain unclear.Aside from the wisps, the Keeler Gap outer edge is the only one of the five sharp edges in the outer part of Saturn's A ring that is reasonably smooth in appearance (Tiscareno et al. 2005, DPS), with occultations indicating residuals less than 1 km upon a possibly non-zero eccentricity (R.G. French, personal communication, 2014). The other four (the inner and outer edges of the Encke Gap, the inner edge of the Keeler Gap, and the outer edge of the A ring itself) are characterized by wavy structure at moderate to high spatial frequencies, with amplitudes ranging from 2 to 30 km (Tiscareno et al. 2005, DPS).We will present a catalogue of wisp detections in Cassini images. We carry out repeated gaussian fits of the radial edge location in order to characterize edge structure and visually scan those fitted edges in order to detect wisps. With extensive coverage in longitude and in time, we will report on how wisps evolve and move, both within an orbit period and on longer timescales. We will also report on the frequency and interpretation of wisps that deviate from the standard morphology. We will discuss the implications of our results for the origin and nature of wisps, and for the larger picture of how masses interact within Saturn's rings.

MRI artifact reduction and quality improvement in the upper abdomen with PROPELLER and prospective acquisition correction (PACE) technique.

PubMed

Hirokawa, Yuusuke; Isoda, Hiroyoshi; Maetani, Yoji S; Arizono, Shigeki; Shimada, Kotaro; Togashi, Kaori

2008-10-01

The purpose of this study was to evaluate the effectiveness of the periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER [BLADE in the MR systems from Siemens Medical Solutions]) with a respiratory compensation technique for motion correction, image noise reduction, improved sharpness of liver edge, and image quality of the upper abdomen. Twenty healthy adult volunteers with a mean age of 28 years (age range, 23-42 years) underwent upper abdominal MRI with a 1.5-T scanner. For each subject, fat-saturated T2-weighted turbo spin-echo (TSE) sequences with respiratory compensation (prospective acquisition correction [PACE]) were performed with and without the BLADE technique. Ghosting artifact, artifacts except ghosting artifact such as respiratory motion and bowel movement, sharpness of liver edge, image noise, and overall image quality were evaluated visually by three radiologists using a 5-point scale for qualitative analysis. The Wilcoxon's signed rank test was used to determine whether a significant difference existed between images with and without BLADE. A p value less than 0.05 was considered to be statistically significant. In the BLADE images, image artifacts, sharpness of liver edge, image noise, and overall image quality were significantly improved (p < 0.001). With the BLADE technique, T2-weighted TSE images of the upper abdomen could provide reduced image artifacts including ghosting artifact and image noise and provide better image quality.

Nonlinear absorption in AlGaAs/GaAs multiple quantum well structures grown by metalorganic chemical vapor deposition

NASA Technical Reports Server (NTRS)

Lee, H. C.; Hariz, A.; Dapkus, P. D.; Kost, A.; Kawase, M.

1987-01-01

This paper reports the study of growth conditions for achieving the sharp exciton resonances and low-intensity saturation of these resonances in AlGaAs-GaAs multiple quantum well structures grown by metalorganic chemical vapor deposition. Low growth temperature is necessary to observe this sharp resonance feature at room temperature. The optimal growth conditions are a tradeoff between the high temperatures required for high quality AlGaAs and low temperatures required for high-purity GaAs. A strong optical saturation of the excitonic absorption has been observed. A saturation density as low as 250 W/sq cm is reported.

37 CFR 2.54 - Requirements for drawings submitted on paper.

Code of Federal Regulations, 2013 CFR

2013-07-01

....) long. One of the shorter sides of the sheet should be regarded as its top edge. The image must be no... the top of the drawing beginning one inch (2.5 cm.) from the top edge; and (d) Depict the mark in..., sharp and solid, and must not be fine or crowded. [68 FR 55764, Sept. 26, 2003] ...

37 CFR 2.54 - Requirements for drawings submitted on paper.

Code of Federal Regulations, 2011 CFR

2011-07-01

....) long. One of the shorter sides of the sheet should be regarded as its top edge. The image must be no... the top of the drawing beginning one inch (2.5 cm.) from the top edge; and (d) Depict the mark in..., sharp and solid, and must not be fine or crowded. [68 FR 55764, Sept. 26, 2003] ...

37 CFR 2.54 - Requirements for drawings submitted on paper.

Code of Federal Regulations, 2014 CFR

2014-07-01

....) long. One of the shorter sides of the sheet should be regarded as its top edge. The image must be no... the top of the drawing beginning one inch (2.5 cm.) from the top edge; and (d) Depict the mark in..., sharp and solid, and must not be fine or crowded. [68 FR 55764, Sept. 26, 2003] ...

37 CFR 2.54 - Requirements for drawings submitted on paper.

Code of Federal Regulations, 2012 CFR

2012-07-01

....) long. One of the shorter sides of the sheet should be regarded as its top edge. The image must be no... the top of the drawing beginning one inch (2.5 cm.) from the top edge; and (d) Depict the mark in..., sharp and solid, and must not be fine or crowded. [68 FR 55764, Sept. 26, 2003] ...

X-ray absorption spectroscopic studies of the active sites of nickel- and copper-containing metalloproteins

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

Tan, Grace O.

1993-06-01

X-ray absorption spectroscopy (XAS) is a useful tool for obtaining structural and chemical information about the active sites of metalloproteins and metalloenzymes. Information may be obtained from both the edge region and the extended X-ray absorption fine structure (EXAFS) or post-edge region of the K-edge X-ray absorption spectrum of a metal center in a compound. The edge contains information about the valence electronic structure of the atom that absorbs the X-rays. It is possible in some systems to infer the redox state of the metal atom in question, as well as the geometry and nature of ligands connected to it,more » from the features in the edge in a straightforward manner. The EXAFS modulations, being produced by the backscattering of the ejected photoelectron from the atoms surrounding the metal atom, provide, when analyzed, information about the number and type of neighbouring atoms, and the distances at which they occur. In this thesis, analysis of both the edge and EXAFS regions has been used to gain information about the active sites of various metalloproteins. The metalloproteins studied were plastocyanin (Pc), laccase and nickel carbon monoxide dehydrogenase (Ni CODH). Studies of Cu(I)-imidazole compounds, related to the protein hemocyanin, are also reported here.« less

Simulation of Near-Edge X-ray Absorption Fine Structure with Time-Dependent Equation-of-Motion Coupled-Cluster Theory.

PubMed

Nascimento, Daniel R; DePrince, A Eugene

2017-07-06

An explicitly time-dependent (TD) approach to equation-of-motion (EOM) coupled-cluster theory with single and double excitations (CCSD) is implemented for simulating near-edge X-ray absorption fine structure in molecular systems. The TD-EOM-CCSD absorption line shape function is given by the Fourier transform of the CCSD dipole autocorrelation function. We represent this transform by its Padé approximant, which provides converged spectra in much shorter simulation times than are required by the Fourier form. The result is a powerful framework for the blackbox simulation of broadband absorption spectra. K-edge X-ray absorption spectra for carbon, nitrogen, and oxygen in several small molecules are obtained from the real part of the absorption line shape function and are compared with experiment. The computed and experimentally obtained spectra are in good agreement; the mean unsigned error in the predicted peak positions is only 1.2 eV. We also explore the spectral signatures of protonation in these molecules.

Review on advanced composite materials boring mechanism and tools

NASA Astrophysics Data System (ADS)

Shi, Runping; Wang, Chengyong

2010-12-01

With the rapid development of aviation and aerospace manufacturing technology, advanced composite materials represented by carbon fibre reinforced plastics (CFRP) and super hybrid composites (fibre/metal plates) are more and more widely applied. The fibres are mainly carbon fibre, boron fibre, Aramid fiber and Sic fibre. The matrixes are resin matrix, metal matrix and ceramic matrix. Advanced composite materials have higher specific strength and higher specific modulus than glass fibre reinforced resin composites of the 1st generation. They are widely used in aviation and aerospace industry due to their high specific strength, high specific modulus, excellent ductility, anticorrosion, heat-insulation, sound-insulation, shock absorption and high&low temperature resistance. They are used for radomes, inlets, airfoils(fuel tank included), flap, aileron, vertical tail, horizontal tail, air brake, skin, baseboards and tails, etc. Its hardness is up to 62~65HRC. The holes are greatly affected by the fibre laminates direction of carbon fibre reinforced composite material due to its anisotropy when drilling in unidirectional laminates. There are burrs, splits at the exit because of stress concentration. Besides there is delamination and the hole is prone to be smaller. Burrs are caused by poor sharpness of cutting edge, delamination, tearing, splitting are caused by the great stress caused by high thrust force. Poorer sharpness of cutting edge leads to lower cutting performance and higher drilling force at the same time. The present research focuses on the interrelation between rotation speed, feed, drill's geometry, drill life, cutting mode, tools material etc. and thrust force. At the same time, holes quantity and holes making difficulty of composites have also increased. It requires high performance drills which won't bring out defects and have long tool life. It has become a trend to develop super hard material tools and tools with special geometry for drilling composite materials.

Compositional inhomogeneities in AlGaN thin films grown by molecular beam epitaxy: Effect on MSM UV photodetectors

NASA Astrophysics Data System (ADS)

Pramanik, Pallabi; Sen, Sayantani; Singha, Chirantan; Roy, Abhra Shankar; Das, Alakananda; Sen, Susanta; Bhattacharyya, A.

2016-10-01

Ultraviolet (UV) MSM photodetectors (PD) based on AlGaN alloys find many applications, including flame sensing. In this work we investigate the dependence of AlGaN based photodetectors grown by MBE on the kinetics of growth. MSM photodetectors were fabricated in the interdigitated configuration with Ni/Au contacts having 400 μm finger length and 10 μm finger spacing. Bulk Al0.4Ga0.6N films were grown on to sapphire substrates using an AlN buffer layer. A series of PDs were developed using the Al0.4Ga0.6N films grown under different group III/V flux ratios ranging from stoichiometric conditions to much higher than unity. Upon testing, it was observed that the otherwise identical photodetectors show significant decrease in dark current as AlGaN deposition conditions change from stoichiometric to excess group III, due to reduction of unintentional incorporation of oxygen-related point defects. In addition, the intensity and spectral dependence of the photocurrent also change, showing an extended low energy tail for the former and a sharp and prominent excitonic peak for the latter. The optical transmission measurements indicate a variation in Urbach energy with deposition conditions of the AlGaN films, although they have the same absorption edge. While all samples show a single red-shifted photoluminescence peak at room temperature, upon cooling, multiple higher energy peaks appear in the photoluminescence (PL) spectra, indicating that the alloys contain complex compositional inhomogeneities. Two types of alloy fluctuations, determined by the growth conditions, have been identified that modulate the optoelectronic properties of AlGaN by changing the spatial localization of excitons, thereby altering their stability. We identified that growth under stoichiometric conditions leads to compositional inhomogeneities that play a detrimental role in the operation of MSM photodetectors, which reduces the sharpness of the sensitivity edge, while growth under excess metal conditions enhances it.

Review on advanced composite materials boring mechanism and tools

NASA Astrophysics Data System (ADS)

Shi, Runping; Wang, Chengyong

2011-05-01

With the rapid development of aviation and aerospace manufacturing technology, advanced composite materials represented by carbon fibre reinforced plastics (CFRP) and super hybrid composites (fibre/metal plates) are more and more widely applied. The fibres are mainly carbon fibre, boron fibre, Aramid fiber and Sic fibre. The matrixes are resin matrix, metal matrix and ceramic matrix. Advanced composite materials have higher specific strength and higher specific modulus than glass fibre reinforced resin composites of the 1st generation. They are widely used in aviation and aerospace industry due to their high specific strength, high specific modulus, excellent ductility, anticorrosion, heat-insulation, sound-insulation, shock absorption and high&low temperature resistance. They are used for radomes, inlets, airfoils(fuel tank included), flap, aileron, vertical tail, horizontal tail, air brake, skin, baseboards and tails, etc. Its hardness is up to 62~65HRC. The holes are greatly affected by the fibre laminates direction of carbon fibre reinforced composite material due to its anisotropy when drilling in unidirectional laminates. There are burrs, splits at the exit because of stress concentration. Besides there is delamination and the hole is prone to be smaller. Burrs are caused by poor sharpness of cutting edge, delamination, tearing, splitting are caused by the great stress caused by high thrust force. Poorer sharpness of cutting edge leads to lower cutting performance and higher drilling force at the same time. The present research focuses on the interrelation between rotation speed, feed, drill's geometry, drill life, cutting mode, tools material etc. and thrust force. At the same time, holes quantity and holes making difficulty of composites have also increased. It requires high performance drills which won't bring out defects and have long tool life. It has become a trend to develop super hard material tools and tools with special geometry for drilling composite materials.

Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy below 100 eV: probing first-row transition-metal M-edges in chemical complexes

PubMed Central

Wang, Hongxin; Young, Anthony T.; Guo, Jinghua; Cramer, Stephen P.; Friedrich, Stephan; Braun, Artur; Gu, Weiwei

2013-01-01

X-ray absorption and scattering spectroscopies involving the 3d transition-metal K- and L-edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M-edges, which are below 100 eV. Synchrotron-based X-ray sources can have higher energy resolution at M-edges. M-edge X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) could therefore provide complementary information to K- and L-edge spectroscopies. In this study, M 2,3-edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M 2,3-edge RIXS on NiO, NiF2 and two other covalent complexes have been performed and different d–d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M-edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high-sensitivity and high-resolution superconducting tunnel junction X-ray detectors below 100 eV is also illustrated and discussed. PMID:23765304

Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy below 100 eV: probing first-row transition-metal M-edges in chemical complexes.

PubMed

Wang, Hongxin; Young, Anthony T; Guo, Jinghua; Cramer, Stephen P; Friedrich, Stephan; Braun, Artur; Gu, Weiwei

2013-07-01

X-ray absorption and scattering spectroscopies involving the 3d transition-metal K- and L-edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M-edges, which are below 100 eV. Synchrotron-based X-ray sources can have higher energy resolution at M-edges. M-edge X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) could therefore provide complementary information to K- and L-edge spectroscopies. In this study, M2,3-edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M2,3-edge RIXS on NiO, NiF2 and two other covalent complexes have been performed and different d-d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M-edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high-sensitivity and high-resolution superconducting tunnel junction X-ray detectors below 100 eV is also illustrated and discussed.

Maintaining knife sharpness in industrial meat cutting: A matter of knife or meat cutter ability.

PubMed

Karltun, J; Vogel, K; Bergstrand, M; Eklund, J

2016-09-01

Knife sharpness is imperative in meat cutting. The aim of this study was to compare the impact of knife blade steel quality with meat cutters' individual ability to maintain the cutting edge sharp in an industrial production setting. Twelve meat cutters in two different companies using three different knives during normal production were studied in this quasi-experimental study. Methods included were measuring knife cutting force before and after knife use, time knives were used, ratings of sharpness and discomfort and interviews. Results showed that the meat cutters' skill of maintaining sharpness during work had a much larger effect on knife sharpness during work than the knife steel differences. The ability was also related to feelings of discomfort and to physical exertion. It was found that meat cutters using more knives were more likely to suffer from discomfort in the upper limbs, which is a risk for developing MSD. Copyright © 2016 Elsevier Ltd. All rights reserved.

SHARP-B2: Flight Test Objectives, Project Implementation and Initial Results

NASA Technical Reports Server (NTRS)

Salute, Joan; Bull, Jeff; Rasky, Dan; Keese, David; Arnold, Jim (Technical Monitor)

2001-01-01

On September 28, 2000 the SHARP-B2 flight experiment was launched from Vandenberg Air Force Base, California. SHARP-B2 is the 2nd Ballistic flight test in the SHARP (Slender Hypervelocity Aerothermodynamic Research Probes) program which develops and tests new thermal protection materials and sharp body concepts. The flight tested Ultra-High Temperature Ceramics (UHTCs), which may radically change the design and performance of future aerospace vehicles. The new designs may overturn an age-old tenet of aerodynamics: that blunt-body aerospace vehicles, but not those with sharp leading edges, can survive the searing temperatures created as the vehicles tear through the atmosphere. Sharp leading edges offer numerous advantages over the blunt-body design currently in use. They could allow a space shuttle or crew return vehicle to maneuver in space more like an airplane and potentially allow astronauts to return to Earth from anywhere on orbit. They may allow improved astronaut safety by decreasing the risk of aborting into the ocean. They may reduce the electromagnetic interference that causes the communications blackouts that plague reentering blunt-body space vehicles. Reducing the amount of drag could lead to a reduction in propulsion requirements. Planetary probes could make use of sharp-body technology for aerobraking and to maximize their maneuvering capability. SHARP-B2 was a joint effort among NASA Ames, Sandia National Laboratories, the U.S. Air Force and the U.S. Army. It was funded by the Pathfinder Program at NASA's Marshall Space Flight Center. The SHARP-B2 payload was carried aboard a U.S. Air Force Minuteman III missile carrying a modified Mk 12A reentry vehicle (RV), which blasted off from Vandenberg Air Force Base near Lompoc, CA, at 3:01 a.m. PDT on Sept. 28. The RV was equipped with four 5. 1 inch-long strakes, or sharp leading edges. Each strake contained three UHTCs: ZrB2/SiC/C; ZrB2/SiC; and HfB2/SiC. Once it reached an altitude of about 400 nautical miles, the RV was released, returning through Earth's atmosphere at speeds exceeding Mach 22. One pair of strakes was designed to retract just before reaching temperatures high enough to cause the material to begin ablating. The other pair was designed to retract shortly after ablation began, at an expected temperature of nearly 5,100 degrees Fahrenheit. Sensors in the strakes measured how closely performance matched pre-flight calculations, and data was successfully collected throughout the 23-minute flight. A parachute was deployed (but not fully inflated) and the RV splashed down in a lagoon at the Kwajalein missile range in the Pacific Ocean. Within 3 hours radar track analysis showed ocean entry to be precisely at the latitude/longitude coordinates estimated during pre-flight simulation. An hour later a ship was deployed by the Army to recover the reentry vehicle, which was recovered in 165 feet of water, just 500 feet from its planned splash-down point. This is the first RV recovery in over a decade.

Image sharpness assessment based on wavelet energy of edge area

NASA Astrophysics Data System (ADS)

Li, Jin; Zhang, Hong; Zhang, Lei; Yang, Yifan; He, Lei; Sun, Mingui

2018-04-01

Image quality assessment is needed in multiple image processing areas and blur is one of the key reasons of image deterioration. Although great full-reference image quality assessment metrics have been proposed in the past few years, no-reference method is still an area of current research. Facing this problem, this paper proposes a no-reference sharpness assessment method based on wavelet transformation which focuses on the edge area of image. Based on two simple characteristics of human vision system, weights are introduced to calculate weighted log-energy of each wavelet sub band. The final score is given by the ratio of high-frequency energy to the total energy. The algorithm is tested on multiple databases. Comparing with several state-of-the-art metrics, proposed algorithm has better performance and less runtime consumption.

Solving intraocular lens-related pigment dispersion syndrome with repositioning of primary sulcus implanted single-piece IOL in the capsular bag.

PubMed

Kohnen, Thomas; Kook, Daniel

2009-08-01

We describe 2 cases of pigment dispersion syndrome (PDS) after uneventful phacoemulsification and implantation of a posterior chamber single-piece intraocular lens (IOL) with a sharp-edge design. In both cases, several days after IOL implantation, marked pigment dispersion was seen on the iris and in the trabecular meshwork, associated with an elevation in intraocular pressure (IOP). Thorough examination showed that the implanted IOL was in the ciliary sulcus. After surgical repositioning of both IOLs in the capsular bag, the pigment dispersion regressed and the IOP returned to normal limits. The 2 cases suggest that particularly in PDS patients, an IOL with an anterior sharp-edge design should be implanted in the capsular bag. Implantation in the ciliary sulcus should be avoided.

The origin of luminescence from di[4-(4-diphenylaminophenyl)phenyl]sulfone (DAPSF), a blue light emitter: an X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) study.

PubMed

Zhang, Duo; Zhang, Hui; Zhang, Xiaohong; Sham, Tsun-Kong; Hu, Yongfeng; Sun, Xuhui

2016-03-07

The electronic structure and optical properties of di[4-(4-diphenylaminophenyl)phenyl]sulfone (denoted as DAPSF), a highly efficient fluorophor, have been investigated using X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) spectroscopy at excitation energies across the C, N, O K-edges and the sulfur K-edge. The results indicate that the blue luminescence is mainly related to the sulfur functional group.

Adsorption and Reduction of Hexavalent Chromium on the Surface of Vivianite at Acidic Environment

NASA Astrophysics Data System (ADS)

HA, S.; Hyun, S. P.; Lee, W.

2016-12-01

Due to the rapid increase of chemical use in industrial activities, acid spills have frequently occurred in Korea. The acid spill causes soil and water acidification and additional problems such as heavy metal leaching from the soil. Hexavalent chromium (Cr(VI)) is relatively mobile in the environment and toxic and mutagenic. Monoclinic octa-hydrated ferrous phosphate, vivianite, is one of commonly found iron-bearing soil minerals occurring in phosphorous-enriched reducing environments. We have investigated reductive sorption of Cr(VI) on the vivianite surfaces using batch experimental tests under diverse groundwater conditions. Cr(VI) (5 mg/L) was added in 6.5 g/L vivianite suspension buffered at pH 5, 7, and 9, using 0.05 M HEPES or tris buffer solution, to check the effect of pH on the reductive sorption of Cr(VI) on the vivianite surface. The aqueous Cr(VI) removal was fastest at pH 5, followed by pH 7, and pH 9. The effect of ionic strength on the removal kinetics of Cr(VI) was negligible. It could be subsequently removed via sorption and reduction on the surface of vivianite of which reactive chemical species could be aqueous Fe(II), iron oxides, and metavivianite. Adsorption test was conducted using the same amount of Cr(III) to check the selectivity of chromium species on the vivianite surface for the reductive adsorption. Through Cr extraction test, amount of strong-bound Cr to vivianite is similar for Cr(III) and Cr(VI) injection but amount of weak-bound Cr is bigger for Cr(VI) injection. Reaction mechanism for the sorption and reductive transformation of Cr(VI) to Cr(III) species at reactive sites of vivianite surface are discussed based on surface complexation modeling and K-edge Fe X-ray absorption near edge structure (XANES) results. Since vivianite is reacted with Cr(VI), two smooth peaks of absorption edge changed to one sharp peak. Pre-edge that contains 1s-3d transition information tends to show high peak when reaction time is increased and pH is low. This fact indicated that the Fe(II) is oxidized to Fe(III) at the surface of viviante and this phenomena is optimized at pH 5 and longer elapsed time.

Multi-epoch Detections of Water Ice Absorption in Edge-on Disks around Herbig Ae Stars: PDS 144N and PDS 453

NASA Astrophysics Data System (ADS)

Terada, Hiroshi; Tokunaga, Alan T.

2017-01-01

We report the multi-epoch detections of water ice in 2.8-4.2 μ {{m}} spectra of two Herbig Ae stars, PDS 144N (A2 IVe) and PDS 453 (F2 Ve), which have an edge-on circumstellar disk. The detected water ice absorption is found to originate from their protoplanetary disks. The spectra show a relatively shallow absorption of water ice of around 3.1 μ {{m}} for both objects. The optical depths of the water ice absorption are ˜0.1 and ˜0.2 for PDS 144N and PDS 453, respectively. Compared to the water ice previously detected in low-mass young stellar objects with an edge-on disk with a similar inclination angle, these optical depths are significantly lower. It suggests that stronger UV radiation from the central stars effectively decreases the water ice abundance around the Herbig Ae stars through photodesorption. The water ice absorption in PDS 453 shows a possible variation of the feature among the six observing epochs. This variation could be due to a change of absorption materials passing through our line of sight to the central star. The overall profile of the water ice absorption in PDS 453 is quite similar to the absorption previously reported in the edge-on disk object d216-0939, and this unique profile may be seen only at a high inclination angle in the range of 76°-80°.

Thermal emission and absorption of radiation in finite inverted-opal photonic crystals

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

Florescu, Marian; Stimpson, Andrew J.; Lee, Hwang

We study theoretically the optical properties of a finite inverted-opal photonic crystal. The light-matter interaction is strongly affected by the presence of the three-dimensional photonic crystal and the alterations of the light emission and absorption processes can be used to suppress or enhance the thermal emissivity and absorptivity of the dielectric structure. We investigate the influence of the absorption present in the system on the relevant band edge frequencies that control the optical response of the photonic crystal. Our study reveals that the absorption processes cause spectral broadening and shifting of the band edge optical resonances, and determine a strongmore » reduction of the photonic band gap spectral range. Using the angular and spectral dependence of the band edge frequencies for stop bands along different directions, we argue that by matching the blackbody emission spectrum peak with a prescribed maximum of the absorption coefficient, it is possible to achieve an angle-sensitive enhancement of the thermal emission/absorption of radiation. This result opens a way to realize a frequency-sensitive and angle-sensitive photonic crystal absorbers/emitters.« less

Accurate Modeling of X-ray Extinction by Interstellar Grains

NASA Astrophysics Data System (ADS)

Hoffman, John; Draine, B. T.

2016-02-01

Interstellar abundance determinations from fits to X-ray absorption edges often rely on the incorrect assumption that scattering is insignificant and can be ignored. We show instead that scattering contributes significantly to the attenuation of X-rays for realistic dust grain size distributions and substantially modifies the spectrum near absorption edges of elements present in grains. The dust attenuation modules used in major X-ray spectral fitting programs do not take this into account. We show that the consequences of neglecting scattering on the determination of interstellar elemental abundances are modest; however, scattering (along with uncertainties in the grain size distribution) must be taken into account when near-edge extinction fine structure is used to infer dust mineralogy. We advertise the benefits and accuracy of anomalous diffraction theory for both X-ray halo analysis and near edge absorption studies. We present an open source Fortran suite, General Geometry Anomalous Diffraction Theory (GGADT), that calculates X-ray absorption, scattering, and differential scattering cross sections for grains of arbitrary geometry and composition.

Near-edge x-ray absorption fine structure spectroscopy at atmospheric pressure with a table-top laser-induced soft x-ray source

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

Kühl, Frank-Christian, E-mail: Frank-christian.kuehl@mail.de; Müller, Matthias, E-mail: matthias.mueller@llg-ev.de; Schellhorn, Meike

2016-07-15

The authors present a table-top soft x-ray absorption spectrometer, accomplishing investigations of the near-edge x-ray absorption fine structure (NEXAFS) in a laboratory environment. The system is based on a low debris plasma ignited by a picosecond laser in a pulsed krypton gas jet, emitting soft x-ray radiation in the range from 1 to 5 nm. For absorption spectroscopy in and around the “water window” (2.3–4.4 nm), a compact helium purged sample compartment for experiments at atmospheric pressure has been constructed and tested. NEXAFS measurements on CaCl{sub 2} and KMnO{sub 4} samples were conducted at the calcium and manganese L-edges, as well asmore » at the oxygen K-edge in air, atmospheric helium, and under vacuum, respectively. The results indicate the importance of atmospheric conditions for an investigation of sample hydration processes.« less

Effect of Fe-substitution on the structure and magnetism of single crystals Mn2-xFexBO4

NASA Astrophysics Data System (ADS)

Platunov, M. S.; Kazak, N. V.; Knyazev, Yu. V.; Bezmaternykh, L. N.; Moshkina, E. M.; Trigub, A. L.; Veligzhanin, A. A.; Zubavichus, Y. V.; Solovyov, L. A.; Velikanov, D. A.; Ovchinnikov, S. G.

2017-10-01

Single crystalline Mn2-xFexBO4 with x = 0.3, 0.5, 0.7 grown by the flux method have been studied by means of X-ray diffraction and X-ray absorption spectroscopy at both Mn and Fe K edges. The compounds were found to crystallize in an orthorhombic warwickite structure (sp. gr. Pnam). The lattice parameters change linearly with x thus obeying the Vegard's law. The Fe3+ substitution for Mn3+ has been deduced from the X-ray absorption near-edge structure (XANES) spectra. Two energy positions of the absorption edges have been observed in Mn K-edge XANES spectra indicating the presence of manganese in two different oxidation states. Extended X-ray absorption fine structure (EXAFS) analysis has shown the reduction of local structural distortions upon Fe substitution. The magnetization data have revealed a spin-glass transition at TSG = 11, 14 and 18 K for x = 0.3, 0.5 and 0.7, respectively.

Dispersion, Mixing, and Combustion in Uniform- and Variable-Density Air-Breathing High-Speed Propulsion Flows

DTIC Science & Technology

2013-08-28

and dispersion whose behavior is relevant to fuel-injection in propulsion devices. The latter investigations were conducted in water that allows...initially sharp scalar gradients in this high Schmidt-number fluid medium ( water : ⁄ ). Generally, such scalar plumes re reported to exhibit... Flowmetering : The Characteristics of Cylindrical Nozzles with Sharp Upstream Edges. Int. J. Heat and Fluid Flow 1(3):123-132. 3. Research personnel

EDGES result versus CMB and low-redshift constraints on ionization histories

NASA Astrophysics Data System (ADS)

Witte, Samuel; Villanueva-Domingo, Pablo; Gariazzo, Stefano; Mena, Olga; Palomares-Ruiz, Sergio

2018-05-01

We examine the results from the Experiment to Detect the Global Epoch of Reionization Signature (EDGES), which has recently claimed the detection of a strong absorption in the 21 cm hyperfine transition line of neutral hydrogen, at redshifts demarcating the early stages of star formation. More concretely, we study the compatibility of the shape of the EDGES absorption profile, centered at a redshift of z ˜17.2 , with measurements of the reionization optical depth, the Gunn-Peterson optical depth, and Lyman-α emission from star-forming galaxies, for a variety of possible reionization models within the standard Λ CDM framework (that is, a Universe with a cosmological constant Λ and cold dark matter CDM). When, conservatively, we only try to accommodate the location of the absorption dip, we identify a region in the parameter space of the astrophysical parameters that successfully explains all of the aforementioned observations. However, one of the most abnormal features of the EDGES measurement is the absorption amplitude, which is roughly a factor of 2 larger than the maximum allowed value in the Λ CDM framework. We point out that the simple considered astrophysical models that produce the largest absorption amplitudes are unable to explain the depth of the dip and of reproducing the observed shape of the absorption profile.

46 CFR 58.16-18 - Installation.

Code of Federal Regulations, 2012 CFR

2012-10-01

... metallic connections to minimize the effect of cylinder movement on the outlet piping. (2) Distribution... substantially secured against vibration by means of soft nonferrous metal clips without sharp edges in contact...

46 CFR 58.16-18 - Installation.

Code of Federal Regulations, 2014 CFR

2014-10-01

... metallic connections to minimize the effect of cylinder movement on the outlet piping. (2) Distribution... substantially secured against vibration by means of soft nonferrous metal clips without sharp edges in contact...

46 CFR 58.16-18 - Installation.

Code of Federal Regulations, 2011 CFR

2011-10-01

... metallic connections to minimize the effect of cylinder movement on the outlet piping. (2) Distribution... substantially secured against vibration by means of soft nonferrous metal clips without sharp edges in contact...

46 CFR 58.16-18 - Installation.

Code of Federal Regulations, 2013 CFR

2013-10-01

... metallic connections to minimize the effect of cylinder movement on the outlet piping. (2) Distribution... substantially secured against vibration by means of soft nonferrous metal clips without sharp edges in contact...

Optical characterization of sputtered YBaCo 4O 7+ δ thin films

NASA Astrophysics Data System (ADS)

Montoya, J. F.; Izquierdo, J. L.; Causado, J. D.; Bastidas, A.; Nisperuza, D.; Gómez, A.; Arnache, O.; Osorio, J.; Marín, J.; Paucar, C.; Morán, O.

2011-02-01

Thin films of YBaCo 4O 7+ δ were deposited on r (1012)-oriented Al 2O 3 substrates by dc magnetron sputtering. The as-grown films were characterized after their structural, morphological and optical properties. Special attention is devoted to the analysis of the optical response of these films as reports on optical properties of YBaCo 4O 7+ δ, especially in thin film form, are not frequently reported in the literature. Transmittance/absorbance measurements allow for determining two well defined energy gaps at 3.7 and 2.2 eV. In turn, infrared (IR) measurements show infrared transparency in the wave length range 4000-2500 nm with a sharp absorption edge at wave lengths less than 2500 nm. Complementary Raman spectra measurements on the thin films allowed for identifying bands associated with vibrating modes of CoO 4 and YO 6 in tetrahedral and octahedral oxygen coordination, respectively. Additional bands which seemed to stem from Co ions in octahedral oxygen coordination were also clearly identified.

First principle investigation of electronic structure, chemical bonding and optical properties of tetrabarium gallium trinitride oxide single crystal

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

Khan, Saleem Ayaz, E-mail: sayaz_usb@yahoo.com; Azam, Sikander

The electronic band structure, valence electron charge density and optical susceptibilities of tetrabarium gallium trinitride (TGT) were calculated via first principle study. The electronic band structure calculation describes TGT as semiconductor having direct band gap of 1.38 eV. The valence electronic charge density contour verified the non-polar covalent nature of the bond. The absorption edge and first peak of dielectric tensor components showed electrons transition from N-p state to Ba-d state. The calculated uniaxial anisotropy (0.4842) and birefringence (−0.0061) of present paper is prearranged as follow the spectral components of the dielectric tensor. The first peak in energy loss functionmore » (ELOS) shows the energy loss of fast traveling electrons in the material. The first sharp peak produced in ELOS around 10.5 eV show plasmon loss having plasma frequencies 0.1536, 0.004 and 0.066 of dielectric tensor components. This plasmon loss also cause decrease in reflectivity spectra.« less

Effect of cutting edge radius on surface roughness in diamond tool turning of transparent MgAl2O4 spinel ceramic

NASA Astrophysics Data System (ADS)

Yue, Xiaobin; Xu, Min; Du, Wenhao; Chu, Chong

2017-09-01

Transparent magnesium aluminate spinel (MgAl2O4) ceramic is one of an important optical materials. However, due to its pronounced hardness and brittleness, the optical machining of this material is very difficult. Diamond turning has advantages over the grinding process in flexibility and material removal rate. However, there is a lack of research that could support the use of diamond turning technology in the machining of MgAl2O4 spinel ceramic. Using brittle-ductile transition theory of brittle material machining, this work provides critical information that may help to realize ductile-regime turning of MgAl2O4 spinel ceramic. A characterization method of determination the cutting edge radius is introduced here. Suitable diamond tools were measured for sharpness and then chosen from a large number of candidate tools. The influence of rounded cutting edges on surface roughness of the MgAl2O4 spinel ceramic is also investigated. These results indicate that surface quality of MgAl2O4 spinel is relate to the radius of diamond tool's cutting edge, cutting speed, and feed rate. Sharp diamond tools (small radius of cutting edge) facilitated ductile-regime turning of MgAl2O4 spinel and shows great potential to reduce surface roughness and produce smoother final surface.

X-ray Absorption and Emission Spectroscopy of CrIII (Hydr)Oxides: Analysis of the K-Pre-Edge Region

NASA Astrophysics Data System (ADS)

Frommer, Jakob; Nachtegaal, Maarten; Czekaj, Izabela; Weng, Tsu-Chien; Kretzschmar, Ruben

2009-10-01

Pre-edge spectral features below the main X-ray absorption K-edge of transition metals show a pronounced chemical sensitivity and are promising sources of structural information. Nevertheless, the use of pre-edge analysis in applied research is limited because of the lack of definite theoretical peak-assignments. The aim of this study was to determine the factors affecting the chromium K-pre-edge features in trivalent chromium-bearing oxides and oxyhydroxides. The selected phases varied in the degree of octahedral polymerization and the degree of iron-for-chromium substitution in the crystal structure. We investigated the pre-edge fine structure by means of high-energy-resolution fluorescence detected X-ray absorption spectroscopy and by 1s2p resonant X-ray emission spectroscopy. Multiplet theory and full multiple-scattering calculations were used to analyze the experimental data. We show that the chromium K-pre-edge contains localized and nonlocalized transitions. Contributions arising from nonlocalized metal-metal transitions are sensitive to the nearest metal type and to the linkage mode between neighboring metal octahedra. Analyzing these transitions opens up new opportunities for investigating the local coordination environment of chromium in poorly ordered solids of environmental relevance.

Crystal structure and electronic states of Co and Gd ions in a Gd0.4Sr0.6CoO2.85 single crystal

NASA Astrophysics Data System (ADS)

Platunov, M. S.; Dudnikov, V. A.; Orlov, Yu. S.; Kazak, N. V.; Solovyov, L. A.; Zubavichus, Ya. V.; Veligzhanin, A. A.; Dorovatovskii, P. V.; Vereshchagin, S. N.; Shaykhutdinov, K. A.; Ovchinnikov, S. G.

2016-02-01

X-ray diffraction and X-ray absorption near edge structure (XANES) spectra have been measured at the Co K-edge and Gd L 3-edge in GdCoO3 and Gd0.4Sr0.6CoO2.85 cobaltites. The effect of Sr substitution on the crystal structure and electronic and magnetic states of Co3+ ions in a Gd0.4Sr0.6CoO2.85 single crystal has been analyzed. The XANES measurements at the Co K-edge have not showed a noticeable shift of the absorption edge with an increase in the concentration of Sr. This indicates that the effective valence of cobalt does not change. An increase in the intensity of absorption at the Gd L 3-edge is due to an increase in the degree of hybridization of the Gd(5 d) and O(2 p) states. The effect of hole doping on the magnetic properties results in the appearance of the ferromagnetic component and in a significant increase in the magnetic moment.

Surface current balance and thermoelectric whistler wings at airless astrophysical bodies: Cassini at Rhea.

PubMed

Teolis, B D; Sillanpää, I; Waite, J H; Khurana, K K

2014-11-01

Sharp magnetic perturbations found by the Cassini spacecraft at the edge of the Rhea flux tube are consistent with field-aligned flux tube currents. The current system results from the difference of ion and electron gyroradii and the requirement to balance currents on the sharp Rhea surface. Differential-type hybrid codes that solve for ion velocity and magnetic field have an intrinsic difficulty modeling the plasma absorber's sharp surface. We overcome this problem by instead using integral equations to solve for ion and electron currents and obtain agreement with the magnetic perturbations at Rhea's flux tube edge. An analysis of the plasma dispersion relations and Cassini data reveals that field-guided whistler waves initiated by (1) the electron velocity anisotropy in the flux tube and (2) interaction with surface sheath electrostatic waves on topographic scales may facilitate propagation of the current system to large distances from Rhea. Current systems like those at Rhea should occur generally, for plasma absorbers of any size such as spacecraft or planetary bodies, in a wide range of space plasma environments. Motion through the plasma is not essential since the current system is thermodynamic in origin, excited by heat flow into the object. The requirements are a difference of ion and electron gyroradii and a sharp surface, i.e., without a significant thick atmosphere. Surface current balance condition yields a current system at astronomical bodiesCurrent system possible for sharp (airless) objects of any sizeCurrent system is thermoelectric and motion through the plasma nonessential.

Surface current balance and thermoelectric whistler wings at airless astrophysical bodies: Cassini at Rhea

PubMed Central

Teolis, B D; Sillanpää, I; Waite, J H; Khurana, K K

2014-01-01

Sharp magnetic perturbations found by the Cassini spacecraft at the edge of the Rhea flux tube are consistent with field-aligned flux tube currents. The current system results from the difference of ion and electron gyroradii and the requirement to balance currents on the sharp Rhea surface. Differential-type hybrid codes that solve for ion velocity and magnetic field have an intrinsic difficulty modeling the plasma absorber's sharp surface. We overcome this problem by instead using integral equations to solve for ion and electron currents and obtain agreement with the magnetic perturbations at Rhea's flux tube edge. An analysis of the plasma dispersion relations and Cassini data reveals that field-guided whistler waves initiated by (1) the electron velocity anisotropy in the flux tube and (2) interaction with surface sheath electrostatic waves on topographic scales may facilitate propagation of the current system to large distances from Rhea. Current systems like those at Rhea should occur generally, for plasma absorbers of any size such as spacecraft or planetary bodies, in a wide range of space plasma environments. Motion through the plasma is not essential since the current system is thermodynamic in origin, excited by heat flow into the object. The requirements are a difference of ion and electron gyroradii and a sharp surface, i.e., without a significant thick atmosphere. Key Points Surface current balance condition yields a current system at astronomical bodies Current system possible for sharp (airless) objects of any size Current system is thermoelectric and motion through the plasma nonessential PMID:26167436

Subsonic balance and pressure investigation of a 60-deg delta wing with leading-edge devices (data report)

NASA Technical Reports Server (NTRS)

Rao, D. M.; Tingas, S. A.

1981-01-01

The drag reduction potential of leading edge devices on a 60 degree delta wing at high lift was examined. Geometric variations of fences, chordwise slots, pylon type vortex generators, leading edge vortex flaps, and sharp leading edge extensions were tested individually and in specific combinations to improve high-alpha drag performance with a minimum of low-alpha drag penalty. The force, moment, and surface static pressure data for angles of attack up to 23 degrees, at Mach and Reynolds numbers of 0.16 and 3.85 x 10 to the 6th power per meter are documented.

Electrical control of flying spin precession in chiral 1D edge states

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

Nakajima, Takashi; Komiyama, Susumu; Lin, Kuan-Ting

2013-12-04

Electrical control and detection of spin precession are experimentally demonstrated by using spin-resolved edge states in the integer quantum Hall regime. Spin precession is triggered at a corner of a biased metal gate, where electron orbital motion makes a sharp turn leading to a nonadiabatic change in the effective magnetic field via spin-orbit interaction. The phase of precession is controlled by the group velocity of edge-state electrons tuned by gate bias voltage: Spin-FET-like coherent control of spin precession is thus realized by all-electrical means.

Femtosecond time-resolved X-ray absorption spectroscopy of anatase TiO2 nanoparticles using XFEL

PubMed Central

Obara, Yuki; Ito, Hironori; Ito, Terumasa; Kurahashi, Naoya; Thürmer, Stephan; Tanaka, Hiroki; Katayama, Tetsuo; Togashi, Tadashi; Owada, Shigeki; Yamamoto, Yo-ichi; Karashima, Shutaro; Nishitani, Junichi; Yabashi, Makina; Suzuki, Toshinori; Misawa, Kazuhiko

2017-01-01

The charge-carrier dynamics of anatase TiO2 nanoparticles in an aqueous solution were studied by femtosecond time-resolved X-ray absorption spectroscopy using an X-ray free electron laser in combination with a synchronized ultraviolet femtosecond laser (268 nm). Using an arrival time monitor for the X-ray pulses, we obtained a temporal resolution of 170 fs. The transient X-ray absorption spectra revealed an ultrafast Ti K-edge shift and a subsequent growth of a pre-edge structure. The edge shift occurred in ca. 100 fs and is ascribed to reduction of Ti by localization of generated conduction band electrons into shallow traps of self-trapped polarons or deep traps at penta-coordinate Ti sites. Growth of the pre-edge feature and reduction of the above-edge peak intensity occur with similar time constants of 300–400 fs, which we assign to the structural distortion dynamics near the surface. PMID:28713842

Surface current balance and thermoelectric whistler wings at airless astrophysical bodies: Cassini at Rhea

NASA Astrophysics Data System (ADS)

Teolis, B. D.; Sillanpää, I.; Waite, J. H.; Khurana, K. K.

2014-11-01

Sharp magnetic perturbations found by the Cassini spacecraft at the edge of the Rhea flux tube are consistent with field-aligned flux tube currents. The current system results from the difference of ion and electron gyroradii and the requirement to balance currents on the sharp Rhea surface. Differential-type hybrid codes that solve for ion velocity and magnetic field have an intrinsic difficulty modeling the plasma absorber's sharp surface. We overcome this problem by instead using integral equations to solve for ion and electron currents and obtain agreement with the magnetic perturbations at Rhea's flux tube edge. An analysis of the plasma dispersion relations and Cassini data reveals that field-guided whistler waves initiated by (1) the electron velocity anisotropy in the flux tube and (2) interaction with surface sheath electrostatic waves on topographic scales may facilitate propagation of the current system to large distances from Rhea. Current systems like those at Rhea should occur generally, for plasma absorbers of any size such as spacecraft or planetary bodies, in a wide range of space plasma environments. Motion through the plasma is not essential since the current system is thermodynamic in origin, excited by heat flow into the object. The requirements are a difference of ion and electron gyroradii and a sharp surface, i.e., without a significant thick atmosphere.

