Laboratory Studies of Thermal Energy Charge Transfer of Multiply Charged Ions in Astrophysical Plasmas

NASA Technical Reports Server (NTRS)

Kwong, Victor H. S.

2003-01-01

The laser ablation/ion storage facility at the UNLV Physics Department has been dedicated to the study of atomic and molecular processes in low temperature plasmas. Our program focuses on the charge transfer (electron capture) of multiply charged ions and neutrals important in astrophysics. The electron transfer reactions with atoms and molecules is crucial to the ionization condition of neutral rich photoionized plasmas. With the successful deployment of the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Chandra X-ray Observatory by NASA high resolution VUV and X-ray emission spectra fiom various astrophysical objects have been collected. These spectra will be analyzed to determine the source of the emission and the chemical and physical environment of the source. The proper interpretation of these spectra will require complete knowledge of all the atomic processes in these plasmas. In a neutral rich environment, charge transfer can be the dominant process. The rate coefficients need to be known accurately. We have also extended our charge transfer measurements to KeV region with a pulsed ion beam. The inclusion of this facility into our current program provides flexibility in extending the measurement to higher energies (KeV) if needed. This flexibility enables us to address issues of immediate interest to the astrophysical community as new observations are made by high resolution space based observatories.

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

Hu, Dehua; Liu, Qing; Tisdale, Jeremy

This paper reports Seebeck effects driven by both surface polarization difference and entropy difference by using intramolecular charge-transfer states in n-type and p-type conjugated polymers, namely IIDT and IIDDT, based on vertical conductor/polymer/conductor thin-film devices. Large Seebeck coefficients of -898 V/K and 1300 V/K from are observed from n-type IIDT p-type IIDDT, respectively, when the charge-transfer states are generated by a white light illumination of 100 mW/cm2. Simultaneously, electrical conductivities are increased from almost insulating states in dark condition to conducting states under photoexcitation in both n-type IIDT and p-type IIDDT devices. We find that the intramolecular charge-transfer states canmore » largely enhance Seebeck effects in the n-type IIDT and p-type IIDDT devices driven by both surface polarization difference and entropy difference. Furthermore, the Seebeck effects can be shifted between polarization and entropy regimes when electrical conductivities are changed. This reveals a new concept to develop Seebeck effects by controlling polarization and entropy regimes based on charge-transfer states in vertical conductor/polymer/conductor thin-film devices.« less

Ambipolar thermoelectric power of chemically-exfoliated RuO2 nanosheets

NASA Astrophysics Data System (ADS)

Kim, Jeongmin; Yoo, Somi; Moon, Hongjae; Kim, Se Yun; Ko, Dong-Su; Roh, Jong Wook; Lee, Wooyoung

2018-01-01

The electrical conductivity and Seebeck coefficient of RuO2 nanosheets are enhanced by metal nanoparticle doping using Ag-acetate solutions. In this study, RuO2 monolayer and bilayer nanosheets exfoliated from layered alkali metal ruthenates are transferred to Si substrates for device fabrication, and the temperature dependence of their conductivity and Seebeck coefficients is investigated. For pristine RuO2 nanosheets, the sign of the Seebeck coefficient changes with temperature from 350-450 K. This indicates that the dominant type of charge carrier is dependent on the temperature, and the RuO2 nanosheets show ambipolar carrier transport behavior. By contrast, the sign of the Seebeck coefficient for Ag nanoparticle-doped RuO2 nanosheets does not change with temperature, indicating that the extra charge carriers from metal nanoparticles promote n-type semiconductor behavior.

Charge Transfer Rate in Collisions of H + Ions with Si Atoms

NASA Astrophysics Data System (ADS)

Kimura, M.; Sannigrahi, A. B.; Gu, J. P.; Hirsch, G.; Buenker, R. J.; Shimamura, I.

1996-12-01

Charge transfer in Si(3P, 1D) + H+ collisions is studied theoretically by using a semiclassical molecular representation with six molecular channels for the triplet manifold and four channels for the singlet manifold at collision energies above 30 eV, and by using a fully quantum mechanical approach with two molecular channels for both triplet and singlet manifolds below 30 eV. The ab initio potential curves and nonadiabatic coupling matrix elements for the HSi+ system are obtained from multireference single- and double-excitation configuration interaction (MRD-CI) calculations employing a relatively large basis set. The present rate coefficients for charge transfer to Si+(4P) formation resulting from H+ + Si(3P) collisions are found to be large with values from 1 x 10-10 cm-3 s-1 at 1000 K to 1 x 10-8 cm-3 s-1 at 100,000 K. The rate coefficient for Si+(2P) formation, resulting from H+ + Si(3P) collisions, is found to be much smaller because of a larger energy defect from the initial state. These calculated rates are much larger than those reported by Baliunas & Butler, who estimated a value of 10-11 cm-3 s-1 in their coronal plasma study. The present result may be relevant to the description of the silicon ionization equilibrium.

Measurements of ion-molecule reactions of He plus, H plus, HeH plus with H sub 2 and D sub 2

NASA Technical Reports Server (NTRS)

Johnsen, R.; Biondi, M. A.

1974-01-01

A drift tube mass spectrometer apparatus has been used to determine the rate coefficient, energy dependence and product ions of the reaction He(+) +H2. The total rate coefficient at 300 K is 1.1 plus or minus 0.1) 10 to minus 13th power cu cm/sec. The reaction proceeds principally by dissociative charge transfer to produce H(+), with the small remainder going by charge transfer to produce H2(+) and by atom rearrangement to produce HeH(+). The rate coefficient increases slowly with increasing ion mean energy, reaching a value of 2.8 x ten to the minus 13th power cu cm sec at 0.18 eV. The corresponding reaction with deuterium, He(+) + D2, exhibits a value (5 plus or minus 1) x 10 to the minus 14th cu cm/sec at 300K. The reaction rates for conversion of H(+) and HeH(+) to H3(+) on collisions with H2 molecules are found to agree well with results of previous investigations.

Spectroscopic characterization of charge-transfer complexes of morpholine with chloranilic and picric acids in organic media: crystal structure of bis(morpholinium 2,4,6-trinitrocyclohexanolate).

PubMed

Refat, Moamen S; El-Zayat, Lamia A; Yeşilel, Okan Zafer

2010-02-01

Electron donor-acceptor interaction of morpholine (morp) with chloranilic acid (cla) and picric acid (pa) as pi-acceptors was investigated spectrophotometrically and found to form stable charge-transfer (CT) complexes (n-pi*) of [(Hmorp)(2)(cla)] and [(Hmorp)(pa)](2). The donor site involved in CT interaction is morpholine nitrogen. These complexes are easily synthesized from the reaction of morp with cla and pa within MeOH and CHCl(3) solvents, respectively. (1)HNMR, IR, elemental analyses, and UV-vis techniques characterize the two morpholinium charge-transfer complexes. Benesi-Hildebrand and its modification methods were applied to the determination of association constant (K), molar extinction coefficient (epsilon). The X-ray crystal structure was carried out for the interpretation the predict structure of the [(Hmorp)(pa)](2) complex. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Spectroscopic and structural characterization of the charge-transfer interaction of N,N'-bis-alkyl derivatives of 1,4,6,8-naphthalenediimide with chloranilic and picric acids.

PubMed

Refat, Moamen S; Ahmed, Hamdy A; Grabchev, Ivo; El-Zayat, Lamia A

2008-09-01

Charge-transfer (CT) complexes formed from the reactions of two N,N'-bis-alkyl derivatives of 1,4,6,8-naphthalenediimide such as N,N'-bis[2-hydroxyethyl)]-1,4,6,8-naphthalenediimide (BHENDI) and N,N'-bis-[2-N,N-dimethylaminoethyl)]-1,4,6,8-naphthalenediimide (BDMAENDI) with chloranilic acid (CLA) and piciric acid (PA) as pi-acceptors, have been studied spectrophotometrically in methanol and chloroform, respectively at 25 degrees C. The photometric titration curves for the reactions indicated that the data obtained refer to 1:1 charge-transfer complexes of [(BHENDI)(CLA)], [(BDMAENDI)(CLA)], [(BHENDI)(PA)] and [(BDMAENDI)(PA)] were formed. Benesi-Hildebrand and its modification methods were applied to the determination of association constant (K), molar extinction coefficient (epsilon). The solid CT complexes have been synthesized and characterization by different spectral methods.

Spectroscopic and structural characterization of the charge-transfer interaction of N,N'-bis-alkyl derivatives of 1,4,6,8-naphthalenediimide with chloranilic and picric acids

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Ahmed, Hamdy A.; Grabchev, Ivo; El-Zayat, Lamia A.

2008-09-01

Charge-transfer (CT) complexes formed from the reactions of two N,N'-bis-alkyl derivatives of 1,4,6,8-naphthalenediimide such as N, N'-bis[2-hydroxyethyl)]-1,4,6,8-naphthalenediimide (BHENDI) and N, N'-bis-[2- N, N-dimethylaminoethyl)]-1,4,6,8-naphthalenediimide (BDMAENDI) with chloranilic acid (CLA) and piciric acid (PA) as π-acceptors, have been studied spectrophotometrically in methanol and chloroform, respectively at 25 °C. The photometric titration curves for the reactions indicated that the data obtained refer to 1:1 charge-transfer complexes of [(BHENDI)(CLA)], [(BDMAENDI)(CLA)], [(BHENDI)(PA)] and [(BDMAENDI)(PA)] were formed. Benesi-Hildebrand and its modification methods were applied to the determination of association constant ( K), molar extinction coefficient ( ɛ). The solid CT complexes have been synthesized and characterization by different spectral methods.

Spectroscopic characterization of charge-transfer complexes of morpholine with chloranilic and picric acids in organic media: Crystal structure of bis(morpholinium 2,4,6-trinitrocyclohexanolate)

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; El-Zayat, Lamia A.; Yeşilel, Okan Zafer

2010-02-01

Electron donor-acceptor interaction of morpholine (morp) with chloranilic acid (cla) and picric acid (pa) as π-acceptors was investigated spectrophotometrically and found to form stable charge-transfer (CT) complexes (n-π*) of [(Hmorp) 2(cla)] and [(Hmorp)(pa)] 2. The donor site involved in CT interaction is morpholine nitrogen. These complexes are easily synthesized from the reaction of morp with cla and pa within MeOH and CHCl 3 solvents, respectively. 1HNMR, IR, elemental analyses, and UV-vis techniques characterize the two morpholinium charge-transfer complexes. Benesi-Hildebrand and its modification methods were applied to the determination of association constant ( K), molar extinction coefficient ( ɛ). The X-ray crystal structure was carried out for the interpretation the predict structure of the [(Hmorp)(pa)] 2 complex.

Associative charge transfer reactions. Temperature effects and mechanism of the gas-phase polymerization of propene initiated by a benzene radical cation.

PubMed

Ibrahim, Yehia; Meot-Ner Mautner, Michael; El-Shall, M Samy

2006-07-13

In associative charge transfer (ACT) reactions, a core ion activates ligand molecules by partial charge transfer. The activated ligand polymerizes, and the product oligomer takes up the full charge from the core ion. In the present system, benzene(+*) (Bz(+*)) reacts with two propene (Pr) molecules to form a covalently bonded ion, C(6)H(6)(+*) + 2 C(3)H(6) --> C(6)H(12)(+*) + C(6)H(6). The ACT reaction is activated by a partial charge transfer from Bz(+*) to Pr in the complex, and driven to completion by the formation of a covalent bond in the polymerized product. An alternative channel forms a stable association product (Bz.Pr)(+*), with an ACT/association product ratio of 60:40% that is independent of pressure and temperature. In contrast to the Bz(+*)/propene system, ACT polymerization is not observed in the Bz(+*)/ethylene (Et) system since charge transfer in the Bz(+*)(Et) complex is inefficient to activate the reaction. The roles of charge transfer in these complexes are verified by ab initio calculations. The overall reaction of Bz(+*) with Pr follows second-order kinetics with a rate constant of k (304 K) = 2.1 x 10(-12) cm(3) s(-1) and a negative temperature coefficient of k = aT(-5.9) (or an activation energy of -3 kcal/mol). The kinetic behavior is similar to sterically hindered reactions and suggests a [Bz(+*) (Pr)]* activated complex that proceeds to products through a low-entropy transition state. The temperature dependence shows that ACT reactions can reach a unit collision efficiency below 100 K, suggesting that ACT can initiate polymerization in cold astrochemical environments.

First principles molecular dynamics of molten NaI: Structure, self-diffusion, polarization effects, and charge transfer

NASA Astrophysics Data System (ADS)

Galamba, N.; Costa Cabral, B. J.

2007-09-01

The structure and self-diffusion of NaI and NaCl at temperatures close to their melting points are studied by first principles Hellmann-Feynman molecular dynamics (HFMD). The results are compared with classical MD using rigid-ion (RI) and shell-model (ShM) interionic potentials. HFMD for NaCl was reported before at a higher temperature [N. Galamba and B. J. Costa Cabral, J. Chem. Phys. 126, 124502 (2007)]. The main differences between the structures predicted by HFMD and RI MD for NaI concern the cation-cation and the anion-cation pair correlation functions. A ShM which allows only for the polarization of I- reproduces the main features of the HFMD structure of NaI. The inclusion of polarization effects for both ionic species leads to a more structured ionic liquid, although a good agreement with HFMD is also observed. HFMD Green-Kubo self-diffusion coefficients are larger than those obtained from RI and ShM simulations. A qualitative study of charge transfer in molten NaI and NaCl was also carried out with the Hirshfeld charge partitioning method. Charge transfer in molten NaI is comparable to that in NaCl, and results for NaCl at two temperatures support the view that the magnitude of charge transfer is weakly state dependent for ionic systems. Finally, Hirshfeld charge distributions indicate that differences between RI and HFMD results are mainly related to polarization effects, while the influence of charge transfer fluctuations is minimal for these systems.

Communication: Modeling of concentration dependent water diffusivity in ionic solutions: Role of intermolecular charge transfer

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

Yao, Yi; Berkowitz, Max L., E-mail: maxb@unc.edu, E-mail: ykanai@unc.edu; Kanai, Yosuke, E-mail: maxb@unc.edu, E-mail: ykanai@unc.edu

2015-12-28

The translational diffusivity of water in solutions of alkali halide salts depends on the identity of ions, exhibiting dramatically different behavior even in solutions of similar salts of NaCl and KCl. The water diffusion coefficient decreases as the salt concentration increases in NaCl. Yet, in KCl solution, it slightly increases and remains above bulk value as salt concentration increases. Previous classical molecular dynamics simulations have failed to describe this important behavior even when polarizable models were used. Here, we show that inclusion of dynamical charge transfer among water molecules produces results in a quantitative agreement with experiments. Our results indicatemore » that the concentration-dependent diffusivity reflects the importance of many-body effects among the water molecules in aqueous ionic solutions. Comparison with quantum mechanical calculations shows that a heterogeneous and extended distribution of charges on water molecules around the ions due to ion-water and also water-water charge transfer plays a very important role in controlling water diffusivity. Explicit inclusion of the charge transfer allows us to model accurately the difference in the concentration-dependent water diffusivity between Na{sup +} and K{sup +} ions in simulations, and it is likely to impact modeling of a wide range of systems for medical and technological applications.« less

Seebeck Effects in N-Type and P-Type Polymers Driven Simultaneously by Surface Polarization and Entropy Differences Based on Conductor/Polymer/Conductor Thin-Film Devices

DOE PAGES

Hu, Dehua; Liu, Qing; Tisdale, Jeremy; ...

2015-04-15

This paper reports Seebeck effects driven by both surface polarization difference and entropy difference by using intramolecular charge-transfer states in n-type and p-type conjugated polymers, namely IIDT and IIDDT, based on vertical conductor/polymer/conductor thin-film devices. Large Seebeck coefficients of -898 V/K and 1300 V/K from are observed from n-type IIDT p-type IIDDT, respectively, when the charge-transfer states are generated by a white light illumination of 100 mW/cm2. Simultaneously, electrical conductivities are increased from almost insulating states in dark condition to conducting states under photoexcitation in both n-type IIDT and p-type IIDDT devices. We find that the intramolecular charge-transfer states canmore » largely enhance Seebeck effects in the n-type IIDT and p-type IIDDT devices driven by both surface polarization difference and entropy difference. Furthermore, the Seebeck effects can be shifted between polarization and entropy regimes when electrical conductivities are changed. This reveals a new concept to develop Seebeck effects by controlling polarization and entropy regimes based on charge-transfer states in vertical conductor/polymer/conductor thin-film devices.« less

Characterization of the Pseudocapacitive Nature of Surface Bound Prussian Blue Analogues

NASA Astrophysics Data System (ADS)

Clark, Daniel; Hampton, Jennifer

With the increased use of intermittent renewable energy sources, more efficient methods of energy storage must be explored. Electrochemical capacitors provide a larger volumetric charge density than physical capacitors while maintaining fast charge and discharge rates. Prussian Blue analogues (nickel and cobalt hexacyanoferrate) are ideal pseudocapacitors for frequent charge and discharge cycles since the crystalline structure does not physically change during switching, causing less stress on the film. This project examines the charge transfer and diffusion coefficients for nickel and nickel-cobalt thin films modified with potassium hexacyanoferrate. The films were examined using a scanning electron microscope, an atomic force microscope and an electrochemical workstation to determine their composition, topography and psuedocapacitive nature. Preliminary data suggest that nickel-cobalt films have a larger quantity of charge and have a lower diffusion coefficient per charge than nickel films. This work is supported by the Hope College Nyenhuis Faculty Development Fund, the Hope College Department of Physics Guess Research Fund, and the National Science Foundation under Grants RUI-DMR-1104725, MRI-CHE-0959282, and MRI-CHE-1126462.

An estimating formula for ion-atom association rates in gases

NASA Technical Reports Server (NTRS)

Chatterjee, B. K.; Johnsen, R.

1990-01-01

A simple estimating formula is derived for rate coefficients of three-body ion atom association in gases and compare its predictions to experimental data on ion association and three-body radiative charge transfer reactions of singly- and doubly-charged rare-gas ions. The formula appears to reproduce most experimental data quite well. It may be useful for estimating the rates of reactions that have not been studied in the laboratory.

Charge transfer complex of some nervous and brain drugs - Part 1: Synthesis, spectroscopic, analytical and biological studies on the reaction between haloperidol antipsychotic drugs with π-acceptors

NASA Astrophysics Data System (ADS)

El-Habeeb, Abeer A.; Al-Saif, Foziah A.; Refat, Moamen S.

2013-02-01

Donor-acceptor interactions between the electron donor haloperidol (HPL) and π-acceptors like 7,7,8,8-tetracyanoquinodimethane (TCNQ) and picric acid (PA) have been studied spectrophotometrically in CH3OH solvent. The donor-acceptor (charge transfer complexes) were discussed in terms of formation constant (KCT), molar extinction coefficient (ɛCT), standard free energy (ΔGo), oscillator strength (ƒ), transition dipole moment (μ), resonance energy (RN) and ionization potential (ID). The stoichiometry of these complexes was found to be 1:1 M ratio and having the formulas [(HPL)(TCNQ)] and [(HPL)(PA)], respectively. The charge transfer interaction was successfully applied to determine of HPL drug using mentioned common π-acceptors also, the results obtained herein are satisfactory for estimation of HPL compound in the pharmaceutical form. The formed solid charge-transfer complexes were also isolated and characterized using elemental analysis, conductivity, (infrared, Raman, and 1H NMR) spectra and X-ray powder diffraction (XRD). The experimental data of elemental analyses are in agreement with calculated data. The infrared spectra of both HPL complexes are confirming the participation of sbnd OH of 4-hydroxy-1-piperidyl moiety in the donor-acceptor chelation. The morphological surface of the resulted charge transfer complexes were investigated using scanning electron microscopy (SEM). The thermogravimetric analysis (TG/DTG) and differential scanning calorimetry (DSC) techniques were performed to give knowledge about the thermal stability behavior of the synthesized charge transfer complexes. Thermodynamic parameters were computed from the thermal decomposition data. These complexes were also tested for their antimicrobial activity against six different microorganisms, and the results were compared with the parent drug.

Charge transfer and ionization in collisions of Si3+ with H from low to high energy

NASA Astrophysics Data System (ADS)

Wang, J. G.; He, B.; Ning, Y.; Liu, C. L.; Yan, J.; Stancil, P. C.; Schultz, D. R.

2006-11-01

Charge transfer processes due to collisions of ground state Si3+(3sS1) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) and classical-trajectory Monte Carlo (CTMC) methods. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained from Herrero [J. Phys. B 29, 5583 (1996)] which were calculated with a full configuration-interaction method. Total and state-selective single-electron capture cross sections are obtained for collision energies from 0.01eV/u to 1MeV/u . Total and state-selective rate coefficients are also presented for temperatures from 2×103K to 107K . Comparison with existing data reveals that the total CTMC cross sections are in good agreement with the experimental measurements at the higher considered energies and that previous Landau-Zener calculations underestimate the total rate coefficients by a factor of up to two. The CTMC calculations of target ionization are presented for high energies.

Spectroscopic and physical measurements on charge-transfer complexes: Interactions between norfloxacin and ciprofloxacin drugs with picric acid and 3,5-dinitrobenzoic acid acceptors

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Elfalaky, A.; Elesh, Eman

2011-03-01

Charge-transfer complexes formed between norfloxacin (nor) or ciprofloxacin (cip) drugs as donors with picric acid (PA) and/or 3,5-dinitrobenzoic acid (DNB) as π-acceptors have been studied spectrophotometrically in methanol solvent at room temperature. The results indicated the formation of CT-complexes with molar ratio1:1 between donor and acceptor at maximum CT-bands. In the terms of formation constant ( KCT), molar extinction coefficient ( ɛCT), standard free energy (Δ Go), oscillator strength ( f), transition dipole moment (μ), resonance energy ( RN) and ionization potential ( ID) were estimated. IR, H NMR, UV-Vis techniques, elemental analyses (CHN) and TG-DTG investigations were used to characterize the structural of charge-transfer complexes. It indicates that the CT interaction was associated with a proton migration from each acceptor to nor or cip donors which followed by appearing intermolecular hydrogen bond. In addition, X-ray investigation was carried out to scrutinize the crystal structure of the resulted CT-complexes.

Spectroscopic and thermal investigations of charge-transfer complexes formed between sulfadoxine drug and different types of acceptors

NASA Astrophysics Data System (ADS)

Refat, Moamen S.

2011-01-01

Charge-transfer reactions between sulfadoxine (SDOX) as a donor with iodine (I 2), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), p-chloranil (CHL) and picric acid (PA) have been studied in solid and solution forms. The stoichiometry of all complexes was found to be 1:1 by molar ratio method between donor and acceptor at a CT-band absorption bands. The data are discussed in terms of formation constant ( KCT), molar extinction coefficient ( ɛCT), standard free energy (Δ Go), oscillator strength (ƒ), transition dipole moment ( μ), resonance energy ( RN) and ionization potential ( ID). The results indicate that the formation constant ( KCT) for the complexes were shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents which were used. IR, 1H NMR and UV-Vis spectroscopic techniques, Elemental analyses (CHN) and TG-DTG investigation were used to characterize the four sulfadoxine charge-transfer complexes.

IR, 1H NMR, mass, XRD and TGA/DTA investigations on the ciprofloxacin/iodine charge-transfer complex.

PubMed

Refat, Moamen S; El-Hawary, W F; Moussa, Mohamed A A

2011-05-01

The charge-transfer complex (CTC) of ciprofloxacin drug (CIP) as a donor with iodine (I(2)) as a sigma acceptor has been studied spectrophotometrically in CHCl(3). At maximum absorption bands, the stoichiometry of CIP:iodine system was found to be 1:1 ratio according to molar ratio method. The essential spectroscopic data like formation constant (K(CT)), molar extinction coefficient (ɛ(CT)), standard free energy (ΔG°), oscillator strength (f), transition dipole moment (μ), resonance energy (R(N)) and ionization potential (I(D)) were estimated. The spectroscopic techniques such as IR, (1)H NMR, mass and UV-vis spectra and elemental analyses (CHN) as well as TG-DTG and DTA investigations were used to characterize the chelating behavior of CIP/iodine charge-transfer complex. The iodine CT interaction was associated with a presence of intermolecular hydrogen bond. The X-ray investigation was carried out to investigate the iodine doping in the synthetic CT complex. Copyright © 2011 Elsevier B.V. All rights reserved.

Charge Transfer in Collisions of S^4+ with H.

NASA Astrophysics Data System (ADS)

Stancil, P. C.; Turner, A. R.; Cooper, D. L.; Schultz, D. R.; Rakovic, M. J.; Fritsch, W.; Zygelman, B.

2001-05-01

Charge transfer processes due to collisions of ground state S^4+ ions with atomic hydrogen were investigated for energies between 1 meV/u and 10 MeV/u using the quantum-mechanical molecular-orbital close-coupling (MOCC), atomic-orbital close-coupling, classical trajectory Monte Carlo (CTMC), and continuum distorted wave methods. The MOCC calculations utilized ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained with the spin-coupled valence-bond approach. A number of variants of the CTMC approach were explored, including different momentum and radial distributions for the initial state, as well as effective charge and quantum-defect models to determine the corresponding quantum state after capture into final partially-stripped S^3+ excited classical states. Hydrogen target isotope effects were explored and rate coefficients for temperatures between 100 and 10^6 K will be presented

Orbital-angular-momentum transfer to optically levitated microparticles in vacuum

NASA Astrophysics Data System (ADS)

Mazilu, Michael; Arita, Yoshihiko; Vettenburg, Tom; Auñón, Juan M.; Wright, Ewan M.; Dholakia, Kishan

2016-11-01

We demonstrate the transfer of orbital angular momentum to an optically levitated microparticle in vacuum. The microparticle is placed within a Laguerre-Gaussian beam and orbits the annular beam profile with increasing angular velocity as the air drag coefficient is reduced. We explore the particle dynamics as a function of the topological charge of the levitating beam. Our results reveal that there is a fundamental limit to the orbital angular momentum that may be transferred to a trapped particle, dependent upon the beam parameters and inertial forces present.

Synthesis, spectral and thermal studies of the newly hydrogen bonded charge transfer complex of o-phenylenediamine with π acceptor picric acid

NASA Astrophysics Data System (ADS)

Khan, Ishaat M.; Ahmad, Afaq

2010-10-01

Newly proton or charge transfer complex [(OPDH) +(PA) -] was synthesized by the reaction of the donor, o-phenylenediamine (OPD) with acceptor, 2,4,6-trinitrophenol (PAH). The chemical reaction has occurred via strong hydrogen bonding followed by migration of proton from acceptor to donor. UV-vis, 1H NMR and FTIR spectra, in addition to the thermal and elemental analysis were used to confirm the proposed occurrence of the chemical reaction and to investigate the newly synthesized solid CT complex. The stoichiometry of the CT complex was found to be 1:1. The formation constant and molar extinction coefficient of the CT complex were evaluated by the Benesi-Hildebrand equation.

Tunable two-dimensional interfacial coupling in molecular heterostructures

DOE PAGES

Xu, Beibei; Chakraborty, Himanshu; Yadav, Vivek K.; ...

2017-08-22

Two-dimensional van der Waals heterostructures are of considerable interest for the next generation nanoelectronics because of their unique interlayer coupling and optoelectronic properties. Here, we report a modified Langmuir–Blodgett method to organize twodimensional molecular charge transfer crystals into arbitrarily and vertically stacked heterostructures, consisting of bis(ethylenedithio)tetrathiafulvalene (BEDT–TTF)/C 60 and poly (3-dodecylthiophene-2,5-diyl) (P3DDT)/C 60 nanosheets. A strong and anisotropic interfacial coupling between the charge transfer pairs is demonstrated. The van der Waals heterostructures exhibit pressure dependent sensitivity with a high piezoresistance coefficient of -4.4 × 10 -6 Pa -1, and conductance and capacitance tunable by external stimuli (ferroelectric field and magneticmore » field). Density functional theory calculations confirm charge transfer between the n-orbitals of the S atoms in BEDT–TTF of the BEDT–TTF/C 60 layer and the π* orbitals of C atoms in C 60 of the P3DDT/C 60 layer contribute to the inter-complex CT. Thus, the two-dimensional molecular van der Waals heterostructures with tunable optical–electronic–magnetic coupling properties are promising for flexible electronic applications.« less

Charge-transfer complexes of sulfamethoxazole drug with different classes of acceptors

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; El-Korashy, Sabry A.; El-Deen, Ibrahim M.; El-Sayed, Shaima M.

2010-09-01

The charge-transfer complexes of the donor sulfamethoxazole (SZ) with iodine (I 2), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), p-chloranil (CHL) and picric acid (PA) have been studied spectrophotometrically in chloroform or methanol at room temperature using absorption spectrophotometer. The results indicate that formation of CT-complexes in case of four acceptors. The stoichiometry of the complexes was found to be 1:1 ratio by molar ratio method between donor and acceptor with maximum absorption bands (CT band). The data are discussed in terms of formation constant ( KCT), molar extinction coefficient ( ɛCT), standard free energy (Δ G°), oscillator strength (ƒ), transition dipole moment ( μ), resonance energy ( RN) and ionization potential ( ID). The results indicate that the formation constant ( KCT) for the complexes were shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents which were used. IR, 1H NMR, mass spectra, UV-Vis techniques, elemental analyses (CHN) and TG-DTG investigation were used to characterize the four sulfamethoxazole charge-transfer complexes.

Studying electron transfer through alkanethiol self-assembled monolayers on a hanging mercury drop electrode using potentiometric measurements.

PubMed

Cohen-Atiya, Meirav; Mandler, Daniel

2006-10-14

A new approach based on measuring the change of the open-circuit potential (OCP) of a hanging mercury drop electrode (HMDE), modified with alkanethiols of different chain length conducted in a solution containing a mixture of Ru(NH3)6(2+) and Ru(NH3)6(3+) is used for studying electron transfer across the monolayer. Following the time dependence of the OCP allowed the extraction of the kinetic parameters, such as the charge transfer resistance (R(ct)) and the electron transfer rate constant (k(et)), for different alkanethiol monolayers. An electron tunneling coefficient, beta, of 0.9 A(-1) was calculated for the monolayers on Hg.

Synthesis, spectral and thermal studies of the newly hydrogen bonded charge transfer complex of o-phenylenediamine with pi acceptor picric acid.

PubMed

Khan, Ishaat M; Ahmad, Afaq

2010-10-01

Newly proton or charge transfer complex [(OPDH)(+)(PA)(-)] was synthesized by the reaction of the donor, o-phenylenediamine (OPD) with acceptor, 2,4,6-trinitrophenol (PAH). The chemical reaction has occurred via strong hydrogen bonding followed by migration of proton from acceptor to donor. UV-vis, (1)H NMR and FTIR spectra, in addition to the thermal and elemental analysis were used to confirm the proposed occurrence of the chemical reaction and to investigate the newly synthesized solid CT complex. The stoichiometry of the CT complex was found to be 1:1. The formation constant and molar extinction coefficient of the CT complex were evaluated by the Benesi-Hildebrand equation. Copyright 2010 Elsevier B.V. All rights reserved.

A high-voltage pulse transformer with a modular ferrite core

NASA Astrophysics Data System (ADS)

Liu, Z.; Winands, G. J. J.; Yan, K.; Pemen, A. J. M.; Van Heesch, E. J. M.

2008-01-01

A high ratio (winding ratio of 1:80) pulse transformer with a modular ferrite core was developed for a repetitive resonant charging system. The magnetic core is constructed from 68 small blocks of ferrites, glued together by epoxy resin. This allows a high degree of freedom in choosing core shape and size. Critical issues related to this modular design are the size tolerance of the individual ferrite blocks, the unavoidable air gap between the blocks, and the saturation of the core. To evaluate the swing of the flux density inside the core during the charging process, an equivalent circuit model was introduced. It was found that when a transformer is used in a resonant charging circuit, the minimal required volume of the magnetic material to keep the core unsaturated depends on the coupling coefficient of the transformer and is independent of the number of turns of the primary winding. Along the flux path, 17 small air gaps are present due to the inevitable joints between the ferrite blocks. The total air gap distance is about 0.67mm. The primary and secondary windings have 16 turns and 1280 turns, respectively, and the actually obtained ratio is about 1:75.4. A coupling coefficient of 99.6% was obtained. Experimental results are in good agreement with the model, and the modular ferrite core works well. Using this transformer, the high-voltage capacitors can be charged up to more than 70kV from a low-voltage capacitor with an initial charging voltage of about 965V. With 26.9J energy transfer, the increased flux density inside the core was about 0.23T, and the core remains unsaturated. The energy transfer efficiency from the primary to the secondary was around 92%.

Charge transfer in ultracold gases via Feshbach resonances

NASA Astrophysics Data System (ADS)

Gacesa, Marko; Côté, Robin

2017-06-01

We investigate the prospects of using magnetic Feshbach resonance to control charge exchange in ultracold collisions of heteroisotopic combinations of atoms and ions of the same element. The proposed treatment, readily applicable to alkali or alkaline-earth metals, is illustrated on cold collisions of +9Be and 10Be. Feshbach resonances are characterized by quantum scattering calculations in a coupled-channel formalism that includes non-Born-Oppenheimer terms originating from the nuclear kinetic operator. Near a resonance predicted at 322 G, we find the charge exchange rate coefficient to rise from practically zero to values greater than 10-12cm3 /s. Our results suggest controllable charge exchange processes between different isotopes of suitable atom-ion pairs, with potential applications to quantum systems engineered to study charge diffusion in trapped cold atom-ion mixtures and emulate many-body physics.

Partition coefficients of methylated DNA bases obtained from free energy calculations with molecular electron density derived atomic charges.

PubMed

Lara, A; Riquelme, M; Vöhringer-Martinez, E

2018-05-11

Partition coefficients serve in various areas as pharmacology and environmental sciences to predict the hydrophobicity of different substances. Recently, they have also been used to address the accuracy of force fields for various organic compounds and specifically the methylated DNA bases. In this study, atomic charges were derived by different partitioning methods (Hirshfeld and Minimal Basis Iterative Stockholder) directly from the electron density obtained by electronic structure calculations in a vacuum, with an implicit solvation model or with explicit solvation taking the dynamics of the solute and the solvent into account. To test the ability of these charges to describe electrostatic interactions in force fields for condensed phases, the original atomic charges of the AMBER99 force field were replaced with the new atomic charges and combined with different solvent models to obtain the hydration and chloroform solvation free energies by molecular dynamics simulations. Chloroform-water partition coefficients derived from the obtained free energies were compared to experimental and previously reported values obtained with the GAFF or the AMBER-99 force field. The results show that good agreement with experimental data is obtained when the polarization of the electron density by the solvent has been taken into account, and when the energy needed to polarize the electron density of the solute has been considered in the transfer free energy. These results were further confirmed by hydration free energies of polar and aromatic amino acid side chain analogs. Comparison of the two partitioning methods, Hirshfeld-I and Minimal Basis Iterative Stockholder (MBIS), revealed some deficiencies in the Hirshfeld-I method related to the unstable isolated anionic nitrogen pro-atom used in the method. Hydration free energies and partitioning coefficients obtained with atomic charges from the MBIS partitioning method accounting for polarization by the implicit solvation model are in good agreement with the experimental values. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Carbon Dioxide-Lubricant Two-Phase Flow Patterns in Small Horizontal Wetted Wall Channels: The Effects of Refrigerant/Lubricant Thermophysical Properties

ERIC Educational Resources Information Center

Seeton, Christopher John

2009-01-01

Microchannel heat exchangers are gaining popularity due to their ability to handle high pressures, reduce refrigerant charge, and reduce heat exchanger package size. These heat exchanger designs provide better heat exchange performance due to increased refrigerant side heat transfer coefficients and geometries that allow for a denser packing…

Extinction coefficients of CC and CC bands in ethyne and ethene molecules interacting with Cu+ and Ag+ in zeolites--IR studies and quantumchemical DFT calculations.

PubMed

Kozyra, Paweł; Góra-Marek, Kinga; Datka, Jerzy

2015-02-05

The values of extinction coefficients of CC and CC IR bands of ethyne and ethene interacting with Cu+ and Ag+ in zeolites were determined in quantitative IR experiments and also by quantumchemical DFT calculations with QM/MM method. Both experimental and calculated values were in very good agreement validating the reliability of calculations. The values of extinction coefficients of ethyne and ethene interacting with bare cations and cations embedded in zeolite-like clusters were calculated. The interaction of organic molecules with Cu+ and Ag+ in zeolites ZSM-5 and especially charge transfers between molecule, cation and zeolite framework was also discussed in relation to the values of extinction coefficients. Copyright © 2014 Elsevier B.V. All rights reserved.

Excitation and charge transfer in low-energy hydrogen atom collisions with neutral oxygen

NASA Astrophysics Data System (ADS)

Barklem, P. S.

2018-02-01

Excitation and charge transfer in low-energy O+H collisions is studied; it is a problem of importance for modelling stellar spectra and obtaining accurate oxygen abundances in late-type stars including the Sun. The collisions have been studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals (LCAO) model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multichannel Landau-Zener model. The method has been extended to include configurations involving excited states of hydrogen using an estimate for the two-electron transition coupling, but this extension was found to not lead to any remarkably high rates. Rate coefficients are calculated for temperatures in the range 1000-20 000 K, and charge transfer and (de)excitation processes involving the first excited S-states, 4s.5So and 4s.3So, are found to have the highest rates. Data are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/vizbin/qcat?J/A+A/610/A57. The data are also available at http://https://github.com/barklem/public-data

Volume changes and electrostriction in the primary photoreactions of various photosynthetic systems: estimation of dielectric coefficient in bacterial reaction centers and of the observed volume changes with the Drude-Nernst equation.

PubMed

Mauzerall, David; Hou, Jian-Min; Boichenko, Vladimir A

2002-01-01

Photoacoustics (PA) allows the determination of enthalpy and volume changes of photoreactions in photosynthetic reaction centers on the 0.1-10 mus time scale. These include the bacterial centers from Rb. sphaeroides, PS I and PS II centers from Synechocystis and in whole cells. In vitro and in vivo PA data on PS I and PS II revealed that both the volume change (-26 A(3)) and reaction enthalpy (-0.4 eV) in PS I are the same as those in the bacterial centers. However the volume change in PS II is small and the enthalpy far larger, -1 eV. Assigning the volume changes to electrostriction allows a coherent explanation of these observations. One can explain the large volume decrease in the bacterial centers with an effective dielectric coefficient of approximately 4. This is a unique approach to this parameter so important in estimation of protein energetics. The value of the volume contraction for PS I can only be explained if the acceptor is the super- cluster (Fe(4)S(4))(Cys(4)) with charge change from -1 to -2. The small volume change in PS II is explained by sub-mus electron transfer from Y(Z) anion to P(680) cation, in which charge is only moved from the Y(Z) anion to the Q(A) with no charge separation or with rapid proton transfer from oxidized Y(Z) to a polar region and thus very little change in electrostriction. At more acid pH equally rapid proton transfer from a neighboring histidine to a polar region may be caused by the electric field of the P(680) cation.

Enabling high rate charge and discharge capability, low internal resistance, and excellent cycleability for Li-ion batteries utilizing graphene additives

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

Tsai, Hsiu-Ling; Hsieh, Chien-Te; Li, Jianlin

A liquid-phase mixing method is adopted to uniformly disperse the graphene nanosheets onto LiNi 1/3Co 1/3Mn 1/3O 2 cathode for high-performance Li-ion batteries (LIBs). The electrochemical performance was characterized using a full pouch cells with state-of-the-art electrode areal loading (compared to half coin cells). The addition of graphene sheets (i.e., only 1 wt%) significantly improves the high rate capability for charging and discharging operation. For example, 6 times improvement in 5 C charging was achieved providing further insights in enabling extreme fast charging for LIBs. Other benefits include longer cycleability, lower internal resistance, and higher lithium ion diffusion coefficient, demonstratedmore » by charge-discharge cycling tests and electrochemical impedance spectroscopy. Higher capacity retention of 88.2% and decreased internal resistance of ~0.9 Ω are observed after 400 cycles. The diffusion coefficient of Li ions is 6.49 × 10 -8 cm 2 s -1 when charged to 4.2 V, which is approximately 1.37 times higher compared to the configuration with no graphene sheet (4.74 × 10 -8 cm 2 s -1). To conclude, the improved performance is ascribed to a robust network among the active materials formed by graphene sheets, which serves as an extended current conductor and facilitates charge transfer, ionic reversibility, and ionic transportation.« less

Enabling high rate charge and discharge capability, low internal resistance, and excellent cycleability for Li-ion batteries utilizing graphene additives

DOE PAGES

Tsai, Hsiu-Ling; Hsieh, Chien-Te; Li, Jianlin; ...

2018-03-27

A liquid-phase mixing method is adopted to uniformly disperse the graphene nanosheets onto LiNi 1/3Co 1/3Mn 1/3O 2 cathode for high-performance Li-ion batteries (LIBs). The electrochemical performance was characterized using a full pouch cells with state-of-the-art electrode areal loading (compared to half coin cells). The addition of graphene sheets (i.e., only 1 wt%) significantly improves the high rate capability for charging and discharging operation. For example, 6 times improvement in 5 C charging was achieved providing further insights in enabling extreme fast charging for LIBs. Other benefits include longer cycleability, lower internal resistance, and higher lithium ion diffusion coefficient, demonstratedmore » by charge-discharge cycling tests and electrochemical impedance spectroscopy. Higher capacity retention of 88.2% and decreased internal resistance of ~0.9 Ω are observed after 400 cycles. The diffusion coefficient of Li ions is 6.49 × 10 -8 cm 2 s -1 when charged to 4.2 V, which is approximately 1.37 times higher compared to the configuration with no graphene sheet (4.74 × 10 -8 cm 2 s -1). To conclude, the improved performance is ascribed to a robust network among the active materials formed by graphene sheets, which serves as an extended current conductor and facilitates charge transfer, ionic reversibility, and ionic transportation.« less

In situ synthesis, photometric and spectroscopic studies of chelating system during the 1,4,7,10,13,16-hexaoxacyclooctadecane charge transfer reaction with different acceptors

NASA Astrophysics Data System (ADS)

Hossan, Aisha S. M.; Abou-Melha, Hanaa M.; Refat, Moamen S.

2011-08-01

Electron donor acceptor complexes (EDA) of the 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) as a rich donor were spectrophotometrically discussed and synthesized in solid form according the interactions with different nine of usual π-acceptors like 2,3,5,6-tetrachlorocyclohexa-2,5-diene-1,4-dione (p-chloranil; p-CHL), tetrachloro-1,2-benzoquinone (o-chloranil; o-CHL), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetracyanoquinodimethane (TCNQ), 2,6-dichloroquinone-4-chloroimide (DCQ), 2,6-dibromoquinone-4-chloroimide (DBQ), 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid; CLA), N-bromosuccinimide (NBS), 2,4,6-trinitrophenol (picric acid; PA). Spectroscopic and physical data such as formation constant ( KCT), molar extinction coefficient ( ɛCT), standard free energy (Δ G°), oscillator strength ( f), transition dipole moment ( μ), resonance energy ( RN) and ionization potential ( Ip) were estimated in chloroform or methanol at 25 °C. Based on the elemental analysis and photometric titrations the CT-complexes were formed indicated the formation of 1:1 charge-transfer complexes for the o-CHL, TCNQ, DCQ, DBQ and NBS acceptors but 1:3 ratio for p-CHL, DDQ, CLA and PA, respectively. The charge-transfer interactions were interpretative according to the formation of dative ion pairs [18C6 rad +, A rad -], where A is acceptor. All of the resulting charge transfer complexes were isolated in amorphous form and the complexes formations on IR and 1H NMR spectra were discussed.

Synthesis, and spectroscopic studies of charge transfer complex of 1,2-dimethylimidazole as an electron donor with π-acceptor 2,4-dinitro-1-naphthol in different polar solvents

NASA Astrophysics Data System (ADS)

Miyan, Lal; Khan, Ishaat M.; Ahmad, Afaq

2015-07-01

The charge transfer (CT) complex of 1,2-dimethylimidazole (DMI) as an electron donor with π acceptor 2,4-dinitro-1-naphthol (DNN) has been studied spectrophotometrically in different solvents like chloroform, acetonitrile, methanol, methylene chloride, etc. at room temperature. The CT complex which is formed through the transfer of lone pair electrons from DMI to DNN exhibits well resolved CT bands and the regions of these bands were remarkably different from those of the donor and acceptor. The stoichiometry of the CT complex was found to be 1:1 by a straight-line method between donor and acceptor with maximum absorption bands. The novel CT complex has been characterized by FTIR, TGA-DTA, powder XRD, 1H NMR and 13C NMR spectroscopic techniques. The Benesi-Hildebrand equation has been used to determine the formation constant (KCT), molar extinction coefficient (εCT), standard gibbs free energy (ΔG°) and other physical parameters of the CT complex. The formation constant recorded higher values and molar extinction coefficient recorded lower values in chloroform compared with methylene chloride, methanol and acetonitrile, confirming the strong interaction between the molecular orbital's of donor and acceptor in the ground state in less polar solvent. This CT complex has been studied by absorption spectra of donor 1,2-dimethylimidazole (DMI) and acceptor 2,4-dinitro-1-naphthol (DNN) by using the spectrophotometric technique in various solvents at room temperature.

Multispecies diffusion models: A study of uranyl species diffusion

NASA Astrophysics Data System (ADS)

Liu, Chongxuan; Shang, Jianying; Zachara, John M.

2011-12-01

Rigorous numerical description of multispecies diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication in imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multispecies diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multispecies diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multispecies U(VI) diffusion under a steady state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that for multispecies U(VI) diffusion under transient chemical conditions, a fully coupled diffusion model could be well approximated by a component-based diffusion model when the diffusion coefficient for each chemical component was properly selected. The component-based diffusion model considers the difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be enforced, if necessary, by adding a secondary migration term resulting from model simplification. The effect of ion activity coefficient gradients on multispecies diffusion is also discussed. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from U.S. Department of Energy's Hanford 300A, where intragranular diffusion is a rate-limiting process controlling U(VI) adsorption and desorption. The grain-scale reactive diffusion model was able to describe U(VI) adsorption/desorption kinetics that had been previously described using a semiempirical, multirate model. Compared with the multirate model, the diffusion models have the advantage to provide spatiotemporal speciation evolution within the diffusion domains.

Charge transfer of O3+ ions with atomic hydrogen

NASA Astrophysics Data System (ADS)

Wang, J. G.; Stancil, P. C.; Turner, A. R.; Cooper, D. L.

2003-01-01

Charge transfer processes due to collisions of ground state O3+(2s22p 2P) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational coupling matrix elements obtained with the spin-coupled valence-bond approach. Total and state-selective cross sections and rate coefficients are presented. Comparison with existing experimental and theoretical data shows our results to be in better agreement with the measurements than the previous calculations, although problems with some of the state-selective measurements are noted. Our calculations demonstrate that rotational coupling is not important for the total cross section, but for state-selective cross sections, its relevance increases with energy. For the ratios of triplet to singlet cross sections, significant departures from a statistical value are found, generally in harmony with experiment.

Spectrophotometric and spectroscopic studies of charge transfer complexes of p-toluidine as an electron donor with picric acid as an electron acceptor in different solvents

NASA Astrophysics Data System (ADS)

Singh, Neeti; Khan, Ishaat M.; Ahmad, Afaq

2010-04-01

The charge transfer complexes of the donor p-toluidine with π-acceptor picric acid have been studied spectrophotometrically in various solvents such as carbon tetrachloride, chloroform, dichloromethane acetone, ethanol, and methanol at room temperature using absorption spectrophotometer. The results indicate that formation of CTC in non-polar solvent is high. The stoichiometry of the complex was found to be 1:1 ratio by straight-line method between donor and acceptor with maximum absorption bands. The data are discussed in terms of formation constant ( KCT), molar extinction coefficient ( ɛCT), standard free energy (Δ Go), oscillator strength ( f), transition dipole moment ( μEN), resonance energy ( RN) and ionization potential ( ID). The results indicate that the formation constant ( KCT) for the complex was shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents that were used.

Spectroscopic studies of multiple charge transfer complexes of p-toluidine with π-acceptor picric acid in different polar solvents

NASA Astrophysics Data System (ADS)

Singh, Neeti; Ahmad, Afaq

2010-04-01

The charge transfer complexes of the donor p-toluidine with π-acceptor picric acid have been studied spectrophotometrically in various solvents such as acetone, ethanol, and methanol at room temperature using absorption spectrophotometer. The results indicate that formation of CTC in less polar solvent is high. The stoichiometry of the complex was found to be 1: 1 ratio by straight line method between donor and acceptor with maximum absorption bands. The data are discussed in terms of formation constant ( K CT), molar extinction coefficient (ɛCT), standard free energy (Δ G°), oscillator strength ( f), transition dipole moment (μEN), resonance energy ( R N) and ionization potential ( I D). The results indicate that the formation constant ( K CT) for the complex were shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents which were used.

Measurements of the O+ plus N2 and O+ plus O2 reaction rates from 300 to 900 K

NASA Technical Reports Server (NTRS)

Chen, A.; Johnsen, R.; Biondi, M. A.

1977-01-01

Rate coefficients for the O(+) + N2 atom transfer and O(+) + O2 charge transfer reactions are determined at thermal energies between 300 K and 900 K difference in a heated drift tube mass spectrometer apparatus. At 300 K the values K(O(+) + N2) = (1.2 plus or minus 0.1) x 10 to the negative 12 power cubic cm/sec and k(O(+) + O2) = (2.1 plus or minus 0.2) x 10 to the negative 11 power cubic cm/sec were obtained, with a 50% difference decrease in the reaction rates upon heating to 700 K. These results are in good agreement with heated flowing afterglow results, but the O(+) + O2 thermal rate coefficients are systematically lower than equivalent Maxwellian rates inferred by conversion of nonthermal drift tube and flow drift data.

Ultraviolet and Visible Emission Mechanisms in Astrophysics

NASA Technical Reports Server (NTRS)

Stancil, Phillip C.; Schultz, David R.

2003-01-01

The project involved the study of ultraviolet (UV) and visible emission mechanisms in astrophysical and atmospheric environments. In many situations, the emission is a direct consequence of a charge transferring collision of an ion with a neutral with capture of an electron to an excited state of the product ion. The process is also important in establishing the ionization and thermal balance of an astrophysical plasma. As little of the necessary collision data are available, the main thrust of the project was the calculation of total and state-selective charge transfer cross sections and rate coefficients for a very large number of collision systems. The data was computed using modern explicit techniques including the molecular-orbital close-coupling (MOCC), classical trajectory Monte Carlo (CTMC), and continuum distorted wave (CDW) methods. Estimates were also made in some instances using the multichannel Landau-Zener (MCLZ) and classical over-the-barrier (COB) models. Much of the data which has been computed has been formatted for inclusion in a charge transfer database on the World Wide Web (cfadc.phy.ornl.gov/astro/ps/data/). A considerable amount of data has been generated during the lifetime of the grant. Some of it has not been analyzed, but it will be as soon as possible, the data placed on our website, and papers ultimately written.

Ab initio quantum chemical calculations of the interaction between radioactive elements and imidazolium based ionic liquids

NASA Astrophysics Data System (ADS)

Saravanan, A. V. Sai; Abishek, B.; Anantharaj, R.

2018-04-01

The fundamental natures of the molecular level interaction and charge transfer between specific radioactive elements and ionic liquids of 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide ([BMIM]+[NTf2]-), 1-Butyl-3-methylimidazolium ethylsulfate ([BMIM]+[ES]-) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]+[BF4]-) were investigated utilising HF theory and B3LYP hybrid DFT. The ambiguity in reaction mechanism of the interacting species dictates to employ Effective Core Potential (ECP) basis sets such as UGBS, SDD, and SDDAll to account for the relativistic effects of deep core electrons in the system involving potential, heavy and hazardous radioactive elements present in nuclear waste. The SCF energy convergence of each system validates the characterisation of the molecular orbitals as a linear combination of atomic orbitals utilising fixed MO coefficients and the optimized geometry of each system is visualised based on which Mulliken partial charge analysis is carried out to account for the polarising behaviour of the radioactive element and charge transfer between the IL phase by comparison with the bare IL species.

Relation between proton and neutron asymptotic normalization coefficients for light mirror nuclei and its relevance to nuclear astrophysics.

PubMed

Timofeyuk, N K; Johnson, R C; Mukhamedzhanov, A M

2003-12-05

We show how the charge symmetry of strong interactions can be used to relate the proton and neutron asymptotic normalization coefficients (ANCs) of the one-nucleon overlap integrals for light mirror nuclei. This relation extends to the case of real proton decay where the mirror analog is a virtual neutron decay of a loosely bound state. In this case, a link is obtained between the proton width and the squared ANC of the mirror neutron state. The relation between mirror overlaps can be used to study astrophysically relevant proton capture reactions based on information obtained from transfer reactions with stable beams.

Transport coefficients of a hot QCD medium and their relative significance in heavy-ion collisions

NASA Astrophysics Data System (ADS)

Mitra, Sukanya; Chandra, Vinod

2017-11-01

The main focus of this article is to obtain various transport coefficients for a hot QCD medium that is likely to be produced while colliding two heavy nuclei ultra-relativistically. The technical approach adopted here is the semiclassical transport theory. The away-from-equilibrium linearized transport equation has been set up by employing the Chapman-Enskog technique from the kinetic theory of a many-particle system with a collision term that includes the binary collisions of quarks/antiquarks and gluons. In order to include the effects of a strongly interacting, thermal medium, a quasi-particle description of a realistic hot QCD equation of state has been employed through the equilibrium modeling of the momentum distributions of gluons and quarks with nontrivial dispersion relations while extending the model for finite but small quark chemical potential. The effective coupling for strong interaction has been redefined following the charge renormalization under the scheme of the quasi-particle model. The consolidated effects on transport coefficients are seen to have a significant impact on their temperature dependence. Finally, the relative significances of momentum and heat transfer, as well as the charge diffusion processes in hot QCD, have been investigated by studying the ratios of the respective transport coefficients indicating different physical laws.

Dependence of charge transfer phenomena during solid-air two-phase flow on particle disperser

NASA Astrophysics Data System (ADS)

Tanoue, Ken-ichiro; Suedomi, Yuuki; Honda, Hirotaka; Furutani, Satoshi; Nishimura, Tatsuo; Masuda, Hiroaki

2012-12-01

An experimental investigation of the tribo-electrification of particles has been conducted during solid-air two-phase turbulent flow. The current induced in a metal plate by the impact of polymethylmethacrylate (PMMA) particles in a high-speed air flow was measured for two different plate materials. The results indicated that the contact potential difference between the particles and a stainless steel plate was positive, while for a nickel plate it was negative. These results agreed with theoretical contact charge transfer even if not only the particle size but also the kind of metal plate was changed. The specific charge of the PMMA particles during solid-air two-phase flow using an ejector, a stainless steel branch pipe, and a stainless steel straight pipe was measured using a Faraday cage. Although the charge was negative in the ejector, the particles had a positive specific charge at the outlet of the branch pipe, and this positive charge increased in the straight pipe. The charge decay along the flow direction could be reproduced by the charging and relaxation theory. However, the proportional coefficients in the theory changed with the particle size and air velocity. Therefore, an unexpected charge transfer occurred between the ejector and the branch pipe, which could not be explained solely by the contact potential difference. In the ejector, an electrical current in air might have been produced by self-discharge of particles with excess charge between the nickel diffuser in the ejector and the stainless steel nozzle or the stainless steel pipe due to a reversal in the contact potential difference between the PMMA and the stainless steel. The sign of the current depended on the particle size, possibly because the position where the particles impacted depended on their size. When dual coaxial glass pipes were used as a particle disperser, the specific charge of the PMMA particles became more positive along the particle flow direction due to the contact potential difference between the PMMA and the stainless steel. Furthermore, the current in air using the dual coaxial glass pipes was less than that using the ejector.

Electrical Transfer Function and Poling Mechanisms for Nonlinear Optical Polymer Modulators

NASA Technical Reports Server (NTRS)

Watson, Michael Dale

2004-01-01

Electro-Optic Polymers hold great promise in increased electro-optic coefficients as compared to their inorganic corollaries. Many researchers have focused on quantum chemistry to describe how the dipoles respond to temperature and electric fields. Much work has also been done for single layer films to confirm these results. For optical applications, waveguide structures are utilized to guide the optical waves in 3 layer stacks. Electrode poling is the only practical poling method for these structures. This research takes an electrical engineering approach to develop poling models and electrical and optical transfer functions of the waveguide structure. The key aspect of the poling model is the large boundary charge density deposited during the poling process. The boundary charge density also has a large effect on the electrical transfer function which is used to explain the transient response of the system. These models are experimentally verified. Exploratory experiment design is used to study poling parameters including time, temperature, and voltage. These studies verify the poling conditions for CLDX/APC and CLDZ/APEC guest host electro optic polymer films in waveguide stacks predicted by the theoretical developments.

Top electrode size effects in the piezoresponse force microscopy of piezoelectric thin films attached to a rigid substrate

NASA Astrophysics Data System (ADS)

Wang, J. H.

2017-10-01

In order to avoid the highly concentrated electric field induced beneath the sharp tip, the technique using a top coating electrode in the piezoresponse force microscopy (PFM) has been developed to detect the piezoelectric coefficients. Reliable theory should be erected to explain the broadly reported top electrode size effects and relate the responses with material constants. In this paper, the surface displacement, electric potential inside the film, electric charge and effective piezoelectric coefficient are expressed as a set of integral equations. Analytical solutions are obtained for two limiting cases, i.e., half space (HS) and infinitely thin film (IT). The effective piezoelectric coefficient of the HS case is proved to be the same as that from the PFM of a piezoelectric half plane without a top coating. For the IT case, it is identical to the well-known piezoelectric coefficient result of piezoelectric thin film clamped between flat rigid electrodes subject to homogeneous external electric field. For PZT4 thin layer, numerical results reveal that the surface displacement obviously decreases and the electric potential distributions inside the film become more and more homogeneous as the electrode radius to film thickness ratio (a/t) enlarges. The electric charge dramatically increases while the effective piezoelectric coefficient evidently decreases and they both transfer from the HS solutions to the IT results when a/t varies from 0.001 to 20. The transition occurs at about a/t = 1 in agreement with the experimental observations. A critical top electrode size, i.e., a/t > 10, is obtained and applicable to other piezoelectric materials. Under such circumstances, one can readily gain the piezoelectric coefficients e 33, d 33 and the dielectric coefficient {\\in }33 if other mechanical coefficients and one piezoelectric constant are known a prior.

Exploring Charge Transport in Guest Molecule Infiltrated Cu 3(BTC) 2 Metal Organic Framework

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

Leonard, Francois Leonard; Stavila, Vitalie; Allendorf, Mark D.

2014-09-01

The goal of this Exploratory Express project was to expand the understanding of the physical properties of our recently discovered class of materials consisting of metal-organic frameworks with electroactive ‘guest’ molecules that together form an electrically conducting charge-transfer complex (molecule@MOF). Thin films of Cu 3(BTC) 2 were grown on fused silica using solution step-by-step growth and were infiltrated with the molecule tetracyanoquinodimethane (TCNQ). The infiltrated MOF films were extensively characterized using optical microscopy, scanning electron microscopy, Raman spectroscopy, electrical conductivity, and thermoelectric properties. Thermopower measurements on TCNQ@Cu 3(BTC) 2 revealed a positive Seebeck coefficient of ~400 μV/k, indicating that holesmore » are the primary carriers in this material. The high value of the Seebeck coefficient and the expected low thermal conductivity suggest that molecule@MOF materials may be attractive for thermoelectric power conversion applications requiring low cost, solution-processable, and non-toxic active materials.« less

Two-dimensional CsPbBr3/PCBM heterojunctions for sensitive, fast and flexible photodetectors boosted by charge transfer

NASA Astrophysics Data System (ADS)

Shen, Yalong; Yu, Dejian; Wang, Xiong; Huo, Chengxue; Wu, Ye; Zhu, Zhengfeng; Zeng, Haibo

2018-02-01

Inorganic halide perovskites exhibited promising potentials for high-performance wide-band photodetectors (PDs) due to their high light absorption coefficients, long carrier diffusion length and wide light absorption ranges. Here, we report two-dimensional (2D) CsPbBr3/PCBM heterojunctions for sensitive, fast and flexible PDs, whose performances can be greatly boosted by the charge transfer through the energy-aligned interface. The 2D CsPbBr3 nanosheets with high crystallinity were fabricated via a simple solution-process at room temperature, and then assembled into flexible heterojunctions films with polymerphenyl-C61-butyric acid methyl ester (PCBM). Significantly, the efficient and fast charge transfer at the heterojunctions interface was evidenced by the obvious photoluminescence quenching and variation of recombination dynamics. Subsequently, such heterojunctions PD exhibited an enhanced responsivity of 10.85 A W-1 and an ultrahigh detectivity of 3.06 × 1013 Jones. In addition, the PD shows a broad linear dynamic range of 73 dB, a fast response speed with rise time of 44 μs and decay time of 390 μs, respectively. Moreover, the PD lying on polyethylene terephthalate substrates exhibited an outstanding mechanical flexibility and a robust electrical stability. These results could provide a new avenue for integration of 2D perovskites and organic functional materials and for high-performance flexible PDs.

Comparative Investigation and Operational Performance Characteristics of a Wick Assisted and Axially Square Grooved Heat Pipe

NASA Astrophysics Data System (ADS)

Naik, Rudra, Dr.; Rama Narasihma, K., Dr.; Anikivi, Atmanand

2018-04-01

The present work reported here involves the experimental investigation and performance evaluation of wick assisted and axially square grooved heat pipes of outer diameter 8mm, inner diameter 4mm with a length of 150mm.The objective of this work is to design, fabricate and test the heat pipes with and without an axial square groove for horizontal and gravity assisted conditions. The performance of the heat pipes was measured in terms of thermal resistance and heat transfer coefficients. In the present investigation four different working fluids were chosen namely acetone, ethanol, methanol and distilled water. Experiments were conducted by varying the heat load from 2 W to 10 W for different fill charge ratios in the range of 25% to 75% of evaporator volume for wick assisted heat pipe and 8 W to 18 W for axially square grooved heat pipe. From the experiments, it was found that there is a steady increase in temperature with the increase in heat input. The overall heat transfer coefficient was found to increase with the increase heat load for wick assisted heat pipe. In case of axially square grooved heat pipe, an attempt was made to experiment the heat pipe in different orientations. The maximum heat transfer coefficient of 7000 W/m2 °C is found for Acetone at 180° orientation.

Polarization transfer in the {sup 4}He(e(pol), e'p(pol)) {sup 3}He reaction at Q{sup 2} = 0.8 and 1.3 GeV/c){sup 2}.

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

Paolone, M.; Malace, S. P.; Strauch, S.

2010-08-12

Proton recoil polarization was measured in the quasielastic 4He(e(pol),e{prime}p(pol)){sup 3}H reaction at Q{sup 2}=0.8 and 1.3(GeV/c){sup 2} with unprecedented precision. The polarization-transfer coefficients are found to differ from those of the {sup 1}H(e(pol),e{prime}p(pol)) reaction, contradicting a relativistic distorted-wave approximation and favoring either the inclusion of medium-modified proton form factors predicted by the quark-meson coupling model or a spin-dependent charge-exchange final-state interaction. For the first time, the polarization-transfer ratio is studied as a function of the virtuality of the proton.

Kinetics Tuning the Electrochemistry of Lithium Dendrites Formation in Lithium Batteries through Electrolytes

DOE PAGES

Tao, Ran; Bi, Xuanxuan; Li, Shu; ...

2017-02-13

Lithium batteries are one of the most advance energy storage devices in the world and have attracted extensive research interests. However, lithium dendrite growth was a safety issue which handicapped the application of pure lithium metal in the negative electrode. In this paper, two solvents, propylene carbonate (PC) and 2-methyl-tetrahydrofuran (2MeTHF), and four Li + salts, LiPF 6, LiAsF 6, LiBF 4 and LiClO 4 were investigated in terms of their effects on the kinetics of lithium dendrite formation in eight electrolyte solutions. The kinetic parameters of charge transfer step (exchange current density, j 0, transfer coefficient, α) of Limore » +/Li redox system, the mass transfer parameters of Li + (transfer number of Li +, t Li+, diffusion coefficient of Li +, D Li+), and the conductivity (κ) of each electrolyte were studied separately. The results demonstrate that the solvents play a critical role in the measured j 0, t Li+, D Li+, and κ of the electrolyte, while the choice of Li + salts only slightly affect the measured parameters. Finally, the understanding of the kinetics will gain insight into the mechanism of lithium dendrite formation and provide guidelines to the future application of lithium metal.« less

Kinetics Tuning the Electrochemistry of Lithium Dendrites Formation in Lithium Batteries through Electrolytes

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

Tao, Ran; Bi, Xuanxuan; Li, Shu

Lithium batteries are one of the most advance energy storage devices in the world and have attracted extensive research interests. However, lithium dendrite growth was a safety issue which handicapped the application of pure lithium metal in the negative electrode. In this paper, two solvents, propylene carbonate (PC) and 2-methyl-tetrahydrofuran (2MeTHF), and four Li + salts, LiPF 6, LiAsF 6, LiBF 4 and LiClO 4 were investigated in terms of their effects on the kinetics of lithium dendrite formation in eight electrolyte solutions. The kinetic parameters of charge transfer step (exchange current density, j 0, transfer coefficient, α) of Limore » +/Li redox system, the mass transfer parameters of Li + (transfer number of Li +, t Li+, diffusion coefficient of Li +, D Li+), and the conductivity (κ) of each electrolyte were studied separately. The results demonstrate that the solvents play a critical role in the measured j 0, t Li+, D Li+, and κ of the electrolyte, while the choice of Li + salts only slightly affect the measured parameters. Finally, the understanding of the kinetics will gain insight into the mechanism of lithium dendrite formation and provide guidelines to the future application of lithium metal.« less

Vaporization inside a mini microfin tube: experimental results and modeling

NASA Astrophysics Data System (ADS)

Diani, A.; Rossetto, L.

