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Sample records for absolute surface energies

  1. Monte Carlo Simulations of Absolute Binding Free Energy of Targeted Nanocarriers to Cell Surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Jin; Zern, B.; Ayyaswamy, P. S.; Eckmann, D. M.; Muzykantov, V. R.; Radhakrishnan, R.

    2010-11-01

    We have developed a computational methodology based on Metropolis Monte Carlo and the weighted histogram analysis method (WHAM) to calculate the absolute binding free energy between functionalized nanocarriers (NC) and endothelial cell (EC) surfaces. The calculated binding affinities agree quantitatively with the measurements of specific antibody coated NCs (100 nm in diameter) to intracellular adhesion molecule-1 (ICAM-1) expressing EC surface in in vitro experiments. We then systematically explore the effects of experimentally tunable parameters including the antibody surface coverage σs of NC, glycocalyx, shear flow and NC size. Of particular biological significance, our model predicts a threshold σs value below which the NC binding affinities reduce drastically and drop below that of single anti-ICAM-1 molecule to ICAM-1; our results reveal that this is due to a change in the multivalency (or number of bonds formed per NC). This trend and threshold value are recovered exactly in the in vivo measurements of the endothelium targeting of NCs in the pulmonary vascular in mice.

  2. Absolute surface energy calculations of Wurtzite (0001)/(000-1): a study of ZnO and GaN

    NASA Astrophysics Data System (ADS)

    Zhang, Jingzhao; Zhang, Yiou; Tse, Kinfai; Deng, Bei; Xu, Hu; Zhu, Junyi

    The accurate absolute surface energies of (0001)/(000-1) surfaces of wurtzite structures are crucial in determining the thin film growth mode of important energy materials. However, the surface energies still remain to be solved due to the intrinsic difficulty of calculating dangling bond energy of asymmetrically bonded surface atoms. We used a pseudo-hydrogen passivation method to estimate the dangling bond energy and calculate the polar surfaces of ZnO and GaN. The calculations were based on the pseudo chemical potentials obtained from a set of tetrahedral clusters or simple pseudo-molecules, using density functional theory approaches, for both GGA and HSE. And the surface energies of (0001)/(000-1) surfaces of wurtzite ZnO and GaN we obtained showed relatively high self-consistencies. A wedge structure calculation with a new bottom surface passivation scheme of group I and group VII elements was also proposed and performed to show converged absolute surface energy of wurtzite ZnO polar surfaces. Part of the computing resources was provided by the High Performance Cluster Computing Centre, Hong Kong Baptist University. This work was supported by the start-up funding and direct Grant with the Project code of 4053134 at CUHK.

  3. Pseudo-Hydrogen Passivation: A Novel Way to Calculate Absolute Surface Energy of Zinc Blende (111)/(¯1 ¯1 ¯1) Surface

    PubMed Central

    Zhang, Yiou; Zhang, Jingzhao; Tse, Kinfai; Wong, Lun; Chan, Chunkai; Deng, Bei; Zhu, Junyi

    2016-01-01

    Determining accurate absolute surface energies for polar surfaces of semiconductors has been a great challenge in decades. Here, we propose pseudo-hydrogen passivation to calculate them, using density functional theory approaches. By calculating the energy contribution from pseudo-hydrogen using either a pseudo molecule method or a tetrahedral cluster method, we obtained (111)/ surfaces energies of Si, GaP, GaAs, and ZnS with high self-consistency. This method quantitatively confirms that surface energy is determined by the number and the energy of dangling bonds of surface atoms. Our findings may greatly enhance the basic understandings of different surfaces and lead to novel strategies in the crystal growth. PMID:26831640

  4. Redetermining CEBAF's Absolute Energy

    NASA Astrophysics Data System (ADS)

    Su, Tong; Jlab Marathon Collaboration

    2015-04-01

    With the upgrade of the Jefferson Lab accelerator (CEBAF) from 6 GeV max energy to 12 GeV, all the dipole magnets in the machine were refurbished. Most of them were switched from open c-shaped to closed h-shaped by adding extra iron. With these upgraded magnets, the energy calibration of the accelerator needed to be redetermined. We will show how an extra external dipole, which is run in series with those in the machine, helps us cross check the current in the magnets as well as precisely map out the integral field for any machine setting. Using knowledge of the relative performance of the dipoles as well as the bend angle into the Hall, has allowed us to already determine a 4th pass 7 GeV beam to better than 7 MeV. In the future, we will use g-2 spin precession as a second independent energy determination. This work is supported by Kent State University, NSF Grant PHY-1405814, and DOE Contract DE-AC05-06OR23177 (JLab).

  5. New approaches for calculating absolute surface energies of wurtzite (0001)/(000 1 ¯ ): A study of ZnO and GaN

    NASA Astrophysics Data System (ADS)

    Zhang, Jingzhao; Zhang, Yiou; Tse, Kinfai; Deng, Bei; Xu, Hu; Zhu, Junyi

    2016-05-01

    The accurate absolute surface energies of (0001)/(000 1 ¯ ) surfaces of wurtzite structures are crucial in determining the thin film growth mode of important energy materials. However, the surface energies still remain to be solved due to the intrinsic difficulty of calculating the dangling bond energy of asymmetrically bonded surface atoms. In this study, we used a pseudo-hydrogen passivation method to estimate the dangling bond energy and calculate the polar surfaces of ZnO and GaN. The calculations were based on the pseudo chemical potentials obtained from a set of tetrahedral clusters or simple pseudo-molecules, using density functional theory approaches. The surface energies of (0001)/(000 1 ¯ ) surfaces of wurtzite ZnO and GaN that we obtained showed relatively high self-consistencies. A wedge structure calculation with a new bottom surface passivation scheme of group-I and group-VII elements was also proposed and performed to show converged absolute surface energy of wurtzite ZnO polar surfaces, and these results were also compared with the above method. The calculated results generally show that the surface energies of GaN are higher than those of ZnO, suggesting that ZnO tends to wet the GaN substrate, while GaN is unlikely to wet ZnO. Therefore, it will be challenging to grow high quality GaN thin films on ZnO substrates; however, high quality ZnO thin film on GaN substrate would be possible. These calculations and comparisons may provide important insights into crystal growth of the above materials, thereby leading to significant performance enhancements in semiconductor devices.

  6. Absolute surface reconstruction by slope metrology and photogrammetry

    NASA Astrophysics Data System (ADS)

    Dong, Yue

    Developing the manufacture of aspheric and freeform optical elements requires an advanced metrology method which is capable of inspecting these elements with arbitrary freeform surfaces. In this dissertation, a new surface measurement scheme is investigated for such a purpose, which is to measure the absolute surface shape of an object under test through its surface slope information obtained by photogrammetric measurement. A laser beam propagating toward the object reflects on its surface while the vectors of the incident and reflected beams are evaluated from the four spots they leave on the two parallel transparent windows in front of the object. The spots' spatial coordinates are determined by photogrammetry. With the knowledge of the incident and reflected beam vectors, the local slope information of the object surface is obtained through vector calculus and finally yields the absolute object surface profile by a reconstruction algorithm. An experimental setup is designed and the proposed measuring principle is experimentally demonstrated by measuring the absolute surface shape of a spherical mirror. The measurement uncertainty is analyzed, and efforts for improvement are made accordingly. In particular, structured windows are designed and fabricated to generate uniform scattering spots left by the transmitted laser beams. Calibration of the fringe reflection instrument, another typical surface slope measurement method, is also reported in the dissertation. Finally, a method for uncertainty analysis of a photogrammetry measurement system by optical simulation is investigated.

  7. Surface Characterization of pNIPAM Under Varying Absolute Humidity

    NASA Astrophysics Data System (ADS)

    Chhabra, Arnav; Kanapuram, Ravitej; Leva, Harrison; Trejo, Juan; Kim, Tae Jin; Hidrovo, Carlos

    2012-11-01

    Poly(N-isopropylacrylamide) has become ubiquitously known as a ``smart'' polymer, showing many promising applications in tissue engineering and drug delivery systems. These applications are particularly reliant on its trenchant, thermally induced hydrophilic-hydrophobic transition that occurs at the lower critical solution temperature (LCST). This feature imparts the pNIPAM programmable adsorption and release capabilities, thus eliminating the need for additional enzymes when removing cells from pNIPAM coated surfaces and leaving the extracellular matrix proteins of the cells largely untouched. The dependence of the LCST on molecular weight, solvent systems, and various salts has been studied extensively. However, what has not been explored is the effect of humidity on the characteristic properties of the polymer, specifically the LCST and the magnitude of the hydrophilic-hydrophobic transition. We studied the surface energy variation of pNIPAM as a function of humidity by altering the absolute humidity and keeping the ambient temperature constant. Our experiments were conducted inside a cuboidal environmental chamber with control over the temperature and humidity inside the chamber. A controlled needle was employed to dispense size-regulated droplets. Throughout this process, a CCD camera was used to image the droplet and the static contact angle was determined using image processing techniques. The behavior of pNIPAM as a function of humidity is presented and discussed.

  8. Absolute Free Energies for Biomolecules in Implicit or Explicit Solvent

    NASA Astrophysics Data System (ADS)

    Berryman, Joshua T.; Schilling, Tanja

    Methods for absolute free energy calculation by alchemical transformation of a quantitative model to an analytically tractable one are discussed. These absolute free energy methods are placed in the context of other methods, and an attempt is made to describe the best practice for such calculations given the current state of the art. Calculations of the equilibria between the four free energy basins of the dialanine molecule and the two right- and left-twisted basins of DNA are discussed as examples.

  9. Enabling Dark Energy and Beyond Science with Precise Absolute Photometry

    NASA Astrophysics Data System (ADS)

    Deustua, Susana E.; Hines, D. C.; Bohlin, R.; Gordon, K. D.

    2014-01-01

    We have obtain WFC3/IR observations of 15 carefully selected stars with the immediate objective of establishing their Absolute Physical Flux (ABF), and an ultimate goal of achieving the sub-1% absolute photometric accuracies required by Dark Energy science with JWST and other facilities. Even with the best data available, the current determination of ABFs is plagued by the reliance on the Vega photometric system, which is known to be problematic primarily due to the fact that Vega is a pole-on rapid rotator with an infrared excess from its circumstellar disk! which makes it difficult to model. Vega is also far too bright for large aperture telescopes. In an effort to remedy these difficulties, teams from the National Institute of Standards (NIST), the University of New Mexico, Johns Hopkins University and STScI have begun to develop a catalog of stars that have spectral energy distributions that are tied directly to NIST (diode) standards with very precisely determined physical characteristics. A key element in this pursuit has been the efforts at STScI to measure the spectra of many of these objects with STIS. We discuss our program to extend this effort into the near-IR which is crucial to reliably extend the SEDs to longer wavelengths, including the mid IR.

  10. Absolute Binding Free Energy Calculations: On the Accuracy of Computational Scoring of Protein-ligand Interactions

    PubMed Central

    Singh, Nidhi; Warshel, Arieh

    2010-01-01

    Calculating the absolute binding free energies is a challenging task. Reliable estimates of binding free energies should provide a guide for rational drug design. It should also provide us with deeper understanding of the correlation between protein structure and its function. Further applications may include identifying novel molecular scaffolds and optimizing lead compounds in computer-aided drug design. Available options to evaluate the absolute binding free energies range from the rigorous but expensive free energy perturbation to the microscopic Linear Response Approximation (LRA/β version) and its variants including the Linear Interaction Energy (LIE) to the more approximated and considerably faster scaled Protein Dipoles Langevin Dipoles (PDLD/S-LRA version), as well as the less rigorous Molecular Mechanics Poisson–Boltzmann/Surface Area (MM/PBSA) and Generalized Born/Surface Area (MM/GBSA) to the less accurate scoring functions. There is a need for an assessment of the performance of different approaches in terms of computer time and reliability. We present a comparative study of the LRA/β, the LIE, the PDLD/S-LRA/β and the more widely used MM/PBSA and assess their abilities to estimate the absolute binding energies. The LRA and LIE methods perform reasonably well but require specialized parameterization for the non-electrostatic term. On the average, the PDLD/S-LRA/β performs effectively. Our assessment of the MM/PBSA is less optimistic. This approach appears to provide erroneous estimates of the absolute binding energies due to its incorrect entropies and the problematic treatment of electrostatic energies. Overall, the PDLD/S-LRA/β appears to offer an appealing option for the final stages of massive screening approaches. PMID:20186976

  11. Absolute calorimetric calibration of low energy brachytherapy sources

    NASA Astrophysics Data System (ADS)

    Stump, Kurt E.

    In the past decade there has been a dramatic increase in the use of permanent radioactive source implants in the treatment of prostate cancer. A small radioactive source encapsulated in a titanium shell is used in this type of treatment. The radioisotopes used are generally 125I or 103Pd. Both of these isotopes have relatively short half-lives, 59.4 days and 16.99 days, respectively, and have low-energy emissions and a low dose rate. These factors make these sources well suited for this application, but the calibration of these sources poses significant metrological challenges. The current standard calibration technique involves the measurement of ionization in air to determine the source air-kerma strength. While this has proved to be an improvement over previous techniques, the method has been shown to be metrologically impure and may not be the ideal means of calbrating these sources. Calorimetric methods have long been viewed to be the most fundamental means of determining source strength for a radiation source. This is because calorimetry provides a direct measurement of source energy. However, due to the low energy and low power of the sources described above, current calorimetric methods are inadequate. This thesis presents work oriented toward developing novel methods to provide direct and absolute measurements of source power for low-energy low dose rate brachytherapy sources. The method is the first use of an actively temperature-controlled radiation absorber using the electrical substitution method to determine total contained source power of these sources. The instrument described operates at cryogenic temperatures. The method employed provides a direct measurement of source power. The work presented here is focused upon building a metrological foundation upon which to establish power-based calibrations of clinical-strength sources. To that end instrument performance has been assessed for these source strengths. The intent is to establish the limits of

  12. Estimation of absolute water surface temperature based on atmospherically corrected thermal infrared multispectral scanner digital data

    NASA Technical Reports Server (NTRS)

    Anderson, James E.

    1986-01-01

    Airborne remote sensing systems, as well as those on board Earth orbiting satellites, sample electromagnetic energy in discrete wavelength regions and convert the total energy sampled into data suitable for processing by digital computers. In general, however, the total amount of energy reaching a sensor system located at some distance from the target is composed not only of target related energy, but, in addition, contains a contribution originating from the atmosphere itself. Thus, some method must be devised for removing or at least minimizing the effects of the atmosphere. The LOWTRAN-6 Program was designed to estimate atmospheric transmittance and radiance for a given atmospheric path at moderate spectral resolution over an operational wavelength region from 0.25 to 28.5 microns. In order to compute the Thermal Infrared Multispectral Scanner (TIMS) digital values which were recorded in the absence of the atmosphere, the parameters derived from LOWTRAN-6 are used in a correction equation. The TIMS data were collected at 1:00 a.m. local time on November 21, 1983, over a recirculating cooling pond for a power plant in southeastern Mississippi. The TIMS data were analyzed before and after atmospheric corrections were applied using a band ratioing model to compute the absolute surface temperature of various points on the power plant cooling pond. The summarized results clearly demonstrate the desirability of applying atmospheric corrections.

  13. ELENA MCP detector: absolute detection efficiency for low-energy neutral atoms

    NASA Astrophysics Data System (ADS)

    Rispoli, R.; De Angelis, E.; Colasanti, L.; Vertolli, N.; Orsini, S.; Scheer, J. A.; Mura, A.; Milillo, A.; Wurz, P.; Selci, S.; Di Lellis, A. M.; Leoni, R.; D'Alessandro, M.; Mattioli, F.; Cibella, S.

    2012-09-01

    Microchannel Plates (MCP) detectors are frequently used in space instrumentation for detecting a wide range of radiation and particles. In particular, the capability to detect non-thermal low energy neutral species is crucial for the sensor ELENA (Emitted Low-Energy Neutral Atoms), part of the package SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) on board the BepiColombo mission of ESA to Mercury to be launched in 2015. ELENA is a Time of Flight (TOF) sensor, based on a novel concept using an ultra-sonic oscillating shutter (Start section), which is operated at frequencies up to 50 kHz; a MCP detector is used as a Stop detector. The scientific objective of ELENA is to detect energetic neutral atoms in the range 10 eV - 5 keV, within 76° FOV, perpendicular to the S/C orbital plane. ELENA will monitor the emission of neutral atoms from the whole surface of Mercury thanks to the spacecraft motion. The major scientific objectives are the interaction between the plasma environment and the planet’s surface, the global particle loss-rate and the remote sensing of the surface properties. In particular, surface release processes are investigated by identifying particles released from the surface, via solar wind-induced ion sputtering (< 1eV - < 100 eV) as well as Hydrogen back-scattered at hundreds eV. MCP absolute detection efficiency for very low energy neutral atoms (E < 30 eV) is a crucial point for this investigation. At the MEFISTO facility of the Physical Institute of the University of Bern (CH), measurements on three different types of MCP (with and without coating) have been performed providing the detection efficiencies in the energy range 10eV - 1keV. Outcomes from such measurements are discussed here.

  14. Absolute beam energy measurements in e+e- storage rings

    NASA Astrophysics Data System (ADS)

    Placidi, M.

    1997-01-01

    The CERN Large Electron Positron collider (LEP) was dedicated to the measurement of the mass Mz and the width Γz of the Z0 resonance during the LEP1 phase which terminated in September 1995. The Storage Ring operated in Energy Scan mode during the 1993 and 1995 physics runs by choosing the beam energy Ebeam to correspond to a center-of-mass (CM) energy at the interaction points (IPs) ECMpeak±1762 MeV. After a short review of the techniques usually adopted to set and control the beam energy, this paper describes in more detail two methods adopted at LEP for precise beam energy determination that are essential to reduce the contribution to the systematic error on Mz and Γz. The positron beam momentum was initially determined at the 20-GeV injection energy by measuring the speed of a less relativistic proton beam circulating on the same orbit, taking advantage of the unique opportunity to inject two beams into the LEP at short time intervals. The positron energy at the Z0 peak was in this case derived by extrapolation. Once transverse polarization became reproducible, the Resonant Depolarization (RD) technique was implemented at the Z0 operating energies, providing a ⩽2×10-5 instantaneous accuracy. RD Beam Energy Calibration has been adopted during the LEP Energy Scan campaigns as well as in Accelerator Physics runs for accurate measurement of machine parameters.

  15. The finite element absolute nodal coordinate formulation incorporated with surface stress effect to model elastic bending nanowires in large deformation

    NASA Astrophysics Data System (ADS)

    He, Jin; Lilley, Carmen M.

    2009-08-01

    Surface stress was incorporated into the finite element absolute nodal coordinate formulation in order to model elastic bending of nanowires in large deformation. The absolute nodal coordinate formulation is a numerical method to model bending structures in large deformation. The generalized Young-Laplace equation was employed to model the surface stress effect on bending nanowires. Effects from surface stress and large deformation on static bending nanowires are presented and discussed. The results calculated with the absolute nodal coordinate formulation incorporated with surface stress show that the surface stress effect makes the bending nanowires behave like softer or stiffer materials depending on the boundary condition. The surface stress effect diminishes as the dimensions of the bending structures increase beyond the nanoscale. The developed algorithm is consistent with the classical absolute nodal coordinate formulation at the macroscale.

  16. ELENA MCP detector: absolute efficiency measurement for low energy neutral atoms

    NASA Astrophysics Data System (ADS)

    Rispoli, R.; De Angelis, E.; Colasanti, L.; Vertolli, N.; Orsini, S.; Scheer, J.; Mura, A.; Milillo, A.; Wurz, P.; Selci, S.; Di Lellis, A. M.; Leoni, R.; D'Alessandro, M.; Mattioli, F.; Cibella, S.

    2012-04-01

    MicroChannel plates (MCP) detectors are frequently used in space instrumentation for detecting a wide range of radiation and particles. In particular, the capability to detect non-thermal low energy neutral species is crucial for the sensor ELENA (Emitted Low-Energy Neutral Atoms), part of the package SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) on board the BepiColombo mission to Mercury to be launched in 2014. ELENA is a TOF sensor, based on a novel concept ultra-sonic oscillating shutter (Start section)which is operated at frequencies up to 50 kHz; a MCP detector is used as a Stop section. It is aimed to detect neutral atoms in the range 10 eV - 5 keV, within 70° FOV, perpendicular to the S/C orbital plane. ELENA will monitor the emission of neutral atoms from the whole surface of Mercury thanks to the spacecraft motion. The major scientific objectives are the interaction between the environment and the planet, the global particle loss-rate and the remote sensing of the surface properties. In particular, surface release processes are investigated by identifying particles release from the surface, via solar wind-induced ion sputtering (<1eV and >100 eV) as well as Hydrogen back-scattered at hundreds eV. MCP absolute detection efficiency for very low energy neutral atoms (E< 30eV) is a crucial point not yet investigated. At the MEFISTO facility of the Physical Institute of University of Bern (CH), measurements on three different type of MCPs coating have been performed providing the behaviors of MCP detection efficiency in the range 10eV-1keV. Outcomes from such measurements are here discussed.

  17. Absolute instability from linear conversion of counter-propagating positive and negative energy waves

    SciTech Connect

    Kaufman, A.N.; Brizard, A.J.; Morehead, J.J.; Tracy, E.R.

    1997-12-31

    The resonant interaction of a negative-energy wave with a positive-energy wave gives rise to a linear instability. Whereas a single crossing of rays in a nonuniform medium leads to a convectively saturated instability, we show that a double crossing can yield an absolute instability.

  18. The visual surface brightness relation and the absolute magnitudes of RR Lyrae stars. I - Theory

    NASA Technical Reports Server (NTRS)

    Manduca, A.; Bell, R. A.

    1981-01-01

    A theoretical relation analogous to the Barnes-Evans relation between stellar surface brightness and V-R color is derived which is applicable to the temperatures and gravities appropriate to RR Lyrae stars. Values of the visual surface brightness and V-R colors are calculated for model stellar atmospheres with effective temperatures between 6000 and 8000 K, log surface gravities from 2.2 to 3.5, and A/H anbundance ratios from -0.5 to -3.0. The resulting relation is found to be in reasonable agreement with the empirical relation of Barnes, Evans and Moffet (1978), with, however, small sensitivities to gravity and metal abundance. The relation may be used to derive stellar angular diameters from (V,R) photometry and to derive radii, distances, and absolute magnitudes for variable stars when combined with a radial velocity curve. The accuracies of the radii and distances (within 10%) and absolute magnitudes (within 0.25 magnitudes) compare favorably with those of the Baade-Wesselink method currently in use.

  19. Ultraviolet photometry from the Orbiting Astronomical Observatory. XXI - Absolute energy distribution of stars in the ultraviolet

    NASA Technical Reports Server (NTRS)

    Bless, R. C.; Code, A. D.; Fairchild, E. T.

    1976-01-01

    The absolute energy distribution in the ultraviolet is given for the stars alpha Vir, eta UMa, and alpha Leo. The calibration is based on absolute heterochromatic photometry between 2920 and 1370 A carried out with an Aerobee sounding rocket. The fundamental radiation standard is the synchrotron radiation from 240-MeV electrons in a certain synchrotron storage ring. On the basis of the sounding-rocket calibration, the preliminary OAO-2 spectrometer calibration has been revised; the fluxes for the three program stars are tabulated in energy per second per square centimeter per unit wavelength interval.

  20. Calculation of absolute free energy of binding for theophylline and its analogs to RNA aptamer using nonequilibrium work values

    NASA Astrophysics Data System (ADS)

    Tanida, Yoshiaki; Ito, Masakatsu; Fujitani, Hideaki

    2007-08-01

    The massively parallel computation of absolute binding free energy with a well-equilibrated system (MP-CAFEE) has been developed [H. Fujitani, Y. Tanida, M. Ito, G. Jayachandran, C.D. Snow, M.R. Shirts, E.J. Sorin, V.S. Pande, J. Chem. Phys. 123 (2005) 084108]. As an application, we perform the binding affinity calculations of six theophylline-related ligands with RNA aptamer. Basically, our method is applicable when using many compute nodes to accelerate simulations, thus a parallel computing system is also developed. To further reduce the computational cost, the adequate non-uniform intervals of coupling constant λ, connecting two equilibrium states, namely bound and unbound, are determined. The absolute binding energies Δ G thus obtained have effective linear relation between the computed and experimental values. If the results of two other different methods are compared, thermodynamic integration (TI) and molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) by the paper of Gouda et al. [H. Gouda, I.D. Kuntz, D.A. Case, P.A. Kollman, Biopolymers 68 (2003) 16], the predictive accuracy of the relative values ΔΔ G is almost comparable to that of TI: the correlation coefficients ( R) obtained are 0.99 (this work), 0.97 (TI), and 0.78 (MM-PBSA). On absolute binding energies meanwhile, a constant energy shift of ˜-7 kcal/mol against the experimental values is evident. To solve this problem, several presumable reasons are investigated.

  1. A Simplified Confinement Method (SCM) for Calculating Absolute Free Energies and Free Energy and Entropy Differences

    PubMed Central

    Ovchinnikov, Victor; Cecchini, Marco; Karplus, Martin

    2013-01-01

    A simple and robust formulation of the path-independent confinement method for the calculation of free energies is presented. The simplified confinement method (SCM) does not require matrix diagonalization or switching off the molecular force field, and has a simple convergence criterion. The method can be readily implemented in molecular dynamics programs with minimal or no code modifications. Because the confinement method is a special case of thermodynamic integration, it is trivially parallel over the integration variable. The accuracy of the method is demonstrated using a model diatomic molecule, for which exact results can be computed analytically. The method is then applied to the alanine dipeptide in vacuum, and to the α-helix ↔ β-sheet transition in a sixteen-residue peptide modeled in implicit solvent. The SCM requires less effort for the calculation of free energy differences than previous formulations because it does not require computing normal modes. The SCM has a diminished advantage for determining absolute free energy values, because it requires decreasing the MD integration step to obtain accurate results. An approximate confinement procedure is introduced, which can be used to estimate directly the configurational entropy difference between two macrostates, without the need for additional computation of the difference in the free energy or enthalpy. The approximation has similar convergence properties as the standard confinement method for the calculation of free energies. The use of the approximation requires about five times less wall-clock simulation time than that needed to compute enthalpy differences to similar precision from an MD trajectory. For the biomolecular systems considered in this study, the errors in the entropy approximation are under 10%. The approximation will therefore be most useful for cases in which the dominant source of error is insufficient sampling in the estimation of enthalpies, as arises in simulations of large

  2. Energy dispersive X-ray analysis on an absolute scale in scanning transmission electron microscopy.

    PubMed

    Chen, Z; D'Alfonso, A J; Weyland, M; Taplin, D J; Allen, L J; Findlay, S D

    2015-10-01

    We demonstrate absolute scale agreement between the number of X-ray counts in energy dispersive X-ray spectroscopy using an atomic-scale coherent electron probe and first-principles simulations. Scan-averaged spectra were collected across a range of thicknesses with precisely determined and controlled microscope parameters. Ionization cross-sections were calculated using the quantum excitation of phonons model, incorporating dynamical (multiple) electron scattering, which is seen to be important even for very thin specimens.

  3. Surface energy of zinc

    SciTech Connect

    Bilello, J.C.; Dew-Hughes, D.; Pucino, A.T.

    1983-04-01

    The influence of temperature and associated dislocation microstructure on the energetics of basal plane cleavage in zinc crystals has been investigated using the method of Hull, Beardmore, and Valentine (HBV). A marked temperature dependence was observed in the zinc surface energy, over the range 77--298 /sup 0/K, contrary to previous expectations. Plastic relaxation was associated with crack initiation at 77 /sup 0/K, but not propagation; while at room temperature a plastic zone of 1200--1500 ..mu..m in depth was produced by crack extension. The surface energy could be estimated, independent of the usual Griffith analysis, by measuring the energy dissipation in a fully relaxed deformed zone associated with an explosively formed precursor crack. This method yielded surface energies of 0.066 to 0.079 J m/sup -2/ which was in good agreement with previous work. It is demonstrated that the cleavage surface energy of zinc is well below the thermodynamic surface energy and that this discrepancy is not related to plastic deformation.

  4. Absolute pulse energy measurements of soft x-rays at the Linac Coherent Light Source.

    PubMed

    Tiedtke, K; Sorokin, A A; Jastrow, U; Juranić, P; Kreis, S; Gerken, N; Richter, M; Arp, U; Feng, Y; Nordlund, D; Soufli, R; Fernández-Perea, M; Juha, L; Heimann, P; Nagler, B; Lee, H J; Mack, S; Cammarata, M; Krupin, O; Messerschmidt, M; Holmes, M; Rowen, M; Schlotter, W; Moeller, S; Turner, J J

    2014-09-01

    This paper reports novel measurements of x-ray optical radiation on an absolute scale from the intense and ultra-short radiation generated in the soft x-ray regime of a free electron laser. We give a brief description of the detection principle for radiation measurements which was specifically adapted for this photon energy range. We present data characterizing the soft x-ray instrument at the Linac Coherent Light Source (LCLS) with respect to the radiant power output and transmission by using an absolute detector temporarily placed at the downstream end of the instrument. This provides an estimation of the reflectivity of all x-ray optical elements in the beamline and provides the absolute photon number per bandwidth per pulse. This parameter is important for many experiments that need to understand the trade-offs between high energy resolution and high flux, such as experiments focused on studying materials via resonant processes. Furthermore, the results are compared with the LCLS diagnostic gas detectors to test the limits of linearity, and observations are reported on radiation contamination from spontaneous undulator radiation and higher harmonic content. PMID:25321502

  5. Diagnosis of Ultrafast Laser-Heated Metal Surfaces and Plasma Expansion with Absolute Displacement Interferometry

    NASA Astrophysics Data System (ADS)

    Rodriguez, G.; Clarke, S. A.; Taylor, A. J.; Forsman, A.

    2004-07-01

    We report on the development of a novel technique to measure the critical surface displacement in intense, ultrashort, laser-solid target experiments. Determination of the critical surface position is important for understanding near solid density plasma dynamics and transport from warm dense matter systems, and for diagnosing short scale length plasma expansion and hydrodynamic surface motion from short pulse, laser-heated, solid targets. Instead of inferring critical surface motion from spectral power shifts using a time-delayed probe pulse or from phase shifts using ultrafast pump-probe frequency domain interferometry (FDI), this technique directly measures surface displacement using a single ultrafast laser heating pulse. Our technique is based on an application of a Michelson Stellar interferometer to microscopic rather than stellar scales, and we report plasma scale length motion as small as 10 nm. We will present results for motion of plasmas generated from several target materials (Au, Al, Au on CH plastic) for a laser pulse intensity range from 1011 to 1016 W/cm2. Varying both, the pulse duration and the pulse energy, explores the dependence of the expansion mechanism on the energy deposited and on the peak intensity. Comparisons with hydrocodes reveal the applicability of hydrodynamic models.

  6. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  7. Absolute polarimeter for the proton-beam energy of 200 MeV

    SciTech Connect

    Zelenski, A. N.; Atoian, G.; Bogdanov, A. A.; Nurushev, S. B.; Pylaev, F. S.; Raparia, D.; Runtso, M. F.; Stephenson, E.

    2013-12-15

    A polarimeter is upgraded and tested in a 200-MeV polarized-proton beam at the accelerator-collider facility of the Brookhaven National Laboratory. The polarimeter is based on the elastic polarizedproton scattering on a carbon target at an angle of 16.2°, in which case the analyzing power is close to unity and was measured to a very high degree of precision. It is shown that, in the energy range of 190–205 MeV, the absolute polarization can be measured to a precision better than ±0.5%.

  8. Probing carbohydrate product expulsion from a processive cellulase with multiple absolute binding free energy methods.

    PubMed

    Bu, Lintao; Beckham, Gregg T; Shirts, Michael R; Nimlos, Mark R; Adney, William S; Himmel, Michael E; Crowley, Michael F

    2011-05-20

    Understanding the enzymatic mechanism that cellulases employ to degrade cellulose is critical to efforts to efficiently utilize plant biomass as a sustainable energy resource. A key component of cellulase action on cellulose is product inhibition from monosaccharide and disaccharides in the product site of cellulase tunnel. The absolute binding free energy of cellobiose and glucose to the product site of the catalytic tunnel of the Family 7 cellobiohydrolase (Cel7A) of Trichoderma reesei (Hypocrea jecorina) was calculated using two different approaches: steered molecular dynamics (SMD) simulations and alchemical free energy perturbation molecular dynamics (FEP/MD) simulations. For the SMD approach, three methods based on Jarzynski's equality were used to construct the potential of mean force from multiple pulling trajectories. The calculated binding free energies, -14.4 kcal/mol using SMD and -11.2 kcal/mol using FEP/MD, are in good qualitative agreement. Analysis of the SMD pulling trajectories suggests that several protein residues (Arg-251, Asp-259, Asp-262, Trp-376, and Tyr-381) play key roles in cellobiose and glucose binding to the catalytic tunnel. Five mutations (R251A, D259A, D262A, W376A, and Y381A) were made computationally to measure the changes in free energy during the product expulsion process. The absolute binding free energies of cellobiose to the catalytic tunnel of these five mutants are -13.1, -6.0, -11.5, -7.5, and -8.8 kcal/mol, respectively. The results demonstrated that all of the mutants tested can lower the binding free energy of cellobiose, which provides potential applications in engineering the enzyme to accelerate the product expulsion process and improve the efficiency of biomass conversion. PMID:21454590

  9. Probing Carbohydrate Product Expulsion from a Processive Cellulase with Multiple Absolute Binding Free Energy Methods*

    PubMed Central

    Bu, Lintao; Beckham, Gregg T.; Shirts, Michael R.; Nimlos, Mark R.; Adney, William S.; Himmel, Michael E.; Crowley, Michael F.

    2011-01-01

    Understanding the enzymatic mechanism that cellulases employ to degrade cellulose is critical to efforts to efficiently utilize plant biomass as a sustainable energy resource. A key component of cellulase action on cellulose is product inhibition from monosaccharide and disaccharides in the product site of cellulase tunnel. The absolute binding free energy of cellobiose and glucose to the product site of the catalytic tunnel of the Family 7 cellobiohydrolase (Cel7A) of Trichoderma reesei (Hypocrea jecorina) was calculated using two different approaches: steered molecular dynamics (SMD) simulations and alchemical free energy perturbation molecular dynamics (FEP/MD) simulations. For the SMD approach, three methods based on Jarzynski's equality were used to construct the potential of mean force from multiple pulling trajectories. The calculated binding free energies, −14.4 kcal/mol using SMD and −11.2 kcal/mol using FEP/MD, are in good qualitative agreement. Analysis of the SMD pulling trajectories suggests that several protein residues (Arg-251, Asp-259, Asp-262, Trp-376, and Tyr-381) play key roles in cellobiose and glucose binding to the catalytic tunnel. Five mutations (R251A, D259A, D262A, W376A, and Y381A) were made computationally to measure the changes in free energy during the product expulsion process. The absolute binding free energies of cellobiose to the catalytic tunnel of these five mutants are −13.1, −6.0, −11.5, −7.5, and −8.8 kcal/mol, respectively. The results demonstrated that all of the mutants tested can lower the binding free energy of cellobiose, which provides potential applications in engineering the enzyme to accelerate the product expulsion process and improve the efficiency of biomass conversion. PMID:21454590

  10. Computations of absolute solvation free energies of small molecules using explicit and implicit solvent model.

    SciTech Connect

    Shivakumar, D.; Deng, Y.; Roux, B.; Biosciences Division; Univ. of Chicago

    2009-01-01

    Accurate determination of absolute solvation free energy plays a critical role in numerous areas of biomolecular modeling and drug discovery. A quantitative representation of ligand and receptor desolvation, in particular, is an essential component of current docking and scoring methods. Furthermore, the partitioning of a drug between aqueous and nonpolar solvents is one of the important factors considered in pharmacokinetics. In this study, the absolute hydration free energy for a set of 239 neutral ligands spanning diverse chemical functional groups commonly found in drugs and drug-like candidates is calculated using the molecular dynamics free energy perturbation method (FEP/MD) with explicit water molecules, and compared to experimental data as well as its counterparts obtained using implicit solvent models. The hydration free energies are calculated from explicit solvent simulations using a staged FEP procedure permitting a separation of the total free energy into polar and nonpolar contributions. The nonpolar component is further decomposed into attractive (dispersive) and repulsive (cavity) components using the Weeks-Chandler-Anderson (WCA) separation scheme. To increase the computational efficiency, all of the FEP/MD simulations are generated using a mixed explicit/implicit solvent scheme with a relatively small number of explicit TIP3P water molecules, in which the influence of the remaining bulk is incorporated via the spherical solvent boundary potential (SSBP). The performances of two fixed-charge force fields designed for small organic molecules, the General Amber force field (GAFF), and the all-atom CHARMm-MSI, are compared. Because of the crucial role of electrostatics in solvation free energy, the results from various commonly used charge generation models based on the semiempirical (AM1-BCC) and QM calculations [charge fitting using ChelpG and RESP] are compared. In addition, the solvation free energies of the test set are also calculated using

  11. Sparse representation for a potential energy surface

    NASA Astrophysics Data System (ADS)

    Seko, Atsuto; Takahashi, Akira; Tanaka, Isao

    2014-07-01

    We propose a simple scheme to estimate the potential energy surface (PES) for which the accuracy can be easily controlled and improved. It is based on model selection within the framework of linear regression using the least absolute shrinkage and selection operator (LASSO) technique. Basis functions are selected from a systematic large set of candidate functions. The sparsity of the PES significantly reduces the computational cost of evaluating the energy and force in molecular dynamics simulations without losing accuracy. The usefulness of the scheme for describing the elemental metals Na and Mg is clearly demonstrated.

  12. Absolute energy calibration of the Telescope Array fluorescence detector with an electron linear accelerator

    NASA Astrophysics Data System (ADS)

    Shibata, T.; Beitollahi, M.; Fukushima, M.; Ikeda, D.; Langely, K.; Matthews, J. N.; Sagawa, H.; Shin, B. K.; Thomas, S. B.; Thomson, G. B.

    2013-06-01

    The Electron Light Source(ELS) is a new light source for the absolute energy calibration of cosmic ray Fluorescence Detector(FD) telescopes. The ELS is a compact electron linear accelerator with a typical output of 109 electrons per pulse at 40 MeV. We fire the electron beam vertically into the air 100 m in front of the telescope. The electron beam excites the gases of the atmosphere in the same way as the charged particles of the cosmic ray induced extensive air shower. The gases give off the same light with the same wavelength dependence. The light passes through a small amount of atmosphere and is collected by the same mirror and camera with their wavelength dependence. In this way we can use the electron beam from ELS to make an end-to-end calibration of the telescope. In September 2010, we began operation of the ELS and the FD telescopes observed the fluorescence photons from the air shower which was generated by the electron beam. In this article, we will reort the status of analysis of the absolute energy calibration with data which was taken in September 2010, and beam monitor study in November 2011.

  13. Absolute Binding Free Energy Calculations Using Molecular Dynamics Simulations with Restraining Potentials

    PubMed Central

    Wang, Jiyao; Deng, Yuqing; Roux, Benoît

    2006-01-01

    The absolute (standard) binding free energy of eight FK506-related ligands to FKBP12 is calculated using free energy perturbation molecular dynamics (FEP/MD) simulations with explicit solvent. A number of features are implemented to improve the accuracy and enhance the convergence of the calculations. First, the absolute binding free energy is decomposed into sequential steps during which the ligand-surrounding interactions as well as various biasing potentials restraining the translation, orientation, and conformation of the ligand are turned “on” and “off.” Second, sampling of the ligand conformation is enforced by a restraining potential based on the root mean-square deviation relative to the bound state conformation. The effect of all the restraining potentials is rigorously unbiased, and it is shown explicitly that the final results are independent of all artificial restraints. Third, the repulsive and dispersive free energy contribution arising from the Lennard-Jones interactions of the ligand with its surrounding (protein and solvent) is calculated using the Weeks-Chandler-Andersen separation. This separation also improves convergence of the FEP/MD calculations. Fourth, to decrease the computational cost, only a small number of atoms in the vicinity of the binding site are simulated explicitly, while all the influence of the remaining atoms is incorporated implicitly using the generalized solvent boundary potential (GSBP) method. With GSBP, the size of the simulated FKBP12/ligand systems is significantly reduced, from ∼25,000 to 2500. The computations are very efficient and the statistical error is small (∼1 kcal/mol). The calculated binding free energies are generally in good agreement with available experimental data and previous calculations (within ∼2 kcal/mol). The present results indicate that a strategy based on FEP/MD simulations of a reduced GSBP atomic model sampled with conformational, translational, and orientational restraining

  14. ABSOLUTE MEASUREMENT OF THE POLARIZATION OF HIGH ENERGY PROTON BEAMS AT RHIC

    SciTech Connect

    MAKDISI,Y.; BRAVAR, A. BUNCE, G. GILL, R.; HUANG, H.; ET AL.

    2007-06-25

    The spin physics program at the Relativistic Heavy Ion Collider (RHIC) requires knowledge of the beam polarization to better than 5%. Such a goal is made the more difficult by the lack of knowledge of the analyzing power of high energy nuclear physics processes. To overcome this, a polarized hydrogen jet target was constructed and installed at one intersection region in RHIC where it intersects both beams and utilizes the precise knowledge of the jet atomic hydrogen beam polarization to measure the analyzing power in proton-proton elastic scattering in the Nuclear Coulomb Interference (CNI) region at the prescribed RHIC proton beam energy. The reverse reaction is used to assess the absolute beam polarization. Simultaneous measurements taken with fast high statistics polarimeters that measure the p-Carbon elastic scattering process also in the CNI region use the jet results to calibrate the latter.

  15. Thermal surface free energy and stress of iron

    PubMed Central

    Schönecker, Stephan; Li, Xiaoqing; Johansson, Börje; Kwon, Se Kyun; Vitos, Levente

    2015-01-01

    Absolute values of surface energy and surface stress of solids are hardly accessible by experiment. Here, we investigate the temperature dependence of both parameters for the (001) and (110) surface facets of body-centered cubic Fe from first-principles modeling taking into account vibrational, electronic, and magnetic degrees of freedom. The monotonic decrease of the surface energies of both facets with increasing temperature is mostly due to lattice vibrations and magnetic disorder. The surface stresses exhibit nonmonotonic behaviors resulting in a strongly temperature dependent excess surface stress and surface stress anisotropy. PMID:26439916

  16. Thermal surface free energy and stress of iron.

    PubMed

    Schönecker, Stephan; Li, Xiaoqing; Johansson, Börje; Kwon, Se Kyun; Vitos, Levente

    2015-01-01

    Absolute values of surface energy and surface stress of solids are hardly accessible by experiment. Here, we investigate the temperature dependence of both parameters for the (001) and (110) surface facets of body-centered cubic Fe from first-principles modeling taking into account vibrational, electronic, and magnetic degrees of freedom. The monotonic decrease of the surface energies of both facets with increasing temperature is mostly due to lattice vibrations and magnetic disorder. The surface stresses exhibit nonmonotonic behaviors resulting in a strongly temperature dependent excess surface stress and surface stress anisotropy. PMID:26439916

  17. Absolute energy calibration for relativistic electron beams with pointing instability from a laser-plasma accelerator

    SciTech Connect

    Cha, H. J.; Choi, I. W.; Kim, H. T.; Kim, I J.; Nam, K. H.; Jeong, T. M.; Lee, J.

    2012-06-15

    The pointing instability of energetic electron beams generated from a laser-driven accelerator can cause a serious error in measuring the electron spectrum with a magnetic spectrometer. In order to determine a correct electron spectrum, the pointing angle of an electron beam incident on the spectrometer should be exactly defined. Here, we present a method for absolutely calibrating the electron spectrum by monitoring the pointing angle using a scintillating screen installed in front of a permanent dipole magnet. The ambiguous electron energy due to the pointing instability is corrected by the numerical and analytical calculations based on the relativistic equation of electron motion. It is also possible to estimate the energy spread of the electron beam and determine the energy resolution of the spectrometer using the beam divergence angle that is simultaneously measured on the screen. The calibration method with direct measurement of the spatial profile of an incident electron beam has a simple experimental layout and presents the full range of spatial and spectral information of the electron beams with energies of multi-hundred MeV level, despite the limited energy resolution of the simple electron spectrometer.

  18. Absolute model ages of mantled surfaces in Malea Planum and Utopia Planitia, Mars.

    NASA Astrophysics Data System (ADS)

    Willmes, M.; Hiesinger, H.; Reiss, D.; Zanetti, M.

    2009-04-01

    The surface of Mars is partially covered by a latitude-dependent ice-rich smooth mantle in the middle and high latitudes (±30-60°) [1, 2]. These deposits relate to changes in the obliquity of Mars which have led to major shifts in the Martian climate and repeated global episodes of deposition [3]. The deposits vary in thickness and are usually independent of local geology, topography and elevation. In this study we have determined absolute model ages for the mantled surface units in Utopia Planitia (northern hemisphere) and Malea Planum (southern hemisphere) using crater statistics [4]. These regions show a specific type of mantle degradation called scalloped terrain, and modelled crater retention ages of the easily eroded mantle in these regions reveal the time since the last resurfacing. Images from the High Resolution Imaging Science Experiment (HiRISE) (25-50 cm/pixel spatial resolution) on board the Mars Reconnaissance Orbiter (MRO) were analyzed, continuous areas of smooth mantle were mapped, and small, fresh, unmodified craters were counted. Both regions show degradation features of the mantle in varying degrees. The mantle in Utopia Planitia appears heavily modified by polygonal fractures and scalloped depressions [5]. Scalloped depressions are also found in Malea Planum, but the mantle appears much smoother and less modified by periglacial processes [5, 6]. The study areas totalled 722 km² in Utopia Planitia, and 296 km² in Malea Planum. Model ages for these regions were determined using the chronology function of Hartmann and Neukum [4] and the production function Ivanov [7]. The model ages show that the mantle unit for the area mapped in Utopia Planitia is 0.65 (+0.35/-0.41) to 2.9 (+0.69/-0.75) Myr old and Malea Planum is 3.0 (+1.5/-1.7) to 4.5 (+1.3/-1.4) Myr old, and that both regions represent very recent Amazonian terrain. This is also in agreement with the observed young degradation features described by [6, 8]. We acknowledge that the

  19. Comparison of observed and theoretical absolute energy distributions in the spectrum of Vega

    SciTech Connect

    Merezhin, V.P.; Ruban, E.V.

    1988-11-01

    The absolute energy distribution observed in the spectrum of Vega in the range 3100-10800 /angstrom/ at the Principal Astronomical Observatory of the USSR Academy of Sciences in 1986 by comparing the radiation of Vega with the radiation of a laboratory source calibrated by means of the Soviet State Standard is compared with the data of models of stellar atmospheres. It is shown that the observed distribution is best described by a model with T/sub eff/ = 9850/degree/K. It is noted that there is an excess of radiation in the interval 7500-10800 /angstrom/ by 7-10% compared with the model data. An attempt is made to explain the observed excess. Vega is probably a rapid rotator (v /approx equal/ 230 km/sec) with angle of inclination of the rotation axis to the line of sight of i = 4/degree/-7/degree/.

  20. In-Flight Measurement of the Absolute Energy Scale of the Fermi Large Area Telescope

    SciTech Connect

    Ackermann, M.; Ajello, M.; Allafort, A.; Atwood, W.B.; Axelsson, M.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E.D.; Bonamente, E.; Borgland, A.W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; /more authors..

    2012-09-20

    The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to survey the gamma-ray sky from 20 MeV to several hundreds of GeV. In this energy band there are no astronomical sources with sufficiently well known and sharp spectral features to allow an absolute calibration of the LAT energy scale. However, the geomagnetic cutoff in the cosmic ray electron-plus-positron (CRE) spectrum in low Earth orbit does provide such a spectral feature. The energy and spectral shape of this cutoff can be calculated with the aid of a numerical code tracing charged particles in the Earth's magnetic field. By comparing the cutoff value with that measured by the LAT in different geomagnetic positions, we have obtained several calibration points between {approx}6 and {approx}13 GeV with an estimated uncertainty of {approx}2%. An energy calibration with such high accuracy reduces the systematic uncertainty in LAT measurements of, for example, the spectral cutoff in the emission from gamma ray pulsars.

  1. In-Flight Measurement of the Absolute Energy Scale of the Fermi Large Area Telescope

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Ajello, M.; Allafort, A.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Barbielini, G; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B,; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Gehrels, N.; Hays, E.; McEnery, J. E.; Thompson, D. J.; Troja, E. J.

    2012-01-01

    The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to survey the gamma-ray sky from 20 MeV to several hundreds of GeV. In this energy band there are no astronomical sources with sufficiently well known and sharp spectral features to allow an absolute calibration of the LAT energy scale. However, the geomagnetic cutoff in the cosmic ray electron- plus-positron (CRE) spectrum in low Earth orbit does provide such a spectral feature. The energy and spectral shape of this cutoff can be calculated with the aid of a numerical code tracing charged particles in the Earth's magnetic field. By comparing the cutoff value with that measured by the LAT in different geomagnetic positions, we have obtained several calibration points between approx. 6 and approx. 13 GeV with an estimated uncertainty of approx. 2%. An energy calibration with such high accuracy reduces the systematic uncertainty in LAT measurements of, for example, the spectral cutoff in the emission from gamma ray pulsars.

  2. Absolute interferometric characterization of an x-ray mirror surface profile

    NASA Astrophysics Data System (ADS)

    Vannoni, Maurizio; Freijo Martìn, Idoia

    2016-02-01

    An approach to achieve absolute planarity characterization of an x-ray mirror through an interferometric method is presented. With three measurements and two nominally flat auxiliary mirrors, the radius of curvature and the slope profile of a nominally flat x-ray mirror are retrieved. The height profile is then calculated through integration of the slope profile and merging this information with the radius of curvature knowledge. The method is explained in detail and a measurement example is provided. A comparison with a state-of-the-art deflectometric method is shown, with an agreement level of about 0.14 nm rms.

  3. Setting Whole-Building Absolute Energy Use Targets for the K-12 School, Retail, and Healthcare Sectors: Preprint

    SciTech Connect

    Leach, M.; Bonnema, E.; Pless, S.; Torcellini, P.

    2012-08-01

    This paper helps owners' efficiency representatives to inform executive management, contract development, and project management staff as to how specifying and applying whole-building absolute energy use targets for new construction or renovation projects can improve the operational energy performance of commercial buildings.

  4. A rare gas optics-free absolute photon flux and energy analyzer to provide absolute photoionization rates of inflowing interstellar neutrals

    NASA Technical Reports Server (NTRS)

    Judge, Darrell L.

    1994-01-01

    A prototype spectrometer has been developed for space applications requiring long term absolute EUV photon flux measurements. The energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

  5. Role of absolute humidity in the inactivation of influenza viruses on stainless steel surfaces at elevated temperatures.

    PubMed

    McDevitt, James; Rudnick, Stephen; First, Melvin; Spengler, John

    2010-06-01

    Influenza virus has been found to persist in the environment for hours to days, allowing for secondary transmission of influenza via inanimate objects known as fomites. We evaluated the efficacy of heat and moisture for the decontamination of surfaces for the purpose of preventing of the spread of influenza. Aqueous suspensions of influenza A virus were deposited onto stainless steel coupons, allowed to dry under ambient conditions, and exposed to temperatures of 55 degrees C, 60 degrees C, or 65 degrees C and relative humidity (RH) of 25%, 50%, or 75% for up to 1 h. Quantitative virus assays were performed on the solution used to wash the viruses from these coupons, and results were compared with the solution used to wash coupons treated similarly but left under ambient conditions. Inactivation of influenza virus on surfaces increased with increasing temperature, RH, and exposure time. Reductions of greater than 5 logs of influenza virus on surfaces were achieved at temperatures of 60 and 65 degrees C, exposure times of 30 and 60 min, and RH of 50 and 75%. Our data also suggest that absolute humidity is a better predictor of surface inactivation than RH and allows the prediction of survival using two parameters rather than three. Modest amounts of heat and adequate moisture can provide effective disinfection of surfaces while not harming surfaces, electrical systems, or mechanical components, leaving no harmful residues behind after treatment and requiring a relatively short amount of time. PMID:20435770

  6. Durable low surface-energy surfaces

    NASA Technical Reports Server (NTRS)

    Willis, Paul B. (Inventor); McElroy, Paul M. (Inventor); Hickey, Gregory H. (Inventor)

    1993-01-01

    A formulation for forming a low surface-energy surface on a substrate having (i) a fluoroalkyl silane having a low surface energy part, (ii) a liquid crystal silane operable for enhancing the orientation of the molecules of the fluoroalkyl silane and for crosslinking with the fluoroalkyl silane, and, (iii) a transport medium for applying the fluoroalkyl silane and the liquid crystal silane to the surface of a substrate. In one embodiment the formulation can includes a crosslinking agent for crosslinking the fluoroalkyl silane. In another embodiment the formulation has a condensation catalyst for enhancing chemical bonding of the fluoroalkyl silane to the substrate. The transport medium can be an alcohol such as methanol or ethanol.

  7. Calculation of the absolute free energy of a smectic-A phase

    NASA Astrophysics Data System (ADS)

    Huang, Chien-Cheng; Ramachandran, Sanoop; Ryckaert, Jean-Paul

    2014-12-01

    In this paper, we provide a scheme to compute the absolute free energy of a smectic-A phase via the "indirect method." The state of interest is connected through a three-step reversible path to a reference state. This state consists of a low-density layer of rods coupled to two external fields maintaining these rods close to the layer's plane and oriented preferably normal to the layer. The low-density free energy of the reference state can be computed on the basis of the relevant second virial coefficients between two rods coupled to the two external fields. We apply this technique to the Gay-Berne potential for calamitics with a parameter set leading to stable isotropic (I), nematic (N), smectic-A (SmA), and crystal (Cr) phases. We locate the I-SmA phase transition at low pressure and the sequence of phase transitions I-N-SmA along higher-pressure isobars and we establish the location of the I-N-SmA triple point. Close to this triple point, we show that the N-SmA transition is clearly first order. Our results are compared to the coexistence lines of the approximate phase diagram elucidated by de Miguel et al. [J. Chem. Phys. 121, 11183 (2004), 10.1063/1.1810472] established through the direct observation of the sequence of phase transitions occurring along isobars under heating or cooling sequences of runs. Finally, we discuss the potential of our technique in studying similar transitions observed on layered phases under confinement.

  8. Calculation of the absolute free energy of a smectic-A phase.

    PubMed

    Huang, Chien-Cheng; Ramachandran, Sanoop; Ryckaert, Jean-Paul

    2014-12-01

    In this paper, we provide a scheme to compute the absolute free energy of a smectic-A phase via the "indirect method." The state of interest is connected through a three-step reversible path to a reference state. This state consists of a low-density layer of rods coupled to two external fields maintaining these rods close to the layer's plane and oriented preferably normal to the layer. The low-density free energy of the reference state can be computed on the basis of the relevant second virial coefficients between two rods coupled to the two external fields. We apply this technique to the Gay-Berne potential for calamitics with a parameter set leading to stable isotropic (I), nematic (N), smectic-A (SmA), and crystal (Cr) phases. We locate the I-SmA phase transition at low pressure and the sequence of phase transitions I-N-SmA along higher-pressure isobars and we establish the location of the I-N-SmA triple point. Close to this triple point, we show that the N-SmA transition is clearly first order. Our results are compared to the coexistence lines of the approximate phase diagram elucidated by de Miguel et al. [J. Chem. Phys. 121, 11183 (2004)] established through the direct observation of the sequence of phase transitions occurring along isobars under heating or cooling sequences of runs. Finally, we discuss the potential of our technique in studying similar transitions observed on layered phases under confinement.

  9. Absolute Calibration of Image Plate for electrons at energy between 100 keV and 4 MeV

    SciTech Connect

    Chen, H; Back, N L; Eder, D C; Ping, Y; Song, P M; Throop, A

    2007-12-10

    The authors measured the absolute response of image plate (Fuji BAS SR2040) for electrons at energies between 100 keV to 4 MeV using an electron spectrometer. The electron source was produced from a short pulse laser irradiated on the solid density targets. This paper presents the calibration results of image plate Photon Stimulated Luminescence PSL per electrons at this energy range. The Monte Carlo radiation transport code MCNPX results are also presented for three representative incident angles onto the image plates and corresponding electron energies depositions at these angles. These provide a complete set of tools that allows extraction of the absolute calibration to other spectrometer setting at this electron energy range.

  10. DAQ Software Contributions, Absolute Scale Energy Calibration and Background Evaluation for the NOvA Experiment at Fermilab

    SciTech Connect

    Flumerfelt, Eric Lewis

    2015-08-01

    The NOvA (NuMI Off-axis ve [nu_e] Appearance) Experiment is a long-baseline accelerator neutrino experiment currently in its second year of operations. NOvA uses the Neutrinos from the Main Injector (NuMI) beam at Fermilab, and there are two main off-axis detectors: a Near Detector at Fermilab and a Far Detector 810 km away at Ash River, MN. The work reported herein is in support of the NOvA Experiment, through contributions to the development of data acquisition software, providing an accurate, absolute-scale energy calibration for electromagnetic showers in NOvA detector elements, crucial to the primary electron neutrino search, and through an initial evaluation of the cosmic background rate in the NOvA Far Detector, which is situated on the surface without significant overburden. Additional support work for the NOvA Experiment is also detailed, including DAQ Server Administration duties and a study of NOvA’s sensitivity to neutrino oscillations into a “sterile” state.

  11. Surface Air Temperature - Long-Term Anomaly Series and Absolute Values (Invited)

    NASA Astrophysics Data System (ADS)

    Jones, P. D.

    2013-12-01

    Of all the possible domains of the Earth's surface, surface air temperature has the longest records extending back at some European locations to the late-17th century. Since that time coverage has expanded to encompass most of the world since the 1950s onwards. It is this domain that provides our long-term record of change providing the yardstick against which we define both cooler and warmer and cooling and warming periods during the last 300 years. Assembling all the recorded data is beset with an array of problems: the reasons for collecting the data during this long period have been many and varied and instruments, exposures, observation times and methods of calculating averages have regularly changed. Even today, there is not a WMO-defined method of calculating the daily and monthly average with countries allowed to use whatever method they deem appropriate. The talk will discuss the history, the problems and the methods that have been used to overcome them. As we move to more automated measurements and dynamical approaches to interpolation (Reanalyses) the talk will conclude with a number of recommendations.

  12. Surface energies of elemental crystals.

    PubMed

    Tran, Richard; Xu, Zihan; Radhakrishnan, Balachandran; Winston, Donald; Sun, Wenhao; Persson, Kristin A; Ong, Shyue Ping

    2016-01-01

    The surface energy is a fundamental property of the different facets of a crystal that is crucial to the understanding of various phenomena like surface segregation, roughening, catalytic activity, and the crystal's equilibrium shape. Such surface phenomena are especially important at the nanoscale, where the large surface area to volume ratios lead to properties that are significantly different from the bulk. In this work, we present the largest database of calculated surface energies for elemental crystals to date. This database contains the surface energies of more than 100 polymorphs of about 70 elements, up to a maximum Miller index of two and three for non-cubic and cubic crystals, respectively. Well-known reconstruction schemes are also accounted for. The database is systematically improvable and has been rigorously validated against previous experimental and computational data where available. We will describe the methodology used in constructing the database, and how it can be accessed for further studies and design of materials. PMID:27622853

  13. Absolute cross sections for vibrational excitations of cytosine by low energy electron impact

    NASA Astrophysics Data System (ADS)

    Michaud, M.; Bazin, M.; Sanche, L.

    2012-09-01

    The absolute cross sections (CSs) for vibrational excitations of cytosine by electron impact between 0.5 and 18 eV were measured by electron-energy loss (EEL) spectroscopy of the molecule deposited at monolayer coverage on an inert Ar substrate. The vibrational energies compare to those that have been reported from IR spectroscopy of cytosine isolated in Ar matrix, IR and Raman spectra of polycrystalline cytosine, and ab initio calculation. The CSs for the various H bending modes at 142 and 160 meV are both rising from their energy threshold up to 1.7 and 2.1 × 10-17 cm2 at about 4 eV, respectively, and then decrease moderately while maintaining some intensity at 18 eV. The latter trend is displayed as well for the CS assigned to the NH2 scissor along with bending of all H at 179 meV. This overall behavior in electron-molecule collision is attributed to direct processes such as the dipole, quadrupole, and polarization contributions, etc. of the interaction of the incident electron with a molecule. The CSs for the ring deformation at 61 meV, the ring deformation with N-H symmetric wag at 77 meV, and the ring deformations with symmetric bending of all H at 119 meV exhibit common enhancement maxima at 1.5, 3.5, and 5.5 eV followed by a broad hump at about 12 eV, which are superimposed on the contribution due to the direct processes. At 3.5 eV, the CS values for the 61-, 77-, and 119-meV modes reach 4.0, 3.0, and 4.5 × 10-17 cm2, respectively. The CS for the C-C and C-O stretches at 202 meV, which dominates in the intermediate EEL region, rises sharply until 1.5 eV, reaches its maximum of 5.7 × 10-17 cm2 at 3.5 eV and then decreases toward 18 eV. The present vibrational enhancements, correspond to the features found around 1.5 and 4.5 eV in electron transmission spectroscopy (ETS) and those lying within 1.5-2.1 eV, 5.2-6.8 eV, and 9.5-10.9 eV range in dissociative electron attachment (DEA) experiments with cytosine in gas phase. While the ETS features are ascribed

  14. Absolute cross sections for vibrational excitations of cytosine by low energy electron impact.

    PubMed

    Michaud, M; Bazin, M; Sanche, L

    2012-09-21

    The absolute cross sections (CSs) for vibrational excitations of cytosine by electron impact between 0.5 and 18 eV were measured by electron-energy loss (EEL) spectroscopy of the molecule deposited at monolayer coverage on an inert Ar substrate. The vibrational energies compare to those that have been reported from IR spectroscopy of cytosine isolated in Ar matrix, IR and Raman spectra of polycrystalline cytosine, and ab initio calculation. The CSs for the various H bending modes at 142 and 160 meV are both rising from their energy threshold up to 1.7 and 2.1 × 10(-17) cm(2) at about 4 eV, respectively, and then decrease moderately while maintaining some intensity at 18 eV. The latter trend is displayed as well for the CS assigned to the NH(2) scissor along with bending of all H at 179 meV. This overall behavior in electron-molecule collision is attributed to direct processes such as the dipole, quadrupole, and polarization contributions, etc. of the interaction of the incident electron with a molecule. The CSs for the ring deformation at 61 meV, the ring deformation with N-H symmetric wag at 77 meV, and the ring deformations with symmetric bending of all H at 119 meV exhibit common enhancement maxima at 1.5, 3.5, and 5.5 eV followed by a broad hump at about 12 eV, which are superimposed on the contribution due to the direct processes. At 3.5 eV, the CS values for the 61-, 77-, and 119-meV modes reach 4.0, 3.0, and 4.5 × 10(-17) cm(2), respectively. The CS for the C-C and C-O stretches at 202 meV, which dominates in the intermediate EEL region, rises sharply until 1.5 eV, reaches its maximum of 5.7 × 10(-17) cm(2) at 3.5 eV and then decreases toward 18 eV. The present vibrational enhancements, correspond to the features found around 1.5 and 4.5 eV in electron transmission spectroscopy (ETS) and those lying within 1.5-2.1 eV, 5.2-6.8 eV, and 9.5-10.9 eV range in dissociative electron attachment (DEA) experiments with cytosine in gas phase. While the ETS features

  15. Surface energy of zinc. [Effective cleavage surface energy

    SciTech Connect

    Bilello, J.C.; Dew-Hughes, D.; Pucino, A.T.

    1981-01-01

    The influence of temperature and associated dislocation microstructure on the energetics of basal plane cleavage in zinc crystals has been investigated using the method of Hull, Beardmore and Valentine (HBV). A marked temperature dependence was observed in the zinc surface energy, over the range 77 to 298/sup 0/K, contrary to previous expectations. Plastic relaxation was associated with crack initiation at 77/sup 0/K, but not propagation, while at room temperature a plastic zone of 1200-1500 ..mu..m in depth was produced by crack extension. The surface energy could be estimated, independent of the usual Griffith analysis, by measuring the energy dissipation in a fully relaxed deformed zone associated with an explosively formed precursor crack. This method yielded surface energies of 0.066 to 0.079 J-m/sup -2/ which was in good agreement with previous work. It is demonstrated that the cleavage surface energy of zinc is well below the thermodynamic surface energy and that this discrepancy is not related to plastic deformation. 7 figures, 1 table.

