Non-fullerene electron acceptors for organic photovoltaic devices

Energy Technology Data Exchange (ETDEWEB)

Jenekhe, Samson A.; Li, Haiyan; Earmme, Taeshik; Ren, Guoqiang

2017-11-07

Non-fullerene electron acceptors for highly efficient organic photovoltaic devices are described. The non-fullerene electron acceptors have an extended, rigid, .pi.-conjugated electron-deficient framework that can facilitate exciton and charge derealization. The non-fullerene electron acceptors can physically mix with a donor polymer and facilitate improved electron transport. The non-fullerene electron acceptors can be incorporated into organic electronic devices, such as photovoltaic cells.

Impact of Nonfullerene Acceptor Core Structure on the Photophysics and Efficiency of Polymer Solar Cells

KAUST Repository

Alamoudi, Maha

2018-03-02

Small-molecule “nonfullerene” acceptors are promising alternatives to fullerene (PC61/71BM) derivatives often used in bulk heterojunction (BHJ) organic solar cells; yet, the efficiency-limiting processes and their dependence on the acceptor structure are not clearly understood. Here, we investigate the impact of the acceptor core structure (cyclopenta-[2,1-b:3,4-b′]dithiophene (CDT) versus indacenodithiophene (IDTT)) of malononitrile (BM)-terminated acceptors, namely CDTBM and IDTTBM, on the photophysical characteristics of BHJ solar cells. Using PCE10 as donor polymer, the IDTT-based acceptor achieves power conversion efficiencies (8.4%) that are higher than those of the CDT-based acceptor (5.6%) because of a concurrent increase in short-circuit current and open-circuit voltage. Using (ultra)fast transient spectroscopy we demonstrate that reduced geminate recombination in PCE10:IDTTBM blends is the reason for the difference in short-circuit currents. External quantum efficiency measurements indicate that the higher energy of interfacial charge-transfer states observed for the IDTT-based acceptor blends is the origin of the higher open-circuit voltage.

Impact of Nonfullerene Acceptor Core Structure on the Photophysics and Efficiency of Polymer Solar Cells

KAUST Repository

Alamoudi, Maha; Khan, Jafar Iqbal; Firdaus, Yuliar; Wang, Kai; Andrienko, Denis; Beaujuge, Pierre; Laquai, Fré dé ric

2018-01-01

Small-molecule “nonfullerene” acceptors are promising alternatives to fullerene (PC61/71BM) derivatives often used in bulk heterojunction (BHJ) organic solar cells; yet, the efficiency-limiting processes and their dependence on the acceptor structure are not clearly understood. Here, we investigate the impact of the acceptor core structure (cyclopenta-[2,1-b:3,4-b′]dithiophene (CDT) versus indacenodithiophene (IDTT)) of malononitrile (BM)-terminated acceptors, namely CDTBM and IDTTBM, on the photophysical characteristics of BHJ solar cells. Using PCE10 as donor polymer, the IDTT-based acceptor achieves power conversion efficiencies (8.4%) that are higher than those of the CDT-based acceptor (5.6%) because of a concurrent increase in short-circuit current and open-circuit voltage. Using (ultra)fast transient spectroscopy we demonstrate that reduced geminate recombination in PCE10:IDTTBM blends is the reason for the difference in short-circuit currents. External quantum efficiency measurements indicate that the higher energy of interfacial charge-transfer states observed for the IDTT-based acceptor blends is the origin of the higher open-circuit voltage.

Synthesis and optoelectronic characterization of some triphenylamine-based compounds containing strong acceptor substituents

Energy Technology Data Exchange (ETDEWEB)

Grigoras, Mircea, E-mail: grim@icmpp.ro; Ivan, Teofilia; Vacareanu, Loredana; Catargiu, Ana Maria; Tigoianu, Radu

2014-09-15

Three novel triphenylamine-based compounds containing strong electron acceptor groups have been synthesized and their comparative photophysical properties are presented. These compounds were obtained by a two-step method: (i) triphenylamine compounds with one, two and three phenylacetylene arms were synthesized by Sonogashira reaction between iodine-substituted triphenylamines and phenylacetylene, followed by (ii) post-modification of these electron-rich alkynes by addition of the strong electron acceptor, tetracyanoethylene. Characterization of all oligomers was made by FTIR, {sup 1}H-NMR, UV–vis and fluorescence spectroscopy. A batochromic shifting of the UV and photoluminescence maxima was observed with the increase of the acceptor group number. The electrochemical behavior was studied by cyclic voltammetry. The cyclic voltammograms have evidenced that triphenylamine-phenylacetylene compounds undergo only oxidation processes while compounds modified with tetracyanoethylene show both oxidation and reduction peaks associated with donor and acceptor groups, respectively. The donor–acceptor compounds coordinate metal ions (i.e., Hg{sup 2+} and Sn{sup 2+}) by cyano groups resulting in the decreasing of charge transfer band intensity, and they can be used as chemosensors. - Highlights: • Three triphenylamine-based ethynylene compounds were prepared by Sonogashira reaction. • Post-modification of ethynylene linkages by tetracyanethylene cycloaddition and retroconversion led to donor–acceptor compounds. • Photophysical properties of donor–acceptor oligomers were studied in different solvents.

Copernicus observations of Iota Herculis velocity variations

Science.gov (United States)

Rogerson, J. B., Jr.

1984-01-01

Observations of Iota Her at 109.61-109.67 nm obtained with the U1 channel of the Copernicus spectrophotometer at resolution 5 pm during 3.6 days in May, 1979, are reported. Radial-velocity variations are detected and analyzed as the sum of two sinusoids with frequencies 0.660 and 0.618 cycles/day and amplitudes 9.18 and 8.11 km/s, respectively. Weak evidence supporting the 13.9-h periodicity seen in line-profile variations by Smith (1978) is found.

Magnetometer-inferred, Equatorial, Daytime Vertical ExB Drift Velocities Observed in the African Longitude Sector

Science.gov (United States)

Anderson, D. N.; Yizengaw, E.

2011-12-01

A recent paper has investigated the sharp longitude gradients in the dayside ExB drift velocities associated with the 4-cell, non-migrating structures thought to be connected with the eastward propagating, diurnal, non-migrating (DE3) tides. Observations of vertical ExB drift velocities obtained from the Ion Velocity Meter (IVM) on the Communication/Navigation Outage Forecast System (C/NOFS) satellite were obtained in the Western Pacific, Eastern Pacific, Peruvian and Atlantic sectors for a few days during the months of October, March and December, 2009. Respective ExB drift velocity gradients at the cell boundaries for these 4 longitude sectors were a.) -1.3m/sec/degree, b.) 3m/sec/degree, c.) -4m/sec/degree and d.) 1m/sec/degree and were observed on a day-to-day basis. In this talk, we estimate the longitude gradients in the dayside, vertical ExB drift velocities from magnetometer H-component observations in the African sector. We briefly describe the technique for obtaining realistic ExB drift velocities associated with the difference in the H-component values between a magnetometer on the magnetic equator and one off the magnetic equator at 6 to 9 degrees dip latitude (delta H). We present magnetometer-inferred, dayside ExB drift velocities obtained from the AMBER (African Meridian B-field Education and Research) magnetometer chain in the East Africa (Ethiopian) longitude sector and the West African (Nigerian) longitude sector. We compare the longitude gradients in ExB drift velocities in the African sector with the C/NOFS- observed longitude gradients mentioned above. We also discuss the advantages of using ground-based magnetometer observations to infer ExB drift velocities compared with the C/NOFS satellite observations.

Acceptor thickness effect of exciplex and electroplex emission at heterojunction interface in organic light-emitting diodes

Science.gov (United States)

Zhang, Wei; Yu, Junsheng; Yuan, Kai; Jiang, Yadong; Zhang, Qing; Cao, Kangli

2010-10-01

Organic light-emitting diodes (OLEDs) consisted of a novel fluorene derivative of 5,6-bis(9,9-dihexyl-9H-fluoren-2-yl)- 2,3-diisocyano-2,3-dihydropyrazine (BDHFLCNPy) and a hole transporting material of N,N'-Di-[(1-naphthalenyl)- N,N'-diphenyl](1,1'-biphenyl)-4,4'-diamine (NPB) were fabricated, and electroluminescence (EL) spectrum of devices were investigated. It was found that light emission around 650 nm observed in devices came from exciplex generated at heterojunction interface by NPB molecules worked as electron donor and BDHFLCNPy molecules worked as electron acceptor. Moreover, a shoulder peak around 500 nm ascribed to BDHFLCNPy exciton was observed. To systemically study the effect of heterojunction structure in exciplex formation, OLEDs with different thickness of acceptor were fabricated. The results illustrated that a shoulder peak around 600 nm occurred in EL when acceptor thickness increases, and BDHFLCNPy exciton emitting strength is relatively altered. The emission band around 600 nm is due to electroplex. The L-V-J properties of OLEDs show that device with the thinnest acceptor layer has the highest luminance and current density. On the contrary, OLEDs with thicker acceptor layer have higher luminance efficiency. The different recombination mechanism of exciton, exciplex and electroplex in heterojunction were studied. Furthermore, the acceptor thickness effect of exciplex and electroplex generating mechanism and energy transferring mechanism between them was also discussed.

Drift velocities of 150-km Field-Aligned Irregularities observed by the Equatorial Atmosphere Radar

Directory of Open Access Journals (Sweden)

Yuichi Otsuka

2013-11-01

Full Text Available Between 130 and 170 km altitude in the daytime ionosphere, the so-called 150-km field-aligned irregularities (FAIs have been observed since the 1960s at equatorial regions with several very high frequency (VHF radars. We report statistical results of 150-km FAI drift velocities on a plane perpendicular to the geomagnetic field, acquired by analyzing the Doppler velocities of 150-km FAIs observed with the Equatorial Atmosphere Radar (EAR at Kototabang, Indonesia during the period from Aug. 2007 to Oct. 2009. We found that the southward/upward perpendicular drift velocity of the 150-km FAIs tends to decrease in the afternoon and that this feature is consistent with that of F-region plasma drift velocities over the magnetic equator. The zonal component of the 150-km FAI drift velocity is westward and decreases with time, whereas the F-region plasma drift velocity observed with the incoherent scatter radar at Jicamarca, Peru, which is westward, reaches a maximum at about noon. The southward/upward and zonal drift velocities of the 150-km FAIs are smaller than that of the F-region plasma drift velocity by approximately 3 m/s and 25 m/s, respectively, on average. The large difference between the 150-km FAI and F-region plasma drift velocities may not arise from a difference in the magnetic latitudes at which their electric fields are generated. Electric fields generated at the altitude at which the 150-km FAIs occur may not be negligible.

Alkyl Radicals as Hydrogen Bond Acceptors: Computational Evidence

DEFF Research Database (Denmark)

Hammerum, Steen

2009-01-01

Spectroscopic, energetic and structural information obtained by DFT and G3-type computational studies demonstrates that charged proton donors can form moderately strong hydrogen bonds to simple alkyl radicals. The presence of these bonds stabilizes the adducts and modifies their structure......, and gives rise to pronounced shifts of IR stretching frequencies and to increased absorption intensities. The hydrogen bond acceptor properties of alkyl radicals equal those of many conventional acceptors, e.g., the bond length changes and IR red-shifts suggest that tert-butyl radicals are slightly better...... acceptors than formaldehyde molecules, while propyl radicals are as good as H2O. The hydrogen bond strength appears to depend on the proton affinity of the proton donor and on the ionization energy of the acceptor alkyl radical, not on the donor-acceptor proton affinity difference, reflecting...

Newly velocity field of Sulawesi Island from GPS observation

Science.gov (United States)

Sarsito, D. A.; Susilo, Simons, W. J. F.; Abidin, H. Z.; Sapiie, B.; Triyoso, W.; Andreas, H.

2017-07-01

Sulawesi microplate Island is located at famous triple junction area of the Eurasian, India-Australian, and Philippine Sea plates. Under the influence of the northward moving Australian plate and the westward motion of the Philippine plate, the island at Eastern part of Indonesia is collide and with the Eurasian plate and Sunda Block. Those recent microplate tectonic motions can be quantitatively determine by GNSS-GPS measurement. We use combine GNSS-GPS observation types (campaign type and continuous type) from 1997 to 2015 to derive newly velocity field of the area. Several strategies are applied and tested to get the optimum result, and finally we choose regional strategy to reduce error propagation contribution from global multi baseline processing using GAMIT/GLOBK 10.5. Velocity field are analyzed in global reference frame ITRF 2008 and local reference frame by fixing with respect alternatively to Eurasian plate - Sunda block, India-Australian plate and Philippine Sea plates. Newly results show dense distribution of velocity field. This information is useful for tectonic deformation studying in geospatial era.

Shallow acceptors in Ge/GeSi heterostructures with quantum wells in magnetic field

International Nuclear Information System (INIS)

Aleshkin, V.Ya.; Antonov, A.V.; Veksler, D.B.; Gavrilenko, V.I.; Erofeeva, I.V.; Ikonnikov, A.V.; Kozlov, D.V.; Spirin, K.E.; Kuznetsov, O.A.

2005-01-01

One investigated both theoretically and experimentally into shallow acceptors in Ge/GeSi heterostructures with quantum wells (QW) in a magnetic field. It is shown that alongside with lines of cyclotron resonance in magnetoabsorption spectra one observes transitions from the ground state of acceptor to the excited ones associated with the Landau levels from the first and the second subbands of dimensional quantization, and resonance caused by ionization of A + -centres. To describe impurity transitions in Ge/GeSi heterostructures with QW in a magnetic field and to interpret the experiment results in detail one uses numerical method of calculation based on expansion of wave function of acceptor in terms of basis of wave functions of holes in QW in the absence of magnetic field [ru

Barbiturate End-Capped Non-Fullerene Acceptors for Organic Solar Cells: Tuning Acceptor Energetics to Suppress Geminate Recombination Losses

KAUST Repository

Tan, Ching-Hong

2018-01-10

We report the synthesis of two barbiturate end-capped non-fullerene acceptors and demonstrate their efficient function in high voltage output organic solar cells. The acceptor with the lower LUMO level is shown to exhibit suppressed geminate recombination losses, resulting in enhanced photocurrent generation and higher overall device efficiency.

Barbiturate End-Capped Non-Fullerene Acceptors for Organic Solar Cells: Tuning Acceptor Energetics to Suppress Geminate Recombination Losses

KAUST Repository

Tan, Ching-Hong; Gorman, Jeffrey; Wadsworth, Andrew; Holliday, Sarah; Subramaniyan, Selvam; Jenekhe, Samson A.; Baran, Derya; McCulloch, Iain; Durrant, James

2018-01-01

We report the synthesis of two barbiturate end-capped non-fullerene acceptors and demonstrate their efficient function in high voltage output organic solar cells. The acceptor with the lower LUMO level is shown to exhibit suppressed geminate recombination losses, resulting in enhanced photocurrent generation and higher overall device efficiency.

CUTLASS HF radar observations of high-velocity E-region echoes

Directory of Open Access Journals (Sweden)

M. V. Uspensky

Full Text Available A short event of high-velocity E-region echo observations by the Pykkvibaer HF radar is analysed to study echo parameters and the echo relation to the Farley-Buneman plasma instability. The echoes were detected in several beams aligned closely to the magnetic L-shell direction. Two echo groups were identified: one group corresponded to the classical type 1 echoes with velocities close to the nominal ion-acoustic speed of 400 ms^–1 , while the other group had significantly larger velocities, of the order of 700 ms^–1 . The mutual relationship between the echo power, Doppler velocity, spectral width and elevation angles for these two groups was studied. Plotting of echo parameters versus slant range showed that all ~700 ms^–1 echoes originated from larger heights and distances of 500–700 km, while all ~400 ms^–1 echoes came from lower heights and from farther distances; 700–1000 km. We argue that both observed groups of echoes occurred due to the Farley-Buneman plasma instability excited by strong ( ~70 mVm^–1 and uniformly distributed electric fields. We show that the echo velocities for the two groups were different because the echoes were received from different heights. Such a separation of echo heights occurred due to the differing amounts of ionospheric refraction at short and large ranges. Thus, the ionospheric refraction and related altitude modulation of ionospheric parameters are the most important factors to consider, when various characteristics of E-region decametre irregularities are derived from HF radar measurements.

Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; polar ionosphere

A Simple and Robust Sliding Mode Velocity Observer for Moving Coil Actuators in Digital Hydraulic Valves

DEFF Research Database (Denmark)

Nørgård, Christian; Schmidt, Lasse; Bech, Michael Møller

2016-01-01

This paper focuses on estimating the velocity and position of fast switching digital hydraulic valves actuated by electromagnetic moving coil actuators, based on measurements of the coil current and voltage. The velocity is estimated by a simple first-order sliding mode observer architecture...... and the position is estimated by integrating the estimated velocity. The binary operation of digi-valves enables limiting and resetting the position estimate since the moving member is switched between the mechanical end-stops of the valve. This enables accurate tracking since drifting effects due to measurement...... noise and integration of errors in the velocity estimate may be circumvented. The proposed observer architecture is presented along with stability proofs and initial experimental results. To reveal the optimal observer performance, an optimization of the observer parameters is carried out. Subsequently...

Intramolecular charge separation in spirobifluorene-based donor–acceptor compounds adsorbed on Au and indium tin oxide electrodes

International Nuclear Information System (INIS)

Heredia, Daniel; Otero, Luis; Gervaldo, Miguel; Fungo, Fernando; Dittrich, Thomas; Lin, Chih-Yen; Chi, Liang-Chen; Fang, Fu-Chuan; Wong, Ken-Tsung

2013-01-01

Surface photovoltage (SPV) measurements were performed with a Kelvin-probe in spirobifluorene-based donor (diphenylamine)–acceptor (dicyano or cyanoacrylic acid moieties) compounds adsorbed from highly diluted solutions onto Au and indium tin oxide electrode surfaces. Strong intramolecular charge separation (negative SPV signals up to more than 0.1 V) due to directed molecule adsorption was observed only for spirobifluorene donor–acceptor compounds with carboxylic acid moiety. SPV signals and onset energies of electronic transitions depended on ambience conditions. - Highlights: ► Fluorene donor–acceptor derivatives were adsorbed at Au and indium tin oxide. ► Surface photovoltage measurements were performed with a Kelvin-probe. ► Strong intra-molecular charge separation was observed. ► SPV signals depended on ambience conditions

Development of Polymer Acceptors for Organic Photovoltaic Cells

Directory of Open Access Journals (Sweden)

Yujeong Kim

2014-02-01

Full Text Available This review provides a current status report of the various n-type polymer acceptors for use as active materials in organic photovoltaic cells (OPVs. The polymer acceptors are divided into four categories. The first section of this review focuses on rylene diimide-based polymers, including perylene diimide, naphthalene diimide, and dithienocoronene diimide-based polymers. The high electron mobility and good stability of rylene diimides make them suitable for use as polymer acceptors in OPVs. The second section deals with fluorene and benzothiadiazole-based polymers such as poly(9,9’-dioctylfluorene-co-benzothiadiazole, and the ensuing section focuses on the cyano-substituted polymer acceptors. Cyano-poly(phenylenevinylene and poly(3-cyano-4-hexylthiophene have been used as acceptors in OPVs and exhibit high electron affinity arising from the electron-withdrawing cyano groups in the vinylene group of poly(phenylenevinylene or the thiophene ring of polythiophene. Lastly, a number of other electron-deficient groups such as thiazole, diketopyrrolopyrrole, and oxadiazole have also been introduced onto polymer backbones to induce n-type characteristics in the polymer. Since the first report on all-polymer solar cells in 1995, the best power conversion efficiency obtained with these devices to date has been 3.45%. The overall trend in the development of n-type polymer acceptors is presented in this review.

Offshore Rayleigh Group Velocity Observations of the South Island, New Zealand, from Ambient Noise Data

KAUST Repository

Yeck, William L.; Sheehan, Anne F.; Stachnik, Joshua C.; Lin, Fan-Chi

2017-01-01

We present azimuthally anisotropic Rayleigh group velocity models from 8 - 35 s both offshore and onshore of the South Island of New Zealand. We use MOANA (Marine Observations of Anisotropy Near Aotearoa) broadband ocean seismic data in combination with on land data from the New Zealand National Seismography Network (NZNSN) to investigate the seismic structure of the flanks of the Australian-Pacific plate boundary. At 8 s, we observe low offshore group velocities best explained by the influence of the water layer and thick water-laden sediments. At long periods (20-30 s), group velocities are lower on the South Island relative to its offshore flanks, due to thickened crust beneath the island, with the lowest velocities primarily beneath the Southern Alps. Group velocity azimuthal anisotropy fast directions near the Alpine Fault align with the direction of relative plate motion between the Australian and Pacific plates. In the southern portion of the island, fast directions rotate anticlockwise, likely in response to a decrease in dextral shearing away from the plate boundary. Azimuthal anisotropy fast directions align with absolute plate motion offshore on the Pacific plate. Based on the depth sensitivity of our observations, we suggest diffuse deformation occurs throughout the crust. Our observations match trends in previous Pn anisotropy and SKS shear wave splitting observations, and therefore suggest a consistent pattern of distributed deformation throughout the lithosphere.

Offshore Rayleigh Group Velocity Observations of the South Island, New Zealand, from Ambient Noise Data

KAUST Repository

Yeck, William L.

2017-02-15

We present azimuthally anisotropic Rayleigh group velocity models from 8 - 35 s both offshore and onshore of the South Island of New Zealand. We use MOANA (Marine Observations of Anisotropy Near Aotearoa) broadband ocean seismic data in combination with on land data from the New Zealand National Seismography Network (NZNSN) to investigate the seismic structure of the flanks of the Australian-Pacific plate boundary. At 8 s, we observe low offshore group velocities best explained by the influence of the water layer and thick water-laden sediments. At long periods (20-30 s), group velocities are lower on the South Island relative to its offshore flanks, due to thickened crust beneath the island, with the lowest velocities primarily beneath the Southern Alps. Group velocity azimuthal anisotropy fast directions near the Alpine Fault align with the direction of relative plate motion between the Australian and Pacific plates. In the southern portion of the island, fast directions rotate anticlockwise, likely in response to a decrease in dextral shearing away from the plate boundary. Azimuthal anisotropy fast directions align with absolute plate motion offshore on the Pacific plate. Based on the depth sensitivity of our observations, we suggest diffuse deformation occurs throughout the crust. Our observations match trends in previous Pn anisotropy and SKS shear wave splitting observations, and therefore suggest a consistent pattern of distributed deformation throughout the lithosphere.

Magnetic field effect on the Coulomb interaction of acceptors in semimagnetic quantum dot

Energy Technology Data Exchange (ETDEWEB)

Kalpana, P.; Merwyn, A.; Nithiananthi, P.; Jayakumar, K., E-mail: kjkumar-gri@rediffmail.com [Nanostructure Lab, Department of Physics, Gandhigram Rural University, Gandhigram-624302 (India); Reuben, Jasper D. [Department of Physics, School of Engineering, Saveetha University, Thandalam, Chennai- 600104 (India)

2015-06-24

The Coulomb interaction of holes in a Semimagnetic Cd{sub 1-x}Mn{sub x}Te / CdTe Spherical and Cubical Quantum Dot (SMQD) in a magnetic field is studied using variational approach in the effective mass approximation. Since these holes in QD show a pronounced collective behavior, while distinct single particle phenomena is suppressed, their interaction in confined potential becomes very significant. It has been observed that acceptor-acceptor interaction is more in cubical QD than in spherical QD which can be controlled by the magnetic field. The results are presented and discussed.

Magnetic field effect on the Coulomb interaction of acceptors in semimagnetic quantum dot

Science.gov (United States)

Kalpana, P.; Merwyn, A.; Reuben, Jasper D.; Nithiananthi, P.; Jayakumar, K.

2015-06-01

The Coulomb interaction of holes in a Semimagnetic Cd1-xMnxTe / CdTe Spherical and Cubical Quantum Dot (SMQD) in a magnetic field is studied using variational approach in the effective mass approximation. Since these holes in QD show a pronounced collective behavior, while distinct single particle phenomena is suppressed, their interaction in confined potential becomes very significant. It has been observed that acceptor-acceptor interaction is more in cubical QD than in spherical QD which can be controlled by the magnetic field. The results are presented and discussed.

Phosphorus acceptor doped ZnO nanowires prepared by pulsed-laser deposition

International Nuclear Information System (INIS)

Cao, B Q; Lorenz, M; Rahm, A; Wenckstern, H von; Czekalla, C; Lenzner, J; Benndorf, G; Grundmann, M

2007-01-01

Phosphorus-doped ZnO (ZnO:P) nanowires were successfully prepared by a novel high-pressure pulsed-laser deposition process using phosphorus pentoxide as the dopant source. Detailed cathodoluminescence studies of single ZnO:P nanowires revealed characteristic phosphorus acceptor-related peaks: neutral acceptor-bound exciton emission (A 0 , X, 3.356 eV), free-to-neutral-acceptor emission (e, A 0 , 3.314 eV), and donor-to-acceptor pair emission (DAP, ∼3.24 and ∼3.04 eV). This means that stable acceptor levels with a binding energy of about 122 meV have been induced in the nanowires by phosphorus doping. Moreover, the induced acceptors are distributed homogeneously along the doped nanowires

Electron paramagnetic resonance study of neutral Mg acceptors in β-Ga2O3 crystals

Science.gov (United States)

Kananen, B. E.; Halliburton, L. E.; Scherrer, E. M.; Stevens, K. T.; Foundos, G. K.; Chang, K. B.; Giles, N. C.

2017-08-01

Electron paramagnetic resonance (EPR) is used to directly observe and characterize neutral Mg acceptors ( M gGa0 ) in a β-Ga2O3 crystal. These acceptors, best considered as small polarons, are produced when the Mg-doped crystal is irradiated at or near 77 K with x rays. During the irradiation, neutral acceptors are formed when holes are trapped at singly ionized Mg acceptors ( M gGa- ). Unintentionally present Fe3+ (3d5) and Cr3+ (3d3) transition-metal ions serve as the corresponding electron traps. The hole is localized in a nonbonding p orbital on a threefold-coordinated oxygen ion adjacent to an Mg ion at a sixfold-coordinated Ga site. These M gGa0 acceptors (S = 1/2) have a slightly anisotropic g matrix (principal values are 2.0038, 2.0153, and 2.0371). There is also partially resolved 69Ga and 71Ga hyperfine structure resulting from unequal interactions with the two Ga ions adjacent to the hole. With the magnetic field along the a direction, hyperfine parameters are 2.61 and 1.18 mT for the 69Ga nuclei at the two inequivalent neighboring Ga sites. The M gGa0 acceptors thermally convert back to their nonparamagnetic M gGa- charge state when the temperature of the crystal is raised above approximately 250 K.

Pulsar velocity observations: Correlations, interpretations, and discussion

International Nuclear Information System (INIS)

Helfand, D.J.; Tademaru, E.

1977-01-01

From an examination of the current sample of 12 pulsars with measured proper motions and the z-distribution of the much larger group of over 80 sources with measured period derivatives, we develop a self-consistent picture of pulsar evolution. The apparent tendency of pulsars to move parallel to the galactic plane is explained as the result of various selection effects. A method for calculating the unmeasurable radial velocity of a pulsar is presented; it is shown that the total space velocities thus obtained are consistent with the assumption of an extreme Population I origin for pulsars which subsequently move away from the plane with a large range of velocities. The time scale for pulsar magnetic field decay is derived from dynamical considerations. A strong correlation of the original pulsar field strength with the magnitude of pulsar velocity is discussed. This results in the division of pulsars into two classes: Class A sources characterized by low space velocities, a small scale height, and low values of P 0 P 0 ; and Class B sources with a large range of velocities (up to 1000 km s -1 ), a much greater scale height, and larger values of initial field strength. It is postulated that Class A sources originate in tight binaries where their impulse acceleration at birth is insufficient to remove them from the system, while the Class B sources arise from single stars or loosely bound binaries and are accelerated to high velocities by their asymmetric radiation force. The evolutionary picture which is developed is shown to be consistent with a number of constraints imposed by supernova rates, the relative frequency of massive binaries and Class A sources, theoretical field-decay times, and the overall pulsar galactic distribution

Alternansucrase acceptor reactions with D-tagatose and L-glucose.

Science.gov (United States)

Côté, Gregory L; Dunlap, Christopher A; Appell, Michael; Momany, Frank A

2005-02-07

Alternansucrase (EC 2.4.1.140) is a d-glucansucrase that synthesizes an alternating alpha-(1-->3), (1-->6)-linked d-glucan from sucrose. It also synthesizes oligosaccharides via d-glucopyranosyl transfer to various acceptor sugars. Two of the more efficient monosaccharide acceptors are D-tagatose and L-glucose. In the presence of d-tagatose, alternansucrase produced the disaccharide alpha-d-glucopyranosyl-(1-->1)-beta-D-tagatopyranose via glucosyl transfer. This disaccharide is analogous to trehalulose. We were unable to isolate a disaccharide product from L-glucose, but the trisaccharide alpha-D-glucopyranosyl-(1-->6)-alpha-d-glucopyranosyl-(1-->4)-l-glucose was isolated and identified. This is analogous to panose, one of the structural units of pullulan, in which the reducing-end D-glucose residue has been replaced by its L-enantiomer. The putative L-glucose disaccharide product, produced by glucoamylase hydrolysis of the trisaccharide, was found to be an acceptor for alternansucrase. The disaccharide, alpha-D-glucopyranosyl-(1-->4)-L-glucose, was a better acceptor than maltose, previously the best known acceptor for alternansucrase. A structure comparison of alpha-D-glucopyranosyl-(1-->4)-L-glucose and maltose was performed through computer modeling to identify common features, which may be important in acceptor affinity by alternansucrase.

Comparison of acceptor properties for interaction of TCNE and DDQ ...

African Journals Online (AJOL)

... with tetracyanoethylene and 2,3-dichloro-5,6-dicyanobezoquinone as acceptors result in charge-transfer adducts of composition 2:1 of acceptor to donor, [(acceptor)2(donor)]. Formation constants, K, as well as the thermodynamic parameters, ΔH°, ΔS°, and ΔG° were determined by UV-Vis titration method for the adducts.

Enantiopure vs. Racemic Naphthalimide End-Capped Helicenic Non-Fullerene Electron Acceptors: Impact on Organic Photovoltaics Performance

OpenAIRE

Josse , Pierre; Favereau , Ludovic; Shen , Chengshuo; Dabos-Seignon , Sylvie; Blanchard , Philippe; Cabanetos , Clement; Crassous , Jeanne

2017-01-01

International audience; Impact of the enantiopurity on organic photovoltaics (OPV) performance was investigated through the synthesis of racemic and enantiomerically pure naphthalimide end-capped helicenes and their application as non-fullerene molecular electron acceptors in OPV devices. A very strong increase of the device performance was observed by simply switching from the racemic to the enantiopure forms of these π-helical non-fullerene acceptors with power conversion efficiencies jumpi...

Nanographenes as electron-deficient cores of donor-acceptor systems.

Science.gov (United States)

Liu, Yu-Min; Hou, Hao; Zhou, Yan-Zhen; Zhao, Xin-Jing; Tang, Chun; Tan, Yuan-Zhi; Müllen, Klaus

2018-05-15

Conjugation of nanographenes (NGs) with electro-active molecules can establish donor-acceptor π-systems in which the former generally serve as the electron-donating moieties due to their electronic-rich nature. In contrast, here we report a series of reversed donor-acceptor structures are obtained by C-N coupling of electron-deficient perchlorinated NGs with electron-rich anilines. Selective amination at the vertexes of the NGs is unambiguously shown through X-ray crystallography. By varying the donating ability of the anilino groups, the optical and assembly properties of donor-acceptor NGs can be finely modulated. The electron-deficient concave core of the resulting conjugates can host electron-rich guest molecules by intermolecular donor-acceptor interactions and gives rise to charge-transfer supramolecular architectures.

CONSTRAINING THE NFW POTENTIAL WITH OBSERVATIONS AND MODELING OF LOW SURFACE BRIGHTNESS GALAXY VELOCITY FIELDS

International Nuclear Information System (INIS)

Kuzio de Naray, Rachel; McGaugh, Stacy S.; Mihos, J. Christopher

2009-01-01

We model the Navarro-Frenk-White (NFW) potential to determine if, and under what conditions, the NFW halo appears consistent with the observed velocity fields of low surface brightness (LSB) galaxies. We present mock DensePak Integral Field Unit (IFU) velocity fields and rotation curves of axisymmetric and nonaxisymmetric potentials that are well matched to the spatial resolution and velocity range of our sample galaxies. We find that the DensePak IFU can accurately reconstruct the velocity field produced by an axisymmetric NFW potential and that a tilted-ring fitting program can successfully recover the corresponding NFW rotation curve. We also find that nonaxisymmetric potentials with fixed axis ratios change only the normalization of the mock velocity fields and rotation curves and not their shape. The shape of the modeled NFW rotation curves does not reproduce the data: these potentials are unable to simultaneously bring the mock data at both small and large radii into agreement with observations. Indeed, to match the slow rise of LSB galaxy rotation curves, a specific viewing angle of the nonaxisymmetric potential is required. For each of the simulated LSB galaxies, the observer's line of sight must be along the minor axis of the potential, an arrangement that is inconsistent with a random distribution of halo orientations on the sky.

Syntheses of donor-acceptor-functionalized dihydroazulenes

DEFF Research Database (Denmark)

Broman, Søren Lindbæk; Jevric, Martyn; Bond, Andrew

2014-01-01

The dihydroazulene (DHA)/vinylheptafulvene (VHF) photo/thermoswitch has been of interest for use in molecular electronics and advanced materials. The switching between the two isomers has previously been found to depend strongly on the presence of donor and acceptor groups. The fine-tuning of opt......The dihydroazulene (DHA)/vinylheptafulvene (VHF) photo/thermoswitch has been of interest for use in molecular electronics and advanced materials. The switching between the two isomers has previously been found to depend strongly on the presence of donor and acceptor groups. The fine...

Wide-range light-harvesting donor-acceptor assemblies through specific intergelator interactions via self-assembly.

Science.gov (United States)

Samanta, Suman K; Bhattacharya, Santanu

2012-12-03

We have synthesized two new low-molecular-mass organogelators based on tri-p-phenylene vinylene derivatives, one of which could be designated as the donor whereas the other one is an acceptor. These were prepared specifically to show the intergelator interactions at the molecular level by using donor-acceptor self-assembly to achieve appropriate control over their macroscopic properties. Intermolecular hydrogen-bonding, π-stacking, and van der Waals interactions operate for both the individual components and the mixtures, leading to the formation of gels in the chosen organic solvents. Evidence for intergelator interactions was acquired from various spectroscopic, microscopic, thermal, and mechanical investigations. Due to the photochromic nature of these molecules, interesting photophysical properties, such as solvatochromism and J-type aggregation, were clearly observed. An efficient energy transfer was exhibited by the mixture of donor-acceptor assemblies. An array of four chromophores was built up by inclusion of two known dyes (anthracene and rhodamine 6G) for the energy-transfer studies. Interestingly, an energy-transfer cascade was observed in the assembly of four chromophores in a particular order (anthracene-donor-acceptor-rhodamine 6G), and if one of the components was removed from the assembly the energy transfer process was discontinued. This allowed the build up of a light-harvesting process with a wide range. Excitation at one end produces an emission at the other end of the assembly. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Radial velocity observations of VB10

Science.gov (United States)

Deshpande, R.; Martin, E.; Zapatero Osorio, M. R.; Del Burgo, C.; Rodler, F.; Montgomery, M. M.

2011-07-01

VB 10 is the smallest star known to harbor a planet according to the recent astrometric study of Pravdo & Shaklan [1]. Here we present near-infrared (J-band) radial velocity of VB 10 performed from high resolution (R~20,000) spectroscopy (NIRSPEC/KECK II). Our results [2] suggest radial velocity variability with amplitude of ~1 km/s, a result that is consistent with the presence of a massive planet companion around VB10 as found via long-term astrometric monitoring of the star by Pravdo & Shaklan. Employing an entirely different technique we verify the results of Pravdo & Shaklan.

Acceptor Type Vacancy Complexes In As-Grown ZnO

International Nuclear Information System (INIS)

Zubiaga, A.; Tuomisto, F.; Zuniga-Perez, J.

2010-01-01

One of the many technological areas that ZnO is interesting for is the construction of opto-electronic devices working in the blue-UV range as its large band gap (∼3.4 eV at 10 K) makes them suitable for that purpose. As-grown ZnO shows generally n-type conductivity partially due to the large concentration of unintentional shallow donors, like H, but impurities can also form complexes with acceptor type defects (Zn vacancy) leading to the creation of compensating defects. Recently, Li Zn and Na Zn acceptors have been measured and H could form similar type of defects. Doppler Broadening Positron Annihilation spectroscopy experimental results on the observation of Zn related vacancy complexes in ZnO thin films, as-grown, O implanted and Al doped will be presented. Results show that as-grown ZnO film show small Zn vacancy related complexed that could be related to presence of H as a unintentional doping element.

Acceptor Type Vacancy Complexes In As-Grown ZnO

Science.gov (United States)

Zubiaga, A.; Tuomisto, F.; Zuñiga-Pérez, J.

2010-11-01

One of the many technological areas that ZnO is interesting for is the construction of opto-electronic devices working in the blue-UV range as its large band gap (˜3.4 eV at 10 K) makes them suitable for that purpose. As-grown ZnO shows generally n-type conductivity partially due to the large concentration of unintentional shallow donors, like H, but impurities can also form complexes with acceptor type defects (Zn vacancy) leading to the creation of compensating defects. Recently, LiZn and NaZn acceptors have been measured and H could form similar type of defects. Doppler Broadening Positron Annihilation spectroscopy experimental results on the observation of Zn related vacancy complexes in ZnO thin films, as-grown, O implanted and Al doped will be presented. Results show that as-grown ZnO film show small Zn vacancy related complexed that could be related to presence of H as a unintentional doping element.

Impact of Thermal Annealing on Organic Photovoltaic Cells Using Regioisomeric Donor-Acceptor-Acceptor Molecules.

Science.gov (United States)

Zhang, Tao; Han, Han; Zou, Yunlong; Lee, Ying-Chi; Oshima, Hiroya; Wong, Ken-Tsung; Holmes, Russell J

2017-08-02

We report a promising set of donor-acceptor-acceptor (D-A-A) electron-donor materials based on coplanar thieno[3,2-b]/[2,3-b]indole, benzo[c][1,2,5]thiadiazole, and dicyanovinylene, which are found to show broadband absorption with high extinction coefficients. The role of the regioisomeric electron-donating thienoindole moiety on the physical and structural properties is examined. Bulk heterojunction (BHJ) organic photovoltaic cells (OPVs) based on the thieno[2,3-b]indole-based electron donor NTU-2, using C 70 as an electron acceptor, show a champion power conversion efficiency of 5.2% under AM 1.5G solar simulated illumination. This efficiency is limited by a low fill factor (FF), as has previously been the case in D-A-A systems. In order to identify the origin of the limited FF, further insight into donor layer charge-transport behavior is realized by examining planar heterojunction OPVs, with emphasis on the evolution of film morphology with thermal annealing. Compared to as-deposited OPVs that exhibit insufficient donor crystallinity, crystalline OPVs based on annealed thin films show an increase in the short-circuit current density, FF, and power conversion efficiency. These results suggest that that the crystallization of D-A-A molecules might not be realized spontaneously at room temperature and that further processing is needed to realize efficient charge transport in these materials.

Optical observations on the CRIT-II Critical Ionization Velocity Experiment

International Nuclear Information System (INIS)

Stenbaek-Nielsen, H.C.; Wescott, E.M.; Haerendel, G.; Valenzuela, A.

1990-01-01

A rocket borne Critical Ionization Velocity (CIV) experiment was carried out from Wallops Island at dusk on May 4, 1989. Two barium shaped charges were released below the solar terminator (to prevent photoionization) at altitudes near 400 km. The ambient ionospheric electron density was 5x10 5 cm -3 . The neutral barium jet was directed upwards and at an angle of nominally 45 degrees to B which gives approximately 3x10 23 neutrals with super critical velocity. Ions created by a CIV process in the region of the neutral jet would travel up along B into sunlight where they can be detected optically. Well defined ion clouds (max. brightness 750 R) were observed in both releases. An ionization rate of 0.8%s -1 (125s ionization time constant) can account for the observed ion cloud near the release field line, but the ionization rate falls off with increasing distance from the release. It is concluded that a CIV process was present in the neutral jet out to about 50 km from the release, which is significantly further than allowed by current theories

Highly solvatochromic emission of electron donor-acceptor compounds containing propanedioato boron electron acceptors

NARCIS (Netherlands)

Brouwer, A.M.; Bakker, N.A.C.; Wiering, P.G.; Verhoeven, J.W.

1991-01-01

Light-induced electron transfer occurs in bifunctional compounds consisting of 1,3-diphenylpropanedioato boron oxalate or fluoride electron acceptors and simple aromatic electron-donor groups, linked by a methylene bridge; fluorescence from the highly polar charge-transfer excited state is

Geotail observations of FTE velocities

Directory of Open Access Journals (Sweden)

G. I. Korotova

2009-01-01

Full Text Available We discuss the plasma velocity signatures expected in association with flux transfer events (FTEs. Events moving faster than or opposite the ambient media should generate bipolar inward/outward (outward/inward flow perturbations normal to the nominal magnetopause in the magnetosphere (magnetosheath. Flow perturbations directly upstream and downstream from the events should be in the direction of event motion. Flows on the flanks should be in the direction opposite the motion of events moving at subsonic and subAlfvénic speeds relative to the ambient plasma. Events moving with the ambient flow should generate no flow perturbations in the ambient plasma. Alfvén waves propagating parallel (antiparallel to the axial magnetic field of FTEs may generate anticorrelated (correlated magnetic field and flow perturbations within the core region of FTEs. We present case studies illustrating many of these signatures. In the examples considered, Alfvén waves propagate along event axes away from the inferred reconnection site. A statistical study of FTEs observed by Geotail over a 3.5-year period reveals that FTEs within the magnetosphere invariably move faster than the ambient flow, while those in the magnetosheath move both faster and slower than the ambient flow.

Progress in ZnO Acceptor Doping: What Is the Best Strategy?

Directory of Open Access Journals (Sweden)

Judith G. Reynolds

2014-01-01

Full Text Available This paper reviews the recent progress in acceptor doping of ZnO that has been achieved with a focus toward the optimum strategy. There are three main approaches for generating p-type ZnO: substitutional group IA elements on a zinc site, codoping of donors and acceptors, and substitution of group VA elements on an oxygen site. The relevant issues are whether there is sufficient incorporation of the appropriate dopant impurity species, does it reside on the appropriate lattice site, and lastly whether the acceptor ionization energy is sufficiently small to enable significant p-type conduction at room temperature. The potential of nitrogen doping and formation of the appropriate acceptor complexes is highlighted although theoretical calculations predict that nitrogen on an oxygen site is a deep acceptor. We show that an understanding of the growth and annealing steps to achieve the relevant acceptor defect complexes is crucial to meet requirements.

Influence of acceptor on charge mobility in stacked π-conjugated polymers

Science.gov (United States)

Sun, Shih-Jye; Menšík, Miroslav; Toman, Petr; Gagliardi, Alessio; Král, Karel

2018-02-01

We present a quantum molecular model to calculate mobility of π-stacked P3HT polymer layers with electron acceptor dopants coupled next to side groups in random position with respect to the linear chain. The hole density, the acceptor LUMO energy and the hybridization transfer integral between the acceptor and polymer were found to be very critical factors to the final hole mobility. For a dopant LUMO energy close and high above the top of the polymer valence band we have found a significant mobility increase with the hole concentration and with the dopant LUMO energy approaching the top of the polymer valence band. Higher mobility was achieved for small values of hybridization transfer integral between polymer and the acceptor, corresponding to the case of weakly bound acceptor. Strong couplings between the polymer and the acceptor with Coulomb repulsion interactions induced from the electron localizations was found to suppress the hole mobility.

Characteristics of ovulation method acceptors: a cross-cultural assessment.

Science.gov (United States)

Klaus, H; Labbok, M; Barker, D

1988-01-01

Five programs of instruction in the ovulation method (OM) in diverse geographic and cultural settings are described, and characteristics of approximately 200 consecutive OM acceptors in each program are examined. Major findings include: the religious background and family size of acceptors are variable, as is the level of previous contraceptive use. Acceptors are drawn from a wide range of socioeconomic and religious backgrounds; however, family planning intention was similarly distributed in all five countries. In sum, the ovulation method is accepted by persons from a variety of backgrounds within and between cultural setting.

Theory of Primary Photoexcitations in Donor-Acceptor Copolymers.

Science.gov (United States)

Aryanpour, Karan; Dutta, Tirthankar; Huynh, Uyen N V; Vardeny, Zeev Valy; Mazumdar, Sumit

2015-12-31

We present a generic theory of primary photoexcitations in low band gap donor-acceptor conjugated copolymers. Because of the combined effects of strong electron correlations and broken symmetry, there is considerable mixing between a charge-transfer exciton and an energetically proximate triplet-triplet state with an overall spin singlet. The triplet-triplet state, optically forbidden in homopolymers, is allowed in donor-acceptor copolymers. For an intermediate difference in electron affinities of the donor and the acceptor, the triplet-triplet state can have a stronger oscillator strength than the charge-transfer exciton. We discuss the possibility of intramolecular singlet fission from the triplet-triplet state, and how such fission can be detected experimentally.

Velocity Drives Greater Power Observed During Back Squat Using Cluster Sets.

Science.gov (United States)

Oliver, Jonathan M; Kreutzer, Andreas; Jenke, Shane C; Phillips, Melody D; Mitchell, Joel B; Jones, Margaret T

2016-01-01

This investigation compared the kinetics and kinematics of cluster sets (CLU) and traditional sets (TRD) during back squat in trained (RT) and untrained (UT) men. Twenty-four participants (RT = 12, 25 ± 1 year, 179.1 ± 2.2 cm, 84.6 ± 2.1 kg; UT = 12, 25 ± 1 year, 180.1 ± 1.8 cm, 85.4 ± 3.8 kg) performed TRD (4 × 10, 120-second rest) and CLU (4 × (2 × 5) 30 seconds between clusters; 90 seconds between sets) with 70% one repetition maximum, randomly. Kinematics and kinetics were sampled through force plate and linear position transducers. Resistance-trained produced greater overall force, velocity, and power; however, similar patterns were observed in all variables when comparing conditions. Cluster sets produced significantly greater force in isolated repetitions in sets 1-3, while consistently producing greater force due to a required reduction in load during set 4 resulting in greater total volume load (CLU, 3302.4 ± 102.7 kg; TRD, 3274.8 ± 102.8 kg). Velocity loss was lessened in CLU resulting in significantly higher velocities in sets 2 through 4. Furthermore, higher velocities were produced by CLU during later repetitions of each set. Cluster sets produced greater power output for an increasing number of repetitions in each set (set 1, 5 repetitions; sets 2 and 3, 6 repetitions; set 4, 8 repetitions), and the difference between conditions increased over subsequent sets. Time under tension increased over each set and was greater in TRD. This study demonstrates greater power output is driven by greater velocity when back squatting during CLU; therefore, velocity may be a useful measure by which to assess power.

High-resolution vertical velocities and their power spectrum observed with the MAARSY radar - Part 1: frequency spectrum

Science.gov (United States)

Li, Qiang; Rapp, Markus; Stober, Gunter; Latteck, Ralph

2018-04-01

The Middle Atmosphere Alomar Radar System (MAARSY) installed at the island of Andøya has been run for continuous probing of atmospheric winds in the upper troposphere and lower stratosphere (UTLS) region. In the current study, we present high-resolution wind measurements during the period between 2010 and 2013 with MAARSY. The spectral analysis applying the Lomb-Scargle periodogram method has been carried out to determine the frequency spectra of vertical wind velocity. From a total of 522 days of observations, the statistics of the spectral slope have been derived and show a dependence on the background wind conditions. It is a general feature that the observed spectra of vertical velocity during active periods (with wind velocity > 10 m s-1) are much steeper than during quiet periods (with wind velocity wind conditions considered together the general spectra are obtained and their slopes are compared with the background horizontal winds. The comparisons show that the observed spectra become steeper with increasing wind velocities under quiet conditions, approach a spectral slope of -5/3 at a wind velocity of 10 m s-1 and then roughly maintain this slope (-5/3) for even stronger winds. Our findings show an overall agreement with previous studies; furthermore, they provide a more complete climatology of frequency spectra of vertical wind velocities under different wind conditions.

Absorption from Neutral Acceptors in GaAs and GaP

DEFF Research Database (Denmark)

Christensen, Ove

1973-01-01

We present a new calculation of the absorption due to transitions of holes between neutral acceptors and the various valence-band sublevels in GaAs and GaP. The acceptor wave function was approximated by a previously suggested expression for ground-state wave functions appropriate to complicated...... band extrema. Numerical calculations of the absorption from intervalence-band transitions of free holes and neutral acceptors have been performed. Good agreement with experimental results is obtained....

Acceptors in ZnO nanocrystals: A reinterpretation

Science.gov (United States)

Gehlhoff, W.; Hoffmann, A.

2012-12-01

In a recent article, Teklemichael et al. reported on the identification of an uncompensated acceptor in ZnO nanocrystals using infrared spectroscopy and electron paramagnetic resonance (EPR) in the dark and under illumination. Most of their conclusions, interpretations, and suggestions turned out to be erroneous. The observed EPR signals were interpreted to originate from axial and nonaxial VZn-H defects. We show that the given interpretation of the EPR results is based on misinterpretations of EPR spectra arising from defects in nanocrystals. The explanation of the infrared absorption lines is in conflict with recent results of valence band ordering and valence band splitting.

Deactivation of group III acceptors in silicon during keV electron irradiation

International Nuclear Information System (INIS)

Sah, C.; Sun, J.Y.; Tzou, J.J.; Pan, S.C.

1983-01-01

Experimental results on p-Si metal-oxide-semiconductor capacitors (MOSC's) are presented which demonstrate the electrical deactivation of the acceptor dopant impurity during 8-keV electron irradiation not only in boron but also aluminum and indium-doped silicon. The deactivation rates of the acceptors during the 8-keV electron irradiation are nearly independent of the acceptor impurity type. The final density of the remaining active acceptor approaches nonzero values N/sub infinity/, with N/sub infinity/(B) Al--H>In-H. These deactivation results are consistent with our hydrogen bond model. The thermal annealing or regeneration rate of the deactivated acceptors in the MOSC's irradiated by 8-keV electron is much smaller than that in the MOSC's that have undergone avalanche electron injection, indicating that the keV electron irradiation gives rise to stronger hydrogen-acceptor bond

Positronium Inhibition and Quenching by Organic Electron Acceptors and Charge Transfer Complexes

DEFF Research Database (Denmark)

Jansen, P.; Eldrup, Morten Mostgaard; Jensen, Bror Skytte

1975-01-01

Positron lifetime measurements were performed on a series of organic electron acceptors and charge-transfer complexes in solution. The acceptors cause both positronium (Ps) inhibition (with maybe one exception) and quenching, but when an acceptor takes part in a charge-transfer complex...... in terms of the spur reaction model of Ps formation. Correlation was also made to gas phase reaction between electron acceptors and free electron, as well as to pulse radiolysis data....

Identification of Ag-acceptors in $^{111}Ag^{111}Cd$ doped ZnTe and CdTe

CERN Document Server

Hamann, J; Deicher, M; Filz, T; Lany, S; Ostheimer, V; Strasser, F; Wolf, H; Wichert, T

2000-01-01

Nominally undoped ZnTe and CdTe crystals were implanted with radioactive /sup 111/Ag, which decays to /sup 111/Cd, and investigated by photoluminescence spectroscopy (PL). In ZnTe, the PL lines caused by an acceptor level at 121 meV are observed: the principal bound exciton (PBE) line, the donor-acceptor pair (DAP) band, and the two-hole transition lines. In CdTe, the PBE line and the DAP band that correspond to an acceptor level at 108 meV appear. Since the intensities of all these PL lines decrease in good agreement with the half-life of /sup 111/Ag of 178.8 h, both acceptor levels are concluded to be associated with defects containing a single Ag atom. Therefore, the earlier assignments to substitutional Ag on Zn- and Cd-lattice sites in the respective II-VI semiconductors are confirmed. The assignments in the literature of the S/sub 1/, S /sub 2/, and S/sub 3/ lines in ZnTe and the X/sub 1//sup Ag/, X/sub 2 //sup Ag//C/sub 1//sup Ag/, and C/sub 2//sup Ag/ lines in CdTe to Ag- related defect complexes are ...

Acceptors in II-IV Semiconductors - Incorporation and Complex Formation

CERN Multimedia

2002-01-01

A strong effort is currently devoted to the investigation of defects and the electrical activation of dopant atoms in II-VI semiconductors. In particular, the knowledge about the behaviour of acceptors, prerequisite for the fabrication of p-type semiconductors, is rather limited. The perturbed $\\,{\\gamma\\gamma}$ -angular correlation technique (PAC) and the photoluminescence spectroscopy (PL) using the radioactive isotopes $^{77}\\!$Br and $^{111}\\!$Ag will be applied for investigating the behaviour of acceptor dopant atoms and their interactions with defects in II-VI semiconductors. The main topic will be the identification of the technical conditions for the incorporation of electrically active acceptors in the II-VI semiconductors ~ZnS, ZnSe, ZnTe, CdS, CdSe, and CdTe with particular emphasis on the compounds~ CdTe, ZnSe, and ZnTe. The investigations will be supplemented by first exploratory PL experiments with the group V acceptors $^{71}\\!$As and $^{121}\\!$Sb. With help of the probe $^{111}\\!$Ag, the pos...

Meteoroid velocity distribution derived from head echo data collected at Arecibo during regular world day observations

Directory of Open Access Journals (Sweden)

M. P. Sulzer

2004-01-01

Full Text Available We report the observation and analysis of ionization flashes associated with the decay of meteoroids (so-called head echos detected by the Arecibo 430 MHz radar during regular ionospheric observations in the spring and autumn equinoxes. These two periods allow pointing well-above and nearly-into the ecliptic plane at dawn when the event rate maximizes. The observation of many thousands of events allows a statistical interpretation of the results, which show that there is a strong tendency for the observed meteoroids to come from the apex as has been previously reported (Chau and Woodman, 2004. The velocity distributions agree with Janches et al. (2003a when they are directly comparable, but the azimuth scan used in these observations allows a new perspective. We have constructed a simple statistical model which takes meteor velocities as input and gives radar line of sight velocities as output. The intent is to explain the fastest part of the velocity distribution. Since the speeds interpreted from the measurements are distributed fairly narrowly about nearly 60 km s-1, double the speed of the earth in its orbit, is consistent with the interpretation that many of the meteoroids seen by the Arecibo radar are moving in orbits about the sun with similar parameters as the earth, but in the retrograde direction. However, it is the directional information obtained from the beam-swinging radar experiment and the speed that together provide the evidence for this interpretation. Some aspects of the measured velocity distributions suggest that this is not a complete description even for the fast part of the distribution, and it certainly says nothing about the slow part first described in Janches et al. (2003a. Furthermore, we cannot conclude anything about the entire dust population since there are probably selection effects that restrict the observations to a subset of the population.

Using observations of slipping velocities to test the hypothesis that reconnection heats the active region corona

Science.gov (United States)

Yang, Kai; Longcope, Dana; Guo, Yang; Ding, Mingde

2017-08-01

Numerous proposed coronal heating mechanisms have invoked magnetic reconnection in some role. Testing such a mechanism requires a method of measuring magnetic reconnection coupled with a prediction of the heat delivered by reconnection at the observed rate. In the absence of coronal reconnection, field line footpoints move at the same velocity as the plasma they find themselves in. The rate of coronal reconnection is therefore related to any discrepancy observed between footpoint motion and that of the local plasma — so-called slipping motion. We propose a novel method to measure this velocity discrepancy by combining a sequence of non-linear force-free field extrapolations with maps of photospheric velocity. We obtain both from a sequence of vector magnetograms of an active region (AR). We then propose a method of computing the coronal heating produced under the assumption the observed slipping velocity was due entirely to coronal reconnection. This heating rate is used to predict density and temperature at points along an equilibrium loop. This, in turn, is used to synthesize emission in EUV and SXR bands. We perform this analysis using a sequence of HMI vector magnetograms of a particular AR and compare synthesized images to observations of the same AR made by SDO. We also compare differential emission measure inferred from those observations to that of the modeled corona.

Fluorescent and colorimetric molecular recognition probe for hydrogen bond acceptors.

Science.gov (United States)

Pike, Sarah J; Hunter, Christopher A

2017-11-22

The association constants for formation of 1 : 1 complexes between a H-bond donor, 1-naphthol, and a diverse range of charged and neutral H-bond acceptors have been measured using UV/vis absorption and fluorescence emission titrations. The performance of 1-naphthol as a dual colorimetric and fluorescent molecular recognition probe for determining the H-bond acceptor (HBA) parameters of charged and neutral solutes has been investigated in three solvents. The data were employed to establish self-consistent H-bond acceptor parameters (β) for benzoate, azide, chloride, thiocyanate anions, a series of phosphine oxides, phosphate ester, sulfoxide and a tertiary amide. The results demonstrate both the transferability of H-bond parameters between different solvents and the utility of the naphthol-based dual molecular recognition probe to exploit orthogonal spectroscopic techniques to determine the HBA properties of neutral and charged solutes. The benzoate anion is the strongest HBA studied with a β parameter of 15.4, and the neutral tertiary amide is the weakest H-bond acceptor investigated with a β parameter of 8.5. The H-bond acceptor strength of the azide anion is higher than that of chloride (12.8 and 12.2 respectively), and the thiocyanate anion has a β value of 10.8 and thus is a significantly weaker H-bond acceptor than both the azide and chloride anions.

The effect of intramolecular donor–acceptor moieties with donor–π-bridge–acceptor structure on the solar photovoltaic performance

Directory of Open Access Journals (Sweden)

T. L. Wang

2015-10-01

Full Text Available A series of intramolecular donor–acceptor polymers containing different contents of (E-1-(2-ethylhexyl-6,9-dioctyl-2-(2-(thiophen-3-ylvinyl-1H-phenanthro[9,10-d]imidazole (thiophene-DOPI moiety and 4,4-diethylhexylcyclopenta[ 2,1-b:3,4-b']dithiophene (CPDT unit was synthesized via Grignard metathesis (GRIM polymerization. The synthesized random copolymers and homopolymer of thiophene-DOPI contain the donor–π-bridge–acceptor conjugated structure to tune the absorption spectra and energy levels of the resultant polymers. UV-vis spectra of the three polymer films exhibit panchromatic absorptions ranging from 300 to 1100 nm and low band gaps from 1.38 to 1.51 eV. It is found that more thiophene-DOPI moieties result in the decrease of band gap and lower the highest occupied molecular orbital (HOMO and lowest unoccupied molecular orbital (LUMO values of polymers. Photovoltaic performance results indicate that if the content of the intramolecular donor–acceptor moiety is high enough, the copolymer structure may be better than homopolymer due to more light-harvesting afforded by both monomer units.

Improving Photoconductance of Fluorinated Donors with Fluorinated Acceptors

Energy Technology Data Exchange (ETDEWEB)

Garner, Logan E.; Larson, Bryon; Oosterhout, Stefan; Owczarczyk, Zbyslaw; Olson, Dana C.; Kopidakis, Nikos; Boltalina, Olga V.; Strauss, Steven H.; Braunecker, Wade A.

2016-11-21

This work investigates the influence of fluorination of both donor and acceptor materials on the generation of free charge carriers in small molecule donor/fullerene acceptor BHJ OPV active layers. A fluorinated and non-fluorinated small molecule analogue were synthesized and their optoelectronic properties characterized. The intrinsic photoconductance of blends of these small molecule donors was investigated using time-resolved microwave conductivity. Blends of the two donor molecules with a traditional non-fluorinated fullerene (PC70BM) as well as a fluorinated fullerene (C60(CF3)2-1) were investigated using 5% and 50% fullerene loading. We demonstrate for the first time that photoconductance in a 50:50 donor:acceptor BHJ blend using a fluorinated fullerene can actually be improved relative to a traditional non-fluorinated fullerene by fluorinating the donor molecule as well.

Spatial structure of single and interacting Mn acceptors in GaAs

Science.gov (United States)

Koenraad, Paul

2005-03-01

Ferromagnetic semiconductors such as Ga1-xMnxAs are receiving a lot of attention at the moment because of their application in spintronic devices. However, despite intense study of deep acceptors in III-V semiconductors such as MnGa, little information has been obtained on their electronic properties at the atomic scale. Yet the spatial shape of the Mn acceptor state will influence the hole-mediated Mn-Mn coupling and thus all of the magnetic properties of ferromagnetic semiconductors such as Ga1-xMnxAs. This study presents an experimental and theoretical description of the spatial symmetry of the Mn acceptor wave-function in GaAs. We present measurements of the spatial mapping of the anisotropic wavefunction of a hole localized at a Mn acceptor. To achieve this, we have used the STM tip not only to image the Mn acceptor but also to manipulate its charge state A^0/A^- at room temperature. Within an envelope function effective mass model (EFM) the anisotropy in the acceptor wave-function can be traced to the influence of the cubic symmetry of the GaAs crystal which selects specific d-states that mix into the ground state due to the spin-orbit interaction in the valence band. Comparison with calculations based on a tight-binding model (TBM) for the Mn acceptor structure supports this conclusion. Using the same experimental and theoretical approach we furthermore explored the interaction between Mn acceptors directly by analyzing close Mn-Mn pairs, which were separated by less than 2 nm. We will discuss some implications of these results for Mn delta-doped layers grown on differently oriented growth surfaces.

Photochemical stability of conjugated polymers, electron acceptors and blends for polymer solar cells resolved in terms of film thickness and absorbance

DEFF Research Database (Denmark)

Tromholt, Thomas; Vesterager Madsen, Morten; Carlé, Jon Eggert

2012-01-01

Photochemical degradation at 1 sun under AM1.5G illumination was performed on six conjugated polymers and five different electron acceptors. Additionally, the respective polymer:PC60BM and P3HT:electron acceptor blends were studied, and all degradations were resolved in terms of film thickness...... within each material group were found to vary for both the pure polymers and the blends. The stability ranking between the materials of the pure polymers was found to be similar to the ranking for their respective blends, implying that the photochemical stability of a pure polymer is a good measure...... of its associated blend stability. Different electron acceptors were found to stabilize P3HT decreasingly with decreasing donor–acceptor LUMO–LUMO gap. Destabilization of P3HT was observed in the case of the electron acceptor ICBA. Additionally, the decreased stabilization of P3HT by high LUMO electron...

A copper-relates shallow acceptor in quenched germanium

International Nuclear Information System (INIS)

Kamiura, Yoichi; Hashimoto, Fumio; Sugiyama, Hazime; Yoneyama, Shin-ichiro

1982-01-01

The temperature variation of hole density was measured in the range 5-200 K after successive annealings at 320sup(o)C. It was found that a shallow acceptor at Esub(v) + 9 meV disappears on annealing, being replaced by a just equal additional density of substitutional copper. This provides experimental proof that the shallow acceptor is a defect complex containing at least one copper atom. (author)

Theory of Primary Photoexcitations in Donor-Acceptor Copolymers

OpenAIRE

Aryanpour, Karan; Dutta, Tirthankar; Huynh, Uyen N. V.; Vardeny, Zeev Valy; Mazumdar, Sumit

2015-01-01

We present a generic theory of primary photoexcitations in low band gap donor-acceptor conjugated copolymers. Because of the combined effects of strong electron correlations and broken symmetry, there is considerable mixing between a charge-transfer exciton and an energetically proximate triplet-triplet state with an overall spin singlet. The triplet-triplet state, optically forbidden in homopolymers, is allowed in donor-acceptor copolymers. For an intermediate difference in electron affiniti...

Synthesis and X-ray crystal structure of the first tetrathiafulvalene-based acceptor-donor-acceptor sandwich

DEFF Research Database (Denmark)

Simonsen, Klaus B.; Thorup, Niels; Cava, Michael P.

1998-01-01

The synthesis and characterization of a bis-macrocyclic A-D-A sandwich produced in a simple one-pot reaction is reported. Only one acceptor unit participates in charge-transfer interactions with the TTF unit in the solid state....

Study of microbial perchlorate reduction: Considering of multiple pH, electron acceptors and donors

Energy Technology Data Exchange (ETDEWEB)

Xu, Xing [Key Laboratory of Water Pollution Control and Recycling (Shandong), School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Gao, Baoyu, E-mail: bygao@sdu.edu.cn [Key Laboratory of Water Pollution Control and Recycling (Shandong), School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Jin, Bo [School of Chemical Engineering, The University of Adelaide, Adelaide SA 5005,Australia (Australia); Zhen, Hu [Key Laboratory of Water Pollution Control and Recycling (Shandong), School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Wang, Xiaoyi [CSIRO Land and Water, Gate 5, Waite Road, Urrbrae, SA 5064 (Australia); Dai, Ming [School of Chemical Engineering, The University of Adelaide, Adelaide SA 5005,Australia (Australia)

2015-03-21

Graphical abstract: Schemes of perchlorate reduction in ClO{sub 4}{sup −}/ClO{sub 3}{sup −}–NO{sub 3}{sup −} e{sup −}acceptor systems. - Highlights: • We created a multiple electron acceptor/donor system for ClO{sub 4}{sup −} reduction. • Nitrate reduction was inhibited when using perchlorate-grown Azospira sp. KJ. • Reduction proceeded as an order of ClO{sub 3}{sup −}, ClO{sub 4}{sup −}and NO{sub 3}{sup −}. • Oxidation of acetate was inhibited by succinate in acetate–succinate series. - Abstract: Bioremediation of perchlorate-cotaminated water by a heterotrophic perchlorate reducing bacterium creates a multiple electron acceptor-donor system. We experimentally determined the perchlorate reduction by Azospira sp. KJ at multiple pH, electron acceptors and donors systems; this was the aim of this study. Perchlorate reduction was drastically inhibited at the pH 6.0, and the maximum reduction of perchlorate by Azospira sp. KJ was observed at pH value of 8.0. Perchlorate reduction was retarded in ClO{sub 4}{sup −}–ClO{sub 3}{sup −}, ClO{sub 4}{sup −}–ClO{sub 3}{sup −}–NO{sub 3}{sup −},and ClO{sub 4}{sup −}–NO{sub 3}{sup −} acceptor systems, while being completely inhibited by the additional O{sub 2} in the ClO{sub 4}{sup −}–O{sub 2} acceptor system. The reduction proceeded as an order of ClO{sub 3}{sup −}, ClO{sub 4}{sup −}, and NO{sub 3}{sup −} in the ClO{sub 4}{sup −}–ClO{sub 3}{sup −}–NO{sub 3}{sup −} system. K{sub S,}v{sub max}, and q{sub max} obtained at different e{sup −} acceptor and donor conditions are calculated as 140.5–190.6 mg/L, 8.7–13.2 mg-perchlorate/L-h, and 0.094–0.16 mg-perchlorate/mg-DW-h, respectively.