2015-11-01

This paper proposes a comparison among the common R134a and the extremely low GWP refrigerant R1234yf during vaporization inside a mini microfin tube. This microfin tube has an internal diameter of 2.4 mm, it has 40 fins, with a fin height of 0.12 mm. Due to the high heat transfer coefficients shown by this tube, this technology can lead to a refrigerant charge reduction. Tests were run in the Heat Transfer in Micro Geometries Lab of the Dipartimento di Ingegneria Industriale of the Università di Padova. Mass velocities range between 375 and 940 kg m-2 s-1, heat fluxes from 10 to 50 kW m-2, vapour qualities from 0.10 to 0.99, at a saturation temperature of 30°C. The comparison among the two fluids is proposed at the same operating conditions, in order to highlight the heat transfer and pressure drop differences among the two refrigerants. In addition, two correlations are proposed to estimate the heat transfer coefficient and frictional pressure drop during refrigerant flow boiling inside mini microfin tubes. These correlations well predict the experimental values, and thus they can be used as a useful tool to design evaporators based on these mini microfin tubes.

Charge-transfer state and large first hyperpolarizability constant in a highly electronically coupled zinc and gold porphyrin dyad.

PubMed

Fortage, Jérôme; Scarpaci, Annabelle; Viau, Lydie; Pellegrin, Yann; Blart, Errol; Falkenström, Magnus; Hammarström, Leif; Asselberghs, Inge; Kellens, Ruben; Libaers, Wim; Clays, Koen; Eng, Mattias P; Odobel, Fabrice

2009-09-14

We report the synthesis and the characterizations of a novel dyad composed of a zinc porphyrin (ZnP) linked to a gold porphyrin (AuP) through an ethynyl spacer. The UV/Vis absorption spectrum and the electrochemical properties clearly reveal that this dyad exhibits a strong electronic coupling in the ground state as evidenced by shifted redox potentials and the appearance of an intense charge-transfer band localized at lambda = 739 nm in dichloromethane. A spectroelectrochemical study of the dyad along with the parent homometallic system (i.e., ZnP-ZnP and AuP-AuP) was undertaken to determine the spectra of the reduced and oxidized porphyrin units. Femtosecond transient absorption spectroscopic analysis showed that the photoexcitation of the heterometallic dyad leads to an ultrafast formation of a charge-separated state ((+)ZnP-AuP(*)) that displays a particularly long lifetime (tau = 4 ns in toluene) for such a short separation distance. The molecular orbitals of the dyad were determined by DFT quantum-chemical calculations. This theoretical study confirms that the observed intense band at lambda = 739 nm corresponds to an interporphyrin charge-transfer transition from the HOMO orbital localized on the zinc porphyrin to LUMO orbitals localized on the gold porphyrin. Finally, a Hyper-Rayleigh scattering study shows that the dyad possesses a large first molecular hyperpolarizability coefficient (beta = 2100x10(-30) esu at lambda = 1064 nm), thus highlighting the valuable nonlinear optical properties of this new type of push-pull porphyrin system.

Influence of fluid dynamic conditions on enzymatic hydrolysis of lignocellulosic biomass: Effect of mass transfer rate.

PubMed

Wojtusik, Mateusz; Zurita, Mauricio; Villar, Juan C; Ladero, Miguel; Garcia-Ochoa, Felix

2016-09-01

The effect of fluid dynamic conditions on enzymatic hydrolysis of acid pretreated corn stover (PCS) has been assessed. Runs were performed in stirred tanks at several stirrer speed values, under typical conditions of temperature (50°C), pH (4.8) and solid charge (20% w/w). A complex mixture of cellulases, xylanases and mannanases was employed for PCS saccharification. At low stirring speeds (<150rpm), estimated mass transfer coefficients and rates, when compared to chemical hydrolysis rates, lead to results that clearly show low mass transfer rates, being this phenomenon the controlling step of the overall process rate. However, for stirrer speed from 300rpm upwards, the overall process rate is controlled by hydrolysis reactions. The ratio between mass transfer and overall chemical reaction rates changes with time depending on the conditions of each run. Copyright © 2016 Elsevier Ltd. All rights reserved.

Usefulness of charge-transfer complexation for the assessment of sympathomimetic drugs: Spectroscopic properties of drug ephedrine hydrochloride complexed with some π-acceptors

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Ibrahim, Omar B.; Saad, Hosam A.; Adam, Abdel Majid A.

2014-05-01

Recently, ephedrine (Eph) assessment in food products, pharmaceutical formulations, human fluids of athletes and detection of drug toxicity and abuse, has gained a growing interest. To provide basic data that can be used to assessment of Eph quantitatively based on charge-transfer (CT) complexation, the CT complexes of Eph with 7‧,8,8‧-tetracyanoquinodimethane (TCNQ), dichlorodicyanobenzoquinone (DDQ), 1,3-dinitrobenzene (DNB) or tetrabromothiophene (TBT) were synthesized and spectroscopically investigated. The newly synthesized complexes have been characterized via elemental analysis, IR, Raman, 1H NMR, and UV-visible spectroscopy. The formation constant (KCT), molar extinction coefficient (εCT) and other spectroscopic data have been determined using the Benesi-Hildebrand method and its modifications. The sharp, well-defined Bragg reflections at specific 2θ angles have been identified from the powder X-ray diffraction patterns. Thermal decomposition behavior of these complexes was also studied, and their kinetic thermodynamic parameters were calculated with Coats-Redfern and Horowitz-Metzger equations.

Quadratic Electro-optic Effect in a Novel Nano-optical Polymer (iodine-doped polyisoprene)

NASA Astrophysics Data System (ADS)

Swamy, Rajendra; Titus, Jitto; Thakur, Mrinal

2004-03-01

In this report, exceptionally large quadratic electro-optic effect in a novel nano-optical polymer will be discussed. The material involved is cis-1,4-polyisoprene or natural rubber which is a nonconjugated conductive polymer[1,2].Upon doping with an acceptor such as iodine, an electron is transferred from its isolated double bond to the dopant leading to a charge-transfer complex. The positive charge (hole) thus created is localized around the double-bond site, within a nanometer dimension - thus, forming a nano-optical material. The quadratic electro-optic measurement on the doped polyisoprene film was made using field-induced birefringence method. The measured Kerr coefficient is about sixty six times that of nitrobenzene at 632 nm. Significant electroabsorption was also observed in this material at 632 nm. 1. M. Thakur, J. Macromol. Sci. - PAC, 2001, A38(12), 1337. 2. M. Thakur, S. Khatavkar and E.J. Parish, J. Macromol. Sci. - PAC, 2003, A40 (12), 1397.

Spectrophotometric and spectroscopic studies of charge transfer complexes of p-toluidine as an electron donor with picric acid as an electron acceptor in different solvents.

PubMed

Singh, Neeti; Khan, Ishaat M; Ahmad, Afaq

2010-04-01

The charge transfer complexes of the donor p-toluidine with pi-acceptor picric acid have been studied spectrophotometrically in various solvents such as carbon tetrachloride, chloroform, dichloromethane acetone, ethanol, and methanol at room temperature using absorption spectrophotometer. The results indicate that formation of CTC in non-polar solvent is high. The stoichiometry of the complex was found to be 1:1 ratio by straight-line method between donor and acceptor with maximum absorption bands. The data are discussed in terms of formation constant (K(CT)), molar extinction coefficient (epsilon(CT)), standard free energy (DeltaG(o)), oscillator strength (f), transition dipole moment (mu(EN)), resonance energy (R(N)) and ionization potential (I(D)). The results indicate that the formation constant (K(CT)) for the complex was shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents that were used. Copyright 2010 Elsevier B.V. All rights reserved.

The effects of surface-charged submicron polystyrene particles on the structure and performance of PSF forward osmosis membrane

NASA Astrophysics Data System (ADS)

Zuo, Hao-Ran; Fu, Jia-Bei; Cao, Gui-Ping; Hu, Nian; Lu, Hui; Liu, Hui-Qing; Chen, Peng-Peng; Yu, Jie

2018-04-01

Monodisperse surface-charged submicron polystyrene particles were designed, synthesized, and blended into polysulfone (PSF) support layer to prepare forward osmosis (FO) membrane with high performance. The membrane incorporated with particles were characterized with respect to morphology, porosity, and internal osmotic pressure (IOP). Results showed that the polymer particles not only increased the hydrophilicity and porosity of support layer, but also generated considerable IOP, which helped markedly decreasing the structure parameter from 1550 to 670 μm. The measured mass transfer parameters further confirmed the beneficial effects of the surface-charged submicron polymer particles on the performance of FO membrane. For instance, the water permeability coefficient (5.37 L m-2 h-1 bar-1) and water flux (49.7 L m-2 h-1) of the FO membrane incorporated with 5 wt% particles were almost twice as much as that of FO membrane without incorporation. This study suggests that monodisperse surface-charged submicron polymer particles are potential modifiers for improving the performance of FO membranes.

Simulation-Based Approach to Determining Electron Transfer Rates Using Square-Wave Voltammetry.

PubMed

Dauphin-Ducharme, Philippe; Arroyo-Currás, Netzahualcóyotl; Kurnik, Martin; Ortega, Gabriel; Li, Hui; Plaxco, Kevin W

2017-05-09

The efficiency with which square-wave voltammetry differentiates faradic and charging currents makes it a particularly sensitive electroanalytical approach, as evidenced by its ability to measure nanomolar or even picomolar concentrations of electroactive analytes. Because of the relative complexity of the potential sweep it uses, however, the extraction of detailed kinetic and mechanistic information from square-wave data remains challenging. In response, we demonstrate here a numerical approach by which square-wave data can be used to determine electron transfer rates. Specifically, we have developed a numerical approach in which we model the height and the shape of voltammograms collected over a range of square-wave frequencies and amplitudes to simulated voltammograms as functions of the heterogeneous rate constant and the electron transfer coefficient. As validation of the approach, we have used it to determine electron transfer kinetics in both freely diffusing and diffusionless surface-tethered species, obtaining electron transfer kinetics in all cases in good agreement with values derived using non-square-wave methods.

Multinucleon transfer in central collisions of 238U+238U

NASA Astrophysics Data System (ADS)

Ayik, S.; Yilmaz, B.; Yilmaz, O.; Umar, A. S.; Turan, G.

2017-08-01

Quantal diffusion mechanism of nucleon exchange is studied in the central collisions of 238U+238U in the framework of the stochastic mean-field (SMF) approach. For bombarding energies considered in this work, the dinuclear structure is maintained during the collision. Hence, it is possible to describe nucleon exchange as a diffusion process for mass and charge asymmetry. Quantal neutron and proton diffusion coefficients, including memory effects, are extracted from the SMF approach and the primary fragment distributions are calculated.

Long-range correlations and charge transport properties of DNA sequences

NASA Astrophysics Data System (ADS)

Liu, Xiao-liang; Ren, Yi; Xie, Qiong-tao; Deng, Chao-sheng; Xu, Hui

2010-04-01

By using Hurst's analysis and transfer approach, the rescaled range functions and Hurst exponents of human chromosome 22 and enterobacteria phage lambda DNA sequences are investigated and the transmission coefficients, Landauer resistances and Lyapunov coefficients of finite segments based on above genomic DNA sequences are calculated. In a comparison with quasiperiodic and random artificial DNA sequences, we find that λ-DNA exhibits anticorrelation behavior characterized by a Hurst exponent 0.5

Molecular dynamics simulation of imidazolium-based ionic liquids. I. Dynamics and diffusion coefficient.

PubMed

Kowsari, M H; Alavi, Saman; Ashrafizaadeh, Mahmud; Najafi, Bijan

2008-12-14

Molecular dynamics simulations are used to study the dynamics and transport properties of 12 room-temperature ionic liquids of the 1-alkyl-3-methylimidazolium [amim](+) (alkyl = methyl, ethyl, propyl, and butyl) family with PF(6)(-), NO(3)(-), and Cl(-) counterions. The explicit atom transferable force field of Canongia Lopes et al. [J. Phys. Chem. B 108, 2038 (2004)] is used in the simulations. In this first part, the dynamics of the ionic liquids are characterized by studying the mean-square displacement (MSD) and the velocity autocorrelation function (VACF) for the centers of mass of the ions at 400 K. Trajectory averaging was employed to evaluate the diffusion coefficients at two temperatures from the linear slope of MSD(t) functions in the range of 150-300 ps and from the integration of the VACF(t) functions at 400 K. Detailed comparisons are made between the diffusion results from the MSD and VACF methods. The diffusion coefficients from the integration of the VACFs are closer to experimental values than the diffusion coefficients calculated from the slope of MSDs. Both methods can show good agreement with experiment in predicting relative trends in the diffusion coefficients and determining the role of the cation and anion structures on the dynamical behavior of this family of ionic liquids. The MSD and self-diffusion of relatively heavier imidazolium cations are larger than those of the lighter anions from the Einstein results, except for the case of [bmim][Cl]. The cationic transference number generally decreases with temperature, in good agreement with experiments. For the same anion, the cationic transference numbers decrease with increasing length of the alkyl chain, and for the same cation, the trends in the cationic transference numbers are [NO(3)](-) < [Cl](-) < [PF(6)](-). The trends in the diffusion coefficient in the series of cations with identical anions are [emim](+) > [pmim](+) > [bmim](+) and those for anions with identical cations are [NO(3)](-) > [PF(6)](-) > [Cl](-). The [dmim](+) has a relatively low diffusion coefficient due to its symmetric structure and good packing in the liquid phase. The major factor for determining the magnitude of the self-diffusion is the geometric shape of the anion of the ionic liquid. Other important factors are the ion size and the charge delocalization in the anion.

Cerium Ion Mobility and Diffusivity Rates in Perfluorosulfonic Acid Membranes Measured via Hydrogen Pump Operation

DOE PAGES

Baker, Andrew M.; Babu, Siddharth Komini; Mukundan, Rangachary; ...

2017-09-21

Ion mobility and diffusivity coefficients were determined for cerium ions in Nafion XL perfluorosulfonic acid ionomer membranes at 100% and 50% relative humidity in a conductivity cell using a hydrogen pump. We quantified Ce ion migration profiles as a function of charge transfer through the cell using X-ray fluorescence (XRF). To decouple simultaneous effects of Ce ion mobility and back-diffusion which occur due to potential and concentration gradients, respectively, a one-dimensional model was developed and fit to these intermittent XRF profiles. The resulting mobility and diffusivity coefficients demonstrate the dramatic effects of potential and concentration gradients on Ce ion migrationmore » during PEM fuel cell operation.« less

Cerium Ion Mobility and Diffusivity Rates in Perfluorosulfonic Acid Membranes Measured via Hydrogen Pump Operation

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

Baker, Andrew M.; Babu, Siddharth Komini; Mukundan, Rangachary

Ion mobility and diffusivity coefficients were determined for cerium ions in Nafion XL perfluorosulfonic acid ionomer membranes at 100% and 50% relative humidity in a conductivity cell using a hydrogen pump. We quantified Ce ion migration profiles as a function of charge transfer through the cell using X-ray fluorescence (XRF). To decouple simultaneous effects of Ce ion mobility and back-diffusion which occur due to potential and concentration gradients, respectively, a one-dimensional model was developed and fit to these intermittent XRF profiles. The resulting mobility and diffusivity coefficients demonstrate the dramatic effects of potential and concentration gradients on Ce ion migrationmore » during PEM fuel cell operation.« less

Electrochemical Behavior of Sulfur in Aqueous Alkaline Solutions

NASA Astrophysics Data System (ADS)

Mamyrbekova, Aigul; Mamitova, A. D.; Mamyrbekova, Aizhan

2018-03-01

The kinetics and mechanism of the electrode oxidation-reduction of sulfur on an electrically conductive sulfur-graphite electrode in an alkaline solution was studied by the potentiodynamic method. To examine the mechanism of electrode processes occurring during AC polarization on a sulfur-graphite electrode, the cyclic polarization in both directions and anodic polarization curves were recorded. The kinetic parameters: charge transfer coefficients (α), diffusion coefficients ( D), heterogeneous rate constants of electrode process ( k s), and effective activation energies of the process ( E a) were calculated from the results of polarization measurements. An analysis of the results and calculated kinetic parameters of electrode processes showed that discharge ionization of sulfur in alkaline solutions occurs as a sequence of two stages and is a quasireversible process.

Molecular features determining different partitioning patterns of papain and bromelain in aqueous two-phase systems.

PubMed

Rocha, Maria Victoria; Nerli, Bibiana Beatriz

2013-10-01

The partitioning patterns of papain (PAP) and bromelain (BR), two well-known cysteine-proteases, in polyethyleneglycol/sodium citrate aqueous two-phase systems (ATPSs) were determined. Polyethyleneglycols of different molecular weight (600, 1000, 2000, 4600 and 8000) were assayed. Thermodynamic characterization of partitioning process, spectroscopy measurements and computational calculations of protein surface properties were also carried out in order to explain their differential partitioning behavior. PAP was observed to be displaced to the salt-enriched phase in all the assayed systems with partition coefficients (KpPAP) values between 0.2 and 0.9, while BR exhibited a high affinity for the polymer phase in systems formed by PEGs of low molecular weight (600 and 1000) with partition coefficients (KpBR) values close to 3. KpBR values resulted higher than KpPAP in all the cases. This difference could be assigned neither to the charge nor to the size of the partitioned biomolecules since PAP and BR possess similar molecular weight (23,000) and isoelectric point (9.60). The presence of highly exposed tryptophans and positively charged residues (Lys, Arg and His) in BR molecule would be responsible for a charge transfer interaction between PEG and the protein and, therefore, the uneven distribution of BR in these systems. Copyright © 2013 Elsevier B.V. All rights reserved.

Charge transfer in TATB and HMX under extreme conditions.

PubMed

Zhang, Chaoyang; Ma, Yu; Jiang, Daojian

2012-11-01

Charge transfer is usually accompanied by structural changes in materials under different conditions. However, the charge transfer in energetic materials that are subjected to extreme conditions has seldom been explored by researchers. In the work described here, the charge transfer in single molecules and unit cells of the explosives TATB and HMX under high temperatures and high pressures was investigated by performing static and dynamic calculations using three DFT methods, including the PWC functional of LDA, and the BLYP and PBE functionals of GGA. The results showed that negative charge is transferred from the nitro groups of molecular or crystalline TATB and HMX when they are heated. All DFT calculations for the compressed TATB unit cell indicate that, generally, negative charge transfer occurs to its nitro groups as the compression increases. PWC and PBE calculations for crystalline HMX show that negative charge is first transferred to the nitro groups but, as the compression increases, the negative charge is transferred from the nitro groups. However, the BLYP calculations indicated that there was gradual negative charge transfer to the nitro groups of HMX, similar to the case for TATB. The unrelaxed state of the uniformly compressed TATB causes negative charge to be transferred from its nitro groups, in contrast to what is seen in the relaxed state. Charge transfer in TATB is predicted to occur much more easily than in HMX.

Molecular control of pentacene/ZnO photoinduced charge transfer

NASA Astrophysics Data System (ADS)

Spalenka, Josef W.; Paoprasert, Peerasak; Franking, Ryan; Hamers, Robert J.; Gopalan, Padma; Evans, Paul G.

2011-03-01

Photoinduced charge transfer modifies the device properties of illuminated pentacene field effect transistors (FETs) incorporating ZnO quantum dots at the gate insulator/pentacene interface. The transferred charge is trapped on electronic states associated with the ZnO quantum dots, with a steady state population approximately proportional to the rate of organic-inorganic charge transfer. Trapped charge shifts the threshold voltage of the FETs, providing the means to evaluate the rate of organic/inorganic charge transfer and the effects of interface modification. Monolayers of the wide-gap alkane stearic acid and the conjugated oligomer terthiophene attached to the ZnO suppress or permit charge transfer, respectively.

Synthesis and characterization of highly conductive charge-transfer complexes using positron annihilation spectroscopy

NASA Astrophysics Data System (ADS)

Adam, Abdel Majid A.; Refat, Moamen S.; Sharshar, T.; Heiba, Z. K.

Molecular charge-transfer complexes of the tetramethylethylenediamine (TMEDA) with picric acid (Pi-OH), benzene-1,4-diol (QL), tin(IV) tetrachloride (SnCl4), iodine, bromine, and zinc chloride (ZnCl2) have been synthesized and investigated by elemental and thermal analysis, electronic, infrared, Raman and proton-NMR, energy-dispersive X-ray spectroscopy, X-ray powder diffraction and positron annihilation lifetime spectroscopy, and scanning electron microscopy. In this work, three types of acceptors π-acceptors (Pi-OH and QL), σ-acceptors (iodine and bromine), and vacant orbital acceptors (SnCl4 and ZnCl2) were covered. The results of elemental analysis indicated that the CT complexes were formed with ratios 1:1 and 1:2 for QL, SnCl4, and ZnCl2 acceptors and iodine, Pi-OH, and Br2 acceptors, respectively. The type of chelating between the TMEDA donor and the mentioned acceptors depends upon the behavior of both items. The positron annihilation lifetime parameters were found to be dependent on the structure, electronic configuration, and the power of acceptors. The correlation between these parameters and the molecular weight and biological activities of studied complexes was also observed. Regarding the electrical properties, the AC conductivity and the dielectric coefficients were measured as a function of frequency at room temperature. The TMEDA charge-transfer complexes were screened against antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa) and antifungal (Aspergillus flavus and Candida albicans) activities.

The Influence of Particle Charge on Heterogeneous Reaction Rate Coefficients

NASA Technical Reports Server (NTRS)

Aikin, A. C.; Pesnell, W. D.

2000-01-01

The effects of particle charge on heterogeneous reaction rates are presented. Many atmospheric particles, whether liquid or solid are charged. This surface charge causes a redistribution of charge within a liquid particle and as a consequence a perturbation in the gaseous uptake coefficient. The amount of perturbation is proportional to the external potential and the square of the ratio of debye length in the liquid to the particle radius. Previous modeling has shown how surface charge affects the uptake coefficient of charged aerosols. This effect is now included in the heterogeneous reaction rate of an aerosol ensemble. Extension of this analysis to ice particles will be discussed and examples presented.

MULTI-SCALE MODELING AND APPROXIMATION ASSISTED OPTIMIZATION OF BARE TUBE HEAT EXCHANGERS

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

Bacellar, Daniel; Ling, Jiazhen; Aute, Vikrant

2014-01-01

Air-to-refrigerant heat exchangers are very common in air-conditioning, heat pump and refrigeration applications. In these heat exchangers, there is a great benefit in terms of size, weight, refrigerant charge and heat transfer coefficient, by moving from conventional channel sizes (~ 9mm) to smaller channel sizes (< 5mm). This work investigates new designs for air-to-refrigerant heat exchangers with tube outer diameter ranging from 0.5 to 2.0mm. The goal of this research is to develop and optimize the design of these heat exchangers and compare their performance with existing state of the art designs. The air-side performance of various tube bundle configurationsmore » are analyzed using a Parallel Parameterized CFD (PPCFD) technique. PPCFD allows for fast-parametric CFD analyses of various geometries with topology change. Approximation techniques drastically reduce the number of CFD evaluations required during optimization. Maximum Entropy Design method is used for sampling and Kriging method is used for metamodeling. Metamodels are developed for the air-side heat transfer coefficients and pressure drop as a function of tube-bundle dimensions and air velocity. The metamodels are then integrated with an air-to-refrigerant heat exchanger design code. This integration allows a multi-scale analysis of air-side performance heat exchangers including air-to-refrigerant heat transfer and phase change. Overall optimization is carried out using a multi-objective genetic algorithm. The optimal designs found can exhibit 50 percent size reduction, 75 percent decrease in air side pressure drop and doubled air heat transfer coefficients compared to a high performance compact micro channel heat exchanger with same capacity and flow rates.« less

Dynamics of charge-transfer excitons in type-II semiconductor heterostructures

NASA Astrophysics Data System (ADS)

Stein, M.; Lammers, C.; Richter, P.-H.; Fuchs, C.; Stolz, W.; Koch, M.; Vänskä, O.; Weseloh, M. J.; Kira, M.; Koch, S. W.

2018-03-01

The formation, decay, and coherence properties of charge-transfer excitons in semiconductor heterostructures are investigated by applying four-wave-mixing and terahertz spectroscopy in combination with a predictive microscopic theory. A charge-transfer process is identified where the optically induced coherences decay directly into a charge-transfer electron-hole plasma and exciton states. It is shown that charge-transfer excitons are more sensitive to the fermionic electron-hole substructure than regular excitons.

Discharge, Relaxation, and Charge Model for the Lithium Trivanadate Electrode: Reactions, Phase Change, and Transport

DOE PAGES

Brady, Nicholas W.; Zhang, Qing; Knehr, K. W.; ...

2016-10-26

The electrochemical behavior of lithium trivanadate (LiV 3O 8) during lithiation, delithiation, and voltage recovery experiments is simulated using a crystal-scale model that accounts for solid-state diffusion, charge-transfer kinetics, and phase transformations. The kinetic expression for phase change was modeled using an approach inspired by the Avrami formulation for nucleation and growth. Numerical results indicate that the solid-state diffusion coefficient of lithium in LiV 3O 8 is ~ 10 -13 cm 2 s -1 and the equilibrium compositions in the two phase region (~2.5 V) are Li 2.5V 3O 8:Li 4V 3O 8. Agreement between the simulated and experimental resultsmore » is excellent. Relative to the lithiation curves, the experimental delithiation curves show significantly less overpotential and at low levels of lithiation (end of charge). Simulations are only able to capture this result by assuming that the solid-state mass-transfer resistance is less during delithiation. The proposed rationale for this difference is that the (100) face is inactive during lithiation, but active during delithiation. Finally, by assuming non-instantaneous phase-change kinetics, estimates are made for the overpotential due to imperfect phase change (supersaturation).« less

Density functional tight-binding and infrequent metadynamics can capture entropic effects in intramolecular hydrogen transfer reactions

NASA Astrophysics Data System (ADS)

Oliveira, Luiz F. L.; Fu, Christopher D.; Pfaendtner, Jim

2018-04-01

Infrequent metadynamics uses biased simulations to estimate the unbiased kinetics of a system, facilitating the calculation of rates and barriers. Here the method is applied to study intramolecular hydrogen transfer reactions involving peroxy radicals, a class of reactions that is challenging to model due to the entropic contributions of the formation of ring structures in the transition state. Using the self-consistent charge density-functional based tight-binding (DFTB) method, we applied infrequent metadynamics to the study of four intramolecular H-transfer reactions, demonstrating that the method can qualitatively reproduce these high entropic contributions, as observed in experiments and those predicted by transition state theory modeled by higher levels of theory. We also show that infrequent metadynamics and DFTB are successful in describing the relationship between transition state ring size and kinetic coefficients (e.g., activation energies and the pre-exponential factors).

Charge-transfer cross sections in collisions of ground-state Ca and H+

NASA Astrophysics Data System (ADS)

Dutta, C. M.; Oubre, C.; Nordlander, P.; Kimura, M.; Dalgarno, A.

2006-03-01

We have investigated collisions of Ca(4s2) with H+ in the energy range of 200eV/u-10keV/u using the semiclassical molecular-orbital close-coupling (MOCC) method with 18 coupled molecular states ( 11Σ+1 and seven Π+1 states) to determine charge-transfer cross sections. Except for the incoming channel 6Σ+1 , the molecular states all correspond to charge-transfer channels. Inclusion of Ca2+-H- is crucial in the configuration-interaction calculation for generating the molecular wave functions and potentials. Because of the Coulomb attraction, the state separating to Ca2+-H- creates many avoided crossings, even though at infinite separation it lies energetically above all other states that we included. Because of the avoided crossings between the incoming channel 6Σ+1 and the energetically close charge-transfer channel 7Σ+1 the charge-transfer interaction occurs at long range. This makes calculations of charge-transfer cross sections by the MOCC method very challenging. The total charge-transfer cross sections increase monotonically from 3.4×10-15cm2 at 200eV/u to 4.5×10-15cm2 at 10keV/u . Charge transfer occurs mostly to the excited Ca+(5p) state in the entire energy range, which is the sum of the charge transfer to 7Σ+1 and 4Π+1 . It accounts for ˜47% of the total charge transfer cross sections at 200eV/u . However, as the energy increases, transfer to Ca+(4d) increases, and at 10keV/u the charge-transfer cross sections for Ca+(5p) and Ca+(4d) become comparable, each giving ˜38% of the total cross section.

Nanoscale phase engineering of thermal transport with a Josephson heat modulator.

PubMed

Fornieri, Antonio; Blanc, Christophe; Bosisio, Riccardo; D'Ambrosio, Sophie; Giazotto, Francesco

2016-03-01

Macroscopic quantum phase coherence has one of its pivotal expressions in the Josephson effect, which manifests itself both in charge and energy transport. The ability to master the amount of heat transferred through two tunnel-coupled superconductors by tuning their phase difference is the core of coherent caloritronics, and is expected to be a key tool in a number of nanoscience fields, including solid-state cooling, thermal isolation, radiation detection, quantum information and thermal logic. Here, we show the realization of the first balanced Josephson heat modulator designed to offer full control at the nanoscale over the phase-coherent component of thermal currents. Our device provides magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a maximum of the flux-to-temperature transfer coefficient reaching 200 mK per flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the exact correspondence in the phase engineering of charge and heat currents, breaking ground for advanced caloritronic nanodevices such as thermal splitters, heat pumps and time-dependent electronic engines.

Ab initio study of charge transfer in B2+ low-energy collisions with atomic hydrogen

NASA Astrophysics Data System (ADS)

Turner, A. R.; Cooper, D. L.; Wang, J. G.; Stancil, P. C.

2003-07-01

Charge transfer processes due to collisions of ground state B2+(2s 2S) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational coupling matrix elements obtained with the spin-coupled valence-bond approach. Total and state-selective cross sections and rate coefficients are presented. Comparison with the existing experiments shows our results to be in good agreement. When E<80 eV/u, the differences between the current total MOCC cross sections with and without rotational coupling are small (<3%). Rotational coupling becomes more important with increasing energy: for collision energies E>400 eV/u, inclusion of rotational coupling increases the total cross section by 50% 80%, improving the agreement between the current calculations and experiments. For state-selective cross sections, rotational coupling induces mixing between different symmetries; however, its effect, especially at low collision energies, is not as important as had been suggested in previous work.

Synthesis, characterization, and nonlinear optical (NLO) properties of truxene-cored diphenylamine derivatives

NASA Astrophysics Data System (ADS)

Li, Fusheng; Zhao, Baodong; Chen, Yu; Zhang, Yufei; Wang, Tao; Xue, Song

2017-10-01

Three star-shaped compounds based on a truxene core (FS11, FS12 and FS13) were prepared. The truxene core is incorporating with asymmetric diphenylamines, including one phenyl of diphenylamine substituted by methoxy group and the other phenyl substituted by tolyl, fluorophenyl and phenylethynyl for FS11, FS12 and FS13, respectively. Their one-photon, two-photon absorption, geometric structures, electrochemical behavior and thermal properties were investigated. The absorption maxima of charge transfer band for FS11, FS12 and FS13 are 375 nm, 373 nm and 383 nm, and the corresponding molar extinction coefficients of FS11, FS12 and FS13 is 79,950 M- 1 cm- 1, 67,220 M- 1 cm- 1 and 108,780 M- 1 cm- 1. The ;pull-push; structure promotes charge transfer between asymmetric diphenylamine branches and the truxene core. Their two-photon absorbtion property is measured by two-photon induced fluorescence. The maximum two-photon cross-sections values of FS11, FS12 and FS13 are excited at 750 nm, which are 260 GM, 204GM and 367 GM, respectively.

Nanoscale phase engineering of thermal transport with a Josephson heat modulator

NASA Astrophysics Data System (ADS)

Fornieri, Antonio; Blanc, Christophe; Bosisio, Riccardo; D'Ambrosio, Sophie; Giazotto, Francesco

2016-03-01

Macroscopic quantum phase coherence has one of its pivotal expressions in the Josephson effect, which manifests itself both in charge and energy transport. The ability to master the amount of heat transferred through two tunnel-coupled superconductors by tuning their phase difference is the core of coherent caloritronics, and is expected to be a key tool in a number of nanoscience fields, including solid-state cooling, thermal isolation, radiation detection, quantum information and thermal logic. Here, we show the realization of the first balanced Josephson heat modulator designed to offer full control at the nanoscale over the phase-coherent component of thermal currents. Our device provides magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a maximum of the flux-to-temperature transfer coefficient reaching 200 mK per flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the exact correspondence in the phase engineering of charge and heat currents, breaking ground for advanced caloritronic nanodevices such as thermal splitters, heat pumps and time-dependent electronic engines.

The OI/1S/ state - Its quenching by O2 and formation by the dissociative recombination of vibrationally excited O2/+/ ions

NASA Technical Reports Server (NTRS)

Zipf, E. C.

1979-01-01

The rate coefficient for the quenching of metastable O(1S) atoms by O2 was measured as a function of temperature from 250 to 550 K. The resulting Arrhenius expression correlates well with previous laboratory work. It is suggested that the much larger value of the rate coefficient inferred from an analysis of artificial auroral experiment, Precede, may be explained by overestimation of the contribution of O(1S) production from O2(+) dissociative recombination. The possibility that O(1S) atoms are produced only by the dissociative recombination of vibrationally excited O2(+) ions is examined; such excited ions would not exist in the Precede experiment because of the rapid cooling of the ions by resonant charge transfer processes.

Measurement of the transition probability of the C III 190.9 nanometer intersystem line

NASA Technical Reports Server (NTRS)

Kwong, Victor H. S.; Fang, Z.; Gibbons, T. T.; Parkinson, W. H.; Smith, Peter L.

1993-01-01

A radio-frequency ion trap has been used to store C(2+) ions created by electron bombardment of CO. The transition probability for the 2s2p 3Po1-2s2 1S0 intersystem line of C m has been measured by recording the radiative decay at 190.9 nm. The measured A-value is 121 +/- 7/s and agrees, within mutual uncertainty limits, with that of Laughlin et al. (1978), but is 20 percent larger than that of Nussbaumer and Storey (1978). The effective collision mixing rate coefficient among the fine structure levels of 3Po and the combined quenching and charge transfer rate coefficients out of the 3Po1 level with the CO source gas have also been measured.

Synthesis, spectroscopic, thermal and antimicrobial investigations of charge-transfer complexes formed from the drug procaine hydrochloride with quinol, picric acid and TCNQ

NASA Astrophysics Data System (ADS)

Adam, Abdel Majid A.

2012-12-01

Intermolecular charge-transfer or proton-transfer complexes between the drug procaine hydrochloride (PC-HCl) as a donor and quinol (QL), picric acid (PA) or 7,7',8,8'-tetracyanoquinodimethane (TCNQ) as a π-acceptor have been synthesized and spectroscopically studied in methanol at room temperature. Based on elemental analyses and photometric titrations, the stoichiometry of the complexes (donor:acceptor molar ratios) was determined to be 1:1 for all three complexes. The formation constant (KCT), molar extinction coefficient (ɛCT) and other spectroscopic data have been determined using the Benesi-Hildebrand method and its modifications. The newly synthesized CT complexes have been characterized via elemental analysis, IR, Raman, 1H NMR, and electronic absorption spectroscopy. The morphological features of these complexes were investigated using scanning electron microscopy (SEM), and the sharp, well-defined Bragg reflections at specific 2θ angles have been identified from the powder X-ray diffraction patterns. Thermogravimetric analyses (TGAs) and kinetic thermodynamic parameters were also used to investigate the thermal stability of the synthesized solid CT complexes. Finally, the CT complexes were screened for their antibacterial and antifungal activities against various bacterial and fungal strains, and only the complex obtained using picric acid exhibited moderate antibacterial activity against all of the tested strains.

Consideration of Cost of Care in Pediatric Emergency Transfer-An Opportunity for Improvement.

PubMed

Gattu, Rajender K; De Fee, Ann-Sophie; Lichenstein, Richard; Teshome, Getachew

2017-05-01

Pediatric interhospital transfers are an economic burden to the health care, especially when deemed unnecessary. Physicians may be unaware of the cost implications of pediatric emergency transfers. A cost analysis may be relevant to reduce cost. To characterize children transferred from outlying emergency departments (EDs) to pediatric ED (PED) with a specific focus on transfers who were discharged home in 12 hours or less after transfer without intervention in PED and analyze charges associated with them. Charts of 352 patients (age, 0-18 years) transferred from 31 outlying EDs to PED during July 2009 to June 2010 were reviewed. Data were collected on the range, unit charge and volume of services provided in PED, length of stay, and final disposition. The average charge per patient transfer is calculated based on unit charge times total service units per 1000 patients per year and divided by 1000. Hospital charges were divided into fixed and variable. Of 352 patients transferred, 108 (30.7%) were admitted to pediatric inpatient service, 42 (11.9%) to intensive care; 36 (10.2%) went to the operating room, and 166 (47.2%) were discharged home. The average hospital charge per transfer was US $4843. Most (89%) of the charges were fixed, and 11% were variable. One hundred one (28.7%) patients were discharged home from PED in 12 hours or less without intervention. The hospital charges for these transfers were US $489,143. Significant number of transfers was discharged 12 hours or less without any additional intervention in PED. Fixed charges contribute to majority of total charges. Cost saving can be achieved by preventing unnecessary transfer.

Molecular Electronic Coupling Controls Charge Recombination Kinetics in Organic Solar Cells of Low Bandgap Diketopyrrolopyrrole, Carbazole, and Thiophene Polymers

PubMed Central

2013-01-01

Low-bandgap diketopyrrolopyrrole- and carbazole-based polymer bulk-heterojunction solar cells exhibit much faster charge carrier recombination kinetics than that encountered for less-recombining poly(3-hexylthiophene). Solar cells comprising these polymers exhibit energy losses caused by carrier recombination of approximately 100 mV, expressed as reduction in open-circuit voltage, and consequently photovoltaic conversion efficiency lowers in more than 20%. The analysis presented here unravels the origin of that energy loss by connecting the limiting mechanism governing recombination dynamics to the electronic coupling occurring at the donor polymer and acceptor fullerene interfaces. Previous approaches correlate carrier transport properties and recombination kinetics by means of Langevin-like mechanisms. However, neither carrier mobility nor polymer ionization energy helps understanding the variation of the recombination coefficient among the studied polymers. In the framework of the charge transfer Marcus theory, it is proposed that recombination time scale is linked with charge transfer molecular mechanisms at the polymer/fullerene interfaces. As expected for efficient organic solar cells, small electronic coupling existing between donor polymers and acceptor fullerene (Vif < 1 meV) and large reorganization energy (λ ≈ 0.7 eV) are encountered. Differences in the electronic coupling among polymer/fullerene blends suffice to explain the slowest recombination exhibited by poly(3-hexylthiophene)-based solar cells. Our approach reveals how to directly connect photovoltaic parameters as open-circuit voltage to molecular properties of blended materials. PMID:23662167

Quantum Theory of Atoms in Molecules Charge-Charge Transfer-Dipolar Polarization Classification of Infrared Intensities.

PubMed

Duarte, Leonardo J; Richter, Wagner E; Silva, Arnaldo F; Bruns, Roy E

2017-10-26

Fundamental infrared vibrational transition intensities of gas-phase molecules are sensitive probes of changes in electronic structure accompanying small molecular distortions. Models containing charge, charge transfer, and dipolar polarization effects are necessary for a successful classification of the C-H, C-F, and C-Cl stretching and bending intensities. C-H stretching and in-plane bending vibrations involving sp 3 carbon atoms have small equilibrium charge contributions and are accurately modeled by the charge transfer-counterpolarization contribution and its interaction with equilibrium charge movement. Large C-F and C═O stretching intensities have dominant equilibrium charge movement contributions compared to their charge transfer-dipolar polarization ones and are accurately estimated by equilibrium charge and the interaction contribution. The C-F and C-Cl bending modes have charge and charge transfer-dipolar polarization contribution sums that are of similar size but opposite sign to their interaction values resulting in small intensities. Experimental in-plane C-H bends have small average intensities of 12.6 ± 10.4 km mol -1 owing to negligible charge contributions and charge transfer-counterpolarization cancellations, whereas their average out-of-plane experimental intensities are much larger, 65.7 ± 20.0 km mol -1 , as charge transfer is zero and only dipolar polarization takes place. The C-F bending intensities have large charge contributions but very small intensities. Their average experimental out-of-plane intensity of 9.9 ± 12.6 km mol -1 arises from the cancellation of large charge contributions by dipolar polarization contributions. The experimental average in-plane C-F bending intensity, 5.8 ± 7.3 km mol -1 , is also small owing to charge and charge transfer-counterpolarization sums being canceled by their interaction contributions. Models containing only atomic charges and their fluxes are incapable of describing electronic structure changes for simple molecular distortions that are of interest in classifying infrared intensities. One can expect dipolar polarization effects to also be important for larger distortions of chemical interest.

Thermally coupled moving boundary model for charge-discharge of LiFePO4/C cells

NASA Astrophysics Data System (ADS)

Khandelwal, Ashish; Hariharan, Krishnan S.; Gambhire, Priya; Kolake, Subramanya Mayya; Yeo, Taejung; Doo, Seokgwang

2015-04-01

Optimal thermal management is a key requirement in commercial utilization of lithium ion battery comprising of phase change electrodes. In order to facilitate design of battery packs, thermal management systems and fast charging profiles, a thermally coupled electrochemical model that takes into account the phase change phenomenon is required. In the present work, an electrochemical thermal model is proposed which includes the biphasic nature of phase change electrodes, such as lithium iron phosphate (LFP), via a generalized moving boundary model. The contribution of phase change to the heat released during the cell operation is modeled using an equivalent enthalpy approach. The heat released due to phase transformation is analyzed in comparison with other sources of heat such as reversible, irreversible and ohmic. Detailed study of the thermal behavior of the individual cell components with changing ambient temperature, rate of operation and heat transfer coefficient is carried out. Analysis of heat generation in the various regimes is used to develop cell design and operating guidelines. Further, different charging protocols are analyzed and a model based methodology is suggested to design an efficient quick charging protocol.

Spectrophotometric determination of fenoprofen calcium drug in pure and pharmaceutical preparations. Spectroscopic characterization of the charge transfer solid complexes

NASA Astrophysics Data System (ADS)

Mohamed, Marwa E.; Frag, Eman Y. Z.; Hathoot, Abla A.; Shalaby, Essam A.

2018-01-01

Simple, accurate and robust spectrophotometric method was developed for determination of fenoprofen calcium drug (FPC). The proposed method was based on the charge transfer (CT) reaction of FPC drug (as n-electron donor) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,4,6-trinitrophenol (picric acid, PA) or 1,2,5,8-tetrahydroxyanthraquinone (Quinalizarin, QZ) (as π-acceptors) to give highly colored charge transfer complexes. Different variables affecting the reaction such as reagent concentration, temperature and time have been carefully optimized to achieve the highest sensitivity. Beer's law was obeyed over the concentration ranges of 2-60, 0.6-90 and 4-30 μg mL- 1 using DDQ, PA and QZ CT reagents, respectively, with correlation coefficients of 0.9986, 0.9989 and 0.997 and detection limits of 1.78, 0.48 and 2.6 μg mL- 1 for the CT reagents in the same order. Elucidation of the chemical structure of the solid CT complexes formed via reaction between the drug under study and π-acceptors was done using elemental, thermal analyses, IR, 1H NMR and mass spectrometry. X-ray diffraction was used to estimate the crystallinity of the CT complexes. Their biological activities were screened against different bacterial and fungal organisms. The method was applied successfully with satisfactory results for the determination of FPC drug in fenoprofen capsules. The method was validated with respect to linearity, limit of detection and quantification, inter- and intra-days precision and accuracy. The proposed method gave comparable results with the official method.

On the meaning of the diffusion layer thickness for slow electrode reactions.

PubMed

Molina, A; González, J; Laborda, E; Compton, R G

2013-02-21

A key concept underpinning electrochemical science is that of the diffusion layer - the zone of depletion around an electrode accompanying electrolysis. The size of this zone can be found either from the simulated or measured concentration profiles (yielding the 'true' diffusion layer thickness) or, in the case of the Nernst ('linear') diffusion layer by extrapolating the concentration gradient at the electrode surface to the distance at which the concentration takes its bulk value. The latter concept is very well developed in the case of fast (so-called reversible) electrode processes, however the study of the linear diffusion layer has received scant attention in the case of slow charge transfer processes, despite its study being of great interest in the analysis of the influence of different experimental variables which determine the electrochemical response. Analytical explicit solutions for the concentration profiles, surface concentrations and real and linear diffusion layers corresponding to the application of a potential step to a slow charge transfer process are presented. From these expressions the dependence of the diffusion layer thickness on the potential, pulse time, heterogeneous rate constant and ratio of bulk concentrations of electroactive species and of diffusion coefficients is quantified. A profound influence of the reversibility degree of the charge transfer on the diffusion layer thickness is clear, showing that for non-reversible processes the real and linear diffusion layers reveal a minimum thickness which coincides with the equilibrium potential of the redox couple in the former case and with the reversible half-wave potential in the latter one.

Charge Transfer Inefficiency in Pinned Photodiode CMOS image sensors: Simple Montecarlo modeling and experimental measurement based on a pulsed storage-gate method

NASA Astrophysics Data System (ADS)

Pelamatti, Alice; Goiffon, Vincent; Chabane, Aziouz; Magnan, Pierre; Virmontois, Cédric; Saint-Pé, Olivier; de Boisanger, Michel Breart

2016-11-01

The charge transfer time represents the bottleneck in terms of temporal resolution in Pinned Photodiode (PPD) CMOS image sensors. This work focuses on the modeling and estimation of this key parameter. A simple numerical model of charge transfer in PPDs is presented. The model is based on a Montecarlo simulation and takes into account both charge diffusion in the PPD and the effect of potential obstacles along the charge transfer path. This work also presents a new experimental approach for the estimation of the charge transfer time, called pulsed Storage Gate (SG) method. This method, which allows reproduction of a ;worst-case; transfer condition, is based on dedicated SG pixel structures and is particularly suitable to compare transfer efficiency performances for different pixel geometries.

Charge transfer efficiency improvement of 4T pixel for high speed CMOS image sensor

NASA Astrophysics Data System (ADS)

Jin, Xiangliang; Liu, Weihui; Yang, Hongjiao; Tang, Lizhen; Yang, Jia

2015-03-01

The charge transfer efficiency improvement method is proposed by optimizing the electrical potential distribution along the transfer path from the PPD to the FD. In this work, we present a non-uniform doped transfer transistor channel, with the adjustments to the overlap length between the CPIA layer and the transfer gate, and the overlap length between the SEN layer and transfer gate. Theory analysis and TCAD simulation results show that the density of the residual charge reduces from 1e11 /cm3 to 1e9 /cm3, and the transfer time reduces from 500 ns to 143 ns, and the charge transfer efficiency is about 77 e-/ns. This optimizing design effectively improves the charge transfer efficiency of 4T pixel and the performance of 4T high speed CMOS image sensor.

The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures

DOE PAGES

Wang, Han; Bang, Junhyeok; Sun, Yiyang; ...

2016-05-10

Here, the success of van der Waals (vdW) heterostructures, made of graphene, metal dichalcogenides, and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that vdW heterostructues can exhibit ultra-fast charge transfer despite the weak binding of the heterostructure. Using time-dependent density functional theory molecular dynamics, we identify a strong dynamic coupling between the vdW layers associated with charge transfer. This dynamic coupling results in rapid nonlinear coherentmore » charge oscillations which constitute a purely electronic phenomenon and are shown to be a general feature of vdW heterostructures provided they have a critical minimum dipole coupling. Application to MoS2/WS2 heterostructure yields good agreement with experiment, indicating near complete charge transfer within a timescale of 100 fs.The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the interface. Application to the MoS2/WS2 heterostructure yields good agreement with experiments, indicating near complete charge transfer within a timescale of 100 fs.« less

The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures

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

Wang, Han; Bang, Junhyeok; Sun, Yiyang

Here, the success of van der Waals (vdW) heterostructures, made of graphene, metal dichalcogenides, and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that vdW heterostructues can exhibit ultra-fast charge transfer despite the weak binding of the heterostructure. Using time-dependent density functional theory molecular dynamics, we identify a strong dynamic coupling between the vdW layers associated with charge transfer. This dynamic coupling results in rapid nonlinear coherentmore » charge oscillations which constitute a purely electronic phenomenon and are shown to be a general feature of vdW heterostructures provided they have a critical minimum dipole coupling. Application to MoS2/WS2 heterostructure yields good agreement with experiment, indicating near complete charge transfer within a timescale of 100 fs.The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the interface. Application to the MoS2/WS2 heterostructure yields good agreement with experiments, indicating near complete charge transfer within a timescale of 100 fs.« less

Poly(methylene blue) functionalized graphene modified carbon ionic liquid electrode for the electrochemical detection of dopamine.

PubMed

Sun, Wei; Wang, Yuhua; Zhang, Yuanyuan; Ju, Xiaomei; Li, Guangjiu; Sun, Zhenfan

2012-11-02

An ionic liquid 1-butylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) was used as the substrate electrode and a poly(methylene blue) (PMB) functionalized graphene (GR) composite film was co-electrodeposited on CILE surface by cyclic voltammetry. The PMB-GR/CILE exhibited better electrochemical performances with higher conductivity and lower electron transfer resistance. Electrochemical behavior of dopamine (DA) was further investigated by cyclic voltammetry and a pair of well-defined redox peaks appeared with the peak-to-peak separation (ΔE(p)) as 0.058V in 0.1 mol L(-1) pH 6.0 phosphate buffer solution, which proved a fast quasi-reversible electron transfer process on the modified electrode. Electrochemical parameters of DA on PMB-GR/CILE were calculated with the electron transfer number as 1.83, the charge transfer coefficients as 0.70, the apparent heterogeneous electron transfer rate constant as 1.72 s(-1) and the diffusional coefficient (D) as 3.45×10(-4) cm(2) s(-1), respectively. Under the optimal conditions with differential pulse voltammetric measurement, the linear relationship between the oxidation peak current of DA and its concentration was obtained in the range from 0.02 to 800.0 μmol L(-1) with the detection limit as 5.6 nmol L(-1) (3σ). The coexisting substances exhibited no interference and PMB-GR/CILE was applied to the detection of DA injection samples and human urine samples with satisfactory results. Copyright © 2012 Elsevier B.V. All rights reserved.

Radiative loss and charge exchange in low energy Na - Ca+ collisions

NASA Astrophysics Data System (ADS)

McLaughlin, B. M.; McAlpine, K.; McCann, J. F.; Pattillo, R.; Stancil, P. C.; Forrey, R. C.; Babb, J. F.

2016-05-01

Experiments on radiative loss and capture are currently being performed at the University of Connecticut. In response to this experimental effort we have performed detailed calculations for a variety of loss and capture processes. Several low lying states of the NaCa+ cation are used with the accurate potentials energy curves, transition dipole moments and non-adiabatic coupling matrix elements between the states, obtained at the MRCI+Q level of approximation with the MOLPRO suite of quantum chemistry codes. Cross sections and rate coefficients are calculated for radiative charge transfer (RCX), radiative association (RA) and charge exchange in a fully quantum molecular close-coupling (MOCC) approximation at the higher energies. We use a variety of approaches, the optical potential method, semi-classical and MOCC methods to compare and contrast approximations. In addition a kinetic theory recently applied to SiO is utilized which illustrates the dramatic impact resonances have on the radiative association rates. Supported by NASA and HLRS at Stuttgart University.

Electron Scattering from MERCURY-198 and Mercury -204.

NASA Astrophysics Data System (ADS)

Laksanaboonsong, Jarungsaeng

This experiment is the first electron scattering study on mercury isotopes. Electron scattering from ^{198}Hg and ^{204 }Hg has been performed at the NIKHEF-K Medium Energy Accelerator. Measured cross sections cover an effective momentum transfer range from 0.4 to 2.9 fm^ {-1}. Elastic cross sections were determined for scattering from both isotopes. Cross section for inelastic excitations in ^{198}Hg below 3 MeV were also determined. Measured cross sections were fit using DWBA phase shift codes to determine coefficients for Fourier-Bessel expansions of ground state and transition charge densities. Differences between the ground state charge densities of the two isotopes reveal the effect of the polarization of the proton core in response to the addition of neutrons. Spin and parity of several excited states of ^{198}Hg were determined. Extracted transition densities of these states show their predominantly collective nature. Charge densities for members of the ground state rotational band were compared with axially symmetric Hartree-Fock and geometrical model predictions.

Quantum simulation of an ultrathin body field-effect transistor with channel imperfections

NASA Astrophysics Data System (ADS)

Vyurkov, V.; Semenikhin, I.; Filippov, S.; Orlikovsky, A.

2012-04-01

An efficient program for the all-quantum simulation of nanometer field-effect transistors is elaborated. The model is based on the Landauer-Buttiker approach. Our calculation of transmission coefficients employs a transfer-matrix technique involving the arbitrary precision (multiprecision) arithmetic to cope with evanescent modes. Modified in such way, the transfer-matrix technique turns out to be much faster in practical simulations than that of scattering-matrix. Results of the simulation demonstrate the impact of realistic channel imperfections (random charged centers and wall roughness) on transistor characteristics. The Landauer-Buttiker approach is developed to incorporate calculation of the noise at an arbitrary temperature. We also validate the ballistic Landauer-Buttiker approach for the usual situation when heavily doped contacts are indispensably included into the simulation region.

Quantal diffusion description of multinucleon transfers in heavy-ion collisions

NASA Astrophysics Data System (ADS)

Ayik, S.; Yilmaz, B.; Yilmaz, O.; Umar, A. S.

2018-05-01

Employing the stochastic mean-field (SMF) approach, we develop a quantal diffusion description of the multi-nucleon transfer in heavy-ion collisions at finite impact parameters. The quantal transport coefficients are determined by the occupied single-particle wave functions of the time-dependent Hartree-Fock equations. As a result, the primary fragment mass and charge distribution functions are determined entirely in terms of the mean-field properties. This powerful description does not involve any adjustable parameter, includes the effects of shell structure, and is consistent with the fluctuation-dissipation theorem of the nonequilibrium statistical mechanics. As a first application of the approach, we analyze the fragment mass distribution in 48Ca+ 238U collisions at the center-of-mass energy Ec.m.=193 MeV and compare the calculations with the experimental data.

Effect of various refining processes for Kenaf Bast non-wood pulp fibers suspensions on heat transfer coefficient in circular pipe heat exchanger

NASA Astrophysics Data System (ADS)

Ahmed, Syed Muzamil; Kazi, S. N.; Khan, Ghulamullah; Sadri, Rad; Dahari, Mahidzal; Zubir, M. N. M.; Sayuti, M.; Ahmad, Pervaiz; Ibrahim, Rushdan

2018-03-01

Heat transfer coefficients were obtained for a range of non-wood kenaf bast pulp fiber suspensions flowing through a circular pipe heat exchanger test loop. The data were produced over a selected temperature and range of flow rates from the flow loop. It was found that the magnitude of the heat transfer coefficient of a fiber suspension is dependent on characteristics, concentration and pulping method of fiber. It was observed that at low concentration and high flow rates, the heat transfer coefficient values of suspensions were observed higher than that of the heat transfer coefficient values of water, on the other hand the heat transfer coefficient values of suspensions decreases at low flow rates and with the increase of their concentration. The heat transfer were affected by varying fiber characteristics, such as fiber length, fiber flexibility, fiber chemical and mechanical treatment as well as different pulping methods used to liberate the fibers. Heat transfer coefficient was decreased with the increase of fiber flexibility which was also observed by previous researchers. In the present work, the characteristics of fibers are correlated with the heat transfer coefficient of suspensions of the fibers. Deviations in fiber properties can be monitored from the flowing fiber suspensions by measuring heat transfer coefficient to adjust the degree of fiber refining treatment so that papers made from those fibers will be more uniform, consistent, within the product specification and retard the paper production loss.

Charge migration and charge transfer in molecular systems

PubMed Central

Wörner, Hans Jakob; Arrell, Christopher A.; Banerji, Natalie; Cannizzo, Andrea; Chergui, Majed; Das, Akshaya K.; Hamm, Peter; Keller, Ursula; Kraus, Peter M.; Liberatore, Elisa; Lopez-Tarifa, Pablo; Lucchini, Matteo; Meuwly, Markus; Milne, Chris; Moser, Jacques-E.; Rothlisberger, Ursula; Smolentsev, Grigory; Teuscher, Joël; van Bokhoven, Jeroen A.; Wenger, Oliver

2017-01-01

The transfer of charge at the molecular level plays a fundamental role in many areas of chemistry, physics, biology and materials science. Today, more than 60 years after the seminal work of R. A. Marcus, charge transfer is still a very active field of research. An important recent impetus comes from the ability to resolve ever faster temporal events, down to the attosecond time scale. Such a high temporal resolution now offers the possibility to unravel the most elementary quantum dynamics of both electrons and nuclei that participate in the complex process of charge transfer. This review covers recent research that addresses the following questions. Can we reconstruct the migration of charge across a molecule on the atomic length and electronic time scales? Can we use strong laser fields to control charge migration? Can we temporally resolve and understand intramolecular charge transfer in dissociative ionization of small molecules, in transition-metal complexes and in conjugated polymers? Can we tailor molecular systems towards specific charge-transfer processes? What are the time scales of the elementary steps of charge transfer in liquids and nanoparticles? Important new insights into each of these topics, obtained from state-of-the-art ultrafast spectroscopy and/or theoretical methods, are summarized in this review. PMID:29333473

DFT-INDO/S modeling of new high molar extinction coefficient charge-transfer sensitizers for solar cell applications.

PubMed

Nazeeruddin, Mohammad K; Wang, Qing; Cevey, Le; Aranyos, Viviane; Liska, Paul; Figgemeier, Egbert; Klein, Cedric; Hirata, Narukuni; Koops, Sara; Haque, Saif A; Durrant, James R; Hagfeldt, Anders; Lever, A B P; Grätzel, Michael

2006-01-23

A new ruthenium(II) complex, tetrabutylammonium [ruthenium (4-carboxylic acid-4'-carboxylate-2,2'-bipyridine)(4,4'-di(2-(3,6-dimethoxyphenyl)ethenyl)-2,2'-bipyridine)(NCS)(2)] (N945H), was synthesized and characterized by analytical, spectroscopic, and electrochemical techniques. The absorption spectrum of the N945H sensitizer is dominated by metal-to-ligand charge-transfer (MLCT) transitions in the visible region, with the lowest allowed MLCT bands appearing at 25 380 and 18 180 cm(-1). The molar extinction coefficients of these bands are 34 500 and 18 900 M(-1) cm(-1), respectively, and are significantly higher when compared to than those of the standard sensitizer cis-dithiocyanatobis(4,4'-dicarboxylic acid-2,2'-bipyridine)ruthenium(II). An INDO/S and density functional theory study of the electronic and optical properties of N945H and of N945 adsorbed on TiO(2) was performed. The calculations point out that the top three frontier-filled orbitals have essentially ruthenium 4d (t(2g) in the octahedral group) character with sizable contribution coming from the NCS ligand orbitals. Most critically the calculations reveal that, in the TiO(2)-bound N945 sensitizer, excitation directs charge into the carboxylbipyridine ligand bound to the TiO(2) surface. The photovoltaic data of the N945 sensitizer using an electrolyte containing 0.60 M butylmethylimidazolium iodide, 0.03 M I(2), 0.10 M guanidinium thiocyanate, and 0.50 M tert-butylpyridine in a mixture of acetonitrile and valeronitrile (volume ratio = 85:15) exhibited a short-circuit photocurrent density of 16.50 +/- 0.2 mA cm(-2), an open-circuit voltage of 790 +/- 30 mV, and a fill factor of 0.72 +/- 0.03, corresponding to an overall conversion efficiency of 9.6% under standard AM (air mass) 1.5 sunlight, and demonstrated a stable performance under light and heat soaking at 80 degrees C.

Comparison of diffusivity data derived from electrochemical and NMR investigations of the SeCN¯/(SeCN)2/(SeCN)3¯ system in ionic liquids.

PubMed

Solangi, Amber; Bond, Alan M; Burgar, Iko; Hollenkamp, Anthony F; Horne, Michael D; Rüther, Thomas; Zhao, Chuan

2011-06-02

Electrochemical studies in room temperature ionic liquids are often hampered by their relatively high viscosity. However, in some circumstances, fast exchange between participating electroactive species has provided beneficial enhancement of charge transport. The iodide (I¯)/iodine (I(2))/triiodide (I(3)¯) redox system that introduces exchange via the I¯ + I(2) ⇌ I(3)¯ process is a well documented example because it is used as a redox mediator in dye-sensitized solar cells. To provide enhanced understanding of ion movement in RTIL media, a combined electrochemical and NMR study of diffusion in the {SeCN¯-(SeCN)(2)-(SeCN)(3)¯} system has been undertaken in a selection of commonly used RTILs. In this system, each of the Se, C and N nuclei is NMR active. The electrochemical behavior of the pure ionic liquid, [C(4)mim][SeCN], which is synthesized and characterized here for the first time, also has been investigated. Voltammetric studies, which yield readily interpreted diffusion-limited responses under steady-state conditions by means of a Random Assembly of Microdisks (RAM) microelectrode array, have been used to measure electrochemically based diffusion coefficients, while self-diffusion coefficients were measured by pulsed field gradient NMR methods. The diffusivity data, derived from concentration and field gradients respectively, are in good agreement. The NMR data reveal that exchange processes occur between selenocyanate species, but the voltammetric data show the rates of exchange are too slow to enhance charge transfer. Thus, a comparison of the iodide and selenocyanate systems is somewhat paradoxical in that while the latter give RTILs of low viscosity, sluggish exchange kinetics prevent any significant enhancement of charge transfer through direct electron exchange. In contrast, faster exchange between iodide and its oxidation products leads to substantial electron exchange but this effect does not compensate sufficiently for mass transport limitations imposed by the higher viscosity of iodide RTILs.

Transport of the highly charged myo-inositol hexakisphosphate molecule across the red blood cell membrane: a phase transfer and biological study.

PubMed

Vincent, Stéphane P; Lehn, Jean-Marie; Lazarte, Jaime; Nicolau, Claude

2002-09-01

To address the problem of delivering highly charged small molecules, such as phytic acid (InsP(6) or IHP), across biological membranes, we investigated an approach based on a non-covalent interaction between transport molecule(s) and IHP. Thus, we synthesized a collection of compounds containing IHP ionically bound to lipophilic (but non-lipidic) ammonium or poly-ammonium cations. First, we assessed the ability of these water-soluble salts to cross a biological membrane by measuring the partition coefficients between human serum and 1-octanol. In view of the ability of IHP to act as potent effector for oxygen release, the O(2)-hemoglobin dissociation curves were then measured for the most efficient salts on whole blood. From both the biological and the physical properties of IHP-ammonium salts we determined that cycloalkylamines (or poly-amines) were the best transport molecules, especially cycloheptyl- and cyclooctylamine. Indeed, the octanol/serum partition coefficient of IHP undecacyclooctylammonium salt, is superior to 1, which is very favorable for potential uptake into the red blood cell membrane. A qualitative correlation was found between the partitioning experiments and the biological evaluations performed on whole blood.

Accurate on-chip measurement of the Seebeck coefficient of high mobility small molecule organic semiconductors

NASA Astrophysics Data System (ADS)

Warwick, C. N.; Venkateshvaran, D.; Sirringhaus, H.

2015-09-01

We present measurements of the Seebeck coefficient in two high mobility organic small molecules, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) and 2,9-didecyl-dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (C10-DNTT). The measurements are performed in a field effect transistor structure with high field effect mobilities of approximately 3 cm2/V s. This allows us to observe both the charge concentration and temperature dependence of the Seebeck coefficient. We find a strong logarithmic dependence upon charge concentration and a temperature dependence within the measurement uncertainty. Despite performing the measurements on highly polycrystalline evaporated films, we see an agreement in the Seebeck coefficient with modelled values from Shi et al. [Chem. Mater. 26, 2669 (2014)] at high charge concentrations. We attribute deviations from the model at lower charge concentrations to charge trapping.

Impact of charge-transfer excitons in regioregular polythiophene on the charge separation at polythiophene-fullerene heterojunctions

NASA Astrophysics Data System (ADS)

Polkehn, M.; Tamura, H.; Burghardt, I.

2018-01-01

This study addresses the mechanism of ultrafast charge separation in regioregular oligothiophene-fullerene assemblies representative of poly-3-hexylthiophene (P3HT)-[6,6]-phenyl-C61 butyric acid methyl ester (PCBM) heterojunctions, with special emphasis on the inclusion of charge transfer excitons in the oligothiophene phase. The formation of polaronic inter-chain charge separated species in highly ordered oligothiophene has been demonstrated in recent experiments and could have a significant impact on the net charge transfer to the fullerene acceptor. The present approach combines a first-principles parametrized multi-site Hamiltonian, based on time-dependent density functional theory calculations, with accurate quantum dynamics simulations using the multi-layer multi-configuration time-dependent Hartree method. Quantum dynamical studies are carried out for up to 182 electronic states and 112 phonon modes. The present analysis follows up on our previous study of (Huix-Rotllant et al 2015 J. Phys. Chem. Lett. 6 1702) and significantly expands the scope of this analysis by including the dynamical role of charge transfer excitons. Our investigation highlights the pronounced mixing of photogenerated Frenkel excitons with charge transfer excitons in the oligothiophene domain, and the opening of new transfer channels due the creation of such charge-separated species. As a result, it turns out that the interfacial donor/acceptor charge transfer state can be largely circumvented due to the presence of charge transfer excitons. However, the latter states in turn act as a trap, such that the free carrier yield observed on ultrafast time scales is tangibly reduced. The present analysis underscores the complexity of the transfer pathways at P3HT-PCBM type junctions.