  16. Absolute Photoionization Cross Sections for Br2+ in the 4 p --> 4d and 3d --> 4p Energy Regions

    NASA Astrophysics Data System (ADS)

    Aguilar, A.; Juarez, A. M.; Bilodeau, R. C.; Esteves, D. A.; Hardy, D. A.; Red, E. C.

    2011-05-01

    Absolute single photoionization cross-section measurements are reported for Br2+ in the 31 eV to 46 eV and 64 eV to 72 eV photon energy ranges. The first energy range includes the low-lying 2P3 / 2 , 1 / 2 and 2D5 / 2 , 3 / 2 metastable state thresholds and extends for 10 eV above the 4S3 / 2 ground state threshold. Strong photoexcitation-autoionization resonances due to 4p --> nd transitions are seen in the cross-section spectrum and identified based on a quantum-defect analysis of the series. The systematic behavior of the quantum defect parameter of some of the Rydberg series observed in the Br2+ spectrum as well as in previously measured Se+ spectrum, are analyzed as a function of the nuclear charge. The 64 eV to 72 eV energy range contains discrete structure that arises from 3d --> np excitations. The R-matrix photoionization cross section calculations of Cummings and O'Sullivan, PRA, 54 (1996) are compared to our absolute cross section measurements in this energy range. Absolute single photoionization cross-section measurements are reported for Br2+ in the 31 eV to 46 eV and 64 eV to 72 eV photon energy ranges. The first energy range includes the low-lying 2P3 / 2 , 1 / 2 and 2D5 / 2 , 3 / 2 metastable state thresholds and extends for 10 eV above the 4S3 / 2 ground state threshold. Strong photoexcitation-autoionization resonances due to 4p --> nd transitions are seen in the cross-section spectrum and identified based on a quantum-defect analysis of the series. The systematic behavior of the quantum defect parameter of some of the Rydberg series observed in the Br2+ spectrum as well as in previously measured Se+ spectrum, are analyzed as a function of the nuclear charge. The 64 eV to 72 eV energy range contains discrete structure that arises from 3d --> np excitations. The R-matrix photoionization cross section calculations of Cummings and O'Sullivan, PRA, 54 (1996) are compared to our absolute cross section measurements in this energy range. This work is

  17. Surface energies of elemental crystals

    PubMed Central

    Tran, Richard; Xu, Zihan; Radhakrishnan, Balachandran; Winston, Donald; Sun, Wenhao; Persson, Kristin A.; Ong, Shyue Ping

    2016-01-01

    The surface energy is a fundamental property of the different facets of a crystal that is crucial to the understanding of various phenomena like surface segregation, roughening, catalytic activity, and the crystal’s equilibrium shape. Such surface phenomena are especially important at the nanoscale, where the large surface area to volume ratios lead to properties that are significantly different from the bulk. In this work, we present the largest database of calculated surface energies for elemental crystals to date. This database contains the surface energies of more than 100 polymorphs of about 70 elements, up to a maximum Miller index of two and three for non-cubic and cubic crystals, respectively. Well-known reconstruction schemes are also accounted for. The database is systematically improvable and has been rigorously validated against previous experimental and computational data where available. We will describe the methodology used in constructing the database, and how it can be accessed for further studies and design of materials. PMID:27622853

  18. Absolute Photoionization Cross Section with an Ultra-high Energy Resolution for Ne in the Region of 1s Rydberg States

    SciTech Connect

    Kato, M.; Morishita, Y.; Suzuki, I. H.; Saito, N.; Oura, M.; Yamaoka, H.; Okada, K.; Matsudo, T.; Gejo, T.

    2007-01-19

    The high-resolution absolute photoabsorption cross section with an absolute photon energy scale for Ne in the energy region of 864-872 eV (1s-1np Rydberg states) has been measured using a multi-electrode ionization chamber and monochromatized synchrotron radiation. The natural lifetime width of Ne 1s-13p resonance state has been obtained to be 252 {+-} 5 meV. The Ne+ (1s-1) ionization potential is determined to be 870.16 {+-} 0.04 eV by using the Rydberg formula. These absolute values are supposed to be more reliable than those previously reported.

  19. Absolute energy calibration of FD by an electron linear accelerator for Telescope Array

    SciTech Connect

    Shibata, T.; Fukushima, M.; Ikeda, D.; Enomoto, A.; Fukuda, S.; Furukawa, K.; Ikeda, M.; Iwase, H.; Kakihara, K.; Kamitani, T.; Kondo, Y.; Ohsawa, S.; Sagawa, H.; Sanami, T.; Satoh, M.; Shidara, T.; Sugimura, T.; Yoshida, M.; Matthews, J. N.; Ogio, S.

    2011-09-22

    The primary energy of the ultra-high energy cosmic rays(UHECR) are measured with the number of fluorescence photons which are detected with fluorescence detectors(FD) in the Telescope Array experiment(TA). Howevery since there is large uncertinty as 19% in the measurement of the energy scale, the most important theme is improvement of the energy calibration. The electron light source(ELS) is a small electron linear accelerator for new energy calibration. The ELS is located 100 m far from the FD station, and injects electron beam which is accelerated to 40 MeV energy into the sky. We can calibrate the FD energy scale by detection the air shower directly which is generated by the electron beam. The ELS was developed in KEK Japan, and moved to the TA site in March 2009. We started the beam operation in September 2010, in consequence we detected the air shower which was generated by electron beam in the air. The output kinetic energy of the electron beam was 41.1 MeV, we adjusted the output charge from 40 to 140 pC/pulse. We expect that we can improve the uncertinty of the energy scale to about 10% with the ELS, futhermore ELS will be a very useful apparatus for R and D of future UHECR observation.

  20. Absolute Beam Energy Measurement using Elastic ep Scattering at Thomas Jefferson National Accelerator Facility

    NASA Astrophysics Data System (ADS)

    Deur, Alexandre

    1999-10-01

    The Jefferson Lab beam energy measurement in Hall A using the elastic ep scattering will be described. This new, non-magnetic, energy measurement method allows a ( triangle E/E=10-4 ) precision. First-order corrections are canceled by the measurements of the electron and proton scattering angles for two symmetric kinematics. The measurement principle will be presented as well as the device and measurement results. Comparison with independent magnetic energy measurements of the same accuracy will be shown. This project is the result of a collaboration between the LPC: université Blaise Pascal/in2p3), Saclay and Jefferson Lab.

  1. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  2. Surface meteorology and Solar Energy

    NASA Technical Reports Server (NTRS)

    Stackhouse, Paul W. (Principal Investigator)

    The Release 5.1 Surface meteorology and Solar Energy (SSE) data contains parameters formulated for assessing and designing renewable energy systems. Parameters fall under 11 categories including: Solar cooking, solar thermal applications, solar geometry, tilted solar panels, energy storage systems, surplus product storage systems, cloud information, temperature, wind, other meteorological factors, and supporting information. This latest release contains new parameters based on recommendations by the renewable energy industry and it is more accurate than previous releases. On-line plotting capabilities allow quick evaluation of potential renewable energy projects for any region of the world. The SSE data set is formulated from NASA satellite- and reanalysis-derived insolation and meteorological data for the 10-year period July 1983 through June 1993. Results are provided for 1 degree latitude by 1 degree longitude grid cells over the globe. Average daily and monthly measurements for 1195 World Radiation Data Centre ground sites are also available. [Mission Objectives] The SSE project contains insolation and meteorology data intended to aid in the development of renewable energy systems. Collaboration between SSE and technology industries such as the Hybrid Optimization Model for Electric Renewables ( HOMER ) may aid in designing electric power systems that employ some combination of wind turbines, photovoltaic panels, or diesel generators to produce electricity. [Temporal_Coverage: Start_Date=1983-07-01; Stop_Date=1993-06-30] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180].

  3. Absolute elastic differential electron scattering cross sections in the intermediate energy region. III - SF6 and UF6

    NASA Technical Reports Server (NTRS)

    Srivastava, S. K.; Trajmar, S.; Chutjian, A.; Williams, W.

    1976-01-01

    A recently developed technique has been used to measure the ratios of elastic differential electron scattering cross sections (DCS) for SF6 and UF6 to those of He at electron impact energies of 5, 10, 15, 20, 30, 40, 50, 60, and 75 eV and at scattering angles of 20 to 135 deg. In order to obtain the absolute values of DCS from these ratios, He DCS of McConkey and Preston have been employed in the 20 to 90 deg range. At angles in the 90 to 135 deg range the recently determined cross sections of Srivastava and Trajmar have been utilized. From these DCS, elastic integral and momentum transfer cross sections have been obtained.

  4. Absolute cross section for low-energy-electron damage to condensed macromolecules: A case study of DNA

    NASA Astrophysics Data System (ADS)

    Rezaee, Mohammad; Cloutier, Pierre; Bass, Andrew D.; Michaud, Marc; Hunting, Darel J.; Sanche, Léon

    2012-09-01

    Cross sections (CSs) for the interaction of low-energy electrons (LEE) with condensed macromolecules are essential parameters for accurate modeling of radiation-induced molecular decomposition and chemical synthesis. Electron irradiation of dry nanometer-scale macromolecular solid films has often been employed to measure CSs and other quantitative parameters for LEE interactions. Since such films have thicknesses comparable with electron thermalization distances, energy deposition varies throughout the film. Moreover, charge accumulation occurring inside the films shields a proportion of the macromolecules from electron irradiation. Such effects complicate the quantitative comparison of the CSs obtained in films of different thicknesses and limit the applicability of such measurements. Here, we develop a simple mathematical model, termed the molecular survival model, that employs a CS for a particular damage process together with an attenuation length related to the total CS, to investigate how a measured CS might be expected to vary with experimental conditions. As a case study, we measure the absolute CS for the formation of DNA strand breaks (SBs) by electron irradiation at 10 and 100 eV of lyophilized plasmid DNA films with thicknesses between 10 and 30 nm. The measurements are shown to depend strongly on the thickness and charging condition of the nanometer-scale films. Such behaviors are in accord with the model and support its validity. Via this analysis, the CS obtained for SB damage is nearly independent of film thickness and charging effects. In principle, this model can be adapted to provide absolute CSs for electron-induced damage or reactions occurring in other molecular solids across a wider range of experimental conditions.

  5. Absolute energy distribution in the spectra of 32 Cygni. Eclipses of 1987 and 1990

    NASA Astrophysics Data System (ADS)

    Burnashev, V. I.; Burnasheva, B. A.

    2011-06-01

    The photometric observations during 1953-1994 were used for the construction of the summary light curve for 32 Cygni in the photometric UBV-system. On the basis of energy distribution data, the spectral classes and luminosities of the components of this binary system were obtained. The column density of HI during several ingresses and egresses was estimated, suggesting that the depression at λ 3650 Å was caused by hydrogen absorption.

  6. Offset-corrected Δ -Kohn-Sham scheme for semiempirical prediction of absolute x-ray photoelectron energies in molecules and solids

    NASA Astrophysics Data System (ADS)

    Walter, Michael; Moseler, Michael; Pastewka, Lars

    2016-07-01

    Absolute binding energies of core electrons in molecules and bulk materials can be efficiently calculated by spin paired density-function theory employing a Δ -Kohn-Sham (Δ KS ) scheme corrected by offsets that are highly transferable. These offsets depend on core level and atomic species and can be determined by comparing Δ KS energies to experimental molecular x-ray photoelectron spectra. We demonstrate the correct prediction of absolute and relative binding energies on a wide range of molecules, metals, and insulators.

  7. Absolute elastic differential electron scattering cross sections in the intermediate energy region. IV - CO

    NASA Technical Reports Server (NTRS)

    Tanaka, H.; Srivastava, S. K.; Chutjian, A.

    1978-01-01

    Using a crossed electron beam-molecular beam scattering geometry and a relative-flow technique, ratios of elastic differential cross sections of CO to those of He have been measured at electron impact energies of 3, 5, 7.5, 9.9, 15, 20, 30, 50, 75, and 100 eV. At each energy, an angular range of 15 to 130 deg has been covered. These ratios have been multiplied by previously known He elastic differential cross sections to obtain elastic differential cross sections for CO. Since pure rotational excitations were not resolved, the elastic differential cross sections are a sum of elastic and pure rotational excitations at room temperature. From a knowledge of differential cross sections (DCS), integral and momentum transfer cross sections have been calculated. Both the DCS and integral cross sections are compared at 50, 75, and 100 eV to a recent two-potential theory of e-molecule scattering. Present results show that the isoelectronic molecules CO and N2 have very similar magnitudes and shapes of their differential cross sections.

  8. Absolute measurements of x-ray backlighter sources at energies above 10 keV

    SciTech Connect

    Maddox, B. R.; Park, H. S.; Remington, B. A.; Chen, C.; Chen, S.; Prisbrey, S. T.; Comley, A.; Back, C. A.; Szabo, C.; Seely, J. F.; Feldman, U.; Hudson, L. T.; Seltzer, S.; Haugh, M. J.; Ali, Z.

    2011-05-15

    Line emission and broadband x-ray sources with x-ray energies above 10 keV have been investigated using a range of calibrated x-ray detectors for use as x-ray backlighters in high energy density (HED) experiments. The conversion efficiency of short- and long-pulse driven Mo and Ag line-emission backlighters at 17 and 22 keV was measured to investigate the crossover region between short- and long-pulse conversion efficiency. It was found that significant 17 and 22 keV line emissions were observed using a 3 {omega}, 1 ns long-pulse drive for Mo and Ag targets and a comparison between the measured Mo x-ray spectrum and calculations using an atomic physics code suggests that the line emission is due to thermal emission from N-like Mo atoms. Electron temperatures derived from fits to the continuum region of the x-ray spectra agree well with the T{sub hot} scaling as 100x(I{lambda}{sup 2}){sup 1/3}. The continuum emissions from empty and 1 atm Kr-filled imploded CH shell targets were also measured for the use as broadband backlighters.

  9. A rare gas optics-free absolute photon flux and energy analyzer for solar and planetary observations

    NASA Technical Reports Server (NTRS)

    Judge, Darrell L.

    1994-01-01

    We have developed a prototype spectrometer for space applications requiring long term absolute EUV photon flux measurements. In this recently developed spectrometer, the energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

  10. Measurement of Absolute Excitation Cross Sections in Highly-Charged Ions Using Electron Energy Loss and Merged Beams

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Smith, Steven J.; Lozano, J.

    2002-01-01

    There is increasing emphasis during this decade on understanding energy balance and phenomena observed in high electron temperature plasmas. The UV spectral return from FUSE, the X-ray spectral return from the HETG on Chandra and the LETGS 011 XMM-Newton are just beginning. Line emissions are almost entirely from highly-charged ions (HCIs) of C, N, 0, Ne, Mg, S, Si, Ca, and Fe. The Constellation-X mission will provide X-ray spectroscopy up to photon energies of 0.12 nm (10 keV) where primary line emitters will be HCIs. A variety of atomic parameters are required to model the stellar and solar plasma. These include cross sections for excitation, ionization, charge-exchange, X-ray emission, direct and indirect recombination, lifetimes and branching ratios, and dependences on l, m mixing by external E and B fields. In almost all cases the atomic quantities are calculated, and few comparisons to experiment have been carried out. Collision strengths and Einstein A-values are required to convert the observed spectral intensities to electron temperatures and densities in the stellar plasma. The JPL electron energy-loss and merged beam approach has been used to measure absolute collision strengths in a number of ions, with critical comparison made to the best available theories.

  11. Length scales in alloy dissolution and measurement of absolute interfacial free energy.

    PubMed

    Rugolo, J; Erlebacher, J; Sieradzki, K

    2006-12-01

    De-alloying is the selective dissolution of one or more of the elemental components of an alloy. In binary alloys that exhibit complete solid solubility, de-alloying of the less noble component results in the formation of nanoporous metals, a materials class that has attracted attention for applications such as catalysis, sensing and actuation. In addition, the occurrence of de-alloying in metallic alloy systems under stress is known to result in stress-corrosion cracking, a key failure mechanism in fossil fuel and nuclear plants, ageing aircraft, and also an important concern in the design of nuclear-waste storage containers. Central to the design of corrosion-resistant alloys is the identification of a composition-dependent electrochemical critical potential, Vcrit, above which the current rises dramatically with potential, signalling the onset of bulk de-alloying. Below Vcrit, the surface is passivated by the accumulation of up to several monolayers of the more noble component. The current understanding of the processes that control Vcrit is incomplete. Here, we report on de-alloying results of Ag/Au superlattices that clarify the role of pre-existing length scales in alloy dissolution. Our data motivated us to re-analyse existing data on critical potentials of Ag-Au alloys and develop a simple unifying picture that accounts for the compositional dependence of solid-solution alloy critical potentials.

  12. Energy conservation potential of surface modification technologies

    SciTech Connect

    Le, H.K.; Horne, D.M.; Silberglitt, R.S.

    1985-09-01

    This report assesses the energy conservation impact of surface modification technologies on the metalworking industries. The energy conservation impact of surface modification technologies on the metalworking industries is assessed by estimating their friction and wear tribological sinks and the subsequent reduction in these sinks when surface modified tools are used. Ion implantation, coatings, and laser and electron beam surface modifications are considered.

  13. Probing non-covalent interactions with a second generation energy decomposition analysis using absolutely localized molecular orbitals.

    PubMed

    Horn, Paul R; Mao, Yuezhi; Head-Gordon, Martin

    2016-08-17

    An energy decomposition analysis (EDA) separates a calculated interaction energy into as many interpretable contributions as possible; for instance, permanent and induced electrostatics, Pauli repulsions, dispersion and charge transfer. The challenge is to construct satisfactory definitions of all terms in the chemically relevant regime where fragment densities overlap, rendering unique definitions impossible. Towards this goal, we present an improved EDA for Kohn-Sham density functional theory (DFT) with properties that have previously not been simultaneously attained. Building on the absolutely localized molecular orbital (ALMO)-EDA, this second generation ALMO-EDA is variational and employs valid antisymmetric electronic wavefunctions to produce all five contributions listed above. These contributions moreover all have non-trivial complete basis set limits. We apply the EDA to the water dimer, the T-shaped and parallel-displaced benzene dimer, the p-biphthalate dimer "anti-electrostatic" hydrogen bonding complex, the biologically relevant binding of adenine and thymine in stacked and hydrogen-bonded configurations, the triply hydrogen-bonded guanine-cytosine complex, the interaction of Cl(-) with s-triazine and with the 1,3-dimethyl imidazolium cation, which is relevant to the study of ionic liquids, and the water-formaldehyde-vinyl alcohol ter-molecular radical cationic complex formed in the dissociative photoionization of glycerol. PMID:27492057

  14. Energy Decomposition Analysis Based on Absolutely Localized Molecular Orbitals for Large-Scale Density Functional Theory Calculations in Drug Design.

    PubMed

    Phipps, M J S; Fox, T; Tautermann, C S; Skylaris, C-K

    2016-07-12

    We report the development and implementation of an energy decomposition analysis (EDA) scheme in the ONETEP linear-scaling electronic structure package. Our approach is hybrid as it combines the localized molecular orbital EDA (Su, P.; Li, H. J. Chem. Phys., 2009, 131, 014102) and the absolutely localized molecular orbital EDA (Khaliullin, R. Z.; et al. J. Phys. Chem. A, 2007, 111, 8753-8765) to partition the intermolecular interaction energy into chemically distinct components (electrostatic, exchange, correlation, Pauli repulsion, polarization, and charge transfer). Limitations shared in EDA approaches such as the issue of basis set dependence in polarization and charge transfer are discussed, and a remedy to this problem is proposed that exploits the strictly localized property of the ONETEP orbitals. Our method is validated on a range of complexes with interactions relevant to drug design. We demonstrate the capabilities for large-scale calculations with our approach on complexes of thrombin with an inhibitor comprised of up to 4975 atoms. Given the capability of ONETEP for large-scale calculations, such as on entire proteins, we expect that our EDA scheme can be applied in a large range of biomolecular problems, especially in the context of drug design.

  15. An energy decomposition analysis for second-order Møller–Plesset perturbation theory based on absolutely localized molecular orbitals

    SciTech Connect

    Thirman, Jonathan Head-Gordon, Martin

    2015-08-28

    An energy decomposition analysis (EDA) of intermolecular interactions is proposed for second-order Møller–Plesset perturbation theory (MP2) based on absolutely localized molecular orbitals (ALMOs), as an extension to a previous ALMO-based EDA for self-consistent field methods. It decomposes the canonical MP2 binding energy by dividing the double excitations that contribute to the MP2 wave function into classes based on how the excitations involve different molecules. The MP2 contribution to the binding energy is decomposed into four components: frozen interaction, polarization, charge transfer, and dispersion. Charge transfer is defined by excitations that change the number of electrons on a molecule, dispersion by intermolecular excitations that do not transfer charge, and polarization and frozen interactions by intra-molecular excitations. The final two are separated by evaluations of the frozen, isolated wave functions in the presence of the other molecules, with adjustments for orbital response. Unlike previous EDAs for electron correlation methods, this one includes components for the electrostatics, which is vital as adjustment to the electrostatic behavior of the system is in some cases the dominant effect of the treatment of electron correlation. The proposed EDA is then applied to a variety of different systems to demonstrate that all proposed components behave correctly. This includes systems with one molecule and an external electric perturbation to test the separation between polarization and frozen interactions and various bimolecular systems in the equilibrium range and beyond to test the rest of the EDA. We find that it performs well on these tests. We then apply the EDA to a halogen bonded system to investigate the nature of the halogen bond.

  16. An energy decomposition analysis for second-order Møller-Plesset perturbation theory based on absolutely localized molecular orbitals.

    PubMed

    Thirman, Jonathan; Head-Gordon, Martin

    2015-08-28

    An energy decomposition analysis (EDA) of intermolecular interactions is proposed for second-order Møller-Plesset perturbation theory (MP2) based on absolutely localized molecular orbitals (ALMOs), as an extension to a previous ALMO-based EDA for self-consistent field methods. It decomposes the canonical MP2 binding energy by dividing the double excitations that contribute to the MP2 wave function into classes based on how the excitations involve different molecules. The MP2 contribution to the binding energy is decomposed into four components: frozen interaction, polarization, charge transfer, and dispersion. Charge transfer is defined by excitations that change the number of electrons on a molecule, dispersion by intermolecular excitations that do not transfer charge, and polarization and frozen interactions by intra-molecular excitations. The final two are separated by evaluations of the frozen, isolated wave functions in the presence of the other molecules, with adjustments for orbital response. Unlike previous EDAs for electron correlation methods, this one includes components for the electrostatics, which is vital as adjustment to the electrostatic behavior of the system is in some cases the dominant effect of the treatment of electron correlation. The proposed EDA is then applied to a variety of different systems to demonstrate that all proposed components behave correctly. This includes systems with one molecule and an external electric perturbation to test the separation between polarization and frozen interactions and various bimolecular systems in the equilibrium range and beyond to test the rest of the EDA. We find that it performs well on these tests. We then apply the EDA to a halogen bonded system to investigate the nature of the halogen bond. PMID:26328835

  17. Measurement of Absolute Excitation Cross Sections in Highly-Charged Ions Using Electron Energy Loss and Merged Beams

    NASA Astrophysics Data System (ADS)

    Chutjian, A.; Smith, Steven J.; Lozano, J. A.

    2002-11-01

    There is increasing emphasis within this decade on understanding energy balance and new phenomena observed in high electron temperature plasmas. The UV spectral return from FUSE, and the X-ray spectral return from the HETG on Chandra and the LETGS on XMM-Newton are just beginning. The line emissions are almost entirely from highly-charged ions (HCIs) of C, N, O, Ne, Mg, S, Si, Ca, and Fe. In addition, the Constellation-X mission, currently in the planning stages, will provide high-throughput X-ray spectroscopy up to photon energies of 0.12 nm (10 keV), where the primary line emitters will again be the HCIs. This array of space instruments is providing an overwhelming return of HCI spectral data from a variety of astrophysical objects. Collision strengths and Einstein A-values are required to convert the observed spectral intensities to electron temperatures and densities in the stellar plasma [1]. The JPL electron energy-loss and merged-beams approach [2] has been used to measure absolute collision strengths in a number of ions, with critical comparisons to the best available theories. Experimental methods will be reviewed, and results presented on experimental comparisons to R-Matrix and Breit-Pauli theoretical results in C3+[3], O2+[4], O5+[5], S2+[6], and Fe9+ [7]. Work is planned for comparisons in Mgq+, and higher charge states Fe(10-15)+. J. Lozano thanks the National Research Council for a fellowship though the NASA- NRC program. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, and was supported under contract with the National Aeronautics and Space Administration.

  18. Measured Absolute Cross Section of Charge Transfer in H + H2+ at Low Energy: Signature of vi = 2 and Trajectory Effects

    NASA Astrophysics Data System (ADS)

    Strom, R. A.; Bacani, K. G.; Chi, R. M.; Heczko, S. L.; Singh, B. N.; Tobar, J. A.; Vassantachart, A. K.; Andrianarijaona, V. M.; Seely, D. G.; Havener, C. C.

    2015-04-01

    Measurements of absolute cross sections of charge transfer (CT) in H + H2+--> H+ + H2 were conducted at the merged-beam apparatus at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, which can reliably create and access collision energies as low as 0.1 eV/u. The measured absolute cross section shows evidence of trajectory effects at low energy. Also, the comparison to state-to-state calculations (PRA 67 022708 (2003) suggests a strong contribution from vi = 2 of the H2+that are produced by the electron cyclotron resonance ion source. The data analysis will be presented here. Research supported by the NASA Solar & Heliospheric Physics Program NNH07ZDA001N, the Office of Fusion Energy Sciences and the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy, the National Science Foundation through Grant No. PHY-1068877.

  19. Modification of Surface Energy via Direct Laser Ablative Surface Patterning

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J., Jr. (Inventor); Belcher, Marcus A. (Inventor); Connell, John W. (Inventor); Hopkins, John W. (Inventor)

    2015-01-01

    Surface energy of a substrate is changed without the need for any template, mask, or additional coating medium applied to the substrate. At least one beam of energy directly ablates a substrate surface to form a predefined topographical pattern at the surface. Each beam of energy has a width of approximately 25 micrometers and an energy of approximately 1-500 microJoules. Features in the topographical pattern have a width of approximately 1-500 micrometers and a height of approximately 1.4-100 micrometers.

  20. Ultraviolet photochemistry of buta-1,3- and buta-1,2-dienes: laser spectroscopic absolute hydrogen atom quantum yield and translational energy distribution measurements.

    PubMed

    Hanf, A; Volpp, H-R; Sharma, P; Mittal, J P; Vatsa, R K

    2010-07-14

    Using pulsed H-atom Lyman-alpha laser-induced fluorescence spectroscopy along with a photolytic calibration approach, absolute H-atom product quantum yields of phi(H-b13d) = (0.32+/-0.04) and phi(H-b12d) = (0.36+/-0.04) were measured under collision-free conditions for the 193 nm gas-phase laser flash photolysis of buta-1,3- and buta-1,2-diene at room temperature, which demonstrate that nascent H-atom formation is of comparable importance for both parent molecules. Comparison of the available energy fraction, f(T-b13d) = (0.22+/-0.03) and f(T-b12d) = (0.13+/-0.01), released as H+C(4)H(5) product translational energy with results of impulsive and statistical energy partitioning modeling calculations indicates that for both, buta-1,3- and buta-1,2-diene, H-atom formation is preceded by internal conversion to the respective electronic ground state (S(0)) potential energy surfaces. In addition, values of sigma(b-1,3-d-L alpha) = (3.5+/-0.2)x10(-17) cm(2) and sigma(b-1,2-d-L alpha) = (4.4+/-0.2)x10(-17) cm(2) for the previously unknown Lyman-alpha (121.6 nm) radiation photoabsorption cross sections of buta-1,3- and buta-1,2-diene in the gas-phase were determined.

  1. Evaluations of the Absolute and Relative Free Energies for Antidepressant Binding to the Amino Acid Membrane Transporter LeuT with Free Energy Simulations.

    PubMed

    Zhao, Chunfeng; Caplan, David A; Noskov, Sergei Yu

    2010-06-01

    The binding of ligands to protein receptors with high affinity and specificity is central to many cellular processes. The quest for the development of computational models capable of accurately evaluating binding affinity remains one of the main goals of modern computational biophysics. In this work, free energy perturbation/molecular dynamics simulations were used to evaluate absolute and relative binding affinity for three different antidepressants to a sodium-dependent membrane transporter, LeuT, a bacterial homologue of human serotonin and dopamine transporters. Dysfunction of these membrane transporters in mammals has been implicated in multiple diseases of the nervous system, including bipolar disorder and depression. Furthermore, these proteins are key targets for antidepressants including fluoxetine (aka Prozac) and tricyclic antidepressants known to block transport activity. In addition to being clinically relevant, this system, where multiple crystal structures are readily available, represents an ideal testing ground for methods used to study the molecular mechanisms of ligand binding to membrane proteins. We discuss possible pitfalls and different levels of approximation required to evaluate binding affinity, such as the dependence of the computed affinities on the strength of constraints and the sensitivity of the computed affinities to the particular partial charges derived from restrained electrostatic potential fitting of quantum mechanics electrostatic potential. Finally, we compare the effects of different constraint schemes on the absolute and relative binding affinities obtained from free energy simulations.

  2. Multilayer Relaxation and Surface Energies of Metallic Surfaces

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Rodriguez, Agustin M.; Ferrante, John

    1994-01-01

    The perpendicular and parallel multilayer relaxations of fcc (210) surfaces are studied using equivalent crystal theory (ECT). A comparison with experimental and theoretical results is made for AI(210). The effect of uncertainties in the input parameters on the magnitudes and ordering of surface relaxations for this semiempirical method is estimated. A new measure of surface roughness is proposed. Predictions for the multilayer relaxations and surface energies of the (210) face of Cu and Ni are also included.

  3. Exam Question Exchange: Potential Energy Surfaces.

    ERIC Educational Resources Information Center

    Alexander, John J., Ed.

    1988-01-01

    Presents three examination questions, graded in difficulty, that explore the topic of potential energy surfaces using a diagrammatic approach. Provides and discusses acceptable solutions including diagrams. (CW)

  4. Present-day Surface Deformation and Vertical Motion In The Central Alborz (iran) From GPS and Absolute Gravity Measurements.

    NASA Astrophysics Data System (ADS)

    Masson, F.; Sedighi, M.; Hinderer, J.; Bayer, R.; Nilforoushan, F.; Luck, J.-M.; Vernant, P.; Chéry, J.

    The present tectonic of Iran results from the north-south convergence between Eura- sia and Arabia, with a rate of about 3 cm/year. The deformation of Iran is concen- trated in major belts along the south-western border (Zagros), the southern shore of the Caspian Sea (Alborz) and along the north-east border (Kopet-Dag). The Alborz range is an east-west mountain range which accommodates about 1 cm/year of short- ening between the Central Iranian Desert and the south Caspian Sea. The main tec- tonic structures are generally overthrusting range-parallel faults northward dipping in the south (North Tehran fault, Mosha fault) and southward dipping in the north (Amir fault, North Border fault). The compressive tectonic in the Alborz range is certainly accommodated by large vertical motions along the major faults. To study the defor- mation (horizontal and vertical movement) we have installed and measured a GPS network of 14 sites crossing the Alborz range east of Tehran. The GPS network is measured during campaigns performed each year. In order to well constrained the ver- tical deformation of the southern border of the Alborz, we have performed colocated GPS and absolute gravity measurements in 3 sites, one near the Mosha fault (Abali), one in the frontal thrust area of Tehran and one in the stable central Iranian block (Chesmeh-Sour). After two measures (2000 and 2001), some interesting preliminary results will be shown. The observed gravity variation for one year (Sept. 2000 - Sept. 2001) is -3.0 mgal +-2.6 mgal (Abali), -24.2 mgal +-4.8 mgal (Tehran) and +4.7 mgal +-2.3 mgal (Chesmeh-Sour). These results could be explained respectively by a tec- tonic uplift of about 10 mm/year in the Alborz, water pumping in the Tehran area and (unexplained) subsidence at Chesmeh-Sour. These results will be compared to the first estimation of the deformation obtained by GPS (horizontal repeatability < 3 mm and vertical repeatability < 5 mm).

  5. Durable, Low-Surface-Energy Treatments

    NASA Technical Reports Server (NTRS)

    Willis, Paul B.; Mcelroy, Paul M.; Hickey, Gregory S.

    1992-01-01

    Chemical treatment for creation of durable, low-surface-energy coatings for glass, ceramics and other protonated surfaces easily applied, and creates very thin semipermanent film with extremely low surface tension. Exhibits excellent stability; surfaces retreated if coating becomes damaged or eroded. Uses include water-repellent surfaces, oil-repellent surfaces, antimigration barriers, corrosion barriers, mold-release agents, and self-cleaning surfaces. Film resists wetting by water, alcohols, hydrocarbon solvents, and silicone oil. Has moderate resistance to abrasion, such as rubbing with cloths, and compression molding to polymers and composite materials.

  6. Absolute cascade-free cross-sections for the 2S to 2P transition in Zn(+) using electron-energy-loss and merged-beams methods

    NASA Technical Reports Server (NTRS)

    Smith, Steven J.; Man, K.-F.; Chutjian, A.; Mawhorter, R. J.; Williams, I. D.

    1991-01-01

    Absolute cascade-free excitation cross-sections in an ion have been measured for the resonance 2S to 2P transition in Zn(+) using electron-energy-loss and merged electron-ion beams methods. Measurements were carried out at electron energies of below threshold to 6 times threshold. Comparisons are made with 2-, 5-, and 15-state close-coupling and distorted-wave theories. There is good agreement between experiment and the 15-state close-coupling cross-sections over the energy range of the calculations.

  7. Absolute calibration of photostimulable image plate detectors used as (0.5-20 MeV) high-energy proton detectors.

    PubMed

    Mancić, A; Fuchs, J; Antici, P; Gaillard, S A; Audebert, P

    2008-07-01

    In this paper, the absolute calibration of photostimulable image plates (IPs) used as proton detectors is presented. The calibration is performed in a wide range of proton energies (0.5-20 MeV) by exposing simultaneously the IP and calibrated detectors (radiochromic films and solid state detector CR39) to a source of broadband laser-accelerated protons, which are spectrally resolved. The final result is a calibration curve that enables retrieving the proton number from the IP signal. PMID:18681694

  8. A negative surface energy for alumina.

    PubMed

    Łodziana, Zbigniew; Topsøe, Nan-Yu; Nørskov, Jens K

    2004-05-01

    The surface energy of a solid measures the energy cost of increasing the surface area. All normal solids therefore have a positive surface energy-if it had been negative, the solid would disintegrate. For this reason it is also generally believed that when certain ceramics can be found in a highly porous form, this is a metastable state, which will eventually sinter into the bulk solid at high temperatures. We present theoretical evidence suggesting that for theta-alumina, the surface energy is strongly dependent on the size of the crystallites, and that for some facets it is negative for thicknesses larger than approximately 1 nm. This suggests a completely new picture of porous alumina in which the high-surface-area, nanocrystalline form is the thermodynamic ground state. The negative surface energy is found to be related to a particularly strongly adsorbed state of dissociated water on some alumina surfaces. We also present new experimental evidence based on infrared spectroscopy, in conjunction with X-ray diffraction and surface-area measurements, that theta-alumina has indeed very stable surface OH groups at high temperatures, and that this form of alumina does not sinter even at temperatures up to 1,300 K.

  9. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  10. Solar energy converter using surface plasma waves

    NASA Technical Reports Server (NTRS)

    Anderson, L. M. (Inventor)

    1984-01-01

    Sunlight is dispersed over a diffraction grating formed on the surface of a conducting film on a substrate. The angular dispersion controls the effective grating period so that a matching spectrum of surface plasmons is excited for parallel processing on the conducting film. The resulting surface plasmons carry energy to an array of inelastic tunnel diodes. This solar energy converter does not require different materials for each frequency band, and sunlight is directly converted to electricity in an efficient manner by extracting more energy from the more energetic photons.

  11. Absolute calibration of Kodak Biomax-MS film response to x rays in the 1.5- to 8-keV energy range

    NASA Astrophysics Data System (ADS)

    Marshall, F. J.; Knauer, J. P.; Anderson, D.; Schmitt, B. L.

    2006-10-01

    The absolute response of Kodak Biomax-MS film to x rays in the range from 1.5- to 8-keV has been measured using a laboratory electron-beam generated x-ray source. The measurements were taken at specific line energies by using Bragg diffraction to produce monochromatic beams of x rays. Multiple exposures were taken on Biomax MS film up to levels exceeding optical densities of 2 as measured by a microdensitometer. The absolute beam intensity for each exposure was measured with a Si (Li) detector. Additional response measurements were taken with Kodak direct exposure film (DEF) so as to compare the results of this technique to previously published calibrations. The Biomax-MS results have been fitted to a semiempirical mathematical model (Knauer et al., these proceedings). Users of the model can infer absolute fluences from observed exposure levels at either interpolated or extrapolated energies. To summarize the results: Biomax MS has comparable sensitivity to DEF film below 3keV but has reduced sensitivity above 3keV (˜50%). The lower exposure results from thinner emulsion layers, designed for use with phosphor screens. The ease with which Biomax-MS can be used in place of DEF (same format film, same developing process, and comparable sensitivity) makes it a good replacement.

  12. Measurement of the absolute penetration depth and surface resistance of superconductors and normal metals with the variable spacing parallel plate resonator

    NASA Astrophysics Data System (ADS)

    Talanov, Vladimir V.; Mercaldo, Lucia V.; Anlage, Steven M.; Claassen, John H.

    2000-05-01

    The variable spacing parallel plate resonator (VSPPR) is a microwave transmission line resonator with a continuously variable thickness of the dielectric spacer between the superconducting or metallic plates, filled by cryogenic liquid or vacuum. We measure the dielectric spacer thickness dependencies of the resonator frequency and quality factor, and fit them to theoretical forms, in order to extract the absolute values of penetration depth, λ, and surface resistance, Rs. A cryogenic micropositioning setup is developed to vary the spacer thickness from 0 to 100 μm with a resolution of 8.5 nm, and to maintain parallelism of the resonator plates. Measurement of ac capacitance between the plates is utilized to directly determine the separation between the resonator plates and to reduce the effect of their tilt and nonflatness on the accuracy of the measured Rs and λ. Because the operating temperature is fixed (77 K), the result for a superconductor is independent of an a priori model for the penetration depth versus temperature. This technique can also be employed as a surface impedance standard for characterization of high temperature superconducting films for microwave applications.

  13. A global potential energy surface and dipole moment surface for silane

    SciTech Connect

    Owens, Alec; Yurchenko, Sergei N.; Yachmenev, Andrey; Thiel, Walter

    2015-12-28

    A new nine-dimensional potential energy surface (PES) and dipole moment surface (DMS) for silane have been generated using high-level ab initio theory. The PES, CBS-F12{sup HL}, reproduces all four fundamental term values for {sup 28}SiH{sub 4} with sub-wavenumber accuracy, resulting in an overall root-mean-square error of 0.63 cm{sup −1}. The PES is based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set limit, and incorporates a range of higher-level additive energy corrections to account for core-valence electron correlation, higher-order coupled cluster terms, and scalar relativistic effects. Systematic errors in computed intra-band rotational energy levels are reduced by empirically refining the equilibrium geometry. The resultant Si–H bond length is in excellent agreement with previous experimental and theoretical values. Vibrational transition moments, absolute line intensities of the ν{sub 3} band, and the infrared spectrum for {sup 28}SiH{sub 4} including states up to J = 20 and vibrational band origins up to 5000 cm{sup −1} are calculated and compared with available experimental results. The DMS tends to marginally overestimate the strength of line intensities. Despite this, band shape and structure across the spectrum are well reproduced and show good agreement with experiment. We thus recommend the PES and DMS for future use.

  14. A global potential energy surface and dipole moment surface for silane

    NASA Astrophysics Data System (ADS)

    Owens, Alec; Yurchenko, Sergei N.; Yachmenev, Andrey; Thiel, Walter

    2015-12-01

    A new nine-dimensional potential energy surface (PES) and dipole moment surface (DMS) for silane have been generated using high-level ab initio theory. The PES, CBS-F12HL, reproduces all four fundamental term values for 28SiH4 with sub-wavenumber accuracy, resulting in an overall root-mean-square error of 0.63 cm-1. The PES is based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set limit, and incorporates a range of higher-level additive energy corrections to account for core-valence electron correlation, higher-order coupled cluster terms, and scalar relativistic effects. Systematic errors in computed intra-band rotational energy levels are reduced by empirically refining the equilibrium geometry. The resultant Si-H bond length is in excellent agreement with previous experimental and theoretical values. Vibrational transition moments, absolute line intensities of the ν3 band, and the infrared spectrum for 28SiH4 including states up to J = 20 and vibrational band origins up to 5000 cm-1 are calculated and compared with available experimental results. The DMS tends to marginally overestimate the strength of line intensities. Despite this, band shape and structure across the spectrum are well reproduced and show good agreement with experiment. We thus recommend the PES and DMS for future use.

  15. A global potential energy surface and dipole moment surface for silane.

    PubMed

    Owens, Alec; Yurchenko, Sergei N; Yachmenev, Andrey; Thiel, Walter

    2015-12-28

    A new nine-dimensional potential energy surface (PES) and dipole moment surface (DMS) for silane have been generated using high-level ab initio theory. The PES, CBS-F12(HL), reproduces all four fundamental term values for (28)SiH4 with sub-wavenumber accuracy, resulting in an overall root-mean-square error of 0.63 cm(-1). The PES is based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set limit, and incorporates a range of higher-level additive energy corrections to account for core-valence electron correlation, higher-order coupled cluster terms, and scalar relativistic effects. Systematic errors in computed intra-band rotational energy levels are reduced by empirically refining the equilibrium geometry. The resultant Si-H bond length is in excellent agreement with previous experimental and theoretical values. Vibrational transition moments, absolute line intensities of the ν3 band, and the infrared spectrum for (28)SiH4 including states up to J = 20 and vibrational band origins up to 5000 cm(-1) are calculated and compared with available experimental results. The DMS tends to marginally overestimate the strength of line intensities. Despite this, band shape and structure across the spectrum are well reproduced and show good agreement with experiment. We thus recommend the PES and DMS for future use.

  16. Surface Energy Balance System (SEBS) Handbook

    SciTech Connect

    Cook, DR

    2011-02-14

    A Surface Energy Balance System (SEBS) has been installed collocated with each deployed ECOR system at the Southern Great Plains (SGP), North Slope of Alaska (NSA), Tropical Western Pacific (TWP), ARM Mobile Facility 1 (AMF1), and ARM Mobile Facility 2 (AMF2). The surface energy balance system consists of upwelling and downwelling solar and infrared radiometers within one net radiometer, a wetness sensor, and soil measurements. The SEBS measurements allow the comparison of ECOR sensible and latent heat fluxes with the energy balance determined from the SEBS and provide information on wetting of the sensors for data quality purposes.

  17. Harnessing surface plasmons for solar energy conversion

    NASA Technical Reports Server (NTRS)

    Anderson, L. M.

    1983-01-01

    NASA research on the feasibility of solar-energy conversion using surface plasmons is reviewed, with a focus on inelastic-tunnel-diode techniques for power extraction. The need for more efficient solar converters for planned space missions is indicated, and it is shown that a device with 50-percent efficiency could cost up to 40 times as much per sq cm as current Si cells and still be competitive. The parallel-processing approach using broadband carriers and tunable diodes is explained, and the physics of surface plasmons on metal surfaces is outlined. Technical problems being addressed include phase-matching sunlight to surface plasmons, minimizing ohmic losses and reradiation in energy transport, coupling into the tunnels by mode conversion, and gaining an understanding of the tunnel-diode energy-conversion process. Diagrams illustrating the design concepts are provided.

  18. Absolute cross sections for the dissociation of hydrogen cluster ions in high-energy collisions with helium atoms

    SciTech Connect

    Eden, S.; Tabet, J.; Samraoui, K.; Louc, S.; Farizon, B.; Farizon, M.; Ouaskit, S.; Maerk, T. D.

    2006-02-15

    Absolute dissociation cross sections are reported for H{sub n}{sup +} clusters of varied mass (n=3,5,...,35) following collisions with He atoms at 60 keV/amu. Initial results have been published previously for a smaller range of cluster sizes [Ouaskit et al., Phys. Rev. A 49, 1484 (1994)]. The present extended study includes further experimental results, reducing the statistical errors associated with the absolute cross sections. The previously suggested quasilinear dependence of the H{sub n}{sup +} dissociation cross sections upon n is developed with reference to expected series of geometrical shells of H{sub 2} molecules surrounding a H{sub 3}{sup +} core. Recent calculations identify n=9 as corresponding to the first closed H{sub 2} shell [e.g., Stich et al., J. Chem. Phys. 107, 9482 (1997)]. Recurrence of the distinct characteristics observed in the dissociation-cross-section dependence upon cluster size around n=9 provides the basis for the presently proposed subsequent closed shells at n=15, 21, 27, and 33, in agreement with the calculations of Nagashima et al. [J. Phys. Chem. 96, 4294 (1992)].

  19. Surface energy and surface tension at holes and cracks

    NASA Technical Reports Server (NTRS)

    Rajapakse, Y. D. S.

    1975-01-01

    The concept of surface tension and surface energy of solids was used by Griffith to obtain a criterion for the extension of cracks in brittle materials. Griffith, however, neglected the stresses due to the normal traction at the crack implied by the surface tension. A complete solution to the problem of an elliptic hole in an infinite plate with surface tension loading at the hole is given. Complex potentials are given in closed form in terms of elliptic integrals of the first, second, and third kinds. Stress distributions are studied. For a flat crack, the nature of the singularity at the tip is shown to be radically different from that usually encountered in fracture mechanics. The implications of our analysis for theories of fracture in brittle materials are discussed.

  20. Eosinophil count - absolute

    MedlinePlus

    Eosinophils; Absolute eosinophil count ... the white blood cell count to give the absolute eosinophil count. ... than 500 cells per microliter (cells/mcL). Normal value ranges may vary slightly among different laboratories. Talk ...

  1. Examination of the hydrogen-bonding networks in small water clusters (n = 2-5, 13, 17) using absolutely localized molecular orbital energy decomposition analysis.

    PubMed

    Cobar, Erika A; Horn, Paul R; Bergman, Robert G; Head-Gordon, Martin

    2012-11-28

    Using the ωB97X-D and B3LYP density functionals, the absolutely localized molecular orbital energy decomposition method (ALMO-EDA) is applied to the water dimer through pentamer, 13-mer and 17-mer clusters. Two-body, three-body, and total interaction energies are decomposed into their component energy terms: frozen density interaction energy, polarization energy, and charge transfer energy. Charge transfer, polarization, and frozen orbital interaction energies are all found to be significant contributors to the two-body and total interaction energies; the three-body interaction energies are dominated by polarization. Each component energy term for the two-body interactions is highly dependent on the associated hydrogen bond distance. The favorability of the three-body terms associated with the 13- and 17-mer structures depends on the hydrogen-donor or hydrogen-acceptor roles played by each of the three component waters. Only small errors arise from neglect of three-body interactions without two adjacent water molecules, or beyond three-body interactions. Interesting linear correlations are identified between the contributions of charge-transfer and polarization terms to the two and three-body interactions, which permits elimination of explicit calculation of charge transfer to a good approximation.

  2. Quantification of surface amorphous content using dispersive surface energy: the concept of effective amorphous surface area.

    PubMed

    Brum, Jeffrey; Burnett, Daniel

    2011-09-01

    We investigate the use of dispersive surface energy in quantifying surface amorphous content, and the concept of effective amorphous surface area is introduced. An equation is introduced employing the linear combination of surface area normalized square root dispersive surface energy terms. This equation is effective in generating calibration curves when crystalline and amorphous references are used. Inverse gas chromatography is used to generate dispersive surface energy values. Two systems are investigated, and in both cases surface energy data collected for physical mixture samples comprised of amorphous and crystalline references fits the predicted response with good accuracy. Surface amorphous content of processed lactose samples is quantified using the calibration curve, and interpreted within the context of effective amorphous surface area. Data for bulk amorphous content is also utilized to generate a thorough picture of how disorder is distributed throughout the particle. An approach to quantifying surface amorphous content using dispersive surface energy is presented. Quantification is achieved by equating results to an effective amorphous surface area based on reference crystalline, and amorphous materials. PMID:21725707

  3. Quasistatic Cracks and Minimal Energy Surfaces

    SciTech Connect

    Raeisaenen, V.I.; Seppala, E.T.; Alava, M.J.; Raeisaenen, V.I.; Alava, M.J.; Alava, M.J.; Duxbury, P.M.

    1998-01-01

    We compare the roughness of minimal energy (ME) surfaces and scalar quasistatic fracture (SQF) surfaces. Two-dimensional ME and SQF surfaces have {ital the same roughness scaling,} w{approximately}L{sup {zeta}} (L is the system size) with {zeta}=(2)/(3). The 3{ital d} ME and SQF results at strong disorder are consistent with the random-bond Ising exponent {zeta}(d{ge}3){approx}0.21(5{minus}d) (d is the bulk dimension). However, 3{ital d} SQF surfaces are {ital rougher} than ME surfaces due to a larger prefactor. ME surfaces undergo a weakly rough to algebraically rough{close_quotes} transition in 3{ital d}, suggesting a similar behavior in fracture. {copyright} {ital 1998} {ital The American Physical Society}

  4. Surface Plasmon-Assisted Solar Energy Conversion.

    PubMed

    Dodekatos, Georgios; Schünemann, Stefan; Tüysüz, Harun

    2016-01-01

    The utilization of localized surface plasmon resonance (LSPR) from plasmonic noble metals in combination with semiconductors promises great improvements for visible light-driven photocatalysis, in particular for energy conversion. This review summarizes the basic principles of plasmonic photocatalysis, giving a comprehensive overview about the proposed mechanisms for enhancing the performance of photocatalytically active semiconductors with plasmonic devices and their applications for surface plasmon-assisted solar energy conversion. The main focus is on gold and, to a lesser extent, silver nanoparticles in combination with titania as semiconductor and their usage as active plasmonic photocatalysts. Recent advances in water splitting, hydrogen generation with sacrificial organic compounds, and CO2 reduction to hydrocarbons for solar fuel production are highlighted. Finally, further improvements for plasmonic photocatalysts, regarding performance, stability, and economic feasibility, are discussed for surface plasmon-assisted solar energy conversion.

  5. Surface free energy and microarray deposition technology.

    PubMed

    McHale, Glen

    2007-03-01

    Microarray techniques use a combinatorial approach to assess complex biochemical interactions. The fundamental goal is simultaneous, large-scale experimentation analogous to the automation achieved in the semiconductor industry. However, microarray deposition inherently involves liquids contacting solid substrates. Liquid droplet shapes are determined by surface and interfacial tension forces, and flows during drying. This article looks at how surface free energy and wetting considerations may influence the accuracy and reliability of spotted microarray experiments.

  6. Photodissociation of methane: Exploring potential energy surfaces

    NASA Astrophysics Data System (ADS)

    van Harrevelt, Rob

    2006-09-01

    The potential energy surface for the first excited singlet state (S1) of methane is explored using multireference singles and doubles configuration interaction calculations, employing a valence triple zeta basis set. A larger valence quadruple zeta basis is used to calculate the vertical excitation energy and dissociation energies. All stationary points found on the S1 surface are saddle points and have imaginary frequencies for symmetry-breaking vibrations. By studying several two-dimensional cuts through the potential energy surfaces, it is argued that CH4 in the S1 state will distort to planar structures. Several conical intersection seams between the ground state surface S0 and the S1 surface have been identified at planar geometries. The conical intersections provide electronically nonadiabatic pathways towards products CH3(X˜A2″2)+H, CH2(ãA11)+H2, or CH2(X˜B13)+H +H. The present results thereby make it plausible that the CH3(X˜A2″2)+H and CH2(ãA11)+H2 channels are major dissociation channels, as has been observed experimentally.

  7. Study of hair surface energy and conditioning.

    PubMed

    Gao, Timothy; He, Yingxia; Landa, Peter; Tien, Jung-Mei

    2011-01-01

    A new test method has been developed to determine surface energy of hair fibers through measurements of contact angles at two hair/liquid interfaces. By measuring changes in surface energy of the same hair fiber before and after a cosmetic treatment, effects of active ingredients and the performance of tested formulations can be evaluated.The establishment of the method is based on Fowkes theory (1,2) described with two components, a dispersive and a non-dispersive component. The non-polar liquid used in this study was diiodomethane, and the polar liquid was benzyl alcohol. A Kruss 100 Tensiometer was used to measure contact angles of hair fibers. Virgin dark brown and regular bleached hairs were treated with selected conditioner formulations. Reductions in combing forces of hair tresses before and after respective treatments were correlated with decreases in average surface energy of hair fibers obtained from the corresponding tresses.Experimental results indicate that the average surface energy of hair fibers treated with conditioners decreases and the hydrophobicity of the hair surface increases, the results correlate well with the reduction in combing forces after respective treatments. This research work provides a new methodology to evaluate/screen conditioning performance of hair care ingredients and formulations for development of better products. PMID:21635842

  8. Study of hair surface energy and conditioning.

    PubMed

    Gao, Timothy; He, Yingxia; Landa, Peter; Tien, Jung-Mei

    2011-01-01

    A new test method has been developed to determine surface energy of hair fibers through measurements of contact angles at two hair/liquid interfaces. By measuring changes in surface energy of the same hair fiber before and after a cosmetic treatment, effects of active ingredients and the performance of tested formulations can be evaluated.The establishment of the method is based on Fowkes theory (1,2) described with two components, a dispersive and a non-dispersive component. The non-polar liquid used in this study was diiodomethane, and the polar liquid was benzyl alcohol. A Kruss 100 Tensiometer was used to measure contact angles of hair fibers. Virgin dark brown and regular bleached hairs were treated with selected conditioner formulations. Reductions in combing forces of hair tresses before and after respective treatments were correlated with decreases in average surface energy of hair fibers obtained from the corresponding tresses.Experimental results indicate that the average surface energy of hair fibers treated with conditioners decreases and the hydrophobicity of the hair surface increases, the results correlate well with the reduction in combing forces after respective treatments. This research work provides a new methodology to evaluate/screen conditioning performance of hair care ingredients and formulations for development of better products.

  9. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Levin, Eugene

    1993-01-01

    A new global potential energy surface (PES) is being generated for O(P-3) + H2 yields OH + H. This surface is being fit using the rotated Morse oscillator method, which was used to fit the previous POL-CI surface. The new surface is expected to be more accurate and also includes a much more complete sampling of bent geometries. A new study has been undertaken of the reaction N + O2 yields NO + O. The new studies have focused on the region of the surface near a possible minimum corresponding to the peroxy form of NOO. A large portion of the PES for this second reaction has been mapped out. Since state to state cross sections for the reaction are important in the chemistry of high temperature air, these studies will probably be extended to permit generation of a new global potential for reaction.

  10. Absolute dose measurements by means of a small cylindrical ionization chamber for very high dose per pulse high energy electron beams

    SciTech Connect

    Karaj, E.; Righi, S.; Di Martino, F.

    2007-03-15

    Very high dose per pulse (3-13 cGy/pulse) high energy electron beams are currently produced by special linear accelerators (linac) dedicated to Intra Operative Radiation Therapy (IORT). The electron beams produced by such linacs are collimated by special Perspex applicators of various size and cylindrically shaped. The biggest problems from the dosimetric point of view are caused by the high dose-per-pulse values and the use of inclined applicators. In this work measurements of absolute dose for the inclined applicators were done by using a small cylindrical ionization chamber, type CC01 (Wellhofer), a parallel plane ionization chamber type Markus (PTW 23343) and radiochromic films type EBT. We show a method which allows calculating the quality correction factors for CC01 chamber with an uncertainty of 1% and the absolute dose value for the inclined applicators using CC01 with an uncertainty of 3.1% for electron beams of energy of 6 and 7 MeV produced by the linac dedicated to IORT Novac7.

  11. Stable Electron Beams With Low Absolute Energy Spread From a LaserWakefield Accelerator With Plasma Density Ramp Controlled Injection

    SciTech Connect

    Geddes, Cameron G.R.; Cormier-Michel, E.; Esarey, E.; Leemans,W.P.; Nakamura, K.; Panasenko, D.; Plateau, Guillaume R.; Schroeder, CarlB.; Toth, Csaba; Cary, J.R.

    2007-06-25

    Laser wakefield accelerators produce accelerating gradientsup to hundreds of GeV/m, and recently demonstrated 1-10 MeV energy spreadat energies up to 1 GeV using electrons self-trapped from the plasma.Controlled injection and staging may further improve beam quality bycircumventing tradeoffs between energy, stability, and energyspread/emittance. We present experiments demonstrating production of astable electron beam near 1 MeV with hundred-keV level energy spread andcentral energy stability by using the plasma density profile to controlselfinjection, and supporting simulations. Simulations indicate that suchbeams can be post accelerated to high energies,potentially reducingmomentum spread in laser acceleratorsby 100-fold or more.

  12. Small angle neutron scattering on an absolute intensity scale and the internal surface of diatom frustules from three species of differing morphologies.

    PubMed

    Garvey, C J; Strobl, M; Percot, A; Saroun, J; Haug, J; Vyverman, W; Chepurnov, V A; Ferris, J M

    2013-05-01

    The internal nanostructure of the diatoms Cyclotella meneghiniana, Seminavis robusta and Achnanthes subsessilis was investigated using small angle neutron scattering (SANS) to examine thin biosilica samples, consisting of isotropic (powder) from their isolated cell walls. The interpretation of SANS data was assisted by several other measurements. The N2 adsorption, interpreted within the Branuer-Emmet-Teller isotherm, yielded the specific surface area of the material. Fourier transform infrared (FTIR) and Raman spectroscopy indicates that the isolated material is amorphous silica with small amounts of organic cell wall materials acting as a filling material between the silica particles. A two-phase (air and amorphous silica) model was used to interpret small angle neutron scattering data. After correction for instrumental resolution, the measurements on two SANS instruments covered an extended range of scattering vectors 0.0011 nm(-1) < q < 5.6 nm(-1), giving an almost continuous SANS curve over a range of scattering vectors, q, on an absolute scale of intensity for each sample. Each of the samples gave a characteristic scattering curve where log (intensity) versus log (q) has a -4 dependence, with other features superimposed. In the high-q regime, departure from this behaviour was observed at a length-scales equivalent to the proposed unitary silica particle. The limiting Porod scattering law was used to determine the specific area per unit of volume of each sample illuminated by the neutron beam. The Porod behaviour, and divergence from this behaviour, is discussed in terms of various structural features and the proposed mechanisms for the bio-assembly of unitary silica particles in frustules.

  13. Comparison of high energy gamma rays from absolute value of b greater than 30 deg with the galactic neutral hydrogen distribution

    NASA Technical Reports Server (NTRS)

    Ozel, M. E.; Ogelman, H.; Tumer, T.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Thompson, F. J.

    1978-01-01

    High-energy gamma-ray (energy above 35 MeV) data from the SAS 2 satellite have been used to compare the intensity distribution of gamma rays with that of neutral hydrogen (H I) density along the line of sight, at high galactic latitudes (absolute values greater than 30 deg). A model has been constructed for the case where the observed gamma-ray intensity has been assumed to be the sum of a galactic component proportional to the H I distribution plus an isotropic extragalactic emission. A chi-squared test of the model parameters indicates that about 30% of the total high-latitude emission may originate within the Galaxy.

  14. Exploring multidimensional free energy surfaces of peptides

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Kuczera, Krzysztof

    1997-03-01

    A new statistical mechanics thermodynamic integration method is presented, enabling exploration of multidimensional conformational free energy surfaces of large flexible molecules. In this approach a single molecular dynamics simulation in which a set of coordinates has been constrained to fixed values yields the free energy gradient with respect to all coordinates in the set. The availability of the multidimensional gradient opens new possibilities for exploration of molecular conformational free energy surfaces, including free energy optimization to locate free energy minima, calculation of higher free energy derivatives, and finding optimal free energy paths between states. Additionally, choosing of all "soft" degrees of freedom as the constrained set leads to accelerated convergence of averages, effectively overcoming the sampling problem of free energy simulations. Two applications of the method are presented: Helical states of model peptides. For model peptides (Ala)n and (Aib)n where n=6,8,10 and Aib is α-methylalanine in vacuum, free energy maps and free energy optimization in φ-ψ space are used to locate free energy minima corresponding to α-, π- and 3_10-helical structures. The stability of the minima is characterized by calculating numerical second derivatives of the free energy. Free energy decomposition is employed to reveal the molecular mechanism for the improved stability of the 3_10h relative to the ah in Aib-containing peptides. DPDPE peptide pre-organization. For the linear form of the opioid peptide DPDPE in aqueous solution, the effective local sampling made possible by fixing all soft degrees of freedom is used to calculate the free energy difference between the open and cyclic-like structures, providing an estimate of the free energy of pre-organizing the peptide for disulfide bond formation. The open structure was found to be more stable by 4.0 ± 0.8 kcal/mol. The cyclic-like conformation was much better solvated than the open

  15. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2012-05-15

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  16. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2010-07-13

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  17. The Surface Energy Budget in Urban Environments

    NASA Astrophysics Data System (ADS)

    Twine, T. E.; Snyder, P. K.; Hertel, W.

    2011-12-01

    Urban heat islands (UHIs) occur when urban and suburban areas experience elevated temperatures relative to their rural surroundings because of differences in vegetation cover, buildings and other development, and infrastructure. Most cities in the United States are warming at twice the rate of the outlying rural areas and the planet as a whole. This difference in temperature is proportional to the size of the city and can be in excess of 2-5°C during the daytime and as much as 10°C at night. UHIs can exacerbate the warming during heat waves and play a role in additional heat-related mortality, an increase in tropospheric ozone, and economic losses that total in the billions of dollars from excess energy consumption. Many cities are experimenting with strategies to reduce urban warming. A number of mitigation strategies involve manipulating the surface energy budget to either reduce the amount of solar radiation absorbed at the surface or offset absorbed energy through latent cooling. Options include using building materials with different properties of reflectivity and emissivity, increasing the reflectivity of parking lots, covering roofs with vegetation, and increasing the amount of vegetation overall through tree planting or increasing green space. The goal of the Islands in the Sun project is to understand the formation and behavior of urban heat islands and to mitigate their effects through sensible city engineering and design practices. Methods include analysis of global remotely sensed datasets, the development of a reduced-complexity urban model, and evaluation of measurements made in the Twin Cities Metropolitan Area (TCMA). The TCMA is a 7,700 square kilometer urban and suburban region located in east central Minnesota that includes the two cities of Minneapolis and Saint Paul. Mitigation of the UHI in northern latitude cities, such as the TCMA, is a challenge because (1) residents in more northerly cities are more likely to suffer heat-related illness

  18. Energy flow and energy dissipation in a free surface.

    NASA Astrophysics Data System (ADS)

    Goldburg, Walter; Cressman, John

    2005-11-01

    Turbulent flows on a free surface are strongly compressible [1] and do not conserve energy in the absence of viscosity as bulk fluids do. Despite violation of assumptions essential to Kolmogorov's theory of 1941 (K41) [2, 3], surface flows show strong agreement with Kolmogorov scaling, though intermittency is larger there. Steady state turbulence is generated in a tank of water, and the spatially averaged energy flux is measured from the four-fifth's law at each instant of time. Likewise, the energy dissipation rate as measured from velocity gradients is also a random variable in this experiment. The energy flux - dissipation rate cross-correlation is measured to be correlated in incompressible bulk flows, but strongly anti-correlated on the surface. We argue that the reason for this discrepancy between surface and bulk flows is due to compressible effects present on the surface. [1] J. R. Cressman, J. Davoudi, W. I. Goldburg, and J. Schumacher, New Journal of Physics, 6, 53, 2004. [2] U. Frisch. Turbulence: The legacy of A. N. Kolmogorov, Cambridge University Press, Cambridge, 1995. [3] A. N. Kolmogorov, Doklady Akad. Nauk SSSR, 32, 16, 1941.