Oxide ion diffusion mechanism related to Co and Fe ions in (Ba0.5Sr0.5)(Co0.8Fe0.2)O3-δ using in-situ X-ray absorption spectroscopy

NASA Astrophysics Data System (ADS)

Itoh, Takanori; Imai, Hideto

2018-03-01

The time changes of the white line and pre-edge intensities of Co and Fe K-edge in (Ba0.5Sr0.5)(Co0.8Fe0.2)O3-δ (BSCF) were observed to estimate the oxide ion diffusion related to Co and Fe ions by using in - situ X-ray absorption spectroscopy (XAS) during oxidation. The 20 μm self-standing BSCF film was prepared for in - situ XAS measurements. The time changes of absorption were fitted to the exponential decay function with two terms. The longer relaxation time (τ), related to the oxide ion diffusion during the oxidation of BSCF, is dependent on temperature. The oxide ion diffusion coefficients (D) were calculated from the τ s estimated by in - situ XAS. The values of the activation energy (Ea) for D related to Co K-edge white line, Co pre-edge, and Fe pre-edge were 1.8-2.0 eV. The value of Ea for D related to Fe K-edge white line, however, was higher than other absorption values at approximately 2.3 eV. We discussed the oxide ion diffusion mechanism related to Co and Fe ions in BSCF using in - situ XAS.

Large-scale Atmospheric Transport Processes

NASA Technical Reports Server (NTRS)

Plumb, R. Alan

2004-01-01

Continuing earlier work, we continued an investigation of the seasonal behavior of the edges of the stratospheric surf zone. These edges form a barrier between the rapidly mixed surf zone and the relatively isolated tropics. In collaboration with Dr Lynn Sparling at GSFC, we used a statistical analysis of HALOE and CLAES trace gas data from UARS to identify and locate these edges during each UARS observing period. We found that the edges on both sides of the equator are present all year (a fact that is important for conceptual models of stratospheric transport), though that on the summer side of the equator is much less sharp than the winter edge. The edges migrate seasonally into the summer hemisphere. Their location also shows influence of the QBO, together with the SAO at higher altitudes. Comparisons with effective diffusivities, and the edge locations, suggest that the edge is sustained by surf zone entrainment during winter, but by the residual circulation during summer.

46 CFR 56.50-70 - Gasoline fuel systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

.... (1) Fuel supply piping to the engines shall be of seamless drawn annealed copper pipe or tubing... sharp edges. Where passing through steel decks or bulkheads, fuel lines shall be protected by close...

46 CFR 56.50-70 - Gasoline fuel systems.

Code of Federal Regulations, 2014 CFR

2014-10-01

.... (1) Fuel supply piping to the engines shall be of seamless drawn annealed copper pipe or tubing... sharp edges. Where passing through steel decks or bulkheads, fuel lines shall be protected by close...

46 CFR 56.50-70 - Gasoline fuel systems.

Code of Federal Regulations, 2012 CFR

2012-10-01

.... (1) Fuel supply piping to the engines shall be of seamless drawn annealed copper pipe or tubing... sharp edges. Where passing through steel decks or bulkheads, fuel lines shall be protected by close...

46 CFR 56.50-70 - Gasoline fuel systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

.... (1) Fuel supply piping to the engines shall be of seamless drawn annealed copper pipe or tubing... sharp edges. Where passing through steel decks or bulkheads, fuel lines shall be protected by close...

46 CFR 56.50-70 - Gasoline fuel systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

.... (1) Fuel supply piping to the engines shall be of seamless drawn annealed copper pipe or tubing... sharp edges. Where passing through steel decks or bulkheads, fuel lines shall be protected by close...

46 CFR 160.017-13 - Construction.

Code of Federal Regulations, 2010 CFR

2010-10-01

... of the first step is approximately 600 mm (24 in.). (c) Lashing rings. A lashing ring must be...) Workmanship. A ladder must not have splinters, burrs, sharp edges, corners, projections, or other defects that...

46 CFR 160.176-9 - Construction.

Code of Federal Regulations, 2010 CFR

2010-10-01

...) Not have edges, projections, or corners, either external or internal, that are sharp enough to damage... inflation mechanism must be waterproof, permanent, and readable from a distance of 2.5 m (8 feet). (c...

16 CFR 1512.4 - Mechanical requirements.

Code of Federal Regulations, 2010 CFR

2010-01-01

... those possessed by an adult of normal intelligence and ability. (b) Sharp edges. There shall be no... Documents, U.S. Government Printing Office, Washington, D.C. 20402. 2 Copies may be obtained from: American...

The competitive growth of cubic domains in Ti(1-x)AlxN films studied by diffraction anomalous near-edge structure spectroscopy.

PubMed

Pinot, Y; Tuilier, M-H; Pac, M-J; Rousselot, C; Thiaudière, D

2015-11-01

Titanium and aluminium nitride films deposited by magnetron sputtering generally grow as columnar domains made of oriented nanocrystallites with cubic or hexagonal symmetry depending on Al content, which are embedded in more disordered grain boundaries. The substitution of Al atoms for Ti in the cubic lattice of the films improves their resistance to wear and oxidation, allowing their use as protective coatings. Ti K-edge X-ray absorption spectroscopy, which probes both crystallized and more disordered grain boundaries, and X-ray diffraction anomalous fine structure, which is sensitive to short- and long-range order within a given crystallized domain, are carried out on a set of Ti(1-x)AlxN films deposited by magnetron sputtering on Si substrates. Attention is paid to the shape of the pre-edge region, which is sensitive to the symmetry of the site occupied by Ti atoms, either octahedral in face-centred-cubic Ti-rich (TiN, Ti0.54Al0.46N) samples or tetrahedral in hexagonal-close-packed Al-rich (Ti0.32Al0.68N) films. In order to obain information on the titanium environment in the well crystallized areas, subtraction of the smooth part of the energy-dependent structure factor for the Bragg reflections is applied to the pre-edge region of the diffraction anomalous data in order to restore their spectroscopic appearance. A flat pre-edge is related to the typical octahedral environment of Ti atoms for cubic reflections. The difference observed between pre-edge spectra associated with face-centred-cubic 200 and 111 Bragg reflections of Ti0.54Al0.46N is assigned to Ti enrichment of 111 large well ordered domains compared with the more disordered 200 ones. The sharp peak observed in the spectrum recorded from the hexagonal 002 peak of Ti0.32Al0.68N can be regarded as a standard for the pure tetrahedral Ti environment in hexagonal-close-packed nitride.

Microfabricated instrument for tissue biopsy and analysis

DOEpatents

Krulevitch, Peter A.; Lee, Abraham P.; Northrup, M. Allen; Benett, William J.

2001-01-01

A microfabricated biopsy/histology instrument which has several advantages over the conventional procedures, including minimal specimen handling, smooth cutting edges with atomic sharpness capable of slicing very thin specimens (approximately 2 .mu.m or greater), micro-liter volumes of chemicals for treating the specimens, low cost, disposable, fabrication process which renders sterile parts, and ease of use. The cutter is a "cheese-grater" style design comprising a block or substrate of silicon and which uses anisotropic etching of the silicon to form extremely sharp and precise cutting edges. As a specimen is cut, it passes through the silicon cutter and lies flat on a piece of glass which is bonded to the cutter. Microchannels are etched into the glass or silicon substrates for delivering small volumes of chemicals for treating the specimen. After treatment, the specimens can be examined through the glass substrate.

SHEFEX - the vehicle and sub-systems for a hypersonic re-entry flight experiment

NASA Astrophysics Data System (ADS)

Turner, John; Hörschgen, Marcus; Turner, Peter; Ettl, Josef; Jung, Wolfgang; Stamminger, Andreas

2005-08-01

The purpose of the Sharp Edge Flight Experiment (SHEFEX) is to investigate the aerodynamic behaviour and thermal problems of an unconventional shape for re-entry vehicles, comprising multi-facetted surfaces with sharp edges. The main object of this experiment is the correlation of numerical analysis with real flight data in terms of the aerodynamic effects and structural concept for the thermal protection system (TPS). The Mobile Rocket Base of the German Aerospace Center (DLR) is responsible for the test flight of SHEFEX on a two stage unguided solid propellant sounding rocket which is required to provide a velocity of the order of March 7 for more than 30 seconds during atmospheric re-entry. This paper discusses the problems associated with the mission requirements and the solutions developed for the vehicle and sub-systems.

Fabrication of lithium/C-103 alloy heat pipes for sharp leading edge cooling

NASA Astrophysics Data System (ADS)

Ai, Bangcheng; Chen, Siyuan; Yu, Jijun; Lu, Qin; Han, Hantao; Hu, Longfei

2018-05-01

In this study, lithium/C-103 alloys heat pipes are proposed for sharp leading edge cooling. Three models of lithium/C-103 alloy heat pipes were fabricated. And their startup properties were tested by radiant heat tests and aerothermal tests. It is found that the startup temperature of lithium heat pipe was about 860 °C. At 1000 °C radiant heat tests, the operating temperature of lithium/C-103 alloy heat pipe is lower than 860 °C. Thus, startup failure occurs. At 1100 °C radiant heat tests and aerothermal tests, the operating temperature of lithium/C-103 alloy heat pipe is higher than 860 °C, and the heat pipe starts up successfully. The startup of lithium/C-103 alloy heat pipe decreases the leading edge temperature effectively, which endows itself good ablation resistance. After radiant heat tests and aerothermal tests, all the heat pipe models are severely oxidized because of the C-103 poor oxidation resistance. Therefore, protective coatings are required for further applications of lithium/C-103 alloy heat pipes.

Interstellar X-Ray Absorption Spectroscopy of the Crab Pulsar with the LETGS

NASA Technical Reports Server (NTRS)

Paerels, Frits; Weisskopf, Martin C.; Tennant, Allyn F.; ODell, Stephen L.; Swartz, Douglas A.; Kahn, Steven M.; Behar, Ehud; Becker, Werner; Whitaker, Ann F. (Technical Monitor)

2001-01-01

We study the interstellar X-ray absorption along the line of sight to the Crab Pulsar. The Crab was observed with the Low Energy Transmission Grating Spectrometer on the Chandra X-ray Observatory, and the pulsar, a point source, produces a full resolution spectrum. The continuum spectrum appears smooth, and we compare its parameters with other measurements of the pulsar spectrum. The spectrum clearly shows absorption edges due to interstellar Ne, Fe, and O. The O edge shows spectral structure that is probably due to O bound in molecules or dust. We search for near-edge structure (EXAFS) in the O absorption spectrum. The Fe L absorption spectrum is largely due to a set of unresolved discrete n=2-3 transitions in neutral or near-neutral Fe, and we analyze it using a new set of dedicated atomic structure calculations, which provide absolute cross sections. In addition to being interesting in its own right, the ISM absorption needs to be understood in quantitative detail in order to derive spectroscopic constraints on possible soft thermal radiation from the pulsar.

Calculation of optical and K pre-edge absorption spectra for ferrous iron of distorted sites in oxide crystals

NASA Astrophysics Data System (ADS)

Vercamer, Vincent; Hunault, Myrtille O. J. Y.; Lelong, Gérald; Haverkort, Maurits W.; Calas, Georges; Arai, Yusuke; Hijiya, Hiroyuki; Paulatto, Lorenzo; Brouder, Christian; Arrio, Marie-Anne; Juhin, Amélie

2016-12-01

Advanced semiempirical calculations have been performed to compute simultaneously optical absorption and K pre-edge x-ray absorption spectra of Fe2 + in four distinct site symmetries found in minerals. The four symmetries, i.e., a distorted octahedron, a distorted tetrahedron, a square planar site, and a trigonal bipyramidal site, are representative of the Fe2 + sites found in crystals and glasses. A particular attention has been paid to the definition of the p -d hybridization Hamiltonian which occurs for noncentrosymmetric symmetries in order to account for electric dipole transitions. For the different sites under study, an excellent agreement between calculations and experiments was found for both optical and x-ray absorption spectra, in particular in terms of relative intensities and energy positions of electronic transitions. To our knowledge, these are the first calculations of optical absorption spectra on Fe2 + placed in such diverse site symmetries, including centrosymmetric sites. The proposed theoretical model should help to interpret the features of both the optical absorption and the K pre-edge absorption spectra of 3 d transition metal ions and to go beyond the usual fingerprint interpretation.

Band-edge absorption coefficients from photoluminescence in semiconductor multiple quantum wells

NASA Technical Reports Server (NTRS)

Kost, Alan; Zou, Yao; Dapkus, P. D.; Garmire, Elsa; Lee, H. C.

1989-01-01

A novel approach to determining absorption coefficients in thin films using luminescence is described. The technique avoids many of the difficulties typically encountered in measurements of thin samples, Fabry-Perot effects, for example, and can be applied to a variety of materials. The absorption edge for GaAs/AlGaAs multiple quantum well structures, with quantum well widths ranging from 54 to 193 A is examined. Urbach (1953) parameters and excitonic linewidths are tabulated.

Brush seal bristle flexure and hard-rub characteristics

NASA Technical Reports Server (NTRS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1993-01-01

The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping', and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.

Brush seal low surface speed hard-rub characteristics

NASA Technical Reports Server (NTRS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1993-01-01

The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping,' and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.

Brush seal bristle flexure and hard-rub characteristics

NASA Technical Reports Server (NTRS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1992-01-01

The bristles of a 38.1-mm (1.5-in) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping,' and hot spots and streaks were found. With a smooth-plug rotor post-test leakage increased 30 percent over pretest leakage.

Influence of numerical dissipation in computing supersonic vortex-dominated flows

NASA Technical Reports Server (NTRS)

Kandil, O. A.; Chuang, A.

1986-01-01

Steady supersonic vortex-dominated flows are solved using the unsteady Euler equations for conical and three-dimensional flows around sharp- and round-edged delta wings. The computational method is a finite-volume scheme which uses a four-stage Runge-Kutta time stepping with explicit second- and fourth-order dissipation terms. The grid is generated by a modified Joukowski transformation. The steady flow solution is obtained through time-stepping with initial conditions corresponding to the freestream conditions, and the bow shock is captured as a part of the solution. The scheme is applied to flat-plate and elliptic-section wings with a leading edge sweep of 70 deg at an angle of attack of 10 deg and a freestream Mach number of 2.0. Three grid sizes of 29 x 39, 65 x 65 and 100 x 100 have been used. The results for sharp-edged wings show that they are consistent with all grid sizes and variation of the artificial viscosity coefficients. The results for round-edged wings show that separated and attached flow solutions can be obtained by varying the artificial viscosity coefficients. They also show that the solutions are independent of the way time stepping is done. Local time-stepping and global minimum time-steeping produce same solutions.

Cut marks on bone surfaces: influences on variation in the form of traces of ancient behaviour

PubMed Central

Braun, David R.; Pante, Michael; Archer, William

2016-01-01

Although we know that our lineage has been producing sharp-edged tools for over 2.6 Myr, our knowledge of what they were doing with these tools is far less complete. Studies of these sharp-edged stone tools show that they were most probably used as cutting implements. However, the only substantial evidence of this is the presence of cut marks on the bones of animals found in association with stone tools in ancient deposits. Numerous studies have aimed to quantify the frequency and placement of these marks. At present there is little consensus on the meaning of these marks and how the frequency relates to specific behaviours in the past. Here we investigate the possibility that mechanical properties associated with edges of stone tools as well as the properties of bones themselves may contribute to the overall morphology of these marks and ultimately their placement in the archaeological record. Standardized tests of rock mechanics (Young's modulus and Vickers hardness) indicate that the hardness of tool edges significantly affects cut-mark morphology. In addition, we show that indentation hardness of bones also impacts the overall morphology of cut marks. Our results show that rock type and bone portions influence the shape and prevalence of cut marks on animal bones. PMID:27274806

Brush seal bristle flexure and hard-rub characteristics

NASA Astrophysics Data System (ADS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1992-08-01

The bristles of a 38.1-mm (1.5-in) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping,' and hot spots and streaks were found. With a smooth-plug rotor post-test leakage increased 30 percent over pretest leakage.

Brush seal bristle flexure and hard-rub characteristics

NASA Astrophysics Data System (ADS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1993-10-01

The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping', and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.

Brush seal low surface speed hard-rub characteristics

NASA Astrophysics Data System (ADS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1993-06-01

The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping,' and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.

Natural laminar flow and airplane stability and control

NASA Technical Reports Server (NTRS)

Vandam, Cornelis P.

1986-01-01

Location and mode of transition from laminar to turbulent boundary layer flow have a dominant effect on the aerodynamic characteristics of an airfoil section. The influences of these parameters on the sectional lift and drag characteristics of three airfoils are examined. Both analytical and experimental results demonstrate that when the boundary layer transitions near the leading edge as a result of surface roughness, extensive trailing-edge separation of the turbulent boundary layer may occur. If the airfoil has a relatively sharp leading-edge, leading-edge stall due to laminar separation can occur after the leading-edge suction peak is formed. These two-dimensional results are used to examine the effects of boundary layer transition behavior on airplane longitudinal and lateral-directional stability and control.

ACCURATE MODELING OF X-RAY EXTINCTION BY INTERSTELLAR GRAINS

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

Hoffman, John; Draine, B. T., E-mail: jah5@astro.princeton.edu, E-mail: draine@astro.princeton.edu

Interstellar abundance determinations from fits to X-ray absorption edges often rely on the incorrect assumption that scattering is insignificant and can be ignored. We show instead that scattering contributes significantly to the attenuation of X-rays for realistic dust grain size distributions and substantially modifies the spectrum near absorption edges of elements present in grains. The dust attenuation modules used in major X-ray spectral fitting programs do not take this into account. We show that the consequences of neglecting scattering on the determination of interstellar elemental abundances are modest; however, scattering (along with uncertainties in the grain size distribution) must bemore » taken into account when near-edge extinction fine structure is used to infer dust mineralogy. We advertise the benefits and accuracy of anomalous diffraction theory for both X-ray halo analysis and near edge absorption studies. We present an open source Fortran suite, General Geometry Anomalous Diffraction Theory (GGADT), that calculates X-ray absorption, scattering, and differential scattering cross sections for grains of arbitrary geometry and composition.« less

Emission and absorption x-ray edges of Li

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

Callcott, T A; Arakawa, E T; Ederer, D L

1977-01-01

Measurements of the K X-ray absorption and emission edges of Li are reported. They were made with the same spectrometer at the NBS storage ring and serve to establish a 0.1 eV separation between the edges with no possibility of instrument calibration error. These results are compared with recent theories of Almbladh and Mahan describing the effects of incomplete phonon relaxation about the core hole. It is concluded that these theories give a satisfactory explanation of the data.

Single shot near edge x-ray absorption fine structure spectroscopy in the laboratory

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

Mantouvalou, I., E-mail: ioanna.mantouvalou@tu-berlin.de; Witte, K.; Martyanov, W.

With the help of adapted off-axis reflection zone plates, near edge X-ray absorption fine structure spectra at the C and N K-absorption edge have been recorded using a single 1.2 ns long soft X-ray pulse. The transmission experiments were performed with a laser-produced plasma source in the laboratory rendering time resolved measurements feasible independent on large scale facilities. A resolving power of E/ΔE ∼ 950 at the respective edges could be demonstrated. A comparison of single shot spectra with those collected with longer measuring time proves that all features of the used reference samples (silicon nitrate and polyimide) can be resolved in 1.2 ns.more » Hence, investigations of radiation sensitive biological specimen become possible due to the high efficiency of the optical elements enabling low dose experiments.« less

Boundary-Layer Edge Conditions and Transition Reynolds Number Data for a Flight Test at Mach 20 (Reentry F)

NASA Technical Reports Server (NTRS)

Johnson, Charles B.; Stainback, P. Calvin; Wicker, Kathleen C.; Boney, Lillian R.

1972-01-01

A flight experiment, designated Reentry F, was conducted to measure heat-transfer rates for laminar, transitional, and turbulent boundary layers on a 5 deg half-angle cone 3.962 m (13 ft) long with a preflight nose radius of 2.54 mm (0.10 in.). Data were obtained over an altitude range from 36.58 to 18.29 km (120 000 to 60 000 ft) at a flight velocity of about 6.096 km/sec (20 000 ft/sec). The nominal values of the free-stream total enthalpy, sharp-cone Mach number, and the wall-to-total enthalpy ratio were 18 MJ/kg (8000 Btu/lb), 15, and 0.03, respectively. Calculated boundary-layer edge conditions that account for effects of the entropy layer and corresponding local transition Reynolds numbers are reported in the present paper. Fully developed turbulent flow occurred with essentially constant boundary-layer edge conditions near the sharp-cone values. Transition data were obtained with local edge Mach numbers ranging from about 5.55 to 15. Transition Reynolds numbers, based on local condition, were as high as 6.6 x 10(exp 7) with an edge Mach number of about 14.4 at an altitude of 24.38 km (80 000 ft). The transition could be correlated with previous flight data taken over a Mach number range from 3 to 12 in terms of parameters including the effects of local unit Reynolds number, boundary-layer wall-to-edge enthalpy ratio, and local Mach number.

The Sharpness of Blades Used in Dermatologic Surgery.

PubMed

Awadalla, Farah; Hexsel, Camile; Goldberg, Leonard H

2016-01-01

There are numerous blades available for use in dermatologic procedures. There are different advantages that are inhere.nt to different blades due to their shape and size. One aspect of the blade that is instrumental to its performance, but is not objectively defined, is sharpness. This information could be useful when choosing a blade for a particular procedure. This study aims to objectively define the sharpness of blades used in dermatologic surgery. The Sharpness Tester (Cutlery and Allied Trades Research Association, Sheffield, UK) was used to test the force in Newtons a blade requires to cut through a silicone cylinder. New blades were used to determine a standard for the sharpness of new blades. Blades used for surgery were tested to determine the sharpness after use. The sharpest blade is the double-edged razor blade (0.395 N) followed by the dermablade (0.46 N), plastic handled #15 (0.541 N), #15c (0.575 N), #10 (0.647 N), and the #15 blade (0.664 N). The sharpness of a blade is an important factor in its ability to perform a task and should be taken into account when choosing a particular blade for a particular procedure.

Accurate and facile determination of the index of refraction of organic thin films near the carbon 1s absorption edge.

PubMed

Yan, Hongping; Wang, Cheng; McCarn, Allison R; Ade, Harald

2013-04-26

A practical and accurate method to obtain the index of refraction, especially the decrement δ, across the carbon 1s absorption edge is demonstrated. The combination of absorption spectra scaled to the Henke atomic scattering factor database, the use of the doubly subtractive Kramers-Kronig relations, and high precision specular reflectivity measurements from thin films allow the notoriously difficult-to-measure δ to be determined with high accuracy. No independent knowledge of the film thickness or density is required. High confidence interpolation between relatively sparse measurements of δ across an absorption edge is achieved. Accurate optical constants determined by this method are expected to greatly improve the simulation and interpretation of resonant soft x-ray scattering and reflectivity data. The method is demonstrated using poly(methyl methacrylate) and should be extendable to all organic materials.

Photochemically Generated Thiyl Free Radicals Observed by X-ray Absorption Spectroscopy

DOE PAGES

Sneeden, Eileen Y.; Hackett, Mark J.; Cotelesage, Julien J. H.; ...

2017-07-27

Sulfur-based thiyl radicals are known to be involved in a wide range of chemical and biological processes, but they are often highly reactive, which makes them difficult to observe directly. We report herein X-ray absorption spectra and analysis that support the direct observation of two different thiyl species generated photochemically by X-ray irradiation. The thiyl radical sulfur K-edge X-ray absorption spectra of both species are characterized by a uniquely low energy transition at about 2465 eV, which occurs at a lower energy than any previously observed feature at the sulfur K-edge and corresponds to a 1s → 3p transition tomore » the singly occupied molecular orbital of the free radical. In conclusion, our results constitute the first observation of substantial levels of thiyl radicals generated by X-ray irradiation and detected by sulfur K-edge X-ray absorption spectroscopy.« less

Electronic structure and optical properties of CdSxSe1-x solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

NASA Astrophysics Data System (ADS)

Murphy, M. W.; Yiu, Y. M.; Ward, M. J.; Liu, L.; Hu, Y.; Zapien, J. A.; Liu, Yingkai; Sham, T. K.

2014-11-01

The electronic structure and optical properties of a series of iso-electronic and iso-structural CdSxSe1-x solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed.

Accurate predictions of iron redox state in silicate glasses: A multivariate approach using X-ray absorption spectroscopy

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

Dyar, M. Darby; McCanta, Molly; Breves, Elly

2016-03-01

Pre-edge features in the K absorption edge of X-ray absorption spectra are commonly used to predict Fe3+ valence state in silicate glasses. However, this study shows that using the entire spectral region from the pre-edge into the extended X-ray absorption fine-structure region provides more accurate results when combined with multivariate analysis techniques. The least absolute shrinkage and selection operator (lasso) regression technique yields %Fe3+ values that are accurate to ±3.6% absolute when the full spectral region is employed. This method can be used across a broad range of glass compositions, is easily automated, and is demonstrated to yield accurate resultsmore » from different synchrotrons. It will enable future studies involving X-ray mapping of redox gradients on standard thin sections at 1 × 1 μm pixel sizes.« less

Accurate predictions of iron redox state in silicate glasses: A multivariate approach using X-ray absorption spectroscopy

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

Dyar, M. Darby; McCanta, Molly; Breves, Elly

2016-03-01

Pre-edge features in the K absorption edge of X-ray absorption spectra are commonly used to predict Fe 3+ valence state in silicate glasses. However, this study shows that using the entire spectral region from the pre-edge into the extended X-ray absorption fine-structure region provides more accurate results when combined with multivariate analysis techniques. The least absolute shrinkage and selection operator (lasso) regression technique yields %Fe 3+ values that are accurate to ±3.6% absolute when the full spectral region is employed. This method can be used across a broad range of glass compositions, is easily automated, and is demonstrated to yieldmore » accurate results from different synchrotrons. It will enable future studies involving X-ray mapping of redox gradients on standard thin sections at 1 × 1 μm pixel sizes.« less

Vanadium K-edge X-ray absorption spectroscopy of bromoperoxidase from Ascophyllum nodosum

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

Arber, J.M.; de Boer, E.; Garner, C.D.

Bromoperoxidase from Ascophyllum nodusum was the first vanadium-containing enzyme to be isolated. X-ray absorption spectra have now been collected in order to investigate the coordination of vanadium in the native, native plus bromide, native plus hydrogen peroxide, and dithionite-reduced forms of the enzyme. The edge and X-ray absorption near-edge structures show that, in the four samples studied, it is only on reduction of the native enzyme that the metal site is substantially altered. In addition, these data are consistent with the presence of vanadium(IV) in the reduced enzyme and vanadium(V) in the other samples. Extended X-ray absorption fine structure datamore » confirm that there are structural changes at the metal site on reduction of the native enzyme, notably a lengthening of the average inner-shell distance, and the presence of terminal oxygen together with histidine and oxygen-donating residues.« less

Photoemission and Photoabsorption Investigation of the Electronic Structure of Ytterbium Doped Strontium Fluoroapatite

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

Nelson, A J; van Buuren, T; Bostedt, C

X-ray photoemission and x-ray photoabsorption were used to study the composition and the electronic structure of ytterbium doped strontium fluoroapatite (Yb:S-FAP). High resolution photoemission measurements on the valence band electronic structure was used to evaluate the density of occupied states of this fluoroapatite. Element specific density of unoccupied electronic states in Yb:S-FAP were probed by x-ray absorption spectroscopy (XAS) at the Yb 4d (N{sub 4,5}-edge), Sr 3d (M{sub 4,5}-edge), P 2p (L{sub 2,3}-edge), F 1s and O 1s (K-edges) absorption edges. These results provide the first measurements of the electronic structure and surface chemistry of this material.

[New technique for safe removal of impacted foreign bodies in the upper gastrointestinal tract using reusable variceal "cap" (cup, cap or cylinder)].

PubMed

Chávez Rossell, Miguel

2012-01-01

The ingestion of a foreign body is one of the most common endoscopic emergencies. Foreign bodies in the upper gastrointestinal tract should be extracted as soon as possible to avoid serious complications such as perforation o bleeding. However, removals of foreign bodies with sharp edges are very difficult and can develop complications during their removal. Various devices have therefore been developed to prevent mucosal injury from the sharp edges during endoscopic extraction. We report a new technique for the successful foreign body extraction of upper digestive tract using the cap from six shooter variceal banding reused. We present 17 cases (9 males and 8 females). The types of foreign bodies removed were: chicken bones (n:7), fish bones (n:3), denture prosthesis (n:2), food bolus (n:2), long pin (n:1), golden thumb tack (n: 1) and press-through package (n:1). There were no complications. This new technique is safe and effective. Highlights its advantages: enhanced sight pharyngo esophageal junction, foreign bodies disimpact at that level, food bolus suck, avoid sharp object damage mucosal or scope and decrease time removal.

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

Hasegawa, Tomo; Shahed, Syed Mohammad Fakruddin; Sainoo, Yasuyuki

We formed an epitaxial film of CeO{sub 2}(111) by sublimating Ce atoms on Ru(0001) surface kept at elevated temperature in an oxygen ambient. X-ray photoemission spectroscopy measurement revealed a decrease of Ce{sup 4+}/Ce{sup 3+} ratio in a small temperature window of the growth temperature between 1070 and 1096 K, which corresponds to the reduction of the CeO{sub 2}(111). Scanning tunneling microscope image showed that a film with a wide terrace and a sharp step edge was obtained when the film was grown at the temperatures close to the reduction temperature, and the terrace width observed on the sample grown atmore » 1060 K was more than twice of that grown at 1040 K. On the surface grown above the reduction temperature, the surface with a wide terrace and a sharp step was confirmed, but small dots were also seen in the terrace part, which are considerably Ce atoms adsorbed at the oxygen vacancies on the reduced surface. This experiment demonstrated that it is required to use the substrate temperature close to the reduction temperature to obtain CeO{sub 2}(111) with wide terrace width and sharp step edges.« less

X-ray absorption spectroscopy investigations on oxidized Ni/Au contacts to p-GaN.

PubMed

Jan, J C; Asokan, K; Chiou, J W; Pong, W F; Tseng, P K; Chen, L C; Chen, F R; Lee, J F; Wu, J S; Lin, H J; Chen, C T

2001-03-01

X-ray absorption spectroscopy was used to investigate the electronic structure of as-deposited and oxidized Ni/Au contacts to p-GaN and to elucidate the mechanism responsible for low impedance. X-ray absorption near edge spectra of Ni K- and L3,2-edges clearly indicate formation of NiO on the sample surface after annealing. The reason for low impedance may be attributed to increase in hole concentration and existence of p-NiO layer on the surface.

Creation of forest edges has a global impact on forest vertebrates

PubMed Central

Peres, CA; Banks-Leite, C; Wearn, OR; Marsh, CJ; Butchart, SHM; Arroyo-Rodríguez, V; Barlow, J; Cerezo, A; Cisneros, L; D’Cruze, N; Faria, D; Hadley, A; Harris, S; Klingbeil, BT; Kormann, U; Lens, L; Medina-Rangel, GF; Morante-Filho, JC; Olivier, P; Peters, SL; Pidgeon, A; Ribeiro, DB; Scherber, C; Schneider-Maunory, L; Struebig, M; Urbina-Cardona, N; Watling, JI; Willig, MR; Wood, EM; Ewers, RM

2017-01-01

Summary Forest edges influence more than half the world’s forests and contribute to worldwide declines in biodiversity and ecosystem functions. However, predicting these declines is challenging in heterogeneous fragmented landscapes. We assembled an unmatched global dataset on species responses to fragmentation and developed a new statistical approach for quantifying edge impacts in heterogeneous landscapes to quantify edge-determined changes in abundance of 1673 vertebrate species. We show that 85% of species’ abundances are affected, either positively or negatively, by forest edges. Forest core species, which were more likely to be listed as threatened by the IUCN, only reached peak abundances at sites farther than 200-400 m from sharp high-contrast forest edges. Smaller-bodied amphibians, larger reptiles and medium-sized non-volant mammals experienced a larger reduction in suitable habitat than other forest core species. Our results highlight the pervasive ability of forest edges to restructure ecological communities on a global scale. PMID:29088701

Effects of acoustic- and optical-phonon sidebands on the fundamental optical-absorption edge in crystals and disordered semiconductors

NASA Astrophysics Data System (ADS)

Grein, C. H.; John, Sajeev

1990-04-01

We present the results of a parameter-free first-principles theory for the fine structure of the Urbach optical-absorption edge in crystalline and disordered semiconductors. The dominant features are recaptured by means of a simple physical argument based on the most probable potential-well analogy. At finite temperatures, the overall linear exponential Urbach behavior of the subgap optical-absorption coefficient is a consequence of multiple LA-phonon emission and absorption sidebands that accompany the electronic transition. The fine structure of subgap absorption spectra observed in some materials is accounted for by multiple TO-, LO-, and TA-phonon absorption and emission sidebands. Good agreement is found with experimental data on crystalline silicon. The effects of nonadiabaticity in the electron-phonon interaction are calculated.

Calculating and Mitigating the Risk of a Cut Glove to a Space Walking Astronaut

NASA Technical Reports Server (NTRS)

Castillo, Theresa; Haught, Megan

2013-01-01

One of the high risk operations on the International Space Station (ISS) is conducting a space walk, or an Extra Vehicular Activity (EVA). Threats to the space walking crew include airlock failures, space suit failures, and strikes from micro ]meteoroids and orbital debris (MM/OD). There are risks of becoming untethered from the space station, being pinched between the robotic arm and a piece of equipment, tearing your suit on a sharp edge, and other human errors that can be catastrophic. For decades NASA identified and tried to control sharp edges on external structure and equipment by design; however a new and unexpected source of sharp edges has since become apparent. Until recently, one of the underappreciated environmental risks was damage to EVA gloves during a spacewalk. The ISS has some elements which have been flying in the environment of space for over 14 years. It has and continues to be bombarded with MM/OD strikes that have created small, sharp craters all over the structure, including the dedicated EVA handrails and surrounding structure. These craters are capable of cutting through several layers of the EVA gloves. Starting in 2006, five EVA crewmembers reported cuts in their gloves so large they rendered the gloves unusable and in some cases cut the spacewalk short for the safety of the crew. This new hazard took engineers and managers by surprise. NASA has set out to mitigate this risk to safety and operations by redesigning the spacesuit gloves to be more resilient and designing a clamp to isolate MM/OD strikes on handrails, and is considering the necessity of an additional tool to repair strikes on non ]handrail surfaces (such as a file). This paper will address how the ISS Risk Team quantified an estimate of the MM/OD damage to the ISS, and the resulting likelihood of sustaining a cut glove in order to measure the effectiveness of the solutions being investigated to mitigate this risk to the mission and crew.

Silicon K-edge XANES spectra of silicate minerals

NASA Astrophysics Data System (ADS)

Li, Dien; Bancroft, G. M.; Fleet, M. E.; Feng, X. H.

1995-03-01

Silicon K-edge x-ray absorption near-edge structure (XANES) spectra of a selection of silicate and aluminosilicate minerals have been measured using synchrotron radiation (SR). The spectra are qualitatively interpreted based on MO calculation of the tetrahedral SiO{4/4-}cluster. The Si K-edge generally shifts to higher energy with increased polymerization of silicates by about 1.3 eV, but with considerable overlap for silicates of different polymerization types. The substitution of Al for Si shifts the Si K-edge to lower energy. The chemical shift of Si K-edge is also sensitive to cations in more distant atom shells; for example, the Si K-edge shifts to lower energy with the substitution of Al for Mg in octahedral sites. The shifts of the Si K-edge show weak correlation with average Si-O bond distance (dSi-O), Si-O bond valence (sSi-O) and distortion of SiO4 tetrahedra, due to the crystal structure complexity of silicate minerals and multiple factors effecting the x-ray absorption processes.

Temperature dependence of pre-edge features in Ti K-edge XANES spectra for ATiO₃ (A = Ca and Sr), A₂TiO₄ (A = Mg and Fe), TiO₂ rutile and TiO₂ anatase.

PubMed

Hiratoko, Tatsuya; Yoshiasa, Akira; Nakatani, Tomotaka; Okube, Maki; Nakatsuka, Akihiko; Sugiyama, Kazumasa

2013-07-01

XANES (X-ray absorption near-edge structure) spectra of the Ti K-edges of ATiO3 (A = Ca and Sr), A2TiO4 (A = Mg and Fe), TiO2 rutile and TiO2 anatase were measured in the temperature range 20-900 K. Ti atoms for all samples were located in TiO6 octahedral sites. The absorption intensity invariant point (AIIP) was found to be between the pre-edge and post-edge. After the AIIP, amplitudes damped due to Debye-Waller factor effects with temperature. Amplitudes in the pre-edge region increased with temperature normally by thermal vibration. Use of the AIIP peak intensity as a standard point enables a quantitative comparison of the intensity of the pre-edge peaks in various titanium compounds over a wide temperature range.

X-ray absorption spectroscopy: EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near Edge Structure)

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

Alp, E.E.; Mini, S.M.; Ramanathan, M.

1990-04-01

The x-ray absorption spectroscopy (XAS) had been an essential tool to gather spectroscopic information about atomic energy level structure in the early decades of this century. It has also played an important role in the discovery and systematization of rare-earth elements. The discovery of synchrotron radiation in 1952, and later the availability of broadly tunable synchrotron based x-ray sources have revitalized this technique since the 1970's. The correct interpretation of the oscillatory structure in the x-ray absorption cross-section above the absorption edge by Sayers et. al. has transformed XAS from a spectroscopic tool to a structural technique. EXAFS (Extended X-raymore » Absorption Fine Structure) yields information about the interatomic distances, near neighbor coordination numbers, and lattice dynamics. An excellent description of the principles and data analysis techniques of EXAFS is given by Teo. XANES (X-ray Absorption Near Edge Structure), on the other hand, gives information about the valence state, energy bandwidth and bond angles. Today, there are about 50 experimental stations in various synchrotrons around the world dedicated to collecting x-ray absorption data from the bulk and surfaces of solids and liquids. In this chapter, we will give the basic principles of XAS, explain the information content of essentially two different aspects of the absorption process leading to EXAFS and XANES, and discuss the source and samples limitations.« less

Ultrafast X-Ray Absorption Spectroscopy of Isochorically Heated Warm Dense Matter

NASA Astrophysics Data System (ADS)

Engelhorn, Kyle Craig

This dissertation will present a series of new tools, together with new techniques, focused on the understanding of warm and dense matter. We report on the development of a high time resolution and high detection efficiency x-ray camera. The camera is integrated with a short pulse laser and an x-ray beamline at the Advanced Light Source synchrotron. This provides an instrument for single shot, broadband x-ray absorption spectroscopy of warm and dense matter with 2 picosecond time resolution. Warm and dense matter is created by isochorically heating samples of known density with an ultrafast optical laser pulse, and X-ray absorption spectroscopy probes the unoccupied electronic density of states before the onset of hydrodynamic expansion and electron-ion equilibrium is reached. Measured spectra from a variety of materials are compared with first principle molecular dynamics and density functional theory calculations. In heated silicon dioxide spectra, two novel pre-edge features are observed, a peak below the band gap and absorption within the band gap, while a reduction was observed in the features above the edge. From consideration of the calculated spectra, the peak below the gap is attributed to valence electrons that have been promoted to the conduction band, the absorption within the gap is attributed to broken Si-O bonds, and the reduction above the edge is attributed to an elevated ionic temperature. In heated copper spectra, a time-dependent shift and broadening of the absorption edge are observed, consistent with and elevated electron temperature. The temporal evolution of the electronic temperature is accurately determined by fitting the measured spectra with calculated spectra. The electron-ion equilibration is studied with a two-temperature model. In heated nickel spectra, a shift of the absorption edge is observed. This shift is found to be inconsistent with calculated spectra and independent of incident laser fluence. A shift of the chemical potential is applied to the calculated spectra to obtain satisfactory agreement with measured spectra.

Geometries for roughness shapes in laminar flow

NASA Technical Reports Server (NTRS)

Holmes, Bruce J. (Inventor); Martin, Glenn L. (Inventor); Domack, Christopher S. (Inventor); Obara, Clifford J. (Inventor); Hassan, Ahmed A. (Inventor)

1986-01-01

A passive interface mechanism between upper and lower skin structures, and a leading edge structure of a laminar flow airfoil is described. The interface mechanism takes many shapes. All are designed to be different than the sharp orthogonal arrangement prevalent in the prior art. The shapes of the interface structures are generally of two types: steps away from the centerline of the airfoil with a sloping surface directed toward the trailing edge and, the other design has a gap before the sloping surface. By properly shaping the step, the critical step height is increased by more than 50% over the orthogonal edged step.

Experimental study of delta wing leading-edge devices for drag reduction at high lift

NASA Technical Reports Server (NTRS)

Johnson, T. D., Jr.; Rao, D. M.

1982-01-01

The drag reduction devices selected for evaluation were the fence, slot, pylon-type vortex generator, and sharp leading-edge extension. These devices were tested on a 60 degree flatplate delta (with blunt leading edges) in the Langley Research Center 7- by 10-foot high-speed tunnel at low speed and to angles of attack of 28 degrees. Balance and static pressure measurements were taken. The results indicate that all the devices had significant drag reduction capability and improved longitudinal stability while a slight loss of lift and increased cruise drag occurred.

A sharp knife for high temperatures

NASA Technical Reports Server (NTRS)

Heisman, R. M.; Iceland, W. F.

1978-01-01

Electrically heated nickel-chrome-steel alloy knife may be used to cut heat resistant plastic felt and similar materials with relative ease. Blade made of commercially available alloy RA 330 retains edge at temperatures as high as 927 C.

Microfabricated injectable drug delivery system

DOEpatents

Krulevitch, Peter A.; Wang, Amy W.

2002-01-01

A microfabricated, fully integrated drug delivery system capable of secreting controlled dosages of multiple drugs over long periods of time (up to a year). The device includes a long and narrow shaped implant with a sharp leading edge for implantation under the skin of a human in a manner analogous to a sliver. The implant includes: 1) one or more micromachined, integrated, zero power, high and constant pressure generating osmotic engine; 2) low power addressable one-shot shape memory polymer (SMP) valves for switching on the osmotic engine, and for opening drug outlet ports; 3) microfabricated polymer pistons for isolating the pressure source from drug-filled microchannels; 4) multiple drug/multiple dosage capacity, and 5) anisotropically-etched, atomically-sharp silicon leading edge for penetrating the skin during implantation. The device includes an externally mounted controller for controlling on-board electronics which activates the SMP microvalves, etc. of the implant.

Mantle structure beneath the western edge of the Colorado Plateau

USGS Publications Warehouse

Sine, C.R.; Wilson, D.; Gao, W.; Grand, S.P.; Aster, R.; Ni, J.; Baldridge, W.S.

2008-01-01

Teleseismic traveltime data are inverted for mantle Vp and Vs variations beneath a 1400 km long line of broadband seismometers extending from eastern New Mexico to western Utah. The model spans 600 km beneath the moho with resolution of ???50 km. Inversions show a sharp, large-magnitude velocity contrast across the Colorado Plateau-Great Basin transition extending ???200 km below the crust. Also imaged is a fast anomaly 300 to 600 km beneath the NW portion of the array. Very slow velocities beneath the Great Basin imply partial melting and/or anomalously wet mantle. We propose that the sharp contrast in mantle velocities across the western edge of the Plateau corresponds to differential lithospheric modification, during and following Farallon subduction, across a boundary defining the western extent of unmodified Proterozoic mantle lithosphere. The deep fast anomaly corresponds to thickened Farallon plate or detached continental lithosphere at transition zone depths. Copyright 2008 by the American Geophysical Union.

Aerodynamic and Aerothermodynamic Layout of the Hypersonic Flight Experiment Shefex

NASA Astrophysics Data System (ADS)

Eggers, Th.

2005-02-01

The purpose of the SHarp Edge Flight EXperiment SHEFEX is the investigation of possible new shapes for future launcher or reentry vehicles [1]. The main focus is the improvement of common space vehicle shapes by application of facetted surfaces and sharp edges. The experiment will enable the time accurate investigation of the flow effects and their structural answer during the hypersonic flight from 90 km down to an altitude of 20 km. The project, being performed under responsibility of the German Aerospace Center (DLR) is scheduled to fly on top of a two-stage solid propellant sounding rocket for the first half of 2005. The paper contains a survey of the aerodynamic and aerothermodynamic layout of the experimental vehicle. The results are inputs for the definition of the structural layout, the TPS and the flight instrumentation as well as for the preparation of the flight test performed by the Mobile Rocket Base of DLR.

Shefex -a Low Cost Highly Efficient Flight Experiment

NASA Astrophysics Data System (ADS)

Longo, J. M. A.