Prediction of mass transfer coefficient in rotating bed contactor (Higee) using artificial neural network

NASA Astrophysics Data System (ADS)

Saha, Dipendu

2009-02-01

The feasibility of drastically reducing the contactor size in mass transfer processes utilizing centrifugal field has generated a lot of interest in rotating packed bed (Higee). Various investigators have proposed correlations to predict mass transfer coefficients in Higee, but, none of the correlations was more than 20-30% accurate. In this work, artificial neural network (ANN) is employed for predicting mass transfer coefficient data. Results show that ANN provides better estimation of mass transfer coefficient with accuracy 5-15%.

Substituent and Solvent Effects on Excited State Charge Transfer Behavior of Highly Fluorescent Dyes Containing Thiophenylimidazole-Based Aldehydes

NASA Technical Reports Server (NTRS)

Santos, Javier; Bu, Xiu R.; Mintz, Eric A.

2001-01-01

The excited state charge transfer for a series of highly fluorescent dyes containing thiophenylimidazole moiety was investigated. These systems follow the Twisted Intramolecular Charge Transfer (TICT) model. Dual fluorescence was observed for each substituted dye. X-ray structures analysis reveals a twisted ground state geometry for the donor substituted aryl on the 4 and 5 position at the imidazole ring. The excited state charge transfer was modeled by a linear solvation energy relationship using Taft's pi and Dimroth's E(sub T)(30) as solvent parameters. There is linear relation between the energy of the fluorescence transition and solvent polarity. The degree of stabilization of the excited state charge transfer was found to be consistent with the intramolecular molecular charge transfer. Excited dipole moment was studied by utilizing the solvatochromic shift method.

Development of a fully integrated falling film microreactor for gas-liquid-solid biotransformation with surface immobilized O2 -dependent enzyme.

PubMed

Bolivar, Juan M; Krämer, Christina E M; Ungerböck, Birgit; Mayr, Torsten; Nidetzky, Bernd

2016-09-01

Microstructured flow reactors are powerful tools for the development of multiphase biocatalytic transformations. To expand their current application also to O2 -dependent enzymatic conversions, we have implemented a fully integrated falling film microreactor that provides controllable countercurrent gas-liquid phase contacting in a multi-channel microstructured reaction plate. Advanced non-invasive optical sensing is applied to measure liquid-phase oxygen concentrations in both in- and out-flow as well as directly in the microchannels (width: 600 μm; depth: 200 μm). Protein-surface interactions are designed for direct immobilization of catalyst on microchannel walls. Target enzyme (here: d-amino acid oxidase) is fused to the positively charged mini-protein Zbasic2 and the channel surface contains a negatively charged γ-Al2 O3 wash-coat layer. Non-covalent wall attachment of the chimeric Zbasic2 _oxidase resulted in fully reversible enzyme immobilization with fairly uniform surface coverage and near complete retention of biological activity. The falling film at different gas and liquid flow rates as well as reactor inclination angles was shown to be mostly wavy laminar. The calculated film thickness was in the range 0.5-1.3 × 10(-4)  m. Direct O2 concentration measurements at the channel surface demonstrated that the liquid side mass transfer coefficient (KL ) for O2 governed the overall gas/liquid/solid mass transfer and that the O2 transfer rate (≥0.75 mM · s(-1) ) vastly exceeded the maximum enzymatic reaction rate in a wide range of conditions. A value of 7.5 (±0.5) s(-1) was determined for the overall mass transfer coefficient KL a, comprising a KL of about 7 × 10(-5)  m · s(-1) and a specific surface area of up to 10(5)  m(-1) . Biotechnol. Bioeng. 2016;113: 1862-1872. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Kinetics of nickel electrodeposition from low electrolyte concentration and at a narrow interelectrode gap

NASA Astrophysics Data System (ADS)

Widayatno, Tri

2015-12-01

Electrodeposition of nickel onto copper in a system of low Ni2+ concentration and at a narrow interelectrode gap has been carried out. This electrochemical system was required for maskless pattern transfer through electroplating (Enface technique). Kinetics of Electrochemical reaction of Nickel is relatively slow, where such electrochemical system has never been used in this technology. Study on the kinetics of the electrochemical reaction of nickel in such system is essential due to the fact that the quality of an electrodeposited nickel is affected by kinetics. Analytical and graphical methods were utilised to determine kinetic parameters. The kinetic model was approximated by Butler-Volmer and j-η equation. Kinetic parameters such as exchange current density (j0) and charge transfer coefficient (α) were also graphically determined using the plot of η vs. log|j| known as Tafel plot. The polarisation data for an unstirred 0.19 M nickel sulfamate solution at 0.5 mV/s scan rate and RDE system was used. The results indicate that both methods are fairly accurate. For the analytical, the Tafel slope, the exchange current density, and charge transfer coefficient were found to be 149 mV/dec, 1.60 × 10-4 mA/cm2, and 0.39 respectively, whilst for the graphical method were 159 mV/dec, 3.16 × 10-4 mA/cm2, and 0.37. The kinetics parameters in this current study were also compared to those in literature. Significant differences were observed which might be due to the effect of composition and concentration of the electrolytes, operating temperature, and pH leading to the different reaction mechanism. However, the results obtained in this work are in the range of acceptable values. These kinetic parameters will then be used in further study of nickel deposition by modelling and simulation

Spontaneous charged lipid transfer between lipid vesicles.

PubMed

Richens, Joanna L; Tyler, Arwen I I; Barriga, Hanna M G; Bramble, Jonathan P; Law, Robert V; Brooks, Nicholas J; Seddon, John M; Ces, Oscar; O'Shea, Paul

2017-10-03

An assay to study the spontaneous charged lipid transfer between lipid vesicles is described. A donor/acceptor vesicle system is employed, where neutrally charged acceptor vesicles are fluorescently labelled with the electrostatic membrane probe Fluoresceinphosphatidylethanolamine (FPE). Upon addition of charged donor vesicles, transfer of negatively charged lipid occurs, resulting in a fluorescently detectable change in the membrane potential of the acceptor vesicles. Using this approach we have studied the transfer properties of a range of lipids, varying both the headgroup and the chain length. At the low vesicle concentrations chosen, the transfer follows a first-order process where lipid monomers are transferred presumably through the aqueous solution phase from donor to acceptor vesicle. The rate of transfer decreases with increasing chain length which is consistent with energy models previously reported for lipid monomer vesicle interactions. Our assay improves on existing methods allowing the study of a range of unmodified lipids, continuous monitoring of transfer and simplified experimental procedures.

Laboratory Studies of Thermal Energy Charge Transfer of Silicon and Iron Ions in Astrophysical Plasmas

NASA Technical Reports Server (NTRS)

Kwong, Victor H. S.

1996-01-01

Charge transfer at electron-volt energies between multiply charged atomic ions and neutral atoms and molecules is of considerable importance in astrophysics, plasma physics, and in particular, fusion plasmas. In the year covered by this report, several major tasks were completed. These include: (1) the re-calibration of the ion gauge to measure the absolute particle densities of H2, He, N2, and CO for our current measurements; (2) the analysis of data for charge transfer reactions of N(exp 2 plus) ion and He, H2, N2, and CO; (3) measurement and data analysis of the charge transfer reaction of (Fe(exp 2 plus) ion and H2; (4) charge transfer measurement of Fe(exp 2 plus) ion and H2; and (5) redesign and modification of the ion detection and data acquisition system for the low energy beam facility (reflection time of flight mass spectrometer) dedicated to the study of state select charge transfer.

Molecular orbital (SCF-Xα-SW) theory of metal-metal charge transfer processes in minerals - II. Application to Fe2+ --> Ti4+ charge transfer transitions in oxides and silicates

USGS Publications Warehouse

Sherman, David M.

1987-01-01

A molecular orbital description, based on Xα-Scattered wave calculations on a (FeTiO10)14− cluster, is given for Fe2+ → Ti4+ charge transfer transitions in minerals. The calculated energy for the lowest Fe2+ → Ti4+ metal-metal charge transfer transition is 18040 cm−1 in reasonable agreement with energies observed in the optical spectra of Fe-Ti oxides and silicates. As in the case of Fe2+ → Fe3+ charge transfer in mixed-valence iron oxides and silicates, Fe2+ → Ti4+ charge transfer is associated with Fe-Ti bonding across shared polyhedral edges. Such bonding results from the overlap of the Fe(t 2g ) and Ti(t 2g ) 3d orbitals.

Charge transfer transitions in optical spectra of NicMg1-cO oxides

NASA Astrophysics Data System (ADS)

Churmanov, V. N.; Sokolov, V. I.; Pustovarov, V. A.; Gruzdev, N. B.; Uimin, M. A.; Byzov, I. V.; Druzhinin, A. V.; Korolyov, A. V.; Kim, G. A.; Zatsepin, A. F.; Kuznetsova, J. A.

2017-04-01

Radiative recombination with charge transfer was observed in NicMg1-cO (c = 0.008) oxides over the 8-300 K temperature range. This recombination occurs as a result of strong hybridization of the Ni2+ ion 3d-states and the band states. The charge transfer radiation excitation spectrum shows vibrational LO repeats of two exciton lines having charge transfer energy intervals of about 35 meV. The NiO nanocrystal absorption spectrum shows two weak peaks with energies of 3.510 and 3.543 eV, which are highly dependent on temperature. They are interpreted as charge transfer excitons at the edge of NiO fundamental absorption. The distance between the charge transfer exciton lines in the NicMg1-cO oxide spectra are caused by spin-orbit splitting of the valence band peak that was formed by the p-states of the oxygen ion.

Introduction of gold nanoparticles into myoglobin-Nafion film for direct electrochemistry application.

PubMed

Xie, Wenting; Kong, Linlin; Kan, Meixiu; Han, Dongmei; Wang, Xueji; Zhang, Hui-Min

2010-10-01

An effective myoglobin-Nafion film is prepared by introducing gold nanoparticles in through a simple procedure by ion-exchange combined with electrochemical reduction. Gold nanoparticles are highly dispersed in myoglobin-Nafion film with an average size of 2.3 +/- 0.2 nm. The electrochemical behavior of myoglobin entrapped in the film has been carefully investigated with cyclic voltammetry. The results show that the introduction of gold nanoparticles into myoglobin-Nafion film makes the direct electron transfer of myoglobin efficient. A pair of well-defined redox peaks for myoglobin heme Fe(II)/Fe(III) is observed with a formal potential of -0.150 V in 0.1 M phosphate buffer (pH 7.0). The electrochemical parameters of myoglobin in the composite film are further calculated with the results of the electron-transfer rate constant (k(s)) as 0.93 s(-1) and the charge transfer coefficient (alpha) as 0.69. The experimental results also demonstrate that the immobilized myoglobin retains its electrocatalytic activity for the reduction of hydrogen peroxide and the catalytic reduction peak of myoglobin appear in a linear relationship with H2O2 concentration in the range of 10.0-235.0 microM with correlation coefficient of 0.9970. Thus fabricated Au/Mb/Nafion electrode should give a new approach for developing redox protein or enzyme-based biosensors.

Investigation of two-phase heat transfer coefficients of argon-freon cryogenic mixed refrigerants

NASA Astrophysics Data System (ADS)

Baek, Seungwhan; Lee, Cheonkyu; Jeong, Sangkwon

2014-11-01

Mixed refrigerant Joule Thomson refrigerators are widely used in various kinds of cryogenic systems these days. Although heat transfer coefficient estimation for a multi-phase and multi-component fluid in the cryogenic temperature range is necessarily required in the heat exchanger design of mixed refrigerant Joule Thomson refrigerators, it has been rarely discussed so far. In this paper, condensation and evaporation heat transfer coefficients of argon-freon mixed refrigerant are measured in a microchannel heat exchanger. A Printed Circuit Heat Exchanger (PCHE) with 340 μm hydraulic diameter has been developed as a compact microchannel heat exchanger and utilized in the experiment. Several two-phase heat transfer coefficient correlations are examined to discuss the experimental measurement results. The result of this paper shows that cryogenic two-phase mixed refrigerant heat transfer coefficients can be estimated by conventional two-phase heat transfer coefficient correlations.

Seebeck coefficient of one electron

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

Durrani, Zahid A. K., E-mail: z.durrani@imperial.ac.uk

2014-03-07

The Seebeck coefficient of one electron, driven thermally into a semiconductor single-electron box, is investigated theoretically. With a finite temperature difference ΔT between the source and charging island, a single electron can charge the island in equilibrium, directly generating a Seebeck effect. Seebeck coefficients for small and finite ΔT are calculated and a thermally driven Coulomb staircase is predicted. Single-electron Seebeck oscillations occur with increasing ΔT, as one electron at a time charges the box. A method is proposed for experimental verification of these effects.

Evaluation of generalized heat-transfer coefficients in pilot AFBC units

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

Grewal, N.S.

Experimental data for heat transfer rates as obtained in a 0.209m/sup 2/ AFBC unit at the GFETC is examined in the light of the existing four correlations for heat transfer coefficient between an immersed staggered array of horizontal tubes and a gas-solid fluidized bed. The predicted values of heat transfer coefficient from the correlations proposed by Grewal and Bansal are found to be in good agreement with the experimental values of heat transfer coefficient when the contribution due to radiation is also included.

Evaluation of generalized heat transfer coefficients in pilot AFBC units

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

Grewal, N.S.

Experimental data for heat transfer rates as obtained in a 0.209m/sup 2/ AFBC unit at the GFETC is examined in the light of the existing four correlations for heat transfer coefficient between an immersed staggered array of horizontal tubes and a gas-solid fluidized bed. The predicted values of heat transfer coefficient from the correlations proposed by Grewal and Bansal are found to be in good agreement with the experimental values of heat transfer coefficient when the contribution due to radiation is also included.

Calculation of rates of exciton dissociation into hot charge-transfer states in model organic photovoltaic interfaces

NASA Astrophysics Data System (ADS)

Vázquez, Héctor; Troisi, Alessandro

2013-11-01

We investigate the process of exciton dissociation in ordered and disordered model donor/acceptor systems and describe a method to calculate exciton dissociation rates. We consider a one-dimensional system with Frenkel states in the donor material and states where charge transfer has taken place between donor and acceptor. We introduce a Green's function approach to calculate the generation rates of charge-transfer states. For disorder in the Frenkel states we find a clear exponential dependence of charge dissociation rates with exciton-interface distance, with a distance decay constant β that increases linearly with the amount of disorder. Disorder in the parameters that describe (final) charge-transfer states has little effect on the rates. Exciton dissociation invariably leads to partially separated charges. In all cases final states are “hot” charge-transfer states, with electron and hole located far from the interface.

Pool-Boiling Heat-Transfer Enhancement on Cylindrical Surfaces with Hybrid Wettable Patterns.

PubMed

Kumar C S, Sujith; Chang, Yao Wen; Chen, Ping-Hei

2017-04-10

In this study, pool-boiling heat-transfer experiments were performed to investigate the effect of the number of interlines and the orientation of the hybrid wettable pattern. Hybrid wettable patterns were produced by coating superhydrophilic SiO2 on a masked, hydrophobic, cylindrical copper surface. Using de-ionized (DI) water as the working fluid, pool-boiling heat-transfer studies were conducted on the different surface-treated copper cylinders of a 25-mm diameter and a 40-mm length. The experimental results showed that the number of interlines and the orientation of the hybrid wettable pattern influenced the wall superheat and the HTC. By increasing the number of interlines, the HTC was enhanced when compared to the plain surface. Images obtained from the charge-coupled device (CCD) camera indicated that more bubbles formed on the interlines as compared to other parts. The hybrid wettable pattern with the lowermost section being hydrophobic gave the best heat-transfer coefficient (HTC). The experimental results indicated that the bubble dynamics of the surface is an important factor that determines the nucleate boiling.

Electron capture in collisions of S4+ with helium

NASA Astrophysics Data System (ADS)

Wang, J. G.; Turner, A. R.; Cooper, D. L.; Schultz, D. R.; Rakovic, M. J.; Fritsch, W.; Stancil, P. C.; Zygelman, B.

2002-07-01

Charge transfer due to collisions of ground-state S4+(3s2 1S) ions with helium is investigated for energies between 0.1 meV u-1 and 10 MeV u-1. Total and state-selective single electron capture (SEC) cross sections and rate coefficients are obtained utilizing the quantum mechanical molecular-orbital close-coupling (MOCC), atomic-orbital close-coupling (AOCC), classical trajectory Monte Carlo (CTMC) and continuum distorted wave methods. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained with the spin-coupled valence-bond approach. Previous data are limited to a calculation of the total SEC rate coefficient using the Landau-Zener model that is, in comparison to the results presented here, three orders of magnitude smaller. The MOCC SEC cross sections at low energy reveal a multichannel interference effect. True double capture is also investigated with the AOCC and CTMC approaches while autoionizing double capture and transfer ionization (TI) is explored with CTMC. SEC is found to be the dominant process except for E>200 keV u-1 when TI becomes the primary capture channel. Astrophysical implications are briefly discussed.

Design and development of low pressure evaporator/condenser unit for water-based adsorption type climate control systems

NASA Astrophysics Data System (ADS)

Venkataramanan, Arjun; Rios Perez, Carlos A.; Hidrovo, Carlos H.

2016-11-01

Electric vehicles (EVs) are the future of clean transportation and driving range is one of the important parameters which dictates its marketability. In order to increase driving range, electrical battery energy consumption should be minimized. Vapor-compression refrigeration systems currently employed in EVs for climate control consume a significant fraction of the battery charge. Thus, by replacing this traditional heating ventilation and air-conditioning system with an adsorption based climate control system one can have the capability of increasing the drive range of EVs.The Advanced Thermo-adsorptive Battery (ATB) for climate control is a water-based adsorption type refrigeration cycle. An essential component of the ATB is a low pressure evaporator/condenser unit (ECU) which facilitates both the evaporation and condensation processes. The thermal design of the ECU relies predominantly on the accurate prediction of evaporation/boiling heat transfer coefficients since the standard correlations for predicting boiling heat transfer coefficients have large uncertainty at the low operating pressures of the ATB. This work describes the design and development of a low pressure ECU as well as the thermal performance of the actual ECU prototype.

Capillary electrophoresis electrospray ionization mass spectrometry interface

DOEpatents

Smith, Richard D.; Severs, Joanne C.

1999-01-01

The present invention is an interface between a capillary electrophoresis separation capillary end and an electrospray ionization mass spectrometry emitter capillary end, for transporting an anolyte sample from a capillary electrophoresis separation capillary to a electrospray ionization mass spectrometry emitter capillary. The interface of the present invention has: (a) a charge transfer fitting enclosing both of the capillary electrophoresis capillary end and the electrospray ionization mass spectrometry emitter capillary end; (b) a reservoir containing an electrolyte surrounding the charge transfer fitting; and (c) an electrode immersed into the electrolyte, the electrode closing a capillary electrophoresis circuit and providing charge transfer across the charge transfer fitting while avoiding substantial bulk fluid transfer across the charge transfer fitting. Advantages of the present invention have been demonstrated as effective in providing high sensitivity and efficient analyses.

Spectrophotometric determination of fenoprofen calcium drug in pure and pharmaceutical preparations. Spectroscopic characterization of the charge transfer solid complexes.

PubMed

Mohamed, Marwa E; Frag, Eman Y Z; Hathoot, Abla A; Shalaby, Essam A

2018-01-15

Simple, accurate and robust spectrophotometric method was developed for determination of fenoprofen calcium drug (FPC). The proposed method was based on the charge transfer (CT) reaction of FPC drug (as n-electron donor) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,4,6-trinitrophenol (picric acid, PA) or 1,2,5,8-tetrahydroxyanthraquinone (Quinalizarin, QZ) (as π-acceptors) to give highly colored charge transfer complexes. Different variables affecting the reaction such as reagent concentration, temperature and time have been carefully optimized to achieve the highest sensitivity. Beer's law was obeyed over the concentration ranges of 2-60, 0.6-90 and 4-30μgmL -1 using DDQ, PA and QZ CT reagents, respectively, with correlation coefficients of 0.9986, 0.9989 and 0.997 and detection limits of 1.78, 0.48 and 2.6μgmL -1 for the CT reagents in the same order. Elucidation of the chemical structure of the solid CT complexes formed via reaction between the drug under study and π-acceptors was done using elemental, thermal analyses, IR, 1 H NMR and mass spectrometry. X-ray diffraction was used to estimate the crystallinity of the CT complexes. Their biological activities were screened against different bacterial and fungal organisms. The method was applied successfully with satisfactory results for the determination of FPC drug in fenoprofen capsules. The method was validated with respect to linearity, limit of detection and quantification, inter- and intra-days precision and accuracy. The proposed method gave comparable results with the official method. Copyright © 2017 Elsevier B.V. All rights reserved.

Depletion of mesospheric sodium during extended period of pulsating aurora

NASA Astrophysics Data System (ADS)

Takahashi, T.; Hosokawa, K.; Nozawa, S.; Tsuda, T. T.; Ogawa, Y.; Tsutsumi, M.; Hiraki, Y.; Fujiwara, H.; Kawahara, T. D.; Saito, N.; Wada, S.; Kawabata, T.; Hall, C.

2017-01-01

We quantitatively evaluated the Na density depletion due to charge transfer reactions between Na atoms and molecular ions produced by high-energy electron precipitation during a pulsating aurora (PsA). An extended period of PsA was captured by an all-sky camera at the European Incoherent Scatter (EISCAT) radar Tromsø site (69.6°N, 19.2°E) during a 2 h interval from 00:00 to 02:00 UT on 25 January 2012. During this period, using the EISCAT very high frequency (VHF) radar, we detected three intervals of intense ionization below 100 km that were probably caused by precipitation of high-energy electrons during the PsA. In these intervals, the sodium lidar at Tromsø observed characteristic depletion of Na density at altitudes between 97 and 100 km. These Na density depletions lasted for 8 min and represented 5-8% of the background Na layer. To examine the cause of this depletion, we modeled the depletion rate based on charge transfer reactions with NO+ and O2+ while changing the R value which is defined as the ratio of NO+ to O2+ densities, from 1 to 10. The correlation coefficients between observed and modeled Na density depletion calculated with typical value R = 3 for time intervals T1, T2, and T3 were 0.66, 0.80, and 0.67, respectively. The observed Na density depletion rates fall within the range of modeled depletion rate calculated with R from 1 to 10. This suggests that the charge transfer reactions triggered by the auroral impact ionization at low altitudes are the predominant process responsible for Na density depletion during PsA intervals.

Experimental investigation of forced convective heat transfer performance in nanofluids of Al2O3/water and CuO/water in a serpentine shaped micro channel heat sink

NASA Astrophysics Data System (ADS)

Sivakumar, A.; Alagumurthi, N.; Senthilvelan, T.

2016-07-01

The microchannels are device used to remove high heat fluxes from smaller area. In this experimental research work the heat transfer performance of nanofluids of Al2O3/water and CuO/water were compared. The important character of such fluids is the enhanced thermal conductivity, in comparison with base fluid without considerable alteration in physical and chemical properties. The effect of forced convective heat transfer coefficient was calculated using serpentine shaped microchannel heat exchanger. Furthermore we calculated the forced convective heat transfer coefficient of the nanofluids using theoretical correlations in order to compare the results with the experimental data. The heat transfer coefficient for different particle concentration and temperature were analysed using forced convection heat transfer using nanofluids. The findings indicate considerable enhancement in convective heat transfer coefficient of the nanofluids as compared to the basefluid. The results also shows that CuO/water nanofluid has increased heat transfer coefficient compared with Al2O3/water and base fluids. Moreover the experimental results indicate there is increased forced convective heat transfer coefficient with the increase in nano particle concentration.

User's Manual for Thermal Analysis Program of Axially Grooved Heat Pipe (HTGAP)

NASA Technical Reports Server (NTRS)

Kamotani, Y.

1978-01-01

A computer program that numerically predicts the steady state temperature distribution inside an axially grooved heat pipe wall for a given groove geometry and working fluid under various heat input and output modes is described. The program computes both evaporator and condenser film coefficients. The program is able to handle both axisymmetric and nonaxisymmetric heat transfer cases. Non-axisymmetric heat transfer results either from non-uniform input at the evaporator or non-uniform heat removal from the condenser, or from both. The presence of a liquid pool in the condenser region under one-g condition also causes non-axisymmetric heat transfer, and its effect on the pipe wall temperature distribution is included in the present program. The hydrodynamic aspect of an axially grooved heat pipe is studied in the Groove Analysis Program (GAP). The present thermal analysis program assumes that the GAP program (or other similar programs) is run first so that the heat transport limit and optimum fluid charge of the heat pipe are known a priori.

Optimization and experimental validation of a thermal cycle that maximizes entropy coefficient fisher identifiability for lithium iron phosphate cells

NASA Astrophysics Data System (ADS)

Mendoza, Sergio; Rothenberger, Michael; Hake, Alison; Fathy, Hosam

2016-03-01

This article presents a framework for optimizing the thermal cycle to estimate a battery cell's entropy coefficient at 20% state of charge (SOC). Our goal is to maximize Fisher identifiability: a measure of the accuracy with which a parameter can be estimated. Existing protocols in the literature for estimating entropy coefficients demand excessive laboratory time. Identifiability optimization makes it possible to achieve comparable accuracy levels in a fraction of the time. This article demonstrates this result for a set of lithium iron phosphate (LFP) cells. We conduct a 24-h experiment to obtain benchmark measurements of their entropy coefficients. We optimize a thermal cycle to maximize parameter identifiability for these cells. This optimization proceeds with respect to the coefficients of a Fourier discretization of this thermal cycle. Finally, we compare the estimated parameters using (i) the benchmark test, (ii) the optimized protocol, and (iii) a 15-h test from the literature (by Forgez et al.). The results are encouraging for two reasons. First, they confirm the simulation-based prediction that the optimized experiment can produce accurate parameter estimates in 2 h, compared to 15-24. Second, the optimized experiment also estimates a thermal time constant representing the effects of thermal capacitance and convection heat transfer.

Multi-charge-state molecular dynamics and self-diffusion coefficient in the warm dense matter regime

NASA Astrophysics Data System (ADS)

Fu, Yongsheng; Hou, Yong; Kang, Dongdong; Gao, Cheng; Jin, Fengtao; Yuan, Jianmin

2018-01-01

We present a multi-ion molecular dynamics (MIMD) simulation and apply it to calculating the self-diffusion coefficients of ions with different charge-states in the warm dense matter (WDM) regime. First, the method is used for the self-consistent calculation of electron structures of different charge-state ions in the ion sphere, with the ion-sphere radii being determined by the plasma density and the ion charges. The ionic fraction is then obtained by solving the Saha equation, taking account of interactions among different charge-state ions in the system, and ion-ion pair potentials are computed using the modified Gordon-Kim method in the framework of temperature-dependent density functional theory on the basis of the electron structures. Finally, MIMD is used to calculate ionic self-diffusion coefficients from the velocity correlation function according to the Green-Kubo relation. A comparison with the results of the average-atom model shows that different statistical processes will influence the ionic diffusion coefficient in the WDM regime.

Site energies and charge transfer rates near pentacene grain boundaries from first-principles calculations

NASA Astrophysics Data System (ADS)

Kobayashi, Hajime; Tokita, Yuichi

2015-03-01

Charge transfer rates near pentacene grain boundaries are derived by calculating the site energies and transfer integrals of 37 pentacene molecules using first-principles calculations. The site energies decrease considerably near the grain boundaries, and electron traps of up to 300 meV and hole barriers of up to 400 meV are generated. The charge transfer rates across the grain boundaries are found to be reduced by three to five orders of magnitude with a grain boundary gap of 4 Å because of the reduction in the transfer integrals. The electron traps and hole barriers also reduce the electron and hole transfer rates by factors of up to 10 and 50, respectively. It is essential to take the site energies into consideration to determine charge transport near the grain boundaries. We show that the complex site energy distributions near the grain boundaries can be represented by an equivalent site energy difference, which is a constant for any charge transfer pass. When equivalent site energy differences are obtained for various grain boundary structures by first-principles calculations, the effects of the grain boundaries on the charge transfer rates are introduced exactly into charge transport simulations, such as the kinetic Monte Carlo method.

Charge Transfer and Orbital Level Alignment at Inorganic/Organic Interfaces: The Role of Dielectric Interlayers.

PubMed

Hollerer, Michael; Lüftner, Daniel; Hurdax, Philipp; Ules, Thomas; Soubatch, Serguei; Tautz, Frank Stefan; Koller, Georg; Puschnig, Peter; Sterrer, Martin; Ramsey, Michael G

2017-06-27

It is becoming accepted that ultrathin dielectric layers on metals are not merely passive decoupling layers, but can actively influence orbital energy level alignment and charge transfer at interfaces. As such, they can be important in applications ranging from catalysis to organic electronics. However, the details at the molecular level are still under debate. In this study, we present a comprehensive analysis of the phenomenon of charge transfer promoted by a dielectric interlayer with a comparative study of pentacene adsorbed on Ag(001) with and without an ultrathin MgO interlayer. Using scanning tunneling microscopy and photoemission tomography supported by density functional theory, we are able to identify the orbitals involved and quantify the degree of charge transfer in both cases. Fractional charge transfer occurs for pentacene adsorbed on Ag(001), while the presence of the ultrathin MgO interlayer promotes integer charge transfer with the lowest unoccupied molecular orbital transforming into a singly occupied and singly unoccupied state separated by a large gap around the Fermi energy. Our experimental approach allows a direct access to the individual factors governing the energy level alignment and charge-transfer processes for molecular adsorbates on inorganic substrates.

Preoperative prognostic value of dynamic contrast-enhanced MRI-derived contrast transfer coefficient and plasma volume in patients with cerebral gliomas.

PubMed

Nguyen, T B; Cron, G O; Mercier, J F; Foottit, C; Torres, C H; Chakraborty, S; Woulfe, J; Jansen, G H; Caudrelier, J M; Sinclair, J; Hogan, M J; Thornhill, R E; Cameron, I G

2015-01-01

The prognostic value of dynamic contrast-enhanced MR imaging-derived plasma volume obtained in tumor and the contrast transfer coefficient has not been well-established in patients with gliomas. We determined whether plasma volume and contrast transfer coefficient in tumor correlated with survival in patients with gliomas in addition to other factors such as age, type of surgery, preoperative Karnofsky score, contrast enhancement, and histopathologic grade. This prospective study included 46 patients with a new pathologically confirmed diagnosis of glioma. The contrast transfer coefficient and plasma volume obtained in tumor maps were calculated directly from the signal-intensity curve without T1 measurements, and values were obtained from multiple small ROIs placed within tumors. Survival curve analysis was performed by dichotomizing patients into groups of high and low contrast transfer coefficient and plasma volume. Univariate analysis was performed by using dynamic contrast-enhanced parameters and clinical factors. Factors that were significant on univariate analysis were entered into multivariate analysis. For all patients with gliomas, survival was worse for groups of patients with high contrast transfer coefficient and plasma volume obtained in tumor (P < .05). In subgroups of high- and low-grade gliomas, survival was worse for groups of patients with high contrast transfer coefficient and plasma volume obtained in tumor (P < .05). Univariate analysis showed that factors associated with lower survival were age older than 50 years, low Karnofsky score, biopsy-only versus resection, marked contrast enhancement versus no/mild enhancement, high contrast transfer coefficient, and high plasma volume obtained in tumor (P < .05). In multivariate analysis, a low Karnofsky score, biopsy versus resection in combination with marked contrast enhancement, and a high contrast transfer coefficient were associated with lower survival rates (P < .05). In patients with glioma, those with a high contrast transfer coefficient have lower survival than those with low parameters. © 2015 by American Journal of Neuroradiology.

External Heat Transfer Coefficient Measurements on a Surrogate Indirect Inertial Confinement Fusion Target

DOE PAGES

Miles, Robin; Havstad, Mark; LeBlanc, Mary; ...

2015-09-15

External heat transfer coefficients were measured around a surrogate Indirect inertial confinement fusion (ICF) based on the Laser Inertial Fusion Energy (LIFE) design target to validate thermal models of the LIFE target during flight through a fusion chamber. Results indicate that heat transfer coefficients for this target 25-50 W/m 2∙K are consistent with theoretically derived heat transfer coefficients and valid for use in calculation of target heating during flight through a fusion chamber.

Multiconfiguration Pair-Density Functional Theory Outperforms Kohn-Sham Density Functional Theory and Multireference Perturbation Theory for Ground-State and Excited-State Charge Transfer.

PubMed

Ghosh, Soumen; Sonnenberger, Andrew L; Hoyer, Chad E; Truhlar, Donald G; Gagliardi, Laura

2015-08-11

The correct description of charge transfer in ground and excited states is very important for molecular interactions, photochemistry, electrochemistry, and charge transport, but it is very challenging for Kohn-Sham (KS) density functional theory (DFT). KS-DFT exchange-correlation functionals without nonlocal exchange fail to describe both ground- and excited-state charge transfer properly. We have recently proposed a theory called multiconfiguration pair-density functional theory (MC-PDFT), which is based on a combination of multiconfiguration wave function theory with a new type of density functional called an on-top density functional. Here we have used MC-PDFT to study challenging ground- and excited-state charge-transfer processes by using on-top density functionals obtained by translating KS exchange-correlation functionals. For ground-state charge transfer, MC-PDFT performs better than either the PBE exchange-correlation functional or CASPT2 wave function theory. For excited-state charge transfer, MC-PDFT (unlike KS-DFT) shows qualitatively correct behavior at long-range with great improvement in predicted excitation energies.

Review on charge transfer and chemical activity of TiO2: Mechanism and applications

NASA Astrophysics Data System (ADS)

Cai, Yongqing; Feng, Yuan Ping

2016-12-01

Charge separation and transfer at the interface between two materials play a significant role in various atomic-scale processes and energy conversion systems. In this review, we present the mechanism and outcome of charge transfer in TiO2, which is extensively explored for photocatalytic applications in the field of environmental science. We list several experimental and computational methods to estimate the amount of charge transfer. The effects of the work function, defects and doping, and employment of external electric field on modulating the charge transfer are presented. The interplay between the band bending and carrier transport across the surface and interface consisting of TiO2 is discussed. We show that the charge transfer can also strongly affect the behavior of deposited nanoparticles on TiO2 through built-in electric field that it creates. This review encompasses several advances of composite materials where TiO2 is combined with two-dimensional materials like graphene, MoS2, phosphorene, etc. The charge transport in the TiO2-organohalide perovskite with respect to the electron-hole separation at the interface is also discussed.

Measurements of Heat-Transfer and Friction Coefficients for Helium Flowing in a Tube at Surface Temperatures up to 5900 Deg R

NASA Technical Reports Server (NTRS)

Taylor, Maynard F.; Kirchgessner, Thomas A.

1959-01-01

Measurements of average heat transfer and friction coefficients and local heat transfer coefficients were made with helium flowing through electrically heated smooth tubes with length-diameter ratios of 60 and 92 for the following range of conditions: Average surface temperature from 1457 to 4533 R, Reynolds numbe r from 3230 to 60,000, heat flux up to 583,200 Btu per hr per ft2 of heat transfer area, and exit Mach numbe r up to 1.0. The results indicate that, in the turbulent range of Reynolds number, good correlation of the local heat transfer coefficients is obtained when the physical properties and density of helium are evaluated at the surface temperature. The average heat transfer coefficients are best correlated on the basis that the coefficient varies with [1 + (L/D))(sup -0,7)] and that the physical properties and density are evaluated at the surface temperature. The average friction coefficients for the tests with no heat addition are in complete agreement with the Karman-Nikuradse line. The average friction coefficients for heat addition are in poor agreement with the accepted line.

[Correlation of molecular weight and nanofiltration mass transfer coefficient of phenolic acid composition from Salvia miltiorrhiza].

PubMed

Li, Cun-Yu; Wu, Xin; Gu, Jia-Mei; Li, Hong-Yang; Peng, Guo-Ping

2018-04-01

Based on the molecular sieving and solution-diffusion effect in nanofiltration separation, the correlation between initial concentration and mass transfer coefficient of three typical phenolic acids from Salvia miltiorrhiza was fitted to analyze the relationship among mass transfer coefficient, molecular weight and concentration. The experiment showed a linear relationship between operation pressure and membrane flux. Meanwhile, the membrane flux was gradually decayed with the increase of solute concentration. On the basis of the molecular sieving and solution-diffusion effect, the mass transfer coefficient and initial concentration of three phenolic acids showed a power function relationship, and the regression coefficients were all greater than 0.9. The mass transfer coefficient and molecular weight of three phenolic acids were negatively correlated with each other, and the order from high to low is protocatechualdehyde >rosmarinic acid> salvianolic acid B. The separation mechanism of nanofiltration for phenolic acids was further clarified through the analysis of the correlation of molecular weight and nanofiltration mass transfer coefficient. The findings provide references for nanofiltration separation, especially for traditional Chinese medicine with phenolic acids. Copyright© by the Chinese Pharmaceutical Association.

Electron capture in collisions of S4+ with atomic hydrogen

NASA Astrophysics Data System (ADS)

Stancil, P. C.; Turner, A. R.; Cooper, D. L.; Schultz, D. R.; Rakovic, M. J.; Fritsch, W.; Zygelman, B.

2001-06-01

Charge transfer processes due to collisions of ground state S4+(3s2 1S) ions with atomic hydrogen are investigated for energies between 1 meV u-1 and 10 MeV u-1 using the quantum mechanical molecular-orbital close-coupling (MOCC), atomic-orbital close-coupling, classical trajectory Monte Carlo (CTMC) and continuum distorted wave methods. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained with the spin-coupled valence-bond approach. A number of variants of the CTMC approach were explored, including different momentum and radial distributions for the initial state, as well as effective charge and quantum-defect models to determine the corresponding quantum state after capture into final partially stripped S3+ excited classical states. Hydrogen target isotope effects are explored and rate coefficients for temperatures between 100 and 106 K are also presented.

A FORTRAN Program for Elastic Scattering of Deuterons with an Optical Model Containing Tensorial Potentials; PROGRAMME FORTRAN POUR LA DIFFUSION ELASTIQUE DE DEUTONS AVEC UN MODELE OPTIQUE CONTENANT DES TERMES TENSORIELS

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

Raynal, J.

1963-01-01

The FORTRAN program 5PM 037 calculates the effective elastic scattering cross section, polarizations, the effective total reaction cross section, and the polarization transfer coefficients for spin-1 particles of low charge and mass incident on a low charge and mass target at medium energy. The number of partial waves can not exceed 38, and calculations for different values of parameters for the optical model used can be made. The effect of tensorial potentials constructed from the distance of the deuteron from the target, and its angular momentum with respect to it, can also be studied. The optical model, necessary data, numericalmore » methods, and description of the problem are discussed. The program is described, and tables of equivalent statements necessary for modifying it are included. (auth)« less

Characterization of Custom-Designed Charge-Coupled Devices for Applications to Gas and Aerosol Monitoring Sensorcraft Instrument

NASA Technical Reports Server (NTRS)

Refaat, Tamer F.; Abedin, M. Nurul; Farnsworth, Glenn R.; Garcia, Christopher S.; Zawodny, Joseph M.

2005-01-01

Custom-designed charge-coupled devices (CCD) for Gas and Aerosols Monitoring Sensorcraft instrument were developed. These custom-designed CCD devices are linear arrays with pixel format of 512x1 elements and pixel size of 10x200 sq m. These devices were characterized at NASA Langley Research Center to achieve a full well capacity as high as 6,000,000 e-. This met the aircraft flight mission requirements in terms of signal-to-noise performance and maximum dynamic range. Characterization and analysis of the electrical and optical properties of the CCDs were carried out at room temperature. This includes measurements of photon transfer curves, gain coefficient histograms, read noise, and spectral response. Test results obtained on these devices successfully demonstrated the objectives of the aircraft flight mission. In this paper, we describe the characterization results and also discuss their applications to future mission.

Simple liquid models with corrected dielectric constants

PubMed Central

Fennell, Christopher J.; Li, Libo; Dill, Ken A.

2012-01-01

Molecular simulations often use explicit-solvent models. Sometimes explicit-solvent models can give inaccurate values for basic liquid properties, such as the density, heat capacity, and permittivity, as well as inaccurate values for molecular transfer free energies. Such errors have motivated the development of more complex solvents, such as polarizable models. We describe an alternative here. We give new fixed-charge models of solvents for molecular simulations – water, carbon tetrachloride, chloroform and dichloromethane. Normally, such solvent models are parameterized to agree with experimental values of the neat liquid density and enthalpy of vaporization. Here, in addition to those properties, our parameters are chosen to give the correct dielectric constant. We find that these new parameterizations also happen to give better values for other properties, such as the self-diffusion coefficient. We believe that parameterizing fixed-charge solvent models to fit experimental dielectric constants may provide better and more efficient ways to treat solvents in computer simulations. PMID:22397577

Technical characterization of dialysis fluid flow and mass transfer rate in dialyzers with various filtration coefficients using dimensionless correlation equation.

PubMed

Fukuda, Makoto; Yoshimura, Kengo; Namekawa, Koki; Sakai, Kiyotaka

2017-06-01

The objective of the present study is to evaluate the effect of filtration coefficient and internal filtration on dialysis fluid flow and mass transfer coefficient in dialyzers using dimensionless mass transfer correlation equations. Aqueous solution of vitamin B 12 clearances were obtained for REXEED-15L as a low flux dialyzer, and APS-15EA and APS-15UA as high flux dialyzers. All the other design specifications were identical for these dialyzers except for filtration coefficient. The overall mass transfer coefficient was calculated, moreover, the exponents of Reynolds number (Re) and film mass transfer coefficient of the dialysis-side fluid (k D ) for each flow rate were derived from the Wilson plot and dimensionless correlation equation. The exponents of Re were 0.4 for the low flux dialyzer whereas 0.5 for the high flux dialyzers. Dialysis fluid of the low flux dialyzer was close to laminar flow because of its low filtration coefficient. On the other hand, dialysis fluid of the high flux dialyzers was assumed to be orthogonal flow. Higher filtration coefficient was associated with higher k D influenced by mass transfer rate through diffusion and internal filtration. Higher filtration coefficient of dialyzers and internal filtration affect orthogonal flow of dialysis fluid.

Physicochemical and Nonlinear Optical Properties of Novel Environmentally Benign Heterocyclic Azomethine Dyes: Experimental and Theoretical Studies

PubMed Central

Afzal, S. M.; Razvi, M. A. N.; Khan, Salman A.; Osman, Osman I.; Bakry, Ahmed H.; Asiri, Abdullah M.

2016-01-01

Novel heterocyclic azomethine dyes were prepared by the reaction of anthracene-9-carbaldehyde with different heterocyclic amines under microwave irradiation. Structures of the azomethine dyes were confirmed by the elemental analysis, mass spectrometry and several spectroscopic techniques. We studied absorbance and fluorescence spectra of the azomethine dyes in various solvents. They are found to be good absorbers and emitters. We also report photophysical properties like, extinction coefficient, oscillator strength, stokes shift and transition dipole moment. This reflects physicochemical behaviors of synthesized dyes. In addition, their intramolecular charge transfer and nonlinear optical properties, supported by natural bond orbital technique, were also studied computationally by density functional theory. The negative nonlinear refractive index and nonlinear absorption coefficient were measured for these dyes using the closed and open aperture Z-scan technique with a continuous wave helium-neon laser. These are found to vary linearly with solution concentration. PMID:27631371

What Controls the Rate of Ultrafast Charge Transfer and Charge Separation Efficiency in Organic Photovoltaic Blends.

PubMed

Jakowetz, Andreas C; Böhm, Marcus L; Zhang, Jiangbin; Sadhanala, Aditya; Huettner, Sven; Bakulin, Artem A; Rao, Akshay; Friend, Richard H

2016-09-14

In solar energy harvesting devices based on molecular semiconductors, such as organic photovoltaics (OPVs) and artificial photosynthetic systems, Frenkel excitons must be dissociated via charge transfer at heterojunctions to yield free charges. What controls the rate and efficiency of charge transfer and charge separation is an important question, as it determines the overall power conversion efficiency (PCE) of these systems. In bulk heterojunctions between polymer donor and fullerene acceptors, which provide a model system to understand the fundamental dynamics of electron transfer in molecular systems, it has been established that the first step of photoinduced electron transfer can be fast, of order 100 fs. But here we report the first study which correlates differences in the electron transfer rate with electronic structure and morphology, achieved with sub-20 fs time resolution pump-probe spectroscopy. We vary both the fullerene substitution and donor/fullerene ratio which allow us to control both aggregate size and the energetic driving force for charge transfer. We observe a range of electron transfer times from polymer to fullerene, from 240 fs to as short as 37 fs. Using ultrafast electro-optical pump-push-photocurrent spectroscopy, we find the yield of free versus bound charges to be weakly dependent on the energetic driving force, but to be very strongly dependent on fullerene aggregate size and packing. Our results point toward the importance of state accessibility and charge delocalization and suggest that energetic offsets between donor and acceptor levels are not an important criterion for efficient charge generation. This provides design rules for next-generation materials to minimize losses related to driving energy and boost PCE.

Heat transfer coefficient of cryotop during freezing.

PubMed

Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J

2013-01-01

Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).

Incorporation of charge transfer into the explicit polarization fragment method by grand canonical density functional theory.

PubMed

Isegawa, Miho; Gao, Jiali; Truhlar, Donald G

2011-08-28

Molecular fragmentation algorithms provide a powerful approach to extending electronic structure methods to very large systems. Here we present a method for including charge transfer between molecular fragments in the explicit polarization (X-Pol) fragment method for calculating potential energy surfaces. In the conventional X-Pol method, the total charge of each fragment is preserved, and charge transfer between fragments is not allowed. The description of charge transfer is made possible by treating each fragment as an open system with respect to the number of electrons. To achieve this, we applied Mermin's finite temperature method to the X-Pol wave function. In the application of this method to X-Pol, the fragments are open systems that partially equilibrate their number of electrons through a quasithermodynamics electron reservoir. The number of electrons in a given fragment can take a fractional value, and the electrons of each fragment obey the Fermi-Dirac distribution. The equilibrium state for the electrons is determined by electronegativity equalization with conservation of the total number of electrons. The amount of charge transfer is controlled by re-interpreting the temperature parameter in the Fermi-Dirac distribution function as a coupling strength parameter. We determined this coupling parameter so as to reproduce the charge transfer energy obtained by block localized energy decomposition analysis. We apply the new method to ten systems, and we show that it can yield reasonable approximations to potential energy profiles, to charge transfer stabilization energies, and to the direction and amount of charge transferred. © 2011 American Institute of Physics

Incorporation of charge transfer into the explicit polarization fragment method by grand canonical density functional theory

PubMed Central

Isegawa, Miho; Gao, Jiali; Truhlar, Donald G.

2011-01-01

Molecular fragmentation algorithms provide a powerful approach to extending electronic structure methods to very large systems. Here we present a method for including charge transfer between molecular fragments in the explicit polarization (X-Pol) fragment method for calculating potential energy surfaces. In the conventional X-Pol method, the total charge of each fragment is preserved, and charge transfer between fragments is not allowed. The description of charge transfer is made possible by treating each fragment as an open system with respect to the number of electrons. To achieve this, we applied Mermin's finite temperature method to the X-Pol wave function. In the application of this method to X-Pol, the fragments are open systems that partially equilibrate their number of electrons through a quasithermodynamics electron reservoir. The number of electrons in a given fragment can take a fractional value, and the electrons of each fragment obey the Fermi–Dirac distribution. The equilibrium state for the electrons is determined by electronegativity equalization with conservation of the total number of electrons. The amount of charge transfer is controlled by re-interpreting the temperature parameter in the Fermi–Dirac distribution function as a coupling strength parameter. We determined this coupling parameter so as to reproduce the charge transfer energy obtained by block localized energy decomposition analysis. We apply the new method to ten systems, and we show that it can yield reasonable approximations to potential energy profiles, to charge transfer stabilization energies, and to the direction and amount of charge transferred. PMID:21895159

Performing the Millikan experiment at the molecular scale: Determination of atomic Millikan-Thomson charges by computationally measuring atomic forces.

PubMed

Rogers, T Ryan; Wang, Feng

2017-10-28

An atomic version of the Millikan oil drop experiment is performed computationally. It is shown that for planar molecules, the atomic version of the Millikan experiment can be used to define an atomic partial charge that is free from charge flow contributions. We refer to this charge as the Millikan-Thomson (MT) charge. Since the MT charge is directly proportional to the atomic forces under a uniform electric field, it is the most relevant charge for force field developments. The MT charge shows good stability with respect to different choices of the basis set. In addition, the MT charge can be easily calculated even at post-Hartree-Fock levels of theory. With the MT charge, it is shown that for a planar water dimer, the charge transfer from the proton acceptor to the proton donor is about -0.052 e. While both planar hydrated cations and anions show signs of charge transfer, anions show a much more significant charge transfer to the hydration water than the corresponding cations. It might be important to explicitly model the ion charge transfer to water in a force field at least for the anions.

Effects of Charge-Transfer Excitons on the Photophysics of Organic Semiconductors

NASA Astrophysics Data System (ADS)

Hestand, Nicholas J.

The field of organic electronics has received considerable attention over the past several years due to the promise of novel electronic materials that are cheap, flexible and light weight. While some devices based on organic materials have already emerged on the market (e.g. organic light emitting diodes), a deeper understanding of the excited states within the condensed phase is necessary both to improve current commercial products and to develop new materials for applications that are currently in the commercial pipeline (e.g. organic photovoltaics, wearable displays, and field effect transistors). To this end, a model for pi-conjugated molecular aggregates and crystals is developed and analyzed. The model considers two types of electronic excitations, namely Frenkel and charge-transfer excitons, both of which play a prominent role in determining the nature of the excited states within tightly-packed organic systems. The former consist of an electron-hole pair bound to the same molecule while in the later the electron and hole are located on different molecules. The model also considers the important nuclear reorganization that occurs when the system switches between electronic states. This is achieved using a Holstein-style Hamiltonian that includes linear vibronic coupling of the electronic states to the nuclear motion associated with the high frequency vinyl-stretching and ring-breathing modes. Analysis of the model reveals spectroscopic signatures of charge-transfer mediated J- and H-aggregation in systems where the photophysical properties are determined primarily by charge-transfer interactions. Importantly, such signatures are found to be sensitive to the relative phase of the intermolecular electron and hole transfer integrals, and the relative energy of the Frenkel and charge-transfer states. When the charge-transfer integrals are in phase and the energy of the charge-transfer state is higher than the Frenkel state, the system exhibits J-aggregate characteristics including a positive band curvature, a red shifted main absorption peak, and an increase in the ratio of the first two vibronic peaks relative to the monomer. On the other hand, when the charge-transfer integrals are out of phase and the energy of the charge-transfer state is higher than the Frenkel state, the system exhibits H-aggregate characteristics including a negative band curvature, a blue shifted main absorption peak, and a decrease in the ratio of the first two vibronic peaks relative to the monomer. Notably, these signatures are consistent with those exhibited by Coulombically coupled J- and H-aggregates. Additional signatures of charge-transfer J- and H-aggregation are also discovered, the most notable of which is the appearance of a second absorption band when the charge-transfer integrals are in phase and the charge-transfer and Frenkel excitons are near resonance. In such instances, the peak-to-peak spacing is found to be proportional to the sum of the electron and hole transfer integrals. Further analysis of the charge-transfer interactions within the context of an effective Frenkel exciton coupling reveals that the charge-transfer interactions interfere directly with the intermolecular Coulombic coupling. The interference can be either constructive or destructive resulting in either enhanced or suppressed J- or H- aggregate behavior relative to what is expected based on Coulombic coupling alone. Such interferences result in four new aggregate types, namely HH-, HJ-, JH-, and JJ-aggregates, where the first letter indicates the nature of the Coulombic coupling and the second indicates the nature of the charge-transfer coupling. Vibronic signatures of such aggregates are developed and provide a means by which to rapidly screen materials for certain electronic characteristics. Notably, a large total (Coulombic plus charge-transfer) exciton coupling is associated with an absorption spectrum in which the ratio of the first two vibronic peaks deviates significantly from that of the unaggregated monomer. Hence, strongly coupled, high exciton mobility aggregates can be readily distinguished from low mobility aggregates by the ratio of their first two vibronic peaks. (Abstract shortened by ProQuest.).

Creating and optimizing interfaces for electric-field and photon-induced charge transfer.

PubMed

Park, Byoungnam; Whitham, Kevin; Cho, Jiung; Reichmanis, Elsa

2012-11-27

We create and optimize a structurally well-defined electron donor-acceptor planar heterojunction interface in which electric-field and/or photon-induced charge transfer occurs. Electric-field-induced charge transfer in the dark and exciton dissociation at a pentacene/PCBM interface were probed by in situ thickness-dependent threshold voltage shift measurements in field-effect transistor devices during the formation of the interface. Electric-field-induced charge transfer at the interface in the dark is correlated with development of the pentacene accumulation layer close to PCBM, that is, including interface area, and dielectric relaxation time in PCBM. Further, we demonstrate an in situ test structure that allows probing of both exciton diffusion length and charge transport properties, crucial for optimizing optoelectronic devices. Competition between the optical absorption length and the exciton diffusion length in pentacene governs exciton dissociation at the interface. Charge transfer mechanisms in the dark and under illumination are detailed.

Quantum theory of atoms in molecules charge-charge flux-dipole flux models for the infrared intensities of X(2)CY (X = H, F, Cl; Y = O, S) molecules.

PubMed

Faria, Sergio H D M; da Silva, João Viçozo; Haiduke, Roberto L A; Vidal, Luciano N; Vazquez, Pedro A M; Bruns, Roy E

2007-08-16

The molecular dipole moments, their derivatives, and the fundamental IR intensities of the X2CY (X = H, F, Cl; Y = O, S) molecules are determined from QTAIM atomic charges and dipoles and their fluxes at the MP2/6-311++G(3d,3p) level. Root-mean-square errors of +/-0.03 D and +/-1.4 km mol(-1) are found for the molecular dipole moments and fundamental IR intensities calculated using quantum theory of atoms in molecules (QTAIM) parameters when compared with those obtained directly from the MP2/6-311++G(3d,3p) calculations and +/-0.05 D and 51.2 km mol(-1) when compared with the experimental values. Charge (C), charge flux (CF), and dipole flux (DF) contributions are reported for all the normal vibrations of these molecules. A large negative correlation coefficient of -0.83 is calculated between the charge flux and dipole flux contributions and indicates that electronic charge transfer from one side of the molecule to the other during vibrations is accompanied by a relaxation effect with electron density polarization in the opposite direction. The characteristic substituent effect that has been observed for experimental infrared intensity parameters and core electron ionization energies has been applied to the CCFDF/QTAIM parameters of F2CO, Cl2CO, F2CS, and Cl2CS. The individual atomic charge, atomic charge flux, and atomic dipole flux contributions are seen to obey the characteristic substituent effect equation just as accurately as the total dipole moment derivative. The CH, CF, and CCl stretching normal modes of these molecules are shown to have characteristic sets of charge, charge flux, and dipole flux contributions.

The role of intra-NAPL diffusion on mass transfer from MGP residuals

NASA Astrophysics Data System (ADS)

Shafieiyoun, Saeid; Thomson, Neil R.

2018-06-01

An experimental and computational study was performed to investigate the role of multi-component intra-NAPL diffusion on NAPL-water mass transfer. Molecular weight and the NAPL component concentrations were determined to be the most important parameters affecting intra-NAPL diffusion coefficients. Four NAPLs with different viscosities but the same quantified mass were simulated. For a spherical NAPL body, a combination of NAPL properties and interphase mass transfer rate can result in internal diffusion limitations. When the main intra-NAPL diffusion coefficients are in the range of self-diffusion coefficients (10-5 to 10-6 cm2/s), dissolution is not limited by internal diffusion except for high mass transfer rate coefficients (>180 cm/day). For a complex and relatively high viscous NAPL (>50 g/(cm s)), smaller intra-NAPL diffusion coefficients (<10-8) are expected and even low mass transfer rate coefficients ( 6 cm/day) can result in diffusion-limited dissolution.

Robust Stacking-Independent Ultrafast Charge Transfer in MoS2/WS2 Bilayers.

PubMed

Ji, Ziheng; Hong, Hao; Zhang, Jin; Zhang, Qi; Huang, Wei; Cao, Ting; Qiao, Ruixi; Liu, Can; Liang, Jing; Jin, Chuanhong; Jiao, Liying; Shi, Kebin; Meng, Sheng; Liu, Kaihui

2017-12-26

Van der Waals-coupled two-dimensional (2D) heterostructures have attracted great attention recently due to their high potential in the next-generation photodetectors and solar cells. The understanding of charge-transfer process between adjacent atomic layers is the key to design optimal devices as it directly determines the fundamental response speed and photon-electron conversion efficiency. However, general belief and theoretical studies have shown that the charge transfer behavior depends sensitively on interlayer configurations, which is difficult to control accurately, bringing great uncertainties in device designing. Here we investigate the ultrafast dynamics of interlayer charge transfer in a prototype heterostructure, the MoS 2 /WS 2 bilayer with various stacking configurations, by optical two-color ultrafast pump-probe spectroscopy. Surprisingly, we found that the charge transfer is robust against varying interlayer twist angles and interlayer coupling strength, in time scale of ∼90 fs. Our observation, together with atomic-resolved transmission electron characterization and time-dependent density functional theory simulations, reveals that the robust ultrafast charge transfer is attributed to the heterogeneous interlayer stretching/sliding, which provides additional channels for efficient charge transfer previously unknown. Our results elucidate the origin of transfer rate robustness against interlayer stacking configurations in optical devices based on 2D heterostructures, facilitating their applications in ultrafast and high-efficient optoelectronic and photovoltaic devices in the near future.

Supramolecular networks with electron transfer in two dimensions

DOEpatents

Stupp, Samuel I.; Stoddart, J. Fraser; Shveyd, Alexander K.; Tayi, Alok S.; Sue, Chi-Hau; Narayanan, Ashwin

2016-09-13

Organic charge-transfer (CT) co-crystals in a crossed stack system are disclosed. The co-crystals exhibit bidirectional charge transfer interactions where one donor molecule shares electrons with two different acceptors, one acceptor face-to-face and the other edge-to-face. The assembly and charge transfer interaction results in a pleochroic material whereby the optical absorption continuously changes depending on the polarization angle of incident light.

Effect of Atomic Charges on Octanol-Water Partition Coefficient Using Alchemical Free Energy Calculation.

PubMed

Ogata, Koji; Hatakeyama, Makoto; Nakamura, Shinichiro

2018-02-15

The octanol-water partition coefficient (log P ow ) is an important index for measuring solubility, membrane permeability, and bioavailability in the drug discovery field. In this paper, the log P ow values of 58 compounds were predicted by alchemical free energy calculation using molecular dynamics simulation. In free energy calculations, the atomic charges of the compounds are always fixed. However, they must be recalculated for each solvent. Therefore, three different sets of atomic charges were tested using quantum chemical calculations, taking into account vacuum, octanol, and water environments. The calculated atomic charges in the different environments do not necessarily influence the correlation between calculated and experimentally measured ∆ G water values. The largest correlation coefficient values of the solvation free energy in water and octanol were 0.93 and 0.90, respectively. On the other hand, the correlation coefficient of log P ow values calculated from free energies, the largest of which was 0.92, was sensitive to the combination of the solvation free energies calculated from the calculated atomic charges. These results reveal that the solvent assumed in the atomic charge calculation is an important factor determining the accuracy of predicted log P ow values.

The measurement of the heat-transfer coefficient between high-temperature liquids and solid surfaces

NASA Astrophysics Data System (ADS)

Utigard, T. A.; Warczok, A.; Desclaux, P.

1994-01-01

Two experimental techniques were developed for the purpose of measuring the heat-transfer coefficient between liquid slags/salts and solid surfaces. This was carried out because the heat-transfer coefficient is important for the design and operation of metallurgical reactors. A “cold-finger” technique was developed for the purpose of carrying out heat-transfer measurements during steady-state conditions simulating heat fluxes through furnace sidewalls. A lump capacitance method was developed and tested for the purpose of simulating transient conditions. To determine the effect of fluid flow on the heat-transfer coefficient, nitrogen gas stirring was used. The two techniques were tested in molten (1) and NaNO3, (2) NaCl, (3) Na3AlF6, and (4) 2FeO·SiO2, giving consistent results. It was found that the heat-transfer coefficient increases with increasing bath superheat and stirring.

Influence of Oil on Refrigerant Evaporator Performance

NASA Astrophysics Data System (ADS)

Kim, Jong-Soo; Nagata, Karsuya; Katsuta, Masafumi; Tomosugi, Hiroyuki; Kikuchi, Kouichiro; Horichi, Toshiaki

In vapor compression refrigeration system using oil-lubricated compressors, some amount of oil is always circulated through the system. Oil circulation can have a significant influence on the evaporator performance of automotive air conditioner which is especially required to cool quickly the car interior after a period standing in the sun. An experimental investigation was carried out an electrically heated horizontal tube to measure local heat transfer coefficients for various flow rates and heat fluxes during forced convection boiling of pure refrigerant R12 and refrigerant-oil mixtures (0-11% oil concentration by weight) and the results were compared with oil free performance. Local heat transfer coefficients increased at the region of low vapor quality by the addition of oil. On the other hand, because the oil-rich liquid film was formed on the heat transfer surface, heat transfer coefficients gradually decreased as the vapor quality became higher. Average heat transfer coefficient reached a maximum at about 4% oil concentration and this trend agreed well with the results of Green and Furse. Previous correlations, using the properties of the refrigerant-oil mixture, could not predict satisfactorily the local heat transfer coefficients data. New correlation modified by oil concentration factor was developed for predicting the corresponding heat transfer coefficient for refrigerant-oil mixture convection boiling. The maximum percent deviation between predicted and measured heat transfer coefficient was within ±30%.

Charge transfer polarisation wave and carrier pairing in the high T(sub c) copper oxides

NASA Technical Reports Server (NTRS)

Chakraverty, B. K.

1990-01-01

The High T(sub c) oxides are highly polarizable materials and are charge transfer insulators. The charge transfer polarization wave formalism is developed in these oxides. The dispersion relationships due to long range dipole-dipole interaction of a charge transfer dipole lattice are obtained in 3-D and 2-D. These are high frequency bosons and their coupling with carriers is weak and antiadiabatic in nature. As a result, the mass renormalization of the carriers is negligible in complete contrast to conventional electron-phonon interaction, that give polarons and bipolarons. Both bound and superconducting pairing is discussed for a model Hamiltonian valid in the antiadiabatic regime, both in 3-D and 2-D. The stability of the charge transfer dipole lattice has interesting consequences that are discussed.

A new model to study the phase transition from microstructures to nanostructures in ionic/ionic surfactants mixture.

PubMed

Sohrabi, Beheshteh; Gharibi, Hussein; Javadian, Soheila; Hashemianzadeh, Majid

2007-08-30

The phase behavior and aggregate structures of mixtures of the oppositely charged surfactants cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) are explored at high dilution by pulsed field gradient stimulated echo (PFG-STE) NMR. The aggregation numbers and hydrodynamic radii of vesicles and mixed micelles were determined by a combination of viscosity and self-diffusion coefficient measurements. The average size of the mixed micelles was larger than that of micelles containing uniformly charged head groups. Analysis of the variations of the self-diffusion coefficient and viscosity with changing concentration of CTAB or SDS in the cationic-rich and anionic-rich regions revealed a phase transition from vesicles to mixed micelles. Differences in the lengths of the CTAB and SDS hydrophobic chains stabilize vesicles relative to other microstructures (e.g., liquid crystalline and precipitate phase), and vesicles form spontaneously over a wide range of compositions in both cationic-rich and anionic-rich solutions. The results obtained from conductometry measurements confirmed this transition. Finally, according to the capacitor model, a new model was developed for estimating the surface potentials and electrostatic free energy (g(elec)). Then we investigated the variations of electrostatic and transfer free energy in phase transition between mixed micelle and vesicle.

Local convective heat transfer coefficient and friction factor of CuO/water nanofluid in a microchannel heat sink

NASA Astrophysics Data System (ADS)

Chabi, A. R.; Zarrinabadi, S.; Peyghambarzadeh, S. M.; Hashemabadi, S. H.; Salimi, M.

2017-02-01

Forced convective heat transfer in a microchannel heat sink (MCHS) using CuO/water nanofluids with 0.1 and 0.2 vol% as coolant was investigated. The experiments were focused on the heat transfer enhancement in the channel entrance region at Re < 1800. Hydraulic performance of the MCHS was also estimated by measuring friction factor and pressure drop. Results showed that higher convective heat transfer coefficient was obtained at the microchannel entrance. Maximum enhancement of the average heat transfer coefficient compared with deionized water was about 40 % for 0.2 vol% nanofluid at Re = 1150. Enhancement of the convective heat transfer coefficient of nanofluid decreased with further increasing of Reynolds number.

Two-phase charge-coupled device

NASA Technical Reports Server (NTRS)

Kosonocky, W. F.; Carnes, J. E.

1973-01-01

A charge-transfer efficiency of 99.99% per stage was achieved in the fat-zero mode of operation of 64- and 128-stage two-phase charge-coupled shift registers at 1.0-MHz clock frequency. The experimental two-phase charge-coupled shift registers were constructed in the form of polysilicon gates overlapped by aluminum gates. The unidirectional signal flow was accomplished by using n-type substrates with 0.5 to 1.0 ohm-cm resistivity in conjunction with a channel oxide thickness of 1000 A for the polysilicon gates and 3000 A for the aluminum gates. The operation of the tested shift registers with fat zero is in good agreement with the free-charge transfer characteristics expected for the tested structures. The charge-transfer losses observed when operating the experimental shift registers without the fat zero are attributed to fast interface state trapping. The analytical part of the report contains a review backed up by an extensive appendix of the free-charge transfer characteristics of CCD's in terms of thermal diffusion, self-induced drift, and fringing field drift. Also, a model was developed for the charge-transfer losses resulting from charge trapping by fast interface states. The proposed model was verified by the operation of the experimental two-phase charge-coupled shift registers.