  19. Energy Conversion over Super-hydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Zhao, Hui; Zhai, Shengjie

    2015-11-01

    The streaming potential generated by a pressure-driven flow over a charged slip-stick surface with an arbitrary double layer thickness is both theoretically and experimentally studied. To understand the impact of the slip, the streaming potential is compared against that over a homogenously charged smooth surface. Our results indicate that the streaming potential over a super-hydrophobic surface only can be enhanced under certain conditions. In addition, the Onsager relation which directly relates the magnitude of electro-osmotic effect to that of the streaming current effect has been explicitly proved to be valid for thin and thick double layers and homogeneously charged super-hydrophobic surfaces. Comparisons between the streaming current and electro-osmotic mobility for an arbitrary electric double layer thickness under various conditions indicate that the Onsager relation seems applicable for arbitrary weakly charged super-hydrophobic surfaces though there is no general proof. Knowledge of the streaming potential over a slip-stick surface can provide guidance for designing novel and efficient microfluidic energy-conversion devices using super-hydrophobic surfaces. The work was supported by the NSF Grant No. ECCS-1509866.

  20. Role of Modeling When Designing for Absolute Energy Use Intensity Requirements in a Design-Build Framework: Preprint

    SciTech Connect

    Hirsch, A.; Pless, S.; Guglielmetti, R.; Torcellini, P. A.; Okada, D.; Antia, P.

    2011-03-01

    The Research Support Facility was designed to use half the energy of an equivalent minimally code-compliant building, and to produce as much renewable energy as it consumes on an annual basis. These energy goals and their substantiation through simulation were explicitly included in the project's fixed firm price design-build contract. The energy model had to be continuously updated during the design process and to match the final building as-built to the greatest degree possible. Computer modeling played a key role throughout the design process and in verifying that the contractual energy goals would be met within the specified budget. The main tool was a whole building energy simulation program. Other models were used to provide more detail or to complement the whole building simulation tool. Results from these specialized models were fed back into the main whole building simulation tool to provide the most accurate possible inputs for annual simulations. This paper will detail the models used in the design process and how they informed important program and design decisions on the path from preliminary design to the completed building.

  1. Surface free energy of polyimide aligning layers

    NASA Astrophysics Data System (ADS)

    Borycki, Jerzy; Okulska-Bozek, Malgorzata

    2000-05-01

    Polyimides from four selected dianhydrides and seven diamines were synthesized by two-step polycondensation method. During the first step 10% solutions of poly(amic acid)s in N,N-dimethylformamide and 1-methyl-2-pyrrolidinone were obtained. The thin polyimide layers on soda glass were prepared by thermal cyclodehydration. Contact angles of series of standard liquids for tested polyimide films were measured. The values of surface free energy and its components were calculated accordingly to Zisman, Owens et al. and van Oss equations. Some correlation between the surface properties and the chemical structure of polyimide aligning layers were presented.

  2. Fluorescence resonance energy transfers measurements on cell surfaces via fluorescence polarization.

    PubMed Central

    Cohen-Kashi, Meir; Moshkov, Sergey; Zurgil, Naomi; Deutsch, Mordechai

    2002-01-01

    A method has been developed for the determination of the efficiency of fluorescence resonance energy transfer efficiency between moieties located on cell surfaces by performing individual cell fluorescence polarization (FP) measurements. The absolute value of energy transfer efficiency (E) is calculated on an individual cell basis. The examination of this methodology was carried out using model experiments on human T lymphocyte cells. The cells were labeled with fluorescein-conjugated Concanavalin A (ConA) as donor, or rhodamine-conjugated ConA as acceptor. The experiments and results clearly indicate that determination of E via FP measurements is possible, efficient, and more convenient than other methods. PMID:12202365

  3. Solar energy conversion using surface plasmons for broadband energy transport

    NASA Technical Reports Server (NTRS)

    Anderson, L. M.

    1982-01-01

    A new strategy for efficient solar energy conversion based on parallel processing with surface plasmons is introduced. The approach is unique in identifying: (1) a broadband carrier with suitable range for energy transport, and (2) a technique to extract more energy from the more energetic photons, without sequential losses or unique materials for each frequency band. The aim is to overcome the fundamental losses associated with the broad solar spectrum and to achieve a higher level of spectrum splitting than has been possible in semiconductor systems.

  4. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1994-01-01

    Quantum mechanical methods have been used to compute potential energy surfaces for chemical reactions. The reactions studied were among those believed to be important to the NASP and HSR programs and included the recombination of two H atoms with several different third bodies; the reactions in the thermal Zeldovich mechanism; the reactions of H atom with O2, N2, and NO; reactions involved in the thermal De-NO(x) process; and the reaction of CH(squared Pi) with N2 (leading to 'prompt NO'). These potential energy surfaces have been used to compute reaction rate constants and rates of unimolecular decomposition. An additional application was the calculation of transport properties of gases using a semiclassical approximation (and in the case of interactions involving hydrogen inclusion of quantum mechanical effects).

  5. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1990-01-01

    The objective was to obtain accurate potential energy surfaces (PES's) for a number of reactions which are important in the H/N/O combustion process. The interest in this is centered around the design of the SCRAM jet engine for the National Aerospace Plane (NASP), which was envisioned as an air-breathing hydrogen-burning vehicle capable of reaching velocities as large as Mach 25. Preliminary studies indicated that the supersonic flow in the combustor region of the scram jet engine required accurate reaction rate data for reactions in the H/N/O system, some of which was not readily available from experiment. The most important class of combustion reactions from the standpoint of the NASP project are radical recombinaton reactions, since these reactions result in most of the heat release in the combustion process. Theoretical characterizations of the potential energy surfaces for these reactions are presented and discussed.

  6. SURFACE SYMMETRY ENERGY OF NUCLEAR ENERGY DENSITY FUNCTIONALS

    SciTech Connect

    Nikolov, N; Schunck, N; Nazarewicz, W; Bender, M; Pei, J

    2010-12-20

    We study the bulk deformation properties of the Skyrme nuclear energy density functionals. Following simple arguments based on the leptodermous expansion and liquid drop model, we apply the nuclear density functional theory to assess the role of the surface symmetry energy in nuclei. To this end, we validate the commonly used functional parametrizations against the data on excitation energies of superdeformed band-heads in Hg and Pb isotopes, and fission isomers in actinide nuclei. After subtracting shell effects, the results of our self-consistent calculations are consistent with macroscopic arguments and indicate that experimental data on strongly deformed configurations in neutron-rich nuclei are essential for optimizing future nuclear energy density functionals. The resulting survey provides a useful benchmark for further theoretical improvements. Unlike in nuclei close to the stability valley, whose macroscopic deformability hangs on the balance of surface and Coulomb terms, the deformability of neutron-rich nuclei strongly depends on the surface-symmetry energy; hence, its proper determination is crucial for the stability of deformed phases of the neutron-rich matter and description of fission rates for r-process nucleosynthesis.

  7. Determination of the surface energy distributions of different processed lactose.

    PubMed

    Thielmann, Frank; Burnett, Daniel J; Heng, Jerry Y Y

    2007-11-01

    Particulate interactions between drug and lactose carrier in dry powder inhaler formulations are affected by the heterogenous energy distribution on the surface of the individual compounds. A new method based on Inverse Gas Chromatography at finite concentration is applied to study the energy heterogeneity of untreated, milled, and recrystallized lactose of similar particle size distribution. Energy distributions for the dispersive surface energy and the specific free energy of ethanol are obtained. Milling causes an increase in surface energy due to formation of amorphous regions. Untreated and recrystallized materials have similar surface energies at low surface coverages but show clear differences in energy distribution. PMID:18058321

  8. Absolute neutrino mass measurements

    SciTech Connect

    Wolf, Joachim

    2011-10-06

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2{beta}) searches, single {beta}-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy.Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium {beta}-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope ({sup 137}Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R and D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2{beta} decay and single {beta}-decay.

  9. Cluster-continuum quasichemical theory calculation of the lithium ion solvation in water, acetonitrile and dimethyl sulfoxide: an absolute single-ion solvation free energy scale.

    PubMed

    Carvalho, Nathalia F; Pliego, Josefredo R

    2015-10-28

    Absolute single-ion solvation free energy is a very useful property for understanding solution phase chemistry. The real solvation free energy of an ion depends on its interaction with the solvent molecules and on the net potential inside the solute cavity. The tetraphenyl arsonium-tetraphenyl borate (TATB) assumption as well as the cluster-continuum quasichemical theory (CC-QCT) approach for Li(+) solvation allows access to a solvation scale excluding the net potential. We have determined this free energy scale investigating the solvation of the lithium ion in water (H2O), acetonitrile (CH3CN) and dimethyl sulfoxide (DMSO) solvents via the CC-QCT approach. Our calculations at the MP2 and MP4 levels with basis sets up to the QZVPP+diff quality, and including solvation of the clusters and solvent molecules by the dielectric continuum SMD method, predict the solvation free energy of Li(+) as -116.1, -120.6 and -123.6 kcal mol(-1) in H2O, CH3CN and DMSO solvents, respectively (1 mol L(-1) standard state). These values are compatible with the solvation free energy of the proton of -253.4, -253.2 and -261.1 kcal mol(-1) in H2O, CH3CN and DMSO solvents, respectively. Deviations from the experimental TATB scale are only 1.3 kcal mol(-1) in H2O and 1.8 kcal mol(-1) in DMSO solvents. However, in the case of CH3CN, the deviation reaches a value of 9.2 kcal mol(-1). The present study suggests that the experimental TATB scale is inconsistent for CH3CN. A total of 125 values of the solvation free energy of ions in these three solvents were obtained. These new data should be useful for the development of theoretical solvation models.

  10. An energy decomposition analysis for intermolecular interactions from an absolutely localized molecular orbital reference at the coupled-cluster singles and doubles level

    SciTech Connect

    Azar, R. Julian; Head-Gordon, Martin

    2012-01-14

    We propose a wave function-based method for the decomposition of intermolecular interaction energies into chemically-intuitive components, isolating both mean-field- and explicit correlation-level contributions. We begin by solving the locally-projected self-consistent field for molecular interactions equations for a molecular complex, obtaining an intramolecularly polarized reference of self-consistently optimized, absolutely-localized molecular orbitals (ALMOs), determined with the constraint that each fragment MO be composed only of atomic basis functions belonging to its own fragment. As explicit inter-electronic correlation is integral to an accurate description of weak forces underlying intermolecular interaction potentials, namely, coordinated fluctuations in weakly interacting electronic densities, we add dynamical correlation to the ALMO polarized reference at the coupled-cluster singles and doubles level, accounting for explicit dispersion and charge-transfer effects, which map naturally onto the cluster operator. We demonstrate the stability of energy components with basis set extension, follow the hydrogen bond-breaking coordinate in the C{sub s}-symmetry water dimer, decompose the interaction energies of dispersion-bound rare gas dimers and other van der Waals complexes, and examine charge transfer-dominated donor-acceptor interactions in borane adducts. We compare our results with high-level calculations and experiment when possible.

  11. An energy decomposition analysis for intermolecular interactions from an absolutely localized molecular orbital reference at the coupled-cluster singles and doubles level.

    PubMed

    Azar, R Julian; Head-Gordon, Martin

    2012-01-14

    We propose a wave function-based method for the decomposition of intermolecular interaction energies into chemically-intuitive components, isolating both mean-field- and explicit correlation-level contributions. We begin by solving the locally-projected self-consistent field for molecular interactions equations for a molecular complex, obtaining an intramolecularly polarized reference of self-consistently optimized, absolutely-localized molecular orbitals (ALMOs), determined with the constraint that each fragment MO be composed only of atomic basis functions belonging to its own fragment. As explicit inter-electronic correlation is integral to an accurate description of weak forces underlying intermolecular interaction potentials, namely, coordinated fluctuations in weakly interacting electronic densities, we add dynamical correlation to the ALMO polarized reference at the coupled-cluster singles and doubles level, accounting for explicit dispersion and charge-transfer effects, which map naturally onto the cluster operator. We demonstrate the stability of energy components with basis set extension, follow the hydrogen bond-breaking coordinate in the C(s)-symmetry water dimer, decompose the interaction energies of dispersion-bound rare gas dimers and other van der Waals complexes, and examine charge transfer-dominated donor-acceptor interactions in borane adducts. We compare our results with high-level calculations and experiment when possible.

  12. Low Energy Nuclear Reaction Products at Surfaces

    NASA Astrophysics Data System (ADS)

    Nagel, David J.

    2008-03-01

    This paper examines the evidence for LENR occurring on or very near to the surface of materials. Several types of experimental indications for LENR surface reactions have been reported and will be reviewed. LENR result in two types of products, energy and the appearance of new elements. The level of instantaneous power production can be written as the product of four factors: (1) the total area of the surface on which the reactions can occur, (2) the fraction of the area that is active at any time, (3) the reaction rate, that is, the number of reactions per unit active area per second, and (4) the energy produced per reaction. Each of these factors, and their limits, are reviewed. A graphical means of relating these four factors over their wide variations has been devised. The instantaneous generation of atoms of new elements can also be written as the product of the first three factors and the new elemental mass produced per reaction. Again, a graphical means of presenting the factors and their results over many orders of magnitude has been developed.

  13. Nonintuitive Diabatic Potential Energy Surfaces for Thioanisole.

    PubMed

    Li, Shaohong L; Xu, Xuefei; Hoyer, Chad E; Truhlar, Donald G

    2015-09-01

    Diabatization of potential energy surfaces is a technique that enables convenient molecular dynamics simulations of electronically nonadiabatic processes, but diabatization itself is nonunique and can be inconvenient; the best methods to achieve diabatization are still under study. Here, we present the diabatization of two electronic states of thioanisole in the S-CH3 bond stretching and C-C-S-C torsion two-dimensional nuclear coordinate space containing a conical intersection. We use two systematic methods: the (orbital-dependent) 4-fold way and the (orbital-free) Boys localization diabatization method. These very different methods yield strikingly similar diabatic potential energy surfaces that cross at geometries where the adiabatic surfaces are well separated and do not exhibit avoided crossings, and the contours of the diabatic gap and diabatic coupling are similar for the two methods. The validity of the diabatization is supported by comparing the nonadiabatic couplings calculated from the diabatic matrix elements to those calculated by direct differentiation of the adiabatic states.

  14. Surface Energy Budget Characteristics and Surface Energy Imbalance over Chinese Loess Plateau

    NASA Astrophysics Data System (ADS)

    Li, Hongyu; Zhang, Qiang; Guo, Weidong; Fu, Congbin; Shi, Jinsen

    2013-04-01

    Field observation of land-surface processes is a fundamental approach to quantitatively measure mass and energy exchanges between the land surface and the atmosphere. Chinese Loess Plateau, a unique landscape in the world, is known as a transitional zone both in terms of climate and ecosystem. Land-surface process measurement helps to better understand the aridity trend and the ecosystem change over Chinese Loess Plateau. Based on data collected at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) from June 2008 to June 2010, we analyzed the characteristics of land surface radiation and energy budget in summer, as well as the surface energy imbalance issues over Chinese Loess Plateau. Main results are concluded as follows: (1)By studying impacts of different weather conditions on micrometeorological characteristics, the clouds and the precipitation contribute disturbances by about 25 to each component of energy balance. Weakening impact of clouds and precipitation on surface energy budget is much stronger than that in desert and Gobi region. Furthermore, it shows that the mean climatic characteristics in summer relatively close to those of cloudy days. (2)To investigate the land surface energy imbalance over the Loess Plateau, we estimated the heat storage associated with change of air temperature and humidity as well as the energy stored in plants due to the photosynthesis, which determines the vertical water transport and soil temperature at the shadow soil layers. The peaks of averaged diurnal variation of energy storages by air and plant photosynthesis reach 1.5 and 2.0 W m-2 respectively. In addition, the peak of diurnal variation of mean heat flux transferred by vertical water movement can reach nearly 8.0 W m-2. The closure of energy balance is improved from 88.1% to 89.6% by adding the three additional energy terms mentioned above to the energy balance equation. We found that the special climate background and vegetation

  15. Theoretical studies of potential energy surfaces.

    SciTech Connect

    Harding, L. B.

    2006-01-01

    The goal of this program is to calculate accurate potential energy surfaces for both reactive and nonreactive systems. To do this the electronic Schroedinger equation must be solved. Our approach starts with multiconfiguration self-consistent field (MCSCF) reference wave functions. These reference wavefunctions are designed to be sufficiently flexible to accurately describe changes in electronic structure over a broad range of geometries. Dynamical electron correlation effects are included via multireference, singles and doubles configuration interaction (MRCI) calculations. With this approach, we are able to provide chemically useful predictions of the energetics for many systems. A second aspect of this program is the development of techniques to fit multi-dimensional potential surfaces to convenient, global, analytic functions that can then be used in dynamics calculations.

  16. Absolute biological needs.

    PubMed

    McLeod, Stephen

    2014-07-01

    Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses. PMID:23586876

  17. Absolute biological needs.

    PubMed

    McLeod, Stephen

    2014-07-01

    Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses.

  18. Surface Energy Reduction In Fibrous Monotectic Structures

    NASA Astrophysics Data System (ADS)

    Sandlin, A. C.; Schaefer, R. J.

    1991-08-01

    A study has been made of the morphology of directionally solidified CuAl-Pb monotectic alloys. The structure consisted of a hexagonal array of Pb rods in a Cu-based matrix. In addition, highly curved grain boundaries in the Cu-based matrix with lens-shaped Pb fibers on the boundary and a “denuded zone” depleted of Pb rods were observed. Existence of these boundaries is shown to reduce the overall surface energy of the system leading to the formation of the highly curved grain boundaries.

  19. Theoretical studies of potential energy surfaces

    SciTech Connect

    Harding, L.B.

    1993-12-01

    The goal of this program is to calculate accurate potential energy surfaces (PES) for both reactive and nonreactive systems. To do this the electronic Schrodinger equation must be solved. Our approach to this problem starts with multiconfiguration self-consistent field (MCSCF) reference wavefunctions. These reference wavefunctions are designed to be sufficiently flexible to accurately describe changes in electronic structure over a broad range of geometries. Electron correlation effects are included via multireference, singles and doubles configuration interaction (MRSDCI) calculations. With this approach, the authors are able to provide useful predictions of the energetics for a broad range of systems.

  20. Surface Energy Balance System (SEBS) Handbook

    SciTech Connect

    Cook, D. R.

    2016-01-01

    A Surface Energy Balance System (SEBS) has been installed collocated with each deployed Eddy Correlation Flux Measurement System (ECOR) at the Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Southern Great Plains (SGP) site, North Slope of Alaska (NSA) site, first ARM Mobile Facility (AMF1), second ARM Mobile Facility (AMF2), and third ARM Mobile Facility (AMF3) at Oliktok Point (OLI). A SEBS was also deployed with the Tropical Western Pacific (TWP) site, before it was decommissioned. Data from these sites, including the retired TWP, are available in the ARM Data Archive. The SEBS consists of upwelling and downwelling solar and infrared radiometers within one net radiometer, a wetness sensor, and soil measurements. The SEBS measurements allow the comparison of ECOR sensible and latent heat fluxes with the energy balance determined from the SEBS and provide information on wetting of the sensors for data quality purposes.

  1. Absolute calibration of optical flats

    DOEpatents

    Sommargren, Gary E.

    2005-04-05

    The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.

  2. Potential energy surfaces of superheavy nuclei

    SciTech Connect

    Bender, M.; Rutz, K.; Maruhn, J.A.; Greiner, W.; Reinhard, P.-G. Rutz, K.; Maruhn, J.A.; Greiner, W.

    1998-10-01

    We investigate the structure of the potential energy surfaces of the superheavy nuclei {sub 158}{sup 258}Fm{sub 100}, {sub 156}{sup 264}Hs{sub 108}, {sub 166}{sup 278}112, {sub 184}{sup 298}114, and {sub 172}{sup 292}120 within the framework of self-consistent nuclear models, i.e., the Skyrme-Hartree-Fock approach and the relativistic mean-field model. We compare results obtained with one representative parametrization of each model which is successful in describing superheavy nuclei. We find systematic changes as compared to the potential energy surfaces of heavy nuclei in the uranium region: there is no sufficiently stable fission isomer any more, the importance of triaxial configurations to lower the first barrier fades away, and asymmetric fission paths compete down to rather small deformation. Comparing the two models, it turns out that the relativistic mean-field model gives generally smaller fission barriers. {copyright} {ital 1998} {ital The American Physical Society}

  3. Dynamic wormholes, antitrapped surfaces, and energy conditions

    SciTech Connect

    Hochberg, D.; Visser, M.

    1998-08-01

    It is by now apparent that topology is too crude a tool to accurately characterize a generic traversable wormhole. In two earlier papers we developed a complete characterization of generic but static traversable wormholes, and in the present paper extend the discussion to arbitrary time-dependent (dynamical) wormholes. A local definition of a wormhole throat, free from assumptions about asymptotic flatness, symmetries, future and past null infinities, embedding diagrams, topology, and even time dependence is developed that accurately captures the essence of what a wormhole throat is, and where it is located. Adapting and extending a suggestion due to Page, we define a wormhole throat to be a marginally anti-trapped surface, that is, a closed two-dimensional spatial hypersurface such that one of the two future-directed null geodesic congruences orthogonal to it is just beginning to diverge. Typically a dynamic wormhole will possess {ital two} such throats, corresponding to the two orthogonal null geodesic congruences, and these two throats will not coincide (though they do coalesce into a single throat in the static limit). The divergence property of the null geodesics at the marginally anti-trapped surface generalizes the {open_quotes}flare-out{close_quotes} condition for an arbitrary wormhole. We derive theorems regarding violations of the null energy condition (NEC) at and near these throats and find that, even for wormholes with arbitrary time dependence, the violation of the NEC is a generic property of wormhole throats. We also discuss wormhole throats in the presence of fully antisymmetric torsion and find that the energy condition violations {ital cannot} be dumped into the torsion degrees of freedom. Finally by means of a concrete example we demonstrate that even temporary suspension of energy-condition violations is incompatible with the flare-out property of dynamic throats. {copyright} {ital 1998} {ital The American Physical Society}

  4. The absolute path command

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it canmore » provide the absolute path to a relative directory from the current working directory.« less

  5. The absolute path command

    SciTech Connect

    Moody, A.

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it can provide the absolute path to a relative directory from the current working directory.

  6. Biradical thermochemistry from collision-induced dissociation threshold energy measurements. Absolute heats of formation of ortho-, meta-, and para-benzyne

    SciTech Connect

    Wenthold, P.G.; Squires, R.R. )

    1994-07-13

    The absolute heats of formation of 1,2-, 1,3-, and 1,4-dehydrobenzene (ortho, meta-, and para-benzyne) have been determined from measurements of the threshold energies for collision-induced dissociation (CID) of ortho, meta-, and para-chlorophenyl anions in a flowing afterglow-triple quadrupole apparatus. The 298 K heats of formation for ortho-, meta-, and para-benzyne derived in this manner are 106.6 [+-] 3.0, 122.0 [+-] 3.1, and 137.3 [+-] 3.3 kcal/mol, respectively. The values for meta- and para-benzyne are higher than those reported previously but are in excellent agreement with recently reported MCSCF and CI calculations. Several control experiments are described which demonstrate that the earlier results for meta- and para-benzyne suffered from an acid-catalyzed isomerization of the reactant chlorophenyl anions in the flowing afterglow prior to CID threshold analysis. 70 refs., 5 figs., 4 tabs.

  7. Tensor decomposition in potential energy surface representations.

    PubMed

    Ostrowski, Lukas; Ziegler, Benjamin; Rauhut, Guntram

    2016-09-14

    In order to reduce the operation count in vibration correlation methods, e.g., vibrational configuration interaction (VCI) theory, a tensor decomposition approach has been applied to the analytical representations of multidimensional potential energy surfaces (PESs). It is shown that a decomposition of the coefficients within the individual n-mode coupling terms in a multimode expansion of the PES is feasible and allows for convenient contractions of one-dimensional integrals with these newly determined factor matrices. Deviations in the final VCI frequencies of a set of small molecules were found to be negligible once the rank of the factors matrices is chosen appropriately. Recommendations for meaningful ranks are provided and different algorithms are discussed. PMID:27634247

  8. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1988-01-01

    The minimum energy path for the addition of a hydrogen atom to N2 is characterized in CASSCF/CCI calculations using the (4s3p2d1f/3s2p1d) basis set, with additional single point calculations at the stationary points of the potential energy surface using the (5s4p3d2f/4s3p2d) basis set. These calculations represent the most extensive set of ab initio calculations completed to date, yielding a zero point corrected barrier for HN2 dissociation of approx. 8.5 kcal mol/1. The lifetime of the HN2 species is estimated from the calculated geometries and energetics using both conventional Transition State Theory and a method which utilizes an Eckart barrier to compute one dimensional quantum mechanical tunneling effects. It is concluded that the lifetime of the HN2 species is very short, greatly limiting its role in both termolecular recombination reactions and combustion processes.

  9. Nanoparticle energy transfer on the cell surface.

    PubMed

    Bene, László; Szentesi, Gergely; Mátyus, László; Gáspár, Rezso; Damjanovich, Sándor

    2005-01-01

    Membrane topology of receptors plays an important role in shaping transmembrane signalling of cells. Among the methods used for characterizing receptor clusters, fluorescence resonance energy transfer between a donor and acceptor fluorophore plays a unique role based on its capability of detecting molecular level (2-10 nm) proximities of receptors in physiological conditions. Recent development of biotechnology has made possible the usage of colloidal gold particles in a large size range for specific labelling of cells for the purposes of electron microscopy. However, by combining metal and fluorophore labelling of cells, the versatility of metal-fluorophore interactions opens the way for new applications by detecting the presence of the metal particles by the methods of fluorescence spectroscopy. An outstanding feature of the metal nanoparticle-fluorophore interaction is that the metal particle can enhance spontaneous emission of the fluorophore in a distance-dependent fashion, in an interaction range essentially determined by the size of the nanoparticle. In our work enhanced fluorescence of rhodamine and cyanine dyes was observed in the vicinity of immunogold nanoparticles on the surface of JY cells in a flow cytometer. The dyes and the immunogold were targetted to the cell surface receptors MHCI, MHCII, transferrin receptor and CD45 by monoclonal antibodies. The fluorescence enhancement was sensitive to the wavelength of the exciting light, the size and amount of surface bound gold beads, as well as the fluorophore-nanoparticle distance. The intensity of 90 degrees scattering of the incident light beam was enhanced by the immunogold in a concentration and size-dependent fashion. The 90 degrees light scattering varied with the wavelength of the incident light in a manner characteristic to gold nanoparticles of the applied sizes. A reduction in photobleaching time constant of the cyanine dye was observed in the vicinity of gold particles in a digital imaging

  10. Correlation between surface free energy and anchoring energy of 6CHBT on polyimide surface

    NASA Astrophysics Data System (ADS)

    Borycki, Jerzy; Okulska-Bozek, Malgorzata; Kedzierski, Jerzy; Kojdecki, Marek A.

    2002-06-01

    Polyimides were prepared in the classical two-step method via poly(amic acids). Poly(amic acids) were obtained from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'- (hexafluoroisopropylidene)diphthalic anhydride (6FDA), pyromellitic dianhydride (PMDA), 3,3',4,4'- diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'- oxydiphthalic anhydride (ODPA) and amines 4,4'-oxydianiline (ODA), 1,3-phenylenediamine (MPD), 1,4-phenylenediamine (PPD), 4,4'-diaminodiphenylmethane (MDA), 4,4'- ethylenedianiline (DAB), 2,4,6-trimethyl-1,3- phenylenediamine (TMPD), 4-methyl-1,3-phenylenediamine (MMPD) and 2,3,5,6-tetramethyl-1,4-phenylenediamine (DAD) in dimethylformamide. The indium tin oxide (ITO)-glass plates were spin-coated with the poly(amic acids) solutions and dried. A thermal imidization process was then carried out at 250 degree(s)C for 4 h. In this study the anchoring energies of 6CHBT molecules were evaluated on rubbing aligning layers of PI films. The polar anchoring energy coefficient was determined by wedge cell method. The surface free energy and its components of polyimide layers were determined by measuring the contact angles of water, ethylene glycol, formamide and diiodomethane drops on the rubbing polymer surfaces. The Lifshitz-van der Waals and acidic-basic components of surface free energies were found from van Oss equation.

  11. Insights into bacterial contact angles: difficulties in defining hydrophobicity and surface Gibbs energy.

    PubMed

    Gallardo-Moreno, Amparo M; Navarro-Pérez, M Luisa; Vadillo-Rodríguez, Virginia; Bruque, José M; González-Martín, M Luisa

    2011-11-01

    One of the principal techniques for evaluating the surface hydrophobicity of biological samples is contact angle. This method, applied readily to flat-smooth-inert surfaces, gives rise to an important debate when implemented with microbial lawns. After its initial description, in 1984, several authors have carried out modifications of the technique but the results obtained have not been previously judged. This work focuses on the particularities of contact angle measurements on bacterial lawns and enhances the idea of the impossibility of using water contact angle as a universal measurement of bacterial hydrophobicity. Contact angles can only be used as relative indicators of hydrophobicity, in a similar way to tests based on microbial adhesion to solvents. The strong dependence of contact angles on dried bacterial lawns with measuring time and environmental conditions (e.g. pH of the media) preclude the estimation of their absolute values, and so, of the cells surface Gibbs energy. Yet, for a given measuring time, it is found that the hydrophobicity and the apparent bacterial surface Gibbs energy components are qualitatively related to the bacterial surface electrical potential. In particular, a hydrophobic increase is always accompanied by an increase of the cells Lifshitz-Van der Waals component and a decrease of their acid-base component and absolute zeta potential. Therefore, the present study shows that the physico-chemical surface properties that characterize bacteria are not independent, and one of them can be qualitatively described in terms of the others when measuring contact angles at a fixed time after the drying of the microbial beds.

  12. Surface tension, surface energy, and chemical potential due to their difference.

    PubMed

    Hui, C-Y; Jagota, A

    2013-09-10

    It is well-known that surface tension and surface energy are distinct quantities for solids. Each can be regarded as a thermodynamic property related first by Shuttleworth. Mullins and others have suggested that the difference between surface tension and surface energy cannot be sustained and that the two will approach each other over time. In this work we show that in a single-component system where changes in elastic energy can be neglected, the chemical potential difference between the surface and bulk is proportional to the difference between surface tension and surface energy. By further assuming that mass transfer is driven by this chemical potential difference, we establish a model for the kinetics by which mass transfer removes the difference between surface tension and surface energy.

  13. Particle engineering in pharmaceutical solids processing: surface energy considerations.

    PubMed

    Williams, Daryl R

    2015-01-01

    During the past 10 years particle engineering in the pharmaceutical industry has become a topic of increasing importance. Engineers and pharmacists need to understand and control a range of key unit manufacturing operations such as milling, granulation, crystallisation, powder mixing and dry powder inhaled drugs which can be very challenging. It has now become very clear that in many of these particle processing operations, the surface energy of the starting, intermediate or final products is a key factor in understanding the processing operation and or the final product performance. This review will consider the surface energy and surface energy heterogeneity of crystalline solids, methods for the measurement of surface energy, effects of milling on powder surface energy, adhesion and cohesion on powder mixtures, crystal habits and surface energy, surface energy and powder granulation processes, performance of DPI systems and finally crystallisation conditions and surface energy. This review will conclude that the importance of surface energy as a significant factor in understanding the performance of many particulate pharmaceutical products and processes has now been clearly established. It is still nevertheless, work in progress both in terms of development of methods and establishing the limits for when surface energy is the key variable of relevance.

  14. Particle engineering in pharmaceutical solids processing: surface energy considerations.

    PubMed

    Williams, Daryl R

    2015-01-01

    During the past 10 years particle engineering in the pharmaceutical industry has become a topic of increasing importance. Engineers and pharmacists need to understand and control a range of key unit manufacturing operations such as milling, granulation, crystallisation, powder mixing and dry powder inhaled drugs which can be very challenging. It has now become very clear that in many of these particle processing operations, the surface energy of the starting, intermediate or final products is a key factor in understanding the processing operation and or the final product performance. This review will consider the surface energy and surface energy heterogeneity of crystalline solids, methods for the measurement of surface energy, effects of milling on powder surface energy, adhesion and cohesion on powder mixtures, crystal habits and surface energy, surface energy and powder granulation processes, performance of DPI systems and finally crystallisation conditions and surface energy. This review will conclude that the importance of surface energy as a significant factor in understanding the performance of many particulate pharmaceutical products and processes has now been clearly established. It is still nevertheless, work in progress both in terms of development of methods and establishing the limits for when surface energy is the key variable of relevance. PMID:25876912

  15. Surface free energy of chosen polyimides and anchoring energy of 6CHBT on these surfaces

    NASA Astrophysics Data System (ADS)

    Borycki, Jerzy; Wilczek, Maria; Kedzierski, Jerzy; Kojdecki, Marek A.

    2004-09-01

    Poly(amic acids) were prepared from chosen aromatic dianhydrides and diamines in dimethylformamide. The glass or the indium tin oxide (ITO)-glass plates were spin-coated with the poly(amic acids) solutions and dried. A thermal imidization process was then carried out. The polar anchoring energy coefficient of 6CHBT molecules on polyimide and poly(amide imides) surfaces was determined by wedge cell method for. The surface free energies and its components were found from van Oss, Fowkes and Owens equations. It was shown that wettability of polymer layers with the 6CHBT and PCB liquid crystals depend on the imidization temperature. The worst wettability was observed for polyimide layers prepared at 250°C, whereas the best for baked at 350°C.

  16. The radiation of surface wave energy: Implications for volcanic tremor

    NASA Astrophysics Data System (ADS)

    Haney, M. M.; Denolle, M.; Lyons, J. J.; Nakahara, H.

    2015-12-01

    The seismic energy radiated by active volcanism is one common measurement of eruption size. For example, the magnitudes of individual earthquakes in volcano-tectonic (VT) swarms can be summed and expressed in terms of cumulative magnitude, energy, or moment release. However, discrepancies exist in current practice when treating the radiated energy of volcano seismicity dominated by surface waves. This has implications for volcanic tremor, since eruption tremor typically originates at shallow depth and is made up of surface waves. In the absence of a method to compute surface wave energy, estimates of eruption energy partitioning between acoustic and seismic waves typically assume seismic energy is composed of body waves. Furthermore, without the proper treatment of surface wave energy, it is unclear how much volcanic tremor contributes to the overall seismic energy budget during volcanic unrest. To address this issue, we derive, from first principles, the expression of surface wave radiated energy. In contrast with body waves, the surface wave energy equation is naturally expressed in the frequency domain instead of the time domain. We validate our result by reproducing an analytical solution for the radiated power of a vertical force source acting on a free surface. We further show that the surface wave energy equation leads to an explicit relationship between energy and the imaginary part of the surface wave Green's tensor at the source location, a fundamental property recognized within the field of seismic interferometry. With the new surface wave energy equation, we make clear connections to reduced displacement and propose an improved formula for the calculation of surface wave reduced displacement involving integration over the frequency band of tremor. As an alternative to reduced displacement, we show that reduced particle velocity squared is also a valid physical measure of tremor size, one based on seismic energy rate instead of seismic moment rate. These

  17. Advanced Potential Energy Surfaces for Molecular Simulation.

    PubMed

    Albaugh, Alex; Boateng, Henry A; Bradshaw, Richard T; Demerdash, Omar N; Dziedzic, Jacek; Mao, Yuezhi; Margul, Daniel T; Swails, Jason; Zeng, Qiao; Case, David A; Eastman, Peter; Wang, Lee-Ping; Essex, Jonathan W; Head-Gordon, Martin; Pande, Vijay S; Ponder, Jay W; Shao, Yihan; Skylaris, Chris-Kriton; Todorov, Ilian T; Tuckerman, Mark E; Head-Gordon, Teresa

    2016-09-22

    Advanced potential energy surfaces are defined as theoretical models that explicitly include many-body effects that transcend the standard fixed-charge, pairwise-additive paradigm typically used in molecular simulation. However, several factors relating to their software implementation have precluded their widespread use in condensed-phase simulations: the computational cost of the theoretical models, a paucity of approximate models and algorithmic improvements that can ameliorate their cost, underdeveloped interfaces and limited dissemination in computational code bases that are widely used in the computational chemistry community, and software implementations that have not kept pace with modern high-performance computing (HPC) architectures, such as multicore CPUs and modern graphics processing units (GPUs). In this Feature Article we review recent progress made in these areas, including well-defined polarization approximations and new multipole electrostatic formulations, novel methods for solving the mutual polarization equations and increasing the MD time step, combining linear-scaling electronic structure methods with new QM/MM methods that account for mutual polarization between the two regions, and the greatly improved software deployment of these models and methods onto GPU and CPU hardware platforms. We have now approached an era where multipole-based polarizable force fields can be routinely used to obtain computational results comparable to state-of-the-art density functional theory while reaching sampling statistics that are acceptable when compared to that obtained from simpler fixed partial charge force fields.

  18. Advanced Potential Energy Surfaces for Molecular Simulation.

    PubMed

    Albaugh, Alex; Boateng, Henry A; Bradshaw, Richard T; Demerdash, Omar N; Dziedzic, Jacek; Mao, Yuezhi; Margul, Daniel T; Swails, Jason; Zeng, Qiao; Case, David A; Eastman, Peter; Wang, Lee-Ping; Essex, Jonathan W; Head-Gordon, Martin; Pande, Vijay S; Ponder, Jay W; Shao, Yihan; Skylaris, Chris-Kriton; Todorov, Ilian T; Tuckerman, Mark E; Head-Gordon, Teresa

    2016-09-22

    Advanced potential energy surfaces are defined as theoretical models that explicitly include many-body effects that transcend the standard fixed-charge, pairwise-additive paradigm typically used in molecular simulation. However, several factors relating to their software implementation have precluded their widespread use in condensed-phase simulations: the computational cost of the theoretical models, a paucity of approximate models and algorithmic improvements that can ameliorate their cost, underdeveloped interfaces and limited dissemination in computational code bases that are widely used in the computational chemistry community, and software implementations that have not kept pace with modern high-performance computing (HPC) architectures, such as multicore CPUs and modern graphics processing units (GPUs). In this Feature Article we review recent progress made in these areas, including well-defined polarization approximations and new multipole electrostatic formulations, novel methods for solving the mutual polarization equations and increasing the MD time step, combining linear-scaling electronic structure methods with new QM/MM methods that account for mutual polarization between the two regions, and the greatly improved software deployment of these models and methods onto GPU and CPU hardware platforms. We have now approached an era where multipole-based polarizable force fields can be routinely used to obtain computational results comparable to state-of-the-art density functional theory while reaching sampling statistics that are acceptable when compared to that obtained from simpler fixed partial charge force fields. PMID:27513316

  19. Surface binding energies of beryllium/tungsten alloys

    NASA Astrophysics Data System (ADS)

    Gyoeroek, Michael; Kaiser, Alexander; Sukuba, Ivan; Urban, Jan; Hermansson, Kersti; Probst, Michael

    2016-04-01

    Binding energies of beryllium and tungsten atoms on surfaces of the alloys Be2W and Be12W were obtained from density functional theory calculations. Values of 4.08-5.63 eV for beryllium and 6.81-10.04 eV for tungsten were obtained. An analytical force field agrees for beryllium, but its tungsten surface atoms are too strongly bound. The surface binding energies of Be and W on Be12W surfaces is slightly smaller than on the pure Be and W surfaces, respectively. For higher tungsten content, i.e. for Be2W, the situation is more complicated. For some surfaces of this alloy the surface binding energies are enhanced while for others they are diminished, compared to the pure metal surfaces. The dependency of the cohesive energy on the mole fraction follows a linear relationship.

  20. Semiconductor surface sublimation energies and atom-atom interactions

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, Srinivasan; Berding, M. A.; Sher, A.; Chen, A.-B.

    1990-01-01

    The energy required to remove an atom from semiconductor surfaces is calculated using a Green's-function approach. Contrary to intuition, it is found that, in some cases, less energy is needed to remove an atom from the nearly full surface than from a nearly empty surface. The results are explained in terms of the relative energies of anion and cation dangling bonds, and the charge transfers between them. The deducted effective pair-interaction energies and their effects on surface morphology and growth perfection are discussed.

  1. Cosmology with negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony

    2016-08-01

    Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < ‑1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.

  2. Cosmology with negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony

    2016-08-01

    Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < -1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.

  3. Triton's surface-atmosphere energy balance

    NASA Technical Reports Server (NTRS)

    Stansberry, John A.; Yelle, Roger V.; Lunine, Jonathan I.; Mcewen, Alfred S.

    1992-01-01

    A model encompassing the turbulent transfer of sensible heat as well as insolation, reradiation, and latent heat transport is presently used to investigate the energetics of the surface-atmosphere system of Triton. Under the assumption of a physically plausible range of heat transfer coefficients, the atmospheric temperature 1 km above the surface is found to be 1-3 K hotter than the Triton surface. The observed N2 frosts must have an emissivity lower than unity in order to match a frost temperature at the surface of about 38 K.

  4. Accurate calculation of the absolute free energy of binding for drug molecules† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5sc02678d Click here for additional data file.

    PubMed Central

    Aldeghi, Matteo; Heifetz, Alexander; Bodkin, Michael J.; Knapp, Stefan

    2016-01-01

    Accurate prediction of binding affinities has been a central goal of computational chemistry for decades, yet remains elusive. Despite good progress, the required accuracy for use in a drug-discovery context has not been consistently achieved for drug-like molecules. Here, we perform absolute free energy calculations based on a thermodynamic cycle for a set of diverse inhibitors binding to bromodomain-containing protein 4 (BRD4) and demonstrate that a mean absolute error of 0.6 kcal mol–1 can be achieved. We also show a similar level of accuracy (1.0 kcal mol–1) can be achieved in pseudo prospective approach. Bromodomains are epigenetic mark readers that recognize acetylation motifs and regulate gene transcription, and are currently being investigated as therapeutic targets for cancer and inflammation. The unprecedented accuracy offers the exciting prospect that the binding free energy of drug-like compounds can be predicted for pharmacologically relevant targets. PMID:26798447

  5. Estimation of spatially distributed surface energy fluxes using remotely-sensed data for agricultural fields

    NASA Astrophysics Data System (ADS)

    Melesse, Assefa M.; Nangia, Vijay

    2005-09-01

    Land surface energy fluxes are required in many environmental studies, including hydrology, agronomy and meteorology. Surface energy balance models simulate microscale energy exchange processes between the ground surface and the atmospheric layer near ground level. Spatial variability of energy fluxes limits point measurements to be used for larger areas. Remote sensing provides the basis for spatial mapping of energy fluxes. Remote-sensing-based surface energy flux-mapping was conducted using seven Landsat images from 1997 to 2002 at four contiguous crop fields located in Polk County, northwestern Minnesota. Spatially distributed surface energy fluxes were estimated and mapped at 30 m pixel level from Landsat Thematic Mapper and Enhanced Thematic Mapper images and weather information. Net radiation was determined using the surface energy balance algorithm for land (SEBAL) procedure. Applying the two-source energy balance (TSEB) model, the surface temperature and the latent and sensible heat fluxes were partitioned into vegetation and soil components and estimated at the pixel level. Yield data for wheat and soybean from 1997 to 2002 were mapped and compared with latent heat (evapotranspiration) for four of the fields at pixel level. The spatial distribution and the relation of latent heat flux and Bowen ratio (ratio of sensible heat to latent heat) to crop yield were studied. The root-mean-square error and the mean absolute percentage of error between the observed and predicted energy fluxes were between 7 and 22 W m-2 and 12 and 24% respectively. Results show that latent heat flux and Bowen ratio were correlated (positive and negative) to the yield data. Wheat and soybean yields were predicted using latent heat flux with mean R2 = 0.67 and 0.70 respectively, average residual means of -4.2 bushels/acre and 0.11 bushels/acre respectively, and average residual standard deviations of 16.2 bushels/acre and 16.6 bushels/acre respectively (1 bushel/acre 0.087 m3 ha-1

  6. ABSOLUTE POLARIMETRY AT RHIC.

    SciTech Connect

    OKADA; BRAVAR, A.; BUNCE, G.; GILL, R.; HUANG, H.; MAKDISI, Y.; NASS, A.; WOOD, J.; ZELENSKI, Z.; ET AL.

    2007-09-10

    Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy Of {Delta}P{sub beam}/P{sub beam} < 5%. The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features proton-proton elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power A{sub N} of this process has allowed us to achieve {Delta}P{sub beam}/P{sub beam} = 4.2% in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of AN in the CNI region (four-momentum transfer squared 0.001 < -t < 0.032 (GeV/c){sup 2}) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.

  7. Procedure for estimating fracture energy from fracture surface roughness

    DOEpatents

    Williford, Ralph E.

    1989-01-01

    The fracture energy of a material is determined by first measuring the length of a profile of a section through a fractured surface of the material taken on a plane perpendicular to the mean plane of that surface, then determining the fractal dimensionality of the surface. From this, the yield strength of the material, and the Young's Modulus of that material, the fracture energy is calculated.

  8. Effect of milling temperatures on surface area, surface energy and cohesion of pharmaceutical powders.

    PubMed

    Shah, Umang V; Wang, Zihua; Olusanmi, Dolapo; Narang, Ajit S; Hussain, Munir A; Tobyn, Michael J; Heng, Jerry Y Y

    2015-11-10

    Particle bulk and surface properties are influenced by the powder processing routes. This study demonstrates the effect of milling temperatures on the particle surface properties, particularly surface energy and surface area, and ultimately on powder cohesion. An active pharmaceutical ingredient (API) of industrial relevance (brivanib alaninate, BA) was used to demonstrate the effect of two different, but most commonly used milling temperatures (cryogenic vs. ambient). The surface energy of powders milled at both cryogenic and room temperatures increased with increasing milling cycles. The increase in surface energy could be related to the generation of surface amorphous regions. Cohesion for both cryogenic and room temperature milled powders was measured and found to increase with increasing milling cycles. For cryogenic milling, BA had a surface area ∼ 5× higher than the one obtained at room temperature. This was due to the brittle nature of this compound at cryogenic temperature. By decoupling average contributions of surface area and surface energy on cohesion by salinization post-milling, the average contribution of surface energy on cohesion for powders milled at room temperature was 83% and 55% at cryogenic temperature.

  9. Absolute Equilibrium Entropy

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    1997-01-01

    The entropy associated with absolute equilibrium ensemble theories of ideal, homogeneous, fluid and magneto-fluid turbulence is discussed and the three-dimensional fluid case is examined in detail. A sigma-function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H-theorems of ideal turbulence). It is shown that the two approaches are complimentary though conceptually different: H-theorems show that an isolated system tends to equilibrium while sigma-functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids.

  10. Application of radiometric surface temperature for surface energy balance estimation: John Monteith's contributions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Over 25 years ago, Huband and Monteith paper’s investigating the radiative surface temperature and the surface energy balance of a wheat canopy, highlighted the key issues in computing fluxes with radiometric surface temperature. These included the relationship between radiometric and aerodynamic s...

  11. Role of surface energy coefficients and nuclear surface diffuseness in the fusion of heavy-ions

    NASA Astrophysics Data System (ADS)

    Dutt, Ishwar; Puri, Rajeev K.

    2010-04-01

    We discuss the effect of surface energy coefficients as well as nuclear surface diffuseness in the proximity potential and ultimately in the fusion of heavy-ions. Here we employ different versions of surface energy coefficients. Our analysis reveals that these technical parameters can influence the fusion barriers by a significant amount. A best set of these parameters is also given that explains the experimental data nicely.

  12. On surface energy and the continuum thermodynamics of brittle fracture

    NASA Technical Reports Server (NTRS)

    Eftis, J.; Liebowitz, H.

    1976-01-01

    When a separating body is viewed as a nonequilibrium thermodynamic process, the full thermodynamic nature of the surface energy induced by crack propagation becomes apparent. Within such a general framework it is no longer possible to view the surface energy as a material constant. For the self-propagating crack the induced surface energy is shown to depend explicitly on the square of the crack propagation speed. It is also shown that a separating body produces entropy even though the mechanical response of the solid may be elastic. The introduction of surface quantities such as surface energy into the continuum description of the fracture process forces a major departure from the mechanics appropriate to the nonseparating body. Local equations of balance are no longer obtainable as derived consequences of postulated global balance equations. They must instead be imposed as separate additional postulates.

  13. Issues in Absolute Spectral Radiometric Calibration: Intercomparison of Eight Sources

    NASA Technical Reports Server (NTRS)

    Goetz, Alexander F. H.; Kindel, Bruce; Pilewskie, Peter

    1998-01-01

    The application of atmospheric models to AVIRIS and other spectral imaging data to derive surface reflectance requires that the sensor output be calibrated to absolute radiance. Uncertainties in absolute calibration are to be expected, and claims of 92% accuracy have been published. Measurements of accurate surface albedos and cloud absorption to be used in radiative balance calculations depend critically on knowing the absolute spectral-radiometric response of the sensor. The Earth Observing System project is implementing a rigorous program of absolute radiometric calibration for all optical sensors. Since a number of imaging instruments that provide output in terms of absolute radiance are calibrated at different sites, it is important to determine the errors that can be expected among calibration sites. Another question exists about the errors in the absolute knowledge of the exoatmospheric spectral solar irradiance.

  14. Triton's surface-atmosphere energy balance

    USGS Publications Warehouse

    Stansberry, J.A.; Yelle, R.V.; Lunine, J.I.; McEwen, A.S.

    1992-01-01

    We explore the energetics of Triton's surface-atmosphere system using a model that includes the turbulent transfer of sensible heat as well as insolation, reradiation, and latent heat transport. The model relies on a 1?? by 1?? resolution hemispheric bolometric albedo map of Triton for determining the atmospheric temperature, the N2 frost emissivity, and the temperatures of unfrosted portions of the surface consistent with a frost temperature of ???38 K. For a physically plausible range of heat transfer coefficients, we find that the atmospheric temperature roughly 1 km above the surface is approximately 1 to 3 K hotter than the surface. Atmospheric temperatures of 48 K suggested by early analysis of radio occultation data cannot be obtained for plausible values of the heat transfer coefficients. Our calculations indicate that Triton's N2 frosts must have an emissivity well below unity in order to have a temperature of ???38 K, consistent with previous results. We also find that convection over small hot spots does not significantly cool them off, so they may be able to act as continous sources of buoyancy for convective plumes, but have not explored whether the convection is vigorous enough to entrain particulate matter thereby forming a dust devil. Our elevated atmospheric temperatures make geyser driven plumes with initial upward velocities ???10 m s-1 stagnate in the lower atmosphere. These "wimpy" plumes provide a possible explanation for Triton's "wind streaks.". ?? 1992.

  15. Dual hierarchical biomimic superhydrophobic surface with three energy states

    NASA Astrophysics Data System (ADS)

    Chen, Ming-Hung; Hsu, Tsung-Hsing; Chuang, Yun-Ju; Tseng, Fan-Gang

    2009-07-01

    A low hysteresis surface prepared by two-length-scaled hierarchical textures to mimic the Lotus effect is proposed. The fabricated textures incorporate self-masked nanorods on microextrusions. A high static contact angle (160°) and low hysteresis (˜2.7°) are obtained and comparable to the surface properties of a natural lotus leaf. The stability of hydrophobicity is described with respect to three energy states (nonwetting, microwetting, and nanowetting) based on dynamic contact angle analysis by droplet impinging onto the surface. The estimated texture-induced energy barrier based on the principle of energy conservation is in good agreement to those estimated from Laplace's law.

  16. Surface diffusion activation energy determination using ion beam microtexturing

    NASA Technical Reports Server (NTRS)

    Rossnagel, S. M.; Robinson, R. S.

    1982-01-01

    The activation energy for impurity atom (adatom) surface diffusion can be determined from the temperature dependence of the spacing of sputter cones. These cones are formed on the surface during sputtering while simultaneously adding impurities. The impurities form clusters by means of surface diffusion, and these clusters in turn initiate cone formation. Values are given for the surface diffusion activation energies for various materials on polycrystalline Cu, Al, Pb, Au, and Ni. The values for different impurity species on each of these substrates are approximately independent of impurity species within the experimental uncertainty, suggesting the absence of strong chemical bonding effects on the diffusion.

  17. Potential energy surfaces of Polonium isotopes

    NASA Astrophysics Data System (ADS)

    Nerlo-Pomorska, B.; Pomorski, K.; Schmitt, C.; Bartel, J.

    2015-11-01

    The evolution of the potential energy landscape is analysed in detail for ten even-even polonium isotopes in the mass range 188\\lt A\\lt 220 as obtained within the macroscopic-microscopic approach, relying on the Lublin-Strasbourg drop model and the Yukawa-folded single-particle energies for calculating the microscopic shell and pairing corrections. A variant of the modified Funny-Hills nuclear shape parametrization is used to efficiently map possible fission paths. The approach explains the main features of the fragment partition as measured in low-energy fission along the polonium chain. The latter lies in a transitional region of the nuclear chart, and will be essential to consistently understand the evolution of fission properties from neutron-deficient mercury to heavy actinides. The ability of our method to predict fission observables over such an extended region looks promising.

  18. Surface Energy Heat Fluxes Using Remotely Sensed Parameters

    NASA Technical Reports Server (NTRS)

    Toll, David L.; Vukovich, Fred M.; Pontikes, Elizabeth G.

    1997-01-01

    Realistic estimates of surface energy heat fluxes are needed for the study of water and energy interactions between the land and atmosphere. The primary objective of this work is to study the estimation of surface heat energy fluxes using remote sensing derived parameters under different spatial and temporal conditions. Surface energy fluxes and remote sensing derived data from two sources were analyzed. First, we used surface heat flux, remote sensing, and ancillary data from the International Satellite Land Surface Climatology Project (ISLSCP), mapped at a 1 deg. x 1 deg. grid. Second, we used NOAA AVHRR (1 km), weather station, and ancillary data to derive estimates of surface latent and sensible heat energy fluxes over a 100 sq kilometers area for three test sites: 1) First ISLSCP Field Experiment (FIFE) grassland site, Konza Prairie, Kansas; 2) Howland, Maine Forest Ecosystem Dynamics Site; and 3) Walnut Gulch, scrubland site, surrounding Tombstone, Arizona. Satellite derived estimates of land surface temperature, surface albedo, and spectral vegetation index are used in selected models to provide estimates of surface heat fluxes. Analysis of results from the 1 deg. x 1 deg. grid for North America indicated there were similar, overall correlations between sensible and latent heat energy fluxes versus remotely sensed vegetation index and ground temperature during dry and wet year conditions. However, there were significant differences in correlations between years when stratified by land cover class. Analysis of 100 km x 100 km data (1 km resolution) indicated partitioning the areas in to primary versus secondary cover, with the secondary cover comprising less than 5% of the area, significantly improved surface heat energy flux estimates.

  19. The evaporative fraction as a measure of surface energy partitioning

    SciTech Connect

    Nichols, W.E. ); Cuenca, R.H. )

    1990-01-01

    The evaporative fraction is a ratio that expresses the proportion of turbulent flux energy over land surfaces devoted to evaporation and transpiration (evapotranspiration). It has been used to characterize the energy partition over land surfaces and has potential for inferring daily energy balance information based on mid-day remote sensing measurements. The HAPEX-MOBILHY program's SAMER system provided surface energy balance data over a range of agricultural crops and soil types. The databases from this large-scale field experiment was analyzed for the purpose of studying the behavior and daylight stability of the evaporative fraction in both ideal and general meteorological conditions. Strong linear relations were found to exist between the mid-day evaporative fraction and the daylight mean evaporative fraction. Statistical tests however rejected the hypothesis that the two quantities were equal. The relations between the evaporative fraction and the surface soil moisture as well as soil moisture in the complete vegetation root zone were also explored.

  20. Energy-decomposition analysis for viscous free-surface flows.

    PubMed

    Colagrossi, Andrea; Bouscasse, Benjamin; Marrone, Salvatore

    2015-11-01

    This work is dedicated to the energy decomposition analysis of a viscous free-surface flow. In the presence of a free surface, the viscous dissipation for a Newtonian liquid can be decomposed into two terms: an enstrophy component and a free-surface deformation component. The latter requires the evaluation of volume and surface integrals in the meshless framework. The analysis is based on the weakly compressible smoothed particle hydrodynamics formalism. The behavior of the energy terms is studied in standing wave problems by changing the viscosity and the wave amplitude. Finally, an analysis of a complex shallow water breaking wave case is provided. It is shown that in presence of intense breaking phenomena the two energy components are always comparable, whereas generally the free surface component is dominant on the viscous dissipation of gravity waves. PMID:26651775

  1. Energy-decomposition analysis for viscous free-surface flows

    NASA Astrophysics Data System (ADS)

    Colagrossi, Andrea; Bouscasse, Benjamin; Marrone, Salvatore

    2015-11-01

    This work is dedicated to the energy decomposition analysis of a viscous free-surface flow. In the presence of a free surface, the viscous dissipation for a Newtonian liquid can be decomposed into two terms: an enstrophy component and a free-surface deformation component. The latter requires the evaluation of volume and surface integrals in the meshless framework. The analysis is based on the weakly compressible smoothed particle hydrodynamics formalism. The behavior of the energy terms is studied in standing wave problems by changing the viscosity and the wave amplitude. Finally, an analysis of a complex shallow water breaking wave case is provided. It is shown that in presence of intense breaking phenomena the two energy components are always comparable, whereas generally the free surface component is dominant on the viscous dissipation of gravity waves.

  2. Modelling of binding free energy of targeted nanocarriers to cell surface

    NASA Astrophysics Data System (ADS)

    Liu, Jin; Ayyaswamy, Portonovo S.; Eckmann, David M.; Radhakrishnan, Ravi

    2014-03-01

    We have developed a numerical model based on Metropolis Monte Carlo and the weighted histogram analysis method that enables the calculation of the absolute binding free energy between functionalized nanocarriers (NC) and endothelial cell (EC) surfaces. The binding affinities are calculated according to the free energy landscapes. The model predictions quantitatively agree with the analogous measurements of specific antibody coated NCs (100 nm in diameter) to intracellular adhesion molecule-1 (ICAM-1) expressing EC surface in in vitro cell culture experiments. The model also enables an investigation of the effects of a broad range of parameters that include antibody surface coverage of NC, glycocalyx in both in vivo and in vitro conditions, shear flow and NC size. Using our model we explore the effects of shear flow and reproduce the shear-enhanced binding observed in equilibrium measurements in collagen-coated tube. Furthermore, our results indicate that the bond stiffness, representing the specific antibody-antigen interaction, significantly impacts the binding affinities. The predictive success of our computational protocol represents a sound quantitative approach for model driven design and optimization of functionalized NC in targeted vascular drug delivery.

  3. Evaluation of the surface free energy of plant surfaces: toward standardizing the procedure

    PubMed Central

    Fernández, Victoria; Khayet, Mohamed

    2015-01-01

    Plant surfaces have been found to have a major chemical and physical heterogeneity and play a key protecting role against multiple stress factors. During the last decade, there is a raising interest in examining plant surface properties for the development of biomimetic materials. Contact angle measurement of different liquids is a common tool for characterizing synthetic materials, which is just beginning to be applied to plant surfaces. However, some studies performed with polymers and other materials showed that for the same surface, different surface free energy values may be obtained depending on the number and nature of the test liquids analyzed, materials' properties, and surface free energy calculation methods employed. For 3 rough and 3 rather smooth plant materials, we calculated their surface free energy using 2 or 3 test liquids and 3 different calculation methods. Regardless of the degree of surface roughness, the methods based on 2 test liquids often led to the under- or over-estimation of surface free energies as compared to the results derived from the 3-Liquids method. Given the major chemical and structural diversity of plant surfaces, it is concluded that 3 different liquids must be considered for characterizing materials of unknown physico-chemical properties, which may significantly differ in terms of polar and dispersive interactions. Since there are just few surface free energy data of plant surfaces with the aim of standardizing the calculation procedure and interpretation of the results among for instance, different species, organs, or phenological states, we suggest the use of 3 liquids and the mean surface tension values provided in this study. PMID:26217362

  4. Evaluation of the surface free energy of plant surfaces: toward standardizing the procedure.

    PubMed

    Fernández, Victoria; Khayet, Mohamed

    2015-01-01

    Plant surfaces have been found to have a major chemical and physical heterogeneity and play a key protecting role against multiple stress factors. During the last decade, there is a raising interest in examining plant surface properties for the development of biomimetic materials. Contact angle measurement of different liquids is a common tool for characterizing synthetic materials, which is just beginning to be applied to plant surfaces. However, some studies performed with polymers and other materials showed that for the same surface, different surface free energy values may be obtained depending on the number and nature of the test liquids analyzed, materials' properties, and surface free energy calculation methods employed. For 3 rough and 3 rather smooth plant materials, we calculated their surface free energy using 2 or 3 test liquids and 3 different calculation methods. Regardless of the degree of surface roughness, the methods based on 2 test liquids often led to the under- or over-estimation of surface free energies as compared to the results derived from the 3-Liquids method. Given the major chemical and structural diversity of plant surfaces, it is concluded that 3 different liquids must be considered for characterizing materials of unknown physico-chemical properties, which may significantly differ in terms of polar and dispersive interactions. Since there are just few surface free energy data of plant surfaces with the aim of standardizing the calculation procedure and interpretation of the results among for instance, different species, organs, or phenological states, we suggest the use of 3 liquids and the mean surface tension values provided in this study.

  5. Bond-Energy and Surface-Energy Calculations in Metals

    ERIC Educational Resources Information Center

    Eberhart, James G.; Horner, Steve

    2010-01-01

    A simple technique appropriate for introductory materials science courses is outlined for the calculation of bond energies in metals from lattice energies. The approach is applied to body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal-closest-packed (hcp) metals. The strength of these bonds is tabulated for a variety metals and is…

  6. CORTICAL SURFACE PARAMETERIZATION BY P-HARMONIC ENERGY MINIMIZATION

    PubMed Central

    JOSHI, ANAND A.; SHATTUCK, DAVID W.; THOMPSON, PAUL M.; LEAHY, RICHARD M.

    2010-01-01

    Cortical surface parameterization has several applications in visualization and analysis of the brain surface. Here we propose a scheme for parameterizing the surface of the cerebral cortex. The parameterization is formulated as the minimization of an energy functional in the pth norm. A numerical method for obtaining the solution is also presented. Brain surfaces from multiple subjects are brought into common parameter space using the scheme. 3D spatial averages of the cortical surfaces are generated by using the correspondences induced by common parameter space. PMID:20721316

  7. Surface energy fluxes in complex terrain

    NASA Technical Reports Server (NTRS)

    Reiter, E. R.; Sheaffer, J. D.; Bossert, J. E.

    1986-01-01

    The emphasis of the 1985 NASA project activity was on field measurements of wind data and heat balance data. Initiatives included a 19 station mountaintop monitoring program, testing and refining the surface flux monitoring systems and packing and shipping equipment to the People's Republic of China in preparation for the 1986 Tibet Experiment. Other work included more extensive analyses of the 1984 Gobi Desert and Rocky Mountain observations plus some preliminary analyses of the 1985 mountaintop network data. Details of our field efforts are summarized and results of our data analyses are presented.

  8. Ab Initio Calculations for the Surface Energy of Silver Nanoclusters

    NASA Astrophysics Data System (ADS)

    Medasani, Bharat; Vasiliev, Igor; Park, Young Ho

    2007-03-01

    We apply first principles computational methods to study the surface energy and the surface stress of silver nanoparticles. The structures, energies and lattice contractions of spherical Ag nanoclusters are calculated in the framework of density functional theory combined with the generalized gradient approximation. Our calculations predict the surface energies of Ag nanoclusters to be in the range of 1-2 J/m^2. These values are close to the bulk surface energy of silver, but are significantly lower than the recently reported value of 7.2 J/m^2 derived from the Kelvin equation for free Ag nanoparticles. From the lattice contraction and the nearest neighbor interatomic distance, we estimate the surface stress of the silver nanoclusters to be in the the range of 1-1.45 N/m. This result suggests that a liquid droplet model can be employed to evaluate the surface energy and the surface stress of Ag nanoparticles. K. K. Nanda et al., Phys. Rev. Lett. 91, 106102 (2003).

