Anisotropic Eliashberg theory of MgB 2: Tc, isotope effects, superconducting energy gaps, quasiparticles, and specific heat

NASA Astrophysics Data System (ADS)

Choi, Hyoung Joon; Cohen, Marvin L.; Louie, Steven G.

2003-03-01

The anisotropic Eliashberg formalism, employing results from the ab initio pseudopotential density functional calculations, is applied to study the superconducting properties of MgB 2. It is shown that the relatively high transition temperature of MgB 2 originates from strong electron-phonon coupling of the hole states in the boron σ-bonds although the coupling strength averaged over the Fermi surface is moderate, and the reduction of the isotope effect arises from the large anharmonicity of the relevant phonons. The superconducting energy gap is nodeless but its value varies strongly on different pieces of the Fermi surface. The gap values Δ( k) cluster into two groups at low temperature, a small value of ∼2 meV and a large value of ∼7 meV, resulting in two thresholds in the quasiparticle density of states and an increase in the specific heat at low temperature due to quasiparticle excitations over the small gap. All of these results are in good agreement with corresponding experiments and support the view that MgB 2 is a phonon-mediated multiple-gap superconductor.

Spectral Gap Energy Transfer in Atmospheric Boundary Layer

NASA Astrophysics Data System (ADS)

Bhushan, S.; Walters, K.; Barros, A. P.; Nogueira, M.

2012-12-01

Experimental measurements of atmospheric turbulence energy spectra show E(k) ~ k-3 slopes at synoptic scales (~ 600 km - 2000 km) and k-5/3 slopes at the mesoscales (< 400 km). The -5/3 spectra is presumably related to 3D turbulence which is dominated by the classical Kolmogrov energy cascade. The -3 spectra is related to 2D turbulence, which is dominated by strong forward scatter of enstrophy and weak forward scatter of energy. In classical 2D turbulence theory, it is expected that a strong backward energy cascade would develop at the synoptic scale, and that circulation would grow infinitely. To limit this backward transfer, energy arrest at macroscales must be introduced. The most commonly used turbulence models developed to mimic the above energy transfer include the energy backscatter model for 2D turbulence in the horizontal plane via Large Eddy Simulation (LES) models, dissipative URANS models in the vertical plane, and Ekman friction for the energy arrest. One of the controversial issues surrounding the atmospheric turbulence spectra is the explanation of the generation of the 2D and 3D spectra and transition between them, for energy injection at the synoptic scales. Lilly (1989) proposed that the existence of 2D and 3D spectra can only be explained by the presence of an additional energy injection in the meso-scale region. A second issue is related to the observations of dual peak spectra with small variance in meso-scale, suggesting that the energy transfer occurs across a spectral gap (Van Der Hoven, 1957). Several studies have confirmed the spectral gap for the meso-scale circulations, and have suggested that they are enhanced by smaller scale vertical convection rather than by the synoptic scales. Further, the widely accepted energy arrest mechanism by boundary layer friction is closely related to the spectral gap transfer. This study proposes an energy transfer mechanism for atmospheric turbulence with synoptic scale injection, wherein the generation

Role of surface energy on the morphology and optical properties of GaP micro & nano structures grown on polar and non-polar substrates

NASA Astrophysics Data System (ADS)

Roychowdhury, R.; Kumar, Shailendra; Wadikar, A.; Mukherjee, C.; Rajiv, K.; Sharma, T. K.; Dixit, V. K.

2017-10-01

Role of surface energy on the morphology, crystalline quality, electronic structure and optical properties of GaP layer grown on Si (001), Si (111), Ge (111) and GaAs (001) is investigated. GaP layers are grown on four different substrates under identical growth kinetics by metal organic vapour phase epitaxy. The atomic force microscopy images show that GaP layer completely covers the surface of GaAs substrate. On the other hand, the surfaces of Si (001), Si (111), Ge (111) substrates are partially covered with crystallographically morphed GaP island type micro and nano-structures. Origin of these crystallographically morphed GaP island is explained by the theoretical calculation of surface energy of the layer and corresponding substrates respectively. The nature of GaP island type micro and nano-structures and layers are single crystalline with existence of rotational twins on Si and Ge (111) substrates which is confirmed by the phi, omega and omega/2theta scans of high resolution x-ray diffraction. The electronic valence band offsets between the GaP and substrates have been determined from the valence band spectra of ultraviolet photoelectron spectroscopy. The valence electron plasmon of GaP are investigated by studying the energy values of Ga (3d) core level along with loss peaks in the energy dependent photoelectron spectra. The peak observed within the range of 3-6 eV from the Ga (3d) core level in the photoelectron spectra are associated to inter band transitions as their energy values are estimated from the pseudo dielectric function by the spectroscopic ellipsometry.

Development of Low Energy Gap and Fully Regioregular Polythienylenevinylene Derivative

DOE PAGES

David, Tanya M. S.; Zhang, Cheng; Sun, Sam-Shajing

2014-01-01

Low energy gap and fully regioregular conjugated polymers find its wide use in solar energy conversion applications. This paper will first briefly review this type of polymers and also report synthesis and characterization of a specific example new polymer, a low energy gap, fully regioregular, terminal functionalized, and processable conjugated polymer poly-(3-dodecyloxy-2,5-thienylene vinylene) or PDDTV. The polymer exhibited an optical energy gap of 1.46 eV based on the UV-vis-NIR absorption spectrum. The electrochemically measured highest occupied molecular orbital (HOMO) level is −4.79 eV, resulting in the lowest unoccupied molecular orbital (LUMO) level of −3.33 eV based on optical energy gap. The polymer wasmore » synthesized via Horner-Emmons condensation and is fairly soluble in common organic solvents such as tetrahydrofuran and chloroform with gentle heating. DSC showed two endothermic peaks at 67°C and 227°C that can be attributed to transitions between crystalline and liquid states. The polymer is thermally stable up to about 300°C. This polymer appears very promising for cost-effective solar cell applications.« less

Tidal stresses and energy gaps in microstate geometries

NASA Astrophysics Data System (ADS)

Tyukov, Alexander; Walker, Robert; Warner, Nicholas P.

2018-02-01

We compute energy gaps and study infalling massive geodesic probes in the new families of scaling, microstate geometries that have been constructed recently and for which the holographic duals are known. We find that in the deepest geometries, which have the lowest energy gaps, the geodesic deviation shows that the stress reaches the Planck scale long before the probe reaches the cap of the geometry. Such probes must therefore undergo a stringy transition as they fall into microstate geometry. We discuss the scales associated with this transition and comment on the implications for scrambling in microstate geometries.

Energy gap in graphene nanoribbons with structured external electric potentials

NASA Astrophysics Data System (ADS)

Apel, W.; Pal, G.; Schweitzer, L.

2011-03-01

The electronic properties of graphene zigzag nanoribbons with electrostatic potentials along the edges are investigated. Using the Dirac-fermion approach, we calculate the energy spectrum of an infinitely long nanoribbon of finite width w, terminated by Dirichlet boundary conditions in the transverse direction. We show that a structured external potential that acts within the edge regions of the ribbon can induce a spectral gap and thus switch the nanoribbon from metallic to insulating behavior. The basic mechanism of this effect is the selective influence of the external potentials on the spinorial wave functions that are topological in nature and localized along the boundary of the graphene nanoribbon. Within this single-particle description, the maximal obtainable energy gap is Emax∝πℏvF/w, i.e., ≈0.12 eV for w=15 nm. The stability of the spectral gap against edge disorder and the effect of disorder on the two-terminal conductance is studied numerically within a tight-binding lattice model. We find that the energy gap persists as long as the applied external effective potential is larger than ≃0.55×W, where W is a measure of the disorder strength. We argue that there is a transport gap due to localization effects even in the absence of a spectral gap.

Energy gap law of electron transfer in nonpolar solvents.

PubMed

Tachiya, M; Seki, Kazuhiko

2007-09-27

We investigate the energy gap law of electron transfer in nonpolar solvents for charge separation and charge recombination reactions. In polar solvents, the reaction coordinate is given in terms of the electrostatic potentials from solvent permanent dipoles at solutes. In nonpolar solvents, the energy fluctuation due to solvent polarization is absent, but the energy of the ion pair state changes significantly with the distance between the ions as a result of the unscreened strong Coulomb potential. The electron transfer occurs when the final state energy coincides with the initial state energy. For charge separation reactions, the initial state is a neutral pair state, and its energy changes little with the distance between the reactants, whereas the final state is an ion pair state and its energy changes significantly with the mutual distance; for charge recombination reactions, vice versa. We show that the energy gap law of electron-transfer rates in nonpolar solvents significantly depends on the type of electron transfer.

Theoretical and experimental evidence for a nodal energy gap in MgB2

NASA Astrophysics Data System (ADS)

Agassi, Y. Dan; Oates, Daniel E.

2017-11-01

We present a phenomenological model that strongly suggests that the smaller of the two energy gaps in MgB2, the so-called π gap, contains nodal lines with a six-fold symmetry (i-wave). The model also indicates that the larger gap, the so-called σ gap, is conventional s-wave. The model is an extension of the BCS gap equation that accounts for the elastic anisotropy in MgB2 and the Coulomb repulsion. It is based on a phononic pairing mechanism and assumes no coupling between the two energy gaps in MgB2 at zero temperature. All of the parameters of the model, such as sound velocities and masses, are independently determined material constants. The results agree with a previous ad-hoc hypothesis that the π energy gap has six nodal lines. That hypothesis was motivated by low-temperature measurements of the surface impedance and intermodulation distortion in high-quality thin films. We briefly review experimental evidence in the literature that is relevant to the energy-gap symmetry. We find that the evidence from the literature for s-wave is inconclusive. Our finding is that the π gap has six nodal lines.

Tuning the Energy Gap of SiCH3 Nanomaterials Under Elastic Strain

NASA Astrophysics Data System (ADS)

Ma, Shengqian; Li, Feng; Geng, Jiguo; Zhu, Mei; Li, Suyan; Han, Juguang

2018-05-01

SiCH3 nanomaterials have been studied using the density functional theory. When the nanosheets and nanoribbons (armchair and zigzag) are introduced, their energy gap is modulated under elastic strain and width. The results show that the band gap of SiCH3 nanomaterials can be easily tuned using elastic strains and widths. Surprisingly, the band gap can be modulated along two directions, namely, compressing and stretching. The band gap decreases when increasing stretching strain or decreasing compressing strain. In addition, the band gap decreases when increasing the nanoribbon width. For energy gap engineering, the band gap can be tuned by strains and widths. Therefore, the SiCH3 nanomaterials play important roles in potential applications for strain sensors, electronics, and optical electronics.

On the size and temperature dependence of the energy gap in cadmium-selenide quantum dots embedded in fluorophosphate glasses

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

Lipatova, Zh. O., E-mail: zluka-yo@mail.ru; Kolobkova, E. V.; Babkina, A. N.

2017-03-15

The temperature and size dependences of the energy gap in CdSe quantum dots with diameters of 2.4, 4.0, and 5.2 nm embedded in fluorophosphate glasses are investigated. It is shown that the temperature coefficient of the band gap dE{sub g}/dT in the quantum dots differs from the bulk value and depends strictly on the dot size. It is found that, furthermore, the energy of each transition in these quantum dots is characterized by an individual temperature coefficient dE/dT.

Gap length effect on electron energy distribution in capacitive radio frequency discharges

NASA Astrophysics Data System (ADS)

You, S. J.; Kim, S. S.; Kim, Jung-Hyung; Seong, Dae-Jin; Shin, Yong-Hyeon; Chang, H. Y.

2007-11-01

A study on the dependence of electron energy distribution function (EEDF) on discharge gap size in capacitive rf discharges was conducted. The evolution of the EEDF over a gap size range from 2.5to7cm in 65mTorr Ar discharges was investigated both experimentally and theoretically. The measured EEDFs exhibited typical bi-Maxwellian forms with low energy electron groups. A significant depletion in the low energy portion of the bi-Maxwellian was found with decreasing gap size. The results show that electron heating by bulk electric fields, which is the main heating process of the low-energy electrons, is greatly enhanced as the gap size decreases, resulting in the abrupt change of the EEDF. The calculated EEDFs based on nonlocal kinetic theory are in good agreement with the experiments.

Calculation of Energy Diagram of Asymmetric Graded-Band-Gap Semiconductor Superlattices.

PubMed

Monastyrskii, Liubomyr S; Sokolovskii, Bogdan S; Alekseichyk, Mariya P

2017-12-01

The paper theoretically investigates the peculiarities of energy diagram of asymmetric graded-band-gap superlattices with linear coordinate dependences of band gap and electron affinity. For calculating the energy diagram of asymmetric graded-band-gap superlattices, linearized Poisson's equation has been solved for the two layers forming a period of the superlattice. The obtained coordinate dependences of edges of the conduction and valence bands demonstrate substantial transformation of the shape of the energy diagram at changing the period of the lattice and the ratio of width of the adjacent layers. The most marked changes in the energy diagram take place when the period of lattice is comparable with the Debye screening length. In the case when the lattice period is much smaller that the Debye screening length, the energy diagram has the shape of a sawtooth-like pattern.

Value of eddy-covariance data for individual-based, forest gap models

NASA Astrophysics Data System (ADS)

Roedig, Edna; Cuntz, Matthias; Huth, Andreas

2014-05-01

Individual-based forest gap models simulate tree growth and carbon fluxes on large time scales. They are a well established tool to predict forest dynamics and successions. However, the effect of climatic variables on processes of such individual-based models is uncertain (e.g. the effect of temperature or soil moisture on the gross primary production (GPP)). Commonly, functional relationships and parameter values that describe the effect of climate variables on the model processes are gathered from various vegetation models of different spatial scales. Though, their accuracies and parameter values have not been validated for the specific model scales of individual-based forest gap models. In this study, we address this uncertainty by linking Eddy-covariance (EC) data and a forest gap model. The forest gap model FORMIND is applied on the Norwegian spruce monoculture forest at Wetzstein in Thuringia, Germany for the years 2003-2008. The original parameterizations of climatic functions are adapted according to the EC-data. The time step of the model is reduced to one day in order to adapt to the high resolution EC-data. The FORMIND model uses functional relationships on an individual level, whereas the EC-method measures eco-physiological responses at the ecosystem level. However, we assume that in homogeneous stands as in our study, functional relationships for both methods are comparable. The model is then validated at the spruce forest Waldstein, Germany. Results show that the functional relationships used in the model, are similar to those observed with the EC-method. The temperature reduction curve is well reflected in the EC-data, though parameter values differ from the originally expected values. For example at the freezing point, the observed GPP is 30% higher than predicted by the forest gap model. The response of observed GPP to soil moisture shows that the permanent wilting point is 7 vol-% lower than the value derived from the literature. The light

Energy-gap spectroscopy of superconductors using a tunneling microscope

NASA Technical Reports Server (NTRS)

Le Duc, H. G.; Kaiser, W. J.; Stern, J. A.

1987-01-01

A unique scanning tunneling microscope (STM) system has been developed for spectroscopy of the superconducting energy gap. High-resolution control of tunnel current and voltage allows for measurement of superconducting properties at tunnel resistance levels 100-1000 greater than that achieved in prior work. The previously used STM methods for superconductor spectroscopy are compared to those developed for the work reported here. Superconducting energy-gap spectra are reported for three superconductors, Pb, PbBi, and NbN, over a range of tunnel resistance. The measured spectra are compared directly to theory.

Enhanced Andreev reflection in gapped graphene

NASA Astrophysics Data System (ADS)

Majidi, Leyla; Zareyan, Malek

2012-08-01

We theoretically demonstrate unusual features of superconducting proximity effect in gapped graphene that presents a pseudospin symmetry-broken ferromagnet with a net pseudomagnetization. We find that the presence of a band gap makes the Andreev conductance of graphene superconductor/pseudoferromagnet (S/PF) junction to behave similar to that of a graphene ferromagnet-superconductor junction. The energy gap ΔN can enhance the pseudospin inverted Andreev conductance of S/PF junction to reach a limiting maximum value for ΔN≫μ, which depending on the bias voltage can be larger than the value for the corresponding junction with no energy gap. We further demonstrate a damped-oscillatory behavior for the local density of states of the PF region of S/PF junction and a long-range crossed Andreev reflection process in PF/S/PF structure with antiparallel alignment of pseudomagnetizations of PFs, which confirm that, in this respect, the gapped normal graphene behaves like a ferromagnetic graphene.

Measurement of a superconducting energy gap in a homogeneously amorphous insulator.

PubMed

Sherman, D; Kopnov, G; Shahar, D; Frydman, A

2012-04-27

We present tunneling spectroscopy measurements that directly reveal the existence of a superconducting gap in the insulating state of homogenously disordered amorphous indium oxide films. Two films on both sides of the disorder induced superconductor to insulator transition show the same energy gap scale. This energy gap persists up to relatively high magnetic fields and is observed across the magnetoresistance peak typical of disordered superconductors. The results provide useful information for understanding the nature of the insulating state in the disorder induced superconductor to insulator transition.

A novel theoretical model for the temperature dependence of band gap energy in semiconductors

NASA Astrophysics Data System (ADS)

Geng, Peiji; Li, Weiguo; Zhang, Xianhe; Zhang, Xuyao; Deng, Yong; Kou, Haibo

2017-10-01

We report a novel theoretical model without any fitting parameters for the temperature dependence of band gap energy in semiconductors. This model relates the band gap energy at the elevated temperature to that at the arbitrary reference temperature. As examples, the band gap energies of Si, Ge, AlN, GaN, InP, InAs, ZnO, ZnS, ZnSe and GaAs at temperatures below 400 K are calculated and are in good agreement with the experimental results. Meanwhile, the band gap energies at high temperatures (T  >  400 K) are predicted, which are greater than the experimental results, and the reasonable analysis is carried out as well. Under low temperatures, the effect of lattice expansion on the band gap energy is very small, but it has much influence on the band gap energy at high temperatures. Therefore, it is necessary to consider the effect of lattice expansion at high temperatures, and the method considering the effect of lattice expansion has also been given. The model has distinct advantages compared with the widely quoted Varshni’s semi-empirical equation from the aspect of modeling, physical meaning and application. The study provides a convenient method to determine the band gap energy under different temperatures.

Application of back-propagation artificial neural network (ANN) to predict crystallite size and band gap energy of ZnO quantum dots

NASA Astrophysics Data System (ADS)

Pelicano, Christian Mark; Rapadas, Nick; Cagatan, Gerard; Magdaluyo, Eduardo

2017-12-01

Herein, the crystallite size and band gap energy of zinc oxide (ZnO) quantum dots were predicted using artificial neural network (ANN). Three input factors including reagent ratio, growth time, and growth temperature were examined with respect to crystallite size and band gap energy as response factors. The generated results from neural network model were then compared with the experimental results. Experimental crystallite size and band gap energy of ZnO quantum dots were measured from TEM images and absorbance spectra, respectively. The Levenberg-Marquardt (LM) algorithm was used as the learning algorithm for the ANN model. The performance of the ANN model was then assessed through mean square error (MSE) and regression values. Based on the results, the ANN modelling results are in good agreement with the experimental data.

A direct method for computing extreme value (Gumbel) parameters for gapped biological sequence alignments.

PubMed

Quinn, Terrance; Sinkala, Zachariah

2014-01-01

We develop a general method for computing extreme value distribution (Gumbel, 1958) parameters for gapped alignments. Our approach uses mixture distribution theory to obtain associated BLOSUM matrices for gapped alignments, which in turn are used for determining significance of gapped alignment scores for pairs of biological sequences. We compare our results with parameters already obtained in the literature.

Animating Research with Counseling Values: A Training Model to Address the Research-to-Practice Gap

ERIC Educational Resources Information Center

Lee, Kristi A.; Dewell, John A.; Holmes, Courtney M.

2014-01-01

The persistent research-to-practice gap poses a problem for counselor education. The gap may be caused by conflicts between the humanistic values that guide much of counseling and the values that guide research training. In this article, the authors address historical concerns regarding research training for students and the conducting of research…

Energy splitting of excitons in gapped Dirac materials

NASA Astrophysics Data System (ADS)

Xiao, Di; Zhou, Jianhui; Shan, Wenyu; Yao, Wang; Okamoto, Satoshi

2015-03-01

We show that there is an energy splitting between excitons with opposite angular momentum in gapped Dirac materials, such as monolayers of transition metal dichalcogenides and gapped surface states of topological insulators. This splitting can be traced back to the chiral nature of Dirac electrons. We also discuss the optical selection rule of excitons in gap Dirac materials and clarify the relationship to its single-particle counterpart. A simple estimation of the splitting (~ 10 meV) in monolayer transition metal dichalcogenides is given . Our result reveals the limitation of the venerable hydrogenic model of excitons, and highlights the importance of the Berry phase in This work is supported by DOE (No. DE-SC0012509), and AFOSR (No. FA9550-14-1-0277).

Minding the Gap: Synthetic Strategies for Tuning the Energy Gap in Conjugated Molecules

ERIC Educational Resources Information Center

Christensen, Dana; Cohn, Pamela G.

2016-01-01

While structure-property relationships are commonly developed in applications of physical organic chemistry to real-world problems at the graduate level, they have not been generally emphasized in the undergraduate chemistry curriculum. For instance, the ability to modify the energy gap between the highest occupied molecular orbital (HOMO) and the…

Closing Achievement Gaps with a Utility-Value Intervention: Disentangling Race and Social Class

PubMed Central

Harackiewicz, Judith M.; Canning, Elizabeth A.; Tibbetts, Yoi; Priniski, Stacy J.; Hyde, Janet S.

2015-01-01

Many college students abandon their goal of completing a degree in STEM when confronted with challenging introductory-level science courses. In the U.S., this trend is more pronounced for underrepresented minority (URM) and first-generation (FG) students, and contributes to persisting racial and social-class achievement gaps in higher education. Previous intervention studies have focused exclusively on race or social class, but have not examined how the two may be confounded and interact. This research therefore investigates the independent and interactive effects of race and social class as moderators of an intervention designed to promote performance, measured by grade in the course. In a double-blind randomized experiment conducted over four semesters of an introductory biology course (N = 1040), we tested the effectiveness of a utility-value intervention in which students wrote about the personal relevance of course material. The utility-value intervention was successful in reducing the achievement gap for FG-URM students by 61%: the performance gap for FG-URM students, relative to CG-Majority students, was large in the control condition, .84 grade points (d = .98), and the treatment effect for FG-URM students was .51 grade points (d = 0.55). The UV intervention helped students from all groups find utility value in the course content, and mediation analyses showed that the process of writing about utility value was particularly powerful for FG-URM students. Results highlight the importance of examining the independent and interactive effects of race and social class when evaluating interventions to close achievement gaps and the mechanisms through which they may operate. PMID:26524001

Probing optical band gaps at the nanoscale in NiFe₂O₄ and CoFe₂O₄ epitaxial films by high resolution electron energy loss spectroscopy

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

Dileep, K.; Loukya, B.; Datta, R., E-mail: ranjan@jncasr.ac.in

2014-09-14

Nanoscale optical band gap variations in epitaxial thin films of two different spinel ferrites, i.e., NiFe₂O₄ (NFO) and CoFe₂O₄ (CFO), have been investigated by spatially resolved high resolution electron energy loss spectroscopy. Experimentally, both NFO and CFO show indirect/direct band gaps around 1.52 eV/2.74 and 2.3 eV, and 1.3 eV/2.31 eV, respectively, for the ideal inverse spinel configuration with considerable standard deviation in the band gap values for CFO due to various levels of deviation from the ideal inverse spinel structure. Direct probing of the regions in both the systems with tetrahedral A site cation vacancy, which is distinct frommore » the ideal inverse spinel configuration, shows significantly smaller band gap values. The experimental results are supported by the density functional theory based modified Becke-Johnson exchange correlation potential calculated band gap values for the different cation configurations.« less

Simple Experimental Verification of the Relation between the Band-Gap Energy and the Energy of Photons Emitted by LEDs

ERIC Educational Resources Information Center

Precker, Jurgen W.

2007-01-01

The wavelength of the light emitted by a light-emitting diode (LED) is intimately related to the band-gap energy of the semiconductor from which the LED is made. We experimentally estimate the band-gap energies of several types of LEDs, and compare them with the energies of the emitted light, which ranges from infrared to white. In spite of…

Energy band gap and optical transition of metal ion modified double crossover DNA lattices.

PubMed

Dugasani, Sreekantha Reddy; Ha, Taewoo; Gnapareddy, Bramaramba; Choi, Kyujin; Lee, Junwye; Kim, Byeonghoon; Kim, Jae Hoon; Park, Sung Ha

2014-10-22

We report on the energy band gap and optical transition of a series of divalent metal ion (Cu(2+), Ni(2+), Zn(2+), and Co(2+)) modified DNA (M-DNA) double crossover (DX) lattices fabricated on fused silica by the substrate-assisted growth (SAG) method. We demonstrate how the degree of coverage of the DX lattices is influenced by the DX monomer concentration and also analyze the band gaps of the M-DNA lattices. The energy band gap of the M-DNA, between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO), ranges from 4.67 to 4.98 eV as judged by optical transitions. Relative to the band gap of a pristine DNA molecule (4.69 eV), the band gap of the M-DNA lattices increases with metal ion doping up to a critical concentration and then decreases with further doping. Interestingly, except for the case of Ni(2+), the onset of the second absorption band shifts to a lower energy until a critical concentration and then shifts to a higher energy with further increasing the metal ion concentration, which is consistent with the evolution of electrical transport characteristics. Our results show that controllable metal ion doping is an effective method to tune the band gap energy of DNA-based nanostructures.

Data on energy-band-gap characteristics of composite nanoparticles obtained by modification of the amorphous potassium polytitanate in aqueous solutions of transition metal salts

PubMed Central

Zimnyakov, D.A.; Sevrugin, A.V.; Yuvchenko, S.A.; Fedorov, F.S.; Tretyachenko, E.V.; Vikulova, M.A.; Kovaleva, D.S.; Krugova, E.Y.; Gorokhovsky, A.V.

2016-01-01

Here we present the data on the energy-band-gap characteristics of composite nanoparticles produced by modification of the amorphous potassium polytitanate in aqueous solutions of different transition metal salts. Band gap characteristics are investigated using diffuse reflection spectra of the obtained powders. Calculated logarithmic derivative quantity of the Kubelka–Munk function reveals a presence of local maxima in the regions 0.5–1.5 eV and 1.6–3.0 eV which correspond to band gap values of the investigated materials. The values might be related to the constituents of the composite nanoparticles and intermediate products of their chemical interaction. PMID:27158654

NREL Tests Energy Storage System to Fill Renewable Gaps | News | NREL

Science.gov Websites

Tests Energy Storage System to Fill Renewable Gaps NREL Tests Energy Storage System to Fill -megawatt energy storage system from Renewable Energy Systems (RES) Americas will assist research that aims to optimize the grid for wind and solar plants. The system arrived at NREL's National Wind Technology

Closing achievement gaps with a utility-value intervention: Disentangling race and social class.

PubMed

Harackiewicz, Judith M; Canning, Elizabeth A; Tibbetts, Yoi; Priniski, Stacy J; Hyde, Janet S

2016-11-01

Many college students abandon their goal of completing a degree in science, technology, engineering, or math (STEM) when confronted with challenging introductory-level science courses. In the U.S., this trend is more pronounced for underrepresented minority (URM) and first-generation (FG) students, and contributes to persisting racial and social-class achievement gaps in higher education. Previous intervention studies have focused exclusively on race or social class, but have not examined how the 2 may be confounded and interact. This research therefore investigates the independent and interactive effects of race and social class as moderators of an intervention designed to promote performance, measured by grade in the course. In a double-blind randomized experiment conducted over 4 semesters of an introductory biology course (N = 1,040), we tested the effectiveness of a utility-value intervention in which students wrote about the personal relevance of course material. The utility-value intervention was successful in reducing the achievement gap for FG-URM students by 61%: the performance gap for FG-URM students, relative to continuing generation (CG)-Majority students, was large in the control condition, .84 grade points (d = .98), and the treatment effect for FG-URM students was .51 grade points (d = 0.55). The UV intervention helped students from all groups find utility value in the course content, and mediation analyses showed that the process of writing about utility value was particularly powerful for FG-URM students. Results highlight the importance of intersectionality in examining the independent and interactive effects of race and social class when evaluating interventions to close achievement gaps and the mechanisms through which they may operate. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Extended Acceleration in Slot Gaps and Pulsar High-Energy Emission

NASA Technical Reports Server (NTRS)

White, Nicholas E. (Technical Monitor); Muslimov, Alex G.; Harding, Alice K.

2003-01-01

We revise the physics of primary electron acceleration in the "slot gap" (SG) above the pulsar polar caps (PCs), a regime originally proposed by Arons and Scharlemann (1979) in their electrodynamic model of pulsar PCs. We employ the standard definition of the SG as a pair-free space between the last open field lines and the boundary of the pair plasma column which is expected to develop above the bulk of the PC. The rationale for our revision is that the proper treatment of primary acceleration within the pulsar SGs should take into account the effect of the narrow geometry of the gap on the electrodynamics within the gap and also to include the effect of inertial frame dragging on the particle acceleration. We show that the accelerating electric field within the gap, being significantly boosted by the effect of frame dragging, becomes reduced because of the gap geometry by a factor proportional to the square of the SG width. The combination of the effects of frame dragging and geometrical screening in the gap region naturally gives rise to a regime of extended acceleration, that is not limited to favorably curved field lines as in earlier models, and the possibility of multiple-pair production by curvature photons at very high altitudes, up to several stellar radii. We present our estimates of the characteristic SG thickness across the PC, energetics of primaries accelerated within the gap, high-energy bolometric luminosities emitted from the high altitudes in the gaps, and maximum heating luminosities produced by positrons returning from the elevated pair fronts. The estimated theoretical high-energy luminosities are in good agreement with the corresponding empirical relationships for gamma-ray pulsars. We illustrate the results of our modeling of the pair cascades and gamma-ray emission from the high altitudes in the SG for the Crab pulsar. The combination of the frame-dragging field and high-altitude SG emission enables both acceleration at the smaller

Modeling US Adult Obesity Trends: A System Dynamics Model for Estimating Energy Imbalance Gap

PubMed Central

Rahmandad, Hazhir; Huang, Terry T.-K.; Bures, Regina M.; Glass, Thomas A.

2014-01-01

Objectives. We present a system dynamics model that quantifies the energy imbalance gap responsible for the US adult obesity epidemic among gender and racial subpopulations. Methods. We divided the adult population into gender–race/ethnicity subpopulations and body mass index (BMI) classes. We defined transition rates between classes as a function of metabolic dynamics of individuals within each class. We estimated energy intake in each BMI class within the past 4 decades as a multiplication of the equilibrium energy intake of individuals in that class. Through calibration, we estimated the energy gap multiplier for each gender–race–BMI group by matching simulated BMI distributions for each subpopulation against national data with maximum likelihood estimation. Results. No subpopulation showed a negative or zero energy gap, suggesting that the obesity epidemic continues to worsen, albeit at a slower rate. In the past decade the epidemic has slowed for non-Hispanic Whites, is starting to slow for non-Hispanic Blacks, but continues to accelerate among Mexican Americans. Conclusions. The differential energy balance gap across subpopulations and over time suggests that interventions should be tailored to subpopulations’ needs. PMID:24832405

Asian cultural values gap, cognitive flexibility, coping strategies, and parent-child conflicts among Korean Americans.

PubMed

Ahn, Annie J; Kim, Bryan S K; Park, Yong S

2008-10-01

The study examined Korean American college students' perceived Asian cultural values gap between themselves and their parents, cognitive flexibility, and coping strategies. The relationships between these factors were studied with the intensities and types of parent-child conflicts. The results indicated that the participants adhered less strongly to Asian values than their parents. When faced with conflicts, the participants reported using problem solving coping strategy to the greatest extent, followed by social support coping strategy, and then avoidance coping strategy. Simultaneous regression analyses revealed a positive relationship between the participant-perceived parent-child values gap and the intensity of conflicts, particularly in the area of dating and marriage. There were inverse relationships between cognitive flexibility and the intensity of conflicts, specifically in the area of dating and marriage. A positive relationship was observed between the use of social support coping strategy and intensity of conflicts. Hierarchical regression analyses revealed a significant interaction effect in which participant-perceived parent-child values gap and cognitive flexibility were related to increased frequency of dating and marriage conflicts.

Influence of the ordering of impurities on the appearance of an energy gap and on the electrical conductance of graphene.

PubMed

Repetsky, S P; Vyshyvana, I G; Kruchinin, S P; Bellucci, Stefano

2018-06-14

In the one-band model of strong coupling, the influence of substitutional impurity atoms on the energy spectrum and electrical conductance of graphene is studied. It is established that the ordering of substitutional impurity atoms on nodes of the crystal lattice causes the appearance of a gap in the energy spectrum of graphene with width η|δ| centered at the point yδ, where η is the parameter of ordering, δ is the difference of the scattering potentials of impurity atoms and carbon atoms, and y is the impurity concentration. The maximum value of the parameter of ordering is [Formula: see text]. For the complete ordering of impurity atoms, the energy gap width equals [Formula: see text]. If the Fermi level falls in the region of the mentioned gap, then the electrical conductance [Formula: see text] at the ordering of graphene, i.e., the metal-dielectric transition arises. If the Fermi level is located outside the gap, then the electrical conductance increases with the parameter of order η by the relation [Formula: see text]. At the concentration [Formula: see text], as the ordering of impurity atoms η →1, the electrical conductance of graphene [Formula: see text], i.e., the transition of graphene in the state of ideal electrical conductance arises.

A Thin Lens Model for Charged-Particle RF Accelerating Gaps

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

Allen, Christopher K.

Presented is a thin-lens model for an RF accelerating gap that considers general axial fields without energy dependence or other a priori assumptions. Both the cosine and sine transit time factors (i.e., Fourier transforms) are required plus two additional functions; the Hilbert transforms the transit-time factors. The combination yields a complex-valued Hamiltonian rotating in the complex plane with synchronous phase. Using Hamiltonians the phase and energy gains are computed independently in the pre-gap and post-gap regions then aligned using the asymptotic values of wave number. Derivations of these results are outlined, examples are shown, and simulations with the model aremore » presented.« less

Machine Learning Prediction of the Energy Gap of Graphene Nanoflakes Using Topological Autocorrelation Vectors.

PubMed

Fernandez, Michael; Abreu, Jose I; Shi, Hongqing; Barnard, Amanda S

2016-11-14

The possibility of band gap engineering in graphene opens countless new opportunities for application in nanoelectronics. In this work, the energy gaps of 622 computationally optimized graphene nanoflakes were mapped to topological autocorrelation vectors using machine learning techniques. Machine learning modeling revealed that the most relevant correlations appear at topological distances in the range of 1 to 42 with prediction accuracy higher than 80%. The data-driven model can statistically discriminate between graphene nanoflakes with different energy gaps on the basis of their molecular topology.

A detailed analysis of the energy levels configuration existing in the band gap of supersaturated silicon with titanium for photovoltaic applications

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

Pérez, E.; Dueñas, S.; Castán, H.

2015-12-28

The energy levels created in supersaturated n-type silicon substrates with titanium implantation in the attempt to create an intermediate band in their band-gap are studied in detail. Two titanium ion implantation doses (10{sup 13 }cm{sup -2} and 10{sup 14 }cm{sup -2}) are studied in this work by conductance transient technique and admittance spectroscopy. Conductance transients have been measured at temperatures of around 100 K. The particular shape of these transients is due to the formation of energy barriers in the conduction band, as a consequence of the band-gap narrowing induced by the high titanium concentration. Moreover, stationary admittance spectroscopy results suggest the existencemore » of different energy level configuration, depending on the local titanium concentration. A continuum energy level band is formed when titanium concentration is over the Mott limit. On the other hand, when titanium concentration is lower than the Mott limit, but much higher than the donor impurity density, a quasi-continuum energy level distribution appears. Finally, a single deep center appears for low titanium concentration. At the n-type substrate, the experimental results obtained by means of thermal admittance spectroscopy at high reverse bias reveal the presence of single levels located at around E{sub c}-425 and E{sub c}-275 meV for implantation doses of 10{sup 13 }cm{sup −2} and 10{sup 14 }cm{sup −2}, respectively. At low reverse bias voltage, quasi-continuously distributed energy levels between the minimum of the conduction bands, E{sub c} and E{sub c}-450 meV, are obtained for both doses. Conductance transients detected at low temperatures reveal that the high impurity concentration induces a band gap narrowing which leads to the formation of a barrier in the conduction band. Besides, the relationship between the activation energy and the capture cross section values of all the energy levels fits very well to the Meyer-Neldel rule. As it is

Energy Gap in the Aetiology of Body Weight Gain and Obesity: A Challenging Concept with a Complex Evaluation and Pitfalls

PubMed Central

Schutz, Yves; Byrne, Nuala M.; Dulloo, Abdul; Hills, Andrew P.

2014-01-01

The concept of energy gap(s) is useful for understanding the consequence of a small daily, weekly, or monthly positive energy balance and the inconspicuous shift in weight gain ultimately leading to overweight and obesity. Energy gap is a dynamic concept: an initial positive energy gap incurred via an increase in energy intake (or a decrease in physical activity) is not constant, may fade out with time if the initial conditions are maintained, and depends on the ‘efficiency’ with which the readjustment of the energy imbalance gap occurs with time. The metabolic response to an energy imbalance gap and the magnitude of the energy gap(s) can be estimated by at least two methods, i.e. i) assessment by longitudinal overfeeding studies, imposing (by design) an initial positive energy imbalance gap; ii) retrospective assessment based on epidemiological surveys, whereby the accumulated endogenous energy storage per unit of time is calculated from the change in body weight and body composition. In order to illustrate the difficulty of accurately assessing an energy gap we have used, as an illustrative example, a recent epidemiological study which tracked changes in total energy intake (estimated by gross food availability) and body weight over 3 decades in the US, combined with total energy expenditure prediction from body weight using doubly labelled water data. At the population level, the study attempted to assess the cause of the energy gap purported to be entirely due to increased food intake. Based on an estimate of change in energy intake judged to be more reliable (i.e. in the same study population) and together with calculations of simple energetic indices, our analysis suggests that conclusions about the fundamental causes of obesity development in a population (excess intake vs. low physical activity or both) is clouded by a high level of uncertainty. PMID:24457473

Energy gap in the aetiology of body weight gain and obesity: a challenging concept with a complex evaluation and pitfalls.

PubMed

Schutz, Yves; Byrne, Nuala M; Dulloo, Abdul; Hills, Andrew P

2014-01-01

The concept of energy gap(s) is useful for understanding the consequence of a small daily, weekly, or monthly positive energy balance and the inconspicuous shift in weight gain ultimately leading to overweight and obesity. Energy gap is a dynamic concept: an initial positive energy gap incurred via an increase in energy intake (or a decrease in physical activity) is not constant, may fade out with time if the initial conditions are maintained, and depends on the 'efficiency' with which the readjustment of the energy imbalance gap occurs with time. The metabolic response to an energy imbalance gap and the magnitude of the energy gap(s) can be estimated by at least two methods, i.e. i) assessment by longitudinal overfeeding studies, imposing (by design) an initial positive energy imbalance gap; ii) retrospective assessment based on epidemiological surveys, whereby the accumulated endogenous energy storage per unit of time is calculated from the change in body weight and body composition. In order to illustrate the difficulty of accurately assessing an energy gap we have used, as an illustrative example, a recent epidemiological study which tracked changes in total energy intake (estimated by gross food availability) and body weight over 3 decades in the US, combined with total energy expenditure prediction from body weight using doubly labelled water data. At the population level, the study attempted to assess the cause of the energy gap purported to be entirely due to increased food intake. Based on an estimate of change in energy intake judged to be more reliable (i.e. in the same study population) and together with calculations of simple energetic indices, our analysis suggests that conclusions about the fundamental causes of obesity development in a population (excess intake vs. low physical activity or both) is clouded by a high level of uncertainty. © 2014 S. Karger GmbH, Freiburg.

The Wind Energy Workforce Gap in the United States

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

Tegen, Suzanne I; Keyser, David J

There are more than 100,000 jobs in the U.S. wind industry today, and the second-fastest growing job in the United States in 2017 was wind technician. A vibrant wind industry needs workers, and students who graduate from wind energy education and training programs need jobs. The goal of this research is to better understand the needs of wind-related businesses, education and training requirements, and the make-up of current and future domestic workforces. Educators are developing and training future workers. Educational institutions need to know which courses to provide to connect students with potential employers and to justify their wind energymore » programs by being able to place graduates into well-paying jobs. In interviews with 250 wind energy firms and 50 educational institutions, many respondents reported difficulty hiring qualified candidates, while many educational institutions reported graduates not finding jobs in the wind industry. We refer to this mismatch as the 'workforce gap.' This conference poster explores this gap.« less

Tuning Ferritin’s band gap through mixed metal oxide nanoparticle formation

NASA Astrophysics Data System (ADS)

Olsen, Cameron R.; Embley, Jacob S.; Hansen, Kameron R.; Henrichsen, Andrew M.; Peterson, J. Ryan; Colton, John S.; Watt, Richard K.

2017-05-01

This study uses the formation of a mixed metal oxide inside ferritin to tune the band gap energy of the ferritin mineral. The mixed metal oxide is composed of both Co and Mn, and is formed by reacting aqueous Co2+ with {{{{MnO}}}4}- in the presence of apoferritin. Altering the ratio between the two reactants allowed for controlled tuning of the band gap energies. All minerals formed were indirect band gap materials, with indirect band gap energies ranging from 0.52 to 1.30 eV. The direct transitions were also measured, with energy values ranging from 2.71 to 3.11 eV. Tuning the band gap energies of these samples changes the wavelengths absorbed by each mineral, increasing ferritin’s potential in solar-energy harvesting. Additionally, the success of using {{{{MnO}}}4}- in ferritin mineral formation opens the possibility for new mixed metal oxide cores inside ferritin.

Effect of a gap opening on the conductance of graphene with magnetic barrier structures

NASA Astrophysics Data System (ADS)

Esmailpour, Mohammad

2018-04-01

In the present study Klein tunneling in a single-layer gapped graphene was investigated by transfer matrix method under normal magnetic field for one and two magnetic barriers. Calculations show that electron transmission through a magnetic barrier is deflected to positive angles and reduces as the magnitude of magnetic field and especially the energy gap increases. This reduction is even more significant in larger fields so that after reaching a specific value of energy gap, an effective confinement for fermions and suppression of Klein tunneling is reached particularly in normal incidence and the conductance becomes zero. Unlike one barrier, the process of tunneling through two magnetic barriers induces symmetric transmission probability versus the incident angle; even, for lower energy gaps, electron transmission probability increases which in turn reduces total conductance via proper changes in the value of the magnetic field and energy gap. In general, it is concluded that confining electrons in asymmetric transmission through one barrier is conducted better than two barriers.

Reducing the gender achievement gap in college science: a classroom study of values affirmation.

PubMed

Miyake, Akira; Kost-Smith, Lauren E; Finkelstein, Noah D; Pollock, Steven J; Cohen, Geoffrey L; Ito, Tiffany A

2010-11-26

In many science, technology, engineering, and mathematics disciplines, women are outperformed by men in test scores, jeopardizing their success in science-oriented courses and careers. The current study tested the effectiveness of a psychological intervention, called values affirmation, in reducing the gender achievement gap in a college-level introductory physics class. In this randomized double-blind study, 399 students either wrote about their most important values or not, twice at the beginning of the 15-week course. Values affirmation reduced the male-female performance and learning difference substantially and elevated women's modal grades from the C to B range. Benefits were strongest for women who tended to endorse the stereotype that men do better than women in physics. A brief psychological intervention may be a promising way to address the gender gap in science performance and learning.

Two-dimensional topological insulators with large bulk energy gap

NASA Astrophysics Data System (ADS)

Yang, Z. Q.; Jia, Jin-Feng; Qian, Dong

2016-11-01

Two-dimensional (2D) topological insulators (TIs, or quantum spin Hall insulators) are special insulators that possess bulk 2D electronic energy gap and time-reversal symmetry protected one-dimensional (1D) edge state. Carriers in the edge state have the property of spin-momentum locking, enabling dissipation-free conduction along the 1D edge. The existence of 2D TIs was confirmed by experiments in semiconductor quantum wells. However, the 2D bulk gaps in those quantum wells are extremely small, greatly limiting potential application in future electronics and spintronics. Despite this limitation, 2D TIs with a large bulk gap attracted plenty of interest. In this paper, recent progress in searching for TIs with a large bulk gap is reviewed briefly. We start by introducing some theoretical predictions of these new materials and then discuss some recent important achievements in crystal growth and characterization. Project supported by the National Natural Science Foundation of China (Grant Nos. U1632272, 11574201, and 11521404). D. Q. acknowledges support from the Changjiang Scholars Program, China and the Program for Professor of Special Appointment (Eastern Scholar), China.

Development of an Abort Gap Monitor for High-Energy Proton Rings

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

Beche, J.-F.; Byrd, J.; De Santis, S.

2004-11-10

The fill pattern in proton synchrotrons usually features an empty gap, longer than the abort kicker raise time, for machine protection. This gap is referred to as the 'abort gap', and any particles, which may accumulate in it due to injection errors and diffusion between RF buckets, would be lost inside the ring, rather than in the beam dump, during the kicker firing. In large proton rings, due to the high energies involved, it is vital to monitor the build up of charges in the abort gap with a high sensitivity. We present a study of an abort gap monitormore » based on a photomultiplier with a gated microchannel plate, which would allow for detecting low charge densities by monitoring the synchrotron radiation emitted. We show results of beam test experiments at the Advanced Light Source using a Hamamatsu 5916U MCP-PMT and compare them to the specifications for the Large Hadron Collider.« less

Development of an abort gap monitor for high-energy proton rings

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

Beche, Jean-Francois; Byrd, John; De Santis, Stefano

2004-05-03

The fill pattern in proton synchrotrons usually features an empty gap, longer than the abort kicker raise time, for machine protection. This gap is referred to as the ''abort gap'' and any particles, which may accumulate in it due to injection errors and diffusion between RF buckets, would be lost inside the ring, rather than in the beam dump, during the kicker firing. In large proton rings, due to the high energies involved, it is vital to monitor the build up of charges in the abort gap with a high sensitivity. We present a study of an abort gap monitormore » based on a photomultiplier with a gated microchannel plate, which would allow for detecting low charge densities by monitoring the synchrotron radiation emitted. We show results of beam test experiments at the Advanced Light Source using a Hamamatsu 5916U MCP-PMT and compare them to the specifications for the Large Hadron Collider« less

Energy band gap and spectroscopic studies in Mn{sub 1-x}Cu{sub x}WO{sub 4} (0 ≤ x ≤ 0.125)

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

Mal, Priyanath; Rambabu, P.; Turpu, G. R.

2016-05-06

A study on the effect of nonmagnetic Cu{sup 2+} substitution at Mn{sup 2+} site on the structural and energy band gap of the MnWO{sub 4} is reported. Convenient solid state reaction route has been adopted for the synthesis of Mn{sub 1-x}Cu{sub x}WO{sub 4}. X-ray diffraction (XRD) pattern showed high crystalline quality of the prepared samples. Raman spectroscopic studies were carried out to understand the structural aspects of the doping. 15 Raman active modes were identified out of 18, predicted for wolframite type monoclinic structure of MnWO{sub 4}. UV-visible diffuse reflectance spectra were recorded and analyzed to get energy band gapmore » of the studied system and are found in the range of 2.5 eV to 2.04 eV with a systematic decrease with the increase in Cu{sup 2+} concentration. Energy band gap values are verified by Density Functional Theory calculations based on projector augmented wave (PAW) method. The calculated values are in good agreement with the experimental data.« less

Comparison of energy flows in deep inelastic scattering events with and without a large rapidity gap

NASA Astrophysics Data System (ADS)

Derrick, M.; Krakauer, D.; Magill, S.; Musgrave, B.; Repond, J.; Schlereth, J.; Stanek, R.; Talaga, R. L.; Thron, J.; Arzarello, F.; Ayad, R.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Bruni, P.; Romeo, G. Cara; Castellini, G.; Chiarini, M.; Cifarelli, L.; Cindolo, F.; Ciralli, F.; Contin, A.; D'Auria, S.; Del Papa, C.; Frasconi, F.; Giusti, P.; Iacobucci, G.; Laurenti, G.; Levi, G.; Maccarrone, G.; Margotti, A.; Massam, T.; Nania, R.; Nemoz, C.; Palmonari, F.; Polini, A.; Sartorelli, G.; Timellini, R.; Garcia, Y. Zamora; Zichichi, A.; Bargende, A.; Crittenden, J.; Desch, K.; Diekmann, B.; Doeker, T.; Feld, L.; Frey, A.; Geerts, M.; Geitz, G.; Grothe, M.; Hartmann, H.; Haun, D.; Heinloth, K.; Hilger, E.; Jakob, H.-P.; Katz, U. F.; Mari, S. M.; Mass, A.; Mengel, S.; Mollen, J.; Paul, E.; Rembser, Ch.; Schattevoy, R.; Schneider, J.-L.; Schramm, D.; Stamm, J.; Wedemeyer, R.; Campbell-Robson, S.; Cassidy, A.; Dyce, N.; Foster, B.; George, S.; Gilmore, R.; Heath, G. P.; Heath, H. F.; Llewellyn, T. J.; Morgado, C. J. S.; Norman, D. J. P.; O'Mara, J. A.; Tapper, R. J.; Wilson, S. S.; Yoshida, R.; Rau, R. R.; Arneodo, M.; Iannotti, L.; Schioppa, M.; Susinno, G.; Bernstein, A.; Caldwell, A.; Gialas, I.; Parsons, J. A.; Ritz, S.; Sciulli, F.; Straub, P. B.; Wai, L.; Yang, S.; Borzemski, P.; Chwastowski, J.; Eskreys, A.; Piotrzkowski, K.; Zachara, M.; Zawiejski, L.; Adamczyk, L.; Bednarek, B.; Eskreys, K.; Jeleń, K.; Kisielewska, D.; Kowalski, T.; Rulikowska-Zarȩbska, E.; Suszycki, L.; Zajaç, J.; Kȩdzierski, T.; Kotański, A.; Przybycień, M.; Bauerdick, L. A. T.; Behrens, U.; Bienlein, J. K.; Böttcher, S.; Coldewey, C.; Drews, G.; Flasiński, M.; Gilkinson, D. J.; Göttlicher, P.; Gutjahr, B.; Haas, T.; Hagge, L.; Hain, W.; Hasell, D.; Heßling, H.; Hultschig, H.; Iga, Y.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Köpke, L.; Kötz, U.; Kowalski, H.; Kröger, W.; Krüger, J.; Labs, J.; Ladage, A.; Löhr, B.; Löwe, M.; Lüke, D.; Mainusch, J.; Mańczak, O.; Ng, J. S. T.; Nickel, S.; Notz, D.; Ohrenberg, K.; Roco, M.; Rohde, M.; Roldán, J.; Schneekloth, U.; Schroeder, J.; Schulz, W.; Selonke, F.; Stiliaris, E.; Voß, T.; Westphal, D.; Wolf, G.; Youngman, C.; Grabosch, H. J.; Leich, A.; Meyer, A.; Rethfeldt, C.; Schlenstedt, S.; Barbagli, G.; Pelfer, P.; Anzivino, G.; De Pasquale, S.; Qian, S.; Votano, L.; Bamberger, A.; Freidhof, A.; Poser, T.; Söldner-Rembold, S.; Theisen, G.; Trefzger, T.; Brook, N. H.; Bussey, P. J.; Doyle, A. T.; Fleck, I.; Forbes, J. R.; Jamieson, V. A.; Raine, C.; Saxon, D. H.; Stavrianakou, M.; Wilson, A. S.; Dannemann, A.; Holm, U.; Horstmann, D.; Kammerlocher, H.; Krebs, B.; Neumann, T.; Sinkus, R.; Wick, K.; Badura, E.; Burow, B. D.; Fürtjes, A.; Lohrmann, E.; Milewski, J.; Nakahata, M.; Pavel, N.; Poelz, G.; Schott, W.; Terron, J.; Zetsche, F.; Bacon, T. C.; Beuselinck, R.; Butterworth, I.; Gallo, E.; Harris, V. L.; Hung, B. H.; Long, K. R.; Miller, D. B.; Morawitz, P. P. O.; Prinias, A.; Sedgbeer, J. K.; Whitfield, A. F.; Mallik, U.; McCliment, E.; Wang, M. Z.; Zhang, Y.; Cloth, P.; Filges, D.; An, S. H.; Hong, S. M.; Kim, C. O.; Kim, T. Y.; Nam, S. W.; Park, S. K.; Suh, M. H.; Yon, S. H.; Imlay, R.; Kartik, S.; Kim, H.-J.; McNeil, R. R.; Metcalf, W.; Nadendla, V. K.; Barreiro, F.; Cases, G.; Graciani, R.; Hernández, J. M.; Hervás, L.; Labarga, L.; del Peso, J.; Puga, J.; de Trocóniz, J. F.; Ikraiam, F.; Mayer, J. K.; Smith, G. R.; Corriveau, F.; Hanna, D. S.; Hartmann, J.; Hung, L. W.; Lim, J. N.; Matthews, C. G.; Mitchell, J. W.; Patel, P. M.; Sinclair, L. E.; Stairs, D. G.; Laurent, M. St.; Ullmann, R.; Bashkirov, V.; Dolgoshein, B. A.; Stifutkin, A.; Bashindzhagyan, G. L.; Ermolov, P. F.; Gladilin, L. K.; Golubkov, Y. A.; Kobrin, V. D.; Kuzmin, V. A.; Proskuryakov, A. S.; Savin, A. A.; Shcheglova, L. M.; Solomin, A. N.; Zotov, N. P.; Bentvelsen, S.; Botje, M.; Chlebana, F.; Dake, A.; Engelen, J.; de Jong, P.; de Kamps, M.; Kooijman, P.; Kruse, A.; O'Dell, V.; Tenner, A.; Tiecke, H.; Verkerke, W.; Vreeswijk, M.; Wiggers, L.; de Wolf, E.; van Woudenberg, R.; Acosta, D.; Bylsma, B.; Durkin, L. S.; Honscheid, K.; Li, C.; Ling, T. Y.; McLean, K. W.; Murray, W. N.; Park, I. H.; Romanowski, T. A.; Seidlein, R.; Bailey, D. S.; Blair, G. A.; Byrne, A.; Cashmore, R. J.; Cooper-Sarkar, A. M.; Daniels, D.; Devenish, R. C. E.; Harnew, N.; Lancaster, M.; Luffman, P. E.; McFall, J.; Nath, C.; Quadt, A.; Uijterwaal, H.; Walczak, R.; Wilson, F. F.; Yip, T.; Abbiendi, G.; Bertolin, A.; Brugnera, R.; Carlin, R.; Dal Corso, F.; De Giorgi, M.; Dosselli, U.; Gasparini, F.; Limentani, S.; Morandin, M.; Posocco, M.; Stanco, L.; Stroili, R.; Voci, C.; Bulmahn, J.; Butterworth, J. M.; Feild, R. G.; Oh, B. Y.; Whitmore, J. J.; D'Agostini, G.; Iori, M.; Marini, G.; Mattioli, M.; Nigro, A.; Hart, J. C.; McCubbin, N. A.; Prytz, K.; Shah, T. P.; Short, T. L.; Barberis, E.; Cartiglia, N.; Dubbs, T.; Heusch, C.; Van Hook, M.; Hubbard, B.; Lockman, W.; Sadrozinski, H. F.-W.; Seiden, A.; Biltzinger, J.; Seifert, R. J.; Walenta, A. H.; Zech, G.; Abramowicz, H.; Dagan, S.; Levy, A.; Hasegawa, T.; Hazumi, M.; Ishii, T.; Kuze, M.; Mine, S.; Nagasawa, Y.; Nagira, T.; Nakao, M.; Suzuki, I.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Chiba, M.; Hamatsu, R.; Hirose, T.; Homma, K.; Kitamura, S.; Nagayama, S.; Nakamitsu, Y.; Cirio, R.; Costa, M.; Ferrero, M. I.; Lamberti, L.; Maselli, S.; Peroni, C.; Sacchi, R.; Solano, A.; Staiano, A.; Dardo, M.; Bailey, D. C.; Bandyopadhyay, D.; Benard, F.; Brkic, M.; Crombie, M. B.; Gingrich, D. M.; Hartner, G. F.; Joo, K. K.; Levman, G. M.; Martin, J. F.; Orr, R. S.; Sampson, C. R.; Teuscher, R. J.; Catterall, C. D.; Jones, T. W.; Kaziewicz, P. B.; Lane, J. B.; Saunders, R. S.; Shulman, J.; Blankenship, K.; Kochocki, J.; Lu, B.; Mo, L. W.; Bogusz, W.; Charchuła, K.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprzak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Tymieniecka, T.; Wróblewski, A. K.; Zakrzewski, J. A.; Żarnecki, A. F.; Adamus, M.; Eisenberg, Y.; Glasman, C.; Karshon, U.; Revel, D.; Shapira, A.; Ali, I.; Behrens, B.; Dasu, S.; Fordham, C.; Foudas, C.; Goussiou, A.; Loveless, R. J.; Reeder, D. D.; Silverstein, S.; Smith, W. H.; Tsurugai, T.; Bhadra, S.; Frisken, W. R.; Furutani, K. M.; ZEUS Collaboration

1994-11-01

Energy flows in deep inelastic electron-proton scattering are investigated at a centre-of-mass energy of 269 GeV for the range Q2 ≥ 10 GeV 2 using the ZEUS detector. A comparison is made between events with and without a large rapidity gap between the hadronic system and the proton direction. The energy flows, corrected for detector acceptance and resolution, are shown for these two classes of events in both the HERA laboratory frame and the Breit frame. From the differences in the shapes of these energy flows we conclude that QCD radiation is suppressed in the large-rapidity-gap eents compared to the events without a large rapidity gap.