A quantum mechanical-Poisson-Boltzmann equation approach for studying charge flow between ions and a dielectric continuum

NASA Astrophysics Data System (ADS)

Gogonea, Valentin; Merz, Kenneth M.

2000-02-01

This paper presents a theoretical model for the investigation of charge transfer between ions and a solvent treated as a dielectric continuum media. The method is a combination of a semiempirical effective Hamiltonian with a modified Poisson-Boltzmann equation which includes charge transfer in the form of a surface charge density positioned at the dielectric interface. The new Poisson-Boltzmann equation together with new boundary conditions results in a new set of equations for the electrostatic potential (or polarization charge densities). Charge transfer adds a new free energy component to the solvation free energy term, which accounts for all interactions between the transferred charge at the dielectric interface, the solute wave function and the solvent polarization charges. Practical calculations on a set of 19 anions and 17 cations demonstrate that charge exchange with a dielectric is present and it is in the range of 0.06-0.4 eu. Furthermore, the pattern of the magnitudes of charge transfer can be related to the acid-base properties of the ions in many cases, but exceptions are also found. Finally, we show that the method leads to an energy decomposition scheme of the total electrostatic energy, which can be used in mechanistic studies on protein and DNA interaction with water.

Charge-transfer potentials for ionic crystals: Cauchy violation, LO-TO splitting, and the necessity of an ionic reference state.

PubMed

Sukhomlinov, Sergey V; Müser, Martin H

2015-12-14

In this work, we study how including charge transfer into force fields affects the predicted elastic and vibrational Γ-point properties of ionic crystals, in particular those of rock salt. In both analytical and numerical calculations, we find that charge transfer generally leads to a negative contribution to the Cauchy pressure, P(C) ≡ C12 - C66, where C12 and C66 are elements of the elastic tensor. This contribution increases in magnitude with pressure for different charge-transfer approaches in agreement with results obtained with density functional theory (DFT). However, details of the charge-transfer models determine the pressure dependence of the longitudinal optical-transverse optical splitting and that for partial charges. These last two quantities increase with density as long as the chemical hardness depends at most weakly on the environment while experiments and DFT find a decrease. In order to reflect the correct trends, the charge-transfer expansion has to be made around ions and the chemical (bond) hardness has to increase roughly exponentially with inverse density or bond lengths. Finally, the adjustable force-field parameters only turn out meaningful, when the expansion is made around ions.

Charge-transfer potentials for ionic crystals: Cauchy violation, LO-TO splitting, and the necessity of an ionic reference state

NASA Astrophysics Data System (ADS)

Sukhomlinov, Sergey V.; Müser, Martin H.

2015-12-01

In this work, we study how including charge transfer into force fields affects the predicted elastic and vibrational Γ-point properties of ionic crystals, in particular those of rock salt. In both analytical and numerical calculations, we find that charge transfer generally leads to a negative contribution to the Cauchy pressure, PC ≡ C12 - C66, where C12 and C66 are elements of the elastic tensor. This contribution increases in magnitude with pressure for different charge-transfer approaches in agreement with results obtained with density functional theory (DFT). However, details of the charge-transfer models determine the pressure dependence of the longitudinal optical-transverse optical splitting and that for partial charges. These last two quantities increase with density as long as the chemical hardness depends at most weakly on the environment while experiments and DFT find a decrease. In order to reflect the correct trends, the charge-transfer expansion has to be made around ions and the chemical (bond) hardness has to increase roughly exponentially with inverse density or bond lengths. Finally, the adjustable force-field parameters only turn out meaningful, when the expansion is made around ions.

Charge Transfer from n-Doped Nanocrystals: Mimicking Intermediate Events in Multielectron Photocatalysis.

PubMed

Wang, Junhui; Ding, Tao; Wu, Kaifeng

2018-06-12

In multielectron photocatalytic reactions, an absorbed photon triggers charge transfer from the light-harvester to the attached catalyst, leaving behind a charge of the opposite sign in the light-harvester. If this charge is not scavenged before the absorption of the following photons, photoexcitation generates not neutral but charged excitons from which the extraction of charges should become more difficult. This is potentially an efficiency-limiting intermediate event in multielectron photocatalysis. To study the charge dynamics in this event, we doped CdS nanocrystal quantum dots (QDs) with an extra electron and measured hole transfer from n-doped QDs to attached acceptors. We find that the Auger decay of charged excitons lowers the charge separation yield to 68.6% from 98.4% for neutral excitons. In addition, the hole transfer rate in the presence of two electrons (1290 ps) is slower than that in the presence one electron (776 ps), and the recombination rate of charge separated states is about 2 times faster in the former case. This model study provides important insights into possible efficiency-limiting intermediate events involved in photocatalysis.

Artificial Neural Network with Hardware Training and Hardware Refresh

NASA Technical Reports Server (NTRS)

Duong, Tuan A. (Inventor)

2003-01-01

A neural network circuit is provided having a plurality of circuits capable of charge storage. Also provided is a plurality of circuits each coupled to at least one of the plurality of charge storage circuits and constructed to generate an output in accordance with a neuron transfer function. Each of a plurality of circuits is coupled to one of the plurality of neuron transfer function circuits and constructed to generate a derivative of the output. A weight update circuit updates the charge storage circuits based upon output from the plurality of transfer function circuits and output from the plurality of derivative circuits. In preferred embodiments, separate training and validation networks share the same set of charge storage circuits and may operate concurrently. The validation network has a separate transfer function circuits each being coupled to the charge storage circuits so as to replicate the training network s coupling of the plurality of charge storage to the plurality of transfer function circuits. The plurality of transfer function circuits may be constructed each having a transconductance amplifier providing differential currents combined to provide an output in accordance with a transfer function. The derivative circuits may have a circuit constructed to generate a biased differential currents combined so as to provide the derivative of the transfer function.

Thermodynamic and kinetic studies of As2O3 toxicological effects on human insulin in generation diabetes mellitus

NASA Astrophysics Data System (ADS)

Mohsennia, Mohsen; Motaharinejad, Atieh; Rafiee-Pour, Hossain-Ali; Torabbeigi, Marzieh

2017-12-01

The interaction of arsenic trioxide with human insulin was investigated by circular dichroism (CD), cyclic voltammetry and electrophoresis techniques. The interfacial behavior of insulin in presence of As2O3 onto the Ag electrode surface was studied at 310 K in phosphate buffer solution (PBS). According to Far-UV CD spectroscopy results, As2O3 caused to decrease in structural compactness and variety of alpha helix into beta structures. Near-UV CD indicated that As2O3 dissociates disulfide linkage in insulin structure. The kinetic parameters, including charge-transfer coefficient and apparent heterogeneous electron transfer rate constant were also determined. The thermodynamic parameters of insulin denaturation in presence of arsenic trioxide were calculated and reported. The obtained results indicated strong adsorption of insulin in presence of arsenic trioxide onto the Ag surface via chemisorptions.

Phase-coherent engineering of electronic heat currents with a Josephson modulator

NASA Astrophysics Data System (ADS)

Fornieri, Antonio; Blanc, Christophe; Bosisio, Riccardo; D'Ambrosio, Sophie; Giazotto, Francesco

In this contribution we report the realization of the first balanced Josephson heat modulator designed to offer full control at the nanoscale over the phase-coherent component of electronic thermal currents. The ability to master the amount of heat transferred through two tunnel-coupled superconductors by tuning their phase difference is the core of coherent caloritronics, and is expected to be a key tool in a number of nanoscience fields, including solid state cooling, thermal isolation, radiation detection, quantum information and thermal logic. Our device provides magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a maximum of the flux-to-temperature transfer coefficient reaching 200 mK per flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the exact correspondence in the phase-engineering of charge and heat currents, breaking ground for advanced caloritronic nanodevices such as thermal splitters, heat pumps and time-dependent electronic engines.

Tuning charge transfer in the LaTiO3/RO/LaNiO3 (R = rare-earth) superlattices by the rare-earth oxides interfaces from a first-principles calculation

NASA Astrophysics Data System (ADS)

Yao, Fen; Zhang, Lifang; Meng, Junling; Liu, Xiaojuan; Zhang, Xiong; Zhang, Wenwen; Meng, Jian; Zhang, Hongjie

2018-03-01

We investigate the internal charge transfer at the isopolar interfaces in LaTiO3/RO/LaNiO3 (R = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu) superlattices by means of density functional theory calculations. The charge transfer from Ti sites to Ni sites in all superlattices is induced by the electronegativity difference between the elements Ti and Ni, and the lanthanide oxides interfaces can modulate the amount of charge transfer. Comparison of the perovskite heterostructures with the different rare-earth interfaces shows that increasing the deviations of bond angles from 180.0° and the oxygen motions near the interfaces enhance charge transfer. The 4f electrons themselves of rare-earth elements have faint influences on charge transfer. In addition, the reasons why our calculated 4f states of Sm and Tm elements disagree with the experimental systems have been provided. It is hoped that all the calculated results could be used to design new functional nanoelectronic devices in perovskite oxides.

An Ab Initio Exciton Model Including Charge-Transfer Excited States

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

Li, Xin; Parrish, Robert M.; Liu, Fang

Here, the Frenkel exciton model is a useful tool for theoretical studies of multichromophore systems. We recently showed that the exciton model could be used to coarse-grain electronic structure in multichromophoric systems, focusing on singly excited exciton states. However, our previous implementation excluded charge-transfer excited states, which can play an important role in light-harvesting systems and near-infrared optoelectronic materials. Recent studies have also emphasized the significance of charge-transfer in singlet fission, which mediates the coupling between the locally excited states and the multiexcitonic states. In this work, we report on an ab initio exciton model that incorporates charge-transfer excited statesmore » and demonstrate that the model provides correct charge-transfer excitation energies and asymptotic behavior. Comparison with TDDFT and EOM-CC2 calculations shows that our exciton model is robust with respect to system size, screening parameter, and different density functionals. Inclusion of charge-transfer excited states makes the exciton model more useful for studies of singly excited states and provides a starting point for future construction of a model that also includes double-exciton states.« less

An Ab Initio Exciton Model Including Charge-Transfer Excited States

DOE PAGES

Li, Xin; Parrish, Robert M.; Liu, Fang; ...

2017-06-15

Here, the Frenkel exciton model is a useful tool for theoretical studies of multichromophore systems. We recently showed that the exciton model could be used to coarse-grain electronic structure in multichromophoric systems, focusing on singly excited exciton states. However, our previous implementation excluded charge-transfer excited states, which can play an important role in light-harvesting systems and near-infrared optoelectronic materials. Recent studies have also emphasized the significance of charge-transfer in singlet fission, which mediates the coupling between the locally excited states and the multiexcitonic states. In this work, we report on an ab initio exciton model that incorporates charge-transfer excited statesmore » and demonstrate that the model provides correct charge-transfer excitation energies and asymptotic behavior. Comparison with TDDFT and EOM-CC2 calculations shows that our exciton model is robust with respect to system size, screening parameter, and different density functionals. Inclusion of charge-transfer excited states makes the exciton model more useful for studies of singly excited states and provides a starting point for future construction of a model that also includes double-exciton states.« less

Interlayer‐State‐Coupling Dependent Ultrafast Charge Transfer in MoS2/WS2 Bilayers

PubMed Central

Zhang, Jin; Hong, Hao; Lian, Chao; Ma, Wei; Xu, Xiaozhi; Zhou, Xu; Fu, Huixia

2017-01-01

Light‐induced interlayer ultrafast charge transfer in 2D heterostructures provides a new platform for optoelectronic and photovoltaic applications. The charge separation process is generally hypothesized to be dependent on the interlayer stackings and interactions, however, the quantitative characteristic and detailed mechanism remain elusive. Here, a systematical study on the interlayer charge transfer in model MoS2/WS2 bilayer system with variable stacking configurations by time‐dependent density functional theory methods is demonstrated. The results show that the slight change of interlayer geometry can significantly modulate the charge transfer time from 100 fs to 1 ps scale. Detailed analysis further reveals that the transfer rate in MoS2/WS2 bilayers is governed by the electronic coupling between specific interlayer states, rather than the interlayer distances, and follows a universal dependence on the state‐coupling strength. The results establish the interlayer stacking as an effective freedom to control ultrafast charge transfer dynamics in 2D heterostructures and facilitate their future applications in optoelectronics and light harvesting. PMID:28932669

An Ab Initio Exciton Model Including Charge-Transfer Excited States.

PubMed

Li, Xin; Parrish, Robert M; Liu, Fang; Kokkila Schumacher, Sara I L; Martínez, Todd J

2017-08-08

The Frenkel exciton model is a useful tool for theoretical studies of multichromophore systems. We recently showed that the exciton model could be used to coarse-grain electronic structure in multichromophoric systems, focusing on singly excited exciton states [ Acc. Chem. Res. 2014 , 47 , 2857 - 2866 ]. However, our previous implementation excluded charge-transfer excited states, which can play an important role in light-harvesting systems and near-infrared optoelectronic materials. Recent studies have also emphasized the significance of charge-transfer in singlet fission, which mediates the coupling between the locally excited states and the multiexcitonic states. In this work, we report on an ab initio exciton model that incorporates charge-transfer excited states and demonstrate that the model provides correct charge-transfer excitation energies and asymptotic behavior. Comparison with TDDFT and EOM-CC2 calculations shows that our exciton model is robust with respect to system size, screening parameter, and different density functionals. Inclusion of charge-transfer excited states makes the exciton model more useful for studies of singly excited states and provides a starting point for future construction of a model that also includes double-exciton states.

Experimental estimation of convective heat transfer coefficient from pulsating semi-confined impingement air slot jet by using inverse method

NASA Astrophysics Data System (ADS)

Farahani, Somayeh Davoodabadi; Kowsary, Farshad

2017-09-01

An experimental study on pulsating impingement semi-confined slot jet has been performed. The effect of pulsations frequency was examined for various Reynolds numbers and Nozzle to plate distances. Convective heat transfer coefficient is estimated using the measured temperatures in the target plate and conjugate gradient method with adjoint equation. Heat transfer coefficient in Re < 3000 tended to increase with increasing frequency. The pulsations enhance mixing, which results in an enhancement of mean flow velocity. In case of turbulent jet (Re > 3000), heat transfer coefficient is affected by the pulsation from particular frequency. In this study, the threshold Strouhal number (St) is 0.11. No significant heat transfer enhancement was obtained for St < 0.11. The thermal resistance is smaller each time due to the newly forming thermal boundary layers. Heat transfer coefficient increases due to decrease thermal resistance. This study shows that maximum enhancement in heat transfer due to pulsations occurs in St = 0.169. Results show the configuration geometry has an important effect on the heat transfer performances in pulsed impinging jet. Heat transfer enhancement can be described to reflect flow by the confinement plate.

Nanoscale charge transfer and diffusion at the MoS2/SiO2 interface by atomic force microscopy: contact injection versus triboelectrification.

PubMed

Xu, Rui; Ye, Shili; Xu, Kunqi; Lei, Le; Hussain, Sabir; Zheng, Zhiyue; Pang, Fei; Xing, Shuya; Liu, Xinmeng; Ji, Wei; Cheng, Zhihai

2018-08-31

Understanding the process of charge generation, transfer, and diffusion between two-dimensional (2D) materials and their supporting substrates is very important for potential applications of 2D materials. Compared with the systematic studies of triboelectric charging in a bulk sample, a fundamental understanding of the triboelectrification of the 2D material/insulator system is rather limited. Here, the charge transfer and diffusion of both the SiO 2 surface and MoS 2 /SiO 2 interface through contact electrification and frictional electrification are investigated systematically in situ by scanning Kelvin probe microscopy and dual-harmonic electrostatic force microscopy. Different from the simple static charge transfer between SiO 2 and the PtSi alloy atomic force microscope (AFM) tip, the charge transfer between the tip and the MoS 2 /SiO 2 system is complicated. Triboelectric charges, generated by contact or frictional electrification with the AFM tip, are trapped at the MoS 2 /SiO 2 interface and act as floating gates. The local charge discharge processes can be obtained by monitoring the surface potential. The charge decay time (τ) of the MoS 2 /SiO 2 interface is one (or two) orders of magnitude larger than the decay time τ of the SiO 2 surface. This work facilitates an understanding of the triboelectric and de-electrification of the interface between 2D materials and substrates. In addition to the charge transfer and diffusion, we demonstrate the nanopatterns of surface and interfacial charges, which have great potential for the application of self-assembly of charged nanostructures.

Optimal Electricity Charge Strategy Based on Price Elasticity of Demand for Users

NASA Astrophysics Data System (ADS)

Li, Xin; Xu, Daidai; Zang, Chuanzhi

The price elasticity is very important for the prediction of electricity demand. This paper mainly establishes the price elasticity coefficient for electricity in single period and inter-temporal. Then, a charging strategy is established based on these coefficients. To evaluate the strategy proposed, simulations of the two elastic coefficients are carried out based on the history data of a certain region.

Length scale dependence of the dynamic properties of hyaluronic acid solutions in the presence of salt.

PubMed

Horkay, Ferenc; Falus, Peter; Hecht, Anne-Marie; Geissler, Erik

2010-12-02

In solutions of the charged semirigid biopolymer hyaluronic acid in salt-free conditions, the diffusion coefficient D(NSE) measured at high transfer momentum q by neutron spin echo is more than an order of magnitude smaller than that determined by dynamic light scattering, D(DLS). This behavior contrasts with neutral polymer solutions. With increasing salt content, D(DLS) approaches D(NSE), which is independent of ionic strength. Contrary to theoretical expectation, the ion-polymer coupling, which dominates the low q dynamics of polyelectrolyte solutions, already breaks down at distance scales greater than the Debye-Hückel length.

Planar versus bulk heterojunction perovskite microstructures: Impact of morphology on photovoltaic properties and recombination dynamics

NASA Astrophysics Data System (ADS)

Singh, Ranbir; Shukla, Vivek Kumar

2018-05-01

In this work, we compare the planar and bulk heterojunction (BHJ) perovskite thin films for their morphologies, photovoltaic properties, and recombination dynamics. The BHJ perovskite thin films were prepared with the addition of fullerene derivative [6, 6]-Phenyl-C60 butyric acid methyl ester (PC60BM). The addition of PC60BM in perovskite provides a pinhole free film with high absorption coefficient and better charge transfer. The solar cells fabricated with BHJ perovskite exhibits power conversion efficiency (PCE) of 13.5%, with remarkably increased short-circuit current density (JSC) of 20.1 mAcm-2 and reduced recombination rate.

Large photorefractive effect in a thermally decomposed polymer compared with that in molecularly doped systems

NASA Astrophysics Data System (ADS)

Yokoyama, Kenji; Arishima, Koichi; Sukegawa, Ken

1994-07-01

Photorefractive polymers with the same electro-optic effect were fabricated to investigate the photorefractive effects in different photoconductive systems. The photoconduction in the polymers was varied by the addition of squarylium dye to diethylaminobenzaldehyde-diphenylhydrazone (DEH), by the formation of a charge-transfer complex between tetracyanoquinodimethane and DEH, and by the thermal decomposition of DEH. The largest photorefractive effect was observed in the thermally decomposed polymer among these polymers. A diffraction efficiency of 1.1% and a beam-coupling gain coefficient of 10 cm-1 were achieved in a 34.9 V/μm dc electric field.

The mechanisms of delayed fluorescence in charge-transfer crystal of tetracyanobenzene-hexamethylbenzene

NASA Astrophysics Data System (ADS)

Kozankiewicz, B.; Prochorow, J.

1989-08-01

Fluorescence, phosphorescence and delayed fluorescence emission characteristics of tetracyanobenzene-hexamethylbenzene (TCNB-HMB) charge-transfer crystal have been studied in the 1.7-340 K temperature range. Delayed fluorescence, originating from heterogeneous triplet-triplet annihilation indicates the presence of mobile charge-transfer triplet excitons at a temperature as low as 1.7 K. However, the behaviour of triplet excitons in TCNB-HMB crystal is strongly controlled by a very efficient trapping process in the whole temperature range investigated. It was found that thermally activated delayed fluorescence, which is a dominating emission of the crystal at elevated temperatures (>60 K), has a different origin (a different initial state) at different temperatures. These observations were analysed and interpreted in terms of a photokinetic model, which is considered to be typical for charge-transfer crystals with high charge-transfer character of triplet excitons.

Lowest energy Frenkel and charge transfer exciton intermixing in one-dimensional copper phthalocyanine molecular lattice

NASA Astrophysics Data System (ADS)

Bondarev, I. V.; Popescu, A.; Younts, R. A.; Hoffman, B.; McAfee, T.; Dougherty, D. B.; Gundogdu, K.; Ade, H. W.

2016-11-01

We report the results of the combined experimental and theoretical studies of the low-lying exciton states in crystalline copper phthalocyanine. We derive the eigen energy spectrum for the two lowest intramolecular Frenkel excitons coupled to the intermolecular charge transfer exciton state and compare it with temperature dependent optical absorption spectra measured experimentally, to obtain the parameters of the Frenkel-charge-transfer exciton intermixing. The two Frenkel exciton states are spaced apart by 0.26 eV, and the charge transfer exciton state is 50 meV above the lowest Frenkel exciton. Both Frenkel excitons are strongly mixed with the charge transfer exciton, showing the coupling constant 0.17 eV which agrees with earlier experimental measurements. These results can be used for the proper interpretation of the physical properties of crystalline phthalocyanines.

Experimental and theoretical studies of the He(2+)-He system - Differential cross sections for direct, single-, and double-charge-transfer scattering at keV energies

NASA Technical Reports Server (NTRS)

Gao, R. S.; Dutta, C. M.; Lane, N. F.; Smith, K. A.; Stebbings, R. F.; Kimura, M.

1992-01-01

Measurements and calculations of differential cross sections for direct scattering, single-charge transfer, and double-charge transfer in collisions of 1.5-, 2.0-, 6.0-, and 10.0-keV (He-3)2+ with an He-4 target are reported. The measurements cover laboratory scattering angles below 1.5 deg with an angular resolution of about 0.03 deg. A quantum-mechanical molecular-state representation is employed in the calculations; in the case of single-charge transfer a two-state close-coupling calculation is carried out taking into account electron-translation effects. The theoretical calculations agree well with the experimental results for direct scattering and double-charge transfer. The present calculation identifies the origins of oscillatory structures observed in the differential cross sections.

Transfer coefficients in ultracold strongly coupled plasma

NASA Astrophysics Data System (ADS)

Bobrov, A. A.; Vorob'ev, V. S.; Zelener, B. V.

2018-03-01

We use both analytical and molecular dynamic methods for electron transfer coefficients in an ultracold plasma when its temperature is small and the coupling parameter characterizing the interaction of electrons and ions exceeds unity. For these conditions, we use the approach of nearest neighbor to determine the average electron (ion) diffusion coefficient and to calculate other electron transfer coefficients (viscosity and electrical and thermal conductivities). Molecular dynamics simulations produce electronic and ionic diffusion coefficients, confirming the reliability of these results. The results compare favorably with experimental and numerical data from earlier studies.

33 CFR 156.115 - Person in charge: Limitations.

Code of Federal Regulations, 2011 CFR

2011-07-01

... transfer operations on more than one vessel at a time during transfers between vessels or between two or... (CONTINUED) POLLUTION OIL AND HAZARDOUS MATERIAL TRANSFER OPERATIONS Oil and Hazardous Material Transfer... charge of both a vessel and a facility during transfer operations unless authorized by the COTP. [CGD 75...

33 CFR 156.115 - Person in charge: Limitations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... transfer operations on more than one vessel at a time during transfers between vessels or between two or... (CONTINUED) POLLUTION OIL AND HAZARDOUS MATERIAL TRANSFER OPERATIONS Oil and Hazardous Material Transfer... charge of both a vessel and a facility during transfer operations unless authorized by the COTP. [CGD 75...

33 CFR 156.115 - Person in charge: Limitations.

Code of Federal Regulations, 2010 CFR

2010-07-01

... transfer operations on more than one vessel at a time during transfers between vessels or between two or... (CONTINUED) POLLUTION OIL AND HAZARDOUS MATERIAL TRANSFER OPERATIONS Oil and Hazardous Material Transfer... charge of both a vessel and a facility during transfer operations unless authorized by the COTP. [CGD 75...

33 CFR 156.115 - Person in charge: Limitations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... transfer operations on more than one vessel at a time during transfers between vessels or between two or... (CONTINUED) POLLUTION OIL AND HAZARDOUS MATERIAL TRANSFER OPERATIONS Oil and Hazardous Material Transfer... charge of both a vessel and a facility during transfer operations unless authorized by the COTP. [CGD 75...

33 CFR 156.115 - Person in charge: Limitations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... transfer operations on more than one vessel at a time during transfers between vessels or between two or... (CONTINUED) POLLUTION OIL AND HAZARDOUS MATERIAL TRANSFER OPERATIONS Oil and Hazardous Material Transfer... charge of both a vessel and a facility during transfer operations unless authorized by the COTP. [CGD 75...

High Pressure Optical Studies of the Thallous Halides and of Charge-Transfer Complexes

NASA Astrophysics Data System (ADS)

Jurgensen, Charles Willard

High pressure was used to study the insulator -to-metal transition in sulfur and the thallous halides and to study the intermolecular interactions in charge -transfer complexes. The approach to the band overlap insulator -to-metal transition was studied in three thallous halides and sulfur by optical absorption measurements of the band gap as a function of pressure. The band gap of sulfur continuously decreases with pressure up to the insulator -to-metal transition which occurs between 450 and 485 kbars. The results on the thallous halides indicate that the indirect gap decreases more rapidly than the direct gap; the closing of the indirect gap is responsible for the observed insulator -to-metal transitions. High pressure electronic and vibrational spectroscopic measurements on the solid-state complexes of HMB-TCNE were used to study the intermolecular interactions of charge -transfer complexes. The vibrational frequency shifts indicate that the degree of charge transfer increases with pressure which is independently confirmed by an increase in the molar absorptivity of the electronic charge-transfer peak. Induction and dispersion forces contribute towards a red shift of the charge-transfer peak; however, charge-transfer resonance contributes toward a blue shift and this effect is dominant for the HMB-TCNE complexes. High pressure electronic spectra were used to study the effect of intermolecular interactions on the electronic states of TCNQ and its complexes. The red shifts with pressure of the electronic spectra of TCNQ and (TCNQ)(' -) in polymer media and of crystalline TCNQ can be understood in terms of Van der Waals interactions. None of the calculations which considered intradimer distance obtained the proper behavior for either the charge-transfer of the locally excited states of the complexes. The qualitative behavior of both states can be interpreted as the effect of increased mixing of the locally excited and charge transfer states.

Investigations on the charge transfer mechanism at donor/acceptor interfaces in the quest for descriptors of organic solar cell performance.

PubMed

Muraoka, Azusa; Fujii, Mikiya; Mishima, Kenji; Matsunaga, Hiroki; Benten, Hiroaki; Ohkita, Hideo; Ito, Shinzaburo; Yamashita, Koichi

2018-05-07

Herein, we theoretically and experimentally investigated the mechanisms of charge separation processes of organic thin-film solar cells. PTB7, PTB1, and PTBF2 have been chosen as donors and PC 71 BM has been chosen as an acceptor considering that effective charge generation depends on the difference between the material combinations. Experimental results of transient absorption spectroscopy show that the hot process is a key step for determining external quantum efficiency (EQE) in these systems. From the quantum chemistry calculations, it has been found that EQE tends to increase as the transferred charge, charge transfer distance, and variation of dipole moments between the ground and excited states of the donor/acceptor complexes increase; this indicates that these physical quantities are a good descriptor to assess the donor-acceptor charge transfer quality contributing to the solar cell performance. We propose that designing donor/acceptor interfaces with large values of charge transfer distance and variation of dipole moments of the donor/acceptor complexes is a prerequisite for developing high-efficiency polymer/PCBM solar cells.

Reduced Charge Transfer Exciton Recombination in Organic Semiconductor Heterojunctions by Molecular Doping

NASA Astrophysics Data System (ADS)

Deschler, Felix; da Como, Enrico; Limmer, Thomas; Tautz, Raphael; Godde, Tillmann; Bayer, Manfred; von Hauff, Elizabeth; Yilmaz, Seyfullah; Allard, Sybille; Scherf, Ullrich; Feldmann, Jochen

2011-09-01

We investigate the effect of molecular doping on the recombination of electrons and holes localized at conjugated-polymer-fullerene interfaces. We demonstrate that a low concentration of p-type dopant molecules (<4% weight) reduces the interfacial recombination via charge transfer excitons and results in a favored formation of separated carriers. This is observed by the ultrafast quenching of photoluminescence from charge transfer excitons and the increase in photoinduced polaron density by ˜70%. The results are consistent with a reduced formation of emissive charge transfer excitons, induced by state filling of tail states.

Heat transfer in freeboard region of fluidized beds

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

Biyikli, S.; Tuzla, K.; Chen, J.C.

1983-10-01

This research involved the study of heat transfer and fluid mechanic characteristics around a horizontal tube in the freeboard region of fluidized beds. Heat transfer coefficients were experimetnally measured for different bed temperatures, particle sizes, gas flow rates, and tube elevations in the freeboard region of air fluidized beds at atmospheric pressure. Local heat transfer coefficients were found to vary significantly with angular position around the tube. Average heat transfer coefficients were found to decrease with increasing freeboard tube elevation and approach the values for gas convection plus radiation for any given gas velocity. For a fixed tube elevation, heatmore » transfer coefficients generally increased with increasing gas velocity and with high particle entrainment they can approach the magnitudes found for immersed tubes. Heat transfer coefficients were also found to increase with increasing bed temperature. It was concluded that this increase is partly due to increase of radiative heat transfer and partly due to change of thermal properties of the fluidizing gas and particles. To investigate the fluid mechanic behavior of gas and particles around a freeboard tube, transient particle tube contacts were measured with a special capacitance probe in room temperature experiments. The results indicated that the tube surface experiences alternating dense and lean phase contacts. Quantitative information for local characteristics was obtained from the capacitance signals and used to develop a phenomenological model for prediction of the heat transfer coefficients around freeboard tubes. The packet renewal theory was modified to account for the dense phase heat transfer and a new model was suggested for the lean phase heat transfer. Finally, an empirical freeboard heat transfer correlation was developed from functional analysis of the freeboard heat transfer data using nondimensional groups representing gas velocity and tube elevation.« less

Recombination of open-f-shell tungsten ions

NASA Astrophysics Data System (ADS)

Krantz, C.; Badnell, N. R.; Müller, A.; Schippers, S.; Wolf, A.

2017-03-01

We review experimental and theoretical efforts aimed at a detailed understanding of the recombination of electrons with highly charged tungsten ions characterised by an open 4f sub-shell. Highly charged tungsten occurs as a plasma contaminant in ITER-like tokamak experiments, where it acts as an unwanted cooling agent. Modelling of the charge state populations in a plasma requires reliable thermal rate coefficients for charge-changing electron collisions. The electron recombination of medium-charged tungsten species with open 4f sub-shells is especially challenging to compute reliably. Storage-ring experiments have been conducted that yielded recombination rate coefficients at high energy resolution and well-understood systematics. Significant deviations compared to simplified, but prevalent, computational models have been found. A new class of ab initio numerical calculations has been developed that provides reliable predictions of the total plasma recombination rate coefficients for these ions.

Characteristics of heat exchange in the region of injection into a supersonic high-temperature flow

NASA Technical Reports Server (NTRS)

Bakirov, F. G.; Shaykhutdinov, Z. G.

1985-01-01

An experimental investigation of the local heat transfer coefficient distribution during gas injection into the supersonic-flow portion of a Laval nozzle is discussed. The controlling dimensionless parameters of the investigated process are presented in terms of a generalized relation for the maximum value of the heat transfer coefficient in the nozzle cross section behind the injection hole. Data on the heat transfer coefficient variation along the nozzle length as a function of gas injection rate are also presented, along with the heat transfer coefficient distribution over a cross section of the nozzle.

Scientific Computation Application Partnerships in Materials and Chemical Sciences, Charge Transfer and Charge Transport in Photoactivated Systems, Developing Electron-Correlated Methods for Excited State Structure and Dynamics in the NWChem Software Suite

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

Cramer, Christopher J.

Charge transfer and charge transport in photoactivated systems are fundamental processes that underlie solar energy capture, solar energy conversion, and photoactivated catalysis, both organometallic and enzymatic. We developed methods, algorithms, and software tools needed for reliable treatment of the underlying physics for charge transfer and charge transport, an undertaking with broad applicability to the goals of the fundamental-interaction component of the Department of Energy Office of Basic Energy Sciences and the exascale initiative of the Office of Advanced Scientific Computing Research.

Topological Effects of Charge Transfer in Telomere G-Quadruplex Mechanism on Telomerase Activation and Inhibition

NASA Astrophysics Data System (ADS)

Wang, Xin; Liang, Shi-Dong

2013-02-01

We explore the charge transfer in the telomere G-Quadruplex (TG4) DNA theoretically by the nonequilibrium Green's function method, and reveal the topological effect of the charge transport in TG4 DNA. The consecutive TG4 (CTG4) is semiconducting with 0.2 0.3 eV energy gap. Charges transfer favorably in the CTG4, but are trapped in the nonconsecutive TG4 (NCTG4). The global conductance is inversely proportional to the local conductance for NCTG4. The topological structure transition from NCTG4 to CTG4 induces abruptly 3nA charge current, which provide a microscopic clue to understand the telomerase activated or inhibited by TG4. Our findings reveal the fundamental property of charge transfer in TG4 and its relationship with the topological structure of TG4.

78 FR 63268 - Self-Regulatory Organizations; Financial Industry Regulatory Authority, Inc.; Notice of Filing...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-23

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33 CFR 155.710 - Qualifications of person in charge.

Code of Federal Regulations, 2010 CFR

2010-07-01

... available to the PIC on the tankship at all times during the transfer or cargo-tank cleaning; and (iii) Is... Transfer Personnel, Procedures, Equipment, and Records § 155.710 Qualifications of person in charge. (a) On... the vessel, or the person who arranges and hires a person to be in charge either of a transfer of...

Multiphasic modeling of charged solute transport across articular cartilage: Application of multi-zone finite-bath model.

PubMed

Arbabi, Vahid; Pouran, Behdad; Weinans, Harrie; Zadpoor, Amir A

2016-06-14

Charged and uncharged solutes penetrate through cartilage to maintain the metabolic function of chondrocytes and to possibly restore or further breakdown the cartilage tissue in different stages of osteoarthritis. In this study the transport of charged solutes across the various zones of cartilage was quantified, taken into account the physicochemical interactions between the solute and the cartilage constituents. A multiphasic finite-bath finite element (FE) model was developed to simulate equine cartilage diffusion experiments that used a negatively charged contrast agent (ioxaglate) in combination with serial micro-computed tomography (micro-CT) to measure the diffusion. By comparing the FE model with the experimental data both the diffusion coefficient of ioxaglate and the fixed charge density (FCD) were obtained. In the multiphasic model, cartilage was divided into multiple (three) zones to help understand how diffusion coefficient and FCD vary across cartilage thickness. The direct effects of charged solute-FCD interaction on diffusion were investigated by comparing the diffusion coefficients derived from the multiphasic and biphasic-solute models. We found a relationship between the FCD obtained by the multiphasic model and ioxaglate partitioning obtained from micro-CT experiments. Using our multi-zone multiphasic model, diffusion coefficient of the superficial zone was up to ten-fold higher than that of the middle zone, while the FCD of the middle zone was up to almost two-fold higher than that of the superficial zone. In conclusion, the developed finite-bath multiphasic model provides us with a non-destructive method by which we could obtain both diffusion coefficient and FCD of different cartilage zones. The outcomes of the current work will also help understand how charge of the bath affects the diffusion of a charged molecule and also predict the diffusion behavior of a charged solute across articular cartilage. Copyright © 2016 Elsevier Ltd. All rights reserved.

Heat Transfer and Flow on the Squealer Tip of a Gas Turbine Blade

NASA Technical Reports Server (NTRS)

Azad, Gm S.; Han, Je-Chin; Boyle, Robert J.

2000-01-01

Experimental investigations are performed to measure the detailed heat transfer coefficient and static pressure distributions on the squealer tip of a gas turbine blade in a five-bladed stationary linear cascade. The blade is a 2-dimensional model of a modem first stage gas turbine rotor blade with a blade tip profile of a GE-E(sup 3) aircraft gas turbine engine rotor blade. A squealer (recessed) tip with a 3.77% recess is considered here. The data on the squealer tip are also compared with a flat tip case. All measurements are made at three different tip gap clearances of about 1%, 1.5%, and 2.5% of the blade span. Two different turbulence intensities of 6.1% and 9.7% at the cascade inlet are also considered for heat transfer measurements. Static pressure measurements are made in the mid-span and near-tip regions, as well as on the shroud surface opposite to the blade tip surface. The flow condition in the test cascade corresponds to an overall pressure ratio of 1.32 and an exit Reynolds number based on the axial chord of 1.1 x 10(exp 6). A transient liquid crystal technique is used to measure the heat transfer coefficients. Results show that the heat transfer coefficient on the cavity surface and rim increases with an increase in tip clearance. 'Me heat transfer coefficient on the rim is higher than the cavity surface. The cavity surface has a higher heat transfer coefficient near the leading edge region than the trailing edge region. The heat transfer coefficient on the pressure side rim and trailing edge region is higher at a higher turbulence intensity level of 9.7% over 6.1 % case. However, no significant difference in local heat transfer coefficient is observed inside the cavity and the suction side rim for the two turbulence intensities. The squealer tip blade provides a lower overall heat transfer coefficient when compared to the flat tip blade.

Charge transfer in model peptides: obtaining Marcus parameters from molecular simulation.

PubMed

Heck, Alexander; Woiczikowski, P Benjamin; Kubař, Tomáš; Giese, Bernd; Elstner, Marcus; Steinbrecher, Thomas B

2012-02-23

Charge transfer within and between biomolecules remains a highly active field of biophysics. Due to the complexities of real systems, model compounds are a useful alternative to study the mechanistic fundamentals of charge transfer. In recent years, such model experiments have been underpinned by molecular simulation methods as well. In this work, we study electron hole transfer in helical model peptides by means of molecular dynamics simulations. A theoretical framework to extract Marcus parameters of charge transfer from simulations is presented. We find that the peptides form stable helical structures with sequence dependent small deviations from ideal PPII helices. We identify direct exposure of charged side chains to solvent as a cause of high reorganization energies, significantly larger than typical for electron transfer in proteins. This, together with small direct couplings, makes long-range superexchange electron transport in this system very slow. In good agreement with experiment, direct transfer between the terminal amino acid side chains can be dicounted in favor of a two-step hopping process if appropriate bridging groups exist. © 2012 American Chemical Society

A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

NASA Technical Reports Server (NTRS)

Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

1991-01-01

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high speed flow fields.

A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

NASA Technical Reports Server (NTRS)

Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

1991-01-01

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high-speed flowfields.

Modeling of the heat transfer performance of plate-type dispersion nuclear fuel elements

NASA Astrophysics Data System (ADS)

Ding, Shurong; Huo, Yongzhong; Yan, XiaoQing

2009-08-01

Considering the mutual actions between fuel particles and the metal matrix, the three-dimensional finite element models are developed to simulate the heat transfer behaviors of dispersion nuclear fuel plates. The research results indicate that the temperatures of the fuel plate might rise more distinctly with considering the particle swelling and the degraded surface heat transfer coefficients with increasing burnup; the local heating phenomenon within the particles appears when their thermal conductivities are too low. With rise of the surface heat transfer coefficients, the temperatures within the fuel plate decrease; the temperatures of the fuel plate are sensitive to the variations of the heat transfer coefficients whose values are lower, but their effects are weakened and slight when the heat transfer coefficients increase and reach a certain extent. Increasing the heat generation rate leads to elevating the internal temperatures. The temperatures and the maximum temperature differences within the plate increase along with the particle volume fractions. The surface thermal flux goes up along with particle volume fractions and heat generation rates, but the effects of surface heat transfer coefficients are not evident.

Sphere Drag and Heat Transfer

NASA Astrophysics Data System (ADS)

Duan, Zhipeng; He, Boshu; Duan, Yuanyuan

2015-07-01

Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body.

Sphere Drag and Heat Transfer.

PubMed

Duan, Zhipeng; He, Boshu; Duan, Yuanyuan

2015-07-20

Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body.

Study on structures and properties of ammonia clusters (NH3)n (n=1-5) and liquid ammonia in terms of ab initio method and atom-bond electronegativity equalization method ammonia-8P fluctuating charge potential model.

PubMed

Yu, Ling; Yang, Zhong-Zhi

2010-05-07

Structures, binding energies, and vibrational frequencies of (NH(3))(n) (n=2-5) isomers and dynamical properties of liquid ammonia have been explored using a transferable intermolecular potential eight point model including fluctuating charges and flexible body based on a combination of the atom-bond electronegativity equalization and molecular (ABEEM) mechanics (ABEEM ammonia-8P) in this paper. The important feature of this model is to divide the charge sites of one ammonia molecule into eight points region containing four atoms, three sigma bonds, and a lone pair, and allows the charges in system to fluctuate responding to the ambient environment. Due to the explicit descriptions of charges and special treatment of hydrogen bonds, the results of equilibrium geometries, dipole moments, cluster interaction energies, vibrational frequencies for the gas phase of small ammonia clusters, and radial distribution function for liquid ammonia calculated with the ABEEM ammonia-8P potential model are in good agreement with those measured by available experiments and those obtained from high level ab initio calculations. The properties of ammonia dimer are studied in detail involving the structure and one-dimensional, two-dimensional potential energy surface. As for interaction energies, the root mean square deviation is 0.27 kcal/mol, and the linear correlation coefficient reaches 0.994.

Determination of blade-to-coolant heat-transfer coefficients on a forced-convection, water-cooled, single-stage turbine

NASA Technical Reports Server (NTRS)

Freche, John C; Schum, Eugene F

1951-01-01

Blade-to-coolant convective heat-transfer coefficients were obtained on a forced-convection water-cooled single-stage turbine over a large laminar flow range and over a portion of the transition range between laminar and turbulent flow. The convective coefficients were correlated by the general relation for forced-convection heat transfer with laminar flow. Natural-convection heat transfer was negligible for this turbine over the Grashof number range investigated. Comparison of turbine data with stationary tube data for the laminar flow of heated liquids showed good agreement. Calculated average midspan blade temperatures using theoretical gas-to-blade coefficients and blade-to-coolant coefficients from stationary-tube data resulted in close agreement with experimental data.

Influence of fused aromatic ring on the stability of charge transfer complex between iodine and some five membered heterocyclic molecules through ultrasonic and spectral studies

NASA Astrophysics Data System (ADS)

Ulagendran, V.; Balu, P.; Kannappan, V.; Kumar, R.; Jayakumar, S.

2017-08-01

The charge transfer (CT) interaction between two fused heterocyclic compounds with basic pyrrole group as donors, viz., indole (IND) and carbazole (CAR), and iodine (acceptor) in DMSO medium is investigated by ultrasonic and UV-visible spectral methods at 303 K. The formation of CT complex in these systems is established from the trend in acoustical and excess thermo acoustical properties with molar concentration. The frequency acoustic spectra (FAS) is also carried out on these two systems for two fixed concentrations 0.002 M and 0.02 M, and in the frequency range 1 MHz-10 MHz to justify the frequency chosen for ultrasonic study. The absorption coefficient values in solution are computed and discussed. The formation constants of these complexes are determined using Kannappan equation in ultrasonic method. The formation of 1:1 complexes between iodine and IND, CAR was established by the theory of Benesi - Hildebrand in the UV-visible spectroscopic method. The stability constants of the CT complexes determined by spectroscopic and ultrasonic methods show a similar trend. These values also indicate that the presence of fused aromatic ring influences significantly when compared with K values of similar CT complexes of parent five membered heterocyclic compound (pyrrole) reported by us earlier.

Lithium-ions diffusion kinetic in LiFePO4/carbon nanoparticles synthesized by microwave plasma chemical vapor deposition for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Gao, Chao; Zhou, Jian; Liu, Guizhen; Wang, Lin

2018-03-01

Olivine structure LiFePO4/carbon nanoparticles are synthesized successfully using a microwave plasma chemical vapor deposition (MPCVD) method. Microwave is an effective method to synthesize nanomaterials, the LiFePO4/carbon nanoparticles with high crystallinity can shorten diffusion routes for ionic transfer and electron tunneling. Meanwhile, a high quality, complete and homogenous carbon layer with appropriate thickness coating on the surface of LiFePO4 particles during in situ chemical vapor deposition process, which can ensure that electrons are able to transfer fast enough from all sides. Electrochemical impedance spectroscopy (EIS) is carried out to collect information about the kinetic behavior of lithium diffusion in LiFePO4/carbon nanoparticles during the charging and discharging processes. The chemical diffusion coefficients of lithium ions, DLi, are calculated in the range of 10-15-10-9 cm2s-1. Nanoscale LiFePO4/carbon particles show the longer regions of the faster solid-solution diffusion, and corresponding to the narrower region of the slower two-phase diffusion during the insertion/exaction of lithium ions. The CV and galvanostatic charge-discharge measurements show that the LiFePO4/carbon nanoparticles perform an excellent electrochemical performance, especially the high rate capacity and cycle life.

Unusual photoelectric behaviors of Mo-doped TiO2 multilayer thin films prepared by RF magnetron co-sputtering: effect of barrier tunneling on internal charge transfer

NASA Astrophysics Data System (ADS)

Yan, B. X.; Luo, S. Y.; Mao, X. G.; Shen, J.; Zhou, Q. F.

2013-01-01

Mo-doped TiO2 multilayer thin films were prepared by RF magnetron co-sputtering. Microstructures, crystallite parameters and the absorption band were investigated with atomic force microscopy, X-ray diffraction and ultraviolet-visible spectroscopy. Internal carrier transport characteristics and the photoelectric property of different layer-assemble modes were examined on an electrochemical workstation under visible light. The result indicates that the double-layer structure with an undoped surface layer demonstrated a red-shifted absorption edge and a much stronger photocurrent compared to the uniformly doped sample, signifying that the electric field implanted at the interface between particles in different layers accelerated internal charge transfer effectively. However, a heavily doped layer implanted at the bottom of the three-layer film merely brought about negative effects on the photoelectric property, mainly because of the Schottky junction existing above the substrate. Nevertheless, this obstacle was successfully eliminated by raising the Mo concentration to 1020 cm-3, where the thickness of the depletion layer fell into the order of angstroms and the tunneling coefficient manifested a dramatic increase. Under this circumstance, the Schottky junction disappeared and the strongest photocurrent was observed in the three-layer film.

Hydration and conformational equilibria of simple hydrophobic and amphiphilic solutes.

PubMed Central

Ashbaugh, H S; Kaler, E W; Paulaitis, M E

1998-01-01

We consider whether the continuum model of hydration optimized to reproduce vacuum-to-water transfer free energies simultaneously describes the hydration free energy contributions to conformational equilibria of the same solutes in water. To this end, transfer and conformational free energies of idealized hydrophobic and amphiphilic solutes in water are calculated from explicit water simulations and compared to continuum model predictions. As benchmark hydrophobic solutes, we examine the hydration of linear alkanes from methane through hexane. Amphiphilic solutes were created by adding a charge of +/-1e to a terminal methyl group of butane. We find that phenomenological continuum parameters fit to transfer free energies are significantly different from those fit to conformational free energies of our model solutes. This difference is attributed to continuum model parameters that depend on solute conformation in water, and leads to effective values for the free energy/surface area coefficient and Born radii that best describe conformational equilibrium. In light of these results, we believe that continuum models of hydration optimized to fit transfer free energies do not accurately capture the balance between hydrophobic and electrostatic contributions that determines the solute conformational state in aqueous solution. PMID:9675177

Determination of diffusion coefficient in disordered organic semiconductors

NASA Astrophysics Data System (ADS)

Rani, Varsha; Sharma, Akanksha; Ghosh, Subhasis

2016-05-01

Charge carrier transport in organic semiconductors is dominated by positional and energetic disorder in Gaussian density of states (GDOS) and is characterized by hopping through localized states. Due to the immobilization of charge carriers in these localized states, significant non-uniform carrier distribution exists, resulting diffusive transport. A simple, nevertheless powerful technique to determine diffusion coefficient D in disordered organic semiconductors has been presented. Diffusion coefficients of charge carriers in two technologically important organic molecular semiconductors, Pentacene and copper phthalocyanine (CuPc) have been measured from current-voltage (J-V) characteristics of Al/Pentacene/Au and Al/CuPc/Au based Schottky diodes. Ideality factor g and carrier mobility μ have been calculated from the exponential and space charge limited region respectively of J-V characteristics. Classical Einstein relation is not valid in organic semiconductors due to energetic disorders in DOS. Using generalized Einstein relation, diffusion coefficients have been obtained to be 1.31×10-6 and 1.73×10-7 cm2/s for Pentacene and CuPc respectively.

Charge transfer induced by MoO3 at boron subphthalocyanine chloride/α-sexithiophene heterojunction interface

NASA Astrophysics Data System (ADS)

Foggiatto, Alexandre L.; Sakurai, Takeaki

2018-03-01

The energy-level alignment of boron subphthalocyanine chloride (SubPc)/α-sexithiophene (6T) grown on MoO3 was investigated using ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS). We demonstrated that the p-doping effect generated by the MoO3 layer can induce charge transfer at the organic-organic heterojunction interface. After the deposition of 6T on MoO3, the fermi level becomes pinned close to the 6T highest occupied molecular orbital (HOMO) level and when SubPc is deposited, owing to its tail states, charge transfer occurs in order to achieve thermodynamic equilibrium. We also demonstrated that the charge transfer can be reduced by annealing the film. We suggested that the reduction of the misalignment on the film induces a reduction in the density of gap states, which controls the charge transfer.

Understanding the Charge Transfer at the Interface of Electron Donors and Acceptors: TTF–TCNQ as an Example

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

Park, Changwon; Atalla, Viktor; Smith, Sean

Charge transfer between an electron donor and an electron acceptor is widely accepted as being independent of their relative configurations if the interaction between them is weak; however, the limit of this concept for an interacting system has not yet been well established. Our study of prototypical electron donor–acceptor molecules, tetrathiafulvalene–tetracyanoquinodimethane, using density functional theory based on an advanced functional, clearly demonstrates that for interacting molecules, their configurational arrangement is as important as their individual electronic properties in the asymptotic limit to determine the charge transfer direction. For the first time, we demonstrate that by changing their relative orientation, onemore » can reverse the charge transfer direction of the pair, causing the molecules to exchange roles as donor and acceptor. In conclusion, our theory has important implications for understanding the interfacial charge-transfer mechanism of hybrid systems and related phenomena.« less

Interfacial charge transfer absorption: Application to metal molecule assemblies

NASA Astrophysics Data System (ADS)

Creutz, Carol; Brunschwig, Bruce S.; Sutin, Norman

2006-05-01

Optically induced charge transfer between adsorbed molecules and a metal electrode was predicted by Hush to lead to new electronic absorption features, but has been only rarely observed experimentally. Interfacial charge transfer absorption (IFCTA) provides information concerning the barriers to charge transfer between molecules and the metal/semiconductor and the magnitude of the electronic coupling and could thus provide a powerful tool for understanding interfacial charge-transfer kinetics. Here, we utilize a previously published model [C. Creutz, B.S. Brunschwig, N. Sutin, J. Phys. Chem. B 109 (2005) 10251] to predict IFCTA spectra of metal-molecule assemblies and compare the literature observations to these predictions. We conclude that, in general, the electronic coupling between molecular adsorbates and the metal levels is so small that IFCTA is not detectable. However, few experiments designed to detect IFCTA have been done. We suggest approaches to optimizing the conditions for observing the process.

Understanding the Charge Transfer at the Interface of Electron Donors and Acceptors: TTF–TCNQ as an Example

DOE PAGES

Park, Changwon; Atalla, Viktor; Smith, Sean; ...

2017-06-16

Charge transfer between an electron donor and an electron acceptor is widely accepted as being independent of their relative configurations if the interaction between them is weak; however, the limit of this concept for an interacting system has not yet been well established. Our study of prototypical electron donor–acceptor molecules, tetrathiafulvalene–tetracyanoquinodimethane, using density functional theory based on an advanced functional, clearly demonstrates that for interacting molecules, their configurational arrangement is as important as their individual electronic properties in the asymptotic limit to determine the charge transfer direction. For the first time, we demonstrate that by changing their relative orientation, onemore » can reverse the charge transfer direction of the pair, causing the molecules to exchange roles as donor and acceptor. In conclusion, our theory has important implications for understanding the interfacial charge-transfer mechanism of hybrid systems and related phenomena.« less

Collisional charging of individual submillimeter particles: Using ultrasonic levitation to initiate and track charge transfer

NASA Astrophysics Data System (ADS)

Lee, Victor; James, Nicole M.; Waitukaitis, Scott R.; Jaeger, Heinrich M.

2018-03-01

Electrostatic charging of insulating fine particles can be responsible for numerous phenomena ranging from lightning in volcanic plumes to dust explosions. However, even basic aspects of how fine particles become charged are still unclear. Studying particle charging is challenging because it usually involves the complexities associated with many-particle collisions. To address these issues, we introduce a method based on acoustic levitation, which makes it possible to initiate sequences of repeated collisions of a single submillimeter particle with a flat plate, and to precisely measure the particle charge in situ after each collision. We show that collisional charge transfer between insulators is dependent on the hydrophobicity of the contacting surfaces. We use glass, which we modify by attaching nonpolar molecules to the particle, the plate, or both. We find that hydrophilic surfaces develop significant positive charges after contacting hydrophobic surfaces. Moreover, we demonstrate that charging between a hydrophilic and a hydrophobic surface is suppressed in an acidic environment and enhanced in a basic one. Application of an electric field during each collision is found to modify the charge transfer, again depending on surface hydrophobicity. We discuss these results within the context of contact charging due to ion transfer, and we show that they lend strong support to O H- ions as the charge carriers.

Electron Transfer Dissociation: Effects of Cation Charge State on Product Partitioning in Ion/Ion Electron Transfer to Multiply Protonated Polypeptides

PubMed Central

Liu, Jian; McLuckey, Scott A.

2012-01-01

The effect of cation charge state on product partitioning in the gas-phase ion/ion electron transfer reactions of multiply protonated tryptic peptides, model peptides, and relatively large peptides with singly charged radical anions has been examined. In particular, partitioning into various competing channels, such as proton transfer (PT) versus electron transfer (ET), electron transfer with subsequent dissociation (ETD) versus electron transfer with no dissociation (ET,noD), and fragmentation of backbone bonds versus fragmentation of side chains, was measured quantitatively as a function of peptide charge state to allow insights to be drawn about the fundamental aspects of ion/ion reactions that lead to ETD. The ET channel increases relative to the PT channel, ETD increases relative to ET,noD, and fragmentation at backbone bonds increases relative to side-chain cleavages as cation charge state increases. The increase in ET versus PT with charge state is consistent with a Landau-Zener based curve-crossing model. An optimum charge state for ET is predicted by the model for the ground state-to-ground state reaction. However, when the population of excited product ion states is considered, it is possible that a decrease in ET efficiency as charge state increases will not be observed due to the possibility of the population of excited electronic states of the products. Several factors can contribute to the increase in ETD versus ET,noD and backbone cleavage versus side-chain losses. These factors include an increase in reaction exothermicity and charge state dependent differences in precursor and product ion structures, stabilities, and sites of protonation. PMID:23264749

Bacterial attachment to RO membranes surface-modified by concentration-polarization-enhanced graft polymerization.

PubMed

Bernstein, Roy; Belfer, Sofia; Freger, Viatcheslav

2011-07-15

Concentration polarization-enhanced radical graft polymerization, a facile surface modification technique, was examined as an approach to reduce bacterial deposition onto RO membranes and thus contribute to mitigation of biofouling. For this purpose an RO membrane ESPA-1 was surface-grafted with a zwitterionic and negatively and positively charged monomers. The low monomer concentrations and low degrees of grafting employed in modifications moderately reduced flux (by 20-40%) and did not affect salt rejection, yet produced substantial changes in surface chemistry, charge and hydrophilicity. The propensity to bacterial attachment of original and modified membranes was assessed using bacterial deposition tests carried out in a parallel plate flow setup using a fluorescent strain of Pseudomonas fluorescens. Compared to unmodified ESPA-1 the deposition (mass transfer) coefficient was significantly increased for modification with the positively charged monomer. On the other hand, a substantial reduction in bacterial deposition rates was observed for membranes modified with zwitterionic monomer and, still more, with very hydrophilic negatively charged monomers. This trend is well explained by the effects of surface charge (as measured by ζ-potential) and hydrophilicity (contact angle). It also well correlated with force distance measurements by AFM using surrogate spherical probes with a negative surface charge mimicking the bacterial surface. The positively charged surface showed a strong hysteresis with a large adhesion force, which was weaker for unmodified ESPA-1 and still weaker for zwitterionic surface, while negatively charged surface showed a long-range repulsion and negligible hysteresis. These results demonstrate the potential of using the proposed surface- modification approach for varying surface characteristics, charge and hydrophilicity, and thus minimizing bacterial deposition and potentially reducing propensity biofouling.

Data on inelastic processes in low-energy potassium-hydrogen and rubidium-hydrogen collisions

NASA Astrophysics Data System (ADS)

Yakovleva, S. A.; Barklem, P. S.; Belyaev, A. K.

2018-01-01

Two sets of rate coefficients for low-energy inelastic potassium-hydrogen and rubidium-hydrogen collisions were computed for each collisional system based on two model electronic structure calculations, performed by the quantum asymptotic semi-empirical and the quantum asymptotic linear combinations of atomic orbitals (LCAO) approaches, followed by quantum multichannel calculations for the non-adiabatic nuclear dynamics. The rate coefficients for the charge transfer (mutual neutralization, ion-pair formation), excitation and de-excitation processes are calculated for all transitions between the five lowest lying covalent states and the ionic states for each collisional system for the temperature range 1000-10 000 K. The processes involving higher lying states have extremely low rate coefficients and, hence, are neglected. The two model calculations both single out the same partial processes as having large and moderate rate coefficients. The largest rate coefficients correspond to the mutual neutralization processes into the K(5s 2S) and Rb(4d 2D) final states and at temperature 6000 K have values exceeding 3 × 10-8 cm3 s-1 and 4 × 10-8 cm3 s-1, respectively. It is shown that both the semi-empirical and the LCAO approaches perform equally well on average and that both sets of atomic data have roughly the same accuracy. The processes with large and moderate rate coefficients are likely to be important for non-LTE modelling in atmospheres of F, G and K-stars, especially metal-poor stars.

Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger.

PubMed

Aghayari, Reza; Maddah, Heydar; Zarei, Malihe; Dehghani, Mehdi; Kaskari Mahalle, Sahar Ghanbari

2014-01-01

This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (γ-AL2O3) with a particle size of 20 nm and volume fraction of 0.1%-0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipe heat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations shows an acceptable agreement. Experimental results show a considerable increase in heat transfer coefficient and Nusselt number up to 19%-24%, respectively. Also, it has been observed that the heat transfer coefficient increases with the operating temperature and concentration of nanoparticles.

Through-Space Intervalence Charge Transfer as a Mechanism for Charge Delocalisation in Metal-Organic Frameworks.

PubMed

Hua, Carol; Doheny, Patrick William; Ding, Bowen; Chan, Bun; Yu, Michelle; Kepert, Cameron J; D'Alessandro, Deanna M

2018-05-04

Understanding the nature of charge transfer mechanisms in 3-dimensional Metal-Organic Frameworks (MOFs) is an important goal owing to the possibility of harnessing this knowledge to design conductive frameworks. These materials have been implicated as the basis for the next generation of technological devices for applications in energy storage and conversion, including electrochromic devices, electrocatalysts, and battery materials. After nearly two decades of intense research into MOFs, the mechanisms of charge transfer remain relatively poorly understood, and new strategies to achieve charge mobility remain elusive and challenging to experimentally explore, validate and model. We now demonstrate that aromatic stacking interactions in Zn(II) frameworks containing cofacial thiazolo[5,4-d]thiazole units lead to a mixed-valence state upon electrochemical or chemical reduction. This through-space Intervalence Charge Transfer (IVCT) phenomenon represents a new mechanism for charge delocalisation in MOFs. Computational modelling of the optical data combined with application of Marcus-Hush theory to the IVCT bands for the mixed-valence framework has enabled quantification of the degree of delocalisation using both in situ and ex situ electro- and spectro-electrochemical methods. A distance dependence for the through-space electron transfer has also been identified on the basis of experimental studies and computational calculations. This work provides a new window into electron transfer phenomena in 3-dimensional coordination space, of relevance to electroactive MOFs where new mechanisms for charge transfer are highly sought after, and to understanding biological light harvesting systems where through-space mixed-valence interactions are operative.

Process techniques of charge transfer time reduction for high speed CMOS image sensors

NASA Astrophysics Data System (ADS)

Zhongxiang, Cao; Quanliang, Li; Ye, Han; Qi, Qin; Peng, Feng; Liyuan, Liu; Nanjian, Wu

2014-11-01

This paper proposes pixel process techniques to reduce the charge transfer time in high speed CMOS image sensors. These techniques increase the lateral conductivity of the photo-generated carriers in a pinned photodiode (PPD) and the voltage difference between the PPD and the floating diffusion (FD) node by controlling and optimizing the N doping concentration in the PPD and the threshold voltage of the reset transistor, respectively. The techniques shorten the charge transfer time from the PPD diode to the FD node effectively. The proposed process techniques do not need extra masks and do not cause harm to the fill factor. A sub array of 32 × 64 pixels was designed and implemented in the 0.18 μm CIS process with five implantation conditions splitting the N region in the PPD. The simulation and measured results demonstrate that the charge transfer time can be decreased by using the proposed techniques. Comparing the charge transfer time of the pixel with the different implantation conditions of the N region, the charge transfer time of 0.32 μs is achieved and 31% of image lag was reduced by using the proposed process techniques.

Photoinduced electron transfer in a molecular dyad by nanosecond pump-pump-probe spectroscopy.

PubMed

Ha-Thi, M-H; Pham, V-T; Pino, T; Maslova, V; Quaranta, A; Lefumeux, C; Leibl, W; Aukauloo, A

2018-06-01

The design of robust and inexpensive molecular photocatalysts for the conversion of abundant stable molecules like H2O and CO2 into an energetic carrier is one of the major fundamental questions for scientists nowadays. The outstanding challenge is to couple single photoinduced charge separation events with the sequential accumulation of redox equivalents at the catalytic unit for performing multielectronic catalytic reactions. Herein, double excitation by nanosecond pump-pump-probe experiments was used to interrogate the photoinduced charge transfer and charge accumulation on a molecular dyad composed of a porphyrin chromophore and a ruthenium-based catalyst in the presence of a reversible electron acceptor. An accumulative charge transfer state is unattainable because of rapid reverse electron transfer to the photosensitizer upon the second excitation and the low driving force of the forward photodriven electron transfer reaction. Such a method allows the fundamental understanding of the relaxation mechanism after two sequential photon absorptions, deciphering the undesired electron transfer reactions that limit the charge accumulation efficiency. This study is a step toward the improvement of synthetic strategies of molecular photocatalysts for light-induced charge accumulation and more generally, for solar energy conversion.

Evaluation of Contact Heat Transfer Coefficient and Phase Transformation during Hot Stamping of a Hat-Type Part

PubMed Central

Kim, Heung-Kyu; Lee, Seong Hyeon; Choi, Hyunjoo

2015-01-01

Using an inverse analysis technique, the heat transfer coefficient on the die-workpiece contact surface of a hot stamping process was evaluated as a power law function of contact pressure. This evaluation was to determine whether the heat transfer coefficient on the contact surface could be used for finite element analysis of the entire hot stamping process. By comparing results of the finite element analysis and experimental measurements of the phase transformation, an evaluation was performed to determine whether the obtained heat transfer coefficient function could provide reasonable finite element prediction for workpiece properties affected by the hot stamping process. PMID:28788046

Analysis of charge transport in gels containing polyoxometallates using methods of different sensitivity to migration.

PubMed

Caban, Karolina; Lewera, Adam; Zukowska, Grazyna Z; Kulesza, Pawel J; Stojek, Zbigniew; Jeffrey, Kenneth R

2006-08-04

Two methods have been used for examination of transport of charge in gels soaked with DMF and containing dissolved polyoxometallates. The first method is based on the analysis of both Cottrellian and steady-state currents and therefore is capable of giving the concentration of the electroactive redox centres and their transport (diffusion-type) coefficient. The second method provides the real diffusion coefficients, i.e. transport coefficients free of migrational influence, for both the substrate and the product of the electrode reaction. Several gels based on poly(methyl methacrylate), with charged (addition of 1-acrylamido-2-methyl-2-propanesulphonic acid to the polymerization mixture) and uncharged chains, have been used in the investigation. The ratio obtained for the diffusion coefficient (second method) and transport coefficient (first method) was smaller for the gels containing charged polymer chains than for the gels with uncharged chains. In part these changes could be explained by the contribution of migration to the transport of polyoxomatallates in the gels. However, the impact of the changes in the polymer-channel capacity at the electrode surface while the electrode process proceeds was also considered. These structural changes should affect differently the methods based on different time domains.

Volatilization of ethylene dibromide from water

USGS Publications Warehouse

Rathbun, R.E.; Tai, D.Y.

1987-01-01

Overall mass-transfer coefficients for the volatilization of ethylene dibromide from water were measured simultaneously with the oxygen absorption coefficient in a laboratory stirred tank. Coefficients were measured as a function of mixing conditions in the water for two windspeeds. The ethylene dibromide mass-transfer coefficient depended on windspeed; the ethylene dibromide liquid-film coefficient did not, in agreement with theory. A constant relation existed between the liquid-film coefficients for ethylene dibromide and oxygen.