Effects of different external carbon sources and electron acceptors on interactions between denitrification and phosphorus removal in biological nutrient removal processes.

Science.gov (United States)

Hu, Xiang; Sobotka, Dominika; Czerwionka, Krzysztof; Zhou, Qi; Xie, Li; Makinia, Jacek

The effects of two different external carbon sources (acetate and ethanol) and electron acceptors (dissolved oxygen, nitrate, and nitrite) were investigated under aerobic and anoxic conditions with non-acclimated process biomass from a full-scale biological nutrient removal-activated sludge system. When acetate was added as an external carbon source, phosphate release was observed even in the presence of electron acceptors. The release rates were 1.7, 7.8, and 3.5 mg P/(g MLVSS·h) (MLVSS: mixed liquor volatile suspended solids), respectively, for dissolved oxygen, nitrate, and nitrite. In the case of ethanol, no phosphate release was observed in the presence of electron acceptors. Results of the experiments with nitrite showed that approximately 25 mg NO 2 -N/L of nitrite inhibited anoxic phosphorus uptake regardless of the concentration of the tested external carbon sources. Furthermore, higher denitrification rates were obtained with acetate (1.4 and 0.8 mg N/(g MLVSS·h)) compared to ethanol (1.1 and 0.7 mg N/ (g MLVSS·h)) for both anoxic electron acceptors (nitrate and nitrite).

SPECTROSCOPIC OBSERVATIONS OF SN 2012fr: A LUMINOUS, NORMAL TYPE Ia SUPERNOVA WITH EARLY HIGH-VELOCITY FEATURES AND A LATE VELOCITY PLATEAU

International Nuclear Information System (INIS)

Childress, M. J.; Scalzo, R. A.; Sim, S. A.; Tucker, B. E.; Yuan, F.; Schmidt, B. P.; Cenko, S. B.; Filippenko, A. V.; Silverman, J. M.; Contreras, C.; Hsiao, E. Y.; Phillips, M.; Morrell, N.; Jha, S. W.; McCully, C.; Anderson, J. P.; De Jaeger, T.; Forster, F.; Benetti, S.; Bufano, F.

2013-01-01

We present 65 optical spectra of the Type Ia SN 2012fr, 33 of which were obtained before maximum light. At early times, SN 2012fr shows clear evidence of a high-velocity feature (HVF) in the Si II λ6355 line that can be cleanly decoupled from the lower velocity ''photospheric'' component. This Si II λ6355 HVF fades by phase –5; subsequently, the photospheric component exhibits a very narrow velocity width and remains at a nearly constant velocity of ∼12,000 km s –1 until at least five weeks after maximum brightness. The Ca II infrared triplet exhibits similar evidence for both a photospheric component at v ≈ 12,000 km s –1 with narrow line width and long velocity plateau, as well as an HVF beginning at v ≈ 31,000 km s –1 two weeks before maximum. SN 2012fr resides on the border between the ''shallow silicon'' and ''core-normal'' subclasses in the Branch et al. classification scheme, and on the border between normal and high-velocity Type Ia supernovae (SNe Ia) in the Wang et al. system. Though it is a clear member of the ''low velocity gradient'' group of SNe Ia and exhibits a very slow light-curve decline, it shows key dissimilarities with the overluminous SN 1991T or SN 1999aa subclasses of SNe Ia. SN 2012fr represents a well-observed SN Ia at the luminous end of the normal SN Ia distribution and a key transitional event between nominal spectroscopic subclasses of SNe Ia.

Single and double acceptor-levels of a carbon-hydrogen defect in n-type silicon

Energy Technology Data Exchange (ETDEWEB)

Stübner, R.; Scheffler, L.; Kolkovsky, Vl., E-mail: kolkov@ifpan.edu.pl; Weber, J. [Technische Universität Dresden, 01062 Dresden (Germany)

2016-05-28

In the present study, we discuss the origin of two dominant deep levels (E42 and E262) observed in n-type Si, which is subjected to hydrogenation by wet chemical etching or a dc H-plasma treatment. Their activation enthalpies determined from Laplace deep level transient spectroscopy measurements are E{sub C}-0.06 eV (E42) and E{sub C}-0.51 eV (E262). The similar annealing behavior and identical depth profiles of E42 and E262 correlate them with two different charge states of the same defect. E262 is attributed to a single acceptor state due to the absence of the Poole-Frenkel effect and the lack of a capture barrier for electrons. The emission rate of E42 shows a characteristic enhancement with the electric field, which is consistent with the assignment to a double acceptor state. In samples with different carbon and hydrogen content, the depth profiles of E262 can be explained by a defect with one H-atom and one C-atom. From a comparison with earlier calculations [Andersen et al., Phys. Rev. B 66, 235205 (2002)], we attribute E42 to the double acceptor and E262 to the single acceptor state of the CH{sub 1AB} configuration, where one H atom is directly bound to carbon in the anti-bonding position.

2012 Gordon Research Conference, Electron donor-acceptor interactions, August 5-10 2012

Energy Technology Data Exchange (ETDEWEB)

McCusker, James [Michigan State Univ., East Lansing, MI (United States)

2012-08-10

The upcoming incarnation of the Gordon Research Conference on Electron Donor Acceptor Interactions will feature sessions on classic topics including proton-coupled electron transfer, dye-sensitized solar cells, and biological electron transfer, as well as emerging areas such as quantum coherence effects in donor-acceptor interactions, spintronics, and the application of donor-acceptor interactions in chemical synthesis.

Influence of Blend Morphology and Energetics on Charge Separation and Recombination Dynamics in Organic Solar Cells Incorporating a Nonfullerene Acceptor

KAUST Repository

Cha, Hyojung

2017-11-27

Nonfullerene acceptors (NFAs) in blends with highly crystalline donor polymers have been shown to yield particularly high device voltage outputs, but typically more modest quantum yields for photocurrent generation as well as often lower fill factors (FF). In this study, we employ transient optical and optoelectronic analysis to elucidate the factors determining device photocurrent and FF in blends of the highly crystalline donor polymer PffBT4T-2OD with the promising NFA FBR or the more widely studied fullerene acceptor PC71BM. Geminate recombination losses, as measured by ultrafast transient absorption spectroscopy, are observed to be significantly higher for PffBT4T-2OD:FBR blends. This is assigned to the smaller LUMO-LUMO offset of the PffBT4T-2OD:FBR blends relative to PffBT4T-2OD:PC71BM, resulting in the lower photocurrent generation efficiency obtained with FBR. Employing time delayed charge extraction measurements, these geminate recombination losses are observed to be field dependent, resulting in the lower FF observed with PffBT4T-2OD:FBR devices. These data therefore provide a detailed understanding of the impact of acceptor design, and particularly acceptor energetics, on organic solar cell performance. Our study concludes with a discussion of the implications of these results for the design of NFAs in organic solar cells.

Influence of Blend Morphology and Energetics on Charge Separation and Recombination Dynamics in Organic Solar Cells Incorporating a Nonfullerene Acceptor

KAUST Repository

Cha, Hyojung; Wheeler, Scot; Holliday, Sarah; Dimitrov, Stoichko D.; Wadsworth, Andrew; Lee, Hyun Hwi; Baran, Derya; McCulloch, Iain; Durrant, James R.

2017-01-01

Nonfullerene acceptors (NFAs) in blends with highly crystalline donor polymers have been shown to yield particularly high device voltage outputs, but typically more modest quantum yields for photocurrent generation as well as often lower fill factors (FF). In this study, we employ transient optical and optoelectronic analysis to elucidate the factors determining device photocurrent and FF in blends of the highly crystalline donor polymer PffBT4T-2OD with the promising NFA FBR or the more widely studied fullerene acceptor PC71BM. Geminate recombination losses, as measured by ultrafast transient absorption spectroscopy, are observed to be significantly higher for PffBT4T-2OD:FBR blends. This is assigned to the smaller LUMO-LUMO offset of the PffBT4T-2OD:FBR blends relative to PffBT4T-2OD:PC71BM, resulting in the lower photocurrent generation efficiency obtained with FBR. Employing time delayed charge extraction measurements, these geminate recombination losses are observed to be field dependent, resulting in the lower FF observed with PffBT4T-2OD:FBR devices. These data therefore provide a detailed understanding of the impact of acceptor design, and particularly acceptor energetics, on organic solar cell performance. Our study concludes with a discussion of the implications of these results for the design of NFAs in organic solar cells.

A rhodanine flanked nonfullerene acceptor for solution-processed organic photovoltaics

KAUST Repository

Holliday, Sarah

2015-01-21

A novel small molecule, FBR, bearing 3-ethylrhodanine flanking groups was synthesized as a nonfullerene electron acceptor for solution-processed bulk heterojunction organic photovoltaics (OPV). A straightforward synthesis route was employed, offering the potential for large scale preparation of this material. Inverted OPV devices employing poly(3-hexylthiophene) (P3HT) as the donor polymer and FBR as the acceptor gave power conversion efficiencies (PCE) up to 4.1%. Transient and steady state optical spectroscopies indicated efficient, ultrafast charge generation and efficient photocurrent generation from both donor and acceptor. Ultrafast transient absorption spectroscopy was used to investigate polaron generation efficiency as well as recombination dynamics. It was determined that the P3HT:FBR blend is highly intermixed, leading to increased charge generation relative to comparative devices with P3HT:PC60BM, but also faster recombination due to a nonideal morphology in which, in contrast to P3HT:PC60BM devices, the acceptor does not aggregate enough to create appropriate percolation pathways that prevent fast nongeminate recombination. Despite this nonoptimal morphology the P3HT:FBR devices exhibit better performance than P3HT:PC60BM devices, used as control, demonstrating that this acceptor shows great promise for further optimization.

Non-Fullerene Electron Acceptors for Use in Organic Solar Cells

KAUST Repository

Nielsen, Christian B.

2015-10-27

The active layer in a solution processed organic photovoltaic device comprises a light absorbing electron donor semiconductor, typically a polymer, and an electron accepting fullerene acceptor. Although there has been huge effort targeted to optimize the absorbing, energetic, and transport properties of the donor material, fullerenes remain as the exclusive electron acceptor in all high performance devices. Very recently, some new non-fullerene acceptors have been demonstrated to outperform fullerenes in comparative devices. This Account describes this progress, discussing molecular design considerations and the structure–property relationships that are emerging. The motivation to replace fullerene acceptors stems from their synthetic inflexibility, leading to constraints in manipulating frontier energy levels, as well as poor absorption in the solar spectrum range, and an inherent tendency to undergo postfabrication crystallization, resulting in device instability. New acceptors have to address these limitations, providing tunable absorption with high extinction coefficients, thus contributing to device photocurrent. The ability to vary and optimize the lowest unoccupied molecular orbital (LUMO) energy level for a specific donor polymer is also an important requirement, ensuring minimal energy loss on electron transfer and as high an internal voltage as possible. Initially perylene diimide acceptors were evaluated as promising acceptor materials. These electron deficient aromatic molecules can exhibit good electron transport, facilitated by close packed herringbone crystal motifs, and their energy levels can be synthetically tuned. The principal drawback of this class of materials, their tendency to crystallize on too large a length scale for an optimal heterojunction nanostructure, has been shown to be overcome through introduction of conformation twisting through steric effects. This has been primarily achieved by coupling two units together, forming dimers

Observations of high-velocity molecular gas near Herbig-Haro objects: HH 24--27 and HH 1--2

International Nuclear Information System (INIS)

Snell, R.L.; Edwards, S.

1982-01-01

High-velocity CO has been detected in the vicinity of the Herbig-Haro objects HH 24--27. These observations indicate that there are two sources of high-velocity outflow; one centered on an infrared source near HH 26, and the second centered roughly 2' south of HH 24. The redshifted and blueshifted wings in both sources are spatially separated suggesting that the high-velocity gas is due to energetic bipolar outflow from young stars embedded in the molecular cloud. The association of Herbig-Haro objects with regions of high-velocity gas suggests a common origin for both in the interaction of a stellar wind with the ambient molecular cloud. The mass loss rates implied by our observations, assuming that the rate of mass loss has been constant throughout the dynamical lifetime of the bipolar lobes, are roughly 10 -6 M/sub sun/ yr -1 for both sources. We have also searched for high-velocity gas near HH 1--2 but found no evidence for mass outflow in this region

Some experiments on the primary electron acceptor in reaction centres from Rhodopseudomanas sphaeroides

Energy Technology Data Exchange (ETDEWEB)

Wraight, C A; Cogdell, R J; Clayton, R K

1975-01-01

The bacterial reaction center absorbance change at 450 nm (A-450), assigned to an anionic semiquinone, has been suggested as a candidate for the reduced form of the primary electron acceptor in bacterial photosynthesis. In reaction centers of Rhodopseudomonas sphaeroides we have found kinetic discrepancies between the decay of A-450 and the recovery of photochemical competence. In addition, no proton uptake is measurable on the first turnover, although subsequent ones elicit one proton bound per electron. These results are taken to indicate that the acceptor reaction after a long dark period may be different for the first turnover than for subsequent ones. It is suggested that A-450 is still a likely candidate for the acceptor function but that in reaction centers, additional quinone may act as an adventitious primary acceptor when the ''true'' primary acceptor is reduced. Alternatively, the primary acceptor may act in a ''ping-pong'' fashion with respect to subsequent photoelectrons.

Non-fullerene acceptors for organic solar cells

Science.gov (United States)

Yan, Cenqi; Barlow, Stephen; Wang, Zhaohui; Yan, He; Jen, Alex K.-Y.; Marder, Seth R.; Zhan, Xiaowei

2018-03-01

Non-fullerene acceptors (NFAs) are currently a major focus of research in the development of bulk-heterojunction organic solar cells (OSCs). In contrast to the widely used fullerene acceptors (FAs), the optical properties and electronic energy levels of NFAs can be readily tuned. NFA-based OSCs can also achieve greater thermal stability and photochemical stability, as well as longer device lifetimes, than their FA-based counterparts. Historically, the performance of NFA OSCs has lagged behind that of fullerene devices. However, recent developments have led to a rapid increase in power conversion efficiencies for NFA OSCs, with values now exceeding 13%, demonstrating the viability of using NFAs to replace FAs in next-generation high-performance OSCs. This Review discusses the important work that has led to this remarkable progress, focusing on the two most promising NFA classes to date: rylene diimide-based materials and materials based on fused aromatic cores with strong electron-accepting end groups. The key structure-property relationships, donor-acceptor matching criteria and aspects of device physics are discussed. Finally, we consider the remaining challenges and promising future directions for the NFA OSCs field.

Constraint on the velocity dependent dark matter annihilation cross section from gamma-ray and kinematic observations of ultrafaint dwarf galaxies

Science.gov (United States)

Zhao, Yi; Bi, Xiao-Jun; Yin, Peng-Fei; Zhang, Xinmin

2018-03-01

Searching for γ rays from dwarf spheroidal galaxies (dSphs) is a promising approach to detect dark matter (DM) due to the high DM densities and low baryon components in dSphs. The Fermi-LAT observations from dSphs have set stringent constraints on the velocity independent annihilation cross section. However, the constraints from dSphs may change in velocity dependent annihilation scenarios because of the different velocity dispersions in galaxies. In this work, we study how to set constraints on the velocity dependent annihilation cross section from the combined Fermi-LAT observations of dSphs with the kinematic data. In order to calculate the γ ray flux from the dSph, the correlation between the DM density profile and velocity dispersion at each position should be taken into account. We study such correlation and the relevant uncertainty from kinematic observations by performing a Jeans analysis. Using the observational results of three ultrafaint dSphs with large J-factors, including Willman 1, Reticulum II, and Triangulum II, we set constraints on the p-wave annihilation cross section in the Galaxy as an example.

COMPARISON OF ACCEPTOR PROPERTIES FOR INTERACTION ...

African Journals Online (AJOL)

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determined by UV-Vis titration method for the adducts. Surprisingly, the ... Interaction of. TCNE and DDQ as π-acceptors with hydrocarbon donors such as cycloalkanes, alkenes, ... obtained from a Shimadzu GC-MS model QP5050 instrument.

Simulation study on the effects of chemical structure and molecular size on the acceptor strength in poly(3-hexylthiophene)-based copolymer with alternating donor and acceptor for photovoltaic applications

Science.gov (United States)

Rassamesard, Areefen; Pengpan, Teparksorn

2017-02-01

This research assessed the effects of various chemical structures and molecular sizes on the simulated geometric parameters, electron structures, and spectroscopic properties of single-chain complex alternating donor-acceptor (D-A) monomers and copolymers that are intended for use as photoactive layer in a polymer solar cell by using Kohn-Sham density functional theory with B3LYP exchange-correlation functional. The 3-hexylthiophene (3HT) was selected for electron donor, while eight chemicals, namely thiazole (Z), thiadiazole (D), thienopyrazine (TP), thienothiadiazole (TD), benzothiadiazole (BT), thiadiazolothieno-pyrazine (TPD), oxadiazole (OXD) and 5-diphenyl-1,2,4-triazole (TAZ), were employed as electron acceptor functional groups. The torsional angle, bridge bond length, intramolecular charge transfer, energy levels, and molecular orbitals were analyzed. The simulation results reveal that the geometry and electron structure of donor-acceptor monomer and copolymer are significantly impacted by heterocyclic rings, heteroatoms, fused rings, degree of steric hindrance and coplanarity of the acceptor molecular structure. Planar conformation was obtained from the D copolymer, and a pseudo-planar structure with the TD copolymer. The TAZ acceptor exhibited strong steric hindrance due to its bulky structure and non-planarity of its structure. An analysis of the electron structures indicated that the degree of intramolecular electron-withdrawing capability had the rank order TAZ  gaps of TD as well as TPD copolymer indicate that these two copolymers can be used in transparent conducting materials. The copolymer based on BT acceptor exhibited good intramolecular charge transfer and absorbed at 656 nm wavelength which is close to the maximum flux of solar spectrum. Hence, the BT acceptor functional group provides a compromise in the characteristics of a donor-acceptor copolymer, useful in a polymeric candidate material for the photoactive layer in a polymer solar

The height variation of supergranular velocity fields determined from simultaneous OSO 8 satellite and ground-based observations

Science.gov (United States)

November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W.

1979-01-01

Results are reported for simultaneous satellite and ground-based observations of supergranular velocities in the sun, which were made using a UV spectrometer aboard OSO 8 and a diode-array instrument operating at the exit slit of an echelle spectrograph attached to a vacuum tower telescope. Observations of the steady Doppler velocities seen toward the limb in the middle chromosphere and the photosphere are compared; the observed spectral lines of Si II at 1817 A and Fe I at 5576 A are found to differ in height of formation by about 1400 km. The results show that supergranular motions are able to penetrate at least 11 density scale heights into the middle chromosphere, that the patterns of motion correlate well with the cellular structure seen in the photosphere, and that the motion increases from about 800 m/s in the photosphere to at least 3000 m/s in the middle chromosphere. These observations imply that supergranular velocities should be evident in the transition region and that strong horizontal shear layers in supergranulation should produce turbulence and internal gravity waves.

Revisiting the stellar velocity ellipsoid-Hubble-type relation: observations versus simulations

Science.gov (United States)

Pinna, F.; Falcón-Barroso, J.; Martig, M.; Martínez-Valpuesta, I.; Méndez-Abreu, J.; van de Ven, G.; Leaman, R.; Lyubenova, M.

2018-04-01

The stellar velocity ellipsoid (SVE) in galaxies can provide important information on the processes that participate in the dynamical heating of their disc components (e.g. giant molecular clouds, mergers, spiral density waves, and bars). Earlier findings suggested a strong relation between the shape of the disc SVE and Hubble type, with later-type galaxies displaying more anisotropic ellipsoids and early types being more isotropic. In this paper, we revisit the strength of this relation using an exhaustive compilation of observational results from the literature on this issue. We find no clear correlation between the shape of the disc SVE and morphological type, and show that galaxies with the same Hubble type display a wide range of vertical-to-radial velocity dispersion ratios. The points are distributed around a mean value and scatter of σz/σR = 0.7 ± 0.2. With the aid of numerical simulations, we argue that different mechanisms might influence the shape of the SVE in the same manner and that the same process (e.g. mergers) does not have the same impact in all the galaxies. The complexity of the observational picture is confirmed by these simulations, which suggest that the vertical-to-radial axis ratio of the SVE is not a good indicator of the main source of disc heating. Our analysis of those simulations also indicates that the observed shape of the disc SVE may be affected by several processes simultaneously and that the signatures of some of them (e.g. mergers) fade over time.

Symmetry-Breaking Charge Transfer in a Zinc Chlorodipyrrin Acceptor for High Open Circuit Voltage Organic Photovoltaics

KAUST Repository

Bartynski, Andrew N.

2015-04-29

© 2015 American Chemical Society. Low open-circuit voltages significantly limit the power conversion efficiency of organic photovoltaic devices. Typical strategies to enhance the open-circuit voltage involve tuning the HOMO and LUMO positions of the donor (D) and acceptor (A), respectively, to increase the interfacial energy gap or to tailor the donor or acceptor structure at the D/A interface. Here, we present an alternative approach to improve the open-circuit voltage through the use of a zinc chlorodipyrrin, ZCl [bis(dodecachloro-5-mesityldipyrrinato)zinc], as an acceptor, which undergoes symmetry-breaking charge transfer (CT) at the donor/acceptor interface. DBP/ZCl cells exhibit open-circuit voltages of 1.33 V compared to 0.88 V for analogous tetraphenyldibenzoperyflanthrene (DBP)/C60-based devices. Charge transfer state energies measured by Fourier-transform photocurrent spectroscopy and electroluminescence show that C60 forms a CT state of 1.45 ± 0.05 eV in a DBP/C60-based organic photovoltaic device, while ZCl as acceptor gives a CT state energy of 1.70 ± 0.05 eV in the corresponding device structure. In the ZCl device this results in an energetic loss between ECT and qVOC of 0.37 eV, substantially less than the 0.6 eV typically observed for organic systems and equal to the recombination losses seen in high-efficiency Si and GaAs devices. The substantial increase in open-circuit voltage and reduction in recombination losses for devices utilizing ZCl demonstrate the great promise of symmetry-breaking charge transfer in organic photovoltaic devices.

An overview of molecular acceptors for organic solar cells

Directory of Open Access Journals (Sweden)

Hudhomme Piétrick

2013-07-01

Full Text Available Organic solar cells (OSCs have gained serious attention during the last decade and are now considered as one of the future photovoltaic technologies for low-cost power production. The first dream of attaining 10% of power coefficient efficiency has now become a reality thanks to the development of new materials and an impressive work achieved to understand, control and optimize structure and morphology of the device. But most of the effort devoted to the development of new materials concerned the optimization of the donor material, with less attention for acceptors which to date remain dominated by fullerenes and their derivatives. This short review presents the progress in the use of non-fullerene small molecules and fullerene-based acceptors with the aim of evaluating the challenge for the next generation of acceptors in organic photovoltaics.

Observations of intense velocity shear and associated electrostatic waves near an auroral arc

International Nuclear Information System (INIS)

Kelley, M.C.; Carlson, C.W.

1977-01-01

An intense shear in plasma flow velocity of magnitude 20 (m/s)m -1 has been detected at the edge of an auroral arc. The region of shear appears to display structure with two characteristic scale sizes. The larger structures were of the order of a few kilometers in size and were identified by a deviation of the direction of the charge sheets crossed by the rocket from a direction parallel to the visible arc. As is shown in the companion paper (Carlson and Kelley, 1977), the average (undisturbed) charge sheet was parallel to the arc. These observations are consistent with television studies which often display such structures propagating along the edges of auroral forms. Additional intense irregularities were detected with characteristic wavelengths smaller than the scale size of the shear. The irregularities are discussed in light of the branches of a velocity shear driven instability suggested by several workers: the Kelvin-Helmholtz instability operating at the longest wavelengths and the drift shear instability at the shorter. Neither mode has wavelengths as short as those observed however. A velocity shear mechanism operating at wavelengths short in comparison with the shear scale length, such as those observed here, would be of significant geophysical importance. For example, it could be responsible for production of high-latitude irregularities which exist throughout the polar cap and for the short-wavelength waves responsible for intense 3-m backscatter during equatorial spread F conditions. Since the wavelengths produced by the short-wavelength mode are in the range of typical auroral E region radars, such data must be carefully checked for F region contamination

Direct Observation of Surface Potential Distribution in Insulation Resistance Degraded Acceptor-Doped BaTiO3 Multilayered Ceramic Capacitors

Science.gov (United States)

Hong, Kootak; Lee, Tae Hyung; Suh, Jun Min; Park, Jae-Sung; Kwon, Hyung-Soon; Choi, Jaeho; Jang, Ho Won

2018-05-01

Insulation resistance (IR) degradation in BaTiO3 is a key issue for developing miniaturized multilayer ceramic capacitors (MLCCs) with high capacity. Despite rapid progress in BaTiO3-based MLCCs, the mechanism of IR degradation is still controversial. In this study, we demonstrate the Al doping effect on IR degradation behavior of BaTiO3 MLCCs by electrical measurements and scanning Kelvin probe microscopy (SKPM). As the Al doping concentration in BaTiO3 increases, IR degradation of MLCCs seems to be suppressed from electrical characterization results. However, SKPM results reveal that the conductive regions near the cathode become lager with Al doping after IR degradation. The formation of conducting regions is attributed to the migration of oxygen vacancies, which is the origin of IR degradation in BaTiO3, in dielectric layers. These results imply that acceptor doping in BaTiO3 solely cannot suppress the IR degradation in MLCC even though less asymmetric IR characteristics and IR degradation in MLCCs with higher Al doping concentration are observed from electrical characterization. Our results strongly suggest that observing the surface potential distribution in IR degraded dielectric layers using SKPM is an effective method to unravel the mechanism of IR degradation in MLCCs.

A survey of acceptor dopants for β-Ga2O3

Science.gov (United States)

Lyons, John L.

2018-05-01

With a wide band gap, high critical breakdown voltage and commercially available substrates, Ga2O3 is a promising material for next-generation power electronics. Like most wide-band-gap semiconductors, obtaining better control over its electrical conductivity is critically important, but has proven difficult to achieve. Although efficient p-type doping in Ga2O3 is not expected, since theory and experiment indicate the self-trapping of holes, the full development of this material will require a better understanding of acceptor dopants. Here the properties of group 2, group 5 and group 12 acceptor impurities in β-Ga2O3 are explored using hybrid density functional calculations. All impurities are found to exhibit acceptor transition levels above 1.3 eV. After examining formation energies as a function of chemical potential, Mg (followed closely by Be) is determined to be the most stable acceptor species.

Donor assists acceptor binding and catalysis of human α1,6-fucosyltransferase.

Science.gov (United States)

Kötzler, Miriam P; Blank, Simon; Bantleon, Frank I; Wienke, Martin; Spillner, Edzard; Meyer, Bernd

2013-08-16

α1,6-Core-fucosyltransferase (FUT8) is a vital enzyme in mammalian physiological and pathophysiological processes such as tumorigenesis and progress of, among others, non-small cell lung cancer and colon carcinoma. It was also shown that therapeutic antibodies have a dramatically higher efficacy if the α1,6-fucosyl residue is absent. However, specific and potent inhibitors for FUT8 and related enzymes are lacking. Hence, it is crucial to elucidate the structural basis of acceptor binding and the catalytic mechanism. We present here the first structural model of FUT8 in complex with its acceptor and donor molecules. An unusually large acceptor, i.e., a hexasaccharide from the core of N-glycans, is required as minimal structure. Acceptor substrate binding of FUT8 is being dissected experimentally by STD NMR and SPR and theoretically by molecular dynamics simulations. The acceptor binding site forms an unusually large and shallow binding site. Binding of the acceptor to the enzyme is much faster and stronger if the donor is present. This is due to strong hydrogen bonding between O6 of the proximal N-acetylglucosamine and an oxygen atom of the β-phosphate of GDP-fucose. Therefore, we propose an ordered Bi Bi mechanism for FUT8 where the donor molecule binds first. No specific amino acid is present that could act as base during catalysis. Our results indicate a donor-assisted mechanism, where an oxygen of the β-phosphate deprotonates the acceptor. Knowledge of the mechanism of FUT8 is now being used for rational design of targeted inhibitors to address metastasis and prognosis of carcinomas.

Transglycosylation reactions of Bacillus stearothermophilus maltogenic amylase with acarbose and various acceptors

International Nuclear Information System (INIS)

Hwa Park, K.; Jeong Kim, M.; Seob Lee, H.; Kim, D.; Soo Han, N.; Robyt, J.F.

1998-01-01

It was observed that Bacillus stearothermophilus maltogenic amylase cleaved the first glycosidic bond of acarbose to produce glucose and a pseudotrisaccharide (PTS) that was transferred to C-6 of the glucose to give an α-(1-6) glycosidic linkage and the formation of isoacarbose. The addition of a number of different carbohydrates to the digest gave transfer products in which PTS was primarily attached α-(1-6) to d-glucose, d-mannose, d-galactose, and methyl α-d-glucopyranoside. With d-fructopyranose and d-xylopyranose, PTS was linked α-(1-5) and α-(1-4), respectively. PTS was primarily transferred to C-6 of the nonreducing residue of maltose, cellobiose, lactose, and gentiobiose. Lesser amounts of α-(1-3) and/or α-(1-4) transfer products were also observed for these carbohydrate acceptors. The major transfer product to sucrose gave PTS linked α-(1-4) to the glucose residue. α,α-Trehalose gave two major products with PTS linked α-(1-6) and α-(1-4). Maltitol gave two major products with PTS linked α-(1-6) and α-(1-4) to the glucopyranose residue. Raffinose gave two major products with PTS linked α-(1-6) and α-(1-4) to the d-galactopyranose residue. Maltotriose gave two major products with PTS linked α-(1-6) and α-(1-4) to the nonreducing end glucopyranose residue. Xylitol gave PTS linked α-(1-5) as the major product and d-glucitol gave PTS linked α-(1-6) as the only product. The structures of the transfer products were determined using thin layer-chromatography, high-performance ion chromatography, enzyme hydrolysis, methylation analysis and 13 C NMR spectroscopy. The best acceptor was gentiobiose, followed closely by maltose and cellobiose, and the weakest acceptor was d-glucitol. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Transglycosylation reactions of Bacillus stearothermophilus maltogenic amylase with acarbose and various acceptors

Energy Technology Data Exchange (ETDEWEB)

Hwa Park, K; Jeong Kim, M; Seob Lee, H; Kim, D [Department of Food Science and Technology and Research Center for New Bio-Materials in Agriculture, Seoul National University, Suwon (Korea, Republic of); Soo Han, N; Robyt, J F [Laboratory for Carbohydrate Chemistry and Enzymology, Department of Biochemistry and Biophysics, Iowa State University, Ames, IA (United States)

1998-12-15

It was observed that Bacillus stearothermophilus maltogenic amylase cleaved the first glycosidic bond of acarbose to produce glucose and a pseudotrisaccharide (PTS) that was transferred to C-6 of the glucose to give an {alpha}-(1-6) glycosidic linkage and the formation of isoacarbose. The addition of a number of different carbohydrates to the digest gave transfer products in which PTS was primarily attached {alpha}-(1-6) to d-glucose, d-mannose, d-galactose, and methyl {alpha}-d-glucopyranoside. With d-fructopyranose and d-xylopyranose, PTS was linked {alpha}-(1-5) and {alpha}-(1-4), respectively. PTS was primarily transferred to C-6 of the nonreducing residue of maltose, cellobiose, lactose, and gentiobiose. Lesser amounts of {alpha}-(1-3) and/or {alpha}-(1-4) transfer products were also observed for these carbohydrate acceptors. The major transfer product to sucrose gave PTS linked {alpha}-(1-4) to the glucose residue. {alpha},{alpha}-Trehalose gave two major products with PTS linked {alpha}-(1-6) and {alpha}-(1-4). Maltitol gave two major products with PTS linked {alpha}-(1-6) and {alpha}-(1-4) to the glucopyranose residue. Raffinose gave two major products with PTS linked {alpha}-(1-6) and {alpha}-(1-4) to the d-galactopyranose residue. Maltotriose gave two major products with PTS linked {alpha}-(1-6) and {alpha}-(1-4) to the nonreducing end glucopyranose residue. Xylitol gave PTS linked {alpha}-(1-5) as the major product and d-glucitol gave PTS linked {alpha}-(1-6) as the only product. The structures of the transfer products were determined using thin layer-chromatography, high-performance ion chromatography, enzyme hydrolysis, methylation analysis and {sup 13}C NMR spectroscopy. The best acceptor was gentiobiose, followed closely by maltose and cellobiose, and the weakest acceptor was d-glucitol. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

The Dynamics of M15: Observations of the Velocity Dispersion Profile and Fokker-Planck Models

Science.gov (United States)

Dull, J. D.; Cohn, H. N.; Lugger, P. M.; Murphy, B. W.; Seitzer, P. O.; Callanan, P. J.; Rutten, R. G. M.; Charles, P. A.

1997-05-01

We report a new measurement of the velocity dispersion profile within 1' (3 pc) of the center of the globular cluster M15 (NGC 7078), using long-slit spectra from the 4.2 m William Herschel Telescope at La Palma Observatory. We obtained spatially resolved spectra for a total of 23 slit positions during two observing runs. During each run, a set of parallel slit positions was used to map out the central region of the cluster; the position angle used during the second run was orthogonal to that used for the first. The spectra are centered in wavelength near the Ca II infrared triplet at 8650 Å, with a spectral range of about 450 Å. We determined radial velocities by cross-correlation techniques for 131 cluster members. A total of 32 stars were observed more than once. Internal and external comparisons indicate a velocity accuracy of about 4 km s-1. The velocity dispersion profile rises from about σ = 7.2 +/- 1.4 km s-1 near 1' from the center of the cluster to σ = 13.9 +/- 1.8 km s-1 at 20". Inside of 20", the dispersion remains approximately constant at about 10.2 +/- 1.4 km s-1 with no evidence for a sharp rise near the center. This last result stands in contrast with that of Peterson, Seitzer, & Cudworth who found a central velocity dispersion of 25 +/- 7 km s-1, based on a line-broadening measurement. Our velocity dispersion profile is in good agreement with those determined in the recent studies of Gebhardt et al. and Dubath & Meylan. We have developed a new set of Fokker-Planck models and have fitted these to the surface brightness and velocity dispersion profiles of M15. We also use the two measured millisecond pulsar accelerations as constraints. The best-fitting model has a mass function slope of x = 0.9 (where 1.35 is the slope of the Salpeter mass function) and a total mass of 4.9 × 105 M⊙. This model contains approximately 104 neutron stars (3% of the total mass), the majority of which lie within 6" (0.2 pc) of the cluster center. Since the

Nano-scale control of energy transfer in the system 'donor-acceptor'

International Nuclear Information System (INIS)

Malyukin, Yu.V.; Yefimova, S.L.; Lebedenko, A.N.; Sorokin, A.V.; Borovoy, I.A.

2005-01-01

Fluorescence resonance energy transfer (FRET) in a cascade scheme between three amphiphilic dyes 3,3'-dioctadecyloxacarbocyanine perchlorate (DiOC 18 (3), donor), 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiIC 18 (3), acceptor/donor) and 1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine perchlorate (DiIC 18 (5), acceptor) has been investigated at low dye concentration (10 -5 mol/l) in water-micellar solutions due to a forced assembling of dyes in nanoscale volume. The experimental data have revealed that sodium dodecyl sulfate (SDS) micelles solubilize dye molecules such that their hydrophilic heads are in contact with water, while hydrophobic tails are embedded into the hydrocarbon core of the micelle. FRET efficiency has been found to depend on the concentration of dyes in micelles and the most effective when each SDS micelle contains 1 donor (DiOC 18 (3)), 2 acceptor/donor (DiIC 18 (3)) and 4 acceptor (DiIC 18 (5)) molecules

Acceptors in cadmium telluride. Identification and electronic structure

International Nuclear Information System (INIS)

Molva, E.

1983-11-01

It is shown that electronic properties of CdTe are determined by impurities more than by intrinsic defects like vacancies or interstitials in Cd or Te contrary to classical theories. These results are based on annealing, diffusion, implantation and electron irradiation at 4 K. Centers appearing in treated samples are accurately identified by photoluminescence, cathodoluminescence infra-red absorption, electrical measurements and magneto-optic properties. Acceptors identified are Li, Na, Cu, Ag and Au impurities in Cd and N, P and As in Te. Energy levels of all acceptors and fine structure of excitons are determined [fr

Optical observations on critical ionization velocity experiments in space

International Nuclear Information System (INIS)

Stenbaek-Nielsen, H.C.

1993-01-01

A number of Critical Ionization Velocity (CIV) experiments have been performed in space. CIV has been observed in laboratory experiments, but experiments in space have been inconclusive. Most space experiments have used barium which ionizes easily, and with emission lines from both neutrals and ions in the visible optical observations can be made from the ground. Also other elements, such as xenon, strontium and calcium, have been used. High initial ionization in some barium release experiments has been claimed due to CIV. However, a number of reactions between barium and the ambient plasma have been suggested as more likely processes. Currently the most popular process in this debate is charge exchange with O + . This process has a large cross section, but is it large enough? The cross section for charge exchange with calcium should be even larger, but in a double release of barium and calcium (part of the NASA CRRES release experiments) most ionization was observed from the barium release. Moreover, if charge exchange is the dominant process, the amount of ionization should relate to the oxygen ion density, and that does not appear to be the case. Other processes, such as associative ionization, have also been proposed, but yields are uncertain because the reaction rates are very poorly known

Halocarbons as hydrogen bond acceptors: a spectroscopic study of haloethylbenzenes (PhCH2CH2X, X = F, Cl, Br) and their hydrate clusters.

Science.gov (United States)

Robertson, Patrick A; Villani, Luigi; Dissanayake, Uresha L M; Duncan, Luke F; Abbott, Belinda M; Wilson, David J D; Robertson, Evan G

2018-03-28

The electronic spectra of 2-bromoethylbenzene and its chloro and fluoro analogues have been recorded by resonant two-photon ionisation (R2PI) spectroscopy. Anti and gauche conformers have been assigned by rotational band contour analysis and IR-UV ion depletion spectroscopy in the CH region. Hydrate clusters of the anti conformers have also been observed, allowing the role of halocarbons as hydrogen bond acceptors to be examined in this context. The donor OH stretch of water bound to chlorine is red-shifted by 36 cm -1 , or 39 cm -1 in the case of bromine. Although classed as weak H-bond acceptors, halocarbons are favourable acceptor sites compared to π systems. Fluorine stands out as the weakest H-bond acceptor amongst the halogens. Chlorine and bromine are also weak H-bond acceptors, but allow for more geometric lability, facilitating complimentary secondary interactions within the host molecule. Ab initio and DFT quantum chemical calculations, both harmonic and anharmonic, aid the structural assignments and analysis.

Perylene-Diimide Based Donor-Acceptor-Donor Type Small-Molecule Acceptors for Solution-Processable Organic Solar Cells

Science.gov (United States)

Ganesamoorthy, Ramasamy; Vijayaraghavan, Rajagopalan; Sakthivel, Pachagounder

2017-12-01

Development of nonfullerene acceptors plays an important role in the commercial availability of plastic solar cells. We report herein synthesis of bay-substituted donor-acceptor-donor (D-A-D)-type perylene diimide (PDI)-based small molecules (SM-1 to SM-4) by Suzuki coupling method and their use as acceptors in bulk heterojunction organic solar cells (BHJ-OSCs) with poly(3-hexylthiophene) (P3HT) polymer donor. We varied the number of electron-rich thiophene units and the solubilizing side chains and also evaluated the optical and electrochemical properties of the small molecules. The synthesized small molecules were confirmed by Fourier-transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and high-resolution mass spectroscopy (HR-MS). The small molecules showed extensive and strong absorption in the ultraviolet-visible (UV-Vis) region up to 750 nm, with bandgap (E_{{g}}^{{opt}} ) reduced below use as electron-accepting materials. The small molecules showed good thermal stability up to 300°C. BHJ-OSCs with SM-1 and P3HT polymer donor showed maximum power conversion efficiency (PCE) of 0.19% with V oc of 0.30 V, J sc of 1.72 mA cm-2, and fill factor (FF) of 37%. The PCE decreased with the number of thiophene units. The PCE of SM-2 was lower than that of SM-1. This difference in PCE can be explained by the higher aggregation tendency of the bithiophene compared with the thiophene unit. Introduction of the solubilizing group in the bay position increased the aggregation property, leading to much lower PCE than for the small molecules without solubilizing group.

Dye-Incorporated Polynaphthalenediimide Acceptor for Additive-Free High-Performance All-Polymer Solar Cells.

Science.gov (United States)

Chen, Dong; Yao, Jia; Chen, Lie; Yin, Jingping; Lv, Ruizhi; Huang, Bin; Liu, Siqi; Zhang, Zhi-Guo; Yang, Chunhe; Chen, Yiwang; Li, Yongfang

2018-04-16

All-polymer solar cells (all-PSCs) can offer unique advantages for applications in flexible devices, and naphthalene diimide (NDI)-based polymer acceptors are the widely used polymer acceptors. However, their power conversion efficiency (PCE) still lags behind that of state-of-the-art polymer solar cells, due to low light absorption, suboptimal energy levels and the strong aggregation of the NDI-based polymer acceptor. Herein, a rhodanine-based dye molecule was introduced into the NDI-based polymer acceptor by simple random copolymerization and showed an improved light absorption coefficient, an up-shifted lowest unoccupied molecular orbital level and reduced crystallization. Consequently, additive-free all-PSCs demonstrated a high PCE of 8.13 %, which is one of the highest performance characteristics reported for all-PSCs to date. These results indicate that incorporating a dye into the n-type polymer gives insight into the precise design of high-performance polymer acceptors for all-PSCs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic resonance studies of the Mg acceptor in thick free-standing and thin-film GaN

Science.gov (United States)

Zvanut, Mary Ellen

Mg, the only effective p-type dopant for the nitrides, substitutes for Ga and forms an acceptor with a defect level of about 0.16 eV. The magnetic resonance of such a center should be highly anisotropic, yet early work employing both optically detected magnetic resonance (ODMR) and electron paramagnetic resonance (EPR) spectroscopies revealed a defect with a nearly isotropic g-tensor. The results were attributed to crystal fields caused by compensation and/or strain typical of the heteroepitaxially grown films. The theory was supported by observation of the expected highly anisotropic ODMR signature in homoepitaxially grown films in which dislocation-induced non-uniform strain and compensation are reduced. The talk will review EPR measurements of thin films and describe new work which takes advantage of the recently available thick free-standing GaN:Mg substrates grown by hydride vapor phase epitaxy (HVPE) and high nitrogen pressure solution growth (HNPS). Interestingly, the films and HVPE substrates exhibit characteristically different types of EPR signals, and no EPR response could be induced in the HNPS substrates, with or without illumination. In the heteroepitaxial films, a curious angular dependent line-shape is observed in addition to the nearly isotropic g-tensor characteristic of the Mg-related acceptor. On the other hand, the free-standing HVPE crystals reveal a clear signature of a highly anisotropic shallow acceptor center. Comparison with SIMS measurements implies a direct relation to the Mg impurity, and frequency-dependent EPR studies demonstrate the influence of the anisotropic crystal fields. Overall, the measurements of the thick free-standing crystals show that the Mg acceptor is strongly affected by the local environment. The ODMR was performed by Evan Glaser, NRL and the free-standing Mg-doped HVPE crystals were grown by Jacob Leach, Kyma Tech. The work at UAB is supported by NSF Grant No. DMR-1308446.

Conduction electrons in acceptor-doped GaAs/GaAlAs heterostructures: a review

International Nuclear Information System (INIS)

Zawadzki, Wlodek; Raymond, Andre; Kubisa, Maciej

2016-01-01

We review magneto-optical and magneto-transport effects in GaAs/GaAlAs heterostructures doped in GaAlAs barriers with donors, providing two-dimensional (2D) electron gas (2DEG) in GaAs quantum wells (QWS), and additionally doped with smaller amounts of acceptors (mostly Be atoms) in the vicinity of 2DEG. One may also deal with residual acceptors (mostly C atoms). The behavior of such systems in the presence of a magnetic field differs appreciably from those doped in the vicinity of 2DEG with donors. Three subjects related to the acceptor-doped heterostructures are considered. First is the problem of bound states of conduction electrons confined to the vicinity of negatively charged acceptors by the joint effect of a QW and an external magnetic field parallel to the growth direction. A variational theory of such states is presented, demonstrating that an electron turning around a repulsive center has discrete energies above the corresponding Landau levels. Experimental evidence for the discrete electron energies comes from the work on interband photo-magneto-luminescence, intraband cyclotron resonance and quantum magneto-transport (the Quantum Hall and Shubnikov–de Haas effects). An electron rain-down effect at weak electric fields and a boil-off effect at strong electric fields are introduced. It is demonstrated, both theoretically and experimentally, that a negatively charged acceptor can localize more than one electron. The second subject describes experiment and theory of asymmetric quantized Hall and Shubnikov–de Haas plateaus in acceptor-doped GaAs/GaAlAs heterostructures. It is shown that the main features of the plateau asymmetry can be attributed to asymmetric density of Landau states in the presence of acceptors. However, at high magnetic fields, the rain-down effect is also at work. The third subject deals with the so-called disorder modes (DMs) in the cyclotron resonance of conduction electrons. The DMs originate from random distributions of

Comparison of relativity theories with observer-independent scales of both velocity and length/mass

International Nuclear Information System (INIS)

Amelino-Camelia, Giovanni; Benedetti, Dario; D'Andrea, Francesco; Procaccini, Andrea

2003-01-01

We consider the two most studied proposals of relativity theories with observer-independent scales of both velocity and length/mass: the one discussed by Amelino-Camelia as an illustrative example for the original proposal (Preprint gr-qc/0012051) of theories with two relativistic invariants, and an alternative more recently proposed by Magueijo and Smolin (Preprint hep-th/0112090). We show that these two relativistic theories are much more closely connected than it would appear on the basis of a naive analysis of their original formulations. In particular, in spite of adopting a rather different formal description of the deformed boost generators, they end up assigning the same dependence of momentum on rapidity, which can be described as the core feature of these relativistic theories. We show that this observation can be used to clarify the concepts of particle mass, particle velocity and energy-momentum conservation rules in these theories with two relativistic invariants

Interaction of 125I-labeled botulinum neurotoxins with nerve terminals. II. Autoradiographic evidence for its uptake into motor nerves by acceptor-mediated endocytosis

International Nuclear Information System (INIS)

Black, J.D.; Dolly, J.O.

1986-01-01

Using pharmacological and autoradiographic techniques it has been shown that botulinum neurotoxin (BoNT) is translocated across the motor nerve terminal membrane to reach a postulated intraterminal target. In the present study, the nature of this uptake process was investigated using electron microscopic autoradiography. It was found that internalization is acceptor-mediated and that binding to specific cell surface acceptors involves the heavier chain of the toxin. In addition, uptake was shown to be energy and temperature-dependent and to be accelerated by nerve stimulation, a treatment which also shortens the time course of the toxin-induced neuroparalysis. These results, together with the observation that silver grains were often associated with endocytic structures within the nerve terminal, suggested that acceptor-mediated endocytosis is responsible for toxin uptake. Possible recycling of BoNT acceptors (an important aspect of acceptor-mediated endocytosis of toxins) at motor nerve terminals was indicated by comparing the extent of labeling in the presence and absence of metabolic inhibitors. On the basis of these collective results, it is concluded that BoNT is internalized by acceptor-mediated endocytosis and, hence, the data support the proposal that this toxin inhibits release of acetylcholine by interaction with an intracellular target

Effect of anneal and quench on the nature of the dominant acceptors in ZnTe

International Nuclear Information System (INIS)

Bensahel, D.; Magnea, N.; Pautrat, J.L.; Pfister, J.C.; Revoil, L.

1978-01-01

Anneal and quench studies on high purity ZnTe have shown the dominant role of impurities and their solubilities as functions of stoichiometrical conditions. The role of 'b' acceptor, related to lithium, 'g' acceptor, related to silver, and 'a' acceptor of unknown nature is reported

Electroluminescence from charge transfer states in Donor/Acceptor solar cells

DEFF Research Database (Denmark)

Sherafatipour, Golenaz; Madsen, Morten

Charge photocurrent generation is a key process in solar energy conversion systems. Effective dissociation of the photo-generated electron-hole pairs (excitons) has a strong influence on the efficiency of the organic solar cells. Charge dissociation takes place at the donor/acceptor interface via...... which the maximum open-circuit voltage can be estimated, and further can be used in the modeling and optimization of the OPV devices. [1] C. Deibe, T. Strobe, and V. Dyakonov, “Role of the charge transfer state in organic donor-acceptor solar cells,” Adv. Mater., vol. 22, pp. 4097–4111, 2010. [2] K...... charge transfer (CT) excitons, which is Coulombically bound interfacial electron- hole pairs residing at the donor/acceptor heterojunctions. The CT state represents an intermediate state between the exciton dissociation and recombination back to the ground state. Since the recombination of photo...

Shell-like configuration in O+ ion velocity distribution at high altitudes in the dayside magnetosphere observed by Cluster/CIS

Directory of Open Access Journals (Sweden)

S. Joko

2004-07-01

Full Text Available We report shell-like configurations seen in O+ ion velocity distributions. One case was observed above 8RE in radial distance in the dayside magnetosphere, presumably in the mantle region, during the observation period of 09:30-10:00 UT on 12 April 2001 by the CIS instrument on board the Cluster satellite. This shell-like configuration was different from so-called "conics" or "beams": the lower energy (cold population and the higher energy partial shell part were seen together, but there was no obvious signature of heating process. With respect to H+ ion velocity distributions observed simultaneously, transverse heating (so-called in "pan-cake" shape or field-aligned energisation configurations were seen as the result of heating/energisation processes and the upward-going part of the distribution also formed a half spherical thick shell configuration. Concerning O+ ion heating in the case of 12 April 2001, it was obviously observed when the spacecraft passed through the mantle region close to the poleward cusp. As the spacecraft moved toward the dayside cusp shell-like (or dome shape velocity distributions appeared apparently and continued to be observed until the spacecraft reached the magnetopause according to two other different cases (13 February 2001 and 14 April 2001. Two other cases were observed in the Southern Hemisphere and the spacecraft was supposed to pass through the dayside cusp toward the mantle region at higher altitudes (9-11RE. O+ ion velocity distributions in these cases show pre-/post-structured shell-like configurations, depending on the observation sites (mantle or dayside cusp.

Propagation of the Semidiurnal Internal Tide: Phase Velocity Versus Group Velocity

Science.gov (United States)

Zhao, Zhongxiang

2017-12-01

The superposition of two waves of slightly different wavelengths has long been used to illustrate the distinction between phase velocity and group velocity. The first-mode M2 and S2 internal tides exemplify such a two-wave model in the natural ocean. The M2 and S2 tidal frequencies are 1.932 and 2 cycles per day, respectively, and their superposition forms a spring-neap cycle in the semidiurnal band. The spring-neap cycle acts like a wave, with its frequency, wave number, and phase being the differences of the M2 and S2 internal tides. The spring-neap cycle and energy of the semidiurnal internal tide propagate at the group velocity. Long-range propagation of M2 and S2 internal tides in the North Pacific is observed by satellite altimetry. Along a 3,400 km beam spanning 24°-54°N, the M2 and S2 travel times are 10.9 and 11.2 days, respectively. For comparison, it takes the spring-neap cycle 21.1 days to travel over this distance. Spatial maps of the M2 phase velocity, the S2 phase velocity, and the group velocity are determined from phase gradients of the corresponding satellite observed internal tide fields. The observed phase and group velocities agree with theoretical values estimated using the World Ocean Atlas 2013 annual-mean ocean stratification.

Charge Carrier Dynamics at Silver Nanocluster-Molecular Acceptor Interfaces

KAUST Repository

Almansaf, Abdulkhaleq

2017-07-01

A fundamental understanding of interfacial charge transfer at donor-acceptor interfaces is very crucial as it is considered among the most important dynamical processes for optimizing performance in many light harvesting systems, including photovoltaics and photo-catalysis. In general, the photo-generated singlet excitons in photoactive materials exhibit very short lifetimes because of their dipole-allowed spin radiative decay and short diffusion lengths. In contrast, the radiative decay of triplet excitons is dipole forbidden; therefore, their lifetimes are considerably longer. The discussion in this thesis primarily focuses on the relevant parameters that are involved in charge separation (CS), charge transfer (CT), intersystem crossing (ISC) rate, triplet state lifetime, and carrier recombination (CR) at silver nanocluster (NCs) molecular-acceptors interfaces. A combination of steady-state and femto- and nanosecond broadband transient absorption spectroscopies were used to investigate the charge carrier dynamics in various donor-acceptor systems. Additionally, this thesis was prolonged to investigate some important factors that influence the charge carrier dynamics in Ag29 silver NCs donor-acceptor systems, such as the metal doping and chemical structure of the nanocluster and molecular acceptors. Interestingly, clear correlations between the steady-state measurements and timeresolved spectroscopy results are found. In the first study, we have investigated the interfacial charge transfer dynamics in positively charged meso units of 5, 10, 15, 20-tetra (1- methyl-4-pyridino)-porphyrin tetra (p-toluene sulfonate) (TMPyP) and neutral charged 5, 10, 15, 20-tetra (4-pyridyl)-porphyrin (TPyP), with negatively charged undoped and gold (Au)- doped silver Ag29 NCs. Moreover, this study showed the impact of Au doping on the charge carrier dynamics of the system. In the second study, we have investigated the interfacial charge transfer dynamics in [Pt2 Ag23 Cl7 (PPh3

Ultrafast Photoinduced Electron Transfer in Bimolecular Donor-Acceptor Systems

KAUST Repository

Alsulami, Qana A.

2016-11-30

The efficiency of photoconversion systems, such as organic photovoltaic (OPV) cells, is largely controlled by a series of fundamental photophysical processes occurring at the interface before carrier collection. A profound understanding of ultrafast interfacial charge transfer (CT), charge separation (CS), and charge recombination (CR) is the key determinant to improving the overall performances of photovoltaic devices. The discussion in this dissertation primarily focuses on the relevant parameters that are involved in photon absorption, exciton separation, carrier transport, carrier recombination and carrier collection in organic photovoltaic devices. A combination of steady-state and femtosecond broadband transient spectroscopies was used to investigate the photoinduced charge carrier dynamics in various donor-acceptor systems. Furthermore, this study was extended to investigate some important factors that influence charge transfer in donor-acceptor systems, such as the morphology, energy band alignment, electronic properties and chemical structure. Interestingly, clear correlations among the steady-state measurements, time-resolved spectroscopy results, grain alignment of the electron transporting layer (ETL), carrier mobility, and device performance are found. In this thesis, we explored the significant impacts of ultrafast charge separation and charge recombination at donor/acceptor (D/A) interfaces on the performance of a conjugated polymer PTB7-Th device with three fullerene acceptors: PC71BM, PC61BM and IC60BA. Time-resolved laser spectroscopy and high-resolution electron microscopy can illustrate the basis for fabricating solar cell devices with improved performances. In addition, we studied the effects of the incorporation of heavy metals into π-conjugated chromophores on electron transfer by monitoring the triplet state lifetime of the oligomer using transient absorption spectroscopy, as understanding the mechanisms controlling intersystem crossing and

Spectroscopic studies of charge transfer complexes of some amino aromatic donors with some acceptors

International Nuclear Information System (INIS)

Al-Ani, S.S.

1989-01-01

Charge transfer (C.T.) complexes are the products of the weak reversible interactions between electron donors and electron acceptors. Sixteen novel C.T. complexes were studied and discussed. These complexes were formed from aromatic electron donors with various electron acceptors in absolute ethyl alcohol at 20 0 C. Electronic absorption spectra of these complexes and their donors and acceptors were taken. New charge transfer absorption bands appeared for these complexes in the UV-VIS region. The donors used are tetramethyl diamino benzophenone, P-amino-N:N-dimethyl aniline, tetramethyl-diamino-diphenylmethane, P-amino-azobenzene and benzidine, while the acceptors are iodine, bromine, picric acid, 2,4-dinitrophenol, trifluoroacetic acid and trichloroacetic acid. The results showed a disappearance of some donors and acceptors absorption bands. The energy of C.T. bands were calculated from which the ionization potentials of donors were obtained. The results showed that energies of C.T. Bands for complexes of a given donor with a series of acceptors are very similar. Some C.T. complexes showed low value of energy and high values of electrical conductivity. These are ionic complexes rather than molecular ones. 4 tabs.; 2 figs.; 99 refs

Observation of E×B Flow Velocity Profile Change Using Doppler Reflectometry in HL-2A

Institute of Scientific and Technical Information of China (English)

XIAO Wei-Wen; ZOU Xiao-Lan; DING Xuan-Tong; DONG Jia-Qi; LIU Ze-Tian; SONG Shao-Dong; GAO Ya-Dong; YAO Liang-Hua; FENG Bei-Bin; SONG Xian-Ming; CHEN Cheng-Yuan; SUN Hong-Juan; LI Yong-Gao; YANG Qing-Wei; YAN Long-Wen; LIU Yi; DUAN Xu-Ru; PAN Chuan-Hong; LIU Yong

2009-01-01

A broadband,O-mode sweeping Doppler reflectometry designed for measuring plasma E×B flow velocity profiles is operated in HL-2A.The main feature of the Doppler reflectometry is its capability to be tuned to any selected frequency in total waveband from 26-40 GHz.This property enables us to probe several plasma layers within a short time interval during a discharge,permitting the characterization of the radial distribution of plasma fluctuations.The system allows us to extract important information about the velocity change layer,namely its spatial localization.In purely Ohmic discharge a change of the E×B flow velocity profiles has been observed in the region for 28 ＜ r ＜ 30cm if only the line average density exceeds 2.2×1019 m-3.The density gradient change is measured in the same region,too.

Donor-Acceptor Block Copolymers: Synthesis and Solar Cell Applications

Directory of Open Access Journals (Sweden)

Kazuhiro Nakabayashi

2014-04-01

Full Text Available Fullerene derivatives have been widely used for conventional acceptor materials in organic photovoltaics (OPVs because of their high electron mobility. However, there are also considerable drawbacks for use in OPVs, such as negligible light absorption in the visible-near-IR regions, less compatibility with donor polymeric materials and high cost for synthesis and purification. Therefore, the investigation of non-fullerene acceptor materials that can potentially replace fullerene derivatives in OPVs is increasingly necessary, which gives rise to the possibility of fabricating all-polymer (polymer/polymer solar cells that can deliver higher performance and that are potentially cheaper than fullerene-based OPVs. Recently, considerable attention has been paid to donor-acceptor (D-A block copolymers, because of their promising applications as fullerene alternative materials in all-polymer solar cells. However, the synthesis of D-A block copolymers is still a challenge, and therefore, the establishment of an efficient synthetic method is now essential. This review highlights the recent advances in D-A block copolymers synthesis and their applications in all-polymer solar cells.

An Unfused-Core-Based Nonfullerene Acceptor Enables High-Efficiency Organic Solar Cells with Excellent Morphological Stability at High Temperatures.

Science.gov (United States)

Li, Shuixing; Zhan, Lingling; Liu, Feng; Ren, Jie; Shi, Minmin; Li, Chang-Zhi; Russell, Thomas P; Chen, Hongzheng

2018-02-01

Most nonfullerene acceptors developed so far for high-performance organic solar cells (OSCs) are designed in planar molecular geometry containing a fused-ring core. In this work, a new nonfullerene acceptor of DF-PCIC is synthesized with an unfused-ring core containing two cyclopentadithiophene (CPDT) moieties and one 2,5-difluorobenzene (DFB) group. A nearly planar geometry is realized through the F···H noncovalent interaction between CPDT and DFB for DF-PCIC. After proper optimizations, the OSCs with DF-PCIC as the acceptor and the polymer PBDB-T as the donor yield the best power conversion efficiency (PCE) of 10.14% with a high fill factor of 0.72. To the best of our knowledge, this efficiency is among the highest values for the OSCs with nonfullerene acceptors owning unfused-ring cores. Furthermore, no obvious morphological changes are observed for the thermally treated PBDB-T:DF-PCIC blended films, and the relevant devices can keep ≈70% of the original PCEs upon thermal treatment at 180 °C for 12 h. This tolerance of such a high temperature for so long time is rarely reported for fullerene-free OSCs, which might be due to the unique unfused-ring core of DF-PCIC. Therefore, the work provides new idea for the design of new nonfullerene acceptors applicable in commercial OSCs in the future. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymer solar cells with novel fullerene-based acceptor

International Nuclear Information System (INIS)

Riedel, I.; Martin, N.; Giacalone, F.; Segura, J.L.; Chirvase, D.; Parisi, J.; Dyakonov, V.

2004-01-01

Alternative acceptor materials are possible candidates to improve the optical absorption and/or the open circuit voltage of polymer-fullerene solar cells. We studied a novel fullerene-type acceptor, DPM-12, for application in polymer-fullerene bulk heterojunction photovoltaic devices. Though DPM-12 has the identical redox potentials as methanofullerene PCBM, surprisingly high open circuit voltages in the range V OC =0.95 V were measured for OC 1 C 10 -PPV:DPM-12-based samples. The potential for photovoltaic application was studied by means of photovoltaic characterization of solar cells including current-voltage measurements and external quantum yield spectroscopy. Further studies were carried out by profiling the solar cell parameters vs. temperature and white light intensity

Fluorescent and Colorimetric Molecular Recognition Probe for Hydrogen Bond Acceptors

OpenAIRE

Pike, Sarah Jane; Hunter, Christopher Alexander

2018-01-01

The association constants for formation of 1 : 1 complexes between a H-bond donor, 1-naphthol, and a diverse range of charged and neutral H-bond acceptors have been measured using UV/vis absorption and fluorescence emission titrations. The performance of 1-naphthol as a dual colorimetric and fluorescent molecular recognition probe for determining the H-bond acceptor (HBA) parameters of charged and neutral solutes has been investigated in three solvents. The data were employed to establish sel...

Direct view at colossal permittivity in donor-acceptor (Nb, In) co-doped rutile TiO2

International Nuclear Information System (INIS)

Mandal, Suman; Pal, Somnath; Hazarika, Abhijit; Kundu, Asish K.; Menon, Krishnakumar S. R.; Rioult, Maxime; Belkhou, Rachid

2016-01-01

Topical observations of colossal permittivity (CP) with low dielectric loss in donor-acceptor cations co-doped rutile TiO 2 have opened up several possibilities in microelectronics and energy-storage devices. Yet, the precise origin of the CP behavior, knowledge of which is essential to empower the device integration suitably, is highly disputed in the literature. From spectromicroscopic approach besides dielectric measurements, we explore that microscopic electronic inhomogeneities along with the nano-scale phase boundaries and the low temperature polaronic relaxation are mostly responsible for such a dielectric behavior, rather than electron-pinned defect-dipoles/grain-boundary effects as usually proposed. Donor-acceptor co-doping results in a controlled carrier-hopping inevitably influencing the dielectric loss while invariably upholding the CP value.

Methods for the synthesis of donor-acceptor cyclopropanes

Science.gov (United States)

Tomilov, Yu V.; Menchikov, L. G.; Novikov, R. A.; Ivanova, O. A.; Trushkov, I. V.

2018-03-01

The interest in cyclopropane derivatives is caused by the facts that, first, the three-carbon ring is present in quite a few natural and biologically active compounds and, second, compounds with this ring are convenient building blocks for the synthesis of diverse molecules (acyclic, alicyclic and heterocyclic). The carbon–carbon bonds in cyclopropane are kinetically rather inert; hence, they need to be activated to be involved in reactions. An efficient way of activation is to introduce vicinal electron-donating and electron-withdrawing substituents into the ring; these substrates are usually referred to as donor-acceptor cyclopropanes. This review gives a systematic account of the key methods for the synthesis of donor-acceptor cyclopropanes. The most important among them are reactions of nucleophilic alkenes with diazo compounds and iodonium ylides and approaches based on reactions of electrophilic alkenes with sulfur ylides (the Corey–Chaykovsky reaction). Among other methods used for this purpose, noteworthy are cycloalkylation of CH-acids, addition of α-halocarbonyl compounds to alkenes, cyclization via 1,3-elimination, reactions of alkenes with halocarbenes followed by reduction, the Simmons–Smith reaction and some other. The scope of applicability and prospects of various methods for the synthesis of donor-acceptor cyclopropanes are discussed. The bibliography includes 530 references.

Magnetospheric Multiscale (MMS) Observation of Plasma Velocity-Space Cascade Processes

Science.gov (United States)

Parashar, T. N.; Servidio, S.; Matthaeus, W. H.; Chasapis, A.; Perrone, D.; Valentini, F.; Veltri, P.; Gershman, D. J.; Schwartz, S. J.; Giles, B. L.; Fuselier, S. A.; Phan, T.; Burch, J.

2017-12-01

Plasma turbulence is investigated using high-resolution ion velocity distributions, measured by theMagnetospheric Multiscale Mission (MMS) in the Earth's magnetosheath. The particle distributionmanifests large fluctuations, suggesting a cascade-like process in velocity space, invoked by theoristsfor many years. This complex velocity space structure is investigated using a three-dimensional Hermitetransform that reveals a power law distribution of moments. A Kolmogorov approach leads directlyto a range of predictions for this phase-space cascade. The scaling theory is in agreement withobservations, suggesting a new path for the study of plasma turbulence in weakly collisional spaceand astrophysical plasmas.