Public perceptions and information gaps in solar energy in Texas

NASA Astrophysics Data System (ADS)

Rai, Varun; Beck, Ariane L.

2015-07-01

Studying the behavioral aspects of the individual decision-making process is important in identifying and addressing barriers in the adoption of residential solar photovoltaic (PV). However, there is little systematic research focusing on these aspects of residential PV in Texas, an important, large, populous state, with a range of challenges in the electricity sector including increasing demand, shrinking reserve margins, constrained water supply, and challenging emissions reduction targets under proposed federal regulations. This paper aims to address this gap through an empirical investigation of a new survey-based dataset collected in Texas on solar energy perceptions and behavior. The results of this analysis offer insights into the perceptions and motivations influencing intentions and behavior toward solar energy in a relatively untapped market and help identify information gaps that could be targeted to alleviate key barriers to adopting solar, thereby enabling significant emissions reductions in the residential sector in Texas.

Electronic characterization of defects in narrow gap semiconductors: Comparison of electronic energy levels and formation energies in mercury cadmium telluride, mercury zinc telluride, and mercury zinc selenide

NASA Technical Reports Server (NTRS)

Patterson, James D.; Li, Wei-Gang

1995-01-01

The project has evolved to that of using Green's functions to predict properties of deep defects in narrow gap materials. Deep defects are now defined as originating from short range potentials and are often located near the middle of the energy gap. They are important because they affect the lifetime of charge carriers and hence the switching time of transistors. We are now moving into the arena of predicting formation energies of deep defects. This will also allow us to make predictions about the relative concentrations of the defects that could be expected at a given temperature. The narrow gap materials mercury cadmium telluride (MCT), mercury zinc telluride (MZT), and mercury zinc selenide (MZS) are of interest to NASA because they have commercial value for infrared detecting materials, and because there is a good possibility that they can be grown better in a microgravity environment. The uniform growth of these crystals on earth is difficult because of convection (caused by solute depletion just ahead of the growing interface, and also due to thermal gradients). In general it is very difficult to grow crystals with both radial and axial homogeneity.

Electronic transport in Thue-Morse gapped graphene superlattice under applied bias

NASA Astrophysics Data System (ADS)

Wang, Mingjing; Zhang, Hongmei; Liu, De

2018-04-01

We investigate theoretically the electronic transport properties of Thue-Morse gapped graphene superlattice under an applied electric field. The results indicate that the combined effect of the band gap and the applied bias breaks the angular symmetry of the transmission coefficient. The zero-averaged wave-number gap can be greatly modulated by the band gap and the applied bias, but its position is robust against change of the band gap. Moreover, the conductance and the Fano factor are strongly dependent not only on the Fermi energy but also on the band gap and the applied bias. In the vicinity of the new Dirac point, the minimum value of the conductance obviously decreases and the Fano factor gradually forms a Poissonian value plateau with increasing of the band gap.

Energy Impacts of Wide Band Gap Semiconductors in U.S. Light-Duty Electric Vehicle Fleet.

PubMed

Warren, Joshua A; Riddle, Matthew E; Graziano, Diane J; Das, Sujit; Upadhyayula, Venkata K K; Masanet, Eric; Cresko, Joe

2015-09-01

Silicon carbide and gallium nitride, two leading wide band gap semiconductors with significant potential in electric vehicle power electronics, are examined from a life cycle energy perspective and compared with incumbent silicon in U.S. light-duty electric vehicle fleet. Cradle-to-gate, silicon carbide is estimated to require more than twice the energy as silicon. However, the magnitude of vehicle use phase fuel savings potential is comparatively several orders of magnitude higher than the marginal increase in cradle-to-gate energy. Gallium nitride cradle-to-gate energy requirements are estimated to be similar to silicon, with use phase savings potential similar to or exceeding that of silicon carbide. Potential energy reductions in the United States vehicle fleet are examined through several scenarios that consider the market adoption potential of electric vehicles themselves, as well as the market adoption potential of wide band gap semiconductors in electric vehicles. For the 2015-2050 time frame, cumulative energy savings associated with the deployment of wide band gap semiconductors are estimated to range from 2-20 billion GJ depending on market adoption dynamics.

Intrinsic energy localization through discrete gap breathers in one-dimensional diatomic granular crystals.

PubMed

Theocharis, G; Boechler, N; Kevrekidis, P G; Job, S; Porter, Mason A; Daraio, C

2010-11-01

We present a systematic study of the existence and stability of discrete breathers that are spatially localized in the bulk of a one-dimensional chain of compressed elastic beads that interact via Hertzian contact. The chain is diatomic, consisting of a periodic arrangement of heavy and light spherical particles. We examine two families of discrete gap breathers: (1) an unstable discrete gap breather that is centered on a heavy particle and characterized by a symmetric spatial energy profile and (2) a potentially stable discrete gap breather that is centered on a light particle and is characterized by an asymmetric spatial energy profile. We investigate their existence, structure, and stability throughout the band gap of the linear spectrum and classify them into four regimes: a regime near the lower optical band edge of the linear spectrum, a moderately discrete regime, a strongly discrete regime that lies deep within the band gap of the linearized version of the system, and a regime near the upper acoustic band edge. We contrast discrete breathers in anharmonic Fermi-Pasta-Ulam (FPU)-type diatomic chains with those in diatomic granular crystals, which have a tensionless interaction potential between adjacent particles, and note that the asymmetric nature of the tensionless interaction potential can lead to hybrid bulk-surface localized solutions.

Intrinsic energy localization through discrete gap breathers in one-dimensional diatomic granular crystals

NASA Astrophysics Data System (ADS)

Theocharis, G.; Boechler, N.; Kevrekidis, P. G.; Job, S.; Porter, Mason A.; Daraio, C.

2010-11-01

We present a systematic study of the existence and stability of discrete breathers that are spatially localized in the bulk of a one-dimensional chain of compressed elastic beads that interact via Hertzian contact. The chain is diatomic, consisting of a periodic arrangement of heavy and light spherical particles. We examine two families of discrete gap breathers: (1) an unstable discrete gap breather that is centered on a heavy particle and characterized by a symmetric spatial energy profile and (2) a potentially stable discrete gap breather that is centered on a light particle and is characterized by an asymmetric spatial energy profile. We investigate their existence, structure, and stability throughout the band gap of the linear spectrum and classify them into four regimes: a regime near the lower optical band edge of the linear spectrum, a moderately discrete regime, a strongly discrete regime that lies deep within the band gap of the linearized version of the system, and a regime near the upper acoustic band edge. We contrast discrete breathers in anharmonic Fermi-Pasta-Ulam (FPU)-type diatomic chains with those in diatomic granular crystals, which have a tensionless interaction potential between adjacent particles, and note that the asymmetric nature of the tensionless interaction potential can lead to hybrid bulk-surface localized solutions.

Edge currents shunt the insulating bulk in gapped graphene

NASA Astrophysics Data System (ADS)

Zhu, M. J.; Kretinin, A. V.; Thompson, M. D.; Bandurin, D. A.; Hu, S.; Yu, G. L.; Birkbeck, J.; Mishchenko, A.; Vera-Marun, I. J.; Watanabe, K.; Taniguchi, T.; Polini, M.; Prance, J. R.; Novoselov, K. S.; Geim, A. K.; Ben Shalom, M.

2017-02-01

An energy gap can be opened in the spectrum of graphene reaching values as large as 0.2 eV in the case of bilayers. However, such gaps rarely lead to the highly insulating state expected at low temperatures. This long-standing puzzle is usually explained by charge inhomogeneity. Here we revisit the issue by investigating proximity-induced superconductivity in gapped graphene and comparing normal-state measurements in the Hall bar and Corbino geometries. We find that the supercurrent at the charge neutrality point in gapped graphene propagates along narrow channels near the edges. This observation is corroborated by using the edgeless Corbino geometry in which case resistivity at the neutrality point increases exponentially with increasing the gap, as expected for an ordinary semiconductor. In contrast, resistivity in the Hall bar geometry saturates to values of about a few resistance quanta. We attribute the metallic-like edge conductance to a nontrivial topology of gapped Dirac spectra.

Energy technology and American democratic values

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

Thompson, G.M.

1988-01-01

Today, the benefits of liberal democracy have increasingly been cast into doubt. The debate over alternative energy policies illustrates the problems associated with liberal democracy. For many, it is the realization that energy choices and the selection of social and political values amount to much the same thing. Simply put, energy policy decisions, and the concomitant energy technologies, carry implications of an ethical, social and political nature. The argument of the social and political effects of energy technology flows from the more general thesis that all forms of technological practice condition social and political relations. That is, technological systems, beyondmore » performing the specific functions for which they were designed, act upon and influence social and political arrangements. Seen in this light, energy technologies are as important to the promotion and preservation of this country's political values as are its institutions and laws. Further, there is evidence to suggest that this country's cherished democratic value of freedom is slowly being eclipsed by the values attendant to corporate capitalism and its singular pursuit of growth. It is this dominance of economic values over political values which provides the environment within which the technological debate is waged. Ultimately, tracing the historic linkage between property and liberty, it is concluded that the preservation of our freedom require new thinking regarding the present configuration of ownership patterns. The questions surrounding energy policy serve to illuminate these concerns.« less

Energy Impacts of Wide Band Gap Semiconductors in U.S. Light-Duty Electric Vehicle Fleet

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

Warren, Joshua A.; Riddle, Matthew E.; Graziano, Diane J.

2015-08-12

Silicon carbide and gallium nitride, two leading wide band gap semiconductors with significant potential in electric vehicle power electronics, are examined from a life cycle energy perspective and compared with incumbent silicon in U.S. light-duty electric vehicle fleet. Cradle-to-gate, silicon carbide is estimated to require more than twice the energy as silicon. However, the magnitude of vehicle use phase fuel savings potential is comparatively several orders of magnitude higher than the marginal increase in cradle-to-gate energy. Gallium nitride cradle-to-gate energy requirements are estimated to be similar to silicon, with use phase savings potential similar to or exceeding that of siliconmore » carbide. Potential energy reductions in the United States vehicle fleet are examined through several scenarios that consider the market adoption potential of electric vehicles themselves, as well as the market adoption potential of wide band gap semiconductors in electric vehicles. For the 2015–2050 time frame, cumulative energy savings associated with the deployment of wide band gap semiconductors are estimated to range from 2–20 billion GJ depending on market adoption dynamics.« less

Dynamical Energy Gap Engineering in Graphene via Oscillating Out-of-Plane Deformations

NASA Astrophysics Data System (ADS)

Sandler, Nancy; Zhai, Dawei

The close relation between electronic properties and mechanical deformations in graphene has been the topic of active research in recent years. Interestingly, the effect of deformations on electronic properties can be understood in terms of pseudo-magnetic fields, whose spatial distribution and intensity are controllable via the deformation geometry. Previous results showed that electromagnetic fields (light) have the potential to induce dynamical gaps in graphene's energy bands, transforming graphene from a semimetal to a semiconductor. However, laser frequencies required to achieve these regimes are in the THz regime, which imposes challenges for practical purposes. In this talk we report a novel method to create dynamical gaps using oscillating mechanical deformations, i.e., via time-dependent pseudo-magnetic fields. Using the Floquet formalism we show the existence of a dynamical gap in the band structure at energies set by the frequency of the oscillation, and with a magnitude tuned by the geometry of the deformation. This dynamical-mechanical manipulation strategy appears as a promising venue to engineer electronic properties of suspended graphene devices. Work supported by NSF-DMR 1508325.

Nonlocal kinetic energy functional from the jellium-with-gap model: Applications to orbital-free density functional theory

NASA Astrophysics Data System (ADS)

Constantin, Lucian A.; Fabiano, Eduardo; Della Sala, Fabio

2018-05-01

Orbital-free density functional theory (OF-DFT) promises to describe the electronic structure of very large quantum systems, being its computational cost linear with the system size. However, the OF-DFT accuracy strongly depends on the approximation made for the kinetic energy (KE) functional. To date, the most accurate KE functionals are nonlocal functionals based on the linear-response kernel of the homogeneous electron gas, i.e., the jellium model. Here, we use the linear-response kernel of the jellium-with-gap model to construct a simple nonlocal KE functional (named KGAP) which depends on the band-gap energy. In the limit of vanishing energy gap (i.e., in the case of metals), the KGAP is equivalent to the Smargiassi-Madden (SM) functional, which is accurate for metals. For a series of semiconductors (with different energy gaps), the KGAP performs much better than SM, and results are close to the state-of-the-art functionals with sophisticated density-dependent kernels.

Pressure-Induced Structural Transition and Enhancement of Energy Gap of CuAlO2

NASA Astrophysics Data System (ADS)

Nakanishi, Akitaka

2011-02-01

By using first-principles calculations, we studied the stable crystal structures and energy gaps of CuAlO2 under high pressure. Our simulation shows that CuAlO2 transforms from a delafossite structure to a leaning delafossite structure. The critical pressure of the transition was determined to be 60 GPa. The energy gap of CuAlO2 increases through the structural transition due to the enhanced covalency of Cu 3d and O 2p states. We found that a chalcopyrite structure does not appear as a stable structure under high pressure.

Time-varying value of electric energy efficiency

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

Mims, Natalie A.; Eckman, Tom; Goldman, Charles

Electric energy efficiency resources save energy and may reduce peak demand. Historically, quantification of energy efficiency benefits has largely focused on the economic value of energy savings during the first year and lifetime of the installed measures. Due in part to the lack of publicly available research on end-use load shapes (i.e., the hourly or seasonal timing of electricity savings) and energy savings shapes, consideration of the impact of energy efficiency on peak demand reduction (i.e., capacity savings) has been more limited. End-use load research and the hourly valuation of efficiency savings are used for a variety of electricity planningmore » functions, including load forecasting, demand-side management and evaluation, capacity and demand response planning, long-term resource planning, renewable energy integration, assessing potential grid modernization investments, establishing rates and pricing, and customer service. This study reviews existing literature on the time-varying value of energy efficiency savings, provides examples in four geographically diverse locations of how consideration of the time-varying value of efficiency savings impacts the calculation of power system benefits, and identifies future research needs to enhance the consideration of the time-varying value of energy efficiency in cost-effectiveness screening analysis. Findings from this study include: -The time-varying value of individual energy efficiency measures varies across the locations studied because of the physical and operational characteristics of the individual utility system (e.g., summer or winter peaking, load factor, reserve margin) as well as the time periods during which savings from measures occur. -Across the four locations studied, some of the largest capacity benefits from energy efficiency are derived from the deferral of transmission and distribution system infrastructure upgrades. However, the deferred cost of such upgrades also exhibited the greatest

Molecular gap and energy level diagram for pentacene adsorbed on filled d-band metal surfaces

NASA Astrophysics Data System (ADS)

Baldacchini, Chiara; Mariani, Carlo; Betti, Maria Grazia; Gavioli, L.; Fanetti, M.; Sancrotti, M.

2006-10-01

The authors present a combined photoemission and scanning-tunneling spectroscopy study of the filled electronic states, the molecular energy gap, and the energy level diagram of highly ordered arrays of pentacene deposited on the Cu(119) vicinal surface. The states localized at the interface are clearly singled out, comparing the results at different pentacene thicknesses and with gas-phase photoemission data. The molecular gap of 2.35eV, the hole injection barrier of 1.05eV, and the electron injection barrier of 1.30eV determine the energy level diagram of the states localized at the pentacene molecules.

Anisotropy of the Fermi surface, Fermi velocity, many-body enhancement, and superconducting energy gap in Nb

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

Crabtree, G.W.; Dye, D.H.; Karim, D.P.

1987-02-01

The detailed angular dependence of the Fermi radius k/sub F/, the Fermi velocity v/sub F/(k), the many-body enhancement factor lambda(k), and the superconducting energy gap ..delta..(k), for electrons on the Fermi surface of Nb are derived with use of the de Haas--van Alphen (dHvA) data of Karim, Ketterson, and Crabtree (J. Low Temp. Phys. 30, 389 (1978)), a Korringa-Kohn-Rostoker parametrization scheme, and an empirically adjusted band-structure calculation of Koelling. The parametrization is a nonrelativistic five-parameter fit allowing for cubic rather than spherical symmetry inside the muffin-tin spheres. The parametrized Fermi surface gives a detailed interpretation of the previously unexplained kappa,more » ..cap alpha..', and ..cap alpha..'' orbits in the dHvA data. Comparison of the parametrized Fermi velocities with those of the empirically adjusted band calculation allow the anisotropic many-body enhancement factor lambda(k) to be determined. Theoretical calculations of the electron-phonon interaction based on the tight-binding model agree with our derived values of lambda(k) much better than those based on the rigid-muffin-tin approximation. The anisotropy in the superconducting energy gap ..delta..(k) is estimated from our results for lambda(k), assuming weak anisotropy.« less

Anisotropy of the Fermi surface, Fermi velocity, many-body enhancement, and superconducting energy gap in Nb

NASA Astrophysics Data System (ADS)

Crabtree, G. W.; Dye, D. H.; Karim, D. P.; Campbell, S. A.; Ketterson, J. B.

1987-02-01

The detailed angular dependence of the Fermi radius kF, the Fermi velocity vF(k), the many-body enhancement factor λ(k), and the superconducting energy gap Δ(k), for electrons on the Fermi surface of Nb are derived with use of the de Haas-van Alphen (dHvA) data of Karim, Ketterson, and Crabtree [J. Low Temp. Phys. 30, 389 (1978)], a Korringa-Kohn-Rostoker parametrization scheme, and an empirically adjusted band-structure calculation of Koelling. The parametrization is a nonrelativistic five-parameter fit allowing for cubic rather than spherical symmetry inside the muffin-tin spheres. The parametrized Fermi surface gives a detailed interpretation of the previously unexplained κ, α', and α'' orbits in the dHvA data. Comparison of the parametrized Fermi velocities with those of the empirically adjusted band calculation allow the anisotropic many-body enhancement factor λ(k) to be determined. Theoretical calculations of the electron-phonon interaction based on the tight-binding model agree with our derived values of λ(k) much better than those based on the rigid-muffin-tin approximation. The anisotropy in the superconducting energy gap Δ(k) is estimated from our results for λ(k), assuming weak anisotropy.

Relating the defect band gap and the density functional band gap

NASA Astrophysics Data System (ADS)

Schultz, Peter; Edwards, Arthur

2014-03-01

Density functional theory (DFT) is an important tool to probe the physics of materials. The Kohn-Sham (KS) gap in DFT is typically (much) smaller than the observed band gap for materials in nature, the infamous ``band gap problem.'' Accurate prediction of defect energy levels is often claimed to be a casualty--the band gap defines the energy scale for defect levels. By applying rigorous control of boundary conditions in size-converged supercell calculations, however, we compute defect levels in Si and GaAs with accuracies of ~0.1 eV, across the full gap, unhampered by a band gap problem. Using GaAs as a theoretical laboratory, we show that the defect band gap--the span of computed defect levels--is insensitive to variations in the KS gap (with functional and pseudopotential), these KS gaps ranging from 0.1 to 1.1 eV. The defect gap matches the experimental 1.52 eV gap. The computed defect gaps for several other III-V, II-VI, I-VII, and other compounds also agree with the experimental gap, and show no correlation with the KS gap. Where, then, is the band gap problem? This talk presents these results, discusses why the defect gap and the KS gap are distinct, implying that current understanding of what the ``band gap problem'' means--and how to ``fix'' it--need to be rethought. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy's NNSA under contract DE-AC04-94AL85000.

Reaching the healthy people goals for reducing childhood obesity: closing the energy gap.

PubMed

Wang, Y Claire; Orleans, C Tracy; Gortmaker, Steven L

2012-05-01

The federal government has set measurable goals for reducing childhood obesity to 5% by 2010 (Healthy People 2010), and 10% lower than 2005-2008 levels by 2020 (Healthy People 2020). However, population-level estimates of the changes in daily energy balance needed to reach these goals are lacking. To estimate needed per capita reductions in youths' daily "energy gap" (calories consumed over calories expended) to achieve Healthy People goals by 2020. Analyses were conducted in 2010 to fit multivariate models using National Health and Nutrition Examination Surveys 1971-2008 (N=46,164) to extrapolate past trends in obesity prevalence, weight, and BMI among youth aged 2-19 years. Differences in average daily energy requirements between the extrapolated 2020 levels and Healthy People scenarios were estimated. During 1971-2008, mean BMI and weight among U.S. youth increased by 0.55 kg/m(2) and by 1.54 kg per decade, respectively. Extrapolating from these trends to 2020, the average weight among youth in 2020 would increase by ∼1.8 kg from 2007-2008 levels. Averting this increase will require an average reduction of 41 kcal/day in youth's daily energy gap. An additional reduction of 120 kcal/day and 23 kcal/day would be needed to reach Healthy People 2010 and Healthy People 2020 goals, respectively. Larger reductions are needed among adolescents and racial/ethnic minority youth. Aggressive efforts are needed to reverse the positive energy imbalance underlying the childhood obesity epidemic. The energy-gap metric provides a useful tool for goal setting, intervention planning, and charting progress. Copyright © 2012 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.

Determination of the optical band-gap energy of cubic and hexagonal boron nitride using luminescence excitation spectroscopy

NASA Astrophysics Data System (ADS)

Evans, D. A.; McGlynn, A. G.; Towlson, B. M.; Gunn, M.; Jones, D.; Jenkins, T. E.; Winter, R.; Poolton, N. R. J.

2008-02-01

Using synchrotron-based luminescence excitation spectroscopy in the energy range 4-20 eV at 8 K, the indirect Γ-X optical band-gap transition in cubic boron nitride is determined as 6.36 ± 0.03 eV, and the quasi-direct band-gap energy of hexagonal boron nitride is determined as 5.96 ± 0.04 eV. The composition and structure of the materials are self-consistently established by optically detected x-ray absorption spectroscopy, and both x-ray diffraction and Raman measurements on the same samples give independent confirmation of their chemical and structural purity: together, the results are therefore considered as providing definitive measurements of the optical band-gap energies of the two materials.

Optical absorption spectra and energy band gap in manganese containing sodium zinc phosphate glasses

NASA Astrophysics Data System (ADS)

Sardarpasha, K. R.; Hanumantharaju, N.; Gowda, V. C. Veeranna

2018-05-01

Optical band gap energy in the system 25Na2O-(75-x)[0.6P2O5-0.4ZnO]-xMnO2 (where x = 0.5,1,5,10 and 20 mol.%) have been studied. The intensity of the absorption band found to increase with increase of MnO2 content. The decrease in the optical band gap energy with increase in MnO2 content in the investigated glasses is attributed to shifting of absorption edge to a longer wavelength region. The obtained results were discussed in view of the structure of phosphate glass network.

Far-Infrared Optical Conductivity Gap in Superconducting MgB2 Films

NASA Astrophysics Data System (ADS)

Kaindl, Robert A.; Carnahan, Marc A.; Orenstein, Joseph; Chemla, Daniel S.; Christen, Hans M.; Zhai, Hong-Ying; Paranthaman, Mariappan; Lowndes, Doug H.

2002-01-01

We report the first study of the optical conductivity of MgB 2 covering the range of its lowest-energy superconducting gap. Terahertz time-domain spectroscopy is utilized to determine the complex, frequency-dependent conductivity σ(ω) of thin films. The imaginary part reveals an inductive response due to the emergence of the superconducting condensate. The real part exhibits a strong depletion of oscillator strength near 5 meV resulting from the opening of a superconducting energy gap. The gap ratio of 2Δ0/kBTC~1.9 is well below the weak-coupling value, pointing to complex behavior in this novel superconductor.

Momentum dependence of the superconducting gap and in-gap states in MgB 2 multiband superconductor

DOE PAGES

Mou, Daixiang; Jiang, Rui; Taufour, Valentin; ...

2015-06-29

We use tunable laser-based angle-resolved photoemission spectroscopy to study the electronic structure of the multiband superconductor MgB 2. These results form the baseline for detailed studies of superconductivity in multiband systems. We find that the magnitude of the superconducting gap on both σ bands follows a BCS-like variation with temperature with Δ 0 ~ 7meV. Furthermore, the value of the gap is isotropic within experimental uncertainty and in agreement with a pure s-wave pairing symmetry. We observe in-gap states confined to k F of the σ band that occur at some locations of the sample surface. As a result, themore » energy of this excitation, ~ 3 meV, was found to be somewhat larger than the previously reported gap on π Fermi sheet and therefore we cannot exclude the possibility of interband scattering as its origin.« less

Role of superconducting energy gap in extended BCS-Bose crossover theory

NASA Astrophysics Data System (ADS)

Chávez, I.; García, L. A.; de Llano, M.; Grether, M.

2017-10-01

The generalized Bose-Einstein condensation (GBEC) theory of superconductivity (SC) is briefly surveyed. It hinges on three distinct new ingredients: (i) Treatment of Cooper pairs (CPs) as actual bosons since they obey Bose statistics, in contrast to BCS pairs which do not obey Bose commutation relations; (ii) inclusion of two-hole Cooper pairs (2hCPs) on an equal footing with two-electron Cooper pairs (2eCPs), thus making this a complete boson-fermion (BF) model; and (iii) inclusion in the resulting ternary ideal BF gas with particular BF vertex interactions that drive boson formation/disintegration processes. GBEC subsumes as special cases both BCS (having its 50-50 symmetry of both kinds of CPs) and ordinary BEC theories (having no 2hCPs), as well as the now familiar BCS-Bose crossover theory. We extended the crossover theory with the explicit inclusion of 2hCPs and construct a phase diagram of Tc/TF versus n/nf, where Tc and TF are the critical and Fermi temperatures, n is the total number density and nf that of unbound electrons at T = 0. Also, with this extended crossover one can construct the energy gap Δ(T)/Δ(0) versus T/Tc for some elemental SCs by solving at least two equations numerically: a gap-like and a number equation. In 50-50 symmetry, the energy gap curve agrees quite well with experimental data. But ignoring 2hCPs altogether leads to the gap curve falling substantially below that with 50-50 symmetry which already fits the data quite well, showing that 2hCPs are indispensable to describe SCs.

Capacity value of energy storage considering control strategies.

PubMed

Shi, Nian; Luo, Yi

2017-01-01

In power systems, energy storage effectively improves the reliability of the system and smooths out the fluctuations of intermittent energy. However, the installed capacity value of energy storage cannot effectively measure the contribution of energy storage to the generator adequacy of power systems. To achieve a variety of purposes, several control strategies may be utilized in energy storage systems. The purpose of this paper is to study the influence of different energy storage control strategies on the generation adequacy. This paper presents the capacity value of energy storage to quantitatively estimate the contribution of energy storage on the generation adequacy. Four different control strategies are considered in the experimental method to study the capacity value of energy storage. Finally, the analysis of the influence factors on the capacity value under different control strategies is given.

Capacity value of energy storage considering control strategies

PubMed Central

Luo, Yi

2017-01-01

In power systems, energy storage effectively improves the reliability of the system and smooths out the fluctuations of intermittent energy. However, the installed capacity value of energy storage cannot effectively measure the contribution of energy storage to the generator adequacy of power systems. To achieve a variety of purposes, several control strategies may be utilized in energy storage systems. The purpose of this paper is to study the influence of different energy storage control strategies on the generation adequacy. This paper presents the capacity value of energy storage to quantitatively estimate the contribution of energy storage on the generation adequacy. Four different control strategies are considered in the experimental method to study the capacity value of energy storage. Finally, the analysis of the influence factors on the capacity value under different control strategies is given. PMID:28558027

Energy and American values

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

Barbour, I.; Brooks, H.; Lakoff, S.

A multi-disciplinary team consisting of an engineer, a political scientist, an historian, and a professor of religion and physics view the question of energy and values from each other's perspective. The result is a synthesis of the team's views on all aspects of energy technology and how it affects human life in general as well as the lives of different classes and specific groups in our society. It begins with an historic overview of the way an abundance of energy has shaped America's use of it. It continues by considering the energy debate as a conflict between Jeffersonians who believemore » in decentralized, appropriate technology and the centralized, efficient technology of Hamiltonians. The authors wrestle with regional and geographical differences in energy resources, environmental impacts, and ethical problems. 384 references.« less

Conductance modulation in Weyl semimetals with tilted energy dispersion without a band gap

NASA Astrophysics Data System (ADS)

Yesilyurt, Can; Siu, Zhuo Bin; Tan, Seng Ghee; Liang, Gengchiau; Jalil, Mansoor B. A.

2017-06-01

We investigate the tunneling conductance of Weyl semimetal with tilted energy dispersion by considering electron transmission through a p-n-p junction with one-dimensional electric and magnetic barriers. In the presence of both electric and magnetic barriers, we found that a large conductance gap can be produced with the aid of tilted energy dispersion without a band gap. The origin of this effect is the shift of the electron wave-vector at barrier boundaries caused by (i) the pseudo-magnetic field induced by electrical potential, i.e., a newly discovered feature that is only possible in the materials possessing tilted energy dispersion, (ii) the real magnetic field induced by a ferromagnetic layer deposited on the top of the system. We use a realistic barrier structure applicable in current nanotechnology and analyze the temperature dependence of the tunneling conductance. The new approach presented here may resolve a major problem of possible transistor applications in topological semimetals, i.e., the absence of normal backscattering and gapless band structure.

Exponential vanishing of the ground-state gap of the quantum random energy model via adiabatic quantum computing

NASA Astrophysics Data System (ADS)

Adame, J.; Warzel, S.

2015-11-01

In this note, we use ideas of Farhi et al. [Int. J. Quantum. Inf. 6, 503 (2008) and Quantum Inf. Comput. 11, 840 (2011)] who link a lower bound on the run time of their quantum adiabatic search algorithm to an upper bound on the energy gap above the ground-state of the generators of this algorithm. We apply these ideas to the quantum random energy model (QREM). Our main result is a simple proof of the conjectured exponential vanishing of the energy gap of the QREM.

Exponential vanishing of the ground-state gap of the quantum random energy model via adiabatic quantum computing

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

Adame, J.; Warzel, S., E-mail: warzel@ma.tum.de

In this note, we use ideas of Farhi et al. [Int. J. Quantum. Inf. 6, 503 (2008) and Quantum Inf. Comput. 11, 840 (2011)] who link a lower bound on the run time of their quantum adiabatic search algorithm to an upper bound on the energy gap above the ground-state of the generators of this algorithm. We apply these ideas to the quantum random energy model (QREM). Our main result is a simple proof of the conjectured exponential vanishing of the energy gap of the QREM.

Density functional theory calculations for the band gap and formation energy of Pr4-xCaxSi12O3+xN18-x; a highly disordered compound with low symmetry and a large cell size.

PubMed

Hong, Sung Un; Singh, Satendra Pal; Pyo, Myoungho; Park, Woon Bae; Sohn, Kee-Sun

2017-06-28

A novel oxynitride compound, Pr 4-x Ca x Si 12 O 3+x N 18-x , synthesized using a solid-state route has been characterized as a monoclinic structure in the C2 space group using Rietveld refinement on synchrotron powder X-ray diffraction data. The crystal structure of this compound was disordered due to the random distribution of Ca/Pr and N/O ions at various Wyckoff sites. A pragmatic approach for an ab initio calculation based on density function theory (DFT) for this disordered compound has been implemented to calculate an acceptable value of the band gap and formation energy. In general, for the DFT calculation of a disordered compound, a sufficiently large super cell and infinite variety of ensemble configurations is adopted to simulate the random distribution of ions; however, such an approach is time consuming and cost ineffective. Even a single unit cell model gave rise to 43 008 independent configurations as an input model for the DFT calculations. Since it was nearly impossible to calculate the formation energy and the band gap energy for all 43 008 configurations, an elitist non-dominated sorting genetic algorithm (NSGA-II) was employed to find the plausible configurations. In the NSGA-II, all 43 008 configurations were mathematically treated as genomes and the calculated band gap and the formation energy as the objective (fitness) function. Generalized gradient approximation (GGA) was first employed in the preliminary screening using NSGA-II, and thereafter a hybrid functional calculation (HSE06) was executed only for the most plausible GGA-relaxed configurations with lower formation and higher band gap energies. The final band gap energy (3.62 eV) obtained after averaging over the selected configurations, resembles closely the experimental band gap value (4.11 eV).

Optical band gaps of organic semiconductor materials

NASA Astrophysics Data System (ADS)

Costa, José C. S.; Taveira, Ricardo J. S.; Lima, Carlos F. R. A. C.; Mendes, Adélio; Santos, Luís M. N. B. F.

2016-08-01

UV-Vis can be used as an easy and forthright technique to accurately estimate the band gap energy of organic π-conjugated materials, widely used as thin films/composites in organic and hybrid electronic devices such as OLEDs, OPVs and OFETs. The electronic and optical properties, including HOMO-LUMO energy gaps of π-conjugated systems were evaluated by UV-Vis spectroscopy in CHCl3 solution for a large number of relevant π-conjugated systems: tris-8-hydroxyquinolinatos (Alq3, Gaq3, Inq3, Al(qNO2)3, Al(qCl)3, Al(qBr)3, In(qNO2)3, In(qCl)3 and In(qBr)3); triphenylamine derivatives (DDP, p-TTP, TPB, TPD, TDAB, m-MTDAB, NPB, α-NPD); oligoacenes (naphthalene, anthracene, tetracene and rubrene); oligothiophenes (α-2T, β-2T, α-3T, β-3T, α-4T and α-5T). Additionally, some electronic properties were also explored by quantum chemical calculations. The experimental UV-Vis data are in accordance with the DFT predictions and indicate that the band gap energies of the OSCs dissolved in CHCl3 solution are consistent with the values presented for thin films.

Energy Gaps and Layer Polarization of Integer and Fractional Quantum Hall States in Bilayer Graphene.

PubMed

Shi, Yanmeng; Lee, Yongjin; Che, Shi; Pi, Ziqi; Espiritu, Timothy; Stepanov, Petr; Smirnov, Dmitry; Lau, Chun Ning; Zhang, Fan

2016-02-05

Owing to the spin, valley, and orbital symmetries, the lowest Landau level in bilayer graphene exhibits multicomponent quantum Hall ferromagnetism. Using transport spectroscopy, we investigate the energy gaps of integer and fractional quantum Hall (QH) states in bilayer graphene with controlled layer polarization. The state at filling factor ν=1 has two distinct phases: a layer polarized state that has a larger energy gap and is stabilized by high electric field, and a hitherto unobserved interlayer coherent state with a smaller gap that is stabilized by large magnetic field. In contrast, the ν=2/3 quantum Hall state and a feature at ν=1/2 are only resolved at finite electric field and large magnetic field. These results underscore the importance of controlling layer polarization in understanding the competing symmetries in the unusual QH system of BLG.

Rapidity gaps between jets in photoproduction at HERA

NASA Astrophysics Data System (ADS)

Derrick, M.; Krakauer, D.; Magill, S.; Mikunas, D.; Musgrave, B.; Repond, J.; Stanek, R.; Talaga, R. L.; Zhang, H.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Bruni, P.; Cara Romeo, G.; Castellini, G.; Chiarini, M.; Cifarelli, L.; Cindolo, F.; Contin, A.; Corradi, M.; Gialas, I.; Giusti, P.; Iacobucci, G.; Laurenti, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Nemoz, C.; Palmonari, F.; Polini, A.; Sartorelli, G.; Timellini, R.; Zamora Garcia, Y.; Zichichi, A.; Bornheim, A.; Crittenden, J.; Desch, K.; Diekmann, B.; Doeker, T.; Eckert, M.; Feld, L.; Frey, A.; Geerts, M.; Grothe, M.; Hartmann, H.; Heinloth, K.; Heinz, L.; Hilger, E.; Jakob, H.-P.; Katz, U. F.; Mengel, S.; Mollen, J.; Paul, E.; Pfeiffer, M.; Rembser, Ch.; Schramm, D.; Stamm, J.; Wedemeyer, R.; Campbell-Robson, S.; Cassidy, A.; Cottingham, W. N.; Dyce, N.; Foster, B.; George, S.; Hayes, M. E.; Heath, G. P.; Heath, H. F.; Morgado, C. J. S.; O'Mara, J. A.; Piccioni, D.; Roff, D. G.; Tapper, R. J.; Yoshida, R.; Rau, R. R.; Arneodo, M.; Ayad, R.; Capua, M.; Garfagnini, A.; Iannotti, L.; Schioppa, M.; Susinno, G.; Bernstein, A.; Caldwell, A.; Cartiglia, N.; Parsons, J. A.; Ritz, S.; Sciulli, F.; Straub, P. B.; Wai, L.; Yang, S.; Zhu, Q.; Borzemski, P.; Chwastowski, J.; Eskreys, A.; Piotrzkowski, K.; Zachara, M.; Zawiejski, L.; Adamczyk, L.; Bednarek, B.; Jeleń, K.; Kisielewska, D.; Kowalski, T.; Przybycień, M.; Rulikowska-Zarȩbska, E.; Suszycki, L.; Zajaç, J.; Kotański, A.; Bauerdick, L. A. T.; Behrens, U.; Beier, H.; Bienlein, J. K.; Coldewey, C.; Deppe, O.; Desler, K.; Drews, G.; Flasiński, M.; Gilkinson, D. J.; Glasman, C.; Göttlicher, P.; Groß-Knetter, J.; Gutjahr, B.; Haas, T.; Hain, W.; Hasell, D.; Heßling, H.; Iga, Y.; Johnson, K. F.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Köpke, L.; Kötz, U.; Kowalski, H.; Labs, J.; Ladage, A.; Löhr, B.; Löwe, M.; Lüke, D.; Mainusch, J.; Mańczak, O.; Monteiro, T.; Ng, J. S. T.; Nickel, S.; Notz, D.; Ohrenberg, K.; Roco, M.; Rohde, M.; Roldán, J.; Schneekloth, U.; Schulz, W.; Selonke, F.; Stiliaris, E.; Surrow, B.; Voß, T.; Westphal, D.; Wolf, G.; Youngman, C.; Zeuner, W.; Zhou, J. F.; Grabosch, H. J.; Kharchilava, A.; Leich, A.; Mari, S. M.; Mattingly, M. C. K.; Meyer, A.; Schlenstedt, S.; Wulff, N.; Barbagli, G.; Gallo, E.; Pelfer, P.; Anzivino, G.; Maccarrone, G.; De Pasquale, S.; Votano, L.; Bamberger, A.; Eisenhardt, S.; Freidhof, A.; Söldner-Rembold, S.; Schroeder, J.; Trefzger, T.; Brook, N. H.; Bussey, P. J.; Doyle, A. T.; Saxon, D. H.; Utley, M. L.; Wilson, A. S.; Dannemann, A.; Holm, U.; Horstmann, D.; Neumann, T.; Sinkus, R.; Wick, K.; Badura, E.; Burow, B. D.; Hagge, L.; Lohrmann, E.; Milewski, J.; Nakahata, M.; Pavel, N.; Poelz, G.; Schott, W.; Zetsche, F.; Bacon, T. C.; Bruemmer, N.; Butterworth, I.; Harris, V. L.; Hung, B. Y. H.; Long, K. R.; Miller, D. B.; Morawitz, P. P. O.; Prinias, A.; Sedgbeer, J. K.; Whitfield, A. F.; Mallik, U.; McCliment, E.; Wang, M. Z.; Wang, S. M.; Wu, J. T.; Cloth, P.; Filges, D.; An, S. H.; Hong, S. M.; Nam, S. V.; Park, S. K.; Suh, M. H.; Yon, S. H.; Imlay, R.; Kartik, S.; Kim, H.-J.; McNeil, R. R.; Metcalf, W.; Nadendla, V. K.; Barreiro, F.; Cases, G.; Fernandez, J. P.; Graciani, R.; Hernández, J. M.; Hervás, L.; Labarga, L.; Martinez, M.; del Peso, J.; Puga, J.; Terron, J.; de Trocóniz, J. F.; Smith, G. R.; Corriveau, F.; Hanna, D. S.; Hartmann, J.; Hung, L. W.; Lim, J. N.; Matthews, C. G.; Patel, P. M.; Sinclair, L. E.; Stairs, D. G.; St. Laurent, M.; Ullmann, R.; Zacek, G.; Bashkirov, V.; Dolgoshein, B. A.; Stifutkin, A.; Bashindzhagyan, G. L.; Ermolov, P. F.; Gladilin, L. K.; Golubkov, Yu. A.; Kobrin, V. D.; Korzhavina, I. A.; Kuzmin, V. A.; Lukina, O. Yu.; Proskuryakov, A. S.; Savin, A. A.; Shcheglova, L. M.; Solomin, A. N.; Zotov, N. P.; Botje, M.; Chlebana, F.; Dake, A.; Engelen, J.; de Kamps, M.; Kooijman, P.; Kruse, A.; Tiecke, H.; Verkerke, W.; Vreeswijk, M.; Wiggers, L.; de Wolf, E.; van Woudenberg, R.; Acosta, D.; Bylsma, B.; Durkin, L. S.; Gilmore, J.; Honscheid, K.; Li, C.; Ling, T. Y.; McLean, K. W.; Nylander, P.; Park, I. H.; Romanowski, T. A.; Seidlein, R.; Bailey, D. S.; Byrne, A.; Cashmore, R. J.; Cooper-Sarkar, A. M.; Devenish, R. C. E.; Harnew, N.; Lancaster, M.; Lindemann, L.; McFall, J. D.; Nath, C.; Noyes, V. A.; Quadt, A.; Tickner, J. R.; Uijterwaal, H.; Walczak, R.; Waters, D. S.; Wilson, F. F.; Yip, T.; Abbiendi, G.; Bertolin, A.; Brugnera, R.; Carlin, R.; Dal Corso, F.; De Giorgi, M.; Dosselli, U.; Limentani, S.; Morandin, M.; Posocco, M.; Stanco, L.; Stroili, R.; Voci, C.; Bulmahn, J.; Butterworth, J. M.; Feild, R. G.; Oh, B. Y.; Okrasinski, J. R.; Whitmore, J. J.; D'Agostini, G.; Marini, G.; Nigro, A.; Tassi, E.; Hart, J. C.; McCubbin, N. A.; Prytz, K.; Shah, T. P.; Short, T. L.; Barberis, E.; Dubbs, T.; Heusch, C.; Van Hook, M.; Lockman, W.; Rahn, J. T.; Sadrozinski, H. F.-W.; Seiden, A.; Williams, D. C.; Biltzinger, J.; Seifert, R. J.; Schwarzer, O.; Walenta, A. H.; Zech, G.; Abramowicz, H.; Briskin, G.; Dagan, S.; Händel-Pikielny, C.; Levy, A.; Fleck, J. I.; Hasegawa, T.; Hazumi, M.; Ishii, T.; Kuze, M.; Mine, S.; Nagasawa, Y.; Nakao, M.; Suzuki, I.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Chiba, M.; Hamatsu, R.; Hirose, T.; Homma, K.; Kitamura, S.; Nakamitsu, Y.; Yamauchi, K.; Cirio, R.; Costa, M.; Ferrero, M. I.; Lamberti, L.; Maselli, S.; Peroni, C.; Sacchi, R.; Solano, A.; Staiano, A.; Dardo, M.; Bailey, D. C.; Bandyopadhyay, D.; Benard, F.; Brkic, M.; Gingrich, D. M.; Hartner, G. F.; Joo, K. K.; Levman, G. M.; Martin, J. F.; Orr, R. S.; Polenz, S.; Sampson, C. R.; Teuscher, R. J.; Catterall, C. D.; Jones, T. W.; Kaziewicz, P. B.; Lane, J. B.; Saunders, R. L.; Shulman, J.; Blankenship, K.; Lu, B.; Mo, L. W.; Bogusz, W.; Charchuła, K.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprzak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Tymieniecka, T.; Wróblewski, A. K.; Zakrzewski, J. A.; Żarnecki, A. F.; Adamus, M.; Eisenberg, Y.; Karshon, U.; Revel, D.; Zer-Zion, D.; Ali, I.; Badgett, W. F.; Behrens, B.; Dasu, S.; Fordham, C.; Foudas, C.; Goussiou, A.; Loveless, R. J.; Reeder, D. D.; Silverstein, S.; Smith, W. H.; Vaiciulis, A.; Wodarczyk, M.; Tsurugai, T.; Bhadra, S.; Cardy, M. L.; Fagerstroem, C.-P.; Frisken, W. R.; Furutani, K. M.; Khakzad, M.; Murray, W. N.; Schmidke, W. B.; ZEUS Collaboration

1996-02-01

Photoproduction events which have two or more jets have been studied in the Wγp range 135 GeV < Wγp < 280 GeV with the ZEUS detector at HERA. A class of events is observed with little hadronic activity between the jets. The jets are separated by pseudorapidity intervals (Δη) of up to four units and have transverse energies greater than 6 GeV. A gap is defined as the absence between the jets of particles with transverse energy greater than 300 MeV. The fraction of events containing a gap is measured as a function of Δη. It decreases exponentially as expected for processes in which colour is exchanged between the jets, up to a value of Δη ˜ 3, then reaches a cconstant value of about 0.1. The excess above the exponential fall-off can be interpreted as evidence for hard diffractive scattering via a strongly interacting colour singlet object.

Synthesis and Exciton Dynamics of Donor-Orthogonal Acceptor Conjugated Polymers: Reducing the Singlet-Triplet Energy Gap.

PubMed

Freeman, David M E; Musser, Andrew J; Frost, Jarvist M; Stern, Hannah L; Forster, Alexander K; Fallon, Kealan J; Rapidis, Alexandros G; Cacialli, Franco; McCulloch, Iain; Clarke, Tracey M; Friend, Richard H; Bronstein, Hugo

2017-08-16

The presence of energetically low-lying triplet states is a hallmark of organic semiconductors. Even though they present a wealth of interesting photophysical properties, these optically dark states significantly limit optoelectronic device performance. Recent advances in emissive charge-transfer molecules have pioneered routes to reduce the energy gap between triplets and "bright" singlets, allowing thermal population exchange between them and eliminating a significant loss channel in devices. In conjugated polymers, this gap has proved resistant to modification. Here, we introduce a general approach to reduce the singlet-triplet energy gap in fully conjugated polymers, using a donor-orthogonal acceptor motif to spatially separate electron and hole wave functions. This new generation of conjugated polymers allows for a greatly reduced exchange energy, enhancing triplet formation and enabling thermally activated delayed fluorescence. We find that the mechanisms of both processes are driven by excited-state mixing between π-π*and charge-transfer states, affording new insight into reverse intersystem crossing.

Free Energy Gap and Statistical Thermodynamic Fidelity of DNA Codes

DTIC Science & Technology

2007-10-01

reverse-complement unless otherwise stated. For strand x, let Nx denote its complement. A (perfect) Watson - Crick duplex is the joining of complement...is possible for complementary sequences to form a non-perfectly aligned duplex, we will call any x W Nx duplex a Watson - Crick (WC) duplex. Two...DATES COVERED (From - To) 4. TITLE AND SUBTITLE FREE ENERGY GAP AND STATISTICAL THERMODYNAMIC FIDELITY OF DNA CODES 5a. CONTRACT NUMBER FA8750-07

[Reference values of energy for the Venezuelan population].

PubMed

Landaeta-Jiménez, Maritza; Aliaga, Carla; Sifontes, Yaritza; Vásquez, Maura; Ramírez, Guillermo; Falque Madrid, Luís; Herrera, Marianella; María Reyes, Ana; Emilia, Elzakem; Herrera, Ctor; Bernal, Jennifer

2013-12-01

The project of updating the Venezuelan energy reference values respond to the recommendations made by an FAO experts committee, several decades ago for the countries assuming this work. Because of the dramatic changes experienced globally regarding energy intake/expenditure and particularly variations on the Venezuelan nutritional scenario with the presence of "the double burden of malnutrition" it a review of Energy Reference Values (VRE) from a more integral approach is pertinent. This report follows the methodology proposed by FAO/WHO/UNU 2004 experts committee and energy reference values were established by group of age and gender, also average energy values for Venezuelan population were obtained. For calculation of these requirements, the energy expenditure was included by taking into account Basal Metabolic Rate and physical activity level for some specific groups. The score average values updated in 2012 of 2.200 kcal/dia reported to be lower than those of 2000 at all ages for masculine gender except for the 16-17 age group and for feminine gender just until ages 10-12 years and from there are slightly above the values obtained in 2000.

Quasiparticle band gap of organic-inorganic hybrid perovskites: Crystal structure, spin-orbit coupling, and self-energy effects

NASA Astrophysics Data System (ADS)

Gao, Weiwei; Gao, Xiang; Abtew, Tesfaye A.; Sun, Yi-Yang; Zhang, Shengbai; Zhang, Peihong

2016-02-01

The quasiparticle band gap is one of the most important materials properties for photovoltaic applications. Often the band gap of a photovoltaic material is determined (and can be controlled) by various factors, complicating predictive materials optimization. An in-depth understanding of how these factors affect the size of the gap will provide valuable guidance for new materials discovery. Here we report a comprehensive investigation on the band gap formation mechanism in organic-inorganic hybrid perovskites by decoupling various contributing factors which ultimately determine their electronic structure and quasiparticle band gap. Major factors, namely, quasiparticle self-energy, spin-orbit coupling, and structural distortions due to the presence of organic molecules, and their influences on the quasiparticle band structure of organic-inorganic hybrid perovskites are illustrated. We find that although methylammonium cations do not contribute directly to the electronic states near band edges, they play an important role in defining the band gap by introducing structural distortions and controlling the overall lattice constants. The spin-orbit coupling effects drastically reduce the electron and hole effective masses in these systems, which is beneficial for high carrier mobilities and small exciton binding energies.

Determining Perceptual Gaps of Service Quality and Value in Higher Education: A Midwestern Bible College

ERIC Educational Resources Information Center

McIntosh, Benjamin T.

