Why Density Dependent Propulsion?

NASA Technical Reports Server (NTRS)

Robertson, Glen A.

2011-01-01

In 2004 Khoury and Weltman produced a density dependent cosmology theory they call the Chameleon, as at its nature, it is hidden within known physics. The Chameleon theory has implications to dark matter/energy with universe acceleration properties, which implies a new force mechanism with ties to the far and local density environment. In this paper, the Chameleon Density Model is discussed in terms of propulsion toward new propellant-less engineering methods.

Modern foraging: Presence of food and energy density influence motivational processing of food advertisements.

PubMed

Bailey, Rachel L

2016-12-01

More energy dense foods are preferable from an optimal foraging perspective, which suggests these foods are more motivationally relevant due to their greater capability of fulfilling biological imperatives. This increase in motivational relevance may be exacerbated in circumstances where foraging will be necessary. This study examined how food energy density and presence of food in the immediate environment interacted to influence motivational processing of food advertisements. N = 58 adults viewed advertisements for foods varying in energy density in contexts where the advertised food was actually present in the viewing room or not. Advertisements for more energy dense foods elicited greater skin conductivity level compared to ads for less energy dense foods when food was not present. All ads elicited decreases in corrugator supercilii activation indicating positive emotional response resultant from appetitive motivational activation, though the greatest activation was exhibited toward higher energy density foods when food was present. This supports an optimal foraging perspective and has implications for healthy eating interventions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dark energy in the environments of the Local Group, the M 81 group, and the CenA group: the normalized Hubble diagram

NASA Astrophysics Data System (ADS)

Teerikorpi, P.; Chernin, A. D.; Karachentsev, I. D.; Valtonen, M. J.

2008-05-01

Context: Type Ia supernova observations on scales of thousands of Mpc show that the global expansion of the universe is accelerated by antigravity produced by the enigmatic dark energy contributing 3/4 of the total energy of the universe. Aims: Does antigravity act on small scales as well as large? As a continuation of our efforts to answer this crucial question we combine high accuracy observations of the galaxy flows around the Local Group and the nearby M 81 and CenA groups to observe the effect of the dark energy density on local scales of a few Mpc. Methods: We use an analytical model to describe non-uniform static space-time regions around galaxy groups. In this context it is useful to present the Hubble flow in a normalized Hubble diagram V/Hv Rv vs. r/R_v, where the vacuum Hubble constant Hv depends only on the cosmological vacuum density and the zero-gravity distance Rv depends on the vacuum density and on the mass of the galaxy group. We have prepared the normalized Hubble diagrams for the LG, M 81 and CenA group environments for different values of the assumed vacuum energy density, using a total of about 150 galaxies, for almost all of which the distances have been measured by the HST. Results: The normalized Hubble diagram, where we identify dynamically different regions, is in agreement with the standard vacuum density (Ωv = 0.77~h_70-2), the out-flow of galaxies clearly being controlled by the minimum energy condition imposed by the central mass plus the vacuum density. A high vacuum density 1.6~h_70-2 violates the minimum energy limit, while a low density 0.1~h_70-2 leaves the start of the Hubble flow around 1-2 Mpc with the slope close to the global value obscure. We also consider the subtle relation of the zero-gravity radius Rv to the zero-velocity distance R0 appearing in the usual retarded expansion around a mass M: in a vacuum-dominated flat universe R0 ≈ 0.76 R_v. Conclusions: The normalized Hubble diagram appears to be a good way to present and analyze physically different regions around mass clumps embedded in cosmological vacuum. The most natural interpretation of the diagram is that the local density of the dark energy is approximately equal to the density known from studies on global scales.

Lightning under water: Diverse reactive environments and evidence of synergistic effects for material treatment and activation

NASA Astrophysics Data System (ADS)

Levchenko, Igor; Bazaka, Kateryna; Baranov, Oleg; Sankaran, R. Mohan; Nomine, Alexandre; Belmonte, Thierry; Xu, Shuyan

2018-06-01

This focused review aims to reveal and illustrate some unique features of processes triggered by high-density energy applied to liquids and gas-liquid interfaces and to highlight a wide spectrum of their technological applications capable of producing various advantageous effects, ranging from nanosynthesis to biological and medical applications. Plasma, electric discharges, laser, and ultrasound power effects were selected as representative examples of high-density energy and liquid interactions, yet the available possibilities are not limited by these quite different types of power and thus the reader could extrapolate the outlined features and effects to other kinds of powerful impacts. The basic physical mechanisms are briefly reviewed with the aim to familiarize the readers with the potential capabilities of high-density energy processes in liquids. These will be of direct interest to researchers tasked with the development, optimization, and characterization of processes and highly reactive environments for highly controlled transformation of matter in abiotic and biological systems. It could also be highly useful for under- and post-graduate students specializing in the related fields and general physical audience involved in various plasma, materials, energy conversion, and other concurrent research activities.

Fission Systems for Mars Exploration

NASA Technical Reports Server (NTRS)

Houts, Michael G.; Kim, T.; Dorney, D. J.; Swint, Marion Shayne

2012-01-01

Fission systems are used extensively on earth, and 34 such systems have flown in space. The energy density of fission is over 10 million times that of chemical reactions, giving fission the potential to eliminate energy density constraints for many space missions. Potential safety and operational concerns with fission systems are well understood, and strategies exist for affordably developing such systems. By enabling a power-rich environment and highly efficient propulsion, fission systems could enable affordable, sustainable exploration of Mars.

Occurrence of high-beta superthermal plasma events in the close environment of Jupiter's bow shock as observed by Ulysses

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

Marhavilas, P. K.; Sarris, E. T.; Anagnostopoulos, G. C.

2011-01-04

The ratio of the plasma pressure to the magnetic field pressure (or of their energy densities) which is known as the plasma parameter 'beta'({beta}) has important implications to the propagation of energetic particles and the interaction of the solar wind with planetary magnetospheres. Although in the scientific literature the contribution of the superthermal particles to the plasma pressure is generally assumed negligible, we deduced, by analyzing energetic particles and magnetic field measurements recorded by the Ulysses spacecraft, that in a series of events, the energy density contained in the superthermal tail of the particle distribution is comparable to or evenmore » higher than the energy density of the magnetic field, creating conditions of high-beta plasma. More explicitly, in this paper we analyze Ulysses/HI-SCALE measurements of the energy density ratio (parameter {beta}{sub ep}) of the energetic ions'(20 keV to {approx}5 MeV) to the magnetic field's in order to find occurrences of high-beta ({beta}{sub ep}>1) superthermal plasma conditions in the environment of the Jovian magnetosphere, which is an interesting plasma laboratory and an important source of emissions in our solar system. In particular, we examine high-beta ion events close to Jupiter's bow shock, which are produced by two processes: (a) bow shock ion acceleration and (b) ion leakage from the magnetosphere.« less

The high-energy-density counterpropagating shear experiment and turbulent self-heating

DOE PAGES

Doss, F. W.; Fincke, J. R.; Loomis, E. N.; ...

2013-12-06

The counterpropagating shear experiment has previously demonstrated the ability to create regions of shockdriven shear, balanced symmetrically in pressure and experiencing minimal net drift. This allows for the creation of a high-Mach-number high-energy-density shear environment. New data from the counterpropagating shear campaign is presented, and both hydrocode modeling and theoretical analysis in the context of a Reynolds-averaged-Navier-Stokes model suggest turbulent dissipation of energy from the supersonic flow bounding the layer is a significant driver in its expansion. A theoretical minimum shear flow Mach number threshold is suggested for substantial thermal-turbulence coupling.

Theoretical Calculation of the Electron Transport Parameters and Energy Distribution Function for CF3I with noble gases mixtures using Monte Carlo simulation program

NASA Astrophysics Data System (ADS)

Jawad, Enas A.

2018-05-01

In this paper, The Monte Carlo simulation program has been used to calculation the electron energy distribution function (EEDF) and electric transport parameters for the gas mixtures of The trif leoroiodo methane (CF3I) ‘environment friendly’ with a noble gases (Argon, Helium, kryptos, Neon and Xenon). The electron transport parameters are assessed in the range of E/N (E is the electric field and N is the gas number density of background gas molecules) between 100 to 2000Td (1 Townsend = 10-17 V cm2) at room temperature. These parameters, namely are electron mean energy (ε), the density –normalized longitudinal diffusion coefficient (NDL) and the density –normalized mobility (μN). In contrast, the impact of CF3I in the noble gases mixture is strongly apparent in the values for the electron mean energy, the density –normalized longitudinal diffusion coefficient and the density –normalized mobility. Note in the results of the calculation agreed well with the experimental results.

Energy as a Constraint on Habitability in the Subsurface

NASA Astrophysics Data System (ADS)

Hoehler, T.

2008-12-01

All living things must obtain energy from the environment to grow, to maintain a metabolic steady state, or simply to preserve viability. The availability of energy sources in the environment thus represents a key factor in determining the size, distribution, and activity of biological populations, and ultimately constrains the possibility for life itself. Lacking the abundant energy provided by solar radiation or the products of oxygenic photosynthesis, life in subsurface environments may be limited by energy availability as much as any other factor. The biological requirement for energy is expressed in two dimensions - analogous to the power and voltage requirements of electrical devices - and consideration and quantification of these requirements establishes quantitative boundary conditions on subsurface habitability. The magnitude of these requirements depends significantly on physicochemical environment, as does the provision of biologically-accessible energy from subsurface sources. With this conceptual basis, we are developing an 'energy balance' model that is designed to ultimately predict the habitability of a given environment, with respect to a given metabolism, in quantitative terms (as 'biomass density potential'). The model will develop from conceptual to quantitative as experimental and observational work constrains and quantifies, in natural populations adapted to low energy conditions, the magnitude of the biological energy requirements and the impacts of physicochemical environmental conditions on energy demand and supply.

Effect of conductive additives to gel electrolytes on activated carbon-based supercapacitors

NASA Astrophysics Data System (ADS)

Barzegar, Farshad; Dangbegnon, Julien K.; Bello, Abdulhakeem; Momodu, Damilola Y.; Johnson, A. T. Charlie; Manyala, Ncholu

2015-09-01

This article is focused on polymer based gel electrolyte due to the fact that polymers are cheap and can be used to achieve extended potential window for improved energy density of the supercapacitor devices when compared to aqueous electrolytes. Electrochemical characterization of a symmetric supercapacitor devices based on activated carbon in different polyvinyl alcohol (PVA) based gel electrolytes was carried out. The device exhibited a maximum energy density of 24 Wh kg-1 when carbon black was added to the gel electrolyte as conductive additive. The good energy density was correlated with the improved conductivity of the electrolyte medium which is favorable for fast ion transport in this relatively viscous environment. Most importantly, the device remained stable with no capacitance lost after 10,000 cycles.

The Built Food Environment and Dietary Intake among African-American Adults

PubMed Central

Reitzel, Lorraine R.; Okamoto, Hiroe; Hernandez, Daphne C.; Regan, Seann D.; McNeill, Lorna H.; Obasi, Ezemenari M.

2016-01-01

Objectives The built food environment surrounding people's homes may influence their dietary intake. This exploratory study examined how the density of different sources of food in the residential environment was associated with dietary consumption among 77 African-American adults in Houston, Texas. Methods The number of fast-food-type restaurants, large grocery stores, and convenience-type stores within 2- and 5-mile residential buffers were divided by the respective areas to obtain food environment density variables. Intake of fruit and vegetables [FV], fiber [FI], and percent energy from fat [PEF] was assessed using National Health Interview Survey items. Covariate-adjusted regressions were used to assess relations of interest. Results Greater density of fast-food-type restaurants within 2 miles was associated with greater FV, FI, and PEF (ps ≤ .012); and for FV and FI within 5 miles (ps < .004). Density of large grocery stores was unrelated to intake. Greater density of convenience-type stores within 2 miles was negatively associated with FV and FI (ps ≤ .03); results became marginal at 5 miles for FV (p = .10) but not FI (p = .03). Conclusion Maximizing healthy offerings in venue-rich metropolitan areas might provide direction for policies to reduce obesity. PMID:26685808

Extra-metabolic energy use and the rise in human hyper-density

NASA Astrophysics Data System (ADS)

Burger, Joseph R.; Weinberger, Vanessa P.; Marquet, Pablo A.

2017-03-01

Humans, like all organisms, are subject to fundamental biophysical laws. Van Valen predicted that, because of zero-sum dynamics, all populations of all species in a given environment flux the same amount of energy on average. Damuth’s ’energetic equivalence rule’ supported Van Valen´s conjecture by showing a tradeoff between few big animals per area with high individual metabolic rates compared to abundant small species with low energy requirements. We use metabolic scaling theory to compare variation in densities and individual energy use in human societies to other land mammals. We show that hunter-gatherers occurred at densities lower than the average for a mammal of our size. Most modern humans, in contrast, concentrate in large cities at densities up to four orders of magnitude greater than hunter-gatherers, yet consume up to two orders of magnitude more energy per capita. Today, cities across the globe flux greater energy than net primary productivity on a per area basis. This is possible by importing enormous amounts of energy and materials required to sustain hyper-dense, modern humans. The metabolic rift with nature created by modern cities fueled largely by fossil energy poses formidable challenges for establishing a sustainable relationship on a rapidly urbanizing, yet finite planet.

Extra-metabolic energy use and the rise in human hyper-density.

PubMed

Burger, Joseph R; Weinberger, Vanessa P; Marquet, Pablo A

2017-03-02

Humans, like all organisms, are subject to fundamental biophysical laws. Van Valen predicted that, because of zero-sum dynamics, all populations of all species in a given environment flux the same amount of energy on average. Damuth's 'energetic equivalence rule' supported Van Valen´s conjecture by showing a tradeoff between few big animals per area with high individual metabolic rates compared to abundant small species with low energy requirements. We use metabolic scaling theory to compare variation in densities and individual energy use in human societies to other land mammals. We show that hunter-gatherers occurred at densities lower than the average for a mammal of our size. Most modern humans, in contrast, concentrate in large cities at densities up to four orders of magnitude greater than hunter-gatherers, yet consume up to two orders of magnitude more energy per capita. Today, cities across the globe flux greater energy than net primary productivity on a per area basis. This is possible by importing enormous amounts of energy and materials required to sustain hyper-dense, modern humans. The metabolic rift with nature created by modern cities fueled largely by fossil energy poses formidable challenges for establishing a sustainable relationship on a rapidly urbanizing, yet finite planet.

Predicting In-Situ X-ray Diffraction for the SrTiO3/Liquid Interface from First Principles

NASA Astrophysics Data System (ADS)

Letchworth-Weaver, Kendra; Gunceler, Deniz; Sundararaman, Ravishankar; Huang, Xin; Brock, Joel; Arias, T. A.

2013-03-01

Recent advances in experimental techniques, such as in-situ x-ray diffraction, allow researchers to probe the solid-liquid interface in electrochemical systems under operating conditions. These advances offer an unprecedented opportunity for theory to predict properties of electrode materials in aqueous environments and inform the design of energy conversion and storage devices. To compare with experiment, these theoretical studies require microscopic details of both the liquid and the electrode surface. Joint Density Functional Theory (JDFT), a computationally efficient alternative to molecular dynamics, couples a classical density-functional, which captures molecular structure of the liquid, to a quantum-mechanical functional for the electrode surface. We present a JDFT exploration of SrTiO3, which can catalyze solar-driven water splitting, in an electrochemical environment. We determine the geometry of the polar SrTiO3 surface and the equilibrium structure of the contacting liquid, as well as the influence of the liquid upon the electronic structure of the surface. We then predict the effect of the fluid environment on x-ray diffraction patterns and compare our predictions to in-situ measurements performed at the Cornell High Energy Synchrotron Source (CHESS). This material is based upon work supported by the Energy Materials Center at Cornell (EMC2), an Energy Frontier Research Center funded by the U.S. Department of Energy.

Relationship between wave energy and free energy from pickup ions in the Comet Halley environment

NASA Technical Reports Server (NTRS)

Huddleston, D. E.; Johnstone, A. D.

1992-01-01

The free energy available from the implanted heavy ion population at Comet Halley is calculated by assuming that the initial unstable velocity space ring distribution of the ions evolves toward a bispherical shell. Ultimately this free energy adds to the turbulence in the solar wind. Upstream and downstream free energies are obtained separately for the conditions observed along the Giotto spacecraft trajectory. The results indicate that the waves are mostly upstream propagating in the solar wind frame. The total free energy density always exceeds the measured wave energy density because, as expected in the nonlinear process of ion scattering, the available energy is not all immediately released. An estimate of the amount which has been released can be obtained from the measured oxygen ion distributions and again it exceeds that observed. The theoretical analysis is extended to calculate the k spectrum of the cometary-ion-generated turbulence.

Efficient calculation of the energy of a molecule in an arbitrary electric field

NASA Astrophysics Data System (ADS)

Pulay, Peter; Janowski, Tomasz

In thermodynamic (e.g., Monte Carlo) simulations with electronic embedding, the energy of the active site or solute must be calculated for millions of configurations of the environment (solvent or protein matrix) to obtain reliable statistics. This precludes the use of accurate but expensive ab initio and density functional techniques. Except for the immediate neighbors, the effect of the environment is electrostatic. We show that the energy of a molecule in the irregular field of the environment can be determined very efficiently by expanding the electric potential in known functions, and precalculating the first and second order response of the molecule to the components of the potential. These generalized multipole moments and polarizabilities allow the calculation of the energy of the system without further ab initio calculations. Several expansion functions were explored: polynomials, distributed inverse powers, and sine functions. The latter provide the numerically most stable fit but require new types of integrals. Distributed inverse powers can be simulated using dummy atoms, and energies calculated this way provide a very good approximation to the actual energies in the field of the environment.

Hydrogen: the future energy carrier.

PubMed

Züttel, Andreas; Remhof, Arndt; Borgschulte, Andreas; Friedrichs, Oliver

2010-07-28

Since the beginning of the twenty-first century the limitations of the fossil age with regard to the continuing growth of energy demand, the peaking mining rate of oil, the growing impact of CO2 emissions on the environment and the dependency of the economy in the industrialized world on the availability of fossil fuels became very obvious. A major change in the energy economy from fossil energy carriers to renewable energy fluxes is necessary. The main challenge is to efficiently convert renewable energy into electricity and the storage of electricity or the production of a synthetic fuel. Hydrogen is produced from water by electricity through an electrolyser. The storage of hydrogen in its molecular or atomic form is a materials challenge. Some hydrides are known to exhibit a hydrogen density comparable to oil; however, these hydrides require a sophisticated storage system. The system energy density is significantly smaller than the energy density of fossil fuels. An interesting alternative to the direct storage of hydrogen are synthetic hydrocarbons produced from hydrogen and CO2 extracted from the atmosphere. They are CO2 neutral and stored like fossil fuels. Conventional combustion engines and turbines can be used in order to convert the stored energy into work and heat.

Water-Lubricated Intercalation in V2 O5 ·nH2 O for High-Capacity and High-Rate Aqueous Rechargeable Zinc Batteries.

PubMed

Yan, Mengyu; He, Pan; Chen, Ying; Wang, Shanyu; Wei, Qiulong; Zhao, Kangning; Xu, Xu; An, Qinyou; Shuang, Yi; Shao, Yuyan; Mueller, Karl T; Mai, Liqiang; Liu, Jun; Yang, Jihui

2018-01-01

Low-cost, environment-friendly aqueous Zn batteries have great potential for large-scale energy storage, but the intercalation of zinc ions in the cathode materials is challenging and complex. Herein, the critical role of structural H 2 O on Zn 2+ intercalation into bilayer V 2 O 5 ·nH 2 O is demonstrated. The results suggest that the H 2 O-solvated Zn 2+ possesses largely reduced effective charge and thus reduced electrostatic interactions with the V 2 O 5 framework, effectively promoting its diffusion. Benefited from the "lubricating" effect, the aqueous Zn battery shows a specific energy of ≈144 Wh kg -1 at 0.3 A g -1 . Meanwhile, it can maintain an energy density of 90 Wh kg -1 at a high power density of 6.4 kW kg -1 (based on the cathode and 200% Zn anode), making it a promising candidate for high-performance, low-cost, safe, and environment-friendly energy-storage devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect on structure and mechanical property of tungsten irradiated by high intensity pulsed ion beam

NASA Astrophysics Data System (ADS)

Mei, Xianxiu; Zhang, Xiaonan; Liu, Xiaofei; Wang, Younian

2017-09-01

The anti-thermal radiation performance of tungsten was investigated by high intensity pulsed ion beam technology. The ion beam was mainly composed of Cn+ (70%) and H+ (30%) at an acceleration voltage of 250 kV under different energy densities for different number of pulses. GIXRD analysis showed that no obvious phase structural changes occurred on the tungsten, and microstress generated. SEM analysis exhibited that there was no apparent irradiation damage on the surface of tungsten at the low irradiation frequency (3 times and 10 times) and at the low energy density (0.25 J/cm2 and 0.7 J/cm2). Cracks appeared on the surface of tungsten after 100-time and 300-time irradiation. Shedding phenomenon even appeared on the surface of tungsten at the energy densities of 1.4 J/cm2 and 2.0 J/cm2. The surface nano-hardness of tungsten decreased with the increase of the pulse times and the energy density. The tungsten has good anti-thermal radiation properties under certain heat load environment.

The Use of Boron-doped Diamond Electrode on Yeast-based Microbial Fuel Cell for Electricity Production

NASA Astrophysics Data System (ADS)

Hanzhola, G.; Tribidasari, A. I.; Endang, S.

2018-01-01

The dependency of fossil energy in Indonesia caused the crude oil production to be drastically decreased since 2001, while energy consumption increased. In addition, The use of fossil energy can cause several environmental problems. Therefore, we need an alternative environment-friendly energy as solution for these problems. A microbial fuel cell is one of the prospective alternative source of an environment-friendly energy source to be developed. In this study, Boron-doped diamond electrode was used as working electrode and Candida fukuyamaensis as biocatalyst in microbial fuel cell. Different pH of anode compartment (pH 6.5-7.5) and mediator concentration (10-100 μM) was used to produce an optimal electricity. MFC was operated for 3 hours. During operation, the current and voltage density was measured with potensiostat. The maximum power and current density are 425,82 mW/m2 and 440 mA/m2, respectively, for MFC using pH 7.5 at anode compartment without addition of methylene blue. The addition of redox mediator is lowering the produced electricity because of its anti microbial properties that can kill the microbe.

The Role of Resource Density on Energy Allocation in the Neotropical Termite Nasutitermes aff. coxipoensis (Termitidae: Nasutitermitinae).

PubMed

Cristaldo, P F; Almeida, C S; Cruz, N G; Ribeiro, E J M; Rocha, M L C; Santos, A A; Santana, A S; Araújo, A P A

2018-06-01

Organisms acquire energy from environment and must allocate it among different life traits (growth, maintenance and reproduction). Social insects must manage the energy allocation to various levels such as colony growth and caste functions. Here, we addressed the question of whether resource density affects the energy allocation to the number of individuals and caste functions as well as nest's growth rate in the Neotropical termite Nasutitermes aff. coxipoensis (Homgren) (Termitidae: Nasutitermitinae). In a manipulative field experiment, colonies of N. aff. coxipoensis, with known volume, were maintained in plots with three different resource's density (0.32, 0.64 and 1.92 baits/m 2 ) over 3 months. After this period, the number of individuals as well as the caste identity and nest volume were measured. Surprisingly, our results showed that colonies reared in the extremes of resource's density (0.32 and 1.92 baits/m 2 ) produced a higher number of individuals compared with colonies reared with intermediate resource density (0. 64 baits/m 2 ). The mean number of workers increased linearly with resource density; however, the average number of immature was higher in colonies reared with 0.32 baits/m 2 compared with colonies reared with 0.64 and 1.92 baits/m 2 . No significant differences of resource density were observed in the mean number of soldiers, worker/soldier ratio as well as in the nest's growth rate. In conclusion, the resource's density seems to play an important role in determining the investment of energy in the number of individuals and caste in N. aff. coxipoensis colonies.

Modelling radiation fluxes in simple and complex environments: basics of the RayMan model.

PubMed

Matzarakis, Andreas; Rutz, Frank; Mayer, Helmut

2010-03-01

Short- and long-wave radiation flux densities absorbed by people have a significant influence on their energy balance. The heat effect of the absorbed radiation flux densities is parameterised by the mean radiant temperature. This paper presents the physical basis of the RayMan model, which simulates the short- and long-wave radiation flux densities from the three-dimensional surroundings in simple and complex environments. RayMan has the character of a freely available radiation and human-bioclimate model. The aim of the RayMan model is to calculate radiation flux densities, sunshine duration, shadow spaces and thermo-physiologically relevant assessment indices using only a limited number of meteorological and other input data. A comparison between measured and simulated values for global radiation and mean radiant temperature shows that the simulated data closely resemble measured data.

Talbot-Lau x-ray interferometry for high energy density plasma diagnostic.

PubMed

Stutman, D; Finkenthal, M

2011-11-01

High resolution density diagnostics are difficult in high energy density laboratory plasmas (HEDLP) experiments due to the scarcity of probes that can penetrate above solid density plasmas. Hard x-rays are one possible probe for such dense plasmas. We study the possibility of applying an x-ray method recently developed for medical imaging, differential phase-contrast with Talbot-Lau interferometers, for the diagnostic of electron density and small-scale hydrodynamic instabilities in HEDLP experiments. The Talbot method uses micro-periodic gratings to measure the refraction and ultra-small angle scatter of x-rays through an object and is attractive for HEDLP diagnostic due to its capability to work with incoherent and polychromatic x-ray sources such as the laser driven backlighters used for HEDLP radiography. Our paper studies the potential of the Talbot method for HEDLP diagnostic, its adaptation to the HEDLP environment, and its extension of high x-ray energy using micro-periodic mirrors. The analysis is illustrated with experimental results obtained using a laboratory Talbot interferometer. © 2011 American Institute of Physics

Observation and analysis of emergent coherent structures in a high-energy-density shock-driven planar mixing layer experiment

DOE PAGES

Doss, Forrest William; Flippo, Kirk Adler; Merritt, Elizabeth Catherine

2016-08-03

Coherent emergent structures have been observed in a high-energy-density supersonic mixing layer experiment. A millimeter-scale shock tube uses lasers to drive Mbar shocks into the tube volume. The shocks are driven into initially solid foam (60 mg/cm 3) hemicylinders separated by an Al or Ti metal tracer strip; the components are vaporized by the drive. Before the experiment disassembles, the shocks cross at the tube center, creating a very fast (ΔU > 200 km/s) shear-unstable zone. After several nanoseconds, an expanding mixing layer is measured, and after 10+ ns we observe the appearance of streamwise-periodic, spanwise-aligned rollers associated with themore » primary Kelvin-Helmholtz instability of mixing layers. We additionally image roller pairing and spanwise-periodic streamwise-aligned filaments associated with secondary instabilities. New closures are derived to connect length scales of these structures to estimates of fluctuating velocity data otherwise unobtainable in the high-energy-density environment. Finally, this analysis indicates shear-induced specific turbulent energies 10 3 – 10 4 times higher than the nearest conventional experiments. Because of difficulties in continuously driving systems under these conditions and the harshness of the experimental environment limiting the usable diagnostics, clear evidence of these developing structures has never before been observed in this regime.« less

Talbot-Lau x-ray deflectometry phase-retrieval methods for electron density diagnostics in high-energy density experiments.

PubMed

Valdivia, Maria Pia; Stutman, Dan; Stoeckl, Christian; Mileham, Chad; Begishev, Ildar A; Bromage, Jake; Regan, Sean P

2018-01-10

Talbot-Lau x-ray interferometry uses incoherent x-ray sources to measure refraction index changes in matter. These measurements can provide accurate electron density mapping through phase retrieval. An adaptation of the interferometer has been developed in order to meet the specific requirements of high-energy density experiments. This adaptation is known as a moiré deflectometer, which allows for single-shot capabilities in the form of interferometric fringe patterns. The moiré x-ray deflectometry technique requires a set of object and reference images in order to provide electron density maps, which can be costly in the high-energy density environment. In particular, synthetic reference phase images obtained ex situ through a phase-scan procedure, can provide a feasible solution. To test this procedure, an object phase map was retrieved from a single-shot moiré image obtained from a plasma-produced x-ray source. A reference phase map was then obtained from phase-stepping measurements using a continuous x-ray tube source in a small laboratory setting. The two phase maps were used to retrieve an electron density map. A comparison of the moiré and phase-stepping phase-retrieval methods was performed to evaluate single-exposure plasma electron density mapping for high-energy density and other transient plasma experiments. It was found that a combination of phase-retrieval methods can deliver accurate refraction angle mapping. Once x-ray backlighter quality is optimized, the ex situ method is expected to deliver electron density mapping with improved resolution. The steps necessary for improved diagnostic performance are discussed.

Cosmic ray acceleration in magnetic circumstellar bubbles

NASA Astrophysics Data System (ADS)

Zirakashvili, V. N.; Ptuskin, V. S.

2018-03-01

We consider the diffusive shock acceleration in interstellar bubbles created by powerful stellar winds of supernova progenitors. Under the moderate stellar wind magnetization the bubbles are filled by the strongly magnetized low density gas. It is shown that the maximum energy of particles accelerated in this environment can exceed the "knee" energy in the observable cosmic ray spectrum.

Regenerative fuel cell study for satellites in GEO orbit

NASA Technical Reports Server (NTRS)

Vandine, Leslie; Gonzalez-Sanabria, Olga; Levy, Alexander

1987-01-01

The results of a 12 month study to identify high performance regenerative hydrogen-oxygen fuel cell concepts for geosynchronous satellite application are summarized. Emphasis was placed on concepts with the potential for high energy density and passive means for water and heat management to maximize system reliability. Both polymer membrane and alkaline electrolyte fuel cells were considered, with emphasis on the alkaline cell because of its high performance, advanced state of development, and proven ability to operate in a launch and space environment. Three alkaline system concepts were studied. Results indicate that using near term technology energy densities between 46 and 52 watt-hour/lb can be achieved at efficiencies of 55 percent. Using advanced light weight cell construction which was achieved in experimental cells, composite tankage material for the reactant gases and the reversible stack concept, system energy densities of 115 watt-hours/lb can be projected.

Highly transparent triboelectric nanogenerator for harvesting water-related energy reinforced by antireflection coating

NASA Astrophysics Data System (ADS)

Liang, Qijie; Yan, Xiaoqin; Gu, Yousong; Zhang, Kui; Liang, Mengyuan; Lu, Shengnan; Zheng, Xin; Zhang, Yue

2015-03-01

Water-related energy is an inexhaustible and renewable energy resource in our environment, which has huge amount of energy and is not largely dictated by daytime and sunlight. The transparent characteristic plays a key role in practical applications for some devices designed for harvesting water-related energy. In this paper, a highly transparent triboelectric nanogenerator (T-TENG) was designed to harvest the electrostatic energy from flowing water. The instantaneous output power density of the T-TENG is 11.56 mW/m2. Moreover, with the PTFE film acting as an antireflection coating, the maximum transmittance of the fabricated T-TENG is 87.4%, which is larger than that of individual glass substrate. The T-TENG can be integrated with silicon-based solar cell, building glass and car glass, which demonstrates its potential applications for harvesting waste water energy in our living environment and on smart home system and smart car system.

Highly transparent triboelectric nanogenerator for harvesting water-related energy reinforced by antireflection coating.

PubMed

Liang, Qijie; Yan, Xiaoqin; Gu, Yousong; Zhang, Kui; Liang, Mengyuan; Lu, Shengnan; Zheng, Xin; Zhang, Yue

2015-03-13

Water-related energy is an inexhaustible and renewable energy resource in our environment, which has huge amount of energy and is not largely dictated by daytime and sunlight. The transparent characteristic plays a key role in practical applications for some devices designed for harvesting water-related energy. In this paper, a highly transparent triboelectric nanogenerator (T-TENG) was designed to harvest the electrostatic energy from flowing water. The instantaneous output power density of the T-TENG is 11.56 mW/m(2). Moreover, with the PTFE film acting as an antireflection coating, the maximum transmittance of the fabricated T-TENG is 87.4%, which is larger than that of individual glass substrate. The T-TENG can be integrated with silicon-based solar cell, building glass and car glass, which demonstrates its potential applications for harvesting waste water energy in our living environment and on smart home system and smart car system.

Equilibrium nuclear ensembles taking into account vaporization of hot nuclei in dense stellar matter

NASA Astrophysics Data System (ADS)

Furusawa, Shun; Mishustin, Igor

2018-02-01

We investigate the high-temperature effect on the nuclear matter that consists of mixture of nucleons and all nuclei in the dense and hot stellar environment. The individual nuclei are described within the compressible-liquid-drop model that is based on Skyrme interactions for bulk energies and that takes into account modifications of the surface and Coulomb energies at finite temperatures and densities. The free-energy density is minimized with respect to the individual equilibrium densities of all heavy nuclei and the nuclear composition. We find that their optimized equilibrium densities become smaller and smaller at high temperatures because of the increase in thermal contributions to bulk free energies and the reduction of surface energies. The neutron-rich nuclei become unstable and disappear one after another at given temperatures. The calculations are performed for two sets of model parameters leading to different values of the slope parameter in the nuclear-symmetry energy. It is found that the larger slope parameter reduces the equilibrium densities and the melting temperatures. We also compare the proposed model with some other approaches and find that the mass fractions of heavy nuclei in the previous calculations that omit vaporization are underestimated at T ≲10 MeV and overestimated at T ≳10 MeV. The further sophistication of calculations of nuclear vaporization and of light clusters would be required to construct the equation of state for explosive astrophysical phenomena.

Influence of density and environmental factors on decomposition kinetics of amorphous polylactide - Reactive molecular dynamics studies.

PubMed

Mlyniec, A; Ekiert, M; Morawska-Chochol, A; Uhl, T

2016-06-01

In this work, we investigate the influence of the surrounding environment and the initial density on the decomposition kinetics of polylactide (PLA). The decomposition of the amorphous PLA was investigated by means of reactive molecular dynamics simulations. A computational model simulates the decomposition of PLA polymer inside the bulk, due to the assumed lack of removal of reaction products from the polymer matrix. We tracked the temperature dependency of the water and carbon monoxide production to extract the activation energy of thermal decomposition of PLA. We found that an increased density results in decreased activation energy of decomposition by about 50%. Moreover, initiation of decomposition of the amorphous PLA is followed by a rapid decline in activation energy caused by reaction products which accelerates the hydrolysis of esters. The addition of water molecules decreases initial energy of activation as well as accelerates the decomposition process. Additionally, we have investigated the dependency of density on external loading. Comparison of pressures needed to obtain assumed densities shows that this relationship is bilinear and the slope changes around a density equal to 1.3g/cm(3). The conducted analyses provide an insight into the thermal decomposition process of the amorphous phase of PLA, which is particularly susceptible to decomposition in amorphous and semi-crystalline PLA polymers. Copyright © 2016 Elsevier Inc. All rights reserved.

Thermodynamic properties of water in confined environments: a Monte Carlo study

NASA Astrophysics Data System (ADS)

Gladovic, Martin; Bren, Urban; Urbic, Tomaž

2018-05-01

Monte Carlo simulations of Mercedes-Benz water in a crowded environment were performed. The simulated systems are representative of both composite, porous or sintered materials and living cells with typical matrix packings. We studied the influence of overall temperature as well as the density and size of matrix particles on water density, particle distributions, hydrogen bond formation and thermodynamic quantities. Interestingly, temperature and space occupancy of matrix exhibit a similar effect on water properties following the competition between the kinetic and the potential energy of the system, whereby temperature increases the kinetic and matrix packing decreases the potential contribution. A novel thermodynamic decomposition approach was applied to gain insight into individual contributions of different types of inter-particle interactions. This decomposition proved to be useful and in good agreement with the total thermodynamic quantities especially at higher temperatures and matrix packings, where higher-order potential-energy mixing terms lose their importance.

Influence of Force Fields and Quantum Chemistry Approach on Spectral Densities of BChl a in Solution and in FMO Proteins

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

Chandrasekaran, Suryanarayanan; Aghtar, Mortaza; Valleau, Stéphanie

2015-08-06

Studies on light-harvesting (LH) systems have attracted much attention after the finding of long-lived quantum coherences in the exciton dynamics of the Fenna–Matthews–Olson (FMO) complex. In this complex, excitation energy transfer occurs between the bacteriochlorophyll a (BChl a) pigments. Two quantum mechanics/molecular mechanics (QM/MM) studies, each with a different force-field and quantum chemistry approach, reported different excitation energy distributions for the FMO complex. To understand the reasons for these differences in the predicted excitation energies, we have carried out a comparative study between the simulations using the CHARMM and AMBER force field and the Zerner intermediate neglect of differential orbitalmore » (ZINDO)/S and time-dependent density functional theory (TDDFT) quantum chemistry methods. The calculations using the CHARMM force field together with ZINDO/S or TDDFT always show a wider spread in the energy distribution compared to those using the AMBER force field. High- or low-energy tails in these energy distributions result in larger values for the spectral density at low frequencies. A detailed study on individual BChl a molecules in solution shows that without the environment, the density of states is the same for both force field sets. Including the environmental point charges, however, the excitation energy distribution gets broader and, depending on the applied methods, also asymmetric. The excitation energy distribution predicted using TDDFT together with the AMBER force field shows a symmetric, Gaussian-like distribution.« less

Precise energy eigenvalues of hydrogen-like ion moving in quantum plasmas

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

Dutta, S.; Saha, Jayanta K.; Mukherjee, T. K.

2015-06-15

The analytic form of the electrostatic potential felt by a slowly moving test charge in quantum plasma is developed. It has been shown that the electrostatic potential is composed of two parts: the Debye-Huckel screening term and the near-field wake potential. The latter depends on the velocity of the test charge as well as on the number density of the plasma electrons. Rayleigh-Ritz variational calculation has been done to estimate precise energy eigenvalues of hydrogen-like carbon ion under such plasma environment. A detailed analysis shows that the energy levels gradually move to the continuum with increasing plasma electron density whilemore » the level crossing phenomenon has been observed with the variation of ion velocity.« less

Density functional study of carbon vacancies in titanium carbide

NASA Astrophysics Data System (ADS)

Råsander, Mikael; Hugosson, Håkan W.; Delin, Anna

2018-01-01

It is well established that TiC contains carbon vacancies not only in carbon-deficient environments but also in carbon-rich environments. We have performed density functional calculations of the vacancy formation energy in TiC for C- as well as Ti-rich conditions using several different approximations to the exchange-correlation functional, and also carefully considering the nature and thermodynamics of the carbon reference state, as well as the effect of varying growth conditions. We find that the formation of carbon vacancies is clearly favorable under Ti-rich conditions, whereas it is slightly energetically unfavorable under C-rich conditions. Furthermore, we find that the relaxations of the atoms close to the vacancy site are rather long-ranged, and that these relaxations contribute significantly to the stabilization of the vacancy. Since carbon vacancies in TiC are also experimentally observed in carbon-rich environments, we conclude that kinetics may play an important role. This conclusion is consistent with the experimentally observed high activation energies and sluggish diffusion of vacancies in TiC, effectively causing a freezing in of the vacancies.

Communication: Biological applications of coupled-cluster frozen-density embedding

NASA Astrophysics Data System (ADS)

Heuser, Johannes; Höfener, Sebastian

2018-04-01

We report the implementation of the Laplace-transform scaled opposite-spin (LT-SOS) resolution-of-the-identity second-order approximate coupled-cluster singles and doubles (RICC2) combined with frozen-density embedding for excitation energies and molecular properties. In the present work, we furthermore employ the Hartree-Fock density for the interaction energy leading to a simplified Lagrangian which is linear in the Lagrangian multipliers. This approximation has the key advantage of a decoupling of the coupled-cluster amplitude and multipliers, leading also to a significant reduction in computation time. Using the new simplified Lagrangian in combination with efficient wavefunction models such as RICC2 or LT-SOS-RICC2 and density-functional theory (DFT) for the environment molecules (CC2-in-DFT) enables the efficient study of biological applications such as the rhodopsin and visual cone pigments using ab initio methods as routine applications.

Extending density functional embedding theory for covalently bonded systems.

PubMed

Yu, Kuang; Carter, Emily A

2017-12-19

Quantum embedding theory aims to provide an efficient solution to obtain accurate electronic energies for systems too large for full-scale, high-level quantum calculations. It adopts a hierarchical approach that divides the total system into a small embedded region and a larger environment, using different levels of theory to describe each part. Previously, we developed a density-based quantum embedding theory called density functional embedding theory (DFET), which achieved considerable success in metals and semiconductors. In this work, we extend DFET into a density-matrix-based nonlocal form, enabling DFET to study the stronger quantum couplings between covalently bonded subsystems. We name this theory density-matrix functional embedding theory (DMFET), and we demonstrate its performance in several test examples that resemble various real applications in both chemistry and biochemistry. DMFET gives excellent results in all cases tested thus far, including predicting isomerization energies, proton transfer energies, and highest occupied molecular orbital-lowest unoccupied molecular orbital gaps for local chromophores. Here, we show that DMFET systematically improves the quality of the results compared with the widely used state-of-the-art methods, such as the simple capped cluster model or the widely used ONIOM method.

Transportation Energy Futures Series. Effects of the Built Environment on Transportation. Energy Use, Greenhouse Gas Emissions, and Other Factors

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

Porter, C. D.; Brown, A.; Dunphy, R. T.

2013-03-15

Planning initiatives in many regions and communities aim to reduce transportation energy use, decrease emissions, and achieve related environmental benefits by changing land use. This report reviews and summarizes findings from existing literature on the relationship between the built environment and transportation energy use and greenhouse gas emissions, identifying results trends as well as potential future actions. The indirect influence of federal transportation and housing policies, as well as the direct impact of municipal regulation on land use are examined for their effect on transportation patterns and energy use. Special attention is given to the 'four D' factors of density,more » diversity, design and accessibility. The report concludes that policy-driven changes to the built environment could reduce transportation energy and GHG emissions from less than 1% to as much as 10% by 2050, the equivalent of 16%-18% of present-day urban light-duty-vehicle travel. This is one of a series of reports produced as a result of the Transportation Energy Futures (TEF) project, a Department of Energy-sponsored multi-agency project initiated to pinpoint underexplored strategies for abating GHGs and reducing petroleum dependence related to transportation.« less

Transportation Energy Futures Series: Effects of the Built Environment on Transportation: Energy Use, Greenhouse Gas Emissions, and Other Factors

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

Porter, C. D.; Brown, A.; Dunphy, R. T.

2013-03-01

Planning initiatives in many regions and communities aim to reduce transportation energy use, decrease emissions, and achieve related environmental benefits by changing land use. This report reviews and summarizes findings from existing literature on the relationship between the built environment and transportation energy use and greenhouse gas emissions, identifying results trends as well as potential future actions. The indirect influence of federal transportation and housing policies, as well as the direct impact of municipal regulation on land use are examined for their effect on transportation patterns and energy use. Special attention is given to the 'four D' factors of density,more » diversity, design and accessibility. The report concludes that policy-driven changes to the built environment could reduce transportation energy and GHG emissions from less than 1% to as much as 10% by 2050, the equivalent of 16%-18% of present-day urban light-duty-vehicle travel. This is one of a series of reports produced as a result of the Transportation Energy Futures (TEF) project, a Department of Energy-sponsored multi-agency project initiated to pinpoint underexplored strategies for abating GHGs and reducing petroleum dependence related to transportation.« less

Spin densities from subsystem density-functional theory: Assessment and application to a photosynthetic reaction center complex model

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

Solovyeva, Alisa; Technical University Braunschweig, Institute for Physical and Theoretical Chemistry, Hans-Sommer-Str. 10, 38106 Braunschweig; Pavanello, Michele

2012-05-21

Subsystem density-functional theory (DFT) is a powerful and efficient alternative to Kohn-Sham DFT for large systems composed of several weakly interacting subunits. Here, we provide a systematic investigation of the spin-density distributions obtained in subsystem DFT calculations for radicals in explicit environments. This includes a small radical in a solvent shell, a {pi}-stacked guanine-thymine radical cation, and a benchmark application to a model for the special pair radical cation, which is a dimer of bacteriochlorophyll pigments, from the photosynthetic reaction center of purple bacteria. We investigate the differences in the spin densities resulting from subsystem DFT and Kohn-Sham DFT calculations.more » In these comparisons, we focus on the problem of overdelocalization of spin densities due to the self-interaction error in DFT. It is demonstrated that subsystem DFT can reduce this problem, while it still allows to describe spin-polarization effects crossing the boundaries of the subsystems. In practical calculations of spin densities for radicals in a given environment, it may thus be a pragmatic alternative to Kohn-Sham DFT calculations. In our calculation on the special pair radical cation, we show that the coordinating histidine residues reduce the spin-density asymmetry between the two halves of this system, while inclusion of a larger binding pocket model increases this asymmetry. The unidirectional energy transfer in photosynthetic reaction centers is related to the asymmetry introduced by the protein environment.« less

Early Cretaceous terrestrial ecosystems in East Asia based on food-web and energy-flow models

USGS Publications Warehouse

Matsukawa, M.; Saiki, K.; Ito, M.; Obata, I.; Nichols, D.J.; Lockley, M.G.; Kukihara, R.; Shibata, K.

2006-01-01

In recent years, there has been global interest in the environments and ecosystems around the world. It is helpful to reconstruct past environments and ecosystems to help understand them in the present and the future. The present environments and ecosystems are an evolving continuum with those of the past and the future. This paper demonstrates the contribution of geology and paleontology to such continua. Using fossils, we can make an estimation of past population density as an ecosystem index based on food-web and energy-flow models. Late Mesozoic nonmarine deposits are distributed widely on the eastern Asian continent and contain various kinds of fossils such as fishes, amphibians, reptiles, dinosaurs, mammals, bivalves, gastropods, insects, ostracodes, conchostracans, terrestrial plants, and others. These fossil organisms are useful for late Mesozoic terrestrial ecosystem reconstruction using food-web and energy-flow models. We chose Early Cretaceous fluvio-lacustrine basins in the Choyr area, southeastern Mongolia, and the Tetori area, Japan, for these analyses and as a potential model for reconstruction of other similar basins in East Asia. The food-web models are restored based on taxa that occurred in these basins. They form four or five trophic levels in an energy pyramid consisting of rich primary producers at its base and smaller biotas higher in the food web. This is the general energy pyramid of a typical ecosystem. Concerning the population densities of vertebrate taxa in 1 km2 in these basins, some differences are recognized between Early Cretaceous and the present. For example, Cretaceous estimates suggest 2.3 to 4.8 times as many herbivores and 26.0 to 105.5 times the carnivore population. These differences are useful for the evaluation of past population densities of vertebrate taxa. Such differences may also be caused by the different metabolism of different taxa. Preservation may also be a factor, and we recognize that various problems occur in past ecosystem reconstructions. Counts of small numbers of confirmed species and estimates of maximum numbers of species present in the basin are used for the analysis and estimation of energy flow. This approach applies the methods of modern ecosystem analysis. ?? 2005 Elsevier Ltd. All rights reserved.

ON THE ORIGIN OF THE {gamma}-RAY/OPTICAL LAGS IN LUMINOUS BLAZARS

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

Janiak, Mateusz; Sikora, Marek; Moderski, Rafal

2012-12-01

Blazars are strongly variable sources that occasionally show spectacular flares visible in various energy bands. These flares are often, but not always, correlated. In a number of cases, the peaks of optical flares are found to be somewhat delayed with respect to the {gamma}-ray peaks. One notable example of such a delay was found in 3C 279 by Hayashida et al. and interpreted as a result of steeper drop with a distance of the energy density of an external radiation field than of the magnetic energy density. In this paper, we demonstrate that, in general, depending on the respective energymore » density profile along the jet, such lags can have both signs and that they can take place for any ratio of these energy densities. We study the dependence of such lags on the ratio of these energy densities at a distance of a maximal energy dissipation in a jet, on their gradients, as well as on the time profile of the relativistic electron injection within the moving source. We show how prominent such lags can be, and their expected timescales. We suggest that studies of such lags can provide a powerful tool to resolve the structure of relativistic jets and their radiative environment. As an example we model the lag observed in 3C 279, showing that in this object the flare is produced at a distance of a few parsecs from the central black hole, consistent with our previous inferences based on the spectra and optical polarization properties.« less

From instinct to intellect: the challenge of maintaining healthy weight in the modern world.

PubMed

Peters, J C; Wyatt, H R; Donahoo, W T; Hill, J O

2002-05-01

The global obesity epidemic is being driven in large part by a mismatch between our environment and our metabolism. Human physiology developed to function within an environment where high levels of physical activity were needed in daily life and food was inconsistently available. For most of mankind's history, physical activity has 'pulled' appetite so that the primary challenge to the physiological system for body weight control was to obtain sufficient energy intake to prevent negative energy balance and body energy loss. The current environment is characterized by a situation whereby minimal physical activity is required for daily life and food is abundant, inexpensive, high in energy density and widely available. Within this environment, food intake 'pushes' the system, and the challenge to the control system becomes to increase physical activity sufficiently to prevent positive energy balance. There does not appear to be a strong drive to increase physical activity in response to excess energy intake and there appears to be only a weak adaptive increase in resting energy expenditure in response to excess energy intake. In the modern world, the prevailing environment constitutes a constant background pressure that promotes weight gain. We propose that the modern environment has taken body weight control from an instinctual (unconscious) process to one that requires substantial cognitive effort. In the current environment, people who are not devoting substantial conscious effort to managing body weight are probably gaining weight. It is unlikely that we would be able to build the political will to undo our modern lifestyle, to change the environment back to one in which body weight control again becomes instinctual. In order to combat the growing epidemic we should focus our efforts on providing the knowledge, cognitive skills and incentives for controlling body weight and at the same time begin creating a supportive environment to allow better management of body weight.

Molecular structure and interactions in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

PubMed

Dhumal, Nilesh R; Noack, Kristina; Kiefer, Johannes; Kim, Hyung J

2014-04-03

Electronic structure theory (density functional and Møller-Plesset perturbation theory) and vibrational spectroscopy (FT-IR and Raman) are employed to study molecular interactions in the room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Different conformers of a cation-anion pair based on their molecular interactions are simulated in the gas phase and in a dielectric continuum solvent environment. Although the ordering of conformers in energy varies with theoretical methods, their predictions for three lowest energy conformers in the gas phase are similar. Strong C-H---N interactions between the acidic hydrogen atom of the cation imidazole ring and the nitrogen atom of the anion are predicted for either the lowest or second lowest energy conformer. In a continuum solvent, different theoretical methods yield the same ion-pair conformation for the lowest energy state. In both phases, the density functional method predicts that the anion is in a trans conformation in the lowest energy ion pair state. The theoretical results are compared with experimental observations from Raman scattering and IR absorption spectroscopies and manifestations of the molecular interactions in the vibrational spectra are discussed. The directions of the frequency shifts of the characteristic vibrations relative to the free anion and cation are explained by calculating the difference electron density coupled with electron density topography.

Beyond Point Charges: Dynamic Polarization from Neural Net Predicted Multipole Moments.

PubMed

Darley, Michael G; Handley, Chris M; Popelier, Paul L A

2008-09-09

Intramolecular polarization is the change to the electron density of a given atom upon variation in the positions of the neighboring atoms. We express the electron density in terms of multipole moments. Using glycine and N-methylacetamide (NMA) as pilot systems, we show that neural networks can capture the change in electron density due to polarization. After training, modestly sized neural networks successfully predict the atomic multipole moments from the nuclear positions of all atoms in the molecule. Accurate electrostatic energies between two atoms can be then obtained via a multipole expansion, inclusive of polarization effects. As a result polarization is successfully modeled at short-range and without an explicit polarizability tensor. This approach puts charge transfer and multipolar polarization on a common footing. The polarization procedure is formulated within the context of quantum chemical topology (QCT). Nonbonded atom-atom interactions in glycine cover an energy range of 948 kJ mol(-1), with an average energy difference between true and predicted energy of 0.2 kJ mol(-1), the largest difference being just under 1 kJ mol(-1). Very similar energy differences are found for NMA, which spans a range of 281 kJ mol(-1). The current proof-of-concept enables the construction of a new protein force field that incorporates electron density fragments that dynamically respond to their fluctuating environment.

Subsonic and Supersonic shear flows in laser driven high-energy-density plasmas

NASA Astrophysics Data System (ADS)

Harding, E. C.; Drake, R. P.; Gillespie, R. S.; Grosskopf, M. J.; Kuranz, C. C.; Visco, A.; Ditmar, J. R.; Aglitskiy, Y.; Weaver, J. L.; Velikovich, A. L.; Hurricane, O. A.; Hansen, J. F.; Remington, B. A.; Robey, H. F.; Bono, M. J.; Plewa, T.

2009-05-01

Shear flows arise in many high-energy-density (HED) and astrophysical systems, yet few laboratory experiments have been carried out to study their evolution in these extreme environments. Fundamentally, shear flows can initiate mixing via the Kelvin-Helmholtz (KH) instability and may eventually drive a transition to turbulence. We present two dedicated shear flow experiments that created subsonic and supersonic shear layers in HED plasmas. In the subsonic case the Omega laser was used to drive a shock wave along a rippled plastic interface, which subsequently rolled-upped into large KH vortices. In the supersonic shear experiment the Nike laser was used to drive Al plasma across a low-density foam surface also seeded with a ripple. Unlike the subsonic case, detached shocks developed around the ripples in response to the supersonic Al flow.

Recoverable Wire-Shaped Supercapacitors with Ultrahigh Volumetric Energy Density for Multifunctional Portable and Wearable Electronics.

PubMed

Shi, Minjie; Yang, Cheng; Song, Xuefeng; Liu, Jing; Zhao, Liping; Zhang, Peng; Gao, Lian

2017-05-24

Wire-shaped supercapacitors (SCs) based on shape memory materials are of considerable interest for next-generation portable and wearable electronics. However, the bottleneck in this field is how to develop the devices with excellent electrochemical performance while well-maintaining recoverability and flexibility. Herein, a unique asymmetric electrode concept is put forward to fabricate smart wire-shaped SCs with ultrahigh energy density, which is realized by using porous carbon dodecahedra coated on NiTi alloy wire and flexible graphene fiber as yarn electrodes. Notably, the wire-shaped SCs not only exhibit high flexibility that can be readily woven into real clothing but also represent the available recoverable ability. When irreversible plastic deformations happen, the deformed shape of the devices can automatically resume the initial predesigned shape in a warm environment (about 35 °C). More importantly, the wire-shaped SCs act as efficient energy storage devices, which display high volumetric energy density (8.9 mWh/cm 3 ), volumetric power density (1080 mW/cm 3 ), strong durability in multiple mechanical states, and steady electrochemical behavior after repeated shape recovery processes. Considering their relative facile fabrication technology and excellent electrochemical performance, this asymmetric electrode strategy produced smart wire-shaped supercapacitors desirable for multifunctional portable and wearable electronics.

EVOLUTION OF GALAXIES AND THEIR ENVIRONMENTS AT z = 0.1-3 IN COSMOS

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

Scoville, N.; Benson, A.; Fu, Hai

2013-05-01

Large-scale structures (LSSs) out to z < 3.0 are measured in the Cosmic Evolution Survey (COSMOS) using extremely accurate photometric redshifts (photoz). The K{sub s} -band-selected sample (from Ultra-Vista) is comprised of 155,954 galaxies. Two techniques-adaptive smoothing and Voronoi tessellation-are used to estimate the environmental densities within 127 redshift slices. Approximately 250 statistically significant overdense structures are identified out to z = 3.0 with shapes varying from elongated filamentary structures to more circularly symmetric concentrations. We also compare the densities derived for COSMOS with those based on semi-analytic predictions for a {Lambda}CDM simulation and find excellent overall agreement between themore » mean densities as a function of redshift and the range of densities. The galaxy properties (stellar mass, spectral energy distributions (SEDs), and star formation rates (SFRs)) are strongly correlated with environmental density and redshift, particularly at z < 1.0-1.2. Classifying the spectral type of each galaxy using the rest-frame b - i color (from the photoz SED fitting), we find a strong correlation of early-type galaxies (E-Sa) with high-density environments, while the degree of environmental segregation varies systematically with redshift out to z {approx} 1.3. In the highest density regions, 80% of the galaxies are early types at z = 0.2 compared to only 20% at z = 1.5. The SFRs and the star formation timescales exhibit clear environmental correlations. At z > 0.8, the SFR density is uniformly distributed over all environmental density percentiles, while at lower redshifts the dominant contribution is shifted to galaxies in lower density environments.« less

Influence of humidity on performance and microscopic dynamics of an ionic liquid in supercapacitor

NASA Astrophysics Data System (ADS)

Osti, Naresh C.; Dyatkin, Boris; Thompson, Matthew W.; Tiet, Felix; Zhang, Pengfei; Dai, Sheng; Tyagi, Madhusudan; Cummings, Peter T.; Gogotsi, Yury; Wesolowski, David J.; Mamontov, Eugene

2017-08-01

We investigated the influence of water molecules on the diffusion, dynamics, and electrosorption of a room temperature ionic liquid (RTIL), [BMI m+] [T f2N-] , confined in carbide-derived carbon with a bimodal nanoporosity. Water molecules in pores improved power densities and rate handling abilities of these materials in supercapacitor electrode configurations. We measured the water-dependent microscopic dynamics of the RTIL cations using quasielastic neutron scatting (QENS). The ionic liquid demonstrated greater mobility with increasing water uptake, facilitated by the nanoporous carbon environment, up to a well-defined saturation point. We concluded that water molecules displaced RTIL ions attached to the pore surfaces and improved the diffusivity of the displaced cations. This effect consequently increased capacitance and rate handling of the electrolyte in water-containing pores. Our findings suggest the possible effect of immiscible co-solvents on energy and power densities of energy storage devices, as well as the operating viability of nonaqueous supercapacitor electrolytes in humid environments.

Layer Splitting in a Complex Plasma

NASA Astrophysics Data System (ADS)

Smith, Bernard; Hyde, Truell; Matthews, Lorin; Johnson, Megan; Cook, Mike; Schmoke, Jimmy

2009-11-01

Dust particle clouds are found in most plasma processing environments and many astrophysical environments. Dust particles suspended within such plasmas often acquire an electric charge from collisions with free electrons in the plasma. Depending upon the ratio of interparticle potential energy to average kinetic energy, charged dust particles can form a gaseous, liquid or crystalline structure with short to longer range ordering. An interesting facet of complex plasma behavior is that particle layers appear to split as the DC bias is increased. This splitting of layers points to a phase transition differing from the normal phase transitions found in two-dimensional solids. In 1993, Dubin noted that as the charged particle density of an initially two-dimensional Coulomb crystal increases the system's layers split at specific charge densities. This work modeled ions in a Paul or Penning trap, but may be applicable to dusty plasma systems as well. This work will discuss this possibility along with splitting observed in the CASPER GEC rf Reference Cell at specific pressures and powers.

An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. I. Model and validation

NASA Astrophysics Data System (ADS)

Hegde, Ganesh; Povolotskyi, Michael; Kubis, Tillmann; Boykin, Timothy; Klimeck, Gerhard

2014-03-01

Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales.

Modeling and Numerical Simulation of Microwave Pulse Propagation in Air Breakdown Environment

NASA Technical Reports Server (NTRS)

Kuo, S. P.; Kim, J.

1991-01-01

Numerical simulation is used to investigate the extent of the electron density at a distant altitude location which can be generated by a high-power ground-transmitted microwave pulse. This is done by varying the power, width, shape, and carrier frequency of the pulse. The results show that once the breakdown threshold field is exceeded in the region below the desired altitude location, electron density starts to build up in that region through cascading breakdown. The generated plasma attenuates the pulse energy (tail erosion) and thus deteriorates the energy transmission to the destined altitude. The electron density saturates at a level limited by the pulse width and the tail erosion process. As the pulse continues to travel upward, though the breakdown threshold field of the background air decreases, the pulse energy (width) is reduced more severely by the tail erosion process. Thus, the electron density grows more quickly at the higher altitude, but saturates at a lower level. Consequently, the maximum electron density produced by a single pulse at 50 km altitude, for instance, is limited to a value below 10(exp 6) cm(exp -3). Three different approaches are examined to determine if the ionization at the destined location can be improved: a repetitive pulse approach, a focused pulse approach, and two intersecting beams. Only the intersecting beam approach is found to be practical for generating the desired density level.

A Miniaturized 0.78-mW/cm2 Autonomous Thermoelectric Energy-Harvesting Platform for Biomedical Sensors.

PubMed

Rozgic, Dejan; Markovic, Dejan

2017-08-01

In order to use thermoelectric energy harvesters (TEHs) as a truly autonomous energy source for size-limited sensing applications, it is essential to improve the power conversion efficiency and energy density. This study presents a thin-film, array-based TEH with a surface area of 0.83 cm 2 . The TEH autonomously supplies a power management IC fabricated in a 65-nm CMOS technology. The IC utilizes a single-inductor topology with integrated analog maximum power point tracking (MPPT), resulting in a 68% peak end-to-end efficiency (92% converter efficiency) and less than 20-ms MPPT. In an in-vivo test, a 645-μW regulated output power (effective 3.5 K of temperature gradient) was harvested from a rat implanted with our TEH, demonstrating true energy independence in a real environment while showing a 7.9 × improvement in regulated power density compared to the state-of-the-art. The system showed autonomous operation down to 65-mV TEH input.

Hybrid Power Management Program Evaluated Fuel Cell/Ultracapacitor Combinations and Developed Other New Applications

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.

2004-01-01

In fiscal year 2003, the continuation of the Hybrid Power Management (HPM) Program through NASA Glenn Research Center's Commercial Technology Office resulted in several new successful applications of this pioneering technology. HPM is the innovative integration of diverse, state-of-the-art power devices in an optimal configuration for space and terrestrial applications. The appropriate application and control of the various power devices significantly improves overall system performance and efficiency. The advanced power devices include ultracapacitors, fuel cells, and photovoltaics. HPM has extremely wide potential, with applications from nanowatts to megawatts--including power generation, transportation systems, biotechnology systems, and space power systems. HPM has the potential to significantly alleviate global energy concerns, improve the environment, and stimulate the economy. Fuel cells provide excellent efficiency and energy density, but do not have good power density. In contrast, ultracapacitors have excellent power density and virtually unlimited cycle life. To improve the power density of the fuel cell, the combination of fuel cells and ultracapacitors was evaluated.

Vacancy-induced initial decomposition of condensed phase NTO via bimolecular hydrogen transfer mechanisms at high pressure: a DFT-D study.

PubMed

Liu, Zhichao; Wu, Qiong; Zhu, Weihua; Xiao, Heming

2015-04-28

Density functional theory with dispersion-correction (DFT-D) was employed to study the effects of vacancy and pressure on the structure and initial decomposition of crystalline 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (β-NTO), a high-energy insensitive explosive. A comparative analysis of the chemical behaviors of NTO in the ideal bulk crystal and vacancy-containing crystals under applied hydrostatic compression was considered. Our calculated formation energy, vacancy interaction energy, electron density difference, and frontier orbitals reveal that the stability of NTO can be effectively manipulated by changing the molecular environment. Bimolecular hydrogen transfer is suggested to be a potential initial chemical reaction in the vacancy-containing NTO solid at 50 GPa, which is prior to the C-NO2 bond dissociation as its initiation decomposition in the gas phase. The vacancy defects introduced into the ideal bulk NTO crystal can produce a localized site, where the initiation decomposition is preferentially accelerated and then promotes further decompositions. Our results may shed some light on the influence of the molecular environments on the initial pathways in molecular explosives.

The development of a high sensitivity neutron displacement damage sensor

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

Tonigan, Andrew M.; Parma, Edward J.; Martin, William J.

Here, the capability to characterize the neutron energy spectrum and fluence received by a test object is crucial to under-standing the damage effects observed in electronic components. For nuclear research reactors and high energy density physics fa-cilities this can pose exceptional challenges, especially with low level neutron fluences. An ASTM test method for characterizing neutron environments utilizes the 2N2222A transistor as a 1-MeV equivalent neutron fluence sensor and is applicable for environ-ments with 1 x 10 12 - 1 x 10 14 1-MeV(Si)-Eqv.-n/cm 2. In this work we seek to extend the range of this test method to lower fluencemore » environments utilizing the 2N1486 transistor. Here, the 2N1486 is shown to be an effective neutron displacement damage sensor as low as 1 x 10 10 1-MeV(Si)-Eqv.-n/cm 2.« less

The development of a high sensitivity neutron displacement damage sensor

DOE PAGES

Tonigan, Andrew M.; Parma, Edward J.; Martin, William J.

2016-11-23

Here, the capability to characterize the neutron energy spectrum and fluence received by a test object is crucial to under-standing the damage effects observed in electronic components. For nuclear research reactors and high energy density physics fa-cilities this can pose exceptional challenges, especially with low level neutron fluences. An ASTM test method for characterizing neutron environments utilizes the 2N2222A transistor as a 1-MeV equivalent neutron fluence sensor and is applicable for environ-ments with 1 x 10 12 - 1 x 10 14 1-MeV(Si)-Eqv.-n/cm 2. In this work we seek to extend the range of this test method to lower fluencemore » environments utilizing the 2N1486 transistor. Here, the 2N1486 is shown to be an effective neutron displacement damage sensor as low as 1 x 10 10 1-MeV(Si)-Eqv.-n/cm 2.« less

Optimal atomic structure of amorphous silicon obtained from density functional theory calculations

NASA Astrophysics Data System (ADS)

Pedersen, Andreas; Pizzagalli, Laurent; Jónsson, Hannes

2017-06-01

Atomic structure of amorphous silicon consistent with several reported experimental measurements has been obtained from annealing simulations using electron density functional theory calculations and a systematic removal of weakly bound atoms. The excess energy and density with respect to the crystal are well reproduced in addition to radial distribution function, angular distribution functions, and vibrational density of states. No atom in the optimal configuration is locally in a crystalline environment as deduced by ring analysis and common neighbor analysis, but coordination defects are present at a level of 1%-2%. The simulated samples provide structural models of this archetypal disordered covalent material without preconceived notion of the atomic ordering or fitting to experimental data.

Improved continuum lowering calculations in screened hydrogenic model with l-splitting for high energy density systems

NASA Astrophysics Data System (ADS)

Ali, Amjad; Shabbir Naz, G.; Saleem Shahzad, M.; Kouser, R.; Aman-ur-Rehman; Nasim, M. H.

2018-03-01

The energy states of the bound electrons in high energy density systems (HEDS) are significantly affected due to the electric field of the neighboring ions. Due to this effect bound electrons require less energy to get themselves free and move into the continuum. This phenomenon of reduction in potential is termed as ionization potential depression (IPD) or the continuum lowering (CL). The foremost parameter to depict this change is the average charge state, therefore accurate modeling for CL is imperative in modeling atomic data for computation of radiative and thermodynamic properties of HEDS. In this paper, we present an improved model of CL in the screened hydrogenic model with l-splitting (SHML) proposed by G. Faussurier and C. Blancard, P. Renaudin [High Energy Density Physics 4 (2008) 114] and its effect on average charge state. We propose the level charge dependent calculation of CL potential energy and inclusion of exchange and correlation energy in SHML. By doing this, we made our model more relevant to HEDS and free from CL empirical parameter to the plasma environment. We have implemented both original and modified model of SHML in our code named OPASH and benchmark our results with experiments and other state-of-the-art simulation codes. We compared our results of average charge state for Carbon, Beryllium, Aluminum, Iron and Germanium against published literature and found a very reasonable agreement between them.

The Neighborhood Energy Balance Equation: Does Neighborhood Food Retail Environment + Physical Activity Environment = Obesity? The CARDIA Study

PubMed Central

Boone-Heinonen, Janne; Diez-Roux, Ana V.; Goff, David C.; Loria, Catherine M.; Kiefe, Catarina I.; Popkin, Barry M.; Gordon-Larsen, Penny

2013-01-01

Background Recent obesity prevention initiatives focus on healthy neighborhood design, but most research examines neighborhood food retail and physical activity (PA) environments in isolation. We estimated joint, interactive, and cumulative impacts of neighborhood food retail and PA environment characteristics on body mass index (BMI) throughout early adulthood. Methods and Findings We used cohort data from the Coronary Artery Risk Development in Young Adults (CARDIA) Study [n=4,092; Year 7 (24-42 years, 1992-1993) followed over 5 exams through Year 25 (2010-2011); 12,921 person-exam observations], with linked time-varying geographic information system-derived neighborhood environment measures. Using regression with fixed effects for individuals, we modeled time-lagged BMI as a function of food and PA resource density (counts per population) and neighborhood development intensity (a composite density score). We controlled for neighborhood poverty, individual-level sociodemographics, and BMI in the prior exam; and included significant interactions between neighborhood measures and by sex. Using model coefficients, we simulated BMI reductions in response to single and combined neighborhood improvements. Simulated increase in supermarket density (from 25th to 75th percentile) predicted inter-exam reduction in BMI of 0.09 kg/m2 [estimate (95% CI): -0.09 (-0.16, -0.02)]. Increasing commercial PA facility density predicted BMI reductions up to 0.22 kg/m2 in men, with variation across other neighborhood features [estimate (95% CI) range: -0.14 (-0.29, 0.01) to -0.22 (-0.37, -0.08)]. Simultaneous increases in supermarket and commercial PA facility density predicted inter-exam BMI reductions up to 0.31 kg/m2 in men [estimate (95% CI) range: -0.23 (-0.39, -0.06) to -0.31 (-0.47, -0.15)] but not women. Reduced fast food restaurant and convenience store density and increased public PA facility density and neighborhood development intensity did not predict reductions in BMI. Conclusions Findings suggest that improvements in neighborhood food retail or PA environments may accumulate to reduce BMI, but some neighborhood changes may be less beneficial to women. PMID:24386458

Dependence of mobility on shallow localized gap states in single-crystal organic field-effect-transistors

NASA Astrophysics Data System (ADS)

Butko, V. Y.; So, W.; Lang, D. V.; Chi, X.; Lashley, J. C.; Ramirez, A. P.

2009-12-01

In order to optimize the performance of molecular organic electronic devices it is important to study the intermolecular density of states and charge transport mechanisms in the environment of crystalline organic material. Using this approach in Field Effect Transistors (FETs) we show that material purification improves carrier mobility and decreases density of the deep localized electronic state. We also report a general exponential energy dependence of the density of localized states in a vicinity of the mobility edge (Fermi energies up to ∼7 times higher than the thermal energy (kT)) in a variety of the extensively purified molecular organic crystal FETs. This observation and the low activation energy of the order of ∼kT suggest that molecular structural misplacements of the sizes that are comparable with thermal molecular modes rather than impurity deep traps play a role in formation of these shallow states. We find that the charge carrier mobility in the FET nanochannels, μeff, is parameterized by two factors, the free-carrier mobility, μ0, and the ratio of the free carrier density to the total carrier density induced by gate bias. Crystalline FETs fabricated from rubrene, pentacene, and tetracene have a high free-carrier mobility, μ0∼50 cm2/Vs, at 300 K with lower device μeff dominated by localized shallow gap states. This relationship suggests that further improvements in electronic performance could be possible with enhanced device quality.

SAFT VES180 SA High Specific Energy Cell Qualification

NASA Astrophysics Data System (ADS)

Borthomieu, Y.; Semerie, J.-P.

2005-05-01

A « high specific energy Li-Ion cell» is under development in the frame of the Artes 8 (Alphabus) programme. The purpose of this cell is to reduce the battery weight for the Alphabus satellite by at least 50 kg. The objective is to increase the specific energy by more than 25 % compared to the existing 140 Wh cell. The specific energy target for the 180Wh is 170 Wh/kg.In addition to improving the energy density, this development aimed to introduce a design improvement of the cell, in order to sustain higher mechanical environments than the state of the art cells.

Theoretical Investigations of Transition Metal Surface Energies under Lattice Strain and CO Environment

DOE PAGES

Tang, Michael T.; Ulissi, Zachary W.; Chan, Karen

2018-05-30

Here, an understanding of the relative stability of surface facets is crucial to develop predictive models of catalyst activity and to fabricate catalysts with a controlled morphology. In this work, we present a systematic density functional theory study of the effect of lattice strain and CO environment on the surface formation energies of Cu, Pt, and Ni. First, we show that both compressive and tensile lattice strains favor the formation of stepped versus low-index terraces such as (111) and (100). Then, we investigate the effect of the CO environment using configurations of CO at various coverages, determined using a greedy,more » systematic approach, inspired by forward stepwise feature selection. We find that the CO environment favors stepped facets on Ni, Cu, and Pt. These trends are illustrated with the corresponding equilibrium Wulff shapes at various strains and CO pressures. In general, the surface energies of the studied transition metals are highly sensitive to strain and CO coverage, which should be considered when rationalizing trends in the catalytic activity.« less

Theoretical Investigations of Transition Metal Surface Energies under Lattice Strain and CO Environment

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

Tang, Michael T.; Ulissi, Zachary W.; Chan, Karen

Here, an understanding of the relative stability of surface facets is crucial to develop predictive models of catalyst activity and to fabricate catalysts with a controlled morphology. In this work, we present a systematic density functional theory study of the effect of lattice strain and CO environment on the surface formation energies of Cu, Pt, and Ni. First, we show that both compressive and tensile lattice strains favor the formation of stepped versus low-index terraces such as (111) and (100). Then, we investigate the effect of the CO environment using configurations of CO at various coverages, determined using a greedy,more » systematic approach, inspired by forward stepwise feature selection. We find that the CO environment favors stepped facets on Ni, Cu, and Pt. These trends are illustrated with the corresponding equilibrium Wulff shapes at various strains and CO pressures. In general, the surface energies of the studied transition metals are highly sensitive to strain and CO coverage, which should be considered when rationalizing trends in the catalytic activity.« less

Hydrodynamic and material properties experiments using pulsed power techniques

NASA Astrophysics Data System (ADS)

Reinovsky, R. E.; Trainor, R. J.

