Highly mismatched GaN1-x Sb x alloys: synthesis, structure and electronic properties

NASA Astrophysics Data System (ADS)

Yu, K. M.; Sarney, W. L.; Novikov, S. V.; Segercrantz, N.; Ting, M.; Shaw, M.; Svensson, S. P.; Martin, R. W.; Walukiewicz, W.; Foxon, C. T.

2016-08-01

Highly mismatched alloys (HMAs) is a class of semiconductor alloys whose constituents are distinctly different in terms of size, ionicity and/or electronegativity. Electronic properties of the alloys deviate significantly from an interpolation scheme based on small deviations from the virtual crystal approximation. Most of the HMAs were only studied in a dilute composition limit. Recent advances in understanding of the semiconductor synthesis processes allowed growth of thin films of HMAs under non-equilibrium conditions. Thus reducing the growth temperature allowed synthesis of group III-N-V HMAs over almost the entire composition range. This paper focuses on the GaN x Sb1-x HMA which has been suggested as a potential material for solar water dissociation devices. Here we review our recent work on the synthesis, structural and optical characterization of GaN1-x Sb x HMA. Theoretical modeling studies on its electronic structure based on the band anticrossing (BAC) model are also reviewed. In particular we discuss the effects of growth temperature, Ga flux and Sb flux on the incorporation of Sb, film microstructure and optical properties of the alloys. Results obtained from two separate MBE growths are directly compared. Our work demonstrates that a large range of direct bandgap energies from 3.4 eV to below 1.0 eV can be achieved for this alloy grown at low temperature. We show that the electronic band structure of GaN1-x Sb x HMA over the entire composition range is well described by a modified BAC model which includes the dependence of the host matrix band edges as well as the BAC model coupling parameters on composition. We emphasize that the modified BAC model of the electronic band structure developed for the full composition of GaN x Sb1-x is general and is applicable to any HMA.

Modeling the Stress Strain Behavior of Woven Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.

2006-01-01

Woven SiC fiber reinforced SiC matrix composites represent one of the most mature composite systems to date. Future components fabricated out of these woven ceramic matrix composites are expected to vary in shape, curvature, architecture, and thickness. The design of future components using woven ceramic matrix composites necessitates a modeling approach that can account for these variations which are physically controlled by local constituent contents and architecture. Research over the years supported primarily by NASA Glenn Research Center has led to the development of simple mechanistic-based models that can describe the entire stress-strain curve for composite systems fabricated with chemical vapor infiltrated matrices and melt-infiltrated matrices for a wide range of constituent content and architecture. Several examples will be presented that demonstrate the approach to modeling which incorporates a thorough understanding of the stress-dependent matrix cracking properties of the composite system.

Effect of Saturation Pressure Difference on Metal–Silicide Nanopowder Formation in Thermal Plasma Fabrication

PubMed Central

Shigeta, Masaya; Watanabe, Takayuki

2016-01-01

A computational investigation using a unique model and a solution algorithm was conducted, changing only the saturation pressure of one material artificially during nanopowder formation in thermal plasma fabrication, to highlight the effects of the saturation pressure difference between a metal and silicon. The model can not only express any profile of particle size–composition distribution for a metal–silicide nanopowder even with widely ranging sizes from sub-nanometers to a few hundred nanometers, but it can also simulate the entire growth process involving binary homogeneous nucleation, binary heterogeneous co-condensation, and coagulation among nanoparticles with different compositions. Greater differences in saturation pressures cause a greater time lag for co-condensation of two material vapors during the collective growth of the metal–silicide nanopowder. The greater time lag for co-condensation results in a wider range of composition of the mature nanopowder. PMID:28344300

The oxygen isotope composition of Almahata Sitta

NASA Astrophysics Data System (ADS)

Rumble, Douglas; Zolensky, Michael E.; Friedrich, Jon M.; Jenniskens, Peter; Shaddad, Muawia H.

2010-10-01

Eleven fragments of the meteorite Almahata Sitta (AHS) have been analyzed for oxygen isotopes. The fragments were separately collected as individual stones from the meteorite's linear strewn field in the Nubian Desert. Each of the fragments represents a sample of a different and distinct portion of asteroid 2008 TC3. Ten of the fragments span the same range of values of δ18O, δ17O, and Δ17O, and follow the same trend along the carbonaceous chondrite anhydrous minerals (CCAM) line as monomict and polymict members of the ureilite family of meteorites. The oxygen isotope composition of fragment #25 is consistent with its resemblance petrographically to an H5 ordinary chondrite. Our results demonstrate that a single small asteroidal parent body, asteroid 2008 TC3, only 4 m in length, encompassed the entire range of variation in oxygen isotope compositions measured for monomict and polymict ureilites.

Effect of Saturation Pressure Difference on Metal-Silicide Nanopowder Formation in Thermal Plasma Fabrication.

PubMed

Shigeta, Masaya; Watanabe, Takayuki

2016-03-07

A computational investigation using a unique model and a solution algorithm was conducted, changing only the saturation pressure of one material artificially during nanopowder formation in thermal plasma fabrication, to highlight the effects of the saturation pressure difference between a metal and silicon. The model can not only express any profile of particle size-composition distribution for a metal-silicide nanopowder even with widely ranging sizes from sub-nanometers to a few hundred nanometers, but it can also simulate the entire growth process involving binary homogeneous nucleation, binary heterogeneous co-condensation, and coagulation among nanoparticles with different compositions. Greater differences in saturation pressures cause a greater time lag for co-condensation of two material vapors during the collective growth of the metal-silicide nanopowder. The greater time lag for co-condensation results in a wider range of composition of the mature nanopowder.

Elastic properties of uniaxial-fiber reinforced composites - General features

NASA Astrophysics Data System (ADS)

Datta, Subhendu; Ledbetter, Hassel; Lei, Ming

The salient features of the elastic properties of uniaxial-fiber-reinforced composites are examined by considering the complete set of elastic constants of composites comprising isotropic uniaxial fibers in an isotropic matrix. Such materials exhibit transverse-isotropic symmetry and five independent elastic constants in Voigt notation: C(11), C(33), C(44), C(66), and C(13). These C(ij) constants are calculated over the entire fiber-volume-fraction range 0.0-1.0, using a scattered-plane-wave ensemple-average model. Some practical elastic constants such as the principal Young moduli and the principal Poisson ratios are considered, and the behavior of these constants is discussed. Also presented are the results for the four principal sound velocities used to study uniaxial-fiber-reinforced composites: v(11), v(33), v(12), and v(13).

Generalized Slater--Pauling curve and the role of metalloids in Fe-based amorphous alloys

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

Sostarich, M.

1990-05-01

A modification of the generalized Slater--Pauling curve so as to consider the concentration dependence of the number of majority-spin {ital sp} electrons per average atom is proposed for amorphous iron-metalloid alloys. In this way an improved matching of the measured magnetic moment dependence on composition is achieved for Fe alloys with B and/or P as metalloids. Comparison of theory with experiment shows that amorphous Fe-P alloys tend to be magnetically rather strong, whereas their Fe-B counterparts are weak itinerant ferromagnets in almost the entire range of compositions.

Understanding band alignments in semiconductor heterostructures: Composition dependence and type-I-type-II transition of natural band offsets in nonpolar zinc-blende AlxGa1 -xN /AlyGa1 -yN composites

NASA Astrophysics Data System (ADS)

Landmann, M.; Rauls, E.; Schmidt, W. G.

2017-04-01

The composition dependence of the natural band alignment at nonpolar AlxGa1 -xN /AlyGa1 -yN heterojunctions is investigated via hybrid functional based density functional theory. Accurate band-gap data are provided using Heyd-Scuseria-Ernzerhof (HSE) type hybrid functionals with a composition dependent exact-exchange contribution. The unstrained band alignment between zincblende (zb) AlxGa1 -xN semiconductor alloys is studied within the entire ternary composition range utilizing the Branch-point technique to align the energy levels related to the bulklike direct Γv→Γc and indirect, pseudodirect, respectively, Γv→Xc type transitions in zb-AlxGa1 -xN . While the zb-GaN/AlxGa1 -xN band edges consistently show a type-I alignment, the relative position of fundamental band edges changes to a type-II alignment in the Al-rich composition ranges of zb-AlxGa1 -xN /AlN and zb-AlxGa1 -xN /AlyGa1 -yN systems. The presence of a direct-indirect band-gap transition at xc=0.63 in zb-AlxGa1 -xN semiconductor alloys gives rise to a notably different composition dependence of band discontinuities in the direct and indirect energy-gap ranges. Below the critical direct-indirect Al/Ga-crossover concentration, the band offsets show a close to linear dependence on the alloy composition. In contrast, notable bowing characteristics of all band discontinuities are observed above the critical crossover composition.

Composition Dependence of the Hydrostatic Pressure Coefficients of the Bandgap of ZnSe(1-x)Te(x) Alloys

NASA Technical Reports Server (NTRS)

Wu, J.; Yu, K. M.; Walukiewicz, W.; Shan, W.; Ager, J. W., III; Haller, E. E.; Miotkowski, I.; Ramdas, A. K.; Su, Ching-Hua

2003-01-01

Optical absorption experiments have been performed using diamond anvil cells to measure the hydrostatic pressure dependence of the fundamental bandgap of ZnSe(sub 1-xTe(sub x) alloys over the entire composition range. The first and second-order pressure coefficients are obtained as a function of composition. Starting from the ZnSe side, the magnitude of both coefficients increases slowly until x approx. 0.7, where the ambient-pressure bandgap reaches a minimum. For larger values of x the coefficients rapidly approach the values of ZnTe. The large deviations of the pressure coefficients from the linear interpolation between ZnSe and ZnTe are explained in terms of the band anticrossing model.

3D hierarchically porous Cu-BiOCl nanocomposite films: one-step electrochemical synthesis, structural characterization and nanomechanical and photoluminescent properties

NASA Astrophysics Data System (ADS)

Guerrero, Miguel; Pané, Salvador; Nelson, Bradley J.; Baró, Maria Dolors; Roldán, Mònica; Sort, Jordi; Pellicer, Eva

2013-11-01

Three-dimensional (3D) hierarchically porous composite Cu-BiOCl films have been prepared by a facile one-step galvanostatic electrodeposition process from acidic electrolytic solutions containing Cu(ii) and Bi(iii) chloride salts and Triton X-100. The films show spherical, micron-sized pores that spread over the whole film thickness. In turn, the pore walls are made of randomly packed BiOCl nanoplates that are assembled leaving micro-nanopore voids beneath. It is believed that Cu grows within the interstitial spaces between the hydrogen bubbles produced from the reduction of H+ ions. Then, the BiOCl sheets accommodate in the porous network defined by the Cu building blocks. The presence of Cu tends to enhance the mechanical stability of the composite material. The resulting porous Cu-BiOCl films exhibit homogeneous and stable-in-time photoluminescent response arising from the BiOCl component that spreads over the entire 3D porous structure, as demonstrated by confocal scanning laser microscopy. A broad-band emission covering the entire visible range, in the wavelength interval 450-750 nm, is obtained. The present work paves the way for the facile and controlled preparation of a new generation of photoluminescent membranes.Three-dimensional (3D) hierarchically porous composite Cu-BiOCl films have been prepared by a facile one-step galvanostatic electrodeposition process from acidic electrolytic solutions containing Cu(ii) and Bi(iii) chloride salts and Triton X-100. The films show spherical, micron-sized pores that spread over the whole film thickness. In turn, the pore walls are made of randomly packed BiOCl nanoplates that are assembled leaving micro-nanopore voids beneath. It is believed that Cu grows within the interstitial spaces between the hydrogen bubbles produced from the reduction of H+ ions. Then, the BiOCl sheets accommodate in the porous network defined by the Cu building blocks. The presence of Cu tends to enhance the mechanical stability of the composite material. The resulting porous Cu-BiOCl films exhibit homogeneous and stable-in-time photoluminescent response arising from the BiOCl component that spreads over the entire 3D porous structure, as demonstrated by confocal scanning laser microscopy. A broad-band emission covering the entire visible range, in the wavelength interval 450-750 nm, is obtained. The present work paves the way for the facile and controlled preparation of a new generation of photoluminescent membranes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03491g

Tribological properties of PM212: A high-temperature, self-lubricating, powder metallurgy composite

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher; Sliney, Harold E.

1989-01-01

This paper describes a research program to develop and evaluate a new high temperature, self-lubricating powder metallurgy composite, PM212. PM212 has the same composition as the plasma-sprayed coating, PS212, which contains 70 wt percent metal-bonded chromium carbide, 15 wt percent silver and 15 wt percent barium fluoride/calcium fluoride eutectic. The carbide acts as a wear resistant matrix and the silver and fluorides act as low and high temperature lubricants, respectively. The material is prepared by sequential cold press, cold isostatic pressing and sintering techniques. In this study, hemispherically tipped wear pins of PM212 were prepared and slid against superalloy disks at temperatures from 25 to 850 C in air in a pin-on-disk tribometer. Friction coefficients range from 0.29 to 0.38 and the wear of both the composite pins and superalloy disks was moderate to low in the 10(exp -5) to 10(exp -6) cubic mm/N-m range. Preliminary tests indicate that the material has a compressive strength of at least 130 MPa over the entire temperature range of 25 to 900 C. This material has promise for use as seal inserts, bushings, small inside diameter parts and other applications where plasma-sprayed coatings are impractical or too costly.

Tribological properties of PM212 - A high temperature, self-lubricating, powder metallurgy composite

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher; Sliney, Harold E.

1990-01-01

This paper describes a research program to develop and evaluate a new high temperature, self-lubricating powder metallurgy composite, PM212. PM212 has the same composition as the plasma-sprayed coating, PS212, which contains 70 wt percent metal-bonded chromium carbide, 15 wt percent silver and 15 wt percent barium fluoride/calcium fluoride eutectic. The carbide acts as a wear resistant matrix and the silver and fluorides act as low and high temperature lubricants, respectively. The material is prepared by sequential cold press, cold isostatic pressing and sintering techniques. In this study, hemispherically tipped wear pins of PM212 were prepared and slid against superalloy disks at temperatures from 25 to 850 C in air in a pin-on-disk tribometer. Friction coefficients range from 0.29 to 0.38 and the wear of both the composite pins and superalloy disks was moderate to low in the 10(exp -5) to 10(exp -6) cubic mm/N-m range. Preliminary tests indicate that the material has a compressive strength of at least 130 MPa over the entire temperature range of 25 to 900 C. This material has promise for use as seal inserts, bushings, small inside diameter parts and other applications where plasma-sprayed coatings are impractical or too costly.

Geochemical studies of rocks from North Ray Crater, Apollo 16

NASA Technical Reports Server (NTRS)

Lindstrom, M. M.; Salpas, P. A.

1982-01-01

The samples included in the study were all collected as individual specimens from Station 11 near the rim of North Ray Crater. Samples were selected to cover the entire range of rock types from anorthosites to subophitic impact melts, giving particular attention to the feldspathic breccias which predominate at the site. The chemical composition of North Ray Crater rocks is discussed along with the compositional variations among North Ray Crater samples, and the relationships between North Ray Crater and other Apollo 16 stations. It is pointed out that the primary objective in sampling the Apollo 16 site was to characterize materials from the Cayley Plains and Descartes Highlands.

Raman spectroscopic investigation of thorium dioxide-uranium dioxide (ThO₂-UO₂) fuel materials.

PubMed

Rao, Rekha; Bhagat, R K; Salke, Nilesh P; Kumar, Arun

2014-01-01

Raman spectroscopic investigations were carried out on proposed nuclear fuel thorium dioxide-uranium dioxide (ThO2-UO2) solid solutions and simulated fuels based on ThO2-UO2. Raman spectra of ThO2-UO2 solid solutions exhibited two-mode behavior in the entire composition range. Variations in mode frequencies and relative intensities of Raman modes enabled estimation of composition, defects, and oxygen stoichiometry in these compounds that are essential for their application. The present study shows that Raman spectroscopy is a simple, promising analytical tool for nondestructive characterization of this important class of nuclear fuel materials.

Enhanced absorption of microwave radiations through flexible polyvinyl alcohol-carbon black/barium hexaferrite composite films

NASA Astrophysics Data System (ADS)

Kumar, Sushil; Datt, Gopal; Santhosh Kumar, A.; Abhyankar, A. C.

2016-10-01

Flexible microwave absorber composite films of carbon black (CB)/barium hexaferrite nano-discs (BaF) in polyvinyl alcohol (PVA) matrix, fabricated by gel casting, exhibit ˜99.5% attenuation of electromagnetic waves in the entire 8-18 GHz (X and Ku-band) range. The X-ray diffraction and Raman spectroscopy studies confirm the formation of CB-BaF-PVA composite films. The electromagnetic absorption properties of composite films are found to be enhanced with CB content due to the synergetic effect of multiple dielectric and magnetic losses. The 25 wt. % CB grafted PVA-BaF flexible composite films with a thickness of ˜ 2 mm exhibit effective electromagnetic shielding of 23.6 dB with a dominant contribution from absorption mechanism (SEA ˜ 21 dB). The dielectric properties of composite films are further discussed by using the Debye model. The detailed analysis reveals that major contribution to dielectric losses is from dipolar and interfacial polarizations, whereas magnetic losses are predominantly from domain wall displacement.

Off-Axis Seamount Lavas at 8°20' N Span the Entire Range of East Pacific Rise MORB Compositions

NASA Astrophysics Data System (ADS)

Anderson, M.; Wanless, V. D.; Perfit, M. R.; Gregg, P. M.; Fornari, D. J.; McCully, E.; Ridley, W. I.

2017-12-01

Lavas erupted at off-axis seamounts can provide a window into mantle heterogeneity and melting systematics that are not easily observed on-axis at fast-spreading mid-ocean ridges (MORs), where melts are efficiently mixed and homogenized within shallow axial magma chambers. To investigate off-axis magmatism, we systematically mapped the 8°20' N seamount chain in November of 2016 on R/V Atlantis using shipboard EM122 multibeam system and AUV Sentry. This 160-km long chain of off-axis seamounts and ridges is located perpendicular to the ridge axis, west of the East Pacific Rise (EPR) and north of the Siqueiros Fracture Zone. The high-resolution surface and AUV-based multibeam and AUV sidescan maps are combined with geochemical analyses of 300 basalt samples, collected using HOV Alvin and dredging, to evaluate magmatic plumbing and sources off-axis. Preliminary major and trace element concentrations reveal remarkable geochemical heterogeneity (including both normal and enriched basalt compositions) across the entire seamount chain and within individual seamounts. For example, (La/Sm)N contents span the entire range of known values for basalts from northern Pacific MORs and seamounts (0.45—2.76). MgO contents vary from 10.25 to 4.56 wt. % across the seamount chain and by as much as 3.61 wt. % from volcanic features sampled at an individual seamount (Beryl). Additionally, K2O/TiO2 ratios range from 4.9 to 61.3 across the seamount chain, and by as much as 54.4 at a single seamount (Beryl), indicating heterogeneous mantle sources or variable extents of melting occur at both regional and local scales. We combine the geochemical results and bathymetric maps with petrologic models to evaluate extents and depths of fractional crystallization and mantle melting in the off-axis environment.

Ion composition of the bulk ring current during a magnetic storm - Observations with the CHEM-instrument on AMPTE-CCE

NASA Technical Reports Server (NTRS)

Stuedemann, W.; Wilken, B.; Kremser, G.; Gloeckler, G.; Ipavich, F. M.

1986-01-01

Ion composition measurements in the entire energy range of the ring current population, obtained with the Charge-, Energy-, Mass-spectrometer instrument on the Charge Composition Explorer in September 1984, are reported. From the energy spectra obtained for all major constituents during the main phase of a magnetic storm, the number densities, energy densities, and mean energies are calculated and displayed as radial profiles. The mean energies of He(2+) are found to be about twice that of H(+) and He(+) throughout this storm, and the time profiles for the mean energies of all major ions are seen to bunch together (when normalizing mean energies by the ionic charge), with the largest variations of the energy densities and mean energies occurring for O(+) ions.

Processes and subdivisions in diogenites, a multivariate statistical analysis

NASA Technical Reports Server (NTRS)

Harriott, T. A.; Hewins, R. H.

1984-01-01

Multivariate statistical techniques used on diogenite orthopyroxene analyses show the relationships that occur within diogenites and the two orthopyroxenite components (class I and II) in the polymict diogenite Garland. Cluster analysis shows that only Peckelsheim is similar to Garland class I (Fe-rich) and the other diogenites resemble Garland class II. The unique diogenite Y 75032 may be related to type I by fractionation. Factor analysis confirms the subdivision and shows that Fe does not correlate with the weakly incompatible elements across the entire pyroxene composition range, indicating that igneous fractionation is not the process controlling total diogenite composition variation. The occurrence of two groups of diogenites is interpreted as the result of sampling or mixing of two main sequences of orthopyroxene cumulates with slightly different compositions.

On a coherent investigation of the spectrum of cosmic rays in the energy range of 1014 - 1018 eV with KASCADE and KASCADE-Grande

NASA Astrophysics Data System (ADS)

Schoo, S.; Apel, W. D.; Arteaga-Velázquez, J. C.; Beck, K.; Bertaina, M.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Fuhrmann, D.; Gherghel-Lascu, A.; Gils, H. J.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Huber, D.; Huege, T.; Kampert, K. H.; Kang, D.; Klages, H. O.; Link, K.; Łuczak, P.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Morello, C.; Oehlschläger, J.; Ostapchenko, S.; Palmieri, N.; Petcu, M.; Pierog, T.; Rebel, H.; Roth, M.; Schieler, H.; Schröder, F. G.; Sima, O.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Zabierowski, J.

2015-08-01

The KASCADE experiment and its extension KASCADE-Grande have significantly contributed to the current knowledge about the energy spectrum and composition of cosmic rays (CRs) with energies between the knee and the ankle. However, the data of both experiments were analysed separately, although Grande used the muon information of the KASCADE-array. A coherent analysis based on the combined data of both arrays is expected to profit from reconstructed shower observables with even higher accuracy compared to the stand-alone analyses. In addition, a significantly larger fiducial area is available. The aim of this analysis is to obtain the spectrum and composition of CRs in the range from 1014 to 1018 eV with a larger number of events and further reduced uncertainties using one unique reconstruction procedure for the entire energy range. This contribution will describe the motivation, the concept, and the current status of the combined analysis.

The prediction of the flash point for binary aqueous-organic solutions.

PubMed

Liaw, Horng-Jang; Chiu, Yi-Yu

2003-07-18

A mathematical model, which may be used for predicting the flash point of aqueous-organic solutions, has been proposed and subsequently verified by experimentally-derived data. The results reveal that this model is able to precisely predict the flash point over the entire composition range of binary aqueous-organic solutions by way of utilizing the flash point data pertaining to the flammable component. The derivative of flash point with respect to composition (solution composition effect upon flash point) can be applied to process safety design/operation in order to identify as to whether the dilution of a flammable liquid solution with water is effective in reducing the fire and explosion hazard of the solution at a specified composition. Such a derivative equation was thus derived based upon the flash point prediction model referred to above and then verified by the application of experimentally-derived data.

Refractive index, molar refraction and comparative refractive index study of propylene carbonate binary liquid mixtures.

PubMed

Wankhede, Dnyaneshwar Shamrao

2012-06-01

Refractive indices (n) have been experimentally determined for the binary liquid-liquid mixtures of Propylene carbonate (PC) (1) with benzene, ethylbenzene, o-xylene and p-xylene (2) at 298.15, 303.15 and 308.15 K over the entire mole fraction range. The experimental values of n are utilised to calculate deviation in refractive index (Δn), molar refraction (R) and deviation in molar refraction (ΔR). A comparative study of Arago-Biot (A-B), Newton (NW), Eyring and John (E-J) equations for determining refractive index of a liquid has been carried out to test their validity for all the binary mixtures over the entire composition range at 298.15 K. Comparison of various mixing relations is represented in terms of average deviation (AVD). The Δn and ΔR values have been fitted to Redlich-Kister equation at 298.15 K and standard deviations have been calculated. The results are discussed in terms of intermolecular interactions present amongst the components.

Atmospheric pressure organometallic vapor-phase epitaxial growth of (Al/x/Ga/1-x/)0.51In0.49P (x from 0 to 1) using trimethylalkyls

NASA Technical Reports Server (NTRS)

Cao, D. S.; Kimball, A. W.; Stringfellow, G. B.

1990-01-01

This paper describes growth of (Al/x/Ga/1-x)0.51In0.49P layers (with x from 0 to 1) lattice-matched to (001)-oriented GaAs substrates by atmospheric-pressure OMVPE, using trimethylindium, trimethylaluminum, and trimethylgallium and PH3 as source materials in a horizontal reactor. Excellent surface morphologies were obtained over the entire range of Al compositions at a growth temperature of 680 C. Photoluminescence (PL) was observed for all samples with x values not below 0.52, with PL peak energies as high as 2.212 eV. The PL FWHM for Ga(0.51)In(0.49)P was 7.2 meV at 10 K and 35 meV at 300 K. At 10 K, the PL intensity was nearly a constant over the composition range from x = 0 to 0.52.

AOTF near-IR spectrometers for study of Lunar and Martian surface composition

NASA Astrophysics Data System (ADS)

Korablev, O.; Kiselev, A.; Vyazovetskiy, N.; Fedorova, A.; Evdokimova, N.; Stepanov, A.; Titov, A.; Kalinnikov, Y.; Kuzmin, R. O.; Bazilevsky, A. T.; Bondarenko, A.; Moiseev, P.

2013-09-01

The series of the AOTF near-IR spectrometers is developed in Moscow Space Research Institute for study of Lunar and Martian surface composition in the vicinity of a lander or a rover. Lunar Infrared Spectrometer (LIS) is an experiment onboard Luna-Glob (launch in 2015) and Luna-Resurs (launch in 2017) Russian surface missions. The LIS is mounted on the mechanic arm of landing module in the field of view (45°) of stereo TV camera. Infrared Spectrometer for ExoMars (ISEM) is an experiment onboard ExoMars (launch in 2018) ESARoscosmos rover. The ISEM instrument is mounted on the rover's mast together with High Resolution camera (HRC). Spectrometers will provide measurements of selected surface area in the spectral range of 1.15-3.3 μm. The electrically commanded acousto-optic filter scans sequentially at a desired sampling, with random access, over the entire spectral range.

Ag–Pt compositional intermetallics made from alloy nanoparticles

DOE PAGES

Pan, Yung -Tin; Yan, Yuqi; Shao, Yu -Tsun; ...

2016-09-07

Intermetallics are compounds with long-range structural order that often lies in a state of thermodynamic minimum. They are usually considered as favorable structures for catalysis due to their high activity and robust stability. However, formation of intermetallic compounds is often regarded as element specific. For instance, Ag and Pt do not form alloy in bulk phase through the conventional metallurgy approach in almost the entire range of composition. Herein, we demonstrate a bottom-up approach to create a new Ag–Pt compositional intermetallic phase from nanoparticles. By thermally treating the corresponding alloy nanoparticles in inert atmosphere, we obtained an intermetallic material thatmore » has an exceptionally narrow Ag/Pt ratio around 52/48 to 53/47, and a structure of interchangeable closely packed Ag and Pt layers with 85% on tetrahedral and 15% on octahedral sites. This rather unique stacking results in wavy patterns of Ag and Pt planes revealed by scanning transmission electron microscope (STEM). Finally, this Ag–Pt compositional intermetallic phase is highly active for electrochemical oxidation of formic acid at low anodic potentials, 5 times higher than its alloy nanoparticles, and 29 times higher than the reference Pt/C at 0.4 V (vs RHE) in current density.« less

Mass spectrometric measurements of the freestream composition in the T4 free-piston shock-tunnel

NASA Astrophysics Data System (ADS)

Boyce, R. R.; Takahashi, M.; Stalker, R. J.

2005-12-01

The freestream composition is an important parameter in ground-based aerodynamic testing, and direct measurement of it is very important. This paper reports extensive composition measurements in the freestream of the T4 free-piston shock-tunnel, employing a recently improved time-of-flight mass spectrometer. A wide range of nozzle reservoir conditions were used. The results show good agreement between measured and theoretical values for nitric oxide over the entire enthalpy range reported (2.5 13 MJ/kg). This provides confidence that the chemistry model is correctly predicting sudden freezing of NO in the nozzle expansion. On the other hand, no monatomic species have been measured other than those produced by dissociative ionisation within the mass spectrometer, even at flow conditions where significant freestream dissociation is expected. Furthermore, excess diatomic oxygen is detected at high enthalpies. These observations are consistent with the possibility that oxygen recombination is not correctly predicted in the nozzle expansion, with sudden freezing occurring significantly later than predicted. However, the observations are also consistent with possible catalytic recombination in the skimmer system. The possibility for producing an empirical correlation between the freestream composition and the reservoir entropy has also been observed.

Ag–Pt compositional intermetallics made from alloy nanoparticles

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

Pan, Yung -Tin; Yan, Yuqi; Shao, Yu -Tsun

Intermetallics are compounds with long-range structural order that often lies in a state of thermodynamic minimum. They are usually considered as favorable structures for catalysis due to their high activity and robust stability. However, formation of intermetallic compounds is often regarded as element specific. For instance, Ag and Pt do not form alloy in bulk phase through the conventional metallurgy approach in almost the entire range of composition. Herein, we demonstrate a bottom-up approach to create a new Ag–Pt compositional intermetallic phase from nanoparticles. By thermally treating the corresponding alloy nanoparticles in inert atmosphere, we obtained an intermetallic material thatmore » has an exceptionally narrow Ag/Pt ratio around 52/48 to 53/47, and a structure of interchangeable closely packed Ag and Pt layers with 85% on tetrahedral and 15% on octahedral sites. This rather unique stacking results in wavy patterns of Ag and Pt planes revealed by scanning transmission electron microscope (STEM). Finally, this Ag–Pt compositional intermetallic phase is highly active for electrochemical oxidation of formic acid at low anodic potentials, 5 times higher than its alloy nanoparticles, and 29 times higher than the reference Pt/C at 0.4 V (vs RHE) in current density.« less

Excess Volumes and Excess Isentropic Compressibilities of Binary Liquid Mixtures of Trichloroethylene with Esters at 303.15 K

NASA Astrophysics Data System (ADS)

Ramanaiah, S.; Rao, C. Narasimha; Nagaraja, P.; Venkateswarlu, P.

2015-11-01

Exces volumes, VE, and excess isentropic compressibilities, κSE, have been reported as a function of composition for binary liquid mixtures of trichloroethylene with ethyl acetate, n-propyl acetate, and n-butyl acetate at 303.15 K. Isentropic compressibilities are calculated using measured sound speeds and density data for pure components and for binary mixtures. Excess volumes and excess isentropic compressibilities are found to be negative for the three systems studied over the entire composition range at 303.15 K, whereas these values become more negative with an increase of carbon chain length. The results are discussed in terms of intermolecular interactions between unlike molecules.

Interlaminar shear fracture toughness and fatigue thresholds for composite materials

NASA Technical Reports Server (NTRS)

Obrien, T. Kevin; Murri, Gretchen B.; Salpekar, Satish A.

1987-01-01

Static and cyclic end notched flexure tests were conducted on a graphite epoxy, a glass epoxy, and graphite thermoplastic to determine their interlaminar shear fracture toughness and fatigue thresholds for delamination in terms of limiting values of the mode II strain energy release rate, G-II, for delamination growth. The influence of precracking and data reduction schemes are discussed. Finite element analysis indicated that the beam theory calculation for G-II with the transverse shear contribution included was reasonably accurate over the entire range of crack lengths. Cyclic loading significantly reduced the critical G-II for delamination. A threshold value of the maximum cyclic G-II below which no delamination occurred after one million cycles was identified for each material. Also, residual static toughness tests were conducted on glass epoxy specimens that had undergone one million cycles without delamination. A linear mixed-mode delamination criteria was used to characterize the static toughness of several composite materials; however, a total G threshold criterion appears to characterize the fatigue delamination durability of composite materials with a wide range of static toughness.

Characterization and device performance of (AgCu)(InGa)Se2 absorber layers

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

Hanket, Gregory; Boyle, Jonathan H.; Shafarman, William N.

The study of (AgCu)(InGa)Se2 absorber layers is of interest in that Ag-chalcopyrites exhibit both wider bandgaps and lower melting points than their Cu counterparts. (AgCu)(InGa)Se2 absorber layers were deposited over the composition range 0 < Ag/(Ag+Cu) < 1 and 0.3 < Ga/(In+Ga) < 1.0 using a variety of elemental co-evaporation processes. Films were found to be singlephase over the entire composition range, in contrast to prior studies. Devices with Ga content 0.3 < Ga/(In+Ga) <0.5 tolerated Ag incorporation up to Ag/(Ag+Cu) = 0.5 without appreciable performance loss. Ag-containing films with Ga/(In+Ga) = 0.8 showed improved device characteristics over Cu-only controlmore » samples, in particular a 30-40% increase in short-circuit current. An absorber layer with composition Ag/(Ag+Cu) = 0.75 and Ga/(In+Ga) = 0.8 yielded a device with VOC = 890 mV, JSC = 20.5mA/cm2, fill factor = 71.3%, and η = 13.0%.« less

Study on the impedance of aligned carbon microcoils embedded in silicone rubber matrix

NASA Astrophysics Data System (ADS)

Zhu, Ya-Bo; Zhang, Lin; Guo, Li-Tong; Xiang, Dong-Hu

2010-12-01

This paper reports that carbon microcoils are grown through a chemical vapour deposit process, they are then embedded in silicone rubber, and manipulated to parallel with each other along their axes in the resulting composite. The impedance |Z| as well as phase angle θ of both the original carbon microcoil sheets and the aligned carbon microcoil/silicone rubber composites are measured. The results illustrate that carbon microcoils in different forms show different alternating current electric properties. The aligned carbon microcoils in the composites show stable parameters for f < 104 Hz but a sharp decrease in both |Z| and θ for frequencies > 104 Hz, which will also change as the carbon microcoils are extended. But, the original sheets have a pure resistance with their parameters stable throughout the entire alternating current frequency range investigated.

Energetics of Sn 2+ isomorphic substitution into hydroxylapatite: First-principles predictions

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

Weck, Philippe F.; Kim, Eunja

2016-11-04

In this study, the energetics of Sn 2+ substitution into the Ca 2+ sublattice of hydroxylapatite (HA), Ca 10(PO 4) 6(OH) 2, has been investigated within the framework of density functional theory. Calculations reveal that Sn 2+ incorporation via coupled substitutions at Ca(II) sites is energetically favourable up to a composition of Sn 6Ca 4(PO 4) 6(OH) 2, and further substitutions at Ca(I) sites proceed once full occupancy of Ca(II) sites by Sn 2+ is achieved. Compositions of Sn xCa 10–x(PO 4) 6(OH) 2 (x = 4–9) are predominant, with an optimal stoichiometry of Sn 8Ca 2(PO 4) 6(OH) 2,more » and Sn-substituted HA follows approximately Vegard's law across the entire composition range.« less

Sensitivities of seismic velocities to temperature, pressure and composition in the lower mantle

NASA Astrophysics Data System (ADS)

Trampert, Jeannot; Vacher, Pierre; Vlaar, Nico

2001-08-01

We calculated temperature, pressure and compositional sensitivities of seismic velocities in the lower mantle using latest mineral physics data. The compositional variable refers to the volume proportion of perovskite in a simplified perovskite-magnesiowüstite mantle assemblage. The novelty of our approach is the exploration of a reasonable range of input parameters which enter the lower mantle extrapolations. This leads to realistic error bars on the sensitivities. Temperature variations can be inferred throughout the lower mantle within a good degree of precision. Contrary to the uppermost mantle, modest compositional changes in the lower mantle can be detected by seismic tomography, with a larger uncertainty though. A likely trade-off between temperature and composition will be largely determined by uncertainties in tomography itself. Given current sources of uncertainties on recent data, anelastic contributions to the temperature sensitivities (calculated using Karato's approach) appear less significant than previously thought. Recent seismological determinations of the ratio of relative S to P velocity heterogeneity can be entirely explain by thermal effects, although isolated spots beneath Africa and the Central Pacific in the lowermost mantle may ask for a compositional origin.

Synthesis of complex oxides with garnet structure by spray drying of an aqueous salt solution

NASA Astrophysics Data System (ADS)

Makeenko, A. V.; Larionova, T. V.; Klimova-Korsmik, O. G.; Starykh, R. V.; Galkin, V. V.; Tolochko, O. V.

2017-04-01

The use of spray drying to obtain powders of complex oxides with a garnet structure has demonstrated. The processes occurring during heating of the synthesized oxide-salt product, leading to the formation of a material with a garnet structure, have been investigated using DTA, TGA, XPS, and XRD. It has been shown that a single-phase garnet structure of system (Y x Gd(3- x))3Al5O12 can be synthesized over the entire range of compositions.

Performance monitoring can boost turboexpander efficiency

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

McIntire, R.

1982-07-05

Focuses on the turboexpander/refrigeration system's radial expander and radial compressor. Explains that radial expander efficiency depends on mass flow rate, inlet pressure, inlet temperature, discharge pressure, gas composition, and shaft speed. Discusses quantifying the performance of the separate components over a range of operating conditions; estimating the increase in performance associated with any hardware change; and developing an analytical (computer) model of the entire system by using the performance curve of individual components. Emphasizes antisurge control and modifying Q/N (flow rate/ shaft speed).

Transparent, immiscible, surrogate liquids with matchable refractive indexes: Increased range of density and viscosity ratios

NASA Astrophysics Data System (ADS)

Cadillon, Jérémy; Saksena, Rajat; Pearlstein, Arne J.

2016-12-01

By replacing the "heavy" silicone oil used in the oil phase of Saksena, Christensen, and Pearlstein ["Surrogate immiscible liquid pairs with refractive indexes matchable over a wide range of density and viscosity ratios," Phys. Fluids 27, 087103 (2015)] by one with a twentyfold higher viscosity, and replacing the "light" silicone oil in that work by one with a viscosity fivefold lower and a density about 10% lower, we have greatly extended the range of viscosity ratio accessible by index-matching the adjustable-composition oil phase to an adjustable-composition 1,2-propanediol + CsBr + H2O aqueous phase and have also extended the range of accessible density ratios. The new system of index-matchable surrogate immiscible liquids is capable of achieving the density and viscosity ratios for liquid/liquid systems consisting of water with the entire range of light or medium crude oils over the temperature range from 40 °F (4.44 °C) to 200 °F (93.3 °C) and can access the density and viscosity ratios for water with some heavy crude oils over part of the same temperature range. It also provides a room-temperature, atmospheric-pressure surrogate for the liquid CO2 + H2O system at 0 °C over almost all of the pressure range of interest in sub-seabed CO2 sequestration.

Benchtop fabrication of three-dimensional reconfigurable microfluidic devices from paper-polymer composite.

PubMed

Han, Yu Long; Wang, Wenqi; Hu, Jie; Huang, Guoyou; Wang, Shuqi; Lee, Won Gu; Lu, Tian Jian; Xu, Feng

2013-12-21

We presented a benchtop technique that can fabricate reconfigurable, three-dimensional (3D) microfluidic devices made from a soft paper-polymer composite. This fabrication approach can produce microchannels at a minimal width of 100 μm and can be used to prototype 3D microfluidic devices by simple bending and stretching. The entire fabrication process can be finished in 2 hours on a laboratory bench without the need for special equipment involved in lithography. Various functional microfluidic devices (e.g., droplet generator and reconfigurable electronic circuit) were prepared using this paper-polymer hybrid microfluidic system. The developed method can be applied in a wide range of standard applications and emerging technologies such as liquid-phase electronics.

Thermophysical properties of energetic ionic liquids/nitric acid mixtures: Insights from molecular dynamics simulationsa)

NASA Astrophysics Data System (ADS)

Hooper, Justin B.; Smith, Grant D.; Bedrov, Dmitry

2013-09-01

Molecular dynamics (MD) simulations of mixtures of the room temperature ionic liquids (ILs) 1-butyl-4-methyl imidazolium [BMIM]/dicyanoamide [DCA] and [BMIM][NO3-] with HNO3 have been performed utilizing the polarizable, quantum chemistry based APPLE&P® potential. Experimentally it has been observed that [BMIM][DCA] exhibits hypergolic behavior when mixed with HNO3 while [BMIM][NO3-] does not. The structural, thermodynamic, and transport properties of the IL/HNO3 mixtures have been determined from equilibrium MD simulations over the entire composition range (pure IL to pure HNO3) based on bulk simulations. Additional (non-equilibrium) simulations of the composition profile for IL/HNO3 interfaces as a function of time have been utilized to estimate the composition dependent mutual diffusion coefficients for the mixtures. The latter have been employed in continuum-level simulations in order to examine the nature (composition and width) of the IL/HNO3 interfaces on the millisecond time scale.

Structure and Thermoelectric Properties of Bi2−xSbxTe3 Nanowires Grown in Flexible Nanoporous Polycarbonate Templates

PubMed Central

Datta, Anuja; Sangle, Abhijeet; Hardingham, Nick; Cooper, Charles; Kraan, Max; Ritchie, David; Narayan, Vijay; Kar-Narayan, Sohini

2017-01-01

We report the room-temperature growth of vertically aligned ternary Bi2−xSbxTe3 nanowires of diameter ~200 nm and length ~12 µm, within flexible track-etched nanoporous polycarbonate (PC) templates via a one-step electrodeposition process. Bi2−xSbxTe3 nanowires with compositions spanning the entire range from pure Bi2Te3 (x = 0) to pure Sb2Te3 (x = 2) were systematically grown within the nanoporous channels of PC templates from a tartaric–nitric acid based electrolyte, at the end of which highly crystalline nanowires of uniform composition were obtained. Compositional analysis showed that the Sb concentration could be tuned by simply varying the electrolyte composition without any need for further annealing of the samples. Thermoelectric properties of the Bi2−xSbxTe3 nanowires were measured using a standardized bespoke setup while they were still embedded within the flexible PC templates. PMID:28772915

Composition Measurements at the Magnetopause and in the Plasma Mantle

NASA Technical Reports Server (NTRS)

Gary, S. P.

1998-01-01

This final report describes activities under NASA grant NAGW-4049 to Lockheed Missiles and Space Company. The report covers the entire period of the grant from 15 August 1994 to 31 January 1998. The original grant was for 3 years ending in August 1997; however the grant was extended 6 months to accomodate additional data analysis that added significantly to the scientific results. This is a grant under the NASA Supporting Research and Technology Program for the analysis and interpretation of the combined scientific data from the ISEE-1 Plasma Composition Experiment and the AMPTE/CCE Hot Plasma Composition Experiment. These combined data sets were used in a study of the Earth's magnetopause to develop a fundamental understanding of plasma entry and dynamics at the boundary and formation and maintenance of the low latitude boundary layer under a variety of solar wind and magnetospheric conditions and at a wide range of local times.

Observatories Combine to Crack Open the Crab Nebula

NASA Image and Video Library

2017-12-08

Astronomers have produced a highly detailed image of the Crab Nebula, by combining data from telescopes spanning nearly the entire breadth of the electromagnetic spectrum, from radio waves seen by the Karl G. Jansky Very Large Array (VLA) to the powerful X-ray glow as seen by the orbiting Chandra X-ray Observatory. And, in between that range of wavelengths, the Hubble Space Telescope's crisp visible-light view, and the infrared perspective of the Spitzer Space Telescope. This composite image of the Crab Nebula, a supernova remnant, was assembled by combining data from five telescopes spanning nearly the entire breadth of the electromagnetic spectrum: the Very Large Array, the Spitzer Space Telescope, the Hubble Space Telescope, the XMM-Newton Observatory, and the Chandra X-ray Observatory. Credits: NASA, ESA, NRAO/AUI/NSF and G. Dubner (University of Buenos Aires) #nasagoddard #space #science

Sources and composition of PM2.5 in the Colorado Front Range during the DISCOVER-AQ study

NASA Astrophysics Data System (ADS)

Valerino, M. J.; Johnson, J. J.; Izumi, J.; Orozco, D.; Hoff, R. M.; Delgado, R.; Hennigan, C. J.

2017-01-01

Measurements of particulate matter (PM2.5) chemical composition were carried out in Golden, CO, during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field study. Chemical composition was dominated by organic compounds, which comprised an average of 75% of the PM2.5 mass throughout the study. Most of the organic matter was secondary (i.e., secondary organic aerosol) and appears to derive predominantly from regional sources, rather than the Denver metropolitan area. The concentration and composition of PM2.5 in Golden were strongly influenced by highly regular wind patterns and the site's close proximity to the mountains ( 5 km). This second factor may be the cause of distinct differences between observations in Golden and those in downtown Denver, despite a distance between the sites of only 15 km. Concentrations of aerosol nitrate, ammonium, and elemental carbon increased significantly during the daytime when the winds were from the northeast, indicating a strong local source for these compounds. Local sources of dust appeared to minimally impact the Golden site, although this was not likely representative of other conditions in the Colorado Front Range. Conversely, dust that had undergone long-range transport from the southwestern U.S. likely impacted the entire Colorado Front Range, including Golden. During this event, water-soluble Ca2+ concentrations exceeded 1 µg m-3, and the PM2.5/PM10 ratio reached its lowest level throughout the study. The long-range transport of wildfire emissions also impacted the Colorado Front Range for 1-2 days during DISCOVER-AQ. The smoke event was characterized by high concentrations of organics and water-soluble K+. The results show a complex array of sources, and atmospheric processes influence summertime PM in the Colorado Front Range.

40 CFR 761.312 - Compositing of samples.

Code of Federal Regulations, 2010 CFR

2010-07-01

... to composite surface wipe test samples and to use the composite measurement to represent the PCB concentration of the entire surface. Composite samples consist of more than one sample gauze extracted and... arithmetic mean of the composited samples. (a) Compositing samples from surfaces to be used or reused. For...

Thermodynamics of iron-aluminum alloys at 1573 K

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Mehrotra, Gopal M.

1993-01-01

The activities of iron and aluminum were measured in Fe-Al alloys at 1573 K, using the ion-current-ratio technique in a high-temperature Knudsen cell mass spectrometer. The Fe-Al solutions exhibited negative deviations from ideality over the entire composition range. The activity coefficients gamma(Fe), and gamma(Al) are given by six following equations as a function of mole fraction, X(Fe), X(Al). The results show good agreement with those obtained from previous investigations at other temperatures by extrapolation of the activity data to 1573 K.

The Enabler: A concept for a lunar work vehicle

NASA Technical Reports Server (NTRS)

Brazell, James W.; Campbell, Craig; Kaser, Ken; Austin, James A.; Beard, Clark; Ceniza, Glenn; Hamby, Thomas; Robinson, Anne; Wooters, Dana

1992-01-01

The Enabler is an earthbound prototype designed to model an actual lunar work vehicle and is able to perform many of the tasks that might be expected of a lunar work vehicle. The vehicle will be constructed entirely from parts made by students and from standard stock parts. The design utilizes only four distinct chassis pieces and sixteen moving parts. The Enabler has non-orthogonal articulating joints that give the vehicle a wide range of mobility and reduce the total number of parts. Composite wheels provide the primary suspension system for the vehicle.

GTA weld cracking-alloy 625 to 304L

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

Patterson, R.A.; Milewski, J.O.

1985-08-01

Autogenous gas tungsten arc welds joining alloy 625 and 304L stainless steel were found to be susceptible to weld solidification cracking. Utilization of pulsed current GTA welding produced a higher sensitivity to solidification cracks than continuous current welding. Spot Varestraint tests show that the sensitivity of this dissimilar metal combination to cracking exists over the entire range of dilutions while the greatest sensitivity is in 304L stainless steel rich compositions. Auger electron spectroscopy indicates that segregation of sulfur and phosphorous to the interdendritic phase promotes the hot cracking.

Application of low-coherence interferometry for in situ nondestructive evaluation of thin and thick multilayered transparent composites

NASA Astrophysics Data System (ADS)

Khomenko, Anton; Cloud, Gary Lee; Haq, Mahmoodul

2015-12-01

Multilayered transparent composites having laminates with polymer interlayers and backing sheets are commonly used in a wide range of applications where visibility, transparency, impact resistance, and safety are essential. Manufacturing flaws or damage during operation can seriously compromise both safety and performance. Most fabrication defects are not discernible until after the entire multilayered transparent composite assembly has been completed, and in-the-field inspection for damage is a problem not yet solved. A robust and reliable nondestructive evaluation (NDE) technique is needed to evaluate structural integrity and identify defects that result from manufacturing issues as well as in-service damage arising from extreme environmental conditions in addition to normal mechanical and thermal loads. Current optical techniques have limited applicability for NDE of such structures. This work presents a technique that employs a modified interferometer utilizing a laser diode or femtosecond fiber laser source to acquire in situ defect depth location inside a thin or thick multilayered transparent composite, respectively. The technique successfully located various defects inside examined composites. The results show great potential of the technique for defect detection, location, and identification in multilayered transparent composites.

Composition dependence of structural and optical properties in epitaxial Sr(Sn1-xTix)O3 films

NASA Astrophysics Data System (ADS)

Liu, Qinzhuang; Li, Bing; Li, Hong; Dai, Kai; Zhu, Guangping; Wang, Wei; Zhang, Yongxing; Gao, Guanyin; Dai, Jianming

2015-03-01

Epitaxial Sr(Sn1-xTix)O3 (SSTO, x = 0-1) thin films were grown on MgO substrates by a pulsed laser deposition technique. The effects of composition on the structural and optical properties of SSTO films were investigated. X-ray diffraction studies show that the lattice parameter decreases from 4.041 to 3.919 Å gradually with increasing Ti content from 0 to 1 in SSTO films. Optical spectra analysis reveals that the band gap energy Eg decreases continuously from 4.44 to 3.78 eV over the entire doping range, which is explained by the decreasing degree of octahedral tilting distortion and thus the increasing tolerance factor caused by the increasing small-Ti-ion doping concentration.

Entire Sky

NASA Image and Video Library

1999-12-01

Aitoff projection of the three-color composite JHKs source count map of the entire sky, based on 95,851,173 stars with Ks 13.5. What appears most prominently are the Galactic plane and the Galactic bulge.

Tephra dispersal during the Campanian Ignimbrite (Italy) eruption: implications for ultra-distal ash transport during the large caldera-forming eruption

NASA Astrophysics Data System (ADS)

Smith, Victoria C.; Isaia, Roberto; Engwell, Sam L.; Albert, Paul. G.

2016-06-01

The Campanian Ignimbrite eruption dispersed ash over much of the central eastern Mediterranean Sea and eastern Europe. The eruption started with a Plinian phase that was followed by a series of pyroclastic density currents (PDCs) associated with the collapse of the Plinian column and the caldera. The glass compositions of the deposits span a wide geochemical range, but the Plinian fallout and PDCs associated with column collapse, the Lower Pumice Flow, only erupted the most evolved compositions. The later PDCs, the Breccia Museo and Upper Pumice Flow, erupted during and after caldera collapse, tap a less evolved component, and intermediate compositions that represent mixing between the end-members. The range of glass compositions in the Campanian Ignimbrite deposits from sites across the central and eastern Mediterranean Sea allow us to trace the dispersal of the different phases of this caldera-forming eruption. We map the fallout from the Plinian column and the plumes of fine material associated with the PDCs (co-PDCs) across the entire dispersal area. This cannot be done using the usual grain-size methods as deposits in these distal regions do not retain characteristics that allow attribution to either the Plinian or co-PDC phases. The glass compositions of the tephra at ultra-distal sites (>1500 km from the vent) match those of the uppermost PDC units, suggesting that most of the ultra-distal dispersal was associated with the late co-PDC plume that was generated during caldera collapse.

Constraining Star Formation in Old Stellar Populations from Theoretical Spectra

NASA Astrophysics Data System (ADS)

Peterson, R. C.

2007-12-01

We are calculating stellar spectra using Kurucz codes, Castelli models, and Kurucz laboratory lines plus guesses; but must first finish adjusting gf values to match stars of solar metallicity and higher. We show that even now, 1D LTE spectral calculations fit a wide range of stellar spectra (from A to K types) over 2200 Å-9000Å once gf values are set to optimize them. Moreover, weighted coadditions of spectral calculations can be constructed that match M31 globular clusters over this entire wavelength range. Both stellar and composite grids will be archived on MAST. The age-metallicity degeneracy can be broken, but only with high-quality data, and only if rare stages of stellar evolution are incorporated where necessary.

Pattern-based, multi-scale segmentation and regionalization of EOSD land cover

NASA Astrophysics Data System (ADS)

Niesterowicz, Jacek; Stepinski, Tomasz F.

2017-10-01

The Earth Observation for Sustainable Development of Forests (EOSD) map is a 25 m resolution thematic map of Canadian forests. Because of its large spatial extent and relatively high resolution the EOSD is difficult to analyze using standard GIS methods. In this paper we propose multi-scale segmentation and regionalization of EOSD as new methods for analyzing EOSD on large spatial scales. Segments, which we refer to as forest land units (FLUs), are delineated as tracts of forest characterized by cohesive patterns of EOSD categories; we delineated from 727 to 91,885 FLUs within the spatial extent of EOSD depending on the selected scale of a pattern. Pattern of EOSD's categories within each FLU is described by 1037 landscape metrics. A shapefile containing boundaries of all FLUs together with an attribute table listing landscape metrics make up an SQL-searchable spatial database providing detailed information on composition and pattern of land cover types in Canadian forest. Shapefile format and extensive attribute table pertaining to the entire legend of EOSD are designed to facilitate broad range of investigations in which assessment of composition and pattern of forest over large areas is needed. We calculated four such databases using different spatial scales of pattern. We illustrate the use of FLU database for producing forest regionalization maps of two Canadian provinces, Quebec and Ontario. Such maps capture the broad scale variability of forest at the spatial scale of the entire province. We also demonstrate how FLU database can be used to map variability of landscape metrics, and thus the character of landscape, over the entire Canada.

THE DIMENSIONS OF COMPOSITION ANNOTATION.

ERIC Educational Resources Information Center

MCCOLLY, WILLIAM

ENGLISH TEACHER ANNOTATIONS WERE STUDIED TO DETERMINE THE DIMENSIONS AND PROPERTIES OF THE ENTIRE SYSTEM FOR WRITING CORRECTIONS AND CRITICISMS ON COMPOSITIONS. FOUR SETS OF COMPOSITIONS WERE WRITTEN BY STUDENTS IN GRADES 9 THROUGH 13. TYPESCRIPTS OF THE COMPOSITIONS WERE ANNOTATED BY CLASSROOM ENGLISH TEACHERS. THEN, 32 ENGLISH TEACHERS JUDGED…

3D hierarchically porous Cu-BiOCl nanocomposite films: one-step electrochemical synthesis, structural characterization and nanomechanical and photoluminescent properties.

PubMed

Guerrero, Miguel; Pané, Salvador; Nelson, Bradley J; Baró, Maria Dolors; Roldán, Mònica; Sort, Jordi; Pellicer, Eva

2013-12-21

Three-dimensional (3D) hierarchically porous composite Cu-BiOCl films have been prepared by a facile one-step galvanostatic electrodeposition process from acidic electrolytic solutions containing Cu(ii) and Bi(iii) chloride salts and Triton X-100. The films show spherical, micron-sized pores that spread over the whole film thickness. In turn, the pore walls are made of randomly packed BiOCl nanoplates that are assembled leaving micro-nanopore voids beneath. It is believed that Cu grows within the interstitial spaces between the hydrogen bubbles produced from the reduction of H(+) ions. Then, the BiOCl sheets accommodate in the porous network defined by the Cu building blocks. The presence of Cu tends to enhance the mechanical stability of the composite material. The resulting porous Cu-BiOCl films exhibit homogeneous and stable-in-time photoluminescent response arising from the BiOCl component that spreads over the entire 3D porous structure, as demonstrated by confocal scanning laser microscopy. A broad-band emission covering the entire visible range, in the wavelength interval 450-750 nm, is obtained. The present work paves the way for the facile and controlled preparation of a new generation of photoluminescent membranes.

Effect of Tunable Surface Potential on the Structure of Spin-Cast Polymeric Blend Films

NASA Astrophysics Data System (ADS)

Hawker, C.; Huang, E.; Russell, T. P.

1998-03-01

The demixing of binary polymeric mixtures has been studied with various surface potentials. This was performed by spin casting polystyrene/poly(methyl methacrylate) mixtures on to silicon substrates that had been modified with an end-grafted random copolymer brush layer. The composition of the random copolymer brush, containing the same monomeric components as the homopolymers can be varied in a precise manner over the entire concentration range. Atomic force and optical microscopy were used to study the morphology formed during spin casting and after annealing. Further insight into the structure was gained by rinsing these films with preferential solvents to remove one of the constituents and by performing the microscopy measurements. Finally, x-ray photoelectron spectroscopy, XPS, was used to elucidate the composition of the film near the air/polymer interface. Our data show that the resulting thin film structure depends strongly on the composition of the end grafted random copolymer film. Furthermore, the effect of thickness, solvent used in casting, and annealing conditions will be addressed.

Biophysical Constraints Arising from Compositional Context in Synthetic Gene Networks.

PubMed

Yeung, Enoch; Dy, Aaron J; Martin, Kyle B; Ng, Andrew H; Del Vecchio, Domitilla; Beck, James L; Collins, James J; Murray, Richard M

2017-07-26

Synthetic gene expression is highly sensitive to intragenic compositional context (promoter structure, spacing regions between promoter and coding sequences, and ribosome binding sites). However, much less is known about the effects of intergenic compositional context (spatial arrangement and orientation of entire genes on DNA) on expression levels in synthetic gene networks. We compare expression of induced genes arranged in convergent, divergent, or tandem orientations. Induction of convergent genes yielded up to 400% higher expression, greater ultrasensitivity, and dynamic range than divergent- or tandem-oriented genes. Orientation affects gene expression whether one or both genes are induced. We postulate that transcriptional interference in divergent and tandem genes, mediated by supercoiling, can explain differences in expression and validate this hypothesis through modeling and in vitro supercoiling relaxation experiments. Treatment with gyrase abrogated intergenic context effects, bringing expression levels within 30% of each other. We rebuilt the toggle switch with convergent genes, taking advantage of supercoiling effects to improve threshold detection and switch stability. Copyright © 2017 Elsevier Inc. All rights reserved.

Composite nanostructures induced by water-confined femtosecond laser pulses irradiation on GaAs/Ge solar cell surface for anti-reflection

NASA Astrophysics Data System (ADS)

Li, Zhibao; Guan, Xiaoxiao; Hua, Yinqun; Hui, Shuangmou

2018-10-01

Composite nanostructures (CNs) composed of random nano-pores and nano-protrusions were fabricated on the surface of the GaAs/Ge solar cell by water-confined femtosecond laser processing. The result of the FESEM and AFM revealed that the size of the CNs is about 300-500 nm. In order to research the evolution of the CNs, a group of laser irradiation under different number of pulses from 50 to 400 was performed on the cell surface. In conclusion, the formation mechanism is concerned to the generation of microbubbles and the interaction between the laser-induced plasma and the nano-roughness. The CNs effectively promote the antireflection performance and suppress the surface reflectivity to 8.9% over the entire wavelength range (300-1200 nm).

Study of thermodynamic and transport properties of binary liquid mixture of diesel with biodiesel at 298.15K

NASA Astrophysics Data System (ADS)

Suthar, Shyam Sunder; Purohit, Suresh

2018-05-01

Properties of diesel and biodiesel (produced from corn oil) are used. Densities and viscosities of binary mixture of diesel with biodiesel (produced from corn oil) have been computed by using liquid binary mixture law over the entire range of compositions at T=298.15K and atmospheric pressure. From the computed values of density and viscosities, viscosity deviation (Δη), the excess molar volume (VE) and excess Gibbs energy of activation of viscous flow (ΔG#E) have been calculated. The results of excess volume, excess Gibbs energy of activation of viscous flow and viscosity deviation have been fitted to Redlich -Kister models to estimate the binary coefficients. The results are communicated in terms of the molecular interactions and the best suited composition has been found.

MESSENGER's first Mercury flyby: A summary of scientific observations

NASA Astrophysics Data System (ADS)

Solomon, Sean C.; McNutt, Ralph L.; Boynton, William V.; Evans, Larry G.; Head, James W.; Krimigis, Stamatios M.; Murchie, Scott; Phillips, Roger J.; Slavin, James A.; Zuber, Maria T.

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, developed under NASA's Discovery Program, will be the first probe to orbit the planet Mercury in March 2011. Launched in August 2004, MESSENGER successfully completed the first of three flybys of Mercury in January 2008. The Mercury Dual Imaging System acquired an 11-color mosaic of part of the hemisphere not seen by Mariner 10, including the entire Caloris basin; several large monochrome mosaics at a range of resolutions; a series of color frames designed for photometric analysis; and inbound and outbound movies. The Mercury Atmospheric and Surface Composition Spectrometer obtained the first high-resolution spectral reflectance measurements (at ultraviolet to near-infrared wavelengths) of surface composition, conducted limb scans of exospheric species, and mapped the composition and structure of the tail region. The Magnetometer measured Mercury's internal field at low latitudes and documented the major plasma boundaries of Mercury's magnetosphere. The Energetic Particle and Plasma Spectrometer made the first measurements of low-energy ions in Mercury's magnetosphere. The Mercury Laser Altimeter carried out the first space altimetric profile of the planet. Other instruments in the payload provided baseline measurements that will aid in the interpretation of data from the mission orbital phase. Together, the MESSENGER flyby observations have begun to advance our understanding of the innermost planet.

Dielectric and spectroscopic study of binary mixture of Acrylonitrile with Chlorobenzene

NASA Astrophysics Data System (ADS)

Deshmukh, Snehal D.; Pattebahadur, K. L.; Mohod, A. G.; Undre, P. B.; Patil, S. S.; Khirade, P. W.

2018-05-01

In this paper, study of binary mixture of Acrylonitrile (ACN) with Chlorobenzene (CBZ) has been carried out at eleven concentrations at room temperature. The determined Dielectric Constant (ɛ0) Density (ρ) and Refractive index (nD) values of binary mixture are used to calculate the excess properties of mixture over the entire composition range and fitted to the Redlich-Kister equation. From the above parameters, intermolecular interaction and dynamics of molecules of binary mixture at molecular level are discussed. The Conformational analysis of the intermolecular interaction between Acrylonitrile and Chlorobenzene is supported by the FTIR spectra.

Mainbelt asteroids - Dual-polarization radar observations

NASA Technical Reports Server (NTRS)

Ostro, S. J.; Campbell, D. B.; Shapiro, I. I.

1985-01-01

Observations of 20 asteroids in the main belt between Mars and Jupiter provide information about the nature of these objects' surfaces at centimeter-to-kilometer scales. At least one asteroid (Pallas) is extremely smooth at centimeter-to-meter scales. Each asteroid appears much rougher than the moon at some scale between several meters and many kilometers. The range of asteroid radar albedos is very broad and implies substantial variations in porosity or metal concentration (or both). The highest albedo estimate, for the asteroid Psyche, is consistent with a surface having porosities typical of lunar soil and a composition nearly entirely metallic.

A cotton fabric modified with a hydrogel containing ZnO nanoparticles. Preparation and properties study

NASA Astrophysics Data System (ADS)

Staneva, Desislava; Atanasova, Daniela; Vasileva-Tonkova, Evgenia; Lukanova, Varbina; Grabchev, Ivo

2015-08-01

Two different methods were used to obtain composite materials based on a ZnO nanoparticles-hydrogel-cotton fabric. The hydrogels, synthesized by photopolymerization, were utilized to provide uniform distribution and binding of the nanoparticles to the fiber surface and to prevent their agglomeration. N-methyldiethanolamine (MDEA) was used as a co-initiator in hydrogel photopolymerization and as an alkaline agent in the synthesis of ZnO nanoparticles. Due to the difference in size, shape and morphology of the nanoparticles, examined by a TEM and SEM, it was found that the materials have distinct photoluminescence properties, e.g. in the entire visible or UV range. The composite materials with small size nanoparticles and photoluminescence in near UV range were investigated for antibiotic activity against the bacterial strains Pseudomonas aeruginosa and Acinetobacter johnsonii known as important pathogens in clinical infections. Significantly high antibacterial effect on the bacteria tested was achieved, especially on A. johnsonii. This suggests potential application of the new formulations as effective wound dressings to control the spread of infections.

Phase fields of nickel silicides obtained by mechanical alloying in the nanocrystalline state

NASA Astrophysics Data System (ADS)

Datta, M. K.; Pabi, S. K.; Murty, B. S.

2000-06-01

Solid state reactions induced by mechanical alloying (MA) of elemental blends of Ni and Si have been studied over the entire composition range of the Ni-Si system. A monotonous increase of the lattice parameter of the Ni rich solid solution, Ni(Si), is observed with refinement of crystallite size. Nanocrystalline phase/phase mixtures of Ni(Si), Ni(Si)+Ni31Si12, Ni31Si12+Ni2Si, Ni2Si+NiSi and NiSi+Si, have been obtained during MA, over the composition ranges of 0-10, 10-28, 28-33, 33-50, and >50 at. % Si, respectively. The results clearly suggest that only congruent melting phases, Ni31Si12, Ni2Si, and NiSi form, while the formation of noncongruent melting phases, Ni3Si, Ni3Si2, and NiSi2, is bypassed in the nanocrystalline state. The phase formation during MA has been discussed based on thermodynamic arguments. The predicted phase fields obtained from effective free energy calculations are quite consistent with those obtained during MA.

Natural and human-induced variability in the composition of fish assemblages in the Northwestern Cuban shelf.

PubMed

González-Sansón, Gaspar; Aguilar, Consuelo; Hernández, Ivet; Cabrera, Yureidy; Suarez-Montes, Noelis; Bretos, Fernando; Guggenheim, David

2009-09-01

The main goal of the study was to obtain field data to build a baseline of fish assemblage composition that can be used comparatively for future analyses of the impact of human actions in the region. A basic network of 68 sampling stations was defined for the entire region (4,050 km2). Fish assemblage species and size composition was estimated using visual census methods at three different spatial scales: a) entire region, b) inside the main reef area and c) along a human impact coastal gradient. Multivariate numerical analyses revealed habitat type as the main factor inducing spatial variability of fish community composition, while the level of human impact appears to play the main role in fish assemblage composition changes along the coast. A trend of decreasing fish size toward the east supports the theory of more severe human impact due to overfishing and higher urban pollution in that direction. This is the first detailed study along the northwest coast of Cuba that focuses on fish community structure and the natural and human-induced variations at different spatial scales for the entire NW shelf. This research also provides input for a more comprehensive understanding of coastal marine fish communities' status in the Gulf of Mexico basin.

Method for Qualification of Composite Repairs for Pipelines: Patch Repairs and Considerations for Cathodic Protection

DOT National Transportation Integrated Search

2009-12-03

While the mechanical properties of composite repairs for pipelines have been investigated extensively, the performance of the entire metal-composite system has not been addressed with regard to corrosion of the substrate, water intrusion at the compo...

Stable Isotope Systematics in Grasshopper Assemblages Along an Elevation Gradient, Colorado

NASA Astrophysics Data System (ADS)

Kohn, M. J.; Evans, S.; Dean, J.; Nufio, C.

2012-12-01

Insects comprise over three quarters of all animal species, yet studies of body water isotopic composition are limited to only the cockroach, the hoverfly, and chironomid flies. These studies suggest that oxygen and hydrogen isotopic compositions in body water are primarily controlled by dietary water sources, with modification from respiratory and metabolic processes. In particular, outward diffusion of isotopically depleted water vapor through insect spiracles at low humidity enriches residual body water in 18O and 2H (D). Stable isotope compositions (δ18O and δD) also respond to gradients in elevation and humidity, but these influences remain poorly understood. In this study, we measured grasshopper body water and local vegetation isotopic compositions along an elevation gradient in Colorado to evaluate three hypotheses: 1) Insect body water isotopic composition is directly related to food source water composition 2) Water vapor transport alters body water isotopic compositions relative to original diet sources, and 3) Elevation gradients influence isotopic compositions in insect body water. Thirty-five species of grasshopper were collected from 14 locations in Colorado grasslands, ranging in elevation from 450 to 800 meters (n=131). Body water was distilled from previously frozen grasshopper specimens using a vacuum extraction line, furnaces (90 °C), and liquid nitrogen traps. Water samples were then analyzed for δ18O and δD on an LGR Liquid Water Isotope Analyzer, housed in the Department of Geosciences, Boise State University. Grasshopper body water isotopic compositions show wide variation, with values ranging between -76.64‰ to +42.82‰ in δD and -3.06‰ to +26.78‰ in δ18O. Precipitation δ18O values over the entire Earth excluding the poles vary by approximately 30‰, comparable to the total range measured in our single study area. Most grasshopper values deviate from the global meteoric water line relating δ18O and δD in precipitation, consistent with evaporative enrichment in food (plants) due to plant transpiration. However, grasshopper body water from any given location is further enriched in 18O and D relative to food. Isotopic values decrease slightly with increasing elevation, but some specific grasshopper species appear more sensitive to elevation. Overall, evaporative enrichment of 18O and D in this relatively dry environment appears the strongest factors influencing grasshopper compositions.

Effect of weight fraction of carbon black and number of plies of E-glass fiber to reflection loss of E-glass/ripoxy composite for radar absorbing structure (RAS)

NASA Astrophysics Data System (ADS)

Widyastuti, Ramadhan, Rizal; Ardhyananta, Hosta; Zainuri, Mochamad

2013-09-01

Nowadays, studies on investigating radar absorbing structure (RAS) using fiber reinforced polymeric (FRP) composite materials are becoming popular research field because the electromagnetic properties of FRP composites can be tailored effectively by just adding some electromagnetic powders, such as carbon black, ferrite, carbonyl iron, and etc., to the matrix of composites. The RAS works not only as a load bearing structure to hold the antenna system, but also has the important function of absorbing the in-band electromagnetic wave coming from the electromagnetic energy of tracking systems. In this study, E-glass fiber reinforced ripoxy resin composite was fabricated by blending the conductive carbon black (Ketjenblack EC300J) with the binder matrix of the composite material and maximizing the coefficient of absorption more than 90% (more than -10 dB) within the X-band frequency (8 - 12 GHz). It was measured by electrical conductivity (LCR meter) and vector network analyzer (VNA). Finally, the composite RAS with 0.02 weight fraction of carbon black and 4 plies of E-glass fiber showed thickness of 2.1 mm, electrical conductivity of 8.33 × 10-6 S/m, and maximum reflection loss of -27.123 dB, which can absorb more than 90% of incident EM wave throughout the entire X-band frequency range, has been developed.

Space use and movements of moose in Massachusetts: implications for conservation of large mammals in a fragmented environment

USGS Publications Warehouse

Wattles, David W.; DeStefano, Stephen

2013-01-01

Moose (Alces alces) have recently re-occupied a portion of their range in the temperate deciduous forest of the northeastern United States after a >200 year absence. In southern New England, moose encounter different forest types, more human development, and higher temperatures than in other parts of their geographic range in North America. We analyzed seasonal minimum convex polygon home ranges, utilization distributions, movement rates, and home range composition of GPS-collared moose in Massachusetts. Seasonal home range sizes were not different for males and females and were within the range reported for low latitudes elsewhere in North America. Seasonal movement patterns reflected the seasonal changes in metabolic rate and the influence of the species’ reproductive cycle and weather. Home ranges consisted almost entirely of forested habitat, included large amounts of conservation land, and had lower road densities as compared to the landscape as a whole, indicating that human development may be a limiting factor for moose in the region. The size and configuration of home ranges, seasonal movement patterns, and use relative to human development have implications for conservation of moose and other wide-ranging species in more highly developed portions of their ranges.

Potential Impacts of Climate Change on Insect Communities: A Transplant Experiment

PubMed Central

Nooten, Sabine S.; Andrew, Nigel R.; Hughes, Lesley

2014-01-01

Climate change will have profound impacts on the distribution, abundance and ecology of all species. We used a multi-species transplant experiment to investigate the potential effects of a warmer climate on insect community composition and structure. Eight native Australian plant species were transplanted into sites approximately 2.5°C (mean annual temperature) warmer than their native range. Subsequent insect colonisation was monitored for 12 months. We compared the insect communities on transplanted host plants at the warmer sites with control plants transplanted within the species' native range. Comparisons of the insect communities were also made among transplanted plants at warmer sites and congeneric plant species native to the warmer transplant area. We found that the morphospecies composition of the colonising Coleoptera and Hemiptera communities differed markedly between transplants at the control compared to the warmer sites. Community structure, as described by the distribution of feeding guilds, was also found to be different between the controls and transplants when the entire Coleoptera and Hemiptera community, including non-herbivore feeding guilds, was considered. However, the structure of the herbivorous insect community showed a higher level of consistency between plants at control and warm sites. There were marked differences in community composition and feeding guild structure, for both herbivores and non-herbivores, between transplants and congenerics at the warm sites. These results suggest that as the climate warms, considerable turnover in the composition of insect communities may occur, but insect herbivore communities may retain elements of their present-day structure. PMID:24465827

The hierarchical structure and mechanics of plant materials.

PubMed

Gibson, Lorna J

2012-11-07

The cell walls in plants are made up of just four basic building blocks: cellulose (the main structural fibre of the plant kingdom) hemicellulose, lignin and pectin. Although the microstructure of plant cell walls varies in different types of plants, broadly speaking, cellulose fibres reinforce a matrix of hemicellulose and either pectin or lignin. The cellular structure of plants varies too, from the largely honeycomb-like cells of wood to the closed-cell, liquid-filled foam-like parenchyma cells of apples and potatoes and to composites of these two cellular structures, as in arborescent palm stems. The arrangement of the four basic building blocks in plant cell walls and the variations in cellular structure give rise to a remarkably wide range of mechanical properties: Young's modulus varies from 0.3 MPa in parenchyma to 30 GPa in the densest palm, while the compressive strength varies from 0.3 MPa in parenchyma to over 300 MPa in dense palm. The moduli and compressive strength of plant materials span this entire range. This study reviews the composition and microstructure of the cell wall as well as the cellular structure in three plant materials (wood, parenchyma and arborescent palm stems) to explain the wide range in mechanical properties in plants as well as their remarkable mechanical efficiency.

The hierarchical structure and mechanics of plant materials

PubMed Central

Gibson, Lorna J.

2012-01-01

The cell walls in plants are made up of just four basic building blocks: cellulose (the main structural fibre of the plant kingdom) hemicellulose, lignin and pectin. Although the microstructure of plant cell walls varies in different types of plants, broadly speaking, cellulose fibres reinforce a matrix of hemicellulose and either pectin or lignin. The cellular structure of plants varies too, from the largely honeycomb-like cells of wood to the closed-cell, liquid-filled foam-like parenchyma cells of apples and potatoes and to composites of these two cellular structures, as in arborescent palm stems. The arrangement of the four basic building blocks in plant cell walls and the variations in cellular structure give rise to a remarkably wide range of mechanical properties: Young's modulus varies from 0.3 MPa in parenchyma to 30 GPa in the densest palm, while the compressive strength varies from 0.3 MPa in parenchyma to over 300 MPa in dense palm. The moduli and compressive strength of plant materials span this entire range. This study reviews the composition and microstructure of the cell wall as well as the cellular structure in three plant materials (wood, parenchyma and arborescent palm stems) to explain the wide range in mechanical properties in plants as well as their remarkable mechanical efficiency. PMID:22874093

Invar alloys: information from the study of iron meteorites.

NASA Astrophysics Data System (ADS)

Goldstein, J. I.; Williams, D. B.; Zhang, J.; Clarke, R.

The iron meteorites were slow cooled (<108years) in their asteroidal bodies and are useful as indicators of the phase transformations which occur in Fe-Ni alloys. In the invar composition range, the iron meteorites contain a cloudy zone structure composed of an ordered tetrataenite phase and a surrounding honeycomb phase either of gamma or alpha phase. This structure is the result of a spinodal reaction below 350°C. The Santa Catharina iron meteorite has the typical invar composition of 36 wt% Ni and its structure is entirely cloudy zone although some of the honeycomb phase has been oxidized by terrestrial corrosion. Invar alloys would contain such a cloudy zone structure if more time was available for cooling. A higher temperature spinodal in the Fe-Ni phase diagram may be operative in invar alloys but has not been observed in the structure of the iron meteorites.

Multimodal correlative investigation of the interplaying micro-architecture, chemical composition and mechanical properties of human cortical bone tissue reveals predominant role of fibrillar organization in determining microelastic tissue properties.