  9. Absolute Energy Calibration of X-ray TESs with 0.04 eV Uncertainty at 6.4 keV in a Hadron-Beam Environment

    NASA Astrophysics Data System (ADS)

    Tatsuno, H.; Doriese, W. B.; Bennett, D. A.; Curceanu, C.; Fowler, J. W.; Gard, J.; Gustafsson, F. P.; Hashimoto, T.; Hayano, R. S.; Hays-Wehle, J. P.; Hilton, G. C.; Iliescu, M.; Ishimoto, S.; Itahashi, K.; Iwasaki, M.; Kuwabara, K.; Ma, Y.; Marton, J.; Noda, H.; O'Neil, G. C.; Okada, S.; Outa, H.; Reintsema, C. D.; Sato, M.; Schmidt, D. R.; Shi, H.; Suzuki, K.; Suzuki, T.; Uhlig, J.; Ullom, J. N.; Widmann, E.; Yamada, S.; Zmeskal, J.; Swetz, D. S.

    2016-08-01

    A performance evaluation of superconducting transition-edge sensors (TESs) in the environment of a pion beam line at a particle accelerator is presented. Averaged across the 209 functioning sensors in the array, the achieved energy resolution is 5.2 eV FWHM at Co K_{α } (6.9 keV) when the pion beam is off and 7.3 eV at a beam rate of 1.45 MHz. Absolute energy uncertainty of ± 0.04 eV is demonstrated for Fe K_{α } (6.4 keV) with in-situ energy calibration obtained from other nearby known X-ray lines. To achieve this small uncertainty, it is essential to consider the non-Gaussian energy response of the TESs and thermal cross-talk pile-up effects due to charged particle hits in the silicon substrate of the TES array.

  10. Components of surface energy balance in a temperate grassland ecosystem

    NASA Technical Reports Server (NTRS)

    Kim, Joon; Verma, Shashi B.

    1990-01-01

    Eddy correlation measurements of moisture, heat, and momentum fluxes were made at a tall grassland site in Kansas during the First International Satellite Land Surface Climatology Project Field Experiment. The fluxes, stomatal conductance, and leaf water potential of three grass species are reported. The species are big bluestem, indiangrass, and switchgrass. The daily and seasonal variation in the components of the surface energy balance and the aerodynamic and canopy surface conductances for prairie vegetation are examined.

  11. Simulated Surface Energy Budgets Over the Southeastern US: The GHCC Satellite Assimilation System and the NCEP Early Eta

    NASA Technical Reports Server (NTRS)

    Lapenta, William M.; Suggs, Ron; McNider, Richard T.; Jedlovec, Gary

    1999-01-01

    A technique has been developed for assimilating GOES-derived skin temperature tendencies and insolation into the surface energy budget equation of a mesoscale model so that the simulated rate of temperature change closely agrees with the satellite observations. A critical assumption of the technique is that the availability of moisture (either from the soil or vegetation) is the least known term in the model's surface energy budget. Therefore, the simulated latent heat flux, which is a function of surface moisture availability, is adjusted based upon differences between the modeled and satellite-observed skin temperature tendencies. An advantage of this technique is that satellite temperature tendencies are assimilated in an energetically consistent manner that avoids energy imbalances and surface stability problems that arise from direct assimilation of surface shelter temperatures. The fact that the rate of change of the satellite skin temperature is used rather than the absolute temperature means that sensor calibration is not as critical. An advantage of this technique for short-range forecasts (0-48h) is that it does not require a complex land-surface formulation within the atmospheric model. As a result, we can avoid having to specify land surface characteristics such as vegetation resistances, green fraction, leaf area index, soil physical and hydraulic characteristics, stream flow, runoff, and the vertical and horizontal distribution of soil moisture.

  12. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Heinemann, K.; Walch, Stephen P.

    1992-01-01

    The work on the NH + NO system which was described in the last progress report was written up and a draft of the manuscript is included in the appendix. The appendix also contains a draft of a manuscript on an Ar + H + H surface. New work which was completed in the last six months includes the following: (1) calculations on the (1)CH2 + H2O, H2 + HCOH, and H2 + H2CO product channels in the CH3 + OH reaction; (2) calculations for the NH2 + O reaction; (3) calculations for the CH3 + O2 reaction; and (4) calculations for CH3O and the two decomposition channels--CH2OH and H + H2CO. Detailed descriptions of this work will be given in manuscripts; however, brief descriptions of the CH3 + OH and CH3 + O2 projects are given.

  13. Multistage DFTB-DFT Strategy for Energy Surface Search

    NASA Astrophysics Data System (ADS)

    Horoi, Mihai; Polovina, Dusan; Horchidan, Bogdan; Jackson, Koblar A.

    2002-03-01

    Recently we proposed a multistage DFTB-DFT strategy to find the absolute minimum energy configuration of a cluster of atoms: (i) in a first stage we use the Density Functional Tight Binding (DFTB) method to generate a collection of candidate optimal structures; (ii) subsequently, we relax the DFTB structures using full Density Functional Theory (DFT). This approach was successfully used to identify new lowest energy configurations of several Sin clusters with n<20 (I. Rata, et al., Phys. Rev. Lett. 85, 546(2000)). In the present contribution we report an improvement to this algorithm based on the observation that there is a strong correlation between the unrelaxed DFT energies of the DFTB clusters and the final energies of the relaxed DFT structures. The modification increases the efficiency of the search algorithm by a factor of 50, allowing the analysis of more DFTB candidate structures. We use the new strategy to analyze the oblate-compact shape transition, from Si_25 to Si_27, observed in the experiment (R.R. Hudgins et al, J.Chem.Phys. 111, 7865 (1999)).

  14. Combined Use of Absolute and Differential Seismic Arrival Time Data to Improve Absolute Event Location

    NASA Astrophysics Data System (ADS)

    Myers, S.; Johannesson, G.

    2012-12-01

    error estimated to be 0.28 seconds and 0.01 seconds, respectively. We will report on the use of absolute and differential time data for several real data sets at the meeting. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-570920.

  15. Absolute Identification by Relative Judgment

    ERIC Educational Resources Information Center

    Stewart, Neil; Brown, Gordon D. A.; Chater, Nick

    2005-01-01

    In unidimensional absolute identification tasks, participants identify stimuli that vary along a single dimension. Performance is surprisingly poor compared with discrimination of the same stimuli. Existing models assume that identification is achieved using long-term representations of absolute magnitudes. The authors propose an alternative…

  16. Be Resolute about Absolute Value

    ERIC Educational Resources Information Center

    Kidd, Margaret L.

    2007-01-01

    This article explores how conceptualization of absolute value can start long before it is introduced. The manner in which absolute value is introduced to students in middle school has far-reaching consequences for their future mathematical understanding. It begins to lay the foundation for students' understanding of algebra, which can change…

  17. Radiative energy transport on the surface of an ice sheet

    NASA Astrophysics Data System (ADS)

    Cathles, Lawrence Maclagan, IV

    Both surface roughness and surface conditions of an ice sheet affect the exchange of energy between the atmosphere and an ice sheet. Potential feedbacks exist where the absorbed energy on the surface changes the surface in such a way that more energy is absorbed. One such feedback occurs when a supraglacial lake absorbs energy and sub-lake melting occurs, which deepens the lake, and reduces the albedo. While another feedback exists from topography which creates non-uniform absorption of sunlight, causing surface geometries to change as melting occurs, affecting how energy is absorbed on the surface. The influence of these feedbacks on the surface energy balance of ice sheet are not well understood, and motivate the work presented here. To assess the influences of surface conditions and surface topography on the radiative budget of an ice sheet, the two feedback cases were studied separately. The effect of the surface condition was determined using a two-stream radiative transfer model for a two layer system, where the top layer could be either ice, snow, or water, and the second layer was ice. An analytical solution for the albedo of a supraglacial lake as a function of water depth was derived, and showed that a supraglacial lake can reduce the albedo by fifty percent. Multispectral analysis is required for surfaces where liquid water is present, but little additional accuracy is gained beyond 18 spectral bands. Complex surface topography has a significant effect on the absorption of energy due to multiple reflections between the surface and its self. A numerical model was developed to determine the absorption of insolation on an arbitrary two-dimensional surface. The absorbed radiation forces an ice ablation model evolving the surface topography through an ablation season. Results from numerical simulations show that there is a strong latitudinal dependence on how surface features evolve through an ablation season. At high latitudes, the aspect ratio of surface

  18. Ab initio Potential Energy Surface for H-H2

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Bauschlicher, Charles W., Jr.; Stallcop, James R.; Levin, Eugene

    1993-01-01

    Ab initio calculations employing large basis sets are performed to determine an accurate potential energy surface for H-H2 interactions for a broad range of separation distances. At large distances, the spherically averaged potential determined from the calculated energies agrees well with the corresponding results determined from dispersion coefficients; the van der Waals well depth is predicted to be 75 +/- (mu)E(sub h). Large basis sets have also been applied to reexamine the accuracy of theoretical repulsive potential energy surfaces. Multipolar expansions of the computed H-H2 potential energy surface are reported for four internuclear separation distances (1.2, 1.401, 1.449, and 1.7a(sub 0) of the hydrogen molecule. The differential elastic scattering cross section calculated from the present results is compared with the measurements from a crossed beam experiment.

  19. Electron hole pair mediated vibrational excitation in CO scattering from Au(111): Incidence energy and surface temperature dependence

    SciTech Connect

    Shirhatti, Pranav R.; Werdecker, Jörn; Golibrzuch, Kai; Wodtke, Alec M.; Bartels, Christof

    2014-09-28

    We investigated the translational incidence energy (E{sub i}) and surface temperature (T{sub s}) dependence of CO vibrational excitation upon scattering from a clean Au(111) surface. We report absolute v = 0 → 1 excitation probabilities for E{sub i} between 0.16 and 0.84 eV and T{sub s} between 473 and 973 K. This is now only the second collision system where such comprehensive measurements are available – the first is NO on Au(111). For CO on Au(111), vibrational excitation occurs via direct inelastic scattering through electron hole pair mediated energy transfer – it is enhanced by incidence translation and the electronically non-adiabatic coupling is about 5 times weaker than in NO scattering from Au(111). Vibrational excitation via the trapping desorption channel dominates at E{sub i} = 0.16 eV and quickly disappears at higher E{sub i}.

  20. Ion Beam Analysis Of Silicon-Based Surfaces And Correlation With Surface Energy Measurements

    NASA Astrophysics Data System (ADS)

    Xing, Qian; Herbots, N.; Hart, M.; Bradley, J. D.; Wilkens, B. J.; Sell, D. A.; Sell, Clive H.; Kwong, Henry Mark; Culbertson, R. J.; Whaley, S. D.

    2011-06-01

    The water affinity of Si-based surfaces is quantified by contact angle measurement and surface free energy to explain hydrophobic or hydrophilic behavior of silicone, silicates, and silicon surfaces. Surface defects such as dangling bonds, surface free energy including Lewis acid-base and Lifshitz-van der Waals components are discussed. Water nucleation and condensation is further explained by surface topography. Tapping mode atomic force microscopy (TMAFM) provides statistical analysis of the topography of these Si-based surfaces. The correlation of the above two characteristics describes the behavior of water condensation at Si-based surfaces. Surface root mean square roughness increasing from several Å to several nm is found to provide nucleation sites that expedite water condensation visibly for silica and silicone. Hydrophilic surfaces have a condensation pattern that forms puddles of water while hydrophobic surfaces form water beads. Polymer adsorption on these surfaces alters the water affinity as well as the surface topography, and therefore controls condensation on Si-based surfaces including silicone intraocular lens (IOL). The polymer film is characterized by Rutherford backscattering spectrometry (RBS) in conjunction with 4.265 MeV 12C(α, α)12C, 3.045 MeV 16O(α,α)16O nuclear resonance scattering (NRS), and 2.8 MeV elastic recoil detection (ERD) of hydrogen for high resolution composition and areal density measurements. The areal density of hydroxypropyl methylcellulose (HPMC) film ranges from 1018 atom/cm2 to 1019 atom/cm2 gives the silica or silicone surface a roughness of several Å and a wavelength of 0.16±0.02 μm, and prevents fogging by forming a complete wetting layer during water condensation.

  1. Ion Beam Analysis Of Silicon-Based Surfaces And Correlation With Surface Energy Measurements

    SciTech Connect

    Xing Qian; Herbots, N.; Hart, M.; Bradley, J. D.; Wilkens, B. J.; Sell, D. A.; Culbertson, R. J.; Whaley, S. D.; Sell, Clive H.; Kwong, Henry Mark Jr.

    2011-06-01

    The water affinity of Si-based surfaces is quantified by contact angle measurement and surface free energy to explain hydrophobic or hydrophilic behavior of silicone, silicates, and silicon surfaces. Surface defects such as dangling bonds, surface free energy including Lewis acid-base and Lifshitz-van der Waals components are discussed. Water nucleation and condensation is further explained by surface topography. Tapping mode atomic force microscopy (TMAFM) provides statistical analysis of the topography of these Si-based surfaces. The correlation of the above two characteristics describes the behavior of water condensation at Si-based surfaces. Surface root mean square roughness increasing from several A ring to several nm is found to provide nucleation sites that expedite water condensation visibly for silica and silicone. Hydrophilic surfaces have a condensation pattern that forms puddles of water while hydrophobic surfaces form water beads. Polymer adsorption on these surfaces alters the water affinity as well as the surface topography, and therefore controls condensation on Si-based surfaces including silicone intraocular lens (IOL). The polymer film is characterized by Rutherford backscattering spectrometry (RBS) in conjunction with 4.265 MeV {sup 12}C({alpha}, {alpha}){sup 12}C, 3.045 MeV {sup 16}O({alpha},{alpha}){sup 16}O nuclear resonance scattering (NRS), and 2.8 MeV elastic recoil detection (ERD) of hydrogen for high resolution composition and areal density measurements. The areal density of hydroxypropyl methylcellulose (HPMC) film ranges from 10{sup 18} atom/cm{sup 2} to 10{sup 19} atom/cm{sup 2} gives the silica or silicone surface a roughness of several A ring and a wavelength of 0.16{+-}0.02 {mu}m, and prevents fogging by forming a complete wetting layer during water condensation.

  2. Nanometer polymer surface features: the influence on surface energy, protein adsorption and endothelial cell adhesion

    NASA Astrophysics Data System (ADS)

    Carpenter, Joseph; Khang, Dongwoo; Webster, Thomas J.

    2008-12-01

    Current small diameter (<5 mm) synthetic vascular graft materials exhibit poor long-term patency due to thrombosis and intimal hyperplasia. Tissue engineered solutions have yielded functional vascular tissue, but some require an eight-week in vitro culture period prior to implantation—too long for immediate clinical bedside applications. Previous in vitro studies have shown that nanostructured poly(lactic-co-glycolic acid) (PLGA) surfaces elevated endothelial cell adhesion, proliferation, and extracellular matrix synthesis when compared to nanosmooth surfaces. Nonetheless, these studies failed to address the importance of lateral and vertical surface feature dimensionality coupled with surface free energy; nor did such studies elicit an optimum specific surface feature size for promoting endothelial cell adhesion. In this study, a series of highly ordered nanometer to submicron structured PLGA surfaces of identical chemistry were created using a technique employing polystyrene nanobeads and poly(dimethylsiloxane) (PDMS) molds. Results demonstrated increased endothelial cell adhesion on PLGA surfaces with vertical surface features of size less than 18.87 nm but greater than 0 nm due to increased surface energy and subsequently protein (fibronectin and collagen type IV) adsorption. Furthermore, this study provided evidence that the vertical dimension of nanometer surface features, rather than the lateral dimension, is largely responsible for these increases. In this manner, this study provides key design parameters that may promote vascular graft efficacy.

  3. Enhancing surface free energy and hydrophilicity through chemical modification of microstructured titanium implant surfaces.

    PubMed

    Rupp, F; Scheideler, L; Olshanska, N; de Wild, M; Wieland, M; Geis-Gerstorfer, J

    2006-02-01

    Roughness-induced hydrophobicity, well-known from natural plant surfaces and intensively studied toward superhydrophobic surfaces, has currently been identified on microstructured titanium implant surfaces. Studies indicate that microstructuring by sandblasting and acid etching (SLA) enhances the osteogenic properties of titanium. The undesired initial hydrophobicity, however, presumably decelerates primary interactions with the aqueous biosystem. To improve the initial wettability and to retain SLA microstructure, a novel surface modification was tested. This modification differs from SLA by its preparation after acid etching, which was done under protective gas conditions following liquid instead of dry storage. We hypothesized that this modification should have increased wettability due to the prevention of contaminations that occurs during air contact. The main outcome of dynamic wettability measurements was that the novel modification shows increased surface free energy (SFE) and increased hydrophilicity with initial water contact angles of 0 degrees compared to 139.9 degrees for SLA. This hydrophilization was kept even after any drying. Reduced hydrocarbon contaminations were identified to play a possible role in altered surface thermodynamics. Such surfaces aim to retain the hydrophilicity and natural high surface energy of the Ti dioxide surface until surgical implants' insertion and are compared in this in vitro study with structural surface variants of titanium to compare roughness and chemically induced wettability. PMID:16270344

  4. Development of sol-gel icephobic coatings: effect of surface roughness and surface energy.

    PubMed

    Fu, Qitao; Wu, Xinghua; Kumar, Divya; Ho, Jeffrey W C; Kanhere, Pushkar D; Srikanth, Narasimalu; Liu, Erjia; Wilson, Peter; Chen, Zhong

    2014-12-10

    Sol-gel coatings with different roughness and surface energy were prepared on glass substrates. Methyl triethoxysilane (MTEOS), 3-Glycidyloxypropyl trimethoxysilane (GLYMO) and fluoroalkylsilane (FAS) were used to obtain a mechanically robust icephobic coating. Different amount of hydrophobic silica nano particles was added as fillers to introduce different roughness and surface energy to the coatings. The microstructure, roughness, and surface energy, together with elemental information and surface chemical state, were investigated at room temperature. The contact angle and sliding angle were measured at different temperatures to correlate the wetting behavior at low temperature with the anti-icing performance. The ice adhesion shear strength was measured inside an ice chamber using a self-designed tester. The factors influencing the ice adhesion were discussed, and the optimum anti-icing performance found in the series of coatings. It was found that lower surface energy leads to lower ice adhesion regardless of the roughness, while the roughness plays a more complicated role. The wetting behavior of the droplet on surface changes as temperature decreases. The anti-icing performance is closely related to the antiwetting property of the surfaces at subzero temperatures.

  5. Quantifying mineral surface energy by scanning force microscopy.

    PubMed

    Sauerer, Bastian; Stukan, Mikhail; Abdallah, Wael; Derkani, Maryam H; Fedorov, Maxim; Buiting, Jan; Zhang, Zhenyu J

    2016-06-15

    Fundamental understanding of the wettability of carbonate formations can potentially be applied to the development of oil recovery strategies in a complex carbonate reservoir. In the present study, surface energies of representative carbonate samples were evaluated by direct quantitative force measurements, using scanning force microscopy (SFM) at sub-micron scale, to develop a reliable method to predict reservoir wettability. Local adhesion force measurements were conducted on appropriate calcite and dolomite samples and performed in air as well as in the presence of polar and nonpolar fluids. This study demonstrated that, by comparing measurements of adhesion forces between samples of the same mineral in different fluids, it is feasible to determine the surface energy of a given mineral as well as its polar and nonpolar components. The derived values are in agreement with literature. A proof-of-principle protocol has been established to quantify surface energy using SFM-based adhesion measurements. This novel methodology complements the conventional contact angle measurement technique, where surface energy can only be examined at large length scale. The reported methodology has great potential for further optimization into a new standard method for fast and accurate surface energy determination, and hence provides a new tool for reservoir rock wettability characterization. PMID:27054773

  6. Development of generalized potential-energy surfaces using many-body expansions, neural networks, and moiety energy approximations

    NASA Astrophysics Data System (ADS)

    Malshe, M.; Narulkar, R.; Raff, L. M.; Hagan, M.; Bukkapatnam, S.; Agrawal, P. M.; Komanduri, R.

    2009-05-01

    A general method for the development of potential-energy hypersurfaces is presented. The method combines a many-body expansion to represent the potential-energy surface with two-layer neural networks (NN) for each M-body term in the summations. The total number of NNs required is significantly reduced by employing a moiety energy approximation. An algorithm is presented that efficiently adjusts all the coupled NN parameters to the database for the surface. Application of the method to four different systems of increasing complexity shows that the fitting accuracy of the method is good to excellent. For some cases, it exceeds that available by other methods currently in literature. The method is illustrated by fitting large databases of ab initio energies for Sin(n =3,4,…,7) clusters obtained from density functional theory calculations and for vinyl bromide (C2H3Br) and all products for dissociation into six open reaction channels (12 if the reverse reactions are counted as separate open channels) that include C-H and C-Br bond scissions, three-center HBr dissociation, and three-center H2 dissociation. The vinyl bromide database comprises the ab initio energies of 71 969 configurations computed at MP4(SDQ) level with a 6-31G(d,p) basis set for the carbon and hydrogen atoms and Huzinaga's (4333/433/4) basis set augmented with split outer s and p orbitals (43321/4321/4) and a polarization f orbital with an exponent of 0.5 for the bromine atom. It is found that an expansion truncated after the three-body terms is sufficient to fit the Si5 system with a mean absolute testing set error of 5.693×10-4 eV. Expansions truncated after the four-body terms for Sin(n =3,4,5) and Sin(n =3,4,…,7) provide fits whose mean absolute testing set errors are 0.0056 and 0.0212 eV, respectively. For vinyl bromide, a many-body expansion truncated after the four-body terms provides fitting accuracy with mean absolute testing set errors that range between 0.0782 and 0.0808 eV. These

  7. Absolute quantitation of phosphorus metabolites in the cerebral cortex of the newborn human infant and in the forearm muscles of young adults using a double-tuned surface coil

    NASA Astrophysics Data System (ADS)

    Cady, Ernest B.

    The application of a double-tuned surface coil with strong coupling for both 31P and 1H to the in vivo measurement of metabolite concentrations by NMR spectroscopy is demonstrated. It is shown that sample loading, although important for a coil tuned to a single frequency, does not necessarily have a significant effect on absolute quantitation results if the coil is strongly coupled to the sample for both nuclei. For the coil used in the present study, the spectrometer calibration coefficient is almost independent of loading and the 1H and 31P flip angles at the coil center produced by fixed length pulses could be arranged to be nearly equal over a range of loading conditions. In seven normal infants, of gestational plus postnatal age 35 to 37 weeks, the cerebral cortex nucleotide triphosphate concentration was 3.7 ± 0.6 m M/liter wet (mean ± SD). Metabolite concentrations were low in the cerebral cortex of a severely birth asphyxiated infant. The adenosine triphosphate concentration in the resting, fresh forearm muscles of six young adults was 6.3 ± 0.8 m M/liter wet.

  8. Superhydrophobic surfaces: A model approach to predict contact angle and surface energy of soil particles

    NASA Astrophysics Data System (ADS)

    Shirtcliffe, Neil; Hamlett, Christopher; McHale, Glen; Newton, Michael; Bachmann, Joerg; Woche, S.

    2010-05-01

    C. Hamlett(a), G. McHALE(a), N. Shirtcliffe(a), M. Newton(a), S.K. Woche(b), and J. BACHMANN(b) aSchool of Science & Technology, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK and bInstitute of Soil Science, Leibniz University Hannover, Herrenhaeuser Str.2, 30419, Hannover, Germany. Summary Wettability of soil affects a wide variety of processes including infiltration, preferential flow and surface runoff. The problem of determining contact angles and surface energy of powders, such as soil particles, remains unsolved. So far, several theories and approaches have been proposed, but formulation of surface and interfacial free energy, as regards its components, is still a very debatable issue. In the present study, the general problem of the interpretation of contact angles and surface free energy on chemically heterogeneous and rough soil particle surfaces are evaluated by a reformulation of the Cassie-Baxter equation assuming that the particles are attached on to a plane and rigid surface. Compared with common approaches, our model considers a roughness factor which depends on the Young's Law contact angle determined by the surface chemistry. Results of the model are discussed and compared with independent contact angle measurements using the Sessile Drop and the Wilhelmy Plate methods. Based on contact angle data, the critical surface tension of the grains were determined by the method proposed by Zisman. Experiments were made with glass beads and three soil materials ranging from sand to clay. Soil particles were coated with different loadings of dichlorodimethylsilane (DCDMS) to vary the wettability. Varying the solid surface tension using DCDMS treatments provided pure water wetting behaviours ranging from wettable to extremely hydrophobic with contact angles >150°. Results showed that the critical surface energy measured on grains with the highest DCDMS loadings was similar to the surface energy measured independently on ideal DCDMS

  9. Challenges of the surface energy budget and proposed ways forward

    NASA Astrophysics Data System (ADS)

    von Schuckmann, Karina; Josey, Simon; Gulev, Sergey; Trenberth, Kevin; Clayson, Carol Anne; Mathieu, Pierre Philippe; Wild, Martin

    2015-04-01

    To understand how the Earth's climate system balances the energy budget, we have to consider processes occurring at three levels: the surface of the Earth, where most solar heating takes place; the Top of the Atmosphere (TOA), where sunlight enters the system; and the atmosphere in between. At each level, the amount of incoming and outgoing energy, or net flux must, on average, be equal on longer time scales in an unchanging climate. Under the influence of external and/or internal climate forcing energy is not balanced anymore, and can hence, lead to a temporal positive or negative Earth's Energy Imbalance, which is currently estimated of the order of 0.5-1 Wm-2 (IPCC, 2013). Although it is known that the majority of this energy is stored in the global ocean (~93%), an overarching scientific challenge faced by the whole climate science community is related to achieving accuracy in the changes in storage and flows of energy throughout the climate system, hereby raising the question: "How is heat entering the global ocean?" This highlights the vital role of understanding the surface flux budget, though it is currently impossible to detect an imbalance equivalent to 1 Wm-2 via the estimation of the surface energy budget. This presentation is discussing the need of quantifying sea surface heat fluxes to the required level of accuracy needed to support the various climate science applications, which is currently a very challenging task of the surface energy budget community. The current level of uncertainties in global ocean mean and trends of heat and moisture fluxes remain higher than is required by many applications and it is still unclear which of the components of surface net heat flux contributes mostly to our uncertainties and where regionally these contributions are most significant. Using constraints on energy budget considerations, and hence, inter-comparisons to other independent observing systems as well as to re-enforce interdisciplinary collaborations for

  10. Surface modification using low energy ground state ion beams

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara (Inventor); Hecht, Michael H. (Inventor); Orient, Otto J. (Inventor)

    1990-01-01

    A method of effecting modifications at the surfaces of materials using low energy ion beams of known quantum state, purity, flux, and energy is presented. The ion beam is obtained by bombarding ion-generating molecules with electrons which are also at low energy. The electrons used to bombard the ion generating molecules are separated from the ions thus obtained and the ion beam is directed at the material surface to be modified. Depending on the type of ion generating molecules used, different ions can be obtained for different types of surface modifications such as oxidation and diamond film formation. One area of application is in the manufacture of semiconductor devices from semiconductor wafers.

  11. Revisit of the Global Surface Energy Balance Using the MEP Model of Surface Heat Fluxes

    NASA Astrophysics Data System (ADS)

    Deng, Y.; Wang, J.; Park, T. W.; Ming, Y.

    2015-12-01

    The recently proposed model of surface heat fluxes, based on the theory of maximum entropy production (MEP), was used to estimate the global evapotranspiration (ET) and heat fluxes. Compared to bulk transfer models, the MEP model has several remote-sensing-friendly features including fewer input variables, automatic closure of surface energy budget, being independent of bulk gradients of temperature and water vapor, not using wind speed and surface roughness as model parameters, and being less sensitive to uncertainties of input variables and model parameters. The MEP model is formulated for the entire range of soil moisture from dryness to saturation over the land surfaces and has even more advantages over water-snow-ice surfaces compared to traditional methods due to its independence of surface humidity data. The MEP model provides the first global maps of water heat fluxes at ocean surfaces as well as conductive heat fluxes at snow/ice covered polar regions. Ten years of Clouds and the Earth's Radiant Energy System (CERES) earth surface radiation fluxes, surface temperature data products supplemented (when needed) by the Modern-Era Retrospective analysis for Research and Applications (MERRA) surface specific humidity data are used to test the MEP model by comparing the MEP based global annual ET and heat fluxes with existing products. The MEP based fluxes over land surfaces agree closely with previous studies. Over the oceans, the MEP modeled ET tends to be lower than previous estimates while those of sensible heat fluxes are in close agreement with previous studies. A counterpart, "off-line" analysis is also carried out using the NOAA GFDL climate model output from a control experiment and a "warming" experiment. Substantial differences in the warming-related changes of ET and Bowen ratio are found over regions such as North Africa and the southwestern U.S. The implications of these differences for understanding trends and variability in regional energy and

  12. Surface free energy analysis of adsorbents used for radioiodine adsorption

    NASA Astrophysics Data System (ADS)

    González-García, C. M.; Román, S.; González, J. F.; Sabio, E.; Ledesma, B.

    2013-10-01

    In this work, the surface free energy of biomass-based activated carbons, both fresh and impregnated with triethylenediamine, has been evaluated. The contribution of Lifshitz van der Waals components was determined by the model proposed by van Oss et al. The results obtained allowed predicting the most probable configurations of the impregnant onto the carbon surface and its influence on the subsequent adsorption of radioactive methyl iodide.

  13. Urban Surface Radiative Energy Budgets Determined Using Aircraft Scanner Data

    NASA Technical Reports Server (NTRS)

    Luvall, Jeffrey C.; Quattrochi, Dale A.; Rickman, Doug L.; Estes, Maury G.; Arnold, James E. (Technical Monitor)

    2002-01-01

    It is estimated that by the year 2025, 80% of the world's population will live in cities. The extent of these urban areas across the world can be seen in an image of city lights from the Defense Meteorological Satellite Program. In many areas of North America and Europe, it is difficult to separate individual cities because of the dramatic growth and sprawl of urbanized areas. This conversion of the natural landscape vegetation into man-made urban structures such as roads and buildings drastically alter the regional surface energy budgets, hydrology, precipitation patterns, and meteorology. One of the earliest recognized and measured phenomena of urbanization is the urban heat island (UHI) which was reported as early as 1833 for London and 1862 for Paris. The urban heat island results from the energy that is absorbed by man-made materials during the day and is released at night resulting in the heating of the air within the urban area. The magnitude of the air temperature difference between the urban and surrounding countryside is highly dependent on the structure of the urban area, amount of solar immolation received during the day, and atmospheric conditions during the night. These night time air temperature differences can be in the range of 2 to 5 C. or greater. Although day time air temperature differences between urban areas and the countryside exists during the day, atmospheric mixing and stability reduce the magnitude. This phenomena is not limited to large urban areas, but also occurs in smaller metropolitan areas. The UHI has significant impacts on the urban air quality, meteorology, energy use, and human health. The UPI can be mitigated through increasing the amount of vegetation and modification of urban surfaces using high albedo materials for roofs and paved surfaces. To understand why the urban heat island phenomenon exists it is useful to define the surface in terms of the surface energy budget. Surface temperature and albedo is a major component of

  14. An adaptive interpolation scheme for molecular potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Kowalewski, Markus; Larsson, Elisabeth; Heryudono, Alfa

    2016-08-01

    The calculation of potential energy surfaces for quantum dynamics can be a time consuming task—especially when a high level of theory for the electronic structure calculation is required. We propose an adaptive interpolation algorithm based on polyharmonic splines combined with a partition of unity approach. The adaptive node refinement allows to greatly reduce the number of sample points by employing a local error estimate. The algorithm and its scaling behavior are evaluated for a model function in 2, 3, and 4 dimensions. The developed algorithm allows for a more rapid and reliable interpolation of a potential energy surface within a given accuracy compared to the non-adaptive version.

  15. An adaptive interpolation scheme for molecular potential energy surfaces.

    PubMed

    Kowalewski, Markus; Larsson, Elisabeth; Heryudono, Alfa

    2016-08-28

    The calculation of potential energy surfaces for quantum dynamics can be a time consuming task-especially when a high level of theory for the electronic structure calculation is required. We propose an adaptive interpolation algorithm based on polyharmonic splines combined with a partition of unity approach. The adaptive node refinement allows to greatly reduce the number of sample points by employing a local error estimate. The algorithm and its scaling behavior are evaluated for a model function in 2, 3, and 4 dimensions. The developed algorithm allows for a more rapid and reliable interpolation of a potential energy surface within a given accuracy compared to the non-adaptive version. PMID:27586901

  16. An adaptive interpolation scheme for molecular potential energy surfaces.

    PubMed

    Kowalewski, Markus; Larsson, Elisabeth; Heryudono, Alfa

    2016-08-28

    The calculation of potential energy surfaces for quantum dynamics can be a time consuming task-especially when a high level of theory for the electronic structure calculation is required. We propose an adaptive interpolation algorithm based on polyharmonic splines combined with a partition of unity approach. The adaptive node refinement allows to greatly reduce the number of sample points by employing a local error estimate. The algorithm and its scaling behavior are evaluated for a model function in 2, 3, and 4 dimensions. The developed algorithm allows for a more rapid and reliable interpolation of a potential energy surface within a given accuracy compared to the non-adaptive version.

  17. Locating landmarks on high-dimensional free energy surfaces.

    PubMed

    Chen, Ming; Yu, Tang-Qing; Tuckerman, Mark E

    2015-03-17

    Coarse graining of complex systems possessing many degrees of freedom can often be a useful approach for analyzing and understanding key features of these systems in terms of just a few variables. The relevant energy landscape in a coarse-grained description is the free energy surface as a function of the coarse-grained variables, which, despite the dimensional reduction, can still be an object of high dimension. Consequently, navigating and exploring this high-dimensional free energy surface is a nontrivial task. In this paper, we use techniques from multiscale modeling, stochastic optimization, and machine learning to devise a strategy for locating minima and saddle points (termed "landmarks") on a high-dimensional free energy surface "on the fly" and without requiring prior knowledge of or an explicit form for the surface. In addition, we propose a compact graph representation of the landmarks and connections between them, and we show that the graph nodes can be subsequently analyzed and clustered based on key attributes that elucidate important properties of the system. Finally, we show that knowledge of landmark locations allows for the efficient determination of their relative free energies via enhanced sampling techniques.

  18. Ab Initio Potential Energy Surface for H-H2

    NASA Technical Reports Server (NTRS)

    Patridge, Harry; Bauschlicher, Charles W., Jr.; Stallcop, James R.; Levin, Eugene

    1993-01-01

    Ab initio calculations employing large basis sets are performed to determine an accurate potential energy surface for H-H2 interactions for a broad range of separation distances. At large distances, the spherically averaged potential determined from the calculated energies agrees well with the corresponding results determined from dispersion coefficients; the van der Waals well depth is predicted to be 75 +/- 3 micro E(h). Large basis sets have also been applied to reexamine the accuracy of theoretical repulsive potential energy surfaces (25-70 kcal/mol above the H-H2 asymptote) at small interatomic separations; the Boothroyd, Keogh, Martin, and Peterson (BKMP) potential energy surface is found to agree with results of the present calculations within the expected uncertainty (+/- 1 kcal/mol) of the fit. Multipolar expansions of the computed H-H2 potential energy surface are reported for four internuclear separation distances (1.2, 1.401, 1.449, and 1.7a(0)) of the hydrogen molecule. The differential elastic scattering cross section calculated from the present results is compared with the measurements from a crossed beam experiment.

  19. Scattered surface wave energy in the seismic coda

    USGS Publications Warehouse

    Zeng, Y.

    2006-01-01

    One of the many important contributions that Aki has made to seismology pertains to the origin of coda waves (Aki, 1969; Aki and Chouet, 1975). In this paper, I revisit Aki's original idea of the role of scattered surface waves in the seismic coda. Based on the radiative transfer theory, I developed a new set of scattered wave energy equations by including scattered surface waves and body wave to surface wave scattering conversions. The work is an extended study of Zeng et al. (1991), Zeng (1993) and Sato (1994a) on multiple isotropic-scattering, and may shed new insight into the seismic coda wave interpretation. The scattering equations are solved numerically by first discretizing the model at regular grids and then solving the linear integral equations iteratively. The results show that scattered wave energy can be well approximated by body-wave to body wave scattering at earlier arrival times and short distances. At long distances from the source, scattered surface waves dominate scattered body waves at surface stations. Since surface waves are 2-D propagating waves, their scattered energies should in theory follow a common decay curve. The observed common decay trends on seismic coda of local earthquake recordings particular at long lapse times suggest that perhaps later seismic codas are dominated by scattered surface waves. When efficient body wave to surface wave conversion mechanisms are present in the shallow crustal layers, such as soft sediment layers, the scattered surface waves dominate the seismic coda at even early arrival times for shallow sources and at later arrival times for deeper events.

  20. Free energy surfaces in the superconducting mixed state

    NASA Technical Reports Server (NTRS)

    Finnemore, D. K.; Fang, M. M.; Bansal, N. P.; Farrell, D. E.

    1989-01-01

    The free energy surface for Tl2Ba2Ca2Cu3O1O has been measured as a function of temperature and magnetic field to determine the fundamental thermodynamic properties of the mixed state. The change in free energy, G(H)-G(O), is found to be linear in temperature over a wide range indicating that the specific heat is independent of field.

  1. Surface Passivation and Junction Formation Using Low Energy Hydrogen Implants

    NASA Technical Reports Server (NTRS)

    Fonash, S. J.

    1985-01-01

    New applications for high current, low energy hydrogen ion implants on single crystal and polycrystal silicon grain boundaries are discussed. The effects of low energy hydrogen ion beams on crystalline Si surfaces are considered. The effect of these beams on bulk defects in crystalline Si is addressed. Specific applications of H+ implants to crystalline Si processing are discussed. In all of the situations reported on, the hydrogen beams were produced using a high current Kaufman ion source.

  2. Singular perturbation of absolute stability.

    NASA Technical Reports Server (NTRS)

    Siljak, D. D.

    1972-01-01

    It was previously shown (author, 1969) that the regions of absolute stability in the parameter space can be determined when the parameters appear on the right-hand side of the system equations, i.e., the regular case. Here, the effect on absolute stability of a small parameter attached to higher derivatives in the equations (the singular case) is studied. The Lur'e-Postnikov class of nonlinear systems is considered.

  3. Geometrically nonlinear continuum thermomechanics with surface energies coupled to diffusion

    NASA Astrophysics Data System (ADS)

    McBride, A. T.; Javili, A.; Steinmann, P.; Bargmann, S.

    2011-10-01

    Surfaces can have a significant influence on the overall response of a continuum body but are often neglected or accounted for in an ad hoc manner. This work is concerned with a nonlinear continuum thermomechanics formulation which accounts for surface structures and includes the effects of diffusion and viscoelasticity. The formulation is presented within a thermodynamically consistent framework and elucidates the nature of the coupling between the various fields, and the surface and the bulk. Conservation principles are used to determine the form of the constitutive relations and the evolution equations. Restrictions on the jump in the temperature and the chemical potential between the surface and the bulk are not a priori assumptions, rather they arise from the reduced dissipation inequality on the surface and are shown to be satisfiable without imposing the standard assumptions of thermal and chemical slavery. The nature of the constitutive relations is made clear via an example wherein the form of the Helmholtz energy is explicitly given.

  4. Effect of Surface Energy on Freezing Temperature of Water.

    PubMed

    Zhang, Yu; Anim-Danso, Emmanuel; Bekele, Selemon; Dhinojwala, Ali

    2016-07-13

    Previous studies have found that superhydrophobic surfaces are effective in delaying freezing of water droplets. However, the freezing process of water droplets on superhydrophobic surfaces depends on factors such as droplet size, surface area, roughness, and cooling rate. The role of surface energy, independent of any other parameters, in delaying freezing of water is not understood. Here, we have used infrared-visible sum frequency generation spectroscopy (SFG) to study the freezing of water next to solid substrates with water contact angles varying from 5° to 110°. We find that the freezing temperature of water decreases with increasing surface hydrophobicity only when the sample volume is small (∼10 μL). For a larger volume of water (∼300 μL), the freezing temperature is independent of surface energy. For water next to the surfaces with contact angle ≥54°, we observe a strong SFG peak associated with highly coordinated water. This research sheds new light on understanding the key factors in designing new anti-icing coatings. PMID:27314147

  5. Quasiparticle energy studies of bulk semiconductors, surfaces and nanotubes

    SciTech Connect

    Blase, X.F.

    1994-12-01

    Effects of many-body effects on electronic excitation energies (quasiparticle band structure) of these materials are explored. GW approximation, including local field effects, for self-energy operator is used to calculate quasi-particle energies. The newly discovered carbon nanotubes are studied; structural stability and band structures are calculated. BN nanotubes are also studied, and their stability is predicted. Unexpected electronic features are predicted for both systems. Filling of carbon nanotubes with metal atoms and the doping of BN nanotubes by carbon and other impurites is also studied. The occupied surface states at H/Si(111)-(1{times}1) surface are studied; it is shown that the electronic structure requires a full quasiparticle calculation even for this simple chemisorption system. The core level shift of the Si 2p levels for atoms near the H/Si(111)-(1{times}1) surface is calculated; a simple first order perturbation theory using pseudopotential and the local density approximation gives good results for the photoemission spectra of the core electrons. The quasiparticle energies of bulk hexagonal BN and those of an isolated BN sheet are studied; this provides an understanding of the quasiparticle band structure of BN nanotubes. A nearly free electron state with a wavefunction in the interlayer or vacuum region composes the bottom of the conduction bands. A mixed-space formalism is presented for calculating the dynamical screening effects and electron self-energy operator in solids; this provides an efficient algorithm to calculate quasiparticle energies for large systems.

  6. Dropwise condensation rate of water breath figures on polymer surfaces having similar surface free energies

    NASA Astrophysics Data System (ADS)

    Ucar, Ikrime O.; Erbil, H. Yildirim

    2012-10-01

    This study investigates the effect of surface roughness, wettability, water contact angle hysteresis (CAH) and wetting hysteresis (WH) of polymeric substrates to the water drop condensation rate. We used five polyolefin coatings whose surface free energies were in a close range of 30-37 mJ/m2 but having different surface roughness and CAH. The formation of water breath figures was monitored at a temperature just below the dew point. The initial number of the condensed droplets per unit area (N0) and droplet surface coverage were determined during the early stage of drop condensation where the droplet coalescence was negligible. It was found that the mean drop diameter of condensed droplets on these polymer surfaces grow according to a power law with exponent 1/3 of time, similar to the previous reports given in the literature. It was determined that surface roughness and corresponding CAH and WH properties of polymers have important effects on the number of nucleation sites and growth rate of the condensed water droplets. N0 values and the surface coverage increased with the increase in surface roughness, CAH and WH of the polymer surfaces. The total condensed water drop volume also increased with the increase in surface roughness in accordance with the increase of the number of nucleated droplets.

  7. Casimir energy in a spherical surface within surface impedance approach: The Drude model

    NASA Astrophysics Data System (ADS)

    Rosa, Luigi; Trozzo, Lucia

    2016-09-01

    The Casimir Energy of a spherical cavity whose surface is characterized by means of its surface impedance is calculated. The material properties of the boundary are described by means of the Drude model, so that a generalization of a previous result, based on plasma model, is obtained. The limits of the proposed approach are analyzed and a possible solution is suggested. The possibility of modulating the sign of the Casimir force from positive (repulsion) to negative (attraction) is studied.

  8. Group and energy velocities of acoustic surface waves in piezoelectrics

    NASA Astrophysics Data System (ADS)

    Chen, Yu

    1996-07-01

    This paper offers a simple proof of the equivalence of the energy velocity and the group velocity for acoustic waves on the flat surface of a piezoelectric half space in the usual quasistatic approximation. The interface conditions of free stresses and the open circuited electric condition are considered. Both the energy velocity and the group velocity are expressed in terms of a Lagrangian density. The energy velocity is obtained by the definition and the group velocity is derived by implicit differentiation from a dispersion equation in an implicit form.

  9. The evaporative fraction as a measure of surface energy partitioning

    SciTech Connect

    Nichols, W.E.; Cuenca, R.H.

    1990-12-31

    The evaporative fraction is a ratio that expresses the proportion of turbulent flux energy over land surfaces devoted to evaporation and transpiration (evapotranspiration). It has been used to characterize the energy partition over land surfaces and has potential for inferring daily energy balance information based on mid-day remote sensing measurements. The HAPEX-MOBILHY program`s SAMER system provided surface energy balance data over a range of agricultural crops and soil types. The databases from this large-scale field experiment was analyzed for the purpose of studying the behavior and daylight stability of the evaporative fraction in both ideal and general meteorological conditions. Strong linear relations were found to exist between the mid-day evaporative fraction and the daylight mean evaporative fraction. Statistical tests however rejected the hypothesis that the two quantities were equal. The relations between the evaporative fraction and the surface soil moisture as well as soil moisture in the complete vegetation root zone were also explored.

  10. Evaluation of surface energy and radiation balance systems for FIFE

    NASA Technical Reports Server (NTRS)

    Fritschen, Leo J.; Qian, Ping

    1988-01-01

    The energy balance and radiation balance components were determined at six sites during the First International Satellite Land Surface Climatology Project Field Experiment (FIFE) conducted south of Manhattan, Kansas during the summer of 1987. The objectives were: to determine the effect of slope and aspect, throughout a growing season, on the magnitude of the surface energy balance fluxes as determined by the Energy Balance Method (EBM); to investigate the calculation of the soil heat flux density at the surface as calculated from the heat capacity and the thermal conductivity equations; and to evaluate the performance of the Surface Energy and Radiation Balance System (SERBS). A total of 17 variables were monitored at each site. They included net, solar (up and down), total hemispherical (up and down), and diffuse radiation, soil temperature and heat flux density, air and wet bulb temperature gradients, wind speed and direction, and precipitation. A preliminary analysis of the data, for the season, indicate that variables including net radiation, air temperature, vapor pressure, and wind speed were quite similar at the sites even though the sites were as much as 16 km apart and represented four cardinal slopes and the top of a ridge.

  11. Structural surface investigations with low-energy backscattered electrons

    NASA Astrophysics Data System (ADS)

    De Crescenzi, Maurizio

    The development of electron spectroscopies based on inelastic scattering fine structure is driven mainly by the need for structural methods which allow the investigation of the geometrical environment of different atomic species of the surface region of the sample. The EELFS (Extended Energy Loss Fine Structure) technique, using low-kinetic-energy electrons (1000-2000 eV) in reflection geometry, has been proven a useful tool for local structural investigation of clean surfaces, thin films and chemisorbed species. The main appeal of this technique, besides its experimental accessibility, is that the data analysis follows the procedure used for EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy to obtain the atomic selectivity, the radial distribution function, the coordination number and the thermal and anisotropic effects. The near-edge energy-loss feature has been used to investigate the density of empty states close to EF and it appeeal particularly sensitive for following the structural changes and for discriminating among various phases and compound formations which occur in the surface region. In this work I review some recent developments, applications and theoretical considerations of the EELFS technique to give local structural parameters and to assess the basic mechanisms which dominate the low-energy electron-surface interaction.

  12. Potential Energy Surface Database of Group II Dimer

    National Institute of Standards and Technology Data Gateway

    SRD 143 NIST Potential Energy Surface Database of Group II Dimer (Web, free access)   This database provides critical atomic and molecular data needed in order to evaluate the feasibility of using laser cooled and trapped Group II atomic species (Mg, Ca, Sr, and Ba) for ultra-precise optical clocks or quantum information processing devices.

  13. Universal binding energy relation for cleaved and structurally relaxed surfaces.

    PubMed

    Srirangarajan, Aarti; Datta, Aditi; Gandi, Appala Naidu; Ramamurty, U; Waghmare, U V

    2014-02-01

    The universal binding energy relation (UBER), derived earlier to describe the cohesion between two rigid atomic planes, does not accurately capture the cohesive properties when the cleaved surfaces are allowed to relax. We suggest a modified functional form of UBER that is analytical and at the same time accurately models the properties of surfaces relaxed during cleavage. We demonstrate the generality as well as the validity of this modified UBER through first-principles density functional theory calculations of cleavage in a number of crystal systems. Our results show that the total energies of all the relaxed surfaces lie on a single (universal) energy surface, that is given by the proposed functional form which contains an additional length-scale associated with structural relaxation. This functional form could be used in modelling the cohesive zones in crack growth simulation studies. We find that the cohesive law (stress-displacement relation) differs significantly in the case where cracked surfaces are allowed to relax, with lower peak stresses occurring at higher displacements. PMID:24356124

  14. Surface Energy Fluxes During Arctic Freeze-Up

    NASA Astrophysics Data System (ADS)

    Persson, Ola; Blomquist, Byron; Guest, Peter; Fairall, Christopher; Stammerjohn, Sharon; Brooks, Ian; Björk, Göran; Tjernström, Michael; Inoue, Jun

    2016-04-01

    This presentation will use atmospheric and ocean mixed-layer observations from three cruises during the past two years to examine the magnitude and variability of the air-ocean energy fluxes, the sources of the variability, the impact of the fluxes on the ocean mixed-layer thermal structure, and how these surface energy fluxes impact the initial ice formation. The measurements were made during the ACSE, Mirai, and Sea State field programs, the first two obtaining measurements near the ice edge in the Laptev and Chukchi Seas in September 2014 and the last along the advancing ice edge in the Beaufort/Chukchi Sea in October 2015. These time periods include the onset of continuous ocean heat loss, the initial episodic ice formation, and the core period for southward advance of the ice. Frequent atmospheric soundings and continuous remote-sensor measurements provide the vertical kinematic and thermodynamic structure in the lower troposphere. Broadband radiometers, turbulent flux sensors, surface temperature sensors, surface characterization instruments, and basic meteorological instrumentation provide continuous measurements of all surface energy flux terms (shortwave/longwave radiation, sensible/latent turbulent heat fluxes), allowing the quantification of the total energy exchange between the ocean and the atmosphere. Furthermore, each cruise provided continuous measurements of the upper-ocean temperature and salinity and frequent CTD measurements of the ocean temperature and salinity profiles, providing estimates of upper-ocean energy evolution. Various methods for characterizing the ocean surface (open ocean, ice cover, ice thickness, wave state, etc.) allow linking energy changes with changes in ocean surface conditions. Analyses of the September and October conditions show persistent ocean heat loss after Sep. 15 because of the reduction of downwelling shortwave radiation and strong impacts of off-ice airflow on turbulent heat fluxes and downwelling longwave

  15. Absolute radiometric calibration of advanced remote sensing systems

    NASA Technical Reports Server (NTRS)

    Slater, P. N.

    1982-01-01

    The distinction between the uses of relative and absolute spectroradiometric calibration of remote sensing systems is discussed. The advantages of detector-based absolute calibration are described, and the categories of relative and absolute system calibrations are listed. The limitations and problems associated with three common methods used for the absolute calibration of remote sensing systems are addressed. Two methods are proposed for the in-flight absolute calibration of advanced multispectral linear array systems. One makes use of a sun-illuminated panel in front of the sensor, the radiance of which is monitored by a spectrally flat pyroelectric radiometer. The other uses a large, uniform, high-radiance reference ground surface. The ground and atmospheric measurements required as input to a radiative transfer program to predict the radiance level at the entrance pupil of the orbital sensor are discussed, and the ground instrumentation is described.

  16. Three-dimensional potential energy surface of Ar–CO

    SciTech Connect

    Sumiyoshi, Yoshihiro; Endo, Yasuki

    2015-01-14

    A three-dimensional intermolecular potential energy surface of the Ar–CO complex has been determined by fitting most of the previously reported spectroscopic data, where observed transition frequencies by microwave, millimeter-wave, submillimeter-wave, and infrared spectroscopy were reproduced simultaneously within their experimental accuracies. A free rotor model Hamiltonian considering all the freedom of motions for an atom-diatom system was applied to calculate vibration-rotation energies. A three-dimensional potential energy surface obtained by ab initio calculations at the CCSD(T)-F12b/aug-cc-pV5Z level of theory was parameterized by a model function consisting of 46 parameters. They were used as initial values for the least-squares analysis of the experimental data. A total of 20 parameters were optimized to reproduce all the spectroscopic data.

  17. Communication: Fitting potential energy surfaces with fundamental invariant neural network

    NASA Astrophysics Data System (ADS)

    Shao, Kejie; Chen, Jun; Zhao, Zhiqiang; Zhang, Dong H.

    2016-08-01

    A more flexible neural network (NN) method using the fundamental invariants (FIs) as the input vector is proposed in the construction of potential energy surfaces for molecular systems involving identical atoms. Mathematically, FIs finitely generate the permutation invariant polynomial (PIP) ring. In combination with NN, fundamental invariant neural network (FI-NN) can approximate any function to arbitrary accuracy. Because FI-NN minimizes the size of input permutation invariant polynomials, it can efficiently reduce the evaluation time of potential energy, in particular for polyatomic systems. In this work, we provide the FIs for all possible molecular systems up to five atoms. Potential energy surfaces for OH3 and CH4 were constructed with FI-NN, with the accuracy confirmed by full-dimensional quantum dynamic scattering and bound state calculations.

  18. Communication: Fitting potential energy surfaces with fundamental invariant neural network.

    PubMed

    Shao, Kejie; Chen, Jun; Zhao, Zhiqiang; Zhang, Dong H

    2016-08-21

    A more flexible neural network (NN) method using the fundamental invariants (FIs) as the input vector is proposed in the construction of potential energy surfaces for molecular systems involving identical atoms. Mathematically, FIs finitely generate the permutation invariant polynomial (PIP) ring. In combination with NN, fundamental invariant neural network (FI-NN) can approximate any function to arbitrary accuracy. Because FI-NN minimizes the size of input permutation invariant polynomials, it can efficiently reduce the evaluation time of potential energy, in particular for polyatomic systems. In this work, we provide the FIs for all possible molecular systems up to five atoms. Potential energy surfaces for OH3 and CH4 were constructed with FI-NN, with the accuracy confirmed by full-dimensional quantum dynamic scattering and bound state calculations.

  19. Communication: Fitting potential energy surfaces with fundamental invariant neural network.

    PubMed

    Shao, Kejie; Chen, Jun; Zhao, Zhiqiang; Zhang, Dong H

    2016-08-21

    A more flexible neural network (NN) method using the fundamental invariants (FIs) as the input vector is proposed in the construction of potential energy surfaces for molecular systems involving identical atoms. Mathematically, FIs finitely generate the permutation invariant polynomial (PIP) ring. In combination with NN, fundamental invariant neural network (FI-NN) can approximate any function to arbitrary accuracy. Because FI-NN minimizes the size of input permutation invariant polynomials, it can efficiently reduce the evaluation time of potential energy, in particular for polyatomic systems. In this work, we provide the FIs for all possible molecular systems up to five atoms. Potential energy surfaces for OH3 and CH4 were constructed with FI-NN, with the accuracy confirmed by full-dimensional quantum dynamic scattering and bound state calculations. PMID:27544080

  20. A modified surface energy balance algorithm for land (M-SEBAL) based on a trapezoidal framework

    NASA Astrophysics Data System (ADS)

    Long, Di; Singh, Vijay P.

    2012-02-01

    The surface energy balance algorithm for land (SEBAL) has been designed and widely used (and misused) worldwide to estimate evapotranspiration across varying spatial and temporal scales using satellite remote sensing over the past 15 yr. It is, however, beset by visual identification of a hot and cold pixel to determine the temperature difference (dT) between the surface and the lower atmosphere, which is assumed to be linearly correlated with surface radiative temperature (Trad) throughout a scene. To reduce ambiguity in flux estimation by SEBAL due to the subjectivity in extreme pixel selection, this study first demonstrates that SEBAL is of a rectangular framework of the contextual relationship between vegetation fraction (fc) and Trad, which can distort the spatial distribution of heat flux retrievals to varying degrees. End members of SEBAL were replaced by a trapezoidal framework of the fc-Trad space in the modified surface energy balance algorithm for land (M-SEBAL). The warm edge of the trapezoidal framework is determined by analytically deriving temperatures of the bare surface with the largest water stress and the fully vegetated surface with the largest water stress implicit in both energy balance and radiation budget equations. Areally averaged air temperature (Ta) across a study site is taken to be the cold edge of the trapezoidal framework. Coefficients of the linear relationship between dT and Trad can vary with fc but are assumed essentially invariant for the same fc or within the same fc class in M-SEBAL. SEBAL and M-SEBAL are applied to the soil moisture-atmosphere coupling experiment (SMACEX) site in central Iowa, U.S. Results show that M-SEBAL is capable of reproducing latent heat flux in terms of an overall root-mean-square difference of 41.1 W m-2 and mean absolute percentage difference of 8.9% with reference to eddy covariance tower-based measurements for three landsat thematic mapper/enhanced thematic mapper plus imagery acquisition dates in

  1. Sampling saddle points on a free energy surface.

    PubMed

    Samanta, Amit; Chen, Ming; Yu, Tang-Qing; Tuckerman, Mark; E, Weinan

    2014-04-28

    Many problems in biology, chemistry, and materials science require knowledge of saddle points on free energy surfaces. These saddle points act as transition states and are the bottlenecks for transitions of the system between different metastable states. For simple systems in which the free energy depends on a few variables, the free energy surface can be precomputed, and saddle points can then be found using existing techniques. For complex systems, where the free energy depends on many degrees of freedom, this is not feasible. In this paper, we develop an algorithm for finding the saddle points on a high-dimensional free energy surface "on-the-fly" without requiring a priori knowledge the free energy function itself. This is done by using the general strategy of the heterogeneous multi-scale method by applying a macro-scale solver, here the gentlest ascent dynamics algorithm, with the needed force and Hessian values computed on-the-fly using a micro-scale model such as molecular dynamics. The algorithm is capable of dealing with problems involving many coarse-grained variables. The utility of the algorithm is illustrated by studying the saddle points associated with (a) the isomerization transition of the alanine dipeptide using two coarse-grained variables, specifically the Ramachandran dihedral angles, and (b) the beta-hairpin structure of the alanine decamer using 20 coarse-grained variables, specifically the full set of Ramachandran angle pairs associated with each residue. For the alanine decamer, we obtain a detailed network showing the connectivity of the minima obtained and the saddle-point structures that connect them, which provides a way to visualize the gross features of the high-dimensional surface.

  2. Sampling saddle points on a free energy surface

    NASA Astrophysics Data System (ADS)

    Samanta, Amit; Chen, Ming; Yu, Tang-Qing; Tuckerman, Mark; E, Weinan

    2014-04-01

    Many problems in biology, chemistry, and materials science require knowledge of saddle points on free energy surfaces. These saddle points act as transition states and are the bottlenecks for transitions of the system between different metastable states. For simple systems in which the free energy depends on a few variables, the free energy surface can be precomputed, and saddle points can then be found using existing techniques. For complex systems, where the free energy depends on many degrees of freedom, this is not feasible. In this paper, we develop an algorithm for finding the saddle points on a high-dimensional free energy surface "on-the-fly" without requiring a priori knowledge the free energy function itself. This is done by using the general strategy of the heterogeneous multi-scale method by applying a macro-scale solver, here the gentlest ascent dynamics algorithm, with the needed force and Hessian values computed on-the-fly using a micro-scale model such as molecular dynamics. The algorithm is capable of dealing with problems involving many coarse-grained variables. The utility of the algorithm is illustrated by studying the saddle points associated with (a) the isomerization transition of the alanine dipeptide using two coarse-grained variables, specifically the Ramachandran dihedral angles, and (b) the beta-hairpin structure of the alanine decamer using 20 coarse-grained variables, specifically the full set of Ramachandran angle pairs associated with each residue. For the alanine decamer, we obtain a detailed network showing the connectivity of the minima obtained and the saddle-point structures that connect them, which provides a way to visualize the gross features of the high-dimensional surface.

  3. Seasonal contrast in the surface energy balance of the Sahel

    NASA Astrophysics Data System (ADS)

    Miller, R. L.; Slingo, A.; Barnard, J. C.; Kassianov, E.

    2009-07-01

    Over much of the world, heating of the surface by sunlight is balanced predominately by evaporative cooling. However, at the Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) in Niamey, Niger, evaporation makes a significant contribution to the surface energy balance only at the height of the rainy season, when precipitation has replenished the reservoir of soil moisture. The AMF was placed at Niamey from late 2005 to early 2007 to provide measurements of surface fluxes in coordination with geostationary satellite retrievals of radiative fluxes at the top of the atmosphere, as part of the RADAGAST experiment to calculate atmospheric radiative divergence. We use observations at the mobile facility to investigate how the surface adjusts to radiative forcing throughout the year. The surface response to solar heating varies with changes in atmospheric water vapor associated with the seasonal reversal of the West African monsoon, which modulates the greenhouse effect and the ability of the surface to radiate thermal energy directly to space. During the dry season, sunlight is balanced mainly by longwave radiation and the turbulent flux of sensible heat. The ability of longwave radiation to cool the surface drops after the onset of southwesterly surface winds at Niamey, when moist, oceanic air flows onshore, increasing local column moisture and atmospheric opacity. Following the onset of southwesterly flow, evaporation remains limited by the supply of moisture from precipitation. By the height of the rainy season, however, sufficient precipitation has accumulated that evaporation is controlled by incident sunlight, and radiative forcing of the surface is balanced comparably by the latent, sensible, and longwave fluxes. Evaporation increases with the leaf area index, suggesting that plants are a significant source of atmospheric moisture and may tap moisture stored beneath the surface that accumulated during a previous rainy season. Surface radiative forcing

  4. From Hubble's NGSL to Absolute Fluxes

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Lindler, Don

    2012-01-01

    Hubble's Next Generation Spectral Library (NGSL) consists of R-l000 spectra of 374 stars of assorted temperature, gravity, and metallicity. Each spectrum covers the wavelength range, 0.18-1.00 microns. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsll. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We are therefore developing an observing procedure that should yield fluxes with uncertainties less than 1 % and will take part in an HST proposal to observe up to 15 stars using this new procedure.

  5. Potential energy surfaces and reaction dynamics of polyatomic molecules

    SciTech Connect

    Chang, Yan-Tyng.

    1991-11-01

    A simple empirical valence bond (EVB) model approach is suggested for constructing global potential energy surfaces for reactions of polyatomic molecular systems. This approach produces smooth and continuous potential surfaces which can be directly utilized in a dynamical study. Two types of reactions are of special interest, the unimolecular dissociation and the unimolecular isomerization. For the first type, the molecular dissociation dynamics of formaldehyde on the ground electronic surface is investigated through classical trajectory calculations on EVB surfaces. The product state distributions and vector correlations obtained from this study suggest very similar behaviors seen in the experiments. The intramolecular hydrogen atom transfer in the formic acid dimer is an example of the isomerization reaction. High level ab initio quantum chemistry calculations are performed to obtain optimized equilibrium and transition state dimer geometries and also the harmonic frequencies.

  6. Artificial ocean upwelling utilizing the energy of surface waves

    NASA Astrophysics Data System (ADS)

    Soloviev, Alexander

    2016-04-01

    Artificial upwelling can bring cold water from below the thermocline to the sea surface. Vershinsky, Pshenichnyy, and Soloviev (1987) developed a prototype device, utilizing the energy of surface waves to create an upward flow of water in the tube. This is a wave-inertia pump consisting of a vertical tube, a valve, and a buoy to keep the device afloat. An outlet valve at the top of the unit synchronizes the operation of the device with surface waves and prevents back-splashing. A single device with a 100 m long and 1.2 m diameter tube is able to produce up to 1 m3s‑1 flow of deep water to the surface. With a 10 oC temperature difference over 100 m depth, the negative heat supply rate to the sea surface is 42 MW, which is equivalent to a 42 Wm‑2 heat flux, if distributed over 1 km2 area. Such flux is comparable to the average net air-sea flux. A system of artificial upwelling devices can cool down the sea surface, modify climate on a regional scale and possibly help mitigate hurricanes. The cold water brought from a deeper layer, however, has a larger density than the surface water and therefore has a tendency to sink back down. In this work, the efficiency of wave-inertia pumps and climatic consequences are estimated for different environmental conditions using a computational fluid dynamics model.