2017-01-01

This doctoral research project examined perceptual gaps of service quality and value in the context of higher education. The researcher performed quantitative analysis of survey data gathered from students at a small, Midwestern Bible college. Students self-selected to participate in this research project and, using class status as an independent…

Effects of quantum confinement and shape on band gap of core/shell quantum dots and nanowires

NASA Astrophysics Data System (ADS)

Gao, Faming

2011-05-01

A quantum confinement model for nanocrystals developed is extended to study for the optical gap shifts in core/shell quantum dots and nanowires. The chemical bond properties and gap shifts in the InP/ZnS, CdSe/CdS, CdSe/ZnS, and CdTe/ZnS core/shell quantum dots are calculated in detail. The calculated band gaps are in excellent agreement with experimental values. The effects of structural taping and twinning on quantum confinement of InP and Si nanowires are elucidated. It is found theoretically that a competition between the positive Kubo energy-gap shift and the negative surface energy shift plays the crucial role in the optical gaps of these nanosystems.

Values Affirmation Intervention Reduces Achievement Gap between Underrepresented Minority and White Students in Introductory Biology Classes

PubMed Central

Jordt, Hannah; Eddy, Sarah L.; Brazil, Riley; Lau, Ignatius; Mann, Chelsea; Brownell, Sara E.; King, Katherine; Freeman, Scott

2017-01-01

Achievement gaps between underrepresented minority (URM) students and their white peers in college science, technology, engineering, and mathematics classrooms are persistent across many white-majority institutions of higher education. Attempts to reduce this phenomenon of underperformance through increasing classroom structure via active learning have been partially successful. In this study, we address the hypothesis that the achievement gap between white and URM students in an undergraduate biology course has a psychological and emotional component arising from stereotype threat. Specifically, we introduced a values affirmation exercise that counters stereotype threat by reinforcing a student’s feelings of integrity and self-worth in three iterations of an intensive active-learning college biology course. On average, this exercise reduced the achievement gap between URM and white students who entered the course with the same incoming grade point average. This result suggests that achievement gaps resulting from the underperformance of URM students could be mitigated by providing students with a learning environment that removes psychological and emotional impediments of performance through short psychosocial interventions. PMID:28710060

The Business Value of Superior Energy Performance

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

McKane, Aimee; Scheihing, Paul; Evans, Tracy

Industrial facilities participating in the U.S. Department of Energy’s (US DOE) Superior Energy Performance (SEP) program are finding that it provides them with significant business value. This value starts with the implementation of ISO 50001-Energy management system standard, which provides an internationally-relevant framework for integration of energy management into an organization’s business processes. The resulting structure emphasizes effective use of available data and supports continual improvement of energy performance. International relevance is particularly important for companies with a global presence or trading interests, providing them with access to supporting ISO standards and a growing body of certified companies representing themore » collective knowledge of communities of practice. This paper examines the business value of SEP, a voluntary program that builds on ISO 50001, inviting industry to demonstrate an even greater commitment through third-party verification of energy performance improvement to a specified level of achievement. Information from 28 facilities that have already achieved SEP certification will illustrate key findings concerning both the value and the challenges from SEP/ISO 50001 implementation. These include the facilities’ experience with implementation, internal and external value of third-party verification of energy performance improvement; attractive payback periods and the importance of SEP tools and guidance. US DOE is working to bring the program to scale, including the Enterprise-Wide Accelerator (SEP for multiple facilities in a company), the Ratepayer-Funded Program Accelerator (supporting tools for utilities and program administrators to include SEP in their program offerings), and expansion of the program to other sectors and industry supply chains.« less

SU-F-T-305: Clinical Effects of Dosimetric Leaf Gap (DLG) Values Between Matched Varian Truebeam (TB) Linacs

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

Mihailidis, D; Mallah, J; Zhu, D

2016-06-15

Purpose: The dosimetric leaf gap (DLG) is an important parameter to be measured for dynamic beam delivery of modern linacs, like the Varian Truebeam (TB). The clinical effects of DLG-values on IMRT and/or VMAT commissioning of two “matched” TB linacs will be presented.Methods and Materials: The DLG values on two TB linacs were measured for all energy modalities (filtered and FFF-modes) as part of the dynamic delivery mode commissioning (IMRT and/or VMAT. After the standard beam data was modeled in eclipse treatment planning system (TPS) and validated, IMRT validation was performed based on TG1191 benchmark, IROC Head-Neck (H&N) phantom andmore » sample of clinical cases, all measured on both linacs. Although there was a single-set of data entered in the TPS, a noticeable difference was observed for the DLG-values between the linacs. The TG119, IROC phantom and selected patient plans were furnished with DLG-values of TB1 for both linacs and the delivery was performed on both TB linacs for comparison. Results: The DLG values of TB1 was first used for both linacs to perform the testing comparisons. The QA comparison of TG119 plans revealed a great dependence of the results to the DLG-values used for the linac for all energy modalities studied, especially when moving from 3%/3mm to 2%/2mm γ-analysis. Conclusion: The DLG-values have a definite influence on the dynamic dose, delivery that increases with the plan complexity. We recommend that the measured DLG-values are assigned to each of the “matched” linacs, even if a single set of beam data describes multiple linacs. The user should perform a detail test of the dynamic delivery of each linac based on end-to-end benchmark suites like TG119 and IROC phantoms.1Ezzel G., et al., “IMRT commissioning: Multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119.” Med. Phys. 36:5359–5373 (2009). partly supported by CAMC Cancer Center and Alliance Oncology.« less

Mechanics of Fluid-Filled Interstitial Gaps. II. Gap Characteristics in Xenopus Embryonic Ectoderm.

PubMed

Barua, Debanjan; Parent, Serge E; Winklbauer, Rudolf

2017-08-22

The ectoderm of the Xenopus embryo is permeated by a network of channels that appear in histological sections as interstitial gaps. We characterized this interstitial space by measuring gap sizes, angles formed between adjacent cells, and curvatures of cell surfaces at gaps. From these parameters, and from surface-tension values measured previously, we estimated the values of critical mechanical variables that determine gap sizes and shapes in the ectoderm, using a general model of interstitial gap mechanics. We concluded that gaps of 1-4 μm side length can be formed by the insertion of extracellular matrix fluid at three-cell junctions such that cell adhesion is locally disrupted and a tension difference between cell-cell contacts and the free cell surface at gaps of 0.003 mJ/m 2 is generated. Furthermore, a cell hydrostatic pressure of 16.8 ± 1.7 Pa and an interstitial pressure of 3.9 ± 3.6 Pa, relative to the central blastocoel cavity of the embryo, was found to be consistent with the observed gap size and shape distribution. Reduction of cell adhesion by the knockdown of C-cadherin increased gap volume while leaving intracellular and interstitial pressures essentially unchanged. In both normal and adhesion-reduced ectoderm, cortical tension of the free cell surfaces at gaps does not return to the high values characteristic of the free surface of the whole tissue. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Local band gap measurements by VEELS of thin film solar cells.

PubMed

Keller, Debora; Buecheler, Stephan; Reinhard, Patrick; Pianezzi, Fabian; Pohl, Darius; Surrey, Alexander; Rellinghaus, Bernd; Erni, Rolf; Tiwari, Ayodhya N

2014-08-01

This work presents a systematic study that evaluates the feasibility and reliability of local band gap measurements of Cu(In,Ga)Se2 thin films by valence electron energy-loss spectroscopy (VEELS). The compositional gradients across the Cu(In,Ga)Se2 layer cause variations in the band gap energy, which are experimentally determined using a monochromated scanning transmission electron microscope (STEM). The results reveal the expected band gap variation across the Cu(In,Ga)Se2 layer and therefore confirm the feasibility of local band gap measurements of Cu(In,Ga)Se2 by VEELS. The precision and accuracy of the results are discussed based on the analysis of individual error sources, which leads to the conclusion that the precision of our measurements is most limited by the acquisition reproducibility, if the signal-to-noise ratio of the spectrum is high enough. Furthermore, we simulate the impact of radiation losses on the measured band gap value and propose a thickness-dependent correction. In future work, localized band gap variations will be measured on a more localized length scale to investigate, e.g., the influence of chemical inhomogeneities and dopant accumulations at grain boundaries.

Gap state analysis in electric-field-induced band gap for bilayer graphene.

PubMed

Kanayama, Kaoru; Nagashio, Kosuke

2015-10-29

The origin of the low current on/off ratio at room temperature in dual-gated bilayer graphene field-effect transistors is considered to be the variable range hopping in gap states. However, the quantitative estimation of gap states has not been conducted. Here, we report the systematic estimation of the energy gap by both quantum capacitance and transport measurements and the density of states for gap states by the conductance method. An energy gap of ~ 250 meV is obtained at the maximum displacement field of ~ 3.1 V/nm, where the current on/off ratio of ~ 3 × 10(3) is demonstrated at 20 K. The density of states for the gap states are in the range from the latter half of 10(12) to 10(13) eV(-1) cm(-2). Although the large amount of gap states at the interface of high-k oxide/bilayer graphene limits the current on/off ratio at present, our results suggest that the reduction of gap states below ~ 10(11) eV(-1) cm(-2) by continual improvement of the gate stack makes bilayer graphene a promising candidate for future nanoelectronic device applications.

Structural and electronic properties of GaAs and GaP semiconductors

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

Rani, Anita; Kumar, Ranjan

2015-05-15

The Structural and Electronic properties of Zinc Blende phase of GaAs and GaP compounds are studied using self consistent SIESTA-code, pseudopotentials and Density Functional Theory (DFT) in Local Density Approximation (LDA). The Lattice Constant, Equillibrium Volume, Cohesive Energy per pair, Compressibility and Band Gap are calculated. The band gaps calcultated with DFT using LDA is smaller than the experimental values. The P-V data fitted to third order Birch Murnaghan equation of state provide the Bulk Modulus and its pressure derivatives. Our Structural and Electronic properties estimations are in agreement with available experimental and theoretical data.

Direct optical band gap measurement in polycrystalline semiconductors: A critical look at the Tauc method

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

Dolgonos, Alex; Mason, Thomas O.; Poeppelmeier, Kenneth R., E-mail: krp@northwestern.edu

2016-08-15

The direct optical band gap of semiconductors is traditionally measured by extrapolating the linear region of the square of the absorption curve to the x-axis, and a variation of this method, developed by Tauc, has also been widely used. The application of the Tauc method to crystalline materials is rooted in misconception–and traditional linear extrapolation methods are inappropriate for use on degenerate semiconductors, where the occupation of conduction band energy states cannot be ignored. A new method is proposed for extracting a direct optical band gap from absorption spectra of degenerately-doped bulk semiconductors. This method was applied to pseudo-absorption spectramore » of Sn-doped In{sub 2}O{sub 3} (ITO)—converted from diffuse-reflectance measurements on bulk specimens. The results of this analysis were corroborated by room-temperature photoluminescence excitation measurements, which yielded values of optical band gap and Burstein–Moss shift that are consistent with previous studies on In{sub 2}O{sub 3} single crystals and thin films. - Highlights: • The Tauc method of band gap measurement is re-evaluated for crystalline materials. • Graphical method proposed for extracting optical band gaps from absorption spectra. • The proposed method incorporates an energy broadening term for energy transitions. • Values for ITO were self-consistent between two different measurement methods.« less

An investigation of the optical constants and band gap of chromium disilicide

NASA Technical Reports Server (NTRS)

Bost, M. C.; Mahan, John E.

1988-01-01

Optical properties of polycrystalline thin films of CrSi2 grown by the diffusion couple method on silicon substrates were investigated. An analysis of the energy dependence of the absorption coefficient indicates that the material is an indirect forbidden gap semiconductor with a band-gap value of slightly less than 0.35 eV. This result was confirmed by measurements of the temperature dependence of the intrinsic conductivity. The value of the bandgap corresponds well to an important window of transparency in the earth's atmosphere (3-5 microns), which makes the material of potential interest for IR detector applications.

Free Energy Gap and Statistical Thermodynamic Fidelity of DNA Codes (Postprint)

DTIC Science & Technology

2007-01-01

reverse-complement unless otherwise stated. For strand x, let Nx denote its complement. A (perfect) Watson - Crick duplex is the joining of complement...is possible for complementary sequences to form a non-perfectly aligned duplex, we will call any x W Nx duplex a Watson - Crick (WC) duplex. Two...DATES COVERED (From - To) 4. TITLE AND SUBTITLE FREE ENERGY GAP AND STATISTICAL THERMODYNAMIC FIDELITY OF DNA CODES 5a. CONTRACT NUMBER FA8750-07

Time-Varying Value of Energy Efficiency in Michigan

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

Mims, Natalie; Eckman, Tom; Schwartz, Lisa C.

Quantifying the time-varying value of energy efficiency is necessary to properly account for all of its benefits and costs and to identify and implement efficiency resources that contribute to a low-cost, reliable electric system. Historically, most quantification of the benefits of efficiency has focused largely on the economic value of annual energy reduction. Due to the lack of statistically representative metered end-use load shape data in Michigan (i.e., the hourly or seasonal timing of electricity savings), the ability to confidently characterize the time-varying value of energy efficiency savings in the state, especially for weather-sensitive measures such as central air conditioning,more » is limited. Still, electric utilities in Michigan can take advantage of opportunities to incorporate the time-varying value of efficiency into their planning. For example, end-use load research and hourly valuation of efficiency savings can be used for a variety of electricity planning functions, including load forecasting, demand-side management and evaluation, capacity planning, long-term resource planning, renewable energy integration, assessing potential grid modernization investments, establishing rates and pricing, and customer service (KEMA 2012). In addition, accurately calculating the time-varying value of efficiency may help energy efficiency program administrators prioritize existing offerings, set incentive or rebate levels that reflect the full value of efficiency, and design new programs.« less

The effect of solvent relaxation time constants on free energy gap law for ultrafast charge recombination following photoinduced charge separation.

PubMed

Mikhailova, Valentina A; Malykhin, Roman E; Ivanov, Anatoly I

2018-05-16

To elucidate the regularities inherent in the kinetics of ultrafast charge recombination following photoinduced charge separation in donor-acceptor dyads in solutions, the simulations of the kinetics have been performed within the stochastic multichannel point-transition model. Increasing the solvent relaxation time scales has been shown to strongly vary the dependence of the charge recombination rate constant on the free energy gap. In slow relaxing solvents the non-equilibrium charge recombination occurring in parallel with solvent relaxation is very effective so that the charge recombination terminates at the non-equilibrium stage. This results in a crucial difference between the free energy gap laws for the ultrafast charge recombination and the thermal charge transfer. For the thermal reactions the well-known Marcus bell-shaped dependence of the rate constant on the free energy gap is realized while for the ultrafast charge recombination only a descending branch is predicted in the whole area of the free energy gap exceeding 0.2 eV. From the available experimental data on the population kinetics of the second and first excited states for a series of Zn-porphyrin-imide dyads in toluene and tetrahydrofuran solutions, an effective rate constant of the charge recombination into the first excited state has been calculated. The obtained rate constant being very high is nearly invariable in the area of the charge recombination free energy gap from 0.2 to 0.6 eV that supports the theoretical prediction.

Tuning the energy gap of bilayer α-graphyne by applying strain and electric field

NASA Astrophysics Data System (ADS)

Yang, Hang; Wu, Wen-Zhi; Jin, Yu; Wan-Lin, Guo

2016-02-01

Our density functional theory calculations show that the energy gap of bilayer α-graphyne can be modulated by a vertically applied electric field and interlayer strain. Like bilayer graphene, the bilayer α-graphyne has electronic properties that are hardly changed under purely mechanical strain, while an external electric field can open the gap up to 120 meV. It is of special interest that compressive strain can further enlarge the field induced gap up to 160 meV, while tensile strain reduces the gap. We attribute the gap variation to the novel interlayer charge redistribution between bilayer α-graphynes. These findings shed light on the modulation of Dirac cone structures and potential applications of graphyne in mechanical-electric devices. Project supported by the National Key Basic Research Program of China (Grant Nos. 2013CB932604 and 2012CB933403), the National Natural Science Foundation of China (Grant Nos. 51472117 and 51535005), the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures, China (Grant No. 0414K01), the Nanjing University of Aeronautics and Astronautics (NUAA) Fundamental Research Funds, China (Grant No. NP2015203), and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

Layer specific optical band gap measurement at nanoscale in MoS{sub 2} and ReS{sub 2} van der Waals compounds by high resolution electron energy loss spectroscopy

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

Dileep, K., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in; Sahu, R.; Datta, R., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in

2016-03-21

Layer specific direct measurement of optical band gaps of two important van der Waals compounds, MoS{sub 2} and ReS{sub 2}, is performed at nanoscale by high resolution electron energy loss spectroscopy. For monolayer MoS{sub 2}, the twin excitons (1.8 and 1.95 eV) originating at the K point of the Brillouin zone are observed. An indirect band gap of 1.27 eV is obtained from the multilayer regions. Indirect to direct band gap crossover is observed which is consistent with the previously reported strong photoluminescence from the monolayer MoS{sub 2}. For ReS{sub 2}, the band gap is direct, and a value of 1.52 andmore » 1.42 eV is obtained for the monolayer and multilayer, respectively. The energy loss function is dominated by features due to high density of states at both the valence and conduction band edges, and the difference in analyzing band gap with respect to ZnO is highlighted. Crystalline 1T ReS{sub 2} forms two dimensional chains like superstructure due to the clustering between four Re atoms. The results demonstrate the power of HREELS technique as a nanoscale optical absorption spectroscopy tool.« less

The Value of the Energy Data Base.

ERIC Educational Resources Information Center

King, Donald W.; And Others

A study was conducted to assess the value of the Energy Data Base (EDB), which is produced by the Technical Information Center (TIC) of the Department of Energy (DOE) in order to provide a means of identifying primary energy information sources, particularly journal articles and technical reports. The volume of energy information distributed to…

Effects of dynamical paths on the energy gap and the corrections to the free energy in path integrals of mean-field quantum spin systems

NASA Astrophysics Data System (ADS)

Koh, Yang Wei

2018-03-01

In current studies of mean-field quantum spin systems, much attention is placed on the calculation of the ground-state energy and the excitation gap, especially the latter, which plays an important role in quantum annealing. In pure systems, the finite gap can be obtained by various existing methods such as the Holstein-Primakoff transform, while the tunneling splitting at first-order phase transitions has also been studied in detail using instantons in many previous works. In disordered systems, however, it remains challenging to compute the gap of large-size systems with specific realization of disorder. Hitherto, only quantum Monte Carlo techniques are practical for such studies. Recently, Knysh [Nature Comm. 7, 12370 (2016), 10.1038/ncomms12370] proposed a method where the exponentially large dimensionality of such systems is condensed onto a random potential of much lower dimension, enabling efficient study of such systems. Here we propose a slightly different approach, building upon the method of static approximation of the partition function widely used for analyzing mean-field models. Quantum effects giving rise to the excitation gap and nonextensive corrections to the free energy are accounted for by incorporating dynamical paths into the path integral. The time-dependence of the trace of the time-ordered exponential of the effective Hamiltonian is calculated by solving a differential equation perturbatively, yielding a finite-size series expansion of the path integral. Formulae for the first excited-state energy are proposed to aid in computing the gap. We illustrate our approach using the infinite-range ferromagnetic Ising model and the Hopfield model, both in the presence of a transverse field.

The Possible Value of a Gap Year: A Case Study

ERIC Educational Resources Information Center

Coetzee, M.; Bester, S.

2009-01-01

The taking of a "gap year", immediately after completing their secondary school education, to explore life before embarking on formal studies or starting their career, is a growing phenomenon among young people in South Africa. This research study explores the experiences of three young people who engaged in a gap year and focuses on the…

High Throughput Light Absorber Discovery, Part 2: Establishing Structure-Band Gap Energy Relationships.

PubMed

Suram, Santosh K; Newhouse, Paul F; Zhou, Lan; Van Campen, Douglas G; Mehta, Apurva; Gregoire, John M

2016-11-14

Combinatorial materials science strategies have accelerated materials development in a variety of fields, and we extend these strategies to enable structure-property mapping for light absorber materials, particularly in high order composition spaces. High throughput optical spectroscopy and synchrotron X-ray diffraction are combined to identify the optical properties of Bi-V-Fe oxides, leading to the identification of Bi 4 V 1.5 Fe 0.5 O 10.5 as a light absorber with direct band gap near 2.7 eV. The strategic combination of experimental and data analysis techniques includes automated Tauc analysis to estimate band gap energies from the high throughput spectroscopy data, providing an automated platform for identifying new optical materials.

Investigating the Gap Between Estimated and Actual Energy Efficiency and Conservation Savings for Public Buildings Projects & Programs in United States

NASA Astrophysics Data System (ADS)

Qaddus, Muhammad Kamil

The gap between estimated and actual savings in energy efficiency and conservation (EE&C) projects or programs forms the problem statement for the scope of public and government buildings. This gap has been analyzed first on impact and then on process-level. On the impact-level, the methodology leads to categorization of the gap as 'Realization Gap'. It then views the categorization of gap within the context of past and current narratives linked to realization gap. On process-level, the methodology leads to further analysis of realization gap on process evaluation basis. The process evaluation criterion, a product of this basis is then applied to two different programs (DESEU and NYC ACE) linked to the scope of this thesis. Utilizing the synergies of impact and process level analysis, it offers proposals on program development and its structure using our process evaluation criterion. Innovative financing and benefits distribution structure is thus developed and will remain part of the proposal. Restricted Stakeholder Crowd Financing and Risk-Free Incentivized return are the products of proposed financing and benefit distribution structure respectively. These products are then complimented by proposing an alternative approach in estimating EE&C savings. The approach advocates estimation based on range-allocation rather than currently utilized unique estimated savings approach. The Way Ahead section thus explores synergy between financial and engineering ranges of energy savings as a multi-discipline approach for future research. Moreover, it provides the proposed program structure with risk aversion and incentive allocation while dealing with uncertainty. This set of new approaches are believed to better fill the realization gap between estimated and actual energy efficiency savings.

Band gap renormalization and Burstein-Moss effect in silicon- and germanium-doped wurtzite GaN up to 1020 cm-3

NASA Astrophysics Data System (ADS)

Feneberg, Martin; Osterburg, Sarah; Lange, Karsten; Lidig, Christian; Garke, Bernd; Goldhahn, Rüdiger; Richter, Eberhard; Netzel, Carsten; Neumann, Maciej D.; Esser, Norbert; Fritze, Stephanie; Witte, Hartmut; Bläsing, Jürgen; Dadgar, Armin; Krost, Alois

2014-08-01

The interplay between band gap renormalization and band filling (Burstein-Moss effect) in n-type wurtzite GaN is investigated. For a wide range of electron concentrations up to 1.6×1020cm-3 spectroscopic ellipsometry and photoluminescence were used to determine the dependence of the band gap energy and the Fermi edge on electron density. The band gap renormalization is the dominating effect up to an electron density of about 9×1018cm-3; at higher values the Burstein-Moss effect is stronger. Exciton screening, the Mott transition, and formation of Mahan excitons are discussed. A quantitative understanding of the near gap transition energies on electron density is obtained. Higher energy features in the dielectric functions up to 10eV are not influenced by band gap renormalization.

Edge effects on band gap energy in bilayer 2H-MoS{sub 2} under uniaxial strain

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

Dong, Liang; Wang, Jin; Dongare, Avinash M., E-mail: dongare@uconn.edu

2015-06-28

The potential of ultrathin MoS{sub 2} nanostructures for applications in electronic and optoelectronic devices requires a fundamental understanding in their electronic structure as a function of strain. Previous experimental and theoretical studies assume that an identical strain and/or stress state is always maintained in the top and bottom layers of a bilayer MoS{sub 2} film. In this study, a bilayer MoS{sub 2} supercell is constructed differently from the prototypical unit cell in order to investigate the layer-dependent electronic band gap energy in a bilayer MoS{sub 2} film under uniaxial mechanical deformations. The supercell contains an MoS{sub 2} bottom layer andmore » a relatively narrower top layer (nanoribbon with free edges) as a simplified model to simulate the as-grown bilayer MoS{sub 2} flakes with free edges observed experimentally. Our results show that the two layers have different band gap energies under a tensile uniaxial strain, although they remain mutually interacting by van der Waals interactions. The deviation in their band gap energies grows from 0 to 0.42 eV as the uniaxial strain increases from 0% to 6% under both uniaxial strain and stress conditions. The deviation, however, disappears if a compressive uniaxial strain is applied. These results demonstrate that tensile uniaxial strains applied to bilayer MoS{sub 2} films can result in distinct band gap energies in the bilayer structures. Such variations need to be accounted for when analyzing strain effects on electronic properties of bilayer or multilayered 2D materials using experimental methods or in continuum models.« less

Complexity of possibly gapped histogram and analysis of histogram.

PubMed

Fushing, Hsieh; Roy, Tania

2018-02-01

We demonstrate that gaps and distributional patterns embedded within real-valued measurements are inseparable biological and mechanistic information contents of the system. Such patterns are discovered through data-driven possibly gapped histogram, which further leads to the geometry-based analysis of histogram (ANOHT). Constructing a possibly gapped histogram is a complex problem of statistical mechanics due to the ensemble of candidate histograms being captured by a two-layer Ising model. This construction is also a distinctive problem of Information Theory from the perspective of data compression via uniformity. By defining a Hamiltonian (or energy) as a sum of total coding lengths of boundaries and total decoding errors within bins, this issue of computing the minimum energy macroscopic states is surprisingly resolved by applying the hierarchical clustering algorithm. Thus, a possibly gapped histogram corresponds to a macro-state. And then the first phase of ANOHT is developed for simultaneous comparison of multiple treatments, while the second phase of ANOHT is developed based on classical empirical process theory for a tree-geometry that can check the authenticity of branches of the treatment tree. The well-known Iris data are used to illustrate our technical developments. Also, a large baseball pitching dataset and a heavily right-censored divorce data are analysed to showcase the existential gaps and utilities of ANOHT.

Complexity of possibly gapped histogram and analysis of histogram

PubMed Central

Roy, Tania

2018-01-01

We demonstrate that gaps and distributional patterns embedded within real-valued measurements are inseparable biological and mechanistic information contents of the system. Such patterns are discovered through data-driven possibly gapped histogram, which further leads to the geometry-based analysis of histogram (ANOHT). Constructing a possibly gapped histogram is a complex problem of statistical mechanics due to the ensemble of candidate histograms being captured by a two-layer Ising model. This construction is also a distinctive problem of Information Theory from the perspective of data compression via uniformity. By defining a Hamiltonian (or energy) as a sum of total coding lengths of boundaries and total decoding errors within bins, this issue of computing the minimum energy macroscopic states is surprisingly resolved by applying the hierarchical clustering algorithm. Thus, a possibly gapped histogram corresponds to a macro-state. And then the first phase of ANOHT is developed for simultaneous comparison of multiple treatments, while the second phase of ANOHT is developed based on classical empirical process theory for a tree-geometry that can check the authenticity of branches of the treatment tree. The well-known Iris data are used to illustrate our technical developments. Also, a large baseball pitching dataset and a heavily right-censored divorce data are analysed to showcase the existential gaps and utilities of ANOHT. PMID:29515829

Complexity of possibly gapped histogram and analysis of histogram

NASA Astrophysics Data System (ADS)

Fushing, Hsieh; Roy, Tania

2018-02-01

We demonstrate that gaps and distributional patterns embedded within real-valued measurements are inseparable biological and mechanistic information contents of the system. Such patterns are discovered through data-driven possibly gapped histogram, which further leads to the geometry-based analysis of histogram (ANOHT). Constructing a possibly gapped histogram is a complex problem of statistical mechanics due to the ensemble of candidate histograms being captured by a two-layer Ising model. This construction is also a distinctive problem of Information Theory from the perspective of data compression via uniformity. By defining a Hamiltonian (or energy) as a sum of total coding lengths of boundaries and total decoding errors within bins, this issue of computing the minimum energy macroscopic states is surprisingly resolved by applying the hierarchical clustering algorithm. Thus, a possibly gapped histogram corresponds to a macro-state. And then the first phase of ANOHT is developed for simultaneous comparison of multiple treatments, while the second phase of ANOHT is developed based on classical empirical process theory for a tree-geometry that can check the authenticity of branches of the treatment tree. The well-known Iris data are used to illustrate our technical developments. Also, a large baseball pitching dataset and a heavily right-censored divorce data are analysed to showcase the existential gaps and utilities of ANOHT.

Zn(x)Cd(1-x)Se nanomultipods with tunable band gaps: synthesis and first-principles calculations.

PubMed

Wei, Hao; Su, Yanjie; Han, Ziyi; Li, Tongtong; Ren, Xinglong; Yang, Zhi; Wei, Liangming; Cong, Fengsong; Zhang, Yafei

2013-06-14

In this paper, we demonstrate that ZnxCd1-xSe nanomultipods can be synthesized via a facile and nontoxic solution-based method. Interesting aspects of composition, morphology and optical properties were deeply explored. The value of Zn/(Zn+Cd) could be altered across the entire range from 0.08 to 0.86 by varying the ratio of cation precursor contents. The band gap energy could be linearly tuned from 1.88 to 2.48 eV with respect to the value of Zn/(Zn+Cd). The experiment also showed that oleylamine played a dominant role in the formation of multipod structure. A possible growth mechanism was further suggested. First-principles calculations of band gap energy and density of states in the Vienna ab initio simulation package code were performed to verify the experimental variation tendency of the band gap. Computational results indicated that dissimilarities of electronic band structures and orbital constitutions determined the tunable band gap of the as-synthesized nanomultipod, which might be promising for versatile applications in relevant areas of solar cells, biomedicine, sensors, catalysts and so on.

The CO₂ GAP Project--CO₂ GAP as a prognostic tool in emergency departments.

PubMed

Shetty, Amith L; Lai, Kevin H; Byth, Karen

2010-12-01

To determine whether CO₂ GAP [(a-ET) PCO₂] value differs consistently in patients presenting with shortness of breath to the ED requiring ventilatory support. To determine a cut-off value of CO₂ GAP, which is consistently associated with measured outcome and to compare its performance against other derived variables. This prospective observational study was conducted in ED on a convenience sample of 412 from 759 patients who underwent concurrent arterial blood gas and ETCO₂ (end-tidal CO₂) measurement. They were randomized to test sample of 312 patients and validation set of 100 patients. The primary outcome of interest was the need for ventilatory support and secondary outcomes were admission to high dependency unit or death during stay in ED. The randomly selected training set was used to select cut-points for the possible predictors; that is, CO₂ GAP, CO₂ gradient, physiologic dead space and A-a gradient. The sensitivity, specificity and predictive values of these predictors were validated in the test set of 100 patients.   Analysis of the receiver operating characteristic curves revealed the CO₂ GAP performed significantly better than the arterial-alveolar gradient in patients requiring ventilator support (area under the curve 0.950 vs 0.726). A CO₂ GAP ≥10 was associated with assisted ventilation outcomes when applied to the validation test set (100% sensitivity 70% specificity). The CO₂ GAP [(a-ET) PCO₂] differs significantly in patients requiring assisted ventilation when presenting with shortness of breath to EDs and further research addressing the prognostic value of CO₂ GAP in this specific aspect is required. © 2010 The Authors. EMA © 2010 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine.

Effects of nanoscale vacuum gap on photon-enhanced thermionic emission devices

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

Wang, Yuan; Liao, Tianjun; Zhang, Yanchao

2016-01-28

A new model of the photon-enhanced thermionic emission (PETE) device with a nanoscale vacuum gap is established by introducing the quantum tunneling effect and the image force correction. Analytic expressions for both the thermionic emission and tunneling currents are derived. The electron concentration and the temperature of the cathode are determined by the particle conservation and energy balance equations. The effects of the operating voltage on the maximum potential barrier, cathode temperature, electron concentration and equilibrium electron concentration of the conduction band, and efficiency of the PETE device are discussed in detail for different given values of the vacuum gapmore » length. The influence of the band gap of the cathode and flux concentration on the efficiency is further analyzed. The maximum efficiency of the PETE and the corresponding optimum values of the band gap and the operating voltage are determined. The results obtained here show that the efficiency of the PETE device can be significantly improved by employing a nanoscale vacuum gap.« less

From the Kohn-Sham band gap to the fundamental gap in solids. An integer electron approach.

PubMed

Baerends, E J

2017-06-21

It is often stated that the Kohn-Sham occupied-unoccupied gap in both molecules and solids is "wrong". We argue that this is not a correct statement. The KS theory does not allow to interpret the exact KS HOMO-LUMO gap as the fundamental gap (difference (I - A) of electron affinity (A) and ionization energy (I), twice the chemical hardness), from which it indeed differs, strongly in molecules and moderately in solids. The exact Kohn-Sham HOMO-LUMO gap in molecules is much below the fundamental gap and very close to the much smaller optical gap (first excitation energy), and LDA/GGA yield very similar gaps. In solids the situation is different: the excitation energy to delocalized excited states and the fundamental gap (I - A) are very similar, not so disparate as in molecules. Again the Kohn-Sham and LDA/GGA band gaps do not represent (I - A) but are significantly smaller. However, the special properties of an extended system like a solid make it very easy to calculate the fundamental gap from the ground state (neutral system) band structure calculations entirely within a density functional framework. The correction Δ from the KS gap to the fundamental gap originates from the response part v resp of the exchange-correlation potential and can be calculated very simply using an approximation to v resp . This affords a calculation of the fundamental gap at the same level of accuracy as other properties of crystals at little extra cost beyond the ground state bandstructure calculation. The method is based on integer electron systems, fractional electron systems (an ensemble of N- and (N + 1)-electron systems) and the derivative discontinuity are not invoked.

Band Gaps for Elastic Wave Propagation in a Periodic Composite Beam Structure Incorporating Microstructure and Surface Energy Effects

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

Zhang, G. Y.; Gao, X. -L.; Bishop, J. E.

Here, a new model for determining band gaps for elastic wave propagation in a periodic composite beam structure is developed using a non-classical Bernoulli–Euler beam model that incorporates the microstructure, surface energy and rotational inertia effects. The Bloch theorem and transfer matrix method for periodic structures are employed in the formulation. The new model reduces to the classical elasticity-based model when both the microstructure and surface energy effects are not considered. The band gaps predicted by the new model depend on the microstructure and surface elasticity of each constituent material, the unit cell size, the rotational inertia, and the volumemore » fraction. To quantitatively illustrate the effects of these factors, a parametric study is conducted. The numerical results reveal that the band gap predicted by the current non-classical model is always larger than that predicted by the classical model when the beam thickness is very small, but the difference is diminishing as the thickness becomes large. Also, it is found that the first frequency for producing the band gap and the band gap size decrease with the increase of the unit cell length according to both the current and classical models. In addition, it is observed that the effect of the rotational inertia is larger when the exciting frequency is higher and the unit cell length is smaller. Furthermore, it is seen that the volume fraction has a significant effect on the band gap size, and large band gaps can be obtained by tailoring the volume fraction and material parameters.« less

Band Gaps for Elastic Wave Propagation in a Periodic Composite Beam Structure Incorporating Microstructure and Surface Energy Effects

DOE PAGES

Zhang, G. Y.; Gao, X. -L.; Bishop, J. E.; ...

2017-11-20

Here, a new model for determining band gaps for elastic wave propagation in a periodic composite beam structure is developed using a non-classical Bernoulli–Euler beam model that incorporates the microstructure, surface energy and rotational inertia effects. The Bloch theorem and transfer matrix method for periodic structures are employed in the formulation. The new model reduces to the classical elasticity-based model when both the microstructure and surface energy effects are not considered. The band gaps predicted by the new model depend on the microstructure and surface elasticity of each constituent material, the unit cell size, the rotational inertia, and the volumemore » fraction. To quantitatively illustrate the effects of these factors, a parametric study is conducted. The numerical results reveal that the band gap predicted by the current non-classical model is always larger than that predicted by the classical model when the beam thickness is very small, but the difference is diminishing as the thickness becomes large. Also, it is found that the first frequency for producing the band gap and the band gap size decrease with the increase of the unit cell length according to both the current and classical models. In addition, it is observed that the effect of the rotational inertia is larger when the exciting frequency is higher and the unit cell length is smaller. Furthermore, it is seen that the volume fraction has a significant effect on the band gap size, and large band gaps can be obtained by tailoring the volume fraction and material parameters.« less

High throughput light absorber discovery, Part 2: Establishing structure–band gap energy relationships

DOE PAGES

Suram, Santosh K.; Newhouse, Paul F.; Zhou, Lan; ...

2016-09-23

Combinatorial materials science strategies have accelerated materials development in a variety of fields, and we extend these strategies to enable structure-property mapping for light absorber materials, particularly in high order composition spaces. High throughput optical spectroscopy and synchrotron X-ray diffraction are combined to identify the optical properties of Bi-V-Fe oxides, leading to the identification of Bi 4V 1.5Fe 0.5O 10.5 as a light absorber with direct band gap near 2.7 eV. Here, the strategic combination of experimental and data analysis techniques includes automated Tauc analysis to estimate band gap energies from the high throughput spectroscopy data, providing an automated platformmore » for identifying new optical materials.« less

High throughput light absorber discovery, Part 2: Establishing structure–band gap energy relationships

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

Suram, Santosh K.; Newhouse, Paul F.; Zhou, Lan

Combinatorial materials science strategies have accelerated materials development in a variety of fields, and we extend these strategies to enable structure-property mapping for light absorber materials, particularly in high order composition spaces. High throughput optical spectroscopy and synchrotron X-ray diffraction are combined to identify the optical properties of Bi-V-Fe oxides, leading to the identification of Bi 4V 1.5Fe 0.5O 10.5 as a light absorber with direct band gap near 2.7 eV. Here, the strategic combination of experimental and data analysis techniques includes automated Tauc analysis to estimate band gap energies from the high throughput spectroscopy data, providing an automated platformmore » for identifying new optical materials.« less

Values Affirmation Intervention Reduces Achievement Gap between Underrepresented Minority and White Students in Introductory Biology Classes.

PubMed

Jordt, Hannah; Eddy, Sarah L; Brazil, Riley; Lau, Ignatius; Mann, Chelsea; Brownell, Sara E; King, Katherine; Freeman, Scott

2017-01-01

Achievement gaps between underrepresented minority (URM) students and their white peers in college science, technology, engineering, and mathematics classrooms are persistent across many white-majority institutions of higher education. Attempts to reduce this phenomenon of underperformance through increasing classroom structure via active learning have been partially successful. In this study, we address the hypothesis that the achievement gap between white and URM students in an undergraduate biology course has a psychological and emotional component arising from stereotype threat. Specifically, we introduced a values affirmation exercise that counters stereotype threat by reinforcing a student's feelings of integrity and self-worth in three iterations of an intensive active-learning college biology course. On average, this exercise reduced the achievement gap between URM and white students who entered the course with the same incoming grade point average. This result suggests that achievement gaps resulting from the underperformance of URM students could be mitigated by providing students with a learning environment that removes psychological and emotional impediments of performance through short psychosocial interventions. © 2017 H. Jordt et al. CBE—Life Sciences Education © 2017 The American Society for Cell Biology. This article is distributed by The American Society for Cell Biology under license from the author(s). It is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Detecting sign-changing superconducting gap in LiFeAs using quasiparticle interference

NASA Astrophysics Data System (ADS)

Altenfeld, D.; Hirschfeld, P. J.; Mazin, I. I.; Eremin, I.

2018-02-01

Using a realistic ten-orbital tight-binding model Hamiltonian fitted to the angle-resolved photoemission spectroscopy data on LiFeAs, we analyze the temperature, frequency, and momentum dependencies of quasiparticle interference to identify gap sign changes in a qualitative way, following our original proposal [Phys. Rev. B 92, 184513 (2015), 10.1103/PhysRevB.92.184513]. We show that all features present for the simple two-band model for the sign-changing s+--wave superconducting gap employed previously are still present in the realistic tight-binding approximation and gap values observed experimentally. We discuss various superconducting gap structures proposed for LiFeAs and identify various features of these superconducting gap functions in the quasiparticle interference patterns. On the other hand, we show that it will be difficult to identify the more complicated possible sign structures of the hole pocket gaps in LiFeAs due to the smallness of the pockets and the near proximity of two of the gap energies.

Giant Enhancement in Radiative Heat Transfer in Sub-30 nm Gaps of Plane Parallel Surfaces.

PubMed

Fiorino, Anthony; Thompson, Dakotah; Zhu, Linxiao; Song, Bai; Reddy, Pramod; Meyhofer, Edgar

2018-06-13

Radiative heat transfer rates that exceed the blackbody limit by several orders of magnitude are expected when the gap size between plane parallel surfaces is reduced to the nanoscale. To date, experiments have only realized enhancements of ∼100 fold as the smallest gap sizes in radiative heat transfer studies have been limited to ∼50 nm by device curvature and particle contamination. Here, we report a 1,200-fold enhancement with respect to the far-field value in the radiative heat flux between parallel planar silica surfaces separated by gaps as small as ∼25 nm. Achieving such small gap sizes and the resultant dramatic enhancement in near-field energy flux is critical to achieve a number of novel near-field based nanoscale energy conversion systems that have been theoretically predicted but remain experimentally unverified.

Formation of quantum spin Hall state on Si surface and energy gap scaling with strength of spin orbit coupling.

PubMed

Zhou, Miao; Ming, Wenmei; Liu, Zheng; Wang, Zhengfei; Yao, Yugui; Liu, Feng

2014-11-19

For potential applications in spintronics and quantum computing, it is desirable to place a quantum spin Hall insulator [i.e., a 2D topological insulator (TI)] on a substrate while maintaining a large energy gap. Here, we demonstrate a unique approach to create the large-gap 2D TI state on a semiconductor surface, based on first-principles calculations and effective Hamiltonian analysis. We show that when heavy elements with strong spin orbit coupling (SOC) such as Bi and Pb atoms are deposited on a patterned H-Si(111) surface into a hexagonal lattice, they exhibit a 2D TI state with a large energy gap of ≥ 0.5 eV. The TI state arises from an intriguing substrate orbital filtering effect that selects a suitable orbital composition around the Fermi level, so that the system can be matched onto a four-band effective model Hamiltonian. Furthermore, it is found that within this model, the SOC gap does not increase monotonically with the increasing strength of SOC. These interesting results may shed new light in future design and fabrication of large-gap topological quantum states.

Formation of quantum spin Hall state on Si surface and energy gap scaling with strength of spin orbit coupling

DOE PAGES

Zhou, Miao; Ming, Wenmei; Liu, Zheng; ...

2014-11-19

For potential applications in spintronics and quantum computing, it is desirable to place a quantum spin Hall insulator [i.e., a 2D topological insulator (TI)] on a substrate while maintaining a large energy gap. Here, we demonstrate a unique approach to create the large-gap 2D TI state on a semiconductor surface, based on first-principles calculations and effective Hamiltonian analysis. We show that when heavy elements with strong spin orbit coupling (SOC) such as Bi and Pb atoms are deposited on a patterned H-Si(111) surface into a hexagonal lattice, they exhibit a 2D TI state with a large energy gap of ≥0.5more » eV. The TI state arises from an intriguing substrate orbital filtering effect that selects a suitable orbital composition around the Fermi level, so that the system can be matched onto a four-band effective model Hamiltonian. Furthermore, it is found that within this model, the SOC gap does not increase monotonically with the increasing strength of SOC. These interesting results may shed new light in future design and fabrication of large-gap topological quantum states.« less

Electronic Characterization of Defects in Narrow Gap Semiconductors-Comparison of Electronic Energy Levels and Formation Energies in Mercury Cadmium Telluride, Mercury Zinc Telluride, and Mercury Zinc Selenide

NASA Technical Reports Server (NTRS)

Patterson, James D.

1996-01-01

We have used a Green's function technique to calculate the energy levels and formation energy of deep defects in the narrow gap semiconductors mercury cadmium telluride (MCT), mercury zinc telluride (MZT) and mercury zinc selenide (MZS). The formation energy is calculated from the difference between the total energy with an impurity cluster and the total energy for the perfect crystal. Substitutional (including antisite), interstitial (self and foreign), and vacancy deep defects are considered. Relaxation effects are calculated (with molecular dynamics). By use of a pseudopotential, we generalize the ideal vacancy model so as to be able to consider relaxation for vacancies. Different charge states are considered and the charged state energy shift (as computed by a modified Haldane-Anderson model) can be twice that due to relaxation. Different charged states for vacancies were not calculated to have much effect on the formation energy. For all cases we find deep defects in the energy gap only for cation site s-like orbitals or anion site p-like orbitals, and for the substitutional case only the latter are appreciably effected by relaxation. For most cases for MCT, MZT, MZS, we consider x (the concentration of Cd or Zn) in the range appropriate for a band gap of 0.1 eV. For defect energy levels, the absolute accuracy of our results is limited, but the precision is good, and hence chemical trends are accurately predicted. For the same reason, defect formation energies are more accurately predicted than energy level position. We attempt, in Appendix B, to calculate vacancy formation energies using relatively simple chemical bonding ideas due to Harrison. However, these results are only marginally accurate for estimating vacancy binding energies. Appendix C lists all written reports and publications produced for the grant. We include abstracts and a complete paper that summarizes our work which is not yet available.

Communication: electronic band gaps of semiconducting zig-zag carbon nanotubes from many-body perturbation theory calculations.

PubMed

Umari, P; Petrenko, O; Taioli, S; De Souza, M M

2012-05-14

Electronic band gaps for optically allowed transitions are calculated for a series of semiconducting single-walled zig-zag carbon nanotubes of increasing diameter within the many-body perturbation theory GW method. The dependence of the evaluated gaps with respect to tube diameters is then compared with those found from previous experimental data for optical gaps combined with theoretical estimations of exciton binding energies. We find that our GW gaps confirm the behavior inferred from experiment. The relationship between the electronic gap and the diameter extrapolated from the GW values is also in excellent agreement with a direct measurement recently performed through scanning tunneling spectroscopy.

A Value Conscious Approach to Energy Education.

ERIC Educational Resources Information Center

Braun, Bonnie; Wilson, Elaine

The paper presents background information, rationale, description, and evaluation of an energy education program used with preschool and kindergarten children and their families. The objective is to describe the use of combined concepts of education, economics, and early childhood in developing a value conscious approach to energy education. The…

Gate-independent energy gap in noncovalently intercalated bilayer graphene on SiC(0001)

NASA Astrophysics Data System (ADS)

Li, Yuanchang

2016-12-01

Our first-principles calculations show that an energy gap around 0.12-0.25 eV can be engineered in epitaxial graphene on SiC(0001) through the noncovalent intercalation of transition or alkali metals but originated from the distinct mechanisms. The former is attributed to the combined effects of a metal-induced perpendicular electric field and interaction, while the latter is solely attributed to the built-in electric field. A great advantage of this scheme is that the gap size is almost independent of the gate voltage up to 1 V/nm, thus reserving the electric means to tune the Fermi level of graphene when configured as field-effect transistors. Given the recent progress in experimental techniques for intercalated graphene, our findings provide a practical way to incorporate graphene in the current semiconductor industry.

[Caloric value and energy allocation of Chloris virgata in northeast grassland].

PubMed

Guo, J; Wang, R; Wang, W

2001-06-01

The rules of seasonal changes in caloric values of individual plant, stem, and leaves of Chloris virgata were similar, which had two peak values from early July to early August, and then decreased gradually. Those of inflorescence assumed U shape, and had two peak values in early August and middle September, respectively. The seasonal changes in caloric values of dead standing were irregular, and the maximum value was appeared in early August. The seasonal changes in existent energy value of the aboveground parts in Chloris virgata population presented double peak curve. The two peak values were appeared in early August and early September respectively, and the maximum value was 7381.27 kJ.m-2 in early September. The energy allocation in different seasons was leaf > stem in early July, stem > leaf > dead standing in middle July, stem > leaf > inflorescence > dead standing in August, stem > inflorescence > leaf > dead standing in early September, and stem > inflorescence > dead standing > leaf in middle September. The vertical structure of energy in the aboveground parts was that the energy value gradually increased from the earth's surface to 20 cm high, and then decreased. The maximum value, which accounted for 25.75% of energy in the aboveground parts, was appeared in the layer of 10-20 cm high. In the underground parts, the energy value progressively decreased with the increase of depth, and the maximum value, which accounted for 74.21% of energy in the underground parts, was appeared in the layer of 0-10 cm depth.

The value of compressed air energy storage in energy and reserve markets

DOE PAGES

Drury, Easan; Denholm, Paul; Sioshansi, Ramteen

2011-06-28

Storage devices can provide several grid services, however it is challenging to quantify the value of providing several services and to optimally allocate storage resources to maximize value. We develop a co-optimized Compressed Air Energy Storage (CAES) dispatch model to characterize the value of providing operating reserves in addition to energy arbitrage in several U.S. markets. We use the model to: (1) quantify the added value of providing operating reserves in addition to energy arbitrage; (2) evaluate the dynamic nature of optimally allocating storage resources into energy and reserve markets; and (3) quantify the sensitivity of CAES net revenues tomore » several design and performance parameters. We find that conventional CAES systems could earn an additional 23 ± 10/kW-yr by providing operating reserves, and adiabatic CAES systems could earn an additional 28 ± 13/kW-yr. We find that arbitrage-only revenues are unlikely to support a CAES investment in most market locations, but the addition of reserve revenues could support a conventional CAES investment in several markets. Adiabatic CAES revenues are not likely to support an investment in most regions studied. As a result, modifying CAES design and performance parameters primarily impacts arbitrage revenues, and optimizing CAES design will be nearly independent of dispatch strategy.« less

Undecidability of the spectral gap.

PubMed

Cubitt, Toby S; Perez-Garcia, David; Wolf, Michael M

2015-12-10

The spectral gap--the energy difference between the ground state and first excited state of a system--is central to quantum many-body physics. Many challenging open problems, such as the Haldane conjecture, the question of the existence of gapped topological spin liquid phases, and the Yang-Mills gap conjecture, concern spectral gaps. These and other problems are particular cases of the general spectral gap problem: given the Hamiltonian of a quantum many-body system, is it gapped or gapless? Here we prove that this is an undecidable problem. Specifically, we construct families of quantum spin systems on a two-dimensional lattice with translationally invariant, nearest-neighbour interactions, for which the spectral gap problem is undecidable. This result extends to undecidability of other low-energy properties, such as the existence of algebraically decaying ground-state correlations. The proof combines Hamiltonian complexity techniques with aperiodic tilings, to construct a Hamiltonian whose ground state encodes the evolution of a quantum phase-estimation algorithm followed by a universal Turing machine. The spectral gap depends on the outcome of the corresponding 'halting problem'. Our result implies that there exists no algorithm to determine whether an arbitrary model is gapped or gapless, and that there exist models for which the presence or absence of a spectral gap is independent of the axioms of mathematics.

A note on anomalous band-gap variations in semiconductors with temperature

NASA Astrophysics Data System (ADS)

Chakraborty, P. K.; Mondal, B. N.

2018-03-01

An attempt is made to theoretically study the band-gap variations (ΔEg) in semiconductors with temperature following the works, did by Fan and O'Donnell et al. based on thermodynamic functions. The semiconductor band-gap reflects the bonding energy. An increase in temperature changes the chemical bondings, and electrons are promoted from valence band to conduction band. In their analyses, they made several approximations with respect to temperature and other fitting parameters leading to real values of band-gap variations with linear temperature dependences. In the present communication, we have tried to re-analyse the works, specially did by Fan, and derived an analytical model for ΔEg(T). Because, it was based on the second-order perturbation technique of thermodynamic functions. Our analyses are made without any approximations with respect to temperatures and other fitting parameters mentioned in the text, leading to a complex functions followed by an oscillating nature of the variations of ΔEg. In support of the existence of the oscillating energy band-gap variations with temperature in a semiconductor, possible physical explanations are provided to justify the experimental observation for various materials.

Dependence of Mobility on Density of Gap States in Organics by GAMEaS - Gate Modulated Activation Energy Spectroscopy

NASA Astrophysics Data System (ADS)

So, Woo-Young; Lang, David; Ramirez, Arthur

2008-03-01

We develop a spectroscopic method for determining the density of states (DOS) in the energy gap - GAte Modulated activation Energy Spectroscopy (GAMEaS), We also report the relationship of these gap states to the mobility of organic field-effect-transistors (FETs). We find that the field-effect mobility is parameterized by two factors: (1) the free-carrier mobility and (2) the ratio of the free carrier density to the total carrier density induced by the gate bias. We show that the highest mobility FETs have shallow exponential band tails of localized states with characteristic slope of 1/kT at 300K. Most remarkably, state-of-the-art crystalline FETs fabricated from rubrene, pentacene, and tetracene all have a very high free-carrier mobility, up to 200cm2/Vsec at 300K, with the somewhat lower effective mobilities dominated by localized gap states. This strongly suggests that further improvements in device performance could be possible with enhanced material quality.

On the sub-band gap optical absorption in heat treated cadmium sulphide thin film deposited on glass by chemical bath deposition technique

NASA Astrophysics Data System (ADS)

Chattopadhyay, P.; Karim, B.; Guha Roy, S.

2013-12-01

The sub-band gap optical absorption in chemical bath deposited cadmium sulphide thin films annealed at different temperatures has been critically analyzed with special reference to Urbach relation. It has been found that the absorption co-efficient of the material in the sub-band gap region is nearly constant up to a certain critical value of the photon energy. However, as the photon energy exceeds the critical value, the absorption coefficient increases exponentially indicating the dominance of Urbach rule. The absorption coefficients in the constant absorption region and the Urbach region have been found to be sensitive to annealing temperature. A critical examination of the temperature dependence of the absorption coefficient indicates two different kinds of optical transitions to be operative in the sub-band gap region. After a careful analyses of SEM images, energy dispersive x-ray spectra, and the dc current-voltage characteristics, we conclude that the absorption spectra in the sub-band gap domain is possibly associated with optical transition processes involving deep levels and the grain boundary states of the material.

Electron Elevator: Excitations across the Band Gap via a Dynamical Gap State.