2000-04-01

Within the last five years, a new approach to the exploration of dynamic material properties and advanced hydrodynamics at extreme conditions has joined the traditional techniques of high velocity guns and explosives. This new application uses electromagnetic energy to accelerate solid density material to produce shocks in a cylindrical target. The principal tool for producing high energy density environments is the high precision, magnetically imploded, near-solid density cylindrical liner. The most attractive pulsed power system for driving such experiments is an ultrahigh current, low impedance, microsecond time scale source that is economical both to build and to operate. Two families of pulsed power systems can be applied to drive such experiments. The 25-MJ Atlas capacitor bank system currently under construction at Los Alamos is the first system of its scale specifically designed to drive high precision solid liners. Delivering 30 MA, Atlas will provide liner velocities 12-15 km/sec and kinetic energies of 1-2 MJ/cm with extensive diagnostics and excellent reproducibility. Explosive flux compressor technology provides access to currents exceeding 100 MA producing liner velocities above 25 km/sec and kinetic energies of 5-20 MJ/cm in single shot operations

Precision Crystal Calorimeters in High Energy Physics

ScienceCinema

Ren-Yuan Zhu

2017-12-09

Precision crystal calorimeters traditionally play an important role in high energy physics experiments. In the last two decades, it faces a challenge to maintain its precision in a hostile radiation environment. This paper reviews the performance of crystal calorimeters constructed for high energy physics experiments and the progress achieved in understanding crystal’s radiation damage as well as in developing high quality scintillating crystals for particle physics. Potential applications of new generation scintillating crystals of high density and high light yield, such as LSO and LYSO, in particle physics experiments is also discussed.

Chromophore-Dependent Intramolecular Exciton-Vibrational Coupling in the FMO Complex: Quantification and Importance for Exciton Dynamics.

PubMed

Padula, Daniele; Lee, Myeong H; Claridge, Kirsten; Troisi, Alessandro

2017-11-02

In this paper, we adopt an approach suitable for monitoring the time evolution of the intramolecular contribution to the spectral density of a set of identical chromophores embedded in their respective environments. We apply the proposed method to the Fenna-Matthews-Olson (FMO) complex, with the objective to quantify the differences among site-dependent spectral densities and the impact of such differences on the exciton dynamics of the system. Our approach takes advantage of the vertical gradient approximation to reduce the computational demands of the normal modes analysis. We show that the region of the spectral density that is believed to strongly influence the exciton dynamics changes significantly in the timescale of tens of nanoseconds. We then studied the impact of the intramolecular vibrations on the exciton dynamics by considering a model of FMO in a vibronic basis and neglecting the interaction with the environment to isolate the role of the intramolecular exciton-vibration coupling. In agreement with the assumptions in the literature, we demonstrate that high frequency modes at energy much larger than the excitonic energy splitting have negligible influence on exciton dynamics despite the large exciton-vibration coupling. We also find that the impact of including the site-dependent spectral densities on exciton dynamics is not very significant, indicating that it may be acceptable to apply the same spectral density on all sites. However, care needs to be taken for the description of the exciton-vibrational coupling in the low frequency part of intramolecular modes because exciton dynamics is more susceptible to low frequency modes despite their small Huang-Rhys factors.

Development of Improved Radiation Drive Environment for High Foot Implosions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hinkel, D. E.; Berzak Hopkins, L. F.; Ma, T.; Ralph, J. E.; Albert, F.; Benedetti, L. R.; Celliers, P. M.; Döppner, T.; Goyon, C. S.; Izumi, N.; Jarrott, L. C.; Khan, S. F.; Kline, J. L.; Kritcher, A. L.; Kyrala, G. A.; Nagel, S. R.; Pak, A. E.; Patel, P.; Rosen, M. D.; Rygg, J. R.; Schneider, M. B.; Turnbull, D. P.; Yeamans, C. B.; Callahan, D. A.; Hurricane, O. A.

2016-11-01

Analyses of high foot implosions show that performance is limited by the radiation drive environment, i.e., the hohlraum. Reported here are significant improvements in the radiation environment, which result in an enhancement in implosion performance. Using a longer, larger case-to-capsule ratio hohlraum at lower gas fill density improves the symmetry control of a high foot implosion. Moreover, for the first time, these hohlraums produce reduced levels of hot electrons, generated by laser-plasma interactions, which are at levels comparable to near-vacuum hohlraums, and well within specifications. Further, there is a noteworthy increase in laser energy coupling to the hohlraum, and discrepancies with simulated radiation production are markedly reduced. At fixed laser energy, high foot implosions driven with this improved hohlraum have achieved a 1.4 ×increase in stagnation pressure, with an accompanying relative increase in fusion yield of 50% as compared to a reference experiment with the same laser energy.

Development of Improved Radiation Drive Environment for High Foot Implosions at the National Ignition Facility.

PubMed

Hinkel, D E; Berzak Hopkins, L F; Ma, T; Ralph, J E; Albert, F; Benedetti, L R; Celliers, P M; Döppner, T; Goyon, C S; Izumi, N; Jarrott, L C; Khan, S F; Kline, J L; Kritcher, A L; Kyrala, G A; Nagel, S R; Pak, A E; Patel, P; Rosen, M D; Rygg, J R; Schneider, M B; Turnbull, D P; Yeamans, C B; Callahan, D A; Hurricane, O A

2016-11-25

Analyses of high foot implosions show that performance is limited by the radiation drive environment, i.e., the hohlraum. Reported here are significant improvements in the radiation environment, which result in an enhancement in implosion performance. Using a longer, larger case-to-capsule ratio hohlraum at lower gas fill density improves the symmetry control of a high foot implosion. Moreover, for the first time, these hohlraums produce reduced levels of hot electrons, generated by laser-plasma interactions, which are at levels comparable to near-vacuum hohlraums, and well within specifications. Further, there is a noteworthy increase in laser energy coupling to the hohlraum, and discrepancies with simulated radiation production are markedly reduced. At fixed laser energy, high foot implosions driven with this improved hohlraum have achieved a 1.4×increase in stagnation pressure, with an accompanying relative increase in fusion yield of 50% as compared to a reference experiment with the same laser energy.

The Plasma Environment at Enceladus and Europa Compared

NASA Astrophysics Data System (ADS)

Rymer, Abigail; Persoon, Ann; Morooka, Michiko; Heuer, Steven; Westlake, Joseph H.

2017-10-01

The plasma environment near Enceladus is complex, as revealed during 16 encounters of the Cassini spacecraft. The well documented Enceladus plumes create a dusty, asymmetric exosphere in which electrons can attach to small ice particles - forming anions, and negatively charged nanograins and dust - to the extent that cations can be the lightest charged particles present and, as a result, the dominant current carriers. Several instruments on the Cassini spacecraft are able to measure this environment in both expected and unexpected ways. Cassini Plasma Spectrometer (CAPS) is designed and calibrated to measure the thermal plasma ions and electrons and also measures the energy/charge of charged nanograins when present. Cassini Radio Plasma Wave Sensor (RPWS) measures electron density as derived from the ‘upper hybrid frequency’ which is a function of the total free electron density and magnetic field strength and provides a vital ground truth measurement for Cassini calibration when the density is sufficiently high for it to be well measured. Cassini Langmuir Probe (LP) measures the electron density and temperature via direct current measurement, and both CAPS and LP can provide estimates for the spacecraft potential which we compare. The plasma environment near Europa is similarly complex and, although not so comprehensively equipped and hampered by the non-deployment of its high gain antenna, the Galileo spacecraft made similar measurements during 9 Europa flybys and recent observations have suggested that, like Enceladus, Europa might have active plume activity. We present a detailed comparison of data from the Cassini and Galileo sensors in order to assess the plasma environment observed by the different instruments, discuss what is consistent and otherwise, and the implications for the plasma environment at Enceladus and Europa in the context of work to date as well as implications for future studies.

Global scenarios of urban density and its impacts on building energy use through 2050.

PubMed

Güneralp, Burak; Zhou, Yuyu; Ürge-Vorsatz, Diana; Gupta, Mukesh; Yu, Sha; Patel, Pralit L; Fragkias, Michail; Li, Xiaoma; Seto, Karen C

2017-08-22

Although the scale of impending urbanization is well-acknowledged, we have a limited understanding of how urban forms will change and what their impact will be on building energy use. Using both top-down and bottom-up approaches and scenarios, we examine building energy use for heating and cooling. Globally, the energy use for heating and cooling by the middle of the century will be between 45 and 59 exajoules per year (corresponding to an increase of 7-40% since 2010). Most of this variability is due to the uncertainty in future urban densities of rapidly growing cities in Asia and particularly China. Dense urban development leads to less urban energy use overall. Waiting to retrofit the existing built environment until markets are ready in about 5 years to widely deploy the most advanced renovation technologies leads to more savings in building energy use. Potential for savings in energy use is greatest in China when coupled with efficiency gains. Advanced efficiency makes the least difference compared with the business-as-usual scenario in South Asia and Sub-Saharan Africa but significantly contributes to energy savings in North America and Europe. Systemic efforts that focus on both urban form, of which urban density is an indicator, and energy-efficient technologies, but that also account for potential co-benefits and trade-offs with human well-being can contribute to both local and global sustainability. Particularly in growing cities in the developing world, such efforts can improve the well-being of billions of urban residents and contribute to mitigating climate change by reducing energy use in urban areas.

Flexible and Self-Healing Aqueous Supercapacitors for Low Temperature Applications: Polyampholyte Gel Electrolytes with Biochar Electrodes.

PubMed

Li, Xinda; Liu, Li; Wang, Xianzong; Ok, Yong Sik; Elliott, Janet A W; Chang, Scott X; Chung, Hyun-Joong

2017-05-10

A flexible and self-healing supercapacitor with high energy density in low temperature operation was fabricated using a combination of biochar-based composite electrodes and a polyampholyte hydrogel electrolyte. Polyampholytes, a novel class of tough hydrogel, provide self-healing ability and mechanical flexibility, as well as low temperature operation for the aqueous electrolyte. Biochar is a carbon material produced from the low-temperature pyrolysis of biological wastes; the incorporation of reduced graphene oxide conferred mechanical integrity and electrical conductivity and hence the electrodes are called biochar-reduced-graphene-oxide (BC-RGO) electrodes. The fabricated supercapacitor showed high energy density of 30 Wh/kg with ~90% capacitance retention after 5000 charge-discharge cycles at room temperature at a power density of 50 W/kg. At -30 °C, the supercapacitor exhibited an energy density of 10.5 Wh/kg at a power density of 500 W/kg. The mechanism of the low-temperature performance excellence is likely to be associated with the concept of non-freezable water near the hydrophilic polymer chains, which can motivate future researches on the phase behaviour of water near polyampholyte chains. We conclude that the combination of the BC-RGO electrode and the polyampholyte hydrogel electrolyte is promising for supercapacitors for flexible electronics and for low temperature environments.

Electronic and thermodynamic properties of α-Pu2O3

NASA Astrophysics Data System (ADS)

Lu, Yong; Yang, Yu; Zheng, Fawei; Zhang, Ping

2014-08-01

Based on density functional theory+U calculations and the quasi-annealing simulation method, we obtain the ground electronic state for α-Pu2O3 and present its phonon dispersion curves as well as various thermodynamic properties, which have seldom been theoretically studied because of the huge unit cell. We find that the Pu-O chemical bonding is weaker in α-Pu2O3 than in fluorite PuO2, and subsequently a frequency gap appears between oxygen and plutonium vibration density of states. Based on the calculated Helmholtz free energies at different temperatures, we further study the reaction energies for Pu oxidation, PuO2 reduction, and transformation between PuO2 and α-Pu2O3. Our reaction energy results are in agreements with available experiment. And it is revealed that high temperature and insufficient oxygen environment are in favor of the formation of α-Pu2O3.

Absorption of solar radiation by alkali vapors. [for efficient high temperature energy converters

NASA Technical Reports Server (NTRS)

Mattick, A. T.

1978-01-01

A theoretical study of the direct absorption of solar radiation by the working fluid of high temperature, high efficiency energy converters has been carried out. Alkali vapors and potassium vapor in particular were found to be very effective solar absorbers and suitable thermodynamically for practical high temperature cycles. Energy loss via reradiation from a solar boiler was shown to reduce the overall efficiency of radiation-heated energy converters, although a simple model of radiation transfer in a potassium vapor solar boiler revealed that self-trapping of the reradiation may reduce this loss considerably. A study was also made of the requirements for a radiation boiler window. It was found that for sapphire, one of the best solar transmitting materials, the severe environment in conjunction with high radiation densities will require some form of window protection. An aerodynamic shield is particularly advantageous in this capacity, separating the window from the absorbing vapor to prevent condensation and window corrosion and to reduce the radiation density at the window.

Chemical-to-Electricity Carbon: Water Device.

PubMed

He, Sisi; Zhang, Yueyu; Qiu, Longbin; Zhang, Longsheng; Xie, Yun; Pan, Jian; Chen, Peining; Wang, Bingjie; Xu, Xiaojie; Hu, Yajie; Dinh, Cao Thang; De Luna, Phil; Banis, Mohammad Norouzi; Wang, Zhiqiang; Sham, Tsun-Kong; Gong, Xingao; Zhang, Bo; Peng, Huisheng; Sargent, Edward H

2018-05-01

The ability to release, as electrical energy, potential energy stored at the water:carbon interface is attractive, since water is abundant and available. However, many previous reports of such energy converters rely on either flowing water or specially designed ionic aqueous solutions. These requirements restrict practical application, particularly in environments with quiescent water. Here, a carbon-based chemical-to-electricity device that transfers the chemical energy to electrical form when coming into contact with quiescent deionized water is reported. The device is built using carbon nanotube yarns, oxygen content of which is modulated using oxygen plasma-treatment. When immersed in water, the device discharges electricity with a power density that exceeds 700 mW m -2 , one order of magnitude higher than the best previously published result. X-ray absorption and density functional theory studies support a mechanism of operation that relies on the polarization of sp 2 hybridized carbon atoms. The devices are incorporated into a flexible fabric for powering personal electronic devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An LDPC Decoder Architecture for Wireless Sensor Network Applications

PubMed Central

Giancarlo Biroli, Andrea Dario; Martina, Maurizio; Masera, Guido

2012-01-01

The pervasive use of wireless sensors in a growing spectrum of human activities reinforces the need for devices with low energy dissipation. In this work, coded communication between a couple of wireless sensor devices is considered as a method to reduce the dissipated energy per transmitted bit with respect to uncoded communication. Different Low Density Parity Check (LDPC) codes are considered to this purpose and post layout results are shown for a low-area low-energy decoder, which offers percentage energy savings with respect to the uncoded solution in the range of 40%–80%, depending on considered environment, distance and bit error rate. PMID:22438724

An LDPC decoder architecture for wireless sensor network applications.

PubMed

Biroli, Andrea Dario Giancarlo; Martina, Maurizio; Masera, Guido

2012-01-01

The pervasive use of wireless sensors in a growing spectrum of human activities reinforces the need for devices with low energy dissipation. In this work, coded communication between a couple of wireless sensor devices is considered as a method to reduce the dissipated energy per transmitted bit with respect to uncoded communication. Different Low Density Parity Check (LDPC) codes are considered to this purpose and post layout results are shown for a low-area low-energy decoder, which offers percentage energy savings with respect to the uncoded solution in the range of 40%-80%, depending on considered environment, distance and bit error rate.

Sandia National Laboratories: Research: R&D 100 Awards

Science.gov Websites

high radiation environments such as space. Watch the video. control system for active damping of inter first commercially available, high-voltage, high-frequency, high-current, high-temperature, single-chip Materials Science Nanodevices & Microsystems Radiation Effects & High Energy Density Science

Landscape-scale distribution and density of raptor populations wintering in anthropogenic-dominated desert landscapes

Treesearch

Adam E. Duerr; Tricia A. Miller; Kerri L. Cornell Duerr; Michael J. Lanzone; Amy Fesnock; Todd E. Katzner

2015-01-01

Anthropogenic development has great potential to affect fragile desert environments. Large-scale development of renewable energy infrastructure is planned for many desert ecosystems. Development plans should account for anthropogenic effects to distributions and abundance of rare or sensitive wildlife; however, baseline data on abundance and distribution of such...

Strongly-Perturbed Non-Equilibrium Gas Physics Model for the Paraxial Diode Transport Cell

DTIC Science & Technology

2003-06-01

species and energy flow is critical to the plasma chemistry . The new model’s slight underestimate of the electron density may be a consequence of the...beam physics and plasma chemistry allows the modeling of intense charged-particle beam transport environments such as the paraxial diode gas cell

Simulations of Rayleigh Taylor Instabilities in the presence of a Strong Radiative shock

NASA Astrophysics Data System (ADS)

Trantham, Matthew; Kuranz, Carolyn; Shvarts, Dov; Drake, R. P.

2016-10-01

Recent Supernova Rayleigh Taylor experiments on the National Ignition Facility (NIF) are relevant to the evolution of core-collapse supernovae in which red supergiant stars explode. Here we report simulations of these experiments using the CRASH code. The CRASH code, developed at the University of Michigan to design and analyze high-energy-density experiments, is an Eulerian code with block-adaptive mesh refinement, multigroup diffusive radiation transport, and electron heat conduction. We explore two cases, one in which the shock is strongly radiative, and another with negligible radiation. The experiments in all cases produced structures at embedded interfaces by the Rayleigh Taylor instability. The weaker shocked environment is cooler and the instability grows classically. The strongly radiative shock produces a warm environment near the instability, ablates the interface, and alters the growth. We compare the simulated results with the experimental data and attempt to explain the differences. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, Grant Number DE-NA0002956.

Landscape characteristics of Rhizophora mangle forests and propagule deposition in coastal environments of Florida (USA)

USGS Publications Warehouse

Sengupta, R.; Middleton, B.; Yan, C.; Zuro, M.; Hartman, H.

2005-01-01

Field dispersal studies are seldom conducted at regional scales even though reliable information on mid-range dispersal distance is essential for models of colonization. The purpose of this study was to examine the potential distance of dispersal of Rhizophora mangle propagules by comparing deposition density with landscape characteristics of mangrove forests. Propagule density was estimated at various distances to mangrove sources (R. mangle) on beaches in southwestern Florida in both high-and low-energy environments, either facing open gulf waters vs. sheltered, respectively. Remote sensing and Geographic Information Systems were used to identify source forests and to determine their landscape characteristics (forest size and distance to deposition area) for the regression analyses. Our results indicated that increasing density of propagules stranded on beaches was related negatively to the distance of the deposition sites from the nearest stands of R. mangle and that deposition was greatly diminished 2 km or more from the source. Measures of fragmentation such as the area of the R. mangle forests were related to propagule deposition but only in low-energy environments. Our results suggest that geographic models involving the colonization of coastal mangrove systems should include dispersal dynamics at mid-range scales, i.e., for our purposes here, beyond the local scale of the forest and up to 5 km distant. Studies of mangrove propagule deposition at various spatial scales are key to understanding regeneration limitations in natural gaps and restoration areas. Therefore, our study of mid-range propagule dispersal has broad application to plant ecology, restoration, and modeling. ?? Springer 2005.

A lithium–oxygen battery with a long cycle life in an air-like atmosphere

NASA Astrophysics Data System (ADS)

Asadi, Mohammad; Sayahpour, Baharak; Abbasi, Pedram; Ngo, Anh T.; Karis, Klas; Jokisaari, Jacob R.; Liu, Cong; Narayanan, Badri; Gerard, Marc; Yasaei, Poya; Hu, Xuan; Mukherjee, Arijita; Lau, Kah Chun; Assary, Rajeev S.; Khalili-Araghi, Fatemeh; Klie, Robert F.; Curtiss, Larry A.; Salehi-Khojin, Amin

2018-03-01

Lithium–air batteries are considered to be a potential alternative to lithium-ion batteries for transportation applications, owing to their high theoretical specific energy. So far, however, such systems have been largely restricted to pure oxygen environments (lithium–oxygen batteries) and have a limited cycle life owing to side reactions involving the cathode, anode and electrolyte. In the presence of nitrogen, carbon dioxide and water vapour, these side reactions can become even more complex. Moreover, because of the need to store oxygen, the volumetric energy densities of lithium–oxygen systems may be too small for practical applications. Here we report a system comprising a lithium carbonate-based protected anode, a molybdenum disulfide cathode and an ionic liquid/dimethyl sulfoxide electrolyte that operates as a lithium–air battery in a simulated air atmosphere with a long cycle life of up to 700 cycles. We perform computational studies to provide insight into the operation of the system in this environment. This demonstration of a lithium–oxygen battery with a long cycle life in an air-like atmosphere is an important step towards the development of this field beyond lithium-ion technology, with a possibility to obtain much higher specific energy densities than for conventional lithium-ion batteries.

A lithium-oxygen battery with a long cycle life in an air-like atmosphere.

PubMed

Asadi, Mohammad; Sayahpour, Baharak; Abbasi, Pedram; Ngo, Anh T; Karis, Klas; Jokisaari, Jacob R; Liu, Cong; Narayanan, Badri; Gerard, Marc; Yasaei, Poya; Hu, Xuan; Mukherjee, Arijita; Lau, Kah Chun; Assary, Rajeev S; Khalili-Araghi, Fatemeh; Klie, Robert F; Curtiss, Larry A; Salehi-Khojin, Amin

2018-03-21

Lithium-air batteries are considered to be a potential alternative to lithium-ion batteries for transportation applications, owing to their high theoretical specific energy. So far, however, such systems have been largely restricted to pure oxygen environments (lithium-oxygen batteries) and have a limited cycle life owing to side reactions involving the cathode, anode and electrolyte. In the presence of nitrogen, carbon dioxide and water vapour, these side reactions can become even more complex. Moreover, because of the need to store oxygen, the volumetric energy densities of lithium-oxygen systems may be too small for practical applications. Here we report a system comprising a lithium carbonate-based protected anode, a molybdenum disulfide cathode and an ionic liquid/dimethyl sulfoxide electrolyte that operates as a lithium-air battery in a simulated air atmosphere with a long cycle life of up to 700 cycles. We perform computational studies to provide insight into the operation of the system in this environment. This demonstration of a lithium-oxygen battery with a long cycle life in an air-like atmosphere is an important step towards the development of this field beyond lithium-ion technology, with a possibility to obtain much higher specific energy densities than for conventional lithium-ion batteries.

Development of biologically modified anodes for energy harvesting using microbial fuel cells

NASA Astrophysics Data System (ADS)

Sumner, James J.; Ganguli, Rahul; Chmelka, Brad

2012-06-01

Biological fuel cells hold promise as an alternative energy source to batteries for unattended ground sensor applications due to the fact that they can be extremely long lived. This lifetime can be extended over batteries by scavenging fuel from the deployed environment. Microbial fuel cells (MFC) are one class of such sources that produce usable energy from small organic compounds (i.e. sugars, alcohols, organic acids, and biopolymers) which can be easily containerized or scavenged from the environment. The use of microorganisms as the anodic catalysts is what makes these systems unique from other biofuel cell designs. One of the main drawbacks of engineering a sensor system powered by an MFC is that power densities and current flux are extremely low in currently reported systems. The power density is limited by the mass transfer of the fuel source to the catalyst, the metabolism of the microbial catalysts and the electron transfer from the organism to the anode. This presentation will focus on the development of a new style of microbially-modified anodes which will increase power density to a level where a practical power source can be engineered. This is being achieved by developing a three dimensional matrix as an artificial, conductive biofilm. These artificial biofilms will allow the capture of a consortium of microbes designed for efficient metabolism of the available fuel source. Also it will keep the microbes close to the electrode allowing ready access by fuel and providing a low resistance passage of the liberated electrons from fuel oxidation.

Search for thermal X-ray features from the Crab nebula with the Hitomi soft X-ray spectrometer

NASA Astrophysics Data System (ADS)

Hitomi Collaboration; Aharonian, Felix; Akamatsu, Hiroki; Akimoto, Fumie; Allen, Steven W.; Angelini, Lorella; Audard, Marc; Awaki, Hisamitsu; Axelsson, Magnus; Bamba, Aya; Bautz, Marshall W.; Blandford, Roger; Brenneman, Laura W.; Brown, Gregory V.; Bulbul, Esra; Cackett, Edward M.; Chernyakova, Maria; Chiao, Meng P.; Coppi, Paolo S.; Costantini, Elisa; de Plaa, Jelle; de Vries, Cor P.; den Herder, Jan-Willem; Done, Chris; Dotani, Tadayasu; Ebisawa, Ken; Eckart, Megan E.; Enoto, Teruaki; Ezoe, Yuichiro; Fabian, Andrew C.; Ferrigno, Carlo; Foster, Adam R.; Fujimoto, Ryuichi; Fukazawa, Yasushi; Furuzawa, Akihiro; Galeazzi, Massimiliano; Gallo, Luigi C.; Gandhi, Poshak; Giustini, Margherita; Goldwurm, Andrea; Gu, Liyi; Guainazzi, Matteo; Haba, Yoshito; Hagino, Kouichi; Hamaguchi, Kenji; Harrus, Ilana M.; Hatsukade, Isamu; Hayashi, Katsuhiro; Hayashi, Takayuki; Hayashida, Kiyoshi; Hiraga, Junko S.; Hornschemeier, Ann; Hoshino, Akio; Hughes, John P.; Ichinohe, Yuto; Iizuka, Ryo; Inoue, Hajime; Inoue, Yoshiyuki; Ishida, Manabu; Ishikawa, Kumi; Ishisaki, Yoshitaka; Kaastra, Jelle; Kallman, Tim; Kamae, Tsuneyoshi; Kataoka, Jun; Katsuda, Satoru; Kawai, Nobuyuki; Kelley, Richard L.; Kilbourne, Caroline A.; Kitaguchi, Takao; Kitamoto, Shunji; Kitayama, Tetsu; Kohmura, Takayoshi; Kokubun, Motohide; Koyama, Katsuji; Koyama, Shu; Kretschmar, Peter; Krimm, Hans A.; Kubota, Aya; Kunieda, Hideyo; Laurent, Philippe; Lee, Shiu-Hang; Leutenegger, Maurice A.; Limousin, Olivier; Loewenstein, Michael; Long, Knox S.; Lumb, David; Madejski, Greg; Maeda, Yoshitomo; Maier, Daniel; Makishima, Kazuo; Markevitch, Maxim; Matsumoto, Hironori; Matsushita, Kyoko; McCammon, Dan; McNamara, Brian R.; Mehdipour, Missagh; Miller, Eric D.; Miller, Jon M.; Mineshige, Shin; Mitsuda, Kazuhisa; Mitsuishi, Ikuyuki; Miyazawa, Takuya; Mizuno, Tsunefumi; Mori, Hideyuki; Mori, Koji; Mukai, Koji; Murakami, Hiroshi; Mushotzky, Richard F.; Nakagawa, Takao; Nakajima, Hiroshi; Nakamori, Takeshi; Nakashima, Shinya; Nakazawa, Kazuhiro; Nobukawa, Kumiko K.; Nobukawa, Masayoshi; Noda, Hirofumi; Odaka, Hirokazu; Ohashi, Takaya; Ohno, Masanori; Okajima, Takashi; Ota, Naomi; Ozaki, Masanobu; Paerels, Frits; Paltani, Stéphane; Petre, Robert; Pinto, Ciro; Porter, Frederick S.; Pottschmidt, Katja; Reynolds, Christopher S.; Safi-Harb, Samar; Saito, Shinya; Sakai, Kazuhiro; Sasaki, Toru; Sato, Goro; Sato, Kosuke; Sato, Rie; Sato, Toshiki; Sawada, Makoto; Schartel, Norbert; Serlemtsos, Peter J.; Seta, Hiromi; Shidatsu, Megumi; Simionescu, Aurora; Smith, Randall K.; Soong, Yang; Stawarz, Łukasz; Sugawara, Yasuharu; Sugita, Satoshi; Szymkowiak, Andrew; Tajima, Hiroyasu; Takahashi, Hiromitsu; Takahashi, Tadayuki; Takeda, Shin'ichiro; Takei, Yoh; Tamagawa, Toru; Tamura, Takayuki; Tanaka, Takaaki; Tanaka, Yasuo; Tanaka, Yasuyuki T.; Tashiro, Makoto S.; Tawara, Yuzuru; Terada, Yukikatsu; Terashima, Yuichi; Tombesi, Francesco; Tomida, Hiroshi; Tsuboi, Yohko; Tsujimoto, Masahiro; Tsunemi, Hiroshi; Tsuru, Takeshi Go; Uchida, Hiroyuki; Uchiyama, Hideki; Uchiyama, Yasunobu; Ueda, Shutaro; Ueda, Yoshihiro; Uno, Shin'ichiro; Urry, C. Megan; Ursino, Eugenio; Watanabe, Shin; Werner, Norbert; Wilkins, Dan R.; Williams, Brian J.; Yamada, Shinya; Yamaguchi, Hiroya; Yamaoka, Kazutaka; Yamasaki, Noriko Y.; Yamauchi, Makoto; Yamauchi, Shigeo; Yaqoob, Tahir; Yatsu, Yoichi; Yonetoku, Daisuke; Zhuravleva, Irina; Zoghbi, Abderahmen; Tominaga, Nozomu; Moriya, Takashi J.

2018-03-01

The Crab nebula originated from a core-collapse supernova (SN) explosion observed in 1054 AD. When viewed as a supernova remnant (SNR), it has an anomalously low observed ejecta mass and kinetic energy for an Fe-core-collapse SN. Intensive searches have been made for a massive shell that solves this discrepancy, but none has been detected. An alternative idea is that SN 1054 is an electron-capture (EC) explosion with a lower explosion energy by an order of magnitude than Fe-core-collapse SNe. X-ray imaging searches were performed for the plasma emission from the shell in the Crab outskirts to set a stringent upper limit on the X-ray emitting mass. However, the extreme brightness of the source hampers access to its vicinity. We thus employed spectroscopic technique using the X-ray micro-calorimeter on board the Hitomi satellite. By exploiting its superb energy resolution, we set an upper limit for emission or absorption features from as yet undetected thermal plasma in the 2-12 keV range. We also re-evaluated the existing Chandra and XMM-Newton data. By assembling these results, a new upper limit was obtained for the X-ray plasma mass of ≲ 1 M⊙ for a wide range of assumed shell radius, size, and plasma temperature values both in and out of collisional equilibrium. To compare with the observation, we further performed hydrodynamic simulations of the Crab SNR for two SN models (Fe-core versus EC) under two SN environments (uniform interstellar medium versus progenitor wind). We found that the observed mass limit can be compatible with both SN models if the SN environment has a low density of ≲ 0.03 cm-3 (Fe core) or ≲ 0.1 cm-3 (EC) for the uniform density, or a progenitor wind density somewhat less than that provided by a mass loss rate of 10-5 M⊙ yr-1 at 20 km s-1 for the wind environment.

Bioinspired fractal electrodes for solar energy storages.

PubMed

Thekkekara, Litty V; Gu, Min

2017-03-31

Solar energy storage is an emerging technology which can promote the solar energy as the primary source of electricity. Recent development of laser scribed graphene electrodes exhibiting a high electrical conductivity have enabled a green technology platform for supercapacitor-based energy storage, resulting in cost-effective, environment-friendly features, and consequent readiness for on-chip integration. Due to the limitation of the ion-accessible active porous surface area, the energy densities of these supercapacitors are restricted below ~3 × 10 -3  Whcm -3 . In this paper, we demonstrate a new design of biomimetic laser scribed graphene electrodes for solar energy storage, which embraces the structure of Fern leaves characterized by the geometric family of space filling curves of fractals. This new conceptual design removes the limit of the conventional planar supercapacitors by significantly increasing the ratio of active surface area to volume of the new electrodes and reducing the electrolyte ionic path. The attained energy density is thus significantly increased to ~10 -1  Whcm -3 - more than 30 times higher than that achievable by the planar electrodes with ~95% coulombic efficiency of the solar energy storage. The energy storages with these novel electrodes open the prospects of efficient self-powered and solar-powered wearable, flexible and portable applications.

Bioinspired fractal electrodes for solar energy storages

PubMed Central

Thekkekara, Litty V.; Gu, Min

2017-01-01

Solar energy storage is an emerging technology which can promote the solar energy as the primary source of electricity. Recent development of laser scribed graphene electrodes exhibiting a high electrical conductivity have enabled a green technology platform for supercapacitor-based energy storage, resulting in cost-effective, environment-friendly features, and consequent readiness for on-chip integration. Due to the limitation of the ion-accessible active porous surface area, the energy densities of these supercapacitors are restricted below ~3 × 10−3 Whcm−3. In this paper, we demonstrate a new design of biomimetic laser scribed graphene electrodes for solar energy storage, which embraces the structure of Fern leaves characterized by the geometric family of space filling curves of fractals. This new conceptual design removes the limit of the conventional planar supercapacitors by significantly increasing the ratio of active surface area to volume of the new electrodes and reducing the electrolyte ionic path. The attained energy density is thus significantly increased to ~10−1 Whcm−3- more than 30 times higher than that achievable by the planar electrodes with ~95% coulombic efficiency of the solar energy storage. The energy storages with these novel electrodes open the prospects of efficient self-powered and solar-powered wearable, flexible and portable applications. PMID:28361924

Electronic structure and partial charge distribution of Doxorubicin in different molecular environments.

PubMed

Poudel, Lokendra; Wen, Amy M; French, Roger H; Parsegian, V Adrian; Podgornik, Rudolf; Steinmetz, Nicole F; Ching, Wai-Yim

2015-05-18

The electronic structure and partial charge of doxorubicin (DOX) in three different molecular environments-isolated, solvated, and intercalated in a DNA complex-are studied by first-principles density functional methods. It is shown that the addition of solvating water molecules to DOX, together with the proximity to and interaction with DNA, has a significant impact on the electronic structure as well as on the partial charge distribution. Significant improvement in estimating the DOX-DNA interaction energy is achieved. The results are further elucidated by resolving the total density of states and surface charge density into different functional groups. It is concluded that the presence of the solvent and the details of the interaction geometry matter greatly in determining the stability of DOX complexation. Ab initio calculations on realistic models are an important step toward a more accurate description of the long-range interactions in biomolecular systems. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Onshore-offshore wind energy resource evaluation based on synergetic use of multiple satellite data and meteorological stations in Jiangsu Province, China

NASA Astrophysics Data System (ADS)

Wei, Xianglin; Duan, Yuewei; Liu, Yongxue; Jin, Song; Sun, Chao

2018-05-01

The demand for efficient and cost-effective renewable energy is increasing as traditional sources of energy such as oil, coal, and natural gas, can no longer satisfy growing global energy demands. Among renewable energies, wind energy is the most prominent due to its low, manageable impacts on the local environment. Based on meteorological data from 2006 to 2014 and multi-source satellite data (i.e., Advanced Scatterometer, Quick Scatterometer, and Windsat) from 1999 to 2015, an assessment of the onshore and offshore wind energy potential in Jiangsu Province was performed by calculating the average wind speed, average wind direction, wind power density, and annual energy production (AEP). Results show that Jiangsu has abundant wind energy resources, which increase from inland to coastal areas. In onshore areas, wind power density is predominantly less than 200 W/m2, while in offshore areas, wind power density is concentrates in the range of 328-500 W/m2. Onshore areas comprise more than 13,573.24 km2, mainly located in eastern coastal regions with good wind farm potential. The total wind power capacity in onshore areas could be as much as 2.06 x 105 GWh. Meanwhile, offshore wind power generation in Jiangsu Province is calculated to reach 2 x 106 GWh, which is approximately four times the electricity demand of the entire Jiangsu Province. This study validates the effective application of Advanced Scatterometer, Quick Scatterometer, and Windsat data to coastal wind energy monitoring in Jiangsu. Moreover, the methodology used in this study can be effectively applied to other similar coastal zones.

Global scenarios of urban density and its impacts on building energy use through 2050

PubMed Central

Güneralp, Burak; Zhou, Yuyu; Ürge-Vorsatz, Diana; Gupta, Mukesh; Yu, Sha; Patel, Pralit L.; Fragkias, Michail; Li, Xiaoma; Seto, Karen C.

2017-01-01

Although the scale of impending urbanization is well-acknowledged, we have a limited understanding of how urban forms will change and what their impact will be on building energy use. Using both top-down and bottom-up approaches and scenarios, we examine building energy use for heating and cooling. Globally, the energy use for heating and cooling by the middle of the century will be between 45 and 59 exajoules per year (corresponding to an increase of 7–40% since 2010). Most of this variability is due to the uncertainty in future urban densities of rapidly growing cities in Asia and particularly China. Dense urban development leads to less urban energy use overall. Waiting to retrofit the existing built environment until markets are ready in about 5 years to widely deploy the most advanced renovation technologies leads to more savings in building energy use. Potential for savings in energy use is greatest in China when coupled with efficiency gains. Advanced efficiency makes the least difference compared with the business-as-usual scenario in South Asia and Sub-Saharan Africa but significantly contributes to energy savings in North America and Europe. Systemic efforts that focus on both urban form, of which urban density is an indicator, and energy-efficient technologies, but that also account for potential co-benefits and trade-offs with human well-being can contribute to both local and global sustainability. Particularly in growing cities in the developing world, such efforts can improve the well-being of billions of urban residents and contribute to mitigating climate change by reducing energy use in urban areas. PMID:28069957

Cosmic distribution of highly ionized metals and their physical conditions in the EAGLE simulations

NASA Astrophysics Data System (ADS)

Rahmati, Alireza; Schaye, Joop; Crain, Robert A.; Oppenheimer, Benjamin D.; Schaller, Matthieu; Theuns, Tom

2016-06-01

We study the distribution and evolution of highly ionized intergalactic metals in the Evolution and Assembly of Galaxies and their Environment (EAGLE) cosmological, hydrodynamical simulations. EAGLE has been shown to reproduce a wide range of galaxy properties while its subgrid feedback was calibrated without considering gas properties. We compare the predictions for the column density distribution functions (CDDFs) and cosmic densities of Si IV, C IV, N V, O VI and Ne VIII absorbers with observations at redshift z = 0 to ˜6 and find reasonable agreement, although there are some differences. We show that the typical physical densities of the absorbing gas increase with column density and redshift, but decrease with the ionization energy of the absorbing ion. The typical metallicity increases with both column density and time. The fraction of collisionally ionized metal absorbers increases with time and ionization energy. While our results show little sensitivity to the presence or absence of AGN feedback, increasing/decreasing the efficiency of stellar feedback by a factor of 2 substantially decreases/increases the CDDFs and the cosmic densities of the metal ions. We show that the impact of the efficiency of stellar feedback on the CDDFs and cosmic densities is largely due to its effect on the metal production rate. However, the temperatures of the metal absorbers, particularly those of strong O VI, are directly sensitive to the strength of the feedback.

Thermodynamic and Kinetic Properties of Intrinsic Defects and Mg Transmutants in 3C-SiC Determined by Density Functional Theory

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

Hu, Shenyang Y.; Setyawan, Wahyu; Van Ginhoven, Renee M.

2014-02-20

Density functional theory (DFT) is used to calculate the thermodynamic and kinetic properties of transmutant Mg in 3C-SiC due to high-energy neutron irradiation associated with the fusion nuclear environment. The formation and binding energies of intrinsic defects, Mg-related defects, and clusters in 3C-SiC are systematically calculated. The minimum energy paths and activation energies during point defect migration and small cluster evolution are studied using a generalized solid-state elastic band (G-SSNEB) method with DFT energy calculations. Stable defect structures and possible defect migration mechanisms are identified. The evolution of binding energies during Mg2Si formation demonstrates that the formation of Mg2Si needsmore » to overcome a critical nucleus size and nucleation barrier. It is also found that a compressive stress field exists around the Mg2Si nucleus. These data are important inputs in meso- and macro-scale modeling and experiments to understand and predict the impact of Mg on phase stability, microstructure evolution, and performance of SiC and SiC-based materials during long-term neutron exposures.« less

Post occupancy evaluation of energy-efficient behavior in informal housing of high density area

NASA Astrophysics Data System (ADS)

Aulia, D. N.; Marpaung, B. O. Y.

2018-02-01

The concept of energy-efficient building emphasizes the critical of efficiency in the use of water, electrical energy, and building materials, beginning with design, construction, to the maintenance of the building in the future. This study was conducted to observe the behavior of Energy Saving of the residents in performing everyday activities in the building. The observed variables are the consumption of natural resources (energy, material, water, and land) and the emissions of air, water, and land related to the environment and health. This research is a descriptive qualitative research with the method of data collection is the distribution of questionnaires and observation. The method of analyzing data is posted occupancy evaluation undertaken to obtain patterns of community-based behavior in urban areas. The informal high-density housing area is a typology of population settlements that found in many big cities in Indonesia. This community represents various community groups regarding occupation, education, income, and race. The results of the study concluded that there are five components of energy-saving behavioral formers in housing namely: residential building components, environmental components in occupancy, external occupancy components, components of social activities and elements of business

Biomolecular Force Field Parameterization via Atoms-in-Molecule Electron Density Partitioning.

PubMed

Cole, Daniel J; Vilseck, Jonah Z; Tirado-Rives, Julian; Payne, Mike C; Jorgensen, William L

2016-05-10

Molecular mechanics force fields, which are commonly used in biomolecular modeling and computer-aided drug design, typically treat nonbonded interactions using a limited library of empirical parameters that are developed for small molecules. This approach does not account for polarization in larger molecules or proteins, and the parametrization process is labor-intensive. Using linear-scaling density functional theory and atoms-in-molecule electron density partitioning, environment-specific charges and Lennard-Jones parameters are derived directly from quantum mechanical calculations for use in biomolecular modeling of organic and biomolecular systems. The proposed methods significantly reduce the number of empirical parameters needed to construct molecular mechanics force fields, naturally include polarization effects in charge and Lennard-Jones parameters, and scale well to systems comprised of thousands of atoms, including proteins. The feasibility and benefits of this approach are demonstrated by computing free energies of hydration, properties of pure liquids, and the relative binding free energies of indole and benzofuran to the L99A mutant of T4 lysozyme.

Rotating assembly working group summary

NASA Technical Reports Server (NTRS)

Kulkarni, S. V.

1984-01-01

The feasibility of a fail safe flywheel system was demonstrated. Three of the major advantages of flywheel systems are: longer operational life, higher electrical efficiency, and higher system energy density. The use of composite material flywheels is important to realize these advantages. Rotor design and dynamics, rotor materials and fabrication, safety, nondestructive testing, and systems operation loads and environment, are outlined.

Meteoroid Environment Modeling: the Meteoroid Engineering Model and Shower Forecasting

NASA Technical Reports Server (NTRS)

Moorhead, Althea V.

2017-01-01

The meteoroid environment is often divided conceptually into meteor showers plus a sporadic background component. The sporadic complex poses the bulk of the risk to spacecraft, but showers can produce significant short-term enhancements of the meteoroid flux. The Meteoroid Environment Office (MEO) has produced two environment models to handle these cases: the Meteoroid Engineering Model (MEM) and an annual meteor shower forecast. Both MEM and the forecast are used by multiple manned spaceflight projects in their meteoroid risk evaluation, and both tools are being revised to incorporate recent meteor velocity, density, and timing measurements. MEM describes the sporadic meteoroid complex and calculates the flux, speed, and directionality of the meteoroid environment relative to a user-supplied spacecraft trajectory, taking the spacecraft's motion into account. MEM is valid in the inner solar system and offers near-Earth and cis-lunar environments. While the current version of MEM offers a nominal meteoroid environment corresponding to a single meteoroid bulk density, the next version of MEMR3 will offer both flux uncertainties and a density distribution in addition to a revised near-Earth environment. We have updated the near-Earth meteor speed distribution and have made the first determination of uncertainty in this distribution. We have also derived a meteor density distribution from the work of Kikwaya et al. (2011). The annual meteor shower forecast takes the form of a report and data tables that can be used in conjunction with an existing MEM assessment. Fluxes are typically quoted to a constant limiting kinetic energy in order to comport with commonly used ballistic limit equations. For the 2017 annual forecast, the MEO substantially revised the list of showers and their characteristics using 14 years of meteor flux measurements from the Canadian Meteor Orbit Radar (CMOR). Defunct or insignificant showers were removed and the temporal profiles of many showers were improved. In 2016 the MEO also adapted the forecast to the cislunar environment for the first time. We plan to make additional improvements to the model in the next two years using optical meteor flux measurements and mass indices.

Characterizing Turbulent Events at a Tidal Energy Site from Acoustic Doppler Velocity Observations

NASA Astrophysics Data System (ADS)

McCaffrey, Katherine; Fox-Kemper, Baylor; Hamlington, Peter

2013-11-01

As interest in marine renewable energy increases, observations are crucial to understanding the environments encountered by energy conversion devices. Data obtained from an acoustic Doppler current profiler and an acoustic Doppler velocimeter at two locations in the Puget Sound, WA are used to perform a detailed analysis of the turbulent environment that is expected to be present at a turbine placed in a tidal strait. Metrics such as turbulence intensity, structure functions, probability density functions, intermittency, coherent turbulence kinetic energy, anisotropy invariants, and linear combinations of eigenvalues are used to characterize the turbulence. The results indicate that coherent turbulence kinetic energy and turbulence intensity can be used to identify and parameterize different turbulent events in the flow. An analysis of the anisotropy characteristics leads to a physical description of turbulent events (defined using both turbulence intensity and coherent turbulent kinetic energy) as being dominated by one component of the Reynolds stresses. During non-turbulent events, the flow is dominated by two Reynolds stress components. The importance of these results for the development of realistic models of energy conversion devices is outlined. Cooperative Institute for Research in Environmental Sciences, Department of Atmospheric and Oceanic Sciences.

Reduction of the ionization energy for 1s-electrons in dense aluminum plasmas

NASA Astrophysics Data System (ADS)

Lin, C.; Reinholz, H.; Röpke, G.

2017-02-01

The properties of a bound multi-electron system immersed in a plasma environment are strongly modified by the surrounding plasma. In particular, the modification of the ionization energy is described by the electronic self-energy within the framework of the quantum statistical theory. We present the energy shift of the eigenstates and the lowering of the continuum edge of free electrons in a plasma. The reduction of the ionization potential is determined by their difference. This ionization potential depression for the 1s-levels in dense aluminum plasmas is calculated. Comparisons with other theories and the experimental data are shown for aluminum plasma at solid density 2.7 g/cm3.

A Microscopic Interpretation of Pump-Probe Vibrational Spectroscopy Using Ab Initio Molecular Dynamics.

PubMed

Lesnicki, Dominika; Sulpizi, Marialore

2018-06-13

What happens when extra vibrational energy is added to water? Using nonequilibrium molecular dynamics simulations, also including the full electronic structure, and novel descriptors, based on projected vibrational density of states, we are able to follow the flow of excess vibrational energy from the excited stretching and bending modes. We find that the energy relaxation, mostly mediated by a stretching-stretching coupling in the first solvation shell, is highly heterogeneous and strongly depends on the local environment, where a strong hydrogen bond network can transport energy with a time scale of 200 fs, whereas a weaker network can slow down the transport by a factor 2-3.

A Gaussian Approximation Potential for Silicon

NASA Astrophysics Data System (ADS)

Bernstein, Noam; Bartók, Albert; Kermode, James; Csányi, Gábor

We present an interatomic potential for silicon using the Gaussian Approximation Potential (GAP) approach, which uses the Gaussian process regression method to approximate the reference potential energy surface as a sum of atomic energies. Each atomic energy is approximated as a function of the local environment around the atom, which is described with the smooth overlap of atomic environments (SOAP) descriptor. The potential is fit to a database of energies, forces, and stresses calculated using density functional theory (DFT) on a wide range of configurations from zero and finite temperature simulations. These include crystalline phases, liquid, amorphous, and low coordination structures, and diamond-structure point defects, dislocations, surfaces, and cracks. We compare the results of the potential to DFT calculations, as well as to previously published models including Stillinger-Weber, Tersoff, modified embedded atom method (MEAM), and ReaxFF. We show that it is very accurate as compared to the DFT reference results for a wide range of properties, including low energy bulk phases, liquid structure, as well as point, line, and plane defects in the diamond structure.

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

Dufresne, Eric M.; Dunford, Robert W.; Kanter, Elliot P.

The performance of a cooled Be compound refractive lens (CRL) has been tested at the Advanced Photon Source (APS) to enable vertical focusing of the pink beam and permit the X-ray beam to spatially overlap with an 80 µm-high low-density plasma that simulates astrophysical environments. Focusing the fundamental harmonics of an insertion device white beam increases the APS power density; here, a power density as high as 500 W mm –2 was calculated. A CRL is chromatic so it does not efficiently focus X-rays whose energies are above the fundamental. Only the fundamental of the undulator focuses at the experiment.more » A two-chopper system reduces the power density on the imaging system and lens by four orders of magnitude, enabling imaging of the focal plane without any X-ray filter. As a result, a method to measure such high power density as well as the performance of the lens in focusing the pink beam is reported.« less

Coarse-grained models using local-density potentials optimized with the relative entropy: Application to implicit solvation

NASA Astrophysics Data System (ADS)

Sanyal, Tanmoy; Shell, M. Scott

2016-07-01

Bottom-up multiscale techniques are frequently used to develop coarse-grained (CG) models for simulations at extended length and time scales but are often limited by a compromise between computational efficiency and accuracy. The conventional approach to CG nonbonded interactions uses pair potentials which, while computationally efficient, can neglect the inherently multibody contributions of the local environment of a site to its energy, due to degrees of freedom that were coarse-grained out. This effect often causes the CG potential to depend strongly on the overall system density, composition, or other properties, which limits its transferability to states other than the one at which it was parameterized. Here, we propose to incorporate multibody effects into CG potentials through additional nonbonded terms, beyond pair interactions, that depend in a mean-field manner on local densities of different atomic species. This approach is analogous to embedded atom and bond-order models that seek to capture multibody electronic effects in metallic systems. We show that the relative entropy coarse-graining framework offers a systematic route to parameterizing such local density potentials. We then characterize this approach in the development of implicit solvation strategies for interactions between model hydrophobes in an aqueous environment.

Achieving DFT accuracy with a machine-learning interatomic potential: Thermomechanics and defects in bcc ferromagnetic iron

NASA Astrophysics Data System (ADS)

Dragoni, Daniele; Daff, Thomas D.; Csányi, Gábor; Marzari, Nicola

2018-01-01

We show that the Gaussian Approximation Potential (GAP) machine-learning framework can describe complex magnetic potential energy surfaces, taking ferromagnetic iron as a paradigmatic challenging case. The training database includes total energies, forces, and stresses obtained from density-functional theory in the generalized-gradient approximation, and comprises approximately 150,000 local atomic environments, ranging from pristine and defected bulk configurations to surfaces and generalized stacking faults with different crystallographic orientations. We find the structural, vibrational, and thermodynamic properties of the GAP model to be in excellent agreement with those obtained directly from first-principles electronic-structure calculations. There is good transferability to quantities, such as Peierls energy barriers, which are determined to a large extent by atomic configurations that were not part of the training set. We observe the benefit and the need of using highly converged electronic-structure calculations to sample a target potential energy surface. The end result is a systematically improvable potential that can achieve the same accuracy of density-functional theory calculations, but at a fraction of the computational cost.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

PubMed Central

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-01-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10–40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage. PMID:24145684

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors.

PubMed

Oakes, Landon; Westover, Andrew; Mares, Jeremy W; Chatterjee, Shahana; Erwin, William R; Bardhan, Rizia; Weiss, Sharon M; Pint, Cary L

2013-10-22

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10-40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Oakes, Landon; Westover, Andrew; Mares, Jeremy W.; Chatterjee, Shahana; Erwin, William R.; Bardhan, Rizia; Weiss, Sharon M.; Pint, Cary L.

2013-10-01

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10-40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

Electron-impact vibrational relaxation in high-temperature nitrogen

NASA Technical Reports Server (NTRS)

Lee, Jong-Hun

1992-01-01

Vibrational relaxation process of N2 molecules by electron-impact is examined for the future planetary entry environments. Multiple-quantum transitions from excited states to higher/lower states are considered for the electronic ground state of the nitrogen molecule N2 (X 1Sigma-g(+)). Vibrational excitation and deexcitation rate coefficients obtained by computational quantum chemistry are incorporated into the 'diffusion model' to evaluate the time variations of vibrational number densities of each energy state and total vibrational energy. Results show a non-Boltzmann distribution of number densities at the earlier stage of relaxation, which in turn suppresses the equilibrium process but affects little the time variation of total vibrational energy. An approximate rate equation and a corresponding relaxation time from the excited states, compatible with the system of flow conservation equations, are derived. The relaxation time from the excited states indicates the weak dependency of the initial vibrational temperature. The empirical curve-fit formula for the improved e-V relaxation time is obtained.

Electrochemical treatment of tannery effluent using a battery integrated DC-DC converter and solar PV power supply--an approach towards environment and energy management.

PubMed

Iyappan, K; Basha, C Ahmed; Saravanathamizhan, R; Vedaraman, N; Tahiyah Nou Shene, C A; Begum, S Nathira

2014-01-01

Electrochemical oxidation of tannery effluent was carried out in batch, batch recirculation and continuous reactor configurations under different conditions using a battery-integrated DC-DC converter and solar PV power supply. The effect of current density, electrolysis time and fluid flow rate on chemical oxygen demand (COD) removal and energy consumption has been evaluated. The results of batch reactor show that a COD reduction of 80.85% to 96.67% could be obtained. The results showed that after 7 h of operation at a current density of 2.5 A dm(-2) and flow rate of 100 L h(-1) in batch recirculation reactor, the removal of COD is 82.14% and the specific energy consumption was found to be 5.871 kWh (kg COD)(-1) for tannery effluent. In addition, the performance of single pass flow reactors (single and multiple reactors) system of various configurations are analyzed.

Piezoelectric-nanowire-enabled power source for driving wireless microelectronics.

PubMed

Xu, Sheng; Hansen, Benjamin J; Wang, Zhong Lin

2010-10-19

Harvesting energy from irregular/random mechanical actions in variable and uncontrollable environments is an effective approach for powering wireless mobile electronics to meet a wide range of applications in our daily life. Piezoelectric nanowires are robust and can be stimulated by tiny physical motions/disturbances over a range of frequencies. Here, we demonstrate the first chemical epitaxial growth of PbZr(x)Ti(1-x)O(3) (PZT) nanowire arrays at 230 °C and their application as high-output energy converters. The nanogenerators fabricated using a single array of PZT nanowires produce a peak output voltage of ~0.7 V, current density of 4 μA cm(-2) and an average power density of 2.8 mW cm(-3). The alternating current output of the nanogenerator is rectified, and the harvested energy is stored and later used to light up a commercial laser diode. This work demonstrates the feasibility of using nanogenerators for powering mobile and even personal microelectronics.

QM/QM approach to model energy disorder in amorphous organic semiconductors.

PubMed

Friederich, Pascal; Meded, Velimir; Symalla, Franz; Elstner, Marcus; Wenzel, Wolfgang

2015-02-10

It is an outstanding challenge to model the electronic properties of organic amorphous materials utilized in organic electronics. Computation of the charge carrier mobility is a challenging problem as it requires integration of morphological and electronic degrees of freedom in a coherent methodology and depends strongly on the distribution of polaron energies in the system. Here we represent a QM/QM model to compute the polaron energies combining density functional methods for molecules in the vicinity of the polaron with computationally efficient density functional based tight binding methods in the rest of the environment. For seven widely used amorphous organic semiconductor materials, we show that the calculations are accelerated up to 1 order of magnitude without any loss in accuracy. Considering that the quantum chemical step is the efficiency bottleneck of a workflow to model the carrier mobility, these results are an important step toward accurate and efficient disordered organic semiconductors simulations, a prerequisite for accelerated materials screening and consequent component optimization in the organic electronics industry.

Combining frozen-density embedding with the conductor-like screening model using Lagrangian techniques for response properties.

PubMed

Schieschke, Nils; Di Remigio, Roberto; Frediani, Luca; Heuser, Johannes; Höfener, Sebastian

2017-07-15

We present the explicit derivation of an approach to the multiscale description of molecules in complex environments that combines frozen-density embedding (FDE) with continuum solvation models, in particular the conductor-like screening model (COSMO). FDE provides an explicit atomistic description of molecule-environment interactions at reduced computational cost, while the outer continuum layer accounts for the effect of long-range isotropic electrostatic interactions. Our treatment is based on a variational Lagrangian framework, enabling rigorous derivations of ground- and excited-state response properties. As an example of the flexibility of the theoretical framework, we derive and discuss FDE + COSMO analytical molecular gradients for excited states within the Tamm-Dancoff approximation (TDA) and for ground states within second-order Møller-Plesset perturbation theory (MP2) and a second-order approximate coupled cluster with singles and doubles (CC2). It is shown how this method can be used to describe vertical electronic excitation (VEE) energies and Stokes shifts for uracil in water and carbostyril in dimethyl sulfoxide (DMSO), respectively. In addition, VEEs for some simplified protein models are computed, illustrating the performance of this method when applied to larger systems. The interaction terms between the FDE subsystem densities and the continuum can influence excitation energies up to 0.3 eV and, thus, cannot be neglected for general applications. We find that the net influence of the continuum in presence of the first FDE shell on the excitation energy amounts to about 0.05 eV for the cases investigated. The present work is an important step toward rigorously derived ab initio multilayer and multiscale modeling approaches. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Characterizing ``Radio Mode'' AGN Outbursts: the Recent 12 Myr History of the Supermassive Black Hole in M87

NASA Astrophysics Data System (ADS)

Forman, William R.; Churazov, Eugene; Jones, Christine; Heinz, Sebastian; Kraft, Ralph P.; Vikhlinin, Alexey

2016-01-01

M87, the bright active galaxy dominating the core of the Virgo cluster, is ideal for studying the interaction of a supermassive black hole with a gas rich environment. We combine results from a deep Chandra observation with a simple shock model to derive the properties of the outburst that created the 13 kpc shock previously reported around M87. The principal constraints for the model are 1) the observed temperature and density profiles, 2) the measured Mach number (about 1.2) and radius of the 13 kpc shock, 3) the observed size of the inner cavity (~3 kpc) that serves as the piston to drive the shock, and 4) the absence of a hot, low density plasma surrounding the central cavity. Qualitatively, the absence of a hot, low density (shocked) region surrounding the inner radio lobes (the piston), requires a "slowly" expanding piston and "long" duration outburst rather than a Sedov-like outburst. Quantitatively, a roughly 5 x 1057 ergs outburst that began about 12 Myr ago and lasted about 2 Myr matches all the constraints. In the context of the model, ~20% of the energy is carried by the shock as it expands to large radii while ~80% of the outburst energy is available to heat the core gas. For an outburst repetition rate of about 12 Myrs (the outburst age), 80% of the outburst energy is sufficient to balance radiative cooling. We discuss the outburst history of M87 as chronicled in its radio and X-ray images and the implications of these outbursts for heating gas rich environments.

Turbulence Statistics of a Buoyant Jet in a Stratified Environment

NASA Astrophysics Data System (ADS)

McCleney, Amy Brooke

Using non-intrusive optical diagnostics, turbulence statistics for a round, incompressible, buoyant, and vertical jet discharging freely into a stably linear stratified environment is studied and compared to a reference case of a neutrally buoyant jet in a uniform environment. This is part of a validation campaign for computational fluid dynamics (CFD). Buoyancy forces are known to significantly affect the jet evolution in a stratified environment. Despite their ubiquity in numerous natural and man-made flows, available data in these jets are limited, which constrain our understanding of the underlying physical processes. In particular, there is a dearth of velocity field data, which makes it challenging to validate numerical codes, currently used for modeling these important flows. Herein, jet near- and far-field behaviors are obtained with a combination of planar laser induced fluorescence (PLIF) and multi-scale time-resolved particle image velocimetry (TR-PIV) for Reynolds number up to 20,000. Deploying non-intrusive optical diagnostics in a variable density environment is challenging in liquids. The refractive index is strongly affected by the density, which introduces optical aberrations and occlusions that prevent the resolution of the flow. One solution consists of using index matched fluids with different densities. Here a pair of water solutions - isopropanol and NaCl - are identified that satisfy these requirements. In fact, they provide a density difference up to 5%, which is the largest reported for such fluid pairs. Additionally, by design, the kinematic viscosities of the solutions are identical. This greatly simplifies the analysis and subsequent simulations of the data. The spectral and temperature dependence of the solutions are fully characterized. In the near-field, shear layer roll-up is analyzed and characterized as a function of initial velocity profile. In the far-field, turbulence statistics are reported for two different scales, one capturing the entire jet at near Taylor microscale resolution, and the other, thanks to the careful refractive index matching of the liquids, resolving the Taylor scale at near Kolmogorov scale resolution. This is accomplished using a combination of TR-PIV and long-distance micro-PIV. The turbulence statistics obtained at various downstream locations and magnifications are obtained for density differences of 0%, 1%, and 3%. To validate the experimental methodology and provide a reference case for validation, the effect of initial velocity profile on the neutrally buoyant jet in the self-preserving regime is studied at two Reynolds numbers of 10,000 and 20,000. For the neutrally buoyant jet, it is found that independent of initial conditions the jet follows a self-similar behavior in the far-field; however, the spreading rate is strongly dependent on initial velocity profile. High magnification analysis at the small turbulent length scales shows a flow field where the mean statistics compare well to the larger field of view case. Investigation of the near-field shows the jet is strongly influenced by buoyancy, where an increase in vortex ring formation frequency and number of pairings occur. The buoyant jet with a 1% density difference shows an alteration of the centerline velocity decay, but the radial distribution of the mean axial velocity collapses well at all measurement locations. Jet formation dramatically changes for a buoyant jet with a 3% density difference, where the jet reaches a terminal height and spreads out horizontally at its neutral buoyancy location. Analysis of both the mean axial velocity and strain rates show the jet is no longer self-similar; for example, the mean centerline velocity does not decay uniformly as the jet develops. The centerline strain rates at this density difference also show trends which are strongly influenced by the altered centerline velocity. The overall centerline analysis shows that turbulence suppression occurs as a result of the stratification for both the 1% and 3% density difference. Analysis on the kinetic energy budget shows that the mean convection, production, transportation, and dissipation of energy is altered from stratification. High resolution data of the jet enable flow structures to be captured in the neutrally buoyant region of the flow. Vortices of different sizes are identified. Longer data sets are necessary to perform a statistical analysis of their distribution and to compare them to homogeneous environment case. This multi-scale analysis shows potential for studying energy transfer between length scales.

Enhancement of Resonant Energy Transfer Due to an Evanescent Wave from the Metal.

PubMed

Poudel, Amrit; Chen, Xin; Ratner, Mark A

2016-03-17

The high density of evanescent modes in the vicinity of a metal leads to enhancement of the near-field Förster resonant energy transfer (FRET) rate. We present a classical approach to calculate the FRET rate based on the dyadic Green's function of an arbitrary dielectric environment and consider the nonlocal limit of material permittivity in the case of the metallic half-space and thin film. In a dimer system, we find that the FRET rate is enhanced due to shared evanescent photon modes bridging a donor and an acceptor. Furthermore, a general expression for the FRET rate for multimer systems is derived. The presence of a dielectric environment and the path interference effect enhance the transfer rate, depending on the combination of distance and geometry.

Nonlocal screening in metal surfaces

NASA Technical Reports Server (NTRS)

Krotscheck, E.; Kohn, W.

1986-01-01

Due to the effect of the nonuniform environment on the static screening of the Coulomb potential, the local-density approximation for the particle-hole interaction is found to be inadequate to determine the surface energy of simple metals. Use of the same set of single-particle states, and thus the same one-body density and the same work function, has eliminated the single-electron states in favor of the structure of the short-ranged correlations as the basis of this effect. A posteriori simplifications of the Fermi hypernetted-chain theory may be found to allow the same calculational accuracy with simpler computational tools.

High performance electrodes in vanadium redox flow batteries through oxygen-enriched thermal activation

NASA Astrophysics Data System (ADS)

Pezeshki, Alan M.; Clement, Jason T.; Veith, Gabriel M.; Zawodzinski, Thomas A.; Mench, Matthew M.

2015-10-01

The roundtrip electrochemical energy efficiency is improved from 63% to 76% at a current density of 200 mA cm-2 in an all-vanadium redox flow battery (VRFB) by utilizing modified carbon paper electrodes in the high-performance no-gap design. Heat treatment of the carbon paper electrodes in a 42% oxygen/58% nitrogen atmosphere increases the electrochemically wetted surface area from 0.24 to 51.22 m2 g-1, resulting in a 100-140 mV decrease in activation overpotential at operationally relevant current densities. An enriched oxygen environment decreases the amount of treatment time required to achieve high surface area. The increased efficiency and greater depth of discharge doubles the total usable energy stored in a fixed amount of electrolyte during operation at 200 mA cm-2.

Stimulated neutrino transformation with sinusoidal density profiles

DOE PAGES

Kneller, J. P.; McLaughlin, G. C.; Patton, K. M.

2013-03-28

Large amplitude oscillations between the states of a quantum system can be stimulated by sinusoidal external potentials with frequencies that are similar to the energy level splitting of the states or a fraction thereof. Situations where the applied frequency is equal to an integer fraction of the energy level splittings are known as parametric resonances. We investigate this effect for neutrinos both analytically and numerically for the case of arbitrary numbers of neutrino flavors. We look for environments where the effect may be observed and find that supernovae are the one realistic possibility due to the necessity of both largemore » densities and large amplitude fluctuations. In conclusion, the comparison of numerical and analytical results of neutrino propagation through a model supernova reveals that it is possible to predict the locations and strengths of the stimulated transitions that occur.« less

The Hubble diagram for a system within dark energy: influence of some relevant quantities

NASA Astrophysics Data System (ADS)

Saarinen, J.; Teerikorpi, P.

2014-08-01

Aims: We study the influence of relevant quantities, including the density of dark energy (DE), to the predicted Hubble outflow around a system of galaxies. In particular, we are interested in the difference between two models: 1) the standard ΛCDM model, with the everywhere constant DE density, and 2) the "Swiss cheese model", where the Universe is as old as the standard model and the DE density is zero on short scales, including the environment of the system. Methods: We calculated the current predicted outflow patterns of dwarf galaxies around the Local Group-like system, using different values for the mass of the group, the local DE density, and the time of ejection of the dwarf galaxies, which are treated as test particles. These results are compared with the observed Hubble flow around the Local Group. Results: The predicted distance-velocity relations around galaxy groups are not very sensitive indicators of the DE density, owing to the observational scatter and the uncertainties caused by the mass used for the group and a range in the ejection times. In general, the Local Group outflow data agree with the local DE density being equal to the global one, if the Local Group mass is about 4 × 1012 M⊙; a lower mass ≲ 2 × 1012 M⊙ could suggest a zero local DE density. The dependence of the inferred DE density on the mass is a handicap in this and other common dynamical methods. This emphasizes the need to use different approaches together, for constraining the local DE density.

Nanoscale triboelectric-effect-enabled energy conversion for sustainably powering portable electronics.

PubMed

Wang, Sihong; Lin, Long; Wang, Zhong Lin

2012-12-12

Harvesting energy from our living environment is an effective approach for sustainable, maintenance-free, and green power source for wireless, portable, or implanted electronics. Mechanical energy scavenging based on triboelectric effect has been proven to be simple, cost-effective, and robust. However, its output is still insufficient for sustainably driving electronic devices/systems. Here, we demonstrated a rationally designed arch-shaped triboelectric nanogenerator (TENG) by utilizing the contact electrification between a polymer thin film and a metal thin foil. The working mechanism of the TENG was studied by finite element simulation. The output voltage, current density, and energy volume density reached 230 V, 15.5 μA/cm(2), and 128 mW/cm(3), respectively, and an energy conversion efficiency as high as 10-39% has been demonstrated. The TENG was systematically studied and demonstrated as a sustainable power source that can not only drive instantaneous operation of light-emitting diodes (LEDs) but also charge a lithium ion battery as a regulated power module for powering a wireless sensor system and a commercial cell phone, which is the first demonstration of the nanogenerator for driving personal mobile electronics, opening the chapter of impacting general people's life by nanogenerators.

Developing a Renewable Energy Awareness Scale for Pre-Service Chemistry Teachers

ERIC Educational Resources Information Center

Morgil, Inci; Secken, Nilgun; Yucel, A. Seda; Ozyalcin Oskay, Ozge; Yavuz, Soner; Ural, Evrim

2006-01-01

In times when human beings used to live in a natural environment, their needs were also provided for by natural resources. With the increase in population over time, human beings started to look for new resources willing to get "the most" and "the fastest". Just like the invention of steam, first, they increased the density of the resources and…

Spacecraft charging and ion wake formation in the near-Sun environment

NASA Astrophysics Data System (ADS)

Ergun, R. E.; Malaspina, D. M.; Bale, S. D.; McFadden, J. P.; Larson, D. E.; Mozer, F. S.; Meyer-Vernet, N.; Maksimovic, M.; Kellogg, P. J.; Wygant, J. R.

2010-07-01

A three-dimensional, self-consistent code is employed to solve for the static potential structure surrounding a spacecraft in a high photoelectron environment. The numerical solutions show that, under certain conditions, a spacecraft can take on a negative potential in spite of strong photoelectron currents. The negative potential is due to an electrostatic barrier near the surface of the spacecraft that can reflect a large fraction of the photoelectron flux back to the spacecraft. This electrostatic barrier forms if (1) the photoelectron density at the surface of the spacecraft greatly exceeds the ambient plasma density, (2) the spacecraft size is significantly larger than local Debye length of the photoelectrons, and (3) the thermal electron energy is much larger than the characteristic energy of the escaping photoelectrons. All of these conditions are present near the Sun. The numerical solutions also show that the spacecraft's negative potential can be amplified by an ion wake. The negative potential of the ion wake prevents secondary electrons from escaping the part of spacecraft in contact with the wake. These findings may be important for future spacecraft missions that go nearer to the Sun, such as Solar Orbiter and Solar Probe Plus.

Global scenarios of urban density and its impacts on building energy use through 2050

DOE PAGES

Guneralp, Burak; Zhou, Yuyu; Urge-Vorsatz, Diana; ...

2017-01-09

Here, urban areas play a significant role in planetary sustainability. While the scale of impending urbanization is well acknowledged, we have a limited understanding on how urban forms will change and what their impact will be on building energy use. Using both top-down and bottom-up approaches and scenarios, we examine building energy use, specifically, for heating and cooling. We also assess associated cobenefits and trade-offs with human well-being. Globally, the energy use for heating and cooling by midcentury will reach anywhere from about 45 EJ/yr to 59 EJ/yr (respectively, increases of 5% to 40% over the 2010 estimate). Most ofmore » this variability is due to the uncertainty in future urban forms of rapidly growing cities in Asia and, particularly, in China. Compact urban development overall leads to less energy use in urban environments. Delaying the retrofit of the existing built environment leads to more savings in building energy use. Potential for savings in the energy use is greatest in China when coupled with efficiency gains. Advanced efficiency makes the least difference compared to the business-as-usual scenario in energy use for heating and cooling in South Asia and Sub-Saharan Africa but significantly contribute to energy savings in North America and Europe. A systemic effort that focuses on both urban form and energy-efficient technologies, but also accounts for potential co-benefits and trade-offs, can contribute to both local and global sustainability. Particularly in mega-urban regions, such efforts can improve local environments for billions of urban residents and contribute to mitigating climate change by reducing energy use in urban areas and associated greenhouse gas emissions.« less

Global scenarios of urban density and its impacts on building energy use through 2050

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

Güneralp, Burak; Zhou, Yuyu; Ürge-Vorsatz, Diana

2017-01-09

Urban areas play a significant role in planetary sustainability. While the scale of impending urbanization is well acknowledged, we have a limited understanding on how urban forms will change and what their impact will be on building energy use. Using both top-down and bottom-up approaches and scenarios, we examine building energy use, specifically, for heating and cooling. We also assess associated cobenefits and trade-offs with human well-being. Globally, the energy use for heating and cooling by midcentury will reach anywhere from about 45 EJ/yr to 59 EJ/yr (respectively, increases of 5% to 40% over the 2010 estimate). Most of thismore » variability is due to the uncertainty in future urban forms of rapidly growing cities in Asia and, particularly, in China. Compact urban development overall leads to less energy use in urban environments. Delaying the retrofit of the existing built environment leads to more savings in building energy use. Potential for savings in the energy use is greatest in China when coupled with efficiency gains. Advanced efficiency makes the least difference compared to the business-as-usual scenario in energy use for heating and cooling in South Asia and Sub-Saharan Africa but significantly contribute to energy savings in North America and Europe. A systemic effort that focuses on both urban form and energy-efficient technologies, but also accounts for potential co-benefits and trade-offs, can contribute to both local and global sustainability. Particularly in mega-urban regions, such efforts can improve local environments for billions of urban residents and contribute to mitigating climate change by reducing energy use in urban areas and associated greenhouse gas emissions.« less

Engineering Polymer Nanocomoposite Aerogels for Energy Storage and Harvesting

NASA Astrophysics Data System (ADS)

Zheng, Qifeng

Various porous polymer nanocomposite aerogels were synthesized using an environmentally friendly freeze-drying process. These polymer nanocomposite aerogels exhibit ultralow densities, high porosities, high specific surface areas and high flexibility. The advantages of these polymer nanocomposites aerogels for energy storage and energy harvesting applications have been demonstrated. Flexible supercapacitors (SCs) are particularly attractive for energy storage applications due to their high power densities and long life cycles. A novel type of highly flexible and all-solid-state SCs using cellulose nanofibril (CNF)-reduced graphene oxide (RGO)-carbon nanotube (CNT) aerogels as electrodes was developed. Due to the porous structure of the CNF/RGO/CNT aerogel electrodes, and the excellent electrolyte absorption properties of the CNFs present in the electrodes, the resulting all-solid-state SCs exhibited excellent electrochemical performance, superior flexibility and cycle stability. To further increase the capacitances and energy densities, pseudocapacitive materials (i.e., MoO3) were incorporated to prepare the free-standing and highly flexible CNF-RGO-molybdenum oxynitride (MoOxNy) aerogel film electrode. Supercapacitors made with the CNF/RGO/MoOxNy aerogel electrodes exhibited outstanding specific capacitances and remarkable energy densities in different electrolytes while maintaining the high power densities and superior cycle stability. Flexible nanogenerators (NGs) that can harvest ubiquitous mechanical energy from ambient environments have attracted significant attention during the past decade. A novel, simple, cost-effective, and scalable technique was developed to fabricate high-performance flexible compact NGs using porous CNF-poly(dimethylsiloxane) (PDMS) aerogel film. Under external stress, the resulting NGs exhibited very stable and high output signals. We hypothesized that the remarkable electric outputs would not only be attributable to the intrinsic piezoelectric properties of the CNFs, but also to the mechanoradicals generated by the porous PDMS coated on the surface of the CNF aerogel film, which can lead to a change in the electric dipole moments and consequently generate electric outputs. A series of systematic studies were carried out to substantiate this new mechanism. These systematic studies have demonstrated that high-performance NGs can be made from porous mechanoradical-generating polymer films. The elucidation of the mechanisms for this family of porous mechanoradical-generating polymers will lead to a new class of energy harvesting materials and high-performance flexible energy generation devices.