Electron Donor Acceptor Interactions. Final Progress Report

Energy Technology Data Exchange (ETDEWEB)

Moore, Ana L. [Arizona State Univ., Tempe, AZ (United States)

2002-08-16

The Gordon Research Conference (GRC) on Electron Donor Acceptor Interactions was held at Salve Regina University, Newport, Rhode Island, 8/11-16/02. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

Effect of deviation from stoichiometry on the nature of shallow acceptor states in CdTe crystals

International Nuclear Information System (INIS)

Agrinskaya, N.V.; Shashkova, V.V.

1988-01-01

Photoconductivity and photoluminescence spectra in the region of donor-acceptor recombination of pure CdTe crystals, grown under conditions of different deviations from stoichiometry are investigated. It is shown that the predominant type of minor acceptors in n-type crystals (with Cd excess) differs from acceptors in p-type crystals (with Te excess). Residual acceptors replacing Te(P, As) prevail in n-type crystals and acceptors replacing Cd(Li, Na) prevail in p-type crystals. As a result of p-type crystal annealing a change of the type of prevailing aceptors accurs in Cd pairs (bands linked with P, As prevail) which testifies to the residual impurity reconstruction in Cd and Te sublattices

High-Performance All-Polymer Solar Cells Achieved by Fused Perylenediimide-Based Conjugated Polymer Acceptors.

Science.gov (United States)

Yin, Yuli; Yang, Jing; Guo, Fengyun; Zhou, Erjun; Zhao, Liancheng; Zhang, Yong

2018-05-09

We report three n-type polymeric electron acceptors (PFPDI-TT, PFPDI-T, and PFPDI-Se) based on the fused perylene diimide (FPDI) and thieno[3,2- b]thiophene, thiophene, or selenophene units for all-polymer solar cells (all-PSCs). These FPDI-based polymer acceptors exhibit strong absorption between 350 and 650 nm with wide optical bandgap of 1.86-1.91 eV, showing good absorption compensation with the narrow bandgap polymer donor. The lowest unoccupied molecular orbital (LUMO) energy levels were located at around -4.11 eV, which are comparable with those of the fullerene derivatives and other small molecular electron acceptors. The conventional all-PSCs based on the three polymer acceptors and PTB7-Th as polymer donor gave remarkable power conversion efficiencies (PCEs) of >6%, and the PFPDI-Se-based all-PSC achieved the highest PCE of 6.58% with a short-circuit current density ( J sc ) of 13.96 mA/cm 2 , an open-circuit voltage ( V oc ) of 0.76 V, and a fill factor (FF) of 62.0%. More interestingly, our results indicate that the photovoltaic performances of the FPDI-based polymer acceptors are mainly determined by the FPDI unit with a small effect from the comonomers, which is quite different from the others reported rylenediimide-based polymer acceptors. This intriguing phenomenon is speculated as the huge geometry configuration of the FPDI unit, which minimizes the effect of the comonomer. These results highlight a promising future for the application of the FPDI-based polymer acceptors in the highly efficient all-PSCs.

UHF RiverSonde Observations of Water Surface Velocity at Threemile Slough, California

National Research Council Canada - National Science Library

Teague, Calvin C; Barrick, Donald E; Lilleboe, Peter M; Cheng, Ralph T; Ruhl, Catherine A

2005-01-01

.... The velocity is measured every 15 minutes by an ultrasonic velocity meter (UVM) which determines the water velocity from two-way acoustic propagation time-difference measurements made across the channel...

Conformational dynamics of semiflexibly bridged electron donor-acceptor systems comprising long aliphatic tails

NARCIS (Netherlands)

Bleisteiner, B.; Marian, T.; Schneider, S.; Brouwer, A.M.; Verhoeven, J.W.

2001-01-01

In continuation of our previous work on the conformational dynamics (harpooning mechanism) of semiflexibly bridged electron donor-acceptor systems we have studied a derivative with two long aliphatic chains tethered to the donor and acceptor moieties, respectively. The fitting of the time- and

Ex-situ activation of magnesium acceptors in InGaN/LED-structures

Energy Technology Data Exchange (ETDEWEB)

Kusch, Gunnar; Frentrup, Martin; Stellmach, Joachim; Kolbe, Tim; Wernicke, Tim; Pristovsek, Markus; Kneissl, Michael [Technische Universitaet Berlin, Institut fuer Festkoerperphysik, Hardenbergstr. 36, 10623 Berlin (Germany)

2011-07-01

One of the main problems limiting the output power of group-III-nitride compound light emitting diodes (LEDs) and laser diodes (LD) is the p-doping of nitrides with magnesium (Mg). During metal-organic vapor phase epitaxy (MOVPE) growth of (Al)GaN:Mg magnesium acceptors are passivated by hydrogen (H). By thermal annealing under nitrogen atmosphere the Mg-H bond can be cracked, thus activating the Mg acceptor. We have investigated ex-situ Mg-activation of the p-GaN layer and p-AlGaN electron blocking layer (EBL) in LEDs grown by MOVPE. Especially the activation of the AlGaN EBL is crucial. Simulations show, that a high doping level is required for effective electron blocking and a high injection efficiency. Additionally the acceptor activation energy is expected to increase with increasing Al-content, reducing the free hole concentration in the EBL. Electroluminescence spectroscopy (EL) was performed to determine the influence of the activation on the external quantum efficiency of the LED structure. Furthermore we used CV measurements to determine the Mg-acceptor concentration.

Sterilisation: characteristics of vasectomy acceptors in Delhi.

Science.gov (United States)

Sarkar, N N

1993-01-01

The place of vasectomy within the sterilisation programme in Delhi over the period 1983-88 is reviewed and data on vasectomy acceptance and characteristics of acceptors are analysed. Findings suggest a need to improve the strategy for the promotion of vasectomy within the metropolis.

Direct view at colossal permittivity in donor-acceptor (Nb, In) co-doped rutile TiO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Mandal, Suman, E-mail: suman.mandal@sscu.iisc.ernet.in; Pal, Somnath; Hazarika, Abhijit [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012 (India); Kundu, Asish K.; Menon, Krishnakumar S. R. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, Kolkata 700064 (India); Rioult, Maxime; Belkhou, Rachid [Synchrotron SOLEIL, L' Orme des Merisiers Saint-Aubin, 91192 Gif-sur-Yvette (France)

2016-08-29

Topical observations of colossal permittivity (CP) with low dielectric loss in donor-acceptor cations co-doped rutile TiO{sub 2} have opened up several possibilities in microelectronics and energy-storage devices. Yet, the precise origin of the CP behavior, knowledge of which is essential to empower the device integration suitably, is highly disputed in the literature. From spectromicroscopic approach besides dielectric measurements, we explore that microscopic electronic inhomogeneities along with the nano-scale phase boundaries and the low temperature polaronic relaxation are mostly responsible for such a dielectric behavior, rather than electron-pinned defect-dipoles/grain-boundary effects as usually proposed. Donor-acceptor co-doping results in a controlled carrier-hopping inevitably influencing the dielectric loss while invariably upholding the CP value.

Atomic scale images of acceptors in III-V semiconductors. Band bending, tunneling paths and wave functions

Energy Technology Data Exchange (ETDEWEB)

Loth, S.

2007-10-26

This thesis reports measurements of single dopant atoms in III-V semiconductors with low temperature Scanning Tunneling Microscopy (STM) and Scanning Tunneling Spectroscopy (STS). It investigates the anisotropic spatial distribution of acceptor induced tunneling processes at the {l_brace}110{r_brace} cleavage planes. Two different tunneling processes are identified: conventional imaging of the squared acceptor wave function and resonant tunneling at the charged acceptor. A thorough analysis of the tip induced space charge layers identifies characteristic bias windows for each tunnel process. The symmetry of the host crystal's band structure determines the spatial distribution of the tunneling paths for both processes. Symmetry reducing effects at the surface are responsible for a pronounced asymmetry of the acceptor contrasts along the principal [001] axis. Uniaxial strain fields due to surface relaxation and spin orbit interaction of the tip induced electric field are discussed on the basis of band structure calculations. High-resolution STS studies of acceptor atoms in an operating p-i-n diode confirm that an electric field indeed changes the acceptor contrasts. In conclusion, the anisotropic contrasts of acceptors are created by the host crystal's band structure and concomitant symmetry reduction effects at the surface. (orig.)

New donor-acceptor-donor molecules based on quinoline acceptor unit with Schiff base bridge: synthesis and characterization

Energy Technology Data Exchange (ETDEWEB)

Kotowicz, Sonia [Institute of Chemistry, University of Silesia, 9 Szkolna Street, 40-006 Katowice (Poland); Siwy, Mariola [Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 34 M. Curie-Sklodowska Str., 41-819 Zabrze (Poland); Filapek, Michal; Malecki, Jan G. [Institute of Chemistry, University of Silesia, 9 Szkolna Street, 40-006 Katowice (Poland); Smolarek, Karolina; Grzelak, Justyna; Mackowski, Sebastian [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, 5 Grudziadzka Str., 87-100 Torun (Poland); Slodek, Aneta, E-mail: aneta.slodek@us.edu.pl [Institute of Chemistry, University of Silesia, 9 Szkolna Street, 40-006 Katowice (Poland); Schab-Balcerzak, Ewa, E-mail: ewa.schab-balcerzak@us.edu.pl [Institute of Chemistry, University of Silesia, 9 Szkolna Street, 40-006 Katowice (Poland); Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 34 M. Curie-Sklodowska Str., 41-819 Zabrze (Poland)

2017-03-15

Three solution-processable small organic molecules bearing quinoline as electron-accepting moiety were synthesized via condensation reaction of novel 6-amino-2-(2,2’-bithiophen-5-yl)-4-phenylquinoline with 2,2’-bithiophene-5-carboxaldehyde, 9-ethyl-9H-carbazole-3-carbaldehyde and 9-phenanthrenecarboxaldehyde. The presence of alternating electron-donating and accepting units results in a donor-acceptor-donor architecture of these molecular systems. Thermal, photophysical, and electrochemical properties of these small molecules were examined and the experimental results were supported by the density functional theory calculations. The obtained molecular systems exhibited high thermal stability with decomposition temperatures (5% weight loss) exceeding 330 °C in nitrogen atmosphere. It was found, based on DSC measurements, that investigated Schiff bases form amorphous material with glass transition temperatures between 88 and 190 °C. They also showed a UV–vis absorption in the range of 250–500 nm both in solution and in solid state as film and blend with PMMA and PVK. Photoluminescence measurements revealed moderately strong blue-light emission of the imines in solution as well as in PMMA blend with quantum yields in the range of 2–26%. In the case of imines dispersed in PVK matrix the emission of green light was mainly observed. In addition, when mixed with plasmonically active silver nanowires, the compounds exhibit relatively strong electroluminescence signal, associated with plasmonics enhancement, as evidenced by high-resolution photoluminescence imaging. The energy band gap estimated based on cyclic voltammetry was between 2.38 and 2.61 eV. - Highlights: • New Schiff bases possess donor-acceptor-imine-bridge-donor architecture were synthesized and examined. • Thorough characterization of optical and electrochemical properties of novel Schiff bases has been carried out. • Optical and electrochemical measurements were compared with DFT

Physics of positronium acceptor complex formation reactions

International Nuclear Information System (INIS)

Gangopadhyay, Debarshi; Ganguly, Bichitra Nandi; Mukherjee, Tapas; Dutta-Roy, Binayak

2002-01-01

Positronium (P s ) reaction rates (κ) with weak Acceptors (Ac) leading to the formation of Ps-Ac complexes show several interesting features: non-monotonic temperature dependence of κ(departing from the usual Arrhenius behaviour), considerable variability of κ with respect to different solvents, and anomalies in response to external pressure at ambient temperature. The object of this work is to explain all these phenomena using a remarkably simple bubble model (the widely used model for the pick-off component of ortho-positronium decay in liquids), which has been revisited several times in the context and as a result smooth diffuse boundary of the bubble was suggested that yields reasonable agreement of the experimental data. The contractile force on the bubble relies much on the surface tension of the liquid, through our calculation the notion of critical surface tension emerges and enables us to explain the experimental observations satisfactorily. (author)

Triplet Tellurophene-Based Acceptors for Organic Solar Cells.

Science.gov (United States)

Yang, Lei; Gu, Wenxing; Lv, Lei; Chen, Yusheng; Yang, Yufei; Ye, Pan; Wu, Jianfei; Hong, Ling; Peng, Aidong; Huang, Hui

2018-01-22

Triplet materials have been employed to achieve high-performing organic solar cells (OSCs) by extending the exciton lifetime and diffusion distances, while the triplet non-fullerene acceptor materials have never been reported for bulk heterojunction OSCs. Herein, for the first time, three triplet molecular acceptors based on tellurophene with different degrees of ring fusing were designed and synthesized for OSCs. Significantly, these molecules have long exciton lifetime and diffusion lengths, leading to efficient power conversion efficiency (7.52 %), which is the highest value for tellurophene-based OSCs. The influence of the extent of ring fusing on molecular geometry and OSCs performance was investigated to show the power conversion efficiencies (PCEs) continuously increased along with increasing the extent of ring fusing. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organic Donor-Acceptor Complexes as Novel Organic Semiconductors.

Science.gov (United States)

Zhang, Jing; Xu, Wei; Sheng, Peng; Zhao, Guangyao; Zhu, Daoben

2017-07-18

Organic donor-acceptor (DA) complexes have attracted wide attention in recent decades, resulting in the rapid development of organic binary system electronics. The design and synthesis of organic DA complexes with a variety of component structures have mainly focused on metallicity (or even superconductivity), emission, or ferroelectricity studies. Further efforts have been made in high-performance electronic investigations. The chemical versatility of organic semiconductors provides DA complexes with a great number of possibilities for semiconducting applications. Organic DA complexes extend the semiconductor family and promote charge separation and transport in organic field-effect transistors (OFETs) and organic photovoltaics (OPVs). In OFETs, the organic complex serves as an active layer across extraordinary charge pathways, ensuring the efficient transport of induced charges. Although an increasing number of organic semiconductors have been reported to exhibit good p- or n-type properties (mobilities higher than 1 or even 10 cm 2 V -1 s -1 ), critical scientific challenges remain in utilizing the advantages of existing semiconductor materials for more and wider applications while maintaining less complicated synthetic or device fabrication processes. DA complex materials have revealed new insight: their unique molecular packing and structure-property relationships. The combination of donors and acceptors could offer practical advantages compared with their unimolecular materials. First, growing crystals of DA complexes with densely packed structures will reduce impurities and traps from the self-assembly process. Second, complexes based on the original structural components could form superior mixture stacking, which can facilitate charge transport depending on the driving force in the coassembly process. Third, the effective use of organic semiconductors can lead to tunable band structures, allowing the operation mode (p- or n-type) of the transistor to be

Economical and accurate protocol for calculating hydrogen-bond-acceptor strengths.

Science.gov (United States)

El Kerdawy, Ahmed; Tautermann, Christofer S; Clark, Timothy; Fox, Thomas

2013-12-23

A series of density functional/basis set combinations and second-order Møller-Plesset calculations have been used to test their ability to reproduce the trends observed experimentally for the strengths of hydrogen-bond acceptors in order to identify computationally efficient techniques for routine use in the computational drug-design process. The effects of functionals, basis sets, counterpoise corrections, and constraints on the optimized geometries were tested and analyzed, and recommendations (M06-2X/cc-pVDZ and X3LYP/cc-pVDZ with single-point counterpoise corrections or X3LYP/aug-cc-pVDZ without counterpoise) were made for suitable moderately high-throughput techniques.

Magnetic thaw-down and boil-off due to magneto acceptors in 2DEG

International Nuclear Information System (INIS)

Chaubet, C.; Raymond, A.; Bisotto, I.; Harmand, J. C.; Kubisa, M.; Zawadzki, W.

2013-01-01

The Quantum Hall Effect (QHE) and Shubnikov-de Haas effect are investigated experimentally using n type modulation-doped GaAs/GaAlAs quantum wells (QWs) additionally doped in the well with beryllium acceptor atoms. It is presently shown that the localized magneto-acceptor (MA) states which possess discrete energies above the corresponding Landau levels (LLs) lead to two observable effects in magneto-transport: magnetic thaw-down and magnetic boil-off of 2D electrons. Both effects are related to the fact that electrons occupying the localized MA states cannot conduct. Thus in the thaw-down effect the electrons fall down from the MA states to the free Landau states. This leads to a shift of the Hall plateau towards higher magnetic fields as a consequence of an increase of the 2D electron density N S . In the boil-off effect the electrons are pushed from the free Landau states to the empty MA states under high enough Hall electric field. This process has an avalanche character leading to a dramatic increase of magneto-resistance, consequence of a decrease of N S

Vacancy clustering and acceptor activation in nitrogen-implanted ZnO

Science.gov (United States)

Børseth, Thomas Moe; Tuomisto, Filip; Christensen, Jens S.; Monakhov, Edouard V.; Svensson, Bengt G.; Kuznetsov, Andrej Yu.

2008-01-01

The role of vacancy clustering and acceptor activation on resistivity evolution in N ion-implanted n -type hydrothermally grown bulk ZnO has been investigated by positron annihilation spectroscopy, resistivity measurements, and chemical profiling. Room temperature 220keV N implantation using doses in the low 1015cm-2 range induces small and big vacancy clusters containing at least 2 and 3-4 Zn vacancies, respectively. The small clusters are present already in as-implanted samples and remain stable up to 1000°C with no significant effect on the resistivity evolution. In contrast, formation of the big clusters at 600°C is associated with a significant increase in the free electron concentration attributed to gettering of amphoteric Li impurities by these clusters. Further annealing at 800°C results in a dramatic decrease in the free electron concentration correlated with activation of 1016-1017cm-3 acceptors likely to be N and/or Li related. The samples remain n type, however, and further annealing at 1000°C results in passivation of the acceptor states while the big clusters dissociate.

Bond of donor-acceptor interaction in metal-ligand system with energies of Fermi electrons

International Nuclear Information System (INIS)

Vlasov, Yu.V.; Khentov, V.Ya.; Velikanova, L.N.; Semchenko, V.V.

1993-01-01

Role of quantum nature of metal (W, Mo and others) in donor-acceptor interaction of metal salicylalaniline - aprotic solvent was discussed. The dependence of dissolution rate and activation energy of donor-acceptor interaction on electron energy was established

On the Molecular Origin of Charge Separation at the Donor-Acceptor Interface

KAUST Repository

Sini, Gjergji

2018-01-22

Fullerene-based acceptors have dominated organic solar cells for almost two decades. It is only within the last few years that alternative acceptors rival their dominance, introducing much more flexibility in the optoelectronic properties of these material blends. However, a fundamental physical understanding of the processes that drive charge separation at organic heterojunctions is still missing, but urgently needed to direct further material improvements. Here a combined experimental and theoretical approach is used to understand the intimate mechanisms by which molecular structure contributes to exciton dissociation, charge separation, and charge recombination at the donor–acceptor (D–A) interface. Model systems comprised of polythiophene-based donor and rylene diimide-based acceptor polymers are used and a detailed density functional theory (DFT) investigation is performed. The results point to the roles that geometric deformations and direct-contact intermolecular polarization play in establishing a driving force (energy gradient) for the optoelectronic processes taking place at the interface. A substantial impact for this driving force is found to stem from polymer deformations at the interface, a finding that can clearly lead to new design approaches in the development of the next generation of conjugated polymers and small molecules.

Preliminary results from the oribiting solar observatory 8: Velocities in the solar chromosphere observed in the Si II lambda1816 line

International Nuclear Information System (INIS)

Chipman, E.G.; Bruner, E.C. Jr.; Shine, R.A.; Lites, B.W.; Rottman, G.J.; Athay, R.G.; White, O.R.

1976-01-01

The University of Colorado instrument on OSO-8 was used to measure repeated line profiles of the Si II lambda1816 line over quiet and active areas of approximately 20'' by 5'' during entire orbits of 60 minutes. Velocity oscillations with periods near 300 s are observed in approximately half of the time series, and periods near 180 s are sometimes observed. Periodic intensity variations are also observed at both of these periods. For both periods, the intensity leads the velocity in phase by approximately 30degree

Optical spacing effect in organic photovoltaic cells incorporating a dilute acceptor layer

Energy Technology Data Exchange (ETDEWEB)

Menke, S. Matthew; Lindsay, Christopher D.; Holmes, Russell J. [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2014-06-16

The addition of spacing layers in organic photovoltaic cells (OPVs) can enhance light absorption by optimizing the spatial distribution of the incident optical field in the multilayer structure. We explore the optical spacing effect in OPVs achieved using a diluted electron acceptor layer of C{sub 60}. While optical spacing is often realized by optimizing buffer layer thickness, we find that optical spacing via dilution leads to cells with similar or enhanced photocurrent. This is observed despite a smaller quantity of absorbing molecules, suggesting a more efficient use of absorbed photons. In fact, dilution is found to concentrate optical absorption near the electron donor-acceptor interface, resulting in a marked increase in the exciton diffusion efficiency. Contrasting the use of changes in thickness to engineer optical absorption, the use of dilution does not significantly alter the overall thickness of the OPV. Optical spacing via dilution is shown to be a viable alternative to more traditional optical spacing techniques and may be especially useful in the continued optimization of next-generation, tandem OPVs where it is important to minimize competition for optical absorption between individual sub-cells.

Optical spacing effect in organic photovoltaic cells incorporating a dilute acceptor layer

International Nuclear Information System (INIS)

Menke, S. Matthew; Lindsay, Christopher D.; Holmes, Russell J.

2014-01-01

The addition of spacing layers in organic photovoltaic cells (OPVs) can enhance light absorption by optimizing the spatial distribution of the incident optical field in the multilayer structure. We explore the optical spacing effect in OPVs achieved using a diluted electron acceptor layer of C 60 . While optical spacing is often realized by optimizing buffer layer thickness, we find that optical spacing via dilution leads to cells with similar or enhanced photocurrent. This is observed despite a smaller quantity of absorbing molecules, suggesting a more efficient use of absorbed photons. In fact, dilution is found to concentrate optical absorption near the electron donor-acceptor interface, resulting in a marked increase in the exciton diffusion efficiency. Contrasting the use of changes in thickness to engineer optical absorption, the use of dilution does not significantly alter the overall thickness of the OPV. Optical spacing via dilution is shown to be a viable alternative to more traditional optical spacing techniques and may be especially useful in the continued optimization of next-generation, tandem OPVs where it is important to minimize competition for optical absorption between individual sub-cells.

Partial purification of xylosyltransferase (XylT) from rat liver and characterization of endogenous acceptors

International Nuclear Information System (INIS)

Klinger, M.; Roden, L.

1986-01-01

The biosynthesis of the carbohydrate-protein linkage region of most proteoglycan species is initiated by transfer of xylose from UDP-xylose to serine hydroxyl groups in the core protein. The XylT catalyzing this reaction has been previously purified from embryonic chick cartilage and from a rat chondrosarcoma but not from a normal mammalian tissue. In this study, XylT was extracted from rat liver by homogenization in buffer containing 1 M KCl and was partially purified by chromatography on heparin-Sepharose, AH-Sepharose, and on Sepharose-linked tryptic fragments of silk fibroin. The eluate from the latter contained more than 40% of the applied activity and less than 5% of the protein. Gel chromatography of XylT eluted from heparin-Sepharose indicated a mol. wt. of 95,000 to 100,000. Incorporation of ( 3 H)xylose into endogenous acceptors in the crude extract amounted to more than 50% of the total observed with added substrate (silk fibroin). Of the total endogenous acceptor activity in the crude extract, 98% was not adsorbed to heparin-Sepharose and yielded a labeled product which was stable to treatment with 0.5 M NaOH at 20 0 C for 16 h; this material may have been glycogen. In contrast, most of the radioactivity incorporated into the endogenous acceptor in the heparin-Sepharose eluate was alkali-labile, as would be expected for the xylosylated core protein of a proteoglycan

Synthesis of OMS Materials and Investigation of Their Acceptor-Donor Characteristics.

Science.gov (United States)

Grajek, H; Paciura-Zadrożna, J; Choma, J; Michalski, E; Witkiewicz, Z

2012-10-01

Three ordered mesoporous siliceous (OMS) materials known as MCM41s-unmodified MCM-41C16 ("C16"), and two MCM41s with different surface functionalities: MCM-41C16-SH ("C16-SH") and MCM-41C16-NH 2 ("C16-NH 2 ")-were synthesized and studied by inverse gas chromatography in order to determine their acceptor-donor properties. The specific retention volumes of nonpolar and polar probes that were chromatographed on these ordered mesoporous silica adsorbents were evaluated under infinite dilution conditions. Two methods were employed to calculate the standard free energy of adsorption, Δ G ads , of each chromatographed probe on the basis its specific retention volume. These Δ G ads values were then employed to estimate the van der Waals contribution and the specific contribution of the free surface energy for each MCM41. DN values (donor numbers, based on the Gutmann scale) and AN* values (acceptor numbers, based on the Riddle-Fowkes scale) were employed to determine the values of parameters that characterize the ability of the MCM41s to act as electron acceptors (parameter: K A ) and donors (parameter: K D ). Considering the different compositions of the probes, each of which has different acceptor-donor properties, a new chromatographic test to supplement the Grob test is suggested.

Positively charged phosphorus as a hydrogen bond acceptor

DEFF Research Database (Denmark)

Hansen, Anne Schou; Du, Lin; Kjærgaard, Henrik Grum

2014-01-01

Phosphorus (P) is an element that is essential to the life of all organisms, and the atmospheric detection of phosphine suggests the existence of a volatile biogeochemical P cycle. Here, we investigate the ability of P to participate in the formation of OH···P hydrogen bonds. Three bimolecular......-stretching frequency red shifts and quantum chemical calculations, we find that P is an acceptor atom similar in strength to O and S and that all three P, O, and S atoms are weaker acceptors than N. The quantum chemical calculations show that both H and P in the OH···P hydrogen bond have partial positive charges......, as expected from their electronegativities. However, the electrostatic potentials show a negative potential area on the electron density surface around P that facilitates formation of hydrogen bonds....

UPDATED ANALYSIS OF THE UPWIND INTERPLANETARY HYDROGEN VELOCITY AS OBSERVED BY THE HUBBLE SPACE TELESCOPE DURING SOLAR CYCLE 23

International Nuclear Information System (INIS)

Vincent, Frederic E.; Ben-Jaffel, Lotfi; Harris, Walter M.

2011-01-01

The interplanetary hydrogen (IPH), a population of neutrals that fill the space between planets inside the heliosphere, carries the signature of the interstellar medium (ISM) and the heliospheric interface. As the incoming ISM-ionized component deflects at the heliopause, charge exchange reactions decelerate the bulk motion of the neutrals that penetrate the heliosphere. Inside the heliosphere, the IPH bulk velocity is further affected by solar gravity, radiation pressure, and ionization processes, with the latter two processes dependent on solar activity. Solar cycle 23 provided the first partial temporal map of the IPH velocity, including measurements from the Hubble Space Telescope (HST) spectrometers (Goddard High Resolution Spectrograph (GHRS) and Space Telescope Imaging Spectrograph (STIS)) and the Solar and Heliospheric Observatory/Solar Wind ANisotropies (SWAN) instrument. We present an updated analysis of IPH velocity measurements from GHRS and STIS and compare these results with those of SWAN and two different time-dependent models. Our reanalysis of STIS data reveals a significant change in IPH velocity relative to earlier reports, because of the contamination by geocoronal oxygen that was not accounted for. While current models of the heliospheric interface predict the observed IPH velocity for solar maximum, they are not consistent with data covering solar minimum. With updates to the HST data points, we now find that all data can be fit by the existing models to within 1σ, with the exception of SWAN observations taken at solar minimum (1997/1998). We conclude that the current data lack the temporal coverage and/or precision necessary to determine the detailed characteristics of the solar cycle dependence. Hence, new observations are merited.

A Nonfullerene Small Molecule Acceptor with 3D Interlocking Geometry Enabling Efficient Organic Solar Cells.

Science.gov (United States)

Lee, Jaewon; Singh, Ranbir; Sin, Dong Hun; Kim, Heung Gyu; Song, Kyu Chan; Cho, Kilwon

2016-01-06

A new 3D nonfullerene small-molecule acceptor is reported. The 3D interlocking geometry of the small-molecule acceptor enables uniform molecular conformation and strong intermolecular connectivity, facilitating favorable nanoscale phase separation and electron charge transfer. By employing both a novel polymer donor and a nonfullerene small-molecule acceptor in the solution-processed organic solar cells, a high-power conversion efficiency of close to 6% is demonstrated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT).

Science.gov (United States)

Slouka, Christoph; Kainz, Theresa; Navickas, Edvinas; Walch, Gregor; Hutter, Herbert; Reichmann, Klaus; Fleig, Jürgen

2016-11-22

The different properties of acceptor-doped (hard) and donor-doped (soft) lead zirconate titanate (PZT) ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La 3+ donor-doped, Fe 3+ acceptor-doped and La 3+ /Fe 3+ -co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT.

The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT

Directory of Open Access Journals (Sweden)

Christoph Slouka

2016-11-01

Full Text Available The different properties of acceptor-doped (hard and donor-doped (soft lead zirconate titanate (PZT ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La3+ donor-doped, Fe3+ acceptor-doped and La3+/Fe3+-co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT.

Collective cell migration without proliferation: density determines cell velocity and wave velocity

Science.gov (United States)

Tlili, Sham; Gauquelin, Estelle; Li, Brigitte; Cardoso, Olivier; Ladoux, Benoît; Delanoë-Ayari, Hélène; Graner, François

2018-05-01

Collective cell migration contributes to embryogenesis, wound healing and tumour metastasis. Cell monolayer migration experiments help in understanding what determines the movement of cells far from the leading edge. Inhibiting cell proliferation limits cell density increase and prevents jamming; we observe long-duration migration and quantify space-time characteristics of the velocity profile over large length scales and time scales. Velocity waves propagate backwards and their frequency depends only on cell density at the moving front. Both cell average velocity and wave velocity increase linearly with the cell effective radius regardless of the distance to the front. Inhibiting lamellipodia decreases cell velocity while waves either disappear or have a lower frequency. Our model combines conservation laws, monolayer mechanical properties and a phenomenological coupling between strain and polarity: advancing cells pull on their followers, which then become polarized. With reasonable values of parameters, this model agrees with several of our experimental observations. Together, our experiments and model disantangle the respective contributions of active velocity and of proliferation in monolayer migration, explain how cells maintain their polarity far from the moving front, and highlight the importance of strain-polarity coupling and density in long-range information propagation.

An Efficient, “Burn in” Free Organic Solar Cell Employing a Nonfullerene Electron Acceptor

KAUST Repository

Cha, Hyojung; Wu, Jiaying; Wadsworth, Andrew; Nagitta, Jade; Limbu, Saurav; Pont, Sebastian; Li, Zhe; Searle, Justin; Wyatt, Mark F.; Baran, Derya; Kim, Ji-Seon; McCulloch, Iain; Durrant, James R.

2017-01-01

polymer blended with either the nonfullerene acceptor EH-IDTBR or the fullerene derivative, [6,6]-phenyl C71 butyric acid methyl ester (PC71 BM) as electron acceptors is reported. Inverted PffBT4T-2OD:EH-IDTBR blend solar cell fabricated without any

Interface effects on acceptor qubits in silicon and germanium

International Nuclear Information System (INIS)

Abadillo-Uriel, J C; Calderón, M J

2016-01-01

Dopant-based quantum computing implementations often require the dopants to be situated close to an interface to facilitate qubit manipulation with local gates. Interfaces not only modify the energies of the bound states but also affect their symmetry. Making use of the successful effective mass theory we study the energy spectra of acceptors in Si or Ge taking into account the quantum confinement, the dielectric mismatch and the central cell effects. The presence of an interface puts constraints to the allowed symmetries and leads to the splitting of the ground state in two Kramers doublets (Mol et al 2015 Appl. Phys. Lett. 106 203110). Inversion symmetry breaking also implies parity mixing which affects the allowed optical transitions. Consequences for acceptor qubits are discussed. (paper)

Substrate dependence of energy level alignment at the donor-acceptor interface in organic photovoltaic devices

International Nuclear Information System (INIS)

Zhou, Y.C.; Liu, Z.T.; Tang, J.X.; Lee, C.S.; Lee, S.T.

2009-01-01

The interface energy level alignment between copper phthalocyanine (CuPC) and fullerene (C60), the widely studied donor-acceptor pair in organic photovoltaics (OPVs), on indium-tin oxide (ITO) and Mg substrate was investigated. The CuPC/C60 interface formed on ITO shows a nearly common vacuum level, but a dipole and band bending exist, resulting in a 0.8 eV band offset at the same interface on Mg. This observation indicates that the energy difference between the highest occupied molecular orbital of CuPC and the lowest unoccupied molecular orbital of C60, which dictates the open circuit voltage of the CuPC/C60 OPV, can be tuned by the work function of the substrate. Furthermore, the substrate effect on the energy alignment at the donor/acceptor interface can satisfactorily explain that a device with an anode of a smaller work function can provide a higher open circuit voltage.

A novel donor-acceptor polymeric electrochromic material containing carbazole and 1,8-naphtalimide as subunit

Energy Technology Data Exchange (ETDEWEB)

Koyuncu, Fatma Baycan, E-mail: fatmabaycan@hotmail.co [Department of Chemistry, Faculty of Sciences and Arts, Canakkale Onsekiz Mart University, 17020 Canakkale (Turkey); Koyuncu, Sermet [Can Vocational School, Canakkale Onsekiz Mart University, 17400 Canakkale (Turkey); Ozdemir, Eyup, E-mail: eozdemir@comu.edu.t [Department of Chemistry, Faculty of Sciences and Arts, Canakkale Onsekiz Mart University, 17020 Canakkale (Turkey)

2010-07-01

We report here the synthesis of a novel polymeric electrochromic material containing carbazole (Cbz)-donor and 1,8-napthalimide-acceptor as subunit. The band gap E{sub g} was measured using UV-vis spectroscopy and compared with that obtained by cyclic voltammetry (CV). Due to intramolecular electron transfer from Cbz-donor to 1,8-napthalimide-acceptor, the fluorescence quenching was observed. When the spectro-electrochemical and electrochromic properties of polymer film were investigated, various tones of green color were obtained on the polymeric film. In the positive regime, the polymer film obtained thereby is dark green resulting from the association of carbazolylium cation radicals at oxidized state and then it can be bleached by electrochemical reduction. Besides, in the negative regime, yellowish green color of film converted to blue attributed to reduction of the 1,8-napthalimide moiety. Finally, the polymeric electrochromic exhibits multi-electrochromic behavior, high redox stability, high coloration efficiency and reasonable response time.

A novel donor-acceptor polymeric electrochromic material containing carbazole and 1,8-naphtalimide as subunit

International Nuclear Information System (INIS)

Koyuncu, Fatma Baycan; Koyuncu, Sermet; Ozdemir, Eyup

2010-01-01

We report here the synthesis of a novel polymeric electrochromic material containing carbazole (Cbz)-donor and 1,8-napthalimide-acceptor as subunit. The band gap E g was measured using UV-vis spectroscopy and compared with that obtained by cyclic voltammetry (CV). Due to intramolecular electron transfer from Cbz-donor to 1,8-napthalimide-acceptor, the fluorescence quenching was observed. When the spectro-electrochemical and electrochromic properties of polymer film were investigated, various tones of green color were obtained on the polymeric film. In the positive regime, the polymer film obtained thereby is dark green resulting from the association of carbazolylium cation radicals at oxidized state and then it can be bleached by electrochemical reduction. Besides, in the negative regime, yellowish green color of film converted to blue attributed to reduction of the 1,8-napthalimide moiety. Finally, the polymeric electrochromic exhibits multi-electrochromic behavior, high redox stability, high coloration efficiency and reasonable response time.

Electron paramagnetic resonance and electron-nuclear double resonance study of the neutral copper acceptor in ZnGeP sub 2 crystals

CERN Document Server

Stevens, K T; Setzler, S D; Schünemann, P G; Pollak, T M

2003-01-01

Electron paramagnetic resonance (EPR) and electron-nuclear double resonance have been used to characterize the neutral copper acceptor in ZnGeP sub 2 crystals. The copper substitutes for zinc and behaves as a conventional acceptor (i.e. the 3d electrons do not play a dominant role). Because of a high degree of compensation from native donors, the copper acceptors in our samples were initially in the nonparamagnetic singly ionized state (Cu sub Z sub n sup -). The paramagnetic neutral state (Cu sub Z sub n sup 0) was observed when the crystals were exposed to 632.8 nm or 1064 nm laser light while being held at a temperature below 50 K. The g matrix of the neutral copper acceptor is axial g sub p sub a sub r = 2.049 and g sub p sub e sub r sub p = 2.030), with the unique principal direction parallel to the tetragonal c axis of the crystal. The hyperfine and nuclear quadrupole matrices also exhibit c-axis symmetry (A sub p sub a sub r = 87.6 MHz, A sub p sub e sub r sub p = 34.8 MHz and P = 0.87 MHz for sup 6 su...

Vertical Rise Velocity of Equatorial Plasma Bubbles Estimated from Equatorial Atmosphere Radar Observations and High-Resolution Bubble Model Simulations

Science.gov (United States)

Yokoyama, T.; Ajith, K. K.; Yamamoto, M.; Niranjan, K.

2017-12-01

Equatorial plasma bubble (EPB) is a well-known phenomenon in the equatorial ionospheric F region. As it causes severe scintillation in the amplitude and phase of radio signals, it is important to understand and forecast the occurrence of EPBs from a space weather point of view. The development of EPBs is presently believed as an evolution of the generalized Rayleigh-Taylor instability. We have already developed a 3D high-resolution bubble (HIRB) model with a grid spacing of as small as 1 km and presented nonlinear growth of EPBs which shows very turbulent internal structures such as bifurcation and pinching. As EPBs have field-aligned structures, the latitude range that is affected by EPBs depends on the apex altitude of EPBs over the dip equator. However, it was not easy to observe the apex altitude and vertical rise velocity of EPBs. Equatorial Atmosphere Radar (EAR) in Indonesia is capable of steering radar beams quickly so that the growth phase of EPBs can be captured clearly. The vertical rise velocities of the EPBs observed around the midnight hours are significantly smaller compared to those observed in postsunset hours. Further, the vertical growth of the EPBs around midnight hours ceases at relatively lower altitudes, whereas the majority of EPBs at postsunset hours found to have grown beyond the maximum detectable altitude of the EAR. The HIRB model with varying background conditions are employed to investigate the possible factors that control the vertical rise velocity and maximum attainable altitudes of EPBs. The estimated rise velocities from EAR observations at both postsunset and midnight hours are, in general, consistent with the nonlinear evolution of EPBs from the HIRB model.

Virtual screening of electron acceptor materials for organic photovoltaic applications

International Nuclear Information System (INIS)

D Halls, Mathew; Giesen, David J; Goldberg, Alexander; Djurovich, Peter J; Sommer, Jonathan; McAnally, Eric; Thompson, Mark E

2013-01-01

Virtual screening involves the generation of structure libraries, automated analysis to predict properties related to application performance and subsequent screening to identify lead systems and estimate critical structure–property limits across a targeted chemical design space. This approach holds great promise for informing experimental discovery and development efforts for next-generation materials, such as organic semiconductors. In this work, the virtual screening approach is illustrated for nitrogen-substituted pentacene molecules to identify systems for development as electron acceptor materials for use in organic photovoltaic (OPV) devices. A structure library of tetra-azapentacenes (TAPs) was generated by substituting four nitrogens for CH at 12 sites on the pentacene molecular framework. Molecular properties (e.g. E LUMO , E g and μ) were computed for each candidate structure using hybrid DFT at the B3LYP/6-311G** level of theory. The resulting TAPs library was then analyzed with respect to intrinsic properties associated with OPV acceptor performance. Marcus reorganization energies for charge transport for the most favorable TAP candidates were then calculated to further determine suitability as OPV electron acceptors. The synthesis, characterization and OPV device testing of TAP materials is underway, guided by these results. (paper)

Lipase-catalyzed biodiesel synthesis with different acyl acceptors

Directory of Open Access Journals (Sweden)

Ognjanović Nevena D.

2008-01-01

Full Text Available Biodiesel is an alternative fuel for diesel engine that is environmentally acceptable. Conventionally, biodiesel is produced by transesterification of triglycerides and short alcohols in the presence of an acid or an alkaline catalyst. There are several problems associated with this kind of production that can be resolved by using lipase as the biocatalyst. The aim of the present work was to investigate novel acyl acceptors for biodiesel production. 2-Propanol and n-butanol have a less negative effect on lipase stability, and they also improve low temperature properties of the fuel. However, excess alcohol leads to inactivation of the enzyme, and glycerol, a major byproduct, can block the immobilized enzyme, resulting in low enzymatic activity. This problem was solved by using methyl acetate as acyl acceptor. Triacetylglycerol is produced instead of glycerol, and it has no negative effect on the activity of the lipase.

Complexes due to donor-acceptor-type transitions in GaAs

International Nuclear Information System (INIS)

Reynolds, D.C.; Litton, C.W.; Almassy, R.J.; McCoy, G.L.; Nam, S.B.

1980-01-01

A sharp line transition at 1.51385 eV has been observed in the photoluminescence spectra of an epitaxially grown crystal of GaAs. A Si 3 N 4 cap was applied by plasma deposition and the crystal was then annealed at 850 0 C for 15 min. The sharp emission line was observed after annealing. This transition was analyzed in perturbing magnetic and strain fields and is shown to result from a donor-acceptor-type complex. Three additional sharp line transitions are reported and the behavior of all of these transitions is compared with the behavior of similar transitions reported in the literature. Models for the complexes involved are re-examined and components of the complexes are suggested. All of the sharp line transitions were introduced in the growing process with the exception of the 1.51385-eV line which was introduced in the capping and annealing process

Excitation and recombination of donor-acceptor pairs in ZnTe

International Nuclear Information System (INIS)

Nakashima, S.; Yasuda, S.

1979-01-01

The photoluminescence spectra and its excitation spectra of the donor-acceptor pairs are observed in ZnTe crystals doped with Li and As in the region below the bandgap energy. The relaxation of electrons and holes into the first excited state of d-a pairs is studied for the three excitation processes: (1) bound-to-bound transitions, (2) bound-to-free transitions, and (3) free-to-free transitions. It is concluded that most of the electrons and holes at the excited states of each impurity level are relaxed rapidly into their ground states before the occurrence of the recombination involving the excited states. For the excitation process (2), conduction electrons are preferentially trapped by positively charged pairs. The redistribution of bound holes by hopping is suggested to explain the broad d-a emission band observed for the bound-to-free excitation for very distant pairs. (author)

Effect of annealing on metastable shallow acceptors in Mg-doped GaN layers grown on GaN substrates

OpenAIRE

Pozina, Galia; Hemmingsson, Carl; Paskov, Plamen P.; Bergman, Peder; Monemar, Bo; Kawashima, T.; Amano, H.; Akasaki, I.; Usui, A.

2008-01-01

Mg-doped GaN layers grown by metal-organic vapor phase epitaxy on GaN substrates produced by the halide vapor phase technique demonstrate metastability of the near-band-gap photoluminescence (PL). The acceptor bound exciton (ABE) line possibly related to the C acceptor vanishes in as-grown samples within a few minutes under UV laser illumination. Annealing activates the more stable Mg acceptors and passivates C acceptors. Consequently, only the ABE line related to Mg is dominant in PL spectra...

Blinking fluorescence of single donor-acceptor pairs: important role of "dark'' states in resonance energy transfer via singlet levels.

Science.gov (United States)

Osad'ko, I S; Shchukina, A L

2012-06-01

The influence of triplet levels on Förster resonance energy transfer via singlet levels in donor-acceptor (D-A) pairs is studied. Four types of D-A pair are considered: (i) two-level donor and two-level acceptor, (ii) three-level donor and two-level acceptor, (iii) two-level donor and three-level acceptor, and (iv) three-level donor and three-level acceptor. If singlet-triplet transitions in a three-level acceptor molecule are ineffective, the energy transfer efficiency E=I_{A}/(I_{A}+I_{D}), where I_{D} and I_{A} are the average intensities of donor and acceptor fluorescence, can be described by the simple theoretical equation E(F)=FT_{D}/(1+FT_{D}). Here F is the rate of energy transfer, and T_{D} is the donor fluorescence lifetime. In accordance with the last equation, 100% of the donor electronic energy can be transferred to an acceptor molecule at FT_{D}≫1. However, if singlet-triplet transitions in a three-level acceptor molecule are effective, the energy transfer efficiency is described by another theoretical equation, E(F)=F[over ¯](F)T_{D}/[1+F[over ¯](F)T_{D}]. Here F[over ¯](F) is a function of F depending on singlet-triplet transitions in both donor and acceptor molecules. Expressions for the functions F[over ¯](F) are derived. In this case the energy transfer efficiency will be far from 100% even at FT_{D}≫1. The character of the intensity fluctuations of donor and acceptor fluorescence indicates which of the two equations for E(F) should be used to find the value of the rate F. Therefore, random time instants of photon emission in both donor and acceptor fluorescence are calculated by the Monte Carlo method for all four types of D-A pair. Theoretical expressions for start-stop correlators (waiting time distributions) in donor and acceptor fluorescence are derived. The probabilities w_{N}^{D}(t) and w_{N}^{A}(t) of finding N photons of donor and acceptor fluorescence in the time interval t are calculated for various values of the energy

Developments in the chemistry and band gap engineering of donor-acceptor substituted conjugated polymers

NARCIS (Netherlands)

Mullekom, van H.A.M.; Vekemans, J.A.J.M.; Havinga, E.E.; Meijer, E.W.

2001-01-01

This paper reviews the tools to manipulate and minimize the band gap of conjugated (co)polymers. The effects of minimization of the bond length alternation and of the incorporation of donor-K-acceptor units are discussed in particular. A systematic study of a series of alternating donor-acceptor

Differences in gene expression of human xylosyltransferases and determination of acceptor specificities for various proteoglycans

Energy Technology Data Exchange (ETDEWEB)

Roch, Christina; Kuhn, Joachim; Kleesiek, Knut [Institut fuer Laboratoriums- und Transfusionsmedizin, Herz- und Diabeteszentrum NRW, Universitaetsklinik der Ruhr-Universitaet Bochum, 32545 Bad Oeynhausen (Germany); Goetting, Christian, E-mail: cgoetting@hdz-nrw.de [Institut fuer Laboratoriums- und Transfusionsmedizin, Herz- und Diabeteszentrum NRW, Universitaetsklinik der Ruhr-Universitaet Bochum, 32545 Bad Oeynhausen (Germany)

2010-01-01

The xylosyltransferase (XT) isoforms XT-I and XT-II initiate the posttranslational glycosaminoglycan (GAG) synthesis. Here, we determined the relative expression of both isoforms in 33 human cell lines. The majority of tested cell lines showed dominant XYLT2 gene expression, while only in 23132/87, JAR, NCI-H510A and THP-1 was the XT-I mRNA expression higher. Nearly equal expression levels were detected in six cell lines. Additionally, to shed light on putative differences in acceptor specificities the acceptor properties of potential acceptor sequences were determined. Peptides were expressed as glutathione-S-transferase fusion proteins containing putative or known GAG attachment sites of in vivo proteoglycans. Kinetic analysis showed that K{sub m} and V{sub max} values for XT-I mediated xylosylation were slightly higher than those for XT-II, and that XT-I showed a lesser stringency concerning the acceptor sequence. Mutagenesis of the bikunin peptide sequence in the G-S-G attachment site and flanking regions generated potential acceptor molecules. Here, mutations on the N-terminal side and the attachment site were found to be more susceptible to a loss of acceptor function than mutations in the C-terminus. Altogether the known consensus sequence a-a-a-a-G-S-G-a-a/G-a ('a' representing Asp or Glu) for XT-I mediated xylosylation could be approved and additionally extended to apply to XT-II as well.

Deep donor-acceptor pair recombination in bulk GaP studied by ODMR and DLTS techniques

International Nuclear Information System (INIS)

Awadelkarim, O.O.; Godlewski, M.; Monemar, B.

1989-01-01

Deep level transient spectroscopy (DLTS) and optically detected magnetic resonance (ODMR) are applied to study deep defect levels with photoluminescence bands observed in the near infrared region in S- and Te-doped bulk GaP crystals grown by the liquid encapsulated Czochralski method. The ODMR data suggest that the emission bands with maxima observed at 8000-8200 A (∼ 1.5 eV), common to both materials, and at 7750 A (1.6 eV), present only in GaP:Te, are due to donor-acceptor pair recombinations. The latter band, reported here for the first time, is tentatively associated with deep states observed by DLTS. (author) 19 refs., 5 figs

Auditory velocity discrimination in the horizontal plane at very high velocities.

Science.gov (United States)

Frissen, Ilja; Féron, François-Xavier; Guastavino, Catherine

2014-10-01

We determined velocity discrimination thresholds and Weber fractions for sounds revolving around the listener at very high velocities. Sounds used were a broadband white noise and two harmonic sounds with fundamental frequencies of 330 Hz and 1760 Hz. Experiment 1 used velocities ranging between 288°/s and 720°/s in an acoustically treated room and Experiment 2 used velocities between 288°/s and 576°/s in a highly reverberant hall. A third experiment addressed potential confounds in the first two experiments. The results show that people can reliably discriminate velocity at very high velocities and that both thresholds and Weber fractions decrease as velocity increases. These results violate Weber's law but are consistent with the empirical trend observed in the literature. While thresholds for the noise and 330 Hz harmonic stimulus were similar, those for the 1760 Hz harmonic stimulus were substantially higher. There were no reliable differences in velocity discrimination between the two acoustical environments, suggesting that auditory motion perception at high velocities is robust against the effects of reverberation. Copyright © 2014 Elsevier B.V. All rights reserved.

On the acceptor-related photoluminescence spectra of GaAs quantum-wire microcrystals: A model calculation

International Nuclear Information System (INIS)

Oliveira, L.E.; Porras Montenegro, N.; Latge, A.

1992-07-01

The acceptor-related photoluminescence spectrum of a GaAs quantum-wire microcrystal is theoretically investigated via a model calculation within the effective-mass approximation, with the acceptor envelope wave functions and binding energies calculated through a variational procedure. Typical theoretical photoluminescence spectra show two peaks associated to transitions from the n = 1 conduction subband electron gas to acceptors at the on-center and on-edge positions in the wire in good agreement with the recent experimental results by Hirum et al. (Appl. Phys. Lett. 59, 431 (1991)). (author). 14 refs, 3 figs

Magnetic thaw-down and boil-off due to magneto acceptors in 2DEG

Energy Technology Data Exchange (ETDEWEB)

Chaubet, C.; Raymond, A. [L2C UMR 5221, CNRS-Université Montpellier 2, Place E. Bataillon, 34090 Montpellier cedex 05 (France); Bisotto, I. [LNCMI, UPR 3228, CNRS-INSA-UJF-UPS, BP166, 38042 Grenoble, Cedex 9 (France); Harmand, J. C. [LPN, CNRS, route de Nozay, 91460 Marcoussis (France); Kubisa, M. [Institute of Physics, Wroclaw University of Technology, 50-370 Wroclaw (Poland); Zawadzki, W. [Institute of Physics, Polish Academy of Sciences, 02668 Warsaw (Poland)

2013-12-04

The Quantum Hall Effect (QHE) and Shubnikov-de Haas effect are investigated experimentally using n type modulation-doped GaAs/GaAlAs quantum wells (QWs) additionally doped in the well with beryllium acceptor atoms. It is presently shown that the localized magneto-acceptor (MA) states which possess discrete energies above the corresponding Landau levels (LLs) lead to two observable effects in magneto-transport: magnetic thaw-down and magnetic boil-off of 2D electrons. Both effects are related to the fact that electrons occupying the localized MA states cannot conduct. Thus in the thaw-down effect the electrons fall down from the MA states to the free Landau states. This leads to a shift of the Hall plateau towards higher magnetic fields as a consequence of an increase of the 2D electron density N{sub S}. In the boil-off effect the electrons are pushed from the free Landau states to the empty MA states under high enough Hall electric field. This process has an avalanche character leading to a dramatic increase of magneto-resistance, consequence of a decrease of N{sub S}.

Optically tunable spin-exchange energy at donor:acceptor interfaces in organic solar cells

International Nuclear Information System (INIS)

Li, Mingxing; Wang, Hongfeng; He, Lei; Zang, Huidong; Xu, Hengxing; Hu, Bin

2014-01-01

Spin-exchange energy is a critical parameter in controlling spin-dependent optic, electronic, and magnetic properties in organic materials. This article reports optically tunable spin-exchange energy by studying the line-shape characteristics in magnetic field effect of photocurrent developed from intermolecular charge-transfer states based on donor:acceptor (P3HT:PCBM) system. Specifically, we divide magnetic field effect of photocurrent into hyperfine (at low field   10 mT) regimes. We observe that increasing photoexcitation intensity can lead to a significant line-shape narrowing in magnetic field effect of photocurrent occurring at the spin-exchange regime. We analyze that the line-shape characteristics is essentially determined by the changing rate of magnetic field-dependent singlet/triplet ratio when a magnetic field perturbs the singlet-triplet transition through spin mixing. Based on our analysis, the line-shape narrowing results indicate that the spin-exchange energy at D:A interfaces can be optically changed by changing photoexcitation intensity through the interactions between intermolecular charge-transfer states. Therefore, our experimental results demonstrate an optical approach to change the spin-exchange energy through the interactions between intermolecular charge-transfer states at donor:acceptor interface in organic materials.

profile of intrauterine contraceptive device acceptors at the university

African Journals Online (AJOL)

ANNALS

Conclusion: The acceptors of intrauterine contraceptive devices in our center were ... Conclusion: Les accepteurs de la contraception de substances médicamentenses dans notre centre .... sterilization due to cultural reasons is very low,13 the.

Förster Resonance Energy Transfer between Quantum Dot Donors and Quantum Dot Acceptors

Science.gov (United States)

Chou, Kenny F.; Dennis, Allison M.

2015-01-01

Förster (or fluorescence) resonance energy transfer amongst semiconductor quantum dots (QDs) is reviewed, with particular interest in biosensing applications. The unique optical properties of QDs provide certain advantages and also specific challenges with regards to sensor design, compared to other FRET systems. The brightness and photostability of QDs make them attractive for highly sensitive sensing and long-term, repetitive imaging applications, respectively, but the overlapping donor and acceptor excitation signals that arise when QDs serve as both the donor and acceptor lead to high background signals from direct excitation of the acceptor. The fundamentals of FRET within a nominally homogeneous QD population as well as energy transfer between two distinct colors of QDs are discussed. Examples of successful sensors are highlighted, as is cascading FRET, which can be used for solar harvesting. PMID:26057041

Mapping the solar wind HI outflow velocity in the inner heliosphere by coronagraphic ultraviolet and visible-light observations

Science.gov (United States)

Dolei, S.; Susino, R.; Sasso, C.; Bemporad, A.; Andretta, V.; Spadaro, D.; Ventura, R.; Antonucci, E.; Abbo, L.; Da Deppo, V.; Fineschi, S.; Focardi, M.; Frassetto, F.; Giordano, S.; Landini, F.; Naletto, G.; Nicolini, G.; Nicolosi, P.; Pancrazzi, M.; Romoli, M.; Telloni, D.

2018-05-01

We investigated the capability of mapping the solar wind outflow velocity of neutral hydrogen atoms by using synergistic visible-light and ultraviolet observations. We used polarised brightness images acquired by the LASCO/SOHO and Mk3/MLSO coronagraphs, and synoptic Lyα line observations of the UVCS/SOHO spectrometer to obtain daily maps of solar wind H I outflow velocity between 1.5 and 4.0 R⊙ on the SOHO plane of the sky during a complete solar rotation (from 1997 June 1 to 1997 June 28). The 28-days data sequence allows us to construct coronal off-limb Carrington maps of the resulting velocities at different heliocentric distances to investigate the space and time evolution of the outflowing solar plasma. In addition, we performed a parameter space exploration in order to study the dependence of the derived outflow velocities on the physical quantities characterising the Lyα emitting process in the corona. Our results are important in anticipation of the future science with the Metis instrument, selected to be part of the Solar Orbiter scientific payload. It was conceived to carry out near-sun coronagraphy, performing for the first time simultaneous imaging in polarised visible-light and ultraviolet H I Lyα line, so providing an unprecedented view of the solar wind acceleration region in the inner corona. The movie (see Sect. 4.2) is available at https://www.aanda.org

Observation of Resonant Behavior in the Energy Velocity of Diffused Light

International Nuclear Information System (INIS)

Sapienza, R.; Garcia, P. D.; Blanco, A.; Lopez, C.; Bertolotti, J.; Wiersma, D. S.; Martin, M. D.; Vina, L.

2007-01-01

In this Letter we demonstrate Mie resonances mediated transport of light in randomly arranged, monodisperse dielectric spheres packed at high filling fractions. By means of both static and dynamic optical experiments we show resonant behavior in the key transport parameters and, in particular, we find that the energy transport velocity, which is lower than the group velocity, also displays a resonant behavior

Deep and shallow acceptor levels in solid solutions Pb0.98Sm0.02S

International Nuclear Information System (INIS)

Hasanov, H.A.; Rahimov, R.Sh.

2010-01-01

It is well known that the metal vacancies the energy levels of which take place between permitted energies of valency band, are the main acceptor centers in the led salts and solid solutions on their base. The aim of the given paper is founding of character of acceptor levels in single crystals Pb 0 .98Sm 0 .02S with low concentrations of charge carrier. The deep and shallow acceptor levels are found at investigation of Hall effect in Pb 0 .98Sm 0 .02S solid solution with character of low concentrations of charge carriers in crystals

Acceptor number-dependent ultrafast photo-physical properties of push-pull chromophores using time-resolved methods

Science.gov (United States)

Chi, Xiao-Chun; Wang, Ying-Hui; Gao, Yu; Sui, Ning; Zhang, Li-Quan; Wang, Wen-Yan; Lu, Ran; Ji, Wen-Yu; Yang, Yan-Qiang; Zhang, Han-Zhuang

2018-04-01

Three push-pull chromophores comprising a triphenylamine (TPA) as electron-donating moiety and functionalized β-diketones as electron acceptor units are studied by various spectroscopic techniques. The time-correlated single-photon counting data shows that increasing the number of electron acceptor units accelerates photoluminescence relaxation rate of compounds. Transient spectra data shows that intramolecular charge transfer (ICT) takes place from TPA units to β-diketones units after photo-excitation. Increasing the number of electron acceptor units would prolong the generation process of ICT state, and accelerate the excited molecule reorganization process and the relaxation process of ICT state.

Amine donor and acceptor influence on the thermodynamics of ω-transaminase reactions

DEFF Research Database (Denmark)

Gundersen, Maria T.; Abu, Rohana; Schürmann, Martin

2015-01-01

In recent years biocatalytic transamination using ω-transaminase has become established as one of the most interesting routes to synthesize chiral amines with a high enantiomeric purity, especially in the pharmaceutical sector where the demand for such compounds is high. Nevertheless, one limitat...... of such reactions because it may be used to help select suitable donor/acceptor combinations. The results presented here give guidance, with respect to thermodynamics, in order to further extend the application of biocatalytic transamination....... limitation for successful implementation and scale-up is that the thermodynamics of such conversions are frequently found unfavourable. Herein we report experimental measurements of apparent equilibrium constants for several industrially relevant transamination reactions in a systematic manner to better...... understand the effect of amine acceptor and donor choice. For example, we have found that ortho-substitution of acetophenone like molecules, had a significant impact on the thermodynamic equilibrium. Likewise, the effect of cyclic amine acceptors was evaluated and compared to similar non-cyclic structures...

Hopping ladder and power relaxation due to donor-acceptor pairs

International Nuclear Information System (INIS)

Kostadinov, I.Z.

1985-11-01

Hopping between donor-acceptor pairs leads to peculiar temperature dependence of the conductivity and the photoconductivity under subband gap illumination in the form of non-linear activation energies ladder. The correlated and uncorrelated distributions of pairs are considered and the conditions for the ladder existence are determined. The relaxation of the carrier concentration fluctuations is studied and power type decay is found. The temperature dependence of the exponent is calculated in agreement with the non-exponential decay of the pulse excited luminescence observed by Dean et al. The temperature dependence of the luminescence intensity also shows variable activation energy as found here. The exponent value α=1.316 is also in agreement with the data for crystalline and amorphous materials. (author)

Velocity Segregation and Systematic Biases In Velocity Dispersion Estimates with the SPT-GMOS Spectroscopic Survey

Science.gov (United States)

Bayliss, Matthew. B.; Zengo, Kyle; Ruel, Jonathan; Benson, Bradford A.; Bleem, Lindsey E.; Bocquet, Sebastian; Bulbul, Esra; Brodwin, Mark; Capasso, Raffaella; Chiu, I.-non; McDonald, Michael; Rapetti, David; Saro, Alex; Stalder, Brian; Stark, Antony A.; Strazzullo, Veronica; Stubbs, Christopher W.; Zenteno, Alfredo

2017-03-01

The velocity distribution of galaxies in clusters is not universal; rather, galaxies are segregated according to their spectral type and relative luminosity. We examine the velocity distributions of different populations of galaxies within 89 Sunyaev Zel’dovich (SZ) selected galaxy clusters spanning 0.28GMOS spectroscopic survey, supplemented by additional published spectroscopy, resulting in a final spectroscopic sample of 4148 galaxy spectra—2868 cluster members. The velocity dispersion of star-forming cluster galaxies is 17 ± 4% greater than that of passive cluster galaxies, and the velocity dispersion of bright (m< {m}* -0.5) cluster galaxies is 11 ± 4% lower than the velocity dispersion of our total member population. We find good agreement with simulations regarding the shape of the relationship between the measured velocity dispersion and the fraction of passive versus star-forming galaxies used to measure it, but we find a small offset between this relationship as measured in data and simulations, which suggests that our dispersions are systematically low by as much as 3% relative to simulations. We argue that this offset could be interpreted as a measurement of the effective velocity bias that describes the ratio of our observed velocity dispersions and the intrinsic velocity dispersion of dark matter particles in a published simulation result. Measuring velocity bias in this way suggests that large spectroscopic surveys can improve dispersion-based mass-observable scaling relations for cosmology even in the face of velocity biases, by quantifying and ultimately calibrating them out.

Fullerene derivatives as electron acceptors for organic photovoltaic cells.

Science.gov (United States)

Mi, Dongbo; Kim, Ji-Hoon; Kim, Hee Un; Xu, Fei; Hwang, Do-Hoon

2014-02-01

Energy is currently one of the most important problems humankind faces. Depletion of traditional energy sources such as coal and oil results in the need to develop new ways to create, transport, and store electricity. In this regard, the sun, which can be considered as a giant nuclear fusion reactor, represents the most powerful source of energy available in our solar system. For photovoltaic cells to gain widespread acceptance as a source of clean and renewable energy, the cost per watt of solar energy must be decreased. Organic photovoltaic cells, developed in the past two decades, have potential as alternatives to traditional inorganic semiconductor photovoltaic cells, which suffer from high environmental pollution and energy consumption during production. Organic photovoltaic cells are composed of a blended film of a conjugated-polymer donor and a soluble fullerene-derivative acceptor sandwiched between a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-coated indium tin oxide positive electrode and a low-work-function metal negative electrode. Considerable research efforts aim at designing and synthesizing novel fullerene derivatives as electron acceptors with up-raised lowest unoccupied molecular orbital energy, better light-harvesting properties, higher electron mobility, and better miscibility with the polymer donor for improving the power conversion efficiency of the organic photovoltaic cells. In this paper, we systematically review novel fullerene acceptors synthesized through chemical modification for enhancing the photovoltaic performance by increasing open-circuit voltage, short-circuit current, and fill factor, which determine the performance of organic photovoltaic cells.

Design principle for efficient charge separation at the donor-acceptor interface for high performance organic solar cell device

Science.gov (United States)

Nie, Wanyi; Gupta, Gautam; Crone, Brian; Wang, Hsing-Lin; Mohite, Aditya; MPA-11 Material synthesis and integrated device Team; MPA-chemistry Team

2014-03-01

The performance of donor (D) /acceptor (A) structure based organic electronic devices, such as solar cell, light emitting devices etc., relays on the charge transfer process at the interface dramatically. In organic solar cell, the photo-induced electron-hole pair is tightly bonded and will form a charge transfer (CT) state at the D/A interface after dissociation. There is a large chance for them to recombine through CT state and thus is a major loss that limit the overall performance. Here, we report three different strategies that allow us to completely suppress the exciplex (or charge transfer state) recombination between any D/A system. We observe that the photocurrent increases by 300% and the power conversion efficiency increases by 4-5 times simply by inserting a spacer layer in the form of an a) insulator b) Oliogomer or using a c) heavy atom at the donor-acceptor interface in a P3HT/C60 bilayer device. By using those different functional mono layers, we successfully suppressed the exciplex recombination in evidence of increased photocurrent and open circuit voltage. Moreover, these strategies are applicable universally to any donor-acceptor interface. And we demonstrated such strategies in a bulk-heterojunction device which improved the power conversion efficiency from 3.5% up to 4.6%.

Photoluminescence quenching through resonant energy transfer in blends of conjugated polymer with low-molecular acceptor

International Nuclear Information System (INIS)

Zapunidi, S. A.; Paraschuk, D. Yu.

2008-01-01

A model is proposed for photoluminescence quenching due to resonant energy transfer in a blend of a conjugated polymer and a low-molecular energy acceptor. An analytical dependence of the normalized photoluminescence intensity on the acceptor concentration is derived for the case of a homogeneous blend. This dependence can be described by two fitting parameters related to the Foerster radii for energy transfer between conjugated segments of the polymer and between the conjugated polymer segment and the energy acceptor. Asymptotic approximations are obtained for the model dependence that make it possible to estimate the contribution from the spatial migration of excitons to the photoluminescence quenching. The proposed model is used to analyze experimental data on the photoluminescence quenching in a blend of the soluble derivative of poly(p-phenylene vinylene) and trinitrofluorenone [13]. The Foerster radius for resonant energy transfer between the characteristic conjugated segment of poly(p-phenylene vinylene) and the energy acceptor is determined to be r F = 2.6 ± 0.3 nm

Charge transfer complex studies between some non-steroidal anti-inflammatory drugs and π-electron acceptors

Science.gov (United States)

Duymus, Hulya; Arslan, Mustafa; Kucukislamoglu, Mustafa; Zengin, Mustafa

2006-12-01

Charge transfer (CT) complexes of some non-steroidal anti-inflammatory drugs, naproxen and etodolac which are electron donors with some π-acceptors, such as tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano- p-benzoquinone (DDQ), p-chloranil ( p-CHL), have been investigated spectrophotometrically in chloroform at 21 °C. The coloured products are measured spectrophotometrically at different wavelength depending on the electronic transition between donors and acceptors. Beer's law is obeyed and colours were produced in non-aqueous media. All complexes were stable at least 2 h except for etodolac with DDQ stable for 5 min. The equilibrium constants of the CT complexes were determined by the Benesi-Hildebrand equation. The thermodynamic parameters Δ H, Δ S, Δ G° were calculated by Van't Hoff equation. Stochiometries of the complexes formed between donors and acceptors were defined by the Job's method of the continuous variation and found in 1:1 complexation with donor and acceptor at the maximum absorption bands in all cases.