PubMed

Lim, A; Foulkes, W M C; Horsfield, A P; Mason, D R; Schleife, A; Draeger, E W; Correa, A A

2016-01-29

We use time-dependent density functional theory to study self-irradiated Si. We calculate the electronic stopping power of Si in Si by evaluating the energy transferred to the electrons per unit path length by an ion of kinetic energy from 1 eV to 100 keV moving through the host. Electronic stopping is found to be significant below the threshold velocity normally identified with transitions across the band gap. A structured crossover at low velocity exists in place of a hard threshold. An analysis of the time dependence of the transition rates using coupled linear rate equations enables one of the excitation mechanisms to be clearly identified: a defect state induced in the gap by the moving ion acts like an elevator and carries electrons across the band gap.

Eddy Covariance Measurements Over a Maize Field: The Contribution of Minor Flux Terms to the Energy Balance Gap

NASA Astrophysics Data System (ADS)

Smidt, J.; Ingwersen, J.; Streck, T.

2015-12-01

The lack of energy balance closure is a long-standing problem in eddy covariance (EC) measurements. The energy balance equation is defined as Rn - G = H + λE, where Rn is net radiation, G is the ground heat flux, H is the sensible heat flux and λE is the latent heat flux. In most cases of energy imbalance, either Rn is overestimated or the ground heat and turbulent fluxes are underestimated. Multiple studies have shown that calculations, incorrect instrument installation/calibration and measurement errors alone do not entirely account for this imbalance. Rather, research is now focused on previously neglected sources of heat storage in the soil, biomass and air beneath the EC station. This project examined the potential of five "minor flux terms" - soil heat storage, biomass heat storage, energy consumption by photosynthesis, air heat storage and atmospheric moisture change, to further close the energy balance gap. Eddy covariance measurements were conducted at a maize (Zea mays) field in southwest Germany during summer 2014. Soil heat storage was measured for six weeks at 11 sites around the field footprint. Biomass and air heat storage were measured for six subsequent weeks at seven sites around the field footprint. Energy consumption by photosynthesis was calculated using the CO2 flux data. Evapotranspiration was calculated using the water balance method and then compared to the flux data processed with three post-closure methods: the sensible heat flux, the latent heat flux and the Bowen ratio post-closure methods. An energy balance closure of 66% was achieved by the EC station measurements over the entire investigation period. During the soil heat flux campaign, EC station closure was 74.1%, and the field footprint soil heat storage contributed 3.3% additional closure. During the second minor flux term measurement period, closure with the EC station data was 91%. Biomass heat storage resulted in 1.1% additional closure, the photosynthesis flux closed the gap

Effect of electron divergence in air gaps on the measurement of the energy of cascades in emulsion chambers

NASA Technical Reports Server (NTRS)

Apanasenko, A. V.; Baradzey, L. T.; Kanevskaya, Y. A.; Smorodin, Y. A.

1975-01-01

The effect of an increase in electron density in the vicinity of the cascade axis caused by an avalanche passing through the gap between lead filters of the emulsion chamber was investigated experimentally. Optical densities were measured in three X-ray films spaced at 400, 800 and 1200 micrometer from the filter surface having a thickness of 6 cascade units. The optical densities of blackening spots caused by electron photon cascades of 1 to 2, 2 to 7 and greater than 7 BeV energies were measured. The results prove the presence of a gap between the filter and the nuclear emulsion which results in the underestimation of energy by several tenths of a percent.

Energy band gaps in graphene nanoribbons with corners

NASA Astrophysics Data System (ADS)

Szczȩśniak, Dominik; Durajski, Artur P.; Khater, Antoine; Ghader, Doried

2016-05-01

In the present paper, we study the relation between the band gap size and the corner-corner length in representative chevron-shaped graphene nanoribbons (CGNRs) with 120° and 150° corner edges. The direct physical insight into the electronic properties of CGNRs is provided within the tight-binding model with phenomenological edge parameters, developed against recent first-principle results. We show that the analyzed CGNRs exhibit inverse relation between their band gaps and corner-corner lengths, and that they do not present a metal-insulator transition when the chemical edge modifications are introduced. Our results also suggest that the band gap width for the CGNRs is predominantly governed by the armchair edge effects, and is tunable through edge modifications with foreign atoms dressing.

Theoretical and Experimental Evidence for a Nodal Energy Gap in MgB2

DTIC Science & Technology

2017-02-17

1   Theoretical and Experimental Evidence for a Nodal Energy Gap in MgB2 Y. Dan Agassia and Daniel E. Oatesb aConsultant, Jerusalem, Israel bMIT...surface impedance and intermodulation distortion in high-quality thin films. We briefly review experimental evidence in support of our hypothesis and...demonstrates, this experimental evidence agrees with the l = 6 hypothesis, while inconsistent with s-wave symmetry. To give the l = 6 hypothesis a

L-Asparagine crystals with wide gap semiconductor features: optical absorption measurements and density functional theory computations.

PubMed

Zanatta, G; Gottfried, C; Silva, A M; Caetano, E W S; Sales, F A M; Freire, V N

2014-03-28

Results of optical absorption measurements are presented together with calculated structural, electronic, and optical properties for the anhydrous monoclinic L-asparagine crystal. Density functional theory (DFT) within the generalized gradient approximation (GGA) including dispersion effects (TS, Grimme) was employed to perform the calculations. The optical absorption measurements revealed that the anhydrous monoclinic L-asparagine crystal is a wide band gap material with 4.95 eV main gap energy. DFT-GGA+TS simulations, on the other hand, produced structural parameters in very good agreement with X-ray data. The lattice parameter differences Δa, Δb, Δc between theory and experiment were as small as 0.020, 0.051, and 0.022 Å, respectively. The calculated band gap energy is smaller than the experimental data by about 15%, with a 4.23 eV indirect band gap corresponding to Z → Γ and Z → β transitions. Three other indirect band gaps of 4.30 eV, 4.32 eV, and 4.36 eV are assigned to α3 → Γ, α1 → Γ, and α2 → Γ transitions, respectively. Δ-sol computations, on the other hand, predict a main band gap of 5.00 eV, just 50 meV above the experimental value. Electronic wavefunctions mainly originating from O 2p-carboxyl, C 2p-side chain, and C 2p-carboxyl orbitals contribute most significantly to the highest valence and lowest conduction energy bands, respectively. By varying the lattice parameters from their converged equilibrium values, we show that the unit cell is less stiff along the b direction than for the a and c directions. Effective mass calculations suggest that hole transport behavior is more anisotropic than electron transport, but the mass values allow for some charge mobility except along a direction perpendicular to the molecular layers of L-asparagine which form the crystal, so anhydrous monoclinic L-asparagine crystals could behave as wide gap semiconductors. Finally, the calculations point to a high degree of optical

Electron elevator: Excitations across the band gap via a dynamical gap state

DOE PAGES

Lim, Anthony; Foulkes, W. M. C.; Horsfield, A. P.; ...

2016-01-27

We use time-dependent density functional theory to study self-irradiated Si. We calculate the electronic stopping power of Si in Si by evaluating the energy transferred to the electrons per unit path length by an ion of kinetic energy from 1 eV to 100 keV moving through the host. Electronic stopping is found to be significant below the threshold velocity normally identified with transitions across the band gap. A structured crossover at low velocity exists in place of a hard threshold. Lastly, an analysis of the time dependence of the transition rates using coupled linear rate equations enables one of themore » excitation mechanisms to be clearly identified: a defect state induced in the gap by the moving ion acts like an elevator and carries electrons across the band gap.« less

Energy transfer between two vacuum-gapped metal plates: Coulomb fluctuations and electron tunneling

NASA Astrophysics Data System (ADS)

Zhang, Zu-Quan; Lü, Jing-Tao; Wang, Jian-Sheng

2018-05-01

Recent experimental measurements for near-field radiative heat transfer between two bodies have been able to approach the gap distance within 2 nm , where the contributions of Coulomb fluctuation and electron tunneling are comparable. Using the nonequilibrium Green's function method in the G0W0 approximation, based on a tight-binding model, we obtain for the energy current a Caroli formula from the Meir-Wingreen formula in the local equilibrium approximation. Also, the Caroli formula is consistent with the evanescent part of the heat transfer from the theory of fluctuational electrodynamics. We go beyond the local equilibrium approximation to study the energy transfer in the crossover region from electron tunneling to Coulomb fluctuation based on a numerical calculation.

Benchmarking singlet and triplet excitation energies of molecular semiconductors for singlet fission: Tuning the amount of HF exchange and adjusting local correlation to obtain accurate functionals for singlet-triplet gaps

NASA Astrophysics Data System (ADS)

Brückner, Charlotte; Engels, Bernd

2017-01-01

Vertical and adiabatic singlet and triplet excitation energies of molecular p-type semiconductors calculated with various DFT functionals and wave-function based approaches are benchmarked against MS-CASPT2/cc-pVTZ reference values. A special focus lies on the singlet-triplet gaps that are very important in the process of singlet fission. Singlet fission has the potential to boost device efficiencies of organic solar cells, but the scope of existing singlet-fission compounds is still limited. A computational prescreening of candidate molecules could enlarge it; yet it requires efficient methods accurately predicting singlet and triplet excitation energies. Different DFT formulations (Tamm-Dancoff approximation, linear response time-dependent DFT, Δ-SCF) and spin scaling schemes along with several ab initio methods (CC2, ADC(2)/MP2, CIS(D), CIS) are evaluated. While wave-function based methods yield rather reliable singlet-triplet gaps, many DFT functionals are shown to systematically underestimate triplet excitation energies. To gain insight, the impact of exact exchange and correlation is in detail addressed.

Band gap tuning of armchair silicene nanoribbons using periodic hexagonal holes

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

Mehdi Aghaei, Sadegh; Calizo, Irene, E-mail: icalizo@fiu.edu

2015-09-14

The popularity of graphene owing to its unique and exotic properties has triggered a great deal of interest in other two-dimensional nanomaterials. Among them silicene shows considerable promise for electronic devices with a carrier mobility comparable to graphene, flexible buckled structure, and expected compatibility with silicon electronics. Using first-principle calculations based on density functional theory, the electronic properties of armchair silicene nanoribbons perforated with periodic nanoholes (ASiNRPNHs) are investigated. Two different configurations of mono-hydrogenated (:H) and di-hydrogenated (:2H) silicene edges are considered. Pristine armchair silicene nanoribbons (ASiNRs) can be categorized into three branches with width W = 3P − 1, 3P, andmore » 3P + 1, P is an integer. The order of their energy gaps change from “E{sub G} (3P − 1) < E{sub G} (3P) < E{sub G} (3P + 1)” for W-ASiNRs:H to “E{sub G} (3P + 1) < E{sub G} (3P − 1) < E{sub G} (3P)” for W-ASiNRs:2H. We found the band gaps of W-ASiNRs:H and (W + 2)-ASiNRs:2H are slightly different, giving larger band gaps for wider ASiNRs:2H. ASiNRPNHs' band gaps changed based on the nanoribbon's width, nanohole's repeat periodicity and position relative to the nanoribbon's edge compared to pristine ASiNRs because of changes in quantum confinement strength. ASiNRPNHs:2H are more stable than ASiNRPNHs:H and their band gaps are noticeably greater than ASiNRPNHs:H. We found that the value of energy band gap for 12-ASiNRPNHs:2H with repeat periodicity of 2 is 0.923 eV. This value is about 2.2 times greater than pristine ASiNR:2H and double that of the 12-ASiNRPNHs:H with repeat periodicity of 2.« less

High-Energy Emission From the Polar Cap and Slot Gap

NASA Technical Reports Server (NTRS)

Harding, Alice K.

2006-01-01

Thirty-five years after the discovery of rotation-powered pulsars, we still do not understand the fundamentals of their pulsed emission at any wavelength. I will review the latest developments in understanding the high-energy emission of rotation-powered pulsars, with particular emphasis on the polar cap and slot gap models. Special and general relativistic effects play important roles in pulsar emission, from inertial frame-dragging near the stellar surface to aberration, time-of-flight and retardation of the magnetic field near the light cylinder. Understanding how these effects determine what we observe at different wavelengths is critical to unraveling the emission physics. I will discuss how the next generation of gamma-ray detectors, AGILE and GLAST, will test prediction of these models.

Electronic energy gap of molecular hydrogen from electrical conductivity measurements at high shock pressures

NASA Technical Reports Server (NTRS)

Nellis, W. J.; Mitchell, A. C.; Mccandless, P. C.; Erskine, D. J.; Weir, S. T.

1992-01-01

Electrical conductivities were measured for liquid D2 and H2 shock compressed to pressures of 10-20 GPa (100-200 kbar), molar volumes near 8 cu cm/mol, and calculated temperatures of 2900-4600 K. The semiconducting energy gap derived from the conductivities is 12 eV, in good agreement with recent quasi-particle calculations and with oscillator frequencies measured in diamond-anvil cells.

Executive summary of NIH workshop on the Use and Biology of Energy Drinks: Current Knowledge and Critical Gaps

PubMed Central

Sorkin, Barbara C; Camp, Kathryn M; Haggans, Carol J; Deuster, Patricia A; Haverkos, Lynne; Maruvada, Padma; Witt, Ellen; Coates, Paul M

2014-01-01

Sales of energy drinks in the United States reached $12.5 billion in 2012. Emergency department visits related to consumption of these products have increased sharply, and while these numbers remain small relative to product sales, they raise important questions regarding biological and behavioral effects. Although some common ingredients of energy drinks have been extensively studied (e.g., caffeine, B vitamins, sugars, inositol), data on other ingredients (e.g., taurine) are limited. Summarized here are data presented elsewhere in this issue on the prevalence and patterns of caffeine-containing energy drink use, the effects of these products on alertness, fatigue, cognitive functions, sleep, mood, homeostasis, as well as on exercise physiology and metabolism, and the biological mechanisms mediating the observed effects. There are substantial data on the effects of some energy drink ingredients, such as caffeine and sugars, on many of these outcomes; however, even for these ingredients many controversies and gaps remain, and data on other ingredients in caffeine-containing energy drinks, and on ingredient interactions, are sparse. This summary concludes with a discussion of critical gaps in the data and potential next steps. PMID:25293538

The Value of Concentrating Solar Power and Thermal Energy Storage

DOE PAGES

Sioshansi, Ramteen; Denholm, Paul

2010-06-14

Our paper examines the value of concentrating solar power (CSP) and thermal energy storage (TES) in a number of regions in the southwestern United States. Our analysis also shows that TES can increase the value of CSP by allowing more thermal energy from a CSP plant's solar field to be used, allowing a CSP plant to accommodate a larger solar field, and by allowing CSP generation to be shifted to hours with higher energy prices. We also analyze the sensitivity of this value to a number of factors, including the optimization period, price and solar forecasting, ancillary service sales, andmore » dry cooling of the CSP plant, and also estimate the capacity value of a CSP plant with TES. We further discuss the value of CSP plants and TES net of capital costs.« less

Thermally induced effect on sub-band gap absorption in Ag doped CdSe thin films

NASA Astrophysics Data System (ADS)

Kaur, Jagdish; Sharma, Kriti; Bharti, Shivani; Tripathi, S. K.

2015-05-01

Thin films of Ag doped CdSe have been prepared by thermal evaporation using inert gas condensation (IGC) method taking Argon as inert gas. The prepared thin films are annealed at 363 K for one hour. The sub-band gap absorption spectra in the as deposited and annealed thin films have been studied using constant photocurrent method (CPM). The absorption coefficient in the sub-band gap region is described by an Urbach tail in both as deposited and annealed thin films. The value of Urbach energy and number density of trap states have been calculated from the absorption coefficient in the sub-band gap region which have been found to increase after annealing treatment indicating increase in disorderness in the lattice. The energy distribution of the occupied density of states below Fermi level has also been studied using derivative procedure of absorption coefficient.

Far-infrared Optical Conductivity Gap in Superconducting MgB2 Films

NASA Astrophysics Data System (ADS)

Carnahan, M. A.; Kaindl, R. A.; Chemla, D. S.; Christen, H. M.; Zhai, H. Y.; Paranthaman, M.; Lowndes, D. H.

2002-03-01

The prospect of unconventional coupling in the superconductor MgB2 motivates experiments which probe the density of states around the superconducting gap. The frequency and temperature dependent optical conductivity contains important spectroscopic information about the fundamental gap excitations as well as providing a contactless measure of the superconducting condensate. Here we present the first measurements of the far-infrared conductivity of MgB2 over a broad frequency range which spans excitations across its lowest-energy superconducting gap [1]. Thin films of MgB2 are grown on Al_2O3 substrates through e-beam evaporation and subsequent ex-situ annealing [2]. Both the real and imaginary parts of the conductivity are obtained - without recourse to Kramers-Kronig transformations - from terahertz time-domain spectroscopy. Below Tc we observe a depletion of oscillator strength due to the opening of a superconducting gap. We find a gap size of 2Δ ≈ 5 meV. This result, a value which is only half that expected in weak-coupling BCS theory, disfavors a conventional isotropic single-gap scenario. [1] R. Kaindl et al., Phys. Rev. Lett. (to appear). [2] M. Paranthaman et al., Appl. Phys. Lett. 78, 3669 (2001).

Modeling of Spark Gap Performance

DTIC Science & Technology

1983-06-01

MODELING OF SPARK GAP PERFORMANCE* A. L. Donaldson, R. Ness, M. Hagler, M. Kristiansen Department of Electrical Engineering and L. L. Hatfield...gas pressure, and chaJ:ging rate on the voltage stability of high energy spark gaps is discussed. Implications of the model include changes in...an extremely useful, and physically reasonable framework, from which the properties of spark gaps under a wide variety of experimental conditions

Optically Discriminating Carrier-Induced Quasiparticle Band Gap and Exciton Energy Renormalization in Monolayer MoS2

NASA Astrophysics Data System (ADS)

Yao, Kaiyuan; Yan, Aiming; Kahn, Salman; Suslu, Aslihan; Liang, Yufeng; Barnard, Edward S.; Tongay, Sefaattin; Zettl, Alex; Borys, Nicholas J.; Schuck, P. James

2017-08-01

Optoelectronic excitations in monolayer MoS2 manifest from a hierarchy of electrically tunable, Coulombic free-carrier and excitonic many-body phenomena. Investigating the fundamental interactions underpinning these phenomena—critical to both many-body physics exploration and device applications—presents challenges, however, due to a complex balance of competing optoelectronic effects and interdependent properties. Here, optical detection of bound- and free-carrier photoexcitations is used to directly quantify carrier-induced changes of the quasiparticle band gap and exciton binding energies. The results explicitly disentangle the competing effects and highlight longstanding theoretical predictions of large carrier-induced band gap and exciton renormalization in two-dimensional semiconductors.

Optically Discriminating Carrier-Induced Quasiparticle Band Gap and Exciton Energy Renormalization in Monolayer MoS_{2}.

PubMed

Yao, Kaiyuan; Yan, Aiming; Kahn, Salman; Suslu, Aslihan; Liang, Yufeng; Barnard, Edward S; Tongay, Sefaattin; Zettl, Alex; Borys, Nicholas J; Schuck, P James

2017-08-25

Optoelectronic excitations in monolayer MoS_{2} manifest from a hierarchy of electrically tunable, Coulombic free-carrier and excitonic many-body phenomena. Investigating the fundamental interactions underpinning these phenomena-critical to both many-body physics exploration and device applications-presents challenges, however, due to a complex balance of competing optoelectronic effects and interdependent properties. Here, optical detection of bound- and free-carrier photoexcitations is used to directly quantify carrier-induced changes of the quasiparticle band gap and exciton binding energies. The results explicitly disentangle the competing effects and highlight longstanding theoretical predictions of large carrier-induced band gap and exciton renormalization in two-dimensional semiconductors.

High-performance gap-closing vibrational energy harvesting using electret-polarized dielectric oscillators

NASA Astrophysics Data System (ADS)

Feng, Yue; Yu, Zejie; Han, Yanhui

2018-01-01

In conventional gap-closing electret-biased electrostatic energy harvesting (EEEH) schemes, electrets with a very low ratio of electret thickness to permittivity are in great demand to allow the attainment of high power output. However, in practice, pursuing such a low ratio introduces unwanted burdens on the electret stability and therefore the reliability of the EEEH devices. In this paper, we propose a dielectric-oscillator-based electrostatic EH (DEEH) scheme as an alternative approach to harvesting electret-biased electrostatic energy. This approach permits the fabrication of an electret-free closed EH circuit. The DEEH architecture directly collects the electrical energy exclusively through the oscillating dielectric body and thus completely circumvents the restrictions imposed by the electret parameters (thickness and permittivity) on power generation. Significantly, without considering the electret thickness and permittivity, both theoretical analysis and experiments have verified the effectiveness of this DEEH strategy, and a high figure of merit (on the order of 10-8 mW cm-2 V-2 Hz-1) was achieved for low-frequency movements.

Beyond cost-of-energy, the value-of-energy metric and value-centric approaches to design, operations, and maintenance of wind turbines

NASA Astrophysics Data System (ADS)

Fernandes, Kevin

This thesis is oriented toward developers, owners, operators and investors of renewable energy projects. With increasing demand of renewables, our energy dependence comes down to reducing costs associated with this sector so as to compete with the existing sources. One way of valuing investment potential is to determine and then compare the overall value derived by investing in a particular project. Several engineering and financial levers, one of which is operation and maintenance, affect this value. This thesis provides a useful visual aid to owners and operators by which they can operate and maintain their wind farm so as to achieve maximum value throughout its lifetime. All the necessary components that go into developing a business model of a wind farm project will be discussed. Finally, this tool is valid within the assumptions that are explicitly stated. Real world data and trends are used to provide a practical approach to the optimization.

A simplified approach to the band gap correction of defect formation energies: Al, Ga, and In-doped ZnO

NASA Astrophysics Data System (ADS)

Saniz, R.; Xu, Y.; Matsubara, M.; Amini, M. N.; Dixit, H.; Lamoen, D.; Partoens, B.

2013-01-01

The calculation of defect levels in semiconductors within a density functional theory approach suffers greatly from the band gap problem. We propose a band gap correction scheme that is based on the separation of energy differences in electron addition and relaxation energies. We show that it can predict defect levels with a reasonable accuracy, particularly in the case of defects with conduction band character, and yet is simple and computationally economical. We apply this method to ZnO doped with group III elements (Al, Ga, In). As expected from experiment, the results indicate that Zn substitutional doping is preferred over interstitial doping in Al, Ga, and In-doped ZnO, under both zinc-rich and oxygen-rich conditions. Further, all three dopants act as shallow donors, with the +1 charge state having the most advantageous formation energy. Also, doping effects on the electronic structure of ZnO are sufficiently mild so as to affect little the fundamental band gap and lowest conduction bands dispersion, which secures their n-type transparent conducting behavior. A comparison with the extrapolation method based on LDA+U calculations and with the Heyd-Scuseria-Ernzerhof hybrid functional (HSE) shows the reliability of the proposed scheme in predicting the thermodynamic transition levels in shallow donor systems.

Band gap tuning of amorphous Al oxides by Zr alloying

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

Canulescu, S., E-mail: stec@fotonik.dtu.dk; Schou, J.; Jones, N. C.

2016-08-29

The optical band gap and electronic structure of amorphous Al-Zr mixed oxides with Zr content ranging from 4.8 to 21.9% were determined using vacuum ultraviolet and X-ray absorption spectroscopy. The light scattering by the nano-porous structure of alumina at low wavelengths was estimated based on the Mie scattering theory. The dependence of the optical band gap of the Al-Zr mixed oxides on the Zr content deviates from linearity and decreases from 7.3 eV for pure anodized Al{sub 2}O{sub 3} to 6.45 eV for Al-Zr mixed oxides with a Zr content of 21.9%. With increasing Zr content, the conduction band minimum changes non-linearlymore » as well. Fitting of the energy band gap values resulted in a bowing parameter of ∼2 eV. The band gap bowing of the mixed oxides is assigned to the presence of the Zr d-electron states localized below the conduction band minimum of anodized Al{sub 2}O{sub 3}.« less

Executive summary of NIH workshop on the Use and Biology of Energy Drinks: Current Knowledge and Critical Gaps.

PubMed

Sorkin, Barbara C; Camp, Kathryn M; Haggans, Carol J; Deuster, Patricia A; Haverkos, Lynne; Maruvada, Padma; Witt, Ellen; Coates, Paul M

2014-10-01

Sales of energy drinks in the United States reached $12.5 billion in 2012. Emergency department visits related to consumption of these products have increased sharply, and while these numbers remain small relative to product sales, they raise important questions regarding biological and behavioral effects. Although some common ingredients of energy drinks have been extensively studied (e.g., caffeine, B vitamins, sugars, inositol), data on other ingredients (e.g., taurine) are limited. Summarized here are data presented elsewhere in this issue on the prevalence and patterns of caffeine-containing energy drink use, the effects of these products on alertness, fatigue, cognitive functions, sleep, mood, homeostasis, as well as on exercise physiology and metabolism, and the biological mechanisms mediating the observed effects. There are substantial data on the effects of some energy drink ingredients, such as caffeine and sugars, on many of these outcomes; however, even for these ingredients many controversies and gaps remain, and data on other ingredients in caffeine-containing energy drinks, and on ingredient interactions, are sparse. This summary concludes with a discussion of critical gaps in the data and potential next steps. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Energy value of soil organic matter and costs of its restoration

NASA Astrophysics Data System (ADS)

Kuczuk, Anna

2017-10-01

From the point of view of the sustainable soil management, the most important characteristic of soil organic matter (SOM) is associated with the energy content in it. This paper reports the results of an estimation of SOM resources and its energy value for the arable land in a selected farm. For this purpose, soil samples were taken in two fields from a soil depth profile of 30 cm. The testing regarding humus content were conducted at District Chemical and Agricultural Station in Opole. The study involved the assessment of organic matter content at a depth of 30 cm converted per 1 ha, energy value of the SOM resources and the theoretical energy potential was determined. In addition, an example of crop rotation was provided for the analyzed soils, which could be applicable in the process of restoring SOM resources. The cost of restoring the SOM resource was estimated and this value was compared with the energy value of fuel. The total cost of SOM restoration over the period of five years was equal to 3122.26-7845.86 PLN·ha-1 depending on the value of the lost revenue of commercial production, and simultaneously equal to the value of 6.2-16 Mg thermal coal.

Importance of the Kinetic Energy Density for Band Gap Calculations in Solids with Density Functional Theory.

PubMed

Tran, Fabien; Blaha, Peter

2017-05-04

Recently, exchange-correlation potentials in density functional theory were developed with the goal of providing improved band gaps in solids. Among them, the semilocal potentials are particularly interesting for large systems since they lead to calculations that are much faster than with hybrid functionals or methods like GW. We present an exhaustive comparison of semilocal exchange-correlation potentials for band gap calculations on a large test set of solids, and particular attention is paid to the potential HLE16 proposed by Verma and Truhlar. It is shown that the most accurate potential is the modified Becke-Johnson potential, which, most noticeably, is much more accurate than all other semilocal potentials for strongly correlated systems. This can be attributed to its additional dependence on the kinetic energy density. It is also shown that the modified Becke-Johnson potential is at least as accurate as the hybrid functionals and more reliable for solids with large band gaps.

Deterministic multidimensional nonuniform gap sampling.

PubMed

Worley, Bradley; Powers, Robert

2015-12-01

Born from empirical observations in nonuniformly sampled multidimensional NMR data relating to gaps between sampled points, the Poisson-gap sampling method has enjoyed widespread use in biomolecular NMR. While the majority of nonuniform sampling schemes are fully randomly drawn from probability densities that vary over a Nyquist grid, the Poisson-gap scheme employs constrained random deviates to minimize the gaps between sampled grid points. We describe a deterministic gap sampling method, based on the average behavior of Poisson-gap sampling, which performs comparably to its random counterpart with the additional benefit of completely deterministic behavior. We also introduce a general algorithm for multidimensional nonuniform sampling based on a gap equation, and apply it to yield a deterministic sampling scheme that combines burst-mode sampling features with those of Poisson-gap schemes. Finally, we derive a relationship between stochastic gap equations and the expectation value of their sampling probability densities. Copyright © 2015 Elsevier Inc. All rights reserved.

Direct band gap measurement of Cu(In,Ga)(Se,S){sub 2} thin films using high-resolution reflection electron energy loss spectroscopy

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

Heo, Sung; College of Information and Communication Engineering, Sungkyunkwan University, Cheoncheon-dong 300, Jangan-gu, Suwon 440-746; Lee, Hyung-Ik

2015-06-29

To investigate the band gap profile of Cu(In{sub 1−x},Ga{sub x})(Se{sub 1−y}S{sub y}){sub 2} of various compositions, we measured the band gap profile directly as a function of in-depth using high-resolution reflection energy loss spectroscopy (HR-REELS), which was compared with the band gap profile calculated based on the auger depth profile. The band gap profile is a double-graded band gap as a function of in-depth. The calculated band gap obtained from the auger depth profile seems to be larger than that by HR-REELS. Calculated band gaps are to measure the average band gap of the spatially different varying compositions with respectmore » to considering its void fraction. But, the results obtained using HR-REELS are to be affected by the low band gap (i.e., out of void) rather than large one (i.e., near void). Our findings suggest an analytical method to directly determine the band gap profile as function of in-depth.« less

Dark gap solitons in exciton-polariton condensates in a periodic potential.

PubMed

Cheng, Szu-Cheng; Chen, Ting-Wei

2018-03-01

We show that dark spatial gap solitons can occur inside the band gap of an exciton-polariton condensate (EPC) in a one-dimensional periodic potential. The energy dispersions of an EPC loaded into a periodic potential show a band-gap structure. Using the effective-mass model of the complex Gross-Pitaevskii equation with pump and dissipation in an EPC in a periodic potential, dark gap solitons are demonstrated near the minimum energy points of the band center and band edge of the first and second bands, respectively. The excitation energies of dark gap solitons are below these minimum points and fall into the band gap. The spatial width of a dark gap soliton becomes smaller as the pump power is increased.

Dark gap solitons in exciton-polariton condensates in a periodic potential

NASA Astrophysics Data System (ADS)

Cheng, Szu-Cheng; Chen, Ting-Wei

2018-03-01

We show that dark spatial gap solitons can occur inside the band gap of an exciton-polariton condensate (EPC) in a one-dimensional periodic potential. The energy dispersions of an EPC loaded into a periodic potential show a band-gap structure. Using the effective-mass model of the complex Gross-Pitaevskii equation with pump and dissipation in an EPC in a periodic potential, dark gap solitons are demonstrated near the minimum energy points of the band center and band edge of the first and second bands, respectively. The excitation energies of dark gap solitons are below these minimum points and fall into the band gap. The spatial width of a dark gap soliton becomes smaller as the pump power is increased.

Permanent-magnet-less machine having an enclosed air gap

DOEpatents

Hsu, John S [Oak Ridge, TN

2012-02-07

A permanent magnet-less, brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by an alternating current. An uncluttered rotor disposed within the magnetic rotating field is spaced apart from the stator to form an air gap relative to an axis of rotation. A stationary excitation core spaced apart from the uncluttered rotor by an axial air gap and a radial air gap substantially encloses the stationary excitation core. Some permanent magnet-less, brushless synchronous systems include stator core gaps to reduce axial flux flow. Some permanent magnet-less, brushless synchronous systems include an uncluttered rotor coupled to outer laminations. The quadrature-axis inductance may be increased in some synchronous systems. Some synchronous systems convert energy such as mechanical energy into electrical energy (e.g., a generator); other synchronous systems may convert any form of energy into mechanical energy (e.g., a motor).

Permanent-magnet-less machine having an enclosed air gap

DOEpatents

Hsu, John S.

2013-03-05

A permanent magnet-less, brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by an alternating current. An uncluttered rotor disposed within the magnetic rotating field is spaced apart from the stator to form an air gap relative to an axis of rotation. A stationary excitation core spaced apart from the uncluttered rotor by an axial air gap and a radial air gap substantially encloses the stationary excitation core. Some permanent magnet-less, brushless synchronous systems include stator core gaps to reduce axial flux flow. Some permanent magnet-less, brushless synchronous systems include an uncluttered rotor coupled to outer laminations. The quadrature-axis inductance may be increased in some synchronous systems. Some synchronous systems convert energy such as mechanical energy into electrical energy (e.g., a generator); other synchronous systems may convert any form of energy into mechanical energy (e.g., a motor).

Measuring energy efficiency in economics: Shadow value approach

NASA Astrophysics Data System (ADS)

Khademvatani, Asgar

For decades, academic scholars and policy makers have commonly applied a simple average measure, energy intensity, for studying energy efficiency. In contrast, we introduce a distinctive marginal measure called energy shadow value (SV) for modeling energy efficiency drawn on economic theory. This thesis demonstrates energy SV advantages, conceptually and empirically, over the average measure recognizing marginal technical energy efficiency and unveiling allocative energy efficiency (energy SV to energy price). Using a dual profit function, the study illustrates how treating energy as quasi-fixed factor called quasi-fixed approach offers modeling advantages and is appropriate in developing an explicit model for energy efficiency. We address fallacies and misleading results using average measure and demonstrate energy SV advantage in inter- and intra-country energy efficiency comparison. Energy efficiency dynamics and determination of efficient allocation of energy use are shown through factors impacting energy SV: capital, technology, and environmental obligations. To validate the energy SV, we applied a dual restricted cost model using KLEM dataset for the 35 US sectors stretching from 1958 to 2000 and selected a sample of the four sectors. Following the empirical results, predicted wedges between energy price and the SV growth indicate a misallocation of energy use in stone, clay and glass (SCG) and communications (Com) sectors with more evidence in the SCG compared to the Com sector, showing overshoot in energy use relative to optimal paths and cost increases from sub-optimal energy use. The results show that energy productivity is a measure of technical efficiency and is void of information on the economic efficiency of energy use. Decomposing energy SV reveals that energy, capital and technology played key roles in energy SV increases helping to consider and analyze policy implications of energy efficiency improvement. Applying the marginal measure, we also

Marcasite revisited: Optical absorption gap at room temperature

NASA Astrophysics Data System (ADS)

Sánchez, C.; Flores, E.; Barawi, M.; Clamagirand, J. M.; Ares, J. R.; Ferrer, I. J.

2016-03-01

Jagadeesh and Seehra published in 1980 that the marcasite band gap energy is 0.34 eV. However, recent calculations and experimental approximations accomplished by several research groups point out that the marcasite band gap energy should be quite similar to that of pyrite (of the order of 0.8-1.0 eV). By using diffuse reflectance spectroscopy (DRS) we have determined that marcasite has no optical absorption gap at photon energies 0.06 ≤ hν ≤ 0.75 eV and that it has two well defined optical transitions at ~ 0.9 eV and ~ 2.2 eV quite similar to those of pyrite. Marcasite optical absorption gap appears to be Eg ≅ 0.83 ± 0.02 eV and it is due to an allowed indirect transition.

Simple intrinsic defects in GaP and InP

NASA Astrophysics Data System (ADS)

Schultz, Peter A.

2012-02-01

To faithfully simulate evolution of defect chemistry and electrical response in irradiated semiconductor devices requires accurate defect reaction energies and energy levels. In III-Vs, good data is scarce, theory hampered by band gap and supercell problems. I apply density functional theory (DFT) to intrinsic defects in GaP and InP, predicting stable charge states, ground state configurations, defect energy levels, and identifying mobile species. The SeqQuest calculations incorporate rigorous charge boundary conditions removing supercell artifacts, demonstrated converged to the infinite limit. Computed defect levels are not limited by a band gap problem, despite Kohn-Sham gaps much smaller than the experimental gap. As in GaAs, [P.A. Schultz and O.A. von Lilienfeld, Modeling Simul. Mater. Sci. Eng. 17, 084007 (2009)], defects in GaP and InP exhibit great complexity---multitudes of charge states, bistabilities, and negative U systems---but show similarities to each other (and to GaAs). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Studies on two-gap superconductivity in 2H-NbS2

NASA Astrophysics Data System (ADS)

Kačmarčík, J.; Pribulová, Z.; Marcenat, C.; Klein, T.; Rodière, P.; Cario, L.; Samuely, P.

2010-12-01

We present the ac-calorimetry measurements of superconducting 2H-NbS2 in the temperature range down to 0.6 K and magnetic fields up to 8 T. The temperature and magnetic field dependence of the electronic specific heat consistently indicate existence of two superconducting energy gaps in the system - one of them with the coupling ratio below the BCS weak-coupling limit and the other above that value. These results support previous findings by scanning tunneling microscopy and spectroscopy measurements [I. Guillamón, H. Suderow, S. Vieira, L. Cario, et al., Phys. Rev. Lett. 101 (2008) 166407] of two pronounced features in density of states related to a two-gap superconductivity in this system.

30 CFR 585.642 - How do I submit my GAP?

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 2 2013-07-01 2013-07-01 false How do I submit my GAP? 585.642 Section 585.642 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY... any project easement as part of your original GAP submission or as a revision to your GAP. ...

30 CFR 585.642 - How do I submit my GAP?

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 2 2012-07-01 2012-07-01 false How do I submit my GAP? 585.642 Section 585.642 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY... any project easement as part of your original GAP submission or as a revision to your GAP. ...

30 CFR 585.642 - How do I submit my GAP?

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 2 2014-07-01 2014-07-01 false How do I submit my GAP? 585.642 Section 585.642 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY... any project easement as part of your original GAP submission or as a revision to your GAP. ...

Band gaps and the possible effect on impact sensitivity for some nitro aromatic explosive materials

NASA Astrophysics Data System (ADS)

Zhang, Hong; Cheung, Frankie; Zhao, Feng; Cheng, Xin-Lu

The first principle density functional theory method SIESTA has been used to compute the band gap of several polynitroaromatic explosives, such as TATB, DATB, TNT, and picric acid. In these systems, the weakest bond is the one between an NO2 group and the aromatic ring. The bond dissociation energy (BDE) alone cannot predicate the relative sensitivity to impact of these four systems correctly. It was found that their relative impact sensitivity could be explained by considering the BDE and the band gap value of the crystal state together.

Electrical transport and optical band gap of NiFe2Ox thin films

NASA Astrophysics Data System (ADS)

Bougiatioti, Panagiota; Manos, Orestis; Klewe, Christoph; Meier, Daniel; Teichert, Niclas; Schmalhorst, Jan-Michael; Kuschel, Timo; Reiss, Günter

2017-12-01

We fabricated NiFe2Ox thin films on MgAl2O4(001) by reactive dc magnetron co-sputtering varying the oxygen partial pressure. The fabrication of a material with a variable oxygen deficiency leads to controllable electrical and optical properties which are beneficial for the investigations of the transport phenomena and could, therefore, promote the use of such materials in spintronic and spin caloritronic applications. We used several characterization techniques to investigate the film properties, focusing on their structural, magnetic, electrical, and optical properties. From the electrical resistivity, we obtained the conduction mechanisms that govern the systems in the high and low temperature regimes. We further extracted low thermal activation energies which unveil extrinsic transport mechanisms. The thermal activation energy decreases in the less oxidized samples revealing the pronounced contribution of a large amount of electronic states localized in the band gap to the electrical conductivity. The Hall coefficient is negative and decreases with increasing conductivity as expected for n-type conduction, while the Hall- and the drift mobilities show a large difference. The optical band gaps were determined via ultraviolet-visible spectroscopy. They follow a similar trend as the thermal activation energies, with lower band gap values in the less oxidized samples.

Subjective experience or objective process: understanding the gap between values and practice for involving patients in designing patient-centred care.

PubMed

Lord, Laura; Gale, Nicola

2014-01-01

Patient-centred care and patient involvement are increasingly central concepts in health policy in the UK and elsewhere. However, there is little consensus regarding their definition or how to achieve "patient-centred" care in everyday practice or how to involve patients in service redesign initiatives. The purpose of this paper is to explore these issues from the perspective of key stakeholders within National Health Service (NHS) hospitals in the UK. Semi-structured interviews, covering a range of topics related to service redesign, were conducted with 77 key stakeholders across three NHS Trusts in the West Midlands. In total, 20 of these stakeholders were re-interviewed 18 months later. Data were managed and analysed using the Framework Method. While patient-centred care and patient involvement were regularly cited as important to the stakeholders, a gap persisted between values and reported practice. This gap is explained through close examination of the ways in which the concepts were used by stakeholders, and identifying the way in which they were adapted to fit other organizational priorities. The value placed on positive subjective experience changed to concerns about objective measurement of the patients as they move through the system. Increased awareness and reflection on the conceptual tensions between objective processes and subjective experiences could highlight reasons why patient-centred values fail to translate into improved practice. The paper describes and explains a previously unarticulated tension in health organisations between values and practice in patient centred care and patient involvement in service redesign.

Family affection as a protective factor against the negative effects of perceived Asian values gap on the parent-child relationship for Asian American male and female college students.

PubMed

Park, Yong S; Vo, Leyna P; Tsong, Yuying

2009-01-01

The study examined whether family affection (i.e., affective responsiveness, affectionate communication, and affective orientation) protected against the negative effects of perceived parent-child Asian values gap on the quality of their parent relationships for 259 female and 77 male Asian American college students. Asian values gap was higher for women than men, and inversely related to a perceived healthy parent-child relationship for both genders. Participants rated the relationship with their mothers as more positive and affectionate than with their fathers. Both parents were reported to communicate more supportive affection than verbal and nonverbal affection. Affective responsiveness was identified as a protective factor in the father-son relationship whereas verbal affection protected the mother-daughter relationship. The study also revealed that daughters' affective orientation had beneficial effects on the father-daughter relationship at lower levels of Asian values gap. Clinical implications and directions for future research are discussed.

From free energy to expected energy: Improving energy-based value function approximation in reinforcement learning.

PubMed

Elfwing, Stefan; Uchibe, Eiji; Doya, Kenji

2016-12-01

Free-energy based reinforcement learning (FERL) was proposed for learning in high-dimensional state and action spaces. However, the FERL method does only really work well with binary, or close to binary, state input, where the number of active states is fewer than the number of non-active states. In the FERL method, the value function is approximated by the negative free energy of a restricted Boltzmann machine (RBM). In our earlier study, we demonstrated that the performance and the robustness of the FERL method can be improved by scaling the free energy by a constant that is related to the size of network. In this study, we propose that RBM function approximation can be further improved by approximating the value function by the negative expected energy (EERL), instead of the negative free energy, as well as being able to handle continuous state input. We validate our proposed method by demonstrating that EERL: (1) outperforms FERL, as well as standard neural network and linear function approximation, for three versions of a gridworld task with high-dimensional image state input; (2) achieves new state-of-the-art results in stochastic SZ-Tetris in both model-free and model-based learning settings; and (3) significantly outperforms FERL and standard neural network function approximation for a robot navigation task with raw and noisy RGB images as state input and a large number of actions. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

The strain induced band gap modulation from narrow gap semiconductor to half-metal on Ti{sub 2}CrGe: A first principles study

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

Li, Jia, E-mail: jiali@hebut.edu.cn; Research Institute for Energy Equipment Materials, Hebei University of Technology, Tianjin 300401; Zhang, Zhidong

The Heusler alloy Ti{sub 2}CrGe is a stable L2{sub 1} phase with antiferromagnetic ordering. With band-gap energy (∼ 0.18 eV) obtained from a first-principles calculation, it belongs to the group of narrow band gap semiconductor. The band-gap energy decreases with increasing lattice compression and disappears until a strain of −5%; moreover, gap contraction only occurs in the spin-down states, leading to half-metallic character at the −5% strain. The Ti{sub 1}, Ti{sub 2}, and Cr moments all exhibit linear changes in behavior within strains of −5%– +5%. Nevertheless, the total zero moment is robust for these strains. The imaginary part ofmore » the dielectric function for both up and down spin states shows a clear onset energy, indicating a corresponding electronic gap for the two spin channels.« less

Closing data gaps for LCA of food products: estimating the energy demand of food processing.

PubMed

Sanjuán, Neus; Stoessel, Franziska; Hellweg, Stefanie

2014-01-21

Food is one of the most energy and CO2-intensive consumer goods. While environmental data on primary agricultural products are increasingly becoming available, there are large data gaps concerning food processing. Bridging these gaps is important; for example, the food industry can use such data to optimize processes from an environmental perspective, and retailers may use this information for purchasing decisions. Producers and retailers can then market sustainable products and deliver the information demanded by governments and consumers. Finally, consumers are increasingly interested in the environmental information of foods in order to lower their consumption impacts. This study provides estimation tools for the energy demand of a representative set of food process unit operations such as dehydration, evaporation, or pasteurization. These operations are used to manufacture a variety of foods and can be combined, according to the product recipe, to quantify the heat and electricity demand during processing. In combination with inventory data on the production of the primary ingredients, this toolbox will be a basis to perform life cycle assessment studies of a large number of processed food products and to provide decision support to the stakeholders. Furthermore, a case study is performed to illustrate the application of the tools.

The energy trilogy: An integrated sustainability model to bridge wastewater treatment plant energy and emissions gaps

NASA Astrophysics Data System (ADS)

Al-Talibi, A. Adhim

An estimated 4% of national energy consumption is used for drinking water and wastewater services. Despite the awareness and optimization initiatives for energy conservation, energy consumption is on the rise owing to population and urbanization expansion and to commercial and industrial business advancement. The principal concern is since energy consumption grows, the higher will be the energy production demand, leading to an increase in CO2 footprints and the contribution to global warming potential. This research is in the area of energy-water nexus, focusing on wastewater treatment plant (WWTP) energy trilogy -- the group of three related entities, which includes processes: (1) consuming energy, (2) producing energy, and (3) the resulting -- CO2 equivalents. Detailed and measurable energy information is not readily obtained for wastewater facilities, specifically during facility preliminary design phases. These limitations call for data-intensive research approach on GHG emissions quantification, plant efficiencies and source reduction techniques. To achieve these goals, this research introduced a model integrating all plant processes and their pertinent energy sources. In a comprehensive and "Energy Source-to-Effluent Discharge" pattern, this model is capable of bridging the gaps of WWTP energy, facilitating plant designers' decision-making for meeting energy assessment, sustainability and the environmental regulatory compliance. Protocols for estimating common emissions sources are available such as for fuels, whereas, site-specific emissions for other sources have to be developed and are captured in this research. The dissertation objectives were met through an extensive study of the relevant literature, models and tools, originating comprehensive lists of processes and energy sources for WWTPs, locating estimation formulas for each source, identifying site specific emissions factors, and linking the sources in a mathematical model for site specific CO2 e

A Semi-parametric Multivariate Gap-filling Model for Eddy Covariance Latent Heat Flux

NASA Astrophysics Data System (ADS)

Li, M.; Chen, Y.

2010-12-01

Quantitative descriptions of latent heat fluxes are important to study the water and energy exchanges between terrestrial ecosystems and the atmosphere. The eddy covariance approaches have been recognized as the most reliable technique for measuring surface fluxes over time scales ranging from hours to years. However, unfavorable micrometeorological conditions, instrument failures, and applicable measurement limitations may cause inevitable flux gaps in time series data. Development and application of suitable gap-filling techniques are crucial to estimate long term fluxes. In this study, a semi-parametric multivariate gap-filling model was developed to fill latent heat flux gaps for eddy covariance measurements. Our approach combines the advantages of a multivariate statistical analysis (principal component analysis, PCA) and a nonlinear interpolation technique (K-nearest-neighbors, KNN). The PCA method was first used to resolve the multicollinearity relationships among various hydrometeorological factors, such as radiation, soil moisture deficit, LAI, and wind speed. The KNN method was then applied as a nonlinear interpolation tool to estimate the flux gaps as the weighted sum latent heat fluxes with the K-nearest distances in the PCs’ domain. Two years, 2008 and 2009, of eddy covariance and hydrometeorological data from a subtropical mixed evergreen forest (the Lien-Hua-Chih Site) were collected to calibrate and validate the proposed approach with artificial gaps after standard QC/QA procedures. The optimal K values and weighting factors were determined by the maximum likelihood test. The results of gap-filled latent heat fluxes conclude that developed model successful preserving energy balances of daily, monthly, and yearly time scales. Annual amounts of evapotranspiration from this study forest were 747 mm and 708 mm for 2008 and 2009, respectively. Nocturnal evapotranspiration was estimated with filled gaps and results are comparable with other studies

Closing the gap between research and management

Treesearch

Deborah M. Finch; Marcia Patton-Mallory

1993-01-01

In this paper, we evaluate the reasons for gaps in communication between researchers and natural resource managers and identify methods to close these gaps. Gaps originate from differing patterns of language use, disparities in organizational culture and values, generation of knowledge that is too narrowly-focused to solve complex problems, failure by managers to relay...

Impact of dietary fiber energy on the calculation of food total energy value in the Brazilian Food Composition Database.

PubMed

Menezes, Elizabete Wenzel de; Grande, Fernanda; Giuntini, Eliana Bistriche; Lopes, Tássia do Vale Cardoso; Dan, Milana Cara Tanasov; Prado, Samira Bernardino Ramos do; Franco, Bernadette Dora Gombossy de Melo; Charrondière, U Ruth; Lajolo, Franco Maria

2016-02-15

Dietary fiber (DF) contributes to the energy value of foods and including it in the calculation of total food energy has been recommended for food composition databases. The present study aimed to investigate the impact of including energy provided by the DF fermentation in the calculation of food energy. Total energy values of 1753 foods from the Brazilian Food Composition Database were calculated with or without the inclusion of DF energy. The energy values were compared, through the use of percentage difference (D%), in individual foods and in daily menus. Appreciable energy D% (⩾10) was observed in 321 foods, mainly in the group of vegetables, legumes and fruits. However, in the Brazilian typical menus containing foods from all groups, only D%<3 was observed. In mixed diets, the DF energy may cause slight variations in total energy; on the other hand, there is appreciable energy D% for certain foods, when individually considered. Copyright © 2015 Elsevier Ltd. All rights reserved.

Understanding band gaps of solids in generalized Kohn-Sham theory.

PubMed

Perdew, John P; Yang, Weitao; Burke, Kieron; Yang, Zenghui; Gross, Eberhard K U; Scheffler, Matthias; Scuseria, Gustavo E; Henderson, Thomas M; Zhang, Igor Ying; Ruzsinszky, Adrienn; Peng, Haowei; Sun, Jianwei; Trushin, Egor; Görling, Andreas

2017-03-14

The fundamental energy gap of a periodic solid distinguishes insulators from metals and characterizes low-energy single-electron excitations. However, the gap in the band structure of the exact multiplicative Kohn-Sham (KS) potential substantially underestimates the fundamental gap, a major limitation of KS density-functional theory. Here, we give a simple proof of a theorem: In generalized KS theory (GKS), the band gap of an extended system equals the fundamental gap for the approximate functional if the GKS potential operator is continuous and the density change is delocalized when an electron or hole is added. Our theorem explains how GKS band gaps from metageneralized gradient approximations (meta-GGAs) and hybrid functionals can be more realistic than those from GGAs or even from the exact KS potential. The theorem also follows from earlier work. The band edges in the GKS one-electron spectrum are also related to measurable energies. A linear chain of hydrogen molecules, solid aluminum arsenide, and solid argon provide numerical illustrations.

Understanding band gaps of solids in generalized Kohn–Sham theory

PubMed Central

Perdew, John P.; Yang, Weitao; Burke, Kieron; Yang, Zenghui; Gross, Eberhard K. U.; Scheffler, Matthias; Scuseria, Gustavo E.; Henderson, Thomas M.; Zhang, Igor Ying; Ruzsinszky, Adrienn; Peng, Haowei; Sun, Jianwei; Trushin, Egor; Görling, Andreas

2017-01-01

The fundamental energy gap of a periodic solid distinguishes insulators from metals and characterizes low-energy single-electron excitations. However, the gap in the band structure of the exact multiplicative Kohn–Sham (KS) potential substantially underestimates the fundamental gap, a major limitation of KS density-functional theory. Here, we give a simple proof of a theorem: In generalized KS theory (GKS), the band gap of an extended system equals the fundamental gap for the approximate functional if the GKS potential operator is continuous and the density change is delocalized when an electron or hole is added. Our theorem explains how GKS band gaps from metageneralized gradient approximations (meta-GGAs) and hybrid functionals can be more realistic than those from GGAs or even from the exact KS potential. The theorem also follows from earlier work. The band edges in the GKS one-electron spectrum are also related to measurable energies. A linear chain of hydrogen molecules, solid aluminum arsenide, and solid argon provide numerical illustrations. PMID:28265085

The effect of carbon nanotubes functionalization on the band-gap energy of TiO2-CNT nanocomposite

NASA Astrophysics Data System (ADS)

Shahbazi, Hessam; Shafei, Alireza; Sheibani, Saeed

2018-01-01

In this paper the morphology and structure of TiO2-CNT nanocomposite powder obtained by an in situ sol-gel process were investigated. The synthesized nanocomposite powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and diffuse reflectance spectroscopy (DRS). The effect of functionalizing of CNT on the properties was studied. XRD results showed amorphous structure before calcination. Also, anatase phase TiO2 was formed after calcination at 400 °C. The SEM results indicate different distributions of TiO2 on CNTs. As a result, well dispersed TiO2 microstructure on the surface of CNTs was observed after functionalizing, while compact and large aggregated particles were found without functionalizing. The average thickness of uniform and well-defined coated TiO2 layer was in the range of 30-40 nm. The DRS results have determined the reflective properties and band gap energies of nanocomposite powders and have shown that functionalizing of CNTs caused the change of band-gap energy from 2.98 to 2.87 eV.

A Quasi-Classical Model of the Hubbard Gap in Lightly Compensated Semiconductors

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

Poklonski, N. A.; Vyrko, S. A.; Kovalev, A. I.