PubMed

Schrof, Susanne; Varga, Peter; Hesse, Bernhard; Schöne, Martin; Schütz, Roman; Masic, Admir; Raum, Kay

2016-10-15

The mechanical competence of bone is crucially determined by its material composition and structural design. To investigate the interaction of the complex hierarchical architecture, the chemical composition and the resulting elastic properties of healthy femoral bone at the level of single bone lamellae and entire structural units, we combined polarized Raman spectroscopy (PRS), scanning acoustic microscopy (SAM) and synchrotron X-ray phase contrast nano tomography (SR-nanoCT). In line with earlier studies, mutual correlation analysis strongly suggested that the characteristic elastic modulations of bone lamellae within single units are the result of the twisting fibrillar orientation, rather than compositional variations, modulations of the mineral particle maturity, or mass density deviations. Furthermore, we show that predominant fibril orientations in entire tissue units can be rapidly assessed from Raman parameter maps. Coexisting twisted and oscillating fibril patterns were observed in all investigated tissue domains. Ultimately, our findings demonstrate in particular the potential of combined PRS and SAM measurements in providing multi-scalar analysis of correlated fundamental tissue properties. In future studies, the presented approach can be applied for non-destructive investigation of small pathologic samples from bone biopsies and a broad range of biological materials and tissues. Bone is a complex structured composite material consisting of collagen fibrils and mineral particles. Various studies have shown that not only composition, maturation, and packing of its components, but also their structural arrangement determine the mechanical performance of the tissue. However, prominent methodologies are usually not able to concurrently describe these factors on the micron scale and complementary tissue characterization remains challenging. In this study we combine X-ray nanoCT, polarized Raman imaging and scanning acoustic microscopy and propose a protocol for fast and easy assessment of predominant fibril orientations in bone. Based on our site-matched analysis of cortical bone, we conclude that the elastic modulations of bone lamellae are mainly determined by the fibril arrangement. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Heated tool for autoclaves

NASA Technical Reports Server (NTRS)

Serafini, T. T.; Vanucci, R. D.; Cavano, P. J.; Winters, W. E.

1980-01-01

Components made of composite materials are heated in autoclaves by employing electrical resistance heating blankets, thus avoiding need to heat entire autoclave volume. Method provides not only significant energy savings compared to heating entire pressure vessel but offers time savings in accelerated heat-up and cool-down cycles.

Sturgeon and paddlefish (Acipenseridae) saggital otoliths are composed of the calcium carbonate polymorphs vaterite and calcite: acipenseridae otoliths are vaterite and calcite

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

Pracheil, Brenda M.; Chakoumakos, Bryan C.; Feygenson, Mikhail

The otoliths of modern fishes are most commonly comprised of the metastable aragonite polymorph of calcium carbonate (CaCO3); however, sturgeons have otoliths reportedly comprised of the least stable of the three most-common polymorphs, vaterite. In this study, we used neutron diffraction to characterize CaCO3 polymorph composition of lake sturgeon and paddlefish otoliths. Based on previous summaries of CaCO3 composition over fish evolutionary history, we hypothesized that sturgeon and paddlefish otoliths would have similar polymorph composition. We found that despite previous reports of sturgeon otoliths being comprised entirely of vaterite, that all otoliths we examined in this study also had amore » calcite fraction that ranged from 17.9+ 6.0 wt. % to 35.9 + 2.9 wt. %. We also conducted a grinding experiment that demonstrated that calcite fractions were due to biological variation and not an artifact of polymorph transformation during preparation. Our study provides the initial characterization of the polymorph composition of the otoliths of lake sturgeon, and paddlefish and also provides the first-ever report of otoliths of Acipenserids as having a calcite fraction.« less

Sturgeon and paddlefish (Acipenseridae) saggital otoliths are composed of the calcium carbonate polymorphs vaterite and calcite: acipenseridae otoliths are vaterite and calcite

DOE PAGES

Pracheil, Brenda M.; Chakoumakos, Bryan C.; Feygenson, Mikhail; ...

2016-07-27

The otoliths of modern fishes are most commonly comprised of the metastable aragonite polymorph of calcium carbonate (CaCO3); however, sturgeons have otoliths reportedly comprised of the least stable of the three most-common polymorphs, vaterite. In this study, we used neutron diffraction to characterize CaCO3 polymorph composition of lake sturgeon and paddlefish otoliths. Based on previous summaries of CaCO3 composition over fish evolutionary history, we hypothesized that sturgeon and paddlefish otoliths would have similar polymorph composition. We found that despite previous reports of sturgeon otoliths being comprised entirely of vaterite, that all otoliths we examined in this study also had amore » calcite fraction that ranged from 17.9+ 6.0 wt. % to 35.9 + 2.9 wt. %. We also conducted a grinding experiment that demonstrated that calcite fractions were due to biological variation and not an artifact of polymorph transformation during preparation. Our study provides the initial characterization of the polymorph composition of the otoliths of lake sturgeon, and paddlefish and also provides the first-ever report of otoliths of Acipenserids as having a calcite fraction.« less

Wear mechanisms in hybrid composites of Graphite-20 Pct SiC in A356 Aluminum Alloy (Al-7 Pct Si-0.3 Pct Mg)

NASA Astrophysics Data System (ADS)

Ames, W.; Alpas, A. T.

1995-01-01

The wear behavior of A356 aluminum alloy (Al-7 Pct Si-0.3 Pct Mg) matrix composites reinforced with 20 vol Pct SiC particles and 3 or 10 vol Pct graphite was investigated. These hybrid composites represent the merging of two philosophies in tribological material design: soft-particle lubrication by graphite and hard-particle reinforcement by carbide particles. The wear tests were performed using a block-on-ring (SAE 52100 steel) wear machine under dry sliding conditions within a load range of 1 to 441 N. The microstructural and compositional changes that took place during wear were characterized using scanning electron microscopy (SEM), Auger electron spectroscopy (AES), energy-dispersive X-ray spectroscopy (EDXA), and X-ray diffractometry (XRD). The wear resistance of 3 Pct graphite-20 Pct SiC-A356 hybrid composite was comparable to 20 Pct SiC-A356 without graphite at low and medium loads. At loads below 20 N, both hybrid and 20 Pct SiC-A356 composites without graphite demonstrated wear rates up to 10 times lower than the unreinforced A356 alloy due to the load-carrying capacity of SiC particles. The wear resistance of 3 Pct graphite 20 Pct SiC-A356 was 1 to 2 times higher than 10 Pct graphite-containing hybrid composites at high loads. However, graphite addition reduced the counterface wear. The unreinforced A356 and 20 Pct SiC-A356 showed a transition from mild to severe wear at 95 N and 225 N, respectively. Hybrid composites with 3 Pct and 10 Pct graphite did not show such a transition over the entire load range, indicating that graphite improved the seizure resistance of the composites. Tribolayers, mainly consisting of a compacted mixture of graphite, iron oxides, and aluminum, were generated on the surfaces of the hybrid composites. In the hybrid composites, the elimination of the severe wear (and hence the improvement in seizure resistance) was attributed to the reduction in friction-induced surface heating due to the presence of graphite- and iron-oxide-containing tribolayers.

Linking Compositional and Functional Predictions to Decipher the Biogeochemical Significance in DFAA Turnover of Abundant Bacterioplankton Lineages in the North Sea.

PubMed

Wemheuer, Bernd; Wemheuer, Franziska; Meier, Dimitri; Billerbeck, Sara; Giebel, Helge-Ansgar; Simon, Meinhard; Scherber, Christoph; Daniel, Rolf

2017-11-05

Deciphering the ecological traits of abundant marine bacteria is a major challenge in marine microbial ecology. In the current study, we linked compositional and functional predictions to elucidate such traits for abundant bacterioplankton lineages in the North Sea. For this purpose, we investigated entire and active bacterioplankton composition along a transect ranging from the German Bight to the northern North Sea by pyrotag sequencing of bacterial 16S rRNA genes and transcripts. Functional profiles were inferred from 16S rRNA data using Tax4Fun. Bacterioplankton communities were dominated by well-known marine lineages including clusters/genera that are affiliated with the Roseobacter group and the Flavobacteria . Variations in community composition and function were significantly explained by measured environmental and microbial properties. Turnover of dissolved free amino acids (DFAA) showed the strongest correlation to community composition and function. We applied multinomial models, which enabled us to identify bacterial lineages involved in DFAA turnover. For instance, the genus Planktomarina was more abundant at higher DFAA turnover rates, suggesting its vital role in amino acid degradation. Functional predictions further indicated that Planktomarina is involved in leucine and isoleucine degradation. Overall, our results provide novel insights into the biogeochemical significance of abundant bacterioplankton lineages in the North Sea.

Optical losses of solar mirrors due to atmospheric contamination at Liberal, Kansas and Oologah, Oklahoma

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

Dake, L.S.; Lind, M.A.

An assessment is presented of the effect of outdoor exposure on mirrors located at two sites selected for potential solar cogeneration/repowering facilities: Liberal, Kansas and Oologah, Oklahoma. Mirror coupons were placed on tracking heliostat simulators located in the proposed heliostat fields and were removed periodically. The spectral hemispherical and diffuse reflectances of these coupons were measured. Representative samples were analyzed for the chemical composition of the dust particulates using SEM/EDX. Other samples were washed with a high pressure spray and recharacterized to determine the effects of the residual dust. Average specular reflectance losses over the entire test period (up tomore » 504 days) were 6 to 12%, with a range of 1 to 30%. Specular reflectance losses varied widely from day to day depending on local weather conditions. The losses due to scattering were 2 to 5 times greater than the losses due to absorptance. The average degradation rate over the first thirty days was an order of magnitude larger than the average degradation rate over the entire sampling period. Specular reflectance loss rates averaged 0.5% per day and greater between periods of natural cleaning. The chemical composition of the dust on the mirrors was characteristic of the indigenous soil, with some samples also showing the presence of sulfur and chlorine, possibly from cooling tower drift.« less

Investigation of intermolecular interaction of binary mixture of acrylonitrile with bromobenzene

NASA Astrophysics Data System (ADS)

Deshmukh, S. D.; Pattebahadur, K. L.; Mohod, A. G.; Patil, S. S.; Khirade, P. W.

2018-04-01

In this paper, study of binary mixture of Acrylonitrile (ACN)with Bromobenzene(BB) has been carried out at eleven concentrations at room temperature. The determined density(ρ) and refractive index (nD) values of binary mixture are used to calculate the excess properties of mixture over the entire composition range. The aforesaid parameters are used to calculate excess parameters and fitted to the Redlich-Kister equation to determine the bj coefficients. From the above parameters, intermolecular interaction and dynamics of molecules of binary mixture at molecular level are discussed. The Conformational analysis of the intermolecular interaction between Acrylonitrile and Bromobenzene is supported by the FTIR spectra.

Evidence from the lamarck granodiorite for rapid late cretaceous crust formation in California

USGS Publications Warehouse

Coleman, D.S.; Frost, T.P.; Glazner, A.F.

1992-01-01

Strontium and neodymium isotopic data for rocks from the voluminous 90-million-year-old Lamarck intrusive suite in the Sierra Nevada batholith, California, show little variation across a compositional range from gabbro to granite. Data for three different gabbro intrusions within the suite are identical within analytical error and are consistent with derivation from an enriched mantle source. Recognition of local involvement of enriched mantle during generation of the Sierran batholith modifies estimates of crustal growth rates in the United States. These data indicate that parts of the Sierra Nevada batholith may consist almost entirely of juvenile crust added during Cretaceous magmatism.

Composition, morphology and surface recombination rate of HCl-isopropanol treated and vacuum annealed InAs(1 1 1)A surfaces

NASA Astrophysics Data System (ADS)

Kesler, V. G.; Seleznev, V. A.; Kovchavtsev, A. P.; Guzev, A. A.

2010-05-01

X-ray photoelectron spectroscopy and atomic force microscopy were used to examine the chemical composition and surface morphology of InAs(1 1 1)A surface chemically etched in isopropanol-hydrochloric acid solution (HCl-iPA) and subsequently annealed in vacuum in the temperature range 200-500 °C. Etching for 2-30 min resulted in the formation of "pits" and "hillocks" on the sample surface, respectively 1-2 nm deep and high, with lateral dimensions 50-100 nm. The observed local formations, whose density was up to 3 × 10 8 cm -2, entirely vanished from the surface after the samples were vacuum-annealed at temperatures above 300 °C. Using a direct method, electron beam microanalysis, we have determined that the defects of the hillock type includes oxygen and excessive As, while the "pits" proved to be identical in their chemical composition to InAs. Vacuum anneals were found to cause a decrease in As surface concentration relative to In on InAs surface, with a concomitant rise of surface recombination rate.

Chemical thermodynamic representations of and

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

Besmann, T.M.; Lindemer, T.B.

1984-01-01

All available oxygen potential-temperature-composition data for the calcium fluorite-structure phase were retrieved from the literature and utilized in the development of a binary solid solution representation of the phase. The data and phase relations are found to be best described by a solution of (Pu/sub 4/3/O/sub 2/) and (PuO/sub 2/) with a temperature dependent interaction energy. The fluorite-structure is assumed to be represented by a combination of the binaries and , and thus treated as a solution of (Pu/sub 4/3/O/sub 2/), (PuO/sub 2/), (UO/sub 2/), and either (U/sub 2/O/sub 4/./sub 5/) or (U/sub 3/O/sub 7/). The resulting equations wellmore » reproduce the large amount of oxygen potential-temperature-composition data for the mixed oxide system, all of which were also retrieved from the literature. These models are the first that appear to display the appropriate oxygen potential-temperature-composition and phase relation behavior over the entire range of existence for the phases. 39 refs., 10 figs., 3 tabs.« less

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

Varley, J. B.; Conway, A. M.; Voss, L. F.

Thallium bromide (TlBr) crystals subjected to hydrochloric acid (HCl) chemical treatments have been shown to advantageously affect device performance and longevity in TlBr-based room temperature radiation detectors, yet the exact mechanisms of the improvements remain poorly understood. Here in this paper, we investigate the influence of several HCl chemical treatments on device-grade TlBr and describe the changes in the composition and electronic structure of the surface. Composition analysis and depth profiles obtained from secondary ion mass spectrometry (SIMS) identify the extent to which each HCl etch condition affects the detector surface region and forms of a graded TlBr/TlBr 1-xCL xmore » surface heterojunction. Using a combination of X-ray photoemission spectroscopy (XPS) and hybrid density functional calculations, we are able to determine the valence band offsets, band gaps, and conduction band offsets as a function of Cl content over the entire composition range of TIBr 1-xC1 X. This study establishes a strong correlation between device process conditions, surface chemistry, and electronic structure with the goal of further optimizing the long-term stability and radiation response of TlBr-based detectors.« less

Theoretical calculation of the melting curve of Cu-Zr binary alloys

DOE PAGES

Gunawardana, K. G.S.H.; Wilson, S. R.; Mendelev, M. I.; ...

2014-11-14

Helmholtz free energies of the dominant binary crystalline solids found in the Cu-Zr system at high temperatures close to the melting curve are calculated. This theoretical approach combines fundamental measure density functional theory (applied to the hard-sphere reference system) and a perturbative approach to include the attractive interactions. The studied crystalline solids are Cu(fcc), Cu 51Zr 14(β), CuZr(B 2), CuZr 2(C11b), Zr(hcp), and Zr(bcc). The calculated Helmholtz free energies of crystalline solids are in good agreement with results from molecular-dynamics (MD) simulations. Using the same perturbation approach, the liquid phase free energies are calculated as a function of composition andmore » temperature, from which the melting curve of the entire composition range of this system can be obtained. Phase diagrams are determined in this way for two leading embedded atom method potentials, and the results are compared with experimental data. Furthermore, theoretical melting temperatures are compared both with experimental values and with values obtained directly from MD simulations at several compositions.« less

Continuous process for forming sheet metal from an alloy containing non-dendritic primary solid

DOEpatents

Flemings, Merton C.; Matsuniya, Tooru

1983-01-01

A homogeneous mixture of liquid-solid metal is shaped by passing the composition from an agitation zone onto a surface moving relative to the exit of the agitation zone. A portion of the composition contacting the moving surface is solidified and the entire composition then is formed.

Dielectric properties of magnetic-ferroelectric CoO-NaNO2-porous glass nanocomposite

NASA Astrophysics Data System (ADS)

Koroleva, E. Yu.; Burdin, D. Yu.; Kumzerov, Yu. A.; Sysoeva, A. A.; Filimonov, A. V.; Vakhrushev, S. B.

2017-10-01

Dielectric properties of the nanostructured multiferroic composite on the basis of silicate porous glass simultaneously filled with ferromagnetic (cobalt oxide CoO) and ferroelectric (sodium nitrite) materials have been investigated in wide temperature (270-570 K) and frequency (10-1-107 Hz) ranges. The mean diameter of pores in the matrix is 7 ± 1 nm. The magnetic material particles are synthesized directly in the pores of the glass matrix and occupy about 10% of the pore volume. The porous glass is well wetted with NaNO2. The latter easily infiltrates into the glass and occupies 90% of the remaining unfilled pore volume. The dielectric response of matrices filled with both the components together and with each component separately is studied. An analysis of the obtained data makes it possible to reveal the contributions of individual components into the dielectric response of the composite and the influence of the confined geometry on their dielectric properties. It is found that the incorporation of CoO nanoparticles leads to an order of magnitude increase in the dielectric permittivity and electrical conductivity of the two-component composite in comparison with these values for the composite filled solely with sodium nitrite and to a decrease in the activation energy over the entire studied temperature range. These studies are of interest not only as a preliminary investigation prior to the study of the effect of a magnetic field on the dielectric properties of the synthesized composite, but are of independent physical interest as well, since they allow one to determine the influence of the confined geometry on the dielectric properties of magnetic metal oxides and on the of their phase transition parameters.

Atomic-level deformation of CuxZr100-x metallic glasses under shock loading

NASA Astrophysics Data System (ADS)

Demaske, Brian J.; Wen, Peng; Phillpot, Simon R.; Spearot, Douglas E.

2018-06-01

Plastic deformation mechanisms in CuxZr100-x bulk metallic glasses (MGs) subjected to shock are investigated using molecular dynamics simulations. MGs with Cu compositions between 30 and 70 at. % subjected to shock waves generated via piston velocities that range from 0.125 to 2.0 km/s are considered. In agreement with prior studies, plastic deformation is initiated via formation of localized regions of high von Mises shear strain, known as shear transformation zones (STZs). At low impact velocities, but above the Hugoniot elastic limit, STZ nucleation is dispersed behind the shock front. As impact velocity is increased, STZ nucleation becomes more homogeneous, eventually leading to shock-induced melting, which is identified in this work via high atomic diffusivity. The shear stress necessary to initiate plastic deformation within the shock front is independent of composition at shock intensities near the elastic limit but increases with increasing Cu content at high shock intensities. By contrast, both the flow stress in the plastically deformed MG and the critical shock pressure associated with melting behind the shock front are found to increase with increasing Cu content over the entire range of impact velocities. The evolution of the short-range order in the MG samples during shock wave propagation is analyzed using a polydisperse Voronoi tessellation method. Cu-centered polyhedra with full icosahedral symmetry are found to be most resistant to change under shock loading independent of the MG composition. A saturation is observed in the involvement of select Cu-centered polyhedra in the plastic deformation processes at a piston velocity around 0.75 km/s.

Role of crustal assimilation and basement compositions in the petrogenesis of differentiated intraplate volcanic rocks: a case study from the Siebengebirge Volcanic Field, Germany

NASA Astrophysics Data System (ADS)

Schneider, K. P.; Kirchenbaur, M.; Fonseca, R. O. C.; Kasper, H. U.; Münker, C.; Froitzheim, N.

2016-06-01

The Siebengebirge Volcanic Field (SVF) in western Germany is part of the Cenozoic Central European Volcanic Province. Amongst these volcanic fields, the relatively small SVF comprises the entire range from silica-undersaturated mafic lavas to both silica-undersaturated and silica-saturated differentiated lavas. Owing to this circumstance, the SVF represents a valuable study area representative of intraplate volcanism in Europe. Compositions of the felsic lavas can shed some new light on differentiation of intraplate magmas and on the extent and composition of potential crustal assimilation processes. In this study, we provide detailed petrographic and geochemical data for various differentiated SVF lavas, including major and trace element concentrations as well as Sr-Nd-Hf-Pb isotope compositions. Samples include tephriphonolites, latites, and trachytes with SiO2 contents ranging between 53 and 66 wt%. If compared to previously published compositions of mafic SVF lavas, relatively unradiogenic 143Nd/144Nd and 176Hf/177Hf coupled with radiogenic 87Sr/86Sr and 207Pb/204Pb lead to the interpretation that the differentiated volcanic rocks have assimilated significant amounts of lower crustal mafic granulites like the ones found as xenoliths in the nearby Eifel volcanic field. These crustal contaminants should possess unradiogenic 143Nd/144Nd and 176Hf/177Hf, radiogenic 87Sr/86Sr, and highly radiogenic 207Pb/204Pb compositions requiring the presence of ancient components in the central European lower crust that are not sampled on the surface. Using energy-constrained assimilation-fractional crystallisation (EC-AFC) model calculations, differentiation of the SVF lithologies can be modelled by approximately 39-47 % fractional crystallisation and 6-15 % crustal assimilation. Notably, the transition from silica-undersaturated to silica-saturated compositions of many felsic lavas in the SVF that is difficult to account for in closed-system models is also well explained by such amounts of crustal assimilation.

An unmetasomatized source for the Malaitan alnoeite (Solomon Islands): Petrogenesis involving zone refining, megacryst fractionation, and assimilation of oceanic lithosphere

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

Neal, C.R.; Davidson, J.P.

The Malaitan alnoite contains a rich and varied megacryst suite of unprecedented compositional range. The authors have undertaken trace element and isotope modeling in order to formulate a petrogenetic scheme which links the host alnoeite to its entrained megacrysts. This requires that a proto-alnoeite magma is the product of zone refining initiated by diapiric upwelling (where the initial melt passes through 200 times its volume of mantle). Isotopic evidence indicates the source of the proto-alnoeite contains a time-integrated LREE-depleted signature. Impingement upon the rigid lithosphere halts or dramatically slows the upward progress of the mantle diapir. At this point, themore » magma cools and megacryst fractionation begins with augites crystallizing first, followed by subcalcic diopsides and finally phlogopites. Garnet probably crystallizes over the entire range of clinopyroxene fractionation. Estimated proportions of fractionating phases are 30% augite, 24.5% subcalcic diopside, 27% garnet, 12.9% phlogopite, 5% bronzite, 0.5% ilmenite, and 0.1% zircon. As this proto-alnoeite magma crystallizes, it assimilates a subducted component of seawater-altered basalt which underplates the Ontong Java Plateau. This is witnessed in the isotopic composition of the megacrysts and alnoeite.« less

Description of Adsorption in Liquid Chromatography under Nonideal Conditions.

PubMed

Ortner, Franziska; Ruppli, Chantal; Mazzotti, Marco

2018-05-15

A thermodynamically consistent description of binary adsorption in reversed-phase chromatography is presented, accounting for thermodynamic nonidealities in the liquid and adsorbed phases. The investigated system involves the adsorbent Zorbax 300SB-C18, as well as phenetole and 4- tert-butylphenol as solutes and methanol and water as inert components forming the eluent. The description is based on adsorption isotherms, which are a function of the liquid-phase activities, to account for nonidealities in the liquid phase. Liquid-phase activities are calculated with a UNIQUAC model established in this work, based on experimental phase equilibrium data. The binary interaction in the adsorbed phase is described by the adsorbed solution theory, assuming an ideal (ideal adsorbed solution theory) or real (real adsorbed solution theory) adsorbed phase. Implementation of the established adsorption model in a chromatographic code achieves a quantitative description of experimental elution profiles, with feed compositions exploiting the entire miscible region, and involving a broad range of different eluent compositions (methanol/water). The quantitative agreement of the model and experimental data serves as a confirmation of the underlying physical (thermodynamic) concepts and of their applicability to a broad range of operating conditions.

Characterization of Sr-substituted W-type hexagonal ferrites synthesized by sol-gel autocombustion method

NASA Astrophysics Data System (ADS)

Ahmad, Mukhtar; Grössinger, R.; Kriegisch, M.; Kubel, F.; Rana, M. U.

2013-04-01

The magnetic and microwave characterization of single phase hexaferrites of entirely new composition Ba1-xSrxCo2AlFe15O27 (x=0.2-1.0) for application in a microwave absorber, have been reported. The samples synthesized by sol-gel method were investigated by differential thermal analyzer, Fourier transform infrared spectroscope, X-ray diffractometer, field emission gun scanning electron microscope, vibrating sample magnetometer and vector network analyzer. Platelet grains exhibit well defined hexagonal shape which is a better shape for microwave absorption. M-H loops for a selected sample were measured for a temperature range of 4.2-400 K. Moreover M-H loops for all Sr-substituted samples were also measured at room temperature up to a maximum applied field of 9 T. Saturation magnetization values were calculated by the law of approach to saturation. The room temperature coercivity for all the samples is found to be a few hundred oersteds which is necessary for electromagnetic materials and makes these ferrites ideal for microwave devices, security, switching and sensing applications. The complex permittivity, permeability and reflection losses of a selected ferrite-epoxy composite were also investigated over a frequency range of 0.5-13 GHz.

Magnetic cluster expansion model for random and ordered magnetic face-centered cubic Fe-Ni-Cr alloys

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

Lavrentiev, M. Yu., E-mail: Mikhail.Lavrentiev@ukaea.uk; Nguyen-Manh, D.; Dudarev, S. L.

A Magnetic Cluster Expansion model for ternary face-centered cubic Fe-Ni-Cr alloys has been developed, using DFT data spanning binary and ternary alloy configurations. Using this Magnetic Cluster Expansion model Hamiltonian, we perform Monte Carlo simulations and explore magnetic structures of alloys over the entire range of compositions, considering both random and ordered alloy structures. In random alloys, the removal of magnetic collinearity constraint reduces the total magnetic moment but does not affect the predicted range of compositions where the alloys adopt low-temperature ferromagnetic configurations. During alloying of ordered fcc Fe-Ni compounds with Cr, chromium atoms tend to replace nickel rathermore » than iron atoms. Replacement of Ni by Cr in ordered alloys with high iron content increases the Curie temperature of the alloys. This can be explained by strong antiferromagnetic Fe-Cr coupling, similar to that found in bcc Fe-Cr solutions, where the Curie temperature increase, predicted by simulations as a function of Cr concentration, is confirmed by experimental observations. In random alloys, both magnetization and the Curie temperature decrease abruptly with increasing chromium content, in agreement with experiment.« less

KASCADE-Grande: Composition studies in the view of the post-LHC hadronic interaction models

NASA Astrophysics Data System (ADS)

Haungs, A.; Apel, W. D.; Arteaga-Velázquez, J. C.; Bekk, K.; Bertaina, M.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; Pierro, F. Di; Doll, P.; Engel, R.; Fuhrmann, D.; Gherghel-Lascu, A.; Gils, H. J.; Glasstetter, R.; Grupen, C.; Heck, D.; Hörandel, J. R.; Huege, T.; Kampert, K.-H.; Kang, D.; Klages, H. O.; Link, K.; Łuczak, P.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Morello, C.; Oehlschläger, J.; Ostapchenko, S.; Pierog, T.; Rebel, H.; Roth, M.; Schieler, H.; Schoo, S.; Schröder, F. G.; Sima, O.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Zabierowski, J.

2017-06-01

The KASCADE-Grande experiment has significantly contributed to the current knowledge about the energy spectrum and composition of cosmic rays for energies between the knee and the ankle. Meanwhile, post-LHC versions of the hadronic interaction models are available and used to interpret the entire data set of KASCADE-Grande. In addition, a new, combined analysis of both arrays, KASCADE and Grande, was developed significantly increasing the accuracy of the shower observables. First results of the new analysis with the entire data set of the KASCADE-Grande experiment will be the focus of this contribution.

Cryptic trace-element alteration of Anorthosite, Stillwater complex, Montana

USGS Publications Warehouse

Czamanske, G.K.; Loferski, P.J.

1996-01-01

Evidence of cryptic alteration and correlations among K, Ba, and LREE concentrations indicate that a post-cumulus, low-density aqueous fluid phase significantly modified the trace-element contents of samples from Anorthosite zones I and II of the Stillwater Complex, Montana. Concentrations of Ba, Ca, Co, Cr, Cu, Fe, Hf, K, Li, Mg, Mn, Na, Ni, Sc, Sr, Th, Zn, and the rare-earth elements (REE) were measured in whole rocks and plagioclase separates from five traverses across the two main plagioclase cumulate (anorthosite) zones and the contiguous cumulates of the Stillwater Complex in an attempt to better understand the origin and solidification of the anorthosites. However, nearly the entire observed compositional range for many trace elements can be duplicated at a single locality by discriminating between samples rich in oikocrystic pyroxene and those which are composed almost entirely of plagioclase and show anhedral-granular texture. Plagioclase separates with high trace-element contents were obtained from the pyroxene-poor samples, for which maps of K concentration show plagioclase grains to contain numerous fractures hosting a fine-grained, K-rich phase, presumed to be sericite. Secondary processes in layered intrusions have the potential to cause cryptic disturbance, and the utmost care must be taken to ensure that samples provide information about primary processes. Although plagioclase from Anorthosite zones I and II shows significant compositional variation, there are no systematic changes in the major- or trace-element compositions of plagioclase over as much as 630 m of anorthosite thickness or 18 km of strike length. Plagioclase in the two major anorthosite zones shows little distinction in trace-element concentrations from plagioclase in the cumulates immediately below, between, and above these zones.

Isentropic expansion and related thermodynamic properties of non-ionic amphiphile-water mixtures.

PubMed

Reis, João Carlos R; Douhéret, Gérard; Davis, Michael I; Fjellanger, Inger Johanne; Høiland, Harald

2008-01-28

A concise thermodynamic formalism is developed for the molar isentropic thermal expansion, ES,m = ( partial differential Vm/ partial differential T)(Sm,x), and the ideal and excess quantities for the molar, apparent molar and partial molar isentropic expansions of binary liquid mixtures. Ultrasound speeds were determined by means of the pulse-echo-overlap method in aqueous mixtures of 2-methylpropan-2-ol at 298.15 K over the entire composition range. These data complement selected extensive literature data on density, isobaric heat capacity and ultrasound speed for 9 amphiphile (methanol, ethanol, propan-1-ol, propan-2-ol, 2-methylpropan-2-ol, ethane-1,2-diol, 2-methoxyethanol, 2-ethoxyethanol or 2-butoxyethanol)-water binary systems, which form the basis of tables listing molar and excess molar isobaric expansions and heat capacities, and molar and excess molar isentropic compressions and expansions at 298.15 K and at 65 fixed mole fractions spanning the entire composition range and fine-grained in the water-rich region. The dependence on composition of these 9 systems is graphically depicted for the excess molar isobaric and isentropic expansions and for the excess partial molar isobaric and isentropic expansions of the amphiphile. The analysis shows that isentropic thermal expansion properties give a much stronger response to amphiphile-water molecular interactions than do their isobaric counterparts. Depending on the pair property-system, the maximum excess molar isentropic value is generally twenty- to a hundred-fold greater than the corresponding maximum isobaric value, and occurs at a lower mole fraction of the amphiphile. Values at infinite dilution of the 9 amphiphiles in water are given for the excess partial molar isobaric heat capacity, isentropic compression, isobaric expansion and isentropic expansion. These values are interpreted in terms of the changes occurring when amphiphile molecules cluster into an oligomeric form. Present results are discussed from theoretical and experimental thermodynamic viewpoints. It is concluded that isentropic thermal expansion properties constitute a new distinct resource for revealing particular features and trends in complex mixing processes, and that analyses using these new properties compare favourably with conventional approaches.

Holocene Vegetation and Fire Dynamics for Ecosystem Management in the Spruce-Moss Domain in Northwestern Québec

NASA Astrophysics Data System (ADS)

Andy, H.; Blarquez, O.; Grondin, P.

2017-12-01

Facing the depletion of the wood resource in Québec and possible threats such as climate change, actors of the forest sector urge the need for a scientific frame to the forest management. A set of reference conditions has been developed for defining management targets that will help to keep forests within their natural range of variability according to the preindustrial period (XIX-XX centuries). Those reference conditions are based on the stands age-class distribution under a given fire regime that enable to define the percentage of old-growth forest (>100 years) to be maintained in a landscape. For the western spruce-moss domain in Québec, the fire return interval (FRI) is equal to 150 years resulting in a target of 48% of old-growth forests. Yet, this target supposes that the environment and the ecosystem processes are homogeneous for an entire bioclimatic domain of 175 000 km2. By using a Redundancy Analysis (RDA) on modern inventories data on natural and human disturbances; climate and physical variables and forest composition, we were able to distinguish 5 main zones where interactions between stands and their environment are homogeneous and where local management targets could be developed. We then used 10 published sedimentary pollens and charcoal series in order to reconstruct the holocene fire and vegetation dynamics for those zones. Vegetation deduced from the analysis of the pollen diagrams showed that the long-term vegetation dynamics are zone specific indicating that the modern forest composition is a result of the Holocene trajectories occurring within each zone. Charcoals series were statistically analyzed for past fire detection and long-term FRI reconstruction. They suggest that for the entire territory the holocene FRI range from 174 to 265 years resulting in old-growth forests percentage within 44 and 65% depending on the zone. Hence, we conclude that current management targets should be revised to fit more with local forests ecosystem variability at the landscape scale and that reference condition should be supplemented with data on the long-term fire dynamics and forest composition variability.

Base compositions of genes encoding alpha-actin and lactate dehydrogenase-A from differently adapted vertebrates show no temperature-adaptive variation in G + C content.

PubMed

Ream, Rachael A; Johns, Glenn C; Somero, George N

2003-01-01

There is a long-standing debate in molecular evolution concerning the putative importance of GC content in adapting the thermal stabilities of DNA and RNA. Most studies of this relationship have examined broad-scale compositional patterns, for example, total GC percentages in genomes and occurrence of GC-rich isochores. Few studies have systematically examined the GC contents of individual orthologous genes from differently thermally adapted species. When this has been done, the emphasis has been on comparing large numbers of genes in only a few species. We have approached the GC-adaptation temperature hypothesis in a different manner by examining patterns of base composition of genes encoding lactate dehydrogenase-A (ldh-a) and alpha-actin (alpha-actin) from 51 species of vertebrates whose adaptation temperatures ranged from -1.86 degrees C (Antarctic fishes) to approximately 45 degrees C (desert reptile). No significant positive correlation was found between any index of GC content (GC content of the entire sequence, GC content of the third codon position [GC(3)], and GC content at fourfold degenerate sites [GC(4)]) and any index of adaptation temperature (maximal, mean, or minimal body temperature). For alpha-actin, slopes of regression lines for all comparisons did not differ significantly from zero. For ldh-a, negative correlations between adaptation temperature and total GC content, GC(3), and GC(4) were observed but were shown to be due entirely to phylogenetic influences (as revealed by independent contrast analyses). This comparison of GC content across a wide range of ectothermic ("cold-blooded") and endothermic ("warm-blooded") vertebrates revealed that frogs of the genus Xenopus, which have commonly been used as a representative cold-blooded species, in fact are outliers among ectotherms for the alpha-actin analyses, raising concern about the appropriateness of choosing these amphibians as representative of ectothermic vertebrates in general. Our study indicates that, whereas GC contents of isochores may show variation among different classes of vertebrates, there is no consistent relationship between adaptation temperature and the percentage of thermal stability-enhancing G + C base pairs in protein-coding genes.

Albanian ophiolites as probes of a mantle heterogeneity study

NASA Astrophysics Data System (ADS)

Meisel, Thomas; Ginley, Stephen; Koller, Friedrich; Walker, Richard J.

2013-04-01

Most ophiolites are believed to be tectonically obducted slivers of oceanic lithosphere. As such they can provide information not only about the history of crust formation, but also about the composition of the chemical composition of the recent and ancient mantle composition. The occurrence of the well preserved Albanian Ophiolite Complex covers the length of Albania (ca. 150 km) is an ideal object not only for the study of the history of Jurassic tectonic event, but also for the study of the heterogeneity of the upper oceanic mantle from a millimeter to a 100 km scale. The occurrence of two almost parallel ophiolite chains, which have been described to be of different petrography presenting different parts of the upper mantle (MOR vs. SSZ type), allows the investigation of additional aspects of mantle heterogeneity. In this study we want to take advantage of the geochemical characteristics of platinum group elements (PGE) and of lithophile elements to estimate the extant of mantle melting, metasomatic and mixing events of a large portion of mantle obducted contemporaneously. In a first step only peridotites from the mantle sections of the ophiolite complexes are studied for the PGE content and the osmium isotopic composition. Together with major and trace element compositional data, following tasks will be addressed: development of a strategy for field and lab sampling, identification of processes that happened before and after obduction such as melt depletion, metasomatism, serpentinisation etc. and the determination of the size of modified and "pristine" domains. Samples from the western Albanian Ophiolite belt have been studied so far. Although the locations spread over the entire belt a remarkable similarity of PGE abundances is observed. In detail deviations from a correlation of Lu and TiO2 concentration data are also reflected in aberrant mantle normalized PGE patterns. Interestingly enough, this behavior is not manifested in a trend in the 187Os/188Os distribution. As a result the Os isotopic compositions of the entire belt represent the range to be expected from a post Archean upper mantle. The observed heterogeneous distribution of osmium isotopic compositions is most likely an image of the long depletion and incomplete remixing history of the upper Earth's mantle which was not significantly modified through event leading to the formation of ophiolite belts.

Composite Material from By-products and Its Properties

NASA Astrophysics Data System (ADS)

Šeps, K.; Broukalová, I.; Vodička, J.

2017-09-01

The paper shows an example of utilization of specific textile admixture - fluffs of torn textiles from waste cars in production of composite with aggregate consisting entirely of unsorted recycled concrete. The admixture in the mixture of recycled concrete and cement binder fills the pores and voids in composite. The elaborated composite has working title STEREDconcrete. In the article, basic mechanical-physical properties of the composite are presented also the fire resistance of STEREDconcrete, which was determined in tests.

Techniques and Tools for Trustworthy Composition of Pre-Designed Embedded Software Components

DTIC Science & Technology

2012-07-01

following option choices. 1. A plain vanilla pi-trie algorithm set to build the entire pi-trie. 2. A pi-trie algorithm filtered for positive prime...implicates only. 3. A plain vanilla pi-trie algorithm to build the entire pi-trie, but recognize variable-disjoint subformulas. 4. A pi-trie

Hydrodynamic Response of a Composite Structure in an Arctic Environment

DTIC Science & Technology

2015-06-01

the navy’s first ship constructed entirely of composite materials. The 24-meter long ship is built from carbon fiber reinforced epoxy. The ship is...allowed for repeatable experimentation. Strain gauges were attached to critical locations of the composite plate towed through the tank . Both plate...SUBJECT TERMS Tow Tank , Fluid Structure Interaction, FSI, Composite Material, E-Glass, ANSYS, Hull Shape, CFX, Arctic. 15. NUMBER OF PAGES 131

pH dominates variation in tropical soil archaeal diversity and community structure.

PubMed

Tripathi, Binu M; Kim, Mincheol; Lai-Hoe, Ang; Shukor, Nor A A; Rahim, Raha A; Go, Rusea; Adams, Jonathan M

2013-11-01

Little is known of the factors influencing soil archaeal community diversity and composition in the tropics. We sampled soils across a range of forest and nonforest environments in the equatorial tropics of Malaysia, covering a wide range of pH values. DNA was PCR-amplified for the V1-V3 region of the 16S rRNA gene, and 454-pyrosequenced. Soil pH was the best predictor of diversity and community composition of Archaea, being a stronger predictor than land use. Archaeal OTU richness was highest in the most acidic soils. Overall archaeal abundance in tropical soils (determined by qPCR) also decreased at higher pH. This contrasts with the opposite trend previously found in temperate soils. Thaumarcheota group 1.1b was more abundant in alkaline soils, whereas group 1.1c was only detected in acidic soils. These results parallel those found in previous studies in cooler climates, emphasizing niche conservatism among broad archaeal groups. Among the most abundant operational taxonomic units (OTUs), there was clear evidence of niche partitioning by pH. No individual OTU occurred across the entire range of pH values. Overall, the results of this study show that pH plays a major role in structuring tropical soil archaeal communities. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Bedrock composition regulates mountain ecosystems and landscape evolution

PubMed Central

Hahm, W. Jesse; Riebe, Clifford S.; Lukens, Claire E.; Araki, Sayaka

2014-01-01

Earth’s land surface teems with life. Although the distribution of ecosystems is largely explained by temperature and precipitation, vegetation can vary markedly with little variation in climate. Here we explore the role of bedrock in governing the distribution of forest cover across the Sierra Nevada Batholith, California. Our sites span a narrow range of elevations and thus a narrow range in climate. However, land cover varies from Giant Sequoia (Sequoiadendron giganteum), the largest trees on Earth, to vegetation-free swaths that are visible from space. Meanwhile, underlying bedrock spans nearly the entire compositional range of granitic bedrock in the western North American cordillera. We explored connections between lithology and vegetation using measurements of bedrock geochemistry and forest productivity. Tree-canopy cover, a proxy for forest productivity, varies by more than an order of magnitude across our sites, changing abruptly at mapped contacts between plutons and correlating with bedrock concentrations of major and minor elements, including the plant-essential nutrient phosphorus. Nutrient-poor areas that lack vegetation and soil are eroding more than two times slower on average than surrounding, more nutrient-rich, soil-mantled bedrock. This suggests that bedrock geochemistry can influence landscape evolution through an intrinsic limitation on primary productivity. Our results are consistent with widespread bottom-up lithologic control on the distribution and diversity of vegetation in mountainous terrain. PMID:24516144

The effect of altered lignin composition on mechanical properties of CINNAMYL ALCOHOL DEHYDROGENASE (CAD) deficient poplars.

PubMed

Özparpucu, Merve; Gierlinger, Notburga; Burgert, Ingo; Van Acker, Rebecca; Vanholme, Ruben; Boerjan, Wout; Pilate, Gilles; Déjardin, Annabelle; Rüggeberg, Markus

2018-04-01

CAD-deficient poplars enabled studying the influence of altered lignin composition on mechanical properties. Severe alterations in lignin composition did not influence the mechanical properties. Wood represents a hierarchical fiber-composite material with excellent mechanical properties. Despite its wide use and versatility, its mechanical behavior has not been entirely understood. It has especially been challenging to unravel the mechanical function of the cell wall matrix. Lignin engineering has been a useful tool to increase the knowledge on the mechanical function of lignin as it allows for modifications of lignin content and composition and the subsequent studying of the mechanical properties of these transgenics. Hereby, in most cases, both lignin composition and content are altered and the specific influence of lignin composition has hardly been revealed. Here, we have performed a comprehensive micromechanical, structural, and spectroscopic analysis on xylem strips of transgenic poplar plants, which are downregulated for cinnamyl alcohol dehydrogenase (CAD) by a hairpin-RNA-mediated silencing approach. All parameters were evaluated on the same samples. Raman microscopy revealed that the lignin of the hpCAD poplars was significantly enriched in aldehydes and reduced in the (relative) amount of G-units. FTIR spectra indicated pronounced changes in lignin composition, whereas lignin content was not significantly changed between WT and the hpCAD poplars. Microfibril angles were in the range of 18°-24° and were not significantly different between WT and transgenics. No significant changes were observed in mechanical properties, such as tensile stiffness, ultimate stress, and yield stress. The specific findings on hpCAD poplar allowed studying the specific influence of lignin composition on mechanics. It can be concluded that the changes in lignin composition in hpCAD poplars did not affect the micromechanical tensile properties.

Shelf Life of PMR Polyimide Monomer Solutions and Prepregs Extended

NASA Technical Reports Server (NTRS)

Alston, William B.; Scheiman, Daniel A.

2000-01-01

PMR (Polymerization of Monomeric Reactants) technology was developed in the mid-1970's at the NASA Glenn Research Center at Lewis Field for fabricating high-temperature stable polyimide composites. This technology allowed a solution of polyimide monomers or prepreg (a fiber, such as glass or graphite, impregnated with PMR polyimide monomers) to be thermally cured without the release of volatiles that cause the formation of voids unlike the non-PMR technology used for polyimide condensation type resins. The initial PMR resin introduced as PMR 15 is still commercially available and is used worldwide by aerospace industries as the state-of-the-art resin for high-temperature polyimide composite applications. PMR 15 offers easy composite processing, excellent composite mechanical property retention, a long lifetime at use temperatures of 500 to 550 F, and relatively low cost. Later, second-generation PMR resin versions, such as PMR II 50 and VCAP 75, offer improvements in the upper-use temperature (to 700 F) and in the useful life at temperature without major compromises in processing and property retention but with significant increases in resin cost. Newer versions of nontoxic (non-methylene dianiline) PMR resins, such as BAX PMR 15, offer similar advantages as originally found for PMR 15 but also with significant increases in resin cost. Thus, the current scope of the entire PMR technology available meets a wide range of aeronautical requirements for polymer composite applications.

Compositionally Dependent Nonlinear Optical Bandgap Behavior of Mixed Anodic Oxides in Niobium-Titanium System.

PubMed

Bleckenwegner, Petra; Mardare, Cezarina Cela; Cobet, Christoph; Kollender, Jan Philipp; Hassel, Achim Walter; Mardare, Andrei Ionut

2017-02-13

Optical bandgap mapping of Nb-Ti mixed oxides anodically grown on a thin film parent metallic combinatorial library was performed via variable angle spectroscopic ellipsometry (VASE). A wide Nb-Ti compositional spread ranging from Nb-90 at.% Ti to Nb-15 at.% Ti deposited by cosputtering was used for this purpose. The Nb-Ti library was stepwise anodized at potentials up to 10 V SHE, and the anodic oxides optical properties were mapped along the Nb-Ti library with 2 at.% resolution. The surface dissimilarities along the Nb-Ti compositional gradient were minimized by tuning the deposition parameters, thus allowing a description of the mixed Nb-Ti oxides based on a single Tauc-Lorentz oscillator for data fitting. Mapping of the Nb-Ti oxides optical bandgap along the entire compositional spread showed a clear deviation from the linear model based on mixing individual Nb and Ti electronegativities proportional to their atomic fractions. This is attributed to the strong amorphization and an in-depth compositional gradient of the mixed oxides. A systematic optical bandgap decrease toward values as low as 2.0 eV was identified at approximately 50 at.% Nb. Mixing of Nb 2 O 5 and TiO 2 with both amorphous and crystalline phases is concluded, whereas the possibility of complex Nb a Ti b O y oxide formation during anodization is unlikely.

Evaluation of polyimide/glass fiber composites for construction of light weight pressure vessels for cryogenic propellants

NASA Technical Reports Server (NTRS)

Petker, I.; Segimoto, M.

1973-01-01

The application of polyimide resin as a matrix for glass filament-wound thin metal-lined pressure vessels was studied over a temperature range of (minus) 320 to 600 F. Keramid 601 polyimide was found to perform quite well over the entire range of temperature. Hoop stress values of 425 ksi were determined at 75 F which is equivalent to epoxy resin in similar structures. At -320 and 600 F, 125 and 80% of this strength was retained. Thermal ageing at 500 F for up to 50 hours was studied with severe reduction in strength, but there is evidence that this reduction could be improved. Another polyimide resin studied was P10PA which was found to have processing characteristics inappropriate for filament-winding. NOL ring tensile and shear data was determined from both resins with S-glass. Pressure vessel design, fabrication and test procedures are described in detail.

Relaxation of photoexcitations in polaron-induced magnetic microstructures

NASA Astrophysics Data System (ADS)

Köhler, Thomas; Rajpurohit, Sangeeta; Schumann, Ole; Paeckel, Sebastian; Biebl, Fabian R. A.; Sotoudeh, Mohsen; Kramer, Stephan C.; Blöchl, Peter E.; Kehrein, Stefan; Manmana, Salvatore R.

2018-06-01

We investigate the evolution of a photoexcitation in correlated materials over a wide range of time scales. The system studied is a one-dimensional model of a manganite with correlated electron, spin, orbital, and lattice degrees of freedom, which we relate to the three-dimensional material Pr1 -xCaxMnO3 . The ground-state phases for the entire composition range are determined and rationalized by a coarse-grained polaron model. At half doping a pattern of antiferromagnetically coupled Zener polarons is realized. Using time-dependent density-matrix renormalization group (tDMRG), we treat the electronic quantum dynamics following the excitation. The emergence of quasiparticles is addressed, and the relaxation of the nonequilibrium quasiparticle distribution is investigated via a linearized quantum-Boltzmann equation. Our approach shows that the magnetic microstructure caused by the Zener polarons leads to an increase of the relaxation times of the excitation.

St. Fergus terminal gets turboexpanders for critical service

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

Lillard, J.K.; Nicol, G.

1994-09-05

To expand the St. Fergus gas-reception terminal for the Scottish Area Gas Evacuation (SAGE) system, Mobil North Sea Ltd. is adding a second separation train and two treatment trains. To meet pipeline-gas specifications over a wide range of low rates and feed-gas compositions, single-stage turboexpander chilling was selected over Joule-Thomson valve expansion. Four turboexpanders (two per process train) will operate in parallel to achieve the required performance over the entire flow range of 90--575 MMscfd per process train. Unusual operating conditions for the turboexpanders include dense-phase inlet gas, expansion near the cricondenbar, and high equilibrium liquid content at the exhaustmore » (up to 50 wt %). The two turboexpanders in each train share common suction and discharge facilities as do their associated brake compressor. Details of the more than 400 million pounds Sterling Phase B discussed here include commissioning, start-up, and operation.« less

Geochemical differentiation processes for arc magma of the Sengan volcanic cluster, Northeastern Japan, constrained from principal component analysis

NASA Astrophysics Data System (ADS)

Ueki, Kenta; Iwamori, Hikaru

2017-10-01

In this study, with a view of understanding the structure of high-dimensional geochemical data and discussing the chemical processes at work in the evolution of arc magmas, we employed principal component analysis (PCA) to evaluate the compositional variations of volcanic rocks from the Sengan volcanic cluster of the Northeastern Japan Arc. We analyzed the trace element compositions of various arc volcanic rocks, sampled from 17 different volcanoes in a volcanic cluster. The PCA results demonstrated that the first three principal components accounted for 86% of the geochemical variation in the magma of the Sengan region. Based on the relationships between the principal components and the major elements, the mass-balance relationships with respect to the contributions of minerals, the composition of plagioclase phenocrysts, geothermal gradient, and seismic velocity structure in the crust, the first, the second, and the third principal components appear to represent magma mixing, crystallizations of olivine/pyroxene, and crystallizations of plagioclase, respectively. These represented 59%, 20%, and 6%, respectively, of the variance in the entire compositional range, indicating that magma mixing accounted for the largest variance in the geochemical variation of the arc magma. Our result indicated that crustal processes dominate the geochemical variation of magma in the Sengan volcanic cluster.

Composite shell spacecraft seat

NASA Technical Reports Server (NTRS)

Barackman, Victor J. (Inventor); Pulley, John K. (Inventor); Simon, Xavier D. (Inventor); McKee, Sandra D. (Inventor)

2008-01-01

A two-part seat (10) providing full body support that is specific for each crew member (30) on an individual basis. The two-part construction for the seat (10) can accommodate many sizes and shapes for crewmembers (30) because it is reconfigurable and therefore reusable for subsequent flights. The first component of the two-part seat construction is a composite shell (12) that surrounds the crewmember's entire body and is generically fitted to their general size in height and weight. The second component of the two-part seat (10) is a cushion (20) that conforms exactly to the specific crewmember's entire body and gives total body support in more complex environment.

Multilayer Composite Pressure Vessels

NASA Technical Reports Server (NTRS)

DeLay, Tom

2005-01-01

A method has been devised to enable the fabrication of lightweight pressure vessels from multilayer composite materials. This method is related to, but not the same as, the method described in gMaking a Metal- Lined Composite-Overwrapped Pressure Vessel h (MFS-31814), NASA Tech Briefs, Vol. 29, No. 3 (March 2005), page 59. The method is flexible in that it poses no major impediment to changes in tank design and is applicable to a wide range of tank sizes. The figure depicts a finished tank fabricated by this method, showing layers added at various stages of the fabrication process. In the first step of the process, a mandrel that defines the size and shape of the interior of the tank is machined from a polyurethane foam or other suitable lightweight tooling material. The mandrel is outfitted with metallic end fittings on a shaft. Each end fitting includes an outer flange that has a small step to accommodate a thin layer of graphite/epoxy or other suitable composite material. The outer surface of the mandrel (but not the fittings) is covered with a suitable release material. The composite material is filament- wound so as to cover the entire surface of the mandrel from the step on one end fitting to the step on the other end fitting. The composite material is then cured in place. The entire workpiece is cut in half in a plane perpendicular to the axis of symmetry at its mid-length point, yielding two composite-material half shells, each containing half of the foam mandrel. The halves of the mandrel are removed from within the composite shells, then the shells are reassembled and bonded together with a belly band of cured composite material. The resulting composite shell becomes a mandrel for the subsequent steps of the fabrication process and remains inside the final tank. The outer surface of the composite shell is covered with a layer of material designed to be impermeable by the pressurized fluid to be contained in the tank. A second step on the outer flange of each end fitting accommodates this layer. Depending on the application, this layer could be, for example, a layer of rubber, a polymer film, or an electrodeposited layer of metal. If the fluid to be contained in the tank is a gas, then the best permeation barrier is electrodeposited metal (typically copper or nickel), which can be effective at a thickness of as little as 0.005 in (.0.13 mm). The electrodeposited metal becomes molecularly bonded to the second step on each metallic end fitting. The permeation-barrier layer is covered with many layers of filament-wound composite material, which could be the same as, or different from, the composite material of the inner shell. Finally, the filament-wound composite material is cured in an ov

Dynamic Material Properties of Orthotropic Polymer and Molybdenum for Use in Next Generation Composite Armor Concept?

DTIC Science & Technology

2011-06-01

1. Shock Compression Experimental Techniques ...............................22 a. Target...3 Figure 2. Composite plate (left) shown by Poh defeating Tantalum projectile while armor grade steel (right) failed...entire target buildup used for a shock compression experiment ..................................................................................23 Figure

Extreme isotopic variations in the upper mantle: evidence from Ronda

NASA Astrophysics Data System (ADS)

Reisberg, Laurie; Zindler, Alan

1986-12-01

The Ronda Ultramafic Complex in southern Spain represents a piece of the Earth's mantle which has been tectonically emplaced into the crust. Nd and Sr isotopic analyses are presented for leached, hand-picked Cr-diopside separates prepared from 15 rock and 18 river sediment samples from Ronda. These results demonstrate that within this small, contiguous body there exists the entire range of Nd isotopic compositions, and much of the range of Sr compositions, found in rocks derived from the sub-oceanic mantle. The sediment cpx samples show that the average isotopic composition of the massif becomes progressively less "depleted" moving from SW to NE along the long axis of the massif. The rock cpx samples document 143Nd/ 144Nd variations from 0.5129 to 0.5126 and 87Sr/ 86Sr variations from 0.7031 to 0.7039 within a uniform outcrop less than 10 m in extent. Thus, extreme isotopic fluctuations exist over a wide range of wavelengths. Sr and Nd isotopes are generally inversely correlated, forming a trend on a Nd-Sr diagram that sharply crosscuts that of the "mantle array". Many of the 143Nd/ 144Nd values, and all of the Sm/Nd values, from one section of the massif are lower than that SCV015SCV0 of the bulk earth, implying that this region existed, or was influenced by a component which existed, in a LREE-enriched environment for a significant period of time. Among the sediment cpxs there is a positive correlation between 143Nd/ 144Nd and 147Sm/ 144Nd. The rock cpx separates display considerably more scatter. A simple, single-stage differentiation event starting with a uniform mantle source cannot explain these results. At least one episode of mixing with a LREE-enriched component is required. If these results from Ronda are typical of the upper mantle, basalts with different isotopic compositions need not derive from spatially separated mantle sources.

Length-scales of chemical and isotopic heterogeneity in the mantle section of the Shetland Ophiolite Complex, Scotland

NASA Astrophysics Data System (ADS)

O'Driscoll, B.; Walker, R. J.; Clay, P. L.; Day, J. M. D.; Ash, R. D.; Daly, J. S.

2018-04-01

Kilometre to sub-metre scale heterogeneities have been inferred in the oceanic mantle based on sampling of both ophiolites and abyssal peridotites. The ∼492 Ma Shetland Ophiolite Complex (SOC) contains a well-preserved mantle section that is dominated by harzburgite (∼70 vol.%) previously reported to have variable major and trace element compositions, yet dominantly chondritic initial 187Os/188Os compositions. To assess the preservation of compositional heterogeneities at sub-metre length-scales in the oceanic mantle, a ∼45 m2 area of the SOC mantle section was mapped and sampled in detail. Harzburgites, dunites and a pyroxenite from this area were analysed for lithophile and highly-siderophile element (HSE) abundances, as well as for 187Os/188Os ratios. Lithophile element data for most rocks are characteristic of supra-subduction zone (SSZ) metasomatic processes. Two dunites have moderately fractionated HSE patterns and suprachondritic γOs(492 Ma) values (+5.1 and +7.5) that are also typical of ophiolitic dunites generated by SSZ melt-rock interactions. By contrast, six harzburgites and four dunites have approximately chondritic-relative abundances of Os, Ir and Ru, and γOs(492 Ma) values ranging only from -0.6 to +2.7; characteristics that imply no significant influence during SSZ processes. Two harzburgites are also characterised by significantly less radiogenic γOs(492 Ma) values (-3.5 and -4), and yield Mesoproterozoic time of Re depletion (TRD) model ages. The range of Os isotope compositions in the studied area is comparable to the range reported for a suite of samples representative of the entire SOC mantle section, and approaches the total isotopic variation of the oceanic mantle, as observed in abyssal peridotites. Mechanisms by which this heterogeneity can be formed and preserved involve inefficient and temporally distinct melt extraction events and strong localised channelling of these melts.

Accelerated Stress Corrosion Crack Initiation of Alloys 600 and 690 in Hydrogenated Supercritical Water

NASA Astrophysics Data System (ADS)

Moss, Tyler; Was, Gary S.

2017-04-01

The objective of this study is to determine whether stress corrosion crack initiation of Alloys 600 and 690 occurs by the same mechanism in subcritical and supercritical water. Tensile bars of Alloys 690 and 600 were strained in constant extension rate tensile experiments in hydrogenated subcritical and supercritical water from 593 K to 723 K (320 °C to 450 °C), and the crack initiation behavior was characterized by high-resolution electron microscopy. Intergranular cracking was observed across the entire temperature range, and the morphology, structure, composition, and temperature dependence of initiated cracks in Alloy 690 were consistent between hydrogenated subcritical and supercritical water. Crack initiation of Alloy 600 followed an Arrhenius relationship and did not exhibit a discontinuity or change in slope after crossing the critical temperature. The measured activation energy was 121 ± 13 kJ/mol. Stress corrosion crack initiation in Alloy 690 was fit with a single activation energy of 92 ± 12 kJ/mol across the entire temperature range. Cracks were observed to propagate along grain boundaries adjacent to chromium-depleted metal, with Cr2O3 observed ahead of crack tips. All measures of the SCC behavior indicate that the mechanism for stress corrosion crack initiation of Alloy 600 and Alloy 690 is consistent between hydrogenated subcritical and supercritical water.

Definition, reporting, and interpretation of composite outcomes in clinical trials: systematic review

PubMed Central

Cordoba, Gloria; Schwartz, Lisa; Woloshin, Steven; Bae, Harold

2010-01-01

Objective To study how composite outcomes, which have combined several components into a single measure, are defined, reported, and interpreted. Design Systematic review of parallel group randomised clinical trials published in 2008 reporting a binary composite outcome. Two independent observers extracted the data using a standardised data sheet, and two other observers, blinded to the results, selected the most important component. Results Of 40 included trials, 29 (73%) were about cardiovascular topics and 24 (60%) were entirely or partly industry funded. Composite outcomes had a median of three components (range 2–9). Death or cardiovascular death was the most important component in 33 trials (83%). Only one trial provided a good rationale for the choice of components. We judged that the components were not of similar importance in 28 trials (70%); in 20 of these, death was combined with hospital admission. Other major problems were change in the definition of the composite outcome between the abstract, methods, and results sections (13 trials); missing, ambiguous, or uninterpretable data (9 trials); and post hoc construction of composite outcomes (4 trials). Only 24 trials (60%) provided reliable estimates for both the composite and its components, and only six trials (15%) had components of similar, or possibly similar, clinical importance and provided reliable estimates. In 11 of 16 trials with a statistically significant composite, the abstract conclusion falsely implied that the effect applied also to the most important component. Conclusions The use of composite outcomes in trials is problematic. Components are often unreasonably combined, inconsistently defined, and inadequately reported. These problems will leave many readers confused, often with an exaggerated perception of how well interventions work. PMID:20719825

Definition, reporting, and interpretation of composite outcomes in clinical trials: systematic review.

PubMed

Cordoba, Gloria; Schwartz, Lisa; Woloshin, Steven; Bae, Harold; Gøtzsche, Peter C

2010-08-18

To study how composite outcomes, which have combined several components into a single measure, are defined, reported, and interpreted. Systematic review of parallel group randomised clinical trials published in 2008 reporting a binary composite outcome. Two independent observers extracted the data using a standardised data sheet, and two other observers, blinded to the results, selected the most important component. Of 40 included trials, 29 (73%) were about cardiovascular topics and 24 (60%) were entirely or partly industry funded. Composite outcomes had a median of three components (range 2-9). Death or cardiovascular death was the most important component in 33 trials (83%). Only one trial provided a good rationale for the choice of components. We judged that the components were not of similar importance in 28 trials (70%); in 20 of these, death was combined with hospital admission. Other major problems were change in the definition of the composite outcome between the abstract, methods, and results sections (13 trials); missing, ambiguous, or uninterpretable data (9 trials); and post hoc construction of composite outcomes (4 trials). Only 24 trials (60%) provided reliable estimates for both the composite and its components, and only six trials (15%) had components of similar, or possibly similar, clinical importance and provided reliable estimates. In 11 of 16 trials with a statistically significant composite, the abstract conclusion falsely implied that the effect applied also to the most important component. The use of composite outcomes in trials is problematic. Components are often unreasonably combined, inconsistently defined, and inadequately reported. These problems will leave many readers confused, often with an exaggerated perception of how well interventions work.

A kirigami approach to engineering elasticity in nanocomposites through patterned defects.

PubMed

Shyu, Terry C; Damasceno, Pablo F; Dodd, Paul M; Lamoureux, Aaron; Xu, Lizhi; Shlian, Matthew; Shtein, Max; Glotzer, Sharon C; Kotov, Nicholas A

2015-08-01

Efforts to impart elasticity and multifunctionality in nanocomposites focus mainly on integrating polymeric and nanoscale components. Yet owing to the stochastic emergence and distribution of strain-concentrating defects and to the stiffening of nanoscale components at high strains, such composites often possess unpredictable strain-property relationships. Here, by taking inspiration from kirigami—the Japanese art of paper cutting—we show that a network of notches made in rigid nanocomposite and other composite sheets by top-down patterning techniques prevents unpredictable local failure and increases the ultimate strain of the sheets from 4 to 370%. We also show that the sheets' tensile behaviour can be accurately predicted through finite-element modelling. Moreover, in marked contrast to other stretchable conductors, the electrical conductance of the stretchable kirigami sheets is maintained over the entire strain regime, and we demonstrate their use to tune plasma-discharge phenomena. The unique properties of kirigami nanocomposites as plasma electrodes open up a wide range of novel technological solutions for stretchable electronics and optoelectronic devices, among other application possibilities.

Conversion of hydrophilic SiOC nanofibrous membrane to robust hydrophobic materials by introducing palladium

NASA Astrophysics Data System (ADS)

Wu, Nan; Wan, Lynn Yuqin; Wang, Yingde; Ko, Frank

2017-12-01

Hydrophobic ceramic nanofibrous membranes have wide applications in the fields of high-temperature filters, oil/water separators, catalyst supports and membrane reactors, for their water repellency property, self-cleaning capability, good environmental stability and long life span. In this work, we fabricated an inherently hydrophobic ceramic nanofiber membrane without any surface modification through pyrolysis of electrospun polycarbosilane nanofibers. The hydrophobicity was introduced by the hierarchical microstructure formed on the surface of the nanofibers and the special surface composition by the addition of trace amounts of palladium. Furthermore, the flexible ceramic mats demonstrated robust chemical resistance properties with consistent hydrophobicity over the entire pH value range and effective water-in-oil emulsion separation performance. Interestingly, a highly cohesive force was found between water droplet and the ceramic membranes, suggesting their great potentials in micro-liquid transportation. This work provides a new route for adjusting the composition of ceramic surface and flexible, recyclable and multifunctional ceramic fibrous membranes for utilization in harsh environments.

Acid rain at Kennedy Space Center, Florida - Recent observations

NASA Technical Reports Server (NTRS)

Madsen, B. C.

1981-01-01

During the period July, 1977 to September, 1979, rainfall was collected in the vicinity of the Kennedy Space Center and subjected to appropriate chemical analysis for purposes of characterization of general composition and acidity. Results obtained form the basis for future comparisons, should significant alteration of the chemical composition of rain occur during the space shuttle era. Acidity extremes calculated on a monthly basis from event samples collected from five sites within a 200 sq km area varied from pH 5.1 in November, 1977, and April, 1978 to pH 4.3 in July, 1978 and July, 1979. Weighted average pH for the entire period was 4.55. Acidity was due to the presence of sulfuric and nitric acids. The mole ratio of excess SO4(-2):NO3(-) was typically greater than one. Monthly weighted average Cl(-) concentrations ranged from 20-240 micromoles/liter. The Cl(-):Na(+) ratio was slightly lower than that present in sea water.

Plato, Derrida, and Writing.

ERIC Educational Resources Information Center

Neel, Jasper

This book discusses and evaluates the implications of the theory of deconstruction for composition and pedagogy. The book analyzes the emerging field of composition studies within the epistemological and ontological debate over writing precipitated by Plato (who would abandon writing entirely) and continued by Jacques Derrida, who argues that all…

Temporal variation in chemical composition of phenocrysts and magmatic temperature at Daisen volcano, southwest Japan

NASA Astrophysics Data System (ADS)

Tsukui, Masashi

1985-12-01

Daisen volcano, located in the San'in district, southwest Japan, started its activity in the middle Pleistocene and continued until at least ca. 20,000 yr B.P. The volcano is composed entirely of dacitic pyroclastic materials, lava domes and subordinate thick lava flows. Its activity is divided into two groups, Older (1.0-0.4 Ma) and Younger (0.4 Ma to ca. 17.000 yr B.P.). Chemical compositions of phenocrysts in the members of the Upper Tephra Group (the last 150,000 years) in the Younger Group were examined in detail by electron microprobe analysis. The compositions of phenocryst minerals change systematically and cyclically with the order of eruptions. Phenocrysts with less differentiated compositions were found in the products of eruptions 60,000 and 20,000 years ago. The variation patterns of inferred magma temperature (estimated by the Fe-Ti oxide geothermometer) with time are well correlated with those of the chemical compositions of phenocrysts. Orthopyroxene phenocrysts generally show both reversed and normal zoning in single rock specimens and the compositional range of rims is much smaller than that of the core, indicating that the process of re-equilibration of two compositionally distinct orthopyroxenes took place. These facts could be explained by injection of less differentiated, higher-temperature magmas from a deeper level into the shallower more differentiated magma reservoir. A relatively active (frequent and/or voluminous) injection episode seems to have taken place twice during the last 150,000 years; 60,000 and 20,000 years ago.

Conformational Entropy of Intrinsically Disordered Proteins from Amino Acid Triads

PubMed Central

Baruah, Anupaul; Rani, Pooja; Biswas, Parbati

2015-01-01

This work quantitatively characterizes intrinsic disorder in proteins in terms of sequence composition and backbone conformational entropy. Analysis of the normalized relative composition of the amino acid triads highlights a distinct boundary between globular and disordered proteins. The conformational entropy is calculated from the dihedral angles of the middle amino acid in the amino acid triad for the conformational ensemble of the globular, partially and completely disordered proteins relative to the non-redundant database. Both Monte Carlo (MC) and Molecular Dynamics (MD) simulations are used to characterize the conformational ensemble of the representative proteins of each group. The results show that the globular proteins span approximately half of the allowed conformational states in the Ramachandran space, while the amino acid triads in disordered proteins sample the entire range of the allowed dihedral angle space following Flory’s isolated-pair hypothesis. Therefore, only the sequence information in terms of the relative amino acid triad composition may be sufficient to predict protein disorder and the backbone conformational entropy, even in the absence of well-defined structure. The predicted entropies are found to agree with those calculated using mutual information expansion and the histogram method. PMID:26138206

Analysis of 2D Transport and Performance Characteristics for Lateral Power Devices Based on AlGaN Alloys

DOE PAGES

Coltrin, Michael E.; Baca, Albert G.; Kaplar, Robert J.

2017-10-26

In this paper, predicted lateral power device performance as a function of alloy composition is characterized by a standard lateral device figure-of-merit (LFOM) that depends on mobility, critical electric field, and sheet carrier density. The paper presents calculations of AlGaN electron mobility in lateral devices such as HEMTs across the entire alloy composition range. Alloy scattering and optical polar phonon scattering are the dominant mechanisms limiting carrier mobility. Due to the significant degradation of mobility from alloy scattering, at room temperature Al fractions greater than about 85% are required for improved LFOM relative to GaN using a conservative sheet chargemore » density of 1 × 10 13 cm –2. However, at higher temperatures at which AlGaN power devices are anticipated to operate, this “breakeven” composition decreases to about 65% at 500 K, for example. For high-frequency applications, the Johnson figure-of-merit (JFOM) is the relevant metric to compare potential device performance across materials platforms. At room temperature, the JFOM for AlGaN alloys is predicted to surpass that of GaN for Al fractions greater than about 40%.« less

Analysis of 2D Transport and Performance Characteristics for Lateral Power Devices Based on AlGaN Alloys

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

Coltrin, Michael E.; Baca, Albert G.; Kaplar, Robert J.

In this paper, predicted lateral power device performance as a function of alloy composition is characterized by a standard lateral device figure-of-merit (LFOM) that depends on mobility, critical electric field, and sheet carrier density. The paper presents calculations of AlGaN electron mobility in lateral devices such as HEMTs across the entire alloy composition range. Alloy scattering and optical polar phonon scattering are the dominant mechanisms limiting carrier mobility. Due to the significant degradation of mobility from alloy scattering, at room temperature Al fractions greater than about 85% are required for improved LFOM relative to GaN using a conservative sheet chargemore » density of 1 × 10 13 cm –2. However, at higher temperatures at which AlGaN power devices are anticipated to operate, this “breakeven” composition decreases to about 65% at 500 K, for example. For high-frequency applications, the Johnson figure-of-merit (JFOM) is the relevant metric to compare potential device performance across materials platforms. At room temperature, the JFOM for AlGaN alloys is predicted to surpass that of GaN for Al fractions greater than about 40%.« less

Total body composition by dual-photon (153Gd) absorptiometry

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

Mazess, R.B.; Peppler, W.W.; Gibbons, M.

1984-10-01

The lean-fat composition (%FATR) of soft tissue and the mineral mass of the skeleton were determined in vivo using dual-photon (153Gd) absorptiometry (dose under 2 mrem). A rectilinear raster scan was made over the entire body in 18 subjects (14 female, 4 male). Single-photon absorptiometry (125I) measured bone mineral content on the radius. Percentage fat (%FATD) was determined in the same subjects using body density (from underwater weighing with correction for residual lung volume). Lean body mass (LBM) was determined using both %FATR and %FATD. Percentage fat from absorptiometry and from underwater density were correlated (r . 0.87). The deviationmore » of %FATD from %FATR was due to the amount of skeletal mineral as a percentage of the LBM (r . 0.90). Therefore, skeletal variability, even in normal subjects, where mineral ranges only from 4 to 8% of the LBM, essentially precludes use of body density as a composition indicator unless skeletal mass is measured. Anthropometry (fatfolds and weight) predicted %FATR and LBM at least as well as did underwater density. The predictive error of %FATR from fatfolds was 5% while the predictive error in predicting LBM from anthropometry was 2 to 3 kg (3%).« less

The color-magnitude distribution of small Kuiper Belt objects

NASA Astrophysics Data System (ADS)

Wong, Ian; Brown, Michael E.

2015-11-01

Occupying a vast region beyond the ice giants is an extensive swarm of minor bodies known as the Kuiper Belt. Enigmatic in their formation, composition, and evolution, these Kuiper Belt objects (KBOs) lie at the intersection of many of the most important topics in planetary science. Improved instruments and large-scale surveys have revealed a complex dynamical picture of the Kuiper Belt. Meanwhile, photometric studies have indicated that small KBOs display a wide range of colors, which may reflect a chemically diverse initial accretion environment and provide important clues to constraining the surface compositions of these objects. Notably, some recent work has shown evidence for bimodality in the colors of non-cold classical KBOs, which would have major implications for the formation and subsequent evolution of the entire KBO population. However, these previous color measurements are few and mostly come from targeted observations of known objects. As a consequence, the effect of observational biases cannot be readily removed, preventing one from obtaining an accurate picture of the true color distribution of the KBOs as a whole.We carried out a survey of KBOs using the Hyper Suprime-Cam instrument on the 8.2-meter Subaru telescope. Our observing fields targeted regions away from the ecliptic plane so as to avoid contamination from cold classical KBOs. Each field was imaged in both the g’ and i’ filters, which allowed us to calculate the g’-i’ color of each detected object. We detected more than 500 KBOs over two nights of observation, with absolute magnitudes from H=6 to H=11. Our survey increases the number of KBOs fainter than H=8 with known colors by more than an order of magnitude. We find that the distribution of colors demonstrates a robust bimodality across the entire observed range of KBO sizes, from which we can categorize individual objects into two color sub-populations -- the red and very-red KBOs. We present the very first analysis of the magnitude distributions of the two color sub-populations.

Free energy of mixing of acetone and methanol: a computer simulation investigation.

PubMed

Idrissi, Abdenacer; Polok, Kamil; Barj, Mohammed; Marekha, Bogdan; Kiselev, Mikhail; Jedlovszky, Pál

2013-12-19

The change of the Helmholtz free energy, internal energy, and entropy accompanying the mixing of acetone and methanol is calculated in the entire composition range by the method of thermodynamic integration using three different potential model combinations of the two compounds. In the first system, both molecules are described by the OPLS, and in the second system, both molecules are described by the original TraPPE force field, whereas in the third system a modified version of the TraPPE potential is used for acetone in combination with the original TraPPE model of methanol. The results reveal that, in contrast with the acetone-water system, all of these three model combinations are able to reproduce the full miscibility of acetone and methanol, although the thermodynamic driving force of this mixing is very small. It is also seen, in accordance with the finding of former structural analyses, that the mixing of the two components is driven by the entropy term corresponding to the ideal mixing, which is large enough to overcompensate the effect of the energy increase and entropy loss due to the interaction of the unlike components in the mixtures. Among the three model combinations, the use of the original TraPPE model of methanol and modified TraPPE model of acetone turns out to be clearly the best in this respect, as it is able to reproduce the experimental free energy, internal energy, and entropy of mixing values within 0.15 kJ/mol, 0.2 kJ/mol, and 1 J/(mol K), respectively, in the entire composition range. The success of this model combination originates from the fact that the use of the modified TraPPE model of acetone instead of the original one in these mixtures improves the reproduction of the entropy of mixing, while it retains the ability of the original model of excellently reproducing the internal energy of mixing.

Structural, thermal, magnetic, and electronic transport properties of the LaNi₂(Ge 1-xP x)₂ system

DOE PAGES

Goetsch, R. J.; Anand, V. K.; Pandey, Abhishek; ...