Potassium acceptor doping of ZnO crystals

Directory of Open Access Journals (Sweden)

Narendra S. Parmar

2015-05-01

Full Text Available ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ∼1 × 1016 cm−3. IR measurements show a local vibrational mode (LVM at 3226 cm−1, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O–H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm−1. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

Potassium acceptor doping of ZnO crystals

Science.gov (United States)

Parmar, Narendra S.; Corolewski, Caleb D.; McCluskey, Matthew D.; Lynn, K. G.

2015-05-01

ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ˜1 × 1016 cm-3. IR measurements show a local vibrational mode (LVM) at 3226 cm-1, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O-H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm-1. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

Potassium acceptor doping of ZnO crystals

Energy Technology Data Exchange (ETDEWEB)

Parmar, Narendra S., E-mail: nparmar@wsu.edu; Lynn, K. G. [Center for Materials Research, Washington State University, Pullman, Washington 99164-2711 (United States); Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States); Corolewski, Caleb D.; McCluskey, Matthew D. [Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States)

2015-05-15

ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ∼1 × 10{sup 16} cm{sup −3}. IR measurements show a local vibrational mode (LVM) at 3226 cm{sup −1}, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O–H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm{sup −1}. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

Förster Resonance Energy Transfer between Quantum Dot Donors and Quantum Dot Acceptors

Directory of Open Access Journals (Sweden)

Kenny F. Chou

2015-06-01

Full Text Available Förster (or fluorescence resonance energy transfer amongst semiconductor quantum dots (QDs is reviewed, with particular interest in biosensing applications. The unique optical properties of QDs provide certain advantages and also specific challenges with regards to sensor design, compared to other FRET systems. The brightness and photostability of QDs make them attractive for highly sensitive sensing and long-term, repetitive imaging applications, respectively, but the overlapping donor and acceptor excitation signals that arise when QDs serve as both the donor and acceptor lead to high background signals from direct excitation of the acceptor. The fundamentals of FRET within a nominally homogeneous QD population as well as energy transfer between two distinct colors of QDs are discussed. Examples of successful sensors are highlighted, as is cascading FRET, which can be used for solar harvesting.

Impact of Assimilating Surface Velocity Observations on the Model Sea Surface Height Using the NCOM-4DVAR

Science.gov (United States)

2016-09-26

the ensemble Kalman filter and the ensemble Kalman smoother: A comparison study using a nonlinear reduced gravity ocean model.OceanModell., 12, 378...using local ensemble transform Kalman filter and optimum-interpolation assimilation schemes. Ocean Modell., 69, 22–38, doi:10.1016/j.ocemod.2013.05.002...observations are assimi- lated. This gives a sense of the added value from the inclusion of velocity observations with the standard set of temperature

Sodium Velocity Maps on Mercury

Science.gov (United States)

Potter, A. E.; Killen, R. M.

2011-01-01

The objective of the current work was to measure two-dimensional maps of sodium velocities on the Mercury surface and examine the maps for evidence of sources or sinks of sodium on the surface. The McMath-Pierce Solar Telescope and the Stellar Spectrograph were used to measure Mercury spectra that were sampled at 7 milliAngstrom intervals. Observations were made each day during the period October 5-9, 2010. The dawn terminator was in view during that time. The velocity shift of the centroid of the Mercury emission line was measured relative to the solar sodium Fraunhofer line corrected for radial velocity of the Earth. The difference between the observed and calculated velocity shift was taken to be the velocity vector of the sodium relative to Earth. For each position of the spectrograph slit, a line of velocities across the planet was measured. Then, the spectrograph slit was stepped over the surface of Mercury at 1 arc second intervals. The position of Mercury was stabilized by an adaptive optics system. The collection of lines were assembled into an images of surface reflection, sodium emission intensities, and Earthward velocities over the surface of Mercury. The velocity map shows patches of higher velocity in the southern hemisphere, suggesting the existence of sodium sources there. The peak earthward velocity occurs in the equatorial region, and extends to the terminator. Since this was a dawn terminator, this might be an indication of dawn evaporation of sodium. Leblanc et al. (2008) have published a velocity map that is similar.

Organic charge transfer phase formation in thin films of the BEDT-TTF/TCNQ donor-acceptor system

DEFF Research Database (Denmark)

Solovyeva, Vita; Keller, K.; Huth, M.

2009-01-01

We have performed charge transfer phase formation studies on the donor/acceptor system bis-(ethylendithio)tetrathiafulvalene (BEDT-TTF)/tetracyanoquinodimethane,(TCNQ) by means of physical vapor deposition. We prepared donor/acceptor bilayer structures on glass and Si(100)/SiO substrates held...

Long-Lived Charge Separation at Heterojunctions between Semiconducting Single-Walled Carbon Nanotubes and Perylene Diimide Electron Acceptors

Energy Technology Data Exchange (ETDEWEB)

Kang, Hyun Suk [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Arias, Dylan H [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Blackburn, Jeffrey L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sisto, Thomas J. [Columbia University; Peurifoy, Samuel [Columbia University; Zhang, Boyuan [Columbia University; Nuckolls, Colin [Columbia University

2018-04-13

Nonfullerene electron acceptors have facilitated a recent surge in the efficiencies of organic solar cells, although fundamental studies of the nature of exciton dissociation at interfaces with nonfullerene electron acceptors are still relatively sparse. Semiconducting single-walled carbon nanotubes (s-SWCNTs), unique one-dimensional electron donors with molecule-like absorption and highly mobile charges, provide a model system for studying interfacial exciton dissociation. Here, we investigate excited-state photodynamics at the heterojunction between (6,5) s-SWCNTs and two perylene diimide (PDI)-based electron acceptors. Each of the PDI-based acceptors, hPDI2-pyr-hPDI2 and Trip-hPDI2, is deposited onto (6,5) s-SWCNT films to form a heterojunction bilayer. Transient absorption measurements demonstrate that photoinduced hole/electron transfer occurs at the photoexcited bilayer interfaces, producing long-lived separated charges with lifetimes exceeding 1.0 us. Both exciton dissociation and charge recombination occur more slowly for the hPDI2-pyr-hPDI2 bilayer than for the Trip-hPDI2 bilayer. To explain such differences, we discuss the potential roles of the thermodynamic charge transfer driving force available at each interface and the different molecular structure and intermolecular interactions of PDI-based acceptors. Detailed photophysical analysis of these model systems can develop the fundamental understanding of exciton dissociation between organic electron donors and nonfullerene acceptors, which has not been systematically studied.

Non-Fullerene Electron Acceptors for Use in Organic Solar Cells

KAUST Repository

Nielsen, Christian B.; Holliday, Sarah; Chen, Hung-Yang; Cryer, Samuel J.; McCulloch, Iain

2015-01-01

The active layer in a solution processed organic photovoltaic device comprises a light absorbing electron donor semiconductor, typically a polymer, and an electron accepting fullerene acceptor. Although there has been huge effort targeted

Modulation of Donor-Acceptor Distance in a Series of Carbazole Push-Pull Dyes; A Spectroscopic and Computational Study

Directory of Open Access Journals (Sweden)

Joshua J. Sutton

2018-02-01

Full Text Available A series of eight carbazole-cyanoacrylate based donor-acceptor dyes were studied. Within the series the influence of modifying the thiophene bridge, linking donor and acceptor and a change in the nature of the acceptor, from acid to ester, was explored. In this joint experimental and computational study we have used electronic absorbance and emission spectroscopies, Raman spectroscopy and computational modeling (density functional theory. From these studies it was found that extending the bridge length allowed the lowest energy transition to be systematically red shifted by 0.12 eV, allowing for limited tuning of the absorption of dyes using this structural motif. Using the aforementioned techniques we demonstrate that this transition is charge transfer in nature. Furthermore, the extent of charge transfer between donor and acceptor decreases with increasing bridge length and the bridge plays a smaller role in electronically mixing with the acceptor as it is extended.

The Physics of Small Molecule Acceptors for Efficient and Stable Bulk Heterojunction Solar Cells

KAUST Repository

Gasparini, Nicola

2018-01-29

Organic bulk heterojunction solar cells based on small molecule acceptors have recently seen a rapid rise in the power conversion efficiency with values exceeding 13%. This impressive achievement has been obtained by simultaneous reduction of voltage and charge recombination losses within this class of materials as compared to fullerene-based solar cells. In this contribution, the authors review the current understanding of the relevant photophysical processes in highly efficient nonfullerene acceptor (NFA) small molecules. Charge generation, recombination, and charge transport is discussed in comparison to fullerene-based composites. Finally, the authors review the superior light and thermal stability of nonfullerene small molecule acceptor based solar cells, and highlight the importance of NFA-based composites that enable devices without early performance loss, thus resembling so-called burn-in free devices.

The Physics of Small Molecule Acceptors for Efficient and Stable Bulk Heterojunction Solar Cells

KAUST Repository

Gasparini, Nicola; Wadsworth, Andrew; Moser, Maximilian; Baran, Derya; McCulloch, Iain; Brabec, Christoph J.

2018-01-01

Organic bulk heterojunction solar cells based on small molecule acceptors have recently seen a rapid rise in the power conversion efficiency with values exceeding 13%. This impressive achievement has been obtained by simultaneous reduction of voltage and charge recombination losses within this class of materials as compared to fullerene-based solar cells. In this contribution, the authors review the current understanding of the relevant photophysical processes in highly efficient nonfullerene acceptor (NFA) small molecules. Charge generation, recombination, and charge transport is discussed in comparison to fullerene-based composites. Finally, the authors review the superior light and thermal stability of nonfullerene small molecule acceptor based solar cells, and highlight the importance of NFA-based composites that enable devices without early performance loss, thus resembling so-called burn-in free devices.

Optimum energy levels and offsets for organic donor/acceptor binary photovoltaic materials and solar cells

International Nuclear Information System (INIS)

Sun, S.-S.

2005-01-01

Optimum frontier orbital energy levels and offsets of an organic donor/acceptor binary type photovoltaic material have been analyzed using classic Marcus electron transfer theory in order to achieve the most efficient photo induced charge separation. This study reveals that, an exciton quenching parameter (EQP) yields one optimum donor/acceptor frontier orbital energy offset that equals the sum of the exciton binding energy and the charge separation reorganization energy, where the photo generated excitons are converted into charges most efficiently. A recombination quenching parameter (RQP) yields a second optimum donor/acceptor energy offset where the ratio of charge separation rate constant over charge recombination rate constant becomes largest. It is desirable that the maximum RQP is coincidence or close to the maximum EQP. A third energy offset is also identified where charge recombination becomes most severe. It is desirable that the most severe charge recombination offset is far away from maximum EQP offset. These findings are very critical for evaluating and fine tuning frontier orbital energy levels of a donor/acceptor pair in order to realize high efficiency organic photovoltaic materials

Ultrasonic velocity measurements in expanded liquid mercury

International Nuclear Information System (INIS)

Suzuki, K.; Inutake, M.; Fujiwaka, S.

1977-10-01

In this paper we present the first results of the sound velocity measurements in expanded liquid mercury. The measurements were made at temperatures up to 1600 0 C and pressures up to 1700 kg/cm 2 by means of an ultrasonic pulse transmission/echo technique which was newly developed for such high temperature/pressure condition. When the density is larger than 9 g/cm 3 , the observed sound velocity decreases linearly with decreasing density. At densities smaller than 9 g/cm 3 , the linear dependence on the density is no longer observed. The observed sound velocity approaches a minimum near the liquid-gas critical point (rho sub(cr) asymptotically equals 5.5 g/cm 3 ). The existing theories for sound velocity in liquid metals fail to explain the observed results. (auth.)

Changing Artificial Playback Speed and Real Movement Velocity Do Not Differentially Influence the Excitability of Primary Motor Cortex during Observation of a Repetitive Finger Movement

Directory of Open Access Journals (Sweden)

Takefumi Moriuchi

2017-11-01

Full Text Available Action observation studies have investigated whether changing the speed of the observed movement affects the action observation network. There are two types of speed-changing conditions; one involves “changes in actual movement velocity,” and the other is “manipulation of video speed.” Previous studies have investigated the effects of these conditions separately, but to date, no study has directly investigated the differences between the effects of these conditions. In the “movement velocity condition,” increased velocity is associated with increased muscle activity; however, this change of muscle activities is not shown in the “video speed condition.” Therefore, a difference in the results obtained under these conditions could be considered to reflect a difference in muscle activity of actor in the video. The aim of the present study was to investigate the effects of different speed-changing conditions and spontaneous movement tempo (SMT on the excitability of primary motor cortex (M1 during action observation, as assessed by motor-evoked potentials (MEPs amplitudes induced by transcranial magnetic stimulation (TMS. A total of 29 healthy subjects observed a video clip of a repetitive index or little finger abduction movement under seven different speed conditions. The video clip in the movement velocity condition showed repetitive finger abduction movements made in time with an auditory metronome, at frequencies of 0.5, 1, 2, and 3 Hz. In the video speed condition, playback of the 1-Hz movement velocity condition video clip was modified to show movement frequencies of 0.5, 2, or 3 Hz (Hz-Fake. TMS was applied at the time of maximal abduction and MEPs were recorded from two right-hand muscles. There were no differences in M1 excitability between the movement velocity and video speed conditions. Moreover, M1 excitability did not vary across the speed conditions for either presentation condition. Our findings suggest that changing

Autonomous Observations of the Upper Ocean Stratification and Velocity Field about the Seasonality Retreating Marginal Ice Zone

Science.gov (United States)

2016-12-30

fluxes of heat, salt, and momentum. Hourly GPS fixes tracked the motion of the supporting ice floes and T/C recorders sampled the ocean waters just... sampled in a range of ice conditions from full ice cover to nearly open water and observed a variety of stratification and ocean velocity signals (e.g...From - To) 12/30/2016 final 01-Nov-2011to 30-Sep-201 6 4. TITLE AND SUBTITLE Sa. CONTRACT NUMBER Autonomous observations of the upper ocean

EPR studies of the vitamin K 1 semiquinone radical anion. Comparison to the electron acceptor A 1 in green plant photosystem I

Science.gov (United States)

Thurnauer, Marion C.; Brown, James W.; Gast, P.; Feezel, Laura L.

Suggestions that the electron acceptor, A 1, in Photosystem I is a quinone have come from both optical and epr experiments. Vitamin K 1 (phylloquinone) is present in the PSI complex with a stoichiometry of two molecules per reaction center. In order to determine if A 1 can be identified with vitamin K 1, X-band and Q-band epr properties of the vitamin K 1 radical anion in frozen alcohol solutions are examined. The results are compared to the epr properties that have been observed for the reduced A 1 acceptor in vivo. The g-values obtained for the vitamin K 1 radical anion are consistent with identifying A 1 with vitamin K 1.

Radial-Velocity Signatures of Magnetic Features on the Sun Observed as a Star

Science.gov (United States)

Palumbo, M. L., III; Haywood, R. D.; Saar, S. H.; Dupree, A. K.; Milbourne, T. W.

2017-12-01

In recent years, the search for Earth-mass planets using radial-velocity measurements has become increasingly limited by signals arising from stellar activity. Individual magnetic features induce localized changes in intensity and velocity, which combine to change the apparent radial velocity of the star. Therefore it is critical to identify an indicator of activity-driven radial-velocity variations on the timescale of stellar rotation periods. We use 617.3 nm photospheric filtergrams, magnetograms, and dopplergrams from SDO/HMI and 170.0 nm chromospheric filtergrams from AIA to identify magnetically-driven solar features and reconstruct the integrated solar radial velocity with six samples per day over the course of 2014. Breaking the solar image up into regions of umbrae, penumbrae, quiet Sun, network, and plages, we find a distinct variation in the center-to-limb intensity-weighted velocity for each region. In agreement with past studies, we find that the suppression of convective blueshift is dominated by plages and network, rather than dark photospheric features. In the future, this work will be highly useful for identifying indicators which correlate with rotationally modulated radial-velocity variations. This will allow us to break the activity barrier that currently precludes the precise characterization of exoplanet properties at the lowest masses. This work was supported by the NSF-REU solar physics program at SAO, grant number AGS-1560313. This work was performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute.

FRET two-hybrid assay by linearly fitting FRET efficiency to concentration ratio between acceptor and donor

Science.gov (United States)

Du, Mengyan; Yang, Fangfang; Mai, Zihao; Qu, Wenfeng; Lin, Fangrui; Wei, Lichun; Chen, Tongsheng

2018-04-01

We here introduce a fluorescence resonance energy transfer (FRET) two-hybrid assay method to measure the maximal donor(D)- and acceptor(A)-centric FRET efficiency (ED,max and EA,max) of the D-A complex and its stoichiometry by linearly fitting the donor-centric FRET efficiency (ED) to the acceptor-to-donor concentration ratio (RC) and acceptor-centric FRET efficiency (EA) to 1/RC, respectively. We performed this method on a wide-field fluorescence microscope for living HepG2 cells co-expressing FRET tandem constructs and free donor/acceptor and obtained correct ED, EA, and stoichiometry values of those tandem constructs. Evaluation on the binding of Bad with Bcl-XL in Hela cells showed that Bad interacted strongly with Bcl-XL to form a Bad-Bcl-XL complex on mitochondria, and one Bad interacted mainly with one Bcl-XL molecule in healthy cells, while with multiple (maybe 2) Bcl-XL molecules in apoptotic cells.

Electron Acceptors Based on α-Substituted Perylene Diimide (PDI) for Organic Solar Cells

Energy Technology Data Exchange (ETDEWEB)

Zhao, Donglin [Department; Wu, Qinghe [Department; Cai, Zhengxu [Department; Zheng, Tianyue [Department; Chen, Wei [Materials; Institute; Lu, Jessica [Department; Yu, Luping [Department

2016-02-02

Perylene diimide (PDI) derivatives functionalized at the ortho-position (αPPID, αPBDT) were synthesized and used as electron acceptors in non-fullerene organic photovoltaic cells. Because of the good planarity and strong π-stacking of ortho-functionalized PDI, the αPPID and αPBDT exhibit a strong tendency to form aggregates, which endow the materials with high electron mobility. The inverted OPVs employing αPDI-based compounds as the acceptors and PBT7-Th as the donor give the highest power conversion efficiency (PCE) values: 4.92% for αPBDT-based devices and 3.61% for αPPID-based devices, which are, respectively, 39% and 4% higher than that of their β-substituted counterparts βPBDT and βPPID. Charge separation studies show more efficient exciton dissociation at interfaces between αPDI-based compounds and PTB7-Th. The results suggest that α-substituted PDI derivatives are more promising electron acceptors for organic photovoltaic (OPV) components than β-isomers.

Efficiency-limiting processes in OPV bulk heterojunctions of GeNIDTBT and IDT-based acceptors

KAUST Repository

Al-Saggaf, Sarah M.

2018-05-16

The successful realization of highly efficient bulk heterojunction OPV devices requires the development of organic donor and acceptor materials with tailored properties. Recently, non-fullerene acceptors (NFAs) have emerged as an alternative to the ubiquitously used fullerene derivatives. NFAs showed a rapid increase in efficiencies, now exceeding a PCE of 13%. In my thesis research, I used two small molecule IDT-based acceptors, namely O-IDTBR and O-IDTBCN, in combination with a wide bandgap donor polymer, GeNIDT-BT, as active material in BHJ solar cells and investigated their photophysical characteristics. The polymer combined with O-IDTBR as acceptor achieved a power conversion efficiency of only 2%, which is significantly lower than that obtained for the system of GeNIDT-BT: O-IDTBCN (5.3%). Using nano- to microsecond transient absorption spectroscopy, I investigated both systems and demonstrated that GeNIDT-BT:O-IDTBR exhibits more geminate recombination of interfacial charge-transfer states, leading to lower short circuit currents. Using time-delayed collection field experiments, I studied the field dependence of charge generation and its impact on the device fill factor. Overall, my results provide a qualitative understanding of the efficiency-limiting processes in both systems and their impact on device performance.

Nonradiative inter- and intramolecular energy transfer from the aromatic donor anisole to a synthesized photoswitchable acceptor system.

Science.gov (United States)

Bardhan, Munmun; Bhattacharya, Sudeshna; Misra, Tapas; Mukhopadhyay, Rupa; De, Asish; Chowdhury, Joydeep; Ganguly, Tapan

2010-02-01

We report steady state and time resolved fluorescence measurements on acetonitrile (ACN) solutions of the model compounds, energy donor anisole (A) and a photoswitchable acceptor N,N'-1,2-phenylene di-p-tosylamide (B) and the multichromophore (M) where A and B are connected by a spacer containing both rigid triple (acetylenic) and flexible methylene bonds. Both steady state and time correlated single photon counting measurements demonstrate that though intermolecular energy transfer, of Forster type, between the donor and acceptor moieties occurs with rate 10(8)s(-1) but when these two reacting components are linked by a spacer (multichromophore, M) the observed transfer rate ( approximately 10(11)s(-1)) enhances. This seemingly indicates that the imposition of the spacer by inserting a triple bond may facilitate in the propagation of electronic excitation energy through bond. The time resolved fluorescence measurements along with the theoretical predictions using Configuration interaction singles (CIS) method by using 6-31G (d,p) basis set, implemented in the Gaussian package indicate the formations of the two excited conformers of B. The experimental findings made from the steady state and time resolved fluorescence measurements demonstrate that, though two different isomeric species of the acceptor B are formed in the excited singlet states, the prevailing singlet-singlet nonradiative energy transfer route was found from the donor A to the relatively longer-lived isomeric species of B. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Steady state and time-resolved spectroscopic investigations on the photoreactions involved within the electronically excited electron acceptor 9-cyanoanthracene in presence of benzotriazole and benzimidazole donors

International Nuclear Information System (INIS)

Bhattacharya, Sudeshna; Bardhan, Munmun; Ganguly, Tapan

2010-01-01

The electrochemical, 'steady-state' and 'time-resolved' spectroscopic investigations were made on the well-known electron acceptor 9-cyanoanthracene (CNA) when interacted with the electron donors benzotriazole (BZT) and benzimidazole (BMI) molecules. Though electrochemical measurements indicate the thermodynamical possibility of occurrences of photoinduced electron transfer reactions within these reacting systems in the lowest excited singlet state (S 1 ) of the acceptor CNA but the steady-state and time-resolved measurements clearly demonstrate only the triplet-initiated charge separation reactions. It was reported earlier that in the cases of disubstituted indole molecules the occurrences of photoinduced electron transfer reactions were apparent both in the excited singlet and triplet states of the acceptor 9-cyanoanthracene, but the similarly structured present donor molecules benzotriazole (and benzimidazole) behave differently from indoles. The weak ground state complex formations within the presently studied reacting systems appear to be responsible for the observed static quenching phenomena as evidenced from the time-resolved fluorescence studies. Time-resolved spectroscopic investigations demonstrate the formation of the ground state of the reacting components (donor and acceptor) through recombination of triplet ion-pairs via formations of contact neutral radical produced by H-abstraction mechanism.

Comparing the Device Physics and Morphology of Polymer Solar Cells Employing Fullerenes and Non-Fullerene Acceptors

KAUST Repository

Bloking, Jason T.

2014-04-23

There is a need to find electron acceptors for organic photovoltaics that are not based on fullerene derivatives since fullerenes have a small band gap that limits the open-circuit voltage (VOC), do not absorb strongly and are expensive. Here, a phenylimide-based acceptor molecule, 4,7-bis(4-(N-hexyl-phthalimide)vinyl)benzo[c]1,2,5-thiadiazole (HPI-BT), that can be used to make solar cells with VOC values up to 1.11 V and power conversion efficiencies up to 3.7% with two thiophene polymers is demonstrated. An internal quantum efficiency of 56%, compared to 75-90% for polymer-fullerene devices, results from less efficient separation of geminate charge pairs. While favorable energetic offsets in the polymer-fullerene devices due to the formation of a disordered mixed phase are thought to improve charge separation, the low miscibility (<5 wt%) of HPI-BT in polymers is hypothesized to prevent the mixed phase and energetic offsets from forming, thus reducing the driving force for charges to separate into the pure donor and acceptor phases where they can be collected. A small molecule electron acceptor, 4,7-bis(4-(N-hexyl-phthalimide)vinyl)benzo[c]1,2,5-thiadiazole (HPI-BT), achieves efficiencies of 3.7% and open-circuit voltage values of 1.11 V in bulk heterojunction (BHJ) devices with polythiophene donor materials. The lower internal quantum efficiency (56%) in these non-fullerene acceptor devices is attributed to an absence of the favorable energetic offsets resulting from nanoscale mixing of donor and acceptor found in comparable fullerene-based devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Peculiarities of defect formation in InP single crystals doped with donor (S, Ge) and acceptor (Zn) impurities

International Nuclear Information System (INIS)

Mikryukova, E.V.; Morozov, A.N.; Berkova, A.V.; Nashel'skij, A.Ya.; Yakobson, S.V.

1988-01-01

Peculiarities of dislocation and microdefect formation in InP monocrystals doped with donor (S,Ge) and acceptor (Zn) impurities are investigated by the metallography. Dependence of dislocation density on the concentration of alloying impurity is established. Microdefects leading to the appearance of 5 different types of etch figures are shown to be observed in doped InP monocrystals. The mechanism of microdefect formation is suggested

Interplay of alternative conjugated pathways and steric interactions on the electronic and optical properties of donor-acceptor conjugated polymers

KAUST Repository

Lima, Igo T.; Risko, Chad; Aziz, Saadullah Gary; Da Silva Filho, Demé trio A Da Silva; Bredas, Jean-Luc

2014-01-01

Donor-acceptor π-conjugated copolymers are of interest for a wide range of electronic applications, including field-effect transistors and solar cells. Here, we present a density functional theory (DFT) study of the impact of varying the conjugation pathway on the geometric, electronic, and optical properties of donor-acceptor systems. We consider both linear ("in series"), traditional conjugation among the donor-acceptor moieties versus structures where the acceptor units are appended orthogonally to the linear, donor-only conjugated backbone. Long-range-corrected hybrid functionals are used in the investigation with the values of the tuned long-range separation parameters providing an estimate of the extent of conjugation as a function of the oligomer architecture. Considerable differences in the electronic and optical properties are determined as a function of the nature of the conjugation pathway, features that should be taken into account in the design of donor-acceptor copolymers.

Comparison of vertical E × B drift velocities and ground-based magnetometer observations of DELTA H in the low latitude under geomagnetically disturbed conditions

Science.gov (United States)

Prabhu, M.; Unnikrishnan, K.

2018-04-01

In the present work, we analyzed the daytime vertical E × B drift velocities obtained from Jicamarca Unattended Long-term Ionosphere Atmosphere (JULIA) radar and ΔH component of geomagnetic field measured as the difference between the magnitudes of the horizontal (H) components between two magnetometers deployed at two different locations Jicamarca, and Piura in Peru for 22 geomagnetically disturbed events in which either SC has occurred or Dstmax values of daytime vertical E × B drift velocity and peak value of ΔH for the three consecutive days of the events. It was observed that 45% of the events have daytime vertical E × B drift velocity peak in the magnitude range 10-20 m/s and 20-30 m/s and 20% have peak ΔH in the magnitude range 50-60 nT and 80-90 nT. It was observed that the time of occurrence of the peak value of both the vertical E × B drift velocity and the ΔH have a maximum (40%) probability in the same time range 11:00-13:00 LT. We also investigated the correlation between E × B drift velocity and Dst index and the correlation between delta H and Dst index. A strong positive correlation is found between E × B drift and Dst index as well as between delta H and Dst Index. Three different techniques of data analysis - linear, polynomial (order 2), and polynomial (order 3) regression analysis were considered. The regression parameters in all the three cases were calculated using the Least Square Method (LSM), using the daytime vertical E × B drift velocity and ΔH. A formula was developed which indicates the relationship between daytime vertical E × B drift velocity and ΔH, for the disturbed periods. The E × B drift velocity was then evaluated using the formulae thus found for the three regression analysis and validated for the 'disturbed periods' of 3 selected events. The E × B drift velocities estimated by the three regression analysis have a fairly good agreement with JULIA radar observed values under different seasons and solar activity

Study of the Contributions of Donor and Acceptor Photoexcitations to Open Circuit Voltage in Bulk Heterojunction Organic Solar Cells

Directory of Open Access Journals (Sweden)

Douglas Yeboah

2017-10-01

Full Text Available One of the key parameters in determining the power conversion efficiency (PCE of bulk heterojunction (BHJ organic solar cells (OSCs is the open circuit voltage . The processes of exciting the donor and acceptor materials individually in a BHJ OSC are investigated and are found to produce two different expressions for . Using the contributions of electron and hole quasi-Fermi levels and charge carrier concentrations, the two different expressions are derived as functions of the energetics of the donor and acceptor materials and the photo-generated charge carrier concentrations, and calculated for a set of donor-acceptor blends. The simultaneous excitation of both the donor and acceptor materials is also considered and the corresponding , which is different from the above two, is derived. The calculated from the photoexcitation of the donor is found to be somewhat comparable with that obtained from the photoexcitation of the acceptor in most combinations of the donor and acceptor materials considered here. It is also found that the calculated from the simultaneous excitations of donor and acceptor in BHJ OSCs is also comparable with the other two . All three thus derived produce similar results and agree reasonably well with the measured values. All three depend linearly on the concentration of the photoexcited charge carriers and hence incident light intensity, which agrees with experimental results. The outcomes of this study are expected to help in finding materials that may produce higher and hence enhanced PCE in BHJ OSCs.

Cosmological streaming velocities and large-scale density maxima

International Nuclear Information System (INIS)

Peacock, J.A.; Lumsden, S.L.; Heavens, A.F.

1987-01-01

The statistical testing of models for galaxy formation against the observed peculiar velocities on 10-100 Mpc scales is considered. If it is assumed that observers are likely to be sited near maxima in the primordial field of density perturbations, then the observed filtered velocity field will be biased to low values by comparison with a point selected at random. This helps to explain how the peculiar velocities (relative to the microwave background) of the local supercluster and the Rubin-Ford shell can be so similar in magnitude. Using this assumption to predict peculiar velocities on two scales, we test models with large-scale damping (i.e. adiabatic perturbations). Allowed models have a damping length close to the Rubin-Ford scale and are mildly non-linear. Both purely baryonic universes and universes dominated by massive neutrinos can account for the observed velocities, provided 0.1 ≤ Ω ≤ 1. (author)

High Performing Ternary Solar Cells through Förster Resonance Energy Transfer between Nonfullerene Acceptors.

Science.gov (United States)

Yang, Lei; Gu, Wenxing; Hong, Ling; Mi, Yang; Liu, Feng; Liu, Ming; Yang, Yufei; Sharma, Bigyan; Liu, Xinfeng; Huang, Hui

2017-08-16

Nonradiative Förster resonance energy transfer (FRET) is an important mechanism of organic solar cells, which can improve the exciton migration over a long distance, resulting in improvement of efficiency of solar cells. However, the current observations of FRET are very limited, and the efficiencies are less than 9%. In this study, FRET effect was first observed between two nonfullerene acceptors in ternary solar cells, which improved both the absorption range and exciton harvesting, leading to the dramatic enhancement in the short circuit current and power conversion efficiency. Moreover, this strategy is proved to be a versatile platform for conjugated polymers with different bandgaps, resulting in a remarkable efficiency of 10.4%. These results demonstrated a novel method to enhance the efficiency of organic soar cells.

Bane of Hydrogen-Bond Formation on the Photoinduced Charge-Transfer Process in Donor–Acceptor Systems

KAUST Repository

Alsam, Amani Abdu

2017-03-14

Controlling the ultrafast dynamical process of photoinduced charge transfer at donor acceptor interfaces remains a major challenge for physical chemistry and solar cell communities. The process is complicated by the involvement of other complex dynamical processes, including hydrogen bond formation, energy transfer, and solvation dynamics occurring on similar time scales. In this study, we explore the remarkable impact of hydrogen-bond formation on the interfacial charge transfer between a negatively charged electron donating anionic porphyrin and a positively charged electron accepting pi-conjugated polymer, as a model system in solvents with different polarities and capabilities for hydiogen bonding using femtosecond transient absorption spectroscopy. Unlike the conventional understanding of the key role of hydrogen bonding in promoting the charge-transfer process, our steadystate and time-resolved results reveal that the intervening hydrogen-bonding environment and, consequently, the probable longer spacing between the donor and acceptor molecules significantly hinders the charge-transfer process between them. These results show that site-specific hydrogen bonding and geometric considerations between donor and acceptor can be exploited to control both the charge-transfer dynamics and its efficiency not only at donor acceptor interfaces but also in complex biological systems.

Discriminating a deep defect from shallow acceptors in supercell calculations: gallium antisite in GaAs

Science.gov (United States)

Schultz, Peter

To make reliable first principles predictions of defect energies in semiconductors, it is crucial to discriminate between effective-mass-like defects--for which existing supercell methods fail--and deep defects--for which density functional theory calculations can yield reliable predictions of defect energy levels. The gallium antisite GaAs is often associated with the 78/203 meV shallow double acceptor in Ga-rich gallium arsenide. Within a framework of level occupation patterns, analyses of structure and spin stabilization can be used within a supercell approach to distinguish localized deep defect states from shallow acceptors such as BAs. This systematic analysis determines that the gallium antisite is inconsistent with a shallow state, and cannot be the 78/203 shallow double acceptor. The properties of the Ga antisite in GaAs are described, predicting that the Ga antisite is a deep double acceptor and has two donor states, one of which might be accidentally shallow. -- Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

A dark green fluorescent protein as an acceptor for measurement of Förster resonance energy transfer.

Science.gov (United States)

Murakoshi, Hideji; Shibata, Akihiro C E; Nakahata, Yoshihisa; Nabekura, Junichi

2015-10-15

Measurement of Förster resonance energy transfer by fluorescence lifetime imaging microscopy (FLIM-FRET) is a powerful method for visualization of intracellular signaling activities such as protein-protein interactions and conformational changes of proteins. Here, we developed a dark green fluorescent protein (ShadowG) that can serve as an acceptor for FLIM-FRET. ShadowG is spectrally similar to monomeric enhanced green fluorescent protein (mEGFP) and has a 120-fold smaller quantum yield. When FRET from mEGFP to ShadowG was measured using an mEGFP-ShadowG tandem construct with 2-photon FLIM-FRET, we observed a strong FRET signal with low cell-to-cell variability. Furthermore, ShadowG was applied to a single-molecule FRET sensor to monitor a conformational change of CaMKII and of the light oxygen voltage (LOV) domain in HeLa cells. These sensors showed reduced cell-to-cell variability of both the basal fluorescence lifetime and response signal. In contrast to mCherry- or dark-YFP-based sensors, our sensor allowed for precise measurement of individual cell responses. When ShadowG was applied to a separate-type Ras FRET sensor, it showed a greater response signal than did the mCherry-based sensor. Furthermore, Ras activation and translocation of its effector ERK2 into the nucleus could be observed simultaneously. Thus, ShadowG is a promising FLIM-FRET acceptor.

Interaction of point intrinsic defects in n-type indium phosphide with acceptor clusters

International Nuclear Information System (INIS)

Vitovskij, N.A.; Lagunova, T.S.; Rakhimov, O.

1984-01-01

The rates of implanting defects of donor- and acceptor type stable at room temperature in n-InP during gamma irradiation are found to vary versus the compensating impurity type. Zinc atoms interact with defects most actively. Irradiation also brings about the growth of acceptor clusters, this growth being most markedly expressed in InP . The presence of an additional mechanism of charge-carriers scattering associated with the existence of clusters of compensating centres is verified, the temperature dependence of the effectiveness of this mechanism μ approximately Tsup(-1.2) is found

A spiro-bifluorene based 3D electron acceptor with dicyanovinylene substitution for solution-processed non-fullerene organic solar cells

KAUST Repository

Xia, Debin

2015-04-20

A novel electron acceptor, namely 2,2′-(12H,12′H-10,10′-spirobi[indeno[2,1-b]fluorene]-12,12′-diylidene)dimalononitrile (4CN-spiro), exhibiting a three-dimensional molecular structure was synthesized and its thermal, photophysical, electrochemical, crystal, and photovoltaic properties were investigated. The novel acceptor exhibits excellent thermal stability with a decomposition temperature of 460 °C, an absorption extending to 600 nm, and a LUMO level of −3.63 eV. Solution processed bulk-heterojunction (BHJ) organic solar cells were fabricated using 4CN-spiro as an acceptor and polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) as a donor polymer. The effect of the donor-to-acceptor ratio and processing conditions on the device performance was investigated. A device processed from tetrachloroethane with a donor to acceptor weight ratio of 1 : 1 yielded a power conversion efficiency (PCE) of 0.80%.

Medium-Bandgap Small-Molecule Donors Compatible with Both Fullerene and Nonfullerene Acceptors.

Science.gov (United States)

Huo, Yong; Yan, Cenqi; Kan, Bin; Liu, Xiao-Fei; Chen, Li-Chuan; Hu, Chen-Xia; Lau, Tsz-Ki; Lu, Xinhui; Sun, Chun-Lin; Shao, Xiangfeng; Chen, Yongsheng; Zhan, Xiaowei; Zhang, Hao-Li

2018-03-21

Much effort has been devoted to the development of new donor materials for small-molecule organic solar cells due to their inherent advantages of well-defined molecular weight, easy purification, and good reproducibility in photovoltaic performance. Herein, we report two small-molecule donors that are compatible with both fullerene and nonfullerene acceptors. Both molecules consist of an (E)-1,2-di(thiophen-2-yl)ethane-substituted (TVT-substituted) benzo[1,2-b:4,5-b']dithiophene (BDT) as the central unit, and two rhodanine units as the terminal electron-withdrawing groups. The central units are modified with either alkyl side chains (DRBDT-TVT) or alkylthio side chains (DRBDT-STVT). Both molecules exhibit a medium bandgap with complementary absorption and proper energy level offset with typical acceptors like PC 71 BM and IDIC. The optimized devices show a decent power conversion efficiency (PCE) of 6.87% for small-molecule organic solar cells and 6.63% for nonfullerene all small-molecule organic solar cells. Our results reveal that rationally designed medium-bandgap small-molecule donors can be applied in high-performance small-molecule organic solar cells with different types of acceptors.

Structural, theoretical and experimental models of photosynthetic antennas, donors and acceptors

International Nuclear Information System (INIS)

Barkigia, K.M.; Chantranupong, L.; Fajer, J.; Kehres, L.A.; Smith, K.M.

1989-01-01

Theoretical calculations, based on recent x-ray studies of bacterial reaction centers, suggest that the light-absorption properties of the special pair phototraps in bacteria are controlled by the interplanar spacing between the bacteriochlorophyll subunits that constitute the special pairs. The calculations offer attractively simple explanations for the range of absorption spectra exhibited by photosynthetic bacteria. The wide range of (bacterio)chlorophyll skeletal conformations revealed by x-ray diffraction studies raise the intriguing possibility that different conformations, imposed by protein constraints, can modulate the light-absorption and redox properties of the chromophores in vivo. Electron-nuclear double resonance data obtained for the primary acceptors in green plants suggest specific substituent orientations and hydrogen bonding that may help optimize the orientations of the acceptors relative to the donors

Mechanism of electron transfer from e-sub(aq) to acceptors in micelles

International Nuclear Information System (INIS)

Graetzel, M.; Henglein, A.; Janata, E.

1975-01-01

Pulse radiolysis experiments were carried out to investigate reactions A + e - sub(aq) → A - of hydrated electrons with acceptors A incorporated in the lipoidic part of micellar 10 -3 M sodium-lauryl-sulfate (SLS) and cetyl-trimethyl-ammonium-bromide (CTAB). The acceptors were 9-nitro-anthracene and pyrene, the latter in both the singlet and triplet state (the triplet was produced by UV-light irradiation shortly before the high energy electron pulse was applied). The triplet state of pyrene reacts in CTAB-micelles with a rate constant smaller by at least a factor of two than the singlet ground state. (orig./HK) [de

Crystallization and preliminary X-ray diffraction analysis of a tRNASer acceptor-stem microhelix

International Nuclear Information System (INIS)

Förster, Charlotte; Krauss, Norbert; Brauer, Arnd B. E.; Szkaradkiewicz, Karol; Brode, Svenja; Hennig, Klaus; Fürste, Jens P.; Perbandt, Markus; Betzel, Christian; Erdmann, Volker A.

2006-01-01

In order to investigate tRNA identity elements, an elongator tRNA Ser acceptor-stem helix was crystallized and a data set was collected to 1.8 Å resolution aiming at a comparison with the corresponding region in suppressor tRNA Sec . In order to understand elongator tRNA Ser and suppressor tRNA Sec identity elements, the respective acceptor-stem helices have been synthesized and crystallized in order to analyse and compare their structures in detail at high resolution. The synthesis, crystallization and preliminary X-ray diffraction results for a seven-base-pair tRNA Ser acceptor-stem helix are presented here. Diffraction data were collected to 1.8 Å, applying synchrotron radiation and cryogenic cooling. The crystals belong to the monoclinic space group C2, with unit-cell parameters a = 36.14, b = 38.96, c = 30.81 Å, β = 110.69°

An overview of electron acceptors in microbial fuel cells

DEFF Research Database (Denmark)

Ucar, Deniz; Zhang, Yifeng; Angelidaki, Irini

2017-01-01

Microbial fuel cells (MFC) have recently received increasing attention due to their promising potential in sustainable wastewater treatment and contaminant removal. In general, contaminants can be removed either as an electron donor via microbial catalyzed oxidization at the anode or removed at t...... acceptors (e.g., nitrate, iron, copper, perchlorate) and mediators....

Fused-Ring Acceptors with Asymmetric Side Chains for High-Performance Thick-Film Organic Solar Cells.

Science.gov (United States)

Feng, Shiyu; Zhang, Cai'e; Liu, Yahui; Bi, Zhaozhao; Zhang, Zhe; Xu, Xinjun; Ma, Wei; Bo, Zhishan

2017-11-01

A kind of new fused-ring electron acceptor, IDT-OB, bearing asymmetric side chains, is synthesized for high-efficiency thick-film organic solar cells. The introduction of asymmetric side chains can increase the solubility of acceptor molecules, enable the acceptor molecules to pack closely in a dislocated way, and form favorable phase separation when blended with PBDB-T. As expected, PBDB-T:IDT-OB-based devices exhibit high and balanced hole and electron mobility and give a high power conversion efficiency (PCE) of 10.12%. More importantly, the IDT-OB-based devices are not very sensitive to the film thickness, a PCE of 9.17% can still be obtained even the thickness of active layer is up to 210 nm. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intensity dependence and transient dynamics of donor-acceptor pair recombination in ZnO thin films grown on (001) silicon

Science.gov (United States)

Guo, Bing; Qiu, Z. R.; Wong, K. S.

2003-04-01

We report room-temperature time-integrated and time-resolved photoluminescence (PL) measurements on a nominally undoped wurtzite ZnO thin film grown on (001) silicon. A linear and sublinear excitation intensity Iex dependence of the PL intensity were observed for the 379.48-nm exciton line and the weak broad green band (˜510 nm), respectively. The green luminescence was found to decay as hyperbolic t-1, and its peak energy was observed to increase nearly logarithmically with increased Iex. These results are in an excellent agreement with the tunnel-assisted donor-deep-acceptor pair (DAP) model so that its large blueshifts of about 25 meV per decade increase in Iex can be accounted for by the screening of the fluctuating impurity potential. Also, the 30-ps fast decay of the exciton emission was attributed to the rapid trapping of carriers at luminescent impurities, while the short lifetime of τ1/e=200 ps for the green luminescence may be due to an alternative trapping by deeper centers in the ZnO. Finally, singly ionized oxygen and zinc vacancies have been tentatively invoked to act as donor-deep-acceptor candidates for the DAP luminescence, respectively.

Propagation of optical pulses in a resonantly absorbing medium: Observation of negative velocity in Rb vapor

International Nuclear Information System (INIS)

Tanaka, H.; Hayami, K.; Furue, S.; Nakayama, K.; Niwa, H.; Kohmoto, T.; Kunitomo, M.; Fukuda, Y.

2003-01-01

Propagation of optical pulses in a resonantly absorbing medium is studied. Propagation time of nanosecond pulses was measured for the Rb D 1 transition. At the center of two absorption lines, delay of the pulse peak which is about ten times as large as the pulse width was observed, where zero delay is defined for the propagation with the light velocity in vacuum. On the other hand, at the peak of an absorption line, negative delay was observed for large absorption, where the advance time is as large as 25% of the pulse width. Simulation including the effect of absorption and phase shift reproduced well the experimental results

A rhodanine flanked nonfullerene acceptor for solution-processed organic photovoltaics

KAUST Repository

Holliday, Sarah; Ashraf, Raja Shahid; Nielsen, Christian Bergenstof; Kirkus, Mindaugas; Rö hr, Jason A.; Tan, Chinghong; Collado-Fregoso, Elisa; Knall, Astrid Caroline; Durrant, James R.; Nelson, Jenny K.; McCulloch, Iain

2015-01-01

3HT:PC60BM devices, the acceptor does not aggregate enough to create appropriate percolation pathways that prevent fast nongeminate recombination. Despite this nonoptimal morphology the P3HT:FBR devices exhibit better performance than P3HT:PC60BM

Decay time shortening of fluorescence from donor-acceptor pair proteins using ultrafast time-resolved fluorescence resonance energy transfer spectroscopy

International Nuclear Information System (INIS)

Baba, Motoyoshi; Suzuki, Masayuki; Ganeev, Rashid A.; Kuroda, Hiroto; Ozaki, Tsuneyuki; Hamakubo, Takao; Masuda, Kazuyuki; Hayashi, Masahiro; Sakihama, Toshiko; Kodama, Tatsuhiko; Kozasa, Tohru

2007-01-01

We improved an ultrafast time-resolved fluorescence resonance energy transfer (FRET) spectroscopy system and measured directly the decrease in the fluorescence decay time of the FRET signal, without any entanglement of components in the picosecond time scale from the donor-acceptor protein pairs (such as cameleon protein for calcium ion indicator, and ligand-activated GRIN-Go proteins pair). The drastic decrease in lifetime of the donor protein fluorescence under the FRET condition (e.g. a 47.8% decrease for a GRIN-Go protein pair) proves the deformation dynamics between donor and acceptor fluorescent proteins in an activated state of a mixed donor-acceptor protein pair. This study is the first clear evidence of physical contact of the GRIN-Go proteins pair using time-resolved FRET system. G protein-coupled receptors (GPCRs) are the most important protein family for the recognition of many chemical substances at the cell surface. They are the targets of many drugs. Simultaneously, we were able to observe the time-resolved spectra of luminous proteins at the initial stage under the FRET condition, within 10 ns from excitation. This new FRET system allows us to trace the dynamics of the interaction between proteins at the ligand-induced activated state, molecular structure change and combination or dissociation. It will be a key technology for the development of protein chip technology

Surface protection during plasma hydrogenation for acceptor passivation in InP

International Nuclear Information System (INIS)

Lopata, J.; Dautremont-Smith, W.C.; Pearton, S.J.; Lee, J.W.; Ha, N.T.; Luftman, H.S.

1990-01-01

Various dielectric and metallic films were examined as H-permeable surface protection layers on InP during H 2 or D 2 plasma exposure for passivation of acceptors in the InP. Plasma deposited SiN x , SiO 2 , and a-Si(H) films ranging in thickness from 85 to 225 angstrom were used to protect p-InP during d 2 plasma exposure at 250 degrees C. Optimum protective layer thicknesses were determined by a trade-off between the effectiveness of the layer to prevent P loss from the wafer surface and the ability to diffuse atomic H or D at a rate greater than or equal to that in the underlying InP. SIMS and capacitance-voltage depth profiling were used to determine the extent of D in-diffusion and acceptor passivation respectively. Sputter deposited W and e-beam evaporated Ti films ∼100 Angstrom thick were also evaluated. The W coated sample yielded similar results to those with dielectric films in that acceptors in p-InP were passivated to a similar depth for the same plasma exposure. The 100 Angstrom Ti film, however, did not allow the D to diffuse into the InP substrate. It is surmised that the Ti film trapped the D, thus preventing diffusion into the substrate

Estimation of the variations of ventilation rate and indoor radon concentration using the observed wind velocity and indoor-outdoor temperature difference

International Nuclear Information System (INIS)

Nagano, Katsuhiro; Inose, Yuichi; Kojima, Hiroshi

2006-01-01

The indoor radon concentration in the building depends on the ventilation rate. Measurement results of indoor-outdoor pressure difference showed the ventilation rate correlated closely with the indoor-outdoor pressure difference. The observation results showed that one of factor of indoor-outdoor pressure difference was the wind velocity. When the wind velocity is small, the ventilation rate is affected by the indoor-outdoor temperature difference and the effect depends on the wind velocity. The temporal variation of indoor radon concentration was predicted by the time depending indoor radon balance model and the ventilation rate estimated from the wind velocity and the indoor-outdoor temperature difference. The temporal variations of predicted radon concentration gave good agreement with the experimental values. The measurement method, indoor radon concentration and ventilation rate, factors of temporal variation of ventilation rate, and prediction of indoor radon concentration are reported. (S.Y.)

KECK NIRSPEC RADIAL VELOCITY OBSERVATIONS OF LATE-M DWARFS

Energy Technology Data Exchange (ETDEWEB)

Tanner, Angelle; White, Russel [Department of Astronomy, Georgia State University, One Park Place, Atlanta, GA 30303 (United States); Bailey, John [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109-1042 (United States); Blake, Cullen [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Ivy Lane, Princeton, NJ 08544 (United States); Blake, Geoffrey [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Cruz, Kelle [Department of Physics and Astronomy, Hunter College, 695 Park Avenue, New York, NY 10065 (United States); Burgasser, Adam J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Kraus, Adam [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

2012-11-15

We present the results of an infrared spectroscopic survey of 23 late-M dwarfs with the NIRSPEC echelle spectrometer on the Keck II telescope. Using telluric lines for wavelength calibration, we are able to achieve measurement precisions of down to 45 m s{sup -1} for our late-M dwarfs over a one- to four-year long baseline. Our sample contains two stars with radial velocity (RV) variations of >1000 m s{sup -1}. While we require more measurements to determine whether these RV variations are due to unseen planetary or stellar companions or are the result of starspots known to plague the surface of M dwarfs, we can place upper limits of <40 M{sub J} sin i on the masses of any companions around those two M dwarfs with RV variations of <160 m s{sup -1} at orbital periods of 10-100 days. We have also measured the rotational velocities for all the stars in our late-M dwarf sample and offer our multi-order, high-resolution spectra over 2.0-2.4 {mu}m to the atmospheric modeling community to better understand the atmospheres of late-M dwarfs.

KECK NIRSPEC RADIAL VELOCITY OBSERVATIONS OF LATE-M DWARFS

International Nuclear Information System (INIS)

Tanner, Angelle; White, Russel; Bailey, John; Blake, Cullen; Blake, Geoffrey; Cruz, Kelle; Burgasser, Adam J.; Kraus, Adam

2012-01-01

We present the results of an infrared spectroscopic survey of 23 late-M dwarfs with the NIRSPEC echelle spectrometer on the Keck II telescope. Using telluric lines for wavelength calibration, we are able to achieve measurement precisions of down to 45 m s –1 for our late-M dwarfs over a one- to four-year long baseline. Our sample contains two stars with radial velocity (RV) variations of >1000 m s –1 . While we require more measurements to determine whether these RV variations are due to unseen planetary or stellar companions or are the result of starspots known to plague the surface of M dwarfs, we can place upper limits of J sin i on the masses of any companions around those two M dwarfs with RV variations of –1 at orbital periods of 10-100 days. We have also measured the rotational velocities for all the stars in our late-M dwarf sample and offer our multi-order, high-resolution spectra over 2.0-2.4 μm to the atmospheric modeling community to better understand the atmospheres of late-M dwarfs.

Ultrafast electron transfer in all-carbon-based SWCNT-C60 donor-acceptor nanoensembles connected by poly(phenylene-ethynylene) spacers

Science.gov (United States)

Barrejón, Myriam; Gobeze, Habtom B.; Gómez-Escalonilla, María J.; Fierro, José Luis G.; Zhang, Minfang; Yudasaka, Masako; Iijima, Sumio; D'Souza, Francis; Langa, Fernando

2016-08-01

Building all-carbon based functional materials for light energy harvesting applications could be a solution to tackle and reduce environmental carbon output. However, development of such all-carbon based donor-acceptor hybrids and demonstration of photoinduced charge separation in such nanohybrids is a challenge since in these hybrids part of the carbon material should act as an electron donating or accepting photosensitizer while the second part should fulfil the role of an electron acceptor or donor. In the present work, we have successfully addressed this issue by synthesizing covalently linked all-carbon-based donor-acceptor nanoensembles using single-walled carbon nanotubes (SWCNTs) as the donor and C60 as the acceptor. The donor-acceptor entities in the nanoensembles were connected by phenylene-ethynylene spacer units to achieve better electronic communication and to vary the distance between the components. These novel SWCNT-C60 nanoensembles have been characterized by a number of techniques, including TGA, FT-IR, Raman, AFM, absorbance and electrochemical methods. The moderate number of fullerene addends present on the side-walls of the nanotubes largely preserved the electronic structure of the nanotubes. The thermodynamic feasibility of charge separation in these nanoensembles was established using spectral and electrochemical data. Finally, occurrence of ultrafast electron transfer from the excited nanotubes in these donor-acceptor nanohybrids has been established by femtosecond transient absorption studies, signifying their utility in building light energy harvesting devices.Building all-carbon based functional materials for light energy harvesting applications could be a solution to tackle and reduce environmental carbon output. However, development of such all-carbon based donor-acceptor hybrids and demonstration of photoinduced charge separation in such nanohybrids is a challenge since in these hybrids part of the carbon material should act as an

Velocity distribution of fragments of catastrophic impacts

Science.gov (United States)

Takagi, Yasuhiko; Kato, Manabu; Mizutani, Hitoshi

1992-01-01

Three dimensional velocities of fragments produced by laboratory impact experiments were measured for basalts and pyrophyllites. The velocity distribution of fragments obtained shows that the velocity range of the major fragments is rather narrow, at most within a factor of 3 and that no clear dependence of velocity on the fragment mass is observed. The NonDimensional Impact Stress (NDIS) defined by Mizutani et al. (1990) is found to be an appropriate scaling parameter to describe the overall fragment velocity as well as the antipodal velocity.

Observation and analysis of abrupt changes in the interplanetary plasma velocity and magnetic field.

Science.gov (United States)

Martin, R. N.; Belcher, J. W.; Lazarus, A. J.

1973-01-01

This paper presents a limited study of the physical nature of abrupt changes in the interplanetary plasma velocity and magnetic field based on 19 day's data from the Pioneer 6 spacecraft. The period was chosen to include a high-velocity solar wind stream and low-velocity wind. Abrupt events were accepted for study if the sum of the energy density in the magnetic field and velocity changes was above a specified minimum. A statistical analysis of the events in the high-velocity solar wind stream shows that Alfvenic changes predominate. This conclusion is independent of whether steady state requirements are imposed on conditions before and after the event. Alfvenic changes do not dominate in the lower-speed wind. This study extends the plasma field evidence for outwardly propagating Alfvenic changes to time scales as small as 1 min (scale lengths on the order of 20,000 km).

Making highly conductive ZnO: creating donors and destroying acceptors

Science.gov (United States)

Look, D. C.; Leedy, K. D.

2012-02-01

We obtain room-temperature resistivities as low as ρ =1.4 x 10-4 Ω-cm in transparent Ga-doped ZnO grown on Al2O3 by pulsed laser deposition (PLD) at 200 °C in 10 mTorr of pure Ar and then annealed in a Zn enfivironment. Donor ND and acceptor NA concentrations are calculated from a recently developed scattering theory that is valid for any degenerate semiconductor material and requires only two input parameters, mobility μ and carrier concentration n measured at any temperature in the range 5 - 300 K. By comparison with SIMS and positron annihilation measurements, it has been shown that the donors in these samples are mostly GaZn, as expected, but that the acceptors are point defects, Zn vacancies VZn. PLD growth in Ar at 200 °C produces a high concentration of donors [GaZn] = 1.4 x 1021 cm-3, but VZn acceptors are produced at the same time, due to self-compensation. Fortunately, a large fraction of the VZn can be eliminated by annealing in a Zn environment. The theory gives ND and NA, and thus [GaZn] and [VZn], at each step of the growth and annealing process. For convenience, the theory is presented graphically, as plots of μ vs n at various values of compensation ratio K = NA/ND. From the value of K corresponding to the experimental values of μ and n, it is possible to calculate ND = n/(1 - K) and NA = nK/(1 - K).

J-V and C-V investigation of the effect of small molecular fullerene and non-fullerene acceptors for CH3NH3PbI3 perovskite solar cell

Science.gov (United States)

Zheng, Yanqiong; Wang, Chao; Yu, Junle; Yang, Fang; Zhang, Jing; Wei, Bin; Li, Weishi

2017-11-01

To find the ideal acceptors for perovskite solar cells (PSCs) and get insight into the dielectric property at the interface between perovskite and acceptor, series of small molecular fullerene and non-fullerene acceptors were comparatively investigated. Fullerene acceptors based PSCs show higher performance than non-fullerene acceptors based PSCs. However, the perylene tetracarboxylic diimide based PSC has achieved a η PCE of 4.70%, implying that it is a promising acceptor candidate for PSCs because of its suitable energy level, high electron mobility, and smooth surface. By employing double acceptors of (6,6)-phenyl-C61-butyric acid methyl ester (PCBM)/C60 or PCBM/3,4,9,10-perylenetetracarboxylic bisbenzimidazole, the PSC stability is greatly improved even without performance enhancement. The perovskite (Pero)/PCBM film shows smooth surface, suggesting that PCBM penetrates into the Pero layer. The hydrophobicity trend of Pero/acceptor composite films is same as the device performance by judging from the water contact angle, and Pero/PCBM as well as Pero/C60 show higher hydrophobicity than other Pero/small-molecular-acceptor composite films. Capacitance-voltage characteristics of the series of single and double acceptor based PSCs were measured. The double acceptor based PSCs show larger depletion layer width (W d) than single acceptor based PSCs. Meanwhile, the defect density (N A) in Pero layer for single acceptor based PSCs is larger than that for double acceptor based PSCs, implying better n-doping of Pero layer by using a single acceptor.

Anaerobic α-Amylase Production and Secretion with Fumarate as the Final Electron Acceptor in Saccharomyces cerevisiae

DEFF Research Database (Denmark)

Liu, Zihe; Österlund, Tobias; Hou, Jin

2013-01-01

In this study, we focus on production of heterologous α-amylase in the yeast Saccharomyces cerevisiae under anaerobic conditions. We compare the metabolic fluxes and transcriptional regulation under aerobic and anaerobic conditions, with the objective of identifying the final electron acceptor...... reticulum are transferred to fumarate as the final electron acceptor. This model is supported by findings that the addition of fumarate under anaerobic (but not aerobic) conditions improves cell growth, specifically in the α-amylase-producing strain, in which it is not used as a carbon source. Our results...... provide a model for the molecular mechanism of anaerobic protein secretion using fumarate as the final electron acceptor, which may allow for further engineering of yeast for improved protein secretion under anaerobic growth conditions....

Influence of substitution of the proton donor and proton acceptor abilities of molecules. 1. The development method of definition proton donor and proton acceptor abilities A-H containing molecules

International Nuclear Information System (INIS)

Nurulloev, M.; Narziev, B.N.; Islomov, Z.; Fayzieva, M.

2005-01-01

The influence of nature of the assistant is investigated in work, it is quantity and a site on proton donor and proton acceptor abilities. A-H containing organic connections and ways, of definition of these abilities are developed by the method, of IR spectroscopy. It is developed model and it offered a technique of definition of these abilities. It is shown that the proton donor and proton acceptor is abilities of molecules as constants, are one of individual physical and chemical characteristics A-H of containing organic connections. These sizes determine the abilities of molecules, to form the intermolecular hydrogen connections, disabilities of the H-complexes formed in condensed, environments concerning to the non replaced molecule

Electron Transfer in Donor-Bridge-Acceptor Systems and Derived Materials

NARCIS (Netherlands)

Oosterbaan, W.D.

2002-01-01

Some aspects of photoinduced electron transfer (ET) in (electron donor)-bridge-(electron acceptor) compounds (D-B-A) and derived materials are investigated. Aim I is to determine how and to which extent non-conjugated double bonds in an otherwise saturated hydrocarbon bridge affect the rate of

Quantum computing with acceptor spins in silicon.

Science.gov (United States)

Salfi, Joe; Tong, Mengyang; Rogge, Sven; Culcer, Dimitrie

2016-06-17

The states of a boron acceptor near a Si/SiO2 interface, which bind two low-energy Kramers pairs, have exceptional properties for encoding quantum information and, with the aid of strain, both heavy hole and light hole-based spin qubits can be designed. Whereas a light-hole spin qubit was introduced recently (arXiv:1508.04259), here we present analytical and numerical results proving that a heavy-hole spin qubit can be reliably initialised, rotated and entangled by electrical means alone. This is due to strong Rashba-like spin-orbit interaction terms enabled by the interface inversion asymmetry. Single qubit rotations rely on electric-dipole spin resonance (EDSR), which is strongly enhanced by interface-induced spin-orbit terms. Entanglement can be accomplished by Coulomb exchange, coupling to a resonator, or spin-orbit induced dipole-dipole interactions. By analysing the qubit sensitivity to charge noise, we demonstrate that interface-induced spin-orbit terms are responsible for sweet spots in the dephasing time [Formula: see text] as a function of the top gate electric field, which are close to maxima in the EDSR strength, where the EDSR gate has high fidelity. We show that both qubits can be described using the same starting Hamiltonian, and by comparing their properties we show that the complex interplay of bulk and interface-induced spin-orbit terms allows a high degree of electrical control and makes acceptors potential candidates for scalable quantum computation in Si.

Phenyl vs Alkyl Polythiophene: A Solar Cell Comparison Using a Vinazene Derivative as Acceptor

KAUST Repository

Woo, Claire H.; Holcombe, Thomas W.; Unruh, David A.; Sellinger, Alan; Fréchet, Jean M. J.

2010-01-01

The solar cell performance of poly[3-(4-n-octyl)-phenylthiophene] (POPT) and poly(3hexylthiophene) (P3HT) are compared in devices using 4,7-bis(2-(l-(2-ethylhexyl)-4,5-dicyanoimidazol-2-yl)vinyi)benzo[c][l,2,5] -thiadiazole (EV-BT) as the electron acceptor. Despite their reduced light absorption, POPT:EV-BT devices generate higher photocurrents in both bilayer and bulk heterojunction (BHJ) architectures than analogous P3HT:EV-BT devices. Optimized POPT:EV-BT BHJ devices achieve 1.4% average efficiency, whereas the analogous P3HT devices only reach 1.1%. Morphology does not account for the large difference in performance as AFM studies of the active layer suggest, comparable levels of phase separation in the two systems. Reverse bias analysis demonstrates that P3HT devices have a higher maximum potential than POPT devices, but P3HT devices appear to be more severely limited by recombination losses under standard operating conditions. A possible explanation for the superior performance in POPT devices is that the pendant phenyl ring in POPT can twist out-of-plane and increase the separation distance with the acceptor molecule. A larger donor/acceptor separation distance can destabilize the geminate pair and lead to more efficient charge separation in POPT:EV-BT devices. Our results emphasize the importance of donor/acceptor pair interactions and its effect on charge separation, processes in polymer solar cells. © 2010 American Chemical Society.

Phenyl vs Alkyl Polythiophene: A Solar Cell Comparison Using a Vinazene Derivative as Acceptor

KAUST Repository

Woo, Claire H.

2010-03-09

The solar cell performance of poly[3-(4-n-octyl)-phenylthiophene] (POPT) and poly(3hexylthiophene) (P3HT) are compared in devices using 4,7-bis(2-(l-(2-ethylhexyl)-4,5-dicyanoimidazol-2-yl)vinyi)benzo[c][l,2,5] -thiadiazole (EV-BT) as the electron acceptor. Despite their reduced light absorption, POPT:EV-BT devices generate higher photocurrents in both bilayer and bulk heterojunction (BHJ) architectures than analogous P3HT:EV-BT devices. Optimized POPT:EV-BT BHJ devices achieve 1.4% average efficiency, whereas the analogous P3HT devices only reach 1.1%. Morphology does not account for the large difference in performance as AFM studies of the active layer suggest, comparable levels of phase separation in the two systems. Reverse bias analysis demonstrates that P3HT devices have a higher maximum potential than POPT devices, but P3HT devices appear to be more severely limited by recombination losses under standard operating conditions. A possible explanation for the superior performance in POPT devices is that the pendant phenyl ring in POPT can twist out-of-plane and increase the separation distance with the acceptor molecule. A larger donor/acceptor separation distance can destabilize the geminate pair and lead to more efficient charge separation in POPT:EV-BT devices. Our results emphasize the importance of donor/acceptor pair interactions and its effect on charge separation, processes in polymer solar cells. © 2010 American Chemical Society.

Results of verification and investigation of wind velocity field forecast. Verification of wind velocity field forecast model

International Nuclear Information System (INIS)

Ogawa, Takeshi; Kayano, Mitsunaga; Kikuchi, Hideo; Abe, Takeo; Saga, Kyoji

1995-01-01

In Environmental Radioactivity Research Institute, the verification and investigation of the wind velocity field forecast model 'EXPRESS-1' have been carried out since 1991. In fiscal year 1994, as the general analysis, the validity of weather observation data, the local features of wind field, and the validity of the positions of monitoring stations were investigated. The EXPRESS which adopted 500 m mesh so far was improved to 250 m mesh, and the heightening of forecast accuracy was examined, and the comparison with another wind velocity field forecast model 'SPEEDI' was carried out. As the results, there are the places where the correlation with other points of measurement is high and low, and it was found that for the forecast of wind velocity field, by excluding the data of the points with low correlation or installing simplified observation stations to take their data in, the forecast accuracy is improved. The outline of the investigation, the general analysis of weather observation data and the improvements of wind velocity field forecast model and forecast accuracy are reported. (K.I.)

