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Sample records for energy transfer spfret

  1. Approaching real-time molecular diagnostics: single-pair fluorescence resonance energy transfer (spFRET) detection for the analysis of low abundant point mutations in K-ras oncogenes.

    PubMed

    Wabuyele, Musundi B; Farquar, Hannah; Stryjewski, Wieslaw; Hammer, Robert P; Soper, Steven A; Cheng, Yu-Wei; Barany, Francis

    2003-06-11

    The aim of this study was to develop new strategies for analyzing molecular signatures of disease states approaching real-time using single pair fluorescence resonance energy transfer (spFRET) to rapidly detect point mutations in unamplified genomic DNA. In addition, the detection process was required to discriminate between normal and mutant (minority) DNAs in heterogeneous populations. The discrimination was carried out using allele-specific primers, which flanked the point mutation in the target gene and were ligated using a thermostable ligase enzyme only when the genomic DNA carried this mutation. The allele-specific primers also carried complementary stem structures with end-labels (donor/acceptor fluorescent dyes, Cy5/Cy5.5, respectively), which formed a molecular beacon following ligation. We coupled ligase detection reaction (LDR) with spFRET to identify a single base mutation in codon 12 of a K-ras oncogene that has high diagnostic value for colorectal cancers. A simple diode laser-based fluorescence system capable of interrogating single fluorescent molecules undergoing FRET was used to detect photon bursts generated from the molecular beacon probes formed upon ligation. LDR-spFRET provided the necessary specificity and sensitivity to detect single-point mutations in as little as 600 copies of human genomic DNA directly without PCR at a level of 1 mutant per 1000 wild type sequences using 20 LDR thermal cycles. We also demonstrate the ability to rapidly discriminate single base differences in the K-ras gene in less than 5 min at a frequency of 1 mutant DNA per 10 normals using only a single LDR thermal cycle of genomic DNA (600 copies). Real-time LDR-spFRET detection of point mutations in the K-ras gene was accomplished in PMMA microfluidic devices using sheath flows.

  2. Ligase detection reaction generation of reverse molecular beacons for near real-time analysis of bacterial pathogens using single-pair fluorescence resonance energy transfer and a cyclic olefin copolymer microfluidic chip.

    PubMed

    Peng, Zhiyong; Soper, Steven A; Pingle, Maneesh R; Barany, Francis; Davis, Lloyd M

    2010-12-01

    Detection of pathogenic bacteria and viruses require strategies that can signal the presence of these targets in near real-time due to the potential threats created by rapid dissemination into water and/or food supplies. In this paper, we report an innovative strategy that can rapidly detect bacterial pathogens using reporter sequences found in their genome without requiring polymerase chain reaction (PCR). A pair of strain-specific primers was designed based on the 16S rRNA gene and were end-labeled with a donor (Cy5) or acceptor (Cy5.5) dye. In the presence of the target bacterium, the primers were joined using a ligase detection reaction (LDR) only when the primers were completely complementary to the target sequence to form a reverse molecular beacon (rMB), thus bringing Cy5 (donor) and Cy5.5 (acceptor) into close proximity to allow fluorescence resonance energy transfer (FRET) to occur. These rMBs were subsequently analyzed using single-molecule detection of the FRET pairs (single-pair FRET; spFRET). The LDR was performed using a continuous flow thermal cycling process configured in a cyclic olefin copolymer (COC) microfluidic device using either 2 or 20 thermal cycles. Single-molecule photon bursts from the resulting rMBs were detected on-chip and registered using a simple laser-induced fluorescence (LIF) instrument. The spFRET signatures from the target pathogens were reported in as little as 2.6 min using spFRET.

  3. Solar Energy: Heat Transfer.

    ERIC Educational Resources Information Center

    Knapp, Henry H., III

    This module on heat transfer is one of six in a series intended for use as supplements to currently available materials on solar energy and energy conservation. Together with the recommended texts and references (sources are identified), these modules provide an effective introduction to energy conservation and solar energy technologies. The…

  4. Dexter energy transfer pathways.

    PubMed

    Skourtis, Spiros S; Liu, Chaoren; Antoniou, Panayiotis; Virshup, Aaron M; Beratan, David N

    2016-07-19

    Energy transfer with an associated spin change of the donor and acceptor, Dexter energy transfer, is critically important in solar energy harvesting assemblies, damage protection schemes of photobiology, and organometallic opto-electronic materials. Dexter transfer between chemically linked donors and acceptors is bridge mediated, presenting an enticing analogy with bridge-mediated electron and hole transfer. However, Dexter coupling pathways must convey both an electron and a hole from donor to acceptor, and this adds considerable richness to the mediation process. We dissect the bridge-mediated Dexter coupling mechanisms and formulate a theory for triplet energy transfer coupling pathways. Virtual donor-acceptor charge-transfer exciton intermediates dominate at shorter distances or higher tunneling energy gaps, whereas virtual intermediates with an electron and a hole both on the bridge (virtual bridge excitons) dominate for longer distances or lower energy gaps. The effects of virtual bridge excitons were neglected in earlier treatments. The two-particle pathway framework developed here shows how Dexter energy-transfer rates depend on donor, bridge, and acceptor energetics, as well as on orbital symmetry and quantum interference among pathways.

  5. Quantum dots for single-pair fluorescence resonance energy transfer in membrane- integrated EFoF1.

    PubMed

    Galvez, Eva; Düser, Monika; Börsch, Michael; Wrachtrup, Jörg; Gräber, Peter

    2008-10-01

    spFRET (single-pair fluorescence resonance energy transfer) with organic fluorophores has been used to demonstrate rotation of the subunits gamma and epsilon in membrane-integrated FoF1 during proton transport-coupled ATP synthesis. Owing to the high light intensities used in single-molecule spectroscopy, organic fluorophores show a high probability for photobleaching. Luminescent CdSe/ZnS nanocrystals with a hydrophilic shell have been covalently bound to FoF1 either to the stator subunit b or to the rotor subunit c. TIRFM (total internal reflection microscopy) shows that covalent binding of the QD (quantum dot) via cysteine to FoF1 leads to a significant decrease in the blinking probability in the microsecond-to-second time range. This effect allows the observation of subunit movements in an extended time range. If the QD is bound to the rotor subunit c, the fluorescence anisotropy shows fluctuations in the presence of ATP, in contrast with the constant anisotropy observed in the absence of ATP.

  6. Luminescence resonance energy transfer

    SciTech Connect

    Selvin, P.R.; Rana, T.M.; Hearst, J.E. Lawrence Berkeley Lab., CA )

    1994-06-29

    Fluorescence resonance energy transfer (FRET), in which a fluorescent donor molecule transfers energy via a nonradiative dipole-dipole interaction to an acceptor molecule (which is usually a fluorescent molecule), is a standard spectroscopic technique for measuring distances in the 10-70 Angstrom range. We have used a luminescent europium chelate as donor and an organic dye, CY-5, as acceptor. This luminescence resonance energy transfer (LRET) has several advantages over the more conventional FRET. The distance at which 50% of the energy is transferred (R[sub 0]) is large, 70 [angstrom]; the donor lifetime is single exponential and long (0.63 ms in H[sub 2]O; 2.5 ms in D[sub 2]O), making lifetime measurements facile and highly accurate; the orientation dependence (k[sup 2]) of energy transfer is minimized by the donor's multiple electronic transitions and long lifetime, limiting uncertainty in the measured distance due to orientation effects to [+-]12% in the worst case; the sensitized emission of the acceptor can be measured with little or no interfering background, yielding a >50-fold improvement in signal to background over standard donor-acceptor pairs and enabling distances several times R[sub 0] to be measured. 13 refs., 4 figs.

  7. Energy transfer in compressible turbulence

    NASA Technical Reports Server (NTRS)

    Bataille, Francoise; Zhou, YE; Bertoglio, Jean-Pierre

    1995-01-01

    This letter investigates the compressible energy transfer process. We extend a methodology developed originally for incompressible turbulence and use databases from numerical simulations of a weak compressible turbulence based on Eddy-Damped-Quasi-Normal-Markovian (EDQNM) closure. In order to analyze the compressible mode directly, the well known Helmholtz decomposition is used. While the compressible component has very little influence on the solenoidal part, we found that almost all of the compressible turbulence energy is received from its solenoidal counterpart. We focus on the most fundamental building block of the energy transfer process, the triadic interactions. This analysis leads us to conclude that, at low turbulent Mach number, the compressible energy transfer process is dominated by a local radiative transfer (absorption) in both inertial and energy containing ranges.

  8. Observation of an angular change in the structure of an RNA complex using Fluorescence Resonance Energy Transfer

    NASA Astrophysics Data System (ADS)

    Rahmanseresht, Sheema; Milas, Peker; Parrot, Louis; Goldner, Lori S.

    Single-molecular-pair FRET is often used to study distance fluctuations of single molecules. It is harder to capture angular changes using FRET, because rotational motion of the dyes tends to wash out the angular sensitivity. Using a dye labeling scheme that minimizes the rotational motion of the dyes with respect to the RNA, we use spFRET to measure an angular change in structure of an RNA kissing complex upon protein binding. The model system studied here, R1inv-R2inv, is derived from the RNAI-RNAII complex in E.coli. RNA II is a primer for replication of the ColE1 plasmid; its function is modulated by interaction with RNA I, Rop protein is known to stabilize the bent R1inv-R2inv kissing complex against dissociation. The effect, if any, of Rop protein on the conformation of the kissing complex is not known. The eight minimized-energy NMR structures reported for R1inv-R2inv show a small difference in end-to-end distances and much larger differences in twist and bend angles. We compare a first-principles model with spFRET data to determine if the observed change in FRET is consistent with an angular change in structure, as suggested by the model. Grant Number: NSF DBI-1152386.

  9. Energy transfer processes in solar energy conversion

    SciTech Connect

    Fayer, M.D.

    1988-01-01

    The program involves the investigation of excitation transport and electron transfer in complex systems. In the area of electron transfer, we have been studying electron back transfer following donor-acceptor photoinduced electron transfer. We are addressing this problem both theoretically and experimentally. In the area of excitation transport, we have been examining transport in solid solutions, liquid solutions, and in clustered excitation transport systems. Again, we are pursuing both experimental and theoretical approaches. The problem of electron back transfer between photogenerated ions is of central importance in both artificial and biological solar energy conversion. Once an electron has been transferred from an optically excited donor to an acceptor, back transfer competes with the ability of the radical ions to go on to do useful chemistry. We are studying the back transfer process using picosecond transient grating experiments in conjunction with time resolved and steady state fluorescence quenching measurements. The transient grating experiments makes the back transfer process a direct experimental observable, while the fluorescence experiments allow the forward transfer to be examined. By combining the experiments, a complete picture emerges. 10 refs.

  10. Energy transfer processes in solar energy conversion

    SciTech Connect

    Fayer, M.D.

    1986-11-01

    By combining picosecond optical experiments and detailed statistical mechanics theory we continue to increase our understanding of the complex interplay of structure and dynamics in important energy transfer situations. A number of different types of problems will be focused on experimentally and theoretically. They are excitation transport among chromophores attached to finite size polymer coils; excitation transport among chromophores in monolayers, bilayers, and finite and infinite stacks of layers; excitation transport in large vesicle systems; and photoinduced electron transfer in glasses and liquids, focusing particularly on the back transfer of the electron from the photogenerated radical anion to the radical cation. 33 refs., 13 figs.

  11. Urea-induced unfolding of the immunity protein Im9 monitored by spFRET.

    PubMed

    Tezuka-Kawakami, Tomoko; Gell, Chris; Brockwell, David J; Radford, Sheena E; Smith, D Alastair

    2006-09-01

    We have studied the urea-induced unfolding of the E colicin immunity protein Im9 using diffusion single-pair fluorescence resonance energy transfer. Detailed examination of the proximity ratio of the native and denatured molecules over a wide range of urea concentrations suggests that the conformational properties of both species are denaturant-dependent. Whereas native molecules become gradually more expanded as urea concentration increases, denatured molecules show a dramatic dependence of the relationship between proximity ratio and denaturant concentration, consistent with substantial compaction of the denatured ensemble at low denaturant concentrations. Analysis of the widths of the proximity ratio distributions for each state suggests that whereas the native state ensemble is relatively narrow and homogeneous, the denatured state may possess heterogeneity in mildly denaturing conditions.

  12. Urea-Induced Unfolding of the Immunity Protein Im9 Monitored by spFRET

    PubMed Central

    Tezuka-Kawakami, Tomoko; Gell, Chris; Brockwell, David J.; Radford, Sheena E.; Smith, D. Alastair

    2006-01-01

    We have studied the urea-induced unfolding of the E colicin immunity protein Im9 using diffusion single-pair fluorescence resonance energy transfer. Detailed examination of the proximity ratio of the native and denatured molecules over a wide range of urea concentrations suggests that the conformational properties of both species are denaturant-dependent. Whereas native molecules become gradually more expanded as urea concentration increases, denatured molecules show a dramatic dependence of the relationship between proximity ratio and denaturant concentration, consistent with substantial compaction of the denatured ensemble at low denaturant concentrations. Analysis of the widths of the proximity ratio distributions for each state suggests that whereas the native state ensemble is relatively narrow and homogeneous, the denatured state may possess heterogeneity in mildly denaturing conditions. PMID:16798813

  13. Energy transfer processes in solar energy conversion

    SciTech Connect

    Fayer, M.D.

    1989-11-01

    We have made substantial progress in experimental and theoretical studies in two areas: Photoinduced donor to acceptor electron transfer followed by back transfer in random solutions; and electronic excitation transport in systems with complex inhomogeneous spatial geometries and inhomogeneous energy distributions. Through the development of accurate statistical mechanical theories, we have been able to relate dynamics in complex systems to experimental observables. We have then used the experimental observables, time resolved fluorescence depolarization and transient grating experiments, to examine well defined molecular systems. The agreement between theory and experiment is excellent. 11 refs.

  14. Conformational substates of calmodulin revealed by single-pair fluorescence resonance energy transfer: influence of solution conditions and oxidative modification.

    PubMed

    Slaughter, Brian D; Unruh, Jay R; Allen, Michael W; Bieber Urbauer, Ramona J; Johnson, Carey K

    2005-03-15

    A calmodulin (CaM) mutant (T34,110C-CaM) doubly labeled with fluorescence probes AlexaFluor 488 and Texas Red in opposing domains (CaM-DA) has been used to examine conformational heterogeneity in CaM by single-pair fluorescence resonance energy transfer (spFRET). Burst-integrated FRET efficiencies of freely diffusing CaM-DA single molecules yielded distributions of distance between domains of CaM-DA. We recently reported distinct conformational substates of Ca(2+)-CaM-DA and apoCaM-DA, with peaks in the distance distributions centered at approximately 28 A, 34-38 A, and 55 A [Slaughter et al. (2004) J. Phys. Chem. B 108, 10388-10397]. In the present study, shifts in the amplitudes and center distances of the conformational substates were detected with variation in solution conditions. The amplitude of an extended conformation was observed to change as a function of Ca(2+) over a free Ca(2+) range that is consistent with binding to the high affinity, C-terminal Ca(2+) binding sites, suggesting the existence of communication between lobes of CaM. Lowering pH shifted the relative amplitudes of the conformations, with a marked increase in the presence of the compact conformations and an almost complete absence of the extended conformation. In addition, the single-molecule distance distribution of apoCaM-DA at reduced ionic strength was shifted to longer distance and showed evidence of an increase in conformational heterogeneity relative to apoCaM-DA at physiological ionic strength. Oxidation of methionine residues in CaM-DA produced a substantial increase in the amplitude of the extended conformation relative to the more compact conformation. The results are considered in light of a hypothesis that suggests that electrostatic interactions between charged amino acid side chains play an important role in determining the most stable CaM conformation under varying solution conditions.

  15. Energy Transfer in Rotating Turbulence

    NASA Technical Reports Server (NTRS)

    Cambon, Claude; Mansour, Nagi N.; Godeferd, Fabien S.; Rai, Man Mohan (Technical Monitor)

    1995-01-01

    The influence or rotation on the spectral energy transfer of homogeneous turbulence is investigated in this paper. Given the fact that linear dynamics, e.g. the inertial waves regime tackled in an RDT (Rapid Distortion Theory) fashion, cannot Affect st homogeneous isotropic turbulent flow, the study of nonlinear dynamics is of prime importance in the case of rotating flows. Previous theoretical (including both weakly nonlinear and EDQNM theories), experimental and DNS (Direct Numerical Simulation) results are gathered here and compared in order to give a self-consistent picture of the nonlinear effects of rotation on tile turbulence. The inhibition of the energy cascade, which is linked to a reduction of the dissipation rate, is shown to be related to a damping due to rotation of the energy transfer. A model for this effect is quantified by a model equation for the derivative-skewness factor, which only involves a micro-Rossby number Ro(sup omega) = omega'/(2(OMEGA))-ratio of rms vorticity and background vorticity as the relevant rotation parameter, in accordance with DNS and EDQNM results fit addition, anisotropy is shown also to develop through nonlinear interactions modified by rotation, in an intermediate range of Rossby numbers (Ro(omega) = (omega)' and Ro(omega)w greater than 1), which is characterized by a marco-Rossby number Ro(sup L) less than 1 and Ro(omega) greater than 1 which is characterized by a macro-Rossby number based on an integral lengthscale L and the micro-Rossby number previously defined. This anisotropy is mainly an angular drain of spectral energy which tends to concentrate energy in tile wave-plane normal to the rotation axis, which is exactly both the slow and the two-dimensional manifold. In Addition, a polarization of the energy distribution in this slow 2D manifold enhances horizontal (normal to the rotation axis) velocity components, and underlies the anisotropic structure of the integral lengthscales. Finally is demonstrated the

  16. Vibrational energy transfer in fluids

    NASA Astrophysics Data System (ADS)

    Miller, David W.; Adelman, Steven A.

    A review of several of the available theories of vibrational energy transfer (VET) in the gas and liquid phases is presented. First the classical theory of gas phase VET mainly due to Landau and Teller, to Jackson and Mott and to Zener is developed in some detail. Next the Schwartz-Slawsky-Herzfeld theory, a framework for analysing VET data based on the classical theory, is outlined. Experimental tests of the classical theory and theoretical critiques of its assumptions are then described. Next a brief review of the modern ab-initio quantum approach to gas phase VET rates, taking as an example the work of Banks, Clary and Werner, is given. Theories of VET at elevated densities are then discussed. The isolated binary collision model is reviewed and a new molecular approach to the density, temperature and isotope dependences of vibrational energy relaxation rates, due to Adelman and co-workers, is outlined.

  17. Energy transfer in macromolecular arrays

    NASA Astrophysics Data System (ADS)

    Andrews, David L.; Jenkins, Robert D.

    2003-11-01

    Macromolecular systems comprised of many light-sensitive centres (the photosynthetic unit, dendrimers, and other highly symmetric multichromophore arrays) are important structures offering challenges to theoreticians and synthetic chemists alike. Here we outline novel photophysical interactions predicted and observed in such arrays. Using the tools of molecular quantum electrodynamics (QED) we present quantum amplitudes for a variety of higher-order resonance energy transfer (RET) schemes associated with well-known nonlinear optical effects such as two- and three-photon absorption. The initial analysis is extended to account for situations where the participant donor species are identical and exist in a highly symmetric environment, leading to the possible formation of excitons. It emerges from the QED theory that such excitons are closely associated with the higher-order RET processes. General results are interpreted by analyzing particular molecular architectures which offer interesting features such as rate enhancement or limitation and exciton pathway quenching. Applications in the areas of photosynthesis, molecular logic gates and low-intensity fluorescence energy transfer are predicted.

  18. Energy Transfer Involving Diatomic Molecules.

    NASA Astrophysics Data System (ADS)

    Gibbons, John Paul

    A three-dimensional, Monte Carlo model for the calculation of vibrational energy relaxation and transfer rates for both diatomic-monatomic and diatomic-diatomic systems was developed, analyzed and implemented. Mediation by internal angular momentum was demonstrated to be important in these energy transfer processes. This was named the TLV mechanism for translation to vibration flow through changes in angular momentum. The equations for the component of vibrational energy change due to the TLV mechanism for the two extreme cases of very hard or very soft collisions were derived. Results of using these equations were compared with those obtained by direct integration of the differential equations of motion and in many cases were found to agree. This mechanism was incorporated into the model in order to achieve statistically significant results within reasonable computer running times. When this was done the variance of a result was frequently reduced by a factor of thirty to fifty or more with little or no increase in the computer times required. This made possible a meaningful study of the full three-dimensional diatomic-diatomic collisional processes and also permitted extension of the mono-diatomic model calculations to much lower temperatures than had been previously investigated. After this calculational procedure was developed for Ar - O(,2) collisions, it was also applied to He - O(,2) and to the near resonant vibration energy exchange process:. CO ((nu)=0)+N(,2)((nu)=1)(--->)CO((nu)=1)+N(,2)((nu)=0). These three processes were investigated at several temperatures between room temperature and 4000K. Exponential repulsive intermolecular potentials were used. The values for the coefficients and characteristic lengths for these potentials were obtained from independent sources both experimental and theoretical. In general, the results, when compared to experiment, are very consistent relative to their dependence on the potential parameters. In every case for all

  19. Geo energy research and development: technology transfer

    SciTech Connect

    Traeger, R.K.

    1982-03-01

    Sandia Geo Energy Programs related to geothermal, coal, oil and gas, and synfuel resources have provided a useful mechanism for transferring laboratory technologies to private industry. Significant transfer of hardware, computer programs, diagnostics and instrumentation, advanced materials, and in situ process understanding has occurred through US/DOE supported programs in the past five years. The text briefly reviews the technology transfer procedures and summarizes 32 items that have been transferred and another 20 technologies that are now being considered for possible transfer to industry. A major factor in successful transfer has been personal interactions between Sandia engineers and the technical staff from private industry during all aspects of the technology development.

  20. Fundamental Interactions Leading to Energy Transfer

    NASA Astrophysics Data System (ADS)

    di Bartolo, Baldassare

    2001-11-01

    The purpose of the lectures reported in this article is to investigate the basic interactions that lead to processes by which excitation energy, initially localized in a particular constituent or restricted region of a material, transfers itself to other parts or degrees of freedom of the system. Energy transfer processes are relevant to such various and important fields as spectroscopy, laser technology, phosphors, artificial solar energy conversion, and photobiology. The subject of the interactions among atoms is introduced by considering first the static and then the dynamic effects of these interactions in a two-atom system. Subsequently the different types of interactions (multipolar, exchange and electromagnetic) in a two-atom system are examined. After reviewing the different modes of excitation of a solid containing both donors and acceptors, a statistical treatment of energy transfer is presented. Firstly the case of energy transfer without migration among donors, and secondly the case of energy transfer in the presence of such migration are considered.

  1. Phosphorescence and Energy Transfer in Rigid Solutions.

    ERIC Educational Resources Information Center

    Enciso, E.; Cabello, A.

    1980-01-01

    Describes an experiment which illustrates the general aspects of intermolecular energy transfer between triplet states in rigid solutions of organic compounds solved in an ethanol-ether mixture. Measurements of quenching and energy transfer processes are made using the chemicals of benzophenone and naphthalene. (CS)

  2. Classical approach to multichromophoric resonance energy transfer.

    PubMed

    Duque, Sebastián; Brumer, Paul; Pachón, Leonardo A

    2015-09-11

    A classical formulation of the quantum multichromophoric theory of resonance energy transfer is developed on the basis of classical electrodynamics. The theory allows for the identification of a variety of processes of different order in the interactions that contribute to the energy transfer in molecular aggregates with intracoupling in donors and acceptor chromophores. Enhanced rates in multichromophoric resonance energy transfer are shown to be well described by this theory. Specifically, in a coupling configuration between N_{A} acceptors and N_{D} donors, the theory correctly predicts an enhancement of the energy transfer rate dependent on the total number of donor-acceptor pairs. As an example, the theory, applied to the transfer rate in light harvesting II, gives results in excellent agreement with experiment. Finally, it is explicitly shown that as long as linear response theory holds, the classical multichromophoric theory formally coincides with the quantum formulation.

  3. Classical approach to multichromophoric resonance energy transfer.

    PubMed

    Duque, Sebastián; Brumer, Paul; Pachón, Leonardo A

    2015-09-11

    A classical formulation of the quantum multichromophoric theory of resonance energy transfer is developed on the basis of classical electrodynamics. The theory allows for the identification of a variety of processes of different order in the interactions that contribute to the energy transfer in molecular aggregates with intracoupling in donors and acceptor chromophores. Enhanced rates in multichromophoric resonance energy transfer are shown to be well described by this theory. Specifically, in a coupling configuration between N_{A} acceptors and N_{D} donors, the theory correctly predicts an enhancement of the energy transfer rate dependent on the total number of donor-acceptor pairs. As an example, the theory, applied to the transfer rate in light harvesting II, gives results in excellent agreement with experiment. Finally, it is explicitly shown that as long as linear response theory holds, the classical multichromophoric theory formally coincides with the quantum formulation. PMID:26406811

  4. Resonance energy transfer: Dye to metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Wari, M. N.; Pujar, G. H.; Inamdar, S. R.

    2015-06-01

    In the present study, surface energy transfer (SET) from Coumarin 540A (C540 A) to Gold nanoparticle (Au) is demonstrated. The observed results show pronounced effect on the photoluminescence intensity and shortening of the lifetime of Coumarin 540A upon interaction with the spherical gold nanoparticle, also there are measured effects on radiative rate of the dye. Experimental results are analyzed with fluorescence resonance energy transfer (FRET) and SET theories. The results obtained from distance-dependent quenching provide experimental evidence that the efficiency curve slope and distance of quenching is best modeled by surface energy transfer process.

  5. Resonance energy transfer: Dye to metal nanoparticles

    SciTech Connect

    Wari, M. N.; Pujar, G. H.; Inamdar, S. R.

    2015-06-24

    In the present study, surface energy transfer (SET) from Coumarin 540A (C540 A) to Gold nanoparticle (Au) is demonstrated. The observed results show pronounced effect on the photoluminescence intensity and shortening of the lifetime of Coumarin 540A upon interaction with the spherical gold nanoparticle, also there are measured effects on radiative rate of the dye. Experimental results are analyzed with fluorescence resonance energy transfer (FRET) and SET theories. The results obtained from distance-dependent quenching provide experimental evidence that the efficiency curve slope and distance of quenching is best modeled by surface energy transfer process.

  6. Dynamics of excitation energy transfer in phycobiliproteins

    NASA Astrophysics Data System (ADS)

    Zheng, Xiguang; Wang, He Z.; Zhao, Fuli; Gao, Zhaolan; Yu, Zhenxin

    1994-08-01

    Theoretical descriptions of excitation energy transfer between chromophores in allophycocyanin are presented, including bilateral energy transfer paths between chromophores, and are expressed, based on Foster interaction mechanism, as Pauli master equations. Group analysis in C3 symmetry is performed to carry out analytic expressions for fluorescence decays which is generally of triexponential with effects of chromophore coupling and exciton splitting taken account. It is pointed out that the time constant of each decay component contains mixed information of different energy transfer paths, and therefore show its dependence on subtle configuration of chromophores, probably related to site heterogeneity and thus to inhomogeneous broadening previously observed.

  7. Energy transfer processes in solar energy conversion

    SciTech Connect

    Fayer, M.D.

    1992-01-01

    During the past year, we have been working in three general areas: electronic excitation transport in clustered chromophore systems and other complex systems, photo-induced electron transfer and back transfer in liquid solutions in which diffusion and charge interactions are important, and the construction of a new two color dye laser system to enhance our experimental capability.

  8. Optical Energy Transfer and Conversion System

    NASA Technical Reports Server (NTRS)

    Stone, William C. (Inventor); Hogan, Bartholomew P. (Inventor)

    2015-01-01

    An optical power transfer system comprising a fiber spooler, a fiber optic rotary joint mechanically connected to the fiber spooler, and an electrical power extraction subsystem connected to the fiber optic rotary joint with an optical waveguide. Optical energy is generated at and transferred from a base station through fiber wrapped around the spooler, through the rotary joint, and ultimately to the power extraction system at a remote mobility platform for conversion to another form of energy.

  9. Single-pair fluorescence resonance energy transfer analysis of mRNA transcripts for highly sensitive gene expression profiling in near real time.

    PubMed

    Peng, Zhiyong; Young, Brandon; Baird, Alison E; Soper, Steven A

    2013-08-20

    Expression analysis of mRNAs transcribed from certain genes can be used as important sources of biomarkers for in vitro diagnostics. While the use of reverse transcription quantitative PCR (RT-qPCR) can provide excellent analytical sensitivity for monitoring transcript numbers, more sensitive approaches for expression analysis that can report results in near real-time are needed for many critical applications. We report a novel assay that can provide exquisite limits-of-quantitation and consists of reverse transcription (RT) followed by a ligase detection reaction (LDR) with single-pair fluorescence resonance energy transfer (spFRET) to provide digital readout through molecular counting. For this assay, no PCR was employed, which enabled short assay turnaround times. To facilitate implementation of the assay, a cyclic olefin copolymer (COC) microchip, which was fabricated using hot embossing, was employed to carry out the LDR in a continuous flow format with online single-molecule detection following the LDR. As demonstrators of the assay's utility, MMP-7 mRNA was expression profiled from several colorectal cancer cell lines. It was found that the RT-LDR/spFRET assay produced highly linear calibration plots even in the low copy number regime. Comparison to RT-qPCR indicated a better linearity over the low copy number range investigated (10-10,000 copies) with an R(2) = 0.9995 for RT-LDR/spFRET and R(2) = 0.98 for RT-qPCR. In addition, differentiating between copy numbers of 10 and 50 could be performed with higher confidence using RT-LDR/spFRET. To demonstrate the short assay turnaround times obtainable using the RT-LDR/spFRET assay, a two thermal cycle LDR was carried out on amphiphysin gene transcripts that can serve as important diagnostic markers for ischemic stroke. The ability to supply diagnostic information on possible stroke events in short turnaround times using RT-LDR/spFRET will enable clinicians to treat patients effectively with appropriate time

  10. Targeting Low-Energy Ballistic Lunar Transfers

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.

    2010-01-01

    Numerous low-energy ballistic transfers exist between the Earth and Moon that require less fuel than conventional transfers, but require three or more months of transfer time. An entirely ballistic lunar transfer departs the Earth from a particular declination at some time in order to arrive at the Moon at a given time along a desirable approach. Maneuvers may be added to the trajectory in order to adjust the Earth departure to meet mission requirements. In this paper, we characterize the (Delta)V cost required to adjust a low-energy ballistic lunar transfer such that a spacecraft may depart the Earth at a desirable declination, e.g., 28.5(white bullet), on a designated date. This study identifies the optimal locations to place one or two maneuvers along a transfer to minimize the (Delta)V cost of the transfer. One practical application of this study is to characterize the launch period for a mission that aims to launch from a particular launch site, such as Cape Canaveral, Florida, and arrive at a particular orbit at the Moon on a given date using a three-month low-energy transfer.

  11. Wireless energy transfer between anisotropic metamaterials shells

    SciTech Connect

    Díaz-Rubio, Ana; Carbonell, Jorge; Sánchez-Dehesa, José

    2014-06-15

    The behavior of strongly coupled Radial Photonic Crystals shells is investigated as a potential alternative to transfer electromagnetic energy wirelessly. These sub-wavelength resonant microstructures, which are based on anisotropic metamaterials, can produce efficient coupling phenomena due to their high quality factor. A configuration of selected constitutive parameters (permittivity and permeability) is analyzed in terms of its resonant characteristics. The coupling to loss ratio between two coupled resonators is calculated as a function of distance, the maximum (in excess of 300) is obtained when the shells are separated by three times their radius. Under practical conditions an 83% of maximum power transfer has been also estimated. -- Highlights: •Anisotropic metamaterial shells exhibit high quality factors and sub-wavelength size. •Exchange of electromagnetic energy between shells with high efficiency is analyzed. •Strong coupling is supported with high wireless transfer efficiency. •End-to-end energy transfer efficiencies higher than 83% can be predicted.

  12. Excitation energy transfer in the photosystem I

    SciTech Connect

    Webber, Andrew N

    2012-09-25

    Photosystem I is a multimeric pigment protein complex in plants, green alage and cyanobacteria that functions in series with Photosystem II to use light energy to oxidize water and reduce carbon dioxide. The Photosystem I core complex contains 96 chlorophyll a molecules and 22 carotenoids that are involved in light harvesting and electron transfer. In eucaryotes, PSI also has a peripheral light harvesting complex I (LHCI). The role of specific chlorophylls in excitation and electron transfer are still unresolved. In particular, the role of so-called bridging chlorophylls, located between the bulk antenna and the core electron transfer chain, in the transfer of excitation energy to the reaction center are unknown. During the past funding period, site directed mutagenesis has been used to create mutants that effect the physical properties of these key chlorophylls, and to explore how this alters the function of the photosystem. Studying these mutants using ultrafast absorption spectroscopy has led to a better understanding of the process by which excitation energy is transferred from the antenna chlorophylls to the electron transfer chain chlorophylls, and what the role of connecting chlorophylls and A_0 chlorophylls is in this process. We have also used these mutants to investigate whch of the central group of six chlorophylls are involved in the primary steps of charge separation and electron transfer.

  13. Chemical activation through super energy transfer collisions.

    PubMed

    Smith, Jonathan M; Nikow, Matthew; Ma, Jianqiang; Wilhelm, Michael J; Han, Yong-Chang; Sharma, Amit R; Bowman, Joel M; Dai, Hai-Lung

    2014-02-01

    Can a molecule be efficiently activated with a large amount of energy in a single collision with a fast atom? If so, this type of collision will greatly affect molecular reactivity and equilibrium in systems where abundant hot atoms exist. Conventional expectation of molecular energy transfer (ET) is that the probability decreases exponentially with the amount of energy transferred, hence the probability of what we label "super energy transfer" is negligible. We show, however, that in collisions between an atom and a molecule for which chemical reactions may occur, such as those between a translationally hot H atom and an ambient acetylene (HCCH) or sulfur dioxide, ET of chemically significant amounts of energy commences with surprisingly high efficiency through chemical complex formation. Time-resolved infrared emission observations are supported by quasi-classical trajectory calculations on a global ab initio potential energy surface. Results show that ∼10% of collisions between H atoms moving with ∼60 kcal/mol energy and HCCH result in transfer of up to 70% of this energy to activate internal degrees of freedom.

  14. Magnetospheric feedbacks in solar wind energy transfer

    NASA Astrophysics Data System (ADS)

    Palmroth, Minna; Pulkkinen, Tuija I.; Anekallu, Chandrasekhar R.; Honkonen, Ilja; Koskinen, Hannu E. J.; Lucek, Elizabeth A.; Dandouras, Iannis

    2010-05-01

    The solar wind kinetic energy, fueling all dynamical processes within the near-Earth space, is extracted by a dynamo process at the magnetopause converting kinetic energy into magnetic energy. We investigate the magnetopause energy transfer both in small and large scales; using Cluster observations as well as a three-dimensional global magnetohydrodynamic (MHD) simulation GUMICS-4. In the simulation, the spatial distribution of the energy transfer exhibits a dependence on the interplanetary magnetic field (IMF) orientation, which is shown to agree with observational local estimates from Cluster spacecraft recordings. In both sythetic runs with artificial solar wind input as well as in reproductions of the observed solar wind we observe a "hysteresis" effect, where the magnetopause energy input stays enhanced longer than the traditional energy transfer proxies (e.g., epsilon) indicate. Specifically we focus in the simulation of a substorm sequence on Feb 18, 2004, during which an exceptional agreement between the simulation results and spacecraft recordings was observed on several orbits within the near-Earth space. In this event, we again observe the hysteresis effect and investigate the processes causing it at the magnetopause. We argue that since GUMICS-4 reproduces the observed signatures of the substorm sequence in question, the simulation results represent physical processes within the magnetosphere. We conclude that as the simulation energy input exhibits delays already at the magnetopause, the delays in the classical substorm loading - unloading cycle may be interpreted in a new light.

  15. Rotational Energy Transfer in N2

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.

    1994-01-01

    Using the N2-N2 intermolecular potential of van der Avoird et al. rotational energy transfer cross sections have been calculated using both the coupled state (CS) and infinite order sudden (IOS) approximations. The rotational energy transfer rate constants at 300 K, calculated in the CS approximation, are in reasonable agreement with the measurements of Sitz and Farrow. The IOS approximation qualitatively reproduces the dependence of the rate constants on the rotational quantum numbers, but consistently overestimates their magnitudes. The treatment of exchange symmetry will be discussed.

  16. Theory of coherent resonance energy transfer

    SciTech Connect

    Jang, Seogjoo; Cheng, Y.-C.; Reichman, David R.; Eaves, Joel D.

    2008-09-14

    A theory of coherent resonance energy transfer is developed combining the polaron transformation and a time-local quantum master equation formulation, which is valid for arbitrary spectral densities including common modes. The theory contains inhomogeneous terms accounting for nonequilibrium initial preparation effects and elucidates how quantum coherence and nonequilibrium effects manifest themselves in the coherent energy transfer dynamics beyond the weak resonance coupling limit of the Foerster and Dexter (FD) theory. Numerical tests show that quantum coherence can cause significant changes in steady state donor/acceptor populations from those predicted by the FD theory and illustrate delicate cooperation of nonequilibrium and quantum coherence effects on the transient population dynamics.

  17. Resonant vibrational energy transfer in ice Ih

    SciTech Connect

    Shi, L.; Li, F.; Skinner, J. L.

    2014-06-28

    Fascinating anisotropy decay experiments have recently been performed on H{sub 2}O ice Ih by Timmer and Bakker [R. L. A. Timmer, and H. J. Bakker, J. Phys. Chem. A 114, 4148 (2010)]. The very fast decay (on the order of 100 fs) is indicative of resonant energy transfer between OH stretches on different molecules. Isotope dilution experiments with deuterium show a dramatic dependence on the hydrogen mole fraction, which confirms the energy transfer picture. Timmer and Bakker have interpreted the experiments with a Förster incoherent hopping model, finding that energy transfer within the first solvation shell dominates the relaxation process. We have developed a microscopic theory of vibrational spectroscopy of water and ice, and herein we use this theory to calculate the anisotropy decay in ice as a function of hydrogen mole fraction. We obtain very good agreement with experiment. Interpretation of our results shows that four nearest-neighbor acceptors dominate the energy transfer, and that while the incoherent hopping picture is qualitatively correct, vibrational energy transport is partially coherent on the relevant timescale.

  18. Optimal Low Energy Earth-Moon Transfers

    NASA Technical Reports Server (NTRS)

    Griesemer, Paul Ricord; Ocampo, Cesar; Cooley, D. S.

    2010-01-01

    The optimality of a low-energy Earth-Moon transfer is examined for the first time using primer vector theory. An optimal control problem is formed with the following free variables: the location, time, and magnitude of the transfer insertion burn, and the transfer time. A constraint is placed on the initial state of the spacecraft to bind it to a given initial orbit around a first body, and on the final state of the spacecraft to limit its Keplerian energy with respect to a second body. Optimal transfers in the system are shown to meet certain conditions placed on the primer vector and its time derivative. A two point boundary value problem containing these necessary conditions is created for use in targeting optimal transfers. The two point boundary value problem is then applied to the ballistic lunar capture problem, and an optimal trajectory is shown. Additionally, the ballistic lunar capture trajectory is examined to determine whether one or more additional impulses may improve on the cost of the transfer.

  19. Low Energy Transfer to the Moon

    NASA Astrophysics Data System (ADS)

    Koon, W. S.; Lo, M. W.; Marsden, J. E.; Ross, S. D.

    In 1991, the Japanese Hiten mission used a low energy transfer with a ballistic capture at the Moon which required less Δ V than a standard Hohmann transfer. In this paper, we apply the dynamical systems techniques developed in our earlier work to reproduce systematically a Hiten-like mission. We approximate the Sun-Earth-Moon-spacecraft 4-body system as two 3-body systems. Using the invariant manifold structures of the Lagrange points of the 3-body systems, we are able to construct low energy transfer trajectories from the Earth which execute ballistic capture at the Moon. The techniques used in the design and construction of this trajectory may be applied in many situations.

  20. Energy transfer of nucleic acid products

    NASA Astrophysics Data System (ADS)

    Jung, Paul M.; Hu, Hsiang-Yun; Khalil, Omar S.

    1995-04-01

    Fluorescence energy transfer was investigated as a homogeneous detection method for the gapped ligase chain reaction (G-LCR). Oligonucleotides of a Chlamydia trachomatic G-LCR probe set were labeled with fluorescein as the donor and Texas Red as the acceptor fluorophore. Amplification and detection of 10 molecules of synthetic target was demonstrated in spiked urine samples.

  1. Energy Efficient Storage and Transfer of Cryogens

    NASA Technical Reports Server (NTRS)

    Fesmire, James E.

    2013-01-01

    Cryogenics is globally linked to energy generation, storage, and usage. Thermal insulation systems research and development is an enabling part of NASA's technology goals for Space Launch and Exploration. New thermal testing methodologies and materials are being transferred to industry for a wide range of commercial applications.

  2. Risk transfer via energy savings insurance

    SciTech Connect

    Mills, Evan

    2001-10-01

    Among the key barriers to investment in energy efficiency improvements are uncertainties about attaining projected energy savings and apprehension about potential disputes over these savings. The fields of energy management and risk management are thus intertwined. While many technical methods have emerged to manage performance risks (e.g. building commissioning), financial risk transfer techniques are less developed in the energy management arena than in other more mature segments of the economy. Energy Savings Insurance (ESI) - formal insurance of predicted energy savings - is one method of transferring financial risks away from the facility owner or energy services contractor. ESI offers a number of significant advantages over other forms of financial risk transfer, e.g. savings guarantees or performance bonds. ESI providers manage risk via pre-construction design review as well as post-construction commissioning and measurement and verification of savings. We found that the two mos t common criticisms of ESI - excessive pricing and onerous exclusions - are not born out in practice. In fact, if properly applied, ESI can potentially reduce the net cost of energy savings projects by reducing the interest rates charged by lenders, and by increasing the level of savings through quality control. Debt service can also be ensured by matching loan payments to projected energy savings while designing the insurance mechanism so that payments are made by the insurer in the event of a savings shortfall. We estimate the U.S. ESI market potential of $875 million/year in premium income. From an energy-policy perspective, ESI offers a number of potential benefits: ESI transfers performance risk from the balance sheet of the entity implementing the energy savings project, thereby freeing up capital otherwise needed to ''self-insure'' the savings. ESI reduces barriers to market entry of smaller energy services firms who do not have sufficiently strong balance sheets to self

  3. Two-photon excitation energy transfer microscopy

    NASA Astrophysics Data System (ADS)

    Periasamy, Ammasi

    2000-04-01

    Fluorescence resonance energy transfer (FRET) imaging is a unique tool used to visualize the spaciotemporal dynamics of protein-protein interactions in living cells. We used FRET to study the dimerization of the pituitary-specific transcription factor of Pit-1 fused with blue flourescent protein and green fluorescent protein. Transcriptional activity of the GFP- and BFP-Pit-1 fusion proteins was demonstrated by their ability to activate the prolactin gene promoter. The energy transfer in the conventional fluorescence microscopy was less efficient due to photobleaching of the BFP-Pit-1 donor molecules. In our studies we developed two-photon excitation energy transfer microscopy, where the photobleaching of blue flourescent protein was considerably reduced. This 2p-FRET imaging system was used to acquire the donor and acceptor images for a living HeLa cell nucleus. We selected 732 nm from the tunable Verdi pumped ti:sapphire laser, in a way that only excites the BFP-Pit-1 and not the GFP-Pit-1 proteins. The efficiency of the 2p-FRET signal increased to 30 percent compared to the conventional FRET imaging, which clearly demonstrates that there is considerable reduction in photobleaching of donor molecules in the 2p-FRET microscopy.

  4. Wireless Energy Transfer Through Magnetic Reluctance Coupling

    NASA Astrophysics Data System (ADS)

    Pillatsch, P.

    2014-11-01

    Energy harvesting from human motion for body worn or implanted devices faces the problem of the wearer being still, e.g. while asleep. Especially for medical devices this can become an issue if a patient is bed-bound for prolonged periods of time and the internal battery of a harvesting system is not recharged. This article introduces a mechanism for wireless energy transfer based on a previously presented energy harvesting device. The internal rotor of the energy harvester is made of mild steel and can be actuated through a magnetic reluctance coupling to an external motor. The internal piezoelectric transducer is consequently actuated and generates electricity. This paper successfully demonstrates energy transfer over a distance of 16 mm in air and an achieved power output of 85 μW at 25 Hz. The device functional volume is 1.85 cm3. Furthermore, it was demonstrated that increasing the driving frequency beyond 25 Hz did not yield a further increase in power output. Future research will focus on improving the reluctance coupling, e.g. by investigating the use of multiple or stronger magnets, in order to increase transmission distance.

  5. Metal Linkage Effects on Ultrafast Energy Transfer.

    PubMed

    Dekkiche, Hervé; Buisson, Antoine; Langlois, Adam; Karsenti, Paul-Ludovic; Ruhlmann, Laurent; Ruppert, Romain; Harvey, Pierre

    2016-07-18

    We report the preparation of several new porphyrin homodimers bridged by a platinum(II) ion in which very intense electronic communication through the coordination link occurs. Moreover, the synthesis of a new porphyrin dyad and its photophysical properties are reported. This dyad exhibits the fastest singlet energy transfer ever reported for synthetic systems between a zinc(II) porphyrin and a porphyrin free base. This extremely fast transfer (∼100 femtoseconds) is in the same range as the fastest one measured in natural systems. This feature is due to the platinum(II) linker, which allows for strong MO couplings between the two porphyrin units as experimentally supported by electrochemistry and corroborated by DFT computations. PMID:27333487

  6. Low-Energy Ballistic Transfers to Lunar Halo Orbits

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.

    2009-01-01

    Recent lunar missions have begun to take advantage of the benefits of low-energy ballistic transfers between the Earth and the Moon rather than implementing conventional Hohmann-like lunar transfers. Both Artemis and GRAIL plan to implement low-energy lunar transfers in the next few years. This paper explores the characteristics and potential applications of many different families of low-energy ballistic lunar transfers. The transfers presented here begin from a wide variety of different orbits at the Earth and follow several different distinct pathways to the Moon. This paper characterizes these pathways to identify desirable low-energy lunar transfers for future lunar missions.

  7. Vibrational energy transfer in high explosives: Nitromethane

    SciTech Connect

    Hong, X.; Hill, J.R.; Dlott, D.D.

    1996-03-01

    Time resolved vibrational spectroscopy with picosecond tunable mid-infrared pulses is used to measure the rates and investigate the detailed mechanisms of multiphonon up-pumping and vibrational cooling in a condensed high explosive, nitromethane. Both processes occur on the 100 ps time scale under ambient conditions. The mechanisms involve sequential climbing or descending the ladder of molecular vibrations. Efficient intermolecular vibrational energy transfer from various molecules to the symmetric stretching excitation of NO2 is observed. The implications of these measurements for understanding shock initiation to detonation and the sensitivities of energetic materials to shock initiation are discussed briefly.

  8. Energy transfer processes in solar energy conversion. Progress report

    SciTech Connect

    Fayer, M.D.

    1989-11-01

    We have made substantial progress in experimental and theoretical studies in two areas: Photoinduced donor to acceptor electron transfer followed by back transfer in random solutions; and electronic excitation transport in systems with complex inhomogeneous spatial geometries and inhomogeneous energy distributions. Through the development of accurate statistical mechanical theories, we have been able to relate dynamics in complex systems to experimental observables. We have then used the experimental observables, time resolved fluorescence depolarization and transient grating experiments, to examine well defined molecular systems. The agreement between theory and experiment is excellent. 11 refs.

  9. Energy transfer in stably stratified turbulence

    NASA Astrophysics Data System (ADS)

    Kimura, Yoshifumi; Herring, Jackson

    2015-11-01

    Energy transfer in forced stable stratified turbulence is investigated using pseudo-spectral DNS of the Navier-Stokes equations under the Boussinesq approximation with 10243 grid points. Making use of the Craya-Herring decomposition, the velocity field is decomposed into vortex (Φ1) and wave (Φ2) modes. To understand the anisotropy of stably stratified turbulence, the energy flues in terms of the spherical, the horizontal and the vertical wave numbers, are investigated for the total kinetic, Φ1, Φ2 energies, respectively. Among the three fluxes, the spherical and the horizontal look similar for strong stratification, and Φ1 flux shows a wave number region of constant value, which implies Kolmogorov's inertial range. The corresponding spectral power are, however, k - 5 / 2 for the spherical and k⊥- 5 / 3 for the horizontal cases. In contrast to these, the vertical energy fluxes show completely different features. We have observed the saturation spectrum E (kz) ~ CN2kz-3 for strong stratification as before, but the mechanism to produce this spectrum seems different from the Kolmogorov picture.

  10. Enhancing radiative energy transfer through thermal extraction

    NASA Astrophysics Data System (ADS)

    Tan, Yixuan; Liu, Baoan; Shen, Sheng; Yu, Zongfu

    2016-06-01

    Thermal radiation plays an increasingly important role in many emerging energy technologies, such as thermophotovoltaics, passive radiative cooling and wearable cooling clothes [1]. One of the fundamental constraints in thermal radiation is the Stefan-Boltzmann law, which limits the maximum power of far-field radiation to P0 = σT4S, where σ is the Boltzmann constant, S and T are the area and the temperature of the emitter, respectively (Fig. 1a). In order to overcome this limit, it has been shown that near-field radiations could have an energy density that is orders of magnitude greater than the Stefan-Boltzmann law [2-7]. Unfortunately, such near-field radiation transfer is spatially confined and cannot carry radiative heat to the far field. Recently, a new concept of thermal extraction was proposed [8] to enhance far-field thermal emission, which, conceptually, operates on a principle similar to oil immersion lenses and light extraction in light-emitting diodes using solid immersion lens to increase light output [62].Thermal extraction allows a blackbody to radiate more energy to the far field than the apparent limit of the Stefan-Boltzmann law without breaking the second law of thermodynamics. Thermal extraction works by using a specially designed thermal extractor to convert and guide the near-field energy to the far field, as shown in Fig. 1b. The same blackbody as shown in Fig. 1a is placed closely below the thermal extractor with a spacing smaller than the thermal wavelength. The near-field coupling transfers radiative energy with a density greater than σT4. The thermal extractor, made from transparent and high-index or structured materials, does not emit or absorb any radiation. It transforms the near-field energy and sends it toward the far field. As a result, the total amount of far-field radiative heat dissipated by the same blackbody is greatly enhanced above SσT4, where S is the area of the emitter. This paper will review the progress in thermal

  11. Anisotropic energy transfers in quasi-static magnetohydrodynamic turbulence

    SciTech Connect

    Reddy, K. Sandeep; Kumar, Raghwendra; Verma, Mahendra K.

    2014-10-15

    We perform direct numerical simulations of quasi-static magnetohydrodynamic turbulence and compute various energy transfers including the ring-to-ring and conical energy transfers, and the energy fluxes of the perpendicular and parallel components of the velocity field. We show that the rings with higher polar angles transfer energy to ones with lower polar angles. For large interaction parameters, the dominant energy transfer takes place near the equator (polar angle θ≈(π)/2 ). The energy transfers are local both in wavenumbers and angles. The energy flux of the perpendicular component is predominantly from higher to lower wavenumbers (inverse cascade of energy), while that of the parallel component is from lower to higher wavenumbers (forward cascade of energy). Our results are consistent with earlier results, which indicate quasi two-dimensionalization of quasi-static magnetohydrodynamic flows at high interaction parameters.

  12. Energy transfer in isotropic turbulence at low Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Domaradzki, J. A.; Rogallo, R. S.

    1988-01-01

    Detailed measurements were made of energy transfer among the scales of motion in incompressible turbulent fields at low Reynolds numbers generated by direct numerical simulation. It was observed that although the transfer resulted from triad interactions that were non-local in k space, the energy always transferred locally. The results are consistent with the notion of non-uniform advection of small weak eddies by larger and stronger ones, similar to transfer processes in the far dissipation range at high Reynolds numbers.

  13. Low Energy Transfer to the Moon

    NASA Astrophysics Data System (ADS)

    Koon, W. S.; Lo, M. W.; Marsden, J. E.; Ross, S. D.

    2001-11-01

    New space missions are increasingly more complex; demand for exotic orbits to solve engineering problems has grown beyond the existing astrodynamic infrastructure based on two-body interactions. The delicate heteroclinic dynamics used by the Genesis Mission dramatically illustrate the need for a new paradigm: dynamical system study of three-body problem. Furthermore, this dynamics has much to say about the morphology and transport of materials within the Solar System. The cross-fertilization of ideas between the natural dynamics of the Solar System and applications to engineering has produced new techniques for constructing spacecraft trajectories with interesting characteristics. Specifically, these techniques are used here to produce a lunar capture mission which uses less fuel than a Hohmann transfer. We approximate the Sun-Earth-Moon-Spacecraft four-body problem as two three-body problems. Using the invariant manifold structures of the Lagrange points of the three-body systems, we are able to construct low energy transfer trajectories from the Earth which exhibit ballistic capture at the Moon. The techniques used in the design and construction of this trajectory may be applied in many situations. This is joint work with Martin W. Lo, Jerrold E. Marsden and Shane D. Ross and was partially supported by the National Science Foundation Grant No. KFI/ATM-9873133 under a contract with the Jet Propulsion Laboratory, NASA.

  14. Infrared radiative energy transfer in gaseous systems

    NASA Technical Reports Server (NTRS)

    Tiwari, Surendra N.

    1991-01-01

    Analyses and numerical procedures are presented to investigate the radiative interactions in various energy transfer processes in gaseous systems. Both gray and non-gray radiative formulations for absorption and emission by molecular gases are presented. The gray gas formulations are based on the Planck mean absorption coefficient and the non-gray formulations are based on the wide band model correlations for molecular absorption. Various relations for the radiative flux and divergence of radiative flux are developed. These are useful for different flow conditions and physical problems. Specific plans for obtaining extensive results for different cases are presented. The procedure developed was applied to several realistic problems. Results of selected studies are presented.

  15. Local energy transfer and nonlocal interactions in homogeneous, isotropic turbulence

    NASA Technical Reports Server (NTRS)

    Domaradzki, J. Andrzej; Rogallo, Robert S.

    1990-01-01

    Detailed computations were made of energy transfer among the scales of motion in incompressible turbulent fields at low Reynolds numbers, generated by direct numerical simulations. It was observed that, although the transfer resulted from triad interactions that were nonlocal in k space, the energy always transferred locally. The energy transfer calculated from the eddy-damped quasi-normal Markovian (EDQNM) theory of turbulence at low Reynolds numbers is in excellent agreement with the results of the numerical simulations. At high Reynolds numbers, the EDQNM theory predicts the same transfer mechanism in the inertial range that is observed at low Reynolds numbers.

  16. Energy and electron transfer in bifunctional non-conjugated dendrimers.

    PubMed

    Justin Thomas, K R; Thompson, Alexis L; Sivakumar, Aathimanikandan V; Bardeen, Christopher J; Thayumanavan, S

    2005-01-12

    Nonconjugated dendrimers, which are capable of funneling energy from the periphery to the core followed by a charge-transfer process from the core to the periphery, have been synthesized. The energy and electron donors involve a diarylaminopyrene unit and are incorporated at the periphery of these dendrimers. The energy and electron acceptor is at the core of the dendrimer, which involves a chromophore based on a benzthiadiazole moiety. The backbone of the dendrimers is benzyl ether based. A direct electron-transfer quenching of the excited state of the periphery or a sequential energy transfer-electron-transfer pathway are the two limiting mechanisms of the observed photophysical properties. We find that the latter mechanism is prevalent in these dendrimers. The energy transfer occurs on a picosecond time scale, while the charge-transfer process occurs on a nanosecond time scale. The lifetime of the charge separated species was found to be in the range of microseconds. Energy transfer efficiencies ranging from 80% to 90% were determined using both steady-state and time-resolved measurements, while charge-transfer efficiencies ranging from 70% to 80% were deduced from fluorescence quenching of the core chromophore. The dependence of the energy and charge-transfer processes on dendrimer generation is analyzed in terms of the backfolding of the flexible benzyl ether backbone, which leads to a weaker dependence of the energy and charge-transfer efficiencies on dendrimer size than would be expected for a rigid system.

  17. Energy transfer in nonlinear network models of proteins

    NASA Astrophysics Data System (ADS)

    Piazza, F.; Sanejouand, Y.-H.

    2009-12-01

    We investigate how nonlinearity and topological disorder affect the energy relaxation of local kicks in coarse-grained network models of proteins. We find that nonlinearity promotes long-range, coherent transfer of substantial energy to specific functional sites, while depressing transfer to generic locations. In some cases, transfer is mediated by the self-localization of discrete breathers at distant locations from the kick, acting as efficient energy-accumulating centers.

  18. Radiation energy transfer in RNA polymers

    NASA Astrophysics Data System (ADS)

    Kempner, E. S.; Salovey, R.; Bernstein, S. L.

    1996-11-01

    Ribozymes are a special class of polyribonucleotide (RNA) molecules which possess intrinsic catalytic activity, capable of cleaving nucleic acid substrates. RNA molecules were synthesized containing a hammerhead ribozyme moiety of 52 nucleotides linked to an inactive leader sequence, for total lengths of either 262 or 1226 nucleotides. These RNAs were frozen and irradiated with high energy electrons. Surviving ribozyme activity was determined, using the ability of the irradiated ribozymes to cleave a labeled substrate. From the same irradiated samples, the amount of intact RNA remaining was determined following denaturing gel electrophoresis. Radiation target analyses of these data revealed a structural target size of 80 kDa and a ribozyme activity target size of 15 kDa for the smaller ribozyme, and 319 and 16 kDa, respectively, for the larger ribozyme. The disparity in target size for activity vs structure indicates that, in contrast to proteins, there is no spread of radiation damage far from the primary site of ionization in RNA molecules. The smaller target size for activity indicates that only primary ionizations occurring in the specific active region are effective. This is similar to the case for oligosaccharides. It is concluded that the presence of the ribose sugar in the polymer chain restricts radiation damage to a small region and prevents major energy transfer throughout the molecule.

  19. Luminescence energy transfer using a terbium chelate: Improvements on fluorescence energy transfer

    SciTech Connect

    Selvin, P.R.; Hearst, J.E.

    1994-10-11

    The authors extend the technique of fluorescence resonance energy transfer (FRET) by introducing a luminescent terbium chelate as a donor and an organic dye, tetramethylrhodamine, as an acceptor. The results are consistent with a Foerster theory of energy transfer, provided the appropriate parameters are used. The use of lanthanide donors in general, and this pair in particular, has many advantages over more conventional FRET pairs, which rely solely on organic dyes. The distance at which 50% energy transfer occurs is large, 65 {angstrom}; the donor lifetime is a single exponential and long (millisecond), making lifetime measurements facile and accurate. Uncertainty in the orientation factor, which creates uncertainty in measured distances, is minimized by the donor`s multiple electronic transitions and long lifetime. The sensitized emission of the acceptor can be measured with little or no interfering background, yielding a >25-fold improvement in the signal-to-background ratio over standard donor-acceptor pairs. These improvements are expected to make distances >100 {angstrom} measurable via FRET. The authors also report measurement of the sensitized emission lifetime, a measurement that is completely insensitive to total concentration and incomplete labeling.

  20. Targeting Low-Energy Transfers to Low Lunar Orbit

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.; Anderson, Rodney L.

    2011-01-01

    A targeting scheme is presented to build trajectories from a specified Earth parking orbit to a specified low lunar orbit via a low-energy transfer and up to two maneuvers. The total transfer delta V (velocity) is characterized as a function of the Earth parking orbit inclination and the departure date for transfers to each given low lunar orbit. The transfer delta V (velocity) cost is characterized for transfers constructed to low lunar polar orbits with any longitude of ascending node and for transfers that arrive at the Moon at any given time during a month.

  1. Nonlinear Energy Transfer in Solar Magnetic Loops

    NASA Astrophysics Data System (ADS)

    Gomez, Daniel O.; Deluca, Edward E.; McClymont, Alexander N.

    1995-08-01

    Active region coronal loops are widely believed to be heated by ohmic dissipation of field-aligned electric currents. These currents are driven by turbulent photospheric motions which twist and shear the magnetic footpoints of loops. Fine-scale structure in the corona is required in order to dissipate the currents rapidly enough to account for coronal heating. A long-standing controversy surrounds the question: is the fine-scale filamentation the result of magnetohydrodynamic (MHD) instabilities, or of dynamical nonequilibrium, or is it merely the direct product of the turbulent footpoint motions themselves? We present a simple model for the evolution of the coronal magnetic field, with no fine-scale structure in the imposed footpoint motions. The model consists of a three-mode truncation of the "reduced" MHD equations. One mode is driven by a stationary velocity field at the footpoints; the other two modes, of different spatial frequencies, are amplified through interaction with the driven mode. After approximately one photospheric turnover time, the coronal field loses equilibrium, and evolves rapidly to a new configuration, transferring energy to the two non-driven modes. The timescale of rapid nonequilibrium evolution is (tAtp)½, where tA is the Alfvén transit time along the loop and tp is the photospheric turnover time. Regarding this simple model as a building block of a much more complex process, we see that dynamical nonequilibrium should be able to produce a cascade of free energy to fine spatial scales where it can be dissipated rapidly enough to account for coronal heating, as envisioned by Parker.

  2. Nanoparticle energy transfer on the cell surface.

    PubMed

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

    2005-01-01

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

  3. Phonon-assisted excitation energy transfer in photosynthetic systems

    NASA Astrophysics Data System (ADS)

    Chen, Hao; Wang, Xin; Fang, Ai-Ping; Li, Hong-Rong

    2016-09-01

    The phonon-assisted process of energy transfer aiming at exploring the newly emerging frontier between biology and physics is an issue of central interest. This article shows the important role of the intramolecular vibrational modes for excitation energy transfer in the photosynthetic systems. Based on a dimer system consisting of a donor and an acceptor modeled by two two-level systems, in which one of them is coupled to a high-energy vibrational mode, we derive an effective Hamiltonian describing the vibration-assisted coherent energy transfer process in the polaron frame. The effective Hamiltonian reveals in the case that the vibrational mode dynamically matches the energy detuning between the donor and the acceptor, the original detuned energy transfer becomes resonant energy transfer. In addition, the population dynamics and coherence dynamics of the dimer system with and without vibration-assistance are investigated numerically. It is found that, the energy transfer efficiency and the transfer time depend heavily on the interaction strength of the donor and the high-energy vibrational mode, as well as the vibrational frequency. The numerical results also indicate that the initial state and dissipation rate of the vibrational mode have little influence on the dynamics of the dimer system. Results obtained in this article are not only helpful to understand the natural photosynthesis, but also offer an optimal design principle for artificial photosynthesis. Project supported by the National Natural Science Foundation of China (Grant No. 11174233).

  4. Visual prosthesis wireless energy transfer system optimal modeling

    PubMed Central

    2014-01-01

    Background Wireless energy transfer system is an effective way to solve the visual prosthesis energy supply problems, theoretical modeling of the system is the prerequisite to do optimal energy transfer system design. Methods On the basis of the ideal model of the wireless energy transfer system, according to visual prosthesis application condition, the system modeling is optimized. During the optimal modeling, taking planar spiral coils as the coupling devices between energy transmitter and receiver, the effect of the parasitic capacitance of the transfer coil is considered, and especially the concept of biological capacitance is proposed to consider the influence of biological tissue on the energy transfer efficiency, resulting in the optimal modeling’s more accuracy for the actual application. Results The simulation data of the optimal model in this paper is compared with that of the previous ideal model, the results show that under high frequency condition, the parasitic capacitance of inductance and biological capacitance considered in the optimal model could have great impact on the wireless energy transfer system. The further comparison with the experimental data verifies the validity and accuracy of the optimal model proposed in this paper. Conclusions The optimal model proposed in this paper has a higher theoretical guiding significance for the wireless energy transfer system’s further research, and provide a more precise model reference for solving the power supply problem in visual prosthesis clinical application. PMID:24428906

  5. Energy transfer and photochemistry in biomimetic solar conversion

    NASA Astrophysics Data System (ADS)

    Boxer, Steven G.

    1989-09-01

    The research program developed methods for studying electron transfer reactions and electron transfer in biomimetic solar energy systems. Over the course of the project results were obtained in several areas. The distance and orientation dependence of energy transfer were measured quantitatively in a completely defined 3-D array of chromophores. Synthetic methods were developed for covalently modifying DNA bases with electron donors and acceptors. Electric field effects were measured on the absorption and emission of photosynthetic systems. This led to the development of a general method for modulating electron transfer reactions in electric fields. Applications of this method to transition metal complexes were developed for the first time.

  6. Nonradiative resonance energy transfer between semiconductor quantum dots

    SciTech Connect

    Samosvat, D. M. Chikalova-Luzina, O. P.; Zegrya, G. G.

    2015-07-15

    A microscopic analysis of the mechanisms of nonradiative energy transfer in a system of two semiconductor QDs caused by Coulomb interaction of donor and acceptor electrons is performed. The energy transfer rate is calculated for QDs based on III–V compounds using the Kane model. Conditions are analyzed under which energy transfer from a donor to an acceptor is possible. The mixing in of the p states of the valence band to the s states of the conduction band is found to give rise to additional contributions to the matrix element of energy transfer. It is shown that these additional contributions play a considerable role in the energy transfer process at distances between QDs close to contact distances or much greater. The influence of the exchange interaction on the energy transfer mechanism is analyzed, and it is shown that this interaction should be taken into account for a quantitative description of the energy transfer when QDs are separated by a distance close to the contact distance.