2005-02-01

The SHarp Edge Flight EXperiment, SHEFEX is aimed to investigate the behavior and the possibilities of an improved shape for aerospace vehicles considering sharp edges and facetted surfaces. It is a basic in-flight experimentation research on hypersonic technologies for future launcher vehicles but not a re-entry experiment, being performed under responsibility of the German Aerospace Center (DLR). Here it is briefly described the overall philosophy of the project, schedule for flight on top of a sounding rocket in the first half of 2005. The approaches adopted on each of the involved disciplines, i.e. mission system and launcher; aerodynamics, aerothermodynamics and in-flight measurement techniques; structure and thermal protection systems, including the passenger experiments are also discussed. The paper is aimed to show that the approach here proposed is an economical way to acquire important knowledge in the physics of the hypersonic flow.

A Three-Dimensional Solution of Flows over Wings with Leading-Edge Vortex Separation. Part 1: Engineering Document

NASA Technical Reports Server (NTRS)

Brune, G. W.; Weber, J. A.; Johnson, F. T.; Lu, P.; Rubbert, P. E.

1975-01-01

A method of predicting forces, moments, and detailed surface pressures on thin, sharp-edged wings with leading-edge vortex separation in incompressible flow is presented. The method employs an inviscid flow model in which the wing and the rolled-up vortex sheets are represented by piecewise, continuous quadratic doublet sheet distributions. The Kutta condition is imposed on all wing edges. Computed results are compared with experimental data and with the predictions of the leading-edge suction analogy for a selected number of wing planforms over a wide range of angle of attack. These comparisons show the method to be very promising, capable of producing not only force predictions, but also accurate predictions of detailed surface pressure distributions, loads, and moments.

Edge Detection Method Based on Neural Networks for COMS MI Images

NASA Astrophysics Data System (ADS)

Lee, Jin-Ho; Park, Eun-Bin; Woo, Sun-Hee

2016-12-01

Communication, Ocean And Meteorological Satellite (COMS) Meteorological Imager (MI) images are processed for radiometric and geometric correction from raw image data. When intermediate image data are matched and compared with reference landmark images in the geometrical correction process, various techniques for edge detection can be applied. It is essential to have a precise and correct edged image in this process, since its matching with the reference is directly related to the accuracy of the ground station output images. An edge detection method based on neural networks is applied for the ground processing of MI images for obtaining sharp edges in the correct positions. The simulation results are analyzed and characterized by comparing them with the results of conventional methods, such as Sobel and Canny filters.

Effects of wing leading-edge radius and Reynolds number on longitudinal aerodynamic characteristics of highly swept wing-body configurations at subsonic speeds

NASA Technical Reports Server (NTRS)

Henderson, W. P.

1976-01-01

An investigation was conducted in the Langley low turbulence pressure tunnel to determine the effects of wing leading edge radius and Reynolds number on the longitudinal aerodynamic characteristics of a series of highly swept wing-body configurations. The tests were conducted at Mach numbers below 0.30, angles of attack up to 16 deg, and Reynolds numbers per meter from 6.57 million to 43.27 million. The wings under study in this investigation had leading edge sweep angles of 61.7 deg, 64.61 deg, and 67.01 deg in combination with trailing edge sweep angles of 0 deg and 40.6 deg. The leading edge radii of each wing planform could be varied from sharp to nearly round.

Subsonic aerodynamic characteristics of interacting lifting surfaces with separated flow around sharp edges predicted by a vortex-lattice method

NASA Technical Reports Server (NTRS)

Lamar, J. E.; Gloss, B. B.

1975-01-01

Because the potential flow suction along the leading and side edges of a planform can be used to determine both leading- and side-edge vortex lift, the present investigation was undertaken to apply the vortex-lattice method to computing side-edge suction force for isolated or interacting planforms. Although there is a small effect of bound vortex sweep on the computation of the side-edge suction force, the results obtained for a number of different isolated planforms produced acceptable agreement with results obtained from a method employing continuous induced-velocity distributions. By using the method outlined, better agreement between theory and experiment was noted for a wing in the presence of a canard than was previously obtained.

Approximating the near-edge mass absorption coefficients for Ni using an ultra-thin bimetal foil

DOE PAGES

Alkire, Randall W.

2016-11-01

In an effort to improve the characteristics of a fluorescing metal-foil-based beam position monitor, a new bimetal ultra-thin (0.98/0.67 µm) Ti–Ni foil was introduced to replace an existing single-element ultra-thin 0.5 µm thick Cr foil. During characterization it was determined that absorption measurements on the bimetal foil could be used to fit the Ni mass absorption coefficients accurately in the vicinity of the NiKedge. Comparison with experimental results from the literature demonstrated that the fitting procedure produced coefficients with uncertainties of the order of ±1%. Once determined, these fit coefficients allowed the thickness of an independently mounted 8 µm thickmore » Ni foil to be computed from absorption measurements instead of relying on a tool-based measurement of the foil thickness. Using the 8 µm thick foil, a continuous map of Ni mass absorption coefficients was produced at 1 eV resolution throughout the near-edge region. Lastly, this high-resolution map marks a significant improvement over the existing NIST XCOM or FFAST database mass absorption coefficients, which have estimated errors of 10–20% for the near-edge region.« less

XANES analysis of dried and calcined bones.

PubMed

Rajendran, Jayapradhi; Gialanella, Stefano; Aswath, Pranesh B

2013-10-01

The structure of dried and calcined bones from chicken, bovine, deer, pig, sheep and chamois was examined using X-ray Absorption Near Edge Structure (XANES) spectroscopy. The oxygen K-edge absorption edge indicates that the surface of dried bone has a larger proportion of carbonate than the interior that is made up of phosphates. The phosphorus L and K edge clearly indicate that pyrophosphates, α-tricalcium phosphate (α-TCP) and hydrogen phosphates of Ca do not exist in either the dried bone or calcined bone and phosphorus exists as either β-tricalcium phosphate (β-TCP) or hydroxyapatite, both in the dried and calcined conditions. The Ca K-edge analysis indicates that β-TCP is the likely form of phosphate in both the dried and calcined conditions. Copyright © 2013 Elsevier B.V. All rights reserved.

Computational study of the absorption spectrum of defected ZnS nanoparticles

NASA Astrophysics Data System (ADS)

Michos, F. I.; Sigalas, M. M.

2018-04-01

Energy levels and absorption spectra of defected ZnS nanoparticles (NPs) were calculated with Density Functional Theory (DFT) and Time Dependent DFT. Several types of defects were examined such as vacancies and substitutions. NPs with S vacancies were found to have their absorption spectra moved to lower energies well inside the visible spectrum with significantly high oscillator strength. Also, NPs with substitution of S atoms with Cl, Br, or I showed significant absorption. In general, this type of defect moves the absorption spectra in lower energies, thus bringing the absorption edge into the visible spectrum, while the unperturbed NPs have absorption edges in the UV region. In addition, ZnS NPs are made from more abundant and less toxic elements than the more commonly used CdSe NPs. For that reason, they may find significant applications in solar cells and other photonic applications, as well as in biosensing applications as biomarkers.

A prospective case study of high boost, high frequency emphasis and two-way diffusion filters on MR images of glioblastoma multiforme.

PubMed

Anoop, B N; Joseph, Justin; Williams, J; Jayaraman, J Sivaraman; Sebastian, Ansa Maria; Sihota, Praveer

2018-06-01

Glioblastoma multiforme (GBM) appears undifferentiated and non-enhancing on magnetic resonance (MR) imagery. As MRI does not offer adequate image quality to allow visual discrimination of the boundary between GBM focus and perifocal vasogenic edema, surgical and radiotherapy planning become difficult. The presence of noise in MR images influences the computation of radiation dosage and precludes the edge based segmentation schemes in automated software for radiation treatment planning. The performance of techniques meant for simultaneous denoising and sharpening, like high boost filters, high frequency emphasize filters and two-way anisotropic diffusion is sensitive to the selection of their operational parameters. Improper selection may cause overshoot and saturation artefacts or noisy grey level transitions can be left unsuppressed. This paper is a prospective case study of the performance of high boost filters, high frequency emphasize filters and two-way anisotropic diffusion on MR images of GBM, for their ability to suppress noise from homogeneous regions and to selectively sharpen the true morphological edges. An objective method for determining the optimum value of the operational parameters of these techniques is also demonstrated. Saturation Evaluation Index (SEI), Perceptual Sharpness Index (PSI), Edge Model based Blur Metric (EMBM), Sharpness of Ridges (SOR), Structural Similarity Index Metric (SSIM), Peak Signal to Noise Ratio (PSNR) and Noise Suppression Ratio (NSR) are the objective functions used. They account for overshoot and saturation artefacts, sharpness of the image, width of salient edges (haloes), susceptibility of edge quality to noise, feature preservation and degree of noise suppression. Two-way diffusion is found to be superior to others in all these respects. The SEI, PSI, EMBM, SOR, SSIM, PSNR and NSR exhibited by two-way diffusion are 0.0016 ± 0.0012, 0.2049 ± 0.0187, 0.0905 ± 0.0408, 2.64 × 10 12  ± 1.6 × 10 12 , 0.9955 ± 0.0024, 38.214 ± 5.2145 and 0.3547 ± 0.0069, respectively.

Markov random field model-based edge-directed image interpolation.

PubMed

Li, Min; Nguyen, Truong Q

2008-07-01

This paper presents an edge-directed image interpolation algorithm. In the proposed algorithm, the edge directions are implicitly estimated with a statistical-based approach. In opposite to explicit edge directions, the local edge directions are indicated by length-16 weighting vectors. Implicitly, the weighting vectors are used to formulate geometric regularity (GR) constraint (smoothness along edges and sharpness across edges) and the GR constraint is imposed on the interpolated image through the Markov random field (MRF) model. Furthermore, under the maximum a posteriori-MRF framework, the desired interpolated image corresponds to the minimal energy state of a 2-D random field given the low-resolution image. Simulated annealing methods are used to search for the minimal energy state from the state space. To lower the computational complexity of MRF, a single-pass implementation is designed, which performs nearly as well as the iterative optimization. Simulation results show that the proposed MRF model-based edge-directed interpolation method produces edges with strong geometric regularity. Compared to traditional methods and other edge-directed interpolation methods, the proposed method improves the subjective quality of the interpolated edges while maintaining a high PSNR level.

Mechanism of Pressure-Induced Phase Transitions, Amorphization, and Absorption-Edge Shift in Photovoltaic Methylammonium Lead Iodide.

PubMed

Szafrański, Marek; Katrusiak, Andrzej

2016-09-01

Our single-crystal X-ray diffraction study of methylammonium lead triiodide, MAPbI3, provides the first comprehensive structural information on the tetragonal phase II in the pressure range to 0.35 GPa, on the cubic phase IV stable between 0.35 and 2.5 GPa, and on the isostructural cubic phase V observed above 2.5 GPa, which undergoes a gradual amorphization. The optical absorption study confirms that up to 0.35 GPa, the absorption edge of MAPbI3 is red-shifted, allowing an extension of spectral absorption. The transitions to phases IV and V are associated with the abrupt blue shifts of the absorption edge. The strong increase of the energy gap in phase V result in a spectacular color change of the crystal from black to red around 3.5 GPa. The optical changes have been correlated with the pressure-induced strain of the MAPbI3 inorganic framework and its frustration, triggered by methylammonium cations trapped at random orientations in the squeezed voids.

[Quantitative evaluation of acrylic and silicone intraocular lenses with a sharp optic edge design].

PubMed

Rabsilber, T M; Reuland, A J; Entz, B B; Holzer, M P; Limberger, I J; Auffarth, G U

2006-01-01

At the Department of Ophthalmology, Heidelberg, Germany, posterior capsule opacification (PCO) of a silicone and an acrylic intraocular lens (IOL) with a sharp optic edge design was evaluated. In a prospective study either the AMO ClariFlex silicone IOL or the Sensar AR40e hydrophobic acrylic IOL were implanted in 47 patients following uneventful phacoemulsification. Mean patient age was 76.2+/-7.8 (ClariFlex) and 73.4+/-12.9 years (AR40e), respectively. The mean follow-up time was 19.7+/-5.34 in the ClariFlex and 21.9+/-1.89 months in the AR40e group. PCO development was evaluated postoperatively using the EPCO 2000 analysis software (scale 0-4). Areas of interest were the total IOL optic, the central 3-mm zone as well as the capsulorhexis. In both groups, all patients achieved a BCVA of 20/32 (AR40e) and 20/25 (ClariFlex), respectively. There was a very low incidence of PCO development with a mean EPCO score of 0.07+/-0.2 (ClariFlex and 0.15+/-0.2 (AR40e). Within the 3-mm zone and the capsulorhexis, there was a tendency for even lower EPCO scores in both groups. We calculated a statistically significant difference for the two lens materials for all investigated IOL areas (Wilcoxon's test, p<0.05). Both IOLs with a sharp edge design showed good functional results, a stable position in the capsular bag as well as a low incidence of PCO development. However, the silicone IOL showed statistically significantly lower PCO scores.

Outer edges of debris discs. How sharp is sharp?

NASA Astrophysics Data System (ADS)

Thébault, P.; Wu, Y.

2008-04-01

Context: Rings or annulus-like features have been observed in most imaged debris discs. Outside the main ring, while some systems (e.g., β Pictoris and AU Mic) exhibit smooth surface brightness profiles (SB) that fall off roughly as ~r-3.5, others (e.g. HR 4796A and HD 139664) display large drops in luminosity at the ring's outer edge and steeper radial luminosity profiles. Aims: We seek to understand this diversity of outer edge profiles under the “natural” collisional evolution of the system, without invoking external agents such as planets or gas. Methods: We use a multi-annulus statistical code to follow the evolution of a collisional population, ranging in size from dust grains to planetesimals and initially confined within a belt (the “birth ring”). The crucial effect of radiation pressure on the dynamics and spatial distribution of the smallest grains is taken into account. We explore the dependence of the resulting disc surface brightness profile on various parameters. Results: The disc typically evolves toward a “standard” steady state, where the radial surface brightness profile smoothly decreases with radius as r-3.5 outside the birth ring. This confirms and extends the semi-analytical study of Strubbe & Chiang (2006, ApJ, 648, 652) and provides a firm basis for interpreting observed discs. Deviations from this typical profile, in the form of a sharp outer edge and a steeper fall-off, occur for two “extreme” cases: 1) when the birth ring is so massive that it becomes radially optically thick for the smallest grains. However, the required disc mass is probably too high here to be realistic; 2) when the dynamical excitation of the dust-producing planetesimals is so low (< e> and < i> ≤ 0.01) that the smallest grains, which otherwise dominate the optical depth of the system, are preferentially depleted. This low-excitation case, although possibly not generic, cannot be ruled out by observations for most systems, . Conclusions: Our “standard” profile provides a satisfactory explanation for a large group of debris discs that show smooth outer edges and SB ∝ r-3.5. Systems with sharper outer edges, barring other confining agents, could still be explained by “natural” collisional evolution if their dynamical excitation is very low. We show that such a dynamically-cold case provides a satisfactory fit to the specific HR4796A ring.

Assignment of Pre-edge Features in the Ru K-edge X-ray Absorption Spectra of Organometallic Ruthenium Complexes

PubMed Central

Getty, Kendra; Delgado-Jaime, Mario Ulises

2010-01-01

The nature of the lowest energy bound-state transition in the Ru K-edge X-ray Absorption Spectra for a series of Grubbs-type ruthenium complexes was investigated. The pre-edge feature was unambiguously assigned as resulting from formally electric dipole forbidden Ru 4d←1s transitions. The intensities of these transitions are extremely sensitive to the ligand environment and the symmetry of the metal centre. In centrosymmetric complexes the pre-edge is very weak since it is limited by the weak electric quadrupole intensity mechanism. By contrast, upon breaking centrosymmetry, Ru 5p-4d mixing allows for introduction of electric dipole allowed character resulting in a dramatic increase in the pre-edge intensity. The information content of this approach is explored as it relates to complexes of importance in olefin metathesis and its relevance as a tool for the study of reactive intermediates. PMID:20151030

Long- and Short-Range Structure of Ferrimagnetic Iron-Chromium Maghemites.

PubMed

García-Guaderrama, Marco; Montero-Cabrera, María E; Morán, Emilio; Alario-Franco, Miguel A; Fuentes-Cobas, Luis E; Macías-Ríos, Edgar; Esparza-Ponce, Hilda E; Fuentes-Montero, María E

2015-12-07

Maghemite-like materials containing Fe(3+) and Cr(3+) in comparable amounts have been prepared by solution-combustion synthesis. The conditions of synthesis and the magnetic properties are described. These materials are ferrimagnetic and are much more stable than pure iron maghemite since their maghemite-hematite transformation takes place at about ∼ 700 °C instead of ∼ 300 °C, as usually reported. These materials were studied by synchrotron radiation X-ray diffraction (XRD) and by X-ray absorption fine structure (XAFS) of the K-absorption edge of two elements. High-resolution XRD patterns were processed by means of the Rietveld method. Thus, maghemites were studied by XAFS in both Fe and Cr K-edges to clarify the short-range structure of the investigated systems. Pre-edge decomposition and theoretical modeling of X-ray absorption near edge structure transitions were performed. The extended X-ray absorption fine structure (EXAFS) spectra were fitted considering the facts that the central atom of Fe is able to occupy octahedral and tetrahedral sites, each with a weight adjustment, while Cr occupies only octahedral sites. Interatomic distances were determined for x = 1, by fitting simultaneously both Fe and Cr K-edges average EXAFS spectra. The results showed that the cation vacancies tend to follow a regular pattern within the structure of the iron-chromium maghemite (FeCrO3).

Electronic structure of transition metal-cysteine complexes from X-ray absorption spectroscopy.

PubMed

Leung, Bonnie O; Jalilehvand, Farideh; Szilagyi, Robert K

2008-04-17

The electronic structures of HgII, NiII, CrIII, and MoV complexes with cysteine were investigated by sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy and density functional theory. The covalency in the metal-sulfur bond was determined by analyzing the intensities of the electric-dipole allowed pre-edge features appearing in the XANES spectra below the ionization threshold. Because of the well-defined structures of the selected cysteine complexes, the current work provides a reference set for further sulfur K-edge XAS studies of bioinorganic active sites with transition metal-sulfur bonds from cysteine residues as well as more complex coordination compounds with thiolate ligands.

Boundary conditions in tunneling via quantum hydrodynamics

NASA Technical Reports Server (NTRS)

Nassar, Antonio B.

1993-01-01

Via the hydrodynamical formulation of quantum mechanics, an approach to the problem of tunneling through sharp-edged potential barriers is developed. Above all, it is shown how more general boundary conditions follow from the continuity of mass, momentum, and energy.

49 CFR 238.233 - Interior fittings and surfaces.

Code of Federal Regulations, 2010 CFR

2010-10-01

... determined by the railroad: (1) Longitudinal: 8g; (2) Vertical: 4g; and (3) Lateral: 4g. (c) Other interior..., except seats, shall be recessed or flush-mounted. (e) Sharp edges and corners in a locomotive cab and a...

Virtual edge illumination and one dimensional beam tracking for absorption, refraction, and scattering retrieval

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

Vittoria, Fabio A., E-mail: fabio.vittoria.12@ucl.ac.uk; Diemoz, Paul C.; Research Complex at Harwell, Harwell Oxford Campus, OX11 0FA Didcot

2014-03-31

We propose two different approaches to retrieve x-ray absorption, refraction, and scattering signals using a one dimensional scan and a high resolution detector. The first method can be easily implemented in existing procedures developed for edge illumination to retrieve absorption and refraction signals, giving comparable image quality while reducing exposure time and delivered dose. The second method tracks the variations of the beam intensity profile on the detector through a multi-Gaussian interpolation, allowing the additional retrieval of the scattering signal.

Anomalous small-angle scattering as a way to solve the Babinet principle problem

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

Boiko, M. E., E-mail: m.e.boiko@mail.ioffe.ru; Sharkov, M. D.; Boiko, A. M.

2013-12-15

X-ray absorption spectra (XAS) have been used to determine the absorption edges of atoms present in a sample under study. A series of small-angle X-ray scattering (SAXS) measurements using different monochromatic X-ray beams at different wavelengths near the absorption edges is performed to solve the Babinet principle problem. The sizes of clusters containing atoms determined by the method of XAS were defined in SAXS experiments. In contrast to differential X-ray porosimetry, anomalous SAXS makes it possible to determine sizes of clusters of different atomic compositions.

Anomalous small-angle scattering as a way to solve the Babinet principle problem

NASA Astrophysics Data System (ADS)

Boiko, M. E.; Sharkov, M. D.; Boiko, A. M.; Bobyl, A. V.

2013-12-01

X-ray absorption spectra (XAS) have been used to determine the absorption edges of atoms present in a sample under study. A series of small-angle X-ray scattering (SAXS) measurements using different monochromatic X-ray beams at different wavelengths near the absorption edges is performed to solve the Babinet principle problem. The sizes of clusters containing atoms determined by the method of XAS were defined in SAXS experiments. In contrast to differential X-ray porosimetry, anomalous SAXS makes it possible to determine sizes of clusters of different atomic compositions.

X-ray absorption spectroscopic studies of mononuclear non-heme iron enzymes

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

Westre, Tami E.

Fe-K-edge X-ray absorption spectroscopy (XAS) has been used to investigate the electronic and geometric structure of the iron active site in non-heme iron enzymes. A new theoretical extended X-ray absorption fine structure (EXAFS) analysis approach, called GNXAS, has been tested on data for iron model complexes to evaluate the utility and reliability of this new technique, especially with respect to the effects of multiple-scattering. In addition, a detailed analysis of the 1s→3d pre-edge feature has been developed as a tool for investigating the oxidation state, spin state, and geometry of iron sites. Edge and EXAFS analyses have then been appliedmore » to the study of non-heme iron enzyme active sites.« less

Comparative investigation of N donor ligand-lanthanide complexes from the metal and ligand point of view

NASA Astrophysics Data System (ADS)

Prüßmann, T.; Denecke, M. A.; Geist, A.; Rothe, J.; Lindqvist-Reis, P.; Löble, M.; Breher, F.; Batchelor, D. R.; Apostolidis, C.; Walter, O.; Caliebe, W.; Kvashnina, K.; Jorissen, K.; Kas, J. J.; Rehr, J. J.; Vitova, T.

2013-04-01

N-donor ligands such as n-Pr-BTP (2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine) studied here preferentially bind An(III) over Ln(III) in liquid-liquid separation of trivalent ac-tinides from spent nuclear fuel. The chemical and physical processes responsible for this selectivity are not yet well understood. We present systematic comparative near-edge X-ray absorption structure (XANES) spectroscopy investigations at the Gd L3 edge of [GdBTP3](NO3)3, [Gd(BTP)3](OTf)3, Gd(NO3)3, Gd(OTf)3 and N K edge of [Gd(BTP)3](NO3)3, Gd(NO3)3 complexes. The pre-edge absorption resonance in Gd L3 edge high-energy resolution X-ray absorption near edge structure spectra (HR-XANES) is explained as arising from 2p3/2 → 4f/5d electronic transitions by calculations with the FEFF9.5 code. Experimental evidence is found for higher electronic density on Gd in [Gd(BTP)3](NO3)3 and [Gd(BTP)3](OTf)3 compared to Gd in Gd(NO3)3 and Gd(OTf)3, and on N in [Gd(BTP)3](NO3)3 compared to n-Pr-BTP. The origin of the pre-edge structure in the N K edge XANES is explained by density functional theory (DFT) with the ORCA code. Results at the N K edge suggest a change in ligand orbital occupancies and mixing upon complexation but further work is necessary to interpret observed spectral variations.

Identifying anthropogenic uranium compounds using soft X-ray near-edge absorption spectroscopy

NASA Astrophysics Data System (ADS)

Ward, Jesse D.; Bowden, Mark; Tom Resch, C.; Eiden, Gregory C.; Pemmaraju, C. D.; Prendergast, David; Duffin, Andrew M.

2017-01-01

Uranium ores mined for industrial use are typically acid-leached to produce yellowcake and then converted into uranium halides for enrichment and purification. These anthropogenic chemical forms of uranium are distinct from their mineral counterparts. The purpose of this study is to use soft X-ray absorption spectroscopy to characterize several common anthropogenic uranium compounds important to the nuclear fuel cycle. Chemical analyses of these compounds are important for process and environmental monitoring. X-ray absorption techniques have several advantages in this regard, including element-specificity, chemical sensitivity, and high spectral resolution. Oxygen K-edge spectra were collected for uranyl nitrate, uranyl fluoride, and uranyl chloride, and fluorine K-edge spectra were collected for uranyl fluoride and uranium tetrafluoride. Interpretation of the data is aided by comparisons to calculated spectra. The effect of hydration state on the sample, a potential complication in interpreting oxygen K-edge spectra, is discussed. These compounds have unique spectral signatures that can be used to identify unknown samples.

Imaging at an x-ray absorption edge using free electron laser pulses for interface dynamics in high energy density systems [Resonant phase contrast imaging for interface physics

DOE PAGES

Beckwith, M. A.; Jiang, S.; Schropp, A.; ...

2017-05-01

Tuning the energy of an x-ray probe to an absorption line or edge can provide material-specific measurements that are particularly useful for interfaces. Simulated hard x-ray images above the Fe K-edge are presented to examine ion diffusion across an interface between Fe 2O 3 and SiO 2 aerogel foam materials. The simulations demonstrate the feasibility of such a technique for measurements of density scale lengths near the interface with submicron spatial resolution. A proof-of-principle experiment is designed and performed at the Linac coherent light source facility. Preliminary data show the change of the interface after shock compression and heating withmore » simultaneous fluorescence spectra for temperature determination. Here, the results provide the first demonstration of using x-ray imaging at an absorption edge as a diagnostic to detect ultrafast phenomena for interface physics in high-energy-density systems.« less

Aerodynamic characteristics of three slender sharp-edge 74 degrees swept wings at subsonic, transonic, and supersonic Mach numbers

NASA Technical Reports Server (NTRS)

Davenport, E. E.

1974-01-01

Slender sharp-edge wings having leading-edge sweep angles of 74 deg have been studied at Mach numbers from 0.60 to 2.80, at angles of attack from about minus 4 deg to 22 deg, and at angles of sideslip from 0 deg to 5 deg. The wings had delta, arrow, and diamond planforms. The experimental tests were made in the Langley 8-foot transonic pressure tunnel and the Langley Unitary Plan wind tunnel test section number 1. The theoretical predictions were made using the theories of NASA TN D-3767 and NASA TN D-6243. The results of the study indicated that the lift and drag characteristics as affected by planform and Mach number could be reasonably well predicted for the delta wing in the subsonic and transonic Mach number range. In the supersonic range, the delta and diamond wings were about equally good in the degree of agreement between experiment and theory. In making drag-due-to-lift predictions the vortex lift effects must be taken into account if reasonable results are to be obtained at moderate or high lift coefficients.

Seeing blur: 'motion sharpening' without motion.

PubMed Central

Georgeson, Mark A; Hammett, Stephen T

2002-01-01

It is widely supposed that things tend to look blurred when they are moving fast. Previous work has shown that this is true for sharp edges but, paradoxically, blurred edges look sharper when they are moving than when stationary. This is 'motion sharpening'. We show that blurred edges also look up to 50% sharper when they are presented briefly (8-24 ms) than at longer durations (100-500 ms) without motion. This argues strongly against high-level models of sharpening based specifically on compensation for motion blur. It also argues against a recent, low-level, linear filter model that requires motion to produce sharpening. No linear filter model can explain our finding that sharpening was similar for sinusoidal and non-sinusoidal gratings, since linear filters can never distort sine waves. We also conclude that the idea of a 'default' assumption of sharpness is not supported by experimental evidence. A possible source of sharpening is a nonlinearity in the contrast response of early visual mechanisms to fast or transient temporal changes, perhaps based on the magnocellular (M-cell) pathway. Our finding that sharpening is not diminished at low contrast sets strong constraints on the nature of the nonlinearity. PMID:12137571

Edge geometry effects on resonance response of electroplated cylindrical Ni/PZT/Ni magnetoelectric composites

NASA Astrophysics Data System (ADS)

Yakubov, Vladislav; Xu, Lirong; Volinsky, Alex A.; Qiao, Lijie; Pan, De'an

2017-08-01

Trilayer Ni/PZT/Ni cylindrical magnetoelectric (ME) composites were prepared by electrodeposition, a process, which creates sub-millimeter raised edges due to current concentration near sharp points. The ME response in both axial and vertical modes was measured with the edges, with only outer edges removed, and with both outer and inner edges removed. The ME voltage coefficient improved at resonance by 40% and 147% without the edges in the vertical and axial modes, respectively. The observed improvements in three different samples were only present at the ME resonance and no changes were detected outside of the ME resonance. Mechanical quality factor at resonance also improved with no effect on the resonant frequency. Experimentally demonstrated minor geometry changes resulted in substantial ME improvement at resonant frequency. This study demonstrates device performance optimization. The observed effects have been attributed to improved vibrations in terms of decreased damping coefficient and enhanced vibration amplitude at resonance.

Edge-based image restoration.

PubMed

Rareş, Andrei; Reinders, Marcel J T; Biemond, Jan

2005-10-01

In this paper, we propose a new image inpainting algorithm that relies on explicit edge information. The edge information is used both for the reconstruction of a skeleton image structure in the missing areas, as well as for guiding the interpolation that follows. The structure reconstruction part exploits different properties of the edges, such as the colors of the objects they separate, an estimate of how well one edge continues into another one, and the spatial order of the edges with respect to each other. In order to preserve both sharp and smooth edges, the areas delimited by the recovered structure are interpolated independently, and the process is guided by the direction of the nearby edges. The novelty of our approach lies primarily in exploiting explicitly the constraint enforced by the numerical interpretation of the sequential order of edges, as well as in the pixel filling method which takes into account the proximity and direction of edges. Extensive experiments are carried out in order to validate and compare the algorithm both quantitatively and qualitatively. They show the advantages of our algorithm and its readily application to real world cases.

Optical absorption in degenerately doped semiconductors: Mott transition or Mahan excitons?

NASA Astrophysics Data System (ADS)

Schleife, André.; Rödl, Claudia; Hannewald, Karsten; Bechstedt, Friedhelm

2012-02-01

In the exploration of material properties, parameter-free calculations are a modern, sophisticated complement to cutting-edge experimental techniques. Ab-initio calculations are now capable of providing a deep understanding of the interesting physics underlying the electronic structure and optical absorption, e.g., of the transparent conductive oxides. Due to electron doping, these materials are conductive even though they have wide fundamental band gaps. The degenerate electron gas in the lowest conduction-band states drastically modifies the Coulomb interaction between the electrons and, hence, the optical properties close to the absorption edge. We describe these effects by developing an ab-initio technique which captures also the Pauli blocking and the Fermi-edge singularity at the optical absorption onset, that occur in addition to quasiparticle and excitonic effects. We answer the question whether free carriers induce an excitonic Mott transition or trigger the evolution of Wannier-Mott excitons into Mahan excitons. The prototypical n-type zinc oxide is studied as an example.

Determining the Edges of the Path of Totality on August 21, 2017

NASA Astrophysics Data System (ADS)

Dunham, David W.; Maley, Paul D.; Kok, Jan; Bruenjes, Fred

2018-01-01

The International Occultation Timing Association (IOTA) attempted a citizen-science project to determine the locations of the edges of the path of totality, similar to what was done visually in New York City during the 1925 eclipse. With ubiquitous smart phones, we asked observers to record the eclipse, preferably with clip-on 8x telephoto lenses. The limits are not sharp since the solar intensity drops off gradually at the path edges. We hoped to determine how accurately the path edges could be determined, and the width of their “fuzziness”. But it was not possible to find any astronomers who weren’t also going to the center, who might otherwise help organize some path edge observations. In 1925, people were less concerned about the possibility of suffering eye damage from quick glimpses at the eclipse. In 2017, several were concerned about damage to their cell phones, although our tests showed this was not a problem for the two minutes desired. The only successes were at Minden, Nebraska where high school students set up 15 stations across the southern limit and recorded the eclipse with iPads, and near Wheatland, Wyoming, where Jan Kok set up 21 pre-pointed smart phones with 8x lenses that he was able to program, to record the eclipse during the critical two minutes. We found that the dynamic range of the smart phone recordings could not distinguish between the corona, and the Baily’s beads around the contacts, so useful times of the duration of “totality” could not be determined. A few IOTA observers recorded Baily’s beads telescopically at a few locations near the eclipse limits. An especially good color recording of Baily’s beads was made by Fred Bruenjes from only 1.3 km inside the southern limit. We hope that similar recordings with accurate time stamping can be obtained at a few locations near both limits of future eclipses. Even better might be recordings of the flash spectrum near both limits, to measure the transition from absorption lines in the photosphere to emission lines of the chomosphere.

The use of C-near edge X-ray absorption fine structure spectroscopy for the elaboration of chemistry in lignocellulosics

Treesearch

Lucian A. Lucia; Hiroki Nanko; Alan W. Rudie; Doug G. Mancosky; Sue Wirick

2006-01-01

The research presented elucidates the oxidation chemistry occurring in hydrogen peroxide bleached kraft pulp fibers by employing carbon near edge x-ray absorption fine structure spectroscopy (C-NEXAFS). C-NEXAFS is a soft x-ray technique that selectively interrogates atomic moieties using photoelectrons (Xrays) of variable energies. The X1A beam line at the National...

Performance of special radiation-hardened optical fibers intended for use in the telecom spectral windows at a megagray level

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

Tomashuk, A.L.; Dianov, E.M.; Golant, K.M.

Gamma-radiation-induced absorption spectra (2.15 MGy(Si)) are compared in N-doped and pure silica fibers fabricated by surface plasma CVD-process under different regimes with the aim to reveal the chief absorption mechanisms in the telecom spectral windows and to work out an optimum fiber design. The long wavelength absorption edge is shown to be the main absorption mechanism at megagray doses. Its value increases with increasing bonded hydrogen concentration in the fiber glass network and is slightly greater in N-doped fibers. No nitrogen-related color centers have been revealed in the short wavelength loss edge, which is determined by chlorine impurity in silica.

A Deep Chandra Observation of the Centaurus Cluster:Bubbles, Filaments and Edges

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

Fabian, A.C.

2005-03-14

X-ray images and gas temperatures taken from a deep {approx}200 ks Chandra observation of the Centaurus cluster are presented. Multiple inner bubbles and outer semicircular edges are revealed, together with wispy filaments of soft X-ray emitting gas. The frothy central structure and eastern edge are likely due to the central radio source blowing bubbles in the intracluster gas. The semicircular edges to the surface brightness maps 32 kpc to the east and 17.5 kpc to the west are marked by sharp temperature increases and abundance drops. The edges could be due to sloshing motions of the central potential, or aremore » possibly enhanced by earlier radio activity. The high abundance of the innermost gas (about 2.5 times Solar) limits the amount of diffusion and mixing taking place.« less

Combined Mössbauer spectroscopic, multi-edge X-ray absorption spectroscopic, and density functional theoretical study of the radical SAM enzyme spore photoproduct lyase.

PubMed

Silver, Sunshine C; Gardenghi, David J; Naik, Sunil G; Shepard, Eric M; Huynh, Boi Hanh; Szilagyi, Robert K; Broderick, Joan B

2014-03-01

Spore photoproduct lyase (SPL), a member of the radical S-adenosyl-L-methionine (SAM) superfamily, catalyzes the direct reversal of the spore photoproduct, a thymine dimer specific to bacterial spores, to two thymines. SPL requires SAM and a redox-active [4Fe-4S] cluster for catalysis. Mössbauer analysis of anaerobically purified SPL indicates the presence of a mixture of cluster states with the majority (40 %) as [2Fe-2S](2+) clusters and a smaller amount (15 %) as [4Fe-4S](2+) clusters. On reduction, the cluster content changes to primarily (60 %) [4Fe-4S](+). The speciation information from Mössbauer data allowed us to deconvolute iron and sulfur K-edge X-ray absorption spectra to uncover electronic (X-ray absorption near-edge structure, XANES) and geometric (extended X-ray absorption fine structure, EXAFS) structural features of the Fe-S clusters, and their interactions with SAM. The iron K-edge EXAFS data provide evidence for elongation of a [2Fe-2S] rhomb of the [4Fe-4S] cluster on binding SAM on the basis of an Fe···Fe scatterer at 3.0 Å. The XANES spectra of reduced SPL in the absence and presence of SAM overlay one another, indicating that SAM is not undergoing reductive cleavage. The X-ray absorption spectroscopy data for SPL samples and data for model complexes from the literature allowed the deconvolution of contributions from [2Fe-2S] and [4Fe-4S] clusters to the sulfur K-edge XANES spectra. The analysis of pre-edge features revealed electronic changes in the Fe-S clusters as a function of the presence of SAM. The spectroscopic findings were further corroborated by density functional theory calculations that provided insights into structural and electronic perturbations that can be correlated by considering the role of SAM as a catalyst or substrate.

Glimpse of Bagnold Dunes Edging Mount Sharp

NASA Image and Video Library

2015-11-16

The dark band in the lower portion of this Martian scene is part of the "Bagnold Dunes" dune field lining the northwestern edge of Mount Sharp, inside Gale Crater. The view combines multiple images taken with the Mast Camera (Mastcam) on NASA's Curiosity Mars rover on Sept. 25, 2015, during the 1,115th Martian day, or sol, of Curiosity's work on Mars. The images are from Mastcam's right-eye camera, which has a telephoto lens. The view is toward south-southeast. Curiosity will visit examples of the Bagnold Dunes on the rover's route to higher layers of Mount Sharp. The informal name for the dune field is a tribute to British military engineer Ralph Bagnold (1896-1990), a pioneer in the study of how winds move sand particles of dunes on Earth. The dune field is evident as a dark band in orbital images of the area inside Gale Crater where Curiosity has been active since landing in 2012, such as a traverse map at PIA20162. Dunes are larger than wind-blown ripples of sand or dust that Curiosity and other rovers have visited previously. The scene is presented with a color adjustment that approximates white balancing, to resemble how the rocks and sand would appear under daytime lighting conditions on Earth. http://photojournal.jpl.nasa.gov/catalog/PIA19929

Macroscopic and stereomicroscopic comparison of hacking trauma of bones before and after carbonization.

PubMed

Alunni, Véronique; Nogueira, Luísa; Quatrehomme, Gérald

2018-03-01

This experimental study examined lesions produced by a hatchet on pig femurs before and after carbonization. A total of 30 lesions were produced and analyzed using stereomicroscopy and then reexamined after carbonization. Not only was the sharp-blunt mechanism of the hacking trauma (V-shape, regularity of one edge, irregularity of the other edge, upraising, lateral pushing back, fossae dug laterally to the edge) still recognizable after carbonization; in some instances, the carbonization actually enhanced the features observed. Carbonization also did not significantly alter the measurements of the lesions. Carbonization tends to alter the structure of the bone especially in areas weakened by the blunt trauma.

Preparation of Cd/Pb Chalcogenide Heterostructured Janus Particles via Controllable Cation Exchange.

PubMed

Zhang, Jianbing; Chernomordik, Boris D; Crisp, Ryan W; Kroupa, Daniel M; Luther, Joseph M; Miller, Elisa M; Gao, Jianbo; Beard, Matthew C

2015-07-28

We developed a strategy for producing quasi-spherical nanocrystals of anisotropic heterostructures of Cd/Pb chalcogenides. The nanostructures are fabricated via a controlled cation exchange reaction where the Cd(2+) cation is exchanged for the Pb(2+) cation. The cation exchange reaction is thermally activated and can be controlled by adjusting the reaction temperature or time. We characterized the particles using TEM, XPS, PL, and absorption spectroscopy. With complete exchange, high quality Pb-chalcogenide quantum dots are produced. In addition to Cd(2+), we also find suitable conditions for the exchange of Zn(2+) cations for Pb(2+) cations. The cation exchange is anisotropic starting at one edge of the nanocrystals and proceeds along the ⟨111⟩ direction producing a sharp interface at a (111) crystallographic plane. Instead of spherical core/shell structures, we produced and studied quasi-spherical CdS/PbS and CdSe/PbSe Janus-type heterostructures. Nontrivial PL behavior was observed from the CdS(e)/PbS(e) heterostructures as the Pb:Cd ratio is increased.

Epitaxial growth and magnetic properties of ultraviolet transparent Ga2O3/(Ga1-xFex)2O3 multilayer thin films.

PubMed

Guo, Daoyou; An, Yuehua; Cui, Wei; Zhi, Yusong; Zhao, Xiaolong; Lei, Ming; Li, Linghong; Li, Peigang; Wu, Zhenping; Tang, Weihua

2016-04-28

Multilayer thin films based on the ferromagnetic and ultraviolet transparent semiconductors may be interesting because their magnetic/electronic/photonic properties can be manipulated by the high energy photons. Herein, the Ga2O3/(Ga1-xFex)2O3 multilayer epitaxial thin films were obtained by alternating depositing of wide band gap Ga2O3 layer and Fe ultrathin layer due to inter diffusion between two layers at high temperature using the laser molecular beam epitaxy technique. The multilayer films exhibits a preferred growth orientation of crystal plane, and the crystal lattice expands as Fe replaces Ga site. Fe ions with a mixed valence of Fe(2+) and Fe(3+) are stratified distributed in the film and exhibit obvious agglomerated areas. The multilayer films only show a sharp absorption edge at about 250 nm, indicating a high transparency for ultraviolet light. What's more, the Ga2O3/(Ga1-xFex)2O3 multilayer epitaxial thin films also exhibits room temperature ferromagnetism deriving from the Fe doping Ga2O3.

Post-annealing effect on optical absorbance of hydrothermally grown zinc oxide nanorods

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

Mohar, Rahmat Setiawan; Djuhana, Dede; Imawan, Cuk

In this study, the optical absorbance of zinc oxide (ZnO) nanorods was investigated. The ZnO thin film were deposited on indium tin oxide (ITO) layers using ultrasonic spray pyrolysis (USP) method and then grown by hydrothermal method. In order to improve the optical absorbance, the ZnO nanorods were then post-annealed for one hour at three different of temperatures, namely 250, 400, and 500 °C. The X-ray diffraction (XRD) spectra and FESEM images show that the ZnO nanorods have the hexagonal wurtzite crystal structure and the increasing of post-annealing temperature resulted in the increasing of crystallite size from 38.2 nm to 48.4 nm.more » The UV-vis spectra shows that all samples of ZnO nanorods exhibited the identical sharp absorption edge at 390 nm indicating that all samples have the same bandgap. The post-annealing process seemed to decrease the optical absorbance in the region of 300-550 nm and increase the optical absorbance in the region of 550-700 nm..« less

X-ray absorption in insulators with non-Hermitian real-time time-dependent density functional theory.

PubMed

Fernando, Ranelka G; Balhoff, Mary C; Lopata, Kenneth

2015-02-10

Non-Hermitian real-time time-dependent density functional theory was used to compute the Si L-edge X-ray absorption spectrum of α-quartz using an embedded finite cluster model and atom-centered basis sets. Using tuned range-separated functionals and molecular orbital-based imaginary absorbing potentials, the excited states spanning the pre-edge to ∼20 eV above the ionization edge were obtained in good agreement with experimental data. This approach is generalizable to TDDFT studies of core-level spectroscopy and dynamics in a wide range of materials.

Absorption and scattering by interstellar dust in the silicon K-edge of GX 5-1

NASA Astrophysics Data System (ADS)

Zeegers, S. T.; Costantini, E.; de Vries, C. P.; Tielens, A. G. G. M.; Chihara, H.; de Groot, F.; Mutschke, H.; Waters, L. B. F. M.; Zeidler, S.

2017-03-01

Context. We study the absorption and scattering of X-ray radiation by interstellar dust particles, which allows us to access the physical and chemical properties of dust. The interstellar dust composition is not well understood, especially on the densest sight lines of the Galactic plane. X-rays provide a powerful tool in this study. Aims: We present newly acquired laboratory measurements of silicate compounds taken at the Soleil synchrotron facility in Paris using the Lucia beamline. The dust absorption profiles resulting from this campaign were used in this pilot study to model the absorption by interstellar dust along the line of sight of the low-mass X-ray binary GX 5-1. Methods: The measured laboratory cross-sections were adapted for astrophysical data analysis and the resulting extinction profiles of the Si K-edge were implemented in the SPEX spectral fitting program. We derive the properties of the interstellar dust along the line of sight by fitting the Si K-edge seen in absorption in the spectrum of GX 5-1. Results: We measured the hydrogen column density towards GX 5-1 to be 3.40 ± 0.1 × 1022 cm-2. The best fit of the silicon edge in the spectrum of GX 5-1 is obtained by a mixture of olivine and pyroxene. In this study, our modeling is limited to Si absorption by silicates with different Mg:Fe ratios. We obtained an abundance of silicon in dust of 4.0 ± 0.3 × 10-5 per H atom and a lower limit for total abundance, considering both gas and dust of >4.4 × 10-5 per H atom, which leads to a gas to dust ratio of >0.22. Furthermore, an enhanced scattering feature in the Si K-edge may suggest the presence of large particles along the line of sight.