  7. Artificial ocean upwelling utilizing the energy of surface waves

    NASA Astrophysics Data System (ADS)

    Soloviev, Alexander

    2016-04-01

    Artificial upwelling can bring cold water from below the thermocline to the sea surface. Vershinsky, Pshenichnyy, and Soloviev (1987) developed a prototype device, utilizing the energy of surface waves to create an upward flow of water in the tube. This is a wave-inertia pump consisting of a vertical tube, a valve, and a buoy to keep the device afloat. An outlet valve at the top of the unit synchronizes the operation of the device with surface waves and prevents back-splashing. A single device with a 100 m long and 1.2 m diameter tube is able to produce up to 1 m3s-1 flow of deep water to the surface. With a 10 oC temperature difference over 100 m depth, the negative heat supply rate to the sea surface is 42 MW, which is equivalent to a 42 Wm-2 heat flux, if distributed over 1 km2 area. Such flux is comparable to the average net air-sea flux. A system of artificial upwelling devices can cool down the sea surface, modify climate on a regional scale and possibly help mitigate hurricanes. The cold water brought from a deeper layer, however, has a larger density than the surface water and therefore has a tendency to sink back down. In this work, the efficiency of wave-inertia pumps and climatic consequences are estimated for different environmental conditions using a computational fluid dynamics model.

  8. Theoretical characterization of the potential energy surface for NH + NO

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1992-01-01

    The potential energy surface (PES) for NH + NO was characterized using complete active space self-consistent field (CASSCF) gradient calculations to determine the stationary point geometries and frequencies followed by CASSCF/internally contracted configuration interaction (CCI) calculations to refine the energetics. The present results are in qualitative accord with the BAC-MP4 calculations, but there are differences as large as 8 kcal/mol in the detailed energetics. Addition of NH to NO on a (2)A' surface, which correlated with N2 + OH or H + N2O products, involves barriers of 3.2 kcal/mol (trans) and 6.3 kcal/mol (cis). Experimental evidence for these barriers is found in earlier works. The (2)A' surface has no barrier to addition, but does not correlate with products. Surface crossings between the barrierless (2)A' surface and the (2)A' surface may be important. Production of N2 + OH products is predicted to occur via a planar saddle point of (2)A' symmetry. This is in accord with the preferential formation of II(A') lambda doublet levels of OH in earlier experiments. Addition of NH (1)delta to NO is found to occur on an excited state surface and is predicted to lead to N2O product as observed in earlier works.

  9. Estimation of land surface water and energy balance parameters using conditional sampling of surface states

    NASA Astrophysics Data System (ADS)

    Farhadi, Leila; Entekhabi, Dara; Salvucci, Guido; Sun, Jian

    2014-02-01

    Numerical models of heat and moisture diffusion in the soil-vegetation-atmosphere continuum are linked through the moisture flux from the surface to the atmosphere. This mass flux represents a heat exchange as latent heat flux, coupling water, and energy balance equations. In this paper, a new approach for estimating key parameters governing moisture and heat diffusion equation and the closure function which links these equations, is introduced. Parameters of the system are estimated by developing objective functions that link atmospheric forcing, surface states, and unknown parameters. This approach is based on conditional averaging of heat and moisture diffusion equations on land surface temperature and moisture states, respectively. A single objective function is expressed that measures moisture and temperature-dependent errors solely in terms of observed forcings and surface states. This objective function is minimized with respect to the parameters to identify evaporation and drainage models and estimate water and energy balance flux components. The approach is calibration free (surface flux observations are not required), it is not hampered by missing data and does not require continuous records. Uncertainty of parameter estimates is obtained from the inverse of Hessian of the objective function, which is an approximation of the error covariance matrix. Uncertainty analysis and analysis of the covariance approximation, guides the formulation of a well-posed estimation problem. Accuracy of this method is examined through its application over three different field sites. This approach can be applied to diverse climates and land surface conditions with different spatial scales, using remotely sensed measurements.

  10. Potential energy surface of triplet N2O2

    NASA Astrophysics Data System (ADS)

    Varga, Zoltan; Meana-Pañeda, Rubén; Song, Guoliang; Paukku, Yuliya; Truhlar, Donald G.

    2016-01-01

    We present a global ground-state triplet potential energy surface for the N2O2 system that is suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation. The surface is based on multi-state complete-active-space second-order perturbation theory/minimally augmented correlation-consistent polarized valence triple-zeta electronic structure calculations plus dynamically scaled external correlation. In the multireference calculations, the active space has 14 electrons in 12 orbitals. The calculations cover nine arrangements corresponding to dissociative diatom-diatom collisions of N2, O2, and nitric oxide (NO), the interaction of a triatomic molecule (N2O and NO2) with the fourth atom, and the interaction of a diatomic molecule with a single atom (i.e., the triatomic subsystems). The global ground-state potential energy surface was obtained by fitting the many-body interaction to 54 889 electronic structure data points with a fitting function that is a permutationally invariant polynomial in terms of bond-order functions of the six interatomic distances.

  11. Potential energy surface of triplet N2O2.

    PubMed

    Varga, Zoltan; Meana-Pañeda, Rubén; Song, Guoliang; Paukku, Yuliya; Truhlar, Donald G

    2016-01-14

    We present a global ground-state triplet potential energy surface for the N2O2 system that is suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation. The surface is based on multi-state complete-active-space second-order perturbation theory/minimally augmented correlation-consistent polarized valence triple-zeta electronic structure calculations plus dynamically scaled external correlation. In the multireference calculations, the active space has 14 electrons in 12 orbitals. The calculations cover nine arrangements corresponding to dissociative diatom-diatom collisions of N2, O2, and nitric oxide (NO), the interaction of a triatomic molecule (N2O and NO2) with the fourth atom, and the interaction of a diatomic molecule with a single atom (i.e., the triatomic subsystems). The global ground-state potential energy surface was obtained by fitting the many-body interaction to 54 889 electronic structure data points with a fitting function that is a permutationally invariant polynomial in terms of bond-order functions of the six interatomic distances.

  12. Hyperthermal Energy Collisions of CF3 + Ions with Modified Surfaces: Surface-Induced Dissociation

    SciTech Connect

    Rezayat, T.; Shukla, A.

    2004-01-01

    Collisions of low-energy ions, especially polyatomic ions, with surfaces have become an active area of research due to their numerous applications in chemistry, physics and material sciences. An interesting aspect of such collisions is the dissociation of ions which has been successfully exploited for the characterization of colliding ions, especially high mass ions from biological molecules. However, detailed studies of the energy transfer and dissociation have been performed only for a few simple systems and hence the mechanism(s) of ions’ excitation and dissociation are not as well understood even for small ions. We have therefore undertaken a study of the dissociation of a small polyatomic ion, CF3+, at several collision energies between 28.8 eV and 159 eV in collision with fluorinated alkyl thiol on gold 111 crystal and a LiF surface. These experiments were performed using a custom built tandem mass spectrometer where the energy and intensity distributions of the scattered fragment ions were measured as a function of the fragment ion mass and scattering angle. In contrast with the previous studies of the dissociation of ethanol and acetone cations where the inelastically scattered primary ions dominated the collision process (up to ~50 eV maximum energy used in those experiments), we did not observe a measurable abundance of inelastically scattered undissociated CF3+ ions at all energies studied here. We observed all fragment ions, CF2+, CF+, F+ and C+ at all energies studied with the relative intensity of the highest energy pathway, C+, increasing with collision energy. Also, the dissociation efficiency decreased significantly as the collision energy was increased from to 159 eV. The energy distributions of nearly all the fragment ions showed two distinct components, one corresponding to the loss of nearly all of the kinetic energy and scattered over a broad angular range while the other corresponding to smaller kinetic energy losses and scattered closer to

  13. Absolute flux scale for radioastronomy

    SciTech Connect

    Ivanov, V.P.; Stankevich, K.S.

    1986-07-01

    The authors propose and provide support for a new absolute flux scale for radio astronomy, which is not encumbered with the inadequacies of the previous scales. In constructing it the method of relative spectra was used (a powerful tool for choosing reference spectra). A review is given of previous flux scales. The authors compare the AIS scale with the scale they propose. Both scales are based on absolute measurements by the ''artificial moon'' method, and they are practically coincident in the range from 0.96 to 6 GHz. At frequencies above 6 GHz, 0.96 GHz, the AIS scale is overestimated because of incorrect extrapolation of the spectra of the primary and secondary standards. The major results which have emerged from this review of absolute scales in radio astronomy are summarized.

  14. Surface energy and relaxation in boron carbide (101¯1) from first principles

    NASA Astrophysics Data System (ADS)

    Beaudet, Todd D.; Smith, John R.; Adams, Jane W.

    2015-10-01

    The surface energy of the boron carbide polytype B11Cp(CBC) for planar separations along {101¯1} was determined to be 3.21 J/m2 via first-principles density-functional computations. Surface atomic relaxations are relatively large, thereby lowering the surface energy significantly. The icosahedra are not intact on the surface, i.e., severed polyhedra are the lowest energy surface configuration. Good agreement was found with an experimental average fracture surface energy.

  15. The molecular potential energy surface and vibrational energy levels of methyl fluoride. Part II.

    PubMed

    Manson, Steven A; Law, Mark M; Atkinson, Ian A; Thomson, Grant A

    2006-06-28

    New analytical bending and stretching, ground electronic state, potential energy surfaces for CH(3)F are reported. The surfaces are expressed in bond-length, bond-angle internal coordinates. The four-dimensional stretching surface is an accurate, least squares fit to over 2000 symmetrically unique ab initio points calculated at the CCSD(T) level. Similarly, the five-dimensional bending surface is a fit to over 1200 symmetrically unique ab initio points. This is an important first stage towards a full nine-dimensional potential energy surface for the prototype CH(3)F molecule. Using these surfaces, highly excited stretching and (separately) bending vibrational energy levels of CH(3)F are calculated variationally using a finite basis representation method. The method uses the exact vibrational kinetic energy operator derived for XY(3)Z systems by Manson and Law (preceding paper, Part I, Phys. Chem. Chem. Phys., 2006, 8, DOI: 10.1039/b603106d). We use the full C(3v) symmetry and the computer codes are designed to use an arbitrary potential energy function. Ultimately, these results will be used to design a compact basis for fully coupled stretch-bend calculations of the vibrational energy levels of the CH(3)F system.

  16. An exploration of the ozone dimer potential energy surface

    SciTech Connect

    Azofra, Luis Miguel; Alkorta, Ibon; Scheiner, Steve

    2014-06-28

    The (O{sub 3}){sub 2} dimer potential energy surface is thoroughly explored at the ab initio CCSD(T) computational level. Five minima are characterized with binding energies between 0.35 and 2.24 kcal/mol. The most stable may be characterized as slipped parallel, with the two O{sub 3} monomers situated in parallel planes. Partitioning of the interaction energy points to dispersion and exchange as the prime contributors to the stability, with varying contributions from electrostatic energy, which is repulsive in one case. Atoms in Molecules analysis of the wavefunction presents specific O⋯O bonding interactions, whose number is related to the overall stability of each dimer. All internal vibrational frequencies are shifted to the red by dimerization, particularly the antisymmetric stretching mode whose shift is as high as 111 cm{sup −1}. In addition to the five minima, 11 higher-order stationary points are identified.

  17. Weissenberg reflection high-energy electron diffraction for surface crystallography.

    PubMed

    Abukawa, Tadashi; Yamazaki, Tomoyuki; Yajima, Kentaro; Yoshimura, Koji

    2006-12-15

    The principle of a Weissenberg camera is applied to surface crystallographic analysis by reflection high-energy electron diffraction. By removing inelastic electrons and measuring hundreds of patterns as a function of sample rotation angle phi, kinematical analysis can be performed over a large volume of reciprocal space. The data set is equivalent to a three-dimensional stack of Weissenberg photographs. The method is applied to analysis of an Si(111)-square root of 3 x square root of 3-Ag surface, and the structural data obtained are in excellent agreement with the known atomic structure.

  18. Bioresponse to polymeric substrates: Effect of surface energy, modulus, topography, and surface graft copolymers

    NASA Astrophysics Data System (ADS)

    Wilson, Leslie Hoipkemeier

    Biofouling is the accumulation of biological matter on a substrate. It is essential to elucidate and model the major factors that affect both biological settlement and adhesion to substrates in order to develop coatings that minimize initial fouling or ease the removal of this fouling. To date, models that have estimated adhesion strength to coatings primarily included bulk elastic modulus and surface energy. Topography, however, has been found to dominate both these terms in the reduction of settlement and has been found to affect the adhesion strength as well. Silicone foul release coatings have demonstrated moderate success in the prevention of marine biofouling because of their low modulus and low surface energy. Problems exist with durability and eventual fouling of the coating due to the overgrowth of foulants that prefer hydrophobic substrates. This research details the characterization and the surface and bulk modification of a commercially available silicone elastomer. The modifications include bulk additives, surface topography, and surface graft copolymers. The effect of these modifications on biological response was then assayed using the alga Ulva as a model for marine biofouling. The unmodified silicone elastomer has a bulk modulus of approximately 1 MPa. The addition of vinyl functional polydimethylsiloxane oils allowed for a greater than 200% increase or a 90% decrease in the bulk modulus of the material. The addition of non-reactive polydimethylsiloxane oils allowed for a change in the surface lubricity of the elastomer without a significant change in the mechanical properties. Topographical modifications of the surface show a profound effect on the bioresponse. Appropriately scaled engineered microtopographies replicated in the silicone elastomer can produce a 250% increase in algal zoospore fouling or an 85% reduction in settlement relative to a smooth silicone elastomer. Finally, the modification of the surface energy of this material was

  19. Permutation invariant polynomial neural network approach to fitting potential energy surfaces. III. Molecule-surface interactions.

    PubMed

    Jiang, Bin; Guo, Hua

    2014-07-21

    The permutation invariant polynomial-neural network (PIP-NN) method for constructing highly accurate potential energy surfaces (PESs) for gas phase molecules is extended to molecule-surface interaction PESs. The symmetry adaptation in the NN fitting of a PES is achieved by employing as the input symmetry functions that fulfill both the translational symmetry of the surface and permutation symmetry of the molecule. These symmetry functions are low-order PIPs of the primitive symmetry functions containing the surface periodic symmetry. It is stressed that permutationally invariant cross terms are needed to avoid oversymmetrization. The accuracy and efficiency are demonstrated in fitting both a model PES for the H2 + Cu(111) system and density functional theory points for the H2 + Ag(111) system.

  20. Permutation invariant polynomial neural network approach to fitting potential energy surfaces. III. Molecule-surface interactions

    NASA Astrophysics Data System (ADS)

    Jiang, Bin; Guo, Hua

    2014-07-01

    The permutation invariant polynomial-neural network (PIP-NN) method for constructing highly accurate potential energy surfaces (PESs) for gas phase molecules is extended to molecule-surface interaction PESs. The symmetry adaptation in the NN fitting of a PES is achieved by employing as the input symmetry functions that fulfill both the translational symmetry of the surface and permutation symmetry of the molecule. These symmetry functions are low-order PIPs of the primitive symmetry functions containing the surface periodic symmetry. It is stressed that permutationally invariant cross terms are needed to avoid oversymmetrization. The accuracy and efficiency are demonstrated in fitting both a model PES for the H2 + Cu(111) system and density functional theory points for the H2 + Ag(111) system.

  1. A graphite calorimeter for absolute measurements of absorbed dose to water: application in medium-energy x-ray filtered beams

    NASA Astrophysics Data System (ADS)

    Pinto, M.; Pimpinella, M.; Quini, M.; D'Arienzo, M.; Astefanoaei, I.; Loreti, S.; Guerra, A. S.

    2016-02-01

    The Italian National Institute of Ionizing Radiation Metrology (ENEA-INMRI) has designed and built a graphite calorimeter that, in a water phantom, has allowed the determination of the absorbed dose to water in medium-energy x-rays with generating voltages from 180 to 250 kV. The new standard is a miniaturized three-bodies calorimeter, with a disc-shaped core of 21 mm diameter and 2 mm thickness weighing 1.134 g, sealed in a PMMA waterproof envelope with air-evacuated gaps. The measured absorbed dose to graphite is converted into absorbed dose to water by means of an energy-dependent conversion factor obtained from Monte Carlo simulations. Heat-transfer correction factors were determined by FEM calculations. At a source-to-detector distance of 100 cm, a depth in water of 2 g cm-2, and at a dose rate of about 0.15 Gy min-1, results of calorimetric measurements of absorbed dose to water, D w, were compared to experimental determinations, D wK, obtained via an ionization chamber calibrated in terms of air kerma, according to established dosimetry protocols. The combined standard uncertainty of D w and D wK were estimated as 1.9% and 1.7%, respectively. The two absorbed dose to water determinations were in agreement within 1%, well below the stated measurement uncertainties. Advancements are in progress to extend the measurement capability of the new in-water-phantom graphite calorimeter to other filtered medium-energy x-ray qualities and to reduce the D w uncertainty to around 1%. The new calorimeter represents the first implementation of in-water-phantom graphite calorimetry in the kilovoltage range and, allowing independent determinations of D w, it will contribute to establish a robust system of absorbed dose to water primary standards for medium-energy x-ray beams.

  2. Absolute Energy Calibration with the Neutron-Activated Liquid-Source System at BaBar's CsI(Tl) Calorimeter

    SciTech Connect

    Bauer, J

    2004-01-05

    The electro-magnetic calorimeter at the BABAR detector, part of the asymmetric B Factory at SLAC, measures photons in the energy range from 20 MeV to 8 GeV with good resolution. The calorimeter is calibrated at the low energy end with 6.13 MeV photons obtained from a liquid source system. During the calibration, a fluorine-rich liquid is activated via a neutron generator and pumped past the front of the calorimeter's crystals. Decays that occur in front of the crystals emit photons of well-defined energy, which are detected in the crystals with the regular data acquisition system. The liquid source system adds only very little material in front of the calorimeter, needs nearly no maintenance, and allows operation at the switch of a key with minimal safety hazards. The report describes the system, presents calibration results obtained from its operation since 1999, shows the crystals' loss of light yield due to radiation damage, and shares experiences gained over the years.

  3. Bifurcations on Potential Energy Surfaces of Organic Reactions

    PubMed Central

    Ess, Daniel H.; Wheeler, Steven E.; Iafe, Robert G.; Xu, Lai; Çelebi-Ölçüm, Nihan; Houk, K. N.

    2009-01-01

    A single transition state may lead to multiple intermediates or products if there is a post-transition state reaction path bifurcation. These bifurcations arise when there are sequential transition states with no intervening energy minimum. For such systems, the shape of the potential energy surface and dynamic effects control selectivity rather than transition state energetics. This minireview covers recent investigations of organic reactions exhibiting reaction pathway bifurcations. Such phenomena are surprisingly general and affect experimental observables such as kinetic isotope effects and product distributions. PMID:18767086

  4. Communication: Separable potential energy surfaces from multiplicative artificial neural networks

    SciTech Connect

    Koch, Werner Zhang, Dong H.

    2014-07-14

    We present a potential energy surface fitting scheme based on multiplicative artificial neural networks. It has the sum of products form required for efficient computation of the dynamics of multidimensional quantum systems with the multi configuration time dependent Hartree method. Moreover, it results in analytic potential energy matrix elements when combined with quantum dynamics methods using Gaussian basis functions, eliminating the need for a local harmonic approximation. Scaling behavior with respect to the complexity of the potential as well as the requested accuracy is discussed.

  5. Low barrier kinetics: dependence on observables and free energy surface.

    PubMed

    Ma, Hairong; Gruebele, Martin

    2006-01-30

    Dynamics on free energy surfaces with high activation barriers are usually treated by few-state kinetics models, yielding characteristic rate coefficients and amplitudes depending on the connectivity of the states. When the barriers are low (< 3 kT), the assumption of instantaneous equilibration of the transition state, and hence, the few-state kinetics treatment, break down. Langevin dynamics is used here to explore the characteristic trends that occur in such cases, as a function of barrier height, number of barriers, dimensionality of the free energy surface, and switching functions that describe how spectroscopic probes vary from reactant to product. The result is a systematic phenomenological description of low barrier kinetics and dynamics.

  6. Seasonal Contrasts in the Surface Energy Balance of the Sahel

    SciTech Connect

    Miller, Ron; Slingo, A.; Barnard, James C.; Kassianov, Evgueni I.

    2009-03-14

    Over most of the world ocean, heating of the surface by sunlight is balanced predominately by evaporative cooling. Even over land, moisture for evaporation is available from vegetation or the soil reservoir. However, at the ARM Mobile Facility in Niamey, Niger, soil moisture is so depleted that evaporation makes a significant contribution to the surface energy balance only at the height of the rainy season, when precipitation has replenished the soil reservoir. Using observations at the Mobile Facility from late 2005 to early 2007, we describe how the surface balances radiative forcing. How the surface compensates time-averaged solar heating varies with seasonal changes in atmospheric water vapor, which modulates the greenhouse effect and the ability of the surface to radiate thermal energy directly to space. During the dry season, sunlight is balanced mainly by longwave radiation and the turbulent flux of sensible heat. The ability of longwave radiation to cool the surface drops after the onset of the West African summer monsoon, when moist, oceanic air flows onshore, increasing local column moisture and atmospheric opacity at these wavelengths. After the monsoon onset, but prior to significant rainfall, solar heating is compensated mainly by the sensible heat flux. During the rainy season, the magnitude of evaporation is initially controlled by the supply of moisture from precipitation. However, by the height of the rainy season, sufficient precipitation has accumulated at the surface that evaporation is related to the flux demanded by solar radiation, and radiative forcing of the surface is balanced comparably by the latent, sensible, and longwave fluxes. Radiative forcing of the surface also varies on a subseasonal time scale due to fluctuations in water vapor, clouds, and aerosol concentration. Except at the height of the rainy season, subseasonal forcing is balanced mainly by sensible heating and longwave anomalies. The efficacy of the sensible heat flux

  7. Electronic structure, molecular bonding and potential energy surfaces

    SciTech Connect

    Ruedenberg, K.

    1993-12-01

    By virtue of the universal validity of the generalized Born-Oppenheimer separation, potential energy surfaces (PES`) represent the central conceptual as well as quantitative entities of chemical physics and provide the basis for the understanding of most physicochemical phenomena in many diverse fields. The research in this group deals with the elucidation of general properties of PES` as well as with the quantitative determination of PES` for concrete systems, in particular pertaining to reactions involving carbon, oxygen, nitrogen and hydrogen molecules.

  8. Theoretical characterization of the potential energy surface for NH + NO

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1993-01-01

    The potential energy surface for NH + NO was characterized using complete active space self-consistent field (CASSCF) gradient calculation to determine the stationary point geometries and frequencies followed by CASSCF/internally contracted configuration interaction calculations to refine the energetics. The present results are in qualitative accord with the BAC-MP4 calculations, but there are differences as large as 8 kcal/mol in the detailed energetics.

  9. MCSCF potential energy surface for photodissociation of formaldehyde

    NASA Technical Reports Server (NTRS)

    Jaffe, R. L.; Morokuma, K.

    1976-01-01

    The ground state potential energy surface for the dissociation of formaldehyde (H2CO to H2 and CO) is calculated with the ab initio MCSCF method with an extended (4-31G) basis set. The location, barrier height, and force constants of the transition state are determined, and the normal coordinate analysis is carried out. The calculated barrier height is 4.5 eV. Based on the calculated quantities, the detailed mechanism of the photochemical dissociation is discussed.

  10. Tuning surface porosity on vanadium surface by low energy He+ ion irradiation

    NASA Astrophysics Data System (ADS)

    Tripathi, J. K.; Novakowski, T. J.; Hassanein, A.

    2016-08-01

    In the present study, we report on tuning the surface porosity on vanadium surfaces using high-flux, low-energy He+ ion irradiation as function of sample temperature. Polished, mirror-finished vanadium samples were irradiated with 100 eV He+ ions at a constant ion-flux of 7.2 × 1020 ions m-2 s-1 for 1 h duration at constant sample temperatures in the wide range of 823-1173 K. Our results show that the surface porosity of V2O5 (naturally oxidized vanadium porous structure, after taking out from UHV) is strongly correlated to the sample temperature and is highly tunable. In fact, the surface porosity significantly increases with reducing sample temperature and reaches up to ∼87%. Optical reflectivity on these highly porous V2O5 surfaces show ∼0% optical reflectivity at 670 nm wavelength, which is very similar to that of "black metal". Combined with the naturally high melting point of V2O5, this very low optical reflectivity suggests potential application in solar power concentration technology. Additionally, this top-down approach guarantees relatively good contact between the different crystallites and avoids electrical conductivity limitations (if required). Since V2O5 is naturally a potential photocatalytic material, the resulting sub-micron-sized cube-shaped porous structures could be used in solar water splitting for hydrogen production in energy applications.

  11. A graphite calorimeter for absolute measurements of absorbed dose to water: application in medium-energy x-ray filtered beams.

    PubMed

    Pinto, M; Pimpinella, M; Quini, M; D'Arienzo, M; Astefanoaei, I; Loreti, S; Guerra, A S

    2016-02-21

    The Italian National Institute of Ionizing Radiation Metrology (ENEA-INMRI) has designed and built a graphite calorimeter that, in a water phantom, has allowed the determination of the absorbed dose to water in medium-energy x-rays with generating voltages from 180 to 250 kV. The new standard is a miniaturized three-bodies calorimeter, with a disc-shaped core of 21 mm diameter and 2 mm thickness weighing 1.134 g, sealed in a PMMA waterproof envelope with air-evacuated gaps. The measured absorbed dose to graphite is converted into absorbed dose to water by means of an energy-dependent conversion factor obtained from Monte Carlo simulations. Heat-transfer correction factors were determined by FEM calculations. At a source-to-detector distance of 100 cm, a depth in water of 2 g cm(-2), and at a dose rate of about 0.15 Gy min(-1), results of calorimetric measurements of absorbed dose to water, D(w), were compared to experimental determinations, D wK, obtained via an ionization chamber calibrated in terms of air kerma, according to established dosimetry protocols. The combined standard uncertainty of D(w) and D(wK) were estimated as 1.9% and 1.7%, respectively. The two absorbed dose to water determinations were in agreement within 1%, well below the stated measurement uncertainties. Advancements are in progress to extend the measurement capability of the new in-water-phantom graphite calorimeter to other filtered medium-energy x-ray qualities and to reduce the D(w) uncertainty to around 1%. The new calorimeter represents the first implementation of in-water-phantom graphite calorimetry in the kilovoltage range and, allowing independent determinations of D(w), it will contribute to establish a robust system of absorbed dose to water primary standards for medium-energy x-ray beams. PMID:26841127

  12. Surface conversion techniques for low energy neutral atom imagers

    NASA Technical Reports Server (NTRS)

    Quinn, J. M.

    1995-01-01

    This investigation has focused on development of key technology elements for low energy neutral atom imaging. More specifically, we have investigated the conversion of low energy neutral atoms to negatively charged ions upon reflection from specially prepared surfaces. This 'surface conversion' technique appears to offer a unique capability of detecting, and thus imaging, neutral atoms at energies of 0.01 - 1 keV with high enough efficiencies to make practical its application to low energy neutral atom imaging in space. Such imaging offers the opportunity to obtain the first instantaneous global maps of macroscopic plasma features and their temporal variation. Through previous in situ plasma measurements, we have a statistical picture of large scale morphology and local measurements of dynamic processes. However, with in situ techniques it is impossible to characterize or understand many of the global plasma transport and energization processes. A series of global plasma images would greatly advance our understanding of these processes and would provide the context for interpreting previous and future in situ measurements. Fast neutral atoms, created from ions that are neutralized in collisions with exospheric neutrals, offer the means for remotely imaging plasma populations. Energy and mass analysis of these neutrals provides critical information about the source plasma distribution. The flux of neutral atoms available for imaging depends upon a convolution of the ambient plasma distribution with the charge exchange cross section for the background neutral population. Some of the highest signals are at relatively low energies (well below 1 keV). This energy range also includes some of the most important plasma populations to be imaged, for example the base of the cleft ion fountain.

  13. Rotational Energy Transfer of N2 Gas Determined Using a New Ab Initio Potential Energy Surface

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Stallcop, James R.; Partridge, Harry; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    Rotational energy transfer between two N2 molecules is a fundamental process of some importance. Exchange is expected to play a role, but its importance is somewhat uncertain. Rotational energy transfer cross sections of N2 also have applications in many other fields including modeling of aerodynamic flows, laser operations, and linewidth analysis in nonintrusive laser diagnostics. A number of N2-N2 rigid rotor potential energy surface (PES) has been reported in the literature.

  14. Chemisorbed-molecule potential energy surfaces and DIET processes

    NASA Astrophysics Data System (ADS)

    Jennison, D. R.; Stechel, E. B.; Burns, A. R.; Li, Y. S.

    1995-06-01

    We report the use of the local-density approximation, with and without gradient corrections, for the calculation of ground-state potential energy surfaces (PESs) for chemisorbed molecules. We focus on chemisorbed NO and ammonia on Pd(1 1 1) and compare our results with the latest experimental information. We then turn to two aspects of excited-state PESs. First, we compare first-principles calculations of the forces on an ammonia ion as a function of distance from the surface. We find that the image-charge model fails significantly at distances which are the most relevant for dynamics, closer than ˜3 Å, and discuss reasons for the failure. We then summarize a purely electronic adiabatic model of the moleuule-surface bond and use empirical parameters to estimate hot carrier-produced excited states of chemisorbed NO. We find multiple PESs and a novel interpretation of the π ∗ resonance, seen in inverse photoemission.

  15. Experimental results for absolute cylindrical wavefront testing

    NASA Astrophysics Data System (ADS)

    Reardon, Patrick J.; Alatawi, Ayshah

    2014-09-01

    Applications for Cylindrical and near-cylindrical surfaces are ever-increasing. However, fabrication of high quality cylindrical surfaces is limited by the difficulty of accurate and affordable metrology. Absolute testing of such surfaces represents a challenge to the optical testing community as cylindrical reference wavefronts are difficult to produce. In this paper, preliminary results for a new method of absolute testing of cylindrical wavefronts are presented. The method is based on the merging of the random ball test method with the fiber optic reference test. The random ball test assumes a large number of interferograms of a good quality sphere with errors that are statistically distributed such that the average of the errors goes to zero. The fiber optic reference test utilizes a specially processed optical fiber to provide a clean high quality reference wave from an incident line focus from the cylindrical wave under test. By taking measurements at different rotation and translations of the fiber, an analogous procedure can be employed to determine the quality of the converging cylindrical wavefront with high accuracy. This paper presents and discusses the results of recent tests of this method using a null optic formed by a COTS cylindrical lens and a free-form polished corrector element.

  16. Surface energy increase of oxygen-plasma-treated PET

    SciTech Connect

    Cioffi, M.O.H.; Voorwald, H.J.C.; Mota, R.P

    2003-03-15

    Prosthetic composite is a widely used biomaterial that satisfies the criteria for application as an organic implant without adverse reactions. Polyethylene therephthalate (PET) fiber-reinforced composites have been used because of the excellent cell adhesion, biodegradability and biocompatibility. The chemical inertness and low surface energy of PET in general are associated with inadequate bonds for polymer reinforcements. It is recognized that the high strength of composites, which results from the interaction between the constituents, is directly related to the interfacial condition or to the interphase. A radio frequency plasma reactor using oxygen was used to treat PET fibers for 5, 20, 30 and 100 s. The treatment conditions were 13.56 MHz, 50 W, 40 Pa and 3.33x10{sup -7} m{sup 3}/s. A Rame-Hart goniometer was used to measure the contact angle and surface energy variation of fibers treated for different times. The experimental results showed contact angle values from 47 deg. to 13 deg. and surface energies from 6.4x10{sup -6} to 8.3x10{sup -6} J for the range of 5 to 100 s, respectively. These results were confirmed by the average ultimate tensile strength of the PET fiber/ polymethylmethacrylate (PMMA) matrix composite tested in tensile mode and by scanning electron microscopy.

  17. Influence of Heterogeneous Land Surfaces on the Surface Energy Budget at - and Large Scales

    NASA Astrophysics Data System (ADS)

    Song, Jie

    1995-11-01

    Discrepancies in temperature and precipitation --between model simulations and observations--have prompted investigators to examine the effects of the subgrid-scale surface variations on climate simulations. The results of the First ISLSCP Field Experiment (FIFE), which was designed to address the scaling up issue through the simultaneous acquisition of satellite, atmospheric, and surface micrometeorological data, is compared to model results. Using a three-dimensional soil-plant-atmosphere mesoscale model and FIFE data, the surface energy fluxes over the FIFE domain have been simulated and compared with measurements. Biophysical processes over the FIFE prairie site play a dominant role in evapotranspiration. The standing brown canopy also appears to be as important as the green canopy. Surface conditions, such as soil moisture availability and vegetation, determine the division of available energy between the land surface and the atmosphere. They also control the partitioning of latent and sensible heat fluxes, and consequently the turbulent exchanges of heat and moisture in the atmospheric boundary layer. Model-simulated surface energy fluxes over the FIFE domain are compared under plausible heterogeneous and homogeneous initial and boundary conditions. Simulated latent heat fluxes are approximately 30 to 40 W m ^{-2} higher and the air temperature is ~eq0.4^circC lower (at noon) when the landsurface is homogeneous. The planetary boundary lazer (PBL) height and turbulent exchanges are lower as well--even though the heterogeneous canopy and soil conditions are only moderately variable in comparison with many landscapes. Further analysis of the influence of heterogeneous land surfaces on the surface energy budget (at GCM scales) was made by randomly prescribing soil-moisture fields that varied from 10% to 100% of soil water-holding capacity. Significant reductions were found in model-simulated average evapotranspiration fields when the initial soil -moisture fields

  18. Relativistic Absolutism in Moral Education.

    ERIC Educational Resources Information Center

    Vogt, W. Paul

    1982-01-01

    Discusses Emile Durkheim's "Moral Education: A Study in the Theory and Application of the Sociology of Education," which holds that morally healthy societies may vary in culture and organization but must possess absolute rules of moral behavior. Compares this moral theory with current theory and practice of American educators. (MJL)

  19. Absolute transition probabilities of phosphorus.

    NASA Technical Reports Server (NTRS)

    Miller, M. H.; Roig, R. A.; Bengtson, R. D.

    1971-01-01

    Use of a gas-driven shock tube to measure the absolute strengths of 21 P I lines and 126 P II lines (from 3300 to 6900 A). Accuracy for prominent, isolated neutral and ionic lines is estimated to be 28 to 40% and 18 to 30%, respectively. The data and the corresponding theoretical predictions are examined for conformity with the sum rules.-

  20. Product energy distributions and energy partitioning in O atom reactions on surfaces

    NASA Technical Reports Server (NTRS)

    Halpern, Bret; Kori, Moris

    1987-01-01

    Surface reactions involving O atoms are likely to be highly exoergic, with different consequences if energy is channeled mostly to product molecules or surface modes. Thus the surface may become a source of excited species which can react elsewhere, or a sink for localized heat deposition which may disrupt the surface. The vibrational energy distribution of the product molecule contains strong clues about the flow of released energy. Two instructive examples of energy partitioning at surfaces are the Pt catalyzed oxidations: (1) C(ads) + O(ads) yields CO* (T is greater than 1000 K); and (2) CO(ads) + O(gas) yields CO2* (T is approx. 300 K). The infrared emission spectra of the excited product molecules were recorded and the vibrational population distributions were determined. In reaction 1, energy appeared to be statistically partitioned between the product CO and several Pt atoms. In reaction 2, partitioning was non-statistical; the CO2 asymmetric stretch distribution was inverted. In gas reactions these results would indicate a long lived and short lived activated complex. The requirement that Pt be heated in O atoms to promote reaction of atomic O and CO at room temperature is specifically addressed. Finally, the fraction of released energy that is deposited in the catalyst is estimated.

  1. Minimum energy paths of wetting transitions on grooved surfaces.

    PubMed

    Pashos, George; Kokkoris, George; Boudouvis, Andreas G

    2015-03-17

    A method that computes minimum energy paths (MEPs) of wetting transitions is developed. The method couples the Cahn-Hilliard formulation of a modified phase-field method with the simplified string method. Its main computational kernel is the fast Fourier transform that is efficiently performed on graphics processing units. The effectiveness of the proposed method is demonstrated on two types of transitions of droplets on grooved surfaces. The first is the transition from the Cassie-Baxter wetting state to the Wenzel state, where it is shown that it progresses in a sequential manner with the droplet wetting each groove successively. The second transition type is a lateral displacement of the droplet against the grooves, where the droplet successively detaches/attaches from/to the rear/front protrusion of the surface (a transition in the reverse order is also possible). The energy barriers of both the transitions are extracted from the MEP; they are useful for the evaluation of the robustness of superhydrophobic surfaces (resistance to the Cassie-Baxter to Wenzel transition) and the droplet mobility on those surfaces (high mobility/small resistance to lateral displacements). The relation of the MEP with the potential transition paths coming from the solution space mapping is discussed. PMID:25715270

  2. Inverse scattering at fixed energy on asymptotically hyperbolic Liouville surfaces

    NASA Astrophysics Data System (ADS)

    Daudé, Thierry; Kamran, Niky; Nicoleau, Francois

    2015-12-01

    In this paper, we study an inverse scattering problem on Liouville surfaces having two asymptotically hyperbolic ends. The main property of Liouville surfaces consists of the complete separability of the Hamilton-Jacobi equations for the geodesic flow. An important related consequence is the fact that the stationary wave equation can be separated into a system of radial and angular ODEs. The full scattering matrix at fixed energy associated to a scalar wave equation on asymptotically hyperbolic Liouville surfaces can be thus simplified by considering its restrictions onto the generalized harmonics corresponding to the angular separated ODE. The resulting partial scattering matrices consists in a countable set of 2 × 2 matrices whose coefficients are the so called transmission and reflection coefficients. It is shown that the reflection coefficients are nothing but generalized Weyl-Titchmarsh (WT) functions for the radial ODE in which the generalized angular momentum is seen as the spectral parameter. Using the complex angular momentum method and recent results on 1D inverse problem from generalized WT functions, we show that the knowledge of the reflection operators at a fixed non-zero energy is enough to determine uniquely the metric of the asymptotically hyperbolic Liouville surface under consideration.

  3. Overview of surface studies on high energy materials at Mound

    SciTech Connect

    Moddeman, W.E.; Collins, L.W.; Wang, P.S.; Haws, L.D.; Wittberg, T.N.

    1980-01-01

    Since 1975 Mound has been examining the surface structure of high energy materials and the interaction of these materials with various metal containers. The high energy materials that have been studied include: the pyrotechnic TiH/sub x//KClO/sub 4/, the Al/Cu/sub 2/O machinable thermite, the PETN, HMX and RDX explosives, and two plastic bonded explosives (PBX). Aluminum and alloys of Fe, Ni and Cr have been used as the containment materials. Two aims in this research are: (1) the elucidation of the mechanism of pyrotechnic ignition and (2) the compatibility of high energy materials with their surroundings. New information has been generated by coupling Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) with thermal data. In particular, AES and XPS studies on the pyrotechnic materials and on thermites have shown the mechanism of ignition to be nearly independent of the type of oxidizer present but directly related to surface chemistry of the fuels. In studies on the two PBX's, PBX-9407 and LX-16, it was concluded that the Exon coating on 9407 was complete and greater than or equal to 100A; whereas in LX-16, the coating was < 100A or even incomplete. AES and scanning Auger have been used to characterize the surface composition and oxide thickness for an iron-nickel alloy and showed the thicker oxides to have the least propensity for atmospheric hydrocarbon adsorption. Data are presented and illustrations made which highlight this new approach to studying ignition and compatibility of high energy materials. Finally, the salient features of the X-SAM-800 purchased by Mound are discussed in light of future studies on high energy materials.

  4. Free Energies of Solvation with Surface, Volume, and Local Electrostatic Effects and Atomic Surface Tensions to Represent the First Solvation Shell.

    PubMed

    Liu, Junjun; Kelly, Casey P; Goren, Alan C; Marenich, Aleksandr V; Cramer, Christopher J; Truhlar, Donald G; Zhan, Chang-Guo

    2010-03-01

    Building on the SVPE (surface and volume polarization for electrostatics) model for electrostatic contributions to the free energy of solvation with explicit consideration of both surface and volume polarization effects, on the SMx approach to including first-solvation-shell contributions, and on the linear relationship between the electric field and short-range electrostatic contributions found by Chipman, we have developed a new method for computing absolute aqueous solvation free energies by combining the SVPE method with semiempirical terms that account for effects beyond bulk electrostatics. The new method is called SMVLE, and the elements it contains are denoted by SVPE-CDSL where SVPE denotes accounting for bulk electrostatic interactions between solute and solvent with both surface and volume contributions, CDS denotes the inclusion of solvent cavitation, changes in dispersion energy, and possible changes in local solvent structure by a semiempirical term utilizing geometry-dependent atomic surface tensions as implemented in SMx models, and L represents the local electrostatic effect derived from the outward-directed normal electric field on the cavity surface. The semiempirical CDS and L terms together represent the deviation of short-range contributions to the free energy of solvation from those accounted for by the SVPE term based on the bulk solvent dielectric constant. A solute training set containing a broad range of molecules used previously in the development of SM6 is used here for SMVLE model calibration. The aqueous solvation free energies predicted by the parameterized SMVLE model correlate exceedingly well with experimental values. The square of the correlation coefficient is 0.9949 and the slope is 1.0079. Comparison of the final SMVLE model against the earlier SMx solvation model shows that the parameterized SMVLE model not only yields good accuracy for neutrals but also significantly increases the accuracy for ions, making it the best

  5. A highly accurate ab initio potential energy surface for methane

    NASA Astrophysics Data System (ADS)

    Owens, Alec; Yurchenko, Sergei N.; Yachmenev, Andrey; Tennyson, Jonathan; Thiel, Walter

    2016-09-01

    A new nine-dimensional potential energy surface (PES) for methane has been generated using state-of-the-art ab initio theory. The PES is based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set limit and incorporates a range of higher-level additive energy corrections. These include core-valence electron correlation, higher-order coupled cluster terms beyond perturbative triples, scalar relativistic effects, and the diagonal Born-Oppenheimer correction. Sub-wavenumber accuracy is achieved for the majority of experimentally known vibrational energy levels with the four fundamentals of 12CH4 reproduced with a root-mean-square error of 0.70 cm-1. The computed ab initio equilibrium C-H bond length is in excellent agreement with previous values despite pure rotational energies displaying minor systematic errors as J (rotational excitation) increases. It is shown that these errors can be significantly reduced by adjusting the equilibrium geometry. The PES represents the most accurate ab initio surface to date and will serve as a good starting point for empirical refinement.

  6. A highly accurate ab initio potential energy surface for methane.

    PubMed

    Owens, Alec; Yurchenko, Sergei N; Yachmenev, Andrey; Tennyson, Jonathan; Thiel, Walter

    2016-09-14

    A new nine-dimensional potential energy surface (PES) for methane has been generated using state-of-the-art ab initio theory. The PES is based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set limit and incorporates a range of higher-level additive energy corrections. These include core-valence electron correlation, higher-order coupled cluster terms beyond perturbative triples, scalar relativistic effects, and the diagonal Born-Oppenheimer correction. Sub-wavenumber accuracy is achieved for the majority of experimentally known vibrational energy levels with the four fundamentals of (12)CH4 reproduced with a root-mean-square error of 0.70 cm(-1). The computed ab initio equilibrium C-H bond length is in excellent agreement with previous values despite pure rotational energies displaying minor systematic errors as J (rotational excitation) increases. It is shown that these errors can be significantly reduced by adjusting the equilibrium geometry. The PES represents the most accurate ab initio surface to date and will serve as a good starting point for empirical refinement. PMID:27634258

  7. A highly accurate ab initio potential energy surface for methane.

    PubMed

    Owens, Alec; Yurchenko, Sergei N; Yachmenev, Andrey; Tennyson, Jonathan; Thiel, Walter

    2016-09-14

    A new nine-dimensional potential energy surface (PES) for methane has been generated using state-of-the-art ab initio theory. The PES is based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set limit and incorporates a range of higher-level additive energy corrections. These include core-valence electron correlation, higher-order coupled cluster terms beyond perturbative triples, scalar relativistic effects, and the diagonal Born-Oppenheimer correction. Sub-wavenumber accuracy is achieved for the majority of experimentally known vibrational energy levels with the four fundamentals of (12)CH4 reproduced with a root-mean-square error of 0.70 cm(-1). The computed ab initio equilibrium C-H bond length is in excellent agreement with previous values despite pure rotational energies displaying minor systematic errors as J (rotational excitation) increases. It is shown that these errors can be significantly reduced by adjusting the equilibrium geometry. The PES represents the most accurate ab initio surface to date and will serve as a good starting point for empirical refinement.

  8. Attachment of Galerucella nymphaeae (Coleoptera, Chrysomelidae) to surfaces with different surface energy.

    PubMed

    Grohmann, Constanze; Blankenstein, Andreas; Koops, Sven; Gorb, Stanislav N

    2014-12-01

    Numerous studies deal with insect attachment onto surfaces with different roughness; however, little is known about insect attachment onto surfaces that have different chemistry. In the present study, we describe the attachment structures of the water-lily leaf beetle Galerucella nymphaeae and test the hypothesis that the larval and adult stages generate the strongest attachment on surfaces with contact angles that are similar to those of leaves of their host plants. The larvae bear a smooth attachment system with arolium-like structures at their legs and a pygopodium at the abdomen tip. Adults have pointed setae on the ventral side of the two proximal tarsomeres and densely arranged spatula-shaped ones on their third tarsomere. In a centrifugal force tester, larvae and adults attained the highest friction forces and safety factors on surfaces with a water contact angle of 83 deg compared to those of 6, 26 and 109 deg. This comes close to the contact angle of their host plant Nuphar lutea (86 deg). The similarity in larval and adult performances might be a result of the similar chemical composition of their attachment fluid. We compare our findings with previous studies on the forces that insects generate on surfaces with different surface energies.

  9. Attachment of Galerucella nymphaeae (Coleoptera, Chrysomelidae) to surfaces with different surface energy.

    PubMed

    Grohmann, Constanze; Blankenstein, Andreas; Koops, Sven; Gorb, Stanislav N

    2014-12-01

    Numerous studies deal with insect attachment onto surfaces with different roughness; however, little is known about insect attachment onto surfaces that have different chemistry. In the present study, we describe the attachment structures of the water-lily leaf beetle Galerucella nymphaeae and test the hypothesis that the larval and adult stages generate the strongest attachment on surfaces with contact angles that are similar to those of leaves of their host plants. The larvae bear a smooth attachment system with arolium-like structures at their legs and a pygopodium at the abdomen tip. Adults have pointed setae on the ventral side of the two proximal tarsomeres and densely arranged spatula-shaped ones on their third tarsomere. In a centrifugal force tester, larvae and adults attained the highest friction forces and safety factors on surfaces with a water contact angle of 83 deg compared to those of 6, 26 and 109 deg. This comes close to the contact angle of their host plant Nuphar lutea (86 deg). The similarity in larval and adult performances might be a result of the similar chemical composition of their attachment fluid. We compare our findings with previous studies on the forces that insects generate on surfaces with different surface energies. PMID:25324345

  10. Self shielding of surfaces irradiated by intense energy fluxes:

    SciTech Connect

    Howell, J.R.; Varghese, P.L.

    1988-02-01

    This report summarizes work completed to date on the study of the effects of the impingement of a very high fluence plasma onto a target surface. Particular emphasis is placed on self-shielding of the target surface caused by initial surface erosion and the resulting presence of heavy metal ions in an ionsized shield slayer near the surface. A high energy hydrogen plasma will be produced by a rail gun coupled to high-current sources (capacitor banks or high-current pulse homoplar generators developed at the University of Texas at Austin). Because of the extremely fast transients presents in the experiments, considerable instrumentation development in necessary to provide the necessary diagnostic tools for characterizing the incident plasma as well as the transient development of the vapor layer. The experimental results will be used to verify and/or modifify a detailed of the dimensional transient computer code that models the complete plasma-surface interaction history. The model includes the effects of evaporated and sputtered wall material and its inteeraction with the incident plasma.

  11. New Material Development for Surface Layer and Surface Technology in Tribology Science to Improve Energy Efficiency

    NASA Astrophysics Data System (ADS)

    Ismail, R.; Tauviqirrahman, M.; Jamari, Jamari; Schipper, D. J.

    2009-09-01

    This paper reviews the development of new material and surface technology in tribology and its contribution to energy efficiency. Two examples of the economic benefits, resulted from the optimum tribology in the transportation sector and the manufacturing industry are discussed. The new materials are proposed to modify the surface property by laminating the bulk material with thin layer/coating. Under a suitable condition, the thin layer on a surface can provide a combination of good wear, a low friction and corrosion resistance for the mechanical components. The innovation in layer technology results molybdenum disulfide (MoS2), diamond like carbon (DLC), cubic boron nitride (CBN) and diamond which perform satisfactory outcome. The application of the metallic coatings to carbon fibre reinforced polymer matrix composites (CFRP) has the capacity to provide considerable weight and power savings for many engineering components. The green material for lubricant and additives such as the use of sunflower oil which possesses good oxidation resistance and the use of mallee leaves as bio-degradable solvent are used to answer the demand of the environmentally friendly material with good performance. The tribology research implementation for energy efficiency also touches the simple things around us such as: erasing the laser-print in a paper with different abrasion techniques. For the technology in the engineering surface, the consideration for generating the suitable surface of the components in running-in period has been discussed in order to prolong the components life and reduce the machine downtime. The conclusion, tribology can result in reducing manufacturing time, reducing the maintenance requirements, prolonging the service interval, improving durability, reliability and mechanical components life, and reducing harmful exhaust emission and waste. All of these advantages will increase the energy efficiency and the economic benefits.

  12. Reducing measurement scale mismatch to improve surface energy flux estimation

    NASA Astrophysics Data System (ADS)

    Iwema, Joost; Rosolem, Rafael; Rahman, Mostaquimur; Blyth, Eleanor; Wagener, Thorsten

    2016-04-01

    Soil moisture importantly controls land surface processes such as energy and water partitioning. A good understanding of these controls is needed especially when recognizing the challenges in providing accurate hyper-resolution hydrometeorological simulations at sub-kilometre scales. Soil moisture controlling factors can, however, differ at distinct scales. In addition, some parameters in land surface models are still often prescribed based on observations obtained at another scale not necessarily employed by such models (e.g., soil properties obtained from lab samples used in regional simulations). To minimize such effects, parameters can be constrained with local data from Eddy-Covariance (EC) towers (i.e., latent and sensible heat fluxes) and Point Scale (PS) soil moisture observations (e.g., TDR). However, measurement scales represented by EC and PS still differ substantially. Here we use the fact that Cosmic-Ray Neutron Sensors (CRNS) estimate soil moisture at horizontal footprint similar to that of EC fluxes to help answer the following question: Does reduced observation scale mismatch yield better soil moisture - surface fluxes representation in land surface models? To answer this question we analysed soil moisture and surface fluxes measurements from twelve COSMOS-Ameriflux sites in the USA characterized by distinct climate, soils and vegetation types. We calibrated model parameters of the Joint UK Land Environment Simulator (JULES) against PS and CRNS soil moisture data, respectively. We analysed the improvement in soil moisture estimation compared to uncalibrated model simulations and then evaluated the degree of improvement in surface fluxes before and after calibration experiments. Preliminary results suggest that a more accurate representation of soil moisture dynamics is achieved when calibrating against observed soil moisture and further improvement obtained with CRNS relative to PS. However, our results also suggest that a more accurate

  13. Measuring surface energy and evapotranspiration across Caribbean mangrove forests

    NASA Astrophysics Data System (ADS)

    Lagomasino, D.; Fatoyinbo, T. E.; Price, R.

    2014-12-01

    Coastal mangroves lose large amounts of water through evapotranspiration (ET) that can be equivalent to the amount of annual rainfall in certain years. Satellite remote sensing has been used to estimate surface energy and ET variability in many forested ecosystems, yet has been widely overlooked in mangrove forests. Using a combination of long-term datasets (30-year) acquired from the NASA Landsat 5 and 7 satellite databases, the present study investigated ET and surface energy balance variability between two mangrove forest sites in the Caribbean: 1) Everglades National Park (ENP; Florida, USA) and 2) Sian Ka'an Biosphere Reserve (SKBR; Quintana Roo, Mexico). A satellite-derived surface energy balance model was used to estimate ET in tall and scrub mangroves environments at ENP and SKBR. Results identified significant differences in soil heat flux measurements and ET between the tall and scrub mangrove environments. Scrub mangroves exhibited the highest soil heat flux coincident with the lowest biophysical indices (i.e., Fractional Vegetation Cover, Normalized Difference Vegetation Index, and Soil-Adjusted Vegetation Index) and ET rates. Mangrove damage and mortality was observed on the satellite images following strong tropical storms and associated with anthropogenic modifications and resulted in low values in spectral vegetation indices, higher soil heat flux, and higher ET. Recovery of the spectral characteristics, soil heat flux and ET was within 1-2 years following hurricane disturbance while, degradation caused by human disturbance persisted for many years. Remotely sensed ET of mangrove forests can provide estimates over a few decades and provide us with some understanding of how these environments respond to disturbances to the landscape in periods where no ground data exists or in locations that are difficult to access. Moreover, relationships between energy and water balance components developed for the coastal mangroves of Florida and Mexico could be

  14. Surface effects on the energy-generating performance of piezoelectric circular nanomembrane energy harvesters under pressure loading

    NASA Astrophysics Data System (ADS)

    Wang, K. F.; Wang, B. L.

    2014-10-01

    The influence of surface effects on the energy-generating performance of piezoelectric circular nanomembrane energy harvesters under blood pressure is studied. The effects of surface elasticity, surface piezoelectricity, residual surface stress and geometry nonlinear strain are incorporated in the present model. An approximated closed-form solution for the electrical energy of the nanomembrane is derived by using the energy method. Results show that positive surface elasticity and residual surface stress reduce the electrical energy and the surface piezoelectricity effect increases the electrical energy. The influence of surface effect on the energy-generating performance of piezoelectric circular membranes is more significant for a membrane with a small thickness and a large radius-to-thickness ratio.

  15. Methods for finding transition states on reduced potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Burger, Steven K.; Ayers, Paul W.

    2010-06-01

    Three new algorithms are presented for determining transition state (TS) structures on the reduced potential energy surface, that is, for problems in which a few important degrees of freedom can be isolated. All three methods use constrained optimization to rapidly find the TS without an initial Hessian evaluation. The algorithms highlight how efficiently the TS can be located on a reduced surface, where the rest of the degrees of freedom are minimized. The first method uses a nonpositive definite quasi-Newton update for the reduced degrees of freedom. The second uses Shepard interpolation to fit the Hessian and starts from a set of points that bound the TS. The third directly uses a finite difference scheme to calculate the reduced degrees of freedom of the Hessian of the entire system, and searches for the TS on the full potential energy surface. All three methods are tested on an epoxide hydrolase cluster, and the ring formations of cyclohexane and cyclobutenone. The results indicate that all the methods are able to converge quite rapidly to the correct TS, but that the finite difference approach is the most efficient.

  16. Theoretical studies of potential energy surfaces and computational methods.

    SciTech Connect

    Shepard, R.

    2006-01-01

    This project involves the development, implementation, and application of theoretical methods for the calculation and characterization of potential energy surfaces (PES) involving molecular species that occur in hydrocarbon combustion. These potential energy surfaces require an accurate and balanced treatment of reactants, intermediates, and products. Most of our work focuses on general multiconfiguration self-consistent-field (MCSCF) and multireference single- and double-excitation configuration interaction (MRSDCI) methods. In contrast to the more common single-reference electronic structure methods, this approach is capable of describing accurately molecular systems that are highly distorted away from their equilibrium geometries, including reactant, fragment, and transition-state geometries, and of describing regions of the potential surface that are associated with electronic wave functions of widely varying nature. The MCSCF reference wave functions are designed to be sufficiently flexible to describe qualitatively the changes in the electronic structure over the broad range of molecular geometries of interest. The necessary mixing of ionic, covalent, and Rydberg contributions, along with the appropriate treatment of the different electron-spin components (e.g. closed shell, high-spin open-shell, low-spin open shell, radical, diradical, etc.) of the wave functions are treated correctly at this level. Further treatment of electron correlation effects is included using large scale multireference CI wave functions, particularly including the single and double excitations relative to the MCSCF reference space. This leads to the most flexible and accurate large-scale MRSDCI wave functions that have been used to date in global PES studies.

  17. Theoretical studies of potential energy surfaces and computational methods

    SciTech Connect

    Shepard, R.

    1993-12-01

    This project involves the development, implementation, and application of theoretical methods for the calculation and characterization of potential energy surfaces involving molecular species that occur in hydrocarbon combustion. These potential energy surfaces require an accurate and balanced treatment of reactants, intermediates, and products. This difficult challenge is met with general multiconfiguration self-consistent-field (MCSCF) and multireference single- and double-excitation configuration interaction (MRSDCI) methods. In contrast to the more common single-reference electronic structure methods, this approach is capable of describing accurately molecular systems that are highly distorted away from their equilibrium geometries, including reactant, fragment, and transition-state geometries, and of describing regions of the potential surface that are associated with electronic wave functions of widely varying nature. The MCSCF reference wave functions are designed to be sufficiently flexible to describe qualitatively the changes in the electronic structure over the broad range of geometries of interest. The necessary mixing of ionic, covalent, and Rydberg contributions, along with the appropriate treatment of the different electron-spin components (e.g. closed shell, high-spin open-shell, low-spin open shell, radical, diradical, etc.) of the wave functions, are treated correctly at this level. Further treatment of electron correlation effects is included using large scale multireference CI wave functions, particularly including the single and double excitations relative to the MCSCF reference space. This leads to the most flexible and accurate large-scale MRSDCI wave functions that have been used to date in global PES studies.

  18. Concrete with carpet recyclates: suitability assessment by surface energy evaluation.

    PubMed

    Schmidt, H; Cieślak, M

    2008-01-01

    Worn out textile floor coverings are burdensome wastes that are degraded in landfill sites after a very long period of time. One of the ways to manage this kind of waste may be the use of carpet recyclate (CR) as an additive for concrete reinforcement. Therefore, an attempt was made to predict the effects of recyclate additives on the durability a concrete-carpet mixture by employing the method of assessing surface properties of components in the concrete-carpet recyclates composite. Testing was performed on carpet wastes, containing polyamide (PA) and polypropylene (PP) piles and butadiene-styrene resin with chalk filler (BSC) as back coating, to assess the suitability of CR additive for concrete reinforcement by surface energy evaluation. Based on the measurements of contact angles, the free surface energy of recyclate components was determined. The reversible work of adhesion at the interface between these components in dry and wet states was also calculated. The results show that CR with both PA and PP fibers form a strong and water-resistant bond with concrete.

  19. Surface Coordination of Adatoms by Scanned Low Energy Photoelectron Diffraction

    NASA Astrophysics Data System (ADS)

    Asensio, M. C.

    In this article, a brief overview of the current activity in the field of low energy photoelectron diffraction is presented. Although alternatively angle and energy-scanned photoelectron diffraction can be used to obtain the surface-structural information, we limit our discussion to the low energy and energy-scanned modes and their use in connection with a new developed direct method. By the use of this most recent approach, adatom-substrate distances and adsorption sites are directly revealed from a discrete mapping of the Fourier transform of scanned energy photoelectron diffraction spectra, measured at a representative set of geometries, which depend on the symmetry of the particular studied system. In addition, a short discussion on the determination of the detailed structure of adsorbed overlayers by the traditional trial-and-error method is included, using model multiple scattering calculations. These latest developments are illustrated with a specific example of an atomic adsorbate, and comments about the capabilities and limitations of photoelectron diffraction as a structural technique in new fields.

  20. The Dynamics of Laurentian Great Lakes Surface Energy Budgets

    NASA Astrophysics Data System (ADS)

    Spence, C.; Blanken, P.; Lenters, J. D.; Gronewold, A.; Kerkez, B.; Xue, P.; Froelich, N.

    2015-12-01

    The Laurentian Great Lakes constitute the largest freshwater surface in the world and are a valuable North American natural and socio-economic resource. In response to calls for improved monitoring and research on the energy and water budgets of the lakes, there has been a growing ensemble of in situ measurements - including offshore eddy flux towers, buoy-based sensors, and vessel-based platforms -deployed through an ongoing, bi-national collaboration known as the Great Lakes Evaporation Network (GLEN). The objective of GLEN is to reduce uncertainty in Great Lakes seasonal and 6-month water level forecasts, as well as climate change projections of the surface energy balance and water level fluctuations. Although It remains challenging to quantify and scale energy budgets and fluxes over such large water bodies, this presentation will report on recent successes in three areas: First, in estimating evaporation rates over each of the Great Lakes; Second, defining evaporation variability among the lakes, especially in winter and; Third, explaining the interaction between ice cover, water temperature, and evaporation across a variety of temporal and spatial scales. Research gaps remain, particularly those related to spatial variability and scaling of turbulent fluxes, so the presentation will also describe how this will be addressed with enhanced instrument and platform arrays.

  1. Optomechanics for absolute rotation detection

    NASA Astrophysics Data System (ADS)

    Davuluri, Sankar

    2016-07-01

    In this article, we present an application of optomechanical cavity for the absolute rotation detection. The optomechanical cavity is arranged in a Michelson interferometer in such a way that the classical centrifugal force due to rotation changes the length of the optomechanical cavity. The change in the cavity length induces a shift in the frequency of the cavity mode. The phase shift corresponding to the frequency shift in the cavity mode is measured at the interferometer output to estimate the angular velocity of absolute rotation. We derived an analytic expression to estimate the minimum detectable rotation rate in our scheme for a given optomechanical cavity. Temperature dependence of the rotation detection sensitivity is studied.

  2. Moral absolutism and ectopic pregnancy.

    PubMed

    Kaczor, C

    2001-02-01

    If one accepts a version of absolutism that excludes the intentional killing of any innocent human person from conception to natural death, ectopic pregnancy poses vexing difficulties. Given that the embryonic life almost certainly will die anyway, how can one retain one's moral principle and yet adequately respond to a situation that gravely threatens the life of the mother and her future fertility? The four options of treatment most often discussed in the literature are non-intervention, salpingectomy (removal of tube with embryo), salpingostomy (removal of embryo alone), and use of methotrexate (MXT). In this essay, I review these four options and introduce a fifth (the milking technique). In order to assess these options in terms of the absolutism mentioned, it will also be necessary to discuss various accounts of the intention/foresight distinction. I conclude that salpingectomy, salpingostomy, and the milking technique are compatible with absolutist presuppositions, but not the use of methotrexate.

  3. Moral absolutism and ectopic pregnancy.

    PubMed

    Kaczor, C

    2001-02-01

    If one accepts a version of absolutism that excludes the intentional killing of any innocent human person from conception to natural death, ectopic pregnancy poses vexing difficulties. Given that the embryonic life almost certainly will die anyway, how can one retain one's moral principle and yet adequately respond to a situation that gravely threatens the life of the mother and her future fertility? The four options of treatment most often discussed in the literature are non-intervention, salpingectomy (removal of tube with embryo), salpingostomy (removal of embryo alone), and use of methotrexate (MXT). In this essay, I review these four options and introduce a fifth (the milking technique). In order to assess these options in terms of the absolutism mentioned, it will also be necessary to discuss various accounts of the intention/foresight distinction. I conclude that salpingectomy, salpingostomy, and the milking technique are compatible with absolutist presuppositions, but not the use of methotrexate. PMID:11262641

  4. The Absolute Spectrum Polarimeter (ASP)

    NASA Technical Reports Server (NTRS)

    Kogut, A. J.

    2010-01-01

    The Absolute Spectrum Polarimeter (ASP) is an Explorer-class mission to map the absolute intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from 30 GHz to 5 THz. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much greater than 1O(raised to the power of { -3}) and Compton distortion y < 10 (raised to the power of{-6}). We describe the ASP instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.

  5. Classification images predict absolute efficiency.

    PubMed

    Murray, Richard F; Bennett, Patrick J; Sekuler, Allison B

    2005-02-24

    How well do classification images characterize human observers' strategies in perceptual tasks? We show mathematically that from the classification image of a noisy linear observer, it is possible to recover the observer's absolute efficiency. If we could similarly predict human observers' performance from their classification images, this would suggest that the linear model that underlies use of the classification image method is adequate over the small range of stimuli typically encountered in a classification image experiment, and that a classification image captures most important aspects of human observers' performance over this range. In a contrast discrimination task and in a shape discrimination task, we found that observers' absolute efficiencies were generally well predicted by their classification images, although consistently slightly (approximately 13%) higher than predicted. We consider whether a number of plausible nonlinearities can account for the slight under prediction, and of these we find that only a form of phase uncertainty can account for the discrepancy.