  7. Nonradiative resonance energy transfer between semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Samosvat, D. M.; Chikalova-Luzina, O. P.; Zegrya, G. G.

    2015-07-01

    A microscopic analysis of the mechanisms of nonradiative energy transfer in a system of two semiconductor QDs caused by Coulomb interaction of donor and acceptor electrons is performed. The energy transfer rate is calculated for QDs based on III-V compounds using the Kane model. Conditions are analyzed under which energy transfer from a donor to an acceptor is possible. The mixing in of the p states of the valence band to the s states of the conduction band is found to give rise to additional contributions to the matrix element of energy transfer. It is shown that these additional contributions play a considerable role in the energy transfer process at distances between QDs close to contact distances or much greater. The influence of the exchange interaction on the energy transfer mechanism is analyzed, and it is shown that this interaction should be taken into account for a quantitative description of the energy transfer when QDs are separated by a distance close to the contact distance.

  8. A planning framework for transferring building energy technologies

    SciTech Connect

    Farhar, B C; Brown, M A; Mohler, B L; Wilde, M; Abel, F H

    1990-07-01

    Accelerating the adoption of new and existing cost-effective technologies has significant potential to reduce the energy consumed in US buildings. This report presents key results of an interlaboratory technology transfer planning effort in support of the US Department of Energy's Office of Building Technologies (OBT). A guiding assumption for planning was that OBT's R D program should forge linkages with existing programs whose goals involved enhancing energy efficiency in buildings. An ad hoc Technology Transfer Advisory Group reviewed the existing analysis and technology transfer program, brainstormed technology transfer approaches, interviewed DOE program managers, identified applicable research results, and developed a framework that management could use in deciding on the best investments of technology transfer resources. Representatives of 22 organizations were interviewed on their views of the potential for transferring energy efficiency technologies through active linking with OBT. The report describes these programs and interview results; outlines OBT tools, technologies, and practices to be transferred; defines OBT audiences; identifies technology transfer functions and presents a framework devised using functions and audiences; presents some 60 example technology transfer activities; and documents the Advisory Group's recommendations. 37 refs., 3 figs., 12 tabs.

  9. Elastic Energy Transfer in Turbulence of Dilute Polymer Solution

    NASA Astrophysics Data System (ADS)

    Xi, Heng-Dong; Bodenschatz, Eberhard; Xu, Haitao

    2012-11-01

    We present an experimental study of the energy transfer in the bulk of a turbulent flow with small amount long-chain polymer additives. By varying the Reynolds numbers Rλ, Wissenberg number Wi and polymer concentration φ. We test quantitively the elastic theory proposed by de Gennes and Tabor (Europhys. Lett., 1986; Physica A, 1986). The rate of energy transfer by polymer elasticity as inferred from the theory is consistent with that measured from the second order Eulerian structure functions. The unknown parameter n in the theory, which represents the flow topology of the stretching field, is found to be nearly 1. Based on energy transfer rate balance, We propose an elastic length scale, rɛ, which describes the effect of polymer elasticity on turbulence energy cascade and captures the scale dependence of the elastic energy transfer rate. We are grateful to the Max Planck Society, the Alexander von Humboldt Foundation and the Deutsche Forschungsgemeinschaft for their support.

  10. Energy transfer performance of mechanical nanoresonators coupled with electromagnetic fields

    PubMed Central

    2012-01-01

    We study the energy transfer performance in electrically and magnetically coupled mechanical nanoresonators. Using the resonant scattering theory, we show that magnetically coupled resonators can achieve the same energy transfer performance as for their electrically coupled counterparts or even outperform them within the scale of interest. Magnetic and electric coupling are compared in the nanotube radio, a realistic example of a nano-scale mechanical resonator. The energy transfer performance is also discussed for a newly proposed bio-nanoresonator composed of magnetosomes coated with a net of protein fibers. PMID:23075029

  11. Energy transfer between a biological labelling dye and gold nanorods

    NASA Astrophysics Data System (ADS)

    Racknor, Chris; Singh, Mahi R.; Zhang, Yinan; Birch, David J. S.; Chen, Yu

    2014-03-01

    We have demonstrated energy transfer between a biological labelling dye (Alexa Fluor 405) and gold nanorods experimentally and theoretically. The fluorescence lifetime imaging microscopy and density matrix method are used to study a hybrid system of dye and nanorods under one- and two-photon excitations. Energy transfer between dye and nanorods via the dipole-dipole interaction is found to cause a decrease in the fluorescence lifetime change. Enhanced energy transfer from dye to nanorods is measured in the presence of an increased density of nanorods. This study has potential applications in fluorescence lifetime-based intra-cellular sensing of bio-analytes as well as nuclear targeting cancer therapy.

  12. Energy Transfer and Triadic Interactions in Compressible Turbulence

    NASA Technical Reports Server (NTRS)

    Bataille, F.; Zhou, Ye; Bertoglio, Jean-Pierre

    1997-01-01

    Using a two-point closure theory, the Eddy-Damped-Quasi-Normal-Markovian (EDQNM) approximation, we have investigated the energy transfer process and triadic interactions of compressible turbulence. In order to analyze the compressible mode directly, the Helmholtz decomposition is used. The following issues were addressed: (1) What is the mechanism of energy exchange between the solenoidal and compressible modes, and (2) Is there an energy cascade in the compressible energy transfer process? It is concluded that the compressible energy is transferred locally from the solenoidal part to the compressible part. It is also found that there is an energy cascade of the compressible mode for high turbulent Mach number (M(sub t) greater than or equal to 0.5). Since we assume that the compressibility is weak, the magnitude of the compressible (radiative or cascade) transfer is much smaller than that of solenoidal cascade. These results are further confirmed by studying the triadic energy transfer function, the most fundamental building block of the energy transfer.

  13. Spectral kinetic energy transfer in turbulent premixed reacting flows.

    PubMed

    Towery, C A Z; Poludnenko, A Y; Urzay, J; O'Brien, J; Ihme, M; Hamlington, P E

    2016-05-01

    Spectral kinetic energy transfer by advective processes in turbulent premixed reacting flows is examined using data from a direct numerical simulation of a statistically planar turbulent premixed flame. Two-dimensional turbulence kinetic-energy spectra conditioned on the planar-averaged reactant mass fraction are computed through the flame brush and variations in the spectra are connected to terms in the spectral kinetic energy transport equation. Conditional kinetic energy spectra show that turbulent small-scale motions are suppressed in the burnt combustion products, while the energy content of the mean flow increases. An analysis of spectral kinetic energy transfer further indicates that, contrary to the net down-scale transfer of energy found in the unburnt reactants, advective processes transfer energy from small to large scales in the flame brush close to the products. Triadic interactions calculated through the flame brush show that this net up-scale transfer of energy occurs primarily at spatial scales near the laminar flame thermal width. The present results thus indicate that advective processes in premixed reacting flows contribute to energy backscatter near the scale of the flame.

  14. Spectral kinetic energy transfer in turbulent premixed reacting flows

    NASA Astrophysics Data System (ADS)

    Towery, C. A. Z.; Poludnenko, A. Y.; Urzay, J.; O'Brien, J.; Ihme, M.; Hamlington, P. E.

    2016-05-01

    Spectral kinetic energy transfer by advective processes in turbulent premixed reacting flows is examined using data from a direct numerical simulation of a statistically planar turbulent premixed flame. Two-dimensional turbulence kinetic-energy spectra conditioned on the planar-averaged reactant mass fraction are computed through the flame brush and variations in the spectra are connected to terms in the spectral kinetic energy transport equation. Conditional kinetic energy spectra show that turbulent small-scale motions are suppressed in the burnt combustion products, while the energy content of the mean flow increases. An analysis of spectral kinetic energy transfer further indicates that, contrary to the net down-scale transfer of energy found in the unburnt reactants, advective processes transfer energy from small to large scales in the flame brush close to the products. Triadic interactions calculated through the flame brush show that this net up-scale transfer of energy occurs primarily at spatial scales near the laminar flame thermal width. The present results thus indicate that advective processes in premixed reacting flows contribute to energy backscatter near the scale of the flame.

  15. INTRAMOLECULAR CHARGE AND ENERGY TRANSFER IN MULTICHROMOPHORIC AROMATIC SYSTEMS

    SciTech Connect

    Edward C. Lim

    2008-09-09

    A concerted experimental and computational study of energy transfer in nucleic acid bases and charge transfer in dialkylaminobenzonitriles, and related electron donor-acceptor molecules, indicate that the ultrafast photoprocesses occur through three-state conical interactions involving an intermediate state of biradical character.

  16. Energy efficient building design. A transfer guide for local governments

    SciTech Connect

    Not Available

    1992-03-01

    The fundamental concepts of the building design process, energy codes and standards, and energy budgets are introduced. These tools were combined into Energy Design Guidelines and design contract requirements. The Guidelines were repackaged for a national audience and a videotape for selling the concept to government executives. An effort to test transfer of the Guidelines to outside agencies is described.

  17. Energy Transfer in MAGNESIUM-OXIDE:CHROMIUM(+3)

    NASA Astrophysics Data System (ADS)

    O'Neill, Mary

    Available from UMI in association with The British Library. Requires signed TDF. Using steady state and time resolved luminescence spectroscopy energy transfer between Cr^ {+3} ions in MgO was investigated. Five sharp zero-phonon lines observed in the excitation spectrum of the < 100> (Cr _sp{Mg}{cdot } V_sp{Mg} {''} Cr_sp {rm Mg}{cdot}) centre are shown to originate from three distinct donor centres from which excitation is transferred to the acceptor < 100> (Cr_sp {Mg}{cdot} V _sp{Mg}{' '} Cr_sp{Mg}{cdot}) centre. The energy transfer process is non resonant involving either emission of a single phonon or the Raman process. For each donor -acceptor pair, the energy transfer rate is measured by analysing the time dependence of luminescence from the acceptor. The magnitude of the electric quadrupole-quadrupole and the electric dipole-quadrupole donor-acceptor interactions, calculated using group and perturbation theories, is insufficient to account for the observed energy transfer rate. An antiferromagnetic superexchange donor-acceptor interaction governs the transfer process. On the basis of such a mechanism, geometric models are proposed which illustrate the relative positions of the donor and acceptor ions in each of the three systems. In addition to this localised process, energy transfer between randomly distributed Cr^{+3} ions in MgO is investigated. Spectroscopic measurements show that energy is transferred from Cr^ {+3} ions in octahedral symmetry sites to tetragonal and orthorhombic symmetry sites, the extent of transfer is found to be small. Transient grating spectroscopic measurements show that spatial energy migration among resonant Cr^{+3} ion is negligible at low Cr^{+3} concentrations but occurs when the Cr^{+3} concentration is increased.

  18. Energy Transfer and a Recurring Mathematical Function

    ERIC Educational Resources Information Center

    Atkin, Keith

    2013-01-01

    This paper extends the interesting work of a previous contributor concerning the analogies between physical phenomena such as mechanical collisions and the transfer of power in an electric circuit. Emphasis is placed on a mathematical function linking these different areas of physics. This unifying principle is seen as an exciting opportunity to…

  19. Shishiodoshi unidirectional energy transfer mechanism in phenylene ethynylene dendrimers.

    PubMed

    Fernandez-Alberti, S; Roitberg, Adrian E; Kleiman, Valeria D; Nelson, T; Tretiak, S

    2012-12-14

    Non-adiabatic excited-state molecular dynamics is used to study the ultrafast intramolecular energy transfer between two-, three-, and four-ring linear polyphenylene ethynylene chromophore units linked through meta-substitutions. Twenty excited-state electronic energies, with their corresponding gradients and nonadiabatic coupling vectors were included in the simulations. The initial laser excitation creates an exciton delocalized between the different absorbing two-ring linear PPE units. Thereafter, we observe an ultrafast directional change in the spatial localization of the transient electronic transition density. The analysis of the intramolecular flux of the transition density shows a sequential through-bond two-ring→three-ring→four-ring transfer as well as an effective through-space direct two-to-four ring transfer. The vibrational excitations of C≡C stretching motions change according to that. Finally, a mechanism of unidirectional energy transfer is presented based on the variation of the energy gaps between consecutive electronic excited states in response to the intramolecular flux of the transition density. The mechanism resembles a Shishiodoshi Japanese bamboo water fountain where, once the electronic population has been transferred to the state directly below in energy, the two states decouple thereby preventing energy transfer in the opposite direction. PMID:23249063

  20. Exciton Transfer in Carbon Nanotube Aggregates for Energy Harvesting Applications

    NASA Astrophysics Data System (ADS)

    Davoody, Amirhossein; Karimi, Farhad; Knezevic, Irena

    Carbon nanotubes (CNTs) are promising building blocks for organic photovoltaic devices, owing to their tunable band gap, mechanical and chemical stability. We study intertube excitonic energy transfer between pairs of CNTs with different orientations and band gaps. The optically bright and dark excitonic states in CNTs are calculated by solving the Bethe-Salpeter equation. We calculate the exciton transfer rates due to the direct and exchange Coulomb interactions, as well as the second-order phonon-assisted processes. We show the importance of phonons in calculating the transfer rates that match the measurements. In addition, we discuss the contribution of optically inactive excited states in the exciton transfer process, which is difficult to determine experimentally. Furthermore, we study the effects of sample inhomogeneity, impurities, and temperature on the exciton transfer rate. The inhomogeneity in the CNT sample dielectric function can increase the transfer rate by about a factor of two. We show that the exciton confinement by impurities has a detrimental effect on the transfer rate between pairs of similar CNTs. The exciton transfer rate increases monotonically with increasing temperature. Support by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC0008712.

  1. Fluorescence resonant energy transfer in the optical near field

    SciTech Connect

    Colas des Francs, Gerard; Girard, Christian; Martin, Olivier J.F.

    2003-05-01

    We develop a versatile theoretical framework for the study of fluorescence resonant energy transfer (FRET, or Foerster transfer) in complex environments, under arbitrary illumination, including optical near fields. By combining the field-susceptibility formalism with the optical Bloch equations method, we derive general equations for the computation of the energy transfer between pairs of donor-acceptor molecules excited by optical near fields and placed in a complex geometry. This approach allows accounting for both the variations of the molecular population rates and the influence of the environment. Several examples illustrate the ability of the technique to analyze recent FRET experiments performed in the optical near field.

  2. Engineering Efficient Exciton Energy Transfer in Artificial Arrays

    NASA Astrophysics Data System (ADS)

    Vogt, Leslie; Perdomo, Alejandro; Saikin, Semion; Aspuru-Guzik, Alan

    2009-03-01

    A critical component of light harvesting devices is efficient transfer of excitonic energy. Biological systems have optimized this process over time for the particular molecular components involved. Understanding this energy transfer in model arrays will allow us to engineer new materials for solar cell technology. In particular, we explore a perturbative approach to optimize both coherent and incoherent transport in small arrays. By following the evolving coherences and populations over time using a density matrix formalism, we gain an intuition about the importance of coherent processes in exciton transfer in natural and designed light harvesting systems.

  3. Ligand reorganization and activation energies in nonadiabatic electron transfer reactions

    NASA Astrophysics Data System (ADS)

    Zhu, Jianjun; Wang, Jianji; Stell, George

    2006-10-01

    The activation energy and ligand reorganization energy for nonadiabatic electron transfer reactions in chemical and biological systems are investigated in this paper. The free energy surfaces and the activation energy are derived exactly in the general case in which the ligand vibration frequencies are not equal. The activation energy is derived by free energy minimization at the transition state. Our formulation leads to the Marcus-Hush [J. Chem. Phys. 24, 979 (1956); 98, 7170 (1994); 28, 962 (1958)] results in the equal-frequency limit and also generalizes the Marcus-Sumi [J. Chem. Phys. 84, 4894 (1986)] model in the context of studying the solvent dynamic effect on electron transfer reactions. It is found that when the ligand vibration frequencies are different, the activation energy derived from the Marcus-Hush formula deviates by 5%-10% from the exact value. If the reduced reorganization energy approximation is introduced in the Marcus-Hush formula, the result is almost exact.

  4. Proton-Coupled Electron Transfer Reactions with Photometric Bases Reveal Free Energy Relationships for Proton Transfer.

    PubMed

    Eisenhart, Thomas T; Howland, William C; Dempsey, Jillian L

    2016-08-18

    The proton-coupled electron transfer (PCET) oxidation of p-aminophenol in acetonitrile was initiated via stopped-flow rapid-mixing and spectroscopically monitored. For oxidation by ferrocenium in the presence of 7-(dimethylamino)quinoline proton acceptors, both the electron transfer and proton transfer components could be optically monitored in the visible region; the decay of the ferrocenium absorbance is readily monitored (λmax = 620 nm), and the absorbance of the 2,4-substituted 7-(dimethylamino)quinoline derivatives (λmax = 370-392 nm) red-shifts substantially (ca. 70 nm) upon protonation. Spectral analysis revealed the reaction proceeds via a stepwise electron transfer-proton transfer process, and modeling of the kinetics traces monitoring the ferrocenium and quinolinium signals provided rate constants for elementary proton and electron transfer steps. As the pKa values of the conjugate acids of the 2,4-R-7-(dimethylamino)quinoline derivatives employed were readily tuned by varying the substituents at the 2- and 4-positions of the quinoline backbone, the driving force for proton transfer was systematically varied. Proton transfer rate constants (kPT,2 = (1.5-7.5) × 10(8) M(-1) s(-1), kPT,4 = (0.55-3.0) × 10(7) M(-1) s(-1)) were found to correlate with the pKa of the conjugate acid of the proton acceptor, in agreement with anticipated free energy relationships for proton transfer processes in PCET reactions. PMID:27500804

  5. Proton-Coupled Electron Transfer Reactions with Photometric Bases Reveal Free Energy Relationships for Proton Transfer.

    PubMed

    Eisenhart, Thomas T; Howland, William C; Dempsey, Jillian L

    2016-08-18

    The proton-coupled electron transfer (PCET) oxidation of p-aminophenol in acetonitrile was initiated via stopped-flow rapid-mixing and spectroscopically monitored. For oxidation by ferrocenium in the presence of 7-(dimethylamino)quinoline proton acceptors, both the electron transfer and proton transfer components could be optically monitored in the visible region; the decay of the ferrocenium absorbance is readily monitored (λmax = 620 nm), and the absorbance of the 2,4-substituted 7-(dimethylamino)quinoline derivatives (λmax = 370-392 nm) red-shifts substantially (ca. 70 nm) upon protonation. Spectral analysis revealed the reaction proceeds via a stepwise electron transfer-proton transfer process, and modeling of the kinetics traces monitoring the ferrocenium and quinolinium signals provided rate constants for elementary proton and electron transfer steps. As the pKa values of the conjugate acids of the 2,4-R-7-(dimethylamino)quinoline derivatives employed were readily tuned by varying the substituents at the 2- and 4-positions of the quinoline backbone, the driving force for proton transfer was systematically varied. Proton transfer rate constants (kPT,2 = (1.5-7.5) × 10(8) M(-1) s(-1), kPT,4 = (0.55-3.0) × 10(7) M(-1) s(-1)) were found to correlate with the pKa of the conjugate acid of the proton acceptor, in agreement with anticipated free energy relationships for proton transfer processes in PCET reactions.

  6. Hole-transfer induced energy transfer in perylene diimide dyads with a donor-spacer-acceptor motif.

    PubMed

    Kölle, Patrick; Pugliesi, Igor; Langhals, Heinz; Wilcken, Roland; Esterbauer, Andreas J; de Vivie-Riedle, Regina; Riedle, Eberhard

    2015-10-14

    We investigate the photoinduced dynamics of perylene diimide dyads based on a donor-spacer-acceptor motif with polyyne spacers of varying length by pump-probe spectroscopy, time resolved fluorescence, chemical variation and quantum chemistry. While the dyads with pyridine based polyyne spacers undergo energy transfer with near-unity quantum efficiency, in the dyads with phenyl based polyyne spacers the energy transfer efficiency drops below 50%. This suggests the presence of a competing electron transfer process from the spacer to the energy donor as the excitation sink. Transient absorption spectra, however, reveal that the spacer actually mediates the energy transfer dynamics. The ground state bleach features of the polyyne spacers appear due to the electron transfer decay with the same time constant present in the rise of the ground state bleach and stimulated emission of the perylene energy acceptor. Although the electron transfer process initially quenches the fluorescence of the donor it does not inhibit energy transfer to the perylene energy acceptor. The transient signatures reveal that electron and energy transfer processes are sequential and indicate that the donor-spacer electron transfer state itself is responsible for the energy transfer. Through the introduction of a Dexter blocker unit into the spacer we can clearly exclude any through bond Dexter-type energy transfer. Ab initio calculations on the donor-spacer and the donor-spacer-acceptor systems reveal the existence of a bright charge transfer state that is close in energy to the locally excited state of the acceptor. Multipole-multipole interactions between the bright charge transfer state and the acceptor state enable the energy transfer. We term this mechanism coupled hole-transfer FRET. These dyads represent a first example that shows how electron transfer can be connected to energy transfer for use in novel photovoltaic and optoelectronic devices. PMID:26347443

  7. Thermal energy transfer system and method

    SciTech Connect

    Knoos, S.

    1985-02-12

    A thermodynamic system for interchanging thermal energy with external sources or sinks while minimizing the dead volume presented to the pressure cycle is based upon a thermodynamic machine which cycles a working fluid bidirectionally through a regenerator means and at least one external heat exchanger for interchanging thermal energy with a heat source or sink. Between the thermodynamic machine and the heat exchanger is a switchable thermal energy storage system using at least one heat load capacitor and two different circulation loops through the storage system. By switching the working fluid paths through the thermal energy storage system, Thermal energy is exchanged but the thermodynamic machine is isolated from the heat exchanger at least predetermined intervals during operation, and the dead space in the external device does not affect the pressure cycle of the machine.

  8. On Kinetics Modeling of Vibrational Energy Transfer

    NASA Technical Reports Server (NTRS)

    Gilmore, John O.; Sharma, Surendra P.; Cavolowsky, John A. (Technical Monitor)

    1996-01-01

    Two models of vibrational energy exchange are compared at equilibrium to the elementary vibrational exchange reaction for a binary mixture. The first model, non-linear in the species vibrational energies, was derived by Schwartz, Slawsky, and Herzfeld (SSH) by considering the detailed kinetics of vibrational energy levels. This model recovers the result demanded at equilibrium by the elementary reaction. The second model is more recent, and is gaining use in certain areas of computational fluid dynamics. This model, linear in the species vibrational energies, is shown not to recover the required equilibrium result. Further, this more recent model is inconsistent with its suggested rate constants in that those rate constants were inferred from measurements by using the SSH model to reduce the data. The non-linear versus linear nature of these two models can lead to significant differences in vibrational energy coupling. Use of the contemporary model may lead to significant misconceptions, especially when integrated in computer codes considering multiple energy coupling mechanisms.

  9. A molecularly based theory for electron transfer reorganization energy

    SciTech Connect

    Zhuang, Bilin; Wang, Zhen-Gang

    2015-12-14

    Using field-theoretic techniques, we develop a molecularly based dipolar self-consistent-field theory (DSCFT) for charge solvation in pure solvents under equilibrium and nonequilibrium conditions and apply it to the reorganization energy of electron transfer reactions. The DSCFT uses a set of molecular parameters, such as the solvent molecule’s permanent dipole moment and polarizability, thus avoiding approximations that are inherent in treating the solvent as a linear dielectric medium. A simple, analytical expression for the free energy is obtained in terms of the equilibrium and nonequilibrium electrostatic potential profiles and electric susceptibilities, which are obtained by solving a set of self-consistent equations. With no adjustable parameters, the DSCFT predicts activation energies and reorganization energies in good agreement with previous experiments and calculations for the electron transfer between metallic ions. Because the DSCFT is able to describe the properties of the solvent in the immediate vicinity of the charges, it is unnecessary to distinguish between the inner-sphere and outer-sphere solvent molecules in the calculation of the reorganization energy as in previous work. Furthermore, examining the nonequilibrium free energy surfaces of electron transfer, we find that the nonequilibrium free energy is well approximated by a double parabola for self-exchange reactions, but the curvature of the nonequilibrium free energy surface depends on the charges of the electron-transferring species, contrary to the prediction by the linear dielectric theory.

  10. Energy Information Transfer in Virginia. A Planning Conference.

    ERIC Educational Resources Information Center

    Hickin, Patricia

    The Virginia Planning Conference for Solar Technology Information Transfer was held in Richmond in February 1978 to elicit suggestions on how to make Virginians aware of libraries as sources of energy information and how Virginia libraries can keep their energy materials and reference services up to date. A summary of this planning session and a…

  11. Photoinduced charge and energy transfer in molecular wires.

    PubMed

    Gilbert, Mélina; Albinsson, Bo

    2015-02-21

    Exploring charge and energy transport in donor-bridge-acceptor systems is an important research field which is essential for the fundamental knowledge necessary to develop future applications. These studies help creating valuable knowledge to respond to today's challenges to develop functionalized molecular systems for artificial photosynthesis, photovoltaics or molecular scale electronics. This tutorial review focuses on photo-induced charge/energy transfer in covalently linked donor-bridge-acceptor (D-B-A) systems. Of utmost importance in such systems is to understand how to control signal transmission, i.e. how fast electrons or excitation energy could be transferred between the donor and acceptor and the role played by the bridge (the "molecular wire"). After a brief description of the electron and energy transfer theory, we aim to give a simple yet accurate picture of the complex role played by the bridge to sustain donor-acceptor electronic communication. Special emphasis is put on understanding bridge energetics and conformational dynamics effects on the distance dependence of the donor-acceptor electronic coupling and transfer rates. Several examples of donor-bridge-acceptor systems from the literature are described as a support to the discussion. Finally, porphyrin-based molecular wires are introduced, and the relationship between their electronic structure and photophysical properties is outlined. In strongly conjugated porphyrin systems, limitations of the existing electron transfer theory to interpret the distance dependence of the transfer rates are also discussed.

  12. Efficient Radioisotope Energy Transfer by Gold Nanoclusters for Molecular Imaging.

    PubMed

    Volotskova, Olga; Sun, Conroy; Stafford, Jason H; Koh, Ai Leen; Ma, Xiaowei; Cheng, Zhen; Cui, Bianxiao; Pratx, Guillem; Xing, Lei

    2015-08-26

    Beta-emitting isotopes Fluorine-18 and Yttrium-90 are tested for their potential to stimulate gold nanoclusters conjugated with blood serum proteins (AuNCs). AuNCs excited by either medical radioisotope are found to be highly effective ionizing radiation energy transfer mediators, suitable for in vivo optical imaging. AuNCs synthesized with protein templates convert beta-decaying radioisotope energy into tissue-penetrating optical signals between 620 and 800 nm. Optical signals are not detected from AuNCs incubated with Technetium-99m, a pure gamma emitter that is used as a control. Optical emission from AuNCs is not proportional to Cerenkov radiation, indicating that the energy transfer between the radionuclide and AuNC is only partially mediated by Cerenkov photons. A direct Coulombic interaction is proposed as a novel and significant mechanism of energy transfer between decaying radionuclides and AuNCs.

  13. International cooperation for renewable energy transfer

    SciTech Connect

    Wolfe, M.H.

    1992-06-01

    This paper reports that in considering the potential of major renewable energy resources in relation to their remoteness from demand centers, it is necessary to take a global view of the implications of their utilization. The present concerns regarding global warming and environmental degradation from fossil fuel combustion could be given active direction if the positive benefits of renewable energy could be realized on a meaningful scale. The dire prospect of global warming looms large in the scientific consciousness, but strategies to counter the effects of increased release of carbon dioxide and other greenhouse gases are just beginning to emerge along with remedial measures to address other environmental threats. One of the ways to achieve this is to place more reliance on renewable energy. As the impact of small-scale dispersed sources of renewable energy is minimal in comparison with fossil fuel usage, a meaningful impact could only be made by drawing upon major sources of renewable energy, mainly hydropower, tidal, and solar, in large capacity installations concentrated at sites relatively far from demand centers. There are sites that warrant serious consideration in the face of the growing environmental impact of fossil fuel usage. However, to realize this objective, an environmental imperative should be adopted that would place the importance of global environmental security on a par with present concerns for national security.

  14. Conformational disorder in energy transfer: beyond Förster theory.

    PubMed

    Nelson, Tammie; Fernandez-Alberti, Sebastian; Roitberg, Adrian E; Tretiak, Sergei

    2013-06-21

    Energy transfer in donor-acceptor chromophore pairs, where the absorption of each species is well separated while donor emission and acceptor absorption overlap, can be understood through a Förster resonance energy transfer model. The picture is more complex for organic conjugated polymers, where the total absorption spectrum can be described as a sum of the individual contributions from each subunit (chromophore), whose absorption is not well separated. Although excitations in these systems tend to be well localized, traditional donors and acceptors cannot be defined and energy transfer can occur through various pathways where each subunit (chromophore) is capable of playing either role. In addition, fast torsional motions between individual monomers can break conjugation and lead to reordering of excited state energy levels. Fast torsional fluctuations occur on the same timescale as electronic transitions leading to multiple trivial unavoided crossings between excited states during dynamics. We use the non-adiabatic excited state molecular dynamics (NA-ESMD) approach to simulate energy transfer between two poly-phenylene vinylene (PPV) oligomers composed of 3-rings and 4-rings, respectively, separated by varying distances. The change in the spatial localization of the transient electronic transition density, initially localized on the donors, is used to determine the transfer rate. Our analysis shows that evolution of the intramolecular transition density can be decomposed into contributions from multiple transfer pathways. Here we present a detailed analysis of ensemble dynamics as well as a few representative trajectories which demonstrate the intertwined role of electronic and conformational processes. Our study reveals the complex nature of energy transfer in organic conjugated polymer systems and emphasizes the caution that must be taken in performing such an analysis when a single simple unidirectional pathway is unlikely. PMID:23657784

  15. Dependence of the energy transfer to graphene on the excitation energy

    SciTech Connect

    Mackowski, Sebastian Kamińska, Izabela

    2015-07-13

    Fluorescence studies of natural photosynthetic complexes on a graphene layer demonstrate pronounced influence of the excitation wavelength on the energy transfer efficiency to graphene. Ultraviolet light yields much faster decay of fluorescence, with average efficiencies of the energy transfer equal to 87% and 65% for excitation at 405 nm and 640 nm, respectively. This implies that focused light changes locally the properties of graphene affecting the energy transfer dynamics, in an analogous way as in the case of metallic nanostructures. Demonstrating optical control of the energy transfer is important for exploiting unique properties of graphene in photonic and sensing architectures.

  16. Multi-neutron transfer reactions at sub-barrier energies.

    SciTech Connect

    Rehm, K. E.

    1998-01-20

    The optimum conditions for multi-neutron transfer have been studied in the system {sup 58}Ni + {sup 124}Sn at bombarding energies at and below the Coulomb barrier. The experiments were performed in inverse kinematics with a {sup 124}Sn beam bombarding a {sup 58}Ni target. The particles were identified with respect to mass and Z in the split-pole spectrograph with a hybrid focal plane detector with mass and Z-resolutions of A/{Delta}A = 150 and Z/{Delta}Z = 70. At all energies the transfer of up to 6 neutrons was observed. The yields for these transfer reactions are found to decrease by about a factor of four for each transferred neutron.

  17. Topological energy transfer in an optomechanical system with exceptional points

    NASA Astrophysics Data System (ADS)

    Xu, H.; Mason, D.; Jiang, Luyao; Harris, J. G. E.

    2016-09-01

    Topological operations can achieve certain goals without requiring accurate control over local operational details; for example, they have been used to control geometric phases and have been proposed as a way of controlling the state of certain systems within their degenerate subspaces. More recently, it was predicted that topological operations can be used to transfer energy between normal modes, provided that the system possesses a specific type of degeneracy known as an exceptional point. Here we demonstrate the transfer of energy between two vibrational modes of a cryogenic optomechanical device using topological operations. We show that this transfer arises from the presence of an exceptional point in the spectrum of the device. We also show that this transfer is non-reciprocal. These results open up new directions in system control; they also open up the possibility of exploring other dynamical effects related to exceptional points, including the behaviour of thermal and quantum fluctuations in their vicinity.

  18. Production and Transfer of Energy and Information in Hamiltonian Systems

    PubMed Central

    Antonopoulos, Chris G.; Bianco-Martinez, Ezequiel; Baptista, Murilo S.

    2014-01-01

    We present novel results that relate energy and information transfer with sensitivity to initial conditions in chaotic multi-dimensional Hamiltonian systems. We show the relation among Kolmogorov-Sinai entropy, Lyapunov exponents, and upper bounds for the Mutual Information Rate calculated in the Hamiltonian phase space and on bi-dimensional subspaces. Our main result is that the net amount of transfer from kinetic to potential energy per unit of time is a power-law of the upper bound for the Mutual Information Rate between kinetic and potential energies, and also a power-law of the Kolmogorov-Sinai entropy. Therefore, transfer of energy is related with both transfer and production of information. However, the power-law nature of this relation means that a small increment of energy transferred leads to a relatively much larger increase of the information exchanged. Then, we propose an “experimental” implementation of a 1-dimensional communication channel based on a Hamiltonian system, and calculate the actual rate with which information is exchanged between the first and last particle of the channel. Finally, a relation between our results and important quantities of thermodynamics is presented. PMID:24586891

  19. Paths to Förster's resonance energy transfer (FRET) theory

    NASA Astrophysics Data System (ADS)

    Masters, B. R.

    2014-02-01

    Theodor Förster (1910-1974) developed a phenomenological theory of nonradiative resonance energy transfer which proved to be transformative in the fields of chemistry, biochemistry, and biology. This paper explores the experimental and the theoretical antecedents of Förster's theory of resonance energy transfer (FRET). Early studies of sensitized fluorescence, fluorescence depolarization, and photosynthesis demonstrated the phenomena of long-range energy transfer. At the same time physicists developed theoretical models which contained common physical mechanisms and parameters: oscillating dipoles as models for the atoms or molecules, dipole-dipole coupling for the interaction, and a distance R0 that is optimal for resonance energy transfer. Early theories predicted R0 that was too large as compared to experiments. Finally, in 1946 Förster developed a classical theory and in 1948 he developed a quantum mechanical theory; both theories predicted an inverse sixth power dependence of the rate of energy transfer and a R0 that agreed with experiments. This paper attempts to determine why Förster succeeded when the other theoreticians failed to develop the correct theory. The putative roles of interdisciplinary education and collaborative research are discussed. Furthermore, I explore the role of science journals and their specific audiences in the popularization of FRET to a broad interdisciplinary community.

  20. Correlated energy transfer between two ultracold atomic species

    NASA Astrophysics Data System (ADS)

    Krönke, Sven; Knörzer, Johannes; Schmelcher, Peter

    2015-05-01

    We study a single atom as an open quantum system, which is initially prepared in a coherent state of low energy and oscillates in a one-dimensional harmonic trap through an interacting ensemble of NA bosons, held in a displaced trap [arXiv:1410.8676]. The non-equilibrium quantum dynamics of the total system is simulated by means of an ab-initio method, giving us access to all properties of the open system and its finite environment. In this talk, we focus on unraveling the interplay of energy exchange and correlations between the subsystems, which are coupled in such a spatio-temporally localized manner. We show that an inter-species interaction-induced level splitting accelerates the energy transfer between the atomic species for larger NA, which becomes less complete at the same time. System-environment correlations prove to be significant except for times when the excess energy distribution among the subsystems is highly imbalanced. These correlations result in incoherent energy transfer processes, which accelerate the early energy donation of the single atom. By analyzing correlations between intra-subsystem excitations, certain energy transfer channels are shown to be (dis-)favored depending on the instantaneous direction of transfer.

  1. Energy transfer between laser beams crossing in ignition hohlraums

    SciTech Connect

    Michel, P; Divol, L; Williams, E A; Thomas, C A; Callahan, D A; Weber, S; Haan, S W; Salmonson, J D; Dixit, S; Hinkel, D E; Edwards, M J; MacGowan, B J; Lindl, J D; Glenzer, S H; Suter, L J

    2008-10-03

    The full scale modeling of power transfer between laser beams crossing in plasmas is presented. A new model was developed, allowing calculation of the propagation and coupling of pairs of laser beams with their associated plasma wave in three dimensions. The full laser beam smoothing techniques used in ignition experiments are modeled, and their effects on crossed-beam energy transfer is investigated. A shift in wavelength between the beams can move the instability off resonance and reduce the transfer, hence preserving the symmetry of the capsule implosion.

  2. Energy transfer at gas-liquid interface: Towards energetic materials

    NASA Astrophysics Data System (ADS)

    Szabo, Tamas

    Physicochemical surface processes have great importance in the different fields of everyday life and science. Computational characterization of collisional energy transfer at a gas-liquid interface is a helpful tool to interpret recent experimental studies and to yield insight into the energy feedback mechanism of multiphase combustion problems. As a first step, a simple Lennard-Jones system was used to investigate the dependence of the collisional energy transfer and the gas atom trapping probabilities on the temperature of the bulk liquid, on the gas/liquid particle mass ratios, on the incident angle of the impinging projectile, and on the gas-liquid interaction strength. We find in accord with the experimental results that the kinematic effects dominate the energy transfer dynamics, but the importance of the role of surface roughening as the temperature of the liquid increases is also seen. The second system, nitromethane was chosen to extend the range of simulations. It is a molecular model system, representing nitramine-type energetic materials. Having had a good potential description for the nitromethane molecule including all internal degrees of freedom, we generated simplified molecular systems based on the original nitromethane model to isolate particular features of the dynamics. We have investigated the effect of the initial incident energy, of the inclusion of the internal degrees of freedom, of the initial incident kinetic energy and of the gas-surface interaction strength. The incorporation of internal degrees of freedom enhanced the collisional energy transfer. These calculations also point to the importance of simple kinematics as it predicts the increase of the ratio of energy transferred with increased initial incident energy of the gas particle.

  3. Radiative energy transfer in molecular gases

    NASA Technical Reports Server (NTRS)

    Tiwari, Surendra N.

    1992-01-01

    Basic formulations, analyses, and numerical procedures are presented to study radiative interactions in gray as well as nongray gases under different physical and flow conditions. After preliminary fluid-dynamical considerations, essential governing equations for radiative transport are presented that are applicable under local and nonlocal thermodynamic equilibrium conditions. Auxiliary relations for relaxation times and spectral absorption models are also provided. For specific applications, several simple gaseous systems are analyzed. The first system considered consists of a gas bounded by two parallel plates having the same temperature. Within the gas there is a uniform heat source per unit volume. For this system, both vibrational nonequilibrium effects and radiation conduction interactions are studied. The second system consists of fully developed laminar flow and heat transfer in a parallel plate duct under the boundary condition of a uniform surface heat flux. For this system, effects of gray surface emittance are studied. With the single exception of a circular geometry, the third system is considered identical to the second system. Here, the influence of nongray walls is also studied.

  4. Tech Transfer Webinar: Energy Absorbing Materials

    SciTech Connect

    Duoss, Eric

    2014-06-17

    A new material has been designed and manufactured at LLNL that can absorb mechanical energy--a cushion--while also providing protection against sheering. This ordered cellular material is 3D printed using direct ink writing techniques under development at LLNL. It is expected to find utility in application spaces that currently use unordered foams, such as sporting and consumer goods as well as defense and aerospace.

  5. Tech Transfer Webinar: Energy Absorbing Materials

    ScienceCinema

    Duoss, Eric

    2016-07-12

    A new material has been designed and manufactured at LLNL that can absorb mechanical energy--a cushion--while also providing protection against sheering. This ordered cellular material is 3D printed using direct ink writing techniques under development at LLNL. It is expected to find utility in application spaces that currently use unordered foams, such as sporting and consumer goods as well as defense and aerospace.

  6. Excitation energy transfer in a classical analogue of photosynthetic antennae.

    PubMed

    Mančal, Tomáš

    2013-09-26

    We formulate a classical pure dephasing system-bath interaction model in a full correspondence to the well-studied quantum model of natural light-harvesting antennae. The equations of motion of our classical model not only represent the correct classical analogy to the quantum description of excitonic systems, but they also have exactly the same functional form. We demonstrate derivation of classical dissipation and relaxation tensor in second order perturbation theory. We find that the only difference between the classical and quantum descriptions is in the interpretation of the state and in certain limitations imposed on the parameters of the model by classical physics. The effects of delocalization, transfer pathway interference, and the transition from coherent to diffusive transfer can be found already in the classical realm. The only qualitatively new effect occurring in quantum systems is the preference for a downhill energy transfer and the resulting possibility of trapping the energy in the lowest energy state.

  7. Forster energy transfer in chlorosomes of green photosynthetic bacteria

    NASA Technical Reports Server (NTRS)

    Causgrove, T. P.; Brune, D. C.; Blankenship, R. E.

    1992-01-01

    Energy transfer properties of whole cells and chlorosome antenna complexes isolated from the green sulfur bacteria Chlorobium limicola (containing bacteriochlorophyll c), Chlorobium vibrioforme (containing bacteriochlorophyll d) and Pelodictyon phaeoclathratiforme (containing bacteriochlorophyll e) were measured. The spectral overlap of the major chlorosome pigment (bacteriochlorophyll c, d or, e) with the bacteriochlorophyll a B795 chlorosome baseplate pigment is greatest for bacteriochlorophyll c and smallest for bacteriochlorophyll e. The absorbance and fluorescence spectra of isolated chlorosomes were measured, fitted to gaussian curves and the overlap factors with B795 calculated. Energy transfer times from the bacteriochlorophyll c, d or e to B795 were measured in whole cells and the results interpreted in terms of the Forster theory of energy transfer.

  8. A new energy transfer model for turbulent free shear flow

    NASA Technical Reports Server (NTRS)

    Liou, William W.-W.

    1992-01-01

    A new model for the energy transfer mechanism in the large-scale turbulent kinetic energy equation is proposed. An estimate of the characteristic length scale of the energy containing large structures is obtained from the wavelength associated with the structures predicted by a weakly nonlinear analysis for turbulent free shear flows. With the inclusion of the proposed energy transfer model, the weakly nonlinear wave models for the turbulent large-scale structures are self-contained and are likely to be independent flow geometries. The model is tested against a plane mixing layer. Reasonably good agreement is achieved. Finally, it is shown by using the Liapunov function method, the balance between the production and the drainage of the kinetic energy of the turbulent large-scale structures is asymptotically stable as their amplitude saturates. The saturation of the wave amplitude provides an alternative indicator for flow self-similarity.

  9. Method and apparatus for transferring energy and mass

    SciTech Connect

    Rockenfeller, U.

    1989-10-24

    This patent describes method of transferring and recovering energy. It comprises forming a slurry of a liquid selected from the group consisting of long chain alcohols, ethers, glycols, glycol ethers, sebecates, phthalates, aldehydes and ketones and a solid sorbate which does not dissolve in the liquid and is capable of forming a solid/gas compound with a gaseous refrigerant, mixing the gaseous refrigerant with the slurry whereby the gas forms a solid/gas compound with the solid sorbate, and exposing the slurry mixture to a heat exchange surface whereby the energy from the formation of the solid/gas compound is transferred to the heat exchange surface.

  10. Spectrum and energy transfer in steady Burgers turbulence

    NASA Technical Reports Server (NTRS)

    Girimaji, Sharath S.; Zhou, YE

    1995-01-01

    The spectrum, energy transfer, and spectral interactions in steady Burgers turbulence are studied using numerically generated data. The velocity field is initially random and the turbulence is maintained steady by forcing the amplitude of a band of low wavenumbers to be invariant in time, while permitting the phase to change as dictated by the equation. The spectrum, as expected, is very different from that of Navier-Stokes turbulence. It is demonstrated that the far range of the spectrum scales as predicted by Burgers. Despite the difference in their spectra, in matters of the spectral energy transfer and triadic interactions Burgers turbulence is similar to Navier-Stokes turbulence.

  11. Classical model for energy transfer in microspherical droplets

    NASA Astrophysics Data System (ADS)

    Pineda, Andrew C.; Ronis, David

    1995-11-01

    A classical electrodynamic model for energy transfer between donor and acceptor molecules in which the molecules are modeled using Drude oscillators is presented for dye solutions in the form of micrometer-sized droplets. The model incorporates multiparticle scattering effects by means of a binary collision expansion. Enhanced energy transfer rates and nontrivial concentration effects appear due to the Mie resonances of the droplet. Theory is discussed in light of the experiments of L. M. Folan, S. Arnold, and S. D. Druger [Chem. Phys. Lett. 118, 322 (1985)].

  12. Efficiency of pulse high-current generator energy transfer into plasma liner energy

    NASA Astrophysics Data System (ADS)

    Oreshkin, V. I.

    2013-08-01

    The efficiency of capacitor-bank energy transfer from a high-current pulse generator into kinetic energy of a plasma liner has been analyzed. The analysis was performed using a model including the circuit equations and equations of the cylindrical shell motion. High efficiency of the energy transfer into kinetic energy of the liner is shown to be achieved only by a low-inductance generator. We considered an "ideal" liner load in which the load current is close to zero in the final of the shell compression. This load provides a high (up to 80%) efficiency of energy transfer and higher stability when compressing the liner.

  13. Spectral Gap Energy Transfer in Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  14. Technology transfer for the US Department of Energy's Energy Storage Program: Volume 1, Recommendations

    SciTech Connect

    Bruneau, C.L.; Fassbender, L.L.

    1988-10-01

    Technologies developed by the US Department of Energy's (DOE) Energy Storage (STOR) Program must be converted into products, processes, or services that benefit the private sector. The process of technology transfer is the primary means of accomplishing this. The purpose of this report is to examine the technology transfer activities of the STOR Program and suggest mechanisms that might make the transfer of technologies from national laboratories and universities to the private sector more effective. A brief summary of recommendations that would improve the effectiveness of the transfer of energy storage technologies from the national laboratories to the private sector is discussed. 33 refs., 2 figs.

  15. Interacting scales and energy transfer in isotropic turbulence

    NASA Technical Reports Server (NTRS)

    Zhou, YE

    1993-01-01

    The dependence of the energy transfer process on the disparity of the interacting scales is investigated in the inertial and far-dissipation ranges of isotropic turbulence. The strategy for generating the simulated flow fields and the choice of a disparity parameter to characterize the scaling of the interactions is discussed. The inertial range is found to be dominated by relatively local interactions, in agreement with the Kolmogorov assumption. The far-dissipation is found to be dominated by relatively non-local interactions, supporting the classical notion that the far-dissipation range is slaved to the Kolmogorov scales. The measured energy transfer is compared with the classical models of Heisenberg, Obukhov, and the more detailed analysis of Tennekes and Lumley. The energy transfer statistics measured in the numerically simulated flows are found to be nearly self-similar for wave numbers in the inertial range. Using the self-similar form measured within the limited scale range of the simulation, an 'ideal' energy transfer function and the corresponding energy flux rate for an inertial range of infinite extent are constructed. From this flux rate, the Kolmogorov constant is calculated to be 1.5, in excellent agreement with experiments.

  16. Optimal Energy Transfer in Light-Harvesting Systems.

    PubMed

    Chen, Lipeng; Shenai, Prathamesh; Zheng, Fulu; Somoza, Alejandro; Zhao, Yang

    2015-08-20

    Photosynthesis is one of the most essential biological processes in which specialized pigment-protein complexes absorb solar photons, and with a remarkably high efficiency, guide the photo-induced excitation energy toward the reaction center to subsequently trigger its conversion to chemical energy. In this work, we review the principles of optimal energy transfer in various natural and artificial light harvesting systems. We begin by presenting the guiding principles for optimizing the energy transfer efficiency in systems connected to dissipative environments, with particular attention paid to the potential role of quantum coherence in light harvesting systems. We will comment briefly on photo-protective mechanisms in natural systems that ensure optimal functionality under varying ambient conditions. For completeness, we will also present an overview of the charge separation and electron transfer pathways in reaction centers. Finally, recent theoretical and experimental progress on excitation energy transfer, charge separation, and charge transport in artificial light harvesting systems is delineated, with organic solar cells taken as prime examples.

  17. Optimal Energy Transfer in Light-Harvesting Systems.

    PubMed

    Chen, Lipeng; Shenai, Prathamesh; Zheng, Fulu; Somoza, Alejandro; Zhao, Yang

    2015-01-01

    Photosynthesis is one of the most essential biological processes in which specialized pigment-protein complexes absorb solar photons, and with a remarkably high efficiency, guide the photo-induced excitation energy toward the reaction center to subsequently trigger its conversion to chemical energy. In this work, we review the principles of optimal energy transfer in various natural and artificial light harvesting systems. We begin by presenting the guiding principles for optimizing the energy transfer efficiency in systems connected to dissipative environments, with particular attention paid to the potential role of quantum coherence in light harvesting systems. We will comment briefly on photo-protective mechanisms in natural systems that ensure optimal functionality under varying ambient conditions. For completeness, we will also present an overview of the charge separation and electron transfer pathways in reaction centers. Finally, recent theoretical and experimental progress on excitation energy transfer, charge separation, and charge transport in artificial light harvesting systems is delineated, with organic solar cells taken as prime examples. PMID:26307957

  18. Technology transfer for the US Department of Energy's Energy Storage Program: Volume 2, Appendices

    SciTech Connect

    Bruneau, C.L.; Fassbender, L.L.

    1988-10-01

    This document contains the appendices to Technology Transfer Recommendations for the US Department of Energy's Storage Program (PNL-6484, Vol. 1). These appendices are a list of projects, publications, and presentations connected with the Energy Storage (STOR) program. In Volume 1, the technology transfer activities of the STOR program are examined and mechanisms for increasing the effectiveness of those activities are recommended.

  19. Förster Resonance Energy Transfer imaging in vivo with approximated Radiative Transfer Equation

    PubMed Central

    Soloviev, Vadim Y.; McGinty, James; Stuckey, Daniel W.; Laine, Romain; Wylezinska-Arridge, Marzena; Wells, Dominic J.; Sardini, Alessandro; Hajnal, Joseph V.; French, Paul M.W.; Arridge, Simon R.

    2012-01-01

    We describe a new light transport model that we have applied to 3-D image reconstruction of in vivo fluorescence lifetime tomography data applied to read out Förster Resonance Energy Transfer in mice. The model is an approximation to the Radiative Transfer Equation and combines light diffusion and rays optics. This approximation is well adopted to wide-field time-gated intensity based data acquisition. Reconstructed image data are presented and compared with results obtained by using the Telegraph Equation approximation. The new approach provides improved recovery of absorption and scattering parameters while returning similar values for the fluorescence parameters. PMID:22193187

  20. Photoexcited energy transfer in a weakly coupled dimer

    DOE PAGESBeta

    Hernandez, Laura Alfonso; Nelson, Tammie; Tretiak, Sergei; Fernandez-Alberti, Sebastian

    2015-01-08

    Nonadiabatic excited-state molecular dynamics (NA-ESMD) simulations have been performed in order to study the time-dependent exciton localization during energy transfer between two chromophore units of the weakly coupled anthracene dimer dithia-anthracenophane (DTA). Simulations are done at both low temperature (10 K) and room temperature (300 K). The initial photoexcitation creates an exciton which is primarily localized on a single monomer unit. Subsequently, the exciton experiences an ultrafast energy transfer becoming localized on either one monomer unit or the other, whereas delocalization between both monomers never occurs. In half of the trajectories, the electronic transition density becomes completely localized on themore » same monomer as the initial excitation, while in the other half, it becomes completely localized on the opposite monomer. In this article, we present an analysis of the energy transfer dynamics and the effect of thermally induced geometry distortions on the exciton localization. Finally, simulated fluorescence anisotropy decay curves for both DTA and the monomer unit dimethyl anthracene (DMA) are compared. As a result, our analysis reveals that changes in the transition density localization caused by energy transfer between two monomers in DTA is not the only source of depolarization and exciton relaxation within a single DTA monomer unit can also cause reorientation of the transition dipole.« less

  1. Photoexcited energy transfer in a weakly coupled dimer

    SciTech Connect

    Hernandez, Laura Alfonso; Nelson, Tammie; Tretiak, Sergei; Fernandez-Alberti, Sebastian

    2015-01-08

    Nonadiabatic excited-state molecular dynamics (NA-ESMD) simulations have been performed in order to study the time-dependent exciton localization during energy transfer between two chromophore units of the weakly coupled anthracene dimer dithia-anthracenophane (DTA). Simulations are done at both low temperature (10 K) and room temperature (300 K). The initial photoexcitation creates an exciton which is primarily localized on a single monomer unit. Subsequently, the exciton experiences an ultrafast energy transfer becoming localized on either one monomer unit or the other, whereas delocalization between both monomers never occurs. In half of the trajectories, the electronic transition density becomes completely localized on the same monomer as the initial excitation, while in the other half, it becomes completely localized on the opposite monomer. In this article, we present an analysis of the energy transfer dynamics and the effect of thermally induced geometry distortions on the exciton localization. Finally, simulated fluorescence anisotropy decay curves for both DTA and the monomer unit dimethyl anthracene (DMA) are compared. As a result, our analysis reveals that changes in the transition density localization caused by energy transfer between two monomers in DTA is not the only source of depolarization and exciton relaxation within a single DTA monomer unit can also cause reorientation of the transition dipole.

  2. Photoexcited Energy Transfer in a Weakly Coupled Dimer.

    PubMed

    Alfonso Hernandez, Laura; Nelson, Tammie; Tretiak, Sergei; Fernandez-Alberti, Sebastian

    2015-06-18

    Nonadiabatic excited-state molecular dynamics (NA-ESMD) simulations have been performed in order to study the time-dependent exciton localization during energy transfer between two chromophore units of the weakly coupled anthracene dimer dithia-anthracenophane (DTA). Simulations are done at both low temperature (10 K) and room temperature (300 K). The initial photoexcitation creates an exciton which is primarily localized on a single monomer unit. Subsequently, the exciton experiences an ultrafast energy transfer becoming localized on either one monomer unit or the other, whereas delocalization between both monomers never occurs. In half of the trajectories, the electronic transition density becomes completely localized on the same monomer as the initial excitation, while in the other half, it becomes completely localized on the opposite monomer. In this article, we present an analysis of the energy transfer dynamics and the effect of thermally induced geometry distortions on the exciton localization. Finally, simulated fluorescence anisotropy decay curves for both DTA and the monomer unit dimethyl anthracene (DMA) are compared. Our analysis reveals that changes in the transition density localization caused by energy transfer between two monomers in DTA is not the only source of depolarization and exciton relaxation within a single DTA monomer unit can also cause reorientation of the transition dipole. PMID:25523832

  3. Plasmon resonance energy transfer and plexcitonic solar cell.

    PubMed

    Nan, Fan; Ding, Si-Jing; Ma, Liang; Cheng, Zi-Qiang; Zhong, Yu-Ting; Zhang, Ya-Fang; Qiu, Yun-Hang; Li, Xiaoguang; Zhou, Li; Wang, Qu-Quan

    2016-08-11

    Plasmon-mediated energy transfer is highly desirable in photo-electronic nanodevices, but the direct injection efficiency of "hot electrons" in plasmonic photo-detectors and plasmon-sensitized solar cells (plasmon-SSCs) is poor. On another front, Fano resonance induced by strong plasmon-exciton coupling provides an efficient channel of coherent energy transfer from metallic plasmons to molecular excitons, and organic dye molecules have a much better injection efficiency in exciton-SSCs than "hot electrons". Here, we investigate enhanced light-harvesting of chlorophyll-a molecules strongly coupled to Au nanostructured films via Fano resonance. The enhanced local field and plasmon resonance energy transfer are experimentally revealed by monitoring the ultrafast dynamical processes of the plexcitons and the photocurrent flows of the assembled plexciton-SSCs. By tuning the Fano factor and anti-resonance wavelengths, we find that the local field is largely enhanced and the efficiency of plexciton-SSCs consisting of ultrathin TiO2 films is significantly improved. Most strikingly, the output power of the plexciton-SSCs is much larger than the sum of those of the individual plasmon- and exciton-SSCs. Our observations provide a practical approach to monitor energy and electron transfer in plasmon-exciton hybrids at a strong coupling regime and also offer a new strategy to design photovoltaic nanodevices. PMID:27481652

  4. Resonance energy transfer in DNA duplexes labeled with localized dyes.

    PubMed

    Cunningham, Paul D; Khachatrian, Ani; Buckhout-White, Susan; Deschamps, Jeffrey R; Goldman, Ellen R; Medintz, Igor L; Melinger, Joseph S

    2014-12-18

    The growing maturity of DNA-based architectures has raised considerable interest in applying them to create photoactive light harvesting and sensing devices. Toward optimizing efficiency in such structures, resonant energy transfer was systematically examined in a series of dye-labeled DNA duplexes where donor-acceptor separation was incrementally changed from 0 to 16 base pairs. Cyanine dyes were localized on the DNA using double phosphoramidite attachment chemistry. Steady state spectroscopy, single-pair fluorescence, time-resolved fluorescence, and ultrafast two-color pump-probe methods were utilized to examine the energy transfer processes. Energy transfer rates were found to be more sensitive to the distance between the Cy3 donor and Cy5 acceptor dye molecules than efficiency measurements. Picosecond energy transfer and near-unity efficiencies were observed for the closest separations. Comparison between our measurements and the predictions of Förster theory based on structural modeling of the dye-labeled DNA duplex suggest that the double phosphoramidite linkage leads to a distribution of intercalated and nonintercalated dye orientations. Deviations from the predictions of Förster theory point to a failure of the point dipole approximation for separations of less than 10 base pairs. Interactions between the dyes that alter their optical properties and violate the weak-coupling assumption of Förster theory were observed for separations of less than four base pairs, suggesting the removal of nucleobases causes DNA deformation and leads to enhanced dye-dye interaction. PMID:25397906

  5. Plasmon resonance energy transfer and plexcitonic solar cell.

    PubMed

    Nan, Fan; Ding, Si-Jing; Ma, Liang; Cheng, Zi-Qiang; Zhong, Yu-Ting; Zhang, Ya-Fang; Qiu, Yun-Hang; Li, Xiaoguang; Zhou, Li; Wang, Qu-Quan

    2016-08-11

    Plasmon-mediated energy transfer is highly desirable in photo-electronic nanodevices, but the direct injection efficiency of "hot electrons" in plasmonic photo-detectors and plasmon-sensitized solar cells (plasmon-SSCs) is poor. On another front, Fano resonance induced by strong plasmon-exciton coupling provides an efficient channel of coherent energy transfer from metallic plasmons to molecular excitons, and organic dye molecules have a much better injection efficiency in exciton-SSCs than "hot electrons". Here, we investigate enhanced light-harvesting of chlorophyll-a molecules strongly coupled to Au nanostructured films via Fano resonance. The enhanced local field and plasmon resonance energy transfer are experimentally revealed by monitoring the ultrafast dynamical processes of the plexcitons and the photocurrent flows of the assembled plexciton-SSCs. By tuning the Fano factor and anti-resonance wavelengths, we find that the local field is largely enhanced and the efficiency of plexciton-SSCs consisting of ultrathin TiO2 films is significantly improved. Most strikingly, the output power of the plexciton-SSCs is much larger than the sum of those of the individual plasmon- and exciton-SSCs. Our observations provide a practical approach to monitor energy and electron transfer in plasmon-exciton hybrids at a strong coupling regime and also offer a new strategy to design photovoltaic nanodevices.

  6. An estimate of spherical impactor energy transfer for mechanical frequency up-conversion energy harvester

    NASA Astrophysics Data System (ADS)

    Corr, L. R.; Ma, D. T.

    2016-08-01

    Vibration energy harvesters, which use the impact mechanical frequency up-conversion technique, utilize an impactor, which gains kinetic energy from low frequency ambient environmental vibrations, to excite high frequency systems that efficiently convert mechanical energy to electrical energy. To take full advantage of the impact mechanical frequency up-conversion technique, it is prudent to understand the energy transfer from the low frequency excitations, to the impactor, and finally to the high frequency systems. In this work, the energy transfer from a spherical impactor to a multi degree of freedom spring / mass system, due to Hertzian impact, is investigated to gain insight on how best to design impact mechanical frequency up-conversion energy harvesters. Through this academic work, it is shown that the properties of the contact (or impact) area, i.e., radius of curvature and material properties, only play a minor role in energy transfer and that the equivalent mass of the target system (i.e., the spring / mass system) dictates the total amount of energy transferred during the impact. The novel approach of utilizing the well-known Hertzian impact methodology to gain an understanding of impact mechanical frequency up-conversion energy harvesters has made it clear that the impactor and the high frequency energy generating systems must be designed together as one system to ensure maximum energy transfer, leading to efficient ambient vibration energy harvesters.

  7. Light increases energy transfer efficiency in a boreal stream.

    PubMed

    Lesutienė, Jūratė; Gorokhova, Elena; Stankevičienė, Daiva; Bergman, Eva; Greenberg, Larry

    2014-01-01

    Periphyton communities of a boreal stream were exposed to different light and nutrient levels to estimate energy transfer efficiency from primary to secondary producers using labeling with inorganic (13)C. In a one-day field experiment, periphyton grown in fast-flow conditions and dominated by opportunistic green algae were exposed to light levels corresponding to sub-saturating (forest shade) and saturating (open stream section) irradiances, and to N and P nutrient additions. In a two-week laboratory experiment, periphyton grown in low-flow conditions and dominated by slowly growing diatoms were incubated under two sub-saturating light and nutrient enrichment levels as well as grazed and non-grazed conditions. Light had significant positive effect on (13)C uptake by periphyton. In the field experiment, P addition had a positive effect on (13)C uptake but only at sub-saturating light levels, whereas in the laboratory experiment nutrient additions had no effect on the periphyton biomass, (13)C uptake, biovolume and community composition. In the laboratory experiment, the grazer (caddisfly) effect on periphyton biomass specific (13)C uptake and nutrient content was much stronger than the effects of light and nutrients. In particular, grazers significantly reduced periphyton biomass and increased biomass specific (13)C uptake and C:nutrient ratios. The energy transfer efficiency, estimated as a ratio between (13)C uptake by caddisfly and periphyton, was positively affected by light conditions, whereas the nutrient effect was not significant. We suggest that the observed effects on energy transfer were related to the increased diet contribution of highly palatable green algae, stimulated by higher light levels. Also, high heterotrophic microbial activity under low light levels would facilitate energy loss through respiration and decrease overall trophic transfer efficiency. These findings suggest that even a small increase in light intensity could result in community

  8. 2013 MOLECULAR ENERGY TRANSFER GORDON RESEARCH CONFERENCE (JANUARY 13-18, 2013 - VENTURA BEACH MARRIOTT, VENTURA CA

    SciTech Connect

    Reid, Scott A.

    2012-10-18

    Sessions covered all areas of molecular energy transfer, with 10 sessions of talks and poster sessions covering the areas of :  Energy Transfer in Inelastic and Reactive Scattering  Energy Transfer in Photoinitiated and Unimolecular Reactions  Non-adiabatic Effects in Energy TransferEnergy Transfer at Surfaces and Interfaces  Energy Transfer in Clusters, Droplets, and Aerosols  Energy Transfer in Solution and Solid  Energy Transfer in Complex Systems  Energy Transfer: New vistas and horizons  Molecular Energy Transfer: Where Have We Been and Where are We Going?

  9. Electro-mechanical energy conversion system having a permanent magnet machine with stator, resonant transfer link and energy converter controls

    DOEpatents

    Skeist, S. Merrill; Baker, Richard H.

    2006-01-10

    An electro-mechanical energy conversion system coupled between an energy source and an energy load comprising an energy converter device including a permanent magnet induction machine coupled between the energy source and the energy load to convert the energy from the energy source and to transfer the converted energy to the energy load and an energy transfer multiplexer to control the flow of power or energy through the permanent magnetic induction machine.

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  11. Triplet-Triplet Energy Transfer Study in Hydrogen Bonding Systems.

    PubMed

    Wang, Zhijia; Zhao, Jianzhang; Guo, Song

    2015-01-01

    The 2,6-diiodoBodipy-styrylBodipy hydrogen bonding system was prepared to study the effect of hydrogen bonding on the triplet-triplet-energy-transfer (TTET) process. 2,6-DiiodoBodipy linked with N-acetyl-2,6-diaminopyridine (D-2) was used as the triplet energy donor, and the styrylBodipy connected with thymine (A-1) was used as triplet energy acceptor, thus the TTET process was established upon photoexcitation. The photophysical processes of the hydrogen bonding system were studied with steady-state UV-vis absorption spectroscopy, fluorescence spectroscopy, fluorescence lifetime measurement and nanosecond time-resolved transient absorption spectroscopies. The TTET of the intramolecular/hydrogen bonding/intermolecular systems were compared through nanosecond transient absorption spectroscopy. The TTET process of the hydrogen bonding system is faster and more efficient (kTTET = 6.9 × 10(4) s(-1), ΦTTET = 94.0%) than intermolecular triplet energy transfer (kTTET = 6.0 × 10(4) s(-1), ΦTTET = 90.9%), but slower and less efficient than intramolecular triplet energy transfer (kTTET > 10(8) s(-1)). These results are valuable for designing self-assembly triplet photosensitizers and for the study of the TTET process of hydrogen bonding systems.