High voltage requirements and issues for the 1990's. [for spacecraft power supplies

NASA Technical Reports Server (NTRS)

Dunbar, W. G.; Faymon, K. A.

1984-01-01

The development of high-power high-voltage space systems will require advances in power generation and processing. The systems must be reliable, adaptable, and durable for space mission success. The issues, which must be resolved in order to produce a high power system, are weight and volume reduction of components and modules and the creation of a reliable high repetition pulse power processor. Capacitor energy density must be increased by twice the present capacity and packaging must be reduced by a factor of 10 to 20 times. The packaging must also protect the system from interaction with the natural space environment and the induced environment, produced from spacecraft systems and environment interaction.

DNA Nucleotides Detection via capacitance properties of Graphene

NASA Astrophysics Data System (ADS)

Khadempar, Nahid; Berahman, Masoud; Yazdanpanah, Arash

2016-05-01

In the present paper a new method is suggested to detect the DNA nucleotides on a first-principles calculation of the electronic features of DNA bases which chemisorbed to a graphene sheet placed between two gold electrodes in a contact-channel-contact system. The capacitance properties of graphene in the channel are surveyed using non-equilibrium Green's function coupled with the Density Functional Theory. Thus, the capacitance properties of graphene are theoretically investigated in a biological environment, and, using a novel method, the effect of the chemisorbed DNA nucleotides on electrical charges on the surface of graphene is deciphered. Several parameters in this method are also extracted including Electrostatic energy, Induced density, induced electrostatic potential, Electron difference potential and Electron difference density. The qualitative and quantitative differences among these parameters can be used to identify DNA nucleotides. Some of the advantages of this approach include its ease and high accuracy. What distinguishes the current research is that it is the first experiment to investigate the capacitance properties of gaphene changes in the biological environment and the effect of chemisorbed DNA nucleotides on the surface of graphene on the charge.

High temperature energy harvesters utilizing ALN/3C-SiC composite diaphragms

NASA Astrophysics Data System (ADS)

Lai, Yun-Ju; Li, Wei-Chang; Felmetsger, Valery V.; Senesky, Debbie G.; Pisano, Albert P.

2014-06-01

Microelectromechanical systems (MEMS) energy harvesting devices aiming at powering wireless sensor systems for structural health monitoring in harsh environments are presented. For harsh environment wireless sensor systems, sensor modules are required to operate at elevated temperatures (> 250°C) with capabilities to resist harsh chemical conditions, thereby the use of battery-based power sources becomes challenging and not economically efficient if considering the required maintenance efforts. To address this issue, energy harvesting technology is proposed to replace batteries and provide a sustainable power source for the sensor systems towards autonomous harsh environment wireless sensor networks. In particular, this work demonstrates a micromachined aluminum nitride/cubic silicon carbide (AlN/3C-SiC) composite diaphragm energy harvester, which enables high temperature energy harvesting from ambient pulsed pressure sources. The fabricated device yields an output power density of 87 μW/cm2 under 1.48-psi pressure pulses at 1 kHz while connected to a 14.6-kΩ load resistor. The effects of pulse profile on output voltage have been studied, showing that the output voltage can be maximized by optimizing the diaphragm resonance frequency based on specific pulse characteristics. In addition, temperature dependence of the diaphragm resonance frequency over the range of 20°C to 600°C has been investigated and the device operation at temperatures as high as 600°C has been verified.

Understanding oxygen adsorption on 9.375 at. % Ga-stabilized δ-Pu (111) surface: A DFT study

DOE PAGES

Hernandez, Sarah C.; Wilkerson, Marianne P.; Huda, Muhammad N.

2015-08-30

Plutonium (Pu) metal reacts rapidly in the presence of oxygen (O), resulting in an oxide layer that will eventually have an olive green rust appearance over time. Recent experimental work suggested that the incorporation of gallium (Ga) as an alloying impurity to stabilize the highly symmetric high temperature δ-phase lattice may also provide resistance against corrosion/oxidation of plutonium. In this paper, we modeled a 9.375 at. % Ga stabilized δ-Pu (111) surface and investigated adsorption of atomic O using all-electron density functional theory. Key findings revealed that the O bonded strongly to a Pu-rich threefold hollow fcc site with amore » chemisorption energy of –5.06 eV. Migration of the O atom to a Pu-rich environment was also highly sensitive to the surface chemistry of the Pu–Ga surface; when the initial on-surface O adsorption site included a bond to a nearest neighboring Ga atom, the O atom relaxed to a Ga deficient environment, thus affirming the O preference for Pu. Only one calculated final on-surface O adsorption site included a Ga-O bond, but this chemisorption energy was energetically unfavorable. Chemisorption energies for interstitial adsorption sites that included a Pu or Pu-Ga environment suggested that over-coordination of the O atom was energetically unfavorable as well. Electronic structure properties of the on-surface sites, illustrated by the partial density of states, implied that the Ga 4p states indirectly but strongly influenced the Pu 6d states strongly to hybridize with the O 2p states, while also weakly influenced the Pu 5f states to hybridize with the O 2p states, even though Ga was not participating in bonding with O.« less

Coarse-Grained Theory of Biological Charge Transfer with Spatially and Temporally Correlated Noise.

PubMed

Liu, Chaoren; Beratan, David N; Zhang, Peng

2016-04-21

System-environment interactions are essential in determining charge-transfer (CT) rates and mechanisms. We developed a computationally accessible method, suitable to simulate CT in flexible molecules (i.e., DNA) with hundreds of sites, where the system-environment interactions are explicitly treated with numerical noise modeling of time-dependent site energies and couplings. The properties of the noise are tunable, providing us a flexible tool to investigate the detailed effects of correlated thermal fluctuations on CT mechanisms. The noise is parametrizable by molecular simulation and quantum calculation results of specific molecular systems, giving us better molecular resolution in simulating the system-environment interactions than sampling fluctuations from generic spectral density functions. The spatially correlated thermal fluctuations among different sites are naturally built-in in our method but are not readily incorporated using approximate spectral densities. Our method has quantitative accuracy in systems with small redox potential differences (

Understanding oxygen adsorption on 9.375 at. % Ga-stabilized δ-Pu (111) surface: A DFT study

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

Hernandez, Sarah C.; Wilkerson, Marianne P.; Huda, Muhammad N.

Plutonium (Pu) metal reacts rapidly in the presence of oxygen (O), resulting in an oxide layer that will eventually have an olive green rust appearance over time. Recent experimental work suggested that the incorporation of gallium (Ga) as an alloying impurity to stabilize the highly symmetric high temperature δ-phase lattice may also provide resistance against corrosion/oxidation of plutonium. In this paper, we modeled a 9.375 at. % Ga stabilized δ-Pu (111) surface and investigated adsorption of atomic O using all-electron density functional theory. Key findings revealed that the O bonded strongly to a Pu-rich threefold hollow fcc site with amore » chemisorption energy of –5.06 eV. Migration of the O atom to a Pu-rich environment was also highly sensitive to the surface chemistry of the Pu–Ga surface; when the initial on-surface O adsorption site included a bond to a nearest neighboring Ga atom, the O atom relaxed to a Ga deficient environment, thus affirming the O preference for Pu. Only one calculated final on-surface O adsorption site included a Ga-O bond, but this chemisorption energy was energetically unfavorable. Chemisorption energies for interstitial adsorption sites that included a Pu or Pu-Ga environment suggested that over-coordination of the O atom was energetically unfavorable as well. Electronic structure properties of the on-surface sites, illustrated by the partial density of states, implied that the Ga 4p states indirectly but strongly influenced the Pu 6d states strongly to hybridize with the O 2p states, while also weakly influenced the Pu 5f states to hybridize with the O 2p states, even though Ga was not participating in bonding with O.« less

Energy density of bloaters in the upper Great Lakes

USGS Publications Warehouse

Pothoven, Steven A.; Bunnell, David B.; Madenjian, Charles P.; Gorman, Owen T.; Roseman, Edward F.

2012-01-01

We evaluated the energy density of bloaters Coregonus hoyi as a function of fish size across Lakes Michigan, Huron, and Superior in 2008–2009 and assessed how differences in energy density are related to factors such as biomass density of bloaters and availability of prey. Additional objectives were to compare energy density between sexes and to compare energy densities of bloaters in Lake Michigan between two time periods (1998–2001 and 2008–2009). For the cross-lake comparisons in 2008, energy density increased with fish total length (TL) only in Lake Michigan. Mean energy density adjusted for fish size was 8% higher in bloaters from Lake Superior than in bloaters from Lake Huron. Relative to fish in these two lakes, small (175 mm TL) bloaters had higher energy density. In 2009, energy density increased with bloater size, and mean energy density adjusted for fish size was about 9% higher in Lake Michigan than in Lake Huron (Lake Superior was not sampled during 2009). Energy density of bloaters in Lake Huron was generally the lowest among lakes, reflecting the relatively low densities of opossum shrimp Mysis diluviana and the relatively high biomass of bloaters reported for that lake. Other factors, such as energy content of prey, growing season, or ontogenetic differences in energy use strategies, may also influence cross-lake variation in energy density. Mean energy density adjusted for length was 7% higher for female bloaters than for male bloaters in Lakes Michigan and Huron. In Lake Superior, energy density did not differ between males and females. Finally, energy density of bloaters in Lake Michigan was similar between the periods 2008–2009 and 1998–2001, possibly due to a low population abundance of bloaters, which could offset food availability changes linked to the loss of prey such as the amphipods Diporeia spp.

Irradiation response of commercial, high-Tc superconducting tapes: Electromagnetic transport properties

DOE PAGES

Gapud, A. A.; Greenwood, N. T.; Alexander, J. A.; ...

2015-07-01

Effects of low dose irradiation on the electrical transport current properties of commercially available high-temperature superconducting, coated-conductor tapes were investigated, in view of potential applications in the irradiative environment of fusion reactors. Three different tapes, each with unique as-grown flux-pinning structures, were irradiated with Au and Ni ions at energies that provide a range of damage effects, with accumulated damage levels near that expected for conductors in a fusion reactor environment. Measurements using transport current determined the pre- and post-irradiation resistivity, critical current density, and pinning force density, yielding critical temperatures, irreversibility lines, and inferred vortex creep rates. Results showmore » that at the irradiation damage levels tested, any detriment to as-grown pre-irradiation properties is modest; indeed in one case already-superior pinning forces are enhanced, leading to higher critical currents.« less

The energetics of relativistic jets in active galactic nuclei with various kinetic powers

NASA Astrophysics Data System (ADS)

Musoke, Gibwa Rebecca; Young, Andrew; Molnar, Sandor; Birkinshaw, Mark

2018-01-01

Numerical simulations are an important tool in understanding the physical processes behind relativistic jets in active galactic nuclei. In such simulations different combinations of intrinsic jet parameters can be used to obtain the same jet kinetic powers. We present a numerical investigation of the effects of varying the jet power on the dynamic and energetic characteristics of the jets for two kinetic power regimes; in the first regime we change the jet density whilst maintaining a fixed velocity, in the second the jet density is held constant while the velocity is varied. We conduct 2D axisymmetric hydrodynamic simulations of bipolar jets propagating through an isothermal cluster atmosphere using the FLASH MHD code in pure hydrodynamics mode. The jets are simulated with kinetic powers ranging between 1045 and 1046 erg/s and internal Mach numbers ranging from 5.6 to 21.5.As the jets begin to propagate into the intracluster medium (ICM), the injected jet energy is converted into the thermal, kinetic and gravitational potential energy components of the jet cocoon and ICM. We explore the temporal evolution of the partitioning of the injected jet energy into the cocoon and the ICM and quantify the importance of entrainment process on the energy partitioning. We investigate the fraction of injected energy transferred to the thermal energy component of the jet-ICM system in the context of heating the cluster environments, noting that the jets simulated display peak thermalisation efficiencies of least 65% and a marked dependence on the jet density. We compare the efficiencies of the energy partitioning between the cocoon and ICM for the two kinetic power regimes and discuss the resulting efficiency-power scaling relations of each regime.

Associations among the food environment, diet quality and weight status in Cree children in Québec.

PubMed

Downs, Shauna M; Arnold, Amber; Marshall, Dru; McCargar, Linda J; Raine, Kim D; Willows, Noreen D

2009-09-01

To explore the relationship among children's diet quality, weight status and food environment in subarctic Canada. In the cross-sectional study, children's BMI was calculated, diet quality was assessed using three 24 h dietary recalls and children were asked about their home food environment and source of meals. Two Aboriginal Cree communities in northern Québec. Two hundred and one children in grades 4-6. The majority (64.2%) of children were overweight (29.9%) or obese (34.3%). Weight status was not associated with reported restaurant meal frequency or the home food environment. The 18% of children who consumed three or more restaurant meals in the three days of recall consumed, on average, 2004 kJ (479 kcal) more energy daily than children consuming no restaurant meals and had higher intakes of fat, saturated fat, Ca and soda. Most foods contributing to energy and dietary fat were energy-dense market foods of low nutritional value such as sweetened beverages and snack foods. Only 68% of children reported often having fruits and vegetables in the home and 98.5% of children consumed less than 5 fruits and vegetables daily. Many children (42.8%) were at risk of Zn inadequacy. Only 19% of children consumed 2 or more servings of milk daily, and the mean intakes of Ca and vitamin D were below the recommended adequate intake. Traditional game meat was consumed infrequently, but contributed significantly to Fe and Zn intake. Childhood obesity in subarctic communities prevailed in a food environment typified by high-energy-density commercial foods of low nutritional value.

Signatures of Solvation Thermodynamics in Spectra of Intermolecular Vibrations

PubMed Central

2017-01-01

This study explores the thermodynamic and vibrational properties of water in the three-dimensional environment of solvated ions and small molecules using molecular simulations. The spectrum of intermolecular vibrations in liquid solvents provides detailed information on the shape of the local potential energy surface, which in turn determines local thermodynamic properties such as the entropy. Here, we extract this information using a spatially resolved extension of the two-phase thermodynamics method to estimate hydration water entropies based on the local vibrational density of states (3D-2PT). Combined with an analysis of solute–water and water–water interaction energies, this allows us to resolve local contributions to the solvation enthalpy, entropy, and free energy. We use this approach to study effects of ions on their surrounding water hydrogen bond network, its spectrum of intermolecular vibrations, and resulting thermodynamic properties. In the three-dimensional environment of polar and nonpolar functional groups of molecular solutes, we identify distinct hydration water species and classify them by their characteristic vibrational density of states and molecular entropies. In each case, we are able to assign variations in local hydration water entropies to specific changes in the spectrum of intermolecular vibrations. This provides an important link for the thermodynamic interpretation of vibrational spectra that are accessible to far-infrared absorption and Raman spectroscopy experiments. Our analysis provides unique microscopic details regarding the hydration of hydrophobic and hydrophilic functional groups, which enable us to identify interactions and molecular degrees of freedom that determine relevant contributions to the solvation entropy and consequently the free energy. PMID:28783431

Creation of Two-Particle Entanglement in Open Macroscopic Quantum Systems

DOE PAGES

Merkli, M.; Berman, G. P.; Borgonovi, F.; ...

2012-01-01

We considermore » an open quantum system of N not directly interacting spins (qubits) in contact with both local and collective thermal environments. The qubit-environment interactions are energy conserving. We trace out the variables of the thermal environments and N − 2 qubits to obtain the time-dependent reduced density matrix for two arbitrary qubits. We numerically simulate the reduced dynamics and the creation of entanglement (concurrence) as a function of the parameters of the thermal environments and the number of qubits, N . Our results demonstrate that the two-qubit entanglement generally decreases as N increases. We show analytically that, in the limit N → ∞ , no entanglement can be created. This indicates that collective thermal environments cannot create two-qubit entanglement when many qubits are located within a region of the size of the environment coherence length. We discuss possible relevance of our consideration to recent quantum information devices and biosystems.« less

Quantum nuclear pasta and nuclear symmetry energy

NASA Astrophysics Data System (ADS)

Fattoyev, F. J.; Horowitz, C. J.; Schuetrumpf, B.

2017-05-01

Complex and exotic nuclear geometries, collectively referred to as "nuclear pasta," are expected to appear naturally in dense nuclear matter found in the crusts of neutron stars and supernovae environments. The pasta geometries depend on the average baryon density, proton fraction, and temperature and are critically important in the determination of many transport properties of matter in supernovae and the crusts of neutron stars. Using a set of self-consistent microscopic nuclear energy density functionals, we present the first results of large scale quantum simulations of pasta phases at baryon densities 0.03 ≤ρ ≤0.10 fm-3 , proton fractions 0.05 ≤Yp≤0.40 , and zero temperature. The full quantum simulations, in particular, allow us to thoroughly investigate the role and impact of the nuclear symmetry energy on pasta configurations. We use the Sky3D code that solves the Skyrme Hartree-Fock equations on a three-dimensional Cartesian grid. For the nuclear interaction we use the state-of-the-art UNEDF1 parametrization, which was introduced to study largely deformed nuclei, hence is suitable for studies of the nuclear pasta. Density dependence of the nuclear symmetry energy is simulated by tuning two purely isovector observables that are insensitive to the current available experimental data. We find that a minimum total number of nucleons A =2000 is necessary to prevent the results from containing spurious shell effects and to minimize finite size effects. We find that a variety of nuclear pasta geometries are present in the neutron star crust, and the result strongly depends on the nuclear symmetry energy. The impact of the nuclear symmetry energy is less pronounced as the proton fractions increase. Quantum nuclear pasta calculations at T =0 MeV are shown to get easily trapped in metastable states, and possible remedies to avoid metastable solutions are discussed.

On strain and stress in living cells

NASA Astrophysics Data System (ADS)

Cox, Brian N.; Smith, David W.

2014-11-01

Recent theoretical simulations of amelogenesis and network formation and new, simple analyses of the basic multicellular unit (BMU) allow estimation of the order of magnitude of the strain energy density in populations of living cells in their natural environment. A similar simple calculation translates recent measurements of the force-displacement relation for contacting cells (cell-cell adhesion energy) into equivalent volume energy densities, which are formed by averaging the changes in contact energy caused by a cell's migration over the cell's volume. The rates of change of these mechanical energy densities (energy density rates) are then compared to the order of magnitude of the metabolic activity of a cell, expressed as a rate of production of metabolic energy per unit volume. The mechanical energy density rates are 4-5 orders of magnitude smaller than the metabolic energy density rate in amelogenesis or bone remodeling in the BMU, which involve modest cell migration velocities, and 2-3 orders of magnitude smaller for innervation of the gut or angiogenesis, where migration rates are among the highest for all cell types. For representative cell-cell adhesion gradients, the mechanical energy density rate is 6 orders of magnitude smaller than the metabolic energy density rate. The results call into question the validity of using simple constitutive laws to represent living cells. They also imply that cells need not migrate as inanimate objects of gradients in an energy field, but are better regarded as self-powered automata that may elect to be guided by such gradients or move otherwise. Thus Ġel=d/dt 1/2 >[(C11+C12)ɛ02+2μγ02]=(C11+C12)ɛ0ɛ˙0+2μγ0γ˙0 or Ġel=ηEɛ0ɛ˙0+η‧Eγ0γ˙0 with 1.4≤η≤3.4 and 0.7≤η‧≤0.8 for Poisson's ratio in the range 0.2≤ν≤0.4 and η=1.95 and η‧=0.75 for ν=0.3. The spatial distribution of shear strains arising within an individual cell as cells slide past one another during amelogenesis is not known in detail. However, estimates can be inferred from the known relative velocities of the cells' centers of mass. When averaged over a volume comparable to the cell size, representative values of the strain are, to order of magnitude, ɛ0≈0.1 and γ0≈0.1. The shape distortions of cells seen, for example, in Fig. 1c, imply peak strains in minor segments of a cell of magnitude unity, ɛ0≈1 and γ0≈1; these values represent the upper bound of plausible values and are included for discussion of the extremes of attainable strain energy rates.Given the strain magnitudes, the strain rates follow from the fact that a cell switches from one contacting neighbor in the adjacent row to the next in approximately 0.25 d, during which motion the strains might vary from zero to their maximum values and back again. Thus the most probable shear strain rate is inferred to be γ˙0=10-6 s-1 and the most probable tensile strain rate is inferred to be ɛ˙0≈10-6 s-1, with high bounds γ˙0=10-5 s-1 and ɛ˙0=10-5 s-1.

The Plasma Environment at Enceladus

NASA Astrophysics Data System (ADS)

Rymer, Abigail; Morooka, Michiko; Persoon, Ann

2016-10-01

The plasma environment near Enceladus is complex. The well documented Enceladus plumes create a dusty, asymmetric exosphere in which electrons can attach to small ice particles - forming anions, and negatively charged nanograins and dust - to the extent that cations can be the lightest charged particles present and, as a result, the dominant current carriers. Several instruments on the Cassini spacecraft are able to measure this environment in both expected and unexpected ways. Cassini Plasma Spectrometer (CAPS) is designed and calibrated to measure the thermal plasma ions and electrons and also measures the energy/charge of charged nanograins when present. Cassini Radio Plasma Wave Sensor (RPWS) measures electron density as derived from the 'upper hybrid frequency' which is a function of the total free electron density and magnetic field strength and provides a vital ground truth measurement for Cassini calibration when the density is sufficiently high for it to be well measured. Cassini Langmuir Probe (LP) measures the electron density and temperature via direct current measurement, and both CAPS and LP can provide estimates for the spacecraft potential which we compare. Cassini Magnetospheric Imaging Instrument (MIMI) directly measures energetic particles that are manifest in the CAPS measurements as penetrating background in this region and, while not particularly efficient ionisers, create sputtering and surface weathering of Enceladus surface, MIMI also measures energetic neutral atoms produced during the charge exchange interactions in and near the plumes.In this presentation we exploit two almost identical Cassini-Enceladus flybys 'E17' and 'E18' which took place in March/April 2012. We present a detailed comparison of data from these Cassini sensors in order to assess the plasma environment observed by the different instruments, discuss what is consistent and otherwise, and the implications for the plasma environment at Enceladus in the context of work to date as well as implications for future studies.

Coarse-grained models using local-density potentials optimized with the relative entropy: Application to implicit solvation

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

Sanyal, Tanmoy; Shell, M. Scott, E-mail: shell@engineering.ucsb.edu

Bottom-up multiscale techniques are frequently used to develop coarse-grained (CG) models for simulations at extended length and time scales but are often limited by a compromise between computational efficiency and accuracy. The conventional approach to CG nonbonded interactions uses pair potentials which, while computationally efficient, can neglect the inherently multibody contributions of the local environment of a site to its energy, due to degrees of freedom that were coarse-grained out. This effect often causes the CG potential to depend strongly on the overall system density, composition, or other properties, which limits its transferability to states other than the one atmore » which it was parameterized. Here, we propose to incorporate multibody effects into CG potentials through additional nonbonded terms, beyond pair interactions, that depend in a mean-field manner on local densities of different atomic species. This approach is analogous to embedded atom and bond-order models that seek to capture multibody electronic effects in metallic systems. We show that the relative entropy coarse-graining framework offers a systematic route to parameterizing such local density potentials. We then characterize this approach in the development of implicit solvation strategies for interactions between model hydrophobes in an aqueous environment.« less

Space Environment Effects on Flexible, Low-Voltage Organic Thin-Film Transistors.

PubMed

Basiricò, Laura; Basile, Alberto Francesco; Cosseddu, Piero; Gerardin, Simone; Cramer, Tobias; Bagatin, Marta; Ciavatti, Andrea; Paccagnella, Alessandro; Bonfiglio, Annalisa; Fraboni, Beatrice

2017-10-11

Organic electronic devices fabricated on flexible substrates are promising candidates for applications in environments where flexible, lightweight, and radiation hard materials are required. In this work, device parameters such as threshold voltage, charge mobility, and trap density of 13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene)-based organic thin-film transistors (OTFTs) have been monitored for performing electrical measurements before and after irradiation by high-energy protons. The observed reduction of charge carrier mobility following irradiation can be only partially ascribed to the increased trap density. Indeed, we used other techniques to identify additional effects induced by proton irradiation in such devices. Atomic force microscopy reveals morphological defects occurring in the organic dielectric layer induced by the impinging protons, which, in turn, induce a strain on the TIPS-pentacene crystallites lying above. The effects of this strain are investigated by density functional theory simulations of two model structures, which describe the TIPS-pentacene crystalline films at equilibrium and under strain. The two different density of states distributions in the valence band have been correlated with the photocurrent spectra acquired before and after proton irradiation. We conclude that the degradation of the dielectric layer and the organic semiconductor sensitivity to strain are the two main phenomena responsible for the reduction of OTFT mobility after proton irradiation.

Pink-beam focusing with a one-dimensional compound refractive lens

DOE PAGES

Dufresne, Eric M.; Dunford, Robert W.; Kanter, Elliot P.; ...

2016-07-28

The performance of a cooled Be compound refractive lens (CRL) has been tested at the Advanced Photon Source (APS) to enable vertical focusing of the pink beam and permit the X-ray beam to spatially overlap with an 80 µm-high low-density plasma that simulates astrophysical environments. Focusing the fundamental harmonics of an insertion device white beam increases the APS power density; here, a power density as high as 500 W mm –2 was calculated. A CRL is chromatic so it does not efficiently focus X-rays whose energies are above the fundamental. Only the fundamental of the undulator focuses at the experiment.more » A two-chopper system reduces the power density on the imaging system and lens by four orders of magnitude, enabling imaging of the focal plane without any X-ray filter. As a result, a method to measure such high power density as well as the performance of the lens in focusing the pink beam is reported.« less

Polarizable embedding with a multiconfiguration short-range density functional theory linear response method

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

Hedegård, Erik Donovan, E-mail: erik.hedegard@phys.chem.ethz.ch; Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense; Olsen, Jógvan Magnus Haugaard

2015-03-21

We present here the coupling of a polarizable embedding (PE) model to the recently developed multiconfiguration short-range density functional theory method (MC-srDFT), which can treat multiconfigurational systems with a simultaneous account for dynamical and static correlation effects. PE-MC-srDFT is designed to combine efficient treatment of complicated electronic structures with inclusion of effects from the surrounding environment. The environmental effects encompass classical electrostatic interactions as well as polarization of both the quantum region and the environment. Using response theory, molecular properties such as excitation energies and oscillator strengths can be obtained. The PE-MC-srDFT method and the additional terms required for linearmore » response have been implemented in a development version of DALTON. To benchmark the PE-MC-srDFT approach against the literature data, we have investigated the low-lying electronic excitations of acetone and uracil, both immersed in water solution. The PE-MC-srDFT results are consistent and accurate, both in terms of the calculated solvent shift and, unlike regular PE-MCSCF, also with respect to the individual absolute excitation energies. To demonstrate the capabilities of PE-MC-srDFT, we also investigated the retinylidene Schiff base chromophore embedded in the channelrhodopsin protein. While using a much more compact reference wave function in terms of active space, our PE-MC-srDFT approach yields excitation energies comparable in quality to CASSCF/CASPT2 benchmarks.« less

Silicon-Based Lithium-Ion Capacitor for High Energy and High Power Application

NASA Technical Reports Server (NTRS)

Wu, James J.; Demattia, Brianne; Loyselle, Patricia; Reid, Concha; Kohout, Lisa

2017-01-01

Si-based Li-ion capacitor has been developed and demonstrated. The results show it is feasible to improve both power density and energy density in this configuration. The applied current density impacts the power and energy density: low current favors energy density while high current favors power density. Active carbon has a better rate capability than Si. Next StepsFuture Directions. Si electrode needs to be further studied and improved. Further optimization of SiAC ratio and evaluation of its impact on energy density and power density.

Effects of thermal treatment on energy density and hardness of torrefied wood pellets

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

Peng, Jianghong; Wang, Jingsong; Bi, Xiaotao T.

Here, three types of wood pellets samples, including two types of commercial pellets and one type of lab-made control pellets were torrefied in a fixed bed unit to study the effect of thermal pretreatment on the quality of wood pellets. The quality of wood pellets was mainly characterized by the pellet density, bulk density, higher heating value, Meyer hardness, saturated moisture uptake, volumetric energy density, and energy yield. Results showed that torrefaction significantly decreased the pellet density, hardness, volumetric energy density, and energy yield. The higher heating value increased and the saturated moisture content decreased after torrefaction. In view ofmore » the lower density, lower hardness, lower volumetric energy density, and energy yield of torrefied pellets, it is recommended that biomass should be torrefied and then compressed to make strong pellets of high hydrophobicity and volumetric energy density.« less

Effects of thermal treatment on energy density and hardness of torrefied wood pellets

DOE PAGES

Peng, Jianghong; Wang, Jingsong; Bi, Xiaotao T.; ...

2014-09-27

Here, three types of wood pellets samples, including two types of commercial pellets and one type of lab-made control pellets were torrefied in a fixed bed unit to study the effect of thermal pretreatment on the quality of wood pellets. The quality of wood pellets was mainly characterized by the pellet density, bulk density, higher heating value, Meyer hardness, saturated moisture uptake, volumetric energy density, and energy yield. Results showed that torrefaction significantly decreased the pellet density, hardness, volumetric energy density, and energy yield. The higher heating value increased and the saturated moisture content decreased after torrefaction. In view ofmore » the lower density, lower hardness, lower volumetric energy density, and energy yield of torrefied pellets, it is recommended that biomass should be torrefied and then compressed to make strong pellets of high hydrophobicity and volumetric energy density.« less

PEDOT as a Flexible Organic Electrode for a Thin Film Acoustic Energy Harvester.

PubMed

Kim, Younghoon; Na, Jongbeom; Park, Chihyun; Shin, Haijin; Kim, Eunkyoung

2015-08-05

An efficient thin film acoustic energy harvester was explored using flexible poly(3,4-ethylene dioxythiophene) (PEDOT) films as electrodes in an all-organic triboelectric generator (AO-TEG). A thin film AO-TEG structured as PEDOT/Kapton//PET/PEDOT was prepared by the solution casting polymerization(SCP) on the dielectric polymer films. As-prepared AO-TEG showed high flexibility and durability due to the strong adhesion between the electrodes and the dielectric polymer. The short-circuit current density (Jsc), open-circuit voltage (Voc), and maximum power density (Pw) reached 50 mA/m(2), 700 V, and 12.9 W/m(2) respectively. The output current density decreased with the increase in the electrode resistance (Re), but the energy loss in the organic electrodes was negligible. The AO-TEG could light up 180 LEDs instantaneously upon touching of the AO-TEG with a palm (∼120 N). With the flexible structure, the AO-TEG was worn as clothes and generated electricity to light LEDs upon regular human movement. Furthermore, the AO-TEG was applicable as a thin film acoustic energy harvester, which used music to generate electricity enough for powering of 5 LEDs. An AO-TEG with a PEDOT electrode (Re = 200 Ω) showed instantaneous peak-to-peak voltage generation of 11 V under a sound pressure level (SPL) of 90-100 dB. The harvested acoustic energy through the AO-TEG was 350 μJ from the 4 min playing of the same single song. This is the first demonstration of a flexible triboelectric generator (TEG) using an organic electrode for harvesting acoustic energy from ambient environment.

Large Energy Density, Excellent Thermal Stability, and High Cycling Endurance of Lead-Free BaZr0.2Ti0.8O3 Film Capacitors.

PubMed

Sun, Zixiong; Ma, Chunrui; Wang, Xi; Liu, Ming; Lu, Lu; Wu, Ming; Lou, Xiaojie; Wang, Hong; Jia, Chun-Lin

2017-05-24

A large energy storage density (ESD) of 30.4 J/cm 3 and high energy efficiency of 81.7% under an electrical field of 3 MV/cm was achieved at room temperature by the fabrication of environmentally friendly lead-free BaZr 0.2 Ti 0.8 O 3 epitaxial thin films on Nb-doped SrTiO 3 (001) substrates by using a radio-frequency magnetron sputtering system. Moreover, the BZT film capacitors exhibit great thermal stability of the ESD from 16.8 J/cm 3 to 14.0 J/cm 3 with efficiency of beyond 67.4% and high fatigue endurance (up to 10 6 cycles) in a wide temperature range from room temperature to 125 °C. Compared to other BaTiO 3 -based energy storage capacitor materials and even Pb-based systems, BaZr 0.2 Ti 0.8 O 3 thin film capacitors show either high ESD or great energy efficiency. All of these excellent results revealed that the BaZr 0.2 Ti 0.8 O 3 film capacitors have huge potential in the application of modern electronics, such as locomotive and pulse power, in harsh working environments.

Manufacturing and testing of a magnetically suspended composite flywheel energy storage system

NASA Technical Reports Server (NTRS)

Wells, Stephen; Pang, Da-Chen

1994-01-01

This paper presents the work performed to develop a multiring composite material flywheel and improvements of a magnetically suspended energy storage system. The flywheel is constructed of filament would graphite/epoxy and is interference assembled for better stress distribution to obtain higher speeds. The stationary stack in the center of the disk supports the flywheel with two magnetic bearings and provides power transfer to the flywheel with a motor/generator. The system operates under a 10(exp -4) torr environment and has been demonstrated to 20,000 rpm with a total stored energy of 15.9 Wh. When this flywheel cycles between its design speeds (45,000 to 90,000 rpm), it will deliver 242 Wh and have a usable specific energy density of 42.6 Wh/kg.

Using Passive Sensing to Estimate Relative Energy Expenditure for Eldercare Monitoring

PubMed Central

2012-01-01

This paper describes ongoing work in analyzing sensor data logged in the homes of seniors. An estimation of relative energy expenditure is computed using motion density from passive infrared motion sensors mounted in the environment. We introduce a new algorithm for detecting visitors in the home using motion sensor data and a set of fuzzy rules. The visitor algorithm, as well as a previous algorithm for identifying time-away-from-home (TAFH), are used to filter the logged motion sensor data. Thus, the energy expenditure estimate uses data collected only when the resident is home alone. Case studies are included from TigerPlace, an Aging in Place community, to illustrate how the relative energy expenditure estimate can be used to track health conditions over time. PMID:25266777

Multi-service highly sensitive rectifier for enhanced RF energy scavenging.

PubMed

Shariati, Negin; Rowe, Wayne S T; Scott, James R; Ghorbani, Kamran

2015-05-07

Due to the growing implications of energy costs and carbon footprints, the need to adopt inexpensive, green energy harvesting strategies are of paramount importance for the long-term conservation of the environment and the global economy. To address this, the feasibility of harvesting low power density ambient RF energy simultaneously from multiple sources is examined. A high efficiency multi-resonant rectifier is proposed, which operates at two frequency bands (478-496 and 852-869 MHz) and exhibits favorable impedance matching over a broad input power range (-40 to -10 dBm). Simulation and experimental results of input reflection coefficient and rectified output power are in excellent agreement, demonstrating the usefulness of this innovative low-power rectification technique. Measurement results indicate an effective efficiency of 54.3%, and an output DC voltage of 772.8 mV is achieved for a multi-tone input power of -10 dBm. Furthermore, the measured output DC power from harvesting RF energy from multiple services concurrently exhibits a 3.14 and 7.24 fold increase over single frequency rectification at 490 and 860 MHz respectively. Therefore, the proposed multi-service highly sensitive rectifier is a promising technique for providing a sustainable energy source for low power applications in urban environments.

Design of wearable hybrid generator for harvesting heat energy from human body depending on physiological activity

NASA Astrophysics Data System (ADS)

Kim, Myoung-Soo; Kim, Min-Ki; Kim, Kyongtae; Kim, Yong-Jun

2017-09-01

We developed a prototype of a wearable hybrid generator (WHG) that is used for harvesting the heat energy of the human body. This WHG is constructed by integrating a thermoelectric generator (TEG) in a circular mesh polyester knit fabric, circular-shaped pyroelectric generator (PEG), and quick sweat-pickup/dry-fabric. The fabric packaging enables the TEG part of the WHG to generate energy steadily while maintaining a temperature difference in extreme temperature environments. Moreover, when the body sweats, the evaporation heat of the sweat leads to thermal fluctuations in the WHG. This phenomenon further leads to an increase in the output power of the WHG. These characteristics of the WHG make it possible to produce electrical energy steadily without reduction in the conversion efficiency, as both TEG and PEG use the same energy source of the human skin and the ambient temperature. Under a temperature difference of ˜6.5 °C and temperature change rate of ˜0.62 °C s-1, the output power and output power density of the WHG, respectively, are ˜4.5 nW and ˜1.5 μW m-2. Our hybrid approach will provide a framework to enhance the output power of the wearable generators that harvest heat energy from human body in various environments.

Multi-Service Highly Sensitive Rectifier for Enhanced RF Energy Scavenging

PubMed Central

Shariati, Negin; Rowe, Wayne S. T.; Scott, James R.; Ghorbani, Kamran

2015-01-01

Due to the growing implications of energy costs and carbon footprints, the need to adopt inexpensive, green energy harvesting strategies are of paramount importance for the long-term conservation of the environment and the global economy. To address this, the feasibility of harvesting low power density ambient RF energy simultaneously from multiple sources is examined. A high efficiency multi-resonant rectifier is proposed, which operates at two frequency bands (478–496 and 852–869 MHz) and exhibits favorable impedance matching over a broad input power range (−40 to −10 dBm). Simulation and experimental results of input reflection coefficient and rectified output power are in excellent agreement, demonstrating the usefulness of this innovative low-power rectification technique. Measurement results indicate an effective efficiency of 54.3%, and an output DC voltage of 772.8 mV is achieved for a multi-tone input power of −10 dBm. Furthermore, the measured output DC power from harvesting RF energy from multiple services concurrently exhibits a 3.14 and 7.24 fold increase over single frequency rectification at 490 and 860 MHz respectively. Therefore, the proposed multi-service highly sensitive rectifier is a promising technique for providing a sustainable energy source for low power applications in urban environments. PMID:25951137

Reduced graphene oxide hydrogels deposited in nickel foam for supercapacitor applications: Toward high volumetric capacitance

DOE PAGES

Pham, Viet Hung; Dickerson, James H.

2016-02-21

Graphene hydrogels have been considered as ideal materials for high-performance supercapacitors. However, their low volumetric capacitance significantly limits its real application. In this study, we report an environment-friendly and scalable method to prepare high packing density, electrochemically reduced graphene oxide hydrogels (ERGO) for supercapacitor application by the electrophoretic deposition of graphene oxide onto nickel foam, followed by the electrochemical reduction and hydraulic compression of the deposited materials. The as-prepared ERGO on nickel foam was hydraulic compressed up to 20 tons, resulting in an increase of the packing density of ERGO from 0.0098 to 1.32 g cm –3. Consequently, the volumetricmore » capacitance and volumetric energy density of ERGOs greatly increased from 1.58 F cm –3 and 0.053 Wh cm –3 (as-prepared ERGO) to 176.5 F cm –3 and 6.02 Wh cm –3 (ERGO compressed at 20 tons), respectively. The ERGOs also exhibited long-term electrochemical stability with a capacitance retention in the range of approximately 79–90% after 10 000 cycles. Lastly, we believe that these high packing density ERGOs are promising for real-world energy storage devices for which scalable, cost-effective manufacturing is of significance and for which space constraints are paramount.« less

Reduced graphene oxide hydrogels deposited in nickel foam for supercapacitor applications: Toward high volumetric capacitance

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

Pham, Viet Hung; Dickerson, James H.

Graphene hydrogels have been considered as ideal materials for high-performance supercapacitors. However, their low volumetric capacitance significantly limits its real application. In this study, we report an environment-friendly and scalable method to prepare high packing density, electrochemically reduced graphene oxide hydrogels (ERGO) for supercapacitor application by the electrophoretic deposition of graphene oxide onto nickel foam, followed by the electrochemical reduction and hydraulic compression of the deposited materials. The as-prepared ERGO on nickel foam was hydraulic compressed up to 20 tons, resulting in an increase of the packing density of ERGO from 0.0098 to 1.32 g cm –3. Consequently, the volumetricmore » capacitance and volumetric energy density of ERGOs greatly increased from 1.58 F cm –3 and 0.053 Wh cm –3 (as-prepared ERGO) to 176.5 F cm –3 and 6.02 Wh cm –3 (ERGO compressed at 20 tons), respectively. The ERGOs also exhibited long-term electrochemical stability with a capacitance retention in the range of approximately 79–90% after 10 000 cycles. Lastly, we believe that these high packing density ERGOs are promising for real-world energy storage devices for which scalable, cost-effective manufacturing is of significance and for which space constraints are paramount.« less

Polarization of the prompt gamma-ray emission from the gamma-ray burst of 6 December 2002.

PubMed

Coburn, Wayne; Boggs, Steven E

2003-05-22

Observations of the afterglows of gamma-ray bursts (GRBs) have revealed that they lie at cosmological distances, and so correspond to the release of an enormous amount of energy. The nature of the central engine that powers these events and the prompt gamma-ray emission mechanism itself remain enigmatic because, once a relativistic fireball is created, the physics of the afterglow is insensitive to the nature of the progenitor. Here we report the discovery of linear polarization in the prompt gamma-ray emission from GRB021206, which indicates that it is synchrotron emission from relativistic electrons in a strong magnetic field. The polarization is at the theoretical maximum, which requires a uniform, large-scale magnetic field over the gamma-ray emission region. A large-scale magnetic field constrains possible progenitors to those either having or producing organized fields. We suggest that the large magnetic energy densities in the progenitor environment (comparable to the kinetic energy densities of the fireball), combined with the large-scale structure of the field, indicate that magnetic fields drive the GRB explosion.

Vertically Aligned Carbon Nanotube Arrays as Efficient Supports for Faradaic Capacitive Electrodes

NASA Astrophysics Data System (ADS)

Oguntoye, Moses; Holleran, Mary-Kate; Roberts, Katherine; Pesika, Noshir

Supercapacitors are notable for their ability to deliver energy at higher power (compared to batteries) and store energy at higher density (compared to capacitors) as well as exhibit a long cycle life. In our efforts to further the development of supercapacitors, our focus is on using vertically aligned carbon nanotubes (VACNT) as supports for faradaic capacitive electrode materials. The objective is to develop electrodes functioning in an inexpensive aqueous environment with small potential windows, that store energy at a higher density than carbon materials alone. We describe the different approaches explored to overcome the challenges of non-uniform deposition, poor wetting and array collapse. Materials that are electrochemically anchored to VACNT supports include NiCo2O4, VOx, Fe2O3 and Co-Mn mixed oxides. In each case, the specific capacitance obtained using the VACNT arrays as supports is significantly more than that obtained by direct deposition onto current collectors or by using VACNT alone. The ease of VACNT growth and the degree of coating control achievable using electrodeposition means there is much potential in exploring them as supports for capacitive electrode materials.

Aluminum/vacuum multilayer configuration for spatial high-energy electron shielding via electron return effects induced by magnetic field.

PubMed

Chen, Tuo; Tang, Xiaobin; Chen, Feida; Ni, Minxuan; Huang, Hai; Zhang, Yun; Chen, Da

2017-06-26

Radiation shielding of high-energy electrons is critical for successful space missions. However, conventional passive shielding systems exhibit several limitations, such as heavy configuration, poor shielding ability, and strong secondary bremsstrahlung radiation. In this work, an aluminum/vacuum multilayer structure was proposed based on the electron return effects induced by magnetic field. The shielding property of several configurations was evaluated by using the Monte Carlo method. Results showed that multilayer systems presented improved shielding ability to electrons, and less secondary x-ray transmissions than those of conventional systems. Moreover, the influences of magnetic flux density and number of layers on the shielding property of multilayer systems were investigated using a female Chinese hybrid reference phantom based on cumulative dose. In the case of two aluminum layers, the cumulative dose in a phantom gradually decreased with increasing magnetic flux density. The maximum decline rate was found within 0.4-1 Tesla. With increasing layers of configuration, the cumulative dose decreased and the shielding ability improved. This research provides effective shielding measures for future space radiation protection in high-energy electron environments.

Particle energization in magnetic reconnection in high-energy-density plasmas

NASA Astrophysics Data System (ADS)

Deng, W.; Fox, W.; Bhattacharjee, A.

2014-10-01

Significant particle energization is inferred to occur in many astrophysical environments and magnetic reconnection has been proposed to be the driver in many cases. Recent observation of magnetic reconnection in high-energy-density (HED) plasmas on the Vulcan, Omega and Shenguang laser facilities has opened up a new regime of reconnection study of great interest to laboratory and plasma astrophysics. In these experiments, plasma bubbles, excited by laser shots on solid targets and carrying magnetic fields, expand into one another, squeezing the opposite magnetic fields together to drive reconnection. 2D particle-in-cell (PIC) simulations have been performed to study the particle energization in such experiments. Two energization mechanisms have been identified. The first is a Fermi acceleration process between the expanding plasma bubbles, wherein the electromagnetic fields of the expanding plasma bounce particles, acting as moving walls. Particles can gain significant energy through multiple bounces between the bubbles. The second mechanism is a subsequent direct acceleration by electric field at the reconnection X-line when the bubbles collide into each other and drive reconnection.

High energy density capacitors for vacuum operation with a pulsed plasma load

NASA Technical Reports Server (NTRS)

Guman, W. J.

1976-01-01

Results of the effort of designing, fabricating, and testing of a 40 joules/lb (88.2 joules/Kg) high voltage energy storage capacitor suitable for operating a pulsed plasma thruster in a vacuum environment for millions of pulses are presented. Using vacuum brazing and heli-arc welding techniques followed by vacuum and high pressure helium leak tests it was possible to produce a hermetically sealed relatively light weight enclosure for the dielectric system. An energy density of 40 joules/lb was realized with a KF-polyvinylidene fluoride dielectric system. One capacitor was D.C. life tested at 4 KV (107.8 joules/lb) for 2,000 hours before it failed. Another exceeded 2,670 hours without failure at 38.3 joules/lb. Pulse life testing in a vacuum exceeded 300,000 discharges with testing still in progress. The D.C. life test data shows a small decrease in capacitance and an increase in dissipation factor with time. Heat transfer from the load to the capacitor must also be considered besides the self-heat generated by the capacitor.

Lithium-Ion Performance and Abuse Evaluation Using Lithium Technologies 9Ah cell

NASA Technical Reports Server (NTRS)

Hall, Albert Daniel; Jeevarajan, Judith A.

2006-01-01

Lithium-ion batteries in a pouch form offer high energy density and safety in their designs and more recently they are offering performance at higher rates. Lithium Technologies 9Ah high-power pouch cells were studied at different rates, thermal environments, under vacuum and several different conditions of abuse including overcharge, over-discharge and external short circuit. Results of this study will be presented.

Biomimicking of a Swim Bladder and Its Application as a Mini-Generator.

PubMed

Song, Mengmeng; Cheng, Mengjiao; Xiao, Meng; Zhang, Lina; Ju, Guannan; Shi, Feng

2017-02-01

A model fish with a man-made swim bladder achieves fast vertical motions based on density adjustments in a pressure-responsive way. When exposed to a magnetic field, a mini-generator is achieved by harvesting energy from the environment, working with pressure differences in the blood-pressure range and at the frequency of a beating heart. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Are energy-dense foods really cheaper? Reexamining the relation between food price and energy density.

PubMed

Lipsky, Leah M

2009-11-01

The inverse relation between energy density (kcal/g) and energy cost (price/kcal) has been interpreted to suggest that produce (fruit, vegetables) is more expensive than snacks (cookies, chips). The objective of this study was to show the methodologic weakness of comparing energy density with energy cost. The relation between energy density and energy cost was replicated in a random-number data set. Additionally, observational data were collected for produce and snacks from an online supermarket. Variables included total energy (kcal), total weight (g), total number of servings, serving size (g/serving), and energy density (kcal/g). Price measures included energy cost ($/kcal), total price ($), unit price ($/g), and serving price ($/serving). Two-tailed t tests were used to compare price measures by food category. Relations between energy density and price measures within food categories were examined with the use of Spearman rank correlation analysis. The relation between energy density and energy cost was shown to be driven by the algebraic properties of these variables. Food category was strongly correlated with both energy density and food price measures. Energy cost was higher for produce than for snacks. However, total price and unit price were lower for produce. Serving price and serving size were greater for produce than for snacks. Within food categories, energy density was uncorrelated with most measures of food price, except for a weak positive correlation with serving price within the produce category. The findings suggest the relation between energy density and food price is confounded by food category and depends on which measure of price is used.

Search for Thermal X-ray Features from the Crab nebula with Hitomi Soft X-ray Spectrometer

NASA Astrophysics Data System (ADS)

Tsujimoto, M.; Mori, K.; Lee, S.; Yamaguchi, H.; Tominaga, N.; Moriya, T.; Sato, T.; Bamba, A.

2017-10-01

The Crab nebula originates from a core-collapse SN in 1054. It has an anomalously low observed ejecta mass for a Fe-core collapse SN. Intensive searches were made for an undetected massive shell to solve this discrepancy. An alternative idea is that the SN1054 is an electron-capture (EC) explosion with a lower explosion energy than Fe-core collapse SNe. In the X-rays, imaging searches were performed for the plasma emission from the shell in the Crab outskirts. However, the extreme brightness hampers access to its vicinity. We used spectroscopic technique using the X-ray micro-calorimeter onboard Hitomi. We searched for the emission or absorption features by the thermal plasma and set a new limit. We re-evaluated the existing data to claim that the X-ray plasma mass is < 1 M_{⊙} for a wide range of assumed parameters. We further performed hydrodynamic simulation for two SN models (Fe core versus EC) under two environments (uniform ISM versus progenitor wind). We found that the observed mass limit can be compatible with both SN models if the environment has a low density of <0.03 cm^{-3} (Fe core) or <0.1 cm^{-3} (EC) for the uniform density, or <10^{14} g cm^{-1} for the wind density parameter for the wind environment.

Differential interferometry for measurement of density fluctuations and fluctuation-induced transport (invited)

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

Lin, L.; Ding, W. X.; Brower, D. L.

2010-10-15

Differential interferometry employs two parallel laser beams with a small spatial offset (less than beam width) and frequency difference (1-2 MHz) using common optics and a single mixer for a heterodyne detection. The differential approach allows measurement of the electron density gradient, its fluctuations, as well as the equilibrium density distribution. This novel interferometry technique is immune to fringe skip errors and is particularly useful in harsh plasma environments. Accurate calibration of the beam spatial offset, accomplished by use of a rotating dielectric wedge, is required to enable broad application of this approach. Differential interferometry has been successfully used onmore » the Madison Symmetric Torus reversed-field pinch plasma to directly measure fluctuation-induced transport along with equilibrium density profile evolution during pellet injection. In addition, by combining differential and conventional interferometry, both linear and nonlinear terms of the electron density fluctuation energy equation can be determined, thereby allowing quantitative investigation of the origin of the density fluctuations. The concept, calibration, and application of differential interferometry are presented.« less

Amorphous and liquid samples structure and density measurements at high pressure - high temperature using diffraction and imaging techniques

NASA Astrophysics Data System (ADS)

Guignot, N.; King, A.; Clark, A. N.; Perrillat, J. P.; Boulard, E.; Morard, G.; Deslandes, J. P.; Itié, J. P.; Ritter, X.; Sanchez-Valle, C.

2016-12-01

Determination of the density and structure of liquids such as iron alloys, silicates and carbonates is a key to understand deep Earth structure and dynamics. X-ray diffraction provided by large synchrotron facilities gives excellent results as long as the signal scattered from the sample can be isolated from its environment. Different techniques already exist; we present here the implementation and the first results given by the combined angle- and energy-dispersive structural analysis and refinement (CAESAR) technique introduced by Wang et al. in 2004, that has never been used in this context. It has several advantages in the study of liquids: 1/ the standard energy-dispersive technique (EDX), fast and compatible with large multi-anvil presses frames, is used for fast analysis free of signal pollution from the sample environment 2/ some limitations of the EDX technique (homogeneity of the sample, low resolution) are irrelevant in the case of liquid signals, others (wrong intensities, escape peaks artifacts, background subtraction) are solved by the CAESAR technique 3/ high Q data (up to 15 A-1 and more) can be obtained in a few hours (usually less than 2). We present here the facilities available on the PSICHE beamline (SOLEIL synchrotron, France) and a few results obtained using a Paris-Edinburgh (PE) press and a 1200 tons load capacity multi-anvil press with a (100) DIA compression module. X-ray microtomography, used in conjunction with a PE press featuring rotating anvils (RotoPEc, Philippe et al., 2013) is also very effective, by simply measuring the 3D volume of glass or liquid spheres at HPHT, thus providing density. This can be done in conjunction with the CAESAR technique and we illustrate this point. Finally, absorption profiles can be obtained via imaging techniques, providing another independent way to measure the density of these materials. References Y. Wang et al., A new technique for angle-dispersive powder diffraction using an energy-dispersive setup and synchrotron radiation (2004), J. Appl. Cryst. (2004). 37, 947-956 J. Philippe, Y. Le Godec, F. Bergame et M. Morand, Patent INPI 11 62335 (2013)

Reducing the energy density of an entrée decreases children's energy intake at lunch.

PubMed

Leahy, Kathleen E; Birch, Leann L; Rolls, Barbara J

2008-01-01

Strategies need to be developed to reduce preschool children's energy intake. To test the effect of reducing the energy density of an entrée on children's ad libitum energy intake. Subjects were 2- to 5-year-old children (37 boys and 40 girls) in a university day-care facility. In this within-subjects crossover study, children were served a test lunch once per week for 6 weeks. Two versions of a macaroni and cheese entrée were formulated to differ in energy density while maintaining similar palatability. Each version was served to children three times. The higher-energy-density entrée had 2.0 kcal/g and the other entrée was 30% lower in energy density. Lunch, consumed ad libitum, also included broccoli, applesauce, and milk. Food intake and energy intake were measured. A mixed linear model tested effect of energy density of the entrée on food intake and energy intake. Results are reported as mean+/-standard error. Decreasing the energy density of the entrée by 30% significantly (P<0.0001) reduced children's energy intake from the entrée by 25% (72.3+/-8.3 kcal) and total lunch energy intake by 18% (71.8+/-7.9 kcal). Children consumed significantly more of the lower-energy-density entrée (10.1+/-4.2 g; P<0.05). Children's sex-specific body mass index-for-age percentiles did not affect the relationship between energy density of the entrée and children's intakes. Decreasing the energy density of a lunch entrée resulted in a reduction in children's energy intake from the entrée and from the total meal. Reducing the energy density of foods may be an effective strategy to moderate children's energy intake.

Templated assembly of photoswitches significantly increases the energy-storage capacity of solar thermal fuels.

PubMed

Kucharski, Timothy J; Ferralis, Nicola; Kolpak, Alexie M; Zheng, Jennie O; Nocera, Daniel G; Grossman, Jeffrey C

2014-05-01

Large-scale utilization of solar-energy resources will require considerable advances in energy-storage technologies to meet ever-increasing global energy demands. Other than liquid fuels, existing energy-storage materials do not provide the requisite combination of high energy density, high stability, easy handling, transportability and low cost. New hybrid solar thermal fuels, composed of photoswitchable molecules on rigid, low-mass nanostructures, transcend the physical limitations of molecular solar thermal fuels by introducing local sterically constrained environments in which interactions between chromophores can be tuned. We demonstrate this principle of a hybrid solar thermal fuel using azobenzene-functionalized carbon nanotubes. We show that, on composite bundling, the amount of energy stored per azobenzene more than doubles from 58 to 120 kJ mol(-1), and the material also maintains robust cyclability and stability. Our results demonstrate that solar thermal fuels composed of molecule-nanostructure hybrids can exhibit significantly enhanced energy-storage capabilities through the generation of template-enforced steric strain.

Electronic, magnetic, and magnetocrystalline anisotropy properties of light lanthanides

DOE PAGES

Hackett, Timothy A.; Baldwin, D. J.; Paudyal, Durga

2017-05-17

Theoretical understanding of interactions between localized and mobile electrons and the crystal environment in light lanthanides is important because of their key role in much needed magnetic anisotropy in permanent magnet materials that have a great impact in automobile and wind turbine applications. We report electronic, magnetic, and magnetocrystalline properties of these basic light lanthanide elements studied from advanced density functional theory (DFT) calculations. We find that the inclusion of onsite 4f electron correlation and spin orbit coupling within the full-potential band structure is needed to understand the unique magnetocrystalline properties of these light lanthanides. The onsite electron correlation, spinmore » orbit coupling, and full potential for the asphericity of charge densities must be taken into account for the proper treatment of 4f states. We find the variation of total energy as a function of lattice constants that indicate multiple structural phases in Ce contrasting to a single stable structure obtained in other light lanthanides. The 4f orbital magnetic moments are partially quenched as a result of crystalline electric field splitting that leads to magnetocrystalline anisotropy. The charge density plots have similar asphericity and environment in Pr and Nd indicating similar magnetic anisotropy. However, Ce and Sm show completely different asphericity and environment as both orbital moments are significantly quenched. In addition, the Fermi surface structures exemplified in Nd indicate structural stability and unravel a cause of anisotropy. The calculated magnetocrystalline anisotropy energy (MAE) reveals competing c-axis and in-plane anisotropies, and also predicts possibilities of unusual structural deformations in light lanthanides. The uniaxial magnetic anisotropy is obtained in the double hexagonal closed pack structures of the most of the light lanthanides, however, the anisotropy is reduced or turned to planar in the low symmetry structures. As a result, through crystal field calculations we also illustrate the crystal field ground state 4f multiplets of light lanthanides.« less

Electronic, magnetic, and magnetocrystalline anisotropy properties of light lanthanides

NASA Astrophysics Data System (ADS)

Hackett, Timothy A.; Baldwin, D. J.; Paudyal, D.

2017-11-01

Theoretical understanding of interactions between localized and mobile electrons and the crystal environment in light lanthanides is important because of their key role in much needed magnetic anisotropy in permanent magnet materials that have a great impact in automobile and wind turbine applications. We report electronic, magnetic, and magnetocrystalline properties of these basic light lanthanide elements studied from advanced density functional theory (DFT) calculations. We find that the inclusion of onsite 4f electron correlation and spin orbit coupling within the full-potential band structure is needed to understand the unique magnetocrystalline properties of these light lanthanides. The onsite electron correlation, spin orbit coupling, and full potential for the asphericity of charge densities must be taken into account for the proper treatment of 4f states. We find the variation of total energy as a function of lattice constants that indicate multiple structural phases in Ce contrasting to a single stable structure obtained in other light lanthanides. The 4f orbital magnetic moments are partially quenched as a result of crystalline electric field splitting that leads to magnetocrystalline anisotropy. The charge density plots have similar asphericity and environment in Pr and Nd indicating similar magnetic anisotropy. However, Ce and Sm show completely different asphericity and environment as both orbital moments are significantly quenched. In addition, the Fermi surface structures exemplified in Nd indicate structural stability and unravel a cause of anisotropy. The calculated magnetocrystalline anisotropy energy (MAE) reveals competing c-axis and in-plane anisotropies, and also predicts possibilities of unusual structural deformations in light lanthanides. The uniaxial magnetic anisotropy is obtained in the double hexagonal closed pack structures of the most of the light lanthanides, however, the anisotropy is reduced or turned to planar in the low symmetry structures. Through crystal field calculations we also illustrate the crystal field ground state 4f multiplets of light lanthanides.

Electronic, magnetic, and magnetocrystalline anisotropy properties of light lanthanides

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

Hackett, Timothy A.; Baldwin, D. J.; Paudyal, Durga

Theoretical understanding of interactions between localized and mobile electrons and the crystal environment in light lanthanides is important because of their key role in much needed magnetic anisotropy in permanent magnet materials that have a great impact in automobile and wind turbine applications. We report electronic, magnetic, and magnetocrystalline properties of these basic light lanthanide elements studied from advanced density functional theory (DFT) calculations. We find that the inclusion of onsite 4f electron correlation and spin orbit coupling within the full-potential band structure is needed to understand the unique magnetocrystalline properties of these light lanthanides. The onsite electron correlation, spinmore » orbit coupling, and full potential for the asphericity of charge densities must be taken into account for the proper treatment of 4f states. We find the variation of total energy as a function of lattice constants that indicate multiple structural phases in Ce contrasting to a single stable structure obtained in other light lanthanides. The 4f orbital magnetic moments are partially quenched as a result of crystalline electric field splitting that leads to magnetocrystalline anisotropy. The charge density plots have similar asphericity and environment in Pr and Nd indicating similar magnetic anisotropy. However, Ce and Sm show completely different asphericity and environment as both orbital moments are significantly quenched. In addition, the Fermi surface structures exemplified in Nd indicate structural stability and unravel a cause of anisotropy. The calculated magnetocrystalline anisotropy energy (MAE) reveals competing c-axis and in-plane anisotropies, and also predicts possibilities of unusual structural deformations in light lanthanides. The uniaxial magnetic anisotropy is obtained in the double hexagonal closed pack structures of the most of the light lanthanides, however, the anisotropy is reduced or turned to planar in the low symmetry structures. As a result, through crystal field calculations we also illustrate the crystal field ground state 4f multiplets of light lanthanides.« less

The energy density distribution of an ideal gas and Bernoulli’s equations

NASA Astrophysics Data System (ADS)

Santos, Leonardo S. F.

2018-05-01

This work discusses the energy density distribution in an ideal gas and the consequences of Bernoulli’s equation and the corresponding relation for compressible fluids. The aim of this work is to study how Bernoulli’s equation determines the energy flow in a fluid, although Bernoulli’s equation does not describe the energy density itself. The model from molecular dynamic considerations that describes an ideal gas at rest with uniform density is modified to explore the gas in motion with non-uniform density and gravitational effects. The difference between the component of the speed of a particle that is parallel to the gas speed and the gas speed itself is called ‘parallel random speed’. The pressure from the ‘parallel random speed’ is denominated as parallel pressure. The modified model predicts that the energy density is the sum of kinetic and potential gravitational energy densities plus two terms with static and parallel pressures. The application of Bernoulli’s equation and the corresponding relation for compressible fluids in the energy density expression has resulted in two new formulations. For incompressible and compressible gas, the energy density expressions are written as a function of stagnation, static and parallel pressures, without any dependence on kinetic or gravitational potential energy densities. These expressions of the energy density are the main contributions of this work. When the parallel pressure was uniform, the energy density distribution for incompressible approximation and compressible gas did not converge to zero for the limit of null static pressure. This result is rather unusual because the temperature tends to zero for null pressure. When the gas was considered incompressible and the parallel pressure was equal to static pressure, the energy density maintained this unusual behaviour with small pressures. If the parallel pressure was equal to static pressure, the energy density converged to zero for the limit of the null pressure only if the gas was compressible. Only the last situation describes an intuitive behaviour for an ideal gas.

Propulsion Physics Using the Chameleon Density Model

NASA Technical Reports Server (NTRS)

Robertson, Glen A.

2011-01-01

To grow as a space faring race, future spaceflight systems will require a new theory of propulsion. Specifically one that does not require mass ejection without limiting the high thrust necessary to accelerate within or beyond our solar system and return within a normal work period or lifetime. The Chameleon Density Model (CDM) is one such model that could provide new paths in propulsion toward this end. The CDM is based on Chameleon Cosmology a dark matter theory; introduced by Khrouy and Weltman in 2004. Chameleon as it is hidden within known physics, where the Chameleon field represents a scalar field within and about an object; even in the vacuum. The CDM relates to density changes in the Chameleon field, where the density changes are related to matter accelerations within and about an object. These density changes in turn change how an object couples to its environment. Whereby, thrust is achieved by causing a differential in the environmental coupling about an object. As a demonstration to show that the CDM fits within known propulsion physics, this paper uses the model to estimate the thrust from a solid rocket motor. Under the CDM, a solid rocket constitutes a two body system, i.e., the changing density of the rocket and the changing density in the nozzle arising from the accelerated mass. Whereby, the interactions between these systems cause a differential coupling to the local gravity environment of the earth. It is shown that the resulting differential in coupling produces a calculated value for the thrust near equivalent to the conventional thrust model used in Sutton and Ross, Rocket Propulsion Elements. Even though imbedded in the equations are the Universe energy scale factor, the reduced Planck mass and the Planck length, which relates the large Universe scale to the subatomic scale.

Quantum simulations of nuclei and nuclear pasta with the multiresolution adaptive numerical environment for scientific simulations

NASA Astrophysics Data System (ADS)

Sagert, I.; Fann, G. I.; Fattoyev, F. J.; Postnikov, S.; Horowitz, C. J.

2016-05-01

Background: Neutron star and supernova matter at densities just below the nuclear matter saturation density is expected to form a lattice of exotic shapes. These so-called nuclear pasta phases are caused by Coulomb frustration. Their elastic and transport properties are believed to play an important role for thermal and magnetic field evolution, rotation, and oscillation of neutron stars. Furthermore, they can impact neutrino opacities in core-collapse supernovae. Purpose: In this work, we present proof-of-principle three-dimensional (3D) Skyrme Hartree-Fock (SHF) simulations of nuclear pasta with the Multi-resolution ADaptive Numerical Environment for Scientific Simulations (MADNESS). Methods: We perform benchmark studies of 16O, 208Pb, and 238U nuclear ground states and calculate binding energies via 3D SHF simulations. Results are compared with experimentally measured binding energies as well as with theoretically predicted values from an established SHF code. The nuclear pasta simulation is initialized in the so-called waffle geometry as obtained by the Indiana University Molecular Dynamics (IUMD) code. The size of the unit cell is 24 fm with an average density of about ρ =0.05 fm-3 , proton fraction of Yp=0.3 , and temperature of T =0 MeV. Results: Our calculations reproduce the binding energies and shapes of light and heavy nuclei with different geometries. For the pasta simulation, we find that the final geometry is very similar to the initial waffle state. We compare calculations with and without spin-orbit forces. We find that while subtle differences are present, the pasta phase remains in the waffle geometry. Conclusions: Within the MADNESS framework, we can successfully perform calculations of inhomogeneous nuclear matter. By using pasta configurations from IUMD it is possible to explore different geometries and test the impact of self-consistent calculations on the latter.

Electronic energy density in chemical reaction systems

NASA Astrophysics Data System (ADS)

Tachibana, Akitomo

2001-08-01

The energy of chemical reaction is visualized in real space using the electronic energy density nE(r⃗) associated with the electron density n(r⃗). The electronic energy density nE(r⃗) is decomposed into the kinetic energy density nT(r⃗), the external potential energy density nV(r⃗), and the interelectron potential energy density nW(r⃗). Using the electronic energy density nE(r⃗) we can pick up any point in a chemical reaction system and find how the electronic energy E is assigned to the selected point. We can then integrate the electronic energy density nE(r⃗) in any region R surrounding the point and find out the regional electronic energy ER to the global E. The kinetic energy density nT(r⃗) is used to identify the intrinsic shape of the reactants, the electronic transition state, and the reaction products along the course of the chemical reaction coordinate. The intrinsic shape is identified with the electronic interface S that discriminates the region RD of the electronic drop from the region RA of the electronic atmosphere in the density distribution of the electron gas. If the R spans the whole space, then the integral gives the total E. The regional electronic energy ER in thermodynamic ensemble is realized in electrochemistry as the intrinsic Volta electric potential φR and the intrinsic Herring-Nichols work function ΦR. We have picked up first a hydrogen-like atom for which we have analytical exact expressions of the relativistic kinetic energy density nTM(r⃗) and its nonrelativistic version nT(r⃗). These expressions are valid for any excited bound states as well as the ground state. Second, we have selected the following five reaction systems and show the figures of the nT(r⃗) as well as the other energy densities along the intrinsic reaction coordinates: a protonation reaction to He, addition reactions of HF to C2H4 and C2H2, hydrogen abstraction reactions of NH3+ from HF and NH3. Valence electrons possess their unique delocalized drop region remote from those heavily localized drop regions adhered to core electrons. The kinetic energy density nT(r⃗) and the tension density τ⃗S(r⃗) can vividly demonstrate the formation of the chemical bond. Various basic chemical concepts in these chemical reaction systems have been clearly visualized in real three-dimensional space.

Muon radiography in Russia with emulsion technique. First experiments future perspectives

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

Aleksandrov, A. B.; Bagulya, A. V.; Chernyavsky, M. M.

Cosmic ray muon radiography is a novel technique for imaging the internal structures of massive objects. It exploits the capability of high energy muons from cosmic-rays in order to obtain a density map of investigated object and trying to guess information on the variation in the density distribution. Nuclear emulsions are tracking detectors well suited to be employed in this context since they have an excellent angular resolution (few mrad), they are cheap, compact and robust, easily transportable, able to work in harsh environments, and do not require power supply. This work presents the first successful results in the fieldmore » of muon radiography in Russia with nuclear emulsions.« less

Internal Charging

NASA Technical Reports Server (NTRS)

Minow, Joseph I.

2014-01-01

(1) High energy (>100keV) electrons penetrate spacecraft walls and accumulate in dielectrics or isolated conductors; (2) Threat environment is energetic electrons with sufficient flux to charge circuit boards, cable insulation, and ungrounded metal faster than charge can dissipate; (3) Accumulating charge density generates electric fields in excess of material breakdown strenght resulting in electrostatic discharge; and (4) System impact is material damage, discharge currents inside of spacecraft Faraday cage on or near critical circuitry, and RF noise.

ESTIMATION OF EFFECTIVE DOSE FROM EXTERNAL EXPOSURE DUE TO SHORT-LIVED NUCLIDES IN THE PREFECTURES SURROUNDING FUKUSHIMA.

PubMed

Miyatake, Hirokazu; Yoshizawa, Nobuaki; Suzuki, Gen

2018-05-11

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident resulted in a release of radionuclides into the environment. Since the accident, measurements of radiation in the environment such as air dose rate and deposition density of radionuclides have been performed by various organizations and universities. In particular, Japan Atomic Energy Agency (JAEA) has been performing observations of air dose rate using a car-borne survey system continuously over widespread areas. Based on the data measured by JAEA, we estimated effective dose from external exposure in the prefectures surrounding Fukushima. Since car-borne survey started a few months after the accident, the main contribution to measured data comes from 137Cs and 134Cs whose half-lives are relatively long. Using air dose rate of 137Cs and 134Cs and the ratio of deposition density of short-lived nuclides to that of 137Cs and 134Cs, we also estimated contributions to the effective dose from other short-lived nuclides.

Energy band alignment and electronic states of amorphous carbon surfaces in vacuo and in aqueous environment

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

Caro, Miguel A., E-mail: mcaroba@gmail.com; Department of Applied Physics, COMP Centre of Excellence in Computational Nanoscience, Aalto University, Espoo; Määttä, Jukka

2015-01-21

In this paper, we obtain the energy band positions of amorphous carbon (a–C) surfaces in vacuum and in aqueous environment. The calculations are performed using a combination of (i) classical molecular dynamics (MD), (ii) Kohn-Sham density functional theory with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional, and (iii) the screened-exchange hybrid functional of Heyd, Scuseria, and Ernzerhof (HSE). PBE allows an accurate generation of a-C and the evaluation of the local electrostatic potential in the a-C/water system, HSE yields an improved description of energetic positions which is critical in this case, and classical MD enables a computationally affordable description of water. Ourmore » explicit calculation shows that, both in vacuo and in aqueous environment, the a-C electronic states available in the region comprised between the H{sub 2}/H{sub 2}O and O{sub 2}/H{sub 2}O levels of water correspond to both occupied and unoccupied states within the a-C pseudogap region. These are localized states associated to sp{sup 2} sites in a-C. The band realignment induces a shift of approximately 300 meV of the a-C energy band positions with respect to the redox levels of water.« less

Dietary energy density: Applying behavioural science to weight management.