2012-02-29

Polycrystalline samples of LaNi₂(Ge 1-xP x)₂ (x=0,0.25,0.50,0.75,1) were synthesized and their properties investigated by x-ray diffraction (XRD) measurements at room temperature and by heat capacity C p, magnetic susceptibility χ, and electrical resistivity ρ measurements versus temperature T from 1.8 to 350 K. Rietveld refinements of powder XRD patterns confirm that these compounds crystallize in the body-centered-tetragonal ThCr₂Si₂-type structure (space group I4/mmm) with composition-dependent lattice parameters that slightly deviate from Vegard's law. The ρ(T) measurements showed a positive temperature coefficient for all samples from 1.8 to 300 K, indicating that all compositions in this system are metallic. The low-T Cmore » p measurements yield a rather large Sommerfeld electronic specific heat coefficient γ=12.4(2) mJ/mol K² for x=0, reflecting a large density of states at the Fermi energy that is comparable with the largest values found for the AFe₂As₂ class of materials with the same crystal structure. The γ decreases approximately linearly with x to 7.4(1) mJ/mol K² for x=1. The χ measurements show nearly temperature-independent paramagnetic behavior across the entire range of compositions except for LaNi₂Ge₂, where a broad peak is observed at ≈300 K from χ(T) measurements up to 1000 K that may arise from short-range antiferromagnetic correlations in a quasi-two-dimensional magnetic system. High-accuracy Padé approximants representing the Debye lattice heat capacity and Bloch-Grüneisen electron-phonon resistivity functions versus T are presented and are used to analyze our experimental C p(T) and ρ(T) data, respectively, for 1.8K≤T≤300 K. The T dependences of ρ for all samples are well-described over this T range by the Bloch-Grüneisen model, although the observed ρ(300 K) values are larger than calculated from this model. A significant T dependence of the Debye temperature determined from the C p(T) data was observed for each composition. No clear evidence for bulk superconductivity or any other long-range phase transition was found for any of the LaNi₂(Ge 1-xP x)₂ compositions studied.« less

Characterizing forest composition of the Allegheny Mountains using extensive forest inventory data

Treesearch

W. H. McWilliams; R. Riemann Hershey; D. A. Drake; C. L. Alerich

1993-01-01

There is a general lack of information that describes forest composition at the landscape level, e.g. for entire physiographic provinces. Studies in the ecological literature usually are local in scope and combining data from such studies is questionable due to different design methodology.

49 CFR 178.707 - Standards for composite IBCs.

Code of Federal Regulations, 2013 CFR

2013-10-01

... designed to bear the entire stacking load. The inner receptacle and outer packaging form an integral... outer packaging. (2) A composite IBC with a fully enclosing outer packaging must be designed to permit assessment of the integrity of the inner container following the leakproofness and hydraulic tests. The outer...

Normal families and value distribution in connection with composite functions

NASA Astrophysics Data System (ADS)

Clifford, E. F.

2005-12-01

We prove a value distribution result which has several interesting corollaries. Let , let and let f be a transcendental entire function with order less than 1/2. Then for every nonconstant entire function g, we have that (f[circle, open]g)(k)-[alpha] has infinitely many zeros. This result also holds when k=1, for every transcendental entire function g. We also prove the following result for normal families. Let , let f be a transcendental entire function with [rho](f)<1/k, and let a0,...,ak-1,a be analytic functions in a domain [Omega]. Then the family of analytic functions g such that in [Omega], is a normal family.

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

Hong, Young Joon; Lee, Chul -Ho; Yoo, Jinkyoung

Integration of nanostructure lighting source arrays with well-defined emission wavelengths is of great importance for optoelectronic integrated monolithic circuitry. We report on the fabrication and optical properties of GaN-based p–n junction multishell nanotube microarrays with composition-modulated nonpolar m-plane In xGa 1–xN/GaN multiple quantum wells (MQWs) integrated on c-sapphire or Si substrates. The emission wavelengths were controlled in the visible spectral range of green to violet by varying the indium mole fraction of the In xGa 1–xN MQWs in the range 0.13 ≤ x ≤ 0.36. Homogeneous emission from the entire area of the nanotube LED arrays was achieved via themore » formation of MQWs with uniform QW widths and composition by heteroepitaxy on the well-ordered nanotube arrays. Importantly, the wavelength-invariant electroluminescence emission was observed above a turn-on of 3.0 V because both the quantum-confinement Stark effect and band filling were suppressed due to the lack of spontaneous inherent electric field in the m-plane nanotube nonpolar MQWs. Lastly, the method of fabricating the multishell nanotube LED microarrays with controlled emission colors has potential applications in monolithic nonpolar photonic and optoelectronic devices on commonly used c-sapphire and Si substrates.« less

Epoxy/Fluoroether Composites

NASA Technical Reports Server (NTRS)

Rosser, R. W.; Taylor, M. S.

1986-01-01

Composite materials made from unfilled and glass-fiber-reinforced epoxy toughened by copolymerization with elastomeric prepolymers of perfluoroalkyl ether diacyl fluoride (EDAF). Improved properties due to hydrogen bonding between rubber phase and epoxy matrix, plus formation of rubberlike phase domains that molecularly interpenetrate with epoxy matrix. With optimum rubber content, particle size, and particle shape, entire molecular structure reinforced and toughened. Improved composites also show increased failure strength, stiffness, glass-transition temperature, and resistance to water.

Variations on morphology and elemental composition of mineral dust particles from local, regional, and long-range transport meteorological scenarios

NASA Astrophysics Data System (ADS)

Coz, Esther; Gómez-Moreno, Francisco J.; Casuccio, Gary S.; ArtíñAno, BegoñA.

2010-06-01

Mineral dust is the second major source of PM10 in Madrid, reaching up to 80% of the PM10 mass during certain long-range dust transport events. Three different types of scenarios have been found to be associated with the high particle concentration episodes in the city: local anthropogenic, regional recirculation, and African dust transport processes. The present study focuses on the characterization of the individual mineral dust particles related to some chemical and morphological features during these three types of episodes, with special attention to local and regional episodes. To achieve this purpose, four different samples were selectively collected during the 2004-2005 period campaigns, one corresponding to each type of scenario and other sample from an Atlantic ventilated one. Meteorological situation, dust source identification, impact on ambient concentrations, size range distribution, and particle individual analysis have been characterized for each of them. Elemental composition and morphology of more than 30,000 mineral particles were analyzed by computer-controlled scanning electron microscopy. Particles were grouped into clusters based on their elemental composition, and the aspect ratio (AR) of each cluster or category was compared for each type of episode. The AR was related to the mineralogical crystal structure of each chemical cluster. The dates chosen for microscopy analysis were in good agreement in size distribution and chemical composition with the average of the dates in the entire campaign and with those from previous campaigns. Major differences between local/regional and long-range transported mineral dust were found in the relative abundance between carbonates and silicates, with much higher abundance of calcium carbonates in the first ones. These differences between silicate and carbonate contents were consistent with the results found in previous campaigns and were directly related to the composition of the parent topsoil by studying the Ca/Si ratios of similar episodes recorded all over the Iberian Peninsula. Differences in morphology were also found for these scenarios. The predominance of calcium carbonate under regional and local influence is scientifically relevant since this mineral is known to react with both SO2 and HNO3 in the atmosphere. Larger average AR values were found for dust particles from long-range transport, and smaller average AR values were found for particles from local and regional resuspended dust. The increasing average AR value has been linked to the silicate cluster presence, whereas a reduction has been observed within the carbonate cluster.

Frontal slab composite magnetic resonance neurography of the brachial plexus: implications for infraclavicular block approaches.

PubMed

Raphael, David T; McIntee, Diane; Tsuruda, Jay S; Colletti, Patrick; Tatevossian, Ray

2005-12-01

Magnetic resonance neurography (MRN) is an imaging method by which nerves can be selectively highlighted. Using commercial software, the authors explored a variety of approaches to develop a three-dimensional volume-rendered MRN image of the entire brachial plexus and used it to evaluate the accuracy of infraclavicular block approaches. With institutional review board approval, MRN of the brachial plexus was performed in 10 volunteer subjects. MRN imaging was performed on a GE 1.5-tesla magnetic resonance scanner (General Electric Healthcare Technologies, Waukesha, WI) using a phased array torso coil. Coronal STIR and T1 oblique sagittal sequences of the brachial plexus were obtained. Multiple software programs were explored for enhanced display and manipulation of the composite magnetic resonance images. The authors developed a frontal slab composite approach that allows single-frame reconstruction of a three-dimensional volume-rendered image of the entire brachial plexus. Automatic segmentation was supplemented by manual segmentation in nearly all cases. For each of three infraclavicular approaches (posteriorly directed needle below midclavicle, infracoracoid, or caudomedial to coracoid), the targeting error was measured as the distance from the MRN plexus midpoint to the approach-targeted site. Composite frontal slabs (coronal views), which are single-frame three-dimensional volume renderings from image-enhanced two-dimensional frontal view projections of the underlying coronal slices, were created. The targeting errors (mean +/- SD) for the approaches-midclavicle, infracoracoid, caudomedial to coracoid-were 0.43 +/- 0.67, 0.99 +/- 1.22, and 0.65 +/- 1.14 cm, respectively. Image-processed three-dimensional volume-rendered MNR scans, which allow visualization of the entire brachial plexus within a single composite image, have educational value in illustrating the complexity and individual variation of the plexus. Suggestions for improved guidance during infraclavicular block procedures are presented.

Lithological, Chemical and Chronological Constraints on Melt Extraction from the Mantle Section of the ~492 Ma Shetland Ophiolite Complex, Scotland

NASA Astrophysics Data System (ADS)

O'Driscoll, B.; Walker, R. J.; Clay, P. L.; Day, J. M.; Ash, R. D.; Daly, J. S.

2015-12-01

The mantle sections of ophiolites offer a means of studying the composition and structure of the oceanic mantle. In particular, the relations between different lithologies can be established in the field, permitting an assessment of the relative timing of processes such as melt extraction and melt-rock reaction. The Shetland Ophiolite Complex (SOC) contains a well-preserved mantle section that is dominated by harzburgite (≥70 vol.%), with dominantly chondritic present-day 187Os/188Os compositions1. Melt extraction and melt-rock reaction is evident in the form of dunite and chromitite layers and lenses, with thicknesses ranging from millimetres-to-metres. These lithologies are characteristic of supra-subduction zone processing and are considered to relate to closure of the Iapetus Ocean at ~492 Ma1. However, evidence of much earlier melt extraction has been suggested for some SOC harzburgites, which have relatively unradiogenic 187Os/188Os compositions that yield TRD model ages as old as ~1.4 Ga1. In order to assess the scales at which such compositional heterogeneities are preserved in the mantle, a small (45 m2) area of the SOC mantle section was selected for detailed lithological mapping and sampling. A selection of harzburgites (n=8), dunites (n=6) and pyroxenites (n=2) from this area has been analysed for their Os isotope and highly-siderophile element (HSE) compositions. Six of the harzburgites and four of the dunites have relative HSE abundances and gOs values that are approximately chondritic, with gOs ranging only from -0.6 to +2.7 (n=10). Two dunites have more radiogenic gOs (up to +7.5), that is correlated with enhanced concentrations of accessory base-metal sulphides, suggesting formation via melt percolation and melt-rock reaction. The two remaining harzburgites have less radiogenic gOs (-3.5 and -4), yielding Mesoproterozoic TRD ages. The new data indicate that a comparable range of Os isotope compositions to that previously measured across the entire SOC mantle section is present in the mapped area, i.e., at the m2 scale, revealing the modest scale of isotopic and chemical heterogeneity in the oceanic mantle. 1O'Driscoll B, Day JMD, Walker RJ, Daly JS, McDonough WF, Piccoli PM (2012). Earth and Planetary Science Letters 333-334: 226-237.

Full-Spectrum-Analysis Isotope ID

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

Mitchell, Dean J.; Harding, Lee; Thoreson, Gregory G.

2017-06-28

FSAIsotopeID analyzes gamma ray spectra to identify radioactive isotopes (radionuclides). The algorithm fits the entire spectrum with combinations of pre-computed templates for a comprehensive set of radionuclides with varying thicknesses and compositions of shielding materials. The isotope identification algorithm is suitable for the analysis of spectra collected by gamma-ray sensors ranging from medium-resolution detectors, such a NaI, to high-resolution detectors, such as HPGe. In addition to analyzing static measurements, the isotope identification algorithm is applied for the radiation search applications. The search subroutine maintains a running background spectrum that is passed to the isotope identification algorithm, and it also selectsmore » temporal integration periods that optimize the responsiveness and sensitivity. Gain stabilization is supported for both types of applications.« less

Physical and mechanical metallurgy of NiAl

NASA Technical Reports Server (NTRS)

Noebe, Ronald D.; Bowman, Randy R.; Nathal, Michael V.

1994-01-01

Considerable research has been performed on NiAl over the last decade, with an exponential increase in effort occurring over the last few years. This is due to interest in this material for electronic, catalytic, coating and especially high-temperature structural applications. This report uses this wealth of new information to develop a complete description of the properties and processing of NiAl and NiAl-based materials. Emphasis is placed on the controlling fracture and deformation mechanisms of single and polycrystalline NiAl and its alloys over the entire range of temperatures for which data are available. Creep, fatigue, and environmental resistance of this material are discussed. In addition, issues surrounding alloy design, development of NiAl-based composites, and materials processing are addressed.

Thermo-acoustical molecular interaction study in binary mixtures of glycerol and ethylene glycol

NASA Astrophysics Data System (ADS)

Kaur, Kirandeep; Juglan, K. C.; Kumar, Harsh

2017-07-01

Ultrasonic velocity, density and viscosity are measured over the entire composition range for binary liquid mixtures of glycerol (CH2OH-CHOH-CH2OH) and ethylene glycol (HOCH2CH2OH) at different temperatures and constant frequency of 2MHz using ultrasonic interferometer, specific gravity bottle and viscometer respectively. Measured experimental values are used to obtained various acoustical parameters such as adiabatic compressibility, acoustic impedance, intermolecular free length, relaxation time, ultrasonic attenuation, effective molar weight, free volume, available volume, molar volume, Wada's constant, Rao's constant, Vander Waal's constant, internal pressure, Gibb's free energy and enthalpy. The variation in acoustical parameters are interpreted in terms of molecular interactions between the components of molecules of binary liquid mixtures.

Implications of L1 Observations for Slow Solar Wind Formation by Solar Reconnection

NASA Technical Reports Server (NTRS)

Kepko, L.; Viall, N. M.; Antiochos, S. K.; Lepri, S. T.; Kasper, J. C.; Weberg, M.

2016-01-01

While the source of the fast solar wind is known to be coronal holes, the source of the slow solar wind has remained a mystery. Long time scale trends in the composition and charge states show strong correlations between solar wind velocity and plasma parameters, yet these correlations have proved ineffective in determining the slow wind source. We take advantage of new high time resolution (12 min) measurements of solar wind composition and charge state abundances at L1 and previously identified 90 min quasi periodic structures to probe the fundamental timescales of slow wind variability. The combination of new high temporal resolution composition measurements and the clearly identified boundaries of the periodic structures allows us to utilize these distinct solar wind parcels as tracers of slowwind origin and acceleration. We find that each 90 min (2000 Mm) parcel of slow wind has near-constant speed yet exhibits repeatable, systematic charge state and composition variations that span the entire range of statistically determined slow solar wind values. The classic composition-velocity correlations do not hold on short, approximately hour long, time scales. Furthermore, the data demonstrate that these structures were created by magnetic reconnection. Our results impose severe new constraints on slow solar wind origin and provide new, compelling evidence that the slow wind results from the sporadic release of closed field plasma via magnetic reconnection at the boundary between open and closed flux in the Sun's atmosphere.

Determination of lattice parameters, strain state and composition in semipolar III-nitrides using high resolution X-ray diffraction

NASA Astrophysics Data System (ADS)

Frentrup, Martin; Hatui, Nirupam; Wernicke, Tim; Stellmach, Joachim; Bhattacharya, Arnab; Kneissl, Michael

2013-12-01

In group-III-nitride heterostructures with semipolar or nonpolar crystal orientation, anisotropic lattice and thermal mismatch with the buffer or substrate lead to a complex distortion of the unit cells, e.g., by shearing of the lattice. This makes an accurate determination of lattice parameters, composition, and strain state under assumption of the hexagonal symmetry impossible. In this work, we present a procedure to accurately determine the lattice constants, strain state, and composition of semipolar heterostructures using high resolution X-ray diffraction. An analysis of the unit cell distortion shows that four independent lattice parameters are sufficient to describe this distortion. Assuming only small deviations from an ideal hexagonal structure, a linear expression for the interplanar distances dhkl is derived. It is used to determine the lattice parameters from high resolution X-ray diffraction 2ϑ-ω-scans of multiple on- and off-axis reflections via a weighted least-square fit. The strain and composition of ternary alloys are then evaluated by transforming the elastic parameters (using Hooke's law) from the natural crystal-fixed coordinate system to a layer-based system, given by the in-plane directions and the growth direction. We illustrate our procedure taking an example of (112¯2) AlκGa1-κN epilayers with Al-contents over the entire composition range. We separately identify the in-plane and out-of-plane strains and discuss origins for the observed anisotropy.

Composition Theory: Taking It Apart and Putting It Back Together Again.

ERIC Educational Resources Information Center

Sydow, Debbie L.

Despite the fact that social constructivism is accepted as the guiding theory in Composition, that this theory is the field's theoretical center of gravity, it does not account for, nor explain, the entire writing process. Two major challenges to social constructivism must also be considered in theoretical discussions: (1) the cognitive dimension…

Carbon Materials Research

DTIC Science & Technology

2005-08-01

is an angular surface. This phenomena has important applications in areas as diverse as heat exchange and catalysis. JOURNAL PAPERS W.P...densify these composites. In addressing the oxidation protection of carbon-carbon composites, the entirely new field of microtube technology was born...nozzle; exit cone; missile nosetip; hypersonic vehicle; oxidation resistance; cost; densification; MEMs; surface tension; microtube 16. SECURITY

Synthesis and characterization of mesoporous ceria/alumina nanocomposite materials via mixing of the corresponding ceria and alumina gel precursors.

PubMed

Khalil, Kamal M S

2007-03-01

Mesoporous ceria/alumina, CeO(2)/Al(2)O(3), composites containing 10, 20 and 30% (w/w) ceria were prepared by a novel gel mixing method. In the method, ceria gel (formed via hydrolysis of ammonium cerium(IV) nitrate by aqueous ammonium carbonate solution) and alumina gel (formed via controlled hydrolysis of aluminum tri-isopropoxide) were mixed together. The mixed gel was subjected to subsequent drying and calcination for 3 h at 400, 600, 800 and 1000 degrees C. The uncalcined (dried at 110 degrees C) and the calcined composites were investigated by different techniques including TGA, DSC, FTIR, XRD, SEM and nitrogen adsorption/desorption isotherms. Results indicated that composites calcined for 3 h at 800 degrees C mainly kept amorphous alumina structure and gamma-alumina formed only upon calcinations at 1000 degrees C. On the other hand, CeO(2) was found to crystallize in the common ceria, cerinite, phase and it kept this structure over the entire calcination range (400-1000 degrees C). Therefore, high surface areas, stable surface textures, and non-aggregated nano-sized ceria dispersions were obtained. A systematic texture change based on ceria ratio was observed, however in all cases mesoporous composite materials exposing thermally stable texture and structure were obtained. The presented method produces composite ceria/alumina materials that suit different applications in the field of catalysis and membranes technology, and throw some light on physicochemical factors that determine textural morphology and thermal stability of such important composite.

Time-Dependent Stress Rupture Strength Degradation of Hi-Nicalon Fiber-Reinforced Silicon Carbide Composites at Intermediate Temperatures

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.

2016-01-01

The stress rupture strength of silicon carbide fiber-reinforced silicon carbide composites with a boron nitride fiber coating decreases with time within the intermediate temperature range of 700 to 950 degree Celsius. Various theories have been proposed to explain the cause of the time-dependent stress rupture strength. The objective of this paper is to investigate the relative significance of the various theories for the time-dependent strength of silicon carbide fiber-reinforced silicon carbide composites. This is achieved through the development of a numerically based progressive failure analysis routine and through the application of the routine to simulate the composite stress rupture tests. The progressive failure routine is a time-marching routine with an iterative loop between a probability of fiber survival equation and a force equilibrium equation within each time step. Failure of the composite is assumed to initiate near a matrix crack and the progression of fiber failures occurs by global load sharing. The probability of survival equation is derived from consideration of the strength of ceramic fibers with randomly occurring and slow growing flaws as well as the mechanical interaction between the fibers and matrix near a matrix crack. The force equilibrium equation follows from the global load sharing presumption. The results of progressive failure analyses of the composite tests suggest that the relationship between time and stress-rupture strength is attributed almost entirely to the slow flaw growth within the fibers. Although other mechanisms may be present, they appear to have only a minor influence on the observed time-dependent behavior.

Musical rhythm spectra from Bach to Joplin obey a 1/f power law.

PubMed

Levitin, Daniel J; Chordia, Parag; Menon, Vinod

2012-03-06

Much of our enjoyment of music comes from its balance of predictability and surprise. Musical pitch fluctuations follow a 1/f power law that precisely achieves this balance. Musical rhythms, especially those of Western classical music, are considered highly regular and predictable, and this predictability has been hypothesized to underlie rhythm's contribution to our enjoyment of music. Are musical rhythms indeed entirely predictable and how do they vary with genre and composer? To answer this question, we analyzed the rhythm spectra of 1,788 movements from 558 compositions of Western classical music. We found that an overwhelming majority of rhythms obeyed a 1/f(β) power law across 16 subgenres and 40 composers, with β ranging from ∼0.5-1. Notably, classical composers, whose compositions are known to exhibit nearly identical 1/f pitch spectra, demonstrated distinctive 1/f rhythm spectra: Beethoven's rhythms were among the most predictable, and Mozart's among the least. Our finding of the ubiquity of 1/f rhythm spectra in compositions spanning nearly four centuries demonstrates that, as with musical pitch, musical rhythms also exhibit a balance of predictability and surprise that could contribute in a fundamental way to our aesthetic experience of music. Although music compositions are intended to be performed, the fact that the notated rhythms follow a 1/f spectrum indicates that such structure is no mere artifact of performance or perception, but rather, exists within the written composition before the music is performed. Furthermore, composers systematically manipulate (consciously or otherwise) the predictability in 1/f rhythms to give their compositions unique identities.

From the Cover: Musical rhythm spectra from Bach to Joplin obey a 1/f power law

NASA Astrophysics Data System (ADS)

Levitin, Daniel J.; Chordia, Parag; Menon, Vinod

2012-03-01

Much of our enjoyment of music comes from its balance of predictability and surprise. Musical pitch fluctuations follow a 1/f power law that precisely achieves this balance. Musical rhythms, especially those of Western classical music, are considered highly regular and predictable, and this predictability has been hypothesized to underlie rhythm's contribution to our enjoyment of music. Are musical rhythms indeed entirely predictable and how do they vary with genre and composer? To answer this question, we analyzed the rhythm spectra of 1,788 movements from 558 compositions of Western classical music. We found that an overwhelming majority of rhythms obeyed a 1/fβ power law across 16 subgenres and 40 composers, with β ranging from ∼0.5-1. Notably, classical composers, whose compositions are known to exhibit nearly identical 1/f pitch spectra, demonstrated distinctive 1/f rhythm spectra: Beethoven's rhythms were among the most predictable, and Mozart's among the least. Our finding of the ubiquity of 1/f rhythm spectra in compositions spanning nearly four centuries demonstrates that, as with musical pitch, musical rhythms also exhibit a balance of predictability and surprise that could contribute in a fundamental way to our aesthetic experience of music. Although music compositions are intended to be performed, the fact that the notated rhythms follow a 1/f spectrum indicates that such structure is no mere artifact of performance or perception, but rather, exists within the written composition before the music is performed. Furthermore, composers systematically manipulate (consciously or otherwise) the predictability in 1/f rhythms to give their compositions unique identities.

Temperature-dependence of stress and elasticity in wet-transferred graphene membranes

NASA Astrophysics Data System (ADS)

De Alba, Roberto; Abhilash, T. S.; Hui, Aaron; Storch, Isaac R.; Craighead, Harold G.; Parpia, Jeevak M.

2018-03-01

We report measurements of the mechanical properties of two suspended graphene membranes in the temperature range of 80 K to 550 K. For this entire range, the resonant frequency and quality factor of each device were monitored continuously during cooling and heating. Below 300 K, we have additionally measured the resonant frequency's tunability via electrostatic force, and modeled this data to determine graphene's tension and elastic modulus; both of these parameters are found to be strongly temperature-dependent in this range. Above 300 K, we observe a resonant frequency (and therefore tension) minimum near room temperature. This suggests that the thermal expansion coefficient is positive for temperatures below roughly 315 K, and negative for higher temperatures. Lastly, we observe a large, reproducible hysteresis in the resonant frequency as our graphene devices are cycled between 300 K and 550 K. After returning to 300 K, the measured frequency evolves exponentially in time with a time constant of ˜24 h. Our results clash with expectations for pristine graphene membranes, but are consistent with expectations for composite membranes composed of graphene coated by a thin layer of polymer residue.

A steady-state high-temperature apparatus for measuring thermal conductivity of ceramics

NASA Astrophysics Data System (ADS)

Filla, B. James

1997-07-01

A one-sided very-high-temperature guarded hot plate has been built to measure thermal conductivity of monolithic ceramics, ceramic composites, thermal barrier coatings, functional graded materials, and high-temperature metal alloys. It is an absolute, steady-state measurement device with an operational temperature range of 400-1400 K. Measurements are made in an atmosphere of low-pressure helium. Specimens examined in this apparatus are 70 mm in diameter, with thicknesses ranging between 1 and 8 mm. Optimal specimen thermal conductivities fall in the range of 0.5-30 W/(mK). Internal heated components are composed entirely of high-purity aluminum oxide, boron nitride, beryllium oxide, and fibrous alumina insulation board. Pure nickel and thermocouple-grade platinum-based alloys are the only metals used in the system. Apparatus design, modeling, and operation are described, along with the methods of data analysis that are unique to this system. An analysis of measurement uncertainty yields a combined measurement uncertainty of ±5%. Experimental measurements on several materials are presented to illustrate the precision and bias of the apparatus.

Analysis and seismic tests of composite shear walls with CFST columns and steel plate deep beams

NASA Astrophysics Data System (ADS)

Dong, Hongying; Cao, Wanlin; Wu, Haipeng; Zhang, Jianwei; Xu, Fangfang

2013-12-01

A composite shear wall concept based on concrete filled steel tube (CFST) columns and steel plate (SP) deep beams is proposed and examined in this study. The new wall is composed of three different energy dissipation elements: CFST columns; SP deep beams; and reinforced concrete (RC) strips. The RC strips are intended to allow the core structural elements — the CFST columns and SP deep beams — to work as a single structure to consume energy. Six specimens of different configurations were tested under cyclic loading. The resulting data are analyzed herein. In addition, numerical simulations of the stress and damage processes for each specimen were carried out, and simulations were completed for a range of location and span-height ratio variations for the SP beams. The simulations show good agreement with the test results. The core structure exhibits a ductile yielding mechanism characteristic of strong column-weak beam structures, hysteretic curves are plump and the composite shear wall exhibits several seismic defense lines. The deformation of the shear wall specimens with encased CFST column and SP deep beam design appears to be closer to that of entire shear walls. Establishing optimal design parameters for the configuration of SP deep beams is pivotal to the best seismic behavior of the wall. The new composite shear wall is therefore suitable for use in the seismic design of building structures.

Body composition in athletes: assessment and estimated fatness.

PubMed

Malina, Robert M

2007-01-01

The study of body composition attempts to partition and quantify body weight or mass into its basic components. Body weight is a gross measure of the mass of the body, which can be studied at several levels from basic chemical elements and specific tissues to the entire body. Body composition is a factor that can influence athletic performance and as such is of considerable interest to athletes and coaches. This article provides an overview of models and methods used for studying body composition, changes in body composition during adolescence and the transition into adulthood, and applications to adolescent and young adult athletes.

Melting relations in the MgO-MgSiO3 system up to 70 GPa

NASA Astrophysics Data System (ADS)

Ohnishi, Satoka; Kuwayama, Yasuhiro; Inoue, Toru

2017-06-01

Melting experiments in a binary system MgO-MgSiO3 were performed up to 70 GPa using a CO2 laser heated diamond anvil cell. The quenched samples were polished and analyzed by a dualbeam focused ion beam (FIB) and a field emission scanning electron microscope (FE-SEM), respectively. The liquidus phase and the eutectic composition were determined on the basis of textual and chemical analyses of sample cross sections. Our experimental results show that the eutectic composition is the Si/Mg molar ratio of 0.76 at 35 GPa and it decreases with increasing pressure. Above 45 GPa, it becomes relatively constant at about 0.64-0.65 Si/Mg molar ratio. Using our experimental data collected at a wide pressure range up to 70 GPa together with previous experimental data, we have constructed a thermodynamic model of the eutectic composition of the MgO-MgSiO3 system. The eutectic composition extrapolated to the pressure and temperature conditions at the base of the mantle is about 0.64 Si/Mg molar ratio. The modeled eutectic composition is quite consistent with a previous prediction from ab initio calculations (de Koker et al. in Earth Planet Sci Lett 361:58-63, 2013), suggesting that the simple assumption of a non-ideal regular solution model can well describe the melting relation of the MgO-MgSiO3 system at high pressure. Our results show that the liquidus phase changes from MgO-periclase to MgSiO3-bridgmanite at 35 GPa for the simplified pyrolite composition ( 0.7 Si/Mg molar ratio), while MgSiO3-bridgmanite is the liquidus phase at the entire lower mantle conditions for the chondritic composition ( 0.84 Si/Mg molar ratio).

Mineral and chemical variations within an ash-flow sheet from Aso caldera, Southwestern Japan

USGS Publications Warehouse

Lipman, P.W.

1967-01-01

Although products of individual volcanic eruptions, especially voluminous ash-flow eruptions, have been considered among the best available samples of natural magmas, detailed petrographic and chemical study indicates that bulk compositions of unaltered Pleistocene ash-flow tuffs from Aso caldera, Japan, deviate significantly from original magmatic compositions. The last major ash-flow sheet from Aso caldera is as much as 150 meters thick and shows a general vertical compositional change from phenocryst-poor rhyodacite upward into phenocryst-rich trachyandesite; this change apparently reflects in inverse order a compositionally zoned magma chamber in which more silicic magma overlay more mafic magma. Details of these magmatic variations were obscured, however, by: (1) mixing of compositionally distinct batches of magma during upwelling in the vent, as indicated by layering and other heterogeneities within single pumice lumps; (2) mixing of particulate fragments-pumice lumps, ash, and phenocrysts-of varied compositions during emplacement, with the result that separate pumice lenses from a single small outcrop may have a compositional range nearly as great as the bulk-rook variation of the entire sheet; (3) density sorting of phenocrysts and ash during eruption and emplacement, resulting in systematic modal variations with distance from the caldera; (4) addition of xenocrysts, resulting in significant contamination and modification of proportions of crystals in the tuffs; and (5) ground-water leaching of glassy fractions during hydration after cooling. Similar complexities characterize ash-flow tuffs under study in southwestern Nevada and in the San Juan Mountains, Colorado, and probably are widespread in other ash-flow fields as well. Caution and careful planning are required in study of the magmatic chemistry and phenocryst mineralogy of these rocks. ?? 1967 Springer-Verlag.

Automatized sspKa measurements of dihydrogen phosphate and Tris(hydroxymethyl) aminomethane in acetonitrile/water mixtures from 20 to 60°C.

PubMed

Acquaviva, A; Tascon, M; Padró, J M; Gagliardi, L G; Castells, C B

2014-09-01

We measured pKa values of Tris(hydroxymethyl)aminomethane and dihydrogen phosphate; both are commonly used to prepare buffers for reverse-phase liquid chromatography (RPLC), in acetonitrile/water mixtures from 0% to 70% (v/v) (64.6% (w/w)) acetonitrile and at 20, 30, 40, 50, and 60°C. The procedure is based on potentiometric measurements of pH of buffer solutions of variable solvent compositions using a glass electrode and a novel automated system. The method consists in the controlled additions of small volumes of a thermostated solution from an automatic buret into another isothermal solution containing exactly the same buffer-component concentrations, but a different solvent composition. The continuous changes in the solvent composition induce changes in the potentials. Thus, only two sequences of additions are needed: increasing the amount of acetonitrile from pure water and decreasing the content of acetonitrile from 70% (v/v) (64.6% (w/w)). In the procedure with homemade apparatus, times for additions, stirring, homogenization, and data acquisition are entirely controlled by software programmed for this specific routine. This rapid, fully automated method was applied to acquire more than 40 potential data covering the whole composition range (at each temperature) in about two hours and allowed a systematic study of the effect of temperature and acetonitrile composition on acid-base equilibria of two widely used substances to control pH close to 7. The experimental pKa results were fitted to empirical functions between pKa and temperature and acetonitrile composition. These equations allowed predictions of pKa to estimate the pH of mixtures at any composition and temperature, which would be very useful, for instance, during chromatographic method development. Copyright © 2014 Elsevier B.V. All rights reserved.

Thermodynamics of Quantum Gases for the Entire Range of Temperature

ERIC Educational Resources Information Center

Biswas, Shyamal; Jana, Debnarayan

2012-01-01

We have analytically explored the thermodynamics of free Bose and Fermi gases for the entire range of temperature, and have extended the same for harmonically trapped cases. We have obtained approximate chemical potentials for the quantum gases in closed forms of temperature so that the thermodynamic properties of the quantum gases become…

Factors affecting reproducibility between genome-scale siRNA-based screens

PubMed Central

Barrows, Nicholas J.; Le Sommer, Caroline; Garcia-Blanco, Mariano A.; Pearson, James L.

2011-01-01

RNA interference-based screening is a powerful new genomic technology which addresses gene function en masse. To evaluate factors influencing hit list composition and reproducibility, we performed two identically designed small interfering RNA (siRNA)-based, whole genome screens for host factors supporting yellow fever virus infection. These screens represent two separate experiments completed five months apart and allow the direct assessment of the reproducibility of a given siRNA technology when performed in the same environment. Candidate hit lists generated by sum rank, median absolute deviation, z-score, and strictly standardized mean difference were compared within and between whole genome screens. Application of these analysis methodologies within a single screening dataset using a fixed threshold equivalent to a p-value ≤ 0.001 resulted in hit lists ranging from 82 to 1,140 members and highlighted the tremendous impact analysis methodology has on hit list composition. Intra- and inter-screen reproducibility was significantly influenced by the analysis methodology and ranged from 32% to 99%. This study also highlighted the power of testing at least two independent siRNAs for each gene product in primary screens. To facilitate validation we conclude by suggesting methods to reduce false discovery at the primary screening stage. In this study we present the first comprehensive comparison of multiple analysis strategies, and demonstrate the impact of the analysis methodology on the composition of the “hit list”. Therefore, we propose that the entire dataset derived from functional genome-scale screens, especially if publicly funded, should be made available as is done with data derived from gene expression and genome-wide association studies. PMID:20625183

Viscoelastic properties of uncured resin composites: Dynamic oscillatory shear test and fractional derivative model.

PubMed

Petrovic, Ljubomir M; Zorica, Dusan M; Stojanac, Igor Lj; Krstonosic, Veljko S; Hadnadjev, Miroslav S; Janev, Marko B; Premovic, Milica T; Atanackovic, Teodor M

2015-08-01

In this study we analyze viscoelastic properties of three flowable (Wave, Wave MV, Wave HV) and one universal hybrid resin (Ice) composites, prior to setting. We developed a mathematical model containing fractional derivatives in order to describe their properties. Isothermal experimental study was conducted on a rheometer with parallel plates. In dynamic oscillatory shear test, storage and loss modulus, as well as the complex viscosity where determined. We assumed four different fractional viscoelastic models, each belonging to one particular class, derivable from distributed-order fractional constitutive equation. The restrictions following from the Second law of thermodynamics are imposed on each model. The optimal parameters corresponding to each model are obtained by minimizing the error function that takes into account storage and loss modulus, thus obtaining the best fit to the experimental data. In the frequency range considered, we obtained that for Wave HV and Wave MV there exist a critical frequency for which loss and storage modulus curves intersect, defining a boundary between two different types of behavior: one in which storage modulus is larger than loss modulus and the other in which the situation is opposite. Loss and storage modulus curves for Ice and Wave do not show this type of behavior, having either elastic, or viscous effects dominating in entire frequency range considered. The developed models may be used to predict behavior of four tested composites in different flow conditions (different deformation speed), thus helping to estimate optimal handling characteristics for specific clinical applications. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

In(x)Ga(₁-x)As nanowires on silicon: one-dimensional heterogeneous epitaxy, bandgap engineering, and photovoltaics.

PubMed

Shin, Jae Cheol; Kim, Kyou Hyun; Yu, Ki Jun; Hu, Hefei; Yin, Leijun; Ning, Cun-Zheng; Rogers, John A; Zuo, Jian-Min; Li, Xiuling

2011-11-09

We report on the one-dimensional (1D) heteroepitaxial growth of In(x)Ga(1-x)As (x = 0.2-1) nanowires (NWs) on silicon (Si) substrates over almost the entire composition range using metalorganic chemical vapor deposition (MOCVD) without catalysts or masks. The epitaxial growth takes place spontaneously producing uniform, nontapered, high aspect ratio NW arrays with a density exceeding 1 × 10(8)/cm(2). NW diameter (∼30-250 nm) is inversely proportional to the lattice mismatch between In(x)Ga(1-x)As and Si (∼4-11%), and can be further tuned by MOCVD growth condition. Remarkably, no dislocations have been found in all composition In(x)Ga(1-x)As NWs, even though massive stacking faults and twin planes are present. Indium rich NWs show more zinc-blende and Ga-rich NWs exhibit dominantly wurtzite polytype, as confirmed by scanning transmission electron microscopy (STEM) and photoluminescence spectra. Solar cells fabricated using an n-type In(0.3)Ga(0.7)As NW array on a p-type Si(111) substrate with a ∼ 2.2% area coverage, operates at an open circuit voltage, V(oc), and a short circuit current density, J(sc), of 0.37 V and 12.9 mA/cm(2), respectively. This work represents the first systematic report on direct 1D heteroepitaxy of ternary In(x)Ga(1-x)As NWs on silicon substrate in a wide composition/bandgap range that can be used for wafer-scale monolithic heterogeneous integration for high performance photovoltaics.

Continental sedimentary processes decouple Nd and Hf isotopes

NASA Astrophysics Data System (ADS)

Garçon, Marion; Chauvel, Catherine; France-Lanord, Christian; Huyghe, Pascale; Lavé, Jérôme

2013-11-01

The neodymium and hafnium isotopic compositions of most crustal and mantle rocks correlate to form the "Terrestrial Array". However, it is now well established that whereas coarse detrital sediments follow this trend, fine-grained oceanic sediments have high Hf ratios relative to their Nd isotopic ratios. It remains uncertain whether this "decoupling" of the two isotopic systems only occurs in the oceanic environment or if it is induced by sedimentary processes in continental settings. In this study, the hafnium and neodymium isotopic compositions of sediments in large rivers is expressly used to constrain the behavior of the two isotopic systems during erosion and sediment transport from continent to ocean. We report major and trace element concentrations together with Nd and Hf isotopic compositions of bedloads, suspended loads and river banks from the Ganges River and its tributaries draining the Himalayan Range i.e. the Karnali, the Narayani, the Kosi and the Marsyandi Rivers. The sample set includes sediments sampled within the Himalayan Range in Nepal, at the Himalayan mountain front, and also downstream on the floodplain and at the outflow of the Ganges in Bangladesh. Results show that hydrodynamic sorting of minerals explains the entire Hf isotopic range, i.e. more than 10 εHf units, observed in the river sediments but does not affect the Nd isotopic composition. Bedloads and bank sediments have systematically lower εHf values than suspended loads sampled at the same location. Coarse-grained sediments lie below or on the Terrestrial Array in an εHf vs. εNd diagram. In contrast, fine-grained sediments, including most of the suspended loads, deviate from the Terrestrial Array toward higher εHf relative to their εNd, as is the case for oceanic terrigenous clays. The observed Nd-Hf decoupling is explained by mineralogical sorting processes that enrich bottom sediments in coarse and dense minerals, including unradiogenic zircons, while surface sediments are enriched in fine material with radiogenic Hf signatures. The data also show that Nd-Hf isotopic decoupling increases with sediment transport in the floodplain to reach its maximum at the river mouth. This implies that the Nd-Hf isotopic decoupling observed in worldwide oceanic clays and river sediments is likely to have the same origin. Finally, we estimated the Nd-Hf isotopic composition of the present-day mantle if oceanic sediments had never been subducted and conclude that the addition of oceanic sediments with their anomalous Nd-Hf isotopic compositions has slowly shifted the composition of the Earth's mantle towards more radiogenic Hf values through time.

Resolution of coi-dominant phytoplankton species in a eutrophiclake using synchrotron-based Fourier transform infraredspectroscopy

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

Dean, A.P.; Martin, Michael C.; Sigee, D.C.

2006-10-09

Synchrotron-based Fourier-transform infrared (FTIR)microspectroscopy was used to distinguish micropopulations of thecodominant algae Microcystis aeruginosa (Cyanophyceae) and Ceratiumhirundinella (Dinophyceae) in mixed phytoplankton samples taken from thewater column of a stratified eutrophic lake (Rostherne Mere, UK). FTIRspectra of the two algae showed a closely similar sequence of 10 bandsover the wave-number range 4000-900 cm-1. These were assigned to a rangeof vibrationally active chemical groups using published band assignmentsand on the basis of correlation and factor analysis. In both algae,intracellular concentrations of macromolecular components (determined asband intensity) varied considerably within the same population,indicating substantial intraspecific heterogeneity. Interspecificdifferences were separately analysed in relation tomore » discrete bands and bymultivariate analysis of the entire spectral region 1750-900 cm-1. Interms of discrete bands, comparison of individual intensities (normalisedto amide 1) demonstrated significant (99 percent probability level)differences in relation to six bands between the two algal species. Keyinterspecific differences were also noted in relation to the positions ofbands 2, 10 (carbohydrate) and 7 (protein) and in the 3-D plots derivedby principal component analysis (PCA) of the sequence of bandintensities. PCA of entire spectral regions showed clear resolutionofspecies in the PCA plot, with indication of separation on the basis ofprotein (region 1700-1500 cm1) and carbohydrate (region 1150-900 cm1)composition in the loading plot. Hierarchical cluster analysis (Wardalgorithm) of entire spectral regions also showed clear discrimination ofthe two species within the resulting dendrogram.« less

Spatial scale of land-use impacts on riverine drinking source water quality

NASA Astrophysics Data System (ADS)

Hurley, Tim; Mazumder, Asit

2013-03-01

Drinking water purveyors are increasingly relying on land conservation and management to ensure the safety of the water that they provide to consumers. To cost-effectively implement any such landscape initiatives, resources must be targeted to the appropriate spatial scale to address quality impairments of concern in a cost-effective manner. Using data gathered from 40 Canadian rivers across four ecozones, we examined the spatial scales at which land use was most closely associated with drinking source water quality metrics. Exploratory linear mixed-effects models accounting for climatic, hydrological, and physiographic variation among sites suggested that different spatial areas of land-use influence drinking source water quality depending on the parameter and season investigated. Escherichia coli spatial variability was only associated with land use at a local (5-10 km) spatial scale. Turbidity measures exhibited a complex association with land use, suggesting that the land-use areas of greatest influence can range from a 1 km subcatchment to the entire watershed depending on the season. Total organic carbon concentrations were only associated with land use characterized at the entire watershed scale. The Canadian Council of Ministers of the Environment Water Quality Index was used to calculate a composite measure of seasonal drinking source water quality but did not provide additional information beyond the analyses of individual parameters. These results suggest that entire watershed management is required to safeguard drinking water sources with more focused efforts at targeted spatial scales to reduce specific risk parameters.

Risk-adjusted hospital outcomes for children's surgery.

PubMed

Saito, Jacqueline M; Chen, Li Ern; Hall, Bruce L; Kraemer, Kari; Barnhart, Douglas C; Byrd, Claudia; Cohen, Mark E; Fei, Chunyuan; Heiss, Kurt F; Huffman, Kristopher; Ko, Clifford Y; Latus, Melissa; Meara, John G; Oldham, Keith T; Raval, Mehul V; Richards, Karen E; Shah, Rahul K; Sutton, Laura C; Vinocur, Charles D; Moss, R Lawrence

2013-09-01

BACKGROUND The American College of Surgeons National Surgical Quality Improvement Program-Pediatric was initiated in 2008 to drive quality improvement in children's surgery. Low mortality and morbidity in previous analyses limited differentiation of hospital performance. Participating institutions included children's units within general hospitals and free-standing children's hospitals. Cases selected by Current Procedural Terminology codes encompassed procedures within pediatric general, otolaryngologic, orthopedic, urologic, plastic, neurologic, thoracic, and gynecologic surgery. Trained personnel abstracted demographic, surgical profile, preoperative, intraoperative, and postoperative variables. Incorporating procedure-specific risk, hierarchical models for 30-day mortality and morbidities were developed with significant predictors identified by stepwise logistic regression. Reliability was estimated to assess the balance of information versus error within models. In 2011, 46 281 patients from 43 hospitals were accrued; 1467 codes were aggregated into 226 groupings. Overall mortality was 0.3%, composite morbidity 5.8%, and surgical site infection (SSI) 1.8%. Hierarchical models revealed outlier hospitals with above or below expected performance for composite morbidity in the entire cohort, pediatric abdominal subgroup, and spine subgroup; SSI in the entire cohort and pediatric abdominal subgroup; and urinary tract infection in the entire cohort. Based on reliability estimates, mortality discriminates performance poorly due to very low event rate; however, reliable model construction for composite morbidity and SSI that differentiate institutions is feasible. The National Surgical Quality Improvement Program-Pediatric expansion has yielded risk-adjusted models to differentiate hospital performance in composite and specific morbidities. However, mortality has low utility as a children's surgery performance indicator. Programmatic improvements have resulted in actionable data.

Writing Across the Curriculum: Writing Assignments. TWI Resource File.

ERIC Educational Resources Information Center

Rish, Shirley; Lapidus-Saltz, Wendy

1982-01-01

THE FOLLOWING IS THE FULL TEXT OF THIS DOCUMENT: If you teach a composition class which is affiliated with a subject-matter course, one of the following assignments may be appropriate for your students. If, on the other hand, you teach a traditionallly constituted composition class, you might give your students the entire list with instructions to…

Effect of the Graded-Gap Layer Composition on the Formation of n + -n - -p Structures in Boron-Implanted Heteroepitaxial Cd x Hg1- x Te Layers

NASA Astrophysics Data System (ADS)

Talipov, N. Kh.; Voitsekhovskii, А. V.; Grigor'ev, D. V.

2014-07-01

Processes of formation of n + -n--p-structures in boron-implanted heteroepitaxial (HEL) CdxHg1-xTe (CMT) layers of p-type grown by molecular beam epitaxy (HEL CMT MBE) with different compositions of the upper graded-gap layer are studied. It is shown that the surface composition (xs) of HEL CMT MBE significantly affects both the electrical parameters of the implanted layer and the spatial distribution of radiation defects of donor type. For HEL CMT MBE with the small surface composition xs = 0.22-0.33, it is found that the layer electron concentration (Ns) is decreased after saturation with accumulation of radiation defects, as the dose of B+ ions is increased in the range of D = 1ṡ1011-3ṡ1015 сm-2. An increase of the surface composition up to xs = 0.49-0.56 results in a significant decrease in Ns and a disappearance of the saturation of concentration in the whole dose range. The value of Ns monotonically increases with the energy (E) of boron ions and composition xs. It is found that for B+-ion energies E = 20-100 keV, the depth of the surface n + -layer increases with increasing energy and exceeds the total projected path of boron ions. However, in the energy range E = 100-150 keV, the depth of n+-layer stops increasing with the increase of the surface composition. The depth (dn) of a lightly doped n--layer monotonically decreases with increasing energy of boron ions in the entire range of E = 20-150 keV. With increasing dose (D) of B+ ions in the interval D = 1ṡ1014-1ṡ1015сm-2, deep n--layers with dn = 4-5 μm are formed only in the HEL CMT MBE with xs = 0.22-0.33. For the samples with xs = 0.49-0.56, the depth changes in the interval dn = 1.5-2.5 μm. At D ≤ 3ṡ1013сm-2, n + -n--p-structure is not formed for all surface compositions, if implantation is performed at room temperature. However, implantation at T = 130°C leads to the formation of a deep n--layer. Planar photodiodes with the n-p-junction area of A = 35×35 μm2 made on the basis of the boron implanted HEL CMT MBE with the surface compositions xs = 0.33-0.56 had high differential resistance Rd = 3ṡ106-107 Ω•cm2 and high product R0 Aeff = 9.0-20.7 Ω•cm2, where Aeff is the effective area of the charge carrier collecting. The values of Rd and R0 Aeff increased with increasing xs. It is found that the layer electron concentration in the boron implanted HEL CMT MBE with different surface compositions is increased, when exposed to normal conditions for a few years.

Composite structural materials

NASA Technical Reports Server (NTRS)

Loewy, Robert G.; Wiberley, Stephen E.

1987-01-01

The development and application of composite materials to aerospace vehicle structures which began in the mid 1960's has now progressed to the point where what can be considered entire airframes are being designed and built using composites. Issues related to the fabrication of non-resin matrix composites and the micro, mezzo and macromechanics of thermoplastic and metal matrix composites are emphasized. Several research efforts are presented. They are entitled: (1) The effects of chemical vapor deposition and thermal treatments on the properties of pitch-based carbon fiber; (2) Inelastic deformation of metal matrix laminates; (3) Analysis of fatigue damage in fibrous MMC laminates; (4) Delamination fracture toughness in thermoplastic matrix composites; (5) Numerical investigation of the microhardness of composite fracture; and (6) General beam theory for composite structures.

A highly conspicuous mineralized composite photonic architecture in the translucent shell of the blue-rayed limpet.

PubMed

Li, Ling; Kolle, Stefan; Weaver, James C; Ortiz, Christine; Aizenberg, Joanna; Kolle, Mathias

2015-02-26

Many species rely on diverse selections of entirely organic photonic structures for the manipulation of light and the display of striking colours. Here we report the discovery of a mineralized hierarchical photonic architecture embedded within the translucent shell of the blue-rayed limpet Patella pellucida. The bright colour of the limpet's stripes originates from light interference in a periodically layered zig-zag architecture of crystallographically co-oriented calcite lamellae. Beneath the photonic multilayer, a disordered array of light-absorbing particles provides contrast for the blue colour. This unique mineralized manifestation of a synergy of two distinct optical elements at specific locations within the continuum of the limpet's translucent protective shell ensures the vivid shine of the blue stripes, which can be perceived under water from a wide range of viewing angles. The stripes' reflection band coincides with the spectral range of minimal light absorption in sea water, raising intriguing questions regarding their functional significance.

A highly conspicuous mineralized composite photonic architecture in the translucent shell of the blue-rayed limpet

NASA Astrophysics Data System (ADS)

Li, Ling; Kolle, Stefan; Weaver, James C.; Ortiz, Christine; Aizenberg, Joanna; Kolle, Mathias

2015-02-01

Many species rely on diverse selections of entirely organic photonic structures for the manipulation of light and the display of striking colours. Here we report the discovery of a mineralized hierarchical photonic architecture embedded within the translucent shell of the blue-rayed limpet Patella pellucida. The bright colour of the limpet’s stripes originates from light interference in a periodically layered zig-zag architecture of crystallographically co-oriented calcite lamellae. Beneath the photonic multilayer, a disordered array of light-absorbing particles provides contrast for the blue colour. This unique mineralized manifestation of a synergy of two distinct optical elements at specific locations within the continuum of the limpet’s translucent protective shell ensures the vivid shine of the blue stripes, which can be perceived under water from a wide range of viewing angles. The stripes’ reflection band coincides with the spectral range of minimal light absorption in sea water, raising intriguing questions regarding their functional significance.

Fiber optic shape sensing for monitoring of flexible structures

NASA Astrophysics Data System (ADS)

Lally, Evan M.; Reaves, Matt; Horrell, Emily; Klute, Sandra; Froggatt, Mark E.

2012-04-01

Recent advances in materials science have resulted in a proliferation of flexible structures for high-performance civil, mechanical, and aerospace applications. Large aspect-ratio aircraft wings, composite wind turbine blades, and suspension bridges are all designed to meet critical performance targets while adapting to dynamic loading conditions. By monitoring the distributed shape of a flexible component, fiber optic shape sensing technology has the potential to provide valuable data during design, testing, and operation of these smart structures. This work presents a demonstration of such an extended-range fiber optic shape sensing technology. Three-dimensional distributed shape and position sensing is demonstrated over a 30m length using a monolithic silica fiber with multiple optical cores. A novel, helicallywound geometry endows the fiber with the capability to convert distributed strain measurements, made using Optical Frequency-Domain Reflectometry (OFDR), to a measurement of curvature, twist, and 3D shape along its entire length. Laboratory testing of the extended-range shape sensing technology shows

Ablation and Thermal Response Property Model Validation for Phenolic Impregnated Carbon Ablator

NASA Technical Reports Server (NTRS)

Milos, F. S.; Chen, Y.-K.

2009-01-01

Phenolic Impregnated Carbon Ablator was the heatshield material for the Stardust probe and is also a candidate heatshield material for the Orion Crew Module. As part of the heatshield qualification for Orion, physical and thermal properties were measured for newly manufactured material, included emissivity, heat capacity, thermal conductivity, elemental composition, and thermal decomposition rates. Based on these properties, an ablation and thermal-response model was developed for temperatures up to 3500 K and pressures up to 100 kPa. The model includes orthotropic and pressure-dependent thermal conductivity. In this work, model validation is accomplished by comparison of predictions with data from many arcjet tests conducted over a range of stagnation heat flux and pressure from 107 Watts per square centimeter at 2.3 kPa to 1100 Watts per square centimeter at 84 kPa. Over the entire range of test conditions, model predictions compare well with measured recession, maximum surface temperatures, and in depth temperatures.

A highly conspicuous mineralized composite photonic architecture in the translucent shell of the blue-rayed limpet

DOE PAGES

Li, Ling; Kolle, Stefan; Weaver, James C.; ...

2015-02-26

Many species rely on diverse selections of entirely organic photonic structures for the manipulation of light and the display of striking colours. Here we report the discovery of a mineralized hierarchical photonic architecture embedded within the translucent shell of the blue-rayed limpet Patella pellucida. The bright colour of the limpet’s stripes originates from light interference in a periodically layered zig-zag architecture of crystallographically co-oriented calcite lamellae. Beneath the photonic multilayer, a disordered array of light-absorbing particles provides contrast for the blue colour. This unique mineralized manifestation of a synergy of two distinct optical elements at specific locations within the continuummore » of the limpet’s translucent protective shell ensures the vivid shine of the blue stripes, which can be perceived under water from a wide range of viewing angles. The stripes’ reflection band coincides with the spectral range of minimal light absorption in sea water, raising intriguing questions regarding their functional significance.« less

Home-range use patterns and movements of the Siberian flying squirrel in urban forests: Effects of habitat composition and connectivity.

PubMed

Mäkeläinen, Sanna; de Knegt, Henrik J; Ovaskainen, Otso; Hanski, Ilpo K

2016-01-01

Urbanization causes modification, fragmentation and loss of native habitats. Such landscape changes threaten many arboreal and gliding mammals by limiting their movements through treeless parts of a landscape and by making the landscape surrounding suitable habitat patches more inhospitable. Here, we investigate the effects of landscape structure and habitat availability on the home-range use and movement patterns of the Siberian flying squirrel (Pteromys volans) at different spatial and temporal scales. We followed radio-tagged individuals in a partly urbanized study area in Eastern Finland, and analysed how landscape composition and connectivity affected the length and speed of movement bursts, distances moved during one night, and habitat and nest-site use. The presence of urban habitat on movement paths increased both movement lengths and speed whereas nightly distances travelled by males decreased with increasing amount of urban habitat within the home range. The probability of switching from the present nest site to another nest site decreased with increasing distance among the nest sites, but whether the nest sites were connected or unconnected by forests did not have a clear effect on nest switching. Flying squirrels preferred to use mature forests for their movements at night. Our results suggest that the proximity to urban habitats modifies animal movements, possibly because animals try to avoid such habitats by moving faster through them. Urbanization at the scale of an entire home range can restrict their movements. Thus, maintaining a large enough amount of mature forests around inhabited landscape fragments will help protect forest specialists in urban landscapes. The effect of forested connections remains unclear, highlighting the difficulty of measuring and preserving connectivity in a species-specific way.

On the Physical Environment in the Galactic Nuclei. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Beall, J. H.

1979-01-01

Galactic nuclei and quasars emit radiation over the entire electromagnetic spectrum. This suggests that concurrent observations over a wide frequency range may provide useful information in determining appropriate models for the physical environment in which the radiation is produced. In conjunction with observations by the high energy spectrometer on OSO-8, four sources have been studied in this manner; the nucleus of the elliptical galaxy, Centaurus A (NGG 5128); the quasar, 30273; the Seyfert galaxy, NGC 4151 and the nucleus of the Milky Way (GCX). Concurrent observations are used to construct the composite spectra (from radio to X-ray) for Cen A and NGC 4151 while the composite spectra of 30273 and GCX are derived from the OSO-8 data and from other observers. A skymap technique used to analyze observations of the galactic center region yielded data consistent with a significant, hard X-ray source at the radio and infrared position of the nucleus of the Milky Way. A theoretical analysis of the temporal variability of the Cen A data is undertaken and its implications discussed. Similarities between the composite spectra of the observed sources suggest that radio-bright and radio-quiet quasars may represent the emission from galactic nuclei with elliptical and Seyfert-like morphologies, respectively.

Effect of chlorination on the TlBr band edges for improved room temperature radiation detectors: Effect of chlorination on the TlBr band edges for radiation detectors

DOE PAGES

Varley, J. B.; Conway, A. M.; Voss, L. F.; ...

2015-02-09

Thallium bromide (TlBr) crystals subjected to hydrochloric acid (HCl) chemical treatments have been shown to advantageously affect device performance and longevity in TlBr-based room temperature radiation detectors, yet the exact mechanisms of the improvements remain poorly understood. Here in this paper, we investigate the influence of several HCl chemical treatments on device-grade TlBr and describe the changes in the composition and electronic structure of the surface. Composition analysis and depth profiles obtained from secondary ion mass spectrometry (SIMS) identify the extent to which each HCl etch condition affects the detector surface region and forms of a graded TlBr/TlBr 1-xCL xmore » surface heterojunction. Using a combination of X-ray photoemission spectroscopy (XPS) and hybrid density functional calculations, we are able to determine the valence band offsets, band gaps, and conduction band offsets as a function of Cl content over the entire composition range of TIBr 1-xC1 X. This study establishes a strong correlation between device process conditions, surface chemistry, and electronic structure with the goal of further optimizing the long-term stability and radiation response of TlBr-based detectors.« less

Synthesis and characterization of goethite and goethite-hematite composite: experimental study and literature survey.

PubMed

Kosmulski, Marek; Maczka, Edward; Jartych, Elzbieta; Rosenholm, Jarl B

2003-03-19

Aging of synthetic goethite at 140 degrees C overnight leads to a composite material in which hematite is detectable by Mössbauer spectroscopy, but X-ray diffraction does not reveal any hematite peaks. The pristine point of zero charge (PZC) of synthetic goethite was found at pH 9.4 as the common intersection point of potentiometric titration curves at different ionic strengths and the isoelectric point (IEP). For the goethite-hematite composite, the common intersection point (pH 9.4), and the IEP (pH 8.8) do not match. The electrokinetic potential of goethite at ionic strengths up to 1 mol dm(-3) was determined. Unlike metal oxides, for which the electrokinetic potential is reversed to positive over the entire pH range at sufficiently high ionic strength, the IEP of goethite is rather insensitive to the ionic strength. A literature survey of published PZC/IEP values of iron oxides and hydroxides indicated that the average PZC/IEP does not depend on the degree of hydration (oxide or hydroxide). Our material showed a higher PZC and IEP than most published results. The present results confirm the allegation that electroacoustic measurements produce a higher IEP than the average IEP obtained by means of classical electrokinetic methods.

Electromagnetic Spectroscopy of Normal Breast Tissue Specimens Obtained From Reduction Surgeries: Comparison of Optical and Microwave Properties

PubMed Central

Lazebnik, Mariya; Zhu, Changfang; Palmer, Gregory M.; Harter, Josephine; Sewall, Sarah; Ramanujam, Nirmala; Hagness, Susan C.

2009-01-01

Techniques utilizing electromagnetic energy at microwave and optical frequencies have been shown to be promising for breast cancer detection and diagnosis. Since different biophysical mechanisms are exploited at these frequencies to discriminate between healthy and diseased tissue, combining these two modalities may result in a more powerful approach for breast cancer detection and diagnosis. Toward this end, we performed microwave dielectric spectroscopy and optical diffuse reflectance spectroscopy measurements at the same sites on freshly-excised normal breast tissues obtained from reduction surgeries at the University of Wisconsin Hospital, using microwave and optical probes with very similar sensing volumes. We found that the microwave dielectric constant and effective conductivity are correlated with tissue composition across the entire measurement frequency range (|r|~0.5–0.6, p<0.01), and that the optical absorption coefficient at 460 nm and optical scattering coefficient are correlated with tissue composition (|r|~ 0.4–0.6, p<0.02). Finally, we found that the optical absorption coefficient at 460 nm is correlated with the microwave dielectric constant and effective conductivity (r=−0.55, p<0.01). Our results suggest that combining optical and microwave modalities for analyzing breast tissue samples may serve as a crosscheck and provide complementary information about tissue composition. PMID:18838370

Electromagnetic spectroscopy of normal breast tissue specimens obtained from reduction surgeries: comparison of optical and microwave properties.

PubMed

Lazebnik, Mariya; Zhu, Changfang; Palmer, Gregory M; Harter, Josephine; Sewall, Sarah; Ramanujam, Nirmala; Hagness, Susan C

2008-10-01

Techniques utilizing electromagnetic energy at microwave and optical frequencies have been shown to be promising for breast cancer detection and diagnosis. Since different biophysical mechanisms are exploited at these frequencies to discriminate between healthy and diseased tissue, combining these two modalities may result in a more powerful approach for breast cancer detection and diagnosis. Toward this end, we performed microwave dielectric spectroscopy and optical diffuse reflectance spectroscopy measurements at the same sites on freshly excised normal breast tissues obtained from reduction surgeries at the University of Wisconsin Hospital, using microwave and optical probes with very similar sensing volumes. We found that the microwave dielectric constant and effective conductivity are correlated with tissue composition across the entire measurement frequency range (|r| approximately 0.5-0.6, p<0.01) and that the optical absorption coefficient at 460 nm and optical scattering coefficient are correlated with tissue composition (|r| approximately 0.4-0.6, p<0.02). Finally, we found that the optical absorption coefficient at 460 nm is correlated with the microwave dielectric constant and effective conductivity (r=-0.55, p<0.01). Our results suggest that combining optical and microwave modalities for analyzing breast tissue samples may serve as a crosscheck and provide complementary information about tissue composition.

Heliosphere Instrument for Spectra, Composition and Anisotropy at Low Energies

NASA Technical Reports Server (NTRS)

Lanzerotti, L. J.; Gold, R. E.; Anderson, K. A.; Armstrong, T. P.; Lin, R. P.; Krimigis, S. M.; Pick, M.; Roelof, E. C.; Sarris, E. T.; Simnett, G. M.

1992-01-01

The Heliosphere Instrument for Spectra, Composition, and Anisotropy at Low Energies (HI-SCALE) is designed to make measurements of interplanetary ions and electrons throughout the entire Ulysses mission. The ions (E(i) greater than about 50 keV) and electrons (E(e) greater than about 30 keV) are identified uniquely and detected by five separate solid-state detector telescopes that are oriented to give nearly complete pitch-angle coverage from the spinning spacecraft. Ion elemental abundances are determined by Delta E vs E telescope using a thin (5 microns) front solid state detector element in a three-element telescope. Experimental operation is controlled by a microprocessor-based data system. Inflight calibration is provided by radioactive sources mounted on telescope covers which can be closed for calibration purposes and for radiation protection during the course of the mission. Ion and electron spectral information is determined using both broad-energy-range rate channels and a 32 channel pulse-height analyzer for more detailed spectra. Some initial in-ecliptic measurements are presented which demonstrate the features of the instrument.

Thermodynamic analysis and experimental study on the oxidation of the Zn-Al-Mg coating baths

NASA Astrophysics Data System (ADS)

Su, Xuping; Zhou, Jie; Wang, Jianhua; Wu, Changjun; Liu, Ya; Tu, Hao; Peng, Haoping

2017-02-01

Surface oxidation of molten Zn-6Al baths containing 0.0, 3.0 and 6.0 wt. % Mg were analyzed using X-ray photoelectron spectroscopy. γ-Al2O3 is formed on the surface of the Zn-6Al bath, while MgAl2O4 and MgO occur at 460 °C in the Zn-6Al-3Mg and Zn-6Al-6Mg baths, respectively. Thermodynamic analysis on the oxidation of the Zn-Al-Mg baths was performed. Calculated phase diagrams at 460 °C and 560 °C show good agreements with the experimental results. MgO or MgAl2O4 exists in almost the entire composition range of the calculated oxidation diagrams. According to the calculation, oxidation products depend on the composition and temperature of the baths. The primary and secondary oxidation products of the Zn-Al-Mg baths can be reasonably explained by oxidation phase diagrams. Utilizing these results, the favorable practical bath melts and operating conditions can be designed.

Space Processing Applications Rocket (SPAR) project: SPAR 10

NASA Technical Reports Server (NTRS)

Poorman, R. (Compiler)

1986-01-01

The Space Processing Applications Rocket Project (SPAR) X Final Report contains the compilation of the post-flight reports from each of the Principal Investigators (PIs) on the four selected science payloads, in addition to the engineering report as documented by the Marshall Space Flight Center (MSFC). This combined effort also describes pertinent portions of ground-based research leading to the ultimate selection of the flight sample composition, including design, fabrication and testing, all of which are expected to contribute to an improved comprehension of materials processing in space. The SPAR project was coordinated and managed by MSFC as part of the Microgravity Science and Applications (MSA) program of the Office of Space Science and Applications (OSSA) of NASA Headquarters. This technical memorandum is directed entirely to the payload manifest flown in the tenth of a series of SPAR flights conducted at the White Sands Missile Range (WSMR) and includes the experiments entitled, Containerless Processing Technology, SPAR Experiment 76-20/3; Directional Solidification of Magnetic Composites, SPAR Experiment 76-22/3; Comparative Alloy Solidification, SPAR Experiment 76-36/3; and Foam Copper, SPAR Experiment 77-9/1R.

On Growth and Form of the Zebrafish Gut Microbiome

NASA Astrophysics Data System (ADS)

Jemielita, Matthew; Taormina, Michael; Rolig, Annah; Burns, Adam; Hampton, Jennifer; Guillemin, Karen; Parthasarathy, Raghuveer

2014-03-01

The vertebrate gut is home to a diverse microbial community whose composition has a strong influence on the development and health of the host organism. Researchers can identify the members of the microbiota, yet little is known about the spatial and temporal dynamics of these microbial communities, including the mechanisms guiding their nucleation, growth, and interactions. We address these issues using the larval zebrafish (Danio rerio) as a model organism, which are raised microbe-free and then inoculated with controlled compositions of fluorophore-expressing bacteria. Live imaging using light sheet fluorescence microscopy enables visualization of the gut's entire microbial population over the first 24 hours of colonization. Image analysis allows us to quantify microbial populations that range from a few individuals to tens of thousands of microbes, and analyze the structure and growth kinetics of gut bacterial communities. We find that genetically-identical microbes can show surprisingly different growth rates and colonization abilities depending on their order of arrival. This demonstrates that knowing only the constituents of the gut community is insufficient to determine their dynamics; rather, the history of colonization matters.

Changes in texture, colour and fatty acid composition of male and female pig shoulder fat due to different dietary fat sources.

PubMed

Hallenstvedt, E; Kjos, N P; Overland, M; Thomassen, M

2012-03-01

Two experiments with 72 slaughter pigs in each were conducted. Entire males and females were individually fed restricted. Palm kernel-, soybean- and fish-oil were used in varying combinations, giving different dietary fat levels (29-80g/kg) and iodine values ranging from 50 to 131. Shoulder fat was analysed for fatty acid composition (inner and outer layer), firmness and colour. A clear dose-response relationship was seen between fatty acids in diets and in shoulder fat. Interestingly, the very long chain n-3 fatty acids seemed to be deposited more efficiently when additional fat was included in the diet. Both high and low dietary iodine values changed towards less extreme iodine values in fat. Low-fat diets enhanced de novo synthesis of fatty acids. Males revealed a higher percentage of PUFA and a lower percentage of C18:1 and MUFA. Fat firmness, but not colour, was influenced by sex and dietary fat source. Copyright © 2011 Elsevier Ltd. All rights reserved.

Percolation in suspensions of hard nanoparticles: From spheres to needles

NASA Astrophysics Data System (ADS)

Schilling, Tanja; Miller, Mark A.; van der Schoot, Paul

2015-09-01

We investigate geometric percolation and scaling relations in suspensions of nanorods, covering the entire range of aspect ratios from spheres to extremely slender needles. A new version of connectedness percolation theory is introduced and tested against specialised Monte Carlo simulations. The theory accurately predicts percolation thresholds for aspect ratios of rod length to width as low as 10. The percolation threshold for rod-like particles of aspect ratios below 1000 deviates significantly from the inverse aspect ratio scaling prediction, thought to be valid in the limit of infinitely slender rods and often used as a rule of thumb for nanofibres in composite materials. Hence, most fibres that are currently used as fillers in composite materials cannot be regarded as practically infinitely slender for the purposes of percolation theory. Comparing percolation thresholds of hard rods and new benchmark results for ideal rods, we find that i) for large aspect ratios, they differ by a factor that is inversely proportional to the connectivity distance between the hard cores, and ii) they approach the slender rod limit differently.

Viscosities of Fe Ni, Fe Co and Ni Co binary melts

NASA Astrophysics Data System (ADS)

Sato, Yuzuru; Sugisawa, Koji; Aoki, Daisuke; Yamamura, Tsutomu

2005-02-01

Viscosities of three binary molten alloys consisting of the iron group elements, Fe, Ni and Co, have been measured by using an oscillating cup viscometer over the entire composition range from liquidus temperatures up to 1600 °C with high precision and excellent reproducibility. The viscosities measured showed good Arrhenius linearity for all the compositions. The viscosities of Fe, Ni and Co as a function of temperature are as follows: \\eqalign{ & \\log \\eta={-}0.6074 + 2493/T\\qquad for\\quad Fe\\\\ & \\log \\eta={-}0.5695 + 2157/T\\qquad for\\quad Ni \\\\ & \\log \\eta={-}0.6620 + 2430/T\\qquad for\\quad Co.} The isothermal viscosities of Fe-Ni and Fe-Co binary melts increase monotonically with increasing Fe content. On the other hand, in Ni-Co binary melt, the isothermal viscosity decreases slightly and then increases with increasing Co. The activation energy of Fe-Co binary melt increased slightly on mixing, and those of Fe-Ni and Ni-Co melts decreased monotonically with increasing Ni content. The above behaviour is discussed based on the thermodynamic properties of the alloys.

AVHRR composite period selection for land cover classification

USGS Publications Warehouse

Maxwell, S.K.; Hoffer, R.M.; Chapman, P.L.

2002-01-01

Multitemporal satellite image datasets provide valuable information on the phenological characteristics of vegetation, thereby significantly increasing the accuracy of cover type classifications compared to single date classifications. However, the processing of these datasets can become very complex when dealing with multitemporal data combined with multispectral data. Advanced Very High Resolution Radiometer (AVHRR) biweekly composite data are commonly used to classify land cover over large regions. Selecting a subset of these biweekly composite periods may be required to reduce the complexity and cost of land cover mapping. The objective of our research was to evaluate the effect of reducing the number of composite periods and altering the spacing of those composite periods on classification accuracy. Because inter-annual variability can have a major impact on classification results, 5 years of AVHRR data were evaluated. AVHRR biweekly composite images for spectral channels 1-4 (visible, near-infrared and two thermal bands) covering the entire growing season were used to classify 14 cover types over the entire state of Colorado for each of five different years. A supervised classification method was applied to maintain consistent procedures for each case tested. Results indicate that the number of composite periods can be halved-reduced from 14 composite dates to seven composite dates-without significantly reducing overall classification accuracy (80.4% Kappa accuracy for the 14-composite data-set as compared to 80.0% for a seven-composite dataset). At least seven composite periods were required to ensure the classification accuracy was not affected by inter-annual variability due to climate fluctuations. Concentrating more composites near the beginning and end of the growing season, as compared to using evenly spaced time periods, consistently produced slightly higher classification values over the 5 years tested (average Kappa) of 80.3% for the heavy early/late case as compared to 79.0% for the alternate dataset case).

Geochemical Relationships between Middle- to Upper-Crustal Exposures of the Alisitos Oceanic Arc (Baja California, Mexico): An Outstanding Field Analog to Active Extensional Oceanic Arcs

NASA Astrophysics Data System (ADS)

Morris, R.; DeBari, S. M.; Busby, C.; Medynski, S.

2016-12-01

The southern volcano-bounded basin of the Rosario segment of the Cretaceous Alisitos oceanic arc provides outstanding 3-D exposures of an extensional arc, where crustal generation processes are recorded in the upper-crustal volcanic units and underlying middle-crustal plutonic rocks. Geochemical linkages between exposed crustal levels provide an analog for extensional arc systems such as the Izu-Bonin-Mariana (IBM) Arc. Upper-crustal units comprise a 3-5 km thick volcanic-volcaniclastic stratigraphy with hypabyssal intrusions. Deep-seated plutonic rocks intrude these units over a transition of <500m, where rafted volcanic blocks and evidence of magma mingling are exposed. Thermobarometry suggests <6 km emplacement depths. Compositional ranges (basalt to rhyolite) and mineral assemblages are similar in both middle-crustal and upper-crustal units, with striking compositional overlap. The most mafic compositions occur in upper-crustal hypabyssal units, and as amphibole cumulates in the plutonic rocks ( 51% SiO2). The most felsic compositions occur in welded ignimbrites and a tonalite pluton ( 71% SiO2). All units are low K with flat REE patterns, and show LILE enrichment and HFSE depletion. Trace element ratios show limited variation throughout the crustal section. Zr/Y and Nb/Y ratios are similar to the Izu active ( 3 Ma to present) zone of extension immediately behind the arc front, suggesting comparable mantle melt % during extension. Th/Zr ratios are more enriched in Alisitos compared to Izu, suggesting greater subducted sediment input. The Alisitos crustal section shows a limited range in ɛNd (5.7-7.1), but a wider range in 87Sr/86Sr (0.7035-0.7055) and 206Pb/204Pb (18.12-19.12); the latter is likely alteration effects. Arc magmas were derived from a subduction-modified MORB mantle source, less depleted than Izu arc front and less enriched than the rear arc, but is a good match with the zone of extension that lies between. Differentiation occurred in a closed system (i.e., fractional crystallization/self-melting with back mixing), producing the entire crustal section in <3 Ma.

Emission color-tuned light-emitting diode microarrays of nonpolar In xGa 1–xN/GaN multishell nanotube heterostructures

DOE PAGES

Hong, Young Joon; Lee, Chul -Ho; Yoo, Jinkyoung; ...

2015-12-09

Integration of nanostructure lighting source arrays with well-defined emission wavelengths is of great importance for optoelectronic integrated monolithic circuitry. We report on the fabrication and optical properties of GaN-based p–n junction multishell nanotube microarrays with composition-modulated nonpolar m-plane In xGa 1–xN/GaN multiple quantum wells (MQWs) integrated on c-sapphire or Si substrates. The emission wavelengths were controlled in the visible spectral range of green to violet by varying the indium mole fraction of the In xGa 1–xN MQWs in the range 0.13 ≤ x ≤ 0.36. Homogeneous emission from the entire area of the nanotube LED arrays was achieved via themore » formation of MQWs with uniform QW widths and composition by heteroepitaxy on the well-ordered nanotube arrays. Importantly, the wavelength-invariant electroluminescence emission was observed above a turn-on of 3.0 V because both the quantum-confinement Stark effect and band filling were suppressed due to the lack of spontaneous inherent electric field in the m-plane nanotube nonpolar MQWs. Lastly, the method of fabricating the multishell nanotube LED microarrays with controlled emission colors has potential applications in monolithic nonpolar photonic and optoelectronic devices on commonly used c-sapphire and Si substrates.« less

Performance metric comparison study for non-magnetic bi-stable energy harvesters

NASA Astrophysics Data System (ADS)

Udani, Janav P.; Wrigley, Cailin; Arrieta, Andres F.