  12. The Role of Resonant Vibrations in Electronic Energy Transfer

    PubMed Central

    Somsen, Oscar J. G.; Novoderezhkin, Vladimir I.; Mančal, Tomáš; van Grondelle, Rienk

    2016-01-01

    Abstract Nuclear vibrations play a prominent role in the spectroscopy and dynamics of electronic systems. As recent experimental and theoretical studies suggest, this may be even more so when vibrational frequencies are resonant with transitions between the electronic states. Herein, a vibronic multilevel Redfield model is reported for excitonically coupled electronic two‐level systems with a few explicitly included vibrational modes and interacting with a phonon bath. With numerical simulations the effects of the quantized vibrations on the dynamics of energy transfer and coherence in a model dimer are illustrated. The resonance between the vibrational frequency and energy gap between the sites leads to a large delocalization of vibronic states, which then results in faster energy transfer and longer‐lived mixed coherences. PMID:26910485

  13. Long range energy transfer in graphene hybrid structures

    NASA Astrophysics Data System (ADS)

    Gonçalves, Hugo; Bernardo, César; Moura, Cacilda; Ferreira, R. A. S.; André, P. S.; Stauber, Tobias; Belsley, Michael; Schellenberg, Peter

    2016-08-01

    In this work we quantify the distance dependence for the extraction of energy from excited chromophores by a single layer graphene flake over a large separation range. To this end hybrid structures were prepared, consisting of a thin (2 nm) layer of a polymer matrix doped with a well chosen strongly fluorescent organic molecule, followed by an un-doped spacer layer of well-defined thicknesses made of the same polymer material and an underlying single layer of pristine, undoped graphene. The coupling strength is assessed through the variation of the fluorescence decay kinetics as a function of distance between the graphene and the excited chromophore molecules. Non-radiative energy transfer to the graphene was observed at distances of up to 60 nm a range much greater than typical energy transfer distances observed in molecular systems.

  14. Analysis of medium-energy transfers to the Moon

    NASA Astrophysics Data System (ADS)

    Oshima, Kenta; Topputo, Francesco; Campagnola, Stefano; Yanao, Tomohiro

    2016-09-01

    This study analyzes a recently discovered class of exterior transfers to the Moon. These transfers terminate in retrograde ballistic capture orbits, i.e., orbits with negative Keplerian energy and angular momentum with respect to the Moon. Yet, their Jacobi constant is relatively low, for which no forbidden regions exist, and the trajectories do not appear to mimic the dynamics of the invariant manifolds of the Lagrange points. This paper shows that these orbits shadow instead lunar collision orbits. We investigate the dynamics of singular, lunar collision orbits in the Earth-Moon planar circular restricted three-body problem, and reveal their rich phase space structure in the medium-energy regime, where invariant manifolds of the Lagrange point orbits break up. We show that lunar retrograde ballistic capture trajectories lie inside the tube structure of collision orbits. We also develop a method to compute medium-energy transfers by patching together orbits inside the collision tube and those whose apogees are located in the appropriate quadrant in the Sun-Earth system. The method yields the novel family of transfers as well as those ending in direct capture orbits, under particular energetic and geometrical conditions.

  15. Rates of mass, momentum, and energy transfer at the magnetopause

    NASA Technical Reports Server (NTRS)

    Hill, T. W.

    1979-01-01

    Empirical estimates of the global rates of transfer of solar wind mass, tangential momentum, and energy at the Earth's magnetopause are presented for comparison against model estimates based on the four principal mechanisms that have been proposed to explain such transfer. The comparisons, although not quite conclusive, strongly favor a model that incorporates some combination of direct magnetic connection and anomalous cross field diffusion. An additional global constraint, the rate at which magnetic flux is cycled through the magnetospheric convection system, strongly suggests that direct magnetic connection plays a significant if not dominant role in the solar wind/magnetosphere interaction.

  16. DNA chips with conjugated polyelectrolytes in resonance energy transfer mode.

    PubMed

    Wigenius, Jens A; Magnusson, Karin; Björk, Per; Andersson, Olof; Inganäs, Olle

    2010-03-01

    We show how to use well-defined conjugated polyelectrolytes (CPEs) combined with surface energy patterning to fabricate DNA chips utilizing fluorescence signal amplification. Cholesterol-modified DNA strands in complex with a CPE are adsorbed to a surface energy pattern, formed by printing with soft elastomer stamps. Hybridization of the surface bound DNA strands with a short complementary strand from solution is monitored using both fluorescence microscopy and imaging surface plasmon resonance. The CPEs act as antennas, enhancing resonance energy transfer to the dye-labeled DNA when complementary hybridization of the double strand occurs.

  17. Coherent or hopping like energy transfer in the chlorosome ?

    SciTech Connect

    Nalbach, Peter

    2014-08-20

    Chlorosomes, as part of the light-harvesting system of green bacteria, are the largest and most efficient antennae systems in nature. We have studied energy transfer dynamics in the chlorosome in a simplified toy model employing a master equation. Dephasing and relaxation due to environmental fluctuations are included by Lindblad dephasing and Redfield thermalization rates. We find at room temperature three separate time scales, i.e. 25 fs, 250 fs and 2.5 ps and determine the according energy pathways through the hierarchical structure in the chlorosome. Quantum coherence lives up to 150 fs at which time the energy is spread over roughly 12 pigments in our model.

  18. K/S Lambert problem. [energy requirements for transfer orbits

    NASA Technical Reports Server (NTRS)

    Jezewski, D. J.

    1975-01-01

    The Lambert problem in orbital mechanics is formulated in Kustaanheimo/Stiefel variables. The problem is to determine the required energy and the value of the generalized eccentric anomaly such that a particle at the initial position vector will transfer to the final position vector in a physical time interval. The fictitious time solution results in two nonlinear equations in the two unknowns, energy and fictitious time. The generalized eccentric anomaly solution, however, results in only one nonlinear equation in the one unknown, the eccentric anomaly. This simplification is possible because the energy equation is separable in the eccentric anomaly formulation.

  19. Molding resonant energy transfer by colloidal crystal: Dexter transfer and electroluminescence

    NASA Astrophysics Data System (ADS)

    González-Urbina, Luis; Kolaric, Branko; Libaers, Wim; Clays, Koen

    2010-05-01

    Building photonic crystals by combination of colloidal ordering and metal sputtering we were able to construct a system sensitive to an electrical field. In corresponding crystals we embedded the Dexter pair (Ir(ppy3) and BAlq) and investigated the influence of the band gap on the resonant energy transfer when the system is excited by light and by an electric field respectively. Our investigations extend applications of photonic crystals into the field of electroluminescence and LED technologies.

  20. Energy Transfer in the Earth-Sun System

    NASA Astrophysics Data System (ADS)

    Lui, A. T. Y.; Kamide, Y.

    2007-02-01

    Conference on Earth-Sun System Exploration: Energy Transfer; Kailua-Kona, Hawaii, USA, 16-20 January 2006; The goal of this conference, which was supported by several agencies and organizations, was to provide a forum for physicists engaged in the Earth-Sun system as well as in laboratory experiments to discuss and exchange knowledge and ideas on physical processes involving energy transfer. The motivation of the conference stemmed from the following realization: Space assets form an important fabric of our society, performing functions such as television broadcasting, cell- phone communication, navigation, and remote monitoring of tropospheric weather. There is increasing awareness of how much our daily activities can be adversely affected by space disturbances stretching all the way back to the Sun. In some of these energetic phenomena, energy in various forms can propagate long distances from the solar surface to the interplanetary medium and eventually to the Earth's immediate space environment, namely, its magnetosphere, ionosphere, and thermosphere. In addition, transformation of energy can take place in these space disturbances, allowing charged-particle energy to be transformed to electromagnetic energy or vice versa. In- depth understanding of energy transformation and transmission in the Earth-Sun system will foster the identification of physical processes responsible for space disturbances and the prediction of their occurrences and effects. Participants came from 15 countries.

  1. Regulation control and energy management scheme for wireless power transfer

    SciTech Connect

    Miller, John M.

    2015-12-29

    Power transfer rate at a charging facility can be maximized by employing a feedback scheme. The state of charge (SOC) and temperature of the regenerative energy storage system (RESS) pack of a vehicle is monitored to determine the load due to the RESS pack. An optimal frequency that cancels the imaginary component of the input impedance for the output signal from a grid converter is calculated from the load of the RESS pack, and a frequency offset f* is made to the nominal frequency f.sub.0 of the grid converter output based on the resonance frequency of a magnetically coupled circuit. The optimal frequency can maximize the efficiency of the power transfer. Further, an optimal grid converter duty ratio d* can be derived from the charge rate of the RESS pack. The grid converter duty ratio d* regulates wireless power transfer (WPT) power level.

  2. Reduced density matrix hybrid approach: application to electronic energy transfer.

    PubMed

    Berkelbach, Timothy C; Markland, Thomas E; Reichman, David R

    2012-02-28

    Electronic energy transfer in the condensed phase, such as that occurring in photosynthetic complexes, frequently occurs in regimes where the energy scales of the system and environment are similar. This situation provides a challenge to theoretical investigation since most approaches are accurate only when a certain energetic parameter is small compared to others in the problem. Here we show that in these difficult regimes, the Ehrenfest approach provides a good starting point for a dynamical description of the energy transfer process due to its ability to accurately treat coupling to slow environmental modes. To further improve on the accuracy of the Ehrenfest approach, we use our reduced density matrix hybrid framework to treat the faster environmental modes quantum mechanically, at the level of a perturbative master equation. This combined approach is shown to provide an efficient and quantitative description of electronic energy transfer in a model dimer and the Fenna-Matthews-Olson complex and is used to investigate the effect of environmental preparation on the resulting dynamics.

  3. Structure and energy transfer in photosystems of oxygenic photosynthesis.

    PubMed

    Nelson, Nathan; Junge, Wolfgang

    2015-01-01

    Oxygenic photosynthesis is the principal converter of sunlight into chemical energy on Earth. Cyanobacteria and plants provide the oxygen, food, fuel, fibers, and platform chemicals for life on Earth. The conversion of solar energy into chemical energy is catalyzed by two multisubunit membrane protein complexes, photosystem I (PSI) and photosystem II (PSII). Light is absorbed by the pigment cofactors, and excitation energy is transferred among the antennae pigments and converted into chemical energy at very high efficiency. Oxygenic photosynthesis has existed for more than three billion years, during which its molecular machinery was perfected to minimize wasteful reactions. Light excitation transfer and singlet trapping won over fluorescence, radiation-less decay, and triplet formation. Photosynthetic reaction centers operate in organisms ranging from bacteria to higher plants. They are all evolutionarily linked. The crystal structure determination of photosynthetic protein complexes sheds light on the various partial reactions and explains how they are protected against wasteful pathways and why their function is robust. This review discusses the efficiency of photosynthetic solar energy conversion.

  4. Modelling excitonic-energy transfer in light-harvesting complexes

    SciTech Connect

    Kramer, Tobias; Kreisbeck, Christoph

    2014-01-08

    The theoretical and experimental study of energy transfer in photosynthesis has revealed an interesting transport regime, which lies at the borderline between classical transport dynamics and quantum-mechanical interference effects. Dissipation is caused by the coupling of electronic degrees of freedom to vibrational modes and leads to a directional energy transfer from the antenna complex to the target reaction-center. The dissipative driving is robust and does not rely on fine-tuning of specific vibrational modes. For the parameter regime encountered in the biological systems new theoretical tools are required to directly compare theoretical results with experimental spectroscopy data. The calculations require to utilize massively parallel graphics processor units (GPUs) for efficient and exact computations.

  5. Energy transfer processes in solar energy conversion. Final report

    SciTech Connect

    Fayer, M.D.

    1984-01-01

    The following were studied experimentally and/or theoretically: dynamics of energy transport and trapping in two-component systems (using rhodamine 6G and malachite green as traps), electronic excited state transport among molecules randomly distributed in a finite volume, electronic excitation transport in polymer systems, and excitation transport in synthetic Zn-chlorophyllide substituted hemoglobin. (DLC)

  6. Detection of programmed cell death using fluorescence energy transfer.

    PubMed Central

    Xu, X; Gerard, A L; Huang, B C; Anderson, D C; Payan, D G; Luo, Y

    1998-01-01

    Fluorescence energy transfer (FRET) can be generated when green fluorescent protein (GFP) and blue fluorescent protein (BFP) are covalently linked together by a short peptide. Cleavage of this linkage by protease completely eliminates FRET effect. Caspase-3 (CPP32) is an important cellular protease activated during programmed cell death. An 18 amino acid peptide containing CPP32 recognition sequence, DEVD, was used to link GFP and BFP together. CPP32 activation can be monitored by FRET assay during the apoptosis process. PMID:9518501

  7. Response of silicon-Based Linear Energy Transfer Spectrometers

    NASA Technical Reports Server (NTRS)

    Aman, A.; Bman, B.; Badhwar, G. D.; ONeill, P. M. O.

    2000-01-01

    Silicon-based linear energy transfer (LET) telescope,(e. g., DOSTEL and RRMD) have recently been flown in space. LET spectra measured using tissue equivalent proportional counters show differences that need to be fully understood. A Monte Carlo technique based on: 1. radiation transport cluster intra-cascade model. 2. Landau-Vavilov distribution, 3. telescope geometry and detector coincidence & discriminator settings, 4. spacecraft shielding geometry, and 5. the external free space radiation environment, including recent albedo measurements, was developed.

  8. Modeling coherent excitation energy transfer in photosynthetic light harvesting systems

    NASA Astrophysics Data System (ADS)

    Huo, Pengfei

    2011-12-01

    Recent non-linear spectroscopy experiments suggest the excitation energy transfer in some biological light harvesting systems initially occurs coherently. Treating such processes brings significant challenge for conventional theoretical tools that usually involve different approximations. In this dissertation, the recently developed Iterative Linearized Density Matrix (ILDM) propagation scheme, which is non-perturbative and non-Markovian is extended to study coherent excitation energy transfer in various light harvesting complexes. It is demonstrated that the ILDM approach can successfully describe the coherent beating of the site populations on model systems and gives quantitative agreement with both experimental results and the results of other theoretical methods have been developed recently to going beyond the usual approximations, thus providing a new reliable theoretical tool to study this phenomenon. This approach is used to investigate the excited energy transfer dynamics in various experimentally studied bacteria light harvesting complexes, such as Fenna-Matthews-Olsen (FMO) complex, Phycocyanin 645 (PC645). In these model calculations, quantitative agreement is found between computed de-coherence times and quantum beating pattens observed in the non-linear spectroscopy. As a result of these studies, it is concluded that the stochastic resonance behavior is important in determining the optimal throughput. To begin addressing possible mechanics for observed long de-coherence time, various models which include correlation between site energy fluctuations as well as correlation between site energy and inter-site coupling are developed. The influence of both types of correlation on the coherence and transfer rate is explored using with a two state system-bath hamiltonian parametrized to model the reaction center of Rhodobacter sphaeroides bacteria. To overcome the disadvantages of a fully reduced approach or a full propagation method, a brownian dynamics

  9. Energy release and transfer in guide field reconnection

    NASA Astrophysics Data System (ADS)

    Birn, J.; Hesse, M.

    2010-01-01

    Properties of energy release and transfer by magnetic reconnection in the presence of a guide field are investigated on the basis of 2.5-dimensional magnetohydrodynamic (MHD) and particle-in-cell (PIC) simulations. Two initial configurations are considered: a plane current sheet with a uniform guide field of 80% of the reconnecting magnetic field component and a force-free current sheet in which the magnetic field strength is constant but the field direction rotates by 180° through the current sheet. The onset of reconnection is stimulated by localized, temporally limited compression. Both MHD and PIC simulations consistently show that the outgoing energy fluxes are dominated by (redirected) Poynting flux and enthalpy flux, whereas bulk kinetic energy flux and heat flux (in the PIC simulation) are small. The Poynting flux is mainly associated with the magnetic energy of the guide field which is carried from inflow to outflow without much alteration. The conversion of annihilated magnetic energy to enthalpy flux (that is, thermal energy) stems mainly from the fact that the outflow occurs into a closed field region governed by approximate force balance between Lorentz and pressure gradient forces. Therefore, the energy converted from magnetic to kinetic energy by Lorentz force acceleration becomes immediately transferred to thermal energy by the work done by the pressure gradient force. Strong similarities between late stages of MHD and PIC simulations result from the fact that conservation of mass and entropy content and footpoint displacement of magnetic flux tubes, imposed in MHD, are also approximately satisfied in the PIC simulations.

  10. Understanding Protein Folding from Advances of Fluorescence Energy Transfer.

    NASA Astrophysics Data System (ADS)

    Tcherkasskaya, Olga; Gronenborn, Angela M.

    2001-03-01

    A multi-site fluorescence energy transfer method was developed for the study of protein folding. Technique uses "tyrosine-phenylalanine" substitution mutagenesis to place the "tyrosine-guest" into positions of interest into the protein structure. Tetranitromethane modification of the tyrosine-guest renders this amino acid an acceptor of the tryptophan fluorescence. This approach can be applied to any protein system, and, most importantly, does not require single- or double-labeling of the protein molecule by a donor and/or an acceptor fluorophore. It is equally suited for equilibrium as well as kinetic studies of folding. We tested the methodology to monitor the equilibrium (un)folding of the immunoglobulin binding domain B1 of streptococcal protein G (GB1) induced by guanidine hydrochloride. Wild-type GB1 contains three tyrosines located at positions 3, 33, 45 and a single tryptophan residue at position 43. Two of the three tyrosines were replaced in turn, thereby allowing us to measure the energy transfer from Trp43 to each particular tyrosine. Overall, multi-parametrical experiments on GB1 including circular dichroism, steady state and time-resolved fluorescence, as well as fluorescence energy transfer revealed the existence of highly stable unfolded intermediates, which precede the formation of the rigid (native) secondary structure.

  11. Resonant energy transfer based biosensor for detection of multivalent proteins.

    SciTech Connect

    Song, X.; Swanson, Basil I.

    2001-01-01

    We have developed a new fluorescence-based biosensor for sensitive detection of species involved in a multivslent interaction. The biosensor system utilizes specific interactions between proteins and cell surface receptors, which trigger a receptor aggregation process. Distance-dependent fluorescence self-quenching and resonant energy transfer mechanisms were coupled with a multivalent interaction to probe the receptor aggregation process, providing a sensitive and specific signal transduction method for such a binding event. The fluorescence change induced by the aggregation process can be monitored by different instrument platforms, e.g. fluorimetry and flow cytometry. In this article, a sensitive detection of pentavalent cholera toxin which recognizes ganglioside GM1 has been demonstrated through the resonant energy transfer scheme, which can achieve a double color change simultaneously. A detection sensitivity as high as 10 pM has been achieved within a few minutes (c.a. 5 minutes). The simultaneous double color change (an increase of acceptor fluorescence and a decrease of donor fluorescence intensity) of two similar fluorescent probes provides particularly high detection reliability owing to the fact that they act as each other's internal reference. Any external perturbation such as environmental temperature change causes no significant change in signal generation. Besides the application for biological sensing, the method also provides a useful tool for investigation of kinetics and thermodynamics of a multivalent interaction. Keywords: Biosensor, Fluorescence resonant energy transfer, Multivalent interaction, Cholera Toxin, Ganglioside GM1, Signal Transduction

  12. Homopolar machine for reversible energy storage and transfer systems

    DOEpatents

    Stillwagon, Roy E.

    1981-01-01

    A homopolar machine designed to operate as a generator and motor in reversibly storing and transferring energy between the machine and a magnetic load coil for a thermo-nuclear reactor. The machine rotor comprises hollow thin-walled cylinders or sleeves which form the basis of the system by utilizing substantially all of the rotor mass as a conductor thus making it possible to transfer substantially all the rotor kinetic energy electrically to the load coil in a highly economical and efficient manner. The rotor is divided into multiple separate cylinders or sleeves of modular design, connected in series and arranged to rotate in opposite directions but maintain the supply of current in a single direction to the machine terminals. A stator concentrically disposed around the sleeves consists of a hollow cylinder having a number of excitation coils each located radially outward from the ends of adjacent sleeves. Current collected at an end of each sleeve by sleeve slip rings and brushes is transferred through terminals to the magnetic load coil. Thereafter, electrical energy returned from the coil then flows through the machine which causes the sleeves to motor up to the desired speed in preparation for repetition of the cycle. To eliminate drag on the rotor between current pulses, the brush rigging is designed to lift brushes from all slip rings in the machine.

  13. Homopolar machine for reversible energy storage and transfer systems

    DOEpatents

    Stillwagon, Roy E.

    1978-01-01

    A homopolar machine designed to operate as a generator and motor in reversibly storing and transferring energy between the machine and a magnetic load coil for a thermo-nuclear reactor. The machine rotor comprises hollow thin-walled cylinders or sleeves which form the basis of the system by utilizing substantially all of the rotor mass as a conductor thus making it possible to transfer substantially all the rotor kinetic energy electrically to the load coil in a highly economical and efficient manner. The rotor is divided into multiple separate cylinders or sleeves of modular design, connected in series and arranged to rotate in opposite directions but maintain the supply of current in a single direction to the machine terminals. A stator concentrically disposed around the sleeves consists of a hollow cylinder having a number of excitation coils each located radially outward from the ends of adjacent sleeves. Current collected at an end of each sleeve by sleeve slip rings and brushes is transferred through terminals to the magnetic load coil. Thereafter, electrical energy returned from the coil then flows through the machine which causes the sleeves to motor up to the desired speed in preparation for repetition of the cycle. To eliminate drag on the rotor between current pulses, the brush rigging is designed to lift brushes from all slip rings in the machine.

  14. Energy and charge transfer in ionized argon coated water clusters

    SciTech Connect

    Kočišek, J. E-mail: michal.farnik@jh-inst.cas.cz Lengyel, J.; Fárník, M. E-mail: michal.farnik@jh-inst.cas.cz; Slavíček, P. E-mail: michal.farnik@jh-inst.cas.cz

    2013-12-07

    We investigate the electron ionization of clusters generated in mixed Ar-water expansions. The electron energy dependent ion yields reveal the neutral cluster composition and structure: water clusters fully covered with the Ar solvation shell are formed under certain expansion conditions. The argon atoms shield the embedded (H{sub 2}O){sub n} clusters resulting in the ionization threshold above ≈15 eV for all fragments. The argon atoms also mediate more complex reactions in the clusters: e.g., the charge transfer between Ar{sup +} and water occurs above the threshold; at higher electron energies above ∼28 eV, an excitonic transfer process between Ar{sup +}* and water opens leading to new products Ar{sub n}H{sup +} and (H{sub 2}O){sub n}H{sup +}. On the other hand, the excitonic transfer from the neutral Ar* state at lower energies is not observed although this resonant process was demonstrated previously in a photoionization experiment. Doubly charged fragments (H{sub 2}O){sub n}H{sub 2}{sup 2+} and (H{sub 2}O){sub n}{sup 2+} ions are observed and Intermolecular Coulomb decay (ICD) processes are invoked to explain their thresholds. The Coulomb explosion of the doubly charged cluster formed within the ICD process is prevented by the stabilization effect of the argon solvent.

  15. Linear energy relationships in ground state proton transfer and excited state proton-coupled electron transfer.

    PubMed

    Gamiz-Hernandez, Ana P; Magomedov, Artiom; Hummer, Gerhard; Kaila, Ville R I

    2015-02-12

    Proton-coupled electron transfer (PCET) processes are elementary chemical reactions involved in a broad range of radical and redox reactions. Elucidating fundamental PCET reaction mechanisms are thus of central importance for chemical and biochemical research. Here we use quantum chemical density functional theory (DFT), time-dependent density functional theory (TDDFT), and the algebraic diagrammatic-construction through second-order (ADC(2)) to study the mechanism, thermodynamic driving force effects, and reaction barriers of both ground state proton transfer (pT) and photoinduced proton-coupled electron transfer (PCET) between nitrosylated phenyl-phenol compounds and hydrogen-bonded t-butylamine as an external base. We show that the obtained reaction barriers for the ground state pT reactions depend linearly on the thermodynamic driving force, with a Brønsted slope of 1 or 0. Photoexcitation leads to a PCET reaction, for which we find that the excited state reaction barrier depends on the thermodynamic driving force with a Brønsted slope of 1/2. To support the mechanistic picture arising from the static potential energy surfaces, we perform additional molecular dynamics simulations on the excited state energy surface, in which we observe a spontaneous PCET between the donor and the acceptor groups. Our findings suggest that a Brønsted analysis may distinguish the ground state pT and excited state PCET processes.

  16. State-to-state dynamics of molecular energy transfer

    SciTech Connect

    Gentry, W.R.; Giese, C.F.

    1993-12-01

    The goal of this research program is to elucidate the elementary dynamical mechanisms of vibrational and rotational energy transfer between molecules, at a quantum-state resolved level of detail. Molecular beam techniques are used to isolate individual molecular collisions, and to control the kinetic energy of collision. Lasers are used both to prepare specific quantum states prior to collision by stimulated-emission pumping (SEP), and to measure the distribution of quantum states in the collision products by laser-induced fluorescence (LIF). The results are interpreted in terms of dynamical models, which may be cast in a classical, semiclassical or quantum mechanical framework, as appropriate.

  17. Optimizing energy transfer efficiency in highly branched nanoplasmonic waveguides

    NASA Astrophysics Data System (ADS)

    Voronine, Dmitri; Traverso, Andrew; Wang, Kai; Yi, Zhenhuan; Sokolov, Alexei

    2011-03-01

    Energy transfer in highly branched nanoplasmonic particle waveguides is simulated and optimized by varying the waveguide branching geometry and composition. The periodically branched nanostructures provide a new route towards efficient nanoscale light concentration and local field enhancement. On the one hand, they mimick the analogous randomly branched plasmonic nanostructures which have been previously used for surface-enhanced optical spectroscopy such as SERS. On the other hand, the design is inspired by branched molecular aggregates used for energy funneling. The proposed nanostructures may find applications in sensing, light harvesting and nanophotonics.

  18. Vibrational Energy Transfer of Diatomic Gases in Hypersonic Expanding Flows.

    NASA Astrophysics Data System (ADS)

    Ruffin, Stephen Merrick

    In high temperature flows related to vehicles at hypersonic speeds significant excitation of the vibrational energy modes of the gas can occur. Accurate predictions of the vibrational state of the gas and the rates of vibrational energy transfer are essential to achieve optimum engine performance, for design of heat shields, and for studies of ground based hypersonic test facilities. The Landau -Teller relaxation model is widely used because it has been shown to give accurate predictions in vibrationally heating flows such as behind forebody shocks. However, a number of experiments in nozzles have indicated that it fails to accurately predict the rate of energy transfer in expanding, or cooling, flow regions and fails to predict the distribution of energy in the vibrational quantum levels. The present study examines the range of applicability of the Landau -Teller model in expanding flows and develops techniques which provide accurate predictions in expanding flows. In the present study, detailed calculations of the vibrational relaxation process of N_2 and CO in cooling flows are conducted. A coupled set of vibrational transition rate equations and quasi one-dimensional fluid dynamic equations is solved. Rapid anharmonic Vibration-Translation transition rates and Vibration -Vibration exchange collisions are found to be responsible for vibrational relaxation acceleration in situations of high vibrational temperature and low translational temperature. The predictions of the detailed master equation solver are in excellent agreement with experimental results. The exact degree of acceleration is cataloged in this study for N_2 and is found to be a function of both the translational temperature (T) and the ratio of vibrational to translational temperatures (T_{vib}/T). Non-Boltzmann population distributions are observed for values of T _{vib}/T as low as 2.0. The local energy transfer rate is shown to be an order of magnitude or more faster than the Landau-Teller model

  19. Rotational And Rovibrational Energy Transfer In Electron Collisions With Molecules

    NASA Technical Reports Server (NTRS)

    Thuemmel, Helmar T.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Air flows around a hypervelocity reentry vehicle undergo dissociation, rovibrational excitation and ionization. More specifically the air, initially 80% N2 and 20% O2, in the shock layer consists of species such as N, O, N2, O2, NO, N+, O+, N+, O+, NO+ and 2 free electrons. It was pointed out in multi temperature models'' that the temperature of the rotational energy modes and the gas-kinetic translational temperature are quickly equilibrated by a few collisions and rise rapidly to high temperatures as 50000K before falling off to equilibrium value of 10000K. Contrary, the electronic and vibrational temperatures state energy distributions remain low (less than 15000K) because of the slow equilibration. Electron vibrational energy transfer is thought to play a crucial role in such a ionizing flow regime since chemical reaction rates and dissociation depend strongly on the vibrational temperatures. Modeling of these flowfields in principle require the rovibrational excitation and de-excitation cross section data for average electron energies from threshold up to several eV (leV=11605.4 K). In this lecture we focus on theoretical description of rotational effects i.e. energy transfer of electrons to molecules such that the molecular rotational (vojo goes to voj) or vibrational and rotational (v(sub 0)j(sub 0) goes to vj) states are changed. Excitation and de-excitation of electronic states was discussed in a previous talk at this conference.

  20. Micro-beam friction liner and method of transferring energy

    DOEpatents

    Mentesana, Charles

    2007-07-17

    A micro-beam friction liner adapted to increase performance and efficiency and reduce wear in a piezoelectric motor or actuator or other device using a traveling or standing wave to transfer energy in the form of torque and momentum. The micro-beam friction liner comprises a dense array of micro-beam projections having first ends fixed relative to a rotor and second ends projecting substantially toward a plurality of teeth of a stator, wherein the micro-beam projections are compressed and bent during piezoelectric movement of the stator teeth, thereby storing the energy, and then react against the stator teeth to convert the stored energy stored to rotational energy in the rotor.

  1. Heat transfer and flow in solar energy and bioenergy systems

    NASA Astrophysics Data System (ADS)

    Xu, Ben

    The demand for clean and environmentally benign energy resources has been a great concern in the last two decades. To alleviate the associated environmental problems, reduction of the use of fossil fuels by developing more cost-effective renewable energy technologies becomes more and more significant. Among various types of renewable energy sources, solar energy and bioenergy take a great proportion. This dissertation focuses on the heat transfer and flow in solar energy and bioenergy systems, specifically for Thermal Energy Storage (TES) systems in Concentrated Solar Power (CSP) plants and open-channel algal culture raceways for biofuel production. The first part of this dissertation is the discussion about mathematical modeling, numerical simulation and experimental investigation of solar TES system. First of all, in order to accurately and efficiently simulate the conjugate heat transfer between Heat Transfer Fluid (HTF) and filler material in four different solid-fluid TES configurations, formulas of an e?ective heat transfer coe?cient were theoretically developed and presented by extending the validity of Lumped Capacitance Method (LCM) to large Biot number, as well as verifications/validations to this simplified model. Secondly, to provide design guidelines for TES system in CSP plant using Phase Change Materials (PCM), a general storage tank volume sizing strategy and an energy storage startup strategy were proposed using the enthalpy-based 1D transient model. Then experimental investigations were conducted to explore a novel thermal storage material. The thermal storage performances were also compared between this novel storage material and concrete at a temperature range from 400 °C to 500 °C. It is recommended to apply this novel thermal storage material to replace concrete at high operating temperatures in sensible heat TES systems. The second part of this dissertation mainly focuses on the numerical and experimental study of an open-channel algae

  2. Energy transfer and constrained simulations in isotropic turbulence

    NASA Technical Reports Server (NTRS)

    Jimenez, Javier

    1993-01-01

    The defining characteristic of turbulent flows is their ability to dissipate energy, even in the limit of zero viscosity. The Euler equations, if constrained in such a way that the velocity derivatives remain bounded, conserve energy. But when they arise as the limit of the Navier-Stokes (NS) equations, when the Reynolds number goes to infinity, there is persuasive empirical evidence that the gradients become singular as just the right function of Re for the dissipation to remain non-zero and to approach a well defined limit. It is generally believed that this limiting value of the dissipation is a property of the Euler equations themselves, independent of the particular dissipative mechanism involved, and that it can be normalized with the large scale properties of the turbulent flow (e.g. the kinetic energy per unit volume u'(exp 2)/2, and the integral scale L) without reference to the Reynolds number or to other dissipative quantities. This is usually taken to imply that the low wave number end of the energy spectrum, far from the dissipative range, is also independent of the particular mechanism chosen to dispose of the energy transfer. In the following sections, we present some numerical experiments on the effect of substituting different dissipation models into the truncated Euler equations. We will see that the effect is mainly felt in the 'near dissipation' range of the energy spectrum, but that this range can be quite wide in some cases, contaminating a substantial range of wave numbers. In the process, we will develop a 'practical' approximation to the subgrid energy transfer in isotropic turbulence, and we will gain insight into the structure of the nonlinear interactions among turbulent scales of comparable size, and into the nature of energy backscatter. Some considerations on future research directions are offered at the end.

  3. A stochastic reorganizational bath model for electronic energy transfer

    SciTech Connect

    Fujita, Takatoshi E-mail: aspuru@chemistry.harvard.edu; Huh, Joonsuk; Aspuru-Guzik, Alán E-mail: aspuru@chemistry.harvard.edu

    2014-06-28

    Environmentally induced fluctuations of the optical gap play a crucial role in electronic energy transfer dynamics. One of the simplest approaches to incorporate such fluctuations in energy transfer dynamics is the well known Haken-Strobl-Reineker (HSR) model, in which the energy-gap fluctuation is approximated as white noise. Recently, several groups have employed molecular dynamics simulations and excited-state calculations in conjunction to account for excitation energies’ thermal fluctuations. On the other hand, since the original work of HSR, many groups have employed stochastic models to simulate the same transfer dynamics. Here, we discuss a rigorous connection between the stochastic and the atomistic bath models. If the phonon bath is treated classically, time evolution of the exciton-phonon system can be described by Ehrenfest dynamics. To establish the relationship between the stochastic and atomistic bath models, we employ a projection operator technique to derive the generalized Langevin equations for the energy-gap fluctuations. The stochastic bath model can be obtained as an approximation of the atomistic Ehrenfest equations via the generalized Langevin approach. Based on this connection, we propose a novel scheme to take account of reorganization effects within the framework of stochastic models. The proposed scheme provides a better description of the population dynamics especially in the regime of strong exciton-phonon coupling. Finally, we discuss the effect of the bath reorganization in the absorption and fluorescence spectra of ideal J-aggregates in terms of the Stokes shifts. We find a simple expression that relates the reorganization contribution to the Stokes shifts – the reorganization shift – to the ideal or non-ideal exciton delocalization in a J-aggregate. The reorganization shift can be described by three parameters: the monomer reorganization energy, the relaxation time of the optical gap, and the exciton delocalization length

  4. Molecular mimicry of photosynthetic energy and electron transfer

    SciTech Connect

    Gust, D.; Moore, T.A.; Moore, A.L. )

    1993-04-01

    Proper application of reaction design considerations can yield artificial photosynthetic devices which credibility mimic the three natural photochemical processes. One approach is to use pigments and electron donors and acceptors related to those found in natural photosynthesis (and thus presumably optimal for that system), but to replace the protein with covalent bonds as an organizing precept. Molecular pentads described herein exemplify the success of this approach. At the heart of these molecules, are two covalently linked synthetic porphyrin moieties (P-P). One of these models for chlorophyll is attached to a carotenoid polyene (C), whereas the other is linked to a rigid diquinone (Q-Q). As discussed later in this paper, excitation of such a pentad is followed by photoinitiated electron transfer steps which ultimately give a C[sup [center dot]+]-P-P-Q-Q[sup [center dot]-] charge-separated state. Depending upon the structure of the pentad and the conditions, these states are formed with quantum yields of up to 0.83, have lifetimes approaching 0.5 ms, and store about one-half of the energy of the exciting singlet state. Related photosynthesis mimics display singlet-singlet energy transfer from carotenoid polyenes to porphyrins and among porphyrin chromophores, and rapid quenching of porphyrin triplet states by attached carotenoids. How have the structures of these and other successful artificial reaction centers evolved, and what will be the next steps in their development The authors will address these questions from the point of view of photoinitiated electron transfer, and then singlet and triplet energy transfer will briefly be considered. 37 refs., 4 figs.

  5. Direct contact heat transfer for thermal energy storage

    SciTech Connect

    Wright, J. D.

    1980-11-01

    Direct contact heat exchange offers the potential for increased efficiency and lower heat transfer costs in a variety of thermal energy storage sytems. SERI models of direct contact heat transfer based on literature information have identified dispersed phase drop size, the mechanism of heat transfer within the drop, and dispersed phase holdup as the parameters controlling direct contact system performance. However, current information is insufficient to predict these factors a priori. Therefore, tests have been defined and equipment constructed to provide independent determination of drop size, heat transfer mechanism, and hold up. In experiments with heptane dispersed in water, the equation of Kagen et. al. was found to most closely predict the drop size. The velocity at which drop formation changes from dropwise to jetting was overpredicted by all literature correlations. Further experiments are needed to conclusively determine whether the salt in a salt hydrate melt acts to block internal circulation. In addition, the potential of low temperature oil/salt hydrate latent heat storage systems is being evaluated in the laboratory.

  6. Energy transfer processes in solar energy conversion. Progress report, January 1, 1988--December 31, 1988

    SciTech Connect

    Fayer, M.D.

    1988-12-31

    The program involves the investigation of excitation transport and electron transfer in complex systems. In the area of electron transfer, we have been studying electron back transfer following donor-acceptor photoinduced electron transfer. We are addressing this problem both theoretically and experimentally. In the area of excitation transport, we have been examining transport in solid solutions, liquid solutions, and in clustered excitation transport systems. Again, we are pursuing both experimental and theoretical approaches. The problem of electron back transfer between photogenerated ions is of central importance in both artificial and biological solar energy conversion. Once an electron has been transferred from an optically excited donor to an acceptor, back transfer competes with the ability of the radical ions to go on to do useful chemistry. We are studying the back transfer process using picosecond transient grating experiments in conjunction with time resolved and steady state fluorescence quenching measurements. The transient grating experiments makes the back transfer process a direct experimental observable, while the fluorescence experiments allow the forward transfer to be examined. By combining the experiments, a complete picture emerges. 10 refs.

  7. Firefly Luciferase-Based Sequential Bioluminescence Resonance Energy Transfer (BRET)-Fluorescence Resonance Energy Transfer (FRET) Protease Assays.

    PubMed

    Branchini, Bruce

    2016-01-01

    We describe here the preparation of ratiometric luminescent probes that contain two well-separated emission peaks produced by a sequential bioluminescence resonance energy transfer (BRET)-fluorescence resonance energy transfer (FRET) process. The probes are single soluble fusion proteins consisting of a thermostable firefly luciferase variant that catalyzes yellow-green (560 nm maximum) bioluminescence and a red fluorescent protein covalently labeled with a near-Infrared fluorescent dye. The two proteins are connected by a decapeptide containing a protease recognition site specific for factor Xa, thrombin, or caspase 3. The rates of protease cleavage of the fusion protein substrates were monitored by recording emission spectra and plotting the change in peak ratios over time. Detection limits of 0.41 nM for caspase 3, 1.0 nM for thrombin, and 58 nM for factor Xa were realized with a scanning fluorometer. This method successfully employs an efficient sequential BRET-FRET energy transfer process based on firefly luciferase bioluminescence to assay physiologically important protease activities and should be generally applicable to the measurement of any endoprotease lacking accessible cysteine residues. PMID:27424898

  8. Firefly Luciferase-Based Sequential Bioluminescence Resonance Energy Transfer (BRET)-Fluorescence Resonance Energy Transfer (FRET) Protease Assays.

    PubMed

    Branchini, Bruce

    2016-01-01

    We describe here the preparation of ratiometric luminescent probes that contain two well-separated emission peaks produced by a sequential bioluminescence resonance energy transfer (BRET)-fluorescence resonance energy transfer (FRET) process. The probes are single soluble fusion proteins consisting of a thermostable firefly luciferase variant that catalyzes yellow-green (560 nm maximum) bioluminescence and a red fluorescent protein covalently labeled with a near-Infrared fluorescent dye. The two proteins are connected by a decapeptide containing a protease recognition site specific for factor Xa, thrombin, or caspase 3. The rates of protease cleavage of the fusion protein substrates were monitored by recording emission spectra and plotting the change in peak ratios over time. Detection limits of 0.41 nM for caspase 3, 1.0 nM for thrombin, and 58 nM for factor Xa were realized with a scanning fluorometer. This method successfully employs an efficient sequential BRET-FRET energy transfer process based on firefly luciferase bioluminescence to assay physiologically important protease activities and should be generally applicable to the measurement of any endoprotease lacking accessible cysteine residues.

  9. A bifurcated molecular pentad capable of sequential electronic energy transfer and intramolecular charge transfer.

    PubMed

    Harriman, Anthony; Stachelek, Patrycja; Sutter, Alexandra; Ziessel, Raymond

    2015-10-21

    An extended molecular array, comprising three distinct types of chromophores and two additional redox-active subunits, that harvests photons over most of the visible spectral range has been synthesized and characterised. The array exhibits a rich variety of electrochemical waves when examined by cyclic voltammetry but assignment can be made on the basis of control compounds and molecular orbital calculations. Stepwise electronic energy transfer occurs along the molecular axis, corresponding to a gradient of excitation energies, to populate the lowest-energy excited state of the ultimate acceptor. The latter species, which absorbs and emits in the far-red region, enters into light-induced charge transfer with a terminal amine group. The array is relatively stable under illumination with white light but degrades slowly via a series of well-defined steps, the first of which is autocatalytic. One of the main attributes of this system is the capability to harvest an unusually high fraction of sunlight while providing protection against exposure to UV light.

  10. Excitation energy transfer in vitro between phycobiliproteins and thylakoid photosystem II of higher plants

    NASA Astrophysics Data System (ADS)

    Wu, Xiaonan; Tseng, C. K.

    1992-12-01

    The excitation energy transfer from phycobiliproteins to thylakoid PSII of higher plants was investigated. When incubated with spinach thylakoids, phycobiliproteins isolated from red and blue-green algae transferred light energy absorbed to spinach PSII. The efficiency of energy transfer was dependent on the kind of phycobiliproteins used. If spinach thylakoids were replaced by the thylakoids of Brassica chinensis, R-phycoerythin or C-phycocyanin did not transfer their excitation energy to PSII of Brassica chinensis unless allophycocyanin was present.

  11. Gamma-ray transfer and energy deposition in supernovae

    NASA Technical Reports Server (NTRS)

    Swartz, Douglas A.; Sutherland, Peter G.; Harkness, Robert P.

    1995-01-01

    Solutions to the energy-independent (gray) radiative transfer equations are compared to results of Monte Carlo simulations of the Ni-56 and Co-56 decay gamma-ray energy deposition in supernovae. The comparison shows that an effective, purely absorptive, gray opacity, kappa(sub gamma) approximately (0. 06 +/- 0.01)Y(sub e) sq cm/g, where Y is the total number of electrons per baryon, accurately describes the interaction of gamma-rays with the cool supernova gas and the local gamma-ray energy deposition within the gas. The nature of the gamma-ray interaction process (dominated by Compton scattering in the relativistic regime) creates a weak dependence of kappa(sub gamma) on the optical thickness of the (spherically symmetric) supernova atmosphere: The maximum value of kappa(sub gamma) applies during optically thick conditions when individual gamma-rays undergo multiple scattering encounters and the lower bound is reached at the phase characterized by a total Thomson optical depth to the center of the atmosphere tau(sub e) approximately less than 1. Gamma-ray deposition for Type Ia supernova models to within 10% for the epoch from maximum light to t = 1200 days. Our results quantitatively confirm that the quick and efficient solution to the gray transfer problem provides an accurate representation of gamma-ray energy deposition for a broad range of supernova conditions.

  12. Optimal aeroassisted coplanar orbital transfer using an energy model

    NASA Astrophysics Data System (ADS)

    Halyo, Nesim; Taylor, Deborah B.

    1989-05-01

    The atmospheric portion of the trajectories for the aeroassisted coplanar orbit transfer was investigated. The equations of motion for the problem are expressed using reduced order model and total vehicle energy, kinetic plus potential, as the independent variable rather than time. The order reduction is achieved analytically without an approximation of the vehicle dynamics. In this model, the problem of coplanar orbit transfer is seen as one in which a given amount of energy must be transferred from the vehicle to the atmosphere during the trajectory without overheating the vehicle. An optimal control problem is posed where a linear combination of the integrated square of the heating rate and the vehicle drag is the cost function to be minimized. The necessary conditions for optimality are obtained. These result in a 4th order two-point-boundary-value problem. A parametric study of the optimal guidance trajectory in which the proportion of the heating rate term versus the drag varies is made. Simulations of the guidance trajectories are presented.

  13. Charge transfer and negative curvature energy in magnesium boride nanotubes

    NASA Astrophysics Data System (ADS)

    Tang, Hui; Ismail-Beigi, Sohrab

    2016-07-01

    Using first-principles calculations based on density functional theory, we study the energetics and charge transfer effects in MgBx nanotubes and two-dimensional (2D) sheets. The behavior of adsorbed Mg on 2D boron sheets is found to depend on the amount of electron transfer between the two subsystems. The amount is determined by both the density of adsorbed Mg as well as the atomic-scale structure of the boron subsystem. The degree of transfer can lead to repulsive or attractive Mg-Mg interactions. In both cases, model MgBx nanotubes built from 2D MgBx sheets can display negative curvature energy: a relatively unusual situation in nanosystems where the energy cost to curve the parent 2D sheet into a small-diameter nanotube is negative. Namely, the small-diameter nanotube is energetically preferred over the corresponding flat sheet. We also discuss how these findings may manifest themselves in experimentally synthesized MgBx nanotubes.

  14. Optimal aeroassisted coplanar orbital transfer using an energy model

    NASA Technical Reports Server (NTRS)

    Halyo, Nesim; Taylor, Deborah B.

    1989-01-01

    The atmospheric portion of the trajectories for the aeroassisted coplanar orbit transfer was investigated. The equations of motion for the problem are expressed using reduced order model and total vehicle energy, kinetic plus potential, as the independent variable rather than time. The order reduction is achieved analytically without an approximation of the vehicle dynamics. In this model, the problem of coplanar orbit transfer is seen as one in which a given amount of energy must be transferred from the vehicle to the atmosphere during the trajectory without overheating the vehicle. An optimal control problem is posed where a linear combination of the integrated square of the heating rate and the vehicle drag is the cost function to be minimized. The necessary conditions for optimality are obtained. These result in a 4th order two-point-boundary-value problem. A parametric study of the optimal guidance trajectory in which the proportion of the heating rate term versus the drag varies is made. Simulations of the guidance trajectories are presented.

  15. Fluorescence resonance energy transfer studies on anthrax lethal toxin.

    PubMed

    Croney, John C; Cunningham, Kristina M; Collier, R John; Jameson, David M

    2003-08-28

    Anthrax lethal toxin is a binary bacterial toxin consisting of two proteins, protective antigen (PA) and lethal factor (LF), that self-assemble on receptor-bearing eukaryotic cells to form toxic, non-covalent complexes. PA(63), a proteolytically activated form of PA, spontaneously oligomerizes to form ring-shaped heptamers that bind LF and translocate it into the cell. Site-directed mutagenesis was used to substitute cysteine for each of three residues (N209, E614 and E733) at various levels on the lateral face of the PA(63) heptamer and for one residue (E126) on LF(N), the 30 kDa N-terminal PA binding domain of LF. Cysteine residues in PA were labeled with IAEDANS and that in LF(N) was labeled with Alexa 488 maleimide. The mutagenesis and labeling did not significantly affect function. Time-resolved fluorescence methods were used to study fluorescence resonance energy transfer (FRET) between the AEDANS and Alexa 488 probes after the complex assembled in solution. The results clearly indicate energy transfer between AEDANS labeled at residue N209C on PA and the Alexa 488-labeled LF(N), whereas transfer from residue E614C on PA was slight, and none was observed from residue E733C. These results support a model in which LF(N) binds near the top of the ring-shaped (PA(63))(7) heptamer.

  16. Photoinduced Charge and Energy Transfer Processes in Molecular Aggregates

    SciTech Connect

    John F. Endicott

    2009-10-20

    This project involved the experimental probing of the electronic excited states generated by photoinduced (center-to-center) electron and energy transfer processes in several classes of transition metal donor/acceptor (D/A) complexes. Some of the general properties inferred from these studies should be useful in the design of new systems for energy conversion applications. Pursuit of the project goals has involved the determination of electron transfer efficiencies and the detailed study of variations in the electronic spectra of D/A complexes. This has resulted in the study of some very fundamental issues of photoinduced charge transfer and the identification of some of the constraints on its efficiency. The experimental studies of the competition between the degradative non-radiative unimolecular relaxation of transition metal excited states and their transfer of charge from these excited states to external acceptors have involved a range of techniques such as transient decay kinetics, photoacoustic calorimetry and transient or stationary state spectroscopy. The substrates synthesized for these studies were selected to provide model systems, or series of model systems to probe the validity of models of electronic excited states and their reactivity. The work during the last few years has focused largely, but not exclusively, on the use of emission spectral band shapes to probe the properties of charge transfer (CT) excited states. Bandshape variations are one of the very few approaches for systematically probing electronic excited states and good band shape resolution is necessary in order to gain information about the structural variations that correlate with excited state reactivity. Differences in molecular structure correlate with differences in chemical reactivity, and the variations in emission bandshapes are well known to relate to variations in the molecular structural differences between the excited and ground electronic states. However, it is has been

  17. Heat transfer in vertically aligned phase change energy storage systems

    SciTech Connect

    El-Dessouky, H.T.; Bouhamra, W.S.; Ettouney, H.M.; Akbar, M.

    1999-05-01

    Convection effects on heat transfer are analyzed in low temperature and vertically aligned phase change energy storage systems. This is performed by detailed temperature measurements in the phase change material (PCM) in eighteen locations forming a grid of six radial and three axial positions. The system constitutes a double pipe configuration, where commercial grade paraffin wax is stored in the annular space between the two pipes and water flows inside the inner pipe. Vertical alignment of the system allowed for reverse of the flow direction of the heat transfer fluid (HTF), which is water. Therefore, the PCM is heated from the bottom for HTF flow from bottom to top and from the top as the HTF flow direction is reversed. For the former case, natural convection affects the melting process. Collected data are used to study variations in the transient temperature distribution at axial and radial positions as well as for the two-dimensional temperature field. The data are used to calculate the PCM heat transfer coefficient and to develop correlations for the melting Fourier number. Results indicate that the PCM heat transfer coefficient is higher for the case of PCM heating from bottom to top. Nusselt number correlations are developed as a function of Rayleigh, Stefan, and Fourier numbers for the HTF flow from bottom to top and as a function of Stefan and Fourier numbers for HTF flow from top to bottom. The enhancement ratio for heat transfer caused by natural convection increases and then levels off as the inlet temperature of the HTF is increased.

  18. Energy transfer in mesoscopic vibrational systems enabled by eigenfrequency fluctuations

    NASA Astrophysics Data System (ADS)

    Atalaya, Juan

    Energy transfer between low-frequency vibrational modes can be achieved by means of nonlinear coupling if their eigenfrequencies fulfill certain nonlinear resonance conditions. Because of the discreteness of the vibrational spectrum at low frequencies, such conditions may be difficult to satisfy for most low-frequency modes in typical mesoscopic vibrational systems. Fluctuations of the vibrational eigenfrequencies can also be relatively strong in such systems. We show that energy transfer between modes can occur in the absence of nonlinear resonance if frequency fluctuations are allowed. The case of three modes with cubic nonlinear coupling and no damping is particularly interesting. It is found that the system has a non-thermal equilibrium state which depends only on the initial conditions. The rate at which the system approaches to such state is determined by the parameters such as the noise strength and correlation time, the nonlinearity strength and the detuning from exact nonlinear resonance. We also discuss the case of many weakly coupled modes. Our results shed light on the problem of energy relaxation of low-frequency vibrational modes into the continuum of high-frequency vibrational modes. The results have been obtained with Mark Dykman. Alternative email: jatalaya2012@gmail.com.

  19. Detecting Plasmon Resonance Energy Transfer with Differential Interference Contrast Microscopy

    SciTech Connect

    Augspurger, Ashley E.; Stender, Anthony S.; Han, Rui; Fang, Ning

    2013-12-30

    Gold nanoparticles are ideal probes for studying intracellular environments and energy transfer mechanisms due to their plasmonic properties. Plasmon resonance energy transfer (PRET) relies on a plasmonic nanoparticle to donate energy to a nearby resonant acceptor molecule, a process which can be observed due to the plasmonic quenching of the donor nanoparticle. In this study, a gold nanosphere was used as the plasmonic donor, while the metalloprotein cytochrome c was used as the acceptor molecule. Differential interference contrast (DIC) microscopy allows for simultaneous monitoring of complex environments and noble metal nanoparticles in real time. Using DIC and specially designed microfluidic channels, we were able to monitor PRET at the single gold particle level and observe the reversibility of PRET upon the introduction of phosphate-buffered saline to the channel. In an additional experiment, single gold particles were internalized by HeLa cells and were subsequently observed undergoing PRET as the cell hosts underwent morphological changes brought about by ethanol-induced apoptosis.

  20. Entanglement versus energy in the entanglement transfer problem

    SciTech Connect

    Cavalcanti, Daniel; Oliveira, J. G. Jr.; Santos, Marcelo Franca; Peixoto de Faria, J. G.; Terra Cunha, Marcelo O.

    2006-10-15

    We study the relation between energy and entanglement in an entanglement transfer problem. We first analyze the general setup of two entangled qubits ('a' and 'b') exchanging this entanglement with two other independent qubits ('A' and 'B'). Qubit 'a' ('b') interacts with qubit 'A' ('B') via a spin-exchange-like unitary evolution. A physical realization of this scenario could be the problem of two-level atoms transferring entanglement to resonant cavities via independent Jaynes-Cummings interactions. We study the dynamics of entanglement and energy for the second pair of qubits (tracing out the originally entangled ones) and show that these quantities are closely related. For example, the allowed quantum states occupy a restricted area in a phase diagram entanglement vs energy. Moreover, the curve which bounds this area is exactly the one followed if both interactions are equal and the entire four qubit system is isolated. We also consider the case when the target pair of qubits is subjected to losses and can spontaneously decay.

  1. Heat transfer research for ocean thermal energy conversion

    SciTech Connect

    Kreith, F.; Bharathan, D.

    1987-03-01

    In this lecture an overview of the heat- and mass-transfer phenomena of importance in ocean thermal energy conversion (OTEC) is presented with particular emphasis on open-cycle OTEC systems. Also included is a short historical review of OTEC developments in the past century and a comparison of open- and closed-cycle thermodynamics. Finally, results of system analyses, showing the effect of plant size on cost and the near-term potential of using OTEC for combined power production and desalination systems are briefly discussed.

  2. Heat transfer research for ocean thermal energy conversion

    SciTech Connect

    Kreith, F.; Bharathan, D.

    1988-02-01

    In this lecture an overview of the heat and mass-transfer phenomena of importance in ocean thermal energy conversion (OTEC) is presented with particular emphasis on open-cycle OTEC systems. Also included is a short historical review of OTEC developments in the past century and a comparison of open and closed-cycle thermodynamics. Finally, results of system analyses, showing the effect of plant size on cost and the near-term potential of using OTEC for combined power production and desalination systems, are briefly discussed.

  3. Nanoparticles for heat transfer and thermal energy storage

    SciTech Connect

    Singh, Dileep; Cingarapu, Sreeram; Timofeeva, Elena V.; Moravek, Michael

    2015-07-14

    An article of manufacture and method of preparation thereof. The article of manufacture and method of making the article includes an eutectic salt solution suspensions and a plurality of nanocrystalline phase change material particles having a coating disposed thereon and the particles capable of undergoing the phase change which provides increase in thermal energy storage. In addition, other articles of manufacture can include a nanofluid additive comprised of nanometer-sized particles consisting of copper decorated graphene particles that provide advanced thermal conductivity to heat transfer fluids.

  4. Rotational-translational energy transfer in rarefied nonequilibrium flows

    NASA Technical Reports Server (NTRS)

    Boyd, Iain D.

    1990-01-01

    A new model for simulating the transfer of energy between the translational and rotational modes is derived for a homogeneous gas of diatomic molecules. The model has been developed specifically for use in discrete particle simulation methods where molecular motion and intermolecular collisions are treated at the molecular level. A temperature dependence is introduced which has been predicted by theory and observed in experiment. The new model is applied to the relaxation of rotational temperature, and is found to produce significant differences in comparison with the model normally employed at both high and low temperatures. Calculations have also been performed for a Mach 7 normal shock wave.

  5. Monitoring integrin activation by fluorescence resonance energy transfer.

    PubMed

    Lefort, Craig T; Hyun, Young-Min; Kim, Minsoo

    2012-01-01

    Aberrant integrin activation is associated with several immune pathologies. In leukocyte adhesion deficiency (LAD), the absence or inability of β(2) integrins to undergo affinity upregulation contributes to recurrent infectious episodes and impaired wound healing, while excessive integrin activity leads to an exaggerated inflammatory response with associated tissue damage. Therefore, integrin activation is an attractive target for immunotherapies, and monitoring the effect of agents on integrin activation is necessary during preclinical drug development. The activation of integrins involves the structural rearrangement of both the extracellular and cytoplasmic domains. Here, we describe methods for monitoring integrin conformational activation using fluorescence resonance energy transfer (FRET).

  6. Baryon-Number Transfer in High-Energy hp Collisions

    SciTech Connect

    Bopp, F.; Shabelski, Yu. M.

    2005-12-01

    The processes of baryon-number transfer due to string-junction propagation in rapidity is considered. It has a significant effect on the net baryon production in pp collisions at mid-rapidities and an even larger effect in the forward hemisphere in the cases of {pi}p and {gamma}p interactions. The results of numerical calculations in the framework of the quark-gluon string model are in reasonable agreement with the data with the same parameter values for different energies.

  7. Sensitization of ultra-long-range excited-state electron transfer by energy transfer in a polymerized film

    PubMed Central

    Ito, Akitaka; Stewart, David J.; Fang, Zhen; Brennaman, M. Kyle; Meyer, Thomas J.

    2012-01-01

    Distance-dependent energy transfer occurs from the Metal-to-Ligand Charge Transfer (MLCT) excited state to an anthracene-acrylate derivative (Acr-An) incorporated into the polymer network of a semirigid poly(ethyleneglycol)dimethacrylate monolith. Following excitation, to Acr-An triplet energy transfer occurs followed by long-range, Acr-3An—Acr-An → Acr-An—Acr-3An, energy migration. With methyl viologen dication (MV2+) added as a trap, Acr-3An + MV2+ → Acr-An+ + MV+ electron transfer results in sensitized electron transfer quenching over a distance of approximately 90 Å. PMID:22949698

  8. Rotational Energy Transfer and Collisional Induced Raman Linewidths in N2 Gas. 1; Energy Transfer Rates

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Green, Sheldon; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Rotationally inelastic transitions of N2 have been studied in the coupled state (CS) and infinite-order-sudden (IOS) approximations, using the N2-N2 rigidrotor potential of van der Avoird et al. For benchmarking purposes, close coupling (CC) calculations have also been carried out over a limited energy range. The CC and CS cross sections have been obtained both with and without identical molecule exchange symmetry, whereas exchange was neglected in the IOS calculations. The CS results track the CC cross sections rather well; between 113 - 219 cm(exp -1) the average deviation is 14%. Comparison between the CS and IOS cross sections at the high energy end of the CS calculation, 500 - 680 cm(exp -1), shows that IOS is sensitive to the amount of inelasticity and the results for large DELTA J transitions are subject to larger errors. It is found that the state-to-state cross sections with even and odd exchange symmetry agree to better than 2% and are well represented as a sum of direct and exchange cross sections for distinguishable molecules, an indication of the applicability of a classical treatment for this system. This result, however, does not apply to partial cross sections for given total J, but arises from a near cancellation in summing over partial waves. In order to use rigid-rotor results for the calculation of effective rotational excitation rates of N2 in the v=1 vibrational level colliding with bath N2 molecules in the v=0 level, it is assumed that exchange scattering between molecules in different vibrational levels is negligible and direct scattering is independent of Y. Good agreement with room temperature experimental data is obtained. The effective rates determined using the IOS and energy corrected sudden (ECS) approximations are also in reasonable agreement with experiment, with the ECS results being somewhat better. The problem with a degeneracy factor in earlier cross section expressions for collisions between identical molecules is pointed out

  9. Detection of Medium-Sized Polycyclic Aromatic Hydrocarbons via Fluorescence Energy Transfer

    PubMed Central

    Serio, Nicole; Prignano, Lindsey; Peters, Sean; Levine, Mindy

    2015-01-01

    Reported herein is the use of proximity-induced non-covalent energy transfer for the detection of medium-sized polycyclic aromatic hydrocarbons (PAHs). This energy transfer occurs within the cavity of γ-cyclodextrin in various aqueous environments, including human plasma and coconut water. Highly efficient energy transfer was observed, and the efficiency of the energy transfer is independent of the concentration of γ-cyclodextrin used, demonstrating the importance of hydrophobic binding in facilitating such energy transfer. Low limits of detection were also observed for many of the PAHs investigated, which is promising for the development of fluorescence-based detection schemes. PMID:25821390

  10. Protein Transfer Free Energy Obeys Entropy-Enthalpy Compensation.

    PubMed

    Mills, Eric A; Plotkin, Steven S

    2015-11-01

    We have found significant entropy-enthalpy compensation for the transfer of a diverse set of two-state folding proteins from water into water containing a diverse set of cosolutes, including osmolytes, denaturants, and crowders. In extracting thermodynamic parameters from experimental data, we show the potential importance of accounting for the cosolute concentration-dependence of the heat capacity change upon unfolding, as well as the potential importance of the temperature-dependence of the heat capacity change upon unfolding. We introduce a new Monte Carlo method to estimate the experimental uncertainty in the thermodynamic data and use this to show by bootstrapping methods that entropy-enthalpy compensation is statistically significant, in spite of large, correlated scatter in the data. We show that plotting the data at the transition midpoint provides the most accurate experimental values by avoiding extrapolation errors due to uncertainty in the heat capacity, and that this representation exhibits the strongest evidence of compensation. Entropy-enthalpy compensation is still significant at lab temperature however. We also find that compensation is still significant when considering variations due to heat capacity models, as well as typical measurement discrepancies lab-to-lab when such data is available. Extracting transfer entropy and enthalpy along with their uncertainties can provide a valuable consistency check between experimental data and simulation models, which may involve tests of simulated unfolded ensembles and/or models of the transfer free energy; we include specific applications to cold shock protein and protein L.

  11. Autologous Germline Mitochondrial Energy Transfer (AUGMENT) in Human Assisted Reproduction.

    PubMed

    Woods, Dori C; Tilly, Jonathan L

    2015-11-01

    Ovarian aging is characterized by a decline in both the total number and overall quality of oocytes, the latter of which has been experimentally tied to mitochondrial dysfunction. Clinical studies in the late 1990s demonstrated that transfer of cytoplasm aspirated from eggs of young female donors into eggs of infertile women at the time of intracytoplasmic sperm injection improved pregnancy success rates. However, donor mitochondria were identified in offspring, and the United States Food and Drug Administration raised questions about delivery of foreign genetic material into human eggs at the time of fertilization. Accordingly, heterologous cytoplasmic transfer, while promising, was in effect shut down as a clinical protocol. The recent discovery of adult oogonial (oocyte-generating) stem cells in mice, and subsequently in women, has since re-opened the prospects of delivering a rich source of pristine and patient-matched germline mitochondria to boost egg health and embryonic developmental potential without the need for young donor eggs to obtain cytoplasm. Herein we overview the science behind this new protocol, which has been patented and termed autologous germline mitochondrial energy transfer, and its use to date in clinical studies for improving pregnancy success in women with a prior history of assisted reproduction failure.

  12. Autologous Germline Mitochondrial Energy Transfer (AUGMENT) in Human Assisted Reproduction.

    PubMed

    Woods, Dori C; Tilly, Jonathan L

    2015-11-01

    Ovarian aging is characterized by a decline in both the total number and overall quality of oocytes, the latter of which has been experimentally tied to mitochondrial dysfunction. Clinical studies in the late 1990s demonstrated that transfer of cytoplasm aspirated from eggs of young female donors into eggs of infertile women at the time of intracytoplasmic sperm injection improved pregnancy success rates. However, donor mitochondria were identified in offspring, and the United States Food and Drug Administration raised questions about delivery of foreign genetic material into human eggs at the time of fertilization. Accordingly, heterologous cytoplasmic transfer, while promising, was in effect shut down as a clinical protocol. The recent discovery of adult oogonial (oocyte-generating) stem cells in mice, and subsequently in women, has since re-opened the prospects of delivering a rich source of pristine and patient-matched germline mitochondria to boost egg health and embryonic developmental potential without the need for young donor eggs to obtain cytoplasm. Herein we overview the science behind this new protocol, which has been patented and termed autologous germline mitochondrial energy transfer, and its use to date in clinical studies for improving pregnancy success in women with a prior history of assisted reproduction failure. PMID:26574741

  13. Technology transfer at the Department of Energy (DOE) National Laboratories

    SciTech Connect

    Harrer, B.J.; Good, M.S.; Lemon, D.K.; Morgen, G.P.

    1996-12-31

    Over the past 15 years, efforts to move technology generated from government-funded research and development activities at the Department of Energy (DOE) laboratories into commercial application by the private sector have faced an ever-changing environment. This environment has been primarily dictated by changes in the governing political philosophies of the Congress and the Administration that fund the laboratories and direct their activities. To review the role of the DOE laboratories, the following are discussed: the past, current, and potential future legislative and political environment impacting upon technology transfer from the laboratories; mechanisms of technology transfer; and three selected projects involving transfer of nondestructive evaluation technologies to the private sector. The technologies include computer-aided fabric evaluation (CAFE), measurement of the depth to which steel parts are hardened, and compensation for wear variations in the grinding wheel during the fabrication of wood shaper tools. These respectively deal with a large partnership of companies and institutes, a single but large manufacturing company, and a small business.

  14. Information systems and technology transfer programs on geothermal energy and other renewable sources of energy

    SciTech Connect

    Lippmann, M.J.; Antunez, E.