2016-03-15

A quasi-classical method for calculating the narrowing of the Hubbard gap between the A{sup 0} and A{sup +} acceptor bands in a hole semiconductor or the D{sup 0} and D{sup –} donor bands in an electron semiconductor is suggested. This narrowing gives rise to the phenomenon of a semiconductor transition from the insulator to metal state with an increase in doping level. The major (doping) impurity can be in one of three charge states (–1, 0, or +1), while the compensating impurity can be in states (+1) or (–1). The impurity distribution over the crystal is assumed to be randommore » and the width of Hubbard bands (levels), to be much smaller than the gap between them. It is shown that narrowing of the Hubbard gap is due to the formation of electrically neutral acceptor (donor) states of the quasicontinuous band of allowed energies for holes (electrons) from excited states. This quasicontinuous band merges with the top of the valence band (v band) for acceptors or with the bottom of the conduction band (c band) for donors. In other words, the top of the v band for a p-type semiconductor or the bottom of the c band for an n-type semiconductor is shifted into the band gap. The value of this shift is determined by the maximum radius of the Bohr orbit of the excited state of an electrically neutral major impurity atom, which is no larger than half the average distance between nearest impurity atoms. As a result of the increasing dopant concentration, the both Hubbard energy levels become shallower and the gap between them narrows. Analytical formulas are derived to describe the thermally activated hopping transition of holes (electrons) between Hubbard bands. The calculated gap narrowing with increasing doping level, which manifests itself in a reduction in the activation energy ε{sub 2} is consistent with available experimental data for lightly compensated p-Si crystals doped with boron and n-Ge crystals doped with antimony.« less

Study on the characteristics of a two gap capillary discharge

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

Huang, D.; Yang, L. J., E-mail: yanglj@mail.xjtu.edu.cn; Huo, P.

2015-02-15

The paper presents a new two-gap capillary (TGC) discharge structure. The prominent innovation is the introduction of the middle electrode, which divides the capillary into the trigger gap and the main gap. The discharge circuit of the TGC comprises the trigger circuit and the main circuit. The two circuits are used for the pre-ionization of the trigger gap and providing energy of 450 J for the main gap arc discharging, respectively. When the discharge initiates, the trigger gap is pre-ionized under high voltage pulse produced by trigger circuit, and meanwhile, the weakly ionized plasma is generated. The main circuit then maintainsmore » the expansion of the plasma, which is called soft capillary discharge. Afterwards, the main gap is shorted and discharges under a relatively low voltage. With the optimization of the circuit parameter, both the energy deposition ratio in main gap and the degree of plasma ionization are enhanced. The efficiency of the energy deposition is almost twice higher compared with that of the conventional capillary structure. The life performance test indicates that the erosion of the middle electrode and the trigger gap carbonization are the key factors that limit the life performance of the TGC.« less

Energy gap opening by crossing drop cast single-layer graphene nanoribbons.

PubMed

Yamada, Toyo Kazu; Fukuda, Hideto; Fujiwara, Taizo; Liu, Polin; Nakamura, Kohji; Kasai, Seiya; Vazquez de Parga, Amadeo L; Tanaka, Hirofumi

2018-08-03

Band gap opening of a single-layer graphene nanoribbon (sGNR) sitting on another sGNR, fabricated by drop casting GNR solution on Au(111) substrate in air, was studied by means of scanning tunneling microscopy and spectroscopy in an ultra-high vacuum at 78 K and 300 K. GNRs with a width of ∼45 nm were prepared by unzipping double-walled carbon nanotubes (diameter ∼15 nm) using the ultrasonic method. In contrast to atomically-flat GNRs fabricated via the bottom-up process, the drop cast sGNRs were buckled on Au(111), i.e., some local points of the sGNR are in contact with the substrate (d ∼ 0.5 nm), but other parts float (d ∼ 1-3 nm), where d denotes the measured distance between the sGNR and the substrate. In spite of the fact that the nanoribbons were buckled, dI/dV maps confirmed that each buckled sGNR had a metallic character (∼3.5 G o ) with considerable uniform local density of states, comparable to a flat sGNR. However, when two sGNRs crossed each other, the crossed areas showed a band gap between -50 and +200 meV around the Fermi energy, i.e., the only upper sGNR electronic property changed from metallic to p-type semiconducting, which was not due to the bending, but the electronic interactions between the up and down sGNRs.

Cow's milk quality and energy value during different lactation stages.

PubMed

Salamończyk, Ewa

2013-01-01

The quality of dairy products, raw milk in particular, depends on many factors. Low bacterial and somatic cell counts are basic determinants of the appropriate raw milk quality. The objective of the work was to assess the effect of selected factors, that is, the age of cows and their daily milk performance, on cytological quality (somatic cell count) and energy value of milk produced at individual stages of lactation. Somatic cell count and energy value of cow's milk were assessed. A total of 229 792 milk samples were examined. Data for analysis were taken from milk records of 350 dairy herds. It was demonstrated that, of all the lactations studied, the fi rst lactation (from calving to the 100th day of lactation) was characterised by the highest daily milk performance (25.1 kg) and the lowest somatic cell count (356 thous./1 ml), fat, protein and dry matter contents (4.06, 2.96 and 12.41%, respectively) and milk calorific value (732 kcal/kg). The highest energy value was recorded in cow's milk produced towards the end of lactation, that is from day 300 till the end of lactation (842 kcal/kg). High milk calorific value in late lactation and high fat and protein contents were accompanied by low raw milk quality.

Energy band-gap calculations of short-period (ZnTe)m(ZnSe)n and (ZnS)m(ZnSe)n strained-layer superlattices

NASA Astrophysics Data System (ADS)

Wu, Yi-hong; Fujita, Shizuo; Fujita, Shigeo

1990-01-01

We report on the calculations of energy band gaps based on the semiempirical tight-binding model for short-period (ZnTe)m(ZnSe)n and (ZnS)m(ZnSe)n strained-layer superlattices (SLSs). During the calculation, much attention has been paid to the modeling of strain effect. It is found that (ZnTe)m(ZnSe)n superlattices grown on InAs, InP, and GaAs substrates show very different electronic properties from each other, which is consistent with experimental results now available. Assuming that the emission observed for (ZnTe)m(ZnSe)n SLS originates from intrinsic luminescence, we obtain an unstrained valence-band offset of 1.136±0.1 eV for this superlattice. On the other hand, the band gap of (ZnS)m(ZnSe)n superlattice grown coherently on GaP is found to exhibit a much stronger structure dependence than that grown coherently on GaAs. The difference of energy gap between superlattice with equal monolayers (m=n) and the corresponding alloy with equal chalcogenide composition is also discussed.

Understanding the carbon dioxide gaps.

PubMed

Scheeren, Thomas W L; Wicke, Jannis N; Teboul, Jean-Louis

2018-06-01

The current review attempts to demonstrate the value of several forms of carbon dioxide (CO2) gaps in resuscitation of the critically ill patient as monitor for the adequacy of the circulation, as target for fluid resuscitation and also as predictor for outcome. Fluid resuscitation is one of the key treatments in many intensive care patients. It remains a challenge in daily practice as both a shortage and an overload in intravascular volume are potentially harmful. Many different approaches have been developed for use as target of fluid resuscitation. CO2 gaps can be used as surrogate for the adequacy of cardiac output (CO) and as marker for tissue perfusion and are therefore a potential target for resuscitation. CO2 gaps are easily measured via point-of-care analysers. We shed light on its potential use as nowadays it is not widely used in clinical practice despite its potential. Many studies were conducted on partial CO2 pressure differences or CO2 content (cCO2) differences either alone, or in combination with other markers for outcome or resuscitation adequacy. Furthermore, some studies deal with CO2 gap to O2 gap ratios as target for goal-directed fluid therapy or as marker for outcome. CO2 gap is a sensitive marker of tissue hypoperfusion, with added value over traditional markers of tissue hypoxia in situations in which an oxygen diffusion barrier exists such as in tissue oedema and impaired microcirculation. Venous-to-arterial cCO2 or partial pressure gaps can be used to evaluate whether attempts to increase CO should be made. Considering the potential of the several forms of CO2 measurements and its ease of use via point-of-care analysers, it is recommendable to implement CO2 gaps in standard clinical practice.

Impact of Wind and Solar on the Value of Energy Storage

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

Denholm, Paul; Jorgenson, Jennie; Hummon, Marissa

2013-11-01

This analysis evaluates how the value of energy storage changes when adding variable generation (VG) renewable energy resources to the grid. A series of VG energy penetration scenarios from 16% to 55% were generated for a utility system in the western United States. This operational value of storage (measured by its ability to reduce system production costs) was estimated in each VG scenario, considering provision of different services and with several sensitivities to fuel price and generation mix. Overall, the results found that the presence of VG increases the value of energy storage by lowering off-peak energy prices more thanmore » on-peak prices, leading to a greater opportunity to arbitrage this price difference. However, significant charging from renewables, and consequently a net reduction in carbon emissions, did not occur until VG penetration was in the range of 40%-50%. Increased penetration of VG also increases the potential value of storage when providing reserves, mainly by increasing the amount of reserves required by the system. Despite this increase in value, storage may face challenges in capturing the full benefits it provides. Due to suppression of on-/off-peak price differentials, reserve prices, and incomplete capture of certain system benefits (such as the cost of power plant starts), the revenue obtained by storage in a market setting appears to be substantially less than the net benefit (reduction in production costs) provided to the system. Furthermore, it is unclear how storage will actually incentivize large-scale deployment of renewables needed to substantially increase VG penetration. This demonstrates some of the additional challenges for storage deployed in restructured energy markets.« less

The perceived value of using BIM for energy simulation

NASA Astrophysics Data System (ADS)

Lewis, Anderson M.

Building Information Modeling (BIM) is becoming an increasingly important tool in the Architectural, Engineering & Construction (AEC) industries. Some of the benefits associated with BIM include but are not limited to cost and time savings through greater trade and design coordination, and more accurate estimating take-offs. BIM is a virtual 3D, parametric design software that allows users to store information of a model within and can be used as a communication platform between project stakeholders. Likewise, energy simulation is an integral tool for predicting and optimizing a building's performance during design. Creating energy models and running energy simulations can be a time consuming activity due to the large number of parameters and assumptions that must be addressed to achieve reasonably accurate results. However, leveraging information imbedded within Building Information Models (BIMs) has the potential to increase accuracy and reduce the amount of time required to run energy simulations and can facilitate continuous energy simulations throughout the design process, thus optimizing building performance. Although some literature exists on how design stakeholders perceive the benefits associated with leveraging BIM for energy simulation, little is known about how perceptions associated with leveraging BIM for energy simulation differ between various green design stakeholder user groups. Through an e-survey instrument, this study seeks to determine how perceptions of using BIMs to inform energy simulation differ among distinct design stakeholder groups, which include BIM-only users, energy simulation-only users and BIM and energy simulation users. Additionally, this study seeks to determine what design stakeholders perceive as the main barriers and benefits of implementing BIM-based energy simulation. Results from this study suggest that little to no correlation exists between green design stakeholders' perceptions of the value associated with using

Graphene field effect transistor without an energy gap.

PubMed

Jang, Min Seok; Kim, Hyungjun; Son, Young-Woo; Atwater, Harry A; Goddard, William A

2013-05-28

Graphene is a room temperature ballistic electron conductor and also a very good thermal conductor. Thus, it has been regarded as an ideal material for postsilicon electronic applications. A major complication is that the relativistic massless electrons in pristine graphene exhibit unimpeded Klein tunneling penetration through gate potential barriers. Thus, previous efforts to realize a field effect transistor for logic applications have assumed that introduction of a band gap in graphene is a prerequisite. Unfortunately, extrinsic treatments designed to open a band gap seriously degrade device quality, yielding very low mobility and uncontrolled on/off current ratios. To solve this dilemma, we propose a gating mechanism that leads to a hundredfold enhancement in on/off transmittance ratio for normally incident electrons without any band gap engineering. Thus, our saw-shaped geometry gate potential (in place of the conventional bar-shaped geometry) leads to switching to an off state while retaining the ultrahigh electron mobility in the on state. In particular, we report that an on/off transmittance ratio of 130 is achievable for a sawtooth gate with a gate length of 80 nm. Our switching mechanism demonstrates that intrinsic graphene can be used in designing logic devices without serious alteration of the conventional field effect transistor architecture. This suggests a new variable for the optimization of the graphene-based device--geometry of the gate electrode.

Free energy gap laws for the pulse-induced and stationary fluorescence quenching by reversible charge transfer in polar solutions.

PubMed

Khokhlova, Svetlana S; Burshtein, Anatoly I

2011-01-21

The Stern-Volmer constants for either pulse-induced or stationary fluorescence being quenched by a contact charge transfer are calculated and their free energy dependencies (the free energy gap laws) are specified. The reversibility of charge transfer is taken into account as well as spin conversion in radical ion pairs, followed by their recombination in either singlet or triplet neutral products. The natural decay of triplets as well as their impurity quenching by ionization are accounted for when estimating the fluorescence quantum yield and its free energy dependence.

Multiple interactions and rapidity gap survival

NASA Astrophysics Data System (ADS)

Khoze, V. A.; Martin, A. D.; Ryskin, M. G.

2018-05-01

Observations of rare processes containing large rapidity gaps at high energy colliders may be exceptionally informative. However the cross sections of these events are small in comparison with that for the inclusive processes since there is a large probability that the gaps may be filled by secondary particles arising from additional soft interactions or from gluon radiation. Here we review the calculations of the probability that the gaps survive population by particles from these effects for a wide range of different processes.

Band Gap Engineering of Titania Systems Purposed for Photocatalytic Activity

NASA Astrophysics Data System (ADS)

Thurston, Cameron

Ab initio computer aided design drastically increases candidate population for highly specified material discovery and selection. These simulations, carried out through a first-principles computational approach, accurately extrapolate material properties and behavior. Titanium Dioxide (TiO2 ) is one such material that stands to gain a great deal from the use of these simulations. In its anatase form, titania (TiO2 ) has been found to exhibit a band gap nearing 3.2 eV. If titania is to become a viable alternative to other contemporary photoactive materials exhibiting band gaps better suited for the solar spectrum, then the band gap must be subsequently reduced. To lower the energy needed for electronic excitation, both transition metals and non-metals have been extensively researched and are currently viable candidates for the continued reduction of titania's band gap. The introduction of multicomponent atomic doping introduces new energy bands which tend to both reduce the band gap and recombination loss. Ta-N, Nb-N, V-N, Cr-N, Mo-N, and W-N substitutions were studied in titania and subsequent energy and band gap calculations show a favorable band gap reduction in the case of passivated systems.

Characteristics and dispersity of a two gap capillary discharge applied for long spark gap ignition in air

NASA Astrophysics Data System (ADS)

Huang, Dong; Yang, Lanjun; Guo, Haishan; Zhang, Zhiyuan; Jiang, Hongqiu; Xu, Haipeng

2017-07-01

In this paper, the characteristics and dispersity of a two gap capillary (TGC) discharge applied for long spark gap ignition are studied. Under the same discharge condition, 30 repetitive discharges are done to get a certain number of data samples. Accordingly, the change trend of the characteristics and the dispersity with the charging voltage of C1 are analyzed statistically. The delay of soft capillary discharge is determined by the saturation rate of the magnetic core of the pulse transformer and decreases with the increase in the charging voltage. The main discharge delay decreases from 1.0 kV to 2.0 kV and stops the decreasing trend when the charging voltage increases to 2.5 kV. In contrast, the current amplitude of soft capillary discharge and main discharge increases with charging voltage. Long tail extinction is witnessed at the charging voltage of 1.0 kV and the major cause is the insufficient pressure in the post discharge. The waveform of the capillary arc resistivity is U-like shape and the minimum resistivity decreases with the increase in the charging voltage. Meanwhile, the arc resistivity in the ascending stage is much higher than that in the descending stage with the same value of the discharge current. The energy consumption of the TGC discharge can be mainly divided into four parts and more than 70% of the energy is consumed in main discharge.

Pairing matrix elements and pairing gaps with bare, effective, and induced interactions

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

Barranco, F.; Bortignon, P.F.; Colo, G.

2005-11-01

The dependence on the single-particle states of the pairing matrix elements of the Gogny force and of the bare low-momentum nucleon-nucleon potential v{sub low-k}--designed so as to reproduce the low-energy observables avoiding the use of a repulsive core--is studied for a typical finite, superfluid nucleus ({sup 120}Sn). It is found that the matrix elements of v{sub low-k} follow closely those of v{sub Gogny} on a wide range of energy values around the Fermi energy e{sub F}, those associated with v{sub low-k} being less attractive. This result explains the fact that around e{sub F} the pairing gap {delta}{sub Gogny} associated withmore » the Gogny interaction (and with a density of single-particle levels corresponding to an effective k mass m{sub k}{approx_equal}0.7 m) is a factor of about 2 larger than {delta}{sub low-k}, being in agreement with {delta}{sub exp}=1.4 MeV. The exchange of low-lying collective surface vibrations among pairs of nucleons moving in time-reversal states gives rise to an induced pairing interaction v{sub ind} peaked at e{sub F}. The interaction (v{sub low-k}+v{sub ind}) Z{sub {omega}} arising from the renormalization of the bare nucleon-nucleon potential and of the single-particle motion ({omega}-mass and quasiparticle strength Z{sub {omega}}) associated with the particle-vibration coupling mechanism, leads to a value of the pairing gap at the Fermi energy {delta}{sub ren} that accounts for the experimental value. An important question that remains to be studied quantitatively is to what extent {delta}{sub Gogny}, which depends on average parameters, and {delta}{sub ren}, which explicitly depends on the parameters describing the (low-energy) nuclear structure, display or not a similar isotopic dependence and whether this dependence is borne out by the data.« less

Effect of solvents on optical band gap of silicon-doped graphene oxide

NASA Astrophysics Data System (ADS)

Tul Ain, Qura; Al-Modlej, Abeer; Alshammari, Abeer; Naeem Anjum, Muhammad

2018-03-01

The objective of this study was to determine the influence on the optical band gap when the same amount of silicon-doped graphene oxide was dissolved in three different solvents namely, distilled water, benzene, and dichloroethane. Ultraviolet-visible spectroscopy was used to analyse the optical properties of the solutions. Among all these solutions distilled water containing silicon-doped graphene oxide has the smallest optical band gap of 2.9 eV and is considered a semiconductor. Other solutions are not considered as semiconductors as they have optical band gaps greater than 4 eV. It was observed that there is an increase in the value of optical band gap of distilled water, benzene, and dichloroethane solutions indicating a rise in the insulating behaviour. In this experiment, graphene oxide was synthesised from graphite powder by modified Hummer’s method and was then doped with silicon. Synthesis and doping of graphene oxide were confirmed by various characterization techniques. Fourier transmission infrared spectroscopy was used for identification of surface functional groups. X-ray diffraction was carried out to confirm the formation of crystalline graphene oxide and silicon doped graphene oxide. In x-ray diffraction pattern, shifting of intensity peak from a 2θ value of 26.5° to 10° confirmed the synthesis of graphene oxide and various intensity peaks at different values of 2θ confirmed doping of graphene oxide with silicon. Scanning electron microscopy images indicated that graphene oxide sheets were decorated with spherical silicon nanoparticles. Energy dispersive x-ray spectroscopy showed that silicon doped graphene oxide powder contained 63.36% carbon, 34.05% oxygen, and 2.6% silicon.

To Close the Skills Gap, Re-Value the Associate Degree

ERIC Educational Resources Information Center

Custodia-Lora, Noemi; Glenn, Lane A.; Legg, David R.

2012-01-01

A number of economists, policymakers, elected officials, and employers cite a "skills gap" as the reason the nation is not putting more people back to work. The problem, they reason, is that too many people have the wrong skills for today's jobs, and colleges and universities are not doing enough to prepare people with the right skills.…

The temperature-dependency of the optical band gap of ZnO measured by electron energy-loss spectroscopy in a scanning transmission electron microscope

NASA Astrophysics Data System (ADS)

Granerød, Cecilie S.; Galeckas, Augustinas; Johansen, Klaus Magnus; Vines, Lasse; Prytz, Øystein

2018-04-01

The optical band gap of ZnO has been measured as a function of temperature using Electron Energy-Loss Spectroscopy (EELS) in a (Scanning) Transmission Electron Microscope ((S)TEM) from approximately 100 K up towards 1000 K. The band gap narrowing shows a close to linear dependency for temperatures above 250 K and is accurately described by Varshni, Bose-Einstein, Pässler and Manoogian-Woolley models. Additionally, the measured band gap is compared with both optical absorption measurements and photoluminescence data. STEM-EELS is here shown to be a viable technique to measure optical band gaps at elevated temperatures, with an available temperature range up to 1500 K and the benefit of superior spatial resolution.

Correcting the anion gap for hypoalbuminaemia does not improve detection of hyperlactataemia

PubMed Central

Dinh, C H; Ng, R; Grandinetti, A; Joffe, A; Chow, D C

2006-01-01

Background An elevated lactate level reflects impaired tissue oxygenation and is a predictor of mortality. Studies have shown that the anion gap is inadequate as a screen for hyperlactataemia, particularly in critically ill and trauma patients. A proposed explanation for the anion gap's poor sensitivity and specificity in detecting hyperlactataemia is that the serum albumin is frequently low. This study therefore, sought to compare the predictive values of the anion gap and the anion gap corrected for albumin (cAG) as an indicator of hyperlactataemia as defined by a lactate ⩾2.5 mmol/l. Methods A retrospective review of 639 sets of laboratory values from a tertiary care hospital. Patients' laboratory results were included in the study if serum chemistries and lactate were drawn consecutively. The sensitivity, specificity, and predictive values were obtained. A receiver operator characteristics curve (ROC) was drawn and the area under the curve (AUC) was calculated. Results An anion gap ⩾12 provided a sensitivity, specificity, positive predictive value, and negative predictive value of 39%, 89%, 79%, and 58%, respectively, and a cAG ⩾12 provided a sensitivity, specificity, positive predictive value, and negative predictive value of 75%, 59%, 66%, and 69%, respectively. The ROC curves between anion gap and cAG as a predictor of hyperlactataemia were almost identical. The AUC was 0.757 and 0.750, respectively. Conclusions The sensitivities, specificities, and predictive values of the anion gap and cAG were inadequate in predicting the presence of hyperlactataemia. The cAG provides no additional advantage over the anion gap in the detection of hyperlactataemia. PMID:16858097

A method to estimate the additional uncertainty in gap-filled NEE resulting from long gaps in the CO2 flux record

Treesearch

Andrew D. Richardson; David Y. Hollinger

2007-01-01

Missing values in any data set create problems for researchers. The process by which missing values are replaced, and the data set is made complete, is generally referred to as imputation. Within the eddy flux community, the term "gap filling" is more commonly applied. A major challenge is that random errors in measured data result in uncertainty in the gap-...

Optical properties of II-VI structures for solar energy utilization

NASA Astrophysics Data System (ADS)

Schrier, Joshua; Demchenko, Denis; Wang, Lin-Wang

2007-03-01

Although II-VI semiconductor materials are abundant, stable, and have direct band gaps, the band gaps are too large for optimal photovoltaic efficiency. However, staggered band alignments of pairs of these materials, and also the formation of intermediate impurity levels in the band gap (which has been demonstrated to increase the efficiency as compared to both single-junction devices), could be utilized to improve the suitability of these materials for solar energy utilization. Previous theoretical studies of these materials are limited, due to the well-known band gap underestimation by density-functional theory. To calculate the absorption spectra, we utilize a band-corrected planewave pseudopotential approach, which gives agreements of within 0.1 eV of the bulk optical gaps values. In this talk, I will present our work on predicting the optical properties of ZnO/ZnS and ZnO/ZnTe heterostructures, nanostructures, and alloys. This work was supported by U.S. Department of Energy under Contract No.DE-AC02-05CH11231 and used the resources of the National Energy Research Scientific Computing Center.

Tuning the energy band gap of ternary alloyed Cd1-xPbxS quantum dots for photovoltaic applications

NASA Astrophysics Data System (ADS)

Badawi, Ali

2016-02-01

Tuning the energy band gap of ternary alloyed Cd1-xPbxS (x: 0, 0.33, 0.5, 0.67 and 1) quantum dots (QDs) for photovoltaic applications is studied. Alloyed Cd1-xPbxS QDs were adsorbed onto TiO2 nanoparticles (NPs) using ssuccessive ionic layer adsorption and reaction (SILAR) methode. EDX measurements ensure the success adsorption of alloyed Cd1-xPbxS QDs onto the TiO2 electrode. At 100 mW/cm2 (AM 1.5) sun illumination, the photovoltaic performance of alloyed Cd1-xPbxS QDs sensitized solar cells (QDSSCs) was measured. The maximum values of Jsc (1.92 mA/cm2) and η (0.36%) for the alloyed Cd1-xPbxS QDSSCs were obtained when the molar ratio of Cd/Pb is 0.33/0.67. the open circuit voltage (Voc) is equal 0.61 ± 0.01 V for all alloyed Cd1-xPbxS QDSSCs. The electron back recombination rates decrease considerably for alloyed Cd1-xPbxS QDSSCs as x value increases, peaking at 0.67. The electron lifetime (τ) for Cd0.33Pb0.67S QDSSCs is one order of magnitude larger than that of the other alloyed Cd1-xPbxS QDSSCs with different x value. Under ON-OFF cycles to solar illumination, the open circuit voltage decay measurements show the high sensitivity and reproducibility of alloyed Cd1-xPbxS QDSSCs.

A Low-Energy-Gap Thienochrysenocarbazole Dye for Highly Efficient Mesoscopic Titania Solar Cells: Understanding the Excited State and Charge Carrier Dynamics.

PubMed

Wang, Junting; Xie, Xinrui; Weng, Guorong; Yuan, Yi; Zhang, Jing; Wang, Peng

2018-05-09

Maintaining both a high external quantum efficiency and a large open-circuit photovoltage of dye-sensitized solar cells (DSSCs) is a crucial challenge in the process of developing narrow-energy-gap dyes for the capture of infrared solar photons. Herein, we report two donor-acceptor organic dyes, C294 and C295, with a polycyclic heteroaromatic unit, 6,11-dihydrothieno[3',2':8,9]chryseno[10,11,12,1-bcdefg]carbazole (TCC), as the central module of the electron donor, and ethylbenzothiadiazole-benzioc acid as the electron acceptor. The interfacial charge recombination was successfully mitigated by introducing an additional branched aliphatic chain in C295. Furthermore, the O⋅⋅⋅S nonbonding interaction between the oxygen atom of the alkoxy group and the sulfur atom of the thiophene in C295 controlled the conformation of C295, resulting in a narrow energy-gap. Time-resolved spectroscopic measurements on C294 and the model dye C272 indicated that the elevation of the HOMO energy level decreased the kinetics and yield of hole injection owing to a reduction in the driving force and that the shortened excited-state lifetime caused by the narrowing of the energy gap was unfavorable for electron injection. By fine tuning the composition of the electrolyte, C294 and C295 eventually achieved high power conversion efficiencies of 11.5 % and 12.4 %, respectively, under full sunlight of air mass 1.5 global conditions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The prognostic value of the strong ion gap in acute pancreatitis.

PubMed

Shen, Xiao; Ke, Lu; Yang, Dongliang; Sun, Jing; Tong, Zhihui; Li, Baiqiang; Li, Gang; Li, Weiqin; Li, Jieshou; Bellomo, Rinaldo

2016-12-01

In this study, we aimed to evaluate the predictive value of Stewart-derived parameters for the development of severe type of acute pancreatitis (AP) and for AP-related mortality. We studied 186 patients admitted to the hospital with AP. We performed blood gas and biochemical analysis for each patient on admission. We calculated multiple metrics according to the Stewart's acid-base theory and assessed their accuracy as predictors of AP severity and mortality. Of the 186 patients presenting with AP, 85 (45.7%) developed severe AP and 33 (17.7%) died during hospitalization. Patients with severe AP had significantly higher median strong ion gap (SIG) than did patients with mild or moderate AP (7.88 vs 2.11 mEq/L, P< .001). In multivariate logistic regression analysis, SIG had an odds ratio (OR) of 1.56 (P< .001). In addition, SIG had good predictive power for mortality (OR, 1.26; P= .014) as well as acute kidney injury (OR, 1.34; P< .001). In a cohort of patients with AP, SIG was a strong independent predictor of severity and mortality. Besides, SIG might also be an early marker for acute kidney injury in AP patients. Additional research is needed to identify the nature of the unmeasured anions responsible for such findings. Copyright © 2016 Elsevier Inc. All rights reserved.

True metabolisable energy, heat increment and net energy values of two high fibre foodstuffs in cockerels.

PubMed

Sarmiento-Franco, L; MacLeod, M G; McNab, J M

2000-12-01

1. The yields of true metabolisable energy (TME) and net energy (NE) from chaya leaf meal and wheatfeed were mcasured in tube-fed cockerels. 2. TME, 5.76 MJ/kg, from chava leaf meal was lower than from wheatfeed, 8.39 MJ/kg. The total heat increment attributable to the feeding of chaya leaf meal was 1-7 times greater than that of wheatfeed. 3. The net efficiency of utilisation of ME (k) from chaya leaf meal was 0.64, while that from wheatfeed was 0.86. The role of different chemical composition, especially the high fibre content of the materials, is discussed. 4. The metabolisable energy and net energy values derived from chava leaf meal represented 0.34 and 0.23 respectively of its gross energy content. The combination of lower TME and lower net efficiency of utilisation led to chaya having a NE value, 3.86 MJ/kg, which was only 0.53 that of wheatfeed.

Linear Scaling of the Exciton Binding Energy versus the Band Gap of Two-Dimensional Materials

NASA Astrophysics Data System (ADS)

Choi, Jin-Ho; Cui, Ping; Lan, Haiping; Zhang, Zhenyu

2015-08-01

The exciton is one of the most crucial physical entities in the performance of optoelectronic and photonic devices, and widely varying exciton binding energies have been reported in different classes of materials. Using first-principles calculations within the G W -Bethe-Salpeter equation approach, here we investigate the excitonic properties of two recently discovered layered materials: phosphorene and graphene fluoride. We first confirm large exciton binding energies of, respectively, 0.85 and 2.03 eV in these systems. Next, by comparing these systems with several other representative two-dimensional materials, we discover a striking linear relationship between the exciton binding energy and the band gap and interpret the existence of the linear scaling law within a simple hydrogenic picture. The broad applicability of this novel scaling law is further demonstrated by using strained graphene fluoride. These findings are expected to stimulate related studies in higher and lower dimensions, potentially resulting in a deeper understanding of excitonic effects in materials of all dimensionalities.

Public Constructs of Energy Values and Behaviors in Implementing Taiwan's "Energy-Conservation/Carbon-Reduction" Declarations

ERIC Educational Resources Information Center

Chiu, Mei-Shiu; Yeh, Huei-Ming; Spangler, Jonathan

2016-01-01

The emergent crisis of global warming calls for energy education for people of all ages and social groups. The Taiwanese government has publicized 10 declarations on energy conservation and carbon reduction as public behavior guidelines to mitigate global warming. This study uses interviews with quantitative assessment to explore the values and…

Energy gap states and tunneling currents in semiconducting graphene

NASA Astrophysics Data System (ADS)

Szczesniak, Dominik; Hoehn, Ross; Kais, Sabre

It has been predicted that when graphene is supported on a substrate or doped with foreign atom species, the inherent linear electronic dispersion of its pristine form can be strongly altered. Worthy of special attention is the situation when the interactions between graphene and the substrate or dopants lead to an opening of the finite electronic gap in the fermionic spectrum of this nano-material, and strongly influence its transport and optical properties. Herein, the fundamental electronic transport properties of such perturbed graphene are discussed in the framework of the complex band structure analysis, which not only accounts for the propagating but also the evanescent electronic states. Various scenarios responsible for the band gap opening and manipulation of its characteristics are considered, these considerations may entirely account for the aforementioned perturbations to the pristine graphene. It is shown, that the these perturbations are responsible for inducing gap states which allow electrons to directly tunnel between the conduction and valence bands in perturbed graphene. The resulting tunneling states are analyzed in a comprehensive manner, suggesting their great importance for the transport processes across graphene-based semiconducting nanostructures.

Design, conditioning, and performance of a high voltage, high brightness dc photoelectron gun with variable gap

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

Maxson, Jared; Bazarov, Ivan; Dunham, Bruce

2014-09-15

A new high voltage photoemission gun has been constructed at Cornell University which features a segmented insulator and a movable anode, allowing the cathode-anode gap to be adjusted. In this work, we describe the gun's overall mechanical and high voltage design, the surface preparation of components, as well as the clean construction methods. We present high voltage conditioning data using a 50 mm cathode-anode gap, in which the conditioning voltage exceeds 500 kV, as well as at smaller gaps. Finally, we present simulated emittance results obtained from a genetic optimization scheme using voltage values based on the conditioning data. Thesemore » results indicate that for charges up to 100 pC, a 30 mm gap at 400 kV has equal or smaller 100% emittance than a 50 mm gap at 450 kV, and also a smaller core emittance, when placed as the source for the Cornell energy recovery linac photoinjector with bunch length constrained to be <3 ps rms. For 100 pC up to 0.5 nC charges, the 50 mm gap has larger core emittance than the 30 mm gap, but conversely smaller 100% emittance.« less

Superconducting gap symmetry in the superconductor BaFe1.9Ni0.1As2

NASA Astrophysics Data System (ADS)

Kuzmicheva, T. E.; Kuzmichev, S. A.; Sadakov, A. V.; Gavrilkin, S. Yu.; Tsvetkov, A. Yu.; Lu, X.; Luo, H.; Vasiliev, A. N.; Pudalov, V. M.; Chen, Xiao-Jia; Abdel-Hafiez, Mahmoud

2018-06-01

We report on the Andreev spectroscopy and specific heat of high-quality single crystals of BaFe1.9Ni0.1As2 . The intrinsic multiple Andreev reflection spectroscopy reveals two anisotropic superconducting gaps ΔL≈3.2 -4.5 meV , ΔS≈1.2 -1.6 meV (the ranges correspond to the minimum and maximum value of the coupling energy in the kxky plane). The 25 %-30 % anisotropy shows the absence of nodes in the superconducting gaps. Using a two-band model with s -wave-like gaps ΔL≈3.2 meV and ΔS≈1.6 meV , the temperature dependence of the electronic specific heat can be well described. A linear magnetic field dependence of the low-temperature specific heat offers further support of s -wave type of the order parameter. We find that a d -wave or single-gap BCS theory under the weak-coupling approach cannot describe our experiments.

Width-Dependent Band Gap in Armchair Graphene Nanoribbons Reveals Fermi Level Pinning on Au(111)

PubMed Central

2017-01-01

We report the energy level alignment evolution of valence and conduction bands of armchair-oriented graphene nanoribbons (aGNR) as their band gap shrinks with increasing width. We use 4,4″-dibromo-para-terphenyl as the molecular precursor on Au(111) to form extended poly-para-phenylene nanowires, which can subsequently be fused sideways to form atomically precise aGNRs of varying widths. We measure the frontier bands by means of scanning tunneling spectroscopy, corroborating that the nanoribbon’s band gap is inversely proportional to their width. Interestingly, valence bands are found to show Fermi level pinning as the band gap decreases below a threshold value around 1.7 eV. Such behavior is of critical importance to understand the properties of potential contacts in GNR-based devices. Our measurements further reveal a particularly interesting system for studying Fermi level pinning by modifying an adsorbate’s band gap while maintaining an almost unchanged interface chemistry defined by substrate and adsorbate. PMID:29049879

Multi-energy spectral CT: adding value in emergency body imaging.

PubMed

Punjabi, Gopal V

2018-04-01

Most vendors offer scanners capable of dual- or multi-energy computed tomography (CT) imaging. Advantages of multi-energy CT scanning include superior tissue characterization, detection of subtle iodine uptake differences, and opportunities to reduce contrast dose. However, utilization of this technology in the emergency department (ED) remains low. The purpose of this pictorial essay is to illustrate the value of multi-energy CT scanning in emergency body imaging.

Western values and the Russian energy weapon

NASA Astrophysics Data System (ADS)

Domingues, Bennett K.

become heavily involved in oil and gas extraction projects in the region, in particular in Kazakhstan. Yet, efforts to transport that energy to western markets without Russian involvement have met with strong resistance. This thesis demonstrates that part of the reason western firms have been less successful than they hoped to be is because western firms, in particular American firms, are so bound by western ethical norms and the statues that codify them, that they have lost their competitive advantage. The thesis concludes with a discussion of the current day balance of energy resources in Europe, noting that Europe is rapidly growing heavily dependent on Russian oil and gas resources. Given the precedents shown in Georgia and Ukraine, it is only a matter of time before Europe grows so dependent on Russian energy that the individual countries will lose their political and economic independence and in turn, their ability to project western values and values-based ideas throughout the world with impunity.

Optical band gap studies on lithium aluminum silicate glasses doped with Cr3+ ions

NASA Astrophysics Data System (ADS)

El-Diasty, Fouad; Abdel Wahab, Fathy A.; Abdel-Baki, Manal

2006-11-01

Lithium aluminum silicate glass system (LAS) implanted with chromium ions is prepared. The reflectance and transmittance measurements are used to determine the dispersion of absorption coefficient. The optical data are explained in terms of the different oxidation states adopted by the chromium ions into the glass network. It is found that the oxidation state of the chromium depends on its concentration. Across a wide spectral range, 0.2-1.6μm, analysis of the fundamental absorption edge provides values for the average energy band gaps for allowed direct and indirect transitions. The optical absorption coefficient just below the absorption edge varies exponentially with photon energy indicating the presence of Urbach's tail. Such tail is decreased with the increase of the chromium dopant. From the analysis of the optical absorption data, the absorption peak at ground state exciton energy, the absorption at band gap, and the free exciton binding energy are determined. The extinction coefficient data are used to determine the Fermi energy level of the studied glasses. The metallization criterion is obtained and discussed exploring the nature of the glasses. The measured IR spectra of the different glasses are used to throw some light on the optical properties of the present glasses correlating them with their structure and composition.

The Expanded Large Scale Gap Test

DTIC Science & Technology

1987-03-01

NSWC TR 86-32 DTIC THE EXPANDED LARGE SCALE GAP TEST BY T. P. LIDDIARD D. PRICE RESEARCH AND TECHNOLOGY DEPARTMENT ’ ~MARCH 1987 Ap~proved for public...arises, to reduce the spread in the LSGT 50% gap value.) The worst charges, such as those with the highest or lowest densities, the largest re-pressed...Arlington, VA 22217 PE 62314N INS3A 1 RJ14E31 7R4TBK 11 TITLE (Include Security CIlmsilficatiorn The Expanded Large Scale Gap Test . 12. PEIRSONAL AUTHOR() T

Design of a gap tunable flux qubit with FastHenry

NASA Astrophysics Data System (ADS)

Akhtar, Naheed; Zheng, Yarui; Nazir, Mudassar; Wu, Yulin; Deng, Hui; Zheng, Dongning; Zhu, Xiaobo

2016-12-01

In the preparations of superconducting qubits, circuit design is a vital process because the parameters and layout of the circuit not only determine the way we address the qubits, but also strongly affect the qubit coherence properties. One of the most important circuit parameters, which needs to be carefully designed, is the mutual inductance among different parts of a superconducting circuit. In this paper we demonstrate how to design a gap-tunable flux qubit by layout design and inductance extraction using a fast field solver FastHenry. The energy spectrum of the gap-tunable flux qubit shows that the measured parameters are close to the design values. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374344, 11404386, and 91321208), the National Basic Research Program of China (Grant No. 2014CB921401), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB07010300).

Self-Interaction Corrected Electronic Structure and Energy Gap of CuAlO2 beyond Local Density Approximation

NASA Astrophysics Data System (ADS)

Nakanishi, Akitaka

2011-05-01

We implemented a self-interaction correction (SIC) into first-principles calculation code to go beyond local density approximation and applied it to CuAlO2. Our simulation shows that the valence band width calculated within the SIC is narrower than that calculated without the SIC because the SIC makes the d-band potential deeper. The energy gap calculated within the SIC expands and is close to experimental data.

Replica and extreme-value analysis of the Jarzynski free-energy estimator

NASA Astrophysics Data System (ADS)

Palassini, Matteo; Ritort, Felix

2008-03-01

We analyze the Jarzynski estimator of free-energy differences from nonequilibrium work measurements. By a simple mapping onto Derrida's Random Energy Model, we obtain a scaling limit for the expectation of the bias of the estimator. We then derive analytical approximations in three different regimes of the scaling parameter x = log(N)/W, where N is the number of measurements and W the mean dissipated work. Our approach is valid for a generic distribution of the dissipated work, and is based on a replica symmetry breaking scheme for x >> 1, the asymptotic theory of extreme value statistics for x << 1, and a direct approach for x near one. The combination of the three analytic approximations describes well Monte Carlo data for the expectation value of the estimator, for a wide range of values of N, from N=1 to large N, and for different work distributions. Based on these results, we introduce improved free-energy estimators and discuss the application to the analysis of experimental data.

Energy Value Housing Award Guide: How to Build and Profit with Energy Efficiency in New Home Construction

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

Sikora, J. L.

2001-06-01

As concern over the environment grows, builders have the potential to fulfill a market niche by building homes that use fewer resources and have lower environmental impact than conventional construction. Builders can increase their marketability and customer satisfaction and, at the same time, reduce the environmental impact of their homes. However, it takes dedication to build environmentally sound homes along with a solid marketing approach to ensure that customers recognize the added value of energy and resource efficiency. This guide is intended for builders seeking suggestions on how to improve energy and resource efficiency in their new homes. It ismore » a compilation of ideas and concepts for designing, building, and marketing energy- and resource-efficient homes based on the experience of recipients of the national Energy Value Housing Award (EVHA).« less

Low-Symmetry Gap Functions of Organic Superconductors

NASA Astrophysics Data System (ADS)

Mori, Takehiko

2018-04-01

Superconducting gap functions of various low-symmetry organic superconductors are investigated starting from the tight-binding energy band and the random phase approximation by numerically solving Eliashberg's equation. The obtained singlet gap function is approximately represented by an asymmetrical dx2 - y2 form, where two cosine functions are mixed in an appropriate ratio. This is usually called d + s wave, where the ratio of the two cosine functions varies from 1:1 in the two-dimensional limit to 1:0 in the one-dimensional limit. A single cosine function does not make a superconducting gap in an ideal one-dimensional conductor, but works as a relevant gap function in quasi-one-dimensional conductors with slight interchain transfer integrals. Even when the Fermi surface is composed of small pockets, the gap function is obtained supposing a globally connected elliptical Fermi surface. In such a case, we have to connect the second energy band in the second Brillouin zone. The periodicity of the resulting gap function is larger than the first Brillouin zone. This is because the susceptibility has peaks at 2kF, where the periodicity has to be twice the size of the global Fermi surface. In general, periodicity of gap function corresponds to one electron or two molecules in the real space. In the κ-phase, two axes are nonequivalent, but the exact dx2 - y2 symmetry is maintained because the diagonal transfer integral introduced to a square lattice is oriented to the node direction of the dx2 - y2 wave. By contrast, the θ-phase gap function shows considerable anisotropy because a quarter-filled square lattice has a different dxy symmetry.

Latitude character and evolution of Gnevyshev gap

NASA Astrophysics Data System (ADS)

Pandey, K. K.; Hiremath, K. M.; Yellaiah, G.

2017-06-01

The time interval, between two highest peaks of the sunspot maximum, during which activity energy substantially absorbed is called Gnevyshev gap. In this study we focus on mysterious evolution of the Gnevyshev gap by analyzing and comparing the integrated (over the whole Sun) characteristics of magnetic field strength of sunspot groups, soft x-ray flares, filaments or prominences and polar faculae. The time latitude distribution of these solar activities from photosphere to coronal height, for the low (≤50°) and high (≥50°) latitudes, shows the way Gnevyshev gap is evolved. The presence of double peak structure is noticed in high latitude (≥50°) activity. During activity maximum the depression (or valley) appearing, in different activity processes, probably due to shifting, spreading, and transfer of energy from higher to lower latitudes with the progress of solar cycle. The morphology of successive lower latitude zones, considering it as a wave pulse, appears to be modified/scattered, by certain degree due to shifting of magnetic energy to empower higher or lower latitudes.

Gap-minimal systems of notations and the constructible hierarchy

NASA Technical Reports Server (NTRS)

Lucian, M. L.

1972-01-01

If a constructibly countable ordinal alpha is a gap ordinal, then the order type of the set of index ordinals smaller than alpha is exactly alpha. The gap ordinals are the only points of discontinuity of a certain ordinal-valued function. The notion of gap minimality for well ordered systems of notations is defined, and the existence of gap-minimal systems of notations of arbitrarily large constructibly countable length is established.

How does the plasmonic enhancement of molecular absorption depend on the energy gap between molecular excitation and plasmon modes: a mixed TDDFT/FDTD investigation.

PubMed

Sun, Jin; Li, Guang; Liang, WanZhen

2015-07-14

A real-time time-dependent density functional theory coupled with the classical electrodynamics finite difference time domain technique is employed to systematically investigate the optical properties of hybrid systems composed of silver nanoparticles (NPs) and organic adsorbates. The results demonstrate that the molecular absorption spectra throughout the whole energy range can be enhanced by the surface plasmon resonance of Ag NPs; however, the absorption enhancement ratio (AER) for each absorption band differs significantly from the others, leading to the quite different spectral profiles of the hybrid complexes in contrast to those of isolated molecules or sole NPs. Detailed investigations reveal that the AER is sensitive to the energy gap between the molecular excitation and plasmon modes. As anticipated, two separate absorption bands, corresponding to the isolated molecules and sole NPs, have been observed at a large energy gap. When the energy gap approaches zero, the molecular excitation strongly couples with the plasmon mode to form the hybrid exciton band, which possesses the significantly enhanced absorption intensity, a red-shifted peak position, a surprising strongly asymmetric shape of the absorption band, and the nonlinear Fano effect. Furthermore, the dependence of surface localized fields and the scattering response functions (SRFs) on the geometrical parameters of NPs, the NP-molecule separation distance, and the external-field polarizations has also been depicted.

The Los Alamos Gap Stick Test

NASA Astrophysics Data System (ADS)

Preston, Daniel; Hill, Larry; Johnson, Carl

2015-06-01

In this paper we describe a novel shock sensitivity test, the Gap Stick Test, which is a generalized variant of the ubiquitous Gap Test. Despite the popularity of the Gap Test, it has some disadvantages: multiple tests must be fired to obtain a single metric, and many tests must be fired to obtain its value to high precision and confidence. Our solution is a test wherein multiple gap tests are joined in series to form a rate stick. The complex re-initiation character of the traditional gap test is thereby retained, but the propagation speed is steady when measured at periodic intervals, and initiation delay in individual segments acts to decrement the average speed. We measure the shock arrival time before and after each inert gap, and compute the average detonation speed through the HE alone (discounting the gap thicknesses). We perform tests for a range of gap thicknesses. We then plot the aforementioned propagation speed as a function of gap thickness. The resulting curve has the same basic structure as a Diameter Effect (DE) curve, and (like the DE curve) terminates at a failure point. Comparison between experiment and hydrocode calculations using ALE3D and the Ignition and Growth reactive burn model calibrated for short duration shock inputs in PBX 9501 is discussed.

Esaki Diodes in van der Waals Heterojunctions with Broken-Gap Energy Band Alignment.

PubMed

Yan, Rusen; Fathipour, Sara; Han, Yimo; Song, Bo; Xiao, Shudong; Li, Mingda; Ma, Nan; Protasenko, Vladimir; Muller, David A; Jena, Debdeep; Xing, Huili Grace

2015-09-09

van der Waals (vdW) heterojunctions composed of two-dimensional (2D) layered materials are emerging as a solid-state materials family that exhibits novel physics phenomena that can power a range of electronic and photonic applications. Here, we present the first demonstration of an important building block in vdW solids: room temperature Esaki tunnel diodes. The Esaki diodes were realized in vdW heterostructures made of black phosphorus (BP) and tin diselenide (SnSe2), two layered semiconductors that possess a broken-gap energy band offset. The presence of a thin insulating barrier between BP and SnSe2 enabled the observation of a prominent negative differential resistance (NDR) region in the forward-bias current-voltage characteristics, with a peak to valley ratio of 1.8 at 300 K and 2.8 at 80 K. A weak temperature dependence of the NDR indicates electron tunneling being the dominant transport mechanism, and a theoretical model shows excellent agreement with the experimental results. Furthermore, the broken-gap band alignment is confirmed by the junction photoresponse, and the phosphorus double planes in a single layer of BP are resolved in transmission electron microscopy (TEM) for the first time. Our results represent a significant advance in the fundamental understanding of vdW heterojunctions and broaden the potential applications of 2D layered materials.

Approach to the evaluation of a patient with an increased serum osmolal gap and high-anion-gap metabolic acidosis.

PubMed

Kraut, Jeffrey A; Xing, Shelly Xiaolei

2011-09-01

An increase in serum osmolality and serum osmolal gap with or without high-anion-gap metabolic acidosis is an important clue to exposure to one of the toxic alcohols, which include methanol, ethylene glycol, diethylene glycol, propylene glycol, or isopropanol. However, the increase in serum osmolal gap and metabolic acidosis can occur either together or alone depending on several factors, including baseline serum osmolal gap, molecular weight of the alcohol, and stage of metabolism of the alcohol. In addition, other disorders, including diabetic or alcoholic ketoacidosis, acute kidney injury, chronic kidney disease, and lactic acidosis, can cause high-anion-gap metabolic acidosis associated with an increased serum osmolal gap and therefore should be explored in the differential diagnosis. It is essential for clinicians to understand the value and limitations of osmolal gap to assist in reaching the correct diagnosis and initiating appropriate treatment. In this teaching case, we present a systematic approach to diagnosing high serum osmolality and increased serum osmolal gap with or without high-anion-gap metabolic acidosis. Published by Elsevier Inc.

Narrow Energy Gap between Triplet and Singlet Excited States of Sn2+ in Borate Glass

PubMed Central

Masai, Hirokazu; Yamada, Yasuhiro; Suzuki, Yuto; Teramura, Kentaro; Kanemitsu, Yoshihiko; Yoko, Toshinobu

2013-01-01

Transparent inorganic luminescent materials have attracted considerable scientific and industrial attention recently because of their high chemical durability and formability. However, photoluminescence dynamics of ns2-type ions in oxide glasses has not been well examined, even though they can exhibit high quantum efficiency. We report on the emission property of Sn2+-doped strontium borate glasses. Photoluminescence dynamics studies show that the peak energy of the emission spectrum changes with time because of site distribution of emission centre in glass. It is also found that the emission decay of the present glass consists of two processes: a faster S1-S0 transition and a slower T1-S0 relaxation, and also that the energy difference between T1 and S1 states was found to be much smaller than that of (Sn, Sr)B6O10 crystals. We emphasize that the narrow energy gap between the S1 and T1 states provides the glass phosphor a high quantum efficiency, comparable to commercial crystalline phosphors. PMID:24345869

Temperature dependence of the band gap of GaAsSb epilayers

NASA Astrophysics Data System (ADS)

Lukic-Zrnic, R.; Gorman, B. P.; Cottier, R. J.; Golding, T. D.; Littler, C. L.; Norman, A. G.

2002-12-01

We have optically characterized a series of GaAs1-xSbx epilayers (0.19gap at each temperature was determined from the photon energy dependence of the absorption coefficient and compared with theoretical predictions. From our results we have obtained the Varshni coefficients, α=(4.2±0.1)×10-4 eV/K and β=(189±9) K, which describe well not only the temperature dependence of the band gap for the entire alloy range of our samples, but also for the past experimental work of others. These values differ significantly from what we believe are the only other reported values by K. G. Merkel et al. [K. G. Merkel et al., Appl. Phys. Lett. 65, 2442 (1994)].

Spark gap device for precise switching

DOEpatents

Boettcher, Gordon E.

1984-01-01

A spark gap device for precise switching of an energy storage capacitor into an exploding bridge wire load is disclosed. Niobium electrodes having a melting point of 2,415 degrees centrigrade are spaced apart by an insulating cylinder to define a spark gap. The electrodes are supported by conductive end caps which, together with the insulating cylinder, form a hermetically sealed chamber filled with an inert, ionizable gas, such as pure xenon. A quantity of solid radioactive carbon-14 within the chamber adjacent the spark gap serves as a radiation stabilizer. The sides of the electrodes and the inner wall of the insulating cylinder are spaced apart a sufficient distance to prevent unwanted breakdown initiation. A conductive sleeve may envelop the outside of the insulating member from the midpoint of the spark gap to the cap adjacent the cathode. The outer metallic surfaces of the device may be coated with a hydrogen-impermeable coating to lengthen the shelf life and operating life of the device. The device breaks down at about 1,700 volts for input voltage rates up to 570 volts/millisecond and allows peak discharge currents of up to 3,000 amperes from a 0.3 microfarad energy storage capacitor for more than 1,000 operations.

Spark gap device for precise switching

DOEpatents

Boettcher, G.E.

1984-10-02

A spark gap device for precise switching of an energy storage capacitor into an exploding bridge wire load is disclosed. Niobium electrodes having a melting point of 2,415 degrees centigrade are spaced apart by an insulating cylinder to define a spark gap. The electrodes are supported by conductive end caps which, together with the insulating cylinder, form a hermetically sealed chamber filled with an inert, ionizable gas, such as pure xenon. A quantity of solid radioactive carbon-14 within the chamber adjacent the spark gap serves as a radiation stabilizer. The sides of the electrodes and the inner wall of the insulating cylinder are spaced apart a sufficient distance to prevent unwanted breakdown initiation. A conductive sleeve may envelop the outside of the insulating member from the midpoint of the spark gap to the cap adjacent the cathode. The outer metallic surfaces of the device may be coated with a hydrogen-impermeable coating to lengthen the shelf life and operating life of the device. The device breaks down at about 1,700 volts for input voltage rates up to 570 volts/millisecond and allows peak discharge currents of up to 3,000 amperes from a 0.3 microfarad energy storage capacitor for more than 1,000 operations. 3 figs.

Energy and nutritional value of the meals in kindergartens in Nis (Serbia).