Molecular designing of novel ternary copolymers of donor-acceptor polymers using genetic algorithm

International Nuclear Information System (INIS)

Arora, Vinita; Bakhshi, A.K.

2010-01-01

Graphical abstract: Alternate arrangement of donor acceptor moieties in the carbon backbone chain of an organic conjugated polymer is capable of inducing charge transfer and affects the electronic properties of the copolymer. Genetic algorithm along with simple NFC (negative factor counting) and IIM (inverse iteration method) has been used to optimize the properties of novel ternary copolymers based on polypyrrole PPy, polythiophene PTh and polyfuran PFu (as donor moieties) and containing >C=O and >C=CF 2 bridging units as acceptor moieties. - Abstract: An efficient designing route to novel ternary copolymers consisting of polypyrrole (PPy), polythiophene (PTh) and polyfuran (PFu) is developed with the help of genetic algorithm. Using the band structure results obtained from ab initio crystal orbital (CO) calculations, the electronic structures and conduction properties of real ternary copolymers based on donor acceptor type polymers are investigated. The electron rich heterocyclic rings in the backbone chain of the copolymer are joined together by electron withdrawing groups Y, carbonyl group (>C=O) and difluoromethylene group (>C=CF 2 ) in an attempt to design the conducting polymer with lowest band gap. A comparative study of various electronic properties is presented. The effects of substitution on the behaviour and properties of the copolymers as well as on the density of states (DOS) are discussed. Band gap decreases as a result of substitution on the polymer backbone chain due to decrease in ionization potential and increase in electron affinity values. This is expected to enhance the intrinsic conductivity of the resulting copolymer. Use of alternate donor acceptor moieties within the repeat units should maximize the extended π conjugation.

Molecular designing of novel ternary copolymers of donor-acceptor polymers using genetic algorithm

Energy Technology Data Exchange (ETDEWEB)

Arora, Vinita [Department of Chemistry, University of Delhi, Delhi 110 007 (India); Bakhshi, A.K., E-mail: akbakhshi2000@yahoo.com [Department of Chemistry, University of Delhi, Delhi 110 007 (India)

2010-08-03

Graphical abstract: Alternate arrangement of donor acceptor moieties in the carbon backbone chain of an organic conjugated polymer is capable of inducing charge transfer and affects the electronic properties of the copolymer. Genetic algorithm along with simple NFC (negative factor counting) and IIM (inverse iteration method) has been used to optimize the properties of novel ternary copolymers based on polypyrrole PPy, polythiophene PTh and polyfuran PFu (as donor moieties) and containing >C=O and >C=CF{sub 2} bridging units as acceptor moieties. - Abstract: An efficient designing route to novel ternary copolymers consisting of polypyrrole (PPy), polythiophene (PTh) and polyfuran (PFu) is developed with the help of genetic algorithm. Using the band structure results obtained from ab initio crystal orbital (CO) calculations, the electronic structures and conduction properties of real ternary copolymers based on donor acceptor type polymers are investigated. The electron rich heterocyclic rings in the backbone chain of the copolymer are joined together by electron withdrawing groups Y, carbonyl group (>C=O) and difluoromethylene group (>C=CF{sub 2}) in an attempt to design the conducting polymer with lowest band gap. A comparative study of various electronic properties is presented. The effects of substitution on the behaviour and properties of the copolymers as well as on the density of states (DOS) are discussed. Band gap decreases as a result of substitution on the polymer backbone chain due to decrease in ionization potential and increase in electron affinity values. This is expected to enhance the intrinsic conductivity of the resulting copolymer. Use of alternate donor acceptor moieties within the repeat units should maximize the extended {pi} conjugation.

Comparative evaluation of the acceptor properties of quinone derivatized polypyridinic ligands

Energy Technology Data Exchange (ETDEWEB)

Norambuena, Ester [Departamento de Quimica, Facultad de Ciencias Basicas, Universidad Metropolitana de Ciencias de la Educacion, Santiago (Chile); Olea-Azar, Claudio [Facultad de Ciencias Quimicas y Farmaceuticas, Universidad de Chile, Santiago (Chile); Delgadillo, Alvaro [Departamento de Quimica, Facultad de Ciencias, Universidad de La Serena, Casilla 599, La Serena (Chile); Barrera, Mauricio [Facultad de Quimica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago (Chile); Loeb, Barbara, E-mail: bloeb@puc.cl [Facultad de Quimica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago (Chile)

2009-05-18

The reduction properties of four acceptor polipyridyl ligands modified with quinones were studied by different experimental methods, as cyclic voltammetry and ESR spectroscopy, and by theoretical calculations. ESR spectra for the reduced ligands show different patterns among them, suggesting that the quinone moiety plays an important role in the delocalization of the received electron. The hyperfine coupling constants calculated for the magnetic nucleus were in good agreement with experimental data. The results were additionally interpreted with the help of two theoretical predictors: the electrophilicity index and the Fukui function obtained through the spin density. The results suggest that 12,17-dihydronaphtho-[2,3-h]dipyrido[3,2-a:2',3'-c]-phenazine-12,17-dione, Aqphen, shows the most promising behavior to be employed as an acceptor ligand in complexes with potential application in NLO devices.

Comparative evaluation of the acceptor properties of quinone derivatized polypyridinic ligands

International Nuclear Information System (INIS)

Norambuena, Ester; Olea-Azar, Claudio; Delgadillo, Alvaro; Barrera, Mauricio; Loeb, Barbara

2009-01-01

The reduction properties of four acceptor polipyridyl ligands modified with quinones were studied by different experimental methods, as cyclic voltammetry and ESR spectroscopy, and by theoretical calculations. ESR spectra for the reduced ligands show different patterns among them, suggesting that the quinone moiety plays an important role in the delocalization of the received electron. The hyperfine coupling constants calculated for the magnetic nucleus were in good agreement with experimental data. The results were additionally interpreted with the help of two theoretical predictors: the electrophilicity index and the Fukui function obtained through the spin density. The results suggest that 12,17-dihydronaphtho-[2,3-h]dipyrido[3,2-a:2',3'-c]-phenazine-12,17-dione, Aqphen, shows the most promising behavior to be employed as an acceptor ligand in complexes with potential application in NLO devices.

An effective Hamiltonian approach for Donor-Bridge-Acceptor electronic transitions: Exploring the role of bath memory

Directory of Open Access Journals (Sweden)

E.R. Bittner

2016-03-01

Full Text Available We present here a formally exact model for electronic transitions between an initial (donor and final (acceptor states linked by an intermediate (bridge state. Our model incorporates a common set of vibrational modes that are coupled to the donor, bridge, and acceptor states and serves as a dissipative bath that destroys quantum coherence between the donor and acceptor. Taking the memory time of the bath as a free parameter, we calculate transition rates for a heuristic 3-state/2 mode Hamiltonian system parameterized to represent the energetics and couplings in a typical organic photovoltaic system. Our results indicate that if the memory time of the bath is of the order of 10-100 fs, a two-state kinetic (i.e., incoherent hopping model will grossly underestimate overall transition rate.

Fullerene-based materials for solar cell applications: design of novel acceptors for efficient polymer solar cells--a DFT study.

Science.gov (United States)

Mohajeri, Afshan; Omidvar, Akbar

2015-09-14

Fossil fuel alternatives, such as solar energy, are moving to the forefront in a variety of research fields. Polymer solar cells (PSCs) hold promise for their potential to be used as low-cost and efficient solar energy converters. PSCs have been commonly made from bicontinuous polymer:fullerene composites or so-called bulk heterojunctions. The conjugated polymer donors and the fullerene derivative acceptors are the key materials for high performance PSCs. In the present study, we have performed density functional theory calculations to investigate the electronic structures and magnetic properties of several representative C60 fullerene derivatives, seeking ways to improve their efficiency as acceptors of photovoltaic devices. In our survey, we have successfully correlated the LUMO energy level as well as chemical hardness, hyper-hardness, nucleus-independent chemical shift, and static dipole polarizability of PC60BM-like fullerene derivative acceptors with the experimental open circuit voltage of the photovoltaic device based on the P3HT:fullerene blend. The obtained structure-property correlations allow finding the best fullerene acceptor match for the P3HT donor. For this purpose, four new fullerene derivatives are proposed and the output parameters for the corresponding P3HT-based devices are predicted. It is found that the proposed fullerene derivatives exhibit better photovoltaic properties than the traditional PC60BM acceptor. The present study opens the way for manipulating fullerene derivatives and developing promising acceptors for solar cell applications.

Mechanism and Dynamics of Charge Transfer in Donor-Bridge-Acceptor Systems

NARCIS (Netherlands)

Gorczak-Vos, N.

2016-01-01

Photoinduced charge transfer in organic materials is a fundamental process in various biological and technological areas. Donor-bridge-acceptor (DBA) molecules are used as model systems in numerous theoretical and experimental work to systematically study and unravel the underlying mechanisms of

Observations of the radial velocity of the Sun as measured with the novel SONG spectrograph

DEFF Research Database (Denmark)

Pallé, P. L.; Grundahl, F.; Hage, A. Triviño

2013-01-01

Deployment of the prototype node of the SONG project took place in April 2012 at Observatorio del Teide (Canary Islands). Its key instrument (echelle spectrograph) was installed and operational a few weeks later while its 1 m feeding telescope suffered a considerable delay to meet the required...... specifications. Using a fibre-feed, solar light could be fed to the spectrograph and we carried out a 1-week observing campaign in June 2012 to evaluate its performance for measuring precision radial velocities. In this work we present the first results of this campaign by comparing the sensitivity of the SONG...

Characteristics of vertical velocity in marine stratocumulus: comparison of large eddy simulations with observations

International Nuclear Information System (INIS)

Guo Huan; Liu Yangang; Daum, Peter H; Senum, Gunnar I; Tao, W-K

2008-01-01

We simulated a marine stratus deck sampled during the Marine Stratus/Stratocumulus Experiment (MASE) with a three-dimensional large eddy simulation (LES) model at different model resolutions. Various characteristics of the vertical velocity from the model simulations were evaluated against those derived from the corresponding aircraft in situ observations, focusing on standard deviation, skewness, kurtosis, probability density function (PDF), power spectrum, and structure function. Our results show that although the LES model captures reasonably well the lower-order moments (e.g., horizontal averages and standard deviations), it fails to simulate many aspects of the higher-order moments, such as kurtosis, especially near cloud base and cloud top. Further investigations of the PDFs, power spectra, and structure functions reveal that compared to the observations, the model generally underestimates relatively strong variations on small scales. The results also suggest that increasing the model resolutions improves the agreements between the model results and the observations in virtually all of the properties that we examined. Furthermore, the results indicate that a vertical grid size <10 m is necessary for accurately simulating even the standard-deviation profile, posing new challenges to computer resources.

π-Bridge-Independent 2-(Benzo[c][1,2,5]thiadiazol-4-ylmethylene)malononitrile-Substituted Nonfullerene Acceptors for Efficient Solar Cells

KAUST Repository

Wang, Kai

2016-02-25

Molecular acceptors are promising alternatives to fullerenes (e.g. PC61/71BM) in the fabrication of high-efficiency bulk-heterojunction (BHJ) solar cells. While solution-processed polymer-fullerene BHJ devices have recently met the 10% efficiency threshold, molecular acceptors have yet to prove comparably efficient with polymer donors. At this point in time, it is important to forge a better understanding of the design parameters that directly impact small-molecule (SM) acceptor performance in BHJ solar cells. In this report, we show that 2-(benzo[c][1,2,5]thiadiazol-4-ylmethylene)malononitrile (BM)-terminated SM acceptors can achieve efficiencies as high as 5.3% in BHJ solar cells with the polymer donor PCE10. Through systematic device optimization and characterization studies, we find that the nonfull-erene analogues (FBM, CBM and CDTBM) all perform comparably well, independent of the molecular structure and electronics of the π-bridge that links the two electron-deficient BM end groups. With estimated electron affinities within range of those of common fullerenes (4.0-4.3 eV), and a wider range of ionization potentials (6.2-5.6 eV), the SM acceptors absorb in the visible spectrum and effectively contribute to the BHJ device photocurrent. BM-substituted SM acceptors are promising alterna-tives to fullerenes in solution-processed BHJ solar cells.

π-Bridge-Independent 2-(Benzo[c][1,2,5]thiadiazol-4-ylmethylene)malononitrile-Substituted Nonfullerene Acceptors for Efficient Solar Cells

KAUST Repository

Wang, Kai; Firdaus, Yuliar; Babics, Maxime; Cruciani, Federico; Saleem, Qasim; El Labban, Abdulrahman; Alamoudi, Maha; Marszalek, Tomasz; Pisula, Wojciech; Laquai, Fré dé ric; Beaujuge, Pierre

2016-01-01

Molecular acceptors are promising alternatives to fullerenes (e.g. PC61/71BM) in the fabrication of high-efficiency bulk-heterojunction (BHJ) solar cells. While solution-processed polymer-fullerene BHJ devices have recently met the 10% efficiency threshold, molecular acceptors have yet to prove comparably efficient with polymer donors. At this point in time, it is important to forge a better understanding of the design parameters that directly impact small-molecule (SM) acceptor performance in BHJ solar cells. In this report, we show that 2-(benzo[c][1,2,5]thiadiazol-4-ylmethylene)malononitrile (BM)-terminated SM acceptors can achieve efficiencies as high as 5.3% in BHJ solar cells with the polymer donor PCE10. Through systematic device optimization and characterization studies, we find that the nonfull-erene analogues (FBM, CBM and CDTBM) all perform comparably well, independent of the molecular structure and electronics of the π-bridge that links the two electron-deficient BM end groups. With estimated electron affinities within range of those of common fullerenes (4.0-4.3 eV), and a wider range of ionization potentials (6.2-5.6 eV), the SM acceptors absorb in the visible spectrum and effectively contribute to the BHJ device photocurrent. BM-substituted SM acceptors are promising alterna-tives to fullerenes in solution-processed BHJ solar cells.

TAURUS observations of the emission-line velocity field of Centaurus A (NGC 5128)

International Nuclear Information System (INIS)

Taylor, K.; Atherton, P.D.

1983-01-01

Using TAURUS - an Imaging Fabry Perot system in conjunction with the IPCS on the AAT, the authors have studied the velocity field of the Hα emission line at a spatial resolution of 1.7'' over the dark lane structure of Centaurus A. The derived velocity field is quite symmetrical and strongly suggests that the emission line material is orbiting the elliptical component, as a warped disc. (orig.)

2004 Electron Donor Acceptor Interactions Gordon Conference - August 8-13, 2004

Energy Technology Data Exchange (ETDEWEB)

GUILFORD JONES; S ST

2005-09-14

The 2004 Gordon Conference on Donor/Acceptor Interactions will take place at Salve Regina University in Newport, Rhode Island on August 8-13, 2004. The conference will be devoted to the consequences of charge interaction and charge motion in molecular and materials systems.

The role of acceptor-rich domain in optoelectronic properties of photovoltaic diodes based on polymer blends

Science.gov (United States)

Dou, Fei; Silva, Carlos; Zhang, Xinping

2013-09-01

We investigate how the acceptor-rich domain influences the microstructure and photoluminescence properties, and consequently the external quantum efficiency of photovoltaic diodes based on blend films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(N,N'-diphenyl)-N,N'di(p-butyl-oxy-pheyl)-1,4-diaminobenzene)] (PFB) and poly[9,9-dioctylfluorenyl-2,7-diyl)-co-1,4-benzo-{2,1'-3}-thiadiazole)] (F8BT). We find that the interfacial area depends strongly on the size and density of acceptor- or F8BT-rich domains in the phase-separation scheme. There exists an optimized density and size distribution of the F8BT-rich domains, which favors spatial charge dissociation. Meanwhile, the balance of charge percolation between the donor(PFB)- and acceptor(F8BT)-rich domains also plays important roles in charge extraction and collection.

Attenuation and velocity dispersion in the exploration seismic frequency band

Science.gov (United States)

Sun, Langqiu

In an anelastic medium, seismic waves are distorted by attenuation and velocity dispersion, which depend on petrophysical properties of reservoir rocks. The effective attenuation and velocity dispersion is a combination of intrinsic attenuation and apparent attenuation due to scattering, transmission response, and data acquisition system. Velocity dispersion is usually neglected in seismic data processing partly because of insufficient observations in the exploration seismic frequency band. This thesis investigates the methods of measuring velocity dispersion in the exploration seismic frequency band and interprets the velocity dispersion data in terms of petrophysical properties. Broadband, uncorrelated vibrator data are suitable for measuring velocity dispersion in the exploration seismic frequency band, and a broad bandwidth optimizes the observability of velocity dispersion. Four methods of measuring velocity dispersion in uncorrelated vibrator VSP data are investigated, which are the sliding window crosscorrelation (SWCC) method, the instantaneous phase method, the spectral decomposition method, and the cross spectrum method. Among them, the SWCC method is a new method and has satisfactory robustness, accuracy, and efficiency. Using the SWCC method, velocity dispersion is measured in the uncorrelated vibrator VSP data from three areas with different geological settings, i.e., Mallik gas hydrate zone, McArthur River uranium mines, and Outokumpu crystalline rocks. The observed velocity dispersion is fitted to a straight line with respect to log frequency for a constant (frequency-independent) Q value. This provides an alternative method for calculating Q. A constant Q value does not directly link to petrophysical properties. A modeling study is implemented for the Mallik and McArthur River data to interpret the velocity dispersion observations in terms of petrophysical properties. The detailed multi-parameter petrophysical reservoir models are built according to

Global catalog of earthquake rupture velocities shows anticorrelation between stress drop and rupture velocity

Science.gov (United States)

Chounet, Agnès; Vallée, Martin; Causse, Mathieu; Courboulex, Françoise

2018-05-01

Application of the SCARDEC method provides the apparent source time functions together with seismic moment, depth, and focal mechanism, for most of the recent earthquakes with magnitude larger than 5.6-6. Using this large dataset, we have developed a method to systematically invert for the rupture direction and average rupture velocity Vr, when unilateral rupture propagation dominates. The approach is applied to all the shallow (z earthquakes of the catalog over the 1992-2015 time period. After a careful validation process, rupture properties for a catalog of 96 earthquakes are obtained. The subsequent analysis of this catalog provides several insights about the seismic rupture process. We first report that up-dip ruptures are more abundant than down-dip ruptures for shallow subduction interface earthquakes, which can be understood as a consequence of the material contrast between the slab and the overriding crust. Rupture velocities, which are searched without any a-priori up to the maximal P wave velocity (6000-8000 m/s), are found between 1200 m/s and 4500 m/s. This observation indicates that no earthquakes propagate over long distances with rupture velocity approaching the P wave velocity. Among the 23 ruptures faster than 3100 m/s, we observe both documented supershear ruptures (e.g. the 2001 Kunlun earthquake), and undocumented ruptures that very likely include a supershear phase. We also find that the correlation of Vr with the source duration scaled to the seismic moment (Ts) is very weak. This directly implies that both Ts and Vr are anticorrelated with the stress drop Δσ. This result has implications for the assessment of the peak ground acceleration (PGA) variability. As shown by Causse and Song (2015), an anticorrelation between Δσ and Vr significantly reduces the predicted PGA variability, and brings it closer to the observed variability.

Giant first hyperpolarizabilities of donor-acceptor substituted graphyne: An ab initio study.

Science.gov (United States)

Chakraborti, Himadri

2016-01-15

Graphyne (Gy), a theoretically proposed material, has been utilized, for the first time, in a phenomenal donor-Gy-acceptor (D-Gy-A) structure to plan a superior nonlinear optical material. Owing to the extraordinary character of graphyne, this conjugate framework shows strikingly extensive static first hyperpolarizability (β(tot)) up to 128×10(-30) esu which is an enormous improvement than that of the bare graphyne. The donor-acceptor separation plays a key role in the change of β(tot) value. The π-conjugation of graphyne backbone has spread throughout some of the D-A attached molecules and leads to a low band gap state. Finally, two level model clarifies that the molecule having low transition energy should have high first hyperpolarizability. Copyright © 2015 Elsevier B.V. All rights reserved.

On the Molecular Origin of Charge Separation at the Donor-Acceptor Interface

KAUST Repository

Sini, Gjergji; Schubert, Marcel; Risko, Chad; Roland, Steffen; Lee, Olivia P.; Chen, Zhihua; Richter, Thomas V.; Dolfen, Daniel; Coropceanu, Veaceslav; Ludwigs, Sabine; Scherf, Ullrich; Facchetti, Antonio; Frechet, Jean; Neher, Dieter

2018-01-01

and theoretical approach is used to understand the intimate mechanisms by which molecular structure contributes to exciton dissociation, charge separation, and charge recombination at the donor–acceptor (D–A) interface. Model systems comprised of polythiophene

The radial velocity, velocity dispersion, and mass-to-light ratio of the Sculptor dwarf galaxy

Science.gov (United States)

Armandroff, T. E.; Da Costa, G. S.

1986-01-01

The radial velocity, velocity dispersion, and mass-to-light ratio for 16 K giants in the Sculptor dwarf galaxy are calculated. Spectra at the Ca II triplet are analyzed using cross-correlation techniques in order to obtain the mean velocity of + 107.4 + or - 2.0 km/s. The dimensional velocity dispersion estimated as 6.3 (+1.1, -1.3) km/s is combined with the calculated core radius and observed central surface brightness to produce a mass-to-light ratio of 6.0 in solar units. It is noted that the data indicate that the Sculptor contains a large amount of mass not found in globular clusters, and the mass is either in the form of remnant stars or low-mass dwarfs.

GALAXIES IN ΛCDM WITH HALO ABUNDANCE MATCHING: LUMINOSITY-VELOCITY RELATION, BARYONIC MASS-VELOCITY RELATION, VELOCITY FUNCTION, AND CLUSTERING

International Nuclear Information System (INIS)

Trujillo-Gomez, Sebastian; Klypin, Anatoly; Primack, Joel; Romanowsky, Aaron J.

2011-01-01

It has long been regarded as difficult if not impossible for a cosmological model to account simultaneously for the galaxy luminosity, mass, and velocity distributions. We revisit this issue using a modern compilation of observational data along with the best available large-scale cosmological simulation of dark matter (DM). We find that the standard cosmological model, used in conjunction with halo abundance matching (HAM) and simple dynamical corrections, fits—at least on average—all basic statistics of galaxies with circular velocities V circ > 80 km s –1 calculated at a radius of ∼10 kpc. Our primary observational constraint is the luminosity-velocity (LV) relation—which generalizes the Tully-Fisher and Faber-Jackson relations in allowing all types of galaxies to be included, and provides a fundamental benchmark to be reproduced by any theory of galaxy formation. We have compiled data for a variety of galaxies ranging from dwarf irregulars to giant ellipticals. The data present a clear monotonic LV relation from ∼50 km s –1 to ∼500 km s –1 , with a bend below ∼80 km s –1 and a systematic offset between late- and early-type galaxies. For comparison to theory, we employ our new ΛCDM 'Bolshoi' simulation of DM, which has unprecedented mass and force resolution over a large cosmological volume, while using an up-to-date set of cosmological parameters. We use HAM to assign rank-ordered galaxy luminosities to the DM halos, a procedure that automatically fits the empirical luminosity function and provides a predicted LV relation that can be checked against observations. The adiabatic contraction of DM halos in response to the infall of the baryons is included as an optional model ingredient. The resulting predictions for the LV relation are in excellent agreement with the available data on both early-type and late-type galaxies for the luminosity range from M r = –14 to M r = –22. We also compare our predictions for the 'cold' baryon mass (i

Surface wave velocity tracking by bisection method

International Nuclear Information System (INIS)

Maeda, T.

2005-01-01

Calculation of surface wave velocity is a classic problem dating back to the well-known Haskell's transfer matrix method, which contributes to solutions of elastic wave propagation, global subsurface structure evaluation by simulating observed earthquake group velocities, and on-site evaluation of subsurface structure by simulating phase velocity dispersion curves and/or H/V spectra obtained by micro-tremor observation. Recently inversion analysis on micro-tremor observation requires efficient method of generating many model candidates and also stable, accurate, and fast computation of dispersion curves and Raleigh wave trajectory. The original Haskell's transfer matrix method has been improved in terms of its divergence tendency mainly by the generalized transmission and reflection matrix method with formulation available for surface wave velocity; however, root finding algorithm has not been fully discussed except for the one by setting threshold to the absolute value of complex characteristic functions. Since surface wave number (reciprocal to the surface wave velocity multiplied by frequency) is a root of complex valued characteristic function, it is intractable to use general root finding algorithm. We will examine characteristic function in phase plane to construct two dimensional bisection algorithm with consideration on a layer to be evaluated and algorithm for tracking roots down along frequency axis. (author)

Cocrystals of 6-methyl-2-thiouracil: presence of the acceptor-donor-acceptor/donor-acceptor-donor synthon.

Science.gov (United States)

Hützler, Wilhelm Maximilian; Egert, Ernst

2015-03-01

The results of seven cocrystallization experiments of the antithyroid drug 6-methyl-2-thiouracil (MTU), C(5)H(6)N(2)OS, with 2,4-diaminopyrimidine, 2,4,6-triaminopyrimidine and 6-amino-3H-isocytosine (viz. 2,6-diamino-3H-pyrimidin-4-one) are reported. MTU features an ADA (A = acceptor and D = donor) hydrogen-bonding site, while the three coformers show complementary DAD hydrogen-bonding sites and therefore should be capable of forming an ADA/DAD N-H...O/N-H...N/N-H...S synthon with MTU. The experiments yielded one cocrystal and six cocrystal solvates, namely 6-methyl-2-thiouracil-2,4-diaminopyrimidine-1-methylpyrrolidin-2-one (1/1/2), C(5)H(6)N(2)OS·C(4)H(6)N(4)·2C(5)H(9)NO, (I), 6-methyl-2-thiouracil-2,4-diaminopyrimidine (1/1), C(5)H(6)N(2)OS·C(4)H(6)N(4), (II), 6-methyl-2-thiouracil-2,4-diaminopyrimidine-N,N-dimethylacetamide (2/1/2), 2C(5)H(6)N(2)OS·C(4)H(6)N(4)·2C(4)H(9)NO, (III), 6-methyl-2-thiouracil-2,4-diaminopyrimidine-N,N-dimethylformamide (2/1/2), C(5)H(6)N(2)OS·0.5C(4)H(6)N(4)·C(3)H(7)NO, (IV), 2,4,6-triaminopyrimidinium 6-methyl-2-thiouracilate-6-methyl-2-thiouracil-N,N-dimethylformamide (1/1/2), C(4)H(8)N(5)(+)·C(5)H(5)N(2)OS(-)·C(5)H(6)N(2)OS·2C(3)H(7)NO, (V), 6-methyl-2-thiouracil-6-amino-3H-isocytosine-N,N-dimethylformamide (1/1/1), C(5)H(6)N(2)OS·C(4)H(6)N(4)O·C(3)H(7)NO, (VI), and 6-methyl-2-thiouracil-6-amino-3H-isocytosine-dimethyl sulfoxide (1/1/1), C(5)H(6)N(2)OS·C(4)H(6)N(4)O·C(2)H(6)OS, (VII). Whereas in cocrystal (I) an R(2)(2)(8) interaction similar to the Watson-Crick adenine/uracil base pair is formed and a two-dimensional hydrogen-bonding network is observed, the cocrystals (II)-(VII) contain the triply hydrogen-bonded ADA/DAD N-H...O/N-H...N/N-H...S synthon and show a one-dimensional hydrogen-bonding network. Although 2,4-diaminopyrimidine possesses only one DAD hydrogen-bonding site, it is, due to orientational disorder, triply connected to two MTU molecules in (III) and (IV).

tRNA acceptor-stem and anticodon bases embed separate features of amino acid chemistry

Science.gov (United States)

Carter, Charles W.; Wolfenden, Richard

2016-01-01

abstract The universal genetic code is a translation table by which nucleic acid sequences can be interpreted as polypeptides with a wide range of biological functions. That information is used by aminoacyl-tRNA synthetases to translate the code. Moreover, amino acid properties dictate protein folding. We recently reported that digital correlation techniques could identify patterns in tRNA identity elements that govern recognition by synthetases. Our analysis, and the functionality of truncated synthetases that cannot recognize the tRNA anticodon, support the conclusion that the tRNA acceptor stem houses an independent code for the same 20 amino acids that likely functioned earlier in the emergence of genetics. The acceptor-stem code, related to amino acid size, is distinct from a code in the anticodon that is related to amino acid polarity. Details of the acceptor-stem code suggest that it was useful in preserving key properties of stereochemically-encoded peptides that had developed the capacity to interact catalytically with RNA. The quantitative embedding of the chemical properties of amino acids into tRNA bases has implications for the origins of molecular biology. PMID:26595350

Reduction of low potential electron acceptors requires the CbcL inner membrane cytochrome of Geobacter sulfurreducens.

Science.gov (United States)

Zacharoff, Lori; Chan, Chi Ho; Bond, Daniel R

2016-02-01

The respiration of metals by the bacterium Geobacter sulfurreducens requires electrons generated by metabolism to pass from the interior of the cell to electron acceptors beyond the cell membranes. The G. sulfurreducens inner membrane multiheme c-type cytochrome ImcH is required for respiration to extracellular electron acceptors with redox potentials greater than -0.1 V vs. SHE, but ImcH is not essential for electron transfer to lower potential acceptors. In contrast, deletion of cbcL, encoding an inner membrane protein consisting of b-type and multiheme c-type cytochrome domains, severely affected reduction of low potential electron acceptors such as Fe(III)-oxides and electrodes poised at -0.1 V vs. SHE. Catalytic cyclic voltammetry of a ΔcbcL strain growing on poised electrodes revealed a 50 mV positive shift in driving force required for electron transfer out of the cell. In non-catalytic conditions, low-potential peaks present in wild type biofilms were absent in ∆cbcL mutants. Expression of cbcL in trans increased growth at low redox potential and restored features to cyclic voltammetry. This evidence supports a model where CbcL is a component of a second electron transfer pathway out of the G. sulfurreducens inner membrane that dominates when redox potential is at or below -0.1 V vs. SHE. Copyright © 2015. Published by Elsevier B.V.

Donor–acceptor graphene-based hybrid materials facilitating photo-induced electron-transfer reactions

Directory of Open Access Journals (Sweden)

Anastasios Stergiou

2014-09-01

Full Text Available Graphene research and in particular the topic of chemical functionalization of graphene has exploded in the last decade. The main aim is to increase the solubility and thereby enhance the processability of the material, which is otherwise insoluble and inapplicable for technological applications when stacked in the form of graphite. To this end, initially, graphite was oxidized under harsh conditions to yield exfoliated graphene oxide sheets that are soluble in aqueous media and amenable to chemical modifications due to the presence of carboxylic acid groups at the edges of the lattice. However, it was obvious that the high-defect framework of graphene oxide cannot be readily utilized in applications that are governed by charge-transfer processes, for example, in solar cells. Alternatively, exfoliated graphene has been applied toward the realization of some donor–acceptor hybrid materials with photo- and/or electro-active components. The main body of research regarding obtaining donor–acceptor hybrid materials based on graphene to facilitate charge-transfer phenomena, which is reviewed here, concerns the incorporation of porphyrins and phthalocyanines onto graphene sheets. Through illustrative schemes, the preparation and most importantly the photophysical properties of such graphene-based ensembles will be described. Important parameters, such as the generation of the charge-separated state upon photoexcitation of the organic electron donor, the lifetimes of the charge-separation and charge-recombination as well as the incident-photon-to-current efficiency value for some donor–acceptor graphene-based hybrids, will be discussed.

Design, synthesis and photovoltaic properties of a series of new acceptor-pended conjugated polymers

Institute of Scientific and Technical Information of China (English)

Zhihong; Wu; Yongxiang; Zhu; Wei; Li; Yunping; Huang; Junwu; Chen; Chunhui; Duan; Fei; Huang; Yong; Cao

2016-01-01

A series of novel acceptor-pended conjugated polymers featuring a newly developed carbazole-derived unit are designed and synthesized. The relationships between chemical structure and optoelectronic properties of the polymers are systematically investigated.The control of UV-Vis absorption spectra and energy levels in resulting polymers are achieved by introducing suitable pended acceptor units. The photovoltaic properties of the resulting polymers are evaluated by blending the polymers with(6,6)-phenyl-C71-butyric acid methyl ester. The resulting solar cells exhibit moderate performances with high open-circuit voltage. Charge transport properties and morphology were investigated to understand the performance of corresponding solar cells.

Shape-Tunable Charge Carrier Dynamics at the Interfaces between Perovskite Nanocrystals and Molecular Acceptors

KAUST Repository

Ahmed, Ghada H.

2016-09-19

Hybrid organic/inorganic perovskites have recently emerged as an important class of materials and have exhibited remarkable performance in photovoltaics. To further improve their device efficiency, an insightful understanding of the interfacial charge transfer (CT) process is required. Here, we report the first direct experimental observation of the tremendous effect that the shape of perovskite nanocrystals (NCs) has on interfacial CT in the presence of a molecular acceptor. A dramatic change in CT dynamics at the interfaces of three different NC shapes, spheres, platelets, and cubes, is recorded. Our results clearly demonstrate that the mechanism of CT is significantly affected by the NC shape. More importantly, the results demonstrate that complexation on the NC surface acts as an additional driving force not only to tune the CT dynamics but also to control the reaction mechanism at the interface. This observation opens a new venue for further developing perovskite NCs-based applications.

Shape-Tunable Charge Carrier Dynamics at the Interfaces between Perovskite Nanocrystals and Molecular Acceptors

KAUST Repository

Ahmed, Ghada H.; Liu, Jiakai; Parida, Manas R.; Banavoth, Murali; Bose, Riya; AlYami, Noktan; Hedhili, Mohamed N.; Peng, Wei; Pan, Jun; Besong, Tabot M.D.; Bakr, Osman; Mohammed, Omar F.

2016-01-01

Hybrid organic/inorganic perovskites have recently emerged as an important class of materials and have exhibited remarkable performance in photovoltaics. To further improve their device efficiency, an insightful understanding of the interfacial charge transfer (CT) process is required. Here, we report the first direct experimental observation of the tremendous effect that the shape of perovskite nanocrystals (NCs) has on interfacial CT in the presence of a molecular acceptor. A dramatic change in CT dynamics at the interfaces of three different NC shapes, spheres, platelets, and cubes, is recorded. Our results clearly demonstrate that the mechanism of CT is significantly affected by the NC shape. More importantly, the results demonstrate that complexation on the NC surface acts as an additional driving force not only to tune the CT dynamics but also to control the reaction mechanism at the interface. This observation opens a new venue for further developing perovskite NCs-based applications.

Intramolecular Charge-Transfer Interaction of Donor-Acceptor-Donor Arrays Based on Anthracene Bisimide.

Science.gov (United States)

Iwanaga, Tetsuo; Ogawa, Marina; Yamauchi, Tomokazu; Toyota, Shinji

2016-05-20

We designed anthracene bisimide (ABI) derivatives having two triphenylamine (TPA) groups as donor units at the 9,10-positions to form a novel π-conjugated donor-acceptor system. These compounds and their analogues with ethynylene linkers were synthesized by Suzuki-Miyaura and Sonogashira coupling reactions, respectively. In UV-vis spectra, the linker-free derivatives showed broad absorption bands arising from intramolecular charge-transfer interactions. Introducing ethynylene linkers resulted in a considerable red shift of the absorption bands. In fluorescence spectra, the ethynylene derivatives showed intense emission bands at 600-650 nm. Their photophysical and electrochemical properties were compared with those of the corresponding mono TPA derivatives on the basis of theoretical calculations and cyclic voltammetry to evaluate the intramolecular electronic interactions between the donor and acceptor units.

Merocyanines: polyene-polymethine transition in donor-acceptor-substituted stilbenes and polyenes

International Nuclear Information System (INIS)

Rettig, Wolfgang; Dekhtyar, Marina

2003-01-01

Three series of donor-acceptor-substituted conjugated compounds, namely, stilbenes, the open-chain polyenes of equivalent length, and the species of intermediate structure (polyenes terminated with only one phenyl ring) have been studied by the AM1 and HMO methods to elucidate and compare the structural prerequisites of the ideal polymethinic state ('cyanine limit'). The transition from polyenic to polymethinic properties has been traced in terms of bond-length (bond-order) alternation using the variation of terminal donor and acceptor substituents. Stilbenes manifest themselves as notably 'retarded' polyenes since a larger electronic asymmetry is necessary for them to reach the same degree of polymethinic character. The ground and the excited state have been shown to differ much more strongly for stilbenes than for polyenes with respect to the position of the bond equalization point on the scale of donor-acceptor difference. For the compounds containing one phenyl ring, the features revealed are intermediate between stilbenes and polyenes. The large S 0 -S 1 discrepancy in terms of bond alternation is a general property of aromatic ring-terminated chains (stilbenes) and is related to the influence of the aromatic character which can be quantified in this way. In this context, the most relevant definition for the cyanine limit (based on the bond invariance upon excitation) was selected from the existing definitions. The major trends revealed in the polyenic/polymethinic behaviour of the molecules can be interpreted on a topological basis within HMO or even simpler models with some additional influence due to the interelectronic repulsion which is taken into account in the AM1 treatment

Metabolism of Fructophilic Lactic Acid Bacteria Isolated from the Apis mellifera L. Bee Gut: Phenolic Acids as External Electron Acceptors

Science.gov (United States)

Filannino, Pasquale; Addante, Rocco; Pontonio, Erica; Gobbetti, Marco

2016-01-01

ABSTRACT Fructophilic lactic acid bacteria (FLAB) are strongly associated with the gastrointestinal tracts (GITs) of Apis mellifera L. worker bees due to the consumption of fructose as a major carbohydrate. Seventy-seven presumptive lactic acid bacteria (LAB) were isolated from GITs of healthy A. mellifera L. adults, which were collected from 5 different geographical locations of the Apulia region of Italy. Almost all of the isolates showed fructophilic tendencies: these isolates were identified as Lactobacillus kunkeei (69%) or Fructobacillus fructosus (31%). A high-throughput phenotypic microarray targeting 190 carbon sources was used to determine that 83 compounds were differentially consumed. Phenotyping grouped the strains into two clusters, reflecting growth performance. The utilization of phenolic acids, such as p-coumaric, caffeic, syringic, or gallic acids, as electron acceptors was investigated in fructose-based medium. Almost all FLAB strains showed tolerance to high phenolic acid concentrations. p-Coumaric acid and caffeic acid were consumed by all FLAB strains through reductases or decarboxylases. Syringic and gallic acids were partially metabolized. The data collected suggest that FLAB require external electron acceptors to regenerate NADH. The use of phenolic acids as external electron acceptors by the 4 FLAB showing the highest phenolic acid reductase activity was investigated in glucose-based medium supplemented with p-coumaric acid. Metabolic responses observed through a phenotypic microarray suggested that FLAB may use p-coumaric acid as an external electron acceptor, enhancing glucose dissimilation but less efficiently than other external acceptors such as fructose or pyruvic acid. IMPORTANCE Fructophilic lactic acid bacteria (FLAB) remain to be fully explored. This study intends to link unique biochemical features of FLAB with their habitat. The quite unique FLAB phenome within the group lactic acid bacteria (LAB) may have practical relevance

S-N secular ocean tide: explanation of observably coastal velocities of increase of a global mean sea level and mean sea levels in northern and southern hemispheres and prediction of erroneous altimetry velocities

Science.gov (United States)

Barkin, Yury

2010-05-01

The phenomenon of contrast secular changes of sea levels in the southern and northern hemispheres, predicted on the basis of geodynamic model about the forced relative oscillations and displacements of the Earth shells, has obtained a theoretical explanation. In northern hemisphere the mean sea level of ocean increases with velocity about 2.45±0.32 mm/yr, and in a southern hemisphere the mean sea level increases with velocity about 0.67±0.30 mm/yr. Theoretical values of velocity of increase of global mean sea level of ocean has been estimated in 1.61±0.36 mm/yr. 1 Introduction. The secular drift of the centre of mass of the Earth in the direction of North Pole with velocity about 12-20 mm/yr has been predicted by author in 1995 [1], [2], and now has confirmed with methods of space geodesy. For example the DORIS data in period 1999-2008 let us to estimate velocity of polar drift in 5.24±0.29 mm/yr [3]. To explain this fundamental planetary phenomenon it is possible only, having admitted, that similar northern drift tests the centre of mass of the liquid core relatively to the centre of mass of viscous-elastic and thermodynamically changeable mantle with velocity about 2-3 cm/yr in present [4]. The polar drift of the Earth core with huge superfluous mass results in slow increase of a gravity in northern hemisphere with a mean velocity about 1.4 ?Gal and to its decrease approximately with the same mean velocity in southern hemisphere [5]. This conclusion-prediction has obtained already a number of confirmations in precision gravimetric observations fulfilled in last decade around the world [6]. Naturally, a drift of the core is accompanied by the global changes (deformations) of all layers of the mantle and the core, by inversion changes of their tension states when in one hemisphere the tension increases and opposite on the contrary - decreases. Also it is possible that thermodynamical mechanism actively works with inversion properties of molting and

SDSS IV MaNGA—Rotation Velocity Lags in the Extraplanar Ionized Gas from MaNGA Observations of Edge-on Galaxies

Energy Technology Data Exchange (ETDEWEB)

Bizyaev, D.; Pan, K.; Brinkmann, J. [Apache Point Observatory and New Mexico State University, Sunspot, NM 88349 (United States); Walterbos, R. A. M. [Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States); Yoachim, P. [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Riffel, R. A. [Departamento de Física, CCNE, Universidade Federal de Santa Maria, Av. Roraima, 1000-97105-900, Santa Maria, RS (Brazil); Fernández-Trincado, J. G. [Institut Utinam, CNRS UMR 6213, Université de Franche-Comté, OSU THETA Franche-Comté-Bourgogne, Observatoire de Besançon, BP 1615, F-25010 Besançon Cedex (France); Diamond-Stanic, A. M. [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States); Jones, A. [Max-Planck Institute for Astrophysics, Karl-Schwarzschild-Str 1, Garching, D-85748 (Germany); Thomas, D. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth PO1 3FX (United Kingdom); Cleary, J. [Department of Physics and Astronomy, Johns Hopkins University, Bloomberg Center, 3400 North Charles Street, Baltimore, MD 21218 (United States)

2017-04-20

We present a study of the kinematics of the extraplanar ionized gas around several dozen galaxies observed by the Mapping of Nearby Galaxies at the Apache Point Observatory (MaNGA) survey. We considered a sample of 67 edge-on galaxies out of more than 1400 extragalactic targets observed by MaNGA, in which we found 25 galaxies (or 37%) with regular lagging of the rotation curve at large distances from the galactic midplane. We model the observed H α emission velocity fields in the galaxies, taking projection effects and a simple model for the dust extinction into account. We show that the vertical lag of the rotation curve is necessary in the modeling, and estimate the lag amplitude in the galaxies. We find no correlation between the lag and the star formation rate in the galaxies. At the same time, we report a correlation between the lag and the galactic stellar mass, central stellar velocity dispersion, and axial ratio of the light distribution. These correlations suggest a possible higher ratio of infalling-to-local gas in early-type disk galaxies or a connection between lags and the possible presence of hot gaseous halos, which may be more prevalent in more massive galaxies. These results again demonstrate that observations of extraplanar gas can serve as a potential probe for accretion of gas.

SDSS IV MaNGA—Rotation Velocity Lags in the Extraplanar Ionized Gas from MaNGA Observations of Edge-on Galaxies

International Nuclear Information System (INIS)

Bizyaev, D.; Pan, K.; Brinkmann, J.; Walterbos, R. A. M.; Yoachim, P.; Riffel, R. A.; Fernández-Trincado, J. G.; Diamond-Stanic, A. M.; Jones, A.; Thomas, D.; Cleary, J.

2017-01-01

We present a study of the kinematics of the extraplanar ionized gas around several dozen galaxies observed by the Mapping of Nearby Galaxies at the Apache Point Observatory (MaNGA) survey. We considered a sample of 67 edge-on galaxies out of more than 1400 extragalactic targets observed by MaNGA, in which we found 25 galaxies (or 37%) with regular lagging of the rotation curve at large distances from the galactic midplane. We model the observed H α emission velocity fields in the galaxies, taking projection effects and a simple model for the dust extinction into account. We show that the vertical lag of the rotation curve is necessary in the modeling, and estimate the lag amplitude in the galaxies. We find no correlation between the lag and the star formation rate in the galaxies. At the same time, we report a correlation between the lag and the galactic stellar mass, central stellar velocity dispersion, and axial ratio of the light distribution. These correlations suggest a possible higher ratio of infalling-to-local gas in early-type disk galaxies or a connection between lags and the possible presence of hot gaseous halos, which may be more prevalent in more massive galaxies. These results again demonstrate that observations of extraplanar gas can serve as a potential probe for accretion of gas.

SDSS IV MaNGA—Rotation Velocity Lags in the Extraplanar Ionized Gas from MaNGA Observations of Edge-on Galaxies

Science.gov (United States)

Bizyaev, D.; Walterbos, R. A. M.; Yoachim, P.; Riffel, R. A.; Fernández-Trincado, J. G.; Pan, K.; Diamond-Stanic, A. M.; Jones, A.; Thomas, D.; Cleary, J.; Brinkmann, J.

2017-04-01

We present a study of the kinematics of the extraplanar ionized gas around several dozen galaxies observed by the Mapping of Nearby Galaxies at the Apache Point Observatory (MaNGA) survey. We considered a sample of 67 edge-on galaxies out of more than 1400 extragalactic targets observed by MaNGA, in which we found 25 galaxies (or 37%) with regular lagging of the rotation curve at large distances from the galactic midplane. We model the observed Hα emission velocity fields in the galaxies, taking projection effects and a simple model for the dust extinction into account. We show that the vertical lag of the rotation curve is necessary in the modeling, and estimate the lag amplitude in the galaxies. We find no correlation between the lag and the star formation rate in the galaxies. At the same time, we report a correlation between the lag and the galactic stellar mass, central stellar velocity dispersion, and axial ratio of the light distribution. These correlations suggest a possible higher ratio of infalling-to-local gas in early-type disk galaxies or a connection between lags and the possible presence of hot gaseous halos, which may be more prevalent in more massive galaxies. These results again demonstrate that observations of extraplanar gas can serve as a potential probe for accretion of gas.

Ligand-bound Structures and Site-directed Mutagenesis Identify the Acceptor and Secondary Binding Sites of Streptomyces coelicolor Maltosyltransferase GlgE*

Science.gov (United States)

Syson, Karl; Stevenson, Clare E. M.; Miah, Farzana; Barclay, J. Elaine; Tang, Minhong; Gorelik, Andrii; Rashid, Abdul M.; Lawson, David M.; Bornemann, Stephen

2016-01-01

GlgE is a maltosyltransferase involved in α-glucan biosynthesis in bacteria that has been genetically validated as a target for tuberculosis therapies. Crystals of the Mycobacterium tuberculosis enzyme diffract at low resolution so most structural studies have been with the very similar Streptomyces coelicolor GlgE isoform 1. Although the donor binding site for α-maltose 1-phosphate had been previously structurally defined, the acceptor site had not. Using mutagenesis, kinetics, and protein crystallography of the S. coelicolor enzyme, we have now identified the +1 to +6 subsites of the acceptor/product, which overlap with the known cyclodextrin binding site. The sugar residues in the acceptor subsites +1 to +5 are oriented such that they disfavor the binding of malto-oligosaccharides that bear branches at their 6-positions, consistent with the known acceptor chain specificity of GlgE. A secondary binding site remote from the catalytic center was identified that is distinct from one reported for the M. tuberculosis enzyme. This new site is capable of binding a branched α-glucan and is most likely involved in guiding acceptors toward the donor site because its disruption kinetically compromises the ability of GlgE to extend polymeric substrates. However, disruption of this site, which is conserved in the Streptomyces venezuelae GlgE enzyme, did not affect the growth of S. venezuelae or the structure of the polymeric product. The acceptor subsites +1 to +4 in the S. coelicolor enzyme are well conserved in the M. tuberculosis enzyme so their identification could help inform the design of inhibitors with therapeutic potential. PMID:27531751

The Influence of Solvent Additive on Polymer Solar Cells Employing Fullerene and Non-Fullerene Acceptors

KAUST Repository

Song, Xin

2017-11-27

Small-molecule-based non-fullerene acceptors (NFAs) are emerging as a new field in organic photovoltaics, due to their structural versatility, the tunability of their energy levels, and their ease of synthesis. High-efficiency polymer donors have been tested with these non-fullerene acceptors in order to further boost the efficiency of organic solar cells. Most of the polymer:fullerene systems are optimized with solvent additives for high efficiency, while little attention has been paid to NFA-based solar cells so far. In this report, the effect of the most common additive, 1,8-diiodooctane (DIO), on PTB7-Th:PC71BM solar cells is investigated and it is compared with non-fullerene acceptor 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno-[1,2-b:5,6b′]di-thiophene (ITIC) devices. It is interesting that the high boiling solvent additive does have a negative impact on the power conversion efficiency when PTB7-Th is blended with ITIC acceptor. The solar cell devices are studied in terms of their optical, photophysical, and morphological properties and find out that PTB7-Th:ITIC devices with DIO results in coarser domains, reduced absorption strength, and slightly lower mobility, while DIO improves the absorption strength of the PTB7-Th:PC71BM blend film and increase the aggregation of PC71BM in the blend, resulting in higher fill factor and Jsc.

The Influence of Solvent Additive on Polymer Solar Cells Employing Fullerene and Non-Fullerene Acceptors

KAUST Repository

Song, Xin; Gasparini, Nicola; Baran, Derya

2017-01-01

Small-molecule-based non-fullerene acceptors (NFAs) are emerging as a new field in organic photovoltaics, due to their structural versatility, the tunability of their energy levels, and their ease of synthesis. High-efficiency polymer donors have been tested with these non-fullerene acceptors in order to further boost the efficiency of organic solar cells. Most of the polymer:fullerene systems are optimized with solvent additives for high efficiency, while little attention has been paid to NFA-based solar cells so far. In this report, the effect of the most common additive, 1,8-diiodooctane (DIO), on PTB7-Th:PC71BM solar cells is investigated and it is compared with non-fullerene acceptor 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno-[1,2-b:5,6b′]di-thiophene (ITIC) devices. It is interesting that the high boiling solvent additive does have a negative impact on the power conversion efficiency when PTB7-Th is blended with ITIC acceptor. The solar cell devices are studied in terms of their optical, photophysical, and morphological properties and find out that PTB7-Th:ITIC devices with DIO results in coarser domains, reduced absorption strength, and slightly lower mobility, while DIO improves the absorption strength of the PTB7-Th:PC71BM blend film and increase the aggregation of PC71BM in the blend, resulting in higher fill factor and Jsc.

Human tRNAGly acceptor-stem microhelix: crystallization and preliminary X-ray diffraction analysis at 1.2 Å resolution

International Nuclear Information System (INIS)

Förster, Charlotte; Szkaradkiewicz, Karol; Perbandt, Markus; Brauer, Arnd B. E.; Borowski, Tordis; Fürste, Jens P.; Betzel, Christian; Erdmann, Volker A.

2007-01-01

The human tRNA Gly acceptor-stem microhelix was crystallized and preliminary X-ray diffraction analysis revealed diffraction to a resolution of up to 1.2 Å. The major dissimilarities between the eukaryotic/archaebacterial-type and eubacterial-type glycyl-tRNA synthetase systems (GlyRS; class II aminoacyl-tRNA synthetases) represent an intriguing example of evolutionarily divergent solutions to similar biological functions. The differences in the identity elements of the respective tRNA Gly systems are located within the acceptor stem and include the discriminator base U73. In the present work, the human tRNA Gly acceptor-stem microhelix was crystallized in an attempt to analyze the structural features that govern the correct recognition of tRNA Gly by the eukaryotic/archaebacterial-type glycyl-tRNA synthetase. The crystals of the human tRNA Gly acceptor-stem helix belong to the monoclinic space group C2, with unit-cell parameters a = 37.12, b = 37.49, c = 30.38 Å, α = γ = 90, β = 113.02°, and contain one molecule per asymmetric unit. A high-resolution data set was acquired using synchrotron radiation and the data were processed to 1.2 Å resolution

The effect of molecular geometry on the photovoltaic property of diketopyrrolopyrrole based non-fullerene acceptors

DEFF Research Database (Denmark)

Zhang, Fei; Brandt, Rasmus Guldbæk; Gu, Zhuowei

2015-01-01

The non-fullerene acceptors with different geometric structures have great impact on light absorption, exciton dissociation, and charge transportation in the active layer of organic solar cells (OSCs). In this paper, we designed and synthesized two diketopyrrolopyrrole based non-fullerene acceptors......) while compared to Ph(DPP)2. Therefore, the resulting P3HT:PhDMe(DPP)2 based OSCs shows a better power conversion efficiency (PCE) of 0.65%, higher than that from P3HT:Ph(DPP)2 based OSCs (0.48%), which can be ascribed to more efficient exciton dissociation and electron transportation in the active layer...

Influence of Velocity on Variability in Gait Kinematics

DEFF Research Database (Denmark)

Yang, Sylvia X M; Larsen, Peter K; Alkjær, Tine

2014-01-01

the concurrence of joint angles throughout a gait cycle at three different velocities (3.0, 4.5, 6.0 km/h). Six datasets at each velocity were collected from 16 men. A variability range VR throughout the gait cycle at each velocity for each joint angle for each person was calculated. The joint angles at each...... velocity were compared pairwise, and whenever this showed values within the VR of this velocity, the case was positive. By adding the positives throughout the gait cycle, phases with high and low concurrences were located; peak concurrence was observed at mid-stance phase. Striving for the same velocity...

Synthesis of an A-D-A type of molecule used as electron acceptor for improving charge transfer in organic solar cells

Energy Technology Data Exchange (ETDEWEB)

Zhang, Chao-Zhi, E-mail: chzhzhang@sohu.com [Department of Chemistry, Nanjing University of Information Science & Technology, Nanjing 210044 (China); Gu, Shu-Duo; Shen, Dan; Yuan, Yang [Department of Chemistry, Nanjing University of Information Science & Technology, Nanjing 210044 (China); Zhang, Mingdao, E-mail: matchlessjimmy@163.com [Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Nanjing University of Information Science & Technology, Nanjing 210044 (China)

2016-08-22

Electron-accepting molecules play an important role in developing organic solar cells. A new type of A-D-A molecule, 3,6-di([7-(5-bromothiophen-2-yl)-1,5,2,4,6,8-dithiotetrazocin-3-yl]thiophen -2-yl)-9-(2-ethylhexyl)carbazole, was synthesized. The lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels are −3.55 and −5.85 eV, respectively. Therefore, the A-D-A type of compound could be used as electron acceptor for fabricating organic solar cell with a high open circuit voltage. Gibbs free energy (−49.2 kJ/mol) reveals that the process of A-D-A acceptor accepting an electron from poly(3-hexylthiophene) at excited state is spontaneous. The value of entropy (118 J/mol) in the process of an electron transferring from P3HT to the A-D-A acceptor at organic interface suggests that electrons generated from separation of electron-hole pairs at donor/acceptor interface would be delocalized efficiently. Therefore, the A-D-A molecule would be a potential acceptor for efficient organic BHJ solar cells.

Template Dimerization Promotes an Acceptor Invasion-Induced Transfer Mechanism during Human Immunodeficiency Virus Type 1 Minus-Strand Synthesis

Science.gov (United States)

Balakrishnan, Mini; Roques, Bernard P.; Fay, Philip J.; Bambara, Robert A.

2003-01-01

The biochemical mechanism of template switching by human immunodeficiency virus type 1 (HIV-1) reverse transcriptase and the role of template dimerization were examined. Homologous donor-acceptor template pairs derived from the HIV-1 untranslated leader region and containing the wild-type and mutant dimerization initiation sequences (DIS) were used to examine the efficiency and distribution of transfers. Inhibiting donor-acceptor interaction was sufficient to reduce transfers in DIS-containing template pairs, indicating that template dimerization, and not the mere presence of the DIS, promotes efficient transfers. Additionally, we show evidence that the overall transfer process spans an extended region of the template and proceeds through a two-step mechanism. Transfer is initiated through an RNase H-facilitated acceptor invasion step, while synthesis continues on the donor template. The invasion then propagates towards the primer terminus by branch migration. Transfer is completed with the translocation of the primer terminus at a site distant from the invasion point. In our system, most invasions initiated before synthesis reached the DIS. However, transfer of the primer terminus predominantly occurred after synthesis through the DIS. The two steps were separated by 60 to 80 nucleotides. Sequence markers revealed the position of primer terminus switch, whereas DNA oligomers designed to block acceptor-cDNA interactions defined sites of invasion. Within the region of homology, certain positions on the template were inherently more favorable for invasion than others. In templates with DIS, the proximity of the acceptor facilitates invasion, thereby enhancing transfer efficiency. Nucleocapsid protein enhanced the overall efficiency of transfers but did not alter the mechanism. PMID:12663778

Optical and electrical properties of zinc oxide thin films with low resistivity via Li-N dual-acceptor doping

Energy Technology Data Exchange (ETDEWEB)

Zhang Daoli, E-mail: zhang_daoli@mail.hust.edu.cn [Department of Electronic Science and Technology, Huazhong University of Science and Technology, No. 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Wuhan National Laboratory for Optoelectronics, 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Zhang Jianbing [Department of Electronic Science and Technology, Huazhong University of Science and Technology, No. 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Wuhan National Laboratory for Optoelectronics, 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Guo Zhe [Department of Electronic Science and Technology, Huazhong University of Science and Technology, No. 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Miao Xiangshui [Department of Electronic Science and Technology, Huazhong University of Science and Technology, No. 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Wuhan National Laboratory for Optoelectronics, 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China)

2011-05-19

Highlights: > Zinc oxide films have been deposited on glass substrates by Li-N dual-acceptor doping method via a modified SILAR method. > The resistivity of ZnO film was found to be 1.04 {Omega} cm with a Hall mobility of 0.749 cm{sup 2} V{sup -1} s{sup -1}, carrier concentration of 8.02 x 1018 cm{sup -3}, and transmittance of about 80% in visible range showing good crystallinity with prior c-axis orientation. > A shallow acceptor level of 91 meV is identified from free-to-neutral-acceptor transitions. > Another deep level of 255 meV was ascribed to Li{sub Zn}-Li{sub i} complex. - Abstract: Zinc oxide thin films with low resistivity have been deposited on glass substrates by Li-N dual-acceptor doping method via a modified successive ionic layer adsorption and reaction process. The thin films were systematically characterized via scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction, ultraviolet-visible spectrophotometry and fluorescence spectrophotometry. The resistivity of zinc oxide film was found to be 1.04 {Omega} cm with a Hall mobility of 0.749 cm{sup 2} V{sup -1} s{sup -1} and carrier concentration of 8.02 x 10{sup 18} cm{sup -3}. The Li-N dual-acceptor doped zinc oxide films showed good crystallinity with prior c-axis orientation, and high transmittance of about 80% in visible range. Moreover, the effects of Li doping level and other parameters on crystallinity, electrical and ultraviolet emission of zinc oxide films were investigated.

Thought experiments at superluminal relative velocities

International Nuclear Information System (INIS)

Corben, H.C.

1976-01-01

It is imagined that our World is being examined from a similar world which is moving relative to us with a velocity greater than that of light. The two worlds are supposed to be similar in that the particles in each appear to any observer in that world to have real measurable properties. However, the enormous relative velocity so distorts the observations that each world makes on the other that the squares of certain real quantities appear to the other observer to be negative. Neglect of this fact has led to the erroneous belief that a free charged tachyon would emit Cherenkov radiation and that the existence of tachyons would lead to logical paradoxes. (author)

Two-receiver measurements of phase velocity: cross-validation of ambient-noise and earthquake-based observations

NARCIS (Netherlands)

Kästle, Emanuel D.; Soomro, Riaz; Weemstra, C.; Boschi, Lapo; Meier, Thomas

2016-01-01

Phase velocities derived from ambient-noise cross-correlation are compared with phase velocities calculated from cross-correlations of waveform recordings of teleseismic earthquakes whose epicentres are approximately on the station–station great circle. The comparison is conducted both for Rayleigh

Organic solar cells based on anthracene-containing PPE–PPVs and non-fullerene acceptors

KAUST Repository

Alam, Shahidul

2018-04-13

Lately, non-fullerene acceptors (NFAs) have received increasing attention for use in polymer-based bulk-heterojunction (BHJ) organic solar cells (OSCs), as improved photovoltaic performance compared to classical polymer–fullerene blends could be demonstrated. In this study, polymer solar cells based on a statistically substituted anthracene-containing poly(p-phenylene ethynylene)-alt-poly(p-phenylene vinylene)s (PPE–PPVs) copolymer (AnE-PVstat) as donor in combination with a number of different electron accepting materials were investigated. Strong photoluminescence quenching of the polymer donor indicates intimate intermixing of both materials. However, the photovoltaic performances were found to be poor compared to blends that use fullerene as acceptor. Time-delayed collection field (TDCF) measurements demonstrate: charge generation is field-independent, but bimolecular recombination processes limit the fill factor and thus the efficiency of devices.

Organic solar cells based on anthracene-containing PPE–PPVs and non-fullerene acceptors

KAUST Repository

Alam, Shahidul; Meitzner, Rico; Nwadiaru, Ogechi V.; Friebe, Christian; Cann, Jonathan; Ahner, Johannes; Ulbricht, Christoph; Kan, Zhipeng; Hö ppener, Stephanie; Hager, Martin D.; Egbe, Daniel A. M.; Welch, Gregory C.; Laquai, Fré dé ric; Schubert, Ulrich S.; Hoppe, Harald

2018-01-01

Lately, non-fullerene acceptors (NFAs) have received increasing attention for use in polymer-based bulk-heterojunction (BHJ) organic solar cells (OSCs), as improved photovoltaic performance compared to classical polymer–fullerene blends could be demonstrated. In this study, polymer solar cells based on a statistically substituted anthracene-containing poly(p-phenylene ethynylene)-alt-poly(p-phenylene vinylene)s (PPE–PPVs) copolymer (AnE-PVstat) as donor in combination with a number of different electron accepting materials were investigated. Strong photoluminescence quenching of the polymer donor indicates intimate intermixing of both materials. However, the photovoltaic performances were found to be poor compared to blends that use fullerene as acceptor. Time-delayed collection field (TDCF) measurements demonstrate: charge generation is field-independent, but bimolecular recombination processes limit the fill factor and thus the efficiency of devices.

Trapped electron decay by the thermally-assisted tunnelling to electron acceptors in glassy matrices. A computer simulation study

International Nuclear Information System (INIS)

Feret, B.; Bartczak, W.M.; Kroh, J.

1991-01-01

The Redi-Hopefield quantum mechanical model of the thermally-assisted electron transfer has been applied to simulate the decay of trapped electrons by tunnelling to electron acceptor molecules added to the glassy matrix. It was assumed that the electron energy levels in donors and acceptors are statistically distributed and the electron excess energy after transfer is dissipated in the medium by the electron-phonon coupling. The electron decay curves were obtained by the method of computer simulation. It was found that for a given medium there exists a certain preferred value of the electronic excess energy which can be effectively converted into the matrix vibrations. If the mismatch of the electron states on the donor and acceptor coincides with the ''resonance'' energy the overall kinetics of electron transfer is accelerated. (author)

Critical review of the molecular design progress in non-fullerene electron acceptors towards commercially viable organic solar cells

KAUST Repository

Wadsworth, Andrew; Moser, Maximilian; Marks, Adam; Little, Mark S.; Gasparini, Nicola; Brabec, Christoph J.; Baran, Derya; McCulloch, Iain

2018-01-01

Fullerenes have formed an integral part of high performance organic solar cells over the last 20 years, however their inherent limitations in terms of synthetic flexibility, cost and stability have acted as a motivation to develop replacements; the so-called non-fullerene electron acceptors. A rapid evolution of such materials has taken place over the last few years, yielding a number of promising candidates that can exceed the device performance of fullerenes and provide opportunities to improve upon the stability and processability of organic solar cells. In this review we explore the structure-property relationships of a library of non-fullerene acceptors, highlighting the important chemical modifications that have led to progress in the field and provide an outlook for future innovations in electron acceptors for use in organic photovoltaics.

Critical review of the molecular design progress in non-fullerene electron acceptors towards commercially viable organic solar cells

KAUST Repository

Wadsworth, Andrew

2018-04-26

Fullerenes have formed an integral part of high performance organic solar cells over the last 20 years, however their inherent limitations in terms of synthetic flexibility, cost and stability have acted as a motivation to develop replacements; the so-called non-fullerene electron acceptors. A rapid evolution of such materials has taken place over the last few years, yielding a number of promising candidates that can exceed the device performance of fullerenes and provide opportunities to improve upon the stability and processability of organic solar cells. In this review we explore the structure-property relationships of a library of non-fullerene acceptors, highlighting the important chemical modifications that have led to progress in the field and provide an outlook for future innovations in electron acceptors for use in organic photovoltaics.

OBSERVATIONAL DETECTION OF DRIFT VELOCITY BETWEEN IONIZED AND NEUTRAL SPECIES IN SOLAR PROMINENCES

Energy Technology Data Exchange (ETDEWEB)

Khomenko, Elena; Collados, Manuel [Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain); Díaz, Antonio J., E-mail: khomenko@iac.es, E-mail: mcv@iac.es, E-mail: aj.diaz@uib.es [Universitat de les Illes Balears, 07122, Crta Valldemossa, km 7.5, Palma de Mallorca (Spain)

2016-06-01

We report the detection of differences in the ion and neutral velocities in prominences using high-resolution spectral data obtained in 2012 September at the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife). A time series of scans of a small portion of a solar prominence was obtained simultaneously with high cadence using the lines of two elements with different ionization states, namely, Ca ii 8542 Å and He i 10830 Å. The displacements, widths, and amplitudes of both lines were carefully compared to extract dynamical information about the plasma. Many dynamical features are detected, such as counterstreaming flows, jets, and propagating waves. In all of the cases, we find a very strong correlation between the parameters extracted from the lines of both elements, confirming that both lines trace the same plasma. Nevertheless, we also find short-lived transients where this correlation is lost. These transients are associated with ion-neutral drift velocities of the order of several hundred m s{sup −1}. The patches of non-zero drift velocity show coherence in time–distance diagrams.