2017-04-01

Energy harvesting employing non-linear systems offers considerable advantages over linear systems given the broadband resonant response which is favorable for applications involving diverse input vibrations. In this respect, the rich dynamics of bi-stable systems present a promising means for harvesting vibrational energy from ambient sources. Harvesters deriving their bi-stability from thermally induced stresses as opposed to magnetic forces are receiving significant attention as it reduces the need for ancillary components and allows for bio- compatible constructions. However, the design of these bi-stable harvesters still requires further optimization to completely exploit the dynamic behavior of these systems. This study presents a comparison of the harvesting capabilities of non-magnetic, bi-stable composite laminates under variations in the design parameters as evaluated utilizing established power metrics. Energy output characteristics of two bi-stable composite laminate plates with a piezoelectric patch bonded on the top surface are experimentally investigated for variations in the thickness ratio and inertial mass positions for multiple load conditions. A particular design configuration is found to perform better over the entire range of testing conditions which include single and multiple frequency excitation, thus indicating that design optimization over the geometry of the harvester yields robust performance. The experimental analysis further highlights the need for appropriate design guidelines for optimization and holistic performance metrics to account for the range of operational conditions.

Studies of the Coldest Brown Dwarfs With The James Webb Space Telescope

NASA Astrophysics Data System (ADS)

Roellig, Thomas L.; Greene, Thomas P.; Beichman, Charles; Meyer, Michael; Rieke, Marcia

2016-07-01

The coolest T and Y-class Brown Dwarf objects are very faint and are therefore very poorly understood, since they are barely detectable with the current astronomical instrumentation. The upcoming James Webb Space Telescope now in development for a launch in the Fall of 2018 will have vastly increased sensitivity in the near and mid-infrared compared to any current facilities and will not be affected by telluric absorption over its entire wavelength range of operations. As a result it will be an ideal tool to obtain information about the composition and temperature-pressure structure in these objects' atmospheres. This presentation outlines the JWST guaranteed time observing plans for these studies. These plans comprise both spectro-photometric and spectroscopic observations of a selection of late T and Y-dwarf targets.

NM-Scale Anatomy of an Entire Stardust Carrot Track

NASA Technical Reports Server (NTRS)

Nakamura-Messenger, K.; Keller, L. P.; Clemett, S. J.; Messenger, S.

2009-01-01

Comet Wild-2 samples collected by NASA s Stardust mission are extremely complex, heterogeneous, and have experienced wide ranges of alteration during the capture process. There are two major types of track morphologies: "carrot" and "bulbous," that reflect different structural/compositional properties of the impactors. Carrot type tracks are typically produced by compact or single mineral grains which survive essentially intact as a single large terminal particle. Bulbous tracks are likely produced by fine-grained or organic-rich impactors [1]. Owing to their challenging nature and especially high value of Stardust samples, we have invested considerable effort in developing both sample preparation and analytical techniques tailored for Stardust sample analyses. Our report focuses on our systematic disassembly and coordinated analysis of Stardust carrot track #112 from the mm to nm-scale.

Refractive index of B1-xGaxN semiconductors

NASA Astrophysics Data System (ADS)

Vyas, P. S.; Baria, J. K.; Jivani, A. R.; Gajjar, P. N.; Jani, A. R.

2013-06-01

A theoretical procedure is presented for the study of refractive index of ternary alloy B1-xGaxN. The calculations based on the pseudopotential formalism in which local potential coupled with the virtual crystal approximation (VCA) is applied to evaluate energy band gap at point X on the Jones-zone face, refractive index for the entire range of the alloy composition x of the ternary alloy B1-xGaxN. To include exchange and correlation effects, local field correction function due to Nagy is employed. Our results for parent compounds are compared to experiment and other available theoretical findings and showed generally good agreement. During present study it is found that the refractive index of the ternary alloy B1-xGaxN has minimum value at gallium concentration x = 0.4.

Low loading of carbon nanotubes to enhance acoustical properties of poly(ether)urethane foams

NASA Astrophysics Data System (ADS)

Basirjafari, Sedigheh; Malekfar, Rasoul; Esmaielzadeh Khadem, Siamak

2012-11-01

The aim of this paper is to fabricate a sound absorber flexible semi-open cell polymeric foam based on polyether urethane (PEU) with carboxylic functionalized multi-walled carbon nanotubes (COOH-MWCNTs) as an energy decaying filler at low loadings up to 0.20 wt. %. This paper provides the relationship between the mentioned foam microstructure via field emission scanning electron microscopy and different acoustical and non-acoustical properties of PEU/COOH-MWCNT composites. Addition of just 0.05 wt. % COOH-MWCNTs enhanced the sound absorption coefficient of the mentioned nanocomposite foam over the entire frequency range. Raman spectra revealed the better dispersion of COOH-MWCNTs in the PEU matrix leading to more stress transfer between them to cause a significant dissipation of energy.

Study on Solution Properties of Binary Mixtures of Some Industrially Important Solvents with Cyclohexylamine and Cyclohexanone at 298.15 K

NASA Astrophysics Data System (ADS)

Roy, Mahendra Nath; Das, Rajesh Kumar; Chanda, Riju

2010-03-01

Densities and viscosities were measured for the binary mixtures of cyclohexylamine and cyclohexanone with butyl acetate, butanone, butylamine, tert-butylamine, and 2-butoxyethanol at 298.15 K over the entire composition range. From density data, the values of the excess molar volume ( V E) have been calculated. The experimental viscosity data were correlated by means of the equation of Grunberg-Nissan. The density and viscosity data have been analyzed in terms of some semiempirical viscosity models. The results are discussed in terms of molecular interactions and structural effects. The excess molar volume is found to be either negative or positive depending on the molecular interactions and the nature of the liquid mixtures and is discussed in terms of molecular interactions and structural changes.

Space processing applications rocket project. SPAR 8

NASA Technical Reports Server (NTRS)

Chassay, R. P. (Editor)

1984-01-01

The Space Processing Applications Rocket Project (SPAR) VIII Final Report contains the engineering report prepared at the Marshall Space Flight Center (MSFC) as well as the three reports from the principal investigators. These reports also describe pertinent portions of ground-based research leading to the ultimate selection of the flight sample composition, including design, fabrication, and testing, all of which are expected to contribute immeasurably to an improved comprehension of materials processing in space. This technical memorandum is directed entirely to the payload manifest flown in the eighth of a series of SPAR flights conducted at the White Sands Missile Range (WSMR) and includes the experiments entitled Glass Formation Experiment SPAR 74-42/1R, Glass Fining Experiment in Low-Gravity SPAR 77-13/1, and Dynamics of Liquid Bubbles SPAR Experiment 77-18/2.

Polymer film composite transducer

DOEpatents

Owen, Thomas E.

2005-09-20

A composite piezoelectric transducer, whose piezoeletric element is a "ribbon wound" film of piezolectric material. As the film is excited, it expands and contracts, which results in expansion and contraction of the diameter of the entire ribbon winding. This is accompanied by expansion and contraction of the thickness of the ribbon winding, such that the sound radiating plate may be placed on the side of the winding.

Surface tensions of inorganic multicomponent aqueous electrolyte solutions and melts.

PubMed

Dutcher, Cari S; Wexler, Anthony S; Clegg, Simon L

2010-11-25

A semiempirical model is presented that predicts surface tensions (σ) of aqueous electrolyte solutions and their mixtures, for concentrations ranging from infinitely dilute solution to molten salt. The model requires, at most, only two temperature-dependent terms to represent surface tensions of either pure aqueous solutions, or aqueous or molten mixtures, over the entire composition range. A relationship was found for the coefficients of the equation σ = c(1) + c(2)T (where T (K) is temperature) for molten salts in terms of ion valency and radius, melting temperature, and salt molar volume. Hypothetical liquid surface tensions can thus be estimated for electrolytes for which there are no data, or which do not exist in molten form. Surface tensions of molten (single) salts, when extrapolated to normal temperatures, were found to be consistent with data for aqueous solutions. This allowed surface tensions of very concentrated, supersaturated, aqueous solutions to be estimated. The model has been applied to the following single electrolytes over the entire concentration range, using data for aqueous solutions over the temperature range 233-523 K, and extrapolated surface tensions of molten salts and pure liquid electrolytes: HCl, HNO(3), H(2)SO(4), NaCl, NaNO(3), Na(2)SO(4), NaHSO(4), Na(2)CO(3), NaHCO(3), NaOH, NH(4)Cl, NH(4)NO(3), (NH(4))(2)SO(4), NH(4)HCO(3), NH(4)OH, KCl, KNO(3), K(2)SO(4), K(2)CO(3), KHCO(3), KOH, CaCl(2), Ca(NO(3))(2), MgCl(2), Mg(NO(3))(2), and MgSO(4). The average absolute percentage error between calculated and experimental surface tensions is 0.80% (for 2389 data points). The model extrapolates smoothly to temperatures as low as 150 K. Also, the model successfully predicts surface tensions of ternary aqueous mixtures; the effect of salt-salt interactions in these calculations was explored.

Ca-rich carbonates associated with ultrabasic-ultramafic melts: Carbonatite or limestone xenoliths? A case study from the late Miocene Morron de Villamayor volcano (Calatrava Volcanic Field, central Spain)

NASA Astrophysics Data System (ADS)

Lustrino, Michele; Prelević, Dejan; Agostini, Samuele; Gaeta, Mario; Di Rocco, Tommaso; Stagno, Vincenzo; Capizzi, Luca Samuele

2016-07-01

The volcanic products of the late Miocene Morron de Villamayor volcano (Calatrava Volcanic Field, central Spain) are known for being one of the few outcrops of leucitites in the entire circum-Mediterranean area. These rocks are important because aragonite of mantle origin has been reported as inclusion in olivine macrocrysts. We use petrographic observations, mineral compositions, as well as oxygen and carbon isotope ratios coupled with experimental petrology to understand the origin of carbonate phase in these olivine-phyric rocks. Groundmass and macrocryst olivines range from δ18OVSMOW of +4.8‰, typical of mantle olivine values, to +7.4‰, indicating contamination by sedimentary carbonate. Carbonates are characterized by heavy oxygen isotope compositions (δ18OVSMOW >+24‰), and relatively light carbon isotopes (δ13CPDB <-11‰), resembling skarn values, and distinct from typical mantle carbonatite compositions. Petrography, mineral compositions such as low Mg# of clinopyroxene and biotite, low Ca# and low incompatible element abundance of the carbonate, and isotopic ratios of O and C, do not support a mantle origin for the carbonate. Rather, the carbonate inclusions found in the olivine macrocrysts are interpreted as basement limestone fragments entrapped by the rising crystallizing magma. Comparison with experimental carbonatitic and silicate-carbonatitic melts indicates that low-degree partial melts of a carbonated peridotite must have a dolomitic rather than the aragonitic/calcitic composition as those found trapped in the Morron de Villamayor olivine macrocrysts.

Tunable Twin Matching Frequency (fm1/fm2) Behavior of Ni1−xZnxFe2O4/NBR Composites over 2–12.4 GHz: A Strategic Material System for Stealth Applications

PubMed Central

Saini, Lokesh; Patra, Manoj Kumar; Jani, Raj Kumar; Gupta, Goutam Kumar; Dixit, Ambesh; Vadera, Sampat Raj

2017-01-01

The gel to carbonate precipitate route has been used for the synthesis of Ni1−xZnxFe2O4 (x = 0, 0.25, 0.5 and 0.75) bulk inverse spinel ferrite powder samples. The optimal zinc (50%) substitution has shown the maximum saturation magnetic moment and resulted into the maximum magnetic loss tangent (tanδm) > −1.2 over the entire 2–10 GHz frequency range with an optimum value ~−1.75 at 6 GHz. Ni0.5Zn0.5Fe2O4- Acrylo-Nitrile Butadiene Rubber (NBR) composite samples are prepared at different weight percentage (wt%) of ferrite loading fractions in rubber for microwave absorption evaluation. The 80 wt% loaded Ni0.5Zn0.5Fe2O4/NBR composite (FMAR80) sample has shown two reflection loss (RL) peaks at 5 and 10 GHz. Interestingly, a single peak at 10 GHz for 3.25 mm thickness, can be scaled down to 5 GHz by increasing the thickness up to 4.6 mm. The onset of such twin matching frequencies in FMAR80 composite sample is attributed to the spin resonance relaxation at ~5 GHz (fm1) and destructive interference at λm/4 matched thickness near ~10 GHz (fm2) in these composite systems. These studies suggest the potential of tuning the twin frequencies in Ni0.5Zn0.5Fe2O4/NBR composite samples for possible microwave absorption applications. PMID:28294151

Tunable Twin Matching Frequency (fm1/fm2) Behavior of Ni1-xZnxFe2O4/NBR Composites over 2-12.4 GHz: A Strategic Material System for Stealth Applications.

PubMed

Saini, Lokesh; Patra, Manoj Kumar; Jani, Raj Kumar; Gupta, Goutam Kumar; Dixit, Ambesh; Vadera, Sampat Raj

2017-03-15

The gel to carbonate precipitate route has been used for the synthesis of Ni 1-x Zn x Fe 2 O 4 (x = 0, 0.25, 0.5 and 0.75) bulk inverse spinel ferrite powder samples. The optimal zinc (50%) substitution has shown the maximum saturation magnetic moment and resulted into the maximum magnetic loss tangent (tanδ m ) > -1.2 over the entire 2-10 GHz frequency range with an optimum value ~-1.75 at 6 GHz. Ni 0.5 Zn 0.5 Fe 2 O 4 - Acrylo-Nitrile Butadiene Rubber (NBR) composite samples are prepared at different weight percentage (wt%) of ferrite loading fractions in rubber for microwave absorption evaluation. The 80 wt% loaded Ni 0.5 Zn 0.5 Fe 2 O 4 /NBR composite (FMAR80) sample has shown two reflection loss (RL) peaks at 5 and 10 GHz. Interestingly, a single peak at 10 GHz for 3.25 mm thickness, can be scaled down to 5 GHz by increasing the thickness up to 4.6 mm. The onset of such twin matching frequencies in FMAR80 composite sample is attributed to the spin resonance relaxation at ~5 GHz (f m1 ) and destructive interference at λ m /4 matched thickness near ~10 GHz (f m2 ) in these composite systems. These studies suggest the potential of tuning the twin frequencies in Ni 0.5 Zn 0.5 Fe 2 O 4 /NBR composite samples for possible microwave absorption applications.

Tunable Twin Matching Frequency (fm1/fm2) Behavior of Ni1-xZnxFe2O4/NBR Composites over 2-12.4 GHz: A Strategic Material System for Stealth Applications

NASA Astrophysics Data System (ADS)

Saini, Lokesh; Patra, Manoj Kumar; Jani, Raj Kumar; Gupta, Goutam Kumar; Dixit, Ambesh; Vadera, Sampat Raj

2017-03-01

The gel to carbonate precipitate route has been used for the synthesis of Ni1-xZnxFe2O4 (x = 0, 0.25, 0.5 and 0.75) bulk inverse spinel ferrite powder samples. The optimal zinc (50%) substitution has shown the maximum saturation magnetic moment and resulted into the maximum magnetic loss tangent (tanδm) > -1.2 over the entire 2-10 GHz frequency range with an optimum value ~-1.75 at 6 GHz. Ni0.5Zn0.5Fe2O4- Acrylo-Nitrile Butadiene Rubber (NBR) composite samples are prepared at different weight percentage (wt%) of ferrite loading fractions in rubber for microwave absorption evaluation. The 80 wt% loaded Ni0.5Zn0.5Fe2O4/NBR composite (FMAR80) sample has shown two reflection loss (RL) peaks at 5 and 10 GHz. Interestingly, a single peak at 10 GHz for 3.25 mm thickness, can be scaled down to 5 GHz by increasing the thickness up to 4.6 mm. The onset of such twin matching frequencies in FMAR80 composite sample is attributed to the spin resonance relaxation at ~5 GHz (fm1) and destructive interference at λm/4 matched thickness near ~10 GHz (fm2) in these composite systems. These studies suggest the potential of tuning the twin frequencies in Ni0.5Zn0.5Fe2O4/NBR composite samples for possible microwave absorption applications.

Relationship between topological order and glass forming ability in densely packed enstatite and forsterite composition glasses

PubMed Central

Kohara, S.; Akola, J.; Morita, H.; Suzuya, K.; Weber, J. K. R.; Wilding, M. C.; Benmore, C. J.

2011-01-01

The atomic structures of magnesium silicate melts are key to understanding processes related to the evolution of the Earth’s mantle and represent precursors to the formation of most igneous rocks. Magnesium silicate compositions also represent a major component of many glass ceramics, and depending on their composition can span the entire fragility range of glass formation. The silica rich enstatite (MgSiO3) composition is a good glass former, whereas the forsterite (Mg2SiO4) composition is at the limit of glass formation. Here, the structure of MgSiO3 and Mg2SiO4 composition glasses obtained from levitated liquids have been modeled using Reverse Monte Carlo fits to diffraction data and by density functional theory. A ring statistics analysis suggests that the lower glass forming ability of the Mg2SiO4 glass is associated with a topologically ordered and very narrow ring distribution. The MgOx polyhedra have a variety of irregular shapes in MgSiO3 and Mg2SiO4 glasses and a cavity analysis demonstrates that both glasses have almost no free volume due to a large contribution from edge sharing of MgOx-MgOx polyhedra. It is found that while the atomic volume of Mg cations in the glasses increases compared to that of the crystalline phases, the number of Mg-O contacts is reduced, although the effective chemical interaction of Mg2+ remains similar. This unusual structure-property relation of Mg2SiO4 glass demonstrates that by using containerless processing it may be possible to synthesize new families of dense glasses and glass ceramics with zero porosity. PMID:21873237

Sr isotopic variations in Upper Proterozoic carbonates from Svalbard and East Greenland.

PubMed

Derry, L A; Keto, L S; Jacobsen, S B; Knoll, A H; Swett, K

1989-01-01

We report initial 87Sr/86Sr values from an Upper Proterozoic carbonate succession from Svalbard and East Greenland. This succession, now tectonically separated into three sequences, is thick, relatively continuous, and well preserved. The relative ages of the samples from within the basin are well constrained by litho-, bio-, and chemostratigraphic techniques. The data from this study and related data from the literature are used to construct a curve of 87Sr/86Sr for Upper Proterozoic seawater. The new data reported in this study substantially improve the isotopic record of Sr in seawater for the period between 650 and 800 Ma. The data indicate that delta 87Sr values of seawater were variable but low (delta 87Sr approximately -500 to -250) between 900 and 650 Ma, and rose rapidly to approximately +30 by 600 Ma. The range of variation of delta 87Sr in seawater during the Riphean-Vendian exceeds the entire range of delta 87Sr in seawater during the Phanerozoic. While variation in the average isotopic composition of Sr delivered to the oceans by rivers can account for some of the observed range, changes in the ratio of submarine hydrothermal flux to river water (continental) flux are responsible for the large variation in seawater Sr isotopic composition. Changes in the continental flux of Sr to the oceans can be related to tectonic factors. Large changes in the hydrothermal flux to river water flux ratio indicated by the data could have significant consequences for the chemistry of the ocean-atmosphere system.

Database for the Geologic Map of Upper Eocene to Holocene Volcanic and Related Rocks of the Cascade Range, Oregon

USGS Publications Warehouse

Nimz, Kathryn; Ramsey, David W.; Sherrod, David R.; Smith, James G.

2008-01-01

Since 1979, Earth scientists of the Geothermal Research Program of the U.S. Geological Survey have carried out multidisciplinary research in the Cascade Range. The goal of this research is to understand the geology, tectonics, and hydrology of the Cascades in order to characterize and quantify geothermal resource potential. A major goal of the program is compilation of a comprehensive geologic map of the entire Cascade Range that incorporates modern field studies and that has a unified and internally consistent explanation. This map is one of three in a series that shows Cascade Range geology by fitting published and unpublished mapping into a province-wide scheme of rock units distinguished by composition and age; map sheets of the Cascade Range in Washington (Smith, 1993) and California will complete the series. The complete series forms a guide to exploration and evaluation of the geothermal resources of the Cascade Range and will be useful for studies of volcano hazards, volcanology, and tectonics. This digital release contains all the information used to produce the geologic map published as U.S. Geological Survey Geologic Investigations Series I-2569 (Sherrod and Smith, 2000). The main component of this digital release is a geologic map database prepared using ArcInfo GIS. This release also contains files to view or print the geologic map and accompanying descriptive pamphlet from I-2569.

A domain-specific design architecture for composite material design and aircraft part redesign

NASA Technical Reports Server (NTRS)

Punch, W. F., III; Keller, K. J.; Bond, W.; Sticklen, J.

1992-01-01

Advanced composites have been targeted as a 'leapfrog' technology that would provide a unique global competitive position for U.S. industry. Composites are unique in the requirements for an integrated approach to designing, manufacturing, and marketing of products developed utilizing the new materials of construction. Numerous studies extending across the entire economic spectrum of the United States from aerospace to military to durable goods have identified composites as a 'key' technology. In general there have been two approaches to composite construction: build models of a given composite materials, then determine characteristics of the material via numerical simulation and empirical testing; and experience-directed construction of fabrication plans for building composites with given properties. The first route sets a goal to capture basic understanding of a device (the composite) by use of a rigorous mathematical model; the second attempts to capture the expertise about the process of fabricating a composite (to date) at a surface level typically expressed in a rule based system. From an AI perspective, these two research lines are attacking distinctly different problems, and both tracks have current limitations. The mathematical modeling approach has yielded a wealth of data but a large number of simplifying assumptions are needed to make numerical simulation tractable. Likewise, although surface level expertise about how to build a particular composite may yield important results, recent trends in the KBS area are towards augmenting surface level problem solving with deeper level knowledge. Many of the relative advantages of composites, e.g., the strength:weight ratio, is most prominent when the entire component is designed as a unitary piece. The bottleneck in undertaking such unitary design lies in the difficulty of the re-design task. Designing the fabrication protocols for a complex-shaped, thick section composite are currently very difficult. It is in fact this difficulty that our research will address.

Modern sands of South America: composition, provenance and global significance

NASA Astrophysics Data System (ADS)

Potter, P. E.

1994-03-01

Standard petrographic methods were used to study 604 modern sands from South America, of which 351 came from rivers and 253 from beaches. In spite of the wide geomorphic contrasts, these sands belong to only three great families: (1) an immature Andean family of lithic arenites rich in volcanic and metamorphic grains that covers about 30% of South America; (2) a cratonic association rich in quartz that covers about 62% of the continent; and (3) a transitional, molasse association, which occurs between these two and covers only about 8% of the continent. The grand arithmetic average Q:F: Rf ratio for the entire continent is 60:11:29 and the area-weighted, carbonate-free average Qa:Fa:Rfa is 68:10:22, a superior continental estimate, and the first ever for an entire continent. Rock fragments are the most informative of all the provenance indicators and in South America they range from tropical alterites of the cratonic family through the dominant volcanic and metamorphic grains of the Andean family to biogenic carbonate in beach sands. Carbonate grains are almost totally absent in modern South American rivers because of present day tropical weathering and a long geological evolution that has favored sand production. They are present in many of the beach sands, however, and are most abundant along the tropical Brazilian and Caribbean coasts. Metamorphic grains rival volcanics as earmarks of the Andean family and survive tropical weathering far better than volcanic grains. There is a strong association between continental soil types and the composition of river sand, but the ultimate controls are tectonic history — the ancient landscapes preserved on the Gondwana shields of South America versus the tectonically young landscapes of the Andes — and climate. Climate can either cause ‘leaks’ to a far distant ocean where weathering is retarded by aridity or it can serve as a barrier to continental sand dispersion, where tropical weathering eliminates unstable grains in transit to the sea. When provenance studies are conducted across an entire, unglaciated continent, events in the far distant past need to be considered when seeking fundamental explanations of its contemporary, surficial sands.

High-throughput continuous hydrothermal synthesis of an entire nanoceramic phase diagram.

PubMed

Weng, Xiaole; Cockcroft, Jeremy K; Hyett, Geoffrey; Vickers, Martin; Boldrin, Paul; Tang, Chiu C; Thompson, Stephen P; Parker, Julia E; Knowles, Jonathan C; Rehman, Ihtesham; Parkin, Ivan; Evans, Julian R G; Darr, Jawwad A

2009-01-01

A novel High-Throughput Continuous Hydrothermal (HiTCH) flow synthesis reactor was used to make directly and rapidly a 66-sample nanoparticle library (entire phase diagram) of nanocrystalline Ce(x)Zr(y)Y(z)O(2-delta) in less than 12 h. High resolution PXRD data were obtained for the entire heat-treated library (at 1000 degrees C/1 h) in less than a day using the new robotic beamline I11, located at Diamond Light Source (DLS). This allowed Rietveld-quality powder X-ray diffraction (PXRD) data collection of the entire 66-sample library in <1 day. Consequently, the authors rapidly mapped out phase behavior and sintering behaviors for the entire library. Out of the entire 66-sample heat-treated library, the PXRD data suggests that 43 possess the fluorite structure, of which 30 (out of 36) are ternary compositions. The speed, quantity and quality of data obtained by our new approach, offers an exciting new development which will allow structure-property relationships to be accessed for nanoceramics in much shorter time periods.

Global burned-land estimation in Latin America using MODIS composite data.

PubMed

Chuvieco, Emilio; Opazo, Sergio; Sione, Walter; Del Valle, Hector; Anaya, Jesús; Di Bella, Carlos; Cruz, Isabel; Manzo, Lilia; López, Gerardo; Mari, Nicolas; González-Alonso, Federico; Morelli, Fabiano; Setzer, Alberto; Csiszar, Ivan; Kanpandegi, Jon Ander; Bastarrika, Aitor; Libonati, Renata

2008-01-01

This paper presents results of the AQL2004 project, which has been develope within the GOFC-GOLD Latin American network of remote sensing and forest fires (RedLatif). The project intended to obtain monthly burned-land maps of the entire region, from Mexico to Patagonia, using MODIS (moderate-resolution imaging spectroradiometer) reflectance data. The project has been organized in three different phases: acquisition and preprocessing of satellite data; discrimination of burned pixels; and validation of results. In the first phase, input data consisting of 32-day composites of MODIS 500-m reflectance data generated by the Global Land Cover Facility (GLCF) of the University of Maryland (College Park, Maryland, U.S.A.) were collected and processed. The discrimination of burned areas was addressed in two steps: searching for "burned core" pixels using postfire spectral indices and multitemporal change detection and mapping of burned scars using contextual techniques. The validation phase was based on visual analysis of Landsat and CBERS (China-Brazil Earth Resources Satellite) images. Validation of the burned-land category showed an agreement ranging from 30% to 60%, depending on the ecosystem and vegetation species present. The total burned area for the entire year was estimated to be 153 215 km2. The most affected countries in relation to their territory were Cuba, Colombia, Bolivia, and Venezuela. Burned areas were found in most land covers; herbaceous vegetation (savannas and grasslands) presented the highest proportions of burned area, while perennial forest had the lowest proportions. The importance of croplands in the total burned area should be taken with reserve, since this cover presented the highest commission errors. The importance of generating systematic products of burned land areas for different ecological processes is emphasized.

Ballistic-electron-emission spectroscopy of Al{sub x}Ga{sub 1{minus}x}As/GaAs heterostructures: Conduction-band offsets, transport mechanisms, and band-structure effects

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

OShea, J.J.; Brazel, E.G.; Rubin, M.E.

1997-07-01

We report an extensive investigation of semiconductor band-structure effects in single-barrier Al{sub x}Ga{sub 1{minus}x}As/GaAs heterostructures using ballistic-electron-emission spectroscopy (BEES). The transport mechanisms in these single-barrier structures were studied systematically as a function of temperature and Al composition over the full compositional range (0{le}x{le}1). The initial ({Gamma}) BEES thresholds for Al{sub x}Ga{sub 1{minus}x}As single barriers with 0{le}x{le}0.42 were extracted using a model which includes the complete transmission probability of the metal-semiconductor interface and the semiconductor heterostructure. Band offsets measured by BEES are in good agreement with previous measurements by other techniques which demonstrates the accuracy of this technique. BEES measurements atmore » 77 K give the same band-offset values as at room temperature. When a reverse bias is applied to the heterostructures, the BEES thresholds shift to lower voltages in good agreement with the expected bias-induced band-bending. In the indirect band-gap regime ({ital x}{gt}0.45), spectra show a weak ballistic-electron-emission microscopy current contribution due to intervalley scattering through Al{sub x}Ga{sub 1{minus}x}As {ital X} valley states. Low-temperature spectra show a marked reduction in this intervalley current component, indicating that intervalley phonon scattering at the GaAs/Al{sub x}Ga{sub 1{minus}x}As interface produces a significant fraction of this{ital X} valley current. A comparison of the BEES thresholds with the expected composition dependence of the Al{sub x}Ga{sub 1{minus}x}As {Gamma}, {ital L}, and {ital X} points yields good agreement over the entire composition range. {copyright} {ital 1997} {ital The American Physical Society}« less

Environmental and ecological controls of coral community metabolism on Palmyra Atoll

NASA Astrophysics Data System (ADS)

Koweek, David; Dunbar, Robert B.; Rogers, Justin S.; Williams, Gareth J.; Price, Nichole; Mucciarone, David; Teneva, Lida

2015-03-01

Accurate predictions of how coral reefs may respond to global climate change hinge on understanding the natural variability to which these ecosystems are exposed and to which they contribute. We present high-resolution estimates of net community calcification (NCC) and net community production (NCP) from Palmyra Atoll, an uninhabited, near-pristine coral reef ecosystem in the central Pacific. In August-October 2012, we employed a combination of Lagrangian and Eulerian frameworks to establish high spatial (~2.5 km2) and temporal (hourly) resolution coral community metabolic estimates. Lagrangian drifts, all conducted during daylight hours, resulted in NCC estimates of -51 to 116 mmol C m-2 h-1, although most NCC estimates were in the range of 0-40 mmol C m-2 h-1. Lagrangian drift NCP estimates ranged from -7 to 67 mmol C m-2 h-1. In the Eulerian setup, we present carbonate system parameters (dissolved inorganic carbon, total alkalinity, pH, and pCO2) at sub-hourly resolution through several day-night cycles and provide hourly NCC and NCP rate estimates. We compared diel cycles of all four carbonate system parameters to the offshore surface water (0-50 m depth) and show large departures from offshore surface water chemistry. Hourly Eulerian estimates of NCC aggregated over the entire study ranged from 14 to 53 mmol C m-2 h-1, showed substantial variability during daylight hours, and exhibited a diel cycle with elevated NCC in the afternoons and depressed, but positive, NCC at night. The Eulerian NCP range was very high (-55 to 177 mmol C m-2 h-1) and exhibited strong variability during daylight hours. Principal components analysis revealed that NCC and NCP were most closely aligned with diel cycle forcing, whereas the NCC/NCP ratio was most closely aligned with reef community composition. Our analysis demonstrates that ecological community composition is the primary determinant of coral reef biogeochemistry on a near-pristine reef and that reef biogeochemistry is likely to be responsive to human behaviors that alter community composition.

Nanomembrane structures having mixed crystalline orientations and compositions

DOEpatents

Lagally, Max G.; Scott, Shelley A.; Savage, Donald E.

2014-08-12

The present nanomembrane structures include a multilayer film comprising a single-crystalline layer of semiconductor material disposed between two other single-crystalline layers of semiconductor material. A plurality of holes extending through the nanomembrane are at least partially, and preferably entirely, filled with a filler material which is also a semiconductor, but which differs from the nanomembrane semiconductor materials in composition, crystal orientation, or both.

Water Quality Conditions in the Missouri River Mainstem System 2007 Report

DTIC Science & Technology

2008-06-01

Inicrocystins, and phytoplankton taxa occmTence and relative abundance . 3.1.2 BACTERIA MONITORING AT SWIMMING BEACHES The Distiict has cooperated with the... abundant algae throughout the entire sampling period based on percent composition (Plates 80 - 83). The Shannon-Weaver genera diversity indices...most abundant algae based on percent composition (Plate 180). The Shannon-Weaver genera diversity indices calculated for the 18 phytoplankton samples

Developing the MD Explorer

NASA Astrophysics Data System (ADS)

Howie, Philip V.

1993-04-01

The MD Explorer is an eight-seat twin-turbine engine helicopter which is being developed using integrated product definition (IPD) team methodology. New techniques include NOTAR antitorque system for directional control, a composite fuselage, an all-composite bearingless main rotor, and digital cockpit displays. Three-dimensional CAD models are the basis of the entire Explorer design. Solid models provide vendor with design clarification, removing much of the normal drawing interpretation errors.

Divergent composition but similar function of soil food webs of individual plants: plant species and community effects.

PubMed

Bezemer, T M; Fountain, M T; Barea, J M; Christensen, S; Dekker, S C; Duyts, H; van Hal, R; Harvey, J A; Hedlund, K; Maraun, M; Mikola, J; Mladenov, A G; Robin, C; de Ruiter, P C; Scheu, S; Setälä, H; Smilauer, P; van der Putten, W H

2010-10-01

Soils are extremely rich in biodiversity, and soil organisms play pivotal roles in supporting terrestrial life, but the role that individual plants and plant communities play in influencing the diversity and functioning of soil food webs remains highly debated. Plants, as primary producers and providers of resources to the soil food web, are of vital importance for the composition, structure, and functioning of soil communities. However, whether natural soil food webs that are completely open to immigration and emigration differ underneath individual plants remains unknown. In a biodiversity restoration experiment we first compared the soil nematode communities of 228 individual plants belonging to eight herbaceous species. We included grass, leguminous, and non-leguminous species. Each individual plant grew intermingled with other species, but all plant species had a different nematode community. Moreover, nematode communities were more similar when plant individuals were growing in the same as compared to different plant communities, and these effects were most apparent for the groups of bacterivorous, carnivorous, and omnivorous nematodes. Subsequently, we analyzed the composition, structure, and functioning of the complete soil food webs of 58 individual plants, belonging to two of the plant species, Lotus corniculatus (Fabaceae) and Plantago lanceolata (Plantaginaceae). We isolated and identified more than 150 taxa/groups of soil organisms. The soil community composition and structure of the entire food webs were influenced both by the species identity of the plant individual and the surrounding plant community. Unexpectedly, plant identity had the strongest effects on decomposing soil organisms, widely believed to be generalist feeders. In contrast, quantitative food web modeling showed that the composition of the plant community influenced nitrogen mineralization under individual plants, but that plant species identity did not affect nitrogen or carbon mineralization or food web stability. Hence, the composition and structure of entire soil food webs vary at the scale of individual plants and are strongly influenced by the species identity of the plant. However, the ecosystem functions these food webs provide are determined by the identity of the entire plant community.

Elliptic generation of composite three-dimensional grids about realistic aircraft

NASA Technical Reports Server (NTRS)

Sorenson, R. L.

1986-01-01

An elliptic method for generating composite grids about realistic aircraft is presented. A body-conforming grid is first generated about the entire aircraft by the solution of Poisson's differential equation. This grid has relatively coarse spacing, and it covers the entire physical domain. At boundary surfaces, cell size is controlled and cell skewness is nearly eliminated by inhomogeneous terms, which are found automatically by the program. Certain regions of the grid in which high gradients are expected, and which map into rectangular solids in the computational domain, are then designated for zonal refinement. Spacing in the zonal grids is reduced by adding points with a simple, algebraic scheme. Details of the grid generation method are presented along with results of the present application, a wing-body configuration based on the F-16 fighter aircraft.

Thermomechanical testing of high-temperature composites - Thermomechanical fatigue (TMF) behavior of SiC(SCS-6)/Ti-15-3

NASA Technical Reports Server (NTRS)

Castelli, Michael G.; Bartolotta, Paul; Ellis, John R.

1992-01-01

Thermomechanical testing techniques recently developed for monolithic structural alloys were successfully extended to continuous fiber reinforced composite materials in plate form. The success of this adaptation was verified on a model metal matrix composite (MMC) material, namely SiC(SCS-6)/Ti-15V-3Cr-3Al-3Sn. Effects of heating system type and specimen preparation are also addressed. Cyclic lives determined under full thermomechanical conditions were shown to be significantly reduced from those obtained under comparable isothermal and in-phase bi-thermal conditions. Fractography and metallography from specimens subjected to isothermal, out-of-phase and in-phase conditions reveal distinct differences in damage-failure modes. Isothermal metallography revealed extensive matrix cracking associated with fiber damage throughout the entire cross-section of the specimen. Out-of-phase metallography revealed extensive matrix damage associated with minimal (if any) fiber cracking. However, the damage was located exclusively at surface and near-surface locations. In-phase conditions produced extensive fiber cracking throughout the entire cross-section, associated with minimal (if any) matrix damage.

Thermomechanical testing techniques for high-temparature composites: TMF behavior of SiC(SCS-6)/Ti-15-3

NASA Technical Reports Server (NTRS)

Castelli, Michael G.; Ellis, J. Rodney; Bartolotta, Paul A.

1990-01-01

Thermomechanical testing techniques recently developed for monolithic structural alloys were successfully extended to continuous fiber reinforced composite materials in plate form. The success of this adaptation was verified on a model metal matrix composite (MMC) material, namely SiC(SCS-6)/Ti-15V-3Cr-3Al-3Sn. Effects of heating system type and specimen preparation are also addressed. Cyclic lives determined under full thermo-mechanical conditions were shown to be significantly reduced from those obtained under comparable isothermal and in-phase bi-thermal conditions. Fractography and metallography from specimens subjected to isothermal, out-of-phase and in-phase conditions reveal distinct differences in damage-failure modes. Isothermal metallography revealed extensive matrix cracking associated with fiber damage throughout the entire cross-section of the specimen. Out-of-phase metallography revealed extensive matrix damage associated with minimal (if any) fiber cracking. However, the damage was located exclusively at surface and near-surface locations. In-phase conditions produced extensive fiber cracking throughout the entire cross-section, associated with minimal (if any) matrix damage.

Building on Sub-Arctic Soil: Geopolymerization of Muskeg to a Densified Load-Bearing Composite.

PubMed

Waetzig, Gregory R; Cho, Junsang; Lacroix, Max; Banerjee, Sarbajit

2017-11-07

The marshy water-saturated soil typical of the sub-Arctic represents a considerable impediment to the construction of roads, thereby greatly hindering human habitation and geological excavation. Muskeg, the native water-laden topsoil characteristic of the North American sub-Arctic, represents a particularly vexing challenge for road construction. Muskeg must either be entirely excavated, or for direct construction on muskeg, a mix of partial excavation and gradual compaction with the strategic placement of filling materials must be performed. Here, we demonstrate a novel and entirely reversible geopolymerization method for reinforcing muskeg with wood fibers derived from native vegetation with the addition of inorganic silicate precursors and without the addition of extraneous metal precursors. A continuous siloxane network is formed that links together the muskeg, wood fibers, and added silicates yielding a load-bearing and low-subsidence composite. The geopolymerization approach developed here, based on catalyzed formation of a siloxane network with further incorporation of cellulose, allows for an increase of density as well as compressive strength while reducing the compressibility of the composite.

Tilted Magnetic Levitation Enables Measurement of the Complete Range of Densities of Materials with Low Magnetic Permeability.

PubMed

Nemiroski, Alex; Soh, Siowling; Kwok, Sen Wai; Yu, Hai-Dong; Whitesides, George M

2016-02-03

Magnetic levitation (MagLev) of diamagnetic or weakly paramagnetic materials suspended in a paramagnetic solution in a magnetic field gradient provides a simple method to measure the density of small samples of solids or liquids. One major limitation of this method, thus far, has been an inability to measure or manipulate materials outside of a narrow range of densities (0.8 g/cm(3) < ρ < 2.3 g/cm(3)) that are close in density to the suspending, aqueous medium. This paper explores a simple method-"tilted MagLev"-to increase the range of densities that can be levitated magnetically. Tilting the MagLev device relative to the gravitational vector enables the magnetic force to be decreased (relative to the magnetic force) along the axis of measurement. This approach enables many practical measurements over the entire range of densities observed in matter at ambient conditions-from air bubbles (ρ ≈ 0) to osmium and iridium (ρ ≈ 23 g/cm(3)). The ability to levitate, simultaneously, objects with a broad range of different densities provides an operationally simple method that may find application to forensic science (e.g., for identifying the composition of miscellaneous objects or powders), industrial manufacturing (e.g., for quality control of parts), or resource-limited settings (e.g., for identifying and separating small particles of metals and alloys).

Composite material consisting of microporous β-TCP ceramic and alginate for delayed release of antibiotics.

PubMed

Seidenstuecker, Michael; Ruehe, Juergen; Suedkamp, Norbert P; Serr, Annerose; Wittmer, Annette; Bohner, Marc; Bernstein, Anke; Mayr, Hermann O

2017-03-15

The aim of this study was to produce a novel composite of microporous β-TCP filled with alginate and Vancomycin (VAN) to prolong the release behavior of the antibiotic for up to 28days. Using the flow chamber developed by the group, porous ceramics in a directional flow were filled with alginates of different composition containing 50mg/mL of antibiotics. After cross-linking the alginate with calcium ions, incubation took place in 10mL double-distilled water for 4weeks at 37°C. At defined times (1, 2, 3, 6, 9, 14, 20 and 28days), the liquid was completely exchanged and analyzed by capillary zone electrophoresis and microtiter trials. For statistical purposes, the mean and standard deviation were calculated and analyzed by ANOVA. The release of VAN from alginate was carried out via an external calcium source over the entire period with concentrations above the minimal inhibitory concentration (MIC). The burst release measured 35.2±1.5%. The release of VAN from alginate with an internal calcium source could only be observed over 14days. The burst release here was 61.9±4.3%. The native alginate's burst release was 54.1±7.8%; that of the sterile alginate 40.5±6.4%. The microtiter experiments revealed efficacy over the entire study period for VAN. The MIC value was determined in the release experiments as well in a range of 0.5-2.0μg/mL against Staphylococcus aureus. Drug release systems based on β-TCP and hydrogels are well documented in literature. However, in all described systems the ceramic, as granule or powder, is inserted into a hydrogel. In our work, we do the opposite, a hydrogel which acts as reservoir for antibiotics is placed into a porous biodegradable ceramic. Eventually, this system should be applied as treatment of bone infections. Contrary to the "granule in hydrogel" composites it has the advantage of mechanical stability. Thus, it can take over functions of the bone during the healing process. For a quicker translation from our scientific research into clinical use, only FDA approved materials were used in this work. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

78 FR 34608 - Proposed Establishment of Class D Airspace; Bryant AAF, Anchorage, AK

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-10

... Association (AOPA), Alaska Airmen's Association (AAA), and the Alaskan Aviation Safety Foundation (AASF). One... D airspace. The AAA requested additional time to review the proposal and that the entire composition...

Meteorite Material Model for Structural Properties

NASA Astrophysics Data System (ADS)

Agrawal, P.; Carlozzi, A. A.; Karajeh, Z. S.; Bryson, K. L.

2017-07-01

In order to prepare material models for the entire family of asteroids, meteorite units are developed for ordinary chondrites. The meteorite unit is a representative volume that accounts for diverse minerals, porosity, cracks and matrix composition.

Ultra-High Performance, High-Temperature Superconducting Wires via Cost-effective, Scalable, Co-evaporation Process

PubMed Central

Kim, Ho-Sup; Oh, Sang-Soo; Ha, Hong-Soo; Youm, Dojun; Moon, Seung-Hyun; Kim, Jung Ho; Dou, Shi Xue; Heo, Yoon-Uk; Wee, Sung-Hun; Goyal, Amit

2014-01-01

Long-length, high-temperature superconducting (HTS) wires capable of carrying high critical current, Ic, are required for a wide range of applications. Here, we report extremely high performance HTS wires based on 5 μm thick SmBa2Cu3O7 − δ (SmBCO) single layer films on textured metallic templates. SmBCO layer wires over 20 meters long were deposited by a cost-effective, scalable co-evaporation process using a batch-type drum in a dual chamber. All deposition parameters influencing the composition, phase, and texture of the films were optimized via a unique combinatorial method that is broadly applicable for co-evaporation of other promising complex materials containing several cations. Thick SmBCO layers deposited under optimized conditions exhibit excellent cube-on-cube epitaxy. Such excellent structural epitaxy over the entire thickness results in exceptionally high Ic performance, with average Ic over 1,000 A/cm-width for the entire 22 meter long wire and maximum Ic over 1,500 A/cm-width for a short 12 cm long tape. The Ic values reported in this work are the highest values ever reported from any lengths of cuprate-based HTS wire or conductor. PMID:24752189

Petrology of Aztec Wash pluton, Eldorado Mountains, southern Nevada

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

Falkner, C.M.; Miller, C.F.; Wooden, J.L.

1993-04-01

Aztec Wash pluton, a 50 km[sup 2] intrusive complex in the northern Eldorado Mountains, was emplaced ca. 16 Ma (Faulds et al., 1990) during extension within the Colorado River Corridor. The pluton displays extreme compositional variability, ranging from olivine gabbro (ca. 50 wt% SiO[sub 2]) to highly evolved aplite (76% SiO[sub 2]). Most of the intrusion is medium grained, homogeneous granite (ca. 72% SiO[sub 2]), but 1/3 is highly heterogeneous and dominated by mafic to intermediate rocks; a 6 [times] 3km, N-S mafic zone almost bisects the pluton. Well-displayed magma mingling and late mafic and felsic dikes verify the coexistencemore » of mafic and felsic melts. Hornblende barometry indicates that the entire exposed portion of Aztec Wash pluton was emplaced at very shallow depth (« less

Mapping the Space Radiation Environment in LEO Orbit by the SATRAM Timepix Payload On Board the Proba-V Satellite

NASA Astrophysics Data System (ADS)

Granja, Carlos; Polansky, Stepan; Sospisil, Stanislav; Owens, Alan; Mellab, Karim

2016-08-01

The compact spacecraft payload SATRAM is operating in LEO orbit since 2013 on board the Proba-V satellite from ESA and provides high-resolution wide-range radiation monitoring of the satellite environment. Equipped with the pixel detector Timepix, the technology demonstration payload determines the composition (particle types) and spectral characterization (stopping power) of the mixed radiation field with quantum imaging sensitivity, charged particle tracking, energy loss and directionality capability. With a polar orbit (sun synchronous, 98° inclination) and altitude of 820 km the space radiation field is continuously sampled over the entire planet every few days. Results are given in the form of spatial- and time- correlated maps of dose rate and particle flux. Comparison is made between quiescent and geomagnetic storm activity periods.

Composite embedded fiber optic data links in Standard Electronic Modules

NASA Astrophysics Data System (ADS)

Ehlers, S. L.; Jones, K. J.; Morgan, R. E.; Hixson, Jay

1990-12-01

The goal of this project is to fabricate a chassis/circuit card demonstration entirely 'wired' with embedded and interconnected optical fibers. Graphite/epoxy Standard Electronic Module E (SEM-E) configured panels have been successfully fabricated. Fiber-embedded SEM-E configured panels have been subjected to simultaneous signal transmission and vibration testing. Packaging constraints will require tapping composite-embedded optical fibers at right angles to the direction of optical transmission.

Development of graphite/polyimide honeycomb core materials

NASA Technical Reports Server (NTRS)

Stone, R. H.

1978-01-01

Honeycomb panel constructions consisting entirely of graphite/polyimide composites were developed and evaluated. Graphite/polyimide composites, were used in the honeycomb core webs and in pre-cured sandwich skins. Polyimide adhesives were also developed and evaluated for use in skin-core bonding. The purpose of this program was to develop light weight sandwich constructions for high temperature applications which could provide comparable shear strength and stiffness to metallic honeycomb constructions.

SIMBIO-SYS for BepiColombo: status and issues.

NASA Astrophysics Data System (ADS)

Flamini, E.; Capaccioni, F.; Cremonese, G.; Palumbo, P.; Formaro, R.; Mugnuolo, R.; Debei, S.; Ficai Veltroni, I.; Dami, M.; Tommasi, L.; SIMBIO-SYS Team

The SIMBIO-SYS (Spectrometer and Imaging for MPO BepiColombo Integrated Observatory SYStem) is a complex instrument suite part of the scientific payload of the Mercury Planetary Orbiter for the BepiColombo mission, the last of the cornerstone missions of the European Space Agency (ESA) Horizon+ science program. The BepiColombo mission is compose by two scientific satellites on, Mercury Magnetic Orbiter-MMO, realized by the Japanese Space Agency JAXA, devoted to the study of the planet environment and the other, the Mercury Planetary Orbiter realized by ESA, devoted to the detailed study of the Hermean surface and interior. The SIMBIOSYS instrument will provide all the science imaging capability of the Bepicolombo MPO spacecraft. It consists of three channels: the STereo imaging Channel (STC), with broad spectral band in the 400-950 nm range and medium spatial resolution (up to 50 m/px), that will provide Digital Terrain Model of the entire surface of the planet with an accuracy better than 80 m; the High Resolution Imaging Channel HRIC), with broad spectral bands in the 400-900 nm range and high spatial resolution (up to 5 m/px), that will provide high resolution images of about 20% of the surface, and the Visible and near-Infrared Hyperspectral Imaging channel (VIHI), with high spectral resolution (up to 6 nm) in the 400-2000 nm range and spatial resolution up to 100 m/px, it will provide the global covergae at 400 m/px with the spectral information. SIMBIO-SYS will provide unprecedented high-resolution images, the Digital Terrain Model of the entire surface, and the surface composition in wide spectral range, at resolutions and coverage higher than the MESSENGER mission with a full co-alignememt of the three channels. The main scientific objectives can be summarized as follows: Definition of the impact flux in the inner Solar System: based on the impact crater population records Understanding of the accretional model of an end member of the Solar System: based on the type and distribution of mineral species Reconstruction of the surface geology and stratigraphic history: based on the combination of stereo and high- resolution imaging along with compositional information coming from the spectrometer Relative surface age by impact craters population density and distribution: based on the global imaging including the high-resolution mode Surface degradation processes and global resurfacing: derived from the erosional status of the impact crater and ejecta Identification of volcanic landforms and style: using the morphological and compositional information Crustal dynamics and mechanical properties of the lithosphere: based on the identification and classification of tectonic structures from visible images and detailed DTM Surface composition and crustal differentiation: based on the identification and distribution of mineral species as seen by the NIR hyperspectral imager Soil maturity and alteration processes: based on the measure of the spectral slope derived by the hyperspectral imager and the colour capabilities of the stereo camera Determination of moment of inertia of the planet: the high-resolution imaging channel as landmark pairs of surface features that can be observed on the periside as support for the libration experiment Surface-Atmosphere interaction processes and origin of the exosphere: knowledge of the surface composition is also crucial to unambiguously identify the source minerals for each of the constituents of the Mercury.s exosphere The instrument has been realized by Selex-ES under the contract and management of the Italian Space Agency (ASI) that have signed an MoU with CNES for the development of VIHI Proximity Electronics, the Main Electronics, and the instrument final calibration . All the realization and calibration has been carried on under the scientific supervision of the SIMBIO-SYS science team SIMBIOSYS has been delivered to ESA on April 2015 for the final integration on the BepiColombo MPO spacecraft.

Explosive to Effusive Transition in Intermediate Volcanism: An Analysis of Changing Magma System Conditions in Dominica

NASA Astrophysics Data System (ADS)

Bersson, J.; Waters, L. E.; Frey, H. M.; Nicolaysen, K. P.; Manon, M. R. F.

2017-12-01

The oscillation between explosive and effusive intermediate (59-62 wt% SiO2) volcanism in the Roseau Valley on Dominica, an island in the Lesser Antilles Arc, provides an opportunity to investigate temporal changes in the magmatic system. Here, we test the relationship between the Roseau ignimbrites (1-65 ka) and the Micotrin dome ( 1.1 ka) which are proposed to originate from the same magmatic system, with a detailed petrologic analysis of phenocrysts to determine commonalities or changes in pre-eruptive conditions (i.e., intensive variables). The ignimbrites are saturated in five phenocrysts (plagioclase + orthopyroxene + clinopyroxene + ilmenite + magnetite ± amphibole ± quartz), and the lava dome contains the same assemblage, but with notable differences: amphiboles are entirely reacted, and quartz occurs in greater abundance. Plagioclase in the ignimbrites ranges in composition from An46-93, and those in the dome range from An46-85. Two Fe-Ti oxide geo-thermometry reveal pre-eruptive temperatures from 730-820°C for three different ignimbrite units, whereas the pre-eruptive temperature for the dome is slightly hotter (850±23°C). Values of fO2 (relative to NNO) derived from Fe-Ti oxide oxygen-barometry range from +0.3 to +1.32 ΔNNO for the ignimbrites, which overlap with those from the dome (+0.5 to +0.9 ΔNNO). Pre-eruptive temperatures, plagioclase compositions, whole rock and glass compositions are incorporated into a plagioclase-liquid hygrometer to determine pre-eruptive melt H2O contents for each sample. H2O contents for ignimbrites range from 7.1-9.3 wt%, and those from the lava dome range from 6.7-7.1 wt%. Application of a H2O solubility model shows that water contents for the Roseau magmas correspond to pressures of 3-5 kbar. The most notable difference between the explosive and effusive magmas is that the lava dome has a higher pre-eruptive temperature than the ignimbrites. However, the results collectively suggest that more recent volcanism in the Roseau Valley (<5 ka) has hotter pre-eruptive temperatures, regardless of eruptive style, and that these intermediate magmas originate from sources in the deep crust (>5 kb). Understanding the magmatic system beneath Micotrin is important, as the capital of Roseau (pop. 15,000), is at the foot of the valley, built on old pyroclastic deposits.

VIRTIS/Rosetta Observes Comet 67P/Churyumov-Gerasimenko: Nucleus and Coma Derived Composition and Physical Properties.

NASA Astrophysics Data System (ADS)

Capaccioni, F.; Filacchione, G.; Erard, S.; Arnold, G.; De Sanctis, M. C.; Bockelée-Morvan, D.; Leyrat, C.; Tosi, F.; Ciarniello, M.; Raponi, A.; Migliorini, A.; Quirico, E.; Rinaldi, G.; Schmitt, B.; Carlson, R. W.; Combi, M. R.; Fink, U.; Tozzi, G. P.; Palomba, E.; Longobardo, A.; Formisano, M.; Debout, V.; Drossart, P.; Piccioni, G.; Fougere, N.

2015-12-01

The paper will describe the major results obtained throughout the nominal mission by the instrument VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer), the dual channel spectrometer onboard Rosetta, on the surface composition and thermal properties of the nucleus of comet 67P/Churyumov-Gerasimenko and on the 2D distribution of H2O and CO2 in the coma. VIRTIS is a dual channel spectrometer; VIRTIS-M (M for Mapper) is a hyper spectral imager covering a wide spectral range from 0.25 through 5μm. VIRTIS-M uses a slit and a scan mirror to generate images with spatial resolution of 250 μrad over a FOV of 3.7°. The second channel is VIRTIS-H (H for High-resolution), a point spectrometer with high spectral resolution (λ/Δλ=3000 @3μm) in the range 2-5 μm. The nucleus observations have been performed in a wide range of conditions with best spatial resolution of 2.5m. The surface temperature has been determined since the first distant observations when the nucleus filled one single VIRTIS-M pixel and continuously monitored since. Maximum temperature determined until April 2015 are as high as 300K at the subsolar point. Modeling of the thermophysical properties allowed to derive the thermal inertia of the crust. The VIRTIS composition analysis has showed evidence of carbon-bearing compounds on the nucleus of the comet 67P/Churyumov-Gerasimenko. The very low reflectance of the nucleus (normal albedo of 0.060 ± 0.003 at 0.55 μm), the spectral slopes in VIS and IR ranges (5-25 and 1.5-5 % kÅ-1) and the broad absorption feature in the 2.9-3.6 μm range present across the entire illuminated surface, are compatible with a surface crust made of a complex mixture of dark disordered poly-aromatic compounds, opaque minerals and several chemical species containing: -COOH, CH2 / CH3, -OH (in Alcohols) and possibly NH4+. Both channels are contributing to the determination of the spatial distribution of H2O and CO2 in the coma; their abundances as a function of altitude and of time of day. Authors acknowledge the support from national funding agencies.

The statistical extended-range (10-30-day) forecast of summer rainfall anomalies over the entire China

NASA Astrophysics Data System (ADS)

Zhu, Zhiwei; Li, Tim

2017-01-01

The extended-range (10-30-day) rainfall forecast over the entire China was carried out using spatial-temporal projection models (STPMs). Using a rotated empirical orthogonal function analysis of intraseasonal (10-80-day) rainfall anomalies, China is divided into ten sub-regions. Different predictability sources were selected for each of the ten regions. The forecast skills are ranked for each region. Based on temporal correlation coefficient (TCC) and Gerrity skill score, useful skills are found for most parts of China at a 20-25-day lead. The southern China and the mid-lower reaches of Yangtze River Valley show the highest predictive skills, whereas southwestern China and Huang-Huai region have the lowest predictive skills. By combining forecast results from ten regional STPMs, the TCC distribution of 8-year (2003-2010) independent forecast for the entire China is investigated. The combined forecast results from ten STPMs show significantly higher skills than the forecast with just one single STPM for the entire China. Independent forecast examples of summer rainfall anomalies around the period of Beijing Olympic Games in 2008 and Shanghai World Expo in 2010 are presented. The result shows that the current model is able to reproduce the gross pattern of the summer intraseasonal rainfall over China at a 20-day lead. The present study provides, for the first time, a guide on the statistical extended-range forecast of summer rainfall anomalies for the entire China. It is anticipated that the ideas and methods proposed here will facilitate the extended-range forecast in China.

Preparing GMAT for Operational Maneuver Planning of the Advanced Composition Explorer (ACE)

NASA Technical Reports Server (NTRS)

Qureshi, Rizwan Hamid; Hughes, Steven P.

2014-01-01

The General Mission Analysis Tool (GMAT) is an open-source space mission design, analysis and trajectory optimization tool. GMAT is developed by a team of NASA, private industry, public and private contributors. GMAT is designed to model, optimize and estimate spacecraft trajectories in flight regimes ranging from low Earth orbit to lunar applications, interplanetary trajectories and other deep space missions. GMAT has also been flight qualified to support operational maneuver planning for the Advanced Composition Explorer (ACE) mission. ACE was launched in August, 1997 and is orbiting the Sun-Earth L1 libration point. The primary science objective of ACE is to study the composition of both the solar wind and the galactic cosmic rays. Operational orbit determination, maneuver operations and product generation for ACE are conducted by NASA Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF). This paper discusses the entire engineering lifecycle and major operational certification milestones that GMAT successfully completed to obtain operational certification for the ACE mission. Operational certification milestones such as gathering of the requirements for ACE operational maneuver planning, gap analysis, test plans and procedures development, system design, pre-shadow operations, training to FDF ACE maneuver planners, shadow operations, Test Readiness Review (TRR) and finally Operational Readiness Review (ORR) are discussed. These efforts have demonstrated that GMAT is flight quality software ready to support ACE mission operations in the FDF.

Average composition of the tonalite-trondhjemite-granodiorite association: Possibilities of application

NASA Astrophysics Data System (ADS)

Chekulaev, V. P.; Glebovitsky, V. A.

2017-01-01

The possibilities of using the average compositions of tonalite-trondhjemite-granodiorite association rocks (TTG), which make up a significant part of the Archaean continental crust, have been examined. The results of the TTG average compositions obtained by other researchers and the authors' data of the average compositions of TTG from the Baltic and Ukrainian shields and the entire Archaean crust are given. It is shown that the average compositions of the Archaean TTG of continental large crustal fragments (cratons or provinces) practically do not bear any information on their sources or conditions of their formation. The possibility of obtaining of such information by means of analysis of the average compositions of TTG, composing smaller fragments of the crust, exemplified by rocks of the Karelian subprovinces of the Baltic Shield has been demonstrated.

Melting Processes at the Base of the Mantle Wedge: Melt Compositions and Melting Reactions for the First Melts of Vapor-Saturated Lherzolite

NASA Astrophysics Data System (ADS)

Grove, T. L.; Till, C. B.

2014-12-01

Vapor-saturated melting experiments have been performed at pressures near the base of the mantle wedge (3.2 GPa). The starting composition is a metasomatized lherzolite containing 3 wt. % H2O. Near-solidus melts and coexisting mineral phases have been characterized in experiments that span 925 to 1100 oC with melt % varying from 6 to 9 wt. %. Olivine, orthopyroxene, clinopyroxene and garnet coexist with melt over the entire interval and rutile is also present at < 1000 oC. Melt is andesitic in composition and varies from 60 wt. % SiO2 at 950 oC to 52 wt. % at 1075 oC. The Al2O3 contents of the melt are 13 to 14 wt. %, and CaO contents range from 1 and 4 wt. %. Melting is peritectic with orthopyroxene + liquid produced by melting of garnet + olivine + high-Ca pyroxene. In addition to quenched melt, we observe a quenched silicate component that is rhyolitic (>72 % SiO2) that we interpret as a precipitate from the coexisting supercritical H2O-rich vapor. Extrapolation of the measured compositional variation toward the solidus suggests that the first melt may be very SiO2 rich (i.e., granitic). We suggest that these granitic melts are the first melts of the mantle near the slab-wedge interface. As these SiO2-rich melts ascend into shallower, hotter overlying mantle, they continue to interact with the surrounding mantle and evolve in composition. These first melts may elucidate the geochemical and physical processes that accompany the beginnings of H2O flux melting.

Constraints on the magmatic evolution of the oceanic crust from plagiogranite intrusions in the Oman ophiolite

NASA Astrophysics Data System (ADS)

Haase, Karsten M.; Freund, Sarah; Beier, Christoph; Koepke, Jürgen; Erdmann, Martin; Hauff, Folkmar

2016-05-01

We present major and trace element as well as Sr, Nd, and Hf isotope data on a suite of 87 plutonic rock samples from 27 felsic crustal intrusions in seven blocks of the Oman ophiolite. The rock compositions of the sample suite including associated more mafic rocks range from 48 to 79 wt% SiO2, i.e. from gabbros to tonalites. The samples are grouped into a Ti-rich and relatively light rare earth element (LREE)-enriched P1 group [(Ce/Yb) N > 0.7] resembling the early V1 lavas, and a Ti-poor and LREE-depleted P2 group [(Ce/Yb) N < 0.7] resembling the late-stage V2 lavas. Based on the geochemical differences and in agreement with previous structural and petrographic models, we define phase 1 (P1) and phase 2 (P2) plutonic rocks. Felsic magmas in both groups formed by extensive fractional crystallization of olivine, clinopyroxene, plagioclase, apatite, and Ti-magnetite from mafic melts. The incompatible element compositions of P1 rocks overlap with those from mid-ocean ridges but have higher Ba/Nb and Th/Nb trending towards the P2 rock compositions and indicating an influence of a subducting slab. The P2 rocks formed from a more depleted mantle source but show a more pronounced slab signature. These rocks also occur in the southern blocks (with the exception of the Tayin block) of the Oman ophiolite implying that the entire ophiolite formed above a subducting slab. Initial Nd and Hf isotope compositions suggest an Indian-MORB-type mantle source for the Oman ophiolite magmas. Isotope compositions and high Th/Nb in some P2 rocks indicate mixing of a melt from subducted sediment into this mantle.

Nature of diamonds in Yakutian eclogites: views from eclogite tomography and mineral inclusions in diamonds

NASA Astrophysics Data System (ADS)

Anand, Mahesh; Taylor, Lawrence A.; Misra, Kula C.; Carlson, William D.; Sobolev, Nikolai V.

2004-09-01

We have performed dissections of two diamondiferous eclogites (UX-1 and U33/1) from the Udachnaya kimberlite, Yakutia in order to understand the nature of diamond formation and the relationship between the diamonds, their mineral inclusions, and host eclogite minerals. Diamonds were carefully recovered from each xenolith, based upon high-resolution X-ray tomography images and three-dimensional models. The nature and physical properties of minerals, in direct contact with diamonds, were investigated at the time of diamond extraction. Polished sections of the eclogites were made, containing the mould areas of the diamonds, to further investigate the chemical compositions of the host minerals and the phases that were in contact with diamonds. Major- and minor-element compositions of silicate and sulfide mineral inclusions in diamonds show variations among each other, and from those in the host eclogites. Oxygen isotope compositions of one garnet and five clinopyroxene inclusions in diamonds from another Udachnaya eclogite (U51) span the entire range recorded for eclogite xenoliths from Udachnaya. In addition, the reported compositions of almost all clinopyroxene inclusions in U51 diamonds exhibit positive Eu anomaly. This feature, together with the oxygen isotopic characteristics, is consistent with the well-established hypothesis of subduction origin for Udachnaya eclogite xenoliths. It is intuitive to expect that all eclogite xenoliths in a particular kimberlite should have common heritage, at least with respect to their included diamonds. However, the variation in the composition of multiple inclusions within diamonds, and among diamonds, from the same eclogite indicates the involvement of complex processes in diamond genesis, at least in the eclogite xenoliths from Yakutia that we have studied.

Progressive Damage and Failure Analysis of Composite Laminates

NASA Astrophysics Data System (ADS)

Joseph, Ashith P. K.

Composite materials are widely used in various industries for making structural parts due to higher strength to weight ratio, better fatigue life, corrosion resistance and material property tailorability. To fully exploit the capability of composites, it is required to know the load carrying capacity of the parts made of them. Unlike metals, composites are orthotropic in nature and fails in a complex manner under various loading conditions which makes it a hard problem to analyze. Lack of reliable and efficient failure analysis tools for composites have led industries to rely more on coupon and component level testing to estimate the design space. Due to the complex failure mechanisms, composite materials require a very large number of coupon level tests to fully characterize the behavior. This makes the entire testing process very time consuming and costly. The alternative is to use virtual testing tools which can predict the complex failure mechanisms accurately. This reduces the cost only to it's associated computational expenses making significant savings. Some of the most desired features in a virtual testing tool are - (1) Accurate representation of failure mechanism: Failure progression predicted by the virtual tool must be same as those observed in experiments. A tool has to be assessed based on the mechanisms it can capture. (2) Computational efficiency: The greatest advantages of a virtual tools are the savings in time and money and hence computational efficiency is one of the most needed features. (3) Applicability to a wide range of problems: Structural parts are subjected to a variety of loading conditions including static, dynamic and fatigue conditions. A good virtual testing tool should be able to make good predictions for all these different loading conditions. The aim of this PhD thesis is to develop a computational tool which can model the progressive failure of composite laminates under different quasi-static loading conditions. The analysis tool is validated by comparing the simulations against experiments for a selected number of quasi-static loading cases.

A Numerical Solution Routine for Investigating Oxidation-Induced Strength Degradation Mechanisms in SiC/SiC Composites

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.

2015-01-01

The stress rupture strength of silicon carbide fiber-reinforced silicon carbide (SiCSiC) composites with a boron nitride (BN) fiber coating decreases with time within the intermediate temperature range of 700-950 C. Various theories have been proposed to explain the cause of the time dependent stress rupture strength. Some previous authors have suggested that the observed composite strength behavior is due to the inherent time dependent strength of the fibers, which is caused by the slow growth of flaws within the fibers. Flaw growth is supposedly enabled by oxidation of free carbon at the grain boundaries. The objective of this paper is to investigate the relative significance of the various theories for the time-dependent strength of SiCSiC composites. This is achieved through the development of a numerically-based progressive failure analysis routine and through the application of the routine to simulate the composite stress rupture tests. The progressive failure routine is a time marching routine with an iterative loop between a probability of fiber survival equation and a force equilibrium equation within each time step. Failure of the composite is assumed to initiate near a matrix crack and the progression of fiber failures occurs by global load sharing. The probability of survival equation is derived from consideration of the strength of ceramic fibers with randomly occurring and slow growing flaws as well as the mechanical interaction between the fibers and matrix near a matrix crack. The force equilibrium equation follows from the global load sharing presumption. The results of progressive failure analyses of the composite tests suggest that the relationship between time and stress-rupture strength is attributed almost entirely to the slow flaw growth within the fibers. Although other mechanisms may be present, they appear to have only a minor influence on the observed time dependent behavior.

The KASCADE-Grande experiment

NASA Astrophysics Data System (ADS)

Apel, W. D.; Arteaga, J. C.; Badea, A. F.; Bekk, K.; Bertaina, M.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Buchholz, P.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Engler, J.; Finger, M.; Fuhrmann, D.; Ghia, P. L.; Gils, H. J.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Kickelbick, D.; Klages, H. O.; Link, K.; łuczak, P.; Ludwig, M.; Mathes, H. J.; Mayer, H. J.; Melissas, M.; Milke, J.; Mitrica, B.; Morello, C.; Navarra, G.; Nehls, S.; Oehlschläger, J.; Ostapchenko, S.; Over, S.; Palmieri, N.; Petcu, M.; Pierog, T.; Rebel, H.; Roth, M.; Schieler, H.; Schröder, F.; Sima, O.; Stümpert, M.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Wommer, M.; Zabierowski, J.

2010-08-01

KASCADE-Grande is the enlargement of the KASCADE extensive air shower detector, realized to expand the cosmic ray studies from the previous 10 14-10 17 eV primary energy range to 10 18 eV. This is performed by extending the area covered by the KASCADE electromagnetic array from 200×200 to 700×700 m 2 by means of 37 scintillator detector stations of 10 m 2 area each. This new array is named Grande and provides measurements of the all-charged particle component of extensive air showers ( Nch), while the original KASCADE array particularly provides information on the muon content (Nμ). Additional dense compact detector set-ups being sensitive to energetic hadrons and muons are used for data consistency checks and calibration purposes. The performance of the Grande array and its integration into the entire experimental complex is discussed. It is demonstrated that the overall observable resolutions are adequate to meet the physical requirements of the measurements, i.e. primary energy spectrum and elemental composition studies in the primary cosmic ray energy range of 10 16-10 18 eV.

Enthalpy of mixing of liquid systems for lead free soldering: Ni-Sb-Sn system.

PubMed

Elmahfoudi, A; Fürtauer, S; Sabbar, A; Flandorfer, H

2012-04-20

The partial and integral enthalpies of mixing of liquid ternary Ni-Sb-Sn alloys were determined along five sections x Sb / x Sn  = 3:1, x Sb / x Sn  = 1:1, x Sb / x Sn  = 1:3, x Ni / x Sn  = 1:4, and x Ni / x Sb  = 1:4 at 1000 °C in a large compositional range using drop calorimetry techniques. The mixing enthalpy of Ni-Sb alloys was determined at the same temperature and described by a Redlich-Kister polynomial. The other binary data were carefully evaluated from literature values. Our measured ternary data were fitted on the basis of an extended Redlich-Kister-Muggianu model for substitutional solutions. Additionally, a comparison of these results to the extrapolation model of Toop is given. The entire ternary system shows exothermic values of Δ mix H ranging from approx. -1300 J/mol, the minimum in the Sb-Sn binary system down to approx. -24,500 J/mol towards Ni-Sb. No significant ternary interaction could be deduced from our data.

Thermophysical properties of aqueous solution of ammonium-based ionic liquids.

PubMed

Umapathi, Reddicherla; Attri, Pankaj; Venkatesu, Pannuru

2014-06-05

Experimental densities (ρ), ultrasonic sound velocities (u), viscosities (η), and refractive indices (n(D)) of binary mixtures of ammonium-based ionic liquids (ILs) such as diethylammonium acetate (DEAA) [(CH3CH2)2NH][CH3COO], triethylammonium acetate (TEAA) [(CH3CH2)3NH][CH3COO], diethylammonium hydrogen sulfate (DEAS) [(CH3CH2)2NH][HSO4], triethylammonium hydrogen sulfate (TEAS) [(CH3CH2)3NH][HSO4], trimethylammonium acetate (TMAA) [(CH3)3NH][CH3COO], and trimethylammonium hydrogen sulfate (TMAS) [(CH3)3NH][HSO4] with water are reported over the wide composition range at 25 °C under atmospheric pressure. The excess molar volumes (V(E)), deviation in isentropic compressibilities (Δκ(s)), deviation in viscosities (Δη) and deviation in refractive indices (Δn(D)) are calculated from experimental values and are correlated by Redlich-Kister polynomial equations. The V(E) and Δκ(s) values for the aforesaid systems are negative over the entire composition range while the Δη and Δn(D) values are positive under the same experimental conditions. The intermolecular interactions and structural effects were analyzed on the basis of measured and derived properties. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions and hydrogen bonding between ILs and water. Furthermore, the hydrogen bonding features between ILs with water were analyzed by using a molecular modeling program with the help of HyperChem7.

Synthesis of MoS2-reduced graphene oxide/Fe3O4 nanocomposite for enhanced electromagnetic interference shielding effectiveness

NASA Astrophysics Data System (ADS)

Prasad, Jagdees; Singh, Ashwani Kumar; Shah, Jyoti; Kotnala, R. K.; Singh, Kedar

2018-05-01

This article presents a facile two step hydrothermal process for the synthesis of MoS2-reduced graphene oxide/Fe3O4 (MoS2-rGO/Fe3O4) nanocomposite and its application as an excellent electromagnetic interference shielding material. Characterization tools like; scanning electron microscope, transmission electron microscope, x-ray diffraction, and Raman spectroscopy were used to confirm the formation of nanocomposite and found that spherical Fe3O4 nanoparticles are well dispersed over MoS2-rGO composite with average particle size ∼25–30 nm was confirmed by TEM. Structural characterization done by XRD was found inconsistent with the known lattice parameter of MoS2 nanosheet, reduced graphene oxide and Fe3O4 nanoparticles. Electromagnetic shielding effectiveness of MoS2-rGO/Fe3O4 nanocomposite was evaluated and found to be an excellent EMI shielding material in X-band range (8.0–12.0 GHz). MoS2-rGO composite shows poor shielding capacity (SET ∼ 3.81 dB) in entire range as compared to MoS2-rGO/Fe3O4 nanocomposite (SET ∼ 8.27 dB). It is due to interfacial polarization in the presence of EM field. The result indicates that MoS2-rGO/Fe3O4 nanocomposite provide a new stage for the next generation in high-performance EM wave absorption and EMI shielding effectiveness.

Volumetric Properties and Fluid Phase Equilibria of CO2 + H2O

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

Capobianco, Ryan; Gruszkiewicz, Miroslaw; Wesolowski, David J

2013-01-01

The need for accurate modeling of fluid-mineral processes over wide ranges of temperature, pressure and composition highlighted considerable uncertainties of available property data and equations of state, even for the CO2 + H2O binary system. In particular, the solubility, activity, and ionic dissociation equilibrium data for the CO2-rich phase, which are essential for understanding dissolution/precipitation, fluid-matrix reactions, and solute transport, are uncertain or missing. In this paper we report the results of a new experimental study of volumetric and phase equilibrium properties of CO2 + H2O, to be followed by measurements for bulk and confined multicomponent fluid mixtures. Mixture densitiesmore » were measured by vibrating tube densimetry (VTD) over the entire composition range at T = 200 and 250 C and P = 20, 40, 60, and 80 MPa. Initial analysis of the mutual solubilities, determined from volumetric data, shows good agreement with earlier results for the aqueous phase, but finds that the data of Takenouchi and Kennedy (1964) significantly overestimated the solubility of water in supercritical CO2 (by a factor of more than two at 200 C). Resolving this well-known discrepancy will have a direct impact on the accuracy of predictive modeling of CO2 injection in geothermal reservoirs and geological carbon sequestration through improved equations of state, needed for calibration of predictive molecular-scale models and large-scale reactive transport simulations.« less

U-Pb ages and Hf isotope compositions of zircons in plutonic rocks from the central Famatinian arc, Argentina

NASA Astrophysics Data System (ADS)

Otamendi, Juan E.; Ducea, Mihai N.; Cristofolini, Eber A.; Tibaldi, Alina M.; Camilletti, Giuliano C.; Bergantz, George W.