Liquid-film electron stripper

DOEpatents

Leemann, Beat T.; Yourd, Roland B.

1984-01-01

A thin freestanding oil film is produced in vacuum by directing an oil stream radially inward to the hollow-ground sharp outer edge of a rotating disc. The sides of the edge are roughened somewhat to aid in dispersing oil from the disc. Oil is removed from the surface of disc to prevent formation of oil droplets which might spin off the disc and disrupt the oil film. An ion beam is directed through the thin oil film so that electrons are stripped from the ions to increase their charge.

Liquid-film electron stripper

DOEpatents

Leemann, B.T.; Yourd, R.B.

1982-03-09

A thin freestanding oil film is produced in vacuum by directing an oil stream radially inward to the hollow-ground sharp outer edge of a rotating disc. The sides of the edge are roughened somewhat to aid in dispersing oil from the disc. Oil is removed from the surface of disc to prevent formation of oil droplets which might spin off the disc and disrupt the oil film. An ion beam is directed through the thin oil film so that electrons are stripped from the ions to increase their charge.

Detection of metal stress in boreal forest species using the 0.67-micron chlorophyll absorption band

NASA Technical Reports Server (NTRS)

Singhroy, Vernon H.; Kruse, Fred A.

1991-01-01

Several recent studies have shown that a shift of the red-edge inflection near 0.70 micron in vegetation reflectance spectra is an indicator of metal stress, partially attributable to changes in chlorophyll concentration. This 'red-edge shift', however, is difficult to detect and has been reported both toward longer (red) and shorter (blue) wavelengths. Our work demonstrates that direct measurement of the depth and width of the chlorophyll absorption band at 0.67 micron using digital feature extraction and absorption band characterization procedures developed for the analysis of mineral spectra is a more consistent indicator of metal stress. Additionally, the magnitude of these parameters is generally greater than that of the red edge shift and thus should be more amenable to detection and mapping using field and aircraft spectrometers.

Soft x-ray absorption spectra of ilmenite family.

PubMed

Agui, A; Mizumaki, M; Saitoh, Y; Matsushita, T; Nakatani, T; Fukaya, A; Torikai, E

2001-03-01

We have carried out soft x-ray absorption spectroscopy to study the electronic structure of ilmenite family, such as MnTiO3, FeTiO3, and CoTiO3 at the soft x-ray beamline, BL23SU, at the SPring-8. The Ti and M L2,3 absorption spectra of MTiO3 (M=Mn, Fe, and Co) show spectra of Ti4+ and M2+ electron configurations, respectively. Except the Fe L2,3 spectrum, those spectra were understood within the O(h) symmetry around the transition metal ions. The Fe L3-edge spectrum clearly shows a doublet peak at the L3 edge, which is attributed to Fe2+ state, moreover the very high-resolution the L-edge spectra of transition metals show fine structures. The spectra of those ilmenites are compared.

Dynamical Study of Femtosecond-Laser-Ablated Liquid-Aluminum Nanoparticles Using Spatiotemporally Resolved X-Ray-Absorption Fine-Structure Spectroscopy

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

Oguri, Katsuya; Okano, Yasuaki; Nishikawa, Tadashi

2007-10-19

We study the temperature evolution of aluminum nanoparticles generated by femtosecond laser ablation with spatiotemporally resolved x-ray-absorption fine-structure spectroscopy. We successfully identify the nanoparticles based on the L-edge absorption fine structure of the ablation plume in combination with the dependence of the edge structure on the irradiation intensity and the expansion velocity of the plume. In particular, we show that the lattice temperature of the nanoparticles is estimated from the L-edge slope, and that its spatial dependence reflects the cooling of the nanoparticles during plume expansion. The results reveal that the emitted nanoparticles travel in a vacuum as a condensedmore » liquid phase with a lattice temperature of about 2500 to 4200 K in the early stage of plume expansion.« less

Creation of forest edges has a global impact on forest vertebrates.

PubMed

Pfeifer, M; Lefebvre, V; Peres, C A; Banks-Leite, C; Wearn, O R; Marsh, C J; Butchart, S H M; Arroyo-Rodríguez, V; Barlow, J; Cerezo, A; Cisneros, L; D'Cruze, N; Faria, D; Hadley, A; Harris, S M; Klingbeil, B T; Kormann, U; Lens, L; Medina-Rangel, G F; Morante-Filho, J C; Olivier, P; Peters, S L; Pidgeon, A; Ribeiro, D B; Scherber, C; Schneider-Maunoury, L; Struebig, M; Urbina-Cardona, N; Watling, J I; Willig, M R; Wood, E M; Ewers, R M

2017-11-09

Forest edges influence more than half of the world's forests and contribute to worldwide declines in biodiversity and ecosystem functions. However, predicting these declines is challenging in heterogeneous fragmented landscapes. Here we assembled a global dataset on species responses to fragmentation and developed a statistical approach for quantifying edge impacts in heterogeneous landscapes to quantify edge-determined changes in abundance of 1,673 vertebrate species. We show that the abundances of 85% of species are affected, either positively or negatively, by forest edges. Species that live in the centre of the forest (forest core), that were more likely to be listed as threatened by the International Union for Conservation of Nature (IUCN), reached peak abundances only at sites farther than 200-400 m from sharp high-contrast forest edges. Smaller-bodied amphibians, larger reptiles and medium-sized non-volant mammals experienced a larger reduction in suitable habitat than other forest-core species. Our results highlight the pervasive ability of forest edges to restructure ecological communities on a global scale.

Creation of forest edges has a global impact on forest vertebrates

NASA Astrophysics Data System (ADS)

Pfeifer, M.; Lefebvre, V.; Peres, C. A.; Banks-Leite, C.; Wearn, O. R.; Marsh, C. J.; Butchart, S. H. M.; Arroyo-Rodríguez, V.; Barlow, J.; Cerezo, A.; Cisneros, L.; D'Cruze, N.; Faria, D.; Hadley, A.; Harris, S. M.; Klingbeil, B. T.; Kormann, U.; Lens, L.; Medina-Rangel, G. F.; Morante-Filho, J. C.; Olivier, P.; Peters, S. L.; Pidgeon, A.; Ribeiro, D. B.; Scherber, C.; Schneider-Maunoury, L.; Struebig, M.; Urbina-Cardona, N.; Watling, J. I.; Willig, M. R.; Wood, E. M.; Ewers, R. M.

2017-11-01

Forest edges influence more than half of the world’s forests and contribute to worldwide declines in biodiversity and ecosystem functions. However, predicting these declines is challenging in heterogeneous fragmented landscapes. Here we assembled a global dataset on species responses to fragmentation and developed a statistical approach for quantifying edge impacts in heterogeneous landscapes to quantify edge-determined changes in abundance of 1,673 vertebrate species. We show that the abundances of 85% of species are affected, either positively or negatively, by forest edges. Species that live in the centre of the forest (forest core), that were more likely to be listed as threatened by the International Union for Conservation of Nature (IUCN), reached peak abundances only at sites farther than 200-400 m from sharp high-contrast forest edges. Smaller-bodied amphibians, larger reptiles and medium-sized non-volant mammals experienced a larger reduction in suitable habitat than other forest-core species. Our results highlight the pervasive ability of forest edges to restructure ecological communities on a global scale.

Spectrophotometer properties of vein blood plasma in UF-region patients with sharp surgical pathology of abdominal region organs

NASA Astrophysics Data System (ADS)

Guminestskij, S. G.; Polianski, I. J.; Motrich, A. V.; Grunchuk, F. W.

2006-05-01

It is set that there are two maximums in UF- region absorption of vein blood plasma of a man: at λ = 235 nm and at λ = 280 nm. It is shown that there are the substantial changes of values of the optical density D comparative with controls (for donors) exactly in a maximum at development of sharp surgical diseases of organs of abdominal region λ = 280 nm, in that time as maximum at λ = 235 nm in this plan is not informing. Resulted results of researches of dynamics of changes of optical properties of vein blood plasma in UF- region of patients with pathology of abdominal region organs in after operating period (sharp appendicitis, sharp pancreatitis, intestinal impassability and others like that), which can have the diagnostic value.

Doping and tilting on optics in noncentrosymmetric multi-Weyl semimetals

NASA Astrophysics Data System (ADS)

Mukherjee, S. P.; Carbotte, J. P.

2018-01-01

We calculate the absorptive part of the ac optical conductivity of a multi-Weyl semimetal with winding number J in both the direction of the tilt σz z(Ω ) and perpendicular to it σx x(Ω ) as a function of photon energy Ω , tilt C, and chemical potential μ (doping). For zero tilt there is a discontinuous rise in the conductivity at twice the value of the chemical potential Ω =2 μ . Below 2 μ , both σx x(Ω ) and σz z(Ω ) are zero and above 2 μ they merge with their value at charge neutrality and display a linear in Ω dependence for J =1 while for J =2 , σx x(Ω ) remains linear but σz z(Ω ) is instead constant. For finite tilt the sharp jump at Ω =2 μ is lost and the onset of absorption starts instead from zero at a lower photon energy Ω =2 μ /(1 +C ) after which it acquires a quasilinear rise to merge with the undoped untilted interband background at Ω =2 μ /(1 -C ) for type I Weyl while for type II the undoped untilted background is never recovered. For noncentrosymmetric materials the energies of a pair of opposite chirality Weyl nodes become shifted by ±Q0 and this leads to two separate absorption edges corresponding to the effective chemical potential of each of the two nodes at 2 (μ +χ Q0) depending on chirality χ =± . We provide analytic expressions for the conductivity in this case which depend only on the ratio Q0/μ and tilt when plotted against Ω /μ . The signature of finite energy shift Q0 is more pronounced for σz z and J =2 than for the other cases.

Examination of the Measurement of Absorption Using the Reverberant Room Method for Highly Absorptive Acoustic Foam

NASA Technical Reports Server (NTRS)

Hughes, William O.; McNelis, Anne M.; Chris Nottoli; Eric Wolfram

2015-01-01

The absorption coefficient for material specimens are needed to quantify the expected acoustic performance of that material in its actual usage and environment. The ASTM C423-09a standard, "Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberant Room Method" is often used to measure the absorption coefficient of material test specimens. This method has its basics in the Sabine formula. Although widely used, the interpretation of these measurements are a topic of interest. For example, in certain cases the measured Sabine absorption coefficients are greater than 1.0 for highly absorptive materials. This is often attributed to the diffraction edge effect phenomenon. An investigative test program to measure the absorption properties of highly absorbent melamine foam has been performed at the Riverbank Acoustical Laboratories. This paper will present and discuss the test results relating to the effect of the test materials' surface area, thickness and edge sealing conditions. A follow-on paper is envisioned that will present and discuss the results relating to the spacing between multiple piece specimens, and the mounting condition of the test specimen.

Computational analysis of blunt, thin airfoil sections at supersonic and subsonic speeds

NASA Astrophysics Data System (ADS)

Goodsell, Aga Myung

The past decade has brought renewed interest in commercial supersonic aircraft design. Recent wing designs have included regions of low sweep resulting in supersonic leading edges at cruise. Thin biconvex sections are used in those regions to minimize wave drag and skin-friction drag. However, airfoil sections with sharp leading edges exhibit poor aerodynamic behavior at subsonic flight conditions. Blunt leading edges may improve performance by delaying the onset of separation at subsonic and transonic speeds. Their disadvantage is that they increase both wave drag, due to the formation of a detached bow wave, and skin-friction drag, from a loss of laminar flow. The effect of adding bluntness to a 4%-thick biconvex section was investigated using computational analysis tools. The aerodynamic performance of biconvex sections with circular leading edges was computed at supersonic, transonic, and takeoff conditions. At supersonic cruise, the increase in wave drag due to bluntness is a function of Mach number and leading-edge diameter. Some of the drag penalty is offset by the suction created downstream of the circular leading edge. The possibility of further drag reduction was explored with the development of a semi-analytical method to design blunt airfoil shapes which minimize wave drag. The effect on the transition location was evaluated using linear stability analyses of laminar boundary-layer profiles and the eN method. The analysis showed that laminar boundary layers on blunt airfoil sections are considerably less stable to Tollmien-Schlichting waves than that on a sharp biconvex. At transonic speeds, the results suggest a possible improvement in the lift-to-drag ratio over a limited range of angles of attack. At the takeoff condition, slight blunting of the leading edge does improve the lift-to-drag ratio at low angles of attack, but has little effect on maximum lift. It is concluded that the benefit of a blunt leading edge at off-design conditions is not sufficient to warrant the resulting drag penalty at supersonic cruise. Furthermore, if maintaining laminar flow is critical to the design and some bluntness is necessary for manufacturing purposes, then the leading-edge diameter should be minimized to prevent transition and to reduce wave drag.

Development of FEA Models to Study Contusion Patterning in Layered Tissue and the Shaft Loaded Blister Test

NASA Astrophysics Data System (ADS)

Giuffre, Christopher James

In the natural world there is no such thing as a perfectly sharp edge, either thru wear or machining imprecation at the macroscopic scale all edges have curvature. This curvature can have significant impact when comparing results with theory. Both numerical and analytic models for the contact of an object with a sharp edge predict infinite stresses which are not present in the physical world. It is for this reason that the influence of rounded edges must be studied to better understand how they affect model response. Using a commercial available finite element package this influence will be studied in two different problems; how this edge geometry effects the shape of a contusion (bruise) and the accuracy of analytic models for the shaft loaded blister test (SLBT). The contusion study presents work that can be used to enable medical examiners to better determine if the object in question was capable of causing the contusions present. Using a simple layered tissue model which represents a generic location on the human body, a sweep of objects with different edges properties is studied using a simple strain based injury metric. This analysis aims to examine the role that contact area and energy have on the formation, location, and shape of the resulting contusion. In studying the SLBT with finite element analysis and cohesive zone modeling, the assessment of various analytic models will provide insight into how to accurately measure the fracture energy for both the simulation and experiment. This provides insight into the interactions between a film, the substrate it is bonded to and the loading plug. In addition, parametric studies are used to examine potential experimental designs and enable future work in this field. The final product of this project provides tools and insight into future study of the effect rounded edges have on contact and this work enables for more focused studies within desired regimes of interest.

Temperature dependence of the fundamental optical absorption edge in crystals and disordered semiconductors

NASA Astrophysics Data System (ADS)

Grein, C. H.; John, Sajeev

1989-04-01

We present a first principles theory of the temperature dependence of the Urbach optical absorption edge in crystals and disordered semiconductors which incorporates the effects of short range correlated static disorder and the non-adiabatic quantum dynamics of the coupled electron-phonon system. At finite temperatures the dominant features of the Urbach tail are accounted for by multiple phonon absorption and emission side bands which accompany the optically induced electronic transition and which provide a dynamic polaronic potential well that localizes the electron. Excellent agreement is found with experimental data on both crystalline and amorphous silicon.

Internal standards in fluorescent X-ray spectroscopy1 1 Publication authorized by the Director, U.S. Geological Survey.

USGS Publications Warehouse

Adler, I.; Axelrod, J.M.

1955-01-01

The use of internal standards in the analysis of ores and minerals of widely-varying matrix by means of fluorescent X-ray spectroscopy is frequently the most practical approach. Internal standards correct for absorption and enhancement effects except when an absorption edge falls between the comparison lines or a very strong emission line falls between the absorption edges responsible for the comparison lines. Particle size variations may introduce substantial errors. One method of coping with the particle size problem is grinding the sample with an added abrasive. ?? 1955.

Ultrapressure materials science

NASA Technical Reports Server (NTRS)

Ruoff, A. L.

1984-01-01

Three active areas of research at ultra pressure are pursued, i.e., diffraction studies with the Cornell High Energy Synchrotron Source (CHESS), band gap and absorption edge effects, indentor-anvil experiments and theory and research to attain higher pressures. The range over which X-ray diffraction data and absorption edge data are obtained is extended to 700 kbars. Using the indentor technique pressures of 2.1 Mbars are obtained. Research results and methods are discussed.

Novel visualization studies of lignocellulosic oxidation chemistry by application of C-near edge X-ray absorption fine structure spectroscopy

Treesearch

Douglas G. Mancosky; Lucian A. Lucia; Hiroki Nanko; Sue Wirick; Alan W. Rudie; Robert Braun

2005-01-01

The research presented herein is the first attempt to probe the chemical nature of lignocellulosic samples by the application of carbon near edge X-ray absorption fine structure spectroscopy (C-NEXAFS). C-NEXAFS is a soft X-ray technique that principally provides selective interrogation of discrete atomic moieties using photoelectrons of variable energies. The X1A beam...

A high pressure La K-edge X-ray absorption fine structure spectroscopy investigation of La1/3NbO3

NASA Astrophysics Data System (ADS)

Marini, C.; Joseph, B.; Noked, O.; Shuker, R.; Kennedy, B. J.; Mathon, O.; Pascarelli, S.; Sterer, E.

2018-01-01

La K-edge X-ray absorption spectroscopy has been used to elucidate the changes in the local electronic and lattice structure that occur in the A-site deficient double perovskite La?NbO? up to 6 GPa. The pressure evolution of the oxygen dodecahedrum around the A-site has been examined. XANES (X-ray absorption near edge structure) data show modifications ascribed to the increase of bands overlapping as a consequence of the bond distance contraction, which has been directly probed by EXAFS (extended x-ray absorption fine structure) spectra. The La-O Debye Waller factors (DWFs) tend to increase whereas the La-Nb bond DWFs show only a tendency to decrease indicating the robustness of the crystal lattice structure, even in presence of the oxygen disordering. This permits the system to reverse back to its original conditions in this pressure range as evident from the measurements upon pressure release. The present results have been interpreted in the light of charge transfer related to the two-step reduction mechanism acting at the Nb site (with niobium ions passing from Nb? to Nb?) which also results in the elongation of the Nb-O bond distances in the octahedra, in agreement with the Nb K-edge results reported earlier.

The influence of coordination geometry and valency on the K-edge absorption near edge spectra of selected chromium compounds

NASA Astrophysics Data System (ADS)

Pantelouris, A.; Modrow, H.; Pantelouris, M.; Hormes, J.; Reinen, D.

2004-05-01

X-ray absorption spectra at the chromium K-edge are reported for a number of selected chromium compounds of known chemical structure. The spectra were obtained with use of synchrotron radiation available at the ELectron Stretcher Accelerator ELSA in Bonn. The compounds studied include the tetrahedrally coordinated compounds Ca 2Ge 0.8Cr 0.2O 4, Ba 2Ge 0.1Cr 0.9O 4, Sr 2CrO 4, Ca 2(PO 4) x(CrO 4) 1- xCl ( x=0.25,0.5), Ca 5(CrO 4) 3Cl, CrO 3, the octahedrally coordinated compounds Cr(II)-acetate, CrCl 3, CrF 3, Cr 2O 3, KCr(SO 4) 2 · 12H 2O, CrO 2 and cubic coordinated metallic chromium. In these compounds chromium exhibits a wide range of formal oxidation states (0 to VI). The absorption features in the near edge region are shown to be characteristic of the spatial environment of the absorbing atom. The occurrence of a single pre-edge line easily allows one to distinguish between tetrahedral and octahedral coordination geometry, whereas the energy position of the absorption edge is found to be very sensitive to the valency of the excited chromium atom. Calculations of the ionisation potential of Cr in different oxidation states using the non-relativistic Hartree-Fock method (Froese-Fischer) confirm that the ionisation limit shifts to higher energy with increasing Cr valency. More detailed information on the electronic structure of the different compounds is gained by real-space full multiple scattering calculations using the FEFF8 code.

Local structure in LaMnO3 and CaMnO3 perovskites: A quantitative structural refinement of Mn K -edge XANES data

NASA Astrophysics Data System (ADS)

Monesi, C.; Meneghini, C.; Bardelli, F.; Benfatto, M.; Mobilio, S.; Manju, U.; Sarma, D. D.

2005-11-01

Hole-doped perovskites such as La1-xCaxMnO3 present special magnetic and magnetotransport properties, and it is commonly accepted that the local atomic structure around Mn ions plays a crucial role in determining these peculiar features. Therefore experimental techniques directly probing the local atomic structure, like x-ray absorption spectroscopy (XAS), have been widely exploited to deeply understand the physics of these compounds. Quantitative XAS analysis usually concerns the extended region [extended x-ray absorption fine structure (EXAFS)] of the absorption spectra. The near-edge region [x-ray absorption near-edge spectroscopy (XANES)] of XAS spectra can provide detailed complementary information on the electronic structure and local atomic topology around the absorber. However, the complexity of the XANES analysis usually prevents a quantitative understanding of the data. This work exploits the recently developed MXAN code to achieve a quantitative structural refinement of the Mn K -edge XANES of LaMnO3 and CaMnO3 compounds; they are the end compounds of the doped manganite series LaxCa1-xMnO3 . The results derived from the EXAFS and XANES analyses are in good agreement, demonstrating that a quantitative picture of the local structure can be obtained from XANES in these crystalline compounds. Moreover, the quantitative XANES analysis provides topological information not directly achievable from EXAFS data analysis. This work demonstrates that combining the analysis of extended and near-edge regions of Mn K -edge XAS spectra could provide a complete and accurate description of Mn local atomic environment in these compounds.

Nitrogen K-edge x-ray absorption near edge structure of pyrimidine-containing nucleotides in aqueous solution

NASA Astrophysics Data System (ADS)

Shimada, Hiroyuki; Minami, Hirotake; Okuizumi, Naoto; Sakuma, Ichiro; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

2015-05-01

X-ray absorption near edge structure (XANES) was measured at energies around the N K-edge of the pyrimidine-containing nucleotides, cytidine 5'-monophosphate (CMP), 2'-deoxythymidine 5'-monophosphate (dTMP), and uridine 5'-monophosphate (UMP), in aqueous solutions and in dried films under various pH conditions. The features of resonant excitations below the N K-edge in the XANES spectra for CMP, dTMP, and UMP changed depending on the pH of the solutions. The spectral change thus observed is systematically explained by the chemical shift of the core-levels of N atoms in the nucleobase moieties caused by structural changes due to protonation or deprotonation at different proton concentrations. This interpretation is supported by the results of theoretical calculations using density functional theory for the corresponding nucleobases in the neutral and protonated or deprotonated forms.

Nitrogen K-edge x-ray absorption near edge structure of pyrimidine-containing nucleotides in aqueous solution

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

Shimada, Hiroyuki, E-mail: hshimada@cc.tuat.ac.jp; Minami, Hirotake; Okuizumi, Naoto

2015-05-07

X-ray absorption near edge structure (XANES) was measured at energies around the N K-edge of the pyrimidine-containing nucleotides, cytidine 5′-monophosphate (CMP), 2′-deoxythymidine 5′-monophosphate (dTMP), and uridine 5′-monophosphate (UMP), in aqueous solutions and in dried films under various pH conditions. The features of resonant excitations below the N K-edge in the XANES spectra for CMP, dTMP, and UMP changed depending on the pH of the solutions. The spectral change thus observed is systematically explained by the chemical shift of the core-levels of N atoms in the nucleobase moieties caused by structural changes due to protonation or deprotonation at different proton concentrations.more » This interpretation is supported by the results of theoretical calculations using density functional theory for the corresponding nucleobases in the neutral and protonated or deprotonated forms.« less

Interaction of Nanostructured Calcium Silicate Hydrate with Ibuprofen Drug Molecules: X-ray Absorption Near Edge Structure (XANES) Study at the Ca, Si and O K-edge

NASA Astrophysics Data System (ADS)

Guo, X. X.; Sham, T. K.; Zhu, Y. J.; Hu, Y. F.

2013-04-01

Mesoporous calcium silicate hydrate (CSH) nanostructure has been proven to be bioactive and biocompatible, and has a bright future in the application of bone treatment among other applications. X-ray absorption near edge structure (XANES) is a powerful tool for the study of the interactions of calcium silicate hydrates with drug molecules because it is element specific and it probes the unoccupied electronic states. Herein, we report the use of the calcium, silicon and oxygen K-edge XANES spectroscopy to identify how drug molecules interact with different groups in calcium silicate hydrate mesoporous nano-carriers with different morphologies. Significant changes are observed in XANES spectra after drug loading into the calcium silicate hydrate system, especially at the Si and O K-edge. The implications of these findings are discussed.

Electronic Structure of Ytterbium-Doped Strontium Fluoroapatite: Photoemission and Photoabsorption Investigation

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

Nelson, Art J.; Van Buuren, Tony W.; Bostedt, C

X-ray photoemission and x-ray photoabsorption were used to study the composition and the electronic structure of ytterbium-doped strontium fluoroapatite (Yb:S-FAP). High resolution photoemission measurements on the valence band electronic structure and Sr 3d, P 2p and 2s, Yb 4d and 4p, F 1s and O 1s core lines were used to evaluate the surface and near surface chemistry of this fluoroapatite. Element specific density of unoccupied electronic states in Yb:S-FAP were probed by x-ray absorption spectroscopy (XAS) at the Yb 4d (N4,5-edge), Sr 3d (M4,5-edge), P 2p (L2,3-edge), F 1s and O 1s (K-edges) absorption edges. These results provide themore » first measurements of the electronic structure and surface chemistry of this material.« less

Optical absorption edge of ZnO thin films: The effect of substrate

NASA Astrophysics Data System (ADS)

Srikant, V.; Clarke, D. R.

1997-05-01

The optical absorption edge and the near-absorption edge characteristics of undoped ZnO films grown by laser ablation on various substrates have been investigated. The band edge of films on C [(0001)] and R-plane [(1102)] sapphire, 3.29 and 3.32 eV, respectively, are found to be very close to the single crystal value of ZnO (3.3 eV) with the differences being accounted for in terms of the thermal mismatch strain using the known deformation potentials of ZnO. In contrast, films grown on fused silica consistently exhibit a band edge ˜0.1 eV lower than that predicted using the known deformation potential and the thermal mismatch strains. This behavior is attributed to the small grain size (50 nm) realized in these films and the effect of electrostatic potentials that exist at the grain boundaries. Additionally, the spread in the tail (E0) of the band edge for the different films is found to be very sensitive to the defect structure in the films. For films grown on sapphire substrates, values of E0 as low as 30 meV can be achieved on annealing in air, whereas films on fused silica always show a value >100 meV. We attribute this difference to the substantially higher density of high-angle grain boundaries in the films on fused silica.

Leading-edge vortex lifts swifts.

PubMed

Videler, J J; Stamhuis, E J; Povel, G D E

2004-12-10

The current understanding of how birds fly must be revised, because birds use their hand-wings in an unconventional way to generate lift and drag. Physical models of a common swift wing in gliding posture with a 60 degrees sweep of the sharp hand-wing leading edge were tested in a water tunnel. Interactions with the flow were measured quantitatively with digital particle image velocimetry at Reynolds numbers realistic for the gliding flight of a swift between 3750 and 37,500. The results show that gliding swifts can generate stable leading-edge vortices at small (5 degrees to 10 degrees) angles of attack. We suggest that the flow around the arm-wings of most birds can remain conventionally attached, whereas the swept-back hand-wings generate lift with leading-edge vortices.

Probing ultrafast ππ*/nπ* internal conversion in organic chromophores via K-edge resonant absorption

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

Wolf, T. J. A.; Myhre, R. H.; Cryan, J. P.

Many photoinduced processes including photosynthesis and human vision happen in organic molecules and involve coupled femtosecond dynamics of nuclei and electrons. Organic molecules with heteroatoms often possess an important excited-state relaxation channel from an optically allowed ππ* to a dark nπ* state. The ππ*/nπ* internal conversion is difficult to investigate, as most spectroscopic methods are not exclusively sensitive to changes in the excited-state electronic structure. Here, we report achieving the required sensitivity by exploiting the element and site specificity of near-edge soft X-ray absorption spectroscopy. As a hole forms in the n orbital during ππ*/nπ* internal conversion, the absorption spectrummore » at the heteroatom K-edge exhibits an additional resonance. We demonstrate the concept using the nucleobase thymine at the oxygen K-edge, and unambiguously show that ππ*/nπ* internal conversion takes place within (60 ± 30) fs. Furthermore, high-level-coupled cluster calculations confirm the method’s impressive electronic structure sensitivity for excited-state investigations.« less

Probing ultrafast ππ*/nπ* internal conversion in organic chromophores via K-edge resonant absorption

DOE PAGES

Wolf, T. J. A.; Myhre, R. H.; Cryan, J. P.; ...

2017-06-22

Many photoinduced processes including photosynthesis and human vision happen in organic molecules and involve coupled femtosecond dynamics of nuclei and electrons. Organic molecules with heteroatoms often possess an important excited-state relaxation channel from an optically allowed ππ* to a dark nπ* state. The ππ*/nπ* internal conversion is difficult to investigate, as most spectroscopic methods are not exclusively sensitive to changes in the excited-state electronic structure. Here, we report achieving the required sensitivity by exploiting the element and site specificity of near-edge soft X-ray absorption spectroscopy. As a hole forms in the n orbital during ππ*/nπ* internal conversion, the absorption spectrummore » at the heteroatom K-edge exhibits an additional resonance. We demonstrate the concept using the nucleobase thymine at the oxygen K-edge, and unambiguously show that ππ*/nπ* internal conversion takes place within (60 ± 30) fs. Furthermore, high-level-coupled cluster calculations confirm the method’s impressive electronic structure sensitivity for excited-state investigations.« less

Mitigation of EMU Cut Glove Hazard from Micrometeoroid and Orbital Debris Impacts on ISS Handrails

NASA Technical Reports Server (NTRS)

Ryan, Shannon; Christiansen, Eric L.; Davis, Bruce A.; Ordonez, Erick

2009-01-01

Recent cut damages sustained on crewmember gloves during extravehicular activity (ISS) onboard the International Space Station (ISS) have been caused by contact with sharp edges or a pinch point according to analysis of the damages. One potential source are protruding sharp edged crater lips from micrometeoroid and orbital debris (MMOD) impacts on metallic handrails along EVA translation paths. A number of hypervelocity impact tests were performed on ISS handrails, and found that mm-sized projectiles were capable of inducing crater lip heights two orders of magnitude above the minimum value for glove abrasion concerns. Two techniques were evaluated for mitigating the cut glove hazard of MMOD impacts on ISS handrails: flexible overwraps which act to limit contact between crewmember gloves and impact sites, and; alternate materials which form less hazardous impact crater profiles. In parallel with redesign efforts to increase the cut resilience of EMU gloves, the modifications to ISS handrails evaluated in this study provide the means to significantly reduce cut glove risk from MMOD impact craters

An experimental study of three-dimensional shock wave/boundary layer interactions generated by sharp fins

NASA Technical Reports Server (NTRS)

Lu, F. K.; Settles, G. S.; Bogdonoff, S. M.

1983-01-01

The interaction between a turbulent boundary layer and a shock wave generated by a sharp fin with leading edge sweepback was investigated. The incoming flow was at Mach 2.96 and at a unit Reynolds number of 63 x 10 to the 6th power 0.1 m. The approximate incoming boundary layer thickness was either 4 mm or 17 mm. The fins used were at 5 deg, 9 deg and 15 deg incidence and had leading edge sweepback from 0 deg to 65 deg. The tests consisted of surface kerosene lampblack streak visualization, surface pressure measurements, shock wave shape determination by shadowgraphs, and localized vapor screen visualization. The upstream influence lengths of the fin interactions were correlated using viscous and inviscid flow parameters. The parameters affecting the surface features close to the fin and way from the fin were also identified. Essentially, the surface features in the farfield were found to be conical.

Oxidation Behavior of HfB2-SiC Materials in Dissociated Environments

NASA Technical Reports Server (NTRS)

Ellerby, Don; Irby, Edward; Johnson, Sylvia M.; Beckman, Sarah; Gusman, Michael; Gasch, Matthew

2002-01-01

Hafnium diboride based materials have shown promise for use in extremely high temperature applications, such as sharp leading edges on future reentry vehicles. During reentry, the oxygen and nitrogen in the atmosphere are dissociated by the shock layer ahead of the sharp leading edge such that surface reactions are determined by reactions of monatomic oxygen and nitrogen rather than O2, and N2. Simulation of the reentry environment on the ground requires the use of arc jet (plasma jet) facilities that provide monatomic species and are the closest approximation to actual flight conditions. Simple static or flowing oxidation studies under ambient pressures and atmospheres are not adequate to develop an understanding of a materials behavior in flight. Arc jet testing is required to provide the appropriate stagnation pressures, heat fluxes, enthalpies, heat loads and atmospheres encountered during flight. This work looks at the response of HfB2/SiC materials exposed to various simulated reentry environments.

Highly stable, extremely high-temperature, nonvolatile memory based on resistance switching in polycrystalline Pt nanogaps

PubMed Central

Suga, Hiroshi; Suzuki, Hiroya; Shinomura, Yuma; Kashiwabara, Shota; Tsukagoshi, Kazuhito; Shimizu, Tetsuo; Naitoh, Yasuhisa

2016-01-01

Highly stable, nonvolatile, high-temperature memory based on resistance switching was realized using a polycrystalline platinum (Pt) nanogap. The operating temperature of the memory can be drastically increased by the presence of a sharp-edged Pt crystal facet in the nanogap. A short distance between the facet edges maintains the nanogap shape at high temperature, and the sharp shape of the nanogap densifies the electric field to maintain a stable current flow due to field migration. Even at 873 K, which is a significantly higher temperature than feasible for conventional semiconductor memory, the nonvolatility of the proposed memory allows stable ON and OFF currents, with fluctuations of less than or equal to 10%, to be maintained for longer than eight hours. An advantage of this nanogap scheme for high-temperature memory is its secure operation achieved through the assembly and disassembly of a Pt needle in a high electric field. PMID:27725705

Post Flight Analysis Of SHEFEX I: Shock Tunnel Testing And Related CFD Analysis

NASA Astrophysics Data System (ADS)

Schramm, Jan Martinez; Barth, Tarik; Wagner, Alexander; Hannemann, Klaus

2011-05-01

The SHarp Edge Flight EXperiment (SHEFEX) program of the German Aerospace Center (DLR) is primarily focused on the investigation of the potential to utilise improved shapes for space vehicles by considering sharp edges and facetted surfaces. One goal is to set up a sky based test facility to gain knowledge of the physics of hypersonic flow, complemented by numerical analysis and ground based testing. Further, the series of SHEFEX flight experiments is an excellent test bed for new technological concepts and flight instrumentation, and it is a source of motivation for young scientist and engineers providing an excellent school for future space-program engineers and managers. After the successful first SHEFEX flight in October 2005, a second flight is scheduled for September 2011 and additional flights are planned for 2015 ff. With the SHEFEX-I flight and the subsequent numerical and experimental post flight analysis, DLR could for the first time close the loop between the three major disciplines of aerothermodynamic research namely CFD, ground based testing and flight.

How sharp is sharp? Towards quantification of the sharpness and penetration ability of kitchen knives used in stabbings.

PubMed

Hainsworth, S V; Delaney, R J; Rutty, G N

2008-07-01

Stabbing is the most common method for violent death in the UK. As part of their investigation, forensic pathologists are commonly asked to estimate or quantify the degree of force required to create a wound. The force required to penetrate the skin and body by a knife is a complex function of the sharpness of the knife, the area of the body and alignment with cleavage lines of the skin, the angle of attack and the relative movement of the person stabbing relative to the victim being stabbed. This makes it difficult for the forensic pathologist to give an objective answer to the question; hence, subjective estimations are often used. One area where some degree of quantification is more tractable is in assessing how sharp an implement (particularly a knife) is. This paper presents results of a systematic study of how the different aspects of knife geometry influence sharpness and presents a simple test for assessing knife sharpness using drop testing. The results show that the radius of the blunt edge at the tip is important for controlling the penetration ability of a kitchen knife. Using high-speed video, it also gives insight into the mechanism of knife penetration into the skin. The results of the study will aid pathologists in giving a more informed answer to the question of the degree of force used in stabbing.

Heat Transfer and Flow on the First Stage Blade Tip of a Power Generation Gas Turbine. Part 2; Simulation Results

NASA Technical Reports Server (NTRS)

Ameri, A. A.; Bunker, R. S.

1999-01-01

A combined experimental and computational study has been performed to investigate the detailed distribution of convective heat transfer coefficients on the first stage blade tip surface for a geometry typical of large power generation turbines (>1OOMW). This paper is concerned with the numerical prediction of the tip surface heat transfer. Good comparison with the experimental measured distribution was achieved through accurate modeling of the most important features of the blade passage and heating arrangement as well as the details of experimental rig likely to affect the tip heat transfer. A sharp edge and a radiused edge tip were considered. The results using the radiused edge tip agreed better with the experimental data. This improved agreement was attributed to the absence of edge separation on the tip of the radiused edge blade.

Characterization of local atomic structure in Co/Zn based ZIFs by XAFS

NASA Astrophysics Data System (ADS)

Podkovyrina, Yulia; Butova, Vera; Bulanova, Elena; Budnyk, Andriy; Kremennaya, Maria; Soldatov, Alexander; Lamberti, Carlo

2018-03-01

The local atomic structure in bimetallic Co/Zn zeolitic imidazolate frameworks (ZIFs) was studied using X-ray Absorption Fine Structure (XAFS) spectroscopy and theoretical calculations. The experimental Co K-edge and Zn K-edge XANES (X-ray Absorption Near Edge Structure) spectra of Zn1-xCoxC8H10N4 samples (x = 0.05, 0.25, 0.75) synthesized by microwave synthesis were compared with the data for the ZIF-67 (x=1) and ZIF-8 (x=0). Theoretical XANES spectra for the bimetallic ZIFs were calculated. It was shown that in bimetallic ZIFs the Co and Zn atoms have the similar local environment.

Study on Coloration Mechanism of Chinese Ancient Ceramics by X-ray Absorption Near-edge Structure

NASA Astrophysics Data System (ADS)

Peng, Y. H.; Xie, Z.; He, J. F.; Liu, Q. H.; Pan, Z. Y.; Cheng, W. R.; Wei, S. Q.

2013-04-01

The Fe K-edge X-ray absorption near-edge structure (XANES) spectra of a series of ceramic shards were measured by fluorescence mode to reveal the color-generating techniques of Chinese porcelain. The analysis disclosed relationships among the chemical form of the iron, the firing conditions and the colors of the ceramics. The results indicate that the coloration for different ceramics depend on the valence states of iron as the main color element in glaze and the proportion of Fe2+ and Fe3+ was attributed to the baking technology. The findings provide important information for archaeologist on the coloration researches.

Identifying anthropogenic uranium compounds using soft X-ray near-edge absorption spectroscopy

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

Ward, Jesse D.; Bowden, Mark; Tom Resch, C.

2017-01-01

Uranium ores mined for industrial use are typically acid-leached to produce yellowcake and then converted into uranium halides for enrichment and purification. These anthropogenic chemical forms of uranium are distinct from their mineral counterparts. The purpose of this study is to use soft X-ray absorption spectroscopy to characterize several common anthropogenic uranium compounds important to the nuclear fuel cycle. Non-destructive chemical analyses of these compounds is important for process and environmental monitoring and X-ray absorption techniques have several advantages in this regard, including element-specificity, chemical sensitivity, and high spectral resolution. Oxygen K-edge spectra were collected for uranyl nitrate, uranyl fluoride,more » and uranyl chloride, and fluorine K-edge spectra were collected for uranyl fluoride and uranium tetrafluoride. Interpretation of the data is aided by comparisons to calculated spectra. These compounds have unique spectral signatures that can be used to identify unknown samples.« less

X-ray spectroscopy of the super soft source RXJ0925.7-475

NASA Technical Reports Server (NTRS)

Ebisawa, Ken; Asai, Kazumi; Dotani, Tadayasu; Mukai, Koji; Smale, Alan

1996-01-01

The super soft source (SSS) RXJ 0925.7-475 was observed with the Advanced Satellite for Cosmology and Astrophysics (ASCA) solid state spectrometer and its energy spectrum was analyzed. A simple black body model does not fit the data, and several absorption edges of ionized heavy elements are required. Without the addition of absorption edges, the best-fit black body radius and the estimated bolometric luminosity are 6800 (d/1 kpc) km and 1.2 x 10(exp 37) (d/1 kps)(exp 2) erg/s, respectively. The introduction of absorption edges significantly reduces the best-fit radius and luminosity to 140 (d/1 KPS) km and 6 x 10(exp 34) (d/1 kpc)(exp 2) erg/s, respectively. This suggests that the estimation of the emission region size and luminosity of SSS based on the black body model fit to the observed data is not reliable.

Theoretical X-ray production cross sections at incident photon energies across Li (i=1-3) absorption edges of Br

NASA Astrophysics Data System (ADS)

Puri, Sanjiv

2015-08-01

The X-ray production (XRP) cross sections, σLk (k = l, η, α, β6, β1, β3, β4, β9,10, γ1,5, γ2,3) have been evaluated at incident photon energies across the Li(i=1-3) absorption edge energies of 35Br using theoretical data sets of different physical parameters, namely, the Li(i=1-3) sub-shell the X-ray emission rates based on the Dirac-Fock (DF) model, the fluorescence and Coster Kronig yields based on the Dirac-Hartree-Slater (DHS) model, and two sets of the photoionisation cross sections based on the relativistic Hartree-Fock-Slater (RHFS) model and the Dirac-Fock (DF) model, in order to highlight the importance of electron exchange effects at photon energies in vicinity of absorption edge energies.

Identification of Uranyl Minerals Using Oxygen K-Edge X Ray Absorption Spectroscopy

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

Ward, Jesse D.; Bowden, Mark E.; Resch, Charles T.

2016-03-01

Uranium analysis is consistently needed throughout the fuel cycle, from mining to fuel fabrication to environmental monitoring. Although most of the world’s uranium is immobilized as pitchblende or uraninite, there exists a plethora of secondary uranium minerals, nearly all of which contain the uranyl cation. Analysis of uranyl compounds can provide clues as to a sample’s facility of origin and chemical history. X-ray absorption spectroscopy is one technique that could enhance our ability to identify uranium minerals. Although there is limited chemical information to be gained from the uranium X-ray absorption edges, recent studies have successfully used ligand NEXAFS tomore » study the physical chemistry of various uranium compounds. This study extends the use of ligand NEXAFS to analyze a suite of uranium minerals. We find that major classes of uranyl compounds (carbonate, oxyhydroxide, silicate, and phosphate) exhibit characteristic lineshapes in the oxygen K-edge absorption spectra. As a result, this work establishes a library of reference spectra that can be used to classify unknown uranyl minerals.« less

Understanding the shrinkage of optical absorption edges of nanostructured Cd-Zn sulphide films for photothermal applications

NASA Astrophysics Data System (ADS)

Hossain, Md. Sohrab; Kabir, Humayun; Rahman, M. Mahbubur; Hasan, Kamrul; Bashar, Muhammad Shahriar; Rahman, Mashudur; Gafur, Md. Abdul; Islam, Shariful; Amri, Amun; Jiang, Zhong-Tao; Altarawneh, Mohammednoor; Dlugogorski, Bogdan Z.

2017-01-01

In this article Cd-Zn sulphide thin films deposited onto soda lime glass substrates via chemical bath deposition (CBD) technique were investigated for photovoltaic applications. The synthesized films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet visible (UV-vis) spectroscopic methodologies. A higher degree of crystallinity of the films was attained with the increase of film thicknesses. SEM micrographs exhibited a partial crystalline structure with a particulate appearance surrounded by the amorphous grain boundaries. The optical absorbance and absorption coefficient of the films were also enhanced significantly with the increase in film thicknesses. Optical band-gap analysis indicated a monotonic decrease in direct and indirect band-gaps with the increase of thicknesses of the films. The presence of direct and indirect transitional energies due to the exponential falling edges of the absorption curves may either be due to the lack of long-range order or to the existence of defects in the films. The declination of the optical absorption edges was also confirmed via Urbach energy and steepness parameters studies.