  6. How important is getting the land surface energy exchange correct in WRF for wind energy forecasting?

    NASA Astrophysics Data System (ADS)

    Wharton, S.; Simpson, M.; Osuna, J. L.; Newman, J. F.; Biraud, S.

    2013-12-01

    Wind power forecasting is plagued with difficulties in accurately predicting the occurrence and intensity of atmospheric conditions at the heights spanned by industrial-scale turbines (~ 40 to 200 m above ground level). Better simulation of the relevant physics would enable operational practices such as integration of large fractions of wind power into power grids, scheduling maintenance on wind energy facilities, and deciding design criteria based on complex loads for next-generation turbines and siting. Accurately simulating the surface energy processes in numerical models may be critically important for wind energy forecasting as energy exchange at the surface strongly drives atmospheric mixing (i.e., stability) in the lower layers of the planetary boundary layer (PBL), which in turn largely determines wind shear and turbulence at heights found in the turbine rotor-disk. We hypothesize that simulating accurate a surface-atmosphere energy coupling should lead to more accurate predictions of wind speed and turbulence at heights within the turbine rotor-disk. Here, we tested 10 different land surface model configurations in the Weather Research and Forecasting (WRF) model including Noah, Noah-MP, SSiB, Pleim-Xiu, RUC, and others to evaluate (1) the accuracy of simulated surface energy fluxes to flux tower measurements, (2) the accuracy of forecasted wind speeds to observations at rotor-disk heights, and (3) the sensitivity of forecasting hub-height rotor disk wind speed to the choice of land surface model. WRF was run for four, two-week periods covering both summer and winter periods over the Southern Great Plains ARM site in Oklahoma. Continuous measurements of surface energy fluxes and lidar-based wind speed, direction and turbulence were also available. The SGP ARM site provided an ideal location for this evaluation as it centrally located in the wind-rich Great Plains and multi-MW wind farms are rapidly expanding in the area. We found significant differences in

  7. Oxidation of nickel surfaces by low energy ion bombardment

    NASA Astrophysics Data System (ADS)

    Saric, Iva; Peter, Robert; Kavre, Ivna; Badovinac, Ivana Jelovica; Petravic, Mladen

    2016-03-01

    We have studied formation of oxides on Ni surfaces by low energy oxygen bombardment using X-ray photoemission spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). Different oxidation states of Ni ions have been identified in XPS spectra measured around Ni 2p and O 1s core-levels. We have compared our results with thermal oxidation of Ni and shown that ion bombardment is more efficient in creating thin oxide films on Ni surfaces. The dominant Ni-oxide in both oxidation processes is NiO (Ni2+ oxidation state), while some Ni2O3 contributions (Ni3+ oxidation state) are still present in all oxidised samples. The oxide thickness of bombarded Ni samples, as determined by SIMS, was shown to be related to the penetration depth of oxygen ions in Ni.

  8. Surface analysis of zeolites: An XPS, variable kinetic energy XPS, and low energy ion scattering study

    NASA Astrophysics Data System (ADS)

    Bare, Simon R.; Knop-Gericke, Axel; Teschner, Detre; Hävacker, Michael; Blume, Raoul; Rocha, Tulio; Schlögl, Robert; Chan, Ally S. Y.; Blackwell, N.; Charochak, M. E.; ter Veen, Rik; Brongersma, Hidde H.

    2016-06-01

    The surface Si/Al ratio in a series of zeolite Y samples has been obtained using laboratory XPS, synchrotron (variable kinetic energy) XPS, and low energy ion scattering (LEIS) spectroscopy. The non-destructive depth profile obtained using variable kinetic energy XPS is compared to that from the destructive argon ion bombardment depth profile from the lab XPS instrument. All of the data indicate that the near surface region of both the ammonium form and steamed Y zeolites is strongly enriched in aluminum. It is shown that when the inelastic mean free path of the photoelectrons is taken into account the laboratory XPS of aluminosilicates zeolites does not provide a true measurement of the surface stoichiometry, while variable kinetic energy XPS results in a more surface sensitive measurement. A comprehensive Si/Al concentration profile as a function of depth is developed by combining the data from the three surface characterization techniques. The LEIS spectroscopy reveals that the topmost atomic layer is further enriched in Al compared to subsequent layers.

  9. Absolute and relative diffusion in a turbulent compressibile system

    NASA Astrophysics Data System (ADS)

    Cressman, J. R.; Goldburg, W. I.

    2002-11-01

    Floating Particles that move on the surface of a tank of water driven into turbulent motion, move in a plane. Calling the coordinates of this plane x and y, with z=0 at the surface, the velocity of the floating particles obeys the equation partialx u_x(x,y,0,t) +partial_yu_y(x,y,0,t)= - partial_zu_z(x,y,0,t), assuring that their motion is compressible. From PIV measurements made at the surface, one can deduce the absolute and the relative motion of the floaters (Richardson diffusion). The relative diffusion measurements are compared with the Richardson result, t^3 and with computer simulations of Eckhardt and Schumacher [1]. The dimensionless compressibility l C is roughly 0.5 for the floaters, which is large enough to raise questions about the validity of the Kolmogorov paradigm, according to which energy is passed from large to small spatial scales [2]. References 1. G. Falkovich et al., Rev. Mod. Phys. 73 913 (2001). 2. J. Schumacher and B. Eckhardt, Phys. Rev. E 66, 017303 (2002).

  10. Novel Local Free Energy Minimum on the Cu(001) Surface

    NASA Astrophysics Data System (ADS)

    Ovsyanko, Mikhail; Stoian, Georgiana; Wormeester, Herbert; Poelsema, Bene

    2004-08-01

    High-resolution LEED (low-energy electron diffraction) data of Cu(001) reveal an uniaxial in-plane lattice reconstruction by 1%. One-dimensional nanogrooves induced by ion bombardment involve the creation of steps that enable this reconstruction. This is the first verification of van der Merwe’s prediction of step facilitated reconstruction. We confirm the predicted dependence on step orientation: <100> steps allow stress-relief and <110> steps do not, consistent with the known elastic anisotropy. Similar behavior is predicted for other nonreconstructed (001) surfaces of 3d and 4d metals.

  11. A global potential energy surface for ArH2

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Walch, Stephen P.; Taylor, Peter R.

    1992-01-01

    We describe a simple analytic representation of the ArH2 potential energy surface which well reproduces the results of extensive ab initio electronic structure calculations. The analytic representation smoothly interpolates between the dissociated H2 and strong bonding limits. In the fitting process, emphasis is made on accurately reproducing regions of the potential expected to be important for high temperature (ca. 3000 K) collision processes. Overall, the anisotropy and H2 bond length dependence of the analytic representation well reproduce the input data.

  12. A global potential energy surface for ArH2

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Walch, Stephen P.; Taylor, Peter R.

    1993-01-01

    We describe a simple analytic representation of the ArH2 potential energy surface which well reproduces the results of extensive ab initio electronic structure calculations. The analytic representation smoothly interpolates between the dissociated H2 and strong bonding limits. In the fitting process, emphasis is made on accurately reproducing regions of the potential expected to be important for high temperature (ca. 3000 K) collision processes. Overall, the anisotropy and H2 bond length dependence of the analytic representation well reproduce the input data.

  13. Energy storage considerations for a robotic Mars surface sampler

    NASA Technical Reports Server (NTRS)

    O'Donnell, P. M.; Cataldo, R. L.; Gonzalez-Sanabria, O. D.

    1988-01-01

    The characteristics of various energy storage systems (including Ni-Cd, Ni-H2, Ag-Zn, Li-XS, Na-S, PbSO4, and regenerative fuel cell systems) considered for a robotic Mars surface sampler are reviewed. It is concluded that the bipolar nickel-hydrogen battery and the sodium-sulfur battery are both viable candidates as storage systems for the rover's Radioisotope Thermoelectric Generator. For a photovoltaic storage system, the regenerative fuel cell and the bipolar nickel-hydrogen battery are the primary candidates.

  14. Stabilized quasi-Newton optimization of noisy potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Schaefer, Bastian; Ghasemi, S. Alireza; Roy, Shantanu; Goedecker, Stefan; Goedecker Group Team

    Optimizations of atomic positions belong to the most frequently performed tasks in electronic structure calculations. Many simulations like global minimum searches or the identification of chemical reaction pathways can require the computation of hundreds or thousands of minimizations or saddle points. To automatize these tasks, optimization algorithms must not only be efficient but also very reliable. Unfortunately, computational noise in forces and energies is inherent to electronic structure codes. This computational noise poses a severe problem to the stability of efficient optimization methods like the limited-memory Broyden-Fletcher-Goldfarb-Shanno algorithm. In this talk a recently published technique that allows to obtain significant curvature information of noisy potential energy surfaces is presented. This technique was used to construct both, a stabilized quasi-Newton minimization method and a stabilized quasi-Newton saddle finding approach. With the help of benchmarks both the minimizer and the saddle finding approach were demonstrated to be superior to comparable existing methods.

  15. Stabilized quasi-Newton optimization of noisy potential energy surfaces

    SciTech Connect

    Schaefer, Bastian; Goedecker, Stefan; Alireza Ghasemi, S.; Roy, Shantanu

    2015-01-21

    Optimizations of atomic positions belong to the most commonly performed tasks in electronic structure calculations. Many simulations like global minimum searches or characterizations of chemical reactions require performing hundreds or thousands of minimizations or saddle computations. To automatize these tasks, optimization algorithms must not only be efficient but also very reliable. Unfortunately, computational noise in forces and energies is inherent to electronic structure codes. This computational noise poses a severe problem to the stability of efficient optimization methods like the limited-memory Broyden–Fletcher–Goldfarb–Shanno algorithm. We here present a technique that allows obtaining significant curvature information of noisy potential energy surfaces. We use this technique to construct both, a stabilized quasi-Newton minimization method and a stabilized quasi-Newton saddle finding approach. We demonstrate with the help of benchmarks that both the minimizer and the saddle finding approach are superior to comparable existing methods.

  16. Accurate global potential energy surface for the H + OH+ collision

    NASA Astrophysics Data System (ADS)

    Gannouni, M. A.; Jaidane, N. E.; Halvick, P.; Stoecklin, T.; Hochlaf, M.

    2014-05-01

    We mapped the global three-dimensional potential energy surface (3D-PES) of the water cation at the MRCI/aug-cc-pV5Z including the basis set superposition (BSSE) correction. This PES covers the molecular region and the long ranges close to the H + OH+(X3Σ-), the O + H2+(X2Σg+), and the hydrogen exchange channels. The quality of the PES is checked after comparison to previous experimental and theoretical results of the spectroscopic constants of H2O+(tilde X2B1) and of the diatomic fragments, the vibronic spectrum, the dissociation energy, and the barrier to linearity for H2O+(tilde X2B1). Our data nicely approach those measured and computed previously. The long range parts reproduce quite well the diatomic potentials. In whole, a good agreement is found, which validates our 3D-PES.

  17. Stabilized quasi-Newton optimization of noisy potential energy surfaces.

    PubMed

    Schaefer, Bastian; Alireza Ghasemi, S; Roy, Shantanu; Goedecker, Stefan

    2015-01-21

    Optimizations of atomic positions belong to the most commonly performed tasks in electronic structure calculations. Many simulations like global minimum searches or characterizations of chemical reactions require performing hundreds or thousands of minimizations or saddle computations. To automatize these tasks, optimization algorithms must not only be efficient but also very reliable. Unfortunately, computational noise in forces and energies is inherent to electronic structure codes. This computational noise poses a severe problem to the stability of efficient optimization methods like the limited-memory Broyden-Fletcher-Goldfarb-Shanno algorithm. We here present a technique that allows obtaining significant curvature information of noisy potential energy surfaces. We use this technique to construct both, a stabilized quasi-Newton minimization method and a stabilized quasi-Newton saddle finding approach. We demonstrate with the help of benchmarks that both the minimizer and the saddle finding approach are superior to comparable existing methods.

  18. Sampling saddle points on the free energy surface

    NASA Astrophysics Data System (ADS)

    Samanta, Amit

    2014-03-01

    We develop an algorithm for finding the saddle points on the free energy surface ``on-the-fly'' without having to find the free energy function itself. This is done by using the general strategy of the heterogeneous multi-scale method, applying a macro-scale solver, here the gentlest ascent dynamics algorithm, with the needed force and Hessian values computed on-the-fly using a micro-scale model such as molecular dynamics. The algorithm is capable of dealing with problems involving many coarse-grained variables. The utility of the algorithm is illustrated by studying the saddle points associated with (a) the isomerization transition of the alanine dipeptide using two coarse-grained variables, specifically the Ramachandran dihedral angles, and (b) the beta-hairpin structure of the alanine decamer using twenty coarse-grained variables, specifically the full set of Ramachandran angle pairs associated with each residue.

  19. Novel mixture model for the representation of potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Pham, Tien Lam; Kino, Hiori; Terakura, Kiyoyuki; Miyake, Takashi; Dam, Hieu Chi

    2016-10-01

    We demonstrate that knowledge of chemical physics on a materials system can be automatically extracted from first-principles calculations using a data mining technique; this information can then be utilized to construct a simple empirical atomic potential model. By using unsupervised learning of the generative Gaussian mixture model, physically meaningful patterns of atomic local chemical environments can be detected automatically. Based on the obtained information regarding these atomic patterns, we propose a chemical-structure-dependent linear mixture model for estimating the atomic potential energy. Our experiments show that the proposed mixture model significantly improves the accuracy of the prediction of the potential energy surface for complex systems that possess a large diversity in their local structures.

  20. Computed rotational rainbows from realistic potential energy surfaces

    SciTech Connect

    Gianturco, F.A.; Palma, A.

    1985-08-01

    The quantal IOS approximation in here employed to study interference structures in the rotationally inelastic, state-to-state differential cross sections for polar diatomic targets (LiH, FH, and CO) interacting with He atoms. Quite realistic expressions are used to describe the relevant potential energy surfaces (PES) which were taken from previous works that tested them against accurate experimental findings for total and partial differential cross sections. Specific features like short-range anisotropy and well depth, long-range attractive regions and overall range of action for each potential employed are analyzed and discussed in relation to their influence on rotational rainbows appearance and on the possible observation of cross section extrema in rotational energy distributions.

  1. Designing Free Energy Surfaces That Match Experimental Data with Metadynamics

    DOE PAGES

    White, Andrew D.; Dama, James F.; Voth, Gregory A.

    2015-04-30

    Creating models that are consistent with experimental data is essential in molecular modeling. This is often done by iteratively tuning the molecular force field of a simulation to match experimental data. An alternative method is to bias a simulation, leading to a hybrid model composed of the original force field and biasing terms. Previously we introduced such a method called experiment directed simulation (EDS). EDS minimally biases simulations to match average values. We also introduce a new method called experiment directed metadynamics (EDM) that creates minimal biases for matching entire free energy surfaces such as radial distribution functions and phi/psimore » angle free energies. It is also possible with EDM to create a tunable mixture of the experimental data and free energy of the unbiased ensemble with explicit ratios. EDM can be proven to be convergent, and we also present proof, via a maximum entropy argument, that the final bias is minimal and unique. Examples of its use are given in the construction of ensembles that follow a desired free energy. Finally, the example systems studied include a Lennard-Jones fluid made to match a radial distribution function, an atomistic model augmented with bioinformatics data, and a three-component electrolyte solution where ab initio simulation data is used to improve a classical empirical model.« less

  2. Designing Free Energy Surfaces That Match Experimental Data with Metadynamics

    SciTech Connect

    White, Andrew D.; Dama, James F.; Voth, Gregory A.

    2015-04-30

    Creating models that are consistent with experimental data is essential in molecular modeling. This is often done by iteratively tuning the molecular force field of a simulation to match experimental data. An alternative method is to bias a simulation, leading to a hybrid model composed of the original force field and biasing terms. Previously we introduced such a method called experiment directed simulation (EDS). EDS minimally biases simulations to match average values. We also introduce a new method called experiment directed metadynamics (EDM) that creates minimal biases for matching entire free energy surfaces such as radial distribution functions and phi/psi angle free energies. It is also possible with EDM to create a tunable mixture of the experimental data and free energy of the unbiased ensemble with explicit ratios. EDM can be proven to be convergent, and we also present proof, via a maximum entropy argument, that the final bias is minimal and unique. Examples of its use are given in the construction of ensembles that follow a desired free energy. Finally, the example systems studied include a Lennard-Jones fluid made to match a radial distribution function, an atomistic model augmented with bioinformatics data, and a three-component electrolyte solution where ab initio simulation data is used to improve a classical empirical model.

  3. Designing free energy surfaces that match experimental data with metadynamics.

    PubMed

    White, Andrew D; Dama, James F; Voth, Gregory A

    2015-06-01

    Creating models that are consistent with experimental data is essential in molecular modeling. This is often done by iteratively tuning the molecular force field of a simulation to match experimental data. An alternative method is to bias a simulation, leading to a hybrid model composed of the original force field and biasing terms. We previously introduced such a method called experiment directed simulation (EDS). EDS minimally biases simulations to match average values. In this work, we introduce a new method called experiment directed metadynamics (EDM) that creates minimal biases for matching entire free energy surfaces such as radial distribution functions and phi/psi angle free energies. It is also possible with EDM to create a tunable mixture of the experimental data and free energy of the unbiased ensemble with explicit ratios. EDM can be proven to be convergent, and we also present proof, via a maximum entropy argument, that the final bias is minimal and unique. Examples of its use are given in the construction of ensembles that follow a desired free energy. The example systems studied include a Lennard-Jones fluid made to match a radial distribution function, an atomistic model augmented with bioinformatics data, and a three-component electrolyte solution where ab initio simulation data is used to improve a classical empirical model.

  4. Designing free energy surfaces that match experimental data with metadynamics.

    PubMed

    White, Andrew D; Dama, James F; Voth, Gregory A

    2015-06-01

    Creating models that are consistent with experimental data is essential in molecular modeling. This is often done by iteratively tuning the molecular force field of a simulation to match experimental data. An alternative method is to bias a simulation, leading to a hybrid model composed of the original force field and biasing terms. We previously introduced such a method called experiment directed simulation (EDS). EDS minimally biases simulations to match average values. In this work, we introduce a new method called experiment directed metadynamics (EDM) that creates minimal biases for matching entire free energy surfaces such as radial distribution functions and phi/psi angle free energies. It is also possible with EDM to create a tunable mixture of the experimental data and free energy of the unbiased ensemble with explicit ratios. EDM can be proven to be convergent, and we also present proof, via a maximum entropy argument, that the final bias is minimal and unique. Examples of its use are given in the construction of ensembles that follow a desired free energy. The example systems studied include a Lennard-Jones fluid made to match a radial distribution function, an atomistic model augmented with bioinformatics data, and a three-component electrolyte solution where ab initio simulation data is used to improve a classical empirical model. PMID:26575545

  5. Critical Surface Tension, Critical Surface Energy and Parachor of MnSO3 Thin Film

    NASA Astrophysics Data System (ADS)

    Kariper, I. A.

    2016-02-01

    This study examines the critical surface energy of manganese sulfite (MnSO3) crystalline thin film, produced via chemical bath deposition (CBD) on substrates. In addition, parachor, which is an important parameter of chemical physics, and its relationship with grain size, film thickness, etc., has been investigated for thin films. For this purpose, MnSO3 thin films were deposited at room temperature using different deposition times. Structural properties of the films, such as film thickness and average grain size, were examined using X-ray diffraction; film thickness and surface properties were measured by and atomic force microscope; and critical surface tension of MnSO3 thin films was measured with Optical Tensiometer and calculated using Zisman method. The results showed that critical surface tension and parachor of the films have varied with average grain size and film thickness. Critical surface tension was calculated as 32.97, 24.55, 21.03 and 12.76mN/m for 14.66, 30.84, 37.07 and 44.56nm grain sizes, respectively. Film thickness and average grain size have been increased with the deposition time and they were found to be negatively correlated with surface tension and parachor. The relationship between film thickness and parachor was found as P=-0.1856t+183.45; whereas the relationship between average grain size and parachor was found as P=-0.8911D+150.52. We also showed the relationships between parachor and some thin films parameters.

  6. Front instability and energy of the free surface

    NASA Astrophysics Data System (ADS)

    Beltrame, Philippe

    2014-05-01

    In recent years, there has been a proliferation of research devoted to the formation of preferential flow paths occurring without macroscopic heterogeneity of the porous media. DiCarlo (2013) points out the connection between "overshoot" and the front instability. Extension of the standard Richards equation is required to capture this phenomenon. In most of the improvements, interfacial phenomena as the triple line at the front are considered. For instance, velocity dependent contact angle (Wang et al., 2013) or contact angle hysteresis (Rätz and Schweizer, 2012) allow to simulate successfully the instability. Another approach proposed by Cueto-Felgueroso and Juanes (2009) introduces a macroscopic surface tension related to the existence of the water/air interface. As previously, the simulation of an advancing front displays physical looking fingering displacements. The goal of this contribution is to better understand the role of the different surface energies in the emergence of the front instability. We propose a model involving both the macroscopic surface tension and the soil wettability. This latter allows to define a contact angle and possibly hysteresis using heterogeneous wettability (Beltrame et al., 2011). Therefore, we employ the phase field approach developed by Felgueroso and Juanes, 2009 to which we add a free energy term corresponding to the wettability: a disjoining or conjoining pressure resulting from effective molecular interactions between the substrate and the free surface (DeGennes, 1985). The difference with the classical suction pressure is the hydrophobic behavior for ultra-thin film (small water saturation). Such a water repellency was recently estimated in the soil (Diamantopoulos et al. 2013). Stability analysis of an advancing front in an uniform porous media shows that macroscopic surface tension and wettability may independently produce the instability growth. In contrast, for a front stopping when reaching the layers interface of

  7. Coupling of surface energy with electric potential makes superhydrophobic surfaces corrosion-resistant.

    PubMed

    Ramachandran, Rahul; Nosonovsky, Michael

    2015-10-14

    We study the correlation of wetting properties and corrosion rates on hydrophobized cast iron. Samples of different surface roughnesses (abraded by sandpaper) are studied without coating and with two types of hydrophobic coatings (stearic acid and a liquid repelling spray). The contact angles and contact angle hysteresis are measured using a goniometer while corrosion rates are measured by a potentiodynamic polarization test. The data show a decrease in corrosion current density and an increase in corrosion potential after superhydrophobization. A similar trend is also found in the recent literature data. We conclude that a decrease in the corrosion rate can be attributed to the changing open circuit potential of a coated surface and increased surface area making the non-homogeneous (Cassie-Baxter) state possible. We interpret these results in light of the idea that the inherent surface energy is coupled with the electric potential in accordance with the Lippmann law of electrowetting and Le Châtelier's principle and, therefore, hydrophobization leads to a decrease in the corrosion potential. This approach can be used for novel anti-corrosive coatings. PMID:26344151

  8. A compact and accurate semi-global potential energy surface for malonaldehyde from constrained least squares regression

    SciTech Connect

    Mizukami, Wataru Tew, David P.; Habershon, Scott

    2014-10-14

    We present a new approach to semi-global potential energy surface fitting that uses the least absolute shrinkage and selection operator (LASSO) constrained least squares procedure to exploit an extremely flexible form for the potential function, while at the same time controlling the risk of overfitting and avoiding the introduction of unphysical features such as divergences or high-frequency oscillations. Drawing from a massively redundant set of overlapping distributed multi-dimensional Gaussian functions of inter-atomic separations we build a compact full-dimensional surface for malonaldehyde, fit to explicitly correlated coupled cluster CCSD(T)(F12*) energies with a root mean square deviations accuracy of 0.3%–0.5% up to 25 000 cm{sup −1} above equilibrium. Importance-sampled diffusion Monte Carlo calculations predict zero point energies for malonaldehyde and its deuterated isotopologue of 14 715.4(2) and 13 997.9(2) cm{sup −1} and hydrogen transfer tunnelling splittings of 21.0(4) and 3.2(4) cm{sup −1}, respectively, which are in excellent agreement with the experimental values of 21.583 and 2.915(4) cm{sup −1}.

  9. A compact and accurate semi-global potential energy surface for malonaldehyde from constrained least squares regression

    NASA Astrophysics Data System (ADS)

    Mizukami, Wataru; Habershon, Scott; Tew, David P.

    2014-10-01

    We present a new approach to semi-global potential energy surface fitting that uses the least absolute shrinkage and selection operator (LASSO) constrained least squares procedure to exploit an extremely flexible form for the potential function, while at the same time controlling the risk of overfitting and avoiding the introduction of unphysical features such as divergences or high-frequency oscillations. Drawing from a massively redundant set of overlapping distributed multi-dimensional Gaussian functions of inter-atomic separations we build a compact full-dimensional surface for malonaldehyde, fit to explicitly correlated coupled cluster CCSD(T)(F12*) energies with a root mean square deviations accuracy of 0.3%-0.5% up to 25 000 cm-1 above equilibrium. Importance-sampled diffusion Monte Carlo calculations predict zero point energies for malonaldehyde and its deuterated isotopologue of 14 715.4(2) and 13 997.9(2) cm-1 and hydrogen transfer tunnelling splittings of 21.0(4) and 3.2(4) cm-1, respectively, which are in excellent agreement with the experimental values of 21.583 and 2.915(4) cm-1.

  10. An Ab Initio Based Potential Energy Surface for Water

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Schwenke, David W.; Langhoff, Stephen R. (Technical Monitor)

    1996-01-01

    We report a new determination of the water potential energy surface. A high quality ab initio potential energy surface (PES) and dipole moment function of water have been computed. This PES is empirically adjusted to improve the agreement between the computed line positions and those from the HITRAN 92 data base. The adjustment is small, nonetheless including an estimate of core (oxygen 1s) electron correlation greatly improves the agreement with experiment. Of the 27,245 assigned transitions in the HITRAN 92 data base for H2(O-16), the overall root mean square (rms) deviation between the computed and observed line positions is 0.125/cm. However the deviations do not correspond to a normal distribution: 69% of the lines have errors less than 0.05/cm. Overall, the agreement between the line intensities computed in the present work and those contained in the data base is quite good, however there are a significant number of line strengths which differ greatly.

  11. A study of the surface energy balance on slopes in a tallgrass prairie

    NASA Technical Reports Server (NTRS)

    Nie, D.; Demetriades-Shah, T.; Kanemasu, E. T.

    1990-01-01

    Four slopes (north, south, east, and west) were selected on the Konza Prairie Research Natural Area to study the effect of topography on surface energy balance and other micrometeorological variables. Energy fluxes, air temperature, and vapor pressure were measured on the sloped throughout the 1988 growing season. Net radiation was the highest on the south-facing slope and lowest on the north-facing slope, and the difference was more than 150 W/sq m (20 to 30 percent) at solar noon. For daily averages, the difference was 25 W/sq m (15 percent) early in the season and increased to 60 W/sq m (30 to 50 percent) in September. The east-facing and west-facing slopes had the same daily average net radiation, but the time of day when maximum net radiation occurred was one hour earlier for the east-facing slope and one hour later for the west-facing slope relative to solar noon. Soil heat fluxes were similar for all the slopes. The absolute values of sensible heat flux (h) was consistently lower on the north-facing slope compared with other slopes. Typical difference in the values of H between the north-facing and the south-facing slopes was 15 to 30 W/sq m. The south-facing slope had the greatest day to day fluctuation in latent heat flux as a result of interaction of net radiation, soil moisture, and green leaf area. The north-facing slope had higher air temperatures during the day and higher vapor pressures both during the day and at night when the wind was from the south.

  12. Modes of variability of global sea surface temperature, free atmosphere temperature and oceanic surface energy flux

    SciTech Connect

    Hu, Wenjie; Newell, R.E.; Wu, Zhong-Xiang

    1994-11-01

    Monthly mean sea surface temperature (SST), free air temperature from satellite microwave sounding units (MSU) and oceanic surface energy fluxes are subjected to empirical orthogonal function (EOF) analysis for a common decade to investigate the physical relationships involved. The first seasonal modes of surface solar energy flux and SST show similar inter-hemispheric patterns with an annual cycle. Solar flux appears to control this pattern of SST. The first seasonal mode of MSU is similar with, additionally, land-sea differences; MSU is apparently partly controlled by absorption of solar near-infrared radiation and partly by sensible heat from from the land surface. The second and third seasonal eigenvector of SST and solar flux exhibit semi-annual oscillations associated with a pattern of cloudiness in the subtropics accompanying the translation of the Hadley cell rising motion between the hemispheres. The second seasonal mode of MSU is dominated by an El Nino Signal. The first nonseasonal EOFs of SST and solar flux exhibit El Nino characteristics with solar pattern being governed by west-to-east translation of a Walker cell type pattern. The first non-seasonal EOF of MSU shows a tropical strip pattern for the El Nino mode, which is well correlated with the latent heat fluxes in the tropical east Pacific but not in the tropical west Pacific. Two possible explanations are: an increase in subsidence throughout the tropical strip driven by extra evaporation in the tropical east Pacific and consequent additional latent heat liberation; a decrease of meridional heat flux out of the tropics. 56 refs., 12 figs., 5 tabs.

  13. The AFGL absolute gravity program

    NASA Technical Reports Server (NTRS)

    Hammond, J. A.; Iliff, R. L.

    1978-01-01

    A brief discussion of the AFGL's (Air Force Geophysics Laboratory) program in absolute gravity is presented. Support of outside work and in-house studies relating to gravity instrumentation are discussed. A description of the current transportable system is included and the latest results are presented. These results show good agreement with measurements at the AFGL site by an Italian system. The accuracy obtained by the transportable apparatus is better than 0.1 microns sq sec 10 microgal and agreement with previous measurements is within the combined uncertainties of the measurements.

  14. Familial Aggregation of Absolute Pitch

    PubMed Central

    Baharloo, Siamak; Service, Susan K.; Risch, Neil; Gitschier, Jane; Freimer, Nelson B.

    2000-01-01

    Absolute pitch (AP) is a behavioral trait that is defined as the ability to identify the pitch of tones in the absence of a reference pitch. AP is an ideal phenotype for investigation of gene and environment interactions in the development of complex human behaviors. Individuals who score exceptionally well on formalized auditory tests of pitch perception are designated as “AP-1.” As described in this report, auditory testing of siblings of AP-1 probands and of a control sample indicates that AP-1 aggregates in families. The implications of this finding for the mapping of loci for AP-1 predisposition are discussed. PMID:10924408

  15. Energy Crops and their Implications on Soil Carbon Sequestration, Surface Energy and Water Balance

    NASA Astrophysics Data System (ADS)

    Song, Y.; Barman, R.; Jain, A. K.

    2011-12-01

    The quest to meet growing energy demand with low greenhouse gas emissions has increased attention on the potential of existing and advanced biomass energy crops. Potential energy crops include row crops such as corn, and perennial grasses such as switchgrass. However, a massive expansion of bioenergy crops raises many questions such as: how and where to grow energy crops; and what will be the impacts of growing large scale biofuel crops on the terrestrial hydrological cycle, the surface energy budget, soil carbon sequestration and the concurrent effects on the climate system. An integrated modeling system is being developed with in the framework of a land surface model, the Integrated Science Assessment Model (ISAM), and being applied to address these questions.This framework accounts for the biophysical, physiological and biogeochemical systems governing important processes that regulate crop growth including water, energy and nutrient cycles within the soil-plant-atmosphere system. One row crop (Corn) and two energy crops (Switchgrass and Miscanthus) are studied in current framework. Dynamic phenology processes and parameters for simulating each crop have been developed using observed data from a north to south gradient of field trial sites. This study will specifically focus on the agricultural regions in the US and in Europe. The potential productivity of these three crops will be assessed in terms of carbon sequestration, surface energy and water balance and their spatial variability. This study will help to quantify the importance of various environmental aspects towards modeling bioenergy crops and to better understand the spatial and temporal dynamics of bioenergy crop yields.

  16. Potential energy surface and rovibrational energy levels of the H2-CS van der Waals complex.

    PubMed

    Denis-Alpizar, Otoniel; Stoecklin, Thierry; Halvick, Philippe; Dubernet, Marie-Lise; Marinakis, Sarantos

    2012-12-21

    Owing to its large dipole, astrophysicists use carbon monosulfide (CS) as a tracer of molecular gas in the interstellar medium, often in regions where H(2) is the most abundant collider. Predictions of the rovibrational energy levels of the weakly bound complex CS-H(2) (not yet observed) and also of rate coefficients for rotational transitions of CS in collision with H(2) should help to interpret the observed spectra. This paper deals with the first goal, i.e., the calculation of the rovibrational energy levels. A new four-dimensional intermolecular potential energy surface for the H(2)-CS complex is presented. Ab initio potential energy calculations were carried out at the coupled-cluster level with single and double excitations and a perturbative treatment of triple excitations, using a quadruple-zeta basis set and midbond functions. The potential energy surface was obtained by an analytic fit of the ab initio data. The equilibrium structure of the H(2)-CS complex is found to be linear with the carbon pointing toward H(2) at the intermolecular separation of 8.6 a(o). The corresponding well depth is -173 cm(-1). The potential was used to calculate the rovibrational energy levels of the para-H(2)-CS and ortho-H(2)-CS complexes. The present work provides the first theoretical predictions of these levels. The calculated dissociation energies are found to be 35.9 cm(-1) and 49.9 cm(-1), respectively, for the para and ortho complexes. The second virial coefficient for the H(2)-CS pair has also been calculated for a large range of temperature. These results could be used to assign future experimental spectra and to check the accuracy of the potential energy surface.

  17. High surface area aerogels for energy storage and efficiency

    NASA Astrophysics Data System (ADS)

    Maloney, Ryan Patrick

    ADAI are demonstrated in a third-generation prototypical thermoelectric generator for automotive waste heat recovery. The second chapter then details two different aerogel-based materials for electrochemical energy storage. It begins with lithium titanate aerogel, which takes advantage of the high surface area of the aerogel morphology to display a batt-cap behavior. This should allow the lithium titanate aerogel to perform at higher rates than would normally be expected for the bulk oxide material. Additionally, the flexibility of the sol-gel process is demonstrated through the incorporation of electrically conductive high-surface area exfoliated graphite nanoplatelets in the oxide. The last section describes the characterization of a LiMn2O 4 spinel coated carbon nanofoam in a non-aqueous electrolyte. The short diffusion path, high surface area and intimately wired architecture of the nanofoam allows the oxide to retain its capacity at significantly higher rates when compared with literature values for the bulk oxide. Additionally, the nanometric length scale improves cycle life, and the high surface area dramatically increases the insertion capacity by providing a higher concentration of surface defects. Taken together, it is clear that aerogels are an extremely attractive class of material for applications pertaining to energy and efficiency, and further research in this area will provide valuable solutions for pressing societal needs. (Abstract shortened by UMI.).

  18. The Absolute Radiometric Calibration of Space - Sensors.

    NASA Astrophysics Data System (ADS)

    Holm, Ronald Gene

    1987-09-01

    The need for absolute radiometric calibration of space-based sensors will continue to increase as new generations of space sensors are developed. A reflectance -based in-flight calibration procedure is used to determine the radiance reaching the entrance pupil of the sensor. This procedure uses ground-based measurements coupled with a radiative transfer code to characterize the effects the atmosphere has on the signal reaching the sensor. The computed radiance is compared to the digital count output of the sensor associated with the image of a test site. This provides an update to the preflight calibration of the system and a check on the on-board internal calibrator. This calibration procedure was used to perform a series of five calibrations of the Landsat-5 Thematic Mapper (TM). For the 12 measurements made in TM bands 1-3, the RMS variation from the mean as a percentage of the mean is (+OR-) 1.9%, and for measurements in the IR, TM bands 4,5, and 7, the value is (+OR-) 3.4%. The RMS variation for all 23 measurements is (+OR-) 2.8%. The absolute calibration techniques were put to another test with a series of three calibration of the SPOT-1 High Resolution Visible, (HRV), sensors. The ratio, HRV-2/HRV-1, of absolute calibration coefficients compared very well with ratios of histogrammed data obtained when the cameras simultaneously imaged the same ground site. Bands PA, B1 and B3 agreed to within 3%, while band B2 showed a 7% difference. The procedure for performing a satellite calibration was then used to demonstrate how a calibrated satellite sensor can be used to quantitatively evaluate surface reflectance over a wide range of surface features. Predicted reflectance factors were compared to values obtained from aircraft -based radiometer data. This procedure was applied on four dates with two different surface conditions per date. A strong correlation, R('2) = .996, was shown between reflectance values determined from satellite imagery and low-flying aircraft

  19. Estimation of the advection effects induced by surface heterogeneities in the surface energy budget

    NASA Astrophysics Data System (ADS)

    Cuxart, Joan; Wrenger, Burkhard; Martínez-Villagrasa, Daniel; Reuder, Joachim; Jonassen, Marius O.; Jiménez, Maria A.; Lothon, Marie; Lohou, Fabienne; Hartogensis, Oscar; Dünnermann, Jens; Conangla, Laura; Garai, Anirban

    2016-07-01

    The effect of terrain heterogeneities in one-point measurements is a continuous subject of discussion. Here we focus on the order of magnitude of the advection term in the equation of the evolution of temperature as generated by documented terrain heterogeneities and we estimate its importance as a term in the surface energy budget (SEB), for which the turbulent fluxes are computed using the eddy-correlation method. The heterogeneities are estimated from satellite and model fields for scales near 1 km or broader, while the smaller scales are estimated through direct measurements with remotely piloted aircraft and thermal cameras and also by high-resolution modelling. The variability of the surface temperature fields is not found to decrease clearly with increasing resolution, and consequently the advection term becomes more important as the scales become finer. The advection term provides non-significant values to the SEB at scales larger than a few kilometres. In contrast, surface heterogeneities at the metre scale yield large values of the advection, which are probably only significant in the first centimetres above the ground. The motions that seem to contribute significantly to the advection term in the SEB equation in our case are roughly those around the hectometre scales.

  20. Pseudospectral Gaussian quantum dynamics: Efficient sampling of potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Heaps, Charles W.; Mazziotti, David A.

    2016-04-01

    Trajectory-based Gaussian basis sets have been tremendously successful in describing high-dimensional quantum molecular dynamics. In this paper, we introduce a pseudospectral Gaussian-based method that achieves accurate quantum dynamics using efficient, real-space sampling of the time-dependent basis set. As in other Gaussian basis methods, we begin with a basis set expansion using time-dependent Gaussian basis functions guided by classical mechanics. Unlike other Gaussian methods but characteristic of the pseudospectral and collocation methods, the basis set is tested with N Dirac delta functions, where N is the number of basis functions, rather than using the basis function as test functions. As a result, the integration for matrix elements is reduced to function evaluation. Pseudospectral Gaussian dynamics only requires O ( N ) potential energy calculations, in contrast to O ( N 2 ) evaluations in a variational calculation. The classical trajectories allow small basis sets to sample high-dimensional potentials. Applications are made to diatomic oscillations in a Morse potential and a generalized version of the Henon-Heiles potential in two, four, and six dimensions. Comparisons are drawn to full analytical evaluation of potential energy integrals (variational) and the bra-ket averaged Taylor (BAT) expansion, an O ( N ) approximation used in Gaussian-based dynamics. In all cases, the pseudospectral Gaussian method is competitive with full variational calculations that require a global, analytical, and integrable potential energy surface. Additionally, the BAT breaks down when quantum mechanical coherence is particularly strong (i.e., barrier reflection in the Morse oscillator). The ability to obtain variational accuracy using only the potential energy at discrete points makes the pseudospectral Gaussian method a promising avenue for on-the-fly dynamics, where electronic structure calculations become computationally significant.

  1. Pseudospectral Gaussian quantum dynamics: Efficient sampling of potential energy surfaces.

    PubMed

    Heaps, Charles W; Mazziotti, David A

    2016-04-28

    Trajectory-based Gaussian basis sets have been tremendously successful in describing high-dimensional quantum molecular dynamics. In this paper, we introduce a pseudospectral Gaussian-based method that achieves accurate quantum dynamics using efficient, real-space sampling of the time-dependent basis set. As in other Gaussian basis methods, we begin with a basis set expansion using time-dependent Gaussian basis functions guided by classical mechanics. Unlike other Gaussian methods but characteristic of the pseudospectral and collocation methods, the basis set is tested with N Dirac delta functions, where N is the number of basis functions, rather than using the basis function as test functions. As a result, the integration for matrix elements is reduced to function evaluation. Pseudospectral Gaussian dynamics only requires O(N) potential energy calculations, in contrast to O(N(2)) evaluations in a variational calculation. The classical trajectories allow small basis sets to sample high-dimensional potentials. Applications are made to diatomic oscillations in a Morse potential and a generalized version of the Henon-Heiles potential in two, four, and six dimensions. Comparisons are drawn to full analytical evaluation of potential energy integrals (variational) and the bra-ket averaged Taylor (BAT) expansion, an O(N) approximation used in Gaussian-based dynamics. In all cases, the pseudospectral Gaussian method is competitive with full variational calculations that require a global, analytical, and integrable potential energy surface. Additionally, the BAT breaks down when quantum mechanical coherence is particularly strong (i.e., barrier reflection in the Morse oscillator). The ability to obtain variational accuracy using only the potential energy at discrete points makes the pseudospectral Gaussian method a promising avenue for on-the-fly dynamics, where electronic structure calculations become computationally significant.

  2. Pseudospectral Gaussian quantum dynamics: Efficient sampling of potential energy surfaces.

    PubMed

    Heaps, Charles W; Mazziotti, David A

    2016-04-28

    Trajectory-based Gaussian basis sets have been tremendously successful in describing high-dimensional quantum molecular dynamics. In this paper, we introduce a pseudospectral Gaussian-based method that achieves accurate quantum dynamics using efficient, real-space sampling of the time-dependent basis set. As in other Gaussian basis methods, we begin with a basis set expansion using time-dependent Gaussian basis functions guided by classical mechanics. Unlike other Gaussian methods but characteristic of the pseudospectral and collocation methods, the basis set is tested with N Dirac delta functions, where N is the number of basis functions, rather than using the basis function as test functions. As a result, the integration for matrix elements is reduced to function evaluation. Pseudospectral Gaussian dynamics only requires O(N) potential energy calculations, in contrast to O(N(2)) evaluations in a variational calculation. The classical trajectories allow small basis sets to sample high-dimensional potentials. Applications are made to diatomic oscillations in a Morse potential and a generalized version of the Henon-Heiles potential in two, four, and six dimensions. Comparisons are drawn to full analytical evaluation of potential energy integrals (variational) and the bra-ket averaged Taylor (BAT) expansion, an O(N) approximation used in Gaussian-based dynamics. In all cases, the pseudospectral Gaussian method is competitive with full variational calculations that require a global, analytical, and integrable potential energy surface. Additionally, the BAT breaks down when quantum mechanical coherence is particularly strong (i.e., barrier reflection in the Morse oscillator). The ability to obtain variational accuracy using only the potential energy at discrete points makes the pseudospectral Gaussian method a promising avenue for on-the-fly dynamics, where electronic structure calculations become computationally significant. PMID:27131532

  3. An accurate global potential energy surface, dipole moment surface, and rovibrational frequencies for NH3

    NASA Astrophysics Data System (ADS)

    Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.

    2008-12-01

    A global potential energy surface (PES) that includes short and long range terms has been determined for the NH3 molecule. The singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations and the internally contracted averaged coupled-pair functional electronic structure methods have been used in conjunction with very large correlation-consistent basis sets, including diffuse functions. Extrapolation to the one-particle basis set limit was performed and core correlation and scalar relativistic contributions were included directly, while the diagonal Born-Oppenheimer correction was added. Our best purely ab initio PES, denoted "mixed," is constructed from two PESs which differ in whether the ic-ACPF higher-order correlation correction was added or not. Rovibrational transition energies computed from the mixed PES agree well with experiment and the best previous theoretical studies, but most importantly the quality does not deteriorate even up to 10300cm-1 above the zero-point energy (ZPE). The mixed PES was improved further by empirical refinement using the most reliable J =0-2 rovibrational transitions in the HITRAN 2004 database. Agreement between high-resolution experiment and rovibrational transition energies computed from our refined PES for J =0-6 is excellent. Indeed, the root mean square (rms) error for 13 HITRAN 2004 bands for J =0-2 is 0.023cm-1 and that for each band is always ⩽0.06cm-1. For J =3-5 the rms error is always ⩽0.15cm-1. This agreement means that transition energies computed with our refined PES should be useful in the assignment of new high-resolution NH3 spectra and in correcting mistakes in previous assignments. Ideas for further improvements to our refined PES and for extension to other isotopolog are discussed.

  4. Absolute flux measurements for swift atoms

    NASA Technical Reports Server (NTRS)

    Fink, M.; Kohl, D. A.; Keto, J. W.; Antoniewicz, P.

    1987-01-01

    While a torsion balance in vacuum can easily measure the momentum transfer from a gas beam impinging on a surface attached to the balance, this measurement depends on the accommodation coefficients of the atoms with the surface and the distribution of the recoil. A torsion balance is described for making absolute flux measurements independent of recoil effects. The torsion balance is a conventional taut suspension wire design and the Young modulus of the wire determines the relationship between the displacement and the applied torque. A compensating magnetic field is applied to maintain zero displacement and provide critical damping. The unique feature is to couple the impinging gas beam to the torsion balance via a Wood's horn, i.e., a thin wall tube with a gradual 90 deg bend. Just as light is trapped in a Wood's horn by specular reflection from the curved surfaces, the gas beam diffuses through the tube. Instead of trapping the beam, the end of the tube is open so that the atoms exit the tube at 90 deg to their original direction. Therefore, all of the forward momentum of the gas beam is transferred to the torsion balance independent of the angle of reflection from the surfaces inside the tube.

  5. Exploring the free energy surface using ab initio molecular dynamics

    DOE PAGES

    Samanta, Amit; Morales, Miguel A.; Schwegler, Eric

    2016-04-22

    Efficient exploration of the configuration space and identification of metastable structures are challenging from both computational as well as algorithmic perspectives. Here, we extend the recently proposed orderparameter aided temperature accelerated sampling schemes to efficiently and systematically explore free energy surfaces, and search for metastable states and reaction pathways within the framework of density functional theory based molecular dynamics. The sampling method is applied to explore the relevant parts of the configuration space in prototypical materials SiO2 and Ti to identify the different metastable structures corresponding to different phases in these materials. In addition, we use the string method inmore » collective variables to study the melting pathways in the high pressure cotunnite phase of SiO2 and the hcp to fcc phase transition in Ti.« less

  6. Nuclear momentum distribution and potential energy surface in hexagonal ice

    NASA Astrophysics Data System (ADS)

    Lin, Lin; Morrone, Joseph; Car, Roberto; Parrinello, Michele

    2011-03-01

    The proton momentum distribution in ice Ih has been recently measured by deep inelastic neutron scattering and calculated from open path integral Car-Parrinello simulation. Here we report a detailed investigation of the relation between momentum distribution and potential energy surface based on both experiment and simulation results. The potential experienced by the proton is largely harmonic and characterized by 3 principal frequencies, which can be associated to weighted averages of phonon frequencies via lattice dynamics calculations. This approach also allows us to examine the importance of quantum effects on the dynamics of the oxygen nuclei close to the melting temperature. Finally we quantify the anharmonicity that is present in the potential acting on the protons. This work is supported by NSF and by DOE.

  7. Improved DFT Potential Energy Surfaces via Improved Densities.

    PubMed

    Kim, Min-Cheol; Park, Hansol; Son, Suyeon; Sim, Eunji; Burke, Kieron

    2015-10-01

    Density-corrected DFT is a method that cures several failures of self-consistent semilocal DFT calculations by using a more accurate density instead. A novel procedure employs the Hartree-Fock density to bonds that are more severely stretched than ever before. This substantially increases the range of accurate potential energy surfaces obtainable from semilocal DFT for many heteronuclear molecules. We show that this works for both neutral and charged molecules. We explain why and explore more difficult cases, for example, CH(+), where density-corrected DFT results are even better than sophisticated methods like CCSD. We give a simple criterion for when DC-DFT should be more accurate than self-consistent DFT that can be applied for most cases. PMID:26722874

  8. Computed Potential Energy Surfaces and Minimum Energy Pathways for Chemical Reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Langhoff, S. R. (Technical Monitor)

    1994-01-01

    Computed potential energy surfaces are often required for computation of such parameters as rate constants as a function of temperature, product branching ratios, and other detailed properties. For some dynamics methods, global potential energy surfaces are required. In this case, it is necessary to obtain the energy at a complete sampling of all the possible arrangements of the nuclei, which are energetically accessible, and then a fitting function must be obtained to interpolate between the computed points. In other cases, characterization of the stationary points and the reaction pathway connecting them is sufficient. These properties may be readily obtained using analytical derivative methods. We have found that computation of the stationary points/reaction pathways using CASSCF/derivative methods, followed by use of the internally contracted CI method to obtain accurate energetics, gives usefull results for a number of chemically important systems. The talk will focus on a number of applications including global potential energy surfaces, H + O2, H + N2, O(3p) + H2, and reaction pathways for complex reactions, including reactions leading to NO and soot formation in hydrocarbon combustion.

  9. Satellite remote sensing of surface energy balance - Success, failures, and unresolved issues in FIFE

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G.; Huemmrich, Karl F.; Goetz, Scott J.; Sellers, Piers J.; Nickeson, Jaime E.

    1992-01-01

    Utilizing single-view-angle visible and NIR satellite observations, it was possible to make the necessary radiometric corrections to produce reliable estimates of the simple ratio and the normalized difference vegetation index as inputs to surface evaporation models. Agreement was achieved between helicopter and satellite measures of surface reflectance to within +/-1 percent absolute for both the visible and the NIR bands. A theoretical calculation utilizing radiative transfer models indicates that this translates into a +/-10 percent error in the estimation in Fpar.

  10. Satellite remote sensing of surface energy balance - Success, failures, and unresolved issues in FIFE

    SciTech Connect

    Hall, F.G.; Huemmrich, K.F.; Goetz, S.J.; Sellers, P.J.; Nickeson, J.E. )

    1992-11-01

    Utilizing single-view-angle visible and NIR satellite observations, it was possible to make the necessary radiometric corrections to produce reliable estimates of the simple ratio and the normalized difference vegetation index as inputs to surface evaporation models. Agreement was achieved between helicopter and satellite measures of surface reflectance to within +/-1 percent absolute for both the visible and the NIR bands. A theoretical calculation utilizing radiative transfer models indicates that this translates into a +/-10 percent error in the estimation in Fpar. 56 refs.

  11. Mimicking enzymatic active sites on surfaces for energy conversion chemistry.

    PubMed

    Gutzler, Rico; Stepanow, Sebastian; Grumelli, Doris; Lingenfelder, Magalí; Kern, Klaus

    2015-07-21

    centers are adequately separated by the linking molecules and constitute promising candiates for heterogeneous catalysts. Recent advances in synthesis, characterization, and catalytic performance of metal-organic networks are highlighted in this Account. Experimental results like structure determination of the networks, charge and spin distribution in the metal centers, and catalytic mechanisms for electrochemical reactions are presented. In particular, we describe the activity of two networks for the oxygen reduction reaction in a combined scanning tunneling microscopy and electrochemical study. The similarities and differences of the networks compared to metallo-enzymes will be discussed, such as the metal surface that operates as a geometric template and concomitantly functions as an electron reservoir, and how this leads to a new class of bioinspired catalysts. The possibility to create functional two-dimensional coordination complexes at surfaces taking inspiration from nature opens up a new route for the design of potent nanocatalyst materials for energy conversion.

  12. Absolute geostrophic currents in global tropical oceans

    NASA Astrophysics Data System (ADS)

    Yang, Lina; Yuan, Dongliang

    2016-11-01

    A set of absolute geostrophic current (AGC) data for the period January 2004 to December 2012 are calculated using the P-vector method based on monthly gridded Argo profiles in the world tropical oceans. The AGCs agree well with altimeter geostrophic currents, Ocean Surface Current Analysis-Real time currents, and moored current-meter measurements at 10-m depth, based on which the classical Sverdrup circulation theory is evaluated. Calculations have shown that errors of wind stress calculation, AGC transport, and depth ranges of vertical integration cannot explain non-Sverdrup transport, which is mainly in the subtropical western ocean basins and equatorial currents near the Equator in each ocean basin (except the North Indian Ocean, where the circulation is dominated by monsoons). The identified non-Sverdrup transport is thereby robust and attributed to the joint effect of baroclinicity and relief of the bottom (JEBAR) and mesoscale eddy nonlinearity.

  13. The puckering free-energy surface of proline

    NASA Astrophysics Data System (ADS)

    Wu, Di

    2013-03-01

    Proline has two preferred puckering states, which are often characterized by the pseudorotation phase angle and amplitude. Although proline's five endocyclic torsion angles can be utilized to calculate the phase angle and amplitude, it is not clear if there is any direct correlation between each torsion angle and the proline-puckering pathway. Here we have designed five proline puckering pathways utilizing each torsion angle χj (j = 1˜5) as the reaction coordinate. By examining the free-energy surfaces of the five puckering pathways, we find they can be categorized into two groups. The χ2 pathway (χ2 is about the Cβ—Cγ bond) is especially meaningful in describing proline puckering: it changes linearly with the puckering amplitude and symmetrically with the phase angle. Our results show that this conclusion applies to both trans and cis proline conformations. We have also analyzed the correlations of proline puckering and its backbone torsion angles ϕ and ψ. We show proline has preferred puckering states at the specific regions of ϕ, ψ angles. Interestingly, the shapes of ψ-χ2 free-energy surfaces are similar among the trans proline in water, cis proline in water and cis proline in the gas phase, but they differ substantially from that of the trans proline in the gas phase. Our calculations are conducted using molecular simulations; we also verify our results using the proline conformations selected from the Protein Data Bank. In addition, we have compared our results with those calculated by the quantum mechanical methods.

  14. Converting chemical energy into electricity through a functionally cooperating device with diving-surfacing cycles.

    PubMed

    Song, Mengmeng; Cheng, Mengjiao; Ju, Guannan; Zhang, Yajun; Shi, Feng

    2014-11-01

    A smart device that can dive or surface in aqueous medium has been developed by combining a pH-responsive surface with acid-responsive magnesium. The diving-surfacing cycles can be used to convert chemical energy into electricity. During the diving-surfacing motion, the smart device cuts magnetic flux lines and produces a current, demonstrating that motional energy can be realized by consuming chemical energy of magnesium, thus producing electricity. PMID:25146589

  15. Converting chemical energy into electricity through a functionally cooperating device with diving-surfacing cycles.

    PubMed

    Song, Mengmeng; Cheng, Mengjiao; Ju, Guannan; Zhang, Yajun; Shi, Feng

    2014-11-01

    A smart device that can dive or surface in aqueous medium has been developed by combining a pH-responsive surface with acid-responsive magnesium. The diving-surfacing cycles can be used to convert chemical energy into electricity. During the diving-surfacing motion, the smart device cuts magnetic flux lines and produces a current, demonstrating that motional energy can be realized by consuming chemical energy of magnesium, thus producing electricity.

  16. Numerical values of the surface free energies of solid chemical elements

    NASA Astrophysics Data System (ADS)

    Mezey, L. Z.; Giber, J.

    1984-10-01

    The applicability of a 'standard table' of values of surface free energies (or enthalpies) obtained by the CCSS (complex calculation of surface segregation) method is demonstrated by comparing calculated surface-free-energy values with several recently published experimental results. The investigation (encompassing temperatures from 1023 to 2075 K) shows that a simplified variation of the second step of CCSS is applicable in the calculation of the surface free energies of polycrystalline solid elements for any temperature of interest.

  17. Efficient characterization of stationary points on potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Deglmann, Peter; Furche, Filipp

    2002-12-01

    Traditional methods for characterizing an optimized molecular structure as a minimum or as a saddle point on the nuclear potential energy surface require the full Hessian. However, if f denotes the number of nuclear degrees of freedom, a full Hessian calculation is more expensive than a single point geometry optimization step by the order of magnitude of f. Here we present a method which allows to determine the lowest vibrational frequencies of a molecule at significantly lower cost. Our approach takes advantage of the fact that only a few perturbed first-order wave functions need to be computed in an iterative diagonalization scheme instead of f ones in a full Hessian calculation. We outline an implementation for Hartree-Fock and density functional methods. Applications indicate a scaling similar to that of a single point energy or gradient calculation, but with a larger prefactor. Depending on the number of soft vibrational modes, the iterative method becomes effective for systems with more than 30-50 atoms.

  18. Energy regimes for aeolian sand grain surface textures

    NASA Astrophysics Data System (ADS)

    Marshall, J. R.; Bull, P. A.; Morgan, R. M.

    2012-05-01

    An experimental study of aeolian sand grain surface texture development was undertaken with an air-driven grain-recirculating desktop apparatus. Scanning electron microscope analysis of resulting textures indicated that different texture types can be associated with distinct zones in a grain-shape/grain speed matrix. In particular, for subrounded and rounded grains, low and high energy transport can be unequivocally distinguished by the occurrence of upturned plates and Hertzian frustra respectively. Textural development does not have a simple relationship to grain velocity, but appears to relate to the energy expended per unit area within the contact zone generated by elastic deformation during impact. Hertzian theory was adapted to irregular sand grain shapes and close agreement was found between experimental results and theoretical predictions for textural development. Results of this study improve our ability to reconstruct palaeoaeolian environments and therefore our ability to determine grain provenance; in particular, the latter is shown to have direct relevance to forensic inquiries and terrorism investigations.

  19. An Accurate Potential Energy Surface for H2O

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Partridge, Harry; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    We have carried out extensive high quality ab initio electronic structure calculations of the ground state potential energy surface (PES) and dipole moment function (DMF) for H2O. A small adjustment is made to the PES to improve the agreement of line positions from theory and experiment. The theoretical line positions are obtained from variational ro-vibrational calculations using the exact kinetic energy operator. For the lines being fitted, the root-mean-square error was reduced from 6.9 to 0.08 /cm. We were then able to match 30,092 of the 30,117 lines from the HITRAN 96 data base to theoretical lines, and 80% of the line positions differed less than 0.1 /cm. About 3% of the line positions in the experimental data base appear to be incorrect. Theory predicts the existence of many additional weak lines with intensities above the cutoff used in the data base. To obtain results of similar accuracy for HDO, a mass dependent correction to the PH is introduced and is parameterized by simultaneously fitting line positions for HDO and D2O. The mass dependent PH has good predictive value for T2O and HTO. Nonadiabatic effects are not explicitly included. Line strengths for vibrational bands summed over rotational levels usually agree well between theory and experiment, but individual line strengths can differ greatly. A high temperature line list containing about 380 million lines has been generated using the present PES and DMF

  20. Crystallization of glass-forming liquids: Specific surface energy

    NASA Astrophysics Data System (ADS)

    Schmelzer, Jürn W. P.; Abyzov, Alexander S.

    2016-08-01

    A generalization of the Stefan-Skapski-Turnbull relation for the melt-crystal specific interfacial energy is developed in terms of the generalized Gibbs approach extending its standard formulation to thermodynamic non-equilibrium states. With respect to crystal nucleation, this relation is required in order to determine the parameters of the critical crystal clusters being a prerequisite for the computation of the work of critical cluster formation. As one of its consequences, a relation for the dependence of the specific surface energy of critical clusters on temperature and pressure is derived applicable for small and moderate deviations from liquid-crystal macroscopic equilibrium states. Employing the Stefan-Skapski-Turnbull relation, general expressions for the size and the work of formation of critical crystal clusters are formulated. The resulting expressions are much more complex as compared to the respective relations obtained via the classical Gibbs theory. Latter relations are retained as limiting cases of these more general expressions for moderate undercoolings. By this reason, the formulated, here, general relations for the specification of the critical cluster size and the work of critical cluster formation give a key for an appropriate interpretation of a variety of crystallization phenomena occurring at large undercoolings which cannot be understood in terms of the Gibbs' classical treatment.

  1. Microscopically derived potential energy surfaces from mostly structural considerations

    NASA Astrophysics Data System (ADS)

    Ermamatov, M. J.; Hess, Peter O.

    2016-08-01

    A simple procedure to estimate the quadrupole Potential-Energy-Surface (PES) is presented, using mainly structural information, namely the content of the shell model space and the Pauli exclusion principle. Further microscopic properties are implicitly contained through the use of results from the Möller and Nix tables or experimental information. A mapping to the geometric potential is performed yielding the PES. The General Collective Model is used in order to obtain an estimate on the spectrum and quadrupole transitions, adjusting only the mass parameter. First, we test the conjecture on known nuclei, deriving the PES and compare them to known data. We will see that the PES approximates very well the structure expected. Having acquired a certain confidence, we predict the PES of several chain of isotopes of heavy and super-heavy nuclei and at the end we investigate the structure of nuclei in the supposed island of stability. One of the main points to show is that simple assumptions can provide already important information on the structure of nuclei outside known regions and that spectra and electromagnetic transitions can be estimated without using involved calculations and assumptions. The procedure does not allow to calculate binding energies. The method presented can be viewed as a starting point for further improvements.

  2. Reaction profiles and energy surfaces of compressed species.

    PubMed

    Spooner, Jacob; Yanciw, Brandon; Wiebe, Brandon; Weinberg, Noham

    2014-01-30

    Both experiment and first principles calculations unequivocally indicate that properties of elements and their compounds undergo a tremendous transformation at ultrahigh pressures exceeding 1 Mbar due to the fact that the difference between intra- and intermolecular interactions disappears under such conditions. Yet, even at much milder pressures of 50-300 kbar, when molecules still retain their individual identity, their chemical properties and reactivity change dramatically. Since kinetics and mechanisms of condensed-phase reactions are described in terms of their potential energy (PES) or Gibbs energy (GES) surfaces, chemical effects of high pressure can be assessed through analysis of pressure-induced deformations of GES of solvated reaction systems. We use quantum mechanical and molecular dynamics simulations to construct GES and reaction profiles of compressed species, and analyze how topography of GES changes in response to compression. We also discuss the important role of volume profiles in assessing pressure-induced deformations and show that the high-pressure GES are well described in terms of these volume profiles and the reference zero-pressure GES.

  3. Apparatus for absolute pressure measurement

    NASA Technical Reports Server (NTRS)

    Hecht, R. (Inventor)

    1969-01-01

    An absolute pressure sensor (e.g., the diaphragm of a capacitance manometer) was subjected to a superimposed potential to effectively reduce the mechanical stiffness of the sensor. This substantially increases the sensitivity of the sensor and is particularly useful in vacuum gauges. An oscillating component of the superimposed potential induced vibrations of the sensor. The phase of these vibrations with respect to that of the oscillating component was monitored, and served to initiate an automatic adjustment of the static component of the superimposed potential, so as to bring the sensor into resonance at the frequency of the oscillating component. This establishes a selected sensitivity for the sensor, since a definite relationship exists between resonant frequency and sensitivity.

  4. Absolute Measurement of Electron Cloud Density

    SciTech Connect

    Covo, M K; Molvik, A W; Cohen, R H; Friedman, A; Seidl, P A; Logan, G; Bieniosek, F; Baca, D; Vay, J; Orlando, E; Vujic, J L

    2007-06-21

    Beam interaction with background gas and walls produces ubiquitous clouds of stray electrons that frequently limit the performance of particle accelerator and storage rings. Counterintuitively we obtained the electron cloud accumulation by measuring the expelled ions that are originated from the beam-background gas interaction, rather than by measuring electrons that reach the walls. The kinetic ion energy measured with a retarding field analyzer (RFA) maps the depressed beam space-charge potential and provides the dynamic electron cloud density. Clearing electrode current measurements give the static electron cloud background that complements and corroborates with the RFA measurements, providing an absolute measurement of electron cloud density during a 5 {micro}s duration beam pulse in a drift region of the magnetic transport section of the High-Current Experiment (HCX) at LBNL.

  5. Rotational Energy Transfer of N2 Determined Using a New Ab Initio Potential Energy Surface

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Stallcop, James R.; Partridge, Harry; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    A new N2-N2 rigid-rotor surface has been determined using extensive Ab Initio quantum chemistry calculations together with recent experimental data for the second virial coefficient. Rotational energy transfer is studied using the new potential energy surface (PES) employing the close coupling method below 200 cm(exp -1) and coupled state approximation above that. Comparing with a previous calculation based on the PES of van der Avoird et al.,3 it is found that the new PES generally gives larger cross sections for large (delta)J transitions, but for small (delta)J transitions the cross sections are either comparable or smaller. Correlation between the differences in the cross sections and the two PES will be attempted. The computed cross sections will also be compared with available experimental data.