Proton transfer to charged platinum electrodes. A molecular dynamics trajectory study.

PubMed

Wilhelm, Florian; Schmickler, Wolfgang; Spohr, Eckhard

2010-05-05

A recently developed empirical valence bond (EVB) model for proton transfer on Pt(111) electrodes (Wilhelm et al 2008 J. Phys. Chem. C 112 10814) has been applied in molecular dynamics (MD) simulations of a water film in contact with a charged Pt surface. A total of seven negative surface charge densities σ between -7.5 and -18.9 µC cm(-2) were investigated. For each value of σ, between 30 and 84 initial conditions of a solvated proton within a water slab were sampled, and the trajectories were integrated until discharge of a proton occurred on the charged surfaces. We have calculated the mean rates for discharge and for adsorption of solvated protons within the adsorbed water layer in contact with the metal electrode as a function of surface charge density. For the less negative values of σ we observe a Tafel-like exponential increase of discharge rate with decreasing σ. At the more negative values this exponential increase levels off and the discharge process is apparently transport limited. Mechanistically, the Tafel regime corresponds to a stepwise proton transfer: first, a proton is transferred from the bulk into the contact water layer, which is followed by transfer of a proton to the charged surface and concomitant discharge. At the more negative surface charge densities the proton transfer into the contact water layer and the transfer of another proton to the surface and its discharge occur almost simultaneously.

Charge transport in electrically doped amorphous organic semiconductors.

PubMed

Yoo, Seung-Jun; Kim, Jang-Joo

2015-06-01

This article reviews recent progress on charge generation by doping and its influence on the carrier mobility in organic semiconductors (OSs). The doping induced charge generation efficiency is generally low in OSs which was explained by the integer charge transfer model and the hybrid charge transfer model. The ionized dopants formed by charge transfer between hosts and dopants can act as Coulomb traps for mobile charges, and the presence of Coulomb traps in OSs broadens the density of states (DOS) in doped organic films. The Coulomb traps strongly reduce the carrier hopping rate and thereby change the carrier mobility, which was confirmed by experiments in recent years. In order to fully understand the doping mechanism in OSs, further quantitative and systematic analyses of charge transport characteristics must be accomplished. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

TDDFT study of twisted intramolecular charge transfer and intermolecular double proton transfer in the excited state of 4‧-dimethylaminoflavonol in ethanol solvent

NASA Astrophysics Data System (ADS)

Wang, Ye; Shi, Ying; Cong, Lin; Li, Hui

2015-02-01

Time-dependent density functional theory method at the def-TZVP/B3LYP level was employed to investigate the intramolecular and intermolecular hydrogen bonding dynamics in the first excited (S1) state of 4‧-dimethylaminoflavonol (DMAF) monomer and in ethanol solution. In the DMAF monomer, we demonstrated that the intramolecular charge transfer (ICT) takes place in the S1 state. This excited state ICT process was followed by intramolecular proton transfer. Our calculated results are in good agreement with the mechanism proposed in experimental work. For the hydrogen-bonded DMAF-EtOH complex, it was demonstrated that the intermolecular hydrogen bonds can induce the formation of the twisted intramolecular charge transfer (TICT) state and the conformational twisting is along the C3-C4 bond. Moreover, the intermolecular hydrogen bonds can also facilitate the intermolecular double proton transfer in the TICT state. A stepwise intermolecular double proton transfer process was revealed. Therefore, the intermolecular hydrogen bonds can alter the mechanism of intramolecular charge transfer and proton transfer in the excited state for the DMAF molecule.

Study on heat transfer coefficients during cooling of PET bottles for food beverages

NASA Astrophysics Data System (ADS)

Liga, Antonio; Montesanto, Salvatore; Mannella, Gianluca A.; La Carrubba, Vincenzo; Brucato, Valerio; Cammalleri, Marco

2016-08-01

The heat transfer properties of different cooling systems dealing with Poly-Ethylene-Terephthalate (PET) bottles were investigated. The heat transfer coefficient (Ug) was measured in various fluid dynamic conditions. Cooling media were either air or water. It was shown that heat transfer coefficients are strongly affected by fluid dynamics conditions, and range from 10 W/m2 K to nearly 400 W/m2 K. PET bottle thickness effect on Ug was shown to become relevant under faster fluid dynamics regimes.

Voltage and frequency dependence of prestin-associated charge transfer

PubMed Central

Sun, Sean X.; Farrell, Brenda; Chana, Matthew S.; Oster, George; Brownell, William E.; Spector, Alexander A.

2009-01-01

Membrane protein prestin is a critical component of the motor complex that generates forces and dimensional changes in cells in response to changes in the cell membrane potential. In its native cochlear outer hair cell, prestin is crucial to the amplification and frequency selectivity of the mammalian ear up to frequencies of tens of kHz. Other cells transfected with prestin acquire voltage-dependent properties similar to those of the native cell. The protein performance is critically dependent on chloride ions, and intrinsic protein charges also play a role. We propose an electro-diffusion model to reveal the frequency and voltage dependence of electric charge transfer by prestin. The movement of the combined charge (i.e., anion and protein charges) across the membrane is described with a Fokker-Planck equation coupled to a kinetic equation that describes the binding of chloride ions to prestin. We found a voltage-and frequency-dependent phase shift between the transferred charge and the applied electric field that determines capacitive and resistive components of the transferred charge. The phase shift monotonically decreases from zero to -90 degree as a function of frequency. The capacitive component as a function of voltage is bell-shaped, and decreases with frequency. The resistive component is bell-shaped for both voltage and frequency. The capacitive and resistive components are similar to experimental measurements of charge transfer at high frequencies. The revealed nature of the transferred charge can help reconcile the high-frequency electrical and mechanical observations associated with prestin, and it is important for further analysis of the structure and function of this protein. PMID:19490917

Power generation using different cation, anion, and ultrafiltration membranes in microbial fuel cells.

PubMed

Kim, Jung Rae; Cheng, Shaoan; Oh, Sang-Eun; Logan, Bruce E

2007-02-01

Proton exchange membranes (PEMs) are often used in microbial fuel cells (MFCs) to separate the liquid in the anode and cathode chambers while allowing protons to pass between the chambers. However, negatively or positively charged species present at high concentrations in the medium can also be used to maintain charge balance during power generation. An anion exchange membrane (AEM) produced the largest power density (up to 610 mW/m2) and Coulombic efficiency (72%) in MFCs relative to values achieved with a commonly used PEM (Nafion), a cation exchange membrane (CEM), or three different ultrafiltration (UF) membranes with molecular weight cut offs of 0.5K, 1K, and 3K Daltons in different types of MFCs. The increased performance of the AEM was due to proton charge-transfer facilitated by phosphate anions and low internal resistance. The type of membrane affected maximum power densities in two-chamber, air-cathode cube MFCs (C-MFCs) with low internal resistance (84-91 omega for all membranes except UF-0.5K) but not in two-chamber aqueous-cathode bottle MFCs (B-MFCs) due to their higher internal resistances (1230-1272 omega except UF-0.5K). The UF-0.5K membrane produced very high internal resistances (6009 omega, B-MFC; 1814omega, C-MFC) and was the least permeable to both oxygen (mass transfer coefficient of k(O) = 0.19 x 10(-4) cm/s) and acetate (k(A) = 0.89 x 10(-8) cm/s). Nafion was the most permeable membrane to oxygen (k(O) = 1.3 x 10(-4) cm/s), and the UF-3K membrane was the most permeable to acetate (k(A) = 7.2 x 10(-8) cm/s). Only a small percent of substrate was unaccounted for based on measured Coulombic efficiencies and estimates of biomass production and substrate losses using Nafion, CEM, and AEM membranes (4-8%), while a substantial portion of substrate was lost to unidentified processes for the UF membranes (40-89%). These results show that many types of membranes can be used in two-chambered MFCs, even membranes that transfer negatively charged species.

Molecular Structures and Momentum Transfer Cross Sections: The Influence of the Analyte Charge Distribution.

PubMed

Young, Meggie N; Bleiholder, Christian

2017-04-01

Structure elucidation by ion mobility spectrometry-mass spectrometry methods is based on the comparison of an experimentally measured momentum transfer cross-section to cross-sections calculated for model structures. Thus, it is imperative that the calculated cross-section must be accurate. However, it is not fully understood how important it is to accurately model the charge distribution of an analyte ion when calculating momentum transfer cross-sections. Here, we calculate and compare momentum transfer cross-sections for carbon clusters that differ in mass, charge state, and mode of charge distribution, and vary temperature and polarizability of the buffer gas. Our data indicate that the detailed distribution of the ion charge density is intimately linked to the contribution of glancing collisions to the momentum transfer cross-section. The data suggest that analyte ions with molecular mass ~3 kDa or momentum transfer cross-section 400-500 Å 2 would be significantly influenced by the charge distribution in nitrogen buffer gas. Our data further suggest that accurate structure elucidation on the basis of IMS-MS data measured in nitrogen buffer gas must account for the molecular charge distribution even for systems as large as C 960 (~12 kDa) when localized charges are present and/or measurements are conducted under cryogenic temperatures. Finally, our data underscore that accurate structure elucidation is unlikely if ion mobility data recorded in one buffer gas is converted into other buffer gases when electronic properties of the buffer gases differ. Graphical Abstract ᅟ.

Experimental exploration of the Mulliken-Hush relationship for intramolecular electron transfer reactions.

PubMed

Mukherjee, Tamal; Ito, Naoki; Gould, Ian R

2011-03-17

The Mulliken-Hush (M-H) relationship provides the critical link between optical and thermal electron transfer processes, and yet very little direct experimental support for its applicability has been provided. Dicyanovinylazaadamantane (DCVA) represents a simple two-state (neutral/charge-transfer) intramolecular electron transfer system that exhibits charge-transfer absorption and emission spectra that are readily measurable in solvents with a wide range of polarities. In this regard it represents an ideal model system for studying the factors that control both optical charge separation (absorption) and recombination (emission) processes in solution. Here we explore the applicability of the M-H relation to quantitative descriptions of the optical charge-transfer processes in DCVA. For DCVA, the measured radiative rate constants exhibit a linear dependence on transition energy, and transition dipole moments exhibit an inverse dependence on transition energy, consistent with the M-H relationship.

Heat transfer coefficient distribution over the inconel plate cooled from high temperature by the array of water jets

NASA Astrophysics Data System (ADS)

Malinowski, Z.; Telejko, T.; Cebo-Rudnicka, A.; Szajding, A.; Rywotycki, M.; Hadała, B.

2016-09-01

The industrial rolling mills are equipped with systems for controlled water cooling of hot steel products. A cooling rate affects the final mechanical properties of steel which are strongly dependent on microstructure evolution processes. In case of water jets cooling the heat transfer boundary condition can be defined by the heat transfer coefficient. In the present study one and three dimensional heat conduction models have been employed in the inverse solution to heat transfer coefficient. The inconel plate has been heated to about 900oC and then cooled by one, two and six water jets. The plate temperature has been measured by 30 thermocouples. The heat transfer coefficient distributions at plate surface have been determined in time of cooling.

Challenges to the chiral magnetic wave using charge-dependent azimuthal anisotropies in pPb and PbPb collisions at $$ \\sqrt{\\smash[b]{s_{_{\\mathrm{NN}}}}} = $$ 5.02 TeV

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

Sirunyan, Albert M; et al.

2017-08-29

Charge-dependent anisotropy Fourier coefficients (more » $$v_n$$) of particle azimuthal distributions are measured in pPb and PbPb collisions at $$ \\sqrt{\\smash[b]{s_{_{\\mathrm{NN}}}}} = $$ 5.02 TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients ($$v_2$$) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient, $$v_3$$, shows a similar linear dependence with the same slope as seen for $$v_2$$. The observed similarities between the $$v_2$$ slopes for pPb and PbPb, as well as the similar slopes for $$v_2$$ and $$v_3$$ in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that the observed charge asymmetry dependence of $$v_2$$ in heavy ion collisions arises from a chiral magnetic wave.« less

The contact heat transfer between the heating plate and granular materials in rotary heat exchanger under overloaded condition

NASA Astrophysics Data System (ADS)

Duan, Luanfang; Qi, Chonggang; Ling, Xiang; Peng, Hao

2018-03-01

In the present work, the contact heat transfer between the granular materials and heating plates inside plate rotary heat exchanger (PRHE) was investigated. The heat transfer coefficient is dominated by the contact heat transfer coefficient at hot wall surface of the heating plates and the heat penetration inside the solid bed. A plot scale PRHE with a diameter of Do = 273 mm and a length of L = 1000 mm has been established. Quartz sand with dp = 2 mm was employed as the experimental material. The operational parameters were in the range of ω = 1 - 8 rpm, and F = 15, 20, 25, 30%, and the effect of these parameters on the time-average contact heat transfer coefficient was analyzed. The time-average contact heat transfer coefficient increases with the increase of rotary speed, but decreases with the increase of the filling degree. The measured data of time-average heat transfer coefficients were compared with theoretical calculations from Schlünder's model, a good agreement between the measurements and the model could be achieved, especially at a lower rotary speed and filling degree level. The maximum deviation between the calculated data and the experimental data is approximate 10%.

Photoinduced charge-transfer electronic excitation of tetracyanoethylene/tetramethylethylene complex in dichloromethane

NASA Astrophysics Data System (ADS)

Xu, Long-Kun; Bi, Ting-Jun; Ming, Mei-Jun; Wang, Jing-Bo; Li, Xiang-Yuan

2017-07-01

Based on the previous work on nonequilibrium solvation model by the authors, Intermolecular charge-transfer electronic excitation of tetracyanoethylene (TCE)/tetramethylethylene (TME) π -stacked complex in dichloromethane (DCM) has been investigated. For weak interaction correction, dispersion corrected functional DFT-D3 is adopted for geometry optimization. In order to identify the excitation metric, dipole moment components of each Cartesian direction, atomic charge, charge separation and Δr index are analyzed for TCE/TME complex. Calculation shows that the calculated excitation energy is dependent on the functional choice, when conjuncted with suitable time-dependent density functional, the modified nonequilibrium expression gives satisfied results for intermolecular charge-transfer electronic excitation.

Charge Transfer and Catalysis at the Metal Support Interface

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

Baker, Lawrence Robert

Kinetic, electronic, and spectroscopic characterization of model Pt–support systems are used to demonstrate the relationship between charge transfer and catalytic activity and selectivity. The results show that charge flow controls the activity and selectivity of supported metal catalysts. This dissertation builds on extensive existing knowledge of metal–support interactions in heterogeneous catalysis. The results show the prominent role of charge transfer at catalytic interfaces to determine catalytic activity and selectivity. Further, this research demonstrates the possibility of selectively driving catalytic chemistry by controlling charge flow and presents solid-state devices and doped supports as novel methods for obtaining electronic control over catalyticmore » reaction kinetics.« less

Surfactant-enhanced singlet energy transfer from the charge-transfer excited state of tris(2,2-bipyridine) ruthenium(II)

NASA Astrophysics Data System (ADS)

Mandal, Krishnagopal; Demas, J. N.

1981-12-01

Very efficient (45-75%) sodium lauryl sulfate (NaLS) enhanced singlet enengy transfer has been demonstrated from the spin-orbit charge-transfer excited state of [Ru(bpy) 3] 2+ (bpy = 2,2'-bipyridine) to the xxx violet, oxazine 1, and rhodamine 101 at concentrations of 10 -5 M, Energy transfer occurs in xxx.

Molecular orbital (SCF-X-α-SW) theory of Fe2+-Mn3+, Fe3+-Mn2+, and Fe3+-Mn3+ charge transfer and magnetic exchange in oxides and silicates

USGS Publications Warehouse

Sherman, David M.

1990-01-01

Metal-metal charge-transfer and magnetic exchange interactions have important effects on the optical spectra, crystal chemistry, and physics of minerals. Previous molecular orbital calculations have provided insight on the nature of Fe2+-Fe3+ and Fe2+-Ti4+ charge-transfer transitions in oxides and silicates. In this work, spin-unrestricted molecular orbital calculations on (FeMnO10) clusters are used to study the nature of magnetic exchange and electron delocalization (charge transfer) associated with Fe3+-Mn2+, Fe3+-Mn3+, and Fe2+-Mn3+ interactions in oxides and silicates. 

Improving nanoparticle dispersion and charge transfer in cadmium telluride tetrapod and conjugated polymer blends.

PubMed

Monson, Todd C; Hollars, Christopher W; Orme, Christine A; Huser, Thomas

2011-04-01

The dispersion of CdTe tetrapods in a conducting polymer and the resulting charge transfer is studied using a combination of confocal fluorescence microscopy and atomic force microscopy (AFM). The results of this work show that both the tetrapod dispersion and charge transfer between the CdTe and conducting polymer (P3HT) are greatly enhanced by exchanging the ligands on the surface of the CdTe and by choosing proper solvent mixtures. The ability to experimentally probe the relationship between particle dispersion and charge transfer through the combination of AFM and fluorescence microscopy provides another avenue to assess the performance of polymer/semiconductor nanoparticle composites. © 2011 American Chemical Society

Spectral resolution of states relevant to photoinduced charge transfer in modified pentacene/ZnO field-effect transistors

NASA Astrophysics Data System (ADS)

Spalenka, Josef W.; Mannebach, Ehren M.; Bindl, Dominick J.; Arnold, Michael S.; Evans, Paul G.

2011-11-01

Pentacene field-effect transistors incorporating ZnO quantum dots can be used as a sensitive probe of the optical properties of a buried donor-acceptor interface. Photoinduced charge transfer between pentacene and ZnO in these devices varies with incident photon energy and reveals which energies will contribute most to charge transfer in other structures. A subsequent slow return to the dark state following the end of illumination arises from near-interface traps. Charge transfer has a sharp onset at 1.7 eV and peaks at 1.82 and 2.1 eV due to transitions associated with excitons, features absent in pentacene FETs without ZnO.

Investigation of ground state charge transfer complex between paracetamol and p-chloranil through DFT and UV-visible studies

NASA Astrophysics Data System (ADS)

Shukla, Madhulata; Srivastava, Nitin; Saha, Satyen

2012-08-01

The present report deals with the theoretical investigation on ground state structure and charge transfer (CT) transitions in paracetamol (PA)/p-chloranil (CA) complex using Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT) method. It is found that Cdbnd O bond length of p-chloranil increases on complexation with paracetamol along with considerable amount of charge transfer from PA to CA. TD-DFT calculations have been performed to analyse the observed UV-visible spectrum of PA-CA charge transferred complex. Interestingly, in addition to expected CT transition, a weak symmetry relieved π-π* transition in the chloranil is also observed.

Charge transfer in iridate-manganite superlattices

DOE PAGES

Okamoto, Satoshi; Nichols, John; Sohn, Changhee; ...

2017-03-03

Charge transfer in superlattices consisting of SrIrOmore » $$_3$$ and SrMnO$$_3$$ is investigated using density functional theory. Despite the nearly identical work function and non-polar interfaces between SrIrO$$_3$$ and SrMnO$$_3$$, rather large charge transfer was experimentally reported between them. Our results provide a qualitative understanding to such experimental reports. We further develop a microscopic model that captures the mechanism behind this phenomenon. This leads to unique strain dependence of such charge transfer in iridate-manganite superlattices. The predicted behavior is consistently verified by experiment. Lastly, our work thus demonstrates a new route to control electronic states in non-polar oxide heterostructures.« less

How can we make stable linear monoatomic chains? Gold-cesium binary subnanowires as an example of a charge-transfer-driven approach to alloying.

PubMed

Choi, Young Cheol; Lee, Han Myoung; Kim, Woo Youn; Kwon, S K; Nautiyal, Tashi; Cheng, Da-Yong; Vishwanathan, K; Kim, Kwang S

2007-02-16

On the basis of first-principles calculations of clusters and one dimensional infinitely long subnanowires of the binary systems, we find that alkali-noble metal alloy wires show better linearity and stability than either pure alkali metal or noble metal wires. The enhanced alternating charge buildup on atoms by charge transfer helps the atoms line up straight. The cesium doped gold wires showing significant charge transfer from cesium to gold can be stabilized as linear or circular monoatomic chains.

Inductive High Power Transfer Technologies for Electric Vehicles

NASA Astrophysics Data System (ADS)

Madzharov, Nikolay D.; Tonchev, Anton T.

2014-03-01

Problems associated with "how to charge the battery pack of the electric vehicle" become more important every passing day. Most logical solution currently is the non-contact method of charge, possessing a number of advantages over standard contact methods for charging. This article focuses on methods for Inductive high power contact-less transfer of energy at relatively small distances, their advantages and disadvantages. Described is a developed Inductive Power Transfer (IPT) system for fast charging of electric vehicles with nominal power of 30 kW over 7 to 9 cm air gap.

Charge-pump voltage converter

DOEpatents

Brainard, John P [Albuquerque, NM; Christenson, Todd R [Albuquerque, NM

2009-11-03

A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

Tuning the role of charge-transfer states in intramolecular singlet exciton fission through side-group engineering.

PubMed

Lukman, Steven; Chen, Kai; Hodgkiss, Justin M; Turban, David H P; Hine, Nicholas D M; Dong, Shaoqiang; Wu, Jishan; Greenham, Neil C; Musser, Andrew J

2016-12-07

Understanding the mechanism of singlet exciton fission, in which a singlet exciton separates into a pair of triplet excitons, is crucial to the development of new chromophores for efficient fission-sensitized solar cells. The challenge of controlling molecular packing and energy levels in the solid state precludes clear determination of the singlet fission pathway. Here, we circumvent this difficulty by utilizing covalent dimers of pentacene with two types of side groups. We report rapid and efficient intramolecular singlet fission in both molecules, in one case via a virtual charge-transfer state and in the other via a distinct charge-transfer intermediate. The singlet fission pathway is governed by the energy gap between singlet and charge-transfer states, which change dynamically with molecular geometry but are primarily set by the side group. These results clearly establish the role of charge-transfer states in singlet fission and highlight the importance of solubilizing groups to optimize excited-state photophysics.

Tuning the role of charge-transfer states in intramolecular singlet exciton fission through side-group engineering

PubMed Central

Lukman, Steven; Chen, Kai; Hodgkiss, Justin M.; Turban, David H. P.; Hine, Nicholas D. M.; Dong, Shaoqiang; Wu, Jishan; Greenham, Neil C.; Musser, Andrew J.

2016-01-01

Understanding the mechanism of singlet exciton fission, in which a singlet exciton separates into a pair of triplet excitons, is crucial to the development of new chromophores for efficient fission-sensitized solar cells. The challenge of controlling molecular packing and energy levels in the solid state precludes clear determination of the singlet fission pathway. Here, we circumvent this difficulty by utilizing covalent dimers of pentacene with two types of side groups. We report rapid and efficient intramolecular singlet fission in both molecules, in one case via a virtual charge-transfer state and in the other via a distinct charge-transfer intermediate. The singlet fission pathway is governed by the energy gap between singlet and charge-transfer states, which change dynamically with molecular geometry but are primarily set by the side group. These results clearly establish the role of charge-transfer states in singlet fission and highlight the importance of solubilizing groups to optimize excited-state photophysics. PMID:27924819

Chemical and physical investigations on the charge transfer interaction of organic donors with iodine and its application as non-traditional organic conductors

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Sharshar, T.; Adam, Abdel Majid A.; Elsabawy, Khaled M.; Hemeda, O. M.

2014-09-01

The iso-leucine-iodide and methionine-iodide charge-transfer complexes were prepared and characterized using different spectroscopic techniques. The iodide charge-transfer complexes were synthesized by grinding KI-I2-amino acid with 1:1:1 M ratio in presence of few drops of methanol solvent. The structures of both solid amino acid iodide charge-transfer complexes are discussed with the help of the obtained results of the infrared and Raman laser spectra, Uv-vis. electronic spectra and thermal analyses. The electrical properties (AC resistivity and dielectric constant) of both complexes were investigated. The positron annihilation Doppler broadening (PADB) spectroscopies were also used to probe the structural changes of both complexes. The PADB line-shape parameters (S and W) were found to be dependent on the structure, electronic configuration of the charge transfer complex. The PADB technique is a powerful tool to probe the structural features of the KI-I2-amino acid complexes.

Engineering and Probing Topological Properties of Dirac Semimetal Films by Asymmetric Charge Transfer.

PubMed

Villanova, John W; Barnes, Edwin; Park, Kyungwha

2017-02-08

Dirac semimetals (DSMs) have topologically robust three-dimensional Dirac (doubled Weyl) nodes with Fermi-arc states. In heterostructures involving DSMs, charge transfer occurs at the interfaces, which can be used to probe and control their bulk and surface topological properties through surface-bulk connectivity. Here we demonstrate that despite a band gap in DSM films, asymmetric charge transfer at the surface enables one to accurately identify locations of the Dirac-node projections from gapless band crossings and to examine and engineer properties of the topological Fermi-arc surface states connecting the projections, by simulating adatom-adsorbed DSM films using a first-principles method with an effective model. The positions of the Dirac-node projections are insensitive to charge transfer amount or slab thickness except for extremely thin films. By varying the amount of charge transfer, unique spin textures near the projections and a separation between the Fermi-arc states change, which can be observed by gating without adatoms.

Electrochemical impedance spectroscopy of lithium-titanium disulfide rechargeable cells

NASA Technical Reports Server (NTRS)

Narayanan, S. R.; Shen, D. H.; Surampudi, S.; Attia, A. I.; Halpert, G.

1993-01-01

The two-terminal alternating current impedance of Li/TiS2 rechargeable cells was studied as a function of frequency, state-of-charge, and extended cycling. Analysis based on a plausible equivalent circuit model for the Li/TiS2 cell leads to evaluation of kinetic parameters for the various physicochemical processes occurring at the electrode/electrolyte interfaces. To investigate the causes of cell degradation during extended cycling, the parameters evaluated for cells cycled 5 times were compared with the parameters of cells cycled over 600 times. The findings are that the combined ohmic resistance of the electrolyte and electrodes suffers a tenfold increase after extended cycling, while the charge-transfer resistance and diffusional impedance at the TiS2/electrolyte interface are not significantIy affected. The results reflect the morphological change and increase in area of the anode due to cycling. The study also shows that overdischarge of a cathode-limited cell causes a decrease in the diffusion coefficient of the lithium ion in the cathode.

A flower-like nickel oxide nanostructure: synthesis and application for choline sensing.

PubMed

Sattarahmady, N; Heli, H; Dehdari Vais, R

2014-02-01

Flower-like nickel oxide nanostructure was synthesized by a simple desolvation method. The nanostructure was then employed as the modifier of a carbon paste electrode to fabricate a choline sensor. The mechanism and kinetics of the electrocatalytic oxidation of choline on the modified electrode surface were studied by cyclic voltammetry, steady-state polarization curve, and chronoamperometry. The catalytic rate constant and the charge transfer coefficient of the choline electrooxidation process by an active nickel species, and the diffusion coefficient of choline were reported. An amperometric method was developed for determination of choline with a sensitivity of 60.5 mA mol(-1)Lcm(-2) and a limit of detection of 25.4 μmol L(-1). The sensor had the advantages of high electrocatalytic activity and sensitivity, and long-term stability toward choline, with a simple fabrication method without complications of immobilization steps and using any enzyme or reagent. © 2013 Published by Elsevier B.V.

Ab initio investigation of electron capture by Cl{sup 7+} ions from H

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

Zhao, L. B.; Stancil, P. C.; Watanabe, A.

2007-08-15

An investigation of charge transfer in collisions of ground-state Cl{sup 7+} with H has been conducted based on a fully quantum-mechanical molecular-orbital close-coupling (QMOCC) approach. The charge-transfer process Cl{sup 7+}({sup 1}S)+H{yields}Cl{sup 6+}(2p{sup 6}nl {sup 2}S,{sup 2}P{sup o},{sup 2}D,{sup 2}F{sup o},{sup 2}G)+H{sup +} with n=5 and 6 is taken into account for collision energies between 10{sup -4} eV/u and 1 keV/u. The relevant adiabatic potentials and nonadiabatic coupling matrix elements for the ClH{sup 7+} system are evaluated with the configuration-interaction method. The investigation shows that electron capture into the 5d, 5f, 5g, and 6p states dominates for collision energies less thanmore » {approx}1 eV/u, while above 100 eV/u the 5s, 5p, 5d, and 6p are the primary capture channels. Comparison with experimental data for collisions of Cl{sup 7+}({sup 1}S) with D reveals a discrepancy over the full range of measured energies (5-430 eV/u), while no significant isotope effect is found for QMOCC calculations with deuterium. Furthermore, comparison with a previous calculation of the one-electron N{sup 7+}+H system, as well as measurements of the multielectron Al{sup 7+}+H and Fe{sup 7+}+H systems, suggests that the electronic structure of the core has a non-negligible effect on the charge-transfer process. A one-electron model for relative l distributions is found to agree with the QMOCC results for n=5 between 100 and 1000 eV/u, but fails at lower collision energies. Finally, state-selective and total rate coefficients are given for temperatures between 10 and 200 000 K.« less

Heat transfer coefficient as parameter describing ability of insulating liquid to heat transfer

NASA Astrophysics Data System (ADS)

Nadolny, Zbigniew; Gościński, Przemysław; Bródka, Bolesław

2017-10-01

The paper presents the results of the measurements of heat transfer coefficient of insulating liquids used in transformers. The coefficient describes an ability of the liquid to heat transport. On the basis of the coefficient, effectiveness of cooling system of electric power devices can be estimated. Following liquids were used for the measurements: mineral oil, synthetic ester and natural ester. It was assumed that surface heat load is about 2500 W·m-2, which is equal the load of transformer windings. A height of heat element was 1.6 m, because it makes possible steady distribution of temperature on its surface. The measurements of heat transfer coefficient was made as a function of various position of heat element (vertical, horizontal). In frame of horizontal position of heat element, three suppositions were analysed: top, bottom, and side.

Experiment of flow regime map and local condensing heat transfer coefficients inside three dimensional inner microfin tubes

NASA Astrophysics Data System (ADS)

Du, Yang; Xin, Ming Dao

1999-03-01

This paper developed a new type of three dimensional inner microfin tube. The experimental results of the flow patterns for the horizontal condensation inside these tubes are reported in the paper. The flow patterns for the horizontal condensation inside the new made tubes are divided into annular flow, stratified flow and intermittent flow within the test conditions. The experiments of the local heat transfer coefficients for the different flow patterns have been systematically carried out. The experiments of the local heat transfer coefficients changing with the vapor dryness fraction have also been carried out. As compared with the heat transfer coefficients of the two dimensional inner microfin tubes, those of the three dimensional inner microfin tubes increase 47-127% for the annular flow region, 38-183% for the stratified flow and 15-75% for the intermittent flow, respectively. The enhancement factor of the local heat transfer coefficients is from 1.8-6.9 for the vapor dryness fraction from 0.05 to 1.

Opposites Attract: Organic Charge Transfer Salts

ERIC Educational Resources Information Center

van de Wouw, Heidi L.; Chamorro, Juan; Quintero, Michael; Klausen, Rebekka S.

2015-01-01

A laboratory experiment is described that introduces second-year undergraduate organic chemistry students to organic electronic materials. The discovery of metallic conductivity in the charge transfer salt tetrathiafulvalene tetracyanoquinodimethane (TTF-TCNQ) is a landmark result in the history of organic electronics. The charge transfer…

Optimisation of stability and charge transferability of ferrocene-encapsulated carbon nanotubes

NASA Astrophysics Data System (ADS)

Prajongtat, Pongthep; Sriyab, Suwannee; Zentgraf, Thomas; Hannongbua, Supa

2018-01-01

Ferrocene-encapsulated carbon nanotubes (Fc@CNTs) became promising nanocomposite materials for a wide range of applications due to their superior catalytic, mechanical and electronic properties. To open up new windows of applications, the highly stable and charge transferable encapsulation complexes are required. In this work, we designed the new encapsulation complexes formed from ferrocene derivatives (FcR, where R = -CHO, -CH2OH, -CON3 and -PCl2) and single-walled carbon nanotubes (SWCNTs). The influence of diameter and chirality of the nanotubes on the stability, charge transferability and electronic properties of such complexes has been investigated using density functional theory. The calculations suggest that the encapsulation stability and charge transferability of the encapsulation complexes depend on the size and chirality of the nanotubes. FcR@SWCNTs are more stable than Fc@SWCNTs at the optimum tube diameter. The greatest charge transfer was observed for FcCH2OH@SWCNTs and Fc@SWCNTs since the Fe d levels of FcCH2OH and Fc are nearly equal and close to the Fermi energy level of the nanotubes. The obtained results pave the way to the design of new encapsulated ferrocene derivatives which can give rise to higher stability and charge transferability of the encapsulation complexes.

Nonlocal thermoelectric effects and nonlocal Onsager relations in a three-terminal proximity-coupled superconductor-ferromagnet device.

PubMed

Machon, P; Eschrig, M; Belzig, W

2013-01-25

We study thermal and charge transport in a three-terminal setup consisting of one superconducting and two ferromagnetic contacts. We predict that the simultaneous presence of spin filtering and of spin-dependent scattering phase shifts at each of the two interfaces will lead to very large nonlocal thermoelectric effects both in clean and in disordered systems. The symmetries of thermal and electric transport coefficients are related to fundamental thermodynamic principles by the Onsager reciprocity. Our results show that a nonlocal version of the Onsager relations for thermoelectric currents holds in a three-terminal quantum coherent ferromagnet-superconductor heterostructure including a spin-dependent crossed Andreev reflection and coherent electron transfer processes.

Laser Measurement Of Convective-Heat-Transfer Coefficient

NASA Technical Reports Server (NTRS)

Porro, A. Robert; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.; Keith, Theo G., Jr.

1994-01-01

Coefficient of convective transfer of heat at spot on surface of wind-tunnel model computed from measurements acquired by developmental laser-induced-heat-flux technique. Enables non-intrusive measurements of convective-heat-transfer coefficients at many points across surfaces of models in complicated, three-dimensional, high-speed flows. Measurement spot scanned across surface of model. Apparatus includes argon-ion laser, attenuator/beam splitter electronic shutter infrared camera, and subsystem.

Charge-transfer channel in quantum dot-graphene hybrid materials

NASA Astrophysics Data System (ADS)

Cao, Shuo; Wang, Jingang; Ma, Fengcai; Sun, Mengtao

2018-04-01

The energy band theory of a classical semiconductor can qualitatively explain the charge-transfer process in low-dimensional hybrid colloidal quantum dot (QD)-graphene (GR) materials; however, the definite charge-transfer channels are not clear. Using density functional theory (DFT) and time-dependent DFT, we simulate the hybrid QD-GR nanostructure, and by constructing its orbital interaction diagram, we show the quantitative coupling characteristics of the molecular orbitals (MOs) of the hybrid structure. The main MOs are derived from the fragment MOs (FOs) of GR, and the Cd13Se13 QD FOs merge with the GR FOs in a certain proportion to afford the hybrid system. Upon photoexcitation, electrons in the GR FOs jump to the QD FOs, leaving holes in the GR FOs, and the definite charge-transfer channels can be found by analyzing the complex MOs coupling. The excited electrons and remaining holes can also be localized in the GR or the QD or transfer between the QD and GR with different absorption energies. The charge-transfer process for the selected excited states of the hybrid QD-GR structure are testified by the charge difference density isosurface. The natural transition orbitals, charge-transfer length analysis and 2D site representation of the transition density matrix also verify the electron-hole delocalization, localization, or coherence chacracteristics of the selected excited states. Therefore, our research enhances understanding of the coupling mechanism of low-dimensional hybrid materials and will aid in the design and manipulation of hybrid photoelectric devices for practical application in many fields.

Charge-transfer channel in quantum dot-graphene hybrid materials.

PubMed

Cao, Shuo; Wang, Jingang; Ma, Fengcai; Sun, Mengtao

2018-04-06

The energy band theory of a classical semiconductor can qualitatively explain the charge-transfer process in low-dimensional hybrid colloidal quantum dot (QD)-graphene (GR) materials; however, the definite charge-transfer channels are not clear. Using density functional theory (DFT) and time-dependent DFT, we simulate the hybrid QD-GR nanostructure, and by constructing its orbital interaction diagram, we show the quantitative coupling characteristics of the molecular orbitals (MOs) of the hybrid structure. The main MOs are derived from the fragment MOs (FOs) of GR, and the Cd 13 Se 13 QD FOs merge with the GR FOs in a certain proportion to afford the hybrid system. Upon photoexcitation, electrons in the GR FOs jump to the QD FOs, leaving holes in the GR FOs, and the definite charge-transfer channels can be found by analyzing the complex MOs coupling. The excited electrons and remaining holes can also be localized in the GR or the QD or transfer between the QD and GR with different absorption energies. The charge-transfer process for the selected excited states of the hybrid QD-GR structure are testified by the charge difference density isosurface. The natural transition orbitals, charge-transfer length analysis and 2D site representation of the transition density matrix also verify the electron-hole delocalization, localization, or coherence chacracteristics of the selected excited states. Therefore, our research enhances understanding of the coupling mechanism of low-dimensional hybrid materials and will aid in the design and manipulation of hybrid photoelectric devices for practical application in many fields.

Open-Circuit Voltage Losses in Selenium-Substituted Organic Photovoltaic Devices from Increased Density of Charge-Transfer States

DOE PAGES

Sulas, Dana B.; Yao, Kai; Intemann, Jeremy J.; ...

2015-09-12

Using an analysis based on Marcus theory, we characterize losses in open-circuit voltage (V OC) due to changes in charge-transfer state energy, electronic coupling, and spatial density of charge-transfer states in a series of polymer/fullerene solar cells. Here, we use a series of indacenodithiophene polymers and their selenium-substituted analogs as electron donor materials and fullerenes as the acceptors. By combining device measurements and spectroscopic studies (including subgap photocurrent, electroluminescence, and, importantly, time-resolved photoluminescence of the charge-transfer state) we are able to isolate the values for electronic coupling and the density of charge-transfer states (NCT), rather than the more commonly measuredmore » product of these values. We find values for NCT that are surprisingly large (~4.5 × 10 21–6.2 × 10 22 cm -3), and we find that a significant increase in N CT upon selenium substitution in donor polymers correlates with lower VOC for bulk heterojunction photovoltaic devices. The increase in N CT upon selenium substitution is also consistent with nanoscale morphological characterization. Using transmission electron microscopy, selected area electron diffraction, and grazing incidence wide-angle X-ray scattering, we find evidence of more intermixed polymer and fullerene domains in the selenophene blends, which have higher densities of polymer/fullerene interfacial charge-transfer states. Our results provide an important step toward understanding the spatial nature of charge-transfer states and their effect on the open-circuit voltage of polymer/fullerene solar cells« less

Theoretical studies of charge transfer and proton transfer complex formation between 3,5-dinitrobenzic acid and 1,2-dimethylimidazole

NASA Astrophysics Data System (ADS)

Afroz, Ziya; Faizan, Mohd.; Alam, Mohammad Jane; Ahmad, Shabbir; Ahmad, Afaq

2018-05-01

Natural atomic charge analysis and molecular electrostatic potential (MEP) surface analysis of hydrogen bonded charge transfer (HBCT) and proton transfer (PT) complex of 3,5-dinitrobenzoic acid (DNBA) and 1,2-dimethylimidazole (DMI) have been investigated by theoretical modelling using widely employed DFT/B3LYP/6-311G(d,p) level of theory. Along with this analysis, Hirshfeld surface study of the intermolecular interactions and associated 2D finger plot for reported PT complex between DNBA and DMI have been explored.

Frenkel versus charge-transfer exciton dispersion in molecular crystals

NASA Astrophysics Data System (ADS)

Cudazzo, Pierluigi; Gatti, Matteo; Rubio, Angel; Sottile, Francesco

2013-11-01

By solving the many-body Bethe-Salpeter equation at finite momentum transfer, we characterize the exciton dispersion in two prototypical molecular crystals, picene and pentacene, in which localized Frenkel excitons compete with delocalized charge-transfer excitons. We explain the exciton dispersion on the basis of the interplay between electron and hole hopping and electron-hole exchange interaction, unraveling a simple microscopic description to distinguish Frenkel and charge-transfer excitons. This analysis is general and can be applied to other systems in which the electron wave functions are strongly localized, as in strongly correlated insulators.

Diffusion of Conserved Charges in Relativistic Heavy Ion Collisions

NASA Astrophysics Data System (ADS)

Greif, Moritz; Fotakis, Jan. A.; Denicol, Gabriel S.; Greiner, Carsten

2018-06-01

We demonstrate that the diffusion currents do not depend only on gradients of their corresponding charge density, but that the different diffusion charge currents are coupled. This happens in such a way that it is possible for density gradients of a given charge to generate dissipative currents of another charge. Within this scheme, the charge diffusion coefficient is best viewed as a matrix, in which the diagonal terms correspond to the usual charge diffusion coefficients, while the off-diagonal terms describe the coupling between the different currents. In this Letter, we calculate for the first time the complete diffusion matrix for hot and dense nuclear matter, including baryon, electric, and strangeness charges. We find that the baryon diffusion current is strongly affected by baryon charge gradients but also by its coupling to gradients in strangeness. The electric charge diffusion current is found to be strongly affected by electric and strangeness gradients, whereas strangeness currents depend mostly on strange and baryon gradients.

Determination of the diffusion coefficient and phase-transfer rate parameter in LaNi{sub 5} and MmNi{sub 3.6}Co{sub 0.8}Mn{sub 0.4}Al{sub 0.3} using microelectrodes

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

Lundqvist, A.; Lindbergh, G.

1998-11-01

A potential-step method for determining the diffusion coefficient and phase-transfer parameter in metal hydrides by using microelectrodes was investigated. It was shown that a large potential step is not enough to ensure a completely diffusion-limited mass transfer if a surface-phase transfer reaction takes place at a finite rate. It was shown, using a kinetic expression for the surface phase-transfer reaction, that the slope of the logarithm of the current vs. time curve will be constant both in the case of the mass-transfer limited by diffusion or by diffusion and a surface-phase transfer. The diffusion coefficient and phase-transfer rate parameter weremore » accurately determined for MmNi{sub 3.6}Co{sub 0.8}Mn{sub 0.4}Al{sub 0.3} using a fit to the whole transient. The diffusion coefficient was found to be (1.3 {+-} 0.3) {times} 10{sup {minus}13} m{sup 2}/s. The fit was good and showed that a pure diffusion model was not enough to explain the observed transient. The diffusion coefficient and phase-transfer rate parameter were also estimated for pure LaNi{sub 5}. A fit of the whole curve showed that neither a pure diffusion model nor a model including phase transfer could explain the whole transient.« less

Vertical mass transfer in open channel flow

USGS Publications Warehouse

Jobson, Harvey E.

1968-01-01

The vertical mass transfer coefficient and particle fall velocity were determined in an open channel shear flow. Three dispersants, dye, fine sand and medium sand, were used with each of three flow conditions. The dispersant was injected as a continuous line source across the channel and downstream concentration profiles were measured. From these profiles along with the measured velocity distribution both the vertical mass transfer coefficient and the local particle fall velocity were determined.The effects of secondary currents on the vertical mixing process were discussed. Data was taken and analyzed in such a way as to largely eliminate the effects of these currents on the measured values. A procedure was developed by which the local value of the fall velocity of sand sized particles could be determined in an open channel flow. The fall velocity of the particles in the turbulent flow was always greater than their fall velocity in quiescent water. Reynolds analogy between the transfer of momentum and marked fluid particles was further substantiated. The turbulent Schmidt number was shown to be approximately 1.03 for an open channel flow with a rough boundary. Eulerian turbulence measurements were not sufficient to predict the vertical transfer coefficient. Vertical mixing of sediment is due to three semi-independent processes. These processes are: secondary currents, diffusion due to tangential velocity fluctuations and diffusion due to the curvature of the fluid particle path lines. The diffusion coefficient due to tangential velocity fluctuations is approximately proportional to the transfer coefficient of marked fluid particles. The proportionality constant is less than or equal to 1.0 and decreases with increasing particle size. The diffusion coefficient due to the curvature of the fluid particle path lines is not related to the diffusion coefficient for marked fluid particles and increases with particle size, at least for sediment particles in the sand size range. The total sediment transfer coefficient is equal to the sum of the coefficient due to tangential velocity fluctuations and the coefficient due to the curvature of the fluid particle path lines. A numerical solution to the conservation of mass equation is given. The effects of the transfer coefficient, fall velocity and bed conditions on the predicted concentration profiles are illustrated.

Investigation on the heat transfer characteristics during flow boiling of liquefied natural gas in a vertical micro-fin tube

NASA Astrophysics Data System (ADS)

Xu, Bin; Shi, Yumei; Chen, Dongsheng

2014-03-01

This paper presents an experimental investigation on the heat transfer characteristics of liquefied natural gas flow boiling in a vertical micro-fin tube. The effect of heat flux, mass flux and inlet pressure on the flow boiling heat transfer coefficients was analyzed. The Kim, Koyama, and two kinds of Wellsandt correlations with different Ftp coefficients were used to predict the flow boiling heat transfer coefficients. The predicted results showed that the Koyama correlation was the most accurate over the range of experimental conditions.

Measurement of airfoil heat transfer coefficients on a turbine stage

NASA Technical Reports Server (NTRS)

Dring, R. P.; Blair, M. F.

1984-01-01

The primary basis for heat transfer analysis of turbine airfoils is experimental data obtained in linear cascades. A detailed set of heat transfer coefficients was obtained along the midspan of a stator and a rotor in a rotating turbine stage. The data are to be compared to standard analyses of blade boundary layer heat transfer. A detailed set of heat transfer coefficients was obtained along the midspan of a stator located in the wake of a full upstream turbine stage. Two levels of inlet turbulence (1 and 10 percent) were used. The analytical capability will be examined to improve prediction of the experimental data.

The influence of electric charge transferred during electro-mechanical reshaping on mechanical behavior of cartilage

NASA Astrophysics Data System (ADS)

Protsenko, Dimitry E.; Lim, Amanda; Wu, Edward C.; Manuel, Cyrus; Wong, Brian J. F.

2011-03-01

Electromechanical reshaping (EMR) of cartilage has been suggested as an alternative to the classical surgical techniques of modifying the shape of facial cartilages. The method is based on exposure of mechanically deformed cartilaginous tissue to a low level electric field. Electro-chemical reactions within the tissue lead to reduction of internal stress, and establishment of a new equilibrium shape. The same reactions offset the electric charge balance between collagen and proteoglycan matrix and interstitial fluid responsible for maintenance of cartilage mechanical properties. The objective of this study was to investigate correlation between the electric charge transferred during EMR and equilibrium elastic modulus. We used a finite element model based on the triphasic theory of cartilage mechanical properties to study how electric charges transferred in the electro-chemical reactions in cartilage can change its mechanical responses to step displacements in unconfined compression. The concentrations of the ions, the strain field and the fluid and ion velocities within the specimen subject to an applied mechanical deformation were estimated and apparent elastic modulus (the ratio of the equilibrium axial stress to the axial strain) was calculated as a function of transferred charge. The results from numerical calculations showed that the apparent elastic modulus decreases with increase in electric charge transfer. To compare numerical model with experimental observation we measured elastic modulus of cartilage as a function of electric charge transferred in electric circuit during EMR. Good correlation between experimental and theoretical data suggests that electric charge disbalance is responsible for alteration of cartilage mechanical properties.

Post-Dryout Heat Transfer to a Refrigerant Flowing in Horizontal Evaporator Tubes

NASA Astrophysics Data System (ADS)

Mori, Hideo; Yoshida, Suguru; Kakimoto, Yasushi; Ohishi, Katsumi; Fukuda, Kenichi

Studies of the post-dryout heat transfer were made based on the experimental data for HFC-134a flowing in horizontal smooth and spiral1y grooved (micro-fin) tubes and the characteristics of the post-dryout heat transfer were c1arified. The heat transfer coefficient at medium and high mass flow rates in the smooth tube was lower than the single-phase heat transfer coefficient of the superheated vapor flow, of which mass flow rate was given on the assumption that the flow was in a thermodynamic equilibrium. A prediction method of post-dryout heat transfer coefficient was developed to reproduce the measurement satisfactorily for the smooth tube. The post dryout heat transfer in the micro-fin tube can be regarded approximately as a superheated vapor single-phase heat transfer.

The effect of charge transfer fluctuation on superconductivity in high temperature superconductors

NASA Astrophysics Data System (ADS)

Liu, Yihsuan; Wu, Huan-Kuang; Lee, Ting-Kuo

H i g h - Tc Cuprates have been studied quite often as an effective one band t - J model that neglects charge fluctuation between oxygen 2p6 band and copper 3d10 band, and Zhang-Rice singlet is just a hole in the model. However, recent Scanning Tunneling Spectra(STS) measurement on underdoped Cuprate shows that charge transfer gap is only of order 12 eV. This small gap necessitates a re-examination of the charge transfer fluctuation. Here we modify the t-J model by including charge transfer fluctuation allowing the formation of doubly occupied sites. For certain parameters it is similar with the t-J-U model. This model is studied via variational Monte Carlo method(VMC). Our result shows that this model can give a unified behavior of superconducting dome with different long rang hopping parameters. The anti-correlation between charge transfer gap and pairing is also confirmed. More interestingly the charge fluctuation is found to affect pairing order parameter in different ways in underdoped and overdoped regions. This work is partially supported by Taiwan Ministry of Science and Technology with Grant. MOST 105-2112-M-001-008 and calculation was supported by a National Center of High Performance Computing in Taiwan.

New instrument for tribocharge measurement due to single particle impacts.

PubMed

Watanabe, Hideo; Ghadiri, Mojtaba; Matsuyama, Tatsushi; Ding, Yu Long; Pitt, Kendal G

2007-02-01

During particulate solid processing, particle-particle and particle-wall collisions can generate electrostatic charges. This may lead to a variety of problems ranging from fire and explosion hazards to segregation, caking, and blocking. A fundamental understanding of the particle charging in such situations is therefore essential. For this purpose we have developed a new device that can measure charge transfer due to impact between a single particle and a metal plate. The device consists of an impact test system and two sets of Faraday cage and preamplifier for charge measurement. With current amplifiers, high-resolution measurements of particle charges of approximately 1 and 10 fC have been achieved before and after the impact, respectively. The device allows charge measurements of single particles with a size as small as approximately 100 microm impacting on the target at different incident angles with a velocity up to about 80 m/s. Further analyses of the charge transfer as a function of particle initial charge define an equilibrium charge, i.e., an initial charge level prior to impact for which no net charge transfer would occur as a result of impact.

New instrument for tribocharge measurement due to single particle impacts

NASA Astrophysics Data System (ADS)

Watanabe, Hideo; Ghadiri, Mojtaba; Matsuyama, Tatsushi; Long Ding, Yu; Pitt, Kendal G.

2007-02-01

During particulate solid processing, particle-particle and particle-wall collisions can generate electrostatic charges. This may lead to a variety of problems ranging from fire and explosion hazards to segregation, caking, and blocking. A fundamental understanding of the particle charging in such situations is therefore essential. For this purpose we have developed a new device that can measure charge transfer due to impact between a single particle and a metal plate. The device consists of an impact test system and two sets of Faraday cage and preamplifier for charge measurement. With current amplifiers, high-resolution measurements of particle charges of approximately 1 and 10fC have been achieved before and after the impact, respectively. The device allows charge measurements of single particles with a size as small as ˜100μm impacting on the target at different incident angles with a velocity up to about 80m/s. Further analyses of the charge transfer as a function of particle initial charge define an equilibrium charge, i.e., an initial charge level prior to impact for which no net charge transfer would occur as a result of impact.

Magnetic field enhancement of organic photovoltaic cells performance.

PubMed

Oviedo-Casado, S; Urbina, A; Prior, J

2017-06-27

Charge separation is a critical process for achieving high efficiencies in organic photovoltaic cells. The initial tightly bound excitonic electron-hole pair has to dissociate fast enough in order to avoid photocurrent generation and thus power conversion efficiency loss via geminate recombination. Such process takes place assisted by transitional states that lie between the initial exciton and the free charge state. Due to spin conservation rules these intermediate charge transfer states typically have singlet character. Here we propose a donor-acceptor model for a generic organic photovoltaic cell in which the process of charge separation is modulated by a magnetic field which tunes the energy levels. The impact of a magnetic field is to intensify the generation of charge transfer states with triplet character via inter-system crossing. As the ground state of the system has singlet character, triplet states are recombination-protected, thus leading to a higher probability of successful charge separation. Using the open quantum systems formalism we demonstrate that the population of triplet charge transfer states grows in the presence of a magnetic field, and discuss the impact on carrier population and hence photocurrent, highlighting its potential as a tool for research on charge transfer kinetics in this complex systems.

Application of the two-film model to the volatilization of acetone and t-butyl alcohol from water as a function of temperature

USGS Publications Warehouse

Rathbun, R.E.; Tai, D.Y.

1988-01-01

The two-film model is often used to describe the volatilization of organic substances from water. This model assumes uniformly mixed water and air phases separated by thin films of water and air in which mass transfer is by molecular diffusion. Mass-transfer coefficients for the films, commonly called film coefficients, are related through the Henry's law constant and the model equation to the overall mass-transfer coefficient for volatilization. The films are modeled as two resistances in series, resulting in additive resistances. The two-film model and the concept of additivity of resistances were applied to experimental data for acetone and t-butyl alcohol. Overall mass-transfer coefficients for the volatilization of acetone and t-butyl alcohol from water were measured in the laboratory in a stirred constant-temperature bath. Measurements were completed for six water temperatures, each at three water mixing conditions. Wind-speed was constant at about 0.1 meter per second for all experiments. Oxygen absorption coefficients were measured simultaneously with the measurement of the acetone and t-butyl alcohol mass-transfer coefficients. Gas-film coefficients for acetone, t-butyl alcohol, and water were determined by measuring the volatilization fluxes of the pure substances over a range of temperatures. Henry's law constants were estimated from data from the literature. The combination of high resistance in the gas film for solutes with low values of the Henry's law constants has not been studied previously. Calculation of the liquid-film coefficients for acetone and t-butyl alcohol from measured overall mass-transfer and gas-film coefficients, estimated Henry's law constants, and the two-film model equation resulted in physically unrealistic, negative liquid-film coefficients for most of the experiments at the medium and high water mixing conditions. An analysis of the two-film model equation showed that when the percentage resistance in the gas film is large and the gas-film resistance approaches the overall resistance in value, the calculated liquid-film coefficient becomes extremely sensitive to errors in the Henry's law constant. The negative coefficients were attributed to this sensitivity and to errors in the estimated Henry's law constants. Liquid-film coefficients for the absorption of oxygen were correlated with the stirrer Reynolds number and the Schmidt number. Application of this correlation with the experimental conditions and a molecular-diffusion coefficient adjustment resulted in values of the liquid-film coefficients for both acetone and t-butyl alcohol within the range expected for all three mixing conditions. Comparison of Henry's law constants calculated from these film coefficients and the experimental data with the constants calculated from literature data showed that the differences were small relative to the errors reported in the literature as typical for the measurement or estimation of Henry's law constants for hydrophilic compounds such as ketones and alcohols. Temperature dependence of the mass-transfer coefficients was expressed in two forms. The first, based on thermodynamics, assumed the coefficients varied as the exponential of the reciprocal absolute temperature. The second empirical approach assumed the coefficients varied as the exponential of the absolute temperature. Both of these forms predicted the temperature dependence of the experimental mass-transfer coefficients with little error for most of the water temperature range likely to be found in streams and rivers. Liquid-film and gas-film coefficients for acetone and t-butyl alcohol were similar in value. However, depending on water mixing conditions, overall mass-transfer coefficients for acetone were from two to four times larger than the coefficients for t-butyl alcohol. This difference in behavior of the coefficients resulted because the Henry's law constant for acetone was about three times larger than that of

33 CFR 127.1317 - Declaration of Inspection.

Code of Federal Regulations, 2010 CFR

2010-07-01

...— (1) The name of the vessel and that of the facility; (2) The date and time that the transfer begins... to begin transfer; and (5) The signature of each relief person in charge and the date and time of... Inspection. (a) Each person in charge of transfer for the facility shall ensure that no person transfers LHG...

33 CFR 127.1317 - Declaration of Inspection.

Code of Federal Regulations, 2013 CFR

2013-07-01

...— (1) The name of the vessel and that of the facility; (2) The date and time that the transfer begins... to begin transfer; and (5) The signature of each relief person in charge and the date and time of... Inspection. (a) Each person in charge of transfer for the facility shall ensure that no person transfers LHG...

Cascading electron and hole transfer dynamics in a CdS/CdTe core-shell sensitized with bromo-pyrogallol red (Br-PGR): slow charge recombination in type II regime.

PubMed

Maity, Partha; Debnath, Tushar; Chopra, Uday; Ghosh, Hirendra Nath

2015-02-14

Ultrafast cascading hole and electron transfer dynamics have been demonstrated in a CdS/CdTe type II core-shell sensitized with Br-PGR using transient absorption spectroscopy and the charge recombination dynamics have been compared with those of CdS/Br-PGR composite materials. Steady state optical absorption studies suggest that Br-PGR forms strong charge transfer (CT) complexes with both the CdS QD and CdS/CdTe core-shell. Hole transfer from the photo-excited QD and QD core-shell to Br-PGR was confirmed by both steady state and time-resolved emission spectroscopy. Charge separation was also confirmed by detecting electrons in the conduction band of the QD and the cation radical of Br-PGR as measured from femtosecond transient absorption spectroscopy. Charge separation in the CdS/Br-PGR composite materials was found to take place in three different pathways, by transferring the photo-excited hole of CdS to Br-PGR, electron injection from the photo-excited Br-PGR to the CdS QD, and direct electron transfer from the HOMO of Br-PGR to the conduction band of the CdS QD. However, in the CdS/CdTe/Br-PGR system hole transfer from the photo-excited CdS to Br-PGR and electron injection from the photo-excited Br-PGR to CdS take place after cascading through the CdTe shell QD. Charge separation also takes place via direct electron transfer from the Br-PGR HOMO to the conduction band of CdS/CdTe. Charge recombination (CR) dynamics between the electron in the conduction band of the CdS QD and the Br-PGR cation radical were determined by monitoring the bleach recovery kinetics. The CR dynamics were found to be much slower in the CdS/CdTe/Br-PGR system than in the CdS/Br-PGR system. The formation of the strong CT complex and the separation of charges cascading through the CdTe shell help to slow down charge recombination in the type II regime.

Intramolecular Charge Transfer of Conjugated Liquid Crystal Ferrocene Macromolecules - Synthesis and Characterization

DTIC Science & Technology

2016-04-12

AFRL-AFOSR-CL-TR-2016-0012 Intramolecular Charge Transfer of Conjugated Liquid Crystal Ferrocene Macromolecules Ronald Ziolo CIQA Final Report 07/07...3. DATES COVERED (From - To)  15 Aug 2014 to 14 Jan 2016 4. TITLE AND SUBTITLE Intramolecular Charge Transfer of Conjugated Liquid Crystal Ferrocene...characterization of a new series of conjugated macromolecules bearing ferrocene as a highly efficient electron donor material coupled to 2,5-di(alcoxy) benzene

Excited state electron transfer in systems with a well-defined geometry. [cyclophane

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

Kaufmann, K.J.

1980-12-01

The effect of temperature, dielectric strength and ligand on the structure of the mesopyropheophorbide cyclophanes will be studied. ESR, NMR, emission and absorption spectroscopy, as well as circular dichroism will be used. The changes in structure will be correlated with changes in the photochemical activity. Electron acceptors such as benzoquinone will be utilized to stabilize the charge separation. Charge separation in porphyrin quinone dimers will also be studied. It was found that electron transfer in the cyclophane system is relatively slow. This is presumably due to an orientation requirement for fast electron transfer. Solvent dielectric also is important in producingmore » a charge separation. Decreasing the temperature effects the yield of charge transfer, but not the kinetics.« less

The low-energy, charge-transfer excited states of 4-amino-4-prime-nitrodiphenyl sulfide

NASA Technical Reports Server (NTRS)

O'Connor, Donald B.; Scott, Gary W.; Tran, Kim; Coulter, Daniel R.; Miskowski, Vincent M.; Stiegman, Albert E.; Wnek, Gary E.

1992-01-01

Absorption and emission spectra of 4-amino-4-prime-nitrodiphenyl sulfide in polar and nonpolar solvents were used to characterize and assign the low-energy excited states of the molecule. Fluorescence-excitation anisotropy spectra and fluorescence quantum yields were also used to characterize the photophysics of these states. The lowest-energy fluorescent singlet state was determined to be an intramolecular charge transfer (ICT) state involving transfer of a full electron charge from the amino to the nitro group yielding a dipole moment of about 50 D. A low-energy, intense absorption band is assigned as a transition to a different ICT state involving a partial electron charge transfer from sulfur to the nitro group.

Topologically protected charge transfer along the edge of a chiral p -wave superconductor

NASA Astrophysics Data System (ADS)

Gnezdilov, N. V.; van Heck, B.; Diez, M.; Hutasoit, Jimmy A.; Beenakker, C. W. J.

2015-09-01

The Majorana fermions propagating along the edge of a topological superconductor with px+i py pairing deliver a shot noise power of 1/2 ×e2/h per eV of voltage bias. We calculate the full counting statistics of the transferred charge and find that it becomes trinomial in the low-temperature limit, distinct from the binomial statistics of charge-e transfer in a single-mode nanowire or charge-2 e transfer through a normal-superconductor interface. All even-order correlators of current fluctuations have a universal quantized value, insensitive to disorder and decoherence. These electrical signatures are experimentally accessible, because they persist for temperatures and voltages large compared to the Thouless energy.

Superconductivity, phase separation, and charge-transfer instability in the U = infinity limit of the three-band model of the CuO sub 2 planes

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

Grilli, M.; Raimondi, R.; Castellani, C.

1991-07-08

The {ital U}={infinity} limit of the three-band Hubbard model with nearest-neighbor repulsion {ital V} is studied using the slave-boson approach and the large-{ital N} expansion technique to order 1/{ital N}. A charge-transfer instability is found as in weak-coupling theory. The charge-transfer instability is always associated with a diverging compressibility leading to a phase separation. Near the phase-separation, charge-transfer-instability region we find superconducting instabilities in the {ital s}- and {ital d}-wave channel. The requirement for superconductivity is that {ital V} be on the scale of the Cu-O hopping as suggested by Varma, Schmitt-Rink, and Abrahams.

Field Effect Modulation of Heterogeneous Charge Transfer Kinetics at Back-Gated Two-Dimensional MoS2 Electrodes.

PubMed

Wang, Yan; Kim, Chang-Hyun; Yoo, Youngdong; Johns, James E; Frisbie, C Daniel

2017-12-13

The ability to improve and to modulate the heterogeneous charge transfer kinetics of two-dimensional (2D) semiconductors, such as MoS 2 , is a major challenge for electrochemical and photoelectrochemical applications of these materials. Here we report a continuous and reversible physical method for modulating the heterogeneous charge transfer kinetics at a monolayer MoS 2 working electrode supported on a SiO 2 /p-Si substrate. The heavily doped p-Si substrate serves as a back gate electrode; application of a gate voltage (V BG ) to p-Si tunes the electron occupation in the MoS 2 conduction band and shifts the conduction band edge position relative to redox species dissolved in electrolyte in contact with the front side of the MoS 2 . The gate modulation of both charge density and energy band alignment impacts charge transfer kinetics as measured by cyclic voltammetry (CV). Specifically, cyclic voltammograms combined with numerical simulations suggest that the standard heterogeneous charge transfer rate constant (k 0 ) for MoS 2 in contact with the ferrocene/ferrocenium (Fc 0/+ ) redox couple can be modulated by over 2 orders of magnitude from 4 × 10 -6 to 1 × 10 -3 cm/s, by varying V BG . In general, the field effect offers the potential to tune the electrochemical properties of 2D semiconductors, opening up new possibilities for fundamental studies of the relationship between charge transfer kinetics and independently controlled electronic band alignment and band occupation.

Charge-transfer crystallites as molecular electrical dopants

PubMed Central

Méndez, Henry; Heimel, Georg; Winkler, Stefanie; Frisch, Johannes; Opitz, Andreas; Sauer, Katrein; Wegner, Berthold; Oehzelt, Martin; Röthel, Christian; Duhm, Steffen; Többens, Daniel; Koch, Norbert; Salzmann, Ingo

2015-01-01

Ground-state integer charge transfer is commonly regarded as the basic mechanism of molecular electrical doping in both, conjugated polymers and oligomers. Here, we demonstrate that fundamentally different processes can occur in the two types of organic semiconductors instead. Using complementary experimental techniques supported by theory, we contrast a polythiophene, where molecular p-doping leads to integer charge transfer reportedly localized to one quaterthiophene backbone segment, to the quaterthiophene oligomer itself. Despite a comparable relative increase in conductivity, we observe only partial charge transfer for the latter. In contrast to the parent polymer, pronounced intermolecular frontier-orbital hybridization of oligomer and dopant in 1:1 mixed-stack co-crystallites leads to the emergence of empty electronic states within the energy gap of the surrounding quaterthiophene matrix. It is their Fermi–Dirac occupation that yields mobile charge carriers and, therefore, the co-crystallites—rather than individual acceptor molecules—should be regarded as the dopants in such systems. PMID:26440403

Role of coherence and delocalization in photo-induced electron transfer at organic interfaces

NASA Astrophysics Data System (ADS)

Abramavicius, V.; Pranculis, V.; Melianas, A.; Inganäs, O.; Gulbinas, V.; Abramavicius, D.

2016-09-01

Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrödinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces.