PubMed

Rolls, B J

2017-09-01

Studies conducted by behavioural scientists show that energy density (kcal/g) provides effective guidance for healthy food choices to control intake and promote satiety. Energy density depends upon a number of dietary components, especially water (0 kcal/g) and fat (9 kcal/g). Increasing the proportion of water or water-rich ingredients, such as vegetables or fruit, lowers a food's energy density. A number of studies show that when the energy density of the diet is reduced, both adults and children spontaneously decrease their ad libitum energy intake. Other studies show that consuming a large volume of a low-energy-dense food such as soup, salad, or fruit as a first course preload can enhance satiety and reduce overall energy intake at a meal. Current evidence suggests that energy density influences intake through a complex interplay of cognitive, sensory, gastrointestinal, hormonal and neural influences. Other studies that focus on practical applications show how the strategic incorporation of foods lower in energy density into the diet allows people to eat satisfying portions while improving dietary patterns. This review discusses studies that have led to greater understanding of the importance of energy density for food intake regulation and weight management.

High power density proton exchange membrane fuel cells

NASA Technical Reports Server (NTRS)

Murphy, Oliver J.; Hitchens, G. Duncan; Manko, David J.

1993-01-01

Proton exchange membrane (PEM) fuel cells use a perfluorosulfonic acid solid polymer film as an electrolyte which simplifies water and electrolyte management. Their thin electrolyte layers give efficient systems of low weight, and their materials of construction show extremely long laboratory lifetimes. Their high reliability and their suitability for use in a microgravity environment makes them particularly attractive as a substitute for batteries in satellites utilizing high-power, high energy-density electrochemical energy storage systems. In this investigation, the Dow experimental PEM (XUS-13204.10) and unsupported high platinum loading electrodes yielded very high power densities, of the order of 2.5 W cm(exp -2). A platinum black loading of 5 mg per cm(exp 2) was found to be optimum. On extending the three-dimensional reaction zone of fuel cell electrodes by impregnating solid polymer electrolyte into the electrode structures, Nafion was found to give better performance than the Dow experimental PEM. The depth of penetration of the solid polymer electrolyte into electrode structures was 50-70 percent of the thickness of the platinum-catalyzed active layer. However, the degree of platinum utilization was only 16.6 percent and the roughness factor of a typical electrode was 274.

Soybean Root-Derived Hierarchical Porous Carbon as Electrode Material for High-Performance Supercapacitors in Ionic Liquids.

PubMed

Guo, Nannan; Li, Min; Wang, Yong; Sun, Xingkai; Wang, Feng; Yang, Ru

2016-12-14

Soybeans are extensively cultivated worldwide as human food. However, large quantities of soybean roots (SRs), which possess an abundant three-dimensional (3D) structure, remain unused and produce enormous pressure on the environment. Here, 3D hierarchical porous carbon was prepared by the facile carbonization of SRs followed by chemical activation. The as-prepared material, possessing large specific surface area (2143 m 2 g -1 ), good electrical conductivity, and unique 3D hierarchical porosity, shows outstanding electrochemical performance as an electrode material for supercapacitors, such as a high capacitance (276 F g -1 at 0.5 A g -1 ), superior cycle stability (98% capacitance retention after 10,000 cycles at 5 A g -1 ), and good rate capability in a symmetric two-electrode supercapacitor in 6 M KOH. Furthermore, the maximum energy density of as-assembled symmetric supercapacitor can reach 100.5 Wh kg -1 in neat EMIM BF 4 . Moreover, a value of 40.7 Wh kg -1 is maintained at ultrahigh power density (63000 W kg -1 ). These results show that the as-assembled supercapacitor can simultaneously deliver superior energy and power density.

COULD COSMIC RAYS AFFECT INSTABILITIES IN THE TRANSITION LAYER OF NONRELATIVISTIC COLLISIONLESS SHOCKS?

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

Stroman, Thomas; Pohl, Martin; Niemiec, Jacek

2012-02-10

There is an observational correlation between astrophysical shocks and nonthermal particle distributions extending to high energies. As a first step toward investigating the possible feedback of these particles on the shock at the microscopic level, we perform particle-in-cell (PIC) simulations of a simplified environment consisting of uniform, interpenetrating plasmas, both with and without an additional population of cosmic rays. We vary the relative density of the counterstreaming plasmas, the strength of a homogeneous parallel magnetic field, and the energy density in cosmic rays. We compare the early development of the unstable spectrum for selected configurations without cosmic rays to themore » growth rates predicted from linear theory, for assurance that the system is well represented by the PIC technique. Within the parameter space explored, we do not detect an unambiguous signature of any cosmic-ray-induced effects on the microscopic instabilities that govern the formation of a shock. We demonstrate that an overly coarse distribution of energetic particles can artificially alter the statistical noise that produces the perturbative seeds of instabilities, and that such effects can be mitigated by increasing the density of computational particles.« less

The stability of DOTA-chelated radiopharmaceuticals within 225Ac decay pathway studied with density functional theory.

NASA Astrophysics Data System (ADS)

Karolak, Aleksandra; Khabibullin, Artem; Budzevich, Mikalai; Martinez, M.; Doliganski, Michael; McLaughlin, Mark; Woods, Lilia; Morse, David

Ligand structures encapsulating metal ions play a central role as contrast agents in Magnetic Resonance Imaging (MRI) or as agents delivering toxic cargo directly to tumor cells in targeted cancer therapy. The structural stability and interaction with solutions of such complexes are the key elements in understanding the foundation of delivery process. We present a comparative study for the 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelated to radioactive isotopes of 225Ac, 221Fr, 217At, 213Bi and a control 68Gd. Using density functional theory methods we investigate the structural stability of complexes for cancer therapy including binding energies, charge transfer, electron densities. The van der Waals interactions are included in the simulations to take into account weak dispersion forces present in such structures. Our results reveal that Ac-DOTA, Bi-DOTA and Gd-DOTA are the most stable complexes in the group. We also show that the water environment is a key ingredient for the structural coordination of the DOTA structures. Support from the US Department of Energy under Grant No. DE-FG02-06ER46297 is acknowledged.

Modeling and Simulation of Linear and Nonlinear MEMS Scale Electromagnetic Energy Harvesters for Random Vibration Environments

PubMed Central

Sassani, Farrokh

2014-01-01

The simulation results for electromagnetic energy harvesters (EMEHs) under broad band stationary Gaussian random excitations indicate the importance of both a high transformation factor and a high mechanical quality factor to achieve favourable mean power, mean square load voltage, and output spectral density. The optimum load is different for random vibrations and for sinusoidal vibration. Reducing the total damping ratio under band-limited random excitation yields a higher mean square load voltage. Reduced bandwidth resulting from decreased mechanical damping can be compensated by increasing the electrical damping (transformation factor) leading to a higher mean square load voltage and power. Nonlinear EMEHs with a Duffing spring and with linear plus cubic damping are modeled using the method of statistical linearization. These nonlinear EMEHs exhibit approximately linear behaviour under low levels of broadband stationary Gaussian random vibration; however, at higher levels of such excitation the central (resonant) frequency of the spectral density of the output voltage shifts due to the increased nonlinear stiffness and the bandwidth broadens slightly. Nonlinear EMEHs exhibit lower maximum output voltage and central frequency of the spectral density with nonlinear damping compared to linear damping. Stronger nonlinear damping yields broader bandwidths at stable resonant frequency. PMID:24605063

Influence of stocking density on growth, body composition and energy budget of Atlantic salmon Salmo salar L. in recirculating aquaculture systems

NASA Astrophysics Data System (ADS)

Liu, Baoliang; Liu, Ying; Liu, Ziyi; Qiu, Denggao; Sun, Guoxiang; Li, Xian

2014-09-01

Atlantic salmon Salmo salar were reared at four stocking densities—high density D 1 (final density ˜39 kg/m3), medium densities D 2 (˜29 kg/m3) and D 3 (˜19 kg/m3), and low density D 4 (˜12 kg/m3)—for 40 days to investigate the effect of stocking density on their growth performance, body composition and energy budgets. Stocking density did not significantly affect specific growth rate in terms of weight (SGRw) but did affect specific growth rate in terms of energy (SGRe). Stocking density significantly influenced the ration level (RLw and RLe), feed conversion ratio (FCRw and FCRe) and apparent digestibility rate (ADR). Ration level and FCRw tended to increase with increasing density. Fish at the highest density D 1 and lowest density D 4 showed lower FCRe and higher ADR than at medium densities. Stocking density significantly affected protein and energy contents of the body but did not affect its moisture, lipid, or ash contents. The expenditure of energy for metabolism in the low-density and high-density groups was lower than that in the medium-density groups. Stocking density affected energy utilization from the feces but had no effect on excretion rate. The greater energy allocation to growth at high density and low density may be attributed to reduced metabolic rate and increased apparent digestibility rate. These findings provide information that will assist selection of suitable stocking densities in the Atlantic-salmon-farming industry.

Chemistry in interstellar space. [environment characteristics influencing reaction dynamics

NASA Technical Reports Server (NTRS)

Donn, B.

1973-01-01

The particular characteristics of chemistry in interstellar space are determined by the unique environmental conditions involved. Interstellar matter is present at extremely low densities. Large deviations from thermodynamic equilibrium are, therefore, to be expected. A relatively intense ultraviolet radiation is present in many regions. The temperatures are in the range from 5 to 200 K. Data concerning the inhibiting effect of small activation energies in interstellar clouds are presented in a table. A summary of measured activation energies or barrier heights for exothermic exchange reactions is also provided. Problems of molecule formation are discussed, taking into account gas phase reactions and surface catalyzed processes.

Dark energy fingerprints in the nonminimal Wu-Yang wormhole structure

NASA Astrophysics Data System (ADS)

Balakin, Alexander B.; Zayats, Alexei E.

2014-08-01

We discuss new exact solutions to nonminimally extended Einstein-Yang-Mills equations describing spherically symmetric static wormholes supported by the gauge field of the Wu-Yang type in a dark energy environment. We focus on the analysis of three types of exact solutions to the gravitational field equations. Solutions of the first type relate to the model, in which the dark energy is anisotropic; i.e., the radial and tangential pressures do not coincide. Solutions of the second type correspond to the isotropic pressure tensor; in particular, we discuss the exact solution, for which the dark energy is characterized by the equation of state for a string gas. Solutions of the third type describe the dark energy model with constant pressure and energy density. For the solutions of the third type, we consider in detail the problem of horizons and find constraints for the parameters of nonminimal coupling and for the constitutive parameters of the dark energy equation of state, which guarantee that the nonminimal wormholes are traversable.

A Radiation Dosimeter Concept for the Lunar Surface Environment

NASA Technical Reports Server (NTRS)

Adams, James H.; Christl, Mark J.; Watts, John; Kuznetsov, Eugeny N.; Parnell, Thomas A.; Pendleton, Geoff N.

2007-01-01

A novel silicon detector configuration for radiation dose measurements in an environment where solar energetic particles are of most concern is described. The dosimeter would also measure the dose from galactic cosmic rays. In the lunar environment a large range in particle flux and ionization density must be measured and converted to dose equivalent. This could be accomplished with a thick (e.g. 2mm) silicon detector segmented into cubic volume elements "voxels" followed by a second, thin monolithic silicon detector. The electronics needed to implement this detector concept include analog signal processors (ASIC) and a field programmable gate array (FPGA) for data accumulation and conversion to linear energy transfer (LET) spectra and to dose-equivalent (Sievert). Currently available commercial ASIC's and FPGA's are suitable for implementing the analog and digital systems.

Accelerating atomic structure search with cluster regularization

NASA Astrophysics Data System (ADS)

Sørensen, K. H.; Jørgensen, M. S.; Bruix, A.; Hammer, B.

2018-06-01

We present a method for accelerating the global structure optimization of atomic compounds. The method is demonstrated to speed up the finding of the anatase TiO2(001)-(1 × 4) surface reconstruction within a density functional tight-binding theory framework using an evolutionary algorithm. As a key element of the method, we use unsupervised machine learning techniques to categorize atoms present in a diverse set of partially disordered surface structures into clusters of atoms having similar local atomic environments. Analysis of more than 1000 different structures shows that the total energy of the structures correlates with the summed distances of the atomic environments to their respective cluster centers in feature space, where the sum runs over all atoms in each structure. Our method is formulated as a gradient based minimization of this summed cluster distance for a given structure and alternates with a standard gradient based energy minimization. While the latter minimization ensures local relaxation within a given energy basin, the former enables escapes from meta-stable basins and hence increases the overall performance of the global optimization.

A hybrid electrochemical device based on a synergetic inner combination of Li ion battery and Li ion capacitor for energy storage.

PubMed

Zheng, Jun-Sheng; Zhang, Lei; Shellikeri, Annadanesh; Cao, Wanjun; Wu, Qiang; Zheng, Jim P

2017-02-07

Li ion battery (LIB) and electrochemical capacitor (EC) are considered as the most widely used energy storage systems (ESSs) because they can produce a high energy density or a high power density, but it is a huge challenge to achieve both the demands of a high energy density as well as a high power density on their own. A new hybrid Li ion capacitor (HyLIC), which combines the advantages of LIB and Li ion capacitor (LIC), is proposed. This device can successfully realize a potential match between LIB and LIC and can avoid the excessive depletion of electrolyte during the charge process. The galvanostatic charge-discharge cycling tests reveal that at low current, the HyLIC exhibits a high energy density, while at high current, it demonstrates a high power density. Ragone plot confirms that this device can make a synergetic balance between energy and power and achieve a highest energy density in the power density range of 80 to 300 W kg -1 . The cycle life test proves that HyLIC exhibits a good cycle life and an excellent coulombic efficiency. The present study shows that HyLIC, which is capable of achieving a high energy density, a long cycle life and an excellent power density, has the potential to achieve the winning combination of a high energy and power density.

A hybrid electrochemical device based on a synergetic inner combination of Li ion battery and Li ion capacitor for energy storage

PubMed Central

Zheng, Jun-Sheng; Zhang, Lei; Shellikeri, Annadanesh; Cao, Wanjun; Wu, Qiang; Zheng, Jim P.

2017-01-01

Li ion battery (LIB) and electrochemical capacitor (EC) are considered as the most widely used energy storage systems (ESSs) because they can produce a high energy density or a high power density, but it is a huge challenge to achieve both the demands of a high energy density as well as a high power density on their own. A new hybrid Li ion capacitor (HyLIC), which combines the advantages of LIB and Li ion capacitor (LIC), is proposed. This device can successfully realize a potential match between LIB and LIC and can avoid the excessive depletion of electrolyte during the charge process. The galvanostatic charge-discharge cycling tests reveal that at low current, the HyLIC exhibits a high energy density, while at high current, it demonstrates a high power density. Ragone plot confirms that this device can make a synergetic balance between energy and power and achieve a highest energy density in the power density range of 80 to 300 W kg−1. The cycle life test proves that HyLIC exhibits a good cycle life and an excellent coulombic efficiency. The present study shows that HyLIC, which is capable of achieving a high energy density, a long cycle life and an excellent power density, has the potential to achieve the winning combination of a high energy and power density. PMID:28169329

Near-Field Thermal Radiation for Solar Thermophotovoltaics and High Temperature Thermal Logic and Memory Applications

NASA Astrophysics Data System (ADS)

Elzouka, Mahmoud

This dissertation investigates Near-Field Thermal Radiation (NFTR) applied to MEMS-based concentrated solar thermophotovoltaics (STPV) energy conversion and thermal memory and logics. NFTR is the exchange of thermal radiation energy at nano/microscale; when separation between the hot and cold objects is less than dominant radiation wavelength (˜1 mum). NFTR is particularly of interest to the above applications due to its high rate of energy transfer, exceeding the blackbody limit by orders of magnitude, and its strong dependence on separation gap size, surface nano/microstructure and material properties. Concentrated STPV system converts solar radiation to electricity using heat as an intermediary through a thermally coupled absorber/emitter, which causes STPV to have one of the highest solar-to-electricity conversion efficiency limits (85.4%). Modeling of a near-field concentrated STPV microsystem is carried out to investigate the use of STPV based solid-state energy conversion as high power density MEMS power generator. Numerical results for In 0.18Ga0.82Sb PV cell illuminated with tungsten emitter showed significant enhancement in energy transfer, resulting in output power densities as high as 60 W/cm2; 30 times higher than the equivalent far-field power density. On thermal computing, this dissertation demonstrates near-field heat transfer enabled high temperature NanoThermoMechanical memory and logics. Unlike electronics, NanoThermoMechanical memory and logic devices use heat instead of electricity to record and process data; hence they can operate in harsh environments where electronics typically fail. NanoThermoMechanical devices achieve memory and thermal rectification functions through the coupling of near-field thermal radiation and thermal expansion in microstructures, resulting in nonlinear heat transfer between two temperature terminals. Numerical modeling of a conceptual NanoThermoMechanical is carried out; results include the dynamic response under write/read cycles for a practical silicon-based device. NanoThermoMechanical rectification is achieved experimentally--for the first time--with measurements at a high temperature of 600 K, demonstrating the feasibility of NanoThermoMechanical to operate in harsh environments. The proof-of-concept device has shown a maximum rectification of 10.9%. This dissertation proposes using meshed photonic crystal structures to enhance NFTR between surfaces. Numerical results show thermal rectification as high as 2500%. Incorporating these structures in thermal memory and rectification devices will significantly enhance their functionality and performance.

Dietary energy source and density modulate the expression of immunologic stress in chicks.

PubMed

Benson, B N; Calvert, C C; Roura, E; Klasing, K C

1993-10-01

To determine how dietary energy level and source influence feed intake, growth and energy partitioning drug immunologic stress, growing chicks were fed diets based on cornstarch and casein with varying energy densities and injected every other day for 6 d with either saline (control), Salmonella typhimurium lipopolysaccharide or heat-killed Staphylococcus aureus. Salmonella typhimurium lipopolysaccharide decreased growth and feed consumption at low energy densities. When the dietary energy density was increased above 13.4 kJ/g using cornstarch, but not corn oil, the growth depressing effect of immunogens was eliminated. Immunologically stressed chicks had a greater proportion of gain in visceral organs and less in the carcass, regardless of the nutrient density of the diet. Immunologic stress decreased intake of metabolizable energy of chicks fed a diet with low nutrient density and increased it for those fed a diet with high nutrient density. Chicks injected with S. typhimurium lipopolysaccharide lost more energy as heat than controls when differences in metabolizable energy intakes were accounted for and modified their preference between two diets differing in metabolizable energy density and fat content as a result of the challenge. Control chicks selected between the 11.7 and 14.2 kJ/g diets to obtain an energy density of 13.2 kJ/g compared with 12.5 kJ/g in the S. typhimurium lipopolysaccharide-challenged chicks. The S. typhimurium lipopolysaccharide-challenged chicks consumed similar amounts of the low energy diet but decreased intake of the high energy diet.

Unconventional High Density Vertically Aligned Conducting Polymer

DTIC Science & Technology

2014-08-21

DISTRIBUTION/AVAILABILITY STATEMENT Unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT Supercapacitors are promising energy storage devices due to their higher...order to meet the demands of a wide range of energy technologies, supercapacitors with higher energy and power densities are required. Although many past...applications. Supercapacitors are promising energy storage devices due to their higher energy density than dielectric capacitors and higher power density and

[Ionization energies and infrared spectra studies of histidine using density functional theory].

PubMed

Hu, Qiong; Wang, Guo-Ying; Liu, Gang; Ou, Jia-Ming; Wang, Rui-Li

2010-05-01

Histidines provide axial ligands to the primary electron donors in photosynthetic reaction centers (RCs) and play an important role in the protein environments of these donors. In this paper the authors present a systematic study of ionization energies and vibrational properties of histidine using hybrid density functional theory (DFT). All calculations were undertaken by using B3LYP method in combination with four basis sets: 6-31G(d), 6-31G(df, p), 6-31+G(d) and 6-311+G(2d, 2p) with the aim to investigate how the basis sets influence the calculation results. To investigate solvent effects and gain a detailed understanding of marker bands of histidine, the ionization energies of histidine and the vibrational frequencies of histidine which are unlabeled and 13C, 15N, and 2H labeled in the gas phase, CCl4, protein environment, THF and water solution, which span a wide range of dielectric constant, were also calculated. Our results showed that: (1) The main geometry parameters of histidine were impacted by basis sets and mediums, and C2-N3 and N3-C4 bond of imidazole ring of histidine side chain display the maximum bond lengths in the gas phase; (2) single point energies and frequencies calculated were decreased while ionization energies increased with the increasing level of basis sets and diffuse function applied in the same solvent; (3) with the same computational method, the higher the dielectric constant of the solvent used, the lower the ionization energy and vibrational frequency and the higher the intensity obtained. In addition, calculated ionization energy in the gas phase and marker bands of histidine as well as frequency shift upon 13C and 15N labeling at the computationally more expensive 6-311+G(2d, 2p) level are in good agreement with experimental observations available in literatures. All calculations indicated that the results calculated by using higher level basis set with diffuse function were more accurate and closer to the experimental value. In conclusion, the results provide useful information for the further studies of the functional and vibrational properties of chlorophyll-a ligated to histidine residue in photosynthetic reaction center.

Food environments of young people: linking individual behaviour to environmental context.

PubMed

Tyrrell, Rachel L; Greenhalgh, Fiona; Hodgson, Susan; Wills, Wendy J; Mathers, John C; Adamson, Ashley J; Lake, Amelia A

2017-03-01

We aimed to identify and characterize the food environments from which young people obtain food and to explore associations between the type of food environment and food intakes. Young people (n = 86, mean age 17 years; combined data of two sequential pilot studies (collected in 2008-09) and a study conducted in 2011-12) recorded in 4-day self-complete food diaries what food they consumed and where food was sourced. Nutrient, fruit and vegetable intake was calculated according to the source of food, categorized using a food environment classification tool. Over 4 days, respondents sourced food from an average of 4.3 different food environments. Home food was used daily and was more favourable in terms of nutrient profile than out-of-home food. Food sourced from specialist outlets, convenience stores and retail bakers had the highest energy density. Food from retail bakers and 'takeaway and fast food' outlets were the richest sources of fat while vending machines and convenience stores had the highest percentage of energy from sugar. This work provides details of 'where' young people obtain food and the nutritional consequences of choosing those food environments. While home food was a significant contributor to total dietary intake, food was obtained from a broad range of environments; particularly takeaway, fast food and education establishments. © The Author 2016. Published by Oxford University Press on behalf of Faculty of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Generalized Master Equation with Non-Markovian Multichromophoric Förster Resonance Energy Transfer for Modular Exciton Densities

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

Jang, Seogjoo; Hoyer, Stephan; Fleming, Graham

2014-10-31

A generalized master equation (GME) governing quantum evolution of modular exciton density (MED) is derived for large scale light harvesting systems composed of weakly interacting modules of multiple chromophores. The GME-MED offers a practical framework to incorporate real time coherent quantum dynamics calculations of small length scales into dynamics over large length scales, and also provides a non-Markovian generalization and rigorous derivation of the Pauli master equation employing multichromophoric Förster resonance energy transfer rates. A test of the GME-MED for four sites of the Fenna-Matthews-Olson complex demonstrates how coherent dynamics of excitonic populations over coupled chromophores can be accurately describedmore » by transitions between subgroups (modules) of delocalized excitons. Application of the GME-MED to the exciton dynamics between a pair of light harvesting complexes in purple bacteria demonstrates its promise as a computationally efficient tool to investigate large scale exciton dynamics in complex environments.« less

Fe-Based Amorphous Coatings on AISI 4130 Structural Steel for Corrosion Resistance

NASA Astrophysics Data System (ADS)

Katakam, Shravana; Santhanakrishnan, S.; Dahotre, Narendra B.

2012-06-01

The current study focuses on synthesizing a novel functional coating for corrosion resistance applications, via laser surface alloying. The iron-based (Fe48Cr15Mo14Y2C15B) amorphous precursor powder is used for laser surface alloying on AISI 4130 steel substrate, with a continuous wave ytterbium Nd-YAG fiber laser. The corrosion resistance of the coatings is evaluated for different processing conditions. The microstructural evolution and the response of the microstructure to the corrosive environment is studied using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Microstructural studies indicate the presence of face-centered cubic Fe-based dendrites intermixed within an amorphous matrix along with fine crystalline precipitates. The corrosion resistance of the coatings decrease with an increase in laser energy density, which is attributed to the precipitation and growth of chromium carbide. The enhanced corrosion resistance of the coatings processed with low energy density is attributed to the self-healing mechanism of this amorphous system.

Super high energy density of Li3V2(PO4)3 as cathode materials for lithium ion batteries

NASA Astrophysics Data System (ADS)

Noerochim, Lukman; Amin, Mochammad Karim Al; Susanti, Diah; Triwibowo, Joko

2018-04-01

Lithium ion batteries have many advantages such as high energy density, no memory effect, long time cycleability and friendly environment. One type of cathode material that can be developed is Li3V2(PO4)3. In this study has been carried out the synthesis of Li3V2(PO4)3 with a hydrothermal temperature variation of 140, 160 and 180 °C and calcination temperature at 800 °C. SEM images show that the morphology of Li3V2(PO4)3 has irregular flakes with a size between 1-10 µm. CV results show redox reaction occurs in the range between 3 V to 4.8 V with the highest specific discharge capacity of 136 mAh/g for specimen with temperature hydrothermal and calcination are 180 °C and 800 °C. This result demonstrates that Li3V2(PO4)3 has a great potential as cathode material for lithium ion battery.

Steam torrefaction of Eucalyptus globulus for producing black pellets: A pilot-scale experience.

PubMed

Arteaga-Pérez, Luis E; Grandón, Héctor; Flores, Mauricio; Segura, Cristina; Kelley, Stephen S

2017-08-01

Steam torrefaction of Eucalyptus globulus was performed at temperatures between 245°C and 265°C in a 100kg/h pilot plant. Torrefied biomass was then pelletized in a 300kg/h unit and the pellets were subject to durability, density and combustion tests. The structural changes measured with FTIR were studied along with the combustion behavior of the materials. Compositional analysis showed that increasing the torrefaction temperature reduced both hemicellulose fraction and overall mass yield (MY). Furthermore, there was a linear relationship between the energy yield (EY) and mass yield (EY=[1.04-0.9(1-MY)]) for these samples. The ignition and comprehensive indexes confirmed that the stability of the torrefied biomass in a combustion environment was higher than for untreated biomass. Finally, pellets showed high durability (98%), and had an energy density (13-14GJ/m 3 ), which is comparable to low-rank coals. Copyright © 2017 Elsevier Ltd. All rights reserved.

The strain capacitor: A novel energy storage device

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

Deb Shuvra, Pranoy; McNamara, Shamus, E-mail: shamus.mcnamara@louisville.edu

2014-12-15

A novel electromechanical energy storage device is reported that has the potential to have high energy densities. It can efficiently store both mechanical strain energy and electrical energy in the form of an electric field between the electrodes of a strain-mismatched bilayer capacitor. When the charged device is discharged, both the electrical and mechanical energy are extracted in an electrical form. The charge-voltage profile of the device is suitable for energy storage applications since a larger portion of the stored energy can be extracted at higher voltage levels compared to a normal capacitor. Its unique features include the potential formore » long lifetime, safety, portability, wide operating temperature range, and environment friendliness. The device can be designed to operate over varied operating voltage ranges by selecting appropriate materials and by changing the dimensions of the device. In this paper a finite element model of the device is developed to verify and demonstrate the potential of the device as an energy storage element. This device has the potential to replace conventional energy storage devices.« less

Simulation and Fabrication of Wagon-Wheel-Shaped Piezoelectric Transducer for Raindrop Energy Harvesting Application

NASA Astrophysics Data System (ADS)

Wong, Chin Hong; Dahari, Zuraini; Jumali, Mohammad Hafizuddin; Mohamed, Khairudin; Mohamed, Julie Juliewatty

2017-03-01

Harvesting vibrational energy from impacting raindrops using piezoelectric material has been proven to be a promising approach for future outdoor applications, providing a good alternative resource that can be applied in outdoor rainy environments. We present herein an optimum novel polyvinylidene fluoride (PVDF) piezoelectric transducer specifically developed to harvest raindrop energy. The finite-element method was applied for simulation and optimization of the piezoelectric raindrop energy harvester (PREH) using COMSOL Multiphysics software, investigating the electrical potential, surface charge density, and total displacement for different transducer dimensions. According to the simulation results, the structure that generated the highest electrical potential and surface charge density was a wagon-wheel-shaped structure consisting of six spokes with wheel diameter of 30 mm, spoke width of 2 mm, center pad diameter of 6 mm, and thickness of 25 μm. This optimum wagon-wheel-shaped device was then fabricated by spin coating of PVDF, sputtering of aluminum, a poling process, and computer numerical control machining of a polytetrafluoroethylene stand. The fabricated PREH was characterized by x-ray diffraction analysis and Fourier-transform infrared spectroscopy. Finally, the fabricated PREH was tested under actual rain conditions with an alternating current to direct current converter connected in parallel, revealing that a single cell could generate average peak voltage of 22.5 mV and produce electrical energy of 3.4 nJ from ten impacts in 20 s.

Gedanken densities and exact constraints in density functional theory.

PubMed

Perdew, John P; Ruzsinszky, Adrienn; Sun, Jianwei; Burke, Kieron

2014-05-14

Approximations to the exact density functional for the exchange-correlation energy of a many-electron ground state can be constructed by satisfying constraints that are universal, i.e., valid for all electron densities. Gedanken densities are designed for the purpose of this construction, but need not be realistic. The uniform electron gas is an old gedanken density. Here, we propose a spherical two-electron gedanken density in which the dimensionless density gradient can be an arbitrary positive constant wherever the density is non-zero. The Lieb-Oxford lower bound on the exchange energy can be satisfied within a generalized gradient approximation (GGA) by bounding its enhancement factor or simplest GGA exchange-energy density. This enhancement-factor bound is well known to be sufficient, but our gedanken density shows that it is also necessary. The conventional exact exchange-energy density satisfies no such local bound, but energy densities are not unique, and the simplest GGA exchange-energy density is not an approximation to it. We further derive a strongly and optimally tightened bound on the exchange enhancement factor of a two-electron density, which is satisfied by the local density approximation but is violated by all published GGA's or meta-GGA's. Finally, some consequences of the non-uniform density-scaling behavior for the asymptotics of the exchange enhancement factor of a GGA or meta-GGA are given.

The Role Of Environment In Stellar Mass Growth

NASA Astrophysics Data System (ADS)

Thomas, Daniel

2017-06-01

In this talk I give a brief summary of methods to measure galaxy environment. I then discuss the dependence of stellar population properties on environmental density: it turns out that the latter are driven by galaxy mass, and galaxy environment only plays a secondary role, mostly at late times in low-mass galaxies. I show that this evidence has now been extended to stellar population gradients using the IFU survey SDSS/MaNGA that again turn out to be independent of environment, including central-satellite classification. Finally I present results from the DES, where the dependence of the stellar mass function with redshift and environmental density is explored. It is found that the fraction of massive galaxies is larger in high density environments than in low density environments. The low density and high density components converge with increasing redshift up to z 1.0 where the shapes of the mass function components are indistinguishable. This study shows how high density structures build up around massive galaxies through cosmic time, which sets new valuable constraints on galaxy formation models.

Parametric design criteria of an updated thermoradiative cell operating at optimal states

NASA Astrophysics Data System (ADS)

Zhang, Xin; Peng, Wanli; Lin, Jian; Chen, Xiaohang; Chen, Jincan

2017-11-01

An updated mode of the thermoradiative cell (TRC) with sub-band gap and non-radiative losses is proposed, which can efficiently harvest moderate-temperature heat energy and convert a part of heat into electricity. It is found that when the TRC is operated between the heat source at 800 K and the environment at 300 K , its maximum power output density and efficiency can attain 1490 W m-2 and 27.2 % , respectively. Moreover, the effects of some key parameters including the band gap and voltage output on the performance of the TRC are discussed. The optimally working regions of the power density, efficiency, band gap, and voltage output are determined. The maximum efficiency and power output density of the TRC operated at different temperatures are calculated and compared with those of thermophotovoltaic cells (TPVCs) and thermionic energy converters (TECs), and consequently, it is revealed that the maximum efficiency of the TRC operated at the moderate-temperature range is much higher than that of the TEC or the TPVC and the maximum power output density of the TRC is larger than that of the TEC but smaller than that of the TPVC. Particularly, the TRC is manufactured more easily than the near-field TPVC possessing a nanoscale vacuum gap. The results obtained will be helpful for engineers to choose the semiconductor materials, design and manufacture TRCs, and control operative conditions.

Dietary Energy Density in the Australian Adult Population from National Nutrition Surveys 1995 to 2012.

PubMed

Grech, Amanda Lee; Rangan, Anna; Allman-Farinelli, Margaret

2017-12-01

It is hypothesized that the observed proliferation of energy-dense, nutrient-poor foods globally is an important contributing factor to the development of the obesity epidemic. However, evidence that the population's dietary energy density has increased is sparse. The World Cancer Research Fund recommends that dietary energy density be <1.25 kcal/g to prevent weight gain. The aim of this research was to determine whether the dietary energy density of the Australian population has changed between 1995 and 2012. A secondary analysis of two cross-sectional Australian national nutrition surveys from 1995 and 2011/2012 was conducted. Participants of the surveys included adults aged 18 years and older (1995 n=10,986 and 2011/2012 n=9,435) completing 24-hour dietary recalls, including a second recall for a subset of the population (10.4% in 1995 and 64.6% in 2011/2012). Outcome measures included the change in dietary energy density (calculated as energy/weight of food [kcal/g] for food only) between surveys. The National Cancer Institute method for "estimating ratios of two dietary components that are consumed nearly every day" was used to determine the usual distribution and the percentage of participants reporting energy density <1.25 kcal/g. The mean (standard deviation) dietary energy density was 1.59 (0.26) kcal/g and 1.64 (0.32) kcal/g (P<0.0001) in 1995 and 2011/2012, respectively, with 13% and 5% (P<0.0001) of the population meeting dietary energy-density recommendations. For those aged 70 years and older, the percentage with energy density <1.25 kcal/g decreased from 22% to 6% (P<0.0001) for men and from 33% to 11% (P<0.0001) for women in 1995 and 2011/2012, respectively. Among those aged 18 to 29 years, 1% of men in both surveys (P=0.8) and 4% of women in 1995 and 2% in 2011/2012 (P=0.01) reported energy density <1.25 kcal/g. Dietary energy density has increased between the two surveys and few people consumed low energy-dense diets in line with recommendations. The change was largely due to increased energy density of older adult's diets, while young adults had high dietary energy density at both time points. These data suggest efforts now focus on the evaluation of the role of modifying energy density of the diet to reduce the risk of weight gain in adults. Copyright © 2017 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

Multiconfiguration Pair-Density Functional Theory.

PubMed

Li Manni, Giovanni; Carlson, Rebecca K; Luo, Sijie; Ma, Dongxia; Olsen, Jeppe; Truhlar, Donald G; Gagliardi, Laura

2014-09-09

We present a new theoretical framework, called Multiconfiguration Pair-Density Functional Theory (MC-PDFT), which combines multiconfigurational wave functions with a generalization of density functional theory (DFT). A multiconfigurational self-consistent-field (MCSCF) wave function with correct spin and space symmetry is used to compute the total electronic density, its gradient, the on-top pair density, and the kinetic and Coulomb contributions to the total electronic energy. We then use a functional of the total density, its gradient, and the on-top pair density to calculate the remaining part of the energy, which we call the on-top-density-functional energy in contrast to the exchange-correlation energy of Kohn-Sham DFT. Because the on-top pair density is an element of the two-particle density matrix, this goes beyond the Hohenberg-Kohn theorem that refers only to the one-particle density. To illustrate the theory, we obtain first approximations to the required new type of density functionals by translating conventional density functionals of the spin densities using a simple prescription, and we perform post-SCF density functional calculations using the total density, density gradient, and on-top pair density from the MCSCF calculations. Double counting of dynamic correlation or exchange does not occur because the MCSCF energy is not used. The theory is illustrated by applications to the bond energies and potential energy curves of H2, N2, F2, CaO, Cr2, and NiCl and the electronic excitation energies of Be, C, N, N(+), O, O(+), Sc(+), Mn, Co, Mo, Ru, N2, HCHO, C4H6, c-C5H6, and pyrazine. The method presented has a computational cost and scaling similar to MCSCF, but a quantitative accuracy, even with the present first approximations to the new types of density functionals, that is comparable to much more expensive multireference perturbation theory methods.

Operational specification and forecasting advances for Dst, LEO thermospheric densities, and aviation radiation dose and dose rate

NASA Astrophysics Data System (ADS)

Tobiska, W.; Knipp, D. J.; Burke, W. J.; Bouwer, D.; Bailey, J. J.; Hagan, M. P.; Didkovsky, L. V.; Garrett, H. B.; Bowman, B. R.; Gannon, J. L.; Atwell, W.; Blake, J. B.; Crain, W.; Rice, D.; Schunk, R. W.; Fulgham, J.; Bell, D.; Gersey, B.; Wilkins, R.; Fuschino, R.; Flynn, C.; Cecil, K.; Mertens, C. J.; Xu, X.; Crowley, G.; Reynolds, A.; Azeem, S. I.; Wiley, S.; Holland, M.; Malone, K.

2013-12-01

Space weather's effects upon the near-Earth environment are due to dynamic changes in the energy transfer processes from the Sun's photons, particles, and fields. Of the space environment domains that are affected by space weather, the magnetosphere, thermosphere, and even troposphere are key regions that are affected. Space Environment Technologies (SET) has developed and is producing innovative space weather applications. Key operational systems for providing timely information about the effects of space weather on these domains are SET's Magnetosphere Alert and Prediction System (MAPS), LEO Alert and Prediction System (LAPS), and Automated Radiation Measurements for Aviation Safety (ARMAS) system. MAPS provides a forecast Dst index out to 6 days through the data-driven, redundant data stream Anemomilos algorithm. Anemomilos uses observational proxies for the magnitude, location, and velocity of solar ejecta events. This forecast index is used by satellite operations to characterize upcoming geomagnetic storms, for example. LAPS is the SET fully redundant operational system providing recent history, current epoch, and forecast solar and geomagnetic indices for use in operational versions of the JB2008 thermospheric density model. The thermospheric densities produced by that system, driven by the LAPS data, are forecast to 72-hours to provide the global mass densities for satellite operators. ARMAS is a project that has successfully demonstrated the operation of a micro dosimeter on aircraft to capture the real-time radiation environment due to Galactic Cosmic Rays and Solar Energetic Particles. The dose and dose-rates are captured on aircraft, downlinked in real-time via the Iridium satellites, processed on the ground, incorporated into the most recent NAIRAS global radiation climatology data runs, and made available to end users via the web and smart phone apps. ARMAS provides the 'weather' of the radiation environment to improve air-crew and passenger safety. Many of the data products from MAPS, LAPS, and ARMAS are available on the SpaceWx smartphone app for iPhone, iPad, iPod, and Android professional users and public space weather education. We describe recent forecasting advances for moving the space weather information from these automated systems into operational, derivative products for communications, aviation, and satellite operations uses.

Alternative definitions of the frozen energy in energy decomposition analysis of density functional theory calculations.

PubMed

Horn, Paul R; Head-Gordon, Martin

2016-02-28

In energy decomposition analysis (EDA) of intermolecular interactions calculated via density functional theory, the initial supersystem wavefunction defines the so-called "frozen energy" including contributions such as permanent electrostatics, steric repulsions, and dispersion. This work explores the consequences of the choices that must be made to define the frozen energy. The critical choice is whether the energy should be minimized subject to the constraint of fixed density. Numerical results for Ne2, (H2O)2, BH3-NH3, and ethane dissociation show that there can be a large energy lowering associated with constant density orbital relaxation. By far the most important contribution is constant density inter-fragment relaxation, corresponding to charge transfer (CT). This is unwanted in an EDA that attempts to separate CT effects, but it may be useful in other contexts such as force field development. An algorithm is presented for minimizing single determinant energies at constant density both with and without CT by employing a penalty function that approximately enforces the density constraint.

Investigation of low temperature solid oxide fuel cells for air-independent UUV applications

NASA Astrophysics Data System (ADS)

Moton, Jennie Mariko

Unmanned underwater vehicles (UUVs) will benefit greatly from high energy density (> 500 Wh/L) power systems utilizing high-energy-density fuels and air-independent oxidizers. Current battery-based systems have limited energy densities (< 400 Wh/L), which motivate development of alternative power systems such as solid oxide fuel cells (SOFCs). SOFC-based power systems have the potential to achieve the required UUV energy densities, and the current study explores how SOFCs based on gadolinia-doped ceria (GDC) electrolytes with operating temperatures of 650°C and lower may operate in the unique environments of a promising UUV power plant. The plant would contain a H 2O2 decomposition reactor to supply humidified O2 to the SOFC cathode and exothermic aluminum/H2O combustor to provide heated humidified H2 fuel to the anode. To characterize low-temperature SOFC performance with these unique O2 and H2 source, SOFC button cells based on nickel/GDC (Gd0.1Ce0.9O 1.95) anodes, GDC electrolytes, and lanthanum strontium cobalt ferrite (La0.6Sr0.4Co0.2Fe0.8O3-δ or LSCF)/GDC cathodes were fabricated and tested for performance and stability with humidity on both the anode and the cathode. Cells were also tested with various reactant concentrations of H2 and O2 to simulate gas depletion down the channel of an SOFC stack. Results showed that anode performance depended primarily on fuel concentration and less on the concentration of the associated increase in product H2O. O 2 depletion with humidified cathode flows also caused significant loss in cell current density at a given voltage. With the humidified flows in either the anode or cathode, stability tests of the button cells at 650 °C showed stable voltage is maintained at low operating current (0.17 A/cm2) at up to 50 % by mole H2O, but at higher current densities (0.34 A/cm2), irreversible voltage degradation occurred at rates of 0.8-3.7 mV/hour depending on exposure time. From these button cell results, estimated average current densities over the length of a low-temperature SOFC stack were estimated and used to size a UUV power system based on Al/H 2O oxidation for fuel and H2O2 decomposition for O2. The resulting system design suggested that energy densities above 300 Wh/L may be achieved at neutral buoyancy with seawater if the cell is operated at high reactant utilizations in the SOFC stack for missions longer than 20 hours.

Anion-π aromatic neutral tweezers complexes: are they stable in polar solvents?

PubMed

Sánchez-Lozano, Marta; Otero, Nicolás; Hermida-Ramón, Jose M; Estévez, Carlos M; Mandado, Marcos

2011-03-17

The impact of the solvent environment on the stabilization of the complexes formed by fluorine (T-F) and cyanide (T-CN) substituted tweezers with halide anions has been investigated theoretically. The study was carried out using computational methodologies based on density functional theory (DFT) and symmetry adapted perturbation theory (SAPT). Interaction energies were obtained at the M05-2X/6-31+G* level. The obtained results show a large stability of the complexes in solvents with large dielectric constant and prove the suitability of these molecular tweezers as potential hosts for anion recognition in solution. A detailed analysis of the effects of the solvent on the electron withdrawing ability of the substituents and its influence on the complex stability has been performed. In particular, the interaction energy in solution was split up into intermonomer and solvent-complex terms. In turn, the intermonomer interaction energy was partitioned into electrostatic, exchange, and polarization terms. Polar resonance structures in T-CN complexes are favored by polar solvents, giving rise to a stabilization of the intermonomer interaction, the opposite is found for T-F complexes. The solvent-complex energy increases with the polarity of the solvent in T-CN complexes, nonetheless the energy reaches a maximum and then decreases slowly in T-F complexes. An electron density analysis was also performed before and after complexation, providing an explanation to the trends followed by the interaction energies and their different components in solution.

THE COLOUR GLASS CONDENSATE: AN INTRODUCTION

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

IANCU,E.; LEONIDOV,A.; MCLERRAN,L.

2001-08-06

In these lectures, the authors develop the theory of the Colour Glass Condensate. This is the matter made of gluons in the high density environment characteristic of deep inelastic scattering or hadron-hadron collisions at very high energy. The lectures are self contained and comprehensive. They start with a phenomenological introduction, develop the theory of classical gluon fields appropriate for the Colour Glass, and end with a derivation and discussion of the renormalization group equations which determine this effective theory.

Final Supplemental Environmental Assessment: Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System (JLENS), U.S. Army Dugway Proving Ground, Dugway, Utah

DTIC Science & Technology

2009-09-01

evaluate specific system equipment func- tions, performance, operations, and safety in the field environment. The planned test procedures require free space...emission of radiofrequency (RF) electromagnetic energy within a limited spectral region and controlled power spec- tral density. There would be...for personnel. The applicable DoD standard that provides required guidelines for permissible exposure limits of DoD personnel is DoD Instruction

MSTD 2007 Publications and Patents

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

King, W E

2008-04-01

The Materials Science and Technology Division (MSTD) supports the central scientific and technological missions of the Laboratory, and at the same time, executes world-class, fundamental research and novel technological development over a wide range of disciplines. Our organization is driven by the institutional needs in nuclear weapons stockpile science, high-energy-density science, nuclear reactor science, and energy and environment science and technology. We maintain expertise and capabilities in many diverse areas, including actinide science, electron microscopy, laser-materials interactions, materials theory, simulation and modeling, materials synthesis and processing, materials science under extreme conditions, ultrafast materials science, metallurgy, nanoscience and technology, nuclear fuelsmore » and energy security, optical materials science, and surface science. MSTD scientists play leadership roles in the scientific community in these key and emerging areas.« less

Spectral properties of blast-wave models of gamma-ray burst sources

NASA Technical Reports Server (NTRS)

Meszaros, P.; Rees, M. J.; Papathanassiou, H.

1994-01-01

We calculate the spectrum of blast-wave models of gamma-ray burst sources, for various assumptions about the magnetic field density and the relativistic particle acceleration efficiency. For a range of physically plausible models we find that the radiation efficiency is high and leads to nonthermal spectra with breaks at various energies comparable to those observed in the gamma-ray range. Radiation is also predicted at other wavebands, in particular at X-ray, optical/UV, and GeV/TeV energies. We discuss the spectra as a function of duration for three basic types of models, and for cosmological, halo, and galactic disk distances. We also evaluate the gamma-ray fluences and the spectral characteristics for a range of external densities. Impulsive burst models at cosmological distances can satisfy the conventional X-ray paucity constraint S(sub x)/S(sub gamma)less than a few percent over a wide range of durations, but galactic models can do so only for bursts shorter than a few seconds, unless additional assumptions are made. The emissivity is generally larger for bursts in a denser external environment, with the efficiency increasing up to the point where all the energy input is radiated away.

Importance of Nutrients and Nutrient Metabolism on Human Health

PubMed Central

Chen, Yiheng; Michalak, Marek; Agellon, Luis B.

2018-01-01

Nutrition transition, which includes a change from consumption of traditional to modern diets that feature high-energy density and low nutrient diversity, is associated with acquired metabolic syndromes. The human diet is comprised of diverse components which include both nutrients, supplying the raw materials that drive multiple metabolic processes in every cell of the body, and non-nutrients. These components and their metabolites can also regulate gene expression and cellular function via a variety of mechanisms. Some of these components are beneficial while others have toxic effects. Studies have found that persistent disturbance of nutrient metabolism and/or energy homeostasis, caused by either nutrient deficiency or excess, induces cellular stress leading to metabolic dysregulation and tissue damage, and eventually to development of acquired metabolic syndromes. It is now evident that metabolism is influenced by extrinsic factors (e.g., food, xenobiotics, environment), intrinsic factors (e.g., sex, age, gene variations) as well as host/microbiota interaction, that together modify the risk for developing various acquired metabolic diseases. It is also becoming apparent that intake of diets with low-energy density but high in nutrient diversity may be the key to promoting and maintaining optimal health.

Molecular Orbital Principles of Oxygen-Redox Battery Electrodes.

PubMed

Okubo, Masashi; Yamada, Atsuo

2017-10-25

Lithium-ion batteries are key energy-storage devices for a sustainable society. The most widely used positive electrode materials are LiMO 2 (M: transition metal), in which a redox reaction of M occurs in association with Li + (de)intercalation. Recent developments of Li-excess transition-metal oxides, which deliver a large capacity of more than 200 mAh/g using an extra redox reaction of oxygen, introduce new possibilities for designing higher energy density lithium-ion batteries. For better engineering using this fascinating new chemistry, it is necessary to achieve a full understanding of the reaction mechanism by gaining knowledge on the chemical state of oxygen. In this review, a summary of the recent advances in oxygen-redox battery electrodes is provided, followed by a systematic demonstration of the overall electronic structures based on molecular orbitals with a focus on the local coordination environment around oxygen. We show that a π-type molecular orbital plays an important role in stabilizing the oxidized oxygen that emerges upon the charging process. Molecular orbital principles are convenient for an atomic-level understanding of how reversible oxygen-redox reactions occur in bulk, providing a solid foundation toward improved oxygen-redox positive electrode materials for high energy-density batteries.

Multiconfiguration pair-density functional theory: barrier heights and main group and transition metal energetics.

PubMed

Carlson, Rebecca K; Li Manni, Giovanni; Sonnenberger, Andrew L; Truhlar, Donald G; Gagliardi, Laura

2015-01-13

Kohn-Sham density functional theory, resting on the representation of the electronic density and kinetic energy by a single Slater determinant, has revolutionized chemistry, but for open-shell systems, the Kohn-Sham Slater determinant has the wrong symmetry properties as compared to an accurate wave function. We have recently proposed a theory, called multiconfiguration pair-density functional theory (MC-PDFT), in which the electronic kinetic energy and classical Coulomb energy are calculated from a multiconfiguration wave function with the correct symmetry properties, and the rest of the energy is calculated from a density functional, called the on-top density functional, that depends on the density and the on-top pair density calculated from this wave function. We also proposed a simple way to approximate the on-top density functional by translation of Kohn-Sham exchange-correlation functionals. The method is much less expensive than other post-SCF methods for calculating the dynamical correlation energy starting with a multiconfiguration self-consistent-field wave function as the reference wave function, and initial tests of the theory were quite encouraging. Here, we provide a broader test of the theory by applying it to bond energies of main-group molecules and transition metal complexes, barrier heights and reaction energies for diverse chemical reactions, proton affinities, and the water dimerization energy. Averaged over 56 data points, the mean unsigned error is 3.2 kcal/mol for MC-PDFT, as compared to 6.9 kcal/mol for Kohn-Sham theory with a comparable density functional. MC-PDFT is more accurate on average than complete active space second-order perturbation theory (CASPT2) for main-group small-molecule bond energies, alkyl bond dissociation energies, transition-metal-ligand bond energies, proton affinities, and the water dimerization energy.

Product screening of fast reactions in IR-laser-heated liquid water filaments in a vacuum by mass spectrometry.

PubMed

Charvat, A; Stasicki, B; Abel, B

2006-03-09

In the present article a novel approach for rapid product screening of fast reactions in IR-laser-heated liquid microbeams in a vacuum is highlighted. From absorbed energies, a shock wave analysis, high-speed laser stroboscopy, and thermodynamic data of high-temperature water the enthalpy, temperature, density, pressure, and the reaction time window for the hot water filament could be characterized. The experimental conditions (30 kbar, 1750 K, density approximately 1 g/cm3) present during the lifetime of the filament (20-30 ns) were extreme and provided a unique environment for high-temperature water chemistry. For the probe of the reaction products liquid beam desorption mass spectrometry was employed. A decisive feature of the technique is that ionic species, as well as neutral products and intermediates may be detected (neutrals as protonated aggregates) via time-of-flight mass spectrometry without any additional ionization laser. After the explosive disintegration of the superheated beam, high-temperature water reactions are efficiently quenched via expansion and evaporative cooling. For first exploratory experiments for chemistry in ultrahigh-temperature, -pressure and -density water, we have chosen resorcinol as a benchmark system, simple enough and well studied in high-temperature water environments much below 1000 K. Contrary to oxidation reactions usually present under less extreme and dense supercritical conditions, we have observed hydration and little H-atom abstraction during the narrow time window of the experiment. Small amounts of radicals but no ionic intermediates other than simple proton adducts were detected. The experimental findings are discussed in terms of the energetic and dense environment and the small time window for reaction, and they provide firm evidence for additional thermal reaction channels in extreme molecular environments.

Statistical properties of kinetic and total energy densities in reverberant spaces.

PubMed

Jacobsen, Finn; Molares, Alfonso Rodríguez

2010-04-01

Many acoustical measurements, e.g., measurement of sound power and transmission loss, rely on determining the total sound energy in a reverberation room. The total energy is usually approximated by measuring the mean-square pressure (i.e., the potential energy density) at a number of discrete positions. The idea of measuring the total energy density instead of the potential energy density on the assumption that the former quantity varies less with position than the latter goes back to the 1930s. However, the phenomenon was not analyzed until the late 1970s and then only for the region of high modal overlap, and this analysis has never been published. Moreover, until fairly recently, measurement of the total sound energy density required an elaborate experimental arrangement based on finite-difference approximations using at least four amplitude and phase matched pressure microphones. With the advent of a three-dimensional particle velocity transducer, it has become somewhat easier to measure total rather than only potential energy density in a sound field. This paper examines the ensemble statistics of kinetic and total sound energy densities in reverberant enclosures theoretically, experimentally, and numerically.

Acoustic energy in ducts - Further observations

NASA Technical Reports Server (NTRS)

Eversman, W.

1979-01-01

The transmission of acoustic energy in uniform ducts carrying uniform flow is investigated with the purpose of clarifying two points of interest. The two commonly used definitions of acoustic 'energy' flux are shown to be related by a Legendre transformation of the Lagrangian density exactly as in deriving the Hamiltonian density in mechanics. In the acoustic case the total energy density and the Hamiltonian density are not the same which accounts for two different 'energy' fluxes. When the duct has acoustically absorptive walls neither of the two flux expressions gives correct results. A reevaluation of the basis of derivation of the energy density and energy flux provides forms which yield consistent results for soft walled ducts.

The immediate environment of an astrophysical black hole

NASA Astrophysics Data System (ADS)

Contopoulos, I.

2018-01-01

In view of the upcoming observations with the Event Horizon Telescope (EHT), we present our thoughts on the immediate environment of an astrophysical black hole. We are concerned that two approximations used in general relativistic magnetohydrodynamic numerical simulations, namely numerical density floors implemented near the base of the black hole jet, and a magnetic field that comes from large distances, may mislead our interpretation of the observations. We predict that three physical processes will manifest themselves in EHT observations, namely dynamic pair formation just above the horizon, electromagnetic energy dissipation along the boundary of the black hole jet, and a region of weak magnetic field separating the black hole jet from the disc wind.

Status Report - Cane Fiberboard Properties And Degradation Rates For Storage Of The 9975 Shipping Package In KAC

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

Daugherty, W.

Thermal, mechanical and physical properties have been measured on cane fiberboard samples following accelerated aging for up to approximately 10 years. The aging environments have included elevated temperature < 250 ºF (the maximum allowed service temperature for fiberboard in 9975 packages) and elevated humidity. The results from this testing have been analyzed, and aging models fit to the data. Correlations relating several properties (thermal conductivity, energy absorption, weight, dimensions and density) to their rate of change in potential storage environments have been developed. Combined with an estimate of the actual conditions the fiberboard experiences in KAC, these models allow developmentmore » of service life predictions.« less

Holographic Dark Energy Density

NASA Astrophysics Data System (ADS)

Saadat, Hassan

2011-06-01

In this article we consider the cosmological model based on the holographic dark energy. We study dark energy density in Universe with arbitrary spatially curvature described by the Friedmann-Robertson-Walker metric. We use Chevallier-Polarski-Linder parametrization to specify dark energy density.

Energy-saving analysis of hydraulic hybrid excavator based on common pressure rail.

PubMed

Shen, Wei; Jiang, Jihai; Su, Xiaoyu; Karimi, Hamid Reza

2013-01-01

Energy-saving research of excavators is becoming one hot topic due to the increasing energy crisis and environmental deterioration recently. Hydraulic hybrid excavator based on common pressure rail (HHEC) provides an alternative with electric hybrid excavator because it has high power density and environment friendly and easy to modify based on the existing manufacture process. This paper is focused on the fuel consumption of HHEC and the actuator dynamic response to assure that the new system can save energy without sacrificing performance. Firstly, we introduce the basic principle of HHEC; then, the sizing process is presented; furthermore, the modeling period which combined mathematical analysis and experiment identification is listed. Finally, simulation results show that HHEC has a fast dynamic response which can be accepted in engineering and the fuel consumption can be reduced 21% to compare the original LS excavator and even 32% after adopting another smaller engine.

Energy-Saving Analysis of Hydraulic Hybrid Excavator Based on Common Pressure Rail

PubMed Central

Jiang, Jihai; Su, Xiaoyu

2013-01-01

Energy-saving research of excavators is becoming one hot topic due to the increasing energy crisis and environmental deterioration recently. Hydraulic hybrid excavator based on common pressure rail (HHEC) provides an alternative with electric hybrid excavator because it has high power density and environment friendly and easy to modify based on the existing manufacture process. This paper is focused on the fuel consumption of HHEC and the actuator dynamic response to assure that the new system can save energy without sacrificing performance. Firstly, we introduce the basic principle of HHEC; then, the sizing process is presented; furthermore, the modeling period which combined mathematical analysis and experiment identification is listed. Finally, simulation results show that HHEC has a fast dynamic response which can be accepted in engineering and the fuel consumption can be reduced 21% to compare the original LS excavator and even 32% after adopting another smaller engine. PMID:24194683

Trends in adsorption of electrocatalytic water splitting intermediates on cubic ABO 3 oxides

DOE PAGES

Montoya, Joseph H.; Doyle, Andrew D.; Nørskov, Jens K.; ...

2018-01-19

The reactivity of solid oxide surfaces towards adsorption of oxygen and hydrogen is a key metric for the design of new catalysts for electrochemical water splitting. Here, in this paper, we report on trends in the adsorption energy of different adsorbed intermediates derived from the oxidation and reduction of water for ternary ABO 3 oxides in the cubic perovskite structure. Our findings support a previously reported trend that rationalizes the observed lower bound in oxygen evolution (OER) overpotentials from correlations in OH* and OOH* adsorption energies. In addition, we report hydrogen adsorption energies that may be used to estimate hydrogenmore » evolution (HER) overpotentials along with potential metrics for electrochemical metastability in reducing environments. Finally, we also report and discuss trends between atom-projected density of states and adsorption energies, which may enable a design criteria from the local electronic structure of the active site.« less

Energy transfer and motion synchronization between mechanical oscillators through microhydrodynamic coupling

NASA Astrophysics Data System (ADS)

Wan, Yu; Jin, Kai; Ahmad, Talha J.; Black, Michael J.; Xu, Zhiping

2017-03-01

Fluidic environment is encountered for mechanical components in many circumstances, which not only damps the oscillation but also modulates their dynamical behaviors through hydrodynamic interactions. In this study, we examine energy transfer and motion synchronization between two mechanical micro-oscillators by performing thermal lattice-Boltzmann simulations. The coefficient of inter-oscillator energy transfer is measured to quantify the strength of microhydrodynamic coupling, which depends on their distance and fluid properties such as density and viscosity. Synchronized motion of the oscillators is observed in the simulations for typical parameter sets in relevant applications, with the formation and loss of stable anti-phase synchronization controlled by the oscillating frequency, amplitude, and hydrodynamic coupling strength. The critical ranges of key parameters to assure efficient energy transfer or highly synchronized motion are predicted. These findings could be used to advise mechanical design of passive and active devices that operate in fluid.

Trends in adsorption of electrocatalytic water splitting intermediates on cubic ABO 3 oxides

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

Montoya, Joseph H.; Doyle, Andrew D.; Nørskov, Jens K.

The reactivity of solid oxide surfaces towards adsorption of oxygen and hydrogen is a key metric for the design of new catalysts for electrochemical water splitting. Here, in this paper, we report on trends in the adsorption energy of different adsorbed intermediates derived from the oxidation and reduction of water for ternary ABO 3 oxides in the cubic perovskite structure. Our findings support a previously reported trend that rationalizes the observed lower bound in oxygen evolution (OER) overpotentials from correlations in OH* and OOH* adsorption energies. In addition, we report hydrogen adsorption energies that may be used to estimate hydrogenmore » evolution (HER) overpotentials along with potential metrics for electrochemical metastability in reducing environments. Finally, we also report and discuss trends between atom-projected density of states and adsorption energies, which may enable a design criteria from the local electronic structure of the active site.« less

Time-resolved emission studies of ArF-laser-produced microplasmas

NASA Astrophysics Data System (ADS)

Simeonsson, Josef B.; Miziolek, Andrzej W.

1993-02-01

ArF-laser-produced microplasmas in CO, CO2, methanol, and chloroform are studied by time-resolved emission measurements of the plasma decay. Electron densities are deduced from Stark broadening of the line profiles of atomic H, C, O, and Cl. Plasma ionization and excitation temperatures are determined from measurements of relative populations of ionic and neutral species produced in the plasmas. A discussion of the thermodynamic equilibrium status of ArF laser microplasmas is presented. In general, the ArF-laser-produced microplasma environment is found to be similar in all the gases studied, in terms of both temperature and electron density, despite the considerable differences observed in the breakdown thresholds and relative energies deposited in the various gases.

Comparison of three methods to reduce energy density. Effects on daily energy intake.

PubMed

Williams, Rachel A; Roe, Liane S; Rolls, Barbara J

2013-07-01

Reductions in food energy density can decrease energy intake, but it is not known if the effects depend on the way that energy density is reduced. We investigated whether three methods of reducing energy density (decreasing fat, increasing fruit and vegetables, and adding water) differed in their effects on energy intake across the day. In a crossover design, 59 adults ate breakfast, lunch, and dinner in the laboratory once a week for 4 weeks. Across conditions, the entrées were either standard in energy density or were reduced in energy density by 20% using one of the three methods. Each meal included a manipulated entrée along with unmanipulated side dishes, and all foods were consumed ad libitum. Reducing the energy density of entrées significantly decreased daily energy intake compared to standard entrées (mean intake 2667 ± 77 kcal/day; 11,166 ± 322 kJ/day). The mean decrease was 396 ± 44 kcal/day (1658 ± 184 kJ/day) when fat was reduced, 308 ± 41 kcal/day (1290 ± 172 kJ/day) when fruit and vegetables were increased, and 230 ± 35 kcal/day (963 ± 147 kJ/day) when water was added. Daily energy intake was lower when fat was decreased compared to the other methods. These findings indicate that a variety of diet compositions can be recommended to reduce overall dietary energy density in order to moderate energy intake. Copyright © 2013 Elsevier Ltd. All rights reserved.

Energy density of lake whitefish Coregonus clupeaformis in Lakes Huron and Michigan

USGS Publications Warehouse

Pothoven, S.A.; Nalepa, T.F.; Madenjian, C.P.; Rediske, R.R.; Schneeberger, P.J.; He, J.X.

2006-01-01

We collected lake whitefish Coregonus clupeaformis off Alpena and Tawas City, Michigan, USA in Lake Huron and off Muskegon, Michigan USA in Lake Michigan during 2002–2004. We determined energy density and percent dry weight for lake whitefish from both lakes and lipid content for Lake Michigan fish. Energy density increased with increasing fish weight up to 800 g, and then remained relatively constant with further increases in fish weight. Energy density, adjusted for weight, was lower in Lake Huron than in Lake Michigan for both small (≤800 g) and large fish (>800 g). Energy density did not differ seasonally for small or large lake whitefish or between adult male and female fish. Energy density was strongly correlated with percent dry weight and percent lipid content. Based on data from commercially caught lake whitefish, body condition was lower in Lake Huron than Lake Michigan during 1981–2003, indicating that the dissimilarity in body condition between the lakes could be long standing. Energy density and lipid content in 2002–2004 in Lake Michigan were lower than data for comparable sized fish collected in 1969–1971. Differences in energy density between lakes were attributed to variation in diet and prey energy content as well as factors that affect feeding rates such as lake whitefish density and prey abundance.

Estimation of energy density of Li-S batteries with liquid and solid electrolytes

NASA Astrophysics Data System (ADS)

Li, Chunmei; Zhang, Heng; Otaegui, Laida; Singh, Gurpreet; Armand, Michel; Rodriguez-Martinez, Lide M.

2016-09-01

With the exponential growth of technology in mobile devices and the rapid expansion of electric vehicles into the market, it appears that the energy density of the state-of-the-art Li-ion batteries (LIBs) cannot satisfy the practical requirements. Sulfur has been one of the best cathode material choices due to its high charge storage (1675 mAh g-1), natural abundance and easy accessibility. In this paper, calculations are performed for different cell design parameters such as the active material loading, the amount/thickness of electrolyte, the sulfur utilization, etc. to predict the energy density of Li-S cells based on liquid, polymeric and ceramic electrolytes. It demonstrates that Li-S battery is most likely to be competitive in gravimetric energy density, but not volumetric energy density, with current technology, when comparing with LIBs. Furthermore, the cells with polymer and thin ceramic electrolytes show promising potential in terms of high gravimetric energy density, especially the cells with the polymer electrolyte. This estimation study of Li-S energy density can be used as a good guidance for controlling the key design parameters in order to get desirable energy density at cell-level.

Ground-state properties of light kaonic nuclei signaling symmetry energy at high densities

NASA Astrophysics Data System (ADS)

Yang, Rongyao; Wei, Sina; Jiang, Weizhou

2018-01-01

A sensitive correlation between the ground-state properties of light kaonic nuclei and the symmetry energy at high densities is constructed under the framework of relativistic mean-field theory. Taking oxygen isotopes as an example, we see that a high-density core is produced in kaonic oxygen nuclei, due to the strongly attractive antikaon-nucleon interaction. It is found that the 1{S}1/2 state energy in the high-density core of kaonic nuclei can directly probe the variation of the symmetry energy at supranormal nuclear density, and a sensitive correlation between the neutron skin thickness and the symmetry energy at supranormal density is established directly. Meanwhile, the sensitivity of the neutron skin thickness to the low-density slope of the symmetry energy is greatly increased in the corresponding kaonic nuclei. These sensitive relationships are established upon the fact that the isovector potential in the central region of kaonic nuclei becomes very sensitive to the variation of the symmetry energy. These findings might provide another perspective to constrain high-density symmetry energy, and await experimental verification in the future. Supported by National Natural Science Foundation of China (11775049, 11275048) and the China Jiangsu Provincial Natural Science Foundation (BK20131286)

High Energy Density Plasmas (HEDP) for studies of basic nuclear science relevant to Stellar and Big Bang Nucleosynthesis

NASA Astrophysics Data System (ADS)

Frenje, Johan

2014-06-01

Thermonuclear reaction rates and nuclear processes have been explored traditionally by means of conventional accelerator experiments, which are difficult to execute at conditions relevant to stellar nucleosynthesis. Thus, nuclear reactions at stellar energies are often studied through extrapolations from higher-energy data or in low-background underground experiments. Even when measurements are possible using accelerators at relevant energies, thermonuclear reaction rates in stars are inherently different from those in accelerator experiments. The fusing nuclei are surrounded by bound electrons in accelerator experiments, whereas electrons occupy mainly continuum states in a stellar environment. Nuclear astrophysics research will therefore benefit from an enlarged toolkit for studies of nuclear reactions. In this presentation, we report on the first use of High Energy Density Plasmas for studies of nuclear reactions relevant to basic nuclear science, stellar and Big Bang nucleosynthesis. These experiments were carried out at the OMEGA laser facility at University of Rochester and the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, in which spherical capsules were irradiated with powerful lasers to compress and heat the fuel to high enough temperatures and densities for nuclear reactions to occur. Four experiments will be highlighted in this presentation. In the first experiment, the differential cross section for the elastic neutron-triton (n-T) scattering at 14.1 MeV was measured with significantly higher accuracy than achieved in accelerator experiments. In the second experiment, the T(t,2n)4He reaction, a mirror reaction to the 3He(3He,2p)4He reaction that plays an important role in the proton-proton chain that transforms hydrogen into ordinary 4He in stars like our Sun, was studied at energies in the range 15-40 keV. In the third experiment, the 3He+3He solar fusion reaction was studied directly, and in the fourth experiment, we probed the T+3He reaction, possibly relevant to Big Bang nucleosynthesis.

COMBINATION OF DENSITY AND ENERGY MODULATION IN MICROBUNCHING ANALYSIS

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

Tsai, Cheng Ying; Li, Rui

2016-05-01

Microbunching instability (MBI) has been one of the most challenging issues in the transport of high-brightness electron beams for modern recirculating or energy recovery linac machines. Recently we have developed and implemented a Vlasov solver [1] to calculate the microbunching gain for an arbitrary beamline lattice, based on the extension of existing theoretical formulation [2-4] for the microbunching amplification from an initial density perturbation to the final density modulation. For more thorough analyses, in addition to the case of (initial) density to (final) density amplification, we extend in this paper the previous formulation to more general cases, including energy tomore » density, density to energy and energy to energy amplifications for a recirculation machine. Such semi-analytical formulae are then incorporated into our Vlasov solver, and qualitative agreement is obtained when the semi-analytical Vlasov results are compared with particle tracking simulation using ELEGANT [5].« less

Auroral-polar cap environment and its impact on spacecraft plasma interactions

NASA Technical Reports Server (NTRS)

Garrett, H. B.

1985-01-01

The high density of the plasma at shuttle altitude is likely to increase greatly the possibility of arcing and shorting of exposed high voltage surfaces. For military missions over the polar caps and through the auoroal zones, the added hazards of high energy auroral particle fluxes or solar flares will further increase the hazard to shuttle, its crew, and its mission. A review of the role that the auroral and polar cap environment play in causing these interactions was conducted. A simple, though comprehensive attempt at modelling the shuttle environment at 400 km will be described that can be used to evaluate the importance of the interactions. The results of this evaluation are then used to define areas where adequate environmental measurements will be necessary if a true spacecraft interactions technology is to be developed for the shuttle.

Time-dependent density-functional tight-binding method with the third-order expansion of electron density

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

Nishimoto, Yoshio, E-mail: nishimoto.yoshio@fukui.kyoto-u.ac.jp

2015-09-07

We develop a formalism for the calculation of excitation energies and excited state gradients for the self-consistent-charge density-functional tight-binding method with the third-order contributions of a Taylor series of the density functional theory energy with respect to the fluctuation of electron density (time-dependent density-functional tight-binding (TD-DFTB3)). The formulation of the excitation energy is based on the existing time-dependent density functional theory and the older TD-DFTB2 formulae. The analytical gradient is computed by solving Z-vector equations, and it requires one to calculate the third-order derivative of the total energy with respect to density matrix elements due to the inclusion of themore » third-order contributions. The comparison of adiabatic excitation energies for selected small and medium-size molecules using the TD-DFTB2 and TD-DFTB3 methods shows that the inclusion of the third-order contributions does not affect excitation energies significantly. A different set of parameters, which are optimized for DFTB3, slightly improves the prediction of adiabatic excitation energies statistically. The application of TD-DFTB for the prediction of absorption and fluorescence energies of cresyl violet demonstrates that TD-DFTB3 reproduced the experimental fluorescence energy quite well.« less

Time-dependent density-functional tight-binding method with the third-order expansion of electron density.

PubMed

Nishimoto, Yoshio

2015-09-07

We develop a formalism for the calculation of excitation energies and excited state gradients for the self-consistent-charge density-functional tight-binding method with the third-order contributions of a Taylor series of the density functional theory energy with respect to the fluctuation of electron density (time-dependent density-functional tight-binding (TD-DFTB3)). The formulation of the excitation energy is based on the existing time-dependent density functional theory and the older TD-DFTB2 formulae. The analytical gradient is computed by solving Z-vector equations, and it requires one to calculate the third-order derivative of the total energy with respect to density matrix elements due to the inclusion of the third-order contributions. The comparison of adiabatic excitation energies for selected small and medium-size molecules using the TD-DFTB2 and TD-DFTB3 methods shows that the inclusion of the third-order contributions does not affect excitation energies significantly. A different set of parameters, which are optimized for DFTB3, slightly improves the prediction of adiabatic excitation energies statistically. The application of TD-DFTB for the prediction of absorption and fluorescence energies of cresyl violet demonstrates that TD-DFTB3 reproduced the experimental fluorescence energy quite well.

Dense electron-positron plasmas and ultraintense γ rays from laser-irradiated solids.

PubMed

Ridgers, C P; Brady, C S; Duclous, R; Kirk, J G; Bennett, K; Arber, T D; Robinson, A P L; Bell, A R

2012-04-20

In simulations of a 10 PW laser striking a solid, we demonstrate the possibility of producing a pure electron-positron plasma by the same processes as those thought to operate in high-energy astrophysical environments. A maximum positron density of 10(26) m(-3) can be achieved, 7 orders of magnitude greater than achieved in previous experiments. Additionally, 35% of the laser energy is converted to a burst of γ rays of intensity 10(22) W cm(-2), potentially the most intense γ-ray source available in the laboratory. This absorption results in a strong feedback between both pair and γ-ray production and classical plasma physics in the new "QED-plasma" regime.