2017-07-01

The Famatinian arc formed around the South Iapetus rim during the Ordovician, when oceanic lithosphere subducted beneath the West Gondwana margin. We present combined in situ U-Th-Pb and Lu-Hf isotope analyses for zircon to gain insights into the origin and evolution of Famatinian magmatism. Zircon crystals sampled from four intermediate and silicic plutonic rocks confirm previous observations showing that voluminous magmatism took place during a relatively short pulse between the Early and Middle Ordovician (472-465 Ma). The entire zircon population for the four plutonic rocks yields coherent εHf negative values and spreads over several ranges of initial εHf(t) units (-0.3 to -8.0). The range of εHf units in detrital zircons of Famatinian metasedimentary rocks reflects a prolonged history of the cratonic sources during the Proterozoic to the earliest Phanerozoic. Typical tonalites and granodiorites that contain zircons with evolved Hf isotopic compositions formed upon incorporating (meta)sedimentary materials into calc-alkaline metaluminous magmas. The evolved Hf isotope ratios of zircons in the subduction related plutonic rocks strongly reflect the Hf isotopic character of the metasedimentary contaminant, even though the linked differentiation and growth of the Famatinian arc crust was driven by ascending and evolving mantle magmas. Geochronology and Hf isotope systematics in plutonic zircons allow us understanding the petrogenesis of igneous series and the provenance of magma sources. However, these data could be inadequate for computing model ages and supporting models of crustal evolution.

Sr isotopic variations in Upper Proterozoic carbonates from Svalbard and East Greenland

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

Derry, L.A.; Keto, L.S.; Jacobsen, S.B.

1989-09-01

The authors report initial {sup 87}Sr/{sup 86}Sr values from an Upper Proterozoic carbonate succession from Svalbard and East Greenland. This succession, now tectonically separated into three sequences, is thick, relatively continuous, and well preserved. The relative ages of the samples from within the basin are well constrained by litho-, bio-, and chemostratigraphic techniques. The data from this study and related data from the literature are used to construct a curve of {sup 87}Sr/{sup 86}Sr for Upper Proterozoic seawater. The new data reported in this study substantially improve the isotopic record of Sr in seawater for the period between 650 andmore » 800 Ma. The data indicate that {Delta}{sup 87}Sr values of seawater were variable but low ({Delta}{sup 87}Sr {approximately}{minus}500 to {minus}250) between 900 and 650 Ma, and rose rapidly to {approximately} +30 by 600 Ma. The range of variation of {Delta}{sup 87}Sr in seawater during the Riphean-Vendian exceeds the entire range of {Delta}{sup 87}Sr in seawater during the Phanerozoic. While variation in the average isotopic composition of Sr delivered to the oceans by rivers can account for some of the observed range, changes in the ratio of submarine hydrothermal flux to river water (continental) flux are responsible for the large variation in seawater Sr isotopic composition. Changes in the continental flux of Sr to the oceans can be related to tectonic factors. Large changes in the hydrothermal flux to river water flux ratio indicated by the data could have significant consequences for the chemistry of the ocean-atmosphere system.« less

Planktonic food web structure at a coastal time-series site: I. Partitioning of microbial abundances and carbon biomass

NASA Astrophysics Data System (ADS)

Caron, David A.; Connell, Paige E.; Schaffner, Rebecca A.; Schnetzer, Astrid; Fuhrman, Jed A.; Countway, Peter D.; Kim, Diane Y.

2017-03-01

Biogeochemistry in marine plankton communities is strongly influenced by the activities of microbial species. Understanding the composition and dynamics of these assemblages is essential for modeling emergent community-level processes, yet few studies have examined all of the biological assemblages present in the plankton, and benchmark data of this sort from time-series studies are rare. Abundance and biomass of the entire microbial assemblage and mesozooplankton (>200 μm) were determined vertically, monthly and seasonally over a 3-year period at a coastal time-series station in the San Pedro Basin off the southwestern coast of the USA. All compartments of the planktonic community were enumerated (viruses in the femtoplankton size range [0.02-0.2 μm], bacteria + archaea and cyanobacteria in the picoplankton size range [0.2-2.0 μm], phototrophic and heterotrophic protists in the nanoplanktonic [2-20 μm] and microplanktonic [20-200 μm] size ranges, and mesozooplankton [>200 μm]. Carbon biomass of each category was estimated using standard conversion factors. Plankton abundances varied over seven orders of magnitude across all categories, and total carbon biomass averaged approximately 60 μg C l-1 in surface waters of the 890 m water column over the study period. Bacteria + archaea comprised the single largest component of biomass (>1/3 of the total), with the sum of phototrophic protistan biomass making up a similar proportion. Temporal variability at this subtropical station was not dramatic. Monthly depth-specific and depth-integrated biomass varied 2-fold at the station, while seasonal variances were generally <50%. This study provides benchmark information for investigating long-term environmental forcing on the composition and dynamics of the microbes that dominate food web structure and function at this coastal observatory.

The coefficient of friction, particularly of ice

NASA Astrophysics Data System (ADS)

Mills, Allan

2008-07-01

The static and dynamic coefficients of friction are defined, and values from 0.3 to 0.6 are quoted for common materials. These drop to about 0.15 when oil is added as a lubricant. Water ice at temperatures not far below 0 °C is remarkable for low coefficients of around 0.05 for static friction and 0.04-0.02 for dynamic friction, but these figures increase as the temperature diminishes. Reasons for the slipperiness of ice are summarized, but they are still not entirely clear. One hypothesis suggests that it is related to the transient formation of a lubricating film of liquid water produced by frictional heating. If this is the case, some composition melting a little above ambient temperatures might provide a skating rink that did not require expensive refrigeration. Various compositions have been tested, but an entirely satisfactory material has yet to be found.

Bulk flow strength of forsterite?enstatite composites as a function of forsterite content

NASA Astrophysics Data System (ADS)

Ji, Shaocheng; Wang, Zichao; Wirth, Richard

2001-11-01

Creep experiments have been conducted to investigate the effect of varying forsterite content ( VFo) on the bulk flow strength of dry forsterite-enstatite (Fo-En) aggregates in order to evaluate the applicability of existing theoretical models to two-phase rocks, as well as to understand the rheology of polyphase systems in general. The experiments were performed at temperatures of 1423-1593 K, stresses of 18-100 MPa, oxygen fugacities of 10 -14-10 -2.5 MPa and 0.1 MPa total pressure. The fine-grained (Fo: 10-17 μm; En: 14-31 μm) composites of various Fo volume fractions ( VFo=0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1) were synthesized by isostatically hot-pressing in a gas-medium apparatus at 1523 and 350 MPa. Our experiments show that flow strength contrasts between Fo and En are in the range of 3-8 at the given experimental conditions, with Fo as the stronger phase. The measured stress exponent ( n) and activation energy ( Q) values of the Fo-En composites fall between those of the end-members. The n values show a nearly linear increase from 1.3 to 2.0, while the Q values display a non-linear increase from 472 to 584 kJ/mol with En volume fraction from 0 to 1.0. There is no clear dependence of creep rates on oxygen fugacity for the Fo-En composites. The mechanical data and TEM microstructural observations suggest no change in deformation mechanism of each phase when in the composites, compared to when in a single-phase aggregate, the En deformed mainly by dislocation creep while the Fo deformed by dislocation-accommodated diffusion creep for our grain sizes and experimental conditions. Comparisons between the measured composite strengths and various theoretical models indicate that none of the existing theoretical models can give a precise predication over the entire VFo range from 0 to 1. However, the theoretical models based on weak-phase supported structures (WPS) yield a good prediction for the flow strengths of the composites with VFo<0.4, while those based on strong-phase supported structures (SPS) are better for the composites with VFo>0.6. No model gives a good prediction for the bulk strength of two-phase composites in the transitional regime ( VFo=0.4-0.6). Applications of the WPS- and SPS-based models in the transitional regime result in under- and over-estimations for the composite flow strength, respectively. Thus, the effect of rock microstructure should be taken into consideration in modeling the bulk flow strengths of the crust and upper mantle using laboratory-determined flow laws of single-phase aggregates.

Effect of temporal lakes on avifaunal composition at the Southeast of Isthmus of Tehuantepec, Oaxaca, Mexico.

PubMed

Rioja-Paradela, Tamara; Carrillo-Reyes, Arturo; Espinoza-Medinilla, Eduardo

2014-12-01

Oaxaca hosts one of the greatest biodiversity in México, occupying first place in avian diversity compared to other regions of the country. However, the area is undergoing serious problems such as high defor- estation rates, soil erosion and over exploitation and extinction of species. These factors have all contributed to the current loss of biodiversity. Also, biological inventories are still incomplete. One of the least explored sites is the semiarid zone of Tehuantepec isthmus, around the locality of Santa Maria del Mar, Oaxaca, México. The area includes floodable grasslands, mangrove areas and dry forest, providing a range of potential habitats for different species. Our objective was to evaluate the effect of temporal lakes on spatial and temporal composition of the avifauna in Santa Maria del Mar, in order to generate information regarding this group within the region and the state, and to understand the importance of flood areas for resident and transitory birds. We conducted 12 avifauna surveys between July 2006 and June 2008, and established two transects of 2km length in each of four habitat types (beach, grassland, dry forest, and mangrove). We found a total of 75 species, corresponding to 16 orders and 30 families. Within an area of 26 km2, we significantly found 10.1% of the total number of bird species recorded for the entire state, and 6.6% of the total reported in Mexico. The families most repre- sented were: Ardeidae, Laridae and Scolopacidae. Over the entire study period, dry forest was the most diverse habitat; followed by mangrove, grassland and the beach. Of all the species recorded, 38.6% were found at the edge or in the temporal lakes. We found a significant difference in species composition between seasons in the grassland, but no difference in the other habitats. Our results showed a significant effect of temporary lakes on avian diversity during the wet season; it also demonstrated the importance of grassland conservation given its relevance for presence of waterbirds. We suggested a continued and more intense monitoring; and proposed the designation of the area as an Important Conservation Bird Area (AICA).

The hygroscopicity parameter (κ) of ambient organic aerosol at a field site subject to biogenic and anthropogenic influences: relationship to degree of aerosol oxidation

NASA Astrophysics Data System (ADS)

Chang, R. Y.-W.; Slowik, J. G.; Shantz, N. C.; Vlasenko, A.; Liggio, J.; Sjostedt, S. J.; Leaitch, W. R.; Abbatt, J. P. D.

2010-06-01

Cloud condensation nuclei (CCN) concentrations were measured at Egbert, a rural site in Ontario, Canada during the spring of 2007. The CCN concentrations were compared to values predicted from the aerosol chemical composition and size distribution using κ-Köhler theory, with the specific goal of this work being to determine the hygroscopic parameter (κ) of the oxygenated organic component of the aerosol, assuming that oxygenation drives the hygroscopicity for the entire organic fraction of the aerosol. The hygroscopicity of the oxygenated fraction of the organic component, as determined by an Aerodyne aerosol mass spectrometer (AMS), was characterised by two methods. First, positive matrix factorization (PMF) was used to separate oxygenated and unoxygenated organic aerosol factors. By assuming that the unoxygenated factor is completely non-hygroscopic and by varying κ of the oxygenated factor so that the predicted and measured CCN concentrations are internally consistent and in good agreement, κ of the oxygenated organic factor was found to be 0.22±0.04 for the suite of measurements made during this five-week campaign. In a second, equivalent approach, we continue to assume that the unoxygenated component of the aerosol, with a mole ratio of atomic oxygen to atomic carbon (O/C) ≈ 0, is completely non-hygroscopic, and we postulate a simple linear relationship between κorg and O/C. Under these assumptions, the κ of the entire organic component for bulk aerosols measured by the AMS can be parameterised as κorg=(0.29±0.05)·(O/C), for the range of O/C observed in this study (0.3 to 0.6). These results are averaged over our five-week study at one location using only the AMS for composition analysis. Empirically, our measurements are consistent with κorg generally increasing with increasing particle oxygenation, but high uncertainties preclude us from testing this hypothesis. Lastly, we examine select periods of different aerosol composition, corresponding to different air mass histories, to determine the generality of the campaign-wide findings described above.

Investigation of the Transport of Solar Ions Through the Earth's Magnetosphere

NASA Technical Reports Server (NTRS)

Lennartsson, O. W.; Evans, David (Technical Monitor)

2000-01-01

The objective of this study has been to infer, by statistical means, the most probable mode of entry of solar wind plasma into Earth's magnetotail, using a particular set of archived data from the Lockheed Plasma Composition Experiment on the International Sun-Earth Explorer One (ISEE-1) satellite, jointly sponsored by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) in the 1970's and 80's. Despite their considerable age, the Lockheed ISEE-1 data are still, at the time of this report, the only substantial ion composition data in the sub-keV to keV energy range available from the magnetotail beyond 9 R(sub E), because of various technical problems with ion mass spectrometers on later missions, and are therefore a unique source of information about the mixing of solar and terrestrial origin plasmas in the tail, within the ISEE-1 apogee of almost 23 R(sub E). The entire set of archived data used in this study, covering the 4.5 years of operation of the instrument and comprising not only tail measurements but also data from the inner magnetosphere as well as data from outside the magnetopause, is now available to the public via the WorldWideWeb at the address: http://cis.spasci.com/ISEE_ions The fundamental assumption of this and other studies of magnetosphere ion composition is that He++ and O+ ions are virtually certain "tags" of solar and terrestrial origins, respectively. This is an assumption with strong theoretical basis and it is corroborated by observational evidence, including the often substantial differences between the velocity distribution functions of those two species. The H+ ions can have a dual origin, in principle, but the close resemblance in the ISEE-1 data between the dynamics of H+ and He++ ions indicates a predominantly solar origin of the H+ ions in the tail, at least. By the same token, the usually minor He+ ions are probably almost entirely of terrestrial origin, because of their similarity to the O+ ions.

Ultrastructure of selected struvite-containing urinary calculi from cats.

PubMed

Neumann, R D; Ruby, A L; Ling, G V; Schiffman, P S; Johnson, D L

1996-01-01

To elucidate the ultrastructural details of struvite-containing urinary calculi from cats. Specimens studied were inclusive of the range of textures visible during preliminary analysis by use of a stereoscopic dissecting microscope. Textural types, which were used to infer crystal growth conditions, were differentiated with regard to crystal habit, crystal size, growth orientation, and primary porosity. Thirty specimens were selected from a collection of approximately 1,600 feline urinary calculi: 20 of these were composed entirely of struvite, and 10 consisted of struvite and calcium phosphate (apatite). Qualitative and quantitative analyses of specimens included use of plain and polarized light microscopy, x-ray diffractometry, scanning electron microscopy with backscattered electron imagery, x-ray fluorescence scans, and electron probe microanalysis. Four textural types were recognized among struvite calculi, whereas 2 textural types of struvite-apatite calculi were described. The presence of minute, well interconnected primary pores in struvite-containing urinary calculi from cats is an important feature, which may promote possible interaction of calculi with changes in urine composition. Primary porosity, which can facilitate interaction between the calculus and changing urine composition, may explain the efficacy of dietary or medicinal manipulations to promote the dissolution of struvite-containing uroliths from this species.

Beyond assemblies: system convergence and multi-materiality.

PubMed

Wiscombe, Tom

2012-03-01

The architectural construction industry has become increasingly more specialized over the past 50 years, creating a culture of layer thinking over part-to-whole thinking. Building systems and technologies are often cobbled together in conflicting and uncorrelated ways, even when referred to as 'integrated', such as by way of building information modeling. True integration of building systems requires rethinking how systems and architectural morphologies can push and pull on one another, creating not only innovation in technology but in aesthetics. The revolution in composite materials, with unprecedented plasticity and performance features, opens up a huge range of possibilities for achieving this kind of convergence. Composites by nature fuse envelope and structure, but through various types of inflections, they can also be made to conduct air and fluids through cavities and de-laminations, as well as integrate lighting and energy systems. Assembly as we know it moves away from mineral materials and hardware and toward polymers and 'healing'. Further, when projected into the near-future realm of multi-materiality and 3D manufacturing, possibilities for embedding systems and creating gradients of rigidity and opacity open up, pointing to an entirely new realm of architectural thinking.

Using heterostructural alloying to tune the structure and properties of the thermoelectric Sn 1–xCa xSe

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

Matthews, Bethany E.; Holder, Aaron M.; Schelhas, Laura T.

We grow and kinetically stabilize the isotropic rocksalt phase of SnSe thin films by alloying SnSe with CaSe. Thin polycrystalline films of the metastable heterostructural alloy Sn 1–xCa xSe are synthesized by pulsed laser deposition on amorphous SiO 2 over the entire composition range 0 < x < 1. We observe the theoretically-predicted, composition-driven change from a layered, orthorhombic structure to an isotropic, cubic structure near x = 0.18, in reasonable agreement with the theoretical value of x = 0.13 calculated from first principles. The optical band gap is highly non-linear in x and the trend agrees with theory predictions.more » Compared to the layered end-member SnSe, the isotropic alloy near the orthorhombic-to-rocksalt transition has a p-type electrical resistivity three orders of magnitude lower, and a thermoelectric power factor at least ten times larger. Furthermore manipulation of the structure of a functional material like SnSe via alloying may provide a new path to enhanced functionality, in this case, improved thermoelectric performance.« less

Basin Excavation, Lower Crust, Composition, and Bulk Moon Mass balance in Light of a Thin Crust

NASA Technical Reports Server (NTRS)

Jolliff, B. L.; Korotev, R. L.; Ziegler, R. A.

2013-01-01

New lunar gravity results from GRAIL have been interpreted to reflect an overall thin and low-density lunar crust. Accordingly, crustal thickness has been modeled as ranging from 0 to 60 km, with thinnest crust at the locations of Crisium and Moscoviense basins and thickest crust in the central farside highlands. The thin crust has cosmochemical significance, namely in terms of implications for the Moon s bulk composition, especially refractory lithophile elements that are strongly concentrated in the crust. Wieczorek et al. concluded that the bulk Moon need not be enriched compared to Earth in refractory lithophile elements such as Al. Less Al in the crust means less Al has been extracted from the mantle, permitting relatively low bulk lunar mantle Al contents and low pre- and post-crust-extraction values for the mantle (or the upper mantle if only the upper mantle underwent LMO melting). Simple mass-balance calculations using the method of [4] suggests that the same conclusion might hold for Th and the entire suite of refractory lithophile elements that are incompatible in olivine and pyroxene, including the KREEP elements, that are likewise concentrated in the crust.

Moonage Daydream: Reassessing the Simple Model for Lunar Magma Ocean Crystallization

NASA Technical Reports Server (NTRS)

Rapp, J. F.; Draper, D. S.

2016-01-01

Details of the differentiation of a global-scale lunar magma ocean (LMO) remain enigmatic, as the Moon is not simply composed of highlands anorthosite and a suite of mare basalts as inferred from early studies. Results from recent orbital missions, and the increasingly detailed study of lunar samples, have revealed a much larger range of lithologies, from relatively MgO-rich and "purest anorthosite" discovered on the lunar far side by the M3 instrument on Chandraayan-1 to more exotic lithologies such as Si-rich domes and spinel-rich clasts distributed globally. To understand this increasingly complex geology, we must understand the initial formation and evolution of the LMO, and the composition of the cumulates this differentiation could have produced. Several attempts at modelling such a crystallization sequence have been made, and have raised as many questions as they have answered. We present results from our ongoing experimental simulations of magma ocean crystallization, investigating two end-member bulk compositions (TWM and LPUM) under fully fractional crystallization conditions. These simulations represent melting of the entire silicate portion of the Moon, as an end-member starting point from which to begin assessing the evolution of the lunar interior and formation of the lunar crust.

Automatic thermographic image defect detection of composites

NASA Astrophysics Data System (ADS)

Luo, Bin; Liebenberg, Bjorn; Raymont, Jeff; Santospirito, SP

2011-05-01

Detecting defects, and especially reliably measuring defect sizes, are critical objectives in automatic NDT defect detection applications. In this work, the Sentence software is proposed for the analysis of pulsed thermography and near IR images of composite materials. Furthermore, the Sentence software delivers an end-to-end, user friendly platform for engineers to perform complete manual inspections, as well as tools that allow senior engineers to develop inspection templates and profiles, reducing the requisite thermographic skill level of the operating engineer. Finally, the Sentence software can also offer complete independence of operator decisions by the fully automated "Beep on Defect" detection functionality. The end-to-end automatic inspection system includes sub-systems for defining a panel profile, generating an inspection plan, controlling a robot-arm and capturing thermographic images to detect defects. A statistical model has been built to analyze the entire image, evaluate grey-scale ranges, import sentencing criteria and automatically detect impact damage defects. A full width half maximum algorithm has been used to quantify the flaw sizes. The identified defects are imported into the sentencing engine which then sentences (automatically compares analysis results against acceptance criteria) the inspection by comparing the most significant defect or group of defects against the inspection standards.

Flight-and ground-test evaluation of pyrrone foams

NASA Technical Reports Server (NTRS)

Mclain, A. G.; Kelliher, W. C.

1972-01-01

Two Pyrrone materials, pure Pyrrone foam with a density of 481 kg/cu m and hollow glass microsphere-Pyrrone composite with a density of 962 kg/cu m, were tested in the Langley 20-inch hypersonic arc heated tunnel at pressure levels from 0.06 to 0.27 atm and heating rates from 1.14 to 11.4 MW/sq m. The 481-kg/cu m Pyrrone foam was also flight tested as an experiment aboard a Pacemaker test vehicle. The results of the ground tests indicated that the thermal effectiveness of the 481-kg/cu m Pyrrone foam was superior to the 962-kg/cu m glass sphere-Pyrrone composite. The 481-kg/cu m Pyrrone foam had approximately one-half the thermal effectiveness of low density phenolic nylon. The 481-kg/cu m Pyrrone foam experienced random mechanical char removal over the entire range of test conditions. Char thermal property inputs for an ablation computer program were developed from the ground test data of the 481-kg/cu m Pyrrone foam. The computer program using these developed char thermal properties, as well as the measured uncharred material properties, adequately predicted the in-depth temperature histories measured during the Pacemaker flight.

Using heterostructural alloying to tune the structure and properties of the thermoelectric Sn 1–xCa xSe

DOE PAGES

Matthews, Bethany E.; Holder, Aaron M.; Schelhas, Laura T.; ...

2017-07-21

We grow and kinetically stabilize the isotropic rocksalt phase of SnSe thin films by alloying SnSe with CaSe. Thin polycrystalline films of the metastable heterostructural alloy Sn 1–xCa xSe are synthesized by pulsed laser deposition on amorphous SiO 2 over the entire composition range 0 < x < 1. We observe the theoretically-predicted, composition-driven change from a layered, orthorhombic structure to an isotropic, cubic structure near x = 0.18, in reasonable agreement with the theoretical value of x = 0.13 calculated from first principles. The optical band gap is highly non-linear in x and the trend agrees with theory predictions.more » Compared to the layered end-member SnSe, the isotropic alloy near the orthorhombic-to-rocksalt transition has a p-type electrical resistivity three orders of magnitude lower, and a thermoelectric power factor at least ten times larger. Furthermore manipulation of the structure of a functional material like SnSe via alloying may provide a new path to enhanced functionality, in this case, improved thermoelectric performance.« less

Silicate liquid immiscibility in magmas and in the system K2O-FeO-AI2O3-SiO2: an example of serendipity

USGS Publications Warehouse

Roedder, E.

1978-01-01

The concept of silicate liquid immiscibility was invoked early in the history of petrology to explain certain pairs of compositionally divergent rocks, but. as a result of papers by Greig (Am. J. Sci. 13, 1-44, 133-154) and Bowen (The Evolution of the Igneous Rocks), it fell into disfavor for many years. The discovery of immiscibility in geologically reasonable temperature ranges and compositions in experimental work on the system K2O-FeO-Al2O3-SiO2, and of evidence for immiscibility in a variety of lunar and terrestrial rocks, has reinstated the process. Phase equilibria in the high-silica corner of the tetrahedron representing the system K2O- FeO-Al2O3-SiO2 are presented, in the form of constant FeO sections through the tetrahedron, at 10% increments. Those sections, showing the tentative relationships of the primary phase volumes, are based on 5631 quenching runs on 519 compositions, made in metallic iron containers in pure nitrogen. Thirteen crystalline compounds are involved, of which at least six show two or more crystal modifica-tions. Two separate phase volumes, in each of which two immiscible liquids, one iron-rich and the other iron-poor, are present at the liquidus. One of these volumes is entirely within the quaternary system, astride the 1:1 K2O:Al2O3 plane. No quaternary compounds as such have been found, but evidence does point toward at least partial quaternary solid solution, with rapidly lowering liquidus temperatures, from K2O??Al2O3?? 2SiO2 ('potash nepheline', kalsilite. kaliophilite) to the isostructural compound K2O??FeO??3SiO2, and from K2O??Al2O3??4SiO2 (leucite) to the isostructural compound K2O??FeO??5SiO2, Both of these series apparently involve substitution, in tetrahedral coordination. of a ferrous iron and a silicon ion for two aluminum ions. Some of the 'impurities' found in analyses of the natural phases may reflect these substitutions. As a result of the geometry of the immiscibility volume located entirely within the quaternary system, compositions near it show a number of phase changes and large amounts of crystallization with small temperature changes, generally in the range 1100-1150 C. Similar low-temperature, high-alkali immiscibility was discovered in a few exploratory runs in the equivalent systems with Rb or Cs substituting for K. But not in those with Li or Na. A review of the compositions and general behavior of systems involving immiscibility, both stable and metastable, and of the evidence for natural immiscibility. indicates that it may be a much more common feature than generally thought. Several examples of natural immiscibility are detailed; most yield a felsic. alkali-aluminosilicate melt and a mafic melt. from a wide variety of generally basaltic parental magmas, both under- and over saturated. Unfortunately, the best line of evidence for immiscibility in terrestrial rocks, a sharply defined meniscus between two compositionally disparate glasses, is by its very nature self-destructing, since it is effectively eliminated by either crystallization or gravitative separation and coalescence into separate magmas. Verification of operation of the exosolutionor 'splitting' process on a large scale will probably require careful study of isotopic and trace element partitioning in both laboratory and field. ?? 1978.

Nondestructive atomic compositional analysis of BeMgZnO quaternary alloys using ion beam analytical techniques

NASA Astrophysics Data System (ADS)

Zolnai, Z.; Toporkov, M.; Volk, J.; Demchenko, D. O.; Okur, S.; Szabó, Z.; Özgür, Ü.; Morkoç, H.; Avrutin, V.; Kótai, E.

2015-02-01

The atomic composition with less than 1-2 atom% uncertainty was measured in ternary BeZnO and quaternary BeMgZnO alloys using a combination of nondestructive Rutherford backscattering spectrometry with 1 MeV He+ analyzing ion beam and non-Rutherford elastic backscattering experiments with 2.53 MeV energy protons. An enhancement factor of 60 in the cross-section of Be for protons has been achieved to monitor Be atomic concentrations. Usually the quantitative analysis of BeZnO and BeMgZnO systems is challenging due to difficulties with appropriate experimental tools for the detection of the light Be element with satisfactory accuracy. As it is shown, our applied ion beam technique, supported with the detailed simulation of ion stopping, backscattering, and detection processes allows of quantitative depth profiling and compositional analysis of wurtzite BeZnO/ZnO/sapphire and BeMgZnO/ZnO/sapphire layer structures with low uncertainty for both Be and Mg. In addition, the excitonic bandgaps of the layers were deduced from optical transmittance measurements. To augment the measured compositions and bandgaps of BeO and MgO co-alloyed ZnO layers, hybrid density functional bandgap calculations were performed with varying the Be and Mg contents. The theoretical vs. experimental bandgaps show linear correlation in the entire bandgap range studied from 3.26 eV to 4.62 eV. The analytical method employed should help facilitate bandgap engineering for potential applications, such as solar blind UV photodetectors and heterostructures for UV emitters and intersubband devices.

On the thermal stability of physical vapor deposited oxide-hardened nanocrystalline gold thin films

DOE PAGES

Argibay, Nicolas; Mogonye, J. E.; Michael, Joseph R.; ...

2015-04-08

We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol. % oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 μm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situelectrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilizedmore » grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of E a = 21.6 kJ/mol and A o = 2.3 × 10 -17 m 2/s for Au-1 vol. % ZnO and E a =12.7 kJ/mol and A o = 3.1 × 10 -18 m 2/s for Au-2 vol.% ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol. % ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. As a result, the proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination.« less

Ecological traits and environmental affinity explain Red Sea fish introduction into the Mediterranean.

PubMed

Belmaker, Jonathan; Parravicini, Valeriano; Kulbicki, Michel

2013-05-01

Alien species are considered one of the prime threats to biodiversity, driving major changes in ecosystem structure and function. Identifying the traits associated with alien introduction has been largely restricted to comparing indigenous and alien species or comparing alien species that differ in abundance or impact. However, a more complete understanding may emerge when the entire pool of potential alien species is used as a control, information that is rarely available. In the eastern Mediterranean, the marine environment is undergoing an unparalleled species composition transformation, as a flood of aliens have entered from the Red Sea following the opening of the Suez Canal in 1869. In this study, we compile data on species traits, geographical distribution, and environmental affinity of the entire pool of reef-associated fish species in the Red Sea and more generally across the Indo-Pacific. We use this extensive data to identify the prime characteristics separating Red Sea species that have become alien in the Mediterranean from those that have not. We find that alien species occupy a larger range of environments in their native ranges, explaining their ability to colonize the seasonal Mediterranean. Red Sea species that naturally experience high maximum temperatures in their native range have a high probability of becoming alien. Thus, contrary to predictions of an accelerating number of aliens following increased water temperatures, hotter summers in this region may prevent the establishment of many alien species. We further find that ecological trait diversity of alien species is substantially more evenly spaced and more divergent than random samples from the pool of Red Sea species, pointing at additional processes, such as competition, promoting ecological diversity among alien species. We use these results to provide a first quantitative ranking of the potential of Red Sea species to become established in the eastern Mediterranean. © 2012 Blackwell Publishing Ltd.

Development of a realistic stress analysis for fatigue analysis of notched composite laminates

NASA Technical Reports Server (NTRS)

Humphreys, E. A.; Rosen, B. W.

1979-01-01

A finite element stress analysis which consists of a membrane and interlaminar shear spring analysis was developed. This approach was utilized in order to model physically realistic failure mechanisms while maintaining a high degree of computational economy. The accuracy of the stress analysis predictions is verified through comparisons with other solutions to the composite laminate edge effect problem. The stress analysis model was incorporated into an existing fatigue analysis methodology and the entire procedure computerized. A fatigue analysis is performed upon a square laminated composite plate with a circular central hole. A complete description and users guide for the computer code FLAC (Fatigue of Laminated Composites) is included as an appendix.

Evaluation of flexural, diametral tensile, and shear bond strength of composite repairs.

PubMed

Imbery, T A; Gray, T; DeLatour, F; Boxx, C; Best, A M; Moon, P C

2014-01-01

Repairing composite restorations may be a more conservative treatment than replacing the entire restoration. The objective of this in vitro study was to determine the best repair method by measuring flexural, diametral tensile, and shear bond strength of repaired composites in which the surfaces were treated with chemical primers (Add & Bond or Silane Bond Enhancer), a bonding agent (Optibond Solo Plus [OBSP]), or mechanical retention with a bonding agent. Filtek Supreme Ultra shade B1B was placed in special molds to fabricate specimens that served to test the flexural, diametral tensile, or shear strength of the inherent resin substrate. The same molds were modified to make specimens for testing repair strength of the resin. Repairs were made immediately or after aging in deionized water at 37°C for seven days. All repair sites were finished with coarse Sof-Lex discs to simulate finishing new restorations or partially removing aged restorations. Repair surfaces were treated with one of the following: 1) phosphoric-acid etching and OBSP; 2) Add & Bond; 3) phosphoric-acid etching, Silane Bond Enhancer, and OBSP; or 4) quarter round bur, phosphoric-acid etching, and OBSP. Specimens were placed back in the original molds to fabricate specimens for diametral tensile or flexural testing or in an Ultradent jig to make specimens for shear bond testing. Composite resin in shade B5B was polymerized against the treated surfaces to make repairs. Two negative control groups for the three testing methods consisted of specimens in which repairs were made immediately or after aging without any surface treatments. Controls and experimental repairs were aged (water 37°C, 24 hours) before flexural, diametral tensile, or shear testing in an Instron Universal testing machine at a crosshead speed of 0.5 mm/min. Experimental flexural repair strengths ranged from 26.4% to 88.6% of the inherent substrate strength. Diametral tensile repair strengths ranged from 40% to 80% of the inherent substrate strength, and shear bond strength repairs ranged from 56% to 102%. Geometric means were statistically analyzed with two-way analysis of variance on their log-transformed values. Significant differences were determined using Tukey honestly significant difference (p<0.05). Depending on the mechanical property being tested, surface treatments produced different results. OBSP produced more consistent results than chemical primers.

Method for cracking hydrocarbon compositions using a submerged reactive plasma system

DOEpatents

Kong, P.C.

1997-05-06

A method is described for cracking a liquid hydrocarbon composition (e.g. crude oil) to produce a cracked hydrocarbon product. A liquid hydrocarbon composition is initially provided. An electrical arc is generated directly within the hydrocarbon composition so that the arc is entirely submerged in the composition. Arc generation is preferably accomplished using a primary and secondary electrode each having a first end submerged in the composition. The first ends of the electrodes are separated from each other to form a gap there between. An electrical potential is then applied to the electrodes to generate the arc within the gap. A reactive gas is thereafter delivered to the arc which forms a bubble around the arc. Gas delivery may be accomplished by providing a passageway through each electrode and delivering the gas through the passageways. The arc and gas cooperate to produce a plasma which efficiently cracks the hydrocarbon composition. 6 figs.

Poly-paper: a sustainable material for packaging, based on recycled paper and recyclable with paper.

PubMed

Del Curto, Barbara; Barelli, Nadia; Profaizer, Mauro; Farè, Silvia; Tanzi, Maria Cristina; Cigada, Alberto; Ognibene, Giulia; Recca, Giuseppe; Cicala, Gianluca

2016-11-02

Until now, environmental sustainability issues are almost entirely unsolved for packaging materials. With the final aim of finding materials with a single recycling channel, cellulose fiber/poly(vinyl)alcohol composites were investigated. After extrusion and injection molding, samples of composite with different cellulose fiber content (30%, 50% and 70% w/w) were tested. Tensile mechanical tests exhibited an improvement in composite stiffness when the reinforcement content was increased together with a decrease in composite elongation. Solubility tests performed at room temperature and 45°C showed different behavior depending on the water-resistant film applied on the composite (50% cellulose fiber content). In particular, the uncoated composite showed complete solubility after 2 hours, whereas at the same time point, no solubility occurred when a non-water-soluble varnish was used. The proposed composites, named Poly-paper, appear to warrant further investigation as highly sustainable packaging.

Method for cracking hydrocarbon compositions using a submerged reactive plasma system

DOEpatents

Kong, Peter C.

1997-01-01

A method for cracking a liquid hydrocarbon composition (e.g. crude oil) to produce a cracked hydrocarbon product. A liquid hydrocarbon composition is initially provided. An electrical arc is generated directly within the hydrocarbon composition so that the arc is entirely submerged in the composition. Arc generation is preferably accomplished using a primary and secondary electrode each having a first end submerged in the composition. The first ends of the electrodes are separated from each other to form a gap therebetween. An electrical potential is then applied to the electrodes to generate the arc within the gap. A reactive gas is thereafter delivered to the arc which forms a bubble around the arc. Gas delivery may be accomplished by providing a passageway through each electrode and delivering the gas through the passageways. The arc and gas cooperate to produce a plasma which efficiently cracks the hydrocarbon composition.

High-Speed, Three Dimensional Object Composition Mapping Technology

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

Ishikawa, M Y

2001-02-14

This document overviews an entirely new approach to determining the composition--the chemical-elemental, isotopic and molecular make-up--of complex, highly structured objects, moreover with microscopic spatial resolution in all 3 dimensions. The front cover depicts the new type of pulsed laser system at the heart of this novel technology under adjustment by Alexis Wynne, and schematically indicates two of its early uses: swiftly analyzing the 3-D composition governed structure of a transistor circuit with both optical and mass-spectrometric detectors, and of fossilized dinosaur and turtle bones high-speed probed by optical detection means. Studying the composition-cued 3-D micro-structures of advanced composite materials andmore » the microscopic scale composition-texture of biological tissues are two near-term examples of the rich spectrum of novel applications enabled by this field-opening analytic tool-set.« less

A conifer-friendly high-throughput α-cellulose extraction method for δ13C and δ18O stable isotope ratio analysis

NASA Astrophysics Data System (ADS)

Lin, W.; Noormets, A.; domec, J.; King, J. S.; Sun, G.; McNulty, S.

2012-12-01

Wood stable isotope ratios (δ13C and δ18O) offer insight to water source and plant water use efficiency (WUE), which in turn provide a glimpse to potential plant responses to changing climate, particularly rainfall patterns. The synthetic pathways of cell wall deposition in wood rings differ in their discrimination ratios between the light and heavy isotopes, and α-cellulose is broadly seen as the best indicator of plant water status due to its local and temporal fixation and to its high abundance within the wood. To use the effects of recent severe droughts on the WUE of loblolly pine (Pinus taeda) throughout Southeastern USA as a harbinger of future changes, an effort has been undertaken to sample the entire range of the species and to sample the isotopic composition in a consistent manner. To be able to accommodate the large number of samples required by this analysis, we have developed a new high-throughput method for α-cellulose extraction, which is the rate-limiting step in such an endeavor. Although an entire family of methods has been developed and perform well, their throughput in a typical research lab setting is limited to 16-75 samples per week with intensive labor input. The resin exclusion step in conifersis is particularly time-consuming. We have combined the recent advances of α-cellulose extraction in plant ecology and wood science, including a high-throughput extraction device developed in the Potsdam Dendro Lab and a simple chemical-based resin exclusion method. By transferring the entire extraction process to a multiport-based system allows throughputs of up to several hundred samples in two weeks, while minimizing labor requirements to 2-3 days per batch of samples.

A Nuclear Ramjet Flyer for Exploration of Jovian Atmosphere

NASA Astrophysics Data System (ADS)

Maise, G.; Powell, J.; Paniagua, J.; Lecat, R.

2001-01-01

We investigated the design, operation, and data gathering possibilities of a nuclear-powered ramjet flyer in the Jovian atmosphere. The MITEE nuclear rocket engine can be modified to operate as a ramjet in planetary atmospheres. (Note: MITEE is a compact, ultra-light-weight thermal nuclear rocket which uses hydrogen as the propellant.) To operate as a ramjet, MITEE requires a suitable inlet and diffuser to substitute for the propellant that is pumped from the supply tanks in a nuclear rocket engine. Such a ramjet would fly in the upper Jovian atmosphere, mapping in detail temperatures, pressures, compositions, lightning activity, and wind speeds in the highly turbulent equatorial zone and the Great Red Spot. The nuclear ramjet could operate for months because: (1) the Jovian atmosphere has unlimited propellant, (2) the MITEE nuclear reactor is a (nearly) unlimited power source, and (3) with few moving parts, mechanical wear should be minimal. This paper presents a conceptual design of a ramjet flyer and its nuclear engine. The flyer incorporates a swept-wing design with instruments located in the twin wing-tip pods (away from the radiation source and readily shielded, if necessary). The vehicle is 2 m long with a 2 m wingspan. Its mass is 220 kg, and its nominal flight Mach number is 1.5. Based on combined neutronic and thermal/hydraulic analyses, we calculated that the ambient pressure range over which the flyer can operate to be from about 0.04 to 4 (terrestrial) atmospheres. This altitude range encompasses the three uppermost cloud layers in the Jovian atmosphere: (1) the entire uppermost visible NH3 ice cloud layer (where lightning has been observed), (2) the entire NH4HS ice cloud layer, and (3) the upper portion of the H2O ice cloud layer.

The use of composite fingerprints to quantify sediment sources in a wildfire impacted landscape, Alberta, Canada.

PubMed

Stone, M; Collins, A L; Silins, U; Emelko, M B; Zhang, Y S

2014-03-01

There is increasing global concern regarding the impacts of large scale land disturbance by wildfire on a wide range of water and related ecological services. This study explores the impact of the 2003 Lost Creek wildfire in the Crowsnest River basin, Alberta, Canada on regional scale sediment sources using a tracing approach. A composite geochemical fingerprinting procedure was used to apportion the sediment efflux among three key spatial sediment sources: 1) unburned (reference) 2) burned and 3) burned sub-basins that were subsequently salvage logged. Spatial sediment sources were characterized by collecting time-integrated suspended sediment samples using passive devices during the entire ice free periods in 2009 and 2010. The tracing procedure combines the Kruskal-Wallis H-test, principal component analysis and genetic-algorithm driven discriminant function analysis for source discrimination. Source apportionment was based on a numerical mass balance model deployed within a Monte Carlo framework incorporating both local optimization and global (genetic algorithm) optimization. The mean relative frequency-weighted average median inputs from the three spatial source units were estimated to be 17% (inter-quartile uncertainty range 0-32%) from the reference areas, 45% (inter-quartile uncertainty range 25-65%) from the burned areas and 38% (inter-quartile uncertainty range 14-59%) from the burned-salvage logged areas. High sediment inputs from burned and the burned-salvage logged areas, representing spatial source units 2 and 3, reflect the lasting effects of forest canopy and forest floor organic matter disturbance during the 2003 wildfire including increased runoff and sediment availability related to high terrestrial erosion, streamside mass wasting and river bank collapse. The results demonstrate the impact of wildfire and incremental pressures associated with salvage logging on catchment spatial sediment sources in higher elevation Montane regions where forest growth and vegetation recovery are relatively slow. Copyright © 2013 Elsevier B.V. All rights reserved.

The Impact of Divorce on Children.

ERIC Educational Resources Information Center

Demo, David H.; Acock, Alan C.

1988-01-01

Reviews empirical evidence addressing relationship between divorce, family composition, and children's well-being. Although not entirely consistent, pattern of findings suggests that children's emotional adjustment, gender-role orientation, and antisocial behavior are affected by family structure, whereas other dimensions of well-being are…

The Brain.

ERIC Educational Resources Information Center

Hubel, David H.

1979-01-01

This article on the brain is part of an entire issue about neurobiology and the question of how the human brain works. The brain as an intricate tissue composed of cells is discussed based on the current knowledge and understanding of its composition and structure. (SA)

Microwave heating for thermoplastic composites - Could the technology be used for welding applications?

NASA Astrophysics Data System (ADS)

Barasinski, Anaïs; Tertrais, Hermine; Bechtel, Stéphane; Chinesta, Francisco

2018-05-01

Welding primary structure thermoplastic composites parts is still an issue today, many technologies have been extensively studied: induction, ultrasonic, resistive welding, none is today entirely viable for this application due to various implementation reasons. On the other hand, microwave solutions are not very common in composites forming process, although being widespread in homes. Microwave (MW) technology relies on volumetric heating. Thermal energy is transferred from an electromagnetic field to materials that can absorb it at specific frequencies. Volumetric heating enables better process temperature control and less overall energy losses, which can results in shorter processing cycles and higher process efficiency. Nowadays, the main drawback of this technology is that the complex physics involved in the conversion of electromagnetic energy in thermal energy (heating) is not entirely understood and controlled for complex materials. In that work, the authors propose to look deeper in that way, first proposing a simulation tool, based on a coupling between a commercial code and a home made one, allowing the following of the electromagnetic field very precisely in the thickness of a laminate composite part, the last consisting of a stack of layers with different orientations, each layer made of a resin matrix and carbon fibers. Thermal fields are then computed and validated by experimental measurements. In a second part, the authors propose to look at a common welding case of a stringer, on a skin.

Trace element zoning as a record of chemical disequilibrium during garnet growth

NASA Astrophysics Data System (ADS)

Chernoff, Carlotta B.; Carlson, William D.

1999-06-01

Trace element concentrations in pelitic garnets from the Picuris Range of New Mexico display precipitous changes coincident with abrupt variations in Ca concentration. These patterns probably arise from the transitory participation of different trace element enriched phases in the garnet forming reaction. Changes in the reactant and product assemblages occur at different times during the reaction history for crystals of different size, so they cannot be the result of any event affecting the entire rock, such as a change in pressure, temperature, or fluid composition. Instead, they reflect kinetic factors that cause Ca, Y, Yb, P, Ti, Sc, Zr, Hf, Sr, Na, and Li to fail to achieve chemical equilibrium during garnet growth. Caution is needed to avoid misinterpreting excursions in the concentration of these elements as event markers recording simultaneous rockwide changes in intensive parameters, when in fact they may record transient disequilibrium states that are local in scope, and not contemporaneous.

Order-disorder transition in a two-dimensional boron-carbon-nitride alloy

NASA Astrophysics Data System (ADS)

Lu, Jiong; Zhang, Kai; Feng Liu, Xin; Zhang, Han; Chien Sum, Tze; Castro Neto, Antonio H.; Loh, Kian Ping

2013-10-01

Two-dimensional boron-carbon-nitride materials exhibit a spectrum of electronic properties ranging from insulating to semimetallic, depending on their composition and geometry. Detailed experimental insights into the phase separation and ordering in such alloy are currently lacking. Here we report the mixing and demixing of boron-nitrogen and carbon phases on ruthenium (0001) and found that energetics for such processes are modified by the metal substrate. The brick-and-mortar patchwork observed of stoichiometrically percolated hexagonal boron-carbon-nitride domains surrounded by a network of segregated graphene nanoribbons can be described within the Blume-Emery-Griffiths model applied to a honeycomb lattice. The isostructural boron nitride and graphene assumes remarkable fluidity and can be exchanged entirely into one another by a catalytically assistant substitution. Visualizing the dynamics of phase separation at the atomic level provides the premise for enabling structural control in a two-dimensional network for broad nanotechnology applications.

X-ray observations of AM Herculis from OSO 8

NASA Technical Reports Server (NTRS)

Coe, M. J.; Dennis, B. R.; Dolan, J. F.; Crannell, C. J.; Frost, K. J.; Orwig, I. E.

1979-01-01

X-ray observations of the white dwarf binary system AM Herculis in the range 2 to 250 keV, taken by OSO 8, are presented and compared with balloon and Ariel 5 measurements. The composite spectrum of the 2 to 40 and 20 to 250 keV fluxes determined by the proportional counter and the high energy scintillation spectrometer, respectively, on board the satellite is shown averaged over the entire binary cycle. Variations in spectral shape and intensity between the OSO 8 results and balloon measurements taken 10 to 20 days apart are observed. Results indicate the presence of a spectral break at about 15 keV on some occasions, similar to that seen in Her X-1, however presumably caused by a different mechanism than in the neutron star. It is also considered unlikely that the gamma-ray tail observed by Ariel 5 existed during OSO 8 observations.

Molecular interactions in ethyl acetate-chlorobenzene binary solution: Dielectric, spectroscopic studies and quantum chemical calculations.

PubMed

Karthick, N K; Kumbharkhane, A C; Joshi, Y S; Mahendraprabu, A; Shanmugam, R; Elangovan, A; Arivazhagan, G

2017-05-05

Dielectric studies using Time Domain Reflectometry method has been carried out on the binary solution of Ethyl acetate (EA) with Chlorobenzene (CBZ) over the entire composition range. Spectroscopic (FTIR and 13 C NMR) signatures of neat EA, CBZ and their equimolar binary solution have also been recorded. The results of the spectroscopic studies favour the presence of (CBZ) CH⋯OC (EA), (EA) methylene CH⋯π electrons (CBZ) and (EA) methyl CH⋯Cl (CBZ) contacts which have been validated using quantum chemical calculations. Dimerization of CBZ has been identified. Presence of β-clusters has been identified in all the solutions. Although EA and CBZ molecules have nearly equal molar volumes, CBZ molecules experience larger hindrance for the rotation than EA molecules. Very small excess dielectric constant (ε E ) values may be correlated with weak heteromolecular forces and/or closed heteromolecular association. Copyright © 2017 Elsevier B.V. All rights reserved.

Molecular interactions in ethyl acetate-chlorobenzene binary solution: Dielectric, spectroscopic studies and quantum chemical calculations

NASA Astrophysics Data System (ADS)

Karthick, N. K.; Kumbharkhane, A. C.; Joshi, Y. S.; Mahendraprabu, A.; Shanmugam, R.; Elangovan, A.; Arivazhagan, G.

2017-05-01

Dielectric studies using Time Domain Reflectometry method has been carried out on the binary solution of Ethyl acetate (EA) with Chlorobenzene (CBZ) over the entire composition range. Spectroscopic (FTIR and 13C NMR) signatures of neat EA, CBZ and their equimolar binary solution have also been recorded. The results of the spectroscopic studies favour the presence of (CBZ) Csbnd H ⋯ Odbnd C (EA), (EA) methylene Csbnd H ⋯ π electrons (CBZ) and (EA) methyl Csbnd H ⋯ Cl (CBZ) contacts which have been validated using quantum chemical calculations. Dimerization of CBZ has been identified. Presence of β-clusters has been identified in all the solutions. Although EA and CBZ molecules have nearly equal molar volumes, CBZ molecules experience larger hindrance for the rotation than EA molecules. Very small excess dielectric constant (εE) values may be correlated with weak heteromolecular forces and/or closed heteromolecular association.

Wide-Band Heterodyne Submillimetre Wave Spectrometer for Planetary Atmospheres

NASA Technical Reports Server (NTRS)

Schlecht, Erich

2010-01-01

We present calculations and measurements on a passive submillimetre wave spectroscopic sounder to gather data on the thermal structure, dynamics and composition of the upper atmosphere of a planet, e.g. the stratosphere of Jupiter, or the entire thickness of the atmosphere of Mars. The instrument will be capable of measuring wind speeds, temperature, pressure, and key constituent concentrations in the stratosphere of the target planet. This instrument consists of a Schottky diode based front end and a digital back-end spectrometer. It differs from previous space-based spectrometers in its combination of wide tunability (520-590 GHz), and rapid frequency switching between widely spaced lines within that range. This will enable near simultaneous observation of multiple lines, which is critical to the reconstruction of atmospheric pressure and density versus altitude profiles. At the same time frequency accuracy must be high to enable wind speeds to be determined directly by measurement of the line's Doppler shift.

Volumetric and viscometric study of molecular interactions in the mixtures of some secondary alcohols with equimolar mixture of ethanol and N, N-dimethylacetamide at 308.15 K

NASA Astrophysics Data System (ADS)

Sreekanth, K.; Sravana Kumar, D.; Kondaiah, M.; Krishna Rao, D.

2011-02-01

Densities and viscosities of mixtures of isopropanol, isobutanol and isoamylalcohol with equimolar mixture of ethanol and N, N-dimethylacetamide have been measured at 308.15 K over the entire composition range. Deviations in viscosity, excess molar volume and excess Gibb’s free energy of activation of viscous flow have been calculated from the experimental values of densities and viscosities. Excess properties have been fitted to the Redlich-Kister type polynomial equation and the corresponding standard deviations have been calculated. The experimental data of viscosity have been used to test the applicability of empirical relations of Grunberg-Nissan, Hind-McLaughlin, Katti-Chaudhary and Heric-Brewer for the systems studied. Molecular interactions in the liquid mixtures have been investigated in the light of variation of deviation and of excess values in evaluated properties.

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

Laser diodes with 353 nm wavelength enabled by reduced-dislocation-density AlGaN templates

DOE PAGES

Crawford, Mary H.; Allerman, Andrew A.; Armstrong, Andrew M.; ...

2015-10-30

We fabricated optically pumped and electrically injected ultraviolet (UV) lasers on reduced-threading-dislocation-density (reduced-TDD) AlGaN templates. The overgrowth of sub-micron-wide mesas in the Al 0.32Ga 0.68N templates enabled a tenfold reduction in TDD, to (2–3) × 10 8 cm –2. Optical pumping of AlGaN hetero-structures grown on the reduced-TDD templates yielded a low lasing threshold of 34 kW/cm 2 at 346 nm. Room-temperature pulsed operation of laser diodes at 353 nm was demonstrated, with a threshold of 22.5 kA/cm 2. Furthermore, reduced-TDD templates have been developed across the entire range of AlGaN compositions, presenting a promising approach for extending laser diodesmore » into the deep UV.« less

Experimental and Numerical Study of the Buckling of Composite Profiles with Open Cross Section under Axial Compression

NASA Astrophysics Data System (ADS)

Rozylo, Patryk; Teter, Andrzej; Debski, Hubert; Wysmulski, Pawel; Falkowicz, Katarzyna

2017-10-01

The object of the research are short, thin-walled columns with an open top-hat cross section made of multilayer laminate. The walls of the investigated profiles are made of plate elements. The entire columns are subjected to uniform compression. A detailed analysis allowed us to determine critical forces and post-critical equilibrium paths. It is assumed that the columns are articulately supported on the edges forming their ends. The numerical investigation is performed by the finite element method. The study involves solving the problem of eigenvalue and the non-linear problem of stability of the structure. The numerical analysis is performed by the commercial simulation software ABAQUS®. The numerical results are then validated experimentally. In the discussed cases, it is assumed that the material operates within a linearly-elastic range, and the non-linearity of the FEM model is due to large displacements.

Barrier infrared detector

NASA Technical Reports Server (NTRS)

Ting, David Z. (Inventor); Khoshakhlagh, Arezou (Inventor); Soibel, Alexander (Inventor); Hill, Cory J. (Inventor); Gunapala, Sarath D. (Inventor)

2012-01-01

A superlattice-based infrared absorber and the matching electron-blocking and hole-blocking unipolar barriers, absorbers and barriers with graded band gaps, high-performance infrared detectors, and methods of manufacturing such devices are provided herein. The infrared absorber material is made from a superlattice (periodic structure) where each period consists of two or more layers of InAs, InSb, InSbAs, or InGaAs. The layer widths and alloy compositions are chosen to yield the desired energy band gap, absorption strength, and strain balance for the particular application. Furthermore, the periodicity of the superlattice can be "chirped" (varied) to create a material with a graded or varying energy band gap. The superlattice based barrier infrared detectors described and demonstrated herein have spectral ranges covering the entire 3-5 micron atmospheric transmission window, excellent dark current characteristics operating at least 150K, high yield, and have the potential for high-operability, high-uniformity focal plane arrays.

Recommended direct simulation Monte Carlo collision model parameters for modeling ionized air transport processes

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

Swaminathan-Gopalan, Krishnan; Stephani, Kelly A., E-mail: ksteph@illinois.edu

2016-02-15

A systematic approach for calibrating the direct simulation Monte Carlo (DSMC) collision model parameters to achieve consistency in the transport processes is presented. The DSMC collision cross section model parameters are calibrated for high temperature atmospheric conditions by matching the collision integrals from DSMC against ab initio based collision integrals that are currently employed in the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) and Data Parallel Line Relaxation (DPLR) high temperature computational fluid dynamics solvers. The DSMC parameter values are computed for the widely used Variable Hard Sphere (VHS) and the Variable Soft Sphere (VSS) models using the collision-specific pairing approach.more » The recommended best-fit VHS/VSS parameter values are provided over a temperature range of 1000-20 000 K for a thirteen-species ionized air mixture. Use of the VSS model is necessary to achieve consistency in transport processes of ionized gases. The agreement of the VSS model transport properties with the transport properties as determined by the ab initio collision integral fits was found to be within 6% in the entire temperature range, regardless of the composition of the mixture. The recommended model parameter values can be readily applied to any gas mixture involving binary collisional interactions between the chemical species presented for the specified temperature range.« less

CENTAURUS A: THE EXTRAGALACTIC SOURCE OF COSMIC RAYS WITH ENERGIES ABOVE THE KNEE

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

Biermann, Peter L.; De Souza, Vitor, E-mail: plbiermann@mpifr-bonn.mpg.de, E-mail: vitor@ifsc.usp.br

2012-02-10

The origin of cosmic rays at all energies is still uncertain. In this paper, we present and explore an astrophysical scenario to produce cosmic rays with energy ranging from below 10{sup 15} to 3 Multiplication-Sign 10{sup 20} eV. We show here that just our Galaxy and the radio galaxy Cen A, each with their own galactic cosmic-ray particles but with those from the radio galaxy pushed up in energy by a relativistic shock in the jet emanating from the active black hole, are sufficient to describe the most recent data in the PeV to near ZeV energy range. Data aremore » available over this entire energy range from the KASCADE, KASCADE-Grande, and Pierre Auger Observatory experiments. The energy spectrum calculated here correctly reproduces the measured spectrum beyond the knee and, contrary to widely held expectations, no other extragalactic source population is required to explain the data even at energies far below the general cutoff expected at 6 Multiplication-Sign 10{sup 19} eV, the Greisen-Zatsepin-Kuz'min turnoff due to interaction with the cosmological microwave background. We present several predictions for the source population, the cosmic-ray composition, and the propagation to Earth which can be tested in the near future.« less

Diffusive Transport and Structural Properties of Liquid Iron Alloys at High Pressure

NASA Astrophysics Data System (ADS)

Posner, E.; Rubie, D. C.; Steinle-Neumann, G.; Frost, D. J.

2017-12-01

Diffusive transport properties of liquid iron alloys at high pressures (P) and temperatures (T) place important kinetic constraints on processes related to the origin and evolution of planetary cores. Earth's core composition is largely controlled by the extent of chemical equilibration achieved between liquid metal bodies and a silicate magma ocean during core formation, which can be estimated using chemical diffusion data. In order to estimate the time and length scales of metal-silicate chemical equilibration, we have measured chemical diffusion rates of Si, O and Cr in liquid iron over the P-T range of 1-18 GPa and 1873-2643 K using a multi-anvil apparatus. We have also performed first-principles molecular dynamic simulations of comparable binary liquid compositions, in addition to pure liquid Fe, over a much wider P-T range (1 bar-330 GPa, 2200-5500 K) in order to both validate the simulation results with experimental data at conditions accessible in the laboratory and to extend our dataset to conditions of the Earth's core. Over the entire P-T range studied using both methods, diffusion coefficients are described consistently and well using an exponential function of the homologous temperature relation. Si, Cr and Fe diffusivities of approximately 5 × 10-9 m2 s-1 are constant along the melting curve from ambient to core pressures, while oxygen diffusion is 2-3 times faster. Our results indicate that in order for the composition of the Earth's core to represent chemical equilibrium, impactor cores must have broken up into liquid droplet sizes no larger than a few tens of cm. Structural properties, analyzed using partial radial distribution functions from the molecular dynamics simulations, reveal a pressure-induced structural change in liquid Fe0.96O0.04 at densities of 8 g cm-3, in agreement with previous experimental studies. For densities above 8 g cm-3, the liquid is essentially close packed with a local CsCl-like (B2) packing of Fe around O under conditions of the Earth's core.

Quantum efficiency and dark current evaluation of a backside illuminated CMOS image sensor

NASA Astrophysics Data System (ADS)

Vereecke, Bart; Cavaco, Celso; De Munck, Koen; Haspeslagh, Luc; Minoglou, Kyriaki; Moore, George; Sabuncuoglu, Deniz; Tack, Klaas; Wu, Bob; Osman, Haris

2015-04-01

We report on the development and characterization of monolithic backside illuminated (BSI) imagers at imec. Different surface passivation, anti-reflective coatings (ARCs), and anneal conditions were implemented and their effect on dark current (DC) and quantum efficiency (QE) are analyzed. Two different single layer ARC materials were developed for visible light and near UV applications, respectively. QE above 75% over the entire visible spectrum range from 400 to 700 nm is measured. In the spectral range from 260 to 400 nm wavelength, QE values above 50% over the entire range are achieved. A new technique, high pressure hydrogen anneal at 20 atm, was applied on photodiodes and improvement in DC of 30% for the BSI imager with HfO2 as ARC as well as for the front side imager was observed. The entire BSI process was developed 200 mm wafers and evaluated on test diode structures. The knowhow is then transferred to real imager sensors arrays.

Design of improved ceramic/polymeric composites

NASA Astrophysics Data System (ADS)

Seghi, Steven Monte

This thesis describes an optimized approach for fabrication of boron nitride matrix composites reinforced with carbon fibers. The boron nitride was introduced via liquid infiltration of borazine oligomer to obtain high density (rho ˜ 1.75g/cc) composites and d002 spacings of 3.35A, which afforded excellent hydrolytic stability. The friction and wear properties were explored using an inertial dynamometer for potential replacement of current C/C in aircraft brakes. One set of tested composites provided outstanding wear resistance, incurring nearly zero wear across the entire range tested. In contrast to C/C, the coefficient of friction (COF) was relatively stable with respect to energy level, varying only 0.2 to 0.3. The wear surface morphologies were examined and it was found that low volume BN composites wore by a mechanism similar to C/C. The wear rates were controlled by the formation of a friction film from the wear debris. In the case of BN composites, this film incurred wear via an abrasive and brittle fracture mechanism while C/C exhibited only abrasive wear. As the BN content increased, a film still formed from the debris but large particles of BN emerged that limited direct contact of the surfaces thus effectively eliminating abrasive wear so the underlying film wore via brittle fracture. The removed wear debris was easily reincorporated into the film, with the suspected aid of boron oxide, thus keeping the wear rates low. The last chapter deals with the design, fabrication, and evaluation of a new coupling agent for glass fiber/epoxy matrix composites. This interface consisted of a thin coating of activated carbon (ACI) with high surface area to take advantage of mechanical interlocking. Furthermore, the surface chemistry was modified to provide varying degrees of bonding to the resin. These ACI provided equivalent moduli when compared to similar composites using commercial coupling agents. Hygrothermal aging showed the basic surface chemistry ACI to be extremely resistant to mechanical property degradation. The ACI systems displayed two distinct failure modes, fiber/matrix fracture and fiber debonding, controlled by the interface strength and thus the surface chemistry. These different failure modes led to a damage evolution study via thermoelastic stress analysis.

Planar defects as Ar traps in trioctahedral micas: A mechanism for increased Ar retentivity in phlogopite

NASA Astrophysics Data System (ADS)

Camacho, A.; Lee, J. K. W.; Fitz Gerald, J. D.; Zhao, J.; Abdu, Y. A.; Jenkins, D. M.; Hawthorne, F. C.; Kyser, T. K.; Creaser, R. A.; Armstrong, R.; Heaman, L. W.

2012-08-01

The effects of planar defects and composition on Ar mobility in trioctahedral micas have been investigated in samples from a small marble outcrop (∼500 m2) in the Frontenac Terrane, Grenville Province, Ontario. These micas crystallized during amphibolite-facies metamorphism at ∼1170 Ma and experienced a thermal pulse ∼100 Ma later at shallow crustal levels associated with the emplacement of plutons. 87Rb/86Sr ages of the phlogopites range from ∼950 to ∼1050 Ma, consistent with resetting during the later thermal event. The same phlogopites however, give 40Ar/39Ar ages between ∼950 and 1160 Ma, spanning the age range of the two thermal events. This result is intriguing because these micas have undergone the same thermal history and were not deformed after peak metamorphic conditions. In order to understand this phenomenon, the chemical, crystallographical, and microstructural nature of four mica samples has been characterized in detail using a wide range of analytical techniques. The scanning electron microscope (SEM), electron microprobe (EMP), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data show that the micas are chemically homogeneous (with the exception of Ba) and similar in composition. The Fourier transform infrared spectroscopy and Mossbauer results show that the M sites for three of the micas are dominated by divalent cations and the Fe3+/(Fe2++Fe3+) ratio for all four phlogopites ranges from 0.10 to 0.25. The stable-isotopic data for calcite indicate that this outcrop was not affected by hydrothermal fluids after peak metamorphism. No correlation between chemical composition and 87Rb/86Sr and 40Ar/39Ar age or between crystal size and 40Ar/39Ar age is observed. The only major difference among all of the micas was revealed through transmitted electron microscope (TEM), which shows that the older 1M micas contain significantly more layer stacking defects, associated with crystallization, than the younger micas. We propose that these defect structures, which are enclosed entirely within the mineral grain may serve as Ar traps and effectively increase the Ar retentivity of the mineral. As this phenomenon has not been previously documented in micas, this may have significant implications for the interpretation of 40Ar/39Ar ages of minerals which have similar defect structures.

Study of the structure of 3-D composites based on carbon nanotubes in bovine serum albumin matrix by X-ray microtomography

NASA Astrophysics Data System (ADS)

Ignatov, D.; Zhurbina, N.; Gerasimenko, A.

2017-01-01

3-D composites are widely used in tissue engineering. A comprehensive analysis by X-ray microtomography was conducted to study the structure of the 3-D composites. Comprehensive analysis of the structure of the 3-D composites consisted of scanning, image reconstruction of shadow projections, two-dimensional and three-dimensional visualization of the reconstructed images and quantitative analysis of the samples. Experimental samples of composites were formed by laser vaporization of the aqueous dispersion BSA and single-walled (SWCNTs) and multi-layer (MWCNTs) carbon nanotubes. The samples have a homogeneous structure over the entire volume, the percentage of porosity of 3-D composites based on SWCNTs and MWCNTs - 16.44%, 28.31%, respectively. An average pore diameter of 3-D composites based on SWCNTs and MWCNTs - 45 μm 93 μm. 3-D composites based on carbon nanotubes in bovine serum albumin matrix can be used in tissue engineering of bone and cartilage, providing cell proliferation and blood vessel sprouting.

The difficult mountain: enriched composition in adjective–noun phrases

PubMed Central

Pickering, Martin J.; McElree, Brian

2012-01-01

When readers need to go beyond the straightforward compositional meaning of a sentence (i.e., when enriched composition is required), costly additional processing is the norm. However, this conclusion is based entirely on research that has looked at enriched composition between two phrases or within the verb phrase (e.g., the verb and its complement in … started the book …) where there is a discrepancy between the semantic expectations of the verb and the semantics of the noun. We carried out an eye-tracking experiment investigating enriched composition within a single noun phrase, as in the difficult mountain. As compared with adjective–noun phrases that allow a straightforward compositional interpretation (the difficult exercise), the coerced phrases were more difficult to process. These results indicate that coercion effects can be found in the absence of a typing violation and within a single noun phrase. PMID:21826403

Rapid induction bonding of composites, plastics, and metals

NASA Technical Reports Server (NTRS)

Buckley, John D.; Fox, Robert L.

1991-01-01

The Toroid Bonding Gun is and induction heating device. It is a self contained, portable, low powered induction welding system developed for bonding or joining plastic, ceramic, or metallic parts. Structures can be bonded in a factory or in a the field. This type of equipment allows for applying heat directly to the bond lines and/or to the adhesives without heating the entire structure, supports, and fixtures of a bonding assembly. The induction heating gun originally developed for use in the fabrication of space Gangs of bonders are now used to rapidly join composite sheet and structural components. Other NASA-developed applications of this bonding technique include the joining of thermoplastic composites, thermosetting composites, metals, and combinations of these materials.

Gamma irradiation assisted fungal degradation of the polypropylene/biomass composites

NASA Astrophysics Data System (ADS)

Butnaru, Elena; Darie-Niţă, Raluca Nicoleta; Zaharescu, Traian; Balaeş, Tiberius; Tănase, Cătălin; Hitruc, Gabriela; Doroftei, Florica; Vasile, Cornelia

2016-08-01

White-rot fungus Bjerkandera adusta has been tested for its ability to degrade some biocomposites materials based on polypropylene and biomass (Eucalyptus globulus, pine cones, and Brassica rapa). γ-irradiation was applied to initiate the degradation of relatively inert polypropylene matrix. The degradation process has been studied by scanning electron microscopy, atomic force microscopy, infrared spectroscopy, contact angle measurements, rheological and chemiluminescence tests. These analyses showed that the polypropylene/biomass composites properties are worsen under the action of the selected microorganism. The formation of cracks and scrap particles over the entire matrix surface and the decrease of the complex viscosity values, as well as the dynamic moduli of gamma irradiated PP/biomass composite and exposed to Bjerkandera adusta fungus, indicate fungal efficiency in composite degradation.

DISCO: An object-oriented system for music composition and sound design

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

Kaper, H. G.; Tipei, S.; Wright, J. M.

2000-09-05

This paper describes an object-oriented approach to music composition and sound design. The approach unifies the processes of music making and instrument building by using similar logic, objects, and procedures. The composition modules use an abstract representation of musical data, which can be easily mapped onto different synthesis languages or a traditionally notated score. An abstract base class is used to derive classes on different time scales. Objects can be related to act across time scales, as well as across an entire piece, and relationships between similar objects can replicate traditional music operations or introduce new ones. The DISCO (Digitalmore » Instrument for Sonification and Composition) system is an open-ended work in progress.« less

Compositional and volumetric development of a monogenetic lava flow field: The historical case of Paricutin (Michoacán, Mexico)

NASA Astrophysics Data System (ADS)

Larrea, Patricia; Salinas, Sergio; Widom, Elisabeth; Siebe, Claus; Abbitt, Robbyn J. F.

2017-12-01

Paricutin volcano is the youngest and most studied monogenetic volcano in the Michoacán-Guanajuato volcanic field (Mexico), with an excellent historical record of its nine years (February 1943 to March 1952) of eruptive activity. This eruption offered a unique opportunity to observe the birth of a new volcano and document its entire eruption. Geologists surveyed all of the eruptive phases in progress, providing maps depicting the volcano's sequential growth. We have combined all of those previous results and present a new methodological approach, which utilizes state of the art GIS mapping tools to outline and identify the 23 different eruptive phases as originally defined by Luhr and Simkin (1993). Using these detailed lava flow distribution maps, the volume of each of the flows was estimated with the aid of pre- and post-eruption digital elevation models. Our procedure yielded a total lava flow volume ranging between 1.59 and 1.68 km3 DRE, which is larger than previous estimates based on simpler methods. In addition, compositional data allowed us to estimate magma effusion rates and to determine variations in the relative proportions of the different magma compositions issued during the eruption. These results represent the first comprehensive documentation of the combined chemical, temporal, and volumetric evolution of the Paricutin lava field and provide key constraints for petrological interpretations of the nature of the magmatic plumbing system that fed the eruption.

Limitations of Salivary Osmolality as a Marker of Hydration Status

DTIC Science & Technology

2011-01-01

volunteers were provided with a small, standardized meal (450 kcal; 57% CHO, 30% fat, 13% protein, 450 mg of Na+) and 200 mL of water or apple juice . No...TBW was calculated by dividing TBW by BM loss, with the assumption that corrected BM lost through sweating was entirely water. Body composition was... composition and cortisol in serum and saliva in man. J Dent Res. 1989;68(11):1495–7. 3. Cheuvront SN, Carter R III, Montain SJ, Sawka MN. Daily body mass

A Method for Out-of-autoclave Fabrication of High Fiber Volume Fraction Fiber Reinforced Polymer Composites

DTIC Science & Technology

2012-07-01

Composites 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Larry R. Holmes, Jr., James P. Wolbert, and Jared M...greater than 10 kPa (1.5 psi) pressure change in the vacuum bag. A redundant second vacuum bag was applied over the entire layup to further protect...In order to maintain the increased fvf and decrease the processing time, a second experimental process was conducted using a compacted and pre

Natural organic matter and the event horizon of mass spectrometry.

PubMed

Hertkorn, N; Frommberger, M; Witt, M; Koch, B P; Schmitt-Kopplin, Ph; Perdue, E M

2008-12-01

Soils, sediments, freshwaters, and marine waters contain natural organic matter (NOM), an exceedingly complex mixture of organic compounds that collectively exhibit a nearly continuous range of properties (size-reactivity continuum). NOM is composed mainly of carbon, hydrogen, and oxygen, with minor contributions from heteroatoms such as nitrogen, sulfur, and phosphorus. Suwannee River fulvic acid (SuwFA) is a fraction of NOM that is relatively depleted in heteroatoms. Ultrahigh resolution Fourier transform ion cyclotron (FTICR) mass spectra of SuwFA reveal several thousand molecular formulas, corresponding in turn to several hundred thousand distinct chemical environments of carbon even without accountancy of isomers. The mass difference deltam among adjoining C,H,O-molecules between and within clusters of nominal mass is inversely related to molecular dissimilarity: any decrease of deltam imposes an ever growing mandatory difference in molecular composition. Molecular formulas that are expected for likely biochemical precursor molecules are notably absent from these spectra, indicating that SuwFA is the product of diagenetic reactions that have altered the major components of biomass beyond the point of recognition. The degree of complexity of SuwFA can be brought into sharp focus through comparison with the theoretical limits of chemical complexity, as constrained and quantized by the fundamentals of chemical binding. The theoretical C,H,O-compositional space denotes the isomer-filtered complement of the entire, very vast space of molecular structures composed solely of carbon, hydrogen, and oxygen. The molecular formulas within SuwFA occupy a sizable proportion of the theoretical C,H,O-compositional space. A 100 percent coverage of the theoretically feasible C,H,O-compositional space by SuwFA molecules is attained throughout a sizable range of mass and H/C and O/C elemental ratios. The substantial differences between (and complementarity of) the SuwFA molecular formulas that are observed using six different modes of ionization (APCI, APPI, and ESI in positive and negative modus) imply considerable selectivity of the ionization process and suggest that the observed mass spectra represent simplified projections of still more complex mixtures.

Geochemical and isotopic study of impact melts and spherules from the Lonar impact crater, India, indicate melting of the Precambrian basement beneath the 'target' Deccan basalts

NASA Astrophysics Data System (ADS)

Chakrabarti, R.; Goderis, S.; Banerjee, A.; Gupta, R. D.; Claeys, P.; Vanhaecke, F. F.

2016-12-01

The 1.88 km diameter Lonar impact Crater, with age estimates ranging from 52 -570 ka, is located in the Buldana district of Maharashtra, India. It is an almost circular depression hosted entirely in the 65Ma old basalt flows of the Deccan Traps and is the best-known terrestrial analogue for impact craters in the Inner Solar System. Isotopic studies indicate that the basalts around Lonar correlate with the Poladpur suite, one of the mid-section volcano-stratigraphic units of the Deccan traps. Recently collected samples of the host basalt and impact melts, were analyzed for major and trace element concentrations using ICPMS, as well as for Nd and Sr isotope ratios using TIMS. Relatively more radiogenic Sr and less radiogenic Nd isotopic composition of the melt rocks compared to earlier measurements of similar rocks from Lonar are consistent with melting of the Precambrian basement beneath the Deccan basalt. Spherules ranging in size from 100 mm to 1 mm, were hand-picked under a binocular microscope from unconsolidated soil samples, collected from the south-eastern rim of the crater. Thirty-five spherule samples, screened for surface alteration using SEM were analyzed for major and trace element concentrations including PGEs using LA-ICPMS. The spherules were further classified into two groups using the Chemical Index of Alteration(CIA). Iridium and Cr concentrations of the spherules are consistent with mixing of a chondritic impactor (with 2-8% contribution) with the target rock(s). On a Nb (fluid immobile) -normalized binary plot of Th versus Cr, the composition of the spherules can be explained by mixing between the host basalt and a chondritic impactor with a definite, but minor contribution of the basement beneath Lonar, the composition of which is approximated using the average composition of the upper continental crust (UCC). Variability in the light-REE fractionation of the spherules (La/Sm(N)) can also be explained by a similar three component mixing. Overall, our geochemical data for both the melt rocks and spherules suggest mixing between the chondritic impactor, the Deccan host basalt and the basement rocks at Lonar.

Dynamic crystallization study of barred olivine chondrules

NASA Technical Reports Server (NTRS)

Lofgren, Gary; Lanier, A. B.

1990-01-01

The 'classic' barred olivine (BO) texture was defined by Donaldson (1976) as a single-plate dendrite which shares the entire chondrule with the remaining glass or subsequent crystallization products. This paper describes experiments in which BO textures were produced experimentally from two starting compositions: one modeled after the average BO chondrule composition in L-chondrites determined by Weisberg (1987), and the other after an olivine-rich composition (CH-1) studied by Lofgren (1989). It is shown that most of the textural features observed in natural BO chondrules are replicated in the experimentally produced chondrules. Several new constraints on models for the chondrule-forming process are proposed.

Small-scale density variations in the lunar crust revealed by GRAIL

NASA Astrophysics Data System (ADS)

Jansen, J. C.; Andrews-Hanna, J. C.; Li, Y.; Lucey, P. G.; Taylor, G. J.; Goossens, S.; Lemoine, F. G.; Mazarico, E.; Head, J. W.; Milbury, C.; Kiefer, W. S.; Soderblom, J. M.; Zuber, M. T.