    1996-01-01

    In order to remain competitive, it is necessary to stay informed and use the most advanced technologies available. Recent developments in communication, like the Internet and the World Wide Web, enormously facilitate worldwide data and technology transfer. A compilation of the most important sources of data on renewable energies, especially geothermal, as well as lists of relevant technology transfer programs are presented. Information on how to gain access to, and learn more about them, is also given.

  15. Information systems and technology transfer programs on geothermal energy and other renewable sources of energy

    SciTech Connect

    Lippmann, Marcelo J.; Antunez, Emilio u.

    1996-01-24

    In order to remain competitive it is necessary to stay informed and use the most advanced technologies available. Recent developments in communication, like the Internet and the World Wide Web, enormously facilitate worldwide data and technology transfer. A compilation of the most important sources of data on renewable energies, especially geothermal, as well as lists of relevant technology transfer programs are presented. Information on how to gain access to, and learn more about them is also given.

  16. Coherent vibrational energy transfer along a peptide helix

    NASA Astrophysics Data System (ADS)

    Kobus, Maja; Nguyen, Phuong H.; Stock, Gerhard

    2011-03-01

    To measure the transport of vibrational energy along a peptide helix, Hamm and co-workers [J. Phys. Chem. B 112, 9091 (2008)] performed time-resolved vibrational experiments, which showed that the energy transport rate increases by at least a factor of 4, when a localized C=O mode of the peptide instead of an attached chromophore is excited. This finding raises the question if coherent excitonic energy transfer between the C=O modes may be of importance for the overall energy transport in peptides. With this idea in mind, nonequilibrium molecular dynamics simulations as well as quantum-classical calculations are performed, which qualitatively reproduce the experimental findings. Moreover, the latter model (an exciton Hamiltonian whose matrix elements depend on the instantaneous positions of the peptide and solvent atoms) indeed exhibits the signatures of coherent quantum energy transport, at least within the first few picoseconds and at low temperatures. The origin of the observed decoherence, the absence of vibrational self-trapping, and the possibility of quantum interference between various transport paths are discussed in some detail.

  17. Collisional energy transfer from highly vibrationally excited triatomic molecules

    NASA Astrophysics Data System (ADS)

    Hynes, Robert G.; Sceats, Mark G.

    1989-12-01

    The atom-atom encounter model developed in the accompanying paper [M. G. Sceats, J. Chem. Phys. 91, 0000 (1989)] is applied to the collisional deactivation of highly vibrationally excited triatomic molecules CS2 and SO2 by the monatomic colliders He, Ne, Ar, Kr, and Xe at 300 K. The molecular inputs are a crude normal mode analysis, vibrational frequencies and effective anharmonicities, while the collisional inputs are parameters of the atom-atom potentials. The results for CS2 are compared with the simulations of Bruehl and Schatz and the experiments of Dove, Hippler, and Troe, while those for SO2 are compared with the simulations of Schranz and Troe and the experimental results of Heymann, Hippler, and Troe. Excellent agreement is found with experiment, and the superlinear energy dependence of the average energy transfer is attributed to anharmonicity of the triatomic molecule.

  18. Crossed-beam energy transfer in direct-drive implosions

    SciTech Connect

    Seka, W; Edgell, D H; Michel, D T; Froula, D H; Goncharov, V N; Craxton, R S; Divol, L; Epstein, R; Follett, R; Kelly, J H; Kosc, T Z; Maximov, A V; McCrory, R L; Meyerhofer, D D; Michel, P; Myatt, J F; Sangster, T C; Shvydky, A; Skupsky, S; Stoeckl, C

    2012-05-22

    Direct-drive-implosion experiments on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have showed discrepancies between simulations of the scattered (non-absorbed) light levels and measured ones that indicate the presence of a mechanism that reduces laser coupling efficiency by 10%-20%. This appears to be due to crossed-beam energy transfer (CBET) that involves electromagnetic-seeded, low-gain stimulated Brillouin scattering. CBET scatters energy from the central portion of the incoming light beam to outgoing light, reducing the laser absorption and hydrodynamic efficiency of implosions. One-dimensional hydrodynamic simulations including CBET show good agreement with all observables in implosion experiments on OMEGA. Three strategies to mitigate CBET and improve laser coupling are considered: the use of narrow beams, multicolor lasers, and higher-Z ablators. Experiments on OMEGA using narrow beams have demonstrated improvements in implosion performance.

  19. Estimating three-demensional energy transfer in isotropic turbulence

    NASA Technical Reports Server (NTRS)

    Li, K. S.; Helland, K. N.; Rosenblatt, M.

    1980-01-01

    To obtain an estimate of the spectral transfer function that indicates the rate of decay of energy, an x-wire probe was set at a fixed position, and two single wire probes were set at a number of locations in the same plane perpendicular to the mean flow in the wind tunnel. The locations of the single wire probes are determined by pseudo-random numbers (Monte Carlo). Second order spectra and cross spectra are estimated. The assumption of isotropy relative to second order spectra is examined. Third order spectra are also estimated corresponding to the positions specified. A Monte Carlo Fourier transformation of the downstream bispectra corresponding to integration across the plane perpendicular to the flow is carried out assuming isotropy. Further integration is carried out over spherical energy shells.

  20. Enhanced luminescence excitation via efficient optical energy transfer (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Aad, Roy; Nomenyo, Komla D.; Bercu, Bogdan; Couteau, Christophe; Sallet, Vincent; Rogers, David J.; Molinari, Michael; Lérondel, Gilles

    2015-10-01

    Luminescent nanoscale materials (LNMs) have received widespread interest in sensing and lighting applications due to their enhanced emissive properties. For sensing applications, LNMs offer improved sensitivity and fast response time which allow for lower limits of detection. Meanwhile, for lighting applications, LNMs, such as quantum dots, offer an improved internal quantum efficiency and controlled color rendering which allow for better lighting performances. Nevertheless, due to their nanometric dimensions, nanoscale materials suffer from extremely weak luminescence excitation (i.e. optical absorption) limiting their luminescence intensity, which in turn results in a downgrade in the limits of detection and external quantum efficiencies. Therefore, enhancing the luminescence excitation is a major issue for sensing and lighting applications. In this work, we report on a novel photonic approach to increase the luminescence excitation of nanoscale materials. Efficient luminescence excitation increase is achieved via a gain-assisted waveguided energy transfer (G-WET). The G-WET concept consists on placing nanoscale materials atop of a waveguiding active (i.e. luminescent) layer with optical gain. Efficient energy transfer is thus achieved by exciting the nanoscale material via the tail of the waveguided mode of the active layer emission. The G-WET concept is demonstrated on both a nanothin layer of fluorescent sensitive polymer and on CdSe/ZnS quantum dots coated on ZnO thin film, experimentally proving up to an 8-fold increase in the fluorescence of the polymer and a 3-fold increase in the luminescence of the CdSe/ZnS depending of the active layer emission regime (stimulated vs spontaneous emission). Furthermore, we will discuss on the extended G-WET concept which consists on coating nanoscale materials on a nanostructured active layer. The nanostructured active layer offers the necessary photonic modulation and a high specific surface which can presumably lead to

  1. Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes.

    PubMed

    Lüer, Larry; Carey, Anne-Marie; Henry, Sarah; Maiuri, Margherita; Hacking, Kirsty; Polli, Dario; Cerullo, Giulio; Cogdell, Richard J

    2015-11-01

    Allochromatium vinosum (formerly Chromatium vinosum) purple bacteria are known to adapt their light-harvesting strategy during growth according to environmental factors such as temperature and average light intensity. Under low light illumination or low ambient temperature conditions, most of the LH2 complexes in the photosynthetic membranes form a B820 exciton with reduced spectral overlap with LH1. To elucidate the reason for this light and temperature adaptation of the LH2 electronic structure, we performed broadband femtosecond transient absorption spectroscopy as a function of excitation wavelength in A. vinosum membranes. A target analysis of the acquired data yielded individual rate constants for all relevant elementary energy transfer (ET) processes. We found that the ET dynamics in high-light-grown membranes was well described by a homogeneous model, with forward and backward rate constants independent of the pump wavelength. Thus, the overall B800→B850→B890→ Reaction Center ET cascade is well described by simple triexponential kinetics. In the low-light-grown membranes, we found that the elementary backward transfer rate constant from B890 to B820 was strongly reduced compared with the corresponding constant from B890 to B850 in high-light-grown samples. The ET dynamics of low-light-grown membranes was strongly dependent on the pump wavelength, clearly showing that the excitation memory is not lost throughout the exciton lifetime. The observed pump energy dependence of the forward and backward ET rate constants suggests exciton diffusion via B850→ B850 transfer steps, making the overall ET dynamics nonexponential. Our results show that disorder plays a crucial role in our understanding of low-light adaptation in A. vinosum. PMID:26536265

  2. Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes.

    PubMed

    Lüer, Larry; Carey, Anne-Marie; Henry, Sarah; Maiuri, Margherita; Hacking, Kirsty; Polli, Dario; Cerullo, Giulio; Cogdell, Richard J

    2015-11-01

    Allochromatium vinosum (formerly Chromatium vinosum) purple bacteria are known to adapt their light-harvesting strategy during growth according to environmental factors such as temperature and average light intensity. Under low light illumination or low ambient temperature conditions, most of the LH2 complexes in the photosynthetic membranes form a B820 exciton with reduced spectral overlap with LH1. To elucidate the reason for this light and temperature adaptation of the LH2 electronic structure, we performed broadband femtosecond transient absorption spectroscopy as a function of excitation wavelength in A. vinosum membranes. A target analysis of the acquired data yielded individual rate constants for all relevant elementary energy transfer (ET) processes. We found that the ET dynamics in high-light-grown membranes was well described by a homogeneous model, with forward and backward rate constants independent of the pump wavelength. Thus, the overall B800→B850→B890→ Reaction Center ET cascade is well described by simple triexponential kinetics. In the low-light-grown membranes, we found that the elementary backward transfer rate constant from B890 to B820 was strongly reduced compared with the corresponding constant from B890 to B850 in high-light-grown samples. The ET dynamics of low-light-grown membranes was strongly dependent on the pump wavelength, clearly showing that the excitation memory is not lost throughout the exciton lifetime. The observed pump energy dependence of the forward and backward ET rate constants suggests exciton diffusion via B850→ B850 transfer steps, making the overall ET dynamics nonexponential. Our results show that disorder plays a crucial role in our understanding of low-light adaptation in A. vinosum.

  3. A fluorescence resonance energy transfer activation sensor for Arf6.

    PubMed

    Hall, Brian; McLean, Mark A; Davis, Kathryn; Casanova, James E; Sligar, Steven G; Schwartz, Martin A

    2008-03-15

    The involvement of the small GTPase Arf6 in Rac activation, cell migration, and cancer invasiveness suggests that it is activated in a spatially and temporally regulated manner. Small GTPase activation has been imaged in cells using probes in which the GTPase and a fragment of a downstream effector protein are fused to fluorescent reporter proteins that constitute a fluorescence resonance energy transfer (FRET) donor/acceptor pair. Unlike other Ras family GTPases, the N terminus of Arf6 is critical for membrane targeting and, thus, cannot be modified by fusion to a fluorescent protein. We found that the previously described C-terminal green fluorescent protein (GFP) derivative also shows diminished membrane targeting. Therefore, we inserted a fluorescent protein into an inert loop within the Arf6 sequence. This fusion showed normal membrane targeting, nucleotide-dependent interaction with the downstream effector GGA3, and normal regulation by a GTPase-activating protein (GAP) and a guanine nucleotide exchange factor (GEF). Using the recently developed CyPET/YPET fluorescent proteins as a FRET pair, we found that Arf6-CyPET underwent efficient energy transfer when bound to YPET-GGA3 effector domain in intact cells. The addition of platelet-derived growth factor (PDGF) to fibroblasts triggered a rapid and transient increase in FRET, indicative of Arf6 activation. These reagents should be useful for investigations of Arf6 activation and function.

  4. Resonance Energy Transfer-Based Approaches to Study GPCRs.

    PubMed

    Ayoub, Mohammed Akli

    2016-01-01

    Since their discovery, G protein-coupled receptors (GPCRs) constitute one of the most studied proteins leading to important discoveries and perspectives in terms of their biology and implication in physiology and pathophysiology. This is mostly linked to the remarkable advances in the development and application of the biophysical resonance energy transfer (RET)-based approaches, including bioluminescence and fluorescence resonance energy transfer (BRET and FRET, respectively). Indeed, BRET and FRET have been extensively applied to study different aspects of GPCR functioning such as their activation and regulation either statically or dynamically, in real-time and intact cells. Consequently, our view on GPCRs has considerably changed opening new challenges for the study of GPCRs in their native tissues in the aim to get more knowledge on how these receptors control the biological responses. Moreover, the technological aspect of this field of research promises further developments for robust and reliable new RET-based assays that may be compatible with high-throughput screening as well as drug discovery programs.

  5. Ultrafast Single and Multiexciton Energy Transfer in Semiconductor Nanoplatelets

    NASA Astrophysics Data System (ADS)

    Schaller, Richard

    Photophysical processes such as fluorescence resonance energy transfer (FRET) enable optical antennas, wavelength down-conversion in light-emitting diodes (LEDs), and optical bio-sensing schemes. The rate and efficiency of this donor to acceptor transfer of excitation between chromophores dictates the utility of FRET and can unlock new device operation motifs including quantum-funnel solar cells and reduced gain thresholds. However, the fastest reported FRET time constants involving spherical quantum dots (QDs) (0.12-1 ns), do not outpace biexciton Auger recombination (0.01-0.1 ns), which impedes multiexciton-driven applications including electrically-pumped lasers and carrier-multiplication-enhanced photovoltaics. Precisely controlled, few-monolayer thick semiconductor nano-platelets with tens-of-nanometer diameters exhibit intense optical transitions and hundreds-of-picosecond Auger recombination, but heretofore lack FRET characterizations. We examine binary CdSe NPL solids and show that inter-plate FRET (~6-23 ps, presumably for co-facial arrangements) can occur 15-50 times faster than Auger recombination and demonstrate multiexcitonic FRET, making such materials ideal candidates for advanced technologies. This work was performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility under Contract No. DE-AC02-06CH11357.

  6. An ultra-efficient energy transfer beyond plasmonic light scattering

    SciTech Connect

    Fu, Sze-Ming; Zhong, Yan-Kai; Lin, Albert

    2014-11-14

    The energy transfer between nano-particles is of great importance for, solar cells, light-emitting diodes, nano-particle waveguides, and other photonic devices. This study shows through novel design and algorithm optimization, the energy transfer efficiency between plasmonic and dielectric nano-particles can be greatly improved. Using versatile designs including core-shell wrapping, supercells and dielectric mediated plasmonic scattering, 0.05 dB/μm attenuation can be achieved, which is 20-fold reduction over the baseline plasmonic nano-particle chain, and 8-fold reduction over the baseline dielectric nano-particle chain. In addition, it is also found that the dielectric nano-particle chains can actually be more efficient than the plasmonic ones, at their respective optimized geometry. The underlying physics is that although plasmonic nano-particles provide stronger coupling and field emission, the effect of plasmonic absorption loss is actually more dominant resulting in high attenuation. Finally, the group velocity for all design schemes proposed in this work is shown to be maintained above 0.4c, and it is found that the geometry optimization for transmission also boosts the group velocity.

  7. Calculation of resonance energy transfer in crowded biological membranes.

    PubMed

    Zimet, D B; Thevenin, B J; Verkman, A S; Shohet, S B; Abney, J R

    1995-04-01

    Analytical and numerical models were developed to describe fluorescence resonance energy transfer (RET) in crowded biological membranes. It was assumed that fluorescent donors were linked to membrane proteins and that acceptors were linked to membrane lipids. No restrictions were placed on the location of the donor within the protein or the partitioning of acceptors between the two leaflets of the bilayer; however, acceptors were excluded from the area occupied by proteins. Analytical equations were derived that give the average quantum yield of a donor at low protein concentrations. Monte Carlo simulations were used to generate protein and lipid distributions that were linked numerically with RET equations to determine the average quantum yield and the distribution of donor fluorescence lifetimes at high protein concentrations, up to 50% area fraction. The Monte Carlo results show such crowding always reduces the quantum yield, probably because crowding increases acceptor concentrations near donor-bearing proteins; the magnitude of the reduction increases monotonically with protein concentration. The Monte Carlo results also show that the distribution of fluorescence lifetimes can differ markedly, even for systems possessing the same average lifetime. The dependence of energy transfer on acceptor concentration, protein radius, donor position within the protein, and the fraction of acceptors in each leaflet was also examined. The model and results are directly applicable to the analysis of RET data obtained from biological membranes; their application should result in a more complete and accurate determination of the structures of membrane components. PMID:7787045

  8. Photoinduced energy transfer in transition metal complex oligomers

    SciTech Connect

    1997-06-01

    The work done over the past three years has been directed toward the preparation, characterization and photophysical examination of mono- and bimetallic diimine complexes. The work is part of a broader project directed toward the development of stable, efficient, light harvesting arrays of transition metal complex chromophores. One focus has been the synthesis of rigid bis-bidentate and bis-tridentate bridging ligands. The authors have managed to make the ligand bphb in multigram quantities from inexpensive starting materials. The synthetic approach used has allowed them to prepare a variety of other ligands which may have unique applications (vide infra). They have prepared, characterized and examined the photophysical behavior of Ru(II) and Re(I) complexes of the ligands. Energy donor/acceptor complexes of bphb have been prepared which exhibit nearly activationless energy transfer. Complexes of Ru(II) and Re(I) have also been prepared with other polyunsaturated ligands in which two different long lived (> 50 ns) excited states exist; results of luminescence and transient absorbance measurements suggest the two states are metal-to-ligand charge transfer and ligand localized {pi}{r_arrow}{pi}* triplets. Finally, the authors have developed methods to prepare polymetallic complexes which are covalently bound to various surfaces. The long term objective of this work is to make light harvesting arrays for the sensitization of large band gap semiconductors. Details of this work are provided in the body of the report.

  9. Photoinduced energy transfer in transition metal complex oligomers

    SciTech Connect

    1997-04-01

    The work we have done over the past three years has been directed toward the preparation, characterization and photophysical examination of mono- and bimetallic diimine complexes. The work is part of a broader project directed toward the development of stable, efficient, light harvesting arrays of transition metal complex chromophores. One focus has been the synthesis of rigid bis-bidentate and bis-tridentate bridging ligands. We have managed to make the ligand bphb in multigram quantities from inexpensive starting materials. The synthetic approach used has allowed us prepare a variety of other ligands which may have unique applications (vide infra). We have prepared, characterized and examined the photophysical behavior of Ru(II) and Re(I) complexes of the ligands. Energy donor/acceptor complexes of bphb have been prepared which exhibit nearly activationless energy transfer. Complexes of Ru(II) and Re(I) have also been prepared with other polyunsaturated ligands in which two different long lived ( > 50 ns) excited states exist; results of luminescence and transient absorbance measurements suggest the two states are metal-to-ligand charge transfer and ligand localized {pi}{r_arrow}{pi}* triplets. Finally, we have developed methods to prepare polymetallic complexes which are covalently bound to various surfaces. The long term objective of this work is to make light harvesting arrays for the sensitization of large band gap semiconductors. Details of this work are provided in the body of the report.

  10. Miniature fiber optic sensor based on fluorescence energy transfer

    NASA Astrophysics Data System (ADS)

    Meadows, David L.; Schultz, Jerome S.

    1992-04-01

    Optical fiber biosensors based on fluorescence assays have several distinct advantages when measuring biological analytes such as metabolites, cofactors, toxins, etc. Not only are optical signals immune to electronic interferences, but the polychromatic nature of most fluorochemical assays provides more potentially useful data about the system being studied. One of the most common difficulties normally encountered with optical biosensors is the inability to routinely recalibrate the optical and electronic components of the system throughout the life of the sensor. With this in mind, we present an optical fiber assay system for glucose based on a homogeneous singlet/singlet energy transfer assay along with the electronic instrumentation built to support the sensor system. In the sensor probe, glucose concentrations are indirectly measured from the level of fluorescence quenching caused by the homogeneous competition assay between TRITC labeled concanavalin A (receptor) and FITC labeled Dextran (ligand). The FITC signal is used to indicate glucose concentrations and the TRITC signal is used for internal calibration. Data is also presented on a protein derivatization procedure that was used to prevent aggregation of the receptor protein in solution. Also, a molecular model is described for the singlet/singlet energy transfer interactions that can occur in a model system composed of a monovalent ligand (FITC labeled papain) and a monovalent receptor (TRITC labeled concanavalin A).

  11. 76 FR 49764 - Steve Mason Enterprises, Inc., Green Energy Trans, LLC; Notice of Transfer of Exemption

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-11

    ... Energy Regulatory Commission Steve Mason Enterprises, Inc., Green Energy Trans, LLC; Notice of Transfer... transferred ownership of its exempted project property and facilities for Project No. 7742 to Green Energy.... \\4\\ E.g., John C. Jones, 99 FERC ] 61,372, at 62,580 n.2 (2002). 2. Green Energy Trans, LLC,...

  12. 78 FR 13661 - Energy Transfer Fuel, LP; Notice of Petition for Rate Approval

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-28

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Energy Transfer Fuel, LP; Notice of Petition for Rate Approval Take notice that on February 15, 2013, Energy Transfer Fuel, LP filed for approval of rates for...

  13. Size-Independent Energy Transfer in Biomimetic Nanoring Complexes

    PubMed Central

    2016-01-01

    Supramolecular antenna-ring complexes are of great interest due to their presence in natural light-harvesting complexes. While such systems are known to provide benefits through robust and efficient energy funneling, the relationship between molecular structure, strain (governed by nuclear coordinates and motion), and energy dynamics (arising from electronic behavior) is highly complex. We present a synthetic antenna-nanoring system based on a series of conjugated porphyrin chromophores ideally suited to explore such effects. By systematically varying the size of the acceptor nanoring, we reveal the interplay between antenna-nanoring binding, local strain, and energy dynamics on the picosecond time scale. Binding of the antenna unit creates a local strain in the nanoring, and this strain was measured as a function of the size of the nanoring, by UV–vis-NIR titration, providing information on the conformational flexibility of the system. Strikingly, the energy-transfer rate is independent of nanoring size, indicating the existence of strain-localized acceptor states, spread over about six porphyrin units, arising from the noncovalent antenna-nanoring association. PMID:27176553

  14. Power Loss Analysis and Comparison of Segmented and Unsegmented Energy Coupling Coils for Wireless Energy Transfer

    PubMed Central

    Tang, Sai Chun; McDannold, Nathan J.

    2015-01-01

    This paper investigated the power losses of unsegmented and segmented energy coupling coils for wireless energy transfer. Four 30-cm energy coupling coils with different winding separations, conductor cross-sectional areas, and number of turns were developed. The four coils were tested in both unsegmented and segmented configurations. The winding conduction and intrawinding dielectric losses of the coils were evaluated individually based on a well-established lumped circuit model. We found that the intrawinding dielectric loss can be as much as seven times higher than the winding conduction loss at 6.78 MHz when the unsegmented coil is tightly wound. The dielectric loss of an unsegmented coil can be reduced by increasing the winding separation or reducing the number of turns, but the power transfer capability is reduced because of the reduced magnetomotive force. Coil segmentation using resonant capacitors has recently been proposed to significantly reduce the operating voltage of a coil to a safe level in wireless energy transfer for medical implants. Here, we found that it can naturally eliminate the dielectric loss. The coil segmentation method and the power loss analysis used in this paper could be applied to the transmitting, receiving, and resonant coils in two- and four-coil energy transfer systems. PMID:26640745

  15. Carotenoid to chlorophyll energy transfer in the peridinin–chlorophyll-a–protein complex involves an intramolecular charge transfer state

    PubMed Central

    Zigmantas, Donatas; Hiller, Roger G.; Sundström, Villy; Polívka, Tomáš

    2002-01-01

    Carotenoids are, along with chlorophylls, crucial pigments involved in light-harvesting processes in photosynthetic organisms. Details of carotenoid to chlorophyll energy transfer mechanisms and their dependence on structural variability of carotenoids are as yet poorly understood. Here, we employ femtosecond transient absorption spectroscopy to reveal energy transfer pathways in the peridinin–chlorophyll-a–protein (PCP) complex containing the highly substituted carotenoid peridinin, which includes an intramolecular charge transfer (ICT) state in its excited state manifold. Extending the transient absorption spectra toward near-infrared region (600–1800 nm) allowed us to separate contributions from different low-lying excited states of peridinin. The results demonstrate a special light-harvesting strategy in the PCP complex that uses the ICT state of peridinin to enhance energy transfer efficiency. PMID:12486228

  16. Modular organization of cardiac energy metabolism: energy conversion, transfer and feedback regulation

    PubMed Central

    Guzun, R.; Kaambre, T.; Bagur, R.; Grichine, A.; Usson, Y.; Varikmaa, M.; Anmann, T.; Tepp, K.; Timohhina, N.; Shevchuk, I.; Chekulayev, V.; Boucher, F.; Santos, P. Dos; Schlattner, U.; Wallimann, T.; Kuznetsov, A. V.; Dzeja, P.; Aliev, M.; Saks, V.

    2014-01-01

    To meet high cellular demands, the energy metabolism of cardiac muscles is organized by precise and coordinated functioning of intracellular energetic units (ICEUs). ICEUs represent structural and functional modules integrating multiple fluxes at sites of ATP generation in mitochondria and ATP utilization by myofibrillar, sarcoplasmic reticulum and sarcolemma ion-pump ATPases. The role of ICEUs is to enhance the efficiency of vectorial intracellular energy transfer and fine tuning of oxidative ATP synthesis maintaining stable metabolite levels to adjust to intracellular energy needs through the dynamic system of compartmentalized phosphoryl transfer networks. One of the key elements in regulation of energy flux distribution and feedback communication is the selective permeability of mitochondrial outer membrane (MOM) which represents a bottleneck in adenine nucleotide and other energy metabolite transfer and microcompartmentalization. Based on the experimental and theoretical (mathematical modelling) arguments, we describe regulation of mitochondrial ATP synthesis within ICEUs allowing heart workload to be linearly correlated with oxygen consumption ensuring conditions of metabolic stability, signal communication and synchronization. Particular attention was paid to the structure–function relationship in the development of ICEU, and the role of mitochondria interaction with cytoskeletal proteins, like tubulin, in the regulation of MOM permeability in response to energy metabolic signals providing regulation of mitochondrial respiration. Emphasis was given to the importance of creatine metabolism for the cardiac energy homoeostasis. PMID:24666671

  17. Modular organization of cardiac energy metabolism: energy conversion, transfer and feedback regulation.

    PubMed

    Guzun, R; Kaambre, T; Bagur, R; Grichine, A; Usson, Y; Varikmaa, M; Anmann, T; Tepp, K; Timohhina, N; Shevchuk, I; Chekulayev, V; Boucher, F; Dos Santos, P; Schlattner, U; Wallimann, T; Kuznetsov, A V; Dzeja, P; Aliev, M; Saks, V

    2015-01-01

    To meet high cellular demands, the energy metabolism of cardiac muscles is organized by precise and coordinated functioning of intracellular energetic units (ICEUs). ICEUs represent structural and functional modules integrating multiple fluxes at sites of ATP generation in mitochondria and ATP utilization by myofibrillar, sarcoplasmic reticulum and sarcolemma ion-pump ATPases. The role of ICEUs is to enhance the efficiency of vectorial intracellular energy transfer and fine tuning of oxidative ATP synthesis maintaining stable metabolite levels to adjust to intracellular energy needs through the dynamic system of compartmentalized phosphoryl transfer networks. One of the key elements in regulation of energy flux distribution and feedback communication is the selective permeability of mitochondrial outer membrane (MOM) which represents a bottleneck in adenine nucleotide and other energy metabolite transfer and microcompartmentalization. Based on the experimental and theoretical (mathematical modelling) arguments, we describe regulation of mitochondrial ATP synthesis within ICEUs allowing heart workload to be linearly correlated with oxygen consumption ensuring conditions of metabolic stability, signal communication and synchronization. Particular attention was paid to the structure-function relationship in the development of ICEU, and the role of mitochondria interaction with cytoskeletal proteins, like tubulin, in the regulation of MOM permeability in response to energy metabolic signals providing regulation of mitochondrial respiration. Emphasis was given to the importance of creatine metabolism for the cardiac energy homoeostasis.

  18. Electronic energy transfer: Localized operator partitioning of electronic energy in composite quantum systems

    NASA Astrophysics Data System (ADS)

    Khan, Yaser; Brumer, Paul

    2012-11-01

    A Hamiltonian based approach using spatially localized projection operators is introduced to give precise meaning to the chemically intuitive idea of the electronic energy on a quantum subsystem. This definition facilitates the study of electronic energy transfer in arbitrarily coupled quantum systems. In particular, the decomposition scheme can be applied to molecular components that are strongly interacting (with significant orbital overlap) as well as to isolated fragments. The result defines a consistent electronic energy at all internuclear distances, including the case of separated fragments, and reduces to the well-known Förster and Dexter results in their respective limits. Numerical calculations of coherent energy and charge transfer dynamics in simple model systems are presented and the effect of collisionally induced decoherence is examined.

  19. Energy transfer simulation for radiantly heated and cooled enclosures

    SciTech Connect

    Chapman, K.S.; Zhang, P.

    1996-11-01

    This paper presents the development of a three-dimensional mathematical model to compute heat transfer within a radiantly heated or cooled room, which then calculates the mass-averaged room air temperature and the wall surface temperature distributions. The radiation formulation used in the model accommodates arbitrary placement of walls and objects within the room. The convection model utilizes Nusselt number correlations published in the open literature. The complete energy transfer model is validated by comparing calculated room temperatures to temperatures measured in a radiantly heated room. This three-dimensional model may be applied to a building to assist the heating/cooling system design engineer in sizing a radiant heating/cooling system. By coupling this model with a thermal comfort model, the comfort levels throughout the room can be easily and efficiently mapped for a given radiant heater/cooler location. In addition, obstacles such as airplanes, trucks, furniture, and partitions can be easily incorporated to determine their effect on the radiant heating system performance.

  20. Calibration of fluorescence resonance energy transfer in microscopy

    DOEpatents

    Youvan, Dougalas C.; Silva, Christopher M.; Bylina, Edward J.; Coleman, William J.; Dilworth, Michael R.; Yang, Mary M.

    2003-12-09

    Imaging hardware, software, calibrants, and methods are provided to visualize and quantitate the amount of Fluorescence Resonance Energy Transfer (FRET) occurring between donor and acceptor molecules in epifluorescence microscopy. The MicroFRET system compensates for overlap among donor, acceptor, and FRET spectra using well characterized fluorescent beads as standards in conjunction with radiometrically calibrated image processing techniques. The MicroFRET system also provides precisely machined epifluorescence cubes to maintain proper image registration as the sample is illuminated at the donor and acceptor excitation wavelengths. Algorithms are described that pseudocolor the image to display pixels exhibiting radiometrically-corrected fluorescence emission from the donor (blue), the acceptor (green) and FRET (red). The method is demonstrated on samples exhibiting FRET between genetically engineered derivatives of the Green Fluorescent Protein (GFP) bound to the surface of Ni chelating beads by histidine-tags.

  1. Application of fluorescence resonance energy transfer in protein studies

    PubMed Central

    Ma, Linlin; Yang, Fan; Zheng, Jie

    2014-01-01

    Since the physical process of fluorescence resonance energy transfer (FRET) was elucidated more than six decades ago, this peculiar fluorescence phenomenon has turned into a powerful tool for biomedical research due to its compatibility in scale with biological molecules as well as rapid developments in novel fluorophores and optical detection techniques. A wide variety of FRET approaches have been devised, each with its own advantages and drawbacks. Especially in the last decade or so, we are witnessing a flourish of FRET applications in biological investigations, many of which exemplify clever experimental design and rigorous analysis. Here we review the current stage of FRET methods development with the main focus on its applications in protein studies in biological systems, by summarizing the basic components of FRET techniques, most established quantification methods, as well as potential pitfalls, illustrated by example applications. PMID:25368432

  2. Fluorescence and energy transfer of tryptophans in Aplysia myoglobin.

    PubMed Central

    Janes, S M; Holtom, G; Ascenzi, P; Brunori, M; Hochstrasser, R M

    1987-01-01

    The fluorescence decay of tryptophan residues in apo and met Aplysia limacina myoglobin and sperm whale myoglobin were measured in aqueous solution at 10 degrees-15 degrees C. In all species, multiexponential behavior was observed in which the individual components displayed unique frequency-dependent emission characteristics. The results suggest that the tryptophan fluorescence in all met samples are quenched by rapid Forster energy transfer to the heme as predicted from the crystal geometry. Fluorescence from the apo protein is similar to that in solutions of free tryptophans. In addition, the fluorescence properties of the reversible thermal denaturation of Aplysia limacina met myoglobin was investigated between 25 degrees and 75 degrees C. PMID:3580491

  3. Calibration of fluorescence resonance energy transfer in microscopy

    DOEpatents

    Youvan, Douglas C.; Silva, Christopher M.; Bylina, Edward J.; Coleman, William J.; Dilworth, Michael R.; Yang, Mary M.

    2002-09-24

    Imaging hardware, software, calibrants, and methods are provided to visualize and quantitate the amount of Fluorescence Resonance Energy Transfer (FRET) occurring between donor and acceptor molecules in epifluorescence microscopy. The MicroFRET system compensates for overlap among donor, acceptor, and FRET spectra using well characterized fluorescent beads as standards in conjunction with radiometrically calibrated image processing techniques. The MicroFRET system also provides precisely machined epifluorescence cubes to maintain proper image registration as the sample is illuminated at the donor and acceptor excitation wavelengths. Algorithms are described that pseudocolor the image to display pixels exhibiting radiometrically-corrected fluorescence emission from the donor (blue), the acceptor (green) and FRET (red). The method is demonstrated on samples exhibiting FRET between genetically engineered derivatives of the Green Fluorescent Protein (GFP) bound to the surface of Ni chelating beads by histidine-tags.

  4. Transfer of electronic energy from cyclohexane to benzene to tetramethylphenylenediamine

    SciTech Connect

    Johnston, D.B.; Lipsky, S. )

    1991-03-07

    The absorption of 160-nm light by cyclohexane in mixtures of cyclohexane, benzene, and tetraphenylmethylenediamine results in an emission spectrum consisting of the simultaneous fluorescence from all three components. A mechanism for the development of this spectrum and its dependence on benzene concentration is constructed and shown to be quantitatively consistent with the results of independent measurements on the separate components. In the absence of tetraphenylmethylenediamine, the quenching of cyclohexane fluorescence by benzene is found to be well represented by the standard diffusion model but with important contributions from transient terms. However, the concomitant sensitization of benzene fluorescence via energy transfer from cyclohexane is found to occur with an efficiency factor of only 0.26 {plus minus} 0.02 per encounter.

  5. Resonance energy transfer: The unified theory via vector spherical harmonics

    NASA Astrophysics Data System (ADS)

    Grinter, Roger; Jones, Garth A.

    2016-08-01

    In this work, we derive the well-established expression for the quantum amplitude associated with the resonance energy transfer (RET) process between a pair of molecules that are beyond wavefunction overlap. The novelty of this work is that the field of the mediating photon is described in terms of a spherical wave rather than a plane wave. The angular components of the field are constructed in terms of vector spherical harmonics while Hankel functions are used to define the radial component. This approach alleviates the problem of having to select physically correct solution from non-physical solutions, which seems to be inherent in plane wave derivations. The spherical coordinate system allows one to easily decompose the photon's fields into longitudinal and transverse components and offers a natural way to analyse near-, intermediate-, and far-zone RET within the context of the relative orientation of the transition dipole moments for the two molecules.

  6. Resonance energy transfer: The unified theory via vector spherical harmonics.

    PubMed

    Grinter, Roger; Jones, Garth A

    2016-08-21

    In this work, we derive the well-established expression for the quantum amplitude associated with the resonance energy transfer (RET) process between a pair of molecules that are beyond wavefunction overlap. The novelty of this work is that the field of the mediating photon is described in terms of a spherical wave rather than a plane wave. The angular components of the field are constructed in terms of vector spherical harmonics while Hankel functions are used to define the radial component. This approach alleviates the problem of having to select physically correct solution from non-physical solutions, which seems to be inherent in plane wave derivations. The spherical coordinate system allows one to easily decompose the photon's fields into longitudinal and transverse components and offers a natural way to analyse near-, intermediate-, and far-zone RET within the context of the relative orientation of the transition dipole moments for the two molecules. PMID:27544087

  7. Fluorescence resonance energy transfer-based stoichiometry in living cells.

    PubMed Central

    Hoppe, Adam; Christensen, Kenneth; Swanson, Joel A

    2002-01-01

    Imaging of fluorescence resonance energy transfer (FRET) between fluorescently labeled molecules can measure the timing and location of intermolecular interactions inside living cells. Present microscopic methods measure FRET in arbitrary units, and cannot discriminate FRET efficiency and the fractions of donor and acceptor in complex. Here we describe a stoichiometric method that uses three microscopic fluorescence images to measure FRET efficiency, the relative concentrations of donor and acceptor, and the fractions of donor and acceptor in complex in living cells. FRET stoichiometry derives from the concept that specific donor-acceptor complexes will give rise to a characteristic FRET efficiency, which, if measured, can allow stoichiometric discrimination of interacting components. A first equation determines FRET efficiency and the fraction of acceptor molecules in complex with donor. A second equation determines the fraction of donor molecules in complex by estimating the donor fluorescence lost due to energy transfer. This eliminates the need for acceptor photobleaching to determine total donor concentrations and allows for repeated measurements from the same cell. A third equation obtains the ratio of total acceptor to total donor molecules. The theory and method were confirmed by microscopic measurements of fluorescence from cyan fluorescent protein (CFP), citrine, and linked CFP-Citrine fusion protein, in solutions and inside cells. Together, the methods derived from these equations allow sensitive, rapid, and repeatable detection of donor-, acceptor-, and donor-acceptor complex stoichiometry at each pixel in an image. By accurately imaging molecular interactions, FRET stoichiometry opens new areas for quantitative study of intracellular molecular networks. PMID:12496132

  8. Quantum Process Tomography for Energy Transfer Systems via Ultrafast Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yuen-Zhou, Joel

    2012-02-01

    The description of excited state dynamics in energy transfer systems constitutes a theoretical and experimental challenge in modern chemical physics. A spectroscopic protocol that systematically characterizes both coherent and dissipative processes of the probed chromophores is desired [1,2]. In this talk, I show that a set of two-color photon-echo experiments performs quantum state tomography (QST) of the one-exciton manifold of a dimer by reconstructing its density matrix in real time. This possibility in turn allows for a complete description of excited state dynamics via quantum process tomography (QPT). Simulations of a noisy QPT experiment for an inhomogeneously broadened ensemble of model excitonic dimers show that the protocol distills rich information about dissipative excitonic dynamics, which appears nontrivially hidden in the signal monitored in single realizations of four-wave mixing experiments Progress on the experimental side will be discussed, as well as new insights that QPT has offered on the understanding of 2D electronic and vibrational spectroscopy. [1] J. Yuen-Zhou, J. J. Krich, A. Aspuru-Guzik, Quantum state and process tomography of energy transfer systems via ultrafast spectroscopy Joel Yuen-Zhou, Jacob J. Krich, Masoud Mohseni and Al'an Aspuru-Guzik Proc. Nat. Acad. Sci. USA, Early Edition (2011). [2] J. Yuen-Zhou, A. Aspuru-Guzik, Quantum process tomography of molecular dimers from two-dimensional electronic spectroscopy I: General theory and application to homodimers Joel Yuen-Zhou and Al'an Aspuru-Guzik . Chem. Phys. 134, 134505 (2011).

  9. Adiabatic principles in atom-diatom collisional energy transfer

    SciTech Connect

    Hovingh, W.J.

    1993-01-01

    This work describes the application of numerical methods to the solution of the time dependent Schroedinger equation for non-reactive atom-diatom collisions in which only one of the degrees of freedom has been removed. The basic method involves expanding the wave function in a basis set in two of the diatomic coordinates in a body-fixed frame (with respect to the triatomic complex) and defining the coefficients in that expansion as functions on a grid in the collision coordinate. The wave function is then propagated in time using a split operator method. The bulk of this work is devoted to the application of this formalism to the study of internal rotational predissociation in NeHF, in which quasibound states of the triatom predissociate through the transfer of energy from rotation of the diatom into translational energy in the atom-diatom separation coordinate. The author analyzes the computed time dependent wave functions to calculate the lifetimes for several quasibound states; these are in agreement with time independent quantum calculations using the same potential. Moreover, the time dependent behavior of the wave functions themselves sheds light on the dynamics of the predissociation processes. Finally, the partial cross sections of the products in those processes is determined with multiple exit channels. These show strong selectivity in the orbital angular momentum of the outgoing fragments, which the author explains with an adiabatic channel interpretation of the wave function's dynamics. The author also suggests that the same formalism might profitably be used to investigate the quantum dynamics of [open quotes]quasiresonant vibration-rotation transfer[close quotes], in which remarkably strong propensity rules in certain inelastic atom-diatom collision arise from classical adiabatic invariance theory.

  10. On the use of Lineal Energy Measurements to Estimate Linear Energy Transfer Spectra

    NASA Technical Reports Server (NTRS)

    Adams, David A.; Howell, Leonard W., Jr.; Adam, James H., Jr.

    2007-01-01

    This paper examines the error resulting from using a lineal energy spectrum to represent a linear energy transfer spectrum for applications in the space radiation environment. Lineal energy and linear energy transfer spectra are compared in three diverse but typical space radiation environments. Different detector geometries are also studied to determine how they affect the error. LET spectra are typically used to compute dose equivalent for radiation hazard estimation and single event effect rates to estimate radiation effects on electronics. The errors in the estimations of dose equivalent and single event rates that result from substituting lineal energy spectra for linear energy spectra are examined. It is found that this substitution has little effect on dose equivalent estimates in interplanetary quiet-time environment regardless of detector shape. The substitution has more of an effect when the environment is dominated by solar energetic particles or trapped radiation, but even then the errors are minor especially if a spherical detector is used. For single event estimation, the effect of the substitution can be large if the threshold for the single event effect is near where the linear energy spectrum drops suddenly. It is judged that single event rate estimates made from lineal energy spectra are unreliable and the use of lineal energy spectra for single event rate estimation should be avoided.

  11. Energy Transfer Based Nanocomposite Scintillator for Radiation Detection

    NASA Astrophysics Data System (ADS)

    Aslam, Soha; Sahi, Sunil; Chen, Wei; Ma, Lun; Kenarangui, Rasool

    2014-09-01

    Scintillators are the materials that emit light upon irradiation with high energy radiation like X-ray or gamma-ray. Inorganic single crystal and organic (plastic and liquid) are the two most used scintillator types. Both of these scintillator kinds have advantages and disadvantages. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, single crystal scintillator such as NaI and CsI are very hygroscopic. On the other hand, organic scintillators have low density which limits their applications in gamma spectroscopy. Due to high quantum yield and size dependent emission, nanoparticles have attracted interested in various field of research. Here, we have studies the nanoparticles for radiation detection. We have synthesized nanoparticles of Cerium fluoride (CeF3), Zinc Oxide (ZnO), Cadmium Telluride (CdTe), Copper complex and Zinc sulfide (ZnS). We have used Fluorescence Resonance Energy Transfer (FRET) principle to enhance the luminescence properties of nanocomposite scintillator. Nanocomposites scintillators are structurally characterized with X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). Optical properties are studied using Photoluminescence, UV-Visible and X-ray. Enhancements in the luminescence are observed under UV and X-ray excitation. Preliminary studies shows nanocomposite scintillators are promising for radiation detection. Scintillators are the materials that emit light upon irradiation with high energy radiation like X-ray or gamma-ray. Inorganic single crystal and organic (plastic and liquid) are the two most used scintillator types. Both of these scintillator kinds have advantages and disadvantages. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, single crystal scintillator such as NaI and CsI are very hygroscopic. On the other hand, organic scintillators have low density which limits their applications in gamma spectroscopy. Due to high quantum

  12. Investigation of spectroscopy and the dual energy transfer mechanisms of Sm3+-doped telluroborate glasses

    NASA Astrophysics Data System (ADS)

    Van Do, Phan; Tuyen, Vu Phi; Quang, Vu Xuan; Hung, Le Xuan; Thanh, Luong Duy; Ngoc, Tran; Van Tam, Ngo; Huy, Bui The

    2016-05-01

    The absorption, luminescence, Raman spectra and lifetimes of Sm-doped alkali telluroborate glasses (TB glasses) TB:Sm3+ have been investigated. The dual energy transfers including energy transfer between Sm3+ - Sm3+ pairs and Sm3+ - non-bridging oxygen (NBO) intrinsic defects were investigated. The concentration quenching of luminescence intensity was explained by the non-radiative energy transfer between the Sm3+ ions through the cross-relaxation mechanism. The decay curves are single exponentials with low concentrations (lower 0.10 mol%) and become non-exponentials at higher concentrations. The non-exponential decay curves are fitted to the Inokuti and Hirayama model to give the energy transfer parameters between Sm3+ ions. The dominant interaction mechanism for energy transfer process is dipole-dipole interaction. The energy transfer induced Sm3+ photoluminescence enhancement in tellurite glass was experimentally studied and confirmed.

  13. Monthly Variations of Low-Energy Ballistic Transfers to Lunar Halo Orbits

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.

    2010-01-01

    The characteristics of low-energy transfers between the Earth and Moon vary from one month to the next largely due to the Earth's and Moon's non-circular, non-coplanar orbits in the solar system. This paper characterizes those monthly variations as it explores the trade space of low-energy lunar transfers across many months. Mission designers may use knowledge of these variations to swiftly design desirable low-energy lunar transfers in any given month.

  14. Proton Linear Energy Transfer measurement using Emulsion Cloud Chamber

    NASA Astrophysics Data System (ADS)

    Shin, Jae-ik; Park, Seyjoon; Kim, Haksoo; Kim, Meyoung; Jeong, Chiyoung; Cho, Sungkoo; Lim, Young Kyung; Shin, Dongho; Lee, Se Byeong; Morishima, Kunihiro; Naganawa, Naotaka; Sato, Osamu; Kwak, Jungwon; Kim, Sung Hyun; Cho, Jung Sook; Ahn, Jung Keun; Kim, Ji Hyun; Yoon, Chun Sil; Incerti, Sebastien

    2015-04-01

    This study proposes to determine the correlation between the Volume Pulse Height (VPH) measured by nuclear emulsion and Linear Energy Transfer (LET) calculated by Monte Carlo simulation based on Geant4. The nuclear emulsion was irradiated at the National Cancer Center (NCC) with a therapeutic proton beam and was installed at 5.2 m distance from the beam nozzle structure with various thicknesses of water-equivalent material (PMMA) blocks to position with specific positions along the Bragg curve. After the beam exposure and development of the emulsion films, the films were scanned by S-UTS developed in Nagoya University. The proton tracks in the scanned films were reconstructed using the 'NETSCAN' method. Through this procedure, the VPH can be derived from each reconstructed proton track at each position along the Bragg curve. The VPH value indicates the magnitude of energy loss in proton track. By comparison with the simulation results obtained using Geant4, we found the correlation between the LET calculated by Monte Carlo simulation and the VPH measured by the nuclear emulsion.

  15. 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

  16. Extended emission wavelength of random dye lasers by exploiting radiative and non-radiative energy transfer

    NASA Astrophysics Data System (ADS)

    Wan Ismail, Wan Zakiah; Goldys, Ewa M.; Dawes, Judith M.

    2016-02-01

    We demonstrate long-wavelength operation (>700 nm) of random dye lasers (using a methylene blue dye) with the addition of rhodamine 6G and titania, enabled by radiative and non-radiative energy transfer. The pump energy is efficiently absorbed and transferred to the acceptors, to support lasing in random dye lasers in the near infrared. The optimum random laser performance with the highest emission intensity and the lowest lasing threshold was achieved for a concentration of methylene blue as the acceptor equal to 6× the concentration of rhodamine 6G (donor). Excessive levels of methylene blue increased the lasing threshold and broadened the methylene blue emission linewidth due to dye quenching from re-absorption. This is due to competition between the donor emission and energy transfer and between absorption loss and fluorescence quenching. The radiative and non-radiative energy transfer is analyzed as a function of the acceptor concentration and pump energy density, with consideration of the spectral overlap. The dependence of the radiative and non-radiative transfer efficiency on the acceptor concentration is obtained, and the energy transfer parameters, including the radiative and non-radiative energy transfer rate constants ( K R and K NR), are investigated using Stern-Volmer analysis. The analysis indicates that radiative energy transfer is the dominant energy transfer mechanism in this system.

  17. 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.

  18. Conjugated-polymer-based energy-transfer systems for antimicrobial and anticancer applications.

    PubMed

    Yuan, Huanxiang; Wang, Bing; Lv, Fengting; Liu, Libing; Wang, Shu

    2014-10-29

    Conjugated polymers (CPs) attract a lot of attention in sensing, imaging, and biomedical applications because of recent achievements that are highlighted in this Research News article. A brief review of recent progress in the application of CP-based energy-transfer systems in antimicrobial and anticancer treatments is provided. The transfer of excitation energy from CPs to photosensitizers leads to the generation of reactive oxygen species (ROS) that are able to efficiently kill pathogenic microorganisms and cancer cells in the surroundings. Both fluorescence resonance energy transfer (FRET) and bioluminescence energy transfer (BRET) modes are discussed. PMID:24711269

  19. Local Measurement of Fuel Energy Deposition and Heat Transfer Environment During Fuel Lifetime Using Controlled Calorimetry

    SciTech Connect

    Don W. Miller; Andrew Kauffmann; Eric Kreidler; Dongxu Li; Hanying Liu; Daniel Mills; Thomas D. Radcliff; Joseph Talnagi

    2001-12-31

    A comprehensive description of the accomplishments of the DOE grant titled, ''Local Measurement of Fuel Energy Deposition and Heat Transfer Environment During Fuel Lifetime using Controlled Calorimetry''.

  20. Non-Radiative Energy Transfer Mediated by Hybrid Light-Matter States.

    PubMed

    Zhong, Xiaolan; Chervy, Thibault; Wang, Shaojun; George, Jino; Thomas, Anoop; Hutchison, James A; Devaux, Eloise; Genet, Cyriaque; Ebbesen, Thomas W

    2016-05-17

    We present direct evidence of enhanced non-radiative energy transfer between two J-aggregated cyanine dyes strongly coupled to the vacuum field of a cavity. Excitation spectroscopy and femtosecond pump-probe measurements show that the energy transfer is highly efficient when both the donor and acceptor form light-matter hybrid states with the vacuum field. The rate of energy transfer is increased by a factor of seven under those conditions as compared to the normal situation outside the cavity, with a corresponding effect on the energy transfer efficiency. The delocalized hybrid states connect the donor and acceptor molecules and clearly play the role of a bridge to enhance the rate of energy transfer. This finding has fundamental implications for coherent energy transport and light-energy harvesting.

  1. The transfer between electron bulk kinetic energy and thermal energy in collisionless magnetic reconnection

    SciTech Connect

    Lu, San; Lu, Quanming; Huang, Can; Wang, Shui

    2013-06-15

    By performing two-dimensional particle-in-cell simulations, we investigate the transfer between electron bulk kinetic and electron thermal energy in collisionless magnetic reconnection. In the vicinity of the X line, the electron bulk kinetic energy density is much larger than the electron thermal energy density. The evolution of the electron bulk kinetic energy is mainly determined by the work done by the electric field force and electron pressure gradient force. The work done by the electron gradient pressure force in the vicinity of the X line is changed to the electron enthalpy flux. In the magnetic island, the electron enthalpy flux is transferred to the electron thermal energy due to the compressibility of the plasma in the magnetic island. The compression of the plasma in the magnetic island is the consequence of the electromagnetic force acting on the plasma as the magnetic field lines release their tension after being reconnected. Therefore, we can observe that in the magnetic island the electron thermal energy density is much larger than the electron bulk kinetic energy density.

  2. Interaction mechanism for energy transfer from Ce to Tb ions in silica

    NASA Astrophysics Data System (ADS)

    Seed Ahmed, H. A. A.; Chae, W. S.; Ntwaeaborwa, O. M.; Kroon, R. E.

    2016-01-01

    Energy transfer phenomena can play an important role in the development of luminescent materials. In this study, numerical simulations based on theoretical models of non-radiative energy transfer are compared to experimental results for Ce, Tb co-doped silica. Energy transfer from the donor (Ce) to the acceptor (Tb) resulted in a decrease in the Ce luminescence intensity and lifetime. The decrease in intensity corresponded best with the energy transfer models based on the exchange interaction and the dipole-dipole interaction. The critical transfer distance obtained from the fitting using both these models is around 2 nm. Since the exchange interaction requires a distance shorter than 1 nm to occur, the mechanism most likely to account for the energy transfer is concluded to be the dipole-dipole interaction. This is supported by an analysis of the lifetime data.

  3. Definition and determination of the triplet-triplet energy transfer reaction coordinate.

    PubMed

    Zapata, Felipe; Marazzi, Marco; Castaño, Obis; Acuña, A Ulises; Frutos, Luis Manuel

    2014-01-21

    A definition of the triplet-triplet energy transfer reaction coordinate within the very weak electronic coupling limit is proposed, and a novel theoretical formalism is developed for its quantitative determination in terms of internal coordinates The present formalism permits (i) the separation of donor and acceptor contributions to the reaction coordinate, (ii) the identification of the intrinsic role of donor and acceptor in the triplet energy transfer process, and (iii) the quantification of the effect of every internal coordinate on the transfer process. This formalism is general and can be applied to classical as well as to nonvertical triplet energy transfer processes. The utility of the novel formalism is demonstrated here by its application to the paradigm of nonvertical triplet-triplet energy transfer involving cis-stilbene as acceptor molecule. In this way the effect of each internal molecular coordinate in promoting the transfer rate, from triplet donors in the low and high-energy limit, could be analyzed in detail.

  4. Quantum calculations for rotational energy transfer in nitrogen molecule collisions

    NASA Astrophysics Data System (ADS)

    Huo, Winifred M.; Green, Sheldon

    1996-05-01

    Rotational energy transfer in collisions of nitrogen molecules has been studied theoretically, using the N2-N2 rigid-rotor potential of van der Avoird et al. [J. Chem. Phys. 84, 1629 (1986)]. For benchmarking purposes, converged close coupling (CC) calculations have been carried out to a total energy of about 200 cm-1. Coupled states (CS) approximation calculations have been carried out to a total energy of 680 cm-1, and infinite order sudden (IOS) approximation calculations have also been carried out. The CC and CS cross sections have been obtained both with and without identical molecule exchange symmetry, whereas exchange was neglected in the IOS calculations. The CS results track the CC cross sections rather well: between 113-219 cm-1 the average deviation is 14%, with accuracy improving at higher energy. Comparison between the CS and IOS cross sections at the high energy end of the CS calculations, 500-680 cm-1, shows that IOS is sensitive to the amount of inelasticity and the results for large ΔJ transitions are subject to larger errors. State-to-state cross sections with even and odd exchange symmetry agree to better than 2% and are well represented as a sum of direct and exchange cross sections for distinguishable molecules, an indication of the applicability of a classical treatment for this system. This result, however, does not apply to partial cross sections for given total J, but arises from a near cancellation of the interference terms between even and odd exchange symmetries on summing over partial waves. In order to compare with experimental data for rotational excitation rates of N2 in the n=1 excited vibrational level colliding with ground vibrational level (n=0) bath N2 molecules, it is assumed that exchange scattering between molecules in different vibrational levels is negligible and direct scattering is independent of n so that distinguishable molecule rigid rotor rates may be used. With these assumptions good agreement is obtained. Although

  5. Peculiarities of collisional excitation transfer with excited screened energy levels of atoms

    SciTech Connect

    Gerasimov, V. A.; Gerasimov, V. V.; Pavlinskiy, A. V.

    2007-09-15

    We report an experimental discovery of deviations from the known regularities in collisional excitation transfer processes for metal atoms. The collisional excitation transfer with excited screened energy levels of thulium and dysprosium atoms is studied. The selecting role of the screening 6s shell in collisional excitation transfer is shown.

  6. Low-energy plasma immersion ion implantation to induce DNA transfer into bacterial E. coli

    NASA Astrophysics Data System (ADS)

    Sangwijit, K.; Yu, L. D.; Sarapirom, S.; Pitakrattananukool, S.; Anuntalabhochai, S.

    2015-12-01

    Plasma immersion ion implantation (PIII) at low energy was for the first time applied as a novel biotechnology to induce DNA transfer into bacterial cells. Argon or nitrogen PIII at low bias voltages of 2.5, 5 and 10 kV and fluences ranging from 1 × 1012 to 1 × 1017 ions/cm2 treated cells of Escherichia coli (E. coli). Subsequently, DNA transfer was operated by mixing the PIII-treated cells with DNA. Successes in PIII-induced DNA transfer were demonstrated by marker gene expressions. The induction of DNA transfer was ion-energy, fluence and DNA-size dependent. The DNA transferred in the cells was confirmed functioning. Mechanisms of the PIII-induced DNA transfer were investigated and discussed in terms of the E. coli cell envelope anatomy. Compared with conventional ion-beam-induced DNA transfer, PIII-induced DNA transfer was simpler with lower cost but higher efficiency.

  7. Efficient near-field wireless energy transfer using adiabatic system variations

    DOEpatents

    Hamam, Rafif E; Karalis, Aristeidis; Joannopoulos, John D; Soljacic, Marin

    2014-09-16

    Disclosed is a method for transferring energy wirelessly including transferring energy wirelessly from a first resonator structure to an intermediate resonator structure, wherein the coupling rate between the first resonator structure and the intermediate resonator structure is .kappa..sub.1B, transferring energy wirelessly from the intermediate resonator structure to a second resonator structure, wherein the coupling rate between the intermediate resonator structure and the second resonator structure is .kappa..sub.B2, and during the wireless energy transfers, adjusting at least one of the coupling rates .kappa..sub.1B and .kappa..sub.B2 to reduce energy accumulation in the intermediate resonator structure and improve wireless energy transfer from the first resonator structure to the second resonator structure through the intermediate resonator structure.

  8. Efficient near-field wireless energy transfer using adiabatic system variations

    DOEpatents

    Hamam, Rafif E.; Karalis, Aristeidis; Joannopoulos, John D.; Soljacic, Marin

    2013-01-29

    Disclosed is a method for transferring energy wirelessly including transferring energy wirelessly from a first resonator structure to an intermediate resonator structure, wherein the coupling rate between the first resonator structure and the intermediate resonator structure is .kappa..sub.1B, transferring energy wirelessly from the intermediate resonator structure to a second resonator structure, wherein the coupling rate between the intermediate resonator structure and the second resonator structure is .kappa..sub.B2, and during the wireless energy transfers, adjusting at least one of the coupling rates .kappa..sub.1B and .kappa..sub.B2 to reduce energy accumulation in the intermediate resonator structure and improve wireless energy transfer from the first resonator structure to the second resonator structure through the intermediate resonator structure.

  9. Generalized Förster-Dexter theory of photoinduced intramolecular energy transfer

    NASA Astrophysics Data System (ADS)

    Lin, S. H.; Xiao, W. Z.; Dietz, W.

    1993-05-01

    In this paper, we generalize the Förster-Dexter theory to treat photoinduced electronic energy transfer for a system in dense media and for an isolated system (i.e., a system in the collision-free condition). Instead of expressing the rate of energy transfer in terms of spectral overlap, we obtain the expression of the energy-transfer rate constant by evaluating a Fourier integral using the saddle-point method. In this way, the energy-gap dependence and the effect of temperature and the isotope effect on the energy transfer can be easily studied. The effect of bridge groups connecting between donor and acceptor on the energy transfer is also studied.

  10. Spectral Energy Transfer and Dissipation of Magnetic Energy from Fluid to Kinetic Scales

    SciTech Connect

    Bowers, K.; Li, H.

    2007-01-19

    We investigate the magnetic energy transfer from the fluid to kinetic scales and dissipation processes using three-dimensional fully kinetic particle-in-cell plasma simulations. The nonlinear evolution of a sheet pinch is studied where we show that it exhibits both fluid scale global relaxation and kinetic scale collisionless reconnection at multiple resonant surfaces. The interactions among collisionless tearing modes destroy the original flux surfaces and produce stochastic fields, along with generating sheets and filaments of intensified currents. In addition, the magnetic energy is transferred from the original shear length scale both to the large scales due to the global relaxation and to the smaller, kinetic scales for dissipation. The dissipation is dominated by the thermal or pressure effect in the generalized Ohm's law, and electrons are preferentially accelerated.

  11. Quantal Aspects of - Energy Transfer and Photodissociation of Oscillators.

    NASA Astrophysics Data System (ADS)

    Tanner, John Joseph

    1988-12-01

    Our first chapter examines the mechanism by which molecular rotation enhances vibrational relaxation of a diatomic molecule. Three factors are discussed, lowering by rotational transitions of the vibrational energy defect, coupling due to potential matrix elements off diagonal in rotational state, and additional phase shifts introduced into the incoming and outgoing waves by anisotropy in the intermolecular potential. The distorted wave solution of the coupled states scattering equations elucidates the importance of each factor for H_2(v = 1) - He, CO(v = 1) - H_2, and for vibrational energy transfer from H_2 (v = 1) to CO(v = 0,1,2). Rotation is found to play both an energetic and a dynamical role. In the energetic role, rotation lowers the vibrational energy defect and thereby enhances vibrational relaxation, while the dynamic contribution takes the form of additional phase shifts introduced into the incoming and outgoing waves by the potential anisotropy. Our results suggest that molecular anisotropy in the region of the classical turning point is an important factor in the rotational enhancement observed in recent comparisons of CSA and IOSA vibrational relaxation rate constants for the N_2-He and CO-He systems. In the second chapter we study the response of a highly excited Morse oscillator with 179 bound states to an intense, below resonance electromagnetic field. A dynamic, quantal description of dissociation is obtained from an inspection of the time dependent wavefunction. The bound to continuum transitions which occur during dissociation involve the emission of a high energy, coherent wave which propagates to infinity--a feature not observed in other studies of the periodically driven Morse oscillator. Initially, the exodus of this wave results in a rapid increase in the dissociation probability. However, at longer times the dissociation slows down and concurrently the system is localized in the bound state basis, indicating that even though the classical

  12. Single-collision studies of energy transfer and chemical reaction

    SciTech Connect

    Valentini, J.J.

    1993-12-01

    The research focus in this group is state-to-state dynamics of reaction and energy transfer in collisions of free radicals such as H, OH, and CH{sub 3} with H{sub 2}, alkanes, alcohols and other hydrogen-containing molecules. The motivation for the work is the desire to provide a detailed understanding of the chemical dynamics of prototype reactions that are important in the production and utilization of energy sources, most importantly in combustion. The work is primarily experimental, but with an important and growing theoretical/computational component. The focus of this research program is now on reactions in which at least one of the reactants and one of the products is polyatomic. The objective is to determine how the high dimensionality of the reactants and products differentiates such reactions from atom + diatom reactions of the same kinematics and energetics. The experiments use highly time-resolved laser spectroscopic methods to prepare reactant states and analyze the states of the products on a single-collision time scale. The primary spectroscopic tool for product state analysis is coherent anti-Stokes Raman scattering (CARS) spectroscopy. CARS is used because of its generality and because the extraction of quantum state populations from CARS spectra is straightforward. The combination of the generality and easy analysis of CARS makes possible absolute cross section measurements (both state-to-state and total), a particularly valuable capability for characterizing reactive and inelastic collisions. Reactant free radicals are produced by laser photolysis of appropriate precursors. For reactant vibrational excitation stimulated Raman techniques are being developed and implemented.

  13. Electronic resonance with anticorrelated pigment vibrations drives photosynthetic energy transfer outside the adiabatic framework

    PubMed Central

    Tiwari, Vivek; Peters, William K.; Jonas, David M.

    2013-01-01

    The delocalized, anticorrelated component of pigment vibrations can drive nonadiabatic electronic energy transfer in photosynthetic light-harvesting antennas. In femtosecond experiments, this energy transfer mechanism leads to excitation of delocalized, anticorrelated vibrational wavepackets on the ground electronic state that exhibit not only 2D spectroscopic signatures attributed to electronic coherence and oscillatory quantum energy transport but also a cross-peak asymmetry not previously explained by theory. A number of antennas have electronic energy gaps matching a pigment vibrational frequency with a small vibrational coordinate change on electronic excitation. Such photosynthetic energy transfer steps resemble molecular internal conversion through a nested intermolecular funnel. PMID:23267114

  14. Modeling the Transfer Function for the Dark Energy Survey

    DOE PAGESBeta

    Chang, C.