PubMed

Lazarevic, Konstansa; Stojanovic, Dusica; Bogdanović, Dragan

2014-01-01

It is well known that high-energy diet, rich in fat and carbohydrates, increases the risk of obesity. Preschool age is an important period to acquire the eating habits continued later in adulthood. Therefore, evaluation of child nutrition in kindergartens is especially important in the prevention of future obesity. To determine the energy value and energy density of meals consumed by children in kindergartens in Nis (Serbia), including the different types of food, in respect to a probable risk of obesity. The study had been conducted in the years 1998-2012. Three-hundred samples of the meals were gathered and analysed, and the amount of selected food groups used to prepare the meals in kindergartens was calculated (weight, protein, fat and carbohydrate content) in the accredited laboratory of the Public Health Institute in Nis according to the ISO 17025 recommendation. The mean energy value of meals was 978.9 kcal (range: 810 - 1144 kcal). The energy density was low (mean: 1.02 kcal/g, range: 0.92 - 1.42 kcal/g) and decreased over the years, what would imply a reduction in the risk of obesity. The intake of same high-energy food products, such as fats and oils as well as sweets (13.9% and 7.3%, respectively) was higher compared to low-energy foods (fruits - 5.2% and vegetables - 10.8%). The results of our study indicate that children in kindergarten in Nis, in general, were properly nourished in total energy content. The energy value and energy density of the meals consumed did not pose a risk of developing obesity. However, the distribution of food groups differentiated by the energy density level was unfavourable; the deficit of low-energy foods was observed. Planning the child nutrition in kindergartens, with laboratory control of meals, may be an effective strategy in adequate energy intake and prevention of obesity. Providing the higher amount of low-energy foods (fruits and vegetables) in meals in kindergartens is recommended.

Electronic properties of graphene nano-flakes: energy gap, permanent dipole, termination effect, and Raman spectroscopy.

PubMed

Singh, Sandeep Kumar; Neek-Amal, M; Peeters, F M

2014-02-21

The electronic properties of graphene nano-flakes (GNFs) with different edge passivation are investigated by using density functional theory. Passivation with F and H atoms is considered: C(N(c)) X(N(x)) (X = F or H). We studied GNFs with 10 < Nc < 56 and limit ourselves to the lowest energy configurations. We found that: (i) the energy difference Δ between the highest occupied molecular orbital and the lowest unoccupied molecular orbital decreases with Nc, (ii) topological defects (pentagon and heptagon) break the symmetry of the GNFs and enhance the electric polarization, (iii) the mutual interaction of bilayer GNFs can be understood by dipole-dipole interaction which were found sensitive to the relative orientation of the GNFs, (iv) the permanent dipoles depend on the edge terminated atom, while the energy gap is independent of it, and (v) the presence of heptagon and pentagon defects in the GNFs results in the largest difference between the energy of the spin-up and spin-down electrons which is larger for the H-passivated GNFs as compared to F-passivated GNFs. Our study shows clearly the effect of geometry, size, termination, and bilayer on the electronic properties of small GNFs. This study reveals important features of graphene nano-flakes which can be detected using Raman spectroscopy.

Retaining the Value of PV at High Penetration Workshop

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

Kurtz, Sarah; Bolen, Michael

PV prices have dropped and are now attractive without incentives for peaking applications in some locations. Modeling suggests and, empirically, some regions demonstrate that as PV penetration increases its value decreases, predominantly due to a decrease in energy and capacity value. It is not apparent what technologies and price may be needed for PV to supply tens of percent of electricity in the most economically efficient manner. A 1-day workshop was co-sponsored by EPRI and NREL with support from ASU. A dozen presentations and discussions introduced how the interplay of various technologies impact the value of PV, identified technical challengesmore » and gaps impeding implementation, and discussed future R&D needs and opportunities.« less

Navigating a sea of values: Understanding public attitudes toward the ocean and ocean energy resources

NASA Astrophysics Data System (ADS)

Lilley, Jonathan Charles

In examining ocean values and beliefs, this study investigates the moral and ethical aspects of the relationships that exist between humans and the marine environment. In short, this dissertation explores what the American public thinks of the ocean. The study places a specific focus upon attitudes to ocean energy development. Using both qualitative and quantitative methods, this research: elicits mental models that exist in society regarding the ocean; unearths what philosophies underpin people's attitudes toward the ocean and offshore energy development; assesses whether these views have any bearing on pro-environmental behavior; and gauges support for offshore drilling and offshore wind development. Despite the fact that the ocean is frequently ranked as a second-tier environmental issue, Americans are concerned about the state of the marine environment. Additionally, the data show that lack of knowledge, rather than apathy, prevents people from undertaking pro-environmental action. With regard to philosophical beliefs, Americans hold slightly more nonanthropocentric than anthropocentric views toward the environment. Neither anthropocentrism nor nonanthropocentrism has any real impact on pro-environmental behavior, although nonanthropocentric attitudes reduce support for offshore wind. This research also uncovers two gaps between scientific and public perceptions of offshore wind power with respect to: 1) overall environmental effects; and 2) the size of the resource. Providing better information to the public in the first area may lead to a shift toward offshore wind support among opponents with nonanthropocentric attitudes, and in both areas, is likely to increase offshore wind support.

Direct imaging of band profile in single layer MoS2 on graphite: quasiparticle energy gap, metallic edge states, and edge band bending.

PubMed

Zhang, Chendong; Johnson, Amber; Hsu, Chang-Lung; Li, Lain-Jong; Shih, Chih-Kang

2014-05-14

Using scanning tunneling microscopy and spectroscopy, we probe the electronic structures of single layer MoS2 on graphite. The apparent quasiparticle energy gap of single layer MoS2 is measured to be 2.15 ± 0.06 eV at 77 K, albeit a higher second conduction band threshold at 0.2 eV above the apparent conduction band minimum is also observed. Combining it with photoluminescence studies, we deduce an exciton binding energy of 0.22 ± 0.1 eV (or 0.42 eV if the second threshold is use), a value that is lower than current theoretical predictions. Consistent with theoretical predictions, we directly observe metallic edge states of single layer MoS2. In the bulk region of MoS2, the Fermi level is located at 1.8 eV above the valence band maximum, possibly due to the formation of a graphite/MoS2 heterojunction. At the edge, however, we observe an upward band bending of 0.6 eV within a short depletion length of about 5 nm, analogous to the phenomena of Fermi level pinning of a 3D semiconductor by metallic surface states.

Field induced gap infrared detector

NASA Technical Reports Server (NTRS)

Elliott, C. Thomas (Inventor)

1990-01-01

A tunable infrared detector which employs a vanishing band gap semimetal material provided with an induced band gap by a magnetic field to allow intrinsic semiconductor type infrared detection capabilities is disclosed. The semimetal material may thus operate as a semiconductor type detector with a wavelength sensitivity corresponding to the induced band gap in a preferred embodiment of a diode structure. Preferred semimetal materials include Hg(1-x)Cd(x)Te, x is less than 0.15, HgCdSe, BiSb, alpha-Sn, HgMgTe, HgMnTe, HgZnTe, HgMnSe, HgMgSe, and HgZnSe. The magnetic field induces a band gap in the semimetal material proportional to the strength of the magnetic field allowing tunable detection cutoff wavelengths. For an applied magnetic field from 5 to 10 tesla, the wavelength detection cutoff will be in the range of 20 to 50 micrometers for Hg(1-x)Cd(x)Te alloys with x about 0.15. A similar approach may also be employed to generate infrared energy in a desired band gap and then operating the structure in a light emitting diode or semiconductor laser type of configuration.

Flexion and extension gaps created by the navigation-assisted gap technique show small acceptable mismatches and close mutual correlations.

PubMed

Lee, Dae-Hee; Shin, Young-Soo; Jeon, Jin-Ho; Suh, Dong-Won; Han, Seung-Beom

2014-08-01

The aim of this study was to investigate the mechanism underlying the development of gap differences in total knee arthroplasty using the navigation-assisted gap technique and to assess whether these gap differences have statistical significance. Ninety-two patients (105 knees) implanted with cruciate-retaining prostheses using the navigation-assisted gap balancing technique were prospectively analysed. Medial extension and flexion gaps and lateral extension and flexion gaps were measured at full extension and at 90° of flexion. Repeated measures analysis of variance was used to compare the mean values of these four gaps. The correlation coefficient between each pair of gaps was assessed using Pearson's correlation analysis. Mean intra-operative medial and lateral extension gaps were 20.6 ± 2.1 and 21.7 ± 2.2 mm, respectively, and mean intra-operative medial and lateral flexion gaps were 21.6 ± 2.7 and 22.1 ± 2.5 mm, respectively. The pairs of gaps differed significantly (P < 0.05 each), except for the difference between the medial flexion and lateral extension gaps (n.s.). All four gaps were significantly correlated with each other, with the highest correlation between the medial and lateral flexion gaps (r = 0.890, P < 0.001) and the lowest between the medial flexion and lateral extension gaps (r = 0.701, P < 0.001). Medial and lateral flexion and extension gaps created using the navigation-assisted gap technique differed significantly, although the differences between them were <2 mm, and the gaps were closely correlated. These narrow ranges of statistically acceptable gap differences and the strong correlations between gaps should be considered by surgeons, as should the risks of soft tissue over-release or unintentional increases in extension or flexion gap after preparation of the other gap.

Magnetic gaps in organic tri-radicals: From a simple model to accurate estimates.

PubMed

Barone, Vincenzo; Cacelli, Ivo; Ferretti, Alessandro; Prampolini, Giacomo

2017-03-14

The calculation of the energy gap between the magnetic states of organic poly-radicals still represents a challenging playground for quantum chemistry, and high-level techniques are required to obtain accurate estimates. On these grounds, the aim of the present study is twofold. From the one side, it shows that, thanks to recent algorithmic and technical improvements, we are able to compute reliable quantum mechanical results for the systems of current fundamental and technological interest. From the other side, proper parameterization of a simple Hubbard Hamiltonian allows for a sound rationalization of magnetic gaps in terms of basic physical effects, unraveling the role played by electron delocalization, Coulomb repulsion, and effective exchange in tuning the magnetic character of the ground state. As case studies, we have chosen three prototypical organic tri-radicals, namely, 1,3,5-trimethylenebenzene, 1,3,5-tridehydrobenzene, and 1,2,3-tridehydrobenzene, which differ either for geometric or electronic structure. After discussing the differences among the three species and their consequences on the magnetic properties in terms of the simple model mentioned above, accurate and reliable values for the energy gap between the lowest quartet and doublet states are computed by means of the so-called difference dedicated configuration interaction (DDCI) technique, and the final results are discussed and compared to both available experimental and computational estimates.

Comparison of metabolisable energy values of different foodstuffs determined in ostriches and poultry.

PubMed

Cilliers, S C; Sales, J; Hayes, J P; Chwalibog, A; Du Preez, J J

1999-09-01

Apparent (AMEn) and true (TMEn) metabolisable energy values, corrected for nitrogen retention, of wheat bran, saltbush (Atriplex nummularia), common reed (Phragmites australis), lupins, soyabean oil cake meal (SBOCM), sunflower oil cake meal (SFOCM) and fishmeal were compared in 7 successive trials using 12 mature South African Black ostriches and 10 adult Australorp cockerels per ingredient. TMEn values of 11.91, 7.09, 8.67, 14.61, 13.44, 10.79 and 15.13 MJ/kg for wheat bran, saltbush, common reed, lupins, SBOCM, SFOCM and fishmeal, respectively, were found for ostriches in comparison to lower (P<0.05) values of 8.55, 4.50, 2.79, 9.40, 9.04, 8.89 and 13.95 MJ/kg for cockerels. The higher (P<0.05) ME values for ostriches confirm that the ostrich is capable of digesting foodstuffs, especially those with high fibre concentrations such as drought-resistant fodders, more effectively than poultry. Plant protein sources could make a considerable energy contribution to diets for ostriches. It is concluded that it is essential to use energy values of foodstuffs determined using ostriches and not extrapolated values derived from poultry in diet formulation for ostriches.

On the optical band gap of zinc oxide

NASA Astrophysics Data System (ADS)

Srikant, V.; Clarke, D. R.

1998-05-01

Three different values (3.1, 3.2, and 3.3 eV) have been reported for the optical band gap of zinc oxide single crystals at room temperature. By comparing the optical properties of ZnO crystals using a variety of optical techniques it is concluded that the room temperature band gap is 3.3 eV and that the other values are attributable to a valence band-donor transition at ˜3.15 eV that can dominate the optical absorption when the bulk of a single crystal is probed.

The Value of Seasonal Climate Forecasts in Managing Energy Resources.

NASA Astrophysics Data System (ADS)

Brown Weiss, Edith

1982-04-01

Research and interviews with officials of the United States energy industry and a systems analysis of decision making in a natural gas utility lead to the conclusion that seasonal climate forecasts would only have limited value in fine tuning the management of energy supply, even if the forecasts were more reliable and detailed than at present.On the other hand, reliable forecasts could be useful to state and local governments both as a signal to adopt long-term measures to increase the efficiency of energy use and to initiate short-term measures to reduce energy demand in anticipation of a weather-induced energy crisis.To be useful for these purposes, state governments would need better data on energy demand patterns and available energy supplies, staff competent to interpret climate forecasts, and greater incentive to conserve. The use of seasonal climate forecasts is not likely to be constrained by fear of legal action by those claiming to be injured by a possible incorrect forecast.

Energy Management in Higher Education: Value for Money Study.

ERIC Educational Resources Information Center

Scottish Higher Education Funding Council, Edinburgh.

This Value for Money project provides an update of the 1996 "Energy Management Study in the Higher Education Sector: National Report." It reviews the management arrangement for utilities in the higher education (HE) sector, and it identifies key actions and future issues that must be addressed by HE institutions in developing a strategic…

Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect, and Raman spectroscopy

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

Singh, Sandeep Kumar, E-mail: SandeepKumar.Singh@uantwerpen.be; Peeters, F. M., E-mail: Francois.Peeters@uantwerpen.be; Neek-Amal, M., E-mail: neekamal@srttu.edu

2014-02-21

The electronic properties of graphene nano-flakes (GNFs) with different edge passivation are investigated by using density functional theory. Passivation with F and H atoms is considered: C{sub N{sub c}} X{sub N{sub x}} (X = F or H). We studied GNFs with 10 < N{sub c} < 56 and limit ourselves to the lowest energy configurations. We found that: (i) the energy difference Δ between the highest occupied molecular orbital and the lowest unoccupied molecular orbital decreases with N{sub c}, (ii) topological defects (pentagon and heptagon) break the symmetry of the GNFs and enhance the electric polarization, (iii) the mutual interactionmore » of bilayer GNFs can be understood by dipole-dipole interaction which were found sensitive to the relative orientation of the GNFs, (iv) the permanent dipoles depend on the edge terminated atom, while the energy gap is independent of it, and (v) the presence of heptagon and pentagon defects in the GNFs results in the largest difference between the energy of the spin-up and spin-down electrons which is larger for the H-passivated GNFs as compared to F-passivated GNFs. Our study shows clearly the effect of geometry, size, termination, and bilayer on the electronic properties of small GNFs. This study reveals important features of graphene nano-flakes which can be detected using Raman spectroscopy.« less

Attempting to bridge the gap between laboratory and seismic estimates of fracture energy

USGS Publications Warehouse

McGarr, A.; Fletcher, Joe B.; Beeler, N.M.

2004-01-01

To investigate the behavior of the fracture energy associated with expanding the rupture zone of an earthquake, we have used the results of a large-scale, biaxial stick-slip friction experiment to set the parameters of an equivalent dynamic rupture model. This model is determined by matching the fault slip, the static stress drop and the apparent stress. After confirming that the fracture energy associated with this model earthquake is in reasonable agreement with corresponding laboratory values, we can use it to determine fracture energies for earthquakes as functions of stress drop, rupture velocity and fault slip. If we take account of the state of stress at seismogenic depths, the model extrapolation to larger fault slips yields fracture energies that agree with independent estimates by others based on dynamic rupture models for large earthquakes. For fixed stress drop and rupture speed, the fracture energy scales linearly with fault slip.

Mind the Gap on IceCube: Cosmic neutrino spectrum and muon anomalous magnetic moment

NASA Astrophysics Data System (ADS)

Araki, T.; Kaneko, F.; Konishi, Y.; Ota, T.; Sato, J.; Shimomura, T.

2017-09-01

The high energy cosmic neutrino spectrum reported by the IceCube collaboration shows a gap in the energy range between 500 TeV and 1 PeV. In this presentation, we illustrate that the IceCube gap is reproduced by the neutrino interaction mediated by the new gauge boson associated with a certain combination of the lepton avour number. The gauge interaction also explains the other long-standing gap in the lepton phenomenology: the gap between theory and experiment in the muon anomalous magnetic moment.

Pure wurtzite GaP nanowires grown on zincblende GaP substrates by selective area vapor liquid solid epitaxy

NASA Astrophysics Data System (ADS)

Halder, Nripendra N.; Kelrich, Alexander; Cohen, Shimon; Ritter, Dan

2017-11-01

We report on the growth of single phase wurtzite (WZ) GaP nanowires (NWs) on GaP (111) B substrates by metal organic molecular beam epitaxy following the selective area vapor-liquid-solid (SA-VLS) approach. During the SA-VLS process, precursors are supplied directly to the NW sidewalls, and the short diffusion length of gallium (or its precursors) does not significantly limit axial growth. Transmission electron microscopy (TEM) images reveal that no stacking faults are present along a 600 nm long NW. The lattice constants of the pure WZ GaP obtained from the TEM images agree with values determined previously by x-ray diffraction from non-pure NW ensembles.

Pure wurtzite GaP nanowires grown on zincblende GaP substrates by selective area vapor liquid solid epitaxy.

PubMed

Halder, Nripendra N; Kelrich, Alexander; Cohen, Shimon; Ritter, Dan

2017-11-17

We report on the growth of single phase wurtzite (WZ) GaP nanowires (NWs) on GaP (111) B substrates by metal organic molecular beam epitaxy following the selective area vapor-liquid-solid (SA-VLS) approach. During the SA-VLS process, precursors are supplied directly to the NW sidewalls, and the short diffusion length of gallium (or its precursors) does not significantly limit axial growth. Transmission electron microscopy (TEM) images reveal that no stacking faults are present along a 600 nm long NW. The lattice constants of the pure WZ GaP obtained from the TEM images agree with values determined previously by x-ray diffraction from non-pure NW ensembles.

Suppression of spin and optical gaps in phosphorene quantum dots

NASA Astrophysics Data System (ADS)

Zhang, Yingjie; Sheng, Weidong

2018-05-01

Electronic structure and optical properties of triangular phosphorene quantum dots have been investigated theoretically. Based on systematic configuration interaction calculations, the ground and excited states of the interacting many-electron system together with its optical absorption spectrum are obtained. For the nanodot with 60 phosphorus atoms in various dielectric environments, it is found that the spin gap of the correlated system surprisingly overlaps its optical gap over a large range of the effective dielectric constant. The overlapping of the spin and optical gaps can be attributed to the fact that the extra correlation energy in the spin singlet almost compensates the exchange energy in the spin triplet in the presence of strong long-range electron-electron interactions. Moreover, both the spin and optical gaps are shown to be greatly suppressed as the screening effect becomes strong. When the dielectric constant decreases below 2.65, it is seen that the spin gap becomes negative and the quantum dot undergoes a phase transition from nonmagnetic to ferromagnetic. Our results are compared with the previous experimental and theoretical works.

New Material Transistor with Record-High Field-Effect Mobility among Wide-Band-Gap Semiconductors.

PubMed

Shih, Cheng Wei; Chin, Albert

2016-08-03

At an ultrathin 5 nm, we report a new high-mobility tin oxide (SnO2) metal-oxide-semiconductor field-effect transistor (MOSFET) exhibiting extremely high field-effect mobility values of 279 and 255 cm(2)/V-s at 145 and 205 °C, respectively. These values are the highest reported mobility values among all wide-band-gap semiconductors of GaN, SiC, and metal-oxide MOSFETs, and they also exceed those of silicon devices at the aforementioned elevated temperatures. For the first time among existing semiconductor transistors, a new device physical phenomenon of a higher mobility value was measured at 45-205 °C than at 25 °C, which is due to the lower optical phonon scattering by the large SnO2 phonon energy. Moreover, the high on-current/off-current of 4 × 10(6) and the positive threshold voltage of 0.14 V at 25 °C are significantly better than those of a graphene transistor. This wide-band-gap SnO2 MOSFET exhibits high mobility in a 25-205 °C temperature range, a wide operating voltage of 1.5-20 V, and the ability to form on an amorphous substrate, rendering it an ideal candidate for multifunctional low-power integrated circuit (IC), display, and brain-mimicking three-dimensional IC applications.

Regression method-derived energy value of dried egg albumen for broiler chickens.

PubMed

Hancock, S; Zhang, F; Adeola, O

2018-05-01

The energy value of dried egg albumen (DEA) for broiler chickens was determined with male Ross 708 broilers. Birds were fed a common broiler starter diet from day 0 to 17 and experimental diets from day 17 to 22 post hatching. A total of 192 birds was allotted to 3 diets in a randomized complete block design with 8 replicate cages per diet and 8 birds per cage. The experiment used a corn-soybean meal reference diet and 2 test diets which the DEA was added at 50 or 100 g/kg to partially replace the energy source in the reference diet. The analyzed DM of DEA was 934 g/kg, and the respective analyzed gross energy and CP were 5,310 kcal and 894 g/kg DM. Addition of DEA to the reference diet linearly increased (P < 0.01) ileal DM digestibility, ileal energy digestibility, and ileal digestible energy (IDE), metabolizable energy (ME), and nitrogen-corrected metabolizable energy (MEn), whereas the effect on N retention was quadratic (P < 0.05). The IDE, ME, MEn of DEA values determined by the regression method were 4,777, 4,966, and 4,750 kcal/kg DM, respectively. In conclusion, the current study demonstrated that between 89 and 94% of the gross energy in dried egg albumen is utilized by broiler chickens.

Inter-band optoelectronic properties in quantum dot structure of low band gap III-V semiconductors

NASA Astrophysics Data System (ADS)

Dey, Anup; Maiti, Biswajit; Chanda Sarkar, Debasree

2014-04-01

A generalized theory is developed to study inter-band optical absorption coefficient (IOAC) and material gain (MG) in quantum dot structures of narrow gap III-V compound semiconductor considering the wave-vector (k→) dependence of the optical transition matrix element. The band structures of these low band gap semiconducting materials with sufficiently separated split-off valance band are frequently described by the three energy band model of Kane. This has been adopted for analysis of the IOAC and MG taking InAs, InSb, Hg1-xCdxTe, and In1-xGaxAsyP1-y lattice matched to InP, as example of III-V compound semiconductors, having varied split-off energy band compared to their bulk band gap energy. It has been found that magnitude of the IOAC for quantum dots increases with increasing incident photon energy and the lines of absorption are more closely spaced in the three band model of Kane than those with parabolic energy band approximations reflecting the direct the influence of energy band parameters. The results show a significant deviation to the MG spectrum of narrow-gap materials having band nonparabolicity compared to the parabolic band model approximations. The results reflect the important role of valence band split-off energies in these narrow gap semiconductors.

Passive band-gap reconfiguration born from bifurcation asymmetry.

PubMed

Bernard, Brian P; Mann, Brian P

2013-11-01

Current periodic structures are constrained to have fixed energy transmission behavior unless active control or component replacement is used to alter their wave propagation characteristics. The introduction of nonlinearity to generate multiple stable equilibria is an alternative strategy for realizing distinct energy propagation behaviors. We investigate the creation of a reconfigurable band-gap system by implementing passive switching between multiple stable states of equilibrium, to alter the level of energy attenuation in response to environmental stimuli. The ability to avoid potentially catastrophic loads is demonstrated by tailoring the bandpass and band-gap regions to coalesce for two stable equilibria and varying an external load parameter to trigger a bifurcation. The proposed phenomenon could be utilized in remote or autonomous applications where component modifications and active control are impractical.

Effect of data gaps on correlation dimension computed from light curves of variable stars

NASA Astrophysics Data System (ADS)

George, Sandip V.; Ambika, G.; Misra, R.

2015-11-01

Observational data, especially astrophysical data, is often limited by gaps in data that arises due to lack of observations for a variety of reasons. Such inadvertent gaps are usually smoothed over using interpolation techniques. However the smoothing techniques can introduce artificial effects, especially when non-linear analysis is undertaken. We investigate how gaps can affect the computed values of correlation dimension of the system, without using any interpolation. For this we introduce gaps artificially in synthetic data derived from standard chaotic systems, like the Rössler and Lorenz, with frequency of occurrence and size of missing data drawn from two Gaussian distributions. Then we study the changes in correlation dimension with change in the distributions of position and size of gaps. We find that for a considerable range of mean gap frequency and size, the value of correlation dimension is not significantly affected, indicating that in such specific cases, the calculated values can still be reliable and acceptable. Thus our study introduces a method of checking the reliability of computed correlation dimension values by calculating the distribution of gaps with respect to its size and position. This is illustrated for the data from light curves of three variable stars, R Scuti, U Monocerotis and SU Tauri. We also demonstrate how a cubic spline interpolation can cause a time series of Gaussian noise with missing data to be misinterpreted as being chaotic in origin. This is demonstrated for the non chaotic light curve of variable star SS Cygni, which gives a saturated D2 value, when interpolated using a cubic spline. In addition we also find that a careful choice of binning, in addition to reducing noise, can help in shifting the gap distribution to the reliable range for D2 values.

Energy values for whole trees and crowns of selected species.

Treesearch

James O. Howard

1988-01-01

Energy values, BTU's (British thermal units) per ovendry pound, were determined for whole-tree and crown materials from western hemlock (Tsuga heterophylla (Raf.) Sarg.), coast Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii), and western redcedar (Thuja plicata Donn ex D. Don)....

The Value of CO2-Geothermal Bulk Energy Storage to Reducing CO2 Emissions Compared to Conventional Bulk Energy Storage Technologies

NASA Astrophysics Data System (ADS)

Ogland-Hand, J.; Bielicki, J. M.; Buscheck, T. A.

2016-12-01

Sedimentary basin geothermal resources and CO2 that is captured from large point sources can be used for bulk energy storage (BES) in order to accommodate higher penetration and utilization of variable renewable energy resources. Excess energy is stored by pressurizing and injecting CO2 into deep, porous, and permeable aquifers that are ubiquitous throughout the United States. When electricity demand exceeds supply, some of the pressurized and geothermally-heated CO2 can be produced and used to generate electricity. This CO2-BES approach reduces CO2 emissions directly by storing CO2 and indirectly by using some of that CO2 to time-shift over-generation and displace CO2 emissions from fossil-fueled power plants that would have otherwise provided electricity. As such, CO2-BES may create more value to regional electricity systems than conventional pumped hydro energy storage (PHES) or compressed air energy storage (CAES) approaches that may only create value by time-shifting energy and indirectly reducing CO2 emissions. We developed and implemented a method to estimate the value that BES has to reducing CO2 emissions from regional electricity systems. The method minimizes the dispatch of electricity system components to meet exogenous demand subject to various CO2 prices, so that the value of CO2 emissions reductions can be estimated. We applied this method to estimate the performance and value of CO2-BES, PHES, and CAES within real data for electricity systems in California and Texas over the course of a full year to account for seasonal fluctuations in electricity demand and variable renewable resource availability. Our results suggest that the value of CO2-BES to reducing CO2 emissions may be as much as twice that of PHES or CAES and thus CO2-BES may be a more favorable approach to energy storage in regional electricity systems, especially those where the topography is not amenable to PHES or the subsurface is not amenable to CAES.

Phosphorene for energy and catalytic application—filling the gap between graphene and 2D metal chalcogenides

NASA Astrophysics Data System (ADS)

Jain, Rishabh; Narayan, Rekha; Padmajan Sasikala, Suchithra; Lee, Kyung Eun; Jung, Hong Ju; Ouk Kim, Sang

2017-12-01

Phosphorene, a newly emerging graphene analogous 2D elemental material of phosphorous atoms, is unique on the grounds of its natural direct band gap opening, highly anisotropic and extraordinary physical properties. This review highlights the current status of phosphorene research in energy and catalytic applications. The initial part illustrates the typical physical properties of phosphorene, which successfully bridge the prolonged gap between graphene and 2D metal chalcogenides. Various synthetic methods available for black phosphorus (BP) and the exfoliation/growth techniques for single to few-layer phosphorene are also overviewed. The latter part of this review details the working mechanisms and performances of phosphorene/BP in batteries, supercapacitors, photocatalysis, and electrocatalysis. Special attention has been paid to the research efforts to overcome the inherent shortcomings faced by phosphorene based devices. The relevant device performances are compared with graphene and 2D metal chalcogenides based counterparts. Furthermore, the underlying mechanism behind the unstable nature of phosphorene under ambient condition is discussed along with the various approaches to avoid ambient degradation. Finally, comments are offered for the future prospective explorations and outlook as well as challenges lying in the road ahead for phosphorene research.

Study of radiative heat transfer in Ångström- and nanometre-sized gaps

DOE PAGES

Cui, Longji; Jeong, Wonho; Fernández-Hurtado, Víctor; ...

2017-02-15

Radiative heat transfer in Ångström- and nanometre-sized gaps is of great interest because of both its technological importance and open questions regarding the physics of energy transfer in this regime. Here in this paper we report studies of radiative heat transfer in few Å to 5nm gap sizes, performed under ultrahigh vacuum conditions between a Au-coated probe featuring embedded nanoscale thermocouples and a heated planar Au substrate that were both subjected to various surface-cleaning procedures. By drawing on the apparent tunnelling barrier height as a signature of cleanliness, we found that upon systematically cleaning via a plasma or locally pushingmore » the tip into the substrate by a few nanometres, the observed radiative conductances decreased from unexpectedly large values to extremely small ones—below the detection limit of our probe—as expected from our computational results. Our results show that it is possible to avoid the confounding effects of surface contamination and systematically study thermal radiation in Ångström- and nanometre-sized gaps.« less

Theoretical study on electronic structure of bathocuproine: Renormalization of the band gap in the crystalline state and the large exciton binding energy

NASA Astrophysics Data System (ADS)

Yanagisawa, Susumu; Hatada, Shin-No-Suke; Morikawa, Yoshitada

Bathocuproine (BCP) is a promising organic material of a hole blocking layer in organic light-emitting diodes or an electron buffer layer in organic photovoltaic cells. The nature of the unoccupied electronic states is a key characteristic of the material, which play vital roles in the electron transport. To elucidate the electronic properties of the molecular or crystalline BCP, we use the GW approximation for calculation of the fundamental gap, and the long-range corrected density functional theory for the molecular optical absorption. It is found that the band gap of the BCP single crystal is 4.39 eV, and it is in agreement with the recent low-energy inverse photoemission spectroscopy measurement. The polarization energy is estimated to be larger than 1 eV, demonstrating the large polarization effects induced by the electronic clouds surrounding the injected charge. The theoretical optical absorption energy is 3.68 eV, and the exciton binding energy is estimated to be 0.71 eV, implying the large binding in the eletron-hole pair distributed around the small part of the molecular region. This work was supported by the Grants-in-Aid for Young Scientists (B) (No. 26810009), and for Scientific Research on Innovative Areas ``3D Active-Site Science'' (No. 26105011) from Japan Society for the Promotion of Science.

Mind the gap: financial London and the regional class pay gap.

PubMed

Friedman, Sam; Laurison, Daniel

2017-09-01

The hidden barriers, or 'gender pay gap', preventing women from earning equivalent incomes to men is well documented. Yet recent research has uncovered that, in Britain, there is also a comparable class-origin pay gap in higher professional and managerial occupations. So far this analysis has only been conducted at the national level and it is not known whether there are regional differences within the UK. This paper uses pooled data from the 2014 and 2015 Labour Force Survey (N = 7,534) to stage a more spatially sensitive analysis that examines regional variation in the class pay gap. We find that this 'class ceiling' is not evenly spatially distributed. Instead it is particularly marked in Central London, where those in high-status occupations who are from working-class backgrounds earn, on average, £10,660 less per year than those whose parents were in higher professional and managerial employment. Finally, we inspect the Capital further to reveal that the class pay gap is largest within Central London's banking and finance sector. Challenging policy conceptions of London as the 'engine room' of social mobility, these findings suggest that class disadvantage within high-status occupations is particularly acute in the Capital. The findings also underline the value of investigating regional differences in social mobility, and demonstrate how such analysis can unravel important and previously unrecognized spatial dimensions of class inequality. © London School of Economics and Political Science 2017.

Magnetothermoelectric effects in graphene and their dependence on scatterer concentration, magnetic field, and band gap

NASA Astrophysics Data System (ADS)

Kundu, Arpan; Alrefae, Majed A.; Fisher, Timothy S.

2017-03-01

Using a semiclassical Boltzmann transport equation approach, we derive analytical expressions for electric and thermoelectric transport coefficients of graphene in the presence and absence of a magnetic field. Scattering due to acoustic phonons, charged impurities, and vacancies is considered in the model. Seebeck (Sxx) and Nernst (N) coefficients are evaluated as functions of carrier density, temperature, scatterer concentration, magnetic field, and induced band gap, and the results are compared to experimental data. Sxx is an odd function of Fermi energy, while N is an even function, as observed in experiments. The peak values of both coefficients are found to increase with the decreasing scatterer concentration and increasing temperature. Furthermore, opening a band gap decreases N but increases Sxx. Applying a magnetic field introduces an asymmetry in the variation of Sxx with Fermi energy across the Dirac point. The formalism is more accurate and computationally efficient than the conventional Green's function approach used to model transport coefficients and can be used to explore transport properties of other materials with Dirac cones such as Weyl semimetals.

The effect of exchange interaction on quasiparticle Landau levels in narrow-gap quantum well heterostructures.

PubMed

Krishtopenko, S S; Gavrilenko, V I; Goiran, M

2012-04-04

Using the 'screened' Hartree-Fock approximation based on the eight-band k·p Hamiltonian, we have extended our previous work (Krishtopenko et al 2011 J. Phys.: Condens. Matter 23 385601) on exchange enhancement of the g-factor in narrow-gap quantum well heterostructures by calculating the exchange renormalization of quasiparticle energies, the density of states at the Fermi level and the quasiparticle g-factor for different Landau levels overlapping. We demonstrate that exchange interaction yields more pronounced Zeeman splitting of the density of states at the Fermi level and leads to the appearance of peak-shaped features in the dependence of the Landau level energies on the magnetic field at integer filling factors. We also find that the quasiparticle g-factor does not reach the maximum value at odd filling factors in the presence of large overlapping of spin-split Landau levels. We advance an argument that the behavior of the quasiparticle g-factor in weak magnetic fields is defined by a random potential of impurities in narrow-gap heterostructures. © 2012 IOP Publishing Ltd

Effect of interfacial lattice mismatch on bulk carrier concentration and band gap of InN

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

Kuyyalil, Jithesh; Tangi, Malleswararao; Shivaprasad, S. M.

The issue of ambiguous values of the band gap (0.6 to 2 eV) of InN thin film in literature has been addressed by a careful experiment. We have grown wurtzite InN films by PA-MBE simultaneously on differently modified c-plane sapphire substrates and characterized by complementary structural and chemical probes. Our studies discount Mie resonances caused by metallic In segregation at grain boundaries as the reason for low band gap values ( Almost-Equal-To 0.6 eV) and also the formation of Indium oxides and oxynitrides as the cause for high band gap value ( Almost-Equal-To 2.0 eV). It is observed that polycrystallinitymore » arising from azimuthal miss-orientation of c-oriented wurtzite InN crystals increases the carrier concentration and the band gap values. We have reviewed the band gap, carrier concentration, and effective mass of InN in literature and our own measurements, which show that the Moss-Burstein relation with a non-parabolic conduction band accounts for the observed variation of band gap with carrier concentration.« less

Analyzing Bleriot's propeller gaps in Cassini NAC images

NASA Astrophysics Data System (ADS)

Hoffmann, Holger; Chen, Cheng; Seiß, Martin; Albers, Nicole; Spahn, Frank; Nic

2016-10-01

Among the great discoveries of the Cassini mission are the propeller-shaped structures created by small moonlets embedded in Saturn's dense rings. These moonlets are not massive enough to counteract the viscous ring diffusion to open and maintain circumferential gaps, distinguishing them from ring-moons like Pan and Daphnis.Although one of the defining features of propeller structures, well-formed partial gaps have been resolved by the Imaging Science Subsystem Narrow Angle Camera onboard the Cassini spacecraft only for the largest known propeller named Bleriot. We analyze images of the sunlit side of Saturn's outer A ring showing the propeller Bleriot with clearly visible gaps. By fitting a Gaussian to radial brightness profiles at different azimuthal locations, we obtain the evolution of gap minimum and gap width downstream of the moonlet.We report two findings:1) Numerical simulations indicate that the radial separation of the partial propeller gaps is expected to be 4 Hill radii (Spahn and Sremcevic, 2000, A&A). We infer Bleriot's Hill radius to be a few hundred meters, consistent with values given by Sremcevic et al. (2014, DPS) and Hoffmann et al. (2015, Icarus).2) In order to estimate the ring viscosity in the region of Saturn's outer A ring, where Bleriot orbits, we fit several model functions (one example being the analytic solution derived by Sremcevic, Spahn and Duschl, 2002, MNRAS) describing the azimuthal evolution of the surface density in the propeller gap region to the data obtained from the image analysis. We find viscosity values consistent with the parameterization of ring viscosity by Daisaka et al. (2001, Icarus), but significantly lower than the upper limit given by Esposito et al. (1983, Icarus)

Dynamic response functions, helical gaps, and fractional charges in quantum wires

NASA Astrophysics Data System (ADS)

Meng, Tobias; Pedder, Christopher J.; Tiwari, Rakesh P.; Schmidt, Thomas L.

We show how experimentally accessible dynamic response functions can discriminate between helical gaps due to magnetic field, and helical gaps driven by electron-electron interactions (''umklapp gaps''). The latter are interesting since they feature gapped quasiparticles of fractional charge e / 2 , and - when coupled to a standard superconductor - an 8 π-Josephson effect and topological zero energy states bound to interfaces. National Research Fund, Luxembourg (ATTRACT 7556175), Deutsche Forschungsgemeinschaft (GRK 1621 and SFB 1143), Swiss National Science Foundation.

Significant reduction in NiO band gap upon formation of Lix Ni1-x O alloys: applications to solar energy conversion.

PubMed

Alidoust, Nima; Toroker, Maytal Caspary; Keith, John A; Carter, Emily A

2014-01-01

Long-term sustainable solar energy conversion relies on identifying economical and versatile semiconductor materials with appropriate band structures for photovoltaic and photocatalytic applications (e.g., band gaps of ∼ 1.5-2.0 eV). Nickel oxide (NiO) is an inexpensive yet highly promising candidate. Its charge-transfer character may lead to longer carrier lifetimes needed for higher efficiencies, and its conduction band edge is suitable for driving hydrogen evolution via water-splitting. However, NiO's large band gap (∼ 4 eV) severely limits its use in practical applications. Our first-principles quantum mechanics calculations show band gaps dramatically decrease to ∼ 2.0 eV when NiO is alloyed with Li2O. We show that Lix Ni1-x O alloys (with x=0.125 and 0.25) are p-type semiconductors, contain states with no impurity levels in the gap and maintain NiO's desirable charge-transfer character. Lastly, we show that the alloys have potential for photoelectrochemical applications, with band edges well-placed for photocatalytic hydrogen production and CO2 reduction, as well as in tandem dye-sensitized solar cells as a photocathode. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The acculturation gap-distress model: Extensions and application to Arab Canadian families.

PubMed

Rasmi, Sarah; Chuang, Susan S; Hennig, Karl

2015-10-01

Using a multidomain and bidimensional approach, the present study applied and extended the acculturation gap-distress model with an immigrant Arab Canadian sample. Consistent with this model, immigrant Arab emerging adults (n = 113) perceived acculturation gaps between themselves and their parents with respect to their heritage and settlement culture orientation and values. Some of these gaps, in turn, were associated with poorer outcomes. Extending the model, the most problematic acculturation gaps were those in which the emerging adult perceived themselves to be more oriented to Arab culture and values than their parents. We also found some support for the moderating role of parent-emerging adult relationships. (c) 2015 APA, all rights reserved).

230 s room-temperature storage time and 1.14 eV hole localization energy in In{sub 0.5}Ga{sub 0.5}As quantum dots on a GaAs interlayer in GaP with an AlP barrier

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

Bonato, Leo, E-mail: leo.bonato@tu-berlin.de; Sala, Elisa M.; Stracke, Gernot

2015-01-26

A GaP n{sup +}p-diode containing In{sub 0.5}Ga{sub 0.5}As quantum dots (QDs) and an AlP barrier is characterized electrically, together with two reference samples: a simple n{sup +}p-diode and an n{sup +}p-diode with AlP barrier. Localization energy, capture cross-section, and storage time for holes in the QDs are determined using deep-level transient spectroscopy. The localization energy is 1.14(±0.04) eV, yielding a storage time at room temperature of 230(±60) s, which marks an improvement of 2 orders of magnitude compared to the former record value in QDs. Alternative material systems are proposed for still higher localization energies and longer storage times.

On heat transfer in squish gaps

NASA Astrophysics Data System (ADS)

Spurk, J. H.

1986-06-01

Attention is given to the heat transfer characteristics of a squish gap in an internal combustion engine cylinder, when the piston is nearing top dead center (TDC) on the compression stroke. If the lateral extent of the gap is much larger than its height, the inviscid flow is similar to the stagnation point flow. Surface temperature and pressure histories during compression and expansion are studied. Surface temperature has a maximum near TDC, then drops and rises again during expansion; higher values are actually achieved during expansion than during compression.

Energy value of paraquat-treated and resin-soaked lobolly pine

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

Kossuth, S.V.; Roberts, D.R.; Huffman, J.B.

1984-07-01

With a basal injector, loblolly pines were treated with 5% paraquat cation (weight/weight basis) and harvested after 18 months. The resin acid, turpentine, moisture content (MC) and energy value were measured in three bolts of the stem. In bolt 1, the first 152 cm above the injection site, the increase in resin acids was 392% and in turpentine, 564%. Within the whole stem (the first two 152 cm bolts and the third bolt to a 7.6 cm inside-bark diameter) resin acids and turpentine increased 203 and 296% respectively. Moisture content was reduced 9%, 8%, and 8% in bolts 1, 2more » and 3, respectively. Turpentine from treated and untreated trees had an average heating value of 19,369 cal/g. When weighted for volume, net energy content was 7.8% greater for treated than control trees because of the increase in resin, including turpentine and the lowered MC.« less

Photovoltaics as a terrestrial energy source. Volume 2: System value

NASA Technical Reports Server (NTRS)

Smith, J. L.

1980-01-01

Assumptions and techniques employed by the electric utility industry and other electricity planners to make estimates of the future value of photovoltaic (PV) systems interconnected with U.S. electric utilities were examined. Existing estimates of PV value and their interpretation and limitations are discussed. PV value is defined as the marginal private savings accruing to potential PV owners. For utility-owned PV systems, these values are shown to be the after-tax savings in conventional fuel and capacity displaced by the PV output. For non-utility-owned (distributed) systems, the utility's savings in fuel and capacity must first be translated through the electric rate structure (prices) to the potential PV system owner. Base-case estimates of the average value of PV systems to U.S. utilities are presented. The relationship of these results to the PV Program price goals and current energy policy is discussed; the usefulness of PV output quantity goals is also reviewed.

Resonantly enhanced multiple exciton generation through below-band-gap multi-photon absorption in perovskite nanocrystals.

PubMed

Manzi, Aurora; Tong, Yu; Feucht, Julius; Yao, En-Ping; Polavarapu, Lakshminarayana; Urban, Alexander S; Feldmann, Jochen

2018-04-17

Multi-photon absorption and multiple exciton generation represent two separate strategies for enhancing the conversion efficiency of light into usable electric power. Targeting below-band-gap and above-band-gap energies, respectively, to date these processes have only been demonstrated independently. Here we report the combined interaction of both nonlinear processes in CsPbBr 3 perovskite nanocrystals. We demonstrate nonlinear absorption over a wide range of below-band-gap excitation energies (0.5-0.8 E g ). Interestingly, we discover high-order absorption processes, deviating from the typical two-photon absorption, at specific energetic positions. These energies are associated with a strong enhancement of the photoluminescence intensity by up to 10 5 . The analysis of the corresponding energy levels reveals that the observed phenomena can be ascribed to the resonant creation of multiple excitons via the absorption of multiple below-band-gap photons. This effect may open new pathways for the efficient conversion of optical energy, potentially also in other semiconducting materials.

Ultrafast Gap Dynamics and Electronic Interactions in a Photoexcited Cuprate Superconductor

DOE PAGES

Parham, S.; Li, H.; Nummy, T. J.; ...

2017-10-20

We perform time- and angle-resolved photoemission spectroscopy (trARPES) on optimally doped Bi 2Sr 2CaCu 2O 8+δ (BSCCO-2212) using sufficient energy resolution (9 meV) to resolve the k-dependent near-nodal gap structure on time scales where the concept of an electronic pseudotemperature is a useful quantity, i.e., after electronic thermalization has occurred. We study the ultrafast evolution of this gap structure, uncovering a very rich landscape of decay rates as a function of angle, temperature, and energy. We explicitly focus on the quasiparticle states at the gap edge as well as on the spectral weight inside the gap that “fills” the gap—understoodmore » as an interaction, or self-energy effect—and we also make high resolution measurements of the nodal states, enabling a direct and accurate measurement of the electronic temperature (or pseudotemperature) of the electrons in the system. Rather than the standard method of interpreting these results using individual quasiparticle scattering rates that vary significantly as a function of angle, temperature, and energy, we show that the entire landscape of relaxations can be understood by modeling the system as following a nonequilibrium, electronic pseudotemperature that controls all electrons in the zone. Furthermore, this model has zero free parameters, as we obtain the crucial information of the SC gap Δ and the gap-filling strength Γ TDoS by connecting to static ARPES measurements. The quantitative and qualitative agreement between data and model suggests that the critical parameters and interactions of the system, including the pairing interactions, follow parametrically from the electronic pseudotemperature. In conclusion, we expect that this concept will be relevant for understanding the ultrafast response of a great variety of electronic materials, even though the electronic pseudotemperature may not be directly measurable.« less

Ultrafast Gap Dynamics and Electronic Interactions in a Photoexcited Cuprate Superconductor

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

Parham, S.; Li, H.; Nummy, T. J.

We perform time- and angle-resolved photoemission spectroscopy (trARPES) on optimally doped Bi 2Sr 2CaCu 2O 8+δ (BSCCO-2212) using sufficient energy resolution (9 meV) to resolve the k-dependent near-nodal gap structure on time scales where the concept of an electronic pseudotemperature is a useful quantity, i.e., after electronic thermalization has occurred. We study the ultrafast evolution of this gap structure, uncovering a very rich landscape of decay rates as a function of angle, temperature, and energy. We explicitly focus on the quasiparticle states at the gap edge as well as on the spectral weight inside the gap that “fills” the gap—understoodmore » as an interaction, or self-energy effect—and we also make high resolution measurements of the nodal states, enabling a direct and accurate measurement of the electronic temperature (or pseudotemperature) of the electrons in the system. Rather than the standard method of interpreting these results using individual quasiparticle scattering rates that vary significantly as a function of angle, temperature, and energy, we show that the entire landscape of relaxations can be understood by modeling the system as following a nonequilibrium, electronic pseudotemperature that controls all electrons in the zone. Furthermore, this model has zero free parameters, as we obtain the crucial information of the SC gap Δ and the gap-filling strength Γ TDoS by connecting to static ARPES measurements. The quantitative and qualitative agreement between data and model suggests that the critical parameters and interactions of the system, including the pairing interactions, follow parametrically from the electronic pseudotemperature. In conclusion, we expect that this concept will be relevant for understanding the ultrafast response of a great variety of electronic materials, even though the electronic pseudotemperature may not be directly measurable.« less

Gaps in agricultural climate adaptation research

NASA Astrophysics Data System (ADS)

Davidson, Debra

2016-05-01

The value of the social sciences to climate change research is well recognized, but notable gaps remain in the literature on adaptation in agriculture. Contributions focus on farmer behaviour, with important research regarding gender, social networks and institutions remaining under-represented.

Band gap and electronic structure of MgSiN2

NASA Astrophysics Data System (ADS)

Quirk, J. B.; Râsander, M.; McGilvery, C. M.; Palgrave, R.; Moram, M. A.

2014-09-01

Density functional theory calculations and electron energy loss spectroscopy indicate that the electronic structure of ordered orthorhombic MgSiN2 is similar to that of wurtzite AlN. A band gap of 5.7 eV was calculated for both MgSiN2 (indirect) and AlN (direct) using the Heyd-Scuseria-Ernzerhof approximation. Correction with respect to the experimental room-temperature band gap of AlN indicates that the true band gap of MgSiN2 is 6.2 eV. MgSiN2 has an additional direct gap of 6.3 eV at the Γ point.

Net energy content of canola meal fed to growing pigs and effect of experimental methodology on energy values.

PubMed

Kim, J W; Koo, B; Nyachoti, C M

2018-04-14

An experiment was conducted to determine the digestible energy (DE), metabolizable energy (ME), and net energy (NE) contents of canola meal (CM) and to investigate the effects of basal diet [corn diet vs. corn-soybean meal (SBM) diet] and methodology (difference method vs. regression method) on energy values of CM. Thirty-six growing barrows (20.8 ± 1.0 kg initial body weight [BW]) were individually housed in metabolism crates and randomly allotted to one of six dietary treatments to give six replicates per treatment. The six experimental diets included a corn diet, a corn-SBM diet, a corn diet with 15 or 30% of CM, and a corn-SBM diet with 15 or 30% of CM. The DE, ME, and NE of CM were determined using the corn diet or the corn-SBM diet as a basal diet. In each basal diet, two additional diets containing 15 or 30% of CM were formulated to compare the determined energy values by the difference method and estimated energy values from the regression method. Feeding level was set at 550 kcal ME/kg BW0.6 per day. Pigs were fed experimental diets for 16 d including 10 d for adaptation and 6 d for total collection of feces and urine. Pigs were then moved into indirect calorimetry chambers to determine 24 h heat production (HP) and 12 h fasting HP. The DE, ME, and NE of CM determined by the difference method were within the 95% confidence intervals estimated for the DE, ME, and NE of CM by the regression method regardless of the basal diets used, which indicates that the difference and regression methods give equivalent DE, ME, and NE of CM. However, when the goodness of fit for the linear model was compared, the r2 of the regression analysis from the corn-SBM diet (0.78) was relatively greater than that from corn diet (0.40). The estimated NE of CM by the prediction equations generated by either the corn diet or corn-SBM diets were 2,096 kcal/kg and 1,960 kcal/kg (as-fed basis), respectively, whereas those values determined by the difference method were 2,233 kcal

Local strain-induced band gap fluctuations and exciton localization in aged WS2 monolayers

NASA Astrophysics Data System (ADS)

Krustok, J.; Kaupmees, R.; Jaaniso, R.; Kiisk, V.; Sildos, I.; Li, B.; Gong, Y.

2017-06-01

Optical properties of aged WS2 monolayers grown by CVD method on Si/SiO2 substrates are studied using temperature dependent photoluminescence and reflectance contrast spectroscopy. Aged WS2 monolayers have a typical surface roughness about 0.5 nm and, in addition, a high density of nanoparticles (nanocaps) with the base diameter about 30 nm and average height of 7 nm. The A-exciton of aged monolayer has a peak position at 1.951 eV while in as-grown monolayer the peak is at about 24 meV higher energy at room temperature. This red-shift is explained using local tensile strain concept, where strain value of 2.1% was calculated for these nanocap regions. Strained nanocaps have lower band gap energy and excitons will funnel into these regions. At T=10K a double exciton and trion peaks were revealed. The separation between double peaks is about 20 meV and the origin of higher energy peaks is related to the optical band gap energy fluctuations caused by random distribution of local tensile strain due to increased surface roughness. In addition, a wide defect related exciton band XD was found at about 1.93 eV in all aged monolayers. It is shown that the theory of localized excitons describes well the temperature dependence of peak position and halfwidth of the A-exciton band. The possible origin of nanocaps is also discussed.

Thermoelectric properties of heavily GaP- and P-doped Si0.95Ge0.05

NASA Astrophysics Data System (ADS)

Yamashita, Osamu

2001-06-01

The Seebeck coefficient S, the electrical resistivity ρ and the thermal conductivity κ of Si0.95Ge0.05 samples doped with 0.4 at. % P and/or 0.5-2.0 mol % GaP, which were prepared by a conventional arc melting method, were measured as functions of GaP content and temperature T in the range from 323 to 1208 K. When multidoped with P and GaP, Ga tends to segregate more strongly with Ge to the grain boundaries than P, while when doped with GaP alone, both P and Ga segregate equally strongly with Ge. For multidoped samples, the S values at 323 K have a minimum at 1.0 mol % GaP and then increase with additional GaP, while the values of ρ and κ decrease monotonically with increasing GaP content. The optimum additional content of GaP that gives the largest thermoelectric figures of merit (ZT=S2T/κρ) for multidoped n-type Si0.95Ge0.05 samples was 1.5 mol %, which is slightly less than the 2.0 mol % of GaP added to Si0.8Ge0.2 alloy by hot pressing. The ZT value for multidoped Si0.95Ge0.05 with an optimum content of GaP increases linearly with temperature, and at 1073 K is 18% higher than that obtained previously for Si0.95Ge0.05 doped with only 0.4 at. % P. At 1173 K the ZT value is 1.16, which corresponds to 95% of that obtained previously at the corresponding temperature for Si0.8Ge0.2 alloy doped with 2.0 mol % GaP.

Band gap scaling laws in group IV nanotubes.