Soft x-ray absorption spectroscopy of metalloproteins and high-valent metal-complexes at room temperature using free-electron lasers

PubMed Central

Kubin, Markus; Kern, Jan; Gul, Sheraz; Kroll, Thomas; Chatterjee, Ruchira; Löchel, Heike; Fuller, Franklin D.; Sierra, Raymond G.; Quevedo, Wilson; Weniger, Christian; Rehanek, Jens; Firsov, Anatoly; Laksmono, Hartawan; Weninger, Clemens; Alonso-Mori, Roberto; Nordlund, Dennis L.; Lassalle-Kaiser, Benedikt; Glownia, James M.; Krzywinski, Jacek; Moeller, Stefan; Turner, Joshua J.; Minitti, Michael P.; Dakovski, Georgi L.; Koroidov, Sergey; Kawde, Anurag; Kanady, Jacob S.; Tsui, Emily Y.; Suseno, Sandy; Han, Zhiji; Hill, Ethan; Taguchi, Taketo; Borovik, Andrew S.; Agapie, Theodor; Messinger, Johannes; Erko, Alexei; Föhlisch, Alexander; Bergmann, Uwe; Mitzner, Rolf; Yachandra, Vittal K.; Yano, Junko; Wernet, Philippe

2017-01-01

X-ray absorption spectroscopy at the L-edge of 3d transition metals provides unique information on the local metal charge and spin states by directly probing 3d-derived molecular orbitals through 2p-3d transitions. However, this soft x-ray technique has been rarely used at synchrotron facilities for mechanistic studies of metalloenzymes due to the difficulties of x-ray-induced sample damage and strong background signals from light elements that can dominate the low metal signal. Here, we combine femtosecond soft x-ray pulses from a free-electron laser with a novel x-ray fluorescence-yield spectrometer to overcome these difficulties. We present L-edge absorption spectra of inorganic high-valent Mn complexes (Mn ∼ 6–15 mmol/l) with no visible effects of radiation damage. We also present the first L-edge absorption spectra of the oxygen evolving complex (Mn4CaO5) in Photosystem II (Mn < 1 mmol/l) at room temperature, measured under similar conditions. Our approach opens new ways to study metalloenzymes under functional conditions. PMID:28944255

Soft x-ray absorption spectroscopy of metalloproteins and high-valent metal-complexes at room temperature using free-electron lasers

DOE PAGES

Kubin, Markus; Kern, Jan; Gul, Sheraz; ...

2017-09-01

X-ray absorption spectroscopy at the L-edge of 3d transition metals provides unique information on the local metal charge and spin states by directly probing 3d-derived molecular orbitals through 2p-3d transitions. But, this soft x-ray technique has been rarely used at synchrotron facilities for mechanistic studies of metalloenzymes due to the difficulties of x-ray-induced sample damage and strong background signals from light elements that can dominate the low metal signal. Here, we combine femtosecond soft x-ray pulses from a free-electron laser with a novel x-ray fluorescence-yield spectrometer to overcome these difficulties. We present L-edge absorption spectra of inorganic high-valent Mn complexesmore » (Mn ~ 6-15 mmol/l) with no visible effects of radiation damage. We then present the first L-edge absorption spectra of the oxygen evolving complex (Mn 4 CaO 5 ) in Photosystem II (Mn < 1 mmol/l) at room temperature, measured under similar conditions. Our approach opens new ways to study metalloenzymes under functional conditions.« less

Localized modes in optics of photonic liquid crystals with local anisotropy of absorption

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

Belyakov, V. A., E-mail: bel1937@mail.ru, E-mail: bel@landau.ac.ru; Semenov, S. V.

2016-05-15

The localized optical modes in spiral photonic liquid crystals are theoretically studied for the certainty at the example of chiral liquid crystals (CLCs) for the case of CLC with an anisotropic local absorption. The model adopted here (absence of dielectric interfaces in the structures under investigation) makes it possible to get rid of mixing of polarizations on the surfaces of the CLC layer and of the defect structure and to reduce the corresponding equations to only the equations for light with polarization diffracting in the CLC. The dispersion equations determining connection of the edge mode (EM) and defect mode (DM)more » frequencies with the CLC layer parameters (anisotropy of local absorption, CLC order parameter) and other parameters of the DMS are obtained. Analytic expressions for the transmission and reflection coefficients of CLC layer and DMS for the case of CLC with an anisotropic local absorption are presented and analyzed. It is shown that the CLC layers with locally anisotropic absorption reduce the EM and DM lifetimes (and increase the lasing threshold) in the way different from the case of CLC with an isotropic local absorption. Due to the Borrmann effect revealing of which is different at the opposite stop-band edges in the case of CLC layers with an anisotropic local absorption the EM life-times for the EM frequencies at the opposite stop-bands edges may be significantly different. The options of experimental observations of the theoretically revealed phenomena are briefly discussed.« less

Localized modes in optics of photonic liquid crystals with local anisotropy of absorption

NASA Astrophysics Data System (ADS)

Belyakov, V. A.; Semenov, S. V.

2016-05-01

The localized optical modes in spiral photonic liquid crystals are theoretically studied for the certainty at the example of chiral liquid crystals (CLCs) for the case of CLC with an anisotropic local absorption. The model adopted here (absence of dielectric interfaces in the structures under investigation) makes it possible to get rid of mixing of polarizations on the surfaces of the CLC layer and of the defect structure and to reduce the corresponding equations to only the equations for light with polarization diffracting in the CLC. The dispersion equations determining connection of the edge mode (EM) and defect mode (DM) frequencies with the CLC layer parameters (anisotropy of local absorption, CLC order parameter) and other parameters of the DMS are obtained. Analytic expressions for the transmission and reflection coefficients of CLC layer and DMS for the case of CLC with an anisotropic local absorption are presented and analyzed. It is shown that the CLC layers with locally anisotropic absorption reduce the EM and DM lifetimes (and increase the lasing threshold) in the way different from the case of CLC with an isotropic local absorption. Due to the Borrmann effect revealing of which is different at the opposite stop-band edges in the case of CLC layers with an anisotropic local absorption the EM life-times for the EM frequencies at the opposite stop-bands edges may be significantly different. The options of experimental observations of the theoretically revealed phenomena are briefly discussed.

Automatic detection of artifacts in converted S3D video

NASA Astrophysics Data System (ADS)

Bokov, Alexander; Vatolin, Dmitriy; Zachesov, Anton; Belous, Alexander; Erofeev, Mikhail

2014-03-01

In this paper we present algorithms for automatically detecting issues specific to converted S3D content. When a depth-image-based rendering approach produces a stereoscopic image, the quality of the result depends on both the depth maps and the warping algorithms. The most common problem with converted S3D video is edge-sharpness mismatch. This artifact may appear owing to depth-map blurriness at semitransparent edges: after warping, the object boundary becomes sharper in one view and blurrier in the other, yielding binocular rivalry. To detect this problem we estimate the disparity map, extract boundaries with noticeable differences, and analyze edge-sharpness correspondence between views. We pay additional attention to cases involving a complex background and large occlusions. Another problem is detection of scenes that lack depth volume: we present algorithms for detecting at scenes and scenes with at foreground objects. To identify these problems we analyze the features of the RGB image as well as uniform areas in the depth map. Testing of our algorithms involved examining 10 Blu-ray 3D releases with converted S3D content, including Clash of the Titans, The Avengers, and The Chronicles of Narnia: The Voyage of the Dawn Treader. The algorithms we present enable improved automatic quality assessment during the production stage.

Thickness noise of a propeller and its relation to blade sweep

NASA Astrophysics Data System (ADS)

Amiet, R. K.

1988-07-01

Linear acoustic theory is used to determine the thickness noise produced by a supersonic propeller with sharp leading and trailing edges. The method reveals details of the calculated waveform. Abrupt changes of slope in the pressure-time waveform which are produced by singular points entering or leaving the tip blade are pointed out. It is found that the behavior of the pressure-time waveform is closely related to changes in the retarded rotor shape. The results indicate that logarithmic singularities in the waveform are produced by regions on the blade edges that move towards the observer at sonic speed, with the edge normal to the line joining the source point and the observer.

A study of lateral fall-off (penumbra) optimisation for pencil beam scanning (PBS) proton therapy

NASA Astrophysics Data System (ADS)

Winterhalter, C.; Lomax, A.; Oxley, D.; Weber, D. C.; Safai, S.

2018-01-01

The lateral fall-off is crucial for sparing organs at risk in proton therapy. It is therefore of high importance to minimize the penumbra for pencil beam scanning (PBS). Three optimisation approaches are investigated: edge-collimated uniformly weighted spots (collimation), pencil beam optimisation of uncollimated pencil beams (edge-enhancement) and the optimisation of edge collimated pencil beams (collimated edge-enhancement). To deliver energies below 70 MeV, these strategies are evaluated in combination with the following pre-absorber methods: field specific fixed thickness pre-absorption (fixed), range specific, fixed thickness pre-absorption (automatic) and range specific, variable thickness pre-absorption (variable). All techniques are evaluated by Monte Carlo simulated square fields in a water tank. For a typical air gap of 10 cm, without pre-absorber collimation reduces the penumbra only for water equivalent ranges between 4-11 cm by up to 2.2 mm. The sharpest lateral fall-off is achieved through collimated edge-enhancement, which lowers the penumbra down to 2.8 mm. When using a pre-absorber, the sharpest fall-offs are obtained when combining collimated edge-enhancement with a variable pre-absorber. For edge-enhancement and large air gaps, it is crucial to minimize the amount of material in the beam. For small air gaps however, the superior phase space of higher energetic beams can be employed when more material is used. In conclusion, collimated edge-enhancement combined with the variable pre-absorber is the recommended setting to minimize the lateral penumbra for PBS. Without collimator, it would be favourable to use a variable pre-absorber for large air gaps and an automatic pre-absorber for small air gaps.

Containment of a silicone fluid free surface in reduced gravity using barrier coatings

NASA Technical Reports Server (NTRS)

Pline, Alexander D.; Jacobson, Thomas P.

1988-01-01

In support of the Surface Tension Driven Convection Experiment planned for flight aboard the Space Shuttle, tests were conducted under reduced gravity in the 2.2-sec Drop Tower and the 5.0-sec Zero-G facility at the NASA Lewis Research Center. The dynamics of controlling the test fluid, a 10-cSt viscosity silicone fluid in a low gravity environment were investigated using different container designs and barrier coatings. Three container edge designs were tested without a barrier coating; a square edge, a sharp edge with a 45-deg slope, and a sawtooth edge. All three edge designs were successful in containing the fluid below the edge. G-jitter experiments were made in scaled down containers subjected to horizontal accelerations. The data showed that a barrier coating is effective in containing silicone fluid under g-levels up to 10 sup -1 sub g sub 0. In addition, a second barrier coating was found which has similar anti-wetting characteristics and is also more durable.

78 FR 26720 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-08

..., Revision 2, dated December 22, 2010, terminates the repetitive inspections required by paragraphs (r), (s...; a detailed inspection of certain reveals for a sharp edge and cracking; and corrective action if...-2251. Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor...

Dual reactor for in situ/operando fluorescent mode XAS studies of sample containing low-concentration 3d or 5d metal elements

NASA Astrophysics Data System (ADS)

Nguyen, Luan; Tang, Yu; Li, Yuting; Zhang, Xiaoyan; Wang, Ding; Tao, Franklin Feng

2018-05-01

Transition metal elements are the most important elements of heterogeneous catalysts used for chemical and energy transformations. Many of these catalysts are active at a temperature higher than 400 °C. For a catalyst containing a 3d or 5d metal element with a low concentration, typically their released fluorescence upon the K-edge or L-edge adsorption of X-rays is collected for the analysis of chemical and coordination environments of these elements. However, it is challenging to perform in situ/operando X-ray absorption spectroscopy (XAS) studies of elements of low-energy absorption edges at a low concentration in a catalyst during catalysis at a temperature higher than about 450 °C. Here a unique reaction system consisting two reactors, called a dual reactor system, was designed for performing in situ or operando XAS studies of these elements of low-energy absorption edges in a catalyst at a low concentration during catalysis at a temperature higher than 450 °C in a fluorescent mode. This dual-reactor system contains a quartz reactor for preforming high-temperature catalysis up to 950 °C and a Kapton reactor remaining at a temperature up to 450 °C for collecting data in the same gas of catalysis. With this dual reactor, chemical and coordination environments of low-concentration metal elements with low-energy absorption edges such as the K-edge of 3d metals including Ti, V, Cr, Mn, Fe, Co, Ni, and Cu and L edge of 5d metals including W, Re, Os, Ir, Pt, and Au can be examined through first performing catalysis at a temperature higher than 450 °C in the quartz reactor and then immediately flipping the catalyst in the same gas flow to the Kapton reactor remained up to 450 °C to collect data. The capability of this dual reactor was demonstrated by tracking the Mn K-edge of the MnOx/Na2WO4 catalyst during activation in the temperature range of 300-900 °C and catalysis at 850 °C.

[The morphological features of skin wounds inflicted by joinery hand saws designed for different types of sawing].

PubMed

Sarkisian, B A; Azarov, P A

2014-01-01

The objective of the present work was to study the morphological features of skin wounds inflicted by joinery hand saws designed for longitudinal, transverse, and mixed sawing. A total of 60 injuries to the thigh skin inflicted by the recurring and reciprocating saw movements were simulated. The hand saws had 5 mm high "sharp" and "blunt"-tipped teeth. The analysis of the morphological features of the wounds revealed differences in their length and depth, shape of edge cuts and defects, and the relief of the walls depending on the sawtooth sharpness and the mode of sawing. It is concluded that morphological features of the wounds may be used to determine the type of the saw, the sharpness of its teeth, the direction and frequency of its movements.

Complex Resonance Absorption Structure in the X-Ray Spectrum of IRAS 13349+2438

NASA Technical Reports Server (NTRS)

Sako, M.; Kahn, S. M.; Behar, E.; Kaastra, J. S.; Brinkman, A. C.; Boller, Th.; Puchnarewicz, E. M.; Starling, R.; Liedahl, D. A.; Clavel, J.

2000-01-01

The luminous infrared-loud quasar IRAS 13349+2438 was observed with the XMM - Newton Observatory as part of the Performance Verification program. The spectrum obtained by the Reflection Grating Spectrometer (RGS) exhibits broad (FWHM - 1400 km/s) absorption lines from highly ionized elements including hydrogen- and helium-like carbon, nitrogen, oxygen, and neon, and several iron L - shell ions (Fe XVII - XX). Also shown in the spectrum is the first astrophysical detection of a broad absorption feature around lambda = 16 - 17 A identified as an unresolved transition array (UTA) of 2p - 3d inner-shell absorption by iron M-shell ions in a much cooler medium; a feature that might be misidentified as an O VII edge when observed with moderate resolution spectrometers. No absorption edges are clearly detected in the spectrum. We demonstrate that the RGS spectrum of IRAS 13349+2438 exhibits absorption lines from two distinct regions, one of which is tentatively associated with the medium that produces the optical/UV reddening.

Microanalysis of iron oxidation state in iron oxides using X Ray Absorption Near Edge Structure (XANES)

NASA Technical Reports Server (NTRS)

Sutton, S. R.; Delaney, J.; Bajt, S.; Rivers, M. L.; Smith, J. V.

1993-01-01

An exploratory application of x ray absorption near edge structure (XANES) analysis using the synchrotron x ray microprobe was undertaken to obtain Fe XANES spectra on individual sub-millimeter grains in conventional polished sections. The experiments concentrated on determinations of Fe valence in a suite of iron oxide minerals for which independent estimates of the iron speciation could be made by electron microprobe analysis and x ray diffraction.

Infrared study of the absorption edge of {beta}-InN films grown on GaN/MgO structures

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

Perez-Caro, M.; Rodriguez, A. G.; Vidal, M. A.

2010-07-15

Infrared optical studies were carried out in a group of cubic InN samples grown by gas source molecular beam epitaxy on MgO (001) substrates. Room temperature (RT) reflectance and low-temperature (LT) transmittance measurements were performed by using fast Fourier transform infrared spectrometry. Reflectance fittings allowed to establish that {beta}-InN films have large free-carrier concentrations present (>10{sup 19} cm{sup -3}), a result that is corroborated by Hall effect measurements. Each sample explored exhibited a different optical absorption edge. The Varshni parameters that describe adequately the optical absorption edge responses with temperature are obtained for the set of samples studied. The observedmore » temperatures changes, from LT to RT, are the lowest reported for III-V semiconductor binary compounds. The temperature coefficient of the conduction band depends on the strength of the electron-phonon interaction (e-ph-i), as well as on the thermal expansion. It has been predicted that cubic InN has one of the smallest e-ph-i of all III-V compounds, which is corroborated by these results. The variation in values of absorption edges is clearly consistent with the Burstein-Moss and band renormalization effects, produced by high free electron concentrations. It is shown that the conduction band in {beta}-InN, analogous to wurtzite InN, follows a nonparabolic behavior.« less

Infrared study of the absorption edge of β-InN films grown on GaN/MgO structures

NASA Astrophysics Data System (ADS)

Pérez-Caro, M.; Rodríguez, A. G.; Vidal, M. A.; Navarro-Contreras, H.

2010-07-01

Infrared optical studies were carried out in a group of cubic InN samples grown by gas source molecular beam epitaxy on MgO (001) substrates. Room temperature (RT) reflectance and low-temperature (LT) transmittance measurements were performed by using fast Fourier transform infrared spectrometry. Reflectance fittings allowed to establish that β-InN films have large free-carrier concentrations present (>1019 cm-3), a result that is corroborated by Hall effect measurements. Each sample explored exhibited a different optical absorption edge. The Varshni parameters that describe adequately the optical absorption edge responses with temperature are obtained for the set of samples studied. The observed temperatures changes, from LT to RT, are the lowest reported for III-V semiconductor binary compounds. The temperature coefficient of the conduction band depends on the strength of the electron-phonon interaction (e-ph-i), as well as on the thermal expansion. It has been predicted that cubic InN has one of the smallest e-ph-i of all III-V compounds, which is corroborated by these results. The variation in values of absorption edges is clearly consistent with the Burstein-Moss and band renormalization effects, produced by high free electron concentrations. It is shown that the conduction band in β-InN, analogous to wurtzite InN, follows a nonparabolic behavior.

Near-edge X-ray absorption spectra for metallic Cu and Mn

NASA Astrophysics Data System (ADS)

Greaves, G. N.; Durham, P. J.; Diakun, G.; Quinn, P.

1981-11-01

The measurement of X-ray absorption fine structure of metals- both in the extended region (EXAFS) as well as in the near edge region (XANES)-has been widely discussed (see refs 1-6 for Cu and refs 7-9 for Mn). The recent availability of intense X-ray fluxes from storage rings has usually been exploited for EXAFS leaving the XANES often with poorer resolution than earlier work performed on conventional sources (for example, compare the near edge structure for copper in ref. 1 with refs 3 or 6). In addition, whilst the theory and analysis of EXAFS is relatively well-established2,10, a theory for the strong scattering regime near to the absorption edge has only recently been developed11. We report here the first high resolution XANES spectra for Cu and Mn which were performed at the SRS storage ring at Daresbury. Although both metals have close-packed structures consisting of atoms of similar size their local atomic structure is different in detail. Significant differences are found in their respective XANES reflecting the senstivity of this region of the X-ray absorption fine structure to the local atomic structure. Spectra for the two metals have been analysed using the new multiple scattering formalism. This is a real space calculation and unlike a conventional band structure approach it does not require structural periodicity but works from the local arrangement of atoms.

Electrocautery skin incision for neurosurgery procedures--technical note.

PubMed

Nitta, Naoki; Fukami, Tadateru; Nozaki, Kazuhiko

2011-01-01

The reluctance to incise skin with electrocautery is partly attributable to concerns about excessive scarring and poor wound healing. However, recently no difference was reported in wound complications between the cold scalpel and electrocautery scalpel. We assessed the safety and efficacy of electrocautery skin incision in 22 scalp incisions, including 4 cases of reoperation. Electrocautery skin incisions were created using a sharp needle electrode. The generator unit was set on cutting mode, with power of 6 W and 330 kHz sinusoid waveform. Subcutaneous dissections also used the sharp needle electrode, set on coagulating mode, with power of 10 W and 1 MHz pulse-modulated waveform. Galea incisions used a standard blade tip, set on coagulating mode, with power of 20 W and 1 MHz pulse-modulated waveform. Skin incision with the sharp needle electrode caused no charring of the wound. Little bleeding or oozing were observed and skin clips were not necessary. No wound complication such as necrosis or infection occurred. Electrocautery skin incisions for re-operations were also performed safely without complications. Electrocautery skin incision is sufficiently safe procedure not only for first operation but also for re-operation. Electrocautery skin incision is efficacious, especially for extended operation times, because of little blood loss from the edges of skin incision and possible avoidance of skin edge necrosis or alopecia caused by skin clips.

Does cone beam CT actually ameliorate stab wound analysis in bone?

PubMed

Gaudio, D; Di Giancamillo, M; Gibelli, D; Galassi, A; Cerutti, E; Cattaneo, C

2014-01-01

This study aims at verifying the potential of a recent radiological technology, cone beam CT (CBCT), for the reproduction of digital 3D models which may allow the user to verify the inner morphology of sharp force wounds within the bone tissue. Several sharp force wounds were produced by both single and double cutting edge weapons on cancellous and cortical bone, and then acquired by cone beam CT scan. The lesions were analysed by different software (a DICOM file viewer and reverse engineering software). Results verified the limited performances of such technology for lesions made on cortical bone, whereas on cancellous bone reliable models were obtained, and the precise morphology within the bone tissues was visible. On the basis of such results, a method for differential diagnosis between cutmarks by sharp tools with a single and two cutting edges can be proposed. On the other hand, the metrical computerised analysis of lesions highlights a clear increase of error range for measurements under 3 mm. Metric data taken by different operators shows a strong dispersion (% relative standard deviation). This pilot study shows that the use of CBCT technology can improve the investigation of morphological stab wounds on cancellous bone. Conversely metric analysis of the lesions as well as morphological analysis of wound dimension under 3 mm do not seem to be reliable.

SHEFEX II Flight Instrumentation And Preparation Of Post Flight Analysis

NASA Astrophysics Data System (ADS)

Thiele, Thomas; Siebe, Frank; Gulhan, Ali

2011-05-01

A main disadvantage of modern TPS systems for re- entry vehicles is the expensive manufacturing and maintenance process due to the complex geometry of these blunt nose configurations. To reduce the costs and to improve the aerodynamic performance the German Aerospace Center (DLR) is following a different approach using TPS structures consisting of flat ceramic tiles. To test these new sharp edged TPS structures the SHEFEX I flight experiment was designed and successfully performed by DLR in 2005. To further improve the reliability of the sharp edged TPS design at even higher Mach numbers, a second flight experiment SHEFEX II will be performed in September 2011. In comparison to SHEFEX I the second flight experiment has a fully symmetrical shape and will reach a maximum Mach number of about 11. Furthermore the vehicle has an active steering system using four canards to control the flight attitude during re-entry, e.g. roll angle, angle of attack and sideslip. After a successful flight the evaluation of the flight data will be performed using a combination of numerical and experimental tools. The data will be used for the improvement of the present numerical analysis tools and to get a better understanding of the aerothermal behaviour of sharp TPS structures. This paper presents the flight instrumentation of the SHEFEX II TPS. In addition the concept of the post flight analysis is presented.

CFD-based aero-optical analysis of flow fields over two-dimensional cavities with active flow control

NASA Astrophysics Data System (ADS)

Tan, Yan

Prediction and control of optical wave front distortions and aberrations in a high energy laser beam due to interaction with an unsteady highly non-uniform flow field is of great importance in the development of directed energy weapon systems for Unmanned Air Vehicles (UAV). The unsteady shear layer over the weapons bay cavity is the primary cause of this distortion of the optical wave front. The large scale vortical structure of the shear layer over the cavity can be significantly reduced by employing an active flow control technique combined with passive flow control. This dissertation explores various active and passive control methods to suppress the cavity oscillations and thereby improve the aero-optics of cavity flow. In active flow control technique, a steady or a pulsed jet is applied at the sharp leading edge of cavities of different aspect ratios L/D (=2, 4, 15), where L and D are the width and the depth of a cavity respectively. In the passive flow control approach, the sharp leading or trailing edge of the cavity is modified into a round edge of different radii. Both of these active and passive flow control approaches are studied independently and in combination. Numerical simulations are performed, with and without active flow control for subsonic free stream flow past two-dimensional sharp and round leading or trailing edge cavities using Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with a two-equation Shear Stress Transport (SST) turbulence model or a hybrid SST/Large Eddy Simulation (LES) model. Aero-optical analysis is developed and applied to all the simulation cases. Index of refraction and Optical Path Difference (OPD) are compared for flow fields without and with active flow control. Root-Mean-Square (RMS) value of OPD is calculated and compared with the experimental data, where available. The effect of steady and pulsed blowing on buffet loading on the downstream face of the cavity is also computed. Using the numerical simulations, the most effective approach for controlling the cavity oscillations and aero-optical signatures is determined.

Isotope effects in liquid water probed by transmission mode x-ray absorption spectroscopy at the oxygen K-edge.

PubMed

Schreck, Simon; Wernet, Philippe

2016-09-14

The effects of isotope substitution in liquid water are probed by x-ray absorption spectroscopy at the O K-edge as measured in transmission mode. Confirming earlier x-ray Raman scattering experiments, the D2O spectrum is found to be blue shifted with respect to H2O, and the D2O spectrum to be less broadened. Following the earlier interpretations of UV and x-ray Raman spectra, the shift is related to the difference in ground-state zero-point energies between D2O and H2O, while the difference in broadening is related to the difference in ground-state vibrational zero-point distributions. We demonstrate that the transmission-mode measurements allow for determining the spectral shapes with unprecedented accuracy. Owing in addition to the increased spectral resolution and signal to noise ratio compared to the earlier measurements, the new data enable the stringent determination of blue shift and broadening in the O K-edge x-ray absorption spectrum of liquid water upon isotope substitution. The results are compared to UV absorption data, and it is discussed to which extent they reflect the differences in zero-point energies and vibrational zero-point distributions in the ground-states of the liquids. The influence of the shape of the final-state potential, inclusion of the Franck-Condon structure, and differences between liquid H2O and D2O resulting from different hydrogen-bond environments in the liquids are addressed. The differences between the O K-edge absorption spectra of water from our transmission-mode measurements and from the state-of-the-art x-ray Raman scattering experiments are discussed in addition. The experimentally extracted values of blue shift and broadening are proposed to serve as a test for calculations of ground-state zero-point energies and vibrational zero-point distributions in liquid H2O and D2O. This clearly motivates the need for new calculations of the O K-edge x-ray absorption spectrum of liquid water.

9 CFR 3.6 - Primary enclosures.

Code of Federal Regulations, 2011 CFR

2011-01-01

... WELFARE STANDARDS Specifications for the Humane Handling, Care, Treatment, and Transportation of Dogs and Cats 1 Facilities and Operating Standards § 3.6 Primary enclosures. Primary enclosures for dogs and... they: (i) Have no sharp points or edges that could injure the dogs and cats; (ii) Protect the dogs and...

46 CFR 163.003-13 - Construction.

Code of Federal Regulations, 2010 CFR

2010-10-01

... that can be used for attaching additional ladder sections. (c) Steps. Pilot ladder steps must meet the... instead of the orange color required under paragraph (c)(8) of this section, and must have the special.... A pilot ladder must not have splinters, burrs, sharp edges, corners, projections, or other defects...

Prediction of Cavitating Waterjet Propulsor Performance Using a Boundary Element Method

DTIC Science & Technology

2007-10-01

addressed. Instead, the Young, Y.L., Numerical Modeling of Supercavitating round trailing edge is modified to be a sharp one by and Surface-Piercing... Supercavitating Propeller Flows," Journal of Ship circulation distribution, and thus on the predicted thrust Research, Vol. 47, pp. 48-62, March 2003. and

Manifold to uniformly distribute a solid-liquid slurry

DOEpatents

Kern, Kenneth C.

1983-01-01

This invention features a manifold that divides a stream of coal particles and liquid into several smaller streams maintaining equal or nearly equal mass compositions. The manifold consists of a horizontal, variable area header having sharp-edged, right-angled take-offs which are oriented on the bottom of the header.

9 CFR 3.6 - Primary enclosures.

Code of Federal Regulations, 2010 CFR

2010-01-01

... WELFARE STANDARDS Specifications for the Humane Handling, Care, Treatment, and Transportation of Dogs and Cats 1 Facilities and Operating Standards § 3.6 Primary enclosures. Primary enclosures for dogs and... they: (i) Have no sharp points or edges that could injure the dogs and cats; (ii) Protect the dogs and...

29 CFR 1910.26 - Portable metal ladders.

Code of Federal Regulations, 2010 CFR

2010-07-01

... shall be of sufficient strength to meet the test requirements, and shall be protected against corrosion unless inherently corrosion-resistant. (i)-(ii) [Reserved] (iii) The spacing of rungs or steps shall be... stepladder. The spreader shall have all sharp points or edges covered or removed to protect the user. (4...

Cosmic String Searches

NASA Astrophysics Data System (ADS)

Hoffman, Y.; Hogan, C.

The author discusses observational strategies for finding effects associated with the gravitational lensing of distant objects by strings. In particular, the requirements of a survey to find chains of galaxy image pairs or single galaxies with sharp edges are studied in some detail, and a proposed search program at Steward Observatory is described.

Identification of F impurities in F-doped ZnO by synchrotron X-ray absorption near edge structures

NASA Astrophysics Data System (ADS)

Na-Phattalung, Sutassana; Limpijumnong, Sukit; Min, Chul-Hee; Cho, Deok-Yong; Lee, Seung-Ran; Char, Kookrin; Yu, Jaejun

2018-04-01

Synchrotron X-ray absorption near edge structure (XANES) measurements of F K-edge in conjunction with first-principles calculations are used to identify the local structure of the fluorine (F) atom in F-doped ZnO. The ZnO film was grown by pulsed laser deposition with an Nd:YAG laser, and an oxyfluoridation method was used to introduce F ions into the ZnO films. The measured XANES spectrum of the sample was compared against the first-principles XANES calculations based on various models for local atomic structures surrounding F atoms. The observed spectral features are attributed to ZnF2 and FO defects in wurtzite bulk ZnO.

[Study on the fine structure of K-feldspar of Qichun granite].

PubMed

Du, Deng-Wen; Hong, Han-Lie; Fan, Kan; Wang, Chao-Wen; Yin, Ke

2013-03-01

Fine structure of K-feldspar from the Qichun granite was investigated using X-ray diffraction (XRD), Fourier infrared absorption spectroscopy (FTIR), and inductively coupled plasma mass spectrometry methods to understand the evolution of the granitic magmatism and its correlation to molybdenite mineralization. The XRD results showed that K-feldspar of the potassic alteration veins has higher ordering index and triclinicity and is namely microcline with triclinic symmetry. K-feldspar of the early cretaceous granite has relatively lower ordering index and has widening [131] peak and is locally triclinic ordering. K-feldspar of the late cretaceous granite has lowest ordering index and sharp [131] peak and is honiogeneously monoclinic. The FTIR results showed that the IR spectra of the Qichun K-feldspar are similar to that of orthoclase reported by Farmer (1974). The 640 cm-1 absorption band increases while the 540 cm-' absorption band decreases with increase in K-feldspar ordering index, also, the 1,010 cm-1 absorption band separates into 1,010 and 1,046 cm-1 absorption bands, with a change in the band shape from widening to sharp outline. The ICP-MS results suggested that K-feldspar of the early cretaceous granite has relatively higher metal elements and rare earth elements, and the granite exhibits better mineralization background, K-feldspar of the potassic alteration veins has markedly lower Sr and Ba, indicating that the alteration fluid originated from the granitic magmatism, and hence, potassic alteration is a good indicator for molybdenite exploration.

Effect of aluminum on the local structure of silicon in zeolites as studied by Si K edge X-ray absorption near-edge fine structure: spectra simulation with a non-muffin tin atomic background.

PubMed

Bugaev, Lusegen A; Bokhoven, Jeroen A van; Khrapko, Valerii V

2009-04-09

Experimental Si K edge X-ray absorption near-edge fine structure (XANES) of zeolite faujasite, mordenite, and beta are interpreted by means of the FEFF8 code, replacing the theoretical atomic background mu(0) by a background that was extracted from an experimental spectrum. To some extent, this diminished the effect of the inaccuracy introduced by the MT potential and accounted for the intrinsic loss of photoelectrons. The agreement of the theoretical and experimental spectra at energies above the white lines enabled us to identify structural distortion around silicon, which occurs with increasing aluminum content. The Si K edge XANES spectra are very sensitive to slight distortions in the silicon coordination. Placing an aluminum atom on a nearest neighboring T site causes a distortion in the silicon tetrahedron, shortening one of the silicon-oxygen bonds relative to the other three.

Fermi-Edge Singularity of Spin-Polarized Electrons

NASA Astrophysics Data System (ADS)

Plochocka-Polack, P.; Groshaus, J. G.; Rappaport, M.; Umansky, V.; Gallais, Y.; Pinczuk, A.; Bar-Joseph, I.

2007-05-01

We study the absorption spectrum of a two-dimensional electron gas (2DEG) in a magnetic field. We find that at low temperatures, when the 2DEG is spin polarized, the absorption spectra, which correspond to the creation of spin up or spin down electrons, differ in magnitude, linewidth, and filling factor dependence. We show that these differences can be explained as resulting from the creation of a Mahan exciton in one case, and of a power law Fermi-edge singularity in the other.

Continuum absorption in the vicinity of the toroidicity-induced Alfvén gap

DOE PAGES

Li, M.; Breizman, B. N.; Zheng, L. J.; ...

2015-12-04

Excitation of Alfvén modes is commonly viewed as a concern for energetic particle confinement in burning plasmas. The 3.5 MeValpha particles produced by fusion may be affected as well as other fast ions in both present and future devices. Continuum damping of such modes is one of the key factors that determine their excitation thresholds and saturation levels. This work examines the resonant dissipative response of the Alfvén continuum to an oscillating driving current when the driving frequency is slightly outside the edges of the toroidicity-induced spectral gap. The problem is largely motivated by the need to describe the continuummore » absorption in the frequency sweeping events. Akey element of this problem is the negative interference of the two closely spaced continuum crossing points.Weexplain why the lower and upper edges of the gap can have very different continuum absorption features. Lastly, the difference is associated with an eigenmode whose frequency can be arbitrarily close to the upper edge of the gap whereas the lower edge of the gap is always a finite distance away from the closest eigenmode.« less

Orientational behavior of thin films of poly(3-methylthiophene) on platinium: A FTIR and near edge x-ray absorption fine structure (NEXAFS) study

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

Yang, X.Q.; Chen, J.; Hale, P.D.

1988-01-01

Near edge x-ray absorption fine structure (NEXAFS) and infrared reflection-absorption spectroscopy (IRRAS) have been used to study the orientational behavior of thin films of poly(3-methylthiophene) electrochemically polymerized on a platinum surface. Clear orientational effects, with the thiophene rings predominantly oriented parallel to the platinum surface, were observed when the thickness of the polymer films were within a few hundred /angstrom/A. It was found that more highly ordered films were produced at lower polymerization potential (1.4V vs SCE) than at higher potential (1.8V vs SCE). 5 refs., 4 figs., 2 tabs.

Enantiopure distorted ribbon-shaped nanographene combining two-photon absorption-based upconversion and circularly polarized luminescence.

PubMed

Cruz, Carlos M; Márquez, Irene R; Mariz, Inês F A; Blanco, Victor; Sánchez-Sánchez, Carlos; Sobrado, Jesús M; Martín-Gago, José A; Cuerva, Juan M; Maçôas, Ermelinda; Campaña, Araceli G

2018-04-28

Herein we describe a distorted ribbon-shaped nanographene exhibiting unprecedented combination of optical properties in graphene-related materials, namely upconversion based on two-photon absorption (TPA-UC) together with circularly polarized luminescence (CPL). The compound is a graphene molecule of ca. 2 nm length and 1 nm width with edge defects that promote the distortion of the otherwise planar lattice. The edge defects are an aromatic saddle-shaped ketone unit and a [5]carbohelicene moiety. This system is shown to combine two-photon absorption and circularly polarized luminescence and a remarkably long emission lifetime of 21.5 ns. The [5]helicene is responsible for the chiroptical activity while the push-pull geometry and the extended network of sp 2 carbons are factors favoring the nonlinear absorption. Electronic structure theoretical calculations support the interpretation of the results.

Molecular design of TiO2 for gigantic red shift via sublattice substitution.

PubMed

Shao, Guosheng; Deng, Quanrong; Wan, Lin; Guo, Meilan; Xia, Xiaohong; Gao, Yun

2010-11-01

The effects of 3d transition metal doping in TiO2 phases have been simulated in detail. The results of modelling indicate that Mn has the biggest potential among 3d transition metals, for the reduction of energy gap and the introduction of effective intermediate bands to allow multi-band optical absorption. On the basis of theoretical formulation, we have incorporated considerable amount of Mn in nano-crystalline TiO2 materials. Mn doped samples demonstrate significant red shift in the optical absorption edge, with a secondary absorption edge corresponding to theoretically predicted intermediate bands/states. The gigantic red shift achievable in Mn-doped TiO2 is expected to extend the useful TiO2 functionalities well beyond the UV threshold via the optical absorption of both visible and infrared photon irradiance.

Application of x-ray absorption fine structure (XAFS) to local-order analysis in Fe-Cr maghemite-like materials

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

Montero-Cabrera, M. E., E-mail: elena.montero@cimav.edu.mx; Fuentes-Cobas, L. E.; Macías-Ríos, E.

2015-07-23

The maghemite-like oxide system γ-Fe{sub 2-x}Cr{sub x}O{sub 3} (x=0.75, 1 and 1.25) was studied by X-ray absorption fine structure (XAFS) and by synchrotron radiation X-ray diffraction (XRD). Measurements were performed at the Stanford Synchrotron Radiation Lightsource at room temperature, at beamlines 2-1, 2-3 and 4-3. High-resolution XRD patterns were processed by means of the Rietveld method. In cases of atoms being neighbors in the Periodic Table, the order/disorder degree of the considered solutions is indiscernible by “normal” (absence of “anomalous scattering”) diffraction experiments. Thus, maghemite-like materials were investigated by XAFS in both Fe and Cr K-edges to clarify, via short-rangemore » structure characterization, the local ordering of the investigated system. Athena and Artemis graphic user interfaces for IFEFFIT and FEFF8.4 codes were employed for XAFS spectra interpretation. Pre-edge decomposition and theoretical modeling of X-ray absorption near edge structure (XANES) transitions were performed. By analysis of the Cr K-edge XANES, it has been confirmed that Cr is located in an octahedral environment. Fitting of the extended X-ray absorption fine structure (EXAFS) spectra was performed under the consideration that the central atom of Fe is allowed to occupy octa- and tetrahedral positions, while Cr occupies only octahedral ones. Coordination number of neighboring atoms, interatomic distances and their quadratic deviation average were determined for x=1, by fitting simultaneously the EXAFS spectra of both Fe and Cr K-edges. The results of fitting the experimental spectra with theoretical standards showed that the cation vacancies tend to follow a regular pattern within the structure of the iron-chromium maghemite (FeCrO{sub 3})« less

The Electronic Structure of Mn in Oxides, Coordination Complexes, and the Oxygen-Evolving Complex of Photosystem II Studied by Resonant Inelastic X-ray Scattering

PubMed Central

Yano, Junko; Visser, Hendrik; Robblee, John H.; Gu, Weiwei; de Groot, Frank M. F.; Christou, George; Pecoraro, Vincent L.

2014-01-01

Resonant inelastic X-ray scattering (RIXS) was used to collect Mn K pre-edge spectra and to study the electronic structure in oxides, molecular coordination complexes, as well as the S1 and S2 states of the oxygen-evolving complex (OEC) of photosystem II (PS II). The RIXS data yield two-dimensional plots that can be interpreted along the incident (absorption) energy or the energy transfer axis. The second energy dimension separates the pre-edge (predominantly 1s to 3d transitions) from the main K-edge, and a detailed analysis is thus possible. The 1s2p RIXS final-state electron configuration along the energy transfer axis is identical to conventional L-edge absorption spectroscopy, and the RIXS spectra are therefore sensitive to the Mn spin state. This new technique thus yields information on the electronic structure that is not accessible in conventional K-edge absorption spectroscopy. The line splittings can be understood within a ligand field multiplet model, i.e., (3d,3d) and (2p,3d) two-electron interactions are crucial to describe the spectral shapes in all systems. We propose to explain the shift of the K pre-edge absorption energy upon Mn oxidation in terms of the effective number of 3d electrons (fractional 3d orbital population). The spectral changes in the Mn 1s2p3/2 RIXS spectra between the PS II S1 and S2 states are small compared to that of the oxides and two of the coordination complexes (MnIII(acac)3 and MnIV(sal)2(bipy)). We conclude that the electron in the step from S1 to S2 is transferred from a strongly delocalized orbital. PMID:15303869

Experimental and theoretical comparison of the O K-edge nonresonant inelastic X-ray scattering and X-ray absorption spectra of NaReO4.

PubMed

Bradley, Joseph A; Yang, Ping; Batista, Enrique R; Boland, Kevin S; Burns, Carol J; Clark, David L; Conradson, Steven D; Kozimor, Stosh A; Martin, Richard L; Seidler, Gerald T; Scott, Brian L; Shuh, David K; Tyliszczak, Tolek; Wilkerson, Marianne P; Wolfsberg, Laura E

2010-10-06

Accurate X-ray absorption spectra (XAS) of first row atoms, e.g., O, are notoriously difficult to obtain due to the extreme sensitivity of the measurement to surface contamination, self-absorption, and saturation affects. Herein, we describe a comprehensive approach for determining reliable O K-edge XAS data for ReO(4)(1-) and provide methodology for obtaining trustworthy and quantitative data on nonconducting molecular systems, even in the presence of surface contamination. This involves comparing spectra measured by nonresonant inelastic X-ray scattering (NRIXS), a bulk-sensitive technique that is not prone to X-ray self-absorption and provides exact peak intensities, with XAS spectra obtained by three different detection modes, namely total electron yield (TEY), fluorescence yield (FY), and scanning transmission X-ray microscopy (STXM). For ReO(4)(1-), TEY measurements were heavily influenced by surface contamination, while the FY and STXM data agree well with the bulk NRIXS analysis. These spectra all showed two intense pre-edge features indicative of the covalent interaction between the Re 5d and O 2p orbitals. Density functional theory calculations were used to assign these two peaks as O 1s excitations to the e and t(2) molecular orbitals that result from Re 5d and O 2p covalent mixing in T(d) symmetry. Electronic structure calculations were used to determine the amount of O 2p character (%) in these molecular orbitals. Time dependent-density functional theory (TD-DFT) was also used to calculate the energies and intensities of the pre-edge transitions. Overall, under these experimental conditions, this analysis suggests that NRIXS, STXM, and FY operate cooperatively, providing a sound basis for validation of bulk-like excitation spectra and, in combination with electronic structure calculations, suggest that NaReO(4) may serve as a well-defined O K-edge energy and intensity standard for future O K-edge XAS studies.

Lightweight Thermal Protection System for Atmospheric Entry

NASA Technical Reports Server (NTRS)

Stewart, David; Leiser, Daniel

2007-01-01

TUFROC (Toughened Uni-piece Fibrous Reinforced Oxidation-resistant Composite) has been developed as a new thermal protection system (TPS) material for wing leading edge and nose cap applications. The composite withstands temperatures up to 1,970 K, and consists of a toughened, high-temperature surface cap and a low-thermal-conductivity base, and is applicable to both sharp and blunt leading edge vehicles. This extends the possible application of fibrous insulation to the wing leading edge and/or nose cap on a hypersonic vehicle. The lightweight system comprises a treated carbonaceous cap composed of ROCCI (Refractory Oxidation-resistant Ceramic Carbon Insulation), which provides dimensional stability to the outer mold line, while the fibrous base material provides maximum thermal insulation for the vehicle structure.

The interaction of copper ions with Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli: an X-ray absorption near-edge structure (XANES) spectroscopy study.

PubMed

Zanzen, Ulrike; Bovenkamp-Langlois, Lisa; Klysubun, Wantana; Hormes, Josef; Prange, Alexander

2018-04-01

The antimicrobial properties of copper ions have been known for a long time. However, the exact mechanism of action of the transition metal on microorganisms has long been unclear. X-ray absorption near-edge structure (XANES) spectroscopy at the Cu K edge allows the determination of copper speciation in Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa that have been treated with Cu(II) and Cu(I) solutions. The death/inactivation of the bacteria was observed using plate counting and light microscopy. The Cu K-XANES spectra of the two Gram-negative bacteria are different than those of the Gram-positive strain. The results clearly show that the Cu + -S bond contributes to the antibacterial activity of copper, as in the case of silver. The detailed evaluation of the differentiated absorption spectra shows that Cu + (not Cu 2+ ) is the dominant ion that binds to the bacteria. Because Cu + is not the most common copper ion, copper is not as effective an antibacterial agent as silver, whose common valency is actually + 1. Any reaction of copper with phosphorus from the bacteria can be excluded after the evaluation of the absorption spectra.

Notched strength of beryllium powder and ingot sheets.

NASA Technical Reports Server (NTRS)

Moss, R. G.