Air sparging: Air-water mass transfer coefficients

NASA Astrophysics Data System (ADS)

Braida, Washington J.; Ong, Say Kee

1998-12-01

Experiments investigating the mass transfer of several dissolved volatile organic compounds (VOCs) across the air-water interface were conducted using a single-air- channel air-sparging system. Three different porous media were used in the study. Air velocities ranged from 0.2 cm s-1 to 2.5 cm s-1. The tortuosity factor for each porous medium and the air-water mass transfer coefficients were estimated by fitting experimental data to a one-dimensional diffusion model. The estimated mass transfer coefficients KG ranged from 1.79 × 10-3 cm min-1 to 3.85 × 10-2 cm min-1. The estimated lumped gas phase mass transfer coefficients KGa were found to be directly related to the air diffusivity of the VOC, air velocity, and particle size, and inversely related to the Henry's law constant of the VOCs. Of the four parameters investigated, the parameter that controlled or had a dominant effect on the lumped gas phase mass transfer coefficient was the air diffusivity of the VOC. Two empirical models were developed by correlating the Damkohler and the modified air phase Sherwood numbers with the air phase Peclet number, Henry's law constant, and the reduced mean particle size of porous media. The correlation developed in this study may be used to obtain better predictions of mass transfer fluxes for field conditions.

Experimental determination of heat transfer coefficients in roll bite and air cooling for computer simulations of 1100 MPa carbon steel rolling

NASA Astrophysics Data System (ADS)

Leinonen, Olli; Ilmola, Joonas; Seppälä, Oskari; Pohjonen, Aarne; Paavola, Jussi; Koskenniska, Sami; Larkiola, Jari

2018-05-01

In modeling of hot rolling pass schedules the heat transfer phenomena have to be known. Radiation to ambient, between rolls and a steel slab as well as heat transfer in contacts must be considered to achieve accurate temperature distribution and thereby accurate material behavior in simulations. Additional heat is generated by friction between the slab and the work roll and by plastic deformation. These phenomena must be taken into account when the effective heat transfer coefficient is determined from experimental data. In this paper we determine the effective heat transfer coefficient at the contact interface and emissivity factor of slab surface for 1100MPa strength carbon steel for hot rolling simulations. Experimental pilot rolling test were carried out and slab temperatures gathered right below the interface and at the mid thickness of the slab. Emissivity factor tests were carried out in the same manner but without rolling. Experimental data is utilized to derive contact heat transfer coefficient at the interface and emissivity factor of slab surface. Pilot rolling test is reproduced in FE-analysis to further refine the heat transfer coefficient and emissivity factor. Material mechanical properties at rolling temperatures were determined by Gleeble™ thermo-mechanical simulator and IDS thermodynamic-kinetic-empirical software.

Theoretical Investigation of Charge Transfer in Metal Organic Frameworks for Electrochemical Device Applications

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

Patwardhan, Sameer; Schatz, George C.

For electrochemical device applications metal organic frameworks (MOFs) must exhibit suitable conduction properties. To this end, we have performed computational studies of intermolecular charge transfer in MOFs consisting of hexa-ZrIV nodes and tetratopic carboxylate linkers. This includes an examination of the electronic structure of linkers that are derived from tetraphenyl benzene 1, tetraphenyl pyrene 2, and tetraphenyl porphyrin 3 molecules. These results are used to determine charge transfer propensities in MOFs, within the framework of Marcus theory, including an analysis of the key parameters (charge transfer integral t, reorganization energy λ, and free energy change ΔG0) and evaluation of figuresmore » of merit for charge transfer based on the chemical structures of the linkers. This qualitative analysis indicates that delocalization of the HOMO/LUMO on terminal substituents increases t and decreases λ, while weaker binding to counterions decreases ΔG0, leading to better charge transfer propensity. Subsequently, we study hole transfer in the linker 2 containing MOFs, NU-901 and NU-1000, in detail and describe mechanisms (hopping and superexchange) that may be operative under different electrochemical conditions. Comparisons with experiment are provided where available. On the basis of the redox and catalytic activity of nodes and linkers, we propose three possible schemes for constructing electrochemical devices for catalysis. We believe that the results of this study will lay the foundation for future experimental work on this topic.« less

Neutralized ion beam modification of cellulose membranes for study of ion charge effect on ion-beam-induced DNA transfer

NASA Astrophysics Data System (ADS)

Prakrajang, K.; Sangwijit, K.; Anuntalabhochai, S.; Wanichapichart, P.; Yu, L. D.

2012-02-01

Low-energy ion beam biotechnology (IBBT) has recently been rapidly developed worldwide. Ion-beam-induced DNA transfer is one of the important applications of IBBT. However, mechanisms involved in this application are not yet well understood. In this study plasma-neutralized ion beam was applied to investigate ion charge effect on induction of DNA transfer. Argon ion beam at 7.5 keV was neutralized by RF-driven plasma in the beam path and then bombarded cellulose membranes which were used as the mimetic plant cell envelope. Electrical properties such as impedance and capacitance of the membranes were measured after the bombardment. An in vitro experiment on plasmid DNA transfer through the cellulose membrane was followed up. The results showed that the ion charge input played an important role in the impedance and capacitance changes which would affect DNA transfer. Generally speaking, neutral particle beam bombardment of biologic cells was more effective in inducing DNA transfer than charged ion beam bombardment.

Ultrafast investigation of photoinduced charge transfer in aminoanthraquinone pharmaceutical product

NASA Astrophysics Data System (ADS)

Zhang, Song; Sun, Simei; Zhou, Miaomiao; Wang, Lian; Zhang, Bing

2017-02-01

We investigated the mechanism of intramolecular charge transfer and the following radiationless dynamics of the excited states of 1-aminoanthraquinone using steady state and time-resolved absorption spectroscopy combined with quantum chemical calculations. Following photoexcitation with 460 nm, conformational relaxation via twisting of the amino group, charge transfer and the intersystem crossing (ISC) processes have been established to be the major relaxation pathways responsible for the ultrafast nonradiative of the excited S1 state. Intramolecular proton transfer, which could be induced by intramolecular hydrogen bonding is inspected and excluded. Time-dependent density functional theory (TDDFT) calculations reveal the change of the dipole moments of the S0 and S1 states along the twisted coordinate of the amino group, indicating the mechanism of twisted intra-molecular charge transfer (TICT). The timescale of TICT is measured to be 5 ps due to the conformational relaxation and a barrier on the S1 potential surface. The ISC from the S1 state to the triplet manifold is a main deactivation pathway with the decay time of 28 ps. Our results observed here have yield a physically intuitive and complete picture of the photoinduced charge transfer and radiationless dynamics in anthraquinone pharmaceutial products.

Interfacial characteristics and leakage current transfer mechanisms in organometal trihalide perovskite gate-controlled devices via doping of PCBM

NASA Astrophysics Data System (ADS)

Wang, Yucheng; Zhang, Yuming; Liu, Yintao; Pang, Tiqiang; Hu, Ziyang; Zhu, Yuejin; Luan, Suzhen; Jia, Renxu

2017-11-01

Two types of perovskite (with and without doping of PCBM) based metal-oxide-semiconductor (MOS) gate-controlled devices were fabricated and characterized. The study of the interfacial characteristics and charge transfer mechanisms by doping of PCBM were analyzed by material and electrical measurements. Doping of PCBM does not affect the size and crystallinity of perovskite films, but has an impact on carrier extraction in perovskite MOS devices. The electrical hysteresis observed in capacitance-voltage and current-voltage measurements can be alleviated by doping of PCBM. Experimental results demonstrate that extremely low trap densities are found for the perovskite device without doping, while the doped sample leads to higher density of interface state. Three mechanisms including Ohm’s law, trap-filled-limit (TFL) emission, and child’s law were used to analyze possible charge transfer mechanisms. Ohm’s law mechanism is well suitable for charge transfer of both the perovskite MOS devices under light condition at large voltage, while TFL emission well addresses the behavior of charge transfer under dark at small voltage. This change of charge transfer mechanism is attributed to the impact of the ion drift within perovskites.

Heat transfer and pressure drop characteristics of a plate heat exchanger using water based Al2O3 nanofluid for 30° and 60° chevron angles

NASA Astrophysics Data System (ADS)

Elias, M. M.; Saidur, R.; Ben-Mansour, R.; Hepbasli, A.; Rahim, N. A.; Jesbains, K.

2018-04-01

Nanofluid is a new class of engineering fluid that has good heat transfer characteristics which is essential to increase the heat transfer performance in various engineering applications such as heat exchangers and cooling of electronics. In this study, experiments were conducted to compare the heat transfer performance and pressure drop characteristics in a plate heat exchanger (PHE) for 30° and 60° chevron angles using water based Al2O3 nanofluid at the concentrations from 0 to 0.5 vol.% for different Reynolds numbers. The thermo-physical properties has been determined and presented in this paper. At 0.5 vol% concentration, the maximum heat transfer coefficient, the overall heat transfer coefficient and the heat transfer rate for 60° chevron angle have attained a higher percentage of 15.14%, 7.8% and 15.4%, respectively in comparison with the base fluid. Consequently, when the volume concentration or Reynolds number increases, the heat transfer coefficient and the overall heat transfer coefficient as well as the heat transfer rate of the PHE (Plate Heat Exchangers) increases respectively. Similarly, the pressure drop increases with the volume concentration. 60° chevron angle showed better performance in comparison with 30° chevron angle.

Development of a laser-induced heat flux technique for measurement of convective heat transfer coefficients in a supersonic flowfield

NASA Technical Reports Server (NTRS)

Porro, A. Robert; Keith, Theo G., Jr.; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.

1991-01-01

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the load surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimental results agreed reasonably well with theoretical predictions of convective heat transfer of flat plate laminar boundary layers. The results indicate that this non-intrusive optical measurement technique has the potential to obtain high quality surface convective heat transfer measurements in high speed flowfields.

Spatial distribution of transferred charges across the heterointerface between perovskite transition metal oxides LaNiO{sub 3} and LaMnO{sub 3}

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

Kitamura, Miho; Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization; Horiba, Koji

2016-03-14

To investigate the interfacial charge-transfer phenomena between perovskite transition metal oxides LaNiO{sub 3} (LNO) and LaMnO{sub 3} (LMO), we have performed in situ x-ray absorption spectroscopy (XAS) measurements on LNO/LMO multilayers. The Ni-L{sub 2,3} and Mn-L{sub 2,3} XAS spectra clearly show the occurrence of electron transfer from Mn to Ni ions in the interface region. Detailed analysis of the thickness dependence of these XAS spectra has revealed that the spatial distribution of the transferred charges across the interface is significantly different between the two constituent layers. The observed spatial distribution is presumably described by the charge spreading model that treatsmore » the transfer integral between neighboring transition metal ions and the Coulomb interaction, rather than the Thomas–Fermi screening model.« less

Heat transfer to horizontal tubes in a pilot-scale fluidized-bed combustor burning low-rank coals

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

Grewal, N.S.; Goblirsch, G.

Experimental data are obtained for the heat transfer coefficient between immersed horizontal tube bundles and an atmospheric-fluidized-bed combustor burning low-rank coals. Silica sand and limestone are used as bed material. The tests are conducted, with and without limestone addition and ash recycle, at average bed temperatures ranging from 1047 to 1125 K, superficial fluidizing velocity of 1.66 to 2.04 m/s, and excess air levels of 15 to 40 percent. The experimental data are examined in the light of the existing correlations for the heat transfer coefficient. The predicted values of heat transfer coefficient from the correlations proposed by Grewal andmore » Bansal et al. are found to be within + or - 25 percent of the experimental values of heat transfer coefficient, when the contribution due to radiation is also included.« less

A Physical Interpretation of the Phenomenological Coefficients of Membrane Permeability

PubMed Central

Kedem, O.; Katchalsky, A.

1961-01-01

A "translation" of the phenomenological permeability coefficients into friction and distribution coefficients amenable to physical interpretation is presented. Expressions are obtained for the solute permeability coefficient ω and the reflection coefficient σ for both non-electrolytic and electrolytic permeants. An analysis of the coefficients is given for loose membranes as well as for dense natural membranes where transport may go through capillaries or by solution in the lipoid parts of the membrane. Water diffusion and filtration and the relation between these and capillary pore radius of the membrane are discussed. For the permeation of ions through the charged membranes equations are developed for the case of zero electrical current in the membrane. The correlation of σ with ω and Lp for electrolytes resembles that for non-electrolytes. In this case ω and σ depend markedly on ion concentration and on the charge density of the membrane. The reflection coefficient may assume negative values indicating anomalous osmosis. An analysis of the phenomena of anomalous osmosis was carried out for the model of Teorell and Meyer and Sievers and the results agree with the experimental data of Loeb and of Grim and Sollner. A set of equations and reference curves are presented for the evaluation of ω and σ in the transport of polyvalent ions through charged membranes. PMID:13752127

The relationship between coefficient of restitution and state of charge of zinc alkaline primary LR6 batteries [Bouncing alkaline batteries: A basic solution

DOE PAGES

Bhadra, S.; Hertzberg, B. J.; Croft, M.; ...

2015-03-13

The coefficient of restitution of alkaline batteries had been shown to increase as a function of depth of discharge. In this work, using non-destructive mechanical testing, the change in coefficient of restitution is compared to in situ energy-dispersive x-ray diffraction data to determine the cause of the macroscopic change in coefficient of restitution. The increase in coefficient of restitution correlates to the formation of a percolation pathway of ZnO within the anode of the cell, and that the coefficient of restitution saturates at a value of 0.63 ± .05 at 50% state if charge when the anode has densified intomore » porous ZnO solid. Of note is the sensitivity of coefficient of restitution to the amount of ZnO formation that rivals the sensitivity on in situ energy-dispersive x-ray diffraction spectroscopy.« less

Carbon-, sulfur-, and phosphorus-based charge transfer reactions in inductively coupled plasma-atomic emission spectrometry

NASA Astrophysics Data System (ADS)

Grindlay, Guillermo; Gras, Luis; Mora, Juan; de Loos-Vollebregt, Margaretha T. C.

2016-01-01

In this work, the influence of carbon-, sulfur-, and phosphorus-based charge transfer reactions on the emission signal of 34 elements (Ag, Al, As, Au, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, I, In, Ir, K, Li, Mg, Mn, Na, Ni, P, Pb, Pd, Pt, S, Sb, Se, Sr, Te, and Zn) in axially viewed inductively coupled plasma-atomic emission spectrometry has been investigated. To this end, atomic and ionic emission signals for diluted glycerol, sulfuric acid, and phosphoric acid solutions were registered and results were compared to those obtained for a 1% w w- 1 nitric acid solution. Experimental results show that the emission intensities of As, Se, and Te atomic lines are enhanced by charge transfer from carbon, sulfur, and phosphorus ions. Iodine and P atomic emission is enhanced by carbon- and sulfur-based charge transfer whereas the Hg atomic emission signal is enhanced only by carbon. Though signal enhancement due to charge transfer reactions is also expected for ionic emission lines of the above-mentioned elements, no experimental evidence has been found with the exception of Hg ionic lines operating carbon solutions. The effect of carbon, sulfur, and phosphorus charge transfer reactions on atomic emission depends on (i) wavelength characteristics. In general, signal enhancement is more pronounced for electronic transitions involving the highest upper energy levels; (ii) plasma experimental conditions. The use of robust conditions (i.e. high r.f. power and lower nebulizer gas flow rates) improves carbon, sulfur, and phosphorus ionization in the plasma and, hence, signal enhancement; and (iii) the presence of other concomitants (e.g. K or Ca). Easily ionizable elements reduce ionization in the plasma and consequently reduce signal enhancement due to charge transfer reactions.

Theoretical investigation of the charge-transfer properties in different meso-linked zinc porphyrins for highly efficient dye-sensitized solar cells.

PubMed

Namuangruk, Supawadee; Sirithip, Kanokkorn; Rattanatwan, Rattanawelee; Keawin, Tinnagon; Kungwan, Nawee; Sudyodsuk, Taweesak; Promarak, Vinich; Surakhot, Yaowarat; Jungsuttiwong, Siriporn

2014-06-28

The charge transfer effect of different meso-substituted linkages on porphyrin analogue 1 (A1, B1 and C1) was theoretically investigated using density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. The calculated geometry parameters and natural bond orbital analysis reveal that the twisted conformation between porphyrin macrocycle and meso-substituted linkages leads to blocking of the conjugation of the conjugated backbone, and the frontier molecular orbital plot shows that the intramolecular charge transfer of A1, B1 and C1 hardly takes place. In an attempt to improve the photoinduced intramolecular charge transfer ability of the meso-linked zinc porphyrin sensitizer, a strong electron-withdrawing group (CN) was introduced into the anchoring group of analogue 1 forming analogue 2 (A2, B2 and C2). The density difference plot of A2, B2 and C2 shows that the charge transfer properties dramatically improved. The electron injection process has been performed using TDDFT; the direct charge-transfer transition in the A2-(TiO2)38 interacting system takes place; our results strongly indicated that introducing electron-withdrawing groups into the acceptor part of porphyrin dyes can fine-tune the effective conjugation length of the π-spacer and improve intramolecular charge transfer properties, consequently inducing the electron injection process from the anchoring group of the porphyrin dye to the (TiO2)38 surface which may improve the conversion efficiency of the DSSCs. Our calculated results can provide valuable information and a promising outlook for computation-aided sensitizer design with anticipated good properties in further experimental synthesis.

Transition from capacitive coupling to direct charge transfer in asymmetric terahertz plasmonic assemblies.

PubMed

Ahmadivand, Arash; Sinha, Raju; Gerislioglu, Burak; Karabiyik, Mustafa; Pala, Nezih; Shur, Michael

2016-11-15

We experimentally and numerically analyze the charge transfer THz plasmons using an asymmetric plasmonic assembly of metallic V-shaped blocks. The asymmetric design of the blocks allows for the excitation of classical dipolar and multipolar modes due to the capacitive coupling. Introducing a conductive microdisk between the blocks, we facilitated the excitation of the charge transfer plasmons and studied their characteristics along with the capacitive coupling by varying the size of the disk.

Variationally consistent approximation scheme for charge transfer

NASA Technical Reports Server (NTRS)

Halpern, A. M.

1978-01-01

The author has developed a technique for testing various charge-transfer approximation schemes for consistency with the requirements of the Kohn variational principle for the amplitude to guarantee that the amplitude is correct to second order in the scattering wave functions. Applied to Born-type approximations for charge transfer it allows the selection of particular groups of first-, second-, and higher-Born-type terms that obey the consistency requirement, and hence yield more reliable approximation to the amplitude.

Protein diffusiophoresis and salt osmotic diffusion in aqueous solutions.

PubMed

Annunziata, Onofrio; Buzatu, Daniela; Albright, John G

2012-10-25

Diffusion of a solute can be induced by the concentration gradient of another solute in solution. This transport mechanism is known as cross-diffusion. We have investigated cross-diffusion in a ternary protein-salt-water system. Specifically, we measured the two cross-diffusion coefficients for the lysozyme-NaCl-water system at 25 °C and pH 4.5 as a function of protein and salt concentrations by Rayleigh interferometry. One cross-diffusion coefficient characterizes salt osmotic diffusion induced by a protein concentration gradient, and is related to protein-salt thermodynamic interactions as described by the theories of Donnan membrane equilibrium and protein preferential hydration. The other cross-diffusion coefficient characterizes protein diffusiophoresis induced by a salt concentration gradient, and is described as the difference between a preferential-interaction coefficient and a transport parameter. We first relate our experimental results to the protein net charge and the thermodynamic excess of water near the protein surface. We then extract the Stefan-Maxwell diffusion coefficient describing protein-salt interactions in water. We find that the value of this coefficient is negative, contrary to the friction interpretation of Stefan-Maxwell equations. This result is explained by considering protein hydration. Finally, protein diffusiophoresis is quantitatively examined by considering electrophoretic and hydration effects on protein migration and utilized to accurately estimate lysozyme electrophoretic mobility. To our knowledge, this is the first time that protein diffusiophoresis has been experimentally characterized and a protein-salt Stefan-Maxwell diffusion coefficient reported. This work represents a significant contribution for understanding and modeling the effect of concentration gradients in protein-salt aqueous systems relevant to diffusion-based mass-transfer technologies and transport in living systems.

Study of a high performance evaporative heat transfer surface

NASA Technical Reports Server (NTRS)

Saaski, E. W.; Hamasaki, R. H.

1977-01-01

An evaporative surface is described for heat pipes and other two-phase heat transfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heat transfer coefficient and high heat flux capability relative to conventional open-faced screw thread surfaces. With a groove density of 12.6 cm/1 and ammonia working fluid, heat transfer coefficients in the range of 1 to 2 W/sq cm have been measured along with maximum heat flux densities in excess of 20 W/sq cm. A peak heat transfer coefficient in excess of 2.3 W/sq cm was measured with a 37.8 cm/1 hybrid surface.

Numerical Simulation of Internal Heat Transfer Phenomena Occurring During De-Icing of Aircraft Components

NASA Technical Reports Server (NTRS)

DeWitt, Keneth J.

1996-01-01

An experimental study to determine the convective heat transfer coefficient from castings made from ice-roughened plates is reported. A corresponding topic, 'Measurements of the Convective Heat Transfer Coefficient from Ice Roughened Surfaces in Parallel and Accelerated Flows,' is presented.

Electrochemistry of hemoglobin entrapped in a Nafion/nano-ZnO film on carbon ionic liquid electrode.

PubMed

Sun, Wei; Zhai, ZiQin; Wang, DanDan; Liu, ShuFeng; Jiao, Kui

2009-02-01

A stable composite film composed of the ionomer Nafion, the ZnO nanoparticle and the protein hemoglobin was cast on the surface of an ionic liquid modified carbon paste electrode (CILE) to establish a modified electrode denoted as Nafion/nano-ZnO/Hb/CILE. UV-vis and FT-IR spectrum showed that hemoglobin in the film retained its native conformation. The electrochemical behaviors of hemoglobin entrapped in the film were carefully investigated with cyclic voltammetry. A pair of well-defined and quasi-reversible redox voltammetric peaks for Hb Fe(III)/Fe(II) was obtained with the standard potential (E(0)') located at -0.344 V (vs. SCE) in phosphate buffer solution (PBS, pH 7.0), which was attributed to the direct electron transfer of Hb with electrode in the microenvironments of ZnO nanoparticle and ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF(6)). The electrochemical parameters of Hb in the composite film were further carefully calculated with the results of the electron-transfer rate constant (k(s)) as 0.139 s(-1), the charge transfer coefficient (alpha) as 0.413 and the number of electron transferred (n) as 0.95. The Hb modified electrode showed good electrocatalytic ability toward the reduction of trichloroacetic acid (TCA).

Visualization of oxygen transfer across the air-water interface using a fluorescence oxygen visualization method.

PubMed

Lee, Minhee

2002-04-01

Oxygen concentration fields in a water body were visualized by the fluorescence oxygen visualization (FOV) method. Pyrenebutyric acid (PBA) was used as a fluorescent indicator of oxygen, and an intensive charge coupled-device (ICCD) camera as an image detector. Sequential images (over 2000 images) of the oxygen concentration field around the surface water of the tank (1 x 1 x 0.75 m3) were produced during the 3 h experiment. From image processing, the accurate pathway of oxygen-rich, cold water at the water surface was also visualized. The amount of oxygen transferred through the air-water interface during the experiment was measured and the oxygen transfer coefficient (K(L)) was determined as 0.22 m/d, which was much higher than that is expected in molecular diffusion. Results suggest that vertical penetration of cold water was the main pathway of oxygen in the water body in the tank. The average velocity of cold water penetrating downward in water body was also measured from consecutive images and the value was 0.3-0.6 mm/s. The FOV method used in this research should have wide application in experimental fluid mechanics and can also provide a phenomenological description of oxygen transfer under physically realizable natural conditions in lakes and reservoirs.

R1234yf vs. R134a Flow Boiling Heat Transfer Inside a 3.4 mm ID Microfin Tube

NASA Astrophysics Data System (ADS)

Diani, A.; Mancin, S.; Rossetto, L.

2014-11-01

The refrigerant charge minimization as well as the use of eco-friendly fluids can be considered two of the most important targets for these applications to cope with the new environmental challenges. This paper compares the R1234yf and R134a flow boiling heat transfer and pressure drop measurements inside a small microfin tube with internal diameter at the fin tip of 3.4 mm. This study is carried out in an experimental facility built at the Dipartimento di Ingegneria Industriale of the University of Padova especially designed to study both single and two phase heat transfer processes. The microfin tube is brazed inside a copper plate and electrically heated from the bottom. Several T -type thermocouples are inserted in the wall to measure the temperature distribution during the phase change process. In particular, the experimental measurements were carried out at constant saturation temperature of 30 °C, by varying the refrigerant mass velocity between 190 kg m-2 s-1 and 940 kg m-2 s-1, the vapour quality from 0.2 to 0.99, at different imposed heat fluxes. The two refrigerants are compared considering the values of the two-phase heat transfer coefficient and pressure drop.

Carbon nanostructures modified LiFePO4 cathodes for lithium ion battery applications: optimized porosity and composition

NASA Astrophysics Data System (ADS)

Mahmoud, Lama; Singh Lalia, Boor; Hashaikeh, Raed

2016-12-01

Lithium iron phosphate (LiFePO4) battery cathode was fabricated without using any metallic current collector and polymeric binder. Carbon nanostructures (CNS) were used as microbinders for LiFePO4 particles and at the same time as a 3D current collector. A facile and cost effective method of fabricating composite cathodes of CNS and LiFePO4 was developed. Thick electrodes with high loading of active material (20-25 mg cm-2) were obtained that are almost 2-3 folds higher than commercial electrodes. SEM images confirm that the 3D CNS conductive network encapsulated the LiFePO4 particles homogenously facilitating the charge transfer at the electrode-CNS interface. The composition, scan rate and porosity of the paper-like cathode were sequentially varied and their influence was systematically monitored by means of linear sweep cyclic voltammetry and AC electrochemical impedance spectroscopy. Addition of CNS improved the electrode’s bulk electronic conductivity, mechanical integrity, surface area and double layer capacitance, yet compromised the charge transfer resistance at the electrode-electrolyte interface. Based on a range of the tested binder-free electrodes, this study proposes that electrodes with 20 wt% CNS having 49 ± 2.5% porosity had realized best improvements of two folds and four folds in the electronic conductivity and diffusion coefficient, respectively.

Characteristics of the high-rate discharge capability of a nickel/metal hydride battery electrode

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

Geng, M.; Han, J.; Feng, F.

1999-10-01

The high rate discharge capability of the negative electrode in a Ni/MH battery is mainly determined by the charge transfer process at the interface between the metal hydride (MH) alloy powder and the electrolyte, and the mass transfer process in the bulk MH alloy powder. In this study, the anodic polarization curves of a MH electrode were measured and analyzed. An alloy of nominal composition Mm{sub 0.95}Ti{sub 0.05}Ni{sub 3.85}Co{sub 0.45}Mn{sub 0.35}Al{sub 0.35} was used as the negative electrode material. With increasing number of charge/discharge cycles, the MH alloy powders microcrack into particles several micrometers in diameter. The decrease in themore » MH alloy particle size results in an increase in both the activation surface area and the exchange current density of the MH alloy electrode. The electrode overpotentials of the MH electrode decreases with increasing number of cycles at a large value of anodic polarization current. The decrease in electrode overpotential leads to an increase in the high rate discharge capability of the MH electrode. By using the limiting current, the hydrogen diffusion coefficient in the MH alloy was estimated to be 1.2 x 10{sup {minus}11}cm{sup 2}s{sup {minus}1} assuming an average particle radius of 5 {micro}m.« less

Spectrophotometric Determination of Mycophenolate Mofetil as Its Charge-Transfer Complexes with Two π-Acceptors

PubMed Central

Vinay, K. B.; Revanasiddappa, H. D.; Raghu, M. S.; Abdulrahman, Sameer. A. M.; Rajendraprasad, N.

2012-01-01

Two simple, selective, and rapid spectrophotometric methods are described for the determination of mycophenolate mofetil (MPM) in pure form and in tablets. Both methods are based on charge-transfer complexation reaction of MPM with p-chloranilic acid (p-CA) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in dioxane-acetonitrile medium resulting in coloured product measurable at 520 nm (p-CA) or 580 nm (DDQ). Beer's law is obeyed over the concentration ranges of 40–400 and 12–120 μg mL−1 MPM for p-CA and DDQ, respectively, with correlation coefficients (r) of 0.9995 and 0.9947. The apparent molar absorptivity values are calculated to be 1.06 × 103 and 3.87 × 103 L mol−1 cm−1, respectively, and the corresponding Sandell's sensitivities are 0.4106 and 0.1119 μg cm−1. The limits of detection (LOD) and quantification (LOQ) are also reported for both methods. The described methods were successfully applied to the determination of MPM in tablets. Statistical comparison of the results with those of the reference method showed excellent agreement. No interference was observed from the common excipients present in tablets. Both methods were validated statistically for accuracy and precision. The accuracy and reliability of the methods were further ascertained by recovery studies via standard addition procedure. PMID:22567572

Two Photon Absorption in a Novel Nano-optical Material Based on the Nonconjugated Conductive Polymer, Poly(beta-pinene)

NASA Astrophysics Data System (ADS)

Titus, Jitto; Thakur, Mrinal

2006-03-01

As recently reported, the electrical conductivity of the nonconjugated polymer, poly(beta-pinene) increases by more than ten orders of magnitude upon doping with iodine [1]. The FTIR, optical absorption and EPR measurements have shown that radical cations are formed upon doping and charge-transfer involving the isolated double-bond in poly(beta-pinene). In this report, exceptionally large two-photon absorption in iodine-doped poly(beta-pinene) will be discussed. The linear absorption spectrum of medium-doped poly(beta-pinene) have peaks at about 4 eV and 3.1 eV. The first peak is due to the radical cation and the second due to the charge-transfer between the double bond and the dopant. The two-photon absorption of the medium-doped polymer has been measured at 730-860 nm using open-aperture z-scan with 150 femtosecond pulses from a Ti:Sapphire laser. A two-photon peak at about 1.5 eV with a magnitude of more than 1 cm/MW has been observed. The large magnitude of the two-photon absorption coefficient which is proportional to the imaginary part of the third order susceptibility has been attributed to the special structure of the radical cation and the confinement within a sub-nanometer dimension. [1] Vippa, Rajagopalan and Thakur, J. Poly. Sci. Part B: Poly. Phys., 43, 3695 (2005).

Evaporation heat transfer of carbon dioxide at low temperature inside a horizontal smooth tube

NASA Astrophysics Data System (ADS)

Yoon, Jung-In; Son, Chang-Hyo; Jung, Suk-Ho; Jeon, Min-Ju; Yang, Dong-Il

2017-05-01

In this paper, the evaporation heat transfer coefficient of carbon dioxide at low temperature of -30 to -20 °C in a horizontal smooth tube was investigated experimentally. The test devices consist of mass flowmeter, pre-heater, magnetic gear pump, test section (evaporator), condenser and liquid receiver. Test section is made of cooper tube. Inner and outer diameter of the test section is 8 and 9.52 mm, respectively. The experiment is conducted at mass fluxes from 100 to 300 kg/m2 s, saturation temperature from -30 to -20 °C. The main results are summarized as follows: In case that the mass flux of carbon dioxide is 100 kg/m2 s, the evaporation heat transfer coefficient is almost constant regardless of vapor quality. In case of 200 and 300 kg/m2 s, the evaporation heat transfer coefficient increases steadily with increasing vapor quality. For the same mass flux, the evaporation heat transfer coefficient increases as the evaporation temperature of the refrigerant decreases. In comparison of heat transfer correlations with the experimental result, the evaporation heat transfer correlations do not predict them exactly. Therefore, more accurate heat transfer correlation than the previous one is required.

System and method of active vibration control for an electro-mechanically cooled device

DOEpatents

Lavietes, Anthony D.; Mauger, Joseph; Anderson, Eric H.

2000-01-01

A system and method of active vibration control of an electro-mechanically cooled device is disclosed. A cryogenic cooling system is located within an environment. The cooling system is characterized by a vibration transfer function, which requires vibration transfer function coefficients. A vibration controller generates the vibration transfer function coefficients in response to various triggering events. The environments may differ by mounting apparatus, by proximity to vibration generating devices, or by temperature. The triggering event may be powering on the cooling system, reaching an operating temperature, or a reset action. A counterbalance responds to a drive signal generated by the vibration controller, based on the vibration signal and the vibration transfer function, which adjusts vibrations. The method first places a cryogenic cooling system within a first environment and then generates a first set of vibration transfer function coefficients, for a vibration transfer function of the cooling system. Next, the cryogenic cooling system is placed within a second environment and a second set of vibration transfer function coefficients are generated. Then, a counterbalance is driven, based on the vibration transfer function, to reduce vibrations received by a vibration sensitive element.

Precipitation of energetic neutral atoms and induced non-thermal escape fluxes from the Martian atmosphere

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

Lewkow, N. R.; Kharchenko, V.

2014-08-01

The precipitation of energetic neutral atoms, produced through charge exchange collisions between solar wind ions and thermal atmospheric gases, is investigated for the Martian atmosphere. Connections between parameters of precipitating fast ions and resulting escape fluxes, altitude-dependent energy distributions of fast atoms and their coefficients of reflection from the Mars atmosphere, are established using accurate cross sections in Monte Carlo (MC) simulations. Distributions of secondary hot (SH) atoms and molecules, induced by precipitating particles, have been obtained and applied for computations of the non-thermal escape fluxes. A new collisional database on accurate energy-angular-dependent cross sections, required for description of themore » energy-momentum transfer in collisions of precipitating particles and production of non-thermal atmospheric atoms and molecules, is reported with analytic fitting equations. Three-dimensional MC simulations with accurate energy-angular-dependent cross sections have been carried out to track large ensembles of energetic atoms in a time-dependent manner as they propagate into the Martian atmosphere and transfer their energy to the ambient atoms and molecules. Results of the MC simulations on the energy-deposition altitude profiles, reflection coefficients, and time-dependent atmospheric heating, obtained for the isotropic hard sphere and anisotropic quantum cross sections, are compared. Atmospheric heating rates, thermalization depths, altitude profiles of production rates, energy distributions of SH atoms and molecules, and induced escape fluxes have been determined.« less

Excited State Charge Transfer reaction with dual emission from 5-(4-dimethylamino-phenyl)-penta-2,4-dienenitrile: Spectral measurement and theoretical density functional theory calculation

NASA Astrophysics Data System (ADS)

Jana, Sankar; Dalapati, Sasanka; Ghosh, Shalini; Kar, Samiran; Guchhait, Nikhil

2011-07-01

The excited state intramolecular charge transfer process in donor-chromophore-acceptor system 5-(4-dimethylamino-phenyl)-penta-2,4-dienenitrile (DMAPPDN) has been investigated by steady state absorption and emission spectroscopy in combination with Density Functional Theory (DFT) calculations. This flexible donor acceptor molecule DMAPPDN shows dual fluorescence corresponding to emission from locally excited and charge transfer state in polar solvent. Large solvatochromic emission shift, effect of variation of pH and HOMO-LUMO molecular orbital pictures support excited state intramolecular charge transfer process. The experimental findings have been correlated with the calculated structure and potential energy surfaces based on the Twisted Intramolecular Charge Transfer (TICT) model obtained at DFT level using B3LYP functional and 6-31+G( d, p) basis set. The theoretical potential energy surfaces for the excited states have been generated in vacuo and acetonitrile solvent using Time Dependent Density Functional Theory (TDDFT) and Time Dependent Density Functional Theory Polarized Continuum Model (TDDFT-PCM) method, respectively. All the theoretical results show well agreement with the experimental observations.

Quasi-four-body treatment of charge transfer in the collision of protons with atomic helium: I. Thomas related mechanisms

NASA Astrophysics Data System (ADS)

Safarzade, Zohre; Fathi, Reza; Shojaei Akbarabadi, Farideh; Bolorizadeh, Mohammad A.

2018-04-01

The scattering of a completely bare ion by atoms larger than hydrogen is at least a four-body interaction, and the charge transfer channel involves a two-step process. Amongst the two-step interactions of the high-velocity single charge transfer in an anion-atom collision, there is one whose amplitude demonstrates a peak in the angular distribution of the cross sections. This peak, the so-called Thomas peak, was predicted by Thomas in a two-step interaction, classically, which could also be described through three-body quantum mechanical models. This work discusses a four-body quantum treatment of the charge transfer in ion-atom collisions, where two-step interactions illustrating a Thomas peak are emphasized. In addition, the Pauli exclusion principle is taken into account for the initial and final states as well as the operators. It will be demonstrated that there is a momentum condition for each two-step interaction to occur in a single charge transfer channel, where new classical interactions lead to the Thomas mechanism.

Charge-Transfer Analysis of 2p3d Resonant Inelastic X-ray Scattering of Cobalt Sulfide and Halides

PubMed Central

2017-01-01

We show that with 2p3d resonant inelastic X-ray scattering (RIXS) we can accurately determine the charge-transfer parameters of CoF2, CoCl2, CoBr2, and CoS. The 160 meV resolution RIXS results are compared with charge-transfer multiplet calculations. The improved resolution and the direct observation of the crystal field and charge-transfer excitations allow the determination of more accurate parameters than could be derived from X-ray absorption and X-ray photoemission, both limited in resolution by their lifetime broadening. We derive the crystal field and charge-transfer parameters of the Co2+ ions, which provides the nature of the ground state of the Co2+ ions with respect to symmetry and hybridization. In addition, the increased spectral resolution allows the more accurate determination of the atomic Slater integrals. The results show that the crystal field energy decreases with increasing ligand covalency. The L2 edge RIXS spectra show that the intensity of the (Coster–Kronig induced) nonresonant X-ray emission is a measure of ligand covalency. PMID:29170686

Mechanism of charge transfer and its impacts on Fermi-level pinning for gas molecules adsorbed on monolayer WS2.

PubMed

Zhou, Changjie; Yang, Weihuang; Zhu, Huili

2015-06-07

Density functional theory calculations were performed to assess changes in the geometric and electronic structures of monolayer WS2 upon adsorption of various gas molecules (H2, O2, H2O, NH3, NO, NO2, and CO). The most stable configuration of the adsorbed molecules, the adsorption energy, and the degree of charge transfer between adsorbate and substrate were determined. All evaluated molecules were physisorbed on monolayer WS2 with a low degree of charge transfer and accept charge from the monolayer, except for NH3, which is a charge donor. Band structure calculations showed that the valence and conduction bands of monolayer WS2 are not significantly altered upon adsorption of H2, H2O, NH3, and CO, whereas the lowest unoccupied molecular orbitals of O2, NO, and NO2 are pinned around the Fermi-level when these molecules are adsorbed on monolayer WS2. The phenomenon of Fermi-level pinning was discussed in light of the traditional and orbital mixing charge transfer theories. The impacts of the charge transfer mechanism on Fermi-level pinning were confirmed for the gas molecules adsorbed on monolayer WS2. The proposed mechanism governing Fermi-level pinning is applicable to the systems of adsorbates on recently developed two-dimensional materials, such as graphene and transition metal dichalcogenides.

Charge transfer properties of pentacene adsorbed on silver: DFT study

NASA Astrophysics Data System (ADS)

N, Rekha T.; Rajkumar, Beulah J. M.

2015-06-01

Charge transfer properties of pentacene adsorbed on silver is investigated using DFT methods. Optimized geometry of pentacene after adsorption on silver indicates distortion in hexagonal structure of the ring close to the silver cluster and deviations in co-planarity of carbon atoms due to the variations in bond angles and dihedral angles. Theoretically simulated absorption spectrum has a symmetric surface plasmon resonance peak around 486nm corresponding to the transfer of charge from HOMO-2 to LUMO. Theoretical SERS confirms the process of adsorption, tilted orientation of pentacene on silver surface and the charge transfers reported. Localization of electron density arising from redistribution of electrostatic potential together with a reduced bandgap of pentacene after adsorption on silver suggests its utility in the design of electro active organic semiconducting devices.

An experimental and numerical study of endwall heat transfer in a turbine blade cascade including tangential heat conduction analysis

NASA Astrophysics Data System (ADS)

Ratto, Luca; Satta, Francesca; Tanda, Giovanni

2018-06-01

This paper presents an experimental and numerical investigation of heat transfer in the endwall region of a large scale turbine cascade. The steady-state liquid crystal technique has been used to obtain the map of the heat transfer coefficient for a constant heat flux boundary condition. In the presence of two- and three-dimensional flows with significant spatial variations of the heat transfer coefficient, tangential heat conduction could lead to error in the heat transfer coefficient determination, since local heat fluxes at the wall-to-fluid interface tend to differ from point to point and surface temperatures to be smoothed out, thus making the uniform-heat-flux boundary condition difficult to be perfectly achieved. For this reason, numerical simulations of flow and heat transfer in the cascade including the effect of tangential heat conduction inside the endwall have been performed. The major objective of numerical simulations was to investigate the influence of wall heat conduction on the convective heat transfer coefficient determined during a nominal iso-flux heat transfer experiment and to interpret possible differences between numerical and experimental heat transfer results. Results were presented and discussed in terms of local Nusselt number and a convenient wall heat flux function for two values of the Reynolds number (270,000 and 960,000).

Femtochemistry of Intramolecular Charge and Proton Transfer Reactions in Solution

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

Douhal, Abderrazzak; Sanz, Mikel; Carranza, Maria Angeles

2005-03-17

We report on the first observation of ultrafast intramolecular charge- and proton-transfer reactions in 4'-dimethylaminoflavonol (DAMF) in solution. Upon femtosecond excitation of a non-planar structure of DMAF in apolar medium, the intramolecular charge transfer (ICT) does not occur, and a slow (2 ps) proton motion takes place. However, in polar solvents, the ICT is very fast (100-200 fs) and the produced structure is stabilized that proton motion takes place in few or tens of ps.

Azimuthally and radially excited charge transfer plasmon and Fano lineshapes in conductive sublayer-mediated nanoassemblies.

PubMed

Ahmadivand, Arash; Gerislioglu, Burak; Pala, Nezih

2017-11-01

Here, the plasmon responses of both symmetric and antisymmetric oligomers on a conductive substrate under linear, azimuthal, and radial polarization excitations are analyzed numerically. By observing charge transfer plasmons under cylindrical vector beam (CVB) illumination for what we believe is the first time, we show that our studies open new horizons to induce significant charge transfer plasmons and antisymmetric Fano resonance lineshapes in metallic substrate-mediated plasmonic nanoclusters under both azimuthal and radial excitation as CVBs.

DDT: participation in ultraviolet-detectable, charge-transfer complexation.

PubMed

Wilson, W E; Fishbein, L; Clements, S T

1971-01-15

The chlorophenyl groups of DDT and several of its metabolites are capable of participating in a charge-transfer interaction with tetracyanoethylene detectable in the ultraviolet region of the spectrum. In addition, during a change of state DDT undergoes ultraviolet spectral alterations that closely resemble those previously claimed to support the hypothesis suggesting charge-transfer interaction between this pesticide and a component of insect nerve tissue. The pesticide DDT possesses structural characteristics that would permit it to participate in several types of molecular association.

Coherence, Energy and Charge Transfers in De-Excitation Pathways of Electronic Excited State of Biomolecules in Photosynthesis

NASA Astrophysics Data System (ADS)

Bohr, Henrik G.; Malik, F. Bary

2013-11-01

The observed multiple de-excitation pathways of photo-absorbed electronic excited state in the peridinin-chlorophyll complex, involving both energy and charge transfers among its constituents, are analyzed using the bio-Auger (B-A) theory. It is also shown that the usually used Förster-Dexter theory, which does not allow for charge transfer, is a special case of B-A theory. The latter could, under appropriate circumstances, lead to excimers.

Synthesis and electrochemical studies of charge-transfer complexes of thiazolidine-2,4-dione with σ and π acceptors

NASA Astrophysics Data System (ADS)

Singh, Prashant; Kumar, Pradeep; Katyal, Anju; Kalra, Rashmi; Dass, Sujata K.; Prakash, Satya; Chandra, Ramesh

2010-03-01

In the present work, we report the synthesis and characterization of novel charge-transfer complexes of thiazolidine-2,4-dione (TZD) with sigma acceptor (iodine) and pi acceptors (chloranil, dichlorodicyanoquinone, picric acid and duraquinone). We also evaluated their thermal and electrochemical properties and we conclude that these complexes are frequency dependent. Charge-transfer complex between thiazolidine-2,4-dione and iodine give best conductivity. In conclusion, complex with sigma acceptors are more conducting than with pi acceptors.

Measurement techniques and applications of charge transfer to aerospace research

NASA Technical Reports Server (NTRS)

Smith, A.

1978-01-01

A technique of developing high-velocity low-intensity neutral gas beams for use in aerospace research problems is described. This technique involves ionization of gaseous species with a mass spectrometer and focusing the resulting primary ion beam into a collision chamber containing a static gas at a known pressure and temperature. Equations are given to show how charge-transfer cross sections are obtained from a total-current measurement technique. Important parameters are defined for the charge-transfer process.

CCD charge collection efficiency and the photon transfer technique

NASA Technical Reports Server (NTRS)

Janesick, J.; Klaasen, K.; Elliott, T.

1985-01-01

The charge-coupled device (CCD) has shown unprecendented performance as a photon detector in the areas of spectral response, charge transfer, and readout noise. Recent experience indicates, however, that the full potential for the CCD's charge collection efficiency (CCE) lies well beyond that which is realized in currently available devices. A definition of CCE performance is presented and a standard test tool (the photon transfer technique) for measuring and optimizing this important CCD parameter is introduced. CCE characteristics for different types of CCDs are compared; the primary limitations in achieving high CCE performance are discussed, and the prospects for future improvement are outlined.

Charge-transfer modified embedded atom method dynamic charge potential for Li-Co-O system

NASA Astrophysics Data System (ADS)

Kong, Fantai; Longo, Roberto C.; Liang, Chaoping; Nie, Yifan; Zheng, Yongping; Zhang, Chenxi; Cho, Kyeongjae

2017-11-01

To overcome the limitation of conventional fixed charge potential methods for the study of Li-ion battery cathode materials, a dynamic charge potential method, charge-transfer modified embedded atom method (CT-MEAM), has been developed and applied to the Li-Co-O ternary system. The accuracy of the potential has been tested and validated by reproducing a variety of structural and electrochemical properties of LiCoO2. A detailed analysis on the local charge distribution confirmed the capability of this potential for dynamic charge modeling. The transferability of the potential is also demonstrated by its reliability in describing Li-rich Li2CoO2 and Li-deficient LiCo2O4 compounds, including their phase stability, equilibrium volume, charge states and cathode voltages. These results demonstrate that the CT-MEAM dynamic charge potential could help to overcome the challenge of modeling complex ternary transition metal oxides. This work can promote molecular dynamics studies of Li ion cathode materials and other important transition metal oxides systems that involve complex electrochemical and catalytic reactions.

Charge-transfer modified embedded atom method dynamic charge potential for Li-Co-O system.

PubMed

Kong, Fantai; Longo, Roberto C; Liang, Chaoping; Nie, Yifan; Zheng, Yongping; Zhang, Chenxi; Cho, Kyeongjae

2017-11-29

To overcome the limitation of conventional fixed charge potential methods for the study of Li-ion battery cathode materials, a dynamic charge potential method, charge-transfer modified embedded atom method (CT-MEAM), has been developed and applied to the Li-Co-O ternary system. The accuracy of the potential has been tested and validated by reproducing a variety of structural and electrochemical properties of LiCoO 2 . A detailed analysis on the local charge distribution confirmed the capability of this potential for dynamic charge modeling. The transferability of the potential is also demonstrated by its reliability in describing Li-rich Li 2 CoO 2 and Li-deficient LiCo 2 O 4 compounds, including their phase stability, equilibrium volume, charge states and cathode voltages. These results demonstrate that the CT-MEAM dynamic charge potential could help to overcome the challenge of modeling complex ternary transition metal oxides. This work can promote molecular dynamics studies of Li ion cathode materials and other important transition metal oxides systems that involve complex electrochemical and catalytic reactions.

Aerodynamic Heating Computations for Projectiles. Volume 1. In-Depth Heat Conduction Modifications to the ABRES Shape Change Code (BRLASCC)

DTIC Science & Technology

1984-06-01

preceding the corresponding pressure group of the surface thermochemistry deck as described below. The temperature entries within each section must be... pressure group the transfer coefficient values will be ordered. Within each transfer coefficient section, ablation rate entries need not he ordered in any...may not exceed 5 (and may be only I); the number of transfer coefficient values in each pressure group may not exceed 5 but may be only 1. If no

A fluid-solid coupling simulation method for convection heat transfer coefficient considering the under-vehicle condition

NASA Astrophysics Data System (ADS)

Tian, C.; Weng, J.; Liu, Y.

2017-11-01

The convection heat transfer coefficient is one of the evaluation indexes of the brake disc performance. The method used in this paper to calculate the convection heat transfer coefficient is a fluid-solid coupling simulation method, because the calculation results through the empirical formula method have great differences. The model, including a brake disc, a car body, a bogie and flow field, was built, meshed and simulated in the software FLUENT. The calculation models were K-epsilon Standard model and Energy model. The working condition of the brake disc was considered. The coefficient of various parts can be obtained through the method in this paper. The simulation result shows that, under 160 km/h speed, the radiating ribs have the maximum convection heat transfer coefficient and the value is 129.6W/(m2·K), the average coefficient of the whole disc is 100.4W/(m2·K), the windward of ribs is positive-pressure area and the leeward of ribs is negative-pressure area, the maximum pressure is 2663.53Pa.

An Efficient Non-iterative Bulk Parametrization of Surface Fluxes for Stable Atmospheric Conditions Over Polar Sea-Ice

NASA Astrophysics Data System (ADS)

Gryanik, Vladimir M.; Lüpkes, Christof

2018-02-01

In climate and weather prediction models the near-surface turbulent fluxes of heat and momentum and related transfer coefficients are usually parametrized on the basis of Monin-Obukhov similarity theory (MOST). To avoid iteration, required for the numerical solution of the MOST equations, many models apply parametrizations of the transfer coefficients based on an approach relating these coefficients to the bulk Richardson number Rib. However, the parametrizations that are presently used in most climate models are valid only for weaker stability and larger surface roughnesses than those documented during the Surface Heat Budget of the Arctic Ocean campaign (SHEBA). The latter delivered a well-accepted set of turbulence data in the stable surface layer over polar sea-ice. Using stability functions based on the SHEBA data, we solve the MOST equations applying a new semi-analytic approach that results in transfer coefficients as a function of Rib and roughness lengths for momentum and heat. It is shown that the new coefficients reproduce the coefficients obtained by the numerical iterative method with a good accuracy in the most relevant range of stability and roughness lengths. For small Rib, the new bulk transfer coefficients are similar to the traditional coefficients, but for large Rib they are much smaller than currently used coefficients. Finally, a possible adjustment of the latter and the implementation of the new proposed parametrizations in models are discussed.

Long-lived, charge-shift states in heterometallic, porphyrin-based dendrimers formed via click chemistry.

PubMed

Le Pleux, Loïc; Pellegrin, Yann; Blart, Errol; Odobel, Fabrice; Harriman, Anthony

2011-05-26

A series of multiporphyrin clusters has been synthesized and characterized in which there exists a logical gradient for either energy or electron transfer between the porphyrins. A central free-base porphyrin (FbP), for example, is equipped with peripheral zinc(II) porphyrins (ZnP) which act as ancillary light harvesters and transfer excitation energy to the FbP under visible light illumination. Additional energy-transfer steps occur at the triplet level, and the series is expanded by including magnesium(II) porphyrins and/or tin(IV) porphyrins as chromophores. Light-induced electron transfer is made possible by incorporating a gold(III) porphyrin (AuP(+)) into the array. Although interesting by themselves, these clusters serve as control compounds by which to understand the photophysical processes occurring within a three-stage dendrimer comprising an AuP(+) core, a second layer formed from four FbP units, and an outer layer containing 12 ZnP residues. Here, illumination into a peripheral ZnP leads to highly efficient electronic energy transfer to FbP, followed by charge transfer to the central AuP(+). Charge recombination within the resultant charge-shift state is intercepted by secondary hole transfer to the ZnP, which occurs with a quantum yield of around 20%. The final charge-shift state survives for some microseconds in fluid solution at room temperature.

Synthesis, growth, structural modeling and physio-chemical properties of a charge transfer molecule: Guanidinium tosylate

NASA Astrophysics Data System (ADS)

Era, Paavai; Jauhar, RO. MU.; Vinitha, G.; Murugakoothan, P.

2018-05-01

An organic nonlinear optical material, guanidinium tosylate was synthesized adopting slow evaporation method and the crystals were harvested from aqueous methanolic medium with dimensions 13 × 9 × 3 mm3. Constitution of crystalline material was confirmed by single crystal X-ray diffraction study. The title compound crystallizes in the monoclinic crystal system with space group P21/c. The UV-vis-NIR spectral study of the grown crystal exhibits high transparency of 80% in the entire visible region with lower cut-off wavelength at 282 nm. Optimized molecular geometry of the grown crystal was obtained using density functional theory (DFT) and the frontier energy gaps calculated from the DFT aids to understand the charge transfer taking place in the molecule. The dielectric properties were studied as a function of temperature and frequency to find the charge distribution within the crystal. The titular compound is thermally stable up to 230 °C assessed by thermogravimetric and differential thermal analysis. Anisotropy in the mechanical behavior was observed while measuring for individual planes. The laser induced surface damage threshold of the grown crystal was measured to be 0.344 GW/cm2 for 1064 nm Nd:YAG laser radiation. Z-scan technique confirms the third-order nonlinear optical property with the ascertained nonlinear refractive index (n2), nonlinear absorption coefficient (β) and third order nonlinear susceptibility (χ(3)). Optical limiting study divulges that the transmitted output power step-up linearly with the increase of the input power at lower power realms and saturates from the threshold 24.95 mW/cm2 and amplitude 0.23 mW/cm2.

In situ electrochemical investigations of the kinetic and thermodynamic properties of nickel-metal hydride traction batteries

NASA Astrophysics Data System (ADS)

Yang, Xiao Guang; Liaw, Bor Yann

Although large ampere hour nickel-metal hydride (Ni-MH) traction batteries are in the stage of being commercialized for electric and hybrid vehicle applications, little is known about their performance characteristics. By using a standard Hg/HgO reference electrode in a commercial Ni-MH battery, we were able to conduct in situ measurements to determine both kinetic and thermodynamic properties of the system, including the characteristics of individual electrodes. Using the galvanostatic intermittent titration technique (GITT), we simultaneously and effectively determined the open-circuit voltage of the battery, the equilibrium electrode potentials, and the diffusion coefficient of proton and hydrogen in the nickel and metal hydride electrode, respectively, as a function of the states of charge (SOC). Using the current-step excitation technique, we found that the internal resistance of the battery primarily comes from the metal hydride electrode, which is greater by one order of magnitude than that of the Ni electrode. The cyclic linear micro-polarization experiments, on the other hand, showed that the charge-transfer resistance of the electrochemical reaction at the metal hydride electrode is about twice larger than that of the Ni counterpart above 20% SOC. In comparison, the internal resistance is an order of magnitude smaller than those of the electrochemical charge-transfer reactions. The micro-polarization technique also allowed us to calculate the exchange current densities of the respective electrode electrochemical reactions and the associated specific exchange current densities. These in situ, simple but detailed, characterizations of the thermodynamic and kinetic properties of the Ni-MH system provided valuable information for better understanding of the battery performance.

Coupled sensitizer-catalyst dyads: electron-transfer reactions in a perylene-polyoxometalate conjugate.

PubMed

Odobel, Fabrice; Séverac, Marjorie; Pellegrin, Yann; Blart, Errol; Fosse, Céline; Cannizzo, Caroline; Mayer, Cédric R; Elliott, Kristopher J; Harriman, Anthony

2009-01-01

Ultrafast discharge of a single-electron capacitor: A variety of intramolecular electron-transfer reactions are apparent for polyoxometalates functionalized with covalently attached perylene monoimide chromophores, but these are restricted to single-electron events. (et=electron transfer, cr=charge recombination, csr=charge-shift reaction, PER=perylene, POM=polyoxometalate).A new strategy is introduced that permits covalent attachment of an organic chromophore to a polyoxometalate (POM) cluster. Two examples are reported that differ according to the nature of the anchoring group and the flexibility of the linker. Both POMs are functionalized with perylene monoimide units, which function as photon collectors and form a relatively long-lived charge-transfer state under illumination. They are reduced to a stable pi-radical anion by electrolysis or to a protonated dianion under photolysis in the presence of aqueous triethanolamine. The presence of the POM opens up an intramolecular electron-transfer route by which the charge-transfer state reduces the POM. The rate of this process depends on the molecular conformation and appears to involve through-space interactions. Prior reduction of the POM leads to efficient fluorescence quenching, again due to intramolecular electron transfer. In most cases, it is difficult to resolve the electron-transfer products because of relatively fast reverse charge shift that occurs within a closed conformer. Although the POM can store multiple electrons, it has not proved possible to use these systems as molecular-scale capacitors because of efficient electron transfer from the one-electron-reduced POM to the excited singlet state of the perylene monoimide.

CFD simulation of simultaneous monotonic cooling and surface heat transfer coefficient

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

Mihálka, Peter, E-mail: usarmipe@savba.sk; Matiašovský, Peter, E-mail: usarmat@savba.sk

The monotonic heating regime method for determination of thermal diffusivity is based on the analysis of an unsteady-state (stabilised) thermal process characterised by an independence of the space-time temperature distribution on initial conditions. At the first kind of the monotonic regime a sample of simple geometry is heated / cooled at constant ambient temperature. The determination of thermal diffusivity requires the determination rate of a temperature change and simultaneous determination of the first eigenvalue. According to a characteristic equation the first eigenvalue is a function of the Biot number defined by a surface heat transfer coefficient and thermal conductivity ofmore » an analysed material. Knowing the surface heat transfer coefficient and the first eigenvalue the thermal conductivity can be determined. The surface heat transport coefficient during the monotonic regime can be determined by the continuous measurement of long-wave radiation heat flow and the photoelectric measurement of the air refractive index gradient in a boundary layer. CFD simulation of the cooling process was carried out to analyse local convective and radiative heat transfer coefficients more in detail. Influence of ambient air flow was analysed. The obtained eigenvalues and corresponding surface heat transfer coefficient values enable to determine thermal conductivity of the analysed specimen together with its thermal diffusivity during a monotonic heating regime.« less

Organic solar cells: understanding the role of Förster resonance energy transfer.

PubMed

Feron, Krishna; Belcher, Warwick J; Fell, Christopher J; Dastoor, Paul C

2012-12-12

Organic solar cells have the potential to become a low-cost sustainable energy source. Understanding the photoconversion mechanism is key to the design of efficient organic solar cells. In this review, we discuss the processes involved in the photo-electron conversion mechanism, which may be subdivided into exciton harvesting, exciton transport, exciton dissociation, charge transport and extraction stages. In particular, we focus on the role of energy transfer as described by F¨orster resonance energy transfer (FRET) theory in the photoconversion mechanism. FRET plays a major role in exciton transport, harvesting and dissociation. The spectral absorption range of organic solar cells may be extended using sensitizers that efficiently transfer absorbed energy to the photoactive materials. The limitations of F¨orster theory to accurately calculate energy transfer rates are discussed. Energy transfer is the first step of an efficient two-step exciton dissociation process and may also be used to preferentially transport excitons to the heterointerface, where efficient exciton dissociation may occur. However, FRET also competes with charge transfer at the heterointerface turning it in a potential loss mechanism. An energy cascade comprising both energy transfer and charge transfer may aid in separating charges and is briefly discussed. Considering the extent to which the photo-electron conversion efficiency is governed by energy transfer, optimisation of this process offers the prospect of improved organic photovoltaic performance and thus aids in realising the potential of organic solar cells.

The augmentation of heat transfer in a pipe flow using a swirling perforated twisted (SPT) tape insert

NASA Astrophysics Data System (ADS)

Ahmad, Shahrokh; Oishe, Sadia Noon; Rahman, Md. Lutfor

2017-12-01

The purpose of this research work is to increase the heat transfer coefficient by operating the heat exchangers at smaller revolution per minute. This signifies an achievement of reduction of pressure drop corresponding to less operating cost. This study has used two types of SPT tape insert to observe the various heat transfer coefficient, heat transfer rate and heat transfer augmentation efficiency. One tape was fully twisted and another tape was partially twisted. The shape of the SPT tape creates turbulence effect. The turbulence flow (swirl flow) generated by SPT tape promotes greater mixing and high heat transfer coefficients. An arrangement scheme has been developed for the experimental investigation. For remarking the rate of change of heat transfer, temperature has been measured numerically through the temperature sensors with various flow rates and RPM. The volume flow rate was varied from 10.3448276 LPM to 21.045574 LPM and the rotation of the perforated twisted tape was varied from 50 RPM to 400 RPM. Finally the research study demonstrates the effectiveness of the results of the proposed approaches. It is observed that the suggested method of heat transfer augmentations is much more effective than existing methods, since it results in an increase in heat transfer area and also an increase in the heat transfer coefficient and reduction of cost in the industrial sectors.

The influence of a wall function on turbine blade heat transfer prediction

NASA Technical Reports Server (NTRS)

Whitaker, Kevin W.

1989-01-01

The second phase of a continuing investigation to improve the prediction of turbine blade heat transfer coefficients was completed. The present study specifically investigated how a numeric wall function in the turbulence model of a two-dimensional boundary layer code, STAN5, affected heat transfer prediction capabilities. Several sources of inaccuracy in the wall function were identified and then corrected or improved. Heat transfer coefficient predictions were then obtained using each one of the modifications to determine its effect. Results indicated that the modifications made to the wall function can significantly affect the prediction of heat transfer coefficients on turbine blades. The improvement in accuracy due the modifications is still inconclusive and is still being investigated.

Charged Substrate and Product Together Contribute Like a Nonreactive Species to the Overall Electrostatic Steering in Diffusion-Reaction Processes.

PubMed

Xu, Jingjie; Xie, Yan; Lu, Benzhuo; Zhang, Linbo

2016-08-25

The Debye-Hückel limiting law is used to study the binding kinetics of substrate-enzyme system as well as to estimate the reaction rate of a electrostatically steered diffusion-controlled reaction process. It is based on a linearized Poisson-Boltzmann model and known for its accurate predictions in dilute solutions. However, the substrate and product particles are in nonequilibrium states and are possibly charged, and their contributions to the total electrostatic field cannot be explicitly studied in the Poisson-Boltzmann model. Hence the influences of substrate and product on reaction rate coefficient were not known. In this work, we consider all the charged species, including the charged substrate, product, and mobile salt ions in a Poisson-Nernst-Planck model, and then compare the results with previous work. The results indicate that both the charged substrate and product can significantly influence the reaction rate coefficient with different behaviors under different setups of computational conditions. It is interesting to find that when substrate and product are both considered, under an overall neutral boundary condition for all the bulk charged species, the computed reaction rate kinetics recovers a similar Debye-Hückel limiting law again. This phenomenon implies that the charged product counteracts the influence of charged substrate on reaction rate coefficient. Our analysis discloses the fact that the total charge concentration of substrate and product, though in a nonequilibrium state individually, obeys an equilibrium Boltzmann distribution, and therefore contributes as a normal charged ion species to ionic strength. This explains why the Debye-Hückel limiting law still works in a considerable range of conditions even though the effects of charged substrate and product particles are not specifically and explicitly considered in the theory.

Theoretical study on naphthobischalcogenadiazole conjugated polymer systems and C61 derivative as organic photovoltaic semiconductors

NASA Astrophysics Data System (ADS)

Fujita, Takehiro; Matsui, Toru; Sumita, Masato; Imamura, Yutaka; Morihashi, Kenji

2018-02-01

We investigated the charge-transfer reactions of solar cells including a quaterthiophene copolymer with naphtho-bis-thiadiazole (PNTz4T) and naphtho-bis-oxadiazole (PNOz4T) using constrained density functional theory (CDFT). According to our calculations, the high electron-transfer rate results in a highly efficient solar cell, and the stable charge-transfer state results in low energy loss. Our computations imply that the following three factors are crucial to improve the performance of semiconducting polymers: (i) large structural changes following charge-transfer, (ii) narrow band gap, and (iii) spatially delocalized lowest unoccupied molecular orbital (LUMO) of the ground state.

Heat Transfer Computations of Internal Duct Flows With Combined Hydraulic and Thermal Developing Length

NASA Technical Reports Server (NTRS)

Wang, C. R.; Towne, C. E.; Hippensteele, S. A.; Poinsatte, P. E.

1997-01-01

This study investigated the Navier-Stokes computations of the surface heat transfer coefficients of a transition duct flow. A transition duct from an axisymmetric cross section to a non-axisymmetric cross section, is usually used to connect the turbine exit to the nozzle. As the gas turbine inlet temperature increases, the transition duct is subjected to the high temperature at the gas turbine exit. The transition duct flow has combined development of hydraulic and thermal entry length. The design of the transition duct required accurate surface heat transfer coefficients. The Navier-Stokes computational method could be used to predict the surface heat transfer coefficients of a transition duct flow. The Proteus three-dimensional Navier-Stokes numerical computational code was used in this study. The code was first studied for the computations of the turbulent developing flow properties within a circular duct and a square duct. The code was then used to compute the turbulent flow properties of a transition duct flow. The computational results of the surface pressure, the skin friction factor, and the surface heat transfer coefficient were described and compared with their values obtained from theoretical analyses or experiments. The comparison showed that the Navier-Stokes computation could predict approximately the surface heat transfer coefficients of a transition duct flow.

Three-dimensional nonsteady heat-transfer analysis of an indirect heating furnace

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

Ito, H.; Umeda, Y.; Nakamura, Y.