2017-07-01

Data from the Gravity Recovery and Interior Laboratory (GRAIL) mission have revealed that ∼98% of the power of the gravity signal of the Moon at high spherical harmonic degrees correlates with the topography. The remaining 2% of the signal, which cannot be explained by topography, contains information about density variations within the crust. These high-degree Bouguer gravity anomalies are likely caused by small-scale (10‧s of km) shallow density variations. Here we use gravity inversions to model the small-scale three-dimensional variations in the density of the lunar crust. Inversion results from three non-descript areas yield shallow density variations in the range of 100-200 kg/m3. Three end-member scenarios of variations in porosity, intrusions into the crust, and variations in bulk crustal composition were tested as possible sources of the density variations. We find that the density anomalies can be caused entirely by changes in porosity. Characteristics of density anomalies in the South Pole-Aitken basin also support porosity as a primary source of these variations. Mafic intrusions into the crust could explain many, but not all of the anomalies. Additionally, variations in crustal composition revealed by spectral data could only explain a small fraction of the density anomalies. Nevertheless, all three sources of density variations likely contribute. Collectively, results from this study of GRAIL gravity data, combined with other studies of remote sensing data and lunar samples, show that the lunar crust exhibits variations in density by ± 10% over scales ranging from centimeters to 100‧s of kilometers.

Small-Scale Density Variations in the Lunar Crust Revealed by GRAIL

NASA Technical Reports Server (NTRS)

Jansen, J. C.; Andrews-Hanna, J. C.; Li, Y.; Lucey, P. G.; Taylor, G. J.; Goossens, S.; Lemoine, F. G.; Mazarico, E.; Head, J. W., III; Milbury, C.;

Ab initio investigation of Ti2Al(C,N) solid solutions

NASA Astrophysics Data System (ADS)

Arróyave, Raymundo; Radovic, Miladin

2011-10-01

Mn+1AXn phases (M: early transition metal, A: IIIA- or IVA-group element, X: carbon or nitrogen) are layered ternary compounds that possess both metal- and ceramic-like properties with numerous potential applications in bulk and thin film forms, particularly under high-temperature conditions. In this work, we use the cluster expansion formalism to investigate the energetics of C-N interactions across the entire Ti2AlC-Ti2AlN composition range. It is shown that there is a definite tendency for ordering in the C,N sublattice. However, the molar volume and bulk modulus of the ordered structures found along the Ti2AlC-Ti2AlN composition range show small deviations from the (linear) rule of mixing, indicating that despite the ordering tendencies, the C-N interactions are not strong and the solution becomes disordered at relatively low temperatures. Random solid solutions of Ti2AlC1-xNx are simulated using special quasirandom structures (SQS) with x=0.25, 0.50, and 0.75. The thermodynamic properties of these structures are compared to those of the structures found to belong to the ground state through the cluster expansion approach. It is found that the structural properties of these approximations to random alloys do not deviate significantly from Vegard's law. The trend in the structural parameters of these SQS are found to agree well with available experimental data and the predictions of the bulk modulus suggest a very weak alloying effect—with respect to Vegard's law—on the elastic properties of Ti2AlC1-xNx.

Volatile element content of the heterogeneous upper mantle

NASA Astrophysics Data System (ADS)

Shimizu, K.; Saal, A. E.; Hauri, E. H.; Forsyth, D. W.; Kamenetsky, V. S.; Niu, Y.

2014-12-01

The physical properties of the asthenosphere (e.g., seismic velocity, viscosity, electrical conductivity) have been attributed to either mineral properties at relevant temperature, pressure, and water content or to the presence of a low melt fraction. We resort to the geochemical studies of MORB to unravel the composition of the asthenosphere. It is important to determine to what extent the geochemical variations in axial MORB do represent a homogeneous mantle composition and variations in the physical conditions of magma generation and transport; or alternatively, they represent mixing of melts from a heterogeneous upper mantle. Lavas from intra-transform faults and off-axis seamounts share a common mantle source with axial MORB, but experience less differentiation and homogenization. Therefore they provide better estimates for the end-member volatile budget of the heterogeneous upper mantle. We present major, trace, and volatile element data (H2O, CO2, Cl, F, S) as well as Sr, Nd, and Pb isotopic compositions [1, 2] of basaltic glasses (MgO > 6.0 wt%) from the NEPR seamounts, Quebrada-Discovery-Gofar transform fault system, and Macquarie Island. The samples range from incompatible trace element (ITE) depleted (DMORB: Th/La<0.035) to enriched (EMORB: Th/La>0.07) spanning the entire range of EPR MORB. The isotopic composition of the samples correlates with the degree of trace element enrichment indicating long-lived mantle heterogeneity. Once shallow-level processes (degassing, crystallization, and crustal assimilation) have been considered, we conducted a two-component (DMORB- and EMORB-) mantle melting-mixing model. Our model reproduces the major, trace and volatile element contents and isotopic composition of our samples and suggests that (1) 90% of the upper mantle is highly depleted in ITE (DMORB source) with only 10% of an enriched component (EMORB source), (2) the EMORB source is peridotitic rather than pyroxenitic, and (3) NMORB do not represent an actual mantle source, but the product of magma mixing between D- and E-MORB. Finally we use the volatile to trace element ratios of our samples to estimate the volatile element budget of the end-member components of the upper mantle. [1] Niu, Y. et al. (2002) EPSL, 199, 327-345. [2] Kamenetsky, V. S. et al. (2000) J. Petrology, 41, 411-430.

Calculating Correlated Color Temperatures Across the Entire Gamut of Daylight and Skylight Chromaticities

DTIC Science & Technology

1999-09-20

c o i b f t c c c c w n c s p t s Calculating correlated color temperatures across the entire gamut of daylight and skylight chromaticities Javier...temperature ~CCT!, yet existing equations for calculating CCT from chromaticity coordinates span only part of this range. To improve both the gamut and accuracy...00-1999 to 00-00-1999 4. TITLE AND SUBTITLE Calculating correlated color temperatures across the entire gamut of daylight and skylight

Paleoproterozoic Collisional Structures in the Hudson Bay Lithosphere Constrained by Multi-Observable Probabilistic Inversion

NASA Astrophysics Data System (ADS)

Darbyshire, F. A.; Afonso, J. C.; Porritt, R. W.

2015-12-01

The Paleozoic Hudson Bay intracratonic basin conceals a Paleoproterozoic Himalayan-scale continental collision, the Trans-Hudson Orogen (THO), which marks an important milestone in the assembly of the Canadian Shield. The geometry of the THO is complex due to the double-indentor geometry of the collision between the Archean Superior and Western Churchill cratons. Seismic observations at regional scale show a thick, seismically fast lithospheric keel beneath the entire region; an intriguing feature of recent models is a 'curtain' of slightly lower wavespeeds trending NE-SW beneath the Bay, which may represent the remnants of more juvenile material trapped between the two Archean continental cores. The seismic models alone, however, cannot constrain the nature of this anomaly. We investigate the thermal and compositional structure of the Hudson Bay lithosphere using a multi-observable probabilistic inversion technique. This joint inversion uses Rayleigh wave phase velocity data from teleseismic earthquakes and ambient noise, geoid anomalies, surface elevation and heat flow to construct a pseudo-3D model of the crust and upper mantle. Initially a wide range of possible mantle compositions is permitted, and tests are carried out to ascertain whether the lithosphere is stratified with depth. Across the entire Hudson Bay region, low temperatures and a high degree of chemical depletion characterise the mantle lithosphere. Temperature anomalies within the lithosphere are modest, as may be expected from a tectonically-stable region. The base of the thermal lithosphere lies at depths of >250 km, reaching to ~300 km depth in the centre of the Bay. Lithospheric stratification, with a more-depleted upper layer, is best able to explain the geophysical data sets and surface observables. Some regions, where intermediate-period phase velocities are high, require stronger mid-lithospheric depletion. In addition, a narrow region of less-depleted material extends NE-SW across the Bay, likely associated with the trace of the THO collision and the entrapment of juvenile material between the highly-depleted Archean cores.

Mantle source beneath Turrialba volcano (Costa Rica): a geochemical investigation

NASA Astrophysics Data System (ADS)

Di Piazza, A.; Rizzo, A. L.; Barberi, F.; Carapezza, M. L.; Sortino, F.; De Astis, G.; Romano, C.

2014-12-01

In this study we analysed rocks and noble gas composition of fluid inclusions (FIs) hosted in olivine crystals contained in a suite of eruptive products of the last 10ka of activity of Turrialba volcano, Cordillera Central, Costa Rica. The suite of analyzed rocks display a calc-alkaline affinity, ranging in composition from basaltic-andesite to dacite. Trace element patterns indicate a typical behavior of subduction-related magmas and also the clear contribution of an OIB-like signature at source. A group of andesites displays also adakite-like geochemical features, as evidenced by their constant depletion in HFSE elements. Sr isotope (0.703593 - 0.703678) and Nd isotope ratios (0.512960 - 0.512968) suggest that Turrialba magmas belong to one of the less contaminated mantle source of Central America. The 3He/4He ratio of fluid inclusions from the most mafic eruptive products (basaltic-andesites) varies from 7.86 to 8.07 Ra, while that from andesite lavas varies from 7.03 to 7.18 Ra. In order to understand the mantle source feeding Turrialba volcano, we performed a geochemical investigation on fumarolic gases of summit craters. The He isotope composition of dry gases of Turrialba volcano is characterized by extremely high R/Ra values (7.08-7.96 Ra). The highest 3He/4He ratios were measured at both West and Central Craters (7.93-7.96 Ra and 7.78-7.88 Ra, respectively), and are the highest values of the entire Central America. Despite the observed variability, the 3He/4He ratio of fumarolic gases and FIs from Turrialba volcano is well in the range of arc related volcanism (~7-8 Ra; Hilton et al., 2002), and represents the signature of a mantle wedge in which the contamination by crustal fluids is small to negligible. In addition the occurrence of recent adakite-like magmatism suggests the presence of an abnormal heating of the subducting lithosphere under Turrialba volcano, allowing even old or cold oceanic crust to melt.

The role of magma mixing in the petrogenesis of mafic alkaline lavas, Rockeskyllerkopf Volcanic Complex, West Eifel, Germany

NASA Astrophysics Data System (ADS)

Shaw, Cliff S. J.; Woodland, Alan B.

2012-03-01

The quaternary Rockeskyllerkopf Volcanic Complex (RVC) comprises three spatially and temporally distinct volcanic centers that can also be distinguished on the basis of their geochemical signatures. All the volcanic products in the complex are olivine basanites whose major and trace element compositions span almost the entire range defined for the West Eifel field as a whole. The RVC lavas have lower Al2O3, Na2O and Y contents and higher TiO2, CaO, K2O, Sc, V, Co, Rb, and Ba than the Tertiary lavas in nearby Hocheifel volcanic field. Within the complex, the oldest South East Lammersdorf Center (SEL) comprises primitive lavas with an average MgO content of ˜11 wt.% and LaN/YbN of 29 ± 2. The second center, Mäuseberg, has similar MgO to SEL but is distinct in its much higher LaN/YbN of 42 ± 2. The Rockeskyllerkopf Center, which was erupted after a break in activity, comprises lavas similar in composition to the SEL Center but with distinctly higher Al2O3 and lower MgO contents. Given the lack of evidence for significant fractionation or assimilation in the RVC lavas, we attribute the compositional variations within and between the centers of the RVC to be due to variations in the composition of the source region in combination with magma mixing. Our preferred model involves 1-5% partial melting of LREE-enriched mantle in the garnet stability field, likely within the thermal boundary layer at the base of the lithospheric mantle. These melts mixed to variable degrees with 2-4% partial melts of phlogopite-spinel peridotite formed at higher levels in the modally metasomatised lithospheric mantle.

Genetic link between EMI and EMII: An adakite connection

NASA Astrophysics Data System (ADS)

Shimoda, Gen

2009-10-01

Geochemical modeling of the origin of enriched mantle I (EMI) and enriched mantle II (EMII) is conducted from the perspective of adakite production. For the model, the average composition of adakites is re-estimated from published data for eighteen trace elements. Although the concentrations determined for highly incompatible elements are very high (about 100 times of primitive mantle), these high concentrations can be explained by melting of oceanic crust without sediment contribution. The compiled data further suggest that the mantle-slab melt reaction would play a major role in the production of basic adakites. In addition, crystal fractionation in the magma chamber should produce additional chemical variations in adakites, in particular for acidic adakites. To examine the effect of chemical variations on the isotopic composition of recycled adakites, broad correlations between trace elements and SiO 2 concentrations, and the MELTS program are employed. The results suggest that recycling of a basic adakite (SiO 2 = 55%) can account for EMI isotopic signatures with storage times of about 2.0 Gyr. The isotopic compositions of less-basic adakites and their evolved magmas shift towards EMII values with increasing SiO 2 concentrations. In particular, evolved acidic adakite can yield EMII isotopic signatures. These lines of evidence suggest that the recycling of adakites at various stages of evolution can conceivably produce the entire isotopic range between EMI and EMII reservoirs. Consequently, adakite recycling via sediment subduction or subduction erosion can account for the origins of EMI and EMII reservoirs. In this context, residual garnet under high pressure and plagioclase fractionation at low pressure might play an essential role in producing the chemical variations among adakites that ultimately govern the isotopic compositions of these geochemical reservoirs.

Relative Composition of Fibrous Connective and Fatty/Glandular Tissue in Connective Tissue Grafts Depends on the Harvesting Technique but not the Donor Site of the Hard Palate.

PubMed

Bertl, Kristina; Pifl, Markus; Hirtler, Lena; Rendl, Barbara; Nürnberger, Sylvia; Stavropoulos, Andreas; Ulm, Christian

2015-12-01

Whether the composition of palatal connective tissue grafts (CTGs) varies depending on donor site or harvesting technique in terms of relative amounts of fibrous connective tissue (CT) and fatty/glandular tissue (FGT) is currently unknown and is histologically assessed in the present study. In 10 fresh human cadavers, tissue samples were harvested in the anterior and posterior palate and in areas close to (marginal) and distant from (apical) the mucosal margin. Mucosal thickness, lamina propria thickness (defined as the extent of subepithelial portion of the biopsy containing ≤25% or ≤50% FGT), and proportions of CT and FGT were semi-automatically estimated for the entire mucosa and for CTGs virtually harvested by split-flap (SF) preparation minimum 1 mm deep or after deepithelialization (DE). Palatal mucosal thickness, ranging from 2.35 to 6.89 mm, and histologic composition showed high interindividual variability. Lamina propria thickness (P >0.21) and proportions of CT (P = 0.48) and FGT (P = 0.15) did not differ significantly among the donor sites (anterior, posterior, marginal, apical). However, thicker palatal tissue was associated with higher FGT content (P <0.01) and thinner lamina propria (P ≤0.03). Independent of the donor site, DE-harvested CTG contained a significantly higher proportion of CT and a lower proportion of FGT than an SF-harvested CTG (P <0.04). Despite high interindividual variability in terms of relative tissue composition in the hard palate, DE-harvested CTG contains much larger amounts of CT and much lower amounts of FGT than SF-harvested CTG, irrespective of the harvesting site.

Relating hydrogen-bonding interactions with the phase behavior of naproxen/PVP K 25 solid dispersions: evaluation of solution-cast and quench-cooled films.

PubMed

Paudel, Amrit; Nies, Erik; Van den Mooter, Guy

2012-11-05

In this work, we investigated the relationship between various intermolecular hydrogen-bonding (H-bonding) interactions and the miscibility of the model hydrophobic drug naproxen with the hydrophilic polymer polyvinylpyrrolidone (PVP) across an entire composition range of solid dispersions prepared by quasi-equilibrium film casting and nonequilibrium melt quench cooling. The binary phase behavior in solid dispersions exhibited substantial processing method dependence. The solid state solubility of crystalline naproxen in PVP to form amorphous solid dispersions was 35% and 70% w/w naproxen in solution-cast films and quench-cooled films, respectively. However, the presence of a single mixed phase glass transition indicated the amorphous miscibility to be 20% w/w naproxen for the films, beyond which amorphous-amorphous and/or crystalline phase separations were apparent. This was further supported by the solution state interactions data such as PVP globular size distribution and solution infrared spectral profiles. The borderline melt composition showed cooling rate dependence of amorphization. The glass transition and melting point depression profiles of the system were treated with the analytical expressions based on Flory-Huggins mixing theory to interpolate the equilibrium solid solubility. FTIR analysis and subsequent spectral deconvolution revealed composition and miscibility dependent variations in the strength of drug-polymer intermolecular H-bonding. Two types of H-bonded populations were evidenced from 25% w/w and 35% w/w naproxen in solution-cast films and quench-cooled films, respectively, with the higher fraction of strongly H-bonded population in the drug rich domains of phase separated amorphous film compositions and highly drug loaded amorphous quench-cooled dispersions.

Thermodynamics, Solubility, and Diffusivity of Oxygen in Titanium and Ti-Al Alloys

NASA Technical Reports Server (NTRS)

Mehrotra, Gopal M.

1992-01-01

Titanium aluminides and titanium aluminide-based composites are attractive candidate materials for high-temperature structural applications. As these materials may be exposed to oxidizing environments durine their use at elevated temperatures, it is essential that they possess a good oxidation resistance. Previous studies have shown that the oxidation resistance of Al-rich alloys in the Ti-Al system is superior to that of the Ti-rich alloys. The scales formed on the surface of the Al-rich and Ti-rich alloys have been reported to be predominantly Al2O3 and TiO2, respectively. Since the relative stabilities of the oxides of Al and Ti at various temperatures and oxygen pressures can be assessed from their thermodynamic data, it is possible, With the help of thermodynamic calculations, to determine the compositions of the alloys which would form scales of Al2O3, TiO(x) or a ternary oxide such as TiAl2O5 during oxidation at a given temperature. The thermodynamic calculations require reliable activity data for the Ti-Al system. These data have not been determined for the entire composition and temperature range of interest. Using the data available in the literature, recently performed thermodynamic calculations and concluded that the stable oxide changed from TiO to Al2O3 in the existence region of the tial phase. In the case of titanium aluminide-based composites, another major concern is the mutual chemical compatibility of the matrix material with the reinforcement phase. Fibers of SiC, TiB2 and Al2O3 are currently being investigated for reinforcement of titanium aluminide matrices.

Some General Laws of Chemical Elements Composition Dynamics in the Hydrosphere

NASA Astrophysics Data System (ADS)

Korzh, V.

2012-12-01

The biophysical oceanic composition is a result of substance migration and transformation on river-sea and ocean- atmosphere boundaries. Chemical composition of oceanic water is a fundamental multi-dimensional constant for our planet. Detailed studies revealed three types of chemical element distribution in the ocean: 1) Conservative: concentration normalized to salinity is constant in space and time; 2) Nutrient-type: element concentration in the surface waters decreases due to the biosphere consumption; and 3) Litho-generative: complex character of distribution of elements, which enter the ocean with the river runoff and interred almost entirely in sediments (Fig. 1). The correlation between the chemical compositions of the river and oceanic water is high (r = 0.94). We conclude that biogeochemical features of each element are determined by the relationship between its average concentration in the ocean and the intensity of its migration through hydrosphere boundary zones. In Fig.1 we show intensities of global migration and average concentrations in the ocean in the coordinates lgC - lg τ, where C is an average element concentration and τ is its residual time in the ocean. Fig. 1 shows a relationship between three main geochemical parameters of the dissolved forms of chemical elements in the hydrosphere: 1) average concentration in the ocean, 2) average concentration in the river runoff and 3) the type of distribution in oceanic water. Using knowledge of two of these parameters, it allows gaining theoretical knowledge of the third. The System covers all chemical elements for the entire range of observed concentrations. It even allows to predict the values of the annual river transport of dissolved Be, C, N, Ge, Tl, Re, to refine such estimates for P, V, Zn, Br, I, and to determine the character of distribution in the ocean for Au and U. Furthermore, the System allowed to estimate natural (unaffected by anthropogenic influence) mean concentrations of elements in the river runoff and use them as ecological reference data. Finally, due to the long response time of the ocean, the mean concentrations of elements and patterns of their distribution in the ocean can be used to determine pre-technogenic concentrations of elements in the river runoff. An example of such studies for the Northern Eurasia Arctic Rivers will be presented at the conference. References Korzh 1974: J. de Recher. Atmos, 8, 653-660. Korzh 2008: J. Ecol., 15, 13-21. Korzh 2012: Water: Chem. & Ecol., No. 1, 56-62; Fig.1. The System of chemical elements distribution in the hydrosphere. Types of distribution in the ocean: 1) conservative; 2) nutrient-type; 3) litho-generative.

Voltage controlled current source

DOEpatents

Casne, Gregory M.

1992-01-01

A seven decade, voltage controlled current source is described for use in testing intermediate range nuclear instruments that covers the entire test current range of from 10 picoamperes to 100 microamperes. High accuracy is obtained throughout the entire seven decades of output current with circuitry that includes a coordinated switching scheme responsive to the input signal from a hybrid computer to control the input voltage to an antilog amplifier, and to selectively connect a resistance to the antilog amplifier output to provide a continuous output current source as a function of a preset range of input voltage. An operator controlled switch provides current adjustment for operation in either a real-time simulation test mode or a time response test mode.

An overview of paleogene molluscan biostratigraphy and paleoecology of the Gulf of Alaska region

USGS Publications Warehouse

Marincovich, L.; McCoy, S.

1984-01-01

Paleogene marine strata in the Gulf of Alaska region occur in three geographic areas and may be characterized by their molluscan faunal composition and paleoecology: a western area consisting of the Alaska Peninsula, Kodiak Island, and adjacent islands; a central area encompassing Prince William Sound; and an eastern area extending from the mouth of the Copper River to Icy Point in the Lituya district. Strata in the western area include the Ghost Rocks, Narrow Cape (in part), Sitkalidak, Stepovak, Belkofski, and Tolstoi Formations; in the central area Paleogene strata are assigned entirely to the Orca Group; Paleogene strata in the eastern area include the Kulthieth and Poul Creek Formations and several coeval units. Environments ranging from marginal marine to bathyal and from subtropical to cool-temperate are inferred for the various molluscan faunas. Sediments range from interbedded coal and marine sands to deep-water turbidites. The known Paleogene molluscan faunas of these three southern Alaskan areas permit recognition of biostratigraphic schemes within each area, preliminary correlations between faunas of the three areas, and more general correlations with faunas of the Pacific Northwest, the Far Eastern U.S.S.R., and northern Japan. ?? 1984.

Pairing in half-filled Landau level

NASA Astrophysics Data System (ADS)

Wang, Zhiqiang; Mandal, Ipsita; Chung, Suk Bum; Chakravarty, Sudip

2015-03-01

Pairing of composite fermions in half-filled Landau level state is reexamined by solving the BCS gap equation with full frequency dependent current-current interactions. Our results show that there can be a continuous transition from the Halperin-Lee-Read state to a chiral odd angular momentum Cooper pair state for short-range contact interaction. This is at odds with the previously established conclusion of first order pairing transition, in which the low frequency effective interaction was assumed for the entire frequency range. We find that even if the low frequency effective interaction is repulsive, it is compensated by the high frequency regime, which is attractive. We construct the phase diagrams and show that l = 1 angular momentum channel is quite different from higher angular momentum channel l >= 3 . Remarkably, the full frequency dependent analysis applied to the bilayer Hall system with a total filling fraction ν =1/2 +1/2 is quantitatively changed from the previously established results but not qualitatively. This work was supported by US NSF under the Grant DMR-1004520, the funds from the David S. Saxon Presidential Chair at UCLA(37952), and by the Institute for Basic Science in Korea through the Young Scientist grant (5199-2014003).

Material quality development during the automated tow placement process

NASA Astrophysics Data System (ADS)

Tierney, John Joseph

Automated tow placement (ATP) of thermoplastic composites builds on the existing industrial base for equipment, robotics and kinematic placement of material with the aim of further cost reduction by eliminating the autoclave entirely. During ATP processing, thermoplastic composite tows are deposited on a preconsolidated substrate at rates ranging from 10--100mm/s and consolidated using the localized application of heat and pressure by a tow placement head mounted on a robot. The process is highly non-isothermal subjecting the material to multiple heating and cooling rates approaching 1000°C/sec. The requirement for the ATP process is to achieve the same quality in seconds (low void content, full translation of mechanical properties and degree of bonding and minimal warpage) as the autoclave process achieves in hours. The scientific challenge was to first understand and then model the relationships between processing, material response, microstructure and quality. The important phenomena affecting quality investigated in this study include a steady state heat transfer simulation, consolidation and deconsolidation (void dynamics), intimate contact and polymer interdiffusion (degree of bonding/mechanical properties) and residual stress and warpage (crystallization and viscoelastic response). A fundamental understanding of the role of materials related to these mechanisms and their relationship to final quality is developed and applied towards a method of process control and optimization.

Centrifugal partition chromatography a first dimension for biomass fast pyrolysis oil analysis.

PubMed

Le Masle, Agnès; Santin, Sandra; Marlot, Léa; Chahen, Ludovic; Charon, Nadège

2018-10-31

Biomass fast pyrolysis oils contain molecules having a large variety of chemical functions and a wide range of molecular weights (from several tens to several thousand grams per mole). The good knowledge of their complex composition is essential for optimizing the conversion of bio-oils to biofuels, thereby requiring powerful separation techniques. In this work, we investigate the interest of centrifugal partition chromatography (CPC) as a first dimension for the analysis of a bio-oil. A CPC method is proposed to separate oxygen containing compounds according to their partition coefficients in the solvent system. This approach is a powerful and easy-to-use technique that enables fractionation of a bio-oil at a semi-preparative scale, without any sample loss related to adsorption on the stationary phase. Collected fractions are then injected in liquid chromatography as a second dimension of separation. Contour plot representations of the CPC × LC separation are established to discuss the potential of this approach. These representations can be used as a veritable fingerprint in the comparison of different samples or samples at different steps of a conversion process but also as a powerful tool to identify new compounds and describe the entire composition of the bio-oil. Copyright © 2018 Elsevier B.V. All rights reserved.

Music: Creativity and Structure Transitions

NASA Astrophysics Data System (ADS)

Pietrocini, Emanuela

Music, compared to other complex forms of representation, is fundamentally characterized by constant evolution and a dynamic succession of structure reference models. This is without taking into account historical perspective, the analysis of forms and styles, or questions of a semantic nature; the observation rather refers to the phenomenology of the music system. The more abstract a compositional model, the greater the number and frequency of variables that are not assimilated to the reference structure; this "interference" which happens more often than not in an apparently casual manner, modifies the creative process to varying but always substantial degrees: locally, it produces a disturbance in perceptive, formal and structural parameters, resulting more often than not in a synaesthetic experience; globally, on the other hand, it defines the terms of a transition to a new state, in which the relations between elements and components modify the behavior of the entire system from which they originated. It is possible to find examples of this phenomenon in the whole range of musical production, in particular in improvisations, in the use of the Basso Continuo, and in some contrapuntal works of the baroque period, music whose temporal dimension can depart from the limits of mensurability and symmetry to define an open compositional environment in continuous evolution.

Thermodynamics of Mixing Primary Alkanolamines with Water.

PubMed

Idrissi, Abdenacer; Jedlovszky, Pal

2018-05-17

The volume, energy, entropy, and Helmholtz free energy of mixing of the seven simplest primary alkanolamine molecules, i.e., MEA, MIPA, 2A1P, ABU, AMP, AMP2, and 1A2B with water is investigated by extensive computer simulations and thermodynamic integration. To check the force field dependence of the results, all calculations are repeated with two commonly used water models, namely SPC/E and TIP4P. The obtained results show that the thermodynamics of mixing of alkanolamines and water is largely independent from the type of the alkanolamine molecule. The Helmholtz free energy of mixing is found to be negative for all alkanolamines at every composition, in accordance with the experimentally known full miscibility of these molecules and water. This free energy decrease occurring upon mixing is found to be clearly of energetic origin, as the energy of mixing always turns out to be negative in the entire composition range, while the entropy of mixing is also negative up to high alkanolamine mole fractions. The obtained results suggest that alkanolamines form, on average, stronger hydrogen bonds with water than what is formed by two water molecules, and they induce some ordering of the hydrating water molecules both through the hydrophobic hydration of their side chains and through the strong hydrogen bonding.

Spinel-olivine-pryoxene equilibrium iron isotopic fractionation and applications to natural peridotites

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

Roskosz, Mathieu; Sio, Corliss K. I.; Dauphas, Nicolas

2015-11-15

Eight spinel-group minerals were synthesized by a flux-growth method producing spinels with varying composition and Fe3+/Fe-tot ratios. The mean force constants of iron bonds in these minerals were determined by synchrotron nuclear resonant inelastic X-ray scattering (NRIXS) in order to determine the reduced isotopic partition function ratios (beta-factors) of these spinels. The mean force constants are strongly dependent on the Fe3+/Fe-tot of the spinel but are independent, or weakly dependent on other structural and compositional parameters. From our spectroscopic data, it is found that a single redox-dependent calibration line accounts for the effects of Fe3+/Fe-tot on the beta-factors of spinels.more » This calibration successfully describes the equilibrium Fe isotopes fractionation factors between spinels and silicates (olivine and pyroxenes). Our predictions are in excellent agreement with independent determinations for the equilibrium Fe isotopic fractionations for the magnetite- fayalite and the magnetite-hedenbergite couples. Our calibration applies to the entire range of Fe3+/Fe-tot ratios found in natural spinels and provides a basis for interpreting iron isotopic variations documented in mantle peridotites. Except for a few exceptions, most of the samples measured so far are in isotopic disequilibrium, reflecting metasomatism and partial melting processes.« less

Thermodynamics of mixing water with dimethyl sulfoxide, as seen from computer simulations.

PubMed

Idrissi, Abdenacer; Marekha, Bogdan; Barj, Mohamed; Jedlovszky, Pál

2014-07-24

The Helmholtz free energy, energy, and entropy of mixing of eight different models of dimethyl sulfoxide (DMSO) with four widely used water models are calculated at 298 K over the entire composition range by means of thermodynamic integration along a suitably chosen thermodynamic path, and compared with experimental data. All 32 model combinations considered are able to reproduce the experimental values rather well, within RT (free energy and energy) and R (entropy) at any composition, and quite often the deviation from the experimental data is even smaller, being in the order of the uncertainty of the calculated free energy or energy, and entropy values of 0.1 kJ/mol and 0.1 J/(mol K), respectively. On the other hand, none of the model combinations considered can accurately reproduce all three experimental functions simultaneously. Furthermore, the fact that the entropy of mixing changes sign with increasing DMSO mole fraction is only reproduced by a handful of model pairs. Model combinations that (i) give the best reproduction of the experimental free energy, while still reasonably well reproducing the experimental energy and entropy of mixing, and (ii) that give the best reproduction of the experimental energy and entropy, while still reasonably well reproducing the experimental free energy of mixing, are identified.

Thermal conductivity of molten salt mixtures: Theoretical model supported by equilibrium molecular dynamics simulations.

PubMed

Gheribi, Aïmen E; Chartrand, Patrice

2016-02-28

A theoretical model for the description of thermal conductivity of molten salt mixtures as a function of composition and temperature is presented. The model is derived by considering the classical kinetic theory and requires, for its parametrization, only information on thermal conductivity of pure compounds. In this sense, the model is predictive. For most molten salt mixtures, no experimental data on thermal conductivity are available in the literature. This is a hindrance for many industrial applications (in particular for thermal energy storage technologies) as well as an obvious barrier for the validation of the theoretical model. To alleviate this lack of data, a series of equilibrium molecular dynamics (EMD) simulations has been performed on several molten chloride systems in order to determine their thermal conductivity in the entire range of composition at two different temperatures: 1200 K and 1300 K. The EMD simulations are first principles type, as the potentials used to describe the interactions have been parametrized on the basis of first principle electronic structure calculations. In addition to the molten chlorides system, the model predictions are also compared to a recent similar EMD study on molten fluorides and with the few reliable experimental data available in the literature. The accuracy of the proposed model is within the reported numerical and/or experimental errors.

Development of Electrostatically Clean Solar Array Panels

NASA Technical Reports Server (NTRS)

Stern, Theodore G.

2000-01-01

Certain missions require Electrostatically Clean Solar Array (ECSA) panels to establish a favorable environment for the operation of sensitive scientific instruments. The objective of this program was to demonstrate the feasibility of an ECSA panel that minimizes panel surface potential below 100mV in LEO and GEO charged particle environments, prevents exposure of solar cell voltage and panel insulating surfaces to the ambient environment, and provides an equipotential, grounded structure surrounding the entire panel. An ECSA panel design was developed that uses a Front Side Aperture-Shield (FSA) that covers all inter-cell areas with a single graphite composite laminate, composite edge clips for connecting the FSA to the panel substrate, and built-in tabs that interconnect the FSA to conductive coated coverglasses using a conductive adhesive. Analysis indicated the ability of the design to meet the ECSA requirements. Qualification coupons and a 0.5m x 0.5m prototype panel were fabricated and tested for photovoltaic performance and electrical grounding before and after exposure to acoustic and thermal cycling environments. The results show the feasibility of achieving electrostatic cleanliness with a small penalty in mass, photovoltaic performance and cost, with a design is structurally robust and compatible with a wide range of current solar panel technologies.

A proposal to conduct a Caribbean plate project involving the application of space technology to the study of Caribbean geology

NASA Technical Reports Server (NTRS)

Wadge, G. (Editor)

1981-01-01

The Caribbean plate project is designed to improve current understanding of geological resources and geological hazards within the Caribbean region. Models of mineral occurrence and genesis (including energy resources) on a regional scale, which contribute to nonrenewable resource investigations. Models of lithospheric stress and strain on a regional scale, which contribute to forecasting geological hazards such as earthquakes and major volcanic eruptions are developed. Geological information is synthesize, and research tools provided by space technology the study of the Earth's crust are used. The project was organized in a thematic fashion, to focus on specific geological aspects of the Caribbean plate which are considered to be key factors in developing the types of models described. The project adopts a synoptic perspective in seeking to characterize the three dimensional structure, composition, state of stress, and evolution of the entire Caribbean plate. Geological information derived from analysis of space acquired data is combined with information provided by conventional methods to obtain insight into the structure, composition, and evolution of the Earth's crust. In addition, very long baseline interferometry and laser ranging techniques, which are also based upon the use of space technology, obtain information concerning crustal motion that, in turn, provides insight into the distribution and localization of crustal stress.

Physical properties, chemical composition, and cloud forming potential of particulate emissions from a marine diesel engine at various load conditions.

PubMed

Petzold, A; Weingartner, E; Hasselbach, J; Lauer, P; Kurok, C; Fleischer, F

2010-05-15

Particulate matter (PM) emissions from one serial 4-stroke medium-speed marine diesel engine were measured for load conditions from 10% to 110% in test rig studies using heavy fuel oil (HFO). Testing the engine across its entire load range permitted the scaling of exhaust PM properties with load. Emission factors for particle number, particle mass, and chemical compounds were determined. The potential of particles to form cloud droplets (cloud condensation nuclei, CCN) was calculated from chemical composition and particle size. Number emission factors are (3.43 +/- 1.26) x 10(16) (kg fuel)(-1) at 85-110% load and (1.06 +/- 0.10) x 10(16) (kg fuel)(-1) at 10% load. CCN emission factors of 1-6 x 10(14) (kg fuel)(-1) are at the lower bound of data reported in the literature. From combined thermal and optical methods, black carbon (BC) emission factors of 40-60 mg/(kg fuel) were determined for 85-100% load and 370 mg/(kg fuel) for 10% load. The engine load dependence of the conversion efficiency for fuel sulfur into sulfate of (1.08 +/- 0.15)% at engine idle to (3.85 +/- 0.41)% at cruise may serve as input to global emission calculations for various load conditions.

Non-Destructive Study of Bulk Crystallinity and Elemental Composition of Natural Gold Single Crystal Samples by Energy-Resolved Neutron Imaging

PubMed Central

Tremsin, Anton S.; Rakovan, John; Shinohara, Takenao; Kockelmann, Winfried; Losko, Adrian S.; Vogel, Sven C.

2017-01-01

Energy-resolved neutron imaging enables non-destructive analyses of bulk structure and elemental composition, which can be resolved with high spatial resolution at bright pulsed spallation neutron sources due to recent developments and improvements of neutron counting detectors. This technique, suitable for many applications, is demonstrated here with a specific study of ~5–10 mm thick natural gold samples. Through the analysis of neutron absorption resonances the spatial distribution of palladium (with average elemental concentration of ~0.4 atom% and ~5 atom%) is mapped within the gold samples. At the same time, the analysis of coherent neutron scattering in the thermal and cold energy regimes reveals which samples have a single-crystalline bulk structure through the entire sample volume. A spatially resolved analysis is possible because neutron transmission spectra are measured simultaneously on each detector pixel in the epithermal, thermal and cold energy ranges. With a pixel size of 55 μm and a detector-area of 512 by 512 pixels, a total of 262,144 neutron transmission spectra are measured concurrently. The results of our experiments indicate that high resolution energy-resolved neutron imaging is a very attractive analytical technique in cases where other conventional non-destructive methods are ineffective due to sample opacity. PMID:28102285

Ultrasonic velocity and absorption study of binary mixtures of cyclohexane with acrylonitrile by interferometric method at different frequencies

NASA Astrophysics Data System (ADS)

Pawar, N. R.; Chimankar, O. P.; Bhandakkar, V. D.; Padole, N. N.

2012-12-01

The ultrasonic velocity (u), absorption (α), density (ρ), and viscosity (η) has been measured at different frequencies (1MHz to 10MHz) in the binary mixtures of cyclohexane with acrylonitriile over the entire range of composition at temperature 303K. Vander Waal's constant (b), adiabatic compressibility (βa), acoustic impedance (Z), molar volume (V), free length (Lf), free volume, internal pressure, intermolecular radius and relative association have been also calculated. A special application for acrylonitrile is in the manufacture of carbon fibers. These are produced by paralysis of oriented poly acrylonitrile fibers and are used to reinforce composites for high-performance applications in the aircraft, defense and aerospace industries. Other applications of acrylonitrile are in the production of fatty amines, ion exchange resins and fatty amine amides used in cosmetics, adhesives, corrosion inhibitors and water-treatment resins. Cyclohexane derivatives can be used for the synthesis of pharmaceuticals, dyes, herbicides, plant growth regulator, plasticizers, rubber chemicals, nylon, cyclamens and other organic compounds. In the view of these extensive applications of acrylonitrile and cyclohexane in the engineering process, textile and pharmaceutical industries present study provides qualitative information regarding the nature and strength of interaction in the liquid mixtures through derive parameters from ultrasonic velocity and absorption measurement.

EFFECTS OF NONINDIGENOUS SPECIES ON THE TAXONOMIC DIVERSITY OF ESTUARINE ASSEMBLAGES

EPA Science Inventory

The effects of the few numerically dominant invasive species on benthic community abundance patterns has been documented in a number of estuaries. What is less appreciated is that the entire suite of nonindigenous species may alter the taxonomic composition of a community or biog...

32 CFR 525.3 - Criteria.

Code of Federal Regulations, 2012 CFR

2012-07-01

... AUTHORIZATION REGULATION FOR KWAJALEIN MISSILE RANGE § 525.3 Criteria. (a) General. (1) Entry authorizations may... efficiency, capability or effectiveness of any military installation located within Kwajalein Missile Range... area entirely within the borders of Kwajalein Missile Range is not authorized except when such entry...

32 CFR 525.3 - Criteria.

Code of Federal Regulations, 2013 CFR

2013-07-01

... AUTHORIZATION REGULATION FOR KWAJALEIN MISSILE RANGE § 525.3 Criteria. (a) General. (1) Entry authorizations may... efficiency, capability or effectiveness of any military installation located within Kwajalein Missile Range... area entirely within the borders of Kwajalein Missile Range is not authorized except when such entry...

32 CFR 525.3 - Criteria.

Code of Federal Regulations, 2014 CFR

2014-07-01

... AUTHORIZATION REGULATION FOR KWAJALEIN MISSILE RANGE § 525.3 Criteria. (a) General. (1) Entry authorizations may... efficiency, capability or effectiveness of any military installation located within Kwajalein Missile Range... area entirely within the borders of Kwajalein Missile Range is not authorized except when such entry...

32 CFR 525.3 - Criteria.

Code of Federal Regulations, 2010 CFR

2010-07-01

... AUTHORIZATION REGULATION FOR KWAJALEIN MISSILE RANGE § 525.3 Criteria. (a) General. (1) Entry authorizations may... efficiency, capability or effectiveness of any military installation located within Kwajalein Missile Range... area entirely within the borders of Kwajalein Missile Range is not authorized except when such entry...

32 CFR 525.3 - Criteria.

Code of Federal Regulations, 2011 CFR

2011-07-01

... AUTHORIZATION REGULATION FOR KWAJALEIN MISSILE RANGE § 525.3 Criteria. (a) General. (1) Entry authorizations may... efficiency, capability or effectiveness of any military installation located within Kwajalein Missile Range... area entirely within the borders of Kwajalein Missile Range is not authorized except when such entry...

Influence of ocean acidification on plankton community structure during a winter-to-summer succession: An imaging approach indicates that copepods can benefit from elevated CO2 via indirect food web effects

PubMed Central

Taucher, Jan; Haunost, Mathias; Boxhammer, Tim; Bach, Lennart T.; Algueró-Muñiz, María; Riebesell, Ulf

2017-01-01

Plankton communities play a key role in the marine food web and are expected to be highly sensitive to ongoing environmental change. Oceanic uptake of anthropogenic carbon dioxide (CO2) causes pronounced shifts in marine carbonate chemistry and a decrease in seawater pH. These changes–summarized by the term ocean acidification (OA)–can significantly affect the physiology of planktonic organisms. However, studies on the response of entire plankton communities to OA, which also include indirect effects via food-web interactions, are still relatively rare. Thus, it is presently unclear how OA could affect the functioning of entire ecosystems and biogeochemical element cycles. In this study, we report from a long-term in situ mesocosm experiment, where we investigated the response of natural plankton communities in temperate waters (Gullmarfjord, Sweden) to elevated CO2 concentrations and OA as expected for the end of the century (~760 μatm pCO2). Based on a plankton-imaging approach, we examined size structure, community composition and food web characteristics of the whole plankton assemblage, ranging from picoplankton to mesozooplankton, during an entire winter-to-summer succession. The plankton imaging system revealed pronounced temporal changes in the size structure of the copepod community over the course of the plankton bloom. The observed shift towards smaller individuals resulted in an overall decrease of copepod biomass by 25%, despite increasing numerical abundances. Furthermore, we observed distinct effects of elevated CO2 on biomass and size structure of the entire plankton community. Notably, the biomass of copepods, dominated by Pseudocalanus acuspes, displayed a tendency towards elevated biomass by up to 30–40% under simulated ocean acidification. This effect was significant for certain copepod size classes and was most likely driven by CO2-stimulated responses of primary producers and a complex interplay of trophic interactions that allowed this CO2 effect to propagate up the food web. Such OA-induced shifts in plankton community structure could have far-reaching consequences for food-web interactions, biomass transfer to higher trophic levels and biogeochemical cycling of marine ecosystems. PMID:28178268

Chemical composition of ground water and the locations of permeable zones in the Yucca Mountain area, Nevada

USGS Publications Warehouse

Benson, L.V.; Robison, J.H.; Blankennagel, R.K.; Ogard, A.L.

1983-01-01

Ten wells in the Yucca Mountain area of southern Nevada have been sampled for chemical analysis. Samples were obtained during pumping of water from the entire well bore (composite sample) and in one instance by pumping water from a single isolated interval in well UE-25b number 1. Sodium is the most abundant cation and bicarbonate the most abundant anion in all water samples. Although the general chemical compositions of individual samples are similar, there are significant differences in uncorrected carbon-14 age and in inorganic and stable-isotope composition. Flow surveys of seven wells performed using iodine-131 as a tracer indicate that groundwater production is usually from one or more discrete zones of permeability. (Author 's abstract)

A new percolation model for composite solid electrolytes and dispersed ionic conductors

NASA Astrophysics Data System (ADS)

Risyad Hasyim, Muhammad; Lanagan, Michael T.

2018-02-01

Composite solid electrolytes (CSEs) including conductor/insulator composites known as dispersed ionic conductors (DICs) have motivated the development of novel percolation models that describe their conductivity. Despite the long history, existing models lack in one or more key areas: (1) rigorous foundation for their physical theory, (2) explanation for non-universal conductor-insulator transition, (3) classification of DICs, and (4) extension to frequency-domain. This work describes a frequency-domain effective medium approximation (EMA) of a bond percolation model for CSEs. The EMA is derived entirely from Maxwell’s equations and contains basic microstructure parameters. The model was applied successfully to several composite systems from literature. Simulations and fitting of literature data address these key areas and illustrate the interplay between space charge layer properties and bulk microstructure.

Chemical Composition of Different Botanical Origin Honeys Produced by Sicilian Black Honeybees (Apis mellifera ssp. sicula).

PubMed

Mannina, Luisa; Sobolev, Anatoly P; Di Lorenzo, Arianna; Vista, Silvia; Tenore, Gian Carlo; Daglia, Maria

2015-07-01

In 2008 a Slow Food Presidium was launched in Sicily (Italy) for an early warning of the risk of extinction of the Sicilian native breed of black honeybee (Apis mellifera L. ssp sicula). Today, the honey produced by these honeybees is the only Sicilian honey produced entirely by the black honeybees. In view of few available data regarding the chemical composition of A. mellifera ssp. sicula honeys, in the present investigation the chemical compositions of sulla honey (Hedysarum coronarium L.) and dill honey (Anethum graveolens L.) were studied with a multimethodological approach, which consists of HPLC-PDA-ESI-MSn and NMR spectroscopy. Moreover, three unifloral honeys (lemon honey (obtained from Citrus limon (L.) Osbeck), orange honey (Citrus arantium L.), and medlar honey (Eriobotrya japonica (Thunb.) Lindl)), with known phenol and polyphenol compositions, were studied with NMR spectroscopy to deepen the knowledge about sugar and amino acid compositions.

Redox equilibria of multivalent ions in silicate glasses

NASA Technical Reports Server (NTRS)

Lauer, H. V., Jr.; Morris, R. V.

1977-01-01

Experimental studies were made on the compositional dependence of the redox equilibrium of Eu in synthetic silicate liquids, together with an empirical model describing the observed compositional dependence. Electron paramagnetic resonance (EPR) was used to measure the concentration ratio of Eu(2+) to Eu(3+) in various glasses formed by rapidly quenching silicate liquids. The compositional field studied comprised mixtures of SiO2, TiO2, Al2O3, CaO, MgO, and Na2O. The proposed model describes the Eu(2+)/Eu(3+) ratio over the entire compositional field in terms of parameters easily related to each glass composition. The general applicability and utility of the model is further demonstrated by its application to the Fe(2+)-Fe(3+), Ce(3+)-Ce(4+), and Cr(3+)-Cr(6+) redox reactions in binary alkali oxide silicate glasses of Li, Na, and K.

Unraveling signatures of biogeochemical processes and the depositional setting in the molecular composition of pore water DOM across different marine environments

NASA Astrophysics Data System (ADS)

Schmidt, Frauke; Koch, Boris P.; Goldhammer, Tobias; Elvert, Marcus; Witt, Matthias; Lin, Yu-Shih; Wendt, Jenny; Zabel, Matthias; Heuer, Verena B.; Hinrichs, Kai-Uwe

2017-06-01

Dissolved organic matter (DOM) in marine sediment pore waters derives largely from decomposition of particulate organic matter and its composition is influenced by various biogeochemical and oceanographic processes in yet undetermined ways. Here, we determine the molecular inventory of pore water DOM in marine sediments of contrasting depositional regimes with ultrahigh-resolution mass spectrometry and complementary bulk chemical analyses in order to elucidate the factors that shape DOM composition. Our sample sets from the Mediterranean, Marmara and Black Seas covered different sediment depths, ages and a range of marine environments with different (i) organic matter sources, (ii) balances of organic matter production and preservation, and (iii) geochemical conditions in sediment and water column including anoxic, sulfidic and hypersaline conditions. Pore water DOM had a higher molecular formula richness than overlying water with up to 11,295 vs. 2114 different molecular formulas in the mass range of 299-600 Da and covered a broader range of element ratios (H/C = 0.35-2.19, O/C = 0.03-1.19 vs. H/C = 0.56-2.13, O/C = 0.15-1.14). Formula richness was independent of concentrations of DOC and TOC. Near-surface pore water DOM was more similar to water column DOM than to deep pore water DOM from the same core with respect to formula richness and the molecular composition, suggesting exchange at the sediment-water interface. The DOM composition in the deeper sediments was controlled by organic matter source, selective decomposition of specific DOM fractions and early diagenetic molecule transformations. Compounds in pelagic sediment pore waters were predominantly highly unsaturated and N-bearing formulas, whereas oxygen-rich CHO-formulas and aromatic compounds were more abundant in pore water DOM from terrigenous sediments. The increase of S-bearing molecular formulas in the water column and pore waters of the Black Sea and the Mediterranean Discovery Basin was consistent with elevated HS- concentrations reflecting the incorporation of sulfur into biomolecules during early diagenesis. Sulfurization resulted in an increased average molecular mass of DOM and higher formula richness (up to 5899 formulas per sample). In sediments from the methanogenic zone in the Black Sea, the DOM pool was distinctly more reduced than overlying sediments from the sulfate-reducing zone. Bottom and pore water DOM from the Discovery Basin contained the highest abundances of aliphatic compounds in the entire dataset; a large fraction of abundant N-bearing formulas possibly represented peptide and nucleotide formulas suggesting preservation of these molecules in the life inhibiting environment of the Discovery Basin. Our unique data set provides the basis for a comprehensive understanding of the molecular signatures in pore water DOM and the turnover of sedimentary organic matter in marine sediments.

16 CFR 1616.4 - Sampling and acceptance procedures.

Code of Federal Regulations, 2014 CFR

2014-01-01

... a suitable thread and stitch. The specimen shall include each of the components over its entire... fabric in Tightened Sampling must be discontinued until that part of the process or component which is... otherwise attaching the trim shall be done with thread or fastening material of the same composition and...

Forensic microbiology: Evolving from discriminating distinct microbes to characterizing entire microbial communities on decomposing remains

USDA-ARS?s Scientific Manuscript database

The body of an animal encompasses a multitude of compositionally and functionally unique microbial environments, from the skin to the gastrointestinal system. Each of these systems harbor microbial communities that have adapted in order to cohabitate with their specific host resulting in a distinct...

Geometrical calibration of an AOTF hyper-spectral imaging system

NASA Astrophysics Data System (ADS)

Špiclin, Žiga; Katrašnik, Jaka; Bürmen, Miran; Pernuš, Franjo; Likar, Boštjan

2010-02-01

Optical aberrations present an important problem in optical measurements. Geometrical calibration of an imaging system is therefore of the utmost importance for achieving accurate optical measurements. In hyper-spectral imaging systems, the problem of optical aberrations is even more pronounced because optical aberrations are wavelength dependent. Geometrical calibration must therefore be performed over the entire spectral range of the hyper-spectral imaging system, which is usually far greater than that of the visible light spectrum. This problem is especially adverse in AOTF (Acousto- Optic Tunable Filter) hyper-spectral imaging systems, as the diffraction of light in AOTF filters is dependent on both wavelength and angle of incidence. Geometrical calibration of hyper-spectral imaging system was performed by stable caliber of known dimensions, which was imaged at different wavelengths over the entire spectral range. The acquired images were then automatically registered to the caliber model by both parametric and nonparametric transformation based on B-splines and by minimizing normalized correlation coefficient. The calibration method was tested on an AOTF hyper-spectral imaging system in the near infrared spectral range. The results indicated substantial wavelength dependent optical aberration that is especially pronounced in the spectral range closer to the infrared part of the spectrum. The calibration method was able to accurately characterize the aberrations and produce transformations for efficient sub-pixel geometrical calibration over the entire spectral range, finally yielding better spatial resolution of hyperspectral imaging system.

Temperature distribution of thick thermoset composites

NASA Astrophysics Data System (ADS)

Guo, Zhan-Sheng; Du, Shanyi; Zhang, Boming

2004-05-01

The development of temperature distribution of thick polymeric matrix laminates during an autoclave vacuum bag process was measured and compared with numerically calculated results. The finite element formulation of the transient heat transfer problem was carried out for polymeric matrix composite materials from the heat transfer differential equations including internal heat generation produced by exothermic chemical reactions. Software based on the general finite element software package was developed for numerical simulation of the entire composite process. From the experimental and numerical results, it was found that the measured temperature profiles were in good agreement with the numerical ones, and conventional cure cycles recommended by prepreg manufacturers for thin laminates should be modified to prevent temperature overshoot.

Electrically tunable laser based on oblique heliconical cholesteric liquid crystal

PubMed Central

Xiang, Jie; Varanytsia, Andrii; Minkowski, Fred; Paterson, Daniel A.; Storey, John M. D.; Imrie, Corrie T.; Lavrentovich, Oleg D.; Palffy-Muhoray, Peter

2016-01-01

A cholesteric liquid crystal (CLC) formed by chiral molecules represents a self-assembled one-dimensionally periodic helical structure with pitch p in the submicrometer and micrometer range. Because of the spatial periodicity of the dielectric permittivity, a CLC doped with a fluorescent dye and pumped optically is capable of mirrorless lasing. An attractive feature of a CLC laser is that the pitch p and thus the wavelength of lasing λ¯ can be tuned, for example, by chemical composition. However, the most desired mode to tune the laser, by an electric field, has so far been elusive. Here we present the realization of an electrically tunable laser with λ¯ spanning an extraordinarily broad range (>100 nm) of the visible spectrum. The effect is achieved by using an electric-field-induced oblique helicoidal (OH) state in which the molecules form an acute angle with the helicoidal axis rather than align perpendicularly to it as in a field-free CLC. The principal advantage of the electrically controlled CLCOH laser is that the electric field is applied parallel to the helical axis and thus changes the pitch but preserves the single-harmonic structure. The preserved single-harmonic structure ensures efficiency of lasing in the entire tunable range of emission. The broad tuning range of CLCOH lasers, coupled with their microscopic size and narrow line widths, may enable new applications in areas such as diagnostics, sensing, microscopy, displays, and holography. PMID:27807135

Electrically tunable laser based on oblique heliconical cholesteric liquid crystal.

PubMed

Xiang, Jie; Varanytsia, Andrii; Minkowski, Fred; Paterson, Daniel A; Storey, John M D; Imrie, Corrie T; Lavrentovich, Oleg D; Palffy-Muhoray, Peter

2016-11-15

A cholesteric liquid crystal (CLC) formed by chiral molecules represents a self-assembled one-dimensionally periodic helical structure with pitch [Formula: see text] in the submicrometer and micrometer range. Because of the spatial periodicity of the dielectric permittivity, a CLC doped with a fluorescent dye and pumped optically is capable of mirrorless lasing. An attractive feature of a CLC laser is that the pitch [Formula: see text] and thus the wavelength of lasing [Formula: see text] can be tuned, for example, by chemical composition. However, the most desired mode to tune the laser, by an electric field, has so far been elusive. Here we present the realization of an electrically tunable laser with [Formula: see text] spanning an extraordinarily broad range (>100 nm) of the visible spectrum. The effect is achieved by using an electric-field-induced oblique helicoidal (OH) state in which the molecules form an acute angle with the helicoidal axis rather than align perpendicularly to it as in a field-free CLC. The principal advantage of the electrically controlled CLC OH laser is that the electric field is applied parallel to the helical axis and thus changes the pitch but preserves the single-harmonic structure. The preserved single-harmonic structure ensures efficiency of lasing in the entire tunable range of emission. The broad tuning range of CLC OH lasers, coupled with their microscopic size and narrow line widths, may enable new applications in areas such as diagnostics, sensing, microscopy, displays, and holography.

Combining Hard with Soft Materials in Nanoscale Under High-Pressure High-Temperature Conditions

NASA Technical Reports Server (NTRS)

Palosz, B.; Gierlotka, S.; Swiderska-Sroda, A.; Fietkiewicz, K.; Kalisz, G.; Grzanka, E.; Stel'makh, S.; Palosz, W.

2004-01-01

Nano-composites with a primary nanocrystalline ceramic matrix and a secondary nanocrystalline material (metal or semiconductor) were synthesized by infiltration of an appropriate liquid into ceramic compacts under pressures of up to 8 GPa and temperatures of up to 2000 K. The purpose of our work is to obtain nanocomposites which constitute homoger?ous mixtures of two phases, both forming nano- grains of about 10 nm in size. The high pressure is used to bring the porosity of the compacted powders down to the nano-scale and force a given liquid into the nano-sized pores. The advantage of the infiltration technique is that, in a single, continuous process, we start with a nanocrystalline powder, compress it to form the matrix of the composite, and crystallize and/or synthesize a second nanomaterial in the matrix pores. The key limitation of this technology is, that the pores in the matrix need to stay open during the entire process of infiltration. Thus the initial powder should form a rigid skeleton, otherwise the so-called self-stop process can limit cr block a further flow of the liquid phase and hinder the process of the composite formation. Therefore powders of only very hard ceramic materials like diamond, Sic, or Alz03, which can withstand a substantial external load without undesired deformation, can be used as the primary phase. With this technique, using diamond and S i c ceramic powders infiltrated by liquid metals (AI, Zn, Sn, Ag, Au) and semiconductors (Si, Ge, GaAs, CdTe), we obtained nano-composites with the grain size in the range of 10 - 30 nm. Our work addresses the key problem in manufacturing bulk nanocrystalline materials, i.e. preservation of nano-scale during the fabrication process. In this paper we discuss basic technical and methodological problems associated with nano-infiltration based on the results obtained for Zn-Sic composites.

Onboard calibration igneous targets for the Mars Science Laboratory Curiosity rover and the Chemistry Camera laser induced breakdown spectroscopy instrument

NASA Astrophysics Data System (ADS)

Fabre, C.; Maurice, S.; Cousin, A.; Wiens, R. C.; Forni, O.; Sautter, V.; Guillaume, D.

2011-03-01

Accurate characterization of the Chemistry Camera (ChemCam) laser-induced breakdown spectroscopy (LIBS) on-board composition targets is of prime importance for the ChemCam instrument. The Mars Science Laboratory (MSL) science and operations teams expect ChemCam to provide the first compositional results at remote distances (1.5-7 m) during the in situ analyses of the Martian surface starting in 2012. Thus, establishing LIBS reference spectra from appropriate calibration standards must be undertaken diligently. Considering the global mineralogy of the Martian surface, and the possible landing sites, three specific compositions of igneous targets have been determined. Picritic, noritic, and shergottic glasses have been produced, along with a Macusanite natural glass. A sample of each target will fly on the MSL Curiosity rover deck, 1.56 m from the ChemCam instrument, and duplicates are available on the ground. Duplicates are considered to be identical, as the relative standard deviation (RSD) of the composition dispersion is around 8%. Electronic microprobe and laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS) analyses give evidence that the chemical composition of the four silicate targets is very homogeneous at microscopic scales larger than the instrument spot size, with RSD < 5% for concentration variations > 0.1 wt.% using electronic microprobe, and < 10% for concentration variations > 0.01 wt.% using LA ICP-MS. The LIBS campaign on the igneous targets performed under flight-like Mars conditions establishes reference spectra for the entire mission. The LIBS spectra between 240 and 900 nm are extremely rich, hundreds of lines with high signal-to-noise, and a dynamical range sufficient to identify unambiguously major, minor and trace elements. For instance, a first LIBS calibration curve has been established for strontium from [Sr] = 284 ppm to [Sr] = 1480 ppm, showing the potential for the future calibrations for other major or minor elements.

Aqueous alteration and brecciation in Bells, an unusual, saponite-bearing, CM chondrite

NASA Astrophysics Data System (ADS)

Brearley, Adrian J.

1995-06-01

The petrological and mineralogical characteristics of the unusual CM2 chondrite, Bells, have been investigated in detail by scanning electron microscopy (SEM), electron microprobe analysis (EPMA), and transmission electron microscopy (TEM). Bells is a highly brecciated chondrite which contains few intact chondrules, a very low abundance of refractory inclusions, and is notable in having an unusually high abundance of magnetite, which is disseminated throughout the fine-grained matrix. Fragmental olivines and pyroxenes are common and, based on compositional data, appear to have been derived from chondrules as a result of extensive brecciation. The fine-grained mineralogy of matrix in Bells differs considerably from other CM chondrites and has closer affinities to matrix in CI chondrites. The dominant phases are fine-grained saponite interlayered with serpentine, and phases such as tochilinite and cronstedtite, which are typical of CM chondrite matrices, are entirely absent. Pentlandite, pyrrhotite, magnetite, anhydrite, calcite, and rare Ti-oxides also occur as accessory phases. Based on its oxygen and noble gas isotopic compositions (Zadnik, 1985; Rowe et al., 1994), Bells can be considered to be a CM2 chondrite, although its bulk composition shows some departures from the typical range exhibited by this group. However, these variations in bulk chemistry are entirely consistent with the observed mineralogy of Bells. The unusual fine-grained mineralogy of Bells matrix can be reasonably attributed to the combined effects of aqueous alteration and advanced brecciation in a parent body environment. Extensive brecciation has assisted aqueous alteration by reducing chondrules and mineral grains into progressively smaller grains with high surface areas, which are more susceptible to dissolution reactions involving aqueous fluids. This has resulted in the preferential dissolution of Fe-rich chondrule olivines, which are now completely absent in Bells although present in other CM chondrites. The formation of saponite in Bells probably resulted from the dissolution of relatively silica-rich phases, such as pyroxene and olivine, that were derived from chondrules. The result of such dissolution reactions would be to increase the activity of silica in the fluid phase, at least on a localized scale, stabilizing saponite in preference to serpentine. An increase in aSiO 2 would also have destabilized preexisting cronstedtite which may have reacted to form magnetite and MgFe serpentine under conditions of constant ƒO 2 .

Improving cell mixture deconvolution by identifying optimal DNA methylation libraries (IDOL).

PubMed

Koestler, Devin C; Jones, Meaghan J; Usset, Joseph; Christensen, Brock C; Butler, Rondi A; Kobor, Michael S; Wiencke, John K; Kelsey, Karl T

2016-03-08

Confounding due to cellular heterogeneity represents one of the foremost challenges currently facing Epigenome-Wide Association Studies (EWAS). Statistical methods leveraging the tissue-specificity of DNA methylation for deconvoluting the cellular mixture of heterogenous biospecimens offer a promising solution, however the performance of such methods depends entirely on the library of methylation markers being used for deconvolution. Here, we introduce a novel algorithm for Identifying Optimal Libraries (IDOL) that dynamically scans a candidate set of cell-specific methylation markers to find libraries that optimize the accuracy of cell fraction estimates obtained from cell mixture deconvolution. Application of IDOL to training set consisting of samples with both whole-blood DNA methylation data (Illumina HumanMethylation450 BeadArray (HM450)) and flow cytometry measurements of cell composition revealed an optimized library comprised of 300 CpG sites. When compared existing libraries, the library identified by IDOL demonstrated significantly better overall discrimination of the entire immune cell landscape (p = 0.038), and resulted in improved discrimination of 14 out of the 15 pairs of leukocyte subtypes. Estimates of cell composition across the samples in the training set using the IDOL library were highly correlated with their respective flow cytometry measurements, with all cell-specific R (2)>0.99 and root mean square errors (RMSEs) ranging from [0.97 % to 1.33 %] across leukocyte subtypes. Independent validation of the optimized IDOL library using two additional HM450 data sets showed similarly strong prediction performance, with all cell-specific R (2)>0.90 and R M S E<4.00 %. In simulation studies, adjustments for cell composition using the IDOL library resulted in uniformly lower false positive rates compared to competing libraries, while also demonstrating an improved capacity to explain epigenome-wide variation in DNA methylation within two large publicly available HM450 data sets. Despite consisting of half as many CpGs compared to existing libraries for whole blood mixture deconvolution, the optimized IDOL library identified herein resulted in outstanding prediction performance across all considered data sets and demonstrated potential to improve the operating characteristics of EWAS involving adjustments for cell distribution. In addition to providing the EWAS community with an optimized library for whole blood mixture deconvolution, our work establishes a systematic and generalizable framework for the assembly of libraries that improve the accuracy of cell mixture deconvolution.

The electrical properties of zero-gravity processed immiscibles

NASA Technical Reports Server (NTRS)

Lacy, L. L.; Otto, G. H.

1974-01-01

When dispersed or mixed immiscibles are solidified on earth, a large amount of separation of the constituents takes place due to differences in densities. However, when the immiscibles are dispersed and solidified in zero-gravity, density separation does not occur, and unique composite solids can be formed with many new and promising electrical properties. By measuring the electrical resistivity and superconducting critical temperature, Tc, of zero-g processed Ga-Bi samples, it has been found that the electrical properties of such materials are entirely different from the basic constituents and the ground control samples. Our results indicate that space processed immiscible materials may form an entirely new class of electronic materials.

The Raman spectrum of Ca-Mg-Fe carbonates; Applications in geobiology

NASA Astrophysics Data System (ADS)

van Zuilen, M. A.; Rividi, N.; Ménez, B.; Philippot, P.

2012-04-01

Carbonates form a very important mineral group in geobiological studies. They are a common mineral matrix for putative carbonaceous microfossils in Archean greenstone belts, form an important chemical deposit in seafloor hydrothermal systems, and are a common product in biomineralization processes. In many geobiological studies there is a specific need for simple characterization of carbonate composition while avoiding complex sample preparation or sample destruction. Raman spectroscopy is a highly versatile non-destructive technique enabling in-situ characterization of minerals and carbonaceous materials. It can be combined with confocal microscopy enabling high-resolution Raman mapping of entire rock thin sections, or can be integrated in submersibles and potentially Mars-rovers for direct field-based mineral identification. It is thus important that well-established spectral databases exist which enable unambiguous identification of a wide variety of carbonate minerals. The most common carbonates in the Ca-Mg-Fe system include the CaCO3 polymorphs calcite, aragonite, and vaterite, as well as the solid solutions CaMg(CO3)2-CaFe(CO3)2 (dolomite-ankerite) and MgCO3-FeCO3 (magnesite-siderite). Although various carbonate end-members have been studied exhaustively by Raman spectroscopy, a simple protocol for rapid distinction of various carbonate solid solutions is still lacking. Here we present a detailed study of Raman shifts in various carbonate standards of known composition in the Ca-Mg-Fe system. Carbonates with rhombohedral symmetry display a Raman spectrum with six characteristic vibrational modes - four of these represent vibrations within the (CO3)2- unit and two represent external vibrations of the crystal lattice. We show that Raman band shifts of internal mode 2ν2 (range 1725-1765 cm-1), and external modes T (range 170-215 cm-1) and L (range 285-330 cm-1) for siderite-magnesite and ankerite-dolomite solid solutions display distinct and well defined positive correlations with Mg number (Mg/Mg+Fe+Mn+Ca). Raman shifts calibrated as a function of Mg number were used in turn to evaluate the chemical composition of natural carbonate samples. In particular it is shown that detailed micron-resolution Raman maps can be generated of carbonate crystal-zonation in hydrothermally altered sedimentary deposits from Archean greenstone belts. Large spectral-range analysis (140-2000 cm-1) in static-mode (centered at 1150 cm-1) allows for combined Raman mapping of both carbonate-composition (2ν2, T, L modes) as well as kerogen structural ordering (D1-D4 and G modes in the range 1100-1700 cm-1), and therefore allows for simultaneous characterization of putative organic microfossils and associated carbonate matrix in metamorphosed Archean rock samples. Finally, it will be shown that these carbonate solid solutions can be distinguished from other end-member carbonates such as calcite, vaterite and the orthorhombic polymorph aragonite.

Differences in the spectra of cosmic ray nuclear species below approximately 5 GeV/nuc

NASA Technical Reports Server (NTRS)

Webber, W. R.; Lezniak, J. A.; Kish, J.

1974-01-01

Extension of previous measurements made at high energies, which show clear evidence for energy-dependent changes in cosmic ray composition, to lower energies. The new data point to the fact that these spectral differences extend over the entire energy band from a few hundred MeV/nucleon to several tens of GeV/nucleon. The details of these composition variations are examined by studying in a systematic way the variations of the ratios of secondary to primary and different groups of primary cosmic ray nuclei.

Top-down approach for nanophase reconstruction in bulk heterojunction solar cells.

PubMed

Kong, Jaemin; Hwang, In-Wook; Lee, Kwanghee

2014-09-01

"Top-Down" nanophase reconstruction via a post-additive soaking process is first presented with various BHJ binary composites. By simply rinsing as-cast BHJ films with a solvent mixture containing a few traces of a nanophase-control reagent such as 1,8-diiodooctane, oversized fullerene-rich clusters (>100 nm in dia-meter) in the BHJ film are instataneously disassembled and entirely reorganized into finely intermixed donor/acceptor nanophases (ca. 10 nm) with a 3D compositional homogeneity, without surface segregation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In search of ancestral Kilauea volcano

USGS Publications Warehouse

Lipman, P.W.; Sisson, T.W.; Ui, T.; Naka, J.

2000-01-01

Submersible observations and samples show that the lower south flank of Hawaii, offshore from Kilauea volcano and the active Hilina slump system, consists entirely of compositionally diverse volcaniclastic rocks; pillow lavas are confined to shallow slopes. Submarine-erupted basalt clasts have strongly variable alkalic and transitional basalt compositions (to 41% SiO2, 10.8% alkalies), contrasting with present-day Kilauea tholeiites. The volcaniclastic rocks provide a unique record of ancestral alkalic growth of an archetypal hotspot volcano, including transition to its tholeiitic shield stage, and associated slope-failure events.

Utilization of Molecular, Phenotypic, and Geographical Diversity to Develop Compact Composite Core Collection in the Oilseed Crop, Safflower (Carthamus tinctorius L.) through Maximization Strategy

PubMed Central

Kumar, Shivendra; Ambreen, Heena; Variath, Murali T.; Rao, Atmakuri R.; Agarwal, Manu; Kumar, Amar; Goel, Shailendra; Jagannath, Arun

2016-01-01

Safflower (Carthamus tinctorius L.) is a dryland oilseed crop yielding high quality edible oil. Previous studies have described significant phenotypic variability in the crop and used geographical distribution and phenotypic trait values to develop core collections. However, the molecular diversity component was lacking in the earlier collections thereby limiting their utility in breeding programs. The present study evaluated the phenotypic variability for 12 agronomically important traits during two growing seasons (2011–12 and 2012–13) in a global reference collection of 531 safflower accessions, assessed earlier by our group for genetic diversity and population structure using AFLP markers. Significant phenotypic variation was observed for all the agronomic traits in the representative collection. Cluster analysis of phenotypic data grouped the accessions into five major clusters. Accessions from the Indian Subcontinent and America harbored maximal phenotypic variability with unique characters for a few traits. MANOVA analysis indicated significant interaction between genotypes and environment for both the seasons. Initially, six independent core collections (CC1–CC6) were developed using molecular marker and phenotypic data for two seasons through POWERCORE and MSTRAT. These collections captured the entire range of trait variability but failed to include complete genetic diversity represented in 19 clusters reported earlier through Bayesian analysis of population structure (BAPS). Therefore, we merged the three POWERCORE core collections (CC1–CC3) to generate a composite core collection, CartC1 and three MSTRAT core collections (CC4–CC6) to generate another composite core collection, CartC2. The mean difference percentage, variance difference percentage, variable rate of coefficient of variance percentage, coincidence rate of range percentage, Shannon's diversity index, and Nei's gene diversity for CartC1 were 11.2, 43.7, 132.4, 93.4, 0.47, and 0.306, respectively while the corresponding values for CartC2 were 9.3, 58.8, 124.6, 95.8, 0.46, and 0.301. Each composite core collection represented the complete range of phenotypic and genetic variability of the crop including 19 BAPS clusters. This is the first report describing development of core collections in safflower using molecular marker data with phenotypic values and geographical distribution. These core collections will facilitate identification of genetic determinants of trait variability and effective utilization of the prevalent diversity in crop improvement programs. PMID:27807441

Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

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

Griffis, Timothy J.; Wood, Jeffrey D.; Baker, John M.

Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle – an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotopemore » observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ 18O v ranged from –40.2 to –15.9 ‰ and δ 2H v ranged from –278.7 to –113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess ( d v) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in d v, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratio events ( > 25 mmol mol –1) indicate that regional evaporation can account for 40 to 60 % of the PBL water vapor. These estimates are in relatively good agreement with that derived from numerical weather model simulations. This relatively large fraction of evaporation-derived water vapor implies that evaporation has an important impact on the precipitation recycling ratio within the region. In conclusion, based on multiple constraints, we estimate that the summer season recycling fraction is about 30 %, indicating a potentially important link with convective precipitation.« less

The oxygen isotope composition of Karoo and Etendeka picrites: High δ18O mantle or crustal contamination?

NASA Astrophysics Data System (ADS)

Harris, Chris; le Roux, Petrus; Cochrane, Ryan; Martin, Laure; Duncan, Andrew R.; Marsh, Julian S.; le Roex, Anton P.; Class, Cornelia

2015-07-01

Oxygen isotope compositions of Karoo and Etendeka large igneous province (LIP) picrites and picrite basalts are presented to constrain the effects of crustal contamination versus mantle source variation. Olivine and orthopyroxene phenocrysts from lavas and dykes (Mg# 64-80) from the Tuli and Mwenezi (Nuanetsi) regions of the ca 180 Ma Karoo LIP have δ18O values that range from 6.0 to 6.7 ‰. They appear to have crystallized from magmas having δ18O values about 1-1.5 ‰ higher than expected in an entirely mantle-derived magma. Olivines from picrite and picrite basalt dykes from the ca 135 Ma Etendeka LIP of Namibia and Karoo-age picrite dykes from Dronning Maud Land, Antarctica, do not have such elevated δ18O values. A range of δ18O values from 4.9 to 6.0 ‰, and good correlations between δ18O value and Sr, Nd and Pb isotope ratios for the Etendeka picrites are consistent with previously proposed models of crustal contamination. Explanations for the high δ18O values in Tuli/Mwenezi picrites are limited to (1) alteration, (2) crustal contamination, and (3) derivation from mantle with an abnormally high δ18O. Previously, a variety of models that range from crustal contamination to derivation from the `enriched' mantle lithosphere have been suggested to explain high concentrations of incompatible elements such as K, and average ɛNd and ɛSr values of -8 and +16 in Mwenezi (Nuanetsi) picrites. However, the primitive character of the magmas (Mg# 73), combined with the lack of correlation between δ18O values and radiogenic isotopic compositions, MgO content, or Mg# is inconsistent with crustal contamination. Thus, an 18O-enriched mantle source having high incompatible trace element concentration and enriched radiogenic isotope composition is indicated. High δ18O values are accompanied by negative Nb and Ta anomalies, consistent with the involvement of the mantle lithosphere, whereas the high δ18O themselves are consistent with an eclogitic source. Magma δ18O values about 1 ‰ higher than expected for mantle-derived magma are also a feature of the Bushveld mafic and ultramafic magmas, and the possibility exists that a long-lived 18O-enriched mantle source has existed beneath southern Africa. A mixed eclogite peridotite source could have developed by emplacement of oceanic lithosphere into the cratonic keel during Archaean subduction.

Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

DOE PAGES

Griffis, Timothy J.; Wood, Jeffrey D.; Baker, John M.; ...

2016-04-25

Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle – an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotopemore » observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ 18O v ranged from –40.2 to –15.9 ‰ and δ 2H v ranged from –278.7 to –113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess ( d v) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in d v, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratio events ( > 25 mmol mol –1) indicate that regional evaporation can account for 40 to 60 % of the PBL water vapor. These estimates are in relatively good agreement with that derived from numerical weather model simulations. This relatively large fraction of evaporation-derived water vapor implies that evaporation has an important impact on the precipitation recycling ratio within the region. In conclusion, based on multiple constraints, we estimate that the summer season recycling fraction is about 30 %, indicating a potentially important link with convective precipitation.« less

Energy Finite Element Analysis Developments for Vibration Analysis of Composite Aircraft Structures

NASA Technical Reports Server (NTRS)

Vlahopoulos, Nickolas; Schiller, Noah H.

2011-01-01

The Energy Finite Element Analysis (EFEA) has been utilized successfully for modeling complex structural-acoustic systems with isotropic structural material properties. In this paper, a formulation for modeling structures made out of composite materials is presented. An approach based on spectral finite element analysis is utilized first for developing the equivalent material properties for the composite material. These equivalent properties are employed in the EFEA governing differential equations for representing the composite materials and deriving the element level matrices. The power transmission characteristics at connections between members made out of non-isotropic composite material are considered for deriving suitable power transmission coefficients at junctions of interconnected members. These coefficients are utilized for computing the joint matrix that is needed to assemble the global system of EFEA equations. The global system of EFEA equations is solved numerically and the vibration levels within the entire system can be computed. The new EFEA formulation for modeling composite laminate structures is validated through comparison to test data collected from a representative composite aircraft fuselage that is made out of a composite outer shell and composite frames and stiffeners. NASA Langley constructed the composite cylinder and conducted the test measurements utilized in this work.