    2015-03-04

    We present a forward-modeling simulation framework designed to model the data products from the Dark Energy Survey (DES). This forward-model process can be thought of as a transfer function—a mapping from cosmological/astronomical signals to the final data products used by the scientists. Using output from the cosmological simulations (the Blind Cosmology Challenge), we generate simulated images (the Ultra Fast Image Simulator) and catalogs representative of the DES data. In this work we demonstrate the framework by simulating the 244 deg2 coadd images and catalogs in five bands for the DES Science Verification data. The simulation output is compared with themore » corresponding data to show that major characteristics of the images and catalogs can be captured. We also point out several directions of future improvements. Two practical examples—star-galaxy classification and proximity effects on object detection—are then used to illustrate how one can use the simulations to address systematics issues in data analysis. With clear understanding of the simplifications in our model, we show that one can use the simulations side-by-side with data products to interpret the measurements. This forward modeling approach is generally applicable for other upcoming and future surveys. It provides a powerful tool for systematics studies that is sufficiently realistic and highly controllable.« less

  15. Concentric Förster resonance energy transfer imaging.

    PubMed

    Wu, Miao; Algar, W Russ

    2015-08-18

    Concentric Förster resonance energy transfer (cFRET) configurations based on semiconductor quantum dots (QDs) are promising probes for biological sensing because they offer multiplexing capability in a single vector with robust ratiometric detection by exploiting a network of FRET pathways. To expand the scope and utility of cFRET probes, it is necessary to develop and validate cFRET imaging methodology. In this technical note, we present such a methodology using a protease-sensitive cFRET configuration that comprises a green-emitting QD, Alexa Fluor 555 (A555), and Alexa Fluor 647 (A647). Photoluminescence (PL) images were acquired with three filter-based emission channels to permit measurement of A555/QD and A647/QD PL ratios. With reference to calibration samples, these PL ratios were used to calculate quantitative progress curves for proteolytic activity in regions of interest in the acquired images. Importantly, the imaging methodology reproduces quantitative results obtained with a monochromator-based fluorescence plate reader. Spatiotemporal resolution is demonstrated by tracking the activity of two prototypical proteases, trypsin and chymotrypsin, as they diffuse down the length of a capillary. This methodology is expected to enable the future use of cFRET probes for cellular sensing and other imaging assays. PMID:26214686

  16. Heavy ion mutagenesis: linear energy transfer effects and genetic linkage

    NASA Technical Reports Server (NTRS)

    Kronenberg, A.; Gauny, S.; Criddle, K.; Vannais, D.; Ueno, A.; Kraemer, S.; Waldren, C. A.; Chatterjee, A. (Principal Investigator)

    1995-01-01

    We have characterized a series of 69 independent mutants at the endogenous hprt locus of human TK6 lymphoblasts and over 200 independent S1-deficient mutants of the human x hamster hybrid cell line AL arising spontaneously or following low-fluence exposures to densely ionizing Fe ions (600 MeV/amu, linear energy transfer = 190 keV/microns). We find that large deletions are common. The entire hprt gene (> 44 kb) was missing in 19/39 Fe-induced mutants, while only 2/30 spontaneous mutants lost the entire hprt coding sequence. When the gene of interest (S1 locus = M1C1 gene) is located on a nonessential human chromosome 11, multilocus deletions of several million base pairs are observed frequently. The S1 mutation frequency is more than 50-fold greater than the frequency of hprt mutants in the same cells. Taken together, these results suggest that low-fluence exposures to Fe ions are often cytotoxic due to their ability to create multilocus deletions that may often include the loss of essential genes. In addition, the tumorigenic potential of these HZE heavy ions may be due to the high potential for loss of tumor suppressor genes. The relative insensitivity of the hprt locus to mutation is likely due to tight linkage to a gene that is required for viability.

  17. Theory of coherent resonance energy transfer for coherent initial condition.

    PubMed

    Jang, Seogjoo

    2009-10-28

    A theory of coherent resonance energy transfer [Jang et al., J. Chem. Phys. 129, 101104 (2008)] is extended for coherent initial condition. For the situation where the initial excitation is an arbitrary linear combination of donor and acceptor excitations, a second order time local quantum master equation combined with polaron transformation is derived. Inhomogeneous terms in the resulting equation have contributions not only from initial donor and acceptor populations but also from their coherence terms. Numerical tests are performed for general super Ohmic spectral density where the bath degrees of freedom coupled to donor and acceptor can be correlated with each other. Calculation results demonstrate sensitivity of early nonstationary population dynamics on the relative sign of initial donor and acceptor excitation states. It is shown that contribution of inhomogeneous terms is more significant for coherent initial condition than for localized one. The overall model calculations provide details of the interplay between quantum coherence and nonequilibrium/non-Markovian effects in the time dependent donor population dynamics.

  18. Fluorescence resonance energy transfer in the studies of guanine quadruplexes.

    PubMed

    Juskowiak, Bernard; Takenaka, Shigeori

    2006-01-01

    A guanine (G)-quadruplex DNA motif has recently emerged as a biologically important structure that is believed to interfere with telomere maintenance by telomerase. G-quadruplexes exhibit four-stranded structures containing one or more nucleic acid strands with central channel able to accommodate metal cations. Coordination of certain metal cations stabilizes G-quadruplex as with some promising small organic molecules that promote the formation and/or stabilization of G-quadruplex. Among many techniques employed to explore properties of G-quadruplexes, the fluorescence resonance energy transfer (FRET) technique has been recognized as a powerful tool to study G-quadruplex formation. This review summarizes the current developments in the uses of FRET technique for the fundamental structural investigations and its practical applications. Applications include FRET-based selection of efficient quadruplex-binding ligands, design of a nanomolecular machine, and a molecular aptamer beacon for protein recognition. We also describe a technique for detection of potassium ions in aqueous solution with the use of quadruplex-based sensor (potassium-sensing oligonucleotide).

  19. Ultrafast energy transfer in water-AOT reverse micelles.

    PubMed

    Cringus, Dan; Bakulin, Artem; Lindner, Jörg; Vöhringer, Peter; Pshenichnikov, Maxim S; Wiersma, Douwe A

    2007-12-27

    A spectroscopic investigation of the vibrational dynamics of water in a geometrically confined environment is presented. Reverse micelles of the ternary microemulsion H2O/AOT/n-octane (AOT = bis-2-ethylhexyl sulfosuccinate or aerosol-OT) with diameters ranging from 1 to 10 nm are used as a model system for nanoscopic water droplets surrounded by a soft-matter boundary. Femtosecond nonlinear infrared spectroscopy in the OH-stretching region of H2O fully confirms the core/shell model, in which the entrapped water molecules partition onto two molecular subensembles: a bulk-like water core and a hydration layer near the ionic surfactant headgroups. These two distinct water species display different relaxation kinetics, as they do not exchange vibrational energy. The observed spectrotemporal ultrafast response exhibits a local character, indicating that the spatial confinement influences approximately one molecular layer located near the water-amphiphile boundary. The core of the encapsulated water droplet is similar in its spectroscopic properties to the bulk phase of liquid water, i.e., it does not display any true confinement effects such as droplet-size-dependent vibrational lifetimes or rotational correlation times. Unlike in bulk water, no intermolecular transfer of OH-stretching quanta occurs among the interfacial water molecules or from the hydration shell to the bulk-like core, indicating that the hydrogen bond network near the H2O/AOT interface is strongly disrupted. PMID:18047308

  20. Modeling the Transfer Function for the Dark Energy Survey

    SciTech Connect

    Chang, C.

    2015-03-04

    We present a forward-modeling simulation framework designed to model the data products from the Dark Energy Survey (DES). This forward-model process can be thought of as a transfer function—a mapping from cosmological/astronomical signals to the final data products used by the scientists. Using output from the cosmological simulations (the Blind Cosmology Challenge), we generate simulated images (the Ultra Fast Image Simulator) and catalogs representative of the DES data. In this work we demonstrate the framework by simulating the 244 deg2 coadd images and catalogs in five bands for the DES Science Verification data. The simulation output is compared with the corresponding data to show that major characteristics of the images and catalogs can be captured. We also point out several directions of future improvements. Two practical examples—star-galaxy classification and proximity effects on object detection—are then used to illustrate how one can use the simulations to address systematics issues in data analysis. With clear understanding of the simplifications in our model, we show that one can use the simulations side-by-side with data products to interpret the measurements. This forward modeling approach is generally applicable for other upcoming and future surveys. It provides a powerful tool for systematics studies that is sufficiently realistic and highly controllable.

  1. Reorganization energy of electron transfer processes in ionic fluids: A molecular Debye-Hückel approach

    NASA Astrophysics Data System (ADS)

    Xiao, Tiejun; Song, Xueyu

    2013-03-01

    The reorganization energy of electron transfer processes in ionic fluids is studied under the linear response approximation using a molecule Debye-Hückel theory. Reorganization energies of some model reactants of electron transfer reactions in molten salts are obtained from molecular simulations and a molecule Debye-Hückel approach. Good agreements between simulation results and the results from our theoretical calculations using the same model Hamiltonian are found. Applications of our theory to electron transfer reactions in room temperature ionic liquids further demonstrate that our theoretical approach presents a reliable and accurate methodology for the estimation of reorganization energies of electron transfer reactions in ionic fluids.

  2. Cyanine dyes with high-absorbance cross section as donor chromophores in energy transfer labels

    DOEpatents

    Glazer, A.N.; Mathies, R.A.; Hung, S.C.; Ju, J.

    1998-12-29

    Cyanine dyes are used as the donor fluorophore in energy transfer labels in which light energy is absorbed by a donor fluorophore and transferred to an acceptor fluorophore which responds to the transfer by emitting fluorescent light for detection. The cyanine dyes impart an unusually high sensitivity to the labels thereby improving their usefulness in a wide variety of biochemical procedures, particularly nucleic acid sequencing, nucleic acid fragment sizing, and related procedures. 22 figs.

  3. Forster resonance energy transfer in the system of human serum albumin-xanthene dyes

    NASA Astrophysics Data System (ADS)

    Kochubey, V. I.; Pravdin, A. B.; Melnikov, A. G.; Konstantinova, I.; Alonova, I. V.

    2016-04-01

    The processes of interaction of fluorescent probes: eosin and erythrosine with human serum albumin (HSA) were studied by the methods of absorption and fluorescence spectroscopy. Extinction coefficients of probes were determined. Critical transfer radius and the energy transfer efficiency were defined by fluorescence quenching of HSA. Analysis of the excitation spectra of HSA revealed that the energy transfer process is carried out mainly between tryptophanyl and probes.

  4. Methods of sequencing and detection using energy transfer labels with cyanine dyes as donor chromophores

    DOEpatents

    Glazer, Alexander N.; Mathies, Richard A.; Hung, Su-Chun; Ju, Jingyue

    2000-01-01

    Cyanine dyes are used as the donor fluorophore in energy transfer labels in which light energy is absorbed by a donor fluorophore and transferred to an acceptor fluorophore which responds to the transfer by emitting fluorescent light for detection. The cyanine dyes impart an unusually high sensitivity to the labels thereby improving their usefulness in a wide variety of biochemical procedures, particularly nucleic acid sequencing, nucleic acid fragment sizing, and related procedures.

  5. Cyanine dyes with high-absorbance cross section as donor chromophores in energy transfer labels

    DOEpatents

    Glazer, Alexander N.; Mathies, Richard A.; Hung, Su-Chun; Ju, Jingyue

    1998-01-01

    Cyanine dyes are used as the donor fluorophore in energy transfer labels in which light energy is absorbed by a donor fluorophore and transferred to an acceptor fluorophore which responds to the transfer by emitting fluorescent light for detection. The cyanine dyes impart an unusually high sensitivity to the labels thereby improving their usefulness in a wide variety of biochemical procedures, particularly nucleic acid sequencing, nucleic acid fragment sizing, and related procedures.

  6. Study made of transfer of heat energy through metal joints in vacuum environment

    NASA Technical Reports Server (NTRS)

    Elliot, D. H.

    1967-01-01

    Heat energy transfer is concentrated closely around a melted joint and the temperature drop across it decreases rapidly as the bolt and nut are tightened to a minimum torque level. Flat metal surfaces pressed together display a cyclical improvement in heat energy transfer as the interface pressure is increased.

  7. High resolution IR diode laser study of collisional energy transfer between highly vibrationally excited monofluorobenzene and CO2: the effect of donor fluorination on strong collision energy transfer.

    PubMed

    Kim, Kilyoung; Johnson, Alan M; Powell, Amber L; Mitchell, Deborah G; Sevy, Eric T

    2014-12-21

    Collisional energy transfer between vibrational ground state CO2 and highly vibrationally excited monofluorobenzene (MFB) was studied using narrow bandwidth (0.0003 cm(-1)) IR diode laser absorption spectroscopy. Highly vibrationally excited MFB with E' = ∼41,000 cm(-1) was prepared by 248 nm UV excitation followed by rapid radiationless internal conversion to the electronic ground state (S1→S0*). The amount of vibrational energy transferred from hot MFB into rotations and translations of CO2 via collisions was measured by probing the scattered CO2 using the IR diode laser. The absolute state specific energy transfer rate constants and scattering probabilities for single collisions between hot MFB and CO2 were measured and used to determine the energy transfer probability distribution function, P(E,E'), in the large ΔE region. P(E,E') was then fit to a bi-exponential function and extrapolated to the low ΔE region. P(E,E') and the biexponential fit data were used to determine the partitioning between weak and strong collisions as well as investigate molecular properties responsible for large collisional energy transfer events. Fermi's Golden rule was used to model the shape of P(E,E') and identify which donor vibrational motions are primarily responsible for energy transfer. In general, the results suggest that low-frequency MFB vibrational modes are primarily responsible for strong collisions, and govern the shape and magnitude of P(E,E'). Where deviations from this general trend occur, vibrational modes with large negative anharmonicity constants are more efficient energy gateways than modes with similar frequency, while vibrational modes with large positive anharmonicity constants are less efficient at energy transfer than modes of similar frequency.

  8. Energy transfer and energy level decay processes in Tm{sup 3+}-doped tellurite glass

    SciTech Connect

    Gomes, Laercio; Lousteau, Joris; Milanese, Daniel; Scarpignato, Gerardo C.; Jackson, Stuart D.

    2012-03-15

    The primary excited state decay and energy transfer processes in singly Tm{sup 3+}-doped TeO{sub 2}:ZnO:Bi{sub 2}O{sub 3}:GeO{sub 2} (TZBG) glass relating to the {sup 3}F{sub 4}{yields}{sup 3}H{sub 6}{approx}1.85 {mu}m laser transition have been investigated in detail using time-resolved fluorescence spectroscopy. Selective laser excitation of the {sup 3}H{sub 4} manifold at 794 nm, the {sup 3}H{sub 5} manifold at 1220 nm, and {sup 3}F{sub 4} manifold at 1760 nm has established that the {sup 3}H{sub 5} manifold is entirely quenched by multiphonon relaxation in tellurite glass. The luminescence from the {sup 3}H{sub 4} manifold with an emission peak at 1465 nm suffers strong suppression due to cross relaxation that populates the {sup 3}F{sub 4} level with a near quadratic dependence on the Tm{sup 3+} concentration. The {sup 3}F{sub 4} lifetime becomes longer as the Tm{sup 3+} concentration increases due to energy migration and decreases to 2.92 ms when [Tm{sup 3+}] = 4 mol. % as a result of quasi-resonant energy transfer to free OH{sup -} radicals present in the glass at concentrations between 1 x 10{sup 18} cm{sup -3} and 2 x 10{sup 18} cm{sup -3}. Judd-Ofelt theory in conjunction with absorption measurements were used to obtain the radiative lifetimes and branching ratios of the energy levels located below 25 000 cm{sup -1}. The spectroscopic parameters, the cross relaxation and Tm{sup 3+}({sup 3}F{sub 4}) {yields} OH{sup -} energy transfer rates were used in a numerical model for laser transitions emitting at 2335 nm and 1865 nm.

  9. Irradiation of atactic polystyrene: linear energy transfer effects.

    PubMed

    Ferry, M; Ngono-Ravache, Y; Picq, V; Balanzat, E

    2008-09-01

    Atactic glassy polystyrene (PS) has been irradiated in anoxic conditions by electron and ion beams. The induced modifications were followed, in situ, by Fourier transform infrared spectroscopy (FTIR). In-film modifications and hydrocarbon gas release were followed. In-situ measurements allowed one to avoid any spurious oxidation of the films after irradiation and also permitted studying in detail the evolution with dose of the FTIR spectra. The data were quantitatively analyzed, and we present a complete analysis of the effects of the Linear Energy Transfer (LET) on the radiation chemical yields of several radiation-induced modifications (alkynes, allenes, alkenes, benzene, and disubstituted benzenes). For a better understanding of the LET effects, the in-film modifications are compared to H2 release data from the literature and to our measurements of hydrocarbon gaseous molecule yields obtained by us. The overall destruction yield becomes very significant at high LET, and the radiation sensitivity of this aromatic polymer merges with typical values of aliphatic polymers: the radiation resistance conferred at low LET to polystyrene by the phenyl side groups is lost at high LET. This loss of radiation resistance equally affects the aromatic and aliphatic moieties. Monosubstituted alkynes are created above a LET threshold, whereas the other radiation-induced modifications are observed in the whole LET range. Several observations indicate that the phenyl ring is broken at high LET. Comparison of the alkyne yield in PS, polyethylene, and polycarbonate as well as the formation of nitrile bonds in poly(vinylpyridine- co-styrene) are consistent with a cleavage of the phenyl ring as the prominent source of alkynes. As the competing damage mechanisms do not have the same LET evolution, the relative importance of a specific modification on the global damage depends on LET. Some (benzene and disubstituted benzenes) dominate at low LET, while others (in-film alkyne and

  10. Fluorescence Resonance Energy Transfer Studies of DNA Polymerase β

    PubMed Central

    Towle-Weicksel, Jamie B.; Dalal, Shibani; Sohl, Christal D.; Doublié, Sylvie; Anderson, Karen S.; Sweasy, Joann B.

    2014-01-01

    During DNA repair, DNA polymerase β (Pol β) is a highly dynamic enzyme that is able to select the correct nucleotide opposite a templating base from a pool of four different deoxynucleoside triphosphates (dNTPs). To gain insight into nucleotide selection, we use a fluorescence resonance energy transfer (FRET)-based system to monitor movement of the Pol β fingers domain during catalysis in the presence of either correct or incorrect dNTPs. By labeling the fingers domain with ((((2-iodoacetyl)amino)ethyl)amino)naphthalene-1-sulfonic acid (IAEDANS) and the DNA substrate with Dabcyl, we are able to observe rapid fingers closing in the presence of correct dNTPs as the IAEDANS comes into contact with a Dabcyl-labeled, one-base gapped DNA. Our findings show that not only do the fingers close after binding to the correct dNTP, but that there is a second conformational change associated with a non-covalent step not previously reported for Pol β. Further analyses suggest that this conformational change corresponds to the binding of the catalytic metal into the polymerase active site. FRET studies with incorrect dNTP result in no changes in fluorescence, indicating that the fingers do not close in the presence of incorrect dNTP. Together, our results show that nucleotide selection initially occurs in an open fingers conformation and that the catalytic pathways of correct and incorrect dNTPs differ from each other. Overall, this study provides new insight into the mechanism of substrate choice by a polymerase that plays a critical role in maintaining genome stability. PMID:24764311

  11. Irradiation of atactic polystyrene: linear energy transfer effects.

    PubMed

    Ferry, M; Ngono-Ravache, Y; Picq, V; Balanzat, E

    2008-09-01

    Atactic glassy polystyrene (PS) has been irradiated in anoxic conditions by electron and ion beams. The induced modifications were followed, in situ, by Fourier transform infrared spectroscopy (FTIR). In-film modifications and hydrocarbon gas release were followed. In-situ measurements allowed one to avoid any spurious oxidation of the films after irradiation and also permitted studying in detail the evolution with dose of the FTIR spectra. The data were quantitatively analyzed, and we present a complete analysis of the effects of the Linear Energy Transfer (LET) on the radiation chemical yields of several radiation-induced modifications (alkynes, allenes, alkenes, benzene, and disubstituted benzenes). For a better understanding of the LET effects, the in-film modifications are compared to H2 release data from the literature and to our measurements of hydrocarbon gaseous molecule yields obtained by us. The overall destruction yield becomes very significant at high LET, and the radiation sensitivity of this aromatic polymer merges with typical values of aliphatic polymers: the radiation resistance conferred at low LET to polystyrene by the phenyl side groups is lost at high LET. This loss of radiation resistance equally affects the aromatic and aliphatic moieties. Monosubstituted alkynes are created above a LET threshold, whereas the other radiation-induced modifications are observed in the whole LET range. Several observations indicate that the phenyl ring is broken at high LET. Comparison of the alkyne yield in PS, polyethylene, and polycarbonate as well as the formation of nitrile bonds in poly(vinylpyridine- co-styrene) are consistent with a cleavage of the phenyl ring as the prominent source of alkynes. As the competing damage mechanisms do not have the same LET evolution, the relative importance of a specific modification on the global damage depends on LET. Some (benzene and disubstituted benzenes) dominate at low LET, while others (in-film alkyne and

  12. Intramolecular energy transfer and excitation coupling in metal-to-ligand charge transfer (MLCT) excited states

    NASA Astrophysics Data System (ADS)

    Riesen, Hans; Krausz, Elmars

    1995-02-01

    Several new spectroscopic studies relating to the coupling and dynamics in the spin-forbidden 3MLCT excited states of the chromophores [Ru(bpy)3]2+ and [Os(bpy)3]2+ (bpy equals 2,2'-bipyridine) in the racemic crystal lattices [Ru(bpy)3](PF6)2, [Ru(bpy)3](ClO4)2 and [Zn(bpy)3](ClO4)2 are presented. In the first of these lattices there are three closely related chromophoric sites at low temperatures, each with trigonal (C3) symmetry. In the two, isomorphic perchlorate salts there is a single chromophoric site, which has C2 symmetry. Using time resolved luminescence line narrowing, we have been able to directly measure the excitation transfer rate between two equivalent metal-ligand units in the [Ru(bpy)3]2+ chromophore doped in the [Zn(bpy)3](ClO4)2 lattice. The rate obtained (approximately equals 1 X 108 sec-1) is in excellent accord with estimates made from the observed linewidth in Stark swept transient hole-burning experiments made on the same system and confirm the single ligand, localized nature of the lowest emitting excited states and thus the very weak intramolecular coupling between metal ligand sub-units within this chromophore. The corresponding coupling in the [Os(bpy)3]2+ system is stronger and, in contrast to the ruthenium analogue, gives rise to additional features in the optical spectra in the origin region of the lowest 3MLCT excited states. The magnitude of the coupling can be probed and assessed by preparing modified chromophoric materials, in which one or two of the bpy ligands are perdeuterated (bpy-d8). This selective deuteration breaks the (near) degeneracy of excitations involving crystallographically equivalent ligands by approximately equals 30 - 40 cm-1 and this competes with or completely overrides the exciton coupling process. The exciton coupling is found to be approximately equals 2.4 cm-1 for [Os(bpy)3]2+ doped in [Ru(bpy)3](PF6)2 and can be understood within a mini-exciton description. Stronger couplings for the same chromophore in

  13. Magnetic to magnetic and kinetic to magnetic energy transfers at the top of the Earth's core

    NASA Astrophysics Data System (ADS)

    Huguet, Ludovic; Amit, Hagay; Alboussière, Thierry

    2016-11-01

    We develop the theory for the magnetic to magnetic and kinetic to magnetic energy transfer between different spherical harmonic degrees due to the interaction of fluid flow and radial magnetic field at the top of the Earth's core. We show that non-zero secular variation of the total magnetic energy could be significant and may provide evidence for the existence of stretching secular variation, which suggests the existence of radial motions at the top of the Earth's core-whole core convection or MAC waves. However, the uncertainties of the small scales of the geomagnetic field prevent a definite conclusion. Combining core field and flow models we calculate the detailed magnetic to magnetic and kinetic to magnetic energy transfer matrices. The magnetic to magnetic energy transfer shows a complex behaviour with local and non-local transfers. The spectra of magnetic to magnetic energy transfers show clear maxima and minima, suggesting an energy cascade. The kinetic to magnetic energy transfers, which are much weaker due to the weak poloidal flow, are either local or non-local between degree one and higher degrees. The patterns observed in the matrices resemble energy transfer patterns that are typically found in 3-D MHD numerical simulations.

  14. Energy transfers in large-scale and small-scale dynamos

    NASA Astrophysics Data System (ADS)

    Samtaney, Ravi; Kumar, Rohit; Verma, Mahendra

    2015-11-01

    We present the energy transfers, mainly energy fluxes and shell-to-shell energy transfers in small-scale dynamo (SSD) and large-scale dynamo (LSD) using numerical simulations of MHD turbulence for Pm = 20 (SSD) and for Pm = 0.2 on 10243 grid. For SSD, we demonstrate that the magnetic energy growth is caused by nonlocal energy transfers from the large-scale or forcing-scale velocity field to small-scale magnetic field. The peak of these energy transfers move towards lower wavenumbers as dynamo evolves, which is the reason for the growth of the magnetic fields at the large scales. The energy transfers U2U (velocity to velocity) and B2B (magnetic to magnetic) are forward and local. For LSD, we show that the magnetic energy growth takes place via energy transfers from large-scale velocity field to large-scale magnetic field. We observe forward U2U and B2B energy flux, similar to SSD.

  15. The determination of energy transfer rates in the Ho:Tm:Cr:YAG laser material

    NASA Technical Reports Server (NTRS)

    Koker, Edmond B.

    1988-01-01

    Energy transfer processes occurring between atomic, ionic, or molecular systems are very widespread in nature. The applications of such processes range form radiation physics and chemistry to biology. In the field of laser physics, energy transfer processes have been used to extend the lasing range, increase the output efficiency, and influence the spectral and temporal characteristics of the output pulses of energy transfer dye lasers or solid-state laser materials. Thus in the development of solid state lasers, it is important to investigate the basic energy transfer (ET) mechanisms and processes in order to gain detailed knowledge so that successful technical utilization can be achieved. The aim of the present research is to measure the ET rate from a given manifold associated with the chromium sensitizer atom to a given manifold in the holmium activator atom via the thulium transfer atom, in the Ho:Cr:YAG laser material.

  16. Analytic Methods for Predicting Significant Multi-Quanta Effects in Collisional Molecular Energy Transfer

    NASA Technical Reports Server (NTRS)

    Bieniek, Ronald J.

    1996-01-01

    Collision-induced transitions can significantly affect molecular vibrational-rotational populations and energy transfer in atmospheres and gaseous systems. This, in turn. can strongly influence convective heat transfer through dissociation and recombination of diatomics. and radiative heat transfer due to strong vibrational coupling. It is necessary to know state-to-state rates to predict engine performance and aerothermodynamic behavior of hypersonic flows, to analyze diagnostic radiative data obtained from experimental test facilities, and to design heat shields and other thermal protective systems. Furthermore, transfer rates between vibrational and translational modes can strongly influence energy flow in various 'disturbed' environments, particularly where the vibrational and translational temperatures are not equilibrated.

  17. Photoinduced energy and electron transfer in rubrene-benzoquinone and rubrene-porphyrin systems

    NASA Astrophysics Data System (ADS)

    Khan, Jafar I.; Abbas, Abdullah Saud; Aly, Shawkat M.; Usman, Anwar; Melnikov, Vasily A.; Alarousu, Erkki; Mohammed, Omar F.

    2014-11-01

    Excited-state electron and energy transfer from singlet excited rubrene (Ru) to benzoquinone (BQ) and tetra-(4-aminophenyl) porphyrin (TAPP) were investigated by steady-state absorption and emission, time-resolved transient absorption, and femtosecond (fs)-nanosecond (ns) fluorescence spectroscopy. The low reduction potential of BQ provides the high probability of electron transfer from the excited Ru to BQ. Steady-state and time-resolved results confirm such an excited electron transfer scenario. On the other hand, strong spectral overlap between the emission of Ru and absorption of TAPP suggests that energy transfer is a possible deactivation pathway of the Ru excited state.

  18. Sequential energy and electron transfer in a three-component system aligned on a clay nanosheet.

    PubMed

    Fujimura, Takuya; Ramasamy, Elamparuthi; Ishida, Yohei; Shimada, Tetsuya; Takagi, Shinsuke; Ramamurthy, Vaidhyanathan

    2016-02-21

    To achieve the goal of energy transfer and subsequent electron transfer across three molecules, a phenomenon often utilized in artificial light harvesting systems, we have assembled a light absorber (that also serves as an energy donor), an energy acceptor (that also serves as an electron donor) and an electron acceptor on the surface of an anionic clay nanosheet. Since neutral organic molecules have no tendency to adsorb onto the anionic surface of clay, a positively charged water-soluble organic capsule was used to hold neutral light absorbers on the above surface. A three-component assembly was prepared by the co-adsorption of a cationic bipyridinium derivative, cationic zinc porphyrin and cationic octaamine encapsulated 2-acetylanthracene on an exfoliated anionic clay surface in water. Energy and electron transfer phenomena were monitored by steady state fluorescence and picosecond time resolved fluorescence decay. The excitation of 2-acetylanthracene in the three-component system resulted in energy transfer from 2-acetylanthracene to zinc porphyrin with 71% efficiency. Very little loss due to electron transfer from 2-acetylanthracene in the cavitand to the bipyridinium derivative was noticed. Energy transfer was followed by electron transfer from the zinc porphyrin to the cationic bipyridinium derivative with 81% efficiency. Analyses of fluorescence decay profiles confirmed the occurrence of energy transfer and subsequent electron transfer. Merging the concepts of supramolecular chemistry and surface chemistry we realized sequential energy and electron transfer between three hydrophobic molecules in water. Exfoliated transparent saponite clay served as a matrix to align the three photoactive molecules at a close distance in aqueous solutions. PMID:26820105

  19. Investigation of energy transfer in terbium doped Y 2SiO5 phosphor particles

    NASA Astrophysics Data System (ADS)

    Salis, M.; Carbonaro, C. M.; Corpino, R.; Anedda, A.; Ricci, P. C.

    2012-07-01

    The kinetics of luminescence of sol-gel synthesized terbium doped Y 2SiO5 (YSO) phosphor particles is investigated in detail with reference to Tb concentration in the 0.001%-10% range. By increasing the dopant concentration, the luminescence profile changes from a blue to a green peaked emission spectrum because of the energy transfer among centers. The inter-center energy transfer mechanism is well accounted for by the Inokuti-Hirayama (IH) kinetic model which is based on a statistical average of inter-center distance dependent decay modes of the donor luminescence. The distribution of the decay modes is implemented from the Förster-Dexter resonance theory of energy transfer by assuming a rate constant for the energy transfer by multipolar interactions between donors and acceptors. However, the experimental results recorded in the low concentration limit show the presence of green emission contributions in the luminescence spectrum which cannot be related to the Tb concentration; for this reason an additional internal energy transfer mechanism, occurring among levels of the same center, is proposed to account for the recorded emission properties. Thus, a new and more exhaustive model which includes both the internal and external energy transfer processes is considered; the proposed model allows a better explanation of the spectroscopic features of Tb related centers in YSO crystals and discloses the critical concentration and the quantum yields of the different energy transfer mechanisms.

  20. Nanoscale heat transfer and thermoelectrics for alternative energy

    NASA Astrophysics Data System (ADS)

    Robinson, Richard

    2011-03-01

    In the area of alternative energy, thermoelectrics have experienced an unprecedented growth in popularity because of their ability to convert waste heat into electricity. Wired in reverse, thermoelectrics can act as refrigeration devices, where they are promising because they are small in size and lightweight, have no moving parts, and have rapid on/off cycles. However, due to their low efficiencies bulk thermoelectrics have historically been a niche market. Only in the last decade has thermoelectric efficiency exceeded ~ 20 % due to fabrication of nanostructured materials. Nanoscale materials have this advantage because electronic and acoustic confinement effects can greatly increase thermoelectric efficiency beyond bulk values. In this talk, I will introduce our work in the area of nanoscale heat transfer with the goal of more efficient thermoelectrics. I will discuss our experiments and methods to study acoustic confinement in nanostructures and present some of our new nanostructured thermoelectric materials. To study acoustic confinement we are building a nanoscale phonon spectrometer. The instrument can excite phonon modes in nanostructures in the ~ 100 s of GHz. Ballistic phonons from the generator are used to probe acoustic confinement and surface scattering effects. Transmission studies using this device will help optimize materials and morphologies for more efficient nanomaterial-based thermoelectrics. For materials, our group has synthesized nano-layer superlattices of Na x Co O2 . Sodium cobaltate was recently discovered to have a high Seebeck coeficent and is being studied as an oxide thermoelectric material. The thickness of our nano-layers ranges from 5 nm to 300 nm while the lengths can be varied between 10 μ m and 4 mm. Typical aspect ratios are 40 nm: 4 mm, or 1:100,000. Thermoelectric characterization of samples with tilted multiple-grains along the measurement axis indicate a thermoelectric efficiency on par with current polycrystalline samples

  1. Biomolecular interactions probed by fluorescence resonance energy transfer

    NASA Astrophysics Data System (ADS)

    Lange, Daniela Charlotte

    2000-09-01

    This thesis describes how a physical phenomenon, Fluorescence Resonance Energy Transfer (FRET), can be exploited for the study of interactions between biomolecules. The physical basis of this phenomenon is discussed and it is described how some of its characteristics can be exploited in measurement. A recently introduced method, photobleaching FRET microscopy, was implemented and its image analysis refined to suit our biological context. Further, a new technique is proposed, which combines FRET with confocal laser scanning microscopy to optimize resolution and to allow for 3D-studies in living cells. The first part of this thesis presents the application of FRET to the study of oligomerization of G-protein coupled receptors (GPCRs), which was performed at the Fraser Laboratories at McGill University in Montreal. It is demonstrated how FRET microscopy allowed us to circumvent problems of traditional biochemical approaches and provided the first direct evidence for GPCR oligomerization in intact cells. We found that somatostatin receptors (SSTRs) functionally interact by forming oligomers with their own kind, with different SSTR isoforms, and even with distantly related GPCRs, such as dopamine receptors, the latter of which is breaking with the dogma that GPCRs would only pair up with their own kind. The high sensitivity of the FRET technique allowed us to characterize these interactions under more physiological conditions, which lead to the observation that oligomerization is induced by receptor agonist. We further studied the differential effects of agonists and antagonists on receptor oligomerization, leading to a model for the molecular mechanism underlying agonist/antagonist function and receptor activation. The second part was carried out at the Neurobiology Laboratory of the VA Medical Center in Newington, CT. The objective was to further our understanding of Niemann- Pick type C disease, which is characterized by a defect in intracellular cholesterol

  2. Energy Transfer of Excitons Between Quantum Wells Separated by a Wide Barrier

    SciTech Connect

    LYO,SUNGKWUN K.

    1999-12-06

    We present a microscopic theory of the excitonic Stokes and anti-Stokes energy transfer mechanisms between two widely separated unequal quantum wells with a large energy mismatch ({Delta}) at low temperatures (T). Exciton transfer through dipolar coupling, photon-exchange coupling and over-barrier ionization of the excitons through exciton-exciton Auger processes are examined. The energy transfer rate is calculated as a function of T and the center-to-center distance d between the two wells. The rates depend sensitively on T for plane-wave excitons. For located excitons, the rates depend on T only through the T-dependence of the localization radius.

  3. Excitation energy transfer between erythrosin B and malachite green adsorbed on a microheterogeneous polymer latex

    NASA Astrophysics Data System (ADS)

    Dutta, A. K.

    1995-07-01

    In this article electronic excitation energy transfer between the aggregates of the donor erythrosin B (EB) and the acceptor malachite green (MG) has been studied in polystyrenebutylmethacrylate latex. Steady state flourescence quenching studies reveal that with the increasing latex concentration the rate of quenching decreases initially, attains a minimum and then increases again. Such a behaviour has been attributed to aggregation of the dye molecules at low latex concentration and redistribution at larger latex concentrations. These results illustrate the role of the microenvironment in modifying the energy transfer reaction rates and provides a model system for understanding energy transfer mechanisms in context to photosynthesis in real living systems.

  4. Energy transfer and photochemistry in biomimetic solar conversion

    NASA Astrophysics Data System (ADS)

    Boxer, S. G.

    1987-09-01

    Electron transfer is being studied in several well-defined molecular systems, and techniques for studying electron transfer are being developed. Photo-induced electron transfer lies at the heart of photosynthesis and forms the basis for the approach to biomimetic solar conversion. Electron donors and acceptors are covalently connected to molecular frameworks which permit variation of the distance between sites and the nature of the intervening medium. Myoglobin produced by recombinant DNA methods was modified to place a free sulfhydryl group at various positions on the surface for attachment of electron acceptors. Surface histidine residues are modified with Ru-reagents. Electron donors and acceptors were also attached to double-helical DNA as a first approach to polymer-based donor/acceptor systems. The effects of applied electric fields on the absorption and emission spectra of compounds undergoing electron transfer were studied. The Stark effect spectra of several Ru-complexes were obtained, from which quantitative information on changes in the permanent dipole moment between the ground and the excited state was extracted. It was also shown that, under certain conditions, the electric field can change the rate of electron transfer reactions, and that the effect is easily detected in the electric-field-modulated fluorescence spectrum. These effects were demonstrated for bacterial reaction centers and certain Ru-complexes.

  5. Measuring distances within unfolded biopolymers using fluorescence resonance energy transfer: The effect of polymer chain dynamics on the observed fluorescence resonance energy transfer efficiency

    PubMed Central

    Makarov, Dmitrii E.; Plaxco, Kevin W.

    2009-01-01

    Recent years have seen a number of investigations in which distances within unfolded proteins, polypeptides, and other biopolymers are probed via fluorescence resonance energy transfer, a method that relies on the strong distance dependence of energy transfer between a pair of dyes attached to the molecule of interest. In order to interpret the results of such experiments it is commonly assumed that intramolecular diffusion is negligible during the excited state lifetime. Here we explore the conditions under which this “frozen chain” approximation fails, leading to significantly underestimated donor-acceptor distances, and describe a means of correcting for polymer dynamics in order to estimate these distances more accurately. PMID:19725638

  6. Intense energy transfer and superharmonic resonance in a system of two coupled oscillators.

    PubMed

    Kovaleva, Agnessa; Manevitch, Leonid; Manevitch, Elina

    2010-05-01

    The paper presents the analytic study of energy exchange in a system of coupled nonlinear oscillators subject to superharmonic resonance. The attention is given to complete irreversible energy transfer that occurs in a system with definite initial conditions corresponding to a so-called limiting phase trajectory (LPT). We show that the energy imparted in the system is partitioned among the principal and superharmonic modes but energy exchange can be due to superharmonic oscillations. Using the LPT concept, we construct approximate analytic solutions describing intense irreversible energy transfer in a harmonically excited Duffing oscillator and a system of two nonlinearly coupled oscillators. Numerical simulations confirm the accuracy of the analytic approximations. PMID:20866315

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    A new N2-N2 rigid-rotor surface has been determined using extensive Ab Initio quantum chemistry calculations together with recent experimental data for the second virial coefficient. Rotational energy transfer is studied using the new potential energy surface (PES) employing the close coupling method below 200 cm(exp -1) and coupled state approximation above that. Comparing with a previous calculation based on the PES of van der Avoird et al.,3 it is found that the new PES generally gives larger cross sections for large (delta)J transitions, but for small (delta)J transitions the cross sections are either comparable or smaller. Correlation between the differences in the cross sections and the two PES will be attempted. The computed cross sections will also be compared with available experimental data.

  8. Quasiclassical trajectory study of collisional energy transfer in toluene systems. II. Helium bath gas: Energy and temperature dependences, and angular momentum transfer

    NASA Astrophysics Data System (ADS)

    Lim, Kieran F.

    1994-11-01

    The collisional deactivation of highly vibrationally excited toluene-d0 and toluene-d8 by helium bath gas has been investigated using quasiclassical trajectory simulations. Collisional energy transfer was found to increase with initial toluene internal energy, in agreement with the experiments of Toselli and Barker [J. Chem. Phys. 97, 1809 (1992), and references therein]. The temperature dependence of <ΔE2>1/2 is predicted to be T(0.44±0.10), in agreement with the experiments of Heymann, Hippler, and Troe [J. Chem. Phys. 80, 1853 (1984)]. Toluene is found to have no net angular-momentum (rotational-energy) transfer to helium bath gas, although <ΔJ2>1/2 has a temperature dependence of T(0.31±0.07). Re-evaluation of earlier calculations [``Paper I:'' Lim, J. Chem. Phys. 100, 7385 (1994)] found that rotational energy transfer could be induced by increasing the mass of the collider, or by increasing the strength of the intermolecular interaction: in these cases, angular-momentum transfer depended on the initial excitation energy. In all cases, the final rotational distributions remained Boltzmann.

  9. A spectroscopist's view of energy states, energy transfers, and chemical reactions.

    PubMed

    Moore, C Bradley

    2007-01-01

    This chapter describes a research career beginning at Berkeley in 1960, shortly after Sputnik and the invention of the laser. Following thesis work on vibrational spectroscopy and the chemical reactivity of small molecules, we studied vibrational energy transfers in my own lab. Collision-induced transfers among vibrations of a single molecule, from one molecule to another, and from vibration to rotation and translation were elucidated. My research group also studied the competition between vibrational relaxation and chemical reaction for potentially reactive collisions with one molecule vibrationally excited. Lasers were used to enrich isotopes by the excitation of a predissociative transition of a selected isotopomer. We also tested the hypotheses of transition-state theory for unimolecular reactions of ketene, formaldehyde, and formyl fluoride by (a) resolving individual molecular eigenstates above a dissociation threshold, (b) locating vibrational levels at the transition state, (c) observing quantum resonances in the barrier region for motion along a reaction coordinate, and (d) studying energy release to fragments. PMID:17034339

  10. Inter-phase heat transfer and energy coupling in turbulent dispersed multiphase flows

    NASA Astrophysics Data System (ADS)

    Ling, Y.; Balachandar, S.; Parmar, M.

    2016-03-01

    The present paper addresses important fundamental issues of inter-phase heat transfer and energy coupling in turbulent dispersed multiphase flows through scaling analysis. In typical point-particle or two-fluid approaches, the fluid motion and convective heat transfer at the particle scale are not resolved and the momentum and energy coupling between fluid and particles are provided by proper closure models. By examining the kinetic energy transfer due to the coupling forces from the macroscale to microscale fluid motion, closure models are obtained for the contributions of the coupling forces to the energy coupling. Due to the inviscid origin of the added-mass force, its contribution to the microscale kinetic energy does not contribute to dissipative transfer to fluid internal energy as was done by the quasi-steady force. Time scale analysis shows that when the particle is larger than a critical diameter, the diffusive-unsteady kernel decays at a time scale that is smaller than the Kolmogorov time scale. As a result, the computationally costly Basset-like integral form of diffusive-unsteady heat transfer can be simplified to a non-integral form. Conventionally, the fluid-to-particle volumetric heat capacity ratio is used to evaluate the relative importance of the unsteady heat transfer to the energy balance of the particles. Therefore, for gas-particle flows, where the fluid-to-particle volumetric heat capacity ratio is small, unsteady heat transfer is usually ignored. However, the present scaling analysis shows that for small fluid-to-particle volumetric heat capacity ratio, the importance of the unsteady heat transfer actually depends on the ratio between the particle size and the Kolmogorov scale. Furthermore, the particle mass loading multiplied by the heat capacity ratio is usually used to estimate the importance of the thermal two-way coupling effect. Through scaling argument, improved estimates are established for the energy coupling parameters of each

  11. A model for energy transfer in collisions of atoms with highly excited molecules.

    PubMed

    Houston, Paul L; Conte, Riccardo; Bowman, Joel M

    2015-05-21

    A model for energy transfer in the collision between an atom and a highly excited target molecule has been developed on the basis of classical mechanics and turning point analysis. The predictions of the model have been tested against the results of trajectory calculations for collisions of five different target molecules with argon or helium under a variety of temperatures, collision energies, and initial rotational levels. The model predicts selected moments of the joint probability distribution, P(Jf,ΔE) with an R(2) ≈ 0.90. The calculation is efficient, in most cases taking less than one CPU-hour. The model provides several insights into the energy transfer process. The joint probability distribution is strongly dependent on rotational energy transfer and conservation laws and less dependent on vibrational energy transfer. There are two mechanisms for rotational excitation, one due to motion normal to the intermolecular potential and one due to motion tangential to it and perpendicular to the line of centers. Energy transfer is found to depend strongly on the intermolecular potential and only weakly on the intramolecular potential. Highly efficient collisions are a natural consequence of the energy transfer and arise due to collisions at "sweet spots" in the space of impact parameter and molecular orientation. PMID:25907301

  12. 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.

  13. Chemical Dynamics Simulations of Intermolecular Energy Transfer: Azulene + N2 Collisions.

    PubMed

    Kim, Hyunsik; Paul, Amit K; Pratihar, Subha; Hase, William L

    2016-07-14

    Chemical dynamics simulations were performed to investigate collisional energy transfer from highly vibrationally excited azulene (Az*) in a N2 bath. The intermolecular potential between Az and N2, used for the simulations, was determined from MP2/6-31+G* ab initio calculations. Az* is prepared with an 87.5 kcal/mol excitation energy by using quantum microcanonical sampling, including its 95.7 kcal/mol zero-point energy. The average energy of Az* versus time, obtained from the simulations, shows different rates of Az* deactivation depending on the N2 bath density. Using the N2 bath density and Lennard-Jones collision number, the average energy transfer per collision ⟨ΔEc⟩ was obtained for Az* as it is collisionally relaxed. By comparing ⟨ΔEc⟩ versus the bath density, the single collision limiting density was found for energy transfer. The resulting ⟨ΔEc⟩, for an 87.5 kcal/mol excitation energy, is 0.30 ± 0.01 and 0.32 ± 0.01 kcal/mol for harmonic and anharmonic Az potentials, respectively. For comparison, the experimental value is 0.57 ± 0.11 kcal/mol. During Az* relaxation there is no appreciable energy transfer to Az translation and rotation, and the energy transfer is to the N2 bath. PMID:27182630

  14. Energy spectrum transfer equations of solar wind turbulence

    NASA Technical Reports Server (NTRS)

    Tu, C.-Y.

    1995-01-01

    The recent studies of transfer equations for solar wind magnetohydrodynamic (MHD) turbulence are reviewed with emphasis on the comparison with the statistical observational results. Helios and Voyager missions provide an opportunity to study the the radial evolution of the power spectrum. the cross-helicity the Alfven ratio and the minimum variance direction. Spectrum transfer equations are considered as a tool to explore the nature of this radial evolution of the fluctuations. The transfer equations are derived from incompressible MHD equations. Generally one needs to make assumptions about the nature of the fluctuations and the nature of the turbulent non-linear interactions to obtain numerical results which can be compared with the observations. Some special model results for several simple cases SUCH as for structures or strong mixing. for Alfven waves with weak turbulent interactions. and for a superposition of structures and Alfven waves. are discussed. The difference between the various approaches to derive and handle the transfer equations are also addressed. Finally some theoretical description of the compressible fluctuations are also briefly reviewed.

  15. Picosecond dynamics of energy transfer in porphyrin-sapphyrin noncovalent assemblies

    SciTech Connect

    Springs, S.L.; Gosztola, D.; Wasielewski, M.R.; Kral, V.; Andrievsky, A.; Sessler, J.L.

    1999-03-17

    The picosecond dynamics of noncovalent ensembles for energy transfer based on anion chelation are reported. The photoactive noncovalent complexes are assembled via salt-bridge formation between carboxyl-containing porphyrin photodonors and a monoprotonated pentapyrrolic sapphyrin acceptor. These complexes are formed with a K{sub a} of ca. 10{sup 3} M{sup {minus}1} upon mixing the receptor and substrate in their respective free-acid and free-base forms in CD{sub 2}Cl{sub 2} (as judged by {sup 1}H NMR spectroscopic means). Upon irradiation at 417 nm, singlet-singlet energy transfer from the porphyrin to the sapphyrin subunit takes place readily with energy transfer dynamics that are consistent with a Foerster-type mechanism. The title systems thus appear to be prototypic of a new kind of noncovalent energy transfer modeling that is predicated on the use of anion chelation.

  16. Energy Transfer in Silicon Nanocrystal Solids Made from All-Inorganic Colloidal Silicon Nanocrystals.

    PubMed

    Furuta, Kenta; Fujii, Minoru; Sugimoto, Hiroshi; Imakita, Kenji

    2015-07-16

    Energy transfer between silicon (Si) nanocrystals (NCs) in Si-NC solids was demonstrated by photoluminescence (PL) spectroscopy. Clear differences of PL spectra and the decay rates between solutions and solids of Si-NCs were observed. The change in the PL properties caused by the formation of solids could be explained by the energy transfer from small to large NCs in the size distribution. In order to obtain further evidence of NC-to-NC energy transfer, the size distribution was intentionally modified by mixing solutions of NCs with different size distributions. NC solids made from the mixed solutions exhibited significantly different PL spectral shape and decay rates from those made from unmixed solutions, providing clear evidence of NC-to-NC energy transfer in Si-NC solids.

  17. Simple Model for Gold Nano Particles Concentration Dependence of Resonance Energy Transfer Intensity

    NASA Astrophysics Data System (ADS)

    Hoa, N. M.; Ha, C. V.; Nga, D. T.; Lan, N. T.; Nhung, T. H.; Viet, N. A.

    2016-06-01

    Gold nano particles (GNPs) concentration dependence of the energy transfer occurs between the fluorophores and GNPs is investigated. In the case of theses pairs, GNPs can enhance or quench the fluorescence of fluorophores depending upon the relative magnitudes of two energy transfer mechanisms: i) the plasmonic field enhancement at the fluorophores emission frequencies (plasmon coupled fluorescence enhancement) and ii) the localized plasmon coupled Forster energy transfer from fluorescent particles to gold particles, which quenches the fluorescence. The competition of these mechanisms is depending on the spectral overlap of fluorophores and GNPs, their relative concentration, excitation wavelength. Simple two branches surface plasmon polariton model for GNPs concentration dependence of the energy transfer is proposed. The experimental data and theoretical results confirm our findings.

  18. Temperature dependence of vibrational energy transfer between vibrationally excited polyatomic molecules and bath gases

    NASA Astrophysics Data System (ADS)

    Zalesskaya, G. A.; Yakovlev, D. L.; Sambor, E. G.

    2000-08-01

    Efficiency of vibrational energy transfer (VET) in vibrational quasicontinuum of triplet states was estimated from the dependence of time-resolved delayed fluorescence of benzophenone and anthraquinone on bath gas pressure. The negative temperature dependence for vibration-vibration (V-V) and positive for vibration-translation (V-T) energy transfers from benzophenone and anthraquinone to bath gases (C 2H 4, SF 6, CCl 4, C 5H 12) were obtained between 373 and 553 K. Polarizability and dipole moment of colliding molecules seem to affect the efficiency of V-V relaxation. These data reflect the dominance of long-range attractive interactions in V-V energy transfer and short-range repulsive interactions in V-T energy transfer.

  19. Delocalization-enhanced long-range energy transfer between cryptophyte algae PE545 antenna proteins.

    PubMed

    Hossein-Nejad, Hoda; Curutchet, Carles; Kubica, Aleksander; Scholes, Gregory D

    2011-05-12

    We study the dynamics of interprotein energy transfer in a cluster, consisting of four units of phycoerythrin 545 (PE545) antenna proteins via a hybrid quantum-classical approach. Long-range exciton transport is viewed as a random walk in which the hopping probabilities are determined from a quantum theory. We apply two different formulations of the exciton transport problem to obtain the hopping probabilities, and find that a theory that regards energy transfer as relaxations among the excitonic eigenstates mediated by the vibrational bath, predicts the fastest dynamics. Our results indicate that persistent exciton delocalization is an important implication of the quantum nature of energy transfer on a multiprotein length scale, and that a hybrid quantum-classical approach is a viable starting point in studies of long-range energy transfer in condensed phase biological systems.

  20. Opto-fluidic ring resonator lasers based on highly efficient resonant energy transfer.

    PubMed

    Shopova, Siyka I; Cupps, Jay M; Zhang, Po; Henderson, Edward P; Lacey, Scott; Fan, Xudong

    2007-10-01

    We demonstrate an opto-fluidic ring resonator dye laser using highly efficient energy transfer. The active lasing material consists of a donor and acceptor mixture and flows in a fused silica capillary whose circular cross section forms a ring resonator and supports the whispering gallery modes (WGMs) of high Q-factors (>107). The excited states are created in the donor and transferred to the acceptor through the fluorescence resonant energy transfer (FRET), whose emission is coupled into the WGM. Due to the high energy transfer efficiency and high Q-factors, the acceptor exhibits a lasing threshold as low as 0.3 muJ/mm2. We further analyze the energy transfer mechanisms and find that non-radiative Förster transfer is the dominant effect to support the acceptor lasing. FRET lasers using cascade energy transfer and using quantum dots (QDs) as the donor are also presented. Our study will not only lead to development of novel microfluidic lasers with low lasing thresholds and excitation/emission flexibility, but also open an avenue for future laser intra-cavity bio/chemical sensing.

  1. The energy transfer in the TEMP-4M pulsed ion beam accelerator

    SciTech Connect

    Isakova, Y. I.; Pushkarev, A. I.; Khaylov, I. P.

    2013-07-15

    The results of a study of the energy transfer in the TEMP-4M pulsed ion beam accelerator are presented. The energy transfer efficiency in the Blumlein and a self-magnetically insulated ion diode was analyzed. Optimization of the design of the accelerator allows for 85% of energy transferred from Blumlein to the diode (including after-pulses), which indicates that the energy loss in Blumlein and spark gaps is insignificant and not exceeds 10%–12%. Most losses occur in the diode. The efficiency of energy supplied to the diode to the energy of accelerated ions is 8%–9% for a planar strip self-magnetic MID, 12%–15% for focusing diode and 20% for a spiral self-magnetic MID.

  2. Spectral Properties and Energy Transfer between Ce(3+) and Yb(3+) in the Ca3Sc2Si3O12 Host: Is It an Electron Transfer Mechanism?

    PubMed

    Zhou, Lei; Tanner, Peter A; Ning, Lixin; Zhou, Weijie; Liang, Hongbin; Zheng, Lirong

    2016-07-21

    The downshifting from Ce(3+) blue emission to Yb(3+) near-infrared emission has been studied in the garnet host Ca2.8-2xCe0.1YbxNa0.1+xSc2Si3O12 (x = 0-0.36). The downshifting does not involve quantum cutting, but one incident blue photon is transferred from Ce(3+) to Yb(3+) with an energy transfer efficiency up to 90% when x = 0.36 for the Yb(3+) dopant ion. For x ≤ 0.15, a multiphonon-assisted electric dipole-electric quadrupole mechanism of energy transfer dominates, while for the highest concentration of Yb(3+) employed, the electron transfer mechanism is confirmed. A temperature-dependent increase of the Ce(3+) → Yb(3+) energy transfer rate does not exclusively indicate the electron transfer mechanism. The application of the material to solar energy conversion is indicated. PMID:27331405

  3. Efficient evaluation of collisional energy transfer terms for plasma particle simulations

    NASA Astrophysics Data System (ADS)

    Turrell, A. E.; Sherlock, M.; Rose, S. J.

    2016-02-01

    Particle-based simulations, such as in particle-in-cell (PIC) codes, are widely used in plasma physics research. The analysis of particle energy transfers, as described by the second moment of the Boltzmann equation, is often necessary within these simulations. We present computationally efficient, analytically derived equations for evaluating collisional energy transfer terms from simulations using discrete particles. The equations are expressed as a sum over the properties of the discrete particles.

  4. Synthetic molecular systems based on porphyrins as models for the study of energy transfer in photosynthesis

    NASA Astrophysics Data System (ADS)

    Konovalova, Nadezhda V.; Evstigneeva, Rima P.; Luzgina, Valentina N.

    2001-11-01

    The published data on the synthesis and photochemical properties of porphyrin-based molecular ensembles which represent models of natural photosynthetic light-harvesting complexes are generalised and systematised. The dependence of the transfer of excitation energy on the distance between donor and acceptor components, their mutual arrangement, electronic and environmental factors are discussed. Two mechanisms of energy transfer reactions, viz., 'through space' and 'through bond', are considered. The bibliography includes 96 references.

  5. Universal characteristics of transverse momentum transfer in intermediate energy heavy ion collisions

    NASA Technical Reports Server (NTRS)

    Khan, F.; Townsend, L. W.; Tripathi, R. K.; Cucinotta, F. A.

    1993-01-01

    A microscopic optical model formalism for estimating momentum transfer in intermediate energy heavy ion collisions predicts universal behavior of the transverse component. In particular, for symmetric systems heavier than niobium, it appears that values of P(perpendicular)/A are independent of the mass and charge of the colliding nuclei and vary only with impact parameter and incident beam energy. This suggests that momentum transfer per nucleon saturates to some limiting value with increasing mass.

  6. Energy transfer enhancement by oxygen perturbation of spin-forbidden electronic transitions in aromatic systems

    NASA Astrophysics Data System (ADS)

    Monguzzi, A.; Tubino, R.; Salamone, M. M.; Meinardi, F.

    2010-09-01

    Triplet-triplet energy transfer in multicomponent organic systems is usually entirely ascribed to a Dexter-type mechanism involving only short-range donor/acceptor interactions. We demonstrate that the presence of molecular oxygen introduces a perturbation to the electronic structure of one of the involved moieties which can induce a large increase in the spin-forbidden transition oscillator strength so that the otherwise negligible Förster contribution dominates the overall energy transfer rate.

  7. Energy transfer and energy level decay processes of Er3+ in water-free tellurite glass

    NASA Astrophysics Data System (ADS)

    Gomes, Laercio; Rhonehouse, Daniel; Nguyen, Dan T.; Zong, Jie; Chavez-Pirson, Arturo; Jackson, Stuart D.

    2015-12-01

    This report details the fundamental spectroscopic properties of a new class of water-free tellurite glasses studied for future applications in mid-infrared light generation. The fundamental excited state decay processes relating to the 4I11/2 → 4I13/2 transition in singly Er3+-doped Tellurium Zinc Lanthanum glass have been investigated using time-resolved fluorescence spectroscopy. The excited state dynamics was analyzed for Er2O3 concentrations between 0.5 mol% and 4 mol%. Selective laser excitation of the 4I11/2 energy level at 972 nm and selective laser excitation of the 4I13/2 energy level at 1485 nm has established that in a similar way to other Er3+-doped glasses, a strong energy-transfer upconversion by way of a dipole-dipole interaction between two excited erbium ions in the 4I13/2 level populates the 4I11/2 upper laser level of the 3 μm transition. The 4I13/2 and 4I11/2 energy levels emitted luminescence with peaks located at 1532 nm and 2734 nm respectively with luminescence efficiencies of 100% and 8% for the higher (4 mol.%) concentration sample. Results from numerical simulations showed that a population inversion is reached at a threshold pumping intensity of ∼57 kW cm-2 for a CW laser pump at 976 nm for [Er2O3] = 2 mol.%.

  8. Fluorescence energy transfer between Ca2+ transport ATPase molecules in artificial membranes.

    PubMed

    Vanderkooi, J M; Ierokomas, A; Nakamura, H; Martonosi, A

    1977-04-01

    The purified ATPase of sarcoplasmic reticulum was covalently labeled with N-iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine (1,5-IAEDANS) or with iodoacetamidofluorescein (IAF). In reconstituted vesicles containing both types of ATPase molecules fluorescence energy transfer was observed from the IAEDANS (donor) to the IAF (acceptor) fluorophore as determined by the ratio of donor and acceptor fluorescence intensities, and by nanosecond decay measurements of donor fluorescence in the presence or absence of the acceptor. The observed energy transfer may arise by random collisions between ATPase molecules due to Brownian motion or by formation of complexes containing several ATPase molecules. Experimental distinction between these two models of energy transfer is possible based on predictions derived from mathematical models. Up to tenfold dilution of the lipid phase of reconstituted vesicles with egg lecithin had no measurable effect upon the energy transfer, suggesting that random collision between ATPase molecules in the lipid phase is not the principal cause of the observed effect. Addition of unlabeled ATPase in five- to tenfold molar excess over the labeled molecules abolished energy transfer. These observations together with electron microscopic and chemical cross-linking studies support the existence of ATPase oligomers in the membrane with sufficiently long lifetimes for energy transfer to occur. A hypothetical equilibrium between monomeric and tetrameric forms of the ATPase governed by the membrane potential is proposed as the structural basis of the regulation of Ca uptake and release by sarcoplasmic reticulum membranes during muscle contraction and relaxation.

  9. On the mechanisms of energy transfer between quantum well and quantum dashes

    NASA Astrophysics Data System (ADS)

    Sek, G.; Kudrawiec, R.; Podemski, P.; Misiewicz, J.; Somers, A.; Höfling, S.; Reithmaier, J. P.; Kamp, M.; Forchel, A.

    2012-08-01

    We investigate energy transfer mechanisms from a quantum well (QW) to quantum dashes (QDashes) separated by a few nanometer thick barrier in InAs/InGaAs/InGaAlAs/InP material system. We show that at sufficiently low temperatures excitons, which are non-resonantly photogenerated in the QW and then transferred to the ground state via phonon relaxation, can be retrieved by QDashes. The excess of the transferred energy, defined by the energy difference between the QW and QDash exciton states, can be dissipated via interaction with LO phonons if the respective energy matching is satisfied. This kind of exciton injection from QW to QDashes is a process insensitive to the energy level structure of the individual exciton components, i.e., electrons and holes. It is shown that within the single particle picture, the electron energy in QDashes is higher by more than 50 meV compared to the corresponding QW energy, which prevents the electron transfer from quantum well to the dashes. We show experimentally that despite this unfavorable energy difference for single carriers whole QW excitons are efficiently transferred to QDashes and recombine there radiatively.

  10. Modeling of MeV alpha particle energy transfer to lower hybrid waves

    SciTech Connect

    Schivell, J.; Monticello, D.A.; Fisch, N.; Rax, J.M.

    1993-10-01

    The interaction between a lower hybrid wave and a fusion alpha particle displaces the alpha particle simultaneously in space and energy. This results in coupled diffusion. Diffusion of alphas down the density gradient could lead to their transferring energy to the wave. This could, in turn, put energy into current drive. An initial analytic study was done by Fisch and Rax. Here the authors calculate numerical solutions for the alpha energy transfer and study a range of conditions that are favorable for wave amplification from alpha energy. They find that it is possible for fusion alpha particles to transfer a large fraction of their energy to the lower hybrid wave. The numerical calculation shows that the net energy transfer is not sensitive to the value of the diffusion coefficient over a wide range of practical values. An extension of this idea, the use of a lossy boundary to enhance the energy transfer, is investigated. This technique is shown to offer a large potential benefit.

  11. Ultrafast Charge- and Energy-Transfer Dynamics in Conjugated Polymer: Cadmium Selenide Nanocrystal Blends

    PubMed Central

    2014-01-01

    Hybrid nanocrystal–polymer systems are promising candidates for photovoltaic applications, but the processes controlling charge generation are poorly understood. Here, we disentangle the energy- and charge-transfer processes occurring in a model system based on blends of cadmium selenide nanocrystals (CdSe-NC) with poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) using a combination of time-resolved absorption and luminescence measurements. The use of different capping ligands (n-butylamine, oleic acid) as well as thermal annealing allows tuning of the polymer–nanocrystal interaction. We demonstrate that energy transfer from MDMO-PPV to CdSe-NCs is the dominant exciton quenching mechanism in nonannealed blends and occurs on ultrafast time scales (<1 ps). Upon thermal annealing electron transfer becomes competitive with energy transfer, with a transfer rate of 800 fs independent of the choice of the ligand. Interestingly, we find hole transfer to be much less efficient than electron transfer and to extend over several nanoseconds. Our results emphasize the importance of tuning the organic–nanocrystal interaction to achieve efficient charge separation and highlight the unfavorable hole-transfer dynamics in these blends. PMID:24490650

  12. Long-distance electronic energy transfer in light-harvesting supramolecular polymers.

    PubMed

    Winiger, Christian B; Li, Shaoguang; Kumar, Ganesh R; Langenegger, Simon M; Häner, Robert

    2014-12-01

    The efficient collection of solar energy relies on the design and construction of well-organized light-harvesting systems. Herein we report that supramolecular phenanthrene polymers doped with pyrene are effective collectors of light energy. The linear polymers are formed through the assembly of short amphiphilic oligomers in water. Absorption of light by phenanthrene residues is followed by electronic energy transfer along the polymer over long distances (>100 nm) to the accepting pyrene molecules. The high efficiency of the energy transfer, which is documented by large fluorescence quantum yields, suggests a quantum coherent process.

  13. UV absorption study of collisional energy transfer in vibrationally highly excited SO/sub 2/ molecules

    SciTech Connect

    Heymann, M.; Hippler, H.; Nahr, D.; Plach, H.J.; Troe, J.

    1988-09-22

    Transient UV absorption spectra after UV laser excitation of SO/sub 2/ were recorded and analyzed with respect to collisional energy transfer. Byuse of previously determined calibration curves, the absorption-time signals were converted into average energy-number of collision profiles. Energy-dependent average energies transferred per collision (..delta..E) were derived for 22 different collision partners. The temperature dependence of (..delta..E) was determined over the range 300-1500 K by experiments in a CO/sub 2/ CW laser-heated reactor and in shock waves.

  14. Energy transfer between a nanosystem and its host fluid: A multiscale factorization approach

    SciTech Connect

    Sereda, Yuriy V.; Espinosa-Duran, John M.; Ortoleva, Peter J.

    2014-02-21

    Energy transfer between a macromolecule or supramolecular assembly and a host medium is considered from the perspective of Newton's equations and Lie-Trotter factorization. The development starts by demonstrating that the energy of the molecule evolves slowly relative to the time scale of atomic collisions-vibrations. The energy is envisioned to be a coarse-grained variable that coevolves with the rapidly fluctuating atomistic degrees of freedom. Lie-Trotter factorization is shown to be a natural framework for expressing this coevolution. A mathematical formalism and workflow for efficient multiscale simulation of energy transfer is presented. Lactoferrin and human papilloma virus capsid-like structure are used for validation.

  15. Energy transfer between a nanosystem and its host fluid: A multiscale factorization approach

    NASA Astrophysics Data System (ADS)

    Sereda, Yuriy V.; Espinosa-Duran, John M.; Ortoleva, Peter J.