On the interplay between cosmological shock waves and their environment

NASA Astrophysics Data System (ADS)

Martin-Alvarez, Sergio; Planelles, Susana; Quilis, Vicent

2017-05-01

Cosmological shock waves are tracers of the thermal history of the structures in the Universe. They play a crucial role in redistributing the energy within the cosmic structures and are also amongst the main ingredients of galaxy and galaxy cluster formation. Understanding this important function requires a proper description of the interplay between shocks and the different environments where they can be found. In this paper, an Adaptive Mesh Refinement (AMR) Eulerian cosmological simulation is analysed by means of a shock-finding algorithm that allows to generate shock wave maps. Based on the population of dark matter halos and on the distribution of density contrast in the simulation, we classify the shocks in five different environments. These range from galaxy clusters to voids. The shock distribution function and the shocks power spectrum are studied for these environments dynamics. We find that shock waves on different environments undergo different formation and evolution processes, showing as well different characteristics. We identify three different phases of formation, evolution and dissipation of these shock waves, and an intricate migration between distinct environments and scales. Shock waves initially form at external, low density regions and are merged and amplified through the collapse of structures. Shock waves and cosmic structures follow a parallel evolution. Later on, shocks start to detach from them and dissipate. We also find that most of the power that shock waves dissipate is found at scales of k ˜0.5 Mpc^{-1}, with a secondary peak at k ˜8 Mpc^{-1}. The evolution of the shocks power spectrum confirms that shock waves evolution is coupled and conditioned by their environment.

High-Latitude Neutral Density Structures Investigated by Utilizing Multi-Instrument Satellite Data and NRLMSISE-00 Simulations

NASA Astrophysics Data System (ADS)

Horvath, Ildiko; Lovell, Brian C.

2018-02-01

This study investigates various types of neutral density features developed in the cusp region during magnetically active and quiet times. Multi-instrument Challenging Minisatellite Payload data provide neutral density, electron temperature, neutral wind speed, and small-scale field-aligned current (SS-FAC) values. Gravity Recovery and Climate Experiment neutral density data are also employed. During active times, cusp densities or density spikes appeared with their underlying flow channels (FCs) and enhanced SS-FACs implying upwelling, fueled by Joule heating, within/above FCs. Both the moderate nightside cusp enhancements under disturbed conditions and the minor dayside cusp enhancements under quiet conditions developed without any underlying FC and enhanced SS-FACs implying the role of particle precipitation in their development. Observations demonstrate the relations of FCs, density spikes, and upwelling-related divergent flows and their connections to the underlying (1) dayside magnetopause reconnection depositing magnetospheric energy into the high-latitude region and (2) Joule heating-driven disturbance dynamo effects. Results provide observational evidence that the moderate nightside cusp enhancements and the minor dayside cusp enhancements detected developed due to direct heating by weak particle precipitation. Chemical compositions related to the dayside density spike and low cusp densities are modeled by Naval Research Laboratory Mass Spectrometer Incoherent Scatter Radar Extended 2000. Modeled composition outputs for the dayside density spike's plasma environment depict some characteristic upwelling signatures. Oppositely, in the case of low dayside cusp densities, composition outputs show opposite characteristics due to the absence of upwelling.

High-resolution simulations of the thermophysiological effects of human exposure to 100 MHz RF energy

NASA Astrophysics Data System (ADS)

Nelson, David A.; Curran, Allen R.; Nyberg, Hans A.; Marttila, Eric A.; Mason, Patrick A.; Ziriax, John M.

2013-03-01

Human exposure to radio frequency (RF) electromagnetic energy is known to result in tissue heating and can raise temperatures substantially in some situations. Standards for safe exposure to RF do not reflect bio-heat transfer considerations however. Thermoregulatory function (vasodilation, sweating) may mitigate RF heating effects in some environments and exposure scenarios. Conversely, a combination of an extreme environment (high temperature, high humidity), high activity levels and thermally insulating garments may exacerbate RF exposure and pose a risk of unsafe temperature elevation, even for power densities which might be acceptable in a normothermic environment. A high-resolution thermophysiological model, incorporating a heterogeneous tissue model of a seated adult has been developed and used to replicate a series of whole-body exposures at a frequency (100 MHz) which approximates that of human whole-body resonance. Exposures were simulated at three power densities (4, 6 and 8 mW cm-2) plus a sham exposure and at three different ambient temperatures (24, 28 and 31 °C). The maximum hypothalamic temperature increase over the course of a 45 min exposure was 0.28 °C and occurred in the most extreme conditions (Tamb = 31 °C, PD = 8 mW cm-2). Skin temperature increases attributable to RF exposure were modest, with the exception of a ‘hot spot’ in the vicinity of the ankle where skin temperatures exceeded 39 °C. Temperature increases in internal organs and tissues were small, except for connective tissue and bone in the lower leg and foot. Temperature elevation also was noted in the spinal cord, consistent with a hot spot previously identified in the literature.

Solar wind interaction with comet 67P: Impacts of corotating interaction regions

NASA Astrophysics Data System (ADS)

Edberg, N. J. T.; Eriksson, A. I.; Odelstad, E.; Vigren, E.; Andrews, D. J.; Johansson, F.; Burch, J. L.; Carr, C. M.; Cupido, E.; Glassmeier, K.-H.; Goldstein, R.; Halekas, J. S.; Henri, P.; Koenders, C.; Mandt, K.; Mokashi, P.; Nemeth, Z.; Nilsson, H.; Ramstad, R.; Richter, I.; Wieser, G. Stenberg

2016-02-01

We present observations from the Rosetta Plasma Consortium of the effects of stormy solar wind on comet 67P/Churyumov-Gerasimenko. Four corotating interaction regions (CIRs), where the first event has possibly merged with a coronal mass ejection, are traced from Earth via Mars (using Mars Express and Mars Atmosphere and Volatile EvolutioN mission) to comet 67P from October to December 2014. When the comet is 3.1-2.7 AU from the Sun and the neutral outgassing rate ˜1025-1026 s-1, the CIRs significantly influence the cometary plasma environment at altitudes down to 10-30 km. The ionospheric low-energy (˜5 eV) plasma density increases significantly in all events, by a factor of >2 in events 1 and 2 but less in events 3 and 4. The spacecraft potential drops below -20 V upon impact when the flux of electrons increases. The increased density is likely caused by compression of the plasma environment, increased particle impact ionization, and possibly charge exchange processes and acceleration of mass-loaded plasma back to the comet ionosphere. During all events, the fluxes of suprathermal (˜10-100 eV) electrons increase significantly, suggesting that the heating mechanism of these electrons is coupled to the solar wind energy input. At impact the magnetic field strength in the coma increases by a factor of 2-5 as more interplanetary magnetic field piles up around the comet. During two CIR impact events, we observe possible plasma boundaries forming, or moving past Rosetta, as the strong solar wind compresses the cometary plasma environment. We also discuss the possibility of seeing some signatures of the ionospheric response to tail disconnection events.

High-resolution simulations of the thermophysiological effects of human exposure to 100 MHz RF energy.

PubMed

Nelson, David A; Curran, Allen R; Nyberg, Hans A; Marttila, Eric A; Mason, Patrick A; Ziriax, John M

2013-03-21

Human exposure to radio frequency (RF) electromagnetic energy is known to result in tissue heating and can raise temperatures substantially in some situations. Standards for safe exposure to RF do not reflect bio-heat transfer considerations however. Thermoregulatory function (vasodilation, sweating) may mitigate RF heating effects in some environments and exposure scenarios. Conversely, a combination of an extreme environment (high temperature, high humidity), high activity levels and thermally insulating garments may exacerbate RF exposure and pose a risk of unsafe temperature elevation, even for power densities which might be acceptable in a normothermic environment. A high-resolution thermophysiological model, incorporating a heterogeneous tissue model of a seated adult has been developed and used to replicate a series of whole-body exposures at a frequency (100 MHz) which approximates that of human whole-body resonance. Exposures were simulated at three power densities (4, 6 and 8 mW cm(-2)) plus a sham exposure and at three different ambient temperatures (24, 28 and 31 °C). The maximum hypothalamic temperature increase over the course of a 45 min exposure was 0.28 °C and occurred in the most extreme conditions (T(AMB) = 31 °C, PD = 8 mW cm(-2)). Skin temperature increases attributable to RF exposure were modest, with the exception of a 'hot spot' in the vicinity of the ankle where skin temperatures exceeded 39 °C. Temperature increases in internal organs and tissues were small, except for connective tissue and bone in the lower leg and foot. Temperature elevation also was noted in the spinal cord, consistent with a hot spot previously identified in the literature.

Acoustic power balance in lined ducts

NASA Technical Reports Server (NTRS)

Eversman, W.

1979-01-01

It is shown that the two common definitions of acoustic energy density and intensity in uniform unlined ducts carrying uniform flow are compatible to the extent that both energy densities can be used in an appropriate variational principle to derive the convected wave equation. When the duct walls are lined both energy densities must be modified to account for the wall energy density. This results in a new energy conservation equation which utilizes a modified definition of axial power and accounts for wall dissipation. Computations in specific cases demonstrate the validity of the modified acoustic energy relation.

Supernova remnants and pulsar wind nebulae with Imaging Atmospheric Cherenkov Telescopes (IACTs)

NASA Astrophysics Data System (ADS)

Eger, Peter

2015-08-01

The observation of very-high-energy (VHE, E > 100 GeV) gamma rays is an excellent tool to study the most energetic and violent environments in the Galaxy. This energy range is only accessible with ground-based instruments such as Imaging Atmospheric Cherenkov Telescopes (IACTs) that reconstruct the energy and direction of the primary gamma ray by observing the Cherenkov light from the induced extended air showers in Earths atmosphere. The main goals of Galactic VHE gamma-ray science are the identification of individual sources of cosmic rays (CRs), such as supernova remnants (SNRs), and the study of other extreme astrophysical objects at the highest energies, such as gamma-ray binaries and pulsar wind nebulae (PWNe). One of the main challenges is the discrimination between leptonic and hadronic gamma-ray production channels. To that end, the gamma-ray signal from each individual source needs to be brought into context with the multi-wavelength environment of the astrophysical object in question, particularly with observations tracing the density of the surrounding interstellar medium, or synchrotron radiation from relativistic electrons. In this review presented at the European Cosmic Ray Symposium 2014 (ECRS2014), the most recent developments in the field of Galactic VHE gamma-ray science are highlighted, with particular emphasis on SNRs and PWNe.

Light-controlled plasmon switching using hybrid metal-semiconductor nanostructures.

PubMed

Paudel, Hari P; Leuenberger, Michael N

2012-06-13

We present a proof of concept for the dynamic control over the plasmon resonance frequencies in a hybrid metal-semiconductor nanoshell structure with Ag core and TiO(2) coating. Our method relies on the temporary change of the dielectric function ε of TiO(2) achieved through temporarily generated electron-hole pairs by means of a pump laser pulse. This change in ε leads to a blue shift of the Ag surface plasmon frequency. We choose TiO(2) as the environment of the Ag core because the band gap energy of TiO(2) is larger than the Ag surface plasmon energy of our nanoparticles, which allows the surface plasmon being excited without generating electron-hole pairs in the environment at the same time. We calculate the magnitude of the plasmon resonance shift as a function of electron-hole pair density and obtain shifts up to 126 nm at wavelengths around 460 nm. Using our results, we develop the model of a light-controlled surface plasmon polariton switch.

Energy-Water Modeling and Impacts at Urban and Infrastructure Scales

NASA Astrophysics Data System (ADS)

Saleh, F.; Pullen, J. D.; Schoonen, M. A.; Gonzalez, J.; Bhatt, V.; Fellows, J. D.

2017-12-01

We converge multi-disciplinary, multi-sectoral modeling and data analysis tools on an urban watershed to examine the feedbacks of concentrated and connected infrastructure on the environment. Our focus area is the Lower Hudson River Basin (LHRB). The LHRB captures long-term and short- term energy/water stressors as it represents: 1) a coastal environment subject to sea level rise that is among the fastest in the East impacted by a wide array of various storms; 2) one of the steepest gradients in population density in the US, with Manhattan the most densely populated coastal county in the nation; 3) energy/water infrastructure serving the largest metropolitan area in the US; 4) a history of environmental impacts, ranging from heatwaves to hurricanes, that can be used to hindcast; and 5) a wealth of historic and real-time data, extensive monitoring facilities and existing specific sector models that can be leveraged. We detail two case studies on "water infrastructure and stressors", and "heatwaves and energy-water demands." The impact of a hypothetical failure of Oradell Dam (on the Hackensack River, a tributary of the Hudson River) coincident with a hurricane, and urban power demands under current and future heat waves are examined with high-resolution (meter to km scale) earth system models to illustrate energy water nexus issues where detailed predictions can shape response and mitigation strategies.

Quantum chemistry in arbitrary dielectric environments: Theory and implementation of nonequilibrium Poisson boundary conditions and application to compute vertical ionization energies at the air/water interface

NASA Astrophysics Data System (ADS)

Coons, Marc P.; Herbert, John M.

2018-06-01

Widely used continuum solvation models for electronic structure calculations, including popular polarizable continuum models (PCMs), usually assume that the continuum environment is isotropic and characterized by a scalar dielectric constant, ɛ. This assumption is invalid at a liquid/vapor interface or any other anisotropic solvation environment. To address such scenarios, we introduce a more general formalism based on solution of Poisson's equation for a spatially varying dielectric function, ɛ(r). Inspired by nonequilibrium versions of PCMs, we develop a similar formalism within the context of Poisson's equation that includes the out-of-equilibrium dielectric response that accompanies a sudden change in the electron density of the solute, such as that which occurs in a vertical ionization process. A multigrid solver for Poisson's equation is developed to accommodate the large spatial grids necessary to discretize the three-dimensional electron density. We apply this methodology to compute vertical ionization energies (VIEs) of various solutes at the air/water interface and compare them to VIEs computed in bulk water, finding only very small differences between the two environments. VIEs computed using approximately two solvation shells of explicit water molecules are in excellent agreement with experiment for F-(aq), Cl-(aq), neat liquid water, and the hydrated electron, although errors for Li+(aq) and Na+(aq) are somewhat larger. Nonequilibrium corrections modify VIEs by up to 1.2 eV, relative to models based only on the static dielectric constant, and are therefore essential to obtain agreement with experiment. Given that the experiments (liquid microjet photoelectron spectroscopy) may be more sensitive to solutes situated at the air/water interface as compared to those in bulk water, our calculations provide some confidence that these experiments can indeed be interpreted as measurements of VIEs in bulk water.

Quantum chemistry in arbitrary dielectric environments: Theory and implementation of nonequilibrium Poisson boundary conditions and application to compute vertical ionization energies at the air/water interface.

PubMed

Coons, Marc P; Herbert, John M

2018-06-14

Widely used continuum solvation models for electronic structure calculations, including popular polarizable continuum models (PCMs), usually assume that the continuum environment is isotropic and characterized by a scalar dielectric constant, ε. This assumption is invalid at a liquid/vapor interface or any other anisotropic solvation environment. To address such scenarios, we introduce a more general formalism based on solution of Poisson's equation for a spatially varying dielectric function, ε(r). Inspired by nonequilibrium versions of PCMs, we develop a similar formalism within the context of Poisson's equation that includes the out-of-equilibrium dielectric response that accompanies a sudden change in the electron density of the solute, such as that which occurs in a vertical ionization process. A multigrid solver for Poisson's equation is developed to accommodate the large spatial grids necessary to discretize the three-dimensional electron density. We apply this methodology to compute vertical ionization energies (VIEs) of various solutes at the air/water interface and compare them to VIEs computed in bulk water, finding only very small differences between the two environments. VIEs computed using approximately two solvation shells of explicit water molecules are in excellent agreement with experiment for F - (aq), Cl - (aq), neat liquid water, and the hydrated electron, although errors for Li + (aq) and Na + (aq) are somewhat larger. Nonequilibrium corrections modify VIEs by up to 1.2 eV, relative to models based only on the static dielectric constant, and are therefore essential to obtain agreement with experiment. Given that the experiments (liquid microjet photoelectron spectroscopy) may be more sensitive to solutes situated at the air/water interface as compared to those in bulk water, our calculations provide some confidence that these experiments can indeed be interpreted as measurements of VIEs in bulk water.

Postmortem validation of breast density using dual-energy mammography

PubMed Central

Molloi, Sabee; Ducote, Justin L.; Ding, Huanjun; Feig, Stephen A.

2014-01-01

Purpose: Mammographic density has been shown to be an indicator of breast cancer risk and also reduces the sensitivity of screening mammography. Currently, there is no accepted standard for measuring breast density. Dual energy mammography has been proposed as a technique for accurate measurement of breast density. The purpose of this study is to validate its accuracy in postmortem breasts and compare it with other existing techniques. Methods: Forty postmortem breasts were imaged using a dual energy mammography system. Glandular and adipose equivalent phantoms of uniform thickness were used to calibrate a dual energy basis decomposition algorithm. Dual energy decomposition was applied after scatter correction to calculate breast density. Breast density was also estimated using radiologist reader assessment, standard histogram thresholding and a fuzzy C-mean algorithm. Chemical analysis was used as the reference standard to assess the accuracy of different techniques to measure breast composition. Results: Breast density measurements using radiologist reader assessment, standard histogram thresholding, fuzzy C-mean algorithm, and dual energy were in good agreement with the measured fibroglandular volume fraction using chemical analysis. The standard error estimates using radiologist reader assessment, standard histogram thresholding, fuzzy C-mean, and dual energy were 9.9%, 8.6%, 7.2%, and 4.7%, respectively. Conclusions: The results indicate that dual energy mammography can be used to accurately measure breast density. The variability in breast density estimation using dual energy mammography was lower than reader assessment rankings, standard histogram thresholding, and fuzzy C-mean algorithm. Improved quantification of breast density is expected to further enhance its utility as a risk factor for breast cancer. PMID:25086548

Postmortem validation of breast density using dual-energy mammography

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

Molloi, Sabee, E-mail: symolloi@uci.edu; Ducote, Justin L.; Ding, Huanjun

2014-08-15

Purpose: Mammographic density has been shown to be an indicator of breast cancer risk and also reduces the sensitivity of screening mammography. Currently, there is no accepted standard for measuring breast density. Dual energy mammography has been proposed as a technique for accurate measurement of breast density. The purpose of this study is to validate its accuracy in postmortem breasts and compare it with other existing techniques. Methods: Forty postmortem breasts were imaged using a dual energy mammography system. Glandular and adipose equivalent phantoms of uniform thickness were used to calibrate a dual energy basis decomposition algorithm. Dual energy decompositionmore » was applied after scatter correction to calculate breast density. Breast density was also estimated using radiologist reader assessment, standard histogram thresholding and a fuzzy C-mean algorithm. Chemical analysis was used as the reference standard to assess the accuracy of different techniques to measure breast composition. Results: Breast density measurements using radiologist reader assessment, standard histogram thresholding, fuzzy C-mean algorithm, and dual energy were in good agreement with the measured fibroglandular volume fraction using chemical analysis. The standard error estimates using radiologist reader assessment, standard histogram thresholding, fuzzy C-mean, and dual energy were 9.9%, 8.6%, 7.2%, and 4.7%, respectively. Conclusions: The results indicate that dual energy mammography can be used to accurately measure breast density. The variability in breast density estimation using dual energy mammography was lower than reader assessment rankings, standard histogram thresholding, and fuzzy C-mean algorithm. Improved quantification of breast density is expected to further enhance its utility as a risk factor for breast cancer.« less

High-Capacity Cathode Material with High Voltage for Li-Ion Batteries

DOE PAGES

Shi, Ji -Lei; Xiao, Dong -Dong; Ge, Mingyuan; ...

2018-01-15

Electrochemical energy storage devices with a high energy density are an important technology in modern society, especially for electric vehicles. The most effective approach to improve the energy density of batteries is to search for high-capacity electrode materials. According to the concept of energy quality, a high-voltage battery delivers a highly useful energy, thus providing a new insight to improve energy density. Based on this concept, a novel and successful strategy to increase the energy density and energy quality by increasing the discharge voltage of cathode materials and preserving high capacity is proposed. The proposal is realized in high-capacity Li-richmore » cathode materials. The average discharge voltage is increased from 3.5 to 3.8 V by increasing the nickel content and applying a simple after-treatment, and the specific energy is improved from 912 to 1033 Wh kg-1. The current work provides an insightful universal principle for developing, designing, and screening electrode materials for high energy density and energy quality.« less

High-Capacity Cathode Material with High Voltage for Li-Ion Batteries

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

Shi, Ji -Lei; Xiao, Dong -Dong; Ge, Mingyuan

Electrochemical energy storage devices with a high energy density are an important technology in modern society, especially for electric vehicles. The most effective approach to improve the energy density of batteries is to search for high-capacity electrode materials. According to the concept of energy quality, a high-voltage battery delivers a highly useful energy, thus providing a new insight to improve energy density. Based on this concept, a novel and successful strategy to increase the energy density and energy quality by increasing the discharge voltage of cathode materials and preserving high capacity is proposed. The proposal is realized in high-capacity Li-richmore » cathode materials. The average discharge voltage is increased from 3.5 to 3.8 V by increasing the nickel content and applying a simple after-treatment, and the specific energy is improved from 912 to 1033 Wh kg-1. The current work provides an insightful universal principle for developing, designing, and screening electrode materials for high energy density and energy quality.« less

Ultrastructural remodelling of slow skeletal muscle fibres in creatine kinase deficient mice: a quantitative study.

PubMed

Novotová, Marta; Tarabová, Bohumila; Tylková, Lucia; Ventura-Clapier, Renée; Zahradník, Ivan

2016-10-01

Creatine kinase content, isoform distribution, and participation in energy transfer are muscle type specific. We analysed ultrastructural changes in slow muscle fibres of soleus due to invalidation of creatine kinase (CK) to reveal a difference in the remodelling strategy in comparison with fast muscle fibres of gastrocnemius published previously. We have employed the stereological method of vertical sections and electron microscopy of soleus muscles of wild type (WT) and CK-/- mice. The mitochondrial volume density was 1.4× higher but that of sarcoplasmic reticulum (SR) was almost 5× lower in slow CK-/- muscles fibres than in WT fibres. The volume density of terminal cisterns and of t-tubules was also lower in CK-/- than in WT fibres. The analysis of organelle environment revealed increased neighbourhood of mitochondria and A-bands that resulted from the decreased volume density of SR, from relocation of mitochondria along myofibrils, and from intrusion of mitochondria to myofibrils. These processes direct ATP supply closer to the contractile machinery. The decreased interaction between mitochondria and SR suggests reduced dependence of calcium uptake on oxidative ATP production. In conclusion, the architecture of skeletal muscle cells is under control of a cellular program that optimizes energy utilization specifically for a given muscle type.

Joint density-functional theory for energetics and spectroscopy in complex aqueous and nonaqueous solvents

NASA Astrophysics Data System (ADS)

Gunceler, Deniz

Solvents are of great importance in many technological applications, but are difficult to study using standard, off-the-shelf ab initio electronic structure methods. This is because a single configuration of molecular positions in the solvent (a "snapshot" of the fluid) is not necessarily representative of the thermodynamic average. To obtain any thermodynamic averages (e.g. free energies), the phase space of the solvent must be sampled, typically using molecular dynamics. This greatly increases the computational cost involved in studying solvated systems. Joint density-functional theory has made its mark by being a computationally efficient yet rigorous theory by which to study solvation. It replaces the need for thermodynamic sampling with an effective continuum description of the solvent environment that is in-principle exact, computationally efficient and intuitive (easier to interpret). It has been very successful in aqueous systems, with potential applications in (among others) energy materials discovery, catalysis and surface science. In this dissertation, we develop accurate and fast joint density functional theories for complex, non-aqueous solvent enviroments, including organic solvents and room temperature ionic liquids, as well as new methods for calculating electron excitation spectra in such systems. These theories are then applied to a range of physical problems, from dendrite formation in lithium-metal batteries to the optical spectra of solvated ions.

Ambipolar zinc-polyiodide electrolyte for a high-energy density aqueous redox flow battery

DOE PAGES

Li, Bin; Nie, Zimin; Vijayakumar, M.; ...

2015-02-24

Large-scale energy storage systems are crucial for substantial deployment of renewable energy sources. Energy storage systems with high energy density, high safety, and low cost and environmental friendliness are desired. To overcome the major limitations of the current aqueous redox flow battery systems, namely lower energy density (~25 Wh L -1) and presence of strong acids and/or other hazardous, a high energy density aqueous zinc/polyiodide flow battery (ZIB) is designed with near neutral ZnI 2 solutions as catholytes. The energy density of ZIB could reach 322 Wh L -1 at the solubility limit of ZnI 2 in water (~7 M).more » We demonstrate charge and discharge energy densities of 245.9 Wh/L and 166.7 Wh L-1 with ZnI 2 electrolyte at 5.0 M, respectively. The addition of ethanol (EtOH) in ZnI 2 electrolyte can effectively mitigate the growth of zinc dendrite at the anode and improve the stability of catholytes with wider temperature window (-20 to 50°C), which enable ZIB system to be a promising alternative as a high-energy and high- safety stationary energy storage system.« less

Minimizing lighting power density in office rooms equipped with Anidolic Daylighting Systems

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

Linhart, Friedrich; Scartezzini, Jean-Louis

2010-04-15

Electric lighting is responsible for up to one third of an office building's electricity needs. Making daylight more available in office buildings can not only contribute to significant energy savings but also enhance the occupants' performance and wellbeing. Anidolic Daylighting Systems (ADS) are one type of very effective facade-integrated daylighting systems. All south-facing office rooms within the LESO solar experimental building in Lausanne (Switzerland) are equipped with a given type of ADS. A recent study has shown that these offices' occupants are highly satisfied with their lighting environment. The most energy-efficient south-facing offices have a lighting power density of lessmore » than 5W/m{sup 2}. The lighting situation within these ''best practice''-offices has been assessed using the lighting simulation software RELUX Vision. Because this lighting situation is very much appreciated by the occupants, it was used as a starting point for developing even more energy-efficient office lighting designs. Two new lighting designs, leading to lighting power densities of 3.9W/m{sup 2} and 3W/m{sup 2}, respectively, have been suggested and simulated with RELUX Vision. Simulation results have shown that the expected performances of these new systems are comparable to that of the current lighting installation within the ''best practice''-offices or even better. These simulation results have been confirmed during experiments on 20 human subjects in a test office room recently set up within the LESO building. This article gives engineers, architects and light planers valuable information and ideas on how to design energy-efficient and comfortable electric lighting systems in office rooms with abundant access to daylight. (author)« less

Infrared Photometric Properties of 709 Candidate Stellar Bowshock Nebulae

NASA Astrophysics Data System (ADS)

Kobulnicky, Henry A.; Schurhammer, Danielle P.; Baldwin, Daniel J.; Chick, William T.; Dixon, Don M.; Lee, Daniel; Povich, Matthew S.

2017-11-01

Arcuate infrared nebulae are ubiquitous throughout the Galactic Plane and are candidates for partial shells, bubbles, or bowshocks produced by massive runaway stars. We tabulate infrared photometry for 709 such objects using images from the Spitzer Space Telescope, the Wide-field Infrared Explorer, and the Herschel Space Observatory (HSO). Of the 709 objects identified at 24 or 22 μm, 422 are detected at the HSO 70 μm bandpass. Of these, only 39 are detected at HSO 160 μm. The 70 μm peak surface brightnesses are 0.5-2.5 Jy arcmin-2. Color temperatures calculated from the 24 to 70 μm ratios range from 80 to 400 K. Color temperatures from 70 to 160 μm ratios are systematically lower, 40-200 K. Both of these temperature are, on average, 75% higher than the nominal temperatures derived by assuming that dust is in steady-state radiative equilibrium. This may be evidence of stellar wind bowshocks sweeping up and heating—possibly fragmenting but not destroying—interstellar dust. Infrared luminosity correlates with standoff distance, R 0, as predicted by published hydrodynamical models. Infrared spectral energy distributions are consistent with interstellar dust exposed to either single radiant energy density, U={10}3{--}{10}5 (in more than half of the objects) or a range of radiant energy densities U min = 25 to U max = 103-105 times the mean interstellar value for the remainder. Hence, the central OB stars dominate the energetics, making these enticing laboratories for testing dust models in constrained radiation environments. The spectral energy densities are consistent with polycyclic aromatic hydrocarbon fractions {q}{PAH}≲ 1 % in most objects.

Energy decomposition analysis for exciplexes using absolutely localized molecular orbitals

NASA Astrophysics Data System (ADS)

Ge, Qinghui; Mao, Yuezhi; Head-Gordon, Martin

2018-02-01

An energy decomposition analysis (EDA) scheme is developed for understanding the intermolecular interaction involving molecules in their excited states. The EDA utilizes absolutely localized molecular orbitals to define intermediate states and is compatible with excited state methods based on linear response theory such as configuration interaction singles and time-dependent density functional theory. The shift in excitation energy when an excited molecule interacts with the environment is decomposed into frozen, polarization, and charge transfer contributions, and the frozen term can be further separated into Pauli repulsion and electrostatics. These terms can be added to their counterparts obtained from the ground state EDA to form a decomposition of the total interaction energy. The EDA scheme is applied to study a variety of systems, including some model systems to demonstrate the correct behavior of all the proposed energy components as well as more realistic systems such as hydrogen-bonding complexes (e.g., formamide-water, pyridine/pyrimidine-water) and halide (F-, Cl-)-water clusters that involve charge-transfer-to-solvent excitations.

Nonlinear dielectric thin films for high-power electric storage with energy density comparable with electrochemical supercapacitors.

PubMed

Yao, Kui; Chen, Shuting; Rahimabady, Mojtaba; Mirshekarloo, Meysam Sharifzadeh; Yu, Shuhui; Tay, Francis Eng Hock; Sritharan, Thirumany; Lu, Li

2011-09-01

Although batteries possess high energy storage density, their output power is limited by the slow movement of charge carriers, and thus capacitors are often required to deliver high power output. Dielectric capacitors have high power density with fast discharge rate, but their energy density is typically much lower than electrochemical supercapacitors. Increasing the energy density of dielectric materials is highly desired to extend their applications in many emerging power system applications. In this paper, we review the mechanisms and major characteristics of electric energy storage with electrochemical supercapacitors and dielectric capacitors. Three types of in-house-produced ferroic nonlinear dielectric thin film materials with high energy density are described, including (Pb(0.97)La(0.02))(Zr(0.90)Sn(0.05)Ti(0.05))O(3) (PLZST) antiferroelectric ceramic thin films, Pb(Zn(1/3)Nb(2/3))O(3-)Pb(Mg(1/3)Nb(2/3))O(3-)PbTiO(3) (PZN-PMN-PT) relaxor ferroelectric ceramic thin films, and poly(vinylidene fluoride) (PVDF)-based polymer blend thin films. The results showed that these thin film materials are promising for electric storage with outstandingly high power density and fairly high energy density, comparable with electrochemical supercapacitors.

Reduced energy density of close-up diets decrease ruminal pH and increase concentration of volatile fatty acids postpartum in Holstein cows.

PubMed

Huang, Wenming; Tian, Yujia; Li, Shengli; Wu, Zhaohai; Cao, Zhijun

2017-11-01

The objective of this study was to determine the effect of reduced energy density of close-up diets on ruminal fermentation parameters in transition cows. Fourteen Holstein dry cows were blocked and assigned randomly to three groups fed a high energy density diet (HD, 1.62 Mcal of net energy for lactation (NE L )/kg dry matter (DM)), or a middle energy density diet (MD, 1.47 Mcal NE L /kg DM), or a low energy density diet (LD, 1.30 Mcal NE L /kg DM) prepartum, and were fed the same diet postpartum. The reduced energy density diets decreased the average dry matter intake (DMI) prepartum and tended to increase the DMI postpartum. The ruminal pH of the LD group was significantly higher prepartum and lower during the first week of lactation compared with the other two groups. The reduced energy density diet depressed the average ruminal concentration of propionate and butyrate prepartum, and increased the average concentration of total volatile fatty acids (VFA) postpartum. The LD group had higher populations of Butyrivibrio fibrisolvens and Ruminococcus flavefaciens relative to HD and MD groups on 7 days in milk. In conclusion, the cows fed reduced energy density diet prepartum had higher VFA concentration, but were more susceptible to subacute ruminal acidosis postpartum. © 2017 Japanese Society of Animal Science.

Laboratory electron exposure of TSS-1 thermal control coating

NASA Technical Reports Server (NTRS)

Vaughn, J. A.; Mccollum, M.; Carruth, M. R., Jr.

1995-01-01

RM400, a conductive thermal control coating, was developed for use on the exterior shell of the tethered satellite. Testing was performed by the Engineering Physics Division to quantify effects of the space environment on this coating and its conductive and optical properties. Included in this testing was exposure of RM400 to electrons with energies ranging from 0.1 to 1 keV, to simulate electrons accelerated from the ambient space plasma when the tethered satellite is fully deployed. During this testing, the coating was found to luminesce, and a prolonged exposure of the coating to high-energy electrons caused the coating to darken. This report describes the tests done to quantify the degradation of the thermal control properties caused by electron exposure and to measure the luminescence as a function of electron energy and current density to the satellite.

All 2D materials as electrodes for high power hybrid energy storage applications

NASA Astrophysics Data System (ADS)

Kato, Keiko; Sayed, Farheen N.; Babu, Ganguli; Ajayan, Pulickel M.

2018-04-01

Achieving both high energy and power densities from energy storage devices is a core strategy to meet the increasing demands of high performance portable electronics and electric transportation systems. Li-ion capacitor is a promising hybrid technology that strategically exploits high energy density from a Li-ion battery electrode and high power density from a supercapacitor electrode. However, the performance and safety of hybrid devices are still major concerns due to the use of graphite anodes which form passivation layers with organic electrolytes at lower potentials. Here, we explore 2D nanosheets as both anode and cathode electrodes to build a high power system without compromising energy density. Owing to the high electrical conductivity and multivalent redox activity at higher potentials, the Li-ion intercalation electrode is capable of maintaining large energy density at higher current rates with less safety risk than conventional systems. Hybrid devices consisting of all in all 2D electrodes deliver energy density as high as 121 Wh g-1 (at 240 W kg-1) and retains 29 Wh g-1 at high power density of 3600 W kg-1.

Measures and metrics of sustainable diets with a focus on milk, yogurt, and dairy products

PubMed Central

Drewnowski, Adam

2018-01-01

The 4 domains of sustainable diets are nutrition, economics, society, and the environment. To be sustainable, foods and food patterns need to be nutrient-rich, affordable, culturally acceptable, and sparing of natural resources and the environment. Each sustainability domain has its own measures and metrics. Nutrient density of foods has been assessed through nutrient profiling models, such as the Nutrient-Rich Foods family of scores. The Food Affordability Index, applied to different food groups, has measured both calories and nutrients per penny (kcal/$). Cultural acceptance measures have been based on relative food consumption frequencies across population groups. Environmental impact of individual foods and composite food patterns has been measured in terms of land, water, and energy use. Greenhouse gas emissions assess the carbon footprint of agricultural food production, processing, and retail. Based on multiple sustainability metrics, milk, yogurt, and other dairy products can be described as nutrient-rich, affordable, acceptable, and appealing. The environmental impact of dairy farming needs to be weighed against the high nutrient density of milk, yogurt, and cheese as compared with some plant-based alternatives. PMID:29206982

Wheat production in controlled environments

NASA Technical Reports Server (NTRS)

Salisbury, Frank B.; Bugbee, Bruce; Bubenheim, David

1987-01-01

Conditions are optimized for maximum yield and quality of wheat to be used in a controlled environment life support system (CELSS) in a Lunar or Martian base or a spacecraft. With yields of 23 to 57 g/sq m/d of edible biomass, a minimum size for a CELSS would be between 12 and 30 sq m per person, utilizing about 600 W/sq m of electrical energy for artificial light. Temperature, irradiance, photoperiod, carbon dioxide levels, humidity, and wind velocity are controlled in growth chambers. Nutrient solutions (adjusted for wheat) are supplied to the roots via a recirculating system that controls pH by adding HNO3 and controlling the NO3/NH4 ratio in solution. A rock-wool plant support allows direct seeding and densities up to 10,000 plants sq m. Densities up to 2000 plants/sq m appear to increase seed yield. Biomass production increases almost linearily with increasing irradiance from 400 to 1700 micromol/sq m/s of photosynthetic photon flux, but the efficiency of light utilization decreases over this range. Photoperiod and temperature both have a profound influence on floral initiation, spikelet formation, stem elongation, and fertilization.

Challenges in Wireless System Integration as Enablers for Indoor Context Aware Environments

PubMed Central

Aguirre, Erik

2017-01-01

The advent of fully interactive environments within Smart Cities and Smart Regions requires the use of multiple wireless systems. In the case of user-device interaction, which finds multiple applications such as Ambient Assisted Living, Intelligent Transportation Systems or Smart Grids, among others, large amount of transceivers are employed in order to achieve anytime, anyplace and any device connectivity. The resulting combination of heterogeneous wireless network exhibits fundamental limitations derived from Coverage/Capacity relations, as a function of required Quality of Service parameters, required bit rate, energy restrictions and adaptive modulation and coding schemes. In this context, inherent transceiver density poses challenges in overall system operation, given by multiple node operation which increases overall interference levels. In this work, a deterministic based analysis applied to variable density wireless sensor network operation within complex indoor scenarios is presented, as a function of topological node distribution. The extensive analysis derives interference characterizations, both for conventional transceivers as well as wearables, which provide relevant information in terms of individual node configuration as well as complete network layout. PMID:28704963

High energy density propulsion systems and small engine dynamometer

NASA Astrophysics Data System (ADS)

Hays, Thomas

2009-07-01

Scope and Method of Study. This study investigates all possible methods of powering small unmanned vehicles, provides reasoning for the propulsion system down select, and covers in detail the design and production of a dynamometer to confirm theoretical energy density calculations for small engines. Initial energy density calculations are based upon manufacturer data, pressure vessel theory, and ideal thermodynamic cycle efficiencies. Engine tests are conducted with a braking type dynamometer for constant load energy density tests, and show true energy densities in excess of 1400 WH/lb of fuel. Findings and Conclusions. Theory predicts lithium polymer, the present unmanned system energy storage device of choice, to have much lower energy densities than other conversion energy sources. Small engines designed for efficiency, instead of maximum power, would provide the most advantageous method for powering small unmanned vehicles because these engines have widely variable power output, loss of mass during flight, and generate rotational power directly. Theoretical predictions for the energy density of small engines has been verified through testing. Tested values up to 1400 WH/lb can be seen under proper operating conditions. The implementation of such a high energy density system will require a significant amount of follow-on design work to enable the engines to tolerate the higher temperatures of lean operation. Suggestions are proposed to enable a reliable, small-engine propulsion system in future work. Performance calculations show that a mature system is capable of month long flight times, and unrefueled circumnavigation of the globe.

High-Performance Polymers Sandwiched with Chemical Vapor Deposited Hexagonal Boron Nitrides as Scalable High-Temperature Dielectric Materials.

PubMed

Azizi, Amin; Gadinski, Matthew R; Li, Qi; AlSaud, Mohammed Abu; Wang, Jianjun; Wang, Yi; Wang, Bo; Liu, Feihua; Chen, Long-Qing; Alem, Nasim; Wang, Qing

2017-09-01

Polymer dielectrics are the preferred materials of choice for power electronics and pulsed power applications. However, their relatively low operating temperatures significantly limit their uses in harsh-environment energy storage devices, e.g., automobile and aerospace power systems. Herein, hexagonal boron nitride (h-BN) films are prepared from chemical vapor deposition (CVD) and readily transferred onto polyetherimide (PEI) films. Greatly improved performance in terms of discharged energy density and charge-discharge efficiency is achieved in the PEI sandwiched with CVD-grown h-BN films at elevated temperatures when compared to neat PEI films and other high-temperature polymer and nanocomposite dielectrics. Notably, the h-BN-coated PEI films are capable of operating with >90% charge-discharge efficiencies and delivering high energy densities, i.e., 1.2 J cm -3 , even at a temperature close to the glass transition temperature of polymer (i.e., 217 °C) where pristine PEI almost fails. Outstanding cyclability and dielectric stability over a straight 55 000 charge-discharge cycles are demonstrated in the h-BN-coated PEI at high temperatures. The work demonstrates a general and scalable pathway to enable the high-temperature capacitive energy applications of a wide range of engineering polymers and also offers an efficient method for the synthesis and transfer of 2D nanomaterials at the scale demanded for applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Revisiting Supernova 1987A constraints on dark photons

DOE PAGES

Chang, Jae Hyeok; Essig, Rouven; McDermott, Samuel D.

2017-01-25

We revisit constraints on dark photons with masses below ~ 100 MeV from the observations of Supernova 1987A. If dark photons are produced in sufficient quantity, they reduce the amount of energy emitted in the form of neutrinos, in conflict with observations. For the first time, we include the effects of finite temperature and density on the kinetic-mixing parameter,ϵ, in this environment. This causes the constraints on ϵ to weaken with the dark-photon mass below ~ 15 MeV. For large-enough values of ϵ, it is well known that dark photons can be reabsorbed within the supernova. Since the rates ofmore » reabsorption processes decrease as the dark-photon energy increases, we point out that dark photons with energies above the Wien peak can escape without scattering, contributing more to energy loss than is possible assuming a blackbody spectrum. Furthermore, we estimate the systematic uncertainties on the cooling bounds by deriving constraints assuming one analytic and four different simulated temperature and density profiles of the proto-neutron star. Finally, we estimate also the systematic uncertainty on the bound by varying the distance across which dark photons must propagate from their point of production to be able to affect the star. Finally, this work clarifies the bounds from SN1987A on the dark-photon parameter space.« less

Chlorinated paraffins wrapping of carbon nanotubes: A theoretical investigation

NASA Astrophysics Data System (ADS)

Ding, Qiuyue; Ding, Ning; Chen, Xiangfeng; Wu, Chi-Man Lawrence

2018-04-01

How nanomaterials interact with pollutants is the central for understanding their environmental behavior and practical application. In this work, molecular dynamics (MD) and density functional theoretical (DFT) methods were used to investigated the influence of carbon chain length, degree of chlorination, chain configuration, and chirality of chlorinated paraffin (CP) and diameter of single-walled carbon nanotubes (SWNTs) on the interaction between CPs and SWNTs. The simulation results demonstrated that CP chain length and chlorination degree played considerably important roles in determining interaction strength between SWNTs and CPs. The interaction energies increased with increasing chain length and chlorination degree. The chirality of SWNT exerted negligible influence on the interaction energy between SWNTs and CPs. On the contrary, interaction energy increased with increasing radius of SWNTs due to the surface curvatures. This result was rationalized by considering the decrease in SWNT curvature with increasing radius, which resulted in plane-like CNT wall. The negligible influence of CP chain configurations was attributed to relative flexibility of CP carbon chains, which can wrap on tubes through conformational changes with low-energy barriers. MD results indicated that CPs could adsorb on SWNT surface rapidly in aqueous environment. Charge transfer and electronic density results indicated that the interaction between CPs and SWNTs was physisorption in nature. This work provides fundamental information regarding SWNTs as sorbents for CPs extraction and adsorptive removal from environmental water system.

Network Coded Cooperative Communication in a Real-Time Wireless Hospital Sensor Network.

PubMed

Prakash, R; Balaji Ganesh, A; Sivabalan, Somu

2017-05-01

The paper presents a network coded cooperative communication (NC-CC) enabled wireless hospital sensor network architecture for monitoring health as well as postural activities of a patient. A wearable device, referred as a smartband is interfaced with pulse rate, body temperature sensors and an accelerometer along with wireless protocol services, such as Bluetooth and Radio-Frequency transceiver and Wi-Fi. The energy efficiency of wearable device is improved by embedding a linear acceleration based transmission duty cycling algorithm (NC-DRDC). The real-time demonstration is carried-out in a hospital environment to evaluate the performance characteristics, such as power spectral density, energy consumption, signal to noise ratio, packet delivery ratio and transmission offset. The resource sharing and energy efficiency features of network coding technique are improved by proposing an algorithm referred as network coding based dynamic retransmit/rebroadcast decision control (LA-TDC). From the experimental results, it is observed that the proposed LA-TDC algorithm reduces network traffic and end-to-end delay by an average of 27.8% and 21.6%, respectively than traditional network coded wireless transmission. The wireless architecture is deployed in a hospital environment and results are then successfully validated.

Computational evaluation of sub-nanometer cluster activity of singly exposed copper atom with various coordinative environment in catalytic CO2 transformation

NASA Astrophysics Data System (ADS)

Shanmugam, Ramasamy; Thamaraichelvan, Arunachalam; Ganesan, Tharumeya Kuppusamy; Viswanathan, Balasubramanian

2017-02-01

Metal cluster, at sub-nanometer level has a unique property in the activation of small molecules, in contrast to that of bulk surface. In the present work, singly exposed active site of copper metal cluster at sub-nanometer level was designed to arrive at the energy minimised configurations, binding energy, electrostatic potential map, frontier molecular orbitals and partial density of states. The ab initio molecular dynamics was carried out to probe the catalytic nature of the cluster. Further, the stability of the metal cluster and its catalytic activity in the electrochemical reduction of CO2 to CO were evaluated by means of computational hydrogen electrode via calculation of the free energy profile using DFT/B3LYP level of theory in vacuum. The activity of the cluster is ascertained from the fact that the copper atom, present in a two coordinative environment, performs a more selective conversion of CO2 to CO at an applied potential of -0.35 V which is comparatively lower than that of higher coordinative sites. The present study helps to design any sub-nano level metal catalyst for electrochemical reduction of CO2 to various value added chemicals.

Research issues: the food environment and obesity.

PubMed

Mattes, Richard; Foster, Gary D

2014-12-01

"Research Issues: The Food Environment and Obesity" is an article series commissioned by the American Society for Nutrition and The Obesity Society in an attempt to consider the state of understanding on this topic and identify key knowledge gaps. Roberts and Karl focus on the role of energy density in the regulation of energy intake and body weight and offer recommendations for prioritizing research. Finkelstein et al examine food and beverage purchases as a function of price changes and conclude that targeted food taxes and subsidies alone are unlikely to substantially affect obesity. Pereira points out the difficulty in establishing the strength of the association between intake of sugar-sweetened beverages and weight gain and obesity. Johnson and Wardle review the effects of palatability and variety on eating behavior and weight. Livingstone and Pourshahidi examine the impact of portion size manipulations on energy intake and weight management and find that consumers generally tend to eat proportionally more as portion size increases. Kant focuses on the efficacy and effectiveness of eating frequency manipulation for body weight management and finds that such manipulation has consistently yielded null results. Finally, Gordon-Larsen identifies several limitations of the existing literature regarding neighborhood access to healthy foods. © 2014 American Society for Nutrition.

Density functional theory calculations of the water interactions with ZrO2 nanoparticles Y2O3 doped

NASA Astrophysics Data System (ADS)

Subhoni, Mekhrdod; Kholmurodov, Kholmirzo; Doroshkevich, Aleksandr; Asgerov, Elmar; Yamamoto, Tomoyuki; Lyubchyk, Andrei; Almasan, Valer; Madadzada, Afag

2018-03-01

Development of a new electricity generation techniques is one of the most relevant tasks, especially nowadays under conditions of extreme growth in energy consumption. The exothermic heterogeneous electrochemical energy conversion to the electric energy through interaction of the ZrO2 based nanopowder system with atmospheric moisture is one of the ways of electric energy obtaining. The questions of conversion into the electric form of the energy of water molecules adsorption in 3 mol% Y2O3 doped ZrO2 nanopowder systems were investigated using the density functional theory calculations. The density functional theory calculations has been realized as in the Kohn-Sham formulation, where the exchange-correlation potential is approximated by a functional of the electronic density. The electronic density, total energy and band structure calculations are carried out using the all-electron, full potential, linear augmented plane wave method of the electronic density and related approximations, i.e. the local density, the generalized gradient and their hybrid approximations.

Electron dynamics in high energy density plasma bunch generation driven by intense picosecond laser pulse

NASA Astrophysics Data System (ADS)

Li, M.; Yuan, T.; Xu, Y. X.; Luo, S. N.

2018-05-01

When an intense picosecond laser pulse is loaded upon a dense plasma, a high energy density plasma bunch, including electron bunch and ion bunch, can be generated in the target. We simulate this process through one-dimensional particle-in-cell simulation and find that the electron bunch generation is mainly due to a local high energy density electron sphere originated in the plasma skin layer. Once generated the sphere rapidly expands to compress the surrounding electrons and induce high density electron layer, coupled with that, hot electrons are efficiently triggered in the local sphere and traveling in the whole target. Under the compressions of light pressure, forward-running and backward-running hot electrons, a high energy density electron bunch generates. The bunch energy density is as high as TJ/m3 order of magnitude in our conditions, which is significant in laser driven dynamic high pressure generation and may find applications in high energy density physics.

Dynamics and reactivity of trapped electrons on supported ice crystallites.

PubMed

Stähler, Julia; Gahl, Cornelius; Wolf, Martin

2012-01-17

The solvation dynamics and reactivity of localized excess electrons in aqueous environments have attracted great attention in many areas of physics, chemistry, and biology. This manifold attraction results from the importance of water as a solvent in nature as well as from the key role of low-energy electrons in many chemical reactions. One prominent example is the electron-induced dissociation of chlorofluorocarbons (CFCs). Low-energy electrons are also critical in the radiation chemistry that occurs in nuclear reactors. Excess electrons in an aqueous environment are localized and stabilized by the local rearrangement of the surrounding water dipoles. Such solvated or hydrated electrons are known to play an important role in systems such as biochemical reactions and atmospheric chemistry. Despite numerous studies over many years, little is known about the microscopic details of these electron-induced chemical processes, and interest in the fundamental processes involved in the reactivity of trapped electrons continues. In this Account, we present a surface science study of the dynamics and reactivity of such localized low-energy electrons at D(2)O crystallites that are supported by a Ru(001) single crystal metal surface. This approach enables us to investigate the generation and relaxation dynamics as well as dissociative electron attachment (DEA) reaction of excess electrons under well-defined conditions. They are generated by photoexcitation in the metal template and transferred to trapping sites at the vacuum interface of crystalline D(2)O islands. In these traps, the electrons are effectively decoupled from the electronic states of the metal template, leading to extraordinarily long excited state lifetimes on the order of minutes. Using these long-lived, low-energy electrons, we study the DEA to CFCl(3) that is coadsorbed at very low concentrations (∼10(12) cm(-2)). Using rate equations and direct measurement of the change of surface dipole moment, we estimated the electron surface density for DEA, yielding cross sections that are orders of magnitude higher than the electron density measured in the gas phase.

Density profiles of supernova matter and determination of neutrino parameters

NASA Astrophysics Data System (ADS)

Chiu, Shao-Hsuan

2007-08-01

The flavor conversion of supernova neutrinos can lead to observable signatures related to the unknown neutrino parameters. As one of the determinants in dictating the efficiency of resonant flavor conversion, the local density profile near the Mikheyev-Smirnov-Wolfenstein (MSW) resonance in a supernova environment is, however, not so well understood. In this analysis, variable power-law functions are adopted to represent the independent local density profiles near the locations of resonance. It is shown that the uncertain matter density profile in a supernova, the possible neutrino mass hierarchies, and the undetermined 1-3 mixing angle would result in six distinct scenarios in terms of the survival probabilities of νe and ν¯e. The feasibility of probing the undetermined neutrino mass hierarchy and the 1-3 mixing angle with the supernova neutrinos is then examined using several proposed experimental observables. Given the incomplete knowledge of the supernova matter profile, the analysis is further expanded to incorporate the Earth matter effect. The possible impact due to the choice of models, which differ in the average energy and in the luminosity of neutrinos, is also addressed in the analysis.

Dynamic impact indentation of hydrated biological tissues and tissue surrogate gels

NASA Astrophysics Data System (ADS)

Ilke Kalcioglu, Z.; Qu, Meng; Strawhecker, Kenneth E.; Shazly, Tarek; Edelman, Elazer; VanLandingham, Mark R.; Smith, James F.; Van Vliet, Krystyn J.

2011-03-01

For both materials engineering research and applied biomedicine, a growing need exists to quantify mechanical behaviour of tissues under defined hydration and loading conditions. In particular, characterisation under dynamic contact-loading conditions can enable quantitative predictions of deformation due to high rate 'impact' events typical of industrial accidents and ballistic insults. The impact indentation responses were examined of both hydrated tissues and candidate tissue surrogate materials. The goals of this work were to determine the mechanical response of fully hydrated soft tissues under defined dynamic loading conditions, and to identify design principles by which synthetic, air-stable polymers could mimic those responses. Soft tissues from two organs (liver and heart), a commercially available tissue surrogate gel (Perma-Gel™) and three styrenic block copolymer gels were investigated. Impact indentation enabled quantification of resistance to penetration and energy dissipative constants under the rates and energy densities of interest for tissue surrogate applications. These analyses indicated that the energy dissipation capacity under dynamic impact increased with increasing diblock concentration in the styrenic gels. Under the impact rates employed (2 mm/s to 20 mm/s, corresponding to approximate strain energy densities from 0.4 kJ/m3 to 20 kJ/m3), the energy dissipation capacities of fully hydrated soft tissues were ultimately well matched by a 50/50 triblock/diblock composition that is stable in ambient environments. More generally, the methodologies detailed here facilitate further optimisation of impact energy dissipation capacity of polymer-based tissue surrogate materials, either in air or in fluids.

Parent Diet Quality and Energy Intake Are Related to Child Diet Quality and Energy Intake

PubMed Central

Robson, Shannon M.; Couch, Sarah C.; Peugh, James L.; Glanz, Karen; Zhou, Chuan; Sallis, James F.; Saelens, Brian E.

2016-01-01

Background Parents' diets are believed to influence their children's diets. Previous studies have not adequately and simultaneously assessed the relation of parent and child total diet quality and energy intake. Objective To investigate if parent and child diet quality and energy intakes are related. Design A cross-sectional analysis using baseline dietary intake data from the Neighborhood Impact on Kids (NIK) study collected in 2007-2009. Participants/setting Parents and 6-12 year old children from households in King County (Seattle area), WA and San Diego County, CA, targeted by NIK were recruited. Eligible parent-child dyads (n=698) with two or three 24-hour dietary recalls were included in this secondary analysis. Main Outcome Measures Child diet quality (Healthy Eating Index-2010 [HEI-2010], Dietary Approaches to Stop Hypertension [DASH] score, and energy density (for food-only) and energy intake were derived from the dietary recalls using Nutrition Data Systems for Research. Statistical Analyses Performed Multiple linear regression models examined the relationship between parent diet quality and child diet quality, and the relationship between parent energy intake and child energy intake. In both analyses, we controlled for parent characteristics, child characteristics, household education and neighborhood type. Results Parent diet quality measures were significantly related to corresponding child diet quality measures: HEI-2010 (standardized beta [β] = 0.39, p<0.001); DASH score (β = 0.33, p<0.001); energy density (β = 0.32, p<0.001). Parent daily average energy intake (1763 ± 524 kilocalories) also was significantly related (β = 0.30, p<0.001) to child daily average energy intake (1751 ± 431 kilocalories). Conclusion Parent and child intakes were closely related across various metrics of diet quality and for energy intake. Mechanisms of influence are likely to be shared food environments, shared meals, and parent modeling. PMID:27050725

Reconstructing the galaxy density field with photometric redshifts - II. Environment-dependent galaxy evolution since z ≃ 3

NASA Astrophysics Data System (ADS)

Malavasi, Nicola; Pozzetti, Lucia; Cucciati, Olga; Bardelli, Sandro; Ilbert, Olivier; Cimatti, Andrea

2017-09-01

Although extensively investigated, the role of the environment in galaxy formation is still not well understood. In this context, the galaxy stellar mass function (GSMF) is a powerful tool to understand how environment relates to galaxy mass assembly and the quenching of star formation. In this work, we make use of the high-precision photometric redshifts of the UltraVISTA Survey to study the GSMF in different environments up to z ˜ 3, on physical scales from 0.3 to 2 Mpc, down to masses of M ˜ 1010 M⊙. We witness the appearance of environmental signatures for both quiescent and star-forming galaxies. We find that the shape of the GSMF of quiescent galaxies is different in high- and low-density environments up to z ˜ 2 with the high-mass end (M ≳ 1011 M⊙) being enhanced in high-density environments. On the contrary, for star-forming galaxies, a difference between the GSMF in high- and low-density environments is present for masses M ≲ 1011 M⊙. Star-forming galaxies in this mass range appear to be more frequent in low-density environments up to z < 1.5. Differences in the shape of the GSMF are not visible anymore at z > 2. Our results, in terms of general trends in the shape of the GSMF, are in agreement with a scenario in which galaxies are quenched when they enter hot gas-dominated massive haloes that are preferentially in high-density environments.

Ambipolar zinc-polyiodide electrolyte for a high-energy density aqueous redox flow battery

PubMed Central

Li, Bin; Nie, Zimin; Vijayakumar, M.; Li, Guosheng; Liu, Jun; Sprenkle, Vincent; Wang, Wei

2015-01-01

Redox flow batteries are receiving wide attention for electrochemical energy storage due to their unique architecture and advantages, but progress has so far been limited by their low energy density (~25 Wh l−1). Here we report a high-energy density aqueous zinc-polyiodide flow battery. Using the highly soluble iodide/triiodide redox couple, a discharge energy density of 167 Wh l−1 is demonstrated with a near-neutral 5.0 M ZnI2 electrolyte. Nuclear magnetic resonance study and density functional theory-based simulation along with flow test data indicate that the addition of an alcohol (ethanol) induces ligand formation between oxygen on the hydroxyl group and the zinc ions, which expands the stable electrolyte temperature window to from −20 to 50 °C, while ameliorating the zinc dendrite. With the high-energy density and its benign nature free from strong acids and corrosive components, zinc-polyiodide flow battery is a promising candidate for various energy storage applications. PMID:25709083

Ambipolar zinc-polyiodide electrolyte for a high-energy density aqueous redox flow battery.

PubMed

Li, Bin; Nie, Zimin; Vijayakumar, M; Li, Guosheng; Liu, Jun; Sprenkle, Vincent; Wang, Wei

2015-02-24

Redox flow batteries are receiving wide attention for electrochemical energy storage due to their unique architecture and advantages, but progress has so far been limited by their low energy density (~25 Wh l(-1)). Here we report a high-energy density aqueous zinc-polyiodide flow battery. Using the highly soluble iodide/triiodide redox couple, a discharge energy density of 167 Wh l(-1) is demonstrated with a near-neutral 5.0 M ZnI2 electrolyte. Nuclear magnetic resonance study and density functional theory-based simulation along with flow test data indicate that the addition of an alcohol (ethanol) induces ligand formation between oxygen on the hydroxyl group and the zinc ions, which expands the stable electrolyte temperature window to from -20 to 50 °C, while ameliorating the zinc dendrite. With the high-energy density and its benign nature free from strong acids and corrosive components, zinc-polyiodide flow battery is a promising candidate for various energy storage applications.

Single-particle energies and density of states in density functional theory

NASA Astrophysics Data System (ADS)

van Aggelen, H.; Chan, G. K.-L.

2015-07-01

Time-dependent density functional theory (TD-DFT) is commonly used as the foundation to obtain neutral excited states and transition weights in DFT, but does not allow direct access to density of states and single-particle energies, i.e. ionisation energies and electron affinities. Here we show that by extending TD-DFT to a superfluid formulation, which involves operators that break particle-number symmetry, we can obtain the density of states and single-particle energies from the poles of an appropriate superfluid response function. The standard Kohn- Sham eigenvalues emerge as the adiabatic limit of the superfluid response under the assumption that the exchange- correlation functional has no dependence on the superfluid density. The Kohn- Sham eigenvalues can thus be interpreted as approximations to the ionisation energies and electron affinities. Beyond this approximation, the formalism provides an incentive for creating a new class of density functionals specifically targeted at accurate single-particle eigenvalues and bandgaps.

Predicted energy densitites for nickel-hydrogen and silver-hydrogen cells embodying metallic hydrides for hydrogen storage

NASA Technical Reports Server (NTRS)

Easter, R. W.

1974-01-01

Simplified design concepts were used to estimate gravimetric and volumetric energy densities for metal hydrogen battery cells for assessing the characteristics of cells containing metal hydrides as compared to gaseous storage cells, and for comparing nickel cathode and silver cathode systems. The silver cathode was found to yield superior energy densities in all cases considered. The inclusion of hydride forming materials yields cells with very high volumetric energy densities that also retain gravimetric energy densities nearly as high as those of gaseous storage cells.

Association between Dietary Energy Density and Incident Type 2 Diabetes in the Women's Health Initiative.

PubMed

Hingle, Melanie D; Wertheim, Betsy C; Neuhouser, Marian L; Tinker, Lesley F; Howard, Barbara V; Johnson, Karen; Liu, Simin; Phillips, Lawrence S; Qi, Lihong; Sarto, Gloria; Turner, Tami; Waring, Molly E; Thomson, Cynthia A

2017-05-01

Dietary energy density, or energy available in relation to gram intake, can inform disease risk. The objective of this study was to investigate the association between baseline dietary energy density and risk of incident type 2 diabetes in postmenopausal women. Dietary energy density, weight status, and type 2 diabetes incidence were prospectively characterized in a large cohort of postmenopausal women participating in one or more clinical trials or an observational study. The study involved 161,808 postmenopausal women recruited to the Women's Health Initiative observational study or clinical trials at 40 centers across the United States between 1993 and 1998. The primary outcome was incident type 2 diabetes. The association between dietary energy density quintiles and incident diabetes was tested using Cox proportional hazards regression. A total of 143,204 participants without self-reported diabetes at enrollment completed baseline dietary assessment and were followed for 12.7±4.6 years. Risk of diabetes developing was 24% greater for women in the highest dietary energy density quintile compared with the lowest after adjusting for confounders (95% CI 1.17 to 1.32). Body mass index (calculated as kg/m 2 ) and waist circumference mediated the relationship between dietary energy density and diabetes. In waist circumference-stratified analysis, women in dietary energy density quintiles 2 to 5 with waist circumferences >88 cm were at 9% to 12% greater risk of diabetes developing compared with women with waist circumference ≤88 cm. In this prospective study, a higher baseline dietary energy density was associated with higher incidence of type 2 diabetes among postmenopausal women, both overall, and in women with elevated waist circumference. Copyright © 2017 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

Combining DFT, Cluster Expansions, and KMC to Model Point Defects in Alloys

NASA Astrophysics Data System (ADS)

Modine, N. A.; Wright, A. F.; Lee, S. R.; Foiles, S. M.; Battaile, C. C.; Thomas, J. C.; van der Ven, A.

In an alloy, defect energies are sensitive to the occupations of nearby atomic sites, which leads to a distribution of defect properties. When radiation-induced defects diffuse from their initially non-equilibrium locations, this distribution becomes time-dependent. The defects can become trapped in energetically favorable regions of the alloy leading to a diffusion rate that slows dramatically with time. Density Functional Theory (DFT) allows the accurate determination of ground state and transition state energies for a defect in a particular alloy environment but requires thousands of processing hours for each such calculation. Kinetic Monte-Carlo (KMC) can be used to model defect diffusion and the changing distribution of defect properties but requires energy evaluations for millions of local environments. We have used the Cluster Expansion (CE) formalism to ``glue'' together these seemingly incompatible methods. The occupation of each alloy site is represented by an Ising-like variable, and products of these variables are used to expand quantities of interest. Once a CE is fit to a training set of DFT energies, it allows very rapid evaluation of the energy for an arbitrary configuration, while maintaining the accuracy of the underlying DFT calculations. These energy evaluations are then used to drive our KMC simulations. We will demonstrate the application of our DFT/MC/KMC approach to model thermal and carrier-induced diffusion of intrinsic point defects in III-V alloys. 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 Security Administration under Contract DE.

Exchange-correlation energies of atoms from efficient density functionals: influence of the electron density

DOE PAGES

Tao, Jianmin; Ye, Lin -Hui; Duan, Yuhua

2017-11-20

The primary goal of Kohn–Sham density functional theory is to evaluate the exchange-correlation contribution to electronic properties. However, the accuracy of a density functional can be affected by the electron density. Here we apply the nonempirical Tao–Mo (TM) semilocal functional to study the influence of the electron density on the exchange and correlation energies of atoms and ions, and compare the results with the commonly used nonempirical semilocal functionals local spin-density approximation (LSDA), Perdew–Burke–Ernzerhof (PBE), Tao–Perdew–Staroverov–Scuseria (TPSS), and hybrid functional PBE0. We find that the spin-restricted Hartree–Fock density yields the exchange and correlation energies in good agreement with the Optimizedmore » Effective Potential method, particularly for spherical atoms and ions. However, the errors of these semilocal and hybrid functionals become larger for self-consistent densities. We further find that the quality of the electron density have greater effect on the exchange-correlation energies of kinetic energy density-dependent meta-GGA functionals TPSS and TM than on those of the LSDA and GGA, and therefore, should have greater influence on the performance of meta-GGA functionals. Lastly, we show that the influence of the density quality on PBE0 is slightly reduced, compared to that of PBE, due to the exact mixing.« less

Exchange-correlation energies of atoms from efficient density functionals: influence of the electron density

NASA Astrophysics Data System (ADS)

Tao, Jianmin; Ye, Lin-Hui; Duan, Yuhua

2017-12-01

The primary goal of Kohn-Sham density functional theory is to evaluate the exchange-correlation contribution to electronic properties. However, the accuracy of a density functional can be affected by the electron density. Here we apply the nonempirical Tao-Mo (TM) semilocal functional to study the influence of the electron density on the exchange and correlation energies of atoms and ions, and compare the results with the commonly used nonempirical semilocal functionals local spin-density approximation (LSDA), Perdew-Burke-Ernzerhof (PBE), Tao-Perdew-Staroverov-Scuseria (TPSS), and hybrid functional PBE0. We find that the spin-restricted Hartree-Fock density yields the exchange and correlation energies in good agreement with the Optimized Effective Potential method, particularly for spherical atoms and ions. However, the errors of these semilocal and hybrid functionals become larger for self-consistent densities. We further find that the quality of the electron density have greater effect on the exchange-correlation energies of kinetic energy density-dependent meta-GGA functionals TPSS and TM than on those of the LSDA and GGA, and therefore, should have greater influence on the performance of meta-GGA functionals. Finally, we show that the influence of the density quality on PBE0 is slightly reduced, compared to that of PBE, due to the exact mixing.

Exchange-correlation energies of atoms from efficient density functionals: influence of the electron density

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

Tao, Jianmin; Ye, Lin -Hui; Duan, Yuhua

The primary goal of Kohn–Sham density functional theory is to evaluate the exchange-correlation contribution to electronic properties. However, the accuracy of a density functional can be affected by the electron density. Here we apply the nonempirical Tao–Mo (TM) semilocal functional to study the influence of the electron density on the exchange and correlation energies of atoms and ions, and compare the results with the commonly used nonempirical semilocal functionals local spin-density approximation (LSDA), Perdew–Burke–Ernzerhof (PBE), Tao–Perdew–Staroverov–Scuseria (TPSS), and hybrid functional PBE0. We find that the spin-restricted Hartree–Fock density yields the exchange and correlation energies in good agreement with the Optimizedmore » Effective Potential method, particularly for spherical atoms and ions. However, the errors of these semilocal and hybrid functionals become larger for self-consistent densities. We further find that the quality of the electron density have greater effect on the exchange-correlation energies of kinetic energy density-dependent meta-GGA functionals TPSS and TM than on those of the LSDA and GGA, and therefore, should have greater influence on the performance of meta-GGA functionals. Lastly, we show that the influence of the density quality on PBE0 is slightly reduced, compared to that of PBE, due to the exact mixing.« less

Nonrelativistic Quantum Mechanics with Fundamental Environment

NASA Astrophysics Data System (ADS)

Gevorkyan, Ashot S.

2011-03-01

Spontaneous transitions between bound states of an atomic system, "Lamb Shift" of energy levels and many other phenomena in real nonrelativistic quantum systems are connected within the influence of the quantum vacuum fluctuations ( fundamental environment (FE)) which are impossible to consider in the limits of standard quantum-mechanical approaches. The joint system "quantum system (QS) + FE" is described in the framework of the stochastic differential equation (SDE) of Langevin-Schrödinger (L-Sch) type, and is defined on the extended space R 3 ⊗ R { ξ}, where R 3 and R { ξ} are the Euclidean and functional spaces, respectively. The density matrix for single QS in FE is defined. The entropy of QS entangled with FE is defined and investigated in detail. It is proved that as a result of interaction of QS with environment there arise structures of various topologies which are a new quantum property of the system.

Corrosion Protection of Al/Au/ZnO Anode for Hybrid Cell Application

PubMed Central

Slaughter, Gymama; Stevens, Brian

2015-01-01

Effective protection of power sources from corrosion is critical in the development of abiotic fuel cells, biofuel cells, hybrid cells and biobateries for implantable bioelectronics. Corrosion of these bioelectronic devices result in device inability to generate bioelectricity. In this paper Al/Au/ZnO was considered as a possible anodic substrate for the development of a hybrid cell. The protective abilities of corrosive resistant aluminum hydroxide and zinc phosphite composite films formed on the surface of Al/Au/ZnO anode in various electrolyte environments were examined by electrochemical methods. The presence of phosphate buffer and physiological saline (NaCl) buffer allows for the formation of aluminum hyrdroxide and zinc phosphite composite films on the surface of the Al/Au/ZnO anode that prevent further corrosion of the anode. The highly protective films formed on the Al/Au/ZnO anode during energy harvesting in a physiological saline environment resulted in 98.5% corrosion protective efficiency, thereby demonstrating that the formation of aluminum hydroxide and zinc phosphite composite films are effective in the prevention of anode corrosion during energy harvesting. A cell assembly consisting of the Al/Au/ZnO anode and platinum cathode resulted in an open circuit voltage of 1.03 V. A maximum power density of 955.3 μW/ cm2 in physiological saline buffer at a cell voltage and current density of 345 mV and 2.89 mA/ cm2, respectively. PMID:26580661

Corrosion Protection of Al/Au/ZnO Anode for Hybrid Cell Application.

PubMed

Slaughter, Gymama; Stevens, Brian

2015-11-16

Effective protection of power sources from corrosion is critical in the development of abiotic fuel cells, biofuel cells, hybrid cells and biobateries for implantable bioelectronics. Corrosion of these bioelectronic devices result in device inability to generate bioelectricity. In this paper Al/Au/ZnO was considered as a possible anodic substrate for the development of a hybrid cell. The protective abilities of corrosive resistant aluminum hydroxide and zinc phosphite composite films formed on the surface of Al/Au/ZnO anode in various electrolyte environments were examined by electrochemical methods. The presence of phosphate buffer and physiological saline (NaCl) buffer allows for the formation of aluminum hyrdroxide and zinc phosphite composite films on the surface of the Al/Au/ZnO anode that prevent further corrosion of the anode. The highly protective films formed on the Al/Au/ZnO anode during energy harvesting in a physiological saline environment resulted in 98.5% corrosion protective efficiency, thereby demonstrating that the formation of aluminum hydroxide and zinc phosphite composite films are effective in the prevention of anode corrosion during energy harvesting. A cell assembly consisting of the Al/Au/ZnO anode and platinum cathode resulted in an open circuit voltage of 1.03 V. A maximum power density of 955.3 mW/ cm² in physiological saline buffer at a cell voltage and current density of 345 mV and 2.89 mA/ cm², respectively.

Retrieving acoustic energy densities and local pressure amplitudes in microfluidics by holographic time-lapse imaging.

PubMed

Cacace, Teresa; Bianco, Vittorio; Paturzo, Melania; Memmolo, Pasquale; Vassalli, Massimo; Fraldi, Massimiliano; Mensitieri, Giuseppe; Ferraro, Pietro

2018-06-26

The development of techniques able to characterize and map the pressure field is crucial for the widespread use of acoustofluidic devices in biotechnology and lab-on-a-chip platforms. In fact, acoustofluidic devices are powerful tools for driving precise manipulation of microparticles and cells in microfluidics in non-contact modality. Here, we report a full and accurate characterization of the movement of particles subjected to acoustophoresis in a microfluidic environment by holographic imaging. The particle displacement along the direction of the ultrasound wave propagation, coinciding with the optical axis, is observed and investigated. Two resonance frequencies are explored, varying for each the amplitude of the applied signal. The trajectories of individual tracers, accomplished by holographic measurements, are fitted with the theoretical model thus allowing the retrieval of the acoustic energy densities and pressure amplitudes through full holographic analysis. The absence of prior calibration, being independent of the object shape and the possibility of implementing automatic analysis make the use of holography very appealing for applications in devices for biotechnologies.

Sedimentological Characterization of a Deepwater Methane Hydrate Reservoir in Green Canyon 955, Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Meazell, K.; Flemings, P. B.