High P-T experiments and first principles calculations of the diffusion of Si and Cr in liquid iron

NASA Astrophysics Data System (ADS)

Posner, Esther S.; Rubie, David C.; Frost, Daniel J.; Vlček, Vojtěch; Steinle-Neumann, Gerd

2017-04-01

Chemical diffusion rates of Si and Cr in liquid iron have been measured over the P-T range of 1-18 GPa and 1873-2428 K. The experiments were performed using a multi-anvil apparatus with diffusion couples comprised of pure iron and iron alloy placed end to end in a vertical orientation. In order to extend our dataset to the Earth's core-mantle boundary and to compare experimental data with theoretical diffusion rates calculated under laboratory-accessible conditions, we have also performed first principles molecular dynamic simulations (FP-MD) and calculated self-diffusion coefficients and activation parameters for Si, Cr, and Fe diffusion in liquid Fe, Fe0.92Si0.08 and Fe0.92Cr0.08 compositions over the P-T range of 1 bar-135 GPa and 2200-5500 K. Over the entire range of pressures and temperatures studied using both methods, diffusion coefficients are described well using an exponential function of the homologous temperature relation, D = Dhexp(-gTh), where Th = Tm/T, Tm is the melting temperature at the pressure of interest and g and Dh are constants. Our findings indicate constant diffusivities of approximately 4 × 10-9 m2 s-1 for Si and Cr and 5 × 10-9 m2 s-1 for Fe along the melting curve from ambient to core pressures in all liquid compositions studied, with an increase of ∼0.8 log units at T = 2Tm. Differences between experimental data and computational results are less than 0.1 log units. Structural properties of liquid iron alloys analyzed using partial radial distribution functions (RDFs) show the average distance between two Fe atoms, rFe-Fe, is identical to that of rFe-Si and rFe-Cr over the entire P-T range of study, which supports that the diffusion of Si and Cr (and thus likely other species of similar atomic radii) occurs via direct substitution with Fe. Diffusion coefficients and interatomic distances used to calculate liquid viscosities via the Stokes-Einstein relation yield constant viscosity along the melting curve of ∼6 mPa s for liquid Fe, ∼7 mPa s for liquid Fe0.92Cr0.08, and ∼8 mPa s for liquid Fe0.92Si0.08, with a decrease of ∼0.8 log units at T = 2Tm. The data can also be reproduced within <10% using the Arrhenian model with derivatives of the activation parameters determined over a very wide range of P-T conditions. Verification of a homologous temperature dependence of diffusion in liquid metals, as well as the excellent agreement between experimental results and FP-MD simulations, provides a new and simple framework for interpreting and modeling mass transport processes of liquid iron alloys in all planetary bodies regardless of size. Our results are used to evaluate the kinetics of metal-silicate chemical equilibration during core formation and diffusivity contrasts across a solid-liquid metal interface, i.e. at the inner core boundary.

HILT - A heavy ion large area proportional counter telescope for solar and anomalous cosmic rays

NASA Technical Reports Server (NTRS)

Klecker, Berndt; Hovestadt, Dietrich; Scholer, M.; Arbinger, H.; Ertl, M.; Kaestle, H.; Kuenneth, E.; Laeverenz, P.; Seidenschwang, E.; Blake, J. B.

1993-01-01

The HILT sensor has been designed to measure heavy ion elemental abundances, energy spectra, and direction of incidence in the mass range from He to Fe and in the energy range 4 to 250 MeV/nucleon. With its large geometric factor of 60 sq cm sr the sensor is optimized to provide compositional and spectral measurements for low intensity cosmic rays (i.e. for small solar energetic particle events and for the anomalous component of cosmic rays). The instrument combines a large area ion drift chamber-proportional counter system with two arrays of 16 Li-drift solid state detectors and 16 CsI crystals. The multi dE/dx-E technique provides a low background mass and energy determination. The sensor also measures particle direction. Combining these measurements with the information on the spacecraft position and attitude in the low-altitude polar orbit, it will be possible to infer the ionic charge of the ions from the local cutoff of the Earth's magnetic field. The ionic charge in this energy range is of particular interest because it provides unique clues to the origin of these particles and has not been investigated systematically so far. Together with the other instruments on board SAMPEX (LEICA, MAST, and PET), a comprehensive measurement of the entire solar and anomalous particle population will be achieved.

Comparison of lighting activity and inner radiation belt particle fluxes perturbations

NASA Astrophysics Data System (ADS)

Martinez Calderon, C.; Bortnik, J.; Li, W.; Spence, H. E.; Rodger, C. J.

2016-12-01

Lightning discharges are known to inject whistlers into the inner magnetosphere over a wide range of latitudes around their source. When a discharge occurs, it radiates electromagnetic energy, some of which propagates in the whistler-mode wave through the ionospheric plasma travelling away from the Earth. Previous studies have discussed the effects of whistler-induced electron precipitation and radiation belt losses associated with lightning but there has been little research on the long term effects of these precipitation on the inner radiation belts [Rodger et al. (2004), Clilverd et al. (2004)].Here, we use data from the World Wide Lightning Location Network (WWLLN), which has continuously monitored global lightning since 2004, to examine one year of lightning data and locate the L-shells with high lighting activity. We use Van Allen Probes' Energetic Particle, Composition, and Thermal Plasma Suite (ECT) from both satellites (RBSP-A/B) to measure electron fluxes in the inner radiation belt at the L-shells of interest. We compare these fluxes to a globally-integrated count of lightning strikes and investigate the relationship between global lightning occurrence and RBSP electron fluxes. We examine several factors, such as different energy ranges, timescales ranging from a few weeks to the entire year and seasonal changes in order to quantify the loss process driven by lightning in the inner radiation belts.

Time Resolved Measurements of Speciated Tailpipe Emissions from Motor Vehicles: Trends with Emission Control Technology, Cold Start Effects, and Speciation.

PubMed

Drozd, Greg T; Zhao, Yunliang; Saliba, Georges; Frodin, Bruce; Maddox, Christine; Weber, Robert J; Chang, M-C Oliver; Maldonado, Hector; Sardar, Satya; Robinson, Allen L; Goldstein, Allen H

2016-12-20

Experiments were conducted at the California Air Resources Board Haagen-Smit Laboratory to understand changes in vehicle emissions in response to stricter emissions standards over the past 25 years. Measurements included a wide range of volatile organic compounds (VOCs) for a wide range of spark ignition gasoline vehicles meeting varying levels of emissions standards, including all certifications from Tier 0 up to Partial Zero Emission Vehicle. Standard gas chromatography (GC) and high performance liquid chromatography (HLPC) analyses were employed for drive-cycle phase emissions. A proton-transfer-reaction mass spectrometer measured time-resolved emissions for a wide range of VOCs. Cold-start emissions occur almost entirely in the first 30-60 s for newer vehicles. Cold-start emissions have compositions that are not significantly different across all vehicles tested and are markedly different from neat fuel. Hot-stabilized emissions have varying importance depending on species and may require a driving distance of 200 miles to equal the emissions from a single cold start. Average commute distances in the U.S. suggest the majority of in-use vehicles have emissions dominated by cold starts. The distribution of vehicle ages in the U.S. suggests that within several years only a few percent of vehicles will have significant driving emissions compared to cold-start emissions.

43 CFR 3203.10 - How are lands included in a competitive sale?

Code of Federal Regulations, 2011 CFR

2011-10-01

... within the legal subdivision, section, township, and range; (2) For unsurveyed lands, describe the lands..., include an entire section, township, and range. Do not divide protracted sections into aliquot parts; (4...

Molecular dynamics simulation for the test of calibrated OPLS-AA force field for binary liquid mixture of tri-iso-amyl phosphate and n-dodecane.

PubMed

Das, Arya; Ali, Sk Musharaf

2018-02-21

Tri-isoamyl phosphate (TiAP) has been proposed to be an alternative for tri-butyl phosphate (TBP) in the Plutonium Uranium Extraction (PUREX) process. Recently, we have successfully calibrated and tested all-atom optimized potentials for liquid simulations using Mulliken partial charges for pure TiAP, TBP, and dodecane by performing molecular dynamics (MD) simulation. It is of immense importance to extend this potential for the various molecular properties of TiAP and TiAP/n-dodecane binary mixtures using MD simulation. Earlier, efforts were devoted to find out a suitable force field which can explain both structural and dynamical properties by empirical parameterization. Therefore, the present MD study reports the structural, dynamical, and thermodynamical properties with different mole fractions of TiAP-dodecane mixtures at the entire range of mole fraction of 0-1 employing our calibrated Mulliken embedded optimized potentials for liquid simulation (OPLS) force field. The calculated electric dipole moment of TiAP was seen to be almost unaffected by the TiAP concentration in the dodecane diluent. The calculated liquid densities of the TiAP-dodecane mixture are in good agreement with the experimental data. The mixture densities at different temperatures are also studied which was found to be reduced with temperature as expected. The plot of diffusivities for TiAP and dodecane against mole fraction in the binary mixture intersects at a composition in the range of 25%-30% of TiAP in dodecane, which is very much closer to the TBP/n-dodecane composition used in the PUREX process. The excess volume of mixing was found to be positive for the entire range of mole fraction and the excess enthalpy of mixing was shown to be endothermic for the TBP/n-dodecane mixture as well as TiAP/n-dodecane mixture as reported experimentally. The spatial pair correlation functions are evaluated between TiAP-TiAP and TiAP-dodecane molecules. Further, shear viscosity has been computed by performing the non-equilibrium molecular dynamics employing the periodic perturbation method. The calculated shear viscosity of the binary mixture is found to be in excellent agreement with the experimental values. The use of the newly calibrated OPLS force field embedding Mulliken charges is shown to be equally reliable in predicting the structural and dynamical properties for the mixture without incorporating any arbitrary scaling in the force field or Lennard-Jones parameters. Further, the present MD simulation results demonstrate that the Stokes-Einstein relation breaks down at the molecular level. The present methodology might be adopted to evaluate the liquid state properties of an aqueous-organic biphasic system, which is of great significance in the interfacial science and technology.

Molecular dynamics simulation for the test of calibrated OPLS-AA force field for binary liquid mixture of tri-iso-amyl phosphate and n-dodecane

NASA Astrophysics Data System (ADS)

Das, Arya; Ali, Sk. Musharaf

2018-02-01

Tri-isoamyl phosphate (TiAP) has been proposed to be an alternative for tri-butyl phosphate (TBP) in the Plutonium Uranium Extraction (PUREX) process. Recently, we have successfully calibrated and tested all-atom optimized potentials for liquid simulations using Mulliken partial charges for pure TiAP, TBP, and dodecane by performing molecular dynamics (MD) simulation. It is of immense importance to extend this potential for the various molecular properties of TiAP and TiAP/n-dodecane binary mixtures using MD simulation. Earlier, efforts were devoted to find out a suitable force field which can explain both structural and dynamical properties by empirical parameterization. Therefore, the present MD study reports the structural, dynamical, and thermodynamical properties with different mole fractions of TiAP-dodecane mixtures at the entire range of mole fraction of 0-1 employing our calibrated Mulliken embedded optimized potentials for liquid simulation (OPLS) force field. The calculated electric dipole moment of TiAP was seen to be almost unaffected by the TiAP concentration in the dodecane diluent. The calculated liquid densities of the TiAP-dodecane mixture are in good agreement with the experimental data. The mixture densities at different temperatures are also studied which was found to be reduced with temperature as expected. The plot of diffusivities for TiAP and dodecane against mole fraction in the binary mixture intersects at a composition in the range of 25%-30% of TiAP in dodecane, which is very much closer to the TBP/n-dodecane composition used in the PUREX process. The excess volume of mixing was found to be positive for the entire range of mole fraction and the excess enthalpy of mixing was shown to be endothermic for the TBP/n-dodecane mixture as well as TiAP/n-dodecane mixture as reported experimentally. The spatial pair correlation functions are evaluated between TiAP-TiAP and TiAP-dodecane molecules. Further, shear viscosity has been computed by performing the non-equilibrium molecular dynamics employing the periodic perturbation method. The calculated shear viscosity of the binary mixture is found to be in excellent agreement with the experimental values. The use of the newly calibrated OPLS force field embedding Mulliken charges is shown to be equally reliable in predicting the structural and dynamical properties for the mixture without incorporating any arbitrary scaling in the force field or Lennard-Jones parameters. Further, the present MD simulation results demonstrate that the Stokes-Einstein relation breaks down at the molecular level. The present methodology might be adopted to evaluate the liquid state properties of an aqueous-organic biphasic system, which is of great significance in the interfacial science and technology.

The Effect of Lithospheric Discontinuities on the Composition of Lavas From the Northern Galápagos Platform Extension

NASA Astrophysics Data System (ADS)

Schlitzer, W.; Harpp, K. S.; Mittelstaedt, E. L.; Kurz, M. D.; Geist, D.

2011-12-01

The platform supporting the Galápagos Archipelago extends ~50 km NW toward the Galápagos Spreading Center (GSC) into the Northern Galapagos Volcanic Province (NGVP), where it underlies Pinta, Marchena, and Genovesa Islands. Approximately 45 km north of Pinta is the southern termination of a ~100-km long transform fault, at 90o50'W. The seafloor surrounding the NGVP was surveyed and dredged during the 2010 MV1007 and 2001 DRIFT04 cruises. All the large volcanoes, including the islands, have elongate bathymetric footprints with extensive submarine ridges. Lavas from this small region (<150 km in diameter) exhibit isotopic and trace element signatures that span the compositional range of the entire Galápagos Archipelago. Pinta and its submarine extension have the most enriched signatures, whereas at the eastern end of the platform extension, Genovesa is indistinguishable from normal MORB. Samples dredged around Pinta and Marchena have intermediate compositions. In contrast, lavas from the adjacent transform fault are more depleted than those from Genovesa and anywhere along the GSC for hundreds of km in both directions. Lavas from this region exhibit a range of 3He/4He (6.5-9.5 Ra), significantly lower than the high 3He/4He signature of material erupted by the plume-rich western Galápagos shield volcanoes (>25 Ra). Whereas the compositions of lavas erupted on the Nazca Plate in the NGVP require 3 or more distinct mantle endmembers to explain their compositions, our data indicate that the platform extension region only requires components previously described for the Galápagos Islands. In addition, Sm/Yb decreases abruptly along an E-W transect from Pinta to Genovesa. Gibson and Geist (2010) concluded that Sm/Yb ratios reflect variations in surface wave velocities (Villagomez et al., 2007), enabling them to predict lithospheric thickness. We apply the relationship defined by Gibson and Geist to map lithospheric thickness across our study area. Our results suggest that the lithosphere (and thus minimum melt generation depth) gets progressively shallower from Pinta to Genovesa; this phenomenon may explain unexpected Holocene volcanism in the NGVP. The wide range in Sm/Yb further suggests a complex lithospheric structure underlying the platform extension, which we propose reflects formation of the adjacent GSC transform fault within the last ~3 Ma, possibly through a series of ridge jumps as suggested by modeling of new magnetic data. We propose a model in which heterogeneous plume material with enriched and depleted components (Ito and Mahoney, 2005) is migrating toward the GSC along the base of the lithosphere, having previously lost its primordial helium signature during deep melting near the western shield volcanoes. As the material crosses the complex lithospheric thickness variations in the NGVP, melt generation becomes progressively shallower. The enriched compositions at Pinta thus result from limited, deep melting of enriched compositions owing to a thick lithospheric cap. East of Pinta, the plume melts more extensively and to shallower depths, producing progressively depleted signatures toward Genovesa.

Structural and magnetic characterization of the complete delafossite solid solution (CuAlO₂)₁-x(CuCrO₂)x.

PubMed

Barton, Phillip T; Seshadri, Ram; Knöller, Andrea; Rosseinsky, Matthew J

2012-01-11

We have prepared the complete delafossite solid solution series between diamagnetic CuAlO(2) and the t(2g)(3)frustrated antiferromagnet CuCrO(2). The evolution with composition x in CuAl(1-x)Cr(x)O(2) of the crystal structure and magnetic properties has been studied and is reported here. The room-temperature unit cell parameters follow the Végard law and increase with x as expected. The μ(eff) is equal to the Cr(3+) spin-only S = 3/2 value throughout the entire solid solution. Θ(CW) is negative, indicating that the dominant interactions are antiferromagnetic, and its magnitude increases with Cr substitution. For dilute Cr compositions, the nearest-neighbor exchange coupling constant J(BB) was estimated by mean-field theory to be 3.0 meV. Despite the sizable Θ(CW), long-range antiferromagnetic order does not develop until x is almost 1, and is preceded by glassy behavior. The data presented here, and those on dilute Al substitution from Okuda et al, suggest that the reduction in magnetic frustration due to the presence of non-magnetic Al does not have as dominant an effect on magnetism as chemical disorder and dilution of the magnetic exchange. For all samples, the 5 K isothermal magnetization does not saturate in fields up to 5 T and minimal hysteresis is observed. The presence of antiferromagnetic interactions is clearly evident in the sub-Brillouin behavior with a reduced magnetization per Cr atom. An inspection of the scaled Curie plot reveals that significant short-range antiferromagnetic interactions occur in CuCrO(2) above its Néel temperature, consistent with its magnetic frustration. Uncompensated short-range behavior is present in the Al-substituted samples and is likely a result of chemical disorder.

Structural and magnetic characterization of the complete delafossite solid solution (CuAlO2)1-x(CuCrO2)x

NASA Astrophysics Data System (ADS)

Barton, Phillip T.; Seshadri, Ram; Knöller, Andrea; Rosseinsky, Matthew J.

2012-01-01

We have prepared the complete delafossite solid solution series between diamagnetic CuAlO2 and the t2g3frustrated antiferromagnet CuCrO2. The evolution with composition x in CuAl1-xCrxO2 of the crystal structure and magnetic properties has been studied and is reported here. The room-temperature unit cell parameters follow the Végard law and increase with x as expected. The μeff is equal to the Cr3+ spin-only S = 3/2 value throughout the entire solid solution. ΘCW is negative, indicating that the dominant interactions are antiferromagnetic, and its magnitude increases with Cr substitution. For dilute Cr compositions, the nearest-neighbor exchange coupling constant JBB was estimated by mean-field theory to be 3.0 meV. Despite the sizable ΘCW, long-range antiferromagnetic order does not develop until x is almost 1, and is preceded by glassy behavior. The data presented here, and those on dilute Al substitution from Okuda et al, suggest that the reduction in magnetic frustration due to the presence of non-magnetic Al does not have as dominant an effect on magnetism as chemical disorder and dilution of the magnetic exchange. For all samples, the 5 K isothermal magnetization does not saturate in fields up to 5 T and minimal hysteresis is observed. The presence of antiferromagnetic interactions is clearly evident in the sub-Brillouin behavior with a reduced magnetization per Cr atom. An inspection of the scaled Curie plot reveals that significant short-range antiferromagnetic interactions occur in CuCrO2 above its Néel temperature, consistent with its magnetic frustration. Uncompensated short-range behavior is present in the Al-substituted samples and is likely a result of chemical disorder.

New Approach for Near-Real-Time Measurement of Elemental Composition of Aerosol Using Laser-Induced Breakdown Spectroscopy

PubMed Central

Diwakar, Prasoon; Kulkarni, Pramod; Birch, M. Eileen

2015-01-01

A new approach has been developed for making near-real-time measurement of elemental composition of aerosols using plasma spectroscopy. The method allows preconcentration of miniscule particle mass (pg to ng) directly from the sampled aerosol stream through electrostatic deposition of charged particles (30–900 nm) onto a flat-tip microneedle electrode. The collected material is subsequently ablated from the electrode and monitored by laser-induced breakdown spectroscopy. Atomic emission spectra were collected using a broadband spectrometer with a wavelength range of 200–980 nm. A single-sensor delay time of 1.3 μs was used in the spectrometer for all elements to allow simultaneous measurement of multiple elements. The system was calibrated for various elements including Cd, Cr, Cu, Mn, Na, and Ti. The absolute mass detection limits for these elements were experimentally determined and found to be in the range of 0.018–5 ng. The electrostatic collection technique has many advantages over other substrate-based methods involving aerosol collection on a filter or its focused deposition using an aerodynamic lens. Because the particle mass is collected over a very small area that is smaller than the spatial extent of the laser-induced plasma, the entire mass is available for analysis. This considerably improves reliability of the calibration and enhances measurement accuracy and precision. Further, the aerosol collection technique involves very low pressure drop, thereby allowing higher sample flow rates with much smaller pumps—a desirable feature for portable instrumentation. Higher flow rates also make it feasible to measure trace element concentrations at part per trillion levels. Detection limits in the range of 18–670 ng m−3 can be achieved for most of the elements studied at a flow rate of 1.5 L min−1 with sampling times of 5 min. PMID:26692632

A 1400 km geochemical transect along the Central American Arc: Summary of mafic Holocene volcanism from Guatemala to Panama

NASA Astrophysics Data System (ADS)

Geldmacher, J.; Hoernle, K.; Gill, J. B.; Hauff, F.; Heydolph, K.

2016-12-01

It is generally accepted that subducted oceanic crust and sediments contribute to the composition of arc magmas. Systematic variations of input parameters (including age, subduction angle, and chemical composition of the subducting material) make the Central American Volcanic Arc (CAVA), which extends from Guatemala in the northwest through El Salvador, Honduras, Nicaragua, Costa Rica and Panama to the southeast, a prime study object. We present a comprehensive (major and trace element and Sr-Nd-Pb-Hf isotope data) and consistent (all data generated in the same labs using the same methods and data reduction procedures) compilation of published and unpublished Holocene mafic volcanic rocks sampled along the entire arc. New data include Sr and, for the first time, Hf isotope data from the entire CAVA as well as major and trace element data for 43 samples from southern Nicaragua and central Costa Rica from which only isotopic compositions were previously published. The combined elemental and isotopic data confirm the influence of distinct subduction components on the composition of CAVA magmas. Along-arc geochemical variations (especially delta 208Pb/204Pb) of volcanic front magmas in Costa Rica and Panama have been explained by the different compositions of seamounts/ridges of the isotopically zoned Galápagos hotspot track that covers the subducting Cocos Plate in this sector of the arc (Hoernle et al. 2008, Nature 451). Our new data confirm this relationship with arc lavas from Costa Rica having higher 87Sr/86Sr ratios than those from western Panama reflecting a similar spatial-compositional distinction in the subducting hotspot track beneath them. In contrast, 176Hf/177Hf shows no comparable variations in this sector of the arc, indicating that the Hf is primarily derived from the mantle wedge rather than the subducting slab. Although small degree hydrous melts are believed to fertilize the mantle wedge beneath Costa Rica, residual zircon may hold back the Hf.

Magnetization of small iron-nickel spheres

NASA Technical Reports Server (NTRS)

Wasilewski, P.

1981-01-01

Magnetic properties of small iron-nickel alloy spheres, having compositions which cover the entire Fe-Ni binary, are presented. The spheres were formed during solidification in free fall following the melting of electropolished wires of appropriate composition. The spheres with Ni not greater than 25% acquired a martensitic thermal remanence while those with Ni not less than 30% acquired a thermoremanent magnetization. A magnetic remanence-composition diagram and a coercive force-composition diagram are constructed. Magnetic hysteresis loops and derived parameters demonstrate the difference between metal-bearing and oxide-bearing natural samples. The magnetic remanence varies as the sphere size in conjunction with the microstructure. These results help to explain why coercive force is generally low, remanent coercive force is generally high, and their ratio (R/C) is always large in fine metal dispersions, such as lunar samples and chondrite meteorites.

Bamboo reinforced polymer composite - A comprehensive review

NASA Astrophysics Data System (ADS)

Roslan, S. A. H.; Rasid, Z. A.; Hassan, M. Z.

2018-04-01

Bamboo has greatly attention of researchers due to their advantages over synthetic polymers. It is entirely renewable, environmentally-friendly, non-toxic, cheap, non-abrasive and fully biodegradable. This review paper summarized an oveview of the bamboo, fiber extraction and mechanical behavior of bamboo reinforced composites. A number of studies proved that mechanical properties of bamboo fibers reinforced reinforced polymer composites are excellent and competent to be utilized in high-tech applications. The properties of the laminate are influenced by the fiber loading, fibre orientation, physical and interlaminar adhesion between fibre and matrix. In contrast, the presence of chemical constituents such as cellulose, lignin, hemicellulose and wax substances in natural fibres preventing them from firmly binding with polymer resin. Thus, led to poor mechanical properties for composites. Many attempt has been made in order to overcome this issue by using the chemical treatment.

Effects of a low-shrinkage methacrylate monomer and monoacylphosphine oxide photoinitiator on curing efficiency and mechanical properties of experimental resin-based composites.

PubMed

Manojlovic, Dragica; Dramićanin, Miroslav D; Milosevic, Milos; Zeković, Ivana; Cvijović-Alagić, Ivana; Mitrovic, Nenad; Miletic, Vesna

2016-01-01

This study investigated the degree of conversion, depth of cure, Vickers hardness, flexural strength, flexural modulus and volumetric shrinkage of experimental composite containing a low shrinkage monomer FIT-852 (FIT; Esstech Inc.) and photoinitiator 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO; Sigma Aldrich) compared to conventional composite containing Bisphenol A-glycidyl methacrylate (BisGMA) and camphorquinone-amine photoinitiator system. The degree of conversion was generally higher in FIT-based composites (45-64% range) than in BisGMA-based composites (34-58% range). Vickers hardness, flexural strength and modulus were higher in BisGMA-based composites. A polywave light-curing unit was generally more efficient in terms of conversion and hardness of experimental composites than a monowave unit. FIT-based composite containing TPO showed the depth of cure below 2mm irrespective of the curing light. The depth of cure of FIT-based composite containing CQ and BisGMA-based composites with either photoinitiator was in the range of 2.8-3.0mm. Volumetric shrinkage of FIT-based composite (0.9-5.7% range) was lower than that of BisGMA-based composite (2.2-12% range). FIT may be used as a shrinkage reducing monomer compatible with the conventional CQ-amine system as well as the alternative TPO photoinitiator. However, the depth of cure of FIT_TPO composite requires boosting to achieve clinically recommended thickness of 2mm. Copyright © 2015 Elsevier B.V. All rights reserved.

Bedrock composition limits mountain ecosystem productivity and landscape evolution (Invited)

NASA Astrophysics Data System (ADS)

Riebe, C. S.; Hahm, W.; Lukens, C.

2013-12-01

We used measurements of bedrock geochemistry, forest productivity and cosmogenic nuclides to explore connections among lithology, ecosystem productivity and landscape evolution across a lithosequence of 21 sites in the Sierra Nevada Batholith, California. Our sites span a narrow range in elevations and thus share similar climatic conditions. Meanwhile, underlying bedrock varies from granite to diorite and spans nearly the entire range of geochemical compositions observed in Cordilleran granitoids. Land cover varies markedly, from groves of Giant Sequoia, the largest trees on Earth, to pluton-spanning swaths of little or no soil and vegetative cover. This is closely reflected in measures of forest productivity, such as remotely sensed tree-canopy cover, which varies by more than an order of magnitude across our sites and often changes abruptly at mapped contacts between rock types. We find that tree-canopy cover is closely correlated with the concentrations in bedrock of major and minor elements, including several plant-essential nutrients. For example, tree-canopy cover is virtually zero where there is less than 0.3 mg/g phosphorus in bedrock. Erosion rates from these nearly vegetation-free, nutrient deserts are more than 2.5 times slower on average than they are from surrounding, relatively nutrient-rich, soil-mantled bedrock. Thus by influencing soil and forest cover, bedrock nutrient concentrations may provoke weathering-limited erosion and thus may strongly regulate landscape evolution. Our analysis suggests that variations in bedrock nutrient concentrations can also provoke an intrinsic limitation on primary productivity. These limitations appear to apply across all our sites. To the extent that they are broadly representative of conditions in granitic landscapes elsewhere around the world, our results are consistent with widespread, but previously undocumented lithologic control of the distribution and diversity of vegetation in mountainous terrain.

Effect of Kollidon VA®64 particle size and morphology as directly compressible excipient on tablet compression properties.

PubMed

Chaudhary, R S; Patel, C; Sevak, V; Chan, M

2018-01-01

The study evaluates use of Kollidon VA ® 64 and a combination of Kollidon VA ® 64 with Kollidon VA ® 64 Fine as excipient in direct compression process of tablets. The combination of the two grades of material is evaluated for capping, lamination and excessive friability. Inter particulate void space is higher for such excipient due to the hollow structure of the Kollidon VA ® 64 particles. During tablet compression air remains trapped in the blend exhibiting poor compression with compromised physical properties of the tablets. Composition of Kollidon VA ® 64 and Kollidon VA ® 64 Fine is evaluated by design of experiment (DoE). A scanning electron microscopy (SEM) of two grades of Kollidon VA ® 64 exhibits morphological differences between coarse and fine grade. The tablet compression process is evaluated with a mix consisting of entirely Kollidon VA ® 64 and two mixes containing Kollidon VA ® 64 and Kollidon VA ® 64 Fine in ratio of 77:23 and 65:35. A statistical modeling on the results from the DoE trials resulted in the optimum composition for direct tablet compression as combination of Kollidon VA ® 64 and Kollidon VA ® 64 Fine in ratio of 77:23. This combination compressed with the predicted parameters based on the statistical modeling and applying main compression force between 5 and 15 kN, pre-compression force between 2 and 3 kN, feeder speed fixed at 25 rpm and compression range of 45-49 rpm produced tablets with hardness ranging between 19 and 21 kp, with no friability, capping, or lamination issue.

Thermoelectric Properties of In-Doped Cu2ZnGeSe4

NASA Astrophysics Data System (ADS)

Chetty, R.; Bali, A.; Femi, O. E.; Chattopadhyay, K.; Mallik, R. C.

2016-03-01

Recently, much research has been focused on finding new thermoelectric materials. Cu-based quaternary chalcogenides that belong to A2BCD4 (A = Cu; B = Zn, Cd; C = Sn, Ge; D = S, Se, Te) are wide band gap materials and one of the potential thermoelectric materials due to their complex crystal structures. In this study, In-doped quaternary compounds Cu2ZnGe1- x In x Se4 ( x = 0, 0.025, 0.05, 0.075, 0.1) were prepared by a solid state synthesis method. Powder x-ray diffraction patterns of all the samples showed a tetragonal crystal structure (space group I- 42m) of the main phase with a trace amount of impurity phases, which was further confirmed by Rietveld analysis. The elemental composition of all the samples showed a slight deviation from the nominal composition with the presence of secondary phases. All the transport properties were measured in the temperature range 373-673 K. The electrical resistivity of all the samples initially decreased up to ˜470 K and then increased with increase in temperature upto 673 K, indicating the transition from semiconducting to metallic behavior. Positive Seebeck coefficients for all the samples revealed that holes are the majority carriers in the entire temperature range. The substitution of In3+ on Ge4+ introduces holes and results in the decrease of resistivity as well as the Seebeck coefficient, thereby leading to the optimization of the power factor. The lattice thermal conductivity of all the samples decreased with increasing temperature, indicating the presence of phonon-phonon scattering. As a result, the thermoelectric figure of merit ( zT) of the doped sample showed an increase as compared to the undoped compound.

Oxygen Depletion on the Surface of Mercury: Evidence of Silicon Smelting?

NASA Technical Reports Server (NTRS)

McCubbin, F. M.; Vander Kaaden, K. E.; Peplowski, P. N.; Bell, A. S.; Evans, L. G.; Nittler, L. R.; Boyce, J. W.; Keller, L. P.; McCoy, T. J.

2017-01-01

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft collected data that provided important insights into the structure, chemical makeup, and compositional diversity of Mercury. The X-Ray Spectrometer (XRS) and Gamma-Ray Spectrometer (GRS) onboard MESSENGER provided the first detailed chemical analyses of Mercury's surface. Among the many discoveries included several surprising characteristics about the surface of Mercury, including elevated S abundances (up to 4 percent by weight), low Fe abundances (less than 4 percent by weight), and relatively low O abundances (O/Si ratio of 1.40 plus or minus 0.03). The surface chemistry as determined by MESSENGER has been used to identify up to nine distinct geochemical terranes on Mercury. Numerous modeling and experimental efforts have been undertaken to infer the mineralogy and petrology of mercurian lavas and surface materials. However, all of these efforts have presumed valence states for each of the elements according to the following: Si4+, Ti4+, Al3+, Cr2+, Fe2+, Mn2+, Mg2+, Ca2+, Na+, K+, S2-, Cl-. Based on these valence assignments, cations are charged balanced with the anions O2-, S2-, and Cl- and the compositions are recast in terms of oxides, sulfides, and chlorides. Based on these assumptions, the geochemical terranes that have been identified on Mercury yield O/Si wt. ratios ranging from 1.61 to 1.84, which is substantially higher than the preliminary O/Si ratio of 1.40 plus or minus 0.03 determined by the MESSENGER GRS]. We have re-evaluated the O/Si ratio using the entire MESSENGER dataset to reassess its implications for the geochemistry of Mercury.

Association between adaptive behaviour and age in adults with Down syndrome without dementia: examining the range and severity of adaptive behaviour problems.

PubMed

Makary, A T; Testa, R; Tonge, B J; Einfeld, S L; Mohr, C; Gray, K M

2015-08-01

Studies on adaptive behaviour and ageing in adults with Down syndrome (DS) (without dementia) have typically analysed age-related change in terms of the total item scores on questionnaires. This research extends the literature by investigating whether the age-related changes in adaptive abilities could be differentially attributed to changes in the number or severity (intensity) of behavioural questionnaire items endorsed. The Adaptive Behaviour Assessment System-II Adult (ABAS-II Adult) was completed by parents and caregivers of 53 adults with DS aged between 16 and 56 years. Twenty adults with DS and their parents/caregivers were a part of a longitudinal study, which provided two time points of data. In addition 33 adults with DS and their parents/caregivers from a cross-sectional study were included. Random effects regression analyses were used to examine the patterns in item scores associated with ageing. Increasing age was found to be significantly associated with lower adaptive behaviour abilities for all the adaptive behaviour composite scores, expect for the practical composite. These associations were entirely related to fewer ABAS-II Adult items being selected as present for the older participants, as opposed to the scores being attributable to lower item severity. This study provides evidence for a differential pattern of age-related change for various adaptive behaviour skills in terms of range, but not severity. Possible reasons for this pattern will be discussed. Overall, these findings suggest that adults with DS may benefit from additional support in terms of their social and conceptual abilities as they age. © 2014 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd.

Chemical composition of air masses transported from Asia to the U.S. West Coast during ITCT 2K2: Fossil fuel combustion versus biomass-burning signatures

NASA Astrophysics Data System (ADS)

de Gouw, J. A.; Cooper, O. R.; Warneke, C.; Hudson, P. K.; Fehsenfeld, F. C.; Holloway, J. S.; Hübler, G.; Nicks, D. K., Jr.; Nowak, J. B.; Parrish, D. D.; Ryerson, T. B.; Atlas, E. L.; Donnelly, S. G.; Schauffler, S. M.; Stroud, V.; Johnson, K.; Carmichael, G. R.; Streets, D. G.

2004-12-01

As part of the Intercontinental Transport and Chemical Transformation experiment in 2002 (ITCT 2K2), a National Oceanic and Atmospheric Administration (NOAA) WP-3D research aircraft was used to study the long-range transport of Asian air masses toward the west coast of North America. During research flights on 5 and 17 May, strong enhancements of carbon monoxide (CO) and other species were observed in air masses that had been transported from Asia. The hydrocarbon composition of the air masses indicated that the highest CO levels were related to fossil fuel use. During the flights on 5 and 17 May and other days, the levels of several biomass-burning indicators increased with altitude. This was true for acetonitrile (CH3CN), methyl chloride (CH3Cl), the ratio of acetylene (C2H2) to propane (C3H8), and, on May 5, the percentage of particles measured by the particle analysis by laser mass spectrometry (PALMS) instrument that were attributed to biomass burning based on their carbon and potassium content. An ensemble of back-trajectories, calculated from the U.S. west coast over a range of latitudes and altitudes for the entire ITCT 2K2 period, showed that air masses from Southeast Asia and China were generally observed at higher altitudes than air from Japan and Korea. Emission inventories estimate the contribution of biomass burning to the total emissions to be low for Japan and Korea, higher for China, and the highest for Southeast Asia. Combined with the origin of the air masses versus altitude, this qualitatively explains the increase with altitude, averaged over the whole ITCT 2K2 period, of the different biomass-burning indicators.

Fe-oxidizing microbes are hydrothermal vent ecosystem engineers at the Loihi Seamount (Invited)

NASA Astrophysics Data System (ADS)

Chan, C. S.; McAllister, S.; Leavitt, A.; Emerson, D.; Moyer, C. L.; Glazer, B. T.

2013-12-01

Microaerophilic Fe-oxidizing microorganisms (FeOM) colonize gradients of Fe(II) and oxygen, taking advantage of the available chemical energy. Vast communities of FeOM proliferate at deep sea hydrothermal vents, forming mineralized mats that range from centimeters to meters thick. Because these mats structure the environment for both FeOM and the entire microbial community, the Fe-oxidizers are acting as ecosystem engineers. What organisms are responsible for initiating these mats, and how does the physical structure and community composition develop as the mats mature? By connecting structure, function, and ecology, we can better interpret modern mat structures, as well as ancient fossilized mats. We have been studying Fe microbial mats at Loihi Seamount in Hawaii, a long-term study site that has become a model for Fe oxidation in marine hydrothermal systems. Recent improvements in ROV imaging systems allow us to see a great range of mat textures and colors, which may represent diverse habitats and/or different stages of mat development. With improved imaging and sampling techniques, we have been able to obtain discrete, intact samples of these delicate microbial mats. Previous bulk sampling methods showed that mats consist of a mixture of Fe-mineralized morphologies. Our analyses of intact mats show that mats are initiated by one type of structure-former (either a stalk-former like Mariprofundus ferrooxydans or a Zetaproteobacterial sheath-former). These microbes may be the vanguard organisms that stabilize chemical gradients in this dynamic environment, allowing colonization by other organisms (evidenced by branching tubes, fibrillar nests, and other morphologies). We will show evidence of the composition and development of these mats, and discuss parallels between these marine Fe mats and their freshwater counterparts, supporting the idea that FeOM engineer environments favorable for growth.

Direct surface analysis coupled to high-resolution mass spectrometry reveals heterogeneous composition of the cuticle of Hibiscus trionum petals.

PubMed

Giorio, Chiara; Moyroud, Edwige; Glover, Beverley J; Skelton, Paul C; Kalberer, Markus

2015-10-06

Plant cuticle, which is the outermost layer covering the aerial parts of all plants including petals and leaves, can present a wide range of patterns that, combined with cell shape, can generate unique physical, mechanical, or optical properties. For example, arrays of regularly spaced nanoridges have been found on the dark (anthocyanin-rich) portion at the base of the petals of Hibiscus trionum. Those ridges act as a diffraction grating, producing an iridescent effect. Because the surface of the distal white region of the petals is smooth and noniridescent, a selective chemical characterization of the surface of the petals on different portions (i.e., ridged vs smooth) is needed to understand whether distinct cuticular patterns correlate with distinct chemical compositions of the cuticle. In the present study, a rapid screening method has been developed for the direct surface analysis of Hibiscus trionum petals using liquid extraction surface analysis (LESA) coupled with high-resolution mass spectrometry. The optimized method was used to characterize a wide range of plant metabolites and cuticle monomers on the upper (adaxial) surface of the petals on both the white/smooth and anthocyanic/ridged regions, and on the lower (abaxial) surface, which is entirely smooth. The main components detected on the surface of the petals are low-molecular-weight organic acids, sugars, and flavonoids. The ridged portion on the upper surface of the petal is enriched in long-chain fatty acids, which are constituents of the wax fraction of the cuticle. These compounds were not detected on the white/smooth region of the upper petal surface or on the smooth lower surface.

New biocomposites based on bioplastic flax fibers and biodegradable polymers.

PubMed

Wróbel-Kwiatkowska, Magdalena; Czemplik, Magdalena; Kulma, Anna; Zuk, Magdalena; Kaczmar, Jacek; Dymińska, Lucyna; Hanuza, Jerzy; Ptak, Maciej; Szopa, Jan

2012-01-01

A new generation of entirely biodegradable and bioactive composites with polylactic acid (PLA) or poly-ε-caprolactone (PCL) as the matrix and bioplastic flax fibers as reinforcement were analyzed. Bioplastic fibers contain polyhydroxybutyrate and were obtained from transgenic flax. Biochemical analysis of fibers revealed presence of several antioxidative compounds of hydrophilic (phenolics) and hydrophobic [cannabidiol (CBD), lutein] nature, indicating their high antioxidant potential. The presence of CBD and lutein in flax fibers is reported for the first time. FTIR analysis showed intermolecular hydrogen bonds between the constituents in composite PLA+flax fibers which were not detected in PCL-based composite. Mechanical analysis of prepared composites revealed improved stiffness and a decrease in tensile strength. The viability of human dermal fibroblasts on the surface of composites made of PLA and transgenic flax fibers was the same as for cells cultured without composites and only slightly lower (to 9%) for PCL-based composites. The amount of platelets and Escherichia coli cells aggregated on the surface of the PLA based composites was significantly lower than for pure polymer. Thus, composites made of PLA and transgenic flax fibers seem to have bacteriostatic, platelet anti-aggregated, and non-cytotoxic effect. Copyright © 2012 American Institute of Chemical Engineers (AIChE).

Mozart and Today's Student Musician

ERIC Educational Resources Information Center

Knopper, Rob

2010-01-01

Wolfgang Amadeus Mozart (1756-1791) was the ultimate child prodigy. It is said that Mozart, after attending a service at the Vatican, wrote down an entire sacred piece of music after one hearing. There are countless examples of the amazing feats that Mozart accomplished through his childhood, not to mention his huge compositional output through…

Mozart and Today's Student Musician

ERIC Educational Resources Information Center

Knopper, Rob

2011-01-01

Wolfgang Amadeus Mozart (1756-1791) was the ultimate child prodigy. It is said that Mozart, after attending a service at the Vatican, wrote down an entire sacred piece of music after one hearing. There are countless examples of the amazing feats that Mozart accomplished through his childhood, not to mention his huge compositional output through…

Mozart and Today's Student Musician

ERIC Educational Resources Information Center

Knopper, Rob

2006-01-01

Wolfgang Amadeus Mozart (1756-1791) is the ultimate child prodigy. It is said that Mozart, after attending a service at the Vatican, wrote down an entire sacred piece of music after one hearing. There are countless examples of the amazing feats that Mozart accomplished through his childhood, not to mention his huge compositional output throughout…

Variation in Seed Fatty Acid Composition, and Sequence Divergence in the FAD2 Gene Coding Region between Wild and Cultivated Sesame

USDA-ARS?s Scientific Manuscript database

Sesame germplasm harbors genetic diversity which can be useful for sesame improvement in breeding programs. Seven accessions with different levels of oleic acid were selected from the entire USDA sesame germplasm collection (1232 accessions) and planted for morphological observation and re-examinati...

Safety Evaluation Report: Development of Improved Composite Pressure Vessels for Hydrogen Storage, Lincoln Composites, Lincoln, NE, May 25, 2010

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

Fort, III, William C.; Kallman, Richard A.; Maes, Miguel

2010-12-22

Lincoln Composites operates a facility for designing, testing, and manufacturing composite pressure vessels. Lincoln Composites also has a U.S. Department of Energy (DOE)-funded project to develop composite tanks for high-pressure hydrogen storage. The initial stage of this project involves testing the permeation of high-pressure hydrogen through polymer liners. The company recently moved and is constructing a dedicated research/testing laboratory at their new location. In the meantime, permeation tests are being performed in a corner of a large manufacturing facility. The safety review team visited the Lincoln Composites site on May 25, 2010. The project team presented an overview of themore » company and project and took the safety review team on a tour of the facility. The safety review team saw the entire process of winding a carbon fiber/resin tank on a liner, installing the boss and valves, and curing and painting the tank. The review team also saw the new laboratory that is being built for the DOE project and the temporary arrangement for the hydrogen permeation tests.« less

Unearthing Secrets of the Forest

USGS Publications Warehouse

Beldin, Sarah I.; Perakis, Steven S.

2009-01-01

Forests are a defining feature for large areas of the Pacific northwestern United States from northern California to Alaska. Coniferous temperate rainforests in the western Cascade and coastal mountain ranges are appreciated for their aesthetic value and abundant natural resources. Few people recognize the riches beneath the forest floor; yet, soil is a key ecosystem component that makes each type of forest unique. Soils harbor immense biological diversity and control the release of water and nutrients that support life above ground. Understanding how carbon and nutrients cycle in forests, known as forest biogeochemistry, is crucial for evaluating forest productivity, composition, diversity, and change. At the U.S. Geological Survey (USGS) Forest and Rangeland Ecosystem Science Center, research in the Terrestrial Ecosystems Laboratory focuses on nutrient cycling in five themes: climate change, nutrition and sustainability, fire effects, restoration, and forest-stream linkages. This research is essential to understand the entire forest ecosystem and to use the best science available to make informed policy and management decisions.

Consideration of probability of bacterial growth for Jovian planets and their satellites

NASA Technical Reports Server (NTRS)

Taylor, D. M.; Berkman, R. M.; Divine, N.

1975-01-01

Environmental parameters affecting growth of bacteria (e.g., moisture, temperature, pH, and chemical composition) were compared with current atmospheric models for Jupiter and Saturn, and with the available physical data for their satellites. Different zones of relative probability of growth were identified for Jupiter and Saturn, with the highest in pressure regions of 1-10 million N/sq m (10 to 100 atmospheres) and 3-30 million N/sq m (30 to 300 atmospheres), respectively. Of the more than two dozen satellites, only the largest (Io, Europa, Ganymede, Callisto, and Titan) were found to be interesting biologically. Titan's atmosphere may produce a substantial greenhouse effect providing increased surface temperatures. Models predicting a dense atmosphere are compatible with microbial growth for a range of pressures at Titan's surface. For Titan's surface the probability of growth would be enhanced if (1) the surface is entirely or partially liquid (water), (2) volcanism (in an ice-water-steam system) is present, or (3) access to internal heat sources is significant.

Vlf/elf radiation patterns of arbitrarily oriented electric and magnetic dipoles in a cold lossless multicomponent magnetoplasma.

NASA Technical Reports Server (NTRS)

Wang, T. N. C.; Bell, T. F.

1972-01-01

With the use of a power integral formulation, a study is made of the vlf/elf radiation patterns of arbitrarily oriented electric and magnetic dipoles in a cold lossless multicomponent magnetoplasma. Expressions for the ray patterns are initially developed that apply for arbitrary values of driving frequency, static magnetic-field strength, plasma density, and composition. These expressions are subsequently specialized to vlf/elf radiation in a plasma modeled on the magnetosphere. A series of representative pattern plots are presented for frequencies between the proton and electron gyrofrequencies. These patterns illustrate the fact that focusing effects that arise from the geometrical properties of the refractive index surface tend to dominate the radiation distribution over the entire range from the electron gyrofrequency to 4.6 times the proton gyrofrequency. It is concluded that focusing effects should be of significant importance in the design of a vlf/elf satellite transmitting system in the magnetosphere.

Aerogel Blanket Insulation Materials for Cryogenic Applications

NASA Technical Reports Server (NTRS)

Coffman, B. E.; Fesmire, J. E.; White, S.; Gould, G.; Augustynowicz, S.

2009-01-01

Aerogel blanket materials for use in thermal insulation systems are now commercially available and implemented by industry. Prototype aerogel blanket materials were presented at the Cryogenic Engineering Conference in 1997 and by 2004 had progressed to full commercial production by Aspen Aerogels. Today, this new technology material is providing superior energy efficiencies and enabling new design approaches for more cost effective cryogenic systems. Aerogel processing technology and methods are continuing to improve, offering a tailor-able array of product formulations for many different thermal and environmental requirements. Many different varieties and combinations of aerogel blankets have been characterized using insulation test cryostats at the Cryogenics Test Laboratory of NASA Kennedy Space Center. Detailed thermal conductivity data for a select group of materials are presented for engineering use. Heat transfer evaluations for the entire vacuum pressure range, including ambient conditions, are given. Examples of current cryogenic applications of aerogel blanket insulation are also given. KEYWORDS: Cryogenic tanks, thermal insulation, composite materials, aerogel, thermal conductivity, liquid nitrogen boil-off

Rate-dependent, Li-ion insertion/deinsertion behavior of LiFePO4 cathodes in commercial 18650 LiFePO4 cells.

PubMed

Liu, Qi; He, Hao; Li, Zhe-Fei; Liu, Yadong; Ren, Yang; Lu, Wenquan; Lu, Jun; Stach, Eric A; Xie, Jian

2014-03-12

We have performed operando synchrotron high-energy X-ray diffraction (XRD) to obtain nonintrusive, real-time monitoring of the dynamic chemical and structural changes in commercial 18650 LiFePO4/C cells under realistic cycling conditions. The results indicate a nonequilibrium lithium insertion and extraction in the LiFePO4 cathode, with neither the LiFePO4 phase nor the FePO4 phase maintaining a static composition during lithium insertion/extraction. On the basis of our observations, we propose that the LiFePO4 cathode simultaneously experiences both a two-phase reaction mechanism and a dual-phase solid-solution reaction mechanism over the entire range of the flat voltage plateau, with this dual-phase solid-solution behavior being strongly dependent on charge/discharge rates. The proposed dual-phase solid-solution mechanism may explain the remarkable rate capability of LiFePO4 in commercial cells.

A Structural Molar Volume Model for Oxide Melts Part III: Fe Oxide-Containing Melts

NASA Astrophysics Data System (ADS)

Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

2016-04-01

As part III of this series, the model is extended to iron oxide-containing melts. All available experimental data in the FeO-Fe2O3-Na2O-K2O-MgO-CaO-MnO-Al2O3-SiO2 system were critically evaluated based on the experimental condition. The variations of FeO and Fe2O3 in the melts were taken into account by using FactSage to calculate the Fe2+/Fe3+ distribution. The molar volume model with unary and binary model parameters can be used to predict the molar volume of the molten oxide of the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-FeO-Fe2O3-Al2O3-SiO2 system in the entire range of compositions, temperatures, and oxygen partial pressures from Fe saturation to 1 atm pressure.

Densities and Viscosities of the Quinary System: Cyclohexane (1) + \\varvec{m} -Xylene (2) + Cyclooctane (3) + Chlorobenzene (4) + Decane (5) and Its Quaternary Subsystems at 308.15 K and 313.15 K

NASA Astrophysics Data System (ADS)

Hamzehlouia, Sepehr; Asfour, Abdul-Fattah A.

2013-06-01

The volumetric and viscometric properties of the quinary system: cyclohexane + m -xylene + cyclooctane + chlorobenzene + decane, were measured over the entire composition range at 308.15 K and 313.15 K. The experimental data obtained in the course of the present study were employed to analyze the predictive capability of six semi-theoretical and empirical well-known viscosity models reported in the literature, namely, the generalized McAllister three-body interaction model, the pseudo- binary McAllister model, the group contribution model, the generalized corresponding states principle model, the Allan and Teja correlation, and the Grunberg and Nissan law of viscosity. The predictive capabilities of the models were compared using the percentage average absolute deviation (%AAD). The final results showed that the generalized McAllister model gives the lowest AADs of 3.3 % and 3.7 % at 308.15 K and 313.15 K, respectively.

Thermodynamic and acoustical properties of mixtures p-anisaldehyde—alkanols (C1-C4)—2-methyl-1-propanol at 303.15 K

NASA Astrophysics Data System (ADS)

Saini, Balwinder; Kumar, Ashwani; Rani, Ruby; Bamezai, Rajinder K.

2016-07-01

The density, viscosity and speed of sound of pure p-anisaldehyde and some alkanols, for example, methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol, butan-2-ol, 2-methylpropan-1-ol, and the binary mixtures of p-anisaldehyde with these alkanols were measured over the entire composition range at 303.15 K. From the experimental data, various thermodynamic parameters such as excess molar volume ( V E), excess Gibbs free energy of activation (Δ G*E), and deviation parameters like viscosity (Δη), speed of sound (Δ u), isentropic compressibility (Δκs), are calculated. The excess as well as deviation parameters are fitted to Redlich—Kister equation. Additionally, the viscosity data for the systems has been used to correlate the application of empirical relation given by Grunberg and Nissan, Katti and Chaudhari, and Hind et al. The results are discussed in terms of specific interactions present in the mixtures.

[Genetic Structure of Urban Population of the Common Hamster (Cricetus cricetus)].

PubMed

Feoktistova, N Yu; Meschersky, I G; Surov, A V; Bogomolov, P L; Tovpinetz, N N; Poplavskaya, N S

2016-02-01

Over the past half-century, the common hamster (Cricetus cricetus), along with range-wide decline of natural populations, has actively populated the cities. The study of the genetic structure of urban populations of common hamster may shed light on features of the habitation of this species in urban landscapes. This article is focused on the genetic structure of common hamster populations in Simferopol (Crimea), one of the largest known urban populations of this species. On the basis of the analysis of nucleotide sequences of the cytochrome b gene and mtDNA control region, and the allelic composition of ten microsatellite loci of nDNA, we revealed that, despite the fact that some individuals can move throughout the city at considerable distances, the entire population of the city is represented by separate demes confined to different areas. These demes are characterized by a high degree of the genetic isolation and reduced genetic diversity compared to that found for the city as a whole.

Diversity of Carabidae (Insecta, Coleoptera) in epiphytic Bromeliaceae in central Veracruz, Mexico.

PubMed

Montes de Oca, E; Ball, G E; Spence, J R

2007-06-01

This paper documents the existence of carabid assemblages associated with bromeliads on the Cofre de Perote, Veracruz, Mexico. Based on bromeliads sampled over three altitudinal ranges, the assemblages included at least 26 species with an arboreal lifestyle and another 11 species that are not strictly arboreal. Seven species are new to science, urging us to pay attention to the arboreal fauna in forest conservation studies. Composition of carabid assemblages associated with bromeliads changes with altitude. In lowlands, it is comprised almost entirely of species of Lebiini, with the Platynini dominating assemblages found in bromeliads >1,000 m above sea level. Our data suggest that carabids use bromeliads to reduce stresses associated with drought periods, the exact timing of which depends on altitude. The unexpected low diversity of the carabid fauna associated with bromeliads at middle altitude is explained in terms of anthropogenic conversion of the original forest to pastureland. Given the importance of arboreal elements, further fragmentation of subtropical and tropical mountain forest significantly threatens overall carabid diversity.

Thin Film Synthesis of New Complex Titanates.

NASA Astrophysics Data System (ADS)

Salvador, Paul

2008-03-01

Thin film deposition methods allow for one to synthesize rationally specific compositions in targeted crystal structures. Because most of the thermodynamic and kinetic variables that control the range of materials that can be synthesized are unknown for specific compounds/processes, epitaxial stabilization and design of artificially layered crystals are driven through empirical investigations. Using examples taken primarily from the family of complex titanates, which exhibit a range of interesting physicochemical behaviors, the thermodynamic and kinetic factors that control materials design using thin film deposition are discussed. The phase competition between the pyrochlore and the (110) layered perovskite structure in the RE2Ti2O7 family (RE = rare-earth, Bi) will be explored, using pulsed laser deposition as a synthesis method. For RE = Gd, Sm, Nd, and La, the phase stability over a wide range of conditions is dictated entirely by substrate choice, indicating that the free energies of the phases are similar enough such that by controlling nucleation one controls the phase formation. In a related fashion, the growth of AETi2O5 films (AE = Ba or Sr) will be discussed with respect to the formation of single-phase films or films that phase separate into AETiO3 and TiO2. The entire Ba1-xSrxTi2O5 series was grown and will be discussed with respect to growth technique (using MBE and PLD) and/or substrate choice. In this case, rock-salt substrates, which are not expected to interact strongly with any phase in the system, allow for the formation of single-phase films. Finally, several examples will be discussed with respect to the (SrO)m(TiO2)n system, which includes the perovskite SrTiO3 and the Ruddlesden-Popper phase Sr2TiO4, grown using layer-by-layer molecular beam epitaxy. The solid phase epitaxial formation of the perovskite SrTiO3 from superlattices of rock-salt SrO and anatase TiO2 is discussed from both a kinetic and thermodynamic perspective by exploring the growth of a range of m and n values. Using similar arguments for stability, new layered intergrowths in the SrmTiO2+m family are presented and their structures are discussed.

A prospective, randomized, comparative clinical study of resin composite and glass ionomer cement for retrograde root filling.

PubMed

Jensen, S S; Nattestad, A; Egdø, P; Sewerin, I; Munksgaard, E C; Schou, S

2002-12-01

To compare the clinical and radiographic treatment outcome of retrograde root filling with either dentin-bonded resin composite (Retroplast, RP) or glass ionomer cement (Chelon-Silver, CS). A prospective, randomized clinical study of 134 consecutive patients with indication of retrograde root filling of an incisor, canine, premolar, or first molar. Either RP or CS was chosen at random as retrograde filling material. Either material was applied onto the entire resection surface after prepared slightly concave. This preparation technique makes a sealing of the entire resection surface possible and prevents marginal contraction gaps during polymerization. A total of 122 patients were available for 1-year follow-up. After 1 year the proportion of successful cases was significantly higher in the RP group (73%) than in the CS group (31%) (p<0.001). Doubtful healing with a need for a longer observation period was seen in 17% of the RP cases and 19% of the CS cases. The proportion of failures in the RP group (10%) was significantly lower than that in the CS group (50%) (p<0.001). Most of the unsuccessful CS cases failed due to loosening of the retrograde filling. Dentin-bonded RP applied onto the entire, slightly concave resection surface is a predictable apical sealant characterized by a high success rate. In contrast, retrograde root filling with CS results in an unacceptably high failure rate due to insufficient bonding strength to the concave resection surface.

Assessment of preoperative nutritional status using BIA-derived phase angle (PhA) in patients with advanced ovarian cancer: Correlation with the extent of cytoreduction and complications.

PubMed

Uccella, Stefano; Mele, Maria Cristina; Quagliozzi, Lorena; Rinninella, Emanuele; Nero, Camilla; Cappuccio, Serena; Cintoni, Marco; Gasbarrini, Antonio; Scambia, Giovanni; Fagotti, Anna

2018-05-01

To investigate whether patients' altered body composition (measured with bioimpedentiometry), due to a poor nutritional status, predicts the incidence of no residual disease at primary debulking and the risk of complications in patients with newly-diagnosed advanced epithelial ovarian cancer (EOC). Data regarding patients with newly-diagnosed stage IIIC-IV EOC undergoing elective nutritional assessment between December 2016 and March 2017, were prospectively collected. Bioelectrical impedance analysis (BIA) with measurement of BIA-derived phase angle [PhA] at 50KHz, was accomplished. Only patients with disease which was considered resectable at staging laparoscopy were submitted to open primary cytoreduction. The rate of residual tumor (RT)=0 and the incidence of complications were assessed. Seventy patients were included. Fifty-two of them were submitted to primary cytoreduction (74.3%) and 48 (68.6% of the entire cohort, 92.3% of those who underwent primary debulking) had RT=0 at the end of surgery. Median values of PhA were significantly lower in patients with RT>vs. =0 (4.7, range: 3.6-5.8 vs. 5.3, range: 4.2-6.8; p=0.001). Twenty-four (out of the 52 operated) patients (46.2%) developed at least one complication. PhA was significantly lower in patients with vs. without complications (5, range: 3.6-6.4, vs. 5.4, range 4.5-6.8; p=0.03). After multivariable analysis, Fagotti score and PhA were the only independent predictors of residual disease (OR:13.56; 95%CI:1.33-137.6; p=0.027 and 9.24; 1.16-73.43; p=0.036, respectively) and of any complication (OR:4.9;95%CI:1.17-20.6; p=0.03 and 7.27; 1.45-36.4; p=0.01, respectively). Derangement of body composition (likely due to disease-related malnutrition) expressed as a low phase angle, is an independent predictor of residual disease and peri-operative complications at the time of upfront cytoreduction for advanced EOC. Copyright © 2018 Elsevier Inc. All rights reserved.

Quantum mechanical studies of complex ferroelectric perovskites

NASA Astrophysics Data System (ADS)

Ramer, Nicholas John

In many electronic device applications, there is a need to interconvert electrical energy and other types of energy. Ferroelectric materials, which possess a voltage-dependent polarization, can enable this energy conversion process. Because of the broad interest in ferroelectric materials for these devices, there is a critical research effort, both experimental and theoretical, to understand these materials and aid in the development of materials with improved properties. This thesis presents detailed quantum mechanical investigations of the behavior of a complex ferroelectric perovskite under applied stress. In particular, we have chosen to study the solid solution PbZr1-xTix O3 (PZT). Since the study of ferroelectricity involves understanding both its structural and electronic signatures in materials, it has necessitated the development of a novel theoretical technique which improves the accuracy of the pseudopotentials used in our density functional theory calculations as well as a new method for constructing three-dimensional atomistic responses to small amounts of external stress. To examine the material's behavior under larger amounts of stress, we have studied the behavior of a composition of PZT lying near a structural phase boundary. On either side of the phase boundary, the material is characterized by a different polarization direction and may easily be switched between phases by applying external stress. In addition to stress-induced phase transitions, most ferroelectric materials also have composition dependent phase boundaries. Since different compositions of PZT would require increased computational effort, we have formulated an improved virtual crystal approach that makes tractable the study of the entire composition range. Using this method, we have been able to show for the first time via first-principles calculations, a composition dependent phase transition in a ferroelectric material. This thesis has accomplished three important goals: new theoretical methodology has been developed to enable accurate modeling of complex materials; application of these methods has been demonstrated for the study of ferroelectric oxides; and these investigations have revealed new insights into the relationships between stress, chemical composition, and ferroelectricity in oxides. This set of accomplishments enables the future study of even more complex perovskites and other multi-component systems.

Kankan diamonds (Guinea) III: δ13C and nitrogen characteristics of deep diamonds

NASA Astrophysics Data System (ADS)

Stachel, T.; Harris, J. W.; Aulbach, S.; Deines, P.

Diamonds from the Kankan area in Guinea formed over a large depth profile beginning within the cratonic mantle lithosphere and extending through the asthenosphere and transition zone into the lower mantle. The carbon isotopic composition, the concentration of nitrogen impurities and the nitrogen aggregation level of diamonds representing this entire depth range have been determined. Peridotitic and eclogitic diamonds of lithospheric origin from Kankan have carbon isotopic compositions (δ13C: peridotitic -5.4 to -2.2‰ eclogitic -19.7 to -0.7‰) and nitrogen characteristics (N: peridotitic 17-648 atomic ppm; eclogitic 0-1,313 atomic ppm; aggregation from IaA to IaB) which are generally typical for diamonds of these two suites worldwide. Geothermobarometry of peridotitic and eclogitic inclusion parageneses (worldwide sources) indicates that both suites formed under very similar conditions within the cratonic lithosphere, which is not consistent with a derivation of diamonds with light carbon isotopic composition from subducted organic matter within subducting oceanic slabs. Diamonds containing majorite garnet inclusions fall to the isotopically heavy side (δ13C: -3.1‰ to +0.9‰) of the worldwide diamond population. Nitrogen contents are low (0-126 atomic ppm) and one of the two nitrogen-bearing diamonds shows such a low level of nitrogen aggregation (30% B-centre) that it cannot have been exposed to ambient temperatures of the transition zone (>=1,400 °C) for more than 0.2 Ma. This suggests rapid upward transport and formation of some Kankan diamonds pene-contemporaneous to Cretaceous kimberlite activity. Similar to these diamonds from the asthenosphere and the transition zone, lower mantle diamonds show a small shift towards isotopic heavy compositions (-6.6 to -0.5‰, mode at -3.5‰). As already observed for other mines, the nitrogen contents of lower mantle diamonds were below detection (using FTIRS). The mutual shift of sublithospheric diamonds towards isotopic heavier compositions suggests a common carbon source, which may have inherited an isotopic heavy composition from a component consisting of subducted carbonates.

Kankan diamonds (Guinea) III: δ13C and nitrogen characteristics of deep diamonds

NASA Astrophysics Data System (ADS)

Stachel, T.; Harris, J. W.; Aulbach, S.; Deines, P.

2001-08-01

Diamonds from the Kankan area in Guinea formed over a large depth profile beginning within the cratonic mantle lithosphere and extending through the asthenosphere and transition zone into the lower mantle. The carbon isotopic composition, the concentration of nitrogen impurities and the nitrogen aggregation level of diamonds representing this entire depth range have been determined. Peridotitic and eclogitic diamonds of lithospheric origin from Kankan have carbon isotopic compositions (δ13C: peridotitic -5.4 to -2.2‰ eclogitic -19.7 to -0.7‰) and nitrogen characteristics (N: peridotitic 17-648 atomic ppm; eclogitic 0-1,313 atomic ppm; aggregation from IaA to IaB) which are generally typical for diamonds of these two suites worldwide. Geothermobarometry of peridotitic and eclogitic inclusion parageneses (worldwide sources) indicates that both suites formed under very similar conditions within the cratonic lithosphere, which is not consistent with a derivation of diamonds with light carbon isotopic composition from subducted organic matter within subducting oceanic slabs. Diamonds containing majorite garnet inclusions fall to the isotopically heavy side (δ13C: -3.1‰ to +0.9‰) of the worldwide diamond population. Nitrogen contents are low (0-126 atomic ppm) and one of the two nitrogen-bearing diamonds shows such a low level of nitrogen aggregation (30% B-centre) that it cannot have been exposed to ambient temperatures of the transition zone (>=1,400 °C) for more than 0.2 Ma. This suggests rapid upward transport and formation of some Kankan diamonds pene-contemporaneous to Cretaceous kimberlite activity. Similar to these diamonds from the asthenosphere and the transition zone, lower mantle diamonds show a small shift towards isotopic heavy compositions (-6.6 to -0.5‰, mode at -3.5‰). As already observed for other mines, the nitrogen contents of lower mantle diamonds were below detection (using FTIRS). The mutual shift of sublithospheric diamonds towards isotopic heavier compositions suggests a common carbon source, which may have inherited an isotopic heavy composition from a component consisting of subducted carbonates.

The Million-Body Problem: Particle Simulations in Astrophysics

ScienceCinema

Rasio, Fred

2018-05-21

Computer simulations using particles play a key role in astrophysics. They are widely used to study problems across the entire range of astrophysical scales, from the dynamics of stars, gaseous nebulae, and galaxies, to the formation of the largest-scale structures in the universe. The 'particles' can be anything from elementary particles to macroscopic fluid elements, entire stars, or even entire galaxies. Using particle simulations as a common thread, this talk will present an overview of computational astrophysics research currently done in our theory group at Northwestern. Topics will include stellar collisions and the gravothermal catastrophe in dense star clusters.

Development of ingan quantum dots by the Stranski-Krastanov method and droplet heteroepitaxy

NASA Astrophysics Data System (ADS)

Woodward, Jeffrey Michael

The development of InGaN quantum dots (QDs) is both scienti?cally challenging and promising for applications in visible spectrum LEDs, lasers, detectors, electroabsorption modulators and photovoltaics. Such QDs are typically grown using the Stranski-Krastanov (SK) growth mode, in which accumulated in-plane compressive strain induces a transition from 2D to 3D growth. This method has a number of inherent limitations, including the unavoidable formation of a 2D wetting layer and the di?culty of controlling the composition, areal density, and size of the dots. In this research, I have developed InGaN QDs by two methods using a plasma-assisted molecular beam epitaxy reactor. In the ?rst method, InGaN QDs were formed by SK growth mode on (0001) GaN/sapphire. In the second, I have addressed the limitations of the SK growth of InGaN QDs by developing a novel alternative method, which was utilized to grow on both (0001) GaN/sapphire and AlN/sapphire. This method relies upon the ability to form thermodynamically stable In-Ga liquid solutions throughout the entire compositional range at relatively low temperatures. Upon simultaneous or sequential deposition of In and Ga on a substrate, the adatoms form a liquid solution, whose composition is controlled by the ratio of the fluxes of the two constituents FIn/(FIn+FGa ). Depending on the interfacial free energy between the liquid deposit and substrate, the liquid deposit and vapor, and the vapor and substrate, the liquid deposit forms Inx-Ga1- x nano-droplets on the substrate. These nano-droplets convert into InxGa1-xN QDs upon exposure to nitrogen RF plasma. InGaN QDs produced by both methods were investigated in-situ by reflection high-energy electron diffraction and ex-situ by atomic force microscopy, field emission scanning electron microscopy, transmission electron microscopy, high resolution x-ray diffraction, and grazing incidence small angle x-ray scattering. The optical activity and device potential of the QDs were investigated by photoluminescence measurements and the formation and evaluation of PIN devices (in which the intrinsic region contains QDs embedded within a higher bandgap matrix). InGaN QDs with areal densities ranging from 109 to 1011 cm -2 and diameters ranging from 11 to 39 nm were achieved.

The power and robustness of maximum LOD score statistics.

PubMed

Yoo, Y J; Mendell, N R

2008-07-01

The maximum LOD score statistic is extremely powerful for gene mapping when calculated using the correct genetic parameter value. When the mode of genetic transmission is unknown, the maximum of the LOD scores obtained using several genetic parameter values is reported. This latter statistic requires higher critical value than the maximum LOD score statistic calculated from a single genetic parameter value. In this paper, we compare the power of maximum LOD scores based on three fixed sets of genetic parameter values with the power of the LOD score obtained after maximizing over the entire range of genetic parameter values. We simulate family data under nine generating models. For generating models with non-zero phenocopy rates, LOD scores maximized over the entire range of genetic parameters yielded greater power than maximum LOD scores for fixed sets of parameter values with zero phenocopy rates. No maximum LOD score was consistently more powerful than the others for generating models with a zero phenocopy rate. The power loss of the LOD score maximized over the entire range of genetic parameters, relative to the maximum LOD score calculated using the correct genetic parameter value, appeared to be robust to the generating models.

The System of Chemical Elements Distribution in the Hydrosphere

NASA Astrophysics Data System (ADS)

Korzh, Vyacheslav D.

2013-04-01

The chemical composition of the hydrosphere is a result of substance migration and transformation on lithosphere-river, river-sea, and ocean-atmosphere boundaries. The chemical elements composition of oceanic water is a fundamental multi-dimensional constant for our planet. Detailed studies revealed three types of chemical element distribution in the ocean: 1) Conservative: concentration normalized to salinity is the constant in space and time; 2) Nutrient-type: element concentration in the surface waters decreases due to the biosphere consumption; and 3) Litho-generative: complex character of distribution of elements, which enter the ocean with the river runoff and interred almost entirely in sediments. The correlation between the chemical elements compositions of the river and oceanic water is high (r = 0.94). We conclude that biogeochemical features of each chemical element are determined by the relationship between its average concentration in the ocean and the intensity of its migration through hydrosphere boundary zones. In our presentation, we shall show intensities of global migration and average concentrations in the ocean in the co ordinates lgC - lg [tau], where C is an average element concentration and [tau] is its residence time in the ocean. We have derived a relationship between three main geochemical parameters of the dissolved forms of chemical elements in the hydrosphere: 1) average concentration in the ocean, 2) average concentration in the river runoff and 3) the type of distribution in oceanic water. Using knowledge of two of these parameters, it allows gaining theoretical knowledge of the third. The System covers all chemical elements for the entire range of observed concentrations. It even allows to predict the values of the annual river transport of dissolved Be, C, N, Ge, Tl, Re, to refine such estimates for P, V, Zn, Br, I, and to determine the character of distribution in the ocean for Au and U. Furthermore, the System allowed estimating natural (unaffected by anthropogenic influence) mean concentrations of elements in the river runoff and using them as ecological reference data. Finally, due to the long response time of the ocean, the mean concentrations of elements and patterns of their distribution in the ocean can be used to determine pre-techno-generative concentrations of elements in the river runoff. In our presentation, we shall show several examples of implementation of the System for studying the sediments' transport by the rivers of the Arctic slope of Northern Eurasia. References 1. Korzh V.D. 1974: Some general laws governing the turnover of substance within the ocean-atmosphere-continent-ocean cycle. Journal de Recherches Atmospheriques, 8, 653-660. 2. Korzh V.D. 2008: The general laws in the formation of the element composition of the Hydrosphere and Biosphere. J. Ecologica, 15, 13-21. 3. Korzh V.D. 2012: Determination of general laws of the chemical element composition in Hydrosphere. Water: Chemistry & Ecology, Journal of Water Science and its Practical Application. No. 1, 56-62.

Behaviour of Structural Carbonate Stable Carbon and Oxygen Isotope Compositions in Bioapatite During Burning of Bone

NASA Astrophysics Data System (ADS)

Munro, L. E.; Longstaffe, F. J.; White, C. D.

2003-12-01

Bioapatite, the principal inorganic phase comprising bone, commonly contains a small fraction of carbonate, which has been substituted into the phosphate structure during bone formation. The isotopic compositions of both the phosphate oxygen and the structural carbonate oxygen are now commonly used in palaeoclimatological and bioarchaeological investigations. The potential for post-mortem alteration of these isotopic compositions, therefore, is of interest, with the behaviour of structural carbonate being of most concern. In bioarchaeological studies, alteration of bone isotopic compositions has the potential to occur not only during low-temperature processes associated with burial but also during food preparation involving heating (burning, boiling). Here, we examine the stable isotopic behaviour of structural carbonate oxygen and carbon, and coexisting phosphate oxygen during the burning of bone. Freshly deceased (6<8 months) white-tailed deer leg bones (Odocoileus virginianus) were collected from Pinery Provincial Park, Ontario, Canada. Each long bone was sectioned and incrementally heated from 25 to 900° C, in 25° intervals. The samples were then ground to a standardized grain-size (45<63μ m), and changes in bioapatite crystallinity (CI) were determined using powder X-ray diffraction (pXRD), and Fourier transform infra-red spectroscopy (FTIR). Combined differential thermal and thermogravimetric analyses (DTA/TG) were used to evaluate weight loss and associated reactions during heating. Stable carbon isotope compositions of the bioapatite remain relatively constant (+/-1‰ ) during heating to 650° C. A 4‰ increase in stable carbon isotopic composition then occurs between 650-750° C, accompanied by an increase in CI, followed by a 10‰ decline at temperatures above 800° C, as carbonate carbon is lost. Carbonate and phosphate oxygen isotopic compositions are correlated over the entire heating range, with carbonate being enriched relative to phosphate by about 8-10‰ below 500° C, 5-6‰ between 500-700° C, and 8-10‰ above 700° C. CI and oxygen isotopic compositions of carbonate and phosphate are not well correlated. Only modest CI changes are recorded from 25-675° C, compared with much larger changes in oxygen isotopic composition, especially above 300° C. On average, original isotopic compositions are largely preserved for both phosphate (+/-1‰ ) and carbonate (+/-2‰ ) oxygen at <300° C. At higher temperatures, however, both phosphate and carbonate oxygen in the bioapatite are systematically depleted of oxygen-18 relative to original values.

National Composite Center-A new roof for composite industries in Malaysia

NASA Astrophysics Data System (ADS)

Abdullah, Abu; Yuhazri, M. Y.; Sulaiman, Mohd Yusoff

2016-03-01

Today's Malaysia has more than 70 companies that are actively involved in composite activities. The activities are ranging from various business sectors, using different technology and material. Composites has been used in a wide range of applications in Malaysia and contributes to growth in a diverse range of industry value chains from utilities through to boat building, manufacturing and industrial applications, aerospace, consumer products and construction products. Thus, a key part of this strategy is the establishment of the National Composites Centre (NCC), which will bring together dynamic companies and enterprising academics to develop new technologies for the design and rapid manufacture of high-quality composite products.

Adiposity to muscle ratio predicts incident physical limitation in a cohort of 3,153 older adults--an alternative measurement of sarcopenia and sarcopenic obesity.