Settling velocities in batch sedimentation

International Nuclear Information System (INIS)

Fricke, A.M.; Thompson, B.E.

1982-10-01

The sedimentation of mixtures containing one and two sizes of spherical particles (44 and 62 μm in diameter) was studied. Radioactive tracing with 57 Co was used to measure the settling velocities. The ratio of the settling velocity U of uniformly sized particles to the velocity predicted to Stokes' law U 0 was correlated to an expression of the form U/U 0 = epsilon/sup α/, where epsilon is the liquid volume fraction and α is an empirical constant, determined experimentally to be 4.85. No effect of viscosity on the ratio U/U 0 was observed as the viscosity of the liquid medium was varied from 1x10 -3 to 5x10 -3 Pa.s. The settling velocities of particles in a bimodal mixture were fit by the same correlation; the ratio U/U 0 was independent of the concentrations of different-sized particles

Recent advances in photoinduced donor/acceptor copolymerization

International Nuclear Information System (INIS)

Joensson, S.; Viswanathan, K.; Hoyle, C.E.; Clark, S.C.; Miller, C.; Morel, F.; Decker, C.

1999-01-01

Photoinitiated free radical polymerization of donor (D)/acceptor (A) type monomers has gained considerable interest due to the possibility to efficiently photopolymerize non-acrylate based systems. Furthermore, this photoinduced alternating copolymerization can be accomplished without the presence of a conventional free radical generating photoinitiator. In the past, we have shown that the structural influences in the direct photolysis of N-Alkyl and N-Arylmaleimides as well as their corresponding ground state charge transfer complexes (CTC) with suitable donors have carefully been investigated. For certain combinations of A and D type monomers, a direct photolysis of the ground state complex or the excitation of the acceptor, followed by the formation of an exciplex, has been shown to initiate the copolymerization. Herein, we show that the main route of initiation is based on inter or intra molecular H-abstraction from an excited state maleimide, whereby no exciplex formation takes place. H-abstraction will predominantly take place in systems where easily abstractable hydrogens are present. Our laser flash photolysis investigation, ESR (A. Hiroshi, I. Takasi, T. Nosi, Macromol. Chem. 190 (1989) 2821) and phosphorescence emissions (K.S. Chen, T. Foster, J.K.S. Wan, J. Phys. Chem. 84 (1980) 2473; C.J. Seliskar, S.P. McGlynn, J. Chem. Phys. 55 (1971) 4337) studies show that triplet excited states of N-alkyl substituted maleimides (RMI), which are well known strong precursors for direct H-abstractions from aliphatic ethers and secondary alcohols, are formed upon excitation. Rates of copolymerization and degrees of conversion for copolymerization of maleimide/vinyl ether pairs in air and nitrogen have been measured as a function of hydrogen abstractability of the excited triplet state MI as well as the influence of concentration and hydrogen donating effect of the hydrogen donor

Template Dimerization Promotes an Acceptor Invasion-Induced Transfer Mechanism during Human Immunodeficiency Virus Type 1 Minus-Strand Synthesis

OpenAIRE

Balakrishnan, Mini; Roques, Bernard P.; Fay, Philip J.; Bambara, Robert A.

2003-01-01

The biochemical mechanism of template switching by human immunodeficiency virus type 1 (HIV-1) reverse transcriptase and the role of template dimerization were examined. Homologous donor-acceptor template pairs derived from the HIV-1 untranslated leader region and containing the wild-type and mutant dimerization initiation sequences (DIS) were used to examine the efficiency and distribution of transfers. Inhibiting donor-acceptor interaction was sufficient to reduce transfers in DIS-containin...

Magnesium acceptor in gallium nitride. II. Koopmans-tuned Heyd-Scuseria-Ernzerhof hybrid functional calculations of its dual nature and optical properties

Science.gov (United States)

Demchenko, D. O.; Diallo, I. C.; Reshchikov, M. A.

2018-05-01

The problem of magnesium acceptor in gallium nitride is that experimental photoluminescence measurements clearly reveal a shallow defect state, while most theoretical predictions favor a localized polaronic defect state. To resolve this contradiction, we calculate properties of magnesium acceptor using the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional, tuned to fulfill the generalized Koopmans condition. We test Koopmans tuning of HSE for defect calculations in GaN using two contrasting test cases: a deep state of gallium vacancy and a shallow state of magnesium acceptor. The obtained parametrization of HSE allows calculations of optical properties of acceptors using neutral defect-state eigenvalues, without relying on corrections due to charged defects in periodic supercells. Optical transitions and vibrational properties of M gGa defect are analyzed to bring the dual (shallow and deep) nature of this defect into accord with experimental photoluminescence measurements of the ultraviolet band in Mg-doped GaN samples.

Spatially Extended and High-Velocity Dispersion Molecular Component in Spiral Galaxies: Single-Dish Versus Interferometric Observations

Science.gov (United States)

Caldú-Primo, Anahi; Schruba, Andreas; Walter, Fabian; Leroy, Adam; Bolatto, Alberto D.; Vogel, Stuart

2015-02-01

Recent studies of the molecular medium in nearby galaxies have provided mounting evidence that the molecular gas can exist in two phases: one that is clumpy and organized as molecular clouds and another one that is more diffuse. This last component has a higher velocity dispersion than the clumpy one. In order to investigate these two molecular components further, we compare the fluxes and line widths of CO in NGC 4736 and NGC 5055, two nearby spiral galaxies for which high-quality interferometric as well as single-dish data sets are available. Our analysis leads to two main results: (1) employing three different methods, we determine the flux recovery of the interferometer as compared to the single-dish to be within a range of 35%-74% for NGC 4736 and 81%-92% for NGC 5055, and (2) when focusing on high (S/N ≥ 5) lines of sight (LOSs), the single-dish line widths are larger by ˜(40 ± 20)% than the ones derived from interferometric data, which is in agreement with stacking all LOSs. These results point to a molecular gas component that is distributed over spatial scales larger than 30″(˜1 kpc), and is therefore filtered out by the interferometer. The available observations do not allow us to distinguish between a truly diffuse gas morphology and a uniform distribution of small clouds that are separated by less than the synthesized beam size (˜3″ or ˜100 pc), as they would both be invisible for the interferometer. This high velocity dispersion component has a dispersion similar to what is found in the atomic medium, as traced through observations of the H i line.

Electron acceptors for anaerobic oxidation of methane drive microbial community structure and diversity in mud volcanoes.

Science.gov (United States)

Ren, Ge; Ma, Anzhou; Zhang, Yanfen; Deng, Ye; Zheng, Guodong; Zhuang, Xuliang; Zhuang, Guoqiang; Fortin, Danielle

2018-04-06

Mud volcanoes (MVs) emit globally significant quantities of methane into the atmosphere, however, methane cycling in such environments is not yet fully understood, as the roles of microbes and their associated biogeochemical processes have been largely overlooked. Here, we used data from high-throughput sequencing of microbial 16S rRNA gene amplicons from six MVs in the Junggar Basin in northwest China to quantify patterns of diversity and characterize the community structure of archaea and bacteria. We found anaerobic methanotrophs and diverse sulfate- and iron-reducing microbes in all of the samples, and the diversity of both archaeal and bacterial communities was strongly linked to the concentrations of sulfate, iron and nitrate, which could act as electron acceptors in anaerobic oxidation of methane (AOM). The impacts of sulfate/iron/nitrate on AOM in the MVs were verified by microcosm experiments. Further, two representative MVs were selected to explore the microbial interactions based on phylogenetic molecular ecological networks. The sites showed distinct network structures, key species and microbial interactions, with more complex and numerous linkages between methane-cycling microbes and their partners being observed in the iron/sulfate-rich MV. These findings suggest that electron acceptors are important factors driving the structure of microbial communities in these methane-rich environments. © 2018 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

Evidence of the Zn vacancy acting as the dominant acceptor in n-type ZnO.

Science.gov (United States)

Tuomisto, F; Ranki, V; Saarinen, K; Look, D C

2003-11-14

We have used positron annihilation spectroscopy to determine the nature and the concentrations of the open volume defects in as-grown and electron irradiated (E(el)=2 MeV, fluence 6 x 10(17) cm(-2)) ZnO samples. The Zn vacancies are identified at concentrations of [V(Zn)] approximately 2 x 10(15) cm(-3) in the as-grown material and [V(Zn)] approximately 2 x 10(16) cm(-3) in the irradiated ZnO. These concentrations are in very good agreement with the total acceptor density determined by temperature dependent Hall experiments. Thus, the Zn vacancies are dominant acceptors in both as-grown and irradiated ZnO.

Evidence of the Zn vacancy acting as the dominant acceptor in n-type ZnO

International Nuclear Information System (INIS)

Tuomisto, F.; Ranki, V.; Saarinen, K.; Look, D.C.

2003-01-01

We have used positron annihilation spectroscopy to determine the nature and the concentrations of the open volume defects in as-grown and electron irradiated (E el =2 MeV, fluence 6x10 17 cm -2 ) ZnO samples. The Zn vacancies are identified at concentrations of [V Zn ]≅2x10 15 cm -3 in the as-grown material and [V Zn ]≅2x10 16 cm -3 in the irradiated ZnO. These concentrations are in very good agreement with the total acceptor density determined by temperature dependent Hall experiments. Thus, the Zn vacancies are dominant acceptors in both as-grown and irradiated ZnO

Enabling Velocity-Resolved Science with Advanced Processing of Herschel/HIFI Observations

Science.gov (United States)

Morris, Patrick

The Herschel/HIFI instrument was a heterodyne spectrometer with technology demonstrating and flight components built by NASA/JPL, and acquired over 9000 astronomical observations at velocity resolutions of better than 1 km/s between 480 -1910 GHz (157 - 612 microns). Its performances designed around the scientific goals of exploring the cyclical interrelation of stars and the ISM in diverse environments unified by copious amounts molecular and atomic gas and dust have resulted in over 350 refereed scientific publications, providing a successful foundation and inspiration for current and future science with terahertz instrumentation above the Earth's atmosphere. Nonetheless, almost 60% of the valid observations in the Herschel Science Archive (HSA) are unpublished. This is in largest part due to the limitations of the automated pipeline, and the complexities of interactive treatment the data to bring them to science-ready quality. New users of the archive lacking knowledge of the nuances of heterodyne instrumentation and/or experience with the data processing system are particularly challenged to optimize the data around their science interests or goals with ultra-high resolution spectra. Similarly, the effort to remove quality-degrading instrument artifacts and apply noise performance enhancements is a challenge at this stage even for more experienced users and original program observers who have not yet exploited their observations, either in part or in full as many published observations may also be further harvested for new science results. Recognizing that this situation will likely not improve over time, the HIFI instrument team put substantial effort during the funded post-cryo phase into interactively creating Highly Processed Data Products (HPDPs) from a set of observations in need of corrections and enhancements, in order to promote user accessibility and HIFI's scientific legacy. A set HPDPs created from 350 spectral mapping observations were created in

Spatially-resolved velocities of thermally-produced spray droplets using a velocity-divided Abel inversion of photographed streaks

Science.gov (United States)

Kawaguchi, Y.; Kobayashi, N.; Yamagata, Y.; Miyazaki, F.; Yamasaki, M.; Muraoka, K.

2017-10-01

Droplet velocities of thermal spray are known to have profound effects on important coating qualities, such as adhesive strength, porosity, and hardness, for various applications. For obtaining the droplet velocities, therefore, the TOF (time-of-flight) technique has been widely used, which relies on observations of emitted radiation from the droplets, where all droplets along the line-of-sight contribute to signals. Because droplets at and near the flow axis mostly contribute coating layers, it has been hoped to get spatially resolved velocities. For this purpose, a velocity-divided Abel inversion was devised from CMOS photographic data. From this result, it has turned out that the central velocity is about 25% higher than that obtained from the TOF technique for the case studied (at the position 150 mm downstream of the plasma spray gun, where substrates for spray coatings are usually placed). Further implications of the obtained results are discussed.

Free Carrier Generation in Fullerene Acceptors and Its Effect on Polymer Photovoltaics

KAUST Repository

Burkhard, George F.; Hoke, Eric T.; Beiley, Zach M.; McGehee, Michael D.

2012-01-01

Early research on C60 led to the discovery that the absorption of photons with energy greater than 2.35 eV by bulk C60 produces free charge carriers at room temperature. We find that not only is this also true for many of the soluble fullerene derivatives commonly used in organic photovoltaics, but also that the presence of these free carriers has significant implications for the modeling, characterization, and performance of devices made with these materials. We demonstrate that the discrepancy between absorption and quantum efficiency spectra in P3HT:PCBM is due to recombination of such free carriers in large PCBM domains before they can be separated at a donor/acceptor interface. Since most theories assume that all free charges result from the separation of excitons at a donor/acceptor interface, the presence of free carrier generation in fullerenes can have a significant impact on the interpretation of data generated by numerous field-dependent techniques. © 2012 American Chemical Society.

Free Carrier Generation in Fullerene Acceptors and Its Effect on Polymer Photovoltaics

KAUST Repository

Burkhard, George F.

2012-12-20

Early research on C60 led to the discovery that the absorption of photons with energy greater than 2.35 eV by bulk C60 produces free charge carriers at room temperature. We find that not only is this also true for many of the soluble fullerene derivatives commonly used in organic photovoltaics, but also that the presence of these free carriers has significant implications for the modeling, characterization, and performance of devices made with these materials. We demonstrate that the discrepancy between absorption and quantum efficiency spectra in P3HT:PCBM is due to recombination of such free carriers in large PCBM domains before they can be separated at a donor/acceptor interface. Since most theories assume that all free charges result from the separation of excitons at a donor/acceptor interface, the presence of free carrier generation in fullerenes can have a significant impact on the interpretation of data generated by numerous field-dependent techniques. © 2012 American Chemical Society.

Polymer solar cells based on poly(3-hexylthiophene) and fullerene: Pyrene acceptor systems

Energy Technology Data Exchange (ETDEWEB)

Cominetti, Alessandra; Pellegrino, Andrea; Longo, Luca [Research Center for Renewable Energies and Environment, Istituto Donegani, Eni S.p.A, Via Fauser 4, IT-28100 Novara (Italy); Po, Riccardo, E-mail: riccardo.po@eni.com [Research Center for Renewable Energies and Environment, Istituto Donegani, Eni S.p.A, Via Fauser 4, IT-28100 Novara (Italy); Tacca, Alessandra; Carbonera, Chiara; Salvalaggio, Mario [Research Center for Renewable Energies and Environment, Istituto Donegani, Eni S.p.A, Via Fauser 4, IT-28100 Novara (Italy); Baldrighi, Michele; Meille, Stefano Valdo [Dipartimento di Chimica, Materiali e Ingegneria Chimica “G. Natta”, Politecnico di Milano, via Mancinelli 7, IT-20131 Milano (Italy)

2015-06-01

The replacement of widely used fullerene derivatives, e.g. [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), with unfunctionalized C60 and C70 is an effective approach to reduce the costs of organic photovoltaics. However, solubility issues of these compounds have always represented an obstacle to their use. In this study, bulk-heterojunction solar cells made of poly(3-hexylthiophene) donor polymer, C60 or C70 acceptors and a pyrene derivative (1-pyrenebutiric acid butyl ester) are reported. Butyl 1-pyrenebutirate limits the aggregation of fullerenes and improves the active layer morphology, plausibly due to the formation of pyrene-fullerene complexes which, in the case of pyrene-C70, were also obtained in a crystalline form. Maximum power conversion efficiencies of 1.54% and 2.50% have been obtained using, respectively, C60 or C70 as acceptor. Quantum mechanical modeling provides additional insight into the formation of plausible supermolecular structures via π-π interactions and on the redox behaviour of pyrene-fullerene systems. - Highlights: • Pyrene derivatives favour the dispersion of unfunctionalized fullerenes. • Polymer solar cells with pyrene: C60 adduct as acceptor have efficiencies of 1.54%. • When C60 is substituted with C70 the efficiency is increased to 2.50%. • DFT calculations support the plausibility of the formation of pyrene: fullerene adducts. • The use of unfunctionalized fullerenes may decrease the costs of polymer solar cells.

Structure and electronic properties of Alq3 derivatives with electron acceptor/donor groups at the C4 positions of the quinolate ligands: a theoretical study.

Science.gov (United States)

Rao, Joshi Laxmikanth; Bhanuprakash, Kotamarthi

2011-12-01

The molecular structures of the ground (S(0)) and first singlet excited (S(1)) states of Alq3 derivatives in which pyrazolyl and 3-methylpyrazolyl groups are substituted at the C4 positions of the 8-hydroxyquinolate ligands as electron acceptors, and piperidinyl and N-methylpiperazinyl groups are substituted at the same positions as electron donors, have been optimized using the B3LYP/6-31G and CIS/6-31G methods, respectively. In order to analyze the electronic transitions in these derivatives, the frontier molecular orbital characteristics were analyzed systematically, and it was found that the highest occupied molecular orbital is localized on the A ligand while the lowest unoccupied molecular orbital is localized on the B ligand in their ground states, similar to what is seen for mer-Alq3. The absorption and emission spectra were evaluated at the TD-PBE0/6-31G level, and it was observed that electron acceptor substitution causes a red-shift in the emission spectra, which is also seen experimentally. The reorganization energies were calculated at the B3LYP/6-31G level and the results show that acceptor/donor substitution has a significant effect on the intrinsic charge mobilities of these derivatives as compared to mer-Alq3.

Electron Acceptor Materials Engineering in Colloidal Quantum Dot Solar Cells

KAUST Repository

Liu, Huan

2011-07-15

Lead sulfide colloidal quantum dot (CQD) solar cells with a solar power conversion efficiency of 5.6% are reported. The result is achieved through careful optimization of the titanium dioxide electrode that serves as the electron acceptor. Metal-ion-doped sol-gel-derived titanium dioxide electrodes produce a tunable-bandedge, well-passivated materials platform for CQD solar cell optimization. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of Ubiquitous Electron Acceptors on In Situ Anaerobic Biotransformation of RDX in Groundwater

National Research Council Canada - National Science Library

Wani, Altaf

2003-01-01

A series of column studies, with aquifer material from the former Nebraska Ordnance Plant, were performed to explore the phenomenon of electron competition from ubiquitous inorganic electron acceptors (nitrate and sulfate...

Photoelectric Radial Velocities, Paper XIX Additional Spectroscopic ...

Indian Academy of Sciences (India)

ian velocity curve that does justice to the measurements, but it cannot be expected to have much predictive power. Key words. Stars: late-type—stars: radial velocities—spectroscopic binaries—orbits. 0. Preamble. The 'Redman K stars' are a lot of seventh-magnitude K stars whose radial velocities were first observed by ...

Effect of uniaxial stress on the acceptor ground state and on the hopping conduction in p-type germanium and silicon

International Nuclear Information System (INIS)

Buczko, R.; Chroboczek, J.A.

1983-08-01

We constructed variational wave functions, with correct asymptotic behaviour, for the ground state of shallow acceptors in Ge and Si, utilizing the spherical tensor representation of the effective mass hamiltonian of Baldereschi and Lipari (1973), at uniaxial stress, X, resulting from the application of a tensile or compressive force along the [001] orientation (respectively X 0). Energies of the components of the ground state, computed variationally, account very well for the X-induced displacements of the binding energies and the stress splitting of shallow acceptors in both Ge and Si, at X>0 (no data for X 0. However, they account only qualitatively for the rho(X) data available for Si (X>0 only), probably because of a larger chemical shift of the acceptor ground state in Si and its possible variation with X. At larger acceptor concentrations rho(X) decreases, at large X, much stronger than predicted for both Ge and Si. We attribute this discrepancy to the increase of the contribution to electron transport of multiple hopping transitions at large X values. (author)

In vitro fermentation of alternansucrase raffinose acceptor products by human gut bacteria

Science.gov (United States)

In this work, in vitro fermentation of alternansucrase raffinose acceptor products, previously fractionated according to their degree of polymerization (DP; from DP4 to DP10) was carried out using pH-controlled small scale batch cultures at 37ºC under anaerobic conditions with human faeces. Bifidog...

Liquid velocity in upward and downward air-water flows

International Nuclear Information System (INIS)

Sun Xiaodong; Paranjape, Sidharth; Kim, Seungjin; Ozar, Basar; Ishii, Mamoru

2004-01-01

Local characteristics of the liquid phase in upward and downward air-water two-phase flows were experimentally investigated in a 50.8-mm inner-diameter round pipe. An integral laser Doppler anemometry (LDA) system was used to measure the axial liquid velocity and its fluctuations. No effect of the flow direction on the liquid velocity radial profile was observed in single-phase liquid benchmark experiments. Local multi-sensor conductivity probes were used to measure the radial profiles of the bubble velocity and the void fraction. The measurement results in the upward and downward two-phase flows are compared and discussed. The results in the downward flow demonstrated that the presence of the bubbles tended to flatten the liquid velocity radial profile, and the maximum liquid velocity could occur off the pipe centerline, in particular at relatively low flow rates. However, the maximum liquid velocity always occurred at the pipe center in the upward flow. Also, noticeable turbulence enhancement due to the bubbles in the two-phase flows was observed in the current experimental flow conditions. Furthermore, the distribution parameter and the void-weighted area-averaged drift velocity were obtained based on the definitions

Velocity Dispersion of Ionized Gas and Multiple Supernova Explosions

Directory of Open Access Journals (Sweden)

Vasiliev E. O.

2015-06-01

Full Text Available We use 3D numerical simulations to study the evolution of the Hα intensity and velocity dispersion for single and multiple supernova (SN explosions. We find that the IHα– σ diagram obtained for simulated gas flows is similar in shape to that observed in dwarf galaxies. We conclude that colliding SN shells with significant difference in age are responsible for high velocity dispersion that reaches up to ≳ 100 km s−1. Such a high velocity dispersion could be hardly obtained for a single SN remnant. Peaks of velocity dispersion in the IHα– σ diagram may correspond to several isolated or merged SN remnants with moderately different ages. Degrading the spatial resolution in the Hα intensity and velocity dispersion maps makes the simulated IHα– σ diagrams close to those observed in dwarf galaxies not only in shape, but also quantitatively.

Velocity distribution in snow avalanches

Science.gov (United States)

Nishimura, K.; Ito, Y.

1997-12-01

In order to investigate the detailed structure of snow avalanches, we have made snow flow experiments at the Miyanomori ski jump in Sapporo and systematic observations in the Shiai-dani, Kurobe Canyon. In the winter of 1995-1996, a new device to measure static pressures was used to estimate velocities in the snow cloud that develops above the flowing layer of avalanches. Measurements during a large avalanche in the Shiai-dani which damaged and destroyed some instruments indicate velocities increased rapidly to more than 50 m/s soon after the front. Velocities decreased gradually in the following 10 s. Velocities of the lower flowing layer were also calculated by differencing measurement of impact pressure. Both recordings in the snow cloud and in the flowing layer changed with a similar trend and suggest a close interaction between the two layers. In addition, the velocity showed a periodic change. Power spectrum analysis of the impact pressure and the static pressure depression showed a strong peak at a frequency between 4 and 6 Hz, which might imply the existence of either ordered structure or a series of surges in the flow.

Identifying Clusters with Mixture Models that Include Radial Velocity Observations

Science.gov (United States)

Czarnatowicz, Alexis; Ybarra, Jason E.

2018-01-01

The study of stellar clusters plays an integral role in the study of star formation. We present a cluster mixture model that considers radial velocity data in addition to spatial data. Maximum likelihood estimation through the Expectation-Maximization (EM) algorithm is used for parameter estimation. Our mixture model analysis can be used to distinguish adjacent or overlapping clusters, and estimate properties for each cluster.Work supported by awards from the Virginia Foundation for Independent Colleges (VFIC) Undergraduate Science Research Fellowship and The Research Experience @Bridgewater (TREB).

Crack velocity measurement by induced electromagnetic radiation

International Nuclear Information System (INIS)

Frid, V.; Rabinovitch, A.; Bahat, D.

2006-01-01

Our model of electromagnetic radiation (EMR) emanated from fracture implies that EMR amplitude is proportional to crack velocity. Soda lime glass samples were tested under uniaxial tension. Comparison of crack velocity observed by Wallner line analysis and the peak amplitude of EMR signals registered during the test, showed very good correlation, validating this proportionality

Crack velocity measurement by induced electromagnetic radiation

Energy Technology Data Exchange (ETDEWEB)

Frid, V. [Deichmann Rock Mechanics Laboratory of the Negev, Geological and Environmental Sciences Department, Ben Gurion University of the Negev, Beer Sheva (Israel)]. E-mail: vfrid@bgu.ac.il; Rabinovitch, A. [Deichmann Rock Mechanics Laboratory of the Negev, Physics Department, Ben Gurion University of the Negev, Beer Sheva (Israel); Bahat, D. [Deichmann Rock Mechanics Laboratory of the Negev, Geological and Environmental Sciences Department, Ben Gurion University of the Negev, Beer Sheva (Israel)

2006-07-31

Our model of electromagnetic radiation (EMR) emanated from fracture implies that EMR amplitude is proportional to crack velocity. Soda lime glass samples were tested under uniaxial tension. Comparison of crack velocity observed by Wallner line analysis and the peak amplitude of EMR signals registered during the test, showed very good correlation, validating this proportionality.

Jovian cloud structure and velocity fields

International Nuclear Information System (INIS)

Mitchell, J.L.; Terrile, R.J.; Collins, S.A.; Smith, B.A.; Muller, J.P.; Ingersoll, A.P.; Hunt, G.E.; Beebe, R.F.

1979-01-01

A regional comparison of the cloud structures and velocity fields (meridional as well as zonal velocities) in the jovian atmosphere (scales > 200 km) as observed by the Voyager 1 imaging system is given. It is shown that although both hemispheres of Jupiter show similar patterns of diminishing and alternating eastward and westward jets as one progresses polewards, there is a pronounced asymmetry in the structural appearance of the two hemispheres. (UK)

STARE velocities: 2. Evening westward electron flow

Directory of Open Access Journals (Sweden)

M. Uspensky

2004-04-01

Full Text Available Four evening events and one morning event of joint EISCAT/STARE observations during ~22h are considered and the differences between observed STARE line-of-sight (l-o-s velocities and EISCAT electron drift velocities projected onto the STARE beams are studied. We demonstrate that the double-pulse technique, which is currently in use in the STARE routine data handling, typically underestimates the true phase velocity as inferred from the multi-pulse STARE data. We show that the STARE velocities are persistently smaller (1.5–2 times than the EISCAT velocities, even for the multi-pulse data. The effect seems to be more pronounced in the evening sector when the Finland radar observes at large flow angles. We evaluate the performance of the ion-acoustic approach (IAA, Nielsen and Schlegel, 1985 and the off-orthogonal fluid approach (OOFA, Uspensky et al., 2003 techniques to predict the true electron drift velocity for the base event of 12 February 1999. The IAA technique predicts the convection reasonably well for enhanced flows of >~1000m/s, but not so well for slower ones. By considering the EISCAT N(h profiles, we derive the effective aspect angle and effective altitude of backscatter, and use this information for application of the OOFA technique. We demonstrate that the OOFA predictions for the base event are superior over the IAA predictions and thus, we confirm that OOFA predicts the electron velocities reasonably well in the evening sector, in addition to the morning sector, as concluded by Uspensky et al. (2003. To check how "robust" the OOFA model is and how successful it is for convection estimates without the EISCAT support, we analysed three additional evening events and one additional morning event for which information on N(h profiles was intentionally ignored. By accepting the mean STARE/EISCAT velocity ratio of 0.55 and the mean azimuth rotation of 9° (derived for the basic event, we show that the OOFA performs

Equivalence of donor and acceptor fits of temperature dependent Hall carrier density and Hall mobility data: Case of ZnO

International Nuclear Information System (INIS)

Brochen, Stéphane; Feuillet, Guy; Pernot, Julien

2014-01-01

In this work, statistical formulations of the temperature dependence of ionized and neutral impurity concentrations in a semiconductor, needed in the charge balance equation and for carrier scattering calculations, have been developed. These formulations have been used in order to elucidate a confusing situation, appearing when compensating acceptor (donor) levels are located sufficiently close to the conduction (valence) band to be thermally ionized and thereby to emit (capture) an electron to (from) the conduction (valence) band. In this work, the temperature dependent Hall carrier density and Hall mobility data adjustments are performed in an attempt to distinguish the presence of a deep acceptor or a deep donor level, coexisting with a shallower donor level and located near the conduction band. Unfortunately, the present statistical developments, applied to an n-type hydrothermal ZnO sample, lead in both cases to consistent descriptions of experimental Hall carrier density and mobility data and thus do not allow to determine the nature, donor or acceptor, of the deep level. This demonstration shows that the emission of an electron in the conduction band, generally assigned to a (0/+1) donor transition from a donor level cannot be applied systematically and could also be attributed to a (−1/0) donor transition from an acceptor level. More generally, this result can be extended for any semiconductor and also for deep donor levels located close to the valence band (acceptor transition)

Selection of electron acceptors and strategies for in situ bioremediation

International Nuclear Information System (INIS)

Norris, R.D.

1995-01-01

The most critical aspect of designing in situ bioremediation systems is, typically, the selection and method of delivery of the electron acceptor. Nitrate, sulfate, and several forms of oxygen can be introduced, depending on the contaminants and the site conditions. Oxygen can be added as air, pure oxygen, hydrogen peroxide, or an oxygen release compound. Simplistic cost calculations can illustrate the advantages of some methods over others, providing technical requirements can be met

Control of Geminate Recombination by the Material Composition and Processing Conditions in Novel Polymer: Nonfullerene Acceptor Photovoltaic Devices.

Science.gov (United States)

Zhang, Jiangbin; Gu, Qinying; Do, Thu Trang; Rundel, Kira; Sonar, Prashant; Friend, Richard H; McNeill, Christopher R; Bakulin, Artem A

2018-02-08

Herein, we report on the charge dynamics of photovoltaic devices based on two novel small-molecule nonfullerene acceptors featuring a central ketone unit. Using ultrafast near-infrared spectroscopy with optical and photocurrent detection methods, we identify one of the key loss channels in the devices as geminate recombination (GR) of interfacial charge transfer states (CTSs). We find that the magnitude of GR is highly sensitive to the choice of solvent and annealing conditions. Interestingly, regardless of these processing conditions, the same lifetime for GR (∼130 ps) is obtained by both detection methods upon decomposing the complex broadband transient optical spectra, suggesting this time scale is inherent and independent of morphology. These observations suggest that the CTSs in the studied material blends are mostly strongly bound, and that charge generation from these states is highly inefficient. We further rationalize our results by considering the impact of the processing on the morphology of the mixed donor and acceptor domains and discuss the potential consequences of the early charge dynamics on the performance of emerging nonfullerene photovoltaic devices. Our results demonstrate that careful choice of processing conditions enables enhanced exciton harvesting and suppression of GR by more than 3 orders of magnitude.

Spatially extended and high-velocity dispersion molecular component in spiral galaxies: Single-dish versus interferometric observations

International Nuclear Information System (INIS)

Caldú-Primo, Anahi; Walter, Fabian; Schruba, Andreas; Leroy, Adam; Bolatto, Alberto D.; Vogel, Stuart

2015-01-01

Recent studies of the molecular medium in nearby galaxies have provided mounting evidence that the molecular gas can exist in two phases: one that is clumpy and organized as molecular clouds and another one that is more diffuse. This last component has a higher velocity dispersion than the clumpy one. In order to investigate these two molecular components further, we compare the fluxes and line widths of CO in NGC 4736 and NGC 5055, two nearby spiral galaxies for which high-quality interferometric as well as single-dish data sets are available. Our analysis leads to two main results: (1) employing three different methods, we determine the flux recovery of the interferometer as compared to the single-dish to be within a range of 35%–74% for NGC 4736 and 81%–92% for NGC 5055, and (2) when focusing on high (S/N ≥ 5) lines of sight (LOSs), the single-dish line widths are larger by ∼(40 ± 20)% than the ones derived from interferometric data, which is in agreement with stacking all LOSs. These results point to a molecular gas component that is distributed over spatial scales larger than 30″(∼1 kpc), and is therefore filtered out by the interferometer. The available observations do not allow us to distinguish between a truly diffuse gas morphology and a uniform distribution of small clouds that are separated by less than the synthesized beam size (∼3″ or ∼100 pc), as they would both be invisible for the interferometer. This high velocity dispersion component has a dispersion similar to what is found in the atomic medium, as traced through observations of the H i line.

Donor and Acceptor Polymers for Bulk Hetero Junction Solar Cell and Photodetector Applications

KAUST Repository

Cruciani, Federico

2018-04-01

Bulk heterojunction (BHJ) devices represent a very versatile family of organic cells for both the fields of solar energy conversion and photodetection. Organic photovoltaics (OPV) are an attractive alternative to their silicon-based counterparts because of their potential for low-cost roll-to-roll printing, and their intended application in light-weight mechanically conformable devices and in window-type semi-transparent PV modules. Of all proposed OPV candidates, polymer donor with different absorption range are especially promising when used in conjunction with complementary absorbing acceptor materials, like fullerene derivatives (PCBM), conjugated molecules or polymers, achieving nowadays power conversion efficiencies (PCEs) in the range of 10-13% and being a step closer to practical applications. Among the photodetectors (PD), low band gap polymer blended with PCBM decked out the attention, given their extraordinary range of detection from UV to IR and high detectivity values reached so far, compared to the inorganic devices. Since the research has been focused on the enhancement of those numbers for an effective commercialization of organic cells, the topic of the following thesis has been centered on the synthesis of different polymer structures with diverse absorption ranges, used as donor or acceptor, with emphasis on performance in various BHJ devices either for solar cells and photodetectors. In the first part, two new wide band gap polymers, used as donor material in BHJ devices blended with fullerene and small molecule acceptors, are presented. The PBDT_2FT and PBDTT_2FT have shown nice efficiencies from 7% to 9.8%. The device results are implemented with a morphology study and a specific application in a semi-transparent tandem device, reaching a record PCE of 5.4% for average level of transparency of 48%. In another section two new low band gap polymers (Eopt~ 1.26 eV) named DTP_2FBT and (Eopt~ 1.1 eV) named BDTT_BTQ are presented. While the DTP

Quantitative measurements of magnetic polaron binding on acceptors in CdMnTe alloys

Science.gov (United States)

Nhung, Tran Hong; Planel, R.

1983-03-01

The acceptor binding energy is measured as a function of Temperature and composition in Cd1-x Mnx Te alloys, by time resolved spectroscopy. The Bound magnetic polaron effect is measured and compared with a theory accouting for magnetic saturation and fluctuations.

Velocity slip of gas mixtures in free jet expansions

International Nuclear Information System (INIS)

Cattolica, R.J.; Talbot, L.; Coe, D.

1976-11-01

Velocity slip in gas mixtures of argon and helium in axisymmetric free jet expansions has been measured using a grating monochromator together with a computer-controlled Fabry-Perot interferometer to observe the fluorescence excited by an electron beam. The Doppler shift between the fluorescence observed parallel and perpendicular to the centerline of the free jet was used to measure the mean velocity of a particular species along the jet centerline, employing the 4880 A line for argon and the 5016 A line for helium. By alternately tracking the parallel and perpendicular fluorescence, the Doppler shift due to the mean velocity was measured directly with an accuracy of 1 percent. Flow field surveys have been made in the initial acceleration region where the flow becomes hypersonic and in the far field region. The differences between argon and helium mean velocities (velocity slip) are in good agreement with molecular beam data and show a correlation with an inverse Knudsen number

Positron annihilation in liquids and in solutions containing electron acceptors and charge-transfer complexes

International Nuclear Information System (INIS)

Jansen, P.

1976-05-01

Positron lifetime measurements and angular correlation measurements were performed in several organic liquids. The results strongly indicate that positronium is contained in a 'bubble' in the liquids. The radius of the bubble can be estimated by using broadness of the narrow component in the angular correlation distribution, and by using the surface tension of the liquids. Both methods give bubble radii from 4-7 A in the solvents investigated. The bubble influences the reaction mechanism between Ps and weak electron acceptors in such a way that the presence of the bubble decreases the reactivity of Ps. Positron lifetime measurements were also performed on a series of mixtures of organic liquids and on electron acceptors and charge-transfer complexes in solution. The results were is agreement with the spur model of Ps formation. (Auth.)

Tailored Band Gaps in Sulfur- and Nitrogen-Containing Porous Donor-Acceptor Polymers

Czech Academy of Sciences Publication Activity Database

Schwarz, D.; Kochergin, Y. S.; Acharjya, A.; Ichangi, Arun; Opanasenko, Maksym; Čejka, Jiří; Lappan, U.; Arki, P.; He, J.; Schmidt, J.; Nachtigall, P.; Thomas, A.; Tarábek, Ján; Bojdys, Michael J.

2017-01-01

Roč. 23, č. 53 (2017), s. 13023-13027 ISSN 0947-6539 Institutional support: RVO:61388963 ; RVO:61388955 Keywords : conjugated microporous polymers * donor-acceptor dyads * photocatalysis * sulfur * triazine Subject RIV: CC - Organic Chemistry; CF - Physical ; Theoretical Chemistry (UFCH-W) OBOR OECD: Organic chemistry; Physical chemistry (UFCH-W) Impact factor: 5.317, year: 2016

General theory of excitation energy transfer in donor-mediator-acceptor systems.

Science.gov (United States)

Kimura, Akihiro

2009-04-21

General theory of the excitation energy transfer (EET) in the case of donor-mediator-acceptor system was constructed by using generalized master equation (GME). In this theory, we consider the direct and indirect transitions in the EET consistently. Hence, our theory includes the quantum mechanical interference between the direct and indirect transitions automatically. Memory functions in the GME were expressed by the overlap integrals among the time-dependent emission spectrum of the donor, the absorption spectrum of the mediator, the time-dependent emission spectrum of the mediator, and the absorption spectrum of the acceptor. In the Markov limit of the memory functions, we obtained the rate of EET which consists of three terms due to the direct transition, the indirect transition, and the interference between them. We found that the interference works effectively in the limit of slow thermalization at the intermediate state. The formula of EET rate in this limit was expressed by the convolution of the EET interaction and optical spectra. The interference effect strongly depends on the width of the absorption spectrum of mediator molecule and the energy gap between the donor and the mediator molecules.

Constraining cosmology with the velocity function of low-mass galaxies

Science.gov (United States)

Schneider, Aurel; Trujillo-Gomez, Sebastian

2018-04-01

The number density of field galaxies per rotation velocity, referred to as the velocity function, is an intriguing statistical measure probing the smallest scales of structure formation. In this paper we point out that the velocity function is sensitive to small shifts in key cosmological parameters such as the amplitude of primordial perturbations (σ8) or the total matter density (Ωm). Using current data and applying conservative assumptions about baryonic effects, we show that the observed velocity function of the Local Volume favours cosmologies in tension with the measurements from Planck but in agreement with the latest findings from weak lensing surveys. While the current systematics regarding the relation between observed and true rotation velocities are potentially important, upcoming data from H I surveys as well as new insights from hydrodynamical simulations will dramatically improve the situation in the near future.

Stellar Velocity Dispersion: Linking Quiescent Galaxies to Their Dark Matter Halos

Science.gov (United States)

Zahid, H. Jabran; Sohn, Jubee; Geller, Margaret J.

2018-06-01

We analyze the Illustris-1 hydrodynamical cosmological simulation to explore the stellar velocity dispersion of quiescent galaxies as an observational probe of dark matter halo velocity dispersion and mass. Stellar velocity dispersion is proportional to dark matter halo velocity dispersion for both central and satellite galaxies. The dark matter halos of central galaxies are in virial equilibrium and thus the stellar velocity dispersion is also proportional to dark matter halo mass. This proportionality holds even when a line-of-sight aperture dispersion is calculated in analogy to observations. In contrast, at a given stellar velocity dispersion, the dark matter halo mass of satellite galaxies is smaller than virial equilibrium expectations. This deviation from virial equilibrium probably results from tidal stripping of the outer dark matter halo. Stellar velocity dispersion appears insensitive to tidal effects and thus reflects the correlation between stellar velocity dispersion and dark matter halo mass prior to infall. There is a tight relation (≲0.2 dex scatter) between line-of-sight aperture stellar velocity dispersion and dark matter halo mass suggesting that the dark matter halo mass may be estimated from the measured stellar velocity dispersion for both central and satellite galaxies. We evaluate the impact of treating all objects as central galaxies if the relation we derive is applied to a statistical ensemble. A large fraction (≳2/3) of massive quiescent galaxies are central galaxies and systematic uncertainty in the inferred dark matter halo mass is ≲0.1 dex thus simplifying application of the simulation results to currently available observations.

Aggregation-Induced Emission Enhancement from Disilane-Bridged Donor-Acceptor-Donor Luminogens Based on the Triarylamine Functionality.

Science.gov (United States)

Usuki, Tsukasa; Shimada, Masaki; Yamanoi, Yoshinori; Ohto, Tatsuhiko; Tada, Hirokazu; Kasai, Hidetaka; Nishibori, Eiji; Nishihara, Hiroshi

2018-04-18

Six novel donor-acceptor-donor organic dyes containing a Si-Si moiety based on triarylamine functionalities as donor units were prepared by Pd-catalyzed arylation of hydrosilanes. Their photophysical, electrochemical, and structural properties were studied in detail. Most of the compounds showed attractive photoluminescence (PL) and electrochemical properties both in solution and in the solid state because of intramolecular charge transfer (ICT), suggesting these compounds could be useful for electroluminescence (EL) applications. The aggregation-induced emission enhancement (AIEE) characteristics of 1 and 3 were examined in mixed water/THF solutions. The fluorescence intensity in THF/water was stronger in the solution with the highest ratio of water because of the suppression of molecular vibration and rotation in the aggregated state. Single-crystal X-ray diffraction of 4 showed that the reduction of intermolecular π-π interaction led to intense emission in the solid state and restricted intramolecular rotation of the donor and acceptor moieties, thereby indicating that the intense emission in the solid state is due to AIEE. An electroluminescence device employing 1 as an emitter exhibited an external quantum efficiency of up to 0.65% with green light emission. The emission comes solely from 1 because the EL spectrum is identical to that of the PL of 1. The observed luminescence was sufficiently bright for application in practical devices. Theoretical calculations and electrochemical measurements were carried out to aid in understanding the optical and electrochemical properties of these molecules.

The improved photovoltaic performance of phenothiazine-dithienopyrrole based dyes with auxiliary acceptors

Science.gov (United States)

Han, Ming-Liang; Zhu, Yi-Zhou; Liu, Shuang; Liu, Qing-Long; Ye, Dan; Wang, Bing; Zheng, Jian-Yu

2018-05-01

Incorporating alkyl chain decorated dithienopyrrole π-spacer with phenothiazine donor has proven to be efficient strategy for constructing novel dyes, which can achieve both large short-circuit current (Jsc) and high open-circuit voltage (Voc) in dye-sensitized solar cells (DSSCs). To promote the light harvesting capability, auxiliary acceptors including benzotriazole (BTZ), benzothiadiazole (BTD), and quinoxaline (Qu) have been inserted into the skeleton of dyes, and much improved Jsc have been realized. Meantime, the rational design of alkyl chains endows dyes JY53 and JY55 a good shielding effect from the penetration of electrolyte, guaranteeing a high Voc (over 810 mV) through retarding unwanted interfacial charge recombination. As a result, with the assistance of introduced auxiliary acceptors and alkyl chains, the photovoltaic performance of devices have been significantly improved, and dye JY55 has achieved an excellent power conversion efficiency (PCE) of 10.06% with Jsc of 19.18 mA cm-2, Voc of 829 mV, and FF of 0.63 under AM 1.5 G irradiation.

MAVEN Observations of Escaping Planetary Ions from the Martian Atmosphere: Mass, Velocity, and Spatial Distributions

Science.gov (United States)

Dong, Yaxue; Fang, Xiaohua; Brain, D. A.; McFadden, James P.; Halekas, Jasper; Connerney, Jack

2015-04-01

The Mars-solar wind interaction accelerates and transports planetary ions away from the Martian atmosphere through a number of processes, including ‘pick-up’ by electromagnetic fields. The MAVEN spacecraft has made routine observations of escaping planetary ions since its arrival at Mars in September 2014. The SupraThermal And Thermal Ion Composition (STATIC) instrument measures the ion energy, mass, and angular spectra. It has detected energetic planetary ions during most of the spacecraft orbits, which are attributed to the pick-up process. We found significant variations in the escaping ion mass and velocity distributions from the STATIC data, which can be explained by factors such as varying solar wind conditions, contributions of particles from different source locations and different phases during the pick-up process. We also study the spatial distributions of different planetary ion species, which can provide insight into the physics of ion escaping process and enhance our understanding of atmospheric erosion by the solar wind. Our results will be further interpreted within the context of the upstream solar wind conditions measured by the MAVEN Solar Wind Ion Analyzer (SWIA) instrument and the magnetic field environment measured by the Magnetometer (MAG) instrument. Our study shows that the ion spatial distribution in the Mars-Sun-Electric-Field (MSE) coordinate system and the velocity space distribution with respect to the local magnetic field line can be used to distinguish the ions escaping through the polar plume and those through the tail region. The contribution of the polar plume ion escape to the total escape rate will also be discussed.

48-spot single-molecule FRET setup with periodic acceptor excitation

Science.gov (United States)

Ingargiola, Antonino; Segal, Maya; Gulinatti, Angelo; Rech, Ivan; Labanca, Ivan; Maccagnani, Piera; Ghioni, Massimo; Weiss, Shimon; Michalet, Xavier

2018-03-01

Single-molecule Förster resonance energy transfer (smFRET) allows measuring distances between donor and acceptor fluorophores on the 3-10 nm range. Solution-based smFRET allows measurement of binding-unbinding events or conformational changes of dye-labeled biomolecules without ensemble averaging and free from surface perturbations. When employing dual (or multi) laser excitation, smFRET allows resolving the number of fluorescent labels on each molecule, greatly enhancing the ability to study heterogeneous samples. A major drawback to solution-based smFRET is the low throughput, which renders repetitive measurements expensive and hinders the ability to study kinetic phenomena in real-time. Here we demonstrate a high-throughput smFRET system that multiplexes acquisition by using 48 excitation spots and two 48-pixel single-photon avalanche diode array detectors. The system employs two excitation lasers allowing separation of species with one or two active fluorophores. The performance of the system is demonstrated on a set of doubly labeled double-stranded DNA oligonucleotides with different distances between donor and acceptor dyes along the DNA duplex. We show that the acquisition time for accurate subpopulation identification is reduced from several minutes to seconds, opening the way to high-throughput screening applications and real-time kinetics studies of enzymatic reactions such as DNA transcription by bacterial RNA polymerase.

Synthesis and photovoltaic properties from inverted geometry cells and roll-to-roll coated large area cells from dithienopyrrole-based donor-acceptor polymers

DEFF Research Database (Denmark)

Yue, Wei; Larsen-Olsen, Thue Trofod; Hu, Xiaolian

2013-01-01

A series of donor-acceptor low band gap polymers composed of alternating dithienopyrrole or its derivative as donors and phthalimide or thieno[3,4-c]pyrrole-4,6-dione as acceptors (P1-P4) are synthesized by Stille coupling polymerization. All polymers show strong absorption in the visible region......, for P2 and P4 possessing thieno[3,4-c]pyrrole-4,6-dione as an acceptor, their film absorption covers the region of 500-800 nm and 500-750 nm respectively, which makes them attractive as low band gap polymer solar cell (PSC) materials. With the incorporation of thiophene bridges, P3 and P4 have 0...

Ghost peaks observed after AP-MALDI experiment may disclose new ionization mechanism of matrix assisted hypersonic velocity impact ionization

Science.gov (United States)

Moskovets, Eugene

2015-01-01

RATIONALE Understanding the mechanisms of MALDI promises improvements in the sensitivity and specificity of many established applications in the field of mass spectrometry. This paper reports a serendipitous observation of a significant ion yield in a post-ionization experiment conducted after the sample has been removed from a standard atmospheric pressure (AP)-MALDI source. This post-ionization is interpreted in terms of collisions of microparticles moving with a hypersonic velocity into a solid surface. Calculations show that the thermal energy released during such collisions is close to that absorbed by the top matrix layer in traditional MALDI. The microparticles, containing both the matrix and analytes, could be detached from a film produced inside the inlet capillary during the sample ablation and accelerated by the flow rushing through the capillary. These observations contribute some new perspective to ion formation in both laser and laserless matrix-assisted ionization. METHODS An AP-MALDI ion source hyphenated with a three-stage high-pressure ion funnel system was utilized for peptide mass analysis. After the laser was turned off and MALDI sample was removed, ions were detected during a gradual reduction of the background pressure in the first funnel. The constant-rate pressure reduction led to the reproducible appearance of different singly- and doubly-charged peptide peaks in mass spectra taken a few seconds after the end of the MALDI analysis of a dried-droplet spot. RESULTS The ion yield as well as the mass range of ions observed with a significant delay after a completion of the primary MALDI analysis depended primarily on the background pressure inside the first funnel. The production of ions in this post-ionization step was exclusively observed during the pressure drop. A lower matrix background and significant increase in relative yield of double-protonated ions are reported. CONCLUSIONS The observations were partially consistent with a model of

Pronounced Effects of a Triazine Core on Photovoltaic Performance-Efficient Organic Solar Cells Enabled by a PDI Trimer-Based Small Molecular Acceptor.

Science.gov (United States)

Duan, Yuwei; Xu, Xiaopeng; Yan, He; Wu, Wenlin; Li, Zuojia; Peng, Qiang

2017-02-01

A novel-small molecular acceptor with electron-deficient 1,3,5-triazine as the core and perylene diimides as the arms is developed as the acceptor material for efficient bulk heterojunction organic solar cells with an efficiency of 9.15%. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical properties of metastable shallow acceptors in Mg-doped GaN layers grown by metal-organic vapor phase epitaxy

OpenAIRE

Pozina, Galia; Hemmingsson, Carl; Bergman, Peder; Kawashima, T.; Amano, H.; Akasaki, I.; Usui, A.; Monemar, Bo

2010-01-01

GaN layers doped by Mg show a metastable behavior of the near-band-gap luminescence caused by electron irradiation or UV excitation. At low temperatures < 30 K the changes in luminescence are permanent. Heating to room temperature recovers the initial low temperature spectrum shape completely. Two acceptors are involved in the recombination process as confirmed by transient PL. In as-grown samples a possible candidate for the metastable acceptor is C-N, while after annealing a second m...

Rayleigh wave group velocity and shear wave velocity structure in the San Francisco Bay region from ambient noise tomography

Science.gov (United States)

Li, Peng; Thurber, Clifford

2018-06-01

We derive new Rayleigh wave group velocity models and a 3-D shear wave velocity model of the upper crust in the San Francisco Bay region using an adaptive grid ambient noise tomography algorithm and 6 months of continuous seismic data from 174 seismic stations from multiple networks. The resolution of the group velocity models is 0.1°-0.2° for short periods (˜3 s) and 0.3°-0.4° for long periods (˜10 s). The new shear wave velocity model of the upper crust reveals a number of important structures. We find distinct velocity contrasts at the Golden Gate segment of the San Andreas Fault, the West Napa Fault, central part of the Hayward Fault and southern part of the Calaveras Fault. Low shear wave velocities are mainly located in Tertiary and Quaternary basins, for instance, La Honda Basin, Livermore Valley and the western and eastern edges of Santa Clara Valley. Low shear wave velocities are also observed at the Sonoma volcanic field. Areas of high shear wave velocity include the Santa Lucia Range, the Gabilan Range and Ben Lomond Plutons, and the Diablo Range, where Franciscan Complex or Silinian rocks are exposed.

Remote determination of the velocity index and mean streamwise velocity profiles

Science.gov (United States)

Johnson, E. D.; Cowen, E. A.

2017-09-01

When determining volumetric discharge from surface measurements of currents in a river or open channel, the velocity index is typically used to convert surface velocities to depth-averaged velocities. The velocity index is given by, k=Ub/Usurf, where Ub is the depth-averaged velocity and Usurf is the local surface velocity. The USGS (United States Geological Survey) standard value for this coefficient, k = 0.85, was determined from a series of laboratory experiments and has been widely used in the field and in laboratory measurements of volumetric discharge despite evidence that the velocity index is site-specific. Numerous studies have documented that the velocity index varies with Reynolds number, flow depth, and relative bed roughness and with the presence of secondary flows. A remote method of determining depth-averaged velocity and hence the velocity index is developed here. The technique leverages the findings of Johnson and Cowen (2017) and permits remote determination of the velocity power-law exponent thereby, enabling remote prediction of the vertical structure of the mean streamwise velocity, the depth-averaged velocity, and the velocity index.

Ramifications of projectile velocity on the ballistic dart penetration of sand

Science.gov (United States)

Sable, Peter Anthony

With the advent of novel in-situ experimental measurement techniques, highly resolved quantitative observations of dynamic events within granular media can now be made. In particular, high speed imagery and digital analysis now allow for the ballistic behaviors of sand to be examined not only across a range of event velocities but across multiple length scales. In an attempt to further understand the dynamic behavior of granular media, these new experimental developments were implemented utilizing high speed photography coupled with piezo-electric stress gauges to observe visually accessible ballistic events of a dart penetrating Ottawa sand. Projectile velocities ranged from 100 to over 300 meters per second with two distinct chosen fields of view to capture bulk and grain-scale behaviors. Each event was analyzed using the digital image correlation technique, particle image velocimetry from which two dimensional, temporally resolved, velocity fields were extracted, from which bulk granular flow and compaction wave propagation were observed and quantified. By comparing bulk, in situ, velocity field behavior resultant from dart penetration, momentum transfer could be quantified measuring radius of influence or dilatant fluid approximations from which a positive correlation was found across the explored velocity regime, including self similar tendencies. This was, however, not absolute as persistent scatter was observed attributed to granular heterogeneous effects. These were tentatively measured in terms of an irreversible energy amount calculated via energy balance. Grain scale analysis reveals analogous behavior to the bulk response with more chaotic structure, though conclusions were limited by the image processing method to qualitative observations. Even so, critical granular behaviors could be seen, such as densification, pore collapse, and grain fracture from which basic heterogeneous phenomena could be examined. These particularly dominated near nose

Stellar Velocity Dispersion: Linking Quiescent Galaxies to their Dark Matter Halos

OpenAIRE

Zahid, H. Jabran; Sohn, Jubee; Geller, Margaret J.

2018-01-01

We analyze the Illustris-1 hydrodynamical cosmological simulation to explore the stellar velocity dispersion of quiescent galaxies as an observational probe of dark matter halo velocity dispersion and mass. Stellar velocity dispersion is proportional to dark matter halo velocity dispersion for both central and satellite galaxies. The dark matter halos of central galaxies are in virial equilibrium and thus the stellar velocity dispersion is also proportional to dark matter halo mass. This prop...

Electrodes as Terminal Electron Acceptors in Anaerobic Ammonium Oxidation

Science.gov (United States)

Ruiz-Urigüen, M.; Jaffe, P. R.

2017-12-01

Anaerobic ammonium (NH4+) oxidation under iron (Fe) reducing conditions is a microbial- mediated process known as Feammox. This is a novel pathway in the nitrogen cycle, and a key process for alleviating NH4+ accumulation in anoxic soils, wetlands, and wastewater. Acidimicrobiaceae-bacterium A6, phylum Actinobacteria, are one type of autotrophic bacteria linked to this process. The Feammox-bacteria obtain their energy by oxidizing NH4+ and transferring the electrons to a terminal electron acceptor (TEA). Under environmental conditions, iron oxides are the TEAs. However, in this study we show that electrodes in Microbial Electrolysis Cells (MECs) or electrodes set in the field can be used as TEAs by Feammox-bacteria. The potential difference between electrodes is the driving force for electron transfer, making the reaction energetically feasible. Our results show that MECs containing Feammox cultures can remove NH4+ up to 3.5 mg/L in less than 4 hours, compared to an average of 9 mg/L in 2 weeks when cultured under traditional conditions. Concomitantly, MECs produce an average current of 30.5 A/m3 whilst dead bacteria produced low (Actinobacteria when compared to bulk soil. Electrodes as TEAs enhance electrogenic bacteria recovery and culturing. The use of MECs for the productions of Feammox-bacteria eliminates the dependence of Fe, a finite electron acceptor, therefore, allowing for continuous NH4+ removal. Finally, Fe-free Feammox-bacteria can be applied to reduce other metals of environmental concern; therefore, opening the range of possible application of Feammox-bacteria.

Background velocity inversion by phase along reflection wave paths

KAUST Repository

Yu, Han; Guo, Bowen; Schuster, Gerard T.

2014-01-01

A background velocity model containing the correct lowwavenumber information is desired for both the quality of the migration image and the success of waveform inversion. We propose to invert for the low-wavenumber part of the velocity model by minimizing the phase difference between predicted and observed reflections. The velocity update is exclusively along the reflection wavepaths and, unlike conventional FWI, not along the reflection ellipses. This allows for reconstructing the smoothly varying parts of the background velocity model. Tests with synthetic data show both the benefits and limitations of this method.

Background velocity inversion by phase along reflection wave paths

KAUST Repository

Yu, Han

2014-08-05

A background velocity model containing the correct lowwavenumber information is desired for both the quality of the migration image and the success of waveform inversion. We propose to invert for the low-wavenumber part of the velocity model by minimizing the phase difference between predicted and observed reflections. The velocity update is exclusively along the reflection wavepaths and, unlike conventional FWI, not along the reflection ellipses. This allows for reconstructing the smoothly varying parts of the background velocity model. Tests with synthetic data show both the benefits and limitations of this method.

Maximal intended velocity training induces greater gains in bench press performance than deliberately slower half-velocity training.

Science.gov (United States)

González-Badillo, Juan José; Rodríguez-Rosell, David; Sánchez-Medina, Luis; Gorostiaga, Esteban M; Pareja-Blanco, Fernando

2014-01-01

The purpose of this study was to compare the effect on strength gains of two isoinertial resistance training (RT) programmes that only differed in actual concentric velocity: maximal (MaxV) vs. half-maximal (HalfV) velocity. Twenty participants were assigned to a MaxV (n = 9) or HalfV (n = 11) group and trained 3 times per week during 6 weeks using the bench press (BP). Repetition velocity was controlled using a linear velocity transducer. A complementary study (n = 10) aimed to analyse whether the acute metabolic (blood lactate and ammonia) and mechanical response (velocity loss) was different between the MaxV and HalfV protocols used. Both groups improved strength performance from pre- to post-training, but MaxV resulted in significantly greater gains than HalfV in all variables analysed: one-repetition maximum (1RM) strength (18.2 vs. 9.7%), velocity developed against all (20.8 vs. 10.0%), light (11.5 vs. 4.5%) and heavy (36.2 vs. 17.3%) loads common to pre- and post-tests. Light and heavy loads were identified with those moved faster or slower than 0.80 m · s(-1) (∼ 60% 1RM in BP). Lactate tended to be significantly higher for MaxV vs. HalfV, with no differences observed for ammonia which was within resting values. Both groups obtained the greatest improvements at the training velocities (≤ 0.80 m · s(-1)). Movement velocity can be considered a fundamental component of RT intensity, since, for a given %1RM, the velocity at which loads are lifted largely determines the resulting training effect. BP strength gains can be maximised when repetitions are performed at maximal intended velocity.

A glance at velocity structure of Izmir

Energy Technology Data Exchange (ETDEWEB)

Özer, Çağlar, E-mail: caglar.ozer@deu.edu.tr [Dokuz Eylul University, Faculty of Engineering, Geophysical Engineering Department, Izmir (Turkey); Dokuz Eylul University, The Graduate School of Natural and Applied Sciences, Department of Geophysical Engineering, Izmir (Turkey); Polat, Orhan, E-mail: orhan.polat@deu.edu.tr [Dokuz Eylul University, Faculty of Engineering, Geophysical Engineering Department, Izmir (Turkey)

2016-04-18

In this study; we investigated velocity structure of Izmir and surroundings. We used local earthquake data which was recorded by different type of instruments and obtained high resolution 3D sections. We selected more than 400 earthquakes which were occurred between 2010 and 2013. Examined tomographic sections especially in Izmir along coastal areas (Mavisehir-Inciraltı); revealed the low speed zone. Along this low-speed zone; it is consistent with the results obtained from the stratigraphic section and surface geology. While; low velocity zones are associated with faults and water content; high velocity is related to magmatic rocks or compact rocks. Along Karsıyaka, Seferihisar, Orhanlı, Izmir fault zones; low P velocity was observed. When examined higher elevations of the topography; which are composed of soured magmatic material is dominated by high P velocity. In all horizontal sections; resolution decreasing with increasing depth. The reason for this; the reduction of earthquakes causes ray tracing problems.

Velocities of Auroral Coherent Echoes At 12 and 144 Mhz

Science.gov (United States)

Koustov, A. V.; Danskin, D. W.; Makarevitch, R. A.; Uspensky, M. V.; Janhunen, P.; Nishitani, N.; Nozawa, N.; Lester, M.; Milan, S.

Two Doppler coherent radar systems are currently working at Hankasalmi, Finland, the STARE and CUTLASS radars operating at 144 MHz and 12 MHz, respectively. The STARE beam 3 is nearly co-located with the CUTLASS beam 5 providing an opportunity for echo velocity comparison along the same direction but at significantly different radar frequencies. In this study we consider one event when STARE radar echoes are detected t the same ranges as CUTLASS radar echoes. The observations are complemented by EISCAT measurements of the ionospheric electric field and elec- tron density behavior at one range of 900 km. Two separate situations are studied; for the first one, CUTLASS observed F-region echoes (including the range of the EIS- CAT measurements) while for the second one CUTLASS observed E-region echoes. In both cases STARE E-region measurements were available. We show that F-region CUTLASS velocities agree well with the convection component along the CUTLASS radar beam while STARE velocities are sometimes smaller by a factor of 2-3. For the second case, STARE velocities are found to be either smaller or larger than CUTLASS velocities, depending on range. Plasma physics of E- and F-region irregularities is dis- cussed in attempt to explain inferred relationship between various velocities. Special attention is paid to ionospheric refraction that is important for the detection of 12-MHz echoes.

Electrolytic formation of technetium complexes with π-acceptor ligands

International Nuclear Information System (INIS)

Cerda, F.; Kremer, C.; Gambino, D.; Kremer, E.

1994-01-01

Electrolytic reduction of pertechnetate was performed in aqueous solution containing π-acceptor ligands. Cyanide and 1,10-phenanthroline were the selected ligands. In both cases, electrolyses produced a cathodic TcO 2 deposit and soluble Tc complexes. When cyanide was the ligand, the complexes formed were [Tc(CN) 6 ] 5- and [TcO 2 (CN) 4 ] 3- . When working with the amine, [Tc(phen) 3 ] 2+ and another positively charged species were found after reaction. Results are compared with previous studies with amines, and the usefulness of the electrolytic route to obtain Tc complexes is evaluated. (author) 11 refs.; 2 figs.; 1 tab

Bane of Hydrogen-Bond Formation on the Photoinduced Charge-Transfer Process in Donor–Acceptor Systems

KAUST Repository

Alsam, Amani Abdu; Adhikari, Aniruddha; Parida, Manas R.; Aly, Shawkat Mohammede; Bakr, Osman; Mohammed, Omar F.

2017-01-01

Controlling the ultrafast dynamical process of photoinduced charge transfer at donor acceptor interfaces remains a major challenge for physical chemistry and solar cell communities. The process is complicated by the involvement of other complex

High velocity properties of the dynamic frictional force between ductile metals

International Nuclear Information System (INIS)

Hammerberg, James Edward; Hollan, Brad L.; Germann, Timothy C.; Ravelo, Ramon J.

2010-01-01

The high velocity properties of the tangential frictional force between ductile metal interfaces seen in large-scale NonEquilibrium Molecular Dynamics (NEMD) simulations are characterized by interesting scaling behavior. In many cases a power law decrease in the frictional force with increasing velocity is observed at high velocities. We discuss the velocity dependence of the high velocity branch of the tangential force in terms of structural transformation and ultimate transition, at the highest velocities, to confined fluid behavior characterized by a critical strain rate. The particular case of an Al/Al interface is discussed.

Influence of Coherent Tunneling and Incoherent Hopping on the Charge Transfer Mechanism in Linear Donor-Bridge-Acceptor Systems.

Science.gov (United States)

Li, Guangqi; Govind, Niranjan; Ratner, Mark A; Cramer, Christopher J; Gagliardi, Laura

2015-12-17

The mechanism of charge transfer has been observed to change from tunneling to hopping with increasing numbers of DNA base pairs in polynucleotides and with the length of molecular wires. The aim of this paper is to investigate this transition by examining the population dynamics using a tight-binding Hamiltonian with model parameters to describe a linear donor-bridge-acceptor (D-B-A) system. The model includes a primary vibration and an electron-vibration coupling at each site. A further coupling of the primary vibration with a secondary phonon bath allows the system to dissipate energy to the environment and reach a steady state. We apply the quantum master equation (QME) approach, based on second-order perturbation theory in a quantum dissipative system, to examine the dynamical processes involved in charge-transfer and follow the population transfer rate at the acceptor, ka, to shed light on the transition from tunneling to hopping. With a small tunneling parameter, V, the on-site population tends to localize and form polarons, and the hopping mechanism dominates the transfer process. With increasing V, the population tends to be delocalized and the tunneling mechanism dominates. The competition between incoherent hopping and coherent tunneling governs the mechanism of charge transfer. By varying V and the total number of sites, we also examine the onset of the transition from tunneling to hopping with increasing length.

Part I. Synthesis and characterization of donor-pi-acceptor compounds with pentadienyl-bridged indoline and tetrahydroquinoline donors and aldehyde and thiobarbituric acid acceptors Part II. Longitudinal study comparing online versus face-to-face course delivery in introductory chemistry

Science.gov (United States)

Greco, Patrick F.