PubMed

Wang, Chongze; Fu, Xiaonan; Guo, Yangyang; Guo, Zhengxiao; Xia, Congxin; Jia, Yu

2017-03-17

By using the first-principles calculations, the band gap properties of nanotubes formed by group IV elements have been investigated systemically. Our results reveal that for armchair nanotubes, the energy gaps at K points in the Brillouin zone decrease as 1/r scaling law with the radii (r) increasing, while they are scaled by -1/r 2  + C at Γ points, here, C is a constant. Further studies show that such scaling law of K points is independent of both the chiral vector and the type of elements. Therefore, the band gaps of nanotubes for a given radius can be determined by these scaling laws easily. Interestingly, we also predict the existence of indirect band gap for both germanium and tin nanotubes. Our new findings provide an efficient way to determine the band gaps of group IV element nanotubes by knowing the radii, as well as to facilitate the design of functional nanodevices.

Assigning value to energy storage systems at multiple points in an electrical grid

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

Balducci, Patrick J.; Alam, M. Jan E.; Hardy, Trevor D.

This article presents a taxonomy for assigning benefits to the services provided by energy storage systems (ESSs), defines approaches for monetizing the value associated with these services, assigns values to major ESS applications by region based on a review of an extensive set of literature, and summarizes and evaluates the capabilities of several tools currently used to estimate value for specific ESS deployments.

Assigning value to energy storage systems at multiple points in an electrical grid

DOE PAGES

Balducci, Patrick J.; Alam, M. Jan E.; Hardy, Trevor D.; ...

2018-01-01

This article presents a taxonomy for assigning benefits to the services provided by energy storage systems (ESSs), defines approaches for monetizing the value associated with these services, assigns values to major ESS applications by region based on a review of an extensive set of literature, and summarizes and evaluates the capabilities of several tools currently used to estimate value for specific ESS deployments.

SOF Integration with Conventional Forces: A Doctrine Gap?

DTIC Science & Technology

2011-12-01

close tolerances, friction in an engine can be reduced considerably. However, there will always be energy lost in the system as heat. The goal is to...armed peshmerga. The combat power analysis favored the Iraqis on the ground. JSOTF planners only recourse was to rely on air power to close this gap . A...Approved for Public Release; Distribution is Unlimited SOF Integration with Conventional Forces: A Doctrine Gap ? A Monograph by MAJ Gregory M

Optical characterization of poly(methyl methacrylate) implanted with low energy ions

NASA Astrophysics Data System (ADS)

Gupta, Renu; Kumar, Vijay; Goyal, Parveen Kumar; Kumar, Shyam

2012-12-01

The samples of poly(methyl methacrylate) (PMMA) were subjected to 100 keV N+ and Ar+ ion implantation up to a maximum fluence of 2 × 1016 ions/cm2. The effect of ion implantation on the optical energy gap and the refractive index has been studied through UV-visible spectroscopy. The results clearly indicate a decrease in the values of optical energy gap and an increase in the values of refractive index as an effect of ion implantation corresponding to both of the ions. It has also been observed that the changes induced by the implanted ions are more pronounced for N+ ions in comparison to Ar+ ions. This variation has been correlated with the calculated ranges of these ions in PMMA polymer using Stopping and Range of Ions in Matter (SRIM) code. Finally, an attempt has been made to correlate all the observed changes with the induced structural changes as revealed through Raman spectroscopy.

Effects of optical band gap energy, band tail energy and particle shape on photocatalytic activities of different ZnO nanostructures prepared by a hydrothermal method

NASA Astrophysics Data System (ADS)

Klubnuan, Sarunya; Suwanboon, Sumetha; Amornpitoksuk, Pongsaton

2016-03-01

The dependence of the crystallite size and the band tail energy on the optical properties, particle shape and oxygen vacancy of different ZnO nanostructures to catalyse photocatalytic degradation was investigated. The ZnO nanoplatelets and mesh-like ZnO lamellae were synthesized from the PEO19-b-PPO3 modified zinc acetate dihydrate using aqueous KOH and CO(NH2)2 solutions, respectively via a hydrothermal method. The band tail energy of the ZnO nanostructures had more influence on the band gap energy than the crystallite size. The photocatalytic degradation of methylene blue increased as a function of the irradiation time, the amount of oxygen vacancy and the intensity of the (0 0 0 2) plane. The ZnO nanoplatelets exhibited a better photocatalytic degradation of methylene blue than the mesh-like ZnO lamellae due to the migration of the photoelectrons and holes to the (0 0 0 1) and (0 0 0 -1) planes, respectively under the internal electric field, that resulted in the enhancement of the photocatalytic activities.

Self-amplified photo-induced gap quenching in a correlated electron material

PubMed Central

Mathias, S.; Eich, S.; Urbancic, J.; Michael, S.; Carr, A. V.; Emmerich, S.; Stange, A.; Popmintchev, T.; Rohwer, T.; Wiesenmayer, M.; Ruffing, A.; Jakobs, S.; Hellmann, S.; Matyba, P.; Chen, C.; Kipp, L.; Bauer, M.; Kapteyn, H. C.; Schneider, H. C.; Rossnagel, K.; Murnane, M. M.; Aeschlimann, M.

2016-01-01

Capturing the dynamic electronic band structure of a correlated material presents a powerful capability for uncovering the complex couplings between the electronic and structural degrees of freedom. When combined with ultrafast laser excitation, new phases of matter can result, since far-from-equilibrium excited states are instantaneously populated. Here, we elucidate a general relation between ultrafast non-equilibrium electron dynamics and the size of the characteristic energy gap in a correlated electron material. We show that carrier multiplication via impact ionization can be one of the most important processes in a gapped material, and that the speed of carrier multiplication critically depends on the size of the energy gap. In the case of the charge-density wave material 1T-TiSe2, our data indicate that carrier multiplication and gap dynamics mutually amplify each other, which explains—on a microscopic level—the extremely fast response of this material to ultrafast optical excitation. PMID:27698341

Self-amplified photo-induced gap quenching in a correlated electron material

DOE PAGES

Mathias, S.; Eich, S.; Urbancic, J.; ...

2016-10-04

Capturing the dynamic electronic band structure of a correlated material presents a powerful capability for uncovering the complex couplings between the electronic and structural degrees of freedom. When combined with ultrafast laser excitation, new phases of matter can result, since far-from-equilibrium excited states are instantaneously populated. Here, we elucidate a general relation between ultrafast non-equilibrium electron dynamics and the size of the characteristic energy gap in a correlated electron material. Here, we show that carrier multiplication via impact ionization can be one of the most important processes in a gapped material, and that the speed of carrier multiplication critically dependsmore » on the size of the energy gap. In the case of the charge-density wave material 1T-TiSe 2, our data indicate that carrier multiplication and gap dynamics mutually amplify each other, which explains—on a microscopic level—the extremely fast response of this material to ultrafast optical excitation.« less

Band gap engineering for graphene by using Na{sup +} ions

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

Sung, S. J.; Lee, P. R.; Kim, J. G.

2014-08-25

Despite the noble electronic properties of graphene, its industrial application has been hindered mainly by the absence of a stable means of producing a band gap at the Dirac point (DP). We report a new route to open a band gap (E{sub g}) at DP in a controlled way by depositing positively charged Na{sup +} ions on single layer graphene formed on 6H-SiC(0001) surface. The doping of low energy Na{sup +} ions is found to deplete the π* band of graphene above the DP, and simultaneously shift the DP downward away from Fermi energy indicating the opening of E{sub g}.more » The band gap increases with increasing Na{sup +} coverage with a maximum E{sub g}≥0.70 eV. Our core-level data, C 1s, Na 2p, and Si 2p, consistently suggest that Na{sup +} ions do not intercalate through graphene, but produce a significant charge asymmetry among the carbon atoms of graphene to cause the opening of a band gap. We thus provide a reliable way of producing and tuning the band gap of graphene by using Na{sup +} ions, which may play a vital role in utilizing graphene in future nano-electronic devices.« less

Damping Resonant Current in a Spark-Gap Trigger Circuit to Reduce Noise

DTIC Science & Technology

2009-06-01

DAMPING RESONANT CURRENT IN A SPARK- GAP TRIGGER CIRCUIT TO REDUCE NOISE E. L. Ruden Air Force Research Laboratory, Directed Energy Directorate, AFRL...REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Damping Resonant Current In A Spark- Gap Trigger Circuit To Reduce Noise 5a...thereby triggering 2 after delay 0, is 1. Each of the two rail- gaps (represented by 2) is trig- gered to close after the spark- gap (1) in the

New insights into the opening band gap of graphene oxides

NASA Astrophysics Data System (ADS)

Tran, Ngoc Thanh Thuy; Lin, Shih-Yang; Lin, Ming-Fa

Electronic properties of oxygen absorbed few-layer graphenes are investigated using first-principle calculations. They are very sensitive to the changes in the oxygen concentration, number of graphene layer, and stacking configuration. The feature-rich band structures exhibit the destruction or distortion of the Dirac cone, opening of band gap, anisotropic energy dispersions, O- and (C,O)-dominated energy dispersions, and extra critical points. The band decomposed charge distributions reveal the π-bonding dominated energy gap. The orbital-projected density of states (DOS) have many special structures mainly coming from a composite energy band, the parabolic and partially flat ones. The DOS and spatial charge distributions clearly indicate the critical orbital hybridizations in O-O, C-O and C-C bonds, being responsible for the diversified properties. All of the few-layer graphene oxides are semi-metals except for the semiconducting monolayer ones.

Ninth Graders' Energy Balance Knowledge and Physical Activity Behavior: An Expectancy-Value Perspective

ERIC Educational Resources Information Center

Chen, Senlin; Chen, Ang

2012-01-01

Expectancy beliefs and task values are two essential motivators in physical education. This study was designed to identify the relation between the expectancy-value constructs (Eccles & Wigfield, 1995) and high school students' physical activity behavior as associated with their energy balance knowledge. High school students (N = 195) in two…

Optical Band Gap Alteration of Graphene Oxide via Ozone Treatment.

PubMed

Hasan, Md Tanvir; Senger, Brian J; Ryan, Conor; Culp, Marais; Gonzalez-Rodriguez, Roberto; Coffer, Jeffery L; Naumov, Anton V

2017-07-25

Graphene oxide (GO) is a graphene derivative that emits fluorescence, which makes GO an attractive material for optoelectronics and biotechnology. In this work, we utilize ozone treatment to controllably tune the band gap of GO, which can significantly enhance its applications. Ozone treatment in aqueous GO suspensions yields the addition/rearrangement of oxygen-containing functional groups suggested by the increase in vibrational transitions of C-O and C=O moieties. Concomitantly it leads to an initial increase in GO fluorescence intensity and significant (100 nm) blue shifts in emission maxima. Based on the model of GO fluorescence originating from sp 2 graphitic islands confined by oxygenated addends, we propose that ozone-induced functionalization decreases the size of graphitic islands affecting the GO band gap and emission energies. TEM analyses of GO flakes confirm the size decrease of ordered sp 2 domains with ozone treatment, whereas semi-empirical PM3 calculations on model addend-confined graphitic clusters predict the inverse dependence of the band gap energies on sp 2 cluster size. This model explains ozone-induced increase in emission energies yielding fluorescence blue shifts and helps develop an understanding of the origins of GO fluorescence emission. Furthermore, ozone treatment provides a versatile approach to controllably alter GO band gap for optoelectronics and bio-sensing applications.

Measurement of knee joint gaps without bone resection: "physiologic" extension and flexion gaps in total knee arthroplasty are asymmetric and unequal and anterior and posterior cruciate ligament resections produce different gap changes.

PubMed

Nowakowski, Andrej Maria; Majewski, Martin; Müller-Gerbl, Magdalena; Valderrabano, Victor

2012-04-01

General agreement is that flexion and extension gaps should be equal and symmetrical in total knee arthroplasty (TKA) procedures. However, comparisons using a standard TKA approach to normal knee joints that have not undergone bone resection are currently unavailable. Since bony preparation can influence capsule and ligament tension, our purpose was to perform measurements without this influence. Ten normal cadaveric knees were assessed using a standard medial parapatellar TKA approach with patellar subluxation. Gap measurements were carried out twice each alternating 100 and 200 N per compartment using a prototypical force-determining ligament balancer without the need for bony resection. Initial measurements were performed in extension, followed by 908 of flexion. The ACL was then resected, and finally the PCL was resected, and measurements were carried out in an analogous fashion. In general, the lateral compartment could be stretched further than the medial compartment, and the corresponding flexion gap values were significantly larger. ACL resection predominantly increased extension gaps, while PCL resection increased flexion gaps. Distraction force of 100 N per compartment appeared adequate; increasing to 200 N did not improve the results.

Determination of shift in energy of band edges and band gap of ZnSe spherical quantum dot

NASA Astrophysics Data System (ADS)

Siboh, Dutem; Kalita, Pradip Kumar; Sarma, Jayanta Kumar; Nath, Nayan Mani

2018-04-01

We have determined the quantum confinement induced shifts in energy of band edges and band gap with respect to size of ZnSe spherical quantum dot employing an effective confinement potential model developed in our earlier communication "arXiv:1705.10343". We have also performed phenomenological analysis of our theoretical results in comparison with available experimental data and observe a very good agreement in this regard. Phenomenological success achieved in this regard confirms validity of the confining potential model as well as signifies the capability and applicability of the ansatz for the effective confining potential to have reasonable information in the study of real nano-structured spherical systems.

Remote modulation of singlet-triplet gaps in carbenes

NASA Astrophysics Data System (ADS)

Alkorta, Ibon; Montero-Campillo, M. Merced; Elguero, José

2018-02-01

The modulation of the singlet-triplet (S/T) gap of phenyl-carbene derivatives by hydrogen bond formation has been studied using the G4(MP2) computational method. The complexation of the aromatic ring substituents (-NH2, -OH, -PH2, -SH) in meta- and para-positions with water and the protonation or deprotonation of such groups have a remarkable influence on the S/T gaps, reaching S/T gap variations from 25.7 to 93.7 kJ mol-1. This variation is linearly related to the binding energy difference of the S/T configurations. Importantly, the triplet and singlet electronic configurations are systematically favored in the protonated and deprotonated forms, respectively, in all cases.

Rebranding exercise: closing the gap between values and behavior

PubMed Central

2011-01-01

Background Behavior can only be understood by identifying the goals to which it is attached. Superordinate-level goals are linked to individuals' values, and may offer insights into how to connect exercise with their core values and increase participation in sustainable ways. Methods A random sample of healthy midlife women (aged 40-60y) was selected to participate in a year-long mixed-method study (n = 226). Superordinate goals were measured inductively and analyzed using grounded theory analysis. Attainment Value and Exercise Participation were quantitatively measured. An ANOVA and pairwise comparisons were conducted to investigate the differences between superordinate exercise goals in attainment value. This study fit a Linear Mixed Model to the data to investigate the fixed effects of superordinate goals on exercise participation, controlling for BMI and social support. Results Participants mainly exercised to achieve Healthy-Aging, Quality-of-Life, Current-Health, and Appearance/Weight superordinate goals. Despite equally valuing Healthy-Aging, Quality-of-Life, and Current-Health goals, participants with Quality-of-Life goals reported participating in more exercise than those with Current-Health (p < 0.01), and Healthy-Aging (p = 0.06) goals. Conclusions Superordinate exercise goals related to health and healthy aging are associated with less exercise than those related to enhancing daily quality of life, despite being equally valued. While important, pursuing distant benefits from exercise such as health promotion, disease prevention, and longevity might not be as compelling to busy individuals compared to their other daily priorities and responsibilities. By shifting our paradigm from medicine to marketing, we can glean insights into how we can better market and "sell" exercise. Because immediate payoffs motivate behavior better than distant goals, a more effective "hook" for promoting sustainable participation might be to rebrand exercise as a primary way

Rebranding exercise: closing the gap between values and behavior.

PubMed

Segar, Michelle L; Eccles, Jacquelynne S; Richardson, Caroline R

2011-08-31

Behavior can only be understood by identifying the goals to which it is attached. Superordinate-level goals are linked to individuals' values, and may offer insights into how to connect exercise with their core values and increase participation in sustainable ways. A random sample of healthy midlife women (aged 40-60y) was selected to participate in a year-long mixed-method study (n = 226). Superordinate goals were measured inductively and analyzed using grounded theory analysis. Attainment Value and Exercise Participation were quantitatively measured. An ANOVA and pairwise comparisons were conducted to investigate the differences between superordinate exercise goals in attainment value. This study fit a Linear Mixed Model to the data to investigate the fixed effects of superordinate goals on exercise participation, controlling for BMI and social support. Participants mainly exercised to achieve Healthy-Aging, Quality-of-Life, Current-Health, and Appearance/Weight superordinate goals. Despite equally valuing Healthy-Aging, Quality-of-Life, and Current-Health goals, participants with Quality-of-Life goals reported participating in more exercise than those with Current-Health (p < 0.01), and Healthy-Aging (p = 0.06) goals. Superordinate exercise goals related to health and healthy aging are associated with less exercise than those related to enhancing daily quality of life, despite being equally valued. While important, pursuing distant benefits from exercise such as health promotion, disease prevention, and longevity might not be as compelling to busy individuals compared to their other daily priorities and responsibilities. By shifting our paradigm from medicine to marketing, we can glean insights into how we can better market and "sell" exercise. Because immediate payoffs motivate behavior better than distant goals, a more effective "hook" for promoting sustainable participation might be to rebrand exercise as a primary way individuals can enhance the quality of

GapBlaster-A Graphical Gap Filler for Prokaryote Genomes.

PubMed

de Sá, Pablo H C G; Miranda, Fábio; Veras, Adonney; de Melo, Diego Magalhães; Soares, Siomar; Pinheiro, Kenny; Guimarães, Luis; Azevedo, Vasco; Silva, Artur; Ramos, Rommel T J

2016-01-01

The advent of NGS (Next Generation Sequencing) technologies has resulted in an exponential increase in the number of complete genomes available in biological databases. This advance has allowed the development of several computational tools enabling analyses of large amounts of data in each of the various steps, from processing and quality filtering to gap filling and manual curation. The tools developed for gap closure are very useful as they result in more complete genomes, which will influence downstream analyses of genomic plasticity and comparative genomics. However, the gap filling step remains a challenge for genome assembly, often requiring manual intervention. Here, we present GapBlaster, a graphical application to evaluate and close gaps. GapBlaster was developed via Java programming language. The software uses contigs obtained in the assembly of the genome to perform an alignment against a draft of the genome/scaffold, using BLAST or Mummer to close gaps. Then, all identified alignments of contigs that extend through the gaps in the draft sequence are presented to the user for further evaluation via the GapBlaster graphical interface. GapBlaster presents significant results compared to other similar software and has the advantage of offering a graphical interface for manual curation of the gaps. GapBlaster program, the user guide and the test datasets are freely available at https://sourceforge.net/projects/gapblaster2015/. It requires Sun JDK 8 and Blast or Mummer.

GaP betavoltaic cells as a power source

NASA Technical Reports Server (NTRS)

Pool, F. S.; Stella, Paul M.; Anspaugh, B.

1991-01-01

Maximum power output for the GaP cells of this study was found to be on the order of 1 microW. This resulted from exposure to 200 and 40 KeV electrons at a flux of 2 x 10(exp 9) electrons/sq cm/s, equivalent to a 54 mCurie source. The efficiencies of the cells ranged from 5 to 9 percent for 200 and 40 KeV electrons respectively. The lower efficiency at higher energy is due to a substantial fraction of energy deposition in the substrate, further than a diffusion length from the depletion region of the cell. Radiation damage was clearly observed in GaP after exposure to 200 KeV electrons at a fluence of 2 x 10(exp 12) electrons/sq cm. No discernable damage was observed after exposure to 40 KeV electrons at the same fluence. Analysis indicates that a GaP betavoltaic system would not be practical if limited to low energy beta sources. The power available would be too low even in the ideal case. By utilizing high activity beta sources, such as Sr-90/Y-90, it may be possible to achieve performance that could be suitable for some space power applications. However, to utilize such a source the problem of radiation damage in the beta cell material must be overcome.

Competence-Based Approach in Value Chain Processes

NASA Astrophysics Data System (ADS)

Azevedo, Rodrigo Cambiaghi; D'Amours, Sophie; Rönnqvist, Mikael

There is a gap between competence theory and value chain processes frameworks. While individually considered as core elements in contemporary management thinking, the integration of the two concepts is still lacking. We claim that this integration would allow for the development of more robust business models by structuring value chain activities around aspects such as capabilities and skills, as well as individual and organizational knowledge. In this context, the objective of this article is to reduce this gap and consequently open a field for further improvements of value chain processes frameworks.

The composition, heating value and renewable share of the energy content of mixed municipal solid waste in Finland.

PubMed

Horttanainen, M; Teirasvuo, N; Kapustina, V; Hupponen, M; Luoranen, M

2013-12-01

For the estimation of greenhouse gas emissions from waste incineration it is essential to know the share of the renewable energy content of the combusted waste. The composition and heating value information is generally available, but the renewable energy share or heating values of different fractions of waste have rarely been determined. In this study, data from Finnish studies concerning the composition and energy content of mixed MSW were collected, new experimental data on the compositions, heating values and renewable share of energy were presented and the results were compared to the estimations concluded from earlier international studies. In the town of Lappeenranta in south-eastern Finland, the share of renewable energy ranged between 25% and 34% in the energy content tests implemented for two sample trucks. The heating values of the waste and fractions of plastic waste were high in the samples compared to the earlier studies in Finland. These high values were caused by good source separation and led to a low share of renewable energy content in the waste. The results showed that in mixed municipal solid waste the renewable share of the energy content can be significantly lower than the general assumptions (50-60%) when the source separation of organic waste, paper and cardboard is carried out successfully. The number of samples was however small for making extensive conclusions on the results concerning the heating values and renewable share of energy and additional research is needed for this purpose. Copyright © 2013 Elsevier Ltd. All rights reserved.

High efficiency GaP power conversion for Betavoltaic applications

NASA Astrophysics Data System (ADS)

Sims, Paul E.; Dinetta, Louis C.; Barnett, Allen M.

1994-09-01

AstroPower is developing a gallium phosphide (GaP) based energy converter optimized for radio luminescent light-based power supplies. A 'two-step' or 'indirect' process is used where a phosphor is excited by radioactive decay products to produce light that is then converted to electricity by a photovoltaic energy converter. This indirect conversion of beta-radiation to electrical energy can be realized by applying recent developments in tritium based radio luminescent (RL) light sources in combination with the high conversion efficiencies that can be achieved under low illumination with low leakage, gallium phosphide based devices. This tritium to light approach is inherently safer than battery designs that incorporate high activity radionuclides because the beta particles emitted by tritium are of low average energy and are easily stopped by a thin layer of glass. GaP layers were grown by liquid phase epitaxy and p/n junction devices were fabricated and characterized for low light intensity power conversion. AstroPower has demonstrated the feasibility of the GaP based energy converter with the following key results: 23.54 percent conversion efficiency under 968 muW/sq cm 440 nm blue light, 14.59 percent conversion efficiency for 2.85 muW/sq cm 440 nm blue light, and fabrication of working 5 V array. We have also determined that at least 20 muW/sq cm optical power is available for betavoltaic power systems. Successful developments of this device is an enabling technology for low volume, safe, high voltage, milliwatt power supplies with service lifetimes in excess of 12 years.

High efficiency GaP power conversion for Betavoltaic applications

NASA Technical Reports Server (NTRS)

Sims, Paul E.; Dinetta, Louis C.; Barnett, Allen M.

1994-01-01

AstroPower is developing a gallium phosphide (GaP) based energy converter optimized for radio luminescent light-based power supplies. A 'two-step' or 'indirect' process is used where a phosphor is excited by radioactive decay products to produce light that is then converted to electricity by a photovoltaic energy converter. This indirect conversion of beta-radiation to electrical energy can be realized by applying recent developments in tritium based radio luminescent (RL) light sources in combination with the high conversion efficiencies that can be achieved under low illumination with low leakage, gallium phosphide based devices. This tritium to light approach is inherently safer than battery designs that incorporate high activity radionuclides because the beta particles emitted by tritium are of low average energy and are easily stopped by a thin layer of glass. GaP layers were grown by liquid phase epitaxy and p/n junction devices were fabricated and characterized for low light intensity power conversion. AstroPower has demonstrated the feasibility of the GaP based energy converter with the following key results: 23.54 percent conversion efficiency under 968 muW/sq cm 440 nm blue light, 14.59 percent conversion efficiency for 2.85 muW/sq cm 440 nm blue light, and fabrication of working 5 V array. We have also determined that at least 20 muW/sq cm optical power is available for betavoltaic power systems. Successful developments of this device is an enabling technology for low volume, safe, high voltage, milliwatt power supplies with service lifetimes in excess of 12 years.

Field-Induced-Gap Infrared Detectors

NASA Technical Reports Server (NTRS)

Elliott, C. Thomas

1990-01-01

Semimetals become semiconductors under applied magnetic fields. New detectors require less cooling equipment because they operate at temperatures higher than liquid-helium temperatures required by extrinsic-semiconductor detectors. Magnetic fields for detectors provided by electromagnets based on recently-discovered high-transition-temperature superconducting materials. Detector material has to be semiconductor, in which photon absorbed by exciting electron/hole pair across gap Eg of forbidden energies between valence and conduction energy bands. Magnetic- and compositional-tuning effects combined to obtain two-absorber detector having narrow passband. By variation of applied magnetic field, passband swept through spectrum of interest.

Disappearance of nodal gap across the insulator-superconductor transition in a copper-oxide superconductor.

PubMed

Peng, Yingying; Meng, Jianqiao; Mou, Daixiang; He, Junfeng; Zhao, Lin; Wu, Yue; Liu, Guodong; Dong, Xiaoli; He, Shaolong; Zhang, Jun; Wang, Xiaoyang; Peng, Qinjun; Wang, Zhimin; Zhang, Shenjin; Yang, Feng; Chen, Chuangtian; Xu, Zuyan; Lee, T K; Zhou, X J

2013-01-01

The parent compound of the copper-oxide high-temperature superconductors is a Mott insulator. Superconductivity is realized by doping an appropriate amount of charge carriers. How a Mott insulator transforms into a superconductor is crucial in understanding the unusual physical properties of high-temperature superconductors and the superconductivity mechanism. Here we report high-resolution angle-resolved photoemission measurement on heavily underdoped Bi₂Sr₂-xLaxCuO(₆+δ) system. The electronic structure of the lightly doped samples exhibit a number of characteristics: existence of an energy gap along the nodal direction, d-wave-like anisotropic energy gap along the underlying Fermi surface, and coexistence of a coherence peak and a broad hump in the photoemission spectra. Our results reveal a clear insulator-superconductor transition at a critical doping level of ~0.10 where the nodal energy gap approaches zero, the three-dimensional antiferromagnetic order disappears, and superconductivity starts to emerge. These observations clearly signal a close connection between the nodal gap, antiferromagnetism and superconductivity.

The composition, heating value and renewable share of the energy content of mixed municipal solid waste in Finland

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

Horttanainen, M., E-mail: mika.horttanainen@lut.fi; Teirasvuo, N.; Kapustina, V.

Highlights: • New experimental data of mixed MSW properties in a Finnish case region. • The share of renewable energy of mixed MSW. • The results were compared with earlier international studies. • The average share of renewable energy was 30% and the average LHVar 19 MJ/kg. • Well operating source separation decreases the renewable energy content of MSW. - Abstract: For the estimation of greenhouse gas emissions from waste incineration it is essential to know the share of the renewable energy content of the combusted waste. The composition and heating value information is generally available, but the renewable energymore » share or heating values of different fractions of waste have rarely been determined. In this study, data from Finnish studies concerning the composition and energy content of mixed MSW were collected, new experimental data on the compositions, heating values and renewable share of energy were presented and the results were compared to the estimations concluded from earlier international studies. In the town of Lappeenranta in south-eastern Finland, the share of renewable energy ranged between 25% and 34% in the energy content tests implemented for two sample trucks. The heating values of the waste and fractions of plastic waste were high in the samples compared to the earlier studies in Finland. These high values were caused by good source separation and led to a low share of renewable energy content in the waste. The results showed that in mixed municipal solid waste the renewable share of the energy content can be significantly lower than the general assumptions (50–60%) when the source separation of organic waste, paper and cardboard is carried out successfully. The number of samples was however small for making extensive conclusions on the results concerning the heating values and renewable share of energy and additional research is needed for this purpose.« less

Detection thresholds for gaps, overlaps, and no-gap-no-overlaps.

PubMed

Heldner, Mattias

2011-07-01

Detection thresholds for gaps and overlaps, that is acoustic and perceived silences and stretches of overlapping speech in speaker changes, were determined. Subliminal gaps and overlaps were categorized as no-gap-no-overlaps. The established gap and overlap detection thresholds both corresponded to the duration of a long vowel, or about 120 ms. These detection thresholds are valuable for mapping the perceptual speaker change categories gaps, overlaps, and no-gap-no-overlaps into the acoustic domain. Furthermore, the detection thresholds allow generation and understanding of gaps, overlaps, and no-gap-no-overlaps in human-like spoken dialogue systems. © 2011 Acoustical Society of America

The value of health information technology: filling the knowledge gap.

PubMed

Rudin, Robert S; Jones, Spencer S; Shekelle, Paul; Hillestad, Richard J; Keeler, Emmett B

2014-11-01

Despite rapid growth in the rate of adoption of health information technology (HIT), and in the volume of evaluation studies, the existing knowledge base for the value of HIT is not advancing at a similar rate. Most evaluation articles are limited in that they use incomplete measures of value and fail to report the important contextual and implementation characteristics that would allow for an adequate understanding of how the study results were achieved. To address these deficiencies, we present a conceptual framework for measuring HIT value and we propose a checklist of characteristics that should be considered in HIT evaluation studies. The framework consists of 3 key principles: 1) value includes both costs and benefits; 2) value accrues over time; and 3) value depends on which stakeholder's perspective is used. Through examples, we show how these principles can be used to guide and improve HIT evaluation studies. The checklist includes a list of contextual and implementation characteristics that are important for interpretation of results. These improvements will make future studies more useful for policy makers and more relevant to the current needs of the healthcare system.

Compositional dependence of optical band gap and refractive index in lead and bismuth borate glasses

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

Mallur, Saisudha B.; Czarnecki, Tyler; Adhikari, Ashish

2015-08-15

Highlights: • Refractive indices increase with increasing PbO/Bi{sub 2}O{sub 3} content. • Optical band gap arises due to direct forbidden transition. • Optical band gaps decrease with increasing PbO/Bi{sub 2}O{sub 3} content. • New empirical relation between the optical band gap and the refractive index. - Abstract: We prepared a series of lead and bismuth borate glasses by varying PbO/Bi{sub 2}O{sub 3} content and studied refractive index and optical band gap as a function of glass composition. Refractive indices were measured very accurately using a Brewster’s angle set up while the optical band gaps were determined by analyzing the opticalmore » absorption edge using the Mott–Davis model. Using the Lorentz–Lorentz method and the effective medium theory, we calculated the refractive indices and then compared them with the measured values. Bismuth borate glasses show better agreement between the calculated values of the refractive index and experimental values. We used a differential method based on Mott–Davis model to obtain the type of transition and optical band gap (E{sub opt}) which in turn was compared with the value of E{sub opt} obtained using the extinction coefficient. Our analysis shows that in both lead and bismuth borate glasses, the optical band gap arises due to direct forbidden transition. With increasing PbO/Bi{sub 2}O{sub 3} content, the absorption edge shifts toward longer wavelengths and the optical band gap decreases. This behavior can be explained in terms of changes to the Pb−O/Bi−O chemical bonds with glass composition. We obtained a new empirical relation between the optical band gap and the refractive index which can be used to accurately determine the electronic oxide polarizability in lead and bismuth oxide glasses.« less

GaAsP on GaP top solar cells

NASA Technical Reports Server (NTRS)

Mcneely, J. B.; Negley, G. H.; Barnett, A. M.

1985-01-01

GaAsP on GaP top solar cells as an attachment to silicon bottom solar cells are being developed. The GaAsP on GaP system offers several advantages for this top solar cell. The most important is that the gallium phosphide substrate provides a rugged, transparent mechanical substrate which does not have to be removed or thinned during processing. Additional advantages are that: (1) gallium phosphide is more oxidation resistant than the III-V aluminum compounds, (2) a range of energy band gaps higher than 1.75 eV is readily available for system efficiency optimization, (3) reliable ohmic contact technology is available from the light-emitting diode industry, and (4) the system readily lends itself to graded band gap structures for additional increases in efficiency.

Bifurcation Gaps in Asymmetric and High-Dimensional Hypercycles

NASA Astrophysics Data System (ADS)

Puig, Júlia; Farré, Gerard; Guillamon, Antoni; Fontich, Ernest; Sardanyés, Josep

Hypercycles are catalytic systems with cyclic architecture. These systems have been suggested to play a key role in the maintenance and increase of information in prebiotic replicators. It is known that for a large enough number of hypercycle species (n > 4) the coexistence of all hypercycle members is governed by a stable periodic orbit. Previous research has characterized saddle-node (s-n) bifurcations involving abrupt transitions from stable hypercycles to extinction of all hypercycle members, or, alternatively, involving the outcompetition of the hypercycle by so-called mutant sequences or parasites. Recently, the presence of a bifurcation gap between a s-n bifurcation of periodic orbits and a s-n of fixed points has been described for symmetric five-member hypercycles. This gap was found between the value of the replication quality factor Q from which the periodic orbit vanishes (QPO) and the value where two unstable (nonzero) equilibrium points collide (QSS). Here, we explore the persistence of this gap considering asymmetries in replication rates in five-member hypercycles as well as considering symmetric, larger hypercycles. Our results indicate that both the asymmetry in Malthusian replication constants and the increase in hypercycle members enlarge the size of this gap. The implications of this phenomenon are discussed in the context of delayed transitions associated to the so-called saddle remnants.

Band-gap bowing and p-type doping of (Zn, Mg, Be)O wide-gap semiconductor alloys: a first-principles study

NASA Astrophysics Data System (ADS)

Shi, H.-L.; Duan, Y.

2008-12-01

Using a first-principles band-structure method and a special quasirandom structure (SQS) approach, we systematically calculate the band gap bowing parameters and p-type doping properties of (Zn, Mg, Be)O related random ternary and quaternary alloys. We show that the bowing parameters for ZnBeO and MgBeO alloys are large and dependent on composition. This is due to the size difference and chemical mismatch between Be and Zn(Mg) atoms. We also demonstrate that adding a small amount of Be into MgO reduces the band gap indicating that the bowing parameter is larger than the band-gap difference. We select an ideal N atom with lower p atomic energy level as dopant to perform p-type doping of ZnBeO and ZnMgBeO alloys. For N doped in ZnBeO alloy, we show that the acceptor transition energies become shallower as the number of the nearest neighbor Be atoms increases. This is thought to be because of the reduction of p- d repulsion. The NO acceptor transition energies are deep in the ZnMgBeO quaternary alloy lattice-matched to GaN substrate due to the lower valence band maximum. These decrease slightly as there are more nearest neighbor Mg atoms surrounding the N dopant. The important natural valence band alignment between ZnO, MgO, BeO, ZnBeO, and ZnMgBeO quaternary alloy is also investigated.

Gap analysis: assessing the value perception of consultant pharmacist services and the performance of consultant pharmacists.

PubMed

Clark, Thomas R

2008-09-01

To understand the importance of services provided by consultant pharmacists and to assess perception of their performance of services. Cross-sectional; nursing facility team. Random e-mail survey of consultant pharmacists; phone survey of team members. 233 consultant pharmacists (practicing in a nursing facility); 540 team members (practicing in a nursing facility, interacting with > or = 1 consultant pharmacist): 120 medical directors, 210 directors of nursing, 210 administrators. Consultant pharmacists, directors of nursing, medical directors, and administrators rating importance/performance of 21 services. Gap between teams' ratings of importance and consultant pharmacists' performance is assessed to categorize services. Importance/performance ranked on five-point scale. Mean scores used for gap analysis to cluster services into four categories. Per combined group, six services categorized as "Keep It Up" (important, good performance), consensus with individual groups, except discrepancy with medical directors, for one service. Six services each categorized as "Improve" (important, large gap) and "Improve Second" (lower importance, large gap), with varied responses by individual groups. Three different services were categorized into "Don't Worry," with consensus within individual groups. Consensus from all groups found 5 of 21 services are important and performed well by consultant pharmacists, indicating to maintain performance of services. For three services, consultant pharmacists do not need to worry about their performance. Thirteen services require improvement in consultant pharmacists' performance; various groups differ on extent of improvement needed. Results can serve as benchmark comparisons with results obtained by consultant pharmacists in their own facilities.

Torsional wave band gap properties in a circular plate of a two-dimensional generalized phononic crystal

NASA Astrophysics Data System (ADS)

Zhao, Lei; Shu, Haisheng; Liang, Shanjun; Shi, Xiaona; An, Shuowei; Ren, Wanyue; Zhu, Jie

2018-05-01

The torsional wave band gap properties of a two-dimensional generalized phononic crystal (GPC) are investigated in this paper. The GPC structure considered is consisted of two different materials being arranged with radial and circumferential periodicities simultaneously. Based on the viewpoint of energy distribution and the finite element method, the power flow, energy density, sound intensity vector together with the stress field of the structure excited by torsional load are numerically calculated and discussed. Our results show that, the band gap of Bragg type exists in these two-dimensional composite structures, and the band gap range is mainly determined by radial periodicity while the circumferential periodicity would result in some transmission peaks within the band gap. These peaks are mainly produced by two different mechanisms, the energy leakage occurred in circumferential channels and the excitation of the local eigenmodes of certain scatterers. These results may be useful in torsional vibration control for various rotational parts and components, and in the application of energy harvesting, etc.

30 CFR 285.652 - How long do I have to conduct activities under an approved GAP?

Code of Federal Regulations, 2011 CFR

2011-07-01

... an approved GAP? 285.652 Section 285.652 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT... FACILITIES ON THE OUTER CONTINENTAL SHELF Plans and Information Requirements Activities Under An Approved Gap § 285.652 How long do I have to conduct activities under an approved GAP? After MMS approves your GAP...

Theoretical approach to resonant inelastic x-ray scattering in iron-based superconductors at the energy scale of the superconducting gap

PubMed Central

Marra, Pasquale; van den Brink, Jeroen; Sykora, Steffen

2016-01-01

We develop a phenomenological theory to predict the characteristic features of the momentum-dependent scattering amplitude in resonant inelastic x-ray scattering (RIXS) at the energy scale of the superconducting gap in iron-based super-conductors. Taking into account all relevant orbital states as well as their specific content along the Fermi surface we evaluate the charge and spin dynamical structure factors for the compounds LaOFeAs and LiFeAs, based on tight-binding models which are fully consistent with recent angle-resolved photoemission spectroscopy (ARPES) data. We find a characteristic intensity redistribution between charge and spin dynamical structure factors which discriminates between sign-reversing and sign-preserving quasiparticle excitations. Consequently, our results show that RIXS spectra can distinguish between s± and s++ wave gap functions in the singlet pairing case. In addition, we find that an analogous intensity redistribution at small momenta can reveal the presence of a chiral p-wave triplet pairing. PMID:27151253

Linear solvation energy relationships: "rule of thumb" for estimation of variable values

USGS Publications Warehouse

Hickey, James P.; Passino-Reader, Dora R.

1991-01-01

For the linear solvation energy relationship (LSER), values are listed for each of the variables (Vi/100, π*, &betam, αm) for fundamental organic structures and functional groups. We give the guidelines to estimate LSER variable values quickly for a vast array of possible organic compounds such as those found in the environment. The difficulty in generating these variables has greatly discouraged the application of this quantitative structure-activity relationship (QSAR) method. This paper present the first compilation of molecular functional group values together with a utilitarian set of the LSER variable estimation rules. The availability of these variable values and rules should facilitate widespread application of LSER for hazard evaluation of environmental contaminants.

Forward energy flow, central charged-particle multiplicities, and pseudorapidity gaps in W and Z boson events from pp collisions at $$\\sqrt{s}= 7$$ TeV

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

Chatrchyan, Serguei; et al.

2012-01-01

A study of forward energy flow and central charged-particle multiplicity in events with W and Z bosons decaying into leptons is presented. The analysis uses a sample of 7 TeV pp collisions, corresponding to an integrated luminosity of 36 inverse picobarns, recorded by the CMS experiment at the LHC. The observed forward energy depositions, their correlations, and the central charged-particle multiplicities are not well described by the available non-diffractive soft-hadron production models. A study of about 300 events with no significant energy deposited in one of the forward calorimeters, corresponding to a pseudorapidity gap of at least 1.9 units, ismore » also presented. An indication for a diffractive component in these events comes from the observation that the majority of the charged leptons from the (W/Z) decays are found in the hemisphere opposite to the gap. When fitting the signed lepton pseudorapidity distribution of these events with predicted distributions from an admixture of diffractive (POMPYT) and non-diffractive (PYTHIA) Monte Carlo simulations, the diffractive component is determined to be (50.0 +/- 9.3 (stat.) +/- 5.2 (syst.))%.« less

Sizable band gap in organometallic topological insulator

NASA Astrophysics Data System (ADS)

Derakhshan, V.; Ketabi, S. A.

2017-01-01

Based on first principle calculation when Ceperley-Alder and Perdew-Burke-Ernzerh type exchange-correlation energy functional were adopted to LSDA and GGA calculation, electronic properties of organometallic honeycomb lattice as a two-dimensional topological insulator was calculated. In the presence of spin-orbit interaction bulk band gap of organometallic lattice with heavy metals such as Au, Hg, Pt and Tl atoms were investigated. Our results show that the organometallic topological insulator which is made of Mercury atom shows the wide bulk band gap of about ∼120 meV. Moreover, by fitting the conduction and valence bands to the band-structure which are produced by Density Functional Theory, spin-orbit interaction parameters were extracted. Based on calculated parameters, gapless edge states within bulk insulating gap are indeed found for finite width strip of two-dimensional organometallic topological insulators.

Spark gaps synchronization using electrical trigger pulses

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

Agarwal, Ritu; Saroj, P.C.; Sharma, Archana

In pulse power systems, it is required to have synchronized triggering of two or more high voltage spark gaps capable of switching large currents, using electrical trigger pulses. This paper intends to study the synchronization of spark gaps using electrical trigger. The trigger generator consists of dc supply, IGBT switch and driver circuit which generates 8kV, 400ns (FWHM) pulses. The experiment was carried out using two 0.15uF/50kV energy storage capacitors charged to 12kV and discharged through stainless steel spark gaps of diameter 9 mm across 10 ohm non inductive load. The initial experiment shows that synchronization has been achieved withmore » jitter of 50 to 100ns. Further studies carried out to reduce the jitter time by varying various electrical parameters will be presented. (author)« less

Triple Value System Dynamics Modeling to Help Stakeholders Engage with Food-Energy-Water Problems

EPA Science Inventory

Triple Value (3V) Community scoping projects and Triple Value Simulation (3VS) models help decision makers and stakeholders apply systems-analysis methodology to complex problems related to food production, water quality, and energy use. 3VS models are decision support tools that...

30 CFR 285.642 - How do I submit my GAP?

Code of Federal Regulations, 2011 CFR

2011-07-01

... Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION, AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY ALTERNATE USES OF EXISTING FACILITIES ON THE OUTER CONTINENTAL SHELF... submit information on any project easement as part of your original GAP submission or as a revision to...

Comparison of social and physical free energies on a toy model.

PubMed

Kasac, Josip; Stefancic, Hrvoje; Stepanic, Josip

2004-01-01

Social free energy has been recently introduced as a measure of social action obtainable in a given social system, without changes in its structure. The authors of this paper argue that social free energy surpasses the gap between the verbally formulated value sets of social systems and the quantitatively based predictions. This point is further developed by analyzing the relation between the social and the physical free energy. Generically, this is done for a particular type of social dynamics. The extracted type of social dynamics is one of many realistic types of the differing proportion of social and economic elements. Numerically, this has been done for a toy model of interacting agents. The values of the social and physical free energies are, within the numerical accuracy, equivalent in the class of nontrivial, quasistationary model states.

Dynamic traversal of high bumps and large gaps by a small legged robot

NASA Astrophysics Data System (ADS)

Gart, Sean; Winey, Nastasia; de La Tijera Obert, Rafael; Li, Chen

Small animals encounter and negotiate diverse obstacles comparable in size or larger than themselves. In recent experiments, we found that cockroaches can dynamically traverse bumps up to 4 times hip height and gaps up to 1 body length. To better understand the physics that governs these locomotor transitions, we studied a small six-legged robot negotiating high bumps and large gaps and compared it to animal observations. We found that the robot was able to traverse bumps as large as 1 hip height and gaps as wide as 0.5 body length. For the bump, the robot often climbed over to traverse when initial body yaw was small, but was often deflected laterally and failed to traverse when initial body yaw was large. A simple locomotion energy landscape model explained these observations. For the gap, traversal probability decreased with gap width, which was well explained by a simple Lagrangian model of a forward-moving rigid body falling over the gap edge. For both the bump and the gap, animal performance far exceeded that of the robot, likely due to their relatively higher running speeds and larger rotational oscillations prior to and during obstacle traversal. Differences between animal and robot obstacle negotiation behaviors revealed that animals used active strategies to overcome potential energy barriers.

Methods for Analyzing the Economic Value of Concentrating Solar Power with Thermal Energy Storage

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

Denholm, Paul; Jorgenson, Jennie; Miller, Mackay

2015-07-20

Concentrating solar power with thermal energy storage (CSP-TES) provides multiple quantifiable benefits compared to CSP without storage or to solar photovoltaic (PV) technology, including higher energy value, ancillary services value, and capacity value. This report describes modeling approaches to quantifying these benefits that have emerged through state-level policymaking in the United States as well as the potential applicability of these methods in China. The technical potential for CSP-TES in China is significant, but deployment has not yet achieved the targets established by the Chinese government. According to the 12th Five Year Plan for Renewable Energy (2011-2015), CSP was expected tomore » reach 1 GW by 2015 and 3 GW by 2020 in China, yet as of December 2014, deployment totaled only 13.8 MW. One barrier to more rapid deployment is the lack of an incentive specific to CSP, such as a feed-in tariff. The 13th Five Year Plan for Solar Generation (2016-2020), which is under development, presents an opportunity to establish a feed-in tariff specific to CSP. This report, produced under the auspices of the U.S.-China Renewable Energy Partnership, aims to support the development of Chinese incentives that advance CSP deployment goals.« less

Band gap opening in α-graphyne by adsorption of organic molecule

NASA Astrophysics Data System (ADS)

Majidi, R.; Karami, A. R.

2014-09-01

The lack of a band gap limits the application of graphyne in nanoelectronic devices. We have investigated possibility of opening a band gap in α-graphyne by adsorption of tetracyanoethylene. The electronic property of α-graphyne in the presence of different numbers of tetracyanoethylene has been studied using density functional theory. It is found that charge is transferred from graphyne sheet to tetracyanoethylene molecules. In the presence of this electron acceptor molecule, a semimetal α-graphyne shows semiconducting property. The energy band gap at the Dirac point is enhanced by increasing the number of tetracyanoethylene. Our results provide a simple method to create and control the band gap in α-graphyne.

The value of electricity storage in energy-only electricity markets

NASA Astrophysics Data System (ADS)

McConnell, D.; Forcey, T.; Sandiford, M.

2015-12-01

Price volatility and the prospect of increasing renewable energy generation have raised interest in the potential opportunities for storage technologies in energy-only electricity markets. In this paper we explore the value of a price-taking storage device in such a market, the National Electricity Market (NEM) in Australia. Our analysis suggests that under optimal operation, there is little value in having more than six hours of storage in this market. However, the inability to perfectly forecast wholesale prices, particularly extreme price spikes, may warrant some additional storage. We found that storage devices effectively provide a similar service as peak generators (such as Open Cycle Gas Turbines) and are similarly dependent on and exposed to extreme price events, with revenue for a merchant generator highly skewed to a few days of the year. In contrast to previous studies, this results in the round trip efficiency of the storage being relatively insignificant. Financing using hedging strategies similar to a peak generator effectively reduces the variability of revenue and exposure of storage to extreme prices. Our case study demonstrates that storage may have a competitive advantage over other peaking generators on the NEM, due to its ability to earn revenue outside of extreme peak events. As a consequence the outlook for storage options on the NEM is dependent on volatility, in turn dependent on capacity requirements. Further to this, increased integration of renewable energy may both depend on storage and improve the outlook for storage in technologies in electricity markets.

A new method for the determination of optical band gap and the nature of optical transitions in semiconductors

NASA Astrophysics Data System (ADS)

Souri, Dariush; Tahan, Zahra Esmaeili

2015-05-01

A new method (named as DASF: Derivation of absorption spectrum fitting) is proposed for the determination of optical band gap and the nature of optical transitions in semiconductors; this method only requires the measurement of the absorbance spectrum of the sample, avoiding any needs to film thickness or any other parameters. In this approach, starting from absorption spectrum fitting (ASF) procedure and by the first derivation of the absorbance spectrum, the optical band gap and then the type of optical transition can be determined without any presumption about the nature of transition. DASF method was employed on (60-x)V2O5-40TeO2-xAg2O glassy systems (hereafter named as TVAgx), in order to confirm the validity of this new method. For the present glasses, the DASF results were compared with the results of ASF procedure for, confirming a very good agreement between these approaches. These glasses were prepared by using the melt quenching and blowing methods to obtain bulk and film samples, respectively. Results show that the optical band gap variation for TVAgx glasses can be divided into two regions, 0 ≤ x ≤ 20 and 20 ≤ x ≤ 40 mol%. The optical band gap has a maximum value equal to 2.72 eV for x = 40 and the minimum value equal to 2.19 eV for x = 40. Also, some physical quantities such as the width of the band tails (Urbach energy), glass density, molar volume, and optical basicity were reported for the under studied glasses.

Thermophotovoltaic conversion using selective infrared line emitters and large band gap photovoltaic devices

DOEpatents

Brandhorst, Jr., Henry W.; Chen, Zheng

2000-01-01

Efficient thermophotovoltaic conversion can be performed using photovoltaic devices with a band gap in the 0.75-1.4 electron volt range, and selective infrared emitters chosen from among the rare earth oxides which are thermally stimulated to emit infrared radiation whose energy very largely corresponds to the aforementioned band gap. It is possible to use thermovoltaic devices operating at relatively high temperatures, up to about 300.degree. C., without seriously impairing the efficiency of energy conversion.

Year rather than farming system influences protein utilization and energy value of vegetables when measured in a rat model.

PubMed

Jørgensen, Henry; Brandt, Kirsten; Lauridsen, Charlotte

2008-12-01

The aim of the study was to measure protein utilization and energy value of dried apple, carrot, kale, pea, and potato prepared for human consumption and grown in 2 consecutive years with 3 different farming systems: (1) low input of fertilizer without pesticides (LIminusP), (2) low input of fertilizers and high input of pesticides (LIplusP), (3) and high input of fertilizers and high input of pesticides (HIplusP). In addition, the study goal was to verify the nutritional values, taking into consideration the physiologic state. In experiment 1, the nutritive values, including protein digestibility-corrected amino acid score, were determined in single ingredients in trials with young rats (3-4 weeks) as recommended by the Food and Agriculture Organization of the United Nations/World Health Organization for all age groups. A second experiment was carried out with adult rats to assess the usefulness of digestibility values to predict the digestibility and nutritive value of mixed diets and study the age aspect. Each plant material was included in the diet with protein-free basal mixtures or casein to contain 10% dietary protein. The results showed that variations in protein utilization and energy value determined on single ingredients between cultivation strategies were inconsistent and smaller than between harvest years. Overall, dietary crude fiber was negatively correlated with energy digestibility. The energy value of apple, kale, and pea was lower than expected from literature values. A mixture of plant ingredients fed to adult rats showed lower protein digestibility and higher energy digestibility than predicted. The protein digestibility data obtained using young rats in the calculation of protein digestibility-corrected amino acid score overestimates protein digestibility and quality and underestimates energy value for mature rats. The present study provides new data on protein utilization and energy digestibility of some typical plant foods that may

Valuing both critical and creative thinking in clinical practice: narrowing the research-practice gap?

PubMed

Seymour, Beth; Kinn, Sue; Sutherland, Norrie

2003-05-01

Nurturing critical thinking skills in the classroom is considered an important educational activity. It is believed that critical thinking skills are transferable and that they can be applied in practice when appraising, evaluating and implementing research. That more nurses than ever before have been judged academically knowledgeable in research has not guaranteed the transfer of such knowledge to practice. This paper discusses some of the reasons for the failure to narrow the gap between research and practice. In particular we argue that, if nurses are encouraged to develop creative and generative thinking alongside their critical thinking skills, then the art of nursing will have fuller representation in education, research and practice. The successful development of critical thinking skills for academic purposes does not necessarily mean that these skills are used in practice in relation either to research or clinical decision-making. This suggests that the transferability of critical thinking skills is less than straightforward. Indeed, there has been little narrowing of the research-practice gap since students started to learn critical thinking for academic purposes. However, we propose that thinking skills can be encouraged in the context of practice and that regular educational events, such as journal clubs, can contribute to developing critical thinking in the practice environment. The research-practice gap will reduce only if research becomes part of practitioners' ideology, which includes the art and science of nursing. Critical and creative thinking are prerequisites to narrowing the disjuncture between research and practice, and we suggest that educators and practitioners explore structured ways of meeting together to appraise literature as a possible means of making use of their thinking and knowledge in clinical practice.