PubMed

Auyeung, Tung Wai; Lee, Jenny Shun Wah; Leung, Jason; Kwok, Timothy; Woo, Jean

2013-08-01

Conventionally, sarcopenia is defined by muscle mass and physical performance. We hypothesized that the disability caused by sarcopenia and sarcopenic obesity was related to the amount of adiposity or body weight bearing on a unit of muscle mass, or the adiposity to muscle ratio. We therefore examined whether this ratio could predict physical limitation by secondary analysis of the data in our previous study. We recruited 3,153 community-dwelling adults aged >65 years and their body composition was measured by dual-energy X-ray absorptiometry. Assessment of physical limitation was undertaken 4 years later. The relationship between baseline adiposity to muscle ratio and incident physical limitation was examined by logistic regression. In men, the adiposity to muscle ratios, namely total body fat to lower-limb muscle mass, total body fat to fat-free mass (FFM), and body weight to FFM, were predictive of physical limitation before and after adjustment for the covariates: age, Mini-mental Status Examination score, Geriatric Depression Scale score >8, and the diagnosis of chronic obstructive pulmonary disease, diabetes mellitus, hypertension, heart disease, and stroke (all p values < 0.001), when the total body fat to lower-limb muscle mass ratio was greater than or equal to 0.75. In women, throughout the entire range of that ratio, all three adiposity to muscle ratios were associated with physical limitation 4 years later both before and after adjustment for the same set of covariates (all p values < 0.05). Sarcopenia and sarcopenic obesity as measured by the body weight or adiposity bearing on a unit of muscle mass (the adiposity to muscle ratio) could predict incident or worsening physical limitation in older women across the entire range of the total body fat to lower-limb muscle mass ratio; and in older men when this ratio was equal to or greater than 0.75.

Non-crosslinked, amorphous, block copolymer electrolyte for batteries

DOEpatents

Mayes, Anne M.; Ceder, Gerbrand; Chiang, Yet-Ming; Sadoway, Donald R.; Aydinol, Mehmet K.; Soo, Philip P.; Jang, Young-Il; Huang, Biying

2006-04-11

Solid battery components are provided. A block copolymeric electrolyte is non-crosslinked and non-glassy through the entire range of typical battery service temperatures, that is, through the entire range of at least from about 0.degree. C. to about 70.degree. C. The chains of which the copolymer is made each include at least one ionically-conductive block and at least one second block immiscible with the ionically-conductive block. The chains form an amorphous association and are arranged in an ordered nanostructure including a continuous matrix of amorphous ionically-conductive domains and amorphous second domains that are immiscible with the ionically-conductive domains. A compound is provided that has a formula of Li.sub.xM.sub.yN.sub.zO.sub.2. M and N are each metal atoms or a main group elements, and x, y and z are each numbers from about 0 to about 1. y and z are chosen such that a formal charge on the M.sub.yN.sub.z portion of the compound is (4-x). In certain embodiments, these compounds are used in the cathodes of rechargeable batteries. The present invention also includes methods of predicting the potential utility of metal dichalgogenide compounds for use in lithium intercalation compounds. It also provides methods for processing lithium intercalation oxides with the structure and compositional homogeneity necessary to realize the increased formation energies of said compounds. An article is made of a dimensionally-stable, interpenetrating microstructure of a first phase including a first component and a second phase, immiscible with the first phase, including a second component. The first and second phases define interphase boundaries between them, and at least one particle is positioned between a first phase and a second phase at an interphase boundary. When the first and second phases are electronically-conductive and ionically-conductive polymers, respectively, and the particles are ion host particles, the arrangement is an electrode of a battery.

Comparison of Cyclic Hysteresis Behavior between Cross-Ply C/SiC and SiC/SiC Ceramic-Matrix Composites

PubMed Central

Li, Longbiao

2016-01-01

In this paper, the comparison of cyclic hysteresis behavior between cross-ply C/SiC and SiC/SiC ceramic-matrix composites (CMCs) has been investigated. The interface slip between fibers and the matrix existed in the matrix cracking mode 3 and mode 5, in which matrix cracking and interface debonding occurred in the 0° plies are considered as the major reason for hysteresis loops of cross-ply CMCs. The hysteresis loops of cross-ply C/SiC and SiC/SiC composites corresponding to different peak stresses have been predicted using present analysis. The damage parameter, i.e., the proportion of matrix cracking mode 3 in the entire matrix cracking modes of the composite, and the hysteresis dissipated energy increase with increasing peak stress. The damage parameter and hysteresis dissipated energy of C/SiC composite under low peak stress are higher than that of SiC/SiC composite; However, at high peak stress, the damage extent inside of cross-ply SiC/SiC composite is higher than that of C/SiC composite as more transverse cracks and matrix cracks connect together. PMID:28787861

Bonded repair of composite aircraft structures: A review of scientific challenges and opportunities

NASA Astrophysics Data System (ADS)

Katnam, K. B.; Da Silva, L. F. M.; Young, T. M.

2013-08-01

Advanced composite materials have gained popularity in high-performance structural designs such as aerospace applications that require lightweight components with superior mechanical properties in order to perform in demanding service conditions as well as provide energy efficiency. However, one of the major challenges that the aerospace industry faces with advanced composites - because of their inherent complex damage behaviour - is structural repair. Composite materials are primarily damaged by mechanical loads and/or environmental conditions. If material damage is not extensive, structural repair is the only feasible solution as replacing the entire component is not cost-effective in many cases. Bonded composite repairs (e.g. scarf patches) are generally preferred as they provide enhanced stress transfer mechanisms, joint efficiencies and aerodynamic performance. With an increased usage of advanced composites in primary and secondary aerospace structural components, it is thus essential to have robust, reliable and repeatable structural bonded repair procedures to restore damaged composite components. But structural bonded repairs, especially with primary structures, pose several scientific challenges with the current existing repair technologies. In this regard, the area of structural bonded repair of composites is broadly reviewed - starting from damage assessment to automation - to identify current scientific challenges and future opportunities.

Comparison of Cyclic Hysteresis Behavior between Cross-Ply C/SiC and SiC/SiC Ceramic-Matrix Composites.

PubMed

Li, Longbiao

2016-01-19

In this paper, the comparison of cyclic hysteresis behavior between cross-ply C/SiC and SiC/SiC ceramic-matrix composites (CMCs) has been investigated. The interface slip between fibers and the matrix existed in the matrix cracking mode 3 and mode 5, in which matrix cracking and interface debonding occurred in the 0° plies are considered as the major reason for hysteresis loops of cross-ply CMCs. The hysteresis loops of cross-ply C/SiC and SiC/SiC composites corresponding to different peak stresses have been predicted using present analysis. The damage parameter, i.e. , the proportion of matrix cracking mode 3 in the entire matrix cracking modes of the composite, and the hysteresis dissipated energy increase with increasing peak stress. The damage parameter and hysteresis dissipated energy of C/SiC composite under low peak stress are higher than that of SiC/SiC composite; However, at high peak stress, the damage extent inside of cross-ply SiC/SiC composite is higher than that of C/SiC composite as more transverse cracks and matrix cracks connect together.

Considerations for acoustic emission monitoring of spherical Kevlar/epoxy composite pressure vessels

NASA Technical Reports Server (NTRS)

Hamstad, M. A.; Patterson, R. G.

1977-01-01

We are continuing to research the applications of acoustic emission testing for predicting burst pressure of filament-wound Kevlar 49/epoxy pressure vessels. This study has focused on three specific areas. The first area involves development of an experimental technique and the proper instrumentation to measure the energy given off by the acoustic emission transducer per acoustic emission burst. The second area concerns the design of a test fixture in which to mount the composite vessel so that the acoustic emission transducers are held against the outer surface of the composite. Included in this study area is the calibration of the entire test setup including couplant, transducer, electronics, and the instrument measuring the energy per burst. In the third and final area of this study, we consider the number, location, and sensitivity of the acoustic emission transducers used for proof testing composite pressure vessels.

Canopies to Continents: What spatial scales are needed to represent landcover distributions in earth system models?

NASA Astrophysics Data System (ADS)

Guenther, A. B.; Duhl, T.

2011-12-01

Increasing computational resources have enabled a steady improvement in the spatial resolution used for earth system models. Land surface models and landcover distributions have kept ahead by providing higher spatial resolution than typically used in these models. Satellite observations have played a major role in providing high resolution landcover distributions over large regions or the entire earth surface but ground observations are needed to calibrate these data and provide accurate inputs for models. As our ability to resolve individual landscape components improves, it is important to consider what scale is sufficient for providing inputs to earth system models. The required spatial scale is dependent on the processes being represented and the scientific questions being addressed. This presentation will describe the development a contiguous U.S. landcover database using high resolution imagery (1 to 1000 meters) and surface observations of species composition and other landcover characteristics. The database includes plant functional types and species composition and is suitable for driving land surface models (CLM and MEGAN) that predict land surface exchange of carbon, water, energy and biogenic reactive gases (e.g., isoprene, sesquiterpenes, and NO). We investigate the sensitivity of model results to landcover distributions with spatial scales ranging over six orders of magnitude (1 meter to 1000000 meters). The implications for predictions of regional climate and air quality will be discussed along with recommendations for regional and global earth system modeling.

Mutual diffusion of binary liquid mixtures containing methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride

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

Guevara-Carrion, Gabriela; Janzen, Tatjana; Muñoz-Muñoz, Y. Mauricio

Mutual diffusion coefficients of all 20 binary liquid mixtures that can be formed out of methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride without a miscibility gap are studied at ambient conditions of temperature and pressure in the entire composition range. The considered mixtures show a varying mixing behavior from almost ideal to strongly non-ideal. Predictive molecular dynamics simulations employing the Green-Kubo formalism are carried out. Radial distribution functions are analyzed to gain an understanding of the liquid structure influencing the diffusion processes. It is shown that cluster formation in mixtures containing one alcoholic component has a significant impactmore » on the diffusion process. The estimation of the thermodynamic factor from experimental vapor-liquid equilibrium data is investigated, considering three excess Gibbs energy models, i.e., Wilson, NRTL, and UNIQUAC. It is found that the Wilson model yields the thermodynamic factor that best suits the simulation results for the prediction of the Fick diffusion coefficient. Four semi-empirical methods for the prediction of the self-diffusion coefficients and nine predictive equations for the Fick diffusion coefficient are assessed and it is found that methods based on local composition models are more reliable. Finally, the shear viscosity and thermal conductivity are predicted and in most cases favorably compared with experimental literature values.« less

On the Distribution of Protein Refractive Index Increments

PubMed Central

Zhao, Huaying; Brown, Patrick H.; Schuck, Peter

2011-01-01

The protein refractive index increment, dn/dc, is an important parameter underlying the concentration determination and the biophysical characterization of proteins and protein complexes in many techniques. In this study, we examine the widely used assumption that most proteins have dn/dc values in a very narrow range, and reappraise the prediction of dn/dc of unmodified proteins based on their amino acid composition. Applying this approach in large scale to the entire set of known and predicted human proteins, we obtain, for the first time, to our knowledge, an estimate of the full distribution of protein dn/dc values. The distribution is close to Gaussian with a mean of 0.190 ml/g (for unmodified proteins at 589 nm) and a standard deviation of 0.003 ml/g. However, small proteins <10 kDa exhibit a larger spread, and almost 3000 proteins have values deviating by more than two standard deviations from the mean. Due to the widespread availability of protein sequences and the potential for outliers, the compositional prediction should be convenient and provide greater accuracy than an average consensus value for all proteins. We discuss how this approach should be particularly valuable for certain protein classes where a high dn/dc is coincidental to structural features, or may be functionally relevant such as in proteins of the eye. PMID:21539801

Modifying plants for biofuel and biomaterial production.

PubMed

Furtado, Agnelo; Lupoi, Jason S; Hoang, Nam V; Healey, Adam; Singh, Seema; Simmons, Blake A; Henry, Robert J

2014-12-01

The productivity of plants as biofuel or biomaterial crops is established by both the yield of plant biomass per unit area of land and the efficiency of conversion of the biomass to biofuel. Higher yielding biofuel crops with increased conversion efficiencies allow production on a smaller land footprint minimizing competition with agriculture for food production and biodiversity conservation. Plants have traditionally been domesticated for food, fibre and feed applications. However, utilization for biofuels may require the breeding of novel phenotypes, or new species entirely. Genomics approaches support genetic selection strategies to deliver significant genetic improvement of plants as sources of biomass for biofuel manufacture. Genetic modification of plants provides a further range of options for improving the composition of biomass and for plant modifications to assist the fabrication of biofuels. The relative carbohydrate and lignin content influences the deconstruction of plant cell walls to biofuels. Key options for facilitating the deconstruction leading to higher monomeric sugar release from plants include increasing cellulose content, reducing cellulose crystallinity, and/or altering the amount or composition of noncellulosic polysaccharides or lignin. Modification of chemical linkages within and between these biomass components may improve the ease of deconstruction. Expression of enzymes in the plant may provide a cost-effective option for biochemical conversion to biofuel. © 2014 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

Fabrication and Testing of Durable Redundant and Fluted-Core Joints for Composite Sandwich Structures

NASA Technical Reports Server (NTRS)

Lin, Shih-Yung; Splinter, Scott C.; Tarkenton, Chris; Paddock, David A.; Smeltzer, Stanley S.; Ghose, Sayata; Guzman, Juan C.; Stukus, Donald J.; McCarville, Douglas A.

2013-01-01

The development of durable bonded joint technology for assembling composite structures is an essential component of future space technologies. While NASA is working toward providing an entirely new capability for human space exploration beyond low Earth orbit, the objective of this project is to design, fabricate, analyze, and test a NASA patented durable redundant joint (DRJ) and a NASA/Boeing co-designed fluted-core joint (FCJ). The potential applications include a wide range of sandwich structures for NASA's future launch vehicles. Three types of joints were studied -- splice joint (SJ, as baseline), DRJ, and FCJ. Tests included tension, after-impact tension, and compression. Teflon strips were used at the joint area to increase failure strength by shifting stress concentration to a less sensitive area. Test results were compared to those of pristine coupons fabricated utilizing the same methods. Tensile test results indicated that the DRJ design was stiffer, stronger, and more impact resistant than other designs. The drawbacks of the DRJ design were extra mass and complex fabrication processes. The FCJ was lighter than the DRJ but less impact resistant. With barely visible but detectable impact damages, all three joints showed no sign of tensile strength reduction. No compression test was conducted on any impact-damaged sample due to limited scope and resource. Failure modes and damage propagation were also studied to support progressive damage modeling of the SJ and the DRJ.

Rotations and Abundances of Blue Horizontal-Branch Stars in Globular Cluster M15.

PubMed

Behr; Cohen; McCarthy

2000-03-01

High-resolution optical spectra of 18 blue horizontal-branch stars in the globular cluster M15 indicate that their stellar rotation rates and photospheric compositions vary strongly as a function of effective temperature. Among the cooler stars in the sample, at Teff approximately 8500 K, metal abundances are in rough agreement with the canonical cluster metallicity, and the vsini rotations appear to have a bimodal distribution, with eight stars at vsini<15 km s-1 and two stars at vsini approximately 35 km s-1. Most of the stars at Teff>/=10,000 K, however, are slowly rotating, vsini<7 km s-1, and their iron and titanium are enhanced by a factor of 300 to solar abundance levels. Magnesium maintains a nearly constant abundance over the entire range of Teff, and helium is depleted by factors of 10-30 in three of the hotter stars. Diffusion effects in the stellar atmospheres are the most likely explanation for these large differences in composition. Our results are qualitatively very similar to those previously reported for M13 and NGC 6752, but with even larger enhancement amplitudes, presumably due to the increased efficiency of radiative levitation at lower intrinsic [Fe/H]. We also see evidence for faster stellar rotation explicitly preventing the onset of the diffusion mechanisms among a subset of the hotter stars.

On the distribution of protein refractive index increments.

PubMed

Zhao, Huaying; Brown, Patrick H; Schuck, Peter

2011-05-04

The protein refractive index increment, dn/dc, is an important parameter underlying the concentration determination and the biophysical characterization of proteins and protein complexes in many techniques. In this study, we examine the widely used assumption that most proteins have dn/dc values in a very narrow range, and reappraise the prediction of dn/dc of unmodified proteins based on their amino acid composition. Applying this approach in large scale to the entire set of known and predicted human proteins, we obtain, for the first time, to our knowledge, an estimate of the full distribution of protein dn/dc values. The distribution is close to Gaussian with a mean of 0.190 ml/g (for unmodified proteins at 589 nm) and a standard deviation of 0.003 ml/g. However, small proteins <10 kDa exhibit a larger spread, and almost 3000 proteins have values deviating by more than two standard deviations from the mean. Due to the widespread availability of protein sequences and the potential for outliers, the compositional prediction should be convenient and provide greater accuracy than an average consensus value for all proteins. We discuss how this approach should be particularly valuable for certain protein classes where a high dn/dc is coincidental to structural features, or may be functionally relevant such as in proteins of the eye. Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Mind the cell: Seasonal variation in telomere length mirrors changes in leucocyte profile.

PubMed

Beaulieu, Michaël; Benoit, Laure; Abaga, Steven; Kappeler, Peter M; Charpentier, Marie J E

2017-10-01

Leucocytes are typically considered as a whole in studies examining telomere dynamics in mammals. Such an approach may be precarious, as leucocytes represent the only nucleated blood cells in mammals, their composition varies temporally, and telomere length differs between leucocyte types. To highlight this limitation, we examined here whether seasonal variation in leucocyte composition was related to variation in telomere length in free-ranging mandrills (Mandrilllus sphinx). We found that the leucocyte profile of mandrills varied seasonally, with lower lymphocyte proportion being observed during the long dry season presumably because of the combined effects of high nematode infection and stress at that time of the year. Interestingly, this low lymphocyte proportion during the long dry season was associated with shorter telomeres. Accordingly, based on longitudinal data, we found that seasonal changes in lymphocyte proportion were reflected by corresponding seasonal variation in telomere length. Overall, these results suggest that variation in lymphocyte proportion in blood can significantly affect telomere measurements in mammals. However, lymphocyte proportion did not entirely explain variation in telomere length. For instance, a lower lymphocyte proportion with age could not fully explain shorter telomeres in older individuals. Overall, our results show that telomere length and leucocyte profile are strongly although imperfectly intertwined, which may obscure the relationship between telomere dynamics and ageing processes in mammals. © 2017 John Wiley & Sons Ltd.

Estimation of urinary stone composition by automated processing of CT images.

PubMed

Chevreau, Grégoire; Troccaz, Jocelyne; Conort, Pierre; Renard-Penna, Raphaëlle; Mallet, Alain; Daudon, Michel; Mozer, Pierre

2009-10-01

The objective of this article was developing an automated tool for routine clinical practice to estimate urinary stone composition from CT images based on the density of all constituent voxels. A total of 118 stones for which the composition had been determined by infrared spectroscopy were placed in a helical CT scanner. A standard acquisition, low-dose and high-dose acquisitions were performed. All voxels constituting each stone were automatically selected. A dissimilarity index evaluating variations of density around each voxel was created in order to minimize partial volume effects: stone composition was established on the basis of voxel density of homogeneous zones. Stone composition was determined in 52% of cases. Sensitivities for each compound were: uric acid: 65%, struvite: 19%, cystine: 78%, carbapatite: 33.5%, calcium oxalate dihydrate: 57%, calcium oxalate monohydrate: 66.5%, brushite: 75%. Low-dose acquisition did not lower the performances (P < 0.05). This entirely automated approach eliminates manual intervention on the images by the radiologist while providing identical performances including for low-dose protocols.

Timing of wet episodes in Atacama Desert over the last 15 ka. The Groundwater Discharge Deposits (GWD) from Domeyko Range at 25°S.

NASA Astrophysics Data System (ADS)

Sáez, Alberto; Godfrey, Linda V.; Herrera, Christian; Chong, Guillermo; Pueyo, Juan J.

2016-08-01

A chronologically robust reconstruction of timing and dynamics of millennial time scale wet episodes encompassing the entire Atacama Desert during the last 15 ka has been constructed. To accomplish this, a new composite paleoclimatic record from Groundwater Discharge Deposits (GWD) in the Sierra de Varas (Domeyko Range, southern Atacama in Chile at 25°S) has been compiled and compared with other published paleohydrologic records from the Atacama region. In Sierra de Varas (SV), three millennial timescale wet climate phases have been characterized: around 14.5 ka cal BP, 12.2-9.8 ka cal BP, and 4.7 ka cal BP to the present day. These wet phases are interpreted from intervals of GWD facies formed during periods when the springs were active. GWD facies include: (1) black organic peat, rooted mudstones and sandstones formed in local wetland environments, and (2) gypsum-carbonate rich layers formed by interstitial growth. GWD intervals alternate with gravelly alluvial material deposited during arid phases. A trend towards less humid conditions during the Late Holocene wet episode characterizes GWD sedimentary series in Sierra the Varas, suggesting the onset of a dry episode over the last few centuries. Around 0.7 ka BP a very short wet episode is recorded in the central part of the desert suggesting this was the time of maximum humidity for the entire late Holocene wet period. A brief arid phase occurred between 1.5 and 2.0 ka BP indicated by the absence of GWD in the Domeyko Range. The paleoclimatic reconstruction encompassing the entire Atacama region shows that both the intensity and occurrence of wetter conditions were governed mainly by the distance to the source of moisture, and secondarily by the elevation of the sites. In the northern Atacama (16-20°S), four wet phases fed by N-NE summer monsoon precipitations have been proposed: Tauca phase (18-14 ka cal BP) and Coipasa phase (13-10 ka cal BP) during the Late Glacial, followed by Early Holocene and Late Holocene phases. In contrast, southern Atacama records (23-28°S) display only three pluvial periods which result from SE summer monsoon precipitation and outbreaks from the Westerlies during wintertime. The Early Holocene in the southern Atacama was a period of aridity, generating important landscape differences to those in the Northern Atacama where conditions were wetter. The core of Atacama (20-23°S) is the overall driest part of the desert because it is located in the distal limits of both N-NE and SE sources of moisture, the Amazon Basin and Gran Chaco areas, respectively.

DWPF STARTUP FRIT VISCOSITY MEASUREMENT ROUND ROBIN RESULTS

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

Crum, Jarrod V.; Edwards, Tommy B.; Russell, Renee L.

2012-07-31

A viscosity standard is needed to replace the National Institute of Standards and Technology (NIST) glasses currently being used to calibrate viscosity measurement equipment. The current NIST glasses are either unavailable or less than ideal for calibrating equipment to measure the viscosity of high-level waste glasses. This report documents the results of a viscosity round robin study conducted on the Defense Waste Processing Facility (DWPF) startup frit. DWPF startup frit was selected because its viscosity-temperature relationship is similar to most DWPF and Hanford high-level waste glass compositions. The glass underwent grinding and blending to homogenize the large (100 lb) batch.more » Portions of the batch were supplied to the laboratories (named A through H) for viscosity measurements following a specified temperature schedule with a temperature range of 1150 C to 950 C and with an option to measure viscosity at lower temperatures if their equipment was capable of measuring at the higher viscosities. Results were used to fit the Vogel-Tamman-Fulcher and Arrhenius equations to viscosity as a function of temperature for the entire temperature range of 460 C through 1250 C as well as the limited temperature interval of approximately 950 C through 1250 C. The standard errors for confidence and prediction were determined for the fitted models.« less

Effective Identification of Low-Gliadin Wheat Lines by Near Infrared Spectroscopy (NIRS): Implications for the Development and Analysis of Foodstuffs Suitable for Celiac Patients.

PubMed

García-Molina, María Dolores; García-Olmo, Juan; Barro, Francisco

2016-01-01

The aim of this work was to assess the ability of Near Infrared Spectroscopy (NIRS) to distinguish wheat lines with low gliadin content, obtained by RNA interference (RNAi), from non-transgenic wheat lines. The discriminant analysis was performed using both whole grain and flour. The transgenic sample set included 409 samples for whole grain sorting and 414 samples for flour experiments, while the non-transgenic set consisted of 126 and 156 samples for whole grain and flour, respectively. Samples were scanned using a Foss-NIR Systems 6500 System II instrument. Discrimination models were developed using the entire spectral range (400-2500 nm) and ranges of 400-780 nm, 800-1098 nm and 1100-2500 nm, followed by analysis of means of partial least square (PLS). Two external validations were made, using samples from the years 2013 and 2014 and a minimum of 99% of the flour samples and 96% of the whole grain samples were classified correctly. The results demonstrate the ability of NIRS to successfully discriminate between wheat samples with low-gliadin content and wild types. These findings are important for the development and analysis of foodstuff for celiac disease (CD) patients to achieve better dietary composition and a reduction in disease incidence.

Characterization and variability of particle size distributions in Hudson Bay, Canada

NASA Astrophysics Data System (ADS)

Xi, Hongyan; Larouche, Pierre; Tang, Shilin; Michel, Christine

2014-06-01

Particle size distribution (PSD) plays a significant role in many aspects of aquatic ecosystems, including phytoplankton dynamics, sediment fluxes, and optical scattering from particulates. As of yet, little is known on the variability of particle size distribution in marine ecosystems. In this study, we investigated the PSD properties and variability in Hudson Bay based on measurements from a laser diffractometer (LISST-100X Type-B) in concert with biogeochemical parameters collected during summer 2010. Results show that most power-law fitted PSD slopes ranged from 2.5 to 4.5, covering nearly the entire range observed for natural waters. Offshore waters showed a predominance of smaller particles while near the coast, the effect of riverine inputs on PSD were apparent. Particulate inorganic matter contributed more to total suspended matter in coastal waters leading to lower PSD slopes than offshore. The depth distribution of PSD slopes shows that larger particles were associated with the pycnocline. Below the pycnocline, smaller particles dominated the spectra. A comparison between a PSD slope-based method to derive phytoplankton size class (PSC) and pigment-based derived PSC showed the two methods agreed relatively well. This study provides valuable baseline information on particle size properties and phytoplankton composition estimates in a sub-arctic environment subject to rapid environmental change.

Epitaxial growth of InGaN nanowire arrays for light emitting diodes.

PubMed

Hahn, Christopher; Zhang, Zhaoyu; Fu, Anthony; Wu, Cheng Hao; Hwang, Yun Jeong; Gargas, Daniel J; Yang, Peidong

2011-05-24

Significant synthetic challenges remain for the epitaxial growth of high-quality InGaN across the entire compositional range. One strategy to address these challenges has been to use the nanowire geometry because of its strain relieving properties. Here, we demonstrate the heteroepitaxial growth of In(x)Ga(1-x)N nanowire arrays (0.06 ≤ x ≤ 0.43) on c-plane sapphire (Al(2)O(3)(001)) using a halide chemical vapor deposition (HCVD) technique. Scanning electron microscopy and X-ray diffraction characterization confirmed the long-range order and epitaxy of vertically oriented nanowires. Structural characterization by transmission electron microscopy showed that single crystalline nanowires were grown in the ⟨002⟩ direction. Optical properties of InGaN nanowire arrays were investigated by absorption and photoluminescence measurements. These measurements show the tunable direct band gap properties of InGaN nanowires into the yellow-orange region of the visible spectrum. To demonstrate the utility of our HCVD method for implementation into devices, LEDs were fabricated from In(x)Ga(1-x)N nanowires epitaxially grown on p-GaN(001). Devices showed blue (x = 0.06), green (x = 0.28), and orange (x = 0.43) electroluminescence, demonstrating electrically driven color tunable emission from this p-n junction.

Composition and molecular weight distribution of carob germ protein fractions.

PubMed

Smith, Brennan M; Bean, Scott R; Schober, Tilman J; Tilley, Michael; Herald, Thomas J; Aramouni, Fadi

2010-07-14

Biochemical properties of carob germ proteins were analyzed using a combination of selective extraction, reversed-phase high-performance liquid chromatography (RP-HPLC), size exclusion chromatography (SEC) coupled with multiangle laser light scattering (SEC-MALS), and electrophoretic analysis. Using a modified Osborne extraction procedure, carob germ flour proteins were found to contain approximately 32% albumin and globulin and approximately 68% glutelin with no prolamins detected. The albumin and globulin fraction was found to contain low amounts of disulfide-bonded polymers with relatively low M(w) ranging up to 5 x 10(6) Da. The glutelin fraction, however, was found to contain large amounts of high molecular weight disulfide-bonded polymers with M(w) up to 8 x 10(7) Da. When extracted under nonreducing conditions and divided into soluble and insoluble proteins as typically done for wheat gluten, carob germ proteins were found to be almost entirely ( approximately 95%) in the soluble fraction with only ( approximately 5%) in the insoluble fraction. As in wheat, SEC-MALS analysis showed that the insoluble proteins had a greater M(w) than the soluble proteins and ranged up to 8 x 10(7) Da. The lower M(w) distribution of the polymeric proteins of carob germ flour may account for differences in functionality between wheat and carob germ flour.

Complete mitochondrial genome of a Asian lion (Panthera leo goojratensis).

PubMed

Li, Yu-Fei; Wang, Qiang; Zhao, Jian-ning

2016-01-01

The entire mitochondrial genome of this Asian lion (Panthera leo goojratensis) was 17,183 bp in length, gene composition and arrangement conformed to other lions, which contained the typical structure of 22 tRNAs, 2 rRNAs, 13 protein-coding genes and a non-coding region. The characteristic of the mitochondrial genome was analyzed in detail.

Genetic diversity and population structure of castor (Ricinus communis L.) germplasm within the U.S. collection assessed with EST-SSR markers

USDA-ARS?s Scientific Manuscript database

Castor is an important oilseed crop and although its oil is inedible, it has multiple industrial and pharmaceutical applications. The entire U.S. castor germplasm collection was previously screened for oil content and fatty acid composition, but its genetic diversity and population structure has not...

Guanidine Soaps As Vehicles For Coating Ceramic Fibers

NASA Technical Reports Server (NTRS)

Philipp, Warren H.; Veitch, Lisa C.; Jaskowiak, Martha H.

1994-01-01

Soaps made from strong organic base guanidine and organic fatty acids serve as vehicles and binders for coating ceramic fibers, various smooth substrates, and other problematic surfaces with thin precious-metal or metal-oxide films. Films needed to serve as barriers to diffusion in fiber/matrix ceramic composite materials. Guanidine soaps entirely organic and burn off, leaving no residues.

Bond Strength of Silorane- and Methacrylate-Based Composites to Resin-Modified Glass Ionomers

DTIC Science & Technology

2012-01-13

genre was given the name of resin-modified glass ionomers (RMGI) (Antonucci et al., 1988). The addition of resin improved many of the drawbacks of...entire surface for 15 seconds then gentle air was used to create an even film over the sample. This layer was cured for 10 seconds using the Bluephase

Star Formation in Nearby Galaxies

NASA Astrophysics Data System (ADS)

O'Connell, Robert

2009-07-01

Star formation is a fundamental astrophysical process; it controls phenomena ranging from the evolution of galaxies and nucleosynthesis to the origins of planetary systems and abodes for life. The WFC3, optimized at both UV and IR wavelengths and equipped with an extensive array of narrow-band filters, brings unique capabilities to this area of study. The WFC3 Scientific Oversight Committee {SOC} proposes an integrated program on star formation in the nearby universe which will fully exploit these new abilities. Our targets range from the well-resolved R136 in 30 Dor in the LMC {the nearest super star cluster} and M82 {the nearest starbursting galaxy} to about half a dozen other nearby galaxies that sample a wide range of star-formation rates and environments. Our program consists of broad-band multiwavelength imaging over the entire range from the UV to the near-IR, aimed at studying the ages and metallicities of stellar populations, revealing young stars that are still hidden by dust at optical wavelengths, and showing the integrated properties of star clusters. Narrow-band imaging of the same environments will allow us to measure star-formation rates, gas pressure, chemical abundances, extinction, and shock morphologies. The primary scientific issues to be addressed are: {1} What triggers star formation? {2} How do the properties of star-forming regions vary among different types of galaxies and environments of different gas densities and compositions? {3} How do these different environments affect the history of star formation? {4} Is the stellar initial mass function universal or determined by local conditions?

Structure of aqueous proline via parallel tempering molecular dynamics and neutron diffraction.

PubMed

Troitzsch, R Z; Martyna, G J; McLain, S E; Soper, A K; Crain, J

2007-07-19

The structure of aqueous L-proline amino acid has been the subject of much debate centering on the validity of various proposed models, differing widely in the extent to which local and long-range correlations are present. Here, aqueous proline is investigated by atomistic, replica exchange molecular dynamics simulations, and the results are compared to neutron diffraction and small angle neutron scattering (SANS) data, which have been reported recently (McLain, S.; Soper, A.; Terry, A.; Watts, A. J. Phys. Chem. B 2007, 111, 4568). Comparisons between neutron experiments and simulation are made via the static structure factor S(Q) which is measured and computed from several systems with different H/D isotopic compositions at a concentration of 1:20 molar ratio. Several different empirical water models (TIP3P, TIP4P, and SPC/E) in conjunction with the CHARMM22 force field are investigated. Agreement between experiment and simulation is reasonably good across the entire Q range although there are significant model-dependent variations in some cases. In general, agreement is improved slightly upon application of approximate quantum corrections obtained from gas-phase path integral simulations. Dimers and short oligomeric chains formed by hydrogen bonds (frequently bifurcated) coexist with apolar (hydrophobic) contacts. These emerge as the dominant local motifs in the mixture. Evidence for long-range association is more equivocal: No long-range structures form spontaneously in the MD simulations, and no obvious low-Q signature is seen in the SANS data. Moreover, associations introduced artificially to replicate a long-standing proposed mesoscale structure for proline correlations as an initial condition are annealed out by parallel tempering MD simulations. However, some small residual aggregates do remain, implying a greater degree of long-range order than is apparent in the SANS data.

Polybenzoxazole-filled nitrile butadiene rubber compositions

NASA Technical Reports Server (NTRS)

Gajiwala, Himansu M. (Inventor); Guillot, David G. (Inventor)

2008-01-01

An insulation composition that comprises at least one nitrile butadiene rubber (NBR) having an acrylonitrile content that ranges from approximately 26% by weight to approximately 35% by weight and polybenzoxazole (PBO) fibers. The NBR may be a copolymer of acrylonitrile and butadiene and may be present in the insulation composition in a range of from approximately 45% by weight to approximately 56% by weight of a total weight of the insulation composition. The PBO fibers may be present in a range of from approximately 3% by weight to approximately 10% by weight of a total weight of the insulation composition. A rocket motor including the insulation composition and a method of insulating a rocket motor are also disclosed.

Small geographic range but not panmictic: how forests structure the endangered Point Arena mountain beaver (Aplodontia rufa nigra)

Treesearch

William J. Zielinski; Fredrick V. Schlexer; Sean A. Parks; Kristine L. Pilgrim; Michael K. Schwartz

2012-01-01

The landscape genetics framework is typically applied to broad regions that occupy only small portions of a species' range. Rarely is the entire range of a taxon the subject of study. We examined the landscape genetic structure of the endangered Point Arena mountain beaver (Aplodontia rufa nigra), whose isolated geographic range is found in a...

Evaluation of effect of different disposable infection control barriers on light intensity of light-curing unit and microhardness of composite - An in vitro study.

PubMed

Khode, Rajiv Tarachand; Shenoi, Pratima Ramakrishna; Kubde, Rajesh R; Makade, Chetana S; Wadekar, Kanchan D; Khode, Priyanka Tarachand

2017-01-01

This study evaluated effect of infection control barriers on light intensity (LI) of light-curing unit (LCU) and microhardness of composite. Four different disposable barriers ( n = 30) were tested against the control. LI for each barrier was measured with Lux meter. One hundred and fifty Teflon molds were equally divided into five groups of thirty each. Composite was filled in bulk in these molds and cured without and with barrier. Microhardness was evaluated on top and bottom surface of composite specimen with microhardness testing machine and hardness ratio (HR) was derived. One-way analysis of variance, Tukey's honestly significant difference test, and paired t -test using SPSS version 18 software. All barriers had significantly reduced the baseline LI of LCU ( P < 0.0001), but only Cure Elastic Steri-Shield and latex cut glove pieces (LCGP) significantly reduced the microhardness of the composite ( P < 0.05). However, HR determined inadequate curing only with LCGP. Although entire tested barrier significantly reduced the LI; none, except LCGP markedly affected the degree of cure of the composite.

A GIS approach to identifying the distribution and structure of coast redwood across its range

Treesearch

Peter Cowan; Emily E. Burns; Richard Campbell

2017-01-01

To better understand the distribution and current structure of coast redwood (Sequoia sempervirens (D.Don) Endl.) forests throughout the range and how it varies by land ownerships, the Save the Redwoods League has conducted a redwood specific analysis of a high resolution forest structure database encompassing the entire natural coast redwood range...

Complex solution of problem of all-season construction of roads and pipelines on universal composite pontoon units

NASA Astrophysics Data System (ADS)

Ryabkov, A. V.; Stafeeva, N. A.; Ivanov, V. A.; Zakuraev, A. F.

2018-05-01

A complex construction consisting of a universal floating pontoon road for laying pipelines in automatic mode on its body all year round and in any weather for Siberia and the Far North has been designed. A new method is proposed for the construction of pipelines on pontoon modules, which are made of composite materials. Pontoons made of composite materials for bedding pipelines with track-forming guides for automated wheeled transport, pipelayer, are designed. The proposed system eliminates the construction of a road along the route, ensures the buoyancy and smoothness of the self-propelled automated stacker in the form of a "centipede", which has a number of significant advantages in the construction and operation of the entire complex in the swamp and watered areas without overburden.

Global-Scale Structure of the Eelgrass Microbiome.

PubMed

Fahimipour, Ashkaan K; Kardish, Melissa R; Lang, Jenna M; Green, Jessica L; Eisen, Jonathan A; Stachowicz, John J

2017-06-15

Plant-associated microorganisms are essential for their hosts' survival and performance. Yet, most plant microbiome studies to date have focused on terrestrial species sampled across relatively small spatial scales. Here, we report the results of a global-scale analysis of microbial communities associated with leaf and root surfaces of the marine eelgrass Zostera marina throughout its range in the Northern Hemisphere. By contrasting host microbiomes with those of surrounding seawater and sediment, we uncovered the structure, composition, and variability of microbial communities associated with eelgrass. We also investigated hypotheses about the assembly of the eelgrass microbiome using a metabolic modeling approach. Our results reveal leaf communities displaying high variability and spatial turnover that mirror their adjacent coastal seawater microbiomes. By contrast, roots showed relatively low compositional turnover and were distinct from surrounding sediment communities, a result driven by the enrichment of predicted sulfur-oxidizing bacterial taxa on root surfaces. Predictions from metabolic modeling of enriched taxa were consistent with a habitat-filtering community assembly mechanism whereby similarity in resource use drives taxonomic cooccurrence patterns on belowground, but not aboveground, host tissues. Our work provides evidence for a core eelgrass root microbiome with putative functional roles and highlights potentially disparate processes influencing microbial community assembly on different plant compartments. IMPORTANCE Plants depend critically on their associated microbiome, yet the structure of microbial communities found on marine plants remains poorly understood in comparison to that for terrestrial species. Seagrasses are the only flowering plants that live entirely in marine environments. The return of terrestrial seagrass ancestors to oceans is among the most extreme habitat shifts documented in plants, making them an ideal testbed for the study of microbial symbioses with plants that experience relatively harsh abiotic conditions. In this study, we report the results of a global sampling effort to extensively characterize the structure of microbial communities associated with the widespread seagrass species Zostera marina , or eelgrass, across its geographic range. Our results reveal major differences in the structure and composition of above- versus belowground microbial communities on eelgrass surfaces, as well as their relationships with the environment and host. Copyright © 2017 Fahimipour et al.

Geostatistical Interpolation of Particle-Size Curves in Heterogeneous Aquifers

NASA Astrophysics Data System (ADS)

Guadagnini, A.; Menafoglio, A.; Secchi, P.

2013-12-01

We address the problem of predicting the spatial field of particle-size curves (PSCs) from measurements associated with soil samples collected at a discrete set of locations within an aquifer system. Proper estimates of the full PSC are relevant to applications related to groundwater hydrology, soil science and geochemistry and aimed at modeling physical and chemical processes occurring in heterogeneous earth systems. Hence, we focus on providing kriging estimates of the entire PSC at unsampled locations. To this end, we treat particle-size curves as cumulative distribution functions, model their densities as functional compositional data and analyze them by embedding these into the Hilbert space of compositional functions endowed with the Aitchison geometry. On this basis, we develop a new geostatistical methodology for the analysis of spatially dependent functional compositional data. Our functional compositional kriging (FCK) approach allows providing predictions at unsampled location of the entire particle-size curve, together with a quantification of the associated uncertainty, by fully exploiting both the functional form of the data and their compositional nature. This is a key advantage of our approach with respect to traditional methodologies, which treat only a set of selected features (e.g., quantiles) of PSCs. Embedding the full PSC into a geostatistical analysis enables one to provide a complete characterization of the spatial distribution of lithotypes in a reservoir, eventually leading to improved predictions of soil hydraulic attributes through pedotransfer functions as well as of soil geochemical parameters which are relevant in sorption/desorption and cation exchange processes. We test our new method on PSCs sampled along a borehole located within an alluvial aquifer near the city of Tuebingen, Germany. The quality of FCK predictions is assessed through leave-one-out cross-validation. A comparison between hydraulic conductivity estimates obtained via FCK approach and those predicted by classical kriging of effective particle diameters (i.e., quantiles of the PSCs) is finally performed.

The UC2-x - Carbon eutectic: A laser heating study

NASA Astrophysics Data System (ADS)

Manara, D.; Boboridis, K.; Morel, S.; De Bruycker, F.

2015-11-01

The UC2-x - carbon eutectic has been studied by laser heating and fast multi-wavelength pyrometry under inert atmosphere. The study has been carried out on three compositions, two of which close to the phase boundary of the UC2-x - C miscibility gap (with C/U atomic ratios 2 and 2.1), and one, more crucial, with a large excess of carbon (C/U = 2.82). The first two compositions were synthesised by arc-melting. This synthesis method could not be applied to the last composition, which was therefore completed directly by laser irradiation. The U - C - O composition of the samples was checked by using a combustion method in an ELTRA® analyser. The eutectic temperature, established to be 2737 K ± 20 K, was used as a radiance reference together with the cubic - tetragonal (α → β) solid state transition, fixed at 2050 K ± 20 K. The normal spectral emissivity of the carbon-richer compounds increases up to 0.7, whereas the value 0.53 was established for pure hypostoichiometric uranium dicarbide at the limit of the eutectic region. This increase is analysed in the light of the demixing of excess carbon, and used for the determination of the liquidus temperature (3220 K ± 50 K for UC2.82). Due to fast solid state diffusion, also fostered by the cubic - tetragonal transition, no obvious signs of a lamellar eutectic structure could be observed after quenching to room temperature. The eutectic surface C/UC2-x composition could be qualitatively, but consistently, followed during the cooling process with the help of the recorded radiance spectra. Whereas the external liquid surface is almost entirely constituted by uranium dicarbide, it gets rapidly enriched in demixed carbon upon freezing. Demixed carbon seems to quickly migrate towards the inner bulk during further cooling. At the α → β transition, uranium dicarbide covers again the almost entire external surface.

Wright Stuff

NASA Image and Video Library

2016-01-14

Scientists with NASA New Horizons mission have assembled the highest-resolution color view of one of two potential cryovolcanoes spotted on the surface of the distant planet by the passing New Horizons spacecraft in July 2015. At about 90 miles (150 kilometers) across and 2.5 miles (4 kilometers) high, the feature -- informally named Wright Mons -- is enormous. If it is in fact a volcano, as suspected, it would be the largest such feature discovered in the outer solar system. Mission scientists are intrigued by the sparse distribution of red material in the image and wonder why it is not more widespread. Also perplexing is that there is only one identified impact crater on Wright Mons itself, telling scientists that the surface (as well as some of the crust underneath) was created relatively recently. This is turn may indicate that Wright Mons was volcanically active late in Pluto's history. This composite image includes pictures taken by the New Horizons spacecraft's Long Range Reconnaissance Imager (LORRI) on July 14, 2015, from a range of about 30,000 miles (48,000 kilometers), showing features as small as 1,500 feet (450 meters) across. Sprinkled across the LORRI mosaic is enhanced color data from the Ralph/Multispectral Visible Imaging Camera (MVIC) gathered about 20 minutes after the LORRI snapshots were taken, from a range of 21,000 miles (34,000 kilometers) and at a resolution of about 2,100 feet (650 meters) per pixel. The entire scene is 140 miles (230 kilometers) across. http://photojournal.jpl.nasa.gov/catalog/PIA20361

Optimization of an extraction protocol for organic matter from soils and sediments using high resolution mass spectrometry: selectivity and biases

NASA Astrophysics Data System (ADS)

Chu, R. K.; Tfaily, M. M.; Tolic, N.; Kyle, J. E.; Robinson, E. R.; Hess, N. J.; Paša-Tolić, L.

2015-12-01

Soil organic matter (SOM) is a complex mixture of above and belowground plant litter and microbial residues, and is a key reservoir for carbon (C) and nutrient biogeochemical cycling in different ecosystems. A limited understanding of the molecular composition of SOM prohibits the ability to routinely decipher chemical processes within soil and predict how terrestrial C fluxes will response to changing climatic conditions. Here, we present that the choice of solvent can be used to selectively extract different compositional fractions from SOM to either target a specific class of compounds or gain a better understanding of the entire composition of the soil sample using 12T Fourier transform ion cyclotron resonance mass spectrometry. Specifically, we found that hexane and chloroform were selective for lipid-like compounds with very low O:C ratios; water was selective for carbohydrates with high O:C ratios; acetonitrile preferentially extracts lignin, condensed structures, and tannin polyphenolic compounds with O:C > 0.5; methanol has higher selectivity towards lignin and lipid compounds characterized with relatively low O:C < 0.5. Hexane, chloroform, methanol, acetonitrile and water increase the number and types of organic molecules extracted from soil for a broader range of chemically diverse soil types. Since each solvent extracts a selective group of compounds, using a suite of solvents with varying polarity for analysis results in more comprehensive representation of the diversity of organic molecules present in soil and a better representation of the whole spectrum of available substrates for microorganisms. Moreover, we have developed a sequential extraction protocol that permits sampling diverse classes of organic compounds while minimizing ionization competition during ESI while increasing sample throughput and decreasing sample volume. This allowed us to hypothesize about possible chemical reactions relating classes of organic molecules that reflect abiotic and biotic processes impacting SOM composition.

Environment of ore deposition in the Creede mining district, San Juan Mountains, Colorado: Part VI. Maximum duration for mineralization of the OH vein

USGS Publications Warehouse

Campbell, W.R.; Barton, P.B.

2005-01-01

The rate at which ore deposits form is one of the least well established parameters in all of economic geology. However, increased detail in sampling, improved technology of dating, and sophistication in modeling are reducing the uncertainties and establishing that ore formation, at least for the porphyry copper-skarn-epithermal base and precious metals deposit package, may take place in surprisingly brief intervals. This contribution applies another approach to examine the duration of mineralization. The degree to which compositional gradients within single crystals has flattened through solid-state diffusion offers a measure of the thermal dose (that is temperature combined with time) that the crystals have been subjected to since deposition. Here we examine the steepness of gradients in iron content within individual single sphalerite crystals from the epithermal silver-lead-zinc deposit in the OH vein at Creede, Colorado. Two initial textures are considered: growth-banded crystals and compositionally contrasting overgrowths that succeed crosscutting dissolution or fractured surfaces. The model used estimates the maximum possible time by assuming a perfectly sharp original compositional step, and it asks how long it would take at a known temperature for the gradient measured today to have formed. Applying the experimentally determined diffusion rates of Mizuta (1988a) to compositional gradients (ranging from 0.4-2.2 mol % FeS/??m) measured by the electron microprobe in 2-??m steps on banded sphalerite formed early in the paragenetic history yields a maximum duration of less than ???10,000 yr. Sphalerite from a solution unconformity in a position midway through the paragenetic sequence is indistinguishable from instantaneous deposition, supporting the conclusion of rapid ore formation. While this formation interval seems very brief, it is consistent with less well constrained estimates using entirely different criteria. ?? 2005 Society of Economic Geologists, Inc.

Thermoviscoplastic analysis of fibrous periodic composites using triangular subvolumes

NASA Technical Reports Server (NTRS)

Walker, Kevin P.; Freed, Alan D.; Jordan, Eric H.

1993-01-01

The nonlinear viscoplastic behavior of fibrous periodic composites is analyzed by discretizing the unit cell into triangular subvolumes. A set of these subvolumes can be configured by the analyst to construct a representation for the unit cell of a periodic composite. In each step of the loading history, the total strain increment at any point is governed by an integral equation which applies to the entire composite. A Fourier series approximation allows the incremental stresses and strains to be determined within a unit cell of the periodic lattice. The nonlinearity arising from the viscoplastic behavior of the constituent materials comprising the composite is treated as fictitious body force in the governing integral equation. Specific numerical examples showing the stress distributions in the unit cell of a fibrous tungsten/copper metal matrix composite under viscoplastic loading conditions are given. The stress distribution resulting in the unit cell when the composite material is subjected to an overall transverse stress loading history perpendicular to the fibers is found to be highly heterogeneous, and typical homogenization techniques based on treating the stress and strain distributions within the constituent phases as homogeneous result in large errors under inelastic loading conditions.

Thermoviscoplastic analysis of fibrous periodic composites by the use of triangular subvolumes

NASA Technical Reports Server (NTRS)

Walker, Kevin P.; Freed, Alan D.; Jordan, Eric H.

1994-01-01

The non-linear viscoplastic behavior of fibrous periodic composites is analyzed by discretizing the unit cell into triangular subvolumes. A set of these subvolumes can be configured by the analyst to construct a representation for the unit cell of a periodic composite. In each step of the loading history the total strain increment at any point is governed by an integral equation which applies to the entire composite. A Fourier series approximation allows the incremental stresses and strains to be determined within a unit cell of the periodic lattice. The non-linearity arising from the viscoplastic behavior of the constituent materials comprising the composite is treated as a fictitious body force in the governing integral equation. Specific numerical examples showing the stress distributions in the unit cell of a fibrous tungsten/copper metal-matrix composite under viscoplastic loading conditions are given. The stress distribution resulting in the unit cell when the composite material is subjected to an overall transverse stress loading history perpendicular to the fibers is found to be highly heterogeneous, and typical homogenization techniques based on treating the stress and strain distributions within the constituent phases as homogeneous result in large errors under inelastic loading conditions.

The UltraLightweight Technology for Research in Astronomy (ULTRA) Project

NASA Astrophysics Data System (ADS)

Twarog, B. A.; Anthony-Twarog, B. J.; Shawl, S. J.; Hale, R.; Taghavi, R.; Fesen, R.; Etzel, P. B.; Martin, R.; Romeo, R.

2004-12-01

The collaborative focus of four academic departments (Univ. of Kansas Aerospace Engineering, Univ. of Kansas Physics & Astronomy, San Diego State University Astronomy and Dartmouth College Astronomy) and a private industry partner (Composite Mirror Applications, Inc.-CMA, Inc.) is a three-year plan to develop and test UltraLightweight Technology for Research in Astronomy (ULTRA). The ULTRA technology, using graphite fiber composites to fabricate mirrors and telescope structures, offers a versatile and cost-effective tool for optical astronomy, including the economical fabrication and operation of telescopes ranging from small (1m or smaller) aperture for education and research to extremely large (30m+) segmented telescopes (ELTs). The specific goal of this NSF-funded three-year Major Research Instrumentation project is to design, build, and test a 1m-class optical tube assembly (OTA) and mirrors constructed entirely from composites. In the first year of the project, the team has built and is field-testing two 0.4m prototypes to validate the optical surfaces and figures of the mirrors and to test and refine the structural dynamics of the OTA. Preparation for design and construction of the 1m telescope is underway. When completed in late 2005, the ULTRA telescope will be operated remotely from Mt. Laguna Observatory east of San Diego, where it will undergo a period of intensive optical and imaging tests. A 0.4m prototype OTA with mirrors (12 kg total weight) will be on display at the meeting. Support of this work by NSF through grants AST-0320784 and AST-0321247, NASA grant NCC5-600, the University of Kansas, and San Diego State University is gratefully acknowledged.

Ant diversity in Brazilian tropical dry forests across multiple vegetation domains

NASA Astrophysics Data System (ADS)

Figueiredo Silva, Luciana; Mello Souza, Rayana; Solar, Ricardo R. C.; de Siqueira Neves, Frederico

2017-03-01

Understanding the environmental drivers of biodiversity persistence and community organization in natural ecosystems is of great importance for planning the conservation of those ecosystems. This comprehension is even more important in severely threatened ecosystems. In this context, we analyzed ant communities in tropical dry forests (TDFs) in Brazil. These forests are embedded within other biomes, such as Cerrado and Caatinga. In this study, we asked whether (i) ant species richness and composition changes between TDFs within different vegetation domains; (ii) whether ant species richness and β-diversity increase north-to-south, possibly related to changes in tree richness and tree density; and (iii) species replacement contributes relatively more to β-diversity than does nestedness. We found that species composition is unique to each TDF within different biomes, and that species richness and β-diversity differ among the vegetation domains, being smaller in the Caatinga. We also found that replacement contributes most to β-diversity, although this contribution is lower in Caatinga than in Cerrado. We show that regional context is the main driver of species diversity, which is likely to be driven by both historical and ecological mechanisms. By analyzing large spatial scale variation in TDF environmental characteristics, we were able to evaluate how ant diversity changes along an environmental gradient. The high levels of species replacement and unique species composition of each region indicates that, to fully conserve TDFs, we need to have various conservation areas distributed across the entire range of vegetation domains in which these forests can be found. Thus, we demonstrate that a landscape-wise planning is urgent and necessary in order to preserve tropical dry forests.

Hydrous melt-rock reaction in the shallow mantle wedge

NASA Astrophysics Data System (ADS)

Mitchell, A.; Grove, T. L.

2017-12-01

In subduction zone magmatism, hotter, deeper hydrous mantle melts rise and interact with the shallower, cooler depleted mantle in the uppermost part of the mantle wedge. Here, we experimentally investigate these hydrous reactions using three different ratios of a 1.6 GPa mantle melt and an overlying 1.2 GPa harzburgite from 1060 to 1260 °C. At low ratios of melt/mantle (20:80 and 5:95), the crystallizing assemblages are dunites, harzburgites, and lherzolites (as a function of temperature). When the ratio of deeper melt to overlying mantle is 70:30, the crystallizing assemblage is a wehrlite. This shows that wehrlites, which are observed in ophiolites and mantle xenoliths, can be formed by large amounts of deeper melt fluxing though the mantle wedge during ascent. In all cases, orthopyroxene dissolves in the melt, and olivine crystallizes along with pyroxenes and spinel. The amount of reaction between deeper melts and overlying mantle, simulated here by the three starting compositions, imposes a strong influence on final melt compositions, particularly in terms of depletion. At the lowest melt/mantle ratios, the resulting melt is an extremely depleted Al-poor, high-Si andesite. As the fraction of melt to mantle increases, final melts resemble primitive basaltic andesites found in arcs globally. Wall rock temperature is a key variable; over a span of <80 °C, reaction with deeper melt creates the entire range of mantle lithologies from a depleted dunite to a harzburgite to a refertilized lherzolite. Together, the experimental phase equilibria, melt compositions, and calculated reaction coefficients provide a framework for understanding how melt-wall rock reaction occurs in the natural system during melt ascent in the mantle wedge.

Structural, optical, and spin properties of hydrogenated amorphous silicon-germanium alloys

NASA Astrophysics Data System (ADS)

Stutzmann, M.; Street, R. A.; Tsai, C. C.; Boyce, J. B.; Ready, S. E.

1989-07-01

We report on a detailed study of structural and electronic properties of hydrogenated amorphous silicon-germanium alloys deposited by rf glow discharge from SiH4 and GeH4 in a diode reactor. The chemical composition of the alloys is related to the deposition conditions, with special emphasis on preferential incorporation of Ge into the solid phase and on the role of inert dilutant gases. Hydrogen bonding in the alloys is investigated with nuclear magnetic resonance and vibrational (Raman and infrared) spectroscopy. The optical properties of a-SiGe:H samples deposited under optimal conditions are analyzed with the help of subgap absorption measurements and band-tail luminescence for the entire range of alloy composi-tions. A large part of the article describes an investigation of the electron-spin-resonance response of undoped alloys. The spin density associated with dangling bond defects localized on Si and Ge atoms has been measured as a function of alloy composition for optimized material. In addition, the dependence of the two defect densities on the detailed deposition conditions (rf power, substrate temperature, and dilution) has been determined in a systematic way for alloys deposited from a plasma with a fixed SiH4/GeH4ratio. The results of this study, especially the preferential creation of Ge dangling bonds, are discussed in the context of our structural data. Furthermore, spin resonance is employed to investigate the light-induced degradation (Staebler-Wronski effect) of a-SiGe:H. Finally, the changes of the spin-resonance spectra of a-Si0.7 Ge0.3 :H upon substitutional doping with phosphorus and boron have been obtained experimentally, and are used to construct a model for the electronic density of states in this material.

An experimental study of pyroxene crystallization during rapid cooling in a thermal gradient: application to komatiites

NASA Astrophysics Data System (ADS)

Bouquain, S.; Arndt, N. T.; Faure, F.; Libourel, G.

2014-07-01

To investigate the crystallization of pyroxene in spinifex-textured komatiites, we undertook a series of experiments in which compositions in the CaO-MgO-Al2O3-SiO2 CMAS system were cooled rapidly in a thermal gradient. Cooling rates were generally between 5 and 10 °C h-1, but some runs were made at 100-200 °C h-1; thermal gradients were between 10 and 20 °C cm-1. These conditions reproduced those at various depths in the crust of komatiite lava flow. The starting composition was chosen to have pigeonite on the liquidus, and most of the experimental charges crystallized zoned pigeonite-diopside crystals like those in komatiite lavas. An intriguing aspect of the experimental results was their lack of reproducibility. Some experiments crystallized forsterite, whereas others that were run under similar conditions crystallized two pyroxenes and no forsterite; some experiments were totally glassy, but others crystallized entirely to pyroxene. The degree of supercooling at the onset of pyroxene crystallization was variable, from less than 25 °C to more than 110 °C. We attribute these results to the difficulty of nucleation of pyroxene under the conditions of the experiments. In some cases forsterite crystallized metastably and modified the liquid composition to inhibit pyroxene crystallization; in others no nucleation took place until a large degree of supercooling was achieved, and then pyroxene crystallized rapidly. Pigeonite crystallized under a wide range of conditions, at cooling rates from 3 to 100 °C h-1. The notion that this mineral only forms at low cooling rates is not correct.

The late Holocene kauri chronology: assessing the potential of a 4500-year record for palaeoclimate reconstruction

NASA Astrophysics Data System (ADS)

Boswijk, G.; Fowler, A. M.; Palmer, J. G.; Fenwick, P.; Hogg, A.; Lorrey, A.; Wunder, J.

2014-04-01

Millennial and multi-millennial tree-ring chronologies can provide useful proxy records of past climate, giving insight into a more complete range of natural climate variability prior to the 20th century. Since the 1980s a multi-millennial tree-ring chronology has been developed from kauri (Agathis australis) from the upper North Island, New Zealand. Previous work has demonstrated the sensitivity of kauri to the El Niño-Southern Oscillation (ENSO). Here we present recent additions and extensions to the late Holocene kauri chronology (LHKC), and assess the potential of a composite master chronology, AGAUc13, for palaeoclimate reconstruction. The updated composite kauri chronology now spans 4491 years (2488 BCE-2002 CE) and includes data from 18 modern sites, 25 archaeological sites, and 18 sub-fossil (swamp) kauri sites. Consideration of the composition and statistical quality of AGAUc13 suggests the LHKC has utility for palaeoclimate reconstruction but there are caveats. These include: (a) differences in character between the three assemblages including growth rate and sensitivity; (b) low sample depth and low statistical quality in the 10th-13th century CE, when the record transitions from modern and archaeological material to the swamp kauri; (c) a potential difference in amplitude of the signal in the swamp kauri; (d) a westerly bias in site distribution prior to 911 CE; (e) variable statistical quality across the entire record associated with variable replication; and (f) complex changes in sample depth and tree age and size which may influence centennial scale trends in the data. Further tree ring data are required to improve statistical quality, particularly in the first half of the second millennium CE.

Thermodynamic optimization of mixed refrigerant Joule- Thomson systems constrained by heat transfer considerations

NASA Astrophysics Data System (ADS)

Hinze, J. F.; Klein, S. A.; Nellis, G. F.

2015-12-01

Mixed refrigerant (MR) working fluids can significantly increase the cooling capacity of a Joule-Thomson (JT) cycle. The optimization of MRJT systems has been the subject of substantial research. However, most optimization techniques do not model the recuperator in sufficient detail. For example, the recuperator is usually assumed to have a heat transfer coefficient that does not vary with the mixture. Ongoing work at the University of Wisconsin-Madison has shown that the heat transfer coefficients for two-phase flow are approximately three times greater than for a single phase mixture when the mixture quality is between 15% and 85%. As a result, a system that optimizes a MR without also requiring that the flow be in this quality range may require an extremely large recuperator or not achieve the performance predicted by the model. To ensure optimal performance of the JT cycle, the MR should be selected such that it is entirely two-phase within the recuperator. To determine the optimal MR composition, a parametric study was conducted assuming a thermodynamically ideal cycle. The results of the parametric study are graphically presented on a contour plot in the parameter space consisting of the extremes of the qualities that exist within the recuperator. The contours show constant values of the normalized refrigeration power. This ‘map’ shows the effect of MR composition on the cycle performance and it can be used to select the MR that provides a high cooling load while also constraining the recuperator to be two phase. The predicted best MR composition can be used as a starting point for experimentally determining the best MR.

On the dynamics of composition of entire functions

NASA Astrophysics Data System (ADS)

Singh, Anand Prakash

2003-01-01

Let f be an entire function. For n in {bb N}, let f(n) denote the nth iterate of f. The set [ F(f)=\\{z:(f^n) is normal in some neighbourhood of z\\} ] is the Fatou set or the set of normality and its complement J(f) is the Julia set. If U is a component of F(f), then f(U) lies in some component V of F(f). If U_ncap U_m=phi for n ≠ m where U_n denotes the component of F(f) which contains f(n(U)) , then U is called a wandering domain, else U is called a pre-periodic domain, and if U_n = U for some n in {bb N} then U is called periodic domain.

The `Strawberry Volcanic Field' of Northeastern Oregon: Another Piece of the CRB Puzzle?

NASA Astrophysics Data System (ADS)

Steiner, A. R.; Streck, M. J.

2010-12-01

The Mid to Late Miocene Strawberry Volcanics field (SVF) located along the southern margin of the John Day valley of NE Oregon, comprise a diverse group of volcanic rocks ranging from basalt to rhyolite. The main outcrop area of the SVF (3,400 km2) is bordered by units from the Columbia River Basalt Group (CRBG), with the main CRB units to the north, the Picture Gorge Basalt to the east and Steens Basalt to the south. The geographic position and age of the Strawberry Volcanics make a genetic relationship to CRB volcanism likely, yet little is known about this diverse volcanic field. This research aims at refining the stratigraphic and age relationships as well as the petrology and geochemistry of magmas associated with the SVF. Previous investigations (e.g. Robyn, 1977) found that the SVF was active between 20 to 10 Ma with the main pulse largely being coeval with the 15 Ma CRBG eruptions. Lavas and tuffs from the SVF are calc-alkaline with low FeO*/MgO (~ 2.56 wt. %), high Al2O3 (~ 16.4 wt. %), low TiO2 (~ 1.12 wt.%), and span the entire compositional range from basalt to rhyolite (47-78 wt. % SiO2) with andesite as the dominant lithology. Basaltic lavas from the SVF have compositional affinities to earlier Steens Basalt, and some trace element concentrations and ratios are indistinguishable from those of CRBG lavas (e.g. Zr, Ba, Sr, and Ce/Y). Andesites are calc-alkaline, but contrary to typical arc (orogenic) andesites, SVF andesites are exceedingly phenocryst poor (<3% phenocrysts with microphenocrysts of plagioclase and lesser pyroxene which occasionally occur in crystal clots instead of single crystals). In addition, some lavas (basaltic-intermediate) are phenocryst-rich (~25%), containing plagioclase, olivine, opx, and cpx. However, phenocrysts in these lavas are strongly zoned and resorbed, and in general, these lavas are volumetrically insignificant compared with the phenocrysts poor andesites. Rhyolitic lavas are also phenocryst poor (< 3%) and appear to be most voluminous in the southwestern portion of the field area from Bear Valley to Logan Valley. Our preliminary interpretation is that the Strawberry Volcanics are largely the product of hot-spot related basaltic magmas interacting with the continental crust. The range in compositions from calc-alkaline andesite to rhyolite may be attributed to the hybridization of mantle-derived and crustal melts, with the more evolved compositions reflecting greater proportions of crustally derived material and/or higher degrees of differentiation. Furthermore, since the earliest SVF eruption is 3 Ma older than the proposed onset of the CRBG (~ 17 Ma Steens Basalt), if the SVF is chemically related to the CRBG then the timing and location of the initiation of the CRBG will need to be reassessed.

26 CFR 1.167(a)-11 - Depreciation based on class lives and asset depreciation ranges for property placed in service...

Code of Federal Regulations, 2014 CFR

2014-04-01

... which would in accordance with Revenue Procedure 64-21 be entitled to use a composite guideline class... depreciation range is in effect for the taxable year, elect to apply this section on the basis of a composite... Procedure 64-21 to such property. The asset depreciation range for such a composite asset guideline class...

26 CFR 1.167(a)-11 - Depreciation based on class lives and asset depreciation ranges for property placed in service...

Code of Federal Regulations, 2012 CFR

2012-04-01

... which would in accordance with Revenue Procedure 64-21 be entitled to use a composite guideline class... depreciation range is in effect for the taxable year, elect to apply this section on the basis of a composite... Procedure 64-21 to such property. The asset depreciation range for such a composite asset guideline class...

26 CFR 1.167(a)-11 - Depreciation based on class lives and asset depreciation ranges for property placed in service...

Code of Federal Regulations, 2011 CFR

2011-04-01

... which would in accordance with Revenue Procedure 64-21 be entitled to use a composite guideline class... depreciation range is in effect for the taxable year, elect to apply this section on the basis of a composite... Procedure 64-21 to such property. The asset depreciation range for such a composite asset guideline class...

26 CFR 1.167(a)-11 - Depreciation based on class lives and asset depreciation ranges for property placed in service...

Code of Federal Regulations, 2013 CFR

2013-04-01

... which would in accordance with Revenue Procedure 64-21 be entitled to use a composite guideline class... depreciation range is in effect for the taxable year, elect to apply this section on the basis of a composite... Procedure 64-21 to such property. The asset depreciation range for such a composite asset guideline class...

Estimation of liquid volume fraction using ultrasound transit time spectroscopy

NASA Astrophysics Data System (ADS)

Al-Qahtani, Saeed M.; Langton, Christian M.

2016-12-01

It has recently been proposed that the propagation of an ultrasound wave through complex structures, consisting of two-materials of differing ultrasound velocity, may be considered as an array of parallel ‘sonic rays’, the transit time of each determined by their relative proportion; being a minimum (t min) in entire higher velocity material, and a maximum (t max) in entire lower velocity material. An ultrasound transit time spectrum (UTTS) describes the proportion of sonic rays at an individual transit time. It has previously been demonstrated that the solid volume fraction of a solid:liquid composite, specifically acrylic step-wedges immersed in water, may be reliably estimated from the UTTS. The aim of this research was to investigate the hypothesis that the volume fraction of a two-component liquid mixture, of unequal ultrasound velocity, may also be estimated by UTTS. A through-transmission technique incorporating two 1 MHz ultrasound transducers within a horizontally-aligned cylindrical tube-housing was utilised, the proportion of silicone oil to water being varied from 0% to 100%. The liquid volume fraction was estimated from the UTTS at each composition, the coefficient of determination (R 2%) being 98.9  ±  0.7%. The analysis incorporated a novel signal amplitude normalisation technique to compensate for absorption within the silicone oil. It is therefore envisaged that the parallel sonic ray concept and the derived UTTS may be further applied to the quantification of liquid mixture composition assessment.

Process model-based atomic service discovery and composition of composite semantic web services using web ontology language for services (OWL-S)

NASA Astrophysics Data System (ADS)

Paulraj, D.; Swamynathan, S.; Madhaiyan, M.

2012-11-01

Web Service composition has become indispensable as a single web service cannot satisfy complex functional requirements. Composition of services has received much interest to support business-to-business (B2B) or enterprise application integration. An important component of the service composition is the discovery of relevant services. In Semantic Web Services (SWS), service discovery is generally achieved by using service profile of Ontology Web Languages for Services (OWL-S). The profile of the service is a derived and concise description but not a functional part of the service. The information contained in the service profile is sufficient for atomic service discovery, but it is not sufficient for the discovery of composite semantic web services (CSWS). The purpose of this article is two-fold: first to prove that the process model is a better choice than the service profile for service discovery. Second, to facilitate the composition of inter-organisational CSWS by proposing a new composition method which uses process ontology. The proposed service composition approach uses an algorithm which performs a fine grained match at the level of atomic process rather than at the level of the entire service in a composite semantic web service. Many works carried out in this area have proposed solutions only for the composition of atomic services and this article proposes a solution for the composition of composite semantic web services.

Establishment of the U.S. castor (Ricinus communis L.) core collection using seed chemical composition analysis and genotyping with EST-SSR markers

USDA-ARS?s Scientific Manuscript database

Natural genetic variation exists in the plant germplasm collections. Normally the germplasm collection for a specific species encompasses many accessions. Due to its large number of accessions, the entire collection is hard to handle and can’t be easily utilized. To facilitate the end-users (such as...

A New Silarylene-Siloxane Monomeric Resin for Structural Composites: Cure-Chemistry Insight and Thermal Properties of the Cured Matrix

DTIC Science & Technology

2013-03-01

remain nonvolatile during the entire fiber-infusion process and curing operation. The resin must offer several days of storage life before the prepreg ...shipboard handling and in-flight cyclic loading. The raw materials for the new resin and the process for making and curing the prepreg must be affordable

Large-Scale Aerosol Modeling and Analysis

DTIC Science & Technology

2008-09-30

novel method of simultaneous real- time measurements of ice-nucleating particle concentrations and size- resolved chemical composition of individual...is to develop a practical predictive capability for visibility and weather effects of aerosol particles for the entire globe for timely use in...prediction follows that used in numerical weather prediction, namely real- time assessment for initialization of first-principles models. The Naval

Optoelectrofluidic field separation based on light-intensity gradients

PubMed Central

Lee, Sanghyun; Park, Hyun Jin; Yoon, Jin Sung; Kang, Kwan Hyoung

2010-01-01

Optoelectrofluidic field separation (OEFS) of particles under light -intensity gradient (LIG) is reported, where the LIG illumination on the photoconductive layer converts the short-ranged dielectrophoresis (DEP) force to the long-ranged one. The long-ranged DEP force can compete with the hydrodynamic force by alternating current electro-osmosis (ACEO) over the entire illumination area for realizing effective field separation of particles. In the OEFS system, the codirectional illumination and observation induce the levitation effect, compensating the attenuation of the DEP force under LIG illumination by slightly floating particles from the surface. Results of the field separation and concentration of diverse particle pairs (0.82–16 μm) are well demonstrated, and conditions determining the critical radius and effective particle manipulation are discussed. The OEFS with codirectional LIG strategy could be a promising particle manipulation method in many applications where a rapid manipulation of biological cells and particles over the entire working area are of interest. PMID:20697461

Optoelectrofluidic field separation based on light-intensity gradients.

PubMed

Lee, Sanghyun; Park, Hyun Jin; Yoon, Jin Sung; Kang, Kwan Hyoung

2010-07-14

Optoelectrofluidic field separation (OEFS) of particles under light -intensity gradient (LIG) is reported, where the LIG illumination on the photoconductive layer converts the short-ranged dielectrophoresis (DEP) force to the long-ranged one. The long-ranged DEP force can compete with the hydrodynamic force by alternating current electro-osmosis (ACEO) over the entire illumination area for realizing effective field separation of particles. In the OEFS system, the codirectional illumination and observation induce the levitation effect, compensating the attenuation of the DEP force under LIG illumination by slightly floating particles from the surface. Results of the field separation and concentration of diverse particle pairs (0.82-16 mum) are well demonstrated, and conditions determining the critical radius and effective particle manipulation are discussed. The OEFS with codirectional LIG strategy could be a promising particle manipulation method in many applications where a rapid manipulation of biological cells and particles over the entire working area are of interest.

Observatories Combine to Crack Open the Crab Nebula

NASA Image and Video Library

2017-12-08

Astronomers have produced a highly detailed image of the Crab Nebula, by combining data from telescopes spanning nearly the entire breadth of the electromagnetic spectrum, from radio waves seen by the Karl G. Jansky Very Large Array (VLA) to the powerful X-ray glow as seen by the orbiting Chandra X-ray Observatory. And, in between that range of wavelengths, the Hubble Space Telescope's crisp visible-light view, and the infrared perspective of the Spitzer Space Telescope. This video starts with a composite image of the Crab Nebula, a supernova remnant that was assembled by combining data from five telescopes spanning nearly the entire breadth of the electromagnetic spectrum: the Very Large Array, the Spitzer Space Telescope, the Hubble Space Telescope, the XMM-Newton Observatory, and the Chandra X-ray Observatory. The video dissolves to the red-colored radio-light view that shows how a neutron star’s fierce “wind” of charged particles from the central neutron star energized the nebula, causing it to emit the radio waves. The yellow-colored infrared image includes the glow of dust particles absorbing ultraviolet and visible light. The green-colored Hubble visible-light image offers a very sharp view of hot filamentary structures that permeate this nebula. The blue-colored ultraviolet image and the purple-colored X-ray image shows the effect of an energetic cloud of electrons driven by a rapidly rotating neutron star at the center of the nebula. Read more: go.nasa.gov/2r0s8VC Credits: NASA, ESA, J. DePasquale (STScI)

Temperature compensated high-temperature/high-pressure Merrill--Bassett diamond anvil cell

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

Schiferl, D.

1987-07-01

A Merrill--Bassett diamond anvil cell for high-temperature/high-pressure studies up to 5 GPa at 1000 K and 13 GPa at 725 K is described. To maintain uniform, well-characterized temperatures, and to protect the diamond anvils from oxidation and graphitization, the entire cell is heated in a vacuum oven. The materials are chosen so that the pressure remains constant to within +-10% over the entire temperature range.

A statistical view of FMRFamide neuropeptide diversity.

PubMed

Espinoza, E; Carrigan, M; Thomas, S G; Shaw, G; Edison, A S

2000-01-01

FMRFamide-like peptide (FLP) amino acid sequences have been collected and statistically analyzed. FLP amino acid composition as a function of position in the peptide is graphically presented for several major phyla. Results of total amino acid composition and frequencies of pairs of FLP amino acids have been computed and compared with corresponding values from the entire GenBank protein sequence database. The data for pairwise distributions of amino acids should help in future structure-function studies of FLPs. To aid in future peptide discovery, a computer program and search protocol was developed to identify FLPs from the GenBank protein database without the use of keywords.

Rheology of interfacial protein-polysaccharide composites

NASA Astrophysics Data System (ADS)

Fischer, P.

2013-05-01

The morphology and mechanical properties of protein adsorption layers can significantly be altered by the presence of surfactants, lipids, particles, other proteins, and polysaccharides. In food emulsions, polysaccharides are primarily considered as bulk thickener but can under appropriate environmental conditions stabilize or destabilize the protein adsorption layer and, thus, the entire emulsion system. Despite their ubiquitous usage as stabilization agent, relatively few investigations focus on the interfacial rheology of composite protein/polysaccharide adsorption layers. The manuscript provides a brief review on both main stabilization mechanisms, thermodynamic phase separation and electrostatic interaction and discusses the rheological response in light of the environmental conditions such as ionic strength and pH.

Quantitative phylogenetic assessment of microbial communities in diverse environments.

PubMed

von Mering, C; Hugenholtz, P; Raes, J; Tringe, S G; Doerks, T; Jensen, L J; Ward, N; Bork, P

2007-02-23

The taxonomic composition of environmental communities is an important indicator of their ecology and function. We used a set of protein-coding marker genes, extracted from large-scale environmental shotgun sequencing data, to provide a more direct, quantitative, and accurate picture of community composition than that provided by traditional ribosomal RNA-based approaches depending on the polymerase chain reaction. Mapping marker genes from four diverse environmental data sets onto a reference species phylogeny shows that certain communities evolve faster than others. The method also enables determination of preferred habitats for entire microbial clades and provides evidence that such habitat preferences are often remarkably stable over time.