1991-01-01

This paper reports on an accurate design method for industrial furnaces from the viewpoint of heat transfer. The authors carried out a three-dimensional nonsteady heat-transfer analysis for a practical-size heat- treatment furnace equipped with radiant heaters. The authors applied three software package programs, STREAM, MORSE, and TRUMP, for the analysis of the combined heat-transfer problems of radiation, conduction, and convection. The authors also carried out experiments of the heating of a charge consisting of packed bolts. The authors found that the air swirled inside the furnace. As for the temperature in each part in the furnace, analytical results were generallymore » in close agreement with the experimental ones. This suggests that our analytical method is useful for a fundamental heat- transfer-based design of a practical-size industrial furnace with an actual charge such as packed bolts. As for the temperature distribution inside the bolt charge (work), the analytical results were also in close agreement with the experimental ones. Consequently, it was found that the heat transfer in the bolt charge could be described with an effective thermal conductivity.« less

Communication: Charge transfer dominates over proton transfer in the reaction of nitric acid with gas-phase hydrated electrons

NASA Astrophysics Data System (ADS)

Lengyel, Jozef; Med, Jakub; Slavíček, Petr; Beyer, Martin K.

2017-09-01

The reaction of HNO3 with hydrated electrons (H2O)n- (n = 35-65) in the gas phase was studied using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and ab initio molecular dynamics simulations. Kinetic analysis of the experimental data shows that OH-(H2O)m is formed primarily via a reaction of the hydrated electron with HNO3 inside the cluster, while proton transfer is not observed and NO3-(H2O)m is just a secondary product. The reaction enthalpy was determined using nanocalorimetry, revealing a quite exothermic charge transfer with -241 ± 69 kJ mol-1. Ab initio molecular dynamics simulations indicate that proton transfer is an allowed reaction pathway, but the overall thermochemistry favors charge transfer.

Fundamentals of Radiation Dosimetry

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

Bos, Adrie J. J.

The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and indicated is how they are related to the mass energy transfer and mass energy absorption coefficients. Definitions of total and restricted mass stopping powers of directly ionizing radiation are given. The dosimetric quantities, kerma, absorbed dose and exposure together with the relations between them are discussed in depth. Finally it is indicated how the absorbed dose can be measured with a calorimeter by measuringmore » the temperature increase and with an ionisation chamber measuring the charge produced by the ionizing radiation and making use of the Bragg-Gray relation.« less

Electron transport in doped fullerene molecular junctions

NASA Astrophysics Data System (ADS)

Kaur, Milanpreet; Sawhney, Ravinder Singh; Engles, Derick

The effect of doping on the electron transport of molecular junctions is analyzed in this paper. The doped fullerene molecules are stringed to two semi-infinite gold electrodes and analyzed at equilibrium and nonequilibrium conditions of these device configurations. The contemplation is done using nonequilibrium Green’s function (NEGF)-density functional theory (DFT) to evaluate its density of states (DOS), transmission coefficient, molecular orbitals, electron density, charge transfer, current, and conductance. We conclude from the elucidated results that Au-C16Li4-Au and Au-C16Ne4-Au devices behave as an ordinary p-n junction diode and a Zener diode, respectively. Moreover, these doped fullerene molecules do not lose their metallic nature when sandwiched between the pair of gold electrodes.

Study on fluorescence characteristics of duloxetine hydrochloride

NASA Astrophysics Data System (ADS)

Liu, Xiangping; Du, Yingxiang; Wu, Xiulan

2008-12-01

The fluorescence characteristics of duloxetine hydrochloride are studied in this paper. The fluorescence emission spectra of duloxetine demonstrate that intramolecular charge-transfer takes place between thiophene ring and napthalenyloxy group upon irradiation. The effects of excitation light, solvent system, variation of solution pH value, metal ions and vitamin C on the fluorescence spectra of duloxetine hydrochloride are elucidated, respectively. A spectrofluorometric method of quantitative determination of duloxetine in dosage form is reported for the first time, the linear range is 7.14 × 10 -8 mol/L to 1.43 × 10 -5 mol/L, the linear correlation coefficient r is equal to 0.9997, and the detection limit is 3.5 × 10 -8 mol/L. The accuracy and the precision are satisfactory.

Electrokinetic and hydrodynamic properties of charged-particles systems. From small electrolyte ions to large colloids

NASA Astrophysics Data System (ADS)

Nägele, G.; Heinen, M.; Banchio, A. J.; Contreras-Aburto, C.

2013-11-01

Dynamic processes in dispersions of charged spherical particles are of importance both in fundamental science, and in technical and bio-medical applications. There exists a large variety of charged-particles systems, ranging from nanometer-sized electrolyte ions to micron-sized charge-stabilized colloids. We review recent advances in theoretical methods for the calculation of linear transport coefficients in concentrated particulate systems, with the focus on hydrodynamic interactions and electrokinetic effects. Considered transport properties are the dispersion viscosity, self- and collective diffusion coefficients, sedimentation coefficients, and electrophoretic mobilities and conductivities of ionic particle species in an external electric field. Advances by our group are also discussed, including a novel mode-coupling-theory method for conduction-diffusion and viscoelastic properties of strong electrolyte solutions. Furthermore, results are presented for dispersions of solvent-permeable particles, and particles with non-zero hydrodynamic surface slip. The concentration-dependent swelling of ionic microgels is discussed, as well as a far-reaching dynamic scaling behavior relating colloidal long- to short-time dynamics.

Thermal energy and charge currents in multi-terminal nanorings

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

Kramer, Tobias; Konrad-Zuse-Zentrum für Informationstechnik Berlin, 14195 Berlin; Kreisbeck, Christoph

2016-06-15

We study in experiment and theory thermal energy and charge transfer close to the quantum limit in a ballistic nanodevice, consisting of multiply connected one-dimensional electron waveguides. The fabricated device is based on an AlGaAs/GaAs heterostructure and is covered by a global top-gate to steer the thermal energy and charge transfer in the presence of a temperature gradient, which is established by a heating current. The estimate of the heat transfer by means of thermal noise measurements shows the device acting as a switch for charge and thermal energy transfer. The wave-packet simulations are based on the multi-terminal Landauer-Büttiker approachmore » and confirm the experimental finding of a mode-dependent redistribution of the thermal energy current, if a scatterer breaks the device symmetry.« less

Absorption spectrometric study of charge transfer complex formation between 4-acetamidophenol (paracetamol) and a series of quinones including Vitamin K 3

NASA Astrophysics Data System (ADS)

Saha, Avijit; Mukherjee, Asok K.

2004-07-01

The formation of charge transfer (CT) complexes of 4-acetamidophenol (commonly called 'paracetamol') and a series of quinones (including Vitamin K 3) has been studied spectrophotometrically in ethanol medium. The vertical ionisation potential of paracetamol and the degrees of charge transfer of the complexes in their ground state has been estimated from the trends in the charge transfer bands. The oscillator and transition dipole strengths of the complexes have been determined from the CT absorption spectra at 298 K. The complexes have been found by Job's method of continuous variation to have the uncommon 2:1 (paracetamol:quinone) stoichiometry in each case. The enthalpies and entropies of formation of the complexes have been obtained by determining their formation constants at five different temperatures.

Probe-based measurement of lateral single-electron transfer between individual molecules

PubMed Central

Steurer, Wolfram; Fatayer, Shadi; Gross, Leo; Meyer, Gerhard

2015-01-01

The field of molecular electronics aims at using single molecules as functional building blocks for electronics components, such as switches, rectifiers or transistors. A key challenge is to perform measurements with atomistic control over the alignment of the molecule and its contacting electrodes. Here we use atomic force microscopy to examine charge transfer between weakly coupled pentacene molecules on insulating films with single-electron sensitivity and control over the atomistic details. We show that, in addition to the imaging capability, the probe tip can be used to control the charge state of individual molecules and to detect charge transfers to/from the tip, as well as between individual molecules. Our approach represents a novel route for molecular charge transfer studies with a host of opportunities, especially in combination with single atom/molecule manipulation and nanopatterning techniques. PMID:26387533

Preparation and spectroscopic studies on charge-transfer complexes of 2,2'-bipyridine with picric and chloranilic acids

NASA Astrophysics Data System (ADS)

Teleb, Said M.; Gaballa, Akmal S.

2005-11-01

Charge-transfer (CT) complexes formed on the reaction of 2,2'-bipyridine with some acceptors such as picric acid (HPA) and chloranilic acid (H 2CA) have been studied in CHCl 3 and MeOH at room temperature. Based on elemental analysis and IR spectra of the solid CT complexes along with the photometric titration curves for the reactions, the data obtained indicate the formation of 1:1 charge-transfer complexes [(bpyH)(PA)] and [(bpyH 2)(CA)], respectively. The infrared and 1H NMR spectroscopic data indicate a charge-transfer interaction associated with a proton migration from the acceptor to the donor followed by intramolecular hydrogen bonding. The formation constants ( KC) for the complexes were shown to be dependent on the structure of the electron acceptors used.

Preparation and spectroscopic studies on charge-transfer complexes of 2,2'-bipyridine with picric and chloranilic acids.

PubMed

Teleb, Said M; Gaballa, Akmal S

2005-11-01

Charge-transfer (CT) complexes formed on the reaction of 2,2'-bipyridine with some acceptors such as picric acid (HPA) and chloranilic acid (H(2)CA) have been studied in CHCl(3) and MeOH at room temperature. Based on elemental analysis and IR spectra of the solid CT complexes along with the photometric titration curves for the reactions, the data obtained indicate the formation of 1:1 charge-transfer complexes [(bpyH)(PA)] and [(bpyH(2))(CA)], respectively. The infrared and (1)H NMR spectroscopic data indicate a charge-transfer interaction associated with a proton migration from the acceptor to the donor followed by intramolecular hydrogen bonding. The formation constants (K(C)) for the complexes were shown to be dependent on the structure of the electron acceptors used.

Hydrodynamics and Heat Transfer in the Case of Combined Flow in a Annular Channel of Small Cross Section

NASA Astrophysics Data System (ADS)

Komov, A. T.; Varava, A. N.; Dedov, A. V.; Zakharenkov, A. V.; Boltenko, É. A.

2017-01-01

The present work is a continuation of experimental investigations conducted at the Moscow Power Engineering Institute (MPEI) on heat-transfer intensification. Brief descriptions of the working section and structure of intensifiers are given and their basic geometric parameters are enumerated. New systematized experimental data on the coefficients of hydraulic resistance and heat transfer in the regime of single-phase convection are given in an extended range of regime parameters and geometric characteristics of the intensifiers. Considerable increase in the heat-transfer coefficient as a function of the geometric characteristics of the intensifier has been established experimentally. The values of the relative fin height, at which these are the maxima of heat transfer and hydraulic resistance, have been established. Calculated dependences for the coefficient of hydraulic resistance and heat transfer have been obtained.

Influence of metal bonding layer on strain transfer performance of FBG

NASA Astrophysics Data System (ADS)

Liu, Hao; Chen, Weimin; Zhang, Peng; Liu, Li; Shu, Yuejie; Wu, Jun

2013-01-01

Metal bonding layer seriously affects the strain transfer performance of Fiber Bragg Grating (FBG). Based on the mode of FBG strain transfer, the influence of the length, the thickness, Poisson's ratio, elasticity modulus of metal bonding layer on the strain transfer coefficient of FBG is analyzed by numerical simulation. FBG is packaged to steel wire using metal bonding technology of FBG. The tensile tests of different bonding lengths and elasticity modulus are carried out. The result shows the strain transfer coefficient of FBGs are 0.9848,0.962 and their average strain sensitivities are 1.076 pm/μɛ,1.099 pm/μɛ when the metal bonding layer is zinc, whose lengths are 15mm, 20mm, respectively. The strain transfer coefficient of FBG packaged by metal bonding layer raises 8.9 percent compared to epoxy glue package. The preliminary experimental results show that the strain transfer coefficient increases with the length of metal bonding layer, decreases with the thickness of metal bonding layer and the influence of Poisson's ratio can be ignored. The experiment result is general agreement with the analysis and provides guidance for metal package of FBG.

Concentration Dependence of Pool Nucleate Boiling Heat Transfer Coefficients for R134a and Polyolester Oil System

NASA Astrophysics Data System (ADS)

Sato, Tomoaki; Takaishi, Yoshinori; Oguchi, Kosei

This paper presents experimental results of the concentration dependence of heat transfer coefficients for mixtures of R134a and polyolester (POE) oil under the conditions of pool nuc1eateboiling. The experiments are conducted by means of ah horizontal platinum wire at saturation tel11peraturesof 9, 19, and 29°C and at oil concentrations from 0 to 8 mass%. The present results show that the boiling heat transfer coefficient for the system concerned decreases with increasing oil concentration as a whole but increases slightly at a low oil concentration of about 4 mass%. A correlation equation is also given as a function of heat flux, temperature and oil concentration to reproduce the experimental boiling heat transfer coefficient within an uncertainly of about±15%.

Reduction of benzene and naphthalene mass transfer from crude oils by aging-induced interfacial films.

PubMed

Ghoshal, Subhasis; Pasion, Catherine; Alshafie, Mohammed

2004-04-01

Semi-rigid films or skins form at the interface of crude oil and water as a result of the accumulation of asphaltene and resin fractions when the water-immiscible crude oil is contacted with water for a period of time or "aged". The time varying patterns of area-independent mass transfer coefficients of two compounds, benzene and naphthalene, for dissolution from crude oil and gasoline were determined. Aqueous concentrations of the compounds were measured in the eluent from flow-through reactors, where a nondispersed oil phase and constant oil-water interfacial area were maintained. For Brent Blend crude oil and for gasoline amended with asphaltenes and resins, a rapid decrease in both benzene and naphthalene mass transfer coefficients over the first few days of aging was observed. The mass transfer coefficients of the two target solutes were reduced by up to 80% over 35 d although the equilibrium partition coefficients were unchanged. Aging of gasoline, which has negligible amounts of asphaltene and resin, did not result in a change in the solute mass transfer coefficients. The study demonstrates that formation of crude oil-water interfacial films comprised of asphaltenes and resins contribute to time-dependent decreases in rates of release of environmentally relevant solutes from crude oils and may contribute to the persistence of such solutes at crude oil-contaminated sites. It is estimated that the interfacial film has an extremely low film mass transfer coefficient in the range of 10(-6) cm/min.

Experimental determination of surface heat transfer coefficient in a dry ice-ethanol cooling bath using a numerical approach.

PubMed

Santos, M V; Sansinena, M; Zaritzky, N; Chirife, J

BACKGROUND: Dry ice-ethanol bath (-78 degree C) have been widely used in low temperature biological research to attain rapid cooling of samples below freezing temperature. The prediction of cooling rates of biological samples immersed in dry ice-ethanol bath is of practical interest in cryopreservation. The cooling rate can be obtained using mathematical models representing the heat conduction equation in transient state. Additionally, at the solid cryogenic-fluid interface, the knowledge of the surface heat transfer coefficient (h) is necessary for the convective boundary condition in order to correctly establish the mathematical problem. The study was to apply numerical modeling to obtain the surface heat transfer coefficient of a dry ice-ethanol bath. A numerical finite element solution of heat conduction equation was used to obtain surface heat transfer coefficients from measured temperatures at the center of polytetrafluoroethylene and polymethylmetacrylate cylinders immersed in a dry ice-ethanol cooling bath. The numerical model considered the temperature dependence of thermophysical properties of plastic materials used. A negative linear relationship is observed between cylinder diameter and heat transfer coefficient in the liquid bath, the calculated h values were 308, 135 and 62.5 W/(m 2 K) for PMMA 1.3, PTFE 2.59 and 3.14 cm in diameter, respectively. The calculated heat transfer coefficients were consistent among several replicates; h in dry ice-ethanol showed an inverse relationship with cylinder diameter.

Impact of improved momentum transfer coefficients on the dynamics and thermodynamics of the north Indian Ocean

NASA Astrophysics Data System (ADS)

Parekh, Anant; Gnanaseelan, C.; Jayakumar, A.

2011-01-01

Long time series of in situ observations from the north Indian Ocean are used to compute the momentum transfer coefficients over the north Indian Ocean. The transfer coefficients behave nonlinearly for low winds (<4 m/s), when most of the known empirical relations assume linear relations. Impact of momentum transfer coefficients on the upper ocean parameters is studied using an ocean general circulation model. The model experiments revealed that the Arabian Sea and Equatorial Indian Ocean are more sensitive to the momentum transfer coefficients than the Bay of Bengal and south Indian Ocean. The impact of momentum transfer coefficients on sea surface temperature is up to 0.3°C-0.4°C, on mixed layer depth is up to 10 m, and on thermocline depth is up to 15 m. Furthermore, the impact on the zonal current is maximum over the equatorial Indian Ocean (i.e., about 0.12 m/s in May and 0.15 m/s in October; both May and October are the period of Wyrtki jets and the difference in current has potential impact on the seasonal mass transport). The Sverdrup transport has maximum impact in the Bay of Bengal (3 to 4 Sv in August), whereas the Ekman transport has maximum impact in the Arabian Sea (4 Sv during May to July). These highlight the potential impact of accurate momentum forcing on the results from current ocean models.

Energy gap law of electron transfer in nonpolar solvents.

PubMed

Tachiya, M; Seki, Kazuhiko

2007-09-27

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

The Role of FRET in Non-Fullerene Organic Solar Cells: Implications for Molecular Design.

PubMed

Gautam, Bhoj R; Younts, Robert; Carpenter, Joshua; Ade, Harald; Gundogdu, Kenan

2018-04-19

Non-fullerene acceptors (NFAs) have been demonstrated to be promising candidates for highly efficient organic photovoltaic (OPV) devices. The tunability of absorption characteristics of NFAs can be used to make OPVs with complementary donor-acceptor absorption to cover a broad range of the solar spectrum. However, both charge transfer from donor to acceptor moieties and energy (energy) transfer from high-bandgap to low-bandgap materials are possible in such structures. Here, we show that when charge transfer and exciton transfer processes are both present, the coexistence of excitons in both domains can cause a loss mechanism. Charge separation of excitons in a low-bandgap material is hindered due to exciton population in the larger bandgap acceptor domains. Our results further show that excitons in low-bandgap material should have a relatively long lifetime compared to the transfer time of excitons from higher bandgap material in order to contribute to the charge separation. These observations provide significant guidance for design and development of new materials in OPV applications.

Temperature Coefficient for Modeling Denitrification in Surface Water Sediments Using the Mass Transfer Coefficient

Treesearch

T. W. Appelboom; G. M. Chescheir; R. W. Skaggs; J. W. Gilliam; Devendra M. Amatya

2006-01-01

Watershed modeling has become an important tool for researchers with the high costs of water quality monitoring. When modeling nitrate transport within drainage networks, denitrification within the sediments needs to be accounted for. Birgand et. al. developed an equation using a term called a mass transfer coefficient to mathematically describe sediment...

Temperature coefficient for modeling denitrification in surface water sediments using the mass transfer coefficient

Treesearch

T.W. Appelboom; G.M. Chescheir; F. Birgand; R.W. Skaggs; J.W. Gilliam; D. Amatya

2010-01-01

Watershed modeling has become an important tool for researchers. Modeling nitrate transport within drainage networks requires quantifying the denitrification within the sediments in canals and streams. In a previous study, several of the authors developed an equation using a term called a mass transfer coefficient to mathematically describe sediment denitrification....

Temperature coefficient for modeling denitrification in surface water sediments using the mass transfer coefficient.

Treesearch

T.W. Appelboom; G.M. Chescheir; F. Birgand; R.W. Skaggs; J.W. Gilliam; D. Amatya

2010-01-01

Watershed modeling has become an important tool for researchers. Modeling nitrate transport within drainage networks requires quantifying the denitrification within the sediments in canals and streams. In a previous study, several of the authors developed an equation using a term called a mass transfer coefficient to mathematically describe sediment denitrification....

Heat Transfer Measurements on Surfaces with Natural Ice Castings and Modeled Roughness

NASA Technical Reports Server (NTRS)

Breuer, Kenneth S.; Torres, Benjamin E.; Orr, D. J.; Hansman, R. John

1997-01-01

An experimental method is described to measure and compare the convective heat transfer coefficient of natural and simulated ice accretion roughness and to provide a rational means for determining accretion-related enhanced heat transfer coefficients. The natural ice accretion roughness was a sample casting made from accretions at the NASA Lewis Icing Research Tunnel (IRT). One of these castings was modeled using a Spectral Estimation Technique (SET) to produce three roughness elements patterns that simulate the actual accretion. All four samples were tested in a flat-plate boundary layer at angle of attack in a "dry" wind tunnel test. The convective heat transfer coefficient was measured using infrared thermography. It is shown that, dispite some problems in the current data set, the method does show considerable promise in determining roughness-induced heat transfer coefficients, and that, in addition to the roughness height and spacing in the flow direction, the concentration and spacing of elements in the spanwise direction are important parameters.

Local heat-transfer measurements on a large, scale-model turbine blade airfoil using a composite of a heater element and liquid crystals

NASA Technical Reports Server (NTRS)

Hippensteele, S. A.; Russell, L. M.; Torres, F. J.

1985-01-01

Local heat transfer coefficients were experimentally mapped along the midchord of a five-time-size turbine blade airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a mylar sheet with a layer of cholesteric liquid crystals, that change color with temperature, and a heater sheet made of a carbon-impregnated paper, that produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. The local heat transfer coefficients are presented for Reynolds numbers from 2.8 x 10 to the 5th power to 7.6 x 10 to the 5th power. Comparisons are made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code. Also, a leading edge separation bubble was revealed by thermal and flow visualization.

Heat transfer to horizontal tubes in a pilot-scale fluidized-bed combustor burning low-rank coals

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

Grewal, N.S.; Goblirsch, G.

Experimental data are obtained for the heat transfer coefficient between immersed horizontal tube bundles and an atmospheric-fluidized-bed combustor burning low-rank coals. Silica sand (d/sub p/ = 888 to 1484 ..mu..m) and limestone (d/sub p/ = 716 to 1895 ..mu..m) are used as bed material. The tests are conducted, with and without limestone addition and ash recycle, at average bed temperatures ranging from 1047 to 1125/sup 0/K, superficial fluidizing velocity of 1.66 to 2.04 m/s, and excess air levels of 15 to 40 percent. The experimental data are examined in the light of the existing correlations for the heat transfer coefficient.more » The predicted values of heat transfer coefficient from the correlations proposed by Grewal (1981) and Bansal et al. (1980) are found to be within +-25 percent of the experimental values of heat transfer coefficient, when the contribution due to radiation is also included. 5 figures, 5 tables.« less

Integration Of Heat Transfer Coefficient In Glass Forming Modeling With Special Interface Element

NASA Astrophysics Data System (ADS)

Moreau, P.; César de Sá, J.; Grégoire, S.; Lochegnies, D.

2007-05-01

Numerical modeling of the glass forming processes requires the accurate knowledge of the heat exchange between the glass and the forming tools. A laboratory testing is developed to determine the evolution of the heat transfer coefficient in different glass/mould contact conditions (contact pressure, temperature, lubrication…). In this paper, trials are performed to determine heat transfer coefficient evolutions in experimental conditions close to the industrial blow-and-blow process conditions. In parallel of this work, a special interface element is implemented in a commercial Finite Element code in order to deal with heat transfer between glass and mould for non-meshing meshes and evolutive contact. This special interface element, implemented by using user subroutines, permits to introduce the previous heat transfer coefficient evolutions in the numerical modelings at the glass/mould interface in function of the local temperatures, contact pressures, contact time and kind of lubrication. The blow-and-blow forming simulation of a perfume bottle is finally performed to assess the special interface element performance.

Evaluation of Computational Fluid Dynamics and Coupled Fluid-Solid Modeling for a Direct Transfer Preswirl System.

PubMed

Javiya, Umesh; Chew, John; Hills, Nick; Dullenkopf, Klaus; Scanlon, Timothy

2013-05-01

The prediction of the preswirl cooling air delivery and disk metal temperature are important for the cooling system performance and the rotor disk thermal stresses and life assessment. In this paper, standalone 3D steady and unsteady computation fluid dynamics (CFD), and coupled FE-CFD calculations are presented for prediction of these temperatures. CFD results are compared with previous measurements from a direct transfer preswirl test rig. The predicted cooling air temperatures agree well with the measurement, but the nozzle discharge coefficients are under predicted. Results from the coupled FE-CFD analyses are compared directly with thermocouple temperature measurements and with heat transfer coefficients on the rotor disk previously obtained from a rotor disk heat conduction solution. Considering the modeling limitations, the coupled approach predicted the solid metal temperatures well. Heat transfer coefficients on the rotor disk from CFD show some effect of the temperature variations on the heat transfer coefficients. Reasonable agreement is obtained with values deduced from the previous heat conduction solution.

Radiative heat transfer and nonequilibrium Casimir-Lifshitz force in many-body systems with planar geometry

NASA Astrophysics Data System (ADS)

Latella, Ivan; Ben-Abdallah, Philippe; Biehs, Svend-Age; Antezza, Mauro; Messina, Riccardo

2017-05-01

A general theory of photon-mediated energy and momentum transfer in N -body planar systems out of thermal equilibrium is introduced. It is based on the combination of the scattering theory and the fluctuational-electrodynamics approach in many-body systems. By making a Landauer-like formulation of the heat transfer problem, explicit formulas for the energy transmission coefficients between two distinct slabs as well as the self-coupling coefficients are derived and expressed in terms of the reflection and transmission coefficients of the single bodies. We also show how to calculate local equilibrium temperatures in such systems. An analogous formulation is introduced to quantify momentum transfer coefficients describing Casimir-Lifshitz forces out of thermal equilibrium. Forces at thermal equilibrium are readily obtained as a particular case. As an illustration of this general theoretical framework, we show on three-body systems how the presence of a fourth slab can impact equilibrium temperatures in heat-transfer problems and equilibrium positions resulting from the forces acting on the system.

Modeling the Partial Atomic Charges in Inorganometallic Molecules and Solids and Charge Redistribution in Lithium-Ion Cathodes

DOE PAGES

Wang, Bo; Li, Shaohong L.; Truhlar, Donald G.

2014-10-30

Partial atomic charges are widely used for the description of charge distributions of molecules and solids. These charges are useful to indicate the extent of charge transfer and charge flow during chemical reactions in batteries, fuel cells, and catalysts and to characterize charge distributions in capacitors, liquid-phase electrolytes, and solids and at electrochemical interfaces. However, partial atomic charges given by various charge models differ significantly, especially for systems containing metal atoms. In the present study, we have compared various charge models on both molecular systems and extended systems, including Hirshfeld, CM5, MK, ChElPG, Mulliken, MBS, NPA, DDEC, LoProp, and Badermore » charges. Their merits and drawbacks are compared. The CM5 charge model is found to perform well on the molecular systems, with a mean unsigned percentage deviation of only 9% for the dipole moments. We therefore formulated it for extended systems and applied it to study charge flow during the delithiation process in lithium-containing oxides used as cathodes. Our calculations show that the charges given by the CM5 charge model are reasonable and that during the delithiation process, the charge flow can occur not only on the transition metal but also on the anions. The oxygen atoms can lose a significant density of electrons, especially for deeply delithiated materials. We also discuss other methods in current use to analyze the charge transfer and charge flow in batteries, in particular the use of formal charge, spin density, and orbital occupancy. Here, we conclude that CM5 charges provide useful information in describing charge distributions in various materials and are very promising for the study of charge transfer and charge flows in both molecules and solids.« less

Modeling the Partial Atomic Charges in Inorganometallic Molecules and Solids and Charge Redistribution in Lithium-Ion Cathodes.

PubMed

Wang, Bo; Li, Shaohong L; Truhlar, Donald G

2014-12-09

Partial atomic charges are widely used for the description of charge distributions of molecules and solids. These charges are useful to indicate the extent of charge transfer and charge flow during chemical reactions in batteries, fuel cells, and catalysts and to characterize charge distributions in capacitors, liquid-phase electrolytes, and solids and at electrochemical interfaces. However, partial atomic charges given by various charge models differ significantly, especially for systems containing metal atoms. In the present study, we have compared various charge models on both molecular systems and extended systems, including Hirshfeld, CM5, MK, ChElPG, Mulliken, MBS, NPA, DDEC, LoProp, and Bader charges. Their merits and drawbacks are compared. The CM5 charge model is found to perform well on the molecular systems, with a mean unsigned percentage deviation of only 9% for the dipole moments. We therefore formulated it for extended systems and applied it to study charge flow during the delithiation process in lithium-containing oxides used as cathodes. Our calculations show that the charges given by the CM5 charge model are reasonable and that during the delithiation process, the charge flow can occur not only on the transition metal but also on the anions. The oxygen atoms can lose a significant density of electrons, especially for deeply delithiated materials. We also discuss other methods in current use to analyze the charge transfer and charge flow in batteries, in particular the use of formal charge, spin density, and orbital occupancy. We conclude that CM5 charges provide useful information in describing charge distributions in various materials and are very promising for the study of charge transfer and charge flows in both molecules and solids.

Revealing the Double-Edged Sword Role of Graphene on Boosted Charge Transfer versus Active Site Control in TiO2 Nanotube Arrays@RGO/MoS2 Heterostructure.

PubMed

Quan, Quan; Xie, Shunji; Weng, Bo; Wang, Ye; Xu, Yi-Jun

2018-05-01

Charge separation/transfer is generally believed to be the most key factor affecting the efficiency of photocatalysis, which however will be counteracted if not taking the active site engineering into account for a specific photoredox reaction. Here, a 3D heterostructure composite is designed consisting of MoS 2 nanoplatelets decorated on reduced graphene oxide-wrapped TiO 2 nanotube arrays (TNTAs@RGO/MoS 2 ). Such a cascade configuration renders a directional migration of charge carriers and controlled immobilization of active sites, thereby showing much higher photoactivity for water splitting to H 2 than binary TNTAs@RGO and TNTAs/MoS 2 . The photoactivity comparison and mechanistic analysis reveal the double-edged sword role of RGO on boosted charge separation/transfer versus active site control in this composite system. The as-observed inconsistency between boosted charge transfer and lowered photoactivity over TNTAs@RGO is attributed to the decrease of active sites for H 2 evolution, which is significantly different from the previous reports in literature. The findings of the intrinsic relationship of balanced benefits from charge separation/transfer and active site control could promote the rational optimization of photocatalyst design by cooperatively manipulating charge flow and active site control, thereby improving the efficiency of photocatalysis for target photoredox processes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Boundary layer charge dynamics in ionic liquid-ionic polymer transducers

NASA Astrophysics Data System (ADS)

Davidson, Jacob D.; Goulbourne, N. C.

2011-01-01

Ionic polymer transducers (IPTs), also known as ionic polymer-metal composites, are soft sensors and actuators which operate through a coupling of microscale chemical, electrical, and mechanical interactions. The use of an ionic liquid as solvent for an IPT has been shown to dramatically increase transducer lifetime in free-air use, while also allowing for higher applied voltages without electrolysis. In this work, we apply Nernst-Planck/Poisson theory to model charge transport in an ionic liquid IPT by considering a certain fraction of the ionic liquid ions as mobile charge carriers, a phenomenon which is unique to ionic liquid IPTs compared to their water-based counterparts. Numerical simulations are performed using the finite element method to examine how the introduction of another pair of mobile ions affects boundary layer charge dynamics, concentration, and charge density distributions in the electric double layer, and the overall charge transferred and current response of the IPT. Due to interactions with the Nafion ionomer, not all of the ionic liquid ions will function as mobile charge carriers; only a certain fraction will exist as "free" ions. The presence of mobile ionic liquid ions in the transducer will increase the overall charge transferred when a voltage is applied, and cause the current in the transducer to decay more slowly. The additional mobile ions also cause the ionic concentration profiles to exhibit a nonlinear dynamic response, characterized by nonmonotonic ionic concentration profiles in space and time. Although the presence of mobile ionic liquid ions increases the overall amount of charge transferred, this additional charge transfer occurs in a somewhat symmetric manner. Therefore, the additional charge transferred due to the ionic liquid ions does not greatly increase the net bending moment of the transducer; in fact, it is possible that ionic liquid ion movement actually decreases the observed bending response. This suggests that an optimal electromechanical conversion efficiency for bending actuation is achieved by using an ionic liquid where only a relatively small fraction of the ionic liquid ions exist as free ions. Conversely, if it is desired to increase the overall amount of charge transferred, an ionic liquid with a large fraction of free ions should be used. These theoretical considerations are found to be in good qualitative agreement with recent experimental results.

Atomic and electronic structure of trilayer graphene/SiC(0001): Evidence of Strong Dependence on Stacking Sequence and charge transfer.

PubMed

Pierucci, Debora; Brumme, Thomas; Girard, Jean-Christophe; Calandra, Matteo; Silly, Mathieu G; Sirotti, Fausto; Barbier, Antoine; Mauri, Francesco; Ouerghi, Abdelkarim

2016-09-15

The transport properties of few-layer graphene are the directly result of a peculiar band structure near the Dirac point. Here, for epitaxial graphene grown on SiC, we determine the effect of charge transfer from the SiC substrate on the local density of states (LDOS) of trilayer graphene using scaning tunneling microscopy/spectroscopy and angle resolved photoemission spectroscopy (ARPES). Different spectra are observed and are attributed to the existence of two stable polytypes of trilayer: Bernal (ABA) and rhomboedreal (ABC) staking. Their electronic properties strongly depend on the charge transfer from the substrate. We show that the LDOS of ABC stacking shows an additional peak located above the Dirac point in comparison with the LDOS of ABA stacking. The observed LDOS features, reflecting the underlying symmetry of the two polytypes, were reproduced by explicit calculations within density functional theory (DFT) including the charge transfer from the substrate. These findings demonstrate the pronounced effect of stacking order and charge transfer on the electronic structure of trilayer or few layer graphene. Our approach represents a significant step toward understand the electronic properties of graphene layer under electrical field.

Electroluminescence Properties of IrQ(ppy)2 Dual-Emitter Organometallic Compound in Organic Light-Emitting Devices

NASA Astrophysics Data System (ADS)

Ciobotaru, Constantin Claudiu; Polosan, Silviu; Ciobotaru, Iulia Corina

2018-02-01

This paper reports the influence of the charge carrier mobility on the electroluminescent properties of a dual-emitter organometallic compound dispersed in two conjugated organic small-molecule host materials and embedded in organic light-emitting devices (OLEDs). The electroluminescent processes in OLEDs are strongly influenced by the host-guest interaction. The charge carrier mobility in the host material plays an important role in the electroluminescent processes but also depends on the triplet-triplet interaction with the organometallic compound. The low charge carrier mobility in 4,4'-bis( N-carbazolyl)-1,1'-biphenyl (CBP) host material reduces the electroluminescent processes, but they are slightly enhanced by the triplet-triplet exothermic charge transfer. The higher charge carrier mobility in the case of N, N'-bis(3-methylphenyl)- N, N'-diphenylbenzidine (TPD) host material influences the electroluminescent processes by the endothermic energy transfer at room temperature, which facilitates the triplet-triplet harvesting in the host-guest system. The excitation is transferred to the guest molecules by triplet-triplet interaction as a Dexter transfer, which occurs by endothermic transfer from the triplet exciton in the host to the triplet exciton in the guest.

Protein-membrane interaction and fatty acid transfer from intestinal fatty acid-binding protein to membranes. Support for a multistep process.

PubMed

Falomir-Lockhart, Lisandro J; Laborde, Lisandro; Kahn, Peter C; Storch, Judith; Córsico, Betina

2006-05-19

Fatty acid transfer from intestinal fatty acid-binding protein (IFABP) to phospholipid membranes occurs during protein-membrane collisions. Electrostatic interactions involving the alpha-helical "portal" region of the protein have been shown to be of great importance. In the present study, the role of specific lysine residues in the alpha-helical region of IFABP was directly examined. A series of point mutants in rat IFABP was engineered in which the lysine positive charges in this domain were eliminated or reversed. Using a fluorescence resonance energy transfer assay, we analyzed the rates and mechanism of fatty acid transfer from wild type and mutant proteins to acceptor membranes. Most of the alpha-helical domain mutants showed slower absolute fatty acid transfer rates to zwitterionic membranes, with substitution of one of the lysines of the alpha2 helix, Lys27, resulting in a particularly dramatic decrease in the fatty acid transfer rate. Sensitivity to negatively charged phospholipid membranes was also reduced, with charge reversal mutants in the alpha2 helix the most affected. The results support the hypothesis that the portal region undergoes a conformational change during protein-membrane interaction, which leads to release of the bound fatty acid to the membrane and that the alpha2 segment is of particular importance in the establishment of charge-charge interactions between IFABP and membranes. Cross-linking experiments with a phospholipid-photoactivable reagent underscored the importance of charge-charge interactions, showing that the physical interaction between wild-type intestinal fatty acid-binding protein and phospholipid membranes is enhanced by electrostatic interactions. Protein-membrane interactions were also found to be enhanced by the presence of ligand, suggesting different collisional complex structures for holo- and apo-IFABP.

Advanced investigation of two-phase charge-coupled devices

NASA Technical Reports Server (NTRS)

Kosonocky, W. F.; Carnes, J. E.

1973-01-01

The performance of experimental two phase, charge-coupled shift registers constructed using polysilicon gates overlapped by aluminum gates was studied. Shift registers with 64, 128, and 500 stages were built and operated. Devices were operated at the maximum clock frequency of 20 MHz. Loss per transfer of less than .0001 was demonstrated for fat zero operation. The effect upon transfer efficiency of various structural and materials parameters was investigated including substrate orientation, resistivity, and conductivity type; channel width and channel length; and method of channel confinement. Operation of the devices with and without fat zero was studied as well as operation in the complete charge transfer mode and the bias charge, or bucket brigade mode.

Space-dependent perfusion coefficient estimation in a 2D bioheat transfer problem

NASA Astrophysics Data System (ADS)

Bazán, Fermín S. V.; Bedin, Luciano; Borges, Leonardo S.

2017-05-01

In this work, a method for estimating the space-dependent perfusion coefficient parameter in a 2D bioheat transfer model is presented. In the method, the bioheat transfer model is transformed into a time-dependent semidiscrete system of ordinary differential equations involving perfusion coefficient values as parameters, and the estimation problem is solved through a nonlinear least squares technique. In particular, the bioheat problem is solved by the method of lines based on a highly accurate pseudospectral approach, and perfusion coefficient values are estimated by the regularized Gauss-Newton method coupled with a proper regularization parameter. The performance of the method on several test problems is illustrated numerically.

Determination of lateral-stability derivatives and transfer-function coefficients from frequency-response data for lateral motions

NASA Technical Reports Server (NTRS)

Donegan, James J; Robinson, Samuel W , Jr; Gates, Ordway, B , jr

1955-01-01

A method is presented for determining the lateral-stability derivatives, transfer-function coefficients, and the modes for lateral motion from frequency-response data for a rigid aircraft. The method is based on the application of the vector technique to the equations of lateral motion, so that the three equations of lateral motion can be separated into six equations. The method of least squares is then applied to the data for each of these equations to yield the coefficients of the equations of lateral motion from which the lateral-stability derivatives and lateral transfer-function coefficients are computed. Two numerical examples are given to demonstrate the use of the method.

Unravelling Doping Effects on PEDOT at the Molecular Level: From Geometry to Thermoelectric Transport Properties.

PubMed

Shi, Wen; Zhao, Tianqi; Xi, Jinyang; Wang, Dong; Shuai, Zhigang

2015-10-14

Tuning carrier concentration via chemical doping is the most successful strategy to optimize the thermoelectric figure of merit. Nevertheless, how the dopants affect charge transport is not completely understood. Here we unravel the doping effects by explicitly including the scattering of charge carriers with dopants on thermoelectric properties of poly(3,4-ethylenedioxythiophene), PEDOT, which is a p-type thermoelectric material with the highest figure of merit reported. We corroborate that the PEDOT exhibits a distinct transition from the aromatic to quinoid-like structure of backbone, and a semiconductor-to-metal transition with an increase in the level of doping. We identify a close-to-unity charge transfer from PEDOT to the dopant, and find that the ionized impurity scattering dominates over the acoustic phonon scattering in the doped PEDOT. By incorporating both scattering mechanisms, the doped PEDOT exhibits mobility, Seebeck coefficient and power factors in very good agreement with the experimental data, and the lightly doped PEDOT exhibits thermoelectric properties superior to the heavily doped one. We reveal that the thermoelectric transport is highly anisotropic in ordered crystals, and suggest to utilize large power factors in the direction of polymer backbone and low lattice thermal conductivity in the stacking and lamellar directions, which is viable in chain-oriented amorphous nanofibers.

Influence of Processing Additives on Charge-Transfer Time Scales and Sound Velocity in Organic Bulk Heterojunction Films.

PubMed

Kaake, Loren G; Welch, Gregory C; Moses, Daniel; Bazan, Guillermo C; Heeger, Alan J

2012-05-17

The role of processing additives in organic bulk heterojunction thin films was investigated by means of transient absorption spectroscopy. The rate of ultrafast charge transfer was found to increase when a small amount of diiodooctane was used during film formation. In addition, coherent acoustic phonons were observed, and their velocity was determined. A strong correlation between the sound velocity and the charge-transfer time scale was observed, both of which could be explained by a subtle increase in thin film density.

Ion-atom charge-transfer reactions and a hot intercloud medium. [in interstellar space

NASA Technical Reports Server (NTRS)

Steigman, G.

1975-01-01

An investigation is conducted concerning the ionization equilibrium of carbon in a hot intercloud medium (ICM), taking into account various charge-transfer reactions. Attention is given to problems related to observations of carbon along the lines of sight to several unreddened stars. It is pointed out that the observed underabundance of C III and overabundance of C I can be consistent with the presence of a hot, partially ionized ICM, provided that two of the charge-transfer reactions considered are rapid at thermal energies.

Permeability of membranes to amino acids and modified amino acids: mechanisms involved in translocation

NASA Technical Reports Server (NTRS)

Chakrabarti, A. C.; Deamer, D. W. (Principal Investigator); Miller, S. L. (Principal Investigator)

1994-01-01

The amino acid permeability of membranes is of interest because they are one of the key solutes involved in cell function. Membrane permeability coefficients (P) for amino acid classes, including neutral, polar, hydrophobic, and charged species, have been measured and compared using a variety of techniques. Decreasing lipid chain length increased permeability slightly (5-fold), while variations in pH had only minor effects on the permeability coefficients of the amino acids tested in liposomes. Increasing the membrane surface charge increased the permeability of amino acids of the opposite charge, while increasing the cholesterol content decreased membrane permeability. The permeability coefficients for most amino acids tested were surprisingly similar to those previously measured for monovalent cations such as sodium and potassium (approximately 10(-12)-10(-13) cm s-1). This observation suggests that the permeation rates for the neutral, polar and charged amino acids are controlled by bilayer fluctuations and transient defects, rather than partition coefficients and Born energy barriers. Hydrophobic amino acids were 10(2) more permeable than the hydrophilic forms, reflecting their increased partition coefficient values. External pH had dramatic effects on the permeation rates for the modified amino acid lysine methyl ester in response to transmembrane pH gradients. It was established that lysine methyl ester and other modified short peptides permeate rapidly (P = 10(-2) cm s-1) as neutral (deprotonated) molecules. It was also shown that charge distributions dramatically alter permeation rates for modified di-peptides. These results may relate to the movement of peptides through membranes during protein translocation and to the origin of cellular membrane transport on the early Earth.

Electric field changes on Au nanoparticles on semiconductor supports--the molecular voltmeter and other methods to observe adsorbate-induced charge-transfer effects in Au/TiO2 nanocatalysts.

PubMed

McEntee, Monica; Stevanovic, Ana; Tang, Wenjie; Neurock, Matthew; Yates, John T

2015-02-11

Infrared (IR) studies of Au/TiO2 catalyst particles indicate that charge transfer from van der Waals-bound donor or acceptor molecules on TiO2 to or from Au occurs via transport of charge carriers in the semiconductor TiO2 support. The ΔνCO on Au is shown to be proportional to the polarizability of the TiO2 support fully covered with donor or acceptor molecules, producing a proportional frequency shift in νCO. Charge transfer through TiO2 is associated with the population of electron trap sites in the bandgap of TiO2 and can be independently followed by changes in photoluminescence intensity and by shifts in the broad IR absorbance region for electron trap sites, which is also proportional to the polarizability of donors by IR excitation. Density functional theory calculations show that electron transfer from the donor molecules to TiO2 and to supported Au particles produces a negative charge on the Au, whereas the transfer from the Au particles to the TiO2 support into acceptor molecules results in a positive charge on the Au. These changes along with the magnitudes of the shifts are consistent with the Stark effect. A number of experiments show that the ∼3 nm Au particles act as "molecular voltmeters" in influencing ΔνCO. Insulator particles, such as SiO2, do not display electron-transfer effects to Au particles on their surface. These studies are preliminary to doping studies of semiconductor-oxide particles by metal ions which modify Lewis acid/base oxide properties and possibly strongly modify the electron-transfer and catalytic activity of supported metal catalyst particles.

Role of Au(NPs) in the enhanced response of Au(NPs)-decorated MWCNT electrochemical biosensor

PubMed Central

Mehmood, Shahid; Ciancio, Regina; Carlino, Elvio; Bhatti, Arshad S

2018-01-01

Background The combination of Au-metallic-NPs and CNTs are a new class of hybrid nanomaterials for the development of electrochemical biosensor. Concentration of Au(nanoparticles [NPs]) in the electrochemical biosensor is crucial for the efficient charge transfer between the Au-NPs-MWCNTs modified electrode and electrolytic solution. Methods In this work, the charge transfer kinetics in the glassy carbon electrode (GCE) modified with Au(NPs)–multiwalled carbon nanotube (MWCNT) nanohybrid with varied concentrations of Au(NPs) in the range 40–100 nM was studied using electrochemical impedance spectroscopy (EIS). Field emission scanning electron microscopy and transmission electron microscopy confirmed the attachment of Au(NPs) on the surface of MWCNTs. Results The cyclic voltammetry and EIS results showed that the charge transfer mechanism was diffusion controlled and the rate of charge transfer was dependent on the concentration of Au(NPs) in the nanohybrid. The formation of spherical diffusion zone, which was dependent on the concentration of Au(NPs) in nanohybrids, was attributed to result in 3 times the increase in the charge transfer rate ks, 5 times increase in mass transfer, and 5% (9%) increase in Ipa (Ipc) observed in cyclic voltammetry in 80 nM Au(NP) nanohybrid-modified GCE from MWCNT-modified GCE. The work was extended to probe the effect of charge transfer rates at various concentrations of Au(NPs) in the nanohybrid-modified electrodes in the presence of Escherichia coli. The cyclic voltammetry results clearly showed the best results for 80 nM Au(NPs) in nanohybrid electrode. Conclusion The present study suggested that the formation of spherical diffusion zone in nanohybrid-modified electrodes is critical for the enhanced electrochemical biosensing applications. PMID:29713161

Comparative evaluation of methods for the determination of heat transfer coefficients of liquid and gaseous quenching media

NASA Astrophysics Data System (ADS)

Shevchenko, Svetlana Yu.; Melnik, Yury A.; Smirnov, Andrey E.; Htet, Wai Yan Min

2018-03-01

Temperature dependences of heat transfer coefficients of liquid and gaseous quenching media were determined using a gradient probe and prismatic probe of more simple design. The probes of two different designs were tested in the same conditions. Analysis of heat transfer coefficients showed good agreement between the data obtained. The tests were carried out with liquid and gaseous quenching media: water, polymer quenchant, quenching oil and high-pressure nitrogen. Methods of mathematical modeling of steel samples quenching show the adequacy of the results.

Organization and dynamics of pyrene and pyrene lipids in intact lipid bilayers. Photo-induced charge transfer processes.

PubMed Central

Barenholz, Y; Cohen, T; Korenstein, R; Ottolenghi, M

1991-01-01

The dynamics of fluorescence quenching and the organization of a series of pyrene derivatives anchored in various depths in bilayers of phosphatidylcholine small unilamellar vesicles was studied and compared with their behavior in homogeneous solvent systems. The studies include characterization of the environmental polarity of the pyrene fluorophore based on its vibronic peaks, as well as the interaction with three collisional quenchers: the two membrane-soluble quenchers, diethylaniline and bromobenzene, and the water soluble quencher potassium iodide. The system of diethylaniline-pyrene derivatives in the membrane of phosphatidylcholine vesicles was characterized in detail. The diethylaniline partition coefficient between the lipid bilayers and the buffer is approximately 5,800. Up to a diethylaniline/phospholipid mole ratio of 1:3 the perturbation to membrane structure is minimal so that all photophysical studies were performed below this mole ratio. The quenching reaction, in all cases, was shown to take place in the lipid bilayer interior and the relative quenching efficiencies of the various probe molecules was used to provide information on the distribution of both fluorescent probes and quencher molecules in the lipid bilayer. The quenching efficiency by diethylaniline in the lipid bilayer was found to be essentially independent on the length of the methylene chain of the pyrene moiety. These findings suggest that the quenching process, being a diffusion controlled reaction, is determined by the mobility of the diethylaniline quencher (with an effective diffusion coefficient D approximately 10(-7) cm2 s-1) which appears to be homogeneously distributed throughout the lipid bilayer. The pulsed laser photolysis products of the charge-transfer quenching reaction were examined. No exciplex (excited-complex) formation was observed and the yield of the separated radical ions was shown to be tenfold smaller than in homogenous polar solutions. The decay of the radical ions is considerably faster than the corresponding process in homogenous solutions. Relatively high intersystem crossing yields are observed. The results are explained on the basis of the intrinsic properties of a lipid bilayer, primarily, its rigid spatial organization. It is suggested that such properties favor ion-pair formation over exciplex generation. They also enhance primary geminate recombination of initially formed (solvent-shared) ion pairs. Triplet states are generated via secondary geminate recombination of ion pairs in the membrane interior. The results bear on the general mechanism of electron transfer processes in biomembranes. PMID:1883931

Periodic Heat Transfer at Small Pressure Fluctuations

NASA Technical Reports Server (NTRS)

Pfriem, H.

1943-01-01

The effect of cyclic gas pressure variations on the periodic heat transfer at a flat wall is theoretically analyzed and the differential equation describing the process and its solution for relatively. Small pressure fluctuations developed, thus explaining the periodic heat cycle between gas and wall surface. The processes for pure harmonic pressure and temperature oscillations, respectively, in the gas space are described by means of a constant heat transfer coefficient and the equally constant phase angle between the appearance of the maximum values of the pressure and heat flow most conveniently expressed mathematically in the form of a complex heat transfer coefficient. Any cyclic pressure oscillations, can be reduced by Fourier analysis to harmonic oscillations, which result in specific, mutual relationships of heat-transfer coefficients and phase angles for the different harmonics.

Consider a non-spherical elephant: computational fluid dynamics simulations of heat transfer coefficients and drag verified using wind tunnel experiments.

PubMed

Dudley, Peter N; Bonazza, Riccardo; Porter, Warren P

2013-07-01

Animal momentum and heat transfer analysis has historically used direct animal measurements or approximations to calculate drag and heat transfer coefficients. Research can now use modern 3D rendering and computational fluid dynamics software to simulate animal-fluid interactions. Key questions are the level of agreement between simulations and experiments and how superior they are to classical approximations. In this paper we compared experimental and simulated heat transfer and drag calculations on a scale model solid aluminum African elephant casting. We found good agreement between experimental and simulated data and large differences from classical approximations. We used the simulation results to calculate coefficients for heat transfer and drag of the elephant geometry. Copyright © 2013 Wiley Periodicals, Inc.

Measurement of heat transfer coefficient using termoanemometry methods

NASA Astrophysics Data System (ADS)

Dančová, P.; Sitek, P.; Vít, T.

2014-03-01

This work deals with a measurement of heat transfer from a heated flat plate on which a synthetic jet impacts perpendicularly. Measurement of a heat transfer coefficient (HTC) is carried out using the hot wire anemometry method with glue film probe Dantec 55M47. The paper brings also results of velocity profiles measurements and turbulence intensity calculations.

A Simple Geotracer Compositional Correlation Analysis Reveals Oil Charge and Migration Pathways

NASA Astrophysics Data System (ADS)

Yang, Yunlai; Arouri, Khaled

2016-03-01

A novel approach, based on geotracer compositional correlation analysis is reported, which reveals the oil charge sequence and migration pathways for five oil fields in Saudi Arabia. The geotracers utilised are carbazoles, a family of neutral pyrrolic nitrogen compounds known to occur naturally in crude oils. The approach is based on the concept that closely related fields, with respect to filling sequence, will show a higher carbazole compositional correlation, than those fields that are less related. That is, carbazole compositional correlation coefficients can quantify the charge and filling relationships among different fields. Consequently, oil migration pathways can be defined based on the established filling relationships. The compositional correlation coefficients of isomers of C1 and C2 carbazoles, and benzo[a]carbazole for all different combination pairs of the five fields were found to vary extremely widely (0.28 to 0.94). A wide range of compositional correlation coefficients allows adequate differentiation of separate filling relationships. Based on the established filling relationships, three distinct migration pathways were inferred, with each apparently being charged from a different part of a common source kitchen. The recognition of these charge and migration pathways will greatly aid the search for new accumulations.

A Simple Geotracer Compositional Correlation Analysis Reveals Oil Charge and Migration Pathways

PubMed Central

Yang, Yunlai; Arouri, Khaled

2016-01-01

A novel approach, based on geotracer compositional correlation analysis is reported, which reveals the oil charge sequence and migration pathways for five oil fields in Saudi Arabia. The geotracers utilised are carbazoles, a family of neutral pyrrolic nitrogen compounds known to occur naturally in crude oils. The approach is based on the concept that closely related fields, with respect to filling sequence, will show a higher carbazole compositional correlation, than those fields that are less related. That is, carbazole compositional correlation coefficients can quantify the charge and filling relationships among different fields. Consequently, oil migration pathways can be defined based on the established filling relationships. The compositional correlation coefficients of isomers of C1 and C2 carbazoles, and benzo[a]carbazole for all different combination pairs of the five fields were found to vary extremely widely (0.28 to 0.94). A wide range of compositional correlation coefficients allows adequate differentiation of separate filling relationships. Based on the established filling relationships, three distinct migration pathways were inferred, with each apparently being charged from a different part of a common source kitchen. The recognition of these charge and migration pathways will greatly aid the search for new accumulations. PMID:26965479

A Simple Geotracer Compositional Correlation Analysis Reveals Oil Charge and Migration Pathways.

PubMed

Yang, Yunlai; Arouri, Khaled

2016-03-11

A novel approach, based on geotracer compositional correlation analysis is reported, which reveals the oil charge sequence and migration pathways for five oil fields in Saudi Arabia. The geotracers utilised are carbazoles, a family of neutral pyrrolic nitrogen compounds known to occur naturally in crude oils. The approach is based on the concept that closely related fields, with respect to filling sequence, will show a higher carbazole compositional correlation, than those fields that are less related. That is, carbazole compositional correlation coefficients can quantify the charge and filling relationships among different fields. Consequently, oil migration pathways can be defined based on the established filling relationships. The compositional correlation coefficients of isomers of C1 and C2 carbazoles, and benzo[a]carbazole for all different combination pairs of the five fields were found to vary extremely widely (0.28 to 0.94). A wide range of compositional correlation coefficients allows adequate differentiation of separate filling relationships. Based on the established filling relationships, three distinct migration pathways were inferred, with each apparently being charged from a different part of a common source kitchen. The recognition of these charge and migration pathways will greatly aid the search for new accumulations.

The effect of N2/+/ recombination on the aeronomic determination of the charge exchange rate coefficient of O/+//2D/ with N2

NASA Technical Reports Server (NTRS)

Torr, D. G.; Orsini, N.

1978-01-01

The Atmosphere Explorer (AE) data are reexamined in the light of new laboratory measurements of the N2(+) recombination rate coefficient alpha. The new measurements support earlier measurements which yielded values of alpha significantly lower than the AE values. It is found that the values for alpha determined from the satellite data can be reconciled with the laboratory measurements, if the charge exchange rate coefficient for O(+)(2D) with N2 is less than one-quarter of that derived in the laboratory by Rutherford and Vroom (1971).

Charge transfer in dissociating iodomethane and fluoromethane molecules ionized by intense femtosecond X-ray pulses

PubMed Central

Boll, Rebecca; Erk, Benjamin; Coffee, Ryan; Trippel, Sebastian; Kierspel, Thomas; Bomme, Cédric; Bozek, John D.; Burkett, Mitchell; Carron, Sebastian; Ferguson, Ken R.; Foucar, Lutz; Küpper, Jochen; Marchenko, Tatiana; Miron, Catalin; Patanen, Minna; Osipov, Timur; Schorb, Sebastian; Simon, Marc; Swiggers, Michelle; Techert, Simone; Ueda, Kiyoshi; Bostedt, Christoph; Rolles, Daniel; Rudenko, Artem

2016-01-01

Ultrafast electron transfer in dissociating iodomethane and fluoromethane molecules was studied at the Linac Coherent Light Source free-electron laser using an ultraviolet-pump, X-ray-probe scheme. The results for both molecules are discussed with respect to the nature of their UV excitation and different chemical properties. Signatures of long-distance intramolecular charge transfer are observed for both species, and a quantitative analysis of its distance dependence in iodomethane is carried out for charge states up to I21+. The reconstructed critical distances for electron transfer are in good agreement with a classical over-the-barrier model and with an earlier experiment employing a near-infrared pump pulse. PMID:27051675

Charge Transfer Reactions

NASA Astrophysics Data System (ADS)

Dennerl, Konrad

2010-12-01

Charge transfer, or charge exchange, describes a process in which an ion takes one or more electrons from another atom. Investigations of this fundamental process have accompanied atomic physics from its very beginning, and have been extended to astrophysical scenarios already many decades ago. Yet one important aspect of this process, i.e. its high efficiency in generating X-rays, was only revealed in 1996, when comets were discovered as a new class of X-ray sources. This finding has opened up an entirely new field of X-ray studies, with great impact due to the richness of the underlying atomic physics, as the X-rays are not generated by hot electrons, but by ions picking up electrons from cold gas. While comets still represent the best astrophysical laboratory for investigating the physics of charge transfer, various studies have already spotted a variety of other astrophysical locations, within and beyond our solar system, where X-rays may be generated by this process. They range from planetary atmospheres, the heliosphere, the interstellar medium and stars to galaxies and clusters of galaxies, where charge transfer may even be observationally linked to dark matter. This review attempts to put the various aspects of the study of charge transfer reactions into a broader historical context, with special emphasis on X-ray astrophysics, where the discovery of cometary X-ray emission may have stimulated a novel look at our universe.

A simple model of solvent-induced symmetry-breaking charge transfer in excited quadrupolar molecules

NASA Astrophysics Data System (ADS)

Ivanov, Anatoly I.; Dereka, Bogdan; Vauthey, Eric

2017-04-01

A simple model has been developed to describe the symmetry-breaking of the electronic distribution of AL-D-AR type molecules in the excited state, where D is an electron donor and AL and AR are identical acceptors. The origin of this process is usually associated with the interaction between the molecule and the solvent polarization that stabilizes an asymmetric and dipolar state, with a larger charge transfer on one side than on the other. An additional symmetry-breaking mechanism involving the direct Coulomb interaction of the charges on the acceptors is proposed. At the same time, the electronic coupling between the two degenerate states, which correspond to the transferred charge being localised either on AL or AR, favours a quadrupolar excited state with equal amount of charge-transfer on both sides. Because of these counteracting effects, symmetry breaking is only feasible when the electronic coupling remains below a threshold value, which depends on the solvation energy and the Coulomb repulsion energy between the charges located on AL and AR. This model allows reproducing the solvent polarity dependence of the symmetry-breaking reported recently using time-resolved infrared spectroscopy.

Organic Solar Cells: Understanding the Role of Förster Resonance Energy Transfer

PubMed Central

Feron, Krishna; Belcher, Warwick J.; Fell, Christopher J.; Dastoor, Paul C.

2012-01-01

Organic solar cells have the potential to become a low-cost sustainable energy source. Understanding the photoconversion mechanism is key to the design of efficient organic solar cells. In this review, we discuss the processes involved in the photo-electron conversion mechanism, which may be subdivided into exciton harvesting, exciton transport, exciton dissociation, charge transport and extraction stages. In particular, we focus on the role of energy transfer as described by Förster resonance energy transfer (FRET) theory in the photoconversion mechanism. FRET plays a major role in exciton transport, harvesting and dissociation. The spectral absorption range of organic solar cells may be extended using sensitizers that efficiently transfer absorbed energy to the photoactive materials. The limitations of Förster theory to accurately calculate energy transfer rates are discussed. Energy transfer is the first step of an efficient two-step exciton dissociation process and may also be used to preferentially transport excitons to the heterointerface, where efficient exciton dissociation may occur. However, FRET also competes with charge transfer at the heterointerface turning it in a potential loss mechanism. An energy cascade comprising both energy transfer and charge transfer may aid in separating charges and is briefly discussed. Considering the extent to which the photo-electron conversion efficiency is governed by energy transfer, optimisation of this process offers the prospect of improved organic photovoltaic performance and thus aids in realising the potential of organic solar cells. PMID:23235328

Delocalization Drives Free Charge Generation in Conjugated Polymer Films

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

Pace, Natalie A.; Reid, Obadiah G.; Rumbles, Garry

We demonstrate that the product of photoinduced electron transfer between a conjugated polymer host and a dilute molecular sensitizer is controlled by the structural state of the polymer. Ordered semicrystalline solids exhibit free charge generation, while disordered polymers in the melt phase do not. We use photoluminescence (PL) and time-resolved microwave conductivity (TRMC) measurements to sweep through polymer melt transitions in situ. Free charge generation measured by TRMC turns off upon melting, whereas PL quenching of the molecular sensitizers remains constant, implying unchanged electron transfer efficiency. The key difference is the intermolecular order of the polymer host in the solidmore » state compared to the melt. We propose that this order-disorder transition modulates the localization length of the initial charge-transfer state, which controls the probability of free charge formation.« less

Delocalization Drives Free Charge Generation in Conjugated Polymer Films

DOE PAGES

Pace, Natalie A.; Reid, Obadiah G.; Rumbles, Garry

2018-02-19

We demonstrate that the product of photoinduced electron transfer between a conjugated polymer host and a dilute molecular sensitizer is controlled by the structural state of the polymer. Ordered semicrystalline solids exhibit free charge generation, while disordered polymers in the melt phase do not. We use photoluminescence (PL) and time-resolved microwave conductivity (TRMC) measurements to sweep through polymer melt transitions in situ. Free charge generation measured by TRMC turns off upon melting, whereas PL quenching of the molecular sensitizers remains constant, implying unchanged electron transfer efficiency. The key difference is the intermolecular order of the polymer host in the solidmore » state compared to the melt. We propose that this order-disorder transition modulates the localization length of the initial charge-transfer state, which controls the probability of free charge formation.« less

46 CFR 153.957 - Persons in charge of transferring liquid cargo in bulk or cleaning cargo tanks.

Code of Federal Regulations, 2014 CFR

2014-10-01

... SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Operations Cargo Transfer Procedures § 153.957 Persons in charge of...

46 CFR 153.957 - Persons in charge of transferring liquid cargo in bulk or cleaning cargo tanks.

Code of Federal Regulations, 2010 CFR

2010-10-01

... SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Operations Cargo Transfer Procedures § 153.957 Persons in charge of...

46 CFR 153.957 - Persons in charge of transferring liquid cargo in bulk or cleaning cargo tanks.

Code of Federal Regulations, 2013 CFR

2013-10-01

... SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Operations Cargo Transfer Procedures § 153.957 Persons in charge of...

46 CFR 153.957 - Persons in charge of transferring liquid cargo in bulk or cleaning cargo tanks.

Code of Federal Regulations, 2012 CFR

2012-10-01

... SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Operations Cargo Transfer Procedures § 153.957 Persons in charge of...

46 CFR 153.957 - Persons in charge of transferring liquid cargo in bulk or cleaning cargo tanks.

Code of Federal Regulations, 2011 CFR

2011-10-01

... SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Operations Cargo Transfer Procedures § 153.957 Persons in charge of...

Polyoxometalate active charge-transfer material for mediated redox flow battery

DOEpatents

Anderson, Travis Mark; Hudak, Nicholas; Staiger, Chad; Pratt, Harry

2017-01-17

Redox flow batteries including a half-cell electrode chamber coupled to a current collecting electrode are disclosed herein. In a general embodiment, a separator is coupled to the half-cell electrode chamber. The half-cell electrode chamber comprises a first redox-active mediator and a second redox-active mediator. The first redox-active mediator and the second redox-active mediator are circulated through the half-cell electrode chamber into an external container. The container includes an active charge-transfer material. The active charge-transfer material has a redox potential between a redox potential of the first redox-active mediator and a redox potential of the second redox-active mediator. The active charge-transfer material is a polyoxometalate or derivative thereof. The redox flow battery may be particularly useful in energy storage solutions for renewable energy sources and for providing sustained power to an electrical grid.

Ab initio treatment of ion-induced charge transfer dynamics of isolated 2-deoxy-D-ribose.

PubMed

Bacchus-Montabonel, Marie-Christine

2014-08-21

Modeling-induced radiation damage in biological systems, in particular, in DNA building blocks, is of major concern in cancer therapy studies. Ion-induced charge-transfer dynamics may indeed be involved in proton and hadrontherapy treatments. We have thus performed a theoretical approach of the charge-transfer dynamics in collision of C(4+) ions and protons with isolated 2-deoxy-D-ribose in a wide collision energy range by means of ab initio quantum chemistry molecular methods. The comparison of both projectile ions has been performed with regard to previous theoretical and experimental results. The charge transfer appears markedly less efficient with the 2-deoxy-D-ribose target than that with pyrimidine nucleobases, which would induce an enhancement of the fragmentation process in agreement with experimental measurements. The mechanism has been analyzed with regard to inner orbital excitations, and qualitative tendencies have been pointed out for studies on DNA buiding block damage.