2017-12-01

Grain size is a controlling factor of hydrate saturation within a Pleistocene channel-levee system investigated by the UT-GOM2-1 expedition within the deepwater northern Gulf of Mexico. Laser diffraction and settling experiments conducted on sediments from 413-440 meters below the seafloor reveal the presence of two interbedded lithologic units, identified as a silty sand and a clayey silt, according Shepard's classification system. The sand-rich lithofacies has low density and high p-wave velocity, suggesting a high degree of hydrate saturation. Conversely, the clay and silt dominated lithofacies is characterized by a higher density and low p-wave velocity, suggesting low hydrate saturation. The sand-rich lithofacies is well-sorted and displays abundant ripple lamination, indicative of deposition within a high-energy environment. The clayey-silt is poorly-sorted and lacks sedimentary structures. The two lithofacies are interbedded throughout the reservoir unit; however, the relative abundance of the sand-rich lithofacies increases with depth, suggesting a potential decrease in flow energy or sediment flux over time, resulting in the most favorable reservoir properties near the base of the unit.

Advances in space power research and technology at the National Aeronautics and Space Administration

NASA Technical Reports Server (NTRS)

Mullin, J. P.; Randolph, L. P.; Hudson, W. R.; Ambrus, J. H.

1981-01-01

Progress and plans in various areas of the NASA Space Power Program are discussed. Solar cell research is narrowed to GaAs, multibandgap, and thin Si cells for arrays in planar and concentrator configurations, with further work to increase cell efficiency, radiation hardness, develop flexible encapsulants, and reduce cost. Electrochemical research is concentrating on increasing energy and power density, cycle and wet stand life, reliability and cost reduction of batteries. Further development of the Ni-H2 battery and O2-H2 fuel cell to multihundred kW with a 5 year life and 30,000 cycles is noted. Basic research is ongoing for alkali metal anodes for high energy density secondary cells. Nuclear thermoelectric propulsion is being developed for outer planets exploration propulsion systems, using Si-Ge generators, and studies with rare earth chalcogenides and sulfides are mentioned. Power Systems Management seeks to harmonize increasing power supply levels with inner and outer spacecraft environments, circuits, demands, and automatic monitoring. Concomitant development of bipolar transistors, an infrared rectenna, spacecraft charging measurement, and larger heat pipe transport capacity are noted.

Reaction chemistry in rechargeable Li-O2 batteries.

PubMed

Lim, Hee-Dae; Lee, Byungju; Bae, Youngjoon; Park, Hyeokjun; Ko, Youngmin; Kim, Haegyeom; Kim, Jinsoo; Kang, Kisuk

2017-05-22

The seemingly simple reaction of Li-O 2 batteries involving lithium and oxygen makes this chemistry attractive for high-energy-density storage systems; however, achieving this reaction in practical rechargeable Li-O 2 batteries has proven difficult. The reaction paths leading to the final Li 2 O 2 discharge products can be greatly affected by the operating conditions or environment, which often results in major side reactions. Recent research findings have begun to reveal how the reaction paths may be affected by the surrounding conditions and to uncover the factors contributing to the difficulty in achieving the reactions of lithium and oxygen. This progress report describes the current state of understanding of the electrode reaction mechanisms in Li-O 2 batteries; the factors that affect reaction pathways; and the effect of cell components such as solvents, salts, additives, and catalysts on the discharge product and its decomposition during charging. This comprehensive review of the recent progress in understanding the reaction chemistry of the Li-O 2 system will serve as guidelines for future research and aid in the development of reliable high-energy-density rechargeable Li-O 2 batteries.

The “Metabolic Winter” Hypothesis: A Cause of the Current Epidemics of Obesity and Cardiometabolic Disease

PubMed Central

Cronise, Raymond J.; Sinclair, David A.

2014-01-01

Abstract The concept of the “Calorie” originated in the 1800s in an environment with limited food availability, primarily as a means to define economic equivalencies in the energy density of food substrates. Soon thereafter, the energy densities of the major macronutrients—fat, protein, and carbohydrates—were defined. However, within a few decades of its inception, the “Calorie” became a commercial tool for industries to promote specific food products, regardless of health benefit. Modern technology has altered our living conditions and has changed our relationship with food from one of survival to palatability. Advances in agriculture, food manufacturing, and processing have ensured that calorie scarcity is less prevalent than calorie excess in the modern world. Yet, many still approach dietary macronutrients in a reductionist manner and assume that isocalorie foodstuffs are isometabolic. Herein, we discuss a novel way to view the major food macronutrients and human diet in this era of excessive caloric consumption, along with a novel relationship among calorie scarcity, mild cold stress, and sleep that may explain the increasing prevalence of nutritionally related diseases. PMID:24918620

Amodal brain activation and functional connectivity in response to high-energy-density food cues in obesity.

PubMed

Carnell, Susan; Benson, Leora; Pantazatos, Spiro P; Hirsch, Joy; Geliebter, Allan

2014-11-01

The obesogenic environment is pervasive, yet only some people become obese. The aim was to investigate whether obese individuals show differential neural responses to visual and auditory food cues, independent of cue modality. Obese (BMI 29-41, n = 10) and lean (BMI 20-24, n = 10) females underwent fMRI scanning during presentation of auditory (spoken word) and visual (photograph) cues representing high-energy-density (ED) and low-ED foods. The effect of obesity on whole-brain activation, and on functional connectivity with the midbrain/VTA, was examined. Obese compared with lean women showed greater modality-independent activation of the midbrain/VTA and putamen in response to high-ED (vs. low-ED) cues, as well as relatively greater functional connectivity between the midbrain/VTA and cerebellum (P < 0.05 corrected). Heightened modality-independent responses to food cues within the midbrain/VTA and putamen, and altered functional connectivity between the midbrain/VTA and cerebellum, could contribute to excessive food intake in obese individuals. © 2014 The Obesity Society.

All-boron fullerene exhibits a strong affinity to inorganic anions

NASA Astrophysics Data System (ADS)

Colherinhas, Guilherme; Fileti, Eudes Eterno; Chaban, Vitaly V.

2017-03-01

Experimentally observed all-boron fullerene, B-80, inspires systematic investigation of its physical chemical properties and search for possible applications. We hereby report density functional theory calculations to characterize interactions of B-80 with the selected imidazolium room-temperature ionic liquids (RTILs), dimethylimidazolium nitrate and dimethylimidazolium hexafluorophosphate. Whereas the imidazolium cation exhibits a rather poor affinity to B-80, the inorganic anions form polar covalent bonds with the boron atom occupying a central position within a B-6 hexagon. Attachment of the RTIL ion pairs leads to a significant alteration of the electronic spectra, charge density distribution, valence and conduction molecular orbitals. The total binding energies keeping the RTIL@B80 complexes together range 200-250 kcal mol-1, being higher than the energies of many interactions in chemistry. The observed phenomenon predicts an excellent solubility of B-80 in the considered RTILs, but may also reveal a poor stability of B-80 in the polar media. Our results motivate further efforts in studying the behavior of the all-boron fullerene in polar environments.

Study of the Conditions of Irradiating Laser for Removal of Toner from Used Paper

NASA Astrophysics Data System (ADS)

Ihori, Haruo; Inagawa, Yuki; Ito, Naohiro; Fujii, Masaharu; Ninomiya, Hideki

Though it is said to the paper-less age with the spread of personal computer, amount of office papers to be used doesn't have tendency to decrease. In general, used papers are recovered and recycled in order to preserve the environment. The labor and costs are required for the recovery of used papers and a recycled paper is lower in quality. If we could reuse used papers repeatedly without withdrawing those, for example, by copying machine that could print again with removing toner on used paper, it is very convenient and ecological. So, we studied about removing toner from used papers by application of the laser ablation technique. As an optical source, SHG-YAG laser was chosen. For removal of toner from used papers, the energy density to irradiate them with SHG-YAG laser was examined. When approximately 12mJ/mm2 of the energy density, which was average value, toner was removed so much as to be able to reuse again. Moreover, conditions of the laser irradiation, concretely, the velocity scanning the laser and the number of the irradiation, were studied.

Mechanical properties and thermal shock performance of W-Y2O3 composite prepared by high-energy-rate forging

NASA Astrophysics Data System (ADS)

Lian, Youyun; Liu, Xiang; Feng, Fan; Song, Jiupeng; Yan, Binyou; Wang, Yingmin; Wang, Jianbao; Chen, Jiming

2017-12-01

The effects of the addition of Y2O3 and hot-deformation on the mechanical properties of tungsten (W) have been studied. The processing route comprises a doping technique for the distribution of Y2O3 particles in a tungsten matrix, conventional sintering in a hydrogen environment, and high-energy-rate forging (HERF). The microstructure of the composite was characterized by using transmission electron microscopy and electron backscattering diffraction imaging technique, and its mechanical properties were studied by means of tensile testing. The thermal shock response of the HERF processed W-Y2O3 was evaluated by applying edge-localized mode-like loads (100 pulses) with a pulse duration of 1 ms and an absorbed power density of up to 1 GW m-2 at various temperatures between room temperature and 200 °C. HERF processing has produced elongated W grains with preferred orientations and a high density of structure defects in the composite. The composite material exhibits high tensile strength and good ductility, and a thermal shock cracking threshold lower than 100 °C.

Probing the nuclear symmetry energy at high densities with nuclear reactions

NASA Astrophysics Data System (ADS)

Leifels, Y.

2017-11-01

The nuclear equation of state is a topic of highest current interest in nuclear structure and reactions as well as in astrophysics. The symmetry energy is the part of the equation of state which is connected to the asymmetry in the neutron/proton content. During recent years a multitude of experimental and theoretical efforts on different fields have been undertaken to constraint its density dependence at low densities but also above saturation density (ρ_0=0.16 fm ^{-3} . Conventionally the symmetry energy is described by its magnitude S_v and the slope parameter L , both at saturation density. Values of L = 44 -66MeV and S_v=31 -33MeV have been deduced in recent compilations of nuclear structure, heavy-ion reaction and astrophysics data. Apart from astrophysical data on mass and radii of neutron stars, heavy-ion reactions at incident energies of several 100MeV are the only means do access the high density behaviour of the symmetry energy. In particular, meson production and collective flows upto about 1 AGeV are predicted to be sensitive to the slope of the symmetry energy as a function of density. From the measurement of elliptic flow of neutrons with respect to charged particles at GSI, a more stringent constraint for the slope of the symmetry energy at supra-saturation densities has been deduced. Future options to reach even higher densities will be discussed.

A Novel Creep-Fatigue Life Prediction Model for P92 Steel on the Basis of Cyclic Strain Energy Density

NASA Astrophysics Data System (ADS)

Ji, Dongmei; Ren, Jianxing; Zhang, Lai-Chang

2016-11-01

A novel creep-fatigue life prediction model was deduced based on an expression of the strain energy density in this study. In order to obtain the expression of the strain energy density, the load-controlled creep-fatigue (CF) tests of P92 steel at 873 K were carried out. Cyclic strain of P92 steel under CF load was divided into elastic strain, applying and unloading plastic strain, creep strain, and anelastic strain. Analysis of cyclic strain indicates that the damage process of P92 steel under CF load consists of three stages, similar to pure creep. According to the characteristics of the strains above, an expression was defined to describe the strain energy density for each cycle. The strain energy density at stable stage is inversely proportional to the total strain energy density dissipated by P92 steel. However, the total strain energy densities under different test conditions are proportional to the fatigue life. Therefore, the expression of the strain energy density at stable stage was chosen to predict the fatigue life. The CF experimental data on P92 steel were employed to verify the rationality of the novel model. The model obtained from the load-controlled CF test of P92 steel with short holding time could predict the fatigue life of P92 steel with long holding time.

Improvement in Fruit and Vegetable Consumption Associated with More Favorable Energy Density and Nutrient and Food Group Intake, but not Kilocalories.

PubMed

Thompson, Debbe; Ferry, Robert J; Cullen, Karen W; Liu, Yan

2016-09-01

Children generally do not consume adequate amounts of fruits and vegetables (F/V). Eating more F/V can improve energy density and overall diet quality. Our aim was to investigate whether improvements in F/V consumption were associated with improvements in energy density, total calories, and dietary components related to F/V. We performed secondary analyses of dietary data from a successful four-group randomized controlled trial promoting F/V. Data were collected at baseline, immediately after gameplay, and 3 months post intervention. Preadolescent child-parent dyads (n=400) were recruited. Eligibility criteria were 4th- or 5th-grade child (approximately 9 to 11 years old) with Internet access and a parent willing to participate in the intervention. Complete dietary data were collected on 387 of the 400 child participants. The videogame was available online on a secure, password-protected website. Dietary intake was assessed with three unannounced dietary recalls collected at each data-collection period via telephone by trained staff using Nutrition Data System for Research software. Energy density and F/V, nutrient, and food consumption were calculated. A 4×3 (group by time) repeated measures analysis of covariance with mixed-effect linear models was used. Covariates included child's sex, race/ethnicity, and total energy intake as well as parent's age and household education. Energy was excluded as a covariate in the energy density and energy models. Significant changes occurred in energy density. A significant interaction (group by time) was observed (F6, 515=2.40; P<0.05) in energy density from food only, while a significant time effect was observed for energy density from all foods and beverages (F2, 388=13.75; P<0.0001). Desirable changes were also observed in F/V-related dietary components. Increasing F/V consumption improved energy density and diet quality considerably in preadolescent children. Copyright © 2016 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

Effect of plasma density around Io on local electron heating in the Io plasma torus

NASA Astrophysics Data System (ADS)

Tsuchiya, F.; Yoshioka, K.; Kagitani, M.; Kimura, T.; Murakami, G.; Yamazaki, A.; Misawa, H.; Kasaba, Y.; Yoshikawa, I.; Sakanoi, T.; Koga, R.; Ryo, A.; Suzuki, F.; Hikida, R.

2017-12-01

HISAKI observation of Io plasma torus (IPT) with extreme ultraviolet (EUV) wavelength range is a useful probe to access plasma environment in inner magnetosphere of Jupiter. Emissions from sulfur and oxygen ions in EUV range are caused by electron impact excitation and their intensity is well correlated with the abundance of hot electron in IPT. Previous observation showed that the brightness was enhanced downstream of the satellite Io, indicating that efficient electron heating takes place at Io and/or just downstream of Io. Detailed analysis of the emission intensity shows that the brightness depends on the magnetic longitude at Io and primary and secondary peaks appear in the longitude ranges of 100-130 and 250-340 degrees, respectively. The peak position and amplitude are slightly different between dawn and dusk sides. Here, we introduce inhomogeneous IPT density model in order to investigate relation between the emission intensity and local plasma density around Io in detail. An empirical IPT model is used for spatial distribution of ion and electron densities in the meridional plane. To include longitude and local time asymmetry in IPT, we consider (1)dawnward shift of IPT due to global convection electric field, (2) offset of Jupiter's dipole magnetic field, and (3) tilt of IPT with respect to Io's orbital plane. The modeled electron density at the position of Io as a function of magnetic longitude at Io shows similar profile with the ion emission intensity derived from the observation. This result suggests that energy extracted around Io and/or efficiency of electron heating is closely related to the plasma density around Io and longitude and local time dependences is explained by the spatial inhomogeneity of plasma density in IPT. A part of the energy extracted around Io could be transferred to the Jovian ionosphere along the magnetic field line and cause bright aurora spots and strong radio emissions.

Space radiation shielding studies for astronaut and electronic component risk assessment

NASA Astrophysics Data System (ADS)

Fuchs, Jordan; Gersey, Brad; Wilkins, Richard

The space radiation environment is comprised of a complex and variable mix of high energy charged particles, gamma rays and other exotic species. Elements of this radiation field may also interact with intervening matter (such as a spaceship wall) and create secondary radiation particles such as neutrons. Some of the components of the space radiation environment are highly penetrating and can cause adverse effects in humans and electronic components aboard spacecraft. Developing and testing materials capable of providing effective shielding against the space radiation environment presents special challenges to researchers. Researchers at the Cen-ter for Radiation Engineering and Science for Space Exploration (CRESSE) at Prairie View AM University (PVAMU) perform accelerator based experiments testing the effectiveness of various materials for use as space radiation shields. These experiments take place at the NASA Space Radiation Laboratory at Brookhaven National Laboratory, the proton synchrotron at Loma Linda University Medical Center, and the Los Alamos Neutron Science Center at Los Alamos National Laboratory where charged particles and neutrons are produced at energies similar to those found in the space radiation environment. The work presented in this paper constitutes the beginning phase of an undergraduate research project created to contribute to this ongoing space radiation shielding project. Specifically, this student project entails devel-oping and maintaining a database of information concerning the historical data from shielding experiments along with a systematic categorization and storage system for the actual shielding materials. The shielding materials referred to here range in composition from standard materi-als such as high density polyethylene and aluminum to exotic multifunctional materials such as spectra-fiber infused composites. The categorization process for each material includes deter-mination of the density thickness of individual samples and a clear labeling and filing method that allows immediate cross referencing with other material samples during the experimental design process. Density thickness measurements will be performed using a precision scale that will allow for the fabrication of sets of standard density thicknesses of selected materials for ready use in shielding experiments. The historical data from previous shielding experiments consists primarily of measurements of absorbed dose, dose equivalent and dose distributions from a Tissue Equivalent Proportional Counter (TEPC) as measured downstream of various thicknesses of the materials while being irradiated in one of the aforementioned particle beams. This data has been digitally stored and linked to the composition of each material and may be easily accessed for shielding effectiveness inter-comparisons. This work was designed to facili-tate and increase the efficiency of ongoing space radiation shielding research performed at the CRESSE as well as serve as a way to educate new generations of space radiation researchers.

On the equilibrium charge density at tilt grain boundaries

NASA Astrophysics Data System (ADS)

Srikant, V.; Clarke, D. R.

1998-05-01

The equilibrium charge density and free energy of tilt grain boundaries as a function of their misorientation is computed using a Monte Carlo simulation that takes into account both the electrostatic and configurational energies associated with charges at the grain boundary. The computed equilibrium charge density increases with the grain-boundary angle and approaches a saturation value. The equilibrium charge density at large-angle grain boundaries compares well with experimental values for large-angle tilt boundaries in GaAs. The computed grain-boundary electrostatic energy is in agreement with the analytical solution to a one-dimensional Poisson equation at high donor densities but indicates that the analytical solution overestimates the electrostatic energy at lower donor densities.

Size effects on the structural, electronic, and optical properties of (5,0) finite-length carbon nanotube: An ab-initio electronic structure study

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

Tarighi Ahmadpour, Mahdi; Rostamnejadi, Ali; Hashemifar, S. Javad

2016-07-07

We use density functional computations to study the zero temperature structural, electronic, magnetic, and optical properties of (5,0) finite carbon nanotubes (FCNT), with length in the range of 4–44 Å. It is found that the structural and electronic properties of (5,0) FCNTs, in the ground state, converge at a length of about 30 Å, while the excited state properties exhibit long-range edge effects. We discuss that curvature effects enhance energy gap of FCNTs, in contrast to the known trend in the periodic limit. It is seen that compensation of curvature effects in two special small sizes may give rise to spontaneous magnetization.more » The obtained cohesive energies provide some insights into the effects of environment on the growth of FCNTs. The second-order difference of the total energies reveals an important magic size of about 15 Å. The optical and dynamical magnetic responses of the FCNTs to polarized electromagnetic pulses are studied by time dependent density functional theory. The results show that the static and dynamic magnetic properties mainly come from the edge carbon atoms. The optical absorption properties are described in terms of local field effects and characterized by Casida linear response method.« less

Significantly Enhanced Energy Storage Density by Modulating the Aspect Ratio of BaTiO3 Nanofibers

PubMed Central

Zhang, Dou; Zhou, Xuefan; Roscow, James; Zhou, Kechao; Wang, Lu; Luo, Hang; Bowen, Chris R.

2017-01-01

There is a growing need for high energy density capacitors in modern electric power supplies. The creation of nanocomposite systems based on one-dimensional nanofibers has shown great potential in achieving a high energy density since they can optimize the energy density by exploiting both the high permittivity of ceramic fillers and the high breakdown strength of the polymer matrix. In this paper, BaTiO3 nanofibers (NFs) with different aspect ratio were synthesized by a two-step hydrothermal method and the permittivity and energy storage of the P(VDF-HFP) nanocomposites were investigated. It is found that as the BaTiO3 NF aspect ratio and volume fraction increased the permittivity and maximum electric displacement of the nanocomposites increased, while the breakdown strength decreased. The nanocomposites with the highest aspect ratio BaTiO3 NFs exhibited the highest energy storage density at the same electric field. However, the nanocomposites with the lowest aspect ratio BaTiO3 NFs achieved the maximal energy storage density of 15.48 J/cm3 due to its higher breakdown strength. This contribution provides a potential route to prepare and tailor the properties of high energy density capacitor nanocomposites. PMID:28332636

Significantly Enhanced Energy Storage Density by Modulating the Aspect Ratio of BaTiO3 Nanofibers

NASA Astrophysics Data System (ADS)

Zhang, Dou; Zhou, Xuefan; Roscow, James; Zhou, Kechao; Wang, Lu; Luo, Hang; Bowen, Chris R.

2017-03-01

There is a growing need for high energy density capacitors in modern electric power supplies. The creation of nanocomposite systems based on one-dimensional nanofibers has shown great potential in achieving a high energy density since they can optimize the energy density by exploiting both the high permittivity of ceramic fillers and the high breakdown strength of the polymer matrix. In this paper, BaTiO3 nanofibers (NFs) with different aspect ratio were synthesized by a two-step hydrothermal method and the permittivity and energy storage of the P(VDF-HFP) nanocomposites were investigated. It is found that as the BaTiO3 NF aspect ratio and volume fraction increased the permittivity and maximum electric displacement of the nanocomposites increased, while the breakdown strength decreased. The nanocomposites with the highest aspect ratio BaTiO3 NFs exhibited the highest energy storage density at the same electric field. However, the nanocomposites with the lowest aspect ratio BaTiO3 NFs achieved the maximal energy storage density of 15.48 J/cm3 due to its higher breakdown strength. This contribution provides a potential route to prepare and tailor the properties of high energy density capacitor nanocomposites.

Significantly Enhanced Energy Storage Density by Modulating the Aspect Ratio of BaTiO3 Nanofibers.

PubMed

Zhang, Dou; Zhou, Xuefan; Roscow, James; Zhou, Kechao; Wang, Lu; Luo, Hang; Bowen, Chris R

2017-03-23

There is a growing need for high energy density capacitors in modern electric power supplies. The creation of nanocomposite systems based on one-dimensional nanofibers has shown great potential in achieving a high energy density since they can optimize the energy density by exploiting both the high permittivity of ceramic fillers and the high breakdown strength of the polymer matrix. In this paper, BaTiO 3 nanofibers (NFs) with different aspect ratio were synthesized by a two-step hydrothermal method and the permittivity and energy storage of the P(VDF-HFP) nanocomposites were investigated. It is found that as the BaTiO 3 NF aspect ratio and volume fraction increased the permittivity and maximum electric displacement of the nanocomposites increased, while the breakdown strength decreased. The nanocomposites with the highest aspect ratio BaTiO 3 NFs exhibited the highest energy storage density at the same electric field. However, the nanocomposites with the lowest aspect ratio BaTiO 3 NFs achieved the maximal energy storage density of 15.48 J/cm 3 due to its higher breakdown strength. This contribution provides a potential route to prepare and tailor the properties of high energy density capacitor nanocomposites.

Current perspectives on the etiology and manifestation of the “silent” component of the Female Athlete Triad

PubMed Central

Mallinson, Rebecca J; De Souza, Mary Jane

2014-01-01

The Female Athlete Triad (Triad) represents a syndrome of three interrelated conditions that originate from chronically inadequate energy intake to compensate for energy expenditure; this environment results in insufficient stored energy to maintain physiological processes, a condition known as low energy availability. The physiological adaptations associated with low energy availability, in turn, contribute to menstrual cycle disturbances. The downstream effects of both low energy availability and suppressed estrogen concentrations synergistically impair bone health, leading to low bone mineral density, compromised bone structure and microarchitecture, and ultimately, a decrease in bone strength. Unlike the other components of the Triad, poor bone health often does not have overt symptoms, and therefore develops silently, unbeknownst to the athlete. Compromised bone health among female athletes increases the risk of fracture throughout the lifespan, highlighting the long-term health consequences of the Triad. The purpose of this review is to examine the current state of Triad research related to the third component of the Triad, ie, poor bone health, in an effort to summarize what we know, what we are learning, and what remains unknown. PMID:24833922

Energy storage device with large charge separation

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

Holme, Timothy P.; Prinz, Friedrich B.; Iancu, Andrei T.

High density energy storage in semiconductor devices is provided. There are two main aspects of the present approach. The first aspect is to provide high density energy storage in semiconductor devices based on formation of a plasma in the semiconductor. The second aspect is to provide high density energy storage based on charge separation in a p-n junction.

Energy storage device with large charge separation

DOEpatents

Holme, Timothy P.; Prinz, Friedrich B.; Iancu, Andrei

2016-04-12

High density energy storage in semiconductor devices is provided. There are two main aspects of the present approach. The first aspect is to provide high density energy storage in semiconductor devices based on formation of a plasma in the semiconductor. The second aspect is to provide high density energy storage based on charge separation in a p-n junction.

Proton and neutron density distributions at supranormal density in low- and medium-energy heavy-ion collisions

NASA Astrophysics Data System (ADS)

Stone, J. R.; Danielewicz, P.; Iwata, Y.

2017-07-01

Background: The distribution of protons and neutrons in the matter created in heavy-ion collisions is one of the main points of interest for the collision physics, especially at supranormal densities. These distributions are the basis for predictions of the density dependence of the symmetry energy and the density range that can be achieved in a given colliding system. We report results of the first systematic simulation of proton and neutron density distributions in central heavy-ion collisions within the beam energy range of Ebeam≤800 MeV /nucl . The symmetric 40Ca+40Ca , 48Ca+48Ca , 100Sn+100Sn , and 120Sn+120Sn and asymmetric 40Ca+48Ca and 100Sn+120Sn systems were chosen for the simulations. Purpose: We simulate development of proton and neutron densities and asymmetries as a function of initial state, beam energy, and system size in the selected collisions in order to guide further experiments pursuing the density dependence of the symmetry energy. Methods: The Boltzmann-Uhlenbeck-Uehling (pBUU) transport model with four empirical models for the density dependence of the symmetry energy was employed. Results of simulations using pure Vlasov dynamics were added for completeness. In addition, the time-dependent Hartree-Fock (TDHF) model, with the SV-bas Skyrme interaction, was used to model the heavy-ion collisions at Ebeam≤40 MeV /nucl . Maximum proton and neutron densities ρpmax and ρnmax, reached in the course of a collision, were determined from the time evolution of ρp and ρn. Results: The highest total densities predicted at Ebeam=800 MeV /nucl . were of the order of ˜2.5 ρ0 (ρ0=0.16 fm-3 ) for both Sn and Ca systems. They were found to be only weakly dependent on the initial conditions, beam energy, system size, and a model of the symmetry energy. The proton-neutron asymmetry δ =(ρnmax-ρpmax) /(ρnmax+ρpmax) at maximum density does depend, though, on these parameters. The highest value of δ found in all systems and at all investigated beam energies was ˜0.17 . Conclusions: We find that the initial state, beam energy, system size, and a symmetry energy model affect very little the maximum proton and neutron densities, but have a subtle impact on the proton-neutron asymmetry. Most importantly, the variations in the proton-neutron asymmetry at maximum densities are related at most at 50% level to the details in the symmetry energy at supranormal density. The reminder is due to the details in the symmetry energy at subnormal densities and proton and neutron distributions in the initial state. This result brings to the forefront the need for a proper initialization of the nuclei in the simulation, but also brings up the question of microscopy, such as shell effects, that affect initial proton and neutron densities, but cannot be consistently incorporated into semiclassical transport models.

Low Li+ Insertion Barrier Carbon for High Energy Efficient Lithium-Ion Capacitor.

PubMed

Lee, Wee Siang Vincent; Huang, Xiaolei; Tan, Teck Leong; Xue, Jun Min

2018-01-17

Lithium-ion capacitor (LIC) is an attractive energy-storage device (ESD) that promises high energy density at moderate power density. However, the key challenge in its design is the low energy efficient negative electrode, which barred the realization of such research system in fulfilling the current ESD technological inadequacy due to its poor overall energy efficiency. Large voltage hysteresis is the main issue behind high energy density alloying/conversion-type materials, which reduces the electrode energy efficiency. Insertion-type material though averted in most research due to the low capacity remains to be highly favorable in commercial application due to its lower voltage hysteresis. To further reduce voltage hysteresis and increase capacity, amorphous carbon with wider interlayer spacing has been demonstrated in the simulation result to significantly reduce Li + insertion barrier. Hence, by employing such amorphous carbon, together with disordered carbon positive electrode, a high energy efficient LIC with round-trip energy efficiency of 84.3% with a maximum energy density of 133 Wh kg -1 at low power density of 210 W kg -1 can be achieved.

Development of a High Energy Density Capacitor for Plasma Thrusters.

DTIC Science & Technology

1980-10-01

AD-A091 839 MAXWELL LAOS INC SAN DIEGO CA FIG 81/3 DEVELOPMENT OF A HIGH ENERGY DENSITY CAPACITOR FOR PLASMA THRUS--ETC(U) OCT 80 A RAMRUS FO*611-77...of the program was the investigation of certain capacitor impregnants and their influence on high energy density capacitors which are employed in...PERIOD 1704,60~ 13 DEVELOPMENT OF A HIGH ENERGY DENSITY CAPA- Final Technical Report CITOR FOR PLASMA THRUSTERS July 1977 - May 1980 6 PERFORMING

Joint density-functional theory and its application to systems in solution

NASA Astrophysics Data System (ADS)

Petrosyan, Sahak A.

The physics of solvation, the interaction of water with solutes, plays a central role in chemistry and biochemistry, and it is essential for the very existence of life. Despite the central importance of water and the advent of the quantum theory early in the twentieth century, the link between the fundamental laws of physics and the observable properties of water remain poorly understood to this day. The central goal of this thesis is to develop a new formalism and framework to make the study of systems (solutes or surfaces) in contact with liquid water as practical and accurate as standard electronic structure calculations without the need for explicit averaging over large ensembles of configurations of water molecules. The thesis introduces a new form of density functional theory for the ab initio description of electronic systems in contact with a molecular liquid environment. This theory rigorously joins an electron density-functional for the electrons of a solute with a classical density-functional theory for the liquid into a single variational principle for the free energy of the combined system. Using the new form of density-functional theory for the ab initio description of electronic systems in contact with a molecular liquid environment, the thesis then presents the first detailed study of the impact of a solvent on the surface chemistry of Cr2O3, the passivating layer of stainless steel alloys. In comparison to a vacuum, we predict that the presence of water has little impact on the adsorption of chloride ions to the oxygen-terminated surface but has a dramatic effect on the binding of hydrogen to that surface. A key ingredient of a successful joint density functional theory is a good approximate functional for describing the solvent. We explore how the simplest examples of the best known class of approximate forms for the classical density functional fail when applied directly to water. The thesis then presents a computationally efficient density-functional theory for water which overcomes this difficulty and gives reasonable agreement with molecular dynamics simulation data for the solvation of hard spheres in water and sufficient agreement with experimental data for hydration of inert gas atoms to justify its use in a joint theory with standard approximate density functionals used in electronic structure calculations. The last study in the thesis combines the previous ideas and presenting an approximate model density functional which includes a description of cavitation effects through a classical density-functional theory; a description of dielectric effects through a non-local polarizability, and a description of the coupling of the solvent to the electrons of the solute through a pseudopotential. Without any empirical fitting of parameters to solvation data, this theory predicts solvation energies at least as well as state-of-the-art quantum-chemical cavity approaches, which do employ such fitting. Although this agreement without adjustable parameters is very encouraging and shows the promise of the joint density-functional approach, the functionals which we develop here are models and do not yet include all of the microscopic physics. The thesis concludes with a description of the directions future work should take to address this weakness.

Regenerative braking systems with torsional springs made of carbon nanotube yarn

NASA Astrophysics Data System (ADS)

Liu, S.; Martin, C.; Lashmore, D.; Schauer, M.; Livermore, C.

2014-11-01

The demonstration of large stroke, high energy density and high power density torsional springs based on carbon nanotube (CNT) yarns is reported, as well as their application as an energy-storing actuator for regenerative braking systems. Originally untwisted CNT yarn is cyclically loaded and unloaded in torsion, with the maximum rotation angle increasing until failure. The maximum extractable energy density is measured to be as high as 6.13 kJ/kg. The tests also reveal structural reorganization and hysteresis in the torsional loading curves. A regenerative braking system is built to capture the kinetic energy of a wheel and store it as elastic energy in twisted CNT yarns. When the yam's twist is released, the stored energy reaccelerates the wheel. The measured energy and mean power densities of the CNT yarns in the simple regenerative braking system are up to 4.69 kJ/kg and 1.21 kW/kg, respectively. A slightly lower energy density of up to 1.23 kJ/kg and a 0.29 kW/kg mean power density are measured for the CNT yarns in a more complex system that mimics a unidirectional rotating regenerative braking mechanism. The lower energy densities for CNT yarns in the regenerative braking systems as compared with the yarns themselves reflect the frictional losses of the regenerative systems.

Suppression of Allowed Transitions in Al-like Krypton (Kr23+) Due to the Presence of a Magnetic Dipole Transition in the 3s23p 2P Ground Term

NASA Astrophysics Data System (ADS)

Reader, Joseph; Podpaly, Yuri; Ralchenko, Yuri; Gillaspy, John

2013-05-01

Extreme ultraviolet spectra of highly charged krypton atoms were produced with an electron beam ion trap (EBIT) and recorded with a flat-field grazing-incidence spectrometer. The wavelength range was 3-18 nm. Wavelength calibration was provided by known lines of highly ionized Kr as well as spectra of C, O, Xe, and Ba. The observed spectra were interpreted with the aid of collisional-radiative modeling of the EBIT plasma. For the Al-like ion Kr23+ the allowed resonance lines 3s23p 2P-3s23d 2D exhibited extreme deviation from the normal ratios for lines of this multiplet. In particular, the 2P3/2-2D5/2 transition, normally the strongest, was observed to be the weakest. This effect was explained by the fact that in the low electron density environment of EBIT the 2D5/2 level is primarily populated by electron excitation from 2P3/2. However, the presence of a magnetic dipole M1 transition 3s23p 2P1/2-2P3/2 reduces the population of 2P3/2 and hence the population of 2D5/2. We are conducting further modeling with varying electron density to try to reproduce the observed line ratios. This could serve as a diagnostic tool for determining electron density in EBIT and fusion energy devices. Supported by Office of Fusion Energy Sciences of Dept. of Energy.

Comparing Perception-Based and Geographic Information System (GIS)-based characterizations of the local food environment.

PubMed

Moore, Latetia V; Diez Roux, Ana V; Brines, Shannon

2008-03-01

Measuring features of the local food environment has been a major challenge in studying the effect of the environment on diet. This study examined associations between alternate ways of characterizing the local food environment by comparing Geographic Information System (GIS)-derived densities of various types of stores to perception-based measures of the availability of healthy foods. Survey questions rating the availability of produce and low-fat products in neighborhoods were aggregated into a healthy food availability score for 5,774 residents of North Carolina, Maryland, and New York. Densities of supermarkets and smaller stores per square mile were computed for 1 mile around each respondent's residence using kernel estimation. The number of different store types in the area was used to measure variety in the food environment. Linear regression was used to examine associations of store densities and variety with reported availability. Respondents living in areas with lower densities of supermarkets rated the selection and availability of produce and low-fat foods 17% lower than those in areas with the highest densities of supermarkets (95% CL, -18.8, -15.1). In areas without supermarkets, low densities of smaller stores and less store variety were associated with worse perceived availability of healthy foods only in North Carolina (8.8% lower availability, 95% CL, -13.8, -3.4 for lowest vs. highest small-store density; 10.5% lower 95% CL, -16.0, -4.7 for least vs. most store variety). In contrast, higher smaller store densities and more variety were associated with worse perceived healthy food availability in Maryland. Perception- and GIS-based characterizations of the environment are associated but are not identical. Combinations of different types of measures may yield more valid measures of the environment.

Dark Energy and Key Physical Parameters of Clusters of Galaxies

NASA Astrophysics Data System (ADS)

Chernin, A. D.; Bisnovatyi-Kogan, G. S.

We discuss the physics of clusters of galaxies embedded in the cosmic dark energy background and show that 1) the halo cut-off radius of a cluster like the Virgo cluster is practically, if not exactly, equal to the zero-gravity radius at which the dark matter gravity is balanced by the dark energy antigravity; 2) the halo averaged density is equal to two densities of dark energy; 3) the halo edge (cut-off) density is the dark energy density with a numerical factor of the unity order slightly depending on the halo profile.

Dietary Management of Obesity: Cornerstones of Healthy Eating Patterns.

PubMed

Smethers, Alissa D; Rolls, Barbara J

2018-01-01

Several dietary patterns, both macronutrient and food based, can lead to weight loss. A key strategy for weight management that can be applied across dietary patterns is to reduce energy density. Clinical trials show that reducing energy density is effective for weight loss and weight loss maintenance. A variety of practical strategies and tools can help facilitate successful weight management by reducing energy density, providing portion control, and improving diet quality. The flexibility of energy density gives patients options to tailor and personalize their dietary pattern to reduce energy intake for sustainable weight loss. Copyright © 2017 Elsevier Inc. All rights reserved.

Interdependence of different symmetry energy elements

NASA Astrophysics Data System (ADS)

Mondal, C.; Agrawal, B. K.; De, J. N.; Samaddar, S. K.; Centelles, M.; Viñas, X.

2017-08-01

Relations between the nuclear symmetry energy coefficient and its density derivatives are derived. The relations hold for a class of interactions with quadratic momentum dependence and a power-law density dependence. The structural connection between the different symmetry energy elements as obtained seems to be followed by almost all reasonable nuclear energy density functionals, both relativistic and nonrelativistic, suggesting a universality in the correlation structure. This, coupled with known values of some well-accepted constants related to nuclear matter, helps in constraining values of different density derivatives of the nuclear symmetry energy, shedding light on the isovector part of the nuclear interaction.

Extended adiabatic blast waves and a model of the soft X-ray background. [interstellar matter

NASA Technical Reports Server (NTRS)

Cox, D. P.; Anderson, P. R.

1981-01-01

An analytical approximation is generated which follows the development of an adiabatic spherical blast wave in a homogeneous ambient medium of finite pressure. An analytical approximation is also presented for the electron temperature distribution resulting from coulomb collisional heating. The dynamical, thermal, ionization, and spectral structures are calculated for blast waves of energy E sub 0 = 5 x 10 to the 50th power ergs in a hot low-density interstellar environment. A formula is presented for estimating the luminosity evolution of such explosions. The B and C bands of the soft X-ray background, it is shown, are reproduced by such a model explosion if the ambient density is about .000004 cm, the blast radius is roughly 100 pc, and the solar system is located inside the shocked region. Evolution in a pre-existing cavity with a strong density gradient may, it is suggested, remove both the M band and OVI discrepancies.

Operational specification and forecasting advances for Dst, LEO thermospheric densities, and aviation radiation dose and dose rate

NASA Astrophysics Data System (ADS)

Tobiska, W. Kent

Space weather’s effects upon the near-Earth environment are due to dynamic changes in the energy transfer processes from the Sun’s photons, particles, and fields. Of the space environment domains that are affected by space weather, the magnetosphere, thermosphere, and even troposphere are key regions that are affected. Space Environment Technologies (SET) has developed and is producing innovative space weather applications. Key operational systems for providing timely information about the effects of space weather on these domains are SET’s Magnetosphere Alert and Prediction System (MAPS), LEO Alert and Prediction System (LAPS), and Automated Radiation Measurements for Aviation Safety (ARMAS) system. MAPS provides a forecast Dst index out to 6 days through the data-driven, redundant data stream Anemomilos algorithm. Anemomilos uses observational proxies for the magnitude, location, and velocity of solar ejecta events. This forecast index is used by satellite operations to characterize upcoming geomagnetic storms, for example. In addition, an ENLIL/Rice Dst prediction out to several days has also been developed and will be described. LAPS is the SET fully redundant operational system providing recent history, current epoch, and forecast solar and geomagnetic indices for use in operational versions of the JB2008 thermospheric density model. The thermospheric densities produced by that system, driven by the LAPS data, are forecast to 72-hours to provide the global mass densities for satellite operators. ARMAS is a project that has successfully demonstrated the operation of a micro dosimeter on aircraft to capture the real-time radiation environment due to Galactic Cosmic Rays and Solar Energetic Particles. The dose and dose-rates are captured on aircraft, downlinked in real-time via the Iridium satellites, processed on the ground, incorporated into the most recent NAIRAS global radiation climatology data runs, and made available to end users via the web and smart phone apps. ARMAS provides the “weather” of the radiation environment to improve air-crew and passenger safety. Many of the data products from MAPS, LAPS, and ARMAS are available on the SpaceWx smartphone app for iPhone, iPad, iPod, and Android professional users and public space weather education. We describe recent forecasting advances for moving the space weather information from these automated systems into operational, derivative products for communications, aviation, and satellite operations uses.

Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals

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

Zhang, Y., E-mail: thuzhangyu@foxmail.com; Huang, S. L., E-mail: huangsling@tsinghua.edu.cn; Wang, S.

The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency formore » all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert–Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of <1% and thus can act as a universal time-of-flight extraction method for narrowband Lamb wave detection signals.« less

Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals.

PubMed

Zhang, Y; Huang, S L; Wang, S; Zhao, W

2016-05-01

The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency for all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert-Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of <1% and thus can act as a universal time-of-flight extraction method for narrowband Lamb wave detection signals.

Augmented potential, energy densities, and virial relations in the weak- and strong-interaction limits of DFT

NASA Astrophysics Data System (ADS)

Vuckovic, Stefan; Levy, Mel; Gori-Giorgi, Paola

2017-12-01

The augmented potential introduced by Levy and Zahariev [Phys. Rev. Lett. 113, 113002 (2014)] is shifted with respect to the standard exchange-correlation potential of the Kohn-Sham density functional theory by a density-dependent constant that makes the total energy become equal to the sum of the occupied orbital energies. In this work, we analyze several features of this approach, focusing on the limit of infinite coupling strength and studying the shift and the corresponding energy density at different correlation regimes. We present and discuss coordinate scaling properties of the augmented potential, study its connection to the response potential, and use the shift to analyze the classical jellium and uniform gas models. We also study other definitions of the energy densities in relation to the functional construction by local interpolations along the adiabatic connection. Our findings indicate that the energy density that is defined in terms of the electrostatic potential of the exchange-correlation hole is particularly well suited for this purpose.

Derivative discontinuity and exchange-correlation potential of meta-GGAs in density-functional theory.

PubMed

Eich, F G; Hellgren, Maria

2014-12-14

We investigate fundamental properties of meta-generalized-gradient approximations (meta-GGAs) to the exchange-correlation energy functional, which have an implicit density dependence via the Kohn-Sham kinetic-energy density. To this purpose, we construct the most simple meta-GGA by expressing the local exchange-correlation energy per particle as a function of a fictitious density, which is obtained by inverting the Thomas-Fermi kinetic-energy functional. This simple functional considerably improves the total energy of atoms as compared to the standard local density approximation. The corresponding exchange-correlation potentials are then determined exactly through a solution of the optimized effective potential equation. These potentials support an additional bound state and exhibit a derivative discontinuity at integer particle numbers. We further demonstrate that through the kinetic-energy density any meta-GGA incorporates a derivative discontinuity. However, we also find that for commonly used meta-GGAs the discontinuity is largely underestimated and in some cases even negative.

Derivative discontinuity and exchange-correlation potential of meta-GGAs in density-functional theory

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

Eich, F. G., E-mail: eichf@missouri.edu; Hellgren, Maria

2014-12-14

We investigate fundamental properties of meta-generalized-gradient approximations (meta-GGAs) to the exchange-correlation energy functional, which have an implicit density dependence via the Kohn-Sham kinetic-energy density. To this purpose, we construct the most simple meta-GGA by expressing the local exchange-correlation energy per particle as a function of a fictitious density, which is obtained by inverting the Thomas-Fermi kinetic-energy functional. This simple functional considerably improves the total energy of atoms as compared to the standard local density approximation. The corresponding exchange-correlation potentials are then determined exactly through a solution of the optimized effective potential equation. These potentials support an additional bound state andmore » exhibit a derivative discontinuity at integer particle numbers. We further demonstrate that through the kinetic-energy density any meta-GGA incorporates a derivative discontinuity. However, we also find that for commonly used meta-GGAs the discontinuity is largely underestimated and in some cases even negative.« less

High Performance and Economic Supercapacitors for Energy Storage Based on Carbon Nanomaterials

NASA Astrophysics Data System (ADS)

Samuilov, Vladimir; Farshid, Behzad; Frenkel, Alexander; Sensor CAT at Stony Brook Team

2015-03-01

We designed and manufactured very inexpensive prototypes of supercapacitors for energy storage based on carbon nanomaterials comprised of: reduced graphene oxide (RGOs) and carbon nanotubes (CNTs) as electrodes filled with polymer gel electrolytes. The electrochemical properties of supercapacitors made using these materials were compared and analyzed. A significant tradeoff between the energy density and the power density was determined; RGO electrodes demonstrated the highest energy density, while composite RGO/CNT electrodes showed the highest power density. The thickness of the RGO electrode was varied to determine its effect on the power density of the supercapacitor and results showed that with decreasing electrode thickness power density would increase. The specific capacitances of over 600 F/g were observed.

A Novel Electrophototrophic Bacterium Rhodopseudomonas palustris Strain RP2, Exhibits Hydrocarbonoclastic Potential in Anaerobic Environments

PubMed Central

Venkidusamy, Krishnaveni; Megharaj, Mallavarapu

2016-01-01

An electrophototrophic, hydrocarbonoclastic bacterium Rhodopseudomonas palustris stain RP2 was isolated from the anodic biofilms of hydrocarbon fed microbial electrochemical remediation systems (MERS). Salient properties of the strain RP2 were direct electrode respiration, dissimilatory metal oxide reduction, spore formation, anaerobic nitrate reduction, free living diazotrophy and the ability to degrade n-alkane components of petroleum hydrocarbons (PH) in anoxic, photic environments. In acetate fed microbial electrochemical cells, a maximum current density of 305 ± 10 mA/m2 (1000Ω) was generated (power density 131.65 ± 10 mW/m2) by strain RP2 with a coulombic efficiency of 46.7 ± 1.3%. Cyclic voltammetry studies showed that anaerobically grown cells of strain RP2 is electrochemically active and likely to transfer electrons extracellularly to solid electron acceptors through membrane bound compounds, however, aerobically grown cells lacked the electrochemical activity. The ability of strain RP2 to produce current (maximum current density 21 ± 3 mA/m2; power density 720 ± 7 μW/m2, 1000 Ω) using PH as a sole energy source was also examined using an initial concentration of 800 mg l-1 of diesel range hydrocarbons (C9-C36) with a concomitant removal of 47.4 ± 2.7% hydrocarbons in MERS. Here, we also report the first study that shows an initial evidence for the existence of a hydrocarbonoclastic behavior in the strain RP2 when grown in different electron accepting and illuminated conditions (anaerobic and MERS degradation). Such observations reveal the importance of photoorganotrophic growth in the utilization of hydrocarbons from contaminated environments. Identification of such novel petrochemical hydrocarbon degrading electricigens, not only expands the knowledge on the range of bacteria known for the hydrocarbon bioremediation but also shows a biotechnological potential that goes well beyond its applications to MERS. PMID:27462307

Proton elastic scattering from stable and unstable nuclei - Extraction of nuclear densities

NASA Astrophysics Data System (ADS)

Sakaguchi, H.; Zenihiro, J.

2017-11-01

Progress in proton elastic scattering at intermediate energies to determine nuclear density distributions is reviewed. After challenges of about 15 years to explain proton elastic scattering and associated polarization phenomena at intermediate energies, we have reached to some conclusions regarding proton elastic scattering as a means of obtaining nuclear densities. During this same period, physics of unstable nuclei has become of interest, and the density distributions of protons and neutrons play more important roles in unstable nuclei, since the differences in proton and neutron numbers and densities are expected to be significant. As such, proton elastic scattering experiments at intermediate energies using the inverse kinematic method have started to determine density distributions of unstable nuclei. In the region of unstable nuclei, we are confronted with a new problem when attempting to find proton and neutron densities separately from elastic proton scattering data, since electron scattering data for unstable nuclei are not presently available. We introduce a new means of determining proton and neutron densities separately by double-energy proton elastic scattering at intermediate energies.

Metalloid Aluminum Clusters with Fluorine

DTIC Science & Technology

2016-12-01

molecular dynamics, binding energy , siesta code, density of states, projected density of states 15. NUMBER OF PAGES 69 16. PRICE CODE 17. SECURITY...high energy density compared to explosives, but typically release this energy slowly via diffusion-limited combustion. There is recent interest in using...examine the cluster binding energy and electronic structure. Partial fluorine substitution in a prototypical aluminum-cyclopentadienyl cluster results

High Discharge Energy Density at Low Electric Field Using an Aligned Titanium Dioxide/Lead Zirconate Titanate Nanowire Array.

PubMed

Zhang, Dou; Liu, Weiwei; Guo, Ru; Zhou, Kechao; Luo, Hang

2018-02-01

Polymer-based capacitors with high energy density have attracted significant attention in recent years due to their wide range of potential applications in electronic devices. However, the obtained high energy density is predominantly dependent on high applied electric field, e.g., 400-600 kV mm -1 , which may bring more challenges relating to the failure probability. Here, a simple two-step method for synthesizing titanium dioxide/lead zirconate titanate nanowire arrays is exploited and a demonstration of their ability to achieve high discharge energy density capacitors for low operating voltage applications is provided. A high discharge energy density of 6.9 J cm -3 is achieved at low electric fields, i.e., 143 kV mm -1 , which is attributed to the high relative permittivity of 218.9 at 1 kHz and high polarization of 23.35 µC cm -2 at this electric field. The discharge energy density obtained in this work is the highest known for a ceramic/polymer nanocomposite at such a low electric field. The novel nanowire arrays used in this work are applicable to a wide range of fields, such as energy harvesting, energy storage, and photocatalysis.

STAR FORMATION AND SUPERCLUSTER ENVIRONMENT OF 107 NEARBY GALAXY CLUSTERS

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

Cohen, Seth A.; Hickox, Ryan C.; Wegner, Gary A.

We analyze the relationship between star formation (SF), substructure, and supercluster environment in a sample of 107 nearby galaxy clusters using data from the Sloan Digital Sky Survey. Previous works have investigated the relationships between SF and cluster substructure, and cluster substructure and supercluster environment, but definitive conclusions relating all three of these variables has remained elusive. We find an inverse relationship between cluster SF fraction ( f {sub SF}) and supercluster environment density, calculated using the Galaxy luminosity density field at a smoothing length of 8 h {sup −1} Mpc (D8). The slope of f {sub SF} versus D8more » is −0.008 ± 0.002. The f {sub SF} of clusters located in low-density large-scale environments, 0.244 ± 0.011, is higher than for clusters located in high-density supercluster cores, 0.202 ± 0.014. We also divide superclusters, according to their morphology, into filament- and spider-type systems. The inverse relationship between cluster f {sub SF} and large-scale density is dominated by filament- rather than spider-type superclusters. In high-density cores of superclusters, we find a higher f {sub SF} in spider-type superclusters, 0.229 ± 0.016, than in filament-type superclusters, 0.166 ± 0.019. Using principal component analysis, we confirm these results and the direct correlation between cluster substructure and SF. These results indicate that cluster SF is affected by both the dynamical age of the cluster (younger systems exhibit higher amounts of SF); the large-scale density of the supercluster environment (high-density core regions exhibit lower amounts of SF); and supercluster morphology (spider-type superclusters exhibit higher amounts of SF at high densities).« less

Correlation of a Bipolar-Transistor-Based Neutron Displacement Damage Sensor Methodology with Proton Irradiations

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

Tonigan, Andrew M.; Arutt, Charles N.; Parma, Edward J.

For this research, a bipolar-transistor-based sensor technique has been used to compare silicon displacement damage from known and unknown neutron energy spectra generated in nuclear reactor and high-energy-density physics environments. The technique has been shown to yield 1-MeV(Si) equivalent neutron fluence measurements comparable to traditional neutron activation dosimetry. This study significantly extends previous results by evaluating three types of bipolar devices utilized as displacement damage sensors at a nuclear research reactor and at a Pelletron particle accelerator. Ionizing dose effects are compensated for via comparisons with 10-keV x-ray and/or cobalt-60 gamma ray irradiations. Non-ionizing energy loss calculations adequately approximate themore » correlations between particle-device responses and provide evidence for the use of one particle type to screen the sensitivity of the other.« less

Flutter-driven triboelectrification for harvesting wind energy

NASA Astrophysics Data System (ADS)

Bae, Jihyun; Lee, Jeongsu; Kim, Seongmin; Ha, Jaewook; Lee, Byoung-Sun; Park, Youngjun; Choong, Chweelin; Kim, Jin-Baek; Wang, Zhong Lin; Kim, Ho-Young; Park, Jong-Jin; Chung, U.-In

2014-09-01

Technologies to harvest electrical energy from wind have vast potentials because wind is one of the cleanest and most sustainable energy sources that nature provides. Here we propose a flutter-driven triboelectric generator that uses contact electrification caused by the self-sustained oscillation of flags. We study the coupled interaction between a fluttering flexible flag and a rigid plate. In doing so, we find three distinct contact modes: single, double and chaotic. The flutter-driven triboelectric generator having small dimensions of 7.5 × 5 cm at wind speed of 15 ms-1 exhibits high-electrical performances: an instantaneous output voltage of 200 V and a current of 60 μA with a high frequency of 158 Hz, giving an average power density of approximately 0.86 mW. The flutter-driven triboelectric generation is a promising technology to drive electric devices in the outdoor environments in a sustainable manner.

Doping Y 2O 3 with Mn 4+ for energy-efficient lighting

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

Ming, Wenmei; Shi, Hongliang; Du, Mao-Hua

Developing energy-efficient LEDs that emit warm white light requires new red phosphors with appropriate emission wavelengths and band widths. Mn 4+-activated Y 2O 3 is a potential red LED phosphor with narrow emission and improved emission wavelength compared to previously known Mn 4+-activated oxide phosphors. Here in this work, the dopability and the oxidation state of Mn in Y 2O 3 are investigated based on the formation energies of native defects, Mn dopants, and divalent co-dopants (i.e., Ca, Sr, Cd, and Zn) calculated using hybrid density functional theory. We found that Mn 4+ is difficult to form in Y 2Omore » 3 without co-doping. Stabilizing Mn 4+ on Y 3+ sites (forming Mn + Y donors) requires the co-doping of compensating acceptors (Ca or Sr) in oxygen-rich growth environments.« less

Correlation of a Bipolar-Transistor-Based Neutron Displacement Damage Sensor Methodology with Proton Irradiations

DOE PAGES

Tonigan, Andrew M.; Arutt, Charles N.; Parma, Edward J.; ...

2017-11-16

For this research, a bipolar-transistor-based sensor technique has been used to compare silicon displacement damage from known and unknown neutron energy spectra generated in nuclear reactor and high-energy-density physics environments. The technique has been shown to yield 1-MeV(Si) equivalent neutron fluence measurements comparable to traditional neutron activation dosimetry. This study significantly extends previous results by evaluating three types of bipolar devices utilized as displacement damage sensors at a nuclear research reactor and at a Pelletron particle accelerator. Ionizing dose effects are compensated for via comparisons with 10-keV x-ray and/or cobalt-60 gamma ray irradiations. Non-ionizing energy loss calculations adequately approximate themore » correlations between particle-device responses and provide evidence for the use of one particle type to screen the sensitivity of the other.« less

Doping Y 2O 3 with Mn 4+ for energy-efficient lighting

DOE PAGES

Ming, Wenmei; Shi, Hongliang; Du, Mao-Hua

2018-03-28

Developing energy-efficient LEDs that emit warm white light requires new red phosphors with appropriate emission wavelengths and band widths. Mn 4+-activated Y 2O 3 is a potential red LED phosphor with narrow emission and improved emission wavelength compared to previously known Mn 4+-activated oxide phosphors. Here in this work, the dopability and the oxidation state of Mn in Y 2O 3 are investigated based on the formation energies of native defects, Mn dopants, and divalent co-dopants (i.e., Ca, Sr, Cd, and Zn) calculated using hybrid density functional theory. We found that Mn 4+ is difficult to form in Y 2Omore » 3 without co-doping. Stabilizing Mn 4+ on Y 3+ sites (forming Mn + Y donors) requires the co-doping of compensating acceptors (Ca or Sr) in oxygen-rich growth environments.« less

Thermal Peak Management Using Organic Phase Change Materials for Latent Heat Storage in Electronic Applications

PubMed Central

Maxa, Jacob; Novikov, Andrej; Nowottnick, Mathias

2017-01-01

Modern high power electronics devices consists of a large amount of integrated circuits for switching and supply applications. Beside the benefits, the technology exhibits the problem of an ever increasing power density. Nowadays, heat sinks that are directly mounted on a device, are used to reduce the on-chip temperature and dissipate the thermal energy to the environment. This paper presents a concept of a composite coating for electronic components on printed circuit boards or electronic assemblies that is able to buffer a certain amount of thermal energy, dissipated from a device. The idea is to suppress temperature peaks in electronic components during load peaks or electronic shorts, which otherwise could damage or destroy the device, by using a phase change material to buffer the thermal energy. The phase change material coating could be directly applied on the chip package or the PCB using different mechanical retaining jigs.

Spin-Multiplet Components and Energy Splittings by Multistate Density Functional Theory.

PubMed

Grofe, Adam; Chen, Xin; Liu, Wenjian; Gao, Jiali

2017-10-05

Kohn-Sham density functional theory has been tremendously successful in chemistry and physics. Yet, it is unable to describe the energy degeneracy of spin-multiplet components with any approximate functional. This work features two contributions. (1) We present a multistate density functional theory (MSDFT) to represent spin-multiplet components and to determine multiplet energies. MSDFT is a hybrid approach, taking advantage of both wave function theory and density functional theory. Thus, the wave functions, electron densities and energy density-functionals for ground and excited states and for different components are treated on the same footing. The method is illustrated on valence excitations of atoms and molecules. (2) Importantly, a key result is that for cases in which the high-spin components can be determined separately by Kohn-Sham density functional theory, the transition density functional in MSDFT (which describes electronic coupling) can be defined rigorously. The numerical results may be explored to design and optimize transition density functionals for configuration coupling in multiconfigurational DFT.

Cosmological implications of the transition from the false vacuum to the true vacuum state

NASA Astrophysics Data System (ADS)

Stachowski, Aleksander; Szydłowski, Marek; Urbanowski, Krzysztof

2017-06-01

We study cosmology with running dark energy. The energy density of dark energy is obtained from the quantum process of transition from the false vacuum state to the true vacuum state. We use the Breit-Wigner energy distribution function to model the quantum unstable systems and obtain the energy density of the dark energy parametrization ρ _ {de}(t). We also use Krauss and Dent's idea linking properties of the quantum mechanical decay of unstable states with the properties of the observed Universe. In the cosmological model with this parametrization there is an energy transfer between dark matter and dark energy. The intensity of this process, measured by a parameter α , distinguishes two scenarios. As the Universe starts from the false vacuum state, for the small value of α (0<α <0.4) it goes through an intermediate oscillatory (quantum) regime of the density of dark energy, while for α > 0.4 the density of the dark energy jumps down. In both cases the present value of the density of dark energy is reached. From a statistical analysis we find this model to be in good agreement with the astronomical data and practically indistinguishable from the Λ CDM model.

A Low-Cost Neutral Zinc-Iron Flow Battery with High Energy Density for Stationary Energy Storage.

PubMed

Xie, Congxin; Duan, Yinqi; Xu, Wenbin; Zhang, Huamin; Li, Xianfeng

2017-11-20

Flow batteries (FBs) are one of the most promising stationary energy-storage devices for storing renewable energy. However, commercial progress of FBs is limited by their high cost and low energy density. A neutral zinc-iron FB with very low cost and high energy density is presented. By using highly soluble FeCl 2 /ZnBr 2 species, a charge energy density of 56.30 Wh L -1 can be achieved. DFT calculations demonstrated that glycine can combine with iron to suppress hydrolysis and crossover of Fe 3+ /Fe 2+ . The results indicated that an energy efficiency of 86.66 % can be obtained at 40 mA cm -2 and the battery can run stably for more than 100 cycles. Furthermore, a low-cost porous membrane was employed to lower the capital cost to less than $ 50 per kWh, which was the lowest value that has ever been reported. Combining the features of low cost, high energy density and high energy efficiency, the neutral zinc-iron FB is a promising candidate for stationary energy-storage applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Density-based Energy Decomposition Analysis for Intermolecular Interactions with Variationally Determined Intermediate State Energies

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

Wu, Q.; Ayers, P.W.; Zhang, Y.

2009-10-28

The first purely density-based energy decomposition analysis (EDA) for intermolecular binding is developed within the density functional theory. The most important feature of this scheme is to variationally determine the frozen density energy, based on a constrained search formalism and implemented with the Wu-Yang algorithm [Q. Wu and W. Yang, J. Chem. Phys. 118, 2498 (2003) ]. This variational process dispenses with the Heitler-London antisymmetrization of wave functions used in most previous methods and calculates the electrostatic and Pauli repulsion energies together without any distortion of the frozen density, an important fact that enables a clean separation of these twomore » terms from the relaxation (i.e., polarization and charge transfer) terms. The new EDA also employs the constrained density functional theory approach [Q. Wu and T. Van Voorhis, Phys. Rev. A 72, 24502 (2005)] to separate out charge transfer effects. Because the charge transfer energy is based on the density flow in real space, it has a small basis set dependence. Applications of this decomposition to hydrogen bonding in the water dimer and the formamide dimer show that the frozen density energy dominates the binding in these systems, consistent with the noncovalent nature of the interactions. A more detailed examination reveals how the interplay of electrostatics and the Pauli repulsion determines the distance and angular dependence of these hydrogen bonds.« less

Effects of Transition Metals on the Grain Boundary Cohesion in Tungsten

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

Setyawan, Wahyu; Kurtz, Richard J.

2012-04-01

We report on the effects of alloying transition metals on the interfacial cohesion of W {Sigma}27<110>{l_brace}525{r_brace} symmetrical tilt grain boundary (GB). Density-functional-theory calculations show that the effects are related to the sensitivity of the d-orbital's occupation with respect to the atomic environments at the GB. Systematic trends of cleavage energy as a function of the electronic valence of the impurities were observed across different interfacial positions. Segregation formation energies were calculated to study the stability of the substitutional sites. All of the energetically preferred sites also correspond to the positions at which the alloying elements increase the GB cleavage energy.more » For each element, the more stable the configuration, the higher the cleavage energy. This finding is crucial in designing polycrystalline W-alloys with improved fracture toughness. Considering the solubility limit, the results suggest that Ta, Nb, Re, Ru, and Os are potential additives against intergranular fracture.« less

The development of extraterrestrial civilizations and physical laws

NASA Astrophysics Data System (ADS)

Troitskii, V. S.

Consideration is given to the limiting characteristics of extraterrestrial civilizations as allowed by physical laws, and to the possible pathways and levels of development of such civilizations. The concept of an extraterrestrial civilization is defined in terms of the exchange of information, energy and matter both within a community of intelligent beings and between the community and its environment. The possible characteristics of such a civilization are then examined, including amount of populated space, population and population density, energy requirements and supply, information content, transportation capacity and lifetimes, and it is shown that the space occupiable by an extraterrestrial civilization is limited to the space around its star, due to the finite velocity of transport processes. The development of a type II civilization, making use of energy on the order of that put out by its star, is then examined, and constraints on energy production in such a civilization making impossible the establishment of an omnidirectional radio beacon detectable throughout the Galaxy are pointed out.

Development of new sealed bipolar lead-acid battery

NASA Technical Reports Server (NTRS)

Attia, Alan I.; Rowlette, J. J.

1987-01-01

New light weight composite bipolar plates which can withstand the corrosive environment of the lead acid battery have made possible the construction of a sealed bipolar lead acid battery that promises to achieve very high specific power levels and substantially higher energy densities than conventional lead acid batteries. Performance projections based on preliminary experimental results show that the peak specific power of the battery can be as high as 90 kW/kg, and that a specific power of 5 kW/kg can be sustained over several thousand pulses.

Chameleon induced atomic afterglow

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

Brax, Philippe; Burrage, Clare

2010-11-01

The chameleon is a scalar field whose mass depends on the density of its environment. Chameleons are necessarily coupled to matter particles and will excite transitions between atomic energy levels in an analogous manner to photons. When created inside an optical cavity by passing a laser beam through a constant magnetic field, chameleons are trapped between the cavity walls and form a standing wave. This effect will lead to an afterglow phenomenon even when the laser beam and the magnetic field have been turned off, and could be used to probe the interactions of the chameleon field with matter.

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

Dzhioev, Alan A., E-mail: dzhioev@theor.jinr.ru; Vdovin, A. I., E-mail: vdovin@theor.jinr.ru; Stoyanov, Ch., E-mail: stoyanov@inrne.bas.bg

We combine the thermal QRPA approach with the Skyrme energy density functional theory (Skyrme–TQRPA) for modelling the process of electron capture on nuclei in supernova environment. For a sample nucleus, {sup 56}Fe, the Skyrme–TQRPA approach is applied to analyze thermal effects on the strength function of GT{sub +} transitions which dominate electron capture at E{sub e} ≤ 30 MeV. Several Skyrme interactions are used in order to verify the sensitivity of the obtained results to the Skyrme force parameters. Finite-temperature cross sections are calculated and the results are comparedwith those of the other model calculations.

The development of a new sealed bipolar lead-acid battery

NASA Technical Reports Server (NTRS)

Attia, A. I.; Rowlette, J. J.

1988-01-01

New light weight composite bipolar plates which can withstand the corrosive environment of the lead acid battery have made possible the construction of a sealed bipolar lead acid battery that promises to achieve very high specific power levels and substantially higher energy densities than conventional lead acid batteries. Performance projections based on preliminary experimental results show that the peak specific power of the battery can be as high as 90 kW/kg, and that a specific power of 5 kW/kg can be sustained over several thousand pulses.

Peas in a Pod: Environment and Ionization in Green Pea Galaxies

NASA Astrophysics Data System (ADS)

Kurtz, Heather; Jaskot, Anne; Drew, Patrick; Pare, Dylan; Griffin, Jon; Petersen, Michael

2016-01-01

The Green Peas are extreme, highly ionized, starburst galaxies with strong [OIII] 5007 emission. Using the Sloan Digital Sky Survey, we present statistics on the environment of Green Peas and investigate its effects on their ionized gas properties. Although most dwarf starburst galaxies are in low-density environments, we identify a sample of Green Peas in dense environments. Emission line observations with the WIYN 0.9-meter telescope at Kitt Peak reveal that one cluster Green Pea is more highly ionized in the direction of the cluster center. Ram pressure stripping likely generates this ionization gradient. We explore the role of the environment in enhancing star formation rates and ionization, and we compare the nebular properties of Green Peas in high-density environments to those in low-density environments.

Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density

DOE PAGES

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Yong; ...

2016-02-11

Here we demonstrate for the first time that planar Na-NiCl 2 batteries can be operated at an intermediate temperature of 190°C with ultra-high energy density. A specific energy density of 350 Wh/kg, which is 3 times higher than that of conventional tubular Na-NiCl 2 batteries operated at 280°C, was obtained for planar Na-NiCl 2 batteries operated at 190°C over a long-term cell test (1000 cycles). The high energy density and superior cycle stability are attributed to the slower particle growth of the cathode materials (NaCl and Ni) at 190°C. The results reported in this work demonstrate that planar Na-NiCl 2more » batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.« less

Interconfigurational energies in transition-metal atoms using gradient-corrected density-functional theory

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

Kutzler, F.W.; Painter, G.S.

1991-03-15

The rapid variation of charge and spin densities in atoms and molecules provides a severe test for local-density-functional theory and for the use of gradient corrections. In the study reported in this paper, we use the Langreth, Mehl, and Hu (LMH) functional and the generalized gradient approximation (GGA) of Perdew and Yue to calculate {ital s}-{ital d} transition energies, 4{ital s} ionization energies, and 3{ital d} ionization energies for the 3{ital d} transition-metal atoms. These calculations are compared with results from the local-density functional of Vosko, Wilk, and Nusair. By comparison with experimental energies, we find that the gradient functionalsmore » are only marginally more successful than the local-density approximation in calculating energy differences between states in transition-metal atoms. The GGA approximation is somewhat better than the LMH functional for most of the atoms studied, although there are several exceptions.« less

Interference of interchromophoric energy-transfer pathways in π-conjugated macrocycles

DOE PAGES

Alfonso Hernandez, Laura; Nelson, Tammie Renee; Gelin, Maxim F.; ...

2016-11-10

The interchromophoric energy-transfer pathways between weakly coupled units in a π-conjugated phenylene–ethynylene macrocycle and its half-ring analogue have been investigated using the nonadiabatic excited-state molecular dynamics approach. To track the flow of electronic transition density between macrocycle units, we formulate a transition density flux analysis adapted from the statistical minimum flow method previously developed to investigate vibrational energy flow. Following photoexcitation, transition density is primarily delocalized on two chromophore units and the system undergoes ultrafast energy transfer, creating a localized excited state on a single unit. In the macrocycle, distinct chromophore units donate transition density to a single acceptor unitmore » but do not interchange transition density among each other. We find that energy transfer in the macrocycle is slower than in the corresponding half ring because of the presence of multiple interfering energy-transfer pathways. Finally, simulation results are validated by modeling the fluorescence anisotropy decay.« less

Laser Scribed Graphene Cathode for Next Generation of High Performance Hybrid Supercapacitors.

PubMed

Lee, Seung-Hwan; Kim, Jin Hyeon; Yoon, Jung-Rag

2018-05-25

Hybrid supercapacitors have been regarded as next-generation energy storage devices due to their outstanding performances. However, hybrid supercapacitors remain a great challenge to enhance the energy density of hybrid supercapacitors. Herein, a novel approach for high-energy density hybrid supercapacitors based on a laser scribed graphene cathode and AlPO 4 -carbon hybrid coated H 2 Ti 12 O 25 (LSG/H-HTO) was designed. Benefiting from high-energy laser scribed graphene and high-power H-HTO, it was demonstrated that LSG/H-HTO delivers superior energy and power densities with excellent cyclability. Compared to previous reports on other hybrid supercapacitors, LSG/H-HTO electrode composition shows extraordinary energy densities of ~70.8 Wh/kg and power densities of ~5191.9 W/kg. Therefore, LSG/H-HTO can be regarded as a promising milestone in hybrid supercapacitors.

Electrode/Dielectric Strip For High-Energy-Density Capacitor

NASA Technical Reports Server (NTRS)

Yen, Shiao-Ping S.

1994-01-01

Improved unitary electrode/dielectric strip serves as winding in high-energy-density capacitor in pulsed power supply. Offers combination of qualities essential for high energy density: high permittivity of dielectric layers, thinness, and high resistance to breakdown of dielectric at high electric fields. Capacitors with strip material not impregnated with liquid.

Dehydration of seabird prey during transport to the colony: Effects on wet weight energy densities

USGS Publications Warehouse

Montevecchi, W.A.; Piatt, John F.

1987-01-01

We present evidence to indicate that dehydration of prey transported by seabirds from capture sites at sea to chicks at colonies inflates estimates of wet weight energy densities. These findings and a comparison of wet and dry weight energy densities reported in the literature emphasize the importance of (i) accurate measurement of the fresh weight and water content of prey, (ii) use of dry weight energy densities in comparisons among species, seasons, and regions, and (iii) cautious interpretation and extrapolation of existing data sets.

Fluctuations and symmetry energy in nuclear fragmentation dynamics.

PubMed

Colonna, M

2013-01-25

Within a dynamical description of nuclear fragmentation, based on the liquid-gas phase transition scenario, we explore the relation between neutron-proton density fluctuations and nuclear symmetry energy. We show that, along the fragmentation path, isovector fluctuations follow the evolution of the local density and approach an equilibrium value connected to the local symmetry energy. Higher-density regions are characterized by smaller average asymmetry and narrower isotopic distributions. This dynamical analysis points out that fragment final state isospin fluctuations can probe the symmetry energy of the density domains from which fragments originate.

Knot soliton in DNA and geometric structure of its free-energy density.

PubMed

Wang, Ying; Shi, Xuguang

2018-03-01

In general, the geometric structure of DNA is characterized using an elastic rod model. The Landau model provides us a new theory to study the geometric structure of DNA. By using the decomposition of the arc unit in the helical axis of DNA, we find that the free-energy density of DNA is similar to the free-energy density of a two-condensate superconductor. By using the φ-mapping topological current theory, the torus knot soliton hidden in DNA is demonstrated. We show the relation between the geometric structure and free-energy density of DNA and the Frenet equations in differential geometry theory are considered. Therefore, the free-energy density of DNA can be expressed by the curvature and torsion of the helical axis.

Negative vacuum energy densities and the causal diamond measure

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

Salem, Michael P.