Part I. The design and development of organic second-order nonlinear optical (NLO) materials have attracted much interest due to their applications in optoelectronic devices and modern communications technology. Donor-pi-acceptor compounds, D-(CH=CH)n-A, often exhibit hyperpolarizability that results in laser frequency doubling (second harmonic generation) and spectroscopic solvatochromism. To study the effect of donor amine geometry upon properties associated with second-order NLO behavior in simple donor-pi-acceptor compounds, equilibrium geometries and hyperpolarizabilities (beta) for donor-acceptor polyenes with amine donors were calculated at several levels of computational theory. Two new molecules with donors that only differ by one methylene group were chosen for comparison. Thus, 5-(N-methylindolin-5-yl)-2, 4-pentadienal (1a) and 5-(N-methyl-2, 3, 4-trihydroquinolin-6-yl)-2, 4-pentadienal (2a) were synthesized in two steps from starting materials described in the literature. These aldehydes were converted into stronger acceptors in one step to give diethylthiobarbituric acid derivatives 1c and 2c, as well as tricyanofuran derivatives 1d and 2d. Positive UV solvatochromism was observed in all three derivatives. NMR solvatochromism was most pronounced in 1c, and 2c vs. 1a and 2a as measured by changes in chemical shifts. Additionally, coupling constants showed more conjugation in 1c and 2c, where 1a and 2a showed less conjugation. Finally, differential scanning calorimetry and thermal gravimetric analysis were used to compare decomposition and melting temperatures of these compounds to determine their stability. Aldehydes, 1a and 2a had distinct melting points, while the 1c, 2c, 1d, and 2d derivatives decomposed at temperatures above 150 °C. Part II. This longitudinal study focused on an introductory chemistry course taught using two different modes of delivery: online and face-to-face (FtF). The sections of the course using the different delivery modes

Rate dependence of electron transfer on donor-acceptor separation and on free enthalpy change. The Ru(bpy)32+/viologen2+ system

International Nuclear Information System (INIS)

Rau, H.; Frank, R.; Greiner, G.

1986-01-01

By attachment of hydrocarbon chains of different lengths to the bipyridyl ligands in Ru(bpy) 3 2+ we have adjusted the donor-acceptor separation in the electron-transfer system Ru[(C/sub n/H/sub 2n+1/) 2 bpyl 3 2+ /methylviolgen. Two electron-transfer reactions with different ΔG are investigated in fluid solution: the quenching of the excited complexes by methylviologen (MV 2+ ) which is exergonic with -0.4 eV and the thermal back electron transfer which is exergonic with -1.7 eV. We observe an exponential decrease of the quenching rate on distance. The back electron transfer is independent of donor-acceptor separation; electron transfer is found to take place at distances of 1.5 nm and more. The results are discussed in terms of a hypothesis on the interdependence of transfer distance and free enthalpy change and compared with current theories. In the framework of the simple classical Marcus model, the Marcus equation relating transfer rate and free enthalpy change is transposed into the Rehm-Weller equation by simple mathematical manipulations and the implications of this are discussed

Reactivity of vinyl ethers and vinyl ribosides in UV-initiated free radical copolymerization with acceptor monomers.

Science.gov (United States)

Pichavant, Loic; Guillermain, Céline; Coqueret, Xavier

2010-09-13

The reactivity of various vinyl ethers and vinyloxy derivatives of ribose in the presence of diethyl fumarate or diethyl maleate was investigated for evaluating the potential of donor-acceptor-type copolymerization applied to unsaturated monomers derived from renewable feedstock. The photochemically induced polymerization of model monomer blends in the bulk state was monitored by infrared spectroscopy. The method allowed us to examine the influence of monomer pair structure on the kinetic profiles. The simultaneous consumption of both monomers was observed, supporting an alternating copolymerization mechanism. A lower reactivity of the blends containing maleates compared with fumarates was confirmed. The obtained kinetic data revealed a general correlation between the initial polymerization rate and the Hansen parameter δ(H) associated with the H-bonding aptitude of the donor monomer.

Enhanced native acceptor-related blue emission of ZnO thin films annealed in an oxygen ambient

International Nuclear Information System (INIS)

Shim, Eunhee; Lee, Choeun; Jung, Eiwhan; Lee, Jinyong; Kim, Doosoo; Lee, Youngmin; Kim, Deukyoung; Lee, Sejoon

2012-01-01

The thermodynamic behaviors of charged point defects in unintentionally-doped ZnO thin films were investigated. The as-grown sample displayed two different types of blue-emission bands: one at ∼2.95 eV from native-donor zinc interstitial (Zn i ) and the other at ∼3.17 eV from native acceptor zinc vacancies (V Zn ). In the samples annealed at oxygen ambience, V Zn -related emission was dramatically enhanced, and Zn i -related emission was drastically reduced. The behavior was observed to become more apparent when the annealing temperature was increased. The results can be explained by both the increased generation probability and the lowered formation enthalpy of V Zn in an oxygen-rich environment, particularly at higher temperatures.

Enhanced native acceptor-related blue emission of ZnO thin films annealed in an oxygen ambient

Energy Technology Data Exchange (ETDEWEB)

Shim, Eunhee; Lee, Choeun; Jung, Eiwhan; Lee, Jinyong; Kim, Doosoo; Lee, Youngmin; Kim, Deukyoung; Lee, Sejoon [Dongguk University, Seoul (Korea, Republic of)

2012-06-15

The thermodynamic behaviors of charged point defects in unintentionally-doped ZnO thin films were investigated. The as-grown sample displayed two different types of blue-emission bands: one at ∼2.95 eV from native-donor zinc interstitial (Zn{sub i}) and the other at ∼3.17 eV from native acceptor zinc vacancies (V{sub Zn}). In the samples annealed at oxygen ambience, V{sub Zn}-related emission was dramatically enhanced, and Zn{sub i}-related emission was drastically reduced. The behavior was observed to become more apparent when the annealing temperature was increased. The results can be explained by both the increased generation probability and the lowered formation enthalpy of V{sub Zn} in an oxygen-rich environment, particularly at higher temperatures.

Line-of-Sight Velocity As a Tracer of Coronal Cavity Magnetic Structure

International Nuclear Information System (INIS)

Bąk-Stȩślicka, Urszula; Gibson, Sarah E.; Chmielewska, Ewa

2016-01-01

We present a statistical analysis of 66 days of observations of quiescent (non-erupting) coronal cavities and associated velocity and thermal structures. We find that nested rings of LOS-oriented velocity are common in occurrence and spatially well correlated with cavities observed in emission. We find that the majority of cavities possess multiple rings, and a range in velocity on the order of several km∕sec. We find that the tops of prominences lie systematically below the cavity center and location of largest Doppler velocity. Finally, we use DEM analysis to consider the temperature structure of two cavities in relation to cavity, prominence, and flows. These observations yield new constraints on the magnetic structure of cavities, and on the conditions leading up to solar eruptions.

Characterization of the alumina-zirconia ceramic system by ultrasonic velocity measurements

International Nuclear Information System (INIS)

Carreon, Hector; Ruiz, Alberto; Medina, Ariosto; Barrera, Gerardo; Zarate, Juan

2009-01-01

In this work an alumina-zirconia ceramic composites have been prepared with α-Al 2 O 3 contents from 10 to 95 wt.%. The alumina-zirconia ceramic system was characterized by means of precise ultrasonic velocity measurements. In order to find out the factors affecting the variation in wave velocity, the ceramic composite have been examined by X-ray diffraction (XRD) and (SEM) scanning electron microscopy. It was found that the ultrasonic velocity measurements changed considerably with respect to the ceramic composite composition. In particular, we studied the behavior of the physical material property hardness, an important parameter of the ceramic composite mechanical properties, with respect to the variation in the longitudinal and shear wave velocities. Shear wave velocities exhibited a stronger interaction with microstructural and sub-structural features as compared to that of longitudinal waves. In particular, this phenomena was observed for the highest α-Al 2 O 3 content composite. Interestingly, an excellent correlation between ultrasonic velocity measurements and ceramic composite hardness was observed.

Peculiar velocity measurement in a clumpy universe

Science.gov (United States)

Habibi, Farhang; Baghram, Shant; Tavasoli, Saeed

Aims: In this work, we address the issue of peculiar velocity measurement in a perturbed Friedmann universe using the deviations from measured luminosity distances of standard candles from background FRW universe. We want to show and quantify the statement that in intermediate redshifts (0.5 deviations from the background FRW model are not uniquely governed by peculiar velocities. Luminosity distances are modified by gravitational lensing. We also want to indicate the importance of relativistic calculations for peculiar velocity measurement at all redshifts. Methods: For this task, we discuss the relativistic correction on luminosity distance and redshift measurement and show the contribution of each of the corrections as lensing term, peculiar velocity of the source and Sachs-Wolfe effect. Then, we use the SNe Ia sample of Union 2, to investigate the relativistic effects, we consider. Results: We show that, using the conventional peculiar velocity method, that ignores the lensing effect, will result in an overestimate of the measured peculiar velocities at intermediate redshifts. Here, we quantify this effect. We show that at low redshifts the lensing effect is negligible compare to the effect of peculiar velocity. From the observational point of view, we show that the uncertainties on luminosity of the present SNe Ia data prevent us from precise measuring the peculiar velocities even at low redshifts (z < 0.2).

A helical perylene diimide-based acceptor for non-fullerene organic solar cells: synthesis, morphology and exciton dynamics

Science.gov (United States)

Chen, Li; Wu, Mingliang; Shao, Guangwei; Hu, Jiahua; He, Guiying; Bu, Tongle; Yi, Jian-Peng; Xia, Jianlong

2018-05-01

Helical perylene diimide-based (hPDI) acceptors have been established as one of the most promising candidates for non-fullerene organic solar cells (OSCs). In this work, we report a novel hPDI-based molecule, hPDI2-CN2, as an electron acceptor for OSCs. Combining the hPDI2-CN2 with a low-bandgap polymeric donor (PTB7-Th), the blending film morphology exhibited high sensitivity to various treatments (such as thermal annealing and addition of solvent additives), as evidenced by atomic force microscope studies. The power conversion efficiency (PCE) was improved from 1.42% (as-cast device) to 2.76% after thermal annealing, and a PCE of 3.25% was achieved by further addition of 1,8-diiodooctane (DIO). Femtosecond transient absorption (TA) spectroscopy studies revealed that the improved thin-film morphology was highly beneficial for the charge carrier transport and collection. And a combination of fast exciton diffusion rate and the lowest recombination rate contributed to the best performance of the DIO-treated device. This result further suggests that the molecular conformation needs to be taken into account in the design of perylene diimide-based acceptors for OSCs.

High-resolution noncontact AFM and Kelvin probe force microscopy investigations of self-assembled photovoltaic donor–acceptor dyads

Directory of Open Access Journals (Sweden)

Benjamin Grévin

2016-06-01

Full Text Available Self-assembled donor–acceptor dyads are used as model nanostructured heterojunctions for local investigations by noncontact atomic force microscopy (nc-AFM and Kelvin probe force microscopy (KPFM. With the aim to probe the photo-induced charge carrier generation, thin films deposited on transparent indium tin oxide substrates are investigated in dark conditions and upon illumination. The topographic and contact potential difference (CPD images taken under dark conditions are analysed in view of the results of complementary transmission electron microscopy (TEM experiments. After in situ annealing, it is shown that the dyads with longer donor blocks essentially lead to standing acceptor–donor lamellae, where the acceptor and donor groups are π-stacked in an edge-on configuration. The existence of strong CPD and surface photo-voltage (SPV contrasts shows that structural variations occur within the bulk of the edge-on stacks. SPV images with a very high lateral resolution are achieved, which allows for the resolution of local photo-charging contrasts at the scale of single edge-on lamella. This work paves the way for local investigations of the optoelectronic properties of donor–acceptor supramolecular architectures down to the elementary building block level.

Molecular design of novel fullerene-based acceptors for enhancing the open circuit voltage in polymer solar cells

Science.gov (United States)

Tajbakhsh, Mahmood; Kariminasab, Mohaddeseh; Ganji, Masoud Darvish; Alinezhad, Heshmatollah

2017-12-01

Organic solar cells, especially bulk hetero-junction polymer solar cells (PSCs), are the most successful structures for applications in renewable energy. The dramatic improvement in the performance of PSCs has increased demand for new conjugated polymer donors and fullerene derivative acceptors. In the present study, quantum chemical calculations were performed for several representative fullerene derivatives in order to determine their frontier orbital energy levels and electronic structures, thereby helping to enhance their performance in PSC devices. We found correlations between the theoretical lowest unoccupied molecular orbital levels and electrophilicity index of various fullerenes with the experimental open circuit voltage of photovoltaic devices according to the poly(3-hexylthiophene) (P3HT):fullerene blend. The correlations between the structure and descriptors may facilitate screening of the best fullerene acceptor for the P3HT donor. Thus, we considered fullerenes with new functional groups and we predicted the output factors for the corresponding P3HT:fullerene blend devices. The results showed that fullerene derivatives based on thieno-o-quinodimethane-C60 with a methoxy group will have enhanced photovoltaic properties. Our results may facilitate the design of new fullerenes and the development of favorable acceptors for use in photovoltaic applications.

The solidification velocity of nickel and titanium alloys

Science.gov (United States)

Altgilbers, Alex Sho

2002-09-01

The solidification velocity of several Ni-Ti, Ni-Sn, Ni-Si, Ti-Al and Ti-Ni alloys were measured as a function of undercooling. From these results, a model for alloy solidification was developed that can be used to predict the solidification velocity as a function of undercooling more accurately. During this investigation a phenomenon was observed in the solidification velocity that is a direct result of the addition of the various alloying elements to nickel and titanium. The additions of the alloying elements resulted in an additional solidification velocity plateau at intermediate undercoolings. Past work has shown a solidification velocity plateau at high undercoolings can be attributed to residual oxygen. It is shown that a logistic growth model is a more accurate model for predicting the solidification of alloys. Additionally, a numerical model is developed from simple description of the effect of solute on the solidification velocity, which utilizes a Boltzmann logistic function to predict the plateaus that occur at intermediate undercoolings.

The Impact of Donor-Acceptor Phase Separation on the Charge Carrier Dynamics in pBTTT:PCBM Photovoltaic Blends

KAUST Repository

Gehrig, Dominik W.; Howard, Ian A.; Sweetnam, Sean; Burke, Timothy M.; McGehee, Michael D.; Laquai, Fré dé ric

2015-01-01

The effect of donor–acceptor phase separation, controlled by the donor–acceptor mixing ratio, on the charge generation and recombination dynamics in pBTTT-C14:PC70BM bulk heterojunction photovoltaic blends is presented. Transient absorption (TA) spectroscopy spanning the dynamic range from pico- to microseconds in the visible and near-infrared spectral regions reveals that in a 1:1 blend exciton dissociation is ultrafast; however, charges cannot entirely escape their mutual Coulomb attraction and thus predominantly recombine geminately on a sub-ns timescale. In contrast, a polymer:fullerene mixing ratio of 1:4 facilitates the formation of spatially separated, that is free, charges and reduces substantially the fraction of geminate charge recombination, in turn leading to much more efficient photovoltaic devices. This illustrates that spatially extended donor or acceptor domains are required for the separation of charges on an ultrafast timescale (<100 fs), indicating that they are not only important for efficient charge transport and extraction, but also critically influence the initial stages of free charge carrier formation.

The Impact of Donor-Acceptor Phase Separation on the Charge Carrier Dynamics in pBTTT:PCBM Photovoltaic Blends

KAUST Repository

Gehrig, Dominik W.

2015-04-07

The effect of donor–acceptor phase separation, controlled by the donor–acceptor mixing ratio, on the charge generation and recombination dynamics in pBTTT-C14:PC70BM bulk heterojunction photovoltaic blends is presented. Transient absorption (TA) spectroscopy spanning the dynamic range from pico- to microseconds in the visible and near-infrared spectral regions reveals that in a 1:1 blend exciton dissociation is ultrafast; however, charges cannot entirely escape their mutual Coulomb attraction and thus predominantly recombine geminately on a sub-ns timescale. In contrast, a polymer:fullerene mixing ratio of 1:4 facilitates the formation of spatially separated, that is free, charges and reduces substantially the fraction of geminate charge recombination, in turn leading to much more efficient photovoltaic devices. This illustrates that spatially extended donor or acceptor domains are required for the separation of charges on an ultrafast timescale (<100 fs), indicating that they are not only important for efficient charge transport and extraction, but also critically influence the initial stages of free charge carrier formation.

Photophysical properties of novel small acceptor molecules and their application in hybrid small-molecular/polymeric organic solar cells

Energy Technology Data Exchange (ETDEWEB)

Inal, Sahika; Castellani, Mauro; Neher, Dieter [Universitaet Potsdam, Institut fuer Physik und Astronomie, Potsdam-Golm (Germany); Sellinger, Alan [Institute of Materials Research and Engineering, Singapore (Singapore)

2009-07-01

Recent experimental investigations revealed that the photovoltaic properties of our devices are related to the balance between recombination and field-induced dissociation of interfacial excited states such as exciplexes or geminate polaron pairs. This balance was shown to be affected by the nanomorphology at the heterojunction. We have analyzed the photophysical properties of a new materials couple comprising an electron-donating PPV copolymer and a vinazene-based small molecule acceptor. Steady state and time-resolved photoluminescence (PL) spectroscopy in solution and in the solid state showed the formation of excimers within the acceptor. The associated long-range diffusion promise efficient energy harvesting at the heterojunction. On the other hand, blends of the PPV-derivative and the small molecule revealed strong exciplex formation. Therefore, bilayered hybrid small-molecular/polymeric solar cells have been fabricated by consequently spin-coating the macromolecular donor and the small molecule acceptor from two different solvents. The bilayer architecture limits recombination processes enabling high FFs of around 44% and a technologically important open circuit voltage of 1Volt.

Roll-coating fabrication of ITO-free flexible solar cells based on a non-fullerene small molecule acceptor

DEFF Research Database (Denmark)

Liu, Wenqing; Shi, Hangqi; Andersen, Thomas Rieks

2015-01-01

We report organic solar cells (OSCs) with non-fullerene small molecule acceptors (SMAs) prepared in large area via a roll coating process. We employ all solution-processed indium tin oxide (ITO)-free flexible substrates for inverted solar cells with a new SMA of F(DPP)(2)B-2. By utilizing poly(3......-hexylthiophene) as donor blended with F(DPP)(2)B-2 as acceptor, ITO-free large-area flexible SMA based OSCs were produced under ambient conditions with the use of slot-die coating and flexographic printing methods on a lab-scale compact roll-coater that is readily transferrable to roll-to-roll processing...

The Velocity Distribution of Isolated Radio Pulsars

Science.gov (United States)

Arzoumanian, Z.; Chernoff, D. F.; Cordes, J. M.; White, Nicholas E. (Technical Monitor)

2002-01-01

We infer the velocity distribution of radio pulsars based on large-scale 0.4 GHz pulsar surveys. We do so by modelling evolution of the locations, velocities, spins, and radio luminosities of pulsars; calculating pulsed flux according to a beaming model and random orientation angles of spin and beam; applying selection effects of pulsar surveys; and comparing model distributions of measurable pulsar properties with survey data using a likelihood function. The surveys analyzed have well-defined characteristics and cover approx. 95% of the sky. We maximize the likelihood in a 6-dimensional space of observables P, dot-P, DM, absolute value of b, mu, F (period, period derivative, dispersion measure, Galactic latitude, proper motion, and flux density). The models we test are described by 12 parameters that characterize a population's birth rate, luminosity, shutoff of radio emission, birth locations, and birth velocities. We infer that the radio beam luminosity (i) is comparable to the energy flux of relativistic particles in models for spin-driven magnetospheres, signifying that radio emission losses reach nearly 100% for the oldest pulsars; and (ii) scales approximately as E(exp 1/2) which, in magnetosphere models, is proportional to the voltage drop available for acceleration of particles. We find that a two-component velocity distribution with characteristic velocities of 90 km/ s and 500 km/ s is greatly preferred to any one-component distribution; this preference is largely immune to variations in other population parameters, such as the luminosity or distance scale, or the assumed spin-down law. We explore some consequences of the preferred birth velocity distribution: (1) roughly 50% of pulsars in the solar neighborhood will escape the Galaxy, while approx. 15% have velocities greater than 1000 km/ s (2) observational bias against high velocity pulsars is relatively unimportant for surveys that reach high Galactic absolute value of z distances, but is severe for

Development of an optimal velocity selection method with velocity obstacle

Energy Technology Data Exchange (ETDEWEB)

Kim, Min Geuk; Oh, Jun Ho [KAIST, Daejeon (Korea, Republic of)

2015-08-15

The Velocity obstacle (VO) method is one of the most well-known methods for local path planning, allowing consideration of dynamic obstacles and unexpected obstacles. Typical VO methods separate a velocity map into a collision area and a collision-free area. A robot can avoid collisions by selecting its velocity from within the collision-free area. However, if there are numerous obstacles near a robot, the robot will have very few velocity candidates. In this paper, a method for choosing optimal velocity components using the concept of pass-time and vertical clearance is proposed for the efficient movement of a robot. The pass-time is the time required for a robot to pass by an obstacle. By generating a latticized available velocity map for a robot, each velocity component can be evaluated using a cost function that considers the pass-time and other aspects. From the output of the cost function, even a velocity component that will cause a collision in the future can be chosen as a final velocity if the pass-time is sufficiently long enough.

Efficiency-limiting processes in OPV bulk heterojunctions of GeNIDTBT and IDT-based acceptors

KAUST Repository

Al-Saggaf, Sarah M.

2018-01-01

to the ubiquitously used fullerene derivatives. NFAs showed a rapid increase in efficiencies, now exceeding a PCE of 13%. In my thesis research, I used two small molecule IDT-based acceptors, namely O-IDTBR and O-IDTBCN, in combination with a wide bandgap donor

Daytime, low latitude, vertical ExB drift velocities, inferred from ground-based magnetometer observations in the Peruvian, Philippine and Indian longitude sectors under quiet and disturbed conditions

CERN Document Server

Anderson, D; Chau, J; Yumoto, K; Bhattacharya, A; Alex, S

2006-01-01

Daytime, low latitude, vertical ExB drift velocities, inferred from ground-based magnetometer observations in the Peruvian, Philippine and Indian longitude sectors under quiet and disturbed conditions

Method to measure a relative transverse velocity of a source-lens-observer system using gravitational lensing of gravitational waves

International Nuclear Information System (INIS)

Itoh, Yousuke; Futamase, Toshifumi; Hattori, Makoto

2009-01-01

Gravitational waves propagate along null geodesics like light rays in the geometrical optics approximation, and they may have a chance to suffer from gravitational lensing by intervening objects, as is the case for electromagnetic waves. Long wavelengths of gravitational waves and compactness of possible sources may enable us to extract information in the interference among the lensed images. We point out that the interference term contains information of relative transverse velocity of the source-lens-observer system, which may be obtained by possible future space-borne gravitational wave detectors such as BBO/DECIGO.

Multiplexed interfacial transduction of nucleic acid hybridization using a single color of immobilized quantum dot donor and two acceptors in fluorescence resonance energy transfer.

Science.gov (United States)

Algar, W Russ; Krull, Ulrich J

2010-01-01

A multiplexed solid-phase assay for the detection of nucleic acid hybridization was developed on the basis of a single color of immobilized CdSe/ZnS quantum dot (QD) as a donor in fluorescence resonance energy transfer (FRET). This work demonstrated that two channels of detection did not necessitate two different QD donors. Two probe oligonucleotides were coimmobilized on optical fibers modified with QDs, and a sandwich assay was used to associate the acceptor dyes with interfacial hybridization events without target labeling. FRET-sensitized acceptor emission provided an analytical signal that was concentration dependent down to 10 nM. Changes in the ratio of coimmobilized probe oligonucleotides were found to yield linear changes in the relative amounts of acceptor emission. These changes were compared to previous studies that used mixed films of two QD donors for two detection channels. The analysis indicated that probe dilution effects were primarily driven by changes in acceptor number density and that QD dilution effects or changes in mean donor-acceptor distance were secondary. Hybridization kinetics were found to be consistent between different ratios of coimmobilized probes, suggesting that hybridization in this type of system occurred via the accepted model for solid-phase hybridization, where adsorption and then diffusion at the solid interface drove hybridization.

Supersonic laser-induced jetting of aluminum micro-droplets

International Nuclear Information System (INIS)

Zenou, M.; Sa'ar, A.; Kotler, Z.

2015-01-01

The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10–100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets

Supersonic laser-induced jetting of aluminum micro-droplets

Energy Technology Data Exchange (ETDEWEB)

Zenou, M. [Racah Institute of Physics and the Harvey M. Kruger Family Center for Nano-science and Nanotechnology, The Hebrew University of Jerusalem, 91904 Jerusalem (Israel); Additive Manufacturing Lab, Orbotech Ltd., P.O. Box 215, 81101 Yavne (Israel); Sa' ar, A. [Racah Institute of Physics and the Harvey M. Kruger Family Center for Nano-science and Nanotechnology, The Hebrew University of Jerusalem, 91904 Jerusalem (Israel); Kotler, Z. [Additive Manufacturing Lab, Orbotech Ltd., P.O. Box 215, 81101 Yavne (Israel)

2015-05-04

The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10–100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets.

Peptide-Driven Charge-Transfer Organogels Built from Synergetic Hydrogen Bonding and Pyrene-Naphthalenediimide Donor-Acceptor Interactions.

Science.gov (United States)

Bartocci, Silvia; Berrocal, José Augusto; Guarracino, Paola; Grillaud, Maxime; Franco, Lorenzo; Mba, Miriam

2018-02-26

The peptide-driven formation of charge transfer (CT) supramolecular gels featuring both directional hydrogen-bonding and donor-acceptor (D-A) complexation is reported. Our design consists of the coassembly of two dipeptide-chromophore conjugates, namely diphenylalanine (FF) dipeptide conveniently functionalized at the N-terminus with either a pyrene (Py-1, donor) or naphthalene diimide (NDI-1, acceptor). UV/Vis spectroscopy confirmed the formation of CT complexes. FTIR and 1 H NMR spectroscopy studies underlined the pivotal role of hydrogen bonding in the gelation process, and electronic paramagnetic resonance (EPR) measurements unraveled the advantage of preorganized CT supramolecular architectures for charge transport over solutions containing non-coassembled D and A molecular systems. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Line-of-sight velocity as a tracer of coronal cavity magnetic structure

Directory of Open Access Journals (Sweden)

Urszula eBak-Steslicka

2016-03-01

Full Text Available We present a statistical analysis of 66 days of observations of quiescent (non-erupting coronal cavities and associated velocity and thermal structures. We find that nested rings of LOS-oriented velocity are common in occurrence and spatially well correlated with cavities observed in emission. We find that the majority of cavities possess multiple rings, and a range in velocity on the order of several $km/sec$. We find that the tops of prominences lie systematically below the cavity center and location of largest Doppler velocity. Finally, we use DEM analysis to consider the temperature structure of two cavities in relation to cavity, prominence, and flows. These observations yield new constraints on the magnetic structure of cavities, and on the conditions leading up to solar eruptions.

Donor-π-Acceptor Polymer with Alternating Triarylborane and Triphenylamine Moieties.

Science.gov (United States)

Li, Haiyan; Jäkle, Frieder

2010-05-12

A luminescent main chain donor-π-acceptor-type polymer (4) was prepared via organometallic polycondensation reaction followed by post modification. With both electron-rich amine and electron-deficient borane moieties embedded in the main chain, 4 exhibits an interesting ambipolar character: it can be reduced and oxidized electrochemically at moderate potentials and shows a strong solvatochromic effect in the emission spectra. Complexation studies show that 4 selectively binds to fluoride and cyanide; quantitative titration with cyanide reveals a two-step binding process. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Velocity-space observation regions of high-resolution two-step reaction gamma-ray spectroscopy

DEFF Research Database (Denmark)

Salewski, Mirko; Nocente, M.; Gorini, G.

2015-01-01

High-resolution γ-ray spectroscopy (GRS) measurements resolve spectral shapes of Dopplerbroadened γ-rays. We calculate weight functions describing velocity-space sensitivities of any two-step reaction GRS measurements in magnetized plasmas using the resonant nuclear reaction 9Be(α, nγ)12C...

A method to quantify FRET stoichiometry with phasor plot analysis and acceptor lifetime ingrowth.

Science.gov (United States)

Chen, WeiYue; Avezov, Edward; Schlachter, Simon C; Gielen, Fabrice; Laine, Romain F; Harding, Heather P; Hollfelder, Florian; Ron, David; Kaminski, Clemens F

2015-03-10

FRET is widely used for the study of protein-protein interactions in biological samples. However, it is difficult to quantify both the FRET efficiency (E) and the affinity (Kd) of the molecular interaction from intermolecular FRET signals in samples of unknown stoichiometry. Here, we present a method for the simultaneous quantification of the complete set of interaction parameters, including fractions of bound donors and acceptors, local protein concentrations, and dissociation constants, in each image pixel. The method makes use of fluorescence lifetime information from both donor and acceptor molecules and takes advantage of the linear properties of the phasor plot approach. We demonstrate the capability of our method in vitro in a microfluidic device and also in cells, via the determination of the binding affinity between tagged versions of glutathione and glutathione S-transferase, and via the determination of competitor concentration. The potential of the method is explored with simulations. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Laminar Flame Velocity and Temperature Exponent of Diluted DME-Air Mixture

Science.gov (United States)

Naseer Mohammed, Abdul; Anwar, Muzammil; Juhany, Khalid A.; Mohammad, Akram

2017-03-01

In this paper, the laminar flame velocity and temperature exponent diluted dimethyl ether (DME) air mixtures are reported. Laminar premixed mixture of DME-air with volumetric dilutions of carbon dioxides (CO2) and nitrogen (N2) are considered. Experiments were conducted using a preheated mesoscale high aspect-ratio diverging channel with inlet dimensions of 25 mm × 2 mm. In this method, flame velocities are extracted from planar flames that were stabilized near adiabatic conditions inside the channel. The flame velocities are then plotted against the ratio of mixture temperature and the initial reference temperature. A non-linear power law regression is observed suitable. This regression analysis gives the laminar flame velocity at the initial reference temperature and temperature exponent. Decrease in the laminar flame velocity and increase in temperature exponent is observed for CO2 and N2 diluted mixtures. The addition of CO2 has profound influence when compared to N2 addition on both flame velocity and temperature exponent. Numerical prediction of the similar mixture using a detailed reaction mechanism is obtained. The computational mechanism predicts higher magnitudes for laminar flame velocity and smaller magnitudes of temperature exponent compared to experimental data.

Fluorinated arene, imide and unsaturated pyrrolidinone based donor acceptor conjugated polymers: Synthesis, structure-property and device studies

Science.gov (United States)

Liyanage, Arawwawala Don Thilanga

After the discovery of doped polyacetylene, organic semiconductor materials are widely studied as high impending active components in consumer electronics. They have received substantial consideration due to their potential for structural tailoring, low cost, large area and mechanically flexible alternatives to common inorganic semiconductors. To acquire maximum use of these materials, it is essential to get a strong idea about their chemical and physical nature. Material chemist has an enormous role to play in this novel area, including development of efficient synthetic methodologies and control the molecular self-assembly and (opto)-electronic properties. The body of this thesis mainly focuses on the substituent effects: how different substituents affect the (opto)-electronic properties of the donor-acceptor (D-A) conjugated polymers. The main priority goes to understand, how different alkyl substituent effect to the polymer solubility, crystallinity, thermal properties (e.g.: glass transition temperature) and morphological order. Three classes of D-A systems were extensively studied in this work. The second chapter mainly focuses on the synthesis and structure-property study of fluorinated arene (TFB) base polymers. Here we used commercially available 1,4-dibromo-2,3,5,6-tetrafluorobenzene (TFB) as the acceptor material and prepare several polymers using 3,3'-dialkyl(3,3'-R2T2) or 3,3'-dialkoxy bithiophene (3,3'-RO2T2) units as electron donors. A detail study was done using 3,3'-bithiophene donor units incorporating branched alkoxy-functionalities by systematic variation of branching position and chain length. The study allowed disentangling the branching effects on (i) aggregation tendency, intermolecular arrangement, (iii) solid state optical energy gaps, and (iv) electronic properties in an overall consistent picture, which might guide future polymer synthesis towards optimized materials for opto-electronic applications. The third chapter mainly focused on

Donor-acceptor properties of a single-molecule altered by on-surface complex formation

Czech Academy of Sciences Publication Activity Database

Meier, T.; Pawlak, R.; Kawai, S.; Geng, Y.; Liu, X.; Decurtins, S.; Hapala, Prokop; Baratoff, A.; Liu, S.X.; Jelínek, Pavel; Meyer, E.; Glatzel, T.

2017-01-01

Roč. 11, č. 8 (2017), s. 8413-8420 ISSN 1936-0851 R&D Projects: GA ČR GB14-37427G Institutional support: RVO:68378271 Keywords : nc AFM * DFT * acceptor donor Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 13.942, year: 2016

Interferometric phase velocity measurements in the auroral electrojet

International Nuclear Information System (INIS)

Labelle, J.; Kinter, P.M.; Kelley, M.C.

1986-01-01

A double-probe electric field detector and two spatially separated fixed-bias Langmuir probes were flown on a Taurus-Tomahawk sounding rocket launched from Poker Flat Research Range in March 1982. Interesting wave data have been obtained from about 10 s of the downleg portion of the flight during which the rocket passed through the auroral electrojet. Here the electric field receiver and both density fluctuation (deltan/n) receivers responded to a broad band of turbulence centered at 105 km altitude and at frequencies generally below 4 kHz. Closer examination of the two deltan/n turbulent waveforms reveals that they are correlated, and from the phase difference between the two signals, the phase velocity of the waves in the rocket reference frame is inferred. The magnitude and direction of the observed phase velocity are consistent either with waves which travel at the ion sound speed (Csub(s)) or with waves which travel at the electron drift velocity. The observed phase velocity varies by about 50% over a 5 km altitude range - an effect which probably results from shear in the zonal neutral wind, although unfortunately no simultaneous neutral wind measurements exist to confirm this. (author)

Magnetic field dependence of ultrasound velocity in high-Tc superconductors

International Nuclear Information System (INIS)

Higgins, M.J.; Goshorn, D.P.; Bhattacharya, S.; Johnston, D.C.

1989-01-01

The magnetic field dependence of ultrasound velocity in the superconductor La 1.8 Sr 0.2 CuO 4-y is studied. The sound velocity anomaly near T c is shown to be unambiguously related to superconductivity. Below T c , the sound velocity is found to be sensitive to the dynamics of a pinned flux lattice. A combination of sound velocity and magnetization measurements suggests three regimes of pinning behavior. A generic pinning ''phase diagram'' is obtained in the superconducting state. An anomalous peak effect in the magnetization is also observed at intermediate field strengths

Modeling continuous seismic velocity changes due to ground shaking in Chile

Science.gov (United States)

Gassenmeier, Martina; Richter, Tom; Sens-Schönfelder, Christoph; Korn, Michael; Tilmann, Frederik

2015-04-01

In order to investigate temporal seismic velocity changes due to earthquake related processes and environmental forcing, we analyze 8 years of ambient seismic noise recorded by the Integrated Plate Boundary Observatory Chile (IPOC) network in northern Chile between 18° and 25° S. The Mw 7.7 Tocopilla earthquake in 2007 and the Mw 8.1 Iquique earthquake in 2014 as well as numerous smaller events occurred in this area. By autocorrelation of the ambient seismic noise field, approximations of the Green's functions are retrieved. The recovered function represents backscattered or multiply scattered energy from the immediate neighborhood of the station. To detect relative changes of the seismic velocities we apply the stretching method, which compares individual autocorrelation functions to stretched or compressed versions of a long term averaged reference autocorrelation function. We use time windows in the coda of the autocorrelations, that contain scattered waves which are highly sensitive to minute changes in the velocity. At station PATCX we observe seasonal changes in seismic velocity as well as temporary velocity reductions in the frequency range of 4-6 Hz. The seasonal changes can be attributed to thermal stress changes in the subsurface related to variations of the atmospheric temperature. This effect can be modeled well by a sine curve and is subtracted for further analysis of short term variations. Temporary velocity reductions occur at the time of ground shaking usually caused by earthquakes and are followed by a recovery. We present an empirical model that describes the seismic velocity variations based on continuous observations of the local ground acceleration. Our hypothesis is that not only the shaking of earthquakes provokes velocity drops, but any small vibrations continuously induce minor velocity variations that are immediately compensated by healing in the steady state. We show that the shaking effect is accumulated over time and best described by

FdC1 and Leaf-Type Ferredoxins Channel Electrons From Photosystem I to Different Downstream Electron Acceptors.

Science.gov (United States)

Guan, Xiaoqian; Chen, Shuai; Voon, Chia Pao; Wong, Kam-Bo; Tikkanen, Mikko; Lim, Boon L

2018-01-01

Plant-type ferredoxins in Arabidopsis transfer electrons from the photosystem I to multiple redox-driven enzymes involved in the assimilation of carbon, nitrogen, and sulfur. Leaf-type ferredoxins also modulate the switch between the linear and cyclic electron routes of the photosystems. Recently, two novel ferredoxin homologs with extra C-termini were identified in the Arabidopsis genome (AtFdC1, AT4G14890; AtFdC2, AT1G32550). FdC1 was considered as an alternative electron acceptor of PSI under extreme ferredoxin-deficient conditions. Here, we showed that FdC1 could interact with some, but not all, electron acceptors of leaf-type Fds, including the ferredoxin-thioredoxin reductase (FTR), sulfite reductase (SiR), and nitrite reductase (NiR). Photoreduction assay on cytochrome c and enzyme assays confirmed its capability to receive electrons from PSI and donate electrons to the Fd-dependent SiR and NiR but not to the ferredoxin-NADP + oxidoreductase (FNR). Hence, FdC1 and leaf-type Fds may play differential roles by channeling electrons from photosystem I to different downstream electron acceptors in photosynthetic tissues. In addition, the median redox potential of FdC1 may allow it to receive electrons from FNR in non-photosynthetic plastids.

X-ray diffraction analysis of a human tRNAGly acceptor-stem microhelix isoacceptor at 1.18 Å resolution

International Nuclear Information System (INIS)

Eichert, André; Perbandt, Markus; Schreiber, Angela; Fürste, Jens P.; Betzel, Christian; Erdmann, Volker A.; Förster, Charlotte

2008-01-01

The tRNA Gly acceptor-stem microhelix isoacceptor from human cytoplasm was crystallized and X-ray diffraction analysis revealed diffraction to 1.18 Å resolution. The sequence of the microhelix was derived from the gene sequence with tRNA Database ID DG9990. Interest has been focused on comparative X-ray structure analyses of different tRNA Gly acceptor-stem helices. tRNA Gly /glycyl-tRNA synthetase belongs to the so-called class II system, in which the tRNA identity elements consist of simple and unique determinants that are located in the tRNA acceptor stem and the discriminator base. Comparative structure investigations of tRNA Gly microhelices provide insight into the role of tRNA identity elements. Predominant differences in the structures of glycyl-tRNA synthetases and in the tRNA identity elements between prokaryotes and eukaryotes point to divergence during the evolutionary process. Here, the crystallization and high-resolution X-ray diffraction analysis of a human tRNA Gly acceptor-stem microhelix with sequence 5′-G 1 C 2 A 3 U 4 U 5 G 6 G 7 -3′, 5′-C 66 C 67 A 68 A 69 U 70 G 71 C 72 -3′ is reported. The crystals belonged to the monoclinic space group C2, with unit-cell parameters a = 37.32, b = 37.61, c = 30.47 Å, β = 112.60° and one molecule per asymmetric unit. A data set was collected using synchrotron radiation and data were processed within the resolution range 50.0–1.18 Å. The structure was solved by molecular replacement

Relation between radius and expansion velocity in planetary nebulae

International Nuclear Information System (INIS)

Chu, Y.H.; Kwitter, K.B.; Kaler, J.B.

1984-01-01

The expansion velocity-radius (R-V) relation for planetary nebulae is examined using the existing measurements of expansion velocities and recent calculations of radii. It is found that some of the previously alleged R-V relations for PN are not convincingly established. The scatter in the R-V plots may be due largely to stratification of ions in individual nebulae and to heterogeneity in the planetary nebula population. In addition, from new echelle/CCD observations of planetary nebulae, it is found that spatial information is essential in deriving the internal kinematic properties. Future investigations of R-V relations should be pursued separately for groups of planetaries with similar physical properties, and they should employ observations of appropriate low excitation lines in order to measure the expansion velocity at the surface of the nebula. 26 references

A branch point consensus from Arabidopsis found by non-circular analysis allows for better prediction of acceptor sites

DEFF Research Database (Denmark)

Tolstrup, Niels; Rouzé, Pierre; Brunak, Søren

1997-01-01

Little knowledge exists about branch points in plants; it has even been claimed that plant introns lack conserved branch point sequences similar to those found in vertebrate introns. A putative branch point consensus sequence for Arabidopsis thaliana resembling the well known metazoan consensus s...... in the recognition of true acceptor sites; the false positive rate being reduced by a factor of 2. We take this as an indication that the consensus found here is the genuine one and that the branch point does play a role in the proper recognition of the acceptor site in plants.......Little knowledge exists about branch points in plants; it has even been claimed that plant introns lack conserved branch point sequences similar to those found in vertebrate introns. A putative branch point consensus sequence for Arabidopsis thaliana resembling the well known metazoan consensus...... sequence has been proposed, but this is based on search of sequences similar to those in yeast and metazoa. Here we present a novel consensus sequence found by a non-circular approach. A hidden Markov model with a fixed A nucleotide was trained on sequences upstream of the acceptor site. The consensus...

SIMULATIONS OF HIGH-VELOCITY CLOUDS. I. HYDRODYNAMICS AND HIGH-VELOCITY HIGH IONS

International Nuclear Information System (INIS)

Kwak, Kyujin; Henley, David B.; Shelton, Robin L.

2011-01-01

We present hydrodynamic simulations of high-velocity clouds (HVCs) traveling through the hot, tenuous medium in the Galactic halo. A suite of models was created using the FLASH hydrodynamics code, sampling various cloud sizes, densities, and velocities. In all cases, the cloud-halo interaction ablates material from the clouds. The ablated material falls behind the clouds where it mixes with the ambient medium to produce intermediate-temperature gas, some of which radiatively cools to less than 10,000 K. Using a non-equilibrium ionization algorithm, we track the ionization levels of carbon, nitrogen, and oxygen in the gas throughout the simulation period. We present observation-related predictions, including the expected H I and high ion (C IV, N V, and O VI) column densities on sightlines through the clouds as functions of evolutionary time and off-center distance. The predicted column densities overlap those observed for Complex C. The observations are best matched by clouds that have interacted with the Galactic environment for tens to hundreds of megayears. Given the large distances across which the clouds would travel during such time, our results are consistent with Complex C having an extragalactic origin. The destruction of HVCs is also of interest; the smallest cloud (initial mass ∼ 120 M sun ) lost most of its mass during the simulation period (60 Myr), while the largest cloud (initial mass ∼ 4 x 10 5 M sun ) remained largely intact, although deformed, during its simulation period (240 Myr).

Optimizing velocities and transports for complex coastal regions and archipelagos

Science.gov (United States)

Haley, Patrick J.; Agarwal, Arpit; Lermusiaux, Pierre F. J.

2015-05-01

We derive and apply a methodology for the initialization of velocity and transport fields in complex multiply-connected regions with multiscale dynamics. The result is initial fields that are consistent with observations, complex geometry and dynamics, and that can simulate the evolution of ocean processes without large spurious initial transients. A class of constrained weighted least squares optimizations is defined to best fit first-guess velocities while satisfying the complex bathymetry, coastline and divergence strong constraints. A weak constraint towards the minimum inter-island transports that are in accord with the first-guess velocities provides important velocity corrections in complex archipelagos. In the optimization weights, the minimum distance and vertical area between pairs of coasts are computed using a Fast Marching Method. Additional information on velocity and transports are included as strong or weak constraints. We apply our methodology around the Hawaiian islands of Kauai/Niihau, in the Taiwan/Kuroshio region and in the Philippines Archipelago. Comparisons with other common initialization strategies, among hindcasts from these initial conditions (ICs), and with independent in situ observations show that our optimization corrects transports, satisfies boundary conditions and redirects currents. Differences between the hindcasts from these different ICs are found to grow for at least 2-3 weeks. When compared to independent in situ observations, simulations from our optimized ICs are shown to have the smallest errors.

Experimental observation of both negative and positive phase velocities in a two-dimensional sonic crystal

International Nuclear Information System (INIS)

Lu, Ming-Hui; Feng, Liang; Liu, Xiao-Ping; Liu, Xiao-Kang; Chen, Yan-Feng; Zhu, Yong-Yuan; Mao, Yi-Wei; Zi, Jian

2007-01-01

Both negative and positive phase velocities for acoustic waves have been experimentally established in a two-dimensional triangular sonic crystal (SC) consisting of steel cylinders embedded in air at first. With the increase of the SCs thickness layer by layer in the experiments, phase shifts decrease in the second band but increase in the first band, showing the negative and the positive phase velocities, respectively. Moreover, the dispersion relation of the SC is constructed by the phase information, which is consistent well with the theoretical results. These abundant characteristics of acoustic wave propagation in the SC might be useful for the device applications

Propagation Velocity of Solid Earth Tides

Science.gov (United States)

Pathak, S.

2017-12-01

One of the significant considerations in most of the geodetic investigations is to take into account the outcome of Solid Earth tides on the location and its consequent impact on the time series of coordinates. In this research work, the propagation velocity resulting from the Solid Earth tides between the Indian stations is computed. Mean daily coordinates for the stations have been computed by applying static precise point positioning technique for a day. The computed coordinates are used as an input for computing the tidal displacements at the stations by Gravity method along three directions at 1-minute interval for 24 hours. Further the baseline distances are computed between four Indian stations. Computation of the propagation velocity for Solid Earth tides can be done by the virtue of study of the concurrent effect of it in-between the stations of identified baseline distance along with the time consumed by the tides for reaching from one station to another. The propagation velocity helps in distinguishing the impact at any station if the consequence at a known station for a specific time-period is known. Thus, with the knowledge of propagation velocity, the spatial and temporal effects of solid earth tides can be estimated with respect to a known station. As theoretically explained, the tides generated are due to the position of celestial bodies rotating about Earth. So the need of study is to observe the correlation of propagation velocity with the rotation speed of the Earth. The propagation velocity of Solid Earth tides comes out to be in the range of 440-470 m/s. This velocity comes out to be in a good agreement with the Earth's rotation speed.

Effect of flow velocity on erosion-corrosion behaviour of QSn6 alloy

Science.gov (United States)

Huang, Weijiu; Zhou, Yongtao; Wang, Zhenguo; Li, Zhijun; Zheng, Ziqing

2018-05-01

The erosion-corrosion behaviour of QSn6 alloy used as propellers in marine environment was evaluated by erosion-corrosion experiments with/without cathodic protection, electrochemical tests and scanning electron microscope (SEM) observations. The analysis was focused on the effect of flow velocity. The dynamic polarization curves showed that the corrosion rate of the QSn6 alloy increased as the flow velocity increased, due to the protective surface film removal at higher velocities. The lowest corrosion current densities of 1.26 × 10‑4 A cm‑2 was obtained at the flow velocity of 7 m s‑1. Because of the higher particle kinetic energies at higher flow velocity, the mass loss rate of the QSn6 alloy increased as the flow velocity increased. The mass loss rate with cathodic protection was lower than that without cathodic protection under the same conditions. Also, the lowest mass loss rate of 0.7 g m‑2 · h‑1 was acquired at the flow velocity of 7 m s‑1 with cathodic protection. However, the increase rate of corrosion rate and mass loss were decreased with increasing the flow velocity. Through observation the SEM morphologies of the worn surfaces, the main wear mechanism was ploughing with/without cathodic protection. The removal rates of the QSn6 alloy increased as the flow velocity increased in both pure erosion and erosion-corrosion, whereas the erosion and corrosion intensified each other. At the flow velocity of 7 m s‑1, the synergy rate (ΔW) exceeded by 5 times the erosion rate (Wwear). Through establishment and observation the erosion-corrosion mechanism map, the erosion-corrosion was the dominant regime in the study due to the contribution of erosion on the mass loss rate exceeded the corrosion contribution. The QSn6 alloy with cathodic protection is feasible as propellers, there are higher security at lower flow velocity, such as the flow velocity of 7 m s‑1 in the paper.

Measured and modeled dry deposition velocities over the ESCOMPTE area

Science.gov (United States)

Michou, M.; Laville, P.; Serça, D.; Fotiadi, A.; Bouchou, P.; Peuch, V.-H.

2005-03-01

Measurements of the dry deposition velocity of ozone have been made by the eddy correlation method during ESCOMPTE (Etude sur Site pour COntraindre les Modèles de Pollution atmosphérique et de Transport d'Emissions). The strong local variability of natural ecosystems was sampled over several weeks in May, June and July 2001 for four sites with varying surface characteristics. The sites included a maize field, a Mediterranean forest, a Mediterranean shrub-land, and an almost bare soil. Measurements of nitrogen oxide deposition fluxes by the relaxed eddy correlation method have also been carried out at the same bare soil site. An evaluation of the deposition velocities computed by the surface module of the multi-scale Chemistry and Transport Model MOCAGE is presented. This module relies on a resistance approach, with a detailed treatment of the stomatal contribution to the surface resistance. Simulations at the finest model horizontal resolution (around 10 km) are compared to observations. If the seasonal variations are in agreement with the literature, comparisons between raw model outputs and observations, at the different measurement sites and for the specific observing periods, are contrasted. As the simulated meteorology at the scale of 10 km nicely captures the observed situations, the default set of surface characteristics (averaged at the resolution of a grid cell) appears to be one of the main reasons for the discrepancies found with observations. For each case, sensitivity studies have been performed in order to see the impact of adjusting the surface characteristics to the observed ones, when available. Generally, a correct agreement with the observations of deposition velocities is obtained. This advocates for a sub-grid scale representation of surface characteristics for the simulation of dry deposition velocities over such a complex area. Two other aspects appear in the discussion. Firstly, the strong influence of the soil water content to the plant

Influence of substitution on the proton donor and proton acceptor abilities of molecules. III. Study of chlorine and ftorine substitution alcohol

International Nuclear Information System (INIS)

Nurulloev, M.; Narziev, B.N.; Islomov, Z.; Fayzieva, M.

2006-01-01

This work gives the study of influence of chlorine and ftorine atoms as substitutions to proton donor and proton acceptor ability of primary, secondary and tertiary alifatic alcohol. In accordance to developed method the proton donor ability of studied substances are determined. It is shown that the quantity of proton donor ability of reactionary center of the molecules depend on substitution nature and its proton acceptor quantity. Proposed that substitution influence of these molecule mainly transferred by inductive effect

Radial Velocity Survey of T Tauri Stars in Taurus-Auriga

Science.gov (United States)

Crockett, Christopher; Mahmud, N.; Huerta, M.; Prato, L.; Johns-Krull, C.; Hartigan, P.; Jaffe, D.

2009-01-01

Is the frequency of giant planet companions to young stars similar to that seen around old stars? Is the "brown dwarf desert" a product of how low-mass companion objects form, or of how they evolve? Some models indicate that both giant planets and brown dwarfs should be common at young ages within 3 AU of a primary star, but migration induced by massive disks drive brown dwarfs into the parent stars, leaving behind proportionally more giant planets. Our radial velocity survey of young stars will provide a census of the young giant planet and brown dwarf population in Taurus-Auriga. In this poster we present our progress in quantifying how spurious radial velocity signatures are caused by stellar activity and in developing models to help distinguish between companion induced and spot induced radial velocity variations. Early results stress the importance of complementary observations in both visible light and NIR. We present our technique to determine radial velocities by fitting telluric features and model stellar features to our observed spectra. Finally, we discuss ongoing observations at McDonald Observatory, KPNO, and the IRTF, and several new exoplanet host candidates.

Three-dimensional time-lapse velocity tomography of an underground longwall panel

Energy Technology Data Exchange (ETDEWEB)

Luxbacher, K.; Westman, E.; Swanson, P.; Karfakis, M. [Virginia Tech., Blacksburg, VA (United States). Dept. of Mining & Minerals Engineering

2008-06-15

Three-dimensional velocity tomograms were generated to image the stress redistribution around an underground coal longwall panel to produce a better understanding of the mechanisms that lead to ground failure, especially rockbursts. Mining-induced microseismic events provided passive sources for the three-dimensional velocity tomography. Surface-mounted geophones monitored microseismic activity for 18 days. Eighteen tomograms were generated and high-velocity regions correlated with high abutment stresses predicted by numerical modeling. Additionally, the high-velocity regions were observed to redistribute as the longwall face retreated, indicating that velocity tomography may be an appropriate technology for monitoring stress redistribution in underground mines.

Background and Pickup Ion Velocity Distribution Dynamics in Titan's Plasma Environment: 3D Hybrid Simulation and Comparison with CAPS T9 Observations

Science.gov (United States)

Lipatov, A. S.; Sittler, E. C., Jr.; Hartle, R. E.; Cooper, J. F.; Simpson, D. G.

2011-01-01

In this report we discuss the ion velocity distribution dynamics from the 3D hybrid simulation. In our model the background, pickup, and ionospheric ions are considered as a particles, whereas the electrons are described as a fluid. Inhomogeneous photoionization, electron-impact ionization and charge exchange are included in our model. We also take into account the collisions between the ions and neutrals. The current simulation shows that mass loading by pickup ions H(+); H2(+), CH4(+) and N2(+) is stronger than in the previous simulations when O+ ions are introduced into the background plasma. In our hybrid simulations we use Chamberlain profiles for the atmospheric components. We also include a simple ionosphere model with average mass M = 28 amu ions that were generated inside the ionosphere. The moon is considered as a weakly conducting body. Special attention will be paid to comparing the simulated pickup ion velocity distribution with CAPS T9 observations. Our simulation shows an asymmetry of the ion density distribution and the magnetic field, including the formation of the Alfve n wing-like structures. The simulation also shows that the ring-like velocity distribution for pickup ions relaxes to a Maxwellian core and a shell-like halo.

Novel indole-based inhibitors of IMPDH: introduction of hydrogen bond acceptors at indole C-3.

Science.gov (United States)

Watterson, Scott H; Dhar, T G Murali; Ballentine, Shelley K; Shen, Zhongqi; Barrish, Joel C; Cheney, Daniel; Fleener, Catherine A; Rouleau, Katherine A; Townsend, Robert; Hollenbaugh, Diane L; Iwanowicz, Edwin J

2003-04-07

The development of a series of novel indole-based inhibitors of 5'-inosine monophosphate dehydrogenase (IMPDH) is described. Various hydrogen bond acceptors at C-3 of the indole were explored. The synthesis and the structure-activity relationships (SARs) derived from in vitro studies are outlined.

Burning velocity measurements of nitrogen-containing compounds.

Science.gov (United States)

Takizawa, Kenji; Takahashi, Akifumi; Tokuhashi, Kazuaki; Kondo, Shigeo; Sekiya, Akira

2008-06-30

Burning velocity measurements of nitrogen-containing compounds, i.e., ammonia (NH3), methylamine (CH3NH2), ethylamine (C2H5NH2), and propylamine (C3H7NH2), were carried out to assess the flammability of potential natural refrigerants. The spherical-vessel (SV) method was used to measure the burning velocity over a wide range of sample and air concentrations. In addition, flame propagation was directly observed by the schlieren photography method, which showed that the spherical flame model was applicable to flames with a burning velocity higher than approximately 5 cm s(-1). For CH3NH2, the nozzle burner method was also used to confirm the validity of the results obtained by closed vessel methods. We obtained maximum burning velocities (Su0,max) of 7.2, 24.7, 26.9, and 28.3 cm s(-1) for NH3, CH3NH2, C2H5NH2, and C3H7NH2, respectively. It was noted that the burning velocities of NH3 and CH3NH2 were as high as those of the typical hydrofluorocarbon refrigerants difluoromethane (HFC-32, Su0,max=6.7 cm s(-1)) and 1,1-difluoroethane (HFC-152a, Su0,max=23.6 cm s(-1)), respectively. The burning velocities were compared with those of the parent alkanes, and it was found that introducing an NH2 group into hydrocarbon molecules decreases their burning velocity.

Low Band Gap Donor–Acceptor Type Polymers Containing 2,3-Bis(4-(decyloxyphenylpyrido[4,3-b]pyrazine as Acceptor and Different Thiophene Derivatives as Donors

Directory of Open Access Journals (Sweden)

Yan Zhang

2016-10-01

Full Text Available Four donor–acceptor type conducting polymers, namely poly(2,3-bis(4-decyloxyphenyl-5,8-bis(4-thiophen-2-ylpyrido[4,3-b]pyrazine (P1, poly(2,3-bis(4-decyloxyphenyl-5,8-bis(4-butylthiophen-2-ylpyrido[4,3-b]pyrazine (P2, poly(2,3-bis(4-(decyloxyphenyl-5,8-bis(4-hexyloxythiophen-2-ylpyrido[4,3-b]pyrazine (P3 and poly(2,3-bis(4-(decyloxyphenyl-5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-ylpyrido[4,3-b]pyrazine (P4, containing thiophene or its derivative as the donor and pyrido[4,3-b]pyrazine as the acceptor were prepared and characterized by cyclic voltammetry, scanning electron microscopy, and UV-Vis spectroscopy to detect the influence of the donor units’ strength on the electrochromic performances. The results demonstrated that all of the polymers could be reversibly reduced and oxidized by p-type doping and n-type doping, and showed near-infrared activities and different color changes in p-type doping process. Especially, P3 and P4 showed lower optical band gap than P1 and P2 due to the strong electron-donating hexyloxythiophen group of P3 and ethylenedioxythiophene group of P4. Besides, P3 and P4 displayed the saturated green color at the neutral state and the desirable transparency at the oxidized state. All the polymers displayed desirable optical contrasts, satisfactory coloration efficiency, excellent stability and short switching time, which made the polymers fascinating candidates in the electrochromic device applications.

Streaming Velocities and the Baryon Acoustic Oscillation Scale.

Science.gov (United States)

Blazek, Jonathan A; McEwen, Joseph E; Hirata, Christopher M

2016-03-25

At the epoch of decoupling, cosmic baryons had supersonic velocities relative to the dark matter that were coherent on large scales. These velocities subsequently slow the growth of small-scale structure and, via feedback processes, can influence the formation of larger galaxies. We examine the effect of streaming velocities on the galaxy correlation function, including all leading-order contributions for the first time. We find that the impact on the baryon acoustic oscillation (BAO) peak is dramatically enhanced (by a factor of ∼5) over the results of previous investigations, with the primary new effect due to advection: if a galaxy retains memory of the primordial streaming velocity, it does so at its Lagrangian, rather than Eulerian, position. Since correlations in the streaming velocity change rapidly at the BAO scale, this advection term can cause a significant shift in the observed BAO position. If streaming velocities impact tracer density at the 1% level, compared to the linear bias, the recovered BAO scale is shifted by approximately 0.5%. This new effect, which is required to preserve Galilean invariance, greatly increases the importance of including streaming velocities in the analysis of upcoming BAO measurements and opens a new window to the astrophysics of galaxy formation.

Additive-Morphology Interplay and Loss Channels in “All-Small-Molecule” Bulk-heterojunction (BHJ) Solar Cells with the Nonfullerene Acceptor IDTTBM

KAUST Repository

Liang, Ru-Ze

2017-12-16

Achieving efficient bulk-heterojunction (BHJ) solar cells from blends of solution-processable small-molecule (SM) donors and acceptors is proved particularly challenging due to the complexity in obtaining a favorable donor–acceptor morphology. In this report, the BHJ device performance pattern of a set of analogous, well-defined SM donors—DR3TBDTT (DR3), SMPV1, and BTR—used in conjunction with the SM acceptor IDTTBM is examined. Examinations show that the nonfullerene “All-SM” BHJ solar cells made with DR3 and IDTTBM can achieve power conversion efficiencies (PCEs) of up to ≈4.5% (avg. 4.0%) when the solution-processing additive 1,8-diiodooctane (DIO, 0.8% v/v) is used in the blend solutions. The figures of merit of optimized DR3:IDTTBM solar cells contrast with those of “as-cast” BHJ devices from which only modest PCEs <1% can be achieved. Combining electron energy loss spectrum analyses in scanning transmission electron microscopy mode, carrier transport measurements via “metal-insulator-semiconductor carrier extraction” methods, and systematic recombination examinations by light-dependence and transient photocurrent analyses, it is shown that DIO plays a determining role—establishing a favorable lengthscale for the phase-separated SM donor–acceptor network and, in turn, improving the balance in hole/electron mobilities and the carrier collection efficiencies overall.

Additive-Morphology Interplay and Loss Channels in “All-Small-Molecule” Bulk-heterojunction (BHJ) Solar Cells with the Nonfullerene Acceptor IDTTBM

KAUST Repository

Liang, Ru-Ze; Babics, Maxime; Seitkhan, Akmaral; Wang, Kai; Geraghty, Paul Bythell; Lopatin, Sergei; Cruciani, Federico; Firdaus, Yuliar; Caporuscio, Marco; Jones, David J.; Beaujuge, Pierre

2017-01-01

Achieving efficient bulk-heterojunction (BHJ) solar cells from blends of solution-processable small-molecule (SM) donors and acceptors is proved particularly challenging due to the complexity in obtaining a favorable donor–acceptor morphology. In this report, the BHJ device performance pattern of a set of analogous, well-defined SM donors—DR3TBDTT (DR3), SMPV1, and BTR—used in conjunction with the SM acceptor IDTTBM is examined. Examinations show that the nonfullerene “All-SM” BHJ solar cells made with DR3 and IDTTBM can achieve power conversion efficiencies (PCEs) of up to ≈4.5% (avg. 4.0%) when the solution-processing additive 1,8-diiodooctane (DIO, 0.8% v/v) is used in the blend solutions. The figures of merit of optimized DR3:IDTTBM solar cells contrast with those of “as-cast” BHJ devices from which only modest PCEs <1% can be achieved. Combining electron energy loss spectrum analyses in scanning transmission electron microscopy mode, carrier transport measurements via “metal-insulator-semiconductor carrier extraction” methods, and systematic recombination examinations by light-dependence and transient photocurrent analyses, it is shown that DIO plays a determining role—establishing a favorable lengthscale for the phase-separated SM donor–acceptor network and, in turn, improving the balance in hole/electron mobilities and the carrier collection efficiencies overall.

An interferometric velocity calibrator for 73Ge Moessbauer spectrometer

International Nuclear Information System (INIS)

Chow, L.; Kimble, T.

1987-01-01

A velocity calibrator based on a laser driven Michelson interferometer was designed for a 73 Ge Moessbauer spectrometer in the range of 100 to 500 μm/sec. The conventional method of counting the interference fringes cannot be used in this case because the displacement only spans about 3 to 15 μm and only a few fringes can be observed during one velocity sweep. The velocity calibration obtained this way was compared with the calibration obtained from 57 Fe measurement, and excellent agreement was found between the two methods. (orig.)

Self-consistent electronic structure of a model stage-1 graphite acceptor intercalate

International Nuclear Information System (INIS)

Campagnoli, G.; Tosatti, E.

1981-04-01

A simple but self-consistent LCAO scheme is used to study the π-electronic structure of an idealized stage-1 ordered graphite acceptor intercalate, modeled approximately on C 8 AsF 5 . The resulting non-uniform charge population within the carbon plane, band structure, optical and energy loss properties are discussed and compared with available spectroscopic evidence. The calculated total energy is used to estimate migration energy barriers, and the intercalate vibration mode frequency. (author)

Strong Velocity-Weakening of Nanograins at High Slip-Rates

Science.gov (United States)

Han, R.; Hirose, T.; Ando, J.

2008-12-01

It has been observed that slip localization zones in some experimental and natural faults consist of crystalline or amorphous nanograins of different minerals. Prolonged grinding of silicate rocks (e.g., quartz rock and granite) is known to produce amorphous silica nanograins and mechanical properties of the material (especially under wet condition) have been attributed to a mechanism of fault weakening. Also, recent high- velocity friction tests on carbonate rocks showed that faults can be weakened by thermal decomposition of calcite into nanograins of lime and carbon dioxide and the lubrication effect of the nanograins would be critical for the fault weakening. However, mechanical behavior(s) and friction mechanism(s) of fault slip zones with nanograins, especially at high slip-rates, are still poorly understood, despite their potential importance to the understanding of seismic faulting. In this contribution, we show you our experimental results indicating velocity-weakening of nanograins (probably caused by still unknown mechanical behaviors of nanograins) rather than by temperature-related weakening behavior. In our high-velocity friction tests on Carrara marble at seismic slip-rates, we have tried to "cool" the simulated fault with liquid nitrogen and compressed air during frictional sliding, and found, in the simulated fault coated with nanopowders of lime (CaO) formed by thermal decomposition, no correlation between friction and temperature measured with thermocouples (i.e., no temperature-related weakening behavior), although strong "velocity-weakening" behavior appeared. The observation was confirmed by another experiment: from (1) the calculated "maximum" sliding surface temperature [Carslaw and Jaeger, 1959] using the mechanical data, with an assumption of strong slip localization into a very thin layer, and (2) the measured temperature with thermocouples at a place just below the sliding surface and close to the periphery of the specimen, it was found

Study on velocity field in a wire wrapped fuel pin bundle of sodium cooled reactor. Detailed velocity distribution in a subchannel

International Nuclear Information System (INIS)

Sato, Hiroyuki; Kobayashi, Jun; Miyakoshi, Hiroyuki; Kamide, Hideki

2009-01-01

A sodium cooled fast reactor is designed to attain a high burn-up core in a feasibility study on commercialized fast reactor cycle systems. In high burn-up fuel subassemblies, deformation of fuel pin due to the swelling and thermal bowing may decrease local flow velocity via change of flow area in the subassembly and influence the heat removal capability. Therefore, it is of importance to obtain the flow velocity distribution in a wire wrapped pin bundle. A 2.5 times enlarged 7-pin bundle water model was applied to investigate the detailed velocity distribution in an inner subchannel surrounded by 3 pins with wrapping wire. The test section consisted of a hexagonal acrylic duct tube and fluorinated resin pins which had nearly the same refractive index with that of water and a high light transmission rate. The velocity distribution in an inner subchannel with the wrapping wire was measured by PIV (Particle Image Velocimetry) through the front and lateral sides of the duct tube. In the vertical velocity distribution in a narrow space between the pins, the wrapping wire decreased the velocity downstream of the wire and asymmetric flow distribution was formed between the pin and wire. In the horizontal velocity distribution, swirl flow around the wrapping wire was obviously observed. The measured velocity data are useful for code validation of pin bundle thermalhydraulics. (author)

Effect of Conjugation Length on Photoinduced Charge-Transfer in π-Conjugated Oligomer-Acceptor Dyads

KAUST Repository

Jiang, Junlin

2017-05-25

A series of -conjugated oligomer-acceptor dyads were synthesized that feature oligo(phenylene ethynylene) (OPE) conjugated backbones end-capped with a naphthalene diimide (NDI) acceptor. The OPE segments vary in length from 4 to 8 phenylene ethynene units (PEn-NDI, where n = 4, 6 and 8). Fluorescence and transient absorption spectroscopy reveals that intramolecular OPE NDI charge transfer dominates the deactivation of excited states of the PEn-NDI oligomers. Both charge separation (CS) and charge recombination (CR) are strongly exothermic (G0CS ~ -1.1 and G0CR ~ -2.0 eV), and the driving forces do not vary much across the series because the oxidation and reduction potentials and singlet energies of the OPEs do not vary much with their length. Bimolecular photoinduced charge transfer between model OPEs that do not contain the NDI acceptors with methyl viologen was studied, and the results reveal that the absorption of the cation radical state (OPE+•) remains approximately constant ( ~ 575 nm) regardless of oligomer length. This finding suggests that the cation radical (polaron) of the OPE is relatively localized, effectively occupying a confined segment of n 4 repeat units in the longer oligomers. Photoinduced intramolecular electron transfer dynamics in the PEn-NDI series was investigated by UV-visible femtosecond transient absorption spectroscopy with visible and mid-infrared probes. Charge separation occurs on the 1 – 10 ps timescale, with the rates decreasing slightly with increased oligomer length (βCS ~ 0.15 Å-1). The rate for charge-recombination decreases in the sequence PE4-NDI > PE6-NDI ~ PE8-NDI. The discontinuous distance dependence in the rate for charge recombination may be related to the spatial localization of the positive polaron state in the longer oligomers.