Designing a Spin-one Mott Insulator: Complete Charge Transfer in Nickelate-Titanate Heterostructures

NASA Astrophysics Data System (ADS)

Chen, Hanghui; Marianetti, Chris; Millis, Andrew

2013-03-01

Ab initio calculations are performed to show that complete charge transfer may occur from the TiO2 to the NiO2 layers in (LaTiO3)1/(LaNiO3)1 superlattices. Although the two component materials are an S = 1 / 2 Mott insulator and a weakly correlated paramagnetic metal, strong correlation effects on Ni d states can render the superlattice an unusual S = 1 charge transfer insulator, with the Ti- d band empty, the Ni in the d8 state and the oxygen bands filled. The charge transfer gap is set by the Ti/Ni d level splitting. Magnetic, photoemission and x-ray scattering experiments are suggested to test the theory. The results show that heterostructuring can lead to very high levels of electron doping of oxides. This research was supported by the Army Research Office under ARO-Ph 56032 and DOE-ER-046169.

Engineering the Charge Transfer in all 2D Graphene-Nanoplatelets Heterostructure Photodetectors

PubMed Central

Robin, A.; Lhuillier, E.; Xu, X. Z.; Ithurria, S.; Aubin, H.; Ouerghi, A.; Dubertret, B.

2016-01-01

Two dimensional layered (i.e. van der Waals) heterostructures open up great prospects, especially in photodetector applications. In this context, the control of the charge transfer between the constituting layers is of crucial importance. Compared to bulk or 0D system, 2D materials are characterized by a large exciton binding energy (0.1–1 eV) which considerably affects the magnitude of the charge transfer. Here we investigate a model system made from colloidal 2D CdSe nanoplatelets and epitaxial graphene in a phototransistor configuration. We demonstrate that using a heterostructured layered material, we can tune the magnitude and the direction (i.e. electron or hole) of the charge transfer. We further evidence that graphene functionalization by nanocrystals only leads to a limited change in the magnitude of the 1/f noise. These results draw some new directions to design van der Waals heterostructures with enhanced optoelectronic properties. PMID:27143413

Oxygen vacancies promoted interfacial charge carrier transfer of CdS/ZnO heterostructure for photocatalytic hydrogen generation.

PubMed

Xie, Ying Peng; Yang, Yongqiang; Wang, Guosheng; Liu, Gang

2017-10-01

The solid-state Z-scheme trinary/binary heterostructures show the advantage of utilizing the high-energy photogenerated charge carriers in photocatalysis. However, the key factors controlling such Z-scheme in the binary heterostructures are still unclear. In this paper, we showed that oxygen vacancies could act as an interface electron transfer mediator to promote the direct Z-scheme charge transfer process in binary semiconductor heterostructures of CdS/ZnS. Increasing the concentration of surface oxygen vacancies of ZnO crystal can greatly enhance photocatalytic hydrogen generation of CdS/ZnO heterostructure. This was attributed to the strengthened direct Z-scheme charge transfer process in CdS/ZnO, as evidenced by steady-state/time-resolved photoluminescence spectroscopy and selective photodeposition of metal particles on the heterostructure. Copyright © 2017 Elsevier Inc. All rights reserved.

Spectroscopic study of the charge-transfer complexes TiCl4/styrene and TiCl4/polystyrene

NASA Astrophysics Data System (ADS)

Gonçalves, Norberto S.; Noda, Lúcia. K.

2017-10-01

In this work, solutions of TiCl4/styrene and TiCl4/polystyrene charge-transfer complexes in CHCl3 or CDCl3 were investigated by UV-vis, resonance Raman and 1H NMR spectroscopies in order to study their molecular and electronic structures. Both show a yellow colour due to absorption in the 400 nm region, related to a charge-transfer transition. In Raman spectra, as the excitation approaches the resonance region, the primary enhancement of aromatic ring modes was mainly observed, rather than intensification of the vinylic double-bond stretch. Under the experimental conditions it was observed that formation of polystyrene takes place, as showed by 1H NMR spectra, and the most significant interaction occurs at the aromatic ring, as supported by the results from interaction of TiCl4 with polystyrene, as indicated by the charge-transfer band and resonant intensification of the aromatic ring modes.

Metal-to-metal charge transfer transitions - Interpretation of visible-region spectra of the moon and lunar materials

NASA Technical Reports Server (NTRS)

Loeffler, B. M.; Burns, R. G.; Tossell, J. A.

1975-01-01

Prominent bands in the spectral profiles of Fe-Ti phases in lunar samples have been attributed to charge-transfer transitions between Fe and Ti cations, and a model is presented for calculating charge transfer energies from energy levels computed by the SCF-X(alpha) scattered wave molecular orbital method for isolated MO6 octahedral coordination clusters containing Fe(2+), Fe(3+), Ti(3+), and Ti(4+) cations. The calculated charge transfer energy for the Fe(2+) to Ti(4+) transition correlates well with a measured spectral feature around 0.6 micron in ilmenite, and, since ilmenite is a major constituent of mare basalts and dark-mantling material, the observed darkness and blueness of the regolith in lunar black spots is attributed primarily to this transition. The Ti(3+) to Ti(4+) transition is thought to contribute to some phases.

Enhancement of convective heat transfer coefficient of ethylene glycol base cuprous oxide (Cu2O) nanofluids

NASA Astrophysics Data System (ADS)

Hassan, Ali; Ramzan, Naveed; Umer, Asim; Ahmad, Ayyaz; Muryam, Hina

2018-02-01

The enhancement in the convective heat transfer coefficient of the ethylene glycol (EG) base cuprous oxide (Cu2O) nanofluids were investigated. The nanofluids of different volume concentrations i-e 1%, 2.5% and 4.5% were prepared by the two step method. Cuprous oxide (Cu2O) nanoparticles were ultrasonically stirred for four hours in the ethylene glycol (EG). The experimental study has been performed through circular tube geometry in laminar flow regime at average Reynolds numbers 36, 71 and 116. The constant heat flux Q = 4000 (W/m2) was maintained during this work. Substantial enhancement was observed in the convective heat transfer coefficient of ethylene glycol (EG) base cuprous oxide (Cu2O) nanofluids than the base fluid. The maximum 74% enhancement was observed in convective heat transfer coefficient at 4.5 vol% concentration and Re = 116.

Improving microalgal growth with small bubbles in a raceway pond with swing gas aerators.

PubMed

Yang, Zongbo; Cheng, Jun; Liu, Jianzhong; Zhou, Junhu; Cen, Kefa

2016-09-01

A novel swing gas aerator was developed to generate small bubbles for improving the mass transfer coefficient and microalgal growth rate in a raceway pond. A high-speed photography system (HSP) was used to measure the bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure the mass transfer coefficient and mixing time. Bubble generation time and diameter decreased by 21% and 9%, respectively, when rubber gas aerators were swung in the microalgae solution. When water pump power and gas aeration rate increased in a raceway pond with swing gas aerators and oscillating baffles (SGAOB), bubble generation time and diameter decreased but solution velocity and mass transfer coefficient increased. The mass transfer coefficient increased by 25% and the solution velocity increased by 11% when SGAOB was used, and the microalgal biomass yield increased by 18%. Copyright © 2016 Elsevier Ltd. All rights reserved.

Atomic charge transfer-counter polarization effects determine infrared CH intensities of hydrocarbons: a quantum theory of atoms in molecules model.

PubMed

Silva, Arnaldo F; Richter, Wagner E; Meneses, Helen G C; Bruns, Roy E

2014-11-14

Atomic charge transfer-counter polarization effects determine most of the infrared fundamental CH intensities of simple hydrocarbons, methane, ethylene, ethane, propyne, cyclopropane and allene. The quantum theory of atoms in molecules/charge-charge flux-dipole flux model predicted the values of 30 CH intensities ranging from 0 to 123 km mol(-1) with a root mean square (rms) error of only 4.2 km mol(-1) without including a specific equilibrium atomic charge term. Sums of the contributions from terms involving charge flux and/or dipole flux averaged 20.3 km mol(-1), about ten times larger than the average charge contribution of 2.0 km mol(-1). The only notable exceptions are the CH stretching and bending intensities of acetylene and two of the propyne vibrations for hydrogens bound to sp hybridized carbon atoms. Calculations were carried out at four quantum levels, MP2/6-311++G(3d,3p), MP2/cc-pVTZ, QCISD/6-311++G(3d,3p) and QCISD/cc-pVTZ. The results calculated at the QCISD level are the most accurate among the four with root mean square errors of 4.7 and 5.0 km mol(-1) for the 6-311++G(3d,3p) and cc-pVTZ basis sets. These values are close to the estimated aggregate experimental error of the hydrocarbon intensities, 4.0 km mol(-1). The atomic charge transfer-counter polarization effect is much larger than the charge effect for the results of all four quantum levels. Charge transfer-counter polarization effects are expected to also be important in vibrations of more polar molecules for which equilibrium charge contributions can be large.

Charged Particle Diffusion in Isotropic Random Static Magnetic Fields

NASA Astrophysics Data System (ADS)

Subedi, P.; Sonsrettee, W.; Matthaeus, W. H.; Ruffolo, D. J.; Wan, M.; Montgomery, D.

2013-12-01

Study of the transport and diffusion of charged particles in a turbulent magnetic field remains a subject of considerable interest. Research has most frequently concentrated on determining the diffusion coefficient in the presence of a mean magnetic field. Here we consider Diffusion of charged particles in fully three dimensional statistically isotropic magnetic field turbulence with no mean field which is pertinent to many astrophysical situations. We classify different regions of particle energy depending upon the ratio of Larmor radius of the charged particle to the characteristic outer length scale of turbulence. We propose three different theoretical models to calculate the diffusion coefficient each applicable to a distinct range of particle energies. The theoretical results are compared with those from computer simulations, showing very good agreement.

A multi-state fragment charge difference approach for diabatic states in electron transfer: Extension and automation

NASA Astrophysics Data System (ADS)

Yang, Chou-Hsun; Hsu, Chao-Ping

2013-10-01

The electron transfer (ET) rate prediction requires the electronic coupling values. The Generalized Mulliken-Hush (GMH) and Fragment Charge Difference (FCD) schemes have been useful approaches to calculate ET coupling from an excited state calculation. In their typical form, both methods use two eigenstates in forming the target charge-localized diabatic states. For problems involve three or four states, a direct generalization is possible, but it is necessary to pick and assign the locally excited or charge-transfer states involved. In this work, we generalize the 3-state scheme for a multi-state FCD without the need of manual pick or assignment for the states. In this scheme, the diabatic states are obtained separately in the charge-transfer or neutral excited subspaces, defined by their eigenvalues in the fragment charge-difference matrix. In each subspace, the Hamiltonians are diagonalized, and there exist off-diagonal Hamiltonian matrix elements between different subspaces, particularly the charge-transfer and neutral excited diabatic states. The ET coupling values are obtained as the corresponding off-diagonal Hamiltonian matrix elements. A similar multi-state GMH scheme can also be developed. We test the new multi-state schemes for the performance in systems that have been studied using more than two states with FCD or GMH. We found that the multi-state approach yields much better charge-localized states in these systems. We further test for the dependence on the number of state included in the calculation of ET couplings. The final coupling values are converged when the number of state included is increased. In one system where experimental value is available, the multi-state FCD coupling value agrees better with the previous experimental result. We found that the multi-state GMH and FCD are useful when the original two-state approach fails.

Charge transfer during individual collisions in ice growing by riming

NASA Technical Reports Server (NTRS)

Avila, Eldo E.; Caranti, Giorgio M.

1991-01-01

The charging of a target by riming in the wind was studied in the temperature range of (-10, -18 C). For each temperature, charge transfers of both signs are observed and, according to the environmental conditions, one of them prevails. The charge is more positive as the liquid water concentration is increased at any particular temperature. It is found that even at the low impact velocities used (5 m/s) there is abundant evidence of fragmentation following the collision.

A numerical model for boiling heat transfer coefficient of zeotropic mixtures

NASA Astrophysics Data System (ADS)

Barraza Vicencio, Rodrigo; Caviedes Aedo, Eduardo

2017-12-01

Zeotropic mixtures never have the same liquid and vapor composition in the liquid-vapor equilibrium. Also, the bubble and the dew point are separated; this gap is called glide temperature (Tglide). Those characteristics have made these mixtures suitable for cryogenics Joule-Thomson (JT) refrigeration cycles. Zeotropic mixtures as working fluid in JT cycles improve their performance in an order of magnitude. Optimization of JT cycles have earned substantial importance for cryogenics applications (e.g, gas liquefaction, cryosurgery probes, cooling of infrared sensors, cryopreservation, and biomedical samples). Heat exchangers design on those cycles is a critical point; consequently, heat transfer coefficient and pressure drop of two-phase zeotropic mixtures are relevant. In this work, it will be applied a methodology in order to calculate the local convective heat transfer coefficients based on the law of the wall approach for turbulent flows. The flow and heat transfer characteristics of zeotropic mixtures in a heated horizontal tube are investigated numerically. The temperature profile and heat transfer coefficient for zeotropic mixtures of different bulk compositions are analysed. The numerical model has been developed and locally applied in a fully developed, constant temperature wall, and two-phase annular flow in a duct. Numerical results have been obtained using this model taking into account continuity, momentum, and energy equations. Local heat transfer coefficient results are compared with available experimental data published by Barraza et al. (2016), and they have shown good agreement.

Horizontal convective boiling of R448A, R449A, and R452B within a micro-fin tube

PubMed Central

KEDZIERSKI, MARK A.; KANG, DONGGYU

2017-01-01

This article presents local convective boiling measurements in a micro-fin tube for three low global warming potential refrigerants: R448A, R449A, and R452B1. An existing correlation was modified to predict multi-component mixtures, which predicted 98% of the measurements to within ±20%. The new correlation was used to compare the heat transfer coefficient of the three test fluids at the same heat flux, saturated refrigerant temperature, and refrigerant mass flux. The resulting comparison showed that refrigerant R452B exhibited the highest heat transfer, in large part due to its approximately 28% larger liquid thermal conductivity and smaller temperature glide as compared to the tested low-global warming potential refrigerants. For the example case, the heat transfer coefficient for R449A was approximately 8% larger than that for R448A, while the heat transfer coefficient for R452B was more than 59% larger than either R448A or R449A. The heat transfer coefficients for R448A and R449A were roughly between 26 and 48% less than that of R404A for the example case. In contrast, the model predicts that the R452B heat transfer coefficient was approximately 13% larger than that of R404A for the same conditions. PMID:28758148

Effect of aperture geometry on heat transfer in tilted partially open cavities

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

Elsayed, M.M.; Chakroun, W.

1999-11-01

Heat transfer in cavities is receiving increasing attention because of the various applications in engineering; e.g., passive solar heating, energy conservation in buildings, solar concentrating receivers, and electronic equipment. Here, convection from a square, tilted partially open cavity was investigated experimentally. The experiment was carried out to study the effect of the aperture geometry on the heat transfer between the cavity and the surrounding air. Four different geometrical arrangements for the opening were investigated: (1) high wall slit, (2) low wall slit, (3) centered wall slit, and (4) uniform wall slots. Each opening arrangement was studied at opening ratios (i.e.,more » ratio of opening height to cavity height) of 0.25, 0.5, and 0.75. The average heat transfer coefficient between the cavity and the surrounding air was estimated for each geometrical arrangement for tilt angles ranging from {minus}90 deg to +90 deg with increments of 15 deg and at a constant heat flux Grashof number of 5.5 x 10{sup 8}. The results showed that for tilt angles between 90 and 75 deg, the heat transfer coefficient has a small value that is independent of the geometrical arrangement of the opening. The value of the heat transfer coefficient increases sharply with decreasing tilt angle until an angle value of zero degrees is reached. The increase in the heat transfer coefficient continues in the negative range of tilt angle but not in the same rate as in the positive range of the tilt angle. The uniform slot arrangement gave in general higher heat transfer coefficient than the other three arrangements of the opening. Large differences in the heat transfer coefficient were observed between the high and the low wall slits where the high wall slit is found to transfer more heat to the surroundings than the low wall slit. Correlations were developed to predict the average Nusselt number of the cavity in terms of the opening ratio and the cavity tilt angle for cavities with high wall slit, low wall slit, centered wall slit, and the uniform wall slots.« less

Heat transfer coefficients for staggered arrays of short pin fins

NASA Technical Reports Server (NTRS)

Vanfossen, G. J.

1981-01-01

Short pin fins are often used to increase that heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).

Simulation model of stratified thermal energy storage tank using finite difference method

NASA Astrophysics Data System (ADS)

Waluyo, Joko

2016-06-01

Stratified TES tank is normally used in the cogeneration plant. The stratified TES tanks are simple, low cost, and equal or superior in thermal performance. The advantage of TES tank is that it enables shifting of energy usage from off-peak demand for on-peak demand requirement. To increase energy utilization in a stratified TES tank, it is required to build a simulation model which capable to simulate the charging phenomenon in the stratified TES tank precisely. This paper is aimed to develop a novel model in addressing the aforementioned problem. The model incorporated chiller into the charging of stratified TES tank system in a closed system. The model was developed in one-dimensional type involve with heat transfer aspect. The model covers the main factors affect to degradation of temperature distribution namely conduction through the tank wall, conduction between cool and warm water, mixing effect on the initial flow of the charging as well as heat loss to surrounding. The simulation model is developed based on finite difference method utilizing buffer concept theory and solved in explicit method. Validation of the simulation model is carried out using observed data obtained from operating stratified TES tank in cogeneration plant. The temperature distribution of the model capable of representing S-curve pattern as well as simulating decreased charging temperature after reaching full condition. The coefficient of determination values between the observed data and model obtained higher than 0.88. Meaning that the model has capability in simulating the charging phenomenon in the stratified TES tank. The model is not only capable of generating temperature distribution but also can be enhanced for representing transient condition during the charging of stratified TES tank. This successful model can be addressed for solving the limitation temperature occurs in charging of the stratified TES tank with the absorption chiller. Further, the stratified TES tank can be charged with the cooling energy of absorption chiller that utilizes from waste heat from gas turbine of the cogeneration plant.

Charge exchange molecular ion source

DOEpatents

Vella, Michael C.

2003-06-03

Ions, particularly molecular ions with multiple dopant nucleons per ion, are produced by charge exchange. An ion source contains a minimum of two regions separated by a physical barrier and utilizes charge exchange to enhance production of a desired ion species. The essential elements are a plasma chamber for production of ions of a first species, a physical separator, and a charge transfer chamber where ions of the first species from the plasma chamber undergo charge exchange or transfer with the reactant atom or molecules to produce ions of a second species. Molecular ions may be produced which are useful for ion implantation.

Direct Observation of Charge Transfer at a MgO(111) Surface

NASA Astrophysics Data System (ADS)

Subramanian, A.; Marks, L. D.; Warschkow, O.; Ellis, D. E.

2004-01-01

Transmission electron diffraction (TED) combined with direct methods have been used to study the √(3)×√(3)R30° reconstruction on the polar (111) surface of MgO and refine the valence charge distribution. The surface is nonstoichiometric and is terminated by a single magnesium atom. A charge-compensating electron hole is localized in the next oxygen layer and there is a nominal charge transfer from the oxygen atoms to the top magnesium atom. The partial charges that we obtain for the surface atoms are in reasonable agreement with empirical bond-valence estimations.

The study of surface acoustic wave charge transfer device

NASA Technical Reports Server (NTRS)

Papanicolaou, N.; Lin, H. C.

1978-01-01

A surface acoustic wave-charge transfer device, consisting of an n-type silicon substrate, a thermally grown silicon dioxide layer, and a sputtered film of piezoelectric zinc oxide is proposed as a means of circumventing problems associated with charge-coupled device (CCD) applications in memory, signal processing, and imaging. The proposed device creates traveling longitudinal electric fields in the silicon and replaces the multiphase clocks in CCD's. The traveling electric fields create potential wells which carry along charges stored there. These charges may be injected into the wells by light or by using a p-n junction as in conventional CCD's.

An abnormally slow proton transfer reaction in a simple HBO derivative due to ultrafast intramolecular-charge transfer events.

PubMed

Alarcos, Noemí; Gutierrez, Mario; Liras, Marta; Sánchez, Félix; Douhal, Abderrazzak

2015-07-07

We report on the steady-state, picosecond and femtosecond time-resolved studies of a charge and proton transfer dye 6-amino-2-(2'-hydroxyphenyl)benzoxazole (6A-HBO) and its methylated derivative 6-amino-2-(2'-methoxyphenyl)benzoxazole (6A-MBO), in different solvents. With femtosecond resolution and comparison with the photobehaviour of 6A-MBO, we demonstrate for 6A-HBO in solution, the photoproduction of an intramolecular charge-transfer (ICT) process at S1 taking place in ∼140 fs or shorter, followed by solvent relaxation in the charge transferred species. The generated structure (syn-enol charge transfer conformer) experiences an excited-state intramolecular proton-transfer (ESIPT) reaction to produce a keto-type tautomer. This subsequent proton motion occurs in 1.2 ps (n-heptane), 14 ps (DCM) and 35 ps (MeOH). In MeOH, it is assisted by the solvent molecules and occurs through tunneling for which we got a large kinetic isotope effect (KIE) of about 13. For the 6A-DBO (deuterated sample in CD3OD) the global proton-transfer reaction takes place in 200 ps, showing a remarkable slow KIE regime. The slow ESIPT reaction in DCM (14 ps), not through tunnelling as it is not sensitive to OH/OD exchange, has however to overcome an energy barrier using intramolecular as well as solvent coordinates. The rich ESIPT dynamics of 6A-HBO in the used solutions is governed by an ICT reaction, triggered by the amino group, and it is solvent dependent. Thus, the charge injection to a 6A-HBO molecular frame makes the ICT species more stable, and the phenol group less acidic, slowing down the subsequent ESIPT reaction. Our findings bring new insights into the coupling between ICT and ESIPT reactions on the potential-energy surfaces of several barriers.

Numerical investigation of saturated upward flow boiling of water in a vertical tube using VOF model: effect of different boundary conditions

NASA Astrophysics Data System (ADS)

Hasanpour, B.; Irandoost, M. S.; Hassani, M.; Kouhikamali, R.

2018-01-01

In this paper a numerical simulation of upward two-phase flow evaporation in a vertical tube has been studied by considering water as working fluid. To this end, the computational fluid dynamic simulations of this system are performed with heat and mass transfer mechanisms due to energy transfer during the phase change interaction near the heat transfer surface. The volume of fluid model in an available Eulerian-Eulerian approach based on finite volume method is utilized and the mass source term in conservation of mass equation is implemented using a user defined function. The characteristics of water flow boiling such as void fraction and heat transfer coefficient distribution are investigated. The main cause of fluctuations on heat transfer coefficient and volume fraction is velocity increment in the vapor phase rather than the liquid phase. The case study of this research including convective heat transfer coefficient and tube diameter are considered as a parametric study. The operating conditions are considered at high pressure in saturation temperature and the physical properties of water are determined by considering system's inlet temperature and pressure in saturation conditions. Good agreement is achieved between the numerical and the experimental values of heat transfer coefficients.

Numerical investigation of saturated upward flow boiling of water in a vertical tube using VOF model: effect of different boundary conditions

NASA Astrophysics Data System (ADS)

Hasanpour, B.; Irandoost, M. S.; Hassani, M.; Kouhikamali, R.

2018-07-01

In this paper a numerical simulation of upward two-phase flow evaporation in a vertical tube has been studied by considering water as working fluid. To this end, the computational fluid dynamic simulations of this system are performed with heat and mass transfer mechanisms due to energy transfer during the phase change interaction near the heat transfer surface. The volume of fluid model in an available Eulerian-Eulerian approach based on finite volume method is utilized and the mass source term in conservation of mass equation is implemented using a user defined function. The characteristics of water flow boiling such as void fraction and heat transfer coefficient distribution are investigated. The main cause of fluctuations on heat transfer coefficient and volume fraction is velocity increment in the vapor phase rather than the liquid phase. The case study of this research including convective heat transfer coefficient and tube diameter are considered as a parametric study. The operating conditions are considered at high pressure in saturation temperature and the physical properties of water are determined by considering system's inlet temperature and pressure in saturation conditions. Good agreement is achieved between the numerical and the experimental values of heat transfer coefficients.

Integrated exhaust gas recirculation and charge cooling system

DOEpatents

Wu, Ko-Jen

2013-12-10

An intake system for an internal combustion engine comprises an exhaust driven turbocharger configured to deliver compressed intake charge, comprising exhaust gas from the exhaust system and ambient air, through an intake charge conduit and to cylinders of the internal combustion engine. An intake charge cooler is in fluid communication with the intake charge conduit. A cooling system, independent of the cooling system for the internal combustion engine, is in fluid communication with the intake charge cooler through a cooling system conduit. A coolant pump delivers a low temperature cooling medium from the cooling system to and through the intake charge cooler for the transfer of heat from the compressed intake charge thereto. A low temperature cooler receives the heated cooling medium through the cooling system conduit for the transfer or heat therefrom.

Epitaxial growth and electronic properties of well ordered phthalocyanine heterojunctions MnPc/F{sub 16}CoPc

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

Lindner, Susi; Mahns, Benjamin; Treske, Uwe

2014-09-07

We have prepared phthalocyanine heterojunctions out of MnPc and F{sub 16}CoPc, which were studied by means of X-ray absorption spectroscopy. This heterojunction is characterized by a charge transfer at the interface, resulting in charged MnPc{sup δ} {sup +} and F{sub 16}CoPc{sup δ} {sup −} species. Our data reveal that the molecules are well ordered and oriented parallel to the substrate surface. Furthermore, we demonstrate the filling of the Co 3d{sub z{sup 2}} orbital due to the charge transfer, which supports the explanation of the density functional theory, that the charge transfer is local and affects the metal centers only.

Solvent Dependence of Lateral Charge Transfer in a Porphyrin Monolayer

DOE PAGES

Brennan, Bradley J.; Regan, Kevin P.; Durrell, Alec C.; ...

2016-12-19

Lateral charge transport in a redox)active monolayer can be utilized for solar energy harvesting. We chose the porphyrin system to study the influence of the solvent on lateral hole hopping, which plays a crucial role in the charge)transfer kinetics. We also examined the influence of water, acetonitrile, and propylene carbonate as solvents. Hole)hopping lifetimes varied by nearly three orders of magnitude among solvents, ranging from 3 ns in water to 2800 ns in propylene carbonate, and increased nonlinearly as a function of added acetonitrile in aqueous solvent mixtures. Our results elucidate the important roles of solvation, molecular packing dynamics, andmore » lateral charge)transfer mechanisms that have implications for all dye)sensitized photoelectrochemical device designs.« less

Substitution effects on the absorption spectra of nitrophenolate isomers.

PubMed

Wanko, Marius; Houmøller, Jørgen; Støchkel, Kristian; Suhr Kirketerp, Maj-Britt; Petersen, Michael Åxman; Nielsen, Mogens Brøndsted; Nielsen, Steen Brøndsted; Rubio, Angel

2012-10-05

Charge-transfer excitations highly depend on the electronic coupling between the donor and acceptor groups. Nitrophenolates are simple examples of charge-transfer systems where the degree of coupling differs between ortho, meta and para isomers. Here we report the absorption spectra of the isolated anions in vacuo to avoid the complications of solvent effects. Gas-phase action spectroscopy was done with two different setups, an electrostatic ion storage ring and an accelerator mass spectrometer. The results are interpreted on the basis of CC2 quantum chemical calculations. We identified absorption maxima at 393, 532, and 399 nm for the para, meta, and ortho isomer, respectively, with the charge-transfer transition into the lowest excited singlet state. In the meta isomer, this π-π* transition is strongly redshifted and its oscillator strength reduced, which is related to the pronounced charge-transfer character, as a consequence of the topology of the conjugated π-system. Each isomer's different charge distribution in the ground state leads to a very different solvent shift, which in acetonitrile is bathochromic for the para and ortho, but hypsochromic for the meta isomer.

Electron-lattice interactions strongly renormalize the charge-transfer energy in the spin-chain cuprate Li 2CuO 2

DOE PAGES

Johnston, Steve; Monney, Claude; Bisogni, Valentina; ...

2016-02-17

Strongly correlated insulators are broadly divided into two classes: Mott–Hubbard insulators, where the insulating gap is driven by the Coulomb repulsion U on the transition-metal cation, and charge-transfer insulators, where the gap is driven by the charge-transfer energy Δ between the cation and the ligand anions. The relative magnitudes of U and Δ determine which class a material belongs to, and subsequently the nature of its low-energy excitations. These energy scales are typically understood through the local chemistry of the active ions. Here we show that the situation is more complex in the low-dimensional charge-transfer insulator Li 2CuO 2, wheremore » Δ has a large non-electronic component. Combining resonant inelastic X-ray scattering with detailed modelling, we determine how the elementary lattice, charge, spin and orbital excitations are entangled in this material. This results in a large lattice-driven renormalization of Δ, which significantly reshapes the fundamental electronic properties of Li 2CuO 2.« less

Frenkel and Charge-Transfer Excitations in Donor-acceptor Complexes from Many-Body Green's Functions Theory.

PubMed

Baumeier, Björn; Andrienko, Denis; Rohlfing, Michael

2012-08-14

Excited states of donor-acceptor dimers are studied using many-body Green's functions theory within the GW approximation and the Bethe-Salpeter equation. For a series of prototypical small-molecule based pairs, this method predicts energies of local Frenkel and intermolecular charge-transfer excitations with the accuracy of tens of meV. Application to larger systems is possible and allowed us to analyze energy levels and binding energies of excitons in representative dimers of dicyanovinyl-substituted quarterthiophene and fullerene, a donor-acceptor pair used in state of the art organic solar cells. In these dimers, the transition from Frenkel to charge transfer excitons is endothermic and the binding energy of charge transfer excitons is still of the order of 1.5-2 eV. Hence, even such an accurate dimer-based description does not yield internal energetics favorable for the generation of free charges either by thermal energy or an external electric field. These results confirm that, for qualitative predictions of solar cell functionality, accounting for the explicit molecular environment is as important as the accurate knowledge of internal dimer energies.

Molecular dynamics and charge transport in organic semiconductors: a classical approach to modeling electron transfer

DOE PAGES

Pelzer, Kenley M.; Vázquez-Mayagoitia, Álvaro; Ratcliff, Laura E.; ...

2017-01-01

Organic photovoltaics (OPVs) are a promising carbon-neutral energy conversion technology, with recent improvements pushing power conversion efficiencies over 10%. A major factor limiting OPV performance is inefficiency of charge transport in organic semiconducting materials (OSCs). Due to strong coupling with lattice degrees of freedom, the charges form polarons, localized quasi-particles comprised of charges dressed with phonons. These polarons can be conceptualized as pseudo-atoms with a greater effective mass than a bare charge. Here we propose that due to this increased mass, polarons can be modeled with Langevin molecular dynamics (LMD), a classical approach with a computational cost much lower thanmore » most quantum mechanical methods. Here we present LMD simulations of charge transfer between a pair of fullerene molecules, which commonly serve as electron acceptors in OSCs. We find transfer rates consistent with experimental measurements of charge mobility, suggesting that this method may provide quantitative predictions of efficiency when used to simulate materials on the device scale. Our approach also offers information that is not captured in the overall transfer rate or mobility: in the simulation data, we observe exactly when and why intermolecular transfer events occur. In addition, we demonstrate that these simulations can shed light on the properties of polarons in OSCs. In conclusion, much remains to be learned about these quasi-particles, and there are no widely accepted methods for calculating properties such as effective mass and friction. Lastly, our model offers a promising approach to exploring mass and friction as well as providing insight into the details of polaron transport in OSCs.« less

Experimental study on convective heat transfer of TiO2 nanofluids

NASA Astrophysics Data System (ADS)

Vakili, M.; Mohebbi, A.; Hashemipour, H.

2013-08-01

In this study, nanofluids with different TiO2 nanoparticle concentrations were synthesized and measured in different constant heat fluxes for their heat transfer behavior upon flowing through a vertical pipe. Addition of nanoparticles into the base fluid enhances the forced convective heat transfer coefficient. The results show that the enhancement of the convective heat transfer coefficient in the mixture consisting of ethylene glycol and distilled water is more than distilled water as a base fluid.

Physical stage of photosynthesis charge separation

NASA Astrophysics Data System (ADS)

Yakovlev, A. G.; Shuvalov, V. A.

2016-06-01

An analytical review is given concerning the biophysical aspects of light-driven primary charge separation in photosynthesis reaction centers (RCs) which are special pigment-protein complexes residing in a cell membrane. The primary (physical) stage of charge separation occurs in the pico- and femtosecond ranges and consists of transferring an electron along the active A-branch of pigments. The review presents vast factual material on both the general issues of primary photosynthesis and some more specific topics, including (1) the role of the inactive B-branch of pigments, (2) the effect of the protein environment on the charge separation, and (3) the participation of monomeric bacteriochlorophyll BA in primary electron acceptance. It is shown that the electron transfer and stabilization are strongly influenced by crystallographic water and tyrosine M210 molecules from the nearest environment of BA. A linkage between collective nuclear motions and electron transfer upon charge separation is demonstrated. The nature of the high quantum efficiency of primary charge separation reactions is discussed.

Electron transfer beyond the static picture: A TDDFT/TD-ZINDO study of a pentacene dimer

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

Reslan, Randa; Lopata, Kenneth; Arntsen, Christopher

2012-12-14

We use time-dependent density functional theory and time-dependent ZINDO (a semi-empirical method) to study transfer of an extra electron between a pair of pentacene molecules. A measure of the electronic transfer integral is computed in a dynamic picture via the vertical excitation energy from a delocalized anionic ground state. With increasing dimer separation, this dynamical measurement of charge transfer is shown to be significantly larger than the commonly used static approximation (i.e., LUMO+1–LUMO of the neutral dimer, or HOMO–LUMO of the charged dimer), up to an order of magnitude higher at 6 Å. These results offer a word of cautionmore » for calculations involving large separations, as in organic photovoltaics, where care must be taken when using a static picture to model charge transfer.« less

Electron transfer beyond the static picture: A TDDFT/TD-ZINDO study of a pentacene dimer

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

Reslan, Randa; Lopata, Kenneth A.; Arntsen, Christopher D.

2012-12-14

We use time-dependent density functional theory and time-dependent ZINDO (a semi-empirical method) to study transfer of an extra electron between a pair of pentacene dimers. A measure of the electronic transfer integral is computed in a dynamic picture via the vertical excitation energy from a delocalized anionic ground state. With increasing dimer separation, this dynamical measurement of charge transfer is shown to be significantly larger than the commonly used static approximation (i.e., LUMO+1 - LUMO of the neutral dimer, or HOMO - LUMO of the charged dimer), up to an order of magnitude higher at 6 Å. These results offermore » a word of caution for calculations involving large separations, as in organic photovoltaics, where care must be taken when using a static picture to model charge transfer.« less

Effect of local atomic and electronic structures on thermoelectric properties of chemically substituted CoSi

NASA Astrophysics Data System (ADS)

Hsu, C. C.; Pao, C. W.; Chen, J. L.; Chen, C. L.; Dong, C. L.; Liu, Y. S.; Lee, J. F.; Chan, T. S.; Chang, C. L.; Kuo, Y. K.; Lue, C. S.

2014-05-01

We report the effects of Ge partial substitution for Si on local atomic and electronic structures of thermoelectric materials in binary compound cobalt monosilicides (\\text{CoSi}_{1-x}\\text{Ge}_{x}\\text{:}\\ 0 \\le x \\le 0.15 ). Correlations between local atomic/electronic structure and thermoelectric properties are investigated by means of X-ray absorption spectroscopy. The spectroscopic results indicate that as Ge is partially substituted onto Si sites at x \\le 0.05 , Co in CoSi1-xGex gains a certain amount of charge in its 3d orbitals. Contrarily, upon further replacing Si with Ge at x \\ge 0.05 , the Co 3d orbitals start to lose some of their charge. Notably, thermopower is strongly correlated with charge redistribution in the Co 3d orbital, and the observed charge transfer between Ge and Co is responsible for the variation of Co 3d occupancy number. In addition to Seebeck coefficient, which can be modified by tailoring the Co 3d states, local lattice disorder may also be beneficial in enhancing the thermoelectric properties. Extended X-ray absorption fine structure spectrum results further demonstrate that the lattice phonons can be enhanced by Ge doping, which results in the formation of the disordered Co-Co pair. Improvements in the thermoelectric properties are interpreted based on the variation of local atomic and electronic structure induced by lattice distortion through chemical substitution.

Enhancing thermoelectrochemical properties by tethering ferrocene to the anion or cation of ionic liquids: altered thermodynamics and solubility.

PubMed

Aldous, Leigh; Black, Jeffrey J; Elias, Maximo C; Gélinas, Bruno; Rochefort, Dominic

2017-09-13

Entropic changes inherent within a redox process typically result in significant temperature sensitivity. This can be utilised positively or can be a detrimental process. This study has investigated the thermoelectrochemical properties (temperature-dependant electrochemistry) of the ferrocenium|ferrocene redox couple in an ionic liquid, and in particular the effect of covalently tethering this redox couple to fixed positive or negative charges. As such, the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide was employed to dissolve ferrocene, as well as cationic-tethered ferrocene (the 1-ethyl-3-(methylferrocenyl)imidazolium cation) and anionic-tethered ferrocene (the ferrocenylsulfonyl(trifluoromethylsulfonyl)imide anion). These systems were characterised in terms of their voltammetry (apparent formal potentials, diffusion coefficients and electron transfer rate constants) and thermoelectrochemistry (temperature coefficients of the cell potential or 'Seebeck coefficients', short circuit current densities and power density outputs). The oxidised cationic species behaved like a dicationic species and was thus 6-fold more effective at converting waste thermal energy to electrical power within a thermoelectrochemical cell than unmodified ferrocene. This was almost exclusively due to a significant boost in the Seebeck coefficient of this redox couple. Conversely, the oxidised anionic species was formally a zwitterion, but this zwitterionic species behaved thermodynamically like a neutral species. The inverted entropic change upon going from ferrocene to anion-tethered ferrocene allowed development of a largely temperature-insensitive reference potential based upon a mixture of acetylferrocene and ferricenyl(iii)sulfonyl(trifluoromethylsulfonyl)imide.

Forced convective heat transfer in curved diffusers

NASA Technical Reports Server (NTRS)

Rojas, J.; Whitelaw, J. H.; Yianneskis, M.

1987-01-01

Measurements of the velocity characteristics of the flows in two curved diffusers of rectangular cross section with C and S-shaped centerlines are presented and related to measurements of wall heat transfer coefficients along the heated flat walls of the ducts. The velocity results were obtained by laser-Doppler anemometry in a water tunnel and the heat transfer results by liquid crystal thermography in a wind tunnel. The thermographic technique allowed the rapid and inexpensive measurement of wall heat transfer coefficients along flat walls of arbitrary boundary shapes with an accuracy of about 5 percent. The results show that an increase in secondary flow velocities near the heated wall causes an increase in the local wall heat transfer coefficient, and quantify the variation for maximum secondary-flow velocities in a range from 1.5 to 17 percent of the bulk flow velocity.

Air charged and microtip catheters cannot be used interchangeably for urethral pressure measurement: a prospective, single-blind, randomized trial.

PubMed

Zehnder, Pascal; Roth, Beat; Burkhard, Fiona C; Kessler, Thomas M

2008-09-01

We determined and compared urethral pressure measurements using air charged and microtip catheters in a prospective, single-blind, randomized trial. A consecutive series of 64 women referred for urodynamic investigation underwent sequential urethral pressure measurements using an air charged and a microtip catheter in randomized order. Patients were blinded to the type and sequence of catheter used. Agreement between the 2 catheter systems was assessed using the Bland and Altman 95% limits of agreement method. Intraclass correlation coefficients of air charged and microtip catheters for maximum urethral closure pressure at rest were 0.97 and 0.93, and for functional profile length they were 0.9 and 0.78, respectively. Pearson's correlation coefficients and Lin's concordance coefficients of air charged and microtip catheters were r = 0.82 and rho = 0.79 for maximum urethral closure pressure at rest, and r = 0.73 and rho = 0.7 for functional profile length, respectively. When applying the Bland and Altman method, air charged catheters gave higher readings than microtip catheters for maximum urethral closure pressure at rest (mean difference 7.5 cm H(2)O) and functional profile length (mean difference 1.8 mm). There were wide 95% limits of agreement for differences in maximum urethral closure pressure at rest (-24.1 to 39 cm H(2)O) and functional profile length (-7.7 to 11.3 mm). For urethral pressure measurement the air charged catheter is at least as reliable as the microtip catheter and it generally gives higher readings. However, air charged and microtip catheters cannot be used interchangeably for clinical purposes because of insufficient agreement. Hence, clinicians should be aware that air charged and microtip catheters may yield completely different results, and these differences should be acknowledged during clinical decision making.

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

PubMed

Khokhlova, Svetlana S; Burshtein, Anatoly I

2011-01-21

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

Change of electric dipole moment in charge transfer transitions of ferrocene oligomers studied by ultrafast two-photon absorption

NASA Astrophysics Data System (ADS)

Mikhaylov, Alexander; Arias, Eduardo; Moggio, Ivana; Ziolo, Ronald; Uudsemaa, Merle; Trummal, Aleksander; Cooper, Thomas; Rebane, Aleksander

2017-02-01

Change of permanent electric dipole moment in the lower-energy charge transfer transitions for a series of symmetrical and non-symmetrical ferrocene-phenyleneethynylene oligomers were studied by measuring the corresponding femtosecond two-photon absorption cross section spectra, and were determined to be in the range Δμ = 3 - 10 D. Quantum-chemical calculations of Δμ for the non-symmetrical oligomers show good quantitative agreement with the experimental results, thus validating two-photon absorption spectroscopy as a viable experimental approach to study electrostatic properties of organometallics and other charge transfer systems.

Molecular implementation of molecular shift register memories

NASA Technical Reports Server (NTRS)

Beratan, David N. (Inventor); Onuchic, Jose N. (Inventor)

1991-01-01

An electronic shift register memory (20) at the molecular level is described. The memory elements are based on a chain of electron transfer molecules (22) and the information is shifted by photoinduced (26) electron transfer reactions. Thus, multi-step sequences of charge transfer reactions are used to move charge with high efficiency down a molecular chain. The device integrates compositions of the invention onto a VLSI substrate (36), providing an example of a molecular electronic device which may be fabricated. Three energy level schemes, molecular implementation of these schemes, optical excitation strategies, charge amplification strategies, and error correction strategies are described.

Intramolecular Charge Transfer States in the Condensed Phase

NASA Astrophysics Data System (ADS)

Williams, C. F.; Herbert, J. M.

2009-06-01

Time-Dependent Density Functional Theory (TDDFT) with long range corrected functionals can give accurate results for the energies of electronically excited states involving Intramolecular Charge Transfer (ICT) in large molecules. If this is combined with a Molecular Mechanics (MM) representation of the surrounding solvent this technique can be used to interpret the results of condensed phase UV-Vis Spectroscopy. Often the MM region is represented by a set of point charges, however this means that the solvent cannot repolarize to adapt to the new charge distribution as a result of ICT and so the excitation energies to ICT states are overestimated. To solve this problem an algorithm that interfaces TDDFT with the polarizable force-field AMOEBA is presented; the effect of solvation on charge transfer in species such as 4,4'dimethylaminobenzonitrile (DMABN) is discussed. M.A. Rohrdanz, K.M. Martins, and J.M. Herbert, J. Chem. Phys. 130 034107 (2008).

Charge transfer in photorefractive CdTe:Ge at different wavelengths

NASA Astrophysics Data System (ADS)

Shcherbin, K.; Odoulov, S.; Ramaz, F.; Farid, B.; Briat, B.; von Bardeleben, H. J.; Delaye, P.; Roosen, G.

2001-10-01

The charge transfer processes in photorefractive CdTe:Ge were modeled using the data of optical absorption, magnetic circular dichroism (MCD) and electron paramagnetic resonance (EPR) spectroscopies. Within the developed model the variations in the photorefractive properties of different CdTe:Ge samples are explained by differences in the relative concentrations of donor and trap centers. The existence of two different centers of comparable concentrations, each in two charge states, allows charge redistribution between them and gives rise to optical sensitization of some CdTe:Ge samples for photorefractive recording under an auxiliary illumination. In the present article we follow the proposal of pseudo-3D presentation of light-induced absorption to distinguish the main charge transfer processes at different excitation energies and explain the sensitization of CdTe:Ge for photorefractive recording at 1.06, 1.32 and 1.55 μm by light with appropriate wavelength.

Charge-Transfer Processes in Warm Dense Matter: Selective Spectral Filtering for Laser-Accelerated Ion Beams

NASA Astrophysics Data System (ADS)

Braenzel, J.; Barriga-Carrasco, M. D.; Morales, R.; Schnürer, M.

2018-05-01

We investigate, both experimentally and theoretically, how the spectral distribution of laser accelerated carbon ions can be filtered by charge exchange processes in a double foil target setup. Carbon ions at multiple charge states with an initially wide kinetic energy spectrum, from 0.1 to 18 MeV, were detected with a remarkably narrow spectral bandwidth after they had passed through an ultrathin and partially ionized foil. With our theoretical calculations, we demonstrate that this process is a consequence of the evolution of the carbon ion charge states in the second foil. We calculated the resulting spectral distribution separately for each ion species by solving the rate equations for electron loss and capture processes within a collisional radiative model. We determine how the efficiency of charge transfer processes can be manipulated by controlling the ionization degree of the transfer matter.

Structural and spectroscopic characterizations on the charge-transfer interactions of the second generation poly(propylene amine) dendrimers with iodine and picric acid acceptors

NASA Astrophysics Data System (ADS)

El-Sayed, Mohamed Y.; Refat, Moamen S.

2015-02-01

Herein, this study was focused to get a knowledge about the intermolecular charge transfer complexes between the second generation of poly(propylene amine) dendrimer (PPD2) with picric acid (PA) and iodine (I2) as π and σ-acceptors. The charge-transfer interaction of the PPD2 electron donor and the PA acceptor has been studied in CHCl3. The resulted data refereed to the formation of the new CT-complex with the general formula [(PPD2)(PA)4]. The 1:4 stoichiometry of the reaction was discussed upon the on elemental analysis and photometric titration. On the other hand, the 1:3½ iodine-PPD2 heptaiodide (I7-) charge-transfer complex has been studied spectrophotometrically in chloroform at room temperature with general formula [(PPD2)]+I7-. The electronic absorption bands of 2I2·I3- (I7-) are observed at 358 and 294 nm. Raman laser spectrum of the brown solid heptaiodide complex has two clearly vibration bands at 155 and 110 cm-1 due to symmetric stretching νs(Isbnd I) outer and inner bonds, respectively. The 1H NMR spectra and differential scanning calorimetry (DSC) data of PPD2 charge-transfer complexes were discussed.

Abnormal Magnetic Field Effects on Electrogenerated Chemiluminescence

NASA Astrophysics Data System (ADS)

Pan, Haiping; Shen, Yan; Wang, Hongfeng; He, Lei; Hu, Bin

2015-03-01

We report abnormal magnetic field effects on electrogenerated chemiluminescence (MFEECL) based on triplet emission from the Ru(bpy)3Cl2-TPrA electrochemical system: the appearance of MFEECL after magnetic field ceases. In early studies the normal MFEECL have been observed from electrochemical systems during the application of magnetic field. Here, the abnormal MFEECL suggest that the activated charge-transfer [Ru(bpy)33+ … TPrA•] complexes may become magnetized in magnetic field and experience a long magnetic relaxation after removing magnetic field. Our analysis indicates that the magnetic relaxation can gradually increase the density of charge-transfer complexes within reaction region due to decayed magnetic interactions, leading to a positive component in the abnormal MFEECL. On the other hand, the magnetic relaxation facilitates an inverse conversion from triplets to singlets within charge-transfer complexes. The inverse triplet --> singlet conversion reduces the density of triplet light-emitting states through charge-transfer complexes and gives rise to a negative component in the abnormal MFEECL. The combination of positive and negative components can essentially lead to a non-monotonic profile in the abnormal MFEECL after ceasing magnetic field. Nevertheless, our experimental studies may reveal un-usual magnetic behaviors with long magnetic relaxation from the activated charge-transfer [Ru(bpy)33+ … TPrA•] complexes in solution at room temperature.

Charging of Proteins in Native Mass Spectrometry

DOE PAGES

Susa, Anna C.; Xia, Zijie; Tang, Henry Y. H.; ...

2016-10-12

Factors that influence the charging of protein ions formed by electrospray ionization from aqueous solutions in which proteins have native structures and function were investigated. Protein ions ranging in molecular weight from 12.3 to 79.7 kDa and pI values from 5.4 to 9.6 were formed from different solutions and reacted with volatile bases of gas-phase basicities higher than that of ammonia in the cell of a Fourier-transform ion cyclotron resonance mass spectrometer. The charge-state distribution of cytochrome c ions formed from aqueous ammonium or potassium acetate is the same. Moreover, ions formed from these two solutions do not undergo protonmore » transfer to 2-fluoropyridine, which is 8 kcal/mol more basic than ammonia. These results provide compelling evidence that proton transfer between ammonia and protein ions does not limit protein ion charge in native electrospray ionization. Both circular dichroism and ion mobility measurements indicate that there are differences in conformations of proteins in pure water and aqueous ammonium acetate, and these differences can account for the difference in the extent of charging and proton-transfer reactivities of protein ions formed from these solutions. The extent of proton transfer of the protein ions with higher gas-phase basicity bases trends with how closely the protein ions are charged to the value predicted by the Rayleigh limit for spherical water droplets approximately the same size as the proteins. These results indicate that droplet charge limits protein ion charge in native mass spectrometry and are consistent with these ions being formed by the charged residue mechanism.« less

Charging of Proteins in Native Mass Spectrometry

NASA Astrophysics Data System (ADS)

Susa, Anna C.; Xia, Zijie; Tang, Henry Y. H.; Tainer, John A.; Williams, Evan R.

2017-02-01

Factors that influence the charging of protein ions formed by electrospray ionization from aqueous solutions in which proteins have native structures and function were investigated. Protein ions ranging in molecular weight from 12.3 to 79.7 kDa and pI values from 5.4 to 9.6 were formed from different solutions and reacted with volatile bases of gas-phase basicities higher than that of ammonia in the cell of a Fourier-transform ion cyclotron resonance mass spectrometer. The charge-state distribution of cytochrome c ions formed from aqueous ammonium or potassium acetate is the same. Moreover, ions formed from these two solutions do not undergo proton transfer to 2-fluoropyridine, which is 8 kcal/mol more basic than ammonia. These results provide compelling evidence that proton transfer between ammonia and protein ions does not limit protein ion charge in native electrospray ionization. Both circular dichroism and ion mobility measurements indicate that there are differences in conformations of proteins in pure water and aqueous ammonium acetate, and these differences can account for the difference in the extent of charging and proton-transfer reactivities of protein ions formed from these solutions. The extent of proton transfer of the protein ions with higher gas-phase basicity bases trends with how closely the protein ions are charged to the value predicted by the Rayleigh limit for spherical water droplets approximately the same size as the proteins. These results indicate that droplet charge limits protein ion charge in native mass spectrometry and are consistent with these ions being formed by the charged residue mechanism.

Larry car for a coking oven battery

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

Corry, D.B.

A larry car (3) for transporting a charge of pre-heated coal along the top of a battery of coke ovens, from a storage installation including a group of metering bins (1) at one or more filling stations above the battery, to a corresponding group of charge holes for the oven chamber to be charged, the car including a corresponding group of coal transfer hoppers (4) each having valved inlet and discharge apertures (5,21), a sealed connection (2) between each metering bin and transfer hopper, an inert gas reservoir (10) connectable via a valved manifold (13,14) to each transfer hopper, amore » valved connection (7,8,9) for charging the reservoir, and a valved connection (15,16,17) to permit dusty gas to be displaced into the storage bunkers, and control means for the various valved connections to maintain continuous isolation of the interior of each transfer hopper from the atmosphere, to permit dust-laden gases to escape into the storage installation, and to cause inert medium to displace coal discharged from the transfer hoppers.« less

High-surface-area architectures for improved charge transfer kinetics at the dark electrode in dye-sensitized solar cells.

PubMed

Hoffeditz, William L; Katz, Michael J; Deria, Pravas; Martinson, Alex B F; Pellin, Michael J; Farha, Omar K; Hupp, Joseph T

2014-06-11

Dye-sensitized solar cell (DSC) redox shuttles other than triiodide/iodide have exhibited significantly higher charge transfer resistances at the dark electrode. This often results in poor fill factor, a severe detriment to device performance. Rather than moving to dark electrodes of untested materials that may have higher catalytic activity for specific shuttles, the surface area of platinum dark electrodes could be increased, improving the catalytic activity by simply presenting more catalyst to the shuttle solution. A new copper-based redox shuttle that experiences extremely high charge-transfer resistance at conventional Pt dark electrodes yields cells having fill-factors of less than 0.3. By replacing the standard Pt dark electrode with an inverse opal Pt electrode fabricated via atomic layer deposition, the dark electrode surface area is boosted by ca. 50-fold. The resulting increase in interfacial electron transfer rate (decrease in charge-transfer resistance) nearly doubles the fill factor and therefore the overall energy conversion efficiency, illustrating the utility of this high-area electrode for DSCs.

Delayed Triplet-State Formation through Hybrid Charge Transfer Exciton at Copper Phthalocyanine/GaAs Heterojunction.

PubMed

Lim, Heeseon; Kwon, Hyuksang; Kim, Sang Kyu; Kim, Jeong Won

2017-10-05

Light absorption in organic molecules on an inorganic substrate and subsequent electron transfer to the substrate create so-called hybrid charge transfer exciton (HCTE). The relaxation process of the HCTE states largely determines charge separation efficiency or optoelectronic device performance. Here, the study on energy and time-dispersive behavior of photoelectrons at the hybrid interface of copper phthalocyanine (CuPc)/p-GaAs(001) upon light excitation of GaAs reveals a clear pathway for HCTE relaxation and delayed triplet-state formation. According to the ground-state energy level alignment at the interface, CuPc/p-GaAs(001) shows initially fast hole injection from GaAs to CuPc. Thus, the electrons in GaAs and holes in CuPc form an unusual HCTE state manifold. Subsequent electron transfer from GaAs to CuPc generates the formation of the triplet state in CuPc with a few picoseconds delay. Such two-step charge transfer causes delayed triplet-state formation without singlet excitation and subsequent intersystem crossing within the CuPc molecules.

Toxicity prediction of PHDDs and phenols in the light of nucleic acid bases and DNA base pair interaction.

PubMed

Mondal Roy, Sutapa; Roy, Debesh R; Sahoo, Suban K

2015-11-01

The applicability of Density Functional Theory (DFT) based descriptors for the development of quantitative structure-toxicity relationships (QSTR) is assessed for two different series of toxic aromatic compounds, viz., polyhalogenated dibenzo-p-dioxins (PHDDs) and phenols (PHs). A series of 20 compounds each for PHDDs and PHs with their experimental toxicities (IC50 and IGC50) is chosen in the present study to develop DFT based efficient quantum chemical parameters (QCPs) for explaining the toxin potential of the considered compounds. A systematic analysis to find out the electron donation/acceptance nature of these selected compounds with the considered model biosystems, viz., nucleic acid (NA) bases and DNA base pairs, is performed to identify potential QCPs. Accordingly, PHDDs is found to be electron acceptors whereas phenols as donors, during their interaction with biosystems. Two parameter regression model is carried out comprising global charge transfer (ΔN), and local Fukui Function's for nucleophilic attack (fk(+)) for PHDDs and the same for electrophilic attack (fk(-)) in case of PHs. It is heartening to note that our chosen descriptors, viz, charge transfer (ΔN) and Fukui Function (fk(±)) plays a crucial role by explaining more than 90% of the observed toxic behavior (in terms of correlation-coefficient, R) of PHDDs and PHs. The developed QCPs, viz., ΔN and fk(±) can be added as the new descriptors in the QSTR parlance. Copyright © 2015 Elsevier Inc. All rights reserved.

Mediated Electron Transfer at Vertically Aligned Single-Walled Carbon Nanotube Electrodes During Detection of DNA Hybridization.

PubMed

Wallen, Rachel; Gokarn, Nirmal; Bercea, Priscila; Grzincic, Elissa; Bandyopadhyay, Krisanu

2015-12-01

Vertically aligned single-walled carbon nanotube (VASWCNT) assemblies are generated on cysteamine and 2-mercaptoethanol (2-ME)-functionalized gold surfaces through amide bond formation between carboxylic groups generated at the end of acid-shortened single-walled carbon nanotubes (SWCNTs) and amine groups present on the gold surfaces. Atomic force microscopy (AFM) imaging confirms the vertical alignment mode of SWCNT attachment through significant changes in surface roughness compared to bare gold surfaces and the lack of any horizontally aligned SWCNTs present. These SWCNT assemblies are further modified with an amine-terminated single-stranded probe-DNA. Subsequent hybridization of the surface-bound probe-DNA in the presence of complementary strands in solution is followed using impedance measurements in the presence of Fe(CN)6 (3-/4-) as the redox probe in solution, which show changes in the interfacial electrochemical properties, specifically the charge-transfer resistance, due to hybridization. In addition, hybridization of the probe-DNA is also compared when it is attached directly to the gold surfaces without any intermediary SWCNTs. Contrary to our expectations, impedance measurements show a decrease in charge-transfer resistance with time due to hybridization with 300 nM complementary DNA in solution with the probe-DNA attached to SWCNTs. In contrast, an increase in charge-transfer resistance is observed with time during hybridization when the probe-DNA is attached directly to the gold surfaces. The decrease in charge-transfer resistance during hybridization in the presence of VASWCNTs indicates an enhancement in the electron transfer process of the redox probe at the VASWCNT-modified electrode. The results suggest that VASWCNTs are acting as mediators of electron transfer, which facilitate the charge transfer of the redox probe at the electrode-solution interface.

Mediated Electron Transfer at Vertically Aligned Single-Walled Carbon Nanotube Electrodes During Detection of DNA Hybridization

NASA Astrophysics Data System (ADS)

Wallen, Rachel; Gokarn, Nirmal; Bercea, Priscila; Grzincic, Elissa; Bandyopadhyay, Krisanu

2015-06-01

Vertically aligned single-walled carbon nanotube (VASWCNT) assemblies are generated on cysteamine and 2-mercaptoethanol (2-ME)-functionalized gold surfaces through amide bond formation between carboxylic groups generated at the end of acid-shortened single-walled carbon nanotubes (SWCNTs) and amine groups present on the gold surfaces. Atomic force microscopy (AFM) imaging confirms the vertical alignment mode of SWCNT attachment through significant changes in surface roughness compared to bare gold surfaces and the lack of any horizontally aligned SWCNTs present. These SWCNT assemblies are further modified with an amine-terminated single-stranded probe-DNA. Subsequent hybridization of the surface-bound probe-DNA in the presence of complementary strands in solution is followed using impedance measurements in the presence of Fe(CN)6 3-/4- as the redox probe in solution, which show changes in the interfacial electrochemical properties, specifically the charge-transfer resistance, due to hybridization. In addition, hybridization of the probe-DNA is also compared when it is attached directly to the gold surfaces without any intermediary SWCNTs. Contrary to our expectations, impedance measurements show a decrease in charge-transfer resistance with time due to hybridization with 300 nM complementary DNA in solution with the probe-DNA attached to SWCNTs. In contrast, an increase in charge-transfer resistance is observed with time during hybridization when the probe-DNA is attached directly to the gold surfaces. The decrease in charge-transfer resistance during hybridization in the presence of VASWCNTs indicates an enhancement in the electron transfer process of the redox probe at the VASWCNT-modified electrode. The results suggest that VASWCNTs are acting as mediators of electron transfer, which facilitate the charge transfer of the redox probe at the electrode-solution interface.

Dependence of triboelectric charging behavior on material microstructure

NASA Astrophysics Data System (ADS)

Wang, Andrew E.; Gil, Phwey S.; Holonga, Moses; Yavuz, Zelal; Baytekin, H. Tarik; Sankaran, R. Mohan; Lacks, Daniel J.

2017-08-01

We demonstrate that differences in the microstructure of chemically identical materials can lead to distinct triboelectric charging behavior. Contact charging experiments are carried out between strained and unstrained polytetrafluoroethylene samples. Whereas charge transfer is random between samples of identical strain, when one of the samples is strained, systematic charge transfer occurs. No significant changes in the molecular-level structure of the polymer are observed by XRD and micro-Raman spectroscopy after deformation. However, the strained surfaces are found to exhibit void and craze formation spanning the nano- to micrometer length scales by molecular dynamics simulations, SEM, UV-vis spectroscopy, and naked-eye observations. This suggests that material microstructure (voids and crazes) can govern the triboelectric charging behavior of materials.

Spacecraft Charging in Geostationary Transfer Orbit

NASA Technical Reports Server (NTRS)

Parker, Linda Neergaard; Minow, Joseph I.

2014-01-01

The 700 km x 5.8 Re orbit of the two Van Allen Probes spacecraft provide a unique opportunity to investigate spacecraft charging in geostationary transfer orbits. We use records from the Helium Oxygen Proton Electron (HOPE) plasma spectrometer to identify candidate surface charging events based on the "ion line" charging signature in the ion records. We summarize the energetic particle environment and the conditions necessary for charging to occur in this environment. We discuss the altitude, duration, and magnitude of events observed in the Van Allen Probes from the beginning of the mission to present time. In addition, we explore what information the dual satellites provide on the spatial and temporal variations in the charging environments.

Use of a liquid-crystal, heater-element composite for quantitative, high-resolution heat transfer coefficients on a turbine airfoil, including turbulence and surface roughness effects

NASA Astrophysics Data System (ADS)

Hippensteele, Steven A.; Russell, Louis M.; Torres, Felix J.

1987-05-01

Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at roon temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

Use of a liquid-crystal and heater-element composite for quantitative, high-resolution heat-transfer coefficients on a turbine airfoil including turbulence and surface-roughness effects

NASA Astrophysics Data System (ADS)

Hippensteele, S. A.; Russell, L. M.; Torres, F. J.

Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

Use of a liquid-crystal, heater-element composite for quantitative, high-resolution heat transfer coefficients on a turbine airfoil, including turbulence and surface roughness effects

NASA Technical Reports Server (NTRS)

Hippensteele, Steven A.; Russell, Louis M.; Torres, Felix J.

1987-01-01

Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at roon temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

The ultrasonic-enhanced factor of mass-transfer coefficient in the supercritical carbon dioxide extraction

NASA Astrophysics Data System (ADS)

Luo, Benyi; Lu, Yigang

2008-10-01

Based on several hypotheses about the process of supercritical carbon dioxide extraction, the onflow around the solute granule is figured out by the Navier-Stocks equation. In combination with the Higbie’s solute infiltration model, the link between the mass-transfer coefficient and the velocity of flow is found. The mass-transfer coefficient with the ultrasonical effect is compared with that without the ultrasonical effect, and then a new parameter named the ultrasonic-enhanced factor of mass-transfer coefficient is brought forward, which describes the mathematical model of the supercritical carbon dioxide extraction process enhanced by ultrasonic. The model gives out the relationships among the ultrasonical power, the ultrasonical frequency, the radius of solute granule and the ultrasonic-enhanced factor of mass-transfer coefficient. The results calculated by this model fit well with the experimental data, including the extraction of Coix Lacryma-jobi Seed Oil (CLSO) and Coix Lacryma-jobi Seed Ester (CLSE) from coix seeds and the extraction of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) from the alga by means of the ultrasonic-enhanced supercritical carbon dioxide extraction (USFE) and the supercritical carbon dioxide extraction (SFE) respectively. This proves the rationality of the ultrasonic-enhanced factor model. The model provides a theoretical basis for the application of ultrasonic-enhanced supercritical fluid extraction technique.

Energy transfer and energy absorption in photon interactions with matter revisited: A step-by-step illustrated approach

NASA Astrophysics Data System (ADS)

Abdel-Rahman, W.; Podgorsak, E. B.

2010-05-01

A clear understanding of energy transfer and energy absorption in photon interactions with matter is essential for the understanding of radiation dosimetry and development of new dosimetry techniques. The concepts behind the two quantities have been enunciated many years ago and described in many scientific papers, review articles, and textbooks. Data dealing with energy transfer and energy absorption as well as the associated mass energy transfer coefficient and the mass energy absorption coefficient are readily available in web-based tabular forms. However, tables, even when available in detailed and easy to access form, do not lend themselves to serve as visual aid to promote better understanding of the dosimetric quantities related to energy transfer and energy absorption as well as their relationship to the photon energy and absorber atomic number. This paper uses graphs and illustrations, in addition to well-known mathematical relationships, to guide the reader in a systematic manner through the various stages involved in the derivation of energy absorbed in medium and its associated quantity, the mass energy absorption coefficient, from the mass attenuation coefficient.

Modelling mass transfer during venting/soil vapour extraction: Non-aqueous phase liquid/gas mass transfer coefficient estimation

NASA Astrophysics Data System (ADS)

Esrael, D.; Kacem, M.; Benadda, B.

2017-07-01

We investigate how the simulation of the venting/soil vapour extraction (SVE) process is affected by the mass transfer coefficient, using a model comprising five partial differential equations describing gas flow and mass conservation of phases and including an expression accounting for soil saturation conditions. In doing so, we test five previously reported quations for estimating the non-aqueous phase liquid (NAPL)/gas initial mass transfer coefficient and evaluate an expression that uses a reference NAPL saturation. Four venting/SVE experiments utilizing a sand column are performed with dry and non-saturated sand at low and high flow rates, and the obtained experimental results are subsequently simulated, revealing that hydrodynamic dispersion cannot be neglected in the estimation of the mass transfer coefficient, particularly in the case of low velocities. Among the tested models, only the analytical solution of a convection-dispersion equation and the equation proposed herein are suitable for correctly modelling the experimental results, with the developed model representing the best choice for correctly simulating the experimental results and the tailing part of the extracted gas concentration curve.