  6. Effects of surface and interface energies on the bending behavior of nanoscale multilayered beams

    NASA Astrophysics Data System (ADS)

    Wang, K. F.; Wang, B. L.

    2013-12-01

    A modified continuum model of the nanoscale multilayered beams is established by incorporating surface and interface energies. Through the principle of minimum potential energy, the governing equations and boundary conditions are obtained. The closed-form solutions are presented and the overall Young's modulus of the beam is studied. The surface and interface energies are found to have a major influence on the bending behavior and the overall Young's modulus of the beam. The effect of surface and interface energies on the overall Young's modulus depends on the boundary condition of the beam, the values of the surface/interface elasticity constants and the initial surface/interface energy of the system. The results can be used to guide the determinations of the surface/interface elasticity properties and the initial surface/interface energies of the nanoscale multilayered materials through nanoscale beam bending experiments.

  7. Anisotropy analysis of the surface energy of hcp ( c/ a < 1.633) metals

    NASA Astrophysics Data System (ADS)

    Wang, Dou-Dou; Zhang, Jian-Min; Xu, Ke-Wei

    2006-08-01

    In this paper, anisotropy of the surface energy of 5 hcp metals Be, Hf, Ru, Ti and Y have been analyzed. The surface energies of three kinds of representative surfaces, ( h 0 l), ( h h l) and ( h k 0) belong to [0 1 0], [ 1 1¯ 0] and [0 0 1] crystal band, respectively, have been calculated using the modified embedded atom method. For all 5 hcp metals, the (1 1 0) plane has the minimum surface energy in all 35 surfaces studied. Considering surface energy minimization solely, the (1 1 0) texture should be favorable in the hcp films. The fact that the short termination corresponds to much lower surface energy than long one implies the former is more stable for those surfaces having two possible terminations. Such as the prism plane (1 0 0), only the short termination was observed in experiment.

  8. Quantifying Surface Energy Flux Estimation Uncertainty Using Land Surface Temperature Observations

    NASA Astrophysics Data System (ADS)

    French, A. N.; Hunsaker, D.; Thorp, K.; Bronson, K. F.

    2015-12-01

    Remote sensing with thermal infrared is widely recognized as good way to estimate surface heat fluxes, map crop water use, and detect water-stressed vegetation. When combined with net radiation and soil heat flux data, observations of sensible heat fluxes derived from surface temperatures (LST) are indicative of instantaneous evapotranspiration (ET). There are, however, substantial reasons LST data may not provide the best way to estimate of ET. For example, it is well known that observations and models of LST, air temperature, or estimates of transport resistances may be so inaccurate that physically based model nevertheless yield non-meaningful results. Furthermore, using visible and near infrared remote sensing observations collected at the same time as LST often yield physically plausible results because they are constrained by less dynamic surface conditions such as green fractional cover. Although sensitivity studies exist that help identify likely sources of error and uncertainty, ET studies typically do not provide a way to assess the relative importance of modeling ET with and without LST inputs. To better quantify model benefits and degradations due to LST observational inaccuracies, a Bayesian uncertainty study was undertaken using data collected in remote sensing experiments at Maricopa, Arizona. Visible, near infrared and thermal infrared data were obtained from an airborne platform. The prior probability distribution of ET estimates were modeled using fractional cover, local weather data and a Penman-Monteith mode, while the likelihood of LST data was modeled from a two-source energy balance model. Thus the posterior probabilities of ET represented the value added by using LST data. Results from an ET study over cotton grown in 2014 and 2015 showed significantly reduced ET confidence intervals when LST data were incorporated.

  9. Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The recent paper by Morillas et al. [Morillas, L. et al. Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective, Remote Sens. Environ. 136, 234-246, 2013] evaluates the two-source model (TSM) of Norman et al. (1995) with revi...

  10. Energy spectrum measured by the telescope array surface detector

    NASA Astrophysics Data System (ADS)

    Ivanov, Dmitri

    2012-05-01

    Two conflicting measurements of the ultra high energy cosmic ray (UHECR) flux have been reported by the Akeno Giant Air Shower Array (AGASA) and the High Resolution Fly's Eye (HiRes) experiments. HiRes observes a ˜5sigma suppression at E = 1019.75 eV, which is in agreement with the prediction of Greisen-Zatsepin-Kuz'min (GZK) theory. AGASA, in contrast, sees the flux extended well beyond E = 1020 eV with no visible break, suggesting that the flux is limited only by the rate at which the sources can produce the UHECR and not by interaction of energetic particles with the cosmic microwave background, thus challenging the relativistic invariance principle. In response to this discrepancy, a new experiment named the Telescope Array (TA) has been deployed, which combines the detection elements used separately by HiRes and AGASA. We describe the TA surface detector (SD) analysis using a technique new to the field, which consists of a detailed Monte-Carlo (MC) simulation of the SD response to the natural cosmic rays, validating the MC by comparing its distributions with the data, and calculation of the SD aperture from the MC. We will also describe our reconstruction procedure, based solely upon the data, and its application to both data and the MC. Finally, we will describe the energy spectrum resulting from this analysis, which is found to be in excellent agreement with the HiRes result, and as such, is the first confirmation of the GZK effect by a ground array of scintillation counters.

  11. From Hubble's Next Generation Spectral Library (NGSL) to Absolute Fluxes

    NASA Astrophysics Data System (ADS)

    Heap, S. R.; Lindler, D.

    2016-05-01

    Hubble's Next Generation Spectral Library (NGSL) consists of R˜1000 spectra of 374 stars of assorted temperature, gravity, and metallicity. Each spectrum covers the wavelength range, 0.18-1.03 μ. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsl/. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We have therefore developed an observing procedure, data-reduction procedure, and correction algorithms that should yield fluxes with uncertainties less than 1%.

  12. Gyrokinetic Statistical Absolute Equilibrium and Turbulence

    SciTech Connect

    Jian-Zhou Zhu and Gregory W. Hammett

    2011-01-10

    A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence [T.-D. Lee, "On some statistical properties of hydrodynamical and magnetohydrodynamical fields," Q. Appl. Math. 10, 69 (1952)] is taken to study gyrokinetic plasma turbulence: A finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N + 1 quantities are conserved, corresponding to an energy invariant and N entropy-related invariants), the negative temperature states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.

  13. Surface free energy of polyurethane coatings with improved hydrophobicity.

    PubMed

    Król, Piotr; Król, Bożena

    2012-07-01

    The polarity of polyurethane coats was studied on the basis of the goniometric method for determination of wetting angle values, on the basis of calculated surface free energy (SFE) values by the van Oss-Good and Owens-Wendt methods, and on the basis of polarity measurements with the use of the (1)H NMR spectra. Test polyurethanes were synthesised in the reaction of methylene diphenyl 4,4'-diisocyanate (MDI) or 3-izocyanatomethyl -3,5,5- trimethylcyclohexyl isocyanate (IPDI) and polyoxyethylene glycols or polyesters poly(ε-caprolactone) diols and poly(ethyleneadipate) diol with different molecular weights, and some diols as chain extenders, in dioxane. The type of raw material was found to significantly affect the phase structure of the obtained polyurethane elastomers and to control physical interactions within those structures, thus influencing the SFE values. Fundamental reduction in the SFE value of a coating below 28 mJ/m(2) was achieved by the use of 2,2,3,3-tetrafluoro-1,4-butanediol as the urethane prepolymer chain extender.

  14. Statistical Evaluation of the Performance of Energy Surface Search Algorithms

    NASA Astrophysics Data System (ADS)

    Horoi, Mihai; Jackson, Koblar A.

    2001-03-01

    In the last few years several new energy surface search algorithms have been proposed, including Genetic Algorithms (GA), Basin-Hopping Monte Carlo, and a single parent GA (see I. Rata, et al., Phys. Rev. Lett. 85, 546(2000)). Each time a new algorithm was presented, the authors claimed better performance by finding lower minima for previously studied clusters. However, it was not clear if the better result was a consequence of a better algorithm or due to more patience in searching the configuration space. We have done a statistical evaluation of all these algorithms and find that the distribution of the number of search steps required to locate the global minimum from a random starting point is an exponential for each method, with the average equal to the variance. This behavior is a result of the random steps made by each method in searching the configuration space. Understanding the nature of the distribution allows the performance of the methods to be compared statistically and suggests possible improvements. We also show that in some cases (small clusters with Lennard-Jones interactions) a completely random search starting in a "small" box can be more efficient than any of the more complex algorithms.

  15. Experimental study of breaking and energy dissipation in surface waves

    NASA Astrophysics Data System (ADS)

    Ruiz Chavarria, Gerardo; Le Gal, Patrice; Le Bars, Michael

    2014-11-01

    We present an experimental study of the evolution of monochromatic waves produced by a parabolic wave maker. Because of the parabolic shape of the wave front, the waves exhibit spatial focusing and their amplitude dramatically increases over distances of a few wavelengths. Unlike linear waves, the amplitude of the free surface deformation cannot exceed a certain threshold and when this happens the waves break. In order to give a criterion for the appearance of breaking, we calculate the steepness defined as ɛ = H/ λ (where H is the wave height and λ their wavelength) for waves of frequencies in the range 4-10 Hz. We found that wave breaking develops when ɛ attains approximately a value of 0.10. We also evaluate the lost of energy carried by the waves during their breaking by a detailed and accurate measurement of their amplitude using an optical Fourier transform profilometry. G. Ruiz Chavarria acknowledges DGAPA-UNAM by support under Project IN 116312 (Vorticidad y ondas no lineales en fluidos).

  16. Surface free energy activated high-throughput cell sorting.

    PubMed

    Zhang, Xinru; Zhang, Qian; Yan, Tao; Jiang, Zeyi; Zhang, Xinxin; Zuo, Yi Y

    2014-09-16

    Cell sorting is an important screening process in microbiology, biotechnology, and clinical research. Existing methods are mainly based on single-cell analysis as in flow cytometric and microfluidic cell sorters. Here we report a label-free bulk method for sorting cells by differentiating their characteristic surface free energies (SFEs). We demonstrated the feasibility of this method by sorting model binary cell mixtures of various bacterial species, including Pseudomonas putida KT2440, Enterococcus faecalis ATCC 29212, Salmonella Typhimurium ATCC 14028, and Escherichia coli DH5α. This method can effectively separate 10(10) bacterial cells within 30 min. Individual bacterial species can be sorted with up to 96% efficiency, and the cell viability ratio can be as high as 99%. In addition to its capacity of sorting evenly mixed bacterial cells, we demonstrated the feasibility of this method in selecting and enriching cells of minor populations in the mixture (presenting at only 1% in quantity) to a purity as high as 99%. This SFE-activated method may be used as a stand-alone method for quickly sorting a large quantity of bacterial cells or as a prescreening tool for microbial discrimination. Given its advantages of label-free, high-throughput, low cost, and simplicity, this SFE-activated cell sorting method has potential in various applications of sorting cells and abiotic particles. PMID:25184988

  17. Low energy electron elastic reflection from solid surfaces

    NASA Astrophysics Data System (ADS)

    Starý, Vladimír.; Zemek, Josef

    2004-09-01

    Using our Monte-Carlo (MC) code, we calculated the ratio of the coefficients of elastic reflection of electrons from Si, SiO 2 and Au to those of Cu and Al in the electron energy range 0.2-1.0 and 1.5 keV (Au-Cu), respectively. The electron scattering was simulated by a single scattering model. For the MC calculations, we compared the elastic differential cross-sections calculated using a static field approximation with relativistic partial wave analysis on either the Thomas-Fermi-Dirac potential of free atoms (TFD model) or the Hartree-Fock-Wigner-Seitz (muffin-tin) potential of atoms in the solid state (HFWS model). The MC data were compared with the experimental values. For both models, reasonably good agreement for Si-Cu and SiO 2-Cu systems was found. In the Au-Cu system, better agreement was achieved using the TFD model. The addition of C in a surface interaction layer of 2-5 nm improves the agreement between simulated and experimental values for the Si-Al and Si-SiO 2 systems.

  18. Exploring the free energy surface using ab initio molecular dynamics.

    PubMed

    Samanta, Amit; Morales, Miguel A; Schwegler, Eric

    2016-04-28

    Efficient exploration of configuration space and identification of metastable structures in condensed phase systems are challenging from both computational and algorithmic perspectives. In this regard, schemes that utilize a set of pre-defined order parameters to sample the relevant parts of the configuration space [L. Maragliano and E. Vanden-Eijnden, Chem. Phys. Lett. 426, 168 (2006); J. B. Abrams and M. E. Tuckerman, J. Phys. Chem. B 112, 15742 (2008)] have proved useful. Here, we demonstrate how these order-parameter aided temperature accelerated sampling schemes can be used within the Born-Oppenheimer and the Car-Parrinello frameworks of ab initio molecular dynamics to efficiently and systematically explore free energy surfaces, and search for metastable states and reaction pathways. We have used these methods to identify the metastable structures and reaction pathways in SiO2 and Ti. In addition, we have used the string method [W. E, W. Ren, and E. Vanden-Eijnden, Phys. Rev. B 66, 052301 (2002); L. Maragliano et al., J. Chem. Phys. 125, 024106 (2006)] within the density functional theory to study the melting pathways in the high pressure cotunnite phase of SiO2 and the hexagonal closed packed to face centered cubic phase transition in Ti. PMID:27131525

  19. Absolute configuration of isovouacapenol C

    PubMed Central

    Fun, Hoong-Kun; Yodsaoue, Orapun; Karalai, Chatchanok; Chantrapromma, Suchada

    2010-01-01

    The title compound, C27H34O5 {systematic name: (4aR,5R,6R,6aS,7R,11aS,11bR)-4a,6-dihy­droxy-4,4,7,11b-tetra­methyl-1,2,3,4,4a,5,6,6a,7,11,11a,11b-dodeca­hydro­phenanthro[3,2-b]furan-5-yl benzoate}, is a cassane furan­oditerpene, which was isolated from the roots of Caesalpinia pulcherrima. The three cyclo­hexane rings are trans fused: two of these are in chair conformations with the third in a twisted half-chair conformation, whereas the furan ring is almost planar (r.m.s. deviation = 0.003 Å). An intra­molecular C—H⋯O inter­action generates an S(6) ring. The absolute configurations of the stereogenic centres at positions 4a, 5, 6, 6a, 7, 11a and 11b are R, R, R, S, R, S and R, respectively. In the crystal, mol­ecules are linked into infinite chains along [010] by O—H⋯O hydrogen bonds. C⋯O [3.306 (2)–3.347 (2) Å] short contacts and C—H⋯π inter­actions also occur. PMID:21588364

  20. Energy loss of ions at metal surfaces: Band-structure effects

    SciTech Connect

    Alducin, M.; Silkin, V.M.; Juaristi, J.I.; Chulkov, E.V.

    2003-03-01

    We study band-structure effects on the energy loss of protons scattered off the Cu (111) surface. The distance dependent stopping power for a projectile traveling parallel to the surface is calculated within the linear response theory. The self-consistent electronic response of the system is evaluated within the random-phase approximation. In order to characterize the surface band structure, the electronic single-particle wave functions and energies are obtained by solving the Schroedinger equation with a realistic one-dimensional model potential. This potential reproduces the main features of the Cu (111) surface: the energy band gap for electron motion along the surface normal, as well as the binding energy of the occupied surface state and the first image state. Comparison of our results with those obtained within the jellium model allows us to characterize the band-structure effects in the energy loss of protons interacting with the Cu (111) surface.

  1. Mini-implants and miniplates generate sub-absolute and absolute anchorage

    PubMed Central

    Consolaro, Alberto

    2014-01-01

    The functional demand imposed on bone promotes changes in the spatial properties of osteocytes as well as in their extensions uniformly distributed throughout the mineralized surface. Once spatial deformation is established, osteocytes create the need for structural adaptations that result in bone formation and resorption that happen to meet the functional demands. The endosteum and the periosteum are the effectors responsible for stimulating adaptive osteocytes in the inner and outer surfaces.Changes in shape, volume and position of the jaws as a result of skeletal correction of the maxilla and mandible require anchorage to allow bone remodeling to redefine morphology, esthetics and function as a result of spatial deformation conducted by orthodontic appliances. Examining the degree of changes in shape, volume and structural relationship of areas where mini-implants and miniplates are placed allows us to classify mini-implants as devices of subabsolute anchorage and miniplates as devices of absolute anchorage. PMID:25162561

  2. Multilayer Relaxation and Surface Energies of FCC and BCC Metals Using Equivalent Crystal Theory

    NASA Technical Reports Server (NTRS)

    Rodriguez, Agustin M.; Bozzolo, Guillermo; Ferrante, John

    1993-01-01

    The multilayer relaxation of fcc and bcc metal surfaces is calculated using equivalent crystal theory. The results for changes in interplanar spacings of planes close to the surface and the ensuing surface energies are discussed in reference to other theoretical results and compared to available experimental data. The calculation includes high-index surfaces for which no other theoretical results are known.

  3. Frequency-domain analysis of absolute gravimeters

    NASA Astrophysics Data System (ADS)

    Svitlov, S.

    2012-12-01

    An absolute gravimeter is analysed as a linear time-invariant system in the frequency domain. Frequency responses of absolute gravimeters are derived analytically based on the propagation of the complex exponential signal through their linear measurement functions. Depending on the model of motion and the number of time-distance coordinates, an absolute gravimeter is considered as a second-order (three-level scheme) or third-order (multiple-level scheme) low-pass filter. It is shown that the behaviour of an atom absolute gravimeter in the frequency domain corresponds to that of the three-level corner-cube absolute gravimeter. Theoretical results are applied for evaluation of random and systematic measurement errors and optimization of an experiment. The developed theory agrees with known results of an absolute gravimeter analysis in the time and frequency domains and can be used for measurement uncertainty analyses, building of vibration-isolation systems and synthesis of digital filtering algorithms.

  4. Energy Saving Melting and Revert Reduction Technology (Energy-SMARRT): Surface/Near Surface Indication - Characterization of Surface Anomalies from Magnetic Particle and Liquid Penetrant Indications

    SciTech Connect

    Griffin, John

    2014-02-20

    The systematic study and characterization of surface indications has never been conducted. Producers and users of castings do not have any data on which they can reliably communicate the nature of these indications or their effect on the performance of parts. Clearly, the ultimate intent of any work in this area is to eliminate indications that do in fact degrade properties. However, it may be impractical physically and/or financially to eliminate all surface imperfections. This project focused on the ones that actually degrade properties. The initial work was to identify those that degrade properties. Accurate numerical simulations of casting service performance allow designers to use the geometric flexibility of castings and the superior properties of steel to produce lighter weight and more energy efficient components for transportation systems (cars and trucks), construction, and mining. Accurate simulations increase the net melting energy efficiency by improving casting yield and reducing rework and scrap. Conservatively assuming a 10% improvement in yield, approximately 1.33 x 1012 BTU/year can be saved with this technology. In addition, CO2 emissions will be reduced by approximately 117,050 tons per year.

  5. Technique for the estimation of surface temperatures from embedded temperature sensing for rapid, high energy surface deposition.

    SciTech Connect

    Watkins, Tyson R.; Schunk, Peter Randall; Roberts, Scott Alan

    2014-07-01

    Temperature histories on the surface of a body that has been subjected to a rapid, highenergy surface deposition process can be di cult to determine, especially if it is impossible to directly observe the surface or attach a temperature sensor to it. In this report, we explore two methods for estimating the temperature history of the surface through the use of a sensor embedded within the body very near to the surface. First, the maximum sensor temperature is directly correlated with the peak surface temperature. However, it is observed that the sensor data is both delayed in time and greatly attenuated in magnitude, making this approach unfeasible. Secondly, we propose an algorithm that involves tting the solution to a one-dimensional instantaneous energy solution problem to both the sensor data and to the results of a one-dimensional CVFEM code. This algorithm is shown to be able to estimate the surface temperature 20 C.

  6. Surface energy changes produced by ultraviolet-ozone irradiation of poly(methylmethacrylate), polycarbone and polytetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Ponter, A. B.; Jones, W. R., Jr.; Jansen, R. H.

    1994-01-01

    Contact angles of water and methylene iodide were measured as a function of UV/O3 treatment time for three polymers: poly(methylmethacrylate) (PMMA), polycarbonate, and polytetrafluoroethylene (PTFE). Surface roughnesses were also measured. Surface free energies were then calculated using relationships developed by Kaelble and Neumann. The surface energy of polycarbonate was found to increase (60 percent) during UV/O3 treatment. However, calculations on PMMA were hampered by the formation of a water soluble surface product. On PTFE surfaces, the UV/O3 treatment etched the surface causing large increases in surface roughness, rendering contact angle measurements impossible. It is concluded that care must be taken in interpreting contact angle measurements and surface energy calculations on UV/O3 treated polymer surfaces.

  7. Engineering Surface Energy and Nanostructure of Microporous Films for Expanded Membrane Distillation Applications.

    PubMed

    Boo, Chanhee; Lee, Jongho; Elimelech, Menachem

    2016-08-01

    We investigated the factors that determine surface omniphobicity of microporous membranes and evaluated the potential application of these membranes in desalination of low surface tension wastewaters by membrane distillation (MD). Specifically, the effects of surface morphology and surface energy on membrane surface omniphobicity were systematically investigated by evaluating wetting resistance to low surface tension liquids. Single and multilevel re-entrant structures were achieved by using cylindrical glass fibers as a membrane substrate and grafting silica nanoparticles (SiNPs) on the fibers. Surface energy of the membrane was tuned by functionalizing the fiber substrate with fluoroalkylsilane (FAS) having two different lengths of fluoroalkyl chains. Results show that surface omniphobicity of the modified fibrous membrane increased with higher level of re-entrant structure and with lower surface energy. The secondary re-entrant structure achieved by SiNP coating on the cylindrical fibers was found to play a critical role in enhancing the surface omniphobicity. Membranes coated with SiNPs and chemically modified by the FAS with a longer fluoroalkyl chain (or lower surface energy) exhibited excellent surface omniphobicity and showed wetting resistance to low surface tension liquids such as ethanol (22.1 mN m(-1)). We further evaluated performance of the membranes in desalination of saline feed solutions with varying surface tensions by membrane distillation (MD). The engineered membranes exhibited stable MD performance with low surface tension feed waters, demonstrating the potential application omniphobic membranes in desalinating complex, high salinity industrial wastewaters. PMID:27391088

  8. Engineering Surface Energy and Nanostructure of Microporous Films for Expanded Membrane Distillation Applications.

    PubMed

    Boo, Chanhee; Lee, Jongho; Elimelech, Menachem

    2016-08-01

    We investigated the factors that determine surface omniphobicity of microporous membranes and evaluated the potential application of these membranes in desalination of low surface tension wastewaters by membrane distillation (MD). Specifically, the effects of surface morphology and surface energy on membrane surface omniphobicity were systematically investigated by evaluating wetting resistance to low surface tension liquids. Single and multilevel re-entrant structures were achieved by using cylindrical glass fibers as a membrane substrate and grafting silica nanoparticles (SiNPs) on the fibers. Surface energy of the membrane was tuned by functionalizing the fiber substrate with fluoroalkylsilane (FAS) having two different lengths of fluoroalkyl chains. Results show that surface omniphobicity of the modified fibrous membrane increased with higher level of re-entrant structure and with lower surface energy. The secondary re-entrant structure achieved by SiNP coating on the cylindrical fibers was found to play a critical role in enhancing the surface omniphobicity. Membranes coated with SiNPs and chemically modified by the FAS with a longer fluoroalkyl chain (or lower surface energy) exhibited excellent surface omniphobicity and showed wetting resistance to low surface tension liquids such as ethanol (22.1 mN m(-1)). We further evaluated performance of the membranes in desalination of saline feed solutions with varying surface tensions by membrane distillation (MD). The engineered membranes exhibited stable MD performance with low surface tension feed waters, demonstrating the potential application omniphobic membranes in desalinating complex, high salinity industrial wastewaters.

  9. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    SciTech Connect

    Roberts, J.G.

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  10. Computed Potential Energy Surfaces and Minimum Energy Pathway for Chemical Reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Langhoff, S. R. (Technical Monitor)

    1994-01-01

    Computed potential energy surfaces are often required for computation of such observables as rate constants as a function of temperature, product branching ratios, and other detailed properties. We have found that computation of the stationary points/reaction pathways using CASSCF/derivative methods, followed by use of the internally contracted CI method with the Dunning correlation consistent basis sets to obtain accurate energetics, gives useful results for a number of chemically important systems. Applications to complex reactions leading to NO and soot formation in hydrocarbon combustion are discussed.

  11. Strain energy density and surface layer energy for a crack-like ellipse

    NASA Technical Reports Server (NTRS)

    Kipp, M. E.; Sih, G. C.

    1973-01-01

    Some of the fundamental concepts of sharp crack fracture criteria are applied to cracks and narrow ellipses. The strain energy density theory is extended to notch boundaries, where the energy in a surface layer is calculated and the location of failure initiation is determined. The concept of a core region near the notch tip, and its consequences, are examined in detail. The example treated is that of an elliptical cavity loaded uniformly at a large distance from the hole, and at an angle to the hole; the results are shown to approach that of the crack solution for narrow ellipses, and to display quite satisfactory agreement with recently published experimental data under both tensile and compressive loading conditions. Results also indicate that in globally unstable configurations in brittle materials, the original loading and notch geometry are sufficient to predict the subsequent crack trajectory with considerable accuracy.

  12. Potential energy surface of H2O on Al{111} and Rh{111} from theoretical methods

    NASA Astrophysics Data System (ADS)

    Ranea, Víctor A.

    2012-11-01

    The potential energy surfaces of molecular water on the Al{111} and on the Rh{111} metal surfaces have been investigated using density functional theory. Similar landscapes were found on both surfaces. In the only minimum found, the water molecule is monocoordinated to the surface via the oxygen atom (top configuration) with its plane nearly parallel to the surface. The maxima are around the bridge and hollow configurations and no local minima or maxima were found. Along the investigated minimum energy pathways, no strong preferential orientation of the water dipole was found, as long as the molecular plane is nearly parallel to the surface.

  13. Vibrational energies for HFCO using a neural network sum of exponentials potential energy surface.

    PubMed

    Pradhan, Ekadashi; Brown, Alex

    2016-05-01

    A six-dimensional potential energy surface (PES) for formyl fluoride (HFCO) is fit in a sum-of-products form using neural network exponential fitting functions. The ab initio data upon which the fit is based were computed at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations [CCSD(T)-F12]/cc-pVTZ-F12 level of theory. The PES fit is accurate (RMSE = 10 cm(-1)) up to 10 000 cm(-1) above the zero point energy and covers most of the experimentally measured IR data. The PES is validated by computing vibrational energies for both HFCO and deuterated formyl fluoride (DFCO) using block improved relaxation with the multi-configuration time dependent Hartree approach. The frequencies of the fundamental modes, and all other vibrational states up to 5000 cm(-1) above the zero-point energy, are more accurate than those obtained from the previous MP2-based PES. The vibrational frequencies obtained on the PES are compared to anharmonic frequencies at the MP2/aug-cc-pVTZ and CCSD(T)/aug-cc-pVTZ levels of theory obtained using second-order vibrational perturbation theory. The new PES will be useful for quantum dynamics simulations for both HFCO and DFCO, e.g., studies of intramolecular vibrational redistribution leading to unimolecular dissociation and its laser control.

  14. Vibrational energies for HFCO using a neural network sum of exponentials potential energy surface.

    PubMed

    Pradhan, Ekadashi; Brown, Alex

    2016-05-01

    A six-dimensional potential energy surface (PES) for formyl fluoride (HFCO) is fit in a sum-of-products form using neural network exponential fitting functions. The ab initio data upon which the fit is based were computed at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations [CCSD(T)-F12]/cc-pVTZ-F12 level of theory. The PES fit is accurate (RMSE = 10 cm(-1)) up to 10 000 cm(-1) above the zero point energy and covers most of the experimentally measured IR data. The PES is validated by computing vibrational energies for both HFCO and deuterated formyl fluoride (DFCO) using block improved relaxation with the multi-configuration time dependent Hartree approach. The frequencies of the fundamental modes, and all other vibrational states up to 5000 cm(-1) above the zero-point energy, are more accurate than those obtained from the previous MP2-based PES. The vibrational frequencies obtained on the PES are compared to anharmonic frequencies at the MP2/aug-cc-pVTZ and CCSD(T)/aug-cc-pVTZ levels of theory obtained using second-order vibrational perturbation theory. The new PES will be useful for quantum dynamics simulations for both HFCO and DFCO, e.g., studies of intramolecular vibrational redistribution leading to unimolecular dissociation and its laser control. PMID:27155638

  15. Estimating changes in heat energy stored within a column of wetland surface water and factors controlling their importance in the surface energy budget

    USGS Publications Warehouse

    Shoemaker, W.B.; Sumner, D.M.; Castillo, A.

    2005-01-01

    [1] Changes in heat energy stored within a column of wetland surface water can be a considerable component of the surface energy budget, an attribute that is demonstrated by comparing changes in stored heat energy to net radiation at seven sites in the wetland areas of southern Florida, including the Everglades. The magnitude of changes in stored heat energy approached the magnitude of net radiation more often during the winter dry season than during the summer wet season. Furthermore, the magnitude of changes in stored heat energy in wetland surface water generally decreased as surface energy budgets were upscaled temporally. A new method was developed to estimate changes in stored heat energy that overcomes an important data limitation, namely, the limited spatial and temporal availability of water temperature measurements. The new method is instead based on readily available air temperature measurements and relies on the convolution of air temperature changes with a regression-defined transfer function to estimate changes in water temperature. The convolution-computed water temperature changes are used with water depths and heat capacity to estimate changes in stored heat energy within the Everglades wetland areas. These results likely can be adapted to other humid subtropical wetlands characterized by open water, saw grass, and rush vegetation type communities. Copyright 2005 by the American Geophysical Union.

  16. Absolute Income, Relative Income, and Happiness

    ERIC Educational Resources Information Center

    Ball, Richard; Chernova, Kateryna

    2008-01-01

    This paper uses data from the World Values Survey to investigate how an individual's self-reported happiness is related to (i) the level of her income in absolute terms, and (ii) the level of her income relative to other people in her country. The main findings are that (i) both absolute and relative income are positively and significantly…

  17. Investigating Absolute Value: A Real World Application

    ERIC Educational Resources Information Center

    Kidd, Margaret; Pagni, David

    2009-01-01

    Making connections between various representations is important in mathematics. In this article, the authors discuss the numeric, algebraic, and graphical representations of sums of absolute values of linear functions. The initial explanations are accessible to all students who have experience graphing and who understand that absolute value simply…

  18. Preschoolers' Success at Coding Absolute Size Values.

    ERIC Educational Resources Information Center

    Russell, James

    1980-01-01

    Forty-five 2-year-old and forty-five 3-year-old children coded relative and absolute sizes using 1.5-inch, 6-inch, and 18-inch cardboard squares. Results indicate that absolute coding is possible for children of this age. (Author/RH)

  19. Introducing the Mean Absolute Deviation "Effect" Size

    ERIC Educational Resources Information Center

    Gorard, Stephen

    2015-01-01

    This paper revisits the use of effect sizes in the analysis of experimental and similar results, and reminds readers of the relative advantages of the mean absolute deviation as a measure of variation, as opposed to the more complex standard deviation. The mean absolute deviation is easier to use and understand, and more tolerant of extreme…

  20. Monolithically integrated absolute frequency comb laser system

    DOEpatents

    Wanke, Michael C.

    2016-07-12

    Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.

  1. Estimating the absolute wealth of households

    PubMed Central

    Gerkey, Drew; Hadley, Craig

    2015-01-01

    Abstract Objective To estimate the absolute wealth of households using data from demographic and health surveys. Methods We developed a new metric, the absolute wealth estimate, based on the rank of each surveyed household according to its material assets and the assumed shape of the distribution of wealth among surveyed households. Using data from 156 demographic and health surveys in 66 countries, we calculated absolute wealth estimates for households. We validated the method by comparing the proportion of households defined as poor using our estimates with published World Bank poverty headcounts. We also compared the accuracy of absolute versus relative wealth estimates for the prediction of anthropometric measures. Findings The median absolute wealth estimates of 1 403 186 households were 2056 international dollars per capita (interquartile range: 723–6103). The proportion of poor households based on absolute wealth estimates were strongly correlated with World Bank estimates of populations living on less than 2.00 United States dollars per capita per day (R2 = 0.84). Absolute wealth estimates were better predictors of anthropometric measures than relative wealth indexes. Conclusion Absolute wealth estimates provide new opportunities for comparative research to assess the effects of economic resources on health and human capital, as well as the long-term health consequences of economic change and inequality. PMID:26170506

  2. Absolute optical metrology : nanometers to kilometers

    NASA Technical Reports Server (NTRS)

    Dubovitsky, Serge; Lay, O. P.; Peters, R. D.; Liebe, C. C.

    2005-01-01

    We provide and overview of the developments in the field of high-accuracy absolute optical metrology with emphasis on space-based applications. Specific work on the Modulation Sideband Technology for Absolute Ranging (MSTAR) sensor is described along with novel applications of the sensor.

  3. Absolute instability of the Gaussian wake profile

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Aggarwal, Arun K.

    1987-01-01

    Linear parallel-flow stability theory has been used to investigate the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution. The type of local instability, i.e., convective or absolute, is determined by the location of a branch-point singularity with zero group velocity of the complex dispersion relation for the instability waves. The effects of viscosity were found to be weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake half-width, larger than about 400. Absolute instability occurs only for sufficiently large values of the center-line wake defect. The critical value of this parameter increases with decreasing wake Reynolds number, thereby indicating a shrinking region of absolute instability with decreasing wake Reynolds number. If backflow is not allowed, absolute instability does not occur for wake Reynolds numbers smaller than about 38.

  4. Surface Energy and Work Function Control of AlOx/Al Surfaces by Fluorinated Benzylphosphonic Acids.

    PubMed

    Abraham, Ffion; Ford, William E; Scholz, Frank; Nelles, Gabriele; Sandford, Graham; von Wrochem, Florian

    2016-05-11

    The performance of organic electronic devices can be significantly improved by modifying metal electrodes with organic monolayers, which alter the physical and chemical nature of the interface between conductor and semiconductor. In this paper we examine a series of 12 phosphonic acid compounds deposited on the native oxide layer of aluminum (AlOx/Al), an electrode material with widespread applications in organic electronics. This series includes dodecylphosphonic acid as a reference and 11 benzylphosphonic acids, seven of which are fluorinated, including five newly synthesized derivatives. The monolayers are experimentally characterized by contact angle goniometry and by X-ray photoemission spectroscopy (XPS), and work function data obtained by low-intensity XPS are correlated with molecular dipoles obtained from DFT calculations. We find that monolayers are formed with molecular areas ranging from 17.7 to 42.9 Å(2)/molecule, and, by the choice of appropriate terminal groups, the surface energy can be tuned from 23.5 mJ/m(2) to 70.5 mJ/m(2). Depending on the number and position of fluorine substituents on the aromatic rings, a variation in the work function of AlOx/Al substrates over a range of 0.91 eV is achieved, and a renormalization procedure based on molecular density yields a surprising agreement of work function changes with interface dipoles as expected from Helmholtz' equation. The ability to adjust energetics and adhesion at organic semiconductor/AlOx interfaces has immediate applications in devices such as OLEDs, OTFTs, organic solar cells, and printed organic circuits.

  5. Simulating maize production, water and surface energy balance, and canopy temperature under full and deficit irrigation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface energy balance is critical to the understanding of crop evapotranspiration (ET) requirement and crop water stresses. The objective of this study was to evaluate the simulation of crop growth, water and surface energy balance components, and canopy temperature under full and deficit irrigated...

  6. The calculation of surface orbital energies for specific types of active sites on dispersed metal catalysts

    SciTech Connect

    Augustine, R.L.; Lahanas, K.M.; Cole, F.

    1992-11-01

    An angular overlap calculation has been used to determine the s, p, and d orbital energy levels of the different types of surface sites present on dispersed metal catalysts. These data can permit a Frontier Molecular Orbital treatment of specific site activities as long as the surface orbital availability for overlap with adsorbed substrates is considered along with its energy value and symmetry.

  7. The calculation of surface orbital energies for specific types of active sites on dispersed metal catalysts

    SciTech Connect

    Augustine, R.L.; Lahanas, K.M.; Cole, F.

    1992-01-01

    An angular overlap calculation has been used to determine the s, p, and d orbital energy levels of the different types of surface sites present on dispersed metal catalysts. These data can permit a Frontier Molecular Orbital treatment of specific site activities as long as the surface orbital availability for overlap with adsorbed substrates is considered along with its energy value and symmetry.

  8. 3D Printed Potential and Free Energy Surfaces for Teaching Fundamental Concepts in Physical Chemistry

    ERIC Educational Resources Information Center

    Kaliakin, Danil S.; Zaari, Ryan R.; Varganov, Sergey A.

    2015-01-01

    Teaching fundamental physical chemistry concepts such as the potential energy surface, transition state, and reaction path is a challenging task. The traditionally used oversimplified 2D representation of potential and free energy surfaces makes this task even more difficult and often confuses students. We show how this 2D representation can be…

  9. Surface Energy of C60 and the Interfacial Interactions in Aqueous Systems

    EPA Science Inventory

    The surface free energy components of C60 powder in the form of compressed pellets were determined by sessile drop contact angle measurements. Based on van Oss-Chaudhury-Good model to Young-Dupre equation, the surface energy of C60 and the contributions of the apolar (Lifshitz-v...

  10. Vibrational effects on surface energies and band gaps in hexagonal and cubic ice

    NASA Astrophysics Data System (ADS)

    Engel, Edgar A.; Monserrat, Bartomeu; Needs, Richard J.

    2016-07-01

    Surface energies of hexagonal and cubic water ice are calculated using first-principles quantum mechanical methods, including an accurate description of anharmonic nuclear vibrations. We consider two proton-orderings of the hexagonal and cubic ice basal surfaces and three proton-orderings of hexagonal ice prism surfaces, finding that vibrations reduce the surface energies by more than 10%. We compare our vibrational densities of states to recent sum frequency generation absorption measurements and identify surface proton-orderings of experimental ice samples and the origins of characteristic absorption peaks. We also calculate zero point quantum vibrational corrections to the surface electronic band gaps, which range from -1.2 eV for the cubic ice basal surface up to -1.4 eV for the hexagonal ice prism surface. The vibrational corrections to the surface band gaps are up to 12% smaller than for bulk ice.

  11. Tandem filters using frequency selective surfaces for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Dziendziel, Randolph J.; Baldasaro, Paul F.; DePoy, David M.

    2010-09-07

    This invention relates to the field of thermophotovoltaic (TPV) direct energy conversion. In particular, TPV systems use filters to minimize parasitic absorption of below bandgap energy. This invention constitutes a novel combination of front surface filters to increase TPV conversion efficiency by reflecting useless below bandgap energy while transmitting a very high percentage of the useful above bandgap energy. In particular, a frequency selective surface is used in combination with an interference filter. The frequency selective surface provides high transmission of above bandgap energy and high reflection of long wavelength below bandgap energy. The interference filter maintains high transmission of above bandgap energy and provides high reflection of short wavelength below bandgap energy and a sharp transition from high transmission to high reflection.

  12. Tandem filters using frequency selective surfaces for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Dziendziel, Randolph J.; DePoy, David Moore; Baldasaro, Paul Francis

    2007-01-23

    This invention relates to the field of thermophotovoltaic (TPV) direct energy conversion. In particular, TPV systems use filters to minimize parasitic absorption of below bandgap energy. This invention constitutes a novel combination of front surface filters to increase TPV conversion efficiency by reflecting useless below bandgap energy while transmitting a very high percentage of the useful above bandgap energy. In particular, a frequency selective surface is used in combination with an interference filter. The frequency selective surface provides high transmission of above bandgap energy and high reflection of long wavelength below bandgap energy. The interference filter maintains high transmission of above bandgap energy and provides high reflection of short wavelength below bandgap energy and a sharp transition from high transmission to high reflection.

  13. Secondary Ions Sputtered by Low Energy Ion Bombardment of Copper and Aluminum Surfaces.

    NASA Astrophysics Data System (ADS)

    Chen, Liang-Yu.

    1995-11-01

    We have bombarded Cu and Al surfaces with rm O_2^+ ions and measured the relative yields of secondary ions in the energy range from 50 to 500 eV. We have determined both the relative yield as a function of incident ion energy and the kinetic energy distributions of the ejected ions for selected incident ion energies. In addition to looking at rm Cu^+ ions from Cu and rm Al ^+ ions from Al, we have investigated ion signals from alkali impurities in the targets. For the Cu surface, ions ejected by rm Ar^+ bombardment were examined both before and after sputter cleaning of the surface. Data on beam energy dependent secondary ion yields from the literature and this investigation have been fit by an exponential formula Acdotexp( -B/(C + E)), where A, B and C are fitting parameters. The results, with standard deviations for fitting parameters, are reported. A distinct plateau structure has been found for beam energy dependent yields of rm Na^+ and rm K^+ ions sputtered from untreated (long existing) Cu surfaces. A series of well controlled experiments indicate that this structure is caused by a surface excess of sodium and potassium at the surfaces of copper samples. The calculation of beam energy dependent energy deposition shows that the energy deposited on the top surface of a polycrystal copper target by oxygen ions rm (O_2^+) does not further increase with the increase of beam energy above 250 eV. This result very well explains the beam energy dependence of the yield of secondary alkali ions contributed from the surface excess. Combined with the experimental data, thermodynamic calculations indicate that the positive surface excess of alkali metals near Cu surfaces is due to their segregation near the copper surface. Thus, the data for secondary ion yield vs. beam energy at low energy may provide a very surface sensitive probe with high spatial resolution (monolayer) for investigating segregation near solid material surfaces. Compared with secondary ion signals

  14. Surface energy of microcrystalline cellulose determined by capillary intrusion and inverse gas chromatography.

    PubMed

    Steele, D Fraser; Moreton, R Christian; Staniforth, John N; Young, Paul M; Tobyn, Michael J; Edge, Stephen

    2008-09-01

    Surface energy data for samples of microcrystalline cellulose have been obtained using two techniques: capillary intrusion and inverse gas chromatography. Ten microcrystalline cellulose materials, studied using capillary intrusion, showed significant differences in the measured surface energetics (in terms of total surface energy and the acid-base characteristics of the cellulose surface), with variations noted between the seven different manufacturers who produced the microcrystalline cellulose samples. The surface energy data from capillary intrusion was similar to data obtained using inverse gas chromatography with the column maintained at 44% relative humidity for the three samples of microcrystalline cellulose studied. This suggests that capillary intrusion may be a suitable method to study the surface energy of pharmaceutical samples.

  15. Upscale energy transfer and flow topology in free-surface turbulence.

    PubMed

    Lovecchio, Salvatore; Zonta, Francesco; Soldati, Alfredo

    2015-03-01

    Free-surface turbulence, albeit constrained onto a two-dimensional space, exhibits features that barely resemble predictions of simplified two-dimensional modeling. We demonstrate that, in a three-dimensional open channel flow, surface turbulence is characterized by upscale energy transfer, which controls the long-term evolution of the larger scales. We are able to associate downscale and upscale energy transfer at the surface with the two-dimensional divergence of velocity. We finally demonstrate that surface compressibility confirms the strongly three-dimensional nature of surface turbulence.

  16. Surface structures from low energy electron diffraction: Atoms, small molecules and an ordered ice film on metal surfaces

    SciTech Connect

    Materer, N.F.

    1995-09-01

    We investigated the surface bonding of various adsorbates (0, S, C{sub 2}H{sub 3} and NO) along with the resulting relaxation of the Pt(111) surface using low energy electron diffiraction (LEED). LEED experiments have been performed on these ordered overlayers along with theoretical structural analysis using automated tensor LEED (ATLEED). The resulting surface structures of these ordered overlayers exhibit similar adsorbate-induced relaxations. In all cases the adsorbate occupies the fcc hollow site and induces an approximately 0.1 A buckling of the metal surface. The three metal atoms directly bonded to the adsorbate are ``pulled`` out of the surface and the metal atom that is not bound to the adsorbate is `pushed`` inward. In order to understand the reliability of such details, we have carried out a comprehensive study of various non-structural parameters used in a LEED computation. We also studied the adsorption of water on the Pt(lll) surface. We ordered an ultra thin ice film on this surface. The film`s surface is found to be the (0001) face of hexagonal ice. This surface is apparently terminated by a full-bilayer, in which the uppermost water molecules have large vibrational amplitudes even at temperatures as low as 90 K. We examined two other metal surfaces besides Pt(111): Ni(111) and Fe(lll). On Ni(111), we have studied the surface under a high coverage of NO. On both Ni(111) and Pt(111) NO molecules occupy the hollow sites and the N-0 bond distances are practically identical. The challenging sample preparation of an Fe(111) surface has been investigated and a successful procedure has been obtained. The small interlayer spacing found on Fe(111) required special treatment in the LEED calculations. A new ATLEED program has been developed to handle this surface.

  17. Surface modification of structural materials by low-energy high-current pulsed electron beam treatment

    SciTech Connect

    Panin, A. V. E-mail: kms@ms.tsc.ru; Kazachenok, M. S. E-mail: kms@ms.tsc.ru; Sinyakova, E. A.; Borodovitsina, O. M.; Ivanov, Yu. F.; Leontieva-Smirnova, M. V.

    2014-11-14

    Microstructure formation in surface layers of pure titanium and ferritic-martensitic steel subjected to electron beam treatment is studied. It is shown that low energy high-current pulsed electron beam irradiation leads to the martensite structure within the surface layer of pure titanium. Contrary, the columnar ferrite grains grow during solidification of ferritic-martensitic steel. The effect of electron beam energy density on the surface morphology and microstructure of the irradiated metals is demonstrated.

  18. Surface energy of bovine dentin and enamel by means of inverse gas chromatography.

    PubMed

    Okulus, Zuzanna; Strzemiecka, Beata; Czarnecka, Beata; Buchwald, Tomasz; Voelkel, Adam

    2015-04-01

    Adhesion between tooth tissues and dental fillings depends on the surface energy of both connected materials. Bond strength can be determined directly or indirectly as a work of adhesion on the basis of values of surface energy of these materials. Inverse gas chromatography (IGC) is one of the methods of surface energy examination. In this study the values of total surface energy components of wet and dry teeth fragments (enamel, crown dentin and root dentin) were determined with the use of inverse gas chromatography. Inverse gas chromatography has never been used for investigation of surface energy of natural tooth tissues. Different storage conditions were examined - wet and dry. Different values of surface energy are observed according to the type of tooth tissue (dentin or enamel), occurring place (crown or root) and storage conditions (dry or wet). The effect of tissue type and occurring place was the greatest, while storage conditions were of secondary importance. Surface energy depends on composition of tissue, its surface area and the presence of pores.

  19. Nucleation at surfaces: the importance of interfacial energy.

    PubMed

    Wu, W; Gerard, D E; Nancollas, G H

    1999-11-01

    The nucleation and growth of stone-forming minerals on the surfaces of other crystalline phases, cellular material, and immobilized macromolecules must be important in the formation of stones in the urinary tract. The nucleation and growth of calcium oxalate monohydrate (COM) crystals were studied using the constant composition kinetics technique, in solution supersaturated with respect to COM (sigmaCOM = 1.44). The solid phases during the reaction were examined by x-ray diffraction, scanning electron microscopy, and diffuse reflectance Fourier transform infrared spectroscopy. Human serum albumin was found to nucleate COM crystals when immobilized on hydroxyapatite (HAP) surfaces. The induction period for nucleation of COM on HAP surfaces preadsorbed with albumin significantly decreased to about 65 min from about 230 min for pure HAP particles. The initial growth rate of COM on pure HAP particles, Rm approximately/= 0.56 X 10(-7) mol/min per m2, was slower than that for HAP surfaces preadsorbed with albumin, 2.14 x 10(-7) mol/min per m2. The surface properties were characterized using contact angle measurements by sessile drop and thin layer wicking. The thermodynamic results suggested that surfaces with high Lewis base parameter values (gamma-) and low interfacial tension with water (gammaSL) are more effective in the nucleation and growth of crystal phases.

  20. Fuzzy Performance between Surface Fitting and Energy Distribution in Turbulence Runner

    PubMed Central

    Liang, Zhongwei; Liu, Xiaochu; Ye, Bangyan; Brauwer, Richard Kars

    2012-01-01

    Because the application of surface fitting algorithms exerts a considerable fuzzy influence on the mathematical features of kinetic energy distribution, their relation mechanism in different external conditional parameters must be quantitatively analyzed. Through determining the kinetic energy value of each selected representative position coordinate point by calculating kinetic energy parameters, several typical algorithms of complicated surface fitting are applied for constructing microkinetic energy distribution surface models in the objective turbulence runner with those obtained kinetic energy values. On the base of calculating the newly proposed mathematical features, we construct fuzzy evaluation data sequence and present a new three-dimensional fuzzy quantitative evaluation method; then the value change tendencies of kinetic energy distribution surface features can be clearly quantified, and the fuzzy performance mechanism discipline between the performance results of surface fitting algorithms, the spatial features of turbulence kinetic energy distribution surface, and their respective environmental parameter conditions can be quantitatively analyzed in detail, which results in the acquirement of final conclusions concerning the inherent turbulence kinetic energy distribution performance mechanism and its mathematical relation. A further turbulence energy quantitative study can be ensured. PMID:23213287

  1. Evaluation of Surface Energy Balance models for mapping evapotranspiration using very high resolution airborne remote sensing data

    NASA Astrophysics Data System (ADS)

    Paul, George

    Agriculture is the largest (90%) consumer of all fresh water in the world. The consumptive use of water by vegetation represented by the process evapotranspiration (ET) has a vital role in the dynamics of water, carbon and energy fluxes of the biosphere. Consequently, mapping ET is essential for making water a sustainable resource and also for monitoring ecosystem response to water stress and changing climate. Over the past three decades, numerous thermal remote sensing based ET mapping algorithms were developed and these have brought a significant theoretical and technical advancement in the spatial modeling of ET. Though these algorithms provided a robust, economical, and efficient tool for ET estimations at field and regional scales, yet the uncertainties in flux estimations were large, making evaluation a difficult task. The main objective of this study was to evaluate and improve the performance of widely used remote sensing based energy balance models, namely: the Surface Energy Balance Algorithm for Land (SEBAL), Mapping Evapotranspiration at high Resolution and with Internalized Calibration (METRIC), and Surface Energy Balance System (SEBS). Data used in this study was collected as part of a multi-disciplinary and multi-institutional field campaign BEAREX (Bushland Evapotranspiration and Agricultural Remote Sensing Experiment) that was conducted during 2007 and 2008 summer cropping seasons at the USDA-ARS Conservation and Production Research Laboratory (CPRL) in Bushland, Texas. Seventeen high resolution remote sensing images taken from multispectral sensors onboard aircraft and field measurements of the agro-meteorological variables from the campaign were used for model evaluation and improvement. Overall relative error measured in terms of mean absolute percent difference (MAPD) for instantaneous ET (mm h -1) were 22.7%, 23.2%, and 12.6% for SEBAL, METRIC, and SEBS, respectively. SEBAL and METRIC performances for irrigated fields representing higher ET

  2. Probing Potential Energy Surface Exploration Strategies for Complex Systems.

    PubMed

    N'Tsouaglo, Gawonou Kokou; Béland, Laurent Karim; Joly, Jean-François; Brommer, Peter; Mousseau, Normand; Pochet, Pascal

    2015-04-14

    The efficiency of minimum-energy configuration searching algorithms is closely linked to the energy landscape structure of complex systems, yet these algorithms often include a number of steps of which the effect is not always clear. Decoupling these steps and their impacts can allow us to better understand both their role and the nature of complex energy landscape. Here, we consider a family of minimum-energy algorithms based, directly or indirectly, on the well-known Bell-Evans-Polanyi (BEP) principle. Comparing trajectories generated with BEP-based algorithms to kinetically correct off-lattice kinetic Monte Carlo schemes allow us to confirm that the BEP principle does not hold for complex systems since forward and reverse energy barriers are completely uncorrelated. As would be expected, following the lowest available energy barrier leads to rapid trapping. This is why BEP-based methods require also a direct handling of visited basins or barriers. Comparing the efficiency of these methods with a thermodynamical handling of low-energy barriers, we show that most of the efficiency of the BEP-like methods lie first and foremost in the basin management rather than in the BEP-like step. PMID:26574398

  3. Probing Potential Energy Surface Exploration Strategies for Complex Systems.

    PubMed

    N'Tsouaglo, Gawonou Kokou; Béland, Laurent Karim; Joly, Jean-François; Brommer, Peter; Mousseau, Normand; Pochet, Pascal

    2015-04-14

    The efficiency of minimum-energy configuration searching algorithms is closely linked to the energy landscape structure of complex systems, yet these algorithms often include a number of steps of which the effect is not always clear. Decoupling these steps and their impacts can allow us to better understand both their role and the nature of complex energy landscape. Here, we consider a family of minimum-energy algorithms based, directly or indirectly, on the well-known Bell-Evans-Polanyi (BEP) principle. Comparing trajectories generated with BEP-based algorithms to kinetically correct off-lattice kinetic Monte Carlo schemes allow us to confirm that the BEP principle does not hold for complex systems since forward and reverse energy barriers are completely uncorrelated. As would be expected, following the lowest available energy barrier leads to rapid trapping. This is why BEP-based methods require also a direct handling of visited basins or barriers. Comparing the efficiency of these methods with a thermodynamical handling of low-energy barriers, we show that most of the efficiency of the BEP-like methods lie first and foremost in the basin management rather than in the BEP-like step.

  4. 75 FR 7457 - Notice of Public Hearing on Stone Energy Corporation Proposed Surface Water Withdrawal and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-19

    ... COMMISSION Notice of Public Hearing on Stone Energy Corporation Proposed Surface Water Withdrawal and Natural... (DRBC or ``Commission'') will hold a special public hearing on two projects sponsored by the Stone Energy Corporation (hereinafter, ``Stone Energy'') to support natural gas exploration and...

  5. Modification of polymer (PET) surface reactivity by low energy ion bombardment

    NASA Astrophysics Data System (ADS)

    Bertrand, P.; De Puydt, Y.; Beuken, J.-M.; Lutgen, P.; Feyder, G.

    The surface of polyethylene terephtalate (PET) was studied by low energy He + ion scattering (ISS). Modifications of the surface composition induced by the He + and Ar + bombardments are observed. The ion bombardment causes surface damages with bond breaking and it results a highly activated surface for the chemisorption of nitrogen from the residual gas phase. Similar effects were observed on highly oriented pyrolytic graphite when analyzed in the same beam conditions.

  6. Energy surface and minimum energy paths for Fréedericksz transitions in bistable cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Ivanov, A. V.; Bessarab, P. F.; Aksenova, E. V.; Romanov, V. P.; Uzdin, V. M.

    2016-04-01

    The multidimensional energy surface of a cholesteric liquid crystal in a planar cell is investigated as a function of spherical coordinates determining the director orientation. Minima on the energy surface correspond to the stable states with particular director distribution. External electric and magnetic fields deform the energy surface and positions of minima. It can lead to the transitions between states, known as the Fréedericksz effect. Transitions can be continuous or discontinuous depending on parameters of the liquid crystal which determine an energy surface. In a case of discontinuous transition when a barrier between stable states is comparable with the thermal energy, the activation transitions may occur, and it leads to the modification of characteristics of the Fréedericksz effect with temperature without explicit temperature dependencies of liquid crystal parameters. A minimum energy path between stable states on the energy surface for the Fréedericksz transition is found using the geodesic nudged elastic band method. Knowledge of this path, which has maximal statistical weight among all other paths, gives the information about a barrier between stable states and configuration of director orientation during the transition. It also allows one to estimate the stability of states with respect to the thermal fluctuations and their lifetime when the system is close to the Fréedericksz transition.

  7. Hot-electron-mediated desorption rates calculated from excited-state potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Olsen, Thomas; Gavnholt, Jeppe; Schiøtz, Jakob

    2009-01-01

    We present a model for desorption induced by (multiple) electronic transitions [DIET (DIMET)] based on potential energy surfaces calculated with the delta self-consistent field extension of density-functional theory. We calculate potential energy surfaces of CO and NO molecules adsorbed on various transition-metal surfaces and show that classical nuclear dynamics does not suffice for propagation in the excited state. We present a simple Hamiltonian describing the system with parameters obtained from the excited-state potential energy surface and show that this model can describe desorption dynamics in both the DIET and DIMET regimes and reproduce the power-law behavior observed experimentally. We observe that the internal stretch degree of freedom in the molecules is crucial for the energy transfer between the hot electrons and the molecule when the coupling to the surface is strong.

  8. Calculating Ring Pucker Free Energy Surfaces From Reaction Coordinate Forces

    SciTech Connect

    Barnett, Christopher B.; Naidoo, Kevin J.

    2009-03-09

    We implemented the free energy from adaptive reaction coordinate forces (FEARCF) method and applied it to the conformational investigation of carbohydrate ring puckering. The method allows for significantly enhanced sampling of reaction coordinate space. The free energies associated with the ring pucker motion of {beta}-D-ribose (a furanose) and {beta}-D-glucose (a pyranose) were calculated. These can be used to interpret catalytic mechanisms of glycosylases.

  9. Absolute magnitudes of trans-neptunian objects

    NASA Astrophysics Data System (ADS)

    Duffard, R.; Alvarez-candal, A.; Pinilla-Alonso, N.; Ortiz, J. L.; Morales, N.; Santos-Sanz, P.; Thirouin, A.

    2015-10-01

    Accurate measurements of diameters of trans- Neptunian objects are extremely complicated to obtain. Radiomatric techniques applied to thermal measurements can provide good results, but precise absolute magnitudes are needed to constrain diameters and albedos. Our objective is to measure accurate absolute magnitudes for a sample of trans- Neptunian objects, many of which have been observed, and modelled, by the "TNOs are cool" team, one of Herschel Space Observatory key projects grantes with ~ 400 hours of observing time. We observed 56 objects in filters V and R, if possible. These data, along with data available in the literature, was used to obtain phase curves and to measure absolute magnitudes by assuming a linear trend of the phase curves and considering magnitude variability due to rotational light-curve. In total we obtained 234 new magnitudes for the 56 objects, 6 of them with no reported previous measurements. Including the data from the literature we report a total of 109 absolute magnitudes.

  10. A New Gimmick for Assigning Absolute Configuration.

    ERIC Educational Resources Information Center

    Ayorinde, F. O.

    1983-01-01

    A five-step procedure is provided to help students in making the assignment absolute configuration less bothersome. Examples for both single (2-butanol) and multi-chiral carbon (3-chloro-2-butanol) molecules are included. (JN)

  11. The Simplicity Argument and Absolute Morality

    ERIC Educational Resources Information Center

    Mijuskovic, Ben

    1975-01-01

    In this paper the author has maintained that there is a similarity of thought to be found in the writings of Cudworth, Emerson, and Husserl in his investigation of an absolute system of morality. (Author/RK)

  12. An Absolute Measurement of Resonance-Resolved Electron Impact Excitation

    NASA Astrophysics Data System (ADS)

    Reisenfeld, Daniel Brett

    1998-11-01

    An experiment to measure electron-impact excitation (EIE) of multiply-charged ions is described. An absolute measurement has been carried out of the cross section for EIE of Si2+(3s2/ 1S/to3s3p/ 1P) from energies below threshold to 11 eV above. A beams modulation technique with inclined electron and ion beams was used. Radiation at 120.7 nm from the excited ions was detected using an absolutely calibrated optical system. The analysis of the experimental data requires a determination of the population fraction of the Si2+ (3s3p/ 3Po) metastable state in the incident ion beam, which was measured to be 0.210 ± 0.018. The data have been corrected for contributions to the signal from radiative decay following excitation from the metastable state to 3s3p1P and 3p2/ 3P, and excitation of the ground state to levels above 3s3p/ 1P. The experimental 0.56 ± 0.08 eV energy spread has allowed us to resolve complex resonance structure throughout the studied energy range. At the reported ±14% uncertainty level (90% confidence limit), the measured structure and absolute scale of the cross section are in good agreement with 12-state close-coupling R-matrix calculations.

  13. Surface-Driven Sodium Ion Energy Storage in Nanocellular Carbon Foams

    SciTech Connect

    Shao, Yuyan; Xiao, Jie; Wang, Wei; Engelhard, Mark H.; Chen, Xilin; Nie, Zimin; Gu, Meng; Saraf, Laxmikant V.; Exarhos, Gregory J.; Zhang, Jiguang; Liu, Jun

    2013-07-23

    Sodium ion (Na+) batteries have attracted increased attention for energy storage due to the natural abundance of sodium, but their development is hindered by the poor intercalation property of Na+ in electrodes. This paper reports a detailed study of high capacity, high rate sodium ion energy storage in high-surface-area nanocellular carbon foams (NCCF). The energy storage mechanism is surface-driven reactions between Na+ and oxygen-containing functional groups on the surface of NCCF. The surface reaction, rather than a Na+ bulk intercalation reaction, leads to high rate performance and cycling stability due to the enhanced reaction kinetics and the absence of electrode structure change. The NCCF makes more surface area and surface functional groups available for the Na+ reaction. It delivers 152 mAh/g capacity at the rate of 0.1 A/g and a capacity retention of 90% for over 1600 cycles.

  14. Deep Valley Radiation and Surface Energy Budget Microclimates. Part II: Energy Budget.

    NASA Astrophysics Data System (ADS)

    Whiteman, C. David; Allwine, K. Jerry; Fritschen, Leo J.; Orgill, Montie M.; Simpson, James R.

    1989-06-01

    Surface energy budget measurements were made concurrently at five sites located on the valley floor, sidewalls and ridgetop of Colorado's 650-m deep Brush Creek Valley (39°32N, 108°24W) on the nearly clear day of 25 September 1984 using the Bowen ratio energy budget technique.Daily average surface heat flux values for a natural sagebrush ecosystem on the floor of the semiarid valley included an input of 109 W m2 net all-wave radiation and 15 W m2 ground heat flux, and a loss of 48 W m2 latent heat flux and 76 W m2 sensible heat flux. Significant differences in instantaneous, daily, and daytime fluxes occurred from site to site as a function of slope aspect and inclination angles and surface properties, including vegetation cover and soil moisture.Strong contrasts in instantaneous latent and sensible heat fluxes occurred between the opposing northeast-and southwest-facing sidewalls of the valley as solar insolation varied through the course of the day and as shadows propagated across the valley. This differential heating and moistening of the air above the opposing slopes produces cross valley circulations and the resulting moisture and heat transports observed by other investigators.The ridgetop site, with a nearly unobstructed view of the sky and the longest daytime period, received the highest daily total of net radiation (12.12 MJ m2) and lost the highest sensible heat flux total (8.49 MJ m2). The dry southwest-facing slope produced a nearly equivalent daily total sensible heat flux, despite the later sunrise and earlier sunset at this site, because of the dry soil, lack of vegetation, and intense afternoon radiation on the sloping surface. One of the valley floor sites, located in a wheatgrass meadow, produced a daily total latent heat flux (7.37 MJ m2) over four times larger than the dry southwest-facing sidewall. Mean daytime Bowen ratios varied from 0.86 at the valley floor meadow site to 7.60 on the southwest-facing sidewall.Daily total sensible heat

  15. Evaluation of a two source snow-vegetation energy balance model for estimating surface energy fluxes in a rangeland ecosystem

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The utility of a two source snow-vegetation energy balance model for estimating surface energy fluxes is evaluated with field measurements at two sites in a rangeland ecosystem in southwestern Idaho during the winter of 2007: one site dominated by aspen vegetation and the other by sagebrush. Model ...