    2014-02-01

    Energy transfer between a macromolecule or supramolecular assembly and a host medium is considered from the perspective of Newton's equations and Lie-Trotter factorization. The development starts by demonstrating that the energy of the molecule evolves slowly relative to the time scale of atomic collisions-vibrations. The energy is envisioned to be a coarse-grained variable that coevolves with the rapidly fluctuating atomistic degrees of freedom. Lie-Trotter factorization is shown to be a natural framework for expressing this coevolution. A mathematical formalism and workflow for efficient multiscale simulation of energy transfer is presented. Lactoferrin and human papilloma virus capsid-like structure are used for validation.

  16. Combining semiconductor quantum dots and bioscaffolds into nanoscale energy transfer devices.

    PubMed

    Spillmann, Christopher M; Stewart, Michael H; Susumu, Kimihiro; Medintz, Igor L

    2015-11-01

    Significant advances have been made in the development of nanoscale devices capable of exciton transport via Förster resonance energy transfer. Several requirements must be met for effective operation, including a reliable energy-harvesting source along with highly organized, precisely placed energy relay elements. For the latter, biological scaffolds such as DNA provide a customizable, symmetric, and stable structure that can be site-specifically modified with organic fluorophores. Here, advancements in nanoscale energy transfer devices incorporating semiconductor nanocrystals and bioscaffolds are reviewed with discussion of biofunctionalization, linker chemistries, design considerations, and concluding with applications in light harvesting, multiplexed biosensing, and optical logic. PMID:26560627

  17. Observation of the one- to six-neutron transfer reactions at sub-barrier energies

    SciTech Connect

    Jiang, C.L.; Rehm, K.E.; Gehring, J.

    1995-08-01

    It was suggested many years ago that when two heavy nuclei are in contact during a grazing collision, the transfer of several correlated neutron-pairs could occur. Despite considerable experimental effort, however, so far only cross sections for up to four-neutron transfers have been uniquely identified. The main difficulties in the study of multi-neutron transfer reactions are the small cross sections encountered at incident energies close to the barrier, and various experimental uncertainties which can complicate the analysis of these reactions. We have for the first time found evidence for multi-neutron transfer reactions covering the full sequence from one- to six-neutron transfer reactions at sub-barrier energies in the system {sup 58}Ni + {sup 100}Mo.

  18. The role of the concentration scale in the definition of transfer free energies.

    PubMed

    Moeser, Beate; Horinek, Dominik

    2015-01-01

    The Gibbs free energy of transferring a solute at infinite dilution between two solvents quantifies differences in solute-solvent interactions - if the transfer takes place at constant molarity of the solute. Yet, many calculation formulae and measuring instructions that are commonly used to quantify solute-solvent interactions correspond to transfer processes in which not the molarity of the solute but its concentration measured in another concentration scale is constant. Here, we demonstrate that in this case, not only the change in solute-solvent interactions is quantified but also the entropic effect of a volume change during the transfer. Consequently, the "phenomenon" which is known as "concentration-scale dependence" of transfer free energies is simply explained by a volume-entropy effect. Our explanations are of high importance for the study of cosolvent effects on protein stability.

  19. 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.

  20. An electron energy-loss study of picene and chrysene based charge transfer salts

    NASA Astrophysics Data System (ADS)

    Müller, Eric; Mahns, Benjamin; Büchner, Bernd; Knupfer, Martin

    2015-05-01

    The electronic excitation spectra of charge transfer compounds built from the hydrocarbons picene and chrysene, and the strong electron acceptors F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) and TCNQ (7,7,8,8-tetracyanoquinodimethan) have been investigated using electron energy-loss spectroscopy. The corresponding charge transfer compounds have been prepared by co-evaporation of the pristine constituents. We demonstrate that all investigated combinations support charge transfer, which results in new electronic excitation features at low energy. This might represent a way to synthesize low band gap organic semiconductors.

  1. An electron energy-loss study of picene and chrysene based charge transfer salts.

    PubMed

    Müller, Eric; Mahns, Benjamin; Büchner, Bernd; Knupfer, Martin

    2015-05-14

    The electronic excitation spectra of charge transfer compounds built from the hydrocarbons picene and chrysene, and the strong electron acceptors F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) and TCNQ (7,7,8,8-tetracyanoquinodimethan) have been investigated using electron energy-loss spectroscopy. The corresponding charge transfer compounds have been prepared by co-evaporation of the pristine constituents. We demonstrate that all investigated combinations support charge transfer, which results in new electronic excitation features at low energy. This might represent a way to synthesize low band gap organic semiconductors.

  2. Path induced coherent energy transfer in light-harvesting complexes in purple bacteria.

    PubMed

    Sun, Kewei; Ye, Jun; Zhao, Yang

    2014-09-28

    Features of path dependent energy transfer in a dual-ring light-harvesting (LH2) complexes (B850) system have been examined in detail systematically. The Frenkel-Dirac time dependent variational method with the Davydov D1 Ansatz is employed with detailed evolution of polaron dynamics in real space readily obtained. It is found that the phase of the transmission amplitude through the LH2 complexes plays an important role in constructing the coherent excitonic energy transfer. It is also found that the symmetry breaking caused by the dimerization of bacteriochlorophylls and coherence or correlation between two rings will be conducive in enhancing the exciton transfer efficiency. PMID:25273408

  3. Degrees of locality of energy transfer in the inertial range. [Kolmogoroff notion in turbulence theory

    NASA Technical Reports Server (NTRS)

    Zhou, YE

    1993-01-01

    Measured raw transfer interactions from which local energy transfer is argued to result are summed in a way that directly indicates the scale disparity (s) of contributions to the net energy flux across the spectrum. It is found that the dependence upon s closely follows the s exp -4/3 form predicted by classical arguments. As a result, it is concluded that direct numerical simulation measurements lend support to the classical Kolmogorov phenomenology of local interactions and local transfer in an inertial range.

  4. An electron energy-loss study of picene and chrysene based charge transfer salts

    SciTech Connect

    Müller, Eric; Mahns, Benjamin; Büchner, Bernd; Knupfer, Martin

    2015-05-14

    The electronic excitation spectra of charge transfer compounds built from the hydrocarbons picene and chrysene, and the strong electron acceptors F{sub 4}TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) and TCNQ (7,7,8,8-tetracyanoquinodimethan) have been investigated using electron energy-loss spectroscopy. The corresponding charge transfer compounds have been prepared by co-evaporation of the pristine constituents. We demonstrate that all investigated combinations support charge transfer, which results in new electronic excitation features at low energy. This might represent a way to synthesize low band gap organic semiconductors.

  5. Quantum coherent energy transfer over varying pathways in single light-harvesting complexes.

    PubMed

    Hildner, Richard; Brinks, Daan; Nieder, Jana B; Cogdell, Richard J; van Hulst, Niek F

    2013-06-21

    The initial steps of photosynthesis comprise the absorption of sunlight by pigment-protein antenna complexes followed by rapid and highly efficient funneling of excitation energy to a reaction center. In these transport processes, signatures of unexpectedly long-lived coherences have emerged in two-dimensional ensemble spectra of various light-harvesting complexes. Here, we demonstrate ultrafast quantum coherent energy transfer within individual antenna complexes of a purple bacterium under physiological conditions. We find that quantum coherences between electronically coupled energy eigenstates persist at least 400 femtoseconds and that distinct energy-transfer pathways that change with time can be identified in each complex. Our data suggest that long-lived quantum coherence renders energy transfer in photosynthetic systems robust in the presence of disorder, which is a prerequisite for efficient light harvesting.

  6. Mid-range adiabatic wireless energy transfer via a mediator coil

    SciTech Connect

    Rangelov, A.A. Vitanov, N.V.

    2012-09-15

    A technique for efficient mid-range wireless energy transfer between two coils via a mediator coil is proposed. By varying the coil frequencies, three resonances are created: emitter-mediator (EM), mediator-receiver (MR) and emitter-receiver (ER). If the frequency sweeps are adiabatic and such that the EM resonance precedes the MR resonance, the energy flows sequentially along the chain emitter-mediator-receiver. If the MR resonance precedes the EM resonance, then the energy flows directly from the emitter to the receiver via the ER resonance; then the losses from the mediator are suppressed. This technique is robust against noise, resonant constraints and external interferences. - Highlights: Black-Right-Pointing-Pointer Efficient and robust mid-range wireless energy transfer via a mediator coil. Black-Right-Pointing-Pointer The adiabatic energy transfer is analogous to adiabatic passage in quantum optics. Black-Right-Pointing-Pointer Wireless energy transfer is insensitive to any resonant constraints. Black-Right-Pointing-Pointer Wireless energy transfer is insensitive to noise in the neighborhood of the coils.

  7. New model of calculating the energy transfer efficiency for the spherical theta-pinch device

    SciTech Connect

    Xu, G.; Hock, C.; Loisch, G.; Jacoby, J.; Xiao, G.; Zhao, Y.; Weyrich, K.; Li, Y.

    2015-05-15

    Ion-beam-plasma-interaction plays an important role in the field of warm dense matter and inertial confinement fusion. A spherical theta pinch is proposed to act as a plasma target in various applications including a plasma stripper cell. One key parameter for such applications is the free electron density. A linear dependency of this density to the amount of energy transferred into the plasma from an energy storage was found by Teske. Since the amount of stored energy is known, the energy transfer efficiency is a reliable parameter for the design of a spherical theta pinch device. As the main assumption of a constant reflected plasma resistance is contradictory by the measured data, the traditional two models of energy transfer efficiency will lead to wrong results. From measurements, the parasitic resistance is derived as constant. Based on this key parameter, a new model is proposed. Due to no assumption, the new model is considered as exact. Further, a comparison of these three different models is given at a fixed operation voltage for the full range of working gas pressures. Due to the inappropriate assumptions included in the traditional models, one owns a tendency to overestimate the energy transfer efficiency whereas the other leads to an underestimation. Applying our new model to a wide spread set of operation voltages and gas pressures, an overall picture of the energy transfer efficiency results.

  8. Modeling of energy transfer between two crossing smoothed laser beams in a plasma with flow profile

    NASA Astrophysics Data System (ADS)

    Colaitis, A.; Hüller, S.; Tikhonchuk, V. T.; Pesme, D.; Duchateau, G.; Porzio, A.

    2016-05-01

    We study the crossed beam energy transfer (CBET) between laser fields generated by optical smoothing methods. The energy transfer, as well as the angular distribution of the outgoing light fields are investigated for two incident smoothed laser beams in a plasma with a flow gradient, allowing for resonant transfer close to the sonic point. Simulations with the code HARMONY based on time-dependent paraxial light propagation are compared to simulations using a new approach based on paraxial complex geometrical optics (PCGO). Both approaches show good agreement for the average energy transfer past a short transient period, which is a promising result for the use of the PCGO method as a module within a hydrodynamics code to efficiently compute CBET in mm-scale plasma configurations. Statistical aspects related to role of laser speckles in CBET are considered via an ensemble of different phase plate realizations.

  9. Local intermodal energy transfer of the secondary instability in a plane channel

    NASA Technical Reports Server (NTRS)

    Singer, Bart A.; Ferziger, Joel H.; Spalart, Philippe R.; Reed, Helen L.

    1987-01-01

    A mathematical technique for analyzing local energy-transfer rates among wave-vector triads is developed and applied to the data generated by direct numerical simulations of waves with various types of initial conditions. Starting the simulation with a primary two-dimensional wave and random noise produced structures very similar to those which evolved from three-dimensional center modes. The local transfer rates determined in this case help to explain the eventual deformation of the primary two-dimensional wave which was observed in wind-tunnel experiments. Including weak streamwise vortices in the initial flow field results in large amounts of energy being transferred to the K-type modes early in the simulation. The later development of the waves (and hence the energy-transfer rates) is similar to the previous case.

  10. Non-contact pumping of light emitters via non-radiative energy transfer

    DOEpatents

    Klimov, Victor I.; Achermann, Marc

    2010-01-05

    A light emitting device is disclosed including a primary light source having a defined emission photon energy output, and, a light emitting material situated near to said primary light source, said light emitting material having an absorption onset equal to or less in photon energy than the emission photon energy output of the primary light source whereby non-radiative energy transfer from said primary light source to said light emitting material can occur yielding light emission from said light emitting material.

  11. Definition and determination of the triplet-triplet energy transfer reaction coordinate.

    PubMed

    Zapata, Felipe; Marazzi, Marco; Castaño, Obis; Acuña, A Ulises; Frutos, Luis Manuel

    2014-01-21

    A definition of the triplet-triplet energy transfer reaction coordinate within the very weak electronic coupling limit is proposed, and a novel theoretical formalism is developed for its quantitative determination in terms of internal coordinates The present formalism permits (i) the separation of donor and acceptor contributions to the reaction coordinate, (ii) the identification of the intrinsic role of donor and acceptor in the triplet energy transfer process, and (iii) the quantification of the effect of every internal coordinate on the transfer process. This formalism is general and can be applied to classical as well as to nonvertical triplet energy transfer processes. The utility of the novel formalism is demonstrated here by its application to the paradigm of nonvertical triplet-triplet energy transfer involving cis-stilbene as acceptor molecule. In this way the effect of each internal molecular coordinate in promoting the transfer rate, from triplet donors in the low and high-energy limit, could be analyzed in detail. PMID:25669358

  12. Large cross section for super energy transfer from hyperthermal atoms to ambient molecules

    NASA Astrophysics Data System (ADS)

    Ma, Jianqiang; Wilhelm, Michael J.; Smith, Jonathan M.; Dai, Hai-Lung

    2016-04-01

    The experimentally measured cross section for super energy transfer collisions between a hyperthermal H atom and an ambient molecule is presented here. This measurement substantiates an emerging energy transfer mechanism with significant cross section, whereby a major fraction of atomic translational energy is converted into molecular vibrational energy through a transient collision-induced reactive complex. Specifically, using nanosecond time-resolved infrared emission spectroscopy, it is revealed that collisions between hyperthermal hydrogen atoms (with 59 kcal/mol of kinetic energy) and ambient SO2 result in the production of vibrationally highly excited SO2 with >14 000 cm-1 of internal energy. The lower limit of the cross section for this super energy transfer process is determined to be 0.53 ±0.05 Å2, i.e., 2% of all hard-sphere collisions. This cross section is orders of magnitude greater than that predicted by the exponential energy gap law, which is commonly used for describing collisional energy transfer through repulsive interactions.

  13. Experimental Study of RF Energy Transfer System in Indoor Environment

    NASA Astrophysics Data System (ADS)

    Adami, S.-E.; Proynov, P. P.; Stark, B. H.; Hilton, G. S.; Craddock, I. J.

    2014-11-01

    This paper presents a multi-transmitter, 2.43 GHz Radio-Frequency (RF) wireless power transfer (WPT) system for powering on-body devices. It is shown that under typical indoor conditions, the received power range spans several orders of magnitude from microwatts to milliwatts. A body-worn dual-polarised rectenna (rectifying antenna) is presented, designed for situations where the dominant polarization is unpredictable, as is the case for the on-body sensors. Power management circuitry is demonstrated that optimally loads the rectenna even under highly intermittent conditions, and boosts the voltage to charge an on-board storage capacitor.

  14. Radiative and nonradiative exciton energy transfer in monolayers of two-dimensional group-VI transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Manolatou, Christina; Wang, Haining; Chan, Weimin; Tiwari, Sandip; Rana, Farhan

    2016-04-01

    We present results on the rates of interlayer energy transfer between excitons in monolayers of two-dimensional group-VI transition metal dichalcogenides (TMDs). We consider both radiative (mediated by real photons) and nonradiative (mediated by virtual photons) mechanisms of energy transfer using a unified Green's function approach that takes into account modification of the exciton energy dispersions as a result of interactions. The large optical oscillator strengths associated with excitons in TMDs result in very fast energy transfer rates. The energy transfer times depend on the exciton momentum, exciton linewidth, and the interlayer separation and can range from values less than 100 femtoseconds to more than tens of picoseconds. Whereas inside the light cone the energy transfer rates of longitudinal and transverse excitons are comparable, outside the light cone the energy transfer rates of longitudinal excitons far exceed those of transverse excitons. Average energy transfer times for a thermal ensemble of longitudinal and transverse excitons is temperature dependent and can be smaller than a picosecond at room temperature for interlayer separations smaller than 10 nm. Energy transfer times of localized excitons range from values less than a picosecond to several tens of picoseconds. When the exciton scattering and dephasing rates are small, energy transfer dynamics exhibit coherent oscillations. Our results show that electromagnetic interlayer energy transfer can be an efficient mechanism for energy exchange between TMD monolayers.

  15. Collisionless inter-species energy transfer and turbulent heating in drift wave turbulence

    SciTech Connect

    Zhao, L.; Diamond, P. H.

    2012-08-15

    We reconsider the classic problems of calculating 'turbulent heating' and collisionless inter-species transfer of energy in drift wave turbulence. These issues are of interest for low collisionality, electron heated plasmas, such as ITER, where collisionless energy transfer from electrons to ions is likely to be significant. From the wave Poynting theorem at steady state, a volume integral over an annulus r{sub 1}=-S{sub r}|{sub r{sub 1}{sup r{sub 2}}}{ne}0. Here S{sub r} is the wave energy density flux in the radial direction. Thus, a wave energy flux differential across an annular region indeed gives rise to a net heating, in contrast to previous predictions. This heating is related to the Reynolds work by the zonal flow, since S{sub r} is directly linked to the zonal flow drive. In addition to net heating, there is inter-species heat transfer. For collisionless electron drift waves, the total turbulent energy source for collisionless heat transfer is due to quasilinear electron cooling. Subsequent quasilinear ion heating occurs through linear ion Landau damping. In addition, perpendicular heating via ion polarization currents contributes to ion heating. Since at steady state, Reynolds work of the turbulence on the zonal flow must balance zonal flow frictional damping ({approx}{nu}{sub ii}{sup 2}{approx}|(e{phi}(tilde sign)/T)|{sup 4}), it is no surprise that zonal flow friction appears as an important channel for ion heating. This process of energy transfer via zonal flow has not previously been accounted for in analyses of energy transfer. As an application, we compare the rate of turbulent energy transfer in a low collisionality plasma with the rate of the energy transfer by collisions. The result shows that the collisionless turbulent energy transfer is a significant energy coupling process for ITER plasma.

  16. Carotenoid charge transfer states and their role in energy transfer processes in LH1-RC complexes from aerobic anoxygenic phototrophs.

    PubMed

    Šlouf, Václav; Fuciman, Marcel; Dulebo, Alexander; Kaftan, David; Koblížek, Michal; Frank, Harry A; Polívka, Tomáš

    2013-09-26

    Light-harvesting complexes ensure necessary flow of excitation energy into photosynthetic reaction centers. In the present work, transient absorption measurements were performed on LH1-RC complexes isolated from two aerobic anoxygenic phototrophs (AAPs), Roseobacter sp. COL2P containing the carotenoid spheroidenone, and Erythrobacter sp. NAP1 which contains the carotenoids zeaxanthin and bacteriorubixanthinal. We show that the spectroscopic data from the LH1-RC complex of Roseobacter sp. COL2P are very similar to those previously reported for Rhodobacter sphaeroides, including the transient absorption spectrum originating from the intramolecular charge-transfer (ICT) state of spheroidenone. Although the ICT state is also populated in LH1-RC complexes of Erythrobacter sp. NAP1, its appearance is probably related to the polarity of the bacteriorubixanthinal environment rather than to the specific configuration of the carotenoid, which we hypothesize is responsible for populating the ICT state of spheroidenone in LH1-RC of Roseobacter sp. COL2P. The population of the ICT state enables efficient S1/ICT-to-bacteriochlorophyll (BChl) energy transfer which would otherwise be largely inhibited for spheroidenone and bacteriorubixanthinal due to their low energy S1 states. In addition, the triplet states of these carotenoids appear well-tuned for efficient quenching of singlet oxygen or BChl-a triplets, which is of vital importance for oxygen-dependent organisms such as AAPs. PMID:23130956

  17. Solar wind energy transfer through the magnetopause of an open magnetosphere

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Roederer, J. G.

    1982-01-01

    An expression is derived for the total power, transferred from the solar wind to an open magnetosphere, which consists of the electromagnetic energy rate and the particle kinetic energy rate. The total rate of energy transferred from the solar wind to an open magnetosphere mainly consists of kinetic energy, and the kinetic energy flux is carried by particles, penetrating from the solar wind into the magnetosphere, which may contribute to the observed flow in the plasma mantle and which will eventually be convected slowly toward the plasma sheet by the electric field as they flow down the tail. While the electromagnetic energy rate controls the near-earth magnetospheric activity, the kinetic energy rate should dominate the dynamics of the distant magnetotail.

  18. Utilizing Energy Transfer in Binary and Ternary Bulk Heterojunction Organic Solar Cells.

    PubMed

    Feron, Krishna; Cave, James M; Thameel, Mahir N; O'Sullivan, Connor; Kroon, Renee; Andersson, Mats R; Zhou, Xiaojing; Fell, Christopher J; Belcher, Warwick J; Walker, Alison B; Dastoor, Paul C

    2016-08-17

    Energy transfer has been identified as an important process in ternary organic solar cells. Here, we develop kinetic Monte Carlo (KMC) models to assess the impact of energy transfer in ternary and binary bulk heterojunction systems. We used fluorescence and absorption spectroscopy to determine the energy disorder and Förster radii for poly(3-hexylthiophene-2,5-diyl), [6,6]-phenyl-C61-butyric acid methyl ester, 4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]squaraine (DIBSq), and poly(2,5-thiophene-alt-4,9-bis(2-hexyldecyl)-4,9-dihydrodithieno[3,2-c:3',2'-h][1,5]naphthyridine-5,10-dione). Heterogeneous energy transfer is found to be crucial in the exciton dissociation process of both binary and ternary organic semiconductor systems. Circumstances favoring energy transfer across interfaces allow relaxation of the electronic energy level requirements, meaning that a cascade structure is not required for efficient ternary organic solar cells. We explain how energy transfer can be exploited to eliminate additional energy losses in ternary bulk heterojunction solar cells, thus increasing their open-circuit voltage without loss in short-circuit current. In particular, we show that it is important that the DIBSq is located at the electron donor-acceptor interface; otherwise charge carriers will be trapped in the DIBSq domain or excitons in the DIBSq domains will not be able to dissociate efficiently at an interface. KMC modeling shows that only small amounts of DIBSq (<5% by weight) are needed to achieve substantial performance improvements due to long-range energy transfer. PMID:27456294

  19. Utilizing Energy Transfer in Binary and Ternary Bulk Heterojunction Organic Solar Cells.

    PubMed

    Feron, Krishna; Cave, James M; Thameel, Mahir N; O'Sullivan, Connor; Kroon, Renee; Andersson, Mats R; Zhou, Xiaojing; Fell, Christopher J; Belcher, Warwick J; Walker, Alison B; Dastoor, Paul C

    2016-08-17

    Energy transfer has been identified as an important process in ternary organic solar cells. Here, we develop kinetic Monte Carlo (KMC) models to assess the impact of energy transfer in ternary and binary bulk heterojunction systems. We used fluorescence and absorption spectroscopy to determine the energy disorder and Förster radii for poly(3-hexylthiophene-2,5-diyl), [6,6]-phenyl-C61-butyric acid methyl ester, 4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]squaraine (DIBSq), and poly(2,5-thiophene-alt-4,9-bis(2-hexyldecyl)-4,9-dihydrodithieno[3,2-c:3',2'-h][1,5]naphthyridine-5,10-dione). Heterogeneous energy transfer is found to be crucial in the exciton dissociation process of both binary and ternary organic semiconductor systems. Circumstances favoring energy transfer across interfaces allow relaxation of the electronic energy level requirements, meaning that a cascade structure is not required for efficient ternary organic solar cells. We explain how energy transfer can be exploited to eliminate additional energy losses in ternary bulk heterojunction solar cells, thus increasing their open-circuit voltage without loss in short-circuit current. In particular, we show that it is important that the DIBSq is located at the electron donor-acceptor interface; otherwise charge carriers will be trapped in the DIBSq domain or excitons in the DIBSq domains will not be able to dissociate efficiently at an interface. KMC modeling shows that only small amounts of DIBSq (<5% by weight) are needed to achieve substantial performance improvements due to long-range energy transfer.

  20. 77 FR 73654 - Eau Galle Renewable Energy Company, Eau Galle Hydro, LLC; Notice of Transfer of Exemption

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-11

    ... Energy Regulatory Commission Eau Galle Renewable Energy Company, Eau Galle Hydro, LLC; Notice of Transfer of Exemption 1. By letter filed October 12, 2012, Eau Galle Renewable Energy Company informed the..., originally issued March 10, 1987,\\1\\ and transferred to Eau Galle Renewable Energy Company by letter.\\2\\...

  1. Role of an elliptical structure in photosynthetic energy transfer: Collaboration between quantum entanglement and thermal fluctuation.

    PubMed

    Oka, Hisaki

    2016-05-13

    Recent experiments have revealed that the light-harvesting complex 1 (LH1) in purple photosynthetic bacteria has an elliptical structure. Generally, symmetry lowering in a structure leads to a decrease in quantum effects (quantum coherence and entanglement), which have recently been considered to play a role in photosynthetic energy transfer, and hence, elliptical structure seems to work against efficient photosynthetic energy transfer. Here we analyse the effect of an elliptical structure on energy transfer in a purple photosynthetic bacterium and reveal that the elliptical distortion rather enhances energy transfer from peripheral LH2 to LH1 at room temperature. Numerical results show that quantum entanglement between LH1 and LH2 is formed over a wider range of high energy levels than would have been the case with circular LH1. Light energy absorbed by LH2 is thermally pumped via thermal fluctuation and is effectively transferred to LH1 through the entangled states at room temperature rather than at low temperature. This result indicates the possibility that photosynthetic systems adopt an elliptical structure to effectively utilise both quantum entanglement and thermal fluctuation at physiological temperature.

  2. Role of an elliptical structure in photosynthetic energy transfer: Collaboration between quantum entanglement and thermal fluctuation

    NASA Astrophysics Data System (ADS)

    Oka, Hisaki

    2016-05-01

    Recent experiments have revealed that the light-harvesting complex 1 (LH1) in purple photosynthetic bacteria has an elliptical structure. Generally, symmetry lowering in a structure leads to a decrease in quantum effects (quantum coherence and entanglement), which have recently been considered to play a role in photosynthetic energy transfer, and hence, elliptical structure seems to work against efficient photosynthetic energy transfer. Here we analyse the effect of an elliptical structure on energy transfer in a purple photosynthetic bacterium and reveal that the elliptical distortion rather enhances energy transfer from peripheral LH2 to LH1 at room temperature. Numerical results show that quantum entanglement between LH1 and LH2 is formed over a wider range of high energy levels than would have been the case with circular LH1. Light energy absorbed by LH2 is thermally pumped via thermal fluctuation and is effectively transferred to LH1 through the entangled states at room temperature rather than at low temperature. This result indicates the possibility that photosynthetic systems adopt an elliptical structure to effectively utilise both quantum entanglement and thermal fluctuation at physiological temperature.

  3. Role of an elliptical structure in photosynthetic energy transfer: Collaboration between quantum entanglement and thermal fluctuation

    PubMed Central

    Oka, Hisaki

    2016-01-01

    Recent experiments have revealed that the light-harvesting complex 1 (LH1) in purple photosynthetic bacteria has an elliptical structure. Generally, symmetry lowering in a structure leads to a decrease in quantum effects (quantum coherence and entanglement), which have recently been considered to play a role in photosynthetic energy transfer, and hence, elliptical structure seems to work against efficient photosynthetic energy transfer. Here we analyse the effect of an elliptical structure on energy transfer in a purple photosynthetic bacterium and reveal that the elliptical distortion rather enhances energy transfer from peripheral LH2 to LH1 at room temperature. Numerical results show that quantum entanglement between LH1 and LH2 is formed over a wider range of high energy levels than would have been the case with circular LH1. Light energy absorbed by LH2 is thermally pumped via thermal fluctuation and is effectively transferred to LH1 through the entangled states at room temperature rather than at low temperature. This result indicates the possibility that photosynthetic systems adopt an elliptical structure to effectively utilise both quantum entanglement and thermal fluctuation at physiological temperature. PMID:27173144

  4. A simple model for exploring the role of quantum coherence and the environment in excitonic energy transfer.

    PubMed

    Manikandan, Sreenath K; Shaji, Anil

    2015-07-28

    We investigate the role of quantum coherence in modulating the energy transfer rate between two independent energy donors and a single acceptor participating in an excitonic energy transfer process. The energy transfer rate depends explicitly on the nature of the initial coherent superposition state of the two donors and we connect it to the observed absorption profile of the acceptor and the stimulated emission profile of the energy donors. We consider simple models with mesoscopic environments interacting with the donors and the acceptor and compare the expression we obtained for the energy transfer rate with the results of numerical integration.

  5. Energy-Efficient Information Transfer by Visual Pathway Synapses

    PubMed Central

    Harris, Julia J.; Jolivet, Renaud; Engl, Elisabeth; Attwell, David

    2015-01-01

    Summary The architecture of computational devices is shaped by their energy consumption. Energetic constraints are used to design silicon-based computers but are poorly understood for neural computation. In the brain, most energy is used to reverse ion influxes generating excitatory postsynaptic currents (EPSCs) and action potentials. Thus, EPSCs should be small to minimize energy use, but not so small as to impair information transmission. We quantified information flow through the retinothalamic synapse in the visual pathway in brain slices, with cortical and inhibitory input to the postsynaptic cell blocked. Altering EPSC size with dynamic clamp, we found that a larger-than-normal EPSC increased information flow through the synapse. Thus, the evolutionarily selected EPSC size does not maximize retinal information flow to the cortex. By assessing the energy used on postsynaptic ion pumping and action potentials, we show that, instead, the EPSC size optimizes the ratio of retinal information transmitted to energy consumed. These data suggest maximization of information transmission per energy used as a synaptic design principle. PMID:26671670

  6. Generating Excitement: Build Your Own Generator to Study the Transfer of Energy

    ERIC Educational Resources Information Center

    Fletcher, Kurt; Rommel-Esham, Katie; Farthing, Dori; Sheldon, Amy

    2011-01-01

    The transfer of energy from one form to another can be difficult to understand. The electrical energy that turns on a lamp may come from the burning of coal, water falling at a hydroelectric plant, nuclear reactions, or gusts of wind caused by the uneven heating of the Earth. The authors have developed and tested an exciting hands-on activity to…

  7. Measurements of pressure drop, heat transfer coefficient and critical energy of a bundle conductor

    SciTech Connect

    Junghans, D.

    1981-09-01

    Friction factor, saturation temperature, heat transfer coefficient and critical energy of an eight strand bundle conductor were measured in the test facility SULTAN at SIN in Switzerland. The measured values of the critical energy are in good agreement with those calculated by the computer code LONSA. 10 refs.

  8. A Conceptual Change Model for Teaching Heat Energy, Heat Transfer and Insulation

    ERIC Educational Resources Information Center

    Lee, C. K.

    2014-01-01

    This study examines the existing knowledge that pre-service elementary teachers (PSETs) have regarding heat energy, heat transfer and insulation. The PSETs' knowledge of heat energy was initially assessed by using an activity: determining which container would be best to keep hot water warm for the longest period of time. Results showed that…

  9. Experimental studies and computer simulation of the control of energy transfer using inductor-converter bridges

    SciTech Connect

    Hirano, M.; Kustom, R.L.

    1984-03-01

    An inductor-converter bridge (ICB) is a solid state DC-AC-DC power converter system for bidirectional, controllable, energy transfer between two coils. The ICB is suitable for supplying large pulsed power to such magnets as the superconducting equilibrium field coil of the proposed tokamak power reactors from another superconducting energy storage coil.

  10. Investigation of Charge Transfer in Low Energy D2+ + H Collisions using Merged Beams

    SciTech Connect

    Andrianarijaona, Vola M; Rada, J. J.; Rejoub, Riad A; Havener, Charles C

    2009-01-01

    Synopsis The hydrogen - hydrogen (deuterium) molecular ion is the most fundamental ion-molecule two-electron system. Charge transfer proceeds through dynamically coupled electronic, vibrational and rotational degrees of freedom. Using the ion-atom merged-beams apparatus at Oak Ridge National Laboratory absolute charge transfer cross sections for D2+ + H are measured from keV/u collision energies where the collision is considered "ro-vibrationally frozen" to meV/u energies where collision times are long enough to sample vibrational and rotational modes. The measurements benchmark high energy theory and vibrationally specific adiabatic theory.

  11. Two-dimensional free energy surfaces for primary electron transfer in a photosynthetic reaction center

    NASA Astrophysics Data System (ADS)

    Warshel, A.; Chu, Z. T.; Parson, W. W.

    1997-01-01

    Fushiki and Tachiya [Chem. Phys. Lett. 255 (1996) 83] recently analyzed the free energy surfaces of the initial electron-transfer processes in photosynthetic bacterial reaction centers. The authors state that when the results from simulations described by Warshel, Chu and Parson [Photochem. Photobiol. A: Chem. 82 (1994) 123] are analyzed using their formulation, the calculated energy of a key ion-pair state is inconsistent with experiment. They also state that previous analyses of the photosynthetic electron-transfer reactions had been limited to one-dimensional free energy surfaces. We show here that both these assertions are incorrect.

  12. Observation of anisotropic energy transfer in magnetically coupled magnetic vortex pair

    NASA Astrophysics Data System (ADS)

    Hasegawa, N.; Sugimoto, S.; Kumar, D.; Barman, S.; Barman, A.; Kondou, K.; Otani, Y.

    2016-06-01

    We have experimentally investigated the energy transfer and storage in the magnetostatically coupled vortices in a pair of disks. By measuring the frequency dependence of the rectified dc voltage, we observed a specific gyrating motion due to anomalous energy storage at the off-resonant frequency for anti-parallel polarities. Micromagnetic simulations based on the Landau-Lifshitz-Gilbert equation qualitatively reproduce the experimental results and reveal that the behavior arises from the anisotropic energy transfer, i.e., the modulation of effective damping constant of the pair disks, originating from the phase difference between coupled vortex cores. These findings can be of use in magnetic vortex based logic operations.

  13. Nonequilibrium Energy Transfer at Nanoscale: A Unified Theory from Weak to Strong Coupling.

    PubMed

    Wang, Chen; Ren, Jie; Cao, Jianshu

    2015-07-08

    Unraveling the microscopic mechanism of quantum energy transfer across two-level systems provides crucial insights to the optimal design and potential applications of low-dimensional nanodevices. Here, we study the non-equilibrium spin-boson model as a minimal prototype and develop a fluctuation-decoupled quantum master equation approach that is valid ranging from the weak to the strong system-bath coupling regime. The exact expression of energy flux is analytically established, which dissects the energy transfer as multiple boson processes with even and odd parity. Our analysis provides a unified interpretation of several observations, including coherence-enhanced heat flux and negative differential thermal conductance. The results will have broad implications for the fine control of energy transfer in nano-structural devices.

  14. Nonadiabatic molecular dynamics simulations of the energy transfer between building blocks in a phenylene ethynylene dendrimer.

    PubMed

    Fernandez-Alberti, Sebastian; Kleiman, Valeria D; Tretiak, Sergei; Roitberg, Adrian E

    2009-07-01

    The ultrafast dynamics of electronic and vibrational energy transfer between two- and three-ring linear poly(phenylene ethynylene) units linked by meta-substitution is studied by nonadiabatic molecular dynamics simulations. The molecular dynamics with quantum transitions (1, 2) method is used including an "on the fly" calculation of the potential energy surfaces and electronic couplings. The results show that during the first 40 fs after a vertical photoexcitation to the S(2) state, the nonadiabatic coupling between S(2) and S(1) states causes a fast transfer of the electronic populations. A rapid decrease of the S(1)-S(2) energy gap is observed, reaching a first conical intersection at approximately 5 fs. Therefore, the first hopping events take place, and the S(2) state starts to depopulate. The analysis of the structural and energetic properties of the molecule during the jumps reveals the main role that the ethynylene triple bond plays in the unidirectional energy transfer process. PMID:19378966

  15. Nonequilibrium Energy Transfer at Nanoscale: A Unified Theory from Weak to Strong Coupling

    NASA Astrophysics Data System (ADS)

    Wang, Chen; Ren, Jie; Cao, Jianshu

    2015-07-01

    Unraveling the microscopic mechanism of quantum energy transfer across two-level systems provides crucial insights to the optimal design and potential applications of low-dimensional nanodevices. Here, we study the non-equilibrium spin-boson model as a minimal prototype and develop a fluctuation-decoupled quantum master equation approach that is valid ranging from the weak to the strong system-bath coupling regime. The exact expression of energy flux is analytically established, which dissects the energy transfer as multiple boson processes with even and odd parity. Our analysis provides a unified interpretation of several observations, including coherence-enhanced heat flux and negative differential thermal conductance. The results will have broad implications for the fine control of energy transfer in nano-structural devices.

  16. Theoretical study of vibrational energy transfer of free OH groups at the water-air interface.

    PubMed

    Zheng, Renhui; Wei, Wenmei; Sun, Yuanyuan; Song, Kai; Shi, Qiang

    2016-04-14

    Recent experimental studies have shown that the vibrational dynamics of free OH groups at the water-air interface is significantly different from that in bulk water. In this work, by performing molecular dynamics simulations and mixed quantum/classical calculations, we investigate different vibrational energy transfer pathways of free OH groups at the water-air interface. The calculated intramolecular vibrational energy transfer rate constant and the free OH bond reorientation time scale agree well with the experiment. It is also found that, due to the small intermolecular vibrational couplings, the intermolecular vibrational energy transfer pathway that is very important in bulk water plays a much less significant role in the vibrational energy relaxation of the free OH groups at the water-air interface.

  17. Nonequilibrium Energy Transfer at Nanoscale: A Unified Theory from Weak to Strong Coupling

    PubMed Central

    Wang, Chen; Ren, Jie; Cao, Jianshu

    2015-01-01

    Unraveling the microscopic mechanism of quantum energy transfer across two-level systems provides crucial insights to the optimal design and potential applications of low-dimensional nanodevices. Here, we study the non-equilibrium spin-boson model as a minimal prototype and develop a fluctuation-decoupled quantum master equation approach that is valid ranging from the weak to the strong system-bath coupling regime. The exact expression of energy flux is analytically established, which dissects the energy transfer as multiple boson processes with even and odd parity. Our analysis provides a unified interpretation of several observations, including coherence-enhanced heat flux and negative differential thermal conductance. The results will have broad implications for the fine control of energy transfer in nano-structural devices. PMID:26152705

  18. Analysis of optical near-field energy transfer by stochastic model unifying architectural dependencies

    SciTech Connect

    Naruse, Makoto; Akahane, Kouichi; Yamamoto, Naokatsu; Holmström, Petter; Thylén, Lars; Huant, Serge; Ohtsu, Motoichi

    2014-04-21

    We theoretically and experimentally demonstrate energy transfer mediated by optical near-field interactions in a multi-layer InAs quantum dot (QD) structure composed of a single layer of larger dots and N layers of smaller ones. We construct a stochastic model in which optical near-field interactions that follow a Yukawa potential, QD size fluctuations, and temperature-dependent energy level broadening are unified, enabling us to examine device-architecture-dependent energy transfer efficiencies. The model results are consistent with the experiments. This study provides an insight into optical energy transfer involving inherent disorders in materials and paves the way to systematic design principles of nanophotonic devices that will allow optimized performance and the realization of designated functions.

  19. Fermi level pinning and the charge transfer contribution to the energy of adsorption at semiconducting surfaces

    SciTech Connect

    Krukowski, Stanisław; Kempisty, Paweł; Strak, Paweł; Sakowski, Konrad

    2014-01-28

    It is shown that charge transfer, the process analogous to formation of semiconductor p-n junction, contributes significantly to adsorption energy at semiconductor surfaces. For the processes without the charge transfer, such as molecular adsorption of closed shell systems, the adsorption energy is determined by the bonding only. In the case involving charge transfer, such as open shell systems like metal atoms or the dissociating molecules, the energy attains different value for the Fermi level differently pinned. The Density Functional Theory (DFT) simulation of species adsorption at different surfaces, such as SiC(0001) or GaN(0001) confirms these predictions: the molecular adsorption is independent on the coverage, while the dissociative process adsorption energy varies by several electronvolts.

  20. Energy transfer in volume-reflecting heat shields

    NASA Technical Reports Server (NTRS)

    Weston, K. C.

    1974-01-01

    An approximate analysis of radiative transfer in highly scattering materials was developed based on the Kubelka-Munk differential equations--a set of two differential equations representing the spatial rate of change of radiative half-fluxes within the scattering media. These approximate solutions of the Kubelka-Munk equations together with analytic solutions for the steady state temperature distribution for two types of boundary conditions are given. These solutions show the influence of back surface reflectance, scattering power, incident radiative flux parameter and boundary conductive flux parameter on overall reflectance and temperature distributions. This radiation field analysis, adapted to spherical geometry, was applied to the evaluation of the thermal performance of teflon and fritted quartz as heat protection materials for entry into the atmosphere of Jupiter.

  1. Efficient light harvesting and energy transfer in a red phosphorescent iridium dendrimer.

    PubMed

    Cho, Yang-Jin; Hong, Seong Ahn; Son, Ho-Jin; Han, Won-Sik; Cho, Dae Won; Kang, Sang Ook

    2014-12-15

    A series of red phosphorescent iridium dendrimers of the type [Ir(btp)2(pic-PCn)] (Ir-Gn; n = 0, 1, 2, and 3) with two 2-(benzo[b]thiophen-2-yl)pyridines (btp) and 3-hydroxypicolinate (pic) as the cyclometalating and ancillary ligands were prepared in good yields. Dendritic generation was grown at the 3 position of the pic ligand with 4-(9H-carbazolyl)phenyl dendrons connected to 3,5-bis(methyleneoxy)benzyloxy branches (PCn; n = 0, 2, 4, and 8). The harvesting photons on the PCn dendrons followed by efficient energy transfer to the iridium center resulted in high red emissions at ∼600 nm by metal-to-ligand charge transfer. The intensity of the phosphorescence gradually increased with increasing dendrimer generation. Steady-state and time-resolved spectroscopy were used to investigate the energy-transfer mechanism. On the basis of the fluorescence quenching rate constants of the PCn dendrons, the energy-transfer efficiencies for Ir-G1, Ir-G2, and Ir-G3 were 99, 98, and 96%, respectively. The energy-transfer efficiency for higher-generation dendrimers decreased slightly because of the longer distance between the PC dendrons and the core iridium(III) complex, indicating that energy transfer in Ir-Gn is a Förster-type energy transfer. Finally, the light-harvesting efficiencies for Ir-G1, Ir-G2, and Ir-G3 were determined to be 162, 223, and 334%, respectively.

  2. Rovibrational energy transfer and dissociation in O2-O collisions.

    PubMed

    Andrienko, Daniil A; Boyd, Iain D

    2016-03-14

    A set of state-specific transition rates for each rovibrational level is generated for the O2(X(3)Σ(g)(-))-O(3)P system using the quasi-classical trajectory method at temperatures observed in hypersonic flows. A system of master equations describes the relaxation of the rovibrational ensemble to thermal equilibrium under ideal heat bath conditions at a constant translational temperature. Vibrational and rotational relaxation times, obtained from the average internal energies, exhibit a pattern inherent in a chemically reactive collisional pair. An intrinsic feature of the O3 molecular system with a large attractive potential is a weak temperature dependence of the rovibrational transition rates. For this reason, the quasi-steady vibrational and rotational temperatures experience a maximum at increasing translational temperature. The energy rate coefficients, that characterize the average loss of internal energy due to dissociation, quickly diminish at high temperatures, compared to other molecular systems. PMID:26979687

  3. Rovibrational energy transfer and dissociation in O2-O collisions.

    PubMed

    Andrienko, Daniil A; Boyd, Iain D

    2016-03-14

    A set of state-specific transition rates for each rovibrational level is generated for the O2(X(3)Σ(g)(-))-O(3)P system using the quasi-classical trajectory method at temperatures observed in hypersonic flows. A system of master equations describes the relaxation of the rovibrational ensemble to thermal equilibrium under ideal heat bath conditions at a constant translational temperature. Vibrational and rotational relaxation times, obtained from the average internal energies, exhibit a pattern inherent in a chemically reactive collisional pair. An intrinsic feature of the O3 molecular system with a large attractive potential is a weak temperature dependence of the rovibrational transition rates. For this reason, the quasi-steady vibrational and rotational temperatures experience a maximum at increasing translational temperature. The energy rate coefficients, that characterize the average loss of internal energy due to dissociation, quickly diminish at high temperatures, compared to other molecular systems.

  4. Rovibrational energy transfer and dissociation in O2-O collisions

    NASA Astrophysics Data System (ADS)

    Andrienko, Daniil A.; Boyd, Iain D.

    2016-03-01

    A set of state-specific transition rates for each rovibrational level is generated for the O 2 ( X 3 Σg - ) - O (" separators=" 3 P ) system using the quasi-classical trajectory method at temperatures observed in hypersonic flows. A system of master equations describes the relaxation of the rovibrational ensemble to thermal equilibrium under ideal heat bath conditions at a constant translational temperature. Vibrational and rotational relaxation times, obtained from the average internal energies, exhibit a pattern inherent in a chemically reactive collisional pair. An intrinsic feature of the O3 molecular system with a large attractive potential is a weak temperature dependence of the rovibrational transition rates. For this reason, the quasi-steady vibrational and rotational temperatures experience a maximum at increasing translational temperature. The energy rate coefficients, that characterize the average loss of internal energy due to dissociation, quickly diminish at high temperatures, compared to other molecular systems.

  5. Triplet energy transfer in conjugated polymers. I. Experimental investigation of a weakly disordered compound

    NASA Astrophysics Data System (ADS)

    Sudha Devi, Lekshmi; Al-Suti, Mohammad K.; Dosche, Carsten; Khan, Muhammad S.; Friend, Richard H.; Köhler, Anna

    2008-07-01

    Efficient triplet exciton emission has allowed improved operation of organic light-emitting diodes (LEDs). To enhance the device performance, it is necessary to understand what governs the motion of triplet excitons through the organic semiconductor. Here, we have investigated triplet diffusion using a model compound that has weak energetic disorder. The Dexter-type triplet energy transfer is found to be thermally activated down to a transition temperature TT , below which the transfer rate is only weakly temperature dependent. We show that above the transition temperature, Dexter energy transfer can be described within the framework of Marcus theory. We suggest that below TT , the nature of the transfer changes from phonon-assisted hopping to quantum-mechanical tunneling. The lower electron-phonon coupling and higher electronic coupling in the polymer compared to the monomer results in an enhanced triplet diffusion rate.

  6. Interchain vs. intrachain energy transfer in acceptor-capped conjugated polymers.

    PubMed

    Beljonne, D; Pourtois, G; Silva, C; Hennebicq, E; Herz, L M; Friend, R H; Scholes, G D; Setayesh, S; Mullen, K; Bredas, J L

    2002-08-20

    The energy-transfer processes taking place in conjugated polymers are investigated by means of ultrafast spectroscopy and correlated quantum-chemical calculations applied to polyindenofluorenes end-capped with a perylene derivative. Comparison between the time-integrated luminescence and transient absorption spectra measured in solution and in films allows disentangling of the contributions arising from intrachain and from interchain energy-migration phenomena. Intrachain processes dominate in solution where photoexcitation of the polyindenofluorene units induces a rather slow energy transfer to the perylene end moieties. In films, close contacts between chains favors interchain transport of the excited singlet species (from the conjugated bridge of one chain to the perylene unit of a neighboring one); this process is characterized by a 1-order-of-magnitude increase in transfer rate with respect to solution. This description is supported fully by the results of quantum-chemical calculations that go beyond the usual point-dipole model approximation and account for geometric relaxation phenomena in the excited state before energy migration. The calculations indicate a two-step mechanism for intrachain energy transfer with hopping along the conjugated chains as the rate-limiting step; the higher efficiency of the interchain transfer process is mainly due to larger electronic coupling matrix elements between closely lying chains.

  7. Competition between surface trapping and nonradiative energy transfer to gold nanofilm

    PubMed Central

    Yang, Zhenling; Liu, Yuqiang; He, Xing; Wen, Yanan; Yang, Yanqiang

    2010-01-01

    Nonradiative resonant energy transfer from CdSeS quantum dot to gold nanofilm was investigated by taking nanosecond and picosecond time resolved photoluminescence measurements. Surface plasma resonant absorption peak of gold nanofilm was adjusted to meet the near resonant conditions with the fluorescence peak of quantum dot by changing the thickness. Surface trapping state was proved to be the origin of the long lifetime component by comparing fresh and eight months aged quantum dot. It was observed that the excitonic state lifetime of the quantum dots was reduced by nonradiative resonant energy transfer to gold nanofilm. Nonradiative resonant energy transfer time, which was comparable with the surface trapping time, was calculated based on the data of picosecond photoluminescence measurements. No nonradiative energy transfer from surface trapping state to gold nanofilm, thus the lifetime of surface trapping state was not affected obviously. It is suggested that in the assembly combined with quantum dot and gold nanostructure, nonradiative energy transfer will occur after the population of excitonic state, and compete with surface trapping process. The interactions between surface trapping state and gold nanoflim were not exhibited. PMID:21124724

  8. Distance dependence of the energy transfer rate from a single semiconductor nanostructure to graphene.

    PubMed

    Federspiel, François; Froehlicher, Guillaume; Nasilowski, Michel; Pedetti, Silvia; Mahmood, Ather; Doudin, Bernard; Park, Serin; Lee, Jeong-O; Halley, David; Dubertret, Benoît; Gilliot, Pierre; Berciaud, Stéphane

    2015-02-11

    The near-field Coulomb interaction between a nanoemitter and a graphene monolayer results in strong Förster-type resonant energy transfer and subsequent fluorescence quenching. Here, we investigate the distance dependence of the energy transfer rate from individual, (i) zero-dimensional CdSe/CdS nanocrystals and (ii) two-dimensional CdSe/CdS/ZnS nanoplatelets to a graphene monolayer. For increasing distances d, the energy transfer rate from individual nanocrystals to graphene decays as 1/d(4). In contrast, the distance dependence of the energy transfer rate from a two-dimensional nanoplatelet to graphene deviates from a simple power law but is well described by a theoretical model, which considers a thermal distribution of free excitons in a two-dimensional quantum well. Our results show that accurate distance measurements can be performed at the single particle level using graphene-based molecular rulers and that energy transfer allows probing dimensionality effects at the nanoscale. PMID:25607231

  9. An optimized surface plasmon photovoltaic structure using energy transfer between discrete nano-particles.

    PubMed

    Lin, Albert; Fu, Sze-Ming; Chung, Yen-Kai; Lai, Shih-Yun; Tseng, Chi-Wei

    2013-01-14

    Surface plasmon enhancement has been proposed as a way to achieve higher absorption for thin-film photovoltaics, where surface plasmon polariton(SPP) and localized surface plasmon (LSP) are shown to provide dense near field and far field light scattering. Here it is shown that controlled far-field light scattering can be achieved using successive coupling between surface plasmonic (SP) nano-particles. Through genetic algorithm (GA) optimization, energy transfer between discrete nano-particles (ETDNP) is identified, which enhances solar cell efficiency. The optimized energy transfer structure acts like lumped-element transmission line and can properly alter the direction of photon flow. Increased in-plane component of wavevector is thus achieved and photon path length is extended. In addition, Wood-Rayleigh anomaly, at which transmission minimum occurs, is avoided through GA optimization. Optimized energy transfer structure provides 46.95% improvement over baseline planar cell. It achieves larger angular scattering capability compared to conventional surface plasmon polariton back reflector structure and index-guided structure due to SP energy transfer through mode coupling. Via SP mediated energy transfer, an alternative way to control the light flow inside thin-film is proposed, which can be more efficient than conventional index-guided mode using total internal reflection (TIR).

  10. A 'two-point' bound zinc porphyrin-zinc phthalocyanine-fullerene supramolecular triad for sequential energy and electron transfer.

    PubMed

    KC, Chandra B; Ohkubo, Kei; Karr, Paul A; Fukuzumi, Shunichi; D'Souza, Francis

    2013-09-01

    A novel supramolecular triad composed of a zinc porphyrin-zinc phthalocyanine dyad and fullerenes has been assembled using a 'two-point' axial binding approach, and occurrence of efficient photoinduced energy transfer followed by electron transfer is demonstrated.

  11. Mechanical energy generation and transfer in the racket arm during table tennis topspin backhands.

    PubMed

    Iino, Yoichi; Kojima, Takeji

    2016-06-01

    The ability to generate a high racket speed and a large amount of racket kinetic energy on impact is important for table tennis players. The purpose of this study was to understand how mechanical energy is generated and transferred in the racket arm during table tennis backhands. Ten male advanced right-handed table tennis players hit topspin backhands against pre-impact topspin and backspin balls. The joint kinetics at the shoulder, elbow and wrist of the racket arm was determined using inverse dynamics. A majority of the mechanical energy of the racket arm acquired during forward swing (65 and 77% against topspin and backspin, respectively) was due to energy transfer from the trunk. Energy transfer by the shoulder joint force in the vertical direction was the largest contributor to the mechanical energy of the racket arm against both spins and was greater against backspin than against topspin (34 and 28%, respectively). The shoulder joint force directed to the right, which peaked just before impact, transferred additional energy to the racket. Our results suggest that the upward thrust of the shoulder and the late timing of the axial rotation of the upper trunk are important for an effective topspin backhand. PMID:27111711

  12. Outer Membrane Protein Folding and Topology from a Computational Transfer Free Energy Scale.

    PubMed

    Lin, Meishan; Gessmann, Dennis; Naveed, Hammad; Liang, Jie

    2016-03-01

    Knowledge of the transfer free energy of amino acids from aqueous solution to a lipid bilayer is essential for understanding membrane protein folding and for predicting membrane protein structure. Here we report a computational approach that can calculate the folding free energy of the transmembrane region of outer membrane β-barrel proteins (OMPs) by combining an empirical energy function with a reduced discrete state space model. We quantitatively analyzed the transfer free energies of 20 amino acid residues at the center of the lipid bilayer of OmpLA. Our results are in excellent agreement with the experimentally derived hydrophobicity scales. We further exhaustively calculated the transfer free energies of 20 amino acids at all positions in the TM region of OmpLA. We found that the asymmetry of the Gram-negative bacterial outer membrane as well as the TM residues of an OMP determine its functional fold in vivo. Our results suggest that the folding process of an OMP is driven by the lipid-facing residues in its hydrophobic core, and its NC-IN topology is determined by the differential stabilities of OMPs in the asymmetrical outer membrane. The folding free energy is further reduced by lipid A and assisted by general depth-dependent cooperativities that exist between polar and ionizable residues. Moreover, context-dependency of transfer free energies at specific positions in OmpLA predict regions important for protein function as well as structural anomalies. Our computational approach is fast, efficient and applicable to any OMP.

  13. Tunable negligible-loss energy transfer between dipolar-coupled magnetic disks by stimulated vortex gyration.

    PubMed

    Jung, Hyunsung; Lee, Ki-Suk; Jeong, Dae-Eun; Choi, Youn-Seok; Yu, Young-Sang; Han, Dong-Soo; Vogel, Andreas; Bocklage, Lars; Meier, Guido; Im, Mi-Young; Fischer, Peter; Kim, Sang-Koog

    2011-01-01

    A wide variety of coupled harmonic oscillators exist in nature. Coupling between different oscillators allows for the possibility of mutual energy transfer between them and the information-signal propagation. Low-energy input signals and their transport with negligible energy loss are the key technological factors in the design of information-signal processing devices. Here, utilizing the concept of coupled oscillators, we experimentally demonstrated a robust new mechanism for energy transfer between spatially separated dipolar-coupled magnetic disks - stimulated vortex gyration. Direct experimental evidence was obtained by a state-of-the-art experimental time-resolved soft X-ray microscopy probe. The rate of energy transfer from one disk to the other was deduced from the two normal modes' frequency splitting caused by dipolar interaction. This mechanism provides the advantages of tunable energy transfer rates, low-power input signals and negligible energy loss in the case of negligible intrinsic damping. Coupled vortex-state disks might be implemented in applications for information-signal processing.

  14. Tunable negligible-loss energy transfer between dipolar-coupled magnetic disks by stimulated vortex gyration

    PubMed Central

    Jung, Hyunsung; Lee, Ki-Suk; Jeong, Dae-Eun; Choi, Youn-Seok; Yu, Young-Sang; Han, Dong-Soo; Vogel, Andreas; Bocklage, Lars; Meier, Guido; Im, Mi-Young; Fischer, Peter; Kim, Sang-Koog

    2011-01-01

    A wide variety of coupled harmonic oscillators exist in nature. Coupling between different oscillators allows for the possibility of mutual energy transfer between them and the information-signal propagation. Low-energy input signals and their transport with negligible energy loss are the key technological factors in the design of information-signal processing devices. Here, utilizing the concept of coupled oscillators, we experimentally demonstrated a robust new mechanism for energy transfer between spatially separated dipolar-coupled magnetic disks - stimulated vortex gyration. Direct experimental evidence was obtained by a state-of-the-art experimental time-resolved soft X-ray microscopy probe. The rate of energy transfer from one disk to the other was deduced from the two normal modes' frequency splitting caused by dipolar interaction. This mechanism provides the advantages of tunable energy transfer rates, low-power input signals and negligible energy loss in the case of negligible intrinsic damping. Coupled vortex-state disks might be implemented in applications for information-signal processing. PMID:22355578

  15. Mechanical energy generation and transfer in the racket arm during table tennis topspin backhands.

    PubMed

    Iino, Yoichi; Kojima, Takeji

    2016-06-01

    The ability to generate a high racket speed and a large amount of racket kinetic energy on impact is important for table tennis players. The purpose of this study was to understand how mechanical energy is generated and transferred in the racket arm during table tennis backhands. Ten male advanced right-handed table tennis players hit topspin backhands against pre-impact topspin and backspin balls. The joint kinetics at the shoulder, elbow and wrist of the racket arm was determined using inverse dynamics. A majority of the mechanical energy of the racket arm acquired during forward swing (65 and 77% against topspin and backspin, respectively) was due to energy transfer from the trunk. Energy transfer by the shoulder joint force in the vertical direction was the largest contributor to the mechanical energy of the racket arm against both spins and was greater against backspin than against topspin (34 and 28%, respectively). The shoulder joint force directed to the right, which peaked just before impact, transferred additional energy to the racket. Our results suggest that the upward thrust of the shoulder and the late timing of the axial rotation of the upper trunk are important for an effective topspin backhand.

  16. Shandiin/DOE intertribal energy programs: technology transfer series

    SciTech Connect

    Not Available

    1984-01-01

    This project entailed the continuation of solar design and construction workshops for the Navajo, Hopi, and Apache Tribes, including tribal planners, tribal staff, engineers, architects, and installers of energy systems. The project also entailed the continuation of support for the development of an energy self-sufficient community school system for the many rural Navajo communities. Great emphasis was placed in completing the second phase of development of the intertribal computer network. The development of this network will greatly benefit our nation in increased efficiency and coordination of tribal energy programs. A series of workshops was held in energy programs training for planners from the Navajo, Hopi, and Apache Tribes. The initial assessment of this program concludes that the greatest impact and return came from the Navajo Tribe's Division of Economic Development, with lesser impact upon the Community Development branches of the Hopi and Apache Tribes. The impact of microcomputer technologies upon the tribes has been shown to be profound, and the development of the intertribal computer network can be seen as a true asset to both the tribes and to the nation.

  17. Additional correction for energy transfer efficiency calculation in filter-based Förster resonance energy transfer microscopy for more accurate results

    NASA Astrophysics Data System (ADS)

    Sun, Yuansheng; Periasamy, Ammasi

    2010-03-01

    Förster resonance energy transfer (FRET) microscopy is commonly used to monitor protein interactions with filter-based imaging systems, which require spectral bleedthrough (or cross talk) correction to accurately measure energy transfer efficiency (E). The double-label (donor+acceptor) specimen is excited with the donor wavelength, the acceptor emission provided the uncorrected FRET signal and the donor emission (the donor channel) represents the quenched donor (qD), the basis for the E calculation. Our results indicate this is not the most accurate determination of the quenched donor signal as it fails to consider the donor spectral bleedthrough (DSBT) signals in the qD for the E calculation, which our new model addresses, leading to a more accurate E result. This refinement improves E comparisons made with lifetime and spectral FRET imaging microscopy as shown here using several genetic (FRET standard) constructs, where cerulean and venus fluorescent proteins are tethered by different amino acid linkers.

  18. Excitonic energy transfer in light-harvesting complexes in purple bacteria.

    PubMed

    Ye, Jun; Sun, Kewei; Zhao, Yang; Yu, Yunjin; Lee, Chee Kong; Cao, Jianshu

    2012-06-28

    Two distinct approaches, the Frenkel-Dirac time-dependent variation and the Haken-Strobl model, are adopted to study energy transfer dynamics in single-ring and double-ring light-harvesting (LH) systems in purple bacteria. It is found that the inclusion of long-range dipolar interactions in the two methods results in significant increase in intra- or inter-ring exciton transfer efficiency. The dependence of exciton transfer efficiency on trapping positions on single rings of LH2 (B850) and LH1 is similar to that in toy models with nearest-neighbor coupling only. However, owing to the symmetry breaking caused by the dimerization of BChls and dipolar couplings, such dependence has been largely suppressed. In the studies of coupled-ring systems, both methods reveal an interesting role of dipolar interactions in increasing energy transfer efficiency by introducing multiple intra/inter-ring transfer paths. Importantly, the time scale (4  ps) of inter-ring exciton transfer obtained from polaron dynamics is in good agreement with previous studies. In a double-ring LH2 system, non-nearest neighbor interactions can induce symmetry breaking, which leads to global and local minima of the average trapping time in the presence of a non-zero dephasing rate, suggesting that environment dephasing helps preserve quantum coherent energy transfer when the perfect circular symmetry in the hypothetic system is broken. This study reveals that dipolar coupling between chromophores may play an important role in the high energy transfer efficiency in the LH systems of purple bacteria and many other natural photosynthetic systems.

  19. Excitonic energy transfer in light-harvesting complexes in purple bacteria

    SciTech Connect

    Ye Jun; Sun Kewei; Zhao Yang; Lee, Chee Kong; Yu Yunjin; Cao Jianshu

    2012-06-28

    Two distinct approaches, the Frenkel-Dirac time-dependent variation and the Haken-Strobl model, are adopted to study energy transfer dynamics in single-ring and double-ring light-harvesting (LH) systems in purple bacteria. It is found that the inclusion of long-range dipolar interactions in the two methods results in significant increase in intra- or inter-ring exciton transfer efficiency. The dependence of exciton transfer efficiency on trapping positions on single rings of LH2 (B850) and LH1 is similar to that in toy models with nearest-neighbor coupling only. However, owing to the symmetry breaking caused by the dimerization of BChls and dipolar couplings, such dependence has been largely suppressed. In the studies of coupled-ring systems, both methods reveal an interesting role of dipolar interactions in increasing energy transfer efficiency by introducing multiple intra/inter-ring transfer paths. Importantly, the time scale (4 ps) of inter-ring exciton transfer obtained from polaron dynamics is in good agreement with previous studies. In a double-ring LH2 system, non-nearest neighbor interactions can induce symmetry breaking, which leads to global and local minima of the average trapping time in the presence of a non-zero dephasing rate, suggesting that environment dephasing helps preserve quantum coherent energy transfer when the perfect circular symmetry in the hypothetic system is broken. This study reveals that dipolar coupling between chromophores may play an important role in the high energy transfer efficiency in the LH systems of purple bacteria and many other natural photosynthetic systems.

  20. A study of the generation of linear energy transfer spectra for space radiations

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Badavi, Francis F.

    1992-01-01

    The conversion of particle-energy spectra into a linear energy transfer (LET) distribution is a guide in assessing biologically significant components. The mapping of LET to energy is triple valued and can be defined only on open subintervals. A well-defined numerical procedure is found to allow generation of LET spectra on the open subintervals that are integrable in spite of their singular nature.

  1. A state-space analysis of mechanical energy generation, absorption, and transfer during pedaling.

    PubMed

    Fregly, B J; Zajac, F E

    1996-01-01

    Seated ergometer pedaling is a motor task ideal for studying basic mechanisms of human bipedal coordination because, in contrast to standing and walking, fewer degrees of freedom are being controlled and upright balance is not a factor. As a step toward understanding how individual muscles coordinate pedaling, we investigated how individual net muscle joint torques and non-muscular (e.g. centripetal, coriolis, and gravity) forces of the lower limbs generate, absorb, and transfer mechanical energy in order to propel the crank and recover the limb. This was accomplished using a mechanical power analysis derived entirely from the closed-form state-space dynamical equations of a two-legged pedaling model that accounted for both the limb segmental and crank load dynamics. Based on a pedaling simulation that reproduced experimental kinematic and kinetic trajectories, we found that the net ankle and hip extensor joint torques function 'synergistically' to deliver energy to the crank during the downstroke. The net hip extensor joint torque generates energy to the limb, while the net ankle extensor joint torque transfers this energy from the limb to the crank. In contrast, net knee extensor and flexor joint torques function 'independently' by generating energy to the crank through the top and bottom of the stroke, respectively. The net ankle joint torque transfers and the net knee joint torque generates energy to the crank by contributing to the driving component of the pedal reaction force. During the upstroke, net ankle extensor joint torque transfers energy from the crank to the limb to restore the potential energy of the limb. In both halves of the crank cycle, gravity forces augment the crank-limb energy transfer performed by the net ankle extensor joint torque. PMID:8839020

  2. Protein modifications affecting triplet energy transfer in bacterial photosynthetic reaction centers.

    PubMed Central

    Laible, P D; Chynwat, V; Thurnauer, M C; Schiffer, M; Hanson, D K; Frank, H A

    1998-01-01

    The efficiency of triplet energy transfer from the special pair (P) to the carotenoid (C) in photosynthetic reaction centers (RCs) from a large family of mutant strains has been investigated. The mutants carry substitutions at positions L181 and/or M208 near chlorophyll-based cofactors on the inactive and active sides of the complex, respectively. Light-modulated electron paramagnetic resonance at 10 K, where triplet energy transfer is thermally prohibited, reveals that the mutations do not perturb the electronic distribution of P. At temperatures > or = 70 K, we observe reduced signals from the carotenoid in most of the RCs with L181 substitutions. In particular, triplet transfer efficiency is reduced in all RCs in which a lysine at L181 donates a sixth ligand to the monomeric bacteriochlorophyll B(B). Replacement of the native Tyr at M208 on the active side of the complex with several polar residues increased transfer efficiency. The difference in the efficiencies of transfer in the RCs demonstrates the ability of the protein environment to influence the electronic overlap of the chromophores and thus the thermal barrier for triplet energy transfer. PMID:9591686

  3. Computing intramolecular charge and energy transfer rates using optimal modes

    SciTech Connect

    Yang, Xunmo; Bittner, Eric R.