2009-07-15

Arguably a major success of the landscape picture is the prediction of a small, nonzero vacuum energy density. The details of this prediction depend in part on how the diverging spacetime volume of the multiverse is regulated, a question that remains unresolved. One proposal, the causal diamond measure, has demonstrated many phenomenological successes, including predicting a distribution of positive vacuum energy densities in good agreement with observation. In the string landscape, however, the vacuum energy density is expected to take positive and negative values. We find the causal diamond measure gives a poor fit to observation in such a landscapemore » - in particular, 99.6% of observers in galaxies seemingly just like ours measure a vacuum energy density smaller than we do, most of them measuring it to be negative.« less

Crust-core properties of neutron stars in the Nambu–Jona-Lasinio model

NASA Astrophysics Data System (ADS)

Wei, Si-Na; Yang, Rong-Yao; Jiang, Wei-Zhou

2018-05-01

We adopt the Nambu–Jona-Lasinio (NJL) model to study the crust-core transition properties in neutron stars (NSs). For a given momentum cutoff and symmetry energy of saturation density in the NJL model, decreasing the slope of the symmetry energy gives rise to an increase in the crust-core transition density and transition pressure. Given the slope of the symmetry energy at saturation density, the transition density and corresponding transition pressure increase with increasing symmetry energy. The increasing trend between the fraction of the crustal moment of inertia and the slope of symmetry energy at saturation density indicates that a relatively large momentum cutoff of the NJL model is preferred. For a momentum cutoff of 500 MeV, the fraction of the crustal moment of inertia clearly increases with the slope of symmetry energy at saturation density. Thus, at the required fraction (7%) of the crustal moment of inertia, the NJL model with momentum cutoff of 500 MeV and a large slope of the symmetry energy of saturation density can give the upper limit of the mass of the Vela pulsar to be above 1.40 {M}ȯ . Supported by National Natural Science Foundation of China (11775049, 11275048) and the China Jiangsu Provincial Natural Science Foundation (BK20131286)

Combined high-power ultrasound and high-pressure homogenization nanoemulsification: The effect of energy density, oil content and emulsifier type and content.

PubMed

Calligaris, Sonia; Plazzotta, Stella; Valoppi, Fabio; Anese, Monica

2018-05-01

Combinations of ultrasound (US) and high-pressure homogenization (HPH) at low-medium energy densities were studied as alternative processes to individual US and HPH to produce Tween 80 and whey protein stabilized nanoemulsions, while reducing the energy input. To this aim, preliminary trials were performed to compare emulsification efficacy of single and combined HPH and US treatments delivering low-medium energy densities. Results highlighted the efficacy of US-HPH combined process in reducing the energy required to produce nanoemulsions stabilized with both Tween 80 and whey protein isolate. Subsequently, the effect of emulsifier content (1-3% w/w), oil amount (10-20% w/w) and energy density (47-175 MJ/m 3 ) on emulsion mean particle diameter was evaluated by means of a central composite design. Particles of 140-190 nm were obtained by delivering 175 MJ/m 3 energy density at emulsions containing 3% (w/w) Tween 80 and 10% (w/w) oil. In the case of whey protein isolate stabilized emulsions, a reduced emulsifier amount (1% w/w) and intermediate energy density (120 MJ/m 3 ) allowed a minimum droplet size around 220-250 nm to be achieved. Results showed that, in both cases, at least 50% of the energy density should be delivered by HPH to obtain the minimum particle diameter. Copyright © 2018 Elsevier Ltd. All rights reserved.

Vibrational Power Flow Analysis of Rods and Beams

NASA Technical Reports Server (NTRS)

Wohlever, James Christopher; Bernhard, R. J.

1988-01-01

A new method to model vibrational power flow and predict the resulting energy density levels in uniform rods and beams is investigated. This method models the flow of vibrational power in a manner analogous to the flow of thermal power in a heat conduction problem. The classical displacement solutions for harmonically excited, hysteretically damped rods and beams are used to derive expressions for the vibrational power flow and energy density in the rod and beam. Under certain conditions, the power flow in these two structural elements will be shown to be proportional to the energy density gradient. Using the relationship between power flow and energy density, an energy balance on differential control volumes in the rod and beam leads to a Poisson's equation which models the energy density distribution in the rod and beam. Coupling the energy density and power flow solutions for rods and beams is also discussed. It is shown that the resonant behavior of finite structures complicates the coupling of solutions, especially when the excitations are single frequency inputs. Two coupling formulations are discussed, the first based on the receptance method, and the second on the travelling wave approach used in Statistical Energy Analysis. The receptance method is the more computationally intensive but is capable of analyzing single frequency excitation cases. The traveling wave approach gives a good approximation of the frequency average of energy density and power flow in coupled systems, and thus, is an efficient technique for use with broadband frequency excitation.

Electron transport in high aspect ratio semiconductor nanowires and metal-semiconductor interfaces

NASA Astrophysics Data System (ADS)

Sun, Zhuting

We are facing variability problems for modern semiconductor transistors due to the fact that the performances of nominally identical devices in the scale of 10 100 nm could be dramatically different attributed to the small manufacturing variations. Different doping strategies give statistical variations in the number of dopant atom density ND in the channel. The material size gives variations in wire diameter dW. And the immediate environment of the material leads to an additional level of variability. E.g. vacuum-semiconductor interface causes variations in surface state density Ds, metal-semiconductor interface causes variations in Schottky barrier and dielectric semiconductor interface induces dielectric confinement at small scales. To approach these variability problems, I choose Si-doped GaAs nanowires as an example. I investigate transport in Si-doped GaAs nanowire (NW) samples contacted by lithographically patterned Gold-Titanium films as function of temperature T. I find a drastically different temperature dependence between the wire resistance RW, which is relatively weak, and the zero bias resistance RC, which is strong. I show that the data are consistent with a model based on a sharp donor energy level slightly above the bottom of the semiconductor conduction band and develop a simple method for using transport measurements for estimates of the doping density after nanowire growth. I discuss the predictions of effective free carrier density n eff as function of the surface state density Ds and wire size dW. I also describe a correction to the widely used model of Schottky contacts that improves thermodynamic consistency of the Schottky tunnel barrier profile and show that the original theory may underestimate the barrier conductance under certain conditions. I also provide analytical calculations for shallow silicon dopant energy in GaAs crystals, and find the presence of dielectrics (dielectric screening) and free carriers (Coulomb screening) cause a reduction of ionization energy and shift the donor energy level ED upward, accompanying conduction band EC shift downward due to band gap narrowing for doped semiconductor material. The theoretical results are in a reasonable agreement with previous experimental data. I also find that when the material reduces to nanoscale, dielectric confinement and surface depletion compete with both Coulomb screening and dielectric screening that shift the donor level ED down towards the band gap. The calculation should be appropriate for all types of semiconductors and dopant species.

A VLA Study of High-redshift GRBs. I. Multiwavelength Observations and Modeling of GRB 140311A

NASA Astrophysics Data System (ADS)

Laskar, Tanmoy; Berger, Edo; Chornock, Ryan; Margutti, Raffaella; Fong, Wen-fai; Zauderer, B. Ashley

2018-05-01

We present the first results from a recently concluded study of GRBs at z ≳ 5 with the Karl G. Jansky Very Large Array (VLA). Spanning 1 to 85.5 GHz and 7 epochs from 1.5 to 82.3 days, our observations of GRB 140311A are the most detailed joint radio and millimeter observations of a GRB afterglow at z ≳ 5 to date. In conjunction with optical/near-IR and X-ray data, the observations can be understood in the framework of radiation from a single blast wave shock with energy {E}{{K},{iso}}≈ 8.5× {10}53 erg expanding into a constant density environment with density, {n}0≈ 8 {cm}}-3. The X-ray and radio observations require a jet break at {t}jet}≈ 0.6 days, yielding an opening angle of {θ }jet}≈ 4^\\circ and a beaming-corrected blast wave kinetic energy of {E}{{K}}≈ 2.2× {10}50 erg. The results from our radio follow-up and multiwavelength modeling lend credence to the hypothesis that detected high-redshift GRBs may be more tightly beamed than events at lower redshift. We do not find compelling evidence for reverse shock emission, which may be related to fast cooling driven by the moderately high circumburst density.

Nano-sized Mo- and Nb-doped TiO2 as anode materials for high energy and high power hybrid Li-ion capacitors.

PubMed

Bauer, Dustin; Roberts, Alexander J; Matsumi, Noriyoshi; Darr, Jawwad A

2017-05-12

Nano-sized Mo-doped titania (Mo 0.1 Ti 0.9 O 2 ) and Nb-doped titania (Nb 0.25 Ti 0.75 O 2 ) were directly synthesized via a continuous hydrothermal flow synthesis process. Materials characterization was conducted using physical techniques such as transmission electron microscopy, powder x-ray diffraction, x-ray photoelectron spectroscopy, Brunauer-Emmett-Teller specific surface area measurements and energy dispersive x-ray spectroscopy. Hybrid Li-ion supercapacitors were made with either a Mo-doped or Nb-doped TiO 2 negative electrode material and an activated carbon (AC) positive electrode. Cells were evaluated using electrochemical testing (cyclic voltammetry, constant charge discharge cycling). The hybrid Li-ion capacitors showed good energy densities at moderate power densities. When cycled in the potential window 0.5-3.0 V, the Mo 0.1 Ti 0.9 O 2 /AC hybrid supercapacitor showed the highest energy densities of 51 Wh kg -1 at a power of 180 W kg -1 with energy densities rapidly declining with increasing applied specific current. In comparison, the Nb 0.25 Ti 0.75 O 2 /AC hybrid supercapacitor maintained its energy density of 45 Wh kg -1 at 180 W kg -1 better, showing 36 Wh g -1 at 3200 W kg -1 , which is a very promising mix of high energy and power densities. Reducing the voltage window to the range 1.0-3.0 V led to an increase in power density, with the Mo 0.1 Ti 0.9 O 2 /AC hybrid supercapacitor giving energy densities of 12 Wh kg -1 and 2.5 Wh kg -1 at power densities of 6700 W kg -1 and 14 000 W kg -1 , respectively.

Nano-sized Mo- and Nb-doped TiO2 as anode materials for high energy and high power hybrid Li-ion capacitors

NASA Astrophysics Data System (ADS)

Bauer, Dustin; Roberts, Alexander J.; Matsumi, Noriyoshi; Darr, Jawwad A.

2017-05-01

Nano-sized Mo-doped titania (Mo0.1Ti0.9O2) and Nb-doped titania (Nb0.25Ti0.75O2) were directly synthesized via a continuous hydrothermal flow synthesis process. Materials characterization was conducted using physical techniques such as transmission electron microscopy, powder x-ray diffraction, x-ray photoelectron spectroscopy, Brunauer-Emmett-Teller specific surface area measurements and energy dispersive x-ray spectroscopy. Hybrid Li-ion supercapacitors were made with either a Mo-doped or Nb-doped TiO2 negative electrode material and an activated carbon (AC) positive electrode. Cells were evaluated using electrochemical testing (cyclic voltammetry, constant charge discharge cycling). The hybrid Li-ion capacitors showed good energy densities at moderate power densities. When cycled in the potential window 0.5-3.0 V, the Mo0.1Ti0.9O2/AC hybrid supercapacitor showed the highest energy densities of 51 Wh kg-1 at a power of 180 W kg-1 with energy densities rapidly declining with increasing applied specific current. In comparison, the Nb0.25Ti0.75O2/AC hybrid supercapacitor maintained its energy density of 45 Wh kg-1 at 180 W kg-1 better, showing 36 Wh g-1 at 3200 W kg-1, which is a very promising mix of high energy and power densities. Reducing the voltage window to the range 1.0-3.0 V led to an increase in power density, with the Mo0.1Ti0.9O2/AC hybrid supercapacitor giving energy densities of 12 Wh kg-1 and 2.5 Wh kg-1 at power densities of 6700 W kg-1 and 14 000 W kg-1, respectively.

Electron dynamics in complex environments with real-time time dependent density functional theory in a QM-MM framework

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

Morzan, Uriel N.; Ramírez, Francisco F.; Scherlis, Damián A., E-mail: damian@qi.fcen.uba.ar, E-mail: mcgl@qb.ffyb.uba.ar

2014-04-28

This article presents a time dependent density functional theory (TDDFT) implementation to propagate the Kohn-Sham equations in real time, including the effects of a molecular environment through a Quantum-Mechanics Molecular-Mechanics (QM-MM) hamiltonian. The code delivers an all-electron description employing Gaussian basis functions, and incorporates the Amber force-field in the QM-MM treatment. The most expensive parts of the computation, comprising the commutators between the hamiltonian and the density matrix—required to propagate the electron dynamics—, and the evaluation of the exchange-correlation energy, were migrated to the CUDA platform to run on graphics processing units, which remarkably accelerates the performance of the code.more » The method was validated by reproducing linear-response TDDFT results for the absorption spectra of several molecular species. Two different schemes were tested to propagate the quantum dynamics: (i) a leap-frog Verlet algorithm, and (ii) the Magnus expansion to first-order. These two approaches were confronted, to find that the Magnus scheme is more efficient by a factor of six in small molecules. Interestingly, the presence of iron was found to seriously limitate the length of the integration time step, due to the high frequencies associated with the core-electrons. This highlights the importance of pseudopotentials to alleviate the cost of the propagation of the inner states when heavy nuclei are present. Finally, the methodology was applied to investigate the shifts induced by the chemical environment on the most intense UV absorption bands of two model systems of general relevance: the formamide molecule in water solution, and the carboxy-heme group in Flavohemoglobin. In both cases, shifts of several nanometers are observed, consistently with the available experimental data.« less

Electron dynamics in complex environments with real-time time dependent density functional theory in a QM-MM framework

NASA Astrophysics Data System (ADS)

Morzan, Uriel N.; Ramírez, Francisco F.; Oviedo, M. Belén; Sánchez, Cristián G.; Scherlis, Damián A.; Lebrero, Mariano C. González

2014-04-01

This article presents a time dependent density functional theory (TDDFT) implementation to propagate the Kohn-Sham equations in real time, including the effects of a molecular environment through a Quantum-Mechanics Molecular-Mechanics (QM-MM) hamiltonian. The code delivers an all-electron description employing Gaussian basis functions, and incorporates the Amber force-field in the QM-MM treatment. The most expensive parts of the computation, comprising the commutators between the hamiltonian and the density matrix—required to propagate the electron dynamics—, and the evaluation of the exchange-correlation energy, were migrated to the CUDA platform to run on graphics processing units, which remarkably accelerates the performance of the code. The method was validated by reproducing linear-response TDDFT results for the absorption spectra of several molecular species. Two different schemes were tested to propagate the quantum dynamics: (i) a leap-frog Verlet algorithm, and (ii) the Magnus expansion to first-order. These two approaches were confronted, to find that the Magnus scheme is more efficient by a factor of six in small molecules. Interestingly, the presence of iron was found to seriously limitate the length of the integration time step, due to the high frequencies associated with the core-electrons. This highlights the importance of pseudopotentials to alleviate the cost of the propagation of the inner states when heavy nuclei are present. Finally, the methodology was applied to investigate the shifts induced by the chemical environment on the most intense UV absorption bands of two model systems of general relevance: the formamide molecule in water solution, and the carboxy-heme group in Flavohemoglobin. In both cases, shifts of several nanometers are observed, consistently with the available experimental data.

Electron dynamics in complex environments with real-time time dependent density functional theory in a QM-MM framework.

PubMed

Morzan, Uriel N; Ramírez, Francisco F; Oviedo, M Belén; Sánchez, Cristián G; Scherlis, Damián A; Lebrero, Mariano C González

2014-04-28

This article presents a time dependent density functional theory (TDDFT) implementation to propagate the Kohn-Sham equations in real time, including the effects of a molecular environment through a Quantum-Mechanics Molecular-Mechanics (QM-MM) hamiltonian. The code delivers an all-electron description employing Gaussian basis functions, and incorporates the Amber force-field in the QM-MM treatment. The most expensive parts of the computation, comprising the commutators between the hamiltonian and the density matrix-required to propagate the electron dynamics-, and the evaluation of the exchange-correlation energy, were migrated to the CUDA platform to run on graphics processing units, which remarkably accelerates the performance of the code. The method was validated by reproducing linear-response TDDFT results for the absorption spectra of several molecular species. Two different schemes were tested to propagate the quantum dynamics: (i) a leap-frog Verlet algorithm, and (ii) the Magnus expansion to first-order. These two approaches were confronted, to find that the Magnus scheme is more efficient by a factor of six in small molecules. Interestingly, the presence of iron was found to seriously limitate the length of the integration time step, due to the high frequencies associated with the core-electrons. This highlights the importance of pseudopotentials to alleviate the cost of the propagation of the inner states when heavy nuclei are present. Finally, the methodology was applied to investigate the shifts induced by the chemical environment on the most intense UV absorption bands of two model systems of general relevance: the formamide molecule in water solution, and the carboxy-heme group in Flavohemoglobin. In both cases, shifts of several nanometers are observed, consistently with the available experimental data.

Food environment and obesity.

PubMed

Mattes, Richard; Foster, Gary D

2014-12-01

The food environment plays an important and often dominant role in food choice, eating patterns, and ultimately, energy intake. The Obesity Society and the American Society for Nutrition jointly sponsored a series of reviews on topics of interest to both memberships. The goal was to consider the state of understanding on selected issues related to the food environment and obesity and to identify key knowledge gaps. The first article (not necessarily of importance) targeted energy density (ED) and focuses on the role of ED in the regulation of energy intake and body weight. It offers recommendations for prioritizing research. The second article addresses economic factors and examines food and beverage purchases as a function of price changes. It concludes that targeted food taxes and subsidies alone are unlikely to substantially affect obesity. The third article concerns sweetened beverages and points out the difficulty in establishing the strength of the association between intake of sugar-sweetened beverages and weight gain and obesity. In the fourth article, the contributions of palatability and variety to eating behavior and weight are reviewed. Article five explores the influence of portion size on energy intake and weight management. It finds that consumers generally tend to eat proportionally more as portion size increases. The sixth article focuses on the efficacy and effectiveness of eating frequency manipulations for body weight management and finds that such manipulations have consistently yielded null results. Finally, article seven identifies several limitations of the existing literature regarding neighborhood access to healthy foods. This series of reviews addresses important questions regarding the contribution of the food environment to obesity. Independent of physiological/genetic determinants, factors such as ED, cost, food form, palatability, variety, portion size, eating frequency, and access to healthy food are each evaluated for their role in the etiology of obesity and metabolic health. This series of reviews also identifies important gaps in knowledge. © 2014 The Obesity Society and American Society for Nutrition.

Measurements by the plasma diagnostics package on STS-3

NASA Technical Reports Server (NTRS)

Shawhan, S. D.; Murphy, G. B.

1982-01-01

A comprehensive set of measurements about the orbiter environment are provided by the plasma diagnostics package (PDP). Ion and electron particle densities, energies, and spatial distribution functions; ion mass for identification of particular molecular ion species; and magnetic fields, electric fields and electromagnetic waves over a broad frequency range are studied. Shuttle environmental measurements will be made both on the pallet and, by use of the remote manipulator system (RMS), the PDP will be maneuvered in and external to the bay area to continue environmental measurements and to carry on a joint plasma experiment with the Utah State University fast-pulsed electron generator. Results of orbiter environment EMI measurements and S-band field strengths as well as preliminary results from wake search operations indicating wake boundary identifiers are reported.

Probing the Oxygen Environment in UO22+ by Solid-State O-17 Nuclear Magnetic Resonance Spectroscopy and Relativistic Density Functional Calculations

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

Cho, Herman M.; De Jong, Wibe A.; Soderquist, Chuck Z.

A combined theoretical and solid-state O-17 NMR study of the electronic structure of the uranyl ion UO22+ in (NH4)4UO2(CO3)3 and rutherfordine UO2CO3 is presented, the former representing a system with a hydrogen-bonding environment around the uranyl oxygens, and the latter exemplifying a uranyl environment without hydrogens. A fully relativistic ab initio treatment reveals unique features of the U-O covalent bond, including the finding of O-17 chemical shift anisotropies that are among the largest ever reported (>1200 ppm). Computational results for the oxygen electric field gradient tensor are found to be consistently larger in magnitude than experimental solid-state O-17 NMR measurementsmore » in a 7.05 T magnetic field indicate. A modified version of the Solomon theory of the two-spin echo amplitude for a spin-5/2 nucleus is developed and applied to the analysis of the O-17 echo signal of UO22+. The William R. Wiley environmental Molecular Sciences Laboratory is a US Department of Energy national scientific user facility located at Pacific Northwest National Laboratory (PNNL) in Richland, Washington. PNNL is operated by Battelle for the US Department of Energy.« less

Engineered Nanomaterials for Energy Harvesting and Storage Applications

NASA Astrophysics Data System (ADS)

Gullapalli, Hemtej

Energy harvesting and storage are independent mechanisms, each having their own significance in the energy cycle. Energy is generally harvested from temperature variations, mechanical vibrations and other phenomena which are inherently sporadic in nature, harvested energy stands a better chance of efficient utilization if it can be stored and used later, depending on the demand. In essence a comprehensive device that can harness power from surrounding environment and provide a steady and reliable source of energy would be ideal. Towards realizing such a system, for the harvesting component, a piezoelectric nano-composite material consisting of ZnO nanostructures embedded into the matrix of 'Paper' has been developed. Providing a flexible backbone to a brittle material makes it a robust architecture. Energy harvesting by scavenging both mechanical and thermal fluctuations using this flexible nano-composite is discussed in this thesis. On the energy storage front, Graphene based materials developed with a focus towards realizing ultra-thin lithium ion batteries and supercapacitors are introduced. Efforts for enhancing the energy storage performance of such graphitic carbon are detailed. Increasing the rate capability by direct CVD synthesis of graphene on current collectors, enhancing its electrochemical capacity through doping and engineering 3D metallic structures to increase the areal energy density have been studied.

Data analysis and interpretation related to space system/environment interactions at LEO altitude

NASA Technical Reports Server (NTRS)

Raitt, W. John; Schunk, Robert W.

1991-01-01

Several studies made on the interaction of active systems with the LEO space environment experienced from orbital or suborbital platforms are covered. The issue of high voltage space interaction is covered by theoretical modeling studies of the interaction of charged solar cell arrays with the ionospheric plasma. The theoretical studies were complemented by experimental measurements made in a vacuum chamber. The other active system studied was the emission of effluent from a space platform. In one study the emission of plasma into the LEO environment was studied by using initially a 2-D model, and then extending this model to 3-D to correctly take account of plasma motion parallel to the geomagnetic field. The other effluent studies related to the releases of neutral gas from an orbiting platform. One model which was extended and used determined the density, velocity, and energy of both an effluent gas and the ambient upper atmospheric gases over a large volume around the platform. This model was adapted to study both ambient and contaminant distributions around smaller objects in the orbital frame of reference with scale sizes of 1 m. The other effluent studies related to the interaction of the released neutral gas with the ambient ionospheric plasma. An electrostatic model was used to help understand anomalously high plasma densities measured at times in the vicinity of the space shuttle orbiter.

Mesoscopic model for binary fluids

NASA Astrophysics Data System (ADS)

Echeverria, C.; Tucci, K.; Alvarez-Llamoza, O.; Orozco-Guillén, E. E.; Morales, M.; Cosenza, M. G.

2017-10-01

We propose a model for studying binary fluids based on the mesoscopic molecular simulation technique known as multiparticle collision, where the space and state variables are continuous, and time is discrete. We include a repulsion rule to simulate segregation processes that does not require calculation of the interaction forces between particles, so binary fluids can be described on a mesoscopic scale. The model is conceptually simple and computationally efficient; it maintains Galilean invariance and conserves the mass and energy in the system at the micro- and macro-scale, whereas momentum is conserved globally. For a wide range of temperatures and densities, the model yields results in good agreement with the known properties of binary fluids, such as the density profile, interface width, phase separation, and phase growth. We also apply the model to the study of binary fluids in crowded environments with consistent results.

Exploitation of inimitable properties of CuInS2 quantum dots for energy conversion in bulk heterojunction hybrid solar cell

NASA Astrophysics Data System (ADS)

Jindal, Shikha; Giripunje, Sushama M.

2017-11-01

Quantum dots (QDs) are the suitable material for solar cell devices owing to its distinctive optical, electrical and electronic properties. Currently, the most efficient devices have employed the toxic QDs which cause destructive impact on environment. In the present article, we have used environment benign CuInS2 QDs as an acceptor material in bulk heterojunction device of P3HT and QDs. The energy level positions corroborated from UPS spectra substantiates the acceptor property of CuInS2. We scrutinized the hybrid solar cell by tailoring the acceptor content in active layer. The increased acceptor content intensifies the performance of device. The enhancement in photovoltaic parameters is mainly due to the fast dissociation and extraction of photogenerated excitons which occurs with the larger wt% of acceptor QDs. Current density-voltage characteristics describes the greater V oc and I sc in the 60 wt% CuInS2 QDs based solar cell as compared to the low wt% of QDs in the active layer.

Energy harvesting from the cardiovascular system, or how to get a little help from yourself.

PubMed

Pfenniger, Alois; Jonsson, Magnus; Zurbuchen, Adrian; Koch, Volker M; Vogel, Rolf

2013-11-01

Human energy harvesting is envisioned as a remedy to the weight, the size, and the poor energy density of primary batteries in medical implants. The first implant to have necessarily raised the idea of a biological power supply was the pacemaker in the early 1960s. So far, review articles on human energy harvesting have been rather unspecific and no tribute has been given to the early role of the pacemaker and the cardiovascular system in triggering research in the field. The purpose of the present article is to provide an up-to-date review of research efforts targeting the cardiovascular system as an alternative energy source for active medical implants. To this end, a chronological survey of the last 14 most influential publications is proposed. They include experimental and/or theoretical studies based on electromagnetic, piezoelectric, or electrostatic transducers harnessing various forms of energy, such as heart motion, pressure gradients, and blood flow. Technical feasibility does not imply clinical applicability: although most of the reported devices were shown to harvest an interesting amount of energy from a physiological environment, none of them were tested in vivo for a longer period of time.

Large turbulent reservoirs of cold molecular gas around high-redshift starburst galaxies.

PubMed

Falgarone, E; Zwaan, M A; Godard, B; Bergin, E; Ivison, R J; Andreani, P M; Bournaud, F; Bussmann, R S; Elbaz, D; Omont, A; Oteo, I; Walter, F

2017-08-24

Starburst galaxies at the peak of cosmic star formation are among the most extreme star-forming engines in the Universe, producing stars over about 100 million years (ref. 2). The star-formation rates of these galaxies, which exceed 100 solar masses per year, require large reservoirs of cold molecular gas to be delivered to their cores, despite strong feedback from stars or active galactic nuclei. Consequently, starburst galaxies are ideal for studying the interplay between this feedback and the growth of a galaxy. The methylidyne cation, CH + , is a most useful molecule for such studies because it cannot form in cold gas without suprathermal energy input, so its presence indicates dissipation of mechanical energy or strong ultraviolet irradiation. Here we report the detection of CH + (J = 1-0) emission and absorption lines in the spectra of six lensed starburst galaxies at redshifts near 2.5. This line has such a high critical density for excitation that it is emitted only in very dense gas, and is absorbed in low-density gas. We find that the CH + emission lines, which are broader than 1,000 kilometres per second, originate in dense shock waves powered by hot galactic winds. The CH + absorption lines reveal highly turbulent reservoirs of cool (about 100 kelvin), low-density gas, extending far (more than 10 kiloparsecs) outside the starburst galaxies (which have radii of less than 1 kiloparsec). We show that the galactic winds sustain turbulence in the 10-kiloparsec-scale environments of the galaxies, processing these environments into multiphase, gravitationally bound reservoirs. However, the mass outflow rates are found to be insufficient to balance the star-formation rates. Another mass input is therefore required for these reservoirs, which could be provided by ongoing mergers or cold-stream accretion. Our results suggest that galactic feedback, coupled jointly to turbulence and gravity, extends the starburst phase of a galaxy instead of quenching it.

Globally optimal superconducting magnets part I: minimum stored energy (MSE) current density map.

PubMed

Tieng, Quang M; Vegh, Viktor; Brereton, Ian M

2009-01-01

An optimal current density map is crucial in magnet design to provide the initial values within search spaces in an optimization process for determining the final coil arrangement of the magnet. A strategy for obtaining globally optimal current density maps for the purpose of designing magnets with coaxial cylindrical coils in which the stored energy is minimized within a constrained domain is outlined. The current density maps obtained utilising the proposed method suggests that peak current densities occur around the perimeter of the magnet domain, where the adjacent peaks have alternating current directions for the most compact designs. As the dimensions of the domain are increased, the current density maps yield traditional magnet designs of positive current alone. These unique current density maps are obtained by minimizing the stored magnetic energy cost function and therefore suggest magnet coil designs of minimal system energy. Current density maps are provided for a number of different domain arrangements to illustrate the flexibility of the method and the quality of the achievable designs.

Defect Related Dark Currents in III-V MWIR nBn Detectors

DTIC Science & Technology

2014-01-01

theory indicates a thermal activation energy of half the bandgap, and a direct proportionality between dark current density and defect density. 2.2...density due to defects maintains a full bandgap thermal activation energy , and is proportional to the square root of the defect density. Although neutral...photodiodes, and cooling is more efficient in reducing nBn’s dark current due to the full bandgap activation energy . Downloaded From: http

A Dual-Stimuli-Responsive Sodium-Bromine Battery with Ultrahigh Energy Density.

PubMed

Wang, Faxing; Yang, Hongliu; Zhang, Jian; Zhang, Panpan; Wang, Gang; Zhuang, Xiaodong; Cuniberti, Gianaurelio; Feng, Xinliang

2018-06-01

Stimuli-responsive energy storage devices have emerged for the fast-growing popularity of intelligent electronics. However, all previously reported stimuli-responsive energy storage devices have rather low energy densities (<250 Wh kg -1 ) and single stimuli-response, which seriously limit their application scopes in intelligent electronics. Herein, a dual-stimuli-responsive sodium-bromine (Na//Br 2 ) battery featuring ultrahigh energy density, electrochromic effect, and fast thermal response is demonstrated. Remarkably, the fabricated Na//Br 2 battery exhibits a large operating voltage of 3.3 V and an energy density up to 760 Wh kg -1 , which outperforms those for the state-of-the-art stimuli-responsive electrochemical energy storage devices. This work offers a promising approach for designing multi-stimuli-responsive and high-energy rechargeable batteries without sacrificing the electrochemical performance. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quasiparticle energy bands and Fermi surfaces of monolayer NbSe2

NASA Astrophysics Data System (ADS)

Kim, Sejoong; Son, Young-Woo

2017-10-01

A quasiparticle band structure of a single layer 2 H -NbSe2 is reported by using first-principles G W calculation. We show that a self-energy correction increases the width of a partially occupied band and alters its Fermi surface shape when comparing those using conventional mean-field calculation methods. Owing to a broken inversion symmetry in the trigonal prismatic single layer structure, the spin-orbit interaction is included and its impact on the Fermi surface and quasiparticle energy bands are discussed. We also calculate the doping dependent static susceptibilities from the band structures obtained by the mean-field calculation as well as G W calculation with and without spin-orbit interactions. A complete tight-binding model is constructed within the three-band third nearest neighbor hoppings and is shown to reproduce our G W quasiparticle energy bands and Fermi surface very well. Considering variations of the Fermi surface shapes depending on self-energy corrections and spin-orbit interactions, we discuss the formations of charge density wave (CDW) with different dielectric environments and their implications on recent controversial experimental results on CDW transition temperatures.

Effects of Laser Remelting and Oxidation on NiCrAlY/8Y2O3-ZrO2 Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Xu, S. Q.; Zhu, C.; Zhang, Y.

2018-02-01

In this study, three groups of thermal barrier coatings (TBCs) samples were remelted by CO2 laser with different laser energy densities (1, 5 and 10 J/mm2) to seal the surface of yttria-stabilized zirconia (YSZ) coatings. Microscopic observations showed that the cracks size and the remelted depth in YSZ coatings increased. A 50-μm-thick dense layer was formed on the surface of YSZ coating in samples with 1 J/mm2 energy density. Microindentation tests showed that the Vickers hardness of YSZ coatings increases with the increase in laser energy density. After isothermal oxidation at 1200 °C for 200 h, thinner thermally growth oxides were found in laser remelted YSZ samples under energy density of 1 J/mm2 (6.32 ± 0.28 μm). Cyclic oxidation results showed that the weight gain per unit area of low energy density laser remelted TBCs was smaller than that of the high energy density laser remelted and as-sprayed TBCs.

High Discharge Energy Density at Low Electric Field Using an Aligned Titanium Dioxide/Lead Zirconate Titanate Nanowire Array

PubMed Central

Zhang, Dou; Liu, Weiwei; Guo, Ru; Zhou, Kechao

2017-01-01

Abstract Polymer‐based capacitors with high energy density have attracted significant attention in recent years due to their wide range of potential applications in electronic devices. However, the obtained high energy density is predominantly dependent on high applied electric field, e.g., 400–600 kV mm−1, which may bring more challenges relating to the failure probability. Here, a simple two‐step method for synthesizing titanium dioxide/lead zirconate titanate nanowire arrays is exploited and a demonstration of their ability to achieve high discharge energy density capacitors for low operating voltage applications is provided. A high discharge energy density of 6.9 J cm−3 is achieved at low electric fields, i.e., 143 kV mm−1, which is attributed to the high relative permittivity of 218.9 at 1 kHz and high polarization of 23.35 µC cm−2 at this electric field. The discharge energy density obtained in this work is the highest known for a ceramic/polymer nanocomposite at such a low electric field. The novel nanowire arrays used in this work are applicable to a wide range of fields, such as energy harvesting, energy storage, and photocatalysis. PMID:29610724

The mechanical consequences of load bearing in the equine third metacarpal across speed and gait: the nonuniform distributions of normal strain, shear strain, and strain energy density

PubMed Central

Rubin, Clinton T.; Seeherman, Howard; Qin, Yi-Xian; Gross, Ted S.

2013-01-01

Distributions of normal strain, shear strain, and strain energy density (SED) were determined across the midshaft of the third metacarpal (MCIII, or cannon bone) of 3 adult thoroughbred horses as a function of speed and gait. A complete characterization of the mechanical demands of the bone made through the stride and from mild through the extremes of locomotion was possible by using three 3-element rosette strain gauges bonded at the diaphyseal midshaft of the MCIII and evaluating the strain output with beam theory and finite element analysis. Mean ± sd values of normal strain, shear strain, and SED increased with speed and peaked during a canter (−3560±380 microstrain, 1760±470 microstrain, and 119±23 kPa, respectively). While the location of these peaks was similar across animals and gaits, the resulting strain distributions across the cortex were consistently nonuniform, establishing between a 73-fold (slow trot) to a 330-fold (canter) disparity between the sites of maximum and minimum SED for each gait cycle. Using strain power density as an estimate of strain history across the bone revealed a 154-fold disparity between peak and minimum at the walk but fell to ∼32-fold at the canter. The nonuniform, minimally varying, strain environment suggests either that bone homeostasis is mediated by magnitude-independent mechanical signals or that the duration of stimuli necessary to establish and maintain tissue integrity is relatively brief, and thus the vast majority of strain information is disregarded.—Rubin, C. T., Seeherman, H., Qin, Y.-X., Gross, T. S., The mechanical consequences of load bearing in the equine third metacarpal across speed and gait: the nonuniform distributions of normal strain, shear strain, and strain energy density. PMID:23355269

Assessing the Capabilities and Limitations of Physics-Based Models in Capturing the Ionosphere and Thermosphere Storm-Time Response

NASA Astrophysics Data System (ADS)

Fedrizzi, M.; Fuller-Rowell, T. J.; Maruyama, N.; Fang, T. W.; Codrescu, M.

2016-12-01

The Sun can directly impact the Earth's environment during solar storms when the interaction between their magnetic fields can severely modify the quiet-time electric fields and current patterns in the ionosphere, which in turn affect neutral temperature, density, winds and composition, and plasma density. The nature of the various solar wind features and their interaction with the upper atmosphere is likely to channel the response into different pathways. Depending on whether the forcing is impulsive or gradual, of long or short durations, intense or moderate, the partitioning of the energy will be different. For instance, a sudden onset of energy deposition is likely to generate a more intense wave field at the expense of the energy being partitioned into local heating, thermal expansion, and composition change. The net electrodynamic and ionospheric response is likely to be significantly different in the two cases. As the ionosphere and thermosphere constituents are controlled by gravity, diffusion, chemical reactions, and bulk transport, it is essential to understand how these processes determine global responses in O and N2 after heating occurs at high latitudes. Since these disturbances are superimposed on a solar EUV-driven circulation system that is mainly ordered in a geographic coordinate frame that varies with local time and season, the interactions can be complex, and ionosphere-thermosphere responses are very different depending on prevailing conditions. The relative abundances of O and N2 are fundamental to understanding local plasma densities and total mass densities, both of which are key parameters underlying space weather forecast needs. In this study, the Coupled model of the Thermosphere, Ionosphere, Plasmasphere and electrodynamics (CTIPe) and the recently developed Ionosphere-Plasmasphere-Electrodynamics (IPE) models are used to quantitatively assess how well the models reproduce the structure of the O/N2 changes and the negative phase observed during geomagnetic storm events. Various datasets from ground and space are used to validate the model results.

Rural to Urban Population Density Scaling of Crime and Property Transactions in English and Welsh Parliamentary Constituencies.

PubMed

Hanley, Quentin S; Lewis, Dan; Ribeiro, Haroldo V

2016-01-01

Urban population scaling of resource use, creativity metrics, and human behaviors has been widely studied. These studies have not looked in detail at the full range of human environments which represent a continuum from the most rural to heavily urban. We examined monthly police crime reports and property transaction values across all 573 Parliamentary Constituencies in England and Wales, finding that scaling models based on population density provided a far superior framework to traditional population scaling. We found four types of scaling: i) non-urban scaling in which a single power law explained the relationship between the metrics and population density from the most rural to heavily urban environments, ii) accelerated scaling in which high population density was associated with an increase in the power-law exponent, iii) inhibited scaling where the urban environment resulted in a reduction in the power-law exponent but remained positive, and iv) collapsed scaling where transition to the high density environment resulted in a negative scaling exponent. Urban scaling transitions, when observed, took place universally between 10 and 70 people per hectare. This study significantly refines our understanding of urban scaling, making clear that some of what has been previously ascribed to urban environments may simply be the high density portion of non-urban scaling. It also makes clear that some metrics undergo specific transitions in urban environments and these transitions can include negative scaling exponents indicative of collapse. This study gives promise of far more sophisticated scale adjusted metrics and indicates that studies of urban scaling represent a high density subsection of overall scaling relationships which continue into rural environments.

Rural to Urban Population Density Scaling of Crime and Property Transactions in English and Welsh Parliamentary Constituencies

PubMed Central

Hanley, Quentin S.; Lewis, Dan; Ribeiro, Haroldo V.

2016-01-01

Urban population scaling of resource use, creativity metrics, and human behaviors has been widely studied. These studies have not looked in detail at the full range of human environments which represent a continuum from the most rural to heavily urban. We examined monthly police crime reports and property transaction values across all 573 Parliamentary Constituencies in England and Wales, finding that scaling models based on population density provided a far superior framework to traditional population scaling. We found four types of scaling: i) non-urban scaling in which a single power law explained the relationship between the metrics and population density from the most rural to heavily urban environments, ii) accelerated scaling in which high population density was associated with an increase in the power-law exponent, iii) inhibited scaling where the urban environment resulted in a reduction in the power-law exponent but remained positive, and iv) collapsed scaling where transition to the high density environment resulted in a negative scaling exponent. Urban scaling transitions, when observed, took place universally between 10 and 70 people per hectare. This study significantly refines our understanding of urban scaling, making clear that some of what has been previously ascribed to urban environments may simply be the high density portion of non-urban scaling. It also makes clear that some metrics undergo specific transitions in urban environments and these transitions can include negative scaling exponents indicative of collapse. This study gives promise of far more sophisticated scale adjusted metrics and indicates that studies of urban scaling represent a high density subsection of overall scaling relationships which continue into rural environments. PMID:26886219

Comparison of Integrated Radiation Transport Models with TEPC Measurements for the Average Quality Factors in Spaceflights

NASA Technical Reports Server (NTRS)

Kim, Myung-Hee Y.; Nikjoo, Hooshang; Dicello, John F.; Pisacane, Vincent; Cucinotta, Francis A.

2007-01-01

The purpose of this work is to test our theoretical model for the interpretation of radiation data measured in space. During the space missions astronauts are exposed to the complex field of radiation type and kinetic energies from galactic cosmic rays (GCR), trapped protons, and sometimes solar particle events (SPEs). The tissue equivalent proportional counter (TEPC) is a simple time-dependent approach for radiation monitoring for astronauts on board the International Space Station. Another and a newer approach to Microdosimetry is the use of silicon-on-insulator (SOI) technology launched on the MidSTAR-1 mission in low Earth orbit (LEO). In the radiation protection practice, the average quality factor of a radiation field is defined as a function of linear energy transfer (LET), Q(sub ave)(LET). However, TEPC measures the average quality factor as a function of the lineal energy y, Q(sub ave)(y), defined as the average energy deposition in a volume divided by the average chord length of the volume. Lineal energy, y, deviates from LET due to energy straggling, delta-ray escape or entry, and nuclear fragments produced in the detector volume. Monte Carlo track structure simulation was employed to obtain the response of a TEPC irradiated with charged particle for an equivalent site diameter of 1 micron of wall-less counter. The calculated data of the energy absorption in the wall-less counter were compiled for various y values for several ion types at various discrete projectile energy levels. For the simulation of TEPC response from the mixed radiation environments inside a spacecraft, such as, Space Shuttle and International Space Station, the complete microdosimetric TEPC response, f( y, E, Z), were calculated with the Monte Carlo theoretical results by using the first order Lagrangian interpolation for a monovariate function at a given y value (y = 0.1 keV/micron 5000 keV/micron) at any projectile energy level (E = 0.01 MeV/u to 50,000 MeV/u) of each specific radiation type (Z = 1 to 28). Because the anomalous response has been observed at large event sizes in the experiment due to the escape of energy out of sensitive volume by delta-rays and the entry of delta-rays from the high-density wall into the low-density gas-volume cavity, Monte Carlo simulation was also made for the response of a walled-TEPC with wall thickness 2 mm and density 1 g/cm(exp 3). The radius of cavity was set to 6.35 mm and a gas density 7.874 x 10(exp -5) g/cm(exp 3). The response of the walled- and the wall-less counters were compared. The average quality factor Q(sub ave)(y) for trapped protons on STS-89 demonstrated the good agreement between the model calculations and flight TEPC data as shown. Using an integrated space radiation model (this includes the transport codes HZETRN and BRYNTRN, the quantum nuclear interaction model QMSFRG) and the resultant response distribution functions of walled-TEPC from Monte-Carlo track simulations, we compared model calculations with walled-TEPC measurements from NASA missions in LEO and made predictions for the lunar and the Mars missions. The Q(sub ave)(y) values for the trapped or the solar protons ranged from 1.9-2.5. This over-estimates the Qave(LET) values which ranged from 1.4-1.6. Both quantities increase with shield thickness due to nuclear fragmentation. The Q(sub ave)(LET) for the complete GCR spectra was found to be 3.5-4.5, while flight TEPCs measured 2.9-3.4 for Q(sub ave)(y). The GCR values are decreasing with the shield thickness. Our analysis for a proper interpretation of data supports the use of TEPCs for monitoring space radiation environment.

UV TO FAR-IR CATALOG OF A GALAXY SAMPLE IN NEARBY CLUSTERS: SPECTRAL ENERGY DISTRIBUTIONS AND ENVIRONMENTAL TRENDS

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

Hernandez-Fernandez, Jonathan D.; Iglesias-Paramo, J.; Vilchez, J. M., E-mail: jonatan@iaa.es

2012-03-01

In this paper, we present a sample of cluster galaxies devoted to study the environmental influence on the star formation activity. This sample of galaxies inhabits in clusters showing a rich variety in their characteristics and have been observed by the SDSS-DR6 down to M{sub B} {approx} -18, and by the Galaxy Evolution Explorer AIS throughout sky regions corresponding to several megaparsecs. We assign the broadband and emission-line fluxes from ultraviolet to far-infrared to each galaxy performing an accurate spectral energy distribution for spectral fitting analysis. The clusters follow the general X-ray luminosity versus velocity dispersion trend of L{sub X}more » {proportional_to} {sigma}{sup 4.4}{sub c}. The analysis of the distributions of galaxy density counting up to the 5th nearest neighbor {Sigma}{sub 5} shows: (1) the virial regions and the cluster outskirts share a common range in the high density part of the distribution. This can be attributed to the presence of massive galaxy structures in the surroundings of virial regions. (2) The virial regions of massive clusters ({sigma}{sub c} > 550 km s{sup -1}) present a {Sigma}{sub 5} distribution statistically distinguishable ({approx}96%) from the corresponding distribution of low-mass clusters ({sigma}{sub c} < 550 km s{sup -1}). Both massive and low-mass clusters follow a similar density-radius trend, but the low-mass clusters avoid the high density extreme. We illustrate, with ABELL 1185, the environmental trends of galaxy populations. Maps of sky projected galaxy density show how low-luminosity star-forming galaxies appear distributed along more spread structures than their giant counterparts, whereas low-luminosity passive galaxies avoid the low-density environment. Giant passive and star-forming galaxies share rather similar sky regions with passive galaxies exhibiting more concentrated distributions.« less

Probing Earth's State of Stress

NASA Astrophysics Data System (ADS)

Delorey, A. A.; Maceira, M.; Johnson, P. A.; Coblentz, D. D.

2016-12-01

The state of stress in the Earth's crust is a fundamental physical property that controls both engineered and natural systems. Engineered environments including those for hydrocarbon, geothermal energy, and mineral extraction, as well those for storage of wastewater, carbon dioxide, and nuclear fuel are as important as ever to our economy and environment. Yet, it is at spatial scales relevant to these activities where stress is least understood. Additionally, in engineered environments the rate of change in the stress field can be much higher than that of natural systems. In order to use subsurface resources more safely and effectively, we need to understand stress at the relevant temporal and spatial scales. We will present our latest results characterizing the state of stress in the Earth at scales relevant to engineered environments. Two important components of the state of stress are the orientation and magnitude of the stress tensor, and a measure of how close faults are to failure. The stress tensor at any point in a reservoir or repository has contributions from both far-field tectonic stress and local density heterogeneity. We jointly invert seismic (body and surface waves) and gravity data for a self-consistent model of elastic moduli and density and use the model to calculate the contribution of local heterogeneity to the total stress field. We then combine local and plate-scale contributions, using local indicators for calibration and ground-truth. In addition, we will present results from an analysis of the quantity and pattern of microseismicity as an indicator of critically stressed faults. Faults are triggered by transient stresses only when critically stressed (near failure). We show that tidal stresses can trigger earthquakes in both tectonic and reservoir environments and can reveal both stress and poroelastic conditions.

Energy consumption of agitators in activated sludge tanks - actual state and optimization potential.

PubMed

Füreder, K; Svardal, K; Frey, W; Kroiss, H; Krampe, J

2018-02-01

Depending on design capacity, agitators consume about 5 to 20% of the total energy consumption of a wastewater treatment plant. Based on inhabitant-specific energy consumption (kWh PE 120 -1 a -1 ; PE 120 is population equivalent, assuming 120 g chemical oxygen demand per PE per day), power density (W m -3 ) and volume-specific energy consumption (Wh m -3 d -1 ) as evaluation indicators, this paper provides a sound contribution to understanding energy consumption and energy optimization potentials of agitators. Basically, there are two ways to optimize agitator operation: the reduction of the power density and the reduction of the daily operating time. Energy saving options range from continuous mixing with low power densities of 1 W m -3 to mixing by means of short, intense energy pulses (impulse aeration, impulse stirring). However, the following correlation applies: the shorter the duration of energy input, the higher the power density on the respective volume-specific energy consumption isoline. Under favourable conditions with respect to tank volume, tank geometry, aeration and agitator position, mixing energy can be reduced to 24 Wh m -3 d -1 and below. Additionally, it could be verified that power density of agitators stands in inverse relation to tank volume.

Ultra-stiff metallic glasses through bond energy density design.

PubMed

Schnabel, Volker; Köhler, Mathias; Music, Denis; Bednarcik, Jozef; Clegg, William J; Raabe, Dierk; Schneider, Jochen M

2017-07-05

The elastic properties of crystalline metals scale with their valence electron density. Similar observations have been made for metallic glasses. However, for metallic glasses where covalent bonding predominates, such as metalloid metallic glasses, this relationship appears to break down. At present, the reasons for this are not understood. Using high energy x-ray diffraction analysis of melt spun and thin film metallic glasses combined with density functional theory based molecular dynamics simulations, we show that the physical origin of the ultrahigh stiffness in both metalloid and non-metalloid metallic glasses is best understood in terms of the bond energy density. Using the bond energy density as novel materials design criterion for ultra-stiff metallic glasses, we are able to predict a Co 33.0 Ta 3.5 B 63.5 short range ordered material by density functional theory based molecular dynamics simulations with a high bond energy density of 0.94 eV Å -3 and a bulk modulus of 263 GPa, which is 17% greater than the stiffest Co-B based metallic glasses reported in literature.

Band-like transport in highly crystalline graphene films from defective graphene oxides.

PubMed

Negishi, R; Akabori, M; Ito, T; Watanabe, Y; Kobayashi, Y

2016-07-01

The electrical transport property of the reduced graphene oxide (rGO) thin-films synthesized from defective GO through thermal treatment in a reactive ethanol environment at high temperature above 1000 °C shows a band-like transport with small thermal activation energy (Ea~10 meV) that occurs during high carrier mobility (~210 cm(2)/Vs). Electrical and structural analysis using X-ray absorption fine structure, the valence band photo-electron, Raman spectra and transmission electron microscopy indicate that a high temperature process above 1000 °C in the ethanol environment leads to an extraordinary expansion of the conjugated π-electron system in rGO due to the efficient restoration of the graphitic structure. We reveal that Ea decreases with the increasing density of states near the Fermi level due to the expansion of the conjugated π-electron system in the rGO. This means that Ea corresponds to the energy gap between the top of the valence band and the bottom of the conduction band. The origin of the band-like transport can be explained by the carriers, which are more easily excited into the conduction band due to the decreasing energy gap with the expansion of the conjugated π-electron system in the rGO.

Band-like transport in highly crystalline graphene films from defective graphene oxides

NASA Astrophysics Data System (ADS)

Negishi, R.; Akabori, M.; Ito, T.; Watanabe, Y.; Kobayashi, Y.

2016-07-01

The electrical transport property of the reduced graphene oxide (rGO) thin-films synthesized from defective GO through thermal treatment in a reactive ethanol environment at high temperature above 1000 °C shows a band-like transport with small thermal activation energy (Ea~10 meV) that occurs during high carrier mobility (~210 cm2/Vs). Electrical and structural analysis using X-ray absorption fine structure, the valence band photo-electron, Raman spectra and transmission electron microscopy indicate that a high temperature process above 1000 °C in the ethanol environment leads to an extraordinary expansion of the conjugated π-electron system in rGO due to the efficient restoration of the graphitic structure. We reveal that Ea decreases with the increasing density of states near the Fermi level due to the expansion of the conjugated π-electron system in the rGO. This means that Ea corresponds to the energy gap between the top of the valence band and the bottom of the conduction band. The origin of the band-like transport can be explained by the carriers, which are more easily excited into the conduction band due to the decreasing energy gap with the expansion of the conjugated π-electron system in the rGO.

Density functional and theoretical study of the temperature and pressure dependency of the plasmon energy of solids

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

Attarian Shandiz, M., E-mail: mohammad.attarianshandiz@mail.mcgill.ca; Gauvin, R.

The temperature and pressure dependency of the volume plasmon energy of solids was investigated by density functional theory calculations. The volume change of crystal is the major factor responsible for the variation of valence electron density and plasmon energy in the free electron model. Hence, to introduce the effect of temperature and pressure for the density functional theory calculations of plasmon energy, the temperature and pressure dependency of lattice parameter was used. Also, by combination of the free electron model and the equation of state based on the pseudo-spinodal approach, the temperature and pressure dependency of the plasmon energy wasmore » modeled. The suggested model is in good agreement with the results of density functional theory calculations and available experimental data for elements with the free electron behavior.« less

An Electrochemical Capacitor with Applicable Energy Density of 7.4 Wh/kg at Average Power Density of 3000 W/kg.

PubMed

Zhai, Teng; Lu, Xihong; Wang, Hanyu; Wang, Gongming; Mathis, Tyler; Liu, Tianyu; Li, Cheng; Tong, Yexiang; Li, Yat

2015-05-13

Electrochemical capacitors represent a new class of charge storage devices that can simultaneously achieve high energy density and high power density. Previous reports have been primarily focused on the development of high performance capacitor electrodes. Although these electrodes have achieved excellent specific capacitance based on per unit mass of active materials, the gravimetric energy densities calculated based on the weight of entire capacitor device were fairly small. This is mainly due to the large mass ratio between current collector and active material. We aimed to address this issue by a 2-fold approach of minimizing the mass of current collector and increasing the electrode performance. Here we report an electrochemical capacitor using 3D graphene hollow structure as current collector, vanadium sulfide and manganese oxide as anode and cathode materials, respectively. 3D graphene hollow structure provides a lightweight and highly conductive scaffold for deposition of pseudocapacitive materials. The device achieves an excellent active material ratio of 24%. Significantly, it delivers a remarkable energy density of 7.4 Wh/kg (based on the weight of entire device) at the average power density of 3000 W/kg. This is the highest gravimetric energy density reported for asymmetric electrochemical capacitors at such a high power density.

The physical chemistry of coordinated aqua-, ammine-, and mixed-ligand Co2+ complexes: DFT studies on the structure, energetics, and topological properties of the electron density.

PubMed

Varadwaj, Pradeep R; Marques, Helder M

2010-03-07

Spin-unrestricted DFT-X3LYP/6-311++G(d,p) calculations have been performed on a series of complexes of the form [Co(H(2)O)(6-n)(NH(3))(n)](2+) (n = 0-6) to examine their equilibrium gas-phase structures, energetics, and electronic properties in their quartet electronic ground states. In all cases Co(2+) in the energy-minimised structures is in a pseudo-octahedral environment. The calculations overestimate the Co-O and Co-N bond lengths by 0.04 and 0.08 A, respectively, compared to the crystallographically observed mean values. There is a very small Jahn-Teller distortion in the structure of [Co(H(2)O)(6)](2+) which is in contrast to the very marked distortions observed in most (but not all) structures of this cation that have been observed experimentally. The successive replacement of ligated H(2)O by NH(3) leads to an increase in complex stability by 6 +/- 1 kcal mol(-1) per additional NH(3) ligand. Calculations using UB3LYP give stabilisation energies of the complexes about 5 kcal mol(-1) smaller and metal-ligand bond lengths about 0.005 A longer than the X3LYP values since the X3LYP level accounts for the London dispersion energy contribution to the overall stabilisation energy whilst it is largely missing at the B3LYP level. From a natural population analysis (NPA) it is shown that the formation of these complexes is accompanied by ligand-to-metal charge transfer the extent of which increases with the number of NH(3) ligands in the coordination sphere of Co(2+). From an examination of the topological properties of the electron charge density using Bader's quantum theory of atoms in molecules it is shown that the electron density rho(c) at the Co-O bond critical points is generally smaller than that at the Co-N bond critical points. Hence Co-O bonds are weaker than Co-N bonds in these complexes and the stability increases as NH(3) replaces H(2)O in the metal's coordination sphere. Several indicators, including the sign and magnitude of the Laplacian of the charge density nabla(2)rho(c), the ratio of the local potential and kinetic energy densities, |V(c)|/G(c), the sign of the total energy density H(c), and the delocalisation index delta(Co,X), X = O, N, are used to show that whilst the metal-ligand bonds are predominantly ionic in nature, they gain covalent character as NH(3) replaces H(2)O, and the Co-N bond is significantly more covalent than the Co-O bond. We have shown that the delocalisation index delta(Co,X), X = O, N, is strongly correlated with the zero-point corrected stabilisation energy E demonstrating that delta can be used as a measure of the bond stability in these complexes.

Use of nonlinear programming to optimize performance response to energy density in broiler feed formulation.

PubMed

Guevara, V R

2004-02-01

A nonlinear programming optimization model was developed to maximize margin over feed cost in broiler feed formulation and is described in this paper. The model identifies the optimal feed mix that maximizes profit margin. Optimum metabolizable energy level and performance were found by using Excel Solver nonlinear programming. Data from an energy density study with broilers were fitted to quadratic equations to express weight gain, feed consumption, and the objective function income over feed cost in terms of energy density. Nutrient:energy ratio constraints were transformed into equivalent linear constraints. National Research Council nutrient requirements and feeding program were used for examining changes in variables. The nonlinear programming feed formulation method was used to illustrate the effects of changes in different variables on the optimum energy density, performance, and profitability and was compared with conventional linear programming. To demonstrate the capabilities of the model, I determined the impact of variation in prices. Prices for broiler, corn, fish meal, and soybean meal were increased and decreased by 25%. Formulations were identical in all other respects. Energy density, margin, and diet cost changed compared with conventional linear programming formulation. This study suggests that nonlinear programming can be more useful than conventional linear programming to optimize performance response to energy density in broiler feed formulation because an energy level does not need to be set.

Density-functional theory for internal magnetic fields

NASA Astrophysics Data System (ADS)

Tellgren, Erik I.

2018-01-01

A density-functional theory is developed based on the Maxwell-Schrödinger equation with an internal magnetic field in addition to the external electromagnetic potentials. The basic variables of this theory are the electron density and the total magnetic field, which can equivalently be represented as a physical current density. Hence, the theory can be regarded as a physical current density-functional theory and an alternative to the paramagnetic current density-functional theory due to Vignale and Rasolt. The energy functional has strong enough convexity properties to allow a formulation that generalizes Lieb's convex analysis formulation of standard density-functional theory. Several variational principles as well as a Hohenberg-Kohn-like mapping between potentials and ground-state densities follow from the underlying convex structure. Moreover, the energy functional can be regarded as the result of a standard approximation technique (Moreau-Yosida regularization) applied to the conventional Schrödinger ground-state energy, which imposes limits on the maximum curvature of the energy (with respect to the magnetic field) and enables construction of a (Fréchet) differentiable universal density functional.

High Energy Density in Azobenzene-based Materials for Photo-Thermal Batteries via Controlled Polymer Architecture and Polymer-Solvent Interactions.

PubMed

Jeong, Seung Pyo; Renna, Lawrence A; Boyle, Connor J; Kwak, Hyunwook S; Harder, Edward; Damm, Wolfgang; Venkataraman, Dhandapani

2017-12-19

Energy densities of ~510 J/g (max: 698 J/g) have been achieved in azobenzene-based syndiotactic-rich poly(methacrylate) polymers. The processing solvent and polymer-solvent interactions are important to achieve morphologically optimal structures for high-energy density materials. This work shows that morphological changes of solid-state syndiotactic polymers, driven by different solvent processings play an important role in controlling the activation energy of Z-E isomerization as well as the shape of the DSC exotherm. Thus, this study shows the crucial role of processing solvents and thin film structure in achieving higher energy densities.

Solvation effect of bacteriochlorophyll excitons in light-harvesting complex LH2.

PubMed

Urboniene, V; Vrublevskaja, O; Trinkunas, G; Gall, A; Robert, B; Valkunas, L

2007-09-15

We have characterized the influence of the protein environment on the spectral properties of the bacteriochlorophyll (Bchl) molecules of the peripheral light-harvesting (or LH2) complex from Rhodobacter sphaeroides. The spectral density functions of the pigments responsible for the 800 and 850 nm electronic transitions were determined from the temperature dependence of the Bchl absorption spectra in different environments (detergent micelles and native membranes). The spectral density function is virtually independent of the hydrophobic support that the protein experiences. The reorganization energy for the B850 Bchls is 220 cm(-1), which is almost twice that of the B800 Bchls, and its Huang-Rhys factor reaches 8.4. Around the transition point temperature, and at higher temperatures, both the static spectral inhomogeneity and the resonance interactions become temperature-dependent. The inhomogeneous distribution function of the transitions exhibits less temperature dependence when LH2 is embedded in membranes, suggesting that the lipid phase protects the protein. However, the temperature dependence of the fluorescence spectra of LH2 cannot be fitted using the same parameters determined from the analysis of the absorption spectra. Correct fitting requires the lowest exciton states to be additionally shifted to the red, suggesting the reorganization of the exciton spectrum.

Accelerating wavefunction in density-functional-theory embedding by truncating the active basis set

NASA Astrophysics Data System (ADS)

Bennie, Simon J.; Stella, Martina; Miller, Thomas F.; Manby, Frederick R.

2015-07-01

Methods where an accurate wavefunction is embedded in a density-functional description of the surrounding environment have recently been simplified through the use of a projection operator to ensure orthogonality of orbital subspaces. Projector embedding already offers significant performance gains over conventional post-Hartree-Fock methods by reducing the number of correlated occupied orbitals. However, in our first applications of the method, we used the atomic-orbital basis for the full system, even for the correlated wavefunction calculation in a small, active subsystem. Here, we further develop our method for truncating the atomic-orbital basis to include only functions within or close to the active subsystem. The number of atomic orbitals in a calculation on a fixed active subsystem becomes asymptotically independent of the size of the environment, producing the required O ( N 0 ) scaling of cost of the calculation in the active subsystem, and accuracy is controlled by a single parameter. The applicability of this approach is demonstrated for the embedded many-body expansion of binding energies of water hexamers and calculation of reaction barriers of SN2 substitution of fluorine by chlorine in α-fluoroalkanes.

Coaxial wet-spun yarn supercapacitors for high-energy density and safe wearable electronics

NASA Astrophysics Data System (ADS)

Kou, Liang; Huang, Tieqi; Zheng, Bingna; Han, Yi; Zhao, Xiaoli; Gopalsamy, Karthikeyan; Sun, Haiyan; Gao, Chao

2014-05-01

Yarn supercapacitors have great potential in future portable and wearable electronics because of their tiny volume, flexibility and weavability. However, low-energy density limits their development in the area of wearable high-energy density devices. How to enhance their energy densities while retaining their high-power densities is a critical challenge for yarn supercapacitor development. Here we propose a coaxial wet-spinning assembly approach to continuously spin polyelectrolyte-wrapped graphene/carbon nanotube core-sheath fibres, which are used directly as safe electrodes to assembly two-ply yarn supercapacitors. The yarn supercapacitors using liquid and solid electrolytes show ultra-high capacitances of 269 and 177 mF cm-2 and energy densities of 5.91 and 3.84 μWh cm-2, respectively. A cloth supercapacitor superior to commercial capacitor is further interwoven from two individual 40-cm-long coaxial fibres. The combination of scalable coaxial wet-spinning technology and excellent performance of yarn supercapacitors paves the way to wearable and safe electronics.

Toward Low-Cost, High-Energy Density, and High-Power Density Lithium-Ion Batteries

DOE PAGES

Li, Jianlin; Du, Zhijia; Ruther, Rose E.; ...

2017-06-12

Reducing cost and increasing energy density are two barriers for widespread application of lithium-ion batteries in electric vehicles. Although the cost of electric vehicle batteries has been reduced by ~70% from 2008 to 2015, the current battery pack cost (268/kWh in 2015) is still >2 times what the USABC targets (125/kWh). Even though many advancements in cell chemistry have been realized since the lithium-ion battery was first commercialized in 1991, few major breakthroughs have occurred in the past decade. Therefore, future cost reduction will rely on cell manufacturing and broader market acceptance. Here, this article discusses three major aspects formore » cost reduction: (1) quality control to minimize scrap rate in cell manufacturing; (2) novel electrode processing and engineering to reduce processing cost and increase energy density and throughputs; and (3) material development and optimization for lithium-ion batteries with high-energy density. Insights on increasing energy and power densities of lithium-ion batteries are also addressed.« less

Toward Low-Cost, High-Energy Density, and High-Power Density Lithium-Ion Batteries

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

Li, Jianlin; Du, Zhijia; Ruther, Rose E.

Reducing cost and increasing energy density are two barriers for widespread application of lithium-ion batteries in electric vehicles. Although the cost of electric vehicle batteries has been reduced by ~70% from 2008 to 2015, the current battery pack cost (268/kWh in 2015) is still >2 times what the USABC targets (125/kWh). Even though many advancements in cell chemistry have been realized since the lithium-ion battery was first commercialized in 1991, few major breakthroughs have occurred in the past decade. Therefore, future cost reduction will rely on cell manufacturing and broader market acceptance. Here, this article discusses three major aspects formore » cost reduction: (1) quality control to minimize scrap rate in cell manufacturing; (2) novel electrode processing and engineering to reduce processing cost and increase energy density and throughputs; and (3) material development and optimization for lithium-ion batteries with high-energy density. Insights on increasing energy and power densities of lithium-ion batteries are also addressed.« less

Toward Low-Cost, High-Energy Density, and High-Power Density Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Li, Jianlin; Du, Zhijia; Ruther, Rose E.; AN, Seong Jin; David, Lamuel Abraham; Hays, Kevin; Wood, Marissa; Phillip, Nathan D.; Sheng, Yangping; Mao, Chengyu; Kalnaus, Sergiy; Daniel, Claus; Wood, David L.

2017-09-01

Reducing cost and increasing energy density are two barriers for widespread application of lithium-ion batteries in electric vehicles. Although the cost of electric vehicle batteries has been reduced by 70% from 2008 to 2015, the current battery pack cost (268/kWh in 2015) is still >2 times what the USABC targets (125/kWh). Even though many advancements in cell chemistry have been realized since the lithium-ion battery was first commercialized in 1991, few major breakthroughs have occurred in the past decade. Therefore, future cost reduction will rely on cell manufacturing and broader market acceptance. This article discusses three major aspects for cost reduction: (1) quality control to minimize scrap rate in cell manufacturing; (2) novel electrode processing and engineering to reduce processing cost and increase energy density and throughputs; and (3) material development and optimization for lithium-ion batteries with high-energy density. Insights on increasing energy and power densities of lithium-ion batteries are also addressed.

Coaxial wet-spun yarn supercapacitors for high-energy density and safe wearable electronics

PubMed Central

Kou, Liang; Huang, Tieqi; Zheng, Bingna; Han, Yi; Zhao, Xiaoli; Gopalsamy, Karthikeyan; Sun, Haiyan; Gao, Chao

2014-01-01

Yarn supercapacitors have great potential in future portable and wearable electronics because of their tiny volume, flexibility and weavability. However, low-energy density limits their development in the area of wearable high-energy density devices. How to enhance their energy densities while retaining their high-power densities is a critical challenge for yarn supercapacitor development. Here we propose a coaxial wet-spinning assembly approach to continuously spin polyelectrolyte-wrapped graphene/carbon nanotube core-sheath fibres, which are used directly as safe electrodes to assembly two-ply yarn supercapacitors. The yarn supercapacitors using liquid and solid electrolytes show ultra-high capacitances of 269 and 177 mF cm−2 and energy densities of 5.91 and 3.84 μWh cm−2, respectively. A cloth supercapacitor superior to commercial capacitor is further interwoven from two individual 40-cm-long coaxial fibres. The combination of scalable coaxial wet-spinning technology and excellent performance of yarn supercapacitors paves the way to wearable and safe electronics. PMID:24786366

Solvatochromic shifts from coupled-cluster theory embedded in density functional theory

NASA Astrophysics Data System (ADS)

Höfener, Sebastian; Gomes, André Severo Pereira; Visscher, Lucas

2013-09-01

Building on the framework recently reported for determining general response properties for frozen-density embedding [S. Höfener, A. S. P. Gomes, and L. Visscher, J. Chem. Phys. 136, 044104 (2012)], 10.1063/1.3675845, in this work we report a first implementation of an embedded coupled-cluster in density-functional theory (CC-in-DFT) scheme for electronic excitations, where only the response of the active subsystem is taken into account. The formalism is applied to the calculation of coupled-cluster excitation energies of water and uracil in aqueous solution. We find that the CC-in-DFT results are in good agreement with reference calculations and experimental results. The accuracy of calculations is mainly sensitive to factors influencing the correlation treatment (basis set quality, truncation of the cluster operator) and to the embedding treatment of the ground-state (choice of density functionals). This allows for efficient approximations at the excited state calculation step without compromising the accuracy. This approximate scheme makes it possible to use a first principles approach to investigate environment effects with specific interactions at coupled-cluster level of theory at a cost comparable to that of calculations of the individual subsystems in vacuum.

Three-dimensional multi-fluid simulations of Titan's interaction with Saturn's magnetosphere: Comparisons with Cassini's T55 flyby

NASA Astrophysics Data System (ADS)

Snowden, D.; Winglee, R.

2013-08-01

We describe a new multi-fluid model of Titan's interaction with Saturn's magnetosphere that includes finer resolution in Titan's ionosphere, photoionization, electron-impact ionization, dissociative recombination, and ion-neutral coupling in the momentum and energy equations. We compare simulation results to data from Cassini's T55 flyby to show that including magnetospheric electron-impact ionization in Titan's nightside ionosphere is necessary to calculate electron densities, electron temperatures, and ion velocities that are consistent with Cassini observations. However, similar to other studies, we find that the electron-impact ionization rate calculated by the model needs to be significantly reduced to produce an electron density that is in agreement with the observations. We also find that an upstream plasma flow with significant components northward and radially outward from Saturn is needed to reproduce the gradual increase in electron density observed during the ingress portion of T55. This suggests that Titan was in a nonideal environment with a plasma flow oriented away from the direction of corotation during T55 and likely during the subsequent flybys T56, T57, T58, and T59 when similar electron density enhancements were seen on the inbound portion of Cassini's trajectory.

Shellwise Mackay transformation in iron nanoclusters.

PubMed

Rollmann, Georg; Gruner, Markus E; Hucht, Alfred; Meyer, Ralf; Entel, Peter; Tiago, Murilo L; Chelikowsky, James R

2007-08-24

Structure and magnetism of iron clusters with up to 641 atoms have been investigated by means of density functional theory calculations including full geometric optimizations. Body-centered cubic (bcc) isomers are found to be lowest in energy when the clusters contain more than about 100 atoms. In addition, another stable conformation has been identified for magic-number clusters, which lies well within the range of thermal energies as compared to the bcc isomers. Its structure is characterized by a close-packed particle core and an icosahedral surface, while intermediate shells are partially transformed along the Mackay path between icosahedral and cuboctahedral geometry. The gradual transformation results in a favorable bcc environment for the subsurface atoms. For Fe55, the shellwise Mackay-transformed morphology is a promising candidate for the ground state.

Testing of typical spacecraft materials in a simulated substorm environment

NASA Technical Reports Server (NTRS)

Stevens, N. J.; Berkopec, F. D.; Staskus, J. V.; Blech, R. A.; Narciso, S. J.

1977-01-01

The test specimens were spacecraft paints, silvered Teflon, thermal blankets, and solar array segments. The samples, ranging in size from 300 to 1000 sq cm were exposed to monoenergetic electron energies from 2 to 20 keV at a current density of 1 NA/sq cm. The samples generally behaved as capacitors with strong voltage gradient at their edges. The charging characteristics of the silvered Teflon, Kapton, and solar cell covers were controlled by the secondary emission characteristics. Insulators that did not discharge were the spacecraft paints and the quartz fiber cloth thermal blanket sample. All other samples did experience discharges when the surface voltage reached -8 to -16kV. The discharges were photographed. The breakdown voltage for each sample was determined and the average energy lost in the discharge was computed.

Additive Manufacturing of a Microbial Fuel Cell—A detailed study

PubMed Central

Calignano, Flaviana; Tommasi, Tonia; Manfredi, Diego; Chiolerio, Alessandro

2015-01-01

In contemporary society we observe an everlasting permeation of electron devices, smartphones, portable computing tools. The tiniest living organisms on Earth could become the key to address this challenge: energy generation by bacterial processes from renewable stocks/waste through devices such as microbial fuel cells (MFCs). However, the application of this solution was limited by a moderately low efficiency. We explored the limits, if any, of additive manufacturing (AM) technology to fabricate a fully AM-based powering device, exploiting low density, open porosities able to host the microbes, systems easy to fuel continuously and to run safely. We obtained an optimal energy recovery close to 3 kWh m−3 per day that can power sensors and low-power appliances, allowing data processing and transmission from remote/harsh environments. PMID:26611142

Additive Manufacturing of a Microbial Fuel Cell—A detailed study

NASA Astrophysics Data System (ADS)

Calignano, Flaviana; Tommasi, Tonia; Manfredi, Diego; Chiolerio, Alessandro

2015-11-01

In contemporary society we observe an everlasting permeation of electron devices, smartphones, portable computing tools. The tiniest living organisms on Earth could become the key to address this challenge: energy generation by bacterial processes from renewable stocks/waste through devices such as microbial fuel cells (MFCs). However, the application of this solution was limited by a moderately low efficiency. We explored the limits, if any, of additive manufacturing (AM) technology to fabricate a fully AM-based powering device, exploiting low density, open porosities able to host the microbes, systems easy to fuel continuously and to run safely. We obtained an optimal energy recovery close to 3 kWh m-3 per day that can power sensors and low-power appliances, allowing data processing and transmission from remote/harsh environments.

The Morphology-Density Relationship: Looking Back, Thinking Back

NASA Astrophysics Data System (ADS)

Dressler, A.