1972-01-01

The effects of notches in thin beryllium sheets were studied as functions of material variables and notch severity. Double edge notched samples having stress concentration factors of 1.0 to 15.4 were prepared by milling to size, etching, and electrical discharge machining the notches. Strength was not reduced greatly by sharp notches, and duller notches were more deleterious than sharp notches. The trend was for reduced strength for dull notches, increased strength for sharper notches, and reduced strength for very sharp notches. Differences in material purity or source of the sheet had little affect on notch sensitivity. The most important factors appear to be oxide content and directionality of the sheet microstructure; high oxide content and highly directional microstructure tend to give more notch sensitivity than low oxide content, and more bidirectional microstructure. Postulated causes of the change in notched/unnotched strength are given.

X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser

DOE PAGES

Kroll, Thomas; Kern, Jan; Kubin, Markus; ...

2016-09-19

X-ray free electron lasers (XFELs) enable unprecedented new ways to study the electronic structure and dynamics of transition metal systems. L-edge absorption spectroscopy is a powerful technique for such studies and the feasibility of this method at XFELs for solutions and solids has been demonstrated. But, the required x-ray bandwidth is an order of magnitude narrower than that of self-amplified spontaneous emission (SASE), and additional monochromatization is needed. We compare L-edge x-ray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the SASE radiation of the linac coherent light source (LCLS) with a new technique based onmore » self-seeding of LCLS. We demonstrate how L-edge XAS can be performed using the self-seeding scheme without the need of an additional beam line monochromator. Lastly, we show how the spectral shape and pulse energy depend on the undulator setup and how this affects the x-ray spectroscopy measurements.« less

Long-Range Chemical Sensitivity in the Sulfur K-Edge X-ray Absorption Spectra of Substituted Thiophenes

PubMed Central

2015-01-01

Thiophenes are the simplest aromatic sulfur-containing compounds and are stable and widespread in fossil fuels. Regulation of sulfur levels in fuels and emissions has become and continues to be ever more stringent as part of governments’ efforts to address negative environmental impacts of sulfur dioxide. In turn, more effective removal methods are continually being sought. In a chemical sense, thiophenes are somewhat obdurate and hence their removal from fossil fuels poses problems for the industrial chemist. Sulfur K-edge X-ray absorption spectroscopy provides key information on thiophenic components in fuels. Here we present a systematic study of the spectroscopic sensitivity to chemical modifications of the thiophene system. We conclude that while the utility of sulfur K-edge X-ray absorption spectra in understanding the chemical composition of sulfur-containing fossil fuels has already been demonstrated, care must be exercised in interpreting these spectra because the assumption of an invariant spectrum for thiophenic forms may not always be valid. PMID:25116792

Low doping concentration studies of doped PVA-Coumarin nanocomposite films

NASA Astrophysics Data System (ADS)

Tripathi, J.; Tripathi, S.; Bisen, R.; Sharma, A.; Choudhary, A.; Shripathi, T.

2016-05-01

The observations of combination of Poly (vinyl) alcohol and Coumarin properties in nanocmposite films are reported. The X-ray diffraction measurements reveal nanocrystalline nature of PVA film, which remains nanocrystalline after doping Coumarin but along with PVA peaks, additional peak due to dopant crystallinity is seen. The absorption edge shows a double edge feature, where distinct bandgaps for PVA host and dopant Coumarin are obtained. However at a higher doping wt % of 1 and 2, the absorption is mainly dominated by Coumarin and single absorption edge is observed giving a bandgap equal to that of bulk Coumarin (3.3 eV). The composite formation affects the bonding of host drastically and is seen through the bond modification in FTIR spectra. The results suggest that doping below 2 wt% is advantageous as combination of PVA and Coumarin properties are obtained but at 2 wt %, the properties are dominated by mainly Coumarin and the signature of PVA from optical properties is completely lost.

X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser

PubMed Central

Kroll, Thomas; Kern, Jan; Kubin, Markus; Ratner, Daniel; Gul, Sheraz; Fuller, Franklin D.; Löchel, Heike; Krzywinski, Jacek; Lutman, Alberto; Ding, Yuantao; Dakovski, Georgi L.; Moeller, Stefan; Turner, Joshua J.; Alonso-Mori, Roberto; Nordlund, Dennis L.; Rehanek, Jens; Weniger, Christian; Firsov, Alexander; Brzhezinskaya, Maria; Chatterjee, Ruchira; Lassalle-Kaiser, Benedikt; Sierra, Raymond G.; Laksmono, Hartawan; Hill, Ethan; Borovik, Andrew; Erko, Alexei; Föhlisch, Alexander; Mitzner, Rolf; Yachandra, Vittal K.; Yano, Junko; Wernet, Philippe; Bergmann, Uwe

2016-01-01

X-ray free electron lasers (XFELs) enable unprecedented new ways to study the electronic structure and dynamics of transition metal systems. L-edge absorption spectroscopy is a powerful technique for such studies and the feasibility of this method at XFELs for solutions and solids has been demonstrated. However, the required x-ray bandwidth is an order of magnitude narrower than that of self-amplified spontaneous emission (SASE), and additional monochromatization is needed. Here we compare L-edge x-ray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the SASE radiation of the linac coherent light source (LCLS) with a new technique based on self-seeding of LCLS. We demonstrate how L-edge XAS can be performed using the self-seeding scheme without the need of an additional beam line monochromator. We show how the spectral shape and pulse energy depend on the undulator setup and how this affects the x-ray spectroscopy measurements. PMID:27828320

Abnormal blueshift of the absorption edge in graphene nanodots

NASA Astrophysics Data System (ADS)

Sheng, Weidong

2018-06-01

In a conventional semiconductor, when the dielectric screening effect is suppressed, the exciton binding energy increases and the corresponding excitonic transition would exhibit a redshift in the spectrum. In this work, I study the optical properties of hexagonal graphene nanodots by using a configuration interaction approach and reveal that the edge of the absorption spectrum shows an abnormal blueshift as the environmental dielectric constant ɛr decreases. The two dominant many-body effects in the nanodot: the quasiparticle and excitonic effects are both found to scale almost linearly with ɛr-1. The former is shown to have a larger proportionality constant and thus accounts for the blueshift of the absorption edge. In contrast to the long-range Coulomb interaction, the on-site Coulomb energy is found to have a negative impact on the bright excitonic states. In the presence of a strong dielectric screening effect, a strong short-range Coulomb interaction is revealed to be responsible for the disintegration of the bright exciton.

Low doping concentration studies of doped PVA-Coumarin nanocomposite films

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

Tripathi, J., E-mail: jtripathi00@rediffmail.com; Bisen, R.; Choudhary, A.

2016-05-23

The observations of combination of Poly (vinyl) alcohol and Coumarin properties in nanocmposite films are reported. The X-ray diffraction measurements reveal nanocrystalline nature of PVA film, which remains nanocrystalline after doping Coumarin but along with PVA peaks, additional peak due to dopant crystallinity is seen. The absorption edge shows a double edge feature, where distinct bandgaps for PVA host and dopant Coumarin are obtained. However at a higher doping wt % of 1 and 2, the absorption is mainly dominated by Coumarin and single absorption edge is observed giving a bandgap equal to that of bulk Coumarin (3.3 eV). Themore » composite formation affects the bonding of host drastically and is seen through the bond modification in FTIR spectra. The results suggest that doping below 2 wt% is advantageous as combination of PVA and Coumarin properties are obtained but at 2 wt %, the properties are dominated by mainly Coumarin and the signature of PVA from optical properties is completely lost.« less

Theoretical X-ray production cross sections at incident photon energies across L{sub i} (i=1-3) absorption edges of Br

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

Puri, Sanjiv

The X-ray production (XRP) cross sections, σ{sub Lk} (k = l, η, α, β{sub 6}, β{sub 1}, β{sub 3}, β{sub 4}, β{sub 9,10}, γ{sub 1,5}, γ{sub 2,3}) have been evaluated at incident photon energies across the L{sub i}(i=1-3) absorption edge energies of {sub 35}Br using theoretical data sets of different physical parameters, namely, the L{sub i}(i=1-3) sub-shell the X-ray emission rates based on the Dirac-Fock (DF) model, the fluorescence and Coster Kronig yields based on the Dirac-Hartree-Slater (DHS) model, and two sets of the photoionisation cross sections based on the relativistic Hartree-Fock-Slater (RHFS) model and the Dirac-Fock (DF) model, inmore » order to highlight the importance of electron exchange effects at photon energies in vicinity of absorption edge energies.« less

Linear and Nonlinear Optical Properties of Spherical Quantum Dots: Effects of Hydrogenic Impurity and Conduction Band Non-Parabolicity

NASA Astrophysics Data System (ADS)

Rezaei, G.; Vaseghi, B.; Doostimotlagh, N. A.

2012-03-01

Simultaneous effects of an on-center hydrogenic impurity and band edge non-parabolicity on intersubband optical absorption coefficients and refractive index changes of a typical GaAs/AlxGa1-x As spherical quantum dot are theoretically investigated, using the Luttinger—Kohn effective mass equation. So, electronic structure and optical properties of the system are studied by means of the matrix diagonalization technique and compact density matrix approach, respectively. Finally, effects of an impurity, band edge non-parabolicity, incident light intensity and the dot size on the linear, the third-order nonlinear and the total optical absorption coefficients and refractive index changes are investigated. Our results indicate that, the magnitudes of these optical quantities increase and their peaks shift to higher energies as the influences of the impurity and the band edge non-parabolicity are considered. Moreover, incident light intensity and the dot size have considerable effects on the optical absorption coefficients and refractive index changes.

Temperature and radiation effects at the fluorine K-edge in LiF

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

Schwartz, Craig P.; Ponce, Francisco; Friedrich, Stephan

Here, the fluorine K-edge of LiF is studied both experimentally and theoretically as a function of temperature. Instantaneous thermal fluctuations in atomic positions are shown in molecular dynamics simulations to increase in amplitude from 0.029 to 0.064 nm in the temperature range from 40 to 298 K. This is sufficient to cause instantaneous deviations from local octahedral atomic symmetry in this rock-salt crystal, resulting in altered electronic structure. The lowered symmetry of the lowest core-excited states of fluorine atoms is evident in X-ray absorption spectra at the F K-edge. In addition, sufficient radiation exposure produces a new X-ray absorption peak,more » below the F K-edge of LiF, which is assigned to defects in LiF based on both calculations and comparison to previous experiments.« less

Temperature and radiation effects at the fluorine K-edge in LiF

DOE PAGES

Schwartz, Craig P.; Ponce, Francisco; Friedrich, Stephan; ...

2017-05-30

Here, the fluorine K-edge of LiF is studied both experimentally and theoretically as a function of temperature. Instantaneous thermal fluctuations in atomic positions are shown in molecular dynamics simulations to increase in amplitude from 0.029 to 0.064 nm in the temperature range from 40 to 298 K. This is sufficient to cause instantaneous deviations from local octahedral atomic symmetry in this rock-salt crystal, resulting in altered electronic structure. The lowered symmetry of the lowest core-excited states of fluorine atoms is evident in X-ray absorption spectra at the F K-edge. In addition, sufficient radiation exposure produces a new X-ray absorption peak,more » below the F K-edge of LiF, which is assigned to defects in LiF based on both calculations and comparison to previous experiments.« less

Solution XAS Analysis for Exploring the Active Species in Homogeneous Vanadium Complex Catalysis

NASA Astrophysics Data System (ADS)

Nomura, Kotohiro; Mitsudome, Takato; Tsutsumi, Ken; Yamazoe, Seiji

2018-06-01

Selected examples in V K-edge X-ray Absorption Near Edge Structure (XANES) analysis of a series of vanadium complexes containing imido ligands (possessing metal-nitrogen double bond) in toluene solution have been introduced, and their pre-edge and the edge were affected by their structures and nature of ligands. Selected results in exploring the oxidation states of the active species in ethylene dimerization/polymerization using homogeneous vanadium catalysts [consisting of (imido)vanadium(V) complexes and Al cocatalysts] by X-ray absorption spectroscopy (XAS) analyses have been introduced. It has been demonstrated that the method should provide more clear information concerning the active species in situ, especially by combination with the other methods (NMR and ESR spectra, X-ray crystallographic analysis, and reaction chemistry), and should be powerful tool for study of catalysis mechanism as well as for the structural analysis in solution.

The P K-near edge absorption spectra of phosphates

NASA Astrophysics Data System (ADS)

Franke, R.; Hormes, J.

1995-12-01

The X-ray absorption near edge structure (XANES) at the P K-edge in several orthophosphates with various cations, in condensed, and in substituted sodium phosphates have been measured using synchrotron radiation from the ELSA storage ring at the University of Bonn. The measured spectra demonstrate that chemical changes beyond the PO 4- tetrahedra are reflected by energy shifts of the pre-edge and continuum resonances, by the presence of characteristic shoulders and new peaks and by differences in the intensity of the white line. We discuss the energy differences between the white line positions and the corresponding P ls binding energies as a measure of half of the energy gap. The corresponding values correlate with the valence of the cations and the intensity of the white lines. The energy positions of the continuum resonances are discussed on the basis of an empirical bond-length correlation supporting a 1/ r2 - dependence.

Electronic and chemical state of aluminum from the single- (K) and double-electron excitation (KL II&III, KL I) x-ray absorption near-edge spectra of α-alumina, sodium aluminate, aqueous Al³⁺•(H₂O)₆, and aqueous Al(OH)₄⁻

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

Fulton, John L.; Govind, Niranjan; Huthwelker, Thomas

2015-07-02

We probe, at high energy resolution, the double electron excitation (KL II&II) x-ray absorption region that lies approximately 115 eV above the main Al K-edge (1566 eV) of α-alumina and sodium aluminate. The two solid standards, α-alumina (octahedral) and sodium aluminate (tetrahedral) are compared to aqueous species that have the same Al coordination symmetries, Al³⁺•6H₂O (octahedral) and Al(OH)₄⁻ (tetrahedral). For the octahedral species, the edge height of the KL II&III-edge is approximately 10% of the main K-edge however the edge height is much weaker (3% of K-edge height) for Al species with tetrahedral symmetry. For the α-alumina and aqueous Al³⁺•6H₂Omore » the KL II&III spectra contain white line features and extended absorption fine structure (EXAFS) that mimics the K-edge spectra. The KL II&III-edge feature interferes with an important region of the extended-XAFS region of the spectra for the K-edge of the crystalline and aqueous standards. The K-edge spectra and K-edge positions are predicted using time-dependent density functional theory (TDDFT). The TDDFT calculations for the K-edge XANES spectra reproduce the observed transitions in the experimental spectra of the four Al species. The KL II&III and KL I onsets and their corresponding chemical shifts for the four standards are estimated using the delta self-consistent field (ΔSCF) method. Research by JLF, NG, EJB, AV, TDS was supported by U.S. Department of Energy’s (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. NG thanks Amity Andersen for help with the α-Al₂O₃ and tetrahedral sodium aluminate (NaAlO₂) clusters. All the calculations were performed using the Molecular Science Computing Capability at EMSL, a national scientific user facility sponsored by the U.S. Department of Energy’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated for DOE by Battelle under Contract # AC05-76RL01830.« less

Parametric measurements of the effect of in-duct orifice edge shape on its noise damping performance

NASA Astrophysics Data System (ADS)

Ji, Chenzhen; Zhao, Dan; Han, Nuomin; Li, Jing

2016-12-01

Acoustic liners perforated with thousands of millimeter-size orifices are widely used in aero-engines and gas turbine engines as an effective noise damper. In this work, experimental investigations of the acoustic damping effect of in-duct perforated orifices are performed on a cold-flow pipe. A mean flow (also known as bias flow) is applied and its flow rate is variable. Emphasis is placed on the effect of the orifice edge shape. For this, 16 in-duct orifices with different edge shapes and porosities are designed and manufactured by using 3D printing technology and conventional laser cutting technique. The damping effect of these in-duct orifices is characterized by using power absorption coefficient Δ and reflection coefficient χ from 100 to 1000 Hz. The performances of these orifices are found to be either improved or deteriorated, depending on (1) edge shape, (2) the ratio T/d of orifice thickness to its diameter, (3) the bias flow Mach number, (4) downstream pipe length Ld and (5) porosity η via varying either the number N or surface area Ao of the orifices. In addition, modifying orifice edge does not lead to an increase of power absorption at lower frequency (⩽ 700 Hz). However, as the frequency is increased, the orifice with square (S-type) edge is found to be associated with 10 percent more power absorption. It is interesting to find that T/d over the tested range (≤ 0.5) has little influence on its damping capacity. However, the mean bias flow Mach number Ma and porosity η are shown to play critical roles on determining the noise damping performance of these orifices. Maximum power absorption Δmax is found to occur at Ma ≈ 0.018, while the optimum porosity corresponding to Δmax is approximately 7 percent. The present parametric measurements shed light on the roles of orifice edge shape, porosity and mean flow on its noise damping capacity, and facilitate the design of effective perforated liners.

Quantized transport and steady states of Floquet topological insulators

NASA Astrophysics Data System (ADS)

Esin, Iliya; Rudner, Mark S.; Refael, Gil; Lindner, Netanel H.

2018-06-01

Robust electronic edge or surface modes play key roles in the fascinating quantized responses exhibited by topological materials. Even in trivial materials, topological bands and edge states can be induced dynamically by a time-periodic drive. Such Floquet topological insulators (FTIs) inherently exist out of equilibrium; the extent to which they can host quantized transport, which depends on the steady-state population of their dynamically induced edge states, remains a crucial question. In this work, we obtain the steady states of two-dimensional FTIs in the presence of the natural dissipation mechanisms present in solid state systems. We give conditions under which the steady-state distribution resembles that of a topological insulator in the Floquet basis. In this state, the distribution in the Floquet edge modes exhibits a sharp feature akin to a Fermi level, while the bulk hosts a small density of excitations. We determine the regimes where topological edge-state transport persists and can be observed in FTIs.

Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry.

PubMed

Murani, Anil; Kasumov, Alik; Sengupta, Shamashis; Kasumov, Yu A; Volkov, V T; Khodos, I I; Brisset, F; Delagrange, Raphaëlle; Chepelianskii, Alexei; Deblock, Richard; Bouchiat, Hélène; Guéron, Sophie

2017-07-05

The protection against backscattering provided by topology is a striking property. In two-dimensional insulators, a consequence of this topological protection is the ballistic nature of the one-dimensional helical edge states. One demonstration of ballisticity is the quantized Hall conductance. Here we provide another demonstration of ballistic transport, in the way the edge states carry a supercurrent. The system we have investigated is a micrometre-long monocrystalline bismuth nanowire with topological surfaces, that we connect to two superconducting electrodes. We have measured the relation between the Josephson current flowing through the nanowire and the superconducting phase difference at its ends, the current-phase relation. The sharp sawtooth-shaped phase-modulated current-phase relation we find demonstrates that transport occurs selectively along two ballistic edges of the nanowire. In addition, we show that a magnetic field induces 0-π transitions and ϕ 0 -junction behaviour, providing a way to manipulate the phase of the supercurrent-carrying edge states and generate spin supercurrents.

Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry

PubMed Central

Murani, Anil; Kasumov, Alik; Sengupta, Shamashis; Kasumov, Yu A.; Volkov, V. T.; Khodos, I. I.; Brisset, F.; Delagrange, Raphaëlle; Chepelianskii, Alexei; Deblock, Richard; Bouchiat, Hélène; Guéron, Sophie

2017-01-01

The protection against backscattering provided by topology is a striking property. In two-dimensional insulators, a consequence of this topological protection is the ballistic nature of the one-dimensional helical edge states. One demonstration of ballisticity is the quantized Hall conductance. Here we provide another demonstration of ballistic transport, in the way the edge states carry a supercurrent. The system we have investigated is a micrometre-long monocrystalline bismuth nanowire with topological surfaces, that we connect to two superconducting electrodes. We have measured the relation between the Josephson current flowing through the nanowire and the superconducting phase difference at its ends, the current–phase relation. The sharp sawtooth-shaped phase-modulated current–phase relation we find demonstrates that transport occurs selectively along two ballistic edges of the nanowire. In addition, we show that a magnetic field induces 0–π transitions and φ0-junction behaviour, providing a way to manipulate the phase of the supercurrent-carrying edge states and generate spin supercurrents. PMID:28677681

Edge mixing dynamics in graphene p–n junctions in the quantum Hall regime

PubMed Central

Matsuo, Sadashige; Takeshita, Shunpei; Tanaka, Takahiro; Nakaharai, Shu; Tsukagoshi, Kazuhito; Moriyama, Takahiro; Ono, Teruo; Kobayashi, Kensuke

2015-01-01

Massless Dirac electron systems such as graphene exhibit a distinct half-integer quantum Hall effect, and in the bipolar transport regime co-propagating edge states along the p–n junction are realized. Additionally, these edge states are uniformly mixed at the junction, which makes it a unique structure to partition electrons in these edge states. Although many experimental works have addressed this issue, the microscopic dynamics of electron partition in this peculiar structure remains unclear. Here we performed shot-noise measurements on the junction in the quantum Hall regime as well as at zero magnetic field. We found that, in sharp contrast with the zero-field case, the shot noise in the quantum Hall regime is finite in the bipolar regime, but is strongly suppressed in the unipolar regime. Our observation is consistent with the theoretical prediction and gives microscopic evidence that the edge states are uniquely mixed along the p–n junction. PMID:26337445

Photoluminescence properties of a new orange–red emitting Sm{sup 3+}-doped Y{sub 2}Mo{sub 4}O{sub 15} phosphor

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

Deng, Huajuan; Zhao, Ze; Wang, Jing

2015-08-15

A series of novel Y{sub 2}Mo{sub 4}O{sub 15}:xSm{sup 3+} ( (0.01 ≤ x ≤ 0.20) phosphors for white light-emitting (W-LEDs) were successfully prepared by the solid state reaction technology at 973 K for 12 h. X-ray diffraction and photoluminescence spectra were utilized to characterize the structure and luminescence properties of the as-synthesized phosphors. The emission spectra of the Y{sub 2}Mo{sub 4}O{sub 15}:Sm{sup 3+} phosphors consisted of some sharp emission peaks of Sm{sup 3+} ions centered at 565 nm, 605 nm, 650 nm, and 712 nm. The strongest one is located at 605 nm due to {sup 4}G{sub 5/2}–{sup 6}H{sub 7/2}more » transition of Sm{sup 3+}, generating bright orange–red light. The optimum dopant concentration of Sm{sup 3+} ions in Y{sub 2}Mo{sub 4}O{sub 15}:xSm{sup 3+} is around 5 mol% and the critical transfer distance of Sm{sup 3+} is calculated as 23.32 Å. The CIE chromaticity coordinates of the Y{sub 2}Mo{sub 4}O{sub 15}:0.05Sm{sup 3+} phosphors were located in the orange reddish region. The Y{sub 2}Mo{sub 4}O{sub 15}:Sm{sup 3+} phosphors may be potentially used as red phosphors for white light-emitting diodes. - Graphical abstract: The excitation spectrum of Y{sub 2}Mo{sub 4}O{sub 15}:Sm{sup 3+} is composed of a broad band and some sharp f–f transitions. Under 407 nm excitation, the phosphor presents some sharp emission peaks of Sm{sup 3+} ions. - Highlights: • An orange–red emitting Y{sub 2}Mo{sub 4}O{sub 15}:Sm{sup 3+} phosphor has been firstly synthesized. • Their structures, luminescent properties have also been investigated. • The optical absorption edge for the molybdate lies around 325 nm. • The CIE chromaticity coordinates were located in the orange reddish region.« less

9 CFR 93.412 - Ruminant quarantine facilities.

Code of Federal Regulations, 2012 CFR

2012-01-01

... must be free of sharp edges that could cause injury to ruminants. (D) Ventilation and climate control...-changing area must be provided at each end of each shower area. There also must be one or more receptacles... updated with any changes or additions in advance of such person having access to the quarantine facility...

9 CFR 93.412 - Ruminant quarantine facilities.

Code of Federal Regulations, 2013 CFR

2013-01-01

... must be free of sharp edges that could cause injury to ruminants. (D) Ventilation and climate control...-changing area must be provided at each end of each shower area. There also must be one or more receptacles... updated with any changes or additions in advance of such person having access to the quarantine facility...

Air flow in the boundary layer near a plate

NASA Technical Reports Server (NTRS)

Dryden, Hugh L

1937-01-01

The published data on the distribution of speed near a thin flat plate with sharp leading edge placed parallel to the flow (skin friction plate) are reviewed and the results of some additional measurements are described. The purpose of the experiments was to study the basic phenomena of boundary-layer flow under simple conditions.

16 CFR 1512.18 - Tests and test procedures.

Code of Federal Regulations, 2011 CFR

2011-01-01

... plane containing both wheels and the centerlines of the down tube and seat mast. (ii) Post test: The... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Tests and test procedures. 1512.18 Section... REGULATIONS REQUIREMENTS FOR BICYCLES Regulations § 1512.18 Tests and test procedures. (a) Sharp edge test...

16 CFR 1512.18 - Tests and test procedures.

Code of Federal Regulations, 2010 CFR

2010-01-01

... plane containing both wheels and the centerlines of the down tube and seat mast. (ii) Post test: The... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Tests and test procedures. 1512.18 Section... REGULATIONS REQUIREMENTS FOR BICYCLES Regulations § 1512.18 Tests and test procedures. (a) Sharp edge test...

16 CFR 1512.18 - Tests and test procedures.

Code of Federal Regulations, 2014 CFR

2014-01-01

... seat mast. (ii) Post test: The optical axis of the reflector shall remain parallel within 5° to the... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Tests and test procedures. 1512.18 Section... REGULATIONS REQUIREMENTS FOR BICYCLES Regulations § 1512.18 Tests and test procedures. (a) Sharp edge test...

16 CFR 1512.18 - Tests and test procedures.

Code of Federal Regulations, 2012 CFR

2012-01-01

... seat mast. (ii) Post test: The optical axis of the reflector shall remain parallel within 5° to the... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Tests and test procedures. 1512.18 Section... REGULATIONS REQUIREMENTS FOR BICYCLES Regulations § 1512.18 Tests and test procedures. (a) Sharp edge test...

Language Planning and Student Experiences: Intention, Rhetoric and Implementation

ERIC Educational Resources Information Center

Lo Bianco, Joseph; Aliani, Renata

2013-01-01

This book is a timely comparison of the divergent worlds of policy implementation and policy ambition, the messy, often contradictory here-and-now reality of languages in schools and the sharp-edged, shiny, future-oriented representation of languages in policy. Two deep rooted tendencies in Australian political and social life, multiculturalism…

29 CFR 1917.42 - Miscellaneous auxiliary gear.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) Routine inspection. (1) At the completion of each use, loose gear such as slings, chains, bridles, blocks... sling to which they are attached and shall be free of sharp edges. (h) Chains and chain slings used for... for the sizes of wrought iron and alloy steel chains and chain slings used and shall have such ratings...

29 CFR 1917.42 - Miscellaneous auxiliary gear.

Code of Federal Regulations, 2012 CFR

2012-07-01

...) Routine inspection. (1) At the completion of each use, loose gear such as slings, chains, bridles, blocks... sling to which they are attached and shall be free of sharp edges. (h) Chains and chain slings used for... for the sizes of wrought iron and alloy steel chains and chain slings used and shall have such ratings...

29 CFR 1917.42 - Miscellaneous auxiliary gear.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) Routine inspection. (1) At the completion of each use, loose gear such as slings, chains, bridles, blocks... sling to which they are attached and shall be free of sharp edges. (h) Chains and chain slings used for... for the sizes of wrought iron and alloy steel chains and chain slings used and shall have such ratings...

Experiment to Determine the Absorption Coefficient of Gamma Rays as a Function of Energy.

ERIC Educational Resources Information Center

Ouseph, P. J.; And Others

1982-01-01

Simpler than x-ray diffractometer experiments, the experiment described illustrates certain concepts regarding the interaction of electromagnetic rays with matter such as the exponential decrease in the intensity with absorber thickness, variation of the coefficient of absorption with energy, and the effect of the K-absorption edge on the…

Revealing the Bonding Environment of Zn in ALD Zn(O,S) Buffer Layers through X-ray Absorption Spectroscopy

PubMed Central

2017-01-01

Zn(O,S) buffer layer electronic configuration is determined by its composition and thickness, tunable through atomic layer deposition. The Zn K and L-edges in the X-ray absorption near edge structure verify ionicity and covalency changes with S content. A high intensity shoulder in the Zn K-edge indicates strong Zn 4s hybridized states and a preferred c-axis orientation. 2–3 nm thick films with low S content show a subdued shoulder showing less contribution from Zn 4s hybridization. A lower energy shift with film thickness suggests a decreasing bandgap. Further, ZnSO4 forms at substrate interfaces, which may be detrimental for device performance. PMID:29083141

Liquid-film electron stripper

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

Gavin, B.F.

1986-12-02

This patent describes an improved liquid-film electron stripper for high intensity heavy ion beams comprising: at least one rotatable disc mounted in a housing, means for rotating the disc, a liquid reservoir operatively connected to the housing, means for directing liquid from the reservoir onto the rotatable disc for forming a film of liquid as liquid is spun from the disc, the disc being configured to define a sharp edge located at one side of the periphery of the disc, and configured to include a flat, smooth radially outer section located adjacent the sharp edge, the liquid being directed ontomore » the flat, smooth section of the disc, the means for directing liquid onto the disc including a nozzle positioned with respect to the disc so that liquid from the nozzle impinges at about a 90/sup 0/ angle with respect to the flat, smooth surface of the disc, and liquid film terminator means located in spaced relation to the disc and approximately perpendicular to a formed liquid film, the terminator means comprising at least one ribbon of material secured to the housing.« less

Microfabricated instrument for tissue biopsy and analysis

DOEpatents

Krulevitch, Peter A.; Lee, Abraham P.; Northrup, M. Allen; Benett, William J.

1999-01-01

A microfabricated biopsy/histology instrument which has several advantages over the conventional procedures, including minimal specimen handling, smooth cutting edges with atomic sharpness capable of slicing very thin specimens (approximately 2 .mu.m or greater), micro-liter volumes of chemicals for treating the specimens, low cost, disposable, fabrication process which renders sterile parts, and ease of use. The cutter is a "cheese-grater" style design comprising a block or substrate of silicon and which uses anisotropic etching of the silicon to form extremely sharp and precise cutting edges. As a specimen is cut, it passes through the silicon cutter and lies flat on a piece of glass which is bonded to the cutter. Microchannels are etched into the glass or silicon substrates for delivering small volumes of chemicals for treating the specimen. After treatment, the specimens can be examined through the glass substrate. For automation purposes, microvalves and micropumps may be incorporated. Also, specimens in parallel may be cut and treated with identical or varied chemicals. The instrument is disposable due to its low cost and thus could replace current expensive microtome and histology equipment.

A spatiotemporally controllable chemical gradient generator via acoustically oscillating sharp-edge structures.

PubMed

Huang, Po-Hsun; Chan, Chung Yu; Li, Peng; Nama, Nitesh; Xie, Yuliang; Wei, Cheng-Hsin; Chen, Yuchao; Ahmed, Daniel; Huang, Tony Jun

2015-11-07

The ability to generate stable, spatiotemporally controllable concentration gradients is critical for resolving the dynamics of cellular response to a chemical microenvironment. Here we demonstrate an acoustofluidic gradient generator based on acoustically oscillating sharp-edge structures, which facilitates in a step-wise fashion the rapid mixing of fluids to generate tunable, dynamic chemical gradients. By controlling the driving voltage of a piezoelectric transducer, we demonstrated that the chemical gradient profiles can be conveniently altered (spatially controllable). By adjusting the actuation time of the piezoelectric transducer, moreover, we generated pulsatile chemical gradients (temporally controllable). With these two characteristics combined, we have developed a spatiotemporally controllable gradient generator. The applicability and biocompatibility of our acoustofluidic gradient generator are validated by demonstrating the migration of human dermal microvascular endothelial cells (HMVEC-d) in response to a generated vascular endothelial growth factor (VEGF) gradient, and by preserving the viability of HMVEC-d cells after long-term exposure to an acoustic field. Our device features advantages such as simple fabrication and operation, compact and biocompatible device, and generation of spatiotemporally tunable gradients.

Closed-loop separation control over a sharp edge ramp using genetic programming

NASA Astrophysics Data System (ADS)

Debien, Antoine; von Krbek, Kai A. F. F.; Mazellier, Nicolas; Duriez, Thomas; Cordier, Laurent; Noack, Bernd R.; Abel, Markus W.; Kourta, Azeddine

2016-03-01

We experimentally perform open and closed-loop control of a separating turbulent boundary layer downstream from a sharp edge ramp. The turbulent boundary layer just above the separation point has a Reynolds number Re_{θ }≈ 3500 based on momentum thickness. The goal of the control is to mitigate separation and early re-attachment. The forcing employs a spanwise array of active vortex generators. The flow state is monitored with skin-friction sensors downstream of the actuators. The feedback control law is obtained using model-free genetic programming control (GPC) (Gautier et al. in J Fluid Mech 770:442-457, 2015). The resulting flow is assessed using the momentum coefficient, pressure distribution and skin friction over the ramp and stereo PIV. The PIV yields vector field statistics, e.g. shear layer growth, the back-flow area and vortex region. GPC is benchmarked against the best periodic forcing. While open-loop control achieves separation reduction by locking-on the shedding mode, GPC gives rise to similar benefits by accelerating the shear layer growth. Moreover, GPC uses less actuation energy.

A procedure for scaling sensory attributes based on multidimensional measurements: application to sensory sharpness of kitchen knives

NASA Astrophysics Data System (ADS)

Takatsuji, Toshiyuki; Tanaka, Ken-ichi

1996-06-01

A procedure is derived by which sensory attributes can be scaled as a function of various physical and/or chemical properties of the object to be tested. This procedure consists of four successive steps: (i) design and experiment, (ii) fabrication of specimens according to the design parameters, (iii) assessment of a sensory attribute using sensory evaluation and (iv) derivation of the relationship between the parameters and the sensory attribute. In these steps an experimental design using orthogonal arrays, analysis of variance and regression analyses are used strategically. When a specimen with the design parameters cannot be physically fabricated, an alternative specimen having parameters closest to the design is selected from a group of specimens which can be physically made. The influence of the deviation of actual parameters from the desired ones is also discussed. A method of confirming the validity of the regression equation is also investigated. The procedure is applied to scale the sensory sharpness of kitchen knives as a function of the edge angle and the roughness of the cutting edge.

Detailed modeling of electron emission for transpiration cooling of hypersonic vehicles

NASA Astrophysics Data System (ADS)

Hanquist, Kyle M.; Hara, Kentaro; Boyd, Iain D.

2017-02-01

Electron transpiration cooling (ETC) is a recently proposed approach to manage the high heating loads experienced at the sharp leading edges of hypersonic vehicles. Computational fluid dynamics (CFD) can be used to investigate the feasibility of ETC in a hypersonic environment. A modeling approach is presented for ETC, which includes developing the boundary conditions for electron emission from the surface, accounting for the space-charge limit effects of the near-wall plasma sheath. The space-charge limit models are assessed using 1D direct-kinetic plasma sheath simulations, taking into account the thermionically emitted electrons from the surface. The simulations agree well with the space-charge limit theory proposed by Takamura et al. for emitted electrons with a finite temperature, especially at low values of wall bias, which validates the use of the theoretical model for the hypersonic CFD code. The CFD code with the analytical sheath models is then used for a test case typical of a leading edge radius in a hypersonic flight environment. The CFD results show that ETC can lower the surface temperature of sharp leading edges of hypersonic vehicles, especially at higher velocities, due to the increase in ionized species enabling higher electron heat extraction from the surface. The CFD results also show that space-charge limit effects can limit the ETC reduction of surface temperatures, in comparison to thermionic emission assuming no effects of the electric field within the sheath.

Heat transfer in nonequilibrium boundary layer flow over a partly catalytic wall

NASA Astrophysics Data System (ADS)

Wang, Zhi-Hui

2016-11-01

Surface catalysis has a huge influence on the aeroheating performance of hypersonic vehicles. For the reentry flow problem of a traditional blunt vehicle, it is reasonable to assume a frozen boundary layer surrounding the vehicles' nose, and the catalytic heating can be decoupled with the heat conduction. However, when considering a hypersonic cruise vehicle flying in the medium-density near space, the boundary layer flow around its sharp leading-edge is likely to be nonequilibrium rather than frozen due to rarefied gas effects. As a result, there will be a competition between the heat conduction and the catalytic heating. In this paper, the theoretical modeling and the direct simulation Monte Carlo (DSMC) method are employed to study the corresponding rarefied nonequilibrium flow and heat transfer phenomena near the leading edge of the near space hypersonic vehicles. It is found that even under identical rarefication degree, the nonequilibrium degree of the flow and the corresponding heat transfer performance of the sharp leading edges could be different from that of the big blunt noses. A generalized model is preliminarily proposed to describe and to evaluate the competitive effects between the homogeneous recombination of atoms inside the nonequilibrium boundary layer and the heterogeneous recombination of atoms on the catalytic wall surface. The introduced nonequilibrium criterion and the analytical formula are validated and calibrated by the DSMC results, and the physical mechanism is discussed.

The Structure of Chariklo’s Rings from Stellar Occultations

NASA Astrophysics Data System (ADS)

Bérard, D.; Sicardy, B.; Camargo, J. I. B.; Desmars, J.; Braga-Ribas, F.; Ortiz, J.-L.; Duffard, R.; Morales, N.; Meza, E.; Leiva, R.; Benedetti-Rossi, G.; Vieira-Martins, R.; Gomes Júnior, A.-R.; Assafin, M.; Colas, F.; Dauvergne, J.-L.; Kervella, P.; Lecacheux, J.; Maquet, L.; Vachier, F.; Renner, S.; Monard, B.; Sickafoose, A. A.; Breytenbach, H.; Genade, A.; Beisker, W.; Bath, K.-L.; Bode, H.-J.; Backes, M.; Ivanov, V. D.; Jehin, E.; Gillon, M.; Manfroid, J.; Pollock, J.; Tancredi, G.; Roland, S.; Salvo, R.; Vanzi, L.; Herald, D.; Gault, D.; Kerr, S.; Pavlov, H.; Hill, K. M.; Bradshaw, J.; Barry, M. A.; Cool, A.; Lade, B.; Cole, A.; Broughton, J.; Newman, J.; Horvat, R.; Maybour, D.; Giles, D.; Davis, L.; Paton, R. A.; Loader, B.; Pennell, A.; Jaquiery, P.-D.; Brillant, S.; Selman, F.; Dumas, C.; Herrera, C.; Carraro, G.; Monaco, L.; Maury, A.; Peyrot, A.; Teng-Chuen-Yu, J.-P.; Richichi, A.; Irawati, P.; De Witt, C.; Schoenau, P.; Prager, R.; Colazo, C.; Melia, R.; Spagnotto, J.; Blain, A.; Alonso, S.; Román, A.; Santos-Sanz, P.; Rizos, J.-L.; Maestre, J.-L.; Dunham, D.

2017-10-01

Two narrow and dense rings (called C1R and C2R) were discovered around the Centaur object (10199) Chariklo during a stellar occultation observed on 2013 June 3. Following this discovery, we planned observations of several occultations by Chariklo’s system in order to better characterize the physical properties of the ring and main body. Here, we use 12 successful occulations by Chariklo observed between 2014 and 2016. They provide ring profiles (physical width, opacity, edge structure) and constraints on the radii and pole position. Our new observations are currently consistent with the circular ring solution and pole position, to within the ±3.3 km formal uncertainty for the ring radii derived by Braga-Ribas et al. The six resolved C1R profiles reveal significant width variations from ˜5 to 7.5 km. The width of the fainter ring C2R is less constrained, and may vary between 0.1 and 1 km. The inner and outer edges of C1R are consistent with infinitely sharp boundaries, with typical upper limits of one kilometer for the transition zone between the ring and empty space. No constraint on the sharpness of C2R’s edges is available. A 1σ upper limit of ˜20 m is derived for the equivalent width of narrow (physical width < 4 km) rings up to distances of 12,000 km, counted in the ring plane.

Effect of alkaline earth modifier on the optical and structural properties of Cu2+ doped phosphate glasses as a bandpass filter

NASA Astrophysics Data System (ADS)

Farouk, M.; Samir, A.; El Okr, M.

2018-02-01

Glasses of composition [16RO-3Al2O3sbnd 6CuOsbnd 20Na2Osbnd 55P2O5], where R is the alkaline earth (R = Mg, Ca, Sr and Ba mol. %), were prepared by conventional melt quenching technique. The glass samples were characterized by X-ray diffraction, infrared spectroscopy, and spectrophotometer. XRD patterns show no sharp peaks indicating the non-crystalline nature of the prepared glasses. The density and molar volume of the glass systems were determined in order to study their structures. These results revealed that addition of alkaline earth elements leads to the formation of non-bridging oxygens (NBOs) and expands (opens up) the structure. The infrared spectra were analyzed to quantify the present phosphate groups. The optical absorption spectra of Cu2+ ions show the characteristic broadband single of Cu2+ ions in octahedral symmetry. The band gap was estimated following two methodologies. The first method considers the band edge of the transmission, while the second approach relays on the estimated values of the optical constants. A decent agreement for the band gap values using the two methods was obtained.

Broad-Band Spectroscopy of Hercules X-1 with Suzaku

NASA Technical Reports Server (NTRS)

Asami, Fumi; Enoto, Teruaki; Iwakiri, Wataru; Yamada, Shin'ya; Tamagawa, Toru; Mihara, Tatehiro; Nagase, Fumiaki

2014-01-01

Hercules X-1 was observed with Suzaku in the main-on state from 2005 to 2010. The 0.4- 100 keV wide-band spectra obtained in four observations showed a broad hump around 4-9 keV in addition to narrow Fe lines at 6.4 and 6.7 keV. The hump was seen in all the four observations regardless of the selection of the continuum models. Thus it is considered a stable and intrinsic spectral feature in Her X-1. The broad hump lacked a sharp structure like an absorption edge. Thus it was represented by two different spectral models: an ionized partial covering or an additional broad line at 6.5 keV. The former required a persistently existing ionized absorber, whose origin was unclear. In the latter case, the Gaussian fitting of the 6.5-keV line needs a large width of sigma = 1.0-1.5 keV and a large equivalent width of 400-900 eV. If the broad line originates from Fe fluorescence of accreting matter, its large width may be explained by the Doppler broadening in the accretion flow. However, the large equivalent width may be inconsistent with a simple accretion geometry.

Plasmons driven by single electrons in graphene nanoislands

NASA Astrophysics Data System (ADS)

Manjavacas, Alejandro; Thongrattanasiri, Sukosin; de Abajo, F. Javier García

2013-04-01

Plasmons produce large confinement and enhancement of light that enable applications as varied as cancer therapy and catalysis. Adding to these appealing properties, graphene has emerged as a robust, electrically tunable material exhibiting plasmons that strongly depend on the density of doping charges. Here we show that adding a single electron to a graphene nanoisland consisting of hundreds or thousands of atoms switches on infrared plasmons that were previously absent from the uncharged structure. Remarkably, the addition of each further electron produces a dramatic frequency shift. Plasmons in these islands are shown to be tunable down to near infrared wavelengths. These phenomena are highly sensitive to carbon edges. Specifically, armchair nanotriangles display sharp plasmons that are associated with intense near-field enhancement, as well as absorption cross-sections exceeding the geometrical area occupied by the graphene. In contrast, zigzag triangles do not support these plasmons. Our conclusions rely on realistic quantum-mechanical calculations, which are in ostensible disagreement with classical electromagnetic simulations, thus revealing the quantum nature of the plasmons. This study shows a high sensitivity of graphene nanoislands to elementary charges, therefore emphasizing their great potential for novel nano-optoelectronics applications.

Aging effects of the precursor solutions on the properties of spin coated Ga-doped ZnO thin films

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

Serrao, Felcy Jyothi, E-mail: jyothiserrao@gmail.com; Dharmaprakash, S. M.