  16. Absolute V-R colors of trans-Neptunian objects

    NASA Astrophysics Data System (ADS)

    Alvarez-Candal, Alvaro; Ayala-Loera, Carmen; Ortiz, Jose-Luis; Duffard, Rene; Estela, Fernandez-Valenzuela; Santos-Sanz, Pablo

    2016-10-01

    The absolute magnitude of a minor body is the apparent magnitude that the body would have if observed from the Sun at a distance of 1AU. Absolute magnitudes are measured using phase curves, showing the change of the magnitude, normalized to unit helio and geo-centric distance, vs. phase angle. The absolute magnitude is then the Y-intercept of the curve. Absolute magnitudes are related to the total reflecting surface of the body and thus bring information of its size, coupled with the reflecting properties.Since 2011 our team has been collecting data from several telescopes spread in Europe and South America. We complemented our data with those available in the literature in order to construct phase curves of trans-Neptunian objects with at least three points. In a first release (Alvarez-Candal et al. 2016, A&A, 586, A155) we showed results for 110 trans-Neptunian objects using V magnitudes only, assuming an overall linear trend and taking into consideration rotational effects, for objects with known light-curves.In this contribution we show results for more than 130 objects, about 100 of them with phase curves in two filters: V and R. We compute absolute magnitudes and phase coefficients in both filters, when available. The average values are HV = 6.39 ± 2.37, βV = (0.09 ± 0.32) mag per degree, HR = 5.38 ± 2.30, and βR = (0.08 ± 0.42) mag per degree.

  17. Development of aluminum first surface mirrors for solar energy applications

    SciTech Connect

    Almanza, R.; Munoz, F.; Mazari, M. )

    1992-01-01

    The progress in obtaining first surface mirrors by using Si{sub 2}O{sub 3} and SiO films as the front surface over aluminum films thermally evaporated over soda lime glass substrates is given in this study. The size of the mirrors is 30 {times} 30 cm with a 3-mm substrate thickness. A glow discharge produced during 20 min (3 kV and 250 mA) was sufficient to clean the substrate. An aluminum film was deposited after this cleaning. Two types of first surface mirrors were formed. One with SiO, and the other one with Si{sub 2}O{sub 3} as the front surface, each one with a thickness of about 3,000 {angstrom}. The reflectances were 0.82 and 0.86, respectively. After one year of exposure to the environment, no degradation was detected, but after two years, a slight amount of corrosion appeared. Some alternatives are being studied in order to minimize or eliminate this corrosion.

  18. Emission of low-energy positronium from alkali-metal coated single-crystal tungsten surfaces.

    PubMed

    Iida, S; Wada, K; Mochizuki, I; Tachibana, T; Yamashita, T; Hyodo, T; Nagashima, Y

    2016-11-30

    We have measured the time-of-flight of ortho-positronium emitted from Cs-, Na- and Li-coated single-crystal tungsten surfaces. The data obtained after the coating show a new positronium energy component with a specific energy loss in addition to the component whose emission energy is simply determined by the positron and the electron work functions. We suggest that this new component is attributed to the formation of positronium accompanied by inter-band transition and/or surface plasmon excitation at the surfaces. PMID:27662111

  19. Emission of low-energy positronium from alkali-metal coated single-crystal tungsten surfaces

    NASA Astrophysics Data System (ADS)

    Iida, S.; Wada, K.; Mochizuki, I.; Tachibana, T.; Yamashita, T.; Hyodo, T.; Nagashima, Y.

    2016-11-01

    We have measured the time-of-flight of ortho-positronium emitted from Cs-, Na- and Li-coated single-crystal tungsten surfaces. The data obtained after the coating show a new positronium energy component with a specific energy loss in addition to the component whose emission energy is simply determined by the positron and the electron work functions. We suggest that this new component is attributed to the formation of positronium accompanied by inter-band transition and/or surface plasmon excitation at the surfaces.

  20. Emission of low-energy positronium from alkali-metal coated single-crystal tungsten surfaces.

    PubMed

    Iida, S; Wada, K; Mochizuki, I; Tachibana, T; Yamashita, T; Hyodo, T; Nagashima, Y

    2016-11-30

    We have measured the time-of-flight of ortho-positronium emitted from Cs-, Na- and Li-coated single-crystal tungsten surfaces. The data obtained after the coating show a new positronium energy component with a specific energy loss in addition to the component whose emission energy is simply determined by the positron and the electron work functions. We suggest that this new component is attributed to the formation of positronium accompanied by inter-band transition and/or surface plasmon excitation at the surfaces.

  1. Pattern Formation by Phase-Field Relaxation of Bending Energy with Fixed Surface Area and Volume

    PubMed Central

    Banham, Timothy; Li, Bo; Zhao, Yanxiang

    2015-01-01

    We explore a wide variety of patterns of closed surfaces that minimize the elastic bending energy with fixed surface area and volume. To avoid complicated discretization and numerical instabilities for sharp surfaces, we reformulate the underlying constrained minimization problem by constructing phase-field functionals of bending energy with penalty terms for the constraints, and develop stable numerical methods to relax these functionals. We report our extensive computational results with different initial surfaces. These results are discussed in terms of the reduced volume, and are compared with the known results obtained using the sharp-interface approach. Finally, we discuss the implications of our numerical findings. PMID:25314565

  2. Bio-Inspired Stretchable Absolute Pressure Sensor Network.

    PubMed

    Guo, Yue; Li, Yu-Hung; Guo, Zhiqiang; Kim, Kyunglok; Chang, Fu-Kuo; Wang, Shan X

    2016-01-02

    A bio-inspired absolute pressure sensor network has been developed. Absolute pressure sensors, distributed on multiple silicon islands, are connected as a network by stretchable polyimide wires. This sensor network, made on a 4'' wafer, has 77 nodes and can be mounted on various curved surfaces to cover an area up to 0.64 m × 0.64 m, which is 100 times larger than its original size. Due to Micro Electro-Mechanical system (MEMS) surface micromachining technology, ultrathin sensing nodes can be realized with thicknesses of less than 100 µm. Additionally, good linearity and high sensitivity (~14 mV/V/bar) have been achieved. Since the MEMS sensor process has also been well integrated with a flexible polymer substrate process, the entire sensor network can be fabricated in a time-efficient and cost-effective manner. Moreover, an accurate pressure contour can be obtained from the sensor network. Therefore, this absolute pressure sensor network holds significant promise for smart vehicle applications, especially for unmanned aerial vehicles.

  3. Bio-Inspired Stretchable Absolute Pressure Sensor Network

    PubMed Central

    Guo, Yue; Li, Yu-Hung; Guo, Zhiqiang; Kim, Kyunglok; Chang, Fu-Kuo; Wang, Shan X.

    2016-01-01

    A bio-inspired absolute pressure sensor network has been developed. Absolute pressure sensors, distributed on multiple silicon islands, are connected as a network by stretchable polyimide wires. This sensor network, made on a 4’’ wafer, has 77 nodes and can be mounted on various curved surfaces to cover an area up to 0.64 m × 0.64 m, which is 100 times larger than its original size. Due to Micro Electro-Mechanical system (MEMS) surface micromachining technology, ultrathin sensing nodes can be realized with thicknesses of less than 100 µm. Additionally, good linearity and high sensitivity (~14 mV/V/bar) have been achieved. Since the MEMS sensor process has also been well integrated with a flexible polymer substrate process, the entire sensor network can be fabricated in a time-efficient and cost-effective manner. Moreover, an accurate pressure contour can be obtained from the sensor network. Therefore, this absolute pressure sensor network holds significant promise for smart vehicle applications, especially for unmanned aerial vehicles. PMID:26729134

  4. Bio-Inspired Stretchable Absolute Pressure Sensor Network.

    PubMed

    Guo, Yue; Li, Yu-Hung; Guo, Zhiqiang; Kim, Kyunglok; Chang, Fu-Kuo; Wang, Shan X

    2016-01-01

    A bio-inspired absolute pressure sensor network has been developed. Absolute pressure sensors, distributed on multiple silicon islands, are connected as a network by stretchable polyimide wires. This sensor network, made on a 4'' wafer, has 77 nodes and can be mounted on various curved surfaces to cover an area up to 0.64 m × 0.64 m, which is 100 times larger than its original size. Due to Micro Electro-Mechanical system (MEMS) surface micromachining technology, ultrathin sensing nodes can be realized with thicknesses of less than 100 µm. Additionally, good linearity and high sensitivity (~14 mV/V/bar) have been achieved. Since the MEMS sensor process has also been well integrated with a flexible polymer substrate process, the entire sensor network can be fabricated in a time-efficient and cost-effective manner. Moreover, an accurate pressure contour can be obtained from the sensor network. Therefore, this absolute pressure sensor network holds significant promise for smart vehicle applications, especially for unmanned aerial vehicles. PMID:26729134

  5. Direct measurements of chemical bonding at solid surfaces using a unique calorimetric method: Towards understanding surface chemistry in energy technologies

    NASA Astrophysics Data System (ADS)

    Farmer, Jason A.

    Measuring the heat released when gas phase species adsorb onto surfaces provides essential information about the energies of surface species and the reactions they undergo. Here, heats of adsorption of technologically-interesting surface species were measured using a unique microcalorimetric technique in ultrahigh vacuum. Specifically, systems were studied which are relevant to understanding and improving transition metal catalysts and organic electronics. Metal adsorption energies were measured which elucidate metal-to-oxide and metal-to-polymer interfacial binding, and molecule adsorption energies were measured to understand how catalyst structure influences the energies of adsorbed reaction intermediates. Oxide-supported metal nanoparticles form the basis for many industrial catalysts. Nanoparticle activity, selectivity and resistance to sintering can depend strongly on particle size, oxide support, and defects on the oxide. To investigate the dependence of catalytic properties on oxide surface defects, defects were introduced on MgO(100) and CeO2(111), and their affect on the adsorption energy of metal atoms and the energy of supported nanoparticles was measured. These measurements help to explain why transition metal catalysts sinter more slowly and maintain smaller particles when supported on CeO 2 compared to other oxides, and how surface defects influence nanoparticle formation and film growth on oxides. The effect of nanoparticle size on the adsorption energy of CO on different-sized Pd nanoparticles on Fe3O 4(111) was measured, providing the first direct evidence that the heat of adsorption of CO decreases with decreasing Pd nanoparticle size. Knowledge of the direction and magnitude of particle size effects is necessary for improving existing catalysts and designing new ones. The metal/polymer interface is important because it impacts charge injection, extraction, and transport in organic electronics. Large-scale energy production using polymer

  6. Electronic energy transfer from molecules to metal and semiconductor surfaces, and chemisorption-induced changes in optical response of the nickel (111) surface

    SciTech Connect

    Whitmore, P.M.

    1982-10-01

    The evolution of molecular excited states near solid surfaces is investigated. The mechanisms through which energy is transferred to the surface are described within a classical image dipole picture of the interaction. More sophisticated models for the dielectric response of the solid surface add important new decay channels for the energy dissipation. The predictions and applicability of three of these refined theories are discussed.

  7. Energy dependence of the trapping of uranium atoms by aluminum oxide surfaces

    NASA Technical Reports Server (NTRS)

    Librecht, K. G.

    1979-01-01

    The energy dependence of the trapping probability for sputtered U-235 atoms striking an oxidized aluminum collector surface at energies between 1 eV and 184 eV was measured. At the lowest energies, approximately 10% of the uranium atoms are not trapped, while above 10 eV essentially all of them stick. Trapping probabilities averaged over the sputtered energy distribution for uranium incident on gold and mica are also presented.

  8. Absolute Radiometric Calibration of KOMPSAT-3A

    NASA Astrophysics Data System (ADS)

    Ahn, H. Y.; Shin, D. Y.; Kim, J. S.; Seo, D. C.; Choi, C. U.

    2016-06-01

    This paper presents a vicarious radiometric calibration of the Korea Multi-Purpose Satellite-3A (KOMPSAT-3A) performed by the Korea Aerospace Research Institute (KARI) and the Pukyong National University Remote Sensing Group (PKNU RSG) in 2015.The primary stages of this study are summarized as follows: (1) A field campaign to determine radiometric calibrated target fields was undertaken in Mongolia and South Korea. Surface reflectance data obtained in the campaign were input to a radiative transfer code that predicted at-sensor radiance. Through this process, equations and parameters were derived for the KOMPSAT-3A sensor to enable the conversion of calibrated DN to physical units, such as at-sensor radiance or TOA reflectance. (2) To validate the absolute calibration coefficients for the KOMPSAT-3A sensor, we performed a radiometric validation with a comparison of KOMPSAT-3A and Landsat-8 TOA reflectance using one of the six PICS (Libya 4). Correlations between top-of-atmosphere (TOA) radiances and the spectral band responses of the KOMPSAT-3A sensors at the Zuunmod, Mongolia and Goheung, South Korea sites were significant for multispectral bands. The average difference in TOA reflectance between KOMPSAT-3A and Landsat-8 image over the Libya 4, Libya site in the red-green-blue (RGB) region was under 3%, whereas in the NIR band, the TOA reflectance of KOMPSAT-3A was lower than the that of Landsat-8 due to the difference in the band passes of two sensors. The KOMPSAT-3Aensor includes a band pass near 940 nm that can be strongly absorbed by water vapor and therefore displayed low reflectance. Toovercome this, we need to undertake a detailed analysis using rescale methods, such as the spectral bandwidth adjustment factor.

  9. The effect of simple to sophisticated surface processes on the surface energy and hydrologic budgets of a general circulation model

    SciTech Connect

    Meyer, M.K.

    1991-06-01

    Using the Community Climate Model (CCM) of the National Center for Atmospheric Research (NCAR), comparisons have been made of three multi-three simulations in which there is a varying degree of complexity in the land surface parameterization but the model version and prescribed sea surface temperatures are the same. The land surface parameterizations employed are a simple prescription of soil moisture (based on surface type), a 15 cm bucket-type soil moisture and Biosphere-Atmosphere Transfer Scheme (BATS) (which, for the version used, simulates a vegetative canopy and two soil layers). This study has shown that the treatment of the surface in a general circulation model (GCM) can effect the surface energy and hydrologic budgets. Both a simple bucket and more sophisticated parameterization (BATS) led to generally drier conditions over land in the summer hemisphere. These drier conditions were noted with a decrease in precipitation and latent heat flux. With the BATS simulation, the decreased latent heat flux over land was accompanied by a strong increase in sensible heat flux due to an increase in net radiation. With the BATS simulation it is difficult to discern if the changes are due to more detailed treatment to the surface or the inclusion of a diurnal cycle. 8 refs., 5 figs.

  10. Fine powder flow under humid environmental conditions from the perspective of surface energy.

    PubMed

    Karde, Vikram; Ghoroi, Chinmay

    2015-05-15

    The influence of humidity on surface energetics and flow behavior of fine pharmaceutical powders was investigated. Amorphous and crystalline fine powders with hydrophilic (Corn starch and Avicel PH105) and hydrophobic (ibuprofen) nature were considered for this study. The surface energy was determined using surface energy analyzer and flow behavior was measured in terms of unconfined yield stress (UYS) using a shear tester. The study showed that unlike hydrophobic ibuprofen powder, surface energy and flow of hydrophilic excipient powders were affected by relative humidity (RH). The Lifshitz-van der Waals dispersive (γ(LW)) component of surface energy barely changed with varying RH for all pharmaceutical powders. For hydrophilic excipients, the specific component of surface energy (γ(SP)) was found to increase with increasing RH. Furthermore, for these excipients, flow deterioration at elevated RH was observed due to increased capillary bridge formation. Detailed analysis showed that γ(SP) component of surface energy can be an effective indicator for flow behavior of fine powders under varying humid conditions. The present study also brought out the existence of different regimes of probable interparticle forces which dictate the bulk flow behavior of fine hydrophilic powder under humid conditions.

  11. Effect of mechanical denaturation on surface free energy of protein powders.

    PubMed

    Mohammad, Mohammad Amin; Grimsey, Ian M; Forbes, Robert T; Blagbrough, Ian S; Conway, Barbara R

    2016-10-01

    Globular proteins are important both as therapeutic agents and excipients. However, their fragile native conformations can be denatured during pharmaceutical processing, which leads to modification of the surface energy of their powders and hence their performance. Lyophilized powders of hen egg-white lysozyme and β-galactosidase from Aspergillus oryzae were used as models to study the effects of mechanical denaturation on the surface energies of basic and acidic protein powders, respectively. Their mechanical denaturation upon milling was confirmed by the absence of their thermal unfolding transition phases and by the changes in their secondary and tertiary structures. Inverse gas chromatography detected differences between both unprocessed protein powders and the changes induced by their mechanical denaturation. The surfaces of the acidic and basic protein powders were relatively basic, however the surface acidity of β-galactosidase was higher than that of lysozyme. Also, the surface of β-galactosidase powder had a higher dispersive energy compared to lysozyme. The mechanical denaturation decreased the dispersive energy and the basicity of the surfaces of both protein powders. The amino acid composition and molecular conformation of the proteins explained the surface energy data measured by inverse gas chromatography. The biological activity of mechanically denatured protein powders can either be reversible (lysozyme) or irreversible (β-galactosidase) upon hydration. Our surface data can be exploited to understand and predict the performance of protein powders within pharmaceutical dosage forms. PMID:27434157

  12. Effect of mechanical denaturation on surface free energy of protein powders.

    PubMed

    Mohammad, Mohammad Amin; Grimsey, Ian M; Forbes, Robert T; Blagbrough, Ian S; Conway, Barbara R

    2016-10-01

    Globular proteins are important both as therapeutic agents and excipients. However, their fragile native conformations can be denatured during pharmaceutical processing, which leads to modification of the surface energy of their powders and hence their performance. Lyophilized powders of hen egg-white lysozyme and β-galactosidase from Aspergillus oryzae were used as models to study the effects of mechanical denaturation on the surface energies of basic and acidic protein powders, respectively. Their mechanical denaturation upon milling was confirmed by the absence of their thermal unfolding transition phases and by the changes in their secondary and tertiary structures. Inverse gas chromatography detected differences between both unprocessed protein powders and the changes induced by their mechanical denaturation. The surfaces of the acidic and basic protein powders were relatively basic, however the surface acidity of β-galactosidase was higher than that of lysozyme. Also, the surface of β-galactosidase powder had a higher dispersive energy compared to lysozyme. The mechanical denaturation decreased the dispersive energy and the basicity of the surfaces of both protein powders. The amino acid composition and molecular conformation of the proteins explained the surface energy data measured by inverse gas chromatography. The biological activity of mechanically denatured protein powders can either be reversible (lysozyme) or irreversible (β-galactosidase) upon hydration. Our surface data can be exploited to understand and predict the performance of protein powders within pharmaceutical dosage forms.

  13. Absolute spectrum and charge ratio of cosmic ray muons in the energy region from 0.2 GeV to 100 GeV at 600 m above sea level

    NASA Technical Reports Server (NTRS)

    De Pascale, M. P.; Morselli, A.; Picozza, P.; Golden, R. L.; Grimani, C.; Kimbell, B. L.; Stephens, S. A.; Stochaj, S. J.; Webber, W. R.; Basini, G.

    1993-01-01

    We have determined the momentum spectrum and charge ratio of muons in the region from 250 MeV/c to 100 GeV/c using a superconducting magnetic spectrometer. The absolute differential spectrum of muons obtained in this experiment at 600 m above sea level is in good agreement with the previous measurements at sea level. The differential spectrum can be represented by a power law with a varying index, which is consistent with zero below 450 MeV/c and steepens to a value of -2.7 +/- 0.1 between 20 and 100 GeV/c. The integral f1ux of muons measured in this experiment span a very large range of momentum and is in excellent agreement with the earlier results. The positive to negative muon ratio appears to be constant in the entire momentum range covered in this experiment within the errors and the mean value is 1.220 +/- 0.044. The absolute momentum spectrum and the charge ratio measured in this experiment are also consistent with the theoretical expectations. This is the only experiment which covers a wide range of nearly three decades in momentum from a very low momentum.

  14. Band energy control of molybdenum oxide by surface hydration

    SciTech Connect

    Butler, Keith T. Walsh, Aron; Crespo-Otero, Rachel; Buckeridge, John; Scanlon, David O.; Bovill, Edward; Lidzey, David

    2015-12-07

    The application of oxide buffer layers for improved carrier extraction is ubiquitous in organic electronics. However, the performance is highly susceptible to processing conditions. Notably, the interface stability and electronic structure is extremely sensitive to the uptake of ambient water. In this study we use density functional theory calculations to asses the effects of adsorbed water on the electronic structure of MoO{sub x}, in the context of polymer-fullerene solar cells based on PCDTBT. We obtain excellent agreement with experimental values of the ionization potential for pristine MoO{sub 3} (010). We find that IP and EA values can vary by as much as 2.5 eV depending on the oxidation state of the surface and that adsorbed water can either increase or decrease the IP and EA depending on the concentration of surface water.

  15. Energy Landscape of Water and Ethanol on Silica Surfaces

    SciTech Connect

    Wu, Di; Guo, Xiaofeng; Sun, Hui; Navrotsky, Alexandra

    2015-06-26

    Fundamental understanding of small molecule–silica surface interactions at their interfaces is essential for the scientific, technological, and medical communities. We report direct enthalpy of adsorption (Δhads) measurements for ethanol and water vapor on porous silica glass (CPG-10), in both hydroxylated and dehydroxylated (hydrophobic) forms. Results suggest a spectrum of energetics as a function of coverage, stepwise for ethanol but continuous for water. The zero-coverage enthalpy of adsorption for hydroxylated silica shows the most exothermic enthalpies for both water (-72.7 ± 3.1 kJ/mol water) and ethanol (-78.0 ± 1.9 kJ/mol ethanol). The water adsorption enthalpy becomes less exothermic gradually until reaching its only plateau (-20.7 ± 2.2 kJ/mol water) reflecting water clustering on a largely hydrophobic surface, while the enthalpy of ethanol adsorption profile presents two well separated plateaus, corresponding to strong chemisorption of ethanol on adsorbate-free silica surface (-66.4 ± 4.8 kJ/mol ethanol), and weak physisorption of ethanol on ethanol covered silica (-4.0 ± 1.6 kJ/mol ethanol). On the other hand, dehydroxylation leads to missing water–silica interactions, whereas the number of ethanol binding sites is not impacted. The isotherms and partial molar properties of adsorption suggest that water may only bind strongly onto the silanols (which are a minor species on silica glass), whereas ethanol can interact strongly with both silanols and the hydrophobic areas of the silica surface.

  16. Energy Landscape of Water and Ethanol on Silica Surfaces

    DOE PAGES

    Wu, Di; Guo, Xiaofeng; Sun, Hui; Navrotsky, Alexandra

    2015-06-26

    Fundamental understanding of small molecule–silica surface interactions at their interfaces is essential for the scientific, technological, and medical communities. We report direct enthalpy of adsorption (Δhads) measurements for ethanol and water vapor on porous silica glass (CPG-10), in both hydroxylated and dehydroxylated (hydrophobic) forms. Results suggest a spectrum of energetics as a function of coverage, stepwise for ethanol but continuous for water. The zero-coverage enthalpy of adsorption for hydroxylated silica shows the most exothermic enthalpies for both water (-72.7 ± 3.1 kJ/mol water) and ethanol (-78.0 ± 1.9 kJ/mol ethanol). The water adsorption enthalpy becomes less exothermic gradually until reachingmore » its only plateau (-20.7 ± 2.2 kJ/mol water) reflecting water clustering on a largely hydrophobic surface, while the enthalpy of ethanol adsorption profile presents two well separated plateaus, corresponding to strong chemisorption of ethanol on adsorbate-free silica surface (-66.4 ± 4.8 kJ/mol ethanol), and weak physisorption of ethanol on ethanol covered silica (-4.0 ± 1.6 kJ/mol ethanol). On the other hand, dehydroxylation leads to missing water–silica interactions, whereas the number of ethanol binding sites is not impacted. The isotherms and partial molar properties of adsorption suggest that water may only bind strongly onto the silanols (which are a minor species on silica glass), whereas ethanol can interact strongly with both silanols and the hydrophobic areas of the silica surface.« less

  17. Large variation of vacancy formation energies in the surface of crystalline ice.

    PubMed

    Watkins, M; Pan, D; Wang, E G; Michaelides, A; VandeVondele, J; Slater, B

    2011-10-01

    Resolving the atomic structure of the surface of ice particles within clouds, over the temperature range encountered in the atmosphere and relevant to understanding heterogeneous catalysis on ice, remains an experimental challenge. By using first-principles calculations, we show that the surface of crystalline ice exhibits a remarkable variance in vacancy formation energies, akin to an amorphous material. We find vacancy formation energies as low as ~0.1-0.2 eV, which leads to a higher than expected vacancy concentration. Because a vacancy's reactivity correlates with its formation energy, ice particles may be more reactive than previously thought. We also show that vacancies significantly reduce the formation energy of neighbouring vacancies, thus facilitating pitting and contributing to pre-melting and quasi-liquid layer formation. These surface properties arise from proton disorder and the relaxation of geometric constraints, which suggests that other frustrated materials may possess unusual surface characteristics.

  18. Semi-infinite jellium: Thermodynamic potential, chemical potential, and surface energy

    NASA Astrophysics Data System (ADS)

    Kostrobij, P. P.; Markovych, B. M.

    2015-08-01

    A general expression for the thermodynamic potential of the model of semi-infinite jellium is obtained. By using this expression, the surface energy for the infinite barrier model is calculated. The behavior of the surface energy and of the chemical potential as functions of the Wigner-Seitz radius and the influence of the Coulomb interaction between electrons on the calculated values is studied. It is shown that taking into account the Coulomb interaction between electrons leads to growth of the surface energy. The surface energy is positive in the entire area of the Wigner-Seitz radius. It is shown that taking into account the Coulomb interaction between electrons leads to a decrease of the chemical potential.

  19. The PyPES library of high quality semi-global potential energy surfaces.

    PubMed

    Sibaev, Marat; Crittenden, Deborah L

    2015-11-01

    In this article, we present a Python-based library of high quality semi-global potential energy surfaces for 50 polyatomic molecules with up to six atoms. We anticipate that these surfaces will find widespread application in the testing of new potential energy surface construction algorithms and nuclear ro-vibrational structure theories. To this end, we provide the ability to generate the energy derivatives required for Taylor series expansions to sixth order about any point on the potential energy surface in a range of common coordinate systems, including curvilinear internal, Cartesian, and normal mode coordinates. The PyPES package, along with FORTRAN, C, MATLAB and Mathematica wrappers, is available at http://sourceforge.net/projects/pypes-lib.

  20. The PyPES library of high quality semi-global potential energy surfaces.

    PubMed

    Sibaev, Marat; Crittenden, Deborah L

    2015-11-01

    In this article, we present a Python-based library of high quality semi-global potential energy surfaces for 50 polyatomic molecules with up to six atoms. We anticipate that these surfaces will find widespread application in the testing of new potential energy surface construction algorithms and nuclear ro-vibrational structure theories. To this end, we provide the ability to generate the energy derivatives required for Taylor series expansions to sixth order about any point on the potential energy surface in a range of common coordinate systems, including curvilinear internal, Cartesian, and normal mode coordinates. The PyPES package, along with FORTRAN, C, MATLAB and Mathematica wrappers, is available at http://sourceforge.net/projects/pypes-lib. PMID:26407838

  1. Improved Potential Energy Surface of Ozone Constructed Using the Fitting by Permutationally Invariant Polynomial Function

    DOE PAGES

    Ayouz, Mehdi; Babikov, Dmitri

    2012-01-01

    New global potential energy surface for the ground electronic state of ozone is constructed at the complete basis set level of the multireference configuration interaction theory. A method of fitting the data points by analytical permutationally invariant polynomial function is adopted. A small set of 500 points is preoptimized using the old surface of ozone. In this procedure the positions of points in the configuration space are chosen such that the RMS deviation of the fit is minimized. New ab initio calculations are carried out at these points and are used to build new surface. Additional points are addedmore » to the vicinity of the minimum energy path in order to improve accuracy of the fit, particularly in the region where the surface of ozone exhibits a shallow van der Waals well. New surface can be used to study formation of ozone at thermal energies and its spectroscopy near the dissociation threshold.« less

  2. The global land surface energy balance and its representation in CMIP5 models

    NASA Astrophysics Data System (ADS)

    Wild, Martin; Folini, Doris; Hakuba, Maria; Schär, Christoph; Seneviratne, Sonia; Kato, Seiji; Rutan, David; Ammann, Christof; Wood, Eric; König-Langlo, Gert

    2015-04-01

    The energy budget over terrestrial surfaces is a key determinant of the land surface climate and governs a variety of physical, chemical and biological surface processes. The purpose of the present study is to establish new reference estimates for the different components of the energy balance over global land surfaces. Thanks to the impressive progress in space-based observation systems in the past decade, we now know the energy exchanges between our planet and the surrounding space with unprecedented accuracy. However, the energy flows at the Earth's surface have not been established with the same accuracy, since they cannot be directly measured from satellites. Accordingly, estimates on the magnitude of the fluxes at terrestrial surfaces largely vary, and latest climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) still show significant differences in their simulated energy budgets on a land mean basis, which prevents a consistent simulation of the land surface processes in these models. In the present study we use to the extent possible direct observations of surface radiative fluxes from the Global Energy Balance Archive (GEBA) and the Baseline Surface Radiation Network (BSRN) to better constrain the simulated fluxes over global land surfaces. These model-calculated fluxes stem from the comprehensive set of more than 40 global climate from CMIP5 used in the latest IPCC report AR5. The CMIP5 models overall still show a tendency to overestimate the downward solar and underestimate the downward thermal radiation at terrestrial surfaces, a long standing problem in climate modelling. Based on the direct radiation observations and the bias structure of the CMIP5 models we infer best estimates for the downward solar and thermal radiation averaged over global land surfaces. They amount to 184 Wm-2 and 306 Wm-2, respectively. These values closely agree with the respective quantities independently derived by recent state-of-the-art reanalyses

  3. Intercomparison and interpretation of surface energy fluxes in atmospheric general circulation models

    NASA Technical Reports Server (NTRS)

    Randall, D. A.; Cess, R. D.; Blanchet, J. P.; Boer, G. J.; Dazlich, D. A.; Del Genio, A. D.; Deque, M.; Dymnikov, V.; Galin, V.; Ghan, S. J.

    1992-01-01

    Responses of the surface energy budgets and hydrologic cycles of 19 atmospheric general circulation models to an imposed, globally uniform sea surface temperature perturbation of 4 K were analyzed. The responses of the simulated surface energy budgets are extremely diverse and are closely linked to the responses of the simulated hydrologic cycles. The response of the net surface energy flux is not controlled by cloud effects; instead, it is determined primarily by the response of the latent heat flux. The prescribed warming of the oceans leads to major increases in the atmospheric water vapor content and the rates of evaporation and precipitation. The increased water vapor amount drastically increases the downwelling IR radiation at the earth's surface, but the amount of the change varies dramatically from one model to another.

  4. Impact of Dust on Mars Surface Albedo and Energy Flux with LMD General Circulation Model

    NASA Astrophysics Data System (ADS)

    Singh, D.; Flanner, M.; Millour, E.; Martinez, G.

    2015-12-01

    Mars, just like Earth experience different seasons because of its axial tilt (about 25°). This causes growth and retreat of snow cover (primarily CO2) in Martian Polar regions. The perennial caps are the only place on the planet where condensed H2O is available at surface. On Mars, as much as 30% atmospheric CO2 deposits in each hemisphere depending upon the season. This leads to a significant variation on planet's surface albedo and hence effecting the amount of solar flux absorbed or reflected at the surface. General Circulation Model (GCM) of Laboratoire de Météorologie Dynamique (LMD) currently uses observationally derived surface albedo from Thermal Emission Spectrometer (TES) instrument for the polar caps. These TES albedo values do not have any inter-annual variability, and are independent of presence of any dust/impurity on surface. Presence of dust or other surface impurities can significantly reduce the surface albedo especially during and right after a dust storm. This change will also be evident in the surface energy flux interactions. Our work focuses on combining earth based Snow, Ice, and Aerosol Radiation (SNICAR) model with current state of GCM to incorporate the impact of dust on Martian surface albedo, and hence the energy flux. Inter-annual variability of surface albedo and planet's top of atmosphere (TOA) energy budget along with their correlation with currently available mission data will be presented.

  5. Jasminum flexile flower absolute from India--a detailed comparison with three other jasmine absolutes.

    PubMed

    Braun, Norbert A; Kohlenberg, Birgit; Sim, Sherina; Meier, Manfred; Hammerschmidt, Franz-Josef

    2009-09-01

    Jasminum flexile flower absolute from the south of India and the corresponding vacuum headspace (VHS) sample of the absolute were analyzed using GC and GC-MS. Three other commercially available Indian jasmine absolutes from the species: J. sambac, J. officinale subsp. grandiflorum, and J. auriculatum and the respective VHS samples were used for comparison purposes. One hundred and twenty-one compounds were characterized in J. flexile flower absolute, with methyl linolate, benzyl salicylate, benzyl benzoate, (2E,6E)-farnesol, and benzyl acetate as the main constituents. A detailed olfactory evaluation was also performed.

  6. Quantum chemical interaction energy surfaces of ethylene and propene dimers.

    PubMed

    Jalkanen, Jukka-Pekka; Pulkkinen, Sallaraisa; Pakkanen, Tapani A; Rowley, Richard L

    2005-03-31

    Ab initio studies of nonbonding interactions for ethylene and propene dimers were conducted at the MP2/6-311+G(2df,2pd) level. The dimers were attractive in all of the orientations studied; however, the attraction was <0.1 kcal/mol for ethylene D2h and C2h dimers, for which the pi-electron clouds or H atoms interact closely. A previously introduced transferable potential model, NIPE [Jalkanen, J.-P.; Pakkanen, T. A.; Yang, Y.; Rowley, R. L. J. Chem. Phys. 2003, 118, 5474], which is based on quantum chemical calculations of small alkane molecules, was tested against the propene and ethylene dimer data. Comparisons of results showed that interaction energies for orientations dominated by interactions between the propene methyl groups or two hydrogens were accurately predicted with the NIPE model. Interactions involving the double bond were not predicted as well, because the original NIPE regression data set did not contain any information about pi-electron systems. An extension of the NIPE model to include pi-electron interactions is proposed. Additional interaction sites are used with the same energy function as atomic interactions. This addition provides a more accurate description of the interaction energies of both ethylene and propene and extends the transferability of the NIPE model to alkenes.

  7. Intermolecular potential energy surface and thermophysical properties of ethylene oxide

    SciTech Connect

    Crusius, Johann-Philipp Hassel, Egon; Hellmann, Robert; Bich, Eckard

    2014-10-28

    A six-dimensional potential energy hypersurface (PES) for two interacting rigid ethylene oxide (C{sub 2}H{sub 4}O) molecules was determined from high-level quantum-chemical ab initio calculations. The counterpoise-corrected supermolecular approach at the MP2 and CCSD(T) levels of theory was utilized to determine interaction energies for 10178 configurations of two molecules. An analytical site-site potential function with 19 sites per ethylene oxide molecule was fitted to the interaction energies and fine tuned to agree with data for the second acoustic virial coefficient from accurate speed of sound measurements. The PES was validated by computing the second virial coefficient, shear viscosity, and thermal conductivity. The values of these properties are substantiated by the best experimental data as they tend to fall within the uncertainty intervals and also obey the experimental temperature functions, except for viscosity, where experimental data are insufficient. Due to the lack of reliable data, especially for the transport properties, our calculated values are currently the most accurate estimates for these properties of ethylene oxide.

  8. Absolute Quantification of Human Liver Phosphorus-Containing Metabolites In Vivo Using an Inhomogeneous Spoiling Magnetic Field Gradient

    PubMed Central

    Bashir, Adil; Gropler, Robert; Ackerman, Joseph

    2015-01-01

    Purpose Absolute concentrations of high-energy phosphorus (31P) metabolites in liver provide more important insight into physiologic status of liver disease compared to resonance integral ratios. A simple method for measuring absolute concentrations of 31P metabolites in human liver is described. The approach uses surface spoiling inhomogeneous magnetic field gradient to select signal from liver tissue. The technique avoids issues caused by respiratory motion, chemical shift dispersion associated with linear magnetic field gradients, and increased tissue heat deposition due to radiofrequency absorption, especially at high field strength. Methods A method to localize signal from liver was demonstrated using superficial and highly non-uniform magnetic field gradients, which eliminate signal(s) from surface tissue(s) located between the liver and RF coil. A double standard method was implemented to determine absolute 31P metabolite concentrations in vivo. 8 healthy individuals were examined in a 3 T MR scanner. Results Concentrations of metabolites measured in eight healthy individuals are: γ-adenosine triphosphate (ATP) = 2.44 ± 0.21 (mean ± sd) mmol/l of wet tissue volume, α-ATP = 3.2 ± 0.63 mmol/l, β-ATP = 2.98 ± 0.45 mmol/l, inorganic phosphates (Pi) = 1.87 ± 0.25 mmol/l, phosphodiesters (PDE) = 10.62 ± 2.20 mmol/l and phosphomonoesters (PME) = 2.12 ± 0.51 mmol/l. All are in good agreement with literature values. Conclusions The technique offers robust and fast means to localize signal from liver tissue, allows absolute metabolite concentration determination, and avoids problems associated with constant field gradient (linear field variation) localization methods. PMID:26633549

  9. Volume and surface contributions to the nuclear symmetry energy within the coherent density fluctuation model

    NASA Astrophysics Data System (ADS)

    Antonov, A. N.; Gaidarov, M. K.; Sarriguren, P.; Moya de Guerra, E.

    2016-07-01

    The volume and surface components of the nuclear symmetry energy (NSE) and their ratio are calculated within the coherent density fluctuation model (CDFM). The estimations use the results of the model for the NSE in finite nuclei based on the Brueckner energy-density functional for nuclear matter. In addition, we present results for the NSE and its volume and surface contributions obtained by using the Skyrme energy-density functional. The CDFM weight function is obtained using the proton and neutron densities from the self-consistent HF+BCS method with Skyrme interactions. We present and discuss the values of the volume and surface contributions to the NSE and their ratio obtained for the Ni, Sn, and Pb isotopic chains, studying their isotopic sensitivity. The results are compared with estimations of other approaches which have used available experimental data on binding energies, neutron-skin thicknesses, excitation energies to isobaric analog states (IAS), and also with results of other theoretical methods.

  10. New potential energy surface for the HCS(+)-He system and inelastic rate coefficients.

    PubMed

    Dubernet, Marie-Lise; Quintas-Sánchez, Ernesto; Tuckey, Philip

    2015-07-28

    A new high quality potential energy surface is calculated at a coupled-cluster single double triple level with an aug-cc-pV5Z basis set for the HCS(+)-He system. This potential energy surface is used in low energy quantum scattering calculations to provide a set of (de)-excitation cross sections and rate coefficients among the first 20 rotational levels of HCS(+) by He in the range of temperature from 5 K to 100 K. The paper discusses the impact of the new ab initio potential energy surface on the cross sections at low energy and provides a comparison with the HCO(+)-He system. The HCS(+)-He rate coefficients for the strongest transitions differ by factors of up to 2.5 from previous rate coefficients; thus, analysis of astrophysical spectra should be reconsidered with the new rate coefficients.

  11. Universal Cosmic Absolute and Modern Science

    NASA Astrophysics Data System (ADS)

    Kostro, Ludwik

    The official Sciences, especially all natural sciences, respect in their researches the principle of methodic naturalism i.e. they consider all phenomena as entirely natural and therefore in their scientific explanations they do never adduce or cite supernatural entities and forces. The purpose of this paper is to show that Modern Science has its own self-existent, self-acting, and self-sufficient Natural All-in Being or Omni-Being i.e. the entire Nature as a Whole that justifies the scientific methodic naturalism. Since this Natural All-in Being is one and only It should be considered as the own scientifically justified Natural Absolute of Science and should be called, in my opinion, the Universal Cosmic Absolute of Modern Science. It will be also shown that the Universal Cosmic Absolute is ontologically enormously stratified and is in its ultimate i.e. in its most fundamental stratum trans-reistic and trans-personal. It means that in its basic stratum. It is neither a Thing or a Person although It contains in Itself all things and persons with all other sentient and conscious individuals as well, On the turn of the 20th century the Science has begun to look for a theory of everything, for a final theory, for a master theory. In my opinion the natural Universal Cosmic Absolute will constitute in such a theory the radical all penetrating Ultimate Basic Reality and will substitute step by step the traditional supernatural personal Absolute.

  12. A non-classical Mindlin plate model incorporating microstructure, surface energy and foundation effects

    NASA Astrophysics Data System (ADS)

    Gao, X.-L.; Zhang, G. Y.

    2016-07-01

    A non-classical model for a Mindlin plate resting on an elastic foundation is developed in a general form using a modified couple stress theory, a surface elasticity theory and a two-parameter Winkler-Pasternak foundation model. It includes all five kinematic variables possible for a Mindlin plate. The equations of motion and the complete boundary conditions are obtained simultaneously through a variational formulation based on Hamilton's principle, and the microstructure, surface energy and foundation effects are treated in a unified manner. The newly developed model contains one material length-scale parameter to describe the microstructure effect, three surface elastic constants to account for the surface energy effect, and two foundation parameters to capture the foundation effect. The current non-classical plate model reduces to its classical elasticity-based counterpart when the microstructure, surface energy and foundation effects are all suppressed. In addition, the new model includes the Mindlin plate models considering the microstructure dependence or the surface energy effect or the foundation influence alone as special cases, recovers the Kirchhoff plate model incorporating the microstructure, surface energy and foundation effects, and degenerates to the Timoshenko beam model including the microstructure effect. To illustrate the new Mindlin plate model, the static bending and free vibration problems of a simply supported rectangular plate are analytically solved by directly applying the general formulae derived.

  13. Surface energy fluxes at Central Florida during the convection and precipitation electrification experiment

    NASA Technical Reports Server (NTRS)

    Nie, D.; Demetriades-Shah, T. D.; Kanemasu, E. T.

    1993-01-01

    One of the objectives of CaPE is to better understand the convective process in central and south Florida during the warm season. The energy and moisture exchanges between the surface and the atmosphere are closely related to this process. Some recent studies have shown that the surface energy balance plays an important role in the climatic fields (Shukla and Mintz, 1982; Sud and Smith, 1985; Sato et. al, 1989). Surface energy fluxes and related surface processes such as evapotranspiration and sensible heat transfer directly effect the temperature, humidity, cloud formation and precipitation. For example, mesoscale circulation around a discontinuity in vegetation type were shown to be stronger with wet soil than with dry soil using an evapotranspiration model (Pinty et. al, 1989). In order to better describe the processes in the atmosphere at various scales and improve our ability of modeling and predicting weather related events, it is crucial to understand the mechanism of surface energy transfer in relation to atmospheric events. Surface energy flux measurements are required to fully understand the interactions between the atmosphere and the surface.

  14. Competition between surface trapping and nonradiative energy transfer to gold nanofilm

    PubMed Central

    Yang, Zhenling; Liu, Yuqiang; He, Xing; Wen, Yanan; Yang, Yanqiang

    2010-01-01

    Nonradiative resonant energy transfer from CdSeS quantum dot to gold nanofilm was investigated by taking nanosecond and picosecond time resolved photoluminescence measurements. Surface plasma resonant absorption peak of gold nanofilm was adjusted to meet the near resonant conditions with the fluorescence peak of quantum dot by changing the thickness. Surface trapping state was proved to be the origin of the long lifetime component by comparing fresh and eight months aged quantum dot. It was observed that the excitonic state lifetime of the quantum dots was reduced by nonradiative resonant energy transfer to gold nanofilm. Nonradiative resonant energy transfer time, which was comparable with the surface trapping time, was calculated based on the data of picosecond photoluminescence measurements. No nonradiative energy transfer from surface trapping state to gold nanofilm, thus the lifetime of surface trapping state was not affected obviously. It is suggested that in the assembly combined with quantum dot and gold nanostructure, nonradiative energy transfer will occur after the population of excitonic state, and compete with surface trapping process. The interactions between surface trapping state and gold nanoflim were not exhibited. PMID:21124724

  15. Absolute far-ultraviolet spectrophotometry of hot subluminous stars from Voyager

    SciTech Connect

    Holberg, J.B.; Ali, B.; Carone, T.E.; Polidan, R.S. NASA, Goddard Space Flight Center, Greenbelt, MD )

    1991-07-01

    Observations, obtained with the Voyager ultraviolet spectrometers, are presented of absolute fluxes for two well-known hot subluminous stars: BD + 28 deg 4211, an sdO, and G191 - B2B, a hot DA white dwarf. Complete absolute energy distributions for these two stars, from the Lyman limit at 912 A to 1 micron, are given. For BD + 28 deg 4211, a single power law closely represents the entire observed energy distribution. For G191 - B2B, a pure hydrogen model atmosphere provides an excellent match to the entire absolute energy distribution. Voyager absolute fluxes are discussed in relation to those reported from various sounding rocket experiments, including a recent rocket observation of BD + 28 deg 4211. 43 refs.

  16. Absolute far-ultraviolet spectrophotometry of hot subluminous stars from Voyager

    NASA Technical Reports Server (NTRS)

    Holberg, J. B.; Ali, B.; Carone, T. E.; Polidan, R. S.

    1991-01-01

    Observations, obtained with the Voyager ultraviolet spectrometers, are presented of absolute fluxes for two well-known hot subluminous stars: BD + 28 deg 4211, an sdO, and G191 - B2B, a hot DA white dwarf. Complete absolute energy distributions for these two stars, from the Lyman limit at 912 A to 1 micron, are given. For BD + 28 deg 4211, a single power law closely represents the entire observed energy distribution. For G191 - B2B, a pure hydrogen model atmosphere provides an excellent match to the entire absolute energy distribution. Voyager absolute fluxes are discussed in relation to those reported from various sounding rocket experiments, including a recent rocket observation of BD + 28 deg 4211.

  17. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S.; Techert, Simone; Strocov, Vladimir N.; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-01

    Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.

  18. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering

    PubMed Central

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S.; Techert, Simone; Strocov, Vladimir N.; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-01

    Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future. PMID:26821751

  19. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering.

    PubMed

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S; Techert, Simone; Strocov, Vladimir N; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-01

    Thermally driven chemistry as well as materials' functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.

  20. Nanopatterning of mica surface under low energy ion beam sputtering

    SciTech Connect

    Metya, A.; Ghose, D.; Mollick, S. A.; Majumdar, A.

    2012-04-01

    Irradiation of crystalline muscovite mica samples by 500 eV Ar{sup +} ions at different incident angles can induce significant surface morphological variations. A periodic ripple pattern of nano-dimensions forms in the angle window 47 deg. -70 deg. . On the other hand, tilted conical protrusions develop on the surface at grazing incidence angles around 80 deg. . From the derivative of the topographic images the distribution of the side-facet slopes in the ion incidence plane are measured, which is found to be strongly related to the pattern morphology. Additionally, it has been shown that, for the ripple structures, the base angles can be tuned by changing the ion fluence. An asymmetric sawtooth profile of the ripples obtained at low fluence is transformed to a symmetrical triangular profile at high fluence. As the slopes are found to be small, the pattern formation is not provoked by the gradient-dependent erosion mechanism rather it is the general effect of the curvature-dependent sputtering phenomena.

  1. Analysis of surface energy budget data over varying land-cover conditions.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The surface energy budget plays an important role in boundary-layer meteorology and quantifying these budgets over varying land surface types is important in studying land-atmosphere interactions. In late April 2007, eddy covariance towers were erected at four sites in the Little Washita Watershed i...

  2. Analysis of Surface Energy Budget Data Over Varying Land-Cover Conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The surface energy budget plays an important role in boundary-layer meteorology and quantifying these budgets over varying land surface types is important in studying land-atmosphere interactions. In late April 2007, eddy covariance towers were erected at four sites in the Little Washita Watershed ...

  3. Controlled removal of ceramic surfaces with combination of ions implantation and ultrasonic energy

    DOEpatents

    Boatner, Lynn A.; Rankin, Janet; Thevenard, Paul; Romana, Laurence J.

    1995-01-01

    A method for tailoring or patterning the surface of ceramic articles is provided by implanting ions to predetermined depth into the ceramic material at a selected surface location with the ions being implanted at a fluence and energy adequate to damage the lattice structure of the ceramic material for bi-axially straining near-surface regions of the ceramic material to the predetermined depth. The resulting metastable near-surface regions of the ceramic material are then contacted with energy pulses from collapsing, ultrasonically-generated cavitation bubbles in a liquid medium for removing to a selected depth the ion-damaged near-surface regions containing the bi-axially strained lattice structure from the ceramic body. Additional patterning of the selected surface location on the ceramic body is provided by implanting a high fluence of high-energy, relatively-light ions at selected surface sites for relaxing the bi-axial strain in the near-surface regions defined by these sites and thereby preventing the removal of such ion-implanted sites by the energy pulses from the collapsing ultrasonic cavitation bubbles.

  4. Mapping land-surface fluxes of carbon, water and energy from field to regional scales

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A framework for routine mapping of land-surface fluxes of carbon, water, and energy at the field to regional scales has been established for drought monitoring, water resource management, yield forecasting and crop-growth monitoring. The framework uses the ALEXI/DisALEXI suite of land-surface model...

  5. Wetting transition in liquid Ga Bi alloys: light scattering study of surface energy and entropy

    NASA Astrophysics Data System (ADS)

    Ayyad, A. H.; Freyland, W.

    2002-05-01

    We have studied the surface energy, surface entropy and, partly, have received an estimate of the viscosity of liquid Ga-Bi alloys at compositions mainly in the Ga-rich phase region and at temperatures up to 620 K. Measurements have been performed by the noninvasive method of capillary wave spectroscopy which has been applied for the first time to investigate the surface properties of a liquid alloy at high temperatures. Analysis of the concentration dependence of the surface energy according to the Gibbs adsorption equation yields that in the composition range of 10 -2≲ xBi≲10 -1 and at temperatures of 450 K≲ T≲500 K a surface excess of ΓBi˜1.36×10 -5 mol m -2 resides at the liquid-vapour interface corresponding to pure Bi. At lower xBi a reduction of ΓBi occurs which is indicative of a prewetting transition. The variations of surface energy and entropy with composition are not consistent with a description by a simple monolayer model as was deduced from X-ray reflectivity results. Instead it is found that a multilayer model qualitatively accounts for the characteristic change of the surface quantities. The thickness of the multilayer interfacial region is estimated from the change of the relative surface entropy. This yields values between 10 and 20 Å with a trend for an increasing number of surface layers towards the complete wetting transition at the monotectic point. All isopleths of the surface energy exhibit clear kinks at temperatures 10-20 K above the liquidus curve for compositions below the monotectic point. The corresponding discontinuity of the surface entropy is consistent with a first order transition of surface freezing reported recently for the Ga-Bi system.

  6. Stochastic repercussion of land-surface energy budget noise onto a coupled land-atmosphere model

    NASA Astrophysics Data System (ADS)

    Gentine, P.; Entekhabi, D.; Schertzer, E.; Polcher, J.

    2009-04-01

    The present study is based on the work first introduced by Lettau (1951): in this paper Lettau analytically studied the response of a linearized land-atmosphere model to a sinusoidal forcing of net radiation at the land-surface. The model has been first improved to obtain the analytical solution of the temperature and heat flux profiles in the soil and in the Atmospheric Boundary Layer (ABL) in response to any daily forcing of incoming radiation at the land-surface. With this model, the profiles of temperature and heat are expressed in terms of temporal Fourier series. Moreover the surface variables (temperature, specific humidity, surface fluxes) are also derived analytically and their diurnal course is expressed as a function of both surface parameters (friction velocity, vegetation height, aerodynamic resistance, stomatal conductance). In this presentation, we further extend the application of this theoretical model to the study of the error in the land-surface energy budget closure. This closure error could result form either modeling or experimental inaccuracies, leading to incorrect energy partitioning at the land-surface. In particular, the response of the coupled land-atmosphere model to the land-surface energy error is investigated. This noise in the energy budget is introduced in the form of a stochastic Brownian Bridge, which is a Brownian Motion conditioned to vanish at 0h and 24h. First the impact of land-surface noise on the partitioning of land-surface energy partitioning is examined. Moreover the influence of the land-surface noise on Land Surface Temperature and air temperature is carefully analyzed, as it is fundamental for the use of data assimilation in conjunction with land-surface models. Finally, the repercussion of the surface noise in the ABL and the soil is analytically found and its temporal and spatial dependency is studied. In particular, the correlation between the land-surface state and the ABL state is further investigated. These

  7. The Impact of Different Absolute Solar Irradiance Values on Current Climate Model Simulations

    NASA Technical Reports Server (NTRS)

    Rind, David H.; Lean, Judith L.; Jonas, Jeffrey

    2014-01-01

    Simulations of the preindustrial and doubled CO2 climates are made with the GISS Global Climate Middle Atmosphere Model 3 using two different estimates of the absolute solar irradiance value: a higher value measured by solar radiometers in the 1990s and a lower value measured recently by the Solar Radiation and Climate Experiment. Each of the model simulations is adjusted to achieve global energy balance; without this adjustment the difference in irradiance produces a global temperature change of 0.48C, comparable to the cooling estimated for the Maunder Minimum. The results indicate that by altering cloud cover the model properly compensates for the different absolute solar irradiance values on a global level when simulating both preindustrial and doubled CO2 climates. On a regional level, the preindustrial climate simulations and the patterns of change with doubled CO2 concentrations are again remarkably similar, but there are some differences. Using a higher absolute solar irradiance value and the requisite cloud cover affects the model's depictions of high-latitude surface air temperature, sea level pressure, and stratospheric ozone, as well as tropical precipitation. In the climate change experiments it leads to an underestimation of North Atlantic warming, reduced precipitation in the tropical western Pacific, and smaller total ozone growth at high northern latitudes. Although significant, these differences are typically modest compared with the magnitude of the regional changes expected for doubled greenhouse gas concentrations. Nevertheless, the model simulations demonstrate that achieving the highest possible fidelity when simulating regional climate change requires that climate models use as input the most accurate (lower) solar irradiance value.

  8. Quantum theory allows for absolute maximal contextuality

    NASA Astrophysics Data System (ADS)

    Amaral, Barbara; Cunha, Marcelo Terra; Cabello, Adán

    2015-12-01

    Contextuality is a fundamental feature of quantum theory and a necessary resource for quantum computation and communication. It is therefore important to investigate how large contextuality can be in quantum theory. Linear contextuality witnesses can be expressed as a sum S of n probabilities, and the independence number α and the Tsirelson-like number ϑ of the corresponding exclusivity graph are, respectively, the maximum of S for noncontextual theories and for the theory under consideration. A theory allows for absolute maximal contextuality if it has scenarios in which ϑ /α approaches n . Here we show that quantum theory allows for absolute maximal contextuality despite what is suggested by the examination of the quantum violations of Bell and noncontextuality inequalities considered in the past. Our proof is not constructive and does not single out explicit scenarios. Nevertheless, we identify scenarios in which quantum theory allows for almost-absolute-maximal contextuality.

  9. Absolute calibration in vivo measurement systems

    SciTech Connect

    Kruchten, D.A.; Hickman, D.P.

    1991-02-01

    Lawrence Livermore National Laboratory (LLNL) is currently investigating a new method for obtaining absolute calibration factors for radiation measurement systems used to measure internally deposited radionuclides in vivo. Absolute calibration of in vivo measurement systems will eliminate the need to generate a series of human surrogate structures (i.e., phantoms) for calibrating in vivo measurement systems. The absolute calibration of in vivo measurement systems utilizes magnetic resonance imaging (MRI) to define physiological structure, size, and composition. The MRI image provides a digitized representation of the physiological structure, which allows for any mathematical distribution of radionuclides within the body. Using Monte Carlo transport codes, the emission spectrum from the body is predicted. The in vivo measurement equipment is calibrated using the Monte Carlo code and adjusting for the intrinsic properties of the detection system. The calibration factors are verified using measurements of existing phantoms and previously obtained measurements of human volunteers. 8 refs.

  10. Stimulus probability effects in absolute identification.

    PubMed

    Kent, Christopher; Lamberts, Koen

    2016-05-01

    This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of presentation probability on both proportion correct and response times. The effects were moderated by the ubiquitous stimulus position effect. The accuracy and response time data were predicted by an exemplar-based model of perceptual cognition (Kent & Lamberts, 2005). The bow in discriminability was also attenuated when presentation probability for middle items was relatively high, an effect that will constrain future model development. The study provides evidence for item-specific learning in absolute identification. Implications for other theories of absolute identification are discussed. (PsycINFO Database Record

  11. Quantitative standards for absolute linguistic universals.

    PubMed

    Piantadosi, Steven T; Gibson, Edward

    2014-01-01

    Absolute linguistic universals are often justified by cross-linguistic analysis: If all observed languages exhibit a property, the property is taken to be a likely universal, perhaps specified in the cognitive or linguistic systems of language learners and users. In many cases, these patterns are then taken to motivate linguistic theory. Here, we show that cross-linguistic analysis will very rarely be able to statistically justify absolute, inviolable patterns in language. We formalize two statistical methods--frequentist and Bayesian--and show that in both it is possible to find strict linguistic universals, but that the numbers of independent languages necessary to do so is generally unachievable. This suggests that methods other than typological statistics are necessary to establish absolute properties of human language, and thus that many of the purported universals in linguistics have not received sufficient empirical justification.

  12. Absolute photoacoustic thermometry in deep tissue.

    PubMed

    Yao, Junjie; Ke, Haixin; Tai, Stephen; Zhou, Yong; Wang, Lihong V

    2013-12-15

    Photoacoustic thermography is a promising tool for temperature measurement in deep tissue. Here we propose an absolute temperature measurement method based on the dual temperature dependences of the Grüneisen parameter and the speed of sound in tissue. By taking ratiometric measurements at two adjacent temperatures, we can eliminate the factors that are temperature irrelevant but difficult to correct for in deep tissue. To validate our method, absolute temperatures of blood-filled tubes embedded ~9 mm deep in chicken tissue were measured in a biologically relevant range from 28°C to 46°C. The temperature measurement accuracy was ~0.6°C. The results suggest that our method can be potentially used for absolute temperature monitoring in deep tissue during thermotherapy.

  13. Molecular iodine absolute frequencies. Final report

    SciTech Connect

    Sansonetti, C.J.

    1990-06-25

    Fifty specified lines of {sup 127}I{sub 2} were studied by Doppler-free frequency modulation spectroscopy. For each line the classification of the molecular transition was determined, hyperfine components were identified, and one well-resolved component was selected for precise determination of its absolute frequency. In 3 cases, a nearby alternate line was selected for measurement because no well-resolved component was found for the specified line. Absolute frequency determinations were made with an estimated uncertainty of 1.1 MHz by locking a dye laser to the selected hyperfine component and measuring its wave number with a high-precision Fabry-Perot wavemeter. For each line results of the absolute measurement, the line classification, and a Doppler-free spectrum are given.

  14. Seasonal and interannual variability in surface energy partitioning and vegetation cover with grazing at shortgrass steppe

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We evaluated shortgrass steppe energy budgets based on the Bowen Ratio Energy Balance method for three different grazing intensity treatments at the Central Plains Experimental Range Long-Term Ecological Research (CPER-LTER) site. We tested the correlations between aboveground biomass and surface en...

  15. BOREAS TF-6 SSA-YA Surface Energy Flux and Meteorological Data

    NASA Technical Reports Server (NTRS)

    Bessemoulin, Pierre; Puech, Dominique; Hall, Forrest G. (Editor); Huemmrich, Karl (Editor)

    2000-01-01

    The BOREAS TF-6 team collected surface energy flux and meteorology data at the SSA-YA site. The data characterize the energy flux and meteorological conditions at the site from 18-Jul to 20-Sep-1994. The data set does not contain any trace gas exchange measurements. The data are available in tabular ASCII files.

  16. Improvement of early cell adhesion on Thai silk fibroin surface by low energy plasma.

    PubMed

    Amornsudthiwat, Phakdee; Mongkolnavin, Rattachat; Kanokpanont, Sorada; Panpranot, Joongjai; Wong, Chiow San; Damrongsakkul, Siriporn

    2013-11-01

    Low energy plasma has been introduced to treat the surface of Thai silk fibroin which should be enhanced for cell adhesion due to its native hydrophobic surface. Plasma surface treatment could introduce desirable hydrophilic functionalities on the surface without using any chemicals. In this work, nitrogen glow discharge plasma was generated by a low energy AC50Hz power supply system. The plasma operating conditions were optimized to reach the highest nitrogen active species by using optical emission spectroscopy. X-ray photoelectron spectroscopy (XPS) revealed that amine, hydroxyl, ether, and carboxyl groups were induced on Thai silk fibroin surface after plasma treatment. The results on Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy confirmed that the plasma treated effects were only on the outermost layer since there was no change in the bulk chemistry. The surface topography was insignificantly changed from the detection with atomic force microscopy (AFM). The plasma-treated effects were the improved surface wettability and cell adhesion. After a 90-s treatment, the water contact angle was at 20°, while the untreated surface was at 70°. The early cell adhesion of L929 mouse fibroblast was accelerated. L929 cells only took 3h to reach 100% cell adhesion on 90 s N2 plasma-treated surface, while there was less than 50% cell adhesion on the untreated Thai silk fibroin surface after 6h of culture. The cell adhesion results were in agreement with the cytoskeleton development. L929 F-actin was more evident on 90 s N2 plasma-treated surface than others. It could be concluded that a lower energy AC50Hz plasma system enhanced early L929 mouse fibroblast adhesion on Thai silk fibroin surface without any significant change in surface topography and bulk chemistry. PMID:23893032

  17. Absolute thickness metrology with submicrometer accuracy using a low-coherence distance measuring interferometer.

    PubMed

    Zhao, Yang; Schmidt, Greg; Moore, Duncan T; Ellis, Jonathan D

    2015-09-01

    Absolute physical thickness across the sample aperture is critical in determining the index of a refraction profile from the optical path length profile for gradient index (GRIN) materials, which have a designed inhomogeneous refractive index. Motivated by this application, instrumentation was established to measure the absolute thickness of samples with nominally plane-parallel surfaces up to 50 mm thick. The current system is capable of measuring absolute thickness with 120 nm (1σ) repeatability and submicrometer expanded measurement uncertainty. Beside GRIN materials, this method is also capable of measuring other inhomogeneous and opaque materials. PMID:26368894

  18. Serial dilution via surface energy trap-assisted magnetic droplet manipulation.

    PubMed

    Zhang, Yi; Shin, Dong Jin; Wang, Tza-Huei

    2013-12-21

    This paper demonstrates a facile method of generating precise serial dilutions in the form of droplets on an open surface platform. The method relies on the use of surface energy traps (SETs), etched areas of high surface energy on a Teflon coated glass substrate, to assist in the magnetic manipulation of droplets to meter and dispense liquid of defined volumes for the preparation of serial dilutions. The volume of the dispensed liquid can be precisely controlled by the size of the SETs, facilitating generation of concentration profiles of high linearity. We have applied this approach to the generation of serial dilutions of antibiotics for anti-microbial susceptibility testing (AST).

  19. Absolute Stability And Hyperstability In Hilbert Space

    NASA Technical Reports Server (NTRS)

    Wen, John Ting-Yung

    1989-01-01

    Theorems on stabilities of feedback control systems proved. Paper presents recent developments regarding theorems of absolute stability and hyperstability of feedforward-and-feedback control system. Theorems applied in analysis of nonlinear, adaptive, and robust control. Extended to provide sufficient conditions for stability in system including nonlinear feedback subsystem and linear time-invariant (LTI) feedforward subsystem, state space of which is Hilbert space, and input and output spaces having finite numbers of dimensions. (In case of absolute stability, feedback subsystem memoryless and possibly time varying. For hyperstability, feedback system dynamical system.)

  20. Absolute measurements of nonlinear absorption near LIDT at 193 nm

    NASA Astrophysics Data System (ADS)

    Blaschke, Holger; Ristau, Detlev; Welsch, Eberhard; Apel, Oliver

    2001-04-01

    Previous investigations indicate that oxide coatings exhibit non-linear absorption phenomena below 200 nm. Hereby, absorption data of Al2O3 thin film coatings has been determined absolutely by laser calorimetry (LCA) at 193 nm in the low fluence regime. As an alternative, on the basis of the pulsed surface thermal lens technique (STL), photothermal measurements allow to determine the absorption relatively at fluence levels both in the subdamage fluence range far from the damage onset and close to the LIDT. By combining the two measurement techniques, the absolute determination of linear as well as multiphoton absorption can be achieved also in the vicinity of the laser damage fluences. This is of crucial interest because the initiation of damage onset can be observed immediately. Absolute absorption data of Al2O3 coatings at different laser fluences stating of some mJoule/cm2 will be presented for the wavelength 193 nm. Thus, the correlation between the increase of absorption and the onset of breakdown can be illustrated impressively. The evaluation and discussion of the experimental results are focused on the degree of non-linearity of the investigated absorption behavior of oxide single layers initiating the optical breakdown of UV oxide coatings.