The work I did in the late 1970s leading to the morphology-density relation was done in a time of rising interest in how galaxies acquired different morphological types. I describe briefly here how I contributed to this effort by adding a large number of morphologies for galaxies in rich clusters and the field. The strong correlation that I discovered between galaxy type and local galaxy density ran counter to ideas at the time that emphasized processes tied to the global cluster environment. Instead, it provided some of the first evidence for a hierarchical picture - one in which the density of the environment into which a galaxy was born would be its lifetime legacy. Though often cited as a relation between galaxy morphology and the influence of present-epoch environment, the morphology-density relation was interpreted by me, from the first, as the influence of the early environment of galaxy formation, passed down by the hierarchical growth of structure. In fact, it seems increasingly likely that the more fundamental correlation of galaxy morphology is with galaxy mass, and that the morphology-density relation is basically an expression of the prevalence of more massive galaxies in regions of higher galaxy density.

The influence of crowd density on the sound environment of commercial pedestrian streets.

PubMed

Meng, Qi; Kang, Jian

2015-04-01

Commercial pedestrian streets are very common in China and Europe, with many situated in historic or cultural centres. The environments of these streets are important, including their sound environments. The objective of this study is to explore the relationships between the crowd density and the sound environments of commercial pedestrian streets. On-site measurements were performed at the case study site in Harbin, China, and a questionnaire was administered. The sound pressure measurements showed that the crowd density has an insignificant effect on sound pressure below 0.05 persons/m2, whereas when the crowd density is greater than 0.05 persons/m2, the sound pressure increases with crowd density. The sound sources were analysed, showing that several typical sound sources, such as traffic noise, can be masked by the sounds resulting from dense crowds. The acoustic analysis showed that crowd densities outside the range of 0.10 to 0.25 persons/m2 exhibited lower acoustic comfort evaluation scores. In terms of audiovisual characteristics, the subjective loudness increases with greater crowd density, while the acoustic comfort decreases. The results for an indoor underground shopping street are also presented for comparison. Copyright © 2014 Elsevier B.V. All rights reserved.

Environmental variability and population dynamics: Do European and North American ducks play by the same rules?

USGS Publications Warehouse

Pöysä, Hannu; Rintala, Jukka; Johnson, Douglas H.; Kauppinen, Jukka; Lammi, Esa; Nudds, Thomas D.; Väänänen, Veli-Matti

2016-01-01

Density dependence, population regulation, and variability in population size are fundamental population processes, the manifestation and interrelationships of which are affected by environmental variability. However, there are surprisingly few empirical studies that distinguish the effect of environmental variability from the effects of population processes. We took advantage of a unique system, in which populations of the same duck species or close ecological counterparts live in highly variable (north American prairies) and in stable (north European lakes) environments, to distinguish the relative contributions of environmental variability (measured as between-year fluctuations in wetland numbers) and intraspecific interactions (density dependence) in driving population dynamics. We tested whether populations living in stable environments (in northern Europe) were more strongly governed by density dependence than populations living in variable environments (in North America). We also addressed whether relative population dynamical responses to environmental variability versus density corresponded to differences in life history strategies between dabbling (relatively “fast species” and governed by environmental variability) and diving (relatively “slow species” and governed by density) ducks. As expected, the variance component of population fluctuations caused by changes in breeding environments was greater in North America than in Europe. Contrary to expectations, however, populations in more stable environments were not less variable nor clearly more strongly density dependent than populations in highly variable environments. Also, contrary to expectations, populations of diving ducks were neither more stable nor stronger density dependent than populations of dabbling ducks, and the effect of environmental variability on population dynamics was greater in diving than in dabbling ducks. In general, irrespective of continent and species life history, environmental variability contributed more to variation in species abundances than did density. Our findings underscore the need for more studies on populations of the same species in different environments to verify the generality of current explanations about population dynamics and its association with species life history.

Environmental variability and population dynamics: do European and North American ducks play by the same rules?

PubMed

Pöysä, Hannu; Rintala, Jukka; Johnson, Douglas H; Kauppinen, Jukka; Lammi, Esa; Nudds, Thomas D; Väänänen, Veli-Matti

2016-10-01

Density dependence, population regulation, and variability in population size are fundamental population processes, the manifestation and interrelationships of which are affected by environmental variability. However, there are surprisingly few empirical studies that distinguish the effect of environmental variability from the effects of population processes. We took advantage of a unique system, in which populations of the same duck species or close ecological counterparts live in highly variable (north American prairies) and in stable (north European lakes) environments, to distinguish the relative contributions of environmental variability (measured as between-year fluctuations in wetland numbers) and intraspecific interactions (density dependence) in driving population dynamics. We tested whether populations living in stable environments (in northern Europe) were more strongly governed by density dependence than populations living in variable environments (in North America). We also addressed whether relative population dynamical responses to environmental variability versus density corresponded to differences in life history strategies between dabbling (relatively "fast species" and governed by environmental variability) and diving (relatively "slow species" and governed by density) ducks. As expected, the variance component of population fluctuations caused by changes in breeding environments was greater in North America than in Europe. Contrary to expectations, however, populations in more stable environments were not less variable nor clearly more strongly density dependent than populations in highly variable environments. Also, contrary to expectations, populations of diving ducks were neither more stable nor stronger density dependent than populations of dabbling ducks, and the effect of environmental variability on population dynamics was greater in diving than in dabbling ducks. In general, irrespective of continent and species life history, environmental variability contributed more to variation in species abundances than did density. Our findings underscore the need for more studies on populations of the same species in different environments to verify the generality of current explanations about population dynamics and its association with species life history.

A randomized controlled trial for obesity and binge eating disorder: Low-energy-density dietary counseling and cognitive behavioral therapy

PubMed Central

Masheb, Robin M.; Grilo, Carlos M.; Rolls, Barbara J.

2011-01-01

The present study examined a dietary approach – lowering energy density – for producing weight loss in obese patients with binge eating disorder (BED) who also received cognitive-behavioral therapy (CBT) to address binge eating. Fifty consecutive participants were randomly assigned to either a six-month individual treatment of CBT plus a low-Energy-Density diet (CBT+ED) or CBT plus General Nutrition counseling not related to weight loss (CBT+GN). Assessments occurred at six- and twelve-months. Eighty-six percent of participants completed treatment, and of these, 30% achieved at least a 5% weight loss with rates of binge remission ranging from 55–75%. The two treatments did not differ significantly in weight loss or binge remission outcomes. Significant improvements were found for key dietary and metabolic outcomes, with CBT+ED producing significantly better dietary outcomes on energy density, and fruit and vegetable consumption, than CBT+GN. Reductions in energy density and weight loss were significantly associated providing evidence for the specificity of the treatment effect. These favorable outcomes, and that CBT+ED was significantly better at reducing energy density and increasing fruit and vegetable consumption compared to CBT+GN, suggest that low-energy-density dietary counseling has promise as an effective method for enhancing CBT for obese individuals with BED. PMID:22005587

Social Determinants and Poor Diet Quality of Energy-Dense Diets of Australian Young Adults

PubMed Central

Allman-Farinelli, Margaret

2017-01-01

This research aimed to determine the diet quality and socio-demographic determinants by level of energy-density of diets of Australian young adults. Secondary analysis of the Australian National Nutrition and Physical Activity Survey-2011/2012 for adults aged 18–34 years (n = 2397) was conducted. Diet was assessed by 24-h recalls. Dietary energy-density was calculated as dietary energy/grams of food (kJ/g) and the Healthy-Eating-Index-for-Australians (HEIFA-2013) was used to assess diet quality (highest score = 100). Dietary energy-density was examined with respect to diet quality and sociodemographic determinants including gender, highest tertiary-education attainment, country-of-birth, age, income, and socio-economic-index-for-area (SEIFA). Higher dietary energy-density was associated with lower diet quality scores (β = −3.71, t (2394) = −29.29, p < 0.0001) and included fewer fruits and vegetables, and more discretionary foods. The mean dietary energy-density was 7.7 kJ/g and 7.2 kJ/g for men and women, respectively. Subpopulations most at risk of consuming high energy-dense diets included those with lower education, Australian and English-speaking countries of birth, and men with low income and women from areas of lower socio-economic status. Young adults reporting low energy-dense diets had higher quality diets. Intensive efforts are needed to reduce the high energy-density of young adults’ diets, and should ensure they include populations of lower socio-economic status. PMID:28974029

Social Determinants and Poor Diet Quality of Energy-Dense Diets of Australian Young Adults.

PubMed

Grech, Amanda; Rangan, Anna; Allman-Farinelli, Margaret

2017-10-01

This research aimed to determine the diet quality and socio-demographic determinants by level of energy-density of diets of Australian young adults. Secondary analysis of the Australian National Nutrition and Physical Activity Survey-2011/2012 for adults aged 18-34 years ( n = 2397) was conducted. Diet was assessed by 24-h recalls. Dietary energy-density was calculated as dietary energy/grams of food (kJ/g) and the Healthy-Eating-Index-for-Australians (HEIFA-2013) was used to assess diet quality (highest score = 100). Dietary energy-density was examined with respect to diet quality and sociodemographic determinants including gender, highest tertiary-education attainment, country-of-birth, age, income, and socio-economic-index-for-area (SEIFA). Higher dietary energy-density was associated with lower diet quality scores (β = -3.71, t (2394) = -29.29, p < 0.0001) and included fewer fruits and vegetables, and more discretionary foods. The mean dietary energy-density was 7.7 kJ/g and 7.2 kJ/g for men and women, respectively. Subpopulations most at risk of consuming high energy-dense diets included those with lower education, Australian and English-speaking countries of birth, and men with low income and women from areas of lower socio-economic status. Young adults reporting low energy-dense diets had higher quality diets. Intensive efforts are needed to reduce the high energy-density of young adults' diets, and should ensure they include populations of lower socio-economic status.

Acoustic Propagation Modeling for Marine Hydro-Kinetic Applications

NASA Astrophysics Data System (ADS)

Johnson, C. N.; Johnson, E.

2014-12-01

The combination of riverine, tidal, and wave energy have the potential to supply over one third of the United States' annual electricity demand. However, in order to deploy and test prototypes, and commercial installations, marine hydrokinetic (MHK) devices must meet strict regulatory guidelines that determine the maximum amount of noise that can be generated and sets particular thresholds for determining disturbance and injury caused by noise. An accurate model for predicting the propagation of a MHK source in a real-life hydro-acoustic environment has been established. This model will help promote the growth and viability of marine, water, and hydrokinetic energy by confidently assuring federal regulations are meet and harmful impacts to marine fish and wildlife are minimal. Paracousti, a finite difference solution to the acoustic equations, was originally developed for sound propagation in atmospheric environments and has been successfully validated for a number of different geophysical activities. The three-dimensional numerical implementation is advantageous over other acoustic propagation techniques for a MHK application where the domains of interest have complex 3D interactions from the seabed, banks, and other shallow water effects. A number of different cases for hydro-acoustic environments have been validated by both analytical and numerical results from canonical and benchmark problems. This includes a variety of hydrodynamic and physical environments that may be present in a potential MHK application including shallow and deep water, sloping, and canyon type bottoms, with varying sound speed and density profiles. With the model successfully validated for hydro-acoustic environments more complex and realistic MHK sources from turbines and/or arrays can be modeled.

Notepad-like triboelectric generator for efficiently harvesting low-velocity motion energy by interconversion between kinetic energy and elastic potential energy.

PubMed

Liu, Guanlin; Leng, Qiang; Lian, Jiawei; Guo, Hengyu; Yi, Xi; Hu, Chenguo

2015-01-21

Great attention has been paid to nanogenerators that harvest energy from ambient environments lately. In order to give considerable output current, most nanogenerators require high-velocity motion that in most cases can hardly be provided in our daily life. Here we report a notepad-like triboelectric generator (NTEG), which uses simple notepad-like structure to generate elastic deformation so as to turn a low-velocity kinetic energy into high-velocity kinetic energy through the conversion of elastic potential energy. Therefore, the NTEG can achieve high current output under low-velocity motion, which completely distinguishes it from tribogenerators previously reported. The factors that may affect the output performance are explored, including the number of slices, active length of slice, press speed, and vertical displacement. In addition, the working mechanism is systematically studied, indicating that the efficiency of the generator can be greatly enhanced by interconversion between kinetic energy and elastic potential energy. The short-circuit current, the open-circuit voltage, and power density are 205 μA and 470 V and 9.86 W/m(2), respectively, which is powerful enough to light up hundreds of light-emitting diodes (LEDs) and charge a commercial capacitor. Besides, NTEGs have been successfully applied to a self-powered door monitor.

Relationship Between Photochemical Quenching and Non-Photochemical Quenching in Six Species of Cyanobacteria Reveals Species Difference in Redox State and Species Commonality in Energy Dissipation.

PubMed

Misumi, Masahiro; Katoh, Hiroshi; Tomo, Tatsuya; Sonoike, Kintake

2016-07-01

Although the photosynthetic reaction center is well conserved among different cyanobacterial species, the modes of metabolism, e.g. respiratory, nitrogen and carbon metabolism and their mutual interaction, are quite diverse. To explore such uniformity and diversity among cyanobacteria, here we compare the influence of the light environment on the condition of photosynthetic electron transport through Chl fluorescence measurement of six cyanobacterial species grown under the same photon flux densities and at the same temperature. In the dark or under weak light, up to growth light, a large difference in the plastoquinone (PQ) redox condition was observed among different cyanobacterial species. The observed difference indicates that the degree of interaction between respiratory electron transfer and photosynthetic electron transfer differs among different cyanobacterial species. The variation could not be ascribed to the phylogenetic differences but possibly to the light environment of the original habitat. On the other hand, changes in the redox condition of PQ were essentially identical among different species at photon flux densities higher than the growth light. We further analyzed the response to high light by using a typical energy allocation model and found that 'non-regulated' thermal dissipation was increased under high-light conditions in all cyanobacterial species tested. We assume that such 'non-regulated' thermal dissipation may be an important 'regulatory' mechanism in the acclimation of cyanobacterial cells to high-light conditions. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists.

Landscape-scale distribution and density of raptor populations wintering in anthropogenic-dominated desert landscapes

USGS Publications Warehouse

Duerr, Adam E.; Miller, Tricia A.; Cornell Duerr, Kerri L; Lanzone, Michael J.; Fesnock, Amy; Katzner, Todd E.

2015-01-01

Anthropogenic development has great potential to affect fragile desert environments. Large-scale development of renewable energy infrastructure is planned for many desert ecosystems. Development plans should account for anthropogenic effects to distributions and abundance of rare or sensitive wildlife; however, baseline data on abundance and distribution of such wildlife are often lacking. We surveyed for predatory birds in the Sonoran and Mojave Deserts of southern California, USA, in an area designated for protection under the “Desert Renewable Energy Conservation Plan”, to determine how these birds are distributed across the landscape and how this distribution is affected by existing development. We developed species-specific models of resight probability to adjust estimates of abundance and density of each individual common species. Second, we developed combined-species models of resight probability for common and rare species so that we could make use of sparse data on the latter. We determined that many common species, such as red-tailed hawks, loggerhead shrikes, and especially common ravens, are associated with human development and likely subsidized by human activity. Species-specific and combined-species models of resight probability performed similarly, although the former model type provided higher quality information. Comparing abundance estimates with past surveys in the Mojave Desert suggests numbers of predatory birds associated with human development have increased while other sensitive species not associated with development have decreased. This approach gave us information beyond what we would have collected by focusing either on common or rare species, thus it provides a low-cost framework for others conducting surveys in similar desert environments outside of California.

The interaction of the near-field plasma with antennas used in magnetic fusion research

NASA Astrophysics Data System (ADS)

Caughman, John

2015-09-01

Plasma heating and current drive using antennas in the Ion Cyclotron Range of Frequencies (ICRF) are important elements for the success of magnetic fusion. The antennas must operate in a harsh environment, where local plasma densities can be >1018/m3, magnetic fields can range from 0.2-5 Tesla, and antenna operating voltages can be >40 kV. This environment creates operational issues due to the interaction of the near-field of the antenna with the local plasma. In addition to parasitic losses in this plasma region, voltage and current distributions on the antenna structure lead to the formation of high electric fields and RF plasma sheaths, which can lead to enhanced particle and energy fluxes on the antenna and on surfaces intersected by magnetic field lines connected to or passing near the antenna. These issues are being studied using a simple electrode structure and a single-strap antenna on the Prototype Materials Plasma EXperiment (Proto-MPEX) at ORNL, which is a linear plasma device that uses an electron Bernstein wave heated helicon plasma source to create a high-density plasma suitable for use in a plasma-material interaction test stand. Several diagnostics are being used to characterize the near-field interactions, including double-Langmuir probes, a retarding field energy analyzer, and optical emission spectroscopy. The RF electric field is being studied utilizing Dynamic Stark Effect spectroscopy and Doppler-Free Saturation Spectroscopy. Recent experimental results and future plans will be presented. ORNL is managed by UT-Battelle, LLC, for the U.S. DOE under Contract DE-AC-05-00OR22725.

TEMPO-based catholyte for high-energy density nonaqueous redox flow batteries.

PubMed

Wei, Xiaoliang; Xu, Wu; Vijayakumar, Murugesan; Cosimbescu, Lelia; Liu, Tianbiao; Sprenkle, Vincent; Wang, Wei

2014-12-03

A TEMPO-based non-aqueous electrolyte with the TEMPO concentration as high as 2.0 m is demonstrated as a high-energy-density catholyte for redox flow battery applications. With a hybrid anode, Li|TEMPO flow cells using this electrolyte deliver an energy efficiency of ca. 70% and an impressively high energy density of 126 W h L(-1) . © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Behavior of steelhead fry in a laboratory stream is affected by fish density but not rearing environment

USGS Publications Warehouse

Riley, Stephen C.; Tatara, Christopher P.; Berejikian, Barry A.; Flagg, Thomas A.

2009-01-01

We quantified the aggression, feeding, dominance, position choice, and territory size of naturally reared steelhead Oncorhynchus mykiss fry stocked with two types of hatchery-reared fry (from conventional and enriched rearing environments) at two densities in experimental flumes to determine how rearing environment and fish density affect the behavior of steelhead fry. We found that fry density had a significant effect on most response variables but that rearing treatment did not. The rates of threats and attacks were positively correlated with fry density, but the overall feeding rate was negatively correlated. Naturally reared fry were dominant more often at low densities, and hatchery-reared fry were dominant more often at high densities. There were no significant effects of hatchery rearing treatment on aggression, feeding, dominance, or territory size. The only significant effect of rearing treatment was on the position of naturally reared fry, which occupied more upstream positions when stocked with conventional than with enriched hatchery-reared fry. Overall, rearing environment had relatively little influence on the behavior of steelhead fry. Our results indicate that stocking hatchery-reared steelhead fry at low densities may have effects on similar-size wild fish comparable to an equivalent increase in the density of wild fish. We suggest that releasing hatchery-reared steelhead fry as a supplementation strategy may have few direct negative ecological effects on wild fry.

Diet density during the first week of life: Effects on energy and nitrogen balance characteristics of broiler chickens.

PubMed

Lamot, D M; Sapkota, D; Wijtten, P J A; van den Anker, I; Heetkamp, M J W; Kemp, B; van den Brand, H

2017-07-01

This study aimed to determine effects of diet density on growth performance, energy balance, and nitrogen (N) balance characteristics of broiler chickens during the first wk of life. Effects of diet density were studied using a dose-response design consisting of 5 dietary fat levels (3.5, 7.0, 10.5, 14.0, and 17.5%). The relative difference in dietary energy level was used to increase amino acid levels, mineral levels, and the premix inclusion level at the same ratio. Chickens were housed in open-circuit climate respiration chambers from d 0 to 7 after hatch. Body weight was measured on d 0 and 7, whereas feed intake was determined daily. For calculation of energy balances, O2 and CO2 exchange were measured continuously and all excreta from d 0 to 7 was collected and analyzed at d 7. Average daily gain (ADG) and average daily feed intake (ADFI) decreased linearly (P = 0.047 and P < 0.001, respectively), whereas gain to feed ratio increased (P < 0.001) with increasing diet density. Gross energy (GE) intake and metabolizable energy (ME) intake were not affected by diet density, but the ratio between ME and GE intake decreased linearly with increasing diet density (P = 0.006). Fat, N, and GE efficiencies (expressed as gain per unit of nutrient intake), heat production, and respiratory exchange ratio (CO2 to O2 ratio) decreased linearly (P < 0.001) as diet density increased. Energy retention, N intake, and N retention were not affected by diet density. We conclude that a higher diet density in the first wk of life of broiler chickens did not affect protein and fat retention, whereas the ME to GE ratio decreased linearly with increased diet density. This suggests that diet density appears to affect digestibility rather than utilization of nutrients. © 2017 Poultry Science Association Inc.

Dark energy and key physical parameters of clusters of galaxies

NASA Astrophysics Data System (ADS)

Bisnovatyi-Kogan, G. S.; Chernin, A. D.

2012-04-01

We study physics of clusters of galaxies embedded in the cosmic dark energy background. Under the assumption that dark energy is described by the cosmological constant, we show that the dynamical effects of dark energy are strong in clusters like the Virgo cluster. Specifically, the key physical parameters of the dark mater halos in clusters are determined by dark energy: (1) the halo cut-off radius is practically, if not exactly, equal to the zero-gravity radius at which the dark matter gravity is balanced by the dark energy antigravity; (2) the halo averaged density is equal to two densities of dark energy; (3) the halo edge (cut-off) density is the dark energy density with a numerical factor of the unity order slightly depending on the halo profile. The cluster gravitational potential well in which the particles of the dark halo (as well as galaxies and intracluster plasma) move is strongly affected by dark energy: the maximum of the potential is located at the zero-gravity radius of the cluster.

Development of advanced polymer nanocomposite capacitors

NASA Astrophysics Data System (ADS)

Mendoza, Miguel

The current development of modern electronics has driven the need for new series of energy storage devices with higher energy density and faster charge/discharge rate. Batteries and capacitors are two of the most widely used energy storage devices. Compared with batteries, capacitors have higher power density and significant higher charge/discharge rate. Therefore, high energy density capacitors play a significant role in modern electronic devices, power applications, space flight technologies, hybrid electric vehicles, portable defibrillators, and pulse power applications. Dielectric film capacitors represent an exceptional alternative for developing high energy density capacitors due to their high dielectric constants, outstanding breakdown voltages, and flexibility. The implementation of high aspect ratio dielectric inclusions such as nanowires into polymer capacitors could lead to further enhancement of its energy density. Therefore, this research effort is focused on the development of a new series of dielectric capacitors composed of nanowire reinforced polymer matrix composites. This concept of nanocomposite capacitors combines the extraordinary physical and chemical properties of the one-dimension (1D) nanoceramics and high dielectric strength of polymer matrices, leading to a capacitor with improved dielectric properties and energy density. Lead-free sodium niobate (NaNbO3) and lead-containing lead magnesium niobate-lead titanate (0.65PMN-0.35PT) nanowires were synthesized following hydrothermal and sol-gel approaches, respectively. The as-prepared nanowires were mixed with a polyvinylidene fluoride (PVDF) matrix using solution-casting method for nanocomposites fabrication. The dielectric constants and breakdown voltages of the NaNbO3/PVDF and 0.65PMN-0.35PT/PVDF nanocomposites were measured under different frequency ranges and temperatures in order to determine their maximum energy (J/cm3) and specific (J/g) densities. The electrical properties of the synthesized nanoceramics were compared with commercially available barium titanate (BaTiO3) and lead zirconate titanate Pb(ZrxTi1-x)O3 powders embedded into a PVDF matrix. The resulting dielectric film capacitors represent an excellent alternative energy storage device for future high energy density applications.

Exploration of near the origin and the asymptotic behaviors of the Kohn-Sham kinetic energy density for two-dimensional quantum dot systems with parabolic confinement

NASA Astrophysics Data System (ADS)

Jana, Subrata; Samal, Prasanjit

2018-01-01

The behaviors of the positive definite Kohn-Sham kinetic energy density near the origin and at the asymptotic region play a major role in designing meta-generalized gradient approximations (meta-GGAs) for exchange in low-dimensional quantum systems. It is shown that near the origin of the parabolic quantum dot, the Kohn-Sham kinetic energy differs from its von Weizsäcker counterpart due to the p orbital contributions, whereas in the asymptotic region, the difference between the above two kinetic energy densities goes as ˜ρ/(r ) r2 . All these behaviors have been explored using the two-dimensional isotropic quantum harmonic oscillator as a test case. Several meta-GGA ingredients are then studied by making use of the above findings. Also, the asymptotic conditions for the exchange energy density and the potential at the meta-GGA level are proposed using the corresponding behaviors of the two kinetic energy densities.

High energy density and efficiency achieved in nanocomposite film capacitors via structure modulation

NASA Astrophysics Data System (ADS)

Zeng, Yi; Shen, Zhong-Hui; Shen, Yang; Lin, Yuanhua; Nan, Ce-Wen

2018-03-01

Flexible dielectric polymer films with high energy storage density and high charge-discharge efficiency have been considered as promising materials for electrical power applications. Here, we design hierarchical structured nanocomposite films using nonlinear polymer poly(vinylidene fluoride-HFP) [P(VDF-HFP)] with inorganic h-boron nitride (h-BN) nanosheets by electrospinning and hot-pressing methods. Our results show that the addition of h-BN nanosheets and the design of the hierarchical multilayer structure in the nanocomposites can remarkably enhance the charge-discharge efficiency and energy density. A high charge-discharge efficiency of 78% and an energy density of 21 J/cm3 can be realized in the 12-layered PVDF/h-BN nanocomposite films. Phase-field simulation results reveal that the spatial distribution of the electric field in these hierarchical structured films affects the charge-discharge efficiency and energy density. This work provides a feasible route, i.e., structure modulation, to improve the energy storage performances for nanocomposite films.

Exploration of near the origin and the asymptotic behaviors of the Kohn-Sham kinetic energy density for two-dimensional quantum dot systems with parabolic confinement.

PubMed

Jana, Subrata; Samal, Prasanjit

2018-01-14

The behaviors of the positive definite Kohn-Sham kinetic energy density near the origin and at the asymptotic region play a major role in designing meta-generalized gradient approximations (meta-GGAs) for exchange in low-dimensional quantum systems. It is shown that near the origin of the parabolic quantum dot, the Kohn-Sham kinetic energy differs from its von Weizsäcker counterpart due to the p orbital contributions, whereas in the asymptotic region, the difference between the above two kinetic energy densities goes as ∼ρ(r)r 2 . All these behaviors have been explored using the two-dimensional isotropic quantum harmonic oscillator as a test case. Several meta-GGA ingredients are then studied by making use of the above findings. Also, the asymptotic conditions for the exchange energy density and the potential at the meta-GGA level are proposed using the corresponding behaviors of the two kinetic energy densities.

Flexible asymmetric supercapacitors with high energy and high power density in aqueous electrolytes

NASA Astrophysics Data System (ADS)

Cheng, Yingwen; Zhang, Hongbo; Lu, Songtao; Varanasi, Chakrapani V.; Liu, Jie

2013-01-01

Supercapacitors with both high energy and high power densities are critical for many practical applications. In this paper, we discuss the design and demonstrate the fabrication of flexible asymmetric supercapacitors based on nanocomposite electrodes of MnO2, activated carbon, carbon nanotubes and graphene. The combined unique properties of each of these components enable highly flexible and mechanically strong films that can serve as electrodes directly without using any current collectors or binders. Using these flexible electrodes and a roll-up approach, asymmetric supercapacitors with 2 V working voltage were successfully fabricated. The fabricated device showed excellent rate capability, with 78% of the original capacitance retained when the scan rate was increased from 2 mV s-1 to 500 mV s-1. Owing to the unique composite structure, these supercapacitors were able to deliver high energy density (24 W h kg-1) under high power density (7.8 kW kg-1) conditions. These features could enable supercapacitor based energy storage systems to be very attractive for a variety of critical applications, such as the power sources in hybrid electric vehicles and the back-up powers for wind and solar energy, where both high energy density and high power density are required.Supercapacitors with both high energy and high power densities are critical for many practical applications. In this paper, we discuss the design and demonstrate the fabrication of flexible asymmetric supercapacitors based on nanocomposite electrodes of MnO2, activated carbon, carbon nanotubes and graphene. The combined unique properties of each of these components enable highly flexible and mechanically strong films that can serve as electrodes directly without using any current collectors or binders. Using these flexible electrodes and a roll-up approach, asymmetric supercapacitors with 2 V working voltage were successfully fabricated. The fabricated device showed excellent rate capability, with 78% of the original capacitance retained when the scan rate was increased from 2 mV s-1 to 500 mV s-1. Owing to the unique composite structure, these supercapacitors were able to deliver high energy density (24 W h kg-1) under high power density (7.8 kW kg-1) conditions. These features could enable supercapacitor based energy storage systems to be very attractive for a variety of critical applications, such as the power sources in hybrid electric vehicles and the back-up powers for wind and solar energy, where both high energy density and high power density are required. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr33136e

Dissociative adsorption of environment-friendly insulating medium C3F7CN on Cu(111) and Al(111) surface: A theoretical evaluation

NASA Astrophysics Data System (ADS)

Zhang, Xiaoxing; Li, Yi; Chen, Dachang; Xiao, Song; Tian, Shuangshuang; Tang, Ju; Wang, Dibo

2018-03-01

SF6 is extensively used in electrical applications because of its excellent insulation and arc extinguishing performance, but its strong greenhouse effect has negative impact on the atmosphere. The excellent performance of C3F7CN in greenhouse effect, insulation ability, safety, and thermal stability has been demonstrated, indicating that this compound can replace SF6 in electrical applications. However, little information is available on the compatibility of C3F7CN with metals, such as copper and aluminum, in devices. Material compatibility between new gas mixtures and materials used in Gas Insulated Switchgear (GIS) should be investigated to determine the long-term behavior of materials. In this paper, dissociative adsorption of C3F7CN on Cu (1 1 1) and Al (1 1 1) surfaces were analyzed based on density functional theory. Adsorption energy, charge transfer, density of states, and electron density difference of interaction between C3F7CN and two metals were analyzed. It was found that the adsorption energy of C3F7CN adsorbed on Cu (1 1 1) and Al (1 1 1) is both below 0.8 eV. This value indicates that the interaction between them is not very strong. In addition, the dissociation reaction path of gas molecules after adsorption requires certain activation energy. Therefore, C3F7CN and copper or aluminum have certain compatibility and the compatibility of C3F7CN with aluminum is better than that of copper. Related results provide a reference for predicting the aging mechanism of equipment and the selection or modification of major materials for equipment.

Erosion dynamics of tungsten fuzz during ELM-like heat loading

NASA Astrophysics Data System (ADS)

Sinclair, G.; Tripathi, J. K.; Hassanein, A.

2018-04-01

Transient heat loading and high-flux particle loading on plasma facing components in fusion reactors can lead to surface melting and possible erosion. Helium-induced fuzz formation is expected to exacerbate thermal excursions, due to a significant drop in thermal conductivity. The effect of heating in edge-localized modes (ELMs) on the degradation and erosion of a tungsten (W) fuzz surface was examined experimentally in the Ultra High Flux Irradiation-II facility at the Center for Materials Under Extreme Environment. W foils were first exposed to low-energy He+ ion irradiation at a fluence of 2.6 × 1024 ions m-2 and a steady-state temperature of 1223 K. Then, samples were exposed to 1000 pulses of ELM-like heat loading, at power densities between 0.38 and 1.51 GW m-2 and at a steady-state temperature of 1223 K. Comprehensive erosion analysis measured clear material loss of the fuzz nanostructure above 0.76 GW m-2 due to melting and splashing of the exposed surface. Imaging of the surface via scanning electron microscopy revealed that sufficient heating at 0.76 GW m-2 and above caused fibers to form tendrils to conglomerate and form droplets. Repetitive thermal loading on molten surfaces then led to eventual splashing. In situ erosion measurements taken using a witness plate and a quartz crystal microbalance showed an exponential increase in mass loss with energy density. Compositional analysis of the witness plates revealed an increase in the W 4f signal with increasing energy density above 0.76 GW m-2. The reduced thermal stability of the fuzz nanostructure puts current erosion predictions into question and strengthens the importance of mitigation techniques.

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.

Vacuum Energy and Inflation: 3. Newtonian Cosmology & GR

ERIC Educational Resources Information Center

Huggins, Elisha

2013-01-01

This is paper #3 in a series of four papers on "vacuum energy" and inflation. In paper #1 [see EJ1024183] we discussed an example of what we have been calling vacuum energy. It is an energy with negative pressure whose energy density remains constant in an expanding space. We showed that an energy density with these properties exists…

On the effective Stefan-Boltzmann law and the thermodynamic origin of the initial radiation density in warm inflation

NASA Astrophysics Data System (ADS)

Gim, Yongwan; Kim, Wontae

2018-01-01

In this presentation, we are going to explain the thermodynamic origin of warm inflation scenarios by using the effetive Stefan-Boltzmann law. In the warm inflation scenarios, radiation always exists to avoid the graceful exit problem, for which the radiation energy density should be assumed to be finite at the starting point of the warm inflation. To find out the origin of the non-vanishing initial radiation energy density, we derive an effective Stefan-Boltzmann law by considering the non-vanishing trace of the total energy-momentum tensors. The effective Stefan-Boltzmann law successfully shows where the initial radiation energy density is thermodynamically originated from. And by using the above effective Stefan-Boltzmann law, we also study the cosmological scalar perturbation, and obtain the sufficient radiation energy density in order for GUT baryogenesis at the end of inflation. This proceeding is based on Ref. [1

UV irradiation-induced Raman spectra changes in lead silicate glasses

NASA Astrophysics Data System (ADS)

Jia, Hongzhi; Chen, Guanghui; Wang, Wencheng

2006-12-01

The Raman spectra for a series of lead silicate glasses with different PbO content before and after irradiation with different energy density by the frequency-quadrupled output of a Q-switched YAG laser (266 nm, 10 Hz repetition rate) were measured. The intensity of Pb-O band near 140 cm -1 in the Raman spectra decreases after UV irradiation and no new band appears in the Raman spectra. Exposed to the UV beam with high energy density (150 mJ/cm 2), although the total dose is smaller than the dose with low energy density (50 mJ/cm 2), the intensity of the 140 cm -1 band drops heavilier than exposed to the UV beam with low energy density. This shows that the UV irradiation can cause the broken of Pb-O bond in lead silicate glasses and the broken of Pb-O bond is related to the energy density of UV beam.

Energetics and Birth Rates of Supernova Remnants in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Leahy, D. A.

2017-03-01

Published X-ray emission properties for a sample of 50 supernova remnants (SNRs) in the Large Magellanic Cloud (LMC) are used as input for SNR evolution modeling calculations. The forward shock emission is modeled to obtain the initial explosion energy, age, and circumstellar medium density for each SNR in the sample. The resulting age distribution yields a SNR birthrate of 1/(500 yr) for the LMC. The explosion energy distribution is well fit by a log-normal distribution, with a most-probable explosion energy of 0.5× {10}51 erg, with a 1σ dispersion by a factor of 3 in energy. The circumstellar medium density distribution is broader than the explosion energy distribution, with a most-probable density of ˜0.1 cm-3. The shape of the density distribution can be fit with a log-normal distribution, with incompleteness at high density caused by the shorter evolution times of SNRs.

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

Alfonso Hernandez, Laura; Nelson, Tammie Renee; Gelin, Maxim F.

The interchromophoric energy-transfer pathways between weakly coupled units in a π-conjugated phenylene–ethynylene macrocycle and its half-ring analogue have been investigated using the nonadiabatic excited-state molecular dynamics approach. To track the flow of electronic transition density between macrocycle units, we formulate a transition density flux analysis adapted from the statistical minimum flow method previously developed to investigate vibrational energy flow. Following photoexcitation, transition density is primarily delocalized on two chromophore units and the system undergoes ultrafast energy transfer, creating a localized excited state on a single unit. In the macrocycle, distinct chromophore units donate transition density to a single acceptor unitmore » but do not interchange transition density among each other. We find that energy transfer in the macrocycle is slower than in the corresponding half ring because of the presence of multiple interfering energy-transfer pathways. Finally, simulation results are validated by modeling the fluorescence anisotropy decay.« less

Semi-local machine-learned kinetic energy density functional with third-order gradients of electron density

NASA Astrophysics Data System (ADS)

Seino, Junji; Kageyama, Ryo; Fujinami, Mikito; Ikabata, Yasuhiro; Nakai, Hiromi

2018-06-01

A semi-local kinetic energy density functional (KEDF) was constructed based on machine learning (ML). The present scheme adopts electron densities and their gradients up to third-order as the explanatory variables for ML and the Kohn-Sham (KS) kinetic energy density as the response variable in atoms and molecules. Numerical assessments of the present scheme were performed in atomic and molecular systems, including first- and second-period elements. The results of 37 conventional KEDFs with explicit formulae were also compared with those of the ML KEDF with an implicit formula. The inclusion of the higher order gradients reduces the deviation of the total kinetic energies from the KS calculations in a stepwise manner. Furthermore, our scheme with the third-order gradient resulted in the closest kinetic energies to the KS calculations out of the presented functionals.

Effects of Differing Energy Dependences in Three Level-Density Models on Calculated Cross Sections

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

Fu, C.Y.

2000-07-15

Three level-density formalisms commonly used for cross-section calculations are examined. Residual nuclides in neutron interaction with {sup 58}Ni are chosen to quantify the well-known differences in the energy dependences of the three formalisms. Level-density parameters for the Gilbert and Cameron model are determined from experimental information. Parameters for the back-shifted Fermi-gas and generalized superfluid models are obtained by fitting their level densities at two selected energies for each nuclide to those of the Gilbert and Cameron model, forcing the level densities of the three models to be as close as physically allowed. The remaining differences are in their energy dependencesmore » that, it is shown, can change the calculated cross sections and particle emission spectra significantly, in some cases or energy ranges by a factor of 2.« less

Integration of high capacity materials into interdigitated mesostructured electrodes for high energy and high power density primary microbatteries

NASA Astrophysics Data System (ADS)

Pikul, James H.; Liu, Jinyun; Braun, Paul V.; King, William P.

2016-05-01

Microbatteries are increasingly important for powering electronic systems, however, the volumetric energy density of microbatteries lags behind that of conventional format batteries. This paper reports a primary microbattery with energy density 45.5 μWh cm-2 μm-1 and peak power 5300 μW cm-2 μm-1, enabled by the integration of large volume fractions of high capacity anode and cathode chemistry into porous micro-architectures. The interdigitated battery electrodes consist of a lithium metal anode and a mesoporous manganese oxide cathode. The key enabler of the high energy and power density is the integration of the high capacity manganese oxide conversion chemistry into a mesostructured high power interdigitated bicontinuous cathode architecture and an electrodeposited dense lithium metal anode. The resultant energy density is greater than previously reported three-dimensional microbatteries and is comparable to commercial conventional format lithium-based batteries.

Energy density of ionospheric and solar wind origin ions in the near-Earth magnetotail during substorms

NASA Technical Reports Server (NTRS)

Daglis, Loannis A.; Livi, Stefano; Sarris, Emmanuel T.; Wilken, Berend

1994-01-01

Comprehensive energy density studies provide an important measure of the participation of various sources in energization processes and have been relatively rare in the literature. We present a statistical study of the energy density of the near-Earth magnetotail major ions (H(+), O(+), He(++), He(+)) during substorm expansion phase and discuss its implications for the solar wind/magnetosphere/ionosphere coupling. Our aim is to examine the relation between auroral activity and the particle energization during substorms through the correlation between the AE indices and the energy density of the major magnetospheric ions. The data we used here were collected by the charge-energy-mass (CHEM) spectrometer on board the Active Magnetospheric Particle Trace Explorer (AMPTE)/Charge Composition Explorer (CCE) satellite in the near-equatorial nightside magnetosphere, at geocentric distances approximately 7 to 9 R(sub E). CHEM provided the opportunity to conduct the first statistical study of energy density in the near-Earth magnetotail with multispecies particle data extending into the higher energy range (greater than or equal to 20 keV/E). the use of 1-min AE indices in this study should be emphasized, as the use (in previous statistical studies) of the (3-hour) Kp index or of long-time averages of AE indices essentially smoothed out all the information on substorms. Most distinct feature of our study is the excellent correlation of O(+) energy density with the AE index, in contrast with the remarkably poor He(++) energy density - AE index correlation. Furthermore, we examined the relation of the ion energy density to the electrojet activity during substorm growth phase. The O(+) energy density is strongly correlated with the pre-onset AU index, that is the eastward electrojet intensity, which represents the growth phase current system. Our investigation shows that the near-Earth magnetotail is increasingly fed with energetic ionospheric ions during periods of enhanced dissipation of auroral currents. The participation of the ionosphere in the substorm energization processes seems to be closely, although not solely, associated with the solar wind/magnetosphere coupling. That is, the ionosphere influences actively the substorm energization processes by responding to the increased solar wind/magnetosphere coupling as well as to the unloading dissipation of stored energy, with the increased feeding of new material into the magnetosphere.

Tunneling spectroscopy of a phosphorus impurity atom on the Ge(111)-(2 × 1) surface

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

Savinov, S. V.; Oreshkin, A. I., E-mail: oreshkin@spmlab.phys.msu.su, E-mail: oreshkin@spmlab.ru; Oreshkin, S. I.

2015-06-15

We numerically model the Ge(111)-(2 × 1) surface electronic properties in the vicinity of a P donor impurity atom located near the surface. We find a notable increase in the surface local density of states (LDOS) around the surface dopant near the bottom of the empty surface state band π*, which we call a split state due to its limited spatial extent and energetic position inside the band gap. We show that despite the well-established bulk donor impurity energy level position at the very bottom of the conduction band, a surface donor impurity on the Ge(111)-(2 × 1) surface mightmore » produce an energy level below the Fermi energy, depending on the impurity atom local environment. It is demonstrated that the impurity located in subsurface atomic layers is visible in a scanning tunneling microscope (STM) experiment on the Ge(111)-(2 × 1) surface. The quasi-1D character of the impurity image, observed in STM experiments, is confirmed by our computer simulations with a note that a few π-bonded dimer rows may be affected by the presence of the impurity atom. We elaborate a model that allows classifying atoms on the experimental low-temperature STM image. We show the presence of spatial oscillations of the LDOS by the density-functional theory method.« less

Stability of a relativistic rotating electron-positron jet: non-axisymmetric perturbations

NASA Astrophysics Data System (ADS)

Istomin, Ya. N.; Pariev, V. I.

1996-07-01

We investigate the linear stability of a hydrodynamic relativistic flow of magnetized plasma in the simplest case where the energy density of the electromagnetic fields is much greater than the energy density of the matter (including the rest mass energy). This is the force-free approximation. We consider the case of a light cylindrical jet in a cold and dense environment, so that the jet boundary remains at rest. Continuous and discrete spectra of frequencies are investigated analytically. An infinite sequence of eigenfrequencies is found near the edge of the Alfven continuum. Numerical calculations show that modes having reasonable values of azimuthal wavenumber m and radial number n are stable and their attenuation increment gamma is small. The dispersion curves omega=omega(k_----) have a minimum for k_----0~=1/R (R is the jet radius). This results in the accumulation of perturbations inside the jet with wavelengths of the order of the jet radius. The wave crests of the perturbation pattern formed in such a way move along the jet with a velocity exceeding the speed of light. If one has relativistic electrons emitting synchrotron radiation inside the jet, then this pattern will be visible. This provides us with a new type of superluminal source. If the jet is oriented close to the line of sight, then the observer will see knots moving backward to the core.

Vacuum energy density kicked by the electroweak crossover

NASA Astrophysics Data System (ADS)

Klinkhamer, F. R.; Volovik, G. E.

2009-10-01

Using q-theory, we show that the electroweak crossover can generate a remnant vacuum energy density Λ˜Eew8/EPlanck4, with effective electroweak energy scale Eew˜103GeV and reduced Planck-energy scale EPlanck˜1018GeV. The obtained expression for the effective cosmological constant Λ may be a crucial input for the suggested solution by Arkani-Hamed et al. of the triple cosmic coincidence puzzle (why the orders of magnitude of the energy densities of vacuum, matter, and radiation are approximately the same in the present Universe).

Method and apparatus for ceramic analysis

DOEpatents

Jankowiak, Ryszard J.; Schilling, Chris; Small, Gerald J.; Tomasik, Piotr

2003-04-01

The present invention relates to a method and apparatus for ceramic analysis, in particular, a method for analyzing density, density gradients and/or microcracks, including an apparatus with optical instrumentation for analysis of density, density gradients and/or microcracks in ceramics. The method provides analyzing density of a ceramic comprising exciting a component on a surface/subsurface of the ceramic by exposing the material to excitation energy. The method may further include the step of obtaining a measurement of an emitted energy from the component. The method may additionally include comparing the measurement of the emitted energy from the component with a predetermined reference measurement so as to obtain a density for said ceramic.

Ultimate energy density of observable cold baryonic matter.

PubMed

Lattimer, James M; Prakash, Madappa

2005-03-25

We demonstrate that the largest measured mass of a neutron star establishes an upper bound to the energy density of observable cold baryonic matter. An equation of state-independent expression satisfied by both normal neutron stars and self-bound quark matter stars is derived for the largest energy density of matter inside stars as a function of their masses. The largest observed mass sets the lowest upper limit to the density. Implications from existing and future neutron star mass measurements are discussed.

Tunneling of coupled methyl quantum rotors in 4-methylpyridine: Single rotor potential versus coupling interaction

NASA Astrophysics Data System (ADS)

Khazaei, Somayeh; Sebastiani, Daniel

2017-11-01

We study the influence of rotational coupling between a pair of methyl rotators on the tunneling spectrum in condensed phase. Two interacting adjacent methyl groups are simulated within a coupled-pair model composed of static rotational potential created by the chemical environment and the interaction potential between two methyl groups. We solve the two-dimensional time-independent Schrödinger equation analytically by expanding the wave functions on the basis set of two independent free-rotor functions. We investigate three scenarios which differ with respect to the relative strength of single-rotor and coupling potential. For each scenario, we illustrate the dependence of the energy level scheme on the coupling strength. It is found that the main determinant of splitting energy levels tends to be a function of the ratio of strengths of coupling and single-rotor potential. The tunnel splitting caused by coupling is maximized for the coupled rotors in which their total hindering potential is relatively shallow. Such a weakly hindered methyl rotational potential is predicted for 4-methylpyridine at low temperature. The experimental observation of multiple tunneling peaks arising from a single type of methyl group in 4-methylpyridine in the inelastic neutron scattering spectrum is widely attributed to the rotor-rotor coupling. In this regard, using a set of first-principles calculations combined with the nudged elastic band method, we investigate the rotational potential energy surface (PES) of the coaxial pairs of rotors in 4-methylpyridine. A Numerov-type method is used to numerically solve the two-dimensional time-independent Schrödinger equation for the calculated 2D-density functional theory profile. Our computed energy levels reproduce the observed tunneling transitions well. Moreover, the calculated density distribution of the three methyl protons resembles the experimental nuclear densities obtained from the Fourier difference method. By mapping the calculated first-principles PES on the model, it is confirmed that the hindering potential in 4-methylpyridine consists of proportionally shallow single-rotor potential to coupling interaction.

Tunneling of coupled methyl quantum rotors in 4-methylpyridine: Single rotor potential versus coupling interaction.

PubMed

Khazaei, Somayeh; Sebastiani, Daniel

2017-11-21

We study the influence of rotational coupling between a pair of methyl rotators on the tunneling spectrum in condensed phase. Two interacting adjacent methyl groups are simulated within a coupled-pair model composed of static rotational potential created by the chemical environment and the interaction potential between two methyl groups. We solve the two-dimensional time-independent Schrödinger equation analytically by expanding the wave functions on the basis set of two independent free-rotor functions. We investigate three scenarios which differ with respect to the relative strength of single-rotor and coupling potential. For each scenario, we illustrate the dependence of the energy level scheme on the coupling strength. It is found that the main determinant of splitting energy levels tends to be a function of the ratio of strengths of coupling and single-rotor potential. The tunnel splitting caused by coupling is maximized for the coupled rotors in which their total hindering potential is relatively shallow. Such a weakly hindered methyl rotational potential is predicted for 4-methylpyridine at low temperature. The experimental observation of multiple tunneling peaks arising from a single type of methyl group in 4-methylpyridine in the inelastic neutron scattering spectrum is widely attributed to the rotor-rotor coupling. In this regard, using a set of first-principles calculations combined with the nudged elastic band method, we investigate the rotational potential energy surface (PES) of the coaxial pairs of rotors in 4-methylpyridine. A Numerov-type method is used to numerically solve the two-dimensional time-independent Schrödinger equation for the calculated 2D-density functional theory profile. Our computed energy levels reproduce the observed tunneling transitions well. Moreover, the calculated density distribution of the three methyl protons resembles the experimental nuclear densities obtained from the Fourier difference method. By mapping the calculated first-principles PES on the model, it is confirmed that the hindering potential in 4-methylpyridine consists of proportionally shallow single-rotor potential to coupling interaction.

Observations of shear flows in high-energy-density plasmas

NASA Astrophysics Data System (ADS)

Harding, Eric C.

The research discussed in this thesis represents work toward the demonstration of experimental designs for creating a Kelvin-Helmholtz (KH) unstable shear layer in a high-energy-density (HED) plasma. Such plasmas are formed by irradiating materials with several kilo-Joules of laser light over a few nanoseconds, and are defined as having an internal pressure greater than one-million atmospheres. Similar plasmas exist in laboratory fusion experiments and in the astrophysical environment. The KH instability is a fundamental fluid instability that arises when strong velocity gradients exist at the interface between two fluids. The KH instability is important because it drives the mixing of fluids and initiates the transition to turbulence in the flow. Until now, the evolution of the KH instability has remained relatively unexplored in the HED regime This thesis presents the observations and analysis of two novel experiments carried out using two separate laser facilities. The first experiment used 1.4 kJ from the Nike laser to generate a supersonic flow of Al plasma over a low-density, rippled foam surface. The Al flow interacted with the foam and created distinct features that resulted from compressible effects. In this experiment there is little evidence of the KH instability. Nevertheless, this experimental design has perhaps pioneered a new method for generating a supersonic shear flow that has the potential to produce the KH instability if more laser energy is applied. The second experiment was performed on the Omega laser. In this case 4.3 kJ of laser energy drove a blast wave along a rippled foam/plastic interface. In response to the vorticity deposited and the shear flow established by the blast wave, the interface rolls up into large vorticies characteristic of the KH instability. The Omega experiment was the first HED experiment to capture the evolution of the KH instability.

Substrate Engineered Interconnected Graphene Electrodes with Ultrahigh Energy and Power Densities for Energy Storage Applications.

PubMed

Chaichi, Ardalan; Wang, Ying; Gartia, Manas Ranjan

2018-06-27

Supercapacitors combine the advantages of electrochemical storage technologies such as high energy density batteries and high power density capacitors. At 5-10 W h kg -1 , the energy densities of current supercapacitors are still significantly lower than the energy densities of lead acid (20-35 W h kg -1 ), Ni-metal hydride (40-100 W h kg -1 ), and Li-ion (120-170 W h kg -1 ) batteries. Recently, graphene-based supercapacitors have shown an energy density of 40-80 W h kg -1 . However, their performance is mainly limited because of the reversible agglomeration and restacking of individual graphene layers caused by π-π interactions. The restacking of graphene layers leads to significant decrease of ion-accessible surface area and the low capacitance of graphene-based supercapacitors. Here, we introduce a microstructure substrate-based method to produce a fully delaminated and stable interconnected graphene structure using flash reduction of graphene oxide in a few seconds. With this structure, we achieve the highest amount of volumetric capacitance obtained so far by any type of a pure carbon-based material. The affordable and scalable production method is capable of producing electrodes with an energy density of 0.37 W h cm -3 and a power density of 416.6 W cm -3 . This electrode maintained more than 91% of its initial capacitance after 5000 cycles. Moreover, combining with ionic liquid, this solvent-free graphene electrode material is highly promising for on-chip electronics, micro-supercapacitors, as well as high-power applications.

Nanoporous metal/oxide hybrid electrodes for electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Lang, Xingyou; Hirata, Akihiko; Fujita, Takeshi; Chen, Mingwei

2011-04-01

Electrochemical supercapacitors can deliver high levels of electrical power and offer long operating lifetimes, but their energy storage density is too low for many important applications. Pseudocapacitive transition-metal oxides such as MnO2 could be used to make electrodes in such supercapacitors, because they are predicted to have a high capacitance for storing electrical charge while also being inexpensive and not harmful to the environment. However, the poor conductivity of MnO2 (10-5-10-6 S cm-1) limits the charge/discharge rate for high-power applications. Here, we show that hybrid structures made of nanoporous gold and nanocrystalline MnO2 have enhanced conductivity, resulting in a specific capacitance of the constituent MnO2 (~1,145 F g-1) that is close to the theoretical value. The nanoporous gold allows electron transport through the MnO2, and facilitates fast ion diffusion between the MnO2 and the electrolytes while also acting as a double-layer capacitor. The high specific capacitances and charge/discharge rates offered by such hybrid structures make them promising candidates as electrodes in supercapacitors, combining high-energy storage densities with high levels of power delivery.

Nanoporous metal/oxide hybrid electrodes for electrochemical supercapacitors.

PubMed

Lang, Xingyou; Hirata, Akihiko; Fujita, Takeshi; Chen, Mingwei

2011-04-01

Electrochemical supercapacitors can deliver high levels of electrical power and offer long operating lifetimes, but their energy storage density is too low for many important applications. Pseudocapacitive transition-metal oxides such as MnO(2) could be used to make electrodes in such supercapacitors, because they are predicted to have a high capacitance for storing electrical charge while also being inexpensive and not harmful to the environment. However, the poor conductivity of MnO(2) (10(-5)-10(-6) S cm(-1)) limits the charge/discharge rate for high-power applications. Here, we show that hybrid structures made of nanoporous gold and nanocrystalline MnO(2) have enhanced conductivity, resulting in a specific capacitance of the constituent MnO(2) (~1,145 F g(-1)) that is close to the theoretical value. The nanoporous gold allows electron transport through the MnO(2), and facilitates fast ion diffusion between the MnO(2) and the electrolytes while also acting as a double-layer capacitor. The high specific capacitances and charge/discharge rates offered by such hybrid structures make them promising candidates as electrodes in supercapacitors, combining high-energy storage densities with high levels of power delivery.

Effects of alloying and transmutation impurities on stability and mobility of helium in tungsten under a fusion environment

NASA Astrophysics Data System (ADS)

Wu, Xuebang; Kong, Xiang-Shan; You, Yu-Wei; Liu, C. S.; Fang, Q. F.; Chen, Jun-Ling; Luo, G.-N.; Wang, Zhiguang

2013-07-01

The behaviour of helium in metals is particularly significant in fusion research due to the He-induced degradation of materials. A small amount of impurities introduced either by intentional alloying or by transmutation reactions, will interact with He and lead the microstructure and mechanical properties of materials to change. In this paper, we present the results of first-principles calculations on the interactions of He with impurities and He diffusion around them in tungsten (W), including the interstitials Be, C, N, O, and substitutional solutes Re, Ta, Tc, Nb, V, Os, Ti, Si, Zr, Y and Sc. We find that the trapping radii of interstitial atoms on He are much larger than those of substitutional solutes. The binding energies between the substitutional impurities and He increase linearly with the relative charge densities at the He occupation site, indicating that He atoms easily aggregate at the low charge density site. The sequence of diffusion energy barriers of He around the possible alloying elements is Ti > V > Os > Ta > Re. The present results suggest that Ta might be chosen as a relatively suitable alloying element compared with other possible ones.

Back-diffusion plasma generator for ionosphere study

NASA Astrophysics Data System (ADS)

Fang, H. K.; Oyama, K.-I.; Chen, A. B.

2017-11-01

To produce ionospheric plasma environments at ground level is essential to get information not only for the development of CubeSat-class spacecraft but also for the design of ionospheric plasma instruments and to confirm their performance. In this paper, we describe the principle of plasma generation and characteristics of the back-diffusion plasma source, which can produce in-lab plasma similar to the Earth’s ionosphere, E and F regions, conditions of electron and ion temperature and density. The ion and electron energy distributions of the plasma generated by a back-diffusion source are measured by means of a cleaned Langmuir probe and gridded particle energy analyzers. The ion motion in front of the source is investigated by a hard-sphere collision model in SIMION software and the simulation results are comparable with the findings of our experiment. Furthermore, plasma densities and ion temperatures at different positions in front of the source are also demonstrated. The back-diffusion source has been accommodated for ionospheric plasma productions in several Asian institutes. The plasma characteristics of the source shown in this paper will benefit space research groups in the development of space plasma instruments.

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

Schlagmüller, Michael; Liebisch, Tara Cubel; Engel, Felix

Within a dense environment (ρ ≈ 10 14 atoms/cm 3) at ultracold temperatures (T < 1 μK), a single atom excited to a Rydberg state acts as a reaction center for surrounding neutral atoms. At these temperatures, almost all neutral atoms within the Rydberg orbit are bound to the Rydberg core and interact with the Rydberg atom. We have studied the reaction rate and products for nS 87Rb Rydberg states, and we mainly observe a state change of the Rydberg electron to a high orbital angular momentum l, with the released energy being converted into kinetic energy of the Rydberg atom. Unexpectedly, the measurements show a threshold behavior at n ≈ 100 for the inelastic collision time leading to increased lifetimes of the Rydberg state independent of the densities investigated. Even at very high densities (ρ ≈ 4.8 x 10 14 cm -3), the lifetime of a Rydberg atom exceeds 10 μs at n > 140 compared to 1 μs at n = 90. In addition, a second observed reaction mechanism, namely, Rbmore » $$+\\atop{2}$$ molecule formation, was studied. Both reaction products are equally probable for n = 40, but the fraction of Rb + 2 created drops to below 10% for n ≥ 90.« less

Advances in molecular quantum chemistry contained in the Q-Chem 4 program package

NASA Astrophysics Data System (ADS)

Shao, Yihan; Gan, Zhengting; Epifanovsky, Evgeny; Gilbert, Andrew T. B.; Wormit, Michael; Kussmann, Joerg; Lange, Adrian W.; Behn, Andrew; Deng, Jia; Feng, Xintian; Ghosh, Debashree; Goldey, Matthew; Horn, Paul R.; Jacobson, Leif D.; Kaliman, Ilya; Khaliullin, Rustam Z.; Kuś, Tomasz; Landau, Arie; Liu, Jie; Proynov, Emil I.; Rhee, Young Min; Richard, Ryan M.; Rohrdanz, Mary A.; Steele, Ryan P.; Sundstrom, Eric J.; Woodcock, H. Lee, III; Zimmerman, Paul M.; Zuev, Dmitry; Albrecht, Ben; Alguire, Ethan; Austin, Brian; Beran, Gregory J. O.; Bernard, Yves A.; Berquist, Eric; Brandhorst, Kai; Bravaya, Ksenia B.; Brown, Shawn T.; Casanova, David; Chang, Chun-Min; Chen, Yunqing; Chien, Siu Hung; Closser, Kristina D.; Crittenden, Deborah L.; Diedenhofen, Michael; DiStasio, Robert A., Jr.; Do, Hainam; Dutoi, Anthony D.; Edgar, Richard G.; Fatehi, Shervin; Fusti-Molnar, Laszlo; Ghysels, An; Golubeva-Zadorozhnaya, Anna; Gomes, Joseph; Hanson-Heine, Magnus W. D.; Harbach, Philipp H. P.; Hauser, Andreas W.; Hohenstein, Edward G.; Holden, Zachary C.; Jagau, Thomas-C.; Ji, Hyunjun; Kaduk, Benjamin; Khistyaev, Kirill; Kim, Jaehoon; Kim, Jihan; King, Rollin A.; Klunzinger, Phil; Kosenkov, Dmytro; Kowalczyk, Tim; Krauter, Caroline M.; Lao, Ka Un; Laurent, Adèle D.; Lawler, Keith V.; Levchenko, Sergey V.; Lin, Ching Yeh; Liu, Fenglai; Livshits, Ester; Lochan, Rohini C.; Luenser, Arne; Manohar, Prashant; Manzer, Samuel F.; Mao, Shan-Ping; Mardirossian, Narbe; Marenich, Aleksandr V.; Maurer, Simon A.; Mayhall, Nicholas J.; Neuscamman, Eric; Oana, C. Melania; Olivares-Amaya, Roberto; O'Neill, Darragh P.; Parkhill, John A.; Perrine, Trilisa M.; Peverati, Roberto; Prociuk, Alexander; Rehn, Dirk R.; Rosta, Edina; Russ, Nicholas J.; Sharada, Shaama M.; Sharma, Sandeep; Small, David W.; Sodt, Alexander; Stein, Tamar; Stück, David; Su, Yu-Chuan; Thom, Alex J. W.; Tsuchimochi, Takashi; Vanovschi, Vitalii; Vogt, Leslie; Vydrov, Oleg; Wang, Tao; Watson, Mark A.; Wenzel, Jan; White, Alec; Williams, Christopher F.; Yang, Jun; Yeganeh, Sina; Yost, Shane R.; You, Zhi-Qiang; Zhang, Igor Ying; Zhang, Xing; Zhao, Yan; Brooks, Bernard R.; Chan, Garnet K. L.; Chipman, Daniel M.; Cramer, Christopher J.; Goddard, William A., III; Gordon, Mark S.; Hehre, Warren J.; Klamt, Andreas; Schaefer, Henry F., III; Schmidt, Michael W.; Sherrill, C. David; Truhlar, Donald G.; Warshel, Arieh; Xu, Xin; Aspuru-Guzik, Alán; Baer, Roi; Bell, Alexis T.; Besley, Nicholas A.; Chai, Jeng-Da; Dreuw, Andreas; Dunietz, Barry D.; Furlani, Thomas R.; Gwaltney, Steven R.; Hsu, Chao-Ping; Jung, Yousung; Kong, Jing; Lambrecht, Daniel S.; Liang, WanZhen; Ochsenfeld, Christian; Rassolov, Vitaly A.; Slipchenko, Lyudmila V.; Subotnik, Joseph E.; Van Voorhis, Troy; Herbert, John M.; Krylov, Anna I.; Gill, Peter M. W.; Head-Gordon, Martin

2015-01-01

A summary of the technical advances that are incorporated in the fourth major release of the Q-Chem quantum chemistry program is provided, covering approximately the last seven years. These include developments in density functional theory methods and algorithms, nuclear magnetic resonance (NMR) property evaluation, coupled cluster and perturbation theories, methods for electronically excited and open-shell species, tools for treating extended environments, algorithms for walking on potential surfaces, analysis tools, energy and electron transfer modelling, parallel computing capabilities, and graphical user interfaces. In addition, a selection of example case studies that illustrate these capabilities is given. These include extensive benchmarks of the comparative accuracy of modern density functionals for bonded and non-bonded interactions, tests of attenuated second order Møller-Plesset (MP2) methods for intermolecular interactions, a variety of parallel performance benchmarks, and tests of the accuracy of implicit solvation models. Some specific chemical examples include calculations on the strongly correlated Cr2 dimer, exploring zeolite-catalysed ethane dehydrogenation, energy decomposition analysis of a charged ter-molecular complex arising from glycerol photoionisation, and natural transition orbitals for a Frenkel exciton state in a nine-unit model of a self-assembling nanotube.

Simulation and Preliminary Design of a Cold Stream Experiment on Omega EP

NASA Astrophysics Data System (ADS)

Coffing, Shane; Angulo, Adrianna; Trantham, Matt; Malamud, Guy; Kuranz, Carolyn; Drake, R. P.

2017-10-01

Galaxies form within dark matter halos, accreting gas that may clump and eventually form stars. Infalling matter gradually increases the density of the halo, and, if cooling is insufficient, rising pressure forms a shock that slows the infalling gas, reducing star formation. However, galaxies with sufficient cooling become prolific star formers. A recent theory suggests that so called ``stream fed galaxies'' are able to acquire steady streams of cold gas via galactic ``filaments'' that penetrate the halo. The cold, dense filament flowing into a hot, less dense environment is potentially Kelvin-Helmholtz unstable. This instability may hinder the ability of the stream to deliver gas deeply enough into the halo. To study this process, we have begun preliminary design of a well-scaled laser experiment on Omega EP. We present here early simulation results and the physics involved. This work is funded by the U.S. Department of Energy, through the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, Grant Number DE-NA0002956, and the National Laser User Facility Program, Grant Number DE-NA0002719, and through the Laboratory for Laser Energetics, University of Rochester by the NNSA/OICF under Cooperative Agreement No. DE-NA0001944.

Time-Dependent Density Functional Theory for Extreme Environments

NASA Astrophysics Data System (ADS)

Baczewski, Andrew; Magyar, Rudolph; Shulenburger, Luke

2013-10-01

In recent years, DFT-MD has been shown to be a powerful tool for calculating the equation of state and constitutive properties of warm dense matter (WDM). These studies are validated through a number of experiments, including recently developed X-Ray Thomson Scattering (XRTS) techniques. Here, electronic temperatures and densities of WDM are accessible through x-ray scattering data, which is related to the system's dynamic structure factor (DSF)-a quantity that is accessible through DFT-MD calculations. Previous studies predict the DSF within the Born-Oppenheimer approximation, with the electronic state computed using Mermin DFT. A capability for including more general coupled electron-ion dynamics is desirable, to study both the effect on XRTS observables and the broader problem of electron-ion energy transfer in extreme WDM conditions. Progress towards such a capability will be presented, in the form of an Ehrenfest MD framework using TDDFT. Computational challenges and open theoretical questions will be discussed. 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 Security Administration under contract DE-AC04-94AL85000.

Spatial relationship between bone formation and mechanical stimulus within cortical bone: Combining 3D fluorochrome mapping and poroelastic finite element modelling.

PubMed

Carrieroa, A; Pereirab, A F; Wilson, A J; Castagno, S; Javaheri, B; Pitsillides, A A; Marenzana, M; Shefelbine, S J

2018-06-01

Bone is a dynamic tissue and adapts its architecture in response to biological and mechanical factors. Here we investigate how cortical bone formation is spatially controlled by the local mechanical environment in the murine tibia axial loading model (C57BL/6). We obtained 3D locations of new bone formation by performing 'slice and view' 3D fluorochrome mapping of the entire bone and compared these sites with the regions of high fluid velocity or strain energy density estimated using a finite element model, validated with ex-vivo bone surface strain map acquired ex-vivo using digital image correlation. For the comparison, 2D maps of the average bone formation and peak mechanical stimulus on the tibial endosteal and periosteal surface across the entire cortical surface were created. Results showed that bone formed on the periosteal and endosteal surface in regions of high fluid flow. Peak strain energy density predicted only the formation of bone periosteally. Understanding how the mechanical stimuli spatially relates with regions of cortical bone formation in response to loading will eventually guide loading regime therapies to maintain or restore bone mass in specific sites in skeletal pathologies.

Plasma polymerized high energy density dielectric films for capacitors

NASA Technical Reports Server (NTRS)

Yamagishi, F. G.

1983-01-01

High energy density polymeric dielectric films were prepared by plasma polymerization of a variety of gaseous monomers. This technique gives thin, reproducible, pinhole free, conformable, adherent, and insoluble coatings and overcomes the processing problems found in the preparation of thin films with bulk polymers. Thus, devices are prepared completely in a vacuum environment. The plasma polymerized films prepared all showed dielectric strengths of greater than 1000 kV/cm and in some cases values of greater than 4000 kV/cm were observed. The dielectric loss of all films was generally less than 1% at frequencies below 10 kHz, but this value increased at higher frequencies. All films were self healing. The dielectric strength was a function of the polymerization technique, whereas the dielectric constant varied with the structure of the starting material. Because of the thin films used (thickness in the submicron range) surface smoothness of the metal electrodes was found to be critical in obtaining high dielectric strengths. High dielectric strength graft copolymers were also prepared. Plasma polymerized ethane was found to be thermally stable up to 150 C in the presence of air and 250 C in the absence of air. No glass transitions were observed for this material.

Kaon condensation in dense matter

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

Carlson, J.; Heiselberg, H.; Pandharipande, V. R.

The kaon energy in neutron matter is calculated analytically with the Klein-Gordon equation, by making a Wigner-Seitz cell approximation and employing a K{sup -}N square well potential. The transition from the low density Lenz potential, proportional to scattering length, to the high density Hartree potential is found to begin at fairly low densities. Exact nonrelativistic calculations of the kaon energy in a simple cubic crystal of neutrons are used to test the Wigner-Seitz and the Ericson-Ericson approximation methods. In this case the frequently used Erickson-Erickson approximation is found to be fairly accurate up to twice nuclear matter density. All themore » calculations indicate that by {approx}4 times nuclear matter density the Hartree limit is reached. We also show that in the Hartree limit the energy of zero momentum kaons does not have relativistic energy dependent factors present in the low density expansions. The results indicate that the density for kaon condensation is higher than previously estimated.« less

Study of the underlying event at forward rapidity in pp collisions at $$ \\sqrt{s}=0.9,2.76,\\;\\mathrm{and}\\;7\\;\\mathrm{TeV} $$

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

Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.

The underlying event activity in proton-proton collisions at forward pseudo-rapidity (-6.6 < η < -5.2) is studied with the CMS detector at the LHC, using a novel observable: the ratio of the forward energy density, dE/dη, for events with a charged-particle jet produced at central pseudorapidity (|η jet| < 2) to the forward energy density for inclusive events. This forward energy density ratio is measured as a function of the central jet transverse momentum, p (T), at three different pp centre-of-mass energies (more » $$\\sqrt{s}$$ = 0.9, 2.76, and 7 TeV). In addition, the evolution of the forward energy density is studied in inclusive events and in events with a central jet. The results are compared to those of Monte Carlo event generators for pp collisions and are discussed in terms of the underlying event. Whereas the dependence of the forward energy density ratio on jet p T at each separately can be well reproduced by some models, all models fail to simultaneously describe the increase of the forward energy density with in both inclusive events and in events with a central jet.« less

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

NASA Technical Reports Server (NTRS)

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

1986-01-01

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

Self-similar relativistic blast waves with energy injection

NASA Astrophysics Data System (ADS)

van Eerten, Hendrik

2014-08-01

A sufficiently powerful astrophysical source with power-law luminosity in time will give rise to a self-similar relativistic blast wave with a reverse shock travelling into the ejecta and a forward shock moving into the surrounding medium. Once energy injection ceases and the last energy is delivered to the shock front, the blast wave will transit into another self-similar stage depending only on the total amount of energy injected. I describe the effect of limited duration energy injection into environments with density depending on radius as a power law, emphasizing optical/X-ray Gamma-ray Burst afterglows as applications. The blast wave during injection is treated analytically, the transition following last energy injection with one-dimensional simulations. Flux equations for synchrotron emission from the forward and reverse shock regions are provided. The reverse shock emission can easily dominate, especially with different magnetizations for both regions. Reverse shock emission is shown to support both the reported X-ray and optical correlations between afterglow plateau duration and end time flux, independently of the luminosity power-law slope. The model is demonstrated by application to bursts 120521A and 090515, and can accommodate their steep post-plateau light-curve slopes.

Evaluation of the suitability and performance of cassava waste (peel) extracts in a microbial fuel cell for supplementary and sustainable energy production.

PubMed

Adekunle, Ademola; Raghavan, Vijaya

2017-01-01

In a number of energy-poor nations, peel from cassava processing represents one of the most abundant sources of lignocellulosic biomass. This peel is mostly discarded indiscriminately and eventually constitutes a problem to the environment. However, energy can be extracted from this peel in a microbial fuel cell. In this study, the viability of cassava peel extract as a substrate in a single-chamber air cathode microbial fuel cell is demonstrated, and optimum performance conditions are explored. The effects of different pretreatments on the extract are also discussed in the context of observed changes in the internal resistances, conductivity and Coulombic efficiencies. At the best conditions examined, the extract from cassava peel fermented for 168 h and adjusted to a pH of 7.63 attained a peak voltage of 687 mV ± 21 mV, a power density of 155 mW m -3 of reactor volume and a Coulombic efficiency of 11 %. Although this energy is limited to direct use, systems exist that can effectively harvest and boost the energy to levels sufficient for supplementary energy usage in cassava producing regions.

High-efficiency acceleration in the laser wakefield by a linearly increasing plasma density

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

Dong, Kegong; Wu, Yuchi; Zhu, Bin

The acceleration length and the peak energy of the electron beam are limited by the dephasing effect in the laser wakefield acceleration with uniform plasma density. Based on 2D-3V particle in cell simulations, the effects of a linearly increasing plasma density on the electron acceleration are investigated broadly. Comparing with the uniform plasma density, because of the prolongation of the acceleration length and the gradually increasing accelerating field due to the increasing plasma density, the electron beam energy is twice higher in moderate nonlinear wakefield regime. Because of the lower plasma density, the linearly increasing plasma density can also avoidmore » the dark current caused by additional injection. At the optimal acceleration length, the electron energy can be increased from 350 MeV (uniform) to 760 MeV (linearly increasing) with the energy spread of 1.8%, the beam duration is 5 fs and the beam waist is 1.25 μm. This linearly increasing plasma density distribution can be achieved by a capillary with special gas-filled structure, and is much more suitable for experiment.« less