Ultra-wide acoustic band gaps in pillar-based phononic crystal strips

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

Coffy, Etienne, E-mail: etienne.coffy@femto-st.fr; Lavergne, Thomas; Addouche, Mahmoud

2015-12-07

An original approach for designing a one dimensional phononic crystal strip with an ultra-wide band gap is presented. The strip consists of periodic pillars erected on a tailored beam, enabling the generation of a band gap that is due to both Bragg scattering and local resonances. The optimized combination of both effects results in the lowering and the widening of the main band gap, ultimately leading to a gap-to-midgap ratio of 138%. The design method used to improve the band gap width is based on the flattening of phononic bands and relies on the study of the modal energy distributionmore » within the unit cell. The computed transmission through a finite number of periods corroborates the dispersion diagram. The strong attenuation, in excess of 150 dB for only five periods, highlights the interest of such ultra-wide band gap phononic crystal strips.« less

Influence of the ``second gap'' on the optical absorption of transparent conducting oxides

NASA Astrophysics Data System (ADS)

Ha, Viet-Anh; Waroquiers, David; Rignanese, Gian-Marco; Hautier, Geoffroy

Transparent conducting oxides (TCOs) are critical to many technologies (e.g., thin-film solar cells, flat-panel displays or organic light-emitting diodes). TCOs are heavily doped (n or p-type) oxides that satisfy many design criteria such as high transparency to visible light (i.e., a band gap > 3 eV), high concentration and mobility of carriers (leading to high conductivity), ... In such (highly doped) systems, optical transitions from the conduction band minimum to higher energy bands in n-type or from lower energy bands to the valence band maximum in p-type are possible and can degrade transparency. In fact, it has been claimed that a high energy (> 3eV) for any of these transitions made possible by doping, commonly referred as a high ``second gap'', is a necessary design criterion for high performance TCOs. Here, we study the influence of this second gap on the transparency of doped TCOs by using ab initio calculations within the random phase approximation (RPA) for several well-known p-type and n-type TCOs. Our work highlights how the second gap affects the transparency of doped TCOs, shining light on more accurate design criteria for high performance TCOs.

Hydrogen Safety Sensor Performance and Use Gap Analysis: Preprint

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

Buttner, William J; Burgess, Robert M; Schmidt, Kara

Hydrogen sensors are recognized as an important technology for facilitating the safe implementation of hydrogen as an alternative fuel, and there are numerous reports of a sensor alarm successfully preventing a potentially serious event. However, gaps in sensor metrological specifications, as well as in their performance for some applications, exist.The U.S. Department of Energy (DOE) Fuel Cell Technology Office published a short list of critical gaps in the 2007 and 2012 multiyear project plans; more detailed gap analyses were independently performed by the JRC and NREL. There have been, however, some significant advances in sensor technologies since these assessments, includingmore » the commercial availability of hydrogen sensors with fast response times (t90 less than 1 s, which had been an elusive DOE target since 2007), improved robustness to chemical poisons, improved selectivity, and improved lifetime and stability. These improvements, however, have not been universal and typically pertain to select platforms or models. Moreover, as hydrogen markets grow and new applications are being explored, more demands will be imposed on sensor performance. The hydrogen sensor laboratories at NREL and JRC are currently updating the hydrogen safety sensor gap analysis through direct interaction with international stakeholders in the hydrogen community, especially end-users. NREL and the JRC are currently organizing a series of workshops (in Europe and the U.S.) with sensor developers, end-users, and other stakeholders in 2017 to identify technology gaps and to develop a path forward to address them. One workshop is scheduled for May 10 in Brussels, Belgium at the Headquarters of the Fuel Cell and Hydrogen Joint Undertaking. A second workshop is planned at the National Renewable Energy Laboratory in Golden, CO, USA. This presentation will review improvements in sensor technologies in the past 5 to 10 years, identify gaps in sensor performance and use requirements, and

Analyzing the "CareGap": assessing gaps in adherence to clinical guidelines in adult soft tissue sarcoma.

PubMed

Waks, Zeev; Goldbraich, Esther; Farkash, Ariel; Torresani, Michele; Bertulli, Rossella; Restifo, Nicola; Locatelli, Paolo; Casali, Paolo; Carmeli, Boaz

2013-01-01

Clinical decision support systems (CDSSs) are gaining popularity as tools that assist physicians in optimizing medical care. These systems typically comply with evidence-based medicine and are designed with input from domain experts. Nonetheless, deviations from CDSS recommendations are abundant across a broad spectrum of disorders, raising the question as to why this phenomenon exists. Here, we analyze this gap in adherence to a clinical guidelines-based CDSS by examining the physician treatment decisions for 1329 adult soft tissue sarcoma patients in northern Italy using patient-specific parameters. Dubbing this analysis "CareGap", we find that deviations correlate strongly with certain disease features such as local versus metastatic clinical presentation. We also notice that deviations from the guideline-based CDSS suggestions occur more frequently for patients with shorter survival time. Such observations can direct physicians' attention to distinct patient cohorts that are prone to higher deviation levels from clinical practice guidelines. This illustrates the value of CareGap analysis in assessing quality of care for subsets of patients within a larger pathology.

High-Altitude Emission from Pulsar Slot Gaps: The Crab Pulsar

NASA Technical Reports Server (NTRS)

Harding, Alice K.; Stern, Julie V.; Dyks, Jaroslaw; Frackowiak, Michal

2008-01-01

We present results of a 3D model of optical to gamma-ray emission from the slot gap accelerator of a rotation-powered pulsar. Primary electrons accelerating to high-altitudes in the unscreened electric field of the slot gap reach radiation-reaction limited Lorentz factors of approx. 2 x 10(exp 7), while electron-positron pairs from lower-altitude cascades flow along field lines interior to the slot gap. The curvature, synchrotron and inverse Compton radiation of both primary electrons and pairs produce a broad spectrum of emission from infra-red to GeV energies. Both primaries and pairs undergo cyclotron resonant absorption of radio photons, allowing them to maintain significant pitch angles. Synchrotron radiation from pairs with a power-law energy spectrum from gamma = 10(exp 2) - 10(exp 5), dominate the spectrum up to approx. 10 MeV. Synchrotron and curvature radiation of primaries dominates from 10 MeV up to a few GeV. We examine the energy-dependent pulse profiles and phase-resolved spectra for parameters of the Crab pulsar as a function of magnetic inclination alpha and viewing angle zeta, comparing to broad-band data. In most cases, the pulse profiles are dominated by caustics on trailing field lines. We also explore the relation of the high-energy and the radio profiles, as well as the possibility of caustic formation in the radio cone emission. We find that the Crab pulsar profiles and spectrum can be reasonably well reproduced by a model with alpha = 45deg and zeta approx. 100deg or 80deg. This model predicts that the slot gap emission below 200 MeV will exhibit correlations in time and phase with the radio emission.

Gap Year Students in Lithuania: The Value Orientations of Children from Wealthy Social Groups

ERIC Educational Resources Information Center

Leonavicius, Vylius; Ozolinciute, Egle

2015-01-01

The paper seeks to understand the trajectories of students who defer entry to university. The study was conducted in Lithuania, a former Soviet Union republic. The phenomenon of a "gap year" is usually associated with young people, who decide not to enter higher education schools immediately after receiving secondary education, instead…

Order, disorder, and tunable gaps in the spectrum of Andreev bound states in a multiterminal superconducting device

NASA Astrophysics Data System (ADS)

Yokoyama, Tomohiro; Reutlinger, Johannes; Belzig, Wolfgang; Nazarov, Yuli V.

2017-01-01

We consider the spectrum of Andreev bound states (ABSs) in an exemplary four-terminal superconducting structure where four chaotic cavities are connected by quantum point contacts to the terminals and to each other forming a ring. We nickname the resulting device 4T-ring. Such a tunable device can be realized in a 2D electron gas-superconductor or a graphene-based hybrid structure. We concentrate on the limit of a short structure and large conductance of the point contacts where there are many ABS in the device forming a quasicontinuous spectrum. The energies of the ABS can be tuned by changing the superconducting phases of the terminals. We observe the opening and closing of gaps in the spectrum upon changing the phases. This concerns the usual proximity gap that separates the levels from zero energy as well as less usual "smile" gaps that split the levels of the quasicontinuous spectrum. We demonstrate a remarkable crossover in the overall spectrum that occurs upon changing the ratio of conductances of the inner and outer point contacts. At big values of the ratio (closed limit), the levels exhibit a generic behavior expected for the spectrum of a disordered system manifesting level repulsion and Brownian "motion" upon changing the phases. At small values of the ratio (open limit), the levels are squeezed into narrow bunches separated by wide smile gaps. Each bunch consists of almost degenerate ABS formed by Andreev reflection between two adjacent terminals. We study in detail the properties of the spectrum in the limit of a small ratio, paying special attention to the crossings of bunches. We distinguish two types of crossings: (i) with a regular phase dependence of the levels and (ii) crossings where the Brownian motion of the levels leads to an apparently irregular phase dependence. We work out a perturbation theory that explains the observations both at a detailed level of random scattering in the device and at a phenomenological level of positively defined

Estimating yield gaps at the cropping system level.

PubMed

Guilpart, Nicolas; Grassini, Patricio; Sadras, Victor O; Timsina, Jagadish; Cassman, Kenneth G

2017-05-01

Yield gap analyses of individual crops have been used to estimate opportunities for increasing crop production at local to global scales, thus providing information crucial to food security. However, increases in crop production can also be achieved by improving cropping system yield through modification of spatial and temporal arrangement of individual crops. In this paper we define the cropping system yield potential as the output from the combination of crops that gives the highest energy yield per unit of land and time, and the cropping system yield gap as the difference between actual energy yield of an existing cropping system and the cropping system yield potential. Then, we provide a framework to identify alternative cropping systems which can be evaluated against the current ones. A proof-of-concept is provided with irrigated rice-maize systems at four locations in Bangladesh that represent a range of climatic conditions in that country. The proposed framework identified (i) realistic alternative cropping systems at each location, and (ii) two locations where expected improvements in crop production from changes in cropping intensity (number of crops per year) were 43% to 64% higher than from improving the management of individual crops within the current cropping systems. The proposed framework provides a tool to help assess food production capacity of new systems ( e.g. with increased cropping intensity) arising from climate change, and assess resource requirements (water and N) and associated environmental footprint per unit of land and production of these new systems. By expanding yield gap analysis from individual crops to the cropping system level and applying it to new systems, this framework could also be helpful to bridge the gap between yield gap analysis and cropping/farming system design.

Energy as an entanglement witness for quantum many-body systems

NASA Astrophysics Data System (ADS)

Dowling, Mark R.; Doherty, Andrew C.; Bartlett, Stephen D.

2004-12-01

We investigate quantum many-body systems where all low-energy states are entangled. As a tool for quantifying such systems, we introduce the concept of the entanglement gap, which is the difference in energy between the ground-state energy and the minimum energy that a separable (unentangled) state may attain. If the energy of the system lies within the entanglement gap, the state of the system is guaranteed to be entangled. We find Hamiltonians that have the largest possible entanglement gap; for a system consisting of two interacting spin- 1/2 subsystems, the Heisenberg antiferromagnet is one such example. We also introduce a related concept, the entanglement-gap temperature: the temperature below which the thermal state is certainly entangled, as witnessed by its energy. We give an example of a bipartite Hamiltonian with an arbitrarily high entanglement-gap temperature for fixed total energy range. For bipartite spin lattices we prove a theorem demonstrating that the entanglement gap necessarily decreases as the coordination number is increased. We investigate frustrated lattices and quantum phase transitions as physical phenomena that affect the entanglement gap.

Passive gas-gap heat switch for adiabatic demagnetization refrigerator

NASA Technical Reports Server (NTRS)

Shirron, Peter J. (Inventor); Di Pirro, Michael J. (Inventor)

2005-01-01

A passive gas-gap heat switch for use with a multi-stage continuous adiabatic demagnetization refrigerator (ADR). The passive gas-gap heat switch turns on automatically when the temperature of either side of the switch rises above a threshold value and turns off when the temperature on either side of the switch falls below this threshold value. One of the heat switches in this multistage process must be conductive in the 0.25? K to 0.3? K range. All of the heat switches must be capable of switching off in a short period of time (1-2 minutes), and when off to have a very low thermal conductance. This arrangement allows cyclic cooling cycles to be used without the need for separate heat switch controls.

An effective approach for gap-filling continental scale remotely sensed time-series

PubMed Central

Weiss, Daniel J.; Atkinson, Peter M.; Bhatt, Samir; Mappin, Bonnie; Hay, Simon I.; Gething, Peter W.

2014-01-01

The archives of imagery and modeled data products derived from remote sensing programs with high temporal resolution provide powerful resources for characterizing inter- and intra-annual environmental dynamics. The impressive depth of available time-series from such missions (e.g., MODIS and AVHRR) affords new opportunities for improving data usability by leveraging spatial and temporal information inherent to longitudinal geospatial datasets. In this research we develop an approach for filling gaps in imagery time-series that result primarily from cloud cover, which is particularly problematic in forested equatorial regions. Our approach consists of two, complementary gap-filling algorithms and a variety of run-time options that allow users to balance competing demands of model accuracy and processing time. We applied the gap-filling methodology to MODIS Enhanced Vegetation Index (EVI) and daytime and nighttime Land Surface Temperature (LST) datasets for the African continent for 2000–2012, with a 1 km spatial resolution, and an 8-day temporal resolution. We validated the method by introducing and filling artificial gaps, and then comparing the original data with model predictions. Our approach achieved R2 values above 0.87 even for pixels within 500 km wide introduced gaps. Furthermore, the structure of our approach allows estimation of the error associated with each gap-filled pixel based on the distance to the non-gap pixels used to model its fill value, thus providing a mechanism for including uncertainty associated with the gap-filling process in downstream applications of the resulting datasets. PMID:25642100

Engineering of band gap states of amorphous SiZnSnO semiconductor as a function of Si doping concentration.

PubMed

Choi, Jun Young; Heo, Keun; Cho, Kyung-Sang; Hwang, Sung Woo; Kim, Sangsig; Lee, Sang Yeol

2016-11-04

We investigated the band gap of SiZnSnO (SZTO) with different Si contents. Band gap engineering of SZTO is explained by the evolution of the electronic structure, such as changes in the band edge states and band gap. Using ultraviolet photoelectron spectroscopy (UPS), it was verified that Si atoms can modify the band gap of SZTO thin films. Carrier generation originating from oxygen vacancies can modify the band-gap states of oxide films with the addition of Si. Since it is not easy to directly derive changes in the band gap states of amorphous oxide semiconductors, no reports of the relationship between the Fermi energy level of oxide semiconductor and the device stability of oxide thin film transistors (TFTs) have been presented. The addition of Si can reduce the total density of trap states and change the band-gap properties. When 0.5 wt% Si was used to fabricate SZTO TFTs, they showed superior stability under negative bias temperature stress. We derived the band gap and Fermi energy level directly using data from UPS, Kelvin probe, and high-resolution electron energy loss spectroscopy analyses.

Engineering of band gap states of amorphous SiZnSnO semiconductor as a function of Si doping concentration

PubMed Central

Choi, Jun Young; Heo, Keun; Cho, Kyung-Sang; Hwang, Sung Woo; Kim, Sangsig; Lee, Sang Yeol

2016-01-01

We investigated the band gap of SiZnSnO (SZTO) with different Si contents. Band gap engineering of SZTO is explained by the evolution of the electronic structure, such as changes in the band edge states and band gap. Using ultraviolet photoelectron spectroscopy (UPS), it was verified that Si atoms can modify the band gap of SZTO thin films. Carrier generation originating from oxygen vacancies can modify the band-gap states of oxide films with the addition of Si. Since it is not easy to directly derive changes in the band gap states of amorphous oxide semiconductors, no reports of the relationship between the Fermi energy level of oxide semiconductor and the device stability of oxide thin film transistors (TFTs) have been presented. The addition of Si can reduce the total density of trap states and change the band-gap properties. When 0.5 wt% Si was used to fabricate SZTO TFTs, they showed superior stability under negative bias temperature stress. We derived the band gap and Fermi energy level directly using data from UPS, Kelvin probe, and high-resolution electron energy loss spectroscopy analyses. PMID:27812035

DUST COAGULATION IN THE VICINITY OF A GAP-OPENING JUPITER-MASS PLANET

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

Carballido, Augusto; Matthews, Lorin S.; Hyde, Truell W., E-mail: Augusto_Carballido@baylor.edu

We analyze the coagulation of dust in and around a gap opened by a Jupiter-mass planet. To this end, we carry out a high-resolution magnetohydrodynamic (MHD) simulation of the gap environment, which is turbulent due to the magnetorotational instability. From the MHD simulation, we obtain values of the gas velocities, densities, and turbulent stresses (a) close to the gap edge, (b) in one of the two gas streams that accrete onto the planet, (c) inside the low-density gap, and (d) outside the gap. The MHD values are then input into a Monte Carlo dust-coagulation algorithm which models grain sticking andmore » compaction. We also introduce a simple implementation for bouncing, for comparison purposes. We consider two dust populations for each region: one whose initial size distribution is monodisperse, with monomer radius equal to 1 μ m, and another one whose initial size distribution follows the Mathis–Rumpl–Nordsieck distribution for interstellar dust grains, with an initial range of monomer radii between 0.5 and 10 μ m. Without bouncing, our Monte Carlo calculations show steady growth of dust aggregates in all regions, and the mass-weighted (m-w) average porosity of the initially monodisperse population reaches extremely high final values of 98%. The final m-w porosities in all other cases without bouncing range between 30% and 82%. The efficiency of compaction is due to high turbulent relative speeds between dust particles. When bouncing is introduced, growth is slowed down in the planetary wake and inside the gap. Future studies will need to explore the effect of different planet masses and electric charge on grains.« less

Closing the delivery gaps in pediatric HIV care in Togo, West Africa: using the care delivery value chain framework to direct quality improvement.

PubMed

Fiori, Kevin; Schechter, Jennifer; Dey, Monica; Braganza, Sandra; Rhatigan, Joseph; Houndenou, Spero; Gbeleou, Christophe; Palerbo, Emmanuel; Tchangani, Elfamozo; Lopez, Andrew; Bensen, Emily; Hirschhorn, Lisa R

2016-03-01

Providing quality care for all children living with HIV/AIDS remains a global challenge and requires the development of new healthcare delivery strategies. The care delivery value chain (CDVC) is a framework that maps activities required to provide effective and responsive care for a patient with a particular disease across the continuum of care. By mapping activities along a value chain, the CDVC enables managers to better allocate resources, improve communication, and coordinate activities. We report on the successful application of the CDVC as a strategy to optimize care delivery and inform quality improvement (QI) efforts with the overall aim of improving care for Pediatric HIV patients in Togo, West Africa. Over the course of 12 months, 13 distinct QI activities in Pediatric HIV/AIDS care delivery were monitored, and 11 of those activities met or exceeded established targets. Examples included: increase in infants receiving routine polymerase chain reaction testing at 2 months (39-95%), increase in HIV exposed children receiving confirmatory HIV testing at 18 months (67-100%), and increase in patients receiving initial CD4 testing within 3 months of HIV diagnosis (67-100%). The CDVC was an effective approach for evaluating existing systems and prioritizing gaps in delivery for QI over the full cycle of Pediatric HIV/AIDS care in three specific ways: (1) facilitating the first comprehensive mapping of Pediatric HIV/AIDS services, (2) identifying gaps in available services, and (3) catalyzing the creation of a responsive QI plan. The CDVC provided a framework to drive meaningful, strategic action to improve Pediatric HIV care in Togo.

Comprehensive comparison of gap filling techniques for eddy covariance net carbon fluxes

NASA Astrophysics Data System (ADS)

Moffat, A. M.; Papale, D.; Reichstein, M.; Hollinger, D. Y.; Richardson, A. D.; Barr, A. G.; Beckstein, C.; Braswell, B. H.; Churkina, G.; Desai, A. R.; Falge, E.; Gove, J. H.; Heimann, M.; Hui, D.; Jarvis, A. J.; Kattge, J.; Noormets, A.; Stauch, V. J.

2007-12-01

Review of fifteen techniques for estimating missing values of net ecosystem CO2 exchange (NEE) in eddy covariance time series and evaluation of their performance for different artificial gap scenarios based on a set of ten benchmark datasets from six forested sites in Europe. The goal of gap filling is the reproduction of the NEE time series and hence this present work focuses on estimating missing NEE values, not on editing or the removal of suspect values in these time series due to systematic errors in the measurements (e.g. nighttime flux, advection). The gap filling was examined by generating fifty secondary datasets with artificial gaps (ranging in length from single half-hours to twelve consecutive days) for each benchmark dataset and evaluating the performance with a variety of statistical metrics. The performance of the gap filling varied among sites and depended on the level of aggregation (native half- hourly time step versus daily), long gaps were more difficult to fill than short gaps, and differences among the techniques were more pronounced during the day than at night. The non-linear regression techniques (NLRs), the look-up table (LUT), marginal distribution sampling (MDS), and the semi-parametric model (SPM) generally showed good overall performance. The artificial neural network based techniques (ANNs) were generally, if only slightly, superior to the other techniques. The simple interpolation technique of mean diurnal variation (MDV) showed a moderate but consistent performance. Several sophisticated techniques, the dual unscented Kalman filter (UKF), the multiple imputation method (MIM), the terrestrial biosphere model (BETHY), but also one of the ANNs and one of the NLRs showed high biases which resulted in a low reliability of the annual sums, indicating that additional development might be needed. An uncertainty analysis comparing the estimated random error in the ten benchmark datasets with the artificial gap residuals suggested that the

Fullerene-Free Organic Solar Cells with an Efficiency of 10.2% and an Energy Loss of 0.59 eV Based on a Thieno[3,4-c]Pyrrole-4,6-dione-Containing Wide Band Gap Polymer Donor.

PubMed

Hadmojo, Wisnu Tantyo; Wibowo, Febrian Tri Adhi; Ryu, Du Yeol; Jung, In Hwan; Jang, Sung-Yeon

2017-09-27

Although the combination of wide band gap polymer donors and narrow band gap small-molecule acceptors achieved state-of-the-art performance as bulk heterojunction (BHJ) active layers for organic solar cells, there have been only several of the wide band gap polymers that actually realized high-efficiency devices over >10%. Herein, we developed high-efficiency, low-energy-loss fullerene-free organic solar cells using a weakly crystalline wide band gap polymer donor, PBDTTPD-HT, and a nonfullerene small-molecule acceptor, ITIC. The excessive intermolecular stacking of ITIC is efficiently suppressed by the miscibility with PBDTTPD-HT, which led to a well-balanced nanomorphology in the PBDTTPD-HT/ITIC BHJ active films. The favorable optical, electronic, and energetic properties of PBDTTPD-HT with respect to ITIC achieved panchromatic photon-to-current conversion with a remarkably low energy loss (0.59 eV).

Ab-initio study of structural, electronic, and transport properties of zigzag GaP nanotubes.

PubMed

Srivastava, Anurag; Jain, Sumit Kumar; Khare, Purnima Swarup

2014-03-01

Stability and electronic properties of zigzag (3 ≤ n ≤ 16) gallium phosphide nanotubes (GaP NTs) have been analyzed by employing a systematic ab-intio approach based on density functional theory using generalized gradient approximation with revised Perdew Burke Ernzerhoff type parameterization. Diameter dependence of bond length, buckling, binding energy, and band gap has been investigated and the analysis shows that the bond length and buckling decreases with increasing diameter of the tube, highest binding energy of (16, 0) confirms this as the most stable amongst all the NTs taken into consideration. The present GaP NTs shows direct band gap and it increases with diameter of the tubes. Using a two probe model for (4, 0) NT the I-V relationship shows an exponential increase in current on applying bias voltage beyond 1.73 volt.

Controllable asymmetric transmission via gap-tunable acoustic metasurface

NASA Astrophysics Data System (ADS)

Liu, Bingyi; Jiang, Yongyuan

2018-04-01

In this work, we utilize the acoustic gradient metasurface (AGM) of a bilayer configuration to realize the controllable asymmetric transmission. Relying on the adjustable gap between the two composing layers, the metasurface could switch from symmetric transmission to asymmetric transmission at a certain gap value. The underlying mechanism is attributed to the interference between the forward diffracted waves scattered by the surface bound waves at two air-AGM interfaces, which is apparently influenced by the interlayer distance. We further utilize the hybrid acoustic elements to construct the desired gradient metasurface with a tunable gap and validate the controllable asymmetric transmission with full-wave simulations. Our work provides the solution for actively controlling the transmission property of an acoustic element, which shows potential application in acoustic communication as a dynamic tunable acoustic diode.

Gap Resolution

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

Labutti, Kurt; Foster, Brian; Lapidus, Alla

Gap Resolution is a software package that was developed to improve Newbler genome assemblies by automating the closure of sequence gaps caused by repetitive regions in the DNA. This is done by performing the follow steps:1) Identify and distribute the data for each gap in sub-projects. 2) Assemble the data associated with each sub-project using a secondary assembler, such as Newbler or PGA. 3) Determine if any gaps are closed after reassembly, and either design fakes (consensus of closed gap) for those that closed or lab experiments for those that require additional data. The software requires as input a genomemore » assembly produce by the Newbler assembler provided by Roche and 454 data containing paired-end reads.« less

Thermoelectric power factor of La0.9M0.1FeO3 (M = Ca and Ba) system: Structural, band gap and electrical transport evaluations

NASA Astrophysics Data System (ADS)

Karthikeyan, N.; Kumar, R. Ramesh; Jaiganesh, G.; Sivakumar, K.

2018-01-01

The search for thermoelectric materials has been incredibly increased due to the increase in global energy demand. Hence the present work focus on preparation and characterization of thermal transport phenomena of pure and Ba/Ca substituted perovskite LaFeO3 orthoferrite system. The conventional solid state reaction technique is utilized for the preparation of LaFeO3 and La0.9M0.1FeO3 (M = Ca and Ba) compounds. Crystal structure analyses of the prepared samples are analyses using Rietveld refinement process which confirms the orthoferrite crystal structure of all the prepared compounds with induced distortion in position of atoms by the incorporation of substituent atoms. The electronic structure calculations are performed by VASP. As the LaFeO3 compound is a strongly energy correlated system, the Density Functional Theory (DFT) calculations are performed by DFT + U (Hubbard function) method. The computed band gap values are compared with the energy gap values calculated from UV-Vis spectral analysis. Electrical conductivity measurement and Arrhenius behavior for the temperature range of room temperature to 650 K are analyzed and the drift increase in conductivity with respect to temperature is due to the thermally activated mobility of charge carriers. Temperature dependent thermopower analysis is also examined using homemade seebeck coefficient measurement system. The calculation of thermoelectric power factor reveals that the Ba substituted LaFeO3 compound show highest power factor value of 3.73 μW/K2 cm at higher temperature and the superior power factor values observed in the Ba substituted compound determine the material's capability in power generating devices based on thermoelectric effect.

Antideuteron based dark matter search with GAPS: Current progress and future prospects

NASA Astrophysics Data System (ADS)

Hailey, C. J.; Aramaki, T.; Boggs, S. E.; Doetinchem, P. v.; Fuke, H.; Gahbauer, F.; Koglin, J. E.; Madden, N.; Mognet, S. A. I.; Ong, R.; Yoshida, T.; Zhang, T.; Zweerink, J. A.

2013-01-01

The General Antiparticle Spectrometer (GAPS) is a new approach to the indirect detection of dark matter. It relies on searching for primary antideuterons produced in the annihilation of dark matter in the galactic halo. Low energy antideuterons produced through Standard Model processes, such as collisions of cosmic-rays with interstellar baryons, are greatly suppressed compared to primary antideuterons. Thus a low energy antideuteron search provides a clean signature of dark matter. In GAPS antiparticles are slowed down and captured in target atoms. The resultant exotic atom deexcites with the emission of X-rays and annihilation pions, protons and other particles. A tracking geometry allows for the detection of the X-rays and particles, providing a unique signature to identify the mass of the antiparticle. A prototype detector was successfully tested at the KEK accelerator in 2005, and a prototype GAPS balloon flight is scheduled for 2011. This will be followed by a full scale experiment on a long duration balloon from Antarctica in 2014. We discuss the status and future plans for GAPS.

Quantifying the effect of air gap, depth, and range shifter thickness on TPS dosimetric accuracy in superficial PBS proton therapy.

PubMed

Shirey, Robert J; Wu, Hsinshun Terry

2018-01-01

This study quantifies the dosimetric accuracy of a commercial treatment planning system as functions of treatment depth, air gap, and range shifter thickness for superficial pencil beam scanning proton therapy treatments. The RayStation 6 pencil beam and Monte Carlo dose engines were each used to calculate the dose distributions for a single treatment plan with varying range shifter air gaps. Central axis dose values extracted from each of the calculated plans were compared to dose values measured with a calibrated PTW Markus chamber at various depths in RW3 solid water. Dose was measured at 12 depths, ranging from the surface to 5 cm, for each of the 18 different air gaps, which ranged from 0.5 to 28 cm. TPS dosimetric accuracy, defined as the ratio of calculated dose relative to the measured dose, was plotted as functions of depth and air gap for the pencil beam and Monte Carlo dose algorithms. The accuracy of the TPS pencil beam dose algorithm was found to be clinically unacceptable at depths shallower than 3 cm with air gaps wider than 10 cm, and increased range shifter thickness only added to the dosimetric inaccuracy of the pencil beam algorithm. Each configuration calculated with Monte Carlo was determined to be clinically acceptable. Further comparisons of the Monte Carlo dose algorithm to the measured spread-out Bragg Peaks of multiple fields used during machine commissioning verified the dosimetric accuracy of Monte Carlo in a variety of beam energies and field sizes. Discrepancies between measured and TPS calculated dose values can mainly be attributed to the ability (or lack thereof) of the TPS pencil beam dose algorithm to properly model secondary proton scatter generated in the range shifter. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Ferromagnetic Mn-Implanted GaP: Microstructures vs Magnetic Properties.

PubMed

Yuan, Ye; Hübner, René; Liu, Fang; Sawicki, Maciej; Gordan, Ovidiu; Salvan, G; Zahn, D R T; Banerjee, D; Baehtz, Carsten; Helm, Manfred; Zhou, Shengqiang

2016-02-17

Ferromagnetic GaMnP layers were prepared by ion implantation and pulsed laser annealing (PLA). We present a systematic investigation on the evolution of microstructure and magnetic properties depending on the pulsed laser annealing energy. The sample microstructure was analyzed by high-resolution X-ray diffraction (HR-XRD), transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS), ultraviolet Raman spectroscopy (UV-RS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. The presence of X-ray Pendellösung fringes around GaP (004) and RBS channeling prove the epitaxial structure of the GaMnP layer annealed at the optimized laser energy density (0.40 J/cm(2)). However, a forbidden TO vibrational mode of GaP appears and increases with annealing energy, suggesting the formation of defective domains inside the layer. These domains mainly appear in the sample surface region and extend to almost the whole layer with increasing annealing energy. The reduction of the Curie temperature (TC) and of the uniaxial magnetic anisotropy gradually happens when more defects and the domains appear as increasing the annealing energy density. This fact univocally points to the decisive role of the PLA parameters on the resulting magnetic characteristics in the processed layers, which eventually determine the magnetic (or spintronics) figure of merit.

Surface Studies Of Dielectric Materials Used In Spark Gaps

DTIC Science & Technology

1983-06-01

on the virgin sample shows 78.1% carbon, 11.5’% oxygen, 5.2% nitrogen and 5.2% silicon . The usual composition of nylon is C6H110N which would give...copper composite ) electrodes. The spark gap selfbreaks at 40-45kV and switches approximately 1 kJ of energy in 2 ~s at a maximum rep-rate of 2... composite , two different tungsten- copper composites (K-33 and Elkonite), or stainless steel. The spark gap normally operates at a voltage of less than

Quasiparticle and excitonic gaps of one-dimensional carbon chains.

PubMed

Mostaani, E; Monserrat, B; Drummond, N D; Lambert, C J

2016-06-01

We report diffusion quantum Monte Carlo (DMC) calculations of the quasiparticle and excitonic gaps of hydrogen-terminated oligoynes and extended polyyne. The electronic gaps are found to be very sensitive to the atomic structure in these systems. We have therefore optimised the geometry of polyyne by directly minimising the DMC energy with respect to the lattice constant and the Peierls-induced carbon-carbon bond-length alternation. We find the bond-length alternation of polyyne to be 0.136(2) Å and the excitonic and quasiparticle gaps to be 3.30(7) and 3.4(1) eV, respectively. The DMC zone-centre longitudinal optical phonon frequency of polyyne is 2084(5) cm(-1), which is consistent with Raman spectroscopic measurements for large oligoynes.

Evaluating frontier orbital energy and HOMO/LUMO gap with descriptors from density functional reactivity theory.

PubMed

Huang, Ying; Rong, Chunying; Zhang, Ruiqin; Liu, Shubin

2017-01-01

Wave function theory (WFT) and density functional theory (DFT)-the two most popular solutions to electronic structure problems of atoms and molecules-share the same origin, dealing with the same subject yet using distinct methodologies. For example, molecular orbitals are artifacts in WFT, whereas in DFT, electron density plays the dominant role. One question that needs to be addressed when using these approaches to appreciate properties related to molecular structure and reactivity is if there is any link between the two. In this work, we present a piece of strong evidence addressing that very question. Using five polymeric systems as illustrative examples, we reveal that using quantities from DFT such as Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy, Onicescu information energy, Rényi entropy, etc., one is able to accurately evaluate orbital-related properties in WFT like frontier orbital energies and the HOMO (highest occupied molecular orbital)/LUMO (lowest unoccupied molecular orbital) gap. We verified these results at both the whole molecule level and the atoms-in-molecules level. These results provide compelling evidence suggesting that WFT and DFT are complementary to each other, both trying to comprehend the same properties of the electronic structure and molecular reactivity from different perspectives using their own characteristic vocabulary. Hence, there should be a bridge or bridges between the two approaches.

Energy Factors in Commercial Mortgages: Gaps and Opportunities

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

Mathew, Paul; Coleman, Philip; Wallace, Nancy

2016-09-01

The commercial real estate mortgage market is enormous, with almost half a trillion dollars in deals originated in 2015. Relative to other energy efficiency financing mechanisms, very little attention has been paid to the potential of commercial mortgages as a channel for promoting energy efficiency investments. The valuation and underwriting elements of the business are largely driven by the “net operating income” (NOI) metric – essentially, rents minus expenses. While NOI ostensibly includes all expenses, energy factors are in several ways given short shrift in the underwriting process. This is particularly interesting when juxtaposed upon a not insignificant body ofmore » research revealing that there are in fact tangible benefits (such as higher valuations and lower vacancy and default rates) for energy-efficient and “green” commercial buildings. This scoping report characterizes the current status and potential interventions to promote greater inclusion of energy factors in the commercial mortgage process.« less

Energy cost of physical activities in 12-y-old girls: MET values and the influence of body weight.

PubMed

Spadano, J L; Must, A; Bandini, L G; Dallal, G E; Dietz, W H

2003-12-01

Few data exist on the energy cost of specific activities in children. The influence of body weight on the energy cost of activity when expressed as metabolic equivalents (METs) has not been vigorously explored. To provide MET data on five specific activities in 12-y-old girls and to test the hypothesis that measured MET values are independent of body weight. In 17 12-y-old girls, resting metabolic rate (RMR) and the energy expended while sitting, standing, walking on a flat treadmill at 3.2 and at 4.8 km/h, and walking on a treadmill at a 10% incline at 4.8 km/h were measured using indirect calorimetry. MET values were calculated by dividing the energy expenditure of an activity by the subject's RMR. The influence of body weight was assessed using simple linear regression. The observed METs were more consistent with published values for similar activities in adults than those offered for children. Body weight was a statistically significant predictor of the MET of all three walking activities, but not the MET of sitting or standing. Body weight explained 25% of the variance in the MET value for walking at 3.2 km/h, 39% for walking at 4.8 km/h, and 63% for walking at a 10% incline at 4.8 km/h. METs for the three walking activities were not independent of body weight. The use of average MET values to estimate the energy cost of these three activities would result in an underestimation of their energy cost in heavier girls and an overestimation in lighter girls. These results suggest that the estimation of total energy expenditure from activity diary, recall, and direct observation data using average MET values may be biased by body weight.

Energy exchange properties during second-harmonic generation in finite one-dimensional photonic band-gap structures with deep gratings.

PubMed

D'Aguanno, Giuseppe; Centini, Marco; Scalora, Michael; Sibilia, Concita; Bertolotti, Mario; Bloemer, Mark J; Bowden, Charles M

2003-01-01

We study second-harmonic generation in finite, one-dimensional, photonic band-gap structures with large index contrast in the regime of pump depletion and global phase-matching conditions. We report a number of surprising results: above a certain input intensity, field dynamics resemble a multiwave mixing process, where backward and forward components compete for the available energy; the pump field is mostly reflected, revealing a type of optical limiting behavior; and second-harmonic generation becomes balanced in both directions, showing unusual saturation effects with increasing pump intensity. This dynamics was unexpected, and it is bound to influence the way one goes about thinking and designing nonlinear frequency conversion devices in a practical way.

Design, Construction, Demonstration and Delivery of an Automated Narrow Gap Welding System.

DTIC Science & Technology

1983-03-31

evaluated on the Narrow Gap welding system. By using the combinational qas shielding assembly, it is now possible to reduce the gas flow rates to a value...AD-A145 496 DESIGN CONSTRUCTION DEMONSTRATION AND DE IVER OF AN AUTOMATED NARROW GAP WELDING SYSTEM(U) CRC AUTOMATIC WELDING CO HODSTON SX 31 MAR 83...STANDARDS-963 - A CRC REPORT NO. NAV A/W 7 0PHASE 3 REPORT ON SDESIGN, CONSTRUCTION, DEMONSTRATION AND DELIVERY OF AN AUTOMATED NARROW GAP WELDING

Theoretical study of band gap in CuAlO2: Pressure dependence and self-interaction correction

NASA Astrophysics Data System (ADS)

Nakanishi, Akitaka; Katayama-Yoshida, Hiroshi

2012-08-01

By using first-principles calculations, we studied the energy gaps of delafossite CuAlO2: (1) pressure dependence and (2) self-interaction correction (SIC). Our simulation shows that CuAlO2 transforms from a delafossite structure to a leaning delafossite structure at 60 GPa. The energy gap of CuAlO2 increases through the structural transition due to the enhanced covalency of Cu 3d and O 2p states. We implemented a self-interaction correction (SIC) into first-principles calculation code to go beyond local density approximation and applied it to CuAlO2. The energy gap calculated within the SIC is close to experimental data while one calculated without the SIC is about 1 eV smaller than the experimental data.

Theoretical investigations on diamondoids (CnHm, n = 10-41): Nomenclature, structural stabilities, and gap distributions

NASA Astrophysics Data System (ADS)

Wang, Ya-Ting; Zhao, Yu-Jun; Liao, Ji-Hai; Yang, Xiao-Bao

2018-01-01

Combining the congruence check and the first-principles calculations, we have systematically investigated the structural stabilities and gap distributions of possible diamondoids (CnHm) with the carbon numbers (n) from 10 to 41. A simple method for the nomenclature is proposed, which can be used to distinguish and screen the candidates with high efficiency. Different from previous theoretical studies, the possible diamondoids can be enumerated according to our nomenclature, without any pre-determination from experiments. The structural stabilities and electronic properties have been studied by density functional based tight binding and first-principles methods, where a nearly linear correlation is found between the energy gaps obtained by these two methods. According to the formation energy of structures, we have determined the stable configurations as a function of chemical potential. The maximum and minimum energy gaps are found to be dominated by the shape of diamondoids for clusters with a given number of carbon atoms, while the gap decreases in general as the size increases due to the quantum confinement.

Tunnel effect wave energy detection

NASA Technical Reports Server (NTRS)

Kaiser, William J. (Inventor); Waltman, Steven B. (Inventor); Kenny, Thomas W. (Inventor)

1995-01-01

Methods and apparatus for measuring gravitational and inertial forces, magnetic fields, or wave or radiant energy acting on an object or fluid in space provide an electric tunneling current through a gap between an electrode and that object or fluid in space and vary that gap with any selected one of such forces, magnetic fields, or wave or radiant energy acting on that object or fluid. These methods and apparatus sense a corresponding variation in an electric property of that gap and determine the latter force, magnetic fields, or wave or radiant energy in response to that corresponding variation, and thereby sense or measure such parameters as acceleration, position, particle mass, velocity, magnetic field strength, presence or direction, or wave or radiant energy intensity, presence or direction.

Effect of substituents on polarizability and hyperpolarizability values of benzimidazole metal complexes

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

Praveen, P. A.; Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in

2016-05-23

In this report, the polarizability and first and second order hyperpolarizability values of bis benzimidazole Zn(II)-2R and bis benzimidazole Cd(II)-2R complexes, with different electron donating moieties R (R= Cl, Br, I, Acetate) were calculated using time dependent Hartree-Fock (TDHF) formalism embedded in MOPAC2012 package. Further the role of substituents on polarizability and hyperpolarizability values is investigated for the first time by analyzing the frontier molecular orbitals of the complexes with respect to the electronegativity of the substituents. It is found that the increase in electronegativity of the substituents correspondingly increases the energy gap of the molecules, which in turn reducesmore » the polarizability values of both Zn and Cd benzimidazole complexes. Similarly, increase in electronegativity reduces the electric quadrupole moments of both the metal complexes, which in turn reduces the hyperpolarizability values.« less

The Influence of a "Gap Year" on Medical Students

ERIC Educational Resources Information Center

Paterson-Brown, Lucy; Paterson-Brown, Flora; Simon, Elizabeth; Loudon, Joanna; Henderson-Howat, Susanna; Robertson, Josephine; Paterson-Brown, Simon

2015-01-01

This study reports the views of second year medical students from 6 Universities on the value or not of deferring entry to medical school in order to take a "Gap Year" obtained from an anonymous questionnaire. Data were analysed using Fisher's exact test to produce a two tailed P value, with significance defined as p <0.05. A total of…

What is epistemic value in free energy models of learning and acting? A bounded rationality perspective.

PubMed

Ortega, Pedro A; Braun, Daniel A

2015-01-01

Free energy models of learning and acting do not only care about utility or extrinsic value, but also about intrinsic value, that is, the information value stemming from probability distributions that represent beliefs or strategies. While these intrinsic values can be interpreted as epistemic values or exploration bonuses under certain conditions, the framework of bounded rationality offers a complementary interpretation in terms of information-processing costs that we discuss here.

Optimization of air gap for two-dimensional imaging system using synchrotron radiation

NASA Astrophysics Data System (ADS)

Zeniya, Tsutomu; Takeda, Tohoru; Yu, Quanwen; Hyodo, Kazuyuki; Yuasa, Tetsuya; Aiyoshi, Yuji; Hiranaka, Yukio; Itai, Yuji; Akatsuka, Takao

2000-11-01

Since synchrotron radiation (SR) has several excellent properties such as high brilliance, broad continuous energy spectrum and small divergence, we can obtain x-ray images with high contrast and high spatial resolution by using of SR. In 2D imaging using SR, air gap method is very effective to reduce the scatter contamination. However, to use air gap method, the geometrical effect of finite source size of SR must be considered because spatial resolution of image is degraded by air gap. For 2D x-ray imaging with SR, x-ray mammography was chosen to examine the effect of air gap method. We theoretically discussed the optimization of air gap distance suing effective scatter point source model proposed by Muntz, and executed experiment with a newly manufactured monochromator with asymmetrical reflection and an imaging plate.

2D XANES-XEOL mapping: observation of enhanced band gap emission from ZnO nanowire arrays

NASA Astrophysics Data System (ADS)

Wang, Zhiqiang; Guo, Xiaoxuan; Sham, Tsun-Kong

2014-05-01

Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed.Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed. Electronic supplementary information (ESI) available: XEOL spectra with different excitation energies. X-ray attenuation length vs. photon energy. Details of surface defects in ZnO NWs. The second O K-edge and Zn L-edge 2D XANES-XEOL maps. Comparison of the first and second TEY at O K-edge and Zn L-edge scans, respectively. Raman spectra of the ZnO NWs with different IBGE/IDE ratios. See DOI: 10.1039/c4nr01049c

Diffraction studies of the high pressure phases of GaAs and GaP

NASA Technical Reports Server (NTRS)

Baublitz, M., Jr.; Ruoff, A. L.

1982-01-01

High pressure structural phase transitions of GaAs and GaP have been studied by energy dispersive X-ray diffraction with the radiation from the Cornell High Energy Synchrotron Source. GaAs began to transform at 172 + or - 7 kbar to an orthorhombic structure possibly belonging to space group Fmmm. GaP transformed to a tetragonal beta-Sn type phase at 215 + or - 8 kbar. Although pressure transmitting media were used to minimize shear stresses in the specimens, the high pressure diffraction results were interpreted as showing evidence for planar defects in the specimens.

Bridging the Gap: Ideas for water sustainability in the western United States

NASA Astrophysics Data System (ADS)

Tidwell, V. C.; Passell, H. D.; Roach, J. D.

2012-12-01

Incremental improvements in water sustainability in the western U.S. may not be able to close the growing gap between increasing freshwater demand, climate driven variability in freshwater supply, and growing environmental consciousness. Incremental improvements include municipal conservation, improvements to irrigation technologies, desalination, water leasing, and others. These measures, as manifest today in the western U.S., are successful in themselves but limited in their ability to solve long term water scarcity issues. Examples are plainly evident and range from the steady and long term decline of important aquifers and their projected inability to provide water for future agricultural irrigation, projected declines in states' abilities to meet legal water delivery obligations between states, projected shortages of water for energy production, and others. In many cases, measures that can close the water scarcity gap have been identified, but often these solutions simply shift the gap from water to some other sector, e.g., economics. Saline, brackish or produced water purification, for example, could help solve western water shortages in some areas, but will be extremely expensive, and so shift the gap from water to economics. Transfers of water out of agriculture could help close the water scarcity gap in other areas; however, loss of agriculture will shift the gap to regional food security. All these gaps, whether in water, economics, food security, or other sectors, will have a negative impact on the western states. Narrowing these future gaps requires both technical and policy solutions as well as tools to understand the tradeoffs. Here we discuss several examples from across the western U.S. that span differing scales and decision spaces. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear

The subsidiary gap as a means for improving ignition

NASA Technical Reports Server (NTRS)

Gorton, W S

1920-01-01

This report was prepared at the Bureau of Standards for the National Advisory Committee for Aeronautics. Additional or subsidiary gaps have frequently been used in jump-spark ignition systems, in order to cause the resumption of sparking in fouled spark plugs. The series gap, to which the greater part of this report is devoted, is a subsidiary gap in the connection between the high tension terminal of the plug and that of the magneto or coil. A brief account is given of the use of this gap up to the present time and also of the statements concerning it which have gained some currency, most of which are shown to be erroneous. The simple theory of the action of the series gap is discussed and a detailed account given of the effect upon the sparking ability of the plug produced by changes in the values of the electrical resistance of the fouling and of the capacities in parallel with the plug and with the magneto or coil. This report presents the results of an investigation into the utility, action, and design of the auxiliary spark gap as a means for insuring freedom from spark plug failure due to fouling, and also to enable the restarting of fouled plugs.

Features of Superconducting Gaps Revealed by STM/STS in Iron Based Superconductors With and Without Hole Pockets

NASA Astrophysics Data System (ADS)

Wen, Hai-Hu; Hai-Hu Wen Team

The pairing mechanism and gap structure in iron based superconductors (IBS) remains unresolved. We have conducted extensive STM/STS study on the Na(Fe1-xTx) As (T =Co, Cu, Mn), Ba1-xKxFe2As2KFe2As2, and Li1-xFexOHFeSe single crystals. We found the clear evidence of the in-gap quasi-particle states induced by the non-magnetic Cu impurities in Na(Fe0.97- x Co0.03Cux) As, giving strong evidence of the S+/- pairing. Furthermore, we show the presence of the bosonic mode with the energy identical to that of the neutron resonance and a simple linear relation Ω/kBTc ~ 4.3, being explained a consequence of the S+/-pairing. The STS spectrum in Li1-x FexOHFeSe clearly indicates the presence of double superconducting gaps with Δ1 ~ 14.3 meV and Δ2 ~ 8.6 meV. Further analysis based on QPI allows us to assign the larger (smaller) gap to the outer (inner) hybridized electron pockets. The huge value 2Δ1/kBTc = 8.7 discovered here undoubtedly proves the strong coupling mechanism. This work was supported by the Ministry of Science and Technology of China, National Natural Science Foundation of China.

Fundamental gaps with approximate density functionals: The derivative discontinuity revealed from ensemble considerations

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

Kraisler, Eli; Kronik, Leeor

2014-05-14

The fundamental gap is a central quantity in the electronic structure of matter. Unfortunately, the fundamental gap is not generally equal to the Kohn-Sham gap of density functional theory (DFT), even in principle. The two gaps differ precisely by the derivative discontinuity, namely, an abrupt change in slope of the exchange-correlation energy as a function of electron number, expected across an integer-electron point. Popular approximate functionals are thought to be devoid of a derivative discontinuity, strongly compromising their performance for prediction of spectroscopic properties. Here we show that, in fact, all exchange-correlation functionals possess a derivative discontinuity, which arises naturallymore » from the application of ensemble considerations within DFT, without any empiricism. This derivative discontinuity can be expressed in closed form using only quantities obtained in the course of a standard DFT calculation of the neutral system. For small, finite systems, addition of this derivative discontinuity indeed results in a greatly improved prediction for the fundamental gap, even when based on the most simple approximate exchange-correlation density functional – the local density approximation (LDA). For solids, the same scheme is exact in principle, but when applied to LDA it results in a vanishing derivative discontinuity correction. This failure is shown to be directly related to the failure of LDA in predicting fundamental gaps from total energy differences in extended systems.« less

Bandgap and pseudohelicity effects over conductance in gapped graphene junctures

NASA Astrophysics Data System (ADS)

Navarro-Giraldo, J. A.; Quimbay, C. J.

2018-07-01

We study the conductance in gapped single-layer graphene junctures as a function of bangap, pseudohelicity and charge carriers density. To do it, we first calculate the transmission coefficients of massive charge carries for p–n and n–p–n junctures of gapped single-layer graphene. Next, we calculate the conductance for these two systems using the Landauer formula. Only for the p–n juncture case and non-zero bandgap values, we find the existence of a contribution to the conductance from pseudohelicity inversion states, which is small compared to the contribution from pseudohelicity conservation states. Also, we find for both type of junctures that there exists a window of charge carriers densities values where the conductance is zero (conductance gap), in such a way that the size of this window depends on the squared of the bandgap. We observe that the existence of a bandgap in the system leads to valley mixing and this fact could be useful for the future design of devices based on single-layer graphene.

Electrical properties of titanium dioxide nanoparticle on microelectrode: Gap size effect

NASA Astrophysics Data System (ADS)

Nadzirah, Sh.; Hashim, U.; Zakaria, M. R.; Rusop, M.

2018-05-01

TiO2 nanoparticle based interdigitated microelectrode was fabricated by spin-coating and conventional photolithography approaches. Aluminum metal was deposited by thermal evaporator on silicon dioxide substrate. The effect of aluminum microelectrode gap sizes (4, 5 and 6 µm) on the electrical performance was investigated using picoammeter. Extremely small output current values of three different gap sizes were acquired. A characteristic electrical behavior was observed for the studied geometry. The configuration demonstrated a reduction in the output current from 2.28E-10, 1.32E-9 and 2.38E-9 A with increasing gap size.

Testing Mylar Multi-Gap Resistive Plate Chambers

NASA Astrophysics Data System (ADS)

Towell, Cecily; EIC PID Consortium Collaboration

2016-09-01

Quantum Chromodynamics (QCD) is the fundamental theory that successfully explains strong force interactions. To continue the effective study of QCD in nuclear structure, plans are being made to construct an Electron Ion Collider (EIC). Part of the preparation for the EIC includes continued detector development to push beyond their current capabilities. This includes Time of Flight (TOF) detectors, which are used for particle identification. Multi-Gap Resistive Plate Chambers (mRPCs) are a type of TOF detector that typically use glass to make small gas gaps within the detector to produce fast signals when a high energy particle goes through the detector. These extremely thin gaps of 0.2mm are key in achieving the excellent timing resolution capability of these detectors. A new mRPC design is being tested with the goal of reaching a timing resolution of 10ps. This design uses sheets of mylar in place of the glass so that the width of the dividers is smaller, thus vastly increasing the number of gas gaps. Multiple versions of this mylar mRPC have been made and tested. The methods for producing these mRPCs and their performance will be discussed. This research was supported by US DOE MENP Grant DE-FG02-03ER41243.

[Research progress of larger flexion gap than extension gap in total knee arthroplasty].

PubMed

Zhang, Weisong; Hao, Dingjun

2017-05-01

To summarize the progress of larger flexion gap than extension gap in total knee arthro-plasty (TKA). The domestic and foreign related literature about larger flexion gap than extension gap in TKA, and its impact factors, biomechanical and kinematic features, and clinical results were summarized. During TKA, to adjust the relations of flexion gap and extension gap is one of the key factors of successful operation. The biomechanical, kinematic, and clinical researches show that properly larger flexion gap than extension gap can improve both the postoperative knee range of motion and the satisfaction of patients, but does not affect the stability of the knee joint. However, there are also contrary findings. So adjustment of flexion gap and extension gap during TKA is still in dispute. Larger flexion gap than extension gap in TKA is a new joint space theory, and long-term clinical efficacy, operation skills, and related complications still need further study.

An explanation for the tiny value of the cosmological constant and the low vacuum energy density

NASA Astrophysics Data System (ADS)

Nassif, Cláudio

2015-09-01

The paper aims to provide an explanation for the tiny value of the cosmological constant and the low vacuum energy density to represent the dark energy. To accomplish this, we will search for a fundamental principle of symmetry in space-time by means of the elimination of the classical idea of rest, by including an invariant minimum limit of speed in the subatomic world. Such a minimum speed, unattainable by particles, represents a preferred reference frame associated with a background field that breaks down the Lorentz symmetry. The metric of the flat space-time shall include the presence of a uniform vacuum energy density, which leads to a negative pressure at cosmological length scales. Thus, the equation of state for the cosmological constant [ p(pressure) (energy density)] naturally emerges from such a space-time with an energy barrier of a minimum speed. The tiny values of the cosmological constant and the vacuum energy density will be successfully obtained, being in agreement with the observational results of Perlmutter, Schmidt and Riess.