2015-06-24

In this study, gallium doped zinc oxide thin films (GZO) were grown on a glass substrate by a simple sol-gel process and spin coating technique using zinc acetate and gallium nitrate (3at%) as precursors for Zn and Ga ions respectively. The effects of aging time of the precursor solution on the structural and optical properties of the GZO films were investigated. The surface morphology, grain size, film thickness and optical properties of the GZO films were found to depend directly on the sol aging time. XRD studies reveal that the films are polycrystalline with a hexagonal wurtzite structure and showmore » the c-axis grain orientation. Optical transmittance spectra of all the films exhibited transmittance higher than about 82% within the visible wavelength region. A sharp fundamental absorption edge with a slight blue shifting was observed with an increase in sol aging time which can be explained by Burstein-Moss effect. The result indicates that an appropriate aging time of the sol is important for the improvement of the structural and optical properties of GZO thin films derived from sol-gel method.« less

Epitaxial growth and magnetic properties of ultraviolet transparent Ga2O3/(Ga1−xFex)2O3 multilayer thin films

PubMed Central

Guo, Daoyou; An, Yuehua; Cui, Wei; Zhi, Yusong; Zhao, Xiaolong; Lei, Ming; Li, Linghong; Li, Peigang; Wu, Zhenping; Tang, Weihua

2016-01-01

Multilayer thin films based on the ferromagnetic and ultraviolet transparent semiconductors may be interesting because their magnetic/electronic/photonic properties can be manipulated by the high energy photons. Herein, the Ga2O3/(Ga1−xFex)2O3 multilayer epitaxial thin films were obtained by alternating depositing of wide band gap Ga2O3 layer and Fe ultrathin layer due to inter diffusion between two layers at high temperature using the laser molecular beam epitaxy technique. The multilayer films exhibits a preferred growth orientation of crystal plane, and the crystal lattice expands as Fe replaces Ga site. Fe ions with a mixed valence of Fe2+ and Fe3+ are stratified distributed in the film and exhibit obvious agglomerated areas. The multilayer films only show a sharp absorption edge at about 250 nm, indicating a high transparency for ultraviolet light. What’s more, the Ga2O3/(Ga1−xFex)2O3 multilayer epitaxial thin films also exhibits room temperature ferromagnetism deriving from the Fe doping Ga2O3. PMID:27121446

Fabrication and Testing of a Leading-Edge-Shaped Heat Pipe

NASA Technical Reports Server (NTRS)

Glass, David E.; Merrigan, Michael A.; Sena, J. Tom; Reid, Robert S.

1998-01-01

The development of a refractory-composite/heat-pipe-cooled leading edge has evolved from the design stage to the fabrication and testing of a full size, leading-edge-shaped heat pipe. The heat pipe had a 'D-shaped' cross section and was fabricated from arc cast Mo-4lRe. An artery was included in the wick. Several issues were resolved with the fabrication of the sharp leading edge radius heat pipe. The heat pipe was tested in a vacuum chamber at Los Alamos National Laboratory using induction heating and was started up from the frozen state several times. However, design temperatures and heat fluxes were not obtained due to premature failure of the heat pipe resulting from electrical discharge between the induction heating apparatus and the heat pipe. Though a testing anomaly caused premature failure of the heat pipe, successful startup and operation of the heat pipe was demonstrated.

Edge electrospinning: a facile needle-less approach to realize scaled up production of quality nanofibers

NASA Astrophysics Data System (ADS)

Bochinski, J. R.; Curtis, C.; Roman, M. P.; Clarke, L. I.; Wang, Q.; Thoppey, N. M.; Gorga, R. E.

2014-03-01

Utilizing unconfined polymer fluids (e.g., from solution or melt), edge electrospinning provides a straightforward approach for scaled up production of high quality nanofibers through the formation of many parallel jets. From simple geometries (using solution contained within a sharp-edged bowl or on a flat plate), jets form and spontaneously re-arrange on the fluid surface near the edge. Using appropriate control of the electric field induced feed rate, comparable per jet fabrication as traditional single-needle electrospinning can be realized, resulting in nanofibers with similar diameters, diameter distribution, and collected mat porosity. The presence of multiple jets proportionally enhances the production rate of the system, with minimal experimental complexity and without the possibility of clogging. Extending this needle-less approach to commercial polyethylene polymers, micron scale fibers can be melt electrospun using a similar apparatus. Support from National Science Foundation (CMMI-0800237).

Experimental Surface Pressure Data Obtained on 65 deg Delta Wing Across Reynolds Number and Mach Number Ranges. Volume 1; Sharp Leading Edge; [conducted in the Langley National Transonic Facility (NTF)

NASA Technical Reports Server (NTRS)

Chu, Julio; Luckring, James M.

1996-01-01

An experimental wind tunnel test of a 65 deg delta wing model with interchangeable leading edges was conducted in the Langley National Transonic Facility (NTF). The objective was to investigate the effects of Reynolds and Mach numbers on slender-wing leading-edge vortex flows with four values of wing leading-edge bluntness. Experimentally obtained pressure data are presented without analysis in tabulated and graphical formats across a Reynolds number range of 6 x 10(exp 6) to 36 x 10(exp 6) at a Mach number of 0.85 and across a Mach number range of 0.4 to 0.9 at a Reynolds number of 6 x 10(exp 6). Normal-force and pitching-moment coefficient plots for these Reynolds number and Mach number ranges are also presented.

Controllable Edge Feature Sharpening for Dental Applications

PubMed Central

2014-01-01

This paper presents a new approach to sharpen blurred edge features in scanned tooth preparation surfaces generated by structured-light scanners. It aims to efficiently enhance the edge features so that the embedded feature lines can be easily identified in dental CAD systems, and to avoid unnatural oversharpening geometry. We first separate the feature regions using graph-cut segmentation, which does not require a user-defined threshold. Then, we filter the face normal vectors to propagate the geometry from the smooth region to the feature region. In order to control the degree of the sharpness, we propose a feature distance measure which is based on normal tensor voting. Finally, the vertex positions are updated according to the modified face normal vectors. We have applied the approach to scanned tooth preparation models. The results show that the blurred edge features are enhanced without unnatural oversharpening geometry. PMID:24741376

Controllable edge feature sharpening for dental applications.

PubMed

Fan, Ran; Jin, Xiaogang

2014-01-01

This paper presents a new approach to sharpen blurred edge features in scanned tooth preparation surfaces generated by structured-light scanners. It aims to efficiently enhance the edge features so that the embedded feature lines can be easily identified in dental CAD systems, and to avoid unnatural oversharpening geometry. We first separate the feature regions using graph-cut segmentation, which does not require a user-defined threshold. Then, we filter the face normal vectors to propagate the geometry from the smooth region to the feature region. In order to control the degree of the sharpness, we propose a feature distance measure which is based on normal tensor voting. Finally, the vertex positions are updated according to the modified face normal vectors. We have applied the approach to scanned tooth preparation models. The results show that the blurred edge features are enhanced without unnatural oversharpening geometry.

IR-thermography for Quality Prediction in Selective Laser Deburring

NASA Astrophysics Data System (ADS)

Möller, Mauritz; Conrad, Christian; Haimerl, Walter; Emmelmann, Claus

Selective Laser Deburring (SLD) is an innovative edge-refinement process being developed at the Laser Zentrum Nord (LZN) in Hamburg. It offers a wear-free processing of defined radii and bevels at the edges as well as the possibility to deburr several materials with the same laser source. Sheet metal parts of various applications need to be post-processed to remove sharp edges and burrs remaining from the initial production process. Thus, SLD will provide an extended degree of automation for the next generation of manufacturing facilities. This paper investigates the dependence between the deburring result and the temperature field in- and post-process. In order to achieve this, the surface temperature near to the deburred edge is monitored with IR-thermography. Different strategies are discussed for the approach using the IR-information as a quality assurance. Additional experiments are performed to rate the accuracy of the quality prediction method in different deburring applications.

Enhancing the transmission efficiency by edge deletion in scale-free networks

NASA Astrophysics Data System (ADS)

Zhang, Guo-Qing; Wang, Di; Li, Guo-Jie

2007-07-01

How to improve the transmission efficiency of Internet-like packet switching networks is one of the most important problems in complex networks as well as for the Internet research community. In this paper we propose a convenient method to enhance the transmission efficiency of scale-free networks dramatically by kicking out the edges linking to nodes with large betweenness, which we called the “black sheep.” The advantages of our method are of facility and practical importance. Since the black sheep edges are very costly due to their large bandwidth, our method could decrease the cost as well as gain higher throughput of networks. Moreover, we analyze the curve of the largest betweenness on deleting more and more black sheep edges and find that there is a sharp transition at the critical point where the average degree of the nodes ⟨k⟩→2 .

Improved Method for Prediction of Attainable Wing Leading-Edge Thrust

NASA Technical Reports Server (NTRS)

Carlson, Harry W.; McElroy, Marcus O.; Lessard, Wendy B.; McCullers, L. Arnold

1996-01-01

Prediction of the loss of wing leading-edge thrust and the accompanying increase in drag due to lift, when flow is not completely attached, presents a difficult but commonly encountered problem. A method (called the previous method) for the prediction of attainable leading-edge thrust and the resultant effect on airplane aerodynamic performance has been in use for more than a decade. Recently, the method has been revised to enhance its applicability to current airplane design and evaluation problems. The improved method (called the present method) provides for a greater range of airfoil shapes from very sharp to very blunt leading edges. It is also based on a wider range of Reynolds numbers than was available for the previous method. The present method, when employed in computer codes for aerodynamic analysis, generally results in improved correlation with experimental wing-body axial-force data and provides reasonable estimates of the measured drag.

Real-Time Symbol Extraction From Grey-Level Images

NASA Astrophysics Data System (ADS)

Massen, R.; Simnacher, M.; Rosch, J.; Herre, E.; Wuhrer, H. W.

1988-04-01

A VME-bus image pipeline processor for extracting vectorized contours from grey-level images in real-time is presented. This 3 Giga operation per second processor uses large kernel convolvers and new non-linear neighbourhood processing algorithms to compute true 1-pixel wide and noise-free contours without thresholding even from grey-level images with quite varying edge sharpness. The local edge orientation is used as an additional cue to compute a list of vectors describing the closed and open contours in real-time and to dump a CAD-like symbolic image description into a symbol memory at pixel clock rate.

Towards simultaneous measurements of electronic and structural properties in ultra-fast x-ray free electron laser absorption spectroscopy experiments

NASA Astrophysics Data System (ADS)

Gaudin, J.; Fourment, C.; Cho, B. I.; Engelhorn, K.; Galtier, E.; Harmand, M.; Leguay, P. M.; Lee, H. J.; Nagler, B.; Nakatsutsumi, M.; Ozkan, C.; Störmer, M.; Toleikis, S.; Tschentscher, Th; Heimann, P. A.; Dorchies, F.

2014-04-01

The rapidly growing ultrafast science with X-ray lasers unveils atomic scale processes with unprecedented time resolution bringing the so called ``molecular movie'' within reach. X-ray absorption spectroscopy is one of the most powerful x-ray techniques providing both local atomic order and electronic structure when coupled with ad-hoc theory. Collecting absorption spectra within few x-ray pulses is possible only in a dispersive setup. We demonstrate ultrafast time-resolved measurements of the LIII-edge x-ray absorption near-edge spectra of irreversibly laser excited Molybdenum using an average of only few x-ray pulses with a signal to noise ratio limited only by the saturation level of the detector. The simplicity of the experimental set-up makes this technique versatile and applicable for a wide range of pump-probe experiments, particularly in the case of non-reversible processes.

Towards simultaneous measurements of electronic and structural properties in ultra-fast x-ray free electron laser absorption spectroscopy experiments

PubMed Central

Gaudin, J.; Fourment, C.; Cho, B. I.; Engelhorn, K.; Galtier, E.; Harmand, M.; Leguay, P. M.; Lee, H. J.; Nagler, B.; Nakatsutsumi, M.; Ozkan, C.; Störmer, M.; Toleikis, S.; Tschentscher, Th; Heimann, P. A.; Dorchies, F.

2014-01-01

The rapidly growing ultrafast science with X-ray lasers unveils atomic scale processes with unprecedented time resolution bringing the so called “molecular movie” within reach. X-ray absorption spectroscopy is one of the most powerful x-ray techniques providing both local atomic order and electronic structure when coupled with ad-hoc theory. Collecting absorption spectra within few x-ray pulses is possible only in a dispersive setup. We demonstrate ultrafast time-resolved measurements of the LIII-edge x-ray absorption near-edge spectra of irreversibly laser excited Molybdenum using an average of only few x-ray pulses with a signal to noise ratio limited only by the saturation level of the detector. The simplicity of the experimental set-up makes this technique versatile and applicable for a wide range of pump-probe experiments, particularly in the case of non-reversible processes. PMID:24740172

Towards simultaneous measurements of electronic and structural properties in ultra-fast x-ray free electron laser absorption spectroscopy experiments

DOE PAGES

Gaudin, J.; Fourment, C.; Cho, B. I.; ...

2014-04-17

The rapidly growing ultrafast science with X-ray lasers unveils atomic scale processes with unprecedented time resolution bringing the so called “molecular movie” within reach. X-ray absorption spectroscopy is one of the most powerful x-ray techniques providing both local atomic order and electronic structure when coupled with ad-hoc theory. Collecting absorption spectra within few x-ray pulses is possible only in a dispersive setup. We demonstrate ultrafast time-resolved measurements of the LIII-edge x-ray absorption near-edge spectra of irreversibly laser excited Molybdenum using an average of only few x-ray pulses with a signal to noise ratio limited only by the saturation level ofmore » the detector. The simplicity of the experimental set-up makes this technique versatile and applicable for a wide range of pump-probe experiments, particularly in the case of non-reversible processes.« less

Soft X-ray Absorption Edges in LMXBs

NASA Technical Reports Server (NTRS)

2004-01-01

The XMM observation of LMC X-2 is part of our program to study X-ray absorption in the interstellar medium (ISM). This program includes a variety of bright X-ray binaries in the Galaxy as well as the Magellanic Clouds (LMC and SMC). LMC X-2 is located near the heart of the LMC. Its very soft X-ray spectrum is used to determine abundance and ionization fractions of neutral and lowly ionized oxygen of the ISM in the LMC. The RGS spectrum so far allowed us to determine the O-edge value to be for atomic O, the EW of O-I in the ls-2p resonance absorption line, and the same for O-II. The current study is still ongoing in conjunction with other low absorption sources like Sco X-1 and the recently observed X-ray binary 4U 1957+11.

A STEP fault in Central Betics, associated with lateral lithospheric tearing at the northern edge of the Gibraltar arc subduction system

NASA Astrophysics Data System (ADS)

Mancilla, Flor de Lis; Heit, Benjamin; Morales, Jose; Yuan, Xiaohui; Stich, Daniel; Molina-Aguilera, Antonio; Azañon, Jose Miguel; Martín, Rosa

2018-03-01

We study the crustal and lithospheric mantle structure under central Betics in the westernmost Mediterranean region by migrating P-receiver functions along a dense seismic profile (∼2 km interstation distance). The profile, North-South oriented, probes the crustal structure of different geological units, from the Alboran domain in the south with metamorphic rocks, through the External Zones with sedimentary rocks to the Variscan terrains of the Iberian Massif in the north. From north to south, the Moho depth increases from ∼30 km to ∼46 km underneath the Guadix basin, due to the underthrusting of the Iberian crust below the Alboran crust, and suddenly shallows to ∼30 km underneath the Internal Zones with a step of 17 km. This sharp Moho step correlates well with a lithospheric step of ∼40 km, where the thickness of the lithosphere changes abruptly from ∼100 km in the north to ∼50 km in the south. We interpret this sharp and prominent lithospheric step as the termination of the Iberian lithosphere caused by a near-vertical STEP (Subduction-Transform-Edge-Propagator) fault that continues towards the surface as a positive flower tectonic structure of crustal scale. This STEP fault is located at the northern edge of the narrow Westernmost Mediterranean subduction system facilitating the slab rollback motion towards the west. The sharp termination of the Iberian lithosphere occurs under the contact between the Alpujarride and the Nevado-Filabride complexes of the Alboran domain in an ENE-WSW right-lateral transpressive shear zone. The thickest crust and lithosphere do not correlate with the highest topography along the profile suggesting that this high topography is a combined effect of the positive flower structure, and the push up of the asthenosphere produced by the removal of the Iberian lithosphere.

Optical Absorption in Degenerately Doped Semiconductors: Mott Transition or Mahan Excitons?

NASA Astrophysics Data System (ADS)

Schleife, André; Rödl, Claudia; Fuchs, Frank; Hannewald, Karsten; Bechstedt, Friedhelm

2011-12-01

Electron doping turns semiconductors conductive even when they have wide fundamental band gaps. The degenerate electron gas in the lowest conduction-band states, e.g., of a transparent conducting oxide, drastically modifies the Coulomb interaction between the electrons and, hence, the optical properties close to the absorption edge. We describe these effects by developing an ab initio technique which captures also the Pauli blocking and the Fermi-edge singularity at the optical-absorption onset, that occur in addition to quasiparticle and excitonic effects. We answer the question whether free carriers induce an excitonic Mott transition or trigger the evolution of Wannier-Mott excitons into Mahan excitons. The prototypical n-type zinc oxide is studied as an example.

Reduced chromium in olivine grains from lunar basalt 15555 - X-ray Absorption Near Edge Structure (XANES)

NASA Technical Reports Server (NTRS)

Sutton, S. R.; Jones, K. W.; Gordon, B.; Rivers, M. L.; Bajt, S.; Smith, J. V.

1993-01-01

The oxidation state of Cr in 200-micron regions within individual lunar olivine and pyroxene grains from lunar basalt 15555 was inferred using X-ray Absorption Near Edge Structure (XANES). Reference materials had previously been studied by optical absorption spectroscopy and included Cr-bearing borosilicate glasses synthesized under controlled oxygen fugacity and Cr-doped olivines. The energy dependence of XANES spectral features defined by these reference materials indicated that Cr is predominantly divalent in the lunar olivine and trivalent in the pyroxene. These results, coupled with the apparent f(02)-independence of partitioning coefficients for Cr into olivine, imply that the source magma was dominated by divalent Cr at the time of olivine crystallization.

Kα X-Ray Emission Spectra and K X-Ray Absorption-Edge Structures of Fluorine in 3d Transition-Metal Difluorides

NASA Astrophysics Data System (ADS)

Sugiura, Chikara

1991-08-01

The fluorine Kα emission spectra in fluorescence from a series of 3d transition-metal difluorides MF2 (M=Mn, Fe, Co, Ni, Cu and Zn) have been measured with a high-resolution two-crystal vacuum spectrometer. It is shown that the observed FWHM of the Kα1,2 emission band is closely related to the difference in the electronegativity between the metal and fluorine atoms. The measured emission spectra are presented along with the UPS or XPS spectra of the valence bands and the fluorine K absorption spectra of the metal difluorides, reported previously. The structures at the fluorine K absorption edges are interpreted in terms of a molecular orbital (MO) model.

Framework influence of erbium doped oxyfluoride glasses on their optical properties

NASA Astrophysics Data System (ADS)

Środa, Marcin; Cholewa-Kowalska, Katarzyna; Różański, Marek; Nocuń, Marek

2011-01-01

Glasses of different matrix (phosphate, borate, silicate and lead-silicate) were studied for their optical properties. The effect of Er dopant on transmittance and luminescence properties was presented. The significant “red shift” and “blue shift” of UV edge absorption were discussed based on the changes in the framework of the borate and phosphate glasses, respectively. It was showed that the integral intensity of the two main optical absorption transitions monotonically increases with the order: phosphate < borate < silicate < lead-silicate. Ellipsometric measurement was applied to obtain the refractive index of the glasses. The correlation between the shift of edge absorption and the change of refractive index was presented. Effect of glassy matrix on luminescence of Er3+ was discussed.

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic-Inorganic Lead Halide Perovskites.

PubMed

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina; Sadoughi, Golnaz; Habisreutinger, Severin N; Félix, Roberto; Wilks, Regan G; Snaith, Henry J; Bär, Marcus; Draxl, Claudia

2018-04-19

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3 ) hybrid inorganic-organic perovskite and its binary phase PbI 2 . The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. The theoretical analysis complementing experimental observations provides the conceptual insights required for a full characterization of this complex material.

Ca L2,3-edge XANES and Sr K-edge EXAFS study of hydroxyapatite and fossil bone apatite.

PubMed

Zougrou, I M; Katsikini, M; Brzhezinskaya, M; Pinakidou, F; Papadopoulou, L; Tsoukala, E; Paloura, E C

2016-08-01

Upon burial, the organic and inorganic components of hard tissues such as bone, teeth, and tusks are subjected to various alterations as a result of interactions with the chemical milieu of soil, groundwater, and presence of microorganisms. In this study, simulation of the Ca L 2,3-edge X-ray absorption near edge structure (XANES) spectrum of hydroxyapatite, using the CTM4XAS code, reveals that the different symmetry of the two nonequivalent Ca(1) and Ca(2) sites in the unit cell gives rise to specific spectral features. Moreover, Ca L 2,3-edge XANES spectroscopy is applied in order to assess variations in fossil bone apatite crystallinity due to heavy bacterial alteration and catastrophic mineral dissolution, compared to well-preserved fossil apatite, fresh bone, and geologic apatite reference samples. Fossilization-induced chemical alterations are investigated by means of Ca L 2,3-edge XANES and scanning electron microscopy (SEM) and are related to histological evaluation using optical microscopy images. Finally, the variations in the bonding environment of Sr and its preference for substitution in the Ca(1) or Ca(2) sites upon increasing the Sr/Ca ratio is assessed by Sr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy.

Ca L2,3-edge XANES and Sr K-edge EXAFS study of hydroxyapatite and fossil bone apatite

NASA Astrophysics Data System (ADS)

Zougrou, I. M.; Katsikini, M.; Brzhezinskaya, M.; Pinakidou, F.; Papadopoulou, L.; Tsoukala, E.; Paloura, E. C.

2016-08-01

Upon burial, the organic and inorganic components of hard tissues such as bone, teeth, and tusks are subjected to various alterations as a result of interactions with the chemical milieu of soil, groundwater, and presence of microorganisms. In this study, simulation of the Ca L 2,3-edge X-ray absorption near edge structure (XANES) spectrum of hydroxyapatite, using the CTM4XAS code, reveals that the different symmetry of the two nonequivalent Ca(1) and Ca(2) sites in the unit cell gives rise to specific spectral features. Moreover, Ca L 2,3-edge XANES spectroscopy is applied in order to assess variations in fossil bone apatite crystallinity due to heavy bacterial alteration and catastrophic mineral dissolution, compared to well-preserved fossil apatite, fresh bone, and geologic apatite reference samples. Fossilization-induced chemical alterations are investigated by means of Ca L 2,3-edge XANES and scanning electron microscopy (SEM) and are related to histological evaluation using optical microscopy images. Finally, the variations in the bonding environment of Sr and its preference for substitution in the Ca(1) or Ca(2) sites upon increasing the Sr/Ca ratio is assessed by Sr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy.

Temperature dependence of Ti 1s near-edge spectra in Ti-based perovskites: theory and experiment

NASA Astrophysics Data System (ADS)

Shirley, Eric; Cockayne, Eric; Ravel, Bruce; Woicik, Joseph

Ti 1s near-edge spectra (around 4970 eV) in SrTiO3 and PbTiO3 reveal electric-dipole and quadrupole transitions to Ti 3d, 4p and mixed 3d-4p states. Crystal field-split pre-edge features attributed to 1s ->3d transitions are small compared to the main edge jump at the onset of the Ti 4s/4p continuum. Pre-edge and subsequent near-edge features are predicted to be weaker than what is observed, unless one accounts for ferroelectric polarization in PbTiO3 and thermal motion in both compounds. Using density-functional theory molecular dynamics simulations at various temperatures (including sampling two phases of PbTiO3), we capture the statistically averaged root-mean-square deviations of Ti4+ ions from the centers of their oxygen cages. By sampling appropriate snapshots of atomic configurations and averaging Ti 1s absorption spectra computed within a Bethe-Salpeter Equation framework, we obtain absorption spectra that agree well with experiment, including details related to ferroelectric polarization, phase transitions, and fluctuations of atomic coordinates.

Nonlinear refraction at the absorption edge in InAs.

PubMed

Poole, C D; Garmire, E

1984-08-01

The results of measurements of nonlinear refraction at the absorption edge in InAs between 68 and 90 K taken with an HF laser are compared with those of a band-gap resonant model in which the contribution of the light-hole band is included and found to account for more than 40% of the observed nonlinear refraction. A generalized expression for the nonlinear index is derived by using the complete Fermi-Dirac distribution function. Good agreement between theory and experiment is obtained, with no free parameters.

Quantitative study of mammalian cells by scanning transmission soft X-ray microscopy

NASA Astrophysics Data System (ADS)

Shinohara, K.; Ohigashi, T.; Toné, S.; Kado, M.; Ito, A.

2017-06-01

Molecular distribution in mammalian cells was studied by soft X-ray scanning transmission microscopy with respect to the quantitative aspect of analysis. NEXAFS profiles at the C, N and O K-absorption edges were combined and used for the analysis. For the estimation of quantity for nucleic acids and proteins, NEXAFS profiles of DNA and bovine serum albumin (BSA) at the N K-absorption edge were applied assuming that those were their representatives. The method has a potential to explore the other molecular components than nucleic acids and proteins.

Nickel L-edge and K-edge X-ray absorption spectroscopy of non-innocent Ni[S₂C₂(CF₃)₂]₂(n) series (n = -2, -1, 0): direct probe of nickel fractional oxidation state changes.

PubMed

Gu, Weiwei; Wang, Hongxin; Wang, Kun

2014-05-07

A series of nickel dithiolene complexes Ni[S2C2(CF3)2]2(n) (n = -2, -1, 0) has been investigated using Ni L- and K-edge X-ray absorption spectroscopy (XAS). The L3 centroid shifts about 0.3 eV for a change of one unit in the formal oxidation state (or 0.3 eV per oxi), corresponding to ~33% of the shift for Ni oxides or fluorides (about 0.9 eV per oxi). The K-edge XAS edge position shifts about 0.7 eV per oxi, corresponding to ~38% of that for Ni oxides (1.85 eV per oxi). In addition, Ni L sum rule analysis found the Ni(3d) ionicity in the frontier orbitals being 50.5%, 44.0% and 38.5% respectively (for n = -2, -1, 0), in comparison with their formal oxidation states (of Ni(II), Ni(III), and Ni(IV)). For the first time, direct and quantitative measurement of the Ni fractional oxidation state changes becomes possible for Ni dithiolene complexes, illustrating the power of L-edge XAS and L sum rule analysis in such a study. The Ni L-edge and K-edge XAS can be used in a complementary manner to better assess the oxidation states for Ni.

Determination of oxidation state of iron in normal and pathologically altered human aortic valves

NASA Astrophysics Data System (ADS)

Czapla-Masztafiak, J.; Lis, G. J.; Gajda, M.; Jasek, E.; Czubek, U.; Bolechała, F.; Borca, C.; Kwiatek, W. M.

2015-12-01

In order to investigate changes in chemical state of iron in normal and pathologically altered human aortic valves X-ray absorption spectroscopy was applied. Since Fe is suspected to play detrimental role in aortic valve stenosis pathogenesis the oxidation state of this element has been determined. The experimental material consisted of 10 μm sections of valves excised during routine surgery and from autopsies. The experiment was performed at the MicroXAS beamline of the SLS synchrotron facility in Villigen (Switzerland). The Fe K-edge XANES spectra obtained from tissue samples were carefully analyzed and compared with the spectra of reference compounds containing iron in various chemical structures. The analysis of absorption edge position and shape of the spectra revealed that both chemical forms of iron are presented in valve tissue but Fe3+ is the predominant form. Small shift of the absorption edge toward higher energy in the spectra from stenotic valve samples indicates higher content of the Fe3+ form in pathological tissue. Such a phenomenon suggests the role of Fenton reaction and reactive oxygen species in the etiology of aortic valve stenosis. The comparison of pre-edge regions of XANES spectra for control and stenotic valve tissue confirmed no differences in local symmetry or spin state of iron in analyzed samples.

Spectral K-edge subtraction imaging

NASA Astrophysics Data System (ADS)

Zhu, Y.; Samadi, N.; Martinson, M.; Bassey, B.; Wei, Z.; Belev, G.; Chapman, D.

2014-05-01

We describe a spectral x-ray transmission method to provide images of independent material components of an object using a synchrotron x-ray source. The imaging system and process is similar to K-edge subtraction (KES) imaging where two imaging energies are prepared above and below the K-absorption edge of a contrast element and a quantifiable image of the contrast element and a water equivalent image are obtained. The spectral method, termed ‘spectral-KES’ employs a continuous spectrum encompassing an absorption edge of an element within the object. The spectrum is prepared by a bent Laue monochromator with good focal and energy dispersive properties. The monochromator focuses the spectral beam at the object location, which then diverges onto an area detector such that one dimension in the detector is an energy axis. A least-squares method is used to interpret the transmitted spectral data with fits to either measured and/or calculated absorption of the contrast and matrix material-water. The spectral-KES system is very simple to implement and is comprised of a bent Laue monochromator, a stage for sample manipulation for projection and computed tomography imaging, and a pixelated area detector. The imaging system and examples of its applications to biological imaging are presented. The system is particularly well suited for a synchrotron bend magnet beamline with white beam access.

Structuring β-Ga2O3 photonic crystal photocatalyst for efficient degradation of organic pollutants.

PubMed

Li, Xiaofang; Zhen, Xiuzheng; Meng, Sugang; Xian, Jiangjun; Shao, Yu; Fu, Xianzhi; Li, Danzhen

2013-09-03

Coupling photocatalysts with photonic crystals structure is based on the unique property of photonic crystals in confining, controlling, and manipulating the incident photons. This combination enhances the light absorption in photocatalysts and thus greatly improves their photocatalytic performance. In this study, Ga2O3 photonic crystals with well-arranged skeleton structures were prepared via a dip-coating infiltration method. The positions of the electronic band absorption for Ga2O3 photonic crystals could be made to locate on the red edge, on the blue edge, and away from the edge of their photonic band gaps by changing the pore sizes of the samples, respectively. Particularly, the electronic band absorption of the Ga2O3 photonic crystal with a pore size of 135 nm was enhanced more than other samples by making it locate on the red edge of its photonic band gap, which was confirmed by the higher instantaneous photocurrent and photocatalytic activity for the degradation of various organic pollutants under ultraviolet light irradiation. Furthermore, the degradation mechanism over Ga2O3 photonic crystals was discussed. The design of Ga2O3 photonic crystals presents a prospective application of photonic crystals in photocatalysis to address light harvesting and quantum efficiency problems through manipulating photons or constructing photonic crystal structure as groundwork.

Optical Absorption in Liquid Semiconductors

NASA Astrophysics Data System (ADS)

Bell, Florian Gene

An infrared absorption cell has been developed which is suitable for high temperature liquids which have absorptions in the range .1-10('3) cm('-1). The cell is constructed by clamping a gasket between two flat optical windows. This unique design allows the use of any optical windows chemically compatible with the liquid. The long -wavelength limit of the measurements is therefore limited only by the choice of the optical windows. The thickness of the cell can easily be set during assembly, and can be varied from 50 (mu)m to .5 cm. Measurements of the optical absorption edge were performed on the liquid alloy Se(,1-x)Tl(,x) for x = 0, .001, .002, .003, .005, .007, and .009, from the melting point up to 475(DEGREES)C. The absorption was found to be exponential in the photon energy over the experimental range from 0.3 eV to 1.2 eV. The absorption increased linearly with concentration according to the empirical relation (alpha)(,T)(h(nu)) = (alpha)(,1) + (alpha)(,2)x, and the absorption (alpha)(,1) was interpreted as the absorption in the absence of T1. (alpha)(,1) also agreed with the measured absorption in 100% Se at corresponding temperatures and energies. The excess absorption defined by (DELTA)(alpha) = (alpha)(,T)(h(nu))-(alpha)(,1) was interpreted as the absorption associated with Tl and was found to be thermally activated with an activation energy E(,t) = 0.5 eV. The exponential edge is explained as absorption on atoms immersed in strong electric fields surrounding ions. The strong fields give rise to an absorption tail similar to the Franz-Keldysh effect. A simple calculation is performed which is based on the Dow-Redfield theory of absorption in an electric field with excitonic effects included. The excess absorption at low photon energies is proportional to the square of the concentration of ions, which are proposed to exist in the liquid according to the relation C(,i) (PROPORTIONAL) x(' 1/2)(.)e('-E)t('/kT), which is the origin of the thermal activation and the proportionality to Tl concentration. The ionic model satisfactorily explains the observed concentration and temperature dependence of the absorption. It also provides for the first time, a universal explanation of the exponential edge in liquid semiconductors where charged defects are present, and provides a means of measuring the concentration of ions when the absorption can be calibrated.

Consequences of realistic embedding for the L 2,3 edge XAS of α-Fe 2 O 3

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

Bagus, Paul S.; Nelin, Connie J.; Sassi, Michel

Cluster models of condensed systems are often used to simulate the core-level spectra obtained with X-ray Photoelectron Spectroscopy, XPS, or with X-ray Absorption Spectroscopy, XAS, especially for near edge features.

Electronic structure of nickel silicide in subhalf-micron lines and blanket films: An x-ray absorption fine structures study at the Ni and Si L3,2 edge

NASA Astrophysics Data System (ADS)

Naftel, S. J.; Coulthard, I.; Sham, T. K.; Xu, D.-X.; Erickson, L.; Das, S. R.

1999-05-01

We report a Ni and Si L3,2-edge x-ray absorption near edge structures (XANES) study of nickel-silicon interaction in submicron (0.15 and 0.2 μm) lines on a n-Si(100) wafer as well as a series of well characterized Ni-Si blanket films. XANES measurements recorded in both total electron yield and soft x-ray fluorescence yield indicate that under the selected silicidation conditions, the more desirable low resistivity phase, NiSi, is indeed the dominant phase in the subhalf-micron lines although the formation of this phase is less complete as the line becomes narrower and this is accompanied by a Ni rich surface.

Splitting hairs: differentiating between entomological activity, taphonomy, and sharp force trauma on hair.

PubMed

Mazzarelli, Debora; Vanin, Stefano; Gibelli, Daniele; Maistrello, Lara; Porta, Davide; Rizzi, Agostino; Cattaneo, Cristina

2015-03-01

The analysis of hair can provide useful information for the correct evaluation of forensic cases, but studies of trauma on hair are extremely rare. Hair may present lesions caused by traumatic events or by animals: in fact, signs of sharp force weapons on hair may provide important information for the reconstruction of the manner of death, and, for example, may suggest fetishist practice. This study stemmed from a judicial case where it was fundamental to distinguish between sharp force lesions and insect activity on hair. In order to highlight differences between sharp force lesions and insect feeding activity, different experiments were performed with high power microscopy: hair samples were subjected to several lesions by blunt and sharp force trauma; then samples were used as pabulum for two taxa of insects: the common clothes moth (Tineola bisselliella Lepidoptera, Tineidae) and the carpet beetle (Anthrenus sp., Coleoptera, Dermestidae). Hairs were examined from a macroscopic and microscopic point of view by stereomicroscopy and scanning electron microscopy (SEM): the morphological characteristics of the lesions obtained from the different experimental samples were compared. Results show that sharp force trauma produces lesions with regular edges, whereas insects leave concave lesions caused by their "gnawing" activity. These two types of lesions are easily distinguishable from breaking and tearing using SEM. This study demonstrates that insect activity leaves very specific indications on hair and sheds some light on different hair lesions that may be found in forensic cases.

X-Ray and Energy-Loss Spectroscopy | Materials Science | NREL

Science.gov Websites

, we see sharp peaks corresponding to the characteristic X-rays emitted by the atoms of the different ionization edges at high-energy losses, whose onset position is characteristic of the different types of flat c-Si/a-Si interface (see next). A graph with red, green, and blue curves shows different

76 FR 77981 - Build-A-Bear Workshop, Inc., Provisional Acceptance of a Settlement Agreement and Order

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-15

...), and (11). 6. The Chairs are defective because the sharp edges of the Chair's folding wooden frame can... Product Safety Act (``CPSA''). The Agreement and the incorporated attached Order resolve staff's... regulatory agency established pursuant to, and responsible for, the enforcement of the CPSA, 15 U.S.C. 2051...

29 CFR 1918.62 - Miscellaneous auxiliary gear.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., loose gear such as slings, chains, bridles, blocks and hooks shall be so placed as to avoid damage to... sling to which they are attached and shall be free of sharp edges. (h) Chains and chain slings used for... the size of wrought iron and alloy steel chains and chain slings and shall have such ratings available...

29 CFR 1918.62 - Miscellaneous auxiliary gear.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., loose gear such as slings, chains, bridles, blocks and hooks shall be so placed as to avoid damage to... sling to which they are attached and shall be free of sharp edges. (h) Chains and chain slings used for... the size of wrought iron and alloy steel chains and chain slings and shall have such ratings available...

29 CFR 1918.62 - Miscellaneous auxiliary gear.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., loose gear such as slings, chains, bridles, blocks and hooks shall be so placed as to avoid damage to... sling to which they are attached and shall be free of sharp edges. (h) Chains and chain slings used for... the size of wrought iron and alloy steel chains and chain slings and shall have such ratings available...

Characterization of edge effects in precision low-coherence interferometry using broadband light sources

NASA Astrophysics Data System (ADS)

Taudt, Ch.; Baselt, T.; Nelsen, B.; Assmann, H.; Greiner, A.; Koch, E.; Hartmann, P.

2017-06-01

Within this work an alternative approach to precision surface profilometry based on a low-coherence interferometer is presented. Special emphasis is placed on the characterization of edge effects, which influence the measurement result on sharp edges and steep slopes. In contrast to other works, this examination focuses on the comparison of very broadband light sources such as a supercontinuum white-light source (SC; 380 - 1100 nm) and a laser-driven plasma light source (LDP; 200 - 1100 nm) and their influence on the formation of these effects. The interferometer is equipped with one of these broadband light sources and a defined dispersion over a given spectral range. The spectral width of the light sources in combination with the dispersive element defines the possible measurement range and resolution. Instead of detecting the signals only in a one-dimensional manner, an imaging spectrometer on the basis of a high resolution CMOS-camera is set-up. Through the introduction of a defined dispersion, a controlled phase variation in the spectral domain is created. This phase variation is dependent on the optical path difference between both arms and can therefore be used as a measure for the height of a structure which is present in one arm. The results of measurements on a 100 nm height standard with both selected light sources have been compared. Under consideration of the coherence length of both light sources of 1.58 μm for the SC source and 1.81 m for the LDP source differences could be recorded. Especially at sharp edges, the LDP light source could record height changes with slopes twice as steep as the SC source. Furthermore, it became obvious, that measurements with the SC source tend to show edge effects like batwings due to diffraction. Additional effects on the measured roughness and the flatness of the profile were investigated and discussed.

Image reconstruction for x-ray K-edge imaging with a photon counting detector

NASA Astrophysics Data System (ADS)

Meng, Bo; Cong, Wenxiang; Xi, Yan; Wang, Ge

2014-09-01

Contrast agents with high-Z elements have K-absorption edges which significantly change X-ray attenuation coefficients. The K-edge characteristics is different for various kinds of contrast agents, which offers opportunities for material decomposition in biomedical applications. In this paper, we propose a new K-edge imaging method, which not only quantifies a distribution of a contrast agent but also provides an optimized contrast ratio. Our numerical simulation tests demonstrate the feasibility and merits of the proposed methodology.

Mullite and Mullite Ceramics

DTIC Science & Technology

1994-01-01

possible. The here reported measurements were carried out with synchrotron radiation from the electron storage ring ELSA of the Bonn University. All...Physikalisches Institut der Universitdt Bonn , Bonn , Germany Measurements of X-ray absorption spectra near the absorption edge of a selected element (XANES

X-ray absorption spectral studies of copper (II) mixed ligand complexes

NASA Astrophysics Data System (ADS)

Soni, B.; Dar, Davood Ah; Shrivastava, B. D.; Prasad, J.; Srivastava, K.

2014-09-01

X-ray absorption spectra at the K-edge of copper have been studied in two copper mixed ligand complexes, one having tetramethyethylenediamine (tmen) and the other having tetraethyethylenediamine (teen) as one of the ligands. The spectra have been recorded at BL-8 dispersive extended X-ray absorption fine structure (EXAFS) beamline at the 2.5 GeV INDUS- 2 synchrotron, RRCAT, Indore, India. The data obtained has been processed using the data analysis program Athena. The energy of the K-absorption edge, chemical shift, edge-width and shift of the principal absorption maximum in the complexes have been determined and discussed. The values of these parameters have been found to be approximately the same in both the complexes indicating that the two complexes possess similar chemical environment around the copper metal atom. The chemical shift has been utilized to estimate effective nuclear charge on the absorbing atom. The normalized EXAFS spectra have been Fourier transformed. The position of the first peak in the Fourier transform gives the value of first shell bond length, which is shorter than the actual bond length because of energy dependence of the phase factors in the sine function of the EXAFS equation. This distance is thus the phase- uncorrected bond length. Bond length has also been determined by Levy's, Lytle's and Lytle, Sayers and Stern's (LSS) methods. The results obtained from LSS and the Fourier transformation methods are comparable with each other, since both are phase uncorrected bond lengths.

Local structural effects in Sr 3NiRhO 6 across magnetic transitions

DOE PAGES

Singh, Navneet; Khalid, S.; Bindu, R.

2016-04-06

Here, we investigate the temperature dependence of the structural parameters of quasi-one-dimensional Sr 3NiRhO 6 across the region of magnetic phase transitions using Ni K-edge and Sr K-edge x-ray absorption spectroscopy (XAS). The features in the x-ray absorption near-edge region are identified using multiple scattering calculations. The temperature-dependent extended x-ray absorption fine structure (EXAFS) studies show that the setting of the intra-chain super exchange interaction starts at ~200 K, which is well above the first transition temperature (45 K) revealed by magnetic susceptibility studies. The onset of the inter-chain super–super exchange interaction appears to be at ~125 K. Interestingly, themore » role played by direct exchange interaction between the Ni 3d and Rh 4d states in stabilising the magnetic interaction is less significant. The present results shed light on the generic features exhibited by isostructural compounds and may help in identifying the magnetic exchange pathways useful for understanding the unusual properties exhibited by such compounds.« less

Pushing the limits of CMOS optical parametric amplifiers with USRN:Si7N3 above the two-photon absorption edge

PubMed Central

Ooi, K. J. A.; Ng, D. K. T.; Wang, T.; Chee, A. K. L.; Ng, S. K.; Wang, Q.; Ang, L. K.; Agarwal, A. M.; Kimerling, L. C.; Tan, D. T. H.

2017-01-01

CMOS platforms operating at the telecommunications wavelength either reside within the highly dissipative two-photon regime in silicon-based optical devices, or possess small nonlinearities. Bandgap engineering of non-stoichiometric silicon nitride using state-of-the-art fabrication techniques has led to our development of USRN (ultra-silicon-rich nitride) in the form of Si7N3, that possesses a high Kerr nonlinearity (2.8 × 10−13 cm2 W−1), an order of magnitude larger than that in stoichiometric silicon nitride. Here we experimentally demonstrate high-gain optical parametric amplification using USRN, which is compositionally tailored such that the 1,550 nm wavelength resides above the two-photon absorption edge, while still possessing large nonlinearities. Optical parametric gain of 42.5 dB, as well as cascaded four-wave mixing with gain down to the third idler is observed and attributed to the high photon efficiency achieved through operating above the two-photon absorption edge, representing one of the largest optical parametric gains to date on a CMOS platform. PMID:28051064

Temperature studies of optical parameters of (Ag3AsS3)0.6(As2S3)0.4 thin films prepared by rapid thermal evaporation and pulse laser deposition

NASA Astrophysics Data System (ADS)

Studenyak, I. P.; Kutsyk, M. M.; Buchuk, M. Yu.; Rati, Y. Y.; Neimet, Yu. Yu.; Izai, V. Yu.; Kökényesi, S.; Nemec, P.

2016-02-01

(Ag3AsS3)0.6(As2S3)0.4 thin films were deposited using rapid thermal evaporation (RTE) and pulse laser deposition (PLD) techniques. Ag-enriched micrometre-sized cones (RTE) and bubbles (PLD) were observed on the thin film surface. Optical transmission spectra of the thin films were studied in the temperature range 77-300 K. The Urbach behaviour of the optical absorption edge in the thin films due to strong electron-phonon interaction was observed, the main parameters of the Urbach absorption edge were determined. Temperature dependences of the energy position of the exponential absorption edge and the Urbach energy are well described in the Einstein model. Dispersion and temperature dependences of refractive indices were analysed; a non-linear increase of the refractive indices with temperature was revealed. Disordering processes in the thin films were studied and compared with bulk composites, the differences between the thin films prepared by RTE and PLD were analysed.

Modeling L2,3-Edge X-ray Absorption Spectroscopy with Real-Time Exact Two-Component Relativistic Time-Dependent Density Functional Theory.

PubMed

Kasper, Joseph M; Lestrange, Patrick J; Stetina, Torin F; Li, Xiaosong

2018-04-10

X-ray absorption spectroscopy is a powerful technique to probe local electronic and nuclear structure. There has been extensive theoretical work modeling K-edge spectra from first principles. However, modeling L-edge spectra directly with density functional theory poses a unique challenge requiring further study. Spin-orbit coupling must be included in the model, and a noncollinear density functional theory is required. Using the real-time exact two-component method, we are able to variationally include one-electron spin-orbit coupling terms when calculating the absorption spectrum. The abilities of different basis sets and density functionals to model spectra for both closed- and open-shell systems are investigated using SiCl 4 and three transition metal complexes, TiCl 4 , CrO 2 Cl 2 , and [FeCl 6 ] 3- . Although we are working in the real-time framework, individual molecular orbital transitions can still be recovered by projecting the density onto the ground state molecular orbital space and separating contributions to the time evolving dipole moment.

Low temperature perovskite solar cells with an evaporated TiO 2 compact layer for perovskite silicon tandem solar cells

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

Bett, Alexander J.; Schulze, Patricia S. C.; Winkler, Kristina

Silicon-based tandem solar cells can overcome the efficiency limit of single junction silicon solar cells. Perovskite solar cells are particularly promising as a top cell in monolithic tandem devices due to their rapid development towards high efficiencies, a tunable band gap with a sharp optical absorption edge and a simple production process. In monolithic tandem devices, the perovskite solar cell is deposited directly on the silicon cell, requiring low-temperature processes (< 200 °C) to maintain functionality of under-lying layers of the silicon cell in case of highly efficient silicon hetero-junction (SHJ) bottom solar cell. In this work, we present amore » complete low-temperature process for perovskite solar cells including a mesoporous titanium oxide (TiO 2) scaffold - a structure yielding the highest efficiencies for single-junction perovskite solar cells. We show that evaporation of the compact TiO 2 hole blocking layer and ultra-violet (UV) curing for the mesoporous TiO 2 layer allows for good performance, comparable to high-temperature (> 500 °C) processes. With both manufacturing routes, we obtain short-circuit current densities (J SC) of about 20 mA/cm 2, open-circuit voltages (V OC) over 1 V, fill factors (FF) between 0.7 and 0.8 and efficiencies (n) of more than 15%. We further show that the evaporated TiO 2 layer is suitable for the application in tandem devices. The series resistance of the layer itself and the contact resistance to an indium doped tin oxide (ITO) interconnection layer between the two sub-cells are low. Additionally, the low parasitic absorption for wavelengths above the perovskite band gap allow a higher absorption in the silicon bottom solar cell, which is essential to achieve high tandem efficiencies.« less

Spectromicroscopy of boron in human glioblastomas following administration of Na2B12H11SH.

PubMed

Gilbert, B; Perfetti, L; Fauchoux, O; Redondo, J; Baudat, P A; Andres, R; Neumann, M; Steen, S; Gabel, D; Mercanti, D; Ciotti, M T; Perfetti, P; Margaritondo, G; De Stasio, G

2000-07-01

Boron neutron capture therapy (BNCT) is an experimental, binary treatment for brain cancer which requires as the first step that tumor tissue is targeted with a boron-10 containing compound. Subsequent exposure to a thermal neutron flux results in destructive, short range nuclear reaction within 10 microm of the boron compound. The success of the therapy requires than the BNCT agents be well localized in tumor, rather than healthy tissue. The MEPHISTO spectromicroscope, which performs microchemical analysis by x-ray absorption near edge structure (XANES) spectroscopy from microscopic areas, has been used to study the distribution of trace quantities of boron in human brain cancer tissues surgically removed from patients first administered with the compound Na2B12H11SH (BSH). The interpretation of XANES spectra is complicated by interference from physiologically present sulfur and phosphorus, which contribute structure in the same energy range as boron. We addressed this problem with the present extensive set of spectra from S, B, and P in relevant compounds. We demonstrate that a linear combination of sulfate, phosphate and BSH XANES can be used to reproduce the spectra acquired on boron-treated human brain tumor tissues. We analyzed human glioblastoma tissue from two patients administered and one not administered with BSH. As well as weak signals attributed to BSH, x-ray absorption spectra acquired from tissue samples detected boron in a reduced chemical state with respect to boron in BSH. This chemical state was characterized by a sharp absorption peak at 188.3 eV. Complementary studies on BSH reference samples were not able to reproduce this chemical state of boron, indicating that it is not an artifact produced during sample preparation or x-ray exposure. These data demonstrate that the chemical state of BSH may be altered by in vivo metabolism.

Low temperature perovskite solar cells with an evaporated TiO 2 compact layer for perovskite silicon tandem solar cells

DOE PAGES

Bett, Alexander J.; Schulze, Patricia S. C.; Winkler, Kristina; ...

2017-09-21

Silicon-based tandem solar cells can overcome the efficiency limit of single junction silicon solar cells. Perovskite solar cells are particularly promising as a top cell in monolithic tandem devices due to their rapid development towards high efficiencies, a tunable band gap with a sharp optical absorption edge and a simple production process. In monolithic tandem devices, the perovskite solar cell is deposited directly on the silicon cell, requiring low-temperature processes (< 200 °C) to maintain functionality of under-lying layers of the silicon cell in case of highly efficient silicon hetero-junction (SHJ) bottom solar cell. In this work, we present amore » complete low-temperature process for perovskite solar cells including a mesoporous titanium oxide (TiO 2) scaffold - a structure yielding the highest efficiencies for single-junction perovskite solar cells. We show that evaporation of the compact TiO 2 hole blocking layer and ultra-violet (UV) curing for the mesoporous TiO 2 layer allows for good performance, comparable to high-temperature (> 500 °C) processes. With both manufacturing routes, we obtain short-circuit current densities (J SC) of about 20 mA/cm 2, open-circuit voltages (V OC) over 1 V, fill factors (FF) between 0.7 and 0.8 and efficiencies (n) of more than 15%. We further show that the evaporated TiO 2 layer is suitable for the application in tandem devices. The series resistance of the layer itself and the contact resistance to an indium doped tin oxide (ITO) interconnection layer between the two sub-cells are low. Additionally, the low parasitic absorption for wavelengths above the perovskite band gap allow a higher absorption in the silicon bottom solar cell, which is essential to achieve high tandem efficiencies.« less

Modification of fluorescence and optical properties of Rhodamine B dye doped PVA/Chitosan polymer blend films

NASA Astrophysics Data System (ADS)

Padmakumari, R.; Ravindrachary, V.; Mahantesha, B. K.; Sagar, Rohan N.; Sahanakumari, R.; Bhajantri, R. F.

2018-05-01

Pure and Rhodamine B doped Poly (vinyl alcohol)/Chitosan composite films are prepared using solution casting method. Fourier transforms infrared spectra (FTIR), Ultraviolet-Visible (UV-Vis), fluorescence studies were used to characterize the prepared polymer films. The FT-IR results show that the appearance of new peaks along with shift in peak positions indicates the interaction of Rhodamine B with PVA-CS blend. Optical absorption edge, band gap and activation energy were determined from UV-Visible studies. The optical absorption edge increases, band gap decreases and activation energy increases with dopant concentration respectively. The corresponding emission spectra were studied using fluorescence spectroscopy. From the fluorescence study the quenching phenomena are observed in emission wavelength range of 607nm-613nm upon excitation with absorption maxima 443nm.

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic–Inorganic Lead Halide Perovskites

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

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3) hybrid inorganic-organic perovskite and its binary phase PbI 2. The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. Furthermore, the theoretical analysis complementing experimental observationsmore » provides the conceptual insights required for a full characterization of this complex material.« less

Determining thin film properties by fitting optical transmittance

NASA Astrophysics Data System (ADS)

Klein, J. D.; Yen, A.; Cogan, S. F.

1990-08-01

The optical transmission spectra of rf sputtered tungsten oxide films on glass substrates were modeled to determine absorption edge behavior, film thickness, and index of refraction. Removal of substrate reflection and absorption phenomena from the experimental spectra allowed direct examination of thin film optical characteristics. The interference fringe pattern allows determination of the film thickness and the dependence of the real index of refraction on wavelength. Knowledge of the interference fringe behavior in the vicinity of the absorption edge was found essential to unambiguous determination of the optical band gap. In particular, the apparently random deviations commonly observed in the extrapolation of as-acquired data are eliminated by explicitly considering interference fringe phenomena. The multivariable optimization fitting scheme employed allows air-film-substrate reflection losses to be compensated without making reflectance measurements.

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic–Inorganic Lead Halide Perovskites

DOE PAGES

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina; ...

2018-03-23

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3) hybrid inorganic-organic perovskite and its binary phase PbI 2. The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. Furthermore, the theoretical analysis complementing experimental observationsmore » provides the conceptual insights required for a full characterization of this complex material.« less

Uranium XAFS analysis of kidney from rats exposed to uranium

PubMed Central

Kitahara, Keisuke; Numako, Chiya; Terada, Yasuko; Nitta, Kiyohumi; Homma-Takeda, Shino

2017-01-01

The kidney is the critical target of uranium exposure because uranium accumulates in the proximal tubules and causes tubular damage, but the chemical nature of uranium in kidney, such as its chemical status in the toxic target site, is poorly understood. Micro-X-ray absorption fine-structure (µXAFS) analysis was used to examine renal thin sections of rats exposed to uranyl acetate. The U L III-edge X-ray absorption near-edge structure spectra of bulk renal specimens obtained at various toxicological phases were similar to that of uranyl acetate: their edge position did not shift compared with that of uranyl acetate (17.175 keV) although the peak widths for some kidney specimens were slightly narrowed. µXAFS measurements of spots of concentrated uranium in the micro-regions of the proximal tubules showed that the edge jump slightly shifted to lower energy. The results suggest that most uranium accumulated in kidney was uranium (VI) but a portion might have been biotransformed in rats exposed to uranyl acetate. PMID:28244440

Uranium XAFS analysis of kidney from rats exposed to uranium.

PubMed

Kitahara, Keisuke; Numako, Chiya; Terada, Yasuko; Nitta, Kiyohumi; Shimada, Yoshiya; Homma-Takeda, Shino

2017-03-01

The kidney is the critical target of uranium exposure because uranium accumulates in the proximal tubules and causes tubular damage, but the chemical nature of uranium in kidney, such as its chemical status in the toxic target site, is poorly understood. Micro-X-ray absorption fine-structure (µXAFS) analysis was used to examine renal thin sections of rats exposed to uranyl acetate. The U L III -edge X-ray absorption near-edge structure spectra of bulk renal specimens obtained at various toxicological phases were similar to that of uranyl acetate: their edge position did not shift compared with that of uranyl acetate (17.175 keV) although the peak widths for some kidney specimens were slightly narrowed. µXAFS measurements of spots of concentrated uranium in the micro-regions of the proximal tubules showed that the edge jump slightly shifted to lower energy. The results suggest that most uranium accumulated in kidney was uranium (VI) but a portion might have been biotransformed in rats exposed to uranyl acetate.

The edge artifact in the point-spread function-based PET reconstruction at different sphere-to-background ratios of radioactivity.

PubMed

Kidera, Daisuke; Kihara, Ken; Akamatsu, Go; Mikasa, Shohei; Taniguchi, Takafumi; Tsutsui, Yuji; Takeshita, Toshiki; Maebatake, Akira; Miwa, Kenta; Sasaki, Masayuki

2016-02-01

The aim of this study was to quantitatively evaluate the edge artifacts in PET images reconstructed using the point-spread function (PSF) algorithm at different sphere-to-background ratios of radioactivity (SBRs). We used a NEMA IEC body phantom consisting of six spheres with 37, 28, 22, 17, 13 and 10 mm in inner diameter. The background was filled with (18)F solution with a radioactivity concentration of 2.65 kBq/mL. We prepared three sets of phantoms with SBRs of 16, 8, 4 and 2. The PET data were acquired for 20 min using a Biograph mCT scanner. The images were reconstructed with the baseline ordered subsets expectation maximization (OSEM) algorithm, and with the OSEM + PSF correction model (PSF). For the image reconstruction, the number of iterations ranged from one to 10. The phantom PET image analyses were performed by a visual assessment of the PET images and profiles, a contrast recovery coefficient (CRC), which is the ratio of SBR in the images to the true SBR, and the percent change in the maximum count between the OSEM and PSF images (Δ % counts). In the PSF images, the spheres with a diameter of 17 mm or larger were surrounded by a dense edge in comparison with the OSEM images. In the spheres with a diameter of 22 mm or smaller, an overshoot appeared in the center of the spheres as a sharp peak in the PSF images in low SBR. These edge artifacts were clearly observed in relation to the increase of the SBR. The overestimation of the CRC was observed in 13 mm spheres in the PSF images. In the spheres with a diameter of 17 mm or smaller, the Δ % counts increased with an increasing SBR. The Δ % counts increased to 91 % in the 10-mm sphere at the SBR of 16. The edge artifacts in the PET images reconstructed using the PSF algorithm increased with an increasing SBR. In the small spheres, the edge artifact was observed as a sharp peak at the center of spheres and could result in overestimation.

Identification of B-K near edge x-ray absorption fine structure peaks of boron nitride thin films prepared by sputtering deposition

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

Niibe, Masahito; Miyamoto, Kazuyoshi; Mitamura, Tohru

2010-09-15

Four {pi}{sup *} resonance peaks were observed in the B-K near edge x-ray absorption fine structure spectra of boron nitride thin films prepared by magnetron sputtering. In the past, these peaks have been explained as the K-absorption of boron atoms, which are present in environment containing nitrogen vacancies, the number of which is 1-3 corresponding to the three peaks at higher photon energy. However, the authors found that there was a strong correlation between the intensities of these three peaks and that of O-K absorption after wide range scanning and simultaneous measurement of nitrogen and oxygen K-absorptions of the BNmore » films. Therefore, the authors conclude that these three peaks at the higher energy side correspond to boron atoms bound to one-to-three oxygen atoms instead of three nitrogen atoms surrounding the boron atom in the h-BN structure. The result of the first-principles calculation with a simple cluster model supported the validity of this explanation.« less

Optical band gap studies on lithium aluminum silicate glasses doped with Cr3+ ions

NASA Astrophysics Data System (ADS)

El-Diasty, Fouad; Abdel Wahab, Fathy A.; Abdel-Baki, Manal

2006-11-01

Lithium aluminum silicate glass system (LAS) implanted with chromium ions is prepared. The reflectance and transmittance measurements are used to determine the dispersion of absorption coefficient. The optical data are explained in terms of the different oxidation states adopted by the chromium ions into the glass network. It is found that the oxidation state of the chromium depends on its concentration. Across a wide spectral range, 0.2-1.6μm, analysis of the fundamental absorption edge provides values for the average energy band gaps for allowed direct and indirect transitions. The optical absorption coefficient just below the absorption edge varies exponentially with photon energy indicating the presence of Urbach's tail. Such tail is decreased with the increase of the chromium dopant. From the analysis of the optical absorption data, the absorption peak at ground state exciton energy, the absorption at band gap, and the free exciton binding energy are determined. The extinction coefficient data are used to determine the Fermi energy level of the studied glasses. The metallization criterion is obtained and discussed exploring the nature of the glasses. The measured IR spectra of the different glasses are used to throw some light on the optical properties of the present glasses correlating them with their structure and composition.

Vibronic spectra of Cu(2+) in ZnTe

NASA Technical Reports Server (NTRS)

Volz, M. P.; Su, C.-H.; Lehoczky, S. L.; Szofran, F. R.

1992-01-01

Infrared-absorption spectra of substitutional Cu(2+) ions in ZnTe have been measured at 4.6 K. Several distinct absorption peaks are observed between 800 and 2000/cm. Absorption peaks at 1002 and 1069/cm are identified as zero-phonon lines arising from 2T2-2E transitions. Between 1069 and 2000/cm, several sets of sharp absorption lines are seen to recur regularly at an interval of 210/cm, corresponding to the LO phonon energy. Within each set distinct vibronic sidebands that cannot be identified with critical-point energies of TA, LA, TO or LO phonon modes are observed. A dynamic Jahn-Teller effect, involving coupling between a single-phonon mode and the electronic states of the 2E level, is proposed to account for the observed spectra.

Computational analysis of Pelton bucket tip erosion using digital image processing

NASA Astrophysics Data System (ADS)

Shrestha, Bim Prasad; Gautam, Bijaya; Bajracharya, Tri Ratna

2008-03-01

Erosion of hydro turbine components through sand laden river is one of the biggest problems in Himalayas. Even with sediment trapping systems, complete removal of fine sediment from water is impossible and uneconomical; hence most of the turbine components in Himalayan Rivers are exposed to sand laden water and subject to erode. Pelton bucket which are being wildly used in different hydropower generation plant undergoes erosion on the continuous presence of sand particles in water. The subsequent erosion causes increase in splitter thickness, which is supposed to be theoretically zero. This increase in splitter thickness gives rise to back hitting of water followed by decrease in turbine efficiency. This paper describes the process of measurement of sharp edges like bucket tip using digital image processing. Image of each bucket is captured and allowed to run for 72 hours; sand concentration in water hitting the bucket is closely controlled and monitored. Later, the image of the test bucket is taken in the same condition. The process is repeated for 10 times. In this paper digital image processing which encompasses processes that performs image enhancement in both spatial and frequency domain. In addition, the processes that extract attributes from images, up to and including the measurement of splitter's tip. Processing of image has been done in MATLAB 6.5 platform. The result shows that quantitative measurement of edge erosion of sharp edges could accurately be detected and the erosion profile could be generated using image processing technique.

Heat Transfer and Flow on the First Stage Blade Tip of a Power Generation Gas Turbine. Part 1; Experimental Results

NASA Technical Reports Server (NTRS)

Bunker, Ronald S.; Bailey, Jeremy C.; Ameri, Ali A.

1999-01-01

A combined computational and experimental study has been performed to investigate the detailed distribution of convective heat transfer coefficients on the first stage blade tip surface for a geometry typical of large power generation turbines(>100MW). This paper is concerned with the design and execution of the experimental portion of the study. A stationary blade cascade experiment has been run consisting of three airfoils, the center airfoil having a variable tip gap clearance. The airfoil models the aerodynamic tip section of a high pressure turbine blade with inlet Mach number of 0.30, exit Mach number of 0.75, pressure ratio of 1.45, exit Reynolds number based on axial chord of 2.57 x 10(exp 6), and total turning of about 110 degrees. A hue detection based liquid crystal method is used to obtain the detailed heat transfer coefficient distribution on the blade tip surface for flat, smooth tip surfaces with both sharp and rounded edges. The cascade inlet turbulence intensity level took on values of either 5% or 9%. The cascade also models the casing recess in the shroud surface ahead of the blade. Experimental results are shown for the pressure distribution measurements on the airfoil near the tip gap, on the blade tip surface, and on the opposite shroud surface. Tip surface heat transfer coefficient distributions are shown for sharp-edge and rounded-edge tip geometries at each of the inlet turbulence intensity levels.

On the Outer Edges of Protoplanetary Dust Disks

NASA Astrophysics Data System (ADS)

Birnstiel, Tilman; Andrews, Sean M.

2014-01-01

The expectation that aerodynamic drag will force the solids in a gas-rich protoplanetary disk to spiral in toward the host star on short timescales is one of the fundamental problems in planet formation theory. The nominal efficiency of this radial drift process is in conflict with observations, suggesting that an empirical calibration of solid transport mechanisms in a disk is highly desirable. However, the fact that both radial drift and grain growth produce a similar particle size segregation in a disk (such that larger particles are preferentially concentrated closer to the star) makes it difficult to disentangle a clear signature of drift alone. We highlight a new approach, by showing that radial drift leaves a distinctive "fingerprint" in the dust surface density profile that is directly accessible to current observational facilities. Using an analytical framework for dust evolution, we demonstrate that the combined effects of drift and (viscous) gas drag naturally produce a sharp outer edge in the dust distribution (or, equivalently, a sharp decrease in the dust-to-gas mass ratio). This edge feature forms during the earliest phase in the evolution of disk solids, before grain growth in the outer disk has made much progress, and is preserved over longer timescales when both growth and transport effects are more substantial. The key features of these analytical models are reproduced in detailed numerical simulations, and are qualitatively consistent with recent millimeter-wave observations that find gas/dust size discrepancies and steep declines in dust continuum emission in the outer regions of protoplanetary disks.

Theory of extrinsic and intrinsic heterojunctions in thermal equilibrium

NASA Technical Reports Server (NTRS)

Von Ross, O.

1980-01-01

A careful analysis of an abrupt heterojunction consisting of two distinct semiconductors either intrinsic or extrinsic is presented. The calculations apply to a one-dimensional, nondegenerate structure. Taking into account all appropriate boundary conditions, it is shown that the intrinsic Fermi level shows a discontinuity at the interface between the two materials which leads to a discontinuity of the valence band edge equal to the difference in the band gap energies of the two materials. The conduction band edge stays continuous however. This result is independent of possible charged interface states and in sharp contrast to the Anderson model. The reasons for this discrepancy are discussed.

Impact of flow unsteadiness on maneuvers and loads of agile aircraft

NASA Technical Reports Server (NTRS)

Jarrah, M. Ameen; Ashley, Holt

1989-01-01

A program of airload measurements on a family of low-aspect-ratio delta wings with sharp leading edges, subjected to large amplitude pitch transients with angles of attack up to 90 deg, is reviewed. Even for small values of the pitch-rate parameter, representative of maneuvers anticipated for agile aircraft, the force and moment overshoots can exceed by 50 percent their steady-state values. This is explained in terms of the hysteretic behavior of the breakdown locations of leading-edge vortices. An approximate theoretical model is proposed which includes the breakdown hysteresis as part of a three-term representation of the unsteady chordwise load distribution.

Optical Kerr effect and two-photon absorption in monolayer black phosphorus

NASA Astrophysics Data System (ADS)

Margulis, Vl A.; Muryumin, E. E.; Gaiduk, E. A.

2018-05-01

A theoretical treatment of nonlinear refraction and two-photon absorption is presented for a novel two-dimensional material, monolayer black phosphorus (or phosphorene), irradiated by a normally incident and linearly polarized coherent laser beam of frequency ω. It is found that both the nonlinear refractive index n 2(ω) and the two-photon absorption coefficient α 2(ω) of phosphorene depend upon the polarization of the radiation field relative to phosphorene’s crystallographic axes. For the two principal polarization directions considered—viz, the armchair ({ \\mathcal A }{ \\mathcal C }) and zigzag ({ \\mathcal Z }{ \\mathcal Z }), the calculated values of n 2 and α 2 are distinguished by the order of their magnitude, with the n 2 and α 2 values being greater for the { \\mathcal A }{ \\mathcal C } direction. Furthermore, for almost all the incident photon energies below the fundamental absorption edge, except its neighborhood, the signs of n 2 as well as α 2 for the { \\mathcal A }{ \\mathcal C } and { \\mathcal Z }{ \\mathcal Z } polarization directions are opposed to each other. Also, for both the directions, the change of sign of n 2 is predicted to occur in the way between the two-photon absorption edge and the fundamental absorption edge, as well as in the near vicinity of the latter, where the Kerr nonlinearity has a pronounced resonant character and the magnitude of n 2 for the { \\mathcal A }{ \\mathcal C } and { \\mathcal Z }{ \\mathcal Z } polarization directions reaches its largest positive values of the order of 10‑9 and 10‑10 cm2 W‑1, respectively. The implications of the findings for practical all-optical switching applications are discussed.

Chemical forms of sulfur in geological and archeological asphaltenes from Middle East, France, and Spain determined by sulfur K- and L-edge X-ray absorption near-edge structure spectroscopy

NASA Astrophysics Data System (ADS)

Sarret, Géraldine; Connan, Jacques; Kasrai, Masoud; Bancroft, G. Michael; Charrié-Duhaut, Armelle; Lemoine, Sylvie; Adam, Pierre; Albrecht, Pierre; Eybert-Bérard, Laurent

1999-11-01

Asphaltene samples extracted from archeological and geological bitumens from the Middle East, France, and Spain were studied by sulfur K- and L-edge X-ray absorption near-edge structure (XANES) spectroscopy in combination with isotopic analyses (δ 13C and δD). Within each series, the samples were genetically related by their δ 13C values. The gross and elemental composition and the δD values were used to characterize the weathering state of the samples. Sulfur K- and L-edge XANES results show that in all the samples, dibenzothiophenes are the dominant forms of sulfur. In the least oxidized asphaltenes, minor species include disulfides, alkyl and aryl sulfides, and sulfoxides. With increasing alteration the proportion of oxidized sulfur (sulfoxides, sulfones, sulfonates and sulfates) increases, whereas the disulfide and sulfide content decreases. This evolution is observed in all the series, regardless of the origin of the asphaltenes. This work illustrates the advantages of XANES spectroscopy as a selective probe for determining sulfur speciation in natural samples. It also shows that S K- and L-edge XANES spectroscopy are complementary for identifying the oxidized and reduced forms of sulfur, respectively.

10J water-cooled DPSSL system based on Yb:YAG crystal edge-cladded by Cr:YAG ceramics (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zheng, Jian-Gang; Yan, Xiongwei; Jiang, Xinying; Wang, Zhenguo; Li, Mingzhong; Zhang, Jun; Zhu, Qihua; Zheng, Wanguo

2017-05-01

Laser Inertial Fusion Energy (IFE) has been attracting the interests of the researchers around the world, because of the promising to the future energy. The Yb:YAG was broadly used in the research field of high-peak power and large energy laser with repetition-rate for IFE because of its outstanding performance, including significant thermal and mechanical capacities, long upper energy level lifetime, high quantum efficiency and highly doping capacity. But it exhibits high saturation fluence at room temperature because of the small emission and absorption cross-section. And at the same time this gain material exhibits self-absorption of laser because of the thermal population at lower laser level at room temperature. Ant it appears to have been solved by means of the cryogenic temperature, but the total efficiency of the laser system will be decreased as the use of cryogenic temperature. The amplified spontaneous emission (ASE) effect of the amplifier can be relaxed by means of edge-cladded absorption material. And the difficulties of edge cladding can be will solved as the emergence of ceramics. But at present the ceramics exhibits high scattering and many disfigurements, which limited the application in the high-power large-energy laser system. So the edge-cladding of Yb:YAG crystal will be a key issue for solution the ASE in amplifier. In this paper, we will introduce a 10J water-cooled DPSSL system, based on Yb:YAG crystal at room temperature. In this system a new edge cladding method has been used, that the Yb:YAG crystal was edge cladded by Cr:YAG ceramics, which was used as the absorption material of ASE. The amplifier was an active mirror water-cooled room temperature amplifier. With the help of this edge cladding the ASE has been lowered, and about 5 times small signal gain has been obtained in a single pass amplification, which was much higher than the earlier of 2 times. And the wavefront aberrance of the laser beam was also reduced due to the thermal equilibrium between the edge cladding and the gain region. the amplifiers can be stably operated under 10Hz. Finally the output of the laser system was about 7.15J@10Hz and 10.8J@1-2Hz. The total optical-to-optical efficiency was about 8.3% for 1-2Hz (under the condition of 120kW/1ms pumping, 880mJ input and 10.8J output) and 5.6% for 10Hz.

Particle-in-a-box model of exciton absorption and electroabsorption in conjugated polymers

NASA Astrophysics Data System (ADS)

Pedersen, Thomas G.

2000-12-01

The recently proposed particle-in-a-box model of one-dimensional excitons in conjugated polymers is applied in calculations of optical absorption and electroabsorption spectra. It is demonstrated that for polymers of long conjugation length a superposition of single exciton resonances produces a line shape characterized by a square-root singularity in agreement with experimental spectra near the absorption edge. The effects of finite conjugation length on both absorption and electroabsorption spectra are analyzed.

SHARP Demonstration Flight: Video Broadcast System for Research in Intelligent Flight Characterization and Control

NASA Technical Reports Server (NTRS)

Kitts, Christopher

2001-01-01

The NASA Ames Research Center (Thermal Protection Materials and Systems Branch) is investigating new ceramic materials for the thermal protection of atmospheric entry vehicles. An incremental approach to proving the capabilities of these materials calls for a lifting entry flight test of a sharp leading edge component on the proposed SHARP (Slender Hypervelocity Aerothermodynamic Research Probe) vehicle. This flight test will establish the aerothermal performance constraint under real lifting entry conditions. NASA Ames has been developing the SHARP test flight with SSDL (responsible for the SHARP S I vehicle avionics), Montana State University (responsible for the SHARP S I vehicle airframe), the Wickman Spacecraft and Propulsion Company (responsible for the sounding rocket and launch operations), and with the SCU Intelligent Robotics Program, The SCU team was added well after the rest of the development team had formed. The SCU role was to assist with the development of a real-time video broadcast system which would relay onboard flight video to a communication groundstation. The SCU team would also assist with general vehicle preparation as well as flight operations. At the time of the submission of the original SCU proposal, a test flight in Wyoming was originally targeted for September 2000. This date was moved several times into the Fall of 2000. It was then postponed until the Spring of 2001, and later pushed into late Summer 2001. To date, the flight has still not taken place. These project delays resulted in SCU requesting several no-cost extensions to the project. Based on the most recent conversations with the project technical lead, Paul Kolodjiez, the current plan is for the overall SHARP team to assemble what exists of the vehicle, to document the system, and to 'mothball' the vehicle in anticipation of future flight and funding opportunities.

Theoretical and experimental study of a new method for prediction of profile drag of airfoil sections

NASA Technical Reports Server (NTRS)

Goradia, S. H.; Lilley, D. E.

1975-01-01

Theoretical and experimental studies are described which were conducted for the purpose of developing a new generalized method for the prediction of profile drag of single component airfoil sections with sharp trailing edges. This method aims at solution for the flow in the wake from the airfoil trailing edge to the large distance in the downstream direction; the profile drag of the given airfoil section can then easily be obtained from the momentum balance once the shape of velocity profile at a large distance from the airfoil trailing edge has been computed. Computer program subroutines have been developed for the computation of the profile drag and flow in the airfoil wake on CDC6600 computer. The required inputs to the computer program consist of free stream conditions and the characteristics of the boundary layers at the airfoil trailing edge or at the point of incipient separation in the neighborhood of airfoil trailing edge. The method described is quite generalized and hence can be extended to the solution of the profile drag for multi-component airfoil sections.

Adaptive color demosaicing and false color removal

NASA Astrophysics Data System (ADS)

Guarnera, Mirko; Messina, Giuseppe; Tomaselli, Valeria

2010-04-01

Color interpolation solutions drastically influence the quality of the whole image generation pipeline, so they must guarantee the rendering of high quality pictures by avoiding typical artifacts such as blurring, zipper effects, and false colors. Moreover, demosaicing should avoid emphasizing typical artifacts of real sensors data, such as noise and green imbalance effect, which would be further accentuated by the subsequent steps of the processing pipeline. We propose a new adaptive algorithm that decides the interpolation technique to apply to each pixel, according to its neighborhood analysis. Edges are effectively interpolated through a directional filtering approach that interpolates the missing colors, selecting the suitable filter depending on edge orientation. Regions close to edges are interpolated through a simpler demosaicing approach. Thus flat regions are identified and low-pass filtered to eliminate some residual noise and to minimize the annoying green imbalance effect. Finally, an effective false color removal algorithm is used as a postprocessing step to eliminate residual color errors. The experimental results show how sharp edges are preserved, whereas undesired zipper effects are reduced, improving the edge resolution itself and obtaining superior image quality.

Receptivity of Hypersonic Boundary Layers to Acoustic and Vortical Disturbances (Invited)

NASA Technical Reports Server (NTRS)

Balakumar, P.

2015-01-01

Boundary-layer receptivity to two-dimensional acoustic and vortical disturbances for hypersonic flows over two-dimensional and axi-symmetric geometries were numerically investigated. The role of bluntness, wall cooling, and pressure gradients on the receptivity and stability were analyzed and compared with the sharp nose cases. It was found that for flows over sharp nose geometries in adiabatic wall conditions the instability waves are generated in the leading-edge region and that the boundary layer is much more receptive to slow acoustic waves as compared to the fast waves. The computations confirmed the stabilizing effect of nose bluntness and the role of the entropy layer in the delay of boundary layer transition. The receptivity coefficients in flows over blunt bodies are orders of magnitude smaller than that for the sharp cone cases. Wall cooling stabilizes the first mode strongly and destabilizes the second mode. However, the receptivity coefficients are also much smaller compared to the adiabatic case. The adverse pressure gradients increased the unstable second mode regions.

Power spectrum weighted edge analysis for straight edge detection in images

NASA Astrophysics Data System (ADS)

Karvir, Hrishikesh V.; Skipper, Julie A.

2007-04-01

Most man-made objects provide characteristic straight line edges and, therefore, edge extraction is a commonly used target detection tool. However, noisy images often yield broken edges that lead to missed detections, and extraneous edges that may contribute to false target detections. We present a sliding-block approach for target detection using weighted power spectral analysis. In general, straight line edges appearing at a given frequency are represented as a peak in the Fourier domain at a radius corresponding to that frequency, and a direction corresponding to the orientation of the edges in the spatial domain. Knowing the edge width and spacing between the edges, a band-pass filter is designed to extract the Fourier peaks corresponding to the target edges and suppress image noise. These peaks are then detected by amplitude thresholding. The frequency band width and the subsequent spatial filter mask size are variable parameters to facilitate detection of target objects of different sizes under known imaging geometries. Many military objects, such as trucks, tanks and missile launchers, produce definite signatures with parallel lines and the algorithm proves to be ideal for detecting such objects. Moreover, shadow-casting objects generally provide sharp edges and are readily detected. The block operation procedure offers advantages of significant reduction in noise influence, improved edge detection, faster processing speed and versatility to detect diverse objects of different sizes in the image. With Scud missile launcher replicas as target objects, the method has been successfully tested on terrain board test images under different backgrounds, illumination and imaging geometries with cameras of differing spatial resolution and bit-depth.

Mn K-Edge X-ray Absorption Studies of Oxo- and Hydroxo-manganese(IV) Complexes: Experimental and Theoretical Insights into Pre-Edge Properties

PubMed Central

2015-01-01

Mn K-edge X-ray absorption spectroscopy (XAS) was used to gain insights into the geometric and electronic structures of [MnII(Cl)2(Me2EBC)], [MnIV(OH)2(Me2EBC)]2+, and [MnIV(O)(OH)(Me2EBC)]+, which are all supported by the tetradentate, macrocyclic Me2EBC ligand (Me2EBC = 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane). Analysis of extended X-ray absorption fine structure (EXAFS) data for [MnIV(O)(OH)(Me2EBC)]+ revealed Mn–O scatterers at 1.71 and 1.84 Å and Mn–N scatterers at 2.11 Å, providing the first unambiguous support for the formulation of this species as an oxohydroxomanganese(IV) adduct. EXAFS-determined structural parameters for [MnII(Cl)2(Me2EBC)] and [MnIV(OH)2(Me2EBC)]2+ are consistent with previously reported crystal structures. The Mn pre-edge energies and intensities of these complexes were examined within the context of data for other oxo- and hydroxomanganese(IV) adducts, and time-dependent density functional theory (TD-DFT) computations were used to predict pre-edge properties for all compounds considered. This combined experimental and computational analysis revealed a correlation between the Mn–O(H) distances and pre-edge peak areas of MnIV=O and MnIV–OH complexes, but this trend was strongly modulated by the MnIV coordination geometry. Mn 3d-4p mixing, which primarily accounts for the pre-edge intensities, is not solely a function of the Mn–O(H) bond length; the coordination geometry also has a large effect on the distribution of pre-edge intensity. For tetragonal MnIV=O centers, more than 90% of the pre-edge intensity comes from excitations to the Mn=O σ* MO. Trigonal bipyramidal oxomanganese(IV) centers likewise feature excitations to the Mn=O σ* molecular orbital (MO) but also show intense transitions to 3dx2–y2 and 3dxy MOs because of enhanced 3d-4px,y mixing. This gives rise to a broader pre-edge feature for trigonal MnIV=O adducts. These results underscore the importance of reporting experimental pre-edge areas rather than peak heights. Finally, the TD-DFT method was applied to understand the pre-edge properties of a recently reported S = 1 MnV=O adduct; these findings are discussed within the context of previous examinations of oxomanganese(V) complexes. PMID:24901026

Mn K-edge X-ray absorption studies of oxo- and hydroxo-manganese(IV) complexes: experimental and theoretical insights into pre-edge properties.

PubMed

Leto, Domenick F; Jackson, Timothy A

2014-06-16

Mn K-edge X-ray absorption spectroscopy (XAS) was used to gain insights into the geometric and electronic structures of [Mn(II)(Cl)2(Me2EBC)], [Mn(IV)(OH)2(Me2EBC)](2+), and [Mn(IV)(O)(OH)(Me2EBC)](+), which are all supported by the tetradentate, macrocyclic Me2EBC ligand (Me2EBC = 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane). Analysis of extended X-ray absorption fine structure (EXAFS) data for [Mn(IV)(O)(OH)(Me2EBC)](+) revealed Mn-O scatterers at 1.71 and 1.84 Å and Mn-N scatterers at 2.11 Å, providing the first unambiguous support for the formulation of this species as an oxohydroxomanganese(IV) adduct. EXAFS-determined structural parameters for [Mn(II)(Cl)2(Me2EBC)] and [Mn(IV)(OH)2(Me2EBC)](2+) are consistent with previously reported crystal structures. The Mn pre-edge energies and intensities of these complexes were examined within the context of data for other oxo- and hydroxomanganese(IV) adducts, and time-dependent density functional theory (TD-DFT) computations were used to predict pre-edge properties for all compounds considered. This combined experimental and computational analysis revealed a correlation between the Mn-O(H) distances and pre-edge peak areas of Mn(IV)═O and Mn(IV)-OH complexes, but this trend was strongly modulated by the Mn(IV) coordination geometry. Mn 3d-4p mixing, which primarily accounts for the pre-edge intensities, is not solely a function of the Mn-O(H) bond length; the coordination geometry also has a large effect on the distribution of pre-edge intensity. For tetragonal Mn(IV)═O centers, more than 90% of the pre-edge intensity comes from excitations to the Mn═O σ* MO. Trigonal bipyramidal oxomanganese(IV) centers likewise feature excitations to the Mn═O σ* molecular orbital (MO) but also show intense transitions to 3dx(2)-y(2) and 3dxy MOs because of enhanced 3d-4px,y mixing. This gives rise to a broader pre-edge feature for trigonal Mn(IV)═O adducts. These results underscore the importance of reporting experimental pre-edge areas rather than peak heights. Finally, the TD-DFT method was applied to understand the pre-edge properties of a recently reported S = 1 Mn(V)═O adduct; these findings are discussed within the context of previous examinations of oxomanganese(V) complexes.

Development of XAFS Into a Structure Determination Technique

NASA Astrophysics Data System (ADS)

Stern, E. A.

After the detection of diffraction of x-rays by M. Laue in 1912, the technique was soon applied to structure determination by Bragg within a year. On the other hand, although the edge steps in X-Ray absorption were discovered even earlier by Barkla and both the near edge (XANES) and extended X-Ray fine structure (EXAFS) past the edge were detected by 1929, it still took over 40 years to realize the structure information contained in this X-Ray absorption fine structure (XAFS). To understand this delay a brief historical review of the development of the scientific ideas that transformed XAFS into the premiere technique for local structure determination is given. The development includes both advances in theoretical understanding and calculational capabilities, and in experimental facilities, especially synchrotron radiation sources. The present state of the XAFS technique and its capabilities are summarized.

Low Z elements (Mg, Al, and Si) K-edge X-ray absorption spectroscopy in minerals and disordered systems

NASA Astrophysics Data System (ADS)

Ildefonse, Ph.; Calas, G.; Flank, A. M.; Lagarde, P.

1995-05-01

Soft X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy have been performed at the Mg-, Al- and Si-K edges in order to establish the ability of this spectroscopy to derive structural information in disordered solids such as glasses and gels. Mg- and Al-K XANES are good structural probes to determine the coordination state of these elements in important minerals, glasses and gels. In a CaOsbnd MgOsbnd 2SiO2 glass Mg XANES spectra differ from that found in the crystalline equivalent, with a significant shift of the edge maxima to lower energy, consistent with a CN lower than 6. Mg-EXAFS on the same sample are in agreement and indicate the presence of 5-coordinated Mg with Mgsbnd O distances of 2.01Å. In aluminosilicate gels, Alsbnd K XANES has been used to investigate the [4]Al/Altotal ratios. These ratios increase as the Al/Si ratios decrease. Aluminosilicate and ferric-silicate gels were studied by using Sisbnd K edge XANES. XANES spectra differ significantly among the samples studied. Aluminosilicate gels with Al/Si= 1 present a different Al and Si local environment from that known in clay minerals with the same Al/Si ratio. The gel-to-mineral transformation thus implies a dissolution-recrystallization mechanism. On the contrary, ferric-silicate gel presents a Si local environment close to that found in nontronite which may be formed by a long range ordering of the initial gels.

Probing defect emissions in bulk, micro- and nano-sized α-Al2O3 via X-ray excited optical luminescence

NASA Astrophysics Data System (ADS)

Wang, Zhiqiang; Li, Chunlei; Liu, Lijia; Sham, Tsun-Kong

2013-02-01

The electronic structure and optical properties of bulk, micro-sized, and nano-sized α-Al2O3 (wafer, microparticles (MPs), nanowires (NWs), and nanotubes (NTs)) have been investigated using X-ray absorption near-edge structures (XANES) and X-ray excited optical luminescence (XEOL). XANES results show that the wafer, MPs, and NTs have characteristic features of α-Al2O3. The NWs have a core/shell structure with a single crystalline α-Al2O3 core surrounded by an amorphous shell, which is consistent with transmission electron microscopy result. It is found that some Al3+ in the shell and core/shell interface of the NWs as well as the surface of the NTs were reduced to Al2+ or Al1+ during the growth process. XEOL results show that the wafer and MPs have a broad emission at 325 nm and a sharp emission at 694 nm, which are attributed to F+ center and Cr3+ impurities, respectively. The NWs exhibit an intense emission at 404 nm that comes from F center, while the NTs show relatively weak luminescence at 325, 433, and 694 nm, which are attributed to F+ center, F center, and Cr3+ impurities, respectively. The O K-edge XEOL confirms that the emissions of α-Al2O3 in the range of 250-550 nm are related to the oxygen site. Furthermore, on the basis of XEOL and photoluminescence yield, the strong luminescence of the NWs (404 nm) is related to the Al2+ or Al1+ in the shell and core/shell interface, while the luminescence of the NTs at 325 and 433 nm are related to the bulk and the Al2+ or Al1+ on the surface, respectively.

[Study on transition metals in airborne particulate matter in Shanghai city's subway].

PubMed

Bao, Liang-Man; Lei, Qian-Tao; Tan, Ming-Guang; Li, Xiao-Lin; Zhang, Gui-Lin; Liu, Wei; Li, Yan

2014-06-01

PM10 and PM2.5 aerosol particle samples were collected at a subway station in Shanghai and their morphology, chemical composition and transition metal species were studied. The mass concentrations of PM10 and PM2.5 inside the subway station were significantly higher than those measured in aboveground ambient air. The PM levels inside subway were much higher than the state control limit. The aerosol composition in the metro station was quite different from that of the aboveground urban particles. Concentrations of Fe, Mn and Cr were higher than the averages of aboveground urban air particles by factors of 8, 2, and 2, respectively, showing a substantial enrichment in subway. Scanning electron microscope (SEM) analysis showed that the subway particles had flat surfaces in combination with parallel scratches and sharp edges and looked like metal sheets or flakes. Furthermore, analysis of the atomic composition of typical subway particles by energy dispersive X-Ray (EDX) spectroscopy showed that oxygen and iron dominated the mass of the particles. The X-ray absorption near-edge structure (XANES) spectroscopy results showed that a fraction (> 26%) of the total iron in the PM10 was in the form of pure Fe, while in the street particles Fe(III) was shown to be a significant fraction of the total iron. The work demonstrated that the underground subway stations in Shanghai were an important microenvironment for exposure to transition metal aerosol for the people taking subway train for commuting every day and those who work in the subway stations, and the metal particle exposure for people in the subway station should not be ignored.

Near band edge emission characteristics of sputtered nano-crystalline ZnO films

NASA Astrophysics Data System (ADS)

Kunj, Saurabh; Sreenivas, K.

2016-05-01

Sputtered zinc oxide (ZnO) thin films deposited on unheated glass substrate under different sputtering gas mixtures (Ar+O2) have been investigated using X-ray diffraction and photo luminescence spectroscopy. Earlier reported studies on ZnO films prepared by different techniques exhibit either a sharp/broad near band edge (NBE) emission peak depending on the crystalline quality of the film. In the present study zinc oxide films, grown on unheated substrates, are seen to possess a preferred (002) orientation with a microstructure consisting of clustered nano-sized crystallites. The splitting in the near band edge emission (NBE) into three characteristic peaks is attributed to quantum confinement effect, and is observed specifically under an excitation of 270 nm. Deep level emission (DLE) in the range 400 to 700 nm is not observed indicating absence of deep level radiative defects.

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

Wojciech, Blachucki

This work treats of the high energy resolution off-resonant X-ray spectroscopy (HEROS) method of determining the density of unoccupied electronic states in the vicinity of the absorption edge. HEROS is an alternative to the existing X-ray absorption spectroscopy (XAS) methods and opens the way for new studies not achievable before.