    2015-06-28

    In our recent work [X. Yang and E. R. Bittner, J. Phys. Chem. A 118, 5196 (2014)], we showed how to construct a reduced set of nuclear motions that capture the coupling between electronic and nuclear degrees of freedom over the course of an electronic transition. We construct these modes, referred to as “Lanczos modes,” by applying a search algorithm to find linear combinations of vibrational normal modes that optimize the electronic/nuclear coupling operator. Here, we analyze the irreducible representations of the dominant contributions of these modes and find that for the cases considered here, these belong to totally symmetric irreducible representations of the donor and acceptor moieties. Upon investigating the molecular geometry changes following the transition, we propose that the electronic transition process can be broken into two steps, in the agreement of Born-Oppenheimer approximation: a fast excitation transfer occurs, facilitated by the “primary Lanczos mode,” followed by slow nuclear relaxation on the final electronic diabatic surface.

  4. Energy and angular momentum transfer in binary galaxies

    NASA Technical Reports Server (NTRS)

    Namboodiri, P. M. S.; Kochhar, R. K.

    1990-01-01

    The authors numerically studied tidal effects of a massive perturber on a satellite galaxy. The model consists of a spherical satellite galaxy and a point mass perturber and the encounter is non-penetrating. A wide range of density ratios and eccentricities of the relative orbits have been considered. The disruption of the satellite galaxy has been observed when the numerical value of the fractional change in the energy is greater than two. The changes in the energy and angular momentum show smooth variation in the case of unbound orbits and irregular variation in the bound orbit cases. It is shown that for a constant pericentral distance, increasing the density ratio decreases the tidal effects; and for a given density ratio an increase in the eccentricity decreases the tidal effects.

  5. ISTP Global Geospace Science. Energy transfer in geospace

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Solar-terrestrial physics concerns the study of the generation, flow, and dissipation of mass, momentum, and energy between the Sun and the Earth. Mass, momentum, and energy are carried by charged particles that compose the solar wind. When the solar wind reaches the Earth, some solar-wind particles enter the magnetosphere; this coupling between the solar wind and the Earth means that the solar wind can influence the Earth's upper atmosphere. As the first step in addressing the behavior of this solar-terrestrial system, the Global Geospace Science (GGS) Initiative will use the Wind and Polar satellites, provided by NASA, and the Geotail satellite provided by the Japanese Institute of Space and Astronautical Science (ISAS), to perform simultaneous and closely coordinated measurements of the key geospace regions and will add data from equatorial missions. Magnetic field and particle changes that occur when particles are energized during auroral events will be monitored. The intention behind the GGS Initiative is to understand the physical mechanisms and various regions controlling the transport of mass, momentum, and energy in geospace. A summary of the GGS Initiative is presented.

  6. Resonance energy transfer from dibucaine to acriflavine in polystyrene latex dispersions.

    PubMed

    Li, Yuan; Kuwabara, Hiroe; Gong, Yong-Kuan; Takaki, Yuki; Nakashima, Kenichi

    2003-07-01

    Resonance energy transfer from dibucaine (DC) to acriflavine (AF) has been investigated both in homogeneous aqueous solutions and in polystyrene latex dispersions. The energy transfer reaction is observed by monitoring fluorescence quenching of DC as well as sensitized emission of AF. It is found that the energy transfer from DC to AF is remarkably enhanced on going from the aqueous homogeneous solution to the latex dispersion. This is mainly attributed to the fact that both the donor and acceptor are effectively adsorbed onto the latex particles, as evidenced by the measurement of adsorption isotherms. From the adsorption experiments, it is also elucidated that electrostatic interaction is significant at low DC concentration, while hydrophobic interaction dominates at the higher concentration especially at higher pH.

  7. Plasmon-enhanced energy transfer for improved upconversion of infrared radiation in doped-lanthanide nanocrystals.

    PubMed

    Sun, Qi-C; Mundoor, Haridas; Ribot, Josep C; Singh, Vivek; Smalyukh, Ivan I; Nagpal, Prashant

    2014-01-01

    Upconversion of infrared radiation into visible light has been investigated for applications in photovoltaics and biological imaging. However, low conversion efficiency due to small absorption cross-section for infrared light (Yb(3+)), and slow rate of energy transfer (to Er(3+) states) has prevented application of upconversion photoluminescence (UPL) for diffuse sunlight or imaging tissue samples. Here, we utilize resonant surface plasmon polaritons (SPP) waves to enhance UPL in doped-lanthanide nanocrystals. Our analysis indicates that SPP waves not only enhance the electromagnetic field, and hence weak Purcell effect, but also increase the rate of resonant energy transfer from Yb(3+) to Er(3+) ions by 6 fold. While we do observe strong metal mediated quenching (14-fold) of green fluorescence on flat metal surfaces, the nanostructured metal is resonant in the infrared and hence enhances the nanocrystal UPL. This strong Coulombic effect on energy transfer can have important implications for other fluorescent and excitonic systems too.

  8. Resonant energy transfer between Eu luminescent sites and their local geometry in GaN

    SciTech Connect

    Timmerman, Dolf; Wakamatsu, Ryuta; Tanaka, Kazuteru; Lee, Dong-gun; Koizumi, Atsushi; Fujiwara, Yasufumi

    2015-10-12

    Eu-doped GaN is a solid state material with promising features for quantum manipulation. In this study, we investigate the population dynamics of Eu in ions in this system by resonant excitation. From differences in the emission related to transitions between the {sup 5}D{sub 0} and {sup 7}F{sub 2} manifold in the Eu ions, we can distinguish different luminescence sites and observe that a resonant energy transfer takes place between two of these sites which are in proximity of each other. The time constants related to this energy transfer are on the order of 100 μs. By using different substrates, the energy transfer efficiency could be strongly altered, and it is demonstrated that the coupling between ions has an out-of-plane character. Based on these results, a microscopic model of this combined center is presented.

  9. Ultrafast Studies of Resonance Energy Transfer in Myoglobin: A-Helix and Local Conformational Fluctuations

    NASA Astrophysics Data System (ADS)

    Stevens, Jeffrey A.; Link, Justin J.; Kao, Ya-Ting; Zang, Chen; Guo, Lijun; Zhong, Dongping

    2009-06-01

    Myoglobin (Mb), a heme containing protein, is involved in the storage and release of ligands. We report here our studies of resonance energy transfer in Mb using an intrinsic tryptophan (Trp) and the prosthetic heme as an energy transfer pair. With site-directed mutagenesis, we placed one-at-a-time a single Trp donor into four locations on the A-helix. Utilizing the femtosecond up-conversion method, we examined a series of energy transfer dynamics in Mb. A molecular dynamics (MD) simulation was also used to infer structure and dipole orientation fluctuations for specific Trp. Both methodologies were used to characterize the local dynamic nature of Mb in solution compared to the static crystal structure.

  10. Studies of Photosynthetic Energy and Charge Transfer by Two-dimensional Fourier transform electronic spectroscopy

    NASA Astrophysics Data System (ADS)

    Ogilvie, Jennifer

    2010-03-01

    Two-dimensional (2D) Fourier transform electronic spectroscopy has recently emerged as a powerful tool for the study of energy transfer in complex condensed-phase systems. Its experimental implementation is challenging but can be greatly simplified by implementing a pump-probe geometry, where the two phase-stable collinear pump pulses are created with an acousto-optic pulse-shaper. This approach also allows the use of a continuum probe pulse, expanding the available frequency range of the detection axis and allowing studies of energy transfer and electronic coupling over a broad range of frequencies. We discuss several benefits of 2D electronic spectroscopy and present 2D data on the D1-D2 reaction center complex of Photosystem II from spinach. We discuss the ability of 2D spectroscopy to distinguish between current models of energy and charge transfer in this system.

  11. Geometrical effects in the energy transfer mechanism for silicon nanocrystals and Er3+

    NASA Astrophysics Data System (ADS)

    Choy, K.; Lenz, F.; Liang, X. X.; Marsiglio, F.; Meldrum, A.

    2008-12-01

    Silicon nanoclusters (NCs) strongly sensitize the luminescence of Er3+ ions. Attempts to calculate the interaction distance have assumed that the Förster [Ann. Phys. 437, 55 (1948)] and Dexter [J. Chem. Phys. 21, 836 (1953)] relationships for point-to-point energy transfer can be applied to experiments based on multilayered thin-film specimens. Here, the effective finite plane-to-plane relationships are derived for both interaction mechanisms. These relationships show that energy transfer can result from the Förster interaction despite the fact that the measured luminescence intensity varies much more weakly with NC-Er3+ separation than predicted by theory for point dipoles. An effective energy transfer distance is found for the NC-Er3+ system.

  12. Properties of hydrophobic free energy found by gas-liquid transfer.

    PubMed

    Baldwin, Robert L

    2013-01-29

    The hydrophobic free energy in current use is based on transfer of alkane solutes from liquid alkanes to water, and it has been argued recently that these values are incorrect and should be based instead on gas-liquid transfer data. Hydrophobic free energy is measured here by gas-liquid transfer of hydrocarbon gases from vapor to water. The new definition reduces more than twofold the values of the apparent hydrophobic free energy. Nevertheless, the newly defined hydrophobic free energy is still the dominant factor that drives protein folding as judged by ΔCp, the change in heat capacity, found from the free energy change for heat-induced protein unfolding. The ΔCp for protein unfolding agrees with ΔCp values for solvating hydrocarbon gases and disagrees with ΔCp for breaking peptide hydrogen bonds, which has the opposite sign. The ΔCp values for the enthalpy of liquid-liquid and gas-liquid transfer are similar. The plot of free energy against the apparent solvent-exposed surface area is given for linear alkanes, but only for a single conformation, the extended conformation, of these flexible-chain molecules. The ability of the gas-liquid hydrophobic factor to predict protein stability is tested and reasonable agreement is found, using published data for the dependences on temperature of the unfolding enthalpy of ribonuclease T1 and the solvation enthalpies of the nonpolar and polar groups.

  13. Quantum electrodynamical theory of high-efficiency excitation energy transfer in laser-driven nanostructure systems

    NASA Astrophysics Data System (ADS)

    Weeraddana, Dilusha; Premaratne, Malin; Gunapala, Sarath D.; Andrews, David L.

    2016-08-01

    A fundamental theory is developed for describing laser-driven resonance energy transfer (RET) in dimensionally constrained nanostructures within the framework of quantum electrodynamics. The process of RET communicates electronic excitation between suitably disposed emitter and detector particles in close proximity, activated by the initial excitation of the emitter. Here, we demonstrate that the transfer rate can be significantly increased by propagation of an auxiliary laser beam through a pair of nanostructure particles. This is due to the higher order perturbative contribution to the Förster-type RET, in which laser field is applied to stimulate the energy transfer process. We construct a detailed picture of how excitation energy transfer is affected by an off-resonant radiation field, which includes the derivation of second and fourth order quantum amplitudes. The analysis delivers detailed results for the dependence of the transfer rates on orientational, distance, and laser intensity factor, providing a comprehensive fundamental understanding of laser-driven RET in nanostructures. The results of the derivations demonstrate that the geometry of the system exercises considerable control over the laser-assisted RET mechanism. Thus, under favorable conformational conditions and relative spacing of donor-acceptor nanostructures, the effect of the auxiliary laser beam is shown to produce up to 70% enhancement in the energy migration rate. This degree of control allows optical switching applications to be identified.

  14. Intramolecular singlet-singlet energy transfer in antenna-substituted azoalkanes.

    PubMed

    Pischel, Uwe; Huang, Fang; Nau, Werner M

    2004-03-01

    Two novel azoalkane bichromophores and related model compounds have been synthesised and photophysically characterised. Dimethylphenylsiloxy (DPSO) or dimethylnaphthylsiloxy (DNSO) serve as aromatic donor groups (antenna) and the azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) as the acceptor. The UV spectral window of DBO (250-300 nm) allows selective excitation of the donor. Intramolecular singlet-singlet energy transfer to DBO is highly efficient and proceeds with quantum yields of 0.76 with DPSO and 0.99 with DNSO. The photophysical and spectral properties of the bichromophoric systems suggest that energy transfer occurs through diffusional approach of the donor and acceptor within a van der Waals contact at which the exchange mechanism is presumed to dominate. Furthermore, akin to the behaviour of electron-transfer systems in the Marcus inverted region, a rate of energy transfer 2.5 times slower was observed for the system with the more favourable energetics, i.e. singlet-singlet energy transfer from DPSO proceeded slower than from DNSO, although the process is more exergonic for DPSO (-142 kJ mol(-1) for DPSO versus-67 kJ mol(-1) for DNSO).

  15. Long-range plasmon-assisted energy transfer over doped graphene

    NASA Astrophysics Data System (ADS)

    Velizhanin, Kirill; Shahbazyan, Tigran

    2013-03-01

    Förster resonance energy transfer (FRET) between spatially separated donor and acceptor fluorophores, such as dye molecules or semiconductors quantum dots, underpins diverse phenomena in physics, chemistry and biology. However, the range of present and potential applications of FRET is limited by its intrinsically short-range nature (~ 1 /R6). We demonstrate that longitudinal plasmons in doped monolayer graphene can mediate highly efficient long-range (~ 1 / R) energy transfer between nearby fluorophores, e.g., semiconductor quantum dots. We derive a simple analytical expression for the energy transfer efficiency that incorporates all the essential processes involved. We perform numerical calculations of the transfer efficiency for a pair of PbSe quantum dots near graphene for inter-fluorophore distances of up to 1 μm and find that the plasmon-assisted long-range energy transfer can be enhanced by up to a factor of ~104 relative to FRET in vacuum. Work at LANL was performed under the NNSA of the U.S. DOE at LANL under Contract No. DE-AC52- 06NA25396. Work at JSU was supported by the NSF under Grants No. DMR-1206975 and No. HRD-0833178 and under EPSCOR program.

  16. Excitation-energy transfer dynamics of higher plant photosystem I light-harvesting complexes.

    PubMed

    Wientjes, Emilie; van Stokkum, Ivo H M; van Amerongen, Herbert; Croce, Roberta

    2011-03-01

    Photosystem I (PSI) plays a major role in the light reactions of photosynthesis. In higher plants, PSI is composed of a core complex and four outer antennas that are assembled as two dimers, Lhca1/4 and Lhca2/3. Time-resolved fluorescence measurements on the isolated dimers show very similar kinetics. The intermonomer transfer processes are resolved using target analysis. They occur at rates similar to those observed in transfer to the PSI core, suggesting competition between the two transfer pathways. It appears that each dimer is adopting various conformations that correspond to different lifetimes and emission spectra. A special feature of the Lhca complexes is the presence of an absorption band at low energy, originating from an excitonic state of a chlorophyll dimer, mixed with a charge-transfer state. These low-energy bands have high oscillator strengths and they are superradiant in both Lhca1/4 and Lhca2/3. This challenges the view that the low-energy charge-transfer state always functions as a quencher in plant Lhc's and it also challenges previous interpretations of PSI kinetics. The very similar properties of the low-energy states of both dimers indicate that the organization of the involved chlorophylls should also be similar, in disagreement with the available structural data.

  17. Tunable and long-range energy transfer efficiency through a graphene nanodisk

    NASA Astrophysics Data System (ADS)

    Karanikolas, Vasilios D.; Marocico, Cristian A.; Bradley, A. Louise

    2016-01-01

    In this paper, we present a theoretical investigation of the energy transfer efficiency between a pair of quantum emitters placed in proximity to a conducting graphene nanodisk. The energy transfer efficiency quantifies the contribution of the energy transfer process to the relaxation of the donor quantum system, as compared to the spontaneous emission rate of the donor in the absence of the acceptor. We use in our calculations the Green's tensor formalism in the electrostatic limit. This approximation works very well for the nanodisks considered here, for which the radius is much smaller than the emission wavelength of the donor. The approximate analytical solutions obtained are used to investigate the decay rate of a single quantum emitter and the energy transfer rate between quantum emitters in the vicinity of the graphene nanodisk. We find that these rates are enhanced several orders of magnitude compared with their free-space values. We determine the resonance frequencies of the spontaneous emission rate of a single quantum emitter to a graphene nanodisk, and the energy transfer rate between a pair of quantum emitters in proximity to a graphene nanodisk. We identify the surface modes which give the largest contributions to the energy transfer function. We connect the resonance frequency values and their surface plasmon wave numbers, which depend on the radius of the graphene nanodisk, with the dispersion relation of an infinite graphene monolayer at the same chemical potential. Analyzing the distance dependence of these rates, we are able to fit the full numerical results with a simple analytical expression which depends only on the geometrical characteristics of the graphene nanodisk, i.e., its radius. We show that the interaction distance depends on the transition dipole moment orientation and the different order resonance frequencies. The interaction distance between a pair of quantum emitters increases from a free-space value of 20 nm to reach values of

  18. Direct observation of multistep energy transfer in LHCII with fifth-order 3D electronic spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengyang; Lambrev, Petar H.; Wells, Kym L.; Garab, Győző; Tan, Howe-Siang

    2015-07-01

    During photosynthesis, sunlight is efficiently captured by light-harvesting complexes, and the excitation energy is then funneled towards the reaction centre. These photosynthetic excitation energy transfer (EET) pathways are complex and proceed in a multistep fashion. Ultrafast two-dimensional electronic spectroscopy (2DES) is an important tool to study EET processes in photosynthetic complexes. However, the multistep EET processes can only be indirectly inferred by correlating different cross peaks from a series of 2DES spectra. Here we directly observe multistep EET processes in LHCII using ultrafast fifth-order three-dimensional electronic spectroscopy (3DES). We measure cross peaks in 3DES spectra of LHCII that directly indicate energy transfer from excitons in the chlorophyll b (Chl b) manifold to the low-energy level chlorophyll a (Chl a) via mid-level Chl a energy states. This new spectroscopic technique allows scientists to move a step towards mapping the complete complex EET processes in photosynthetic systems.

  19. Mechanism for the thermal dependence of the Cr to Nd energy transfer in garnets

    NASA Technical Reports Server (NTRS)

    Armagan, Guzin; Di Bartolo, Baldassare

    1988-01-01

    The temperature dependence of the Cr-Nd energy transfer is found to be due to the thermal variation of the radiative decay probability of Cr. The validity of this conjecture is checked in the Gd3Sc2Ga3O12 and CaMg2Y2Ge3O12 crystals. It is also found that above 200 K, the nonradiative energy transfer rate from Cr to Nd is greater in Gd3Sc2Ga3O12 than in CaMg2Y2Ge3O12.

  20. Preliminary investigation into the design of thermally responsive Forster resonance energy transfer colloids

    NASA Astrophysics Data System (ADS)

    Bedford, Monte Scott

    While nuclear imaging techniques (Magnetic Resonance Imaging, Computed Tomography, and Positron Emission Tomography) have proven effective for diagnosis and treatment of disease in the human body, fluorescence-enhanced optical imaging offers additional benefits. Fluorescent imaging provides high resolution with real-time response, persistent lifetime (hours to days), cell targeting, and transdermal penetration with minimal physical encumbrance. Malignant cells can be targeted by absorbance of exogenous fluorescent nanoprobe contrast agents. Imaging is improved by fluorescent enhancement, especially by energy transfer between attached dyes. Also for use against cancer are heat-active treatments, such as hyperthermal, photothermal, and chemothermal therapies. Helpful to these treatments is the thermal response from nanoprobes, within human cells, which provide real-time feedback. The present study investigates the design and feasibility of a nanoprobe molecular device, absorbable into malignant human cells, which provides real-time tracking and thermal response, as indicated by enhanced fluorescence by energy transfer. A poly(propargyl acrylate) colloidal suspension was synthesized. The particles were modified with a triblock copolymer, previously shown to be thermally responsive, and an end-attached fluorescent dye. A second dye was modeled for attachment in subsequent work. When two fluorescent dyes are brought within sufficiently close proximity, and excitation light is supplied, energy can be transferred between dyes to give enhanced fluorescence with a large Stokes shift (increase in wavelength between excitation and emission). The dye pair was modeled for overlap of emission and absorbance wavelengths, and energy transfer was demonstrated with 23% efficiency and a 209 nm Stokes shift. The quantum yield of the donor dye was determined at 70%, and the distance for 50% energy transfer was calculated at 2.9 nm, consistent with reports for similar compounds. When

  1. Upscale energy transfer and flow topology in free-surface turbulence.

    PubMed

    Lovecchio, Salvatore; Zonta, Francesco; Soldati, Alfredo

    2015-03-01

    Free-surface turbulence, albeit constrained onto a two-dimensional space, exhibits features that barely resemble predictions of simplified two-dimensional modeling. We demonstrate that, in a three-dimensional open channel flow, surface turbulence is characterized by upscale energy transfer, which controls the long-term evolution of the larger scales. We are able to associate downscale and upscale energy transfer at the surface with the two-dimensional divergence of velocity. We finally demonstrate that surface compressibility confirms the strongly three-dimensional nature of surface turbulence.

  2. Characterization of energy transfer for passively Q-switched laser ignition.

    PubMed

    Lorenz, S; Bärwinkel, M; Heinz, P; Lehmann, S; Mühlbauer, W; Brüggemann, D

    2015-02-01

    Miniaturized passively Q-switched Nd:YAG/Cr(4+):YAG lasers are promising candidates as spark sources for sophisticated laser ignition. The influence of the complex spatial-temporal pulse profile of such lasers on the process of plasma breakdown and on the energy transfer is studied. The developed measurement technique is applied to an open ignition system as well as to prototypes of laser spark plugs. A detected temporal breakdown delay causes an advantageous separation of plasma building phase from energy transfer. In case of fast rising laser pulses, an advantageous reduction of the plasma breakdown delay occurs instead. PMID:25836128

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

    PubMed Central

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

    2002-01-01

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

  4. Computation studies into architecture and energy transfer properties of photosynthetic units from filamentous anoxygenic phototrophs

    SciTech Connect

    Linnanto, Juha Matti; Freiberg, Arvi

    2014-10-06

    We have used different computational methods to study structural architecture, and light-harvesting and energy transfer properties of the photosynthetic unit of filamentous anoxygenic phototrophs. Due to the huge number of atoms in the photosynthetic unit, a combination of atomistic and coarse methods was used for electronic structure calculations. The calculations reveal that the light energy absorbed by the peripheral chlorosome antenna complex transfers efficiently via the baseplate and the core B808–866 antenna complexes to the reaction center complex, in general agreement with the present understanding of this complex system.

  5. Brightening gold nanoparticles: new sensing approach based on plasmon resonance energy transfer.

    PubMed

    Shi, Lei; Jing, Chao; Gu, Zhen; Long, Yi-Tao

    2015-05-11

    Scattering recovered plasmonic resonance energy transfer (SR-PRET) was reported by blocking the plasmon resonance energy transfer (PRET) from gold nanoparticle (GNP) to the adsorbed molecules (RdBS). Due to the selective cleavage of the Si-O bond by F- ions, the quenching is switched off causing an increase in the brightness of the GNPs,detected using dark-field microscopy (DFM) were brightened. This method was successfully applied to the determination of fluoride ions in water. The SR-PRET provides a potential approach for a vitro/vivo sensing with high sensitivity and selectivity.

  6. Amino-functionalized green fluorescent carbon dots as surface energy transfer biosensors for hyaluronidase.

    PubMed

    Liu, Siyu; Zhao, Ning; Cheng, Zhen; Liu, Hongguang

    2015-04-21

    Amino-functionalized fluorescent carbon dots have been prepared by hydrothermal treatment of glucosamine with excess pyrophosphate. The produced carbon dots showed stabilized green emission fluorescence at various excitation wavelengths and pH environments. Herein, we demonstrate the surface energy transfer between the amino-functionalized carbon dots and negatively charged hyaluronate stabilized gold nanoparticles. Hyaluronidase can degrade hyaluronate and break down the hyaluronate stabilized gold nanoparticles to inhibit the surface energy transfer. The developed fluorescent carbon dot/gold nanoparticle system can be utilized as a biosensor for sensitive and selective detection of hyaluronidase by two modes which include fluorescence measurements and colorimetric analysis.

  7. Brightening Gold Nanoparticles: New Sensing Approach Based on Plasmon Resonance Energy Transfer

    PubMed Central

    Shi, Lei; Jing, Chao; Gu, Zhen; Long, Yi-Tao

    2015-01-01

    Scattering recovered plasmonic resonance energy transfer (SR-PRET) was reported by blocking the plasmon resonance energy transfer (PRET) from gold nanoparticle (GNP) to the adsorbed molecules (RdBS). Due to the selective cleavage of the Si-O bond by F− ions, the quenching is switched off causing an increase in the brightness of the GNPs,detected using dark-field microscopy (DFM) were brightened. This method was successfully applied to the determination of fluoride ions in water. The SR-PRET provides a potential approach for a vitro/vivo sensing with high sensitivity and selectivity. PMID:25959016

  8. Nobel lecture. A structural basis of light energy and electron transfer in biology.

    PubMed Central

    Huber, R

    1989-01-01

    Aspects of intramolecular light energy and electron transfer will be discussed for three protein--cofactor complexes, whose three-dimensional structures have been elucidated by X-ray crystallography: components of light-harvesting cyanobacterial phycobilisomes; the purple bacterial reaction centre; and the blue multi-copper oxidases. A wealth of functional data is available for these systems which allows specific correlations between structure and function and general conclusions about light energy and electron transfer in biological materials to be made. Images PMID:2676513

  9. Light yield and energy transfer in a new Gd-loaded liquid scintillator

    NASA Astrophysics Data System (ADS)

    Aberle, C.; Buck, C.; Hartmann, F. X.; Schönert, S.

    2011-11-01

    We investigate a new gadolinium-loaded organic liquid scintillator which is designed to detect electron antineutrinos. A model has been developed to account for the various energy transfer paths possible in a liquid scintillator with multiple solvents, one fluor and a quenching component. Experimental light yield measurements were carried out to determine the relative rates for the energy transfers included in the model. Model predictions were used to tune the luminescent properties of the Gd-loaded target scintillator and the unloaded Gamma Catcher scintillator for the reactor neutrino experiment Double Chooz.

  10. Energy Transfers in Coupled Ordered Granular Chains with No Precompression

    NASA Astrophysics Data System (ADS)

    Vakakis, Alexander; Hasan, Arif M.; Starosvetsky, Yuli; Manevitch, Leonid I.

    2013-03-01

    We study the dynamics of coupled one-dimensional granular chains mounted on elastic foundations. No dissipative effects, such as plasticity or dry friction effects are taken into account in our analysis. Assuming no pre-compression between beads, the dynamics of the system under consideration is strongly nonlinear and, in an acoustic analogy they can be viewed as `sonic vacua'. Sources of strong nonlinearity in these systems are nonlinearizable Hertzian interactions between adjacent beads in compression, and also possible separations between beads in the absence of compressive forces leading to bead collisions. We find that demonstrate that in weakly coupled granular chains there can occur strong energy exchanges in the form of nonlinear beat phenomena of spatially periodic traveling waves, stationary breathers or propagating breathers. We employ analytical techniques to study these dynamical phenomena. This work was supported by MURI grant US ARO W911NF-09-1-0436. Dr. David Stepp is the grant monitor.

  11. Forster Energy Transfer Theory as Reflected in the Structures of Photosynthetic Light-Harvesting Systems

    SciTech Connect

    Sener, Melih; Strumpfer, Johan; Hsin, Jen; Chandler, Danielle; Scheuring, Simon; Hunter, C. Neil; Schulten, Klaus

    2011-02-22

    Förster's theory of resonant energy transfer underlies a fundamental process in nature, namely the harvesting of sunlight by photosynthetic life forms. The theoretical framework developed by Förster and others describes how electronic excitation migrates in the photosynthetic apparatus of plants, algae, and bacteria from light absorbing pigments to reaction centers where light energy is utilized for the eventual conversion into chemical energy. The demand for highest possible efficiency of light harvesting appears to have shaped the evolution of photosynthetic species from bacteria to plants which, despite a great variation in architecture, display common structural themes founded on the quantum physics of energy transfer as described first by Förster. Herein, Förster’s theory of excitation transfer is summarized, including recent extensions, and the relevance of the theory to photosynthetic systems as evolved in purple bacteria, cyanobacteria, and plants is demonstrated. Förster's energy transfer formula, as used widely today in many fields of science, is also derived.

  12. Inhibition of plasmonically enhanced interdot energy transfer in quantum dot solids via photo-oxidation

    SciTech Connect

    Sadeghi, S. M.; Nejat, A.; West, R. G.

    2012-11-15

    We studied the impact of photophysical and photochemical processes on the interdot Forster energy transfer in monodisperse CdSe/ZnS quantum dot solids. For this, we investigated emission spectra of CdSe/ZnS quantum dot solids in the vicinity of gold metallic nanoparticles coated with chromium oxide. The metallic nanoparticles were used to enhance the rate of the energy transfer between the quantum dots, while the chromium oxide coating led to significant increase of their photo-oxidation rates. Our results showed that irradiation of such solids with a laser beam can lead to unique spectral changes, including narrowing and blue shift. We investigate these effects in terms of inhibition of the plasmonically enhanced interdot energy transfer between quantum dots via the chromium-oxide accelerated photo-oxidation process. We demonstrate this considering energy-dependent rate of the interdot energy transfer process, plasmonic effects, and the way photo-oxidation enhances non-radiative decay rates of quantum dots with different sizes.

  13. Photophysics, Dynamics, and Energy Transfer in Rigid Mimics of GFP-based Systems.

    PubMed

    Dolgopolova, Ekaterina A; Rice, Allison M; Smith, Mark D; Shustova, Natalia B

    2016-08-01

    Engineering of novel systems capable of efficient energy capture and transfer in a predesigned pathway could potentially boost applications varying from organic photovoltaics to catalytic platforms and have implications for energy sustainability and green chemistry. While light-harvesting properties of different materials have been studied for decades, recently, there has been great progress in the understanding and modeling of short- and long-range energy transfer processes through utilization of metal-organic frameworks (MOFs). In this Forum Article, the recent advances in efficient multiple-chromophore coupling in well-defined metal-organic materials through mimicking a protein system possessing near 100% energy transfer are discussed. Utilization of a MOF as an efficient replica of a protein β-barrel to maintain chromophore emission was also demonstrated. Furthermore, we established a novel dependence of a photophysical response on an electronic configuration for chromophores with the benzylidene imidazolinone core. For that, we prepared 16 chromophores, in which the benzylidene imidazolinone core was modified with electron-donating and electron-withdrawing substituents. To establish the structure-dependent photophysical properties of the prepared chromophores, 11 novel molecular structures were determined by single-crystal X-ray diffraction. These findings allow one to predict the chromophore emission profile inside a rigid framework as a function of the substituent, a key parameter for achieving the spectral overlap necessary to study and increase resonance energy transfer efficiency in MOF-based materials.

  14. Photophysics, Dynamics, and Energy Transfer in Rigid Mimics of GFP-based Systems.

    PubMed

    Dolgopolova, Ekaterina A; Rice, Allison M; Smith, Mark D; Shustova, Natalia B

    2016-08-01

    Engineering of novel systems capable of efficient energy capture and transfer in a predesigned pathway could potentially boost applications varying from organic photovoltaics to catalytic platforms and have implications for energy sustainability and green chemistry. While light-harvesting properties of different materials have been studied for decades, recently, there has been great progress in the understanding and modeling of short- and long-range energy transfer processes through utilization of metal-organic frameworks (MOFs). In this Forum Article, the recent advances in efficient multiple-chromophore coupling in well-defined metal-organic materials through mimicking a protein system possessing near 100% energy transfer are discussed. Utilization of a MOF as an efficient replica of a protein β-barrel to maintain chromophore emission was also demonstrated. Furthermore, we established a novel dependence of a photophysical response on an electronic configuration for chromophores with the benzylidene imidazolinone core. For that, we prepared 16 chromophores, in which the benzylidene imidazolinone core was modified with electron-donating and electron-withdrawing substituents. To establish the structure-dependent photophysical properties of the prepared chromophores, 11 novel molecular structures were determined by single-crystal X-ray diffraction. These findings allow one to predict the chromophore emission profile inside a rigid framework as a function of the substituent, a key parameter for achieving the spectral overlap necessary to study and increase resonance energy transfer efficiency in MOF-based materials. PMID:27304253

  15. Efficient estimation of energy transfer efficiency in light-harvesting complexes.

    PubMed

    Shabani, A; Mohseni, M; Rabitz, H; Lloyd, S

    2012-07-01

    The fundamental physical mechanisms of energy transfer in photosynthetic complexes is not yet fully understood. In particular, the degree of efficiency or sensitivity of these systems for energy transfer is not known given their realistic with surrounding photonic and phononic environments. One major problem in studying light-harvesting complexes has been the lack of an efficient method for simulation of their dynamics in biological environments. To this end, here we revisit the second order time-convolution (TC2) master equation and examine its reliability beyond extreme Markovian and perturbative limits. In particular, we present a derivation of TC2 without making the usual weak system-bath coupling assumption. Using this equation, we explore the long-time behavior of exciton dynamics of Fenna-Matthews-Olson (FMO) portein complex. Moreover, we introduce a constructive error analysis to estimate the accuracy of TC2 equation in calculating energy transfer efficiency, exhibiting reliable performance for system-bath interactions with weak and intermediate memory and strength. Furthermore, we numerically show that energy transfer efficiency is optimal and robust for the FMO protein complex of green sulfur bacteria with respect to variations in reorganization energy and bath correlation time scales.

  16. Energy transfer kinetics of the np5(n + 1)p excited states of Ne and Kr.

    PubMed

    Kabir, Md Humayun; Heaven, Michael C

    2011-09-01

    Energy transfer rate constants for Ne(2p(5)3p) and Kr(4p(5)5p) atoms colliding with ground state rare gas atoms (Rg) have been measured. In part, this study is motivated by the possibility of using excited rare gas atoms as the active species in optically pumped laser systems. Rg(np(5)(n + 1)s) metastable states may be produced using low-power electrical discharges. The potential then exits for optical pumping and laser action on the np(5)(n + 1)p ↔ np(5)(n + 1)s transitions. Knowledge of the rate constants for collisional energy transfer and deactivation of the np(5)(n + 1)p states is required to evaluate the laser potential for various Rg + buffer gas combinations. In the present study we have characterized energy transfer processes for Ne (2p(5)3p) + He for the six lowest energy states of the multiplet. Rate constants for state-to-state transfer have been determined. Deactivation of the lowest energy level of Kr (4p(5)5p) by He, Ne, and Kr has also been characterized. Initial results suggest that Kr (4p(5)5p) + Ne mixtures may be the best suited for optically pumped laser applications.

  17. Upconversion-induced delayed fluorescence in multicomponent organic systems: Role of Dexter energy transfer

    NASA Astrophysics Data System (ADS)

    Monguzzi, A.; Tubino, R.; Meinardi, F.

    2008-04-01

    The efficiency of the upconversion-induced delayed fluorescence in a solution of multicomponent organic systems is limited by two steps of the overall process: (i) a triplet-triplet energy transfer between a phosphorescent donor and an emitting acceptor, and (ii) a bimolecular acceptor triplet-triplet annihilation generating acceptor singlet excited states from which the high-energy emission takes place. In this work, the energy transfer process has been investigated in a model system constituted by solutions of Pt(II)octaethylporphyrin, which acts as a donor, and 9,10 diphenylanthracene, which acts as an acceptor. At low temperature, the experimental data have been interpreted in the frame of a pure Dexter energy transfer by using the Perrin approximation. A Dexter radius as large as 26.5 Å has been found. At room temperature, the fast diffusion of the molecules in the solution is no longer negligible, which gives rise to a strong increase in the energy transfer rates.

  18. Energy transfer mechanism and Auger effect in Er{sup 3+} coupled silicon nanoparticle samples

    SciTech Connect

    Pitanti, A.; Navarro-Urrios, D.; Garrido, B.; Prtljaga, N.; Daldosso, N.; Pavesi, L.; Gourbilleau, F.; Rizk, R.

    2010-09-15

    We report a spectroscopic study about the energy transfer mechanism among silicon nanoparticles (Si-np), both amorphous and crystalline, and Er ions in a silicon dioxide matrix. From infrared spectroscopic analysis, we have determined that the physics of the transfer mechanism does not depend on the Si-np nature, finding a fast (<200 ns) energy transfer in both cases, while the amorphous nanoclusters reveal a larger transfer efficiency than the nanocrystals. Moreover, the detailed spectroscopic results in the visible range here reported are essential to understand the physics behind the sensitization effect, whose knowledge assumes a crucial role to enhance the transfer rate and possibly employing the material in optical amplifier devices. Joining the experimental data, performed with pulsed and continuous-wave excitation, we develop a model in which the internal intraband recombination within Si-np is competitive with the transfer process via an Auger electron-''recycling'' effect. Posing a different light on some detrimental mechanism such as Auger processes, our findings clearly recast the role of Si-np in the sensitization scheme, where they are able to excite very efficiently ions in close proximity to their surface.

  19. Transferring building energy technologies by linking government and private-sector programs

    SciTech Connect

    Farhar, B.C.

    1990-07-01

    The US Department of Energy's Office of Building Technologies (OBT) may wish to use existing networks and infrastructures wherever possible to transfer energy-efficiency technologies for buildings. The advantages of relying on already existing networks are numerous. These networks have in place mechanisms for reaching audiences interested in energy-efficiency technologies in buildings. Because staffs in trade and professional organizations and in state and local programs have responsibilities for brokering information for their members or client organizations, they are open to opportunities to improve their performance in information transfer. OBT, as an entity with primarily R D functions, is, by cooperating with other programs, spared the necessity of developing an extensive technology transfer program of its own, thus reinventing the wheel.'' Instead, OBT can minimize its investment in technology transfer by relying extensively on programs and networks already in place. OBT can work carefully with staff in other organizations to support and facilitate their efforts at information transfer and getting energy-efficiency tools and technologies into actual use. Consequently, representatives of some 22 programs and organizations were contacted, and face-to-face conversations held, to explore what the potential might be for transferring technology by linking with OBT. The briefs included in this document were derived from the discussions, the newly published Directory of Energy Efficiency Information Services for the Residential and Commercial Sectors, and other sources provided by respondents. Each brief has been sent to persons contacted for their review and comment one or more times, and each has been revised to reflect the review comments.

  20. Imaging charge and energy transfer in molecules using free-electron lasers

    NASA Astrophysics Data System (ADS)

    Rudenko, Artem

    2014-05-01

    Charge and energy transfer reactions drive numerous important processes in physics, chemistry and biology, with applications ranging from X-ray astrophysics to artificial photosynthesis and molecular electronics. Experimentally, the central goal in studies of transfer phenomena is to trace the spatial localization of charge at a given time. Because of their element and site sensitivity, ultrafast X-rays provide a promising tool to address this goal. In this talk I will discuss several experiments where free-electron lasers were employed to study charge and energy transfer dynamics in fragmenting molecules. In a first example, we used intense, 70 femtosecond 1.5 keV pulses from the Linac Coherent Light Source (LCLS) to study distance dependence of electron transfer in laser-dissociated methyl iodide molecules. Inducing well-localized positive charge on the heavy iodine atom, we observe signature of electron transition from the separated methyl group up to the distances of 35 atomic units. In a complementary experiment, we studied charge exchange between two partners in a dissociating molecular iodine employing a pump-probe arrangement with two identical 90 eV pulses from the Free-Electron LASer in Hamburg (FLASH). In both cases, the effective spatial range of the electron transfer can be reasonably described by a classical over-the-barrier model developed for ion-atom collisions. Finally, I will discuss a time-resolved measurement on non-local relaxation mechanism based on a long-range energy transfer, the so-called interatomic Coulombic decay. This work was supported by Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, US Department of Energy and by the Kansas NSF ``First Award'' program.

  1. Site-sensitive energy transfer modes in Ca3Al2O6: Ce(3+)/Tb(3+)/Mn(2+) phosphors.

    PubMed

    Zhang, Jilin; He, Yani; Qiu, Zhongxian; Zhang, Weilu; Zhou, Wenli; Yu, Liping; Lian, Shixun

    2014-12-28

    Ce(3+)/Eu(2+), Tb(3+) and Mn(2+) co-doping in single-phase hosts is a common strategy to achieve white-light phosphors via energy transfer, which provides a high color rendering index (CRI) value and good color stability. However, not all hosts are suitable for white-light phosphors due to inefficient energy transfer. In this study, the site-sensitive energy transfer from different crystallographic sites of Ce(3+) to Tb(3+)/Mn(2+) in Ca3Al2O6 has been investigated in detail. The energy transfer from purplish-blue Ce(3+) to Tb(3+) is an electric dipole-dipole mode, and the calculated critical distance (Rc) suggests the existence of purplish-blue Ce(3+)-Tb(3+) clusters. No energy transfer is observed from purplish-blue Ce(3+) to Mn(2+). In co-doped phosphors based on greenish-blue Ce(3+), however, the radiative mode dominates the energy transfer from Ce(3+) to Tb(3+), and an electric dipole-quadrupole interaction is responsible for the energy transfer from Ce(3+) to Mn(2+). A detailed discussion on the site-sensitive energy transfer modes might provide a new aspect to discuss and understand the possibilities and mechanisms of energy transfer, according to certain crystallographic sites in a complex host with different cation sites, as well as provide a possible approach in searching for single-phase white-light-emitting phosphors.

  2. Scale-to-scale energy transfer in mixing flow induced by the Richtmyer-Meshkov instability

    NASA Astrophysics Data System (ADS)

    Liu, Han; Xiao, Zuoli

    2016-05-01

    The Richtmyer-Meshkov instability (RMI) mixing flow induced by a planar shock wave of Mach 1.6 is investigated using direct numerical simulation method. Interfacial perturbations of different scales between air and sulfur hexafluoride are introduced to study the effect of the initial conditions. Focus is placed on the analysis of the scale-to-scale transfer of kinetic energy in both Fourier and physical spaces. The kinetic energy injected from the perturbation scales is transferred to both larger and smaller scales in an average sense within the inner mixing zone (IMZ) at early times and is mainly passed down into smaller scales at the late stage. The physical-space energy flux due to the subgrid-scale (SGS) stress is studied using a filtering approach in order to shed light on the physical origin of the scale-to-scale kinetic energy transfer. It is found that the pointwise SGS energy flux is highly correlated with the local spike and bubble structures in the IMZ. Moreover, it turns out that the mean SGS energy flux is mainly ascribed to the component in the direction of shock wave propagation. An analysis using the method of conditional averaging manifests that the generation of local SGS energy flux is associated with the property of the surrounding flow induced by quadrupolar or dipolar vortex structures.

  3. Scale-to-scale energy transfer in mixing flow induced by the Richtmyer-Meshkov instability.

    PubMed

    Liu, Han; Xiao, Zuoli

    2016-05-01

    The Richtmyer-Meshkov instability (RMI) mixing flow induced by a planar shock wave of Mach 1.6 is investigated using direct numerical simulation method. Interfacial perturbations of different scales between air and sulfur hexafluoride are introduced to study the effect of the initial conditions. Focus is placed on the analysis of the scale-to-scale transfer of kinetic energy in both Fourier and physical spaces. The kinetic energy injected from the perturbation scales is transferred to both larger and smaller scales in an average sense within the inner mixing zone (IMZ) at early times and is mainly passed down into smaller scales at the late stage. The physical-space energy flux due to the subgrid-scale (SGS) stress is studied using a filtering approach in order to shed light on the physical origin of the scale-to-scale kinetic energy transfer. It is found that the pointwise SGS energy flux is highly correlated with the local spike and bubble structures in the IMZ. Moreover, it turns out that the mean SGS energy flux is mainly ascribed to the component in the direction of shock wave propagation. An analysis using the method of conditional averaging manifests that the generation of local SGS energy flux is associated with the property of the surrounding flow induced by quadrupolar or dipolar vortex structures. PMID:27300983

  4. Dynamics of Energy Transfer in a Conjugated Dendrimer Driven by Ultrafast Localization of Excitations.

    PubMed

    Galindo, Johan F; Atas, Evrim; Altan, Aysun; Kuroda, Daniel G; Fernandez-Alberti, Sebastian; Tretiak, Sergei; Roitberg, Adrian E; Kleiman, Valeria D

    2015-09-16

    Solar energy conversion starts with the harvest of light, and its efficacy depends on the spatial transfer of the light energy to where it can be transduced into other forms of energy. Harnessing solar power as a clean energy source requires the continuous development of new synthetic materials that can harvest photon energy and transport it without significant losses. With chemically-controlled branched architectures, dendrimers are ideally suited for these initial steps, since they consist of arrays of chromophores with relative positioning and orientations to create energy gradients and to spatially focus excitation energies. The spatial localization of the energy delimits its efficacy and has been a point of intense research for synthetic light harvesters. We present the results of a combined theoretical experimental study elucidating ultrafast, unidirectional, electronic energy transfer on a complex molecule designed to spatially focus the initial excitation onto an energy sink. The study explores the complex interplay between atomic motions, excited-state populations, and localization/delocalization of excitations. Our findings show that the electronic energy-transfer mechanism involves the ultrafast collapse of the photoexcited wave function due to nonadiabatic electronic transitions. The localization of the wave function is driven by the efficient coupling to high-frequency vibrational modes leading to ultrafast excited-state dynamics and unidirectional efficient energy funneling. This work provides a long-awaited consistent experiment-theoretical description of excited-state dynamics in organic conjugated dendrimers with atomistic resolution, a phenomenon expected to universally appear in a variety of synthetic conjugated materials.

  5. Dynamics of Energy Transfer in a Conjugated Dendrimer Driven by Ultrafast Localization of Excitations.

    PubMed

    Galindo, Johan F; Atas, Evrim; Altan, Aysun; Kuroda, Daniel G; Fernandez-Alberti, Sebastian; Tretiak, Sergei; Roitberg, Adrian E; Kleiman, Valeria D

    2015-09-16

    Solar energy conversion starts with the harvest of light, and its efficacy depends on the spatial transfer of the light energy to where it can be transduced into other forms of energy. Harnessing solar power as a clean energy source requires the continuous development of new synthetic materials that can harvest photon energy and transport it without significant losses. With chemically-controlled branched architectures, dendrimers are ideally suited for these initial steps, since they consist of arrays of chromophores with relative positioning and orientations to create energy gradients and to spatially focus excitation energies. The spatial localization of the energy delimits its efficacy and has been a point of intense research for synthetic light harvesters. We present the results of a combined theoretical experimental study elucidating ultrafast, unidirectional, electronic energy transfer on a complex molecule designed to spatially focus the initial excitation onto an energy sink. The study explores the complex interplay between atomic motions, excited-state populations, and localization/delocalization of excitations. Our findings show that the electronic energy-transfer mechanism involves the ultrafast collapse of the photoexcited wave function due to nonadiabatic electronic transitions. The localization of the wave function is driven by the efficient coupling to high-frequency vibrational modes leading to ultrafast excited-state dynamics and unidirectional efficient energy funneling. This work provides a long-awaited consistent experiment-theoretical description of excited-state dynamics in organic conjugated dendrimers with atomistic resolution, a phenomenon expected to universally appear in a variety of synthetic conjugated materials. PMID:26122872

  6. Energy transfer efficiency in the chromophore network strongly coupled to a vibrational mode.

    PubMed

    Mourokh, Lev G; Nori, Franco

    2015-11-01

    Using methods from condensed matter and statistical physics, we examine the transport of excitons through the photosynthetic complex from a receiving antenna to a reaction center. Writing the equations of motion for the exciton creation-annihilation operators, we are able to describe the exciton dynamics, even in the regime when the reorganization energy is of the order of the intrasystem couplings. We determine the exciton transfer efficiency in the presence of a quenching field and protein environment. While the majority of the protein vibrational modes are treated as a heat bath, we address the situation when specific modes are strongly coupled to excitons and examine the effects of these modes on the energy transfer efficiency in the steady-state regime. Using the structural parameters of the Fenna-Matthews-Olson complex, we find that, for vibrational frequencies below 16 meV, the exciton transfer is drastically suppressed. We attribute this effect to the formation of a "mixed exciton-vibrational mode" where the exciton is transferred back and forth between the two pigments with the absorption or emission of vibrational quanta, instead of proceeding to the reaction center. The same effect suppresses the quantum beating at the vibrational frequency of 25 meV. We also show that the efficiency of the energy transfer can be enhanced when the vibrational mode strongly couples to the third pigment only, instead of coupling to the entire system.

  7. Energy transfer efficiency in the chromophore network strongly coupled to a vibrational mode

    NASA Astrophysics Data System (ADS)

    Mourokh, Lev G.; Nori, Franco

    2015-11-01

    Using methods from condensed matter and statistical physics, we examine the transport of excitons through the photosynthetic complex from a receiving antenna to a reaction center. Writing the equations of motion for the exciton creation-annihilation operators, we are able to describe the exciton dynamics, even in the regime when the reorganization energy is of the order of the intrasystem couplings. We determine the exciton transfer efficiency in the presence of a quenching field and protein environment. While the majority of the protein vibrational modes are treated as a heat bath, we address the situation when specific modes are strongly coupled to excitons and examine the effects of these modes on the energy transfer efficiency in the steady-state regime. Using the structural parameters of the Fenna-Matthews-Olson complex, we find that, for vibrational frequencies below 16 meV, the exciton transfer is drastically suppressed. We attribute this effect to the formation of a "mixed exciton-vibrational mode" where the exciton is transferred back and forth between the two pigments with the absorption or emission of vibrational quanta, instead of proceeding to the reaction center. The same effect suppresses the quantum beating at the vibrational frequency of 25 meV. We also show that the efficiency of the energy transfer can be enhanced when the vibrational mode strongly couples to the third pigment only, instead of coupling to the entire system.

  8. Disk-to-disk transfer as the rate-limiting step for energy flow in phycobilisomes

    SciTech Connect

    Glazer, A.N.; Yeh, S.W.; Webb, S.P.; Clark, J.H.

    1985-01-25

    A broadly tunable picosecond laser source and an ultrafast streak camera were used to measure temporally and spectrally resolved emission from intact phycobilisomes and from individual phycobiliproteins as a function of excitation wavelength. Both wild-type and mutant phycobilisomes of the unicellular cyanobacterium Synechocystis 6701 were examined, as well as two biliproteins, R-phycoerythrin (240 kilodaltons, 34 bilins) and allophycocyanin (100 kilodaltons, 6 bilins). Measurements of intact phycobilisomes with known structural differences showed that the addition of an average of 1.6 phycoerythrin disks in the phycobilisome rod increased the overall energy transfer time by 30 +/- 5 picoseconds. In the isolated phycobiliproteins the onset of emission was as prompt as that of a solution of rhodamine B laser dye and was independent of excitation wavelength. This imposes an upper limit of 8 picoseconds (instrument-limited) on the transfer time from sensitizing to fluorescing chromophores in these biliproteins. These results indicate that disk-to-disk transfer is the slowest energy transfer process in phycobilisomes and, in combination with previous structural analyses, show that with respect to energy transfer the lattice of approximately 625 light-harvesting chromophores in the Synechocystis 6701 wild-type phycobilisome functions as a linear five-point array.

  9. Vibrational spectroscopy and intramolecular energy transfer in isocyanic acid (HNCO)

    SciTech Connect

    Coffey, M.J.; Berghout, H.L.; Woods, E. III; Crim, F.F.

    1999-06-01

    Room temperature photoacoustic spectra in the region of the first through the fourth overtones (2{nu}{sub 1} to 5{nu}{sub 1}) and free-jet action spectra of the second through the fourth overtones (3{nu}{sub 1} to 5{nu}{sub 1}) of the N{endash}H stretching vibration permit analysis of the vibrational and rotational structure of HNCO. The analysis identifies the strong intramolecular couplings that control the early stages of intramolecular vibrational energy redistribution (IVR) and gives the interaction matrix elements between the zero-order N{endash}H stretching states and the other zero-order states with which they interact. The experimentally determined couplings and zero-order state separations are consistent with {ital ab initio} calculations of East, Johnson, and Allen [J. Chem. Phys. {bold 98}, 1299 (1993)], and comparison with the calculation identifies the coupled states and likely interactions. The states most strongly coupled to the pure N{endash}H stretching zero-order states are ones with a quantum of N{endash}H stretching excitation ({nu}{sub 1}) replaced by different combinations of N{endash}C{endash}O asymmetric or symmetric stretching excitation ({nu}{sub 2} or {nu}{sub 3}) and {ital trans}-bending excitation ({nu}{sub 4}). The two strongest couplings of the n{nu}{sub 1} state are to the states (n{minus}1){nu}{sub 1}+{nu}{sub 2}+{nu}{sub 4} and (n{minus}1){nu}{sub 1}+{nu}{sub 3}+2{nu}{sub 4}, and sequential couplings through a series of low order resonances potentially play a role. The analysis shows that if the pure N{endash}H stretch zero-order state were excited, energy would initially flow out of that mode into the strongly coupled mode in 100 fs to 700 fs, depending on the level of initial excitation. {copyright} {ital 1999 American Institute of Physics.}

  10. The free-energy barrier to hydride transfer across a dipalladium complex.

    PubMed

    Vanston, C R; Kearley, G J; Edwards, A J; Darwish, T A; de Souza, N R; Ramirez-Cuesta, A J; Gardiner, M G

    2015-01-01

    We use density-functional theory molecular dynamics (DFT-MD) simulations to determine the hydride transfer coordinate between palladium centres of the crystallographically observed terminal hydride locations, Pd-Pd-H, originally postulated for the solution dynamics of the complex bis-NHC dipalladium hydride [{(MesIm)2CH2}2Pd2H][PF6], and then calculate the free-energy along this coordinate. We estimate the transfer barrier-height to be about 20 kcal mol(-1) with a hydride transfer rate in the order of seconds at room temperature. We validate our DFT-MD modelling using inelastic neutron scattering which reveals anharmonicity of the hydride environment that is so pronounced that there is complete failure of the harmonic model for the hydride ligand. The simulations are extended to high temperature to bring the H-transfer to a rate that is accessible to the simulation technique. PMID:25652724

  11. The free-energy barrier to hydride transfer across a dipalladium complex.

    PubMed

    Vanston, C R; Kearley, G J; Edwards, A J; Darwish, T A; de Souza, N R; Ramirez-Cuesta, A J; Gardiner, M G

    2015-01-01

    We use density-functional theory molecular dynamics (DFT-MD) simulations to determine the hydride transfer coordinate between palladium centres of the crystallographically observed terminal hydride locations, Pd-Pd-H, originally postulated for the solution dynamics of the complex bis-NHC dipalladium hydride [{(MesIm)2CH2}2Pd2H][PF6], and then calculate the free-energy along this coordinate. We estimate the transfer barrier-height to be about 20 kcal mol(-1) with a hydride transfer rate in the order of seconds at room temperature. We validate our DFT-MD modelling using inelastic neutron scattering which reveals anharmonicity of the hydride environment that is so pronounced that there is complete failure of the harmonic model for the hydride ligand. The simulations are extended to high temperature to bring the H-transfer to a rate that is accessible to the simulation technique.

  12. Minimal Model of Quantum Kinetic Clusters for the Energy-Transfer Network of a Light-Harvesting Protein Complex.

    PubMed

    Wu, Jianlan; Tang, Zhoufei; Gong, Zhihao; Cao, Jianshu; Mukamel, Shaul

    2015-04-01

    The energy absorbed in a light-harvesting protein complex is often transferred collectively through aggregated chromophore clusters. For population evolution of chromophores, the time-integrated effective rate matrix allows us to construct quantum kinetic clusters quantitatively and determine the reduced cluster-cluster transfer rates systematically, thus defining a minimal model of energy-transfer kinetics. For Fenna-Matthews-Olson (FMO) and light-havrvesting complex II (LCHII) monomers, quantum Markovian kinetics of clusters can accurately reproduce the overall energy-transfer process in the long-time scale. The dominant energy-transfer pathways are identified in the picture of aggregated clusters. The chromophores distributed extensively in various clusters can assist a fast and long-range energy transfer.

  13. Study of energy transfer between molecules placed in the vicinity of a bimetal composite nanoparticle

    SciTech Connect

    Daneshfar, Nader E-mail: ndaneshfar@razi.ac.ir

    2015-10-15

    In this study, the problem of energy transfer between two molecules near a bimetallic composite nanoparticle is investigated. The influence of the interaction between metal particles on the intermolecular energy is studied, because when two metal nanoparticles are placed close to each other, their plasmons coupling giving rise to new features. On the other hand, we discuss the transfer of resonance energy between donor and acceptor molecules (a single donor and a single acceptor) in the presence of a nanocomposite containing gold and silver nanoparticles based on the Maxwell-Garnett effective medium theory and within the quasistatic limit. We show that the interaction energy strongly depends on the particle size, the filling factor of metal particles, the intermolecular distance (the distance between the donor and acceptor molecules), and the dielectric constant of host matrix.

  14. Collisional vibrational energy transfer of OH (A 2Sigma + , v'=1)

    NASA Astrophysics Data System (ADS)

    Williams, Leah R.; Crosley, David R.

    1996-05-01

    Vibrational energy transfer (VET) and quenching of the v'=1 level of A 2Σ+ OH have been studied using laser-induced fluorescence in a discharge flow cell at room temperature. VET cross sections (Å2) are N2, 30.1±2.8; O2, 2.8±0.3; Ar, 0.56±0.05; H2O, 8.6±0.6. The rotational energy distribution in v'=0 following the VET event was determined for nine colliders. It is nonthermal, generally populating high rotational levels. There are three broad categories of colliders that cause varying degrees of vibrational to rotational energy transfer; H2, D2, and CH4 show the least; N2, CO2, CF4, and N2O more; and O2 and Ar the most, with about one-third of the vibrational energy appearing as OH rotation.

  15. DNA-length-dependent fluorescent sensing based on energy transfer in self-assembled multilayers.

    PubMed

    Sun, Xiang-Ying; Liu, Bin; Sun, Yan-Feng; Yu, Yaming

    2014-11-15

    In this paper, a novel DNA-length-dependent fluorescent sensor was constructed based on the fluorescence resonance energy transfer. In the self-assembled multilayers (Quartz/GO/PDDA/Tx-DNA/PDDA/ZnO@CdS), ZnO@CdS and graphene oxide(GO) were employed as an energy donor and an energy acceptor, respectively. Single-stranded Tx-DNA (x represents different chain length of DNA) and poly(diallydimethylammonium) chloride (PDDA) were used as a linker. In the presence of complementary Px-DNA, the formation of double-stranded DNA leads to a change in chain length and achieves the purpose of changing the distance between ZnO@CdS and GO. Thereby, it enhances the efficiency of energy transfer between ZnO@CdS and GO resulting in the quench of fluorescence of ZnO@CdS, and thus different length DNA sequence was detected.

  16. Photosynthesis. Structural basis for energy transfer pathways in the plant PSI-LHCI supercomplex.

    PubMed

    Qin, Xiaochun; Suga, Michihiro; Kuang, Tingyun; Shen, Jian-Ren

    2015-05-29

    Photosynthesis converts solar energy to chemical energy by means of two large pigment-protein complexes: photosystem I (PSI) and photosystem II (PSII). In higher plants, the PSI core is surrounded by a large light-harvesting complex I (LHCI) that captures sunlight and transfers the excitation energy to the core with extremely high efficiency. We report the structure of PSI-LHCI, a 600-kilodalton membrane protein supercomplex, from Pisum sativum (pea) at a resolution of 2.8 angstroms. The structure reveals the detailed arrangement of pigments and other cofactors—especially within LHCI—as well as numerous specific interactions between the PSI core and LHCI. These results provide a firm structural basis for our understanding on the energy transfer and photoprotection mechanisms within the PSI-LHCI supercomplex.

  17. Long-range energy transfer in self-assembled quantum dot-DNA cascades

    NASA Astrophysics Data System (ADS)

    Goodman, Samuel M.; Siu, Albert; Singh, Vivek; Nagpal, Prashant

    2015-11-01

    The size-dependent energy bandgaps of semiconductor nanocrystals or quantum dots (QDs) can be utilized in converting broadband incident radiation efficiently into electric current by cascade energy transfer (ET) between layers of different sized quantum dots, followed by charge dissociation and transport in the bottom layer. Self-assembling such cascade structures with angstrom-scale spatial precision is important for building realistic devices, and DNA-based QD self-assembly can provide an important alternative. Here we show long-range Dexter energy transfer in QD-DNA self-assembled single constructs and ensemble devices. Using photoluminescence, scanning tunneling spectroscopy, current-sensing AFM measurements in single QD-DNA cascade constructs, and temperature-dependent ensemble devices using TiO2 nanotubes, we show that Dexter energy transfer, likely mediated by the exciton-shelves formed in these QD-DNA self-assembled structures, can be used for efficient transport of energy across QD-DNA thin films.The size-dependent energy bandgaps of semiconductor nanocrystals or quantum dots (QDs) can be utilized in converting broadband incident radiation efficiently into electric current by cascade energy transfer (ET) between layers of different sized quantum dots, followed by charge dissociation and transport in the bottom layer. Self-assembling such cascade structures with angstrom-scale spatial precision is important for building realistic devices, and DNA-based QD self-assembly can provide an important alternative. Here we show long-range Dexter energy transfer in QD-DNA self-assembled single constructs and ensemble devices. Using photoluminescence, scanning tunneling spectroscopy, current-sensing AFM measurements in single QD-DNA cascade constructs, and temperature-dependent ensemble devices using TiO2 nanotubes, we show that Dexter energy transfer, likely mediated by the exciton-shelves formed in these QD-DNA self-assembled structures, can be used for efficient

  18. Toward understanding as photosynthetic biosignatures: light harvesting and energy transfer calculation

    NASA Astrophysics Data System (ADS)

    Komatsu, Y.; Umemura, M.; Shoji, M.; Shiraishi, K.; Kayanuma, M.; Yabana, K.

    2014-03-01

    Among several proposed biosignatures, red edge is a direct evidence of photosynthetic life if it is detected (Kiang et al 2007). Red edge is a sharp change in reflectance spectra of vegetation in NIR region (about 700-750 nm). The sign of red edge is observed by Earthshine or remote sensing (Wolstencroft & Raven 2002, Woolf et al 2002). But, why around 700-750 nm? The photosynthetic organisms on Earth have evolved to optimize the sunlight condition. However, if we consider about photosynthetic organism on extrasolar planets, they should have developed to utilize the spectra of its principal star. Thus, it is not strange even if it shows different vegetation spectra. In this study, we focused on the light absorption mechanism of photosynthetic organisms on Earth and investigated the fundamental properties of the light harvesting mechanisms, which is the first stage for the light absorption. Light harvesting complexes contain photosynthetic pigments like chlorophylls. Effective light absorption and the energy transfer are accomplished by the electronic excitations of collective photosynthetic pigments. In order to investigate this mechanism, we constructed an energy transfer model by using a dipole-dipole approximation for the interactions between electronic excitations. Transition moments and transition energies of each pigment are calculated at the time-dependent density functional theory (TDDFT) level (Marques & Gross 2004). Quantum dynamics simulation for the excitation energy transfer was calculated by the Liouvelle's equation. We adopted the model to purple bacteria, which has been studied experimentally and known to absorb lower energy. It is meaningful to focus on the mechanism of this bacteria, since in the future mission, M planets will become a important target. We calculated the oscillator strengths in one light harvesting complex and confirmed the validity by comparing to the experimental data. This complex is made of an inner and an outer ring. The

  19. Energy transfer processes in solar energy conversion. Progress report, March 1, 1991--February 29, 1992

    SciTech Connect

    Fayer, M.D.

    1992-07-01

    During the past year, we have been working in three general areas: electronic excitation transport in clustered chromophore systems and other complex systems, photo-induced electron transfer and back transfer in liquid solutions in which diffusion and charge interactions are important, and the construction of a new two color dye laser system to enhance our experimental capability.