Effect of Conjugation Length on Photoinduced Charge-Transfer in π-Conjugated Oligomer-Acceptor Dyads

KAUST Repository

Jiang, Junlin; Alsam, Amani Abdu; Wang, Shanshan; Aly, Shawkat Mohammede; Pan, Zhenxing; Mohammed, Omar F.; Schanze, Kirk S.

2017-01-01

A series of -conjugated oligomer-acceptor dyads were synthesized that feature oligo(phenylene ethynylene) (OPE) conjugated backbones end-capped with a naphthalene diimide (NDI) acceptor. The OPE segments vary in length from 4 to 8 phenylene ethynene units (PEn-NDI, where n = 4, 6 and 8). Fluorescence and transient absorption spectroscopy reveals that intramolecular OPE NDI charge transfer dominates the deactivation of excited states of the PEn-NDI oligomers. Both charge separation (CS) and charge recombination (CR) are strongly exothermic (G0CS ~ -1.1 and G0CR ~ -2.0 eV), and the driving forces do not vary much across the series because the oxidation and reduction potentials and singlet energies of the OPEs do not vary much with their length. Bimolecular photoinduced charge transfer between model OPEs that do not contain the NDI acceptors with methyl viologen was studied, and the results reveal that the absorption of the cation radical state (OPE+•) remains approximately constant ( ~ 575 nm) regardless of oligomer length. This finding suggests that the cation radical (polaron) of the OPE is relatively localized, effectively occupying a confined segment of n 4 repeat units in the longer oligomers. Photoinduced intramolecular electron transfer dynamics in the PEn-NDI series was investigated by UV-visible femtosecond transient absorption spectroscopy with visible and mid-infrared probes. Charge separation occurs on the 1 – 10 ps timescale, with the rates decreasing slightly with increased oligomer length (βCS ~ 0.15 Å-1). The rate for charge-recombination decreases in the sequence PE4-NDI > PE6-NDI ~ PE8-NDI. The discontinuous distance dependence in the rate for charge recombination may be related to the spatial localization of the positive polaron state in the longer oligomers.

Use of γ-hexachlorocyclohexane as a terminal electron acceptor by an anaerobic enrichment culture

International Nuclear Information System (INIS)

Elango, Vijai; Kurtz, Harry D.; Anderson, Christina; Freedman, David L.

2011-01-01

Highlights: ► Use of γ-hexachlorocyclohexane as a terminal electron acceptor was demonstrated. ► H 2 served as the electron donor for an enrichment culture that dechlorinated γ-HCH. ► H 2 consumption for acetogenesis and methanogenesis stopped in HEPES media. ► Addition of vancomycin significantly slowed the rate of γ-HCH dechlorination. ► Previously identified chlororespiring microbes were not detected in the enrichment. - Abstract: The use of γ-hexachlorocyclohexane (HCH) as a terminal electron acceptor via organohalide respiration was demonstrated for the first time with an enrichment culture grown in a sulfate-free HEPES-buffered anaerobic mineral salts medium. The enrichment culture was initially developed with soil and groundwater from an industrial site contaminated with HCH isomers, chlorinated benzenes, and chlorinated ethenes. When hydrogen served as the electron donor, 79–90% of the electron equivalents from hydrogen were used by the enrichment culture for reductive dechlorination of the γ-HCH, which was provided at a saturation concentration of approximately 10 mg/L. Benzene and chlorobenzene were the only volatile transformation products detected, accounting for 25% and 75% of the γ-HCH consumed (on a molar basis), respectively. The enrichment culture remained active with only hydrogen as the electron donor and γ-HCH as the electron acceptor through several transfers to fresh mineral salts medium for more than one year. Addition of vancomycin to the culture significantly slowed the rate of γ-HCH dechlorination, suggesting that a Gram-positive organism is responsible for the reduction of γ-HCH. Analysis of the γ-HCH dechlorinating enrichment culture did not detect any known chlororespiring genera, including Dehalobacter. In bicarbonate-buffered medium, reductive dechlorination of γ-HCH was accompanied by significant levels of acetogenesis as well as methanogenesis.

Magnetic and Velocity Field Variations in the Active Regions NOAA ...

Indian Academy of Sciences (India)

Abstract. We study the magnetic and velocity field evolution in the two magnetically complex active regions NOAA 10486 and NOAA 10488 observed during October–November 2003. We have used the available data to examine net flux and Doppler velocity time profiles to identify changes associated with evolutionary and ...

Direct correlation of charge transfer absorption with molecular donor:acceptor interfacial area via photothermal deflection spectroscopy

KAUST Repository

Domingo, Ester

2015-04-09

We show that the Charge Transfer (CT) absorption signal in bulk-heterojunction (BHJ) solar cell blends, measured by photothermal deflection spectroscopy (PDS), is directly proportional to the density of molecular donor/acceptor interfaces. Since the optical transitions from ground state to the interfacial CT state are weakly allowed at photon energies below the optical gap of both donor and acceptor, we can exploit the use of this sensitive linear absorption spectroscopy for such quantification. Moreover, we determine the absolute molar extinction coefficient of the CT transition for an archetypical polymer-fullerene interface. The latter is ~100 times lower than the extinction coefficient of the donor chromophore involved, allowing us to experimentally estimate the transition dipole moment (0.3 D) and the electronic coupling between ground state and CT state to be on the order of 30 meV.

A prospective observational study of early fetal growth velocity and its association with birth weight, gestational age at delivery, preeclampsia, and perinatal mortality

Energy Technology Data Exchange (ETDEWEB)

Vasudeva, Akhila, E-mail: akhilavasudeva@gmail.com [Department of Obstetrics and Gynaecology, Kasturba Medical College, Manipal University, Manipal 576104, Karnataka State (India); Abraham, Anu Annie, E-mail: anuannieabraham@yahoo.com [Department of Obstetrics and Gynaecology, Kasturba Medical College, Manipal University, Manipal 576104, Karnataka State (India); Kamath, Asha, E-mail: aashakamat@gmail.com [Department of Community Medicine, Kasturba Medical College, Manipal, A Constituent College of Manipal University (India)

2013-08-15

Objectives: We aimed to measure early fetal growth velocity and to correlate this with the birth weight, gestational age at delivery, and with the incidence of adverse pregnancy outcomes specifically preeclampsia and perinatal mortality. Methods: A data based prospective observational study, wherein sonographic biometry data and specific pregnancy outcome related data were collected from pregnant women's records, starting soon after their first antenatal visit. Early fetal growth velocity was measured using BPD growth between 11 and 14 weeks scan and anomaly scan and standardizing this by Z scoring. Results: Out of 607 fetuses, 41 (6.7%) were slow growing, 531 (87.4%) normally growing, and 35 (5.7%) fast growing (Z scoring <10th{sup ,} 10–90th, and >90th percentiles respectively). As fetal growth velocity increased, the mean birth weight decreased from 2958.7 ± 388.9 (<10th centile), 2742.1 ± 576.6 (10–90th centile), to 2339.3 ± 729.4 (>90th centile); and gestational age at delivery decreased from 38.5 ± 1.3 (<10th centile), 37.5 ± 2.1 (10–90th centile), to 36.4 ± 2.2 (>90th centile), and both these trends were statistically significant (p < 0.001).Faster growing fetuses had a higher risk of preterm delivery(spontaneous + indicated) compared to other 2 groups [OR 4.42 (2.18,8.98)], and slower growing fetuses had a higher risk of postdated deliveries compared to other 2 groups [OR 3.042 (1.44, 6.45)].We found no significant association between early fetal growth velocity and incidence of small for gestational age at birth/low birth weight at term, preeclampsia, and perinatal mortality. Conclusions: Early fetal growth velocity between first and second trimesters, may be one of the important factors influencing ultimate birthweight and gestational age at delivery.

A prospective observational study of early fetal growth velocity and its association with birth weight, gestational age at delivery, preeclampsia, and perinatal mortality

International Nuclear Information System (INIS)

Vasudeva, Akhila; Abraham, Anu Annie; Kamath, Asha

2013-01-01

Objectives: We aimed to measure early fetal growth velocity and to correlate this with the birth weight, gestational age at delivery, and with the incidence of adverse pregnancy outcomes specifically preeclampsia and perinatal mortality. Methods: A data based prospective observational study, wherein sonographic biometry data and specific pregnancy outcome related data were collected from pregnant women's records, starting soon after their first antenatal visit. Early fetal growth velocity was measured using BPD growth between 11 and 14 weeks scan and anomaly scan and standardizing this by Z scoring. Results: Out of 607 fetuses, 41 (6.7%) were slow growing, 531 (87.4%) normally growing, and 35 (5.7%) fast growing (Z scoring <10th , 10–90th, and >90th percentiles respectively). As fetal growth velocity increased, the mean birth weight decreased from 2958.7 ± 388.9 (<10th centile), 2742.1 ± 576.6 (10–90th centile), to 2339.3 ± 729.4 (>90th centile); and gestational age at delivery decreased from 38.5 ± 1.3 (<10th centile), 37.5 ± 2.1 (10–90th centile), to 36.4 ± 2.2 (>90th centile), and both these trends were statistically significant (p < 0.001).Faster growing fetuses had a higher risk of preterm delivery(spontaneous + indicated) compared to other 2 groups [OR 4.42 (2.18,8.98)], and slower growing fetuses had a higher risk of postdated deliveries compared to other 2 groups [OR 3.042 (1.44, 6.45)].We found no significant association between early fetal growth velocity and incidence of small for gestational age at birth/low birth weight at term, preeclampsia, and perinatal mortality. Conclusions: Early fetal growth velocity between first and second trimesters, may be one of the important factors influencing ultimate birthweight and gestational age at delivery

Significant Variation of Post-critical SsPmp Amplitude as a Result of Variation in Near-surface Velocity: Observations from the Yellowknife Array

Science.gov (United States)

Ferragut, G.; Liu, T.; Klemperer, S. L.

2017-12-01

In recent years Virtual Deep Seismic Sounding (VDSS) emerged as a novel method to image the Moho, which uses the post-critical reflection P waves at the Moho generated by teleseismic S waves at the free surface near the receivers (SsPmp). However, observed SsPmp sometimes have significantly lower amplitude than predicted, raising doubts among the seismic community on the theoretical basis of the method. With over two decades of continuous digital broadband records and major subduction zones in the range of 30-50 degrees, the Yellowknife Array in northern Canada provides a rich opportunity for observation of post-critical SsPmp. We analyze S wave coda of events with epicenter distances of 30-50°, and pay special attention to earthquakes in a narrow azimuth range that ­­­encompasses the Kamchatka Peninsula. Among 21 events with strong direct S energy on the radial components, we observe significant variation of SsPmp energy. After associating the SsPmp energy with the virtual source location of each event, we observe a general trend of decreasing SsPmp energy from NE to SW. As the trend coincides with the transition from exposed basement of the Slave Craton to Paleozoic platform covered by Phanerozoic sediment, we interpret the decreasing SsPmp energy as a result of lower S velocity at the virtual sources, which reduces S-to-P reflection coefficients. We plan to include more events from the Aleutian Islands, the virtual sources of which are primarily located in the Paleozoic platform. This will allow us to further investigate the relationship between SsPmp amplitude and near-surface velocity.

Positron Spur Reactions with Excess Electrons and Anions in Liquid Organic Mixtures of Electron Acceptors

DEFF Research Database (Denmark)

Lévay, B.; Mogensen, O. E.

1980-01-01

By means of the positron lifetime technique we have measured positronium (Ps) yields in mixtures of nonpolar liquids with various electron scavengers which bind the electron fairly weakly (1–2 eV) in stable anions. The results are discussed with reference to recent excess electron works, and new...... experiments on anions and excess electrons are proposed. The minimum of the Ps yield versus CS2 concentration curves caused by partly delocalization of electrons on several scavenger molecules, which was observed previously in saturated aliphatic hydrocarbons occurred also in the saturated cyclic hydrocarbon...... cyclohexane, but did not appear in the aromatic benzene. This might be explained by the weak electron acceptor property of aromatics. In the Ps yield versus SF6 concentration curve in hexane a similar minimum appeared as in the CS2 case, probably by the same reason. By adding 0.8 M CS2 to the system...

Experimental study on liquid velocity in upward and downward two-phase flows

International Nuclear Information System (INIS)

Sun, X.; Paranjape, S.; Kim, S.; Ozar, B.; Ishii, M.

2003-01-01

Local characteristics of the liquid phase in upward and downward air-water two-phase flows were experimentally investigated in a 50.8-mm inner-diameter round pipe. An integral Laser Doppler Anemometry (LDA) system was used to measure the axial liquid velocity and its fluctuations. No effect of the flow direction on the liquid velocity radial profile was observed in single-phase liquid benchmark experiments. Local multi-sensor conductivity probes were used to measure the radial profiles of the bubble velocity and the void fraction. The measurement results in the upward and downward two-phase flows are compared and discussed. The results in the downward flow demonstrated that the presence of the bubbles tended to flatten the liquid velocity radial profile, and the maximum liquid velocity could occur off the pipe centerline, in particular at relatively low flow rates. However, the maximum liquid velocity always occurred at the pipe center in the upward flow. Also, noticeable turbulence enhancement due to the bubbles in the two-phase flows was observed in the current experimental flow conditions. Furthermore, the distribution parameter and the void weighted area-averaged drift velocity were obtained based on the definitions

Generation of the auroral electron velocity distribution by stochastic acceleration

International Nuclear Information System (INIS)

Bryant, D.A.; Cook, A.C.; Wang, Z.-S.; Angelis, U. de.

1990-07-01

In a further development of the wave theory of the aurora, it is demonstrated, using a Monte-Carlo numerical model, that the characteristic peak in the auroral electron velocity distribution can be generated stochastically through resonant interactions between an initially monotonic distribution and lower-hybrid electrostatic turbulence. The principal requirement is that the velocity spectrum of resonant waves has a sharp cut-off at high velocity. It is then shown that a cut-off is expected as a natural consequence of the difference between the phase and group velocities of lower-hybrid waves. The possibility is considered that a second peak, sometimes observed at lower velocities, is due to the same statistical mechanism, arising from the damping of waves of low phase velocity. An enhancement of wave intensity is found at higher velocities, where momentum flows preferentially from electrons to waves. The relation between the wave theory and the currently prevailing potential-difference theory emerges clearly from the analysis. (author)

Rayleigh-wave phase-velocity maps and three-dimensional shear velocity structure of the western US from local non-plane surface wave tomography

Science.gov (United States)

Pollitz, F.F.; Snoke, J. Arthur

2010-01-01

We utilize two-and-three-quarter years of vertical-component recordings made by the Transportable Array (TA) component of Earthscope to constrain three-dimensional (3-D) seismic shear wave velocity structure in the upper 200 km of the western United States. Single-taper spectral estimation is used to compile measurements of complex spectral amplitudes from 44 317 seismograms generated by 123 teleseismic events. In the first step employed to determine the Rayleigh-wave phase-velocity structure, we implement a new tomographic method, which is simpler and more robust than scattering-based methods (e.g. multi-plane surface wave tomography). The TA is effectively implemented as a large number of local arrays by defining a horizontal Gaussian smoothing distance that weights observations near a given target point. The complex spectral-amplitude measurements are interpreted with the spherical Helmholtz equation using local observations about a succession of target points, resulting in Rayleigh-wave phase-velocity maps at periods over the range of 18–125 s. The derived maps depend on the form of local fits to the Helmholtz equation, which generally involve the nonplane-wave solutions of Friederich et al. In a second step, the phase-velocity maps are used to derive 3-D shear velocity structure. The 3-D velocity images confirm details witnessed in prior body-wave and surface-wave studies and reveal new structures, including a deep (>100 km deep) high-velocity lineament, of width ∼200 km, stretching from the southern Great Valley to northern Utah that may be a relic of plate subduction or, alternatively, either a remnant of the Mojave Precambrian Province or a mantle downwelling. Mantle seismic velocity is highly correlated with heat flow, Holocene volcanism, elastic plate thickness and seismicity. This suggests that shallow mantle structure provides the heat source for associated magmatism, as well as thinning of the thermal lithosphere, leading to relatively high

Transit and radial velocity survey efficiency comparison for a habitable zone Earth

International Nuclear Information System (INIS)

Burke, Christopher J.; McCullough, P. R.

2014-01-01

Transit and radial velocity searches are two techniques for identifying nearby extrasolar planets to Earth that transit bright stars. Identifying a robust sample of these exoplanets around bright stars for detailed atmospheric characterization is a major observational undertaking. In this study we describe a framework that answers the question of whether a transit or radial velocity survey is more efficient at finding transiting exoplanets given the same amount of observing time. Within the framework we show that a transit survey's window function can be approximated using the hypergeometric probability distribution. We estimate the observing time required for a transit survey to find a transiting Earth-sized exoplanet in the habitable zone (HZ) with an emphasis on late-type stars. We also estimate the radial velocity precision necessary to detect the equivalent HZ Earth-mass exoplanet that also transits when using an equal amount of observing time as the transit survey. We find that a radial velocity survey with σ rv ∼ 0.6 m s –1 precision has comparable efficiency in terms of observing time to a transit survey with the requisite photometric precision σ phot ∼ 300 ppm to find a transiting Earth-sized exoplanet in the HZ of late M dwarfs. For super-Earths, a σ rv ∼ 2.0 m s –1 precision radial velocity survey has comparable efficiency to a transit survey with σ phot ∼ 2300 ppm.

Evaluation of force-velocity and power-velocity relationship of arm muscles.

Science.gov (United States)

Sreckovic, Sreten; Cuk, Ivan; Djuric, Sasa; Nedeljkovic, Aleksandar; Mirkov, Dragan; Jaric, Slobodan

2015-08-01

A number of recent studies have revealed an approximately linear force-velocity (F-V) and, consequently, a parabolic power-velocity (P-V) relationship of multi-joint tasks. However, the measurement characteristics of their parameters have been neglected, particularly those regarding arm muscles, which could be a problem for using the linear F-V model in both research and routine testing. Therefore, the aims of the present study were to evaluate the strength, shape, reliability, and concurrent validity of the F-V relationship of arm muscles. Twelve healthy participants performed maximum bench press throws against loads ranging from 20 to 70 % of their maximum strength, and linear regression model was applied on the obtained range of F and V data. One-repetition maximum bench press and medicine ball throw tests were also conducted. The observed individual F-V relationships were exceptionally strong (r = 0.96-0.99; all P stronger relationships. The reliability of parameters obtained from the linear F-V regressions proved to be mainly high (ICC > 0.80), while their concurrent validity regarding directly measured F, P, and V ranged from high (for maximum F) to medium-to-low (for maximum P and V). The findings add to the evidence that the linear F-V and, consequently, parabolic P-V models could be used to study the mechanical properties of muscular systems, as well as to design a relatively simple, reliable, and ecologically valid routine test of the muscle ability of force, power, and velocity production.

The geostrophic velocity field in shallow water over topography

Science.gov (United States)

Charnock, Henry; Killworth, Peter D.

1998-01-01

A recent note (Hopkins, T.S., 1996. A note on the geostrophic velocity field referenced to a point. Continental Shelf Research 16, 1621-1630) suggests a method for evaluating absolute pressure gradients in stratified water over topography. We demonstrate that this method requires no along-slope bottom velocity, in contradiction to what is usually observed, and that mass is not conserved.

Fine-Tuning the Energy Levels of a Nonfullerene Small-Molecule Acceptor to Achieve a High Short-Circuit Current and a Power Conversion Efficiency over 12% in Organic Solar Cells.

Science.gov (United States)

Kan, Bin; Zhang, Jiangbin; Liu, Feng; Wan, Xiangjian; Li, Chenxi; Ke, Xin; Wang, Yunchuang; Feng, Huanran; Zhang, Yamin; Long, Guankui; Friend, Richard H; Bakulin, Artem A; Chen, Yongsheng

2018-01-01

Organic solar cell optimization requires careful balancing of current-voltage output of the materials system. Here, such optimization using ultrafast spectroscopy as a tool to optimize the material bandgap without altering ultrafast photophysics is reported. A new acceptor-donor-acceptor (A-D-A)-type small-molecule acceptor NCBDT is designed by modification of the D and A units of NFBDT. Compared to NFBDT, NCBDT exhibits upshifted highest occupied molecular orbital (HOMO) energy level mainly due to the additional octyl on the D unit and downshifted lowest unoccupied molecular orbital (LUMO) energy level due to the fluorination of A units. NCBDT has a low optical bandgap of 1.45 eV which extends the absorption range toward near-IR region, down to ≈860 nm. However, the 60 meV lowered LUMO level of NCBDT hardly changes the V oc level, and the elevation of the NCBDT HOMO does not have a substantial influence on the photophysics of the materials. Thus, for both NCBDT- and NFBDT-based systems, an unusually slow (≈400 ps) but ultimately efficient charge generation mediated by interfacial charge-pair states is observed, followed by effective charge extraction. As a result, the PBDB-T:NCBDT devices demonstrate an impressive power conversion efficiency over 12%-among the best for solution-processed organic solar cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

Science.gov (United States)

Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.; Chilson, Phillip B.; Wharton, Sonia

2016-12-01

Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance (w'2) from zenith stares. However, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w'2, reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skill in correcting for volume-averaging effects in the calculation of w'2 is also assessed. Additionally, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w'2. Through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w'2. After the autocovariance technique is applied, values of w'2 from the Doppler lidars are generally in close agreement (R2 ≈ 0.95 - 0.98) with those calculated from sonic anemometer measurements.

Simultaneous measurement of quantum yield ratio and absorption ratio between acceptor and donor by linearly unmixing excitation-emission spectra.

Science.gov (United States)

Zhang, C; Lin, F; DU, M; Qu, W; Mai, Z; Qu, J; Chen, T

2018-02-13

Quantum yield ratio (Q A /Q D ) and absorption ratio (K A /K D ) in all excitation wavelengths used between acceptor and donor are indispensable to quantitative fluorescence resonance energy transfer (FRET) measurement based on linearly unmixing excitation-emission spectra (ExEm-spFRET). We here describe an approach to simultaneously measure Q A /Q D and K A /K D values by linearly unmixing the excitation-emission spectra of at least two different donor-acceptor tandem constructs with unknown FRET efficiency. To measure the Q A /Q D and K A /K D values of Venus (V) to Cerulean (C), we used a wide-field fluorescence microscope to image living HepG2 cells separately expressing each of four different C-V tandem constructs at different emission wavelengths with 435 nm and 470 nm excitation respectively to obtain the corresponding excitation-emission spectrum (S DA ). Every S DA was linearly unmixed into the contributions (weights) of three excitation-emission spectra of donor (W D ) and acceptor (W A ) as well as donor-acceptor sensitisation (W S ). Plot of W S /W D versus W A /W D for the four C-V plasmids from at least 40 cells indicated a linear relationship with 1.865 of absolute intercept (Q A /Q D ) and 0.273 of the reciprocal of slope (K A /K D ), which was validated by quantitative FRET measurements adopting 1.865 of Q A /Q D and 0.273 of K A /K D for C32V, C5V, CVC and VCV constructs respectively in living HepG2 cells. © 2018 The Authors Journal of Microscopy © 2018 Royal Microscopical Society.

Superconducting RF for Low-Velocity and Intermediate-Velocity Beams

CERN Document Server

Grimm, Terry L

2005-01-01

Existing superconducting radio frequency (SRF) linacs are used to accelerate ions (protons through uranium) with velocities less than about 15% the speed of light, or electrons with velocities approximately equal to the speed of light. In the last ten years, prototype SRF cavities have completely covered the remaining range of velocities. They have demonstrated that SRF linacs will be capable of accelerating electrons from rest up to the speed of light, and ions from less than 1% up to the speed of light. When the Spallation Neutron Source is operational, SRF ion linacs will have covered the full range of velocities except for v/c ~ 0.15 to v/c ~ 0.5. A number of proposed projects (RIA, EURISOL) would span the latter range of velocities. Future SRF developments will have to address the trade-offs associated with a number of issues, including high gradient operation, longitudinal and transverse acceptance, microphonics, Lorentz detuning, operating temperature, cryogenic load, number of gaps or cells per cavity...

Using the load-velocity relationship for 1RM prediction.

Science.gov (United States)

Jidovtseff, Boris; Harris, Nigel K; Crielaard, Jean-Michel; Cronin, John B

2011-01-01

The purpose of this study was to investigate the ability of the load-velocity relationship to accurately predict a bench press 1 repetition maximum (1RM). Data from 3 different bench press studies (n = 112) that incorporated both 1RM assessment and submaximal load-velocity profiling were analyzed. Individual regression analysis was performed to determine the theoretical load at zero velocity (LD0). Data from each of the 3 studies were analyzed separately and also presented as overall group mean. Thereafter, correlation analysis provided quantification of the relationships between 1RM and LD0. Practically perfect correlations (r = ∼0.95) were observed in our samples, confirming the ability of the load-velocity profile to accurately predict bench press 1RM.

Axial flow velocity patterns in a normal human pulmonary artery model: pulsatile in vitro studies.

Science.gov (United States)

Sung, H W; Yoganathan, A P

1990-01-01

It has been clinically observed that the flow velocity patterns in the pulmonary artery are directly modified by disease. The present study addresses the hypothesis that altered velocity patterns relate to the severity of various diseases in the pulmonary artery. This paper lays a foundation for that analysis by providing a detailed description of flow velocity patterns in the normal pulmonary artery, using flow visualization and laser Doppler anemometry techniques. The studies were conducted in an in vitro rigid model in a right heart pulse duplicator system. In the main pulmonary artery, a broad central flow field was observed throughout systole. The maximum axial velocity (150 cm s-1) was measured at peak systole. In the left pulmonary artery, the axial velocities were approximately evenly distributed in the perpendicular plane. However, in the bifurcation plane, they were slightly skewed toward the inner wall at peak systole and during the deceleration phase. In the right pulmonary artery, the axial velocity in the perpendicular plane had a very marked M-shaped profile at peak systole and during the deceleration phase, due to a pair of strong secondary flows. In the bifurcation plane, higher axial velocities were observed along the inner wall, while lower axial velocities were observed along the outer wall and in the center. Overall, relatively low levels of turbulence were observed in all the branches during systole. The maximum turbulence intensity measured was at the boundary of the broad central flow field in the main pulmonary artery at peak systole.

Development of an enzyme-linked immunosorbent assay-based method for measuring galactosyltransferase activity using a synthetic glycopolymer acceptor substrate.

Science.gov (United States)

Oubihi, M; Kitajima, K; Kobayashi, K; Adachi, T; Aoki, N; Matsuda, T

1998-03-15

A lectin-assisted enzyme-linked immunosorbent assay (ELISA)-based method using a synthetic glycopolymer as an acceptor substrate was developed for measuring beta 1,4-galactosyltransferase (GalT) activity. A polyacrylamide derivative having a beta-linked N-acetylglucosamine (GlcNAc beta) moiety on each monomeric unit was synthesized chemically and immobilized on a polystyrene microtiter plate as an acceptor substrate for GalT. After the plate was incubated with bovine GalT, the enzyme reaction product, beta-linked Gal residue on the polyacrylamide-bound GlcNAc residue, was detected by using Ricinus communis agglutinin 1 (RCA1), rabbit anti-RCA1 antibody, and a peroxidase-labeled anti-rabbit IgG. The lowest GalT concentration detectable by this method was about 0.5 mU/ml, which is comparable to those by the previously reported ELISA-based assays. The unique property of the glycopolymer, PAP(GlcNAc beta), of binding noncovalently but tightly to the polystyrene microtiter plate allowed the use of this acceptor substrate for the GalT activity measurement even in the presence of 1% Triton CF-54 and X-100. Our system was successfully applied to assess GalT activity in milk of various mammals.

Critical velocities in He II for independently varied superfluid and normal fluid velocities

International Nuclear Information System (INIS)

Baehr, M.L.

1984-01-01

Experiments were performed to measure the critical velocity in pure superflow and compare to the theoretical prediction; to measure the first critical velocity for independently varied superfluid and normal fluid velocities; and to investigate the propagation of the second critical velocity from the thermal counterflow line through the V/sub n/,-V/sub s/ quadrant. The experimental apparatus employed a thermal counterflow heater to adjust the normal fluid velocity, a fountain pump to vary the superfluid velocity, and a level sensing capacitor to measure the superfluid velocity. The results of the pure superfluid critical velocity measurements indicate that this velocity is temperature independent contrary to Schwarz's theory. It was found that the first critical velocity for independently varied V/sub n/ and V/sub s/ could be described by a linear function of V/sub n/ and was otherwise temperature independent. It was found that the second critical velocity could only be distinguished near the thermal counterflow line

Kinetic modeling of electron transfer reactions in photosystem I complexes of various structures with substituted quinone acceptors.

Science.gov (United States)

Milanovsky, Georgy E; Petrova, Anastasia A; Cherepanov, Dmitry A; Semenov, Alexey Yu

2017-09-01

The reduction kinetics of the photo-oxidized primary electron donor P 700 in photosystem I (PS I) complexes from cyanobacteria Synechocystis sp. PCC 6803 were analyzed within the kinetic model, which considers electron transfer (ET) reactions between P 700 , secondary quinone acceptor A 1 , iron-sulfur clusters and external electron donor and acceptors - methylviologen (MV), 2,3-dichloro-naphthoquinone (Cl 2 NQ) and oxygen. PS I complexes containing various quinones in the A 1 -binding site (phylloquinone PhQ, plastoquinone-9 PQ and Cl 2 NQ) as well as F X -core complexes, depleted of terminal iron-sulfur F A /F B clusters, were studied. The acceleration of charge recombination in F X -core complexes by PhQ/PQ substitution indicates that backward ET from the iron-sulfur clusters involves quinone in the A 1 -binding site. The kinetic parameters of ET reactions were obtained by global fitting of the P 700 + reduction with the kinetic model. The free energy gap ΔG 0 between F X and F A /F B clusters was estimated as -130 meV. The driving force of ET from A 1 to F X was determined as -50 and -220 meV for PhQ in the A and B cofactor branches, respectively. For PQ in A 1A -site, this reaction was found to be endergonic (ΔG 0  = +75 meV). The interaction of PS I with external acceptors was quantitatively described in terms of Michaelis-Menten kinetics. The second-order rate constants of ET from F A /F B , F X and Cl 2 NQ in the A 1 -site of PS I to external acceptors were estimated. The side production of superoxide radical in the A 1 -site by oxygen reduction via the Mehler reaction might comprise ≥0.3% of the total electron flow in PS I.

All-Polymer Solar Cell Performance Optimized via Systematic Molecular Weight Tuning of Both Donor and Acceptor Polymers.

Science.gov (United States)

Zhou, Nanjia; Dudnik, Alexander S; Li, Ting I N G; Manley, Eric F; Aldrich, Thomas J; Guo, Peijun; Liao, Hsueh-Chung; Chen, Zhihua; Chen, Lin X; Chang, Robert P H; Facchetti, Antonio; Olvera de la Cruz, Monica; Marks, Tobin J

2016-02-03

The influence of the number-average molecular weight (Mn) on the blend film morphology and photovoltaic performance of all-polymer solar cells (APSCs) fabricated with the donor polymer poly[5-(2-hexyldodecyl)-1,3-thieno[3,4-c]pyrrole-4,6-dione-alt-5,5-(2,5-bis(3-dodecylthiophen-2-yl)thiophene)] (PTPD3T) and acceptor polymer poly{[N,N'-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2); N2200) is systematically investigated. The Mn effect analysis of both PTPD3T and N2200 is enabled by implementing a polymerization strategy which produces conjugated polymers with tunable Mns. Experimental and coarse-grain modeling results reveal that systematic Mn variation greatly influences both intrachain and interchain interactions and ultimately the degree of phase separation and morphology evolution. Specifically, increasing Mn for both polymers shrinks blend film domain sizes and enhances donor-acceptor polymer-polymer interfacial areas, affording increased short-circuit current densities (Jsc). However, the greater disorder and intermixed feature proliferation accompanying increasing Mn promotes charge carrier recombination, reducing cell fill factors (FF). The optimized photoactive layers exhibit well-balanced exciton dissociation and charge transport characteristics, ultimately providing solar cells with a 2-fold PCE enhancement versus devices with nonoptimal Mns. Overall, it is shown that proper and precise tuning of both donor and acceptor polymer Mns is critical for optimizing APSC performance. In contrast to reports where maximum power conversion efficiencies (PCEs) are achieved for the highest Mns, the present two-dimensional Mn optimization matrix strategy locates a PCE "sweet spot" at intermediate Mns of both donor and acceptor polymers. This study provides synthetic methodologies to predictably access conjugated polymers with desired Mn and highlights the importance of optimizing Mn for both polymer

Predicting vertical jump height from bar velocity.

Science.gov (United States)

García-Ramos, Amador; Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Strojnik, Vojko; Feriche, Belén

2015-06-01

The objective of the study was to assess the use of maximum (Vmax) and final propulsive phase (FPV) bar velocity to predict jump height in the weighted jump squat. FPV was defined as the velocity reached just before bar acceleration was lower than gravity (-9.81 m·s(-2)). Vertical jump height was calculated from the take-off velocity (Vtake-off) provided by a force platform. Thirty swimmers belonging to the National Slovenian swimming team performed a jump squat incremental loading test, lifting 25%, 50%, 75% and 100% of body weight in a Smith machine. Jump performance was simultaneously monitored using an AMTI portable force platform and a linear velocity transducer attached to the barbell. Simple linear regression was used to estimate jump height from the Vmax and FPV recorded by the linear velocity transducer. Vmax (y = 16.577x - 16.384) was able to explain 93% of jump height variance with a standard error of the estimate of 1.47 cm. FPV (y = 12.828x - 6.504) was able to explain 91% of jump height variance with a standard error of the estimate of 1.66 cm. Despite that both variables resulted to be good predictors, heteroscedasticity in the differences between FPV and Vtake-off was observed (r(2) = 0.307), while the differences between Vmax and Vtake-off were homogenously distributed (r(2) = 0.071). These results suggest that Vmax is a valid tool for estimating vertical jump height in a loaded jump squat test performed in a Smith machine. Key pointsVertical jump height in the loaded jump squat can be estimated with acceptable precision from the maximum bar velocity recorded by a linear velocity transducer.The relationship between the point at which bar acceleration is less than -9.81 m·s(-2) and the real take-off is affected by the velocity of movement.Mean propulsive velocity recorded by a linear velocity transducer does not appear to be optimal to monitor ballistic exercise performance.

Donor-acceptor-pair emission characterization in N-B doped fluorescent SiC

DEFF Research Database (Denmark)

Ou, Yiyu; Jokubavicius, Valdas; Kamiyama, Satoshi

2011-01-01

In the present work, we investigated donor-acceptor-pair emission in N-B doped fluorescent 6H-SiC, by means of photoluminescence, Raman spectroscopy, and angle-resolved photoluminescence. The photoluminescence results were interpreted by using a band diagram with Fermi-Dirac statistics. It is shown...... intensity in a large emission angle range was achieved from angle-resolved photoluminescence. The results indicate N-B doped fluorescent SiC as a good wavelength converter in white LEDs applications....

Highly efficient exciplex organic light-emitting diodes incorporating a heptazine derivative as an electron acceptor.

Science.gov (United States)

Li, Jie; Nomura, Hiroko; Miyazaki, Hiroshi; Adachi, Chihaya

2014-06-11

Highly efficient exciplex systems incorporating a heptazine derivative () as an electron acceptor and 1,3-di(9H-carbazol-9-yl)benzene () as an electron donor are developed. An organic light-emitting diode containing 8 wt% : as an emitting layer exhibits a maximum external quantum efficiency of 11.3%.

Donor–Acceptor Copolymers of Relevance for Organic Photovoltaics: A Theoretical Investigation of the Impact of Chemical Structure Modifications on the Electronic and Optical Properties

KAUST Repository

Pandey, Laxman

2012-08-28

We systematically investigate at the density functional theory level how changes to the chemical structure of donor-acceptor copolymers used in a number of organic electronics applications influences the intrinsic geometric, electronic, and optical properties. We consider the combination of two distinct donors, where a central five-membered ring is fused on both sides by either a thiophene or a benzene ring, with 12 different acceptors linked to the donor either directly or through thienyl linkages. The interplay between the electron richness/deficiency of the subunits as well as the evolution of the frontier electronic levels of the isolated donors/acceptors plays a significant role in determining the electronic and optical properties of the copolymers. © 2012 American Chemical Society.

High-velocity winds from a dwarf nova during outburst

Science.gov (United States)

Cordova, F. A.; Mason, K. O.

1982-01-01

An ultraviolet spectrum of the dwarf nova TW Vir during an optical outburst shows shortward-shifted absorption features with edge velocities as high as 4800 km/s, about the escape velocity of a white dwarf. A comparison of this spectrum with the UV spectra of other cataclysmic variables suggests that mass loss is evident only for systems with relatively high luminosities (more than about 10 solar luminosities) and low inclination angles with respect to the observer's line of sight. The mass loss rate for cataclysmic variables is of order 10 to the -11th solar mass per yr; this is from 0.01 to 0.001 of the mass accretion rate onto the compact star in the binary. The mass loss may occur by a mechanism similar to that invoked for early-type stars, i.e., radiation absorbed in the lines accelerates the accreting gas to the high velocities observed.

Anaerobic arsenite oxidation with an electrode serving as the sole electron acceptor: A novel approach to the bioremediation of arsenic-polluted groundwater

Energy Technology Data Exchange (ETDEWEB)

Pous, Narcis [Laboratory of Chemical and Environmental Engineering (LEQUiA), Institute of the Environment, University of Girona, C/Maria Aurèlia Capmany, 69 E-17071 Girona (Spain); Casentini, Barbara; Rossetti, Simona; Fazi, Stefano [Water Research Institute (IRSA-CNR), National Research Council, Via Salaria Km 29.300, 00015 Monterotondo (Italy); Puig, Sebastià [Laboratory of Chemical and Environmental Engineering (LEQUiA), Institute of the Environment, University of Girona, C/Maria Aurèlia Capmany, 69 E-17071 Girona (Spain); Aulenta, Federico, E-mail: aulenta@irsa.cnr.it [Water Research Institute (IRSA-CNR), National Research Council, Via Salaria Km 29.300, 00015 Monterotondo (Italy)

2015-02-11

Highlights: • As(III) was oxidized to As(V) in a bioelectrochemical system. • A polarized graphite electrode served as electron acceptor. • Gammaproteobacteria were the dominating organisms at the electrode. - Abstract: Arsenic contamination of soil and groundwater is a serious problem worldwide. Here we show that anaerobic oxidation of As(III) to As(V), a form which is more extensively and stably adsorbed onto metal-oxides, can be achieved by using a polarized (+497 mV vs. SHE) graphite anode serving as terminal electron acceptor in the microbial metabolism. The characterization of the microbial populations at the electrode, by using in situ detection methods, revealed the predominance of gammaproteobacteria. In principle, the proposed bioelectrochemical oxidation process would make it possible to provide As(III)-oxidizing microorganisms with a virtually unlimited, low-cost and low-maintenance electron acceptor as well as with a physical support for microbial attachment.

Anaerobic arsenite oxidation with an electrode serving as the sole electron acceptor: A novel approach to the bioremediation of arsenic-polluted groundwater

International Nuclear Information System (INIS)

Pous, Narcis; Casentini, Barbara; Rossetti, Simona; Fazi, Stefano; Puig, Sebastià; Aulenta, Federico

2015-01-01

Highlights: • As(III) was oxidized to As(V) in a bioelectrochemical system. • A polarized graphite electrode served as electron acceptor. • Gammaproteobacteria were the dominating organisms at the electrode. - Abstract: Arsenic contamination of soil and groundwater is a serious problem worldwide. Here we show that anaerobic oxidation of As(III) to As(V), a form which is more extensively and stably adsorbed onto metal-oxides, can be achieved by using a polarized (+497 mV vs. SHE) graphite anode serving as terminal electron acceptor in the microbial metabolism. The characterization of the microbial populations at the electrode, by using in situ detection methods, revealed the predominance of gammaproteobacteria. In principle, the proposed bioelectrochemical oxidation process would make it possible to provide As(III)-oxidizing microorganisms with a virtually unlimited, low-cost and low-maintenance electron acceptor as well as with a physical support for microbial attachment

Ternary Nonfullerene Polymer Solar Cells with 12.16% Efficiency by Introducing One Acceptor with Cascading Energy Level and Complementary Absorption.

Science.gov (United States)

Jiang, Weigang; Yu, Runnan; Liu, Zhiyang; Peng, Ruixiang; Mi, Dongbo; Hong, Ling; Wei, Qiang; Hou, Jianhui; Kuang, Yongbo; Ge, Ziyi

2018-01-01

A novel small-molecule acceptor, (2,2'-((5E,5'E)-5,5'-((5,5'-(4,4,9,9-tetrakis(5-hexylthiophen-2-yl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b']dithiophene-2,7-diyl)bis(4-(2-ethylhexyl)thiophene-5,2-diyl))bis(methanylylidene)) bis(3-hexyl-4-oxothiazolidine-5,2-diylidene))dimalononitrile (ITCN), end-capped with electron-deficient 2-(3-hexyl-4-oxothiazolidin-2-ylidene)malononitrile groups, is designed, synthesized, and used as the third component in fullerene-free ternary polymer solar cells (PSCs). The cascaded energy-level structure enabled by the newly designed acceptor is beneficial to the carrier transport and separation. Meanwhile, the three materials show a complementary absorption in the visible region, resulting in efficient light harvesting. Hence, the PBDB-T:ITCN:IT-M ternary PSCs possess a high short-circuit current density (J sc ) under an optimal weight ratio of donors and acceptors. Moreover, the open-circuit voltage (V oc ) of the ternary PSCs is enhanced with an increase of the third acceptor ITCN content, which is attributed to the higher lowest unoccupied molecular orbital energy level of ITCN than that of IT-M, thus exhibits a higher V oc in PBDB-T:ITCN binary system. Ultimately, the ternary PSCs achieve a power conversion efficiency of 12.16%, which is higher than the PBDB-T:ITM-based PSCs (10.89%) and PBDB-T:ITCN-based ones (2.21%). This work provides an effective strategy to improve the photovoltaic performance of PSCs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

VELOCITY VARIATIONS IN THE PHOENIX–HERMUS STAR STREAM

Energy Technology Data Exchange (ETDEWEB)

Carlberg, R. G. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Grillmair, C. J., E-mail: carlberg@astro.utoronto.ca, E-mail: carl@ipac.caltech.edu [Spitzer Science Center, 1200 E. California Blvd., Pasadena, CA 91125 (United States)

2016-10-20

Measurements of velocity and density perturbations along stellar streams in the Milky Way provide a time-integrated measure of dark matter substructure at larger galactic radius than the complementary instantaneous inner-halo strong lensing detection of dark matter sub-halos in distant galaxies. An interesting case to consider is the proposed Phoenix–Hermus star stream, which is long, thin, and on a nearly circular orbit, making it a particular good target to study for velocity variations along its length. In the presence of dark matter sub-halos, the stream velocities are significantly perturbed in a manner that is readily understood with the impulse approximation. A set of simulations shows that only sub-halos above a few 10{sup 7} M {sub ⊙} lead to reasonably long-lived observationally detectable velocity variations of amplitude of order 1 km s{sup −1}, with an average of about one visible hit per (two-armed) stream over a 3 Gyr interval. An implication is that globular clusters themselves will not have a visible impact on the stream. Radial velocities have the benefit of being completely insensitive to distance errors. Distance errors scatter individual star velocities perpendicular and tangential to the mean orbit, but their mean values remain unbiased. Calculations like these help build the quantitative case to acquire large, fairly deep, precision velocity samples of stream stars.

Charge transfer in the novel donor–acceptor complexes tetra- and hexamethoxypyrene with tetracyanoquinodimethane studied by HAXPES

International Nuclear Information System (INIS)

Medjanik, K.; Gloskovskii, A.; Kutnyakhov, D.; Felser, C.; Chercka, D.; Baumgarten, M.; Müllen, K.; Schönhense, G.

2012-01-01

Highlights: ► The effect of charge transfer in TMP/HMP–TCNQ complexes was studied using HAXPES. ► We examine changes in the core level spectra of TMP/HMP–TCNQ complexes. ► The charge is transferred to a fraction of 60% of the molecules in the complexes. - Abstract: The effect of charge transfer (CT) in complexes of the donors tetra- and hexamethoxyprene (TMP and HMP) with the classical acceptor tetracyanoquinodimethane (TCNQ) was studied using hard X-ray photoemission (HAXPES). Microcrystals of the complex were grown via vapour diffusion from donor–acceptor mixtures. The bulk sensitivity of HAXPES at a photon energy of 6 keV completely eliminates the problem of surface contamination for such delicate organic materials grown from solution. The donor molecules were produced using a novel synthesis route functionalizing polycyclic aromatic hydrocarbons at their periphery. For comparison, spectra were also taken from thin-film samples of the same compounds produced via co-deposition in UHV. Upon complex formation, the oxygen 1s core-level spectra (being a fingerprint of the methoxy-group of the donors) change from the single-line spectrum of pure HMP (TMP) to a spectrum with two distinct lines shifted by 1.4 (0.9) eV and 2.6 (2.3) eV with respect to the position of the oxygen 1s line of the pure donors. The nitrogen 1s spectra (being a fingerprint of the cyano-group in the acceptor) show two peaks as well with a corresponding shift of 0.9 eV and 2.0 eV in comparison with the leading line of pure TCNQ in opposite direction to the oxygen 1s spectra. These values are substantially larger than shifts in near edge X-ray absorption fine structure (NEXAFS) and ultraviolet photoelectron spectroscopy (UPS) spectra of the same complexes. The changes in the spectra are discussed in terms of the CT in the complexes. Residues of pure donor and acceptor materials in the microcrystal fractions of the complexes are evident from the presence of non-shifted lines. Peak

Mean Velocity vs. Mean Propulsive Velocity vs. Peak Velocity: Which Variable Determines Bench Press Relative Load With Higher Reliability?

Science.gov (United States)

García-Ramos, Amador; Pestaña-Melero, Francisco L; Pérez-Castilla, Alejandro; Rojas, Francisco J; Gregory Haff, G

2018-05-01

García-Ramos, A, Pestaña-Melero, FL, Pérez-Castilla, A, Rojas, FJ, and Haff, GG. Mean velocity vs. mean propulsive velocity vs. peak velocity: which variable determines bench press relative load with higher reliability? J Strength Cond Res 32(5): 1273-1279, 2018-This study aimed to compare between 3 velocity variables (mean velocity [MV], mean propulsive velocity [MPV], and peak velocity [PV]): (a) the linearity of the load-velocity relationship, (b) the accuracy of general regression equations to predict relative load (%1RM), and (c) the between-session reliability of the velocity attained at each percentage of the 1-repetition maximum (%1RM). The full load-velocity relationship of 30 men was evaluated by means of linear regression models in the concentric-only and eccentric-concentric bench press throw (BPT) variants performed with a Smith machine. The 2 sessions of each BPT variant were performed within the same week separated by 48-72 hours. The main findings were as follows: (a) the MV showed the strongest linearity of the load-velocity relationship (median r = 0.989 for concentric-only BPT and 0.993 for eccentric-concentric BPT), followed by MPV (median r = 0.983 for concentric-only BPT and 0.980 for eccentric-concentric BPT), and finally PV (median r = 0.974 for concentric-only BPT and 0.969 for eccentric-concentric BPT); (b) the accuracy of the general regression equations to predict relative load (%1RM) from movement velocity was higher for MV (SEE = 3.80-4.76%1RM) than for MPV (SEE = 4.91-5.56%1RM) and PV (SEE = 5.36-5.77%1RM); and (c) the PV showed the lowest within-subjects coefficient of variation (3.50%-3.87%), followed by MV (4.05%-4.93%), and finally MPV (5.11%-6.03%). Taken together, these results suggest that the MV could be the most appropriate variable for monitoring the relative load (%1RM) in the BPT exercise performed in a Smith machine.

Statistical scaling of pore-scale Lagrangian velocities in natural porous media.

Science.gov (United States)

Siena, M; Guadagnini, A; Riva, M; Bijeljic, B; Pereira Nunes, J P; Blunt, M J

2014-08-01

We investigate the scaling behavior of sample statistics of pore-scale Lagrangian velocities in two different rock samples, Bentheimer sandstone and Estaillades limestone. The samples are imaged using x-ray computer tomography with micron-scale resolution. The scaling analysis relies on the study of the way qth-order sample structure functions (statistical moments of order q of absolute increments) of Lagrangian velocities depend on separation distances, or lags, traveled along the mean flow direction. In the sandstone block, sample structure functions of all orders exhibit a power-law scaling within a clearly identifiable intermediate range of lags. Sample structure functions associated with the limestone block display two diverse power-law regimes, which we infer to be related to two overlapping spatially correlated structures. In both rocks and for all orders q, we observe linear relationships between logarithmic structure functions of successive orders at all lags (a phenomenon that is typically known as extended power scaling, or extended self-similarity). The scaling behavior of Lagrangian velocities is compared with the one exhibited by porosity and specific surface area, which constitute two key pore-scale geometric observables. The statistical scaling of the local velocity field reflects the behavior of these geometric observables, with the occurrence of power-law-scaling regimes within the same range of lags for sample structure functions of Lagrangian velocity, porosity, and specific surface area.

RADIAL VELOCITY OBSERVATIONS AND LIGHT CURVE NOISE MODELING CONFIRM THAT KEPLER-91b IS A GIANT PLANET ORBITING A GIANT STAR

International Nuclear Information System (INIS)

Barclay, Thomas; Huber, Daniel; Rowe, Jason F.; Quintana, Elisa V.; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.; Foreman-Mackey, Daniel

2015-01-01

Kepler-91b is a rare example of a transiting hot Jupiter around a red giant star, providing the possibility to study the formation and composition of hot Jupiters under different conditions compared to main-sequence stars. However, the planetary nature of Kepler-91b, which was confirmed using phase-curve variations by Lillo-Box et al., was recently called into question based on a re-analysis of Kepler data. We have obtained ground-based radial velocity observations from the Hobby-Eberly Telescope and unambiguously confirm the planetary nature of Kepler-91b by simultaneously modeling the Kepler and radial velocity data. The star exhibits temporally correlated noise due to stellar granulation which we model as a Gaussian Process. We hypothesize that it is this noise component that led previous studies to suspect Kepler-91b to be a false positive. Our work confirms the conclusions presented by Lillo-Box et al. that Kepler-91b is a 0.73 ± 0.13 M Jup planet orbiting a red giant star

ROTATIONAL VELOCITIES FOR M DWARFS

International Nuclear Information System (INIS)

Jenkins, J. S.; Ramsey, L. W.; Jones, H. R. A.; Pavlenko, Y.; Barnes, J. R.; Pinfield, D. J.; Gallardo, J.

2009-01-01

We present spectroscopic rotation velocities (v sin i) for 56 M dwarf stars using high-resolution Hobby-Eberly Telescope High Resolution Spectrograph red spectroscopy. In addition, we have also determined photometric effective temperatures, masses, and metallicities ([Fe/H]) for some stars observed here and in the literature where we could acquire accurate parallax measurements and relevant photometry. We have increased the number of known v sin i values for mid M stars by around 80% and can confirm a weakly increasing rotation velocity with decreasing effective temperature. Our sample of v sin is peak at low velocities (∼3 km s -1 ). We find a change in the rotational velocity distribution between early M and late M stars, which is likely due to the changing field topology between partially and fully convective stars. There is also a possible further change in the rotational distribution toward the late M dwarfs where dust begins to play a role in the stellar atmospheres. We also link v sin i to age and show how it can be used to provide mid-M star age limits. When all literature velocities for M dwarfs are added to our sample, there are 198 with v sin i ≤ 10 km s -1 and 124 in the mid-to-late M star regime (M3.0-M9.5) where measuring precision optical radial velocities is difficult. In addition, we also search the spectra for any significant Hα emission or absorption. Forty three percent were found to exhibit such emission and could represent young, active objects with high levels of radial-velocity noise. We acquired two epochs of spectra for the star GJ1253 spread by almost one month and the Hα profile changed from showing no clear signs of emission, to exhibiting a clear emission peak. Four stars in our sample appear to be low-mass binaries (GJ1080, GJ3129, Gl802, and LHS3080), with both GJ3129 and Gl802 exhibiting double Hα emission features. The tables presented here will aid any future M star planet search target selection to extract stars with low v

Modulation of Intracellular Quantum Dot to Fluorescent Protein Förster Resonance Energy Transfer via Customized Ligands and Spatial Control of Donor–Acceptor Assembly

Directory of Open Access Journals (Sweden)

Lauren D. Field

2015-12-01

Full Text Available Understanding how to controllably modulate the efficiency of energy transfer in Förster resonance energy transfer (FRET-based assemblies is critical to their implementation as sensing modalities. This is particularly true for sensing assemblies that are to be used as the basis for real time intracellular sensing of intracellular processes and events. We use a quantum dot (QD donor -mCherry acceptor platform that is engineered to self-assemble in situ wherein the protein acceptor is expressed via transient transfection and the QD donor is microinjected into the cell. QD-protein assembly is driven by metal-affinity interactions where a terminal polyhistidine tag on the protein binds to the QD surface. Using this system, we show the ability to modulate the efficiency of the donor–acceptor energy transfer process by controllably altering either the ligand coating on the QD surface or the precise location where the QD-protein assembly process occurs. Intracellularly, a short, zwitterionic ligand mediates more efficient FRET relative to longer ligand species that are based on the solubilizing polymer, poly(ethylene glycol. We further show that a greater FRET efficiency is achieved when the QD-protein assembly occurs free in the cytosol compared to when the mCherry acceptor is expressed tethered to the inner leaflet of the plasma membrane. In the latter case, the lower FRET efficiency is likely attributable to a lower expression level of the mCherry acceptor at the membrane combined with steric hindrance. Our work points to some of the design considerations that one must be mindful of when developing FRET-based sensing schemes for use in intracellular sensing.

Organic Materials in the Undergraduate Laboratory: Microscale Synthesis and Investigation of a Donor-Acceptor Molecule

Science.gov (United States)

Pappenfus, Ted M.; Schliep, Karl B.; Dissanayake, Anudaththa; Ludden, Trevor; Nieto-Ortega, Belen; Lopez Navarrete, Juan T.; Ruiz Delgado, M. Carmen; Casado, Juan

2012-01-01

A series of experiments for undergraduate courses (e.g., organic, physical) have been developed in the area of small molecule organic materials. These experiments focus on understanding the electronic and redox properties of a donor-acceptor molecule that is prepared in a convenient one-step microscale reaction. The resulting intensely colored…

Adsorption of Organic Electron Acceptors on Graphene-like Molecules: Quantum Chemical and Molecular Mechanical Study

Czech Academy of Sciences Publication Activity Database

Haldar, Susanta; Kolář, Michal; Sedlák, Robert; Hobza, Pavel

2012-01-01

Roč. 116, č. 48 (2012), s. 25328-25336 ISSN 1932-7447 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388963 Keywords : graphene * organic electron acceptors * interaction energies * base-pairs * hydrophobic association Subject RIV: CF - Physical ; The oretical Chemistry Impact factor: 4.814, year: 2012

Three-dimensional imaging of absolute blood flow velocity and blood vessel position under low blood flow velocity based on Doppler signal information included in scattered light from red blood cells

Science.gov (United States)

Kyoden, Tomoaki; Akiguchi, Shunsuke; Tajiri, Tomoki; Andoh, Tsugunobu; Hachiga, Tadashi

2017-11-01

The development of a system for in vivo visualization of occluded distal blood vessels for diabetic patients is the main target of our research. We herein describe two-beam multipoint laser Doppler velocimetry (MLDV), which measures the instantaneous multipoint flow velocity and can be used to observe the blood flow velocity in peripheral blood vessels. By including a motorized stage to shift the measurement points horizontally and in the depth direction while measuring the velocity, the path of the blood vessel in the skin could be observed using blood flow velocity in three-dimensional space. The relationship of the signal power density between the blood vessel and the surrounding tissues was shown and helped us identify the position of the blood vessel. Two-beam MLDV can be used to simultaneously determine the absolute blood flow velocity distribution and identify the blood vessel position in skin.

On an illusion of superluminal velocities produced by gravitational lenses

International Nuclear Information System (INIS)

Ingel, L.Kh.

1981-01-01

It is noted that gravitational lenses, by focusing the radiation of an object, increase the angle which it subtends. This in turn produces the illusion of an increase in velocities at right angles to the line of sight. Preliminary estimates are made which indicate a rather high probability of strong distortion of the observed velocities

Controlling Blend Morphology for Ultra-High Current Density in Non-Fullerene Acceptor Based Organic Solar Cells

KAUST Repository

Song, Xin

2018-01-23

Due to the high absorption coefficient and modulated band gap of non-fullerene small molecule acceptors (NFAs), photons can be utilized more efficiently in near-infrared (NIR) range. In this report, we highlight a system with a well-known polymer donor (PTB7-Th) blended with a narrow bandgap non-fullerene acceptor (IEICO-4F) as active layer and 1-chloronaphthalene (CN) as the solvent additive. The optimization of the photoactive layer nanomorphology yields short-circuit current density value (Jsc) of 27.3 mA/cm2, one of the highest value in OSCs reported to date, which competes with other types of solution processed solar cells such as perovskite or quantum dot devices. Along with decent open-circuit voltage (0.71V) and fill factor values (66%), a power conversion efficiency of 12.8% is achieved for the champion devices. Grazing incidence wide-angle X-ray scattering (GIWAXS) patterns and resonant soft X-ray scattering (R-SoXS) elucidate that the origin of this high photocurrent is mainly due to increased π-π coherence length of the acceptor, the domain spacing as well as the mean-square composition variation of the blend. Optoelectronic measurements confirm a balanced hole and electron mobility and reduced trap-assisted recombination for the best devices. These findings unveil the relevant solvent processing-nanostructure-electronic properties correlation in low band gap non-fullerene based solar cells, which provide a helpful guide for maximizing photocurrent that can pave the way for high efficiency organic solar cells.

Controlling Blend Morphology for Ultra-High Current Density in Non-Fullerene Acceptor Based Organic Solar Cells

KAUST Repository

Song, Xin; Gasparini, Nicola; Ye, Long; Yao, Huifeng; Hou, Jianhui; Ade, Harald; Baran, Derya

2018-01-01

Due to the high absorption coefficient and modulated band gap of non-fullerene small molecule acceptors (NFAs), photons can be utilized more efficiently in near-infrared (NIR) range. In this report, we highlight a system with a well-known polymer donor (PTB7-Th) blended with a narrow bandgap non-fullerene acceptor (IEICO-4F) as active layer and 1-chloronaphthalene (CN) as the solvent additive. The optimization of the photoactive layer nanomorphology yields short-circuit current density value (Jsc) of 27.3 mA/cm2, one of the highest value in OSCs reported to date, which competes with other types of solution processed solar cells such as perovskite or quantum dot devices. Along with decent open-circuit voltage (0.71V) and fill factor values (66%), a power conversion efficiency of 12.8% is achieved for the champion devices. Grazing incidence wide-angle X-ray scattering (GIWAXS) patterns and resonant soft X-ray scattering (R-SoXS) elucidate that the origin of this high photocurrent is mainly due to increased π-π coherence length of the acceptor, the domain spacing as well as the mean-square composition variation of the blend. Optoelectronic measurements confirm a balanced hole and electron mobility and reduced trap-assisted recombination for the best devices. These findings unveil the relevant solvent processing-nanostructure-electronic properties correlation in low band gap non-fullerene based solar cells, which provide a helpful guide for maximizing photocurrent that can pave the way for high efficiency organic solar cells.

SEVEN NEW BINARIES DISCOVERED IN THE KEPLER LIGHT CURVES THROUGH THE BEER METHOD CONFIRMED BY RADIAL-VELOCITY OBSERVATIONS

International Nuclear Information System (INIS)

Faigler, S.; Mazeh, T.; Tal-Or, L.; Quinn, S. N.; Latham, D. W.

2012-01-01

We present seven newly discovered non-eclipsing short-period binary systems with low-mass companions, identified by the recently introduced BEER algorithm, applied to the publicly available 138-day photometric light curves obtained by the Kepler mission. The detection is based on the beaming effect (sometimes called Doppler boosting), which increases (decreases) the brightness of any light source approaching (receding from) the observer, enabling a prediction of the stellar Doppler radial-velocity (RV) modulation from its precise photometry. The BEER algorithm identifies the BEaming periodic modulation, with a combination of the well-known Ellipsoidal and Reflection/heating periodic effects, induced by short-period companions. The seven detections were confirmed by spectroscopic RV follow-up observations, indicating minimum secondary masses in the range 0.07-0.4 M ☉ . The binaries discovered establish for the first time the feasibility of the BEER algorithm as a new detection method for short-period non-eclipsing binaries, with the potential to detect in the near future non-transiting brown-dwarf secondaries, or even massive planets.

Synthesis, spectroscopic properties, and photoconductivity of black absorbers consisting of pt(bipyridine)(dithiolate) charge transfer complexes in the presence and absence of nitrofluorenone acceptors.

Science.gov (United States)

Browning, Charles; Hudson, Joshua M; Reinheimer, Eric W; Kuo, Fang-Ling; McDougald, Roy N; Rabaâ, Hassan; Pan, Hongjun; Bacsa, John; Wang, Xiaoping; Dunbar, Kim R; Shepherd, Nigel D; Omary, Mohammad A

2014-11-19

The diimine-dithiolato ambipolar complexes Pt(dbbpy)(tdt) and Pt(dmecb)(bdt) (dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine; tdt(2-) = 3,4-toluenedithiolate; dmecb = 4,4'-dimethoxyester-2,2'-bipyridine; bdt(2-) = benzene-1,2-dithiolate) are prepared herein. Pt(dmecb)(bdt) exhibits photoconductivity that remains constant (photocurrent density of 1.6 mA/cm(2) from a 20 nm thin film) across the entire visible region of the solar spectrum in a Schottky diode device structure. Pt(dbbpy)(tdt) acts as donor when combined with the strong nitrofluorenone acceptors 2,7-dinitro-9-fluorenone (DNF), 2,4,7-trinitro-9-fluorenone (TRNF), or 2,4,5,7-tetranitro-9-fluorenone (TENF). Supramolecular charge transfer stacks form and exhibit various donor-acceptor stacking patterns. The crystalline solids are "black absorbers" that exhibit continuous absorptions spanning the entire visible region and significant ultraviolet and near-infrared wavelengths, the latter including long wavelengths that the donor or acceptor molecules alone do not absorb. Absorption spectra reveal the persistence of donor-acceptor interactions in solution, as characterized by low-energy donor/acceptor charge transfer (DACT) bands. Crystal structures show closely packed stacks with distances that underscore intermolecular DACT. (1)H NMR provides further evidence of DACT, as manifested by upfield shifts of aromatic protons in the binary adducts versus their free components, whereas 2D nuclear Overhauser effect spectroscopy (NOESY) spectra suggest coupling between dithiolate donor protons with nitrofluorenone acceptor protons, in correlation with the solid-state stacking. The NMR spectra also show significant peak broadening, indicating some paramagnetism verified by magnetic susceptibility data. Solid-state absorption spectra reveal further red shifts and increased relative intensities of DACT bands for the solid adducts vs solution, suggesting cooperativity of the DACT phenomenon in the solid state, as further

Characterization of a spectrally diverse set of fluorescent proteins as FRET acceptors for mTurquoise2

NARCIS (Netherlands)

Mastop, M.; Bindels, D.S.; Shaner, N.C.; Postma, M.; Gadella, T.W.J.; Goedhart, J.

2017-01-01

The performance of Förster Resonance Energy Transfer (FRET) biosensors depends on brightness and photostability, which are dependent on the characteristics of the fluorescent proteins that are employed. Yellow fluorescent protein (YFP) is often used as an acceptor but YFP is prone to photobleaching

Diffraction imaging and velocity analysis using oriented velocity continuation

KAUST Repository

Decker, Luke

2014-08-05

We perform seismic diffraction imaging and velocity analysis by separating diffractions from specular reflections and decomposing them into slope components. We image slope components using extrapolation in migration velocity in time-space-slope coordinates. The extrapolation is described by a convection-type partial differential equation and implemented efficiently in the Fourier domain. Synthetic and field data experiments show that the proposed algorithm is able to detect accurate time-migration velocities by automatically measuring the flatness of events in dip-angle gathers.