  20. Energy transfer in Tm,Ho:KYW crystal and diode-pumped microchip laser operation.

    PubMed

    Kurilchik, Sergey; Gusakova, Natali; Demesh, Maxim; Yasukevich, Anatol; Kisel, Viktor; Pavlyuk, Anatoly; Kuleshov, Nikolai

    2016-03-21

    An investigation of Tm-Ho energy transfer in Tm(5at.%),Ho(0.4at.%):KYW single crystal by two independent techiques was performed. Based on fluorescence dynamics measurements, energy transfer parameters P71 and P28 for direct (Tm→Ho) and back (Ho→Tm) transfers, respectively, as well as equilibrium constant Θ were evaluated. The obtained results were supported by calculation of microscopic interaction parameters according to the Förster-Dexter theory for a dipole-dipole interaction. Diode-pumped continuous-wave operation of Tm,Ho:KYW microchip laser was demonstrated, for the first time to our knowledge. Maximum output power of 77 mW at 2070 nm was achieved at the fundamental TEM00 mode. PMID:27136836

  1. Horizontal versus vertical charge and energy transfer in hybrid assemblies of semiconductor nanoparticles

    PubMed Central

    Gotesman, Gilad; Guliamov, Rahamim

    2012-01-01

    Summary We studied the photoluminescence and time-resolved photoluminescence from self-assembled bilayers of donor and acceptor nanoparticles (NPs) adsorbed on a quartz substrate through organic linkers. Charge and energy transfer processes within the assemblies were investigated as a function of the length of the dithiolated linker (DT) between the donors and acceptors. We found an unusual linker-length-dependency in the emission of the donors. This dependency may be explained by charge and energy transfer processes in the vertical direction (from the donors to the acceptors) that depend strongly on charge transfer processes occurring in the horizontal plane (within the monolayer of the acceptor), namely, parallel to the substrate. PMID:23019559

  2. Light Harvesting in Microscale Metal-Organic Frameworks by Energy Migration and Interfacial Electron Transfer Quenching

    SciTech Connect

    Kent, Caleb A.; Liu, Demin; Ma, Liqing; Papanikolas, John M.; Meyer, Thomas J.; Lin, Wenbin

    2011-08-24

    Microscale metal–organic frameworks (MOFs) were synthesized from photoactive Ru(II)-bpy building blocks with strong visible light absorption and long-lived triplet metal-to-ligand charge transfer (³MLCT) excited states. These MOFs underwent efficient luminescence quenching in the presence of either oxidative or reductive quenchers. Up to 98% emission quenching was achieved with either an oxidative quencher (1,4-benzoquinone) or a reductive quencher (N,N,N',N'-tetramethylbenzidine), as a result of rapid energy migration over several hundred nanometers followed by efficient electron transfer quenching at the MOF/solution interface. The photoactive MOFs act as an excellent light-harvesting system by combining intraframework energy migration and interfacial electron transfer quenching.

  3. Vibration excitation and energy transfer during ultrasonically assisted drilling

    NASA Astrophysics Data System (ADS)

    Babitsky, V. I.; Astashev, V. K.; Meadows, A.

    2007-12-01

    Successful application of ultrasonically assisted drilling needs dynamic matching of the transducer with the drill bit considered as a continuous system loaded by the nonlinear processing load. When using standard tools this leads to the compatible choice of the transducer and accurate matching of the transducer and tool. The principal dynamical features of this matching are considered. Optimal position of excitation cross section of the drill bit, which depends on the relationship between elasto-dissipative characteristics of the transducer, the drill bit and the work load, is found in general analytical form. The optimal matching preserves the resonant tuning of the transducer and compensates the additional energy losses in the drill bit and processing. This produces also an amplification of vibration amplitude. The effect is achieved through the generation and maintenance of a nonlinear resonant mode of vibration and by active matching of the oscillating system with the dynamic loads imposed by the cutting process with the help of the intelligent electronic feedback circuitry. A prototype of an ultrasonic drilling system has been designed, manufactured. and tested. Improvements of machining characteristics due to superposition of ultrasonic vibration are demonstrated. Substantial improvements in the cutting performance of drill bits lead to benefits in drilling performance, which include faster penetration rates, reduction of tool wear, improvements in the surface finish, roundness and straightness of holes and, in ductile materials, the reduction or even complete elimination of burrs on both the entrance and exit faces of plates. The reduction in the reactive force experienced also causes greatly reduced deformation when drilling through thin, flexible plates and helps to alleviate delamination hazard.

  4. Energy transfer cassettes based on organic fluorophores: construction and applications in ratiometric sensing.

    PubMed

    Fan, Jiangli; Hu, Mingming; Zhan, Peng; Peng, Xiaojun

    2013-01-01

    This tutorial review presents some recent developments in the construction and applications of cassettes based on resonance energy transfer between fluorescent dyes in the visible and infrared region. We focused on the contributions of different connections between the energy donor and acceptor according to the "through-space" and "through-bond" methods, and emphasised their applications in ratiometric sensing for the detection of ions and small molecules. PMID:23059554

  5. Incorporating the Delphi Technique to investigate renewable energy technology transfer in Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Al-Otaibi, Nasir K.

    Saudi Arabia is a major oil-producing nation facing a rapidly-growing population, high unemployment, climate change, and the depletion of its natural resources, potentially including its oil supply. Technology transfer is regarded as a means to diversify countries' economies beyond their natural resources. This dissertation examined the opportunities and barriers to utilizing technology transfer successfully to build renewable energy resources in Saudi Arabia to diversify the economy beyond oil production. Examples of other developing countries that have successfully used technology transfer to transform their economies are explored, including Japan, Malayasia, and the United Arab Emirates. Brazil is presented as a detailed case study to illustrate its transition to an economy based to a much greater degree than before on renewable energy. Following a pilot study, the Delphi Method was used in this research to gather the opinions of a panel of technology transfer experts consisting of 10 heterogeneous members of different institutions in the Kingdom of Saudi Arabia, including aviation, telecommunication, oil industry, education, health systems, and military and governmental organizations. In three rounds of questioning, the experts identified Education, Dependence on Oil, and Manpower as the 3 most significant factors influencing the potential for success of renewable energy technology transfer for Saudi Arabia. Political factors were also rated toward the "Very Important" end of a Likert scale and were discussed as they impact Education, Oil Dependence, and Manpower. The experts' opinions are presented and interpreted. They form the basis for recommended future research and discussion of how in light of its political system and its dependence on oil, Saudi Arabia can realistically move forward on renewable energy technology transfer and secure its economic future.

  6. Proceedings of the First National Workshop on Energy Efficiency Education Through Technology Transfer.

    ERIC Educational Resources Information Center

    Cohen, Karen C., Ed.

    This publication contains the proceedings from a workshop held in Washington, D.C. in December, 1977. The purpose of the conference was to examine project PROCEED (Program for Continuing Engineering Education) as an innovative approach to technology transfer in energy efficiency education and the potential relationships of the project with the…

  7. Proton transfer pathways, energy landscape, and kinetics in creatine-water systems.

    PubMed

    Ivchenko, Olga; Whittleston, Chris S; Carr, Joanne M; Imhof, Petra; Goerke, Steffen; Bachert, Peter; Wales, David J

    2014-02-27

    We study the exchange processes of the metabolite creatine, which is present in both tumorous and normal tissues and has NH2 and NH groups that can transfer protons to water. Creatine produces chemical exchange saturation transfer (CEST) contrast in magnetic resonance imaging (MRI). The proton transfer pathway from zwitterionic creatine to water is examined using a kinetic transition network constructed from the discrete path sampling approach and an approximate quantum-chemical energy function, employing the self-consistent-charge density-functional tight-binding (SCC-DFTB) method. The resulting potential energy surface is visualized by constructing disconnectivity graphs. The energy landscape consists of two distinct regions corresponding to the zwitterionic creatine structures and deprotonated creatine. The activation energy that characterizes the proton transfer from the creatine NH2 group to water was determined from an Arrhenius fit of rate constants as a function of temperature, obtained from harmonic transition state theory. The result is in reasonable agreement with values obtained in water exchange spectroscopy (WEX) experiments.

  8. DEVELOPMENT OF A REAL-TIME FLUORESCENCE RESONANCE ENERGY TRANSFER (FRET) PCR TO DETECT ARCOBACTER SPECIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A real-time PCR targeting the gyrase A subunit gene outside the quinolone resistance-determining region has been developed to detect Arcobacter species. The species identification was made by probe hybridization and melting curve analysis, using the Fluorescence Resonance Energy Transfer technology...

  9. Combustion and Energy Transfer Experiments: A Laboratory Model for Linking Core Concepts across the Science Curriculum

    ERIC Educational Resources Information Center

    Barreto, Jose C.; Dubetz, Terry A.; Schmidt, Diane L.; Isern, Sharon; Beatty, Thomas; Brown, David W.; Gillman, Edward; Alberte, Randall S.; Egiebor, Nosa O.

    2007-01-01

    Core concepts can be integrated throughout lower-division science and engineering courses by using a series of related, cross-referenced laboratory experiments. Starting with butane combustion in chemistry, the authors expanded the underlying core concepts of energy transfer into laboratories designed for biology, physics, and engineering. This…

  10. DEVELOPMENT OF A REAL-TIME FLUORESCENCE RESONANCE ENERGY TRANSFER PCR TO DETECT ARCOBACTER SPECIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A real-time PCR targeting the gyrase A subunit gene outside the quinolone resistance-determining region has been developed to detect Arcobacter species. The species identification was made by probe hybridization and melting curve analysis, using Fluorescence Resonance Energy Transfer technology. D...

  11. Picosecond spectroscopic studies of energy transfer in phycobiliproteins and model dye systems

    SciTech Connect

    Switalski, S.C.

    1987-02-01

    Energy transfer was investigated in the ..cap alpha beta.. monomer and separated ..cap alpha.. and ..beta.. subunits of C-phycocyanin from Anabaena variabilis and Anacystis nidulans, using steady-state and picosecond spectroscopy. Fluorescence excitation polarization spectra were consistent with a sensitizing (s) - fluorescing (f) model using a Forster energy transfer mechanism. The rise in polarization across the absorption band towards longer wavelength for the ..beta.. subunit and the ..cap alpha beta.. monomer was attributed to energy transfer among the three chromophores in the ..cap alpha beta.. monomer and between the 2 chromophores in the ..beta.. subunit. The constant polarization of the ..cap alpha.. subunit, with one chromophore, is consistent with a lack of any possibility of energy transfer. Fluorescence emission maxima were at 640 nm for the ..cap alpha beta.. monomer and the separated subunits of Anabaena variabilis, and 645 nm for the ..beta.. subunit, 640 nm for the ..cap alpha.. subunit, and 644 nm for ..cap alpha beta.. monomer of Anacystis nidulans. We have shown that the labels s and f are not consistent with all the steady-state spectroscopic results. 171 refs., 32 figs., 15 tabs.

  12. Chaotic oscillation and random-number generation based on nanoscale optical-energy transfer

    PubMed Central

    Naruse, Makoto; Kim, Song-Ju; Aono, Masashi; Hori, Hirokazu; Ohtsu, Motoichi

    2014-01-01

    By using nanoscale energy-transfer dynamics and density matrix formalism, we demonstrate theoretically and numerically that chaotic oscillation and random-number generation occur in a nanoscale system. The physical system consists of a pair of quantum dots (QDs), with one QD smaller than the other, between which energy transfers via optical near-field interactions. When the system is pumped by continuous-wave radiation and incorporates a timing delay between two energy transfers within the system, it emits optical pulses. We refer to such QD pairs as nano-optical pulsers (NOPs). Irradiating an NOP with external periodic optical pulses causes the oscillating frequency of the NOP to synchronize with the external stimulus. We find that chaotic oscillation occurs in the NOP population when they are connected by an external time delay. Moreover, by evaluating the time-domain signals by statistical-test suites, we confirm that the signals are sufficiently random to qualify the system as a random-number generator (RNG). This study reveals that even relatively simple nanodevices that interact locally with each other through optical energy transfer at scales far below the wavelength of irradiating light can exhibit complex oscillatory dynamics. These findings are significant for applications such as ultrasmall RNGs. PMID:25113239

  13. Energy Transfer Sensitization of Luminescent Gold Nanoclusters: More than Just the Classical Förster Mechanism

    PubMed Central

    Oh, Eunkeu; Huston, Alan L.; Shabaev, Andrew; Efros, Alexander; Currie, Marc; Susumu, Kimihiro; Bussmann, Konrad; Goswami, Ramasis; Fatemi, Fredrik K.; Medintz, Igor L.

    2016-01-01

    Luminescent gold nanocrystals (AuNCs) are a recently-developed material with potential optic, electronic and biological applications. They also demonstrate energy transfer (ET) acceptor/sensitization properties which have been ascribed to Förster resonance energy transfer (FRET) and, to a lesser extent, nanosurface energy transfer (NSET). Here, we investigate AuNC acceptor interactions with three structurally/functionally-distinct donor classes including organic dyes, metal chelates and semiconductor quantum dots (QDs). Donor quenching was observed for every donor-acceptor pair although AuNC sensitization was only observed from metal-chelates and QDs. FRET theory dramatically underestimated the observed energy transfer while NSET-based damping models provided better fits but could not reproduce the experimental data. We consider additional factors including AuNC magnetic dipoles, density of excited-states, dephasing time, and enhanced intersystem crossing that can also influence ET. Cumulatively, data suggests that AuNC sensitization is not by classical FRET or NSET and we provide a simplified distance-independent ET model to fit such experimental data. PMID:27774984

  14. Cascaded plasmon-plasmon coupling mediated energy transfer across stratified metal-dielectric nanostructures

    NASA Astrophysics Data System (ADS)

    Golmakaniyoon, Sepideh; Hernandez-Martinez, Pedro Ludwig; Demir, Hilmi Volkan; Sun, Xiao Wei

    2016-10-01

    Surface plasmon (SP) coupling has been successfully applied to nonradiative energy transfer via exciton-plasmon-exciton coupling in conventionally sandwiched donor-metal film-acceptor configurations. However, these structures lack the desired efficiency and suffer poor photoemission due to the high energy loss. Here, we show that the cascaded exciton-plasmon-plasmon-exciton coupling in stratified architecture enables an efficient energy transfer mechanism. The overlaps of the surface plasmon modes at the metal-dielectric and dielectric-metal interfaces allow for strong cross-coupling in comparison with the single metal film configuration. The proposed architecture has been demonstrated through the analytical modeling and numerical simulation of an oscillating dipole near the stratified nanostructure of metal-dielectric-metal-acceptor. Consistent with theoretical and numerical results, experimental measurements confirm at least 50% plasmon resonance energy transfer enhancement in the donor-metal-dielectric-metal-acceptor compared to the donor-metal-acceptor structure. Cascaded plasmon-plasmon coupling enables record high efficiency for exciton transfer through metallic structures.

  15. Parity propensities in rotational energy transfer of OH X 2Pi(i) with helium

    NASA Technical Reports Server (NTRS)

    Wysong, Ingrid J.; Jeffries, Jay B.; Crosley, David R.

    1991-01-01

    Preliminary results of rotational energy transfer in ground state OH in collisions in He are reported. A surprising propensity is found: conservation of total parity is favored in collisions which change in spin-orbit component, the reversible reaction 2Pi3/2 yields 2Pi1/2. This has implications concerning the OH-He potential surface.

  16. Array-Based Detection of Persistent Organic Pollutants via Cyclodextrin Promoted Energy Transfer

    PubMed Central

    Serio, Nicole; Moyano, Daniel F.; Rotello, Vincent M.; Levine, Mindy

    2015-01-01

    We report herein the selective array-based detection of 30 persistent organic pollutants via cyclodextrin-promoted energy transfer. The use of three fluorophores enabled the development of an array that classified 30 analytes with 100% accuracy and identified unknown analytes with 96% accuracy, as well as identifying 92% of analytes in urine. PMID:26096542

  17. Plasmon-enhanced energy transfer between quantum dots and tunable film-coupled nanoparticles

    NASA Astrophysics Data System (ADS)

    Qi, Zhiyang; Wang, Qilong; Zhai, Yusheng; Xu, Ji; Tao, Zhi; Tu, Yan; Lei, Wei; Xia, Jun

    2016-06-01

    The radiative processes associated with quantum dots (QDs), fluorophores and other radiating systems can be profoundly modified by their interaction with plasmonic nanostructures. This interaction is associated with the localized electromagnetic field enhancement and the resonance absorption band. Extreme electromagnetic environments can be created in well-designed plasmonic nanostructures, such as metal film-dielectric layer-metal nanoparticles (NPs). Recently, so called film-coupled NPs have received a significant amount of attentions due to the strong surface plasmon resonances (SPRs). In this paper, we experimentally study the plasmon-enhanced energy transfer between CdSe/ZnS QDs and tunable film-coupled NPs. A facile route of seeding growth of self-assembled particles in situ is primarily presented for the large-area uniform fabrication of film-coupled NPs. The size-dependent energy transfer of Au NPs is demonstrated and the influence of the distribution of top Au NPs is described in detail. The experimental results demonstrate that the metallic nanostructures interact with the CdSe/ZnS QDs with obviously enhanced Förster resonance energy transfer (FRET) probability, and the fluorescence lifetime of QD materials is dramatically shortened. FRET is considered to be responsible for the PL quenching and the nonradiative decay acts as the dominant decay channel. The experimental results are also supported by finite-difference time-domain (FDTD) simulations which intend to collect design paths for the plasmon-enhanced energy transfer.

  18. Enhanced energy transfer in respiratory-deficient endothelial cells probed by microscopic fluorescence excitation spectroscopy

    NASA Astrophysics Data System (ADS)

    Schneckenburger, Herbert; Gschwend, Michael H.; Bauer, Manfred; Strauss, Wolfgang S. L.; Steiner, Rudolf W.

    1996-12-01

    Mitochondrial malfunction may be concomitant with changes of the redox states of the coenzymes nicotinamide adenine dinucleotide (NAD+/NADH), as well as flavin.mononucleotide or dinucleotide. The intrinsic fluorescence of these coenzymes was therefore proposed to be a measure of malfunction. Since mitochondrial fluorescence is strongly superposed by autofluorescence from various cytoplasmatic fluorophores, cultivated endothelial cells were incubated with the mitochondrial marker rhodamine 123 (R123), and after excitation of flavin molecules, energy transfer to R123 was investigated. Due to spectral overlap of flavin and R123 fluorescence, energy transfer flavin yields R123 could not be detected from their emission spectra. Therefore, the method of microscopic fluorescence excitation spectroscopy was established. When detecting R123 fluorescence, excitation maxima at 370 - 390 nm and 420-460 nm were assigned to flavins, whereas a pronounced excitation band at 465 - 490 nm was attributed to R123. Therefore, excitation at 475 nm reflected the intracellular concentration of R123, whereas excitation at 385 nm reflected flavin excitation with a subsequent energy transfer to R123 molecules. An enhanced energy transfer after inhibition of specific enzyme complexes of the respiratory chain is discussed in the present article.

  19. On the transfer of energy to an unstable liquid jet in a coflowing compressible airstream

    NASA Technical Reports Server (NTRS)

    Li, Hsi-Shang; Kelly, Robert E.

    1993-01-01

    The transfer of energy from a compressible airstream to a coflowing unstable liquid jet via the pressure perturbation at the interface is studied as the Mach number varies continuously from subsonic to supersonic values. The 'lift' component of the pressure perturbation has been demonstrated to predominate up to slightly supersonic free-stream Mach numbers, after which the 'drag' component predominates.

  20. Cascaded plasmon-plasmon coupling mediated energy transfer across stratified metal-dielectric nanostructures

    PubMed Central

    Golmakaniyoon, Sepideh; Hernandez-Martinez, Pedro Ludwig; Demir, Hilmi Volkan; Sun, Xiao Wei

    2016-01-01

    Surface plasmon (SP) coupling has been successfully applied to nonradiative energy transfer via exciton-plasmon-exciton coupling in conventionally sandwiched donor-metal film-acceptor configurations. However, these structures lack the desired efficiency and suffer poor photoemission due to the high energy loss. Here, we show that the cascaded exciton-plasmon-plasmon-exciton coupling in stratified architecture enables an efficient energy transfer mechanism. The overlaps of the surface plasmon modes at the metal-dielectric and dielectric-metal interfaces allow for strong cross-coupling in comparison with the single metal film configuration. The proposed architecture has been demonstrated through the analytical modeling and numerical simulation of an oscillating dipole near the stratified nanostructure of metal-dielectric-metal-acceptor. Consistent with theoretical and numerical results, experimental measurements confirm at least 50% plasmon resonance energy transfer enhancement in the donor-metal-dielectric-metal-acceptor compared to the donor-metal-acceptor structure. Cascaded plasmon-plasmon coupling enables record high efficiency for exciton transfer through metallic structures. PMID:27698422

  1. Ultrafast dynamics of Förster resonance energy transfer and photo-induced charge transfer in cationic polyfluorene/dye-labeled DNA complex.

    PubMed

    Kyhm, Kwangseuk; Kim, Inhong; Kang, Mijeong; Woo, Han Young

    2012-10-01

    The ultrafast dynamics of Förster resonance energy transfer (FRET) and photo-induced charge transfer (PCT) has been investigated in an electrostatic complex of a fluorescein-labeled single-stranded DNA (as a FRET acceptor) and a cationic polyfluorene copolymer (as a FRET donor). The donor-acceptor intermolecular distance and total energy transfer efficiency are determined for a polymer/DNA complex with two different counter-ions and compared with those obtained using a theoretical model by considering the competition between FRET and PCT processes. The maximum total energy transfer efficiency (0.47) was estimated at the optimum donor-acceptor intermolecular distance of 39.6 A.

  2. Proton and hydride transfers in solution: hybrid QMmm/MM free energy perturbation study

    SciTech Connect

    Ho, L. Lawrence |; Bash, P.A.; Kerell, A.D., Jr

    1996-03-01

    A hybrid quantum and molecular mechanical (QM/MM) free energy perturbation (FEP) method is implemented in the context of molecular dynamics (MD). The semiempirical quantum mechanical (QM) Hamiltonian (Austin Model 1) represents solute molecules, and the molecular mechanical (MM) CHARMM force field describes the water solvent. The QM/MM FEP method is used to calculate the free energy changes in aqueous solution for (1) a proton transfer from methanol to imidazole and (2) a hydride transfer from methoxide to nicotinamide. The QM/MM interaction energies between the solute and solvent arc calibrated to emulate the solute-solvent interaction energies determined at the Hartee-Fock 6-31G(d) level of ab initio theory. The free energy changes for the proton and hydride transfers are calculated to be 15.1 and {minus}6.3 kcal/mol, respectively, which compare favorably with the corresponding experimental values of 12.9 and {minus}7.4 kcal/mol. An estimate of the reliability of the calculations is obtained through the computation of the forward (15.1 and {minus}6.3 kcal/mol) and backward ({minus}14.1 and 9.1 kcal/mol)free energy changes. The reasonable correspondence between these two independent calculations suggests that adequate phase space sampling is obtained along the reaction pathways chosen to transform the proton and hydride systems between their respective reactant and product states.

  3. Study of energy transfer mechanism from ZnO nanocrystals to Eu(3+) ions.

    PubMed

    Mangalam, Vivek; Pita, Kantisara; Couteau, Christophe

    2016-12-01

    In this work, we investigate the efficient energy transfer occurring between ZnO nanocrystals (ZnO-nc) and europium (Eu(3+)) ions embedded in a SiO2 matrix prepared using the sol-gel technique. We show that a strong red emission was observed at 614 nm when the ZnO-nc were excited using a continuous optical excitation at 325 nm. This emission is due to the radiative (5)D0 → (7)F2 de-excitation of the Eu(3+) ions and has been conclusively shown to be due to the energy transfer from the excited ZnO-nc to the Eu(3+) ions. The photoluminescence excitation spectra are also examined in this work to confirm the energy transfer from ZnO-nc to the Eu(3+) ions. Furthermore, we study various de-excitation processes from the excited ZnO-nc and their contribution to the energy transfer to Eu(3+) ions. We also report the optimum fabrication process for maximum red emission at 614 nm from the samples where we show a strong dependence on the annealing temperature and the Eu(3+) concentration in the sample. The maximum red emission is observed with 12 mol% Eu(3+) annealed at 450 °C. This work provides a better understanding of the energy transfer mechanism from ZnO-nc to Eu(3+) ions and is important for applications in photonics, especially for light emitting devices.

  4. Modulating the electronic structure of chromophores by chemical substituents for efficient energy transfer: application to fluorone.

    PubMed

    Sand, Andrew M; Liu, Claire; Valentine, Andrew J S; Mazziotti, David A

    2014-08-01

    Strong electron correlation within a quasi-spin model of chromophores was recently shown to enhance exciton energy transfer significantly. Here we investigate how the modulation of the electronic structure of the chromophores by chemical substitution can enhance energy-transfer efficiency. Unlike previous work that does not consider the direct effect of the electronic structure on exciton dynamics, we add chemical substituents to the fluorone dimer to study the effect of electron-donating and electron-withdrawing substituents on exciton energy transfer. The exciton dynamics are studied from the solution of a quantum Liouville equation for an open system whose model Hamiltonian is derived from excited-state electronic structure calculations. Both van der Waals energies and coupling energies, arising from the Hellmann-Feynman force generated upon transferring the dimers from infinity to a finite separation, are built into the model Hamiltonian. Though these two effects are implicitly treated in dipole-based models, their explicit and separate treatment as discussed here is critical to forging the correct connection with the electronic structure calculations. We find that the addition of electron-donating substituents to the fluorone system results in an increase in exciton-transfer rates by factors ranging from 1.3-1.9. The computed oscillator strength is consistent with the recent experimental results on a larger heterodimer system containing fluorone. The oscillator strength increases with the addition of electron-donating substituents. Our results indicate that the study of chromophore networks via electronic structure will help in the future design of efficient synthetic light-harvesting systems. PMID:25062094

  5. A fast all-sky radiative transfer model and its implications for solar energy research

    NASA Astrophysics Data System (ADS)

    Xie, Y.; Sengupta, M.

    2015-12-01

    Radiative transfer models simulating broadband solar radiation, e.g. Rapid Radiation Transfer Model (RRTM) and its GCM applications, have been widely used by atmospheric scientists to model solar resource for various energy applications such as operational forecasting. Due to the complexity of solving the radiative transfer equation, simulating solar radiation under cloudy conditions can be extremely time consuming though many approximations, e.g. two-stream approach and delta-M truncation scheme, have been utilized. To provide a new option to approximate solar radiation, we developed a Fast All-sky Radiation Model for Solar applications (FARMS) using simulated cloud transmittance and reflectance from 16-stream RRTM model runs. The solar irradiances at the land surface were simulated by combining parameterized cloud properties with a fast clear-sky radiative transfer model. Using solar radiation measurements from the US Department of Energy's Atmospheric Radiation Measurement (ARM) central facility in Oklahoma as a benchmark against the model simulations, we were able to demonstrate that the accuracy of FARMS was comparable to the two-stream approach. However, FARMS is much more efficient since it does not explicitly solve the radiative transfer equation for each individual cloud condition. We further explored the use of FARMS to promote solar resource assessment and forecasting research through the increased ability to accommodate higher spatial and temporal resolution calculations for the next generation of satellite and numerical weather prediction (NWP) models.

  6. Near-field effects and energy transfer in hybrid metal-oxide nanostructures

    PubMed Central

    Kuerbanjiang, Balati; Benel, Cahit; Papageorgiou, Giorgos; Goncalves, Manuel; Boneberg, Johannes; Leiderer, Paul; Ziemann, Paul; Marek, Peter; Hahn, Horst

    2013-01-01

    Summary One of the big challenges of the 21st century is the utilization of nanotechnology for energy technology. Nanoscale structures may provide novel functionality, which has been demonstrated most convincingly by successful applications such as dye-sensitized solar cells introduced by M. Grätzel. Applications in energy technology are based on the transfer and conversion of energy. Following the example of photosynthesis, this requires a combination of light harvesting, transfer of energy to a reaction center, and conversion to other forms of energy by charge separation and transfer. This may be achieved by utilizing hybrid nanostructures, which combine metallic and nonmetallic components. Metallic nanostructures can interact strongly with light. Plasmonic excitations of such structures can cause local enhancement of the electrical field, which has been utilized in spectroscopy for many years. On the other hand, the excited states in metallic structures decay over very short lifetimes. Longer lifetimes of excited states occur in nonmetallic nanostructures, which makes them attractive for further energy transfer before recombination or relaxation sets in. Therefore, the combination of metallic nanostructures with nonmetallic materials is of great interest. We report investigations of hybrid nanostructured model systems that consist of a combination of metallic nanoantennas (fabricated by nanosphere lithography, NSL) and oxide nanoparticles. The oxide particles were doped with rare-earth (RE) ions, which show a large shift between absorption and emission wavelengths, allowing us to investigate the energy-transfer processes in detail. The main focus is on TiO2 nanoparticles doped with Eu3+, since the material is interesting for applications such as the generation of hydrogen by photocatalytic splitting of water molecules. We use high-resolution techniques such as confocal fluorescence microscopy for the investigation of energy-transfer processes. The experiments

  7. Near-field effects and energy transfer in hybrid metal-oxide nanostructures.

    PubMed

    Herr, Ulrich; Kuerbanjiang, Balati; Benel, Cahit; Papageorgiou, Giorgos; Goncalves, Manuel; Boneberg, Johannes; Leiderer, Paul; Ziemann, Paul; Marek, Peter; Hahn, Horst

    2013-01-01

    One of the big challenges of the 21st century is the utilization of nanotechnology for energy technology. Nanoscale structures may provide novel functionality, which has been demonstrated most convincingly by successful applications such as dye-sensitized solar cells introduced by M. Grätzel. Applications in energy technology are based on the transfer and conversion of energy. Following the example of photosynthesis, this requires a combination of light harvesting, transfer of energy to a reaction center, and conversion to other forms of energy by charge separation and transfer. This may be achieved by utilizing hybrid nanostructures, which combine metallic and nonmetallic components. Metallic nanostructures can interact strongly with light. Plasmonic excitations of such structures can cause local enhancement of the electrical field, which has been utilized in spectroscopy for many years. On the other hand, the excited states in metallic structures decay over very short lifetimes. Longer lifetimes of excited states occur in nonmetallic nanostructures, which makes them attractive for further energy transfer before recombination or relaxation sets in. Therefore, the combination of metallic nanostructures with nonmetallic materials is of great interest. We report investigations of hybrid nanostructured model systems that consist of a combination of metallic nanoantennas (fabricated by nanosphere lithography, NSL) and oxide nanoparticles. The oxide particles were doped with rare-earth (RE) ions, which show a large shift between absorption and emission wavelengths, allowing us to investigate the energy-transfer processes in detail. The main focus is on TiO2 nanoparticles doped with Eu(3+), since the material is interesting for applications such as the generation of hydrogen by photocatalytic splitting of water molecules. We use high-resolution techniques such as confocal fluorescence microscopy for the investigation of energy-transfer processes. The experiments are

  8. A molecular Debye-Hückel approach to the reorganization energy of electron transfer reactions in an electric cell

    SciTech Connect

    Xiao, Tiejun; Song, Xueyu

    2014-10-07

    Electron transfer near an electrode immersed in ionic fluids is studied using the linear response approximation, namely, mean value of the vertical energy gap can be used to evaluate the reorganization energy, and hence any linear response model that can treat Coulomb interactions successfully can be used for the reorganization energy calculation. Specifically, a molecular Debye-Hückel theory is used to calculate the reorganization energy of electron transfer reactions in an electric cell. Applications to electron transfer near an electrode in molten salts show that the reorganization energies from our molecular Debye-Hückel theory agree well with the results from MD simulations.

  9. Energy Transfer Dynamics in an RC-LH1-PufX Tubular Photosynthetic Membrane

    PubMed Central

    Hsin, Jen; Strümpfer, Johan; Sener, Melih; Qian, Pu; Hunter, C. Neil; Schulten, Klaus

    2010-01-01

    Light absorption and the subsequent transfer of excitation energy are the first two steps of the photosynthetic process, carried out by protein-bound pigments, mainly bacteriochlorophylls (BChls), in photosynthetic bacteria. BChls are anchored in light-harvesting (LH) complexes, such as light-harvesting complex I (LH1), which directly associates with the reaction center (RC), forming the RC-LH1 core complex. In Rhodobacter sphaeroides, RC-LH1 core complexes contain an additional protein, PufX, and assemble into dimeric RC-LH1-PufX core complexes. In the absence of light-harvesting complexes II, the former complexes can aggregate into a helically ordered tubular photosynthetic membrane. We examined the excitation transfer dynamics in a single RC-LH1-PufX core complex dimer using the hierarchical equations of motion for dissipative quantum dynamics that accurately, yet computationally costly, treat the coupling between BChls and their protein environment. A widely employed description, generalized Förster theory, was also used to calculate the transfer rates of the same excitonic system in order to verify the accuracy of this computationally cheap method. Additionally, in light of the structural uncertainties in the Rhodobacter sphaeroides RC-LH1-PufX core complex, geometrical alterations were introduced in the BChl organization. It is shown that the energy transfer dynamics is not affected by the considered changes in the BChl organization, and that generalized Förster theory provides accurate transfer rates. An all-atom model for a tubular photosynthetic membrane is then constructed on the basis of electron microscopy data, and the overall energy transfer properties of this membrane are computed. PMID:21152381

  10. Probing Bioluminescence Resonance Energy Transfer in Quantum Rod-Luciferase Nanoconjugates.

    PubMed

    Alam, Rabeka; Karam, Liliana M; Doane, Tennyson L; Coopersmith, Kaitlin; Fontaine, Danielle M; Branchini, Bruce R; Maye, Mathew M

    2016-02-23

    We describe the necessary design criteria to create highly efficient energy transfer conjugates containing luciferase enzymes derived from Photinus pyralis (Ppy) and semiconductor quantum rods (QRs) with rod-in-rod (r/r) microstructure. By fine-tuning the synthetic conditions, CdSe/CdS r/r-QRs were prepared with two different emission colors and three different aspect ratios (l/w) each. These were hybridized with blue, green, and red emitting Ppy, leading to a number of new BRET nanoconjugates. Measurements of the emission BRET ratio (BR) indicate that the resulting energy transfer is highly dependent on QR energy accepting properties, which include absorption, quantum yield, and optical anisotropy, as well as its morphological and topological properties, such as aspect ratio and defect concentration. The highest BR was found using r/r-QRs with lower l/w that were conjugated with red Ppy, which may be activating one of the anisotropic CdSe core energy levels. The role QR surface defects play on Ppy binding, and energy transfer was studied by growth of gold nanoparticles at the defects, which indicated that each QR set has different sites. The Ppy binding at those sites is suggested by the observed BRET red-shift as a function of Ppy-to-QR loading (L), where the lowest L results in highest efficiency and furthest shift. PMID:26760436

  11. Study of energy transfer in table-top X-pinch driven by a water line

    NASA Astrophysics Data System (ADS)

    Beg, F. N.; Zhang, T.; Fedin, D.; Beagen, B.; Chua, E.; Lee, J. Y.; Rawat, R. S.; Lee, P.

    2007-08-01

    The current passing through X-pinches and the energy transferring from the pulse forming line to the load are modelled using a simple LCR circuit. A comparison of the electrical properties of two table-top X-pinch devices is made. It was found that up to 25% of the stored energy is transferred from the water transmission line to the load in the University of California,San Diego (UCSD) table-top X-pinch before x-ray emission starts. The highest energy transmitted (75%) is found after the current peak. In comparison, only 3% of the energy is transferred to the load in the National Institute of Education (NIE) X-pinch device just after the maximum current peak. The highest energy (25%) transmitted to the plasma occurs long after the current peak. The plasma in both devices is visually and qualitatively similar. However, the UCSD device emits intense x-rays with no x-rays observed in the NIE device. This observation is consistent with the electrical circuit analysis.

  12. Carotenoid-bacteriochlorophyll energy transfer in LH2 complexes studied with 10-fs time resolution.

    PubMed

    Polli, Dario; Cerullo, Giulio; Lanzani, Guglielmo; De Silvestri, Sandro; Hashimoto, Hideki; Cogdell, Richard J

    2006-04-01

    In this report, we present a study of carotenoid-bacteriochlorophyll energy transfer processes in two peripheral light-harvesting complexes (known as LH2) from purple bacteria. We use transient absorption spectroscopy with approximately 10 fs temporal resolution, which is necessary to observe the very fast energy relaxation processes. By comparing excited-state dynamics of the carotenoids in organic solvents and inside the LH2 complexes, it has been possible to directly evaluate their energy transfer efficiency to the bacteriochlorophylls. In the case of okenone in the LH2 complex from Chromatium purpuratum, we obtained an energy transfer efficiency of etaET2=63+/-2.5% from the optically active excited state (S2) and etaET1=61+/-2% from the optically dark state (S1); for rhodopin glucoside contained in the LH2 complex from Rhodopseudomonas acidophila these values become etaET2=49.5+/-3.5% and etaET1=5.1+/-1%. The measurements also enabled us to observe vibrational energy relaxation in the carotenoids' S1 state and real-time collective vibrational coherence initiated by the ultrashort pump pulses. Our results are important for understanding the dynamics of early events of photosynthesis and relating it to the structural arrangement of the chromophores.

  13. On the nature of intramolecular vibrational energy transfer in dense molecular environments

    NASA Astrophysics Data System (ADS)

    von Benten, Rebekka S.; Abel, Bernd

    2010-12-01

    Transient femtosecond-IR-pump-UV-absorption probe-spectroscopy has been employed to shed light on the nature of intramolecular vibrational energy transfer (IVR) in dense molecular environments ranging from the diluted gas phase to the liquid. A general feature in our experiments and those of others is that IVR proceeds via multiple timescales if overtones or combination vibrations of high frequency modes are excited. It has been found that collisions enhance IVR if its (slower) timescales can compete with collisions. This enhancement is, however, much more weaker and rather inefficient as opposed to the effect of collisions on intermolecular energy transfer which is well known. In a series of experiments we found that IVR depends not significantly on the average energy transferred in a collision but rather on the number of collisions. The collisions are much less efficient in affecting IVR than VET. We conclude that collision induced broadening of vibrational energy levels reduces the energy gaps and enhances existing couplings between tiers. The present results are an important step forward to rationalize and understand apparently different and not consistent results from different groups on different molecular systems between gas and liquid phases.

  14. Electron, Hole, Singlet, and Triplet Energy Transfer in Photoexcited Porphyrin-Naphthalenediimide Dyads.

    PubMed

    Yushchenko, Oleksandr; Hangarge, Rahul V; Mosquera-Vazquez, Sandra; Boshale, Sheshanath V; Vauthey, Eric

    2015-06-18

    The excited-state dynamics of two molecular dyads, consisting of zinc (1) and free-base (2) porphyrin connected via a peptide linker to a core-substituted naphthalenediimide (NDI) have been investigated using optical spectroscopy. These dyads exhibit rich photophysics because of the large number of electronic excited states below 3 eV. In the case of 1 in apolar solvents, excitation energy transfer from the vibrationally hot singlet excited porphyrin to the NDI takes place with a 500 fs time constant. Electronic energy ends up in the NDI-localized triplet state, which decays to the ground state on a microsecond timescale. In polar solvents, ground-state recovery is faster by 5 orders of magnitude because of the occurrence of charge separation followed by recombination. On the other hand, excitation energy transfer in 2 takes place in the opposite direction, namely from the NDI to the porphyrin, which then undergoes intersystem crossing to the triplet state, followed by triplet energy transfer back to the NDI. Therefore, four distinct local electronic excited states are consecutively populated after excitation of the NDI unit of 2, with the energy shuttling between the two ends of the dyad. PMID:25418961

  15. Charge and energy transferred from a plasma jet to liquid and dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Mussard, M. Dang Van Sung; Foucher, E.; Rousseau, A.

    2015-10-01

    A key parameter in using plasma jets for biomedical applications is the transferred energy to the living tissues. The objective of this paper is to understand which parameters control the energy transfer from the plasma jet to a liquid or a dielectric surface. The plasma jet is flown with helium and ignited by a 600 Hz ac high voltage (up to 15 kV). Capacitors are connected to two measurement electrodes placed in the plasma source region, and under the sample. Charge and energy transferred are estimated by plotting Lissajous cycles; the number of bullets and the charge probability density function are also calculated. It is shown that the applied voltage and the gap (distance between the end of the tube and the sample) have a dramatic influence on the energy deposition on the sample as well as on the charge probability density function. Surprisingly, both gap distance and voltage have very little influence on the number of bullets reaching the sample per cycle. It is also shown that the conductivity of the liquid sample has almost no influence on the energy deposition and charge probability density function.

  16. Optical and Electrical Measurement of Energy Transfer between Nanocrystalline Quantum Dots and Photosystem I

    SciTech Connect

    Jung, Hyeson; Gulis, G.; Gupta, S.; Redding, K.; Gosztola, D. J.; Wiederrecht, Gary P; Stroscio, M. A.; Dutta, M.

    2010-08-31

    In the natural photosynthesis process, light harvesting complexes (LHCs) absorb light and pass excitation energy to photosystem I (PSI) and photosystem II (PSII). In this study, we have used nanocrystalline quantum dots (NQDs) as an artificial LHC by integrating them with PSI to extend their spectral range. We have performed photoluminescence (PL) and ultrafast time-resolved absorption measurements to investigate this process. Our PL experiments showed that emission from the NQDs is quenched, and the fluorescence from PSI is enhanced. Transient absorption and bleaching results can be explained by fluorescence resonance energy transfer (FRET) from the NQDs to the PSI. This nonradiative energy transfer occurs in ~6 ps. Current-voltage (I-V) measurements on the composite NQD-PSI samples demonstrate a clear photoresponse.

  17. Energy transfer from PO excited states to alkali metal atoms in the phosphorus chemiluminescence flame

    PubMed Central

    Khan, Ahsan U.

    1980-01-01

    Phosphorus chemiluminescence under ambient conditions of a phosphorus oxidation flame is found to offer an efficient electronic energy transferring system to alkali metal atoms. The lowest resonance lines, 2P3 / 2,½→2S½, of potassium and sodium are excited by energy transfer when an argon stream at 80°C carrying potassium or sodium atoms intersects a phosphorus vapor stream, either at the flame or in the postflame region. The lowest electronically excited metastable 4IIi state of PO or the (PO[unk]PO)* excimer is considered to be the probable energy donor. The (PO[unk]PO)* excimer results from the interaction of the 4IIi state of one PO molecule with the ground 2IIr state of another. Metastability of the donor state is strongly indicated by the observation of intense sensitized alkali atom fluorescence in the postflame region. PMID:16592925

  18. Giant frequency-selective near-field energy transfer in active-passive structures

    NASA Astrophysics Data System (ADS)

    Khandekar, Chinmay; Jin, Weiliang; Miller, Owen D.; Pick, Adi; Rodriguez, Alejandro W.

    2016-09-01

    We apply a fluctuation electrodynamics framework in combination with semianalytical (dipolar) approximations to study amplified spontaneous energy transfer (ASET) between active and passive bodies. We consider near-field energy transfer between semi-infinite planar media and spherical structures (dimers and lattices) subject to gain, and show that the combination of loss compensation and near-field enhancement (achieved by the proximity, enhanced interactions, and tuning of subwavelength resonances) in these structures can result in orders of magnitude ASET enhancements below the lasing threshold. We examine various possible geometric configurations, including realistic materials, and describe optimal conditions for enhancing ASET, showing that the latter depends sensitively on both geometry and gain, enabling efficient and tunable gain-assisted energy extraction from structured surfaces.

  19. Advection and the Efficiency of Spectral Energy Transfer in Two-Dimensional Turbulence.

    PubMed

    Fang, Lei; Ouellette, Nicholas T

    2016-09-01

    We report measurements of the geometric alignment of the small-scale turbulent stress and the large-scale rate of strain that together lead to the net flux of energy from small scales to large scales in two-dimensional turbulence. We find that the instantaneous alignment between these two tensors is weak and, thus, that the spectral transport of energy is inefficient. We show, however, that the strain rate is much better aligned with the stress at times in the past, suggesting that the differential advection of the two is responsible for the inefficient spectral transfer. We provide evidence for this conjecture by measuring the alignment statistics conditioned on weakly changing stress history. Our results give new insight into the relationship between scale-to-scale energy transfer, geometric alignment, and advection in turbulent flows.

  20. Optical and electrical measurement of energy transfer between nanocrystalline quantum dots and photosystem I.

    PubMed

    Jung, Hyeson; Gulis, Galina; Gupta, Subhadra; Redding, Kevin; Gosztola, David J; Wiederrecht, Gary P; Stroscio, Michael A; Dutta, Mitra

    2010-11-18

    In the natural photosynthesis process, light harvesting complexes (LHCs) absorb light and pass excitation energy to photosystem I (PSI) and photosystem II (PSII). In this study, we have used nanocrystalline quantum dots (NQDs) as an artificial LHC by integrating them with PSI to extend their spectral range. We have performed photoluminescence (PL) and ultrafast time-resolved absorption measurements to investigate this process. Our PL experiments showed that emission from the NQDs is quenched, and the fluorescence from PSI is enhanced. Transient absorption and bleaching results can be explained by fluorescence resonance energy transfer (FRET) from the NQDs to the PSI. This nonradiative energy transfer occurs in ∼6 ps. Current-voltage (I-V) measurements on the composite NQD-PSI samples demonstrate a clear photoresponse.

  1. Advection and the Efficiency of Spectral Energy Transfer in Two-Dimensional Turbulence

    NASA Astrophysics Data System (ADS)

    Fang, Lei; Ouellette, Nicholas T.

    2016-09-01

    We report measurements of the geometric alignment of the small-scale turbulent stress and the large-scale rate of strain that together lead to the net flux of energy from small scales to large scales in two-dimensional turbulence. We find that the instantaneous alignment between these two tensors is weak and, thus, that the spectral transport of energy is inefficient. We show, however, that the strain rate is much better aligned with the stress at times in the past, suggesting that the differential advection of the two is responsible for the inefficient spectral transfer. We provide evidence for this conjecture by measuring the alignment statistics conditioned on weakly changing stress history. Our results give new insight into the relationship between scale-to-scale energy transfer, geometric alignment, and advection in turbulent flows.

  2. Advection and the Efficiency of Spectral Energy Transfer in Two-Dimensional Turbulence.

    PubMed

    Fang, Lei; Ouellette, Nicholas T

    2016-09-01

    We report measurements of the geometric alignment of the small-scale turbulent stress and the large-scale rate of strain that together lead to the net flux of energy from small scales to large scales in two-dimensional turbulence. We find that the instantaneous alignment between these two tensors is weak and, thus, that the spectral transport of energy is inefficient. We show, however, that the strain rate is much better aligned with the stress at times in the past, suggesting that the differential advection of the two is responsible for the inefficient spectral transfer. We provide evidence for this conjecture by measuring the alignment statistics conditioned on weakly changing stress history. Our results give new insight into the relationship between scale-to-scale energy transfer, geometric alignment, and advection in turbulent flows. PMID:27636478

  3. Nano-ranged low-energy ion-beam-induced DNA transfer in biological cells

    NASA Astrophysics Data System (ADS)

    Yu, L. D.; Wongkham, W.; Prakrajang, K.; Sangwijit, K.; Inthanon, K.; Thongkumkoon, P.; Wanichapichart, P.; Anuntalabhochai, S.

    2013-06-01

    Low-energy ion beams at a few tens of keV were demonstrated to be able to induce exogenous macromolecules to transfer into plant and bacterial cells. In the process, the ion beam with well controlled energy and fluence bombarded living cells to cause certain degree damage in the cell envelope in nanoscales to facilitate the macromolecules such as DNA to pass through the cell envelope and enter the cell. Consequently, the technique was applied for manipulating positive improvements in the biological species. This physical DNA transfer method was highly efficient and had less risk of side-effects compared with chemical and biological methods. For better understanding of mechanisms involved in the process, a systematic study on the mechanisms was carried out. Applications of the technique were also expanded from DNA transfer in plant and bacterial cells to DNA transfection in human cancer cells potentially for the stem cell therapy purpose. Low-energy nitrogen and argon ion beams that were applied in our experiments had ranges of 100 nm or less in the cell envelope membrane which was majorly composed of polymeric cellulose. The ion beam bombardment caused chain-scission dominant damage in the polymer and electrical property changes such as increase in the impedance in the envelope membrane. These nano-modifications of the cell envelope eventually enhanced the permeability of the envelope membrane to favor the DNA transfer. The paper reports details of our research in this direction.

  4. Synergistic "ping-pong" energy transfer for efficient light activation in a chromophore-catalyst dyad.

    PubMed

    Quaranta, Annamaria; Charalambidis, Georgios; Herrero, Christian; Margiola, Sofia; Leibl, Winfried; Coutsolelos, Athanassios; Aukauloo, Ally

    2015-10-01

    The synthesis of a porphyrin-Ru(II) polypyridine complex where the porphyrin acts as a photoactive unit and the Ru(II) polypyridine as a catalytic precursor is described. Comparatively, the free base porphyrin was found to outperform the ruthenium based chromophore in the yield of light induced electron transfer. Mechanistic insights indicate the occurrence of a ping-pong energy transfer from the (1)LC excited state of the porphyrin chromophore to the (3)MCLT state of the catalyst and back to the (3)LC excited state of the porphyrin unit. The latter, triplet-triplet energy transfer back to the chromophore, efficiently competes with fast radiationless deactivation of the excited state at the catalyst site. The energy thus recovered by the chromophore allows improved yield of formation of the oxidized form of the chromophore and concomitantly of the oxidation of the catalytic unit by intramolecular charge transfer. The presented results are among the rare examples where a porphyrin chromophore is successfully used to drive an oxidative activation process where reductive processes prevail in the literature.

  5. A Wireless Magnetic Resonance Energy Transfer System for Micro Implantable Medical Sensors

    PubMed Central

    Li, Xiuhan; Zhang, Hanru; Peng, Fei; Li, Yang; Yang, Tianyang; Wang, Bo; Fang, Dongming

    2012-01-01

    Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm3. PMID:23112600

  6. Transfer of the Excitation Energy in Anacystis nidulans Grown to Obtain Different Pigment Ratios

    PubMed Central

    Ghosh, A. K.; Govindjee

    1966-01-01

    The blue-green alga, Anacystis nidulans, was grown in lights of different colors and intensities, and its absorption and fluorescence properties were studied. Strong orange light, absorbed mainly by phycocyanin, causes reduction in the ratio of phycocyanin to chlorophyll a; strong red light, absorbed mainly by chlorophyll, causes an increase in this ratio. This confirms the earlier findings of Brody and Emerson (12) on Porphyridum, and of Jones and Myers (8) on Anacystis. Anacystis cultures grown in light of low intensity show, upon excitation of phycocyanin, emission peaks at 600 mμ and 680 mμ, due to the fluorescence of phycocyanin and chlorophyll a, respectively. Changes in the efficiency of energy transfer from phycocyanin to chlorophyll a are revealed by changes in the ratios of these two bands. A decrease in efficiency of energy transfer from phycocyanin to chlorophyll a seems to occur whenever the ratio of chlorophyll a to phycocyanin deviates from the normal. Algae grown in light of high intensity show, upon excitation of phycocyanin, only a fluorescence band at 660 mμ and no band at 680 mμ. This suggests reduced efficiency of energy transfer from phycocyanin to the strongly fluorescent form of chlorophyll a (chlorophyll a2) and perhaps increased transfer to the weakly fluorescent form of chlorophyll a (chlorophyll a1). PMID:5970565

  7. Directed energy transfer in films of CdSe quantum dots: beyond the point dipole approximation.

    PubMed

    Zheng, Kaibo; Žídek, Karel; Abdellah, Mohamed; Zhu, Nan; Chábera, Pavel; Lenngren, Nils; Chi, Qijin; Pullerits, Tõnu

    2014-04-30

    Understanding of Förster resonance energy transfer (FRET) in thin films composed of quantum dots (QDs) is of fundamental and technological significance in optimal design of QD based optoelectronic devices. The separation between QDs in the densely packed films is usually smaller than the size of QDs, so that the simple point-dipole approximation, widely used in the conventional approach, can no longer offer quantitative description of the FRET dynamics in such systems. Here, we report the investigations of the FRET dynamics in densely packed films composed of multisized CdSe QDs using ultrafast transient absorption spectroscopy and theoretical modeling. Pairwise interdot transfer time was determined in the range of 1.5 to 2 ns by spectral analyses which enable separation of the FRET contribution from intrinsic exciton decay. A rational model is suggested by taking into account the distribution of the electronic transition densities in the dots and using the film morphology revealed by AFM images. The FRET dynamics predicted by the model are in good quantitative agreement with experimental observations without adjustable parameters. Finally, we use our theoretical model to calculate dynamics of directed energy transfer in ordered multilayer QD films, which we also observe experimentally. The Monte Carlo simulations reveal that three ideal QD monolayers can provide exciton funneling efficiency above 80% from the most distant layer. Thereby, utilization of directed energy transfer can significantly improve light harvesting efficiency of QD devices.

  8. Energy-transfer pumping of semiconductor nanocrystals using an epitaxial quantum well

    NASA Astrophysics Data System (ADS)

    Achermann, Marc; Petruska, Melissa A.; Kos, Simon; Smith, Darryl L.; Koleske, Daniel D.; Klimov, Victor I.

    2004-06-01

    As a result of quantum-confinement effects, the emission colour of semiconductor nanocrystals can be modified dramatically by simply changing their size. Such spectral tunability, together with large photoluminescence quantum yields and high photostability, make nanocrystals attractive for use in a variety of light-emitting technologies-for example, displays, fluorescence tagging, solid-state lighting and lasers. An important limitation for such applications, however, is the difficulty of achieving electrical pumping, largely due to the presence of an insulating organic capping layer on the nanocrystals. Here, we describe an approach for indirect injection of electron-hole pairs (the electron-hole radiative recombination gives rise to light emission) into nanocrystals by non-contact, non-radiative energy transfer from a proximal quantum well that can in principle be pumped either electrically or optically. Our theoretical and experimental results indicate that this transfer is fast enough to compete with electron-hole recombination in the quantum well, and results in greater than 50 per cent energy-transfer efficiencies in the tested structures. Furthermore, the measured energy-transfer rates are sufficiently large to provide pumping in the stimulated emission regime, indicating the feasibility of nanocrystal-based optical amplifiers and lasers based on this approach.

  9. Energy transfer from a dye donor to enhance the luminescence of silicon quantum dots.

    PubMed

    Erogbogbo, Folarin; Chang, Ching-Wen; May, Jasmine; Prasad, Paras N; Swihart, Mark T

    2012-08-21

    Quantum dots are known for their superior optical properties; however, when transferred into aqueous media, their luminescent properties are frequently compromised. When encapsulated in micelles for bioimaging applications, luminescent silicon quantum dots can lose as much as 50% of their luminescence depending on the formulation used. Here, we create an energy transfer micelle platform that combines silicon quantum dots with an anthracene-based dye in the hydrophobic core of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG) micelles. These phospholipid micelles are water dispersible, stable, and surrounded by a PEGylated layer with modifiable functional groups. The spectroscopic properties of energy transfer between the anthracene donors and silicon quantum dot acceptors were analyzed based on the observed dependence of the steady-state emission spectrum on concentration ratio, excitation wavelength, pH, and temperature. The luminescence of silicon quantum dots from the core of a 150 nm micelle is enhanced by more than 80% when the anthracene dye is added. This work provides a simple yet readily applicable solution to the long-standing problem of luminescence enhancement of silicon quantum dots and can serve as a template for improving the quantum dot emission yield for biological applications where luminescence signal enhancements are desirable and for solar applications where energy transfer plays a critical role in device performance.

  10. Local Orientational Order in Liquids Revealed by Resonant Vibrational Energy Transfer

    NASA Astrophysics Data System (ADS)

    Panman, M. R.; Shaw, D. J.; Ensing, B.; Woutersen, S.

    2014-11-01

    We demonstrate that local orientational ordering in a liquid can be observed in the decay of the vibrational anisotropy caused by resonant transfer of vibrational excitations between its constituent molecules. We show that the functional form of this decay is determined by the (distribution of) angles between the vibrating bonds of the molecules between which energy transfer occurs, and that the initial drop in the decay reflects the average angle between nearest neighbors. We use this effect to observe the difference in local orientational ordering in the two hydrogen-bonded liquids ethanol and N -methylacetamide.

  11. Nuclear fragmentation energy and momentum transfer distributions in relativistic heavy-ion collisions

    NASA Technical Reports Server (NTRS)

    Khandelwal, Govind S.; Khan, Ferdous

    1989-01-01

    An optical model description of energy and momentum transfer in relativistic heavy-ion collisions, based upon composite particle multiple scattering theory, is presented. Transverse and longitudinal momentum transfers to the projectile are shown to arise from the real and absorptive part of the optical potential, respectively. Comparisons of fragment momentum distribution observables with experiments are made and trends outlined based on our knowledge of the underlying nucleon-nucleon interaction. Corrections to the above calculations are discussed. Finally, use of the model as a tool for estimating collision impact parameters is indicated.

  12. Transferring Gus gene into intact rice cells by low energy ion beam

    NASA Astrophysics Data System (ADS)

    Zengliang, Yu; Jianbo, Yang; Yuejin, Wu; Beijiu, Cheng; Jianjun, He; Yuping, Huo

    1993-06-01

    A new technique of transferring genes by low energy ion beam has been reported in this paper. The Gus and CAT (chloramphenicol acetyltransferase) genes, as "foreign" genetic materials, were introduced into the suspension cells and ripe embryos or rice by implantation of 20-30 keV Ar + at doses ranging from 1 × 10 15 to 4 × 10 15 ions/cm 2. The activities of CAT and Gus were detected in the cells and embryos after several weeks. The results indicate that the transfer was a success.

  13. On the energy transfer between the electromagnetic field and nanomachines for biological applications.

    PubMed

    Bellizzi, G; Bucci, O M; Capozzoli, A

    2008-07-01

    The article presents a simple expression of the power transferred from the electromagnetic field (EMF) to a biological nanomachine (NM) embedded in a background medium (BM). The expression is useful to analyse the interaction mechanism and test the hypothesis on its nature. Furthermore, it should represent a helpful tool to design remotely controlled NMs for bio-medical applications and the relative electromagnetic control apparatuses. Finally, to show its practical usefulness, we used it to discuss the hypothesis on the energy transfer mechanism proposed in the literature to explain intriguing experimental phenomena referring to the remotely controlled dehybridization of DNA molecules attached to gold nanocrystals.

  14. Correlation between the Open-Circuit Voltage and Charge Transfer State Energy in Organic Photovoltaic Cells.

    PubMed

    Zou, Yunlong; Holmes, Russell J

    2015-08-26

    In order to further improve the performance of organic photovoltaic cells (OPVs), it is essential to better understand the factors that limit the open-circuit voltage (VOC). Previous work has sought to correlate the value of VOC in donor-acceptor (D-A) OPVs to the interface energy level offset (EDA). In this work, measurements of electroluminescence are used to extract the charge transfer (CT) state energy for multiple small molecule D-A pairings. The CT state as measured from electroluminescence is found to show better correlation to the maximum VOC than EDA. The difference between EDA and the CT state energy is attributed to the Coulombic binding energy of the CT state. This correlation is demonstrated explicitly by inserting an insulating spacer layer between the donor and acceptor materials, reducing the binding energy of the CT state and increasing the measured VOC. These results demonstrate a direct correlation between maximum VOC and CT state energy.

  15. Numerical Study of the Generation of Linear Energy Transfer Spectra for Space Radiation Applications

    NASA Technical Reports Server (NTRS)

    Badavi, Francis F.; Wilson, John W.; Hunter, Abigail

    2005-01-01

    In analyzing charged particle spectra in space due to galactic cosmic rays (GCR) and solar particle events (SPE), the conversion of particle energy spectra into linear energy transfer (LET) distributions is a convenient guide in assessing biologically significant components of these spectra. The mapping of LET to energy is triple valued and can be defined only on open energy subintervals where the derivative of LET with respect to energy is not zero. Presented here is a well-defined numerical procedure which allows for the generation of LET spectra on the open energy subintervals that are integrable in spite of their singular nature. The efficiency and accuracy of the numerical procedures is demonstrated by providing examples of computed differential and integral LET spectra and their equilibrium components for historically large SPEs and 1977 solar minimum GCR environments. Due to the biological significance of tissue, all simulations are done with tissue as the target material.

  16. Quantum efficiency of energy transfers in non-uniformly doped crystals of Er, Yb: LiNbO3

    NASA Astrophysics Data System (ADS)

    Nalbantov, N. N.; Stroganova, E. V.; Galutskiy, V. V.

    2016-08-01

    Spatial and temporal distribution of quantum efficiency of energy transfers in crystals of lithium niobate with non-uniform concentration profiles of Er3+ and Yb3+ ions has been studied for the cases of Yb3+-Er3+ Foerster transfer and radiative decay of upper energy levels of erbium ions (green and red luminescence).

  17. Novel multistep BRET-FRET energy transfer using nanoconjugates of firefly proteins, quantum dots, and red fluorescent proteins.

    PubMed

    Alam, Rabeka; Zylstra, Joshua; Fontaine, Danielle M; Branchini, Bruce R; Maye, Mathew M

    2013-06-21

    Sequential bioluminescence resonance energy transfer (BRET) and fluorescence resonance energy transfer (FRET) from firefly luciferase to red fluorescent proteins using quantum dot or rod acceptor/donor linkers is described. The effect of morphology and tuned optical properties on the efficiency of this unique BRET-FRET system was evaluated.

  18. Probing energy transfer events in the light harvesting complex 2 (LH2) of Rhodobacter sphaeroides with two-dimensional spectroscopy.

    PubMed

    Fidler, Andrew F; Singh, Ved P; Long, Phillip D; Dahlberg, Peter D; Engel, Gregory S

    2013-10-21

    Excitation energy transfer events in the photosynthetic light harvesting complex 2 (LH2) of Rhodobacter sphaeroides are investigated with polarization controlled two-dimensional electronic spectroscopy. A spectrally broadened pulse allows simultaneous measurement of the energy transfer within and between the two absorption bands at 800 nm and 850 nm. The phased all-parallel polarization two-dimensional spectra resolve the initial events of energy transfer by separating the intra-band and inter-band relaxation processes across the two-dimensional map. The internal dynamics of the 800 nm region of the spectra are resolved as a cross peak that grows in on an ultrafast time scale, reflecting energy transfer between higher lying excitations of the B850 chromophores into the B800 states. We utilize a polarization sequence designed to highlight the initial excited state dynamics which uncovers an ultrafast transfer component between the two bands that was not observed in the all-parallel polarization data. We attribute the ultrafast transfer component to energy transfer from higher energy exciton states to lower energy states of the strongly coupled B850 chromophores. Connecting the spectroscopic signature to the molecular structure, we reveal multiple relaxation pathways including a cyclic transfer of energy between the two rings of the complex.

  19. Energy transfer between fusion biliproteins co-expressed with phycobiliprotein in Escherichia coli.

    PubMed

    Ma, Qiong; Zhou, Nan; Zhou, Ming

    2016-10-01

    In cyanobacteria, phycobiliproteins (PBS) show excellent energy transfer among the chromophores absorbing over most of the visible. The energy transfers are used to study phycobilisome assembly and bioimaging. Using All4261GAF2(C81L) as energy donor, ApcE(1-240/Δ87-130) as energy acceptor, we co-expressed fusion protein ApcE(1-240/Δ87-130)::All4261GAF2(C81L) with phycobiliprotein in Escherichia Coli and studied the energy transfer between two protein domains. With N-terminal His6 tag, ApcE(1-240/Δ87-130)::All4261GAF2(C81L) cannot be purified by nickel-affinity column. We added six histidines in the C-terminal of ApcE(1-240/Δ87-130)::All4261GAF2(C81L) and co-expressed it with phycobiliprotein. ApcE(1-240/Δ87-130)::PCB-All4261GAF2(C81L)His6 was purified successfully and only singly chromophorylated at All4261GAF2(C81L)His6 domain. The singly chromophorylate ApcE(1-240/Δ87-130)::PCB-All4261GAF2(C81L)His6 was incubated with fresh PCB and the doubly chromophorylated PCB-ApcE(1-240/Δ87-130)::PCB-All4261GAF2(C81L)His6 was obtained. The double chromophored fusion protein absorbed light in the range of 615-660 nm, and fluoresced only at 668 nm. Photochemistry analysis showed that excitation energy transfer from the short-wavelength absorbing at All4261GAF2(C81L) domain was achieved successfully to the long-wavelength absorbing at the ApcE(1-240/Δ87-130) domain.

  20. Nonphotochemical Hole-Burning Studies of Energy Transfer Dynamics in Antenna Complexes of Photosynthetic Bacteria

    SciTech Connect

    Satoshi Matsuzaki

    2002-06-27

    This thesis contains the candidate's original work on excitonic structure and energy transfer dynamics of two bacterial antenna complexes as studied using spectral hole-burning spectroscopy. The general introduction is divided into two chapters (1 and 2). Chapter 1 provides background material on photosynthesis and bacterial antenna complexes with emphasis on the two bacterial antenna systems related to the thesis research. Chapter 2 reviews the underlying principles and mechanism of persistent nonphotochemical hole-burning (NPHB) spectroscopy. Relevant energy transfer theories are also discussed. Chapters 3 and 4 are papers by the candidate that have been published. Chapter 3 describes the application of NPHB spectroscopy to the Fenna-Matthews-Olson (FMO) complex from the green sulfur bacterium Prosthecochloris aestuarii; emphasis is on determination of the low energy vibrational structure that is important for understanding the energy transfer process associated within three lowest energy Q{sub y}-states of the complex. The results are compared with those obtained earlier on the FMO complex from Chlorobium tepidum. In Chapter 4, the energy transfer dynamics of the B800 molecules of intact LH2 and B800-deficient LH2 complexes of the purple bacterium Rhodopseudomonas acidophila are compared. New insights on the additional decay channel of the B800 ring of bacteriochlorophyll{sub a} (BChl{sub a}) molecules are provided. General conclusions are given in Chapter 5. A version of the hole spectrum simulation program written by the candidate for the FMO complex study (Chapter 3) is included as an appendix. The references for each chapter are given at the